Control system and method for improving tracking accuracy of a stage through processing of information from previous operations
A precision assembly (10) includes a stage assembly (220) having a first stage (208), a first mover assembly (210) and a control system (24). The first mover assembly (210) moves the first stage (208) during a first iteration (300) and a subsequent second iteration (302) having a similar movement to the first iteration (300). The first iteration (300) generates positioning data that is sent to the control system (24) to control the first mover assembly (210) to adjust movement of the first stage (208) during the second iteration (302) based on at least a portion of the positioning data from the first iteration (300). The positioning data can include the position of the first stage (208) along a first axis, a second axis and/or a third axis. The stage assembly can also include a second stage (206) and a second mover assembly (204) that moves the second stage (206) synchronously with the first stage (208). The second stage (206) generates positioning data that is used by the control system (24) to adjust movement the first mover assembly (210) of the first stage (208) to improve synchronization of movement of the stages. The precision assembly (10) can also include one or more sensors (23) that monitor movement of one or more components of the precision assembly (10) other than the stage assembly (220). Positioning data of such movement is sent to the control system (24) to control movement of the first stage (208).
[0001] This Application claims the benefit on U.S. Provisional Application Serial No. 60/424,506, filed on Nov. 6, 2002. The contents of U.S. Provisional Application Serial No. 60/424,506 are incorporated herein by reference.
FIELD OF THE INVENTION[0002] The present invention relates generally to a control system for controlling the trajectory and alignment of one or more stages.
BACKGROUND[0003] An exposure apparatus is one type of precision assembly that are commonly used to transfer images from a reticle onto a semiconductor wafer during semiconductor processing. A typical exposure apparatus includes an illumination source, a reticle stage assembly that retains a reticle, an optical assembly, a wafer stage assembly that retains a semiconductor wafer, a measurement system, and a control system.
[0004] In one embodiment, the wafer stage assembly includes a wafer stage that retains the wafer, and a wafer mover assembly that precisely positions the wafer stage and the wafer. Somewhat similarly, the reticle stage assembly includes a reticle stage that retains the reticle, and a reticle mover assembly that positions the reticle stage and the reticle. The control system independently directs current to the wafer mover assembly and the reticle mover assembly to generate one or more forces that cause the movement along a “trajectory” of the wafer stage and the reticle stage, respectively.
[0005] The size of the images and features within the images transferred onto the wafer from the reticle are extremely small. Accordingly, the precise positioning of the wafer and the reticle relative to the optical assembly is critical to the manufacture of high density, semiconductor wafers. In some embodiments, numerous identical integrated circuits are derived from each semiconductor wafer. Therefore, during this manufacturing process, the wafer stage and/or the reticle stage can be cyclically and repetitiously moved to emulate an intended trajectory. Each intended trajectory that is similar to a previous intended trajectory of one of the stages is also referred to herein as an “iteration” or “cycle”.
[0006] Unfortunately, during the movement of the stages, a following error of the wafer stage and/or the reticle stage can occur. The following error is defined by the difference between the intended trajectory of the wafer stage and/or the reticle stage and an actual trajectory of the stage at a specified time. For example, the following error can occur due to lack of complete rigidity in the components of the exposure apparatus, which can result in a slight time delay between current being directed to the mover assembly and subsequent movement of the stage.
[0007] Additionally, alignment errors can occur even if the stages are properly positioned relative to each other. For example, periodic vibration disturbances of various mechanical structures of the exposure apparatus can occur. More specifically, oscillation or resonance of the optical assembly and/or other supporting structures can inhibit relative alignment between the stages and the optical assembly. As a result of the following errors and/or the vibration disturbances, precision in the manufacture of the semiconductor wafers can be compromised, potentially leading to production of a lesser quality semiconductor wafer.
[0008] Attempts to decrease following errors include the use of a feedback control loop. In these types of systems, during movement of one of the stages, the measurement system periodically provides information regarding the current position of the stage. This information is utilized by the control system to adjust the level of current to the mover assembly in an attempt to achieve the intended trajectory. Unfortunately, this method is not entirely satisfactory and the control system does not always precisely move each stage along its intended trajectory.
[0009] In light of the above, there is a need for a control system that can improve the accuracy in the positioning of the stage. Further, there is a need for a control system that can accurately adjust the positioning of the wafer stage and/or the reticle stage to produce higher quality semiconductor wafers.
SUMMARY[0010] The present invention is directed to a stage assembly that includes a first stage, a first mover assembly that moves the first stage, and a control system. In one embodiment, the first mover assembly moves the first stage in a first iteration and a subsequent second iteration having a similar movement to the first iteration. In one embodiment, the control system collects positioning data during the first iteration that is utilized during the second iteration to control the first mover assembly to adjust movement of the first stage during the second iteration.
[0011] The control system can include a memory buffer that stores the positioning data. Movement of the first stage can include movement along an X axis, a Y axis and/or about a Z axis. The positioning data can include the position of the first stage along or about any or all of these axes.
[0012] For example, at a time t11 during the first iteration, the first stage can have an intended position and a measured, actual position that can be different than the intended position. The difference between the intended position and the actual position at time t11 is referred to herein as a t11 following error. In one embodiment, the positioning data includes the t1 following error. Further, at a time t21 during the first iteration the first stage can also have an intended position and an actual position that can be different than the intended position, referred to herein as a t21 following error. The positioning data can also include the t21 following error.
[0013] Moreover, the first iteration and the second iteration can each have correspondingly relative similar time points within each iteration that include time t1, time t2 and time t3. In this embodiment, time t1 is prior to time t2, and time t2 is prior to time t3. In one embodiment, the control system controls the first mover assembly to adjust movement of the first stage at time t2 of the second iteration based on the positioning data generated at time t3 of the first iteration.
[0014] In another embodiment, the first mover assembly can move the first stage in a third iteration that precedes the first iteration. The control system collects positioning data during the third iteration that is used by the control system for adjusting current to the first mover assembly to control movement of the first stage during the second iteration based on the positioning data generated during the third iteration.
[0015] In still another embodiment, the stage assembly can include a second stage and a second mover assembly that moves the second stage synchronously with the first stage. Positioning data from movement of the second stage is used to more accurately control positioning of the first stage. For example, the control system can adjust current to the first mover assembly based at least partially on the positioning data generated from the second stage. With this design, the control system can improve synchronization of movement of the stages.
[0016] In yet another embodiment, the present invention is directed toward an exposure apparatus including a stage assembly having a first stage and a first mover assembly, a sensor that provides positioning data relating to movement of a portion of the exposure apparatus other than the stage assembly. The exposure apparatus also includes a control system that receives the positioning data. The control system controls the first mover assembly to adjust movement of the first stage based on at least a portion of the positioning data.
[0017] The present invention is also directed to an exposure apparatus, a wafer, a device, a method for positioning one or more stages of a stage assembly of a precision assembly, a method for making an exposure apparatus, a method for making a wafer, and a method for making a device.
BRIEF DESCRIPTION OF THE DRAWINGS[0018] The novel features of this invention, as well as the invention itself, both as to its structure and its operation, will be best understood from the accompanying drawings, taken in conjunction with the accompanying description, in which similar reference characters refer to similar parts, and in which:
[0019] FIG. 1 is a schematic view of an exposure apparatus having features of the present invention;
[0020] FIG. 2A is a perspective view of a stage assembly having features of the present invention;
[0021] FIG. 2B is a perspective view of a portion of the stage assembly in FIG. 2A;
[0022] FIG. 2C is a perspective view of an actuator pair having features of the present invention;
[0023] FIG. 2D is a perspective view of another stage assembly having features of the present invention;
[0024] FIG. 3A is a simplified example of two iterations of the stage, each iteration including an intended trajectory;
[0025] FIG. 3B is another simplified example of two iterations of the stage, each iteration including an intended trajectory;
[0026] FIG. 3C is another simplified example of two iterations of the stage, each iteration including an intended trajectory;
[0027] FIG. 3D is another simplified example of two iterations of the stage, each iteration including an intended trajectory;
[0028] FIG. 3E is another simplified example of two iterations of the stage, each iteration including an intended trajectory;
[0029] FIG. 3F is another simplified example of two iterations of the stage, each iteration including an intended trajectory;
[0030] FIG. 3G is another simplified example of two iterations of the stage, each iteration including an intended trajectory;
[0031] FIG. 3H is another simplified example of two iterations of the stage, each iteration including an intended trajectory;
[0032] FIG. 31 is another simplified example of two iterations of the stage, each iteration including an intended trajectory;
[0033] FIG. 3J is another simplified example of two iterations of the stage, each iteration including an intended trajectory;
[0034] FIG. 3K is another simplified example of two iterations of the stage, each iteration including an intended trajectory;
[0035] FIG. 3L is another simplified example of two iterations of the stage, each iteration including an intended trajectory;
[0036] FIG. 3M is another simplified example of two iterations of the stage, each iteration including an intended trajectory;
[0037] FIG. 4A is a graph including curves illustrating an intended trajectory and an actual trajectory as a function of time during movement of a stage over a plurality of iterations;
[0038] FIG. 4B is a graph illustrating a following error of the stage in FIG. 4A as a function of time;
[0039] FIG. 4C is a graph illustrating actual trajectory as a function of time during movement of the stage over a plurality of iterations;
[0040] FIG. 5A is a block diagram that illustrates a first embodiment of a control system for controlling a stage assembly;
[0041] FIG. 5B is a block diagram that illustrates a second embodiment of a control system for controlling the stage assembly;
[0042] FIG. 6 is a Bode diagram illustrating magnitude and phase plotted against frequency of a zero-phase FIR (Finite Impulse Response) filter during information processing;
[0043] FIG. 7A is a Bode diagram illustrating magnitude and phase plotted against frequency of a low-pass filter with phase lag during information processing;
[0044] FIG. 7B is another Bode diagram illustrating magnitude and phase plotted against frequency utilizing the low pass filter forward and backward to render low pass effect with zero phase during information processing;
[0045] FIG. 8 is a graph illustrating a series of curves including acceleration, position, Y following error, X following error, and theta Z following error, as a function of time of a stage in a stage assembly having features of the present invention;
[0046] FIG. 9A is a graph illustrating the following error and a vibration disturbance over time during the first several iterations of a stage in a stage assembly having features of the present invention;
[0047] FIG. 9B is a graph illustrating the following error and the vibration disturbance over time during subsequent iterations of the stage of FIG. 9A;
[0048] FIG. 10 is a flow chart that outlines a process for manufacturing a device in accordance with the present invention; and
[0049] FIG. 11 is a flow chart that outlines device processing in more detail.
DESCRIPTION[0050] FIG. 1 is a schematic illustration of a precision assembly, namely an exposure apparatus 10, having features of the present invention. The exposure apparatus 10 illustrated in FIG. 1 includes an apparatus frame 12, an illumination system 14 (irradiation apparatus), an assembly 16 such as an optical assembly, a reticle stage assembly 18, a wafer stage assembly 20, a measurement system 22, one or more sensors 23, and a control system 24. The specific design of the components of the exposure apparatus 10 can be varied to suit the design requirements of the exposure apparatus 10.
[0051] As provided herein, the control system 24 utilizes a position compensation system that improves the accuracy in the control and relative positioning of at least one of the stage assemblies 18, 20.
[0052] A number of Figures include an orientation system that illustrates an X axis, a Y axis that is orthogonal to the X axis, and a Z axis that is orthogonal to the X and Y axis. It should be noted that these axes can also be referred to as the first, second and third axes.
[0053] The exposure apparatus 10 is particularly useful as a lithographic device that transfers a pattern (not shown) of an integrated circuit from a reticle 26 onto a semiconductor wafer 28. The exposure apparatus 10 mounts to a mounting base 30, e.g., the ground, a base, or floor or some other supporting structure.
[0054] There are a number of different types of lithographic devices. For example, the exposure apparatus 10 can be used as scanning type photolithography system that exposes the pattern from the reticle 26 onto the wafer 28 with the reticle 26 and the wafer 28 moving synchronously. In a scanning type lithographic device, the reticle 26 is moved perpendicularly to an optical axis of the assembly 16 by the reticle stage assembly 18 and the wafer 28 is moved perpendicularly to the optical axis of the assembly 16 by the wafer stage assembly 20. Scanning of the reticle 26 and the wafer 28 occurs while the reticle 26 and the wafer 28 are moving synchronously.
[0055] Alternatively, the exposure apparatus 10 can be a step-and-repeat type photolithography system that exposes the reticle 26 while the reticle 26 and the wafer 28 are stationary. In the step and repeat process, the wafer 28 is in a constant position relative to the reticle 26 and the assembly 16 during the exposure of an individual field. Subsequently, between consecutive exposure steps, the wafer 28 is consecutively moved using the wafer stage assembly 20 perpendicularly to the optical axis of the assembly 16 so that the next field of the wafer 28 is brought into position relative to the assembly 16 and the reticle 26 for exposure. Following this process, the images on the reticle 26 are sequentially exposed onto the fields of the wafer 28 so that the next field of the wafer 28 is brought into position relative to the assembly 16 and the reticle 26.
[0056] However, the use of the exposure apparatus 10 provided herein is not limited to a photolithography system for semiconductor manufacturing. The exposure apparatus 10, for example, can be used as an LCD photolithography system that exposes a liquid crystal display device pattern onto a rectangular glass plate or a photolithography system for manufacturing a thin film magnetic head. Further, the present invention can also be applied to a proximity photolithography system that exposes a mask pattern from a mask to a substrate with the mask located close to the substrate without the use of a lens assembly.
[0057] The apparatus frame 12 is rigid and supports the components of the exposure apparatus 10. The apparatus frame 12 illustrated in FIG. 1 supports the assembly 16 and the illumination system 14 above the mounting base 30.
[0058] The illumination system 14 includes an illumination source 34 and an illumination optical assembly 36. The illumination source 34 emits a beam (irradiation) of light energy. The illumination optical assembly 36 guides the beam of light energy from the illumination source 34 to the assembly 16. The beam illuminates selectively different portions of the reticle 26 and exposes the wafer 28. In FIG. 1, the illumination source 34 is illustrated as being supported above the reticle stage assembly 18. Typically, however, the illumination source 34 is secured to one of the sides of the apparatus frame 12 and the energy beam from the illumination source 34 is directed to above the reticle stage assembly 18 with the illumination optical assembly 36.
[0059] The illumination source 34 can be a g-line source (436 nm), an i-line source (365 nm), a KrF excimer laser (248 nm), an ArF excimer laser (193 nm) or a F2 laser (157 nm). Alternatively, the illumination source 34 can generate charged particle beams such as an x-ray or an electron beam. For instance, in the case where an electron beam is used, thermionic emission type lanthanum hexaboride (LaB6) or tantalum (Ta) can be used as a cathode for an electron gun. Furthermore, in the case where an electron beam is used, the structure could be such that either a mask is used or a pattern can be directly formed on a substrate without the use of a mask.
[0060] The assembly 16 can be an optical assembly, for example, that projects and/or focuses the light passing through the reticle 26 to the wafer 28. Depending upon the design of the exposure apparatus 10, the assembly 16 can magnify or reduce the image illuminated on the reticle 26. The assembly 16 need not be limited to a reduction system. It could also be a 1× or a magnification system.
[0061] When far ultra-violet rays such as the excimer laser is used, glass materials such as quartz and fluorite that transmit far ultra-violet rays can be used in the assembly 16. When the F2 type laser or x-ray is used, the assembly 16 can be either catadioptric or refractive (a reticle should also preferably be a reflective type), and when an electron beam is used, electron optics can consist of electron lenses and deflectors. The optical path for the electron beams should be in a vacuum.
[0062] Also, with an exposure device that employs vacuum ultra-violet radiation (VUV) of wavelength 200 nm or lower, use of the catadioptric type optical system can be considered. Examples of the catadioptric type of optical system include the disclosure Japan Patent Application Disclosure No. 8-171054 published in the Official Gazette for Laid-Open Patent Applications and its counterpart U.S. Pat. No. 5,668,672, as well as Japan Patent Application Disclosure No. 10-20195 and its counterpart U.S. Pat. No. 5,835,275. In these cases, the reflecting optical device can be a catadioptric optical system incorporating a beam splitter and concave mirror. Japan Patent Application Disclosure No. 8-334695 published in the Official Gazette for Laid-Open Patent Applications and its counterpart U.S. Pat. No. 5,689,377 as well as Japan Patent Application Disclosure No. 10-3039 and its counterpart U.S. Patent Application No. 873,605 (Application Date: 6-12-97) also use a reflecting-refracting type of optical system incorporating a concave mirror, etc., but without a beam splitter, and can also be employed with this invention. As far as is permitted, the disclosures in the above-mentioned U.S. patents, as well as the Japan patent applications published in the Official Gazette for Laid-Open Patent Applications are incorporated herein by reference.
[0063] The reticle stage assembly 18 holds and positions the reticle 26 relative to the assembly 16 and the wafer 28. Somewhat similarly, the wafer stage assembly 20 holds and positions the wafer 28 with respect to the projected image of the illuminated portions of the reticle 26. The stage assemblies 18, 20 are described in more detail below.
[0064] In photolithography systems, when linear motors (see U.S. Pat. Nos. 5,623,853 or 5,528,118) are used in a reticle stage assembly 18 or a wafer stage assembly 20, the linear motors can be either an air levitation type employing air bearings or a magnetic levitation type using Lorentz force or reactance force. Additionally, the stage can move along a guide, or it can be a guideless type of stage. As far as is permitted, the disclosures in U.S. Pat. Nos. 5,623,853 and 5,528,118 are incorporated herein by reference.
[0065] Alternatively, the reticle stage and/or the wafer stage could be driven by a planar motor. The planar motor drives the stage by an electromagnetic force generated by a magnet unit having two-dimensionally arranged magnets and an armature coil unit having two-dimensionally arranged coils in facing positions. With this type of driving system, either the magnet unit or the armature coil unit is connected to the stage and the other unit is mounted on the moving plane side of the stage.
[0066] Movement of the stages as described above generates reaction forces that can affect performance of the photolithography system. Reaction forces generated by motion of the wafer stage can be mechanically transferred to the floor (ground) by use of a frame member as described in U.S. Pat. No. 5,528,100 and published Japanese Patent Application Disclosure No. 8-136475. Additionally, reaction forces generated by motion of the reticle stage can be mechanically transferred to the floor (ground) by use of a frame member as described in U.S. Pat. No. 5,874,820 and published Japanese Patent Application Disclosure No. 8-330224. As far as is permitted, the disclosures in U.S. Pat. Nos. 5,528,100 and 5,874,820 and Japanese Patent Application Disclosure No. 8-330224 are incorporated herein by reference.
[0067] Typically, numerous integrated circuits are derived from a single wafer 28. Therefore, the process may involve a substantial number of repetitive, identical or substantially similar movements of portions of the reticle stage assembly 18 and/or the wafer stage assembly 20. Each such repetitive movement is also referred to herein as an iteration, iterative movement or cycle, as defined in greater detail below.
[0068] The measurement system 22 monitors movement of the reticle 26 and the wafer 28 relative to the assembly 16 or some other reference. With this information, the control system 24 can control the reticle stage assembly 18 to precisely position the reticle 26 and the wafer stage assembly 20 to precisely position the wafer 28 relative to the assembly 16. For example, the measurement system 22 can utilize multiple laser interferometers, encoders, and/or other measuring devices.
[0069] Additionally, one or more sensors 23 can monitor and/or receive information regarding one or more components of the exposure apparatus. For example, the exposure apparatus 10 can include one or more sensors 23 positioned on or near the assembly 16, the frame 12, or other suitable components. As explained below, information from the sensor(s) 23 can be provided to the control system 24 for processing as provided herein. In the embodiment illustrated in FIG. 1, the exposure apparatus 10 can include two spaced apart, separate sensors 23 that are secured to the apparatus frame 12 and two spaced apart, separate sensors 23 that are secured to the assembly 16. Alternatively, the sensors 23 can be positioned elsewhere. Further, the type of sensor 23 can be varied. For example, one or more of the sensors 23 can be an accelerometer, an interferometer, a gyroscope, and/or other types of sensors.
[0070] The control system 24 receives information from the measurement system 22 and other systems and controls the stage mover assemblies 18, 20 to precisely and synchronously position the reticle 26 and the wafer 28 relative to the assembly 16 or some other reference. The control system 24 includes one or more processors and circuits for performing the functions described herein. The control system 24 is described in greater detail below.
[0071] A photolithography system (an exposure apparatus) according to the embodiments described herein can be built by assembling various subsystems, including each element listed in the appended claims, in such a manner that prescribed mechanical accuracy, electrical accuracy, and optical accuracy are maintained. In order to maintain the various accuracies, prior to and following assembly, every optical system is adjusted to achieve its optical accuracy. Similarly, every mechanical system and every electrical system is adjusted to achieve its respective mechanical and electrical accuracies. The process of assembling each subsystem into a photolithography system includes mechanical interfaces, electrical circuit wiring connections and air pressure plumbing connections between each subsystem. Needless to say, there is also a process where each subsystem is assembled prior to assembling a photolithography system from the various subsystems. Once a photolithography system is assembled using the various subsystems, a total adjustment is performed to make sure that accuracy is maintained in the complete photolithography system. Additionally, it is desirable to manufacture an exposure system in a clean room where the temperature and cleanliness are controlled.
[0072] FIG. 2A is a perspective view of a stage assembly 220 that is used to position a device 200, and a control system 224. The stage assembly 220 can be used as the wafer stage assembly 20 in the exposure apparatus 10 of FIG. 1. In this embodiment, the stage assembly 220 would position the wafer 28 (illustrated in FIG. 1) during manufacturing of the semiconductor wafer 28. As provided herein, the stage assembly 220 can also include a portion or all of the control system 224. Alternatively, the stage assembly 220 can be used to move other types of devices 200 during manufacturing and/or inspection, to move a device under an electron microscope (not shown), or to move a device during a precision measurement operation (not shown).
[0073] Still alternatively, for example, the stage assembly 220 could be used as the reticle stage assembly 18 in the exposure apparatus 10 of FIG. 1. In this example, the stage assembly 220 would position the reticle 26 (illustrated in FIG. 1) during manufacturing of the semiconductor wafer 28.
[0074] In the embodiment illustrated in FIG. 2A, the stage assembly 220 includes a stage base 202, a coarse stage mover assembly 204, a coarse stage 206, a fine stage 208 and a fine stage mover assembly 210. The design of the components of the stage assembly 220 can be varied. For example, in FIG. 2A, the stage assembly 220 includes one coarse stage 206 and one fine stage 208. Alternatively, however, the stage assembly 220 could be designed to include greater or fewer than one coarse stage 206 or greater or fewer than one fine stage 208. As used herein, the terms coarse stage 206 and fine stage 208 can be used interchangeably with the first stage and the second stage, in either order. It should also be recognized that the stage assembly 220 illustrated and described herein is only one example of possible types of stage assemblies, and is in no way intended to limit the scope of the present invention. Further, the stage assembly 220 can be constructed in accordance with industry standards that are generally known to those skilled in the art.
[0075] In FIG. 2A, the stage base 202 is generally rectangular shaped. Alternatively, the stage base 202 can be another shape. The stage base 202 supports some of the components of the stage assembly 220 above the mounting base 30 illustrated in FIG. 2A.
[0076] The design of the coarse stage mover assembly 204 can be varied to suit the movement requirements of the stage assembly 220. In one embodiment, the coarse stage mover assembly 204 includes one or more movers, such as rotary motors, voice coil motors, linear motors utilizing a Lorentz force to generate a driving force, electromagnetic actuators, planar motors, or some other force actuators.
[0077] In FIG. 2A, the coarse stage mover assembly 204 moves the coarse stage 206 relative to the stage base 202 along the X axis, along the Y axis, and about the Z axis (collectively “the planar degrees of freedom”). Additionally, the coarse stage mover assembly 204 could be designed to move and position the coarse stage 206 along the Z axis, about the X axis and/or about the Y axis relative to the stage base 202. Alternatively, for example, the coarse stage mover assembly 204 could be designed to move the coarse stage 206 with less than three degrees of freedom.
[0078] In FIG. 2A, the coarse stage mover assembly 204 includes a planar motor. In this embodiment, the coarse stage mover assembly 204 includes a first mover component 212 that is secured to and moves with the coarse stage 206 and a second mover component 214 (illustrated in phantom) that is secured to the stage base 202. The design of each component can be varied. For example, one of the mover components 212, 214 can include a magnet array having a plurality of magnets and the other of the mover components 214, 212 can include a conductor array having a plurality of conductors.
[0079] In FIG. 2A, the first mover component 212 includes the magnet array and the second mover component 214 includes the conductor array. Alternatively, the first mover component 212 can include the conductor array and the second mover component 214 can include the magnet array. The size and shape of the conductor array and the magnet array and the number of conductors in the conductor array and the number of magnets in the magnet array can be varied to suit design requirements.
[0080] The first mover component 212 can be maintained above the second mover component 214 with vacuum pre-load type air bearings (not shown). With this design, the coarse stage 206 is movable relative to the stage base 202 with three degrees of freedom, namely along the X axis, along the Y axis, and rotatable around the Z axis. Alternatively, the first mover component 212 could be supported above the second mover component 214 by other ways, such as guides, a rolling type bearing, or by the magnetic levitation forces and/or the coarse stage mover assembly 204 could be designed to be movable with up to six degrees of freedom. Still alternatively, the coarse stage mover assembly 204 could be designed to include one or more electromagnetic actuators.
[0081] The control system 224 directs electrical current to one or more of the conductors in the conductor array. The electrical current through the conductors causes the conductors to interact with the magnetic field of the magnet array. This generates a force between the magnet array and the conductor array that can be used to control, move, and position the first mover component 212 and the coarse stage 206 relative to the second mover component 214 and the stage base 202. The control system 224 adjusts and controls the current level for each conductor to achieve the desired resultant forces. Stated another way, the control system 224 directs current to the conductor array to position the coarse stage 206 relative to the stage base 202.
[0082] The fine stage 208 includes a device holder (not shown) that retains the device 200. The device holder can include a vacuum chuck, an electrostatic chuck, or some other type of clamp.
[0083] The fine stage mover assembly 210 moves and adjusts the position of the fine stage 208 relative to the coarse stage 206. For example, the fine stage mover assembly 210 can adjust the position of the fine stage 208 with six degrees of freedom. Alternatively, for example, the fine stage mover assembly 210 can be designed to move the fine stage 208 with only three degrees of freedom. The fine stage mover assembly 210 can include one or more rotary motors, voice coil motors, linear motors, electromagnetic actuators, or other type of actuators. Still alternatively, the fine stage 208 can be fixed to the coarse stage 206.
[0084] FIG. 2B illustrates a perspective view of the coarse stage 206, the fine stage 208, and the fine stage mover assembly 210 of FIG. 2A. In this embodiment, the fine stage mover assembly 210 includes three spaced apart, horizontal movers 216 and three spaced apart, vertical movers 218. The horizontal movers 216 move the fine stage 208 along the X axis, along the Y axis and about the Z axis relative to the coarse stage 206 while the vertical movers 218 move the fine stage 208 about the X axis, about the Y axis and along the Z axis relative to the coarse stage 206.
[0085] In FIG. 2B, each of the horizontal movers 216 and each of the vertical movers 218 includes an actuator pair. 226 comprising two electromagnetic actuators 228 (illustrated as blocks in FIG. 2B). Alternatively, for example, one or more of the horizontal movers 216 and/or one or more of the vertical movers 218 can include a voice coil motor or another type of mover.
[0086] In FIG. 2B, (i) one of the actuator pairs 226 (one of the horizontal movers 216) is mounted so that the attractive forces produced thereby are substantially parallel with the X axis, (ii) two of the actuator pairs 226 (two of the horizontal movers 216) are mounted so that the attractive forces produced thereby are substantially parallel with the Y axis, and (iii) three actuator pairs 226 (the vertical horizontal movers 216) are mounted so that the attractive forces produced thereby are substantially parallel with the Z axis. With this arrangement, (i) the horizontal movers 216 can-make fine adjustments to the position of the fine stage 208 along the X axis, along the Y axis, and about the Z axis, and (ii) the vertical movers 218 can make fine adjustments to the position of the fine stage 208 along the Z axis, about the X axis, and about the Y axis.
[0087] Alternatively, for example, two actuator pairs 226 can be mounted parallel with the X direction and one actuator pair 226 could be mounted parallel with the Y direction. Still alternatively, other arrangements of the actuator pairs 226 can be utilized.
[0088] In one embodiment, the measurement system 22 (illustrated in FIG. 1) includes one or more sensors (not shown in FIG. 2B) that monitor the position of the fine stage 208 relative to the coarse stage 206 and/or the position of fine stage 208 relative to another structure, such as the assembly 16 (illustrated in FIG. 1). Information from the measurement system 22 is provided to the control system 224 as provided herein.
[0089] FIG. 2C is an exploded perspective view of an actuator pair 226 that can be used for one of the horizontal movers or one of the vertical movers. More specifically, FIG. 2C illustrates two attraction only, electromagnetic actuators 228 commonly referred to as an E/I core actuators. Each E/I core actuator is essentially an electo-magnetic attractive device. Each E/I core actuator 228 includes an E shaped core 236 (“E core”), a tubular shaped conductor 238, and an I shaped core 240 (“I core”). The E core 236 and the I core 240 are each made of a magnetic material such as iron, silicon steel or Ni—Fe steel. The conductor 238 is positioned around the center bar of the E core 236.
[0090] The combination of the E core 236 and the conductor 238 is sometimes referred to herein as an electromagnet, while the I core 240 is sometimes referred to herein as a target. As an example, the opposing electromagnets can be mounted to the coarse stage 206 (illustrated in FIG. 2B) and the targets can be secured to the fine stage 208 (illustrated in FIG. 2B) there between the opposing electromagnets. In one embodiment, the I cores 240 are attached to the fine stage 208 in such a way that the pulling forces of the opposing actuator pairs 226 do not substantially distort the fine stage 208. In one embodiment, the I cores 240 can be integrally formed into the fine stage 208. However, the configuration of the cores can be reversed and the I cores can be the secured to the coarse stage 206 and the E cores can be secured to the fine stage 208.
[0091] In this embodiment, the measurement system 222 includes one or more sensors 242 that measure a gap distance between the E core 236 and the I core 240 for each electromagnetic actuator 228. A suitable sensor, for example, can include a capacitor sensor. By measuring the gap distance, the relative positioning of the coarse stage relative to the fine stage can be determined. This positioning data can then be provided to the control system 224 for processing as provided herein.
[0092] FIG. 2D is a perspective view of another embodiment of a stage assembly 220D that can be used to position a device 200D, and a control system 224D having features of the present invention. In the embodiment illustrated in FIG. 2D, the stage assembly 220D includes a stage base 202D, an X mover assembly 204D, a Y mover assembly 206D, a stage 208D that retains the device 200D, and a guide assembly 210D. In this embodiment, the X mover assembly 204D includes a first X mover 250D and a second X mover 252D that move the guide assembly 210D and the stage 208D along the X axis and about the Z axis. The Y mover assembly 206D includes a Y mover 254D that moves the stage 208D along the Y axis. However, the number of X movers and Y movers can vary. In addition, the number of mover assemblies can vary. Further, the design of the other components of the stage assembly 220D can be varied. The stage assembly 220D is described in greater detail in U.S. patent application Ser. No. 09/557,122 filed on Apr. 24, 2000. To the extent permitted, the contents of U.S. patent application Ser. No. 09/557,122 are incorporated herein by reference. The stage assembly 220D can be constructed in accordance with industry standards that are generally known to those skilled in the art and/or in accordance with the stage assembly disclosed in U.S. patent application Ser. No. 09/557,122 filed on Apr. 24, 2000.
[0093] The stage assembly 220D or the stage assembly 220 (illustrated in FIG. 2A) can be used to move the device 200, 200D during one or more iterations. As defined herein, a first iteration is said to be identical or similar to a second iteration if the first iteration includes a first intended trajectory that is identical or a similar to a second intended trajectory of the second iteration. FIGS. 3A through 3M illustrate various non-exclusive examples of the first intended trajectory and the second intended trajectory of the stage that are identical or similar.
[0094] Two or more intended trajectories can be considered iterations or iterative movements relative to each other under-various=circumstances. For example, as illustrated in FIG. 3A, the first intended trajectory 300A (solid line) can be identical to the second intended trajectory 302A (dashed line). Although in this Figure the trajectories 300A, 302A are illustrated as being spaced apart for clarity, the trajectories 300A, 302A are actually overlapping. In this example, the first intended trajectory 300A includes (i) a first starting point 304A that is the same as a second starting point 306A, e.g. same coordinate position along X axis and Y axis, of the second intended trajectory 302A, and (ii) a first intended movement 308A (also referred to herein as a “movement”) that begins from the first starting point 304A that is the same as a second intended movement 310A that begins from the second starting point 306A. The “starting point” can be any point during an overall movement of the stage. As used herein, however, the starting point is representative of the start of the iteration. Moreover, each intended trajectory 300A, 302A can also include a corresponding ending point 312A, 314A, which is representative of the end of the iteration. The starting point and/or the ending point can also be simply referred to herein as a “point”.
[0095] As provided above, each intended trajectory 300A, 302A includes a corresponding ending point (represented by arrows 312A, 314A). Thus, the first intended trajectory 300A includes the first starting point 304A, the first movement 308A and the first ending point 312A. Somewhat similarly, the second intended trajectory 302A includes the second starting point 306A, the second movement 310A and the second ending point 314A. In this embodiment, the first ending point 312A is the same as the second ending point 314A.
[0096] Alternatively, as illustrated in FIG. 3B, two or more intended trajectories can be considered iterations if the first intended trajectory 300B is similar to the second intended trajectory 302B. For example, the first intended trajectory 300B includes (i) the first starting point 304B that is similar to the second starting point 306B of the second intended trajectory 302B, and (ii) the first movement 308B is the same as the second movement 310B. For example, in this embodiment, the first movement 308B is considered to be the same as the second movement 310B when each movement 308B, 310B is exactly the same distance, along exactly the same axis, and in the same direction. In another embodiment, the first movement 308B can be considered the same as the second movement 310B when each movement 308B, 310B follows the same coordinate positions.
[0097] FIG. 3C illustrates another embodiment=wherein the first intended trajectory 300C can be similar to the second intended trajectory 302C. In this embodiment, (i) the first starting point 304C is the same as the second starting point 306C of the second intended trajectory 302C, and (ii) the first movement 308C is similar to the second movement 310C.
[0098] FIG. 3D illustrates yet another embodiment wherein the first intended trajectory 300D can be similar to the second intended trajectory 302D. In this embodiment, (i) the first starting point 304D is similar to the second starting point 306D of the second intended trajectory 302D, and (ii) the first movement 308D is similar to the second movement 310D.
[0099] The definition of similar points can be varied to suit the design requirements of the precision apparatus 10 (illustrated in FIG. 1), and can apply to both starting points and ending points. In one embodiment, the first point of the first intended trajectory is similar to the second point of the second intended trajectory if the distance between the first point and the second point is less than approximately 500 percent of the length of the first intended movement of the stage. In alternative embodiments, the first point is similar to the second point if the distance between the first point and the second point is less than approximately 200 percent, 100 percent, 50 percent, 25 percent, 10 percent, 5 percent, 1 percent, 0.1 percent or 0.01 percent of the total distance of the intended movement of the stage during the iteration. For example, if the distance between the first and second points is 1.0 millimeter, and the length of first movement is 10.0 millimeters, the distance between the first and second points is 10 percent of the first movement. Depending upon the settings for the control system 24 (illustrated in FIG. 1), the distance between the first and second points in this example may or may not be considered similar.
[0100] In another embodiment (not shown), the first movement is similar to the second movement if the first ending point is similar to the second ending point, and the length of the first movement is within approximately 100 percent of the length of the second movement. In alternative embodiments, the first movement can be similar to the second movement if the first ending point is similar to the second ending point, and the length of the first movement is within approximately 75 percent, 50 percent, 25 percent, 10 percent, 5 percent, 1 percent or 0.1 percent of the length of the second movement. Alternatively stated, in one embodiment the first movement can be considered similar to the second movement if each movement is approximately the same distance along approximately the same axis.
[0101] Additionally, although the stage can be capable of moving along or about more than one axis simultaneously, similar iterations can occur based on movement of the stage along one of the axes. For example, in a step-and-repeat photolithography system, movement of the stage along the Y axis may be substantially repeated over time regardless of whether movements of the stage along the X axis and about the Z axis are repetitious. Moreover, in alternative embodiments, movement along the Y axis can be repetitious, if the stage is positioned in the same or different locations along the X axis. In another example, movement of the stage about the Z axis may be substantially repeated over time regardless of whether movements of the stage along the X and Y axes are repetitious.
[0102] In yet another example of similar iterations, more than one component of movement, i.e. along the X axis and the Y axis, may be substantially repeated over time. In still another example, rather than simple back-and-forth movements along the Y axis, the stage can guidelessly and simultaneously be moving in a plane that includes the X axis and the Y axis. Additionally, the stage can guidelessly and simultaneously be moving along the X axis, the Y axis and/or about the Z axis. It is further recognized that any combination of intended trajectories of the stage along or about one or more of the axes that are similar or repetitious are referred to herein as iterations or iterative movements.
[0103] FIG. 3E illustrates another embodiment wherein the first intended trajectory 300E can be similar to the second intended trajectory 302E. In this embodiment, the first starting point 304E is the same as the second starting point 306E, and (ii) the first movement 308E is substantially symmetrical to the second movement 310E relative to the X axis.
[0104] FIG. 3F illustrates another embodiment wherein the first intended trajectory 300F can be similar to the second intended trajectory 302F. In this embodiment, the first starting point 304F is the same as the second starting point 306F, and (ii) the first movement 308F is substantially symmetrical to the second movement 310F relative to the Y axis.
[0105] FIG. 3G illustrates another embodiment wherein the first intended trajectory 300G can be similar to the second intended trajectory 302G. In this embodiment, the first starting point 304G is the same as the second starting point 306G, and (ii) the first movement 308G is substantially symmetrical to the second movement 310G relative to the origin (which can also be referred to as the 0, 0 coordinate). Additionally, the first movement 308G diverges from the second movement 310G.
[0106] FIG. 3H illustrates another embodiment wherein the first intended trajectory 300H can be similar to the second intended trajectory 302H. In this embodiment, the first movement 308H is substantially symmetrical to the second movement 310H relative to the origin (which can also be referred to as the 0, 0 coordinate). However, in this embodiment, the starting points are neither identical nor similar.
[0107] FIG. 31 illustrates another embodiment wherein the first intended trajectory 3001 can be similar to the second intended trajectory 3021. In this embodiment, the first starting point 3041 is the same as the second starting point 3061, and (ii) the first movement 3081 is substantially symmetrical to the second movement 3101 relative to the origin (which can also be referred to as the 0, 0 coordinate). Additionally, the first movement 3081 converges toward the second movement 3101.
[0108] FIG. 3J illustrates still another embodiment wherein the first intended trajectory 300J is similar to the second intended trajectory 302J. As illustrated in FIG. 3J, the first intended trajectory 300J has a first starting point 304J, a first movement 308J and a first ending point 312J. The second intended trajectory 302J has a second movement 310J that includes the first starting point 304J, the entire first movement 308J and the first ending point 312J. Stated another way, the first intended trajectory 300J is only a portion of the second intended trajectory 302J. Although in this Figure the trajectories 300J, 302J are illustrated as being spaced apart for clarity, the trajectories 300J, 302J are actually overlapping. Alternatively, the first trajectory 300J and the second trajectory 302J could be reversed so that the second movement 310J comprises essentially a portion of the first movement 308J.
[0109] FIG. 3K shows yet another embodiment wherein the first intended trajectory 300K is similar to the second intended trajectory 302K. As illustrated in FIG. 3K, the first intended trajectory 300K has a first starting point 304K that is different than a second starting point 306K of the second intended trajectory 302K. Further, the first intended trajectory 300K has a first ending point 312K that is different than a second ending point 314K of the second intended trajectory 302K. However, in this embodiment, the first movement 308K is substantially similar to the second movement 310K. In other words, the first and second movements 308K, 310K have a substantially similar length, and have a similar length of movement along both the X axis and the Y axis. Alternatively, the length of movement for the first and second movements 308K, 310K can be substantially similar along either one of the X or Y axes.
[0110] FIG. 3L illustrates an additional embodiment that describes a first iteration 300L that is similar to a second iteration 302L. This example includes the first iteration 300L having a first movement 308L that includes a first intended trajectory structure, and the second iteration 302L having a second movement 310L that includes a second intended trajectory structure that is the same as the first intended trajectory structure. As used herein, the “intended trajectory structure” is a function of (i) the shape of the intended trajectory, (ii) the percentage of time during the intended trajectory that is represented by acceleration, constant velocity and/or deceleration, (iii) the location of the starting point of the intended trajectory, and/or (iv) the timing of the acceleration, constant velocity and/or deceleration during the intended trajectory.
[0111] In the embodiment illustrated in FIG. 3L, the first intended trajectory 300L has a similar starting point 304L as the second intended trajectory 302L, as defined previously. Further, the first intended trajectory 300L includes a first acceleration 320L during approximately the first 30 percent of the first movement 308L of the stage, a first constant velocity 324L during the next 40 percent of the first movement 308L of the stage, and a first deceleration 328L during the next 30 percent of the first movement 308L of the stage. The total length of the first movement 308L of the stage in this example is 100 millimeters.
[0112] The second intended trajectory 302L includes a second acceleration 322L during the first 30 percent of the second movement 310L of the stage, a second constant velocity 326L during the next 40 percent of the second movement 310L of the stage, and a second deceleration 330L during the next 30 percent of the second movement 310L of the stage. The total length of the second movement 310L of the stage in this example is 200 millimeters. Further, the shapes of the intended trajectories 300L, 302L are similar, i.e. substantially proportional to one another. Stated another way, the second intended trajectory 302L is proportionately larger than the first intended trajectory 300L. Importantly, the percentages provided in this example are provided for ease of discussion only. Any suitable combination of percentages can be used. Further, the first and second trajectories could be reversed.
[0113] FIG. 3M illustrates another embodiment showing two iterations having similar intended trajectories 300M, 302M. This embodiment is somewhat similar to the embodiment illustrated in FIG. 3L, however the first intended trajectory 300M has a different first starting point 304M than the second starting point 306M of the second intended trajectory 302M. In this embodiment, the first starting point 304M is similar to the second starting point 306M as defined previously herein. Further, in this embodiment, the first iteration 300M is similar to the second iteration 302M if the first intended trajectory structure and second intended trajectory structure are substantially similar to one another, as described previously with respect to FIG. 3L.
[0114] The foregoing examples of iterations that include identical and/or similar intended trajectories are not intended to represent an exclusive listing of all possible embodiments of “identical” or “similar” iterations and/or intended trajectories. However, the examples provided herein are illustrative of certain movements of the stage that can be considered similar, and therefore useful, in predicting and adjusting future movements of the stage. The foregoing examples are in no way intended to limit the scope of the present invention, and numerous other possible “similar” intended trajectories, although not explicitly illustrated or described, could be encompassed by the scope of the present invention.
[0115] FIG. 4A is a graph illustrating an overview of an actual and an intended simplified back-and-forth type of iterative movement of a stage, such as the fine stage 208 illustrated in FIG. 2A, or the stage 208D illustrated in FIG. 2D, along a single axis as a function of time over the course of a plurality of substantially similar iterations of the stage. Curve 410 (shown as a solid line) illustrates the actual trajectory of the stage, and curve 412 (shown as a dashed line) illustrates the intended trajectory of the stage. The spacing between the curves 410, 412 has been exaggerated for illustrative purposes.
[0116] It is recognized that FIG. 4A can also be representative of movement of one or more stages other than the fine stage 208 shown in FIG. 2A and/or the stage 208D illustrated in FIG. 2D. For example, the movements described herein can be applied to a stage assembly that does not include a plurality of stages. Alternatively, the stage assembly can include more than two stages.
[0117] For convenience, FIG. 4A includes a first iteration 400, a second iteration 0.402, a third iteration 404 and a portion of a fourth iteration 406, which is also referred to herein as the “current iteration”. Alternatively, the first, second, third and fourth iteration can include only a portion of each of the iterations 4007406 illustrated in FIG. 4A, provided the portions of the iterations are substantially similar in movement. Stated another way, the iterations 400-406 illustrated in FIG. 4A are provided as a single example for ease of discussion, and are in no way intended to limit the scope of possible iterative movements that can be controlled by the control system 24 (illustrated in FIG. 1) provided herein.
[0118] The intended trajectory 412 and number of iterations during the manufacture of an object such as a semiconductor wafer can vary. In this example, the intended trajectory 412 of the stage is substantially similar from one iteration to the next. The control system 24 provided herein is particularly useful to control the actual trajectory 410 of the stage over a plurality of iterations 400-406 having a substantially similar intended trajectory 412. However, the control system 24 can also be effectively utilized to control the actual trajectory 410 of the stage based on positioning data generated from movements of the stage resulting from somewhat different intended trajectories 412, as provided in greater detail below.
[0119] The actual trajectory 410 of an iteration can be substantially similar to the actual trajectory 410 of the previous iteration, although the actual trajectories 410 for each iteration 400-406 may not necessarily be identical. For example, as illustrated in FIG. 4A, during the first iteration 400, at times t11, t21, t31, t41 and t51, the measured position of the stage is located at positions P1, P2, P3, P4 and P5, (hereinafter the “actual position”) respectively. Although only times t11 through t51 are shown in FIG. 4A for clarity, a greater or a fewer number of times can be used in the alternative, or in addition to any of times t11 through t51.
[0120] Somewhat similarly, the second iteration 402 includes times t12 through t52, the third iteration 404 includes times t13 through t53, and the fourth iteration 406 includes t14 through t34. Each of the times t1 through t5 of the second iteration 402 and times t13 through t53 the third iteration 404 have an actual position that is similar, although not necessarily identical, to a corresponding actual position P1 through P5, respectively. Each of the times t1 through t3 of the fourth iteration 406 has an actual position point that is similar, although not necessarily identical, to a corresponding actual position P1 through P3, respectively.
[0121] Additionally, in one embodiment the intended and/or actual trajectory of the stage at times t11 and t12, for example, can have a substantially similar or identical position along the X and Y axes. Similarly, at times t22 and t23, the intended and/or actual trajectory of the stage can have a substantially similar or identical position along the X and Y axes.
[0122] Alternately, the intended trajectory of the stage at times t1 and t12 can have a substantially similar position along the Y axis and a different position along the X axis. In other words, although the intended and/or the actual trajectory along the Y axis may not change from the first iteration 400 to the second iteration 402, the intended and/or actual trajectory along the X axis may be different from the first iteration 400 to the second iteration. This example can be applied to any two or more iterations, along or about any axes.
[0123] It is recognized that the second and third iterations 402, 404, although similar in movement to previous first and second iterations 400, 402, respectively, can vary somewhat as a result of the additional information collected and utilized by the control system 24 and subsequent adjustments that the control system 24 makes in directing current to the one or more mover assemblies to cause forces that more accurately move the stage, as provided herein. Further, it is also recognized that the iterations 400-406 have been denoted as the first, second, third and fourth iterations for the sake of convenience. However, any iteration can be the first, second, third or fourth iteration, and that the labels “first”, “second”, “third” and “fourth” do not necessarily imply a particular sequencing of the iterations.
[0124] The control system 24 provided herein can include one or more control modes. In one embodiment, the control system includes a first control mode and a second control mode. As an overview, the first control mode includes the processing of positioning data received by the control system during a single iteration, e.g. the first iteration 400, to control future movement of the stage also during the first iteration 400. The second control mode includes the processing of positioning data received by the control system during at least one iteration, e.g. the first iteration 400 and the second iteration 402, to control future movement of the stage during the second iteration 402 and/or third iteration 404, as one example.
[0125] As provided in greater detail below, the positioning data can include various types of information to be received and/or processed by the control system. For example, the positioning data can include “time-dependent” positioning data or “position dependent” positioning data. Time-dependent positioning data includes any information relating to the intended and/or actual position of the stage at various times. For instance, an example of time-dependent positioning data includes information regarding a following error of the stage, e.g. the difference between the intended position and the actual position of the stage at various times. Position-dependent positioning data includes information regarding the position of other components of the exposure apparatus that can influence position of the stage. Examples of position-dependent positioning data can include information regarding vibration of the assembly 16 (illustrated in FIG. 1) and/or the apparatus frame 12 (illustrated in FIG. 1).
[0126] The first control mode can be described with reference to the first iteration 400 in FIG. 4A. In a simplified example, in order to determine the amount of current that the control system 24 needs to direct to the mover assemblies to position the stage in accordance with the intended trajectory 410 of the stage at time t41, time-dependent positioning data is provided to the control system 24 from one or more of the previous times t11 through t31. This positioning data is analyzed by the control system 24 along with the intended trajectory 410 to determine the force that is required to move the stage at time t41. With this positioning data, the control system 24 applies an appropriate control law to determine the amount of current to direct to the mover assemblies to obtain the required force distribution for moving the stage to the extent necessary for proper positioning of the stage. The number of data points t11 through t31 used in this analysis can vary. Further, the time duration between data points can vary. The first control mode can be used for movement of the stage with one or more degrees of freedom, i.e. along the X, Y and/or Z axes, and/or about the X, Y and/or Z axes, including any combination of these directions. The control system 24 can also be used to determine the current to be directed to the coarse stage 206, either in conjunction with the stage, or in the alternative. Further, the control system 24 can be utilized to synchronously position a plurality of stages as provided herein.
[0127] The second control mode can selectively be used by the control system 24 depending upon the requirements of the stage assembly. During the second control mode, the control system 24 receives positioning data used for positioning the stage from various sources, as provided in detail below. The positioning data is used to position the stage, or other stages, with greater accuracy.
[0128] The second control mode includes the features of the first control mode described above, as well as the processing of positioning data received by the control system 24 during one or more previous iterations, e.g. the first iteration 400, the second iteration 402 and/or the third iteration 404, to control movement of the stage during the fourth iteration 406. In contrast with the first control mode, the positioning data from a previous iteration, but at a later point in time during the previous iteration, can be used in controlling movement of the stage during the current iteration. For example, to determine the level of current to direct to the mover assembly at time t34, positioning data from times t41 and t51 from the first iteration 400, times t42 and t52 from the second iteration 402, and/or times t43 and t53 from the third iteration 404 can be used. This positioning data can be used in conjunction with or in the alternative to positioning data from times t11 through t31 of the first iteration 400, times t12 through t32 of the second iteration 402, and/or times t13 through t33 of the third iteration 404, or any portions thereof. With this design, a greater amount of positioning data factors into controlling the stage with the control system 24.
[0129] Moreover, the second control mode can also utilize positioning data from the current iteration, e.g. the fourth iteration 406, to control the actual trajectory 410 during the current iteration 406, as provided above during the first control mode. In alternative embodiments, the control system 24 can include either the first control mode or the second control mode.
[0130] Thus, the second control mode of the control system 24 can take into account both intra-iteration and inter-iteration trends in the positioning data. With this design, with each successive iteration, the positioning error is decreased. Stated another way, over time the actual trajectory 410 of the stage becomes closer and closer to the intended trajectory 412.
[0131] FIG. 4B illustrates an example of the following error 414 of the stage over the first, second, third and fourth iterations 400-406 based on the intended trajectory 412 and the actual trajectory 410 illustrated in FIG. 4A. The following error 414 shown in FIG. 4B has been exaggerated for illustrative purposes. As provided herein, the control system 24 (illustrated in FIG. 1) utilizes the following error 414 from prior iterations to control movement of the stage during the current and future iterations.
[0132] FIG. 4C is a graph that illustrates two simplified back-and-forth iterative movements of one or more of the stages illustrated in FIG. 2A or 2D, for example, which include a first iteration 400C and a second iteration 404C, separated in time by a period of other non-iterative movements 402C of the stage. In this embodiment, the second control mode of the control system provided herein does not necessarily require the iterations to be consecutive. For example, referring to FIG. 4C, the control system can store positioning data from the first iteration 400C to be used for positioning the stage during the second iteration 404C.
[0133] The control system provided herein can identify when an intended movement or trajectory of the stage is similar to a previous movement or trajectory of the stage. Once this occurs, the control system can draw from the previously stored positioning data in order to adjust the amount of current to direct to the mover assembly for more accurately positioning the stage in accordance with the intended trajectory of the stage. For purposes of controlling movement of the stage during the second iteration 404C, the control system can disregard the movements of the stage, and any positioning data received, during the irrelevant, non-iterative time period 402C. Rather, the control system utilizes the positioning data from the first iteration 400C, and/or any other similar iterations prior to the first iteration 400C, for controlling movement of the stage during the second iteration 404C.
[0134] FIG. 5A is a schematic diagram illustrating the basic steps of a first embodiment of the control system 524A including the first control mode 500 and the second control mode 501 to control movement of the stage illustrated in FIG. 2A and/or 2D, for example. As previously provided, the steps outlined in FIG. 5A can also be used to control movement of the coarse stage 206, and/or other stages of the precision apparatus-10, either concurrently or separately. It is recognized that not all steps of the first control mode 500 and/or the second control mode 501 illustrated in FIG. 5A are required in each embodiment of the present invention. The sensing and control functions can be used to control the stage assembly of FIG. 2A, another stage assembly of the exposure apparatus, or another type of stage assembly.
[0135] As provided above, with the first control mode 500, the control system 524A analyzes positioning data from within a single iteration to improve positioning of the device to be positioned, i.e. the reticle, the wafer and/or other objects. An intended trajectory 512 of the stage is determined based on the desired path of the device. The intended trajectory 512 can be along the X axis, the Y axis and/or about the Z axis. Additionally, the intended trajectory 512 can also include components about the X axis, about the Y axis and/or along the Z axis, or any combination of these axes.
[0136] In one embodiment, during the first control mode 500, one or more points in time along the intended trajectory 512 are compared with points in time from the actual trajectory 510 to determine whether the stage is properly positioned, and to determine whether the stage will be properly positioned in the immediate future. The actual trajectory 510 is determined by the measurement system 22 (illustrated in FIG. 1) which generates a sensor signal. The measurement system 22 measures the current position of the stage, and thus the object, relative to the assembly 16 (illustrated in FIG. 1). The sensor signal is then sent to the control system 524A. Each sensor signal provides information relating to the actual position of the stage in one or more degrees of freedom at a specific point in time.
[0137] The following error 514A for the stage is determined by computing the difference between the intended trajectory 512 and the actual trajectory 510 at a specific point in time. Based on the extent of the following error 514A, a control law during feedback control 506A determines the extent to which the current to the one or more mover assemblies is adjusted, if at all. The control law during feedback control 506A may be in the form of a PID (proportional integral derivative) controller, proportional gain controller or a lead-lag filter, or other commonly known law in the art of control, for example.
[0138] Once the control law during feedback control 506A determines the current to be applied, the current is distributed to the one or more mover assemblies as appropriate (at step 507). The mechanical system, which includes the mover assemblies, then moves the stage at step 508, causing the stage to more accurately emulate the intended trajectory 512 of the stage. The measurement system measures the position of the stage, which is then used to determine the position of the center of gravity (CG) and/or the position of the object using coordinate transformation at step 509. Information regarding the position of the object is then compared with a desired position of the object based on the intended trajectory 512 in order to increase positioning accuracy. The first control mode 500 can continue in this manner until the present iteration has concluded. Upon commencement of a subsequent iteration, new data regarding the following error 514A is continually generated from within the current iteration. This new data regarding the following error 514A is used in a similar manner during the first control mode 500 as described above.
[0139] The second control mode 501 of the control system 524A collects and assimilates the positioning data in order to determine the appropriate amount of current to direct to the mover assemblies to move the stage with increased accuracy. Positioning data can include one or more of the types of data described herein. Importantly, the positioning data does not need to include all types of data described, although it may.
[0140] The second control mode 501 of the control system 524A can compensate for one or more types of repetitive activities. These repetitive activities can include position-dependent activities such as following errors 514A, and/or periodical, time-dependent disturbances, e.g. unwanted vibration of portions of the mechanical system.
[0141] The second control mode 501 of the control system 524A can include the first control mode 500, in addition to a position compensation system (indicated in dashed box 515) having one or more steps that further increase the accuracy of the positioning and alignment of one or more of the stages. The steps included in the functioning of the position compensation system 515 of the second control mode 501 can vary. The position compensation system 515 can receive and process data from previous iterations to continually decrease the following error 514A and/or offset the effects of any vibration disturbances of the mechanical system in the current and future iterations. In addition, it is recognized that the position compensation system 515 can also be applied to work with a plurality of stages simultaneously, in order to synchronously control movement of a plurality of stages to decrease the following errors 514A, 514B for a first stage and a second stage, for example, and offset the effects of any vibration disturbances of the mechanical system in the current and future iterations.
[0142] In the embodiment illustrated in FIG. 5A, positioning data from one or more iterative movements of the stage is collected and provided to a memory buffer 516 for use during future iterations. The size of the memory buffer 516 can vary, provided the memory buffer 516 is of sufficient size to accommodate the data to be transmitted to the memory buffer 516.
[0143] Further, the number of iterations from which positioning data is collected, and the length of time the positioning data is stored in the memory buffer 516 can be varied. For example, in one embodiment, positioning data from only one prior iteration is stored in the memory buffer 516, which can thereafter be purged upon storage of the positioning data from the next iteration. In alternative embodiments, positioning data from more than one prior iteration is stored in the memory buffer 516. For instance, positioning data from the previous 2, 3, 5, 10, 50, 100, 500 or more iterations can be stored in the memory buffer 516 before being systematically purged, if at all. Still alternatively, positioning data from a different number of iterations can be stored.
[0144] For example, the positioning data can include the intended trajectory 512 at various points in time (illustrated by dotted line 517). Further, the positioning data can include the following error 514A of the stage. The intended trajectory data 517 and the following error data 514A are stored in the memory buffer 516. The amount of positioning data and the duration of time between the collection of positioning data that is provided to the memory buffer 516 during each iteration can vary.
[0145] The positioning data can also include a compilation of following errors 514A, 514B from two or more stages in the exposure apparatus 10, also known as a synchronization error. The synchronization error is a measurement of how accurately two or more stages are moving relative to each other, compared with the intended trajectory 512 of each of the respective stages. For example, movement of the reticle stage and the wafer stage emulates the intended trajectory 512 of each respective stage in order to synchronously move relative to the assembly 16 (illustrated in FIG. 1), for example, and/or to each other. Sensors 523 or another suitable measurement device can be used to monitor whether the actual movement of the stages is properly synchronized. This synchronization error data taken at various points in time can be provided to the memory buffer 516.
[0146] Additionally, the positioning data to be provided to the memory buffer 516 can include the actual position of the stage (illustrated by dotted line 519) at various points in time along the actual trajectory 510 from one or more iterations. Further, the positioning data can include data relating to the movement of the stage, including the position, velocity and/or the acceleration of the stage. This positioning data can be in the form of the CG of the stage assembly, the position of the object and/or the position of the stage, the velocity and/or the acceleration of the stage, all at various times, as non-exclusive examples. It is recognized that the amount of current to be directed to the mover assembly can differ depending upon the location of the stage, which impacts the CG of the stage assembly. The number of actual position data points 519 and the duration of time between the actual position data points 519 provided to the memory buffer 516 can vary.
[0147] The positioning data can further include information relating to the current directed to the mover assemblies (illustrated by dotted line 520) during previous iterations and/or during the current iteration. The control system 524A can monitor and provide to the memory buffer 516 data that includes the specific current directed to each actuator from each mover assembly acting on the stage(s).
[0148] Further, position-dependent positioning data including sensor information (illustrated by dotted line 522), e.g. information from one or more sensors 523 such as an accelerometer, is also provided to the memory buffer 516. For example, one or more accelerometers 523 can be secured to the lens of the assembly 16, the apparatus frame 12 or to other structures of the exposure apparatus 10. The sensors 523 can sense and monitor the position and/or movement at various times, including the vibration, velocity, acceleration and other movements of the structures to which they are attached, and provide information regarding such positions and/or movements to the memory buffer 516. The position and/or movement of the structures being monitored can be in the form of relative position, and need not necessarily be absolute position. This position-dependent positioning data can be taken during the current iteration, or from previous iterations.
[0149] Additionally, positioning data can be provided to the memory buffer 516 immediately following application of the feedback control step 506A from the first control mode of the control system 524A (illustrated by dotted line 526), i.e. prior to application of the position compensation system 515 to control the current to the one or more mover assemblies.
[0150] Moreover, because the stage is capable of moving with one or more degrees of freedom, positioning data for each of the applicable principal axes over one or more iterations, i.e. along the X axis, along the Y axis and/or about the Z axis, or any applicable combination of these axes, can likewise be provided to the memory buffer 516.
[0151] Once a sufficient amount of positioning data has been received by the memory buffer 516, this information can be processed (indicated in step 528) by the control system 524A. During information processing 528, useful information can be extracted from the positioning data that has been collected in the memory buffer 516. Further, the positioning data can be transformed as necessary into information that can be utilized by the control system 524A to more accurately move and position the stage.
[0152] The specific processes utilized by the control system 524A to process the positioning data can be varied. For example, the information processing step 528 can include coordinate transformation of the sensor information 522. For example, positioning data can include data relating to the position or movement of various portions of the mechanical system of the precision apparatus 10. More specifically, positioning data can include the position of the lens assembly of the optical assembly at various times, which can be a measurement reference for the wafer stage. Oscillation of the lens assembly, for example, can cause excitation of the wafer stage. By using coordinate transformation, the sensor information 15-522 from a sensor 523 such as an accelerometer that is attached to the lens assembly can be used to suppress vibrations that may occur in the wafer stage as a result of oscillation of the lens assembly or other parts of the mechanical system.
[0153] In addition, the information processing 528 can include signal smoothing. Positioning data received by the memory buffer 516 may include anomalous data or high frequency noise, for instance. In order to smooth the positioning data, one or more data filters can be utilized. In general, at least two types of filters can be utilized during information processing 528. The first type of filter includes a zero-phase finite impulse response (FIR) filter, such as: 1 Q 1 ( z - 1 ) = 0.5 3 + 0.5 2 z - 1 + 0.5 z - 2 + z - 3 + 0.5 2 z - 4 + 0.5 3 z - 5 + 0.5 3 z - 6 ( 0.5 3 + 0.5 2 + 0.5 + 1 + 0.5 + 0.5 2 + 0.5 3 ) z - 3
[0154] FIG. 6 is a graphical representation illustrating the zero-phase FIR filter that can be used during information processing 528 (illustrated in FIG. 5A) to remove high frequency noise from the positioning data, without sacrificing the phase accuracy at other frequencies. In FIG. 6, the magnitude of the smoothing filter Q1(z−1) is plotted as a function of frequency. Further, phase is plotted as a function of frequency. FIG. 6 illustrates that the filter can have a magnitude attenuation effect at high frequencies without sacrificing the phase accuracy at low frequencies.
[0155] FIGS. 7A and 7B are graphical representations of a zero-phase IIR filter that can be used during information processing. 528 to remove high frequency noise from the positioning data, without sacrificing the phase accuracy at other frequencies. In these instances, a zero-phase forward and reverse filter can be used, such as:
Q2(z−1)=QLP(z−1)QLP(z),
[0156] where QLP(z−1) is a low pass IIR filter.
[0157] Alternatively, other suitable methods of smoothing the positioning data can be used with the present invention.
[0158] Referring back to FIG. 5A, the information processing 528 can also include updating a model of the position compensation system 515 by applying one or more parameter-updating algorithms to incorporate the positioning data into the system model. For example, if a neural network is employed to model the inverse dynamics of the system, a backward propagation method can be used to update the parameters of the position compensation system 515. As a further example, autoregressive and moving average with external input (ARMAX) can be used to model the closed-loop system, including the mechanical system 508 and the feedback control 506A and/or 506B, as follows:
A(z−1)y(t)=B(z−1)u(t−&agr;)+C(z−1)&egr;(t)
[0159] where y(t)=output, u(t)=input, and &egr;(t)=model error.
[0160] When ARMAX is used to model the system, the parameters can be updated using a recursive least squares method, as a non-exclusive example. Alternatively, other suitable methods can be used to update the parameters of the position compensation system 515.
[0161] Further, the information processing step 528 can include a periodic evaluation of the performance of the control system 524A to determine whether the parameters of the position compensation system 515 need to continue to be updated. For example, once the following errors 514A converge to below a predetermined threshold level (which can vary), e.g. 5 nm, 10 nm, 25 nm or some other suitable level, updating of the parameters can be temporarily suspended until the following errors 514A exceed the specified threshold, at which point the parameters can again be updated. With this design, once the following errors 514A have been lowered to below the specified threshold, any high frequency noise or other anomalous data will not contaminate the output of the position compensation system 515.
[0162] Following information processing, a control law 530 is calculated by the control system 524A, and the control law 530 is applied to the processed positioning data. In some embodiments, the control law 530 is a function of both time and vibration disturbance iterations. The control law can be model-based or non-model-based.
[0163] For example, a model-based control law can include inverse dynamics of the closed-loop system or a neural network. More specifically, a model-based control law can include the following equation, for example: 2 u j L ( t ) = k L ∑ i = 0 j - 1 A c ( z - 1 ) B c ( z - 1 ) u j FB ( t + α )
[0164] where
[0165] j—iteration#
[0166] t—time step in an iteration
[0167] &agr;—time delay between system input and output
[0168] kL—learning control gain
[0169] uFB=GFB(z−1)e—feedback control
[0170] GFB(z−1)—feedback controller
[0171] e—following error
[0172] A non-model-based control law may be in the form of a PID controller, as one example. For instance, a relatively simple non-model-based P-type control law can be used, as follows: 3 u j L ( t ) = k L ∑ i = 0 j - 1 e i ( t + α ) = u j - 1 L ( t ) + k L e j - 1 ( t + α )
[0173] where
[0174] j—iteration#
[0175] t—time step in an iteration
[0176] &agr;—time delay between system input and output
[0177] kL—learning control gain
[0178] e—following error
[0179] A PD-type control law may have a faster iteration-wise convergent rate of following errors 514A, such as: 4 u j L ( t ) = k L ∑ i = 0 j - 1 s i ( t + α ) = u j - 1 L ( t ) + k L s j - 1 ( t + α )
[0180] where s1(t)=ej(t)+kdej(t) is a generalized following error 514A with an additional derivative term.
[0181] Additionally, the control system 524A includes logics 532 which allow the position compensation system to be manually turned on or off as necessary.
[0182] In the embodiment illustrated in FIG. 5A, once the control law 530 has been applied to the processed positioning data, the position compensation system 515 is then used as a force feedforward to control the current that is directed to the one or more mover assemblies at step 534A. Thus, the current that has been determined as a result of the feedback control 506B of the first control mode 500 is modified by the position compensation system 515 to more accurately position the stage.
[0183] FIG. 5B illustrates a second embodiment of the control system 524B including the first control mode 500 and the second control mode 501. In general, the functioning of the control system 524B in this embodiment is similar to the control system 524A illustrated in FIG. 5A. However, the output of the position compensation system 515 is used as a position feedforward control to fine-adjust the following error 514B for the first control mode 500 of the control system 524B, as indicated by step 534B. The constitution of the control system 524B in this embodiment provides substantially the same effects and results of the control system 524A from the embodiment illustrated in FIG. 5A.
[0184] FIG. 8 is a series of curves illustrating the ability of the control system to process the positioning data and to adapt in directing current to the one or more mover assemblies over time. With this design, the accuracy of movement of the one or more stages within an exposure apparatus continues to increase while the position compensation control is functioning.
[0185] Curve 800 represents a typical acceleration of a stage over a plurality of iterations as a function of time. Curve 802 illustrates the actual trajectory of the stage of graph 800 over a plurality of iterations. Curve 804 illustrates the following error in a Y direction over time. Curve 806 illustrates the following error in an X direction over time. Curve 808 illustrates the following error in a theta Z direction (about the Z axis) over time. As shown in curves 804-808, the following errors along the X axis, along the Y axis and about the Z axis are relatively large during the first several iterations. However, as the a greater amount of positioning data is provided to the memory buffer and processed by the control system with each successive iteration, the following error in each direction decreases to a relatively low level over time.
[0186] In one embodiment, in FIG. 8, R1, and R2, are equal to 1 and 2, respectively; S1, S2, S3, S4, and S5 are equal to 100 mm, 150 mm, 200 mm, 250 mm, and 300 mm respectively; U1 and U2 are equal to 2500 nm and 5000 nm respectively; Q1 is equal to 2500 nm; and N1 is equal to 10 &mgr;rad.
[0187] In another embodiment, in FIG. 8, R1, and R2, are equal to 2 and 4, respectively; S1, S2, S3, S4, and S5 are equal to 150 mm, 200 mm, 250 mm, 300 mm, and 350 mm respectively; U1 and U2 are equal to 5000 nm and 10000 nm respectively; Q1 is equal to 5000 nm; and N1 is equal to 20 prad.
[0188] In still another embodiment, in FIG. 8, R1, and R2, are equal to 4 and 8, respectively; S1, S2, S3, S4, and S5 are equal to 250 mm, 300 mm, 350 mm, 400 mm, and 450 mm respectively; U1 and U2 are equal to 10000 nm and 20000 nm respectively; Q1 is equal to 10000 nm; and N1 is equal to 30 &mgr;rad.
[0189] FIGS. 9A and 9B are graphs illustrating the effectiveness of the control system at decreasing two different types of errors or disturbances. FIG. 9A shows portions of the first three iterative movements of a reticle stage. At this point, the position compensation system is beginning to receive and process the positioning data. Thus, the following error is relatively large. Moreover, FIG. 9A illustrates a vibration disturbance 900 with a frequency of approximately 32 Hertz that has been experimentally imparted on the mechanical system of the exposure apparatus.
[0190] In one embodiment, in FIG. 9A, D1, D2 and D2, are equal to 25 nm, 50 nm and 75 nm, respectively; and A1, A2, A3, A4, A5, A6, A7, and A8 are equal to 1 nm, 2 nm, 3 nm, 4 nm, 5 nm, 6 nm, 7 nm, and 8 nm respectively.
[0191] In another embodiment, in FIG. 9A, D1, D2 and D2, are equal to 50 nm, 100 nm and 150 nm, respectively; and A1, A2, A3, A4, A5, A6, A7, and A8 are equal to 5 nm, 10 nm, 15 nm, 20 nm, 25 nm, 30 nm, 35 nm, and 40 nm respectively.
[0192] In still embodiment, in FIG. 9A, D1, D2 and D2, are equal to 100 nm, 200 nm and 300 nm, respectively; and A1, A2, A3, A4, A5, A6, A7, and A8 are equal to 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, and 80 nm respectively.
[0193] FIG. 9B illustrates that after the position compensation system has received and processed positioning data, over time, the positioning error of the reticle stage and the vibration disturbance 900 (illustrated in FIG. 9A) have each been substantially reduced.
[0194] In one embodiment, in FIG. 9B, D1, D2 and D2, are equal to 25 nm, 50 nm and 75 nm, respectively; and A1, A2, A3, A4, A5, A6, A7, and A8 are equal to 1 nm, 2 nm, 3 nm, 4 nm, 5 nm, 6 nm, 7 nm, and 8 nm respectively.
[0195] In another embodiment, in FIG. 9B, D1, D2 and D2, are equal to 50 nm, 100 nm and 150 nm, respectively; and A1, A2, A3, A4, A5, A6, A7, and A8 are equal to 5 nm, 10 nm, 15 nm, 20 nm, 25 nm, 30 nm, 35 nm, and 40 nm respectively.
[0196] In still embodiment, in FIG. 9B, D1, D2 and D2, are equal to 100 nm, 200 nm and 300 nm, respectively; and A1, A2, A3, A4, A5, A6, A7, and A8 are equal to 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, and 80 nm respectively.
[0197] Semiconductor devices can be fabricated using the above described systems, by the process shown generally in FIG. 10. In step 1001, the device's function and performance characteristics are designed. Next, in step 1002, a mask (reticle) having a pattern is designed according to the previous designing step, and in a parallel step 1003 a wafer is made from a silicon material. The mask pattern designed in step 1002 is exposed onto the wafer from step 1003 in step 904 by a photolithography system described hereinabove in accordance with the present invention. In step 1005 the semiconductor device is assembled (including the dicing process, bonding process and packaging process), finally, the device is then inspected in step 1006.
[0198] FIG. 11 illustrates a detailed flowchart example of the above-mentioned step 904 in the case of fabricating semiconductor devices. In FIG. 11, in step 1101 (oxidation step), the wafer surface is oxidized. In step 1102 (CVD step), an insulation film is formed on the wafer surface. In step 1103 (electrode formation step), electrodes are formed on the wafer by vapor deposition. In step 1104 (ion implantation step), ions are implanted in the wafer. The above mentioned steps 1101-1104 form the preprocessing steps for wafers during wafer processing, and selection is made at each step according to processing requirements.
[0199] At each stage of wafer processing, when the above-mentioned preprocessing steps have been completed, the following post-processing steps are implemented. During post-processing, first, in step 1105 (photoresist formation step), photoresist is applied to a wafer. Next, in step 1106 (exposure step), the above-mentioned exposure device is used to transfer the circuit pattern of a mask (reticle) to a wafer. Then in step 1107 (developing step), the exposed wafer is developed, and in step 1108 (etching step), parts other than residual photoresist (exposed material surface) are removed by etching. In step 1109 (photoresist removal step), unnecessary photoresist remaining after etching is removed. Multiple circuit patterns are formed by repetition of these preprocessing and post-processing steps.
[0200] While the particular precision apparatus 10 and control system 24 as shown and disclosed herein are fully capable of obtaining the objects and providing the advantages herein before stated, it is to be understood that they are merely illustrative of the presently preferred embodiments of the invention and that no limitations are intended to the details of construction or design herein shown other than as described in the appended claims.
Claims
1. A stage assembly comprising:
- a first stage;
- a first mover assembly that moves the first stage during a first iteration and a subsequent second iteration, the first iteration having a first intended trajectory of the first stage, the second iteration having a second intended trajectory of the first stage that is similar to the first intended trajectory of the first stage, positioning data being generated during the first iteration; and
- a control system that receives the positioning data, the control system controlling the first mover assembly to adjust movement of the first stage during the second iteration based on at least a portion of the positioning data.
2. The stage assembly of claim 1 wherein the control system includes a memory buffer that stores the positioning data.
3. The stage assembly of claim 1 wherein movement of the first stage includes movement along a first axis and wherein the positioning data includes the position of the first stage along the first axis.
4. The stage assembly of claim 3 wherein movement of the first stage includes movement along a second axis that is orthogonal to the first axis, and wherein the positioning data includes the position of the first stage along the second axis.
5. The stage assembly of claim 4 wherein movement of the first stage includes movement about a third axis that is orthogonal to the first and second axes, and wherein the positioning data includes the position of the first stage about the third axis.
6. The stage assembly of claim 1 wherein movement of the first stage includes movement about a first axis, and wherein the positioning data includes the position of the first stage about the first axis.
7. The stage assembly of claim 1 wherein at a time t11 during the first iteration the first stage has an intended position and an actual position, wherein the difference between the intended position and the actual position at time t11 is a t11 following error, and wherein the positioning data includes the t11 following error.
8. A precision apparatus including the stage assembly of claim 7, the precision apparatus further comprising a second stage assembly having a second stage and a second mover assembly that moves the second stage synchronously with the first stage, wherein the positioning data includes second stage positioning information, the control system adjusting movement of the first mover assembly based at least partly on the second stage positioning information to improve synchronization of movement of the stages.
9. The precision apparatus of claim 8 wherein the second stage moves during a first iteration and a subsequent second iteration, the first iteration of the second stage having a first intended trajectory, the second iteration of the second stage having a second intended trajectory that is similar to the first intended trajectory of the second stage, and wherein the positioning data includes second stage positioning information during the first iteration of the second stage.
10. The stage assembly of claim 7 wherein at a time t21 during the first iteration the first stage has an intended position and an actual position, wherein the difference between the intended position and the actual position at time t21 is a t21 following error, and wherein the positioning data includes the t21 following error.
11. The stage assembly of claim 1 wherein the first stage moves along an actual trajectory during the first iteration, and wherein the positioning data includes at least a portion of the actual trajectory of the first stage during the first iteration.
12. The stage assembly of claim 1 wherein the control system includes a noise filter that is applied to the positioning data to remove the high frequency noise from the positioning data.
13. The stage assembly of claim 1 wherein control system updates the positioning data using an adaptive algorithm.
14. The stage assembly of claim 13 wherein the control system selectively pauses updating of the positioning data.
15. The stage assembly of claim 13 wherein the updated positioning data is used in a model-based control law.
16. The stage assembly of claim 1 wherein the control system includes a non-model based control law that is applied to the positioning data.
17. The stage assembly of claim 1 wherein the first mover assembly moves the first stage in a third iteration that precedes the first iteration, wherein positioning data is generated from the third iteration, and wherein the control system controls the first mover assembly to adjust movement of the first stage during the second iteration based on the positioning data generated during the third iteration.
18. The stage assembly of claim 1 wherein the first iteration and the second iteration each have substantially similar points in time within each corresponding iteration that include time t1, time t2 and time t3, wherein time t1 is prior to time t2, and time t2 is prior to time t3, and wherein the control system controls the first mover assembly to adjust movement of the first stage at time t2 of the second iteration based on the positioning data generated at time t3 of the first iteration.
19. The stage assembly of claim 18 wherein the control system controls the first mover assembly to adjust movement of the first stage at time t2 of the second iteration based on the positioning data generated at time t2 of the first iteration.
20. The stage assembly of claim 1 wherein the second intended trajectory of the first stage is identical to the first intended trajectory of the first stage.
21. The stage assembly of claim 1 wherein the first stage is a reticle stage that retains a reticle.
22. The stage assembly of claim 1 wherein the first stage is a wafer stage that retains a wafer.
23. A precision assembly including an illumination source and the stage assembly of claim 1 positioned near the illumination source.
24. The precision assembly of claim 23 further comprising a sensor that senses the movement of a portion of the exposure apparatus other than the stage assembly, wherein the positioning data includes the movement of the portion of the exposure apparatus being monitored by the sensor.
25. The precision assembly of claim 24 wherein the portion of the exposure apparatus is at least a portion of an optical assembly.
26. The precision assembly of claim 24 wherein the portion of the exposure apparatus is at least a portion of an apparatus frame.
27. A device manufactured with the precision assembly according to claim 23.
28. A wafer on which an image has been formed by the precision assembly according to claim 23.
29. A precision assembly comprising:
- a first stage assembly including a first stage and a first mover assembly that moves the first stage;
- a second stage assembly including a second stage and a second mover assembly that moves the second stage synchronously with the first stage, positioning data being generated that includes the position of the second stage; and
- a control system that receives the positioning data, the control system controlling the first mover assembly to adjust movement of the first stage based on the position of the second stage to improve synchronization of movement of the stages.
30. The precision assembly of claim 29 wherein the control system includes a memory buffer that stores the positioning data.
31. The precision assembly of claim 29 wherein the control system includes a noise filter that is applied to the positioning data to remove the high frequency noise from the positioning data.
32. The precision assembly of claim 29 wherein control system updates the positioning data using an adaptive algorithm.
33. The precision assembly of claim 32 wherein the control system selectively pauses updating of the positioning data.
34. The precision assembly of claim 32 wherein the updated positioning data is used in a model-based control law.
35. The precision assembly of claim 29 wherein the control system includes a non-model based control law.
36. The precision assembly of claim 29 wherein the first stage is a reticle stage that retains a reticle, and wherein the second stage is a wafer stage that retains a wafer.
37. The precision assembly of claim 29 wherein the first mover assembly moves the first stage during a first iteration and a subsequent second iteration having a similar movement to the first iteration of the first stage, at least a portion of the positioning data being generated from the first iteration of the first stage, and wherein the control system controls the first mover assembly during the second iteration of the first stage based on at least a portion of the positioning data that is generated from the first iteration of the first stage.
38. The precision assembly of claim 37 wherein the second mover assembly moves the second stage during a first iteration and a subsequent second iteration having a similar movement to the first iteration of the second stage, at least a portion of the positioning data being generated from the first iteration of the second stage, and wherein the control system controls the second mover assembly during the second iteration of the second stage based on at least a portion of the positioning data that is generated from the first iteration of the second stage.
39. The precision assembly of claim 37 wherein at a time t21 during the first iteration the first stage has an intended position and an actual position, wherein the difference between the intended position and the actual position at time t21 is a t21 following error, and wherein the positioning data includes the t21 following error.
40. The precision assembly of claim 37 wherein the first stage moves along an actual trajectory during the first iteration, and wherein the positioning data includes at least a portion of the actual trajectory of the first stage during the first iteration.
41. The precision assembly of claim 37 wherein the first mover assembly moves the first stage in a third iteration that precedes the first iteration, wherein positioning data is generated from the third iteration, and wherein the control system controls the first mover assembly to adjust movement of the first stage during the second iteration based on the positioning data generated from the third iteration.
42. The precision assembly of claim 37 wherein the first iteration and the second iteration each have substantially similar points in time within each corresponding iteration that include time t1, time t2 and time t3, wherein time t1 is prior to time t2, and time t2 is prior to time t3, and wherein the control system controls the first mover assembly to adjust movement of the first stage at time t2 of the second iteration based on the positioning data generated at time t3 of the first iteration.
43. The precision assembly of claim 42 wherein the control system controls the first mover assembly to adjust movement of the first stage at time t2 of the second iteration based on the positioning data generated at time t2 of the first iteration.
44. The precision assembly of claim 42 wherein the control system controls the first mover assembly to adjust movement of the first stage at time t2 of the second iteration based on the positioning data generated at times t1 and t2 of the first iteration.
45. The precision assembly of claim 29 wherein the control system includes a noise filter that is applied to the positioning data to remove the high frequency noise from the positioning data.
46. The precision assembly of claim 29 wherein control system updates the positioning data using an adaptive algorithm.
47. The precision assembly of claim 46 wherein the control system selectively pauses updating of the positioning data.
48. The precision assembly of claim 46 wherein the updated positioning data is used in a model-based control law.
49. The precision assembly of claim 29 wherein the control system includes a non-model based control law.
50. The precision assembly of claim 29 further comprising a sensor that senses the movement of a portion of the exposure apparatus other than the stage assembly, wherein the positioning data includes the movement of the portion of the exposure apparatus being monitored by the sensor.
51. The precision assembly of claim 50 wherein the portion of the precision assembly is at least a portion of an optical assembly.
52. The precision assembly of claim 50 wherein the portion of the precision assembly is at least a portion of an apparatus frame.
53. A device manufactured with the preision assembly according to claim 29.
54. A wafer on which an image has been formed by the precision assembly according to claim 29.
55. A precision assembly comprising:
- a first stage assembly including a first stage and a first mover assembly that moves the first stage;
- a sensor that monitors the position of a portion of the precision assembly other than the stage assembly, the sensor providing positioning data including the position of the portion of the precision assembly being monitored by the sensor; and
- a control system that receives the positioning data, the control system controlling the first mover assembly to adjust movement of the first stage based on at least a portion of the positioning data.
56. The precision assembly of claim 55 wherein the portion of the precision assembly being monitored by the sensor includes at least a portion of an optical assembly.
57. The precision assembly of claim 55 wherein the portion of the precision assembly being monitored by the sensor includes at least a portion of an apparatus frame.
58. The precision assembly of claim 55 wherein the precision assembly includes a second stage assembly having a second stage and a second mover assembly that moves the second stage synchronously with the first stage, wherein the positioning data includes the position of the first and second stages, and wherein the control system controls at least one of the mover assemblies to adjust movement of the first stage based on the positioning data to improve synchronization of movement of the stages.
59. The precision=assembly=of claim 58 wherein the second mover assembly moves the second stage during a first iteration and a subsequent second iteration having a similar movement to the first iteration of the second stage, at least a portion of the positioning data being generated during the first iteration of the second stage, and wherein the control system controls the second mover assembly during the second iteration of the second stage based on at least a portion of the positioning data that is generated during the first iteration of the second stage.
60. The precision assembly of claim 58 wherein the first stage is a reticle stage that retains a reticle, and wherein the second stage is a wafer stage that retains a wafer.
61. The precision assembly of claim 55 wherein the first mover assembly moves the first stage during a first iteration and a subsequent second iteration having a similar movement to the first iteration of the first stage, at least a portion of the positioning data being generated from the first iteration of the first stage, and wherein the control system controls the first mover assembly during the second iteration of the first stage based on at least a portion of the positioning data that is generated during the first iteration of the first stage.
62. The precision assembly of claim 61 wherein at a time t21 during the first iteration the first stage has an intended position and an actual position, wherein the difference between the intended position and the actual position at time t21 is a t21 following error, and wherein the positioning data includes the t21 following error.
63. The precision assembly of claim 62 wherein the first stage moves along an actual trajectory during the first iteration, and wherein the positioning data includes at least a portion of the actual trajectory of the first stage during the first iteration.
64. The precision assembly of claim 61 wherein the first mover assembly moves the first stage in a third iteration that precedes the first iteration, wherein positioning data is generated from the third iteration, and wherein the control system controls the first mover assembly to adjust movement of the first stage during the second iteration based on the positioning data generated from the third iteration.
65. The precision assembly of claim 61 wherein the first iteration and the second iteration each have substantially similar points in time within each corresponding iteration that include time t1, time t2 and time t3, wherein time t1 is prior to time t2, and time t2 is prior to time t3, and wherein the control system controls the first mover assembly to adjust movement of the first stage at time t2 of the second iteration based on the positioning data generated at time t3 of the first iteration.
66. The precision assembly of claim 65 wherein the control system controls the first mover assembly to adjust movement of the first stage at time t2 of the second iteration based on the positioning data generated at time t2 of the first iteration.
67. The precision assembly of claim 65 wherein the control system controls the first mover assembly to adjust movement of the first stage at time t2 of the second iteration based on the positioning data generated at times t1 and t2 of the first iteration.
68. The precision assembly of claim 55 wherein the control system includes a noise filter that is applied to the positioning data to remove the high frequency noise from the positioning data.
69. The precision assembly of claim 55 wherein control system updates the positioning data using an adaptive algorithm.
70. The precision assembly of claim 69 wherein the control system selectively pauses updating of the positioning data.
71. The precision assembly of claim 69 wherein the updated positioning data is used in a model-based control law.
72. The precision assembly of claim 55 wherein the control system includes a non-model based control law.
73. A device manufactured with the precision assembly according to claim 55.
74. A wafer on which an image has been formed by the precision assembly according to claim 55.
75. A method for positioning one or more stages of a precision assembly, the method comprising the steps of:
- moving the first stage during a first iteration and a subsequent second iteration with a first mover assembly, the second iteration having a similar movement to the first iteration;
- generating positioning data from the first iteration that is sent to a control system; and
- controlling the first mover assembly with the control system to adjust movement of the first stage during the second iteration based on at least a portion of the positioning data.
76. The method of claim 75 wherein the step of generating positioning data includes sending the positioning data to a memory buffer that stores the positioning data.
77. The method of claim 76 wherein the step of generating positioning data includes sending positioning data that includes the position of the first stage along a second axis that is orthogonal to the first axis.
78. The method of claim 77 wherein the step of generating positioning data includes sending positioning data that includes the position of the first stage about a third axis that is orthogonal to the first and second axes.
79. The method of claim 75 wherein the step of generating positioning data includes sending positioning data that includes the position of the first stage about a first axis.
80. The method of claim 75 wherein the step of moving the first stage includes the first stage having an intended position at a time t1 during the first iteration and an actual position at time t11, wherein the difference between the intended position and the actual position at time t1 is a t1 following error, and wherein the positioning data includes the t11 following error.
81. The method of claim 80 wherein the step of moving the first stage includes the first stage having an intended position at a time t21 during the first iteration and an actual position at time t21, wherein the difference between the intended position and the actual position at time t21 is a t21 following error, and wherein positioning data includes the t21 following error.
82. The method of claim 75 further comprising the step of processing the positioning data with a noise filter to remove high frequency noise.
83. The method of claim 75 further comprising the step of updating the positioning data using an adaptive algorithm.
84. The method of claim 83 wherein the step of updating the positioning data is selectively paused by the control system.
85. The method of claim 75 further comprising the step of generating positioning data using a sensor that senses movement of a portion of the precision assembly other than the stage assembly.
86. The method of claim 75 further comprising the steps of moving a second stage with a second mover assembly synchronously with the first stage, generating positioning data from movement of the second stage that is sent to the control system, and controlling the first mover assembly with the control system based on the positioning data from movement of the stages to adjust movement of the first stage to improve synchronization of movement of the stages.
87. The method of claim 85 wherein the first stage is a reticle stage that retains a reticle and the second stage is a wafer stage that retains a wafer.
88. A method for manufacturing a device that includes the method of claim 75.
89. A method for manufacturing a wafer on which an image has been formed that includes the method of claim 75.
90. A method for positioning one or more stages of a precision assembly, the method comprising the steps of:
- moving the first stage with a first mover assembly;
- moving a second stage with a second mover assembly synchronously with the first stage;
- generating second stage positioning data that includes the position of the second stage; and
- controlling movement of the first mover assembly with a control system based on the second stage positioning data to improve the synchronization of movement of the stages.
91. The method of claim 90 further comprising the steps of generating first stage positioning data that includes the position of the first stage, and controlling movement of the second mover assembly with the control system based on the first stage positioning data to improve the synchronization of movement of the stages.
92. The method of claim 90 wherein the step of generating positioning data includes sending the positioning data to a memory buffer that stores the positioning data.
93. The method of claim 90 wherein the step of moving the first stage includes moving the first stage during a first iteration and a subsequent second iteration with the first mover assembly, the second iteration having a similar movement to the first iteration, and generating positioning data from the first iteration that is sent to the control system, and wherein the step of controlling movement of the first mover assembly includes controlling the first mover assembly with the control system to adjust movement of the first stage during the second iteration based on at least a portion of the positioning data from the first iteration of the first stage.
94. The method of claim 94 wherein the step of moving the first stage includes the first stage having an intended position at a time t11 during the first iteration and an actual position at time t11, wherein the difference between the intended position and the actual position at time t11 is a t11 following error, and wherein the positioning data of the first stage includes the t11 following error.
95. The method of claim 94 wherein the step of moving the first stage includes the first stage having an intended position at a time t21 during the first iteration and an actual position at time t21, wherein the difference between the intended position and the actual position at time t21 is a t21 following error, and wherein positioning data of the first stage includes the t21 following error.
96. The method of claim 90 further comprising the step of generating positioning data using a sensor that senses movement of a portion of the precision assembly other than the stage assembly.
97. The method of claim 90 wherein the first stage is a reticle stage that retains a reticle and the second stage is a wafer stage that retains a wafer.
98. A method for manufacturing a device that includes the method of claim 90.
99. A method for manufacturing a wafer on which an image has been formed that includes the method of claim 90.
100. A method for positioning one or more stages of a stage assembly of an precision assembly, the method comprising the steps of:
- moving a first stage with a first mover assembly;
- monitoring movement of a portion of the precision assembly other than the stage assembly with a sensor;
- generating positioning data with the sensor, the positioning data including the position of the portion of the precision assembly being monitored by the sensor; and
- controlling movement of the first mover assembly with a control system to adjust movement of the first stage based on at least a portion of the positioning data.
101. The method of claim 100 wherein the step of generating positioning data includes generating positioning data of the position of at least a portion of an optical assembly of the precision assembly.
102. The method of claim 100 wherein the step of generating positioning data includes generating positioning data of the position of at least a portion of an apparatus frame of the precision assembly.
103. The method of claim 100 further comprising the steps of moving a second stage with a second mover assembly synchronously with the first stage, and generating positioning data that includes the position of the second stage, and wherein the step of controlling movement includes controlling movement of the first mover assembly to adjust movement of the first stage based on the second stage positioning data to improve synchronization of movement of the stages.
104. The method of claim 103 wherein the first stage is a reticle stage that retains a reticle, and wherein the second stage is a wafer stage that retains a wafer.
105. The method of claim 100 wherein the step of moving the first stage includes moving the first stage during a first iteration and a subsequent second iteration having a similar movement to the first iteration, and generating first stage positioning data from movement of the first stage during the first iteration, and wherein step of controlling movement of the first mover assembly includes controlling movement of the first mover assembly during the second iteration based on at least a portion of the positioning data that is generated from the first iteration of the first stage.
106. The method of claim 105 wherein the positioning data that is generated from the first iteration of the first stage includes a following error equal to the difference between an intended position and an actual position of the first stage.
107. The method of claim 105 wherein the positioning data that is generated from the first iteration of the first stage includes at least a portion of an actual trajectory of the first stage during the first iteration.
108. The method of claim 100 further comprising the step of processing the positioning data with a noise filter to remove high frequency noise.
109. The method of claim 100 further comprising the step of updating the positioning data using an adaptive algorithm.
110. The method of claim 109 wherein the step of updating the positioning data is selectively paused by the control system.
111. A method for manufacturing a device that includes the method of claim 100.
112. A method for manufacturing a wafer on which an image has been formed that includes the method of claim 100.
113. A first stage assembly comprising:
- a first stage having a first intended trajectory and a second intended trajectory that is similar to the first intended trajectory;
- a first mover assembly that moves the first stage along a first actual trajectory that emulates the first intended trajectory and a subsequent, second actual trajectory that emulates the second intended trajectory, positioning data being generated during the first actual trajectory; and
- a control system that receives the positioning data, the control system controlling the first mover assembly to adjust the second actual trajectory of the first stage based on at least a portion of the positioning data.
114. The stage assembly of claim 113 wherein the first intended trajectory includes a first starting point and the second intended trajectory includes a second starting point, and wherein the first starting point is the same as the second starting point.
115. The stage assembly of claim 114 wherein the first intended trajectory includes a first intended motion and the second intended trajectory includes a second intended motion, and wherein the first intended motion is similar to the second intended motion.
116. The stage assembly of claim 113 wherein the first intended trajectory includes a first intended motion and the second intended trajectory includes a second intended motion, and wherein the first intended motion is the same as the second intended motion.
117. The stage assembly of claim 116 wherein the first intended trajectory includes a first starting point and the second intended trajectory includes a second starting point, and wherein the first starting point is similar to the second starting point.
118. The stage assembly of claim 116 wherein the first intended trajectory includes a first starting point and the second intended trajectory includes a second starting point, and wherein the first starting point is the same as the second starting point.
119. A stage assembly comprising:
- a first stage having (i) a first intended trajectory that includes a first point and a first movement, and (ii) a second intended trajectory that includes a second point and a second movement, the second point being the same as the first point, the second movement being similar to the first movement;
- a first mover assembly that moves the first stage along a first actual trajectory that emulates the first intended trajectory, and a second actual trajectory that emulates the second intended trajectory, positioning data being generated during the first actual trajectory; and
- a control system that receives the positioning data, the control system controlling the first mover assembly to adjust the second actual trajectory of the first stage based on at least a portion of the positioning data.
120. The stage assembly of claim 119 wherein the first movement is the same as the second movement.
121. A stage assembly comprising:
- a first stage having (i) a first intended trajectory that includes a first point and a first movement, and (ii) a second intended trajectory that includes a second point and a second movement, the second point being similar to the first point, the second movement being the same as the first movement;
- a first mover assembly that moves the first stage along a first actual trajectory that emulates the first intended trajectory, and a second actual trajectory that emulates the second intended trajectory, positioning data being generated during the first actual trajectory; and
- a control system that receives the positioning data, the control system controlling the first mover assembly to adjust the second actual trajectory of the first stage based on at least a portion of the positioning data.
122. A method for positioning a first stage of a stage assembly of a precision assembly, the method comprising the steps of:
- providing a first stage having a first intended trajectory and a second intended trajectory that is similar to the first intended trajectory;
- moving the first stage with a first mover assembly along a first actual trajectory that emulates the first intended trajectory and a subsequent, second actual trajectory that emulates the second intended trajectory;
- generating positioning data from the first actual trajectory that is sent to a control system; and
- controlling the first mover assembly with the control system to adjust the second actual trajectory of the first stage based on at least a portion of the positioning data.
123. The method of claim 122 wherein the step of providing a first stage includes the first intended trajectory having a first starting point that is the same as a second starting point of the second intended trajectory.
124. The method of claim 123 wherein the step of providing a first stage includes the first intended trajectory having a first intended motion that is similar to a second intended motion of the second intended trajectory.
125. The method of claim 122 wherein the step of providing a first stage includes the first intended trajectory having a first intended motion that is the same as a second intended motion of the second intended trajectory.
126. The method of claim 125 wherein the step of providing a first stage includes the first intended trajectory having a first starting point that is similar to a second starting point of the second intended trajectory.
127. The method of claim 125 wherein the step of providing a first stage includes the first intended trajectory having a first starting point that is the same as a second starting point of the second intended trajectory.
Type: Application
Filed: Nov 5, 2003
Publication Date: Jul 8, 2004
Inventors: Pai-Hsueh Yang (Palo Alto, CA), Bausan Yuan (San Jose, CA), Susumu Makinouchi (Kanagawa), Yoshiji Itakura (Kumagava), Kazuhiro Hirano (Ageo), Hideyuki Hashimoto (Kumagaya), Ryoichi Kawaguchi (Tokyo)
Application Number: 10703205
