Abstract: Charged-particle-beam (CPB) apparatus and methods are disclosed that achieve efficient correction of imaging conditions such as shape-astigmatic aberrations, etc., caused by differences in the distribution of pattern elements within respective subfields of the reticle. Indices based on the pattern-element distributions within subfields are stored, together with corresponding optical-correction data for the subfields. As the subfields are exposed, respective data are recalled and the exposure is performed with optical corrections made according to the data. The indices are determined beforehand from pattern data at time of reticle manufacture. The tabulated data are rewritable with changes in apparatus parameters such as beam-current density and beam-divergence angle. Intermediate data can be determined by interpolation of tabulated data.

Abstract: Fiducial mark bodies are provided for use in CPB microlithography apparatus and methods. Such bodies are especially useful for attachment to the wafer stage of such apparatus, for measuring a distance between a reference position of the CPB-optical system of the apparatus and a reference position of an optical-based alignment sensor of the apparatus. The mark bodies provide improved accuracy of these and other positional measurements. A typical mark body is made of a substrate plate (e.g., quartz or quartz-ceramic) having a low coefficient of thermal expansion. Mark elements are defined on the substrate plate by a layer of heavy metal (e.g. are Ta, W, or Pt). The mark body includes a surficial or interior layer of an electrically conductive light metal that prevents electrostatic charging of the mark body and can be connected to ground.

Abstract: Charged-particle-beam (CPB) microlithography methods are disclosed in which exposure dose on the lithographic substrate is controlled and adjusted as required to achieve proper exposure and maximal throughput, regardless of beam-transmissivity (e.g., membrane thickness) of the reticle in use. A reticle is provided with a transmitted-current-detection window exhibiting the same beam-transmissivity and forward-scattering behavior as a non-scattering membrane portion of the pattern-defining portion of the reticle. A charged-particle illumination beam is directed at the transmitted-current-detection window of the reticle. The beam current passing through the transmitted-current-detection window and reaching the wafer stage is sensed by a sensor located at or on the wafer stage. From the obtained beam-current data, a controller calculates the beam-current density on the wafer stage and calculates and sets a corresponding exposure time for exposing the wafer with an appropriate amount of exposure energy.

Abstract: A charged-particle-beam exposure apparatus for exposing mask patterns onto a substrate includes a mask illumination system capable of varying the size and/or shape of the beam cross-section (the irradiated or mask-illumination field) at the mask. Initial mask alignment (rough alignment) and calibration are performed by irradiating respective alignment and calibration marks on the mask with a beam having a cross-sectional size smaller than the cross-sectional size of a beam used in the normal exposure process.

Abstract: Methods are disclosed for performing a calibration of a charged-particle-beam (CPB) microlithography apparatus. In an embodiment, a specimen having a crystal-orientation plane is mounted on a specimen stage of the CPB microlithography apparatus. A charged particle beam (e.g., electron beam) produced by a suitable source passes through a CPB-optical system so as to irradiate the surface of the specimen. Using a deflector, the beam is scanned over an area of the specimen surface, and backscattered charged particles produced by the irradiated area of the specimen are detected. A corresponding electrical signal produced by detecting the backscattered particles is produced. The signal has a property that is a function of the specific crystalline properties of the specimen surface. From the signal, the relationship between the angle of incidence of the beam on the specimen surface versus the output of the deflector is determined and used to calibrate the beam axis of the CPB-optical system.

Abstract: Charged-particle-beam (CPB) microlithography systems are disclosed that include a device for measuring the distribution of charged-particle density in a patterned beam. By providing feedback to the CPB microlithography apparatus, the distribution of charged-particle density can be optimized for high-quality exposures. An embodiment of the device includes a pinhole diaphragm defining an aperture having a small cross-dimension compared to the transverse width of the patterned beam produced by the system. The device also desirably includes a downstream scattering-contrast diaphragm defining an aperture having a larger cross dimension than that of the pinhole aperture. A photodiode or the like is downstream of the pinhole aperture and is used for detecting charged particles transmitted by the pinhole diaphragm. A patterned beam is scanned across the pinhole aperture, and charged particles not scattered during passage through the pinhole aperture propagate to the photodiode.

Abstract: Beam-calibration methods are disclosed for a charged-particle-beam (CPB) microlithography system that can be performed in substantially less time than conventional beam-calibration methods. To calibrate a beam, the reticle stage and substrate stage are moved to position the deflection center of the CPB optical system at the center of a group of calibration subfields each containing calibration mark(s). The beam is deflected laterally so as to scan a first row of calibration subfields while measuring beam characteristics at each subfield. Next, the reticle stage and substrate stage are moved to place the deflection center of the CPB optical system at the center of the subfield group. The beam is deflected laterally so as to scan a second row of calibration subfields while measuring beam characteristics at each subfield. Based on the measurements, a respective optical-system-correction coefficient is established for each calibration subfield.

Abstract: Methods and apparatus for alignment of masks and wafers in charged-particle-beam (CPB) pattern-transfer use optical position sensors to determine the positions of a mask or a mask stage with respect to an axis of a CPB optical system. The optical position sensor uses optical reference marks provided on the mask or mask stage. Determination of the position of the mask of the mask stage permits a coarse alignment of the mask or the mask stage. CPB reference marks are provided on masks, mask stages, wafers, and wafer stages, permitting alignment of the mask stage or the mask with respect to the wafer stage or wafer, respectively, using the charged particle beam. The charged particle beam is scanned with respect to the wafer or wafer-stage CPB reference marks to determine a deflection corresponding to an alignment of the CPB reference marks of the mask and wafer (or mask stage and wafer stage). Use of the charged particle beam for such alignment permits a fine alignment.

Abstract: Alignment marks and methods using such marks are provided for use in charged-particle-beam (CPB, e.g., electron-beam) microlithography. The alignment marks are capable of being detected by both an optical-based alignment-mark sensor and a CPB-based alignment-mark sensor. A representative embodiment of such an alignment mark comprises multiple serially arrayed elements having a first period. At least one of the elements comprises multiple serially arrayed sub-elements having a second period that is shorter than the first period. When such a mark is sensed using an optical-based sensor, the period of the sub-elements is not resolvable and the resulting signal will be substantially the same as when none of the elements is subdivided into sub-elements. However, when such a mark is sensed using a CPB-based sensor and scanning the charged particle beam, then the period of the sub-elements is resolvable. Hence, a single alignment mark can be detected using either type of sensor.

Abstract: The subject electrostatic chucking devices hold a semiconductor wafer or analogous sample for microlithography or the like and prevent decreases in accuracy and precision of microlithographic pattern transfer that would otherwise arise due to current leakage to the wafer and to wafer displacement from thermal expansion. The chucking device includes an insulative substrate, multiple electrodes on the substrate, and multiple dielectric layers applied over the electrodes such that the electrodes are sandwiched between the insulator substrate and the dielectric layers. The dielectric layers are disposed so as to define a planar chucking surface divided into multiple regions. For example, a first region is made of a ceramic having a relatively low volume resistivity so as to attract the wafer mainly by a Johnsen-Rahbek force. A second dielectric-layer region is made of a ceramic having a relatively high volume resistivity so as to attract the wafer mainly by a Coulomb force.

Abstract: Alignment marks are disclosed that provide, when scanned by a detection-light beam, an enhanced signal-amplitude change. Such an alignment mark is formed on a mark substrate and is used for performing an alignment in a charged-particle-beam (CPB) microlithography system. The alignment mark includes at least one mark element defined as a corresponding height-difference characteristic in the mark substrate. The mark element includes more than two height-difference edges that would be encountered by a detection-light beam being scanned across the element. The height-difference edges of the element can be defined by multiple individual mark-element components that collectively provide the more than two height-difference edges of the mark element. Alternatively, for example, the element can include two height-difference edges at respective edges of the mark element and at least one height-difference edge situated between the two height-difference edges at respective edges of the mark element.

Abstract: Microlithography methods and apparatus are disclosed that allow reticle deformations to be measured and corrected quickly and accurately. Multiple alignment marks (comprising a “first set” and “second set” of reticle-position-measurement marks) are formed on the reticle. A first set of reticle-deformation data is obtained by detecting the positions of at least some of the first set of reticle-position-measurement marks using an inspection device that is separate from the microlithography apparatus with which the reticle will be used for making lithographic exposures. The first set of reticle-deformation data is stored in a first memory. The reticle then is mounted in the microlithography apparatus, in which a second set of reticle-deformation data is obtained by detecting the positions of at least some of the second set of reticle-position-measurement marks. The second set of reticle-deformation data is stored in a second memory.

Abstract: Charged-particle-beam (CPB) microlithography methods are disclosed in which exposure dose on the lithographic substrate is controlled and adjusted as required to achieve proper exposure and maximal throughput, regardless of beam-transmissivity (e.g., membrane thickness) of the reticle in use. A reticle is provided with a transmitted-current-detection window exhibiting the same beam-transmissivity and forward-scattering behavior as a non-scattering membrane portion of the pattern-defining portion of the reticle. A charged-particle illumination beam is directed at the transmitted-current-detection window of the reticle. The beam current passing through the transmitted-current-detection window and reaching the wafer stage is sensed by a sensor located at or on the wafer stage. From the obtained beam-current data, a controller calculates the beam-current density on the wafer stage and calculates and sets a corresponding exposure time for exposing the wafer with an appropriate amount of exposure energy.

Abstract: Reticle-holding devices (“reticle chucks”) are disclosed that define a downstream-facing reticle-mounting surface configured for holding an upstream-facing surface of a reticle for use in a microlithography apparatus. The reticle chucks can include peripheral regions and struts that define respective portions of the reticle-mounting surface, thereby preventing reticle sag while still allowing the axial distance from the reticle to a projection-optical system to be measured by grazing incidence without obstruction. The reticle can be held by, e.g., electrostatic attraction or vacuum suction to the reticle-mounting surface. The subject chucks also can be used for holding a reticle blank while inscribing a pattern on the reticle blank.

Abstract: Methods are disclosed for reducing effects of thermal expansion of a sensitive substrate arising during microlithographic exposure of the substrate using a charged particle beam. Thermal expansion ordinarily causes lateral shift of exposure position of dies (chips) on the substrate which tends to reduce the positional accuracy with which images of the dies are formed on the substrate. Generally, regions of the substrate where entire dies are formed are exposed first, followed by regions (especially peripheral regions) exposed with only portions of dies. In addition, the substrate can be mounted on a wafer chuck configured to circulate a heat-transfer gas in contact with the substrate to remove heat from the substrate. In addition, the wafer chuck can be maintained at a constant temperature by circulating a liquid coolant through a conduit in the body of the wafer chuck.

Abstract: Electrostatic reticle chucks are disclosed that provide strong reticle-holding force and that can be used in a subatmospheric-pressure environment as encountered in charged-particle-beam microlithography. The chucks are suited especially for holding reticles made from a silicon reticle substrate. The attractive force is established between a reticle-contacting surface of the chuck comprising a dielectric material, and the reticle. Depthwise beneath the dielectric material is at least one electrode. The dielectric material has a property such that, when the electrode is energized, the reticle is attracted to the reticle-contacting surface by a Johnsen-Rahbek force. To such end, by way of example, the dielectric material has a volume resistivity of no greater than 1013 &OHgr;-cm. The Johnsen-Rahbek force holds the reticle much more strongly than the Coulomb force produced by conventional reticle chucks.

Abstract: Fiducial mark bodies are provided for use in CPB microlithography apparatus and methods. Such bodies are especially useful for attachment to the wafer stage of such apparatus, for measuring a distance between a reference position of the CPB-optical system of the apparatus and a reference position of an optical-based alignment sensor of the apparatus. The mark bodies provide improved accuracy of these and other positional measurements. A typical mark body is made of a substrate plate (e.g., quartz or quartz-ceramic) having a low coefficient of thermal expansion. Mark elements are defined on the substrate plate by a layer of heavy metal (e.g. are Ta, W, or Pt). The mark body includes a surficial or interior layer of an electrically conductive light metal that prevents electrostatic charging of the mark body and can be connected to ground.

Abstract: Fiducial mark bodies are provided for use in CPB microlithography apparatus and methods. Such bodies are especially useful for attachment to the wafer stage of such apparatus, for measuring a distance between a reference position of the CPB-optical system of the apparatus and a reference position of an optical-based alignment sensor of the apparatus. The mark bodies provide improved accuracy of these and other positional measurements. A typical mark body is made of a substrate plate (e.g., quartz or quartz-ceramic) having a low coefficient of thermal expansion. Mark elements are defined on the substrate plate by a layer of heavy metal (e.g. are Ta, W, or Pt). The mark body includes a surficial or interior layer of an electrically conductive light metal that prevents electrostatic charging of the mark body and can be connected to ground.

Abstract: Alignment-mark patterns are disclosed that are defined on stencil reticles and that can be transferred lithographically from the reticle to a sensitized substrate using charged-particle-beam microlithography. The corresponding alignment marks as transferred to the substrate are detectable at high accuracy using an optical-based alignment-detection device (e.g., an FIA-based device). The transferred alignment marks can be used in place of alignment marks used in optical microlithography systems. An alignment-mark pattern as defined on a stencil reticle includes pattern elements that are split in any of various ways into respective pattern-element portions separated from each other on the membrane of the stencil reticle by “girders” (band-like membrane portions) that prevent the formation of islands in the stencil reticle and that prevent deformation of the pattern elements on the stencil reticle.

Abstract: Backscattered electron (BSE) detection systems are disclosed that produce a detection-signal waveform exhibiting large signal-level changes with corresponding changes in the locus, on a sample, irradiated by a scanning electron beam. Hence, the position of a pattern feature on a sample is detectable with improved accuracy. An electron beam irradiates a sample comprising a relatively low-mass substrate and a relatively high-mass pattern feature thereon. Backscattered electrons from the substrate and from the pattern element are detected using a first BSE detector having a first energy-sensitivity band, and a second BSE detector having a second energy-sensitivity band that is different from the first energy-sensitivity band. The signal from the first BSE detector is combined with the signal from the second BSE detector to produce a detection-signal waveform exhibiting large changes in signal amplitude with changes in the locus actually irradiated by the electron.