TECHNIQUES AND APPARATUS FOR ELONGATION PATTERNING USING ANGLED ION BEAMS
A method of patterning a substrate may include providing a cavity in a layer, disposed on the substrate. The cavity may have a first length along a first direction and a first width along a second direction, perpendicular to the first direction. The method may include directing first angled ions in a first exposure to the cavity, wherein after the first exposure the cavity has a second length, greater than the first length; directing normal ions in a second exposure to the cavity, wherein the cavity retains the second length after the second exposure; and directing second angled ions to the cavity is a third exposure, subsequent to the second exposure, wherein the cavity has a third length, greater than the second length, after the third exposure.
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This application is a divisional of U.S. Non-Provisional patent application Ser. No. 16/053,329, filed on Aug. 2, 2018, entitled TECHNIQUES AND APPARATUS FOR ELONGATION PATTERNING USING ANGLED ION BEAMS, which claims priority to U.S. Provisional Patent Application No. 62/673,604, file May 18, 2018, entitled TECHNIQUES AND APPARATUS FOR ELONGATION PATTERNING USING ANGLED ION BEAMS, which applications are incorporated by reference herein in their entireties.
FIELDThe present embodiments relate to transistor processing techniques, and more particularly, to etch processing for patterning devices.
BACKGROUNDAs semiconductor devices continue to scale to smaller dimensions, the ability to pattern features becomes increasingly difficult. These difficulties include in one aspect the ability to obtain features at a target size for a given technology generation. Another difficult is the ability to obtain the correct shape of a patterned feature, as well as packing density, and the ability to obtain correct overlay to structures patterned in previous processing operations.
In another example, overlay error represents a challenge to extend lithography to advanced nodes. While multi-patterning has been used to address feature width and pitch reduction of features, overlay becomes an increasing challenge. One reason is as the feature line/space is reduced, the overlay requirement becomes smaller. A second reason is as multiple cut masks are coming into use, multiple overlay issues between cut masks and the other features on a substrate arise.
One further challenge is to print small features such as cavities, where the cavities are separated by a small distance, on the order of nanometers or tens of nanometers in present day technology. As an example, printing of adjacent linear features with the appropriate tip-to-tip distance becomes increasing challenging as overall pitch of device structures continues to shrink.
With respect to these and other considerations the present improvements may be useful.
BRIEF SUMMARYIn one embodiment, a method of patterning a substrate may include providing a cavity in a layer, disposed on the substrate. The cavity may have a first length along a first direction and a first width along a second direction, perpendicular to the first direction. The method may further include directing first angled ions in a first exposure to the cavity, wherein after the first exposure the cavity has a second length, greater than the first length. The method may also include directing normal-incidence ions in a second exposure to the cavity, wherein the cavity retains the second length after the second exposure. The method may include directing second angled ions to the cavity is a third exposure, subsequent to the second exposure, wherein the cavity has a third length, greater than the second length, after the third exposure.
In another embodiment, a system may include a transfer chamber, arranged to transport a substrate between a plurality of locations. The system may include a first angled ion beam chamber, coupled to the transfer chamber, to direct a first angled ion beam to the substrate. The system may further include a vertical etch chamber, the vertical etch chamber coupled to the transfer chamber, to supply vertical ions to the substrate. The system may also include a second angled ion beam chamber, the second angled ion beam chamber coupled to the transfer chamber, to direct a second angled ion beam to the substrate.
In a further embodiment, an apparatus may include a plasma chamber coupled to receive power from a power supply, and a process chamber, electrically coupled to the plasma chamber via a bias supply, the process chamber further including a substrate stage. The apparatus may also include an extraction plate disposed between the plasma chamber and process chamber, and defining an angled ion beam, as well as a controller, coupled to at least one of: the power supply, bias supply, and substrate stage. The controller may include a processor; and a memory unit coupled to the processor, including an ion beam control routine, where the ion beam control routine is operative on the processor to control the angled ion beam. The ion beam control routine may include an angle control processor to receive an endpoint signal, and to send a control signal to adjust operation of at least one of the power supply, bias supply, and substrate stage, based upon the endpoint signal.
The present embodiments will now be described more fully hereinafter with reference to the accompanying drawings, where some embodiments are shown. The subject matter of the present disclosure may be embodied in many different forms and are not to be construed as limited to the embodiments set forth herein. These embodiments are provided so this disclosure will be thorough and complete, and will fully convey the scope of the subject matter to those skilled in the art. In the drawings, like numbers refer to like elements throughout.
The present embodiments provide novel techniques and apparatus to pattern substrates and in particular novel techniques to etch a cavity disposed in a substrate, along a designed direction. Such processing may be deemed elongation patterning, where a feature such as a via or trench may be formed having an initial shape and size, and may be subsequently elongated along the designed direction using a series of etch operations. The designed direction may correspond to a horizontal direction within a plane of the substrate. According to various embodiments, the elongation of the feature may take place along the designed direction (first direction) while the cavity is not enlarged or enlarged to a lesser extent along a perpendicular direction to the designed direction (second direction) within the plane of the substrate. In this manner, a cavity may be selectively elongated along just one direction, providing various concomitant advantages for patterning substrates, as disclosed herein.
Various embodiments may be especially appropriate for etching patterns where the selective elongation of a cavity along a horizontal direction (Y-direction) requires a relatively large initial thickness (along a Z-direction) of a mask layer(s). By way of background, a certain layer thickness is needed to etch a given amount in the horizontal direction using angled ions, since the angled etching etches vertically and horizontally at the same time. As such, to achieve a larger amount of cavity elongation in a single layer in the horizontal direction using angled ions, the thickness of the single layer may need to be increased. This increased thickness of the single layer in turn may produce a higher aspect ratio of a patterned feature in the single layer, such as 5/1, 6/1, or higher. In such structures, the angle of incidence of ions used to perform the cavity elongation may be less than 10 degrees with respect to perpendicular to the substrate plane (horizontal plane), to prevent shadowing in the structure. This severe geometry for incident ions can significantly harm the sidewall profile of a cavity due to faster elongation at the top of the cavity than the bottom of the cavity. These relatively lower beam angles (with respect to perpendicular) may cause a much slower elongation rate in the horizontal direction, due to the glancing angle with respect to the (vertical) sidewall of the structure, rendering such extreme pattern elongation within the given layer too slow to be a practical in some applications. As detailed below, the present embodiments, by modifying such a single layer/single etch approach, may overcome these issues to provide extreme selective elongation of a cavity in a horizontal direction.
Turning to
Turning to
Turning now to
Turning now to
Turning now to
In accordance with various embodiments, the ions 180 may be directed to the device structure 170 in the presence of a reactive ambient containing a reactive species, shown as the reactive species 184, as illustrated by the black dots. The ions 182 and reactive species 184 may be provided by a suitable apparatus capable of providing reactive species as well as a beam of ions. Examples of such apparatus include plasma based apparatus having an extraction system extracting ions through an extraction aperture and directs the ions to a substrate.
Additionally, reactive species 184 may be provided as neutrals, ions, radicals, or a combination of neutrals, ions, and radicals. Ions 182 themselves may be inert ions or may include reactive species. The combination of ions 182 and reactive species 184 may include known recipes for performing reactive ion etching of materials including silicon oxide layers, silicon nitride layers, silicon layers, carbon layers, and other materials systems. The embodiments are not limited in this context.
When ions 182 are used in conjunction with reactive species 184, where the reactive species are designed to promote reactive ion etching, this configuration enables a novel “one dimensional reactive ion etching” process where reactive ion etching can be restricted to targeted features on a substrate surface while not affecting other features. The one-dimensional reactive ion etching may differ from conventional reactive ion etching where ions directed may etch material along the vertical direction as well as along more than one direction within a plane of the substrate perpendicular to the vertical direction. For example, in conventional reactive ion etching (ashing) of via structures formed within a layer the diameter of via structures may be increased in a non-selective manner along an X-direction and Y-direction.
In the example of
Returning to
Moreover, even before the first layer 114 is entirely removed, cavities may begin to etch in a non-ideal fashion along a transverse direction. For example, the profile of cavities in the X-Z plane may begin to round after a given amount of elongation etching along the Y-axis. Accordingly, by transferring a second elongation operation into subjacent layers, such as second layer 116, and third layer 118, further elongation may be accomplished while avoiding non-ideal etching tending to occur with prolonged etching using just one layer as a top layer.
Turning now to
During a directional etching operation, an angled ion beam 210 is extracted through the extraction aperture 208 as shown. The angled ion beam 210 may be extracted when a voltage difference is applied using bias supply 220 between the plasma chamber 202 and substrate 100 as in known systems. The bias supply 220 may be coupled to the process chamber 222, for example, where the process chamber 222 and substrate 110 are held at the same potential. In various embodiments, the angled ion beam 210 may be extracted as a continuous beam or as a pulsed ion beam as in known systems. For example, the bias supply 220 may be configured to supply a voltage difference between plasma chamber 202 and process chamber 222, as a pulsed DC voltage, where the voltage, pulse frequency, and duty cycle of the pulsed voltage may be independently adjusted from one another.
By scanning a substrate stage 214 including substrate 100 with respect to the extraction aperture 208, and thus with respect to the angled ion beam 210, along the scan direction 216, the angled ion beam 210 may etch targeted surfaces of structures, such as the trenches 112, when such structures are oriented, for example, perpendicularly to the scan direction 216, as further shown in
In the example of
As also indicated in
Turning now to
In accordance with various embodiment the processing apparatus 200 or processing apparatus 240 may further include a controller 250, where the operation of controller 250 is detailed below with respect to
Turning now to
The memory unit 254 may comprise an article of manufacture. In one embodiment, the memory unit 254 may comprise any non-transitory computer readable medium or machine readable medium, such as an optical, magnetic or semiconductor storage. The storage medium may store various types of computer executable instructions to implement one or more of logic flows described herein. Examples of a computer readable or machine-readable storage medium may include any tangible media capable of storing electronic data, including volatile memory or non-volatile memory, removable or non-removable memory, erasable or non-erasable memory, writeable or re-writeable memory, and so forth. Examples of computer executable instructions may include any suitable type of code, such as source code, compiled code, interpreted code, executable code, static code, dynamic code, object-oriented code, visual code, and the like. The embodiments are not limited in this context.
As further shown in
The angle control processor 258 may be arranged to send a control signal to adjust operation of at least one of the power supply 230, bias supply 220, or substrate stage 214, based upon receipt of the endpoint signal. Said differently, the angle control processor 258 may adjust operation parameter(s) of at least one component of the processing apparatus 200 in a dynamic fashion based upon feedback during an etch operation, or series of etch operations. As an example, the angle control processor 258 may adjust operating parameters affecting the angle of incidence of the angled ion beam 210. Exemplary parameters affecting angle of incidence include plasma power, bias voltage between plasma chamber and substrate, as well as separation between extraction plate and substrate (along the Z-axis). In a particular example, by varying the separation of extraction plate and substrate between approximately 5 mm and 40 mm, the angle of incidence with respect to perpendicular to a substrate plane of angled ion beam 210 may be varied from between nearly zero to up to 40 degrees. Accordingly, in one implementation, the sequence of operations shown in
The gas flow processor 260 may be arranged to send a control signal to adjust flow of a gas or gases from the gas source 224, based upon receipt of an endpoint signal, for example. In this manner, the gas composition in the plasma chamber 202, and accordingly, the reactive ion etching chemistry, may be changed. For example, the etch chemistry may be altered according to changing of layers to be etched within a stack of layers. In some implementations, the etch chemistry may be altered between different angled ion beam etch operations, while the angle of incidence of ions in an angled ion beam remains the same between the different etch operations. In some implementations, the etch chemistry may be altered between different angled ion beam etch operations, while the angle of incidence is also changed between the different etch operations. In further implementations, the etch chemistry may remain the same between different angled ion beam etch operations, while the angle of incidence is changed between the different etch operations.
As also shown in
As shown in Table I. each recipe for the combination of the first elongation etch and the second elongation etch may be tailored so the first elongation etch etches first layer 114 and second layer 116 selectively with respect to third layer 118, and the second elongation etch selectively etches second layer 116 and third layer 118 with respect to the substrate base 120.
While the embodiments discussed above detail elongation of cavities using two angled ion beam etching processes, in further embodiments, at least three angled ion beam etching processes may be used in a sequence of operations, to extend the ability to elongate a cavity. Addition of a given angled ion beam etching operation may be accompanied by addition of another layer.
At block 406, the cavity is exposed to a reactive ion etch operation where normal-incidence ions are directed to the cavity, meaning the ions are directed along the perpendicular to the substrate plane. As such, the cavity may retain the second length after exposure to the reactive ion etch at normal incidence. In some examples, a first layer may be removed after the reactive ion etch operation, wherein a second layer, initially disposed subjacent the first layer, becomes a top layer. At the same time the cavity may be extended into a third layer, subjacent the second layer.
At block 408 a second angled ion beam etch is performed to elongate the cavity from the second length to a third length. The second angled ion beam etch may entail a second reactive ion etch process where a second ion beam is directed in a reactive ambient at a second non-zero angle of incidence with respect to the plane (X-Y) of the substrate. In some embodiments, after the operations of blocks 404-408 the cavity may retain the first width.
The present embodiments provide various advantages over conventional processing to define features in a substrate. One advantage lies in the ability to selectively elongate a cavity along just one direction, while preserving the dimension of the cavity along a second direction, perpendicular to the first direction. Another advantage is the ability to reduce cavities below the spacing achieved by known lithography processes. An example of this ability is the reduction of tip-to-tip separation between adjacent trenches such as contact trenches. A further advantage is the ability to reduce the number of masks used to generate a pattern of features, where the features may be separated by a distance less than the threshold separation achievable by a single mask. This reducing the number of masks has the further advantageous effect of reducing overlay error for printing the pattern of features.
The present disclosure is not to be limited in scope by the specific embodiments described herein. Indeed, other various embodiments of and modifications to the present disclosure, in addition to those described herein, will be apparent to those of ordinary skill in the art from the foregoing description and accompanying drawings. Thus, such other embodiments and modifications are in the tended to fall within the scope of the present disclosure. Furthermore, the present disclosure has been described herein in the context of a particular implementation in a particular environment for a particular purpose, while those of ordinary skill in the art will recognize the usefulness is not limited thereto and the present disclosure may be beneficially implemented in any number of environments for any number of purposes. Thus, the claims set forth below are to be construed in view of the full breadth and spirit of the present disclosure as described herein.
Claims
1. A system, comprising:
- a transfer chamber, the transfer chamber arranged to transport a substrate between a plurality of locations;
- a first angled ion beam chamber, the first angled ion beam chamber coupled to the transfer chamber, to direct a first angled ion beam to the substrate;
- a vertical etch chamber, the vertical etch chamber coupled to the transfer chamber, to supply vertical ions to the substrate; and
- a second angled ion beam chamber, the second angled ion beam chamber coupled to the transfer chamber, to direct a second angled ion beam to the substrate.
2. The system of claim 1, wherein the first angled ion beam chamber is adapted to direct a first angled ion beam in a first reactive ambient, along a first trajectory at a first non-zero angle of incidence with respect to a perpendicular to a plane of the substrate,
- and wherein the first angled ion beam chamber is adapted to direct the second angled ion beam in a second reactive ambient, along a second trajectory at a second non-zero angle of incidence with respect to the perpendicular to the plane of the substrate.
3. The system of claim 1, wherein the vertical etch chamber comprises a reactive ion etch chamber.
4. The system of claim 1, wherein the transfer chamber, the first angled ion beam chamber, the vertical etch chamber, and the second angled ion beam chamber are maintained at vacuum and for allowing the substrate to be transported therebetween without being exposed to ambient pressure.
5. An apparatus, comprising:
- a plasma chamber coupled to receive power from a power supply;
- a process chamber, electrically coupled to the plasma chamber via a bias supply, the process chamber further including a substrate stage;
- an extraction plate, disposed between the plasma chamber and process chamber, and defining an angled ion beam; and
- a controller, coupled to at least one of: the power supply, the bias supply, and the substrate stage, the controller comprising: a processor; and a memory unit coupled to the processor, including an ion beam control routine, the ion beam control routine operative on the processor to control the angled ion beam, the ion beam control routine comprising an angle control processor to: receive an endpoint signal; and send a control signal to adjust operation of at least one of the power supply, bias supply, and substrate stage, based upon the endpoint signal.
6. The apparatus of claim 5, further comprising a gas manifold coupled to the plasma chamber, the ion beam control routine further comprising a gas flow processor, the gas flow processor to:
- adjust a flow of at least one gas from the gas manifold based upon the endpoint signal, wherein a gas composition in the plasma chamber is changed.
7. The apparatus of claim 4, wherein the angle control processor is adapted to adjust operating parameters affecting an angle of incidence of the angled ion beam on a substrate disposed on the substrate stage based upon the endpoint signal.
8. The apparatus of claim 7, wherein the operating parameters include at least one of a plasma power, a bias voltage between the plasma chamber and the substrate, and a separation between the extraction plate and the substrate.
9. The apparatus of claim 5, wherein the memory unit includes a database containing details of process parameters to be applied to etch operations to be performed for a given sequence of angled ion beam etch operations.
Type: Application
Filed: Aug 17, 2021
Publication Date: Dec 2, 2021
Applicant: Varian Semiconductor Equipment Associates, Inc. (Gloucester, MA)
Inventors: Kevin R. Anglin (Somerville, MA), Simon Ruffell (South Hamilton, MA)
Application Number: 17/404,438