Multi-pitch mesh overlay target for scan overlay metrology

Abstract

A superimposed metrology system having pitches in multiple directions in a single cell is disclosed. The overlay target may include a multi-layer structure on two or more layers of a unit of the sample according to a metrology recipe. The multi-layer structure may include a structure in each layer, the structures having one or more pitches in one or more periodic directions. The multilayer structure may include a structure having a first pitch in a first direction, a second pitch in a second direction, a third pitch in the first direction, and a fourth pitch in the second direction. At least one of the first pitch or the third pitch may be different from at least one of the second pitch or the fourth pitch.

Description

[0001] CROSS REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of U.S. Provisional Application Serial No. 63 / 400,131, filed on August 23, 2022, entitled “New OVL Metrology Target Design for Two-Dimensional Scanning Measurement,” with Yuval Lubashevsky, Itay Gdor, Daria Negri, and Eitan Hajaj as inventors, pursuant to 35 U.S.C. §119(e), the entire text of which is incorporated herein by reference. Technical Field

[0003] The present invention relates generally to overlay metrology, and more particularly to a system and method for overlay metrology that allows for compact pitch design of overlay targets. Background Art

[0004] The demand for decreasing feature size and increasing feature density has resulted in an increased need for accurate and efficient overlay metrology. Overlay metrology refers to the measurement of the relative alignment of layers on a sample such as, but not limited to, a semiconductor device.

[0005] The stacking target is usually formed on the surface of the wafer sample and may include cells with grating structures with various pitches in the overlapping layers. The wafer sample is usually mounted on a translation stage and translated so that the stacking target is sequentially moved into the measurement field of view. In a typical metrology system that employs the Move and Measure (MAM) method, the sample is static during each measurement. However, the time required for the translation stage to stabilize before measurement may negatively affect throughput.

[0006] Furthermore, various sources can introduce errors into the overlay metrology data. Furthermore, the footprint space on the wafer is valuable.

[0007] Therefore, it is desirable to provide systems and methods for eliminating the above-mentioned deficiencies. Summary of the invention

[0008] A stacking metrology system according to one or more illustrative embodiments of the present disclosure is disclosed. In one illustrative embodiment, the stacking metrology system may include a controller including one or more processors configured to execute program instructions, the program instructions causing the one or more processors to execute a metrology recipe. In another illustrative embodiment, the metrology recipe may include receiving detection signals from a stacking target of a sample (e.g., a wafer) from one or more detectors and determining one or more stacking measurements of the stacking target based on the detection signals. In another illustrative embodiment, the stacking target may include a multilayer structure on two or more layers of a unit of the sample. In another illustrative embodiment, the multilayer structure may include a structure in each layer, the structure having one or more pitches in one or more periodic directions. In another illustrative embodiment, the multilayer structure may include a structure having a first pitch in a first direction, a second pitch in a second direction, a third pitch in the first direction, and a fourth pitch in the second direction. In another illustrative embodiment, at least one of the first pitch or the third pitch may be different from at least one of the second pitch or the fourth pitch.

[0009] It should be understood that both the foregoing general description and the following "detailed description" are exemplary and illustrative only and do not necessarily limit the invention as claimed. The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the general description, serve to explain the principles of the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Many of the advantages of the present disclosure may be better appreciated by those skilled in the art by referring to the accompanying drawings.

[0011] Figure 1A is a conceptual diagram of an overlay metering system according to one or more embodiments of the present disclosure.

[0012] Figure 1B is a schematic diagram of an optical subsystem according to one or more embodiments of the present disclosure.

[0013] Figure 2A is a conceptual diagram of an illumination pupil plane distribution of a circular illumination light beam according to one or more embodiments of the present disclosure.

[0014] Figure 2B According to one or more embodiments of the present disclosure Figure 2A Conceptual diagram of the distribution of diffraction orders of a circular illumination beam in the collection pupil plane.

[0015] Figure 3 is a top view of a stacked object formed as an overlapping structure including two structures in two grid-like arrays according to one or more embodiments of the present disclosure.

[0016] Figure 4 is a top view of a stacked target formed as an overlapping structure including structures in a grid-like array and two gratings according to one or more embodiments of the present disclosure.

[0017] Figure 5 is a top view of a superimposed target according to one or more embodiments of the present disclosure, wherein the superimposed target is narrowed along a scanning direction to reduce an occupied area. DETAILED DESCRIPTION

[0018] The present disclosure has been particularly shown and described with respect to certain embodiments and specific features thereof. The embodiments described herein are considered to be illustrative rather than restrictive. It should be readily apparent to one of ordinary skill in the art that various changes and modifications in form and detail may be made without departing from the spirit and scope of the present disclosure. Reference will now be made in detail to the disclosed objects illustrated in the accompanying drawings.

[0019] A variety of overlay metrology techniques may be used to perform overlay metrology. For example, techniques include a static move and measure mode in which the sample is static during measurement and a scanning mode in which the illumination beam is scanned across the sample during measurement. In static scatterometry overlay (SCOL), the use of a charge coupled device (CCD) camera requires time to read and transfer the data to a buffer for storage and may require two separate measurements for each direction. Therefore, measuring the target is relatively time consuming. On the other hand, scanning-based scatterometry measurement techniques may be less time consuming and may include a fast detector to capture the time-varying interference signal generated when scanning the sample. The detector may be placed at an overlapping position between selected diffraction orders in the pupil plane to capture the time-varying interference signal when scanning the sample. Various scanning scatterometry superposition metrology techniques are described in: U.S. Patent Publication No. 2022 / 0034652, filed on February 17, 2021; U.S. Patent Application No. 17 / 119,536, filed on December 11, 2020; U.S. Patent Application No. 17 / 708,958, filed on March 30, 2022; U.S. Patent Application No. 17 / 709,104, filed on March 30, 2022; and U.S. Patent Application No. 17 / 709,200, filed on March 30, 2022; the entireties of which are incorporated herein by reference. Note that such scanning examples are non-limiting and that embodiments herein may include one or more detectors in a field plane and may include various types of detectors, such as one or more diode array sensors.

[0020] The embodiments herein may work well with scanning SCOL techniques, but are not necessarily limited to such techniques.

[0021] In some scanning methods, the scanning target may include a separate target and / or a separate unit for each direction (e.g., X direction and Y direction) that is measured separately. For example, two units may be placed sequentially, as shown in FIG. 6B of U.S. Patent Application No. 18 / 099,798, filed on January 20, 2023, the entire text of which is hereby incorporated by reference. Although U.S. Patent Application No. 18 / 099,798 discloses reducing overlay errors by reversing the pitch order of multilayer gratings in two or more units, the present disclosure may allow for a more compact (e.g., single unit) overlay target.

[0022] Embodiments of the present disclosure are directed to an overlay metrology system configured to determine overlay measurements of an overlay target having single cells with different pitches along each of two orthogonal directions, e.g., X and Y. Having different pitches in each direction allows avoiding crosstalk between overlay measurements in each direction so that data capture of corresponding time-varying X and Y signals can be clearly distinguished.

[0023] Avoiding crosstalk may mean that the X and Y pitch signals can be clearly distinguished from each other. For example, without the present disclosure, if the structures are not spaced differently in the X direction compared to the spacing in the Y direction, a single unit superposition target measured diagonally may cause crosstalk to occur. However, compared to this case, embodiments herein may allow crosstalk to be reduced by using at least one different spacing (i.e., pitch) of structures in each direction. For example, a grid of structures in a single layer having a spacing between rows (i.e., a first pitch) and a second spacing between columns (i.e., a second pitch) may be used (e.g., non-connected rectangles and / or squares in rows and columns). The other two pitches may be embodied in another layer having a grid of structures or in two other layers having gratings in each layer, which may provide at least four pitches. In addition, at least one pitch in each direction is different from each other. For example, the first pitch in the X direction may be different from one of the pitches in the Y direction, such as the second pitch of the grating pitch in the Y direction.

[0024] It should be considered herein that structures characterized by different pitches in each direction can potentially provide different advantages. Notably, these structures can effectively mitigate crosstalk, specifically within the measurement. For example, a scanning measurement of an overlay target can be performed in the X direction and also in the Y direction, and a scan can also be performed diagonally in both the X and Y directions. The measurement in each case can benefit from reduced crosstalk by being based on targets with different pitches in each direction. As the wafer footprint becomes increasingly dense and valuable, minimizing the footprint size of the overlay target can free up valuable space. This can increase wafer chip throughput.

[0025] Figure 1AA conceptual diagram illustrating an overlay metrology system 100 in accordance with one or more embodiments of the present disclosure.

[0026] In an embodiment, the overlay metrology system 100 includes an optical subsystem 102 configured to acquire one or more images from a sample 104 (eg, a wafer) for determining an overlay measurement.

[0027] In an embodiment, the overlay metrology system 100 includes a controller 122. The controller 122 may include one or more processors 124 and a memory 126. For example, the controller 122 may be configured to determine an overlay measurement based on a signal received from a detector of the optical subsystem 102.

[0028] Figure 1B A simplified schematic diagram illustrating optical subsystem 102 in accordance with one or more embodiments of the present disclosure.

[0029] In an embodiment, the optical subsystem 102 includes an illumination subsystem 106 and a light collection subsystem 110 .

[0030] The illumination subsystem 106 is configured to generate illumination in the form of one or more illumination beams 108 to illuminate the sample 104. The light collection subsystem 110 is configured to collect light (e.g., according to a metering recipe) from illuminating the sample 104. In addition, the one or more illumination beams 108 may be spatially confined so that they may illuminate selected portions of the sample 104. For example, each of the one or more illumination beams 108 may be spatially confined to illuminate a specific cell of an overlay target.

[0031] In an embodiment, the illumination beam 108 is split (e.g., via an additional beam splitter) before the sample 104 to produce an external beam (e.g., an auxiliary beam) for the purpose of phase reference (e.g., holography). For example, U.S. Patent Application No. 18 / 110,746, filed on February 16, 2023, the entire contents of which are hereby incorporated by reference, discloses an auxiliary beam that is split and combined with diffraction orders from a sample. For example, an external beam (e.g., a portion of the illumination beam 108) can overlap with selected diffraction orders from the sample 104 to produce a time-varying interference signal suitable for superposition measurements as disclosed herein. This configuration can reduce constraints on the design of the superposition target and can enable features with relatively small pitch that provide little or no overlap between diffraction lobes in the pupil plane.

[0032] For example, the overlay metrology system 100 may be configured to image a particular type of sample according to a metrology recipe. For example, the overlay metrology system 100 may be designed (configured) and / or programmed (e.g., programmed via program instructions) to calculate overlay measurements of a particular type of feature of the sample 104 (e.g., grating-on-grating target) according to a metrology recipe.

[0033] In an embodiment, the optical subsystem 102 may include a translation stage 116 to scan the sample 104 across a measurement field of view of the optical subsystem 102 during overlay measurements.

[0034] As previously described herein, the overlay metrology system 100 may include one or more detectors 112 for scanning overlay metrology. In embodiments, the one or more detectors 112 may include any type of optical detector known in the art suitable for capturing interference signals generated when the sample 104 is translated by the translation stage 116 and / or when the one or more illumination beams 108 are scanned by the optical subsystem 102. For example, the one or more detectors 112 may be a diode array sensor and / or a charge coupled device (CCD) sensor.

[0035] In an embodiment, one or more detectors 112 are positioned in collection pupil plane 114 so that diffraction orders emanating from sample 104 can be measured.

[0036] For example, performing scan-based overlay metrology may include receiving detection signals from one or more detectors 112 while the sample 104 is in motion, such that the detection signals are time-varying interference signals.

[0037] In an embodiment, the optical subsystem 102 may perform a scatterometry overlay measurement on a portion of the sample 104 having a overlay target, such as, but not limited to, a grating-on-grating target.

[0038] It is recognized herein that the distribution of diffraction orders of the illumination beam 108 generated by a periodic structure (e.g., a grating-on-grating target) can be affected by a variety of parameters, such as, but not limited to, the wavelength of the illumination beam 108, the angle of incidence of the illumination beam 108 in elevation and azimuth, the period (i.e., pitch) of the periodic structure, or the numerical aperture (NA) of the collecting lens. For example, the illumination subsystem 106, the collecting subsystem 110, and / or the superposition target can be configured to provide an overlapping distribution of zero-order diffraction and first-order diffraction in the collection pupil plane 114 of the collecting subsystem 110. The illumination subsystem 106 and / or the collecting subsystem 110 can be configured to determine or facilitate measurements of a grating-on-grating target having a selected periodic range that provides an overlapping distribution. As another example, the illumination subsystem, the collecting subsystem 110, and / or the superposition target can be configured to overlap the first-order diffraction from the superposition target with a portion of the illumination beam 108 (e.g., an external beam, an auxiliary beam, or the like). Furthermore, various components of the illumination subsystem 106 and / or the collection subsystem 110 (eg, a stop, pupil, or the like) may be adjusted to provide an overlap profile suitable for a given structure that produces a time-varying signal from which a superposition measurement may be determined.

[0039] The collection subsystem 110 may be configured to collect at least one of a 0 th diffraction order (eg, specular reflection) and + / −1 diffraction orders from the sample 104 associated with the diffraction of the illumination beam 108 .

[0040] In an embodiment, the optical subsystem 102 includes an objective lens 136 to focus the illumination beam 108 onto the sample 104 (e.g., onto a superimposed target having a structure positioned on two or more layers of the sample 104). The objective lens 136 may be configured to collect measurement light emitted from the sample 104 in response to the illumination beam 108 while the sample 104 is scanned along a scan direction.

[0041] The optical subsystem 102 can implement a variety of illumination beam distributions. For example, the illumination beam 108 can be circular, annular, and / or the like.

[0042] Figure 2A Conceptual diagram illustrating an illumination pupil plane distribution 200 for a circular illumination beam 204 in accordance with one or more embodiments of the present disclosure.

[0043] Figure 2B Describe one or more embodiments of the present disclosure Figure 2A 1. Conceptual diagram of a collection pupil plane distribution 202 of diffraction orders of a circular illumination beam 204. For example, the circular illumination beam 204, after emitting from the sample 104, can become a measurement beam that can collect light 138 and form circular diffraction orders in the collection pupil plane 114. For a target having pitch and edges in both the X and Y directions, diffraction orders are generated in the horizontal and vertical directions of the pupil plane, as shown by Figure 2B1 and 2. The circular diffraction orders in the X direction may include a zero (0) circular diffraction order 206a, a first (+1) X circular diffraction order 206c, a first (-1) X circular diffraction order 206b, a second (+1) X circular diffraction order 212c, and a second (-1) X circular diffraction order 212b. In the Y direction, the circular diffraction orders may include a zero (0) circular diffraction order 206a, a first (+1) Y circular diffraction order 206e, a first (-1) Y circular diffraction order 206d, a second (+1) Y circular diffraction order 212e, and a second (-1) Y circular diffraction order 212d. One or more detectors 112 may be placed to capture overlapping regions 208a, 208b of such diffraction orders. For example, detectors 112 (e.g., diode array sensors) may be placed in pupil plane 114 such that one or more detectors 112 capture light corresponding to diffraction orders in the X direction from detected regions 210c, 210b. Note that for clarity and simplicity, only X-direction detection regions 210c, 210b are labeled, but corresponding overlapping regions in the Y direction may be captured by similar detection regions in the Y direction (not shown). Note that detected regions 210c, 210b may be any size, such as less than, equal to, or greater than overlapping regions 208a, 208b.

[0044] When scanning diagonally, the signal may include diffraction orders emanating from structures having pitch in both the X and Y directions, and thus the superposition may be determined in both the X and Y directions using a single diagonal scan. Figure 2B Both X- and Y-direction diffraction orders from pitches in the X and Y directions are accounted for. For example, the (diagonally scanned) detection signal may include a first detection signal corresponding to diffraction orders in a first direction (e.g., the X direction), and a second detection signal corresponding to diffraction orders in a second direction (e.g., the Y direction). In an embodiment, determination of an overlay measurement may include determining a first direction overlay measurement based on the first detection signal; and determining a second direction overlay measurement based on the second detection signal. For example, the first direction overlay measurement may indicate an overlay between the first structure 310 and the second structure 308 in the X direction, which may be used to adjust a manufacturing process to reduce undesired overlay.

[0045] For example, the first detection signal may be based on (e.g., corresponding to) an overlap of the diffraction orders 206a, 210b, 212b, 210c, and / or 212c. For example, the first detection signal may be received from the X-direction detection areas 210c, 210b using a detector 112 (e.g., a photodiode detector) placed in each of the X-direction detection areas 210c, 210b. The second detection signal may be based on an overlap of the diffraction orders 206a, 210d, 212d, 210e, and / or 212e.

[0046] Furthermore, in this manner, determination of the overlay measurement may include: determining a first direction overlay measurement (e.g., X-direction overlay in the X direction) based on the first detection signal; and determining a second direction overlay measurement (e.g., Y-direction overlay) based on the second detection signal. Such determination may be based on differences between various overlap regions, such as differences in the time-varying light intensity of overlap region 208a and overlap region 208b to determine the X-direction overlay. In this manner, a single diagonal scan may be used to simultaneously determine overlay in two directions.

[0047] Figures 3 to 5 is an example of a superimposed target, where a pitch in the X direction that is different from the pitch in the Y direction allows for simultaneous data capture of corresponding time-varying signals in a manner that avoids crosstalk, so that the X and Y signals can be clearly distinguished. Figure 3 is a Moore target with a grid structure on two layers. Figure 4 is a three-layer overlay target with a grid structure on one layer and line / space features on two other layers. This allows measurements to be made between each of the grid and line / space layers for each respective direction. Figure 3 and 4 Both allow scanning diagonally between the X and Y directions to simultaneously determine X and Y overlay measurements or to be used to scan the X and Y directions independently. Figure 5 Describes how to use Figure 4 The superimposed targets are made smaller and narrower.

[0048] Figure 3 A top view 300 of a stacked target 304 formed as an overlapping structure including two sets of structures 308, 310 in two grid-like arrays is illustrated in accordance with one or more embodiments of the present disclosure.

[0049] In an embodiment, the superposition target 304 includes a multilayer structure on two or more layers of the unit of the sample 104. For example, the multilayer structure may include a structure in each layer, the structure having one or more pitches in one or more periodic directions in a single unit. In an embodiment, the superposition target herein may have (at least) four pitches, wherein at least one pitch in a first direction is different from another pitch in a second direction. For example, the superposition target may include a first and a third pitch in a first direction, and a second and a fourth pitch in a second direction. For example, at least one of the first and third pitches may be different from at least one of the second and fourth pitches. In this way, different pitches in each direction are achieved, thereby reducing crosstalk. Such pitches may be in the same layer (e.g., a grid pattern with two pitches, one pitch in each direction) and / or in different layers (e.g., a more conventional diffraction grating with a single pitch in a single direction).

[0050] In an embodiment, the stacking target 304 includes a multilayer structure 304 formed as an overlapping structure with different pitches on two or more layers of the sample 104. For example, the two or more layers of the sample 104 may include at least a first layer and a second layer (as shown). For example, the multilayer structure 304 may include at least two different first direction (e.g., X direction) pitches 320, 330 and at least two different second direction (e.g., Y direction orthogonal to the X direction) pitches 322, 332. The multilayer structure may include at least a first layer array of a first structure 310 having periodicity in the first direction and the second direction. This periodicity may be a first pitch 320 and a second pitch 322, so that the first structure 310 may include a first pitch 320 in the first direction and a second pitch 322 in the second direction.

[0051] In order to achieve two pitches in each direction, various additional layers with various structures may be used in addition to the layer with the grid structure. For example, a second layer of the structure 308 in the second grid may be used, such as Figure 3 Using a (first) grid and a second grid (having one grid on each layer) allows having four total pitches on only two layers in a single unit. By way of another example, two more layers (i.e., a second layer and a third layer) with gratings on each layer may be used, as shown by Figure 4 and 5 In this way, only three layers in a single unit are needed to achieve four pitches (ie, a grid with two pitches in one layer, and another two layers with gratings in each of the other two layers).

[0052] In an embodiment, the multilayer structure 304 may include a second layer array having a second structure 308 having periodicity in the first direction and the second direction. The second structure 308 may include a third pitch 340 in the first direction and a fourth pitch 350 in the second direction. The first pitch 320 and the third pitch 340 in the first direction may be different, and the second pitch 322 and the fourth pitch 350 in the second direction may be different.

[0053] Figure 4 A top view 400 of an overlapping structure 402 formed to include the structure 310 and two gratings 312 , 314 in a grid-like array is illustrated in accordance with one or more embodiments of the present disclosure.

[0054] In an embodiment, the multi-layer structure 304 further includes a second layer grating 312 on the second layer having a third pitch 340 in the first direction.

[0055] In an embodiment, the multilayer structure 304 further includes a third layer grating 314 on the third layer having a fourth pitch 350 in the second direction. The fourth pitch 350 may be different from the first pitch 320 and / or the third pitch 340. In this way, different pitches in each direction are achieved. Alternatively and / or in addition, the second pitch 322 may be different from the first pitch 320 and / or the third pitch 340. In this way, different pitches in each direction are achieved.

[0056] Figure 5 A top view 500 of a superposition target 502 is illustrated that is narrowed along a scan direction 306 to reduce footprint in accordance with one or more embodiments of the present disclosure. The illumination beam 108 is scanned along the scan direction 306. Scanning the superposition target 304 by a length equal to the pitch of the grating-on-grating target may result in a phase shift of 2π in each of the + / - 1 diffraction orders (in opposite directions) and the intensity captured by each of the one or more detectors 112 may oscillate via interference fringes.

[0057] In an embodiment, the multilayer structure is configured to be scanned separately along the first and second directions (eg, along the periodicity of the pitch) and / or along the third direction 306 (ie, diagonally). In an embodiment, the third direction 306 is different from the first and second directions.

[0058] In embodiments, this scanning may be used with a photodiode-based scanning scatterometry overlay (e.g., SCOLAR) system and / or method. For example, the illumination beam 108 may scan each target in the X direction and then in the Y direction, or vice versa. In another example, the illumination beam 108 may scan along a narrow diagonal periodic target (e.g., Figure 5 For example, the third direction 306 may be 45 degrees from the periodic first direction and the second direction, with a difference of no more than 10 degrees.

[0059] In an embodiment, a relatively narrow overlay target 502 is used, such as Figure 5. For example, the multi-layer structure 502 may have a scan length along the third direction 306 (i.e., the total length of the overlay target 502) that is greater than the width of the multi-layer structure 502 (i.e., the total width), where the width is measured orthogonally (i.e., 90 degrees) to the third direction 306. This may define a narrow overlay target 502 that includes edges that are parallel to the scan direction and are configured to scan in a third direction (e.g., diagonally) that is different from the first and second directions. For example, instead of performing a diagonal scan between the corners of a diamond shape (e.g., a rotated square overlay target)—where the far corners on each side protrude outward to the left and right—the design may be cut so that the outer corner edges are trimmed inwardly to be narrower in a sense. Using a narrower overlay target 502 saves space on the sample 104 for other features.

[0060] As shown, the illumination beam 108 may occupy a spot size that is smaller than the superimposed target 304 itself. However, it should be appreciated that Figures 3 to 5 The overlay targets and associated descriptions in are provided for illustrative purposes only and should not be construed as limiting.

[0061] Reference again Figure 1A to 1B , describes additional components of the optical subsystem 102 according to one or more embodiments of the present disclosure. For example, the controller 122 and processor 124 and various optical components are described in detail below for overlay metrology.

[0062] In an embodiment, the controller 122 determines a superposition measurement between layers (e.g., a first layer and a second layer) of the superposition target 304 along a measurement direction based on a comparison of the detection signals. For example, the controller 122 may compare the magnitude and / or phase of the detection signals to determine the superposition measurement. For example, U.S. Pat. No. 10,824,079, issued on November 3, 2020, which is incorporated herein by reference in its entirety, describes collecting diffraction orders in a pupil and further provides a specific relationship between superposition and measured intensity in a pupil plane. It should be considered herein that the systems and methods disclosed herein may extend the teachings of U.S. Pat. No. 10,824,079 to detection signals captured by one or more detectors placed in an overlap region between 0 and + / -1 diffraction orders. In particular, it should be considered herein that the superposition on the sample may be proportional to the relative phase shift between the two detection signals. In another example, the relative intensities of the diffraction orders in the pupil plane may be extracted from the detection signals. In this way, any superposition algorithm based on relative intensity differences of diffraction orders known in the art may be applied to determine the superposition measurement.

[0063] In an embodiment, the overlay metrology system 100 includes a controller 122 communicatively coupled to the optical subsystem 102. The controller 122 may include one or more processors 124 and a memory device 126 or memory. For example, the one or more processors 124 may be configured to execute a set of program instructions maintained in the memory device 126.

[0064] The one or more processors 124 of the controller 122 may include any processor or processing element known in the art. For the purposes of this disclosure, the term "processor" or "processing element" may be broadly defined to encompass any device having one or more processing or logic elements (e.g., one or more microprocessor devices, one or more application specific integrated circuit (ASIC) devices, one or more field programmable gate arrays (FPGAs), or one or more digital signal processors (DSPs)). In this sense, the one or more processors 124 may include any device configured to execute algorithms and / or instructions (e.g., program instructions stored in a memory). In one embodiment, the one or more processors 124 may be embodied as a desktop computer, a mainframe computer system, a workstation, an image computer, a parallel processor, a network computer, or any other computer system configured to execute a program configured to operate the overlay metrology system 100 or operate in conjunction with the overlay metrology system 100 as described throughout this disclosure. In addition, different subsystems of the overlay metrology system 100 may include processors or logic elements suitable for implementing at least a portion of the steps described in this disclosure. Therefore, the above description should not be interpreted as limiting the embodiments of the present disclosure but is merely illustrative. In addition, the steps described throughout the present disclosure may be performed by a single controller or alternatively multiple controllers. In addition, the controller 122 may include one or more controllers housed in a common housing or housed in multiple housings. In this way, any controller or combination of controllers may be individually packaged as a module suitable for integration into the system 100. In addition, the controller 122 may analyze or otherwise process data received from one or more detectors 112 and feed the data to additional components within the superposition metrology system 100 or external to the superposition metrology system 100.

[0065] Furthermore, the memory device 126 may include any storage media known in the art suitable for storing program instructions executable by the associated one or more processors 124. For example, the memory device 126 may include a non-transitory storage medium. As additional examples, the memory device 126 may include, but is not limited to, a read-only memory, a random access memory, a magnetic or optical storage device (e.g., a disk), a tape, a solid-state drive, and the like. It should be further noted that the memory device 126 may be housed in a common controller housing with the one or more processors 124.

[0066] In this regard, the controller 122 may perform any of the various processing steps associated with superposition metrology. For example, the controller 122 may be configured to determine control signals to direct or otherwise control the optical subsystem 102, or any component thereof. For example, the controller 122 may be configured to direct the translation stage 116 to translate the sample 104 along one or more measurement paths or scan zones to scan one or more superposition targets through the measurement field of view of the optical subsystem 102. By another example, the controller 122 may be configured to receive signals corresponding to detection signals from the one or more detectors 112. By another example, the controller 122 may determine correctable terms for one or more additional manufacturing tools based on the superposition measurements from the optical subsystem 102 as feedback and / or feedforward control of the one or more additional manufacturing tools.

[0067] In an embodiment, the controller 122 captures a detection signal detected by one or more detectors 112. The controller 122 may generally use any technique known in the art (such as, but not limited to, one or more phase-locked loops) to capture data such as, but not limited to, the magnitude or phase of the detection signal. In addition, the controller 122 may use any combination of hardware (e.g., circuitry) or software techniques to capture a detection signal (e.g., a detection signal) or any data associated with the detection signal.

[0068] Reference again Figure 1B , various components of the optical subsystem 102 are described in more detail according to one or more embodiments of the present disclosure.

[0069] In an embodiment, the illumination subsystem 106 includes an illumination source 128 configured to generate at least one illumination beam 108. The illumination from the illumination source 128 may include light of one or more selected wavelengths, including but not limited to ultraviolet (UV) radiation, visible radiation, or infrared (IR) radiation.

[0070] In an embodiment, the illumination subsystem 106 includes one or more optical components adapted to modify and / or adjust the illumination beam 108 and direct the illumination beam 108 to the sample 104. For example, the illumination subsystem 106 may include one or more illumination lenses 130 (e.g., to collimate the illumination beam 108, relay an illumination pupil plane 120 and / or an illumination field plane 132, or the like). In another embodiment, the illumination subsystem 106 includes one or more illumination control optics 134 to shape or otherwise control the illumination beam 108. For example, the illumination control optics 134 may include, but are not limited to, one or more field stops, one or more pupil stops, one or more polarizers, one or more filters, one or more beam splitters, one or more diffusers, one or more homogenizers, one or more trackers, one or more beam shapers, or one or more mirrors (e.g., static mirrors, translatable mirrors, scanning mirrors, or the like).

[0071] The collection subsystem 110 may include one or more optical components suitable for modifying and / or conditioning the collected light 138 from the sample 104. In one embodiment, the collection subsystem 110 includes one or more collection lenses 140 (e.g., to collimate the illumination beam 108, relay a pupil and / or field plane, or the like), which may include (but need not include) an objective lens 136. In another embodiment, the collection subsystem 110 includes one or more collection control optics 142 to shape or otherwise control the collected light 138. For example, the collection control optics 142 may include, but are not limited to, one or more field stops, one or more pupil stops, one or more polarizers, one or more filters, one or more beam splitters, one or more diffusers, one or more homogenizers, one or more tracking deflectors, one or more beam shapers, or one or more mirrors (e.g., static mirrors, translatable mirrors, scanning mirrors, or the like). In another example, the light collection subsystem 110 can include one or more light collection field planes 150 .

[0072] In an embodiment, the light collection subsystem 110 includes two or more collection channels 144, each collection channel 144 having a separate detector 112 (or multiple detectors 112). For example, the optical subsystem 102 may include one or more beam splitters 146 configured to split the collected light 138 into the collection channels 144. In addition, the beam splitter 146 may be a polarizing beam splitter, a non-polarizing beam splitter, or a combination thereof.

[0073] Reference again Figure 1A It should be noted herein that one or more components of the superposition metrology system 100 may be communicatively coupled to various other components of the system 100 in any manner known in the art. For example, the one or more processors 124 may be communicatively coupled to each other and to other components via a wired (e.g., copper wire, fiber optic cable, and the like) or wireless connection (e.g., RF coupling, IR coupling, WiMax, Bluetooth, 3G, 4G, 4G LTE, 5G, and the like). By way of another example, the controller 122 may be communicatively coupled to one or more components of the optical subsystem 102 via any wired or wireless connection known in the art.

[0074] In one embodiment, the one or more processors 124 may include any one or more processing elements known in the art. In this sense, the one or more processors 124 may include any microprocessor-type device configured to execute software algorithms and / or instructions. In one embodiment, the one or more processors 124 may be composed of the following: a desktop computer, a mainframe computer system, a workstation, an image computer, a parallel processor, or other computer systems (e.g., network computers) configured to execute programs configured to operate the superposition metrology system 100 as described throughout the present disclosure. It should be recognized that the steps described throughout the present disclosure can be implemented by a single computer system or alternatively multiple computer systems. In addition, it should be recognized that the steps described throughout the present disclosure can be implemented on any one or more of the one or more processors 124. In general, the term "processor" can be broadly defined to cover any device having one or more processing components that execute program instructions from the memory 126. In addition, different subsystems of the superposition metrology system 100 may include processors or logic elements suitable for implementing at least a portion of the steps described throughout the present disclosure. Therefore, the above description should not be interpreted as limiting the present disclosure but is merely illustrative.

[0075] Those skilled in the art will recognize that the components (e.g., operations), devices, objects, and accompanying discussions described herein are used as examples for conceptual clarity and that various configuration modifications are contemplated. Therefore, as used herein, the specific examples set forth and the accompanying discussions are intended to represent their more general class. In general, the use of any specific example is intended to represent its class, and the exclusion of specific components (e.g., operations), devices, and objects should not be considered limiting.

[0076] Those skilled in the art will appreciate that there are a variety of vehicles by which the processes and / or systems and / or other techniques described herein may be implemented (e.g., hardware, software, and / or firmware), and that the preferred vehicle will vary with the environment in which the processes and / or systems and / or other techniques are deployed. For example, if an implementer determines that speed and accuracy are most important, then the implementer may select a primarily hardware and / or firmware vehicle; alternatively, if flexibility is most important, then the implementer may select a primarily software implementation; or, yet alternatively, the implementer may select some combination of hardware, software, and / or firmware. Thus, there are several possible vehicles by which the processes and / or devices and / or other techniques described herein may be effected, none of which is inherently better than another, because any vehicle to be utilized is a choice dependent on the environment in which the vehicle will be deployed and the implementer's particular concerns (e.g., speed, flexibility, or predictability), any of which may vary.

[0077] The previous description is presented to enable one of ordinary skill in the art to make and use the invention as provided in the context of a particular application and its requirements. Various modifications to the described embodiments will be apparent to those skilled in the art, and the general principles defined herein may be applied to other embodiments. Therefore, the present invention is not intended to be limited to the specific embodiments shown and described, but should be accorded the widest scope consistent with the principles and novel features disclosed herein.

[0078] With respect to the use of substantially any plural and / or singular terms herein, those skilled in the art may translate from the plural to the singular and / or from the singular to the plural as the context and / or application requires. For clarity, various singular / plural permutations are not explicitly set forth herein.

[0079] All methods described herein may include storing the result of one or more steps of method embodiments in a memory. The result may include any one of the results described herein and may be stored in any manner known in the art. The memory may include any memory described herein or any other suitable storage media known in the art. After the result has been stored, the result may be accessed in the memory and used by any one of the methods or system embodiments described herein, formatted for display to the user, used by another software module, method or system, and the like. In addition, the result may be stored "permanently", "semi-permanently", "temporarily" or stored for a certain period of time. For example, the memory may be a random access memory (RAM), and the result may not necessarily be stored in the memory indefinitely.

[0080] It should be further considered that each of the embodiments of the method described above may include any other steps of any other method described herein.In addition, each of the embodiments of the method described above may be performed by any of the systems described herein.

[0081] The objectives described herein sometimes illustrate different components contained in or connected to other components. It should be understood that such depicted architectures are exemplary only, and in fact many other architectures that realize the same functionality can be implemented. In a conceptual sense, any arrangement of components to realize the same functionality is effectively "associated" so as to realize the desired functionality. Therefore, any two components combined in this article to realize a specific functionality can be considered to be "associated" with each other so as to realize the desired functionality, without considering the architecture or intermediate components. Similarly, any two components so associated can also be considered to be "connected" or "coupled" to realize the desired functionality, and any two components that can be so associated can also be considered to be "coupleable" to realize the desired functionality. Specific examples that can be coupled include but are not limited to physically matched and / or physically interactive components and / or wirelessly interactive and / or wirelessly interactive components and / or logically interactive and / or logically interactive components.

[0082] In addition, it should be understood that the present invention is defined by the appended claims. Those skilled in the art will understand that, in general, the terms used herein and particularly in the appended claims (e.g., the body of the appended claims) are generally intended to be "open" terms (e.g., the term "including" should be interpreted as "including but not limited to", the term "having" should be interpreted as "having at least", the term "includes" should be interpreted as "including but not limited to", and the like). Those skilled in the art will further understand that if a specific number of claim recitations is intended to be introduced, such intention will be expressly stated in the claim, and in the absence of such a statement, such intention does not exist. For example, as an aid to understanding, the appended claims below may contain the use of the introductory phrases "at least one" and "one or more" to introduce claim recitations. However, the use of such phrases should not be construed as implying that the introduction of a claim recitation by the indefinite article "a" or "an" limits any particular claim containing such introduced claim recitation to an invention containing only one such recitation, even if the same claim contains the introductory phrases "one or more" or "at least one" and an indefinite article such as "a" or "an" (e.g., "a" and / or "an" should generally be construed to mean "at least one" or "one or more"); the above applies equally to the use of definite articles used to introduce claim recitations. In addition, even if a specific number of introduced claim recitations is explicitly recited, one skilled in the art will recognize that such recitation should generally be construed to mean at least that number of recitations (e.g., the bare recitation (without other modifiers) of "two recitations" generally means at least two recitations or two or more recitations). Furthermore, in examples where a convention similar to “at least one of A, B, and C, and the like” is used, this construction is generally intended that those skilled in the art will understand the meaning of the convention (e.g., “a system having at least one of A, B, and C” will include, but is not limited to, systems having only A, only B, only C, both A and B, both A and C, both B and C, and / or both A, B, and C, and the like). In examples where a convention similar to “at least one of A, B, or C, and the like” is used, this construction is generally intended that those skilled in the art will understand the meaning of the convention (e.g., “a system having at least one of A, B, or C” will include, but is not limited to, systems having only A, only B, only C, both A and B, both A and C, both B and C, and / or both A, B, and C, and the like). Those skilled in the art will further understand that virtually any transition word and / or phrase, whether in the description, claims or drawings, presenting two or more alternative items should be understood to contemplate the possibility of including: one of the items, either of the items, or both of the items.For example, the phrase "A or B" will be understood to include the possibilities of "A" or "B" or "A and B."

[0083] It is believed that the present disclosure and its many attendant advantages will be understood from the foregoing description, and it will be appreciated that various changes may be made to the form, construction and arrangement of components without departing from the disclosed object or sacrificing all of its material advantages. The forms described are merely illustrative, and it is intended that such changes be covered and included by the appended claims. Furthermore, it should be understood that the invention is defined by the appended claims.

Claims

1. A superposition metering system, comprising: The lighting subsystem includes: an illumination source configured to generate an illumination beam; A photon collection system, comprising: one or more detectors; and an objective lens configured to collect measurement light emitted from a sample in response to the illumination beam while scanning the sample, wherein the sample includes a superimposed target according to a metrology recipe; and a controller communicatively coupled to the collection subsystem, the controller comprising one or more processors configured to execute program instructions, the program instructions causing the one or more processors to execute the metering recipe by: receiving, from the one or more detectors, detection signals from the superimposed target; determining one or more overlay measurements of the overlay target based on the detection signal; and wherein the stacking target according to the metrology recipe comprises a multilayer structure on two or more layers of the unit of the sample, the multilayer structure comprising a structure in each layer, the structure having one or more pitches in one or more periodic directions, The multilayer structure includes the structure having a first pitch in a first direction, a second pitch in a second direction, a third pitch in the first direction, and a fourth pitch in the second direction, wherein at least one of the first pitch or the third pitch is different from at least one of the second pitch or the fourth pitch. 2 . The overlay metrology system of claim 1 , wherein the scanning of the sample comprises one or more scans in one or more scanning directions, wherein the one or more scanning directions comprise the first direction and the second direction. 3 . The overlay metrology system of claim 1 , wherein the scanning of the sample comprises one or more scans in one or more scanning directions, wherein the one or more scanning directions comprises a third direction different from both the first direction and the second direction. 4 . The superposition metrology system according to claim 3 , wherein the detection signal comprises a first detection signal corresponding to the diffraction order in the first direction, and a second detection signal corresponding to the diffraction order in the second direction.

5. The overlay metrology system of claim 4, wherein the determining of the one or more overlay measurements comprises: determining a first directional superposition measurement based on the first detection signal; and A second directional superposition measurement is determined based on the second detection signal.

6. The superposition metrology system of claim 1, wherein the one or more detectors include at least one detector positioned in a pupil plane.

7. The overlay metrology system of claim 1, wherein the one or more detectors include at least one diode array sensor.

8. The superposition metrology system of claim 1, wherein an illumination pupil plane distribution of the illumination beam is circular.

9. The superposition metrology system of claim 1, wherein the illumination pupil plane distribution of the illumination beam is annular.

10. The superposition metrology system of claim 1, wherein the detection signal comprises a time-varying interference signal associated with an overlap between first and zeroth order diffraction from the multilayer structure.

11. The superposition metrology system of claim 1 , the illumination subsystem further comprising a beam splitter configured to generate an external beam as part of the illumination beam, wherein the detection signal comprises a time-varying interference signal associated with an overlap between a first-order diffraction from the multilayer structure and the external beam.

12. A superimposed metering system, comprising: A controller comprising one or more processors configured to execute program instructions, the program instructions causing the one or more processors to execute a metering recipe by: receiving detection signals of the superimposed targets from the sample from one or more detectors; determining one or more overlay measurements of the overlay target based on the detection signal; and wherein the stacking target according to the metrology recipe comprises a multilayer structure on two or more layers of the unit of the sample, the multilayer structure comprising a structure in each layer, the structure having one or more pitches in one or more periodic directions, The multilayer structure includes the structure having a first pitch in a first direction, a second pitch in a second direction, a third pitch in the first direction, and a fourth pitch in the second direction, wherein at least one of the first pitch or the third pitch is different from at least one of the second pitch or the fourth pitch.

13. The overlay metrology system of claim 12, wherein the controller is further configured to execute the metrology recipe by scanning the sample along one or more scanning directions, wherein the one or more scanning directions include the first direction and the second direction.

14. The overlay metrology system of claim 12, wherein the controller is further configured to execute the metrology recipe by scanning the sample along one or more scanning directions, wherein the one or more scanning directions include a third direction different from both the first direction and the second direction.

15. The superposition metrology system of claim 12, wherein the one or more detectors include at least one detector positioned in a pupil plane.

16. The overlay metrology system of claim 12, wherein the one or more detectors include at least one diode array sensor.

17. A superimposed metrology target, comprising: a multilayer structure on two or more layers of a unit cell of a sample, the multilayer structure comprising a structure in each layer having one or more pitches in one or more periodic directions, The multilayer structure includes the structure having a first pitch in a first direction, a second pitch in a second direction, a third pitch in the first direction, and a fourth pitch in the second direction, wherein at least one of the first pitch or the third pitch is different from at least one of the second pitch or the fourth pitch.

18. The stacking metrology target of claim 17, wherein the multi-layer structure comprises: A first layer array on a first layer has the first pitch in the first direction and the second pitch in the second direction.

19. The stacking metrology target of claim 17, wherein the multi-layer structure comprises: A second layer of gratings on the second layer has the third pitch in the first direction.

20. The stacking metrology target of claim 19, wherein the multi-layer structure comprises: The third layer of grating on the third layer has the fourth pitch in the second direction.

21. The stacking metrology target of claim 20, wherein the multi-layer structure is configured to scan along a third direction, wherein the third direction is different from the first direction and the second direction.

22. The stacking metrology target of claim 21, wherein the multi-layer structure has a scan length along the third direction, the scan length being greater than a width of the multi-layer structure, wherein the width is measured orthogonal to the third direction.

23. The stacking metrology target of claim 17, wherein the multi-layer structure is configured to scan along a third direction, wherein the third direction is different from the first direction and the second direction, wherein the third direction is 45 degrees away from the first direction and the second direction and differs by no more than 10 degrees.

24. The stacking metrology target of claim 17, wherein the multi-layer structure further comprises: The second layer array on the second layer has the third pitch in the first direction and the fourth pitch in the second direction.

Images