Mosaic overlay target

Abstract

A mosaic overlay target may include two or more cell groups distributed across a sample, where each cell group includes one or more cells, wherein each cell group is oriented to have at least one of mirror symmetry with respect to a central axis of the mosaic overlay target or rotational symmetry with respect to a central point of the mosaic overlay target. The group of cells may be configured according to a metrology recipe such that an image of the mosaic overlay target generated based on the metrology recipe contains metrology data suitable for two or more overlay measurements. A particular one of the overlay measurements may be based on a portion of the image associated with at least one of the group of cells. At least two of the two or more overlay measurements may be alternative measurements of a common property of the sample.

Description

[0001] CROSS REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the right under 35 U.S.C. §119(e) to U.S. Provisional Application Serial No. 63 / 411,640, filed on September 30, 2022 by inventor Yoel Feler and entitled “MOSAIC TARGETS AND THEIR MEASUREMENTS MEASUREMENT CONCEPTS,” the entire text of which is incorporated herein by reference. Technical Field

[0003] The present disclosure relates generally to overlay targets and, more particularly, to metrology targets that provide multiple alternative overlay measurements. Background Art

[0004] Overlay metrology measurements (e.g., overlay measurements) characterize the relative registration (or misalignment) of different layers of a sample. Image-based overlay techniques typically produce overlay measurements based on the relative positions of imaged overlay target features. As the size of fabricated features decreases and feature density increases, the demands on overlay metrology systems needed to characterize these features increase. Different overlay metrology techniques may offer different tradeoffs between accuracy, repeatability, or throughput. Therefore, there is a need to develop systems and methods to address the above-mentioned deficiencies. Summary of the invention

[0005] According to one or more illustrative embodiments of the present disclosure, a mosaic overlay target is disclosed. In one illustrative embodiment, the target includes two or more cell groups distributed across a sample, wherein each cell group includes one or more cells, and wherein each cell group is oriented to have at least one of mirror symmetry relative to a central axis of the mosaic overlay target or rotational symmetry relative to a central point of the mosaic overlay target. In another illustrative embodiment, the two or more cell groups are configured according to a metrology recipe so that one or more images of the mosaic overlay target generated according to the metrology recipe include metrology data suitable for two or more overlay measurements, wherein a particular one of the two or more overlay measurements is based on a portion of the one or more images associated with at least one of the two or more cell groups. In another illustrative embodiment, at least two of the two or more overlay measurements are surrogate measurements of a common property of the sample, wherein at least two of the two or more cell groups are configured according to the metrology recipe to provide surrogate portions of the metrology data associated with the surrogate measurements.

[0006] According to one or more illustrative embodiments of the present disclosure, an overlay metrology system is disclosed. In one illustrative embodiment, the system includes an illumination source configured to generate one or more illumination beams. In another illustrative embodiment, the system includes one or more optical elements configured to illuminate a mosaic overlay target on a sample with the one or more illumination beams when implementing a metrology recipe. In another illustrative embodiment, the target includes two or more cell groups distributed across the sample, wherein each cell group includes one or more cells, wherein each cell group is oriented to have at least one of mirror symmetry relative to a central axis of the mosaic overlay target or rotational symmetry relative to a central point of the mosaic overlay target. In another illustrative embodiment, the two or more cell groups are configured according to a metrology recipe such that one or more images of the mosaic overlay target generated according to the metrology recipe include metrology data suitable for two or more overlay measurements, wherein specific ones of the two or more overlay measurements are based on portions of the one or more images associated with at least one of the two or more cell groups. In another illustrative embodiment, at least two of the two or more overlay measurements are surrogate measurements of a common property of the sample, wherein at least two of the two or more unit groups are configured according to the metrology recipe to provide surrogate portions of the metrology data associated with the surrogate measurements. In another illustrative embodiment, the system includes one or more detectors to generate the one or more images of the mosaic overlay target based on the illumination from the one or more illumination beams when implementing the metrology recipe. In another illustrative embodiment, the system includes a controller. In another illustrative embodiment, the controller implements the metrology recipe by the steps of: receiving the one or more images of the mosaic overlay target; generating at least two overlay measurements of the sample based on the one or more images. In another illustrative embodiment, a particular one of the two or more overlay measurements is based on a portion of the one or more images associated with at least one of the two or more cell groups, wherein at least two of the two or more overlay measurements are substitute measurements of a common property of the sample, and wherein at least two of the two or more cell groups are configured according to the metrology recipe to provide substitute portions of the metrology data associated with the substitute measurements.

[0007] According to one or more illustrative embodiments of the present disclosure, an overlay metrology method is disclosed. In one illustrative embodiment, the method includes illuminating one or more mosaic overlay targets on a sample with one or more illumination beams according to a metrology recipe, wherein each of the mosaic overlay targets includes two or more cell groups distributed across the sample. In another illustrative embodiment, each cell group includes one or more cells, wherein each cell group is oriented to have at least one of mirror symmetry relative to a central axis of the mosaic overlay target or rotational symmetry relative to a central point of the mosaic overlay target, wherein the two or more cell groups are configured according to the metrology recipe so that one or more images of the mosaic overlay target generated according to the metrology recipe include metrology data suitable for two or more overlay measurements, and wherein a particular one of the two or more overlay measurements is based on a portion of the one or more images associated with at least one of the two or more cell groups. In another illustrative embodiment, the method includes generating the one or more images of the mosaic overlay target based on the illumination from the one or more illumination beams. In another illustrative embodiment, the method includes generating at least two overlay measurements of the sample based on the one or more images, wherein a particular one of the two or more overlay measurements is based on a portion of the one or more images associated with at least one of the two or more cell groups, wherein at least two of the two or more overlay measurements are substitute measurements of a common property of the sample, and wherein at least two of the two or more cell groups are configured according to the metrology recipe to provide substitute portions of the metrology data associated with the substitute measurements.

[0008] According to one or more illustrative embodiments of the present disclosure, a method for designing a mosaic overlay target is disclosed. In one illustrative embodiment, the method includes selecting two or more overlay measurements for generation with the mosaic overlay target. In another illustrative embodiment, the method includes designing two or more cell groups of the mosaic overlay target. In another illustrative embodiment, the target includes two or more cell groups distributed across a sample, wherein each cell group includes one or more cells, wherein each cell group is oriented to have at least one of mirror symmetry relative to a central axis of the mosaic overlay target or rotational symmetry relative to a central point of the mosaic overlay target, wherein the two or more cell groups are configured according to a metrology recipe, such that one or more images of the mosaic overlay target generated according to the metrology recipe include metrology data suitable for the two or more overlay measurements, and wherein a particular one of the two or more overlay measurements is based on a portion of the one or more images associated with at least one of the two or more cell groups. In another illustrative embodiment, at least two of the two or more overlay measurements are substitute measurements of a common property of the sample, wherein at least two of the two or more unit groups are configured according to the metrology recipe to provide substitute portions of the metrology data associated with the substitute measurements.

[0009] It should be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and do not necessarily limit the invention as claimed. The accompanying drawings, which are incorporated in and constitute a part of the 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 metrology system according to one or more embodiments of the present disclosure.

[0012] Figure 1B is a simplified schematic diagram of an overlay metrology subsystem in accordance with one or more embodiments of the present disclosure.

[0013] Figure 1C is a simplified schematic diagram depicting a first illumination pupil plane providing a single illumination beam at a normal incidence angle in accordance with one or more embodiments of the present disclosure.

[0014] Figure 1D is a simplified schematic diagram of a second illumination pupil plane depicting two illumination beams in a dipole configuration according to one or more embodiments of the present disclosure.

[0015] Figure 1E is a simplified schematic diagram of a third illumination pupil plane depicting four illumination beams in a quadrupole configuration according to one or more embodiments of the present disclosure.

[0016] Figure 2A is a simplified top view of a first design of a mosaic overlay target in accordance with one or more embodiments of the present disclosure.

[0017] Figure 2B is a simplified top view of a second design of a mosaic overlay target in accordance with one or more embodiments of the present disclosure.

[0018] Figure 2C A method for providing multiple alternative overlay measurements along different measurement directions according to one or more embodiments of the present disclosure Figure 2A A top view of the target's changes.

[0019] Figure 3 is a simplified top view of a cell of a mosaic overlay target having a box-in-box feature according to one or more embodiments of the present disclosure.

[0020] Figure 4A is a simplified side view of a unit cell of a mosaic overlay target having overlapping features according to one or more embodiments of the present disclosure.

[0021] Figure 4B According to one or more embodiments of the present disclosure Figure 4A Simplified top view of the cells in .

[0022] Figure 5 is a simplified side view of a cell containing features associated with a single patterning process on a single layer of a sample in accordance with one or more embodiments of the present disclosure.

[0023] Figure 6 is a flow chart illustrating steps performed in a method according to one or more embodiments of the present disclosure.

[0024] Figure 7 is a flow chart illustrating steps performed in a method for designing a mosaic overlay target according to one or more embodiments of the present disclosure. DETAILED DESCRIPTION

[0025] Reference will now be made in detail to the disclosed object, which is illustrated in the accompanying drawings. The present disclosure has been particularly shown and described with respect to specific embodiments and specific features thereof. The embodiments set forth herein are to be understood to be illustrative and not restrictive. It will be apparent to one of ordinary skill in the art that various changes and modifications may be made to the form and details without departing from the spirit and scope of the present disclosure.

[0026] Embodiments of the present disclosure relate to systems and methods for overlay metrology based on imaging a mosaic overlay target designed to provide multiple overlay measurements based on different portions of one or more images of the mosaic overlay target.

[0027] For the purposes of this disclosure, the term overlay is generally used to describe the relative position of features on a sample fabricated by two or more patterning steps (e.g., a photolithographic exposure and a subsequent etching step, a direct etching step, or the like), wherein the term overlay error describes the deviation of the features from the nominal configuration. For example, a multilayer device may include features patterned on multiple sample layers using different patterning steps for each layer, wherein the alignment of features between layers must generally be strictly controlled to ensure proper performance of the resulting device. Accordingly, overlay measurements may characterize the relative position of features on two or more of the sample layers. As another example, multiple patterning steps may be used to fabricate features on a single sample layer. These techniques (commonly referred to as double patterning or multi-patterning techniques) may facilitate the fabrication of high-density features approaching the resolution of a photolithographic system. Overlay measurements in this context may characterize the relative position of features from different photolithographic steps on this single layer. It should be understood that the examples and descriptions related to specific applications of overlay metrology throughout this disclosure are provided for illustrative purposes only and should not be construed as limiting the present disclosure.

[0028] In some embodiments, a mosaic overlay target includes a plurality of cell groups distributed across a sample, wherein each cell group may include one or more cells, and wherein different cell groups may include different feature arrangements suitable for facilitating overlay measurements.

[0029] A mosaic overlay target may be designed to facilitate multiple simultaneous overlay measurements (e.g., two or more overlay measurements) based on one or more images of the mosaic overlay target, wherein different overlay measurements are based on different portions of the images, including different groups of cells or combinations of different groups of cells. As used herein, the term simultaneous overlay measurement is used broadly to indicate that multiple overlay measurements may be generated based on a single set of one or more images of the mosaic overlay target (e.g., taken under different lighting and / or imaging conditions), based on different portions of the one or more images. It is recognized herein that some overlay measurement techniques may generate measurements based on a single image of the overlay target, while other techniques may generate measurements based on multiple images of the overlay target (e.g., taken under different lighting and / or imaging conditions). It is contemplated herein that a mosaic overlay target may enable great flexibility in overlay metrology, may efficiently utilize space on a sample (e.g., provide a relatively small target size), and / or may enable high throughput measurements.

[0030] As an illustration, an overlay metrology tool may illuminate a mosaic overlay target with illumination, collect light emitted from the mosaic overlay target in response to such illumination (e.g., sample light), and generate one or more images of the mosaic overlay target based on at least a portion of such sample light. These images may include any combination of field plane images (where the detector is positioned in a field plane conjugate to the mosaic overlay target (or a sample on which the mosaic overlay target is fabricated)) or pupil plane images (where the detector is positioned in a pupil plane associated with the angular distribution of light emitted from the sample).

[0031] Each cell group on the mosaic overlay target can be designed to facilitate overlay measurements made alone or in combination with one or more additional cell groups. In other words, each cell group can include features designed so that overlay measurements can be generated based on images of that cell group alone or based on images of two or more cell groups. Thus, the image of the mosaic overlay target can be viewed as a composite of the images of the various cell groups so that the various cell groups can be imaged simultaneously.

[0032] A cell may include any distribution of features associated with one or more patterning processes suitable for at least one overlay measurement. Furthermore, these features may be aperiodic or may be periodic (e.g., exhibiting distinct spatial frequencies) in one or more directions. For example, a cell may include overlapping features associated with two or more patterning processes such that an image of the cell may include information associated with the two or more processes. As another example, a cell may include features associated with a single patterning process. In this configuration, an overlay measurement may be based on a cell (or group of cells), each cell including features associated with a different patterning process.

[0033] In a general sense, a mosaic overlay target may include cells of any size or shape. However, in some applications, it may be desirable to design a cell group with rotational and / or mirror symmetry to mitigate undesirable effects, such as, but not limited to, tool induced shift (TIS) errors. For example, a cell group may include one or more pairs of cells (e.g., cell pairs) configured to have mirror symmetry relative to a central axis of the cell group and / or rotational symmetry relative to a central point of the cell group (e.g., 180 degree symmetry, 90 degree symmetry, or the like). As another example, a cell group may include a single cell with mirror and / or rotational symmetry. In addition, the various cell groups of the mosaic overlay target may be configured to all share a common symmetry (e.g., share a common central axis and / or central point), although in some cases, the cell groups may be intentionally offset according to overlay metrology techniques. In this configuration, the mosaic overlay target may include at least one cell group having one or more cell pairs configured with a selected symmetry and optionally a central cell group having a single cell also arranged with a selected symmetry.

[0034] The mosaic overlay target may support multiple overlay measurements based on different cell groups or cell group combinations. For example, different overlay measurements may be generated based on portions of one or more images of the mosaic overlay target associated with different cell groups or different cell group combinations.

[0035] It is recognized herein that the accuracy and / or sensitivity of overlay measurements may depend on a variety of factors, such as, but not limited to, the layout of features on the sample that are characterized during measurement (e.g., size and / or orientation of features, thickness of sample layers, or the like), the properties of the illumination used to facilitate the measurement (e.g., spectrum, polarization, angle of incidence, beam shape, or the like), the properties of light emitted from the sample used during measurement (e.g., spectrum, polarization, angle of emission, or the like), or the focal position of the sample (e.g., working distance between the sample and the overlay metrology tool). Thus, process variations across a particular sample and / or between a batch of samples (e.g., layer thickness variations, or the like) may affect both the actual overlay error (e.g., misalignment between sample layers) and the accuracy and / or sensitivity of a particular overlay measurement technique used to measure the overlay error.

[0036] Numerous overlay metrology techniques have been developed that may require or benefit from different layouts of features on a sample (e.g., different overlay target designs) and / or different configurations of overlay metrology tools (e.g., different illumination and / or collection conditions). These techniques may offer different tradeoffs between measurement accuracy, measurement sensitivity, measurement robustness to process variations, systematic errors, measurement speed (e.g., measurement throughput), or required space on a sample (e.g., required target size, required number or distribution of targets on a sample, or the like). Thus, different overlay metrology techniques implemented at a particular location on a sample may provide different results and / or may produce results with different qualities.

[0037] For example, field plane imaging techniques may determine overlay measurements based on the relative imaged positions of non-overlapping features from different patterning processes. These features may be non-periodic or periodic. Non-limiting examples of associated overlay targets include box-in-box targets, advanced imaging metrology (AIM) targets, or triple AIM (t-AIM) targets. As another example, scatterometry overlay (SCOL) techniques may generate overlay measurements based on pupil plane and / or field plane images of overlapping features from different patterning processes. In some cases, non-overlapping features are formed as overlapping periodic features and may be characterized as grating-on-grating features. In addition, these overlapping periodic features may have the same or different pitches. Non-limiting examples of associated overlay targets include grating-on-grating targets, Moore targets, or robust AIM targets.

[0038] It is contemplated herein that a mosaic overlay target may enable multiple overlay measurements based on different overlay techniques or variations thereof. For example, different cell groups may have different designs or different variations of a similar design.

[0039] In some embodiments, a mosaic overlay target is designed to enable overlay measurements along two or more measurement directions, some of which may be (but are not required to be) orthogonal. For example, a mosaic target may be designed to have features in a first group of one or more cell groups suitable for overlay measurements along a first measurement direction, and may be further designed to have features in a second group of one or more cell groups suitable for overlay measurements along a second measurement direction. As another example, a mosaic target may be designed to have features in one or more cell groups suitable for simultaneous overlay measurements along two or more measurement directions.

[0040] In some embodiments, the mosaic overlay target is designed to enable measurements between different layer combinations. For example, the mosaic overlay target may include three or more cell groups, each cell group having features in a different layer. In this way, overlay measurements between different layer combinations can be generated based on different combinations of associated cell groups.

[0041] In some embodiments, a mosaic overlay target is designed to enable alternative overlay measurements. As used herein, the term alternative overlay measurement is used to refer to multiple measurements of a particular quantity, such as, but not limited to, an overlay measurement between two particular sample layers along a particular measurement direction. For example, the alternative measurements may be based on different features or groups of features within a mosaic overlay target as disclosed herein. It is contemplated herein that these alternative overlay measurements may exhibit different performance characteristics, such as, but not limited to, sensitivity to overlay, measurement accuracy, or robustness to printing errors not related to overlay. Thus, a mosaic overlay target designed to provide alternative overlay measurements may provide increased flexibility and high performance (e.g., as measured by any suitable performance metric) in an overlay metrology process.

[0042] It is further contemplated herein that alternative overlay measurements from a mosaic overlay target may be utilized in various ways.

[0043] For example, an overlay metrology tool may capture one or more images of various mosaic overlay targets distributed across a sample using a set of common illumination and collection conditions (e.g., associated with a metrology recipe). The overlay metrology tool may then select a particular one of the alternative overlay measurements for each of the mosaic overlay targets based on the associated performance metric. Because the performance metric may vary across the sample, different selections from the alternative overlay measurements may be used for different mosaic overlay targets.

[0044] As another example, a mosaic overlay target may enable fine-tuning of a metrology recipe without the need to switch between different target designs. A metrology recipe may generally include a set of parameters associated with an overlay target design, illumination conditions for the overlay target, and / or collection conditions for imaging the overlay target. In this manner, a metrology recipe may specify conditions suitable for obtaining one or more images of an overlay target suitable for overlay measurement. The metrology recipe may further include one or more analysis steps for generating values ​​for overlay measurement based on the one or more images. It is contemplated herein that it may be desirable to adjust one or more aspects of a metrology recipe across samples and / or between batches of samples in response to variations in a manufacturing process. It should be further contemplated herein that a mosaic overlay target as disclosed herein may include different groups of cells with variations in sample features to enable multiple simultaneous metrology recipe variations. Furthermore, capturing additional images of the mosaic overlay target using different illumination and / or collection conditions (e.g., metrology recipe parameters) may enable additional fine-tuning of the metrology recipe.

[0045] Additional embodiments of the present disclosure relate to methods for designing a mosaic overlay target. For example, designing a mosaic overlay target may include selecting a layout of target features in two or more cell groups suitable for providing two or more different simultaneous overlay measurements based on one or more images of the mosaic overlay target.

[0046] Additional embodiments of the present disclosure are directed to an overlay metrology system adapted to image a mosaic overlay target and generate two other overlay measurements based on the image.

[0047] In some embodiments, the overlay metrology system is configured to illuminate the mosaic overlay target using off-axis illumination (e.g., oblique illumination with non-normal angle of incidence). Off-axis illumination may be well suited for, but is not limited to, reducing the pitch of resolvable periodic features and / or reducing cell size. The diffraction angle from the periodic features may be related to both the illumination wavelength and the pitch of the periodic features, where reducing the pitch increases the diffraction angle. Thus, off-axis illumination may enable capturing diffraction from a pitch that is less than normal illumination. As a non-limiting illustration, off-axis illumination may capture diffraction from a pitch less than 600 nm using illumination having a visible wavelength.

[0048] In some embodiments, the overlay metrology system illuminates the mosaic overlay target with two or more off-axis illumination beams (e.g., dipole distribution, quadrupole distribution, or the like). This illumination can be produced simultaneously or sequentially (e.g., producing multiple sequential images that can be combined for overlay measurement). In some embodiments, the illumination beams are arranged in a Littrow condition so that the distance between the poles corresponds to λ / pitch, where λ is the illumination wavelength. Littrow illumination can provide particularly robust measurements.

[0049] In some embodiments, the overlay metrology system illuminates the mosaic overlay target with a quadrupole distribution of illumination beams formed into two dipoles oriented along orthogonal directions, wherein the two dipoles have different properties (e.g., different polarizations, different spectral properties, or the like). The overlay metrology system may further include various components in the collection path to isolate the light associated with each dipole into different collection channels (e.g., polarizers, spectral filters, or the like). In this way, optically isolated overlay measurements along different measurement directions may be produced.

[0050] Reference Figures 1A to 7 , systems and methods for overlay metrology using mosaic overlay targets are described in more detail according to one or more embodiments of the present disclosure.

[0051] Figure 1A is a conceptual diagram illustrating an overlay metrology system 100 according to one or more embodiments of the present disclosure. In some embodiments, the overlay metrology system 100 may be characterized as an overlay metrology tool.

[0052] In some embodiments, the overlay metrology system 100 includes an overlay metrology subsystem 102 to acquire overlay signals from an overlay target based on any number of metrology recipes. For example, the overlay metrology subsystem 102 may direct illumination 104 to a mosaic overlay target 106 on a sample 108, collect light or other radiation (referred to herein as sample light 110) emitted from the mosaic overlay target 106, and generate one or more images of the mosaic overlay target 106 using one or more detectors 112. The images may include one or more field plane images from the detector 112 positioned at a field plane conjugate to the sample 108 (or at least one layer therein), and / or one or more pupil plane images from the detector 112 positioned at a pupil plane (e.g., a diffraction plane) associated with the angular distribution of light emitted from the mosaic overlay target 106.

[0053] The overlay metrology subsystem 102 may further generate two or more measurements based on the one or more images of the mosaic overlay target 106. For example, the overlay metrology subsystem 102 may generate different overlay measurements based on portions of the one or more images associated with different groups of cells of the mosaic overlay target 106.

[0054] In some embodiments, the overlay metrology system 100 includes a controller 114. The controller 114 may include one or more processors 116 configured to execute program instructions maintained on a memory 118 or storage medium. In this regard, the one or more processors 116 of the controller 114 may perform any of the various process steps described throughout the present disclosure. Furthermore, the controller 114 may be communicatively coupled to the overlay metrology subsystem 102 or any component thereof.

[0055] The one or more processors 116 of the controller 114 may include any processor or processing element known in the art. For 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 116 may include any device configured to execute algorithms and / or instructions (e.g., program instructions stored in the memory 118). In some embodiments, the one or more processors 116 may be embodied as a desktop computer, a mainframe computer system, a workstation, an image computer, a parallel processor, a networked computer, or any other computer system configured to execute a program configured to operate or operate in conjunction with the overlay metrology system 100, as described throughout this disclosure.

[0056] Furthermore, the different subsystems of the overlay metrology system 100 may include processors or logic elements suitable for performing at least a portion of the steps described in the present disclosure. Therefore, the above description should not be construed as limiting the embodiments of the present disclosure, but is merely illustrative. Furthermore, the steps described throughout the present disclosure may be performed by a single controller 114 or alternatively multiple controllers. Additionally, the controller 114 may include one or more controllers housed in a common housing or multiple housings. In this way, any controller or combination of controllers may be individually packaged as a module suitable for integration into the overlay metrology system 100.

[0057] The memory 118 may include any storage medium known in the art suitable for storing program instructions executable by the associated one or more processors 116. For example, the memory 118 may include a non-transitory storage medium. By way of another example, the memory 118 may include, but is not limited to, a read-only memory (ROM), a random access memory (RAM), a magnetic or optical storage device (e.g., a disk), a tape, a solid-state drive, and the like. By further note, the memory 118 may be housed in a common controller housing with the one or more processors 116. In some embodiments, the memory 118 may be remotely located relative to the physical location of the one or more processors 116 and the controller 114. For example, the one or more processors 116 of the controller 114 may access a remote memory (e.g., a server) that is accessible via a network (e.g., the Internet, an intranet, and the like).

[0058] Furthermore, the overlay tool may be configurable to generate an overlay signal (e.g., using the controller 114) based on any number of metrology recipes that define conditions for generating one or more images of the mosaic overlay target 106 suitable for two or more overlay measurements. For example, the metrology recipe may include design parameters of the mosaic overlay target 106 or a unit group thereof, such as, but not limited to, the distribution of target features, the pitch of target features, the size of target features (e.g., width, sidewall angle, or the like), the orientation of target features, or the sample height during measurement (e.g., the working distance between the sample 108 and the overlay metrology subsystem 102). As another example, the metrology recipe may include illumination parameters (e.g., properties of the illumination 104), such as, but not limited to, spectrum, polarization, illumination angle (e.g., in elevation and / or azimuth), or illumination field size (e.g., spot size of the illumination 104). As another example, a metrology recipe may include collection parameters associated with light (e.g., portions of the sample light 110) used to image the mosaic overlay target 106, such as, but not limited to, spectrum, polarization, collection angle (e.g., in altitude and / or azimuth), or collection field size. As another example, a metrology recipe may include parameters associated with one or more detectors 112 used to generate one or more images of the mosaic overlay target 106, such as, but not limited to, gain settings or measurement timing settings. As another example, a metrology recipe may include one or more steps to generate at least two overlay measurements based on the one or more images of the mosaic overlay target 106. These steps may (but are not required to) be performed by the controller 114. As an illustration, some overlay techniques may generate overlay measurements by determining symmetry centers of non-overlapping features associated with different patterning processes in one or more field plane images and determining overlay measurements based on the relative positions of these symmetry centers. As another illustration, some overlay techniques may generate overlay measurements based on interference patterns of overlapping features associated with different patterning processes captured using field plane and / or pupil plane images.

[0059] Reference Figure 2A to 2B , the mosaic overlay target 106 is described in more detail according to one or more embodiments of the present disclosure.

[0060] In some embodiments, the mosaic overlay target 106 includes two or more cell groups 202 spatially distributed across the mosaic overlay target 106, wherein each cell group 202 includes one or more cells 204. In addition, each cell 204 may include target features (referred to herein as features) associated with one or more patterning processes. Figure 2A to 2B Instead, cells 204 are depicted with a hatching pattern to illustrate the associated regions of mosaic overlay object 106.

[0061] Figure 2Ais a simplified top view of a first design of a mosaic overlay target 106 in accordance with one or more embodiments of the present disclosure. Figure 2B is a simplified top view of a second design of a mosaic overlay target 106 in accordance with one or more embodiments of the present disclosure.

[0062] exist Figure 2A and 2B In each of the above, the mosaic overlay target 106 is depicted as a series of cells 204 shown as squares, where cells 204 that share a common shading pattern are associated with a common cell group 202. In a general sense, the mosaic overlay target 106 may include two or more cell groups 202, each cell group having one or more cells 204. Furthermore, the cells 204 may generally have any shape and the depicted squares are merely illustrative.

[0063] As an illustration, Figure 2A The mosaic overlay object 106 in FIG. 1 includes 18 cell groups 202 (labeled 202-1 to 202-18), each formed by two cells 204, which can be referred to as cell pairs. As another illustration, Figure 2B The mosaic overlay target 106 in FIG. 1 includes 16 cell groups 202 (labeled 202-1 to 202-8 and 202-11 to 202-18) each having two cells 204 and a central cell group 202 (labeled 202-0) having a single cell 204. However, it should be understood that the cell groups 202 are not limited to the following. Figure 2A and 2B 204 and in some embodiments may have three or more units 204.

[0064] Reference Figures 3 to 5 , various non-limiting feature layouts are described according to one or more embodiments of the present disclosure. In a general sense, the mosaic overlay target 106 can be designed to facilitate multiple overlay measurements (e.g., two or more overlay measurements), where each overlay measurement is based on one or more cell groups 202. Any cell 204 within any of the cell groups 202 can include features associated with a single patterning process or multiple patterning processes, where different patterning processes can be on a common layer (e.g., for overlay measurements associated with multiple patterning techniques) or on different layers (e.g., for overlay measurements between different layers). Different cell groups 202 can include features on different layers or combinations of layers. In addition, different cell groups 202 can have different designs and / or layouts of corresponding features. In other words, there is no requirement for similarity or difference between target features (or more generally cells 204) in different cell groups 202. Therefore, each cell group 202 can have a fully customizable design and different overlay techniques can be used to generate overlay measurements based on features in different cell groups 202.

[0065] The features within any particular cell 204 may have any layout suitable for overlay measurement. For example, the features within any cell 204 may be non-periodic or may be periodic (e.g., exhibiting distinct spatial frequencies) in one or more directions. It is recognized herein that periodic features may produce discrete diffraction orders, particularly when illuminated by an angularly limited illumination beam 104, which may aid in determining overlay. For example, the periodic structure may improve the signal-to-noise ratio associated with an image of the feature (e.g., a resolved image in a field plane image or discrete diffraction orders in a pupil plane image) and thus improve measurement accuracy relative to non-periodic features.

[0066] It should be noted that Figures 3 to 5 Different non-limiting target designs suitable for providing an overlay measurement between a first feature 302 associated with a first patterning process and a second feature 304 associated with a second patterning process are depicted. In particular, Figures 3 to 5 A non-limiting example is depicted in which first feature 302 is positioned on first layer 306 of a sample 108 and second feature 304 is positioned on second layer 308 of sample 108. Thus, the illustrated example may be suitable for determining overlays between layers of sample 108. However, it should be understood that these descriptions are purely for illustrative purposes and not limitations of the present disclosure. For example, it should be noted that sample 108 may include any number of layers on substrate 310 and may include additional layers above, below, and / or between first layer 306 and second layer 308 in some embodiments.

[0067] Figure 3 A non-limiting configuration of cell 204 containing a box-in-box feature associated with two patterning processes on two layers of sample 108 is depicted. Figure 3 is a simplified top view of a cell 204 of a mosaic overlay target 106 having a box-in-box feature according to one or more embodiments of the present disclosure. As an illustration, this cell 204 may be Figure 2B In addition, an overlay measurement may be generated based on this single cell 204.

[0068] like Figure 3 , the first feature 302 may correspond to the center box and the second feature 304 may correspond to the outer frame, wherein the first feature 302 and the second feature 304 do not overlap. In this way, an overlay measurement between the first and second exposures may be determined based on the relative positions of the first feature 302 and the second feature 304 (e.g., as may be observed in a field plane image of the mosaic overlay target 106). For example, when there is no overlay error, the first feature 302 may be centered within the second feature 304 in the X and / or Y directions, such that any deviation from this configuration may be due to overlay error in the X and / or Y directions.

[0069] Figures 4A to 4B A non-limiting configuration of cell 204 containing overlapping features associated with two patterning processes on two layers of sample 108 is depicted. Figure 4A is a simplified side view of a cell 204 of a mosaic overlay target 106 having overlapping features in accordance with one or more embodiments of the present disclosure. Figure 4B According to one or more embodiments of the present disclosure Figure 4A 204 in a simplified top view. As an illustration, this unit 204 may be suitable for Figure 2A to 2B Any one of the unit groups 202 in .

[0070] like Figures 4A to 4B As depicted in , first feature 302 may include a first set of periodic features and second feature 304 may correspond to a second set of periodic features. This configuration may be referred to as a grating-on-grating structure and may produce diffraction orders associated with first feature 302 and second feature 304 individually or in combination (e.g., double diffraction). In some embodiments, as Figures 4A to 4B , the first feature 302 and the second feature 304 have a common pitch (or more generally a periodicity) so that the diffraction orders from the first feature 302 and the second feature 304 overlap and interfere. In some embodiments, although not shown, the first feature 302 and the second feature 304 have different pitches (or more generally a periodicity). This configuration may also be referred to as a Moore structure. In this configuration, the diffraction orders from the first feature 302 and the second feature 304 may have different angles and may partially overlap, although this is not a requirement. In addition, this structure may produce Moore diffraction at different angles (e.g., double diffraction) based on the difference between the pitches of the first feature 302 and the second feature 304.

[0071] First features 302 and / or second features 304 may generally have any periodic distribution along one or more directions and thus may be suitable for facilitating overlay measurements along one or more directions. For example, first features 302 and / or second features 304 may include line / space patterns having any pitch or duty cycle along any direction. Furthermore, either first features 302 or second features 304 may be arranged at two or more feature pitches. As an illustration, either of the features may be segmented at a coarse pitch and a fine pitch.

[0072] The first feature 302 and the second feature 304 of any particular cell 204 may, but are not required to, be intentionally offset along one or more measurement directions. Figures 4A to 4B A configuration with an intended shift f0 is illustrated. In some embodiments, the induced shift is at least an order of magnitude smaller than the size of the cell 204 (eg, the length of the cell 204 in the direction of the intended shift).

[0073] It is contemplated herein that a mosaic overlay target 106 including at least some of the cell groups 202 containing grating-on-grating structures may facilitate overlay measurement using a variety of techniques. Overlay measurement using grating-on-grating structures is generally described in the following patents: U.S. Pat. No. 7,277,172, issued on October 2, 2007; U.S. Pat. No. 7,616,313, issued on November 11, 2009; U.S. Pat. No. 8,004,679, issued on August 23, 2011; U.S. Pat. No. 7,884,936, issued on February 8, 2011; U.S. Pat. No. 8,848,186, issued on September 30, 2014; and U.S. Pat. No. 9,739,702, issued on August 22, 2017; all of which are incorporated herein by reference in their entirety. For example, a zero-order SCOL technique may be based on including cells having a common periodicity but having different expected offsets (e.g., ±f 0,1 and ±f 0,2 ). As another example, the first-order SCOL technique may be based on two unit groups 202 including grating-on-grating structures having a common periodicity but with different expected offsets (e.g., ±f0). As another example, the Moore technique may utilize a first unit group 202 including one or more units 204 in which the first features 302 have a first pitch (P) and the second features 304 have a second pitch (Q) and a second unit group 202 including one or more units 204 in which the first features 302 have a second pitch (Q) and the second features 304 have the first pitch (P). In this configuration, the overlay error may induce a shift of the Moore diffraction along the opposite direction to facilitate self-calibration and self-reference overlay measurement. It should be understood that these examples are merely illustrative and should not be construed as limiting the present disclosure. In any of these configurations, the mosaic overlay target 106 may substantially increase measurement efficiency (e.g., processing power). Unlike existing SCOL techniques in which individual cells 204 with different expected offsets (f0) are measured individually, the mosaic overlay target 106 may enable simultaneous measurement of cells 204 or cell groups 202 with different expected offsets (f0) to increase processing capabilities. In addition, different cell groups 202 with different variations of expected offsets (f0), pitches, or the like may be disposed on the same mosaic overlay target 106 so that alternative measurements with different parameters may be generated based on one or more measurements (e.g., field plane images, pupil plane images, or the like) of the mosaic overlay target 106.

[0074] Figure 5 is a simplified side view of a cell 204 including a feature 502 associated with a single patterning process on a single layer (e.g., first layer 306 or second layer 308) of a sample 108 in accordance with one or more embodiments of the present disclosure. As an illustration, this cell 204 may be suitable for Figure 2A to 2B Any one of the unit groups 202.

[0075] In this paper, it is considered that based on similar Figure 5 Overlay measurements are generated for two or more cell groups 202 of the cell groups depicted in the figure, each cell group having features associated with different patterning processes. For example, a first cell group 202 having features associated with a first patterning process and a second cell group 202 having features associated with a second patterning process can be operated as an advanced imaging metrology (AIM) target so that overlay measurements associated with the first and second patterning processes can be generated using any suitable overlay technique. However, it should be noted that these first and second cell groups 202 can be distributed at any location across the mosaic overlay target 106. This method can be extended to generate overlay measurements between more than two patterning processes on the same or different layers. For example, a first cell group 202 having features associated with a first patterning process, a second cell group 202 having features associated with a second patterning process, and a third cell group 202 having features associated with a third patterning process can be operated as a three-AIM (t-AIM) target so that overlay measurements associated with the first and second patterning processes can be generated using any suitable overlay technique.

[0076] Again, generally refer to Figure 2A to 2B , additional considerations for designing the mosaic overlay target 106 are described in more detail according to one or more embodiments of the present disclosure.

[0077] In some embodiments, at least some of the cell groups 202 may be designed to have mirror symmetry with respect to a central axis and / or rotational symmetry with respect to a central point (e.g., rotational invariance). Such symmetry may be beneficial in mitigating specific noise or error sources in the measurement, such as, but not limited to, tool induced shift (TIS). In the case of rotational symmetry, such a cell group 202 may be invariant for rotation at any angle, such as, but not limited to, 90 degrees (e.g., 90 degree rotational symmetry) or 180 degrees (e.g., 180 degree rotational symmetry). It should be noted that such symmetry may refer to the distribution of target features in the cell group 202 (or the cells 204 therein) across the mosaic overlay target 106 and the shape and orientation of the associated cells 204. For example, the cells 204 at symmetric locations within the cell group 202 may have a common size to provide the desired symmetry across the mosaic overlay target 106.

[0078] As an illustration, Figure 2A The unit groups 202-1 to 202-18 and Figure 2BThe cell pairs in the cell groups 202-1 to 202-8 and 202-11 to 202-18 are distributed with 180-degree rotational symmetry around the center point 206. As another illustration, the cell group 202-0 having a single cell 204 may exhibit mirror symmetry along the vertical center axis 208 or the horizontal center axis 210. As another illustration, the cell group 202-0 having a single cell 204 may exhibit rotational symmetry (e.g., 90-degree or 180-degree rotational symmetry) relative to the center point 206. It should be noted that although Figure 2A and 2B Only the location and shape of the cells 204 are depicted, but target features within the cells 204 of any particular cell group 202 may be configured so that the cell group 202 has a desired symmetry.

[0079] In some embodiments, one or more cell groups 202 are designed to share a common center of symmetry with the mosaic overlay target 106 (or with other cell groups 202) as a whole under certain conditions, such as, but not limited to, zero overlay conditions (e.g., conditions in which features associated with different cell groups 202 are printed without unintentional overlay errors). Figure 2A and 2B , all of the cell groups 202-0 to 202-18 may be 180 degrees rotationally symmetric relative to the center point 206. However, as previously described herein, features within the cell group 202 may be printed with an intentional (e.g., designed) overlay offset that may shift the associated center of symmetry of the cell group 202.

[0080] The ability of the mosaic overlay target 106 to facilitate multiple simultaneous metrology measurements will now be described in greater detail in accordance with one or more embodiments of the present disclosure.

[0081] The mosaic overlay target 106 may be designed to facilitate two or more simultaneous metrology measurements, where each measurement is based on one or more images (e.g., one or more field plane images and / or one or more pupil plane images) of the mosaic overlay target 106. For example, a first metrology measurement may be generated based on a first group of one or more cell groups 202, a second metrology measurement may be generated based on a second group of one or more cell groups 202, and so on. In this example, the first, second, and third groups of cell groups 202 include unique combinations of cell groups 202 from the mosaic overlay target 106. However, in some embodiments, some cell groups 202 may be included in multiple groups of cell groups 202 and thus may be used in different ways to generate multiple metrology measurements.

[0082] It is contemplated herein that the mosaic overlay target 106 can provide great flexibility and efficiency in metrology applications. For example, the mosaic overlay target 106 can enable simultaneous overlay measurements between many sample layers and / or simultaneous alternative metrology measurements of common aspects of the sample 108 (e.g., based on different measurement techniques and / or different feature geometries).

[0083] The mosaic overlay target 106 may be configured to provide simultaneous metrology measurements along multiple measurement directions, which may (but are not required to) be orthogonal. Figure 2A In the context of the description, the cell groups 202 in the upper left and lower right quadrants (e.g., cell groups 202-1 to 202-9) can be configured to provide metrology measurements along a first direction (e.g., the X direction), while the cell groups 202 in the upper right and lower left quadrants (e.g., cell groups 202-10 to 202-18) can be configured to provide metrology measurements along a second direction (e.g., the Y direction).

[0084] In some embodiments, the mosaic overlay target 106 is configured to provide simultaneous metrology measurements between multiple different patterning processes. For example, the mosaic overlay target 106 may include multiple cell groups 202, each cell group having features associated with a different patterning process. Figure 2A , the unit groups 202-1 to 202-9 may each include features suitable for X-direction overlay measurement on different layers of the sample 108. Similarly, the unit groups 202-10 to 202-18 may each include features suitable for Y-direction overlay measurement on different layers of the sample 108. For example, the unit group 202-1 may include features suitable for X-direction measurement on a first layer, the unit group 202-10 may include features suitable for Y-direction measurement on a first layer, the unit group 202-2 may include features suitable for X-direction measurement on a second layer, the unit group 202-11 may include features suitable for Y-direction measurement on a second layer, and so on. In addition, the features on each unit group 202 may include features oriented along the X or Y direction that are suitable for X or Y direction measurement, respectively, such as but not limited to Figure 5 . In this configuration, simultaneous overlay measurements between any combination of nine sample layers along two measurement directions can be generated based on one or more images of the mosaic overlay target 106. For example, this target can be manufactured to have approximately the same size as a conventional AIM target suitable for overlay measurements of two layers or a t-AIM target suitable for overlay measurements of three layers. Therefore, the mosaic overlay target 106 can provide high measurement efficiency (e.g., high processing power). In addition, this technology can be extended to any number of sample layers.

[0085] In some embodiments, at least some of the cell groups 202 of the mosaic overlay target 106 are configured to provide surrogate measurements of common parameters of the sample 108 (e.g., overlay measurements between two specific patterning processes along a specific measurement direction). In this way, the mosaic overlay target 106 can enable robust and flexible measurements.

[0086] As previously described herein, any particular cell group 202 or combination of cell groups 202 may be designed to provide metrology measurements. In some embodiments, the mosaic overlay target 106 may include: a first group of cell groups 202 designed to provide a first overlay measurement between two specific patterning processes along a specific measurement direction; and at least a second group of cell groups 202 designed to provide at least a second overlay measurement between the same two specific patterning processes along the same specific measurement direction. However, the first and second groups of cell groups 202 may include features with different layouts. Thus, the first and second overlay measurements may be generated using different overlay metrology techniques or variations of the same technique. In either case, the measurement accuracy, measurement sensitivity, and / or robustness of the measurement to process deviations on the sample 108 may be different for the first and second overlay measurements.

[0087] As an illustration, Figure 2C A method for providing multiple alternative overlay measurements along different measurement directions according to one or more embodiments of the present disclosure Figure 2A A top view of the target's changes.

[0088] exist Figure 2C , the cell groups 202 in the upper left and lower right quadrants (e.g., cell groups 202-1 to 202-9) can be configured to provide metrology measurements along a first direction (e.g., the X direction), while the cell groups 202 in the upper right and lower left quadrants (e.g., cell groups 202-10 to 202-18) can be configured to provide metrology measurements along a second direction (e.g., the Y direction).

[0089] also, Figure 2C The mosaic overlay target 106 includes a first group (cell groups 202-1, 202-2, 202-4, and 202-5) of cell groups 202 having features (e.g., first features 302) on a first layer 306 suitable for measurement in a first direction but having different cell designs. For example, the cells 204 within this first group of cell groups 202 may all have periodicity in the first direction, but may have different pitches, feature widths (e.g., duty cycles of line / space patterns), fine segmentation, or any other differences. Similarly, Figure 2CThe mosaic overlay target 106 includes a second group (cell groups 202-3, 202-6, 202-7, 202-8, and 202-9) of cell groups 202 having features (eg, second features 304) on a second layer 308 suitable for first direction measurement but having different cell designs.

[0090] Figure 2C The mosaic overlay target 106 further includes a third group (cell groups 202-10, 202-11, 202-13, and 202-14) of cell groups 202 having features (e.g., first features 302) on the first layer 306 suitable for second direction measurement but having different cell designs. For example, the cells 204 within this third group of cell groups 202 may all have periodicity in the second direction, but may have different pitches, feature widths (e.g., duty cycles of line / space patterns), fine segmentation, or any other differences. Figure 2C The mosaic overlay target 106 also includes a fourth group (cell groups 202-12, 202-15, 202-16, 202-17, and 202-18) of cell groups 202 having features (eg, second features 304) on the second layer 308 suitable for second direction measurement but having different cell designs.

[0091] In this configuration, an overlay measurement between the first layer 306 and the second layer 308 along the first direction can be generated based on any combination of the cell groups 202 from the first group and the second group, and an overlay measurement between the first layer 306 and the second layer 308 along the second direction can be generated based on any combination of the cell groups 202 from the third group and the fourth group. In particular, Figure 2C The mosaic overlay target 106 may provide 20 combinations of cell groups 202 along each direction and thus provide 20 alternative overlay measurements between the first layer 306 and the second layer 308 along each direction.

[0092] However, it should be understood that Figure 2Cand associated descriptions are provided for illustrative purposes only and should not be construed as limiting. For example, the mosaic overlay target 106 may generally include any number of groups of cell groups 202 in any arrangement suitable for any number of alternative overlay measurements. As another example, the mosaic overlay target 106 may provide alternative measurements using any overlay metrology technique and any associated cell design. In this manner, the mosaic overlay target 106 may provide alternative measurements using a SCOL technique utilizing grating-on-grating features. In this case, different cell groups 202 may include cells 204 having different intended offsets (f0) as well as (or instead of) different pitches, feature widths (e.g., duty cycle of a line / space pattern), fine segmentation, or any other differences. As another example, the mosaic overlay target 106 may include one or more groups of cell groups 202 suitable for overlay measurement using a first overlay metrology technique (e.g., field plan imaging technique or the like), and one or more additional groups of cell groups 202 suitable for overlay measurement using a second overlay metrology technique (e.g., SCOL technique or the like).

[0093] Reference Figure 6 , a method for providing overlay metrology of an alternative overlay measurement from a mosaic overlay target 106 is described in accordance with one or more embodiments of the present disclosure.

[0094] Figure 6 is a flow chart illustrating steps performed in method 600 according to one or more embodiments of the present disclosure. Applicants should note that the embodiments and enabling techniques previously described herein in the context of the overlay metrology system 100 should be interpreted as extending to method 600. However, it should be further noted that method 600 is not limited to the architecture of the overlay metrology system 100.

[0095] In some embodiments, the method 600 includes a step 602 of illuminating one or more mosaic overlay targets 106 on the sample 108, wherein each mosaic overlay target 106 includes two or more cell groups 202, and wherein at least two of the two or more cell groups 202 are configured according to a metrology recipe to provide surrogate overlay measurements of a common parameter based on one or more images of corresponding portions of the mosaic overlay target 106 generated according to the metrology recipe. For example, the common parameter may be an overlay between two specific process steps along a specific measurement direction.

[0096] In some embodiments, the method 600 includes a step 604 of generating one or more images of each mosaic overlay target 106 based on a metrology recipe. For example, the metrology recipe may define parameters associated with illumination of the mosaic overlay target 106 (e.g., spectrum, polarization, angle of incidence, or the like), parameters associated with collecting light for image formation from the mosaic overlay target 106 (e.g., spectrum, polarization, collection angle), detector parameters, or any other parameters of an overlay metrology tool that may affect overlay measurements.

[0097] In some embodiments, the method 600 includes a step 606 of generating at least one overlay measurement of a common parameter from each mosaic overlay target 106 .

[0098] It is contemplated herein that alternative overlay measurements enabled by the mosaic overlay target 106 may be utilized in various ways within the spirit and scope of the present disclosure. As previously described herein, the alternative overlay measurements may provide different accuracy, sensitivity, and / or robustness to process variations based on specific physical properties of the sample 108 at specific locations of a particular mosaic overlay target 106. Because the alternative overlay measurements may be generated based on a single capture of one or more images of the mosaic overlay target 106 (e.g., based on different portions of the associated images), the measurement processing power may be substantially higher than measuring separate targets and the primary cost of generating the alternative overlay measurements is associated only with the computational resources required to process the images.

[0099] In some embodiments, step 606 may include generating at least some of the alternative overlay measurements enabled by the mosaic overlay targets 106 for at least some of the mosaic overlay targets 106. These alternative overlay measurements may then be used individually and / or combined to generate a composite overlay measurement. For example, step 606 may include combining a plurality of alternative overlay measurements using any suitable technique (e.g., using averaging, weighted averaging, or any suitable technique) to generate a composite overlay measurement that may be more accurate, more sensitive, and / or more robust than any of the individual alternative measurements. Such a composite overlay measurement may be generated for a plurality of mosaic overlay targets 106 distributed across at least one sample 108 and may provide an accurate and sensitive metrology that is relatively highly robust to process variations. Furthermore, the availability of a plurality of alternative overlay measurements enables mitigation of pattern placement error (PPE) or other inaccuracy issues.

[0100] In some embodiments, step 606 may include generating a single one of the alternative pair measurements for at least some of the mosaic pair targets 106. For example, a particular one of the alternative pair measurements having an accuracy and / or sensitivity above a selected threshold (or more generally a quality threshold) may be generated. As an illustration, it may be computationally more efficient to generate a single measurement per mosaic pair target 106 (or a single measurement per direction per mosaic pair target 106) based on a selected cell group 202. As another illustration, it may be the case that process variations in the position of a particular mosaic pair target 106 may result in one or more of the alternative pair measurements being inaccurate or invalid. In such cases, these alternative measurements may be discarded. As long as at least one measurement based on at least one cell group 202 meets the desired threshold, a valid measurement may be obtained from a particular mosaic pair target 106. Thus, the overall measurement processing capacity may remain high.

[0101] Reference is now made Figure 7 , Figure 7 FIG. is a flow chart illustrating the steps performed in a method 700 for designing a mosaic pair target 106 in accordance with one or more embodiments of the present disclosure. The applicant notes that the embodiments and enabling techniques previously described herein in the context of the pair metrology system 100 should be construed as extending to the method 700. However, it should be further noted that the method 700 is not limited to the architecture of the pair metrology system 100.

[0102] It is contemplated herein that it is generally desirable to provide pair measurements within a particular tolerance. However, the particular tolerance requirements may be different for different applications and / or may change over time. As an illustration, the pair tolerance may be characterized as -N < OVL1 < N for one layer and as -M < OVL2 < M for another layer. As another illustration, the pair tolerance may be characterized as -N < OVL1 < N and -M < 2*OVL1 + OVL2 < M. In a general sense, it is desirable to determine the pair within a tolerance sufficient to maintain the electrical robustness of the printed features. As the feature size of the manufactured features decreases, the pair measurement tolerances may become increasingly complex. For example, it may be necessary to implement complex requirements between multiple layers and / or develop non-linear requirements associated with the relationships between different layers.

[0103] It is contemplated herein that the mosaic pair targets 106 as disclosed herein may implement simultaneous or selective pair measurements based on different cell groups 202 and possibly different measurement techniques or algorithms. In this way, a user may be able to meet various pair measurement tolerances or considerations.

[0104] Furthermore, it may be the case that process variations may change the sensitivity of any particular cell group 202. For example, variations in printed line width due to process variations may affect the diffraction efficiency from target features and, in turn, affect measurement sensitivity. Accordingly, it may be desirable to design the mosaic overlay target 106 to include different cell groups 202 having different feature characteristics (e.g., feature widths or the like). In this configuration, the various cell groups 202 may be evaluated in real time based on specific printing characteristics to provide overlay measurements within selected tolerances.

[0105] In some embodiments, the method 700 includes a step 702 of selecting two or more overlay measurements for simultaneous generation with the mosaic overlay target 106, wherein at least two of the two or more overlay measurements correspond to alternative measurements of a common parameter of the sample 108. For example, the two or more overlay measurements may correspond to measurements along two or more directions or measurements between different combinations of patterning processes (e.g., overlay measurements between different combinations of three or more patterning processes on one or more layers). Furthermore, the common parameter may refer to an overlay measurement associated with specific two patterning processes in a specific direction, such that alternative measurements may generate values ​​for this common parameter using different techniques (e.g., associated with different metrology recipes or variations of metrology recipes).

[0106] In some embodiments, method 700 includes designing two or more unit groups 202 having features designed according to a metrology recipe such that one or more images of a mosaic overlay target 106 produced according to this metrology recipe may include a step 704 for generating metrology data for two or more metrology measurements selected in step 702.

[0107] Reference Figure 1B , various additional aspects of the overlay metrology subsystem 102 are described in greater detail according to one or more embodiments of the present disclosure.

[0108] Figure 1B is a simplified schematic diagram of an overlay metrology subsystem 102 in accordance with one or more embodiments of the present disclosure.

[0109] In some embodiments, the overlay metrology subsystem 102 includes an illumination subsystem 120 for generating illumination in the form of one or more illumination beams 122 to illuminate the sample 108 and a collection subsystem 124 for collecting light from the illuminated sample 108 (eg, sample light 110 ).

[0110] In some embodiments, the illumination subsystem 120 includes an illumination source 126 configured to generate at least one illumination beam 122. The illumination from the illumination source 126 may include light of one or more selected wavelengths, including, but not limited to, ultraviolet (UV) radiation, visible radiation, or infrared (IR) radiation. The illumination source 126 may include any type of illumination source suitable for providing the at least one illumination beam 122. In some embodiments, the illumination source 126 is a laser source. For example, the illumination source 126 may include, but not limited to, one or more narrowband laser sources, broadband laser sources, supercontinuum laser sources, white light laser sources, or the like. In this regard, the illumination source 126 may provide an illumination beam 122 having high coherence (e.g., high spatial coherence and / or temporal coherence). In some embodiments, the illumination source 126 includes a laser sustained plasma (LSP) source. For example, the illumination source 126 may include, but not limited to, an LSP lamp, an LSP bulb, or an LSP cavity suitable for housing one or more elements that can emit broadband illumination when excited into a plasma state by a laser source.

[0111] In embodiments having two or more illumination beams 122, a variety of techniques may be used to generate these beams. In some embodiments, the illumination subsystem 120 includes two or more apertures at the illumination field plane 132. In some embodiments, the illumination subsystem 120 includes one or more beam splitters to split the illumination from the illumination source 126 into two or more illumination beams 122. In some embodiments, at least one illumination source 126 directly generates two or more illumination beams 122. In a general sense, each illumination beam 122 may be considered part of a different illumination channel, regardless of the techniques by which the various illumination beams 122 are generated.

[0112] In some embodiments, the illumination subsystem 120 includes one or more optical components suitable for modifying and / or adjusting the one or more illumination beams 122 and directing the one or more illumination beams 122 to the sample 108. For example, the illumination subsystem 120 may include one or more illumination lenses 128 (e.g., to collimate the one or more illumination beams 122, to relay an illumination pupil plane 130 and / or an illumination field plane 132, or the like). In some embodiments, the illumination subsystem 120 includes one or more illumination control optics 134 to shape or otherwise control the one or more illumination beams 122. 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 apodizers, one or more beam shapers, or one or more mirrors (e.g., static mirrors, translatable mirrors, scanning mirrors, or the like).

[0113] In some embodiments, the overlay metrology subsystem 102 includes an objective lens 136 to focus the one or more illumination beams 122 onto the sample 108 (eg, an overlay target having overlay target elements positioned on two or more layers of the sample 108 ).

[0114] In some embodiments, the one or more illumination beams 122 may be angularly constrained on the sample 108 so that the periodic structure in the one or more cells 204 of the mosaic overlay target 106 may produce discrete diffraction orders. In addition, the one or more illumination beams 122 may be spatially constrained so that they may illuminate selected portions of the sample 108. For example, each of the one or more illumination beams 122 may be spatially constrained to the size of the mosaic overlay target 106. In this way, the one or more illumination beams 122 may fully illuminate (e.g., overfill) the mosaic overlay target 106.

[0115] In some embodiments, the collection subsystem 124 includes one or more detectors 112, wherein any detector 112 may be positioned at a collection field plane 138 conjugate to the mosaic overlay target 106, or at a collection pupil plane 140 (e.g., a diffraction plane) associated with the angular distribution of the sample light 110.

[0116] The collection subsystem 124 may include one or more optical elements suitable for modifying and / or conditioning the sample light 110 from the sample 108. In some embodiments, the collection subsystem 124 includes one or more collecting lenses 142 (e.g., to collimate the sample light 110, to relay a pupil and / or field plane, or the like), which may include, but is not required to include, the objective lens 136. In some embodiments, the collection subsystem 124 includes one or more collection control optics 144 to shape or otherwise control the sample light 110. For example, the collection control optics 144 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 apodizers, one or more beam shapers, or one or more mirrors (e.g., static mirrors, translatable mirrors, scanning mirrors, or the like).

[0117] In some embodiments, the overlay metrology subsystem 102 includes a translation stage 146 for positioning the sample 108 relative to the objective 136 during measurement.

[0118] In some embodiments, the collection subsystem 124 includes two or more collection channels 148, each channel having at least one detector 112. For example, Figure 1B, the overlay metrology subsystem 102 may include one or more beam splitters 150 configured to split the sample light 110 into collection channels 148. Furthermore, the beam splitter 150 may be a polarizing beam splitter, a non-polarizing beam splitter, or a combination thereof.

[0119] In some embodiments, Figure 1B As illustrated in , the overlay metrology subsystem 102 includes a beam splitter 152 for combining the illumination subsystem 120 and the collection subsystem 124 so that the objective lens 136 can both direct the illumination 104 to the sample 108 and collect the sample light 110 from the sample 108.

[0120] Reference Figures 1C to 1E , the illumination and collection profiles are described in more detail according to one or more embodiments of the present disclosure.

[0121] In a general sense, the overlay metrology subsystem 102 may illuminate the mosaic overlay target 106 with any combination of one or more illumination beams 122 in any distribution.

[0122] Figure 1C 1 is a simplified schematic diagram of a first illumination pupil plane 130 depicting a single illumination beam 122 providing a normal angle of incidence in accordance with one or more embodiments of the present disclosure. For example, the single illumination beam 122 is centered within a boundary 154 of the illumination pupil plane 130.

[0123] Figure 1D 1 is a simplified schematic diagram of a second illumination pupil plane 130 depicting two illumination beams 122 in a dipole configuration according to one or more embodiments of the present disclosure. This dipole configuration may be well suited for, but not limited to, overlay measurements along an axis separating the two illumination beams 122. Furthermore, the two illumination beams 122 may provide any combination of incident angles. For example, Figure 1D , the two illumination beams 122 may be symmetric in the illumination pupil plane 130 to provide opposite angles of incidence, although this is not a requirement.

[0124] In some embodiments, the two illumination beams 122 are configured (e.g., according to a metrology recipe) to satisfy the Littrow condition for a periodic structure in one or more cells 204 of the mosaic overlay target 106. Under the Littrow condition, the spacing between the illumination beams 122 is equal to λ / pitch, where λ is the wavelength of the illumination beams 122 and pitch is the pitch of the target structure (e.g., along an axis connecting the two illumination beams 122). In this configuration, the first-order diffraction (e.g., specular reflection) of the illumination beam 122 from the associated feature of the mosaic overlay target 106 propagates in the opposite direction of the incident direction of the illumination beam 122. It is contemplated herein that the Littrow condition can provide relatively robust measurements. However, strict adherence to the Littrow condition is not required. In some cases, the separation between the illumination beams 122 in the dipole is selected to be within a specific tolerance of the features in the one or more cells 204.

[0125] Figure 1E is a simplified schematic diagram of a third illumination pupil plane 130 depicting four illumination beams 122 in a quadrupole configuration according to one or more embodiments of the present disclosure. A quadrupole configuration can be viewed as having two dipoles oriented orthogonally. For example, Figure 1E Depicted is a first dipole having illumination beams 122a, 122b directed along the X direction and a second dipole having illumination beams 122c, 122d directed along the Y direction. Figure 1D The description can also be applied to Figure 1E For example, the quadrupole configuration of illumination beams 122a-122d may satisfy the Littrow condition for features oriented along the X and Y directions, noting that the separation distances of the dipoles along the X and Y directions may be different. Figure 1E The separation distance of the two dipoles in is equal, but this is not a requirement.

[0126] The overlay metrology subsystem 102 may be configured in various ways to image the mosaic overlay target 106 with multiple illumination beams 122. In some embodiments, a single image may be generated based on simultaneous illumination of the mosaic overlay target 106 with multiple illumination beams 122. In this configuration, only one collection channel 148 may be required. In some embodiments, the overlay metrology subsystem 102 sequentially illuminates the mosaic overlay target 106 with one or more illumination beams 122 and sequentially generates corresponding images. When various overlay measurements are generated, the images may be analyzed individually (e.g., by the controller 114) or may be combined (e.g., summed, averaged, or the like).

[0127] In some embodiments, the overlay metrology subsystem 102 including two collection channels 148 may generate separate (e.g., isolated) images from different illumination beams 122. This configuration may be particularly useful for, but not limited to, optically isolating overlay measurements along different directions. For example, in the case of quadrupole illumination, one or more first images may be generated in the first collection channel 148 based on a first dipole (e.g., illumination beams 122a, 122b), and one or more second images may be generated in the second collection channel 148 based on a second dipole (e.g., illumination beams 122c, 122d). Furthermore, the illumination beams 122 may be directed to the mosaic overlay target 106 simultaneously or sequentially. For example, the illumination beams 122a, 122c may be directed to the sample 108 first, followed by the illumination beams 122b, 122d.

[0128] The isolated image may be produced using any technique known in the art. Continuing with the above quadrupole example, the illumination beams 122 in the first and second dipoles may have different properties (e.g., different spectra, different polarizations, or the like). In addition, the collection subsystem 124 may include various components (e.g., a beam splitter 150 and / or collection control optics 144 in any of the collection channels 148) to separate or isolate the associated sample light 110 on the detectors 112 in the respective channels. For example, the beam splitter 150 and / or collection control optics 144 may include or operate as a spectral filter, a polarizer, or the like.

[0129] In addition, generally refer to Figures 1C to 1E , each illumination beam 122 may have any desired shape corresponding to the incident angle profile and different illumination beams 122 may have different shapes. Various profiles of illumination beams 122 and associated measurement conditions that may be implemented as part of one or more metrology recipes are generally described in U.S. Patent Publication No. 2022 / 0357674, published on November 10, 2022, which is incorporated herein by reference in its entirety.

[0130] The objects depicted herein sometimes illustrate different components that are contained in or connected to other components. It should be understood that these depicted architectures are merely exemplary, 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 that the desired functionality is realized. Therefore, any two components combined to realize a specific functionality herein can be considered to be "associated" with each other so that the desired functionality is realized, regardless of the architecture or intermediate components. Similarly, any two components so associated can also be considered to be "connected" or "coupled" to each other to realize the desired functionality, and any two components that can be so associated can also be considered to be "coupleable" to each other to realize the desired functionality. Specific examples that can be coupled include (but are not limited to) physically interactive and / or physically interactive components and / or wirelessly interactive and / or wirelessly interactive components and / or logically interactive and / or logically interactive components.

[0131] It is believed that through the foregoing description, the present disclosure and its many attendant advantages can be understood, and it will be apparent that various changes can be made to the form, construction and arrangement of components without departing from the disclosed object or without sacrificing all its material advantages. The described form is merely illustrative, and the appended claims are intended to cover and include such changes. In addition, it should be understood that the invention is defined by the appended claims.

Claims

1. A mosaic overlay target, comprising: two or more cell groups distributed across the sample, wherein each cell group comprises one or more cells, wherein each cell group is oriented to have at least one of mirror symmetry with respect to a central axis of the mosaic overlay target or rotational symmetry with respect to a central point of the mosaic overlay target, wherein the two or more cell groups are configured according to a metrology recipe such that one or more images of the mosaic overlay target generated according to the metrology recipe contain metrology data suitable for two or more overlay measurements, wherein a particular one of the two or more overlay measurements is based on a portion of the one or more images associated with at least one of the two or more cell groups, Wherein at least two of the two or more overlay measurements are surrogate measurements of a common property of the sample, wherein at least two of the two or more cell groups are configured according to the metrology recipe to provide surrogate portions of the metrology data associated with the surrogate measurements.

2. The mosaic overlay target of claim 1, wherein the common properties of the samples include: Overlay measurement associated with two or more patterning processes along a specific measurement direction.

3. The mosaic overlay target of claim 1 , wherein the two or more measurements include: Overlay measurement along two or more directions.

4. The mosaic overlay target of claim 1 , wherein the surrogate measurement comprises: Overlay measurements produced using two or more different overlay metrology techniques.

5. The mosaic overlay target of claim 4, wherein at least one of the two or more different overlay metrology techniques comprises: Scatterometry overlay metrology.

6. The mosaic overlay target of claim 4, wherein at least one of the two or more different overlay metrology techniques comprises: Imaging overlay metrology technology.

7. The mosaic overlay target of claim 1, wherein at least one of the two or more unit groups comprises: One or more cell pairs, each cell pair comprising two cells, wherein the two cells are oriented to have at least one of mirror symmetry relative to the central axis of the mosaic overlay target or rotational symmetry relative to the central point of the mosaic overlay target.

8. The mosaic overlay target of claim 1, wherein at least one of the two or more unit groups comprises: A single unit centered on the center point of the mosaic overlay target, wherein the single unit has at least one of mirror symmetry relative to the center axis of the mosaic overlay target or rotational symmetry relative to the center point of the mosaic overlay target.

9. The mosaic overlay target of claim 1, wherein each of the one or more cells in at least one of the two or more cell groups is 180 degree rotationally symmetric.

10. The mosaic overlay target of claim 1, wherein the one or more cells in at least one of the two or more groups of cells include periodic features.

11. The mosaic overlay target of claim 10, wherein the periodic features are periodic along a single direction corresponding to a measurement direction.

12. The mosaic overlay target of claim 10, wherein the periodic feature is periodic along two directions corresponding to two measurement directions.

13. The mosaic overlay target of claim 1, wherein the one or more cells in at least one of the two or more cell groups comprise overlapping features on two or more layers of the sample.

14. The mosaic overlay target of claim 13, wherein the overlay features include: Periodic characteristics.

15. The mosaic overlay target of claim 14, wherein the periodic features on the two or more layers have a common periodicity.

16. The mosaic overlay target of claim 14, wherein the periodic features on the two or more layers have different pitches along a particular direction.

17. The mosaic overlay target of claim 14, wherein the periodic features on the two or more layers have different pitches along a particular measurement direction.

18. The mosaic overlay target of claim 14, wherein the periodic features on the two or more layers have different pitches along different measurement directions.

19. An overlay metrology system comprising: an illumination source configured to generate one or more illumination beams; One or more optical elements configured to illuminate a mosaic overlay target on a sample with the one or more illumination beams when implementing a metrology recipe, wherein the mosaic overlay target comprises: two or more cell groups distributed across the sample, wherein each cell group comprises one or more cells, wherein each cell group is oriented to have at least one of mirror symmetry with respect to a central axis of the mosaic overlay target or rotational symmetry with respect to a central point of the mosaic overlay target; one or more detectors for generating one or more images of the mosaic overlay target based on the illumination with the one or more illumination beams when implementing the metrology recipe; and A controller comprising one or more processors configured to execute program instructions, thereby causing the one or more processors to implement the metrology recipe by: receiving the one or more images of the mosaic overlay target; and At least two overlay measurements of the sample are generated based on the one or more images, wherein a particular one of the two or more overlay measurements is based on a portion of the one or more images associated with at least one of the two or more cell groups, wherein at least two of the two or more overlay measurements are substitute measurements of a common property of the sample, wherein at least two of the two or more cell groups are configured according to the metrology recipe to provide substitute portions of metrology data associated with the substitute measurements.

20. The overlay metrology system of claim 19, generating synthetic overlay measurements based on at least some of the alternative measurements.

21. The overlay metrology system of claim 19, wherein the one or more illumination beams comprise a single illumination beam.

22. The overlay metrology system of claim 21, wherein the one or more optical elements are configured to illuminate the mosaic overlay target with the single illumination beam at a normal angle of incidence.

23. The overlay metrology system of claim 19, wherein the one or more illumination beams include two illumination beams in a dipole configuration, wherein the one or more optical elements are configured to illuminate the mosaic overlay target with the two illumination beams at an oblique angle of incidence.

24. The overlay metrology system of claim 19, wherein the one or more illumination beams include four illumination beams in a quadrupole configuration, wherein the one or more optical elements are configured to illuminate the mosaic overlay target with the four illumination beams at oblique incidence angles.

25. The overlay metrology system of claim 19, wherein the common properties of the samples include: Overlay measurement associated with two or more patterning processes along a specific measurement direction.

26. The overlay metrology system of claim 19, wherein the two or more measurements include: Overlay measurement along two or more directions.

27. The overlay metrology system of claim 19, wherein the substitute measurement comprises: Overlay measurements produced using two or more different overlay metrology techniques.

28. The overlay metrology system of claim 27, wherein at least one of the two or more different overlay metrology techniques comprises: Scatterometry overlay metrology.

29. The overlay metrology system of claim 27, wherein at least one of the two or more different overlay metrology techniques comprises: Imaging overlay metrology technology.

30. The overlay metrology system of claim 19, wherein at least one of the two or more unit groups comprises: One or more cell pairs, each cell pair comprising two cells, wherein the two cells are oriented to have at least one of mirror symmetry with respect to the central axis of the mosaic overlay target or rotational symmetry with respect to the central point of the mosaic overlay target.

31. The overlay metrology system of claim 19, wherein at least one of the two or more unit groups comprises: A single unit centered on the center point of the mosaic overlay object, wherein the single unit has at least one of mirror symmetry with respect to the center axis of the mosaic overlay object or rotational symmetry with respect to the center point of the mosaic overlay object.

32. The overlay metrology system of claim 19, wherein each of the one or more cells in at least one of the two or more cell groups is 180 degree rotationally symmetric.

33. The overlay metrology system of claim 19, wherein the one or more cells in at least one of the two or more groups of cells include periodic features.

34. The overlay metrology system of claim 33, wherein the periodic feature is periodic along a single direction corresponding to the measurement direction.

35. The overlay metrology system of claim 33, wherein the periodic feature is periodic along two directions corresponding to two measurement directions.

36. The overlay metrology system of claim 19, wherein the one or more cells in at least one of the two or more cell groups comprise overlapping features on two or more layers of the sample.

37. The overlay metrology system of claim 36, wherein the overlay features include: Periodic characteristics.

38. The overlay metrology system of claim 37, wherein the periodic features on the two or more layers have a common periodicity.

39. The overlay metrology system of claim 37, wherein the periodic features on the two or more layers have different pitches along a particular measurement direction.

40. The overlay metrology system of claim 37, wherein the periodic features on the two or more layers have different pitches along different measurement directions.

41. A method for overlay metrology, comprising: One or more mosaic overlay targets are illuminated on the sample with one or more illumination beams according to a metrology recipe, wherein each of the mosaic overlay targets comprises: two or more cell groups distributed across the sample, wherein each cell group comprises one or more cells, wherein each cell group is oriented to have at least one of mirror symmetry with respect to a central axis of the mosaic overlay target or rotational symmetry with respect to a central point of the mosaic overlay target; generating one or more images of the mosaic overlay object based on the illumination with the one or more illumination beams; and At least two overlay measurements of the sample are generated based on the one or more images, wherein a particular one of the two or more overlay measurements is based on a portion of the one or more images associated with at least one of the two or more cell groups, wherein at least two of the two or more overlay measurements are substitute measurements of a common property of the sample, wherein at least two of the two or more cell groups are configured according to the metrology recipe to provide substitute portions of metrology data associated with the substitute measurements.

42. A method for designing a mosaic overlay target, comprising: selecting two or more overlay measurements for generation with the mosaic overlay target; Designing two or more unit groups of the mosaic overlay target, wherein the mosaic overlay target comprises: the two or more cell groups distributed across the sample, wherein each cell group comprises one or more cells, wherein each cell group is oriented to have at least one of mirror symmetry with respect to a central axis of the mosaic overlay target or rotational symmetry with respect to a central point of the mosaic overlay target, wherein the two or more cell groups are configured according to a metrology recipe such that one or more images of the mosaic overlay target generated according to the metrology recipe contain metrology data suitable for the two or more overlay measurements, wherein a particular one of the two or more overlay measurements is based on a portion of the one or more images associated with at least one of the two or more cell groups, Wherein at least two of the two or more overlay measurements are surrogate measurements of a common property of the sample, wherein at least two of the two or more cell groups are configured according to the metrology recipe to provide surrogate portions of the metrology data associated with the surrogate measurements.

43. The method of claim 42, wherein designing the two or more cell groups of the mosaic overlay target comprises: A layout of features in the two or more cell groups is designed.

Images