mosaic overlay target

Abstract

A mosaic overlay target can include two or more cell groups distributed across a sample, where each cell group includes one or more cells, where 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 center point of the mosaic overlay target. The cell groups can be configured according to a metrology recipe such that an image of the mosaic overlay target generated based on the metrology recipe includes metrology data suitable for two or more overlay measurements. A particular one of the overlay measurements can be based on a portion of the image associated with at least one of the cell groups. At least two of the two or more overlay measurements can be alternative measurements of a common property of the sample.

Description

[0001] Cross - Reference to Related Applications

[0002] This application claims the right to U.S. Provisional Application No. 63 / 411,640, filed on September 30, 2022, entitled “MOSAIC TARGETS AND THEIR MEASUREMENTS MEASUREMENT CONCEPTS”, entitled “MOSAIC TARGETS AND THEIR MEASUREMENTS MEASUREMENT CONCEPTS”, the entire contents of which are incorporated herein by reference. Technical Field

[0003] This disclosure generally relates to overlapping targets and, more specifically, to metric targets that provide multiple alternative overlapping measurements. Background Technology

[0004] Overlay metrics (e.g., overlay measurements) characterize the relative registration (or misalignment) of different layers of a sample. Image-based overlay techniques typically generate overlay measurements based on the relative positions of imaged overlay target features. As the size of manufactured features decreases and feature density increases, the demand for overlay metric systems required to characterize these features increases. Different overlay metric techniques offer different trade-offs between accuracy, repeatability, or processing power. Therefore, there is a need to develop systems and methods to address these shortcomings. Summary of the Invention

[0005] According to one or more illustrative embodiments of this disclosure, a mosaic overlay target is disclosed. In one illustrative embodiment, the target comprises two or more unit groups across a sample distribution, wherein each unit group comprises one or more units, and wherein each unit group is 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 center point of the mosaic overlay target. In another illustrative embodiment, the two or more unit groups are configured according to a metric recipe such that one or more images of the mosaic overlay target generated according to the metric recipe contain metric data suitable for two or more overlay measurements, wherein a particular 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 unit groups. In another illustrative embodiment, at least two of the two or more overlay measurements are alternative measurements of common properties of the samples, wherein at least two of the two or more unit groups are alternative portions of the metric data associated with the alternative measurements, configured according to the metric recipe.

[0006] According to one or more illustrative embodiments of this disclosure, a superposition measurement 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 superposition target on a sample with the one or more illumination beams when implementing a measurement formulation. In another illustrative embodiment, the target comprises two or more unit groups across a sample distribution, wherein each unit group comprises one or more units, and each unit group is oriented to have at least one of mirror symmetry relative to the central axis of the mosaic superposition target or rotational symmetry relative to the center point of the mosaic superposition target. In another illustrative embodiment, the two or more unit groups are configured according to a measurement formulation such that one or more images of the mosaic superposition target generated according to the measurement formulation contain measurement data suitable for two or more superposition measurements, wherein a particular of the two or more superposition measurements is based on a portion of the one or more images associated with at least one of the two or more unit groups. In another illustrative embodiment, at least two of the two or more overlapping measurements are alternative measurements of a common property of the sample, wherein at least two of the two or more unit groups are alternative portions of the metrology data associated with the alternative measurements, configured according to the metrology recipe. In another illustrative embodiment, the system includes one or more detectors for generating one or more images of the mosaic overlapping target based on illumination from 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: receiving one or more images of the mosaic overlapping target; and generating at least two overlapping measurements of the sample based on the one or more images. In another illustrative embodiment, a particular 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 unit groups, wherein at least two of the two or more overlay measurements are alternative measurements of common properties of the samples, and wherein at least two of the two or more unit groups are alternative portions of the metrology data associated with the alternative measurements, configured according to the metrology recipe.

[0007] According to one or more illustrative embodiments of this disclosure, a method for overlay metrology 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 formula, wherein each of the mosaic overlay targets comprises two or more unit groups distributed across the sample. In another illustrative embodiment, each unit group comprises one or more units, wherein each unit group is 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 center point of the mosaic overlay target, wherein the two or more unit groups are configured according to the metrology formula such that one or more images of the mosaic overlay target generated according to the metrology formula contain metrology data suitable for two or more overlay measurements, and wherein a particular 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 unit 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 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 unit groups, wherein at least two of the two or more overlay measurements are alternative measurements of a common property of the sample, and wherein at least two of the two or more unit groups are alternative portions of the metrology data associated with the alternative measurements, configured according to the metrology recipe.

[0008] According to one or more illustrative embodiments of this disclosure, a method for designing a mosaic overlay target is disclosed. In one illustrative embodiment, the method includes selecting two or more overlay measurements to be generated together with the mosaic overlay target. In another illustrative embodiment, the method includes designing two or more unit groups of the mosaic overlay target. In another illustrative embodiment, the target comprises two or more unit groups across a sample distribution, wherein each unit group comprises one or more units, wherein each unit group is 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 center point of the mosaic overlay target, wherein the two or more unit groups are configured according to a metric recipe such that one or more images of the mosaic overlay target generated according to the metric recipe contain metric data suitable for the two or more overlay measurements, and wherein a particular 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 unit groups. In another illustrative embodiment, at least two of the two or more stacked measurements are alternative measurements of a common property of the sample, wherein at least two of the two or more unit groups are alternative portions of the metrology data associated with the alternative measurements, configured according to the metrology formula.

[0009] It should be understood that the foregoing general description and the following detailed description are exemplary and illustrative only and are not necessarily limiting of the invention as claimed. The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with the general description, serve to explain the principles of the invention. Attached Figure Description

[0010] By referring to the accompanying drawings, those skilled in the art can better understand the many advantages of this disclosure.

[0011] Figure 1A This is a conceptual diagram of a superimposed measurement system according to one or more embodiments of the present disclosure.

[0012] Figure 1B This is a simplified schematic diagram of a superimposed measurement subsystem according to one or more embodiments of the present disclosure.

[0013] Figure 1C This is a simplified schematic diagram of a first illumination pupil plane that provides a single illumination beam with a normal angle of incidence according to one or more embodiments of the present disclosure.

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

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

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

[0018] Figure 2C This disclosure provides, according to one or more embodiments, multiple alternative overlay measurements along different measurement directions. Figure 2A A top-down view of the changing target.

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

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

[0021] Figure 4B According to one or more embodiments of this disclosure Figure 4A A simplified top view of the unit in the diagram.

[0022] Figure 5 This is a simplified side view of a unit comprising features associated with a single patterning process on a single layer of a sample, according to one or more embodiments of this disclosure.

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

[0024] Figure 7 This is a flowchart illustrating the steps performed in a method for designing a mosaic overlay target according to one or more embodiments of the present disclosure. Detailed Implementation

[0025] Reference will now be made in detail to the disclosed object, which is illustrated in the accompanying drawings. This disclosure has been specifically shown and described with respect to particular embodiments and their specific features. The embodiments set forth herein should be understood as illustrative rather than restrictive. It will be apparent to those skilled in the art that various changes and modifications in form and detail can be made without departing from the spirit and scope of this disclosure.

[0026] Embodiments of this disclosure relate to systems and methods for overlay metrics based on imaging of mosaic overlay targets, wherein the mosaic overlay targets are designed to provide multiple overlay measurements based on different portions of one or more images of the mosaic overlay targets.

[0027] For the purposes of this disclosure, the term "overlap" is generally used to describe the relative positions of features on a sample fabricated by two or more patterning steps (e.g., photolithography exposure and subsequent etching steps, direct etching steps, or the like), while the term "overlap error" describes the deviation of the feature from its nominal configuration. For example, a multilayer device may include features patterned on multiple sample layers using different patterning steps for each layer, where the alignment of features between layers must typically be tightly controlled to ensure proper performance of the resulting device. Accordingly, overlap measurements can characterize the relative positions of features on two or more of the sample layers. As another example, multiple patterning steps can be used to fabricate features on a single sample layer. These techniques (often referred to as dual patterning or multiple patterning techniques) facilitate the fabrication of high-density features with resolutions approaching those of photolithography systems. In this context, overlap measurements can characterize the relative positions of features from different photolithography steps on this single layer. It should be understood that the examples and descriptions relating to specific applications of overlap metrics throughout this disclosure are provided for illustrative purposes only and should not be construed as limiting the scope of this disclosure.

[0028] In some embodiments, the mosaic overlay target comprises multiple unit groups across a sample distribution, wherein each unit group may contain one or more units, and wherein different unit groups may contain different feature arrangements suitable for facilitating overlay measurements.

[0029] Mosaic overlay targets can 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, comprising different sets of units or combinations of different sets of units. As used herein, the term simultaneous overlay measurement is widely used to indicate that multiple overlay measurements can 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), or based on different portions of the one or more images. It should be appreciated herein that some overlay measurement techniques can generate measurements based on a single image of the overlay target, while others can generate measurements based on multiple images of the overlay target (e.g., taken under different lighting and / or imaging conditions). It is considered herein that mosaic overlay targets offer great flexibility in overlay metrics, can efficiently utilize space on the sample (e.g., provide relatively small target sizes), and / or can enable high-processing-capability measurements.

[0030] As an illustration, the overlay measurement tool can illuminate the mosaic overlay target with illumination, collect the light emitted from the mosaic overlay target in response to this illumination (e.g., sample light), and generate one or more images of the mosaic overlay target based on at least a portion of this sample light. These images may comprise 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 the light emitted from the sample).

[0031] Each unit group on a mosaic overlay target can be designed to facilitate overlay measurements, either individually or in combination with one or more additional unit groups. In other words, each unit group can contain features designed to enable overlay measurements to be generated based solely on an image of that unit group or based on images of two or more unit groups. Therefore, an image of a mosaic overlay target can be viewed as a synthesis of images of various unit groups, allowing for simultaneous imaging of the various unit groups.

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

[0033] In a general sense, a mosaic stacking target can contain elements of any size or shape. However, in some applications, it is desirable to design element groups with rotational and / or mirror symmetry to mitigate undesirable effects, such as, but not limited to, tool-induced displacement (TIS) errors. For example, an element group may contain one or more pairs of elements (e.g., element pairs) configured to have mirror symmetry with respect to the central axis of the element group and / or rotational symmetry with respect to the center point of the element group (e.g., 180-degree symmetry, 90-degree symmetry, or the like). As another example, an element group may contain a single element with mirror and / or rotational symmetry. Furthermore, various element groups of a mosaic stacking target may be configured to all share a common symmetry (e.g., share a common central axis and / or center point), although in some cases, the element groups may be intentionally offset according to stacking metric techniques. In this configuration, a mosaic stacking target may contain at least one element group having one or more element pairs configured with a selected symmetry and, where appropriate, a central element group having a single element also arranged with a selected symmetry.

[0034] Mosaic overlay targets can support multiple overlay measurements based on different cell groups or combinations of cell groups. For example, different overlay measurements can be generated based on portions of one or more images of mosaic overlay targets associated with different cell groups or combinations of cell groups.

[0035] It should be understood in this document 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., feature size and / or orientation, sample layer thickness, or the like), the nature of the illumination used to facilitate the measurement (e.g., spectrum, polarization, angle of incidence, beam shape, or the like), the nature of the 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 measurement instrument). Therefore, process variations (e.g., layer thickness variations, or the like) across a particular sample and / or a batch of samples can affect both the actual overlay error (e.g., misalignment between sample layers) and the accuracy and / or sensitivity of the specific 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 the sample (e.g., different designs of overlay targets) and / or different configurations of overlay metrology tools (e.g., different lighting and / or collection conditions). These techniques can offer different trade-offs between measurement accuracy, measurement sensitivity, robustness to process variations, systematic errors, measurement speed (e.g., measurement throughput), or the required space on the sample (e.g., required target size, required number or distribution of targets on the sample, or similar). Therefore, different overlay metrology techniques implemented at specific locations on the sample can provide different results and / or produce results of varying quality.

[0037] For example, field-plane imaging techniques can determine overlay measurements based on the relative imaging positions of non-overlapping features from different patterning processes. These features can be aperiodic or periodic. Non-limiting examples of associated overlay targets include box-in-box targets, Advanced Imaging Metrics (AIM) targets, or triple AIM (t-AIM) targets. As another example, Scatter Measurement Overlay (SCOL) techniques can 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 can be characterized as grating-on-grating features. Furthermore, these overlapping periodic features can have the same or different pitches. Non-limiting examples of associated overlay targets include grating-on-grating targets, Mohr targets, or robust AIM targets.

[0038] In this paper, it is considered that mosaic overlay targets can achieve multiple overlay measurements based on different overlay techniques or variations thereof. For example, different unit groups can have different designs or different variations of similar designs.

[0039] In some embodiments, the mosaic 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, the 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, the 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 combinations of layers. For example, the mosaic overlay target may comprise three or more unit groups, each unit group containing features from different layers. In this way, overlay measurements between different combinations of layers can be generated based on different combinations of associated unit groups.

[0041] In some embodiments, mosaic pairing targets are designed to provide alternative pairing measurements. As used herein, the term alternative pairing measurement is used to refer to multiple measurements of a particular quantity, such as, but not limited to, pairing measurements between two specific sample layers along a particular measurement direction. For example, alternative measurements may be based on different features or sets of features within the mosaic pairing target as disclosed herein. These alternative pairing measurements have been considered herein to exhibit different performance characteristics, such as, but not limited to, sensitivity to pairing, measurement accuracy, or robustness to printing errors unrelated to pairing. Therefore, mosaic pairing targets designed to provide alternative pairing measurements can improve flexibility and performance (e.g., as measured by any suitable performance metric) in the pairing measurement process.

[0042] This paper further considers various ways to utilize alternative overlay measurements from mosaic overlay targets.

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

[0044] As another example, mosaic overlay targets allow for fine-tuning of the metrology formula without requiring switching between different target designs. A metrology formula typically includes a set of parameters associated with the overlay target design, the illumination conditions of the overlay target, and / or the collection conditions used to image the overlay target. In this way, the metrology formula can specify conditions suitable for obtaining one or more images of the overlay target suitable for overlay measurements. The metrology formula may further include one or more analytical steps for generating values ​​for the overlay measurements based on one or more images. As considered herein, it is desirable to adjust one or more aspects of the metrology formula across samples and / or between batches of samples in response to variations in the manufacturing process. It should be further considered herein that mosaic overlay targets, as disclosed herein, may comprise different groups of units with variations in sample characteristics to allow for multiple simultaneous metrology formula variations. Furthermore, additional fine-tuning of the metrology formula can be achieved by capturing additional images of the mosaic overlay target using different illumination and / or collection conditions (e.g., metrology formula parameters).

[0045] Additional embodiments of this disclosure relate to a method for designing mosaic-paired targets. For example, designing a mosaic-paired target may include selecting a layout suitable for providing target features in two or more groups of cells that offer two or more different simultaneous overlay measurements based on one or more images of the mosaic-paired target.

[0046] Additional embodiments of this disclosure relate to a superposition measurement system suitable for imaging mosaic superposition targets and generating two additional superposition measurements based on the image.

[0047] In some embodiments, the overlay measurement system is configured to illuminate the mosaic overlay target using off-axis illumination (e.g., tilted illumination with an illegal incident angle). Off-axis illumination may be well-suited (but not limited to) reducing the pitch of resolvable periodic features and / or reducing the cell size. The diffraction angle from the periodic feature can be related to both the illumination wavelength and the pitch of the periodic feature, where reducing the pitch increases the diffraction angle. Thus, off-axis illumination can capture diffraction from pitches smaller than normal illumination. By way of non-limiting illustration, off-axis illumination can use illumination with visible wavelengths to capture diffraction from pitches smaller than 600 nm.

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

[0049] In some embodiments, the overlay measurement system illuminates the mosaic overlay target with a quadrupole distribution of illumination beams formed of 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 measurement system may further include various components (e.g., polarizers, spectral filters, or the like) in the collection path for isolating the light associated with each dipole into different collection channels. In this way, optically isolated overlay measurements along different measurement directions can be produced.

[0050] For reference Figures 1A to 7 The system and method for using a mosaic-overlapping metric for targets are described in more detail according to one or more embodiments of the present disclosure.

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

[0052] In some embodiments, the overlay measurement system 100 includes an overlay measurement subsystem 102 for acquiring overlay signals from an overlay target based on any number of measurement recipes. For example, the overlay measurement subsystem 102 may direct illumination 104 to a mosaic overlay target 106 on a sample 108, collect light or other radiation emitted from the mosaic overlay target 106 (referred to herein as sample light 110), 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 detectors 112 located at a field plane conjugate to the sample 108 (or at least one layer therein), and / or one or more pupil plane images from detectors 112 located 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 measurement subsystem 102 may further generate two or more measurements based on one or more images of the mosaic overlay target 106. For example, the overlay measurement subsystem 102 may generate different overlay measurements based on portions of one or more images associated with different unit groups of the mosaic overlay target 106.

[0054] In some embodiments, the superimposed measurement system 100 includes a controller 114. The controller 114 may include one or more processors 116 configured to execute program instructions held in memory 118 or a memory medium. In this respect, the one or more processors 116 of the controller 114 may perform any of the various process steps described herein. Furthermore, the controller 114 may be communicatively coupled to the superimposed measurement subsystem 102 or any component thereof.

[0055] One or more processors 116 of controller 114 may comprise any processor or processing element known in the art. For the purposes of this disclosure, the terms “processor” or “processing element” may be broadly defined to encompass any means having one or more processing or logic elements (e.g., one or more microprocessor means, one or more application-specific integrated circuit (ASIC) means, one or more field-programmable gate arrays (FPGAs), or one or more digital signal processors (DSPs)). In this sense, one or more processors 116 may comprise any means configured to execute algorithms and / or instructions (e.g., program instructions stored in memory 118). In some embodiments, one or more processors 116 may be embodied as a desktop computer, mainframe computer system, workstation, graphics computer, parallel processor, networked computer, or any other computer system configured to execute a program configured to operate or in conjunction with the operation of the superimposed measurement system 100, as described throughout this disclosure.

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

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

[0058] Furthermore, the overlay tool can generate overlay signals (e.g., using controller 114) for any number of metric recipes that are configurable and based on conditions defined for generating one or more images of mosaic overlay targets 106 suitable for two or more overlay measurements. For example, a metric recipe may include design parameters for mosaic overlay targets 106 or their unit groups, 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 sample 108 and overlay metric subsystem 102). As another example, a metric recipe may include illumination parameters (e.g., the nature of illumination 104), such as, but not limited to, spectrum, polarization, illumination angle (e.g., in the height and / or azimuth direction), or illumination field size (e.g., the spot size of illumination 104). As another example, the metrology recipe may include collection parameters associated with the light (e.g., a portion of sample light 110) used to image the mosaic overlay target 106, such as, but not limited to, spectral, polarized, collection angle (e.g., in the height and / or azimuth direction), or collection field size. As another example, the 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, the metrology recipe may include one or more steps for generating at least two overlay measurements based on 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 generate overlay measurements by determining the centers of symmetry of non-overlapping features in one or more field-plane images associated with different patterning processes and determining the overlay measurements based on the relative positions of these centers of symmetry. As another illustration, some overlay techniques can 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] For reference Figures 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 stacked target 106 comprises two or more unit groups 202 spatially distributed across the mosaic stacked target 106, wherein each unit group 202 comprises one or more units 204. Furthermore, each unit 204 may include target features (hereinafter simply referred to as features) associated with one or more patterning processes. It should be noted that, for clarity, in Figures 2A to 2B The target features are not described. Instead, unit 204 is depicted with a shading pattern to illustrate the associated area of ​​the mosaic overlay on target 106.

[0061] Figure 2AThis is a simplified top view of a first design of a mosaic overlay of target 106 according to one or more embodiments of the present disclosure. Figure 2B This is a simplified top view of a second design of a mosaic overlay target 106 according to one or more embodiments of the present disclosure.

[0062] exist Figure 2A and 2B In each of these, the mosaic overlay target 106 is depicted as a series of square units 204, wherein units 204 sharing a common shading pattern are associated with a common unit group 202. In a general sense, the mosaic overlay target 106 may comprise two or more unit groups 202, each unit group having one or more units 204. Furthermore, the units 204 can generally have any shape, and the depicted squares are merely illustrative.

[0063] As an explanation, Figure 2A The mosaic stacked target 106 comprises 18 unit groups 202 (labeled 202-1 to 202-18) formed by two units 204, each of which can be freely referred to as unit pairs. As another illustration, Figure 2B The mosaic stacked target 106 comprises 16 unit groups 202 (labeled 202-1 to 202-8 and 202-11 to 202-18), each having two units 204, and a central unit group 202 (labeled 202-0) having a single unit 204. However, it should be understood that the unit group 202 is not limited to... Figure 2A and 2B The description includes one or two units 204, and in some embodiments may include three or more units 204.

[0064] For reference Figures 3 to 5 Various non-limiting feature layouts are described according to one or more embodiments of this disclosure. In a general sense, the mosaic overlay target 106 may be designed to facilitate multiple overlay measurements (e.g., two or more overlay measurements), wherein each overlay measurement is based on one or more unit groups 202. Any unit 204 within any of the unit groups 202 may contain features associated with a single patterning process or multiple patterning processes, wherein different patterning processes may 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 unit groups 202 may contain features on different layers or combinations of layers. Furthermore, different unit groups 202 may have different designs and / or layouts for corresponding features. In other words, there is no requirement for similarity or difference between target features (or more generally, unit 204) in different unit groups 202. Therefore, each unit group 202 may have a fully customizable design and may use different overlay techniques to generate overlay measurements based on features in different unit groups 202.

[0065] Features within any particular cell 204 may have any layout suitable for stack-up measurements. For example, features within any cell 204 may be aperiodic or periodic in one or more directions (e.g., exhibiting distinct spatial frequencies). It should be appreciated herein that periodic features can produce discrete diffraction orders, particularly when illuminated by an angle-limited illumination beam 104, which can aid in determining stack-up pairs. For example, periodic structures can improve the signal-to-noise ratio associated with the image of the features (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 aperiodic features.

[0066] It should be noted that Figures 3 to 5 Different non-limiting target designs are depicted that are suitable for providing superimposed measurements between a first feature 302 associated with a first patterning process and a second feature 304 associated with a second patterning process. Specifically, Figures 3 to 5 The illustration depicts a non-limiting example in which a first feature 302 is positioned on a first layer 306 of a sample 108 and a second feature 304 is positioned on a second layer 308 of the sample 108. Thus, the illustrated examples may be suitable for determining the stacking pairs between layers of the sample 108. However, it should be understood that these descriptions are purely illustrative and not intended to limit the scope of this disclosure. For example, it should be noted that the sample 108 may comprise any number of layers on the substrate 310 and, in some embodiments, may include additional layers above, below, and / or between the first layer 306 and the second layer 308.

[0067] Figure 3 A non-limiting configuration of unit 204 depicting box-in-box features associated with two patterning processes on two layers of sample 108. Figure 3 This is a simplified top view of unit 204 of a mosaic stacking target 106 having a box-in-box feature according to one or more embodiments of this disclosure. For illustration, this unit 204 can be... Figure 2B The central unit group 202-0 is associated with this. Furthermore, stacked measurements can be generated based on this single unit 204.

[0068] like Figure 3 As depicted, 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, the overlay measurement between the first and second exposures can be determined based on the relative positions of the first feature 302 and the second feature 304 (e.g., as can be observed in a field-planar 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 along the X and / or Y directions, such that any deviation from this configuration is due to overlay errors in the X and / or Y directions.

[0069] ​ A non-restrictive configuration of unit 204 depicting overlapping features associated with two patterning processes on two layers of sample 108. ​ This is a simplified side view of unit 204 of mosaic overlay target 106 with overlapping features according to one or more embodiments of the present disclosure. ​ According to one or more embodiments of this disclosure ​ A simplified top view of unit 204. For illustration, this unit 204 can be adapted to... ​ Any one of the units in group 202.

[0070] like ​ As depicted, the first feature 302 may include a first set of periodic features and the 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 (e.g., double diffraction) associated individually or in combination with the first feature 302 and the second feature 304. In some embodiments, such as ​ As depicted, the first feature 302 and the second feature 304 have a common pitch (or more generally periodicity) such 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 periodicity). This configuration may also be referred to as a Mohr configuration. 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 required. Additionally, this configuration can produce Mohr diffraction (e.g., double diffraction) at different angles based on the difference between the pitches of the first feature 302 and the second feature 304.

[0071] The first feature 302 and / or the second feature 304 may typically have any periodic distribution along one or more directions and are therefore suitable for facilitating overlay measurements along one or more directions. For example, the first feature 302 and / or the second feature 304 may comprise a line / space pattern with any pitch or work cycle along any direction. Furthermore, either the first feature 302 or the second feature 304 may be arranged with two or more feature pitches. As an illustration, either of the features may be segmented with both coarse and fine pitches.

[0072] The first feature 302 and the second feature 304 of any particular unit 204 may, but are not required to, be intentionally offset along one or more measurement directions. For example, ​ The configuration with the expected offset f0 is described. In some embodiments, the induced shift is at least an order of magnitude smaller than the size of cell 204 (e.g., the length of cell 204 in the direction of the expected offset).

[0073] As considered herein, a variety of techniques can be used to facilitate stacking measurements for a mosaic stacking target 106 comprising at least some unit groups 202 containing a grating-to-grating structure. Stacking measurements using grating-to-grating structures are generally described in the following patents: U.S. Patent No. 7,277,172, issued October 2, 2007; U.S. Patent No. 7,616,313, issued November 11, 2009; U.S. Patent No. 8,004,679, issued August 23, 2011; U.S. Patent No. 7,884,936, issued February 8, 2011; U.S. Patent No. 8,848,186, issued September 30, 2014; and U.S. Patent No. 9,739,702, issued August 22, 2017; the entire contents of all said U.S. patents are incorporated herein by reference. For example, a zero-order SCOL technique can be based on comprising units having a common periodicity but different expected offsets (e.g., ±). f 0,1 and ± f 0,2 The grating stacked grating structure consists of four unit groups 202. As another example, the first-order SCOL technique can be based on a grating stacked grating structure containing elements having a common periodicity but different expected offsets (e.g., ±). f Two unit groups 202 of a grating-over-grating structure (0). As another example, the Moore technique may utilize a first unit group 202 comprising one or more units 204 wherein the first feature 302 has a first pitch (P) and the second feature 304 has a second pitch (Q), and a second unit group 202 comprising one or more units 204 wherein the first feature 302 has a second pitch (Q) and the second feature 304 has a first pitch (P). In this configuration, overlay errors may induce a shift in Moore diffraction along opposite directions to facilitate self-calibration and self-referenced overlay measurements. It should be understood that these examples are merely illustrative and should not be construed as limiting the scope of this disclosure. In any of these configurations, the mosaic overlay target 106 can substantially increase measurement efficiency (e.g., processing power). Unlike when individual measurements have different expected offsets ( f The existing SCOL technique of individual unit 204 (0) allows mosaic overlay of target 106 to achieve different expected offsets. f Simultaneous measurement of unit 204 or unit group 202 (0) to increase processing capacity. Furthermore, with expected offset ( f 0) Different unit groups 202 with different variations of pitch or the like can be set on the same mosaic stack target 106 such that alternative measurements with different parameters can be generated based on one or more measurements of the mosaic stack target 106 (e.g., field plane image, pupil plane image or the like).

[0074] ​This is a simplified side view of a unit 204 comprising a feature 502 associated with a single patterning process on a single layer (e.g., first layer 306 or second layer 308) of sample 108, according to one or more embodiments of this disclosure. For illustration, this unit 204 may be adapted to... ​ Any one of the units in group 202.

[0075] This paper considers that it can be based on similar... ​ Two or more unit groups 202 depicted herein generate overlay measurements, each unit group having features associated with different patterning processes. For example, a first unit group 202 having features associated with a first patterning process and a second unit group 202 having features associated with a second patterning process can be operated as an Advanced Imaging Metrology (AIM) target, allowing the generation of overlay measurements associated with the first and second patterning processes using any suitable overlay technique. However, it should be noted that these first and second unit groups 202 can be distributed across the mosaic overlay target 106 at any location. 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 unit group 202 having features associated with a first patterning process, a second unit group 202 having features associated with a second patterning process, and a third unit group 202 having features associated with a third patterning process can be operated as a tri-AIM (t-AIM) target, allowing the generation of overlay measurements associated with the first and second patterning processes using any suitable overlay technique.

[0076] Again, for general reference ​ Additional considerations for designing the mosaic stack target 106 are described in more detail according to one or more embodiments of this disclosure.

[0077] In some embodiments, at least some of the unit 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). This symmetry can be beneficial in mitigating certain noise or error sources in measurements, such as, but not limited to, tool-induced displacement (TIS). In the case of rotational symmetry, this unit group 202 may be invariant to rotations of 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 this symmetry may refer to the distribution of the target feature across the mosaic stack relative to the target 106 in the unit group 202 (or the unit 204 therein) and the shape and orientation of the associated unit 204. For example, the units 204 within the unit group 202 at symmetrical positions may have a common size to provide the desired symmetry across the mosaic stack relative to the target 106.

[0078] As an explanation, ​Unit groups 202-1 to 202-18 and ​ The element pairs in element 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, element group 202-0 with a single element 204 can exhibit mirror symmetry along the vertical central axis 208 or the horizontal central axis 210. As another illustration, element group 202-0 with a single element 204 can exhibit rotational symmetry (e.g., 90-degree or 180-degree rotational symmetry) relative to the center point 206. It should be noted that although... ​ and 2B Only the position and shape of unit 204 are described, but the target features within unit 204 of any particular unit group 202 can be configured to give unit group 202 the desired symmetry.

[0079] In some embodiments, one or more unit groups 202 are designed to share a common center of symmetry with the mosaic overlay target 106 (or with other unit groups 202) under specific conditions (e.g., but not limited to zero-overlap conditions, such as printing features associated with different unit groups 202 without unintentional overlap errors)). ​ and 2B As described above, all element groups 202-0 to 202-18 are rotationally symmetric about 180 degrees relative to the center point 206. However, as previously described herein, features within element group 202 may be printed with intentional (e.g., designed) overlap offsets, which can shift the associated center of symmetry of element group 202.

[0080] The ability of mosaic stacked target 106 to facilitate multiple simultaneous measurement will now be described in more detail according to one or more embodiments of the present disclosure.

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

[0082] As considered herein, 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 samples 108 (e.g., based on different measurement techniques and / or different feature geometries).

[0083] The mosaic overlay target 106 can be configured to provide simultaneous metrological measurements along multiple measurement directions, which may (but are not required) be orthogonal. As in ​ As described in the context, 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 metrological measurements along a first direction (e.g., the X direction), while 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 metrological measurements along a second direction (e.g., the Y direction).

[0084] In some embodiments, the mosaic overlay target 106 is configured to provide simultaneous metric measurements between multiple different patterning processes. For example, the mosaic overlay target 106 may comprise multiple unit groups 202, each unit group having features associated with different patterning processes. As a basis... ​ As explained, unit groups 202-1 to 202-9 may each contain features suitable for X-direction overlay measurements on different layers of sample 108. Similarly, unit groups 202-10 to 202-18 may each contain features suitable for Y-direction overlay measurements on different layers of sample 108. For example, unit group 202-1 may contain features suitable for X-direction measurements on a first layer, unit group 202-10 may contain features suitable for Y-direction measurements on a first layer, unit group 202-2 may contain features suitable for X-direction measurements on a second layer, unit group 202-11 may contain features suitable for Y-direction measurements on a second layer, and so on. Furthermore, the features on each unit group 202 may include features oriented along the X or Y direction, respectively, suitable for X or Y direction measurements, such as, but not limited to, features oriented along the X or Y direction. ​ The features described herein. 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 with dimensions approximately the same as those of 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). Furthermore, this technique can be extended to any number of sample layers.

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

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

[0087] As an explanation, ​ This disclosure provides, according to one or more embodiments, multiple alternative overlay measurements along different measurement directions. ​ A top-down view of the changing target.

[0088] exist ​ In the middle, the unit groups 202 in the upper left and lower right quadrants (e.g., unit groups 202-1 to 202-9) can be configured to provide metrological measurements along a first direction (e.g., the X direction), while the unit groups 202 in the upper right and lower left quadrants (e.g., unit groups 202-10 to 202-18) can be configured to provide metrological measurements along a second direction (e.g., the Y direction).

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

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

[0091] In this configuration, the overlay measurement along the first direction between the first layer 306 and the second layer 308 can be generated based on any combination of unit groups 202 from the first and second groups, while the overlay measurement along the second direction between the first layer 306 and the second layer 308 can be generated based on any combination of unit groups 202 from the third and fourth groups. Specifically, ​ The mosaic overlay target 106 can provide 20 combinations of unit groups 202 along each direction and thus provide 20 alternative overlay measurements along each direction between the first layer 306 and the second layer 308.

[0092] However, it should be understood that ​ The descriptions and related information are provided for illustrative purposes only and should not be construed as limiting. For example, a mosaic overlay target 106 may typically comprise any number of groups of cell sets 202 arranged to accommodate any number of alternative overlay measurements. As another example, the mosaic overlay target 106 may provide alternative measurements using any overlay measurement technique and any associated cell design. In this way, the mosaic overlay target 106 may provide alternative measurements using SCOL techniques that utilize the features of grating overlay gratings. In this case, different cell sets 202 may contain cells with different expected offsets ( f0) and (or instead) units 204 with different pitches, feature widths (e.g., work cycles of line / space patterns), fine segmentation, or any other differences. As another example, the mosaic overlay target 106 may include one or more groups of units 202 suitable for overlay measurements using a first overlay metric technique (e.g., field plane imaging technique or similar), and one or more additional groups of units 202 suitable for overlay measurements using a second overlay metric technique (e.g., SCOL technique or similar).

[0093] For reference ​ The present disclosure describes a method for providing an alternative overlay measurement from mosaic overlay target 106, according to one or more embodiments.

[0094] ​ This is a flowchart illustrating the steps performed in method 600 according to one or more embodiments of this disclosure. Applicants should note that the embodiments and enabling techniques previously described herein in the context of the superimposed measurement system 100 should be interpreted as extending to method 600. However, it should further be noted that method 600 is not limited to the architecture of the superimposed measurement system 100.

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

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

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

[0098] As considered herein, alternative overlay measurements enabled by the mosaic overlay target 106 can be utilized in various ways within the spirit and scope of this disclosure. As previously described herein, alternative overlay measurements can provide different levels of accuracy, sensitivity, and / or robustness to process variations based on specific entity properties of sample 108 at specific locations on a particular mosaic overlay target 106. Since alternative overlay measurements can 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 associated images), the measurement processing power can be substantially higher than that for measuring a single target, and the main cost of generating alternative overlay measurements is only related to the computational resources required to process the images.

[0099] In some embodiments, step 606 may include generating at least some alternative overlay measurements enabled by the mosaic overlay targets 106 for at least some of them. These alternative overlay measurements may then be used individually and / or combined to generate a synthetic overlay measurement. For example, step 606 may include combining multiple alternative overlay measurements using any suitable technique (e.g., using averaging, weighted averaging, or any suitable technique) to generate a synthetic overlay measurement that may be more accurate, more sensitive, and / or more robust than any of the individual alternative measurements. This synthetic overlay measurement can be generated for multiple mosaic overlay targets 106 distributed across at least one sample 108, providing an accurate and sensitive metric with relatively high robustness to process variations. Furthermore, the availability of multiple alternative overlay measurements mitigates pattern placement error (PPE) or other inaccuracy problems.

[0100] In some embodiments, step 606 may include generating a single alternative overlay measurement for at least some of the mosaic overlay targets 106. For example, a specific alternative overlay measurement with accuracy and / or sensitivity above a selected threshold (or more generally a quality threshold) may be generated. As an illustration, generating a single measurement per mosaic overlay target 106 (or a single measurement per direction for each mosaic overlay target 106) based on selected unit groups 202 may be computationally more efficient. As another illustration, it is possible that process variations in the position of a particular mosaic overlay target 106 may cause one or more alternative overlay measurements to be inaccurate or invalid. In this case, these alternative measurements may be discarded. A valid measurement can be obtained from a particular mosaic overlay target 106 as long as at least one measurement based on at least one unit group 202 meets the desired threshold. Therefore, the overall measurement processing capacity may remain high.

[0101] For reference ​ , ​This is a flowchart illustrating the steps performed in a method 700 for designing a mosaic overlay target 106 according to one or more embodiments of this disclosure. The applicant should note that the embodiments and enabling techniques previously described herein in the context of the overlay measurement system 100 should be interpreted as extending to method 700. However, it should further be noted that method 700 is not limited to the architecture of the overlay measurement system 100.

[0102] As considered herein, it is generally expected that overlap measurements within a specific tolerance can be provided. However, specific tolerance requirements may differ for different applications and / or may change over time. For illustration, overlap tolerances for a layer can be characterized as follows: ​ 1 <N Furthermore, the other layer can be characterized as ​ 2 <M As another illustration, the overlap tolerance can be characterized as... ​ 1 ​ 1 ​ 2 <M In a general sense, it is desirable to determine the overlap within tolerances sufficient to maintain the electrical robustness of the printed feature. As the feature size of the manufactured feature decreases, the tolerance for overlap measurement may become increasingly complex. For example, it may be necessary to implement complex requirements across multiple layers and / or develop nonlinear requirements associated with the relationships between different layers.

[0103] As considered herein, the mosaic overlay target 106 disclosed herein can be simultaneously or selectively overlaid based on different unit groups 202 and possibly different measurement techniques or algorithms. In this way, users can meet various overlay measurement tolerances or considerations.

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

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

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

[0107] For reference ​ Various additional aspects of the superimposed measurement subsystem 102 are described in more detail according to one or more embodiments of this disclosure.

[0108] ​ This is a simplified schematic diagram of a superimposed measurement subsystem 102 according to one or more embodiments of the present disclosure.

[0109] In some embodiments, the superimposed measurement 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 (e.g., 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. Illumination from the illumination source 126 may include light of one or more selected wavelengths, including (but not limited to) ultraviolet (UV) radiation, visible light radiation, or infrared (IR) radiation. The illumination source 126 may include any type of illumination source suitable for providing 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 is not limited to) one or more narrowband laser sources, broadband laser sources, supercontinuum laser sources, white light laser sources, or the like. In this respect, the illumination source 126 can provide an illumination beam 122 with high coherence (e.g., high spatial coherence and / or temporal coherence). In some embodiments, the illumination source 126 includes a laser continuous plasma (LSP) source. For example, the illumination source 126 may include (but is 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, various techniques can 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 for splitting 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 can be considered as part of a different illumination channel, regardless of the technique used to generate the various illumination beams 122.

[0112] In some embodiments, the illumination subsystem 120 includes one or more optical components adapted to modify and / or adjust one or more illumination beams 122 and guide 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 one or more illumination beams 122, to relay illumination pupil plane 130 and / or illumination field plane 132, or the like). In some embodiments, the illumination subsystem 120 includes one or more illumination control optics 134 for shaping or otherwise controlling 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 equalizers, one or more apodizers, one or more beam shapers, or one or more mirrors (e.g., static mirrors, translation mirrors, scanning mirrors, or the like).

[0113] In some embodiments, the stacking measurement subsystem 102 includes an objective lens 136 for focusing one or more illumination beams 122 onto a sample 108 (e.g., a stacking target having stacking target elements positioned on two or more layers of the sample 108).

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

[0115] In some embodiments, the collection subsystem 124 includes one or more detectors 112, wherein any detector 112 may be located 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 adjusting the sample light 110 from the sample 108. In some embodiments, the collection subsystem 124 includes one or more light-collecting lenses 142 (e.g., to collimate the sample light 110, to relay a pupil and / or a field plane, or the like), which may include, but are not required to include, an objective lens 136. In some embodiments, the collection subsystem 124 includes one or more collection control optics 144 for shaping or otherwise controlling 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 equalizers, one or more apodizers, one or more beam shapers, or one or more mirrors (e.g., static mirrors, translation mirrors, scanning mirrors, or the like).

[0117] In some embodiments, the superimposed measurement subsystem 102 includes a translation stage 146 for positioning the sample 108 relative to the objective lens 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, as ​As described herein, the superimposed measurement 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 polarized beam splitter, an unpolarized beam splitter, or a combination thereof.

[0119] In some embodiments, such as ​ As described, the superimposed measurement subsystem 102 includes a beam splitter 152 for combining the illumination subsystem 120 and the collection subsystem 124 such 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] For reference ​ The lighting 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 measurement subsystem 102 can illuminate the mosaic overlay target 106 with any combination of one or more illumination beams 122 in any distribution.

[0122] ​ This is a simplified schematic diagram of a first illumination pupil plane 130 depicting a single illumination beam 122 providing a normal angle of incidence, according to 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] ​ This 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 very suitable (but not limited to) for superimposed measurements along the axes of the two separate illumination beams 122. Furthermore, the two illumination beams 122 can provide any combination of incident angles. For example, as... ​ As depicted, the two illumination beams 122 may be symmetrical in the illumination pupil plane 130 to provide opposite angles of incidence, although this is not required.

[0124] In some embodiments, the two illumination beams 122 are configured (e.g., according to a metric formula) to satisfy the Litertow condition for a periodic structure in one or more cells 204 of the mosaic stack target 106. Under the Litertow condition, the spacing between the illumination beams 122 is equal to λ / pitch, where λ is the wavelength of the illumination beam 122 and ​This is the pitch of the target structure (e.g., along the axis connecting the two illumination beams 122). In this configuration, the first-order diffraction (e.g., specular reflection) of the illumination beams 122 from the associated features of the mosaic stacked target 106 propagates back along the incident direction of the illumination beams 122. As considered herein, the Littorh condition provides a relatively robust measurement. However, strict adherence to the Littorh condition is not required. In some cases, the separation between the illumination beams 122 in the dipole is chosen to be within specific tolerances of the features in one or more elements 204.

[0125] ​ This is a simplified schematic diagram depicting the third illumination pupil plane 130 of four illumination beams 122 arranged in a quadrupole configuration according to one or more embodiments of the present disclosure. The quadrupole configuration can be considered as two dipoles with orthogonal orientations. For example, ​ A first dipole with illumination beams 122a and 122b oriented along the X direction and a second dipole with illumination beams 122c and 122d oriented along the Y direction are depicted. In this manner, ​ The description can also be applied to ​ For example, the quadrupole configuration of illumination beams 122a to 122d satisfies the Littoral condition for orientation along the X and Y directions; it should be noted that the dipole separation distances along the X and Y directions may differ. Furthermore, although... ​ The two dipoles in the figure are separated by equal distances, but this is not a requirement.

[0126] The overlay measurement subsystem 102 can be configured in various ways to image the mosaic overlay target 106 with multiple illumination beams 122. In some embodiments, a single image can be generated based on the 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 measurement 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, these images can be analyzed individually (e.g., by controller 114) or combined (e.g., summed, averaged, or similar).

[0127] In some embodiments, the overlay measurement subsystem 102, comprising two collection channels 148, can generate individual (e.g., isolated) images from different illumination beams 122. This configuration can 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 can 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 can be generated in the second collection channel 148 based on a second dipole (e.g., illumination beams 122c, 122d). Furthermore, the illumination beams 122 can be directed simultaneously or sequentially to the mosaic overlay target 106. For example, illumination beams 122a, 122c can be directed to the sample 108 first, followed by illumination beams 122b, 122d.

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

[0129] In addition, generally refer to ​ 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 formulations are generally described in U.S. Patent Publication No. 2022 / 0357674, published November 10, 2022, the entire contents of which are incorporated herein by reference.

[0130] The objects described herein sometimes indicate the inclusion of different components housed within or connected to other components. It should be understood that the architectures described are merely exemplary, and many other architectures can in fact be implemented to achieve the same functionality. Conceptually, any arrangement of components used to achieve the same functionality is effectively “associated” to achieve the desired functionality. Therefore, any two components combined herein to achieve a particular functionality can be considered “associated” with each other to achieve the desired functionality, regardless of the architecture or intermediate components. Similarly, any two such associated components can also be considered “connected” or “coupled” to each other to achieve the desired functionality, and any two components that can be suchly associated can also be considered “coupled” to each other to achieve the desired functionality. Specific examples of couplerability include (but are not limited to) physically interactive and / or physically interactive components and / or wirelessly interactive and / or logically interactive and / or logically interactive components.

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

Claims

1. A mosaic overlay target, comprising: Two or more unit groups, spanning a sample distribution, wherein each unit group comprises one or more units, and wherein each unit group is oriented to have at least one of mirror symmetry with respect to the central axis of the mosaic stack target or rotational symmetry with respect to the center point of the mosaic stack target. The two or more unit groups are configured according to a metrology formula such that one or more images of the mosaic overlay target generated according to the metrology formula contain metrology data suitable for two or more overlay measurements, wherein a particular 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 unit groups. Wherein at least two of the two or more stacked measurements are alternative measurements of a common property of the sample, and wherein at least two of the two or more unit groups are alternative portions of the metrology data associated with the alternative measurements, configured according to the metrology formula.

2. The mosaic overlay target according to claim 1, wherein the common property of the samples includes: Overlapping measurements associated with two or more patterning processes along a specific measurement direction.

3. The mosaic overlay target according to claim 1, wherein the two or more overlay measurements include: Overlapping measurements along two or more directions.

4. The mosaic overlay target according to claim 1, wherein the alternative measurement includes: Overlapping measurements are produced using two or more different overlapping measurement techniques.

5. The mosaic overlay target according to claim 4, wherein at least one of the two or more different overlay measurement techniques comprises: Scattering measurement superposition measurement technique.

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

7. The mosaic stacking target according to claim 1, wherein at least one of the two or more unit groups comprises: One or more unit pairs, each unit pair comprising two units, wherein the two units are oriented to have at least one of mirror symmetry with respect to the central axis of the mosaic stack target or rotational symmetry with respect to the center point of the mosaic stack target.

8. The mosaic stacking target according to claim 1, wherein at least one of the two or more unit groups comprises: A single unit centered at the center point of the mosaic stacked target, wherein the single unit has at least one of mirror symmetry with respect to the central axis of the mosaic stacked target or rotational symmetry with respect to the center point of the mosaic stacked target.

9. The mosaic stacking target according to claim 1, wherein each of the one or more units in at least one of the two or more unit groups is 180-degree rotationally symmetric.

10. The mosaic stacking target according to claim 1, wherein at least one of the two or more unit groups comprises a periodic feature.

11. The mosaic stacked target of claim 10, wherein the periodic feature is periodic along a single direction corresponding to the measurement direction.

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

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

14. The mosaic overlapping target according to claim 13, wherein the overlapping feature includes: 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 stacking target of claim 14, wherein the periodic features on the two or more layers have different pitches along a particular direction.

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

19. A superimposed system of weights and measures, comprising: A light source configured to produce one or more light beams; One or more optical elements configured to illuminate a mosaic-overlay target on a sample with the one or more illumination beams during the implementation of a metrology formulation, wherein the mosaic-overlay target includes: Two or more unit groups spanning the sample distribution, wherein each unit group comprises one or more units, wherein each unit group is oriented to have at least one of mirror symmetry with respect to the central axis of the mosaic stack target or rotational symmetry with respect to the center point of the mosaic stack target. One or more detectors are used to generate one or more images of the mosaic overlay target based on the illumination provided by the one or more illumination beams when implementing the metrology formula; and A controller comprising one or more processors configured to execute program instructions that cause the one or more processors to implement the metrology formula by the following steps: Receive 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 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 unit groups, wherein at least two of the two or more overlay measurements are alternative measurements of common properties of the sample, and wherein at least two of the two or more unit groups are alternative portions of metrological data associated with the alternative measurements, configured according to the metrological recipe.

20. The superimposed measurement system of claim 19, which generates a composite superimposed measurement based on at least some of the alternative measurements.

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

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

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

24. The stacking measurement system of claim 19, wherein the one or more illumination beams comprise four illumination beams in a quadrupole configuration, wherein the one or more optical elements are configured to illuminate the mosaic stacking target with the four illumination beams at an oblique angle of incidence.

25. The superimposed measurement system of claim 19, wherein the common property of the samples includes: Overlapping measurements associated with two or more patterning processes along a specific measurement direction.

26. The stacked measurement system of claim 19, wherein the two or more stacked measurements comprise: Overlapping measurements along two or more directions.

27. The superimposed measurement system of claim 19, wherein the alternative measurement comprises: Overlapping measurements are produced using two or more different overlapping measurement techniques.

28. The superimposed measurement system of claim 27, wherein at least one of the two or more different superimposed measurement techniques comprises: Scattering measurement superposition measurement technique.

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

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

31. The stacked measurement 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 stacked target, wherein the single unit has at least one of mirror symmetry with respect to the central axis of the mosaic stacked target or rotational symmetry with respect to the center point of the mosaic stacked target.

32. The stacked measurement system of claim 19, wherein each of the one or more units in at least one of the two or more unit groups is 180-degree rotationally symmetric.

33. The stacked measurement system of claim 19, wherein one or more of the units in at least one of the two or more unit groups contain a periodic feature.

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

35. The superimposed measurement system of claim 33, wherein the periodicity is periodic along two directions corresponding to the two measurement directions.

36. The stacked measurement system of claim 19, wherein at least one of the two or more unit groups comprises overlapping features on two or more layers of the sample.

37. The overlapping measurement system of claim 36, wherein the overlapping feature includes: Periodic characteristics.

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

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

40. The stacked measurement 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 superimposing weights and measures, comprising: According to a metrology formula, one or more mosaic stacked targets on a sample are illuminated with one or more illumination beams, each of said mosaic stacked targets comprising: Two or more unit groups spanning the sample distribution, wherein each unit group comprises one or more units, wherein each unit group is oriented to have at least one of mirror symmetry with respect to the central axis of the mosaic stack target or rotational symmetry with respect to the center point of the mosaic stack target. One or more images of the mosaic overlay target are generated based on the illumination performed using 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 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 unit groups, wherein at least two of the two or more overlay measurements are alternative measurements of common properties of the sample, and wherein at least two of the two or more unit groups are alternative portions of metrological data associated with the alternative measurements, configured according to the metrological recipe.

42. A method for designing mosaic overlay targets, comprising: Select two or more stacking measurements to be generated together with the mosaic stacking target; Design two or more unit groups of the mosaic stacked target, wherein the mosaic stacked target includes: The two or more unit groups, distributed across the sample, wherein each unit group comprises one or more units, and wherein each unit group is oriented to have at least one of mirror symmetry with respect to the central axis of the mosaic stack target or rotational symmetry with respect to the center point of the mosaic stack target. The two or more unit groups are configured according to a metrology formula such that one or more images of the mosaic overlay target generated according to the metrology formula contain metrology data suitable for the two or more overlay measurements, wherein a particular 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 unit groups. Wherein at least two of the two or more stacked measurements are alternative measurements of a common property of the sample, and wherein at least two of the two or more unit groups are alternative portions of the metrology data associated with the alternative measurements, configured according to the metrology formula.

43. The method of claim 42, wherein designing the two or more unit groups of the mosaic stacking target comprises: Design the layout of the features in the two or more unit groups.

Images