Large-scale overlay metrology sampling using multiple measurement rows

Abstract

To provide a system and a method for providing accurate and efficient measurements.SOLUTION: A multi-column metrology tool may include two or more measurement columns distributed along a column direction, where the two or more measurement columns simultaneously probe two or more measurement regions on a sample including metrology targets. A measurement column may include an illumination sub-system to direct illumination to the sample, a collection sub-system including a collection lens to collect measurement signals from the sample and direct it to one or more detectors, and a column-positioning sub-system to adjust a position of the collection lens. A measurement region of a measurement column may be defined by a field of view of the collection lens and a range of the positioning system in the lateral plane. The tool may further include a sample-positioning sub-system to scan the sample along a scan path different than the column direction to position metrology targets within the measurement regions of the measurement columns for measurements.SELECTED DRAWING: Figure 1A

Description

[Technical Field]

[0001] The present disclosure relates generally to optical metrology, and more particularly to optical metrology with multiple measurement rows for high-throughput sampling. [Background technology]

[0002] REFERENCE TO RELATED APPLICATIONS This application claims the benefit under 35 U.S.C. §119(e) of U.S. Provisional Application No. 63 / 116.163 (November 20, 2020, MASSIVE OVERLAY METROLOGY SAMPLING FOR SEMICONDUCTORS WAFER LITHOGRAPHY AND PATTERNING PROCESS CONTROL BY MULTI OPTICAL COLUMNS AND SIGNAL MULTIPLEXING), which is incorporated by reference in its entirety.

[0003] The demand for decreasing feature size and increasing feature density has resulted in a correspondingly increased demand for accurate and efficient metrology.

[0004] One approach to increasing the efficiency and throughput of metrology systems is to utilize optical metrology tools and specialized metrology targets suitable for measurement by the optical metrology tools. For example, optical metrology can generally provide relatively higher throughput measurements than particle-based metrology systems, such as, but not limited to, electron beam (e-beam) metrology systems, but accuracy can be limited by the wavelength of light in the system. Nevertheless, the use of specialized overlay targets and sampling of a larger number of samples distributed across the sample can provide sufficient accuracy using optical techniques with an overall throughput that exceeds that of particle-based systems. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] U.S. Patent Application Publication No. 2018 / 0122668 [Patent Document 2] U.S. Patent No. 5,455,673 Summary of the Invention [Problem to be solved by the invention]

[0006] Next-generation semiconductor devices may require sub-nanometer overlay accuracy requirements related to the relative alignment of successive layers in the semiconductor manufacturing process. As overlay tolerances become tighter, the number of overlay targets needed to provide the necessary level of control continues to increase. Therefore, it is desirable to provide systems and methods for providing accurate and efficient metrology. [Means for solving the problem]

[0007] A multi-column metrology tool is disclosed in accordance with one or more exemplary embodiments of the present disclosure. In one exemplary embodiment, the tool includes two or more measurement columns distributed along a column direction, where the two or more measurement columns simultaneously probe two or more measurement regions on a sample including multiple measurement targets. In another exemplary embodiment, a particular measurement column of the two or more measurement columns includes an illumination subsystem for directing illumination from at least one of the one or more illumination sources toward the sample and a collection subsystem including a collection lens for collecting measurement signals from the sample and directing the measurement signals to one or more detectors. The column positioning subsystem also adjusts the position of the collection lens in a lateral plane parallel to the sample plane for measurement. In another exemplary embodiment, the measurement region of a particular measurement column is defined by the field of view of the collection lens and the extent of the positioning system in the lateral plane. In another exemplary embodiment, the tool includes a sample positioning subsystem for scanning the sample along a scan path different from the column direction, where the scan path positions the measurement targets of the multiple metrology targets within the measurement regions of the two or more measurement columns for measurement. In another exemplary embodiment, the column positioning subsystem of the two or more measurement columns positions the collection lenses of the two or more measurement columns to align the metrology target in the measurement region along the scan path with the field of view of the collection lenses for measurement.

[0008] A multi-column metrology tool is disclosed in accordance with one or more exemplary embodiments of the present disclosure. In one exemplary embodiment, the tool includes two or more measurement arrays distributed in a two-dimensional pattern, where the two or more measurement arrays simultaneously probe two or more measurement regions on a sample including multiple measurement targets, and the measurement regions of the two or more measurement arrays are distributed to cover one or more selected regions of the sample including at least some of the multiple measurement targets. A particular measurement array of the two or more measurement arrays may include an illumination subsystem for directing illumination from at least one of the one or more illumination sources toward the sample and a collection subsystem including a condenser lens for collecting measurement signals from the sample and directing the measurement signals to one or more detectors. A column positioning subsystem also adjusts the position of the condenser lens in a lateral plane parallel to the sample plane for measurement, and the measurement region of the particular measurement array is defined by the field of view of the condenser lens and the range of the positioning system in the lateral plane. In another exemplary embodiment, the column positioning subsystem of the two or more measurement arrays adjusts the position of each condenser lens to align with the measurement targets of the multiple measurement targets in their respective measurement regions.

[0009] A multi-column metrology method is disclosed in accordance with one or more exemplary embodiments of the present disclosure. In one exemplary embodiment, the method includes providing illumination to two or more measurement columns, wherein the two or more measurement columns simultaneously probe two or more measurement regions on a sample including multiple measurement targets. In another exemplary embodiment, a particular measurement column of the two or more measurement columns includes an illumination subsystem for directing illumination from at least one of the one or more illumination sources toward the sample and a collection subsystem including a collection lens for collecting measurement signals from the sample and directing the measurement signals toward one or more detectors. The column positioning subsystem also adjusts the position of the collection lens in a lateral plane parallel to the sample plane for measurement, and the measurement region of the particular measurement column is defined by the field of view of the collection lens and the extent of the positioning system in the lateral plane. In another exemplary embodiment, the method includes directing illumination light to a measurement target within a measurement field of view of the two or more measurement columns. In another exemplary embodiment, the method includes collecting measurement signals multiplexed by the two or more measurement columns. In another exemplary embodiment, the method includes detecting the multiplexed measurement signals on one or more detectors. In another exemplary embodiment, the method includes generating measurement data for the measurement target based on the detected measurement signals.

[0010] A multi-column metrology method is disclosed in accordance with one or more exemplary embodiments of the present disclosure. In one exemplary embodiment, the method includes generating a first calibration measurement set of one or more calibration targets on a sample using one or more calibration measurement arrays of a multi-column metrology tool. In another exemplary embodiment, the method includes generating a second calibration measurement set of one or more calibration targets using one or more test measurement arrays of the multi-column metrology tool, the one or more test measurement arrays providing a different measurement accuracy than the one or more calibration arrays. In another exemplary embodiment, a particular calibration measurement array or a particular test measurement array includes an illumination subsystem for directing illumination from at least one of one or more illumination sources onto the sample and a collection subsystem including a condenser lens for collecting measurement signals from the sample and directing the measurement signals to one or more detectors. Also, a column positioning subsystem adjusts the position of the condenser lens in a lateral plane parallel to the sample plane for measurement, and a measurement region of the particular measurement array is defined by the field of view of the condenser lens and the extent of the positioning system in the lateral plane. In another exemplary embodiment, the method includes calibrating the one or more test measurement arrays based on the first and second sets of calibration measurements. In another exemplary embodiment, a method includes generating one or more calibrated measurements of one or more test targets that are different from the one or more calibration targets using one or more test measurement sequences.

[0011] It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not necessarily restrictive of the invention as claimed. The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the invention and, together with the general description, serve to explain the principles of the invention. [Brief explanation of the drawings]

[0012] The many advantages of the present disclosure may be better understood by those skilled in the art by reference to the accompanying drawings:

[0013] [Figure 1A]FIG. 1 is a conceptual diagram of an optical metrology system having an overlay metrology tool with multiple measurement rows in accordance with one or more embodiments of the present disclosure. [Figure 1B] FIG. 1 is a conceptual diagram of an optical metrology system illustrating the relative positioning of a measurement row and a sample, in accordance with one or more embodiments of the present disclosure. [Figure 1C] FIG. 1 is a conceptual diagram of a portion of a multi-column overlay metrology tool including an optical measurement array with associated illumination sources and detectors that provide illumination and collection through a common lens, in accordance with one or more embodiments of the present disclosure. [Figure 1D] FIG. 1 is a conceptual diagram of a portion of a multi-column overlay metrology tool including an optical measurement array with associated illumination sources and detectors that provide illumination and collection through separate paths, in accordance with one or more embodiments of the present disclosure. [Figure 1E] FIG. 1 is a conceptual diagram of a portion of a multi-column overlay metrology tool including an EUV measurement array with associated EUV illumination sources and detectors, in accordance with one or more embodiments of the present disclosure. [Figure 1F] FIG. 1 is a conceptual diagram of a portion of a multi-column overlay metrology tool including an x-ray measurement array with associated particle illumination sources and detectors, in accordance with one or more embodiments of the present disclosure. [Figure 1G] 1 is a conceptual diagram of a portion of a multi-column overlay metrology tool including a particle-based measurement array 10 with associated particle illumination sources and detectors, in accordance with one or more embodiments of the present disclosure. [Figure 2A] FIG. 1 is a conceptual diagram of a series of measurement columns distributed across a sample that provide independent illumination and collection, in accordance with one or more embodiments of the present disclosure. [Figure 2B] FIG. 1 is a conceptual diagram of a series of measurement sequences distributed across a sample sharing a common illumination source and a common detector, in accordance with one or more embodiments of the present disclosure. [Figure 3A] FIG. 1 is a conceptual diagram of an illumination multiplexer in accordance with one or more embodiments of the present disclosure. [Figure 3B] FIG. 1 is a conceptual diagram of a detection demultiplexer in accordance with one or more embodiments of the present disclosure. [Figure 4A]FIG. 1 is a conceptual diagram of an optical metrology system including a series of measurement columns 104 distributed along a column direction, in accordance with one or more embodiments of the present disclosure. [Figure 4B] FIG. 1 is a conceptual diagram of a measurement swath on a sample including a non-linear distribution of metrology targets, in accordance with one or more embodiments of the present disclosure. [Figure 5] FIG. 1 is a conceptual diagram of an optical metrology system including a two-dimensional distribution of measurement arrays in accordance with one or more embodiments of the present disclosure. [Figure 6] 1 is a flow diagram illustrating steps performed in a method for optical metrology in accordance with one or more embodiments of the present disclosure. [Figure 7] 7 is a flow diagram illustrating steps performed in a method 700 for self-calibration of a multi-column metrology tool in accordance with one or more embodiments of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0014] Reference will now be made in detail to the disclosed subject matter, which is illustrated in the accompanying drawings. The present disclosure has been particularly shown and described with reference to certain embodiments and certain features thereof. The embodiments described herein are to be construed as illustrative and not restrictive. It will be readily apparent to those skilled in the art that various changes and modifications in form and detail may be made therein without departing from the spirit and scope of the present disclosure.

[0015] Embodiments of the present disclosure relate to multi-column overlay metrology that provides high-throughput sampling of overlay targets distributed across a sample. In some embodiments, an overlay metrology tool includes multiple measurement columns, each including an illumination subsystem that directs illumination from an illumination source toward the sample and a collection subsystem that collects light from the sample as a measurement signal and directs the measurement signal to a detector. In addition, at least some of the measurement columns may include dedicated column positioning subsystems (e.g., using one or more translation stages) to provide independent positioning of the measurement columns in any direction. As a result, each measurement column may have a measurement region based on both the measurement field of view of the collection subsystem (e.g., related to the spatial extent of the sample from which the collection subsystem can collect measurement signals) and the range of motion of the column positioning subsystem. It is contemplated herein that multiple measurement columns combined with independent positioning of at least some of the measurement columns may provide a flexible platform for parallel measurement of metrology targets across a sample with high overall measurement throughput.

[0016] As used herein, it is generally contemplated that a measurement array may include any type of illumination source known in the art that is suitable for providing overlay measurements. For example, the measurement array may include an optical measurement array for illuminating a sample with light having a selected spectrum and capturing reflected, diffracted, and / or scattered light from the sample for measurement. The optical measurement array may utilize any selected wavelength of illumination, including, but not limited to, extreme ultraviolet (EUV), deep ultraviolet (DUV), vacuum ultraviolet (VUV), ultraviolet (UV), visible, or infrared (IR) wavelengths. As another example, the measurement array may include an X-ray measurement array for illuminating a sample with X-ray illumination and generating X-ray measurement signals collected from the sample for measurement. As another example, the measurement array may include a particle beam measurement array for illuminating a sample with a particle beam, such as, but not limited to, an electron beam, an ion beam, or a neutral particle beam. The particle beam measurement array may then collect various measurement signals, such as, but not limited to, backscattered electrons, secondary electrons, or luminescence from the sample for measurement. Additionally, a multi-column overlay tool can include any combination of measurement columns with any selected illumination source.

[0017] For purposes of this disclosure, the term overlay metrology broadly refers to measurements of the misalignment of features formed by two or more exposures on a common portion of a specimen. In this regard, overlay metrology can provide measurements of the alignment of features formed on two or more layers on a specimen, as well as measurements of the alignment of features formed through successive exposures on a common specimen layer (e.g., double patterning, triple patterning, etc.). Furthermore, overlay metrology can be performed at any suitable location on the specimen. For example, overlay metrology can be performed on one or more overlay targets designed to provide overlay metrology representative of device features of interest. Such overlay targets can be positioned with a die on the specimen, in a scribe line, or in any other suitable location. As another example, overlay metrology can be performed directly on device features. Furthermore, overlay metrology can be performed on features associated with any step of the manufacturing process. In this regard, the systems and methods disclosed herein are generally applicable to, but not limited to, after develop inspection (ADI), after etch inspection (AEI), or after clean inspection (ACI). For purposes of this disclosure, the term overlay target is used broadly to describe any suitable portion of a specimen that is characterized by the measurement array of an overlay metrology tool, including, but not limited to, a dedicated overlay target or a device feature suitable for direct overlay measurement.

[0018] The speed at which a translation stage within the measurement column can adjust the position of the measurement column may be based at least in part on the mass of the measurement column. The greater the mass, the slower the positioning speed. Therefore, it may be desirable to limit the number and / or mass of components placed within the measurement column. In some embodiments, at least one of the measurement columns receives illumination from an illumination source external to the measurement column. In this manner, the measurement column need not include a mass associated with the illumination source. Similarly, in some embodiments, at least one of the measurement columns directs measurement signals to a detector external to the measurement column. However, it should be understood that the present disclosure extends to metrology systems having any combination of illumination sources or detectors on the measurement column. Furthermore, the measurement column may be coupled to external components (e.g., illumination sources, detectors, etc.) using any technique known in the art, including, but not limited to, fiber optics or free-space optics.

[0019] Further embodiments of the present disclosure are directed to multiplexing and / or demultiplexing illumination from illumination sources or measurement signals directed to detectors. In this way, measurement trains can share illumination sources and / or detectors.

[0020] In some embodiments, illumination from an illumination source is split along multiple paths and directed to multiple measurement trains (e.g., some or all of the measurement trains). For example, the illumination directed to the sample through the various measurement trains may generally have common characteristics (e.g., polarization, wavelength, temporal characteristics, particle energy, etc.) to provide common illumination conditions throughout the various measurement trains. As another example, the illumination directed to the sample through the various measurement trains may have different characteristics. In this configuration, the illumination may be multiplexed based on one or more characteristics of the illumination.

[0021] In some embodiments, measurement signals from multiple measurement columns are directed to a common detector. In this configuration, the measurement signals directed to the common detector from the various measurement columns may have different characteristics (e.g., polarization, wavelength, temporal characteristics, etc.). Furthermore, the measurement signals from the various measurement columns may be multiplexed based on one or more characteristics of the measurement signals. The detector can then receive the measurement signals and generate separate detector signals associated with each measurement column. In another embodiment, the metrology system further includes a detector demultiplexer that receives the multiplexed light from the various measurement columns and places them along a common path before being directed to one or more detectors.

[0022] Further embodiments of the present disclosure are directed to various configurations of independently positionable measurement arrays to facilitate large-scale sampling of many metrology targets distributed across a sample, in some embodiments, multiple measurement arrays are distributed along a line along the array direction.

[0023] For example, the measurement system can include measurement columns along a spatial extent at least as long as the dimensions of the sample. In this manner, the sample can be scanned along a scan direction that may, but need not, be orthogonal to the column direction. In this configuration, the measurement targets can be distributed along a linear path along the scan direction, such that scanning the sample along the scan direction can bring the measurement targets within the measurement regions of the various measurement columns. Furthermore, the column positioning subsystem can adjust the position of the measurement columns as needed to probe the measurement targets.

[0024] As another example, the metrology system may include measurement arrays distributed in a two-dimensional pattern across the sample. In this regard, the measurement regions of the various measurement arrays may be distributed in two dimensions across the sample, and the column positioning subsystem may position each of the measurement arrays to probe a measurement target within its associated measurement region.

[0025] It is further contemplated herein that a metrology system including an independently positionable measurement array can probe a measurement target in either a scanning mode, where the sample is moving during measurement, or a stationary mode (e.g., move and measure or MAM mode), where the sample is stationary during measurement.

[0026] Further embodiments of the present disclosure are directed to self-calibration of multi-column overlay tools having measurement columns with different illumination sources. Overlay metrology tools with different illumination sources may have different trade-offs between measurement accuracy and measurement throughput. For example, particle beam metrology systems (e.g., electron beam metrology systems) may provide relatively high accuracy but relatively low throughput, while optical metrology systems may provide relatively high throughput but relatively low accuracy. However, it is contemplated herein that metrology data from one measurement column of a multi-column overlay tool can be used to calibrate metrology data from another measurement column to provide the benefits of both types of measurement columns. Training one metrology tool with data from a second metrology tool is generally described in U.S. Patent Application Publication No. 2019 / 0003988, published January 3, 2019, and incorporated herein by reference in its entirety. Embodiments of the present disclosure are directed to using a single overlay tool with different types of measurement columns to provide self-calibrated measurement data. Such tools can benefit from rapid self-calibration, reduced complexity, and reduced cost compared to multi-tool systems.

[0027] In some embodiments, a multi-column overlay metrology tool includes one or more measurement columns of a first type and one or more measurement columns of a second type, where the first and second types may have different throughputs and / or measurement accuracies. For example, the first type may have a relatively higher accuracy and a relatively lower throughput than the second type. As a non-limiting example, the first type may include, but is not limited to, a particle beam metrology column or an X-ray metrology column, and the second type may include, but is not limited to, an optical metrology column. The multi-column metrology tool may then generate overlay metrology of one or more overlay targets using both the first and second types of metrology columns and then calibrate the metrology data from the second type of metrology column with the metrology data from the second type of metrology column. In this manner, the calibrated second type of metrology column can provide improved accuracy (e.g., compared to an uncalibrated configuration) while maintaining a relatively high throughput. As a result, the multi-column metrology tool may provide measurements of future overlay targets using only the second type of calibrated measurement column to generate accurate overlay data with high throughput.

[0028] 1A-7, systems and methods for metrology using multiple measurement arrays will be described in more detail, in accordance with one or more embodiments of the present disclosure.

[0029] 1A is a conceptual diagram of an overlay metrology system 100 having a multi-column overlay metrology tool 102 with multiple measurement columns 104, in accordance with one or more embodiments of the present disclosure. For example, FIG. 1A illustrates a multi-column overlay metrology tool 102 having N measurement columns 104. In a general sense, the overlay metrology system 100 can include any number of measurement columns 104.

[0030] In one embodiment, the multi-column overlay metrology tool 102 includes at least one illumination source 106 that generates illumination 134 that is directed toward the sample 108 through one or more measurement columns 104, and at least one detector 110 that captures measurement signals from the sample 108 (e.g., light and / or particles from the sample 108) by the one or more measurement columns 104. Furthermore, any particular measurement column 104 may be configured in a reflective configuration (e.g., the measurement signal includes reflected, diffracted, or scattered light on the same side of the sample 108 as the incident illumination 134) or a transmissive configuration (e.g., the measurement signal includes transmitted, diffracted, or scattered light on the opposite side of the sample 108 from the incident illumination 134).

[0031] Illumination source 106 (e.g., one of one or more illumination sources 106 in overlay metrology system 100) may include any type of source suitable for generating illumination suitable for overlay measurements. For example, illumination source 106 may include an electromagnetic source for generating electromagnetic illumination 134 having a wavelength in any region of the electromagnetic spectrum, including, but not limited to, X-ray, EUV, DUV, VUV, UV, visible, or IR spectral ranges. As another example, illumination source 106 may include a particle beam source for generating particle-based illumination 134, such as, but not limited to, an electron beam (e-beam), an ion beam, or a neutral particle beam.

[0032] In one embodiment, illumination source 106 is a laser source. For example, illumination source 106 may include, but is not limited to, one or more narrowband laser sources, broadband laser sources, supercontinuum laser sources, white light laser sources, etc. In this regard, illumination source 106 may provide illumination having high coherence (e.g., high spatial coherence and / or temporal coherence).

[0033] In another embodiment, illumination source 106 includes a plasma source, such as, but not limited to, a laser-sustained plasma (LSP) source. For example, illumination source 106 may include, but is not limited to, an LSP lamp, an LSP bulb, or an LSP chamber suitable for housing one or more elements capable of emitting broadband illumination when excited into a plasma state by a laser source. In another embodiment, illumination source 106 includes a lamp source. For example, illumination source 106 may include, but is not limited to, an arc lamp, a discharge lamp, an electrodeless lamp, etc. In this regard, illumination source 106 may provide illumination having low coherence (e.g., low spatial coherence and / or temporal coherence).

[0034] In another embodiment, the illumination source 106 includes an X-ray source for generating X-ray illumination 134 of any wavelength, including, but not limited to, hard or soft X-rays. For example, the illumination source 106 may include a hard X-ray source for forming a spatially coherent hard X-ray beam having an energy of approximately 3-20 keV. For example, the illumination 134 may include X-rays having an energy of approximately 5-6 keV. As another example, the illumination source 106 may include a laser-produced plasma (LPP) X-ray source. For example, the illumination source 106 may include a laser source configured to generate a laser beam for exciting a plasma. In response to the laser radiation, the plasma can generate a spatially coherent X-ray beam. As another example, the illumination source 106 may include, but is not limited to, a Compton X-ray source.

[0035] In some embodiments, the illumination source 106 or the multi-column overlay metrology tool 102, more generally, may include any number of conditioning elements configured to improve the coherence of the x-ray illumination 134. For example, the measurement column 104 may include, but is not limited to, one or more x-ray optics for capturing, refocusing, spatially filtering, and / or conditioning the x-ray output from the plasma to achieve a desired level of spatial coherence.

[0036] In another embodiment, the illumination source 106 includes a particle source. For example, the illumination source 106 may include, but is not limited to, an electron gun or an ion gun. In another embodiment, the illumination source 106 is configured to provide a particle beam having an adjustable energy. For example, an illumination source 106 including an electron source may provide an acceleration voltage in the range of 0.1 kV to 30 kV, but is not limited thereto. As another example, an illumination source 106 including an ion source may provide an ion beam having an energy in the range of 1 keV to 50 keV, but this is not required.

[0037] The illumination source 106 may, but need not, provide further illumination in the form of one or more illumination beams or lobes. In this regard, the multi-column overlay metrology tool 102 may provide dipole illumination, orthogonal illumination, etc. The multiple illumination beams can be generated in various ways. In one embodiment, the multi-column overlay metrology tool 102 includes one or more apertures in an illumination pupil plane to split the illumination from the illumination source 106 into one or more illumination beams. In another embodiment, the overlay metrology system 100 directly generates illumination in one or more illumination beams. For example, one or more illumination sources 106 can directly generate illumination in one or more illumination beams. For example, one or more illumination sources 106 may provide light to two or more optical fibers, with the optical output from each optical fiber providing an illumination beam. These optical fibers may be positioned in the illumination pupil or may be paired with separate illumination optics to directly illuminate the sample 108. In another example, illumination source 106 generates multi-lobe illumination by diffracting a light source into two or more diffraction orders, with illumination lobes of the illumination formed from at least some of the diffraction orders of the light source. Efficient generation of multiple illumination lobes through controlled diffraction is generally described in U.S. Patent Application Publication No. 2020 / 0124408, published April 23, 2020, and incorporated herein by reference in its entirety. As another example, overlay metrology system 100 may include one or more beam steering or diffractive optics that selectively adjust the position of at least one illumination beam at an illumination pupil plane to provide selective control over the illumination angle of incidence.

[0038] Additionally, the spatial profile of the illumination comprising one or more illumination beams on the sample 108 can be controlled by the illumination field stop to have any selected spatial profile.

[0039] The multi-column overlay metrology tool 102 may include any number or type of detectors 110 suitable for capturing measurement signals 122 from the sample 108 indicative of overlay. For example, the detectors 110 may include one or more sensors suitable for capturing light at any wavelength in the electromagnetic spectrum (e.g., photodetectors, photomultiplier tubes (PMTs), X-ray detectors, etc.). As another example, the detectors 110 may include one or more particle detectors suitable for capturing particles (e.g., electrons, ions, neutral particles) from the sample 108. As another example, the detectors 110 may include scintillation elements coupled to photodetectors for detecting particles and / or photons from the sample surface.

[0040] In one embodiment, the detector 110 is suitable for characterizing a static sample. In this regard, the multi-column overlay metrology tool 102 can operate in a static mode in which the sample 108 is static during measurements. For example, the detector 110 can include an imaging detector having a 2D pixel array suitable for generating a 2D image (e.g., a field plane image, a pupil plane image, etc.), such as, but not limited to, a charge-coupled device (CCD) or a complementary metal-oxide semiconductor (CMOS) device.

[0041] In another embodiment, the detector 110 includes one or more detectors 110 suitable for characterizing a moving sample (e.g., a scanning sample). In this regard, the multi-column overlay metrology tool 102, or any measurement column 104 therein, can operate in a scanning mode in which the sample 108 is scanned relative to a measurement region during measurement. For example, the detector 110 may include a 2D pixel array having an acquisition time and / or refresh rate sufficient to capture one or more images during a scan within selected image tolerances (e.g., image blur, contrast, sharpness, etc.). As another example, the detector 110 may include a line-scan detector that sequentially generates images of one line of pixels at a time. As another example, the detector 110 may include a time-delay-integration (TDI) detector that generates sequential images of the sample 108 when the movement of the sample 108 is synchronized to a charge-transfer clock signal in the TDI detector.

[0042] In another embodiment, the measurement column 104 (e.g., one or more of the N measurement columns 104) includes a column positioning subsystem 112 to provide independent positioning of the measurement column 104. The column positioning subsystem 112 may include one or more actuators configured to independently position the measurement column 104 along one or more directions. For example, the column positioning subsystem 112 may include, but is not limited to, one or more linear translation stages, one or more rotational translation stages, or one or more tip / tilt actuators. In this manner, the column positioning subsystem 112 of the measurement column 104 can position components of the measurement column 104 relative to the sample 108 along any desired dimension. For example, the column positioning subsystem 112 can facilitate alignment of the measurement column 104 with a measurement target on the sample 108.

[0043] In another embodiment, the overlay metrology system 100 includes a sample positioning system 114 that secures and / or positions the sample 108 relative to any of the measurement columns 104. The sample positioning subsystem 114 can include one or more actuators configured to independently position the sample 108 along one or more directions. For example, the sample positioning system 114 can include, but is not limited to, one or more linear translation stages, one or more rotational translation stages, or one or more tip / tilt actuators. In this manner, the sample positioning subsystem 114 can position the sample 108 at any selected orientation relative to the measurement column 104.

[0044] FIG. 1B is a conceptual diagram of an overlay metrology system 100 illustrating the relative positioning of the measurement columns 104 and the sample 108 in accordance with one or more embodiments of the present disclosure. For clarity, only a single measurement column 104 is shown in FIG. 1B. The overlay metrology system 100 may be mounted on or otherwise include at least one structural support 116 (e.g., a table, wall, ceiling, etc.) to which various components may be secured, such as, but not limited to, a sample positioning system 114 and a column positioning subsystem 112 for each of the measurement columns 104. In FIG. 1B, the sample positioning system 114 orients the sample 108 laterally (here, in the XY plane), and the measurement column 104 illuminates the sample 108 along an axial direction (here, the Z direction). For example, the measurement column 104 may illuminate the sample 108 with normally incident light propagating along the Z axis or with oblique light having at least one directional component along the Z axis. In another embodiment, each measurement column 104 is mounted to a column positioning subsystem 112, which is itself mounted to a structural support 116. In another embodiment, the sample positioning system 114 includes a 3D translation stage that provides lateral translation of the sample 108 along the lateral plane (XY plane) as well as translation along the axial direction (Z direction). In another embodiment, the sample positioning system 114 includes a rotation stage for rotating the sample 108 in the lateral plane.

[0045] It is contemplated herein that various configurations of the measurement column 104, illumination source 106, and detector 110 are possible within the spirit and scope of the present disclosure. For example, the illumination source 106 and / or detector 110 may be located on or external to the associated measurement column 104. For example, positioning the illumination source 106 and / or detector 110 external to the associated measurement column 104 may reduce the mass of the measurement column 104, which may reduce the load on the column positioning subsystem 112. As a result, providing the illumination source 106 and / or detector 110 external to the associated measurement column 104 may facilitate faster and / or more accurate positioning of the measurement column 104 by the column positioning subsystem 112 than if the components were part of the measurement column 104.

[0046] Regardless of the particular positioning of the illumination source 106 and / or detector 110 relative to the associated measurement column 104, each measurement column 104 may be suitable for measuring overlay when coupled with an illumination source 106 and detector 110. In this regard, each measurement column 104 with an associated illumination source 106 and detector 110 may operate as an overlay tool, and the multi-column overlay metrology tool 102 may be characterized as providing multiple overlay tools suitable for multiple parallel overlay measurements of different portions of the sample 108.

[0047] The multi-column overlay metrology tool 102, or any of the metrology columns 104 therein, can operate as any type of overlay metrology tool known in the art. For example, the multi-column overlay metrology tool 102, or any of the metrology columns 104 therein, can operate in an imaging mode, a non-imaging mode, or be selectively switched between imaging and non-imaging modes. As an illustrative example for an optical metrology column 104, a detector 110 positioned at a field plane conjugate to the sample 108 can generate an image of the sample 108. The image can include a bright-field image, a dark-field image, a phase-contrast image, etc., based on the configuration of the respective illumination subsystems 118 and collection subsystems 120. As another example, one or more detectors 110 positioned at a pupil plane can characterize the angular distribution of radiation from the sample 108 (e.g., related to scattering and / or diffraction of radiation by the sample 108). In this manner, the multi-column overlay metrology tool 102, or any of the metrology columns 104 therein, can operate as a scatterometry (SCOL) overlay tool. Additionally, scatterometry overlay measurements may be performed by generating an image of the pupil plane or by capturing light at selected locations in the pupil plane using a non-imaging detector (e.g., a photodiode). For example, scatterometry overlay using a non-imaging detector at the pupil plane is generally described in U.S. Patent Application No. 17 / 142,783 (filed January 6, 2021), which is incorporated herein by reference in its entirety.

[0048] The multi-column overlay metrology tool 102, or any measurement train 104 therein, may be configurable to generate overlay signals based on any number of recipes that define measurement parameters for overlay measurements. For example, a recipe for the optical measurement train 104 may include, but is not limited to, the illumination wavelength, the detection wavelength of light emanating from the sample, the illumination spot size or shape on the sample, the angle of incident illumination, the polarization of the incident illumination, the polarization of the collected light, the position of the beam of incident illumination on the overlay target, the position of the overlay target in the focal volume of the overlay metrology tool, etc. As another example, a recipe for the particle beam measurement train 104 may include, but is not limited to, particle beam energy or beam scan speed. Furthermore, the multi-column overlay metrology tool 102, or any measurement train 104 therein, may be configured to generate overlay measurements in a scanning mode, a static mode, or to selectively switch between a scanning mode and a static mode.

[0049] 1C-1G, the distribution of components throughout the overlay metrology system 100 will be described in more detail in accordance with one or more embodiments of the present disclosure. In particular, FIGS. 1C and 1D show aspects of the optical measurement column 104, FIG. 1E shows aspects of the EUV measurement column 104, FIG. 1F shows aspects of the X-ray measurement column 104, and FIG. 1G shows aspects of the particle beam measurement column 104.

[0050] In one embodiment, the measurement array 104 (e.g., one or more of the N measurement arrays 104) includes an illumination subsystem 118 configured to direct illumination from the illumination source 106 toward the sample 108 (e.g., a measurement target on the sample 108) and a collection subsystem 120 that collects measurement signals 122 from the sample 108 (e.g., light, particles, etc.) and directs the measurement signals 122 to the detector 110. Figures 1C and 1D show non-limiting examples of various configurations of the illumination subsystem 118 and the collection subsystem 120. It is contemplated herein that the various measurement arrays 104 in the sample 108 may have the same or different configurations.

[0051] 1C-1G, the illumination subsystem 118 may include one or more components suitable for modifying and / or conditioning the illumination 134 and directing the illumination 134 toward the sample 108. In one embodiment, the illumination subsystem 118 includes one or more illumination path focusing elements 124 (e.g., to collimate the illumination 134, to relay a pupil plane and / or a field plane, etc.). In another embodiment, the illumination subsystem 118 includes one or more illumination path control elements 126 that shape or otherwise control the illumination 134. For example, the illumination path control elements 126 may include, but are not limited to, one or more field stops, one or more pupil stops, one or more polarizers, one or more filters, one or more beam splitters, one or more diffusers, one or more homogenizers, one or more apodizers, one or more beam shapers, or one or more mirrors (e.g., static mirrors, translatable mirrors, scanning mirrors, etc.).

[0052] Similarly, the collection subsystem 120 can include one or more elements suitable for modifying and / or conditioning the measurement signal 122 from the sample 108. In one embodiment, the collection subsystem 120 includes one or more collection path focusing elements 128 (e.g., to collimate the measurement signal 122, to relay a pupil plane and / or a field plane, etc.). In another embodiment, the collection subsystem 120 includes one or more collection path control elements 130 that shape or otherwise control the measurement signal 122. For example, the collection path control elements 130 may include, but are not limited to, one or more field stops, one or more pupil stops, one or more polarizers, one or more filters, one or more beam splitters, one or more diffusers, one or more homogenizers, one or more apodizers, one or more beam shapers, or one or more mirrors (e.g., static mirrors, translatable mirrors, scanning mirrors, etc.).

[0053] 1C is a conceptual diagram of a portion of a multi-column overlay metrology tool 102 including an optical measurement train 104 with associated illumination sources 106 and detectors 110 that provide illumination and collection through a common lens, in accordance with one or more embodiments of the present disclosure. Additional measurement trains 104 and associated illumination sources 106 and / or detectors 110 are not shown for clarity. In one embodiment, the measurement train 104 includes a collection lens 132 (e.g., an objective lens) for simultaneously directing illumination 134 from the illumination sources 106 to the sample 108 and collecting measurement signals 122 from the sample 108 for detection by the detector 110. In this regard, the measurement train 104 can provide through-the-lens (TTL) illumination of the sample 108.

[0054] FIG. 1D is a conceptual diagram of a portion of a multi-column overlay metrology tool 102 including an optical measurement column 104 with associated illumination sources 106 and detectors 110 that provide illumination and collection through separate paths, in accordance with one or more embodiments of the present disclosure. As with FIG. 1C, the additional measurement column 104 and associated illumination sources 106 and / or detectors 110 are not shown for clarity. In one embodiment, the measurement column 104 includes separate components and / or optical paths for the illumination subsystem 118 and the collection subsystem 120. In this regard, the measurement column 104 can provide out-of-lens (OTL) illumination of the sample 108. For example, as shown in FIG. 1D, the measurement column 104 can include a collection subsystem 120 having a collection lens 132 with an optical axis oriented perpendicular to the sample 108 (e.g., as shown in FIG. 1C). And, the illumination subsystem 118, having two separate illumination path focusing elements 124, is configured to direct illumination 134 from the illumination source 106 toward the sample 108 at an oblique angle outside the numerical aperture (NA) of the collection lens 132. However, while Figure 1D shows oblique illumination and perpendicular collection, it should be understood that the measurement column 104 may provide illumination and collection at any desired angle.

[0055] 1E is a conceptual diagram of a portion of a multi-column overlay metrology tool 102 including an EUV measurement column 104 with an associated EUV illumination source 106 and detector 110, in accordance with one or more embodiments of the present disclosure. It is recognized herein that the EUV measurement column 104 may require different components or layout than optical systems suitable for visible or IR wavelengths due to the high absorption of EUV light in many materials.

[0056] In one embodiment, the multi-column overlay metrology tool 102 includes an EUV illumination path focusing element 124 suitable for collimating or focusing the EUV illumination 134 and a collection path focusing element 128 (e.g., projection optics) suitable for collecting, collimating, and / or focusing the EUV measurement signal 122 from the sample 108. Furthermore, the collection path focusing element 128 can direct the EUV measurement signal 122 to one or more detectors 110. The illumination path focusing element 124 and / or the collection path focusing element 128 may include any type of focusing element suitable for use with the wavelength of light from the illumination source 106. For example, the illumination path focusing element 124 and / or the collection path focusing element 128 may include, but are not limited to, a mirror or other reflective surface (e.g., spherical mirror, parabolic mirror, elliptical mirror, etc.). In this manner, absorption losses can be mitigated or otherwise controlled. Furthermore, the illumination path focusing element 124 may operate at any suitable angle of incidence. For example, a glancing angle mirror may provide efficient reflection.

[0057] 1F is a conceptual diagram of a portion of a multi-column overlay metrology tool 102 including an X-ray measurement column 104 with an associated particle illumination source 106 and detector 110, in accordance with one or more embodiments of the present disclosure. Metrology using X-ray sources is generally described in U.S. Patent 9,846,132 (December 19, 2017), U.S. Patent 10,775,323 (September 15, 2020), and U.S. Patent Application Publication No. 2019 / 0003988, all of which are incorporated by reference herein in their entireties. For example, FIG. 1F shows a transmission-type X-ray measurement column 104.

[0058] In one embodiment, the multi-column overlay metrology tool 102 includes an X-ray illumination path focusing element 124 suitable for collimating or focusing the X-ray illumination 134 and a collection path focusing element 128 suitable for collecting, collimating, and / or focusing the X-ray measurement signal 122 from the sample 108, such as, but not limited to, an X-ray collimating mirror. For example, the multi-column overlay metrology tool 102 can include, but is not limited to, an X-ray collimating mirror, a specular X-ray optic such as a grazing incidence ellipsoidal mirror, a polycapillary optic such as a hollow capillary X-ray waveguide, a multilayer optic, or system, or any combination thereof. In another embodiment, the multi-column overlay metrology tool 102 includes an X-ray illumination path control element 126, such as, but not limited to, an X-ray monochromator (e.g., a crystal monochromator such as a Loxley-Tanner-Bowen monochromator), an X-ray aperture, an X-ray beam stop, or a diffractive optic such as a zone plate.

[0059] FIG. 1G is a conceptual diagram of a portion of a multi-column overlay metrology tool 102 including a particle-based measurement array 104 with an associated particle illumination source 106 and detector 110 in accordance with one or more embodiments of the present disclosure.

[0060] In one embodiment, the multi-column overlay metrology tool 102 includes one or more particle focusing elements. For example, FIG. 1G illustrates an illumination path focusing element 124, a collection path focusing element 128, or the like. For example, the one or more particle focusing elements may include, but are not limited to, a single particle focusing element or one or more particle focusing elements forming a combined system. In another embodiment, the one or more particle focusing elements include a focusing lens 132 configured to direct particle illumination 134 toward the sample 108. Furthermore, the one or more particle focusing elements may include any type of electron lens known in the art, including, but not limited to, an electrostatic, magnetic, monopotential, or bipotential lens. Note that the description of the voltage contrast imaging inspection system as depicted in FIG. 1C and the related description above is provided for illustrative purposes only and should not be construed as limiting. For example, the multi-column overlay metrology tool 102 may include any excitation source known in the art suitable for generating inspection data on the sample 108. In another embodiment, the multi-column overlay metrology tool 102 includes two or more particle beam sources (e.g., electron beam sources or ion beam sources) for generating two or more particle beams. In a further embodiment, the multi-column overlay metrology tool 102 includes one or more components (e.g., one or more electrodes) configured to apply one or more voltages to one or more locations on the sample 108. In this regard, the multi-column overlay metrology tool 102 can generate voltage contrast imaging data.

[0061] In another embodiment, the multi-column overlay metrology tool 102 includes one or more particle detectors 110 for imaging or otherwise detecting particles emanating from the sample 108. In one embodiment, the detector 110 includes an electron collector (e.g., a secondary electron collector, a backscattered electron detector, etc.). In another embodiment, the detector 110 includes a photon detector (e.g., a light detector, an X-ray detector, a scintillator element coupled to a photomultiplier tube (PMT) detector, etc.) for detecting electrons and / or photons from the sample surface.

[0062] Additionally, it is contemplated herein that components associated with illuminating the sample 108 and / or collecting the measurement signal 122 from the sample may be distributed within any of the measurement columns 104, outside any of the measurement columns 104, or shared among any of the measurement columns 104. For example, FIG. 1C illustrates a configuration in which the illumination source 106 and the detector 110 are located outside the measurement column 104. In a configuration in which the illumination source 106 is located outside the measurement column 104, the overlay metrology system 100 may include an illumination connection path 136 that provides a path between the illumination source 106 and the measurement column 104. Similarly, in a configuration in which the detector 110 is located outside the measurement column 104, the overlay metrology system 100 may include a detection connection path 138 that provides a path between the measurement column 104 and the detector 110. The illumination connection path 136 and / or the detection connection path 138 may include any combination of components suitable for providing a path for the illumination 134 and / or the measurement signal 122. As an example, in the case of optical illumination 134, illumination connection path 136 and / or detection connection path 138 may include one or more optical fibers. As another example, illumination connection path 136 and / or detection connection path 138 may include one or more free-space components. For example, illumination connection path 136 and / or detection connection path 138 may include one or more tiltable transmitter free-space components and one or more tiltable receiver free-space components to provide a stable path when measurement column 104 is moving.

[0063] 1C-1G are provided for illustrative purposes only and should not be construed as limiting. Rather, the various components of the multi-column overlay metrology tool 102 may be distributed within one or more measurement columns 104, external to any measurement column 104, or shared among any measurement columns 104. Furthermore, the measurement columns 104 associated with any illumination source 106 may have any suitable layout of elements. For example, the measurement columns 104 associated with any illumination source 106 may be configured in a reflective or transmissive mode. As another example, the measurement columns 104 associated with any illumination source 106 may have a combination of suitable illumination path focusing elements 124, illumination path control elements 126, collection path focusing elements 128, or collection path control elements 130, whether or not shown in FIGS. 1C-1G.

[0064] In another embodiment, not shown in FIGS. 1C-1G, the measurement array 104, the entire multi-column overlay metrology tool 102, or any portion thereof, can be enclosed within a chamber. In this manner, the atmosphere and / or pressure within the chamber can be controlled. For example, the overlay metrology system 100 can include a vacuum pump that creates a desired vacuum strength within the chamber. As another example, the overlay metrology system 100 can include a gas flow system that fills the chamber with a selected gas composition at a selected pressure.

[0065] In some embodiments, the collection subsystem 120 of the measurement column 104 may be configured to generate metrology data at different depths within the sample 108. For example, in the configurations shown in FIGS. 1C-1G, the position of the measurement plane (e.g., image plane) of the collection lens 132 relative to the surface of the sample 108 may be adjusted in a number of ways. In one example, the sample 108 may be translated along the axial direction (Z direction) by the sample positioning system 114. In another embodiment, the measurement column 104 may be adjusted along the axial direction (Z direction) by the column positioning subsystem 112. In another example, one or more of the collection path focusing elements 128 may be adjusted to modify the measurement plane.

[0066] Additionally, measurements at multiple measurement planes may be provided sequentially or simultaneously. For example, sequential measurements may be provided by sequentially moving the sample 108 or measurement array 104 (or portions thereof) to provide sequential measurements. As another example, simultaneous measurements may be provided using multiple detectors 110 and associated collection path focusing elements 128 configured to generate different measurement planes for each of the detectors 110.

[0067] 2A-3B, various illumination and collection implementations are described in more detail in accordance with one or more embodiments of the present disclosure.

[0068] In one embodiment, at least one of the measurement trains 104 includes a dedicated illumination source 106 and / or detector 110. Such a configuration can facilitate independent control and component use of the measurement trains 104. Furthermore, parameters related to illumination and / or collection (e.g., wavelength, polarization, spectrum, temporal characteristics of the illumination 134, detector integration time, etc., of the illumination 134 and / or measurement signals 122 directed to the detector 110) can be independently controlled for each measurement train 104 without affecting the other measurement trains 104. FIG. 2A is a conceptual diagram of a series of measurement trains 104 distributed across a sample 108 that provide independent illumination and collection, in accordance with one or more embodiments of the present disclosure. In FIG. 2A, each measurement train 104 receives illumination 134 from a separate illumination source 106 and directs measurement signals 122 from the sample 108 to a separate detector 110.

[0069] In another embodiment, two or more measurement strings 104 receive illumination from a common illumination source 106. This configuration can reduce system complexity and / or cost if the illumination source 106 provides sufficient power to drive multiple measurement strings 104. Additionally, as discussed in more detail below, illumination from the common illumination source 106 may, but need not, be multiplexed so that different measurement strings 104 receive illumination having distinguishable parameters.

[0070] Similarly, the measurement columns 104 can use dedicated or shared detectors 110. In one embodiment, each detector 110 receives measurement signals 122 from a separate measurement column 104. In another embodiment, a common detector 110 receives measurement signals 122 from two or more measurement columns 104. Figure 2B is a conceptual diagram of a series of measurement columns 104 distributed across a sample 108 sharing a common illumination source 106 and a common detector 110, in accordance with one or more embodiments of the present disclosure.

[0071] It is contemplated herein that detection of measurement signals 122 from multiple measurement columns 104 may require multiplexing / demultiplexing of the measurement signals 122 based on one or more distinguishable optical characteristics of the measurement signals 122, such as, but not limited to, wavelength, polarization, or time characteristics (e.g., relative time delay between the measurement signals 122 from the measurement columns 104). Thus, the measurement signals 122 from the various measurement columns 104 may be distinguishable by the detector 110, which may generate separate detection signals associated with each of the measurement columns 104. In one embodiment, the overlay metrology system 100 includes one or more components that direct the measurement signals 122 from different measurement columns 104 to different portions of the detector 110. For example, the measurement signals 122 from the various measurement columns 104 may be directed to different portions of the detector 110 along separate paths. As another example, if the measurement signals 122 are multiplexed based on wavelength, the detector 110 may include a diffractive element (e.g., a prism, a diffraction grating, etc.) to physically separate the measurement signals 122 from different measurement trains 104 on the detector 110. In another embodiment, if the measurement signals 122 are multiplexed based on a time characteristic (e.g., based on a delay line, etc.), the measurement signals 122 from the various measurement trains 104 may be directed to a common portion of the detector 110 and distinguished based on time.

[0072] In one embodiment, generating the multiplexed measurement signal 122 is implemented, at least in part, by multiplexing the illumination provided to the various measurement columns 104. In this manner, the measurement signals 122 from the various measurement columns 104 can be multiplexed in a similar manner. Furthermore, the illumination provided to the various measurement columns 104 may be multiplexed using multiple techniques. For example, in a configuration where a measurement column 104 has a dedicated illumination source 106, the dedicated illumination source 106 can be configured to provide different illumination parameters than the other measurement columns 104. As another example, components of the illumination subsystem 118 of a measurement column 104 (e.g., illumination path control element 126, illumination path focusing element 124, etc.) can be configured to provide selected illumination parameters that differ from the other measurement columns 104.

[0073] As another example, in a configuration in which two or more measurement columns 104 receive illumination from a common illumination source 106, the overlay metrology system 100 may include an illumination multiplexer 140 for introducing different illumination parameters into the illumination directed to the various measurement columns 104. FIG. 3A is a conceptual diagram of an illumination multiplexer 140 in accordance with one or more embodiments of the present disclosure. In one embodiment, the illumination multiplexer 140 includes one or more beam splitters 302 for splitting the illumination 134 from the illumination source 106 into a selected number of paths 304, with light from each of the paths 304 being directed to a different measurement column 104 (e.g., along an illumination connection path 136). Additionally, the illumination multiplexer 140 may include illumination path control elements 126 and / or illumination path focusing elements 124 in any of the paths 304 to distinguish between the illumination 134 directed to the various measurement columns 104. The illumination path control elements 126 and / or illumination path focusing elements 124 may be substantially the same as those described with respect to the illumination subsystem 118 of the measurement column 104 and may include, but are not limited to, filters, apertures, polarizers, time delay lines, etc. In this regard, illumination multiplexing may occur external to the measurement column 104, within the measurement column 104, or through any combination of the two.

[0074] In another embodiment, generating the multiplexed measurement signal 122 is performed, at least in part, by directly multiplexing the measurement signals 122 from one or more measurement sequences 104. For example, the acquisition subsystem 120 of a measurement sequence 104 may distinguish the measurement signals 122 from that measurement sequence 104 from the measurement signals 122 from other measurement sequences 104. Multiplexing the measurement signals 122 is particularly suited to, but not limited to, multiplexing based on polarization or time characteristics.

[0075] 3B is a conceptual diagram of a detection demultiplexer 142 in accordance with one or more embodiments of the present disclosure. In one embodiment, the detection demultiplexer 142 includes one or more beam combiners 306 for collecting measurement signals 122 from multiple paths 308 (e.g., from multiple detection connection paths 138) into a common path 310 directed to the detector 110. In this manner, the detector 110 can receive the measurement signals 122 from the various paths 308. Additionally, the detection demultiplexer 142 can include collection path control elements 130 and / or collection path focusing elements 128 along any of the paths 308 to cause the measurement signals 122 from each of the measurement columns 104 to be distinguishable by the detector 110.

[0076] However, it should be understood that the diagrams of Figures 3A and 3B, along with the associated description, are provided for illustrative purposes only and should not be construed as limiting. For example, Figures 3A and 3B depict the illumination path focusing element 124 and the collection path focusing element 128 as transmissive lenses used for optical wavelengths. However, it should be understood that the concepts illustrated in Figures 3A and 3B are applicable to any type or combination of measurement arrays 104, including, but not limited to, X-ray measurement arrays 104, EUV measurement arrays 104, or particle beam measurement arrays 104. Accordingly, the illumination multiplexer 140 and / or the detection demultiplexer 142 may include any appropriate components based on the target illumination 134 and measurement signals 122.

[0077] 4A-4B, various physical configurations of the measurement arrays 104 in the overlay metrology system 100 are described in more detail in accordance with one or more embodiments of the present disclosure. It is contemplated herein that the multiple measurement arrays 104 may be distributed in various patterns relative to the sample 108. Furthermore, different distribution patterns of the measurement arrays 104 may be suitable for scanning mode measurements, static mode measurements, or selectively switching between the two.

[0078] In one embodiment, two or more measurement rows 104 are distributed along the column direction. For example, the two or more measurement rows 104 may be distributed linearly along the column direction or along a curved path having at least one directional component along the column direction.

[0079] 4A is a conceptual diagram of an overlay metrology system 100 including a series of measurement columns 104 distributed along a column direction, in accordance with one or more embodiments of the present disclosure. In FIG. 4A, the column direction corresponds to the Y direction.

[0080] 4A , each of the measurement columns 104 may have a measurement region 402 defined by the field of view of the associated collection subsystem 120 (e.g., the field of view of the collection lens 132 in the collection subsystem 120) and the range of motion of the associated column positioning subsystem 112 (e.g., in the lateral XY plane shown in FIG. 4A ). For example, the measurement region 402 of each measurement column 104 is illustrated as a circle in FIG. 4A , which may have a size defined by the radius of the field of view of the collection subsystem 120 (not shown), which is typically circular, and the range of motion of the column positioning subsystem 112 along the X and Y directions. However, the measurement region 402 may generally have any size or shape.

[0081] The measurement column 104 can perform measurements on the measurement targets within its measurement area by aligning the field of view of the collection subsystem 120 with the measurement targets using the column positioning subsystem 112. Additionally, an overlay metrology system 100 including a distribution of measurement columns 104 along the column direction as shown in FIG. 4A can measure multiple measurement targets distributed across the sample 108 by scanning the sample 108 along one or more scan paths different from the column direction to move various measurement targets on the sample 108 through the measurement area 402 of the measurement column 104. For example, the scan paths can include, but are not limited to, scanning along the X direction.

[0082] Additionally, a series of measurement swaths 404 may be defined that include areas on the sample 108 that are brought within the measurement regions 402 of the various measurement columns 104 as the sample 108 passes along the scan path through the overlay metrology system 100. For example, Figure 4A shows a series of parallel measurement swaths 404 along the X direction associated with scanning the sample 108 along the X direction.

[0083] 4B is a conceptual diagram of a measurement swath 404 on a sample 108 that includes a non-linear distribution of measurement targets (or cells thereof), in accordance with one or more embodiments of the present disclosure. For example, FIG. 4B shows a starting position of the field of view 406 of the collection subsystem 120 that is approximately centered within the measurement swath 404 along a column direction 408 that is perpendicular to the scan direction 410. FIG. 4B further shows a first measurement target 412 at a first position along the column direction 408 and a second measurement target 414 at a second position along the column direction 408. In one embodiment, the column positioning subsystem 112 (not shown) can continuously adjust the field of view 406 of the collection subsystem 120 to align with the first measurement target 412 to provide a measurement of the first measurement target 412, and then adjust the field of view 406 of the collection subsystem 120 to align with the second measurement target 414 to provide a measurement of the second measurement target 414 as the sample 108 is scanned along the scan direction 410. Additionally, measurements of the first metrology target 412 and the second metrology target 414 may be performed while the sample 108 is moving along the scan direction 410 (e.g., in a scanning mode) or while the sample 108 is stationary (e.g., in a static mode). In this regard, it should be understood that references to scanning the sample 108 are not limited to scanning mode measurements, but more generally refer to moving the sample 108 to position a selected metrology target within a measurement region of the measurement array 104.

[0084] Referring again to FIG. 4A , it is contemplated herein that the measurement array 104 may be distributed at any density along any length or spatial extent along the array direction. In this regard, the illustration of FIG. 4A is provided merely for illustrative purposes and should not be construed as limiting. For example, FIG. 4A illustrates a distribution of measurement arrays 104 spanning the size of the sample 108 (e.g., the expected size of the sample 108 to be measured), such that measurement targets across the sample 108 may be characterized as the sample 108 is scanned. However, in some embodiments, the measurement array 104 may span a length along the array direction that is greater than or less than the sample 108 (where multiple scans may be required to measure the entire sample 108).

[0085] As another example, FIG. 4A illustrates a distribution of measurement arrays 104 positioned such that the measurement areas 402 provide complete coverage of the sample 108 along the row direction. In this regard, the entire sample 108 can be measured in a single scan. However, in some embodiments, the measurement arrays 104 may be spread out along the row direction such that gaps exist between the measurement areas 402 along the row direction. In this regard, multiple scans may be required to measure the entire sample 108. In one embodiment, the measurement arrays 104 are positioned to correspond to scribe lines on the sample 108 that may include measurement targets. In this case, the measurement targets within the scribe lines along the scan direction can be measured in a single scan, even though gaps exist between the measurement areas 402 along the row direction.

[0086] In another embodiment, the multiple measurement columns 104 are distributed in a two-dimensional pattern. In this regard, the measurement regions 402 associated with the measurement columns 104 may be distributed across the sample 108. Additionally, the column positioning subsystem 112 of each measurement column 104 may adjust the position of the measurement column 104 to align the field of view of the collection subsystem 120 (e.g., the collection lens 132 in the collection subsystem 120) with any metrology target within the associated measurement region 402 for measurement.

[0087] FIG. 5 is a conceptual diagram of an overlay metrology system 100 including a two-dimensional distribution of measurement columns 104 in accordance with one or more embodiments of the present disclosure. For example, FIG. 5 illustrates a configuration of the overlay metrology system 100 having four measurement columns 104, each having a measurement area 402 that spans one-quarter of the sample 108. For example, for a sample 108 having a diameter of 300 mm (e.g., corresponding to one standard size of a semiconductor wafer), the column positioning subsystem 112 for each measurement column 104 can provide approximately 150 mm of movement in both the X and Y directions. Additionally, FIG. 5 illustrates the column positioning subsystem 112 associated with each measurement column 104.

[0088] It is contemplated herein that the measurement array 104 may be distributed to provide any selected distribution or density of measurement areas 402. In one embodiment, the measurement areas 402 of the measurement array 104 may correspond to angular sections (e.g., relative to a center point) of the sample 108. In another embodiment, the measurement areas 402 of the measurement array 104 may be distributed in a two-dimensional array or grid pattern.

[0089] 5 illustrates a configuration in which the measurement regions 402 cover the entire sample 108 such that the entire sample 108 can be measured without requiring translation of the sample 108. In some embodiments, the overlay metrology system 100 is configured to provide gaps between at least some of the measurement regions 402 such that a complete measurement of the sample 108 can be provided by translating the sample 108. In this regard, the required range of each column positioning subsystem 112 can be reduced to facilitate faster and / or more accurate measurement of the metrology target within the associated measurement region 402.

[0090] 1A , in one embodiment, the overlay metrology system 100 includes a controller 144 communicatively coupled to the multi-column overlay metrology tool 102 and / or any components therein. In another embodiment, the controller 144 includes one or more processors 146. For example, the one or more processors 146 may be configured to execute a set of program instructions maintained in a memory device 148 or memory. The one or more processors 146 of the controller 144 may include any processing element known in the art. In this sense, the one or more processors 146 may include any microprocessor-type device configured to execute algorithms and / or instructions.

[0091] The one or more processors 146 of the controller 144 may include any processor or processing element known in the art. For purposes of this disclosure, the term “processor” or “processing element” may be broadly defined to encompass any device having one or more processing or logic elements (e.g., one or more microprocessor devices, one or more application specific integrated circuit (ASIC) devices, one or more field programmable gate arrays (FPGAs), or one or more digital signal processors (DSPs)). In this sense, the one or more processors 146 may include any device configured to execute algorithms and / or instructions (e.g., program instructions stored in a memory). In one embodiment, the one or more processors 146 may be embodied as a desktop computer, a mainframe computer system, a workstation, an image computer, a parallel processor, a networked computer, or any other computer system configured to execute programs that operate or are configured to operate with the overlay metrology system 100 as described throughout this disclosure. Additionally, different subsystems of the overlay metrology system 100 may include processors or logic elements suitable for performing at least some of the steps described in this disclosure. Therefore, the above description should not be construed as a limitation on embodiments of the present disclosure, but merely as an example. Additionally, steps described throughout this disclosure may be performed by a single controller, or alternatively, by multiple controllers. Furthermore, controller 144 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 separately packaged as a module suitable for integration into overlay metrology system 100.

[0092] The memory device 148 may include any storage medium known in the art suitable for storing program instructions executable by the associated one or more processors 146. For example, the memory device 148 may include a non-transitory memory medium. As another example, the memory device 148 may include, but is not limited to, read-only memory (ROM), random access memory (RAM), magnetic or optical memory devices (e.g., disks), magnetic tape, solid-state drives, etc. It is further noted that the memory device 148 may be housed within a common controller housing along with one or more processors 146. In one embodiment, the memory device 148 may be located remotely relative to the physical location of the one or more processors 146 and the controller 144. For example, the one or more processors 146 of the controller 144 may access a remote memory (e.g., a server) accessible via a network (e.g., the Internet, an intranet, etc.).

[0093] In this manner, the controller 144 can direct or receive data (e.g., via control signals) from the multi-column overlay metrology tool 102 or any component therein. The controller 144 may be further configured to perform any of the various process steps described throughout this disclosure, such as, but not limited to, directing the column positioning subsystem 112 to adjust the position of the measurement column 104, directing the sample positioning system 114 to adjust the position of the sample 108, receiving detection signals from one or more detectors 110 associated with a metrology measurement, generating overlay measurements based on the detection signals from the detectors 110, generating correctable values ​​for one or more additional tools based on the overlay measurements, or calibrating at least one measurement column 104 using overlay measurements from at least one additional measurement column 104.

[0094] In another embodiment, overlay metrology system 100 includes a user interface 150 communicatively coupled to controller 144. In one embodiment, user interface 150 may include, but is not limited to, one or more desktops, laptops, tablets, etc. In another embodiment, user interface 150 includes a display used to display data from overlay metrology system 100 to a user. The display of user interface 150 may include any display known in the art. For example, the display may include, but is not limited to, a liquid crystal display (LCD), an organic light-emitting diode (OLED)-based display, or a CRT display. Those skilled in the art will recognize that any display device that can be integrated with user interface 150 is suitable for implementation in the present disclosure. In another embodiment, a user may input selections and / or commands in response to data displayed to the user via a user input device of user interface 150.

[0095] 6 is a flow diagram illustrating steps performed in a method 600 for multi-column metrology in accordance with one or more embodiments of the present disclosure. It should be noted that the embodiments and enabling techniques previously described herein in the context of overlay metrology system 100 should be construed as extending to method 600. However, it should be further noted that method 600 is not limited to the architecture of overlay metrology system 100.

[0096] In one embodiment, method 600 includes step 602 of providing multiplexed illumination to two or more measurement columns configured to simultaneously probe two or more measurement regions on a sample including multiple metrology targets. For example, a particular measurement column can include an illumination subsystem that directs illumination from at least one of one or more illumination sources toward the sample, and a collection subsystem that includes a collection lens configured to collect measurement signals from the sample and direct the measurement signals to one or more detectors. Additionally, a column positioning subsystem is configured to adjust the position of the collection lens in a lateral plane parallel to the sample plane for measurements, and the measurement region of a particular measurement column is defined by the field of view of the collection lens and the extent of the positioning system in the lateral plane.

[0097] In another embodiment, method 600 includes step 604 of directing illumination light toward a metrology target within a measurement field of view of two or more measurement columns. In another embodiment, method 600 includes step 606 of collecting multiplexed measurement signals by the two or more measurement columns. For example, the measurement signals may be multiplexed based on any one or more parameters, including, but not limited to, wavelength, polarization, or temporal characteristics. Furthermore, the measurement signals may be multiplexed in various ways. In one example, the measurement signals may be multiplexed after measurement (e.g., via one or more polarizers, one or more delay lines, etc.). In another example, the illumination light directed toward the two or more measurement columns is multiplexed such that the measurement signals are similarly multiplexed. In another embodiment, method 600 includes step 608 of detecting the multiplexed measurement signals on one or more detectors. In another embodiment, method 600 includes step 610 of generating metrology data for the metrology target based on the detected measurement signals. For example, the metrology data may include, but is not limited to, overlay metrology data.

[0098] 7 is a flow diagram illustrating steps performed in a method 700 for self-calibration of a multi-column metrology tool in accordance with one or more embodiments of the present disclosure. The embodiments and enabling techniques previously described herein in the context of overlay metrology system 100 should be construed as extending to method 700. However, it should be further noted that method 700 is not limited to the architecture of overlay metrology system 100.

[0099] It is contemplated herein that a multi-column metrology tool, such as, but not limited to, a multi-column overlay metrology tool 102 including at least two measurement columns 104 with different measurement accuracies (or other characteristics), may provide self-calibrated metrology data. In particular, metrology data from one measurement column 104 may be used to calibrate and / or train another measurement column 104. For example, there may be cases where measurement columns 104 utilizing different types of illumination sources 106 may naturally exhibit different measurement characteristics, such as accuracy or throughput. For example, a measurement column 104 based on X-ray, EUV, or particle beam illumination 134 often (but not always) provides higher measurement accuracy but lower throughput than a measurement column 104 based on visible or IR illumination 134. However, a higher-throughput measurement column 104 may be calibrated to provide improved accuracy using metrology data from a higher-accuracy measurement column 104.

[0100] In one embodiment, method 700 includes generating 702 a first calibration measurement set of one or more calibration targets on a sample using one or more calibration measurement columns of a multi-column metrology tool. In another embodiment, method 700 includes generating 704 a second calibration measurement set of one or more calibration targets using one or more test measurement columns of the multi-column metrology tool. For example, the one or more test measurement columns may provide different measurement accuracy than the one or more calibration columns, and the different measurement accuracy may, but need not, be the result of using different illumination sources 106.

[0101] However, it should be understood that the terms "test measurement sequence" and "calibration measurement sequence" are used herein for illustrative purposes and should not be construed as limiting. Rather, any or all measurement sequences 104 may be utilized for any desired purpose, including run-time measurements, calibration of other measurement sequences 104, or a combination thereof. As such, the terms "test measurement sequence" and "calibration measurement sequence" are used herein for clarity and to refer to different subsets of measurement sequences 104 when used for self-calibration.

[0102] In another embodiment, method 700 includes calibrating 706 one or more test measurement sequences based on the first and second sets of calibration measurements. In another embodiment, method 700 includes generating 708 one or more calibrated measurements of one or more test targets different from the one or more calibration targets using the one or more test measurement sequences.

[0103] Step 706 of calibrating one or more test measurement sequences may be implemented using various techniques. In one embodiment, step 706 includes identifying correlations or patterns between metrology measurements generated by both the test measurement sequence and the calibration measurement sequence, and then training the test measurement sequence (or a controller 144 connected to one of the measurement sequence) to generate metrology data based on the correlations. In this manner, the test measurement sequence (or a controller connected to one of the test measurement sequence) can generate calibrated metrology data for new test measurement targets using a combination of the measurement signals acquired by the test measurement sequence and the correlations identified in step 706. Furthermore, this calibrated measurement may have greater accuracy than uncalibrated metrology data from the test measurement sequence and may be generated at the throughput of the test measurement sequence.

[0104] Step 706 may include several algorithms. For example, the metrology target may be modeled (parameterized) using any technique known in the art, including, but not limited to, a geometric engine, a process modeling engine, or a combination thereof. The use of process modeling is generally described in U.S. Patent No. 10 / 769,320 (September 8, 2020), which is incorporated herein by reference in its entirety. The geometric engine may, but need not, be implemented by AcuShape software, a product offered by KLA Corp. Additionally, the EM solver may utilize any method known in the art, including, but not limited to, rigorous coupled wave analysis (RCWA), finite element analysis, method of moment analysis, surface integration techniques, volume integration techniques, or finite difference time-domain analysis.

[0105] Step 706 may further include analyzing the metrology data collected from the test or calibration measurement sequence using any data fitting and optimization technique known in the art for applying the collected data to a model, including, but not limited to, libraries, fast reduced order models, regression, machine learning algorithms such as neural networks, support vector machines (SVM), dimensionality reduction algorithms (e.g., principal component analysis (PCA), independent component analysis (ICA), locally linear embedding (LLE), etc.), sparse representations of the data (e.g., Fourier or wavelet transforms, Kalman filters, algorithms that facilitate matching from the same or different tool types, etc.). For example, data collection and / or fitting may be, but need not be, performed by Signal Response Metrology (SRM), a product offered by KLA Corp.

[0106] Furthermore, various implementations of the algorithms may, but need not, be performed by a controller (e.g., controller 144) through firmware, software, or a field programmable gate array (FPGA), or one or more other programmable optical elements.

[0107] Once the model is trained in step 706, step 708 may include implementing the model to provide calibrated metrology data based on new metrology measurements of a new metrology target with a test measurement sequence. Step 708 may incorporate any data fitting or optimization technique known in the art to apply the metrology data collected from the new metrology target to the model. Continuing with the example provided for step 706, this may include, but is not limited to, library searching, regression analysis, implementation of machine learning algorithms, support vector machines (SVMs), dimensionality reduction algorithms, etc. For example, data collection and / or fitting may be, but need not be, performed by Signal Response Measurement (SRM) by KLA Corp.

[0108] The subject matter described herein illustrates different components that are, in some cases, included within or connected to other components. It should be understood that such depicted architectures are merely exemplary, and that in fact many other architectures that achieve the same functionality may be implemented. In a conceptual sense, any arrangement of components to achieve the same functionality is effectively “associated” such that the desired functionality is achieved. Thus, any two components herein that combine to achieve a particular function can be considered to be “associated” with each other such that the desired functionality is achieved, regardless of the architecture or intermediate components. Similarly, any two components so associated can also be considered to be “connected” or “coupled” to each other to achieve the desired functionality, and any two components that can be so associated can also be considered to be “couplable” with each other to achieve the desired functionality. Specific examples of what can be coupled include, but are not limited to, physically interactable and / or physically interacting components and / or wirelessly interactable and / or wirelessly interacting components and / or logically interactable and / or logically interacting components.

[0109] It is believed that the present disclosure and many of its attendant advantages will be understood from the foregoing description, and it will be apparent that various changes can be made in the form, construction, and arrangement of the elements without departing from the disclosed subject matter or sacrificing all of its material advantages. The described forms are merely illustrative, and it is the intent of the following claims to embrace and include such modifications. It is further understood that the invention is defined by the appended claims.

Claims

1. 1. A multi-column metrology tool, comprising: two or more measurement arrays distributed along a row direction, the two or more measurement arrays configured to simultaneously probe two or more measurement regions on a sample including a plurality of measurement targets, the two or more measurement arrays being distributed with gaps in the row direction, and a particular measurement array of the two or more measurement arrays: an illumination subsystem configured to direct illumination from at least one of one or more illumination sources toward the sample; a collection subsystem including a collection lens configured to collect measurement signals from the sample and direct the measurement signals to one or more detectors; a sample positioning subsystem configured to scan the sample along a scan path distinct from a column direction, the scan path positioning a measurement target of the plurality of measurement targets within two or more measurement regions of two or more measurement columns for measurement, the scan path including a plurality of scans covering at least some of the gaps between the two or more measurement regions; A multi-column measurement tool.

2. 10. The multi-column metrology tool of claim 1, wherein at least one of the two or more measurement columns collects the measurement signals from two or more measurement planes and directs the measurement signals from the two or more measurement planes to at least one of the one or more detectors.

3. The multi-column metrology tool of claim 1 , wherein the sample positioning subsystem is further configured to adjust the position of the sample along an axial direction perpendicular to a side surface.

4. 10. The multi-column metrology tool of claim 1, wherein the sample positioning subsystem includes a rotational stage that rotates the sample.

5. 10. The multi-column metrology tool of claim 1, wherein at least one of the one or more detectors comprises a fixed detector located outside of the two or more measurement columns.

6. 6. The multi-column metrology tool of claim 5, wherein the measurement signals provided by at least two of the two or more measurement columns are multiplexed by one or more parameters.

7. The multi-column metrology tool of claim 6 , wherein the one or more parameters include at least one of polarization, wavelength, or time.

8. 7. The multi-column metrology tool of claim 6, wherein the fixed detector provides separate detector data associated with multiplexed measurement signals from at least two of the two or more measurement columns.

9. 7. The multi-column metrology tool of claim 6, further comprising a detector demultiplexer configured to receive multiplexed measurement signals from at least two of the two or more measurement columns and generate two or more demultiplexed measurement signals, the detector demultiplexer further distributing the two or more demultiplexed measurement signals to the fixed detector.

10. 7. The multi-column metrology tool of claim 6, wherein illumination received by at least two of the two or more measurement columns is multiplexed by one or more parameters.

11. The multi-column metrology tool of claim 5 , wherein at least one of the two or more measurement columns directs the measurement signal through one or more optical fibers.

12. 10. The multi-column metrology tool of claim 1, wherein at least one of the one or more detectors comprises a movable detector disposed in at least one of the two or more measurement columns.

13. The multi-column metrology tool of claim 1 , wherein at least one of the one or more illumination sources comprises a fixed illumination source located external to two or more measurement columns.

14. The multi-column metrology tool of claim 13 , wherein at least two of the two or more measurement columns receive illumination from the fixed illumination source.

15. 14. The multi-column metrology tool of claim 13, wherein at least one of the two or more measurement columns receives illumination from the fixed illumination source through one or more optical fibers.

16. The multi-column metrology tool of claim 1 , wherein at least one of the one or more illumination sources comprises a movable illumination source positioned in at least one of the two or more measurement columns.

17. The multi-column metrology tool of claim 1 , wherein at least one of the one or more illumination sources comprises an electromagnetic illumination source.

18. The multi-column metrology tool of claim 1 , wherein at least one of the one or more illumination sources comprises a particle beam illumination source.

19. 10. The multi-column metrology tool of claim 1, wherein at least one of the two or more measurement columns is configured to perform measurements on at least one of the plurality of metrology targets as the sample is moving along a scan direction.

20. 10. The multi-column metrology tool of claim 1, wherein at least one of the two or more measurement columns is configured to perform measurements while the sample is stationary.

21. 2. The multi-column metrology tool of claim 1, wherein the scan path is linear, and at least some of the plurality of metrology targets are linearly arranged to be measured by at least some of the two or more measurement columns as the sample is scanned along the scan path.

22. 10. The multi-column metrology tool of claim 1, wherein the spatial extent of the two or more measurement rows along a row direction corresponds to the size of a desired measurement area on the sample.

23. The multi-column metrology tool of claim 1 , wherein a size of a measurement area of ​​the one or more detectors along a column direction is smaller than a size of the sample along the column direction.

24. The multi-column metrology tool of claim 1 , wherein the focusing lens is an objective lens.

25. The multi-column metrology tool of claim 1 , wherein the metrology target comprises a dedicated metrology target.

26. 10. The multi-column metrology tool of claim 1, wherein the metrology target comprises a device feature on the sample.

27. 10. The multi-column metrology tool of claim 1, wherein the metrology target is formed from at least one of a post-develop feature, a post-etch feature, or a post-clean feature.

28. A multi-column measurement method, comprising: providing illumination to two or more measurement columns, the two or more measurement columns configured to simultaneously probe two or more measurement regions on a sample including a plurality of metrology targets, the sample being scanned along a scan path, the two or more measurement columns being distributed with gaps in the column direction, the scan path being different from the column direction and including a plurality of scans covering at least some of the gaps between the two or more measurement regions, and a particular measurement column of the two or more measurement columns: an illumination subsystem configured to direct illumination from at least one of the one or more illumination sources toward the specimen; a collection subsystem including a collection lens configured to collect measurement signals from the sample and direct the measurement signals to one or more detectors; Equipped with directing illumination light toward a measurement target within a measurement field of view of the two or more measurement arrays; acquiring multiplexed measurement signals by the two or more measurement sequences; detecting the multiplexed measurement signals with one or more detectors; generating measurement data for the measurement target within the measurement field of view of the two or more measurement arrays based on the detected measurement signals; A multi-column measurement method including:

29. 30. The multi-column metrology method of claim 28, wherein the multiplexed measurement signals provided by at least two of the two or more measurement columns are multiplexed by one or more parameters.

30. 30. The multi-column metrology method of claim 29, wherein the multiplexed measurement signals provided by at least two of the two or more measurement columns are multiplexed by at least one of polarization, wavelength, or time.

31. A multi-column measurement method, comprising: generating a first set of calibration measurements of one or more calibration targets on a sample using one or more calibration measurement columns of a multi-column metrology tool; generating a second set of calibration measurements of the one or more calibration targets using one or more test measurement columns of the multi-column metrology tool, the one or more test measurement columns providing a different measurement accuracy than the one or more calibration columns, and a particular calibration measurement column or a particular test measurement column: an illumination subsystem configured to direct illumination from at least one of one or more illumination sources toward the sample; a collection subsystem including a collection lens configured to collect measurement signals from the sample and direct the measurement signals to one or more detectors; a column positioning subsystem configured to adjust the position of the collection lens in a lateral plane parallel to the sample plane for measurement, wherein a measurement region of the particular calibration measurement row is defined by the field of view of the collection lens and the extent of a positioning system in the lateral plane; and Equipped with calibrating one or more test measurement sequences based on the first and second sets of calibration measurement sequences; generating one or more calibrated measurements of one or more test targets that are different from the one or more calibration targets using the one or more test measurement sequences; A multi-column measurement method including:

32. 32. The multi-column metrology method of claim 31, wherein the one or more illumination sources include two or more illumination sources, and the one or more test measurement sequences and the one or more calibration measurement sequences receive measurement signals from different illumination sources among the two or more illumination sources.

33. Calibrating the one or more test measurement sequences based on the first and second sets of calibration measurement sequences includes: identifying correlations between the first and second sets of calibration measurement sequences for the one or more test targets; training the one or more test measurement sequences to generate metrology measurements based on the correlation; The multi-column measurement method according to claim 31, further comprising:

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