Accurate Raman spectroscopy

Abstract

A system, method, and non-transitory computer-readable medium for accurate Raman spectroscopy, comprising: (i) an optical metrology system performing at least one iteration of a calibration process including (a) finding a misalignment between a region of interest defined by a spatial filter and an incident beam of radiation emitted from an illuminated region of a sample, the incident beam incident on the spatial filter, and (b) determining a compensation path of propagation of the incident beam that compensates for the misalignment; and (ii) performing a measurement process to provide one or more Raman spectra when the optical metrology system is configured to provide the compensation path of propagation of the incident beam.

Description

[Technical Field]

[0001] cross reference This application claims priority to U.S. Provisional Patent No. 62 / 961,721, filed January 16, 2020, the entire contents of which are incorporated herein by reference. [Background technology]

[0002] Raman spectroscopy is a well-established technique and its use in the characterization of various materials properties has been extensively documented.

[0003] The Raman spectrum conveys information about various properties of a sample. In particular, different peaks in the spectrum correspond to different materials. If the object being measured is composed of material compounds (e.g., SiGe), specific peaks in the Raman spectrum will correspond to different atom pairs (e.g., Si-Si, Si-Ge, and Ge-Ge).

[0004] Methods for extracting concentration and stress information from the positions of these peaks are well known in the literature. For example, equations relating the three peak positions of SiGe to the germanium composition and layer stress are presented in the following publication: TS Perov et al., "Composition and strain in thin Si-xGex virtual substrates measured by micro-Raman spectroscopy and x-ray diffraction," J. App. Phys. 109, 033502 (2011).

[0005] Another characteristic that influences the Raman spectrum is doping. The carrier concentration resulting from the dopant distribution influences the Raman signal, causing additional shifts of the Raman peaks. Therefore, the level of doping can be incorporated into the fitting procedure, and by monitoring the peak positions, the doping level can be evaluated along with the stress and composition (see, for example, A. Perez-Rodriguez et al., "Effect of stress and composition on Raman spectra of etch-stop SiGeB layers," J. Appl. Phys. 80, 15 (1996)).

[0006] Examples of state-of-the-art systems for generating Raman spectra are provided in PCT Patent Application Publication Nos. WO2017 / 103934 to Barak et al. and WO2017 / 103935 to Barak et al., both of which are incorporated herein by reference.

[0007] The Raman spectrum is very weak, and this weakness requires the collection of many Raman spectra carrying radiation. Summary of the Invention

[0008] Systems, methods, and non-transitory computer-readable media storing instructions for accurate Raman spectroscopy are provided.

[0009] In order to understand the invention and to see how it may be carried out in practice, preferred embodiments will now be described, by way of non-limiting example only, with reference to the accompanying drawings, in which: [Brief explanation of the drawings]

[0010] [Figure 1] Examples of the illumination spot, the intensity distribution of the aligned incident beam, the intensity distribution of the misaligned incident beam, and the region of interest are shown. [Figure 2] The sensor, spatial filter, region of interest, and incident spot are shown. [Figure 3] Shows nine spatial relationships between regions of interest. [Figure 4] 1 is an example of an optical measurement system. [Figure 5] 1 is an example of an optical measurement system. [Figure 6] 1 is an example of an optical measurement system. [Figure 7] 1 is an example of an optical measurement system. [Figure 8] 1 illustrates an example of one or more rotating wedge prisms and a wedge prism rotator. [Figure 9] 1 shows an example of some elements of illumination optics. [Figure 10] An example of the method is shown below. [Figure 11] An example of the method is shown below. [Figure 12] An example of the method is shown below. [Figure 13] An example of pad illumination is shown. [Figure 14] An example of irradiation of regular and irregular areas is shown. DETAILED DESCRIPTION OF THE INVENTION

[0011] In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. However, it will be understood by those skilled in the art that the present invention may be practiced without these specific details. In other instances, well-known methods, procedures, and components have not been described in detail so as not to obscure the present invention.

[0012] The subject matter which is regarded as the invention is particularly pointed out and distinctly claimed in the concluding portion of this specification. However, the invention, both as to organization and method of operation, together with its objects, features, and advantages, may best be understood by reference to the following detailed description read in connection with the accompanying drawings.

[0013] It should be understood that for simplicity and clarity of illustration, elements shown in the drawings have not necessarily been drawn to scale. For example, the dimensions of some elements may be exaggerated relative to other elements for clarity. Further, where considered appropriate, reference numerals may be repeated among the drawings to indicate corresponding or analogous elements.

[0014] Any reference in this specification to any one of a system, method, and non-transitory computer-readable medium should apply mutatis mutandis to any other system, method, and non-transitory computer-readable medium. For example, any reference to a system should apply mutatis mutandis to a method executable by the system and to a non-transitory computer-readable medium capable of storing instructions executable by the system.

[0015] Because at least one of the described embodiments of the invention can be implemented, for the most part, using electronic components and circuits known to those skilled in the art, details will not be described beyond what is considered necessary as described above for the understanding and appreciation of the concepts underlying the invention and to avoid obfuscating or deviating from the teachings of the invention.

[0016] The numbers or values ​​given below should be considered as non-limiting examples.

[0017] It has been found that when a sample contains structural elements, irradiation of some structural elements (especially non-periodic, edge-like, or other irregular structural elements) can cause the structural elements to diffract the radiation, and the diffracted radiation can generate "parasitic" Raman scattered radiation, which can "distort" the Raman spectrum (when detected by the detector of the Raman spectrometer). The "parasitic" Raman scattered radiation can, for example, change the position or shape of one or more of the Raman spectral peaks.

[0018] Analysis of distorted Raman spectra may lead to inaccurate conclusions about the sample material, sample distortion, and inaccuracies related to other properties of the sample.

[0019] There is an increasing need to improve the accuracy of Raman spectroscopy, especially to reduce distortions in Raman spectra for the purpose of semiconductor manufacturing process control.

[0020] Raman spectroscopy can be used in semiconductor wafer manufacturing APC, measurement of patterned structures on wafers, in-die measurement, etc.

[0021] Systems, methods, and non-transitory computer-readable media storing instructions for accurate Raman spectroscopy can be provided.

[0022] An incident beam emanates from an illumination region of the sample and impinges on a spatial filter. The illumination region is illuminated by an illumination beam of radiation (hereinafter "illumination beam").

[0023] The accuracy of Raman spectroscopy is improved by preventing unwanted scattered radiation from the sample from reaching the detector. This can be done by providing a spatial filter that blocks one or more portions of the incident beam of radiation (hereinafter "incident beam") that are outside a region of interest (the region of interest is defined by the spatial filter), thereby preventing said one or more portions of the incident beam from reaching the detector.

[0024] Spatial filtering is required when the illuminated spot "covers" an irregular area. The irregular area may distort the illuminated spot and / or create new sources of scattering in the Raman spectrum and / or may contain a non-periodic arrangement of elements and / or may contain a non-homogeneous arrangement of elements. Non-limiting examples of irregular areas include (a) a spot covering an edge area of ​​a conductor and the vicinity of said edge area, where the edge area is similar in area to the spot (e.g., between 0.1 and 0.9), and (b) a spot covering the edge area of ​​a single conductor and also covering an edge area that includes a slit nearby.

[0025] Spatial filters may be applied during measurements (e.g., strain profiling, crystallinity and dimension profiling) on ​​structures including elements such as through silicon vias (TSVs), shallow trench isolation (STI) (e.g., fill and / or gate oxide), and three-dimensional NAND memory (3D-NAND).

[0026] The spatial filter may include an adjustable spatial filter that may define different regions of interest. Additionally or alternatively, the spatial filter may exhibit controllable transparency and / or define a transparent region of interest surrounded by an opaque region. The adjustable filter may be replaced by a set of spatial filters that differ from one another in spatial filtering characteristics.

[0027] The spatial filter may include a fixed element that defines a fixed region of interest.

[0028] A spatial filter may be utilized in some operating modes of the system and removed or disabled in other operating modes of the system.

[0029] The region of interest may be smaller (or much smaller) than a relevant cross section of the incident beam, which is the cross section formed at the plane of the spatial filter.

[0030] For example, the region of interest may be a portion of the relevant cross section of the incident beam, e.g., the region of interest may be less than 1%, 2%, 5%, 10%, 15%, 20% or 30% of the relevant cross section of the incident beam.

[0031] The illuminated area and the associated cross section of the incident beam may be the same size, may be the same shape, may differ from one another in size and / or may differ from one another in shape.

[0032] Non-limiting examples of these shapes include a rectangular spot, an elliptical spot, a circular spot, a line of illumination, and the like.

[0033] The region of interest can be defined to prevent scattered radiation from reaching the detector. The region of interest can be defined using simulation, actual measurement, etc.

[0034] The small region of interest provides an accurate and sensitive optical metrology system that can be used to evaluate a variety of samples and / or various regions of such samples, including, but not limited to, high density arrays of structural elements, areas exhibiting potentially distorted elements, areas exhibiting steep slopes and / or substantial height changes, peripheral areas, through-silicon vias for measurement, gate oxides of dynamic memories, 3D NAND memory units, post-CMP regions of dynamic memories, etc.

[0035] Because the region of interest is compact, even a slight misalignment between the region of interest and the incident beam can cause the system to block some, most, or even all of the impinging beam.

[0036] When the center of the incident beam is within the region of interest, especially when the center of the incident beam is located at the center of the region of interest, the incident beam can be considered to be aligned with the region of interest.

[0037] The position deviation is caused by system inaccuracy, temperature change, vibration and so on.

[0038] Considering the fact that Raman spectra are formed from relatively weak signals, the effect of misalignment can be very significant.

[0039] Accordingly, systems, methods, and non-transitory computer-readable media are configured to compensate for such misalignment.

[0040] The compensation may include optically aligning (or substantially optically aligning) the region of interest with the incident beam, which may be done by controlling the position of incidence of the incident beam on the spatial filter.

[0041] This control may involve introducing changes to the collection path, such as changing the propagation direction of the incident beam.

[0042] The compensation may be based on feedback about the radiation detected by the detector, which may be provided during the calibration process or at any other time.

[0043] The calibration process may be performed continuously, discontinuously, ad hoc, iteratively, etc.

[0044] The calibration process may be based on the intensity of the radiation detected by the detector (after passing through a spatial filter).

[0045] The calibration process may be based on information other than (or in addition to) the intensity of the radiation detected by the sensor.

[0046] The calibration process may be based on the Raman spectrum sensed by the detector.

[0047] For ease of explanation, some of the following examples illustrate an iterative process in which a calibration process is followed by a measurement process, during which a sample is measured.

[0048] During the calibration process, the object is illuminated using different illumination path configurations, which direct the focused radiation to different locations on the spatial filter, providing different test results.

[0049] One of the test results (e.g., the test result with the highest overall intensity) may be selected, and the illumination path configuration that provided the selected test result may be used in one or more measurement processes after the calibration process. Alternatively, multiple test results may be selected, and an illumination path configuration may be selected that is a function (e.g., a weighted average) of the multiple test results.

[0050] When performing multiple iterations of the calibration process, there is a timing gap between successive calibration processes. The timing gap between successive calibration processes may be fixed or may vary over time.

[0051] The calibration process may be triggered based on an event such as a measurement failure, detection of an error in one or more Raman spectra, detection of a particular temperature change, detection of a particular temperature, detection of a particular vibration, or occurrence of a deviation of one or more measured Raman spectra from an expected Raman spectrum.

[0052] If the illumination path of the system includes different radiation sources, a calibration process may be performed for each radiation source, or for several of the radiation sources. Such a calibration process may simplify the system and even reduce the cost of the system, since it compensates for mechanical and / or optical misalignments associated with the different radiation sources and may allow for the use of less precise illumination and / or collection paths.

[0053] FIG. 1 shows an example of an illumination spot 20, an intensity distribution of an aligned incident beam 21, an intensity distribution of an unaligned incident beam 22, and a region of interest 225.

[0054] In FIG. 1, it is assumed that an image of the illumination spot 20 is formed on a spatial filter.

[0055] FIG. 1 shows the intensity difference (29) due to misalignment between the region of interest 225 and the incident beam.

[0056] FIG. 1 also shows a portion of the sample 300 and an image 225' of a region of interest on the sample.

[0057] FIG. 2 shows a sensor 224, a spatial filter 223, a region of interest 225, and an incident spot 26 formed on the spatial filter by the incident beam.

[0058] The region of interest 225 is of variable size and can be much smaller than the incident spot.

[0059] Figure 3 shows nine spatial relationships 291-299 between the region of interest 227 and the incident spot 26 in nine different configurations of the optical metrology system. Because the sixth configuration shows the best overlap, this configuration can be selected as the desired configuration of the optical metrology system and applied during the next measurement process.

[0060] It should be noted that during the compensation process, the spatial filter may pass radiation through a test region of interest that is larger than the region of interest used during the measurement process.

[0061] FIG. 4 is an example of an optical metrology system 200 .

[0062] The optical measurement unit 200 includes an illumination path, a collection path, a control unit, and a mechanical movement unit 303 that supports the sample 300 and moves the sample 300 relative to the collection path and illumination path. It should be noted that the sample 300 may be stationary while the illumination and / or collection path moves. It should also be noted that both the sample 300 and at least one of the collection path and / or illumination path may move relative to each other.

[0063] 4, the collection path and the illumination path share objective lens 213 and half-wave plate (HWP) 109. Note that the illumination path and the collection path may share more components, other components, or no components at all.

[0064] In Figure 4, the illumination and collection angles are perpendicular to the sample. Note that any other illumination and / or collection angles are also possible.

[0065] The illumination path is configured to control various parameters of the illumination beam, including but not limited to polarization, frequency spectrum, shape, size, coherency, path, intensity, etc. Various elements shown assist in controlling said parameters. Elements that control polarization are referred to as polarization control elements. Elements that control other parameters of the beam are referred to as additional control elements. Note that a single element may control one or more parameters of the beam. Non-limiting examples of elements include polarizers, half-wave plates, quarter-wave plates, analyzers, lenses, grids, apertures, etc.

[0066] The collection path is configured to control various parameters of the incident beam including, but not limited to, polarization, frequency spectrum, shape, size, coherency, path, intensity, etc. Various elements shown assist in controlling said parameters.

[0067] The illumination path is shown as including (a) laser 102, (b) illumination optics 103 including illumination polarization control element 103(1) and additional illumination control element 103(2), (c) a beam splitter such as dichroic beam splitter 210, (d) HWP 209, and (e) objective lens 213. The additional illumination control element may control one or more parameters different from polarization, such as, for example, shape, size, propagation angle, etc.

[0068] The collection path is shown as including (a) a beam splitter such as dichroic beam splitter 210, (b) HWP 209, (c) objective lens 213, (d) collection optics 105 including adjustable optics 105(1) that changes the collection path and thereby compensates for misalignment, an additional collection control element 105(2), and a collection polarization control element 105(3), (e) spatial filter 223, and (f) optical unit 235 including grid 231, a first lens 232 that directs radiation that has passed through the region of interest onto grid 231, and a second lens that directs light from grid 231 to detector 224.

[0069] The optical unit 235 is configurable in the sense that the spatial relationship between the grid 231 and at least the second lens 233 can be changed to direct different radiation lobes from the grid 231 towards the second lens 233. Figure 4 shows a rotation unit 238 that can rotate the grid 231 relative to the first and second lenses. Movements other than rotation may also be used to change the spatial relationships between the elements of the optical unit 235.

[0070] The detector 224 is configured to generate a Raman spectrum. The detector 224 is coupled to a control unit 225 configured to control various components / units / elements of the optical metrology system and configured to control the calibration process.

[0071] FIG. 5 is an example of an optical metrology system 200'.

[0072] Measurement system 200' differs from measurement unit 200 in that it (a) does not include HWP 209, (b) includes multiple lasers 102', and (c) includes a processing unit 234 for processing the detected signals. Illumination optics 103 can be configured to combine or select radiation from multiple lasers. In some cases, only one laser may be active at a time.

[0073] FIG. 6 is an example of an optical metrology system 200''.

[0074] Measurement system 200'' differs from measurement unit 200 in that (a) it does not include HWP 209, and (b) it includes multiple lasers 102'. Illumination optics 103 can be configured to combine or select radiation from multiple lasers. In some cases, only one laser may be active at a time.

[0075] FIG. 7 shows an example of an optical measurement system 201 .

[0076] System 201 includes an illumination path that includes laser 201, entrance aperture stop 203, mirror 204, first illumination lens 206, illumination field stop 207, second illumination lens 208, illumination polarizer 209, beam splitter 210, a HWP such as rotating HWP 211, objective aperture stop / back focal plane 212, and objective lens 213.

[0077] The collection path includes objective lens 213, objective aperture stop / back focal plane 212, sample 300, rotating collection polarizer 215, an HWP such as rotating HWP 211, first collection lens 216, collection aperture stop 217, second collection lens 218, notch filter 219, collection field stop 220, rotating wedge prism 221, wedge prism rotator 225, slit lens 222, spatial filter 223 (which may be a slit that can be opened or closed, or the size and / or shape of the open slit may be fixed or adjustable), optical unit 235, and detector 234.

[0078] The detector 234 may be a spectrometer.

[0079] FIG. 8 shows rotating wedge prism 221, wedge prism rotator 225 surrounding rotating wedge prism 221, input beam 281 entering rotating wedge prism 221, and output beam 282 exiting rotating wedge prism 221.

[0080] FIG. 8 also shows the multiple paths of the output beam provided by different rotational positions of rotating wedge prism 221.

[0081] 8 also shows that the system may include a pair of rotating wedge prisms 221 and 221', which provide more options for directing the output beam. The output beam passes through both rotating prisms.

[0082] Figure 9 shows an example of some elements of the illumination optics: there are three lasers, followed by three sections of the illumination path, terminating in an optical adder that adds the radiation from the three lasers.

[0083] Three lasers (e.g., red, blue, and green lasers) 102(1)-102(3) are followed by three sections of an illumination path, including three collimators 109(1,1)-109(1,3), three isolators 109(2,1)-109(2,3), three clean-up filters 109(3,1)-109(3,3), and three shutters 109(4,1)-109(4,3).

[0084] The three sections are followed by a combiner including three beam splitters, such as dichroic beam splitters 109(5,1) to 109(5,3), and the combiner is followed by an initial mirror 109(5), a cylindrical lens 109(6), and a secondary mirror 204.

[0085] FIG. 10 illustrates an example of a method 400 .

[0086] Method 400 can begin with step 402, in which an optical metrology system performs a calibration process that includes (a) finding a misalignment between a region of interest defined by a spatial filter and an incident beam of radiation emitted from an irradiated region of the sample, the incident beam entering the spatial filter, and (b) determining a compensation path for the propagation of the incident beam that compensates for (corrects) the misalignment.

[0087] The region of interest is shaped and sized to block scattered radiation from the illuminated region from reaching the detector.

[0088] Step 402 may include analyzing at least one Raman spectrum. Additionally or alternatively, step 402 may include analyzing radiation at a frequency different from that of the Raman spectrum. A difference between the two examples of step 402 may include rotating a grid located in the collection path.

[0089] Step 402 can be followed by step 404, in which a measurement process is performed while the optical metrology system is configured to provide a compensated path of propagation of the incident beam to provide one or more Raman spectra.

[0090] Step 404 is followed by step 406, which determines whether to start the next iteration of steps 402 and 404, and if so, jumps back to step 402.

[0091] FIG. 11 illustrates an example of the method 401.

[0092] Method 401 may begin with step 403, in which a calibration process is performed by directing an incident beam to various positions on a spatial filter, irradiating the object using different (various) optical measurement system configurations, sensing radiation that passes through the region of interest to provide different (various) test results, and determining a compensation path for the propagation of the incident beam based on the test results.

[0093] The region of interest may be shaped and sized to block scattered radiation from the illuminated region from reaching the detector.

[0094] Step 403 may include selecting one of the test results to provide a selected test result, and determining a compensation path for the propagation of the incident beam based on the selected test result.

[0095] Step 403 may include selecting the test result with the highest strength from the test results and providing the selected test result.

[0096] It should be noted that determining the compensation path may include selecting a plurality of selected test results and determining the compensation path by defining a path based on the plurality of selected test results, for example, using interpolation, extrapolation, or any other method.

[0097] Step 403 may include rotating a wedge prism of the optical metrology system to find an orientation of the wedge prism that, when applied, will direct the incident beam through a compensated path of propagation of the incident beam.

[0098] Step 403 may include rotating multiple wedge prisms of the optical metrology system to find a combination of orientations of the multiple wedge prisms that, when applied, will direct the incident beam through a compensated path of propagation of the incident beam.

[0099] Step 403 may include analyzing at least one Raman spectrum. Additionally or alternatively, step 403 may include analyzing radiation at a frequency different from that of the Raman spectrum. A difference between the two examples of step 404 may include rotating a grid located in the collection path.

[0100] Step 403 may be followed by step 404, in which a measurement process may be performed while the optical metrology system is configured to provide a compensated path of propagation of the incident beam to provide one or more Raman spectra.

[0101] Step 404 is followed by step 406, which may determine whether to begin the next iteration of steps 402 and 404, and if so, jump to step 402.

[0102] FIG. 12 illustrates a method 500 for selective Raman spectroscopy.

[0103] The method 500 may include a step 510 of receiving or generating irregular region information regarding the location of irregular regions on the specimen.

[0104] Step 510 may be followed by step 520, in which at least one filtering parameter of a spatial filtering process applied to the Raman detector is determined based on the irregular region information.

[0105] Step 520 may include determining the spatial configuration of a filter that precedes the Raman detector.

[0106] Step 520 may include selecting a filter (or adjusting a slit aperture / width) preceding the Raman detector from among a plurality of filters that differ from each other in at least one of their at least one filtering parameters.

[0107] At least one filtering parameter may include an amount of light reaching the Raman detector, wherein the amount of light reaching the Raman detector when illuminating an irregular region is less than the amount of light reaching the Raman detector when illuminating a regular region.

[0108] At least one filtering parameter may include an area of ​​an opening formed in a filter preceding the Raman detector, the area of ​​the opening formed in the filter when irradiating an irregular area being smaller than the area of ​​the opening formed in the filter when irradiating a regular area.

[0109] At least one filtering parameter may include the shape of an opening formed in a filter preceding the Raman detector, wherein the opening formed in the filter when illuminating an irregular area is narrower than the opening formed in the filter when illuminating a regular area.

[0110] If the image (a) of the regular elements of a regular region formed on the filter preceding the Raman detector is narrower than the image (b) of the irregular elements of an irregular region formed on the filter, the width of the opening formed in the filter should be set thinner than the width of the image of the irregular elements.

[0111] Step 520 may include setting the width of the aperture to exceed the width of the image of the irregular feature.

[0112] Step 520 may be followed by step 530, in which Raman spectra of multiple sites on the sample may be acquired while applying filtering parameters.

[0113] Step 530 may include applying at least one filtering parameter that is adapted to the irregular region when illuminating the irregular region, and applying at least one filtering parameter that is adapted to the regular region when illuminating the regular region.

[0114] A method is provided that includes receiving or determining filtering parameters, applying at least one filtering parameter that matches the irregular region when illuminating the irregular region, and applying at least one filtering parameter that matches the regular region when illuminating the regular region.

[0115] FIG. 13 shows an example of irradiation of a pad 602 and the vicinity 604 of the pad.

[0116] Pad 602 and its vicinity 604 are illuminated by a scanning beam of radiation that forms an elliptical spot. Spot 614 illuminates only the vicinity, and spot 610 illuminates only the pad. Spots 610 and 614 illuminate regular areas, and at least one filtering parameter associated with the regular area is applied when focusing.

[0117] The spot 612 illuminates the edge of the pad, hitting both the pad and its vicinity. The spot illuminates the irregular region, and at least one filtering parameter associated with the irregular region is applied when collecting the light.

[0118] FIG. 13 also shows an image 622 of the spot 610 on a filter with a large aperture 632 (at least one filtering parameter associated with a regular area).

[0119] FIG. 13 further shows an image 620 of the spot 612 on a filter with a narrow aperture 630 (at least one filtering parameter associated with the irregular region).

[0120] Narrow opening 630 may be narrower than image 620 but may be wider than (or approximately equal to) image 622 .

[0121] FIG. 14 shows examples of irradiation of regular and irregular areas.

[0122] When illuminating a regular area 730, the spot 730 is not distorted.

[0123] The spot 731 becomes distorted when irradiating an irregular area such as the edge area and vicinity 733 of a via 732, or when irradiating the vicinity of a via that contains a slit 734.

[0124] The analysis of radiation from the detection signal of the detector to determine characteristics of the object and / or the generation of a Raman spectrum, and / or the analysis of the Raman spectrum may be performed at least in part by a controller and / or processing circuitry that does not belong to the optical measurement system and / or is located away from the illumination and / or collection path.

[0125] An arrangement of components to achieve the same functionality is effectively "associated" such that the desired functionality is achieved. Thus, any two components in this specification that combine to achieve a particular functionality may be considered to be "associated" with each other such that the desired functionality is achieved, regardless of architecture or intermediate components. Likewise, any two components so associated may also be considered to be "operably connected" or "operably coupled" with each other to achieve the desired functionality.

[0126] Furthermore, those skilled in the art will recognize that the boundaries between the above-described operations are merely exemplary. Multiple operations may be combined (concatenated) into a single operation, a single operation may be dispersed among additional operations, or operations may be performed with at least partial temporal overlap. Furthermore, alternative embodiments may include multiple instances of an operation, and the order of operations may be changed in various other embodiments.

[0127] Also, for example, in one embodiment, the illustrated examples may be implemented as circuits located on a single integrated circuit or within the same device, or the examples may be implemented as any number of separate integrated circuits or separate devices interconnected with each other in any suitable manner.

[0128] Also, for example, embodiments or portions thereof may be implemented as a soft or code representation of a physical circuit or a logical representation that can be translated into a physical circuit, such as any suitable type of hardware description language.

[0129] However, other modifications, variations, and alternatives are possible. Accordingly, the specification and drawings are to be regarded in an illustrative rather than a restrictive sense.

[0130] In the claims, any reference signs placed between parentheses shall not be construed as limiting the scope of the claim. The word "comprising" does not exclude the presence of elements or steps other than those recited in the claim. Furthermore, the terms "a" or "an," as used in this specification, are defined as one or more. Also, when introductory phrases such as "at least one" and "one or more" are used in the claims, even if a claim contains the introductory phrase "one or more" or "at least one" and an indefinite article such as "a" or "an," the introduction of another claim element with the indefinite article "a" or "an" shall not be construed as meaning to limit any particular claim containing the claim element so introduced to inventions containing only one such element. The same applies to the use of definite articles. Unless otherwise specified, terms such as "first" and "second" are used to arbitrarily distinguish between the elements described by such terms. Thus, these terms are not necessarily intended to indicate a temporal or other priority of such elements. The mere fact that certain measures are recited in mutually different claims does not indicate that a combination of these measures cannot be used to advantage.

[0131] While certain features of the invention have been illustrated and described herein, many modifications, substitutions, changes, and equivalents will occur to those skilled in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the invention.

[0132] The terms "comprising," "comprising," "having," "consisting," and "consisting essentially of" are used interchangeably. For example, a method may include at least the steps included in the figures and / or this specification, or may include only the steps included in the figures and / or this specification.

Claims

1. 1. A method for accurate Raman spectroscopy, comprising: Optical measurement system (A) performing a calibration process including: (a) finding a misalignment between an incident beam of Raman scattered light emitted from an illuminated region of a sample by irradiating the sample with an illumination beam from a laser, and a region of interest defined by a spatial filter on which the incident beam is incident, the region of interest passing a portion of the incident beam that is incident on the spatial filter region of interest and blocking a portion of the incident beam that is incident on a portion of the spatial filter outside the region of interest; and (b) determining a compensation path of propagation of the incident beam that compensates for the misalignment; (B) performing a measurement process to provide one or more Raman spectra while the optical metrology system is configured to provide the compensated path of propagation of the incident beam; the spatial filter is adjustable or controllable, and the spatial filter is adjusted or controlled so that the region of interest defined by the spatial filter is larger in the step of performing (A) than in the step of performing (B); Execute (A) above at least once and execute (B) above at least once; method.

2. The method of claim 1 , wherein performing the calibration process comprises finding the misalignment by analyzing at least one Raman spectrum.

3. 2. The method of claim 1, wherein performing the calibration process includes using different optical metrology system configurations to direct the incident beam to different positions on the spatial filter and sensing portions of the incident beam that pass through the region of interest to provide different test results, and determining a compensation path for propagation of the incident beam is based on the test results.

4. 4. The method of claim 3, wherein determining the compensation path includes selecting one of the test results to provide a selected test result, and determining the compensation path of propagation of the incident beam is based on the selected test result.

5. The method of claim 4 , further comprising selecting a test result from among said test results that has the highest strength to provide said selected test result.

6. The method of claim 1 , wherein the region of interest is shaped and sized to block unwanted Raman scattered light from the illuminated region from reaching a detector.

7. 2. The method of claim 1, comprising rotating a wedge prism of the optical metrology system to find an orientation of the wedge prism that will direct the incident beam through the compensated path of propagation of the incident beam.

8. 10. The method of claim 1, comprising rotating a plurality of wedge prisms of the optical metrology system to find a combination of orientations of the plurality of wedge prisms that will direct the incident beam through a compensated path of propagation of the incident beam.

9. 1. An optical measurement system comprising: an illumination path configured to illuminate the sample; a collection path including an adjustable optical system; A detector; a spatial filter disposed upstream of the detector; a controller configured to (i) perform at least one calibration process, and (ii) control at least the adjustable optical system during at least one measurement process; During the (i) calibration process, the optical measurement system is configured to: (a) find a misalignment between an incident beam of Raman scattered light emitted from an irradiated region of a sample when the sample is irradiated with an illumination beam from a laser, and a region of interest defined in a spatial filter onto which the incident beam is incident, the region of interest transmitting a portion of the incident beam that is incident on the region of interest of the spatial filter and blocking a portion of the incident beam that is incident on a portion outside the region of interest of the spatial filter; and (b) determine a compensation path of propagation of the incident beam that compensates for the misalignment; (ii) during the measurement process, the adjustable optical system is maintained in a configuration that provides the compensated path of propagation of the incident beam, and the optical metrology system is configured to provide one or more Raman spectra; the spatial filter is adjustable or controllable, and the spatial filter is adjusted or controlled so that the region of interest defined by the spatial filter is larger during the (i) calibration process than during the (ii) measurement process; Optical measurement system.

10. 10. The optical metrology system of claim 9, configured to find the misalignment by analyzing at least one Raman spectrum.

11. 10. The optical metrology system of claim 9, wherein the adjustable optical system is configured differently to cause the adjustable optical system to direct the incident beam to different locations on the spatial filter at different times during the calibration process, the detector is configured to sense portions of the incident beam that pass through the region of interest to provide different test results, and the controller is configured to determine the compensated path of propagation of the incident beam based on the test results.

12. 12. The optical metrology system of claim 11, wherein the controller is configured to select one of the test results to provide a selected test result, and determine the compensation path of propagation of the incident beam based on the selected test result.

13. 13. The optical metrology system of claim 12, wherein the controller is configured to select a test result among the test results that has the highest intensity to provide the selected test result.

14. 10. The optical metrology system of claim 9, wherein the region of interest is shaped and sized to block unwanted Raman scattered light from the illuminated region from reaching the detector.

15. 10. The optical metrology system of claim 9, wherein the adjustable optical system includes a wedge prism, and the controller is configured to control rotation of the wedge prism to find an orientation of the wedge prism that will direct the incident beam through the compensated path of propagation of the incident beam.

16. 10. The optical metrology system of claim 9, wherein the adjustable optical system includes a plurality of wedge prisms, and the controller is configured to control rotation of the plurality of wedge prisms to find a combination of orientations of the plurality of wedge prisms that will direct the incident beam through the compensated path of propagation of the incident beam.

17. the adjustable optical system is capable of adjusting the spatial configuration of the spatial filter by applying filtering parameters; 10. The optical metrology system of claim 9, configured to apply at least one filtering parameter adapted to irregular regions when illuminating irregular regions of the sample, and to apply at least one filtering parameter adapted to regular regions when illuminating regular regions of the sample.

18. A non-transitory computer-readable medium, comprising: an optical metrology system performing a calibration process including: (A) finding a misalignment between an incident beam of Raman scattered light emitted from an illuminated region of a sample when the sample is illuminated with an illumination beam from a laser, and a region of interest defined by a spatial filter on which the incident beam is incident, the spatial filter transmitting a portion of the incident beam that is incident on the region of interest of the spatial filter and blocking a portion of the incident beam that is incident on a portion outside the region of interest of the spatial filter; and (b) determining a compensation path of propagation of the incident beam that compensates for the misalignment; (B) performing a measurement process to provide one or more Raman spectra when the optical metrology system is configured to provide the compensated path of propagation of the incident beam; the spatial filter is adjustable or controllable, and the spatial filter is adjusted or controlled so that the region of interest defined by the spatial filter is larger in the step of performing (A) than in the step of performing (B); storing instructions for executing (A) at least once and for executing (B) at least once; Non-transitory computer-readable medium.

19. 20. The non-transitory computer-readable medium of claim 18, wherein performing the calibration includes using different optical metrology system configurations to direct the incident beam to different locations on the spatial filter, sensing portions of the incident beam that pass through the region of interest to provide different test results, and determining the compensated path of propagation of the incident beam based on the test results.

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