Interferometric techniques

Abstract

An interferometric measurement system for evaluating a sample having a region of interest of a given depth, the interferometric measurement system comprising a memory configured to store interference pattern measurements indicative of interference patterns associated with different measurement conditions and different positions of the sample and an analysis unit; the interference pattern measurements are associated with a coherence length less than a given depth; the analysis unit includes processing circuitry configured to: extract coherent interference data from the interference pattern measurements while operating in a first mode; and when operating in the first mode, determining one or more attributes of the region of interest based on the coherent interference data.

Description

[0001] Cross-referencing

[0002] This application claims priority to U.S. Provisional Patent Serial No. 63 / 513,345, filed July 12, 2023, which is incorporated herein in its entirety. Background Technology

[0003] Scattering measurement methods such as spectral reflectometry (SR), spectral ellipsometry (SE), and spectral interferometry (SI) are widely used in semiconductor process control. These techniques provide valuable information about the measured layers and nanostructures, characterizing their size and material properties.

[0004] All these methods face a critical challenge when measuring thick, transparent structures: the reflection spectra from such structures typically include extremely fast oscillations, meaning that reflection changes significantly for very small wavelength differences. To address these spectral characteristics, the measurement equipment (e.g., spectrometers) requires extremely high spectral resolution, which is technically challenging and has various negative impacts on other measurement properties (SNR, cost, complexity) and is simply infeasible for very thick stacks.

[0005] In this situation, the measured spectrum is "fuzzy," meaning that the spectral features cannot be resolved by the measuring device. This leads to a loss of sensitivity and applicability of the metrology solution.

[0006] Another contributing factor to decoherence and sensitivity loss is NA blurring. The reflectance spectrum from thick, transparent structures is also characterized by strong oscillations and / or sharp features in reflectance with respect to the angle of incidence, and, if not cylindrically symmetric, by strong oscillations and / or sharp features in reflectance with respect to the azimuth. Since SR, SE, and SI are essentially incoherent integrals in the pupil plane, these oscillations and sharp features are blurred in the pupil plane, resulting in results that differ from ideal single-ray measurements. This can be viewed as a lack of angular resolution, which complements the lack of adequate spectral resolution.

[0007] As stated, increasing spectral resolution helps address rapid spectral oscillations at the cost of performance, cost, and complexity. Furthermore, such solutions are not scalable—as semiconductor applications become thicker, high-end spectrometers cannot keep up with the required spectral resolution.

[0008] Another possible approach involves using longer wavelengths, namely IR and MIR (infrared and mid-infrared). Very roughly, the frequency of spectral oscillations is proportional to 1 / λ (where λ is the wavelength), resulting in slower oscillations at longer wavelengths. This mitigation has several negative consequences—in terms of lost sensitivity (the UV and Vis wavelength ranges maintain varying degrees of sensitivity to the properties of the measured structure), system complexity, measurement time (due to the lower brightness of the light source and the less efficient detector), and measurement spot size (due to diffraction at longer wavelengths).

[0009] A monochromator-based solution provides a direct solution to the spectral resolution challenge, where a scanning element measures scattered light at a specific wavelength at any given moment. Extremely high spectral resolution can be achieved in such methods, but at the cost of very long measurement times—generally unsuitable for process control and high TPT metrology.

[0010] Another alternative for increasing spectral resolution is provided through Fourier-based methods. In these methods, the integral is measured over a wide spectral range, but different weighted sums of the signal are captured by different measurement instances using a scanning element (typically a mirror). Methods of this class include Fourier transform IR (FTIR) and white light interferometry (WLI). Typically, the final spectral resolution is proportional to the range scanned by the scanning element, thus allowing for very high spectral resolution. However, as mentioned earlier, high resolution comes at the direct cost of measurement time.

[0011] Insufficient angular resolution can be addressed by reducing the ensemble NA to a size where the spectral angle dependence is weaker, thus allowing measurements closer to the ideal measurement of a single ray. The drawback of this approach is the reduced light collected per unit time; therefore, either the measurement time must be increased to collect more light at the expense of throughput, or the measurement time must be kept constant, resulting in a noisy spectrum. If a small NA is insufficient, a moving pinhole can be used, which further slows down the measurement and introduces additional complexity to the measurement system.

[0012] There is an increasing need for cost-effective measurement methods to measure the high-frequency response of samples. Summary of the Invention

[0013] Systems, non-transitory computer-readable media, and methods as shown in the specification and / or claims and / or drawings. Attached Figure Description

[0014] The subject matter considered to be the present invention is specifically pointed out and explicitly claimed in the concluding section of the specification. However, the organization and operation of the invention, as well as its objects, features, and advantages, can be best understood by referring to the following detailed description while reading the accompanying drawings, in which: Figure 1 An example of an interferometric measurement system is shown; and Figure 2 An example of the method is shown. Detailed Implementation

[0015] Figure 1 An example of an interferometric measurement system 10 for evaluating samples of a region of interest with a given depth is shown. The interferometric measurement system includes: a. Memory unit 12, configured to store interference pattern measurement results, indicating interference patterns associated with different measurement conditions and different locations of the sample. The interference pattern measurement results are associated with a coherence length less than a given depth. The memory unit includes at least one integrated circuit or is included in one or more integrated circuits. The memory unit can be a dynamic memory unit or a static memory unit.

[0016] b. Analysis unit 16, including processing circuitry, the processing circuitry being configured to: (i) when operating in the first mode, extract coherent interferometric data (such as...) from the interferometric pattern measurement results. (ii) When operating in the first mode, one or more properties of the region of interest are determined based on the coherent interferometric data. The processing circuitry may include at least one integrated circuit or may be included in one or more integrated circuits.

[0017] c. Communication unit 20, used for communication between units of the system and / or for communication with other computerized systems.

[0018] According to an embodiment, the interferometric measurement system includes an interferometer 18, which is used to provide a plurality of interference pattern information units. An example of an interferometer is shown in U.S. Patent 10,161,885, which is incorporated herein by reference. Figure 1 The interferometer is shown as including an illumination unit (radiation source), a beam splitter, a reference arm with a movable reference mirror, a measurement arm, a sensing unit, and another beam splitter. The sample is shown as including two reflective surfaces—a top surface and a second surface defining the region of interest. This is a simplified sample; more complex samples can be evaluated.

[0019] According to the implementation method, the interferometer is not included in the interferometric measurement system.

[0020] According to the implementation method, different positions of the sample correspond to different sensing elements of the sensing sensor, or to different positions of the light spot.

[0021] According to the implementation method, extracting coherent interference data includes compensating for decoupling associated with the measurement results of the interference pattern.

[0022] According to the implementation method, extracting coherent interference data includes compensating for interference pattern measurement results that are not affected by different measurement conditions.

[0023] According to the implementation, the extraction of coherent interferometric data is based at least in part on the measured or simulated optical properties of one or more optical components involved in generating the interferometric pattern measurement results.

[0024] According to the implementation method, different measurement conditions include different optical path differences between the measuring arm and the reference arm of the interferometer, and the interferometer is used to obtain the measurement results of the interference pattern.

[0025] According to the implementation method, different measurement conditions include different positions of the reference mirror of the reference arm of the interferometer and different positions of the reference arm of the interferometer, and the interferometer is used to obtain the measurement results of the interference pattern.

[0026] According to the implementation, different positions of the reference mirror correspond to surfaces at different depths in the region of interest, wherein the depth difference between adjacent surfaces is less than the coherence length.

[0027] According to an embodiment, the analysis unit is configured to apply vertical traveling scatterometry to coherent interferometric data to determine one or more properties of the region of interest. An example of vertical traveling scatterometry is shown in U.S. Patent Application 2024 / 0085805, which is incorporated herein by reference.

[0028] According to the implementation method, different measurement conditions include different focusing conditions.

[0029] According to the implementation, when it is determined that the measurement results of the interference pattern indicate summed interferences of different wavenumbers, the processing circuit is configured to operate in a second mode.

[0030] According to the implementation, when operating in the second mode, the processing circuit is configured to separate the superimposed interferences to determine the contribution of each interference pattern associated with different wavenumbers.

[0031] According to the implementation, the processing circuit is configured to separate the superimposed interferences by solving a quadratic optimization problem.

[0032] According to the implementation, different measurement conditions include different positions of the reference mirror on the reference arm of the interferometer, the interferometer being used to obtain interference pattern measurement results, wherein the different positions of the reference mirror correspond to surfaces located at different depths in the region of interest, and the number of different positions is at least higher spectral resolution wavenumber (N). K The number of waves (N) is twice that of the measured wavenumber (N). KThe sum of the quantities of ).

[0033] According to the implementation method, different measurement conditions include different focusing conditions.

[0034] Figure 2 An example of a method 100 for evaluating a region of interest with a given depth is shown.

[0035] According to the implementation, method 100 begins at step 110: obtaining an interference pattern measurement result, the interference pattern measurement result indicating an interference pattern associated with different measurement conditions and different locations of the sample; the interference pattern measurement result is associated with a coherence length less than a given depth.

[0036] Acquiring can include generating or receiving.

[0037] According to one implementation, step 110 includes using an interferometer to provide a plurality of interference pattern information units. This may include providing radiation to the interferometer, which in turn provides an interference pattern indicating the sample.

[0038] According to the implementation method, different measurement conditions include different optical path differences between the measuring arm and the reference arm of the interferometer, which is used to obtain the measurement results of the interference pattern.

[0039] According to the implementation method, different measurement conditions include different positions of the reference mirror of the reference arm of the interferometer and different positions of the reference arm of the interferometer, which is used to obtain the measurement results of the interference pattern.

[0040] According to the implementation, different positions of the reference mirror correspond to surfaces at different depths in the region of interest, wherein the depth difference between adjacent surfaces is less than the coherence length.

[0041] According to the implementation method, different positions of the sample correspond to different sensing elements of the sensing sensor, or to different positions of the light spot.

[0042] According to the implementation method, different measurement conditions include different focusing conditions.

[0043] According to the implementation, the different measurement conditions include different positions of the reference mirror of the reference arm of the interferometer used to obtain the measurement results of the interference pattern, wherein the different positions of the reference mirror correspond to the surface located at different depths in the region of interest, and wherein the number of different positions is at least twice the sum of the number of higher spectral resolution wavenumbers and the number of wavenumbers measured.

[0044] According to the implementation method, step 110 is followed by step 120, which stores multiple interference pattern information units.

[0045] According to the implementation, step 120 is followed by step 130, which determines one or more attributes of the region of interest based on multiple interference pattern information units.

[0046] According to the implementation, step 130 includes at least one of steps 131 and 132. In step 131, when the processing circuit is running in a first mode, the processing circuit determines one or more properties of the region of interest based on coherent interferometric data. In step 132, when the processing circuit is running in a second mode, the processing circuit determines one or more properties of the region of interest based on coherent interferometric data.

[0047] According to the implementation, the choice between steps 131 and 132 is based on whether the interferometric pattern measurement results indicate superimposed interference of different wavenumbers. Different wavenumbers represent wavelengths that are far enough apart that the interferences of different waves are significantly different from each other.

[0048] The choice between step 131 and step 132 can be based on whether the results of the interference pattern measurement indicate superimposed interference of different wavenumbers, or any other estimate.

[0049] According to the implementation method, step 131 includes at least one of the following: a. The processing circuit extracts coherent interference data from the measurement results of the interference pattern, and...

[0050] b. The processing circuit determines one or more properties of the region of interest based on coherent interferometric data.

[0051] c. Decoupling related to compensation and interference pattern measurement results.

[0052] d. Compensation for interference pattern measurement results that are not affected by different measurement conditions.

[0053] e. The extraction of coherent interferometric data is based, at least in part, on the measured or simulated optical properties of one or more optical components involved in generating the interferometric pattern measurement results.

[0054] f. Applying vertically traveling scattering measurements to coherent interferometric data to determine one or more properties of a region of interest. An example of a vertically traveling scattering measurement is shown in U.S. Patent Application 2024 / 0085805, which is incorporated herein by reference.

[0055] According to the implementation method, step 132 includes at least one of the following: a. The processing circuit separates the superimposed interferences to determine the contribution of each interference pattern associated with different wavenumbers.

[0056] b. The processing circuit separates the superimposed interferences by solving a quadratic optimization problem.

[0057] After step 140, the following actions may be taken: storing information about one or more attributes; transmitting information about one or more attributes; changing one or more lighting parameters and / or collection parameters and / or interferometer parameters based on information about one or more attributes; granting remote users access to information about one or more attributes; generating manufacturing process alarms; changing the manufacturing parameters of the sample; etc.

[0058] According to an embodiment, a non-transitory computer-readable medium is provided for evaluating samples of a region of interest with a given depth. The non-transitory computer-readable medium stores instructions executable by a processing circuit, which are used to: obtain interferometric pattern measurement results indicating interferometric patterns associated with different measurement conditions and different locations of the sample; associate the interferometric pattern measurement results with a coherence length less than the given depth; store a plurality of interferometric pattern information units; extract coherent interferometric data from the interferometric pattern measurement results when the processing circuit operates in a first mode; and determine one or more properties of the region of interest based on the coherent interferometric data when the processing circuit operates in the first mode.

[0059] According to one embodiment, a novel measurement sequence and algorithmic approach are provided, thereby eliminating concerns about the aforementioned rapid spectral oscillations. According to another embodiment, the interferometric measurement system includes an interferometer and additional hardware components, such as those shown in U.S. Patent 10,161,885, which is incorporated herein by reference.

[0060] In SI measurements, the incident light is split into two parts by a beam splitter (BS): one part is reflected from the sample, and the other part is reflected from the reference mirror. The light reflected from both the sample and the mirror is recombined by the BS, and the resulting interference is measured by a spectrometer. The core of this invention relies on the concept of coherence loss of the interference signal and on the dependence of the interference signal on both wavelength and the position of the reference mirror. We can describe the measured signal in terms of the interference between the light reflected from the sample and the reference mirror. A simplified description of the interference signal collected at wavelength λ can be expressed as: .

[0061] here, It is the field reflectivity of the mirror and It is the field reflectance of the sample. z This represents the path-length difference between two optical paths (see...). Figure 1 From BS to the mirror and back (path "A" in the sketch) and to the top of the sample and back (path "B").

[0062] Clearly, this description is greatly simplified; it does not consider the different transmissions of the two optical paths, the overall system transmission, the light source intensity, the detector collection efficiency, etc. Here and in the following discussion, for the sake of simplicity, all elements that are not important to the invention under discussion are omitted (and can be explained by standard methods and calibrations).

[0063] We can define several technical terms: a. Optical Path Difference (OPD) Matching: Optical path difference is the difference in optical path length between two optical paths. The optical path length of each path is the product of the geometric length of the material through which the light propagates and its refractive index (within a structure, each electromagnetic eigenmode has a different phase velocity, and therefore a different effective refractive index and a different OPD). In interferometry, OPD plays a crucial role in determining the characteristics of the measured signal. OPD matching is the practical process of tuning the system to a specific value or range of that OPD. OPD matching can have a decisive impact on the measurement; for example, if the OPD is too large, coherence may be lost, as explained below.

[0064] b. Coherence: If two electromagnetic waves correlate during the measurement period and thus produce an interference pattern in time or space, then the two electromagnetic waves are said to be coherent. and The intensity of the interference comprises two fields. The contribution of intensity and interference terms Where <·> represents time averaging. If the phase 1 and 2 If the time dependencies are completely uncorrelated, the average will vanish. Similarly, if 1 and 2 If the difference is too great (compared to the reciprocal of the average time), the interference term will be suppressed. Coherence γ is defined as the ratio between the measured interference term (which can be measured, for example, by moving one of these mirrors in a Michaelson interferometer and measuring the amplitude of the resulting oscillation, as described in U.S. Patent 10,161,885, which is incorporated herein by reference) and the interference expected for a fully coherent field.

[0065] One source of decoupling is the limited spectral resolution of the spectrometer. Consider a light wave that leaves the light source and is split into two beams, each traveling an optical path... L 1 and optical path L 2These beams are then recombined in the spectrometer. If the effective resolution of the spectrometer (which is determined by, for example, the spectrometer's pixel width, point spread function (PSF), finite spot size, etc.) collects the wave vectors... k and k+ Δ k The field between them, then the measured interference term is (For simplicity, we assume the integration time is long enough that different wavelengths are completely incoherent and do not interfere.) E 1,2 and Follow k It changes slowly. However, these assumptions are not necessary for this idea.

[0066] if L 2 and L 1 If the difference is too great, the integral will be highly oscillatory and highly suppressed, so the interference term will be small and the coherence γ will be low.

[0067] For high coherence, it should be required that Therefore, the coherence length—exceeding the OPD whose interference is significantly suppressed—is related to the spectral resolution Δ. k Inversely proportional. Therefore, for reasonable coherence, the OPD between the two beams must be sufficiently small, a phenomenon known as OPD matching. In a sufficiently thick measurement sample, it is impossible to match the OPD of both the reflections from the top and the reflections from the bottom with the OPD of the beam passing through the other arm of the interferometer (the reference beam). Consequently, at least one of them will suffer significant decoupling, and therefore its phase relative to the reference beam cannot be measured and is, in effect, undefined.

[0068] For simplicity, let us describe the invention as being applied to a sample with two reflective interfaces. This concept can be applied to any thick sample, but it is simpler to explain in this case.

[0069] The reflection from a sample with two reflective interfaces can be approximated as (this approximation is irrelevant to the present invention and only simplifies the explanation). .

[0070] in It is the field reflectivity from the top interface. It is the field reflectivity from the bottom. H It represents the geometric difference between the interfaces, and n is the refractive index. (Exponential factor) This represents the phase accumulated as light travels through the sample.

[0071] The ideal reflected signal will be .

[0072] However, the interference between the top and bottom is usually not perfectly coherent. As mentioned above, this is due to several physical reasons, such as the limited resolution of the spectrometer. Under such conditions, the measured signal can be approximated as... .

[0073] in, k This is an effective parameter for describing the decoupling mechanism (e.g., spectrometer resolution). Under the same assumptions, the idealized interferometric measurement signal would be After considering the separation, the measured signal will be generated. .

[0074] Please note that although the first interference term ( The divergence coefficient depends only on the sample itself, but other terms ( and The divergence of terms depends on the OPD (via z). Therefore, OPD matching plays an important role in determining which terms will be coherent and which terms will suffer more significantly from divergence. If the matching will be for the top surface, i.e. Then the interference between the top and the mirror will be coherent. On the other hand, if the matching will be for the bottom, i.e. Then the bottom will coherently interfere with the mirror. (If) That is, if the optical path length in the sample is less than the coherence length, then these two conditions can be satisfied.

[0075] Without loss of generality, let us describe the invention with regard to the case of OPD matching with a top surface. The same concept, with the desired modifications, applies to coherent interference occurring with any reflective surface.

[0076] Although for The total measured signal is incoherent, but the coherent portion of the signal can be taken. Consider... The entity can be obtained through direct measurement using a mirror and a sample.

[0077] From the above we can conclude

[0078] Let us emphasize that these are the only terms that depend on z, and therefore they are the only terms that contribute to phase extraction in SI measurements.

[0079] Can utilize the field Will S This is represented as coherent interference of mirrors.

[0080] For the sake of simplicity, and considering the circumstances... Then, with The relevant strength is .

[0081] Notice and The difference between them - in Reflections from interfaces that do not match the mirror's OPD will be attenuated, and only the coherent portion of the reflection will be retained.

[0082] The suggested solution uses (The reflected coherent portion) is the amplitude of the complex SI signal, not... .

[0083] In SI measurements, field reflectance is extracted from a set of measurements.

[0084] As mentioned above, the measured signal undergoes several decoupling processes. Therefore, the interference term... Represented as ,in, It is a factor that describes all divergence effects.

[0085] From this set of measurements, given prior knowledge... and In the case of phase extraction However, as mentioned above, phase With field Instead Related. However, by combining the above analysis with... S Compare the expressions. In fact, it is This is correct for the reasons for separation mentioned above. However, there may be additional separation mechanisms. Let's represent separation due to equipment defects as... .

[0086] Then .if only It is constant and does not depend on the sample being measured, so it can be calibrated.

[0087] Therefore, take the leading factor of the cosine and divide by , thus obtaining coherent amplitude.

[0088] Because the amplitude is now taken from the interferometric terms, it is sensitive to any imperfections in measurements that introduce additional decoupling (e.g., mirror vibration). Such imperfections may not be constant, and their effect on the interferometric signal can be expressed in general functional form, which may contain unknown coefficients. Since these unknown coefficients can vary between measurements, the interferometric signal can be compared or subjected to any other processing only after this factor has been considered. This can be done in several ways. One approach is to fit these coefficients by optimizing some objective function (e.g., maximizing the signal explained by the model) or satisfying other known requirements (e.g., matching between two spectra). Another option is to remove each component with this functional form from all spectra. One way to do this is by projecting the spectra onto the orthogonal complement space of these components.

[0089] Having a coherent signal instead of a mixed signal is a qualitative improvement. One implication is the ability to apply vertical traveling scattering (VTS) measurement algorithms on stacked layers of arbitrary thickness (as disclosed in PCT patent application PCT / IB2022 / 050774 and U.S. patent application US2024 / 0085805, which are incorporated herein by reference).

[0090] Because the signal is coherent, the VTS is well-defined and does not contain non-physical components (e.g., parts that disrupt causality). This allows the use of spectral regions that have undergone ambiguity, thereby improving vertical resolution (depending on the spectral range).

[0091] Another implication is the ability to remove incoherent contributions that limit measurement stability.

[0092] This also allows for the acquisition of more information from the thickly stacked bottom or any other surface—if the mirror matches the bottom OPD, the primary coherent reflection will come from the bottom; similarly, if the OPD matches another surface, the coherent reflection will come from that surface. Now, the VTS can separate the bottom (or any other surface) from the other parts.

[0093] When running in the first mode, apply the above process.

[0094] The above procedure is limited by the system coherence length, which is specified by the effective spectral resolution of the system as described above. If the OPD is matched to a surface in the sample, the SI measurement can capture signals within several coherence lengths on both sides of that surface, while signals further away become incoherent and therefore unusable for VTS.

[0095] One feasible solution to this problem is to perform multiple SI measurements, each with OPD matching against a different surface in the sample, and extract the phase and amplitude separately for each. The time-domain spectra obtained from the VTS algorithm for each of these measurements can then be combined into a single, larger time-domain spectrum based on the mirror position in each measurement. This approach has the following drawbacks: each segment of the time-domain spectrum is based on the result of a single SI measurement rather than utilizing data from all SI measurements, and stitching them together can lead to discontinuous time-domain data because any two segments can be assigned different coherence values ​​to the same z-axis.

[0096] A better approach would be to utilize all the original interferometric measurements together to generate a frequency-domain spectrum with a resolution greater than that of ordinary SI measurements. Higher spectral resolution means a longer coherence length than that of ordinary spectral measurements. This method has the advantage of better scalability: theoretically, the spectral resolution can be arbitrarily increased, at the cost of requiring more measurements and more time.

[0097] The key concept is that when multiple wavelengths contribute to the same effective pixel, the weight of their contributions changes differently as the mirror moves. Measuring the intensity at the pixel at different mirror positions yields different linear combinations of fields of different wavelengths, which allows us to solve for the contribution of each field.

[0098] For example, if The effective pixel (which can be a physical pixel, the spot size on a spectrometer, etc.) has a nominal wavenumber of 1. The effective pixel receives contributions from n wavelengths, the wavenumbers of which are... Then the interference intensity in the effective pixel is .

[0099] in, yes wavelength pair Pixel contribution weights (note that, for example, if the effective pixels are determined by the spot size in the spectrometer, the wavelength can contribute to more than one pixel).

[0100] Therefore, we can conclude that... Having form ,in, and .

[0101] According to the implementation method, the above equation depends on z and the incident angle of the radiation on the sample.

[0102] By taking measurements at a sufficient number of mirror positions z, it is possible to target and Solve the problem (in the sense of least squares, i.e., solve a quadratic optimization problem that is easy to solve). ), and obtained γ and at a spectral resolution higher than that of the measuring instrument. .

[0103] According to the implementation method, the above equation depends on z and the incident angle of the radiation on the sample.

[0104] Higher spectral resolution leads to longer coherence lengths.

[0105] In order to obtain , as well as There should be at least one Individual lens positions (more are recommended to increase noise reduction capabilities), among which... It is a higher spectral resolution wavenumber The number, and This is the number of wavenumbers measured. Clearly, the mirror position should be chosen such that the above formula applies... , as well as Any linear combination of these is not "blind" (or in other words, the corresponding matrix should be non-singular), and therefore has a unique minimum. Furthermore, for each surface of interest, there should exist at least two mirror positions whose OPD with that surface is approximately a coherence length or less; otherwise, any measurement results... Neither of them will contain any coherent signals from that surface, and therefore and It will not have any contribution from that surface.

[0106] A similar method can be used to increase angular resolution. Defocus introduces a radially varying phase on the pupil, causing additional radial phase interference at pupil points of different radii when imaged onto the spectrometer, depending on the degree of defocus. By measuring at different defocus values, known linear combinations of the angular mean field at different radii on the pupil can be obtained, and the angular mean field on the pupil can then be solved in a similar manner to that described above for the effective pixels of the spectrometer. One drawback of this method is that it increases illumination and the collected light spot.

[0107] Specifically, if spatial spearing exists on the pupil but no spectral spearing, then the measured interferometric intensity is ,in, θ It is the angle of incidence. Therefore, we can find that we can discretize the angle of incidence and measure multiple mirror positions. And by optimizing the problem Find and .

[0108] This method is not suitable if both spectral and pupil blurring exist.

[0109] Another method is to tilt the mirror. This shifts the reflections from the mirror, and therefore causes interference at different pupil points (assuming they are in the same coherent region). In this case, the measured interferometric intensity is ,in It is a vector representing the pupil coordinates, and This is due to the pupil shift caused by the tilt of the mirror, which is represented as the pupil vector. It is half the optical path to the tilting mirror and back. It takes into account the coherence between different points on the pupil and the weights of the system’s wavelength and pupil-dependent characteristics.

[0110] By taking several measurements at different tilt angles in two directions, the reflection field in different regions of the pupil plane can then be extracted by optimizing the following problem:

[0111] When running in the second mode, apply the above process.

[0112] According to the implementation method, the implied solution provides at least the following benefits.

[0113] a. Even for thick structures, measure the coherent signal rather than the entire signal. This makes it possible to use algorithms (such as VTS) without any acacia artifacts.

[0114] b. Additional spectral and / or angular resolution can provide access to sensitive spectral and angular features of various properties of interest in the measured sample.

[0115] c. This invention offers scalability: there are no hard barriers to increasing spectral and angular resolution and the resulting coherence length.

[0116] d. The cost in measurement time is lower than that of alternative methods.

[0117] In the foregoing detailed description, numerous specific details have been set forth to provide a thorough understanding of the invention. However, those skilled in the art will understand that the invention can be practiced without these specific details. In other instances, well-known methods, processes, and components have not been described in detail so as not to obscure the invention.

[0118] The subject matter considered to be the present invention is specifically pointed out and explicitly claimed in the concluding section of the specification. However, the organization and operation of the invention, as well as its objects, features, and advantages, can be best understood by referring to the following detailed description while reading the accompanying drawings.

[0119] It should be understood that, for the sake of simplicity and clarity, the elements shown in the figures are not necessarily drawn to scale. For example, some elements may be enlarged relative to others for clarity. Furthermore, reference numerals may be repeated in the figures where deemed appropriate to indicate corresponding or similar elements. Because most of the embodiments illustrated in this invention can be implemented using electronic components and circuits known to those skilled in the art, details will not be explained to any extent deemed necessary beyond what is required for understanding and appreciating the basic concepts of the invention, and in order not to obscure or distract from the teachings of the invention.

[0120] Any references to methods in this specification shall be modified as necessary to apply to systems capable of performing the method and / or to non-transitory computer-readable media storing instructions for implementing the method.

[0121] Any references to the system in this specification shall be modified as necessary to apply to methods that can be performed by the system and / or as necessary to non-transitory computer-readable media that can be performed by the system.

[0122] Any reference in this specification to non-transitory computer-readable media shall be modified as necessary to apply to methods implemented by executing instructions stored in such non-transitory computer-readable media and / or to systems capable of executing such instructions.

[0123] In the foregoing description, the invention has been described with reference to specific examples of embodiments thereof. However, it will be apparent that various modifications and changes can be made to the invention without departing from the broader spirit and scope of the invention as set forth in the appended claims.

[0124] Furthermore, the terms “front,” “rear,” “top,” “bottom,” “above,” “below,” etc., as used in the specification and claims (if any) are for descriptive purposes and are not necessarily used to describe permanent relative positions. It should be understood that the terms thus used are interchangeable where appropriate, such that embodiments of the invention described herein can, for example, operate in orientations other than those shown or otherwise described herein.

[0125] Any arrangement of components that perform the same function is effectively “associated” to achieve the desired functionality. Therefore, any two components combined in this paper to achieve a specific function can be considered “associated” with each other to achieve the desired functionality, regardless of the architecture or intermediate components. Similarly, any two such associated components can also be considered “operably connected” or “operably coupled” to each other to achieve the desired functionality.

[0126] Furthermore, those skilled in the art will recognize that the boundaries between the above operations are merely illustrative. Multiple operations can be combined into a single operation, a single operation can be distributed among additional operations, and operations can be performed at least partially overlapping in time. Moreover, alternative implementations may include multiple instances of a particular operation, and the order of operations can be varied in various other implementations.

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

[0128] However, other modifications, variations, and substitutions are also possible. Therefore, the specification and drawings are to be regarded as illustrative rather than restrictive.

[0129] In the claims, any reference signs placed between parentheses should not be construed as limiting the claims. The word “comprising” does not exclude the presence of other elements or steps besides those listed in the claims. Furthermore, the terms “a” or “an” as used herein are defined as one or more. Similarly, the use of introductory phrases such as “at least one” and “one or more” in the claims should not be construed as implying that the introduction of another claim element by the indefinite article “a” or “an” limits any particular claim containing such an introduced claim element to an invention containing only one such element, even when the same claim includes the introductory phrase “one or more” or “at least one” along with indefinite articles (such as “a” or “an”). This also applies to the use of definite articles. Unless otherwise specified, terms such as “first” and “second” are used to arbitrarily distinguish the elements described by these terms. Therefore, these terms are not necessarily intended to indicate the time or other priority of such elements. The fact that certain measures are recited in mutually different claims does not mean that combinations of these measures cannot be used advantageously.

[0130] While certain features of the invention have been shown and described herein, many modifications, substitutions, alterations, and equivalents will now occur to those skilled in the art. Therefore, it should be understood that the appended claims are intended to cover all such modifications and alterations that fall within the true spirit and scope of the invention.

Claims

1. An interferometric measurement system for evaluating samples of a region of interest with a given depth, the interferometric measurement system comprising: A memory unit is configured to store interference pattern measurement results, which indicate interference patterns associated with different measurement conditions and different locations of the sample; The measurement results of the interference pattern are correlated with a coherence length less than the given depth; as well as The analysis unit includes a processing circuit, which is configured to: When running in the first mode, coherent interference data is extracted from the measurement results of the interference pattern; and When running in the first mode, one or more properties of the region of interest are determined based on the coherent interferometric data.

2. The interferometric measurement system according to claim 1, wherein, Extracting the coherent interference data includes compensating for decoherence associated with the measurement results of the interference pattern.

3. The interferometric measurement system according to claim 1, wherein, Extracting the coherent interference data includes compensating for interference pattern measurement results that are not affected by the different measurement conditions.

4. The interferometric measurement system according to claim 1, wherein, The extraction of the coherent interferometric data is based, at least in part, on the measured or simulated optical properties of one or more optical components involved in generating the measurement results of the interferometric pattern.

5. The interferometric measurement system according to claim 1, wherein, The different measurement conditions include different optical path differences between the measuring arm and the reference arm of the interferometer, and the interferometer is used to obtain the measurement results of the interference pattern.

6. The interferometric measurement system according to claim 1, wherein, The different measurement conditions include different positions of the reference mirror of the interferometer's reference arm and different positions of the interferometer's reference arm, and the interferometer is used to obtain the measurement results of the interference pattern.

7. The interferometric measurement system according to claim 6, wherein, The different positions of the reference mirror correspond to surfaces at different depths in the region of interest, wherein the depth difference between adjacent surfaces is less than the coherence length.

8. The interferometric analysis unit is configured to apply vertical traveling scattering measurements to coherent interferometric data to determine one or more properties of the region of interest.

9. The interferometric measurement system according to claim 1, wherein, The different measurement conditions include different focusing conditions.

10. The interferometric measurement system according to claim 1, wherein, When the measurement results of the interference pattern indicate superimposed interference at different wavenumbers, the processing circuit is configured to operate in a second mode.

11. The interferometric measurement system according to claim 10, wherein, In the second mode, the processing circuitry is configured to separate the superimposed interferences to determine the contribution of each interference pattern associated with the different wavenumbers.

12. The interferometric measurement system of claim 11, wherein the processing circuit is configured to separate the superimposed interferences by solving a quadratic optimization problem.

13. The interferometric measurement system according to claim 11, wherein, The different measurement conditions include different positions of the reference mirror of the reference arm of the interferometer, the interferometer being used to obtain the measurement results of the interference pattern, wherein the different positions of the reference mirror correspond to surfaces located at different depths in the region of interest, and wherein the number of the different positions is at least twice the sum of the number of higher spectral resolution wavenumbers and the number of wavenumbers measured.

14. The interferometric measurement system according to claim 11, wherein, The different measurement conditions include different focusing conditions.

15. The interferometric measurement system according to claim 11, wherein, The different measurement conditions include different reference mirror tilt conditions.

16. The interferometric measurement system according to claim 1, comprising an interferometer, the interferometer being used to obtain the measurement result of the interference pattern.

17. A method for evaluating samples of a region of interest with a given depth, the method comprising: Obtain interference pattern measurement results, which indicate interference patterns associated with different measurement conditions and different positions of the sample; The measurement results of the interference pattern are correlated with a coherence length less than the given depth; Stores multiple interference pattern information units; When the processing circuit is running in the first mode, the processing circuit extracts coherent interference data from the interference pattern measurement results; as well as When the processing circuit operates in the first mode, it determines one or more properties of the region of interest based on the coherent interferometric data.

18. The method of claim 17, comprising: When the measurement results of the interference patterns indicate superimposed interference at different wavenumbers, the processing circuit is operated in a second mode, wherein operating in the second mode includes: separating between the superimposed interferences to determine the contribution of each interference pattern associated with the different wavenumbers.

19. A non-transitory computer-readable medium for evaluating samples of a region of interest having a given depth, the non-transitory computer-readable medium storing instructions executable by processing circuitry, the instructions being used to: Obtain interference pattern measurement results, which indicate interference patterns associated with different measurement conditions and different locations of the sample; the interference pattern measurement results are associated with a coherence length less than the given depth; Stores multiple interference pattern information units; When the processing circuit is running in the first mode, the processing circuit extracts coherent interference data from the interference pattern measurement results; as well as When the processing circuit operates in the first mode, it determines one or more properties of the region of interest based on the coherent interferometric data.

20. The non-transitory computer-readable medium of claim 18, further storing instructions executable by the processing circuitry, the instructions being configured to cause the processing circuitry to operate in a second mode when it is determined that the measurement results of the interferometric pattern indicate superimposed interference of different wavenumbers, wherein, Operating in the second mode includes: separating between the superimposed interferences to determine the contribution of each interference pattern associated with the different wavenumbers.

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