Optical critical dimension (OCD) metrology for thick stacks

Abstract

A method for evaluating a thick transparent layer, the method comprising: (i) generating information about a relationship between a measurement of a spectrometer of an interferometer and an optical path difference (OPD) value of the interferometer, where generating the information comprises illuminating the thick transparent layer by the interferometer; (ii) determining one or more thick transparent layer reflection parameters based on the information about the relationship; and (iii) determining one or more structural characteristics of the thick transparent layer based on the one or more thick transparent layer reflection parameters.

Description

[0001] Cross-references

[0002] This application claims priority to U.S. Provisional Patent Serial No. 63 / 356,531, filed on June 29, 2022, the entirety of which is incorporated herein. Background Art

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

[0004] All of these methods face a serious challenge when measuring thick, transparent structures: the reflection spectra from such structures typically include extremely fast oscillations, which means that the reflection changes significantly for very small differences in wavelength. BRIEF DESCRIPTION OF THE DRAWINGS

[0005] The subject matter which is regarded as the invention is particularly pointed out and distinctly claimed in the concluding portion of the specification. However, the invention both as to its organization and method of operation, together with objects, features, and advantages thereof, may be best understood by reference to the following detailed description when read with the accompanying drawings, in which:

[0006] Figure 1A to Figure 1B An example of a spectral interferometry system is illustrated;

[0007] Figure 2 illustrates a method according to an embodiment of the present invention; and

[0008] Figure 3 Various sinusoidal relationships are illustrated. DETAILED DESCRIPTION

[0009] 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 appreciated by those skilled in the art that the present invention may be practiced without these specific details. In other instances, well-known methods, processes, and components are not described in detail to avoid obscuring the present invention.

[0010] The subject matter which is regarded as the invention is particularly pointed out and distinctly claimed in the concluding portion of the specification.The invention, however, both as to its organization and method of operation, together with objects, features, and advantages thereof, may be best understood by reference to the following detailed description when read with the accompanying drawings.

[0011] It should be understood that for simplicity and clarity of illustration, the elements shown in the figures are not necessarily drawn to scale. For example, for clarity, the size of some of the elements may be enlarged relative to other elements. In addition, reference numerals may be repeated in the figures to indicate corresponding or similar elements where deemed appropriate.

[0012] Because the embodiments of the present invention described can be implemented for the most part using optical components and circuits known to those skilled in the art, in order to understand and appreciate the basic concepts of the present invention and in order not to obscure or distract from the teachings of the present invention, the details will not be explained to any greater extent than is deemed necessary in the above description.

[0013] Any reference to a method in the specification should apply mutatis mutandis to a non-transitory computer readable medium storing instructions which, once executed by a computer, result in the performance of the method.

[0014] Any reference in the specification to a non-transitory computer readable medium shall apply mutatis mutandis to methods executable by a computer reading the instructions stored in the non-transitory computer readable medium.

[0015] In order to resolve the spectral features of thick transparent layers, the measurement equipment (e.g., spectrometer) requires extremely high spectral resolution, which is technically challenging, has various negative impacts on other measurement properties (SNR, cost, complexity) and is simply not feasible for very thick stacks.

[0016] In such cases, the measured spectrum is "smeared" with spectral features that cannot be resolved by the measurement. Such cases result in a loss of sensitivity and applicability of the metrology solution. Furthermore, simulating the expected spectrum under such conditions (a key element in many OCD interpretation schemes) is computationally very expensive in such cases, requiring reflection simulations from a very high number of wavelengths and typically a dense set of incident angles.

[0017] As stated, increased measurement spectral resolution can help resolve fast spectral oscillations, at the expense 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.

[0018] Another possible approach involves using longer wavelengths, namely IR and MIR (infrared and mid-infrared). Very roughly, the frequency of the spectral oscillation is proportional to 1 / λ (where λ is the wavelength), resulting in slower oscillations at longer wavelengths. Such mitigation has several negative aspects in terms of loss of sensitivity (the UV and Vis wavelength ranges retain various unique sensitivities to the properties of the structure being measured) as well as system complexity, measurement time (due to lower brightness sources and less efficient detectors), and measurement spot size (due to diffraction at longer wavelengths).

[0019] A straightforward solution to the spectral resolution challenge is provided by a monochromator-based solution, where a scanning element measures the scattered light of a specific wavelength at any given moment. Very high spectral resolution can be achieved in such an approach, but at the expense of very long measurement times—often unsuitable for process control during high-volume manufacturing and high-throughput metrology.

[0020] Another alternative for increasing spectral resolution is provided by Fourier-based methods. In such methods, the integral over a wide spectral range is measured, but using a scanning element (usually a mirror), different measurement instances capture differently weighted sums of the signal. Methods in this category are Fourier transform infrared (FTIR) and white light interferometry (WLI). In general, the final spectral resolution is proportional to the range swept by the scanning element, allowing very high spectral resolution. However, as before, high resolution comes at the direct expense of measurement time.

[0021] The present disclosure describes a new measurement sequence and supporting algorithm approach that eliminates the concerns of rapid spectral oscillations described above. The method can be applied using various systems and / or different implementations of spectral interferometry. An example of a system configured to perform spectral interferometry is described in U.S. Patent 10,161,885, which is incorporated herein by reference—after being configured (e.g., programmed) to perform the method described in the present disclosure. Other systems can be provided to implement the method described in the present disclosure.

[0022] A spectroscopic interferometry (SI) system for evaluating a thick transparent layer is provided, the SI system comprising (i) an interferometer configured to illuminate the thick transparent layer and provide measurements of a spectrometer of the interferometer; (ii) a processing circuit configured to: generate information about a relationship between the measurements of the spectrometer and optical path difference (OPD) values ​​of the interferometer associated with the measurements; (b) determine one or more thick transparent layer reflection parameters based on the information about the relationship; and (c) determine one or more structural properties of the thick transparent layer based on the one or more thick transparent layer reflection parameters.

[0023] Figure 1A and Figure 1BAn example of SI measurement of a thick layer is illustrated.

[0024] The SI measurement is performed by an SI system including an interferometer 520. The interferometer 520 may include a processing circuit 540. Alternatively, the processing circuit 540 may be included in the SI system and not in the interferometer. The processing circuit 540 may be implemented as a central processing unit (CPU), and / or one or more other integrated circuits (such as an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), a full custom integrated circuit, etc.) or a combination of such integrated circuits.

[0025] Illumination source 510 directs light towards interferometer 520. Light 501 propagates through a first beam splitter 521 of the interferometer. The light propagates towards a second beam splitter 522 of the interferometer and is split into two parts.

[0026] The first portion 502 propagates to the sample and is reflected (one or more times) from the sample (to provide at least one reflected beam) before reaching the second beam splitter.

[0027] When the thick layer is illuminated, the top surface of the thick layer reflects light to provide a first reflected light beam 503 , and the bottom surface of the thick layer reflects light to provide a second reflected light beam 504 .

[0028] The second portion 505 is directed to a movable reference mirror 540 and reflects from the movable mirror (to provide a reference reflected beam 506) and reaches a second beam splitter. The first reflected beam, the second reflected beam, and the reference beam form an interference pattern 508 that propagates to the first beam splitter, which directs the interference pattern to a spectrometer 530 (of an interferometer 520) that provides a spectrometer measurement (such as a spectrum). The spectrometer can be a one-dimensional or multi-dimensional spectrometer.

[0029] We can describe the measured signal in terms of the interference between the light reflected from the sample and the light reflected from the reference mirror. A simplified description of the collected interference signal at wavelength λ can be expressed as:

[0030]

[0031] Here, E m (λ) is the field reflectivity of the mirror and E w (λ) is the field reflectivity of the sample. It is assumed that the reflectivities of the sample, parts of the sample or components of the measurement system are all functions of λ, and their explicit dependence as well as their amplitude and phase will be omitted from now on. z represents the path length difference between the two optical paths - from the second beam splitter to the reference mirror (path "A" in the sketch) and to the top and / or bottom of the sample (paths "B" and C).

[0032] Obviously, this description is extremely simplified; it does not take into account 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, all elements that are not important to the invention in question (and which can be accounted for by standard methods and calibrations) are omitted for simplicity.

[0033] In order to clearly describe the present invention, we can define several technical terms.

[0034] Optical Path Difference (OPD) Matching: The optical path difference is the difference in path length between two optical paths. The optical path length of each path is the product of the geometric length and the refractive index of the material through which the light is propagating. In interferometry, OPD plays an important role in determining the characteristics of the measured signal. OPD matching is the practice of tuning the system to a specific value or range of values ​​of OPD. OPD matching can have a critical effect on the measurement, for example, if the OPD is too large, coherence may be lost, as explained below.

[0035] Coherence: Two electromagnetic waves are said to be coherent if they are correlated during the measurement time and thus produce an interference pattern in time or space. The interference strength of the two fields and Contains the intensity of the two fields |E1| 2 +|E2| 2 and interference terms The contribution of , where <·> denotes time averaging. If the time correlation of the phases φ1 and φ2 is completely uncorrelated, the average will vanish. Similarly, if ω1 is different from ω2, the interference term will be suppressed. The coherence γ is defined as the ratio between the measured interference term (which can be measured, for example, by moving one of the mirrors in an interferometer (e.g., Michaelson) and measuring the amplitude of the resulting oscillation, as described in U.S. Patent No. 10,161,885 noted above) and the interference expected for a perfectly correlated field.

[0036] One source of decoherence is the finite spectral resolution of the spectrometer. Consider a light wave that leaves the source and is split into two beams that travel through optical paths L1 and L2, respectively, and then reunite in the spectrometer. If the effective pixels of the spectrometer (determined by, for example, the pixel width, the point spread function (PSF) of the spectrometer, the finite spot size, etc.) collect the field between wavenumbers k and k+Δk, the measured interference term is (For simplicity, we assume that the integration time is long enough so that the different wavelengths are completely incoherent and do not interfere, and that E 1,2 and φ 1,2 Changes slowly with k.

[0037] However, these assumptions are not necessary for this approach. If L2 differs too much from L1, the integrand will be highly oscillatory and the integral will be highly suppressed, so the interference term will be small and the coherence γ will be low. For high coherence, Δk(L2-L1) << 2π should be required, so the coherence length (the OPD beyond which interference is significantly suppressed) is inversely proportional to the spectral resolution Δk.

[0038] Therefore, in order to have a reasonably high coherence, the OPD between the two beams must be small enough, which is called OPD matching. In a sufficiently thick sample being measured, it is not possible to make both the top reflection and the second reflection (the first reflected beam and the second reflected beam) OPD match the beam passing through the other arm of the interferometer (the reference beam). Therefore, at least one of them will suffer from significant decoherence, so its phase relative to the reference beam cannot be measured and is actually unclear.

[0039] Reference is made to a sample comprising a thick transparent layer comprising two reflective interfaces. This idea can be applied to any thick sample.

[0040] Reflection from a sample with two reflective interfaces can be approximated as

[0041]

[0042] in is the field reflectivity from the top interface, is the field reflectivity from the bottom, H is the geometric difference between the interfaces, and n is the refractive index of the intervening layers. Represents the phase accumulated when light completes a full round trip through a transparent sample.

[0043] The ideal reflected signal would be

[0044]

[0045] However, the interference between the top and bottom is usually not completely coherent. This is due to several physical reasons (e.g., limited spectrometer resolution, etc.), as explained above. In such a situation, the measured signal can be approximated as

[0046]

[0047] where σ k is an effective parameter describing the decoherence mechanism (e.g., spectrometer resolution).

[0048] Under the same assumptions, the idealized interferometric signal would be

[0049]

[0050] After taking decoherence into account, this results in the measured signal

[0051]

[0052] Note that although the first interference term (E top E bottom ) depends only on the sample itself, but the other terms (E top E m and E bottom E m ) depends on the OPD (through z). Therefore, OPD matching plays an important role in determining which terms will be coherent and which terms will be more severely affected by decoherence. If the matching is to the top surface, that is, Then the interference of the top with the reflector will be coherent. On the other hand, if the match will be to the bottom, that is Then the bottom will interfere with the mirror. (If Then both conditions can be satisfied.)

[0053] Without loss of generality, let us describe the invention for the case of top surface OPD matching. The same idea (with required modifications) applies to coherent interference with any reflective surface.

[0054] Although for The total measured signal is incoherent, but the coherent part of the signal can be extracted. Consider S = I measured -|E m | 2 -R measured This entity can be accessed by measuring the mirror and the sample directly. From the above we get

[0055]

[0056] 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.

[0057] S can be written as the coherent interference of the mirror with the field:

[0058]

[0059] For simplicity, consider the situation So, with E c The strength of the correlation is

[0060]

[0061] Note | E c |2 With R measured The difference between |E c | 2 In the example, reflections from interfaces that are not OPD matched to the mirror are attenuated, and only the coherent part of the reflection remains.

[0062] The solution can be to use |E c |(the coherent part of the reflection) as the amplitude of the complex SI signal, instead of

[0063] In SI measurements, the field reflectivity is extracted from a set of measured values

[0064]

[0065] As discussed above, the measured signal undergoes several decoherence processes. Therefore, the interference term S = I measured -|E m | 2 -R measured Written as where γ(λ) is a factor describing all decoherence effects. From a set of such measurements, using |E m | 2 and φ m The prior knowledge of extracting the phase φ w However, as explained above, the phase φ w With field E c Rather than with E w However, by comparing the above analysis with the expression of S, E c Only γE w . This is true for the causes of decoherence described above. However, there may be additional decoherence mechanisms. Let us denote the decoherence due to device imperfections as γ sys .then, As long as γ sys is constant and does not depend on the sample being measured, it can be calibrated.

[0066] Therefore, by taking the leading factor of the cosine and dividing by 2|E m |γ sys , and obtain the coherence amplitude.

[0067] There may be additional decoherence factors that cannot be easily calibrated out. One of these is the effect of vibration on the measurement. If the mirror or the sample vibrates during the measurement, the OPD (z in the above equation) is not well defined. For the leading order, the effect on the spectrum can be written as a multiplicative factor where m is an unknown coefficient that characterizes the amplitude of the vibration in a particular measurement. Since m varies for different measurements, the interferometric signals can only be compared or processed in any other way after taking this factor into account. This can be done in several ways. One approach is to fit m by optimizing some objective function (e.g., maximizing the signal explained by the model) or satisfying other known requirements (e.g., a match between two spectra). Another option is to remove from all spectra those spectra that have the functional form One way to do this is to project the spectrum onto the orthogonal complement of these components. A similar process can be applied to other decoherence factors.

[0068] The significance of measuring the coherent field reflectivity is enormous. The so-called VTS algorithm (disclosed in PCT patent application number PCT / IB2022 / 050774) relies on SI measurements, which consist of amplitude and phase. For thick stacks, the effect of decoherence becomes prominent, and it is crucial that the VTS algorithm be applied to the coherent signal. With the present invention, the spectral applicability range becomes essentially unrestricted. VTS is converted into improved vertical resolution using shorter wavelengths. In addition, it reveals physical information that only exists within these ranges.

[0069] Figure 2 An example of a method 600 for evaluating a thick transparent layer is illustrated.

[0070] The method 600 may include a step 610 of generating information about a relationship between a measurement value of a spectrometer of an interferometer and an optical path difference (OPD) value of the interferometer. The generating of the information includes illuminating a thick transparent layer through the interferometer.

[0071] Assume that the signal measured by the spectrometer is:

[0072]

[0073] The value of can be found in several ways.

[0074] One way is to obtain non-interferometric measurements, whereby the interferometer mirror is tilted and the reflection from it is not returned to the optical path. As explained in

[0038] , such measurements provide The value of .

[0075] The specular reflectance |E can be obtained by removing the sample m | 2 This second measurement can be taken once (or at least infrequently) because the reflectivity of the mirror does not depend on the sample being measured.

[0076] Get I incoherentAnother way to do this is to isolate the part of the interferometric measurement that does not vary with the mirror position. The measurement signal

[0062] can be written as By using a small number (at least 3) of measurements at different values ​​of the mirror position z, I incoherent (λ), A(λ) and φ(λ).

[0077] When the distance (D1) separating the movable mirror from the second beam splitter is substantially equal to the distance (D2) between the top surface of the thick transparent layer and the second beam splitter, The value of is approximately 1.

[0078] in this case, The value of can be approximated as

[0079] E m The values ​​of , λ and z are known. By slightly changing (e.g., changing by tens of nanometers up to hundreds of nanometers) the value of z (while keeping z substantially equal to the distance between the second beam splitter and the top surface), there will be a sinusoidal relationship between the intensity of the frequency components of the spectrum detected by the spectrometer and the value of z. The difference between the maximum value of the first frequency component and the minimum value of the first frequency component will provide E top The value of , because 2*E top *E m is equal to the difference.

[0080] When the distance (D1) separating the movable mirror from the second beam splitter is substantially equal to the distance (D3) between the bottom surface of the thick transparent layer and the second beam splitter, The value of is approximately 1.

[0081] in this case, The value of can be approximated as

[0082] E m The values ​​of , λ and z are known. By slightly changing (e.g., changing by tens of nanometers up to hundreds of nanometers) the value of z (while keeping z substantially equal to the distance between the second beam splitter and the bottom surface), a sinusoidal relationship will exist between the intensity of the frequency components of the spectrum detected by the spectrometer and the value of z. The difference between the maximum value of the first frequency component and the minimum value of the first frequency component will provide E top The value of , because 2*E top *E m is equal to the difference.

[0083] Step 610 may be followed by step 630 of determining one or more thick transparent layer reflectance parameters based on the information about the relationship.

[0084] The thick transparent layer reflectivity parameters may include a field reflectivity of a top portion of the transparent thick layer and / or a field reflectivity of a bottom portion of the transparent thick layer.

[0085] The spectrometer measurements also provide phase information.The one or more thick transparent layer reflectance parameters may also include a relationship between a phase change and a frequency change in any of the field reflectivities.

[0086] Step 630 may be followed by step 640 of determining one or more structural properties of the thick transparent layer based on the one or more thick transparent layer reflectance parameters.

[0087] Step 640 may include applying a mapping between one or more thick transparent layer reflectance parameters and one or more structural properties.

[0088] Step 640 may include a modal-based analysis, which may include attempting to find a matching model that exhibits the same (or sufficiently similar) one or more structural characteristics.

[0089] Figure 3 An example of a sinusoidal relationship reflected by two different frequency components of spectrometer measurements is shown.

[0090] According to an embodiment, a method may be provided which may be performed by a processing circuit which may not be part of an SI system.

[0091] The method may include (a) obtaining information about a relationship between a measurement of a spectrometer and an optical path difference (OPD) value of an interferometer, the interferometer being in optical communication with the spectrometer; wherein the measurement of the spectrum is generated by illuminating the thick transparent layer with the interferometer; (b) determining one or more thick transparent layer reflection parameters based on the information about the relationship; and (c) determining one or more structural characteristics of the thick transparent layer based on the one or more thick transparent layer reflection parameters.

[0092] An alternative approach included in the present invention is to extract the coherent reflectivity from the interferometric measurements after applying a low-pass filter to the interferometric signal. This approach is based on the fact that for thick stacks there is usually a frequency separation, i.e. the reflections from the top and bottom surfaces are well separated in frequency space. Thus, for a signal of the form

[0093]

[0094] The application of a low pass filter will remove the terms associated with the interference of the top and bottom and the terms associated with the surface without OPD matching - terms that suffer from decoherence. However, the terms that do not include interference and the terms that describe the interference of the surface matched with OPD will remain. Therefore, from such a filtered signal, the coherent field reflectivity can be extracted, which will be associated with the surface matched with the reflector OPD.

[0095] The proposed solution enables the use of the entire spectral range, including shorter wavelengths, improving the vertical resolution and exploiting the information encoded in these wavelengths without requiring any new hardware, instead of using a simple software implementation.

[0096] The present invention may also be implemented in a computer program for running on a computer system, the computer program comprising at least a code portion for executing the steps of the method according to the present invention or enabling the programmable device to perform the functions of the apparatus or system according to the present invention when running on a programmable device (such as a computer system). The computer program may cause the storage system to assign a disk drive to a disk drive group.

[0097] A computer program is a list of instructions, such as a specific application program and / or an operating system. For example, a computer program may include one or more of the following: a subroutine, a function, a procedure, an object method, an object implementation, an executable application, an applet, a servlet, source code, object code, a shared library / dynamically loaded library, and / or other instruction sequences designed to be executed on a computer system.

[0098] The computer program may be stored internally on a non-transitory computer-readable medium. All or some of the computer program may be provided on a computer-readable medium that is permanently, removably, or remotely coupled to an information processing system. The computer-readable medium may include, for example, but not limited to, any number of the following media: magnetic storage media, including magnetic disks and tape storage media; optical storage media, such as optical disk media (e.g., CD-ROM, CD-R, etc.) and digital video disk storage media; non-volatile memory storage media, including semiconductor-based memory cells, such as flash memory, EEPROM, EPROM, ROM; ferromagnetic digital memory; MRAM; volatile storage media, including registers, buffers or caches, main memory, RAM, etc.

[0099] A computer process typically consists of a program or portion of a program being executed (running), current program values ​​and state information, and resources used by the operating system to manage the execution of the process. An operating system (OS) is software that manages the sharing of computer resources and provides programmers with interfaces for accessing those resources. An operating system processes system data and user input, and responds as a service to system users and programs by allocating and managing tasks and internal system resources.

[0100] A computer system may, for example, include at least one processing unit, associated memory, and a plurality of input / output (I / O) devices. When executing a computer program, the computer system processes information according to the computer program and generates resultant output information via the I / O devices.

[0101] In the foregoing specification, the invention has been described with reference to specific examples of embodiments of the invention. It will, however, be evident that various modifications and changes may be made thereto without departing from the broader spirit and scope of the invention as set out in the appended claims.

[0102] Furthermore, the terms "front", "rear", "top", "bottom", "upper", "lower", etc., if any, in the specification and claims are used for descriptive purposes and are not necessarily intended to describe permanent relative positions. It is understood that the terms so used are interchangeable under appropriate circumstances such that the embodiments of the invention described herein are, for example, capable of operation in other orientations than those illustrated or otherwise described herein.

[0103] The connection discussed herein can be any type of connection suitable for, for example, transmitting a signal out of or into a corresponding node, unit or device via an intermediate device. Therefore, unless otherwise implied or elaborated, the connection can be, for example, a direct connection or an indirect connection. The connection can be illustrated or described with reference to a single connection, multiple connections, a unidirectional connection or a bidirectional connection. However, different embodiments can change the implementation of the connection. For example, a separate unidirectional connection can be used instead of a bidirectional connection, and vice versa. In addition, multiple connections can be replaced by a single connection that transmits multiple signals serially or in a time multiplexing mode. Similarly, a single connection that carries multiple signals can be separated into various different connections that carry a subset of these signals. Therefore, there are many selections for transmitting signals.

[0104] Although specific conductivity types or polarities of potentials have been described in the examples, it should be understood that the conductivity types and polarities of potentials may be reversed.

[0105] Each signal described herein may be designed as either positive logic or negative logic. In the case of a negative logic signal, the signal is active low, where the logically true state corresponds to a logic level of 0. In the case of a positive logic signal, the signal is active high, where the logically true state corresponds to a logic level of 1. Note that any of the signals described herein may be designed as either a negative logic signal or a positive logic signal. Therefore, in alternative implementations, those signals described as positive logic signals may be implemented as negative logic signals, and those signals described as negative logic signals may be implemented as positive logic signals.

[0106] Additionally, the terms "assertion" or "setting" and "negation" (or "de-assertion" or "clearing") are used herein when referring to a signal, status bit, or similar device assuming its logically true or logically false state, respectively. If the logically true state is a logic level 1, the logically false state is a logic level 0. If the logically true state is a logic level 0, the logically false state is a logic level 1.

[0107] Those skilled in the art will recognize that the boundaries between logic blocks are merely illustrative, and that alternative implementations may merge logic blocks or circuit elements, or impose alternative functional decompositions on various logic blocks or circuit elements. Therefore, it should be understood that the architectures depicted herein are merely exemplary, and that in fact many other architectures that achieve the same functionality may be implemented.

[0108] Any arrangement of components that achieve the same functionality is effectively "associated" so that the desired functionality is achieved. Thus, any two components combined herein to achieve a particular functionality may be considered "associated" with each other so that the desired functionality is achieved, regardless of architecture or intermediate components. Likewise, any two components so associated may also be considered "operably connected" or "operably coupled" to each other so as to achieve the desired functionality.

[0109] Furthermore, those skilled in the art will recognize that the boundaries between the above operations are illustrative only. Multiple operations may be combined into a single operation, a single operation may be distributed in additional operations, and operations may be performed at least partially overlapping in time. Furthermore, alternative embodiments may include multiple instances of a particular operation, and the order of the operations may be changed in various other embodiments.

[0110] For another example, in one implementation, the illustrated examples may be implemented as circuits located on a single integrated circuit or within the same device. Alternatively, the examples may be implemented as any number of separate integrated circuits or separate devices interconnected with each other in an appropriate manner.

[0111] As another example, the examples or portions thereof may be implemented as soft or code representations of physical circuitry or as soft or code representations of logical representations convertible into physical circuitry, such as in any appropriate type of hardware description language.

[0112] In addition, the present invention is not limited to physical devices or units implemented in non-programmable hardware, but can also be applied to programmable devices or units that can perform the desired device functions by operating according to appropriate program code, such as mainframes, minicomputers, servers, workstations, personal computers, notepads, personal digital assistants, electronic games, automobiles and other embedded systems, cellular phones and various other wireless devices (collectively referred to as "computer systems" in this application).

[0113] However, other modifications, changes, and substitutions are possible. Accordingly, the specification and drawings should be regarded in an illustrative rather than a restrictive sense.

[0114] In the claims, any reference numerals placed between brackets should not be interpreted as limiting the claims. The word "comprising" does not exclude the presence of other elements or steps other than those listed in the claims. In addition, the term "one" or "an" as used herein is defined as one or more than one. In addition, the use of introductory phrases (such as "at least one" and "one or more") in the claims should not be interpreted as implying that any particular claim containing such introduced claim elements by the indefinite article "one" or "one" to another claim element is limited to an invention containing only one such element, even when the same claim includes the introductory phrases "one or more" or "at least one" and indefinite articles (such as "one" or "one"). This is also true for the use of definite articles. Unless otherwise stated, terms (such as "first" and "second") are used to arbitrarily distinguish the elements described by such terms. Therefore, these terms are not necessarily intended to indicate the time or other priority of such elements. The mere fact of reciting certain measures in mutually different claims does not indicate that the combination of these measures cannot be used to bring advantages.

[0115] While certain features of the invention have been illustrated and described herein, many modifications, substitutions, changes and equivalents will now occur to those skilled in the art. It should be understood, therefore, that the appended claims are intended to cover all such modifications and changes that fall within the true spirit of the invention.

Claims

1. A spectral interferometry SI system for evaluating thick transparent layers, the SI system comprising: an interferometer configured to illuminate the thick transparent layer and provide measurements of a spectrometer of the interferometer; as well as The processing circuit is configured to: (a) generating information on the relationship between the measurement value of the spectrometer and an optical path difference OPD value of the interferometer, the OPD value being associated with the measurement value; (b) determining one or more thick transparent layer reflection parameters based on said information about said relationship; as well as (c) determining one or more structural properties of the thick transparent layer based on the one or more thick transparent layer reflectance parameters.

2. The SI system according to claim 1, wherein: The measurements of the spectrometer include a top measurement and a bottom measurement; wherein the top measurement is obtained by the SI system while varying the OPD value while maintaining OPD matching relative to the top of the thick transparent layer, and Wherein, the bottom measurement value is obtained by the SI system while changing the OPD value to maintain OPD matching relative to the bottom of the thick transparent layer.

3. The SI system according to claim 2, wherein: The SI system is configured to change the OPD value while maintaining OPD matching by varying the OPD value by up to tens of nanometers.

4. The SI system according to claim 2, wherein: The relationship between the measured value of the spectrometer and the OPD value of the measured value comprises a first sinusoidal relationship between the OPD value of the measured value and a first frequency component of the measured value.

5. The SI system according to claim 4, wherein: The information about the relationship includes a difference between a maximum value of the first frequency component and a minimum value of the first frequency component.

6. The SI system according to claim 5, wherein: The processing circuit is configured to determine one or more transparent layer reflectance parameters by determining a field reflectivity of a top or bottom portion of the transparent layer.

7. A non-transitory computer readable medium for evaluating a thick transparent layer, the non-transitory computer readable medium storing instructions that, when executed by a processing circuit, cause the processing circuit to: Generate information about the relationship between the measured value of the spectrometer of the interferometer and the optical path difference OPD value of the interferometer; wherein, Generating the information includes illuminating the thick transparent layer through the interferometer; obtaining information about a relationship between a measurement of a spectrometer and an optical path difference (OPD) value of an interferometer in optical communication with the spectrometer; wherein the measurement of the spectrum is generated by illuminating the thick transparent layer with the interferometer; determining one or more thick transparent layer reflectance parameters based on the information regarding the relationship; and One or more structural properties of the thick transparent layer are determined based on the one or more thick transparent layer reflectance parameters.

8. The non-transitory computer readable medium of claim 7, wherein: The measurements of the spectrometer include top measurements and bottom measurements, wherein the top measurement is obtained while varying the OPD value while maintaining OPD matching relative to the top of the thick transparent layer, and Wherein the bottom measurement is obtained while varying the OPD value while maintaining OPD matching relative to the bottom of the thick transparent layer.

9. The non-transitory computer readable medium of claim 8, wherein: Changing the OPD values ​​while maintaining OPD matching includes changing the OPD values ​​by as much as tens of nanometers.

10. The non-transitory computer readable medium of claim 9, wherein: The relationship between the measured value of the spectrometer and the OPD value of the measured value comprises a first sinusoidal relationship between the OPD value of the measured value and a first frequency component of the measured value.

11. The non-transitory computer readable medium of claim 10, wherein: The information about the relationship includes a difference between a maximum value of the first frequency component and a minimum value of the first frequency component.

12. The non-transitory computer readable medium of claim 11, wherein: Determining one or more transparent layer reflectance parameters includes determining a field reflectivity of a top or bottom portion of the transparent layer.

13. A method for evaluating a thick transparent layer, the method comprising: Generating information about a relationship between a measurement value of a spectrometer of an interferometer and an optical path difference OPD value of the interferometer; wherein generating the information comprises illuminating the thick transparent layer through the interferometer; determining one or more thick transparent layer reflectance parameters based on the information regarding the relationship; and One or more structural properties of the thick transparent layer are determined based on the one or more thick transparent layer reflectance parameters.

14. The method according to claim 13, wherein: The measurements of the spectrometer include a top measurement and a bottom measurement; wherein the top measurement is obtained while varying the OPD value while maintaining OPD matching relative to the top of the thick transparent layer, and Wherein the bottom measurement is obtained while varying the OPD value while maintaining OPD matching relative to the bottom of the thick transparent layer.

15. The method according to claim 14, wherein: Changing the OPD values ​​while maintaining OPD matching includes changing the OPD values ​​by as much as tens of nanometers.

16. The method according to claim 14, wherein: The relationship between the measured value of the spectrometer and the OPD value of the measured value comprises a first sinusoidal relationship between the OPD value of the measured value and a first frequency component of the measured value.

17. The method according to claim 16, wherein: The information about the relationship includes a difference between a maximum value of the first frequency component and a minimum value of the first frequency component.

18. The method according to claim 17, wherein: Determining one or more transparent layer reflectance parameters includes determining a field reflectivity of a top or bottom portion of the transparent layer.

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