Analytical device, analytical method, interferometric measurement system, and storage medium

Abstract

The present invention relates to an analysis device, an analysis method, an interference measurement system, and a storage medium. The analysis device (200) includes: an acquisition unit (210) for acquiring a plurality of interference images based on light having a plurality of different wavelengths from an interference measurement device; a removal unit (230) for outputting interference components by removing non-interference components contained in interference signals of each pixel in the plurality of interference images; a conversion unit (240) for generating an analysis signal by performing a Hilbert transform on the interference components; and a calculation unit (250) for calculating the distance between a reference surface (132) and a surface of a measurement object (10) by specifying a phase gradient of the wavelength of light irradiated onto the reference surface (132) and the surface of the measurement object (10) based on the interference components and the analysis signal.

Description

Technical Field

[0001] The present invention relates to an analysis device, an analysis method, an interference measurement system and a storage medium. Background Art

[0002] Inspection of the surface geometry of semiconductor wafers and high-precision mirrors may require high precision, and such inspection is performed using a Fizeau laser interferometer or a Twyman-Green interferometer. An interferometer using an ordinary monochromatic laser can measure the geometry of the concave and convex on the surface of the measurement object with nanometer-level accuracy, but since the phase sequence cannot be specified, the geometry of the concave and convex including 1 / 4 wavelength or more wavelength cannot be measured. In order to measure the geometry of such concave and convex including 1 / 4 wavelength or more wavelength, a wavelength scanning interferometer for scanning the wavelength of light output from a light source is known (for example, see non-patent document 1: D. Malacara, "Optical Shop Testing 3rd ed.", Wiley-Interscience, 2007 and non-patent document 2: G. Moschetti, et.al., "Phase and fringe order determination in wavelength scanning interferometry", Opt. Express, 24, #258089, 2016). Summary of the Invention

[0003] Problems to be solved by the invention

[0004] It is known that in wavelength-scanning interferometers, high resolution can be improved by, for example, expanding the wavelength range of the light source used for scanning. However, when the wavelength range of the light source is expanded, the intensity level of the interfering light may fluctuate due to the wavelength dependence of the light intensity level of the light source or the wavelength dependence of the reflectivity of the light reflected from the object being measured. This may result in inability to measure the object with high accuracy.

[0005] The present invention focuses on these points, and an object of the present invention is to measure the concavity and convexity of a measurement target object with high accuracy even if the wavelength range of a light source is expanded to the extent that the light intensity level of interference light fluctuates in a wavelength scanning interferometer.

[0006] Solutions for solving problems

[0007] A first aspect of the present invention provides an analysis device for analyzing an interference image generated by a wavelength scanning interference measurement device, wherein the interference measurement device is used to generate the interference image of reference light and measurement light reflected by irradiating a reference surface and a surface of a measurement object with light having multiple different wavelengths, the analysis device comprising: an acquisition unit for acquiring a plurality of the interference images based on light having the multiple different wavelengths from the interference measurement device; a removal unit for outputting an interference component by removing non-interference components contained in the interference signal of each pixel in the multiple interference images; a conversion unit for generating an analysis signal by performing a Hilbert transform on the interference component; and a calculation unit for calculating the distance between the reference surface and the surface of the measurement object based on the interference component and the analysis signal by specifying a phase gradient of the wavelength of light irradiated onto the reference surface and the surface of the measurement object.

[0008] The calculation unit may include: an instantaneous phase calculation unit for calculating the instantaneous phase of the interference component based on the interference component and the analysis signal; a phase gradient calculation unit for calculating the phase gradient of the interference signal based on the instantaneous phase; and a distance calculation unit for calculating the distance between the reference surface and the surface of the measurement target object for each pixel based on the phase gradient.

[0009] The phase gradient calculation section may calculate the phase gradient of the interference signal after calibrating the wavelength dispersion characteristic of the interferometry device.

[0010] The interference image acquired by the acquisition unit is image data I of N×M pixels. i (x n ,y m ), the removing unit may define the interference signal of each pixel as N×M interference signals S(i) n,m =I i (x n ,y m ), assuming that the interference signal S(i) n,m It is expressed by the following equation:

[0011] [Equation 1]

[0012]

[0013] And the interference signal S(i) is calculated as follows: n,m The influence of the non-interference component contained in the interference component X(k i ) n,m :

[0014] [Equation 2]

[0015]

[0016] Where: i = 1, 2, 3, ..., J, n = 1, 2, 3, ..., N, and m = 1, 2, 3, ..., M, k i =2π / λ i ,λ i is the wavelength of the measurement light and the reference light, k i is the wave number, E i (k i ) is the amplitude of the light irradiated on the object to be measured, r(k) is the amplitude reflectivity of the object to be measured, and is the pixel (x n ,y m ) corresponds to the position (x n ,y m ) and the phase difference caused by the optical path length between the reference surface.

[0017] The conversion unit can be expressed as follows by converting the interference component X(k i ) n,m Perform the Hilbert transform to generate the analysis signal Y(k) n,m :

[0018] [Equation 3]

[0019]

[0020] The instantaneous phase calculation unit can calculate the phase of the interference component X(k i ) n,m and the analytical signal Y(k) n,m To calculate the interference component X(k i ) n,m The instantaneous phase θ(k i ) n,m :

[0021] [Equation 4]

[0022]

[0023] The phase gradient calculation unit can calculate the instantaneous phase θ(k i ) n,m , to calculate the phase gradient dθ(k i ) n,m / dk i ≈dθ n,m / dk, the distance calculation unit can be calculated by using the phase gradient dθ as shown in the following equationn,m / dk, calculate the distance L between the reference surface and the surface of the object to be measured for each pixel n,m :

[0024] [Equation 5]

[0025]

[0026] A second aspect of the present invention provides an analysis method for analyzing an interference image generated by a wavelength scanning interference measurement device, wherein the interference measurement device is used to generate the interference image of the reference light and the measurement light reflected by irradiating the reference surface and the surface of the measurement object with light having multiple different wavelengths, and the analysis method includes the following steps: acquiring a plurality of the interference images based on the light having the multiple different wavelengths from the interference measurement device; outputting an interference component by removing the non-interference component contained in the interference signal of each pixel in the plurality of the interference images; generating an analysis signal by performing a Hilbert transform on the interference component; and calculating the distance between the reference surface and the surface of the measurement object based on the interference component and the analysis signal.

[0027] The third aspect of the present invention provides an interference measurement system, comprising: a wavelength scanning interference measurement device; and an analysis device according to the first aspect, for analyzing the multiple interference images captured by the interference measurement device, wherein the interference measurement device comprises: a light source unit for irradiating the surface of the measurement object with light having multiple different wavelengths; the reference surface, which is arranged on the optical axis of the light having the multiple different wavelengths; and an imaging unit for capturing the interference image of the reference light reflected at the reference surface and the measurement light reflected at the surface of the measurement object.

[0028] A fourth aspect of the present invention provides a storage medium storing a program which, when executed by a computer, causes the computer to function as the analysis apparatus (200) according to the first aspect.

[0029] Effects of the Invention

[0030] According to the present invention, even if the wavelength range of the light source is expanded to such an extent that the light intensity level of the interference light fluctuates in the wavelength scanning interferometer, the concavity and convexity of the measurement target object can be measured with high accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 A configuration example of an interferometry system 1000 and a measurement target object 10 according to the present embodiment are shown.

[0032] Figure 2A structural example of the analysis apparatus 200 according to the present embodiment is shown.

[0033] Figure 3 An example of the operation flow of the analysis apparatus 200 according to the present embodiment is shown.

[0034] Figure 4 An example of the analysis signal converted by the conversion section 240 according to the present embodiment is shown.

[0035] Figure 5 An example of the phase with respect to the wave number calculated by the phase gradient calculation section 254 according to this embodiment is shown.

[0036] Description of Reference Numerals

[0037] 10 Measurement object

[0038] 110 Light Source

[0039] 120 Optical System

[0040] 122 Magnifying Lens

[0041] 124 Collimating lens

[0042] 126 beam splitter

[0043] 128 Imaging Lens

[0044] 130 reference objects

[0045] 132 reference surface

[0046] 140 Camera Department

[0047] 150 Control Department

[0048] 200 analytical equipment

[0049] 210 Acquisition Department

[0050] 220 Storage Department

[0051] 230 Removal

[0052] 240 Conversion Department

[0053] 250 Computing Department

[0054] 252 Instantaneous Phase Calculation Unit

[0055] 254 Phase Gradient Calculation Unit

[0056] 256 Distance Calculation Unit

[0057] 260 Output

[0058] 1000 Interferometry System DETAILED DESCRIPTION

[0059] <Configuration Example of Interference Measurement System 1000>

[0060] Figure 1 The following illustrates an example structure of an interferometry system 1000 according to this embodiment, along with a measurement target object 10. Interferometry system 1000 forms a Fizeau interferometer and measures the surface geometry of measurement target object 10. Measurement target object 10 is, for example, a solid object such as a semiconductor wafer made of Si, GaAs, or GaN, a high-precision mirror, or metal. Interferometry system 1000 includes an interferometry device 100 and an analysis device 200. Interferometry device 100 includes a light source unit 110, an optical system 120, a reference object 130, an imaging unit 140, and a control unit 150.

[0061] Light source unit 110 is a tunable wavelength light source that can change the wavelength of light output according to an input control signal. Light source unit 110 illuminates the surface of object 10 to be measured with light. Light source unit 110 may include, for example, a tunable laser. Furthermore, light source unit 110 may include a combination of a broadband light source for outputting light within a predetermined wavelength range and a variable bandpass filter for changing the wavelengths passed according to an input control signal.

[0062] The optical system 120 irradiates the object 10 to be measured and the reference object 130 with light output from the light source section 110. The optical system 120 also forms an image of reflected light from the object 10 to be measured and the reference object 130 on the imaging section 140. The optical system 120 includes a magnifying lens 122, a collimating lens 124, a beam splitter 126, and an imaging lens 128.

[0063] The magnifying lens 122 magnifies the diameter of the laser light output from the light source unit 110. The collimating lens 124 collimates the light incident from the magnifying lens 122 and illuminates the surface of the object 10 to be measured with the collimated light. Furthermore, light reflected from the surface of the object 10 to be measured is incident on the collimating lens 124, which reduces the diameter of the reflected light and outputs it to the beam splitter 126. Here, the light reflected from the surface of the object 10 to be measured is referred to as measurement light.

[0064] Reference object 130 is disposed between collimating lens 124 and measurement target object 10, and a portion of the collimated light emitted from collimating lens 124 is reflected by reference surface 132 of reference object 130. Thus, collimating lens 124 emits the measurement light and the light reflected by reference surface 132 to beam splitter 126. Here, the light reflected by reference surface 132 is referred to as reference light.

[0065] Beam splitter 126 reflects a portion of the measurement light and reflected light emitted from collimating lens 124 toward imaging unit 140. Beam splitter 126 includes, for example, a half mirror. Imaging lens 128 forms an image of the light reflected by beam splitter 126 on imaging unit 140. In other words, imaging lens 128 forms an interference image, resulting from the interference between the measurement light and the reference light, on imaging unit 140.

[0066] As described above, reference object 130 includes reference surface 132. Reference object 130 is, for example, a half mirror having reference surface 132 as a mirror surface. Reference surface 132 is disposed substantially perpendicular to the optical axis of the laser light output from light source unit 110. Furthermore, reference surface 132 is movably disposed on the optical axis of the laser light.

[0067] The imaging unit 140 captures an interference image of the reference light reflected by the reference surface 132 and the measurement light reflected by the surface of the object 10. The imaging unit 140 includes, for example, a camera, and captures the interference image formed by the optical system 120 in response to a control signal.

[0068] The control unit 150 controls the light source unit 110 and the imaging unit 140 to capture multiple interference images of the reference light and the measurement light at multiple wavelengths. For example, the control unit 150 transmits a control signal to the light source unit 110 that specifies the wavelength of the light to be output. Furthermore, the control unit 150 transmits a control signal to the imaging unit 140 that includes an instruction to capture an interference image. For example, the control unit 150 controls the light source unit 110 and the imaging unit 140 to change the wavelength of the light output by the light source unit 110 at wavelength intervals corresponding to a predetermined phase shift amount, and captures an interference image each time the wavelength of the light changes. The control unit 150 includes, for example, a central processing unit (CPU).

[0069] In this manner, the interferometry apparatus 100 irradiates the reference surface 132 and the surface of the measurement target object 10 with laser light to generate an interference image of the reflected reference light and the measurement light. Figure 1 The interferometric measurement device 100 of the illustrated optical system 120 is called a Fizeau interferometer, and in principle, can measure the geometric shape of the concavities and convexities on the surface of the measurement target object 10 with nanometer-level accuracy.

[0070] Such an interferometry device 100 performs frequency measurement of light intensity modulation by wavelength scanning and analyzes the interference pattern using, for example, a Fourier transform. In this case, the height resolution dh of the geometric measurement corresponds to the frequency resolution of the Fourier transform and is known to be determined as shown in the following equation.

[0071] [Equation 6]

[0072]

[0073] Here, λ max is the longest wavelength of light output by the light source unit 110, and λ min is the shortest wavelength of light output by light source section 110. As can be seen from [Equation 6], if light source section 110 expands the wavelength range used for scanning, the resolution dh of the geometric shape measurement of interferometry apparatus 100 becomes smaller, and higher-resolution measurement can be performed. However, if light source section 110 expands the wavelength range used for scanning, the wavelength dependence of the intensity level of light output by light source section 110 becomes significant, and the fluctuation of the light intensity level within the wavelength scanning range may increase.

[0074] Furthermore, the wavelength dependence of the reflectivity of the light reflected from the object to be measured also becomes significant, and the fluctuation in the light intensity level of the reflected light relative to the wavelength sweep of the light output by the light source unit 110 may increase. Therefore, when the fluctuation in the light intensity level of the interference light increases due to the expansion of the wavelength sweep range by the light source unit 110, an error occurs in the frequency measurement of the light intensity modulation, and accurate measurement of the object to be measured 10 may become impossible.

[0075] Therefore, the analysis device 200 according to this embodiment applies Hilbert transform to the analysis signal of each pixel in the interference image generated by the interferometry device 100 to reduce such errors, thereby easily performing interferometry with high resolution and high accuracy.

[0076] <Structural Example of Analysis Device 200>

[0077] Figure 2 An example structure of an analysis device 200 according to this embodiment is shown. As an example, analysis device 200 is a computer such as a server. Analysis device 200 analyzes interference patterns generated by wavelength-scanning interferometry device 100, which illuminates reference surface 132 and the surface of object 10 to be measured with light having multiple different wavelengths to generate multiple interference patterns of reflected reference light and measurement light. Analysis device 200 can perform at least a portion of the operations of control unit 150 of interferometry device 100. Analysis device 200 includes an acquisition unit 210, a storage unit 220, a removal unit 230, a conversion unit 240, a calculation unit 250, and an output unit 260.

[0078] The acquisition unit 210 acquires a plurality of interference images based on light having a plurality of different wavelengths from the interferometry device 100. The acquisition unit 210 may be connected to the imaging unit 140 of the interferometry device 100 to acquire the interference images, or alternatively, may acquire the interference images via a network or the like. The acquisition unit 210 may acquire the plurality of interference images from an external database or the like. In this case, the acquisition unit 210 acquires, for example, an interference image previously generated by the interferometry device 100.

[0079] The storage unit 220 stores the image data of the interference images acquired by the acquisition unit 210. The storage unit 220 preferably stores the image data of multiple interference images in association with the phase difference between the measurement light and the reference light, or the order of the interference measurement. Furthermore, the storage unit 220 may store intermediate data, calculation results, thresholds, parameters, and the like generated (or used) during the operation of the analysis device 200. Furthermore, in response to a request from various components of the analysis device 200, the storage unit 220 may provide the stored data to the requesting party.

[0080] The storage unit 220 can store information about an operating system (OS) and programs used by a server or the like as the analysis device 200. Furthermore, the storage unit 220 can store various types of information, including databases referenced when executing the programs. For example, a computer such as a server can function as at least a portion of the acquisition unit 210, storage unit 220, removal unit 230, conversion unit 240, calculation unit 250, and output unit 260 by executing the programs stored in the storage unit 220.

[0081] The storage unit 220 includes, for example, a read-only memory (ROM) for storing the basic input / output system (BIOS) of a computer, etc., and a random access memory (RAM) as a work area. Furthermore, the storage unit 220 may also include a large-capacity storage device such as a hard disk drive (HDD) and / or a solid-state drive (SSD). Furthermore, the computer may also include a graphics processing unit (GPU), etc.

[0082] The removal unit 230 removes the non-interference components included in the interference signal for each pixel in the multiple interference images, thereby outputting the interference components. The removal unit 230 generates interference signals for each pixel from the multiple interference images. For example, if the interference image is image data consisting of N×M pixels, the removal unit 230 generates N×M interference signals. The removal unit 230 then removes the non-interference components from each interference signal to output the interference components.

[0083] The conversion section 240 performs a Hilbert transform on the interference component output from the removal section 230 to generate an analysis signal. The calculation section 250 includes an instantaneous phase calculation section 252, a phase gradient calculation section 254, and a distance calculation section 256, and calculates the surface geometry of the object 10 to be measured based on the interference component and the analysis signal. The calculation of the surface geometry of the object 10 to be measured using the conversion section 240 and the calculation section 250 will be described later.

[0084] The output unit 260 outputs the calculation result of the surface geometry to a display device, etc. The output unit 260 can display numerical data and, alternatively or additionally, can schematically display the surface geometry of the object 10 to be measured. In addition, the output unit 260 can store the calculation result of the surface geometry of the object 10 to be measured in an external database, etc.

[0085] The analysis device 200 according to the present embodiment described above generates an interference signal for each pixel from a plurality of interference images, thereby calculating the height corresponding to each pixel from the reference surface of the object 10 to be measured without requiring iterative calculations using multiple parameters. A more specific operation of the analysis device 200 will be described below.

[0086] <Operation Flow of Analysis Device 200>

[0087] Figure 3 An example of the operation flow of the analysis device 200 according to this embodiment is shown. The analysis device 200 performs Figure 3 The operations from step S310 to step S380 in the embodiment are used to calculate and output the surface geometric shape of the object to be measured 10 corrected for the error based on the wavelength scan of the light of the light source unit 110 based on the plurality of interference images.

[0088] First, the acquisition unit 210 acquires a plurality of interference images from the interference measurement device 100 (step S310). In this embodiment, an example will be described in which the acquisition unit 210 acquires J interference images from the interference measurement device 100. Here, it is assumed that the interference image is image data of N×M pixels, and the image data of the interference image acquired by the acquisition unit 210 is referred to as I i (x n ,y m ). Here, i=1, 2, 3, ..., J, n=1, 2, 3, ..., N, and m=1, 2, 3, ..., M.

[0089] Next, the removal unit 230 generates an interference signal for each pixel from the plurality of interference images (step S320). For example, the removal unit 230 generates N×M interference signals S(i) as shown in the following equation: n,m Each interference signal will contain J data.

[0090] [Equation 7]

[0091] S(i) n，m = I i (x n , y m )

[0092] Next, the removing unit 230 removes the non-interference components included in the interference signal and outputs the interference components (step S330). Here, when the wave number k corresponding to the wavelength λ output from the light source unit 110 is defined as k i = 2π / λ i = 2π / λ i , the interference signal S(i) i is shown by using i) the amplitude E n,m (k) of the light irradiated onto the measurement object 10 and ii) the amplitude reflectivity r(k) of the measurement object 10 as follows. It should be noted that k i is abbreviated as k.

[0093] [Equation 8]

[0094]

[0095] Here, is the phase difference caused by the optical path length between the position (x n , y m ) on the surface of the measurement object 10 corresponding to the pixel (x n , y m ) and the reference plane 132. That is, in the interference signal S(k) n,m , the term including is the interference component generated based on interference, and the other terms are non-interference components independent of interference. By differentiating [Equation 8] with respect to k, the interference component from which the influence of the non-interference component is removed can be calculated as follows.

[0096] [Equation 9]

[0097]

[0098] Assuming that the change amount of the wave number k is small, dr / dk << r and dE i (k) / dk << E i (k). Since, as in [Equation 9], the interference component is represented by the product of the term including the phase difference and the function A(k), the function A(k) is the one including the phase difference The envelope function of the term is preferably constant. However, as described above, since the optical properties of the light source unit 110 and the object 10 to be measured have wavelength dependence, the envelope function A(k) will vary depending on the wave number k.

[0099] The removal unit 230 outputs such interference components by numerically differentiating the interference signal for each pixel. Note that if the SN ratio deteriorates due to the influence of noise, the removal unit 230 may perform differentiation processing with noise reduction processing by using an FIR differentiator or the like.

[0100] Next, the conversion unit 240 converts the interference component X(k) of the interference signal from which the non-interference component is removed by the removal unit 230. n,m Perform Hilbert transform to generate the analysis signal Y(k) n,m (Step S340) Hilbert transform is performed by convolution of the interference component X(k) and 1 / πk, for example, and the analysis signal Y(k) is expressed as follows: n,m .

[0101] [Equation 10]

[0102]

[0103] Here, the Hilbert transform H(u)(t) of the function u(t) causes a phase shift of +90° (π / 2) toward the negative frequency components of u(t) and a phase shift of -90° (-π / 2) toward the positive frequency components. Therefore, the analytical signal Y(k) n,m has substantially the same envelope function A(k) as the interference component X(k), and is n,m Compared to the phase shift of π / 2.

[0104] Figure 4 The analysis signal Y(k) converted by the conversion unit 240 according to this embodiment is shown as follows: n,m . Figure 4 The horizontal axis represents the wave number k, and the vertical axis represents the signal level. It should be noted that the signal level is normalized so that the maximum value is 1 and the minimum value is -1. Figure 4 The signal represented by the solid line is the interference component X(k) of the interference signal. n,m , and the signal represented by the dotted line is the analytical signal Y(k) after Hilbert transform n,m . Figure 4 For example, the analysis signal Y(k) is shown as follows: n,m The peak value and interference component X(k) n,m Compared to the horizontal axis direction, the interference component X(k) is shifted by a substantially constant value, and n,mThe envelope function and analytical signal Y(k) n,m The envelope functions are roughly the same.

[0105] Next, the instantaneous phase calculation unit 252 calculates the phase of the interference component X(k) based on the n,m and analytical signal Y(k) n,m To calculate the interference component X(k) n,m The instantaneous phase calculation unit 252 calculates the instantaneous phase θ(k) as follows: n,m .

[0106] [Equation 11]

[0107]

[0108] When the instantaneous phase θ(k) is calculated by the instantaneous phase calculation unit 252, n,m In the processing, as shown in [Equation 11], the analysis signal Y(k) n,m Divide by the interference component X(k) n,m Since the analytical signal Y(k) n,m and interference component X(k) n,m The envelope function A(k) is substantially the same as that of the first phase, so the influence of the envelope function A(k) is almost eliminated by this division. Therefore, the instantaneous phase θ(k) calculated by the instantaneous phase calculation unit 252 is n,m This is a value that very rarely includes the influence of the light from the light source unit 110 and the fluctuation of the light intensity level due to the wavelength sweep of the reflected light from the measurement target object 10 .

[0109] Next, the phase gradient calculation unit 254 calculates the instantaneous phase θ(k) based on n,m The phase gradient calculation unit 254 calculates the phase gradient of the interference signal (step S360). For example, the phase θ(k) of the wave number k is n,m Multiple instantaneous phases θ(k) of multiple wave numbers k of the function n,m Connect and calculate the phase θ(k) n,m The gradient dθ(k) n,m Here, the phase gradient calculation unit 254 is connected so that the phase θ(k) with respect to the wave number k is n,m Change linearly.

[0110] As an example, the phase gradient calculation section 254 calculates the phase θ(k) with respect to the wave number k by using the least square method. n,m Therefore, for example, when the interference image is captured by the imaging unit 140, even if random noise is mixed in the interference image, the phase θ(k) can be expressed by a linear function. n,m To reduce random noise.

[0111] Figure 5 The phase θ(k) calculated by the phase gradient calculation unit 254 according to this embodiment with respect to the wave number k is shown. n,m . Figure 5 The horizontal axis represents the wave number k, and the vertical axis represents the phase θ. Here, the maximum value of the phase θ on the vertical axis is π and the minimum value is -π. It should be noted that due to the wavelength dispersion of the refractive index of the optical members constituting the optical system 120, etc., the instantaneous phase θ(k) with respect to the wave number k is n,m The change may be curved rather than linear.

[0112] In this case, for example, the wavelength dispersion of the refractive index of the optical components provided in the interferometer measurement device 100 is measured in advance and stored in the storage unit 220. Then, the phase gradient calculation unit 254 calculates the phase gradient dθ(k) of the interference signal after calibrating the wavelength dispersion characteristics of the interferometer measurement device 100. n,m As described above, since the phase θ is connected so that the phase θ changes linearly with respect to the wave number k, the phase gradient dθ(k) calculated by the phase gradient calculation unit 254 is n,m / dk becomes substantially constant. Therefore, the phase gradient is expressed as dθ n,m / dk.

[0113] Next, the distance calculation unit 256 calculates the distance of each pixel based on the phase gradient dθ. n,m / dk is used to calculate the distance L between the reference surface 132 and the surface of the object 10 to be measured (step S370). Figure 1 In the illustrated interferometry device 100 , since light from the light source unit 110 reciprocates between the reference surface 132 and the surface of the object 10 to be measured, the distance calculator 256 calculates the distance L as shown in the following equation.

[0114] [Equation 12]

[0115]

[0116] As described above, the calculation unit 250 calculates the interference component X(k) based on the n,m and analytical signal Y(k) n,m The phase gradient dθ of the wavelength of light irradiated on the reference surface 132 and the surface of the object to be measured 10 is specified. n,m / dk, and calculate the distance L between the reference surface 132 and the surface of the measurement target object 10 for each pixel. n,m The calculation unit 250 calculates the distance L of all N×M pixels. n,m , thereby calculating image data corresponding to the surface geometry of the measurement target object 10.

[0117] Next, the output unit 260 outputs the calculated surface geometry to a display device, etc. (step S380). Thus, the analysis device 200 according to this embodiment can accurately measure the surface geometry of the object 10 being measured by reducing errors caused by, for example, the wavelength dependence of the light intensity level of the light source, the wavelength dependence of the reflectivity of the light emitted by the object being measured, and the wavelength dispersion of optical components. Because the analysis device 200 can reduce such errors, the interferometry system 1000 can measure the unevenness of the object 10 being measured with high accuracy and resolution, even if the wavelength range of the light output by the light source unit 110 of the interferometry device 100 is expanded to the extent that the light intensity level of the interference light fluctuates.

[0118] The analysis device 200 performs a Hilbert transform on the interference signal and calculates the ratio of the interference signal to the signal after the Hilbert transform, thereby reducing the influence of fluctuations in optical properties caused by wavelength scanning of the interferometry device 100. Thus, the analysis device 200 can conveniently measure the surface geometry of the object 10 to be measured without directly measuring unknown fluctuations in the signal level caused by wavelength scanning in the light source section 110 and the reflected light of the object 10 to be measured.

[0119] It should be noted that while the analysis device 200 according to this embodiment is described using an example of analyzing an interference image generated by an interferometer 100 having a Fizeau interferometer, the analysis device 200 is not limited thereto. The analysis device 200 can also analyze an interference image using an interferometer 100 including another type of interferometer, as long as the interferometer generates a phase shift error. For example, the interferometer 100 may include a Twyman-Green interferometer.

[0120] The present invention has been described based on these exemplary embodiments. The technical scope of the present invention is not limited to the scope described in the above embodiments, and various changes and modifications can be made within the scope of the present invention. For example, all or part of the device can be configured to be functionally or physically distributed and integrated in arbitrary units. In addition, new exemplary embodiments generated by any combination of these exemplary embodiments are included in the exemplary embodiments of the present invention. The effects of the new embodiments resulting from this combination also have the effects of the original embodiments.

Claims

1. An analysis device for analyzing an interference image generated by a wavelength-scanning interferometry device, the interferometry device generating the interference image of reference light and measurement light reflected by irradiating a reference surface and a surface of an object to be measured with light having a plurality of different wavelengths, the analysis device comprising: an acquisition unit, configured to acquire, from the interference measurement device, a plurality of interference images based on the light having the plurality of different wavelengths; a removing unit configured to output an interference component by removing a non-interference component included in the interference signal of each pixel in the plurality of interference images; a conversion unit, configured to generate an analysis signal by performing a Hilbert transform on the interference component; as well as a calculation unit for calculating the distance between the reference surface and the surface of the object to be measured by specifying a phase gradient of a wavelength of light irradiated onto the reference surface and the surface of the object to be measured based on the interference component and the analysis signal; Wherein, the calculation unit includes: an instantaneous phase calculation unit, configured to calculate the instantaneous phase of the interference component based on the interference component and the analysis signal; a phase gradient calculation unit, configured to calculate a phase gradient of the interference signal based on the instantaneous phase; and A distance calculation unit is configured to calculate the distance between the reference surface and the surface of the object to be measured for each pixel based on the phase gradient.

2. The analysis device according to claim 1, wherein The phase gradient calculation section calculates the phase gradient of the interference signal after calibrating the wavelength dispersion characteristics of the interferometry device.

3. The analysis device according to claim 1, wherein The interference image acquired by the acquisition unit is image data I of N×M pixels. i (x n ,y m ), The removing unit defines the interference signal of each pixel as N×M interference signals S(i) n,m =I i (x n ,y m ), assuming that the interference signal S(i) n,m It is expressed by the following equation: [Equation 1] And the interference signal S(i) is calculated as follows: n,m The influence of the non-interference component contained in the interference component X(k i ) n,m : [Equation 2] Where: i = 1, 2, 3, ..., J, n = 1, 2, 3, ..., N, and m = 1, 2, 3, ..., M, k i =2π / λ i ,λ i is the wavelength of the measurement light and the reference light, k i is the wave number, E i (k i ) is the amplitude of the light irradiated on the object to be measured, r(k) is the amplitude reflectivity of the object to be measured, and The image data I representing the pixels on the surface of the object to be measured is i (x n ,y m ) corresponds to the position (x n ,y m ) and the phase difference caused by the optical path length between the reference surface.

4. The analysis device according to claim 3, wherein The conversion unit is as follows: i ) n,m Perform the Hilbert transform to generate the analysis signal Y(k i ) n,m : [Equation 3] Where: κ is the integration variable.

5. The analysis device according to claim 4, wherein The instantaneous phase calculation unit is as follows, by using the interference component X(k i ) n,m and the analysis signal Y(k i ) n,m To calculate the interference component X(k i ) n,m The instantaneous phase θ(k i ) n,m : [Equation 4] 6. The analysis device according to claim 5, wherein The phase gradient calculation unit calculates the instantaneous phase θ(k i ) n,m , to calculate the phase gradient dθ(k i ) n,m / dk i ≈dθ n,m / dk, The distance calculation unit uses the phase gradient dθ as shown in the following equation: n,m / dk, calculate the distance L between the reference surface and the surface of the object to be measured for each pixel n,m : [Equation 5] 7. An analysis method for analyzing an interference pattern generated by a wavelength-scanning interferometry device, the interference pattern generated by reference light and measurement light reflected by irradiating a reference surface and a surface of an object to be measured with light having a plurality of different wavelengths, the analysis method comprising the following steps: acquiring, from the interferometry device, a plurality of the interference images based on light having the plurality of different wavelengths; outputting an interference component by removing a non-interference component included in the interference signal of each pixel in the plurality of interference images; generating an analysis signal by performing a Hilbert transform on the interference component; as well as calculating the distance between the reference surface and the surface of the measurement target object based on the interference component and the analysis signal, The calculation step includes the following steps: calculating an instantaneous phase of the interference component based on the interference component and the analysis signal; calculating a phase gradient of the interference signal based on the instantaneous phase; and Based on the phase gradient, the distance between the reference plane and the surface of the measurement target object is calculated for each pixel.

8. An interferometry system comprising: Wavelength scanning interferometry equipment; as well as The analysis device according to any one of claims 1 to 6, configured to analyze a plurality of interference images captured by the interference measurement device, Wherein, the interferometric measurement device comprises: a light source unit for irradiating the surface of the object to be measured with light having a plurality of different wavelengths; the reference plane being disposed on an optical axis of the light having the plurality of different wavelengths; and The imaging unit is configured to capture the interference image of the reference light reflected by the reference surface and the measurement light reflected by the surface of the object to be measured. 9 . A storage medium storing a program which, when executed by a computer, causes the computer to function as the analysis apparatus according to claim 1 .

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