White light interferometry using sinusoidal interpolation and sinusoidal interpolation method of white light interferometry

Abstract

Disclosed are: white light interferometry using sinusoidal interpolation in which interference fringes generated by measurement light and reflected light can be expressed naturally; and a sinusoidal interpolation method of the white light interferometry. The white light interferometry using sinusoidal interpolation comprises: a charge coupled device (CCD) image sensor for capturing interference fringes to generate a plurality of interference fringe images; and an image analysis processor for accumulating the plurality of interference fringe images to generate a white light interference fringe signal (WLI fringe signal, I[n]).

Description

White light interferometer utilizing sinusoidal interpolation and sinusoidal interpolation method of the white light interferometer

[0001] The present invention relates to a white light interferometer utilizing sinusoidal interpolation and a sinusoidal interpolation method of the white light interferometer, and more particularly, to a white light interferometer utilizing sinusoidal interpolation for interpolating interference patterns generated by measurement light and reflected light reflected after white light is irradiated onto a sample and a mirror, respectively, through sinusoidal interpolation, and to a sinusoidal interpolation method of the white light interferometer.

[0002] In recent fields of nanoscience, semiconductors, nanophysics, nanochemistry, nanomaterials, nanooptics, surface science, medical imaging, biology, biophysics, medical physics, or biomedical optics, there is a growing demand for measuring three-dimensional shape information of samples with three-dimensional nanostructures or micrometer structures.

[0003] White light interferometry, which utilizes the interference phenomenon of white light, has been used to measure the three-dimensional shape information of samples.

[0004] A typical white light interferometer utilizes a beam splitter to separate the white light source and create separate paths for the sample and mirror, respectively. The white light, which is then reflected by the beam splitter onto the sample and mirror, is then recombined and transmitted to a charge-coupled device (CCD) image sensor. The CCD image sensor captures an interference pattern image created by the combined reflected light from the sample and mirror. An image analysis processor analyzes the interference pattern image captured by the CCD image sensor to generate three-dimensional information about the sample's shape.

[0005] At this time, the sample is placed on the stage, and the stage moves along the path axis (typically the Z-axis) of the light source by a separate drive assembly to generate a path difference between the sample side and the mirror side. The interference pattern image captured by the CCD image sensor forms different interference pattern images according to the change in the path difference between the sample side and the mirror side, and the image analysis processor generates three-dimensional shape information of the sample based on the interference pattern in which different interference pattern images are accumulated.

[0006] Meanwhile, conventional white light interferometers have a problem in that the shape of the white light interference pattern (WLI fringe) is expressed unnaturally depending on the physically limited minimum movable length of the driving assembly that moves the stage to generate a path difference between the sample side and the mirror side, i.e., the Z Step Size.

[0007] The problem of unnatural shape of white light interference pattern (WLI fringe) due to limited Z Step Size has been solved by interpolation using spline interpolation (cubic spline), but spline interpolation has the problem of high computational cost and low accuracy.

[0008] The purpose of the present invention to solve the above-described problem is to provide a white light interferometer utilizing sinusoidal interpolation, which can naturally express the shape of an interference pattern by interpolating an interference pattern generated by measurement light and reflected light that are reflected after white light split by a beam splitter is irradiated to a sample and a mirror, respectively, through sinusoidal interpolation, and a sinusoidal interpolation method of the white light interferometer.

[0009] Another object of the present invention is to provide a white light interferometer utilizing a sinusoidal interpolation method that can provide a fast and accurate interpolation method by utilizing the mathematical conditions of the sinusoidal wavelength, and a sinusoidal interpolation method of the white light interferometer.

[0010] In order to achieve the above-described object, a white light interferometer utilizing a sinusoidal interpolation method according to an embodiment of the present invention includes a light source providing white light, a stage on which a sample is placed, a stage moving assembly for moving the stage in the direction of the path axis of the white light, a mirror having a reflective surface, a beam splitter for dividing the path of the white light provided from the light source into the sample side and the mirror side, a CCD image sensor (Charge Coupled Device image sensor) for receiving measurement light reflected from the sample and reflected light reflected from the mirror from the beam splitter while the stage is moved in the direction of the path axis by the stage moving assembly, photographing interference fringes generated by the measurement light and the reflected light, and generating a plurality of interference fringe images, and an image analysis processor for generating a white light interference fringe signal (WLI fringe signal, I[n]) by accumulating the plurality of interference fringe images, wherein the image analysis processor interpolates the generated white light interference fringe signal (I[n]) through sinusoidal interpolation. Generates an interpolated white light interference pattern signal (I[n]').

[0011] The image analysis processor, when interpolating the white light interference pattern signal (I[n]) using a sinusoidal interpolation method, divides the white light interference pattern signal (I[n]) into components according to amplitude and phase, respectively, to generate an amplitude graph (Envelope, A[n]) and a phase graph (Phase, θ[n]), interpolates the amplitude graph (A[n]) and the phase graph (θ[n]) using the sinusoidal interpolation method, respectively, to generate an interpolated amplitude graph (A[n]') and an interpolated phase graph (θ[n]'), and generates the interpolated white light interference pattern signal (I[n]') based on the interpolated amplitude graph (A[n]') and the interpolated phase graph (θ[n]').

[0012] The image analysis processor, when generating an amplitude graph and a phase graph by dividing the white light interference pattern signal into components according to amplitude and phase, extracts an amplitude component (A[n]) from the white light interference pattern signal (I[n]) based on <Formula 1> below to generate the amplitude graph (Envelope), and extracts a phase component (θ[n]) from the white light interference pattern signal (I[n]) to generate the phase graph (Phase).

[0013] A[n](Envelope) = (c[n] 2 + s[n] 2 ) 1 / 2

[0014] θ[n](Phase) = Atan(s[n], c[n])

[0015] <Formula 1>

[0016] (Here, the A[n] is the amplitude on the pixel of the white light interference pattern signal (Amplitude on Pixel of WLI Fringe), the θ[n] is the phase on the pixel of the white light interference pattern signal (Phase on Pixel of WLI Fringe), the c[n] is the cosine component of the white light interference pattern signal (Cosine Component of WLI Fringe) and is calculated as c[n] = A[n] × cos(θ[n]), and the s[n] is the sine component of the white light interference pattern signal (Sine Component of WLI Fringe) and is calculated as s[n] = A[n] × sin(θ[n]).)

[0017] The image analysis processor, when generating an interpolated amplitude graph (A[n]') and an interpolated phase graph (θ[n]') by interpolating the amplitude graph (A[n]) and the phase graph (θ[n]) through the sinusoid interpolation method, calculates an interpolation value (A[n+0.5], θ[n+0.5]) between the first measurement value (A[n], θ[n]) and the second measurement value (A[n+1], θ[n+1]) of each of the amplitude graph (A[n]) and the phase graph (θ[n]) based on <Formula 2> below.

[0018] A[n + 0.5] = 0.5*(A[n] + A[n + 1])

[0019] θ[n + 0.5] = 0.5*(θ[n] + θ[n + 1])

[0020] <Formula 2>

[0021] (Here, the above A[n] is the amplitude on pixel of the white light interference pattern signal (Amplitude on Pixel of WLI Fringe), and the above θ[n] is the phase on pixel of the white light interference pattern signal (Phase on Pixel of WLI Fringe))

[0022] The image analysis processor generates the interpolated white light interference pattern signal (I[n]') based on the interpolated amplitude graph (A[n]') and the interpolated phase graph (θ[n]'), and, based on <Formula 3> below, generates the interpolated white light interference pattern signal (I[n]') based on the measured values ​​(A[n], θ[n]) of each of the amplitude graph (A[n]) and the phase graph (θ[n]), and the interpolated values ​​(A[n+0.5], θ[n+0.5]) of each of the interpolated amplitude graph (A[n]') and the interpolated phase graph (θ[n]').

[0023] I[n] = A[n] × cos(θ[n])

[0024] <Formula 3>

[0025] (Here, the above A[n] is the amplitude on pixel of the white light interference pattern signal (Amplitude on Pixel of WLI Fringe), and the above θ[n] is the phase on pixel of the white light interference pattern signal (Phase on Pixel of WLI Fringe))

[0026] In order to achieve the above-described object, a white light interferometer utilizing a sinusoidal interpolation method according to an embodiment of the present invention is a white light interferometer utilizing a sinusoidal interpolation method that obtains the shape of the sample by analyzing an interference pattern generated by a measurement light and a reflected light reflected after white light is irradiated to a sample and a mirror, respectively, wherein the white light interferometer includes a charge coupled device (CCD) image sensor that photographs the interference pattern to generate a plurality of interference pattern images, and an image analysis processor that accumulates the plurality of interference pattern images to generate a white light interference pattern signal (WLI fringe signal, I[n]), and the image analysis processor interpolates the generated white light interference pattern signal (I[n]) through sinusoidal interpolation to generate an interpolated white light interference pattern signal (I[n]'), and analyzes the interpolated white light interference pattern signal (I[n]') to derive surface information of the sample.

[0027] The image analysis processor, when interpolating the white light interference pattern signal (I[n]) using a sinusoidal interpolation method, generates an amplitude graph (Envelope, A[n]) and a phase graph (Phase, θ[n]) based on the white light interference pattern signal (I[n]), interpolates the amplitude graph (A[n]) and the phase graph (θ[n]) using the sinusoidal interpolation method, respectively, to generate an interpolated amplitude graph (A[n]') and an interpolated phase graph (θ[n]'), and generates the interpolated white light interference pattern signal (I[n]') based on the interpolated amplitude graph (A[n]') and the interpolated phase graph (θ[n]').

[0028] The image analysis processor, when generating the amplitude graph (A[n]) and the phase graph (θ[n]) based on the white light interference pattern signal (I[n]), extracts components according to amplitude and phase from the white light interference pattern signal (I[n]), thereby generating a linear amplitude graph (A[n]) and phase graph (θ[n]).

[0029] The linear amplitude graph (A[n]) above is an envelope that touches all the peak points of the white light interference pattern signal (I[n]) among the envelopes of the white light interference pattern signal (I[n]).

[0030] The image analysis processor calculates an interpolation value (A[n+0.5], θ[n+0.5]) between a first measurement value (A[n], θ[n]) and a second measurement value (A[n+1], θ[n+1]) of each of the amplitude graph (A[n]) and the phase graph (θ[n]) when interpolating the amplitude graph (A[n]) and the phase graph (θ[n]) using the sinusoid interpolation method, and the interpolation value (A[n+0.5], θ[n+0.5]) is an average value of the first measurement value (A[n], θ[n]) and the second measurement value (A [n+1], θ[n+1]).

[0031] The image analysis processor generates the interpolated white light interference pattern signal (I[n]') based on the interpolated amplitude graph (A[n]') and the interpolated phase graph (θ[n]'), and generates the interpolated white light interference pattern signal (I[n]') based on the measured values ​​(A[n], θ[n]) of each of the amplitude graph (A[n]) and the phase graph (θ[n]), and the interpolated values ​​(A[n+0.5], θ[n+0.5]) of each of the interpolated amplitude graph (A[n]') and the interpolated phase graph (θ[n]').

[0032] The measured values ​​(A[n], θ[n]) of each of the amplitude graph (A[n]) and the phase graph (θ[n]), and the measured values ​​(A[n]', θ[n]') of each of the interpolated amplitude graph (A[n]') and the interpolated phase graph (θ[n]'), have the same values.

[0033] The image analysis processor determines an intensity value of the interpolated white light interference fringe signal (I[n]') based on the measured values ​​(A[n], θ[n]) or the interpolated values ​​(A[n+0.5], θ[n+0.5]) of each of the interpolated amplitude graph (A[n]') and the interpolated phase graph (θ[n]') when generating the interpolated white light interference fringe signal (I[n]') based on the interpolated amplitude graph (A[n]') and the interpolated phase graph (θ[n]'), and when the measured value (A[n]) of the interpolated amplitude graph (A[n]') is maximum and the phase of the interpolated phase graph (θ[n]') is 0°, the measured value (θ[n]) or the interpolated value (θ[n+0.5]) of the interpolated phase graph exceeds -90°. When the angle is less than 90°, the intensity value of the interpolated white light interference fringe signal (I[n]') has a positive (+) value corresponding to the measured value (A[n]) or the interpolated value (A[n+0.5]) of the interpolated amplitude graph (A[n]'), and when the measured value (θ[n]) or the interpolated value (θ[n+0.5]) of the interpolated phase graph is greater than 90° to 270°, the intensity value of the interpolated white light interference fringe signal (I[n]') has a negative (-) value corresponding to the measured value (A[n]) or the interpolated value (A[n+0.5]) of the interpolated amplitude graph (A[n]'), and when the measured value (θ[n]) or the interpolated value (θ[n+0.5]) of the interpolated phase graph is -90°, 90°, and 270°, the interpolated white light interference fringe The intensity value of the signal (I[n]') has a value of 0.

[0034] In order to achieve the above-described object, a sinusoidal interpolation method of a white light interferometer according to an embodiment of the present invention is a sinusoidal interpolation method of a white light interferometer, in which an image analysis processor interpolates a white light interference pattern signal (I[n]) through sinusoidal interpolation to generate an interpolated white light interference pattern signal (I[n]'), wherein the sinusoidal interpolation method of the white light interferometer comprises: a step in which the image analysis processor generates an amplitude graph (Envelope, A[n]) and a phase graph (Phase, θ[n]) based on the white light interference pattern signal (I[n]); a step in which the image analysis processor interpolates the amplitude graph (A[n]) and the phase graph (θ[n]) through the sinusoidal interpolation to generate an interpolated amplitude graph (A[n]') and an interpolated phase graph (θ[n]'); and a step in which the image analysis processor interpolates the interpolated amplitude It includes a step of generating the interpolated white light interference pattern signal (I[n]') based on the graph (A[n]') and the interpolated phase graph (θ[n]').

[0035] The step of generating an amplitude graph (Envelope, A[n]) and a phase graph (Phase, θ[n]) based on the white light interference pattern signal (I[n]) by the image analysis processor includes a step of generating a linear amplitude graph (A[n]) and a phase graph (θ[n]) by extracting components according to amplitude and phase from the white light interference pattern signal (I[n]).

[0036] The step of the image analysis processor extracting components according to amplitude and phase from the white light interference pattern signal (I[n]) and generating a linear amplitude graph (A[n]) and phase graph (θ[n]) includes the step of the image analysis processor extracting components according to amplitude (A[n]) from the white light interference pattern signal (I[n]) based on <Formula 1> below and generating the amplitude graph (Envelope), and extracting components according to phase (θ[n]) from the white light interference pattern signal (I[n]) and generating the phase graph (Phase).

[0037] A[n](Envelope) = (c[n] 2 + s[n] 2 ) 1 / 2

[0038] θ[n](Phase) = Atan(s[n], c[n])

[0039] <Formula 1>

[0040] (Here, the A[n] is the amplitude on the pixel of the white light interference pattern signal (Amplitude on Pixel of WLI Fringe), the θ[n] is the phase on the pixel of the white light interference pattern signal (Phase on Pixel of WLI Fringe), the c[n] is the cosine component of the white light interference pattern signal (Cosine Component of WLI Fringe) and is calculated as c[n] = A[n] × cos(θ[n]), and the s[n] is the sine component of the white light interference pattern signal (Sine Component of WLI Fringe) and is calculated as s[n] = A[n] × sin(θ[n]).)

[0041] The step of generating an interpolated amplitude graph (A[n]') and an interpolated phase graph (θ[n]') by interpolating the amplitude graph (A[n]) and the phase graph (θ[n]) through the sinusoidal interpolation method by the image analysis processor includes a step of calculating an interpolation value (A[n+0.5], θ[n+0.5]) between a first measurement value (A[n], θ[n]) and a second measurement value (A[n+1], θ[n+1]) of each of the amplitude graph (A[n]) and the phase graph (θ[n]), wherein the interpolation value (A[n+0.5], θ[n+0.5]) is an average value of the first measurement value (A[n], θ[n]) and the second measurement value (A [n+1], θ[n+1]).

[0042] The step of calculating an interpolation value (A[n+0.5], θ[n+0.5]) between the first measurement value (A[n], θ[n]) and the second measurement value (A[n+1], θ[n+1]) of each of the amplitude graph (A[n]) and the phase graph (θ[n]) by the image analysis processor includes a step of calculating an interpolation value (A[n+0.5], θ[n+0.5]) between the first measurement value (A[n], θ[n]) and the second measurement value (A[n+1], θ[n+1]) of each of the amplitude graph (A[n]) and the phase graph (θ[n]) based on <Formula 2> below.

[0043] A[n + 0.5] = 0.5*(A[n] + A[n + 1])

[0044] θ[n + 0.5] = 0.5*(θ[n] + θ[n + 1])

[0045] <Formula 2>

[0046] (Here, the above A[n] is the amplitude on pixel of the white light interference pattern signal (Amplitude on Pixel of WLI Fringe), and the above θ[n] is the phase on pixel of the white light interference pattern signal (Phase on Pixel of WLI Fringe))

[0047] The step of generating the interpolated white light interference fringe signal (I[n]') based on the interpolated amplitude graph (A[n]') and the interpolated phase graph (θ[n]') by the image analysis processor includes the step of generating the interpolated white light interference fringe signal (I[n]') based on the measured values ​​(A[n], θ[n]) of each of the amplitude graph (A[n]) and the phase graph (θ[n]), and the interpolated values ​​(A[n+0.5], θ[n+0.5]) of each of the interpolated amplitude graph (A[n]') and the interpolated phase graph (θ[n]').

[0048] The step of generating the interpolated white light interference pattern signal (I[n]') based on the measured values ​​(A[n], θ[n]) of each of the amplitude graph (A[n]) and the phase graph (θ[n]) and the interpolated values ​​(A[n+0.5], θ[n+0.5]) of each of the interpolated amplitude graph (A[n]') and the interpolated phase graph (θ[n]') by the image analysis processor is, based on the <Formula 3> below, generating the interpolated white light interference pattern signal (I[n]') based on the measured values ​​(A[n], θ[n]) of each of the amplitude graph (A[n]) and the phase graph (θ[n]) and the interpolated values ​​(A[n+0.5], θ[n+0.5]) of each of the interpolated amplitude graph (A[n]') and the interpolated phase graph (θ[n]') It includes a step of generating a signal (I[n]').

[0049] I[n] = A[n] × cos(θ[n])

[0050] <Formula 3>

[0051] (Here, the above A[n] is the amplitude on pixel of the white light interference pattern signal (Amplitude on Pixel of WLI Fringe), and the above θ[n] is the phase on pixel of the white light interference pattern signal (Phase on Pixel of WLI Fringe))

[0052] According to the white light interferometer utilizing the sinusoidal interpolation method of the present invention and the sinusoidal interpolation method of the white light interferometer, the shape of the interference pattern acquired from a CCD image sensor can be naturally expressed by interpolating the interference pattern through the sinusoidal interpolation method.

[0053] According to the white light interferometer utilizing the sinusoidal interpolation method of the present invention and the sinusoidal interpolation method of the white light interferometer, an interference pattern acquired from a CCD image sensor can be interpolated quickly and accurately by utilizing the mathematical conditions of the sinusoidal wavelength.

[0054] According to the white light interferometer utilizing the sinusoidal interpolation method of the present invention and the sinusoidal interpolation method of the white light interferometer, the sinusoidal interpolation method has the advantage of being advantageous for acceleration using a GPU, etc., as it is numerically optimized for computation.

[0055] FIG. 1 is a drawing briefly showing one embodiment of a white light interferometer utilizing the sinusoidal interpolation method according to the present invention.

[0056] FIG. 2 is a diagram showing a process of interpolating a white light interference pattern signal generated by an image analysis processor according to the present invention.

[0057] Figure 3 is a diagram showing a white light interference pattern signal of the same sample according to a change in phase and a process in which the white light interference pattern signal is interpolated.

[0058] FIG. 4 is a drawing showing an image analysis processor according to the present invention interpolating a white light interference pattern signal through sinusoidal interpolation to generate an interpolated white light interference pattern signal.

[0059] FIG. 5 is a drawing for briefly explaining the sinusoidal interpolation method of the image analysis processor according to the present invention.

[0060] Figures 6 to 8 are flowcharts of a sinusoidal interpolation method of a white light interferometer according to the present invention.

[0061] Hereinafter, some embodiments of the present invention will be described in detail with reference to exemplary drawings. When designating components in each drawing, it should be noted that, where possible, identical components are given the same reference numerals, even if they appear in different drawings.

[0062] And when describing an embodiment of the present invention, if it is determined that a specific description of a related known configuration or function hinders understanding of the embodiment of the present invention, the detailed description is omitted.

[0063] Additionally, in describing components of embodiments of the present invention, terms such as first, second, A, B, (a), (b), etc. may be used. These terms are only intended to distinguish the components from other components, and the nature, order, or sequence of the components are not limited by the terms.

[0064] In this specification, the singular includes the plural unless specifically stated otherwise. The terms “comprises” and / or “comprising” as used herein do not exclude the presence or addition of one or more other components in addition to the components mentioned.

[0065] Hereinafter, the present invention will be described in more detail with reference to the attached drawings.

[0066]

[0067] FIG. 1 is a drawing briefly showing one embodiment of a white light interferometer (100) utilizing the sinusoidal interpolation method according to the present invention.

[0068] A white light interferometer (100) utilizing the sinusoidal interpolation method according to the present invention (hereinafter referred to as 'white light interferometer (100)') includes a light source (10), a beam splitter (20), a mirror (30), a stage (40), a stage movement assembly (50), a CCD image sensor (60), and an image analysis processor (70), as shown in FIG. 1.

[0069]

[0070] A light source (10) generates white light. The light source (10) provides the white light to a beam splitter (20), and the beam splitter (20) splits the white light provided from the light source (10) and provides it to a sample (41) and a mirror (30).

[0071] A sample (41) is placed on the upper surface of the stage (40). The sample (41) is a measurement target for which surface information is to be measured. The sample (41) may be a nanostructure such as a semiconductor element.

[0072] The stage movement assembly (50) moves the stage (40) toward or away from the beam splitter (20). That is, the stage movement assembly (50) moves the stage (40) in the path axis direction (Z-axis direction) of white light provided from the beam splitter (20) to the stage (40). The stage movement assembly (50) can move the stage (40) in the path axis direction (Z-axis direction) of the white light based on a fine z step size (for example, 68.75 nm, which is λ / 8). As the stage (40) moves by the stage movement assembly (50), a fine path difference occurs between the measurement light transmitted to the CCD image sensor (60) and the reflected light.

[0073] The mirror (30) has a reflective surface on one side facing the beam splitter (20).

[0074]

[0075] The beam splitter (20) splits the path of white light provided from the light source into the sample (41) side and the mirror (30) side. The beam splitter (20) provides some of the white light provided from the light source (10) to the stage (40) side and provides the remainder of the white light to the mirror (30).

[0076] The beam splitter (20) changes the path of the white light so that some of the white light provided from the light source (10) is transmitted to the stage (40) side and the sample (41) side. The white light transmitted to the sample (41) side is reflected back to the beam splitter (20) as measurement light, and is transmitted to the CCD image sensor (60) through the beam splitter (20).

[0077] The beam splitter (20) provides the remainder of the white light provided from the light source (10) to the mirror (30). The white light provided to the mirror (30) is reflected and transmitted back to the beam splitter (20). The beam splitter (20) changes the path of the reflected light so that the reflected light reflected from the mirror (30) is transmitted to the CCD image sensor (60).

[0078] The beam splitter (20) splits white light into the sample (41) side and the reflective surface side of the mirror (30). The measurement light reflected from the sample (41) and the reflected light reflected from the mirror (30) are transmitted to the CCD image sensor (60) by the beam splitter (20). The measurement light reflected from the sample (41) and the reflected light reflected from the mirror (30) generate an interference pattern due to a slight path difference change.

[0079] Centered around the beam splitter (20), separate lenses (not shown) may be further included on the light source (10) side, the sample (41) side, the mirror (30) side, and the CCD image sensor (60) side to focus white light, measurement light, and reflected light, respectively.

[0080] A CCD image sensor (60, Charge Coupled Device image sensor) receives measurement light reflected from a sample (41) and reflected light reflected from a mirror (30) from a beam splitter (20). The CCD image sensor (60) photographs interference patterns of pixels generated by the measurement light and reflected light at preset time intervals while the stage (40) moves in the Z-axis direction step by step according to a constant z-step size by the stage movement assembly (50). The CCD image sensor (60) photographs interference patterns at preset time intervals to generate a plurality of interference pattern images. Here, a pixel means a unit pixel included in the XY plane of the interference pattern image. The CCD image sensor (60) transmits a plurality of interference pattern images photographed at preset time intervals to an image analysis processor (70).

[0081] The image analysis processor (70) accumulates multiple interference pattern images received from the CCD image sensor (60) to generate a white light interference pattern signal (WLI fringe signal, I[n]) as shown in (a) of FIG. 2.

[0082]

[0083] FIG. 2 is a diagram showing a process in which a white light interference pattern signal generated by an image analysis processor (70) according to the present invention is interpolated. Specifically, (a) of FIG. 2 is a diagram showing a graph according to a white light interference pattern signal generated by the image analysis processor (70), (b) of FIG. 2 is a diagram showing an enlarged graph of a main part of the graph according to the white light interference pattern signal shown in (a) of FIG. 2, and (c) of FIG. 2 is a diagram showing an enlarged graph of a main part of the graph according to the interpolated white light interference pattern signal.

[0084] Figure 3 is a drawing showing a white light interference pattern signal of the same sample (41) according to a change in phase and a process in which the white light interference pattern signal is interpolated.

[0085]

[0086] The white light interferometer (100) according to the present invention includes all known white light interferometers capable of obtaining the shape of the sample (41) by analyzing the interference pattern generated by the measurement light and the reflected light, which are split by the beam splitter (20) and irradiated onto the sample (41) and the mirror (30), respectively, and then reflected. At this time, the white light interferometer (100), as is known, includes a CCD image sensor (60) that photographs the interference pattern to generate a plurality of interference pattern images, and an image analysis processor (70) that generates a white light interference pattern signal by accumulating components included in the plurality of interference pattern images, and analyzes the generated white light interference pattern signal to derive surface information of the sample (41).

[0087] The white light interference pattern signal means that when the stage (40) moves in the Z-axis direction step by step according to a constant z step size, the intensity (or intensity) of each of the plurality of interference pattern pixels photographed at preset time intervals is represented as the x-axis coordinate, and the position of the sample (41) that changes according to the movement of the stage (40) is represented as the y-axis coordinate, and the intensity of each pixel is accumulated and displayed as a graph.

[0088] The white light interference pattern signal generated by the image analysis processor (70) is as shown in (a) of Fig. 2. The center of the white light interference pattern signal includes a region (a) where the intensity of the interference pattern changes rapidly, and an enlarged view of the region (a) is shown in (b) of Fig. 2.

[0089] The white light interference pattern signal, as shown in (b) of FIG. 2, has a problem in that the shape of the white light interference pattern signal is expressed unnaturally because the z step size of the stage movement assembly (50) that moves the stage (40) in the z-axis direction at preset intervals when photographing the interference pattern, i.e., the length of movement of the stage (40) in the z-axis direction, is physically limited (for example, 68.75 nm, which is λ / 8). This limited movement distance of the stage (40) due to physical limitations causes limitations in the expression, analysis, and interpretation of the white light interference pattern.

[0090] For example, referring to FIG. 3, the raw white light interference pattern signal generated by photographing a sample (41) is expressed in a different shape depending on the position of the stage (40), i.e., the phase change of the measurement light, even if the sample (41) is the same. This occurs because the minute height change within the z step size (e.g., 68.75 nm) of the stage (40) cannot be accurately expressed through the current white light interferometer (100). However, as the raw white light interference pattern signal is interpolated several times (such as 2 times, 4 times, and 8 times), it can be seen that the shape of each interpolated white light interference pattern signal gradually changes to the same shape.

[0091]

[0092] In the past, as mentioned above, the unnatural shape of the white light interference pattern (WLI Fringe) due to the limited Z Step Size was solved by interpolating according to the spline interpolation method (Cubic Spline). However, the spline interpolation method had a large amount of calculations, and thus had limitations in the speed of generating and analyzing the white light interference pattern.

[0093] Polynomial interpolation also has limitations in applying to white light interference pattern signals with sinusoidal waves. For example, in the case of polynomial interpolation, since a coefficient is required for each order, the number of data points required for fitting is fitting order + 1. However, when sine and cosine waves are sampled at 90° intervals, a 3rd or 4th order polynomial approximation is required for accuracy, but since there are only 3 points in the interval, there is a problem that it is difficult to apply a 3rd or 4th order polynomial approximation.

[0094] On the other hand, the sinusoidal interpolation method according to the present invention requires a minimum of two points for interpolation, and enables accurate sine and cosine fitting by interpolating the midpoint between slowly varying profile points. The sinusoidal interpolation method according to the present invention has the characteristic of being able to apply interpolation while reliably maintaining sine and cosine wave conditions.

[0095]

[0096] The image analysis processor (70) according to the present invention interpolates the white light interference pattern signal (I[n]) shown in (a) and (b) of FIG. 2 through sinusoidal interpolation to generate an interpolated white light interference pattern signal (I[n]'). The image analysis processor (70) can analyze the interpolated white light interference pattern signal (I[n]') to derive surface information of the sample (41).

[0097]

[0098] FIG. 4 is a diagram showing a state in which an image analysis processor (70) according to the present invention interpolates a white light interference pattern signal through sinusoidal interpolation to generate an interpolated white light interference pattern signal. Specifically, (a) of FIG. 4 is a diagram showing a raw white light interference pattern signal graph generated by the image analysis processor (70), (b) of FIG. 4 is a diagram showing an amplitude graph and a phase graph generated by dividing the raw white light interference pattern signal into components according to amplitude and phase, respectively, by the image analysis processor (70), (c) of FIG. 4 is a diagram showing an interpolated graph of the amplitude graph and the phase graph generated by the image analysis processor (70), and (d) of FIG. 4 is a diagram showing a white light interference pattern signal graph interpolated through sinusoidal interpolation by synthesizing the interpolated amplitude graph and phase graph. Figures 4 (a) to (d) briefly illustrate only the main part of the white light interference pattern signal as shown in Figure 2.

[0099]

[0100] The image analysis processor (70) according to the present invention interpolates the white light interference pattern signal (I[n]) using the sinusoidal interpolation method. When the image analysis processor (70) interpolates the white light interference pattern signal (I[n]) using the sinusoidal interpolation method, the image analysis processor (70) calculates a value between two measured values ​​of the white light interference pattern signal (I[n]) and applies the calculated value to generate an interpolated white light interference pattern signal (I[n]'). That is, the image analysis processor (70) calculates the midpoint of two measured values ​​of the white light interference pattern signal (I[n]) and applies the result to interpolate the white light interference pattern signal.

[0101] The image analysis processor (70) according to the present invention interpolates the white light interference pattern signal (I[n]) by calculating the median between two measurement values, thereby increasing the resolution to an exponent value of 2 (e.g., x2, x4, and x8). If interpolation is performed at x8, the z step size is reduced from 68.75 nm to 8.6 nm.

[0102] Hereinafter, the interpolation of the white light interference pattern signal (I[n]) of the image analysis processor (70) will be described in detail with reference to FIG. 4.

[0103]

[0104] The image analysis processor (70) according to the present invention, when interpolating the white light interference pattern signal (I[n]) using the sinusoidal interpolation method, as shown in (a) of FIG. 4, divides the initially generated white light interference pattern signal (I[n]) into components according to amplitude and phase, as shown in (b) of FIG. 4, to generate an amplitude signal graph (Envelope, A[n]) and a phase signal graph (Phase, θ[n]), and as shown in (c) of FIG. 4, calculates the median value of the amplitude signal graph (A[n]) and the phase signal graph (θ[n]) through the sinusoidal interpolation method, and interpolates the median value by applying the calculated value, thereby generating an interpolated amplitude signal graph (A[n]') and an interpolated phase signal graph (θ[n]'), and as shown in (d) of FIG. 4, the interpolated amplitude signal graph (A[n]') and the interpolated phase signal Interpolation of the white light interference pattern signal (I[n]) using the sinusoidal interpolation method is completed by generating an interpolated white light interference pattern signal (I[n]') based on the graph (θ[n]').

[0105] Since the basic white light interference pattern signal (I[n]) or the cosine (Cos) component, sine (Sin) component, etc. have a fast variation (Fast Variation) in which the variation per z step of the interference pattern is similar to the maximum (Max) value, it is difficult to directly calculate the correction value for a sinusoidal wave such as the basic white light interference pattern signal (I[n]).

[0106] However, since the amplitude signal graph (Envelope, A[n]) or phase signal graph (Phase, θ[n]) extracted from the basic white light interference pattern signal (I[n]) has a linear slow variation, each graph (A[n], θ[n]) can be easily interpolated by applying linear interpolation to each of the linear amplitude signal graph (Envelope, A[n]) or linear phase signal graph (Phase, θ[n]). In addition, it is possible to generate an interpolated white light interference pattern signal (I[n]') by converting the interpolated result (A[n]', θ[n]') according to the linear interpolation method back into a white light interference pattern signal, which is a sinusoid wavelength.

[0107]

[0108] The image analysis processor (70) according to the present invention generates an amplitude signal graph (A[n]) and a phase signal graph (θ[n]) by dividing the basic white light interference pattern signal (I[n]) into components according to amplitude and phase, as illustrated in (b) of FIG. 4. When generating the amplitude signal graph (A[n]) and the phase signal graph (θ[n]) based on the white light interference pattern signal (I[n]), the image analysis processor (70) extracts components according to amplitude and phase from the basic white light interference pattern signal (I[n]), thereby generating a linear amplitude graph (A[n]) and a phase graph (θ[n]).

[0109] At this time, the linear amplitude signal graph (A[n]) may be an envelope that touches all the maximum amplitudes of the rising and falling sections of the white light interference pattern signal (I[n]). That is, at this time, the linear amplitude signal graph (A[n]) may be an envelope that touches all the peak points of the white light interference pattern signal (I[n]) among the envelopes of the white light interference pattern signal (I[n]).

[0110]

[0111] The image analysis processor (70) according to the present invention, as one embodiment, when generating an amplitude signal graph (A[n]) and a phase signal graph (θ[n]) by dividing a basic white light interference pattern signal (I[n]) into components according to amplitude and phase, respectively, may extract an amplitude component (A[n]) from the white light interference pattern signal (I[n]) based on <Formula 1> below to generate an amplitude signal graph (Envelope), and may extract a phase component (θ[n]) to generate the phase signal graph (Phase).

[0112]

[0113] A[n](Envelope) = (c[n] 2 + s[n] 2 ) 1 / 2

[0114] θ[n](Phase) = Atan(s[n], c[n])

[0115] <Formula 1>

[0116]

[0117] Here, A[n] is the amplitude on pixel of the basic white light interference pattern signal (Amplitude on Pixel of WLI Fringe), θ[n] is the phase on pixel of the basic white light interference pattern signal (Phase on Pixel of WLI Fringe), c[n] is the cosine component of the white light interference pattern signal (Cosine Component of WLI Fringe), which is calculated as c[n] = A[n] × cos(θ[n]), and s[n] is the sine component of the white light interference pattern signal (Sine Component of WLI Fringe), which is calculated as s[n] = A[n] × sin(θ[n]).

[0118] <Formula 1> means the calculation of the slowly varying component of the WLI fringe (I[n]). Here, A[n] (Envelope) = (c[n] 2 + s[n] 2 ) 1 / 2 is using the Sqrt function, and θ[n] (Phase) = Atan(s[n], c[n]) is using the Atan function.

[0119]

[0120] The image analysis processor (70) according to the present invention calculates the median value of the amplitude signal graph (A[n]) and the phase signal graph (θ[n]) through the sinusoidal interpolation method as shown in (c) of FIG. 4, and interpolates the calculated value by applying the median value to generate an interpolated amplitude signal graph (A[n]') and an interpolated phase signal graph (θ[n]').

[0121] The image analysis processor (70) calculates an interpolation value (A[n+0.5], θ[n+0.5]) which is a median value between the first measurement value (A[n], θ[n]) and the second measurement value (A[n+1], θ[n+1]) of each of the amplitude signal graph (A[n]) and the phase signal graph (θ[n]) when interpolating the amplitude signal graph (A[n]) and the phase signal graph (θ[n]) using the sinusoidal interpolation method, and wherein the interpolation value (A[n+0.5], θ[n+0.5]) may be an average value of the first measurement value (A[n], θ[n]) and the second measurement value (A[n+1], θ[n+1]).

[0122] When the image analysis processor (70) interpolates based on the amplitude signal graph (A[n]) according to the sinusoidal interpolation method, the image analysis processor (70) can calculate an interpolation value, which is a median between the maximum value and the measurement value closest to the maximum value, with the maximum value among the measurement values ​​of the amplitude signal graph (A[n]) as the center. For example, when the first measurement value of the amplitude signal graph is A[1], the second measurement value can be A[2], and the interpolation value here can be A[1.5]. A[1.5] is calculated to have the average value of the values ​​of A[1] and A[2]. The image analysis processor (70) calculates A[n+0.5], which is a median value of a plurality of measurement values ​​A[n] and A[n+1], and applies the calculated values ​​to the amplitude signal graph (A[n]) to generate an interpolated amplitude signal graph (A[n]') having an interpolation value.

[0123] Likewise, when the image analysis processor (70) interpolates based on the phase signal graph (θ[n]) according to the sinusoidal interpolation method, it can calculate an interpolation value which is a median between a measurement value of the phase signal graph (θ[n]) and the measurement value closest to the measurement value. For example, when the first measurement value of the phase signal graph is θ[1], the second measurement value may be θ[2], and the interpolation value here may be θ[1.5]. θ[1.5] is calculated to have an average value of the values ​​of θ[1] and θ[2]. The image analysis processor (70) calculates θ[n+0.5], which is a median value of a plurality of measurement values ​​θ[n] and θ[n+1], and applies the calculated values ​​to the phase signal graph (θ[n]) to generate an interpolated phase signal graph θ[n]') having an interpolation value.

[0124]

[0125] As an example, when the image analysis processor (70) interpolates the amplitude signal graph (A[n]) and the phase signal graph (θ[n]) through the sinusoidal interpolation method to generate an interpolated amplitude signal graph (A[n]') and an interpolated phase signal graph (θ[n]'), the image analysis processor calculates an interpolation value (A[n+0.5], θ[n+0.5]) between the first measurement value (A[n], θ[n]) and the second measurement value (A[n+1], θ[n+1]) of each of the amplitude signal graph (A[n]) and the phase signal graph (θ[n]) based on <Formula 2> below.

[0126]

[0127] A[n + 0.5] = 0.5*(A[n] + A[n + 1])

[0128] θ[n + 0.5] = 0.5*(θ[n] + θ[n + 1])

[0129] <Formula 2>

[0130]

[0131] Here, A[n] represents the amplitude on pixel of the white light interference pattern signal (Amplitude on Pixel of WLI Fringe), and θ[n] represents the phase on pixel of the white light interference pattern signal (Phase on Pixel of WLI Fringe).

[0132] <Formula 2> is a formula for linear interpolation onto binary up-sampling of A[n] & θ[n], and is a formula for calculating correction values ​​corresponding to Subindex(n + 0.5).

[0133]

[0134] The image analysis processor (70) according to the present invention generates an interpolated white light interference pattern signal (I[n]') based on an interpolated amplitude signal graph (A[n]') and an interpolated phase signal graph (θ[n]'), thereby completing interpolation of the white light interference pattern signal (I[n]) using a sinusoidal interpolation method.

[0135] The image analysis processor (70) generates an interpolated white light interference pattern signal (I[n]') based on the interpolated amplitude signal graph (A[n]') and the interpolated phase signal graph (θ[n]'), and generates an interpolated white light interference pattern signal (I[n]') based on the measured values ​​(A[n], θ[n]) of each of the amplitude signal graph (A[n]) and the phase signal graph (θ[n]), and the interpolated values ​​(A[n+0.5], θ[n+0.5]) of each of the interpolated amplitude signal graph (A[n]') and the interpolated phase signal graph (θ[n]').

[0136] That is, the measurement values ​​(A[n], θ[n]) of the amplitude signal graph (A[n]) and the phase signal graph (θ[n]) respectively, and the measurement values ​​(A[n]', θ[n]') of the interpolated amplitude signal graph (A[n]') and the interpolated phase signal graph (θ[n]') respectively, have the same values. For example, referring to the amplitude signal graph (A[n]) and the interpolated amplitude signal graph (A[n]') of Fig. 4 (b) and Fig. 4 (c) together, points located at the same coordinates on each graph (A[n], A[n]') mean the same measurement values ​​in the amplitude signal graph (A[n]) and the interpolated amplitude signal graph (A[n]'), respectively. On the other hand, points that are not expressed in the amplitude signal graph (A[n]) but are newly expressed in the interpolated amplitude signal graph (A[n]') mean newly calculated interpolated values ​​in the interpolated amplitude signal graph (A[n]').

[0137] Similarly, points located at the same coordinates in the phase signal graph (θ[n]) of Fig. 4 (b) and the interpolated phase signal graph (θ[n]') of Fig. 4 (c) are the same measured values, and points newly expressed in the interpolated phase signal graph (θ[n]') of Fig. 4 (c) mean newly calculated interpolated values ​​in the interpolated phase signal graph (θ[n]').

[0138]

[0139] When generating an interpolated white light interference pattern signal (I[n]') based on an interpolated amplitude signal graph (A[n]') and an interpolated phase signal graph (θ[n]'), the image analysis processor (70) determines an intensity value of the interpolated white light interference pattern signal (I[n]') based on the measured values ​​(A[n], θ[n]) and / or interpolated values ​​(A[n+0.5], θ[n+0.5]) of each of the interpolated amplitude signal graph (A[n]') and the interpolated phase signal graph (θ[n]').

[0140] For example, as an embodiment, when the phase of the interpolated phase signal graph (θ[n]') is 0° when the measured value (A[n]) of the interpolated amplitude signal graph (A[n]') is maximum, and when the measured value (θ[n]) and / or the interpolated value (θ[n+0.5]) of the interpolated phase signal graph is greater than -90° and less than 90°, the intensity value of the interpolated white light interference fringe signal (I[n]') corresponding to the measured value (θ[n]) and / or the interpolated value (θ[n+0.5]) of the phase signal graph has a positive (+) value corresponding to the measured value (A[n]) or the interpolated value (A[n+0.5]) of the interpolated amplitude signal graph (A[n]'). When the measured value (θ[n]) and / or the interpolated value (θ[n+0.5]) of the interpolated phase signal graph is greater than 90° to 270°, the intensity value of the interpolated white light interference fringe signal (I[n]') has a negative (-) value corresponding to the measured value (A[n]) and / or the interpolated value (A[n+0.5]) of the interpolated amplitude signal graph (A[n]'). When the measured value (θ[n]) or the interpolated value (θ[n+0.5]) of the interpolated phase graph is -90°, 90°, and 270°, the intensity value of the interpolated white light interference fringe signal (I[n]') has a value of 0.

[0141] More specifically, the image analysis processor (70) has a phase of the interpolated phase signal graph (θ[n]') when the measured value (A[n]) of the interpolated amplitude signal graph (A[n]') is maximum, and when the measured value (θ[n]) and / or the interpolated value (θ[n+0.5]) of the interpolated phase signal graph is 0°, the intensity value of the interpolated white light interference fringe signal (I[n]') corresponding to the measured value (A[n]) and / or the interpolated value (A[n+0.5]) of the interpolated amplitude signal graph (A[n]') has a positive (+) value corresponding to the measured value (A[n]) and / or the interpolated value (A[n+0.5]) of the interpolated phase signal graph, and when the measured value (θ[n]) and / or the interpolated value (θ[n+0.5]) of the interpolated phase signal graph is 90°, the intensity value of the interpolated white light interference fringe signal (I[n]') has a value of 0, and When the measured value (θ[n]) and / or the interpolated value (θ[n+0.5]) is 180°, the intensity value of the interpolated white light interference fringe signal (I[n]') has a negative (-) value corresponding to the measured value (A[n]) and / or the interpolated value (A[n+0.5]) of the interpolated amplitude signal graph (A[n]'), and when the measured value (θ[n]) and / or the interpolated value (θ[n+0.5]) of the interpolated phase signal graph is 45°, the intensity value of the interpolated white light interference fringe signal (I[n]') has a positive (+) value corresponding to the measured value (A[n]) and / or the interpolated value (A[n+0.5]) of the interpolated amplitude signal graph (A[n]'), and when the measured value (θ[n]) and / or the interpolated value (θ[n+0.5]) of the interpolated phase signal graph is 135°. In this case, the intensity value of the interpolated white light interference pattern signal (I[n]') has a negative (-) value corresponding to the measured value (A[n]) or interpolated value (A[n+0.5]) of the interpolated amplitude signal graph (A[n]').

[0142] The image analysis processor (70), as described above, generates an interpolated white light interference pattern signal (I[n]') based on the interpolated amplitude signal graph (A[n]') and the interpolated phase signal graph (θ[n]').

[0143]

[0144] The image analysis processor (70), as an example, generates an interpolated white light interference pattern signal (I[n]') based on the interpolated amplitude graph (A[n]') and the interpolated phase graph (θ[n]'), and generates an interpolated white light interference pattern signal (I[n]') based on the measured values ​​(A[n], θ[n]) of the amplitude signal graph (A[n]) and the phase signal graph (θ[n]), and the interpolated values ​​(A[n+0.5], θ[n+0.5]) of the interpolated amplitude signal graph (A[n]') and the interpolated phase signal graph (θ[n]'), based on <Formula 3> below.

[0145]

[0146] I[n] = A[n] × cos(θ[n])

[0147] <Formula 3>

[0148]

[0149] Here, A[n] represents the amplitude on the pixel of the white light interference pattern signal (Amplitude on Pixel of WLI Fringe), and θ[n] represents the phase on the pixel of the white light interference pattern signal (Phase on Pixel of WLI Fringe). <Formula 3> is a formula that converts I[n + 0.5] from the calculated A[n + 0.5] and θ[n + 0.5].

[0150]

[0151] FIG. 5 is a drawing for briefly explaining the sinusoidal interpolation method of the image analysis processor (70) according to the present invention.

[0152] Interpolation of a white light interference pattern signal (I[n]) using the sinusoidal interpolation method of the image analysis processor (70) has the characteristic of calculating Cos and Sin only at the midpoint (N-1 numbers) and calculating them using the sinusoidal method without using a complex trigonometric function, as shown in FIG. 5. Interpolation of a white light interference pattern signal (I[n]) using the sinusoidal interpolation method of the image analysis processor (70) first generates the Amp of the midpoint by averaging the Amp values ​​of the points on both sides (1st), and then generates the remaining Amp values ​​by moving and averaging a total of 2N-1 interpolated pixels by 3 pixel steps.

[0153]

[0154] Figures 6 to 8 are flowcharts of a sinusoidal interpolation method of a white light interferometer (100) according to the present invention.

[0155] The sinusoidal interpolation method of the white light interferometer (100) according to the present invention is such that the image analysis processor (70) interpolates the white light interference pattern signal (I[n]) through sinusoidal interpolation to generate an interpolated white light interference pattern signal (I[n]').

[0156] The sinusoidal interpolation method of the white light interferometer (100) according to the present invention, with reference to FIGS. 6 to 8, includes a step (S100) in which the image analysis processor (70) generates an amplitude signal graph (Envelope, A[n]) and a phase signal graph (Phase, θ[n]) based on a white light interference pattern signal (I[n]), a step (S200) in which the image analysis processor (70) interpolates the amplitude signal graph (A[n]) and the phase signal graph (θ[n]) through sinusoidal interpolation to generate an interpolated amplitude signal graph (A[n]') and an interpolated phase signal graph (θ[n]'), and a step (S300) in which the image analysis processor (70) generates an interpolated white light interference pattern signal (I[n]') based on the interpolated amplitude graph (A[n]') and the interpolated phase graph (θ[n]').

[0157]

[0158] Step (S100) includes a step (S110) in which an image analysis processor (70) extracts components according to amplitude and phase from a white light interference pattern signal (I[n]) and generates a linear amplitude signal graph (A[n]) and a phase signal graph (θ[n]).

[0159] Step (S110) includes a step (S111) in which the image analysis processor (70) extracts a component (A[n]) according to amplitude from a white light interference pattern signal (I[n]) based on <Formula 1> below to generate an amplitude signal graph (Envelope), and extracts a component (θ[n]) according to phase from the white light interference pattern signal (I[n]) to generate a phase signal graph (Phase).

[0160]

[0161] A[n](Envelope) = (c[n] 2 + s[n] 2 ) 1 / 2

[0162] θ[n](Phase) = Atan(s[n], c[n])

[0163] <Formula 1>

[0164] In <Formula 1>, A[n] is the amplitude on pixel of the white light interference pattern signal (Amplitude on Pixel of WLI Fringe), θ[n] is the phase on pixel of the white light interference pattern signal (Phase on Pixel of WLI Fringe), c[n] is the cosine component of the white light interference pattern signal (Cosine Component of WLI Fringe), which is calculated as c[n] = A[n] × cos(θ[n]), and s[n] is the sine component of the white light interference pattern signal (Sine Component of WLI Fringe), which is calculated as s[n] = A[n] × sin(θ[n]).

[0165]

[0166] Step (S200) includes a step (S210) in which the image analysis processor (70) calculates an interpolation value (A[n+0.5], θ[n+0.5]) between the first measurement value (A[n], θ[n]) and the second measurement value (A[n+1], θ[n+1]) of each of the amplitude signal graph (A[n]) and the phase signal graph (θ[n]), and the interpolation value (A[n+0.5], θ[n+0.5]) is calculated as an average value of the first measurement value (A[n], θ[n]) and the second measurement value (A[n+1], θ[n+1]).

[0167] Step (S210) includes a step (S211) in which the image analysis processor (70) calculates an interpolation value (A[n+0.5], θ[n+0.5]) between the first measurement value (A[n], θ[n]) and the second measurement value (A[n+1], θ[n+1]) of each of the amplitude signal graph (A[n]) and the phase signal graph (θ[n]) based on <Formula 2> below.

[0168]

[0169] A[n + 0.5] = 0.5*(A[n] + A[n + 1])

[0170] θ[n + 0.5] = 0.5*(θ[n] + θ[n + 1])

[0171] <Formula 2>

[0172] In <Formula 2>, A[n] is the amplitude on pixel of the white light interference pattern signal (Amplitude on Pixel of WLI Fringe), and θ[n] is the phase on pixel of the white light interference pattern signal (Phase on Pixel of WLI Fringe).

[0173]

[0174] Step (S300) includes a step (S310) in which the image analysis processor (70) generates an interpolated white light interference pattern signal (I[n]') based on the measured values ​​(A[n], θ[n]) of each of the amplitude signal graph (A[n]) and the phase signal graph (θ[n]), and the interpolated values ​​(A[n+0.5], θ[n+0.5]) of each of the interpolated amplitude signal graph (A[n]') and the interpolated phase signal graph (θ[n]').

[0175] Step (S310) includes a step (S311) in which the image analysis processor (70) generates an interpolated white light interference pattern signal (I[n]') based on the measured values ​​(A[n], θ[n]) of each of the amplitude signal graph (A[n]) and the phase signal graph (θ[n]), and the interpolated values ​​(A[n+0.5], θ[n+0.5]) of each of the interpolated amplitude signal graph (A[n]') and the interpolated phase signal graph (θ[n]'), based on <Formula 3> below.

[0176]

[0177] I[n] = A[n] × cos(θ[n])

[0178] <Formula 3>

[0179] In <Formula 3>, A[n] is the amplitude on pixel of the white light interference pattern signal (Amplitude on Pixel of WLI Fringe), and θ[n] is the phase on pixel of the white light interference pattern signal (Phase on Pixel of WLI Fringe).

[0180]

[0181] The terms described in this specification are defined as shown in Table 1 below.

[0182]

[0183] Table 1

[0184]

[0185] In detail, I[n] means a basic white light interference pattern signal measured by a white light interferometer (100) according to the present invention, and each value (x-axis on the graph) means the intensity (or strength, Intensity) of the interference pattern, and can be expressed as I[n] = A[n]cos(θ[n]) + IDC-Offset. A[n] means the amplitude on pixel of the white light interference pattern signal (Amplitude on Pixel of WLI Fringe), and A[n] = (c[n] 2 + s[n] 2 ) 1 / 2 It can be expressed as follows. θ[n] represents the phase on pixel of the white light interference pattern signal (Phase on Pixel of WLI Fringe) and can be expressed as θ[n] = Atan(s[n], c[n]). c[n] is the cosine component of the white light interference pattern signal (Cosine Component of WLI Fringe) and can be expressed as c[n] = A[n] × cos(θ[n]). s[n] is the sine component of the white light interference pattern signal (Sine Component of WLI Fringe) and can be expressed as s[n] = A[n] × sin(θ[n]).

[0186]

[0187] In this specification, the image analysis processor (70) may include processors that execute sequential execution processes stored in memory. Alternatively, the image analysis processor (70) may operate as software modules driven and controlled by the processor. Furthermore, the image analysis processor (70) may be a hardware device.

[0188] For reference, the sinusoidal interpolation method of the white light interferometer (100) according to one embodiment of the present invention may be implemented in the form of program commands that can be executed through various computer means and recorded on a computer-readable medium. The computer-readable medium may include program commands, data files, data structures, etc., alone or in combination. The program commands recorded on the medium may be those specially designed and configured for the present invention or may be those known and usable to those skilled in the art of computer software. Examples of the computer-readable medium may include magnetic media such as hard disks, floppy disks, and magnetic tapes, optical recording media such as CD-ROMs and DVDs, magneto-optical media such as floptical disks, and hardware devices specially configured to store and execute program commands such as ROMs, RAMs, and flash memories. Examples of the program commands include not only machine codes generated by a compiler but also high-level language codes that can be executed by a computer using an interpreter, etc. The above-described hardware devices may be configured to operate as one or more software modules to perform the operations of the present invention, and vice versa.

[0189] The scope of protection of the present invention is not limited to the description and expression of the embodiments explicitly described above. Furthermore, it should be noted that the scope of protection of the present invention may not be limited by obvious modifications or substitutions within the technical field to which the present invention pertains.

Claims

1. A light source that provides white light; A stage on which a sample is placed; A stage movement assembly that moves the stage in the direction of the path axis of the white light; A mirror having a reflective surface; A beam splitter that divides the path of white light provided from the light source into the sample side and the mirror side; A CCD image sensor (Charge Coupled Device image sensor) that receives the measurement light reflected from the sample and the reflected light reflected from the mirror from the beam splitter while the stage moves in the path axis direction by the stage moving assembly, and photographs the interference pattern generated by the measurement light and the reflected light to generate a plurality of interference pattern images; and An image analysis processor is included that accumulates the plurality of interference pattern images to generate a white light interference pattern signal (WLI fringe signal, I[n]). The above image analysis processor is a white light interferometer utilizing sinusoidal interpolation, which interpolates the generated white light interference pattern signal (I[n]) through sinusoidal interpolation to generate an interpolated white light interference pattern signal (I[n]').

2. In claim 1, The image analysis processor interpolates the white light interference pattern signal (I[n]) using sinusoidal interpolation, The above white light interference pattern signal (I[n]) is divided into components according to amplitude and phase, respectively, to generate an amplitude graph (Envelope, A[n]) and a phase graph (Phase, θ[n]). The above amplitude graph (A[n]) and the above phase graph (θ[n]) are interpolated using the sinusoid interpolation method to generate an interpolated amplitude graph (A[n]') and an interpolated phase graph (θ[n]'), respectively. A white light interferometer utilizing sinusoidal interpolation, characterized in that the interpolated white light interference pattern signal (I[n]') is generated based on the interpolated amplitude graph (A[n]') and the interpolated phase graph (θ[n]').

3. In claim 2, The image analysis processor divides the white light interference pattern signal into components according to amplitude and phase, and generates an amplitude graph and a phase graph. A white light interferometer utilizing sinusoidal interpolation, characterized in that the amplitude graph (Envelope) is generated by extracting a component (A[n]) according to amplitude from the white light interference pattern signal (I[n]) based on <Formula 1> below, and the phase graph (Phase) is generated by extracting a component (θ[n]) according to phase from the white light interference pattern signal (I[n]). A[n](Envelope) = (c[n] 2 + s[n] 2 ) 1 / 2 θ[n](Phase) = Atan(s[n], c[n]) <Formula 1> (Here, the A[n] is the amplitude on the pixel of the white light interference pattern signal (Amplitude on Pixel of WLI Fringe), the θ[n] is the phase on the pixel of the white light interference pattern signal (Phase on Pixel of WLI Fringe), the c[n] is the cosine component of the white light interference pattern signal (Cosine Component of WLI Fringe) and is calculated as c[n] = A[n] × cos(θ[n]), and the s[n] is the sine component of the white light interference pattern signal (Sine Component of WLI Fringe) and is calculated as s[n] = A[n] × sin(θ[n]).) 4. In claim 3, The image analysis processor interpolates the amplitude graph (A[n]) and the phase graph (θ[n]) through the sinusoid interpolation method, respectively, to generate an interpolated amplitude graph (A[n]') and an interpolated phase graph (θ[n]'). A white light interferometer utilizing sinusoidal interpolation, characterized in that it calculates an interpolation value (A[n+0.5], θ[n+0.5]) between the first measurement value (A[n], θ[n]) and the second measurement value (A[n+1], θ[n+1]) of each of the amplitude graph (A[n]) and the phase graph (θ[n]) based on <Formula 2> below. A[n + 0.5] = 0.5*(A[n] + A[n + 1]) θ[n + 0.5] = 0.5*(θ[n] + θ[n + 1]) <Formula 2> (Here, the above A[n] is the amplitude on pixel of the white light interference pattern signal (Amplitude on Pixel of WLI Fringe), and the above θ[n] is the phase on pixel of the white light interference pattern signal (Phase on Pixel of WLI Fringe)) 5. In claim 4, The image analysis processor generates the interpolated white light interference pattern signal (I[n]') based on the interpolated amplitude graph (A[n]') and the interpolated phase graph (θ[n]'). A white light interferometer utilizing sinusoidal interpolation, characterized in that the interpolated white light interference pattern signal (I[n]') is generated based on the measured values ​​(A[n], θ[n]) of each of the amplitude graph (A[n]) and the phase graph (θ[n]), and the interpolated values ​​(A[n+0.5], θ[n+0.5]) of each of the interpolated amplitude graph (A[n]') and the interpolated phase graph (θ[n]'), based on <Formula 3> below. I[n] = A[n] × cos(θ[n]) <Formula 3> (Here, the above A[n] is the amplitude on pixel of the white light interference pattern signal (Amplitude on Pixel of WLI Fringe), and the above θ[n] is the phase on pixel of the white light interference pattern signal (Phase on Pixel of WLI Fringe)) 6. In white light interferometry, which utilizes the sinusoidal interpolation method to obtain the shape of the sample by analyzing the interference pattern generated by the reflected measurement light and the reflected light after white light is irradiated onto the sample and mirror, respectively, The above white light interferometer, A CCD image sensor (Charge Coupled Device image sensor) that captures the interference pattern and generates multiple interference pattern images; and An image analysis processor is included that accumulates the plurality of interference pattern images to generate a white light interference pattern signal (WLI fringe signal, I[n]). The above image analysis processor is a white light interferometer utilizing sinusoidal interpolation, which interpolates the generated white light interference pattern signal (I[n]) through sinusoidal interpolation to generate an interpolated white light interference pattern signal (I[n]').

7. In claim 6, The image analysis processor interpolates the white light interference pattern signal (I[n]) using sinusoidal interpolation, Generate an amplitude graph (Envelope, A[n]) and a phase graph (Phase, θ[n]) based on the above white light interference pattern signal (I[n]), The above amplitude graph (A[n]) and the above phase graph (θ[n]) are interpolated using the sinusoid interpolation method to generate an interpolated amplitude graph (A[n]') and an interpolated phase graph (θ[n]'), respectively. A white light interferometer utilizing sinusoidal interpolation, characterized in that the interpolated white light interference pattern signal (I[n]') is generated based on the interpolated amplitude graph (A[n]') and the interpolated phase graph (θ[n]').

8. In claim 7, The image analysis processor generates the amplitude graph (A[n]) and the phase graph (θ[n]) based on the white light interference pattern signal (I[n]). A white light interferometer utilizing sinusoidal interpolation, characterized in that components according to amplitude and phase are extracted from the white light interference pattern signal (I[n]) and a linear amplitude graph (A[n]) and phase graph (θ[n]) are generated.

9. In claim 8, The linear amplitude graph (A[n]) above is A white light interferometer utilizing sinusoidal interpolation, characterized in that the envelope of the white light interference pattern signal (I[n]) is an envelope that touches all peak points of the white light interference pattern signal (I[n]).

10. In claim 8, The image analysis processor interpolates the amplitude graph (A[n]) and the phase graph (θ[n]) using the sinusoid interpolation method, Compute the interpolation value (A[n+0.5], θ[n+0.5]) between the first measurement value (A[n], θ[n]) and the second measurement value (A[n+1], θ[n+1]) of each of the amplitude graph (A[n]) and the phase graph (θ[n]), A white light interferometer utilizing a sinusoidal interpolation method, characterized in that the interpolated value (A[n+0.5], θ[n+0.5]) is an average value of the first measured value (A[n], θ[n]) and the second measured value (A[n+1], θ[n+1]).

11. In claim 10, The image analysis processor generates the interpolated white light interference pattern signal (I[n]') based on the interpolated amplitude graph (A[n]') and the interpolated phase graph (θ[n]'). A white light interferometer utilizing sinusoidal interpolation, characterized in that the interpolated white light interference pattern signal (I[n]') is generated based on the measured values ​​(A[n], θ[n]) of each of the amplitude graph (A[n]) and the phase graph (θ[n]), and the interpolated values ​​(A[n+0.5], θ[n+0.5]) of each of the interpolated amplitude graph (A[n]') and the interpolated phase graph (θ[n]').

12. In claim 11, The measured values ​​(A[n], θ[n]) of each of the amplitude graph (A[n]) and the phase graph (θ[n]), A white light interferometer utilizing sinusoidal interpolation, characterized in that the measured values ​​(A[n]', θ[n]') of each of the interpolated amplitude graph (A[n]') and the interpolated phase graph (θ[n]') have the same value.

13. In claim 12, The image analysis processor generates the interpolated white light interference pattern signal (I[n]') based on the interpolated amplitude graph (A[n]') and the interpolated phase graph (θ[n]'). The intensity value of the interpolated white light interference pattern signal (I[n]') is determined based on the measured values ​​(A[n], θ[n]) or the interpolated values ​​(A[n+0.5], θ[n+0.5]) of each of the interpolated amplitude graph (A[n]') and the interpolated phase graph (θ[n]'), When the measured value (A[n]) of the interpolated amplitude graph (A[n]') is maximum and the phase of the interpolated phase graph (θ[n]') is 0°, When the measured value (θ[n]) or the interpolated value (θ[n+0.5]) of the interpolated phase graph is greater than -90° and less than 90°, the intensity value of the interpolated white light interference pattern signal (I[n]') has a positive (+) value corresponding to the measured value (A[n]) or the interpolated value (A[n+0.5]) of the interpolated amplitude graph (A[n]'), When the measured value (θ[n]) or the interpolated value (θ[n+0.5]) of the interpolated phase graph is greater than 90° to 270°, the intensity value of the interpolated white light interference pattern signal (I[n]') has a negative (-) value corresponding to the measured value (A[n]) or the interpolated value (A[n+0.5]) of the interpolated amplitude graph (A[n]'), A white light interferometer utilizing sinusoidal interpolation, characterized in that when the measured value (θ[n]) or interpolated value (θ[n+0.5]) of the interpolated phase graph is -90°, 90°, and 270°, the intensity value of the interpolated white light interference pattern signal (I[n]') has a value of 0.

14. In a sinusoidal interpolation method of a white light interferometer, in which an image analysis processor interpolates a white light interference pattern signal (I[n]) through sinusoidal interpolation to generate an interpolated white light interference pattern signal (I[n]'), The sinusoidal interpolation method of the above white light interferometer is, A step in which the image analysis processor generates an amplitude graph (Envelope, A[n]) and a phase graph (Phase, θ[n]) based on the white light interference pattern signal (I[n]); A step in which the image analysis processor interpolates the amplitude graph (A[n]) and the phase graph (θ[n]) through the sinusoid interpolation method to generate an interpolated amplitude graph (A[n]') and an interpolated phase graph (θ[n]'); and A sinusoidal interpolation method of a white light interferometer, comprising a step of generating the interpolated white light interference pattern signal (I[n]') based on the interpolated amplitude graph (A[n]') and the interpolated phase graph (θ[n]'), by the image analysis processor.

15. In claim 14, The step of the image analysis processor generating an amplitude graph (Envelope, A[n]) and a phase graph (Phase, θ[n]) based on the white light interference pattern signal (I[n]) is as follows: A sinusoidal interpolation method of a white light interferometer, comprising a step in which the image analysis processor extracts components according to amplitude and phase from the white light interference pattern signal (I[n]) and generates a linear amplitude graph (A[n]) and phase graph (θ[n]).

16. In claim 15, The step of the image analysis processor extracting components according to amplitude and phase from the white light interference pattern signal (I[n]) and generating a linear amplitude graph (A[n]) and phase graph (θ[n]) is as follows: A sinusoidal interpolation method of a white light interferometer, comprising a step of the image analysis processor extracting an amplitude component (A[n]) from the white light interference pattern signal (I[n]) based on <Formula 1> below to generate the amplitude graph (Envelope), and extracting a phase component (θ[n]) from the white light interference pattern signal (I[n]) to generate the phase graph (Phase). A[n](Envelope) = (c[n] 2 + s[n] 2 ) 1 / 2 θ[n](Phase) = Atan(s[n], c[n]) <Formula 1> (Here, the A[n] is the amplitude on the pixel of the white light interference pattern signal (Amplitude on Pixel of WLI Fringe), the θ[n] is the phase on the pixel of the white light interference pattern signal (Phase on Pixel of WLI Fringe), the c[n] is the cosine component of the white light interference pattern signal (Cosine Component of WLI Fringe) and is calculated as c[n] = A[n] × cos(θ[n]), and the s[n] is the sine component of the white light interference pattern signal (Sine Component of WLI Fringe) and is calculated as s[n] = A[n] × sin(θ[n]).) 17. In claim 14, The step of the image analysis processor interpolating the amplitude graph (A[n]) and the phase graph (θ[n]) through the sinusoid interpolation method to generate an interpolated amplitude graph (A[n]') and an interpolated phase graph (θ[n]'), respectively, is as follows: The image analysis processor includes a step of calculating an interpolation value (A[n+0.5], θ[n+0.5]) between a first measurement value (A[n], θ[n]) and a second measurement value (A[n+1], θ[n+1]) of each of the amplitude graph (A[n]) and the phase graph (θ[n]), A sinusoidal interpolation method of a white light interferometer, characterized in that the interpolated value (A[n+0.5], θ[n+0.5]) is an average value of the first measured value (A[n], θ[n]) and the second measured value (A[n+1], θ[n+1]).

18. In claim 17, The step of the image analysis processor calculating an interpolation value (A[n+0.5], θ[n+0.5]) between the first measurement value (A[n], θ[n]) and the second measurement value (A[n+1], θ[n+1]) of each of the amplitude graph (A[n]) and the phase graph (θ[n]) is as follows: A sinusoidal interpolation method of a white light interferometer, comprising a step of the image analysis processor calculating an interpolation value (A[n+0.5], θ[n+0.5]) between the first measurement value (A[n], θ[n]) and the second measurement value (A[n+1], θ[n+1]) of each of the amplitude graph (A[n]) and the phase graph (θ[n]) based on <Formula 2> below. A[n + 0.5] = 0.5*(A[n] + A[n + 1]) θ[n + 0.5] = 0.5*(θ[n] + θ[n + 1]) <Formula 2> (Here, the above A[n] is the amplitude on pixel of the white light interference pattern signal (Amplitude on Pixel of WLI Fringe), and the above θ[n] is the phase on pixel of the white light interference pattern signal (Phase on Pixel of WLI Fringe)) 19. In claim 14, The step of the image analysis processor generating the interpolated white light interference pattern signal (I[n]') based on the interpolated amplitude graph (A[n]') and the interpolated phase graph (θ[n]') is as follows: A sinusoidal interpolation method of a white light interferometer, comprising a step of generating the interpolated white light interference pattern signal (I[n]') based on the measured values ​​(A[n], θ[n]) of each of the amplitude graph (A[n]) and the phase graph (θ[n]), and the interpolated values ​​(A[n+0.5], θ[n+0.5]) of each of the interpolated amplitude graph (A[n]') and the interpolated phase graph (θ[n]').

20. In claim 19, The step of generating the interpolated white light interference pattern signal (I[n]') based on the measured values ​​(A[n], θ[n]) of each of the amplitude graph (A[n]) and the phase graph (θ[n]) and the interpolated values ​​(A[n+0.5], θ[n+0.5]) of each of the interpolated amplitude graph (A[n]') and the interpolated phase graph (θ[n]') by the image analysis processor is as follows: A sinusoidal interpolation method of a white light interferometer, comprising a step of generating the interpolated white light interference pattern signal (I[n]') based on the measured values ​​(A[n], θ[n]) of each of the amplitude graph (A[n]) and the phase graph (θ[n]), and the interpolated values ​​(A[n+0.5], θ[n+0.5]) of each of the interpolated amplitude graph (A[n]') and the interpolated phase graph (θ[n]'), based on <Formula 3> below. I[n] = A[n] × cos(θ[n]) <Formula 3> (Here, the above A[n] is the amplitude on pixel of the white light interference pattern signal (Amplitude on Pixel of WLI Fringe), and the above θ[n] is the phase on pixel of the white light interference pattern signal (Phase on Pixel of WLI Fringe))

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