WO2011138874A1 - 高さ測定方法及び高さ測定装置 - Google Patents
高さ測定方法及び高さ測定装置 Download PDFInfo
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- WO2011138874A1 WO2011138874A1 PCT/JP2011/002560 JP2011002560W WO2011138874A1 WO 2011138874 A1 WO2011138874 A1 WO 2011138874A1 JP 2011002560 W JP2011002560 W JP 2011002560W WO 2011138874 A1 WO2011138874 A1 WO 2011138874A1
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B11/00—Measuring arrangements characterised by the use of optical techniques
- G01B11/02—Measuring arrangements characterised by the use of optical techniques for measuring length, width or thickness
- G01B11/06—Measuring arrangements characterised by the use of optical techniques for measuring length, width or thickness for measuring thickness ; e.g. of sheet material
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B11/00—Measuring arrangements characterised by the use of optical techniques
- G01B11/02—Measuring arrangements characterised by the use of optical techniques for measuring length, width or thickness
- G01B11/06—Measuring arrangements characterised by the use of optical techniques for measuring length, width or thickness for measuring thickness ; e.g. of sheet material
- G01B11/0608—Height gauges
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
- G06T7/00—Image analysis
- G06T7/50—Depth or shape recovery
- G06T7/55—Depth or shape recovery from multiple images
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
- G06T7/00—Image analysis
- G06T7/50—Depth or shape recovery
- G06T7/55—Depth or shape recovery from multiple images
- G06T7/557—Depth or shape recovery from multiple images from light fields, e.g. from plenoptic cameras
Definitions
- the present invention relates to a height measuring method and a height measuring device.
- the conventional technique uses an optical system for measuring the height of the optical system for obtaining an image of the surface of the object to be measured, for example, a laser irradiation optical system. It is necessary to add a confocal optical system, a white light interference system, or a plurality of detectors of an electron microscope (see, for example, Patent Document 1).
- the present invention has been made in view of such problems, and measures the height with high resolution and high accuracy even if it is composed of a simple optical system such as an imaging system and a relative scanning system of the focal position. It is an object of the present invention to provide a height measuring method and a height measuring device that can be used.
- a height measuring method includes an optical system that forms an image of a measurement object on a first surface and the measurement object on an optical axis of the optical system.
- the relative movement height may be obtained and used as the relative height.
- the optical system for forming an image of the measurement object on the first surface and the measurement object are relatively moved along the optical axis of the optical system
- a second function is defined on the basis of a first function that fits to a characteristic composed of a position on the optical axis and a light intensity value of the pixel, which is obtained for each pixel, and the characteristic obtained at the time of measurement and the second function
- the position on the optical axis when the correlation value with the value indicates an extreme value is set as the relative height value of the measurement object at the position corresponding to the pixel.
- the second function may be an absolute value of a first derivative function of the first function or a function obtained by squaring the first derivative function.
- the second function may be a function obtained by multiplying the first function by a constant.
- a value obtained by partially differentiating a correlation value between the second function moved relative to the optical axis direction by an arbitrary shift amount and the characteristic obtained at the time of measurement with respect to the shift amount is 0.
- the relative height value of the measurement object at the position corresponding to the pixel may be obtained by obtaining the shift amount.
- the height measuring apparatus is configured to make at least one of the optical system capable of forming an image of the measurement object and the measurement object and the optical system relative to each other along the optical axis of the optical system.
- a driving unit that moves the camera; a camera that captures the image; and a control unit that repeatedly performs the relative movement and the imaging and performs the height measurement based on a plurality of obtained imaging results.
- the optical system may be a microscope, and the object to be measured may be moved relative to the measurement object in the optical axis direction for scanning.
- the microscope is any one of a bright-dark field optical microscope, a polarization microscope, a fluorescence microscope, a differential interference microscope, a two-beam interference microscope, a stereomicroscope, and a zoom microscope, and the microscope has a focal position moving mechanism, You may comprise combining an imaging mechanism and a processor for control.
- the microscope may be configured by a two-beam interference microscope, and may be configured to scan by moving the object objective lens relative to the object to be measured in the optical axis direction.
- the microscope may be a two-beam interference microscope, and the reference light objective lens and the reference light forming mirror may be moved together in the optical axis direction for scanning.
- the height measuring method and the height measuring apparatus using this method according to the present invention even if it is constituted by a simple optical system such as an imaging system and a relative scanning system of the focal position, it has high resolution and high accuracy. Height measurements can be made.
- FIG. 1 is an example of a basic configuration of an imaging system of a height measuring device, and an imaging element 30, an objective lens 21 that collects light from a measurement object 10, and light emitted from the objective lens 21 are collected.
- An imaging optical system 20 including an imaging lens 22 that illuminates and forms an image of the measuring object 10 on the focal plane of the objective lens 21 on the imaging element 30;
- the imaging element 30 is disposed so that the imaging surface is positioned at the focal position of the imaging lens 22, and light from the surface of the measurement object 10 enters the imaging lens 22 as a parallel light beam by the objective lens 21.
- the relative position of the measurement object 10 with respect to the objective lens 21 (the relative position of the table that supports the measurement object 10) can be moved and adjusted. For example, it is possible to adjust the vertical position of the objective lens 21 using a piezo drive mechanism to adjust the relative position with very small and high accuracy.
- the objective lens 21 when measuring the height of the measuring object 10, the objective lens 21 is relatively positioned with respect to the measuring object 10 along the optical axis of the imaging optical system 20.
- the object to be measured of the objective lens 21 can be moved by moving (the movement of the objective lens 21 by the piezo drive mechanism as described above, the movement of the stage supporting the object 10 to be measured, or a combination of these).
- the image sensor 30 acquires and stores a plurality of continuous images of the measurement object 10, and associates the relative position on the optical axis when each image is acquired with this image.
- the image is plotted in FIG.
- the density value I of the image acquired through the imaging optical system 20 as described above is determined by the focal plane of the objective lens 21 and the surface (measurement surface) of the measurement object 10. The largest value when matching. Therefore, in the conventional method, the function that best fits the data point sequence M is obtained, and the height of the measuring object 10 is measured by obtaining the position on the optical axis at which the function (concentration value) is maximum. Yes.
- a function that best fits the data point sequence M is determined using Fourier transform, and the phase term of the function is used. This is a method for obtaining height data.
- a function (second function g) set in advance is moved with respect to the data point sequence M along the optical axis as shown below.
- the correlation value of the density value with the data point sequence is obtained, and the height position of the measurement object 10 is calculated from the position where the correlation value becomes maximum.
- a reference plate a flat plate having a uniform reflectance surface
- the first function f that best fits the data point sequence M is obtained.
- the position Zp on the optical axis at which the density value I is the largest (indicating a peak value) in the first function f is defined as the origin.
- a second function g for obtaining the height of the measurement object 10 is obtained, and each position on the surface of the actual measurement object 10 (corresponding to each pixel of the image sensor 30 is obtained using the second function g. ) To measure the height. Specifically, as described later, the correlation value of the density value with the data point sequence M when the second function g is moved along the optical axis with respect to the data point sequence M is obtained, and this correlation value is The height position of the measuring object 10 is calculated from the position where the maximum value is obtained.
- the data point sequence M is acquired as described above, and the function that best fits the acquired data point sequence M is obtained as the first function f.
- the origin (Zp) of the Z axis shown in FIG. 2 is set as the value of Zi that takes the maximum value of the density value Ii obtained by sampling.
- the peak (or peak deviation) of the density value I is obtained using g. That is, the function form that can obtain the correlation value in the portion where the change in the density value I is large before and after the peak portion of the first function f is selected as the second function g.
- the second function g is created by the following method based on the first function f. Since the correlation is obtained at such a large change portion, the height position of the measurement object 10 can be obtained accurately.
- the first function f is also included in the optical system. Can be determined accordingly.
- a method for creating the second function g based on the first function f will be described.
- a first method for creating the second function g will be described with reference to FIG.
- the first function f having the origin (Zp) as the origin (Zp) is shown on the left side, the position that best fits the data point sequence M shown in FIG. 2 and has the maximum density value Ii.
- the square of the first derivative value of the first function f or the absolute value of the first derivative value of the first function f is shown as the second function g on the right side of FIG. .
- the second function g has two local maxima corresponding to the portion where the value of Y increases and the portion where the value Y decreases in the first function f. It becomes a shape that can be.
- the center (center) of the two maximum portions of the second function g is the origin (Zp).
- the origin (Zp) does not necessarily have to be the center (center) of the maximum part.
- a second method for creating the second function g will be described with reference to FIG.
- the first derivative value of the first function f shown on the left side of FIG. 3B monotonously decreases or monotonically increases, the first derivative is maximized at the beginning of the increase or near the end of the decrease.
- the second function g is created using the portion where the first derivative is maximized, the correlation is obtained from sample data having a small density value, which causes an error.
- a function that is maximal or minimal at two points where the first function f becomes equal to a preset threshold is defined as the second function g.
- the second function g has a shape similar to that of the first method.
- the 2nd function g which has a peak in arbitrary two places which can pinch
- a third method for creating the second function g will be described with reference to FIG.
- 1 is set between two points where the first function f becomes equal to a preset threshold value.
- a function in which others are 0 is defined as a second function g.
- the second function g is a step-like function.
- a fourth method for creating the second function g will be described with reference to FIG.
- the first function f and the second function g are the same.
- the second function g is obtained from the result (data point sequence) measured using the reference plate.
- prior measurement is performed using the measurement object 10
- the second function g is obtained from the measurement result. You can ask for it. It is also possible to use the second function g having peaks at two arbitrary positions that can sandwich the peak (focus position) of the first function f without being based on the measurement result.
- FIG. 4B a case where the second function g is determined by the fourth method and the height measurement is performed using the second function g will be described. That is, as shown in FIG. 4A, the first function f that best fits the measured value (data point sequence M) of the reference plate measured through the imaging optical system 20 is multiplied by a constant, and FIG. A case will be described in which the second function g as shown in (b) is determined and the height is measured using the second function g.
- the objective lens 21 is relatively moved with respect to the measurement object 10, the focal position of the objective lens 21 with respect to the measurement object is relatively shifted, and the measurement object 10 is captured by the imaging device 30.
- the change that the density value (light intensity value) Ii of the pixel corresponding to the predetermined position (Xi, Yi) on the upper surface of the measurement object 10 occurs with respect to the height position Zi is: This is shown as a data point sequence M (Zi, Ii) indicated by small dots in FIG.
- the second function g is determined in advance by the procedure shown in FIG.
- a function form (first function f and a function indicated by a solid line in FIG. 4A) that best fits the data point sequence M is determined in advance from data measured using a reference plate.
- the data point sequence M of the specific pixel is extracted from the plurality of images acquired by the imaging device 30 via the imaging optical system 20 while changing the relative position between the objective lens 21 and the measurement object 10, and the first
- the parameter of the function f is determined by the least square method or the like (step S401).
- the second function g is determined by the fourth method (step S402). This second function g is shown in FIG.
- the second function g is shifted in a predetermined range in the optical axis direction (Z-axis direction), and the density value Ii at each measurement point Zi and the measurement point Zi are measured.
- a correlation value E with the value of the second function g is obtained.
- the correlation value E is expressed as the following equation (1).
- a represents the shift amount of the second function g in the Z-axis direction.
- the correlation value E between the density value Ii and the second function g (Zi ⁇ a) is obtained by shifting the shift amount a from minus to plus, as shown in FIG.
- the expression (1) is partially differentiated by the shift amount a as shown in the following expression (2), and this partial differentiation is performed. The shift amount a when the value becomes 0 is obtained.
- the value of the shift amount a at which the correlation value E obtained from the density value Ii and the second function g (Zi ⁇ a) reaches the peak for each height position Zi is obtained from the equation (2), If the value on the Z-axis of the measurement point is Ps + a, the relative height value of the measurement object 10 at the position corresponding to the pixel is Ps + a.
- the correlation value is obtained by shifting the second function g in the optical axis direction with respect to the data point sequence M has been described. It is also possible to obtain a correlation value by shifting in the axial direction.
- the height measurement apparatus 100 includes an imaging device 109 that acquires an image of the upper surface of the measurement target object 105 for each of a plurality of height positions, and controls the operation of the imaging device 109 and the measurement target object 105 based on the acquired image.
- a control processor 110 that calculates a relative height value and a display device 111 that displays a processing result by the control processor 110 are configured.
- the imaging device 109 includes an imaging camera 101 with an imaging device, a microscope barrel device 102 with an optical system (imaging lens), a microscope objective lens 104, and a piezo element.
- a piezo drive device 103 that drives up and down to piezo scan the relative position relative to the measurement object 105, a microscope sample stage 106 on which the measurement object 105 is placed, and white light is emitted to cause the measurement object 105 to move.
- a microscope illumination device 107 in which a light source for illumination is stored, and a microscope base device 102 and a microscope base 108 that supports the microscope illumination device 107 are configured.
- the control processor 110 sends a signal to the piezo driving device 103 to move the focus position of the microscope objective lens 104 to a predetermined position (step S410).
- the light irradiated from the microscope illumination device 107 is irradiated to the measurement object 105 placed on the microscope sample stage 106.
- the light reflected by the surface of the measurement object 105 passes through the microscope objective lens 104 and the microscope barrel device 102 (imaging lens), and is then condensed on the imaging surface of the imaging camera 101 to be captured by the imaging camera 101.
- an image of the measurement object 105 is taken.
- the digital image acquired from the imaging camera 101 in this way is sent to the control processor 110 (step S411).
- the control processor 110 stores the density value of each pixel of the acquired image, or calculates a numerical value (correction value or local focus level for each pixel) obtained by processing the density value by a process described later. (Step 412). Then, the piezo drive device 103 is controlled until the predetermined number of data points is obtained for each pixel, and the movement of the focal position and the capture of the image are repeated (step S413). Further, for each pixel, the shift amount a between the sampling points at which the partial differential of the correlation value E becomes zero is obtained by an analysis method or a numerical calculation method around the sampling point where the correlation value E is maximum, and the value is stored. (Step 413).
- step 412 the numerical value obtained by processing the density value is calculated. This is based on the density value of the pixels around each pixel, rather than using the density value of each pixel of the acquired image as it is. This is because the accuracy of calculating the correlation value E may be higher when the density value is processed and corrected. Therefore, a method for calculating a correction value (local focus degree) for each pixel in step S412 will be described with reference to FIGS.
- the control processor 110 stores captured images sequentially input from the imaging camera 101 in the image memory included in the control processor 110 in units of one image, and stores when the next image is acquired. Update the image.
- the control processor 110 includes three digital image memories 31 to 33.
- the first (first) image P1 is acquired first.
- the image P1 is stored in the first digital image memory 31.
- the image P1 is transferred to and stored in the second digital image memory 32, and this image P2 is stored in the first digital image memory 31 this time.
- the image P1 is transferred to the third digital image memory 33 and the image P2 is transferred to the second digital image memory 32 one after another, and the image P3 inputted this time is stored. It is stored in the first digital image memory 31 (see FIG. 8B).
- the image P4 is transferred to the first digital image memory 31, the image P3 is transferred to the second digital image memory 32, and the image P2 is transferred to the third digital image memory 33 to be stored.
- the first acquired image P1 disappears from the digital image memories 31-33.
- each of the image memories 31 to 33 is in a state in which images acquired by shifting the sampling interval ⁇ P in the vertical direction are stored one by one.
- the control processor 110 performs the following operation every time an image is acquired.
- a pixel for obtaining a local focus degree described later is set.
- the pixel that acquires the local focus degree is described as a pixel of interest.
- the digital data (differential operators) OP10, OP20, and OP30 shown in FIG. 9 are operated from the pixels of the image data stored in the digital image memories 31, 32, and 33, respectively.
- the target pixel is specified.
- the pixel values operated by the digital operators OP10, OP20, and OP30 are multiplied by a coefficient by the digital operator, and the local focus degree is obtained by a predetermined arithmetic expression.
- a candidate value for local focus is acquired from a set of three image data sampled sequentially, and the local focus is acquired.
- These determine the local focus level (LFS) in pixel units. That is, all pixels except the outermost peripheral pixel in the image stored in the second digital image memory 32 are the targets for calculating the local focus degree.
- the local focus degree is calculated by a 3 ⁇ 3 pixel block B20 centered on the target pixel (pixel value G25) in the image Pk20 stored in the second digital image memory 32, and In the image Pk10 stored in the one digital image memory 31, a pixel block B10 of 3 ⁇ 3 pixels corresponding to the pixel block B20 in the image Pk10, and in the image Pk30 stored in the third digital image memory 33, the pixel block B20 has a pixel.
- a 3 ⁇ 3 pixel block B30 corresponding to the position is extracted, and a convolution operation (product-sum operation) is performed between the pixel blocks B10, B20, and B30 and the corresponding digital operators OP10, OP20, and OP30. Done.
- the target pixel (pixel value G25) is a calculation target (reference)
- the pixels located at the four corners among the 3 ⁇ 3 pixels (pixel values G31, G33, G37, and G39).
- the pixels located at the four corners among the 3 ⁇ 3 pixels (pixel values G31, G33, G37, and G39).
- the pixels located at the four corners among the 3 ⁇ 3 pixels (pixel values G31, G33, G37, and G39).
- the pixels pixel values G12, G14, G16, G18 located in a cross shape among 3 ⁇ 3 pixels are the calculation targets.
- the weight of the coefficient for the target pixel (G25) is 24, and the weight of the coefficient for the surrounding pixels (G31, G33,..., G12, G14,. Yes.
- the local focus degree LFS of the target pixel is obtained by convolution calculation using the digital operators OP10 to 30 for these nine pixel values to be calculated.
- the height measuring apparatus 100 is configured to perform the above-described processing using the local focus degree LSF as the corrected density value in the above-described step 412.
- the maximum value of the absolute value of the correlation value E for each pixel calculated and calculated as described above (the coordinate value is Ps) is used to obtain the above formula (1).
- the value of the shift amount “a” is obtained for each pixel by solving the above equation (2) analytically using a numerical calculation method such as Newton's method or sequential substitution method (step 420).
- Ps + a (or a) calculated for each pixel is stored as the relative height value of the pixel (step S421).
- the height measurement method includes a focus position moving mechanism and an imaging for all microscopes including a bright / dark field optical microscope, a polarization microscope, a fluorescence microscope, a differential interference microscope, a two-beam interference microscope, a stereomicroscope, and a zoom microscope. This can be realized by combining a mechanism and a control processor.
- the height resolution in the first embodiment is a value obtained by dividing the sampling interval ⁇ P in the optical axis direction by m, without depending on the focal depth, by selecting an appropriate second function g.
- m is determined from biaxial blurring when the sample (object) is moved relative to the objective lens, an error of the image sensor, an error in calculation when obtaining the shift amount a, and the like. Value.
- d 10 nm
- m 10000
- the height resolution is 0.001 nm.
- the degree of freedom for fitting the acquired data point sequence includes the amplitude term and the phase term. Therefore, there is redundancy in determining the phase term.
- the height resolution was about 0.1 nm.
- this method fixes other than the phase term of the second function g and obtains a phase term that maximizes the correlation value, it achieves a resolution (0.001 nm as described above) that is much higher than the conventional method. Yes.
- the conventional high-resolution height measuring device takes a method that depends on the width of the signal in the optical axis direction near the focal point, it is necessary to use a white interferometer, but by using this method, If the second function g is appropriately selected, a resolution of about 10000 times the sampling interval ⁇ P can be realized even with a bright field microscope having a depth of focus of about 3 ⁇ m.
- the height measuring method according to the present embodiment has been described as applied to a height measuring device using a microscope, but the height measuring device using a scanning electron microscope (SEM). It is also possible to apply to. Also in this case, the processing procedure is the same as that in the first embodiment.
- SEM scanning electron microscope
- the height resolution does not depend on the focal depth by selecting an appropriate second function g, and the sampling interval ⁇ P in the optical axis direction is selected. Divided by m.
- the depth of focus of the scanning electron microscope is about 8 ⁇ m when the magnification is 10,000 times. Since the scanning range is required to be at least three times the depth of focus, if the sampling interval ⁇ P is reduced, the number of acquired images increases and takes time, which is not practical as a height measuring device. Therefore, for example, when the sampling interval ⁇ P is set to 100 nm, when the scanning electron microscope is used, m can be set to 10,000, so that the height resolution is 0.01 nm.
- a conventional height measuring apparatus using SEM uses two or more detectors to determine the inclination from a preset inclination and a calibration curve of the output difference from the difference between the output signals, and integrates it to obtain the height. It was a method to seek. In this method, the height resolution was about 3 nm. However, according to this method, the height resolution can be realized as 0.01 nm as described above, and a normal SEM can be used as it is, so that it can be configured at low cost.
- the height measuring method according to the present embodiment can also be applied to a height measuring device using a camera equipped with a macro lens.
- This height measurement device using a camera equipped with a macro lens is a device in which an imaging camera equipped with a macro lens is mounted on a stage, and the imaging camera is moved relative to the surface of the object to be measured through this stage. An image is acquired and the height is measured using the image.
- the height measurement method is the same as in the first embodiment.
- the resolution in the prior art was about 8 ⁇ m.
- the resolution is 10 nm. Therefore, a low-priced and high-resolution device can be realized at each stage.
- the height measuring method according to the present embodiment can also be applied to a height measuring device configured using a two-beam interference microscope.
- a configuration example of a height measuring device 200 using a two-beam interference microscope is shown in FIG. 11 and the configuration is as follows.
- the apparatus 200 has a two-beam interference microscope as a basic configuration, and includes an image sensor 201, an imaging lens 202, a half mirror 203, an object objective lens 204, a reference light objective lens 206, and a reference light formation.
- a mirror 207 and a mounting table 209 for mounting the measurement object 210 are provided.
- the imaging surface 201a of the imaging element 201 is disposed at the focal position of the imaging lens 202, and the object objective lens 204 and the reference light objective lens 206 are lenses having the same focal length (same optical performance) having the same configuration, and reference light.
- the forming mirror 207 is disposed at the focal position of the reference light objective lens 206.
- an illuminating device that makes illumination light (parallel light beam) incident on the optical path between the imaging lens 202 and the object objective lens 204 is provided.
- the part passes through the half mirror 203, is condensed by the object objective lens 204, and is irradiated on the upper surface of the measurement object 210 placed on the placement table 209.
- the remainder of the illumination light is reflected by the half mirror 203 and enters the reference light objective lens 206, where it is condensed and applied to the reference light forming mirror 207.
- the light irradiated on the reference light forming mirror 207 is totally reflected here and returns to the reference light objective lens 206 to become a parallel light beam, partially reflected by the half mirror 203, condensed by the imaging lens 202, and imaged.
- An image of the surface of the reference light forming mirror 207 is formed on the imaging surface 201 a of the element 201.
- the height position (height position in the optical axis direction) of the mounting table 209 can be adjusted, and the upper surface of the measurement object 210 mounted on the mounting table 209 is adjusted by this position adjustment.
- the optical path length from the imaging surface 201a of the imaging element 201 to the upper surface of the measurement object 210, and the reference light forming mirror 207 from the imaging surface 201a of the imaging element 201 Until the optical path length becomes equal.
- the optical path length (measurement optical path length) from the half mirror 203 to the measurement target position of the measurement object 210, and from the half mirror 203 to the reference light forming mirror 207. are equal in optical path length (reference optical path length).
- the surface of the reference light forming mirror 207 is smooth, but the optical path length varies depending on the unevenness of the surface of the measurement object 210, and optical interference occurs.
- white light is used, measurement is performed. Only the portion where the optical path length and the reference optical path length exactly match is imaged brightly.
- the height measuring apparatus 200 uses the two-beam interference microscope configuration as described above, and has a piezo element to adjust the position of the objective lens 204 for an object in the optical axis direction with high accuracy.
- a configuration including a piezo driving device 205 may also be employed.
- the objective lens 204 for an object is moved in the optical axis direction by the piezo drive device 205, and a plurality of interference images are acquired by the imaging element 201, and the upper surface of the measurement object 210 is obtained using the plurality of interference images. Measure height.
- the height measurement method at this time is the same as in the first embodiment.
- the reference object lens 206 and the reference light forming mirror 207 may be relatively moved in the optical axis direction. it can.
- the piezo driving device 205 instead of (or in combination with) the piezo driving device 205 that moves the object objective lens 204 in the optical axis direction, it is for reference light.
- a configuration using a second piezo driving device 208 that moves the objective lens 206 and the reference light forming mirror 207 together in the direction of the optical axis may be employed.
- a plurality of interference images are captured by the image sensor 201.
- the height of the upper surface of the measuring object 210 can be measured by acquiring and using the plurality of interference images.
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Abstract
Description
第1実施例として、上述した高さ測定方法を顕微鏡装置を用いた高さ測定装置に適用した場合について、図6を用いて説明する。この高さ測定装置100は、測定対象物105の上面の画像を複数の高さ位置毎に取得する撮像装置109と、この撮像装置109の作動の制御及び取得された画像から測定対象物105の相対高さ値を算出する制御用プロセッサ110と、この制御用プロセッサ110による処理結果を表示するディスプレイ装置111と、を有して構成される。
+{-3×(G31+G33+G37+G39)} (3)
上述の第1実施例では、本実施形態に係る高さ測定方法を、顕微鏡を用いた高さ測定装置に適用した場合について説明したが、走査型電子顕微鏡(SEM)を用いた高さ測定装置に適用することも可能である。この場合も、その処理手順は、上述の第1実施例と同様である。
また、本実施例に係る高さ測定方法は、マクロレンズ搭載カメラを用いた高さ測定装置にも適用することができる。このマクロレンズ搭載カメラを用いた高さ測定装置とは、マクロレンズを搭載した撮像カメラをステージに搭載し、このステージを介して撮像カメラを測定対象物の表面に対して相対移動させることによりの画像を取得し、その画像を用いて高さを測定するものである。高さの測定方法は、第1実施例と同様である。
また、本実施例に係る高さ測定方法は、二光束干渉顕微鏡を用いて構成される高さ測定装置にも適用することができる。二光束干渉顕微鏡を用いた高さ測定装置200の構成例を図11に示しており、その構成は以下のようになる。この装置200は、二光束干渉顕微鏡を基本構成としており、撮像素子201と、結像レンズ202と、ハーフミラー203と、対象物用対物レンズ204と、参照光用対物レンズ206と、参照光形成ミラー207と、測定対象物210を載置する載置台209とを備える。結像レンズ202の焦点位置に撮像素子201の撮像面201aが配置され、対象物用対物レンズ204および参照光用対物レンズ206は同一構成の同一焦点長(同一光学性能)レンズであり、参照光形成ミラー207は参照光用対物レンズ206の焦点位置に配置されている。
Claims (11)
- 測定対象物の像を第一面に結像する光学系と前記測定対象物とを該光学系の光軸に沿って相対移動させ、前記第一面での明るさの変化から前記測定対象物の相対高さを測定する高さ測定方法であって、
前記相対移動に対する前記明るさの変化を示す特性であって、前記相対移動に対する前記明るさの変化が大きな部分に基づく第一の特性と、前記測定対象物の測定時の前記相対移動に対する前記明るさの変化を示す第二の特性との相関を求め、当該相関に基づいて前記相対高さを求めることを特徴とする高さ測定方法。 - 前記第一の特性と前記第二の特性とを相対的に移動した時の相関の変化を、前記相対的な移動で偏微分することで前記相関が最大となる相対的な移動量を求め、前記相対高さとすることを特徴とする請求項1に記載の高さ測定方法。
- 測定対象物の像を第一面に結像する光学系と前記測定対象物とを該光学系の光軸に沿って相対移動させ、前記第一面の像を撮像し、該撮像された像から前記測定対象物の相対高さを測定する高さ測定方法であって、
前記相対移動と前記撮像を繰り返し行い、得られた前記複数の像の画素毎に得られる、前記光軸上の位置と当該画素の光強度値とからなる特性にフィットする第1関数に基づき第2関数を定義し、
測定時に得られる前記特性と前記第2関数との相関値が、極値を示すときの前記光軸上の位置を、前記画素に対応する位置にある前記測定対象物の相対高さ値とすることを特徴とする高さ測定方法。 - 前記第2関数は、前記第1関数の一次微分関数の絶対値若しくは当該一次微分関数を二乗した関数であることを特徴とする請求項3に記載の高さ測定方法。
- 前記第2関数は、前記第1関数を定数倍した関数であることを特徴とする請求項3に記載の高さ測定方法。
- 前記光軸方向に任意のシフト量で相対移動させた前記第2関数と測定時に得られる前記特性との相関値を前記シフト量で偏微分した値が0となる当該シフト量を求めることにより、前記画素に対応する位置にある前記測定対象物の相対高さ値とすることを特徴とする請求項2~5のいずれか一項に記載の高さ測定方法。
- 測定対象物の像を結像可能な光学系と、
前記測定対象物と前記光学系との少なくとも一方を前記光学系の光軸に沿って相対移動させる駆動部と、
前記像を撮像するカメラと、
前記相対移動と前記撮像とを繰り返し行い、得られた複数の撮像結果に基づいて請求項1~6のいずれか一項に記載の高さ測定を実行する制御部とを有することを特徴とする高さ測定装置。 - 前記光学系が顕微鏡であり、前記測定対象物に対して前記顕微鏡の対物レンズを光軸方向に相対移動させて走査することを特徴とする請求項7に記載の高さ測定装置。
- 前記顕微鏡が、明暗視野光学顕微鏡、偏光顕微鏡、蛍光顕微鏡、微分干渉顕微鏡、二光束干渉顕微鏡、実体顕微鏡およびズーム顕微鏡のいずれかであり、前記顕微鏡に焦点位置移動機構、撮像機構、制御用プロセッサを組み合わせて構成されることを特徴とする請求項8に記載の高さ測定装置。
- 前記顕微鏡が二光束干渉顕微鏡から構成され、対象物用対物レンズを前記測定対象物に対して光軸方向に相対移動させて走査することを特徴とする請求項8に記載の高さ測定装置。
- 前記顕微鏡が二光束干渉顕微鏡から構成され、参照光用対物レンズおよび参照光形成ミラーを一緒に光軸方向に移動させて走査することを特徴とする請求項8に記載の高さ測定装置。
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