Method for adjusting a shape measuring device

Abstract

To provide a method for adjusting a shape measuring device by which adjustment of a white interference microscope can be easily executed.SOLUTION: A method for adjusting a shape measuring device is to irradiate a master for adjustment and a reference surface with rays of light from a light source as measuring light and reference light, respectively, and measure the shape of a surface to be measured of a measurement object by using multiplexed light of the measurement light and the reference light reflected on the master for adjustment and the reference surface, respectively, and the method includes steps of: acquiring an image of the master for adjustment for each of a plurality of scan positions along a scan direction orthogonal to the master for adjustment, and calculating a matching degree parameter indicating the degree of matching between a focus position and an interference position from the images at the respective scan positions; and calculating a target setting position of the reference surface based on the matching degree parameter.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for adjusting a shape measuring device, and more particularly to a method for adjusting a shape measuring device that measures the shape of a measurement surface of a measurement object. [Background technology]

[0002] A known device for measuring the three-dimensional shape of an object is one that uses a scanning white light interferometer. A scanning white light interferometer uses a white light source as a light source and an optical path interferometer such as a Michelson type or Mirau type to measure the three-dimensional shape of the surface of the object in a non-contact manner.

[0003] Patent Document 1 discloses a shape measuring device that measures the height of a surface to be measured in the optical axis direction by interfering measurement light that is irradiated from a light source onto the surface of an object to be measured through an objective lens and reflected by the surface, with reference light that is irradiated from a light source onto a reference surface through an objective lens and reflected by the reference surface. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-099787 Summary of the Invention [Problem to be solved by the invention]

[0005] In the scanning white light interferometer (white light interference microscope) shown in Figure 15, light L0 from a light source is split by a beam splitter 24b into measurement light L1i and reference light L2i, which are reflected by the measurement surface Wa and reference surface 24c of the measurement object W, respectively. The measurement light L1r and reference light L2r reflected by the measurement surface Wa and reference surface 24c, respectively, are superimposed on the same optical path by the beam splitter 24b to become combined light L3 (in the following description, the measurement light L1i, L1r and the reference light L2i, L2r may be collectively referred to as measurement light L1 and reference light L2, respectively). The shape (e.g., three-dimensional shape, height, etc.) of the measurement surface Wa of the measurement object W can be measured by determining the contrast or phase change of the interference pattern (interference fringes) obtained from this combined light L3.

[0006] Fig. 15(a) shows an example in which the measurement light L1i collected by the objective lens 24a is focused on the measurement surface Wa of the measurement object W. In the following description, the position at which the measurement light L1i is focused on the measurement surface Wa (the positional relationship between the objective lens 24a and the measurement object W when the measurement light L1i is focused on the measurement surface Wa) as shown in Fig. 15(a) is referred to as the focusing position. Note that in the example shown in Fig. 15(a), the optical path length (measurement optical path length) D1(a) of the measurement light L1 is different from the optical path length (reference optical path length) D2(a) of the reference light L2 (D1(a) ≠ D2(a)).

[0007] On the other hand, FIG. 15(b) shows an example in which the measurement optical path length D1(b) and the reference optical path length D2(b) are the same (D1(b) = D2(b)). In this case, the phases of the measurement light L1r and the reference light L2r are the same. In the following description, the position where the measurement optical path length D1(b) and the reference optical path length D2(b) are the same (the positional relationship between the objective lens 24a, the beam splitter 24b, the measurement object W, and the reference surface 24c when the measurement optical path length D1(b) and the reference optical path length D2(b) are the same) is referred to as the interference position (interference fringe generation position). Note that in the example shown in FIG. 15(b), the measurement light L1i collected by the objective lens 24a is not focused on the measurement surface Wa of the measurement object W.

[0008] 15(b), when the measurement light L1i is not focused on the measurement surface Wa, the shape of the measurement surface Wa obtained from the combined light L3 (measured shape F12 in FIG. 16) becomes distorted compared to the actual shape (actual shape F10 in FIG. 16). Furthermore, because the light intensity of the combined light L3 decreases, a decrease in sensitivity may occur, resulting in a decrease in measurement accuracy or even inability to perform measurement.

[0009] Therefore, in the white light interference microscope described above, the focal position and the reference position are adjusted to coincide with each other. Specifically, the measurement light L1i condensed by the objective lens 24a is focused on the measurement surface Wa of the measurement target W, and the measurement optical path length D1 and the reference optical path length D2 are adjusted to coincide with each other.

[0010] In adjusting the white light interference microscope as described above, an operator manually adjusts the position of each optical element while observing a flat substrate on which a pattern is printed and visually checking the focusing state. The operator then manually adjusts the position of the objective lens 24a so that the focusing position on the pattern matches the interference position, and checks the adjustment results.

[0011] In order to ensure the measurement accuracy of the white light interference microscope as described above, it is preferable to frequently adjust and check the white light interference microscope, for example, whenever the measurement object W and the measurement location are changed. However, because the frequency of adjustment and check of the white light interference microscope depends on the operator, there is a possibility that the measurement object W will be measured in an improperly adjusted state in which adjustment has not been performed sufficiently, which can result in the leakage of low-accuracy, unreliable data.

[0012] The present invention has been made in view of the above circumstances, and has an object to provide a method for adjusting a shape measuring device that can easily adjust a white light interferometer. [Means for solving the problem]

[0013] In order to achieve the above-mentioned object, a first aspect of the present invention is a method for adjusting a shape measuring device in which light from a light source is irradiated onto an adjustment master and a reference surface as measurement light and reference light, respectively, and the shape of the measured surface of a measurement object is measured using the combined light of the measurement light and reference light reflected by the adjustment master and the reference surface, respectively, and the method comprises the steps of acquiring an image of the adjustment master for each of a plurality of scanning positions along a scanning direction perpendicular to the adjustment master, calculating a matching parameter indicating the degree of matching between the focus position and the interference position from the image for each scanning position, and calculating a target setting position of the reference surface based on the matching parameter.

[0014] In the method for adjusting a shape measuring device according to the second aspect of the present invention, in the first aspect, the matching parameter is calculated based on a first parameter which is the difference in brightness along a direction on the surface of pixels included in an image of the adjustment master for each scanning position, and a second parameter which is the difference in brightness along the scanning direction.

[0015] A method for adjusting a shape measuring device according to a third aspect of the present invention, in the first or second aspect, comprises the steps of calculating a degree of match parameter for each position of the reference surface, and calculating a target setting position of the reference surface based on the degree of match parameter calculated for each position of the reference surface.

[0016] In the method for adjusting a shape measuring device according to the fourth aspect of the present invention, in the second aspect, the target setting position of the reference surface is a position obtained by moving the reference surface by the difference between the peak values ​​of the first parameter and the second parameter from the position of the reference surface when the image used to calculate the degree of match parameter was acquired. [Effects of the Invention]

[0017] According to the present invention, by calculating the degree-of-match parameter from the image of the adjustment master for each scanning position, it becomes possible to easily adjust the shape measuring device. [Brief explanation of the drawings]

[0018] [Figure 1]FIG. 1 is a diagram showing a shape measuring device according to one embodiment of the present invention. [Figure 2] FIG. 2 shows images of the master acquired at each scanning position. [Figure 3] FIG. 3 is a diagram for explaining an example of calculation of the horizontal contrast parameter. [Figure 4] FIG. 4 is a diagram for explaining an example of calculation of the vertical contrast parameter. [Figure 5] FIG. 5 is a diagram showing an example of calculation of the horizontal contrast parameter. [Figure 6] FIG. 6 is a graph showing the relationship between the horizontal contrast parameter and the vertical contrast parameter and the scanning position (Z position). [Figure 7] FIG. 7 is a graph showing the relationship between the degree of match parameter and the position of the reference surface. [Figure 8] FIG. 8 is a flowchart showing a method for adjusting a shape measuring device according to one embodiment of the present invention. [Figure 9] FIG. 9 is a diagram showing an example of interference fringes. [Figure 10] FIG. 10 is a graph showing the effect of interference fringes on the calculation of the transverse contrast parameter. [Figure 11] FIG. 11 is a diagram illustrating an installation form of the master according to the third embodiment. [Figure 12] FIG. 12 is a diagram illustrating an example of a kernel according to the third embodiment. [Figure 13] FIG. 13 is a diagram showing a shape measuring device according to the first modification. [Figure 14] FIG. 14 is a diagram showing a shape measuring device according to the second modification. [Figure 15] FIG. 15 is a diagram showing an example of a white light interference microscope. [Figure 16] FIG. 16 is a diagram showing the relationship between the actual shape and the measured waveform. DETAILED DESCRIPTION OF THE INVENTION

[0019] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a method for adjusting a shape measuring device according to the present invention will now be described with reference to the accompanying drawings.

[0020] [Shape measuring device] 1 is a diagram showing a shape measuring device according to one embodiment of the present invention, in which, of the mutually orthogonal X, Y and Z directions in the figure, the X and Y directions are parallel to the horizontal direction, and the Z direction is parallel to the vertical direction.

[0021] As shown in FIG. 1, the shape measuring device 1 includes a white light interferometer 10, a driving mechanism 12, a scale 14, and a data processing unit 100.

[0022] The white light interference microscope 10 is a Michelson-type scanning white light interference microscope. The white light interference microscope 10 includes a light source unit 20, a beam splitter 22, an interference objective lens 24, an imaging lens 26, and a camera 28. The interference objective lens 24, the beam splitter 22, the imaging lens 26, and the camera 28 are arranged in this order from the measurement surface Wa upward in the Z direction. The light source unit 20 is also arranged at a position facing the beam splitter 22 in the X direction (or the Y direction).

[0023] Under the control of the data processing unit 100, the light source unit 20 emits a parallel beam of white light L0 (low-coherence light with little coherence) toward the beam splitter 22. Although not shown, the light source unit 20 includes a light source capable of emitting white light L0, such as a light-emitting diode, a semiconductor laser, a halogen lamp, or a high-intensity discharge lamp, and a collector lens that converts the white light L0 emitted from the light source into a parallel beam.

[0024] A half mirror, for example, is used as the beam splitter 22. The beam splitter 22 reflects a portion of the white light L0 incident from the light source unit 20 as measurement light L1i toward the interference objective lens 24 located downward in the Z direction. The beam splitter 22 also transmits a portion of combined light L3 (described below) incident from the interference objective lens 24 toward the upper side in the Z direction, and emits this combined light L3 toward the imaging lens 26.

[0025] The interference objective lens 24 is a Michelson type and includes an objective lens 24a, a beam splitter 24b, and a reference surface 24c. The beam splitter 24b and the objective lens 24a are arranged in this order from the measurement surface Wa upward in the Z direction, and the reference surface 24c is arranged opposite the beam splitter 24b in the X direction (or the Y direction). The following explanation will be given using a Michelson type interference optical system, but the interference optical system is not limited to the Michelson type, and known interference optical systems such as a Mirau type or Linnik type can also be used.

[0026] The objective lens 24a has a light-condensing effect, and condenses the measurement light L1 incident from the beam splitter 22 onto the measurement surface Wa through the beam splitter 24b.

[0027] The beam splitter 24b corresponds to the interference unit of the present invention, and is, for example, a half mirror. The beam splitter 24b splits a portion of the white light L0 incident from the objective lens 24a as reference light L2i, transmits the remaining measurement light L1i, and emits it to the measurement surface Wa, while reflecting the reference light L2i toward the reference surface 24c. Note that the symbol D1 in the figure indicates the measurement optical path length, which is the optical path length of the measurement light L1 between the beam splitter 24b and the measurement surface Wa. After transmitting through the beam splitter 24b, the measurement light L1i is irradiated onto the measurement surface Wa, and is reflected by the measurement surface Wa and returns to the beam splitter 24b.

[0028] The reference surface 24c is, for example, a reflecting mirror, and reflects the reference light L2i incident from the beam splitter 24b toward the beam splitter 24b. The position of this reference surface 24c in the X direction can be manually adjusted by a position adjustment mechanism (e.g., a ball screw mechanism, an actuator, etc.) not shown. This makes it possible to adjust the reference optical path length D2, which is the optical path length of the reference light L2 between the beam splitter 24b and the reference surface 24c. This reference optical path length D2 is adjusted to match (or approximately match) the measurement optical path length D1.

[0029] The beam splitter 24b generates a combined light L3 from the measurement light L1 returning from the measurement surface Wa and the reference light L2 returning from the reference surface 24c, and emits this combined light L3 toward the objective lens 24a on the upper side in the Z direction. This combined light L3 passes through the objective lens 24a and the beam splitter 22 and enters the imaging lens 26.

[0030] The imaging lens 26 forms an image of the combined light L3 incident from the beam splitter 22 on an imaging plane (not shown) of the camera 28. Specifically, the imaging lens 26 forms an image of a point on the focal plane of the objective lens 24a as an image point on the imaging plane of the camera 28.

[0031] Although not shown, the camera 28 includes a CCD (Charge Coupled Device) or CMOS (Complementary Metal Oxide Semiconductor) imaging element. The camera 28 captures an image of the combined light L3 formed on an imaging surface by the imaging lens 26, processes the imaging signal of the combined light L3 obtained by this imaging, and outputs the captured image.

[0032] The driving mechanism 12 corresponds to the scanning unit of the present invention. The driving mechanism 12 is composed of a linear motor or a motor driving mechanism, and holds the white light interferometer 10 so that it can move freely in the Z direction, which is the scanning direction. Under the control of the data processing unit 100, the driving mechanism 12 scans the white light interferometer 10 along the Z direction.

[0033] The drive mechanism 12 only needs to be able to relatively scan the white light interferometer 10 in the Z direction with respect to the measurement surface Wa, and may, for example, scan the measurement surface Wa (the support portion that supports the measurement surface Wa) in the Z direction.

[0034] The scale 14 is a position detection sensor, such as a linear scale, that detects the Z-direction position of the white light interferometer 10. The scale 14 repeatedly detects the Z-direction position of the white light interferometer 10 and repeatedly outputs the position detection result to the data processing unit 100.

[0035] The data processing unit 100 controls the measurement operation of the three-dimensional shape of the measurement target surface Wa by the white light interferometer microscope 10 (shape measuring device 1) in response to operation input from the operation unit 108, and performs calculations of the three-dimensional shape of the measurement target surface Wa, etc. The data processing unit 100 includes a processor (e.g., a CPU (Central Processing Unit), a GPU (Graphics Processing Unit), etc.) that executes various calculations, memory (e.g., a ROM (Read Only Memory) and a RAM (Random Access Memory)), etc.) that serves as a working area for the processor, and a storage device (e.g., an SSD (Solid State Drive) or an HDD (Hard Disk Drive), etc.) for storing various programs and data.

[0036] The data processing unit 100 is capable of realizing various functions (shape measurement unit 102, matching parameter calculation unit 104, and matching determination unit 106) described below by executing programs stored in storage using a processor.

[0037] The functions of the data processing unit 100 may be realized by one processor, or by multiple processors of the same or different types. Also, the functions of the data processing unit 100 may be realized by a general-purpose computer.

[0038] The operation unit 108 includes operation members (for example, a keyboard, a mouse, etc.) for receiving operation inputs to the data processing unit 100 by an operator.

[0039] The output unit 110 is a device for outputting the results of program execution by the data processing unit 100, data of calculation results, etc. The output unit 110 includes, for example, an operation UI (User Interface) and a monitor (for example, a liquid crystal display, etc.) for displaying the detection results. The output unit 110 may also include a printer, a speaker, etc. in addition to or instead of the monitor.

[0040] [Procedure for adjusting the shape measurement device] The data processing unit 100 uses the measurement results of the adjustment master M (hereinafter referred to as master M) to calculate a matching parameter indicating the degree of matching between the focus position and the interference position (the matching parameter indicating the degree of matching for the measurement light L1i to be focused on the master M and for the measurement light L1r and reference light L2r to interfere with each other).Then, using this matching parameter, it becomes possible to evaluate the degree of matching between the focus position and the interference position and adjust the shape measuring device 1.

[0041] (matching parameter) Next, the procedure for calculating the degree-of-match parameter will be described.

[0042] In this embodiment, a master M on which a pattern is printed is used as a measurement object, and images of the pattern on the surface of the master M are repeatedly acquired while the white light interferometer 10 is scanned in the Z direction by the drive mechanism 12.

[0043] Here, the master M may be, for example, a flat plate having an arbitrary shape pattern formed on its surface. The pattern formed on the surface of the master M may be, for example, all or part of a pattern used in various resolution charts, such as a radial (star chart), a checkered pattern, a grid chart, a USAF 1951 target (United States Air Force MIL-STD-150A standard of 1951), or a resolution chart conforming to ISO 12233 (ISO: International Organization for Standardization) (CIPA (Camera & Imaging Products Association) resolution chart). Furthermore, the master M may also be a roughness standard (e.g., a pseudo-roughness standard, a random-shape roughness standard, etc.). The types of shape patterns are not limited to those exemplified above.

[0044] The data processing unit 100 detects the scanning position Z iMaster M's Images per I i is acquired from the white light interference microscope 10. Here, i is a frame number indicating the scanning position in the Z direction, and i=1, 2, ..., N (N≧2) (see FIG. 2).

[0045] The matching parameter calculation unit 104 calculates a first parameter (a parameter for evaluating horizontal contrast, hereinafter referred to as the horizontal contrast parameter) relating to the XY directions on the screen (XY plane) of the camera 28, and a second parameter (a parameter for evaluating vertical contrast, hereinafter referred to as the vertical contrast parameter) relating to the time axis direction (i.e., frame number or Z direction).The matching parameter calculation unit 104 then calculates the scanning position Z from the correlation between the horizontal contrast parameter and the vertical contrast parameter and the scanning position in the Z direction. i Calculate the matching parameter for each.

[0046] The match determination unit 106 determines the scan position Z i The position of the reference surface 24c at which the degree of match is maximum is calculated from the degree-of-match parameters for each point.

[0047] This allows the reference surface 24c to be moved to a position where the degree of match is maximized, making it possible to easily adjust the shape measuring instrument 1.

[0048] 3 and 4 are diagrams for explaining examples of calculation of the horizontal contrast parameter and the vertical contrast parameter, respectively. In the following explanation, i Let the brightness of pixel (x,y) at i(x,y) Let's say.

[0049] When calculating the transverse contrast parameters, image I i For pixel (x, y), the difference in brightness Cp between the adjacent pixels ((x-1, y-1), (x-1, y), (x-1, y+1), (x, y-1), (x, y+1), (x+1, y-1), (x+1, y) and (x+1, y+1)) shown in Figure 3(a) is i(x,y) Calculate.

[0050] Specifically, Cp i(x,y) is the brightness value P of pixel (x,y) and its neighboring pixels. i(x,y) It can be obtained by multiplying the kernel (coefficient) shown in Figure 3(b) by the kernel (coefficient) shown in Figure 3(b). When the kernel (coefficient) shown in Figure 3(b) is applied, Cp i(x,y) is expressed by the following equation (1).

[0051] Cp i(x,y) =|4×P i(x,y) -P i(x-1,y) -P i(x+1,y) -P i(x,y-1) -P i(x,y+1) | ...(1) When calculating the vertical contrast parameters, image I i For pixel (x, y), the image I in the Z direction shown in Figure 4(a) i-1 ,I i+1 The difference in brightness between the pixels at the same position is Ct i(x,y) Calculate.

[0052] Specifically, Ct i(x,y) is the brightness value P of pixel (x,y) and its neighboring pixels. i(x,y) It can be obtained by multiplying the kernel (coefficient) shown in Figure 4(b) by the kernel (coefficient) shown in Figure 4(b). When the kernel (coefficient) shown in Figure 4(b) is applied, Ct i(x,y) is expressed by the following equation (2).

[0053] Ct i(x,y) =|2×P i(x,y) -P (i-1)(x,y) -P (i+1)(x,y) | ...(2) Note that the methods of selecting adjacent pixels shown in Figures 3(a) and 4(b) and the kernels shown in Figures 3(b) and 4(b) are merely examples, and the method of calculating parameters is not limited to the above. For example, for pixels at the ends in the X and Y directions or the end in the Z direction, the method of selecting adjacent pixels or the kernel may be changed.

[0054] Figure 5 shows the horizontal contrast parameter Cp i(x,y)For example, as shown in FIG. 5, i(x,y) When calculating the contrast value (degree of focus), the absolute value of the sum of the luminance values ​​of the neighboring pixels ((x-1,y-1), (x-1,y), (x-1,y+1), (x,y-1), (x,y+1), (x+1,y-1), (x+1,y) and (x+1,y+1)) of the pixel of interest (x,y) is used.

[0055] The horizontal contrast parameter and vertical contrast parameter (Cp, Ct) can be calculated for all pixels in the image Ii or for some extracted pixels, and the sum or median value can be used to calculate the matching parameter.

[0056] Next, as described above, each image I1 to I N For the horizontal contrast parameters Cp1 to Cp N and vertical contrast parameters Ct1~Ct N Calculate the scanning position Z i Correlate with.

[0057] 6 is a graph showing the relationship between the horizontal contrast parameter and the vertical contrast parameter and the scanning position (Z position). In FIG. 6, curves Cp and Ct represent the horizontal contrast parameters Cp1 to Cp N and vertical contrast parameters Ct1 to Ct N is an approximation curve (for example, a curve obtained by least squares approximation or polynomial approximation).

[0058] The matching parameter calculation unit 104 calculates the scanning positions (Zp, Zt) at which the horizontal contrast parameter Cp and the vertical contrast parameter Ct reach their peaks (maximums), respectively. Then, the matching parameter calculation unit 104 calculates a parameter |Zp-Zt| indicating the degree to which Zp and Zt match, as a parameter indicating the degree of match between the in-focus position and the interference position.

[0059] Next, the same measurement is performed while changing the position of the reference surface 24c. The match determination unit 106 then calculates the target setting position of the reference surface 24c from the relationship between the position of the reference surface 24c and the match parameter.

[0060] Fig. 7 is a graph showing the relationship between the degree of match parameter and the position of the reference surface. Fig. 7 shows the value of the degree of match parameter |Zp-Zt| calculated for each position on the reference surface 24c and its approximation curve (for example, a curve obtained by least squares approximation or polynomial approximation).

[0061] The match determination unit 106 searches for the position of the reference surface 24c where the value of the match parameter |Zp-Zt| is minimum, and adopts that position as the target setting position Ao of the specified reference surface.

[0062] In this embodiment, the absolute difference |Zp-Zt| is used as the matching parameter, but the present invention is not limited to this. For example, any parameter indicating the degree of matching between Zp and Zt, such as the square of the difference (Zp-Zt), {min(Zp,Zt) / max(Zp,Zt)}, or [1-{min(Zp,Zt) / max(Zp,Zt)}], can also be used as the matching parameter. Note that when the square of the difference (Zp-Zt) is used as the matching parameter, the position of the reference surface 24c where the matching parameter is minimum can be set as the target setting position. When {min(Zp,Zt) / max(Zp,Zt)} is used as the matching parameter, the position of the reference surface 24c where the matching parameter is closest to 1 can be set as the target setting position. Furthermore, when [1-{min(Zp,Zt) / max(Zp,Zt)}] is used as the degree of match parameter, the position of the reference surface 24c where the degree of match parameter is closest to 0 may be set as the target setting position.

[0063] (Timing for checking match) The following examples are possible timings (time conditions) for checking the degree of match using the master M.

[0064] (a) A check is performed when the number of measurements of the measurement target W exceeds a certain value. In this case, by limiting the number of measurements, it is possible to limit the maximum number of measurements of the measurement target W that are performed in a poorly adjusted state.

[0065] (b) Confirmation is performed after a certain time or a certain number of days have passed. In this case, even if measurement of the measurement object W is performed in a misadjusted state, the measurement object W and measurement data measured in a misadjusted state can be identified by the measurement date, etc. This makes it possible to easily trace the measurement data measured in a misadjusted state and perform remeasurements.

[0066] (c) Check is performed at the start of a measurement batch (e.g., lot). In this case, the measurement target W measured in a misaligned state is limited to the batch. This makes it easy to trace measurement data measured in a misaligned state, and enables remeasurement.

[0067] The timing of the confirmation is not limited to the above examples, and the operator may be able to select or set the above (a) to (c) or a combination thereof.

[0068] [Method for adjusting the shape measurement device] FIG. 8 is a flowchart showing a method for adjusting a shape measuring device according to one embodiment of the present invention.

[0069] First, the master M is set on the stage ST of the white light interferometer 10 (step S10), and the white light interferometer 10 is set to an initial position in the Z direction by the driving mechanism 12 (step S12).

[0070] Next, acquisition of an image of the master M (step S14) and scanning in the Z direction of the white light interference microscope 10 (step S18) are repeated. When scanning in the Z direction is completed (Yes in step S16, each scanning position Z i Image I i A matching parameter is calculated from (step S20).

[0071] Next, the reference surface 24c is scanned in the X direction (step S24), and steps S12 to S20 are repeated. When scanning of the reference surface 24c is completed (Yes in step S22), the target setting position Ao of the reference surface 24c is calculated based on the matching parameter (see FIG. 7) (step S26). Then, the reference surface 24c is moved to the target setting position Ao, thereby completing the adjustment of the shape measuring device 1.

[0072] According to this embodiment, the target position of the reference surface 24c can be calculated numerically, so that the position of the reference surface 24c can be adjusted with high accuracy. Furthermore, the reproducibility of the adjustment of the position of the reference surface 24c can be improved without depending on the individual differences or standards of the operator.

[0073] [Example 1] The distance difference between the peak position Zp (indicating the in-focus position) where the horizontal contrast parameter Cp shown in Figure 7 reaches its peak value and the peak position Zt (indicating the interference position) where the vertical contrast parameter Ct reaches its peak value indicates the optical path difference between the measurement optical path length D1 and the reference optical path length D2.

[0074] The position of the reference surface 24c can be moved by (Zp-Zt) to obtain the target setting position Ao of the reference surface 24c.

[0075] According to the first embodiment, it is not necessary to perform contrast measurement (the loop of steps S22 to S24) while changing the position of the reference surface 24c, so that the shape measuring device 1 can be adjusted in a shorter time, which contributes to improving the efficiency of the device.

[0076] [Example 2] If the interference position is close to the in-focus position (for example, if the deviation is within the range of the focal depth), interference fringes will appear on the screen of camera 28 when calculating the horizontal contrast parameter Cp, as shown in FIG. 9. These interference fringes have an adverse effect on the calculation of the horizontal contrast parameter Cp, resulting in a problem of reduced calculation accuracy for Zp, which indicates the in-focus position, as shown in FIG. 10. In FIG. 10, the shape of the horizontal contrast parameter Cp is distorted like Cpf, and the peak position is shifted from Zp to Zpf. In particular, if the installation angle of master M is to a certain extent, light and dark areas due to interference fringes will be more likely to appear on the screen of camera 28.

[0077] In the second embodiment, when calculating the horizontal contrast parameter Cp, a process is performed in which pixels whose brightness is near the maximum or minimum value of the camera 28 are excluded from the calculation of the horizontal contrast parameter Cp. For example, if the resolution of each pixel is 8 bits (0 to 255), calculation is not performed for pixels whose brightness is near 0 (for example, 0 to 9) or near 255 (for example, 246 to 255), and values ​​calculated for pixels outside the above ranges are used.

[0078] According to the second embodiment, it is possible to eliminate the influence of whiteout and blackout, which are factors that reduce the accuracy of calculation of the horizontal contrast parameter, and therefore it is possible to calculate the horizontal contrast peak with higher accuracy, thereby improving the accuracy and reliability of the three-dimensional shape measurement results of the shape measuring device 1.

[0079] [Example 3] In Example 3, as shown in FIG. 11(b), the master M is installed tilted in a specific direction with respect to the measurement optical axis AX. Here, the tilt amount of the master M is preferably set so that, for example, multiple interference fringes occur within one field of view. If the field of view range is 1 mm square, the height per mm is 0.55 μm (approximately the wavelength). In this case, the tilt angle φ shown in FIG. 11(a) is φ = arctan (0.55 μm / 1 mm). Note that the field of view range differs depending on the magnification of the objective lens.

[0080] Then, as shown in FIG. 11(a), the horizontal contrast is calculated in a direction perpendicular to the direction D1 in which the bright and dark pattern of the interference fringes occurs.

[0081] In FIG. 11, the direction D1 in which the light and dark patterns of the interference fringes occur is the X direction. In this case, the horizontal contrast parameter Cp is calculated using, for example, a kernel such as that shown in FIG. 12. In the kernel shown in FIG. 12, the coefficients for pixels adjacent to the central pixel of interest in the X direction are set to 0. By using such a kernel, the horizontal contrast can be calculated in a direction perpendicular to the direction D1 in which the light and dark patterns of the interference fringes occur.

[0082] According to the third embodiment, the influence of contrast caused by interference fringes can be suppressed, and therefore it is possible to calculate the peak of the horizontal contrast with higher accuracy.

[0083] [Variation 1] FIG. 13 is a diagram showing a shape measuring device according to the first modification.

[0084] As shown in FIG. 13, a profile measuring apparatus 1A according to the first modification adjusts the position of a reference surface 24c using a temperature regulator (a temperature sensor 34 and a temperature control unit 112).

[0085] As shown in FIG. 13, in the shape measuring apparatus 1A, the interference objective lens 24 includes a holder 24d.

[0086] Holder 24d is made of a metallic material such as brass, i.e., a material that undergoes reversible thermal deformation. Holder 24d includes lens barrel 24d1 and reference surface storage section 24d2. Lens barrel 24d1 is formed in a cylindrical shape extending in the Z direction and stores (holds) objective lens 24a and beam splitter 24b. Reference surface storage section 24d2 is formed in a cylindrical shape extending in the X direction from a holding position of beam splitter 24b on lens barrel 24d1 and stores reference surface 24c.

[0087] The temperature adjustment unit 32 is provided near the reference surface housing portion 24d2, and adjusts the temperature between at least the beam splitter 24b and the reference surface 24c, i.e., the temperature of the reference surface housing portion 24d2, under the control of the temperature control unit 112. As the temperature adjustment unit 32, for example, a heater, a Peltier element, or the like is used.

[0088] The reference surface housing portion 24d2 is made of a material that undergoes reversible thermal deformation, and therefore undergoes reversible thermal deformation (expansion or contraction) in response to temperature changes. This allows the temperature of the reference surface housing portion 24d2 to be changed by the temperature adjustment portion 32, thereby thermally deforming the reference surface housing portion 24d2 and adjusting the X-direction position of the reference surface 24c in response to this thermal deformation.

[0089] The temperature sensor 34 corresponds to the temperature measurement unit of the present invention. The temperature sensor 34 is provided near the reference surface housing unit 24d2, measures the temperature of at least the reference surface housing unit 24d2 (between the beam splitter 24b and the reference surface 24c) in the holder 24d, and outputs the temperature measurement result to the temperature acquisition unit 116 of the temperature control unit 112. The measurement result of the temperature sensor 34 is used for the control of the temperature adjustment unit 32 by the temperature control unit 112.

[0090] The heat insulating material 30 is provided so as to cover the entire interference objective lens 24, the temperature adjusting unit 32, and the temperature sensor 34. This prevents the temperature inside the heat insulating material 30, particularly the temperature of the reference surface housing unit 24d2 and its vicinity, from changing due to external influences.

[0091] As shown in FIG. 13, the temperature control unit 112 includes a control target temperature storage unit 114, a temperature acquisition unit 116, a calculation processing unit 118, and an output control unit 120.

[0092] The control target temperature storage unit 114 stores a lookup table LUT that indicates the correspondence between the temperature inside the holder 24d (for example, the temperature of the reference surface storage unit 24d2, the temperature between the beam splitter 24b and the reference surface 24c) and the position (position in the X direction) of the reference surface 24c.

[0093] The calculation processing unit 118 refers to the LUT stored in the control target temperature storage unit 114 and calculates the output of the temperature adjustment unit 32 required to move the reference surface 24c to the set target position. Specifically, the calculation processing unit 118 reads out the temperature (control target temperature) inside the holder 24d corresponding to the set target position of the reference surface 24c from the LUT, and calculates the output of the temperature adjustment unit 32 to bring the temperature inside the holder 24d to the control target temperature.

[0094] The output control unit 120 controls the output of the temperature adjustment unit 32 based on the calculation results of the calculation processing unit 118, and adjusts the temperature inside the holder 24d to the control target temperature. Here, the temperature control inside the holder 24d can be performed by, for example, feedback control, PID control (Proportional-Integral-Differential Controller), etc.

[0095] According to the first modification, the position of the reference surface 24c can be managed using a numerical value, that is, temperature, and therefore adjustment can be performed with higher accuracy, higher resolution, and higher reproducibility.

[0096] [Variation 2] FIG. 14 is a diagram showing a shape measuring device according to the second modification.

[0097] As shown in FIG. 14, a shape measuring apparatus 1B according to the second modification uses a linear motion mechanism using a motor M to adjust the position of a reference surface 24c.

[0098] The motor control unit 130 acquires the position of the reference surface 24c in the X direction and controls (feedback control, PID control) the amount of rotation of the motor M to move the reference surface 24c to a set target position.

[0099] According to the second modification, the position of the reference surface 24c can be controlled using the motor M, which allows adjustment with higher accuracy, higher resolution, and higher reproducibility. Although the second modification employs a linear motion mechanism using the motor M, the present invention is not limited to this. For example, it is also possible to employ a linear motion mechanism using an actuator such as a piezoelectric element. [Explanation of symbols]

[0100] 1, 1A, 1B... Shape measuring device, 10... White light interference microscope, 12... Drive mechanism, 14... Scale, 16... Switching mechanism, 20... Light source unit, 22... Beam splitter, 24... Interference objective lens, 24a... Objective lens, 24b... Beam splitter, 24c... Reference surface, 24d... Holder, 26... Imaging lens, 28... Camera, 30... Heat insulating material, 32... Temperature adjustment unit, 34... Temperature sensor, 100... Data processing unit, 102... Shape measurement unit, 104... Matching parameter calculation unit, 106... Matching determination unit, 108... Operation unit, 110... Output unit, 112... Temperature control unit, 114... Control target temperature storage unit, 116... Temperature acquisition unit, 118... Calculation processing unit, 120... Output control unit, 130... Motor control unit

Claims

1. A method for adjusting a shape measuring device, comprising: irradiating an adjustment master and a reference surface with light from a light source as measurement light and reference light, respectively; and measuring a shape of a surface to be measured of a measurement object using multiplexed light of the measurement light and the reference light reflected by the adjustment master and the reference surface, respectively; acquiring an image of the adjustment master for each of a plurality of scanning positions along a scanning direction perpendicular to the adjustment master, and calculating a matching degree parameter indicating a matching degree between a focus position and an interference position from the image for each of the scanning positions; calculating a target set position of the reference surface based on the match parameter; A method for adjusting a shape measuring device comprising:

2. 2. The method for adjusting a shape measuring device according to claim 1, wherein the degree of match parameter is calculated based on a first parameter which is a difference in luminance along a direction on the surface of pixels included in the image of the adjustment master for each scanning position, and a second parameter which is a difference in luminance along the scanning direction.

3. calculating the degree of match parameter for each position of the reference surface; calculating the target set position of the reference surface based on the degree of match parameter calculated for each position of the reference surface; The method for adjusting a shape measuring device according to claim 1 or 2, comprising:

4. 3. The method for adjusting a shape measuring device according to claim 2, wherein the target setting position of the reference surface is a position obtained by moving the reference surface by the difference between the peak values ​​of the first parameter and the second parameter from the position of the reference surface when the image used to calculate the degree of match parameter was acquired.

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