Surface shape measuring device and surface shape measurement method

Abstract

To provide a surface shape measuring device and a surface shape measurement method capable of easily and efficiently measuring a surface shape of a measurement surface of an object in which a transparent material is disposed.SOLUTION: A surface shape measuring device includes: a light source section; an interference section for generating interference light between measurement light reflected by a measurement surface and reference light reflected by a reference surface; a light detection section for generating a detection signal of interference light; a surface shape data calculation section for calculating surface shape data showing a height position of the surface of a measurement surface on the basis of a change in strength of a detection signal; a distribution calculation section for calculating distribution of a transparent material on the basis of sensitivity data showing detection sensitivity of a detection signal for each position of a measurement surface; an estimation section for estimating base material shape data showing a height position of the surface of a base material in a transparent area in which a transparent material is disposed from surface shape data in a non-transparent area in which no transparent materials are disposed on a measurement surface on the basis of distribution of the transparent material; and a shape data correction section for correcting surface shape data of a transparent area on the basis of base material shape data.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a surface shape measurement apparatus and a surface shape measurement method for measuring the surface shape of a measurement surface of a measurement object on which a transparent material is disposed.

Background Art

[0002] Conventionally, a surface shape measurement apparatus using light has been known for measuring the surface shape of a measurement surface of a measurement object. For example, a surface shape measurement apparatus employing a white light interference method measures the surface shape of a measurement surface of a measurement object by utilizing the interference phenomenon of white light.

[0003] In such a surface shape measurement apparatus using light, when a transparent material is present on the measurement surface of the measurement object, it may be difficult to accurately measure the surface shape of the measurement surface of the measurement object due to the influence of the refractive index of the transparent material.

[0004] For example, Patent Document 1 discloses a measurement apparatus for measuring the film thickness of a transparent material using a white light interference method. In this measurement apparatus, the refractive index of one of the transparent materials applied to the measurement object is measured and stored, and the film thickness of the remaining transparent materials is measured using the stored refractive index.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, in the measurement apparatus of Patent Document 1, information indicating how the transparent material is distributed on the measurement surface of the measurement object is required. Therefore, when such information is not available, it is necessary to identify the transparent material in advance, which causes a factor that the measurement work becomes complicated.

[0007] The present invention has been made in view of such circumstances, and an object thereof is to provide a surface shape measuring apparatus and a surface shape measuring method capable of easily and efficiently measuring the surface shape of a measurement surface of a measurement object on which a transparent material is disposed without causing complication of measurement work.

Means for Solving the Problems

[0008] The surface shape measuring apparatus according to the first aspect is a surface shape measuring apparatus that measures the surface shape of a measurement surface of an object including a base material and a transparent material on the base material, and includes a light source unit having a light source that emits light, and divides the light emitted from the light source into measurement light and reference light, emits the measurement light to the measurement surface and emits the reference light to the reference surface, and generates interference light between the measurement light reflected from the measurement surface and the reference light reflected from the reference surface. An interference unit, a light detection unit that detects a detection signal indicating the interference light, and a surface shape data calculation unit that calculates surface shape data indicating the height position of the surface of the measurement surface based on the change in the intensity of the detection signal when the optical path length difference between the measurement light and the reference light is changed. And a distribution calculation unit that calculates the distribution of the transparent material on the measurement surface based on the sensitivity data indicating the detection sensitivity of the detection signal for each position on the measurement surface, and based on the distribution of the transparent material calculated by the distribution calculation unit, from the surface shape data in the non-transparent region where the transparent material is not disposed on the measurement surface, the height position of the surface of the base material in the transparent region where the transparent material is disposed on the measurement surface. An estimation unit that estimates the base material shape data indicating the shape, and a shape data correction unit that corrects the surface shape data in the transparent region based on the base material shape data estimated by the estimation unit.

[0009] In the surface shape measuring apparatus according to the second aspect, the shape data correction unit calculates the thickness of the transparent material based on the difference between the height position of the surface of the base material in the transparent region obtained from the base material shape data and the height position of the surface of the measurement surface in the transparent region obtained from the surface shape data.

[0010] In the surface shape measuring apparatus according to the third aspect, when the difference is d, the refractive index of the transparent material is n, and the thickness of the transparent material is L, the shape data correction unit calculates the thickness of the transparent material using the following formula, L = d / (n - 1).

[0011] In the surface shape measuring apparatus according to the fourth aspect, the shape data correction unit calculates the corrected surface shape data in the transparent region by adding the thickness of the transparent material to the height position of the surface of the base material in the transparent region from the base material shape data.

[0012] In the surface shape measuring apparatus according to the fifth aspect, the light source is a light source capable of emitting white light or wavelength-swept light.

[0013] The surface shape measuring method according to the sixth aspect is a surface shape measuring method for measuring the surface shape of a measurement surface of an object including a base material and a transparent material on the base material, which divides the light emitted from a light source into measurement light and reference light, emits the measurement light to the measurement surface and the reference light to a reference surface, and generates interference light between the measurement light reflected from the measurement surface and the reference light reflected from the reference surface; a light detection step of detecting a detection signal indicating the interference light; a surface shape data calculation step of calculating surface shape data indicating the height position of the surface of the measurement surface based on the change in the intensity of the detection signal when the optical path length difference between the measurement light and the reference light is changed; a distribution calculation step of calculating the distribution of the transparent material on the measurement surface based on sensitivity data indicating the detection sensitivity of the detection signal for each position on the measurement surface; an estimation step of estimating base material shape data indicating the height position of the surface of the base material in the transparent region where the transparent material is disposed on the measurement surface from the surface shape data in the non-transparent region where the transparent material is not disposed on the measurement surface based on the distribution of the transparent material calculated by the distribution calculation step; and a shape data correction step of correcting the surface shape data in the transparent region based on the base material shape data estimated by the estimation step.

[0014] In the surface shape measuring method according to the seventh aspect, the shape data correction step calculates the thickness of the transparent material based on the difference between the height position of the surface of the base material in the transparent region obtained from the base material shape data and the height position of the surface of the measurement surface in the transparent region obtained from the surface shape data.

[0015] In the surface shape measurement method of the eighth aspect, when the difference is d, the refractive index of the transparent material is n, and the thickness of the transparent material is L, the shape data correction step calculates the thickness of the transparent material using the following formula: L = d / (n - 1).

[0016] In the surface shape measurement method of the ninth aspect, the shape data correction step calculates the corrected surface shape data in the transparent region by adding the thickness of the transparent material to the height position of the surface of the substrate in the transparent region from the substrate shape data.

[0017] In the surface shape measurement method of the tenth aspect, the light source is a light source capable of emitting white light or wavelength-swept light.

Advantages of the Invention

[0018] According to the present invention, it is possible to simply and efficiently measure the surface shape of the measurement surface of an object on which a transparent material is disposed without causing complication of the measurement work.

Brief Description of the Drawings

[0019]

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Figure 9

Best Mode for Carrying Out the Invention

[0020] Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.

[0021] FIG. 1 is a schematic diagram of a surface shape measuring apparatus 10 according to an embodiment. Among the XYZ directions orthogonal to each other in the figure, the XY direction is a direction parallel to the horizontal direction, and the Z direction is a direction parallel to the vertical direction.

[0022] As shown in FIG. 1, the surface shape measuring apparatus 10 measures the surface shape (three-dimensional shape) of the measurement surface of a work W, which is an object to be measured, by the white light interference method. The surface shape measuring apparatus 10 generally includes an optical head 12, a drive unit 16, a scale 18, and a control device 20. The surface shape measuring apparatus 10 shown in FIG. 1 includes a stage 22 and a stage drive unit 24. The work W is placed on the stage 22.

[0023] As shown in FIG. 1, the optical head 12 is composed of a Michelson type white light interference microscope. The optical head 12 includes a camera 14, a light source unit 26, a beam splitter 28, an interference objective lens 30, and an imaging lens 32.

[0024] The interference objective lens 30, the beam splitter 28, the imaging lens 32, and the camera 14 are arranged in this order along the upper side in the Z direction from the work W. The light source unit 26 is arranged at a position facing the beam splitter 28 in the X direction (Y direction is also possible).

[0025] Under the control of the control device 20, the light source unit 26 emits white light (low coherence light with little coherence) of a parallel light beam as measurement light L1 toward the beam splitter 28. The light source unit 26 can include a light source 26a capable of emitting measurement light L1 such as a light emitting diode, a semiconductor laser, a halogen lamp, and a high-intensity discharge lamp, and a collector lens that converts the measurement light L1 emitted from the light source 26a into a parallel light beam. The light source unit 26 is an example of the light source unit of the present invention.

[0026] The beam splitter 28 is, for example, a half mirror. The beam splitter 28 reflects a part of the measurement light L1 incident from the light source unit 26 toward the interference objective lens 30 on the lower side in the Z direction. Further, the beam splitter 28 transmits a part of the combined light L3 (described later) incident from the interference objective lens 30 upward in the Z direction and emits the combined light L3 toward the imaging lens 32.

[0027] The interference objective lens 30 is of the Michelson type and includes an objective lens 30A, a beam splitter 30B, and a reference surface 30C. The beam splitter 30B and the objective lens 30A are arranged in order along the upper side in the Z direction from the workpiece W. Further, the reference surface 30C is arranged at a position facing the beam splitter 30B in the X direction (the Y direction is also possible). The beam splitter 30B is, for example, a half mirror.

[0028] The beam splitter 30B divides the measurement light L1 incident from the objective lens 30A into a reference light L2 passing through the reference optical path and a measurement light L1 passing through the measurement optical path. The reference light L2 is irradiated toward the reference surface 30C. The measurement light L1 is irradiated toward the workpiece W. The measurement light L1 transmitted through the beam splitter 30B is irradiated onto the workpiece W and then reflected by the workpiece W and returns to the beam splitter 30B.

[0029] The reference surface 30C is, for example, a reflection mirror and reflects the reference light L2 incident from the beam splitter 30B toward the beam splitter 30B. The position of the reference surface 30C in the X direction can be manually adjusted by a position adjustment mechanism (not shown). Thereby, the optical path length of the reference light L2 between the beam splitter 30B and the reference surface 30C can be adjusted. This reference optical path length is adjusted to be equal (including substantially equal) to the optical path length of the measurement light L1 between the beam splitter 30B and the workpiece W.

[0030] The beam splitter 30B generates a combined light beam L3 of the measurement light L1 returning from the workpiece W and the reference light L2 returning from the reference surface 30C, and emits this combined light beam L3 upward in the Z direction toward the objective lens 30A. This combined light beam L3 passes through the objective lens 30A and the beam splitter 28 and enters the imaging lens 32. The light source used in the white light interference method is a light source that emits white light (low coherence light). Since white light is light with poor coherence, even if the light passing through each of the reference optical path and the measurement optical path is recombined by the beam splitter 30B again, it does not interfere except under specific conditions. The optical path length of the reference light L2 is constant, but the optical path length of the measurement light L1 changes according to the vertical scanning of the optical head 12. As is well known, when the optical path length difference between the measurement light L1 and the reference light L2 becomes zero (including almost zero), the interference between the measurement light L1 and the reference light L2 in all wavelength ranges of visible light is enhanced, so that the signal intensity of the combined light beam L3 becomes maximum. The combined light beam L3 becomes interference light including interference fringes (see, for example, Japanese Patent Application Laid-Open No. 2017-106860). The beam splitter 30B is an example of the interference unit of the present invention. The combined light beam L3 is an example of the interference light of the present invention.

[0031] The imaging lens 32 forms an image of the combined light beam L3 incident from the beam splitter 28 on the imaging surface (not shown) of the camera 14. Specifically, the imaging lens 32 forms an image of a point on the focal plane of the objective lens 30A as an image point on the imaging surface of the camera 14.

[0032] The camera 14 includes a CCD (Charge Coupled Device) type or CMOS (Complementary Metal Oxide Semiconductor) type imaging element. While scanning the optical head 12 in the scanning direction, the camera 14 detects the combined light beam L3 (interference light) imaged on the imaging surface by the imaging lens 32 within the field of view of the camera 14, and generates a detection image 36 (detection signal of interference light) which is the detection result. The camera 14 is an example of the light detection unit of the present invention.

[0033] The drive unit 16 is composed of a known linear motor or a motor drive mechanism. The drive unit 16 holds the optical head 12 so as to be relatively movable in the Z direction, which is the vertical scanning direction (the optical axis direction of the optical head 12), with respect to the workpiece W. Under the control of the control device 20, the drive unit 16 relatively moves the optical head 12 with respect to the workpiece W within the range of the set scanning speed and scanning direction.

[0034] Note that the drive unit 16 only needs to be able to relatively scan the optical head 12 in the scanning direction with respect to the workpiece W. For example, the stage 22 that supports the workpiece W may be scanned in the scanning direction.

[0035] The stage 22 has a stage surface for supporting the workpiece W. The stage surface is composed of a flat surface that is substantially parallel to the X direction and the Y direction. The stage drive unit 24 is composed of a known linear motor or a motor drive mechanism, and relatively horizontally moves the stage 22 with respect to the optical head 12 within the plane perpendicular to the scanning direction (the X direction and the Y direction) under the control of the control device 20.

[0036] Note that the stage drive unit 24 only needs to be able to relatively move the stage 22 in the X direction and the Y direction with respect to the optical head 12. For example, the optical head 12 may be moved in the X direction and the Y direction with respect to the stage 22 that supports the workpiece W.

[0037] The scale 18 is a position detection sensor that detects the scanning direction position of the optical head 12 with respect to the workpiece W. For example, an optical linear encoder (also referred to as a scale) is used. The optical linear encoder is composed of, for example, a linear scale in which slits are formed at regular intervals, and a light receiving element and a light emitting element that are arranged opposite to each other with the linear scale interposed therebetween. The scale 18 repeatedly detects the scanning direction position (Z direction position) of the optical head 12, and repeatedly outputs a position signal 38 including position information indicating the scanning direction position (Z direction position) to the control device 20.

[0038] The control device 20 comprehensively controls the surface shape measuring device 10, such as switching between the adjustment before measuring the workpiece W (pre-adjustment mode) and the measurement of the workpiece W (measurement mode) according to the input operation on the operation unit 21, setting the measurement conditions in each mode, and calculating the three-dimensional shape in the measurement mode. The display unit 23 displays various information under the control of the control device 20. The control device 20 can calculate the surface shape data of the workpiece W from the detection image 36 generated by the camera 14 and the output from the scale 18.

[0039] The control device 20 includes an arithmetic circuit composed of various processors and memories. The various processors include a CPU (Central Processing Unit), a GPU (Graphics Processing Unit), an ASIC (Application Specific Integrated Circuit), and programmable logic devices [such as SPLD (Simple Programmable Logic Devices), CPLD (Complex Programmable Logic Device), and FPGA (Field Programmable Gate Arrays)]. Note that the various functions of the control device 20 may be realized by one processor or by a plurality of processors of the same type or different types.

[0040] FIG. 2 is a functional block diagram of the control device 20. As shown in FIG. 2, the camera 14 and the light source unit 26 of the optical head 12, the drive unit 16, the stage drive unit 24, the scale 18, and the operation unit 21 are connected to the control device 20.

[0041] The control device 20 functions as a measurement control unit 102 and a shape calculation unit 104 by executing a control program read from a storage unit (not shown).

[0042] The measurement control unit 102 controls the camera 14, the light source unit 26, the drive unit 16, and the stage drive unit 24 in accordance with instructions from the operation unit 21. After starting the emission of the measurement light L1 from the light source unit 26 (light source 26a), the measurement control unit 102 controls the drive unit 16 to scan the optical head 12 in the Z direction. Further, while the drive unit 16 scans the optical head 12 in the Z direction, the measurement control unit 102, based on the detection result of the Z-direction position of the optical head 12 by the scale 18, causes the camera 14 to repeatedly execute imaging of the combined light L3 and output of the detection image 36 to the control device 20 and the position signal 38 from the scale 18 each time the optical head 12 moves by a certain pitch in the Z direction. Note that since the Z-direction position of the camera 14 when imaging the combined light L3 with the camera 14 can be detected by the scale 18, the pitch when scanning the optical head 12 in the Z direction is not limited to a constant pitch and may be a variable pitch.

[0043] Based on a plurality of detection images 36 captured by the camera 14 while the optical head 12 is being scanned in the Z direction and position information (position signal 38 from the scale 18) indicating the Z-direction position of the optical head 12 when each detection image 36 was captured, the shape calculation unit 104 calculates the surface shape of the measurement surface (including the surface on which a transparent material is disposed in a partial region) of the workpiece W.

[0044] The shape calculation unit 104 includes a surface shape data calculation unit 106, a distribution calculation unit 108, a base material shape data estimation unit 110, and a surface shape data correction unit 112.

[0045] The surface shape data calculation unit 106 calculates surface shape data indicating the height position of the surface of the measurement surface of the workpiece W based on a plurality of detection images 36 (detection signals of interference light) captured by the camera 14 when the optical head 12 is scanned in the Z direction. That is, the surface shape data calculation unit 106 calculates, when the measurement is performed while changing the optical path length difference between the measurement light L1 and the reference light L2, surface shape data indicating the height position of the surface of the measurement surface of the workpiece W based on the intensity change of the detection signal of the combined light L3 (interference light) detected by the camera 14 functioning as a light detection unit. The processing of the surface shape data calculation unit 106 will be described later. The surface shape data calculation unit 106 is an example of the surface shape data calculation unit of the present invention.

[0046] The distribution calculation unit 108 calculates the distribution of the transparent material on the measurement surface of the workpiece W based on the sensitivity data indicating the detection sensitivity of the detection signal of the combined light L3 (interference light) for each position on the measurement surface of the workpiece W. The processing of the distribution calculation unit 108 will be described later. The distribution calculation unit 108 is an example of the distribution calculation unit of the present invention.

[0047] The base material shape data estimation unit 110 estimates the base material shape data indicating the height position of the surface of the base material of the workpiece W in the transparent region where the transparent material is arranged on the measurement surface of the workpiece W from the surface shape data in the non-transparent region where the transparent material is not arranged on the measurement surface of the workpiece W based on the distribution of the transparent material calculated by the distribution calculation unit 108. The processing of the base material shape data estimation unit 110 will be described later. The base material shape data estimation unit 110 is an example of the estimation unit of the present invention.

[0048] The surface shape data correction unit 112 corrects the surface shape data in the transparent region where the transparent material is arranged on the measurement surface of the workpiece W based on the base material shape data estimated by the base material shape data estimation unit 110. The processing of the surface shape data correction unit 112 will be described later. The surface shape data correction unit 112 is an example of the shape data correction unit of the present invention.

[0049] Next, an example of a method for measuring the surface shape of the measurement surface of the workpiece W (surface shape measurement method) executed by the surface shape measurement apparatus 10 of the embodiment will be described.

[0050] FIG. 3 is a flowchart showing the procedure of the shape measurement method. FIG. 4 is an enlarged view of the measurement surface S of the workpiece W. FIG. 5 is a diagram for explaining the calculation method of the measurement surface by the shape data calculation unit. FIG. 6 is a diagram for explaining the processing of the surface shape data calculation unit 106. FIG. 7 is a diagram for explaining the processing of the distribution calculation unit 108. FIG. 8 is a diagram for explaining the processing of the base material shape data estimation unit 110. FIG. 9 is a diagram for explaining the processing of the surface shape data correction unit 112.

[0051] First, the workpiece W, which is the object to be measured, is placed on the stage 22 (step S1). As shown in FIG. 4, the workpiece W includes an opaque base material W1 and a transparent material W2 on a part of the base material W1. Here, as an example, the case where the shape of the base material W1 constituting the workpiece W is curved convexly (arc-shaped) upward in the Z direction is shown, but it is not limited thereto, and other shapes may be used. For example, the shape of the base material W1 may be a shape curved concavely downward in the Z direction, or a shape in which unevenness is mixed. Further, it may be a flat shape inclined vertically or obliquely in the Z direction.

[0052] The surface shape measurement apparatus 10 measures the surface shape (height position in the Z direction) of the measurement surface S of the workpiece W. In this specification, the measurement surface S of the workpiece W means the outermost surface of the workpiece W in the Z direction. For example, the measurement surface S of the workpiece W shown in FIG. 4 is the measurement surfaces S1 and S3, which are the outermost surfaces of the base material W1, and the measurement surface S2, which is the outermost surface of the transparent material W2 on the base material W1.

[0053] Next, the measurement of the measurement surface S of the workpiece W is started (step S2). Specifically, the measurement control unit 102 controls the stage drive unit 24 and the light source unit 26 to sequentially move the measurement position of the measurement surface S of the workpiece W facing the optical head 12 in the XY directions. At each measurement position, while irradiating the measurement surface S of the workpiece W with the measurement light L1, the optical head 12 is scanned in the Z direction. While the optical head 12 is being scanned in the Z direction at each measurement position, the measurement control unit 102 repeatedly causes the camera 14 to capture the combined light L3 based on the detection result of the Z-direction position of the optical head 12 by the scale 18 every time the optical head 12 moves by a certain pitch in the Z direction. The plurality of detection images 36 captured by the camera 14 at every certain pitch are sequentially input to the shape calculation unit 104 together with the position information (position signal 38 from the scale 18) indicating the Z-direction position of the optical head 12 when each detection image 36 is captured.

[0054] Next, surface shape data indicating the height position (Z-direction position) of the surface of the measurement surface S of the workpiece W is calculated (step S3). Specifically, the surface shape data calculation unit 106 calculates the surface shape data of the measurement surface S of the workpiece W according to the following procedure.

[0055] The surface shape data calculation unit 106 detects and compares the luminance values of the pixels at the same coordinates of each detection image 36. Next, the surface shape data calculation unit 106 determines the Z-direction position at which the luminance value becomes maximum for each pixel at the same coordinates of each detection image 36, thereby calculating the surface shape data, which is the height information of the surface of the measurement surface S, for each pixel at the same coordinates. That is, when the optical path length difference between the measurement light L1 and the reference light L2 is changed by the Z-direction scanning of the optical head 12, the surface shape data calculation unit 106 calculates the surface shape data indicating the height position of the surface of the measurement surface S based on the luminance change of the interference fringes appearing in each detection image 36 (that is, the change in the intensity of the detection signal of the camera 14).

[0056] Here, FIG. 5 is a diagram showing an example of an interference fringe curve Q at an arbitrary pixel of the detection image 36. When the optical path length of the measurement light L1 is smaller than the optical path length of the reference light L2, the interference is small and the luminance value is substantially constant. Then, when the optical path length of the measurement light L1 is the same as the optical path length of the reference light L2, that is, when the optical path length difference is 0, the interference becomes large and the maximum luminance value is shown. Further, when the optical path length of the measurement light L1 is larger than the optical path length of the reference light L2, the interference becomes small again and the luminance value is substantially constant. As a result, an interference fringe curve Q as shown in FIG. 5 is obtained for each pixel at the same coordinates of each detection image 36. The surface shape data calculation unit 106 calculates the height information of the measurement surface S for each pixel at the same coordinates by determining the Z-direction position at which the luminance value is maximized for each pixel at the same coordinates of each detection image 36. Thereby, surface shape data indicating the height position (Z-direction position) of the surface of the measurement surface S is calculated.

[0057] By the way, when a transparent material W2 is included on the base material W1 as in the workpiece W shown in FIG. 4, the problem shown in FIG. 6 occurs. 6-1 of FIG. 6 shows a problem in the measurement of the surface shape, and 6-2 of FIG. 6 shows a problem in the calculation of the surface shape data.

[0058] First, as shown in 6-1 of FIG. 6, in the non-transparent region AR1 where the transparent material W2 does not exist, the measurement light L1 is reflected by the base material W1 of the workpiece W, so the surface shape data indicating the height position of the base material W1 which is the measurement surface S can be calculated. On the other hand, the transparent material W2 has a low reflectance to light. In the transparent region AR2 where the transparent material W2 exists, the measurement light L1 passes through the transparent material W2 and is reflected by the base material W1 in the transparent region AR2. Therefore, the surface shape data indicating the height position of the surface of the base material W1 which is the back surface of the transparent material W2 instead of the surface of the transparent material W2 which is the measurement surface S is calculated.

[0059] Second, when calculating the surface shape data, the distance that the light used in the surface shape measuring apparatus 10 travels is not the actual distance but the optical distance (optical path length). Therefore, when the refractive index n of the transparent material W2 and the thickness L of the transparent material W2 are considered, the optical distance (optical path length), which is the distance that the light travels when passing through the transparent material W2, is n×L. Thus, as shown in 6-2 of FIG. 6, the calculated surface shape data WS is calculated as a sunken shape with an apparent longer distance in the transparent region AR2 where the transparent material W2 exists. As a result, there is a difference between the measurement surface S of the work W to be measured and the surface shape data WS measured by the surface shape measuring apparatus 10.

[0060] Therefore, based on the above points, the surface shape measuring apparatus 10 according to the embodiment performs the following processes in order to measure the surface shape data on the measurement surface S of the work W including the transparent material W2 on the base material W1.

[0061] As shown in FIG. 3, after calculating the surface shape data of the measurement surface S of the work W (step S3), the distribution of the transparent material W2 on the measurement surface S is calculated (step S4). Specifically, the distribution calculation unit 108 acquires sensitivity data indicating the detection intensity of the detection signal for each position (each pixel of the detection image 36) on the measurement surface S. The sensitivity data is obtained from the maximum luminance value of the interference fringe curve (see FIG. 5) obtained for each pixel having the same coordinates in each detection image 36. In FIG. 7, as an example of the sensitivity data, a graph is shown with the vertical axis representing the signal intensity and the horizontal axis representing the horizontal direction position (position in the X direction or Y direction).

[0062] As shown in FIG. 7, the signal intensity of the detection signal varies according to the presence or absence of the transparent material W2 on the measurement surface S. Specifically, in the non-transparent region AR1, the measurement light L1 reflected by the base material W1 is detected by the camera 14. On the other hand, in the transparent region AR2, the measurement light L1 that has passed through the transparent material W2 and is reflected by the base material W1 is detected by the camera 14. That is, in the transparent region AR2, since the measurement light L1 is attenuated when passing through the transparent material W2, the signal intensity of the detection signal is relatively weaker compared to the non-transparent region AR1. Therefore, by utilizing such a phenomenon, the distribution of the transparent material W2 on the measurement surface S can be obtained.

[0063] After the distribution calculation unit 108 acquires the sensitivity data indicating the detection sensitivity at each position on the measurement surface S, it calculates the distribution of the transparent material W2 on the measurement surface S based on the acquired sensitivity data. In the example shown in FIG. 7, the region where the signal intensity of the detection signal is relatively weak is calculated as the transparent region AR2, and the region where the signal intensity of the detection signal is relatively strong is calculated as the non-transparent region AR1. According to such a calculation method, even when the distribution of the transparent material W2 on the measurement surface S is unknown, information on the distribution of the transparent material W2 on the measurement surface S can be easily obtained from the sensitivity data indicating the detection sensitivity at each position on the measurement surface S. Therefore, the trouble of identifying the transparent material W2 can be eliminated, and the complexity of the measurement work can be prevented.

[0064] After calculating the distribution of the transparent material W2 as described above (step S4), the height position of the surface of the base material W1 in the transparent region AR2 is estimated (step S5). Specifically, the base material shape data estimation unit 110 estimates the base material shape data WS4 indicating the height position of the surface of the base material W1 in the transparent region AR2 where the transparent material W2 is arranged on the measurement surface S, based on the surface shape data in the non-transparent region AR1 where the transparent material W2 is not arranged on the measurement surface S, according to the distribution of the transparent material W2 calculated by the distribution calculation unit 108.

[0065] 8-1 in FIG. 8 shows the surface shape data WS of the measurement surface S calculated by the surface shape data calculation unit 106 in step S2 when measuring the workpiece W shown in FIG. 4. As shown in 8-1 of FIG. 8, this surface shape data WS shows that the surface shape data of the portion corresponding to the transparent region where the transparent material W2 is disposed has a concave shape with a lower height position than the adjacent other surface shape data WS1 and WS3, which is different from the actual shape (the shape of the measurement surface S of the workpiece W shown in FIG. 4).

[0066] 8-2 in FIG. 8 shows the substrate shape data WS4 estimated by the substrate shape data estimation unit 110 for the surface shape data WS shown in 8-1 of FIG. 8. As shown in 8-2 of FIG. 8, based on the distribution of the transparent material W2 calculated by the distribution calculation unit 108, the substrate shape data estimation unit 110 estimates the substrate shape data WS4 in the transparent region AR2 using the surface shape data WS1 and WS3 (calculated by the surface shape data calculation unit 106) in the non-transparent region AR1 adjacent to the transparent region AR2.

[0067] As a method for estimating the substrate shape data WS4 indicating the height position of the surface of the substrate W1 in the transparent region AR2, for example, known methods such as spline interpolation, Lagrange interpolation, or the least squares method can be applied. The surface shape data WS1 and WS are examples of the surface shape data in the non-transparent region on the measurement surface of the present invention. The substrate shape data WS4 is an example of the substrate shape data indicating the height position of the surface of the substrate in the transparent region of the present invention.

[0068] After estimating the substrate shape data WS4 in the transparent region AR2 in this way (step S5), based on the estimated substrate shape data WS4, the surface shape data WS2 in the transparent region AR2 is corrected (step S6). Specifically, the surface shape data correction unit 112 corrects the surface shape data WS2 in the transparent region AR2 by calculating the height position of the surface of the transparent material W2, which is the measurement surface S, using the difference between the surface shape data WS2 and the substrate shape data WS4 in the transparent region AR2.

[0069] A method for correcting the surface shape data WS2 in the transparent region AR2 will be described in detail with reference to FIG. 9. First, as shown in 9-1 of FIG. 9, the surface shape data correction unit 112 obtains the difference d in the Z direction between the surface shape data WS2 and the substrate shape data WS4 at each position in the XY direction in the transparent region AR2.

[0070] Here, the difference d is expressed by the following formula (1) when the refractive index of the transparent material W2 is n and the thickness of the transparent material W2 is L (unknown). d = n×L - L = L(n - 1) ··· (1)

[0071] The surface shape data correction unit 112 calculates the thickness L of the transparent material W2 from the difference d obtained from the surface shape data WS2 and the substrate shape data WS4 and the known refractive index n of the transparent material W2 by the following formula (2). It is assumed that the refractive index n of the transparent material W2 is stored in advance in the storage unit (not shown) of the control device 20. L = d / (n - 1) ··· (2)

[0072] After calculating the thickness L of the transparent material W2 at each position in the XY direction as described above, the surface shape data correction unit 112 corrects the surface shape data WS2 for the transparent region AR2 by adding the calculated thickness L to the substrate shape data WS4 of the transparent region AR2 as shown in 9-2 of FIG. 9. Thereby, the corrected surface shape data WS5 can be obtained.

[0073] Finally, the shape calculation unit 104 determines and outputs, as the surface shape data WS on the measurement surface S of the workpiece W, a combination of the surface shape data WS1 and WS3 in the non-transparent region AR1 and the corrected surface shape data WS5 in the transparent region AR2. The surface shape data WS (surface shape data WS1, WS5, and WS3) obtained in this way corresponds to the actual shape on the surface of the measurement surface S (measurement surfaces S1, S2, and S3) of the workpiece W. Then, this flowchart ends.

[0074] As described above, according to the surface shape measuring apparatus 10 of the embodiment, information on the distribution of the transparent material W2 on the measurement surface S can be easily obtained. Then, based on the distribution of the transparent material W2, the surface shape data WS2 for the transparent region AR2 can be corrected, and finally, the surface shape data WS can be made to correspond to the shape of the actual measurement surface S of the workpiece W.

[0075] In the embodiment, the case where the optical head 12 is a Michelson type white light interference microscope has been described. However, it may be a Mirau type white light interference microscope or a Linnik type white light interference microscope.

[0076] Also, in the embodiment, the case where the present invention is applied to the surface shape measuring apparatus 10 of the white light interference method has been described as an example. However, the present invention is not limited to this. For example, the present invention can also be applied to a surface shape measuring apparatus of the wavelength sweep method. Since the configuration of the surface shape measuring apparatus of the wavelength sweep method is well-known, detailed description thereof is omitted. Mainly, a wavelength sweep light source that emits light while changing the wavelength as incident light, and the incident light emitted from the wavelength sweep light source is split into a reference light and a measurement light, and a reflection light of the measurement light and the reference light are combined as interference light. An interference unit (interferometer), a light detection unit that detects the interference light in which the reflection light and the reference light are combined by the interference unit, and a control device. The control device has functions of calculating surface shape data, calculating the distribution of the transparent region, estimating the base material shape data of the transparent region, and correcting the surface shape data of the transparent region, similar to the control device 20 of the surface shape measuring apparatus 10.

Description of Reference Numerals

[0077] 10…Surface shape measuring device, 12…Optical head, 14…Camera, 16…Drive unit, 18…Scale, 20…Control device, 21…Operation unit, 22…Stage, 23…Display unit, 24…Stage drive unit, 26…Light source unit, 26a…Light source, 28…Beam splitter, 30…Interference objective lens, 30A…Objective lens, 30B…Beam splitter, 30C…Reference surface, 32…Imaging lens, 36…Detected image, 38…Position signal, 102…Measurement control unit, 104…Shape calculation unit, 106…Surface shape data calculation unit, 108…Distribution calculation unit, 110…Base material shape data estimation unit, 112…Surface shape data correction unit, AR1…Non-transparent region, AR2…Transparent region, L…Thickness, L1…Measurement light, L2…Reference light, L3…Combined light, S…Measurement surface, S1…Measurement surface, S2…Measurement surface, S3…Measurement surface, W…Workpiece, W1…Base material, W2…Transparent material, WS…Surface shape data, WS1…Surface shape data, WS2…Surface shape data, WS3…Surface shape data, WS4…Base material shape data, WS5…Surface shape data

Claims

1. A surface shape measuring apparatus for measuring the surface shape of a measurement surface of an object including a base material and a transparent material on the base material, a light source unit having a light source that emits light, a splitting unit that splits the light emitted from the light source into measurement light and reference light, emits the measurement light to the measurement surface and emits the reference light to a reference surface, and generates interference light between the measurement light reflected from the measurement surface and the reference light reflected from the reference surface; a light detection unit that detects the interference light and generates a detection signal of the interference light; a surface shape data calculation unit that calculates surface shape data indicating the height position of the surface of the measurement surface based on a change in the intensity of the detection signal when the optical path length difference between the measurement light and the reference light is changed; a distribution calculation unit that calculates the distribution of the transparent material on the measurement surface based on sensitivity data indicating the detection sensitivity of the detection signal for each position on the measurement surface; an estimation unit that estimates base material shape data indicating the height position of the surface of the base material in a transparent region where the transparent material is disposed on the measurement surface from the surface shape data in a non-transparent region where the transparent material is not disposed on the measurement surface based on the distribution of the transparent material calculated by the distribution calculation unit; a shape data correction unit that corrects the surface shape data in the transparent region based on the base material shape data estimated by the estimation unit; A surface shape measuring apparatus comprising:

2. The shape data correction unit calculates the thickness of the transparent material based on a difference between the height position of the surface of the base material in the transparent region obtained from the base material shape data and the height position of the surface of the measurement surface in the transparent region obtained from the surface shape data. The surface shape measuring apparatus according to claim 1.

3. When the difference is d, the refractive index of the transparent material is n, and the thickness of the transparent material is L, The shape data correction unit calculates the thickness of the transparent material using the following formula: L = d / (n - 1) The surface shape measuring apparatus according to claim 2.

4. The shape data correction unit calculates the corrected surface shape data in the transparent region by adding the thickness of the transparent material to the height position of the surface of the base material in the transparent region from the base material shape data. The surface shape measuring apparatus according to claim 2.

5. The light source is a light source capable of emitting white light or wavelength-swept light. The shape measuring apparatus according to any one of claims 1 to 4.

6. A surface shape measurement method for measuring the surface shape of a measurement surface of an object including a base material and a transparent material on the base material, dividing the light emitted from a light source into measurement light and reference light, emitting the measurement light to the measurement surface and emitting the reference light to a reference surface, and generating interference light between the measurement light reflected by the measurement surface and the reference light reflected by the reference surface; an interference generation step; a light detection step of detecting a detection signal indicating the interference light; a surface shape data calculation step of calculating surface shape data indicating the height position of the surface of the measurement surface based on a change in the intensity of the detection signal when the optical path length difference between the measurement light and the reference light is changed; a distribution calculation step of calculating the distribution of the transparent material on the measurement surface based on sensitivity data indicating the detection sensitivity of the detection signal for each position on the measurement surface; an estimation step of estimating base material shape data indicating the height position of the surface of the base material in a transparent region where the transparent material is disposed on the measurement surface from the surface shape data in a non-transparent region where the transparent material is not disposed on the measurement surface based on the distribution of the transparent material calculated in the distribution calculation step; a shape data correction step of correcting the surface shape data in the transparent region based on the base material shape data estimated in the estimation step; A surface shape measurement method comprising:

7. The shape data correction step calculates the thickness of the transparent material based on the difference between the height position of the surface of the base material in the transparent region obtained from the base material shape data and the height position of the surface of the measurement surface in the transparent region obtained from the surface shape data. The surface shape measurement method according to claim 6.

8. When the difference is d, the refractive index of the transparent material is n, and the thickness of the transparent material is L, the shape data correction step calculates the thickness of the transparent material using the following formula: L = d / (n - 1) The surface shape measurement method according to claim 7.

9. The shape data correction step calculates the corrected surface shape data in the transparent region by adding the thickness of the transparent material to the height position of the surface of the base material in the transparent region from the base material shape data. The surface shape measurement method according to claim 7.

10. The surface shape measurement method according to any one of claims 6 to 9, wherein the light source is a light source capable of emitting white light or wavelength-swept light.

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