Wavelength measuring method, surface irregularity measuring method, wavelength measuring system, and surface irregularity measuring system

Abstract

To heighten the accuracy of detecting the position of irregularity on the surface of an object.SOLUTION: A wavelength measuring system according to the present embodiment includes a measuring device 40 for measuring the wavelength of light in an imaging region S1 via a filter 31 on the basis of a captured image from an imaging device 30 that captures an image of an object P. Pattern light L1 includes light in a complementary wavelength band with which the object P is irradiated by a light source 10. The filter 31 is provided with a first filter 31a where transmittance decreases continuously as the wavelength of light becomes longer in a wavelength band A2, and a second filter 31b where transmittance increases continuously as the wavelength of light becomes longer in the wavelength band A2. The measuring device 40 measures the wavelength of light in the image region S1 on the basis of a signal amount S1 in an image region S11 where images are captured via the first filter 31a and a signal amount S2 in an image region S12 where images are captured via the second filter 31b.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present disclosure relates to a wavelength measurement method, a roughness measurement method, a wavelength measurement system, and a roughness measurement system. [Background technology]

[0002] 2. Description of the Related Art Conventionally, inspection devices that inspect unevenness on the surface of an object are known.

[0003] The inspection device of Patent Document 1 includes a white light source and a holographic diffractive optical element that irradiates the surface of an object to be inspected with irradiation light. The holographic diffractive optical element converts the light from the white light source that passes through it into diffracted light that changes continuously between red, green, and blue.

[0004] The detection device of Patent Document 2 includes a light source, an irradiation optical system that irradiates the light emitted from the light source onto the measured object, a light receiving element that captures the reflected light reflected from the measured object, and a detection unit that detects the measured object based on the reflected light received by the light receiving element. The irradiation optical system has a conversion means that converts the light emitted from the light source into a plurality of regular patterns. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 6908373 [Patent Document 2] JP 2016-166811 A Summary of the Invention [Problem to be solved by the invention]

[0006] As described above, in Patent Document 1, diffracted light in which red, green, and blue change continuously is used when detecting unevenness on the surface of an object. When such diffracted light is used, in a wavelength band where the light intensity of one color is strong, the light intensity of other colors becomes weak, and the wavelength band of the pattern light cannot be detected. In addition, depending on the wavelength sensitivity characteristics of the sensor, it may become impossible to distinguish between the wavelength bands. As a result, the accuracy of detecting the position of unevenness on the surface of the object decreases.

[0007] An object of the present disclosure is to provide a wavelength measurement method, an asperity measurement method, a wavelength measurement system, and an asperity measurement system that improve the accuracy of detecting the positions of asperities on the surface of an object. [Means for solving the problem]

[0008] In order to solve the above problem, a wavelength measurement method according to one embodiment of the present disclosure is a wavelength measurement method using a wavelength measurement system including a measurement device that uses a plurality of light receiving elements that receive light reflected by an object through a filter and measures the wavelength of light received by the light receiving elements based on an image from an imaging device that images the object, wherein the light includes light in a complementary wavelength band irradiated to the object by a light source, the filter includes a first filter whose transmittance decreases continuously as the wavelength of light becomes longer in the complementary wavelength band, and a second filter whose transmittance increases continuously as the wavelength of light becomes longer in the complementary wavelength band, the image includes an image area corresponding to the light receiving elements that received the light in the complementary wavelength band, the image area includes a first image area imaged through the first filter and a second image area imaged through the second filter, and the measurement device measures the wavelength of light in the image area based on a first signal amount in the first image area and a second signal amount in the second image area. Effect of the Invention

[0009] According to the present disclosure, it is possible to improve the accuracy of detecting the positions of projections and recesses on the surface of an object. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a diagram showing a basic configuration of a measurement system according to an embodiment. [Diagram 2] FIG. 4 is a diagram showing an example of pattern light according to the embodiment. [Diagram 3] FIG. 2 is a plan view showing an example of a filter according to the embodiment. [Figure 4] 5 is a graph showing the transmission characteristics versus light wavelength in a first filter and a second filter according to the embodiment. [Diagram 5] FIG. 2 is a diagram showing an example of a captured image according to the embodiment. [Figure 6] 11 is a graph for explaining how the wavelength of the pattern light L1 in the image area S1 is obtained from the ratio between the signal amounts S1 and S2. [Figure 7] 11 is a graph for explaining how the wavelength of the pattern light L1 in the image area S1 is obtained from the difference between the signal amounts S1 and S2. [Figure 8] 10 is a graph showing signal amounts corresponding to two filters according to another embodiment. [Figure 9] 10 is a graph showing signal amounts corresponding to three filters according to another embodiment. [Figure 10] 13 is a graph showing signal magnitudes corresponding to multiple filters according to another embodiment; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, the embodiments of the present invention will be described in detail with reference to the drawings. The following description of the preferred embodiments is merely illustrative in nature and is not intended to limit the present invention, its application, or its uses.

[0012] (First embodiment) FIG. 1 is a diagram showing a basic configuration of a measurement system according to an embodiment.

[0013] As shown in FIG. 1, the measurement system 1 includes a light source 10, a diffraction element 20, an imaging device 30, and a measurement device 40.

[0014] The light source 10 is a light source that irradiates light in a predetermined range of wavelengths. For example, the light source 10 is a white light source constituted by an LED or the like.

[0015] The diffraction element 20 (optical element) is a diffraction element in which a predetermined diffraction grating is formed. The diffraction element 20 transmits light emitted from the light source 10 and emits pattern light L1 (diffracted light). This pattern light L1 is irradiated onto an object P to be inspected. The object P is, for example, a semiconductor substrate, a component mounting substrate, a metal plate, a mold, etc.

[0016] Fig. 2 is a diagram showing an example of the pattern light according to the embodiment. Fig. 2(a) is an example of the pattern light L1 when the distance between the light source 10 and the diffraction element 20 is short, and Fig. 2(b) is an example of the pattern light L1 when the distance between the light source 10 and the diffraction element 20 is long.

[0017] 2(a) and 2(b), the pattern light L1 is composed of a plurality of dot lights L2. The plurality of dot lights L2 are arranged so as to draw a plurality of circles with the zeroth-order diffracted light at the center of the pattern light L1 as the center.

[0018] In addition, the size of the dot light L2 and the distance from the center of the pattern light L1 to the zeroth-order diffracted light change according to the distance T between the light source 10 and the diffraction element 20 and the pattern of the diffraction element. As shown in Figures 2(a) and (b), the pattern light L1 extends outward from the center and becomes farther away from the center as the distance T between the light source 10 and the diffraction element 20 increases. That is, by changing the distance T, the position where the pattern light L1 is irradiated on the object P changes.

[0019] The imaging device 30 is, for example, a camera imaging device, and captures an image of an object P. The imaging device 30 includes a filter 31 and a plurality of light receiving elements 32.

[0020] Filter 31 has the property of transmitting the pattern light L1 reflected by the surface of object P, or the property of transmitting at least the light of the pattern light L1 having a wavelength required for measurement (for example, a bandpass filter that transmits the second wavelength band in Figure 4).

[0021] Fig. 3 is a plan view showing an example of a filter according to an embodiment. As shown in Fig. 3, the filter 31 has a first filter 31a and a second filter 31b. In the filter 31, the first filter 31a and the second filter 31b are arranged in an array. Although not shown, the first filter 31a and the second filter 31b may be arranged alternately in columns or rows. However, the first filter 31a and the second filter 31b are not limited to this.

[0022] The multiple light receiving elements 32 are sensors that capture the pattern light L1 transmitted through the filter 31. The multiple light receiving elements 32 are arranged in an array. The light receiving elements 32 are, for example, a CMOS image sensor or a CCD. Each light receiving element 32 outputs a signal corresponding to the received light to the measurement device 40.

[0023] Fig. 4 is a graph showing the transmission characteristics of the first filter and the second filter according to the embodiment with respect to the wavelength of light. Fig. 4 shows the signal amount S1 (first signal amount) output by the light receiving element 32 corresponding to the first filter 31a and the signal amount S2 (second signal amount) output by the light receiving element 32 corresponding to the second filter 31b. The signal amounts S1 and S2 change according to the wavelength bands of the light transmitted through the first filter 31a and the second filter 31b, respectively.

[0024] Specifically, the first filter 31a has a high transmittance in a wavelength band (first wavelength band) where the wavelength of light is short, and a low transmittance in a wavelength band (third wavelength band) where the wavelength of light is long. The first filter 31a is formed so that the transmittance in a wavelength band (second wavelength band) between the first and third wavelength bands decreases continuously from the first wavelength band to the third wavelength band. For this reason, as shown in FIG. 4, when light in the first wavelength band passes through the first filter 31a, the signal amount S1 increases, and when light in the third wavelength band passes through the first filter 31a, the signal amount S1 decreases. When light in the second wavelength band passes through the first filter 31a, the signal amount S1 decreases continuously from the first wavelength band to the third wavelength band.

[0025] The second filter 31b has a low transmittance in the first wavelength band and a high transmittance in the third wavelength band. The second filter 31b is formed so that the transmittance in the second wavelength band increases continuously from the first wavelength band to the third wavelength band. Therefore, as shown in FIG. 4, when light in the first wavelength band passes through the second filter 31b, the signal amount S2 decreases, and when light in the third wavelength band passes through the second filter 31b, the signal amount S2 increases. When light in the second wavelength band passes through the first filter 31a, the signal amount output by the light receiving element 32 increases continuously from the first wavelength band to the third wavelength band.

[0026] Thus, in the second wavelength band, as the wavelength of light becomes longer, the transmittance of light transmitted through the first filter 31a decreases, so that the amount of signal output by the light receiving element 32 increases, whereas the transmittance of light transmitted through the first filter 31a increases, so that the amount of signal output by the light receiving element 32 increases. For this reason, in the adjacent first filter 31a and second filter 31b, by comparing the signal ratio between the amount of signal S1 output by the light receiving element 32 receiving the light transmitted through the first filter 31a and the amount of signal S2 output by the light receiving element 32 receiving the light transmitted through the second filter 31b, it is possible to accurately detect the wavelength of light in the second wavelength band.

[0027] The measuring device 40 is, for example, a microcomputer including a CPU, a semiconductor memory, etc. The measuring device 40 detects the unevenness formed on the surface of the object P based on the signal received from the light receiving element 32.

[0028] For example, the measurement device 40 stores in advance a reference image of the object P. The reference image is an image captured by the imaging device 30 (light receiving elements 32) when pattern light L1 is irradiated onto design data of the object P. The measurement device 40 detects irregularities formed on the surface of the object P by comparing the reference image with the captured image of the object P based on the signals output from the light receiving elements 32.

[0029] Specifically, the measuring device 40 compares corresponding image regions in the reference image and the captured image, and determines whether or not projections and recesses are formed in the image regions based on the comparison result.

[0030] FIG. 5 is a diagram showing an example of a captured image according to an embodiment. The captured image in FIG. 5 includes an image region S1. The image region S1 includes an image region S11 (first image region) and an image region S12 (second image region). The image region S11 is an image of an area irradiated with light of the second wavelength band among areas irradiated with the pattern light L1 transmitted through the first filter 31a. The image region S12 is an image of an area irradiated with light of the second wavelength band among areas irradiated with the pattern light L1 transmitted through the second filter 31b. That is, the image region S1 is an image of an area irradiated with light of the second wavelength band among areas irradiated with the pattern light L1. As shown in FIG. 5, the image regions S11 and S12 are set in image regions close to each other (within a certain distance) in the captured image. Therefore, in image region S11, a value is calculated by interpolation (linear interpolation, etc.) from the values ​​of the adjacent image region S12, and in image region S12, a value is calculated by interpolation from the values ​​of the adjacent image region S11, making it possible to estimate the wavelength with higher resolution.

[0031] The measuring device 40 detects pixel values ​​(signal amounts S1 and S2 output by the light receiving element 32) in the image area S1 and the image areas S11 and S12, respectively. The measuring device 40 compares the signal amounts S1 and S2 to obtain the wavelength of the pattern light L1 in the image area S1. Specifically, the measuring device 40 obtains the ratio of the signal amounts S1 and S2.

[0032] FIG. 6 is a graph for explaining how the wavelength of the pattern light L1 in the image region S1 is obtained from the ratio between the signal amounts S1 and S2.

[0033] As shown in Fig. 4 and Fig. 6(a)-(b), the second waveband includes wavebands A1-A3. Waveband A1 is a waveband with a short wavelength among the second waveband. Waveband A3 is a waveband with a long wavelength among the second waveband. Waveband A2 is a waveband between wavebands A1 and A3.

[0034] The first filter 31a is formed to have the same transmittance (signal amount S1) in the wavelength band A1 as the first wavelength band. The first filter 31a is formed to have a transmittance (signal amount S1) that decreases as the wavelength becomes longer in the wavelength bands A2 and A3.

[0035] The second filter 31b is formed so that the transmittance (signal amount S2) increases as the wavelength becomes longer in the wavelength bands A1, A2, A2, and A3. The second filter 31b is formed so that the transmittance (signal amount S2) in the wavelength bands A1, A2 is the same as that in the third wavelength band.

[0036] As shown in Fig. 6(a), in wavelength band A1, the signal amount S1 is constant and the signal amount S2 is increasing. Therefore, the ratio of the signal amounts S1 and S2 (S2 / S1) is expressed by the following formula (1). In the following explanation, ΔS1 and ΔS2 are the amounts of change in the signal amounts S1 and S2.

[0037]

number

[0038] 6(b), in wavelength band A2, the signal amount S1 decreases and the signal amount S2 increases. The ratio (S2 / S1) of the signal amounts S1 and S2 is expressed by the following formula (2).

[0039]

number

[0040] 6(c), in the wavelength band A3, the signal amount S1 increases and the signal amount S2 is constant. Therefore, the ratio of the signal amounts S1 and S2 (S2 / S1) is expressed by the following formula (3).

[0041]

number

[0042] As described above, in the second wavelength band, either one of the signal amounts S1 and S2 varies in response to the variation in the wavelength of the pattern light L1. Therefore, by determining the ratio (S2 / S1) of the signal amounts S1 and S2, the wavelength of the pattern light L1 in the image area S1 can be detected with high accuracy. In particular, in the wavelength band A2, both the signal amounts S1 and S2 vary in response to the variation in the wavelength of the pattern light L1. Therefore, in the wavelength band A2, the wavelength of the pattern light L1 in the image area S1 can be detected with high accuracy.

[0043] This wavelength band A2 corresponds to a complementary wavelength band, which refers to a wavelength band in which (1) the signs of the slopes of the fluctuations in the transmittance of the two filters (first filter 31a and second filter 31b) are different from each other, (2) the sign of the slope is constant (does not fluctuate) within the complementary wavelength band, and (3) the slope is not substantially zero within the complementary wavelength band.

[0044] The measuring device 40 compares the signal amount ratio (S2 / S1) of the signal amounts S1 and S2 in the image area S1 with the signal amount ratio (or the wavelength of the pattern light L1) of the corresponding image area in the reference image to determine whether or not unevenness is formed in the image area. For example, when the signal amount ratio (S2 / S1) of the signal amounts S1 and S2 in the image area S1 does not match the signal amount ratio (or the wavelength of the pattern light L1) of the corresponding image area in the reference image, the measuring device 40 determines that unevenness is formed in the image area.

[0045] Furthermore, the measurement device 40 may obtain the wavelength of the pattern light L1 in the image region S1 from the difference between the signal amounts S1 and S2.

[0046] FIG. 7 is a graph for explaining how the wavelength of the pattern light L1 in the image region S1 is obtained from the difference between the signal amounts S1 and S2.

[0047] As described above, in the second wavelength band, either one of the signal amounts S1 or S2 varies in response to fluctuations in the wavelength of the pattern light L1. Therefore, the difference between the signal amounts S1 and S2 (S2-S1) varies in response to fluctuations in the wavelength of the pattern light L1 (see FIG. 7). In particular, in the wavelength band A2, both the signal amounts S1 and S2 vary in response to fluctuations in the wavelength of the pattern light L1. Therefore, in the wavelength band A2, the wavelength of the pattern light L1 in the image area S1 can be detected more accurately.

[0048] (Other embodiments) The filter 31 may include two or more filters. In this case, each filter may have a transmittance that varies continuously according to the wavelength band of light. Each filter may have a wavelength band that is complementary to the other filters.

[0049] Fig. 8 is a graph showing an example in which the filter 31 includes two filters 31 (filters 31a' and 31b). In Fig. 8, the complementary wavelength bands are set to 400 nm to 700 nm. Specifically, the transmittance (signal amount) of the filter 31a' decreases from 400 nm to 700 nm, and the transmittance (signal amount) of the filter 31a' increases from 400 nm to 700 nm.

[0050] FIG. 9 is a graph showing an example in which the filter 31 includes three filters (filters 31c to 31e). Filter 31c transmits mainly light of a hue of "blue". Filter 31d transmits mainly light of a hue of "green". Filter 31e transmits mainly light of a hue of "red". In FIG. 9, the complementary wavelength bands of filters 31c and 31d and the complementary wavelength bands of filters 31d and 31e are set. In the case of a sensor equipped with a general RGB filter, the complementary wavelength bands are respectively in the range of about ±30 nm centered on about 480 nm and about ±30 nm centered on about 580 nm, but even in the case of a sensor with other special color filters, it is possible to set and utilize the complementary wavelength bands depending on the filter characteristics of the sensor.

[0051] Fig. 10 is a graph showing an example in which filter 31 includes multiple (here, 15) filters. In Fig. 10, the transmittance of each filter varies continuously according to the wavelength band of light. Each filter has a wavelength band that is complementary to the other filters.

[0052] In the above embodiment, the filter 31 is provided in the imaging device 30, i.e., between the object P and the light receiving element 32, but this is not limiting. For example, the filter 31 may be provided in the light source 10, i.e., between the light source 10 and the object P.

[0053] The filter 31 may be configured to transmit only light in the complementary wavelength band. In this case, in the above embodiment, the first filter 31a and the second filter 31b are configured to transmit only the wavelength band A2. This improves the measurement accuracy of the wavelength of light and the unevenness.

[0054] In the above embodiment, the measuring device 40 may set multiple image regions S1 for one captured image. In this case, the measuring device 40 may measure the wavelength of light and the unevenness for each image region S1. This allows the wavelength of light and the unevenness to be measured at multiple locations.

[0055] In the above embodiment, a driving mechanism may be provided to change the relative position (distance T, angle of light source 10 with respect to diffraction element 20, etc.) between light source 10 and diffraction element 20. In this case, imaging device 30 may capture an image of object P every time the relative position between light source 10 and diffraction element 20 is changed by the driving mechanism. Then, measuring device 40 may measure the wavelength of light in image region S1 for each captured image captured by imaging device 30. This makes it possible to measure the wavelength of light and unevenness at multiple locations.

[0056] In the above embodiment, a shielding member that blocks light of 500 nm or less may be disposed between the light source 10 and the object P. This makes it possible to measure the wavelength of light and unevenness in the complementary wavelength band between the hues "red" and "green." [Explanation of symbols]

[0057] 1. Measurement system 10 light source 20 Diffractive element (optical element) 30 Imaging device 31 Filters 31a First filter 31b Second filter 32 Photodetector 40 Measuring Equipment A2 Wavelength Band (Complementary Wavelength Band) L1 Pattern light (diffracted light) L2 Dot Light P Object S1 Image area S11 Image area (first image area) S12 Image area (second image area)

Claims

1. A wavelength measurement method using a wavelength measurement system including a measurement device that uses a plurality of light receiving elements that receive light reflected by an object through a filter, and measures the wavelength of light received by the light receiving elements based on an image acquired from an imaging device that images the object, comprising: the light includes light in complementary wavelength bands irradiated onto the object by a light source, The filter comprises: a first filter having a transmittance that continuously decreases as the wavelength of light in the complementary wavelength band increases; a second filter having a transmittance that increases continuously as the wavelength of light in the complementary wavelength band increases, the image includes image regions corresponding to the light receiving elements that receive light in the complementary wavelength bands; the image area includes a first image area captured through the first filter and a second image area captured through the second filter; The measurement device measures a wavelength of light in the image area based on a first signal amount in the first image area and a second signal amount in the second image area.

2. The wavelength measurement method according to claim 1 , wherein the filter transmits only light in the complementary wavelength band.

3. The wavelength measurement method according to claim 1 , wherein the measurement device measures wavelengths of light in a plurality of the image regions for one of the images.

4. The wavelength measurement method according to claim 1 , wherein the measurement system further comprises an optical element that converts the light emitted from the light source into diffracted light.

5. the imaging device captures an image of the object every time a relative position between the light source and the optical element is changed; The wavelength measurement method of claim 4 , wherein the measurement device measures the wavelength of light in the image area for each image of the imaging device.

6. The wavelength measurement method according to claim 1 , wherein the measurement system further comprises a shielding member disposed between the light source and the object, the shielding member blocking light of 500 nm or less.

7. A method for measuring unevenness using the wavelength measurement method according to any one of claims 1 to 6, An unevenness measuring method for measuring unevenness on the surface of the object based on the measurement results of the measuring device.

8. The unevenness measuring method according to claim 7 , wherein the measuring device measures unevenness on the surface of the object based on the measurement result and a reference image which is design data of the object.

9. a measuring device for measuring a wavelength of light received by a plurality of light receiving elements based on an image from an imaging device that captures an image of an object using the light receiving elements that receive light reflected by the object through a filter; the light includes light in complementary wavelength bands irradiated onto the object by a light source, The filter comprises: a first filter having a transmittance that continuously decreases as the wavelength of light in the complementary wavelength band increases; a second filter having a transmittance that increases continuously as the wavelength of light in the complementary wavelength band increases, the image includes image regions corresponding to the light receiving elements that receive light in the complementary wavelength bands; the image area includes a first image area captured through the first filter and a second image area captured through the second filter; The measurement device measures the wavelength of light in the image area based on a first signal amount in the first image area and a second signal amount in the second image area.

10. A wavelength measurement system according to claim 9, The measuring device is an unevenness measuring system that measures unevenness on the surface of the object based on the measurement results of the measuring device.

Images