Measuring device and article manufacturing method

Abstract

To provide a measuring device that can reduce an error due to a pattern on a surface of an object to be measured.SOLUTION: A measuring device measures displacement of an object to be measured, and has: a light receiving optical system that receives diffused reflected light generated on a measurement target surface of the object to be measured; a photoelectric conversion element array that detects the light from the light receiving optical system; and a calculation unit that calculates displacement by using correlation between two images that are output from the photoelectric conversion element array and acquired at different timings. The light receiving optical system has characteristics of forming an image of the measurement target surface linearly in a direction not parallel to the arrangement direction of the photoelectric element array.SELECTED DRAWING: Figure 6

Description

Technical Field

[0001] The present invention relates to a measuring device, a method for manufacturing an article, and the like.

[0002] As a conventional non-contact measuring device, there is a measuring device disclosed in Patent Document 1. This measuring device sequentially images a measurement object moving in the in-plane direction, and calculates displacement from the peak position of the cross-correlation function of images acquired at different timings. A configuration is disclosed in which sub-pixel estimation is performed when determining the peak position of the cross-correlation function to improve the resolution and prevent the accumulation of errors generated during sub-pixel estimation.

[0003] A measuring device disclosed in Patent Document 2 discloses a method for correcting an error caused by the spatial frequency distribution included in an image.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, when using a photoelectric conversion element array arranged one-dimensionally, if there is an angular deviation between the conveyance direction of the measurement object and the arrangement direction of the photoelectric conversion elements, an error caused by the pattern angular distribution on the measurement object will occur.

[0006] For example, when the pattern angular distribution on the surface is uniform, such as in the case of a metal with prominent scratches due to cutting, the error becomes large, and when the pattern angular distribution on the surface is random, such as in the case of a blasted surface, the error tends to be small.

[0007] Since this error is embedded in the image at the time of imaging, it is difficult to correct it during the length measurement operation. Also, it is not easy to make the adjustment to exactly match the conveyance direction of the measurement object and the array direction of the photoelectric conversion element array. When handling various measurement objects, there is a problem that errors occur due to the different pattern angle distributions on the surfaces of the respective measurement objects.

[0008] One object of the present invention is to provide a measuring device capable of reducing errors caused by patterns on the surface of a measurement object.

Means for Solving the Problems

[0009] A measuring device according to one aspect of the present invention is a measuring device for measuring the displacement of a measurement object, a light receiving optical system that receives diffused reflection light generated on the measurement object surface of the measurement object, a photoelectric conversion element array that detects light from the light receiving optical system, and a calculation unit that calculates the displacement using the correlation between two images acquired at different timings for the image output from the photoelectric conversion element array, wherein the light receiving optical system has a characteristic of linearly imaging the image of the measurement object surface in a direction non-parallel to the array direction of the photoelectric conversion element array.

Effects of the Invention

[0010] According to the present invention, it is possible to provide a measuring device capable of reducing errors caused by patterns on the surface of a measurement object.

Brief Description of the Drawings

[0011]

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Figure 9

Mode for Carrying Out the Invention

[0012] Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the present invention is not limited to the following embodiments. In each figure, the same members or elements are denoted by the same reference numerals, and overlapping explanations are omitted or simplified.

[0013] <Embodiment 1> FIGS. 1(A) and (B) are diagrams showing a configuration example of the measuring device according to Embodiment 1 of the present invention. Note that FIG. 1(A) is a cross-sectional view along the xz plane, and FIG. 1(B) is a cross-sectional view along the yz plane.

[0014] As shown in FIG. 1, the measuring device 1 of the present embodiment can non-contact measure the displacement amount of the measurement object 2 arranged to face the measuring device 1 in the direction of the arrow (x direction) in the figure. That is, the measuring device of Embodiment 1 can measure the displacement and the like of a measurement object moving in a predetermined in-plane direction.

[0015] Therefore, for example, while a long measuring object (including a belt conveyor, etc.) is moving, its moving speed, moving amount (displacement amount), etc. can be measured non - contact without using an encoder or the like.

[0016] The light beam emitted from the light source 3 is condensed onto the measurement object 2 by the condensing member 4 and illuminates the measurement object 2. The light source 3 can appropriately select an incoherent light source such as an LED or a halogen lamp.

[0017] The condensing member 4 is composed of a single lens or a lens group. The condensing member 4 only needs to be able to illuminate the light - receiving area, and aberrations etc. are not particularly problematic. It can be appropriately selected according to the size of the area to be illuminated.

[0018] A part of the diffuse - reflected light generated on the measurement symmetry plane of the illuminated measurement object 2 is received by the light - receiving optical system composed of the condensing members 5, 8, 9 and the aperture stop 7, and is condensed onto the sensor 6. The sensor 6 is composed of a one - dimensional array of photoelectric conversion elements, and the photoelectric conversion element array detects the light from the light - receiving optical system. The arrangement direction of the photoelectric conversion elements (pixels) is the direction (x - direction) that coincides with the conveyance direction of the measurement object 2.

[0019] In this embodiment, a bilateral telecentric optical system is adopted as the light - receiving optical system, and a cylindrical lens is added as the condensing member 9. That is, the light - receiving optical system is a telecentric optical system with respect to the measurement direction. The cylindrical lens as the condensing member 9 is arranged to have power in the direction (y - direction) perpendicular to the measurement direction (x - direction).

[0020] That is, the light - receiving optical system of this embodiment includes a cylindrical lens and is configured to linearly image the image of the measurement object surface. However, as will be described later, the light - receiving optical system may include a linear Fresnel lens and be configured to linearly image the image of the measurement object surface.

[0021] The light collecting members 5 and 8 are arranged so that their foci coincide with each other, and an aperture stop 7 is installed at that position. In this embodiment, by adopting a bilateral telecentric optical system, even when the distance (WD (Working Distance)) between the measuring device 1 and the object to be measured 2 changes, the magnification of the optical system is less likely to change, and it is less likely to be affected by displacement due to changes in the installation environment temperature.

[0022] The light collecting members 5 and 8 are composed of a single lens or a lens group, and the magnification of the optical system is determined by the ratio of the focal lengths of the light collecting members 5 and 8. The magnification of the optical system can be appropriately selected according to the desired resolution.

[0023] In addition, when fluctuations in the WD and the installation position of the sensor 6 are not assumed, a non-telecentric imaging optical system may be used. Also, when changes in the WD are assumed but changes in the installation position of the sensor 6 are not assumed, it is also possible to select a telecentric optical system only on the object side.

[0024] The sensor 6 is composed of a photoelectric conversion element array in which photoelectric conversion elements (pixels) are arranged in a one-dimensional direction (x direction). As the photoelectric conversion element array, a CCD sensor or a CMOS sensor can be used.

[0025] The light beam imaged on the sensor 6 is output to the control unit 10 after being photoelectrically converted. The control unit 10 is composed of an FPGA, a microcomputer, etc., calculates the displacement amount based on the image that is the output of the sensor 6, and outputs the measured length value. In this embodiment, the control unit 10 is provided inside the housing of the measuring device, but it may also be configured to be separate from the housing of the measuring device and connected by wire or wirelessly.

[0026] The control unit 10 is composed of an FPGA, a CPU as a computer, etc., functions as a calculation unit that calculates the displacement amount based on the image that is the output of the sensor 6, and outputs the measured length value. In addition, the control unit 10 also functions as a control means for controlling each part of the measuring device 1 by causing the CPU to execute a computer program stored in a memory as a storage medium (not shown).

[0027] When a light beam diffusely reflected from the surface (measurement target surface) of the measurement object 2 forms an image on the sensor 6, a luminance distribution reflecting the surface state of the measurement target surface of the measurement object 2 is obtained. As the displacement of the measurement object 2 changes, the luminance distribution also changes. When calculating the cross-correlation function of the luminance distributions obtained at different timings, the peak position changes according to the displacement of the measurement object 2.

[0028] The control unit calculates the displacement of the measurement object 2 by determining the peak position of the cross-correlation function. At this time, a resolution below the pitch of the photoelectric conversion element array can also be obtained by performing sub-pixel calculation using the data around the peak.

[0029] As described above, in this embodiment, the measurement object is illuminated with incoherent light, the diffusely reflected light generated on the measurement target surface is condensed by the light receiving optical system, and received by the photoelectric conversion element array. Further, the control unit 10 functions as a calculation unit that calculates the displacement using the correlation between two images obtained at different timings for the images sequentially output from the photoelectric conversion element array.

[0030] FIG. 2 is a diagram for explaining a basic configuration example when acquiring an image of the measurement object 2 with the sensor 6 according to Embodiment 1 and performing length measurement. Here, in order to explain the error caused by the surface state of the measurement object 2 which is the problem, the effect of the cylindrical lens of the condensing member 9 is ignored, and it is explained as an image obtained by a normal imaging optical system.

[0031] FIG. 2 shows a state of acquiring two one-dimensional images at different timings with respect to the conveyance direction (x direction) indicated by the dashed-dotted line. A one-dimensional image of the region indicated by the dotted line is acquired at the first sampling, and a one-dimensional image of the region indicated by the solid line is acquired at the second sampling.

[0032] In addition, in this embodiment, the sensor 6 is a single line sensor (one-dimensional sensor). That is, the photoelectric conversion element array is composed of photoelectric conversion elements arranged in one dimension. However, as the photoelectric conversion element array, a plurality of line sensors may be used, or further, a two-dimensional image sensor may be used.

[0033] Still, the vertical stripe pattern shown in FIG. 2 is an example of typical features on the object 2 to be measured. Based on the end face of the sensor 6, if the position of the pattern in the first sampling is X1 and the position of the pattern in the second sampling is X2, the conveyance amount d between samplings coincides with the difference between X1 and X2.

[0034] Next, consider the case where the arrangement of the sensor 6 has an angular error with respect to the conveyance direction. FIGS. 3(A) to (C) show examples of errors in the case of sensor inclination, and show the errors generated according to the inclination of the pattern when the sensor 6 has an angular error with respect to the conveyance direction (x direction) which is the right direction in the figure.

[0035] Here too, in order to explain the error generated by the surface state of the object 2 to be measured which is the problem, the effect of the cylindrical lens of the condensing member 9 is ignored and it is explained as an image obtained by a normal imaging optical system.

[0036] FIG. 3(B) shows the case where, for example, the vertical stripe pattern on the surface of the sensor 6 having an angular error with respect to the conveyance direction and the object 2 intersects. At this time, the difference between X1 and X2 becomes d' (the cosine of the conveyance amount d).

[0037] Except for the special case shown in FIG. 3(B), generally as shown in FIGS. 3(A) and (C), the difference between X1 and X2 does not coincide with d', and an error determined by the sensor angular error and the pattern inclination occurs.

[0038] Depending on the combination of the sensor angular error and the pattern inclination, the above error can be either positive or negative. FIG. 3(A) shows an example where the error is positive, and FIG. 3(C) is a diagram showing an example where the error is negative. Hereinafter, in the present embodiment, the error generated by the sensor angular error and the pattern inclination is referred to as a geometric error.

[0039] FIG. 4 is a diagram showing an example for formulating an error in the case where there is a sensor tilt. The combination of the sensor angle error and the tilt of the pattern is the same as that in FIG. 3(A). Let the angle error, which is the tilt of the sensor 6 with respect to the conveyance direction, be φ, and the tilt of the pattern (the angle formed by the pattern normal and the conveyance direction) be θ. Then, X1 - X2 = d(cosφ + sinφ·tan(θ + φ)) can be expressed.

[0040] Normally, when attaching the measuring device 1 to the measurement object 2, adjustment is made so that the conveyance direction and the arrangement direction of the sensors 6 coincide. Although the angle error φ does not become zero, it can be considered that it does not become extremely large.

[0041] On the other hand, since the tilt θ of the pattern is determined by the texture of the surface of the measurement object 2, it may have a large value. Therefore, it can be considered that the geometric error is generally proportional to the tilt θ of the pattern.

[0042] FIGS. 5(A) and (B) are diagrams showing an example in the case where there are a plurality of patterns on the surface of the measurement object 2. Also here, in order to explain the error generated due to the surface state of the measurement object 2, which is the problem, the effect of the cylindrical lens of the light condensing member 9 is ignored, and it is explained as an image obtained by a normal imaging optical system.

[0043] On the surface of the actual measurement object 2, there are patterns having various angles. As an example, consider a machined surface of a metal having periodic grooves and a blasted surface having a random pattern.

[0044] FIG. 5(A) shows a schematic diagram of the surface state of the machined surface, and FIG. 5(B) shows a schematic diagram of the surface state of the blasted surface. Regarding these surface states, the distribution of the characteristic patterns acquired by the sensor 6 becomes a pattern with aligned angles as shown in FIG. 5(A) for the machined surface of the metal.

[0045] On one hand, on the blast surface, it can be regarded as a pattern with randomly varying angles as shown in Fig. 5(B). The geometric error is the superposition of the effects of all the patterns on the surface and is proportional to the sum of the inclinations θ of each pattern. If the total number of patterns on the surface is N, the geometric error is proportional to the sum from the angle θ1 of the inclination of the first pattern to θN of the Nth one.

[0046] As shown in Fig. 5(A), when the N patterns have the same inclination θ, since the sum of the pattern angles can be written as θ1 = θ2 = ··· = θN = θ, then θ1 + θ2 + ··· + θN = N·θ. The geometric error, which is proportional to the sum of the pattern angles, is proportional to N·θ.

[0047] On the other hand, as shown in Fig. 5(B), when the N patterns have random inclinations, since the random angles cancel each other out, the geometric error is a small value. Thus, the amount of geometric error is determined by the pattern angle distribution on the surface of the measurement object 2. The geometric error is an error that occurs at the stage of capturing the image by the sensor 6 and occurs without relying on length measurement operations including the calculation of the cross-correlation function.

[0048] Fig. 6 is a diagram for explaining an example of imaging by the cylindrical lens according to Embodiment 1, and explains the effect of the cylindrical lens of the light condensing member 9. In the configuration of the measurement device 1 of Embodiment 1 shown in Fig. 1, the arrangement direction (x direction) of the photoelectric conversion elements of the sensor 6 and the generatrix direction of the cylindrical lens (the direction perpendicular to the direction with power) are arranged to coincide.

[0049] The images corresponding to each point on the surface of the measurement object 2 are linearly imaged in the direction perpendicular to the generatrix direction of the cylindrical lens (the direction with power). That is, the pattern having a specific angle on the surface of the measurement object 2 is such that each point constituting the pattern is linearly condensed in the direction perpendicular to the generatrix of the cylindrical lens.

[0050] Therefore, for any pattern, the pattern will be stretched in a direction perpendicular to the array direction of the sensor 6, and as shown in Fig. 3(B), the geometric error will be suppressed.

[0051] Also, in the optical system using a cylindrical lens as in this embodiment, regardless of the pattern, each point forms a linear image in a direction perpendicular to the generatrix of the cylindrical lens. However, the direction of linear light collection does not have to be perpendicular to the array direction of the photoelectric conversion element array of the sensor 6, and it may be a substantially perpendicular direction.

[0052] That is, when the angular error between the generatrix of the cylindrical lens and the array direction of the photoelectric conversion element array is θx, the displacement measured with respect to the actual displacement is cosθx times, but it always becomes a constant systematic error regardless of the inclination angle of the pattern on the surface of the measurement object. Therefore, even if there is an angular error θx during assembly, it is possible to correct it by multiplying by cosθx. However, it is desirable that θx is small.

[0053] Fig. 7 is a diagram showing an example of the change in the pattern image depending on the presence or absence of a cylindrical lens. Here, two-dimensional images of metal surfaces with different pattern angle distributions are shown as samples A and B. When transported in the horizontal direction in Fig. 7, since the pattern angles of samples A and B have opposite signs, the geometric errors that occur when there is no cylindrical lens can also take different positive and negative values.

[0054] On the other hand, in this embodiment, it can be seen that by forming an image through the cylindrical lens, the two-dimensional images of both samples A and B are images having a component in the direction perpendicular to the generatrix of the cylindrical lens. At this time, the geometric error is almost zero for both.

[0055] Fig. 8 is a diagram showing an example of the length measurement accuracy depending on the presence or absence of a cylindrical lens. The length measurement results when transporting 100 mm for 10 types of measurement objects 2 with different pattern angle distributions of samples 1 to 10 are shown.

[0056] In the case where there is no cylindrical lens, an error of more than 1% occurs between samples due to the influence of the pattern angle, whereas when a cylindrical lens is used, the error can be suppressed to 0.1% or less.

[0057] As described above, when the arrangement direction of the sensor 6 is inclined with respect to the conveyance direction of the measurement object 2, the pattern angle distribution such as scratches on the surface of the measurement object 2 becomes an error factor. However, in this embodiment, by using a cylindrical lens, the influence of the pattern angle is eliminated, and highly accurate length measurement independent of the pattern on the surface of the measurement object 2 becomes possible.

[0058] <Other Embodiments> In the measuring device 1 of Embodiment 1, a cylindrical lens is adopted as the condensing member 9, but a linear Fresnel lens may be adopted. For other optical elements, the condensing member 9 may be an optical element having power in one direction, and can be appropriately selected such as a diffractive optical element.

[0059] Also, in the measuring device 1 of Embodiment 1, the condensing member 9 is arranged between the measurement object 2 and the condensing member 5, but it may be arranged between the condensing member 8 and the sensor 6, between the condensing member 5 and the condensing member 8, etc.

[0060] Also, in the measuring device 1 of Embodiment 1, a configuration in which the condensing member 9 is added to the bilateral telecentric optical system is shown, but it is also possible to configure the light receiving optical system with a cylindrical lens. FIGS. 9(A) and (B) are diagrams for explaining an example in which the condensing members 5 and 8 are configured with cylindrical lenses, FIG. 9(A) is a cross-sectional view along the xz plane, and FIG. 9(B) is a cross-sectional view along the yz plane.

[0061] Here, both the condensing members 5 and 8 are cylindrical lenses, but only one of the condensing members 5 and 8 may be a cylindrical lens. That is, a configuration in which at least one of the condensing members 5 and 8 is a cylindrical lens may be employed. Also, at least one of the condensing members 5 and 8 may be a linear Fresnel lens or the like. Further, a combination of a cylindrical lens and a linear Fresnel lens or the like may be used.

[0062] That is, in the present embodiment, the light-receiving optical system may have a characteristic of linearly forming an image of the measurement target surface in a direction non-parallel to the arrangement direction of the photoelectric conversion element array. This non-parallel means that the angle θx between the cylindrical lens generatrix and the arrangement direction of the photoelectric conversion element array is 0 or more and less than 90 degrees.

[0063] Even when this angle is a predetermined angle close to, for example, 10 degrees, 45 degrees, or 90 degrees, the displacement measured with respect to the actual displacement becomes cosθx times, but the measurement is possible and it always becomes a constant systematic error regardless of the inclination angle of the pattern on the surface of the measurement object.

[0064] Therefore, if a constant systematic error is corrected, high-precision measurement can be achieved. However, as described above, since it is desirable that θx be small, it is desirable that the light-receiving optical system linearly form an image of the measurement target surface in a direction substantially perpendicular to the arrangement direction of the photoelectric conversion element array.

[0065] <Embodiment of the method for manufacturing an article> By using the measurement device or the like according to the above embodiment, for example, the productivity and quality in manufacturing an article such as a microdevice such as a semiconductor device or an element having a fine structure can be improved. A method for manufacturing such a device (semiconductor device, magnetic storage medium, liquid crystal display element, etc.) as an article has a measurement step of measuring the displacement of the measurement object by a measurement device.

[0066] Furthermore, the manufacturing process of such an article may include a patterning process of forming a pattern of a mold on the surface of a substrate (wafer, glass plate, film-like substrate, etc.) using a lithography apparatus. Also, the process of transferring the pattern of the mold may include a patterning process of forming a flat pattern.

[0067] In addition, the substrate is not limited to a single base material and may include those having a multilayer structure. Alternatively, it may include a patterning process of exposing a photosensitive body on the substrate using a lithography apparatus.

[0068] Furthermore, the manufacturing process of the article further includes a process of processing the substrate before or after the above patterning process. For example, the processing process may include a process of removing the remaining film of the pattern and a developing process. Also, it may include well-known manufacturing processes such as a process of etching the substrate using the pattern as a mask, a process of cutting out chips from the substrate (dicing), a process of arranging the chips on a frame and electrically connecting them (bonding), and a process of sealing with resin (molding).

[0069] Thus, the manufacturing method of the article in this embodiment has a measuring process of measuring the displacement of a measurement object by a measuring device or the like and a manufacturing process of manufacturing an article using the measured measurement object. According to such a manufacturing method of an article, since the measurement error of the displacement amount and moving speed of the measurement object is small, it is advantageous in terms of the performance, quality, productivity, and production cost of the article.

[0070] As described above, the present invention has been described in detail based on its preferred embodiments. However, the present invention is not limited to the above embodiments, and various modifications and combinations of the above embodiments are possible based on the spirit of the present invention, and they are not excluded from the scope of the present invention. Note that the present invention includes the following combinations.

[0071] (Configuration 1) A measuring device for measuring the displacement of a measurement object, comprising: a light receiving optical system that receives diffusely reflected light generated on a measurement object surface of the measurement object; a photoelectric conversion element array that detects light from the light receiving optical system; and a calculation unit that calculates the displacement using the correlation between two images acquired at different timings for an image output from the photoelectric conversion element array, wherein the light receiving optical system has a characteristic of linearly imaging an image of the measurement object surface in a direction non-parallel to the arrangement direction of the photoelectric conversion element array.

[0072] (Configuration 2) The measuring device according to Configuration 1, wherein the photoelectric conversion element array is composed of photoelectric conversion elements arranged in a one-dimensional manner.

[0073] (Configuration 3) The measuring device according to Configuration 1 or 2, wherein the light receiving optical system linearly images an image of the measurement object surface in a direction substantially perpendicular to the arrangement direction of the photoelectric conversion element array.

[0074] (Configuration 4) The measuring device according to any one of Configurations 1 to 3, wherein the light receiving optical system includes a cylindrical lens and linearly images an image of the measurement object surface.

[0075] (Configuration 5) The measuring device according to any one of Configurations 1 to 4, wherein the light receiving optical system includes a linear Fresnel lens and linearly images an image of the measurement object surface.

[0076] (Configuration 6) The measuring device according to any one of Configurations 1 to 5, wherein the light receiving optical system is a telecentric optical system with respect to the measurement direction.

[0077] (Method) A method for manufacturing an article, comprising: a measurement step of measuring the displacement of a measurement object using the measuring device according to any one of Configurations 1 to 5; and a manufacturing step of manufacturing an article using the measured measurement object.

Explanation of Reference Numerals

[0078] 1: Measuring device 2: Object to be measured 3: Light source 4: Light collecting member 5: Light collecting member 6: Sensor 7: Aperture stop 8: Light collecting member 9: Cylindrical lens

Claims

1. A measuring device for measuring the displacement of a measurement object, comprising: a light-receiving optical system that receives diffusely reflected light generated on a measurement target surface of the measurement object; a photoelectric conversion element array that detects light from the light-receiving optical system; a calculation unit that calculates displacement using the correlation between two images acquired at different timings for an image output from the photoelectric conversion element array; The measuring device, wherein the light-receiving optical system has a characteristic of linearly imaging an image of the measurement target surface in a direction non-parallel to the arrangement direction of the photoelectric conversion element array.

2. The measuring device according to claim 1, wherein the photoelectric conversion element array is composed of photoelectric conversion elements arranged in one dimension.

3. The measuring device according to claim 1, wherein the light-receiving optical system linearly images an image of the measurement target surface in a direction substantially perpendicular to the arrangement direction of the photoelectric conversion element array.

4. The measuring device according to claim 1, wherein the light-receiving optical system includes a cylindrical lens and linearly images an image of the measurement target surface.

5. The measuring device according to claim 1, wherein the light-receiving optical system includes a linear Fresnel lens and linearly images an image of the measurement target surface.

6. The measuring device according to claim 1, wherein the light-receiving optical system is a telecentric optical system with respect to the measurement direction.

7. A manufacturing method of an article, comprising: a measurement step of measuring the displacement of a measurement object by the measuring device according to any one of claims 1 to 5; and a manufacturing step of manufacturing an article using the measured measurement object.

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