JP2007108037A - Position measurement method, distance measurement method and position measurement device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce a measurement time required including a waiting time in high-accuracy position measurement with a large substrate 12 as a measurement object. <P>SOLUTION: A thermal expansion coefficient of a reference scale 13 used for position measurement in an x-direction of the substrate 12 and a thermal expansion coefficient of a linear scale 10 used for position measurement in a y-direction are made to accord with a thermal expansion coefficient of the substrate 12, so that the position measurement of a measurement target part on the substrate 12 is performed without waiting settling of temperature of the substrate 12 and temperature of the scales 10, 13 to temperature determined as a measurement condition. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a position measurement method, a distance measurement method, and a position measurement device for measuring the position or distance of a measurement target location on a substrate such as a glass substrate for a liquid crystal panel.

In order to measure a position on a flat product, as described in Patent Document 1, a camera that images a product on a flat plate and a moving mechanism that relatively moves the camera and the target product are provided. It is used. In addition, a scale provided in the moving mechanism may be used for measuring the position of the moving mechanism such as the XY stage. As a material for such a scale, a material having a thermal expansion coefficient corresponding to the required measurement accuracy is selected. When particularly high measurement accuracy is required, as described in Patent Document 2, quartz glass or the like is used. A material having a thermal expansion coefficient of less than 1 ppm / ° C. (10 ⁻⁶ / ° C.) is selected.
JP2003-28611A JP 2002-130269 A

  Even if the thermal expansion coefficient of the scale provided in the moving mechanism is reduced, the position measurement of the moving mechanism is for the purpose of, for example, dimensional inspection of the substrate placed on the moving mechanism, and the thermal expansion coefficient of the substrate is large. In some cases, it is not possible to perform a dimensional inspection of a substrate with high accuracy unless the temperature of the substrate is precisely adjusted to a temperature determined as a measurement condition.

  For example, a glass substrate for a liquid crystal display panel having a thermal expansion coefficient of 8 ppm / ° C. causes expansion of 0.8 μm per meter with a temperature rise of 0.1 ° C. On the other hand, the dimensional inspection accuracy required for a glass substrate for a liquid crystal display panel is, for example, 0.5 μm per meter. Considering various error factors such as errors caused by the imaging system for imaging the substrate surface, the error due to thermal expansion must be sufficiently smaller than the required dimensional inspection accuracy, for example, only an error of up to 0.3 μm is allowed. . For this reason, before the measurement is started, the error of the substrate temperature with respect to the measurement condition temperature must be within about ± 0.04 ° C., and this temperature setting takes several hours.

  Furthermore, when measuring a plurality of substrates sequentially, it is desirable that the time required for measurement for one substrate is as short as possible. However, it is difficult to make the substrate temperature coincide with the temperature determined as the measurement condition in advance, and even if the position measuring device is installed in a temperature-controlled room and the environmental temperature is set to the measurement condition temperature, It is inevitable that the temperature of the measuring device fluctuates by at least about 0.1 ° C. as it is carried into the temperature-controlled room or placed on the measuring device. Since it is necessary to wait several hours or more for the temperature fluctuation of the substrate and the measuring apparatus to be sufficiently settled, several hours (for example, 3 hours) or more are required as the time required for measurement per substrate.

  Therefore, the present invention uses a large substrate having a thermal expansion coefficient of 4 ppm / ° C. or more and a length in either direction of 500 mm or more as a measurement object, and measures the position of the measurement target portion on the substrate. An object of the present invention is to provide a position measuring method and a position measuring apparatus capable of shortening a time required for measurement including a waiting time when it is necessary to carry out with an error smaller than the thermal expansion amount per 0.1 ° C. And

(1) The position measuring method of the present invention includes a table having a plane that comes into contact with substantially the entire one surface of the substrate when the substrate to be measured is placed, and the substrate when the substrate is placed on the table. A position measuring device is provided that includes a camera for imaging, a moving mechanism that changes the relative position of the table and the camera, and a scale that has a coefficient of thermal expansion of 1 ppm / ° C. or more and is used for measuring the relative position. And
The ambient temperature of the position measuring device is controlled with the temperature determined as a measurement condition as a target, the thermal expansion coefficient is 4 ppm / ° C. or more, and the difference from the thermal expansion coefficient of the scale is 3 ppm / ° C. or less. Place a substrate having a length of 500 mm or more in any direction on a table, and the amount allowed as an error caused by thermal expansion or contraction of the substrate among errors in position measurement regarding the substrate, While the actual thermal expansion or contraction amount of the substrate is larger, the camera captures a plurality of measurement target locations on the substrate, and the scale is used to determine the relative positions of the table and the camera at the time of each imaging. The position of each measurement target location on the substrate is measured using the measured relative position at the time of each imaging and each captured image.

  “A table having a flat surface that is in contact with substantially the entire surface of one side of the substrate” means that, for example, the entire surface of one side of the substrate is compared with a table that actively limits the contact area with the substrate by floating the substrate by a plurality of protrusions. It is something that comes into contact with. The flat surface on the table is preferably made smooth by polishing or the like.

  The “moving mechanism that changes the relative position between the table and the camera” is a mechanism that moves at least one of the table and the camera to change the relative position. The moving mechanism preferably moves the table in one direction and moves the camera in a direction perpendicular to the table. In this case, it is preferable to provide two scales individually corresponding to each direction.

  The scale has a coefficient of thermal expansion of 1 ppm / ° C. or higher. The upper limit of the thermal expansion coefficient of this scale is not particularly limited. For example, if the material is glass, the upper limit of the thermal expansion coefficient of the existing glass is about 10 ppm / ° C. This scale is preferably calibrated at the temperature defined as the measurement condition.

  The substrate has a thermal expansion coefficient of 4 ppm / ° C. or higher as a measurement target. There is no particular upper limit on the thermal expansion coefficient of the substrate, and it is defined by the material used as the substrate.

  The substrate is a large object whose length in either direction is 500 mm or more. The upper limit of the length is not particularly limited and is determined by the size selected as the substrate. For example, a substrate having a length in either direction of 3 m or 4 m may be set as a measurement target.

  The material of the substrate or scale is selected so that the difference between the thermal expansion coefficient of the substrate and the thermal expansion coefficient of the scale is 3 ppm / ° C. or less. The smaller the difference between the thermal expansion coefficients, the better. The thermal expansion coefficients of the substrate and the scale are more preferably the same.

  According to the position measuring method of the present invention, the temperature of the substrate placed on the position measuring device quickly approaches the temperature of the position measuring device, and the values of the thermal expansion coefficient of the substrate and the thermal expansion coefficient of the scale are close. The position of the measurement target on the substrate can be measured with high accuracy without waiting for the temperature of the scale and the temperature of the substrate to reach the temperature determined as the measurement condition. That is, the position measurement can be performed with almost the same accuracy as when the position of the measurement target position is measured at the temperature defined as the measurement condition.

(2) The distance measuring method according to the present invention includes a table having a plane that comes into contact with substantially the entire surface of one side of the substrate when the substrate to be measured is placed, and the substrate when the substrate is placed on the table. A camera that captures an image; a moving mechanism that changes a relative position of the table and the camera; a first scale that is used to measure the relative position; and a heat that is used in combination with the first scale to measure the relative position. Preparing a position measuring device comprising a second scale having an expansion coefficient different from that of the first scale;
A substrate having a thermal expansion coefficient of 4 ppm / ° C. or more and a length in either direction of 500 mm or more is mounted on a table by controlling the ambient temperature around the position measuring device with the temperature set as a measurement condition as a target. And while the actual thermal expansion or contraction amount of the substrate is larger than the amount allowed as an error caused by thermal expansion or contraction of the substrate among errors in position measurement with respect to the substrate, Imaging a plurality of measurement target locations on the substrate with the camera, measuring a relative position between the table and the camera at the time of each imaging using a first scale, and measuring using a second scale, The position of each measurement target location on the substrate is measured using the relative position at the time of each imaging measured using the first scale and each of the captured images, and the measurement at the time of each imaging measured using the second scale. Relative position and image Each image is used to measure the position of each measurement target location on the substrate, and two of the measurement target locations on the substrate are measured using the first scale and the second scale. The position is obtained, and the distance between the two places on the substrate is obtained by complementary calculation using these obtained positions.

  Here, after measuring the position of each measurement target location on the substrate using the first scale and the second scale, two of the measurement target locations on the substrate are measured at the positions measured using the first scale. The distance between the two places based on the position measured using the second scale and the distance between the two places based on the distance between the two places on the substrate by the complementary calculation using these obtained distances The distance may be obtained.

  Alternatively, after measuring the position of each measurement target location on the substrate using the first scale and the second scale, the position measured using the first scale for the first location among the measurement target locations on the substrate And the position measured using the second scale, the position of the first location is obtained by complementary calculation using these obtained locations, and the first location of the second location of the measurement target location on the substrate is determined. The position measured using the scale and the position measured using the second scale are obtained, the position of the second location is obtained by the complementary calculation using these obtained positions, and the first obtained by the complementary calculation is obtained. You may make it obtain | require the distance between a 1st location and a 2nd location from the position of a location, and the position of a 2nd location.

  The first scale and the second scale are preferably calibrated at a temperature determined as a measurement condition. The thermal expansion coefficient of the first scale and the thermal expansion coefficient of the second scale are preferably different by 3 ppm / ° C. or more in order to ensure the accuracy of the complementary calculation. There is no particular upper limit for the difference in thermal expansion coefficient, and it is defined by the material of the scale that can be used.

  Either the first scale or the second scale may have a thermal expansion coefficient of less than 1 ppm / ° C.

  The “complementary calculation” is based on the temperature difference between the temperature determined as the measurement condition and the actual measurement temperature. At the actual measurement temperature, the substrate, the first scale, and the second scale have the respective known thermal expansion coefficients. Therefore, it is preferable to perform the complementary calculation using the fact that the thermal expansion or contraction is applied.

  According to the distance measuring method of the present invention, the temperature of the substrate placed on the position measuring device quickly approaches the temperature of the position measuring device, and the distance based on the position measured using the first scale and the second scale are calculated. Since it is possible to estimate the actual distance between the two measurement target locations on the substrate by complementary calculation from the distance based on the position measured using the scale temperature and the substrate to the temperature defined as the measurement condition It is possible to perform highly accurate distance measurement between measurement target locations on the substrate without waiting for the temperature to settle. In addition, substrates having various values of thermal expansion coefficients can be measured.

  (3) The position measuring apparatus according to the present invention includes a table having a smooth surface that comes into contact with substantially the entire one surface of the substrate when the substrate to be measured is placed, and the substrate when the substrate is placed on the table. , A moving mechanism that changes the relative position of the table and the camera, a first scale that is used to measure the relative position, and a first scale that is used to measure the relative position, A thermal expansion coefficient of the first scale and a second scale different by 3 ppm / ° C. or more.

  The position measuring apparatus according to the present invention can be used to perform highly accurate distance measurement between measurement target portions on a substrate in a short measurement time. In addition, substrates having various values of thermal expansion coefficients can be measured.

  According to the present invention, without waiting for the temperature of the scale and the temperature of the substrate to be set as the measurement conditions, high-precision position measurement of the measurement target location on the substrate or high accuracy between the measurement target locations Distance measurement can be performed, and the time required for measurement including waiting time can be shortened.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

(Embodiment 1)
FIG. 1 is a perspective view showing a schematic configuration of a position measuring system according to one embodiment of the present invention, and FIG. 2 is a plan view of the position measuring apparatus.

  As shown in FIG. 1, the position measurement system of this embodiment includes a position measurement device 1 and a control device 2 connected to the position measurement device 1 so as to be able to transmit information to each other. A computer that executes a control program for controlling the position measuring apparatus 1 is incorporated.

  The position measuring device 1 is installed in a temperature-controlled room (not shown), and the position measuring device 1 is movable along a stone base 3 such as granite and a pair of guide rails 4 installed thereon. A table 5, a gate-type gantry 6 installed at a fixed position on the base 3 across the table 5, a camera movement mechanism (not shown) provided in the gantry 6, and a camera movement mechanism Camera A.

   The temperature-controlled room in which the position measuring device 1 is installed is controlled to a target temperature of 23 ° C., and the wall of the temperature-controlled room is provided with a small door for carrying a substrate. The substrate 12 is carried into the temperature-controlled room and placed on the table 5 of the position measuring device 1.

  The rectangular plate-like table 5 can be moved in the y direction (left and right direction in FIG. 2) by a drive mechanism such as a linear motor (not shown). The camera A can be moved in the x direction by a camera moving mechanism whose movable direction is an x direction (vertical direction in FIG. 2) orthogonal to the y direction.

  On the base 3, a linear scale 10 extending along the y direction that is the moving direction of the table 5 is provided, and an encoder head (not shown) that moves integrally with the table 5 is installed on the lower surface of the table 5. The linear scale 10 and the encoder head constitute a linear encoder that measures the amount of movement of the table 5 in the y direction.

  The material of the linear scale 10 is soda glass having a thermal expansion coefficient of 8 ppm / ° C.

  Two linear scales 10 and two encoder heads are provided to form two linear encoders, and each linear encoder measures the amount of movement of the table 5 on the near side and the far side in FIG.

  Each encoder head includes a light projecting unit and a light receiving unit. The light receiving unit receives reflected light that is emitted from the light projecting unit and modulated by the linear scale 10. A pulse signal can be obtained. In addition, since an origin pattern is provided at one location of each linear scale 10, an origin signal at the table position can be obtained. The two linear scales 10 are provided to correct an error in the amount of table movement caused by yawing (rotation in the horizontal plane) of the posture of the table 5.

  Instead of the linear encoder, a laser interferometer or other various known movement amount measuring devices can be used.

  The table 5 on which the substrate 12 to be measured is placed is made of stone such as granite similarly to the base 3, and the table 5 has positioning pins for positioning the substrate 12 in contact with each other, Suction holes are provided for sucking air from under the substrate 12 to bring the substrate 12 into close contact with the table 5.

  Further, the portion on the surface of the table 5 on which the substrate 12 is placed is polished smoothly so as to be in close contact with the entire bottom surface of the substrate 12, and the surface roughness (Ra) is about 50 μm. As a result, the area where the substrate 12 contacts the surface of the table 5 is about 5% of the area of one side of the substrate 12. The preferable surface roughness (Ra) of the plane portion on which the substrate 12 on the table 5 is placed is 70 μm or less or 100 μm or less. In order not to make it difficult to remove the substrate 12 from the table 5 because the substrate 12 and the table 5 are too close to each other, it is also preferable that the surface roughness (Ra) of the planar portion is 20 μm or more or 5 μm or more. .

  The table 5 is made of stone as described above, and has a much larger heat capacity than the thin glass substrate 12. With these configurations, when the substrate 12 is placed on the table 5, the temperature of the substrate 12 rapidly matches the temperature of the table 5 in about 3 minutes.

  Further, a reference scale 13 extending in the x direction perpendicular to the moving direction (y direction) of the table 5 is installed near one end (the left end in the figure) on the table 5. Information about the position of the visual field of the camera A is given in the captured image when the image is captured.

  The substrate 12 is, for example, a glass substrate for a liquid crystal panel, and has a size of 730 mm in the x direction and 920 mm in the y direction. The material of the substrate 12 is Asahi Glass AN100 having a thermal expansion coefficient of 8 ppm / ° C., and has the same thermal expansion coefficient as the linear scale 10 and the reference scale 13.

  A reference mark and a wiring pattern (not shown) are formed on the substrate 12 by etching the metal film. The cross marks P, Q, R, and S in FIG. 2 are reference marks. Position measurement with an accuracy of ± 0.5 μm over the entire area of the substrate 12 is required.

  The camera moving mechanism built in the gantry 6 moves the camera A that images the substrate 12 placed on the table 5 in the x direction. The camera moving mechanism includes a linear encoder, and moves the camera A to the x coordinate commanded from the control device 2 while measuring the amount of movement of the camera in the x direction with the linear encoder. Since the error of the camera movement amount is corrected by imaging of the reference scale 13, there is no problem even if the linear encoder has a coarse resolution of about 1 μm, for example.

  The camera A has a configuration having an objective lens like a microscope, and includes a two-dimensional CCD image sensor. The imaging magnification can be changed by exchanging the objective lens. The field of view on the substrate 12 when the magnification is highest is 144 μm in the x direction and 110 μm in the y direction in FIG.

  The control device 2 includes a keyboard and a display, and sends a command to the position measurement device 1 in real time, observes an image captured by the position measurement device 1, and controls a program for controlling the position measurement device 1. You can enter. The program for controlling the position measurement device 1 can also be downloaded from the outside via a network.

  3 is an enlarged view of a part of the reference scale 13 in FIG. 2. The x direction (vertical direction) in FIG. 2 corresponds to the vertical direction in FIG. 3, and the y direction (horizontal direction) in FIG. ) Corresponds to the horizontal direction in FIG.

  The material of the reference scale 13 is Asahi Glass AN100 having the same thermal expansion coefficient of 8 ppm / ° C. as that of the substrate 12, and the reference scale 13 and the linear scale 10 are calibrated at 23 ° C. which is a temperature determined as a measurement condition. Yes. It is included in the calibration here to manufacture the reference scale 13 and the linear scale 10 by controlling the temperature so as to show the correct length at 23 ° C. When the reference scale 13 or the linear scale 10 itself is not necessarily manufactured so as to show a correct length at 23 ° C., the length indicated by the reference scale 13 or the linear scale 10 at 23 ° C. is measured, Correction based on the length or position measured using the reference scale 13 or the linear scale 10 is also included in the calibration here.

  The reference scale 13 is formed with a repeating pattern with a period of 100 μm in the x direction (up and down direction). This repeating pattern is a pattern in which the cross pattern is connected to the upper and lower sides in the center of the horizontally long rectangular pattern without being connected to the left and right sides of the rectangular pattern.

  This rectangular pattern has a length in the x direction (up and down direction) of 100 μm, a length in the y direction (left and right direction) of 200 μm, and the length of the central cross pattern in the y direction (left and right direction) is 100 μm. The line width of each line constituting the pattern is 10 μm.

  The change in the position of the field of view of the camera A caused by the movement amount error of the camera A and the posture change of the camera A is made to be sufficiently smaller than 100 μm due to mechanical accuracy. Therefore, by using the command value or measurement value of the camera position in the x direction, it is not indefinite which pattern of the reference scale 13 is being viewed. The x coordinate in the coordinate system with reference to the table 5 of the point on the pattern of the reference scale 13 (for example, the center of the cross pattern closest to the center of the visual field) can be known. It is possible to know the x coordinate of the center of the field of view of the camera A in the coordinate system with reference to.

  Since the fluctuation of the visual field in the y direction is also sufficiently smaller than 100 μm, the reference scale 13 can be surely placed in the visual field of the camera A by moving the table 5 to a predetermined position. At this time, the y coordinate of the center of the field of view of the camera A can be known. The x-coordinate and y-coordinate of the visual field center thus obtained are used for correction when obtaining the coordinates of the measurement target location.

  It should be noted that information on the coordinates of the location is added to the pattern of the reference scale 13 in numerical or graphic form at an interval that allows at least one to enter the field of view of the camera A, and the coordinate value is directly obtained from the captured image. You may make it read. Then, the coordinates of the visual field center can be obtained from only the captured image without using the command value and measurement value of the camera position and table position.

  In the present embodiment, the material of the table 5 and the base 3 is stone (granite) as described above, and the thermal expansion coefficient thereof is 8 ppm / ° C., which coincides with the thermal expansion coefficients of the scales 10 and 13. ing. Therefore, even if the scales 10 and 13 are bonded to the base 3 or the table 5, distortion due to the difference in thermal expansion coefficient hardly occurs, but each scale 10 or 13 has a double-sided adhesive tape on the base 3 or the table 5. Therefore, even if there is a difference in thermal expansion coefficient, the tape absorbs strain.

  FIG. 4 shows an outline of the measurement procedure of the measurement target portion of the substrate 12 using the position measuring apparatus 1. First, the substrate 12 is placed on the table 5 (step n1), and the substrate 12 and the linear scale 10 are displayed. Then, without waiting for the temperature of the reference scale 13 to reach the target temperature, which is a temperature determined as a measurement condition, measurement is performed as described later (step n2), and the substrate 12 is recovered from the table 5. (Step n3), the process ends.

  Next, details of the measurement in step n2 will be described by applying to some specific examples.

  FIG. 5 shows the procedure for measuring the coordinates of the reference mark P, which is the measurement target location on the substrate 12, using the camera A. The positional relationship between the table and the camera and the contents of the processing in steps 1 to 3 are shown. Show.

  Here, the coordinates of the reference mark P mean the center coordinates of the cross mark P in FIG. The cross mark P is also simply referred to as a point P.

  In step 1, the camera moving mechanism is moved to move the camera A in the x direction and the table 5 is moved in the y direction so that the position P is assumed to be within the field of view of the camera A. Then, the positional relationship between the table 5 and the camera A is set to a state a shown in FIG.

  The movement of the camera A and the table 5 is preferably performed simultaneously, but may be performed in order.

  In step 1, if the point P is not in the field of view even if the point A is assumed to be present by the camera A, the camera A and the table 5 are finely moved. As shown in FIG. 4, the region surrounding the first imaging position Z indicated by the oblique lines is imaged in, for example, eight times until the point P enters the field of view. If the point P cannot be picked up yet, the region outside the point P is picked up in multiple times until the point P enters the field of view.

  In FIG. 9, the table 5 is slightly moved once in the y direction from the first imaging position Z indicated by the oblique lines, and the point P is not within the field of view. An example is shown in which the point P is in the field of view by finely moving the image, and the fine movement of the imaging position when the point P is not in the field of view in the second imaging is indicated by a virtual line.

 Next, in step 2 of FIG. 5, the table 5 and the camera are moved by moving only the table 5 in the y direction without moving the camera moving mechanism as it is when the point P is imaged, that is, with the camera A still. The positional relationship of A is set to the state b shown in FIG. 7, and the reference scale 13 is imaged by the camera A.

  In step 3, the coordinates of the point P are calculated by image processing and calculation.

  FIG. 8 schematically shows the positional relationship between the field of view when the point P is imaged and the field of view when the reference scale 13 is imaged and the table 5 in order to explain the calculation of the coordinates of the point P by this image processing and calculation. It is shown as an example.

  First, an image obtained by imaging the point P is processed to obtain the coordinates (x1, y1) of the point P in the visual field coordinate system having the visual field center O shown in FIG.

  Next, the table coordinate system shown in FIG. 8B is processed by processing the image of the reference scale 13 picked up by moving only the table 5 without moving the camera A from the state where the point P is picked up. The coordinates (X1, Y1) of the visual field center O at are obtained. At this time, the coordinates (X1, Y1) of the visual field center O are obtained using the command value or measurement value of the camera position in the x direction and the command value or measurement value of the table position in the y direction. That is, since the coordinates in the x and y directions in the table coordinate system of the points on the pattern of the reference scale 13 in the captured image can be known based on the command value or the measured value, the position of this pattern and the visual field center O From the relationship, the coordinates (X1, Y1) of the visual field center O in the table coordinate system are obtained.

  Furthermore, the movement amount measurement value Δy by the linear encoder is acquired as the movement amount of the table 5 from the time when the point P is imaged until the time when the reference scale 13 is imaged. When it is guaranteed that the command value for the table movement amount matches the measurement value Δy by the linear encoder, this command value may be acquired as the movement amount of the table 5. In this case, the measured value of the movement amount of the table 5 by the linear encoder is indirectly acquired.

  A value (X1 + x1) obtained by adding the x coordinate X1 of the point P in the visual field coordinate system of FIG. 8A to the x coordinate X1 of the visual field center O in the table coordinate system at the time of imaging the reference scale obtained in FIG. 8B. This is the x coordinate of the point P in the table coordinate system.

  The table movement amount Δy and the y coordinate y1 of the point P in the visual field coordinate system of FIG. 8A are added to the y coordinate Y1 of the visual field center O in the table coordinate system at the time of imaging the reference scale obtained in FIG. 8B. The added value (Y1 + Δy + y1) is the y coordinate of the point P in the table coordinate system.

  If the relative positional relationship between the table 5 and the base 3 is found when measuring the movement amount of the table 5, the position of the point P that is a measurement target location with respect to the base 3 is obtained. be able to.

  As described above, the coordinates (position) of the point P are obtained by using three types of information: the image obtained by imaging the reference scale 13, the movement amount of the table 5, and the image obtained by imaging the point P.

  The position (X1, Y1) of the field of view of the camera A at the time of imaging the reference scale can be obtained from the image obtained by imaging the reference scale 13 which is the first information among the three types of information as described above. The position of the visual field is a position based on the position of the reference scale 13 at the time of image capturing of the reference scale, that is, the position of the table 5 at that time. An error occurs in the position of the visual field due to an error in the movement amount of the camera A and a change in the posture of the camera A. Even if there is such an error in the position of the visual field, the error is obtained from the image of the captured reference scale 13. By using the position (X1, Y1) of the visual field, errors in the position of the visual field do not affect the position measurement result.

  That is, even if a camera movement amount error and an error due to posture variation occur, by capturing the reference scale 13 on the table 5, the coordinates of the visual field position (from the positional relationship with the pattern of the reference scale 13 in the visual field ( X1, Y1) is obtained and the coordinates (X1, Y1) are used to eliminate the influence on the position measurement result due to the position error of the visual field.

  When the movement amount Δy of the table 5 between the reference scale imaging and the point P imaging as the second information and the coordinates (X1, Y1) of the visual field position as the first information are used, the reference scale imaging is performed. It is possible to obtain the position of the visual field when the point P is imaged with reference to the position of the table 5 at the time.

  Furthermore, the position (x1, y1) of the point P with reference to the field of view of the camera A when the point P is imaged can be obtained from the image obtained by imaging the point P as the third information as described above. Therefore, by using all the information, the position (X1 + x1, Y1 + Δy + y1) of the point P with reference to the position of the table 5 at the time of imaging the reference scale can be obtained.

  FIG. 10 is a diagram showing a procedure for measuring the coordinates and related dimensions and angles of the reference marks P, Q, R, and S of the substrate 12 using the camera A.

  First, as in FIG. 5 described above, in step 1, the state a in FIG. 6 is set, and the point P is imaged by the camera A, and in step 2, the camera moving mechanism is moved without moving the camera A, that is, Without moving, only the table 5 is moved in the y direction to the state b in FIG. 7, and the reference scale 13 is imaged by the camera A.

  Next, in step 3, without moving the camera moving mechanism, that is, without moving the camera A in the x direction, only the table 5 is moved in the y direction, and the positional relationship between the table 5 and the camera A is shown in FIG. 11, the point A is imaged by the camera A.

  At this time, if the point Q is not in the field of view of the camera A, the point A is searched for the point Q by finely moving the camera A and the table 5 as described with reference to FIG. To do.

  When searching for the point Q, when the camera A is finely moved in the x direction and the point Q is imaged, the process proceeds to step 4 where only the table 5 is moved in the y direction, and the positional relationship between the table 5 and the camera A is In the state b ′ shown in FIG. 12, the reference scale 13 is imaged by the camera A, and the process proceeds to Step 5.

  When searching for the point Q, when the table 5 is finely moved in the y direction to pick up an image of the point Q, the accumulated movement amount obtained by adding the minute movement amount to the movement amount is set as the movement amount of the table 5.

  In step 3, when the point Q exists in the field of view of the camera A and the search is not necessary, or when the search is performed but the camera A is not moved, the camera A Since the reference scale 13 is not moved in the state of being imaged in step S4, the above step 4 for imaging the reference scale 13 with the camera A is skipped, and the process proceeds to step 5.

  Next, in the same way as the points P and Q for the points R and S, in step 5, the camera A is moved in the x direction and the table 5 is moved in the y direction so that the positional relationship between the table 5 and the camera A is In a state d shown in FIG.

  Next, in step 6, without moving the camera A in the x direction, only the table 5 is moved in the y direction, and the positional relationship between the table 5 and the camera A is set to the state e shown in FIG. The scale 13 is imaged.

  Next, in step 7, without moving the camera A in the x direction, only the table 5 is moved in the y direction, and the positional relationship between the table 5 and the camera A is set to the state f shown in FIG. S is imaged. At this time, if the point S is not in the field of view of the camera A, the camera S and the table 5 are finely moved and the point S is searched and imaged as in FIG.

  If the camera A is finely moved in the x direction during the search for the point S, the process proceeds to step 8 where only the table 5 is moved in the y direction and the positional relationship between the table 5 and the camera A is shown in FIG. In the state e ′ shown, the camera A captures the reference scale 13, and the process proceeds to Step 9.

  When searching for the point S, when the table 5 is finely moved in the y direction and the point Q is imaged, the accumulated movement amount obtained by adding the minute movement amount to the above movement amount is set as the movement amount of the table 5.

  In step 7, when the point S exists in the field of view of the camera A and the search is not necessary, or when the search is performed but the camera A is not moved, the camera A performs step 6. Since the reference scale 13 is not moved in the state of being imaged in step S8, the above step 8 for imaging the reference scale 13 with the camera A is skipped, and the process proceeds to step 9.

  In step 9, the coordinates of the points P and Q are set in the same manner as described with reference to FIG. 8, the captured image of the points P and Q by the camera A, the image of the reference scale 13 by the camera A, and the movement amount of the table 5. Similarly, the coordinates of the points R and S are calculated using the captured images of the points R and S by the camera A, the image of the reference scale 13 by the camera A, and the amount of movement of the table 5.

  In step 10, the dimension between the reference marks and the angle formed by two straight lines connecting the reference marks are calculated from the calculated coordinates.

  For example, the distance (dimension) between the reference marks P and Q is calculated from the coordinates of the reference marks P and Q, or, for example, an angle formed by a straight line connecting the reference marks P and Q and a straight line connecting the reference marks Q and S That is, the orthogonality is calculated.

  Thus, by calculating the dimension between the reference marks P, Q, R, and S on the substrate 12 and the angle formed by the straight line connecting them, the distortion and orthogonality of the pattern on the substrate can be grasped.

  FIG. 17 shows the temperature of the table 5 and the temperature of the reference scale 13 when the temperature in the temperature-controlled room rises by 0.15 ° C. from the target temperature of 23 ° C. due to the substrate 12 being brought into the temperature-controlled room and the entry and exit of people. The time change is shown.

  The reason why the measurement result line is stepped in units of 0.01 ° C. is that the resolution of the temperature measuring device is 0.01 ° C. The temperature of the table 5 and the temperature of the reference scale 13 change almost in agreement with a difference of about 0.01 ° C. This change coincides with a change in the temperature in a temperature-controlled room (not shown), and the temperature of the linear scale 10 also changes almost coincident with the measurement result of FIG.

Since the thermal expansion coefficient of the reference scale 13 and the linear scale 10 is 8 ppm / ° C., when trying to suppress a dimensional error due to thermal expansion within 0.3 μm per meter,
1 m × 8 ppm / ° C. × 0.0375 ° C. = 0.3 μm
From the calculation, it is understood that the error from the temperature (23 ° C.) determined as the measurement temperature must be within about 0.04 ° C. In order to set the temperature within this range, a waiting time of 3 hours or more is required with reference to FIG.

  According to the present embodiment, in such a situation, it is possible to perform position measurement with the same accuracy without waiting for the temperature of the reference scale 13 or the linear scale 10 to settle.

  FIG. 18 shows a change between the temperature of the table 5 and the temperature of the substrate 12 from the time when the substrate 12 is loaded from the door provided on the wall of the temperature-controlled room and placed on the table 5 of the position measuring apparatus 1. Yes.

  The temperature of each part such as the table 5, the reference scale 13, and the linear scale 10 of the position measuring device 1 changes substantially in accordance with the temperature in the temperature-controlled room.

  The temperature defined as the measurement condition in the present embodiment is 23 ° C., and the temperature control target in the temperature-controlled room is 23 ° C. accordingly. The temperature in the temperature-controlled room drops by about 0.1 ° C. due to the loading of the substrate 12, and it takes 2 hours or more to settle to the target temperature.

  The temperature of the substrate 12 is about 21 ° C. when it is brought into the temperature-controlled room, and when it is placed on the table 5, it quickly approaches the temperature of the table 5, and after about 3 minutes from the placement, it almost reaches the temperature of the table 5. Accordingly, the difference between the temperature of the table 5 and the temperature of the substrate 12 is within about 0.01 ° C. Depending on conditions such as the thickness of the substrate 12, the temperature of the substrate 12 may substantially match the temperature of the table 5 in one minute from the placement.

  In this embodiment, since the thermal expansion coefficients of the substrate 12, the reference scale 13, and the linear scale 10 are all 8 ppm / ° C., if these temperatures coincide with each other, the temperature is determined as the measurement condition. Even if they differ by about 0.1 ° C., errors due to the difference in thermal expansion hardly occur. Therefore, position measurement can be performed without waiting for the temperature of the linear scale 10 or the reference scale 13 and the temperature of the substrate 12 to be set to the target temperature.

  In the present embodiment, the measurement can be performed after the substrate 12 is placed on the table 5 and 3 minutes have elapsed, but it is also possible to perform the measurement after a longer time has elapsed. If the measurement is performed within one hour, the advantage of the short measurement time including the waiting time of the present embodiment over the prior art is obvious.

Assuming that the scales 10 and 13 are calibrated at the temperature defined as the measurement condition, when the temperature in the temperature-controlled room is the temperature defined as the measurement condition, correct measurement can be performed even if there is a difference in the coefficient of thermal expansion of each part. it can. If the required position measurement error is within ± 0.5 μm per meter, of which ± 0.3 μm is allowed as an error due to thermal expansion or contraction, the coefficient of thermal expansion of the substrate 12 and the reference Some difference is allowed between the thermal expansion coefficients of the scale 13 and the linear scale 10. When measuring when the difference between the temperature in the temperature-controlled room (equal to the temperature of each part) and the temperature set as the measurement condition is 0.1 ° C,
3 ppm / ° C. × 0.1 ° C. = 0.3 μm / m
From the above calculation, the allowable range for the difference in thermal expansion coefficient is about 3 ppm / ° C.

  If the substrate 12 and the scales 10 and 13 are made of glass, the thermal expansion coefficient of the glass is distributed between about 3 ppm / ° C. and about 10 ppm / ° C. depending on the material of the glass. In this range, the materials of the scales 10 and 13 are selected.

(Embodiment 2)
FIG. 19 is a plan view corresponding to FIG. 2 of another embodiment of the present invention, and the same reference numerals are given to the portions corresponding to FIG.

  The position measuring apparatus 1 'according to this embodiment includes a linear scale 10b having a different thermal expansion coefficient, in addition to the linear scale 10 of FIG. 2 (referred to as the linear scale 10a in FIG. 19).

  In addition to the reference scale 13 of FIG. 2 (referred to as reference scale 13a in FIG. 19), a reference scale 13b having a different thermal expansion coefficient is provided.

  The linear scale 10a and the reference scale 13a as the first scale, and the linear scale 10b and the reference scale 13b as the second scale are different in thermal expansion coefficient by 3 ppm / ° C. or more. In this embodiment, the linear scale 10a And the thermal expansion coefficient of the reference scale 13a is 8 ppm / ° C., as in the above-described embodiment, whereas the thermal expansion coefficients of the linear scale 10b and the reference scale 13b are 3 ppm / ° C., and the material is For example, Corning EAGLE2000. Each scale 10a, 10b, 13a. 13b is calibrated at a temperature determined as a measurement condition, as in the above-described embodiment.

  In this embodiment, the linear scale 10a and the reference scale 13a as the first scale are used to measure the position in the same manner as the above-described embodiment, and the linear scale 10b and the reference scale 13b as the second scale are used in the same manner. The final position is calculated from each measured value by complementary calculation.

  For example, on the substrate 12 having a thermal expansion coefficient of 5 ppm / ° C., the distance between two points separated in the moving direction (X direction) of the camera A is measured using the reference scale 13a as the first scale, When the measurement is performed using the reference scale 13b as the second scale and the measurement results are 0.6999980 (m) and 0.70000013 (m), the two points are calculated by performing the complementary calculation as follows. The distance LW between them is calculated.

here,
LW: Distance calculated by complementary calculation L3: Measurement result obtained using the reference scale 13b having a thermal expansion coefficient of 3 ppm / ° C. (0.7000014)
L8: Measurement result obtained using the reference scale 13a having a coefficient of thermal expansion of 8 ppm / ° C. (0.6999980)
CTE3: Thermal expansion coefficient of the reference scale 13b (3 ppm / ° C)
CTE8: Thermal expansion coefficient of the reference scale 13a (8 ppm / ° C)
CTEW: Thermal expansion coefficient of substrate (5 ppm / ° C)
LW = (L3-L8) × [(CTE8-CTEW) / (CTE8
-CTE3)] + L8
= (0.7000014-0.6999980) x {(8 ppm-5 ppm) / (8 ppm-3 ppm)} + 0.6999980
= 3.4 × 10 ⁻⁶ × 0.6 + 0.6999980
= 0.7000000
It becomes.

  FIG. 20 is a diagram for explaining the formula for the complementary calculation. The vertical axis indicates the true distance, and the horizontal axis indicates the temperature.

  Assuming that the true value of the distance between two points on the substrate is 0.7000000 at the target temperature T0, the reference scale 13a having a thermal expansion coefficient of 8 ppm / ° C. and the thermal expansion coefficient of 3 ppm at this target temperature. The true value of 0.7000000 is measured using any of the reference scales 13b at / ° C.

  On the other hand, at the temperature T1 higher than the target temperature T0, the reference scale 13a having a thermal expansion coefficient of 8 ppm / ° C., the reference scale 13b having a thermal expansion coefficient of 3 ppm / ° C., and the substrate 12 having a thermal expansion coefficient of 5 ppm / ° C. Both of these are expanded at a ratio corresponding to the size of the thermal expansion coefficient.

  As a result, although the substrate 12 is also expanded, the distance between the two points on the substrate measured with the reference scale 13a having a larger expansion amount than that of the substrate 12 is less than the true value of 0.7000000. 6999980. On the other hand, the distance between two points on the substrate measured with the reference scale 13b having a smaller expansion amount than that of the substrate 12 is 0.7000014, which is larger than the true value of 0.7000000.

  Therefore, based on the value measured with one reference scale 13a (0.6999980), the difference between the measured values (0.7000014-0.6999980) due to the difference between the thermal expansion coefficients of both reference scales 13a, 13b, The distance between the two points is calculated by proportionally dividing the difference between the thermal expansion coefficients of the reference scales 13a and 13b and the difference between the thermal expansion coefficients of the reference scale 13a and the substrate 12.

  In this example, the case where the distance between two points separated in the moving direction (X direction) of the camera A is measured using the reference scale 13a and the reference scale 13b, respectively, is linear with the reference scales 13a and 13b. The same applies when measuring any point on the substrate 12 using the scales 10a and 10b.

  Thus, since the position of the measurement object location of the board | substrate 12 is measured by complementary calculation using the 1st, 2nd scale from which a thermal expansion coefficient differs, the board | substrate 12 and scale 10,13 like the above-mentioned Embodiment 1. FIG. The position can be measured by performing a complementary calculation with the substrate 12 having a thermal expansion coefficient of an arbitrary value as a measurement target, without being limited to the case where the thermal expansion coefficient between is approximate.

  Moreover, since this complementary calculation formula is established at an arbitrary temperature near the target temperature, highly accurate position measurement is possible without waiting for the temperature of the substrate 12, the reference scales 13a and 13b and the linear scales 10a and 10b to settle. This makes it possible to shorten the time required for measurement including the waiting time.

(Other embodiments)
In each of the above-described embodiments, in order to correct an error in the position of the visual field due to an error in the movement amount of the camera A and a change in the posture of the camera A, the position is measured using an image obtained by capturing the reference scale with the camera A. However, as another embodiment of the present invention, for example, when the error of the position of the visual field can be corrected by other means, the reference scale may be omitted and the reference scale may not be imaged. In this case, for example, the movement amount of the camera moving mechanism built in the gantry 6 by the above-described linear encoder may be used for the calculation of the coordinate in the x direction. The difference between the thermal expansion coefficient of the linear scale constituting the encoder and the thermal expansion coefficient of the substrate may be 3 ppm / ° C. or less. In addition, in the configuration of the second embodiment described above, a linear scale as a second scale having a different thermal expansion coefficient (for example, different by 3 ppm / ° C. or more) may be added separately from the linear scale as the first scale.

  As another embodiment, a position measuring device in which a plurality of cameras are supported by each camera moving mechanism is used, and a measurement target location corresponding to the number of cameras is sequentially imaged while moving the table. Scale imaging may be performed at a common table position.

  The present invention is useful, for example, for dimensional inspection of a substrate.

It is a perspective view showing a schematic structure of a position measuring system concerning one embodiment of the present invention. It is a top view of the position measuring apparatus of FIG. It is an enlarged view of a reference scale. It is a figure which shows the procedure of a position measuring method. It is a figure which shows the measurement procedure of the coordinate of the point P using the camera A. It is a top view of the position measuring apparatus which shows the state a of FIG. It is a top view of the position measuring apparatus which shows the state b of FIG. It is a figure which shows roughly the captured image for demonstrating the calculation of the coordinate of the point P by an image process and a calculation. It is a figure for demonstrating the search procedure of the imaging of a measurement object location. It is a figure which shows the measurement procedure of the coordinate of the points P, Q, R, and S using the camera A. It is a top view of the position measuring device which shows the state c of FIG. It is a top view of the position measuring device which shows the state b 'of FIG. It is a top view of the position measuring apparatus which shows the state d of FIG. It is a top view of the position measuring device which shows the state e of FIG. It is a top view of the position measuring apparatus which shows the state f of FIG. It is a top view of the position measuring device which shows the state e 'of FIG. It is a figure which shows the time change of the temperature of a table and a reference | standard scale from when the air temperature in a temperature-controlled room rose 0.15 degreeC from target temperature. It is a figure which shows the time change of the temperature of a table and a board | substrate from the time of carrying a board | substrate in a thermostat and mounting on a table. It is a top view corresponding to Drawing 2 of other embodiments of the present invention. It is a figure where it uses for description of the formula of a complementary calculation.

Explanation of symbols

1, 1 'position measuring device 2 control device 5 table 6 mount 10, 10a, 10b linear scale 12 substrate 13, 13a, 13b reference scale

Claims (3)

A table having a plane that comes into contact with substantially the entire surface of one side of the substrate when the substrate to be measured is placed;
A camera that images the substrate when the substrate is placed on the table;
A moving mechanism for changing a relative position between the table and the camera;
Preparing a position measuring device having a scale with a coefficient of thermal expansion of 1 ppm / ° C. or more, which is used for measuring the relative position;
Control the temperature around the position measurement device with the temperature set as the measurement condition as the target,
A substrate having a thermal expansion coefficient of 4 ppm / ° C. or more, a difference from the thermal expansion coefficient of the scale of 3 ppm / ° C. or less, and a length in any direction of 500 mm or more placed on a table,
While the actual thermal expansion or contraction amount of the substrate is larger than the amount allowed as an error caused by thermal expansion or contraction of the substrate among the position measurement errors regarding the substrate, the camera Image multiple measurement points on the board,
Measure the relative position of the table and the camera at the time of each imaging using the scale,
A position measurement method for measuring a position of each measurement target portion on a substrate using the measured relative position at the time of each image pickup and each image taken. A table having a plane that comes into contact with substantially the entire surface of one side of the substrate when the substrate to be measured is placed;
A camera that images the substrate when the substrate is placed on the table;
A moving mechanism for changing a relative position between the table and the camera;
A first scale used to measure the relative position;
Preparing a position measuring device including a second scale, which is used in combination with the first scale for measuring the relative position, and having a thermal expansion coefficient different from that of the first scale;
Control the temperature around the position measurement device with the temperature set as the measurement condition as the target,
A substrate having a thermal expansion coefficient of 4 ppm / ° C. or more and a length in either direction of 500 mm or more is placed on the table,
While the actual thermal expansion or contraction amount of the substrate is larger than the amount allowed as an error caused by thermal expansion or contraction of the substrate among the position measurement errors regarding the substrate, the camera Image multiple measurement points on the board,
Measuring the relative position of the table and the camera at the time of each imaging using a first scale and using a second scale;
Measure the position of each measurement target location on the substrate using the relative position at the time of each imaging measured using the first scale and each captured image,
Measure the position of each measurement target location on the substrate using the relative position at the time of each imaging measured using the second scale and each captured image,
The position measured using the first scale and the position measured using the second scale are obtained for two of the measurement target places on the board, and the complementation calculation using these obtained positions is performed on the board. A distance measuring method for obtaining a distance between the two locations. A table having a plane that comes into contact with substantially the entire surface of one side of the substrate when the substrate to be measured is placed;
A camera that images the substrate when the substrate is placed on the table;
A moving mechanism for changing a relative position between the table and the camera;
A first scale used to measure the relative position;
A position measuring device comprising a second scale having a thermal expansion coefficient different from that of the first scale, which is used in combination with the first scale for measuring the relative position.

Images