JP2014006125A - Coordinates correction method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a coordinates correction method which can correct a start position including an accuracy error in a linear scale for managing a position of a stylus using the linear scale.SOLUTION: A coordinates correction method takes a measurement start position of a stylus 6 on a measurement plane of a glass substrate W as a start point, and takes images of two points of indicators formed on the glass substrate W by an imaging means 7, and before correcting the start coordinates on the basis of measurement coordinates of linear scales 4a and 4b provided on respective frame 3 and Y-axis stage 5 and design values of the respective indicators, corrects the measurement coordinates of the respective indicators. The method includes the steps of: calculating a scale ratio on the basis of the design coordinates of the respective indicators and the measurement coordinates of the respective indicators; taking an intersection point of a straight line passing through the respective design coordinates and a straight line passing through the respective measurement coordinates as a rotation center coordinates to calculate an angle made by the rotation center coordinates and both straight lines; and calculating a gravity center position of a work. Then, the method performs similarity transformation on the respective measurement coordinates on the basis of the respective calculated values and corrects the measurement position.

Description

  The present invention relates to a coordinate correction method, and more specifically, in a processing apparatus that performs a predetermined process while relatively moving a processing unit with respect to a work, in order to determine a starting coordinate of a processing start on a processing surface of the work. The present invention relates to an apparatus for imaging two provided indexes by an imaging unit and correcting the measurement coordinates of each captured index.

  Conventionally, a horizontal frame that is perpendicular to each other is defined as an X-axis direction and a Y-axis direction, and a portal frame that can move relative to the workpiece held on the stage in the X-axis direction, and a Y-axis direction at the upper end of the frame. A stylus-type measuring apparatus comprising a Y-axis stage supported on a longitudinal beam so as to be movable in the Y-axis direction via a linear guide, and having a stylus contacting the surface of the workpiece supported on the Y-axis stage is known. (For example, refer to Patent Document 1). In this case, the measured values of the positions of the portal frame and the Y-axis stage are detected by linear scales (linear encoders) provided on the stage and the beam, respectively.

  When measuring the surface shape of a workpiece, such as the thickness of a thin film formed on the substrate surface, with the above stylus type measuring device, the measurement start coordinate is set as the starting position within the workpiece measurement surface (processing surface). The portal frame is moved relative to the substrate on the stage in the X-axis direction, and the Y-axis stage is moved relative to the work, so that the stylus is positioned immediately above the starting position. Then, the stylus is brought into contact with the workpiece, and in this state, the workpiece is relatively moved by an arbitrary predetermined distance in the X-axis direction to measure the surface shape (unevenness) of the measurement surface of the workpiece.

  Here, for example, when the substrate is placed on the stage, there may be a positional shift. For this reason, it is common to detect the amount of deviation of the substrate with respect to the stage and correct the starting point coordinates based on the detected amount. Specifically, at least two alignment marks (indexes) are provided on the measurement surface of the workpiece, and imaging means such as a CCD camera is attached to the Y-axis stage. Then, the alignment mark is imaged by this imaging means, and the rotation direction in which the X axis direction and the Y axis direction and the center of the substrate are rotated from the measured value of the linear scale at this time and the design value of the index formed on the workpiece. The starting point coordinates are corrected by calculating the deviation amount in the (θ direction).

  However, depending on the resolution of the linear scale, there may be a case where the detected measurement value does not match the actual measurement value (that is, there is an error with respect to the exact length measurement). If the starting position is corrected, the correction accuracy deteriorates. This means that when the linear scale has linearity, the accumulated error increases as the size of the workpiece (for example, a substrate having a side of 3 m) increases. In this way, if the starting position changes for each workpiece to be measured, it can no longer be used even when, for example, the formed film thickness is measured and quality control is performed.

JP 7-218207 A

  In view of the above points, the present invention provides a coordinate correction method capable of correcting the starting position including the accuracy error of the linear scale even when the position of the processing means is managed using, for example, a linear scale. That is the issue.

  In order to solve the above-described problems, the present invention allows a workpiece to be held on a stage with its processing surface open, and two horizontal directions orthogonal to each other are defined as an X-axis direction and a Y-axis direction, and the X-axis direction with respect to the stage. In a processing apparatus that performs predetermined processing while relatively moving a processing means mounted on a gate-shaped frame that is relatively movable relative to a workpiece in at least one of the X-axis direction and the Y-axis direction, The position at which processing is started by the processing means is set as the starting point coordinates, and the two indicators provided on the workpiece are respectively imaged by the imaging means, and the linear scale measurement values respectively attached to the frame and the Y-axis stage at this time, Prior to correcting the origin coordinates from the design coordinates of the index, a coordinate correction method for correcting the measurement coordinates of each index, the step of obtaining a scale ratio from the design coordinates of the both indices and the measurement coordinates of each index; , The intersection of the straight line that passes between the measured coordinates and the straight line that passes between the measurement coordinates is set as the rotation center coordinate, and the step of calculating the rotation center coordinate and the angle formed by the two straight lines and the step of determining the center of gravity position of the workpiece are included, respectively. Each measurement coordinate is similarly transformed from the obtained value, and the measurement coordinate is corrected.

  According to the present invention, for example, by using a similarity transformation using a measurement value measured with a linear scale and a design value as a scale ratio, the accuracy error of the linear scale is included without predicting the error rate of the linear scale. Measurement coordinates can be corrected, and in particular, the larger the workpiece size, the more advantageous. As a result, for example, even if a position shift occurs when a substrate is placed on the stage, it is reliably processed for each workpiece. The starting position of the part can be made substantially coincident.

  In addition, this invention is a stylus which the said process means contacts the surface of a workpiece | work, and can be applied to what measures the surface shape.

The front view of the stylus type measuring device of an embodiment of the present invention. The figure explaining the shift | offset | difference of the said board | substrate in the state which mounted the board | substrate on the stage.

  Hereinafter, referring to the drawings, the workpiece is a glass substrate W on which a predetermined thin film is formed, and the processing means is a stylus that moves relative to the surface of the glass substrate. The embodiment of the present invention will be described by taking as an example the case of correcting the coordinates of the starting position.

  Referring to FIG. 1, reference numeral 1 denotes a stylus type measuring device. The stylus measuring device 1 includes a base 2 so that the substrate W is positioned and held on the upper surface of the base. Since a known method for positioning and holding the substrate W can be used, it is omitted here. A gate-shaped frame 3 is disposed on the base 2 so as to straddle the substrate W.

  The portal frame 3 includes columns 31 and 31 on both sides in the Y-axis direction that are erected on the base 2 and a beam 32 that is long in the Y-axis direction and is provided between the upper ends of the columns 31 and 31. In this case, both columns 31, 31 are supported by a pair of other guide rails 33, 33 that are fixed on the base 2 and that are long in the X-axis direction. Then, for example, by moving the portal frame 3 in the X-axis direction via a nut screwed to the ball screw by rotation of a ball screw elongated in the X-axis direction (not shown), the measurement is performed on the measurement surface of the substrate W. The coordinates at which the measurement is started are set as starting positions (starting coordinates), and prior to measurement of the surface shape of the measurement surface, the gate frame 3 is moved relative to the glass substrate W, and the X axis direction position corresponding to the starting coordinates is reached. The stylus is designed to move. In this case, a linear scale (linear encoder) 4a is provided on the upper surface of the base 2 so as to correspond to the column 31, so that the amount of movement of the stylus in the X-axis direction can be measured.

  The Y-axis stage 5 is supported on the beam 32 at the upper end of the portal frame 3 so as to be reciprocally movable by a drive mechanism 51 so as to be movable in the Y-axis direction via a linear guide (not shown). In this case, the driving mechanism 51 is configured to be movable at a predetermined distance (stroke) in the X-axis direction, although not specifically illustrated and described, and a stylus described later with respect to the substrate W is moved by a predetermined distance in the X-axis direction. The relative movement is performed, and the measurement surface (processing surface) surface shape (unevenness) of the substrate W is measured. The drive mechanism 51 may be configured to be rotatable so that the moving direction of the stylus is changed. As the drive mechanism, for example, a known mechanism including a rotation mechanism such as one using a ball screw can be used. The Y-axis stage 5 is also provided with a linear scale 4b so that the amount of movement of the stylus in the Y-axis direction can be measured.

  A support frame 52 that extends downward is attached to the Y-axis stage 5, and a stylus 6 that contacts the surface of the glass substrate W is displaceable in the vertical direction via the Z-axis sensor 61 at the lower end of the support frame 52. Supported, the Z-axis sensor 61 can detect the vertical displacement of the stylus 6. Further, the Y-axis stage 5 is provided with an imaging means 7 having a light source and a CCD camera. The image pickup means 7 is provided with an image processing means (not shown), and image data processed by the image processing means is input to a control means (not shown) so that it can be used for measuring a deviation amount of the glass substrate W with respect to the stage 2. It has become. The control means is a well-known one provided with a microcomputer, a storage element, a sequencer, etc., and includes the operation of the stage 2, the portal frame 3 and the Y-axis stage 5 and the processing of the measured values of the linear scales 4a and 4b. Controls the operation of the needle type measuring device.

  When measuring the surface shape of the glass substrate W by the stylus type measuring device, the origin position where the portal frame 3 is positioned on one side of the base 1 in the X-axis direction and the Y-axis stage 5 is positioned on one side in the Y-axis direction. Then, the glass substrate W as a measurement object is positioned and held on the base 2. Next, the gate-type frame 3 and the Y-axis stage 5 are moved in the X-axis direction and the Y-axis direction, respectively, and the alignment marks (indexes) M1 and M2 formed at the opposite corners of the substrate W are imaged. Respectively, and image processing is performed (see FIG. 2), and the coordinates (measurement coordinates) of the alignment marks M1 and M2 are specified from the measurement values of the linear scales 4a and 4b at this time.

  Next, the starting position (starting coordinates) input to the control means is corrected from the measured coordinates, and the portal frame 3 and the Y-axis stage are positioned so that the stylus 6 is positioned immediately above the starting position in accordance with this correction. 5 are moved in the X-axis direction and the Y-axis direction, respectively. Then, the stylus 6 is brought into contact with the measurement surface of the substrate W, and the Y-axis stage 5 is relatively moved in the X-axis direction in this state, whereby the stylus 6 is scanned in the X-axis direction along the surface of the substrate W. . Then, based on the vertical displacement of the stylus 6 detected by the Z-axis sensor 61 during this scanning, the surface shape (unevenness) along one X-axis direction cross section of the substrate W is measured.

  By the way, as shown in FIG. 2, when the measurement coordinates are obtained by imaging the alignment marks (indexes), the detected measurement values and the glass substrate W are formed depending on the resolution of the linear scales 4 a and 4 b. There are cases where the design values of the alignment marks M1 and M2 do not match (that is, there is an error with respect to strict length measurement). In this case, if the starting position is corrected based on the measurement coordinates, the correction accuracy is deteriorated.

  In the present embodiment, the rotation center coordinate is defined as the intersection of the step of obtaining the scale ratio from the design coordinates and measurement coordinates of both alignment marks M1 and M2, the straight line passing between the design coordinates, and the straight line passing between the measurement coordinates. Including a step of obtaining a rotation center coordinate and an angle formed by both straight lines and a step of obtaining a center of gravity position of the glass substrate W, each measurement coordinate being similarly transformed from the obtained values, and the actual measurement coordinate being corrected. It was.

  Specifically, the design coordinates of the alignment mark M1 when actually formed on the substrate are (m1x, m1y), and the design coordinates of the alignment mark M2 are (m2x, m2y). Further, the measurement coordinates of the alignment mark M3 specified by the imaging means 7 are (M1x, M1y), and the measurement coordinates of the alignment mark M4 are (M2x, M2y). If the distances between the alignment marks M1, M2 and M3, M4 are mlen and Mlen, respectively, the following relational expression is established.

  When the scale ratio is λ, the scale ratio is obtained by the following equation.

Next, if the intersections of the straight lines passing through the alignment marks M1, M2 and M3, M4 are the rotation center coordinates (x0, y0), the rotation center coordinates and the angle θ formed by the two straight lines at that time are: The following procedure is used.
(1) Slope and intercept of straight line passing through (m1x, m1y), (m2x, m2y)

(2) The slope and intercept of the straight line passing through (M1x, M1y) and (M2x, M2y) are

(3) From the above (1) and (2), the intersection coordinates (x0, y0) are obtained as follows. That is,

(4) The rotation angle θ, which is the angle formed by both straight lines, is obtained as follows. That is,

  Next, the glass substrate W is considered to be a complete rectangle, the center of the glass substrate W is defined as the center of gravity, the designed substrate center coordinates (SGx, SGy), and the size of the glass substrate are defined as Gw × Gh. And the actual gravity center position (DGx, DGy) of a glass substrate is calculated | required by the following procedure (Formula 7) from the said Formula 3-Formula 6.

  Finally, from the values obtained above, the measurement coordinates are (x, y), the corrected one is (x ', y'), and each measurement coordinate is transformed by the following formula to correct the actual measurement position. I do. Finally, the starting point coordinates input to the control means are corrected based on the corrected measurement coordinates.

  As described above, according to the present embodiment, the error rate of the linear scales 4a and 4b is predicted by using the similarity transformation using the measurement values measured by the linear scales 4a and 4b and the design values as the scale ratio. The measurement coordinate position including the accuracy error of the linear scales 4a and 4b can be corrected without doing so, and it is particularly advantageous for a large-sized glass substrate W of several meters × several meters. For example, even if a positional deviation occurs when the substrate is held on the stage 2, it is possible to reliably make the starting position substantially coincide with each glass substrate W.

  Next, in order to confirm the above effect, the following experiment was conducted using the stylus type measuring apparatus shown in FIG. That is, if it is assumed that the workpiece is a glass substrate W of 1800 mm × 1500 mm and the linear scales 4a and 4b have an error of 90 μm at 800 mm, there is a possibility that the size is 1800.090 mm × 1500.075 mm. That is, without considering the rotation direction deviation, only the deviation of the glass substrate W in the X-axis direction and the Y-axis direction is considered, and the design coordinates are (m1x, m1y) = (10,10) and (M1x, M1y) = ( (11,11), if only the translation is corrected by the conventional method, (M1x-m1x, M1y-my) = (1,1) becomes the correction value, and the measurement coordinates after correction of the measurement coordinates (sx, sy) Becomes (sx + 1, sy + 1).

On the other hand, when the coordinate correction method of the above embodiment is applied, the measurement coordinates of the alignment mark M1 are evaluated by (m1x, m1y) = (10,10) and (M1x, M1y) = (11.00055,11.00055) The coordinates of the alignment mark M2 are evaluated by (m2x, m2y) = (1790,1490) and (M2x, M2y) = (1791.08955,1491.07455). Next, when calculating the scale ratio, λ = 1.00005, and when the shift in the rotation direction is not considered, the center of gravity (DGx, DGy) = (901.05,751.0425) (λ * (sx-SGx) + DGx, λ * ( sy-SGy) + DGy). And λ is 1.00005, (SGx, SGy) = (900,750), (DGx, DGy) = (901.05,751.0425,
(1.00005 * (sx – 900) + 901.05, 1.00005 * (sy -750) + 751.0425) = (1.00005 * sx + 1.005, 1.00005 * sy + 1.005), which is corrected to (1.005,1.005).

  Therefore, in the present embodiment, it is (1,1), but in this embodiment, it is improved by 0.005 mm. Therefore, the point (1800, 1500) is corrected to (1801.095, 1501.08). The moving average alone is (1801,1501), which is improved by 0.095 mm = 95 μm in the X direction and 0.08 mm = 80 μm in the Y direction.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to said thing. In the above-described embodiment, the example applied to the stylus type measuring apparatus has been described as an example. However, the present invention can also be applied to the case where the position of the nozzle of the ink jet type coating apparatus is corrected.

  W ... Work (glass substrate), 2 ... Stage, 3 ... Portal frame, 4a, 4b ... Linear scale, 5 ... Y-axis stage, 6 ... Stylus (processing means).

Claims (2)

The workpiece is held on the stage with its processing surface open, and the two horizontal directions orthogonal to each other are the X-axis direction and Y-axis direction, and the work is mounted on a portal frame that can move relative to the stage in the X-axis direction. In the processing apparatus that performs predetermined processing while moving the processing means relative to the workpiece in at least one of the X-axis direction and the Y-axis direction, the position where the processing means starts processing on the processing surface is set as the starting coordinate. The two indices provided on the workpiece are respectively imaged by the imaging means, and the starting point coordinates are corrected from the measured values of the linear scales respectively attached to the frame and the Y-axis stage and the design coordinates of both indices. Is a coordinate correction method for correcting the measurement coordinates of each index,
The step of obtaining the scale ratio from the design coordinates of both indices and the measurement coordinates of each index, and the intersection of the straight line passing between the design coordinates and the straight line passing between the measurement coordinates as the rotation center coordinates, the rotation center coordinates and both straight lines A coordinate correction method comprising: a step of obtaining an angle formed by the step S3; and a step of obtaining a position of the center of gravity of the workpiece, wherein each measurement coordinate is subjected to similarity conversion from the obtained values, and the measurement coordinate is corrected. The coordinate measuring method according to claim 1, wherein the processing means is a stylus that contacts the surface of the workpiece and measures the surface shape of the stylus.

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