JP2017044884A - Apparatus and method for measuring position of photomask - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable measurement of a position (including an angle) of a mask pattern on a substrate with regard to the substrate, without taking out a photomask from a case.SOLUTION: In a state housing a photomask 11, a case 10 is placed on a carrier device 30, and illuminated from one side thereof with an illuminating device 32. An image of light transmitting the case and the photomask inside is taken by an imaging device 33, and the image of the light is displayed on a display screen of a display device 34. While carrying the case by the carrier device, at least two prescribed locations of the image of light are aligned respectively with reference marks 50 displayed on the display device, and a distance between the two locations is measured according to a signal showing a travel amount output from the carrier device.SELECTED DRAWING: Figure 4

Description

  The present invention relates to an apparatus and a method for measuring a position (including an angle) of a mask pattern (light shielding film) on a substrate with respect to the substrate.

  One method for measuring the position of the pattern structure on the mask surface is disclosed in Patent Document 1. This method requires a clean environment because the photomask must be taken out of the case. Further, when taking out the photomask from the case, the mask pattern may be damaged.

  Patent Document 2 refers to a photomask storage case that can be inspected without taking out the photomask from the storage case, and an automatic inspection method that performs inspection in a state where the photomask is stored in the storage case. However, what is described in Patent Document 2 is a photomask defect inspection and foreign matter inspection by a photomask defect inspection apparatus, and it is assumed that the photomask defect inspection apparatus itself is already known, so the details will be described. It does not refer to photomask position measurement.

Japanese Patent No. 3488428 Japanese Patent Laid-Open No. 4-93947

  An object of the present invention is to provide an apparatus and a method capable of measuring the position (including the angle) of a mask pattern on a substrate with respect to the substrate without removing the photomask from the case.

  According to the photomask position measuring apparatus of the present invention, an illumination device that irradiates illumination light from one surface of a case containing a photomask, an image of light that passes through the case illuminated by the illumination device and a photomask inside the case. An image pickup apparatus for picking up images, a case for moving at least one of the case and the image pickup apparatus two-dimensionally in a direction parallel to the one surface of the case, and outputting a signal representing the amount of movement, the image pickup apparatus A display device that displays a captured image based on an image signal output from the device, and a distance between at least two points specified on the image displayed on the display device, and a movement amount output from the transport device A distance measuring device for measuring based on the signal to be expressed is provided.

  The case for storing the photomask is transparent or translucent. One surface of the case is irradiated with illumination light, and an optical image of transmitted light emitted from the other surface is captured by the imaging device, and an image of the obtained optical image is displayed on the display device. The transport device moves (relative movement) at least one of the case and the imaging device on a two-dimensional plane parallel to the one surface (and the other surface) of the case. Pay attention to at least two points (one point related to the substrate and the other point related to the mask pattern) of the displayed photomask image, and transport each point to a predetermined position on the display screen. Control the device. The distance between the two points is measured by a signal representing the amount of movement output from the transport device. By measuring the distance between two points for a plurality of pairs of two points on the photomask, data representing the position (including angle) of the mask pattern with respect to the substrate can be obtained. It is preferable that the optical axis of the imaging device is orthogonal to the case or the relative movement two-dimensional plane of the imaging device.

  In this way, the position of the photomask can be measured with the photomask housed in a transparent or translucent case. Since it is not necessary to take out the photomask from the case, position measurement can be performed even in a low clean environment.

  The above two points are, for example, one point (edge) on the alignment mark and one point on the outer edge (end surface) of the substrate in the vicinity (corresponding) (between the edge line of the alignment mark and the outer edge line of the substrate). Distance). If a reference mark is displayed on the display screen of the display device, the case or the imaging device can be moved (stopped after movement) by the transport device so that the two points coincide with the reference mark.

  In one embodiment, a control device may be provided that controls movement and stop of the case or the imaging device by the transport device based on a movement instruction signal. The control device also displays the reference mark on the display screen. The movement instruction (stop instruction) signal may be input by the user from the input device.

  In a preferred embodiment, the imaging device includes a variable magnification lens. If this variable magnification lens is set to a low magnification, the field of view is widened, and it becomes easier to find the above two points (two lines) such as alignment marks. This makes it possible to make precise measurements.

  The case and the imaging device may be moved relatively. In one embodiment, the illuminating device is mounted on a transport table of the transport device, and a case is mounted on a light output surface of the illuminating device. This simplifies the configuration. In this case, as an example, the imaging device is fixed at a predetermined position regardless of the movement of the case by the transport device. In another embodiment, the imaging device is movably supported by the transport device. In this case, in one example, the illumination device is fixed at a predetermined position regardless of the movement of the imaging device by the transport device, and the case is placed on the light emission surface of the illumination device.

  In the photomask position measuring method according to the present invention, a case storing a photomask is illuminated with illumination light from one side thereof, and an image of light transmitted through the illuminated case and the photomask inside the case is captured by an imaging device. , Displaying the picked-up optical image on the display screen of the display device, and transporting at least one of the case and the imaging device two-dimensionally in a direction parallel to the one surface of the case by the transport device. At least two predetermined positions of the image are aligned with the reference marks displayed on the display screen of the display device, and the distance between the two locations is measured based on a signal representing the amount of movement output from the transport device.

The arrangement | positioning relationship between a case and a photomask is shown. It is a top view which shows the structure of a photomask. It is sectional drawing which shows the structure of a photomask. It is a block diagram which shows the structure of one Example of the position measuring apparatus of a photomask. A mode that the outer edge of the board | substrate of a photomask is illuminated with illumination light is shown. An example of the image of the outer edge of the photomask substrate is shown. (A) shows the case of using diffused light and (B) shows the case of using highly directional light. The image of the state which match | combined the board | substrate outer edge (corner) with the reference mark is shown. An image in which the alignment mark is aligned with the reference mark is shown. It is a block diagram which shows the structure of the other Example of the position measuring apparatus of a photomask.

  FIG. 1 shows the positional relationship between a case and a photomask stored in the case. In general, the photomask 11 is stored in the center of the case 10. Although the positional relationship between the photomask 11 and the case 10 is not a problem here, the upper and lower surfaces of the case 10 and the surface of the photomask 11 are kept parallel. In addition, it is important that the photomask 11 is fixedly (not to move) in the case 10. The case 10 is transparent or translucent (may be partially transparent or translucent), and as will be described later, when illumination light is applied from one side of the case, the optical image of the photomask 11 in the case 10 from the other side of the case (Image by light transmitted through case 10 and photomask 11) can be seen.

  2 and 3 show an example of a photomask. The photomask 11 has a mask pattern (light shielding film) 20 formed on one surface of a substrate (generally a glass substrate) 12. The mask pattern 20 includes alignment marks 21, 22, 23, and 24. In this example, alignment marks 21 to 24 are formed slightly apart from the main part at four locations around the main part of the mask pattern (drawn in the center square shape and indicated by the reference numeral 20). Yes. The positional relationship between the main part 20 of the mask pattern and the alignment marks 21 to 24 is precisely defined. The distances to be measured are the distances x1, y1, x2, y2, x3, y3 and x4, y4 between the side edges (end faces, side faces) of the substrate 11 and the corresponding edges of the alignment marks 21-24. From these distances, the position and inclination angle of the mask pattern 20 with respect to the substrate 11 are obtained. All of these distances need not be measured, and may be measured within a range in which the position of the mask pattern 20 relative to the substrate 12 is known. It is a photomask position measuring apparatus and method that determines some of the distances x1 to y4.

  FIG. 4 shows the overall configuration of an embodiment of a photomask position measuring apparatus.

  The XY table device (conveyor device) 30 moves the table in two directions (X direction and Y direction) orthogonal to each other in the horizontal plane, and its X direction position and Y direction position (or X direction movement amount and Y direction movement). (Amount) is detected by a position sensor (or movement amount sensor) 31. The position sensor 31 is, for example, an encoder that outputs signals representing the rotation amounts of the X-direction drive motor and the Y-direction drive motor of the XY table device.

  On the table of the XY table device 30, a surface illumination device 32 is placed and fixed. The surface illumination device 32 emits uniform illumination light from its upper surface. This illumination light may be either diffuse light or highly directional light. As shown in FIG. 5, when illumination light is irradiated onto the glass substrate 12 of the photomask 11 in the case 10 (the case is not shown), even if the end surface 12B of the glass substrate 12 is chamfered, FIG. An optical image as shown in B) is obtained. 6A shows the case of diffused light, and FIG. 6B shows the case of illumination light with strong directivity. In either case, a line indicating the end face (side edge) 12B of the glass substrate 12 appears clearly. ing. The use of illumination light with strong directivity emphasizes the outer edge of the glass substrate and enables position measurement with higher visibility. Illumination light having high directivity can be obtained by arranging a vertical light selective transmission member that selectively transmits light in the thickness direction, such as a light control film, on the light emission surface of the illumination device.

  On the illumination surface of the illumination device 32, the case 10 in which the photomask 11 is housed is placed and fixed. The case 10 is illuminated with illumination light from its lower surface. The illumination surface of the illumination device 32 is a horizontal plane, and the upper and lower surfaces of the case 10 are also in the horizontal plane.

  An imaging device (camera) 33 is fixed above the position where the transport device 30, the illumination device 32, etc. are arranged so that the optical axis thereof is in the vertical direction. The imaging device 33 is fixed regardless of the conveyance by the conveyance device 30. The imaging device 33 images the case 10 illuminated from the lower surface (rear surface) from the upper surface (front surface). That is, the imaging device 33 captures an image of light that has passed through the case 10 and the photomask inside the case 10, and outputs an image signal representing the captured image. The image signal is supplied to the display device 34 through the control device 40 or directly. The imaging device 30 is provided with a variable magnification lens 33A and can capture an enlarged image and a reduced image of the optical image at an arbitrary magnification.

  The control device 40 is realized by a so-called personal computer, and controls the operation of the transport device 30. From the input device (keyboard, screen, mouse, etc.) of the control device 40, it is possible to input a command regarding the transport direction, transport speed, etc. of the transport device 30, a transport start / stop command, and the like. The magnification in the imaging device 33 may also be commanded from the control device 40. The control device 40 also calculates the position of the photomask described later.

  The display device 34 displays the optical image captured by the imaging device 33. As shown in FIGS. 7 and 8, a reference mark 50 is displayed at a predetermined position (for example, the center) of the display screen of the display device 31. Display data of the reference mark 50 is given from the control device 40. The reference mark 50 is not limited to a cross shape, and may be a point, a line, or another figure.

  The light image picked up by the image pickup device 33 is displayed on the display screen of the display device 34 so as to overlap the reference mark 50. The conveyance device 30 is driven by the control device 40, and as shown in FIG. 7, one corner of the image 10A of the glass substrate 10 appearing in the optical image (for example, the outer edge of the upper left corner, adjacent to the substrate image 10A). The illumination device 32 and the case 10 are moved together so that the intersection of the outer edges 10a and 10b) (a point related to the substrate) coincides with the reference mark 50. The user sees the display image and gives an input indicating that they match from the input device of the control device 40 (this match may be detected by image processing). The control device 40 reads the X and Y positions indicated by the position sensor 31 at this time.

  Next, the illumination device 32 and the case 10 are moved again by the transport device 30, and the corner (upper left corner) of the image 21A of the alignment mark 21 (the point related to the mask pattern) is the reference as shown in FIG. Match with mark 50. At this time, the X and Y positions indicated by the position sensor 31 are also read by the control device 40.

  The control device 40 determines the difference between the X and Y positions when the corner of the substrate image 10A coincides with the reference mark 50 and the X and Y positions when the corner of the image 21A of the alignment mark 21 coincides with the reference mark 50. Calculate. This calculation result represents x1 and y1 shown in FIG. Similarly, the position of the other one or more alignment marks 22 to 24 can be measured with respect to the substrate side edge (end face). In this way, the position and angle of the mask pattern 20 with respect to the substrate 12 can be measured with the photomask 11 stored in the case 10.

  If the optical image picked up by the variable magnification lens 33A is reduced (low magnification), the field of view widens and it becomes easier to find the corner of the alignment mark and the glass substrate, and if it is switched to enlargement (high magnification), it matches the reference mark with high accuracy. be able to.

  In this way, it is possible to measure the distance between the outer edge of the photomask substrate and the alignment mark by applying illumination light from one side of the case that houses the photomask and capturing a light image transmitted from the other side. Position and angle can be measured even in a low clean environment with the mask stored in the case.

  FIG. 9 shows another embodiment of the photomask position measuring apparatus. The same components as those shown in FIG. 4 are denoted by the same reference numerals to avoid redundant description, and only different points will be described. The lighting device 32 on which the case 10 is fixedly mounted is fixed. An imaging device 33 is attached to a transfer device 30A provided above the illumination device 32, and faces downward so as to image the case 10. The transport device 30A moves the imaging device 33 in a two-dimensional plane (XY plane) parallel to the upper and lower surfaces of the case 10. The upper and lower surfaces of the case 10 are horizontal, and the optical axis of the imaging device 33 is vertical. As described above, it is preferable that the upper and lower surfaces of the case 10 and the conveying direction by the conveying device 30A are parallel, and the optical axis of the imaging device 33 is orthogonal thereto. The amount of movement by the transport device 33 is output from the sensor 31A and given to the control device 40. The control device 40 controls the transport device 30A. The photomask position measuring method using this position measuring apparatus is the same as described above.

10 cases
11 Photomask
12 Board
20 Mask pattern
21, 22, 23, 24 Alignment mark
30 XY table device (transport device)
30A transfer device
31, 31A Position sensor (travel distance sensor)
32 Lighting equipment
33 Imaging device
33A variable magnification lens
34 Display device
40 Control unit
50 fiducial mark

Claims (7)

A lighting device that emits illumination light from one side of a case that houses a photomask,
An imaging device that captures an image of light transmitted through the case and a photomask inside the case illuminated by the illumination device;
A transport device that two-dimensionally moves at least one of the case and the imaging device in a direction parallel to the one surface of the case, and outputs a signal representing the amount of movement;
A display device that displays a picked-up image based on an image signal output from the image pickup device, and a movement that is output from the transport device at a specified distance between at least two points on the image displayed on the display device A distance measuring device for measuring based on a signal representing a quantity,
A photomask position measuring device comprising:   The photomask position measuring device according to claim 1, further comprising a control device that controls movement and stop of the case or the imaging device by the transport device based on a movement instruction signal.   The photomask position measuring device according to claim 1, wherein the display device displays a reference mark on a display screen.   The photomask position measuring apparatus according to claim 1, wherein the imaging apparatus includes a variable magnification lens.   The illuminating device is mounted on a transport table of the transport device, the case is mounted on a light emission surface of the illuminating device, and the imaging device is placed at a predetermined position regardless of movement of the case by the transport device. The photomask position measuring device according to any one of claims 1 to 4, which is fixed.   The imaging device is movably supported by the transport device, the illuminating device is fixed at a predetermined position regardless of the movement of the imaging device by the transport device, and the case is placed on the light emitting surface of the illuminating device The photomask position measuring device according to claim 1, wherein the photomask position measuring device is used. Illuminate the case containing the photomask with illumination light from one side,
Taking an image of light transmitted through the illuminated case and the photomask inside thereof with an imaging device,
Display the captured optical image on the display screen of the display device,
At least two of the optical image are displayed on the display screen of the display device while two-dimensionally transporting at least one of the case and the imaging device in a direction parallel to the one surface of the case by the transport device According to the reference mark
Measuring the distance between the two locations on the basis of a signal representing the amount of movement output from the conveying device;
Photomask position measurement method.