JPH09229630A - Method for measuring image position formed on transparent substrate and apparatus therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To measure easily and precisely whether the image position on a substrate is precisely reproduced or not by measuring positional dislocation between a measurement point on a transparent reference substrate on which the measurement point is formed precisely and the position of the measurement point on an object substrate to be measured and corresponding to the former point. SOLUTION: A transparent reference substrate 1 on which a measurement point is precisely formed is supported in a stand 9 in parallel to an object substrate 2 to be measured at a prescribed distance through a supporting member 3 in a manner the reference substrate can be changed. The substrate 2 set on an x-y axially movable stand is moved in parallel to the substrate 1 and adjustment is so carried out as to almost conform the image positions of standard points on both substrates. A lighting system 4 illuminates an image to be observed and an image obtained by a camera 5 installed at position corresponding to the image position is sent to an image processing apparatus 8 through a signal switching apparatus 7. The difference between the measurement point of the substrate 1 and the measurement point on the substrate 2 corresponding to the former point is then measured to measure indirectly the position of the measurement point on the substrate 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for precisely measuring the position of an image on a transparent substrate having an image on its surface, and an apparatus therefor. In particular, the present invention relates to a substrate having an image group consisting of a large number of images formed through exposure processing of a photosensitive film using a mask on a transparent substrate, in which direction these image groups are supposed to be. The present invention relates to a method for precisely measuring the degree of stagger formation and an apparatus therefor.

[0002]

2. Description of the Related Art A method of forming an image corresponding to a mask on a substrate by exposure processing using a mask is known.
In this method, a mask having an image is superimposed on a substrate having a photosensitive film, and light is irradiated through the mask to expose the photosensitive film. Since the photosensitive film is chemically changed by exposure to form a latent image corresponding to the image of the mask, when developed by an appropriate means, an image (positive or negative) corresponding to the image of the mask is formed on the substrate.

This method is widely used in many fields that require fine and precise processing because it can efficiently and repeatedly form an image that exactly corresponds to the image of the mask. For example, in a color liquid crystal display device, each electrode on the transparent electrode substrate and the three primary colors of the color filter, blue, red, and green, must correspond exactly, so both the transparent electrode substrate and the color filter must be masked as described above. It is manufactured by the exposure process used.

The accuracy of the image thus produced is
It depends not only on the accuracy of the mask, but also on the quality of the exposure operation itself. That is, when the substrate having the photosensitive film (= the substrate to be exposed) and the mask are set in the exposure apparatus, it is inadequate (a defective state of setting the substrate and the mask, a positioning defect between them, a gap determination between them, etc.), The image of the mask may not be accurately reproduced at a predetermined position on the substrate due to expansion and contraction of the substrate due to temperature and pressure. Therefore, it is necessary to inspect whether or not the image formed on the substrate accurately reproduces the image of the mask within the allowable error range.

Conventionally, in this inspection, in addition to an image group to be formed on a substrate to be exposed on a mask, some measurement point images for inspection are further provided on the outside thereof, and the measurement is reproduced on the substrate. This is done by measuring the positional relationship between the point images or the positional relationship between the measurement point image and a part of the images in the image group. That is, the substrate is placed on an XY axis drive table having extremely high accuracy, and first, the image is accurately aligned with the image selected as the reference measurement point. Next, the drive base is moved to accurately align the next measurement point, and the amount of movement during that time is measured. By performing such measurement at several measurement points, it is possible to know how accurately the image is reproduced.

[0006]

The problem with this conventional inspection method is that it requires an extremely high-precision and therefore expensive measuring device, and that the measuring operation is also complicated. For example, in the case of a color filter, the size of the substrate is 400 x
It has a size of 500 mm, on which four color filter images are usually formed. Therefore, the moving distance at the time of measurement becomes 100 mm or more. On the other hand, since the measurement accuracy is required to be on the order of microns, a dynamic range of 10 ⁵ : 1 or more is required. In order to satisfy such requirements, an extremely high precision drive mechanism such as a special ball screw and a measuring instrument such as a laser interferometer are required, and a special measuring room for maintaining the precision of these instruments is required. Need. Therefore, a large amount of capital investment is required,
Moreover, it takes a lot of time for measurement.

[0007]

According to the present invention, instead of directly measuring the positions between the measuring points formed on the substrate, a transparent standard substrate on which the measuring points are accurately formed is used. The position of the measurement point on the measured substrate is indirectly measured by measuring the positional deviation between the measurement point on the standard substrate and the corresponding measured point on the measured substrate. . According to the present invention, a standard substrate having a reference point image and a measurement point image respectively corresponding to the positions of the reference point image and the measurement point image formed on the substrate to be measured when the exposure processing is performed accurately is performed. It is desirable that the material of the standard substrate is prepared so that the coefficient of thermal expansion is as small as possible in the same manner as the mask used in the exposure process so as not to cause an error.

The substrate to be measured and the standard substrate are arranged in parallel so that the positions of the reference point images of both are at least substantially coincident. The position of the position between the reference point images is measured between the substrate to be measured and the standard substrate. If there is a deviation, measure it.Measure the deviation between the measurement point images of the substrate under measurement and the standard board.Measure the deviation of the position between the reference point images and the position between the measurement point images. A series of procedures for calculating the relational position between the reference point image and the measurement point image on the measured substrate based on the relational position between the reference point image and the measurement point image on the standard substrate from the measured value of the deviation As a result, the positional relationship of the measurement points on the substrate to be measured can be accurately and easily measured using a relatively simple measuring device.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in more detail. The present invention is capable of extremely accurately measuring the relative position of an image formed on a transparent substrate such as a color filter, usually on the order of microns or submicrons. Is the way to do it. In the present invention, as the first step, a mask having a reference point image and a measurement point image is used for the mask used for the exposure processing so that the reference point image and the measurement point image are formed on the substrate to be measured. Although the images originally formed on the mask can be used as these images or a part thereof, the images originally formed on the mask are formed in order to form an image of a shape that can be easily measured. It is preferable to form the reference point image and the measurement point image separately from the above. In the second step, as a measure for measurement, a reference point image and a measurement point image respectively corresponding to the positions of the reference point image and the measurement point image formed on the substrate to be measured when the exposure processing is performed accurately are performed. A standard substrate having the above is prepared. The reference point image and the measurement point image may have the same shape or different shapes as long as it is easy to measure the deviation of the image position between the images corresponding to the standard substrate and the substrate to be measured. In addition, it is preferable that the reference point image and the measurement point image have a positive and negative relationship between the standard substrate and the substrate to be measured. This is to facilitate detection of positional deviation between corresponding images on both substrates when the two substrates are overlapped and irradiated with light. Further, the shapes of the images corresponding to both substrates do not have to be the same shape, but rather different shapes are preferably used to facilitate detection of positional deviation between the corresponding images.

FIG. 1A is a schematic example of a substrate to be measured, in which an L-shaped reference point image B is opaque in the upper right corner and the lower left corner outside the area where the original image group is formed. It is formed as a light section. Further, measurement point images B are formed at the four corners of the area where the image group is formed and inside. The measurement point images at the four corners are formed as non-light-transmitting portions, and the measurement point images inside are formed as light-transmitting portions.

FIG. 1B shows a standard substrate corresponding to the above-mentioned substrate to be measured, on which a corresponding reference point image B and measurement point image B are formed. However, the reference point image is formed as a light-transmitting portion, the measurement point images corresponding to the measurement point images at the four corners are formed as a light transmitting portion, and the measurement point images corresponding to the internal measurement point images are formed as a non-light transmitting portion. Has been done. The shapes of the corresponding reference point image and measurement point image on both boards are designed to fit each other tightly.

In the third step, the standard board and the measured board are set so that their reference point image positions substantially match each other, that is, in the example of FIG. 1, the standard board and the measured board reference point images are substantially fitted. Stack them so that they fit together. It is of course possible to superimpose the two substrates so that the positions of the reference point images exactly coincide with each other, that is, in the example of FIG. A highly accurate positioning mechanism is required. In the present invention, the deviation between the reference points can be accurately measured by the image processing even if the reference points of both substrates are not exactly matched, so that it is not necessary to use a highly accurate positioning mechanism. In addition, when stacking both substrates, without contacting both substrates,
It is preferable to overlap with a slight gap. The surfaces of both substrates are extremely smooth, so if they come into contact with each other, they will stick together, and the standard substrate will become scratched or foreign matter will adhere, making it unsuitable for future use. There is a fear. Both substrates should be superposed with a high degree of parallelism with some clearance. If the parallelism is poor, it is not possible to accurately measure the deviation of the image positions on both substrates. Normally, the inclinations of both substrates are set within 0.03 degrees.

It is necessary to measure how accurately the image on the substrate to be measured reproduces the image on the mask when performing the process verification in the manufacturing process of the substrate to be measured or when shipping the manufactured substrate to be measured. In many cases, the substrates to be measured having the same shape and the same size are measured one after another in a flow operation. Therefore, in this case, as a measuring device, a fixed support table on which a standard substrate is placed, a movable support table that supports the substrate to be measured facing the standard substrate fixedly supported on this table, and this support table. It is preferable to use one having a drive mechanism that moves the support table back and forth and left and right so that the reference point image of the substrate to be measured supported on the top substantially coincides with the reference point image of the standard substrate. Furthermore, it is preferable to provide a supply / discharge mechanism for the substrate to be measured, which sequentially feeds the substrate to be measured to the substrate and removes the substrate to be measured after the measurement is completed.

In the fourth step of the present invention, the reference point images of the superposed standard substrate and the measured substrate are observed, and the positional deviation of the reference point image of the measured substrate with respect to the reference point image of the standard substrate is measured. . This positional deviation usually needs to be measured extremely accurately on the order of submicrons. Based on the measurement value of this position deviation, the measurement value of the position deviation at the subsequent measurement point is corrected, and finally the measurement point of the measured substrate becomes
It is calculated in what direction and to what extent the reference point is offset. Therefore, it is preferable that the reference point image is composed of orthogonal lines so that the positional deviation (in which direction and to what extent) can be easily measured. For example, FIG. 2 is an example of such a combination of reference point images. On a standard substrate, two squares based on two orthogonal straight lines are intersected with each other (this is the reference point). A reference point image having a shape arranged so as to be in contact with is formed, and a reference point image having an L shape (the apex angle on the outer side thereof serves as a reference point) is formed on the substrate to be measured. If the standard substrate and the substrate to be measured are overlapped as shown in FIG. 2, bar Oa and bar O
By measuring b and b, it is possible to easily calculate in which direction and how much the reference point image of the measured substrate is relative to that of the standard substrate, and what the rotation angle (θ) is. . Then, when detecting the positional deviation of the subsequent measurement point image, the actual positional deviation is corrected by the positional deviation data of the reference point image to calculate the true positional deviation.

Therefore, if the positions of the reference point images are made to match exactly, it is advantageous in that the measured values do not have to be corrected when the positional deviation of the measurement point images is measured later.
As described above, it is one of the features of the present invention that the misregistration can be measured without accurately matching the positions of the reference point images. When calculating the rotation angle (θ) of the image on the substrate to be measured, the average value of the measured values at a plurality of points may be used.

In the fifth step, the measurement point images of the superposed standard substrate and the measurement substrate are observed, and the positional deviation of the measurement point image of the measurement substrate with respect to the measurement point image of the standard substrate is measured. Also in the measurement point image, it is easy to detect misalignment,
It is preferable that the reference point image is composed of lines that are orthogonal to each other. When the measurement value of the positional deviation of the measurement point image is corrected by the measurement value of the positional deviation of the reference point image described above, the positional deviation of the measurement point image between both boards, and thus the reference point image and the measurement point image of the board under measurement, The positional relationship of is accurately obtained.

Observation of the image positions in the fourth step and the fifth step is usually performed by a camera with a microscope capable of high-magnification observation, and the obtained image data is processed by an image processing device to measure the standard substrate. It is advantageous to calculate the deviation of the image position of the substrate. As long as the images of both substrates fit within the same field of view of the camera, it is advantageous to fix the camera as much as possible because it simplifies the device and does not reduce measurement accuracy. Normally, it is advantageous to stack both boards so that the reference point images of both boards fit within the same field of view, take the reference point image with a fixed camera, and measure the measurement point image with a fixed camera or a moving camera. Is.

One example of an apparatus for carrying out the present invention is shown in FIG.
1 is a standard substrate and 2 is a substrate to be measured. Reference numeral 3 denotes a supporting member of a supporting device for the standard substrate, which is fixed to the pedestal 9 so as to be replaceable, in parallel with the substrate 2 to be measured and at a certain interval from the substrate 2.
The substrate to be measured 2 is placed on an XY axis drive table (not shown), and the substrate to be measured is moved in parallel with the standard substrate so that the reference point image positions of both are substantially the same. It can be adjusted. In addition, it is preferable that the apparatus is provided with a supply / discharge means for the substrate to be measured, which automatically supplies the substrate to be measured onto the X-Y axis drive table and discharges the substrate to be measured from the table.

Reference numeral 4 denotes an illuminating device, which may illuminate only the image portion to be observed individually or illuminate the entire substrate. The illumination is preferably diffuse light or parallel light at any position so that overlapping images can be measured. 5 is a camera. As described above, it is desirable that the camera is fixedly arranged corresponding to the image position to be measured. The camera is a two-dimensional CCD camera,
An image pickup tube type camera or the like is used. Since the measurement accuracy decreases if the camera is not properly focused, it is preferable to mount the autofocus device 6 and perform the focus for each measurement. The image signal obtained by the camera is input to the image processing device 8 via the signal switching device 7. In the image processing device 8, the positional deviation at each measurement point image position is corrected based on the positional deviation at the reference point image position and the relational position between the reference point and each measurement point on the standard substrate, and the corrected image is measured. The relative position between the reference point and each measurement point is calculated.

[0020]

According to the present invention, it is possible to easily and accurately measure whether or not the image position on the substrate having the image formed by the exposure process using the mask is correctly reproduced.

[Brief description of drawings]

FIG. 1 schematically shows an example of an arrangement of images formed on a substrate.

FIG. 2 shows an example of a method for calculating positional deviation of a reference point image.

FIG. 3 is a diagram showing a basic configuration of an example of an apparatus for carrying out the present invention.

[Explanation of symbols]

 B Measurement point image B Reference point image 1 Standard substrate 2 Substrate to be measured 3 Standard substrate supporting device members 4 Illumination device 5 Camera 6 Autofocus device 7 Signal switching device 8 Image processing device 9 Frame

Claims (6)

[Claims] 1. A method for measuring a relative position of a measurement point image with respect to a reference point image of a substrate to be measured having a measurement point image and a reference point image formed on a transparent substrate by exposing a photosensitive film. , Prepare a standard substrate having the reference point image and the measurement point image corresponding to the positions of the reference point image and the measurement point image formed on the substrate to be measured when the exposure process is performed accurately. The board and the standard board should be placed in parallel so that the reference point image positions of both are at least approximately the same. There is a positional deviation between the reference point images between the board to be measured and the standard board. In that case, measure it.Measure the positional deviation between the measurement point images between the board to be measured and the standard board.Measurement value of the positional deviation between the reference point images of both boards and the measurement point image. Such as the measured value of the gap between the positions , Based on a relationship position between the measurement point image and the reference point images in the standard substrate, wherein the calculating the relationship position between the measurement point image and the reference point images in the substrate to be measured. 2. A camera capable of high-magnification observation of a position of a reference point image and a position of a measurement point image between a standard substrate and a substrate to be measured, and a portion including these images on both substrates. 2. The method according to claim 1, wherein the image data obtained by photographing is processed by an image processing device to calculate the positional deviation. 3. The standard substrate and the substrate to be measured are arranged parallel to each other with a slight gap so that the two substrates do not come into contact with each other.
The described method. 4. The relative position of the measurement point image with respect to the reference point image of the substrate to be measured having the measurement point image and the reference point image on the transparent substrate is determined such that the corresponding measurement point image and the reference point image are accurately arranged. A device for measuring in comparison with a standard substrate which is present, a means for supporting the substrate under measurement and the standard substrate in parallel with each other with a slight gap between them, and maintaining the gap between both substrates. Means for relatively moving, means for irradiating light perpendicularly to the substrate surface through both substrates, a camera for receiving light passing through the reference point image portion and the measurement point image portion, and an image signal obtained by the camera Based on the position between the reference point images between both boards and the position between the measurement point image images obtained by processing, and the relative position between the reference point image and the measurement point image on the standard board, Board reference point image And an image processing means for calculating a relative position of the measurement point image. 5. A fixed support for mounting the standard substrate and a movable support for mounting the substrate to be measured include a means for supporting the substrate to be measured and the standard substrate, and a means for relatively moving both substrates. The apparatus according to claim 4, comprising a table and a drive mechanism for moving the movable support table in the front-rear and left-right directions. 6. The camera for receiving light passing through the reference point image portion is a fixed camera.
Or the device according to item 5.