JP2008166320A - Inspection device - Google Patents

Abstract

【Task】
In wafer alignment, erroneous mark recognition by pattern search is prevented, and alignment accuracy is maintained and throughput is improved.
[Solution]
Means for detecting the first and second marks; means for calculating a wafer correction angle from the coordinates of the first and second marks; and a third mark from the wear correction angle and the first or second coordinates. Means for calculating the coordinates of the third mark, means for calculating the coordinates of the calculated third mark when the stage rotates the correction angle, means for calculating the third mark, and the means for calculating the third mark, The detected third coordinates are compared to perform alignment.
[Selection] Figure 1

Description

  The present invention relates to an inspection apparatus for inspecting a pattern wafer, and more particularly to an inspection apparatus for automatically aligning a positional deviation of a pattern wafer placed on a movable stage.

  Pattern wafers are arranged with chips that are precisely and precisely aligned. In the inspection of the pattern wafer, the wafer needs to be placed in an aligned state with respect to the X and Y directions of the stage. However, immediately after the wafer is transferred to the stage, the wafer is not aligned in the X and Y directions, and alignment is required to rotate the stage and align it in the X and Y directions.

  In the alignment of the pattern wafer, a plurality of correction marks are used, their positions are picked up by a CCD camera or the like, the position is measured by pattern matching processing, and the rotation angle of the stage for correction from a plurality of points is obtained.

  In general, imaging is performed using two types of magnification cameras in alignment. In order to increase the accuracy of the calculated correction angle, it is necessary to detect the position of the correction mark with high accuracy. For this purpose, it is necessary to capture images with a high-magnification camera. However, the imaging field of view of the high-magnification camera is narrow, and the probability of capturing the correction mark with a single imaging is low. For this reason, a method of detecting the position of the large frame with a low magnification camera and switching to a high magnification camera to increase accuracy is performed.

  However, this method has a problem that it takes time for alignment. For this reason, in order to improve the inspection throughput, it is conceivable to derive an optimum magnification from the alignment accuracy and the positional deviation of the stage during conveyance and perform alignment at a single magnification. As related documents, there is the following Patent Document 1.

Japanese Patent Laid-Open No. 11-220006

  However, at a single magnification, there are three correction marks for calculating a correction angle and a confirmation mark for confirming the alignment accuracy in order to detect that another pattern is erroneously recognized as a correction mark. More points are needed. The accuracy of alignment is confirmed by the coordinate position of the correction mark for confirmation being placed at the correct position. However, when the wafer is transported to the stage, the center of the wafer and the center of the stage are misaligned. The coordinate position of the correction mark is also shifted, and it is necessary to detect the coordinate position of the confirmation mark before correction. However, it takes time to move the stage and perform pattern matching. Therefore, it is necessary to calculate the coordinates of the confirmation mark from the detected coordinates of the correction mark.

  One object of the present invention is to improve the inspection throughput of an inspection apparatus.

  One feature of the present invention for achieving the above object is that means for detecting the coordinates of two correction marks and means for calculating the correction angle of the wafer from the coordinates of the two correction marks. The means for calculating the coordinates of the confirmation mark when the wafer is transported to the stage from the correction angle of the wafer, the coordinates of the correction mark and the coordinates of the confirmation mark registered in advance, and the stage is rotated by the correction angle Means for calculating the coordinates of the confirmation mark at the time, means for detecting the coordinates of the confirmation mark, means for comparing the coordinates of the detected confirmation mark with the coordinates of the confirmation mark calculated when the stage rotates It is to have. The above and other features of the present invention will be further explained by the following description.

  According to the present invention, the inspection throughput of the inspection apparatus can be improved. For example, when alignment is performed, the tilt of the wafer is calculated from the coordinates of two points. However, it is necessary to check the correction accuracy after correction, and it takes time to detect the coordinates of the two points for confirmation. For this reason, if the confirmation is performed by detecting the coordinates of another point, the time can be shortened. However, the stage and the center of the wafer are displaced after the wafer is transferred, and the position of the confirmation mark is also displaced. It is necessary to detect the coordinates of the confirmation mark, but it is necessary to detect the confirmation mark before correction by calculating the position of the confirmation mark taking into account the deviation between the center of the stage and the wafer. And alignment can be performed.

  An embodiment of the present invention that realizes high-speed alignment processing and detection of erroneous mark recognition by alignment using two correction marks and one confirmation mark will be described below.

An embodiment of an object inspection apparatus according to the present invention will be described. FIG. 1 shows the configuration of an inspection apparatus according to an embodiment of the present invention. In the figure, 10 is a stage for moving and rotating the wafer 19, 11 is an optical device for irradiating the surface of the wafer 19, 12 is a camera for photographing the surface of the wafer 19 illuminated by the optical device 11, and 13 is a camera. 12 is a capture board for capturing an image of the surface of the wafer 19 imaged at 12, 14 is image data captured by the capture board 13, 15 is main memory for processing the image data 14, and 16 is image data 14. An image processing arithmetic unit for processing, 17 is a stage control arithmetic unit having stage control software for controlling the stage 10, and 18 is a stage controller for controlling the stage 10.
Reference numeral 19 denotes a wafer.

FIG. 2 shows the arrangement of correction marks formed on the wafer 3 according to an embodiment of the present invention.
101 is a correction mark 1, 102 is a correction mark 2, and 103 is a confirmation mark 3. The confirmation mark 3 may be in any position as long as it is in the vicinity of the correction mark 2.

  FIG. 3 shows the movement from the transfer of the wafer 3 to the stage 10 to the alignment. 209 is the position of the wafer immediately after the wafer 19 is transferred to the stage 10, 200 is the center of rotation of the stage 10, 201 is the center of the wafer when the wafer 19 is at the position 209, 203, 204, and 205 are 209 Are the coordinate positions of the correction mark 1, the correction mark 2 and the correction mark 3, respectively, 210 is the position of the wafer 19 after alignment, and 206, 207 and 208 are 210 Are the coordinate positions of the correction mark 1, the correction mark 2, and the correction mark 3.

  FIG. 4 shows a flow of alignment processing in the inspection apparatus.

In step 300, the coordinate position P1 (x1, x1) of the correction mark 101 registered in advance.
The stage 10 is moved to y1). In step 301, the correction mark 1 is imaged by the camera 12. In step 302, pattern matching is performed on the captured image, and the coordinate position of the correction mark 203 is detected. At this time, the wafer 19 is transferred to the stage 10 and is at the position 209, and the correction mark 1 is at the coordinate position 203. In step 302, after acquiring the detected coordinate position 203, the stage 10 is moved to the coordinate position of the correction mark 2 registered in advance in step 303. At this time, the wafer 19 is at the position 209 while being transferred to the stage 10, and the correction mark 2 is at the coordinate position 204. In step 304, the correction mark 2 is imaged by the camera 12. In step 305, pattern matching is performed on the captured image, and the coordinate position of the correction mark 2 is detected. In step 306, a correction angle is calculated from the coordinates 203 and 204 of the correction mark 1 and the correction mark 2 detected in steps 302 and 305. In step 307, the third coordinate before position correction is obtained from the correction angle calculated in step 306, the coordinates of the first correction mark calculated in step 302, and the coordinates of the third registration mark registered in advance. In 308, the coordinate position when the stage 10 is rotated by the correction angle with respect to the coordinate of the third confirmation mark calculated in step 307 is calculated. In step 309, the stage 10 is rotated by the correction angle calculated from step 306, and the stage 10 is moved to the coordinate position calculated in step 309. In step 310, the confirmation mark 3 is imaged by the camera 12. In step 311, the coordinates 208 of the confirmation mark 3 are detected by pattern matching. In step 312, the difference between the coordinate position 208 of the correction mark 3 calculated in step 308 and the coordinate position 208 of the correction mark 3 measured in step 311 is performed. If the difference value is within a threshold value registered in advance, the position correction ends. If it is larger than the threshold value, the processing is repeated from step 303. The embodiment of the present invention is not limited to the above, and can be modified within the scope of its technical idea.

It is a block diagram of the inspection apparatus which concerns on one Example of this invention. It is a correction mark on the wafer used for alignment. It is a state of movement of the wafer and the correction mark by alignment. It is the processing flowchart which showed the implementation method of alignment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Stage 11 Optical apparatus 12 Camera 13 Capture board 14 Image data 15 Main memory 16 Image processing calculator 17 Stage control calculator 18 Stage controller 19 Wafer

Claims (3)

An inspection apparatus for holding a wafer and aligning the wafer with a stage that can move and rotate in the X and Y directions,
Means for detecting the position of the first mark located near the wafer edge, moved to the position of the first mark by the stage;
Means for detecting the position of the mark by moving the second mark to the second mark by the stage, relative to the first mark in the X or Y direction;
Means for calculating a correction angle of the wafer from the positions of the first and second marks;
The third mark is on the same line as the first and second marks and is located in the vicinity of the second mark. The detected first or second mark position, the wafer correction angle, and the previously registered first mark are registered in advance. Means for calculating the position of the third mark from the position of the third mark;
Means for calculating the position of the third mark when the stage is rotated by a correction angle;
Means for rotating and correcting the stage with respect to the correction angle of the wafer;
Means for detecting the position of the mark by moving to the third mark by the stage after correcting the wafer;
An inspection apparatus comprising: The means according to claim 1, wherein the position calculated by the means for calculating the position of the third mark is compared with the position detected by the means for detecting the position of the third mark;
An inspection apparatus comprising: The means for comparing the calculated third mark with the detected third mark according to claim 2, wherein the fourth mark is located in the vicinity of the first mark when the third mark is more than a specific distance, Means for detecting the position by moving to the fourth mark by the stage;
Means for calculating a correction angle from the coordinates of the detected third and fourth marks;
Means for calculating the first mark from the coordinates of the third or fourth mark and the correction angle;
Means for rotating and correcting the stage with respect to the correction angle of the wafer;
Means for detecting the position of the mark by moving to the first mark by the stage after correcting the wafer;
An inspection apparatus comprising:

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