JP4104372B2 - Aligner accuracy measuring apparatus, method thereof, and storage medium storing program thereof - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a configuration of an accuracy measuring apparatus that measures the accuracy of an aligner that performs posture alignment of a wafer such as a semiconductor placed on a swivel.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, automatic guided vehicles that transport and transfer semiconductor wafers and the like in a semiconductor manufacturing factory are known. Such an automatic guided vehicle includes a buffer cassette for storing a wafer, a wafer transfer arm, a posture adjusting device (aligner) for aligning the posture and direction of the wafer, and an ID attached to the wafer. A reading device is mounted.
In addition, the alignment accuracy of the aligner affects the reading of the wafer ID, storage in the cassette at the time of transfer, or placement of the wafer on the semiconductor manufacturing apparatus. The accuracy of the aligner was measured using an apparatus. This is done by placing an accuracy measurement wafer with a mark at the center of the measurement surface at a predetermined position on the aligner mounting table, and taking images of the mark before and after the posture alignment work by an imaging means such as a CCD camera. The displacement amount and the displacement angle were calculated by comparing the above.
[0003]
[Problems to be solved by the invention]
However, in the conventional aligner, the image of a single mark at the center of the measurement surface of the wafer was compared before and after the posture alignment work. However, in this method, the alignment accuracy is substantially the same as the resolution of the imaging means. Must be high. In particular, since the mark image is small, it is difficult to accurately measure the wafer misalignment angle. However, high-resolution imaging means is expensive and has practical problems such as a narrow imaging range.
[0004]
[Means for Solving the Problems]
The problem to be solved by the present invention is as described above. Next, means for solving the problem will be described.
[0005]
In other words, according to the first aspect of the present invention, there is provided an accuracy measuring apparatus for measuring the accuracy of an aligner for adjusting the posture of a wafer placed on the wafer mounting table, and is detachably attached to a reference position on the wafer mounting table. Imaging means for imaging a pair of marks provided on the measurement surface of the wafer for accuracy measurement at a predetermined interval when the wafer is at a reference position and when the wafer is aligned by an aligner; The image processing apparatus measures the accuracy of the aligner based on the image information obtained from the imaging.
[0006]
According to a second aspect of the present invention, when a wafer for accuracy measurement provided with a pair of marks spaced apart from each other on a wafer mounting table of an aligner for aligning the wafer is placed at a reference position, the pair of marks is imaged. Image information obtained by imaging is processed to obtain a reference straight line connecting the pair of marks, and the wafer with the marks is imaged after aligning with the aligner, and the image obtained by this imaging The information is processed to obtain a straight line after the posture alignment connecting the pair of marks, and the alignment angle deviation angle of the aligner is measured from the angle formed by the reference straight line and the straight line after the posture alignment.
[0007]
According to a third aspect of the present invention, image information obtained by capturing an image of an accuracy measuring wafer provided with a pair of marks spaced apart from each other on a wafer mounting table of an aligner for aligning the wafer at a reference position. Is used as a reference image, and an intermediate point between the pair of landmarks is calculated from the reference image, and image information obtained by imaging the wafer after alignment with the aligner is used as a post-operation image. An intermediate point between the pair of marks is calculated from the post-work image, and the amount of misalignment of the aligner posture is calculated by comparing the intermediate points.
According to a fourth aspect of the present invention, the image information of the pair of marks when the accuracy measuring wafer provided with a pair of marks spaced apart from each other on a wafer mounting table of an aligner for aligning the wafers is placed at a reference position. A procedure for obtaining a reference straight line connecting a pair of marks, a procedure for obtaining a straight line after posture alignment connecting the pair of marks from image information after aligning the wafer with the mark by an aligner, and the reference This is a storage medium that can be read by an aligner accuracy measurement device that stores a program for executing a procedure for calculating a misalignment angle of the aligner from the angle formed by the straight line and the straight line after the alignment. .
The image information when the wafer for accuracy measurement provided with a pair of marks spaced apart from each other on a wafer mounting table of an aligner for aligning the wafer is placed at a reference position as a reference image. The intermediate point of the pair of marks is calculated from the procedure for calculating the intermediate point of the pair of marks from the post-working image information after post-positioning when the wafer is aligned by the aligner. This is a storage medium that can be read by the aligner accuracy measuring apparatus that stores a program for executing a procedure for calculating a deviation amount of the alignment of the aligner by comparing these intermediate points.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Next, embodiments of the invention will be described. In this embodiment, an aligner mounted on an automatic guided vehicle is described. However, the present invention can be applied to an aligner attached to an apparatus fixed to a floor surface such as a semiconductor manufacturing apparatus, and is not limited.
1 is a perspective view showing a state of an automatic guided vehicle in a clean room, FIG. 2 is a side sectional view of the automatic guided vehicle, FIG. 3 is a diagram showing an aligner accuracy measuring device, and FIG. 4 is an image on a virtual plane in the image processing device. It is a figure which shows the Example of information processing.
[0009]
As shown in FIGS. 1 and 2, the automatic guided vehicle 1 is a tracked carriage that automatically travels on traveling rails 2 and 2 and is supported by four traveling wheels 3. Are driven by the respective drive motors 4.
[0010]
.. And semiconductor stockers 6 are arranged along the traveling rails 2 and 2, and a plurality of cassettes 7, 7... Are arranged in parallel at predetermined intervals on the stocker 6. Has been. Each of the cassettes 7, 7... Is arranged with its opening directed toward the traveling rails 2 and 2 side. Further, a plurality of shelves 9, 9... That support the end portions of the wafers 8 are projected on the inner side of the cassette 7, and a plurality of wafers are supported so that both ends are supported by the shelves 9. ... Are accommodated horizontally in the cassette 7.
[0011]
In the center of the automatic guided vehicle 1, a transfer device 10 such as a robot arm for transferring the wafers 8, 8... Is mounted, and the directions of the wafers 8, 8. ) And an aligner (attitude alignment device) 11 for aligning the center position, and a buffer cassette 12 for storing and transporting the wafers 8.
The buffer cassette 12 has an opening directed toward the transfer device 10 and is disposed on the buffer table 13. Like the cassette 7, a plurality of shelves 14, 14... Are projected on the inner side of the buffer cassette 12, and a plurality of wafers 8. Are stored horizontally in the buffer cassette 12.
[0012]
The wafer 8 is made of silicon single crystal and has a substantially disk shape. A silicon single crystal is usually manufactured by a CZ (Czochralski) method so that a specific crystal orientation is substantially perpendicular to a disk surface of a disk. Further, an orientation flat or notch is provided on a part of the side surface of the wafer 8 so that the crystal orientation can be specified even when the wafer 8 is rotated about an axis perpendicular to the board surface. An ID mark for process management in which a manufacturing history of each wafer 8 is encoded is provided on the lower surface side of the board surface. Since the crystal orientation of the wafer 8 greatly affects various properties of the semiconductor, it is necessary to accurately transfer the semiconductor 8 to the semiconductor manufacturing apparatus 5 or the like at a predetermined position with a predetermined crystal orientation.
[0013]
Next, the configuration of the aligner 11 will be described.
The aligner 11 includes a casing 16, a mounting table 17, linear sensors 18, 19 and an optical character reader (hereinafter referred to as "OCR") 20.
The casing 16 has an opening 16a on the transfer device 10 side. The transfer device 10 takes out the wafers 8, 8... Stored in the buffer cassette 12 one by one, and the aligner 11 from the opening 16a. Move inside.
The linear sensor 18 includes a projector 18a and a light receiver 18b, and the linear sensor 19 includes a projector 19a and a light receiver 19b. The linear sensor 18 closer to the opening 16a has a diameter of 12 inches on the wafer 8, and the linear sensor 19 farther from the opening 16a has a side surface of the wafer 8 when the diameter of the wafer 8 is 8 inches. The orientation flat or notch provided is detected. In addition, since the same effect is produced even if the projector and the light receiver are configured upside down, the arrangement method is not limited.
The mounting table 17 has a disk shape whose diameter is smaller than that of the wafer 8, and the wafer 8 mounted on the mounting table 17 by the transfer device 10 is provided with suction means (not shown) provided on the upper surface of the mounting table 17. ) Is fixed to the mounting table 17 so that the wafer 8 is not blown off by the centrifugal force during the rotation of the mounting table 17 or the mounting location is not shifted. The suction means of the mounting table 17 includes various methods such as a vacuum chuck, and is not limited.
On the other hand, the OCR 20 is arranged below the mounting table 17 and reads an ID mark provided on the lower surface of the wafer 8. In the present embodiment, an ID mark is provided on the lower surface of the wafer 8, but depending on the type of the semiconductor manufacturing apparatus 5, it may be upside down, and the position of the OCR 20 is not limited.
[0014]
Next, the aligner accuracy measuring device 15 which is a main part of the present invention will be described. As shown in FIGS. 2 and 3, the aligner accuracy measuring device 15 measures the deviation amount and the deviation angle from the predetermined position of the wafer 8 aligned by the aligner 11, grasps the accuracy of the aligner 11, This is a device for correcting the operation of the transfer device 10 and the mounting table 17, and comprises an imaging means 21, an accuracy measuring wafer 22, and an image processing device 23.
The imaging means 21 comprising a CCD camera or the like is composed of a pair of cameras 21a and 21b, and is arranged so as to face the measurement surface (upper surface in this embodiment) of the accuracy measurement wafer 22 placed on the placement table 17. Is done. The cameras 21a and 21b are configured to be able to transmit image information of the imaging areas 25a and 25b (shaded portions in FIG. 3) to the image processing device 23, respectively.
The accuracy measuring wafer 22 has substantially the same shape as the normal wafer 8, and an orientation flat 22c (may be a notch) is provided in a part of the side surface, and fixing holes 22a and 22b are formed. The fixing hole 22a is formed in the center of the accuracy measuring wafer 22, and a fixing screw 26a passes through the fixing hole 22a and is screwed to the center of the mounting table 17. On the other hand, the fixing screw 26b passes through the fixing hole 22b and is screwed near the end of the mounting table 17. With this configuration, the accuracy measurement wafer 22 is fixed to a predetermined position of the mounting table 17 with a predetermined crystal orientation. The fixing screws 26a and 26b are for reliably preventing the accuracy measuring wafer 22 from being displaced from the reference position of the mounting table 17 when the mounting table 17 on which the accuracy measuring wafer 22 is mounted is turned. There may be a pin that is not provided with a thread groove that fits into the fixing hole.
Further, a pair of marks 24a and 24b are provided in the vicinity of both ends of the measurement surface by a method such as marking, and the midpoint of the straight line connecting the marks 24a and 24b is the center of the measurement surface of the accuracy measuring wafer 22 and It is configured to coincide with the center of the fixing hole 22a.
[0015]
When measuring the accuracy of the aligner 11, first, the fixing screws 26a and 26b are set so that the center of the accuracy measuring wafer 22 and the center of the mounting table 17 coincide with each other and the orientation flat 22c and the mounting table 17 are in a predetermined positional relationship. Is tightened to fix the accuracy measuring wafer 22 to the mounting table 17. Subsequently, the cameras 24 a and 24 b in the imaging regions 25 a and 25 b are respectively imaged by the cameras 21 a and 21 b, and the image information is transmitted to the image processing device 23. The image processing device 23 stores the image information as a reference image.
Next, the fixing screws 26a and 26b are removed, the accuracy measuring wafer 22 is taken out from the aligner 11, and stored in the buffer cassette 12 or the cassette 7 of the automatic guided vehicle 1, and is transferred by the transfer device 10 of the automatic guided vehicle 1. The wafer is transferred into the aligner 11 and the same alignment operation (aligner operation) as that of the normal wafer 8 is performed. After the aligner operation, the cameras 21a and 21b capture the marks 24a and 24b in the imaging regions 25a and 25b, respectively, and transmit the image information to the image processing device 23. The image processing apparatus 23 stores the image information as a post-work image.
[0016]
As shown in FIG. 4, in the image processing apparatus 23, based on the reference image, the center point 27a of the mark 24a and the center point 27b of the mark 24b in the reference image are displayed on the virtual plane 31 on the program of the image processing apparatus 23. Plotted. Based on the post-work image, the center point 28a of the mark 24a and the center point 28b of the mark 24b in the post-work image are plotted on the virtual plane 31.
[0017]
By calculating the angle (θ in FIG. 4) formed by the straight line connecting the central point 27a and the central point 27b and the straight line connecting the central point 28a and the central point 28b, the shift angle of the aligner operation in the aligner 11 is obtained. It is possible to measure with high accuracy.
[0018]
Further, by determining the distance (L in FIG. 4) between the intermediate point 29 of the straight line connecting the central point 27a and the central point 27b and the intermediate point 30 of the straight line connecting the central point 28a and the central point 28b. 11 can accurately measure the shift amount of the aligner operation.
[0019]
In the image processing device 23, in addition to storing the reference image and post-work image, calculating and storing the shift angle and shift amount, a control mechanism (not shown) that controls the calculation result of the shift angle and shift amount for the entire automatic guided vehicle system. ), And the operation pattern of the transfer device 10 and the aligner 11 of the automatic guided vehicle 1 can be automatically corrected based on the calculation result.
[0020]
A conventional aligner accuracy measuring apparatus is provided with a mark at one center of the accuracy measuring wafer, and the image information before and after the aligner operation is compared by one imager to measure the shift amount and the shift angle. However, since the resolution of the imaging unit and the measurement accuracy are substantially the same in this method, it is not only possible to use an expensive high-resolution imaging unit to improve the measurement accuracy, but also causes an increase in cost and the imaging area is There are problems such as large restrictions on the device configuration due to narrowing. In addition, there is a problem that the accuracy of the shift angle is particularly low (in order to calculate a rotation amount of a small mark from image information).
Since the aligner measuring apparatus of the present invention performs measurement using a pair of marks provided in the vicinity of both ends of the wafer, a deviation amount and a deviation angle appear on the captured image, and both the deviation amount and the deviation angle have a measurement accuracy. In particular, the effect of improving the accuracy of the deviation angle is great. Further, in recent years, the diameter of wafers has been increasing, but with this, the distance between a pair of marks can be increased, which has the advantage of improving measurement accuracy. Furthermore, in this example, the pair of marks 24a and 24b are respectively imaged by separate cameras so that the imaging means 21 can be imaged by a camera having a lower resolution.
[0021]
In the example of the present embodiment, the imaging means 21 arranges a camera for each pair of landmarks and images each landmark so that even a camera with a lower resolution can be measured with high accuracy. Since the shift amount and the shift angle are large and can be understood with high accuracy, it is possible to image both the two marks with one camera. As for the method of accurately fixing the accuracy measuring wafer 22 to the mounting table 17, even if the number of fixing holes is three or more, the shape of the fixing holes is made to be a square or the like, It may be combined and is not limited.
Furthermore, the shape of the marks 24a and 24b of the accuracy measuring wafer 22 is + in this embodiment. However, other shapes are not limited because the same effect can be obtained. Further, the method of arranging the marks 24a and 24b on the surface of the accuracy measuring wafer 22 on the surface can be corrected by a program in the image processing apparatus 23 even if the intermediate point between them does not coincide with the center of the accuracy measuring wafer 22. Yes, but not limited.
[0022]
【The invention's effect】
Since the present invention is configured as described above, the following effects can be obtained.
[0023]
In other words, an accuracy measuring apparatus for measuring the accuracy of an aligner for aligning the posture of a wafer placed on a wafer mounting table, which is detachably attached to a reference position on the wafer mounting table. Imaging means for imaging a pair of marks provided at a predetermined interval on a measurement surface of the accuracy measurement wafer when the wafer is at a reference position and when the wafer is aligned by an aligner, Since the image processing apparatus measures the accuracy of the aligner based on the image information obtained from the imaging of the image, the shift amount and shift angle of the image to be processed appear larger than the conventional image processing with one mark. The accuracy of the aligner accuracy measuring apparatus can be improved without improving the resolution of the image processing means.
[0024]
According to a second aspect of the present invention, when a wafer for accuracy measurement having a pair of marks spaced apart from each other on a wafer mounting table of an aligner for aligning the wafer is placed at a reference position, the pair of marks is imaged. The image information obtained by this imaging is processed to obtain a reference straight line connecting the pair of marks, and the wafer with the marks is imaged after aligning with the aligner and obtained by this imaging. Since the image information is processed to obtain a straight line after the posture alignment connecting the pair of marks, and the alignment angle of the aligner is measured from the angle formed by the reference straight line and the straight line after the posture alignment, Compared to the image processing with one mark, the deviation angle of the image to be processed appears larger, so the accuracy of the aligner accuracy measuring device can be improved without improving the resolution of the image processing means. .
[0025]
An image obtained by capturing an image of an accuracy measuring wafer provided with a pair of marks spaced apart from each other on a wafer mounting table of an aligner for aligning the position of the wafer at a reference position. Using the information as a reference image, the intermediate point of the pair of landmarks is calculated from the reference image, and the image information obtained by imaging the wafer after alignment with the aligner is used as the post-operation image. Since the midpoint between a pair of landmarks is calculated from the post-work image and the midpoint is compared by calculating the midpoint between the midpoints, it should be processed as compared to the conventional image processing with a single landmark. Since a large amount of image shift appears, the accuracy of the aligner accuracy measuring apparatus can be improved without improving the resolution of the image processing means.
According to the fourth aspect of the present invention, the image information of the pair of marks when the accuracy measuring wafer provided with the pair of marks spaced apart from each other on the wafer mounting table of the aligner for aligning the wafer is placed at the reference position. A procedure for obtaining a reference straight line connecting the pair of marks, a procedure for obtaining a straight line after alignment of the pair of marks from image information after aligning the wafer with the marks on an aligner, Because it is a storage medium that can be read by the aligner accuracy measurement device that stores the program for calculating the alignment angle of the aligner posture from the angle formed by the reference straight line and the straight line after the posture adjustment, Compared to conventional image processing with a single mark, the shift angle of the image to be processed appears larger, so the accuracy of the aligner can be measured without improving the resolution of the image processing means. It is possible to improve the accuracy of the location.
According to a fifth aspect of the present invention, image information obtained by placing an accuracy measuring wafer provided with a pair of marks spaced apart from each other on a wafer mounting table of an aligner for aligning a wafer at a reference position is used as a reference image. The procedure for calculating the intermediate point of the pair of landmarks from the image, the post-positioning image information when the wafer is aligned by the aligner as the post-work image, and the intermediate point of the pair of landmarks from the post-work image Since it is a storage medium that can be read by the aligner accuracy measurement device that stores the program for executing the procedure for calculating and the procedure for calculating the deviation amount of the alignment of the aligner by comparing these intermediate points, Compared to image processing with a single mark, the amount of shift in the image to be processed appears larger, so the accuracy of the aligner can be measured without improving the resolution of the image processing means. It is possible to improve the accuracy of the device.
[Brief description of the drawings]
FIG. 1 is a perspective view showing a state of an automatic guided vehicle in a clean room.
FIG. 2 is a side sectional view of the automatic guided vehicle.
FIG. 3 is a diagram showing an aligner accuracy measuring device.
FIG. 4 is a diagram showing an example of image information processing on a virtual plane in the image processing apparatus.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Automatic guided vehicle 8 Wafer 11 Aligner 15 Aligner accuracy measuring device 17 Mounting table 21 Imaging means 21a and 21b Camera 22 Accuracy measuring wafer 22c Orientation flat (orientation flat)
23 Image processing devices 24a and 24b

Claims (5)

  An accuracy measuring apparatus for measuring the accuracy of an aligner for aligning the posture of a wafer placed on a wafer mounting table, wherein the accuracy measuring device is detachably attached to a reference position on the wafer mounting table. A pair of marks provided at a predetermined interval are imaged when the wafer is at a reference position and when the wafer is aligned by an aligner, and image information obtained from the respective images is used as a basis. An aligner accuracy measuring device comprising an image processing device for measuring the aligner accuracy.   An image obtained by imaging a pair of marks when an accuracy measuring wafer provided with a pair of marks spaced at a predetermined interval is placed at a reference position on a wafer mounting table of an aligner for aligning the position of the wafer. The information is processed to obtain a reference straight line connecting the pair of marks, and the wafer with the marks is imaged after aligning with the aligner, and the image information obtained by the imaging is processed to process the pair of marks. A method for measuring the accuracy of an aligner, comprising: obtaining a straight line after posture alignment connecting the marks and measuring a misalignment angle of the aligner of the aligner from an angle formed by the reference straight line and the straight line after posture alignment.   An image information obtained by imaging an accuracy measuring wafer provided with a pair of marks at a predetermined interval on a wafer mounting table of an aligner for aligning the wafer at a reference position is used as a reference image. An intermediate point between the pair of landmarks is calculated from the image, and image information obtained after posture alignment when the wafer is aligned by the aligner is used as a post-operation image, and a pair of images is obtained from the post-operation image. A method for measuring the accuracy of an aligner, characterized in that an intermediate point of a mark is calculated, and the amount of deviation in alignment of the aligner is calculated by comparing the intermediate points. A reference for connecting the pair of marks from the image information of the pair of marks when a wafer for accuracy measurement having a pair of marks spaced at a predetermined interval is placed on a reference position on the wafer mounting table of the aligner for aligning the position of the wafer A procedure for obtaining a straight line, a procedure for obtaining a post-position alignment straight line connecting the pair of marks from image information after aligning the wafer with the mark on the aligner, and after aligning the reference straight line with the reference line A storage medium readable by an aligner accuracy measuring apparatus storing a program for executing a procedure for calculating a misalignment angle of the aligner from the angle formed by the straight line. Image information when a wafer for accuracy measurement provided with a pair of marks at a predetermined interval is placed on a reference position on a wafer mounting table of an aligner for aligning the position of the wafer is used as a reference image, and the pair of marks is extracted from the reference image. A procedure for calculating an intermediate point, a procedure for calculating an intermediate point of a pair of landmarks from the post-working image using post-working image information after posture alignment when the wafer is aligned by an aligner, these intermediate points A storage medium that can be read by an aligner accuracy measuring apparatus that stores a program for executing a procedure for calculating the amount of alignment deviation of the aligner by comparing.

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