JP2000012657A - Positioning device for semiconductor wafer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a small-sized and inexpensive device and a method for semiconductor wafer positioning which can detect the center position of a semiconductor wafer accurately without contacting. SOLUTION: A couple of sensors 6 and 7 are fixed and provided in a semiconductor wafer conveyance path to detect the front and rear edges of a semiconductor wafer 2 in its moving direction, the center axis of the semiconductor wafer 2 in the moving direction is found by dividing the distance between those edges by two, and the center deviation angle ΔX in an X direction is found from the difference between the center axis and the position F of the sensor set at a specific distance from a supply destination. Further, the deviation quantity ΔY in a Y direction is found from a distance X' corresponding to the deviation quantities of left and right edge points detected by the sensors 6 and 7 and a previously set constant (a) and the positioning of the semiconductor wafer 2 is corrected according to those found deviation quantities ΔX and ΔY.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor wafer positioning device used for positioning a semiconductor wafer.

[0002]

2. Description of the Related Art For example, in a wafer inspection apparatus for inspecting a defect of a semiconductor wafer or the like, a wafer stored in a cassette is taken out by a transfer arm, and from this state, the transfer arm is moved to supply the wafer onto an inspection table. It has become.

In this case, the inspection table to which the wafer is supplied by the transfer arm needs to be supplied with the wafer in an accurately positioned state. Therefore, conventionally, when a wafer is supplied onto an inspection table, a positioning device that pushes the periphery of the wafer with a hammer to match the center of the wafer with the center of the inspection table is used.

However, in the case of pressing the periphery of the wafer with a hammer, there is a possibility that the wafer surface may be scratched or stained by the impact of the hammer or the rubbing with the inspection table surface.

In order to solve this problem, a wafer positioning device disclosed in Japanese Patent Application Laid-Open No. 8-97269 has been proposed. In this method, a wafer in a cassette is accessed by a hand moved by an arm. An edge sensor is provided at a predetermined interval in a head of the hand, and an edge of a wafer is detected based on an output of the edge sensor while moving the hand. At the same time, assuming any two points on the circumference of the detected edge position, the center position of the wafer as the center point of the circumference is determined from these points, and the hand is moved based on this center position. In this way, the wafer can be positioned in a non-contact manner.

[0006]

However, in such a configuration, two arbitrary points on the circumference of the wafer edge position are assumed, and the center of the wafer as the center point of the circumference is assumed from these points. Is determined, complicated calculation processing is required until the wafer center is determined, the configuration of the calculation unit becomes complicated, and the cost becomes high. Also, since the edge sensor is provided on the hand moved by the arm,
There is a problem that the edge detection accuracy of the edge sensor cannot be expected from the viewpoint of mechanical reliability due to the hand movement and the wafer positioning accuracy cannot be sufficiently obtained.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to provide a small and inexpensive semiconductor wafer positioning apparatus capable of accurately detecting the center position of a semiconductor wafer without contact.

[0008]

According to the first aspect of the present invention,
In a semiconductor wafer positioning device for positioning a semiconductor wafer taken out of a cassette at a predetermined supply destination,
A pair of sensors fixedly provided in a wafer transfer path between the cassette and the supply destination and detecting an edge of a semiconductor wafer taken out of the cassette; and a moving direction of the semiconductor wafer detected by at least one of the sensors. The shift amount in the moving direction of the semiconductor wafer is obtained from the relationship between the distance between the front and rear edges and the position of the sensor, and the shift amount between the left and right edges detected by the pair of sensors and a preset constant are used. Calculating means for calculating a shift amount in a direction orthogonal to the moving direction, wherein the positioning of the semiconductor wafer at the supply destination is corrected based on the shift amount obtained by the calculating means.

According to a second aspect of the present invention, in the first aspect of the present invention, the calculating means moves the semiconductor wafer by reducing a distance between the front and rear edges detected by at least one sensor to half. The center axis of the direction is determined, and the amount of center deviation in the moving direction of the semiconductor wafer is determined from the difference between the center axis and the position of the sensor set at a predetermined distance from the supply destination.

[0010] The third aspect of the present invention is the first or second aspect.
In the invention described above, the constant used for the arithmetic means is determined from a ratio of a shift amount in a direction orthogonal to a moving direction of the semiconductor wafer and a difference between distances between edges detected by the pair of sensors. I have.

As a result, according to the first aspect of the present invention,
Since the pair of sensors can be fixedly provided in the semiconductor wafer transfer path, the edge detection accuracy of the sensors can be improved also in terms of mechanical reliability and the like. Further, the configuration of the calculation unit can be simplified without requiring complicated calculation processing for calculating the center shift amount in the movement direction of the semiconductor wafer and the shift amount in the direction orthogonal to the movement direction.

According to the second aspect of the present invention, the configuration of the calculation unit can be simplified without requiring a complicated calculation process for calculating the center shift amount in the moving direction of the semiconductor wafer. According to the third aspect of the present invention, the shift amount in the direction orthogonal to the moving direction of the semiconductor wafer can be obtained by direct approximation, so that the configuration of the calculation unit can be simplified.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a schematic configuration of a semiconductor wafer positioning apparatus to which the present invention is applied. In the drawing, reference numeral 1 denotes a cassette, in which a plurality of semiconductor wafers 2 are accommodated at a predetermined pitch in the stacking direction.

The transfer arm 3 is moved by using the X-direction motor 4 and the Y-direction motor 4 'as driving sources. The transfer arm 3 sucks and holds the semiconductor wafers 2 stored in the cassette 1 one by one and takes out the semiconductor wafers. 2 is transported onto the inspection table 5 which is the supply destination.

Two photoelectric sensors 6, 7 are fixedly provided at predetermined intervals in a semiconductor wafer transport path between the inspection table 5 and the cassette 1. In the present embodiment,
Photoelectric sensors 6 and 7 were arranged on a wafer transfer path near the opening 1a of the cassette 1. These photoelectric sensors 6 and 7
Is composed of a light emitting section and a light receiving section. The light receiving section detects the presence or absence of incident light from a light emitting section (not shown) accompanying the movement of the semiconductor wafer 2 to move the semiconductor wafer 2 as shown in FIG. Each edge of points A and D and points B and C along the direction is detected.

A pulse counter 8 is connected to the photoelectric sensors 6 and 7. The pulse counter 8 counts pulses of a predetermined cycle, and outputs respective count values at the points A and D and the points B and C described above.

Then, the count value of the pulse counter 8 is input to the CPU 9. The CPU 9 outputs a drive command for the transfer arm 3 to the pulse generators 10 and 10 '.
Drive pulse generated from 0, 10 '
1 and 11 ', the X-direction motor 4 is driven by the motor driver 11, and the Y-direction motor 4' is driven by the motor driver 11 '. Also, CP
U9 is the points A and D from the pulse counter 8 and B and C
From the count values of the points, the respective distances between the points A and D and between the points B and C are calculated, and the shift amount of the center position of the selected semiconductor wafer 2 is calculated. 'Moves the transfer arm 3 in the XY directions to correct the center shift of the semiconductor wafer 2.

Next, the operation of the embodiment configured as described above will be described. In this case, as shown in FIG. 2, the transfer distance β of the semiconductor wafer 2 by the transfer arm 3 is assumed to be determined with reference to the inspection table 5, and the distances of the photoelectric sensors 6, 7 from the inspection table 5 are determined. α is also determined.

In this state, when the CPU 9 outputs a drive command for the transfer arm 3 to the pulse generator 10,
In response to this drive command, a drive pulse is output from the pulse generator 10 and the X-direction motor 4 is driven by the motor driver 11. In this case, it is assumed that the movement center of the transfer arm 3 has returned to the center of the semiconductor wafer transfer path.

As a result, the transfer arm 3 moves the cassette 1
Of the transfer arm 3 is inserted into the cassette 1 to hold one selected semiconductor wafer 2 by suction, and then the transfer arm 3 is retracted to the inspection table 5. The semiconductor wafer 2 is supplied onto the inspection table 5 by moving.

In this case, while the semiconductor wafer 2 is moving to the inspection table 5, the light incident on the light receiving portion of the photoelectric sensor 6 is blocked by the semiconductor wafer 2 at the point A as shown in FIG. When the light incident on the light receiving portion of the photoelectric sensor 7 is blocked, the count values at these points A and B are sent from the pulse counter 8 to the CPU 9. Then, at point D,
When the incident light is received by the light receiving portion of the photoelectric sensor 6 and the incident light is received by the light receiving portion of the photoelectric sensor 7 at a point C, the count values at these points D and C are also transmitted from the pulse counter 8 to the CPU.
9

In this state, these A,
The shift of the center position of the semiconductor wafer 2 is calculated based on the count values at four points B, C, and D. First, the amount of shift ΔX of the center of the semiconductor wafer 2 in the X-axis direction, which is the transport direction, is calculated. In this case, the count value at points A and D
The distance between the points (or between the points BC based on the count values of the points B and C) is obtained. And these AD points or B
The center axis E in the X-axis direction of the semiconductor wafer 2 is obtained by halving the distance between the points C, and the sensor position set to the center axis E and the distance α from the inspection table 5 of the photoelectric sensors 6 and 7. F
From the difference, the center shift amount ΔX of the semiconductor wafer 2 in the X-axis direction is obtained. Specifically, the value obtained by subtracting the count value at point A from the count value at point D is halved, and the count value at point A is added. The center shift amount ΔX of the wafer 2 in the X-axis direction is obtained.

Next, a shift amount ΔY of the center in the Y-axis direction orthogonal to the transfer direction of the semiconductor wafer 2 is calculated. in this case,
Between the points A and B (or C
The distance X ′ between the CD point and the point D is calculated from the count value of the point and the point D, and ΔY = aX ′ based on the distance X ′. That is, the center deviation amount ΔY in the Y-axis direction in this case
Is a very small value of 3 mm, for example, when the storage error of the semiconductor wafer 2 in the cassette 1 is 8 inches, so that the constant a = 1.144 in this 8-inch semiconductor wafer 2.
Is obtained by direct approximation. Where the constant a =
1.144 is determined as follows.

FIG. 3 shows an 8-inch semiconductor wafer 2. The photoelectric sensors 6 and 7 are arranged at a distance of 40 mm from the center of the semiconductor wafer 2, respectively. , 7, distances AD1 and BC1 between the points AD and BC are 183.3 mm, respectively.

From this state, the distances AD2 to AD7 between the AD points by the photoelectric sensor 6 when it is moved in the Y direction by 0.5 mm to a maximum of 3 mm, and the BC by the photoelectric sensor 7
The distances BC2 to BC7 between the points are obtained, and the ratio between the moving distance in the Y direction at this time and the difference between the distances between the AD points and the BC points is obtained, and this is set as a constant a. That is, each measurement distance AD2 to AD7, BC2 between the AD point or the BC point
~ BC7 as shown in the figure, 0.5 / (BC2-AD
2), 0.5 / (BC3-AD3), ..., 0.5 / (B
C7-AD7), and a constant a =
1.144 has been determined.

Thereafter, when the transfer arm 3 moves the semiconductor wafer 2 onto the inspection table 5, the correction of the above-described center deviation ΔX in the X-axis direction and the Y
After the correction of the axial center deviation ΔY, the semiconductor wafer 2 is supplied so that the center of the semiconductor wafer 2 finally coincides with the center of the inspection table 5.

In the above description, the semiconductor wafer 2 of 8 inches has been described as an example, but the constant a is determined for semiconductor wafers of other sizes based on the same concept. Therefore, according to this, a pair of sensors 6 and 6 are provided in the semiconductor wafer conveyance path between the cassette 1 and the inspection table 5.
7 are fixedly provided, and the two edges of the semiconductor wafer 2 taken out of the cassette 1 are detected by the sensors 6 and 7, and the distance AD or BC between these two edges is reduced by half. 2, the center axis E in the X direction is obtained from the difference between the center axis E and the position F of the sensor set at a predetermined distance from the center of the inspection table 5 as the supply destination. Further, a deviation amount .DELTA.Y in the Y direction is obtained from a distance X 'corresponding to the deviation amount between the left and right edge AB points (or CD points) detected by the sensors 6 and 7 and a preset constant a, respectively. Semiconductor wafer 2 based on the shift amounts ΔX and ΔY
Is corrected. As a result, the center position of the semiconductor wafer 2 can be detected in a non-contact manner by the sensors 6 and 7 fixed to the cassette 1, thereby improving the edge detection accuracy of the sensor in terms of mechanical reliability and the like. In addition, since the calculation of the center shift amount ΔX in the X direction and the shift amount in the Y direction of the semiconductor wafer 2 does not require a complicated calculation process, the configuration of the calculation unit can be simplified, so that the entire apparatus However, it can be small and inexpensive.

[0028]

As described above, according to the present invention, since the sensor side is fixedly provided in the semiconductor wafer transfer path and the center position of the semiconductor wafer can be detected in a non-contact manner, mechanical reliability and the like can be improved. Therefore, the edge detection accuracy of the sensor can be improved. In addition, since the calculation of the center shift amount in the movement direction of the semiconductor wafer and the shift amount in the direction orthogonal to the movement direction does not require complicated calculation processing, the configuration of the calculation unit can be simplified, so that the entire apparatus also has Small and inexpensive.

[Brief description of the drawings]

FIG. 1 is a diagram showing a schematic configuration of an embodiment of the present invention.

FIG. 2 is a diagram illustrating one embodiment.

FIG. 3 is a diagram illustrating one embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Cassette, 2 ... Semiconductor wafer, 3 ... Transfer arm, 4 ... X direction motor, 4 '... Y direction motor 5 ... Inspection table, 6, 7 ... Photoelectric sensor, 8 ... Pulse counter, 9 ... CPU, 10, 10 '... Pulse generator, 11, 11' ... Motor driver.

Claims (3)

[Claims] 1. A semiconductor wafer positioning apparatus for positioning a semiconductor wafer taken out of a cassette at a predetermined supply destination, wherein the semiconductor wafer is fixedly provided in a wafer transfer path between the cassette and the supply destination and taken out of the cassette. A pair of sensors for detecting an edge of the semiconductor wafer, and a shift in the movement direction of the semiconductor wafer from a relationship between a distance between front and rear edges in a movement direction of the semiconductor wafer detected by at least one sensor and a position of the sensor. Calculating means for calculating the amount of displacement and the amount of displacement in a direction orthogonal to the moving direction from the amount of displacement of the left and right edges detected by the pair of sensors and a preset constant. And correcting the positioning of the semiconductor wafer at the supply destination based on the determined shift amount. C positioning device. 2. The arithmetic means determines a center axis in the moving direction of the semiconductor wafer by halving a distance between the front and rear edges detected by at least one sensor, and calculates the center axis and the supply destination. 2. The semiconductor wafer positioning apparatus according to claim 1, wherein a center shift amount in a moving direction of the semiconductor wafer is obtained from a difference from a sensor position set at a predetermined distance from the sensor. 3. The constant used in the calculation means is determined from a ratio of a shift amount in a direction orthogonal to a moving direction of the semiconductor wafer and a difference between distances between edges detected by the pair of sensors. 3. The semiconductor wafer positioning apparatus according to claim 1, wherein: