JPH04320043A - Positioning mechanism for v-notched wafer - Google Patents

Abstract

PURPOSE:To provide a mechanism for accurately positioning a V-notched wafer on a test stage. CONSTITUTION:A V-notched wafer 1 is placed on a chuck 21 of a test stage. At each of three points at equal intervals around the wafer, there are provided two pins 52 urged by a spring 54 to press the wafer edge, an angle pin 52 adapted to enter the V-notch for orientation, and a stopper 521 for stopping each pin at the correct position around the wafer. Near and opposite sides of the angle pin, two photosensors 56a and 56b are provided; one at the wafer edge and the other at the depth of the notch from the edge. All those pins press the wafer edge to position the wafer center, and then the angular position of the V-notch is determined by the ON/OFF states of the photosensors while the wafer is rotated.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and mechanism for positioning a wafer having a V-notch relative to an inspection stage.

0002

2. Description of the Related Art Wafers used as raw materials for semiconductor ICs are inspected using an optical foreign particle inspection device because the quality of the wafers deteriorates when foreign substances adhere to the surface. Inspection is carried out in an assembly line, in which the wafers housed in a wafer cassette are transported to an inspection stage, air-adsorbed by a chuck section, and rotated.

FIG. 3(a) shows the shape of the wafer, and O
is the center of wafer 1. Previously, an orientation flat (OF or OF') was provided on the wafer 1 by cutting out a part of the circumference as shown by dotted lines. However, OF and OF' have drawbacks such as loss of the cut-out part and stress on the wafer due to the cut-out, which affects the characteristics, so recently V-shaped grooves (
V-notches). The depth of the V-notch is approximately 1 mm. During inspection, as shown in (b) of the figure, the center O of the wafer 1 is aligned with the rotation center O' of the inspection stage 2, and the V notch is moved in a certain angular direction (the y-axis direction in the figure). It is necessary to place and adsorb it. It is of course possible to perform center positioning and V-notch angle adjustment on the inspection stage, but this will reduce the operating rate of the inspection stage, so it is best to perform this in advance before the inspection. is preferred. In response, the inventor of the present invention devised a pre-alignment method, and has filed a patent application as a "wafer pre-alignment method."

An overview of the above prealignment method will be explained with reference to FIG. In the wafer 1 to be inspected housed in the wafer cassette 1', the position of the center O and the direction of the V notch (simply indicated by V) are random. The wafer 1 is transferred to the pre-alignment stage 4 by the handling arm 3, and first the center is aligned, and then V is adjusted to V'.
The pre-alignment is completed by rotating the wafer 1 by an angle θ to the position shown in FIG.

[0005]

[Problem to be solved by the invention] The above pre-alignment method was developed for wafers with OF, and is also quite effective for V-notch wafers, but recent semiconductor ICs are becoming increasingly Due to the high degree of integration, alignment on the inspection stage requires higher accuracy than ever before, and the above pre-alignment method is not quite satisfactory for V-notch wafers. Therefore, it has become necessary to align the V-notch wafer 1 with high accuracy on the inspection stage 2, regardless of whether pre-alignment has been performed or not. The present invention has been made in view of the above, and it is an object of the present invention to provide a method and mechanism for positioning a V-notch wafer placed on an inspection stage with high precision.

[0006]

[Means for Solving the Problems] The present invention is a positioning mechanism for a V-notch wafer on an inspection stage having a chuck section that rotates while placing/adsorbing a V-notch wafer. At three equal points on the circumference, there are two pressing pins that are each biased inwardly by a spring and press the edge of the circumference, an angle determining pin that presses the edge and fits into the V notch, and each pin. A stopper is provided to stop the wafer at the correct position. Further, two optical sensors are arranged on both sides near the angle determining pin, at a position inscribed in the edge and at a position inside the edge by the depth of the V notch. Furthermore, it has three cam grooves into which each pin is inserted, and a cam plate that rotates a certain angle by driving the drive wheel and moves each inserted pin, and a cam plate that supports each pin and presses the edge. A diagonal movement mechanism is provided that moves each pin upward when the pressure is released and retracts it downward when the pressure is released. Further, the diagonal moving mechanism is provided with an optical sensor that detects the timing of releasing the wafer from adsorption.

[0007]

[Operation] In the above positioning mechanism, the wafer placed on the chuck section is first released from suction. On the other hand, the angle determining pin and the two pressing pins, each of which is biased inward by a spring, move along the cam groove and divide the circumference into three equal parts by the rotation of the cam plate driven by the drive wheel. By pressing the edge of the point, each pin is stopped by a stopper and the center of the wafer is correctly positioned. In this case, each pin is moved diagonally downward by a diagonal movement mechanism so as not to interfere with the inspection while not being pressed, and is moved diagonally upward when being pressed. Further, if the center positioning of the wafer is carried out while the wafer is being sucked, the wafer will be damaged, so the above-mentioned release is performed, and the release is performed at a timing obtained by an optical sensor provided in the diagonal movement mechanism. Next, for the wafer whose center has been positioned, V
The notch is angled. Two optical sensors operate on the wafer whose center has been positioned as described above, and when both are OFF, the V notch has already been positioned. However, in general, one is ON and the other is O.
Since it is FF, at that time, the wafer is sucked and rotated in either direction, and the angle is determined by stopping at an angular position where both are OFF. However, when both of them turn ON due to this rotation, it means that the V-notch is aligned with one of the optical sensors, so the angle between that optical sensor and the angle setting pin is further rotated, and it turns OFF and the angle is set. be done.

[0008]

[Embodiment] FIG. 1 shows an embodiment of a V-notch wafer positioning mechanism according to the present invention, (a) is an overall view, and (b) is an overall view.
are partial diagrams, and the configuration will first be explained using these. In FIG. 1A, the inspection stage 2 includes a chuck section 21, a motor 22 that rotates the chuck section, and a Z mechanism 23 that moves the wafer 1 attracted to the chuck section up and down. However, the Z mechanism 23 is not related to this invention. Reference numeral 5 indicates a positioning mechanism, which includes an angle pin 52a, pressing pins 52b, 52c, and three stoppers 521a, 521b, 521c that stop each pin at the correct position on the wafer at three equal points on the circumference of the wafer 1. are arranged respectively, and each pin is biased inwardly by springs 54a, 54b, and 54c, respectively. Cam plate 5 has cam grooves 53a, 53b, 53c into which each pin is inserted.
1, which is connected to four rollers 55a, 55b, 55
c and 55d, and is rotated within a certain angular range by driving a drive wheel 57. Regarding the shape of each cam groove, the width of each cam groove is made slightly larger than the diameter of each pin to provide room for operation. Cam groove 53
The cam grooves 53a and 53b are inwardly shaped like a dogleg along the circumference, and the cam grooves 53c are straight and diagonal, extending across the edges. Also, the biasing force of each spring is spring 5
4a and 54b are set to be the same, but 54c is set to be weaker than this. Next, two optical sensors 56a and 56b are installed on both sides near the angle determining pin 52a, at a position inscribed in the edge and at a position inward from the edge by the depth of the V-notch.
to be placed. The optical sensor may be of a light emitting/receiving type or a reflected light type, but the diameter of the light beam should be about the size of a V-notch,
For example, one with a diameter of 1 mm is used.

FIG. 1B shows a vertical section of a portion of each pin 52, and shows the base 22 fixed to the motor 22.
1, a cam plate 51 is supported by rollers 55. A stopper 521 for each pin is fixed to the base 221 in accordance with the correct position of the wafer, and a diagonal movement mechanism 58 consisting of a fixed part 581 to the base 221 and a moving part 582 connected to this by a link 583
can be installed. Each pin 52 is attached to the moving part 582, and when these pins 52 move along the cam groove 53, they move diagonally up and down as indicated by arrow D by the action of the link 583. Further, an optical sensor 59 is provided in the moving section 582.

To explain the operation and function of the above positioning mechanism, when the cam plate 51 rotates with respect to the wafer 1 placed on the chuck section 21 and each pin 52 moves inward and starts pressing, The pressed position of the pin 52 is detected by the optical sensor 59, and at that timing, air is injected from the chuck section 21 to release the wafer. Next, spring 54
The edge is pressed by the urging force of , the wafer is moved, each pin stops at the stopper 521, and the center O is positioned. In this case, due to the difference in the biasing forces of the springs 54a, 54b and 54c, the pins 52a, 5
Since pin 52c is somewhat free compared to pin 2b, no undue force is applied to the wafer. Two optical sensors 56a and 56b operate on the wafer whose center is positioned, and the angle of the V-notch is determined by the method described below. Note that while each pin 52 is not pressed, it is retracted downward by the operation of the diagonal movement mechanism 58 and does not interfere with the inspection.

The angle determination of the V-notch using both optical sensors will be explained below with reference to FIG. Two optical sensors 56a, 56
Let b be a light emitting/receiving method, and represent these by sa and sb. If both optical sensors are OFF when the center is positioned as described above, the pin pa has just fitted into the V and the angle has been determined as shown in (a). In this case, when the pre-alignment method described above is applied, the angle is often determined immediately as described above, but sometimes this is not done, and when the wafer is directly transferred from the cassette to the inspection stage, the angle is In most cases, the state is not determined and the state is as shown in (b) and (a) in the figure, where the optical sensor sa is ON and the optical sensor sb is OFF.
It becomes F. Now, suppose that the V notch is at the position of the solid line V, and when the wafer is rotated in the direction of θ1 and V comes to the position of pin pa, pin pa is constantly being pressed, so V
As the wafer is inserted into the wafer, the wafer moves upward by a small distance to reach the state shown in (c), and both optical sensors are turned off. At this point, the rotation of the wafer is stopped and the angle is determined. Also, if the V notch is at the position of the dotted line V', θ
When the rotation of 1 is continued, V' goes around once and comes to the position of the optical sensor sb as shown in (b), and both optical sensors are turned on. From this position, optical sensor sb and pin pa
If the wafer is further rotated by the angle θ2 formed by (
C) The angle determination is completed in the state shown below. Angle θ2
is known in advance. In the above, it is of course possible to use reflective type sensors as both optical sensors, but
In that case, ON and OFF of the above-mentioned judgment conditions are reversed.

0012

As explained above, in the positioning mechanism according to the present invention, the wafer placed on the chuck part of the inspection stage is centered by each pin and stopper, and by two optical sensors and the wafer. The angle of the V-notch is determined with high precision through rotation, and each pin is retracted when inspecting a wafer so that it does not interfere with the process. The effect of safe and highly accurate positioning of notch wafers is significant.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of an embodiment of the positioning method according to the present invention, in which (a) is an overall view and (b) is a partial view.

FIG. 2 is an explanatory diagram of determining the angle of the V notch in FIG. 1; This is a diagram.

FIG. 3 is an explanatory diagram of a V-notch on a wafer and positioning of the wafer with respect to an inspection stage.

FIG. 4 is a schematic explanatory diagram of a pre-alignment method for which a patent is pending.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1... Wafer (or V-notch wafer), 1'... Wafer cassette, 2... Inspection stage, 21... Chuck part, 22...
Motor, 221...Base, 23...Z mechanism, 3...Handling arm, 4...Pre-alignment stage, 5...
Positioning mechanism, 51...Cam plate, 52...Each pin, 52a
... Angle determining pin, 52b, 52c ... Pressing pin, 521
a, 521b, 521c...stopper, 53a, 53b,
53c...Cam groove, 54a, 54b, 54c...Spring, 55a, 55b, 55c, 55d...Roller, 5
6a, 56b... Optical sensor, 57... Drive wheel, 58... Diagonal movement mechanism, 581... Fixed part, 582... Moving part, 58
3... Link, 59... Optical sensor.

Claims (1)

[Claims] Claim 1: In an inspection stage having a chuck part that rotates while placing/adsorbing a V-notch wafer, a spring is attached inwardly to each trisecting point of the circumference of the wafer placed on the chuck part. two pressing pins that press the circumferential edge; an angular pin that presses the edge and fits into the V-notch; and a stopper that stops each pin at a correct position on the wafer. and two optical sensors are arranged at a position inscribed in the edge on both sides near the angle determining pin, and at a position inward from the edge by the depth of the V notch, A cam plate has three cam grooves into which each pin is inserted, and is rotated through a certain angle by driving a drive wheel to move each pin inserted into each cam groove, and a cam plate that supports each pin. , a diagonal movement mechanism that moves each pin upward when pressing the edge and retracts it downward when the pressure is released, and an optical sensor that detects the timing of releasing the wafer from adsorption in the diagonal movement mechanism. A V-notch wafer positioning mechanism characterized by: