JPS6245040A - Positioning device of circular sheet element - Google Patents

Abstract

PURPOSE:To enable the positioning of a wafer with an excellent precision not in contact with the specified turning center by a method wherein the shape of wafer and the interval between the first and the second reference positions are calculated; the slip of wafer from the first reference position is detected; and a base loaded with the wafer is alignment-controlled by the output of photoelectric conversion element. CONSTITUTION:A wafer 6 is adsorption-fixed on the surface of a base 7 adsorption-supported on a turntable 8. The turntable 8 is stopped at the position wherein a fine notch 6a is detected by a linear image sensor Ctheta. The wafer 6 is made eccentric from the turning center and the eccentricity is read by 4 each of linear image sensors Ca-Cd arranged slipping by 90 deg. in the radial direction. Finally the adsorption of turntable is released to move the base 7 thus made movable by DELTAx and DELTAy respectively in X and Y directions corresponding to the measured values of eccentricity for correcting the eccentricity of wafer 6 from the turning center O.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of the Invention 1] The present invention relates to a method in which a circular plate-shaped object such as a semiconductor wafer having a notch (orientation flat) as a positioning index is placed in a measuring device, an inspection device, or an exposure device. This invention relates to a positioning device for a circular plate-shaped object, which places the object in a reference position.

[Background of the Invention] An example of a conventional semiconductor wafer positioning device (Japanese Patent Laid-Open No. 58
-18937) is shown in FIG. As shown in the figure, the conventional positioning device includes a rotary table 3 on which a semiconductor wafer 6 (hereinafter referred to as "wafer") is placed and rotates, and a rotating table 3 that rotates toward the center of rotation while maintaining an equal distance from the center of rotation of the rotary table 3. The reciprocating members 2a and 2b move to converge from the center of rotation, and to diverge from the center of rotation.

2c, 2d, 2e, a photoelectric element C1 and a light source disposed at a position facing the photoelectric element C with the wafer sandwiched therebetween.

In this wafer positioning device, the reciprocating parts IJ2a to 2e advance from the periphery of one wafer 6 placed on the rotary table 3 in a freely movable state toward the center of the rotary table 3 while pushing the wafer 6, Move wafer 6 and move wafer 6
and the center of the rotary table 3. Thereafter, the reciprocating members 2a to 2e retreat outward in a direction away from the center of rotation. When this centering is completed, the wafer 6 is suctioned and fixed on the rotating table 3, and the rotating table 3 is rotated to read the area around the wafer 6 in the form of changes in the amount of light incident on the photoelectric element C from the light source. The notch 6a is detected. Furthermore, the eighth
As shown in the figure, in order to correct the slight inclination of this notch, a fixed roller 4a as a reference member is moved by a lever 5.
The wafer 6 is pressed against 4b and 4c to finally position the wafer.

However, in this conventional wafer positioning device, the reciprocating member must be forcibly pressed against the wafer, which may damage the wafer. Further, in this method, the positional accuracy is not very good, and therefore, a final positioning operation is required, and the wafer has to be forcibly pushed away at that time as well, which is disadvantageous.

On the other hand, a non-contact type positioning device is also known as a conventional positioning device (Japanese Patent Application Laid-Open No. 57-198642). This uses a pulse motor to intermittently rotate a rotary table that holds a wafer fixedly. The periphery of the wafer is read by a light source and a photoelectric conversion element placed between the wafer, and the notch of the wafer is detected from the extreme point of the electrical signal from the photoelectric conversion element.In this case, since it is a non-contact type, the wafer There is no risk of damaging the wafer, but since this method uses multiple photoelectric conversion elements arranged in parallel in the radial direction of the wafer to compare changes in the outline of the wafer at the center of rotation, changes in the outline can be seen due to rotation, but the wafer remains stationary. It was difficult to perform high-precision detection on wafers that were

Furthermore, conventional positioning devices include those based on the outer shape of the wafer to a predetermined position and those based on the center point that align the center of the wafer to a predetermined position. For standard size wafers, these can align the wafers to the same position by mutually converting the reference positions.

However, when attempting to position general wafers using devices with different positional references, such as one based on the outer shape and one based on the center, or two devices based on the same outer shape but different parts of the wafer as reference, There is an inconvenience that it deviates from the reference position (converted value) by the dimensional error of its outer shape.

[Objective of the Invention] The present invention solves the problems of the conventional apparatus described above, and provides an apparatus that can accurately position a circular plate-shaped object in a non-contact manner even if it has been processed using different positional standards in the previous process. It is an object.

This purpose, according to the present invention, is to form images of the circumference of a circular plate-shaped object on a photoelectric conversion element at a plurality of positions, and to determine the shape of the object and mutually different positioning standards based on the output of the photoelectric conversion element. The distance between the first and second reference positions is calculated, the amount of deviation of the object from the first reference position is detected, and the @placement table on which the object is placed is determined based on the detected deviation and distance. This is achieved by position control.

[Example] Embodiments of the invention will now be described with reference to the accompanying drawings.

FIG. 1 is a perspective view of a wafer positioning device according to an embodiment of the present invention. As shown in the figure, this wafer positioning device includes a rotary table 8, a mounting table 7 which is releasably fixed to the rotary table 8, and which can move in the X and Y directions when released. Wafer 6 placed on 7
XY deviation detection linear image sensors Ca, Cb, Cc, which are placed around the wafer sandwiching the wafer.
Cd light sources La, Lb, Lc, Ld, linear image sensor Cθ for notch detection placed between the wafer near the periphery of the wafer parallel to the tangential direction of the wafer 6, and light source L
θ.

To further explain in detail with reference to FIG. 2.3.5, the wafer 6 having the small ■-shaped notch 6a is suction-supported by the mounting table 7 having suction grooves 78 as shown in FIG. Furthermore, this mounting table 7 has suction grooves 8 on the rotary table 8.
It is designed to be supported by suction by a. Further, the rotary table 8 is placed on stages 9 and 10 that can move in the XYh directions.

Linear image sensors Ca-cd for detecting the eccentricity of the wafer 6 with respect to the center of rotation of the rotary table 8 are arranged so as to face each other in the diametrical direction of the wafer 6, as shown in FIG. Irradiating light source La~L
d is placed below the wafer 6. Further, a linear image sensor Cθ for detecting a notch is arranged in a direction parallel to the tangential direction of the wafer 6, and is configured to be irradiated with a light source Lθ.

The operation of this embodiment will be explained. First, the wafer 6 is suction-fixed to the upper surface of the mounting table 7, which is suction-supported on the rotary table 8.
Rotate this. Rotation of the rotary table 8 is stopped at the position where the linear image sensor Cθ detects the minute notch 6a.

In this state, the wafer 6 is still eccentric with respect to the center of rotation of the rotating table 8. This amount of eccentricity is read by four linear image sensors Ca-cd arranged at 90'' intervals in the radial direction of the wafer 6, as shown in FIG. 5a.

For example, the amount of eccentricity in the X direction is calculated by linear image sensor Ca.
, CC's digital output difference, and the Y direction is measured to be Δy by the linear image sensors Cb and Cd. Next, the suction of the rotary table 8 is released, and the mounting table 7, which is now movable, is moved by Δx in the X direction and Δy in the Y direction based on the measured value of eccentricity, and rotated as shown in Fig. 5b. Correct the eccentricity of the wafer with respect to the center O. Since the mounting table 7 is moved, the wafer 6 is not pressed into direct contact with the wafer 6, and this eccentricity adjustment can be performed without contact. After the pope finished, placing table 7
is suctioned and fixed to the rotary table 8 again.

The deviation of the minute notch 6a in the rotational direction is detected by a linear image sensor Cθ. As shown in FIGS. 4a and 4b, the center M of the transmitted light from the minute notch 6a is shifted by Δθ with respect to the predetermined center pixel CM of the linear image sensor Cθ. (Fig. 4b), the rotating table 8 is rotated by Δθ to make the center M of the transmitted light coincide with a predetermined center pixel CM, thereby firmly correcting the deviation in the rotational direction (Fig. 4b). FIG. 6 shows a flow chart of the operation of the embodiment. Incidentally, FIG. 9 shows the detection signals of the conventional wafer positioning apparatus in the case of the present invention (No. 4a).

Figure 4b) is shown in comparison.

In the initial state, the linear image sensor Cθ detects the notch 6a of the wafer 6, which is the center of rotation, and stops the rotation.In order to reduce the response of the linear image sensor Cθ and the processing time at that time, and to improve the throughput. The wafer 6 may be rotated at high speed using the analog photoelectric conversion element P and stopped at the position of the linear image sensor Cθ.

Moreover, the radius of the wafer 6 can also be measured by measuring the wafer 6 after the eccentricity has been corrected using the linear image sensors Ca to Cd. This radius measurement can be used as follows. For example, a wafer that was positioned using another wafer positioning device without using this device and underwent an exposure process was printed with a different positioning of 11%. By adjusting the distance between the positioning standards and correcting the position of the X stage 9 and Y stage 10 installed under the rotary table 8 by the necessary amount, it is possible to mix use with devices with different positioning standards. be. In addition, the linear image sensor Ca-Cd that detects eccentricity may be a photoelectric conversion element with an analog output instead of a digital output.In the embodiment, four linear image sensors were used, but one sonia image sensor can be used to The deviation may be detected and then the wafer may be rotated 90' to detect the deviation in the Y direction. Furthermore, a two-dimensional image sensor can be used as a linear image sensor to detect eccentricity and to detect gaps.

Note that in the above description, the linear image sensors Ca,
It is also possible to use an analog photoelectric conversion element similar to element P in place of Cb, Cc, and Cd.

However, as mentioned above, if the peripheral position of the wafer is detected based on the digital output of the linear image sensor, it will not be affected by changes in the light intensity of the light source over time, and a lens can be inserted between the wafer and the linear image sensor. Detection accuracy can be further improved by enlarging the wafer image.

[Effects of the Invention] As described above, according to the present invention, it is possible to accurately position a circular plate-shaped object, such as a wafer, at a predetermined center of rotation in a non-contact manner.

[Brief explanation of the drawing]

1 to 3 are a perspective view, a plan view, and a side view, respectively, showing an embodiment of the wafer positioning device of the present invention. FIG. 4 is a micro-notch position and notch detection in an embodiment of the present invention. FIG. 5 is a schematic diagram showing the relationship with the signals; FIG. 5 is a diagram showing how eccentricity of a wafer is detected in an embodiment of the present invention; FIG. 6 is a flowchart explaining the operation of the embodiment of the present invention; 8 are a perspective view and a plan view of a conventional wafer positioning device, and FIG. 9 is a schematic diagram showing an orientation flat detection signal in the conventional wafer positioning device. In the figure, 6... wafer, 6a... minute notch, ca-cb
-cc-Cd-Cd... linear image sensor, 7.
...Placement stand, 8...Rotary stand, La -Lb -Lc-
Ld-La・Ll)...Light source, 9.10...X stage, Y stage, P...Analog photoelectric conversion element. . Cocoon Figure 40 Figure 4b @ Figure 5a Figure 5b Figure 6

Claims (1)

[Claims] 1. A mounting table that can move in the X direction and the Y direction, and a photoelectric conversion for XY deviation detection that detects the positions of multiple locations around a circular plate-shaped object placed on the mounting table. an element and a light source; means for detecting the amount of deviation of the object from a first reference based on the output of the photoelectric conversion element; detecting the shape of the object based on the output of the photoelectric conversion element; Means for calculating the gap between the first reference position and a second reference position set differently from the first reference position from the shape information; 1. A positioning device for a circular plate-shaped object, comprising means for controlling the drive of a circular plate-shaped object. 2. The positioning device for a circular plate-shaped object according to claim 1, wherein the second reference is a different type of position reference in a previous process. 3. The device according to claim 1 or 2, wherein a plurality of the photoelectric conversion elements for detecting XY deviation and a plurality of light sources are arranged in pairs at a plurality of positions around the circular plate-shaped object. Positioning device for circular plate-shaped objects. 4. Claim 1, wherein a plurality of positions around the circular plate-shaped object are detected by arranging only one set of the photoelectric conversion element for XY deviation detection and the light source, and rotating the mounting table. Alternatively, the positioning device for a circular plate-shaped object according to item 2. 5. The positioning device for a circular plate-shaped object according to any one of claims 1 to 4, wherein the photoelectric conversion element is a linear image sensor.