JP2988594B2 - Wafer center detection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wafer center detecting device used for processing and inspecting a wafer.

[0002]

2. Description of the Related Art In the inspection of a wafer surface and an electrode pattern formed on the surface, a wafer processing step, and the like, it is necessary to accurately determine the center position of the wafer. The conventional method of determining the center position of the wafer is roughly classified into a contact type using a stopper and a method in which the outer periphery of the wafer can be regarded as a circle in relation to required accuracy. There is a non-contact type wherein a center position is obtained by projecting a light beam or the like on the outer periphery of the wafer and detecting the shape of the outer periphery of the wafer.
Since the contact type may damage the wafer, the latter non-contact type has recently been adopted.

In order to detect a non-contact type outer peripheral shape, an optical detecting means is generally used. For example, a light receiving element is arranged at a position where the measuring light source and the measuring light are incident, the wafer is moved in a direction in which the measuring light is blocked, and the shape of the outer periphery of the wafer is detected from the relationship between the moving time and the output of the light receiving element. It is a device to do.

[0004]

However, one or several orientation flats (hereinafter referred to as OF) are formed on the outer periphery of the wafer, and it is possible to regard this as a circle. It is the outer peripheral part except for. Therefore, in the non-contact type wafer center detecting apparatus as described above, as a factor of the detection error, an error due to the presence of the OF must be considered in addition to a factor resulting from the optical measurement. Therefore, complicated processing is required to obtain the center position of the wafer, and the obtained result is not always accurate.

SUMMARY OF THE INVENTION The present invention has been devised in view of the above drawbacks, and an object of the present invention is to provide a wafer center detecting device capable of accurately detecting the center position of a wafer by a simple mechanism.

In order to achieve the above object, the wafer center detecting device of the present invention has the following features. (1) Center position of wafer for detecting center position of wafer
In the position detecting device, moving means for moving the wafer in a predetermined direction, and at least four points having different distances from the moving axis.
A light projecting means for projecting the measuring light and a projecting position of the measuring light.
Corresponding to at least four light receiving units,
Light receiving means for detecting measurement light by means, and the moving means
From the movement information and the output of the light receiving means
Measuring means for obtaining position information of points and from position information of outer peripheral points
Make a combination of three points as one set,
Find circles passing through points and compare the size of each circle with a predetermined reference value
Information that exceeds the reference value from the information for center calculation
The first exclusion unit and the information excluded by the first exclusion unit.
The inclusion frequency is calculated for each peripheral point, and exceeds the predetermined reference frequency.
Second exclusion means for further excluding information including a peripheral point to be obtained
And the remainder not excluded by the first exclusion means and the second exclusion means
Operator that calculates the center position of the wafer based on the information of
Characterized in that it comprises a wafer center calculating means with a stage, a.

[0007]

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is an essential part layout diagram showing an essential part arrangement of an apparatus according to one embodiment of the present invention. 1 is a wafer as a test object,
Reference numeral 2 denotes a transfer arm for transferring the wafer 1. Transfer arc
A portion 2a of the drum 2 has a vacuum suction hole (not shown) at a tip end to suck the wafer 1. The transport arm 2b rotates about a shaft 2c, and the transport arm 2b rotates about a shaft 2d. The portion 2e is rotatable around a fixed rotating shaft 2f by a motor (not shown). Fixed rotating shaft 2f
The rotation of the 2e portion about the axis 2b is about 2b about the axis 2d.
It is linked to the rotation of the part and the rotation of the part 2a about the axis 2c.

Reference numerals 3 and 4 denote light projecting units. Each of the light projecting units 3 and 4 has windows formed therein at two places for emitting light. Two collimator lenses are arranged in the light projecting unit, and the measuring light exits from the exit window as parallel light. The light projecting units 3 and 4 are arranged substantially symmetrically with respect to a movement axis X passing substantially through the center of the portion 2a of the transport arm 2, and the measuring light illuminates a position 40 mm and 55 mm away from the X axis. This arrangement on a straight line is merely for convenience of processing. In short, information on different positions on the wafer can be obtained, and moreover, there is a possibility that 6 or more of them will be OF-related because they are extremely ubiquitous. It can be anywhere unless it is in the right position. Reference numeral 5 denotes a light receiving unit, which houses four photoelectric sensors that receive light beams emitted from the windows of the light emitting units 3 and 4.
In this embodiment, the transmission type detection is performed, but the reflection type detection may be performed. Further, a condenser lens may be arranged before the photoelectric sensor.

FIG. 2 is a block diagram of a main part of the electric system. 6
Is an operation panel of the apparatus, and 7 is a microcomputer which controls the entire apparatus and performs various calculations. Reference numeral 8 denotes a transport arm driving unit for driving a wafer transport arm, and reference numeral 9 denotes an A / D converter for A / D converting a signal from the light receiving unit 5.

The operation of the apparatus having the above configuration will be described with reference to the flowchart of FIG. After the wafer 1 is placed on the portion 2a of the transfer arm 2, the wafer 1 is sucked on the portion 2a of the transfer arm 2 by evacuating from the vacuum suction hole. The measurement is started when the wafer 1 is placed at the initial position and the four light sources in the light emitting unit emit measurement light. The transport arm drive unit 8 is driven by a command from the microcomputer 7, and the 2e unit rotates about the fixed rotary shaft 2f.
Linked with this rotation, a portion 2b around the shaft 2d, the shaft 2
The wafer 1 linearly moves on the movement axis X by rotating the portions 2a around the center c by the same angle (step 1 in FIG. 1).

The four photoelectric sensors in the light receiving unit 5 constantly detect the amount of incident light, and the detection signals are sent to the microcomputer 7 after A / D conversion. Wafer 1
At the start of shading (when an edge is applied) and at the end of shading (when an edge is removed). Since the position of the photoelectric sensor in the Y-axis direction is known, the number of pulses from the reference point (or the time from the start of light shielding to the end of light shielding) when the linear movement axis is set as the pulse feed is determined by the moving speed of the wafer 1. By associating, the position coordinates of the eight peripheral points of the wafer having the origin at the predetermined position are obtained (step 2).

There are obtained 56 combinations of three of the eight outer peripheral points, and the center position and the radius of a circle connecting the three points are calculated for each group by a known method (step 3). As described above, one or several OFs are formed on the outer periphery of the wafer, and there is a possibility that the outer peripheral points obtained in step 2 include those that are applied to the OF. Therefore, the radius of the circle obtained in step 3 is compared with a predetermined reference value, and data exceeding the reference value is excluded from the data for obtaining the center position of the wafer (step 4).

However, in step 4, data whose outer peripheral point is on the OF cannot be completely excluded. Therefore, step 4
The inclusion frequency of each outer peripheral point included in the circle data excluded in the above is calculated, compared with a predetermined reference frequency, and if it exceeds this, the data including this outer peripheral point is excluded (step 5). . The reference frequency is determined by a statistical method in consideration of the required measurement accuracy. Further, for example, when there are two peripheral points having a relatively high inclusion frequency, the inclusion frequency and the reference frequency may be calculated using only data that does not include one of them.

An average center position is calculated by averaging the remaining center position information excluded in steps 4 and 5 (step 6), and the calculated average center position of the wafer 1 is calculated by XY.
The device is moved to a predetermined position of the apparatus by the stage mechanism (step 7).

It will be apparent to those skilled in the art that the above embodiments can be modified in various ways. If the required measurement accuracy allows, step 5 can be skipped, and it is not necessary to use a simple average of the center position information to determine the average center position of the wafer. Further, if necessary, the number of measurement light sources and the number of photoelectric sensors can be further increased.

[0017]

According to the wafer center detecting apparatus of the present invention, the center position of a wafer having a plurality of OFs can be detected by using four light projecting means and light receiving means.

Since the wafer inspection device and the processing device are provided with a transport mechanism, when using an existing transport mechanism, it is sufficient to provide only a light source for measurement and a photoelectric sensor. There is no need to provide a mechanism.

Further, since data including an error related to the OF can be effectively removed, a highly accurate center position can be obtained.

[Brief description of the drawings]

FIG. 1 is a main part layout diagram showing an arrangement of main parts of an apparatus according to one embodiment.

FIG. 2 is a block diagram of a main part of an electric system.

FIG. 3 is a flowchart showing the operation of the apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Wafer 2 Conveying arm 3, 4 Light emitting unit 5 Light receiving unit

Claims (1)

(57) [Claims] 1. A wafer for detecting a center position of a wafer.
In the center position detecting device, a moving means for moving the wafer in a predetermined direction, at least a different distance from the moving axis
Projection means for projecting measurement light to four points, and projection positions of the measurement light
Hold at least four light receiving units corresponding to the
Light receiving means for detecting measurement light by the light emitting means;
Wafer from the movement information of the moving means and the output of the light receiving means
Measuring means for obtaining the position information of the outer peripheral point of the
Create a combination of three points from the report and combine
Find the circle passing through the three points, and determine the size of each circle as a predetermined reference value
Information that exceeds the reference value from the center calculation information
A first exclusion unit to be excluded and the first exclusion unit
The frequency of inclusion is determined for each perimeter point in the information, and the
Second exclusion that further excludes information that includes outer peripheral points that exceed degrees
Means, not excluded by the first exclusion means and the second exclusion means
Calculation of the center position of the wafer based on the remaining information
And a wafer center calculating means having a calculating means .