JPH02153550A - Detecting device of notch part of discal body - Google Patents

Abstract

PURPOSE:To detect the notch part of a discal body having the notch part on part of the body with high accuracy by a method wherein a photoelectric element is used as two pieces of photoelectric elements holding one detection direction in common and the output signals of the photoelectric elements are compared with each other. CONSTITUTION:An orientation flat detecting device is constituted of a wafer rotationally driving part consisting of a stage 2 and a stage driving unit 5 and a detection part consisting of two pieces of illuminating light sources 3 and two pieces of line image sensors 4a and 4b. These light sources 3 are arranged below a wafer 1. Moreover, the sensor 4 is arranged in close contact to the wafer 1 on the upper surface of the wafer 1. The peripheral edge part of the wafer 1 is irradiated by the light source 3 and illuminating light, which is not shielded by the wafer, is incided in the sensor 4. By comparing the output signals of these sensors (4a and 4b) with each other, a notch part of the wafer 1 is detected.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is a notch detecting device for a disc-shaped object having a notch in a part, for example, detecting an orientation flat of a semiconductor wafer, and detecting an orientation flat of a semiconductor wafer. The present invention relates to a device that performs alignment.

[Prior Art] Conventionally, the position of the orientation flat of a semiconductor wafer is detected in a non-contact manner by rotating a wafer 2 held on a stage 1 and using lighting 3 and light receiving elements 4 provided at the periphery.
A device as shown in FIG. 8 using a set of detection means consisting of the following is known.

FIG. 9 is a plan view thereof.

There are mainly two known methods for detecting the position of an orientation flat on a semiconductor wafer using this device. That is, two methods are used: one method is to determine the change point of the brightness signal around the orientation flat, and the other method is to determine the maximum value of the brightness signal value at the center of the orientation flap.

[Problems to be Solved and Problems to be Solved by the Invention] However, in the former method, when there is surface sag at both ends of the orientation flat, it is not possible to clearly grasp the point of change in the brightness and darkness signals.

Furthermore, in the latter method, if there is misalignment between the stage and the wafer, the brightness and darkness signals will not necessarily show the maximum value at the center of the orientation flat. In particular, in the case of a wafer with a plurality of orientation flats, there is a high possibility that the bright and dark signals will not show the maximum value at the center of the orientation flat to be detected.

Further, in either method, there is a problem in that the detection accuracy depends on the resolution of the photoelectric element itself.

SUMMARY OF THE INVENTION In view of the drawbacks of the conventional devices described above, an object of the present invention is to provide a device that can detect with high accuracy a notch in a disc-shaped object having a notch in a portion thereof.

[Structure of the Invention] In order to achieve the above object, the present invention provides a circular object that detects a notch by illuminating the periphery of a disc-shaped object having a notch in a part and sequentially obtaining information on the periphery using a photoelectric element. The notch detection device for a plate-like object is characterized in that the photoelectric element is two photoelectric elements having the same detection direction, and the notch is detected by comparing output signals of the photoelectric elements.

In addition to the configuration of the first invention, the second invention also includes:
The present invention is characterized in that a calculation means is provided for calculating the amount of misalignment between the disc-shaped object and the stage that holds the disc-shaped object from the detection result.

[Embodiments of the invention] Hereinafter, one embodiment of the present invention will be described based on the drawings.

FIG. 1 is a side view of an apparatus for detecting an orientation flat on a wafer according to an embodiment of the present invention, and FIG. 2 is a plan view thereof.

This orientation flat detection device is composed of a wafer rotation drive section consisting of a stage 2 and a stage drive unit 5, and a detection section consisting of two illumination light sources 3 and two line image sensors 4a and 4b.

An illumination light source 3 is arranged below the wafer 1. In order to improve detection accuracy, it may be placed closer to the center of rotation. The illumination light source may be shared, or a plurality of light sources may be provided for each, but the key is to provide uniform illumination. Line image sensor 4 is arranged close to wafer 1 on the upper surface of wafer 1 .

The illumination light source 3 illuminates the periphery of the wafer 1, and the illumination light not blocked by the wafer is incident on the line image sensor 4.

Note that a collimator lens may be inserted between the illumination light source 3 and the wafer 1, and a condensing optical element may be inserted between the line image sensor 4 and the wafer 1.

Roughly speaking, the illumination light source 3 and the line image sensor 4 may be made movable according to the aperture of the wafer, or a plurality of sets of sensors may be arranged in advance and selected according to the aperture.

FIG. 3 is an electrical system block diagram of the orientation flat detection device.

The stage 2 holding the wafer 1 is connected to a motor drive control circuit 10. The motor unit is driven via the motor drive driver 19, and is rotated by a constant angle. The address counter 11 is incremented every time it is driven by a fixed angle, causing the oscillator 12 to start oscillating. The line image sensors 4a and 4b are activated by a clock signal from the oscillator 12. Output signals from the line image sensors 4a, 4b are amplified by preamplifiers 13a, 13b, respectively, and binarized by comparators 14a, 14b.

The value of the data counter 16 at the moment of change from dark to bright from the binary data of the wafer peripheral area obtained in this way is recorded in the latches 15a and 15b. Each recorded data is written to the memory 18 via the multiplexer 17.

The above operation is repeated until the wafer 1 rotates once, and the outer circumference data for one revolution of the wafer is recorded in the memory 18.

Next, after detecting the position of the orientation flat as will be described later (see FIG. 6), the stage drive unit 5 rotates the orientation flat of the wafer again to position it near the line image sensor group. After positioning the orientation flat near the line image sensor 4, rotate it again by a certain angle and
Brightness information of the periphery of the wafer 1 is obtained from the line image sensors 4.

An example of the brightness information of the orientation flat return at this time is shown in FIG. Here, L4a and L4b are line image sensors 4a
, 4b, and the intersection point A of these two signals is
indicates that the orientation flat is perpendicular to the axis X in FIG.

However, if the two line image sensors 4a, 4b are installed at different positions, the orientation flat will not be perpendicular to the axis X at point A, so the line image sensors 4a, 4b
Using the amount of deviation between as a correction value, L4a in FIG.
signal. From this point A becomes the direction of the desired orientation flat.

These processes are executed by a processing circuit consisting of a microcomputer.

The detection accuracy of the orientation flat is determined by the line image sensors 4a and 4.
Letting the interval b be D and the distance between the light receiving parts of the line image sensors 4a and 4b be d (FIG. 5), it can be expressed as (however, d is smaller than the maximum diameter of the orientation flat).

Therefore, by widening the distance d between the light receiving parts, the detection accuracy can be improved more than the detection accuracy inherent to the line image sensors 4a and 4b.

Next, calculation of the misalignment amount will be explained.

FIG. 6 shows an example of outer circumference data for one circumference of the wafer.

The data in FIG. 6 also shows that there is misalignment between stage 2 and wafer 1, and that wafer 1 also has a second orientation flat. Here, between the two points a-a and b-'rf where the amount of data change is large, a-
It can be seen that the first orientation flat exists between d.

FIG. 7 shows a situation where there is a center shift between the wafer 1 and the stage 2.

The amount of center deviation between wafer 1 and stage 2 is (ΔX, Δ
y). The amount of center deviation is determined by using three points on the circumference of the wafer 1 that do not belong to the orientation flat, and the distance from the rotation center P of the stage 2 to each point is R,, R, 2.

By calculating R3, the amount of center deviation (ΔX) between the center P of the wafer 1 and the center 27 of the stage 2 is calculated.

Find Δy).

That is, since the second orientation flat is located at a position rotated by a certain angle from the center of the first orientation flat, three points that do not belong to the circumference of the second orientation flat are extracted from the aforementioned data stored in the memory 18, and a known calculation is performed. The center of the quadratic curve connecting the three points is determined by , and the amount of center deviation (ΔX, Δy) is determined.

[Effects of the Invention] As described above, according to the present invention, it is possible to detect a notch with a high degree of precision exceeding the resolution of the sensor itself. Furthermore, since positional deviation of the sensor can be easily corrected, assembly becomes extremely easy.

In other words, positional deviation with respect to the stage can be detected with high precision, making it possible to perform highly accurate positioning in subsequent processes.

[Brief explanation of the drawing]

FIG. 1 is a side view of a wafer orientation flat detection apparatus according to an embodiment of the present invention, and FIG. 2 is a plan view thereof. Fig. 3 is an electrical system block diagram of the orientation flat detection device, Fig. 4 is a diagram showing an example of brightness information for returning the orientation flat,
FIG. 5 is a diagram illustrating the relationship between the line image sensors 4a, 4b and orientation flat detection accuracy, and FIG. 6 is a diagram showing an example of outer circumference data for one rotation of the wafer. FIG. 7 is a diagram showing a state where there is a center deviation between the wafer and the stage, FIG. 8 is a side view of a conventional wafer orientation flat detection device, and FIG. 9 is a plan view thereof. 1... Wafer 2... Stage 3... Light source for illumination 4... Line image sensor 5... Motor unit

Claims (4)

[Claims] (1) A notch detection device for a disc-shaped object that detects a notch by illuminating the peripheral edge of a disc-shaped object having a notch in a part and sequentially obtaining peripheral edge information using a photoelectric element, wherein the photoelectric element A notch detection device for a disc-shaped object, characterized in that the notch is detected by comparing the output signals of the two photoelectric elements having the same detection direction and by comparing the output signals of the photoelectric elements. (2) A notch detection device for a disc-shaped object that detects a notch by illuminating the peripheral edge of a disc-shaped object having a notch in a part and sequentially obtaining peripheral edge information using a photoelectric element, wherein the photoelectric element are two photoelectric elements with the same detection direction, the notch is detected by comparing the output signals of the photoelectric elements, and the detection result is used to determine the misalignment between the disc-shaped object and the stage that holds the disc-shaped object. 1. A notch detection device for a disc-shaped object, comprising a calculation means for calculating a quantity. (3) A notch detection device for a disc-shaped object, wherein the photoelectric elements according to items 1 and 2 are two line image sensors, and each photoelectric element has a separate light source corresponding to the photoelectric element. (4) A notch detection device for a disc-shaped object, wherein the separate light source corresponding to each photoelectric element as described in item 2 is composed of one or a plurality of light sources arranged in a line.