JPH11255306A - Detection device for wafer in cassette - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect wafers as a whole easily at low cost without inserting thin light emitting elements or photoreceptors between multi-stage wafers in a cassette. SOLUTION: This wafer detection device can detect en bloc the number of wafers 1 set in a cassette 5 and their positions. In this case, mirror-finished light guides 6 cut in their tips 7 to 45 degrees are mounted at the detection positions of the wafers 1 as detecting element therefor. The light introduced into each light guide 6 by each photoreceptor 3 is reflected at the 45 degrees cut part 7 in the right angle direction and goes out of the light guide 6, and then a wafer accommodation part 5A is irradiated with the light. Accordingly, when a wafer 1 is in a defection position, the reflection light returns to a photoreception element 4 through the same path as that of the introduced light.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for collectively detecting the number of wafers and their positions in a cassette having a multi-stage wafer storage section, and is used in a process such as semiconductor manufacturing. is there.

[0002]

2. Description of the Related Art A means for detecting the number of wafers stored in a cassette and a storage position (slot position) in a semiconductor manufacturing apparatus and related apparatuses is disclosed in, for example, JP-A-62-41129. As described above, a method is generally used in which one wafer detection sensor including a pair of light emitting elements and light receiving elements is moved in the vertical direction of the cassette, and the presence / absence of a wafer and the position of each wafer are detected.

Japanese Patent Application Laid-Open No. Sho 62-130938 discloses a device for taking out a wafer from a carrier, in which a take-out arm, a light-emitting fiber and a light-receiving fiber are connected via a prism, and the take-out arm is placed in the carrier. When inserted, light is emitted to the wafer storage side through the light emitting side fiber and prism, and when there is a wafer, the emitted light is reflected and enters the light receiving side fiber, and the reflected light is detected by the photodetector to sequentially reflect the wafer. Detection is being performed.

[0004] The above-described wafer detection method must detect wafers one by one, and cannot meet the need to detect wafers in a cassette simultaneously and collectively.

The following apparatus has been conventionally proposed as an apparatus capable of simultaneously detecting wafers.

This prior art will be described with reference to FIG. This wafer batch detection sensor basically has the same number of wafers as the number of wafers to be detected by the wafer detection sensors (light emitting element 3 and light receiving element 4). In this method, the sensor is inserted at a time through means (wafer collective detection unit) 2 capable of moving forward and backward to detect the presence or absence of a wafer. The wafer batch detection unit 2 is retracted to a position outside the cassette where there is no problem in taking out / storing the wafer except when the wafer is detected.

In this example, the wafers 1 stored in the wafer storage cassette 5 are one at the uppermost part and one below the total, that is, there are no wafers 1 therebelow. When there is no wafer 1, light from the light emitting element 3 is incident on the light receiving element 4. This is converted into an electric signal by the optical / electrical converter 8 and the CPU
Take in 9. This allows the CPU 9 to know that there is no wafer. When the wafer 1 is present, light from the light emitting elements 3 is blocked by the wafer 1 and no light enters the light receiving elements 4. Similarly, this is converted into an electric signal by the optical / electrical converter 8 and taken into the CPU 9. This allows the CPU to know the presence of the wafer. Since this is performed simultaneously for all the wafers, the presence or absence of the wafer can be detected at a time.

In addition, as disclosed in Japanese Patent Application Laid-Open No. 61-248837, a contact, spring, and photosensor corresponding to each wafer are prepared in the wafer batch detection apparatus.
There has been proposed a device that detects a wafer by making the contact penetrate a photosensor when the contact comes into contact with the wafer.

[0009]

In order to detect a wafer, it is desirable to detect the wafer by a non-contact method in order to prevent damage to the sensor.

The pitch between the wafers in the wafer storage cassette is 6.35 mm, and the gap between the wafers is about 5 m.
m, and the wafer detection sensor inserted between the wafer storage units for the batch detection of wafers must not be in contact with the wafer because the wafer must not be damaged. Had to use. For example, in the example of FIG. 3, it is necessary to provide a light-emitting element and a light-receiving element on the sensor support arm 11 for detection other than the uppermost step and the lowermost step. There is a demand for ever thinner devices.

In response to such a demand, it is conceivable to use a fiber (light emitting fiber, light receiving fiber) having a prism connected to the tip as disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 62-130938. In addition, it is necessary to prepare a separate component prism for each fiber, and further, it is necessary to bond the prism. Therefore, the cost is high for a device that uses a large number of sensors, such as a wafer batch detection system, and is not practical.

An object of the present invention is to easily and inexpensively collectively detect wafers without inserting a thin light-emitting element or a light-receiving element between wafers in a cassette (between wafer storage sections formed in multiple stages). And a highly practical device for detecting wafers in a cassette.

[0013]

To solve the above-mentioned problems, the present invention is basically configured as follows.

In order to simultaneously and simultaneously detect the number of wafers and their positions in a cassette in which a wafer storage section is formed in multiple stages, a means capable of moving forward and backward relative to the cassette has 45 At least as many light guides that have been cut and mirror-finished are arranged in accordance with the positions of at least the wafer storage sections necessary for batch detection of the wafers, and the opposite side of each light guide from the 45-degree cut section. A pair of light-emitting elements and a light-receiving element are arranged so as to face one end of the light guide, and the light of the light-emitting elements introduced into each of the light guides is reflected in the 90 ° direction by the 45 ° cut portion and out of the light guide. The path of the light to be guided and guided to the outside is directed to each wafer storage unit when the light guide is inserted into the cassette.

According to the above configuration, a method is employed in which the light guide is inserted instead of inserting the sensor itself between narrow wafers.

The light guide to be inserted between the wafers has its tip cut to 45 degrees and mirror-finished.
This is set at the detection position of the wafer, and the light from the light-emitting element introduced into the light guide is refracted in the 90-degree direction by the 45-degree cut part, guided to the outside of the light guide, and is introduced into each wafer storage part in the cassette. Irradiate. When the wafer is in the storage section, the reflected light returns to the reflected light detection sensor (light receiving element) via the same path as the introduced light. This light reception is converted into an electric signal by the above-mentioned optical / electrical converter, and the electric signal is taken into the CPU, whereby the wafer can be detected. If the wafer is not in the storage section, no light returns to the reflected light detection sensor.

[0017]

1 and 2 show an embodiment of the present invention.
This will be described below. FIG. 1 is an overall configuration diagram of an in-cassette wafer detecting apparatus according to an embodiment of the present invention, and FIG. 2 is a diagram showing a main part thereof. In the figure, the same reference numerals as those in FIG. 3 indicate the same or common elements.

The cassette 5 has a plurality of storage sections 5A for the wafers 1 formed therein. The wafer batch detection unit 2 serves as a means capable of moving forward and backward relative to the cassette 5. The detection unit 2 includes a light guide 6 having a 45-degree cut end and a mirror finishing portion 7. Wafer 1
Are arranged in accordance with the position required for each wafer storage section 5A in the cassette in a number necessary for the batch detection of.

The detection unit 2 includes a pair of light emitting elements 3 and light receiving elements 4 for each light guide 6, and these light emitting elements 3 and light receiving elements 4
It is arranged so as to face one end opposite to the 5-degree cut portion (mirror finishing portion) 7.

The light guide 6 is made of, for example, a wire made of a transparent plastic material, and its entire surface is subjected to precision finishing and mirror-finished. As shown in FIG. 2, the light guide 6 which has been mirror-finished has a circumferential surface and a 45 ° cut portion 7.
A light reflecting film 6A for preventing light traveling in the light guide 6 from escaping to the outside is coated. However, 45
The light from the light emitting element 3 on the end face 6a and the light guide peripheral surface on the opposite side to the angle cut portion 7 is cut by 45 degrees.
Part 6 of the peripheral surface that intersects with the optical path after being reflected in the 90 ° direction at
b has a configuration in which the light reflecting film 6A is not applied to secure light transmission. The light reflecting film 6A is obtained by additionally processing resin plating capable of totally reflecting light on a mirror-finished surface, and thus the 45-degree cut portion 7 is mirror-finished. That is, the resin plating 7 is processed on the light guide 6 except for a boundary surface between the light emitting element 3 and the light receiving element 4 and an optical path for irradiating the wafer 1.

Ideally, the light traveling in the light guide 6 is desirably linear light, but actually travels by irregularly reflecting the wall in the light guide 6. The light reflecting film is coated so that the irregularly reflected light does not escape outside the light guide 6.

Further, the light receiving element 4 is mounted behind the light emitting element 3 as shown in FIG. 2 so as not to allow the direct incident light from the light emitting element 3 to enter.

Now, the wafer 1 in the wafer storage cassette 5 will be described.
Is stored only from the top two. The wafer batch detection unit 2 is usually retracted outside the cassette 5 and enters the cassette as shown in FIG.

The principle of operation will be described below.

When performing a batch detection of wafers, the detection unit 2 is moved forward relative to the cassette 5 and the light guides 6 are moved between the respective wafer storage portions in the cassette 5 (the uppermost and lowermost wafers). Light guide 6 for storage
Is inserted between the upper wall of the cassette or the lower wall of the cassette and the wafer storage section).

According to the example shown in FIG. 1, first, the detection of the presence / absence of a wafer at the uppermost portion and below the uppermost portion will be described. The light output from each of the light emitting elements 3 corresponding to the uppermost part and the lower part thereof passes through the respective light guides 6, is refracted 90 degrees by a 45 ° cut mirror finish 7, and passes through the light transmitting portion 6b on the outer periphery of the light guides. The wafer 1 is irradiated. The irradiated light is reflected by the wafer 1, reenters the light guide 6, passes through the same optical path as the incoming optical path, and enters the light receiving element 4. The received light is converted into an electric signal by the optical / electrical converter 8 and taken into the CPU 9. As a result, the CPU 9 determines that there is a wafer.

Next, detection of the absence of a wafer in the third slot (third stage) from the top will be described. The light output from the light emitting element 3 is applied to the outside of the light guide 6 as described above. Since the irradiated light has no wafer, the light guide 6
Therefore, there is no light incident on the light receiving element 4. This is similarly converted into an electric signal by the optical / electrical converter 8 and taken into the CPU 9. As a result, the CPU 9 determines that there is no wafer.

By performing this operation simultaneously for all slots (all wafer storage sections), the presence or absence of a wafer can be detected at a time. The information on the presence / absence and position of the wafer is displayed on the display panel 10 so that the operator can recognize it. Further, this information is sent to the wafer transfer system in the next process, and is taken as important information for taking out and storing the wafer.

[0029]

According to the present invention, the following effects can be obtained.

(1) By making the light guide extremely thin, it is possible to insert the light guide into the narrow gap between the wafers with a margin when detecting the wafers in a lump. Therefore, the possibility of damaging the wafer is reduced, and the reliability can be improved.

(2) Since the light emitting element and the light receiving element can be located outside the cassette when detecting a wafer, there is no restriction on the shapes of these elements.

(3) It is possible to direct the light path of the light guide inserted between the wafers (between the wafer accommodating sections) toward the wafer accommodating section only by applying mirror finishing to the 45 ° cut section provided on the light guide itself. Since there is no need to connect the light guide and a separate member such as a prism to the tip of the light guide, the light guide changing mechanism of the light guide can be simplified and the cost can be reduced. Even when using, try to reduce the cost,
A highly practical wafer detection device can be realized.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram showing an apparatus for detecting wafers in a cassette according to one embodiment of the present invention.

FIG. 2 is an explanatory view showing a main part of the embodiment.

FIG. 3 is an explanatory view showing a conventional example of a device for detecting a wafer in a cassette.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Wafer, 2 ... Wafer collective detection unit, 3 ... Light emitting element, 4 ... Light receiving element, 5 ... Wafer storage cassette, 5A ...
Wafer storage section, 6: light guide, 7: mirror finish (45 ° cut section), 8: optical / electrical converter, 9: CPU
(Central processing unit), 10 ... Display panel.

Claims (2)

[Claims] A means capable of moving forward and backward relative to said cassette in order to simultaneously and simultaneously detect the number and positions of wafers in a cassette in which a wafer storage section is formed in multiple stages; The light guides that have been cut to 45 degrees and mirror-finished are arranged at least as many as necessary for batch detection of the wafers and in accordance with the positions of the respective wafer storage sections. A pair of light emitting element and light receiving element are arranged so as to face one end on the opposite side, and light of the light emitting element introduced into each of the light guides is reflected in the 90 ° direction by the 45 ° cut portion, and the light guide A wafer in a cassette, wherein a path of light guided to the outside and directed to the outside is directed to each wafer storage portion when the light guide is inserted into the cassette. Detection device. 2. The light guide has a peripheral surface and the light guide
The light reflection film for preventing the light traveling in the light guide from escaping to the outside is covered with the 5 ° cut portion, and the end surface and the light guide peripheral surface on the opposite side to the 45 ° cut portion are covered. A part of the peripheral surface intersecting with the optical path after the light from the light emitting element is reflected in the 90 ° direction at the 45 ° cut portion is not provided with the light reflection film in order to secure light transmission. The apparatus for detecting a wafer in a cassette according to claim 1.