JPH0323647A - Apparatus for counting number of wafers - Google Patents

Abstract

PURPOSE:To easily count the number by a method wherein an ultrasonic sensor provided with a sound-producing part and a sound-receiving part is installed at the lower part of a wafer cassette, a relationship between a reflection state and the number of sheets is set in advance and the number of sheets is counted. CONSTITUTION:When wafers 2 are loaded inside a wafer cassette 1 without leaving no space between them, they are housed at a prescribed pitch; as a result, a distance between a sound-producing face and a sound-receiving face of an ultrasonic sensor 12 at the lower part and the wafer 2 at the lowermost stage corresponds to the number of wafers in 1:1. Consequently, a position distance of the wafer 2 at the lowermost stage is measured by using an ultrasonic sensor controller 13 on the basis of a time difference between a produced sound and a received sound. A corresponding data between a detection signal of the sensor 12 and the number of wafers is input to a computing device 14 in advance; the number of wafers 2 is computed by using a signal of the controller 13. As a result, the wafers are transferred by using a controller 15, a drive part 16 and others. Thereby, the number of detection sensors can be reduced; quality, reliability and productivity can be enhanced.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a wafer counting device in a wafer processing device. [Prior Art] In semiconductor device manufacturing, various treatments such as diffusion and etching are used on silicon wafers, but in such wafer processing equipment, the wafers are taken out from the wafer cassette and processed, and the wafers are returned after the treatment. I am working on putting it back on cassette. The various wafer processing apparatuses mentioned above are equipped with a wafer counting device for checking the number of unprocessed wafers or the number of processed wafers. Conventional wafer counting devices include those shown in Japanese Patent Application Laid-open Nos. 13344-1982 and 743-1983. The wafer counting device shown in these uses a light projecting element and a light receiving element, and detects the presence of a wafer when a wafer blocks the optical path between the light projecting element and the light receiving element.

A brief description will be given below in Figure 3. In the figure, reference numeral 1 indicates a wafer cassette, and reference numeral 2 indicates an optical wafer detection sensor.

The wafer sensor 3 includes a light emitting element 4 and a light receiving element 5, respectively.
and are provided corresponding to each wafer 2 insertion position of the wafer cassette 1. When the wafer 2 is inserted, the periphery of the wafer 2 blocks the optical path of the wafer sensor 3, and the wafer sensor 3 outputs a signal indicating that the wafer 2 has been detected.

[Problems to be Solved by the Invention] However, in the conventional wafer counting device described above, it is necessary to provide as many wafer sensors as the number of wafers stored in a cassette, and it is necessary to install wafer sensors in narrow gaps between wafers. There was also the problem of location constraints, making it expensive and difficult to manufacture. Furthermore, in order to maintain the product quality of the wafer, it is necessary to avoid any contamination, but in the conventional method, the periphery of the wafer 2 is inserted into the eraser part 1a of the wafer sensor 1, so the wafer sensor 3 and If a relative positional shift occurs, there is a risk that the wafer 2 will come into contact with the wafer sensor 3 and be contaminated. In view of the above circumstances, it is an object of the present invention to provide a wafer number counting device that can simply and reliably count the number of wafers, and can completely prevent contact with wafers.

[Means for Solving the Problems] The present invention provides an ultrasonic device that is disposed below a wafer cassette and includes a sounding section that emits ultrasonic waves toward the wafer surface and a sound receiving section that receives the ultrasonic waves reflected from the eight surfaces of the wafer. This system is characterized in that a sonic sensor is installed, a correspondence relationship between the ultrasonic reflection state and the number of eight wafers is set in advance, and the number of wafers is counted based on the ultrasonic reflection state. [Operation] There is a one-to-one correspondence between the number of wafers and the lowest position of the wafer, and the number of wafers can be counted by detecting the wafer at the lowest position by the reflection of ultrasonic waves. [Example] An example of the present invention will be described below with reference to the drawings. Figure 1 shows the case where the present invention is implemented in a wafer transfer device. In the figure, 6 is a processing furnace, and 7 is a boat that holds the wafers 2. The wafers 2 are loaded into and taken out of the processing furnace 6 by an elevator (not shown). Further, the wafer cassette 1 is placed on a cassette holder (not shown). The wafer transfer device 8 transfers the wafer 2 of the wafer cassette 1.
The wafers 2 from the boat 7 are transferred to the boat 7, and the wafers 2 from the boat 7 are transferred to the wafer cassette 1. A beam 9 that can be raised and lowered and is rotatable, and a wafer chuck 10 that can be moved across the beam 9 are horizontally moved. , furthermore, the wafer chuck 1
0 is equipped with multiple sets of tweezers 11. An ultrasonic sensor 12 for wafer detection is provided below the wafer cassette 1 on the cassette pedestal (not shown). The signal from the ultrasonic sensor 12 is sent to the ultrasonic sensor controller 13.
After the necessary signal processing is performed, the arithmetic unit 14
Output to . The calculator 14 calculates the number of wafers from the information from the ultrasonic sensor 12, and inputs the calculation result to the controller 15^. The controller 15 instructs the drive unit 16 of the wafer transfer device 8 to perform an optimal wafer transfer operation according to the number of wafers in the wafer cassette 1. The operation is explained below. Load the wafers into the wafer force set starting from the top without any gaps. Since the wafers 2 are stored at a predetermined pitch in the wafer cassette, the distance between the sounding surface and receiving surface of the ultrasonic sensor 12 and the lowest wafer 2 increases or decreases depending on the number of wafers 2. The distance corresponds to the number of wafers 2 in a ratio of 1:1. Then, the ultrasonic sensor 12 emits ultrasonic waves, the ultrasonic waves reflected by the wafer 2 are received, and the ultrasonic sensor controller 13 measures the position and distance of the lowest wafer 2 based on the time difference. do. Data regarding the correspondence between the detection signal of the ultrasonic sensor 12 and the number of wafers is input to the arithmetic unit 14 in advance, and data regarding the correspondence between the detection signal of the ultrasonic sensor 12 and the number of wafers is inputted in advance.
The result of calculating the number of 9 wafers, which calculates the number of 7-wafers 2, is input to the controller 15 as described above, and is provided for control of the transfer machine. In the above embodiment, the ultrasonic sensor 12 is configured such that the sound generating section and the sound receiving section are integrated, but they may be separated, or the sound axis of the sound generating section may be set on the wafer. The acoustic axis of each sound receiver is parallel to the acoustic axis of the reflected sound, and the acoustic axis of each sound receiver is made parallel to the acoustic axis of the reflected sound, and the sound receivers are shifted by a distance corresponding to the pitch of the wafers to detect the reflection. The sound may be detected by a single sound receiving section, and the number of wafers may be detected based on the position of the detected sound receiving section. [Effects of the Invention] As described above, according to the present invention, the wafer detection sensor can be provided outside the wafer cassette in a location where there is sufficient space and there is no risk of contact with the wafer. The number of can also be significantly reduced. Therefore, it is possible to reduce the price, improve product quality and reliability, and simplify manufacturing.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of one embodiment of the present invention, FIG. 2 is an explanatory diagram showing the relationship between an ultrasonic sensor and a wafer, and FIG. 3 is an explanatory diagram of a conventional example. 1 is a wafer cassette, 2 is a wafer, 12 is an ultrasonic tweezer, 13 is an ultrasonic sensor controller, 14 is an operator, 15 is a controller, and 16 is a drive unit. Patent application Hito Kokusai Electric Co., Ltd.

Claims (1)

[Claims] (1) An ultrasonic sensor is installed below the wafer cassette, consisting of a sounding section that emits ultrasonic waves toward the wafer surface and a sound receiving section that receives the ultrasonic waves reflected from the wafer surface. A wafer counting device characterized in that the number of wafers is counted based on the reflection state of ultrasonic waves by setting a correspondence relationship between the number of wafers and the number of wafers.