JP3075561B2 - Control system for taking out wafers from cassette - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wafer take-out control method in a cassette, and more particularly, to a method of controlling a wafer stored in an arbitrary shelf in a cassette in a semiconductor manufacturing line. The present invention relates to an improvement in a wafer handling process that allows efficient removal.

[Related Art] A wafer, which is a basic material of a semiconductor, is housed in a cassette in a production line, transported between processing apparatuses, and placed at a predetermined position of the apparatuses.

As shown in FIG. 3 (a), a large number of wafers 1 are stacked in the cassette 2 with a certain gap in the vertical direction. In each processing apparatus, as shown in FIG. 2B, a wafer unloading mechanism 4 is provided on the wafer outlet side in front of the cassette 2, and this mechanism is configured such that a vertical movement mechanism 4b is rotated by a motor 4a by a rotating arm 4c. Move vertically and rotate arm 4c
The suction arm 4d provided at the tip of the wafer contacts the wafer 1,
The wafer is taken out by sucking the edge of the wafer from the back side of the wafer 1. When the wafer 1 is stored in the cassette 2, the operation is the reverse of the above. Arrow A in the drawing indicates a suction air pipe for the suction arm 4d.

[Problem to be Solved] A cassette for accommodating wafers is usually made of plastic, and there is a difference in the accommodating pitch between manufacturers and a variation in cassette dimensions due to distortion during molding. Unless the relationship between the wafer and the cassette 2 is finely adjusted, the wafer cannot be automatically taken out.

However, when fine adjustment is performed each time a cassette is mounted, the processing efficiency of the apparatus is reduced.

Further, in the above-described wafer removal, the wafer removal mechanism 4 is controlled by a separate control circuit. This control is performed when the wafers 1 are stored in all positions in the cassette 2, that is, when the wafers 1 are full. As the state, a method of sequentially moving at the above-mentioned constant gap interval is adopted. However, a defective wafer may be removed at a processing stage in each processing apparatus, and a case where the wafer is not full but is partially missing may occur. Performing the above-described suction operation on such a missing portion obviously causes a loss of time.

The present invention solves such a conventional problem. Even if the storage pitches of the cassettes are different or the wafers are missing, the present invention can easily detect the position where the wafers are actually located. It is an object of the present invention to provide a control system for taking out a wafer from a cassette which can perform a handling process.

[Means for Solving the Problems] A feature of the present invention is to detect the presence or absence or the position of a wafer in a cassette when taking out a wafer stored in the cassette with a certain gap in the vertical direction. A light source is provided to a vertical movement mechanism having a suction arm for taking out a wafer, which is provided in front of a cassette for a wafer, and irradiates a light beam to correspond to a light source on a side surface of a mounting table on which a cassette is mounted. At the position where
A one-line image sensor such as a CCD (as an example of a linear optical sensor) is provided substantially corresponding to the height of the cassette, receives a light beam, and a detection signal is received by a data processing device, including the presence or absence of a wafer. Then, the position of each wafer in the cassette is calculated by a data processing device and stored in a memory, and the data processing device efficiently controls a wafer handling mechanism for taking out wafers from the cassette.

However, the configuration of the wafer removal control method in the cassette according to the present invention that achieves the above object is arranged on the rear surface of the cassette opposite to the wafer outlet or on the rear side adjacent to the rear surface so that the wafer can be stored. A linear light sensor having a large number of light receiving elements provided corresponding to the height to be set, and a light source that irradiates a light beam that passes through the predetermined gap with an inclination from the outlet side to the linear light sensor. ,
A moving mechanism for moving the light source up and down along the height direction of the cassette, and a processing device having a memory and receiving an output signal of the linear light sensor are provided. The relationship is that when the light beam is blocked by the wafer, the plurality of light receiving elements of the linear light sensor correspond to each other, and move the light source upward or downward along the height direction of the cassette, and The processing device obtains position data of each wafer using the unit of the light receiving element as a scale based on the output signal of the linear optical sensor obtained in accordance therewith, holds the data in a memory, and takes out the wafer from the cassette based on the data in the memory. The position of the wafer take-out arm of the take-out mechanism is controlled. When the light beam moves vertically by the vertical movement mechanism, the plurality of light receiving elements at corresponding positions of the linear light sensor stop receiving light according to the position where the wafer is stored, being blocked by the wafer in the cassette. So
As a result, the actual position of the wafer in the cassette can be detected.

Moreover, the light beam is made to pass through a certain gap of the wafer with an inclination, and the relationship between the resolution of the linear light sensor and the light beam is determined when the light beam is interrupted by the wafer. Since the elements are set to correspond to each other, they are housed in the cassette at a thin thickness of about 0.6 mm to 0.8 mm and at intervals of about 1 mm, and are arranged in a length of 6 to 12 inches (15 to 30 cm) or more. Also in the wafer, the light beam is blocked not in the thickness direction of the wafer but in the width direction of the wafer. Therefore, the light blocking width of the light beam is a width corresponding to a plurality of light receiving elements, and
Since the light beam is inclined, there is no reflected light from the lower wafer surface, and the presence or absence of the wafer can be accurately detected without being affected by noise.

As a result, the wafer position can be efficiently detected without being affected by the cassette size or pitch shift.

Therefore, the light receiving signal is obtained as the output of the linear optical sensor, and the output signal is subjected to data processing in the processing device, whereby the position of the wafer in the cassette can be calculated, and the calculated position is stored in the memory. If data is used to control the position of a wafer take-out arm or the like in a wafer handling device, etc., positioning control corresponding to a certain position of a wafer can be performed. Wafer removal processing becomes possible.

[Embodiment] FIG. 1 is a block diagram of an embodiment of a control system for taking out a wafer from a cassette according to the present invention. In FIG. 1, a cassette 2 containing a wafer 1 is mounted on a mounting table 3. At the back of the cassette, there is a notch 2a shown in FIG. 3 (a).
3a is provided, and a one-line image sensor 5 is attached here as a CCD linear light sensor. Note that the one-line image sensor 5 corresponds to the height direction in which the wafer 1 is stored directly on the back surface of the cassette 2 on the side opposite to the loading / unloading side of the wafer 1 in the cassette 2 or at a position adjacent to the back surface. What is necessary is just to be provided.

Further, a light source 4e is mounted at an appropriate position of a vertical movement mechanism 4b provided adjacent to the front side of the cassette 2 inlet / outlet. In this way, the light beam B of the light source 4e is received by the one-line image sensor 5 through the gap between the wafers by the movement of the vertical movement mechanism 4b, but when there is a wafer, the light is blocked and the position of the wafer is cut off. Is detected.

The signal thus detected is input to the control device 7 via a signal processing circuit 6 having an amplifier, an A / D converter, and a level determination circuit such as a digital comparator. The control device 7 includes an arithmetic processing device (MPU) 8 having a ROM or the like storing various processing programs, and a memory (MEM) 9 including a RAM or the like storing various data. Is a pixel 5a, which is a unit light receiving element constituting the one-line image sensor 5 through the signal processing circuit 6 and which receives a signal obtained from the one-line image sensor 5.
(The pixel 5a is shown enlarged in the figure.) The corresponding signal is received as “1” and “0” signals, and “0” is
Is processed as a position not receiving light, that is, a position where the wafer 1 exists.

The signal processing circuit 6 determines that there is a wafer when there is a signal equal to or less than the threshold by the level determination circuit and generates a signal of “0”, and otherwise generates a signal of “1”. Occur. In this way, by providing the threshold value and making the determination, it is possible to cancel the variation in the characteristics of each pixel of the one-line image sensor. In this case, “1” and “0”
It is needless to say that the logic may be inverted and used.

By the control of the MPU 8, the processing device 7 moves the light source 4e of the optical detector within the height range of the cassette 2 by the motor 4a and the vertical movement mechanism 4a in advance. At this time, the Z position of the suction arm 4d is detected by counting the number of rotations of the motor 4a by the Z position detector 10, and the one-line image sensor 5 is stored in the address of the memory 9 corresponding to the detected Z position. Is stored. In taking out the wafer, the detection data stored in accordance with the movement of the suction arm 4d in the Z coordinate direction (up and down direction) is read from the memory 9, and the control circuit 11 and the driver 12 move the suction arm 4d to the position where the wafer is present. The wafer is taken out while being sequentially positioned at the Z position. In this case, it is natural that the position where the wafer is missing is jumped.

FIG. 2 shows a detailed block configuration of the processing apparatus 7 with respect to FIG. 1. First, the storage of the detection data of the position of the wafer 1 in the cassette 2 which is performed in advance will be described. The motor 4a is rotated by the driver 11 and the driver 12, and the vertical moving mechanism 4b moves the height range of the cassette 2 in the vertical direction, for example, from bottom to top. The laser beam B from the light source 4e is shielded by the wafer 1 in the cassette 2, the light receiving amount changes with the corresponding pixel 5a of the one-line image sensor 5 of the CCD, and the electric charge proportional to the light receiving amount is accumulated. This charge is sequentially read out by the CCD drive circuit 71, and is detected as a detection signal by the amplifier 74.
The read signal adjusted to an appropriate level by the amplifier 74 is digitized by the A / D converter 75,
The data is input to the digital comparator 76, where a threshold determination is performed.

On the other hand, an appropriate threshold value is previously set in the register 77 by the MPU 8 as a digital value, and the input signal is compared with this threshold value for each pixel, and a digital signal of “1” and “0” is output. It is taken out and stored in the memory 9 as detection data. In this case, each bit of the detection data corresponds to each pixel, and the detection position resolution is
This is a very small amount corresponding to a pixel. Therefore, by sequentially storing bit data corresponding to pixel numbers (assumed to be 0, 1, 2,... From the bottom) and sequentially storing the bit data, data having a position in pixel units as scale is obtained. Therefore, by moving the light source 4e up and down in units of the pixel length, it is possible to calculate and obtain the dimensional data for the wafer storage pitch and the like.

By the way, in storing the detection data in the memory 9, the pixel number is also stored. That is,
The driving pulse of the CCD driving circuit 71 is counted by the counter 72 to generate pixel number data, and this and the data detected corresponding to the pixel are converted into an address signal of the Z position of the suction arm 4d obtained from the Z position detector 10. Is stored at each address of the memory 9. In this manner, each address of the memory 9 can store the presence or absence of a wafer in correspondence with the pixel in correspondence with the Z coordinate of the suction arm 4d.

In this case, since the light beam is inclined, the bit data indicating the presence / absence of a wafer has a plurality of bits. Thus, the wafer can be detected without being affected by noise. In this case, for example, when several bits of “0” follow the bit of “1” and indicate the position of the wafer, the position of the center bit or the like is set as the wafer positioning position. In this case, data conversion may be performed such that the presence or absence of a wafer is indicated by 1-bit data.

Alternatively, the detection data may be stored in the memory 9 using the Z coordinate as an upper address, the pixel number as a lower address, and the pixel number and the Z position as address signals.
In this case, when the detection data is read from the memory 9, the pixel number is sequentially read to determine how many “0” or “1” bits indicating the presence of the wafer continue. The presence or absence of the wafer can be detected by comparing the numerical values of “1” and “0” with the reference value, and the center position of the bit indicating the presence of the wafer can be used as the positioning position.

Further, since the pitch at which the wafer exists is in a specific range, the above-mentioned pixel number is selectively designated, and the state data of “1” and “0” (the presence or absence of the wafer) By obtaining the data, stable wafer detection against noise and the like can be performed, and stable control can be performed.

By storing such data in the memory 9 and reading out the detected data from the memory 9 in correspondence with the address, it is possible to determine whether or not there is a wafer at the position of the Z coordinate. That is, if "0" is stored, the wafer is in the cassette 2
And if "1" is stored, there is no wafer. In this case, "1" and "0" have the opposite relationship if they are stored in an inverted manner.

Here, the illustrated latches 73 and 13 are for latching the count number of the counter 72 and the signal of the Z position detector 10 to take timing of each signal.

Next, in the wafer unloading control, the MPU 8 reads out the detection data in the memory 9 and transfers the data “1” and “0” to the control circuit 11, and controls the driver 12 to determine the position where the wafer does not exist. The wafer is taken out by jumping, stopping the movement of the suction arm at a position where the wafer 1 is located, and taking out all the wafers in the cassette 2 sequentially and efficiently. FIG. 2 (b) shows the light source 4e and the direction of the light beam in detail. A laser diode 41 is used as the light source, collimated by a lens 42, and the beam diameter is narrowed by a slit 43. Beam B is applied to adjacent wafers 1a and 1b
The gap is inclined at an angle just passing through a certain gap G between them, for example, 2 to 3 degrees. Thus, even a thin wafer can be reliably detected without being disturbed by the reflected light on the wafer surface.

As described above, in the embodiment, the CCD one-line image sensor is used. However, the CCD is linearly arranged in the height direction of the wafer, and the signal of the light receiving position is linearly arranged. Any type of linear optical sensor that can be obtained correspondingly may be used.

In the embodiment, the address of the memory is made to correspond to the position of the Z-axis of the suction arm by the up-down movement mechanism. Since it can be calculated, positioning control may be performed based on the dimension data.

The configuration of the optical detector including the light source and the one-line image sensor in the embodiment is not limited to that shown in the embodiment, and any configuration may be used as long as it can obtain detection data.

[Effects of the Invention] In the wafer unloading control method of the present invention having the above configuration, whether or not there is a wafer in the cassette is determined in advance.
That is, the existence position is detected and stored in the memory, and is read out to take out the wafer from the cassette. Therefore, it is possible to automatically handle the wafer taking out of various cassettes having different standards. In addition, it is not necessary to set constants related to the cassette in the control device. In particular, at a position where a wafer is missing, the suction arm jumps and unnecessary operation of the suction arm is omitted, thereby also shortening the time. As a result, it contributes to the improvement of the operation rate of the semiconductor manufacturing line.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of a control system for taking out a wafer from a cassette according to the present invention, FIG. 2 is a block diagram showing a detailed configuration centering on the control part, and FIG. 2 (b). FIG. 3 is a detailed view of the optical detection portion, and FIGS. 3 (a) and 3 (b) are an external view of a cassette containing wafers and an explanatory view of a conventional wafer take-out method for wafers. 1 wafer, 2 cassette, 2a, 3a notch, 3 mounting table, 4 wafer unloading mechanism, 4a motor, 4b vertical movement mechanism, 4c rotating arm, 4d: suction arm, 4e: light source, 5: one-line image sensor, 6: signal processing circuit,
7 ... Control device, 8 ... MPU, 9 ... Memory, 10 ... Z position detector, 71 ... CCD drive circuit, 72 ... Counter, 11,73 ... Latch, 74 ... Amplifier, 75 ... ... A / D converter, 76 ... Comparator, 77 ... Register.

Continuation of the front page (72) Inventor Toshiaki Taniuchi 2-6-2 Otemachi, Chiyoda-ku, Tokyo Hitachi Electronics Engineering Co., Ltd. (56) References JP-A-59-175740 (JP, A) JP-A-63- 300525 (JP, A) JP-A-62-106639 (JP, A) JP-A-63-82248 (JP, A) JP-A-61-258444 (JP, A) JP-A-62-175365 (JP, A) Shokai Sho 61-129340 (JP, U)

Claims (6)

(57) [Claims] 1. A wafer takeout control system for taking out wafers stored in a cassette with a certain gap in a vertical direction, wherein a back surface of the cassette opposite to an outlet of the wafer or adjacent to the back surface of the cassette. Arranged on the back side,
A linear light sensor having a large number of light receiving elements provided corresponding to the height at which the wafer is stored, and a light beam passing through the predetermined gap with an inclination from the outlet side with respect to the linear light sensor. A light source for irradiation, a moving mechanism for moving the light source up and down along the height direction of the cassette, and a processing device having a memory and receiving an output signal of the linear light sensor; The relationship between the resolution and the light beam is such that when the light beam is blocked by the wafer, the plurality of light receiving elements of the linear light sensor correspond, and the light source is moved along the height direction of the cassette. The light is moved upward or downward, and based on the output signal of the linear optical sensor obtained in accordance with the movement, the processing device sets each of the light-receiving elements as a scale in units of light-receiving elements. Its data held in the memory, the wafer unloading control system in the cassette, characterized in that for positioning control of the wafer takeout mechanism for taking out the wafer from the cassette by the data in the memory to obtain the location data. 2. The system according to claim 1, wherein the moving mechanism is a wafer handling mechanism for taking out the wafer from the wafer cassette, and the light source is attached to the wafer handling mechanism. . 3. A linear light sensor is constituted by a CCD in which a plurality of unit light receiving elements are linearly arranged, and light emitted from a light source to the linear light sensor is inclined at an angle of 2 to 3 degrees. 3. The method according to claim 1, wherein the wafer is taken out of the cassette. 4. A wafer unloading control system for unloading wafers stored in a cassette with a certain gap in a vertical direction, wherein the back surface of the cassette opposite to the wafer outlet or the rear surface adjacent to the back surface of the cassette. And a linear light sensor having a number of light receiving elements provided corresponding to the height at which the wafer is stored, and the fixed gap inclined with respect to the linear light sensor from the outlet side. A light source that emits a light beam passing therethrough, a moving mechanism that moves the light source up and down along the height direction of the cassette, and a processing device that receives an output signal of the linear light sensor; The relationship between the resolution of the light beam and the light beam is such that the plurality of light receiving elements of the linear light sensor correspond when the light beam is blocked by the wafer. The processing device has a memory in which an address is associated with a vertical movement position of the vertical movement mechanism, and moves the light source upward or downward along the height direction of the cassette. Then, based on the output signal of the linear optical sensor obtained in accordance with the movement, obtains detection data using the unit of the light receiving element as a scale, and stores this in the memory of the memory corresponding to the movement position of the vertical movement mechanism. A wafer take-out control method in a cassette, wherein the wafer is taken out from a cassette and stored in a position of a corresponding address, and positioning control of a wafer take-out mechanism for taking out a wafer from the cassette is performed. 5. The system according to claim 4, wherein the moving mechanism is a wafer handling mechanism for taking out the wafer from the wafer cassette, and the light source is attached to the wafer handling mechanism. . 6. A linear light sensor is constituted by a CCD in which a plurality of unit light receiving elements are linearly arranged, and light emitted from a light source to the linear light sensor is inclined at an angle of 2 to 3 degrees. 6. The method according to claim 4, wherein the wafer is taken out of the cassette.