JPH07118502B2 - Wafer handling method and device in cassette - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for handling wafers in a cassette, and more particularly, in a semiconductor manufacturing line, a cassette is not affected by a difference in a wafer storage pitch of the cassette. The present invention relates to improvement of a wafer handling process so that a wafer placed inside can be efficiently taken out from a cassette.

[Prior Art] A wafer, which is a basic material of a semiconductor, is housed in a cassette in a manufacturing line, conveyed between processing apparatuses, and placed at a predetermined position of the apparatus.

As shown in FIG. 2A, a large number of wafers 1 are stacked on 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 in front of the cassette 2 on the side of the wafer unloading port. Vertically move the rotating arm 4c
The suction arm 4d provided at the tip of the wafer contacts the wafer 1,
The edge of the wafer is sucked from the back surface side of the wafer 1 to take out the wafer. When the wafer 1 is stored in the cassette 2, the operation is the reverse of the above. Further, an arrow A shown in the figure indicates a suction air tube for the suction arm 4d.

[Problems to be Solved] Since a cassette for storing wafers is usually made of plastic and the storage pitch varies depending on the manufacturer, the relationship between the wafer unloading mechanism 4 and the cassette 2 must be finely adjusted. , The wafer cannot be taken out automatically.

However, if a fine adjustment is made every time the cassette is mounted, the processing efficiency of the device will decrease.

Further, in the above-mentioned wafer taking-out, the wafer taking-out mechanism 4 is controlled by a separate control circuit, but this control is such that the wafer 1 is stored at all positions in the cassette 2, that is, it is full. As a state, a method of sequentially moving at the constant gap interval is adopted. However, a defective wafer may be removed at the processing stage in each processing apparatus, and a case may occur in which the wafer is not full and a part of the wafer is missing. Obviously, performing the above-mentioned suction operation on such a missing portion causes a loss of time.

The present invention solves such a conventional problem and, even if the storage pitches of the cassettes are different or the wafers are missing, the handling Z corresponding to the wafer position in the cassette is performed. An object of the present invention is to provide a method and an apparatus for handling a wafer in a cassette, which is capable of automatically measuring coordinates and a corresponding pixel number and performing a handling process easily based on the data.

[Means for Solving the Problems] The feature of the method for handling a wafer in a cassette of the present invention for achieving such an object is that the wafer is provided on the back surface of the cassette on the side opposite to the wafer outlet or adjacent to this back surface. A linear optical sensor that is fixed to the rear side and is provided corresponding to the height at which wafers are stored, a light source that irradiates the linear optical sensor with light from the outlet side, and this light source is the height of the cassette. A moving mechanism for moving the wafer up and down along the direction, and moving the light source upward or downward along the height direction of the cassette, and the wafer is detected by the output of the linear optical sensor obtained according to the movement. This is to obtain an existing position and position an arm for taking out the wafer at the obtained position.

Further, in addition to the above-mentioned configuration, a feature of the wafer handling device in the cassette is that the wafer is moved upward or downward along the height direction of the cassette over the range in which the wafers in the cassette are stored. A control position for detecting the position of the wafer, storing the position of the wafer in the memory as data, reading this data from the memory, and positioning the arm for taking out the wafer according to this data at a certain position of the wafer. It is a thing.

[Operation] In the detection of the position of the wafer in the cassette having the above-described configuration, when the light beam from the light source moves in the vertical direction by the vertical movement mechanism, the wafer in the cassette is blocked and stored. Since the light receiving element at the corresponding position of the linear optical sensor does not receive light depending on the position, it is possible to detect the actual position of the wafer in the cassette.

That is, when the cassette is mounted, the light source is moved up or down along the height direction of the cassette with respect to the cassette, and the image sensor receives the light to detect the position of the wafer. The light receiving position is dynamically determined every time the cassette is mounted, and the position fixing property as in the case where the light receiving elements of the conventional LED are individually arranged is lost. Therefore, the output of the linear optical sensor obtained according to the movement represents the actual wafer position in each case in correspondence with the cassette.

As a result, if the position where the wafer exists can be obtained, the actual current position of the wafer in the cassette can be detected as it is, regardless of the variation in the size of the cassette, the mounting state, and the mounting state. Because of this, there is no need to make fine adjustments each time the cassette is installed.

By obtaining this received light signal as the output of the linear optical sensor and processing the output signal, for example, the actual position of the wafer in the cassette can be easily obtained, and if necessary, information on the pitch to be stored. You can also get In addition,
If the wafer is missing at a predetermined position, the light beam is received and detected as missing, and the position of the wafer above it is detected.

In this way, if certain position information of the wafer is obtained from the linear optical sensor and sent to the control circuit that controls the handling mechanism, it can be used as position information for positioning the suction arm, and an efficient wafer unloading process can be performed. Is possible.

A laser diode is simple and convenient for the light source of the light beam, and the resolution is improved by narrowing the beam finely, but the wafer is very thin and unnecessary reflection light of the beam is reflected by the wafer surface. When the / N ratio is reduced and reliable detection is not possible, the light beam is obliquely irradiated to the surface at a low angle to ensure that the light beam is blocked by the wafer and the detection is accurate. Can be improved.

[Embodiment] FIGS. 1A and 1B are configuration diagrams of an embodiment of a method and apparatus for handling a wafer in a cassette according to the present invention. In FIG. 1A, the cassette 2 containing the wafer 1 is placed on the placing table 3. Since the notch portion 2a shown in FIG. 2 (a) is provided on the back surface of the cassette, the notch portion 3a is provided at the corresponding position of the mounting table 3 and the 1-line image sensor is provided as a linear optical sensor of the CCD. Attach 5. The 1-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 this back surface. It should be provided.

Further, the light source 4e is attached to an appropriate location of the vertical movement mechanism 4b provided adjacent to the front side of the loading / unloading opening of the cassette 2. In this way, the light beam B of the light source 4e is received by the 1-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, it is blocked and the wafer position is changed. Is detected.

The signal detected in this way is the amplifier and A / D converter,
Then, it is input to the control device 7 via a signal processing circuit 6 having a level determination circuit such as a digital comparator. The control device 7 is an RO that stores various processing programs.
The processing unit 7 includes an arithmetic processing unit (MPU) having M and the like, a memory including RAM for storing various data, and the like, and the processing unit 7 converts the signal obtained from the 1-line image sensor 5 into the signal processing circuit 6 1 line image sensor 5 via
Pixel 5a (each pixel 5a
Is shown enlarged in the figure) "1" and "0" obtained as corresponding signals are received, and the position of "0" among them is the position where light is not received, that is, the position where the wafer 1 exists. To process.

The signal processing circuit 6 is
When there is a signal below the threshold value, it is determined that there is a wafer, and a signal of "0" is generated, and when it is not, a signal of "1" is generated. By thus setting the threshold 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, it goes without saying that "1" and "0" may be used by inverting and inverting the logic.

Now, the processing device 7 moves the light source 4e of the optical detector within the height range of the cassette 2 in advance by the motor 4a and the vertical movement mechanism 4b under the control of the MPU. Also, 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 built-in Z position detector, and the detection obtained by the 1-line image sensor 5 at the memory address corresponding to the detected Z position. Store data.
In taking out the wafer, the detection data stored corresponding to the movement of the suction arm 4d in the Z-coordinate direction (vertical position) is read from the memory, and the suction arm 4d is sequentially positioned at the Z position where the wafer exists. The wafer is taken out.
In this case, it is natural that the position where the wafer is missing is jumped.

Here, the controller 7 receives the wafer position as a continuous “0” bit from the image signal of the 1-line image sensor 5 and processes the information of “1” and “0” by data processing. , The pitch between the wafers and the respective positions are calculated. The calculated pitch or position between the wafers is stored in the memory and sent to the motor 4a of the vertical movement mechanism 4 so that the suction arm 4d is positioned at the desired position of the wafer 1 and the wafer 1 is taken out. Will be. Since the light is blocked even at the bottom position of the cassette 2, the position can be detected, and the positional relationship between the cassette 2 and the wafer 1 arranged inside the cassette 2 with respect to the mounting table 3 can be detected. . Further, even if such a reference position is not calculated and determined, if only the position of the first wafer is known, the positions of all the other wafers can be detected. Then, only the above-mentioned first position may be detected in the conventional manner by controlling the suction arm 4d.

FIG. 2B shows the light source 4e and the direction of the light beam in detail. A laser diode 41 is used as the light source, collimation is performed by a lens 42, and a beam diameter is narrowed down by a pinhole 43. The beam B is inclined at an angle such that it can pass through a constant gap G between the adjacent wafers 1a and 1b, for example, 2 to 3 degrees. As a result, even a thin wafer can be reliably detected without being obstructed by the reflected light from the wafer surface.

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

[Effects of the Invention] As can be understood from the above description, in the present invention, even if the pitch size of the wafer is different, or even if there is a missing wafer, it actually exists. Since the position of the wafer (or its presence / absence) can be reliably detected by a linear optical sensor such as a CCD, the wafer handling mechanism such as the suction arm can be controlled by the detected position data or the data indicating the presence / absence of the wafer. As described above, the useless arm operation is omitted for each wafer position, and the handling process can be performed, and the work time of the wafer handling process from the mounting of the cassette to the taking-out process of the wafer can be shortened and the processing efficiency is improved. be able to.

[Brief description of drawings]

FIGS. 1 (a) and 1 (b) are configuration diagrams of an embodiment of a method and apparatus for handling wafers in a cassette according to the present invention, and FIGS. 2 (a) and 2 (b) show wafers stored in a cassette. It is a perspective external view and explanatory drawing of the conventional wafer removal method of a wafer. 1 ... Wafer, 2 ... Cassette, 2a, 3a ... Notch, 3 ... Mounting table, 4 ... Wafer take-out mechanism, 4a ... Motor, 4b ... Vertical movement mechanism, 4c ... Rotating arm, 4d ... Suction arm, 4e ... Light source, 41 ... Laser diode, 42 ... Lens, 43 ... Pinhole, 5 ... 1 line image sensor.

Claims (4)

[Claims] 1. A method of handling wafers in a cassette for handling wafers housed in a cassette with a certain gap in the up-down direction, directly or on the back surface of the cassette on the side opposite to the outlet of the wafer. A linear optical sensor fixed to one of the positions behind the back surface of the wafer and corresponding to the height at which the wafer is accommodated, and the linear optical sensor emits light from the outlet side. A light source for irradiating and a moving mechanism for moving the light source up and down along the height direction of the cassette, and moving the light source up or down along the height direction of the cassette, and moving the light source. The position of the wafer is obtained from the output of the linear optical sensor obtained in accordance with the above, and the arm for taking out the wafer is positioned at the obtained position. Method of handling a set in the wafer. 2. A wafer handling device in a cassette for handling wafers housed in a cassette with a certain gap in the up-down direction, directly or on the back surface of the cassette on the side opposite to the wafer outlet. A linear photosensor provided at a position which is fixed to one of the positions adjacent to the back surface behind the wafer and corresponds to a height at which the wafer is finished, and light from the exit side to the linear photosensor. 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 mechanism for controlling the moving mechanism to store the light source in the cassette along the height direction of the cassette. The position where the wafer is present is determined by receiving the output of the linear photosensor obtained according to the movement by moving the wafer upward or downward over the range. Each position is detected and stored in the memory as data, and when the wafer is taken out from the cassette, the data is read from the memory and the arm for taking out the wafer from the cassette is positioned at a certain position of the wafer according to the data. A device for handling wafers in a cassette, comprising: a controller. 3. The cassette according to claim 2, wherein the moving mechanism is a wafer handling mechanism having an arm for taking out a wafer from the cassette, and the light source is attached to the wafer handling mechanism. Wafer handling equipment. 4. The linear light sensor is composed of a CCD in which a plurality of unit light receiving elements are linearly arranged, and the light emitted from the light source to the linear light sensor is inclined. Item 2. A wafer handling device in a cassette according to item 2.