JP2005260010A - Method and device for wafer carrying - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wafer carrying device and its carrying method which can restrain contact between a wafer and a wafer receiver and prevent the occurrence of flaws, cracks or the like in the wafer. <P>SOLUTION: When an arm 4 with a wafer thereon moves up and the wafer passes through the detection position, a sensor 7 outputs a signal showing the passage of the wafer to a sensor signal processor 10. The sensor signal processor 10 outputs a signal for stopping the upward movement of the arm to an arm driver 11 based on the signal. The arm driver 11 stops the upward movement of the arm 4 based on the signal. Consequently, it is possible to prevent the wafer (a) from coming into contact with the wafer receiver when the wafer (a) is unloaded from a wafer cassette 1 by the arm 4. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a semiconductor substrate (hereinafter referred to as a wafer) transfer apparatus and a transfer method thereof, and more particularly, to a wafer transfer apparatus having a position correction function that enables reliable transfer of a thin ground wafer that is significantly hung and warped. And a conveying method thereof.

  In recent years, small-sized portable devices represented by mobile phones have used stacked packages in which two or more chips in which semiconductor integrated circuits are built in order to realize complex functions. The wafer is ground and thinned to keep it to the limit. The conventional grinding in which the thickness of the wafer after grinding is 300 μm or more has no problem in the wafer after grinding, but in the thin grinding in which the thickness of the wafer after grinding is 200 μm or less, it sags on the wafer after grinding. And warping occurs. Also, large diameter wafers are likely to sag and warp. If the wafer is warped, when the wafer is loaded into a box-shaped container (wafer cassette) that horizontally stores the wafer, the wafer contacts the wafer receiving portion for supporting the wafers arranged in the wafer cassette. There is a risk of damage. Further, if the wafer is warped, the wafer, the transfer arm, and the wafer receiving portion may come into contact when the wafer is taken out.

  The following two methods are conceivable in order to prevent the wafer from being damaged at the time of transfer even if the thinly ground wafer and the large diameter wafer sag and warp. As a first method, a method for suppressing the sagging of the wafer in a wafer cassette for storing the wafer is conceivable, which is described in Japanese Patent Application Laid-Open No. 2002-76108. The wafer cassette described in FIG. 1 of Patent Document 1 has a structure in which a wafer support portion for supporting a wafer from below is provided on a conventional wafer cassette having only a plurality of wafer receiving portions. It has a structure that can prevent warping. However, since an arm having a shape suitable for the shape of the wafer support portion is necessary, it is necessary to replace the arm of the transfer device.

  As a second method, by storing data on the position of the wafer receiving portion, when the wafer is taken out from the wafer cassette and loaded into the wafer cassette, the wafer receiving portion of the wafer cassette is not contacted. How to make it possible. In the method described in Patent Document 2 (Japanese Patent Laid-Open No. 9-102527), position data (vertical direction, horizontal direction, front and back) of a detection substrate installed at a wafer insertion position of a wafer holding board with a predetermined clearance. This is a method for carrying in the wafer so that the wafer does not come into contact with the wafer receiving portion or the like by carrying out the wafer transfer process based on the direction. However, in the teaching method for providing a predetermined clearance, when wafers having different sag amounts are transferred, it is necessary to perform teaching for each wafer having a different sag amount, which is a burden on the operator. Further, since the clearance amount obtained with a certain amount of sagging wafer is a fixed value, it cannot cope with the sagging variation of each wafer.

  In addition, the technique described in Patent Document 3 (Japanese Patent Laid-Open No. 11-288993) allows the wafer holding portion of the wafer holding board to be detected by a signal from the substrate detection sensor even if the wafer holding board is deformed due to aging. The current position can be grasped and the wafer can be transferred based on the current position, so that the service life of the wafer holding board can be extended. I can't take it. In the technique described in Japanese Patent Laid-Open No. 8-222615, the pitch reference line is provided in the wafer cassette so as to be aligned with the height of the wafer receiving portion of the wafer cassette, and the detection means connected to the lifting mechanism This technique detects the pitch reference line and stops the lifting platform in accordance with the height of the wafer receiving portion with high accuracy, but it cannot cope with the case where the wafer sags or warps.

  A wafer cassette conventionally used for storing wafers is shown in FIGS. 4 (a) and 4 (b). 4A is a front view of a wafer cassette opening when a thin ground wafer is accommodated, and FIG. 4B is a top view of a horizontal section of the wafer cassette. The wafer cassette 1 of the box-shaped container has a structure in which a plurality of wafer receiving portions 2 for supporting the peripheral portion of the wafer a from below and storing it horizontally are arranged in the vertical direction. When the wafer cassette is actually used in a semiconductor device, the wafer cassette is installed in a loader / unloader section (not shown), and the wafer a is loaded and unloaded by a wafer transfer arm (not shown). It is taken in and out from the opening 3 for use.

JP 2002-76108 A JP-A-9-102527 Japanese Patent Laid-Open No. 11-288993 JP-A-8-222615

  There are two problems that arise when the wafer sags and warps. As a first problem, as shown in FIG. 5, when the thin ground wafer a is loaded into the wafer cassette body 1, there is a risk that the warped wafer outer peripheral portion contacts the wafer receiving portion 2 and causes scratches, cracks, and the like. There is a point. When the wafer a is transferred by the transfer arm 4, suction is performed to fix the wafer a to the arm 4. However, in the case of a thin ground wafer, the wafer is in the state shown in FIG. This is because the outer peripheral portion of the head warps upward. Since the conventional wafer has a thickness, it does not warp as in the state shown in FIG.

  Next, the second problem will be described. First, a conventional operation for placing a wafer without warping on the arm 4 and raising it will be described. As shown in FIG. 7, when the wafer a is taken out from the wafer cassette 1, the wafer thickness and position are detected by the wafer position and thickness measuring sensor 5 (not shown), and the upper surface of the upper wafer a1 and the lower surface of the lower wafer a1 are detected. The transfer arm 4 is inserted into a central position P between the upper surfaces of the wafers a2. Then, the inserted arm 4 is raised by a fixed amount β determined by teaching, and the peripheral portion of the wafer a1 placed on the arm 4 after being raised is positioned at the center position Q of the groove of the wafer insertion portion, A method is adopted in which the upper wafer a1 is raised by γ to float the wafer in the air. This is because when the wafer is pulled out, if the wafer remains in contact with the wafer receiving portion 2, the wafer will be scratched and cracked. Thus, in the case of a conventional wafer that has not been thinly ground, as shown in FIG. 7, the arm 4 is inserted into the center position P between the lower surface of the upper wafer a1 and the upper surface of the lower wafer a2, and teaching is performed. What is necessary is just to raise the arm 4 by the fixed amount (beta) determined. On the other hand, in the thinly ground wafer, as shown in FIG. 8, the central portion hangs downward due to the decrease in rigidity, so that the central position P ′ between the lower surface of the upper wafer a3 and the upper surface of the lower wafer a4 is the conventional position. It is below the central position P in the case of a wafer that has not been thinly ground. Further, in the case of a drooping wafer, the amount of ascending arm 4 for floating the wafer in the air increases. This is because if a wafer with sagging is supported from below by the arm 4, sagging is reduced. Here, if the increment of the arm lift in the case of the thinly ground wafer is α relative to the arm lift in the case of the wafer that has not been thinly ground, the arm lift required for the thinly ground wafer is α. Becomes β + α.

  The following problems occur when the operator makes a mistake in switching the amount of lift of the arm 4 or when a variation in droop occurs between wafers. For example, considering the case where a conventional wafer that has not been thin-ground is transported with the setting of the rising amount of the arm 4 set in the case of a thin-grinding wafer, the insertion position P of the arm 4 droops as shown in FIG. Is the central position between the lower surface of the upper wafer a5 where no sag occurs and the upper surface of the lower wafer a6 where sag does not occur, the amount of ascending of the arm 4 is warped (FIG. 8). β + α. Therefore, when the wafer a5 carried into the wafer insertion portion 20 is placed on the arm 4 and rises by β + α, the wafer a5 is pressed against the lower portion of the upper wafer receiving portion 2 to cause scratches and cracks on the wafer. If it is the original rising amount set for the wafer without warping, the position of the central portion of the wafer after rising is the position of the point Q in FIG. 9, and does not come into contact with the lower portion of the upper wafer receiving portion 2.

  Also, if drooping variation occurs between the wafers, the center position between the lower surface of the upper wafer where the transfer arm 4 is inserted and the upper surface of the lower wafer fluctuates due to the variation of dripping, and the fixed amount β + α is set. If it is left as it is, there is a risk that the wafer will come into contact with the wafer receiving portion during transport.

  The present invention has been made in view of such problems, and provides a wafer transfer apparatus and a transfer method thereof that can suppress contact between the wafer and the wafer receiving portion and prevent the wafer from being scratched or cracked. For the purpose.

  The wafer transfer apparatus according to the first aspect of the present invention includes a wafer cassette provided with multiple stages of wafer insertion portions for fitting the peripheral edge of the wafer, and a movable arm that holds the wafer and carries it in and out of the wafer cassette. And an arm drive unit for driving the arm in the loading / unloading direction and the vertical direction with respect to the wafer cassette, and detecting the edge of the wafer at a predetermined position when the wafer is lifted by the raising of the arm in the wafer cassette A first sensor that measures the amount of warpage of the wafer, and the arm drive when the first sensor detects an edge of the wafer when the wafer is taken out of the wafer cassette. The amount of warpage detected by the second sensor when the wafer is carried into the wafer cassette is stopped. And having a control unit for controlling the arm insertion height in the arm drive unit as a correction amount of the zero insertion height.

  The wafer transfer device has a third sensor for detecting a position of the wafer stored in the wafer cassette, and the third sensor is a lower surface of the wafer to be taken out when the wafer is taken out from the wafer cassette. And the upper surface of the lower wafer may be detected, and the control unit may insert an arm at an intermediate position between the detection lower surface and the detection upper surface.

  The control unit raises an arm inserted into the wafer cassette by a predetermined amount to hold the wafer on the arm, and then pulls out the arm so as to take out the wafer. When the first sensor detects the edge of the wafer when the arm is raised, the arm driving unit is controlled to stop the raising of the arm. preferable.

  The first sensor detects a position of an edge portion of the wafer so that the edge portion of the wafer does not contact the upper wafer receiving portion of the wafer insertion portion to which the wafer is to be inserted. It is preferable that the wafer can be moved up and down in accordance with the position of the wafer insertion portion where the wafer is to be inserted.

  When the wafer is inserted into the wafer cassette, the control unit is a wafer receiving unit between the wafer inserting units, and is arranged at the center positions of the upper and lower wafer receiving units of the wafer inserting unit to which the wafer is to be inserted. It is preferable to insert the arm holding the wafer at a height position obtained by subtracting the amount of warpage detected by the second sensor from the reference height position. .

  The arm may hold the wafer by sucking and sucking the wafer.

  The wafer transfer method according to the second aspect of the present invention is a wafer transfer method for taking out a wafer stored in a wafer cassette provided with multiple stages of wafer insertion portions for fitting the peripheral edge of the wafer, below the wafer to be taken out. Inserting the arm into the arm, raising the arm to bring the arm into contact with the lower surface of the wafer and holding the wafer on the arm, and removing the arm from the wafer cassette and taking out the wafer. And a first sensor for detecting the edge of the wafer at a predetermined position, and when the wafer is raised by raising the arm in the wafer cassette, the edge of the wafer is moved by the first sensor. When detected, the raising of the arm is stopped.

  The wafer transfer method according to the third aspect of the present invention is a wafer transfer method in which a wafer is inserted into a wafer cassette provided with multiple stages of wafer insertion portions for fitting the peripheral edge of the wafer. And a step of inserting the arm into the wafer cassette while holding the wafer on the arm, and when the wafer is carried into the wafer cassette. The arm insertion height in the arm drive unit is controlled using the amount of warpage detected by the second sensor as a correction amount of the arm insertion height.

  When the arm is raised when the wafer is taken out from the wafer cassette, the raising of the arm is stopped before the wafer comes into contact with the upper wafer receiving portion based on a signal from the wafer detection sensor. When loading a wafer into the wafer cassette, the arm is inserted into the wafer cassette after the arm is corrected and moved downward by the amount of the warp height measured by the warp height measurement sensor. Do not touch the receiving part. For this reason, when the wafer is taken out from the wafer cassette and when the wafer is carried into the wafer cassette, the contact between the wafer and the wafer receiving portion is prevented, and the occurrence of scratches and cracks can be prevented.

  Hereinafter, embodiments of the present invention will be specifically described with reference to the accompanying drawings. FIG. 1 is a block diagram of a wafer transfer apparatus having a warp correction function of the present invention. FIG. 2 is a diagram showing the positional relationship between the wafer a and the wafer detection sensor 7 when the arm 4 on which the wafer is placed rises. FIG. 3 is a schematic diagram showing a situation where the amount of warpage of the wafer a is measured by the measurement sensor 9.

  The configuration of the embodiment of the present invention will be described with reference to FIG. In FIG. 1, for convenience of illustration, the sensor 5 and the sensor holding column 13 and the sensor 7 and the sensor holding column 13 are arranged on different sides with respect to the wafer cassette 1. The sensor holding column 13, the sensor 7, and the sensor holding column 13 all face the opening 3 (see FIG. 4) of the wafer cassette 1. The wafer cassette 1 is installed on a load / unload table 6. The wafer cassette 1 stores a wafer in a wafer insertion portion 20 between the wafer receiving portions 2 provided therein. The arm 4 adsorbs the wafer on it by air suction and carries it in and out of the wafer cassette 1. The wafer position and thickness measurement sensor 5 measures the position and thickness of the wafer, and acquires data for determining the position where the arm 4 is inserted during wafer transfer. The wafer position and thickness measuring sensor 5 is held by a sensor holding column 13 and is installed in front of the opening of the wafer cassette 1. The sensor holding column 13 includes a drive mechanism that moves the sensor in the vertical direction based on the output from the sensor position control unit 12. The load / unload table 6 is a table for placing a wafer cassette or the like during wafer transfer. The wafer detection sensor 7 is a sensor for detecting the position of the wafer so that the wafer stored in the wafer insertion section 20 is raised too much when it is transported and does not come into contact with the wafer receiving section 2. The wafer detection sensor 7 is held by a sensor holding column 13 and is installed in front of the opening of the wafer cassette 1. The sensor holding column 13 includes a drive mechanism that moves the sensor in the vertical direction based on the output from the sensor position control unit 12. Further, the warp height measurement sensor 9 is held and installed by a sensor holding column 13 on the side of the arm for the convenience of measuring the warp height of the wafer a before inserting the wafer a into the wafer cassette 1. The warp height of the wafer a placed on the arm 4 and sucked by suction is measured. The sensor signal processing unit 10 performs arithmetic processing on the data signals measured by the sensors 5, 7, and 9 and outputs a signal for driving the arm 4 to an appropriate position to the arm driving unit 11. The arm driving unit 11 drives the arm 4 based on the arm control signal input from the sensor signal processing unit 10. The sensor position control drive unit 12 drives the positions of the sensors 5 and 7 to an optimum position for measurement.

  The wafer position and thickness measurement sensor 5, the wafer detection sensor 7, and the warp height measurement sensor 9 can be any one of an optical technique and an electromagnetic technique as long as the wafer position and dimension can be measured. A sensor using may be used. For example, an optical displacement sensor configured by combining a light emitting element and a light position detecting element (PSD). Alternatively, a wafer stored in a wafer cassette or a wafer on the arm 4 may be photographed with a camera, and the position and dimensions of the wafer may be measured using a pattern recognition method by image processing the image.

  Next, the operation of the wafer transfer apparatus configured as described above will be described. First, referring to FIG. 2, the operation when taking out the wafer will be described. The method until the arm 4 is inserted is the same as the conventional method, and the wafer position and thickness measurement sensor 5 detects the thickness and position of the wafer, and the center between the upper wafer lower surface and the lower wafer upper surface. Insert the transfer arm 4 into the section. Next, the wafer detection sensor 7 is moved to substantially the same height as the central portion of the groove of the wafer insertion portion 20 in which the wafer is stored, and the position at which the sensor 7 detects the passage of the wafer is determined. For example, the position is position 8 in FIG. When the arm 4 on which the wafer is placed moves up and the wafer passes through the position 8, the sensor 7 outputs a signal indicating that the wafer has passed to the sensor signal processing unit 10. Based on this signal, the sensor signal processing unit 10 outputs a signal for stopping the upward movement of the arm 4 to the arm driving unit 11. Based on this signal, the arm drive unit 11 stops the upward movement of the arm 4.

  After raising the arm 4 by a predetermined amount, the wafer on the arm 4 is attracted to the arm 4 by suction. Thereafter, the arm 4 is retracted from the wafer cassette 1 and the wafer is taken out.

  As described above, when the sensor 7 detects the rising wafer edge at a predetermined position, the sensor signal processing unit 10 outputs a signal for stopping the upward movement of the arm 4 to the arm driving unit 11. It is possible to prevent the wafer a from coming into contact with the wafer receiving portion 2 when the wafer a is taken out from the arm 4.

  Next, an operation when a wafer is carried in will be described with reference to FIG. In order to measure the warp height of the thin ground wafer when adsorbed to the arm 4 by suction, the warp height measuring sensor 9 has a height b of the outermost peripheral portion of the wafer and a height of the lower surface of the wafer center (the upper surface of the arm 4). C) is measured. Based on the measurement result of the warp height measurement sensor 9, the sensor signal processing unit 10 calculates the warp height bc, and outputs a signal for controlling the arm position to the arm drive unit 11. Then, the arm drive unit 11 drives the arm 4 based on the input signal. Specifically, an intermediate position between the center positions of the upper and lower wafer receiving portions 2 of the wafer insertion portion 20 to which the wafer a is to be loaded is set as a reference height position, and the second height is set with respect to the reference height position. The arm 4 is moved so that the upper surface of the arm 4 is positioned at a height position obtained by subtracting the amount of warpage bc detected by this sensor, and the arm 4 that sucks the wafer a by suction is placed horizontally on the wafer cassette 1. insert. After the wafer a is inserted into the wafer cassette 1, the state where the wafer is attracted by the arm 4 is released, and the arm 4 is lowered. After the arm 4 is lowered and the wafer is carried into the predetermined wafer insertion portion 20, the arm 4 is retracted and the arm 4 is pulled out from the wafer cassette 1.

  As described above, when a wafer is loaded, an intermediate position between the center positions of the upper and lower wafer receiving portions 2 of the wafer insertion portion 20 to which the wafer a is to be loaded is set as a reference height position. The arm 4 is moved so that the upper surface of the arm 4 is positioned at a height position obtained by subtracting the warp amount bc detected by the second sensor with respect to the vertical position, and the arm that sucks the wafer a by suction Since 4 is inserted horizontally into the wafer cassette 1, it can be avoided that the wafer to be inserted comes into contact with the wafer receiver 2.

  Conventionally, the vertical movement distance of the arm 4 when loading a wafer is set to a fixed value by teaching work. However, in the wafer transfer method of the present invention, the above operation is performed for every wafer. The movement distance in the vertical direction of the arm 4 is corrected based on the warpage size of each wafer. For this reason, the wafer transfer method of the present invention has an advantage that teaching work is not necessary.

It is a block diagram of the wafer conveyance apparatus which has the curvature correction function of this invention. It is a figure which shows the positional relationship of a wafer and a wafer detection sensor at the time of the arm which mounted the wafer raises. 6 is a schematic diagram showing a situation where the amount of warpage of the wafer is measured by the measurement sensor 9. FIG. 1A and 1B are views showing a conventional wafer cassette used for storing wafers. FIG. 1A is a front view of a wafer cassette opening when a thin ground wafer is stored, and FIG. It is the figure which looked at the horizontal cross section from the top. It is a figure showing a mode that the curved wafer outer peripheral part is contacting the wafer receiving part, when carrying in a thin ground wafer to a wafer cassette main body. It is a figure which shows the condition of the presence or absence of the curvature of the wafer on an arm. It is a figure which shows the condition where the arm lifted the wafer which has not drooped. It is a figure which shows the condition where the arm lifted the wafer which has drooping. FIG. 10 is a diagram illustrating a situation where an arm lifts a wafer that does not sag, but illustrates a situation where the wafer has been lifted with a rising width necessary to lift a wafer that sags.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1: Wafer cassette 2: Wafer receiving part 3: Wafer cassette opening part 4: Arm 5: Wafer position and thickness measurement sensor 6: Load / unload base 7: Wafer passage detection sensor 8: Wafer passage detection position 9 : Wafer warp height measurement sensor 10: Sensor signal processing unit 11: Arm driving unit 12: Sensor position control driving unit 13: Sensor holding column 20: Wafer insertion unit a: Wafer

Claims (8)

A wafer cassette provided with multiple stages of wafer insertion portions for fitting the peripheral edge of the wafer, a movable arm that holds the wafer and carries it in and out of the wafer cassette, and carries the arm in and out of the wafer cassette An arm driving unit that drives the wafer in a vertical direction and a vertical direction; a first sensor that detects an edge of the wafer at a predetermined position when the wafer is raised by the raising of the arm in the wafer cassette; and a warpage amount of the wafer When the first sensor detects an edge of the wafer when the wafer is taken out from the wafer cassette, the arm drive unit stops raising the arm when the wafer is taken out of the wafer cassette, When the wafer cassette is carried into the wafer cassette, the amount of warpage detected by the second sensor is used as a correction amount for the arm insertion height. Wafer transfer apparatus characterized by a control unit for controlling the arm insertion height at the dynamic part. A third sensor for detecting a position of the wafer stored in the wafer cassette; the third sensor, when taking out the wafer from the wafer cassette, the lower surface of the wafer to be taken out; 2. The wafer transfer apparatus according to claim 1, wherein the control unit inserts an arm at an intermediate position between the detection lower surface and the detection upper surface. The control unit raises an arm inserted into the wafer cassette by a predetermined amount to hold the wafer on the arm, and then pulls out the arm so as to take out the wafer. When the first sensor detects the edge of the wafer when the arm is raised, the arm driving unit is controlled to stop the raising of the arm. The wafer transfer apparatus according to claim 1. The first sensor detects a position of an edge portion of the wafer so that the edge portion of the wafer does not contact the upper wafer receiving portion of the wafer insertion portion to which the wafer is to be inserted. 4. The wafer transfer apparatus according to claim 1, wherein the wafer transfer apparatus is capable of moving up and down in accordance with a position of a wafer insertion portion into which the wafer is to be inserted. 5. When the wafer is inserted into the wafer cassette, the control unit is a wafer receiving unit between the wafer inserting units, and is arranged at the center positions of the upper and lower wafer receiving units of the wafer inserting unit to which the wafer is to be inserted. An intermediate position between them is set as a reference height position, and an arm holding the wafer is inserted at a height position obtained by reducing the amount of warpage detected by the second sensor with respect to the reference height position. The wafer transfer apparatus according to any one of claims 1 to 4. 6. The wafer transfer apparatus according to claim 1, wherein the arm holds the wafer by sucking and sucking the wafer. In a wafer transfer method of taking out a wafer stored in a wafer cassette provided with multi-stage wafer insertion portions for fitting the peripheral edge of the wafer, a step of inserting an arm below the wafer to be taken out; A step of raising the arm to contact the lower surface of the wafer to hold the wafer on the arm; and a step of pulling the arm out of the wafer cassette and taking out the wafer; When the wafer is raised by the rise of the arm in the wafer cassette, the rise of the arm is detected when the edge of the wafer is detected by the first sensor. A wafer transfer method characterized by stopping. A method of detecting a warp height of a wafer to be inserted by a second sensor in a wafer transfer method of inserting a wafer into a wafer cassette provided with multi-stage wafer insertion portions for fitting peripheral edges of the wafer; And a step of inserting the arm into the wafer cassette while holding the wafer on the arm, and the warp detected by the second sensor when the wafer is loaded into the wafer cassette. A wafer transfer method characterized by controlling the arm insertion height in the arm drive unit using the amount as a correction amount of the arm insertion height.

Images