JP2013084738A - Wafer transfer device, solar cell manufacturing device, wafer transfer method, control program and recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wafer transfer device capable of transferring wafers with individually different thicknesses without breakage.SOLUTION: A wafer transferring device 1 according to the present invention comprises: a holding part 4 holding a wafer 2; a movement control part 71 controlling movement of the holding part 4; a holding control part 72 controlling holding of the wafer 2 with the holding part 4; and a determination part 73 for determining whether a distance in a perpendicular direction to an upper face of a tray 3 at a lower end of the wafer 2 is a first distance or not.

Description

  The present invention relates to a wafer transfer apparatus and a wafer transfer method for transferring a wafer.

  In the manufacturing cost of a solar cell made of a wafer such as silicon, the proportion of the wafer is high. Therefore, reducing the manufacturing cost of the solar cell by slicing the wafer thinly and cutting out more wafers from the same amount of ingot is generally performed as a method for reducing the solar cell price.

  However, if the wafer is thinned, the probability of occurrence of breakage such as cracking or chipping increases when the wafer is transported, which causes a deterioration in the manufacturing yield of solar cells.

  On the other hand, Patent Document 1 discloses a technique for performing all processes on a wafer while the wafer is placed on a tray in order to avoid damage to the wafer. In this case, since the wafer is not taken out of the tray and handled directly between the processes, the occurrence rate of breakage can be suppressed even for a thin wafer.

  However, in the technique of Patent Document 1, one tray is required for each wafer, and it is necessary to prepare as many trays as the number of wafers existing in the manufacturing process. There is a problem. Therefore, in order to reduce the manufacturing cost of the solar cell, it is very important to handle and transport the thin wafer directly without damaging it.

  Here, a conventional wafer transfer technique will be described.

  FIG. 10 is a block diagram showing a schematic configuration of a conventional wafer transfer device 21.

  The wafer transfer device 21 is a device that transfers the wafer 22 received from the previous process and places it on the tray 23, and includes a holding unit 24, a servo motor 25, a servo amplifier 26, a sequencer 27, and an electromagnetic valve 28. . The sequencer 27 controls the transfer of the wafer 22 and includes a movement control unit 271 and a holding control unit 272.

  The holding unit 24 includes a mechanism for holding the wafer 22 and is connected to the servo motor 25.

  The servo amplifier 26 supplies power to the servo motor 25 based on the control of the movement control unit 271. As the servo motor 25 rotates, the holding unit 24 moves in the vertical direction and the horizontal direction.

  The movement control unit 271 controls the movement of the holding unit 24 by transmitting information such as the moving distance, moving direction, speed, and acceleration of the holding unit 24 to the servo amplifier 26.

  The holding control unit 272 controls holding of the wafer 22 by the holding unit 24 via the electromagnetic valve 28.

  FIG. 11 is a diagram illustrating a specific configuration of the holding unit 24 of the wafer conveyance device 21.

  The holding part 24 includes clamp parts 241a and 241b, shafts 242a and 242b, air cylinders 243a and 243b, and a movable part 244. The clamp part 241a, the shaft 242a, the air cylinder 243a and the clamp part 241b, the shaft 242b, and the air cylinder 243b are arranged symmetrically.

  The left and right clamp portions 241 a and 241 b have L-shaped cross sections, and can hold two end portions that are symmetrical with respect to the center of the wafer 22. The clamp portions 241a and 241b are connected to the left and right shafts 242a and 242b, respectively, and the shafts 242a and 242b can be moved in the left and right directions by the left and right air cylinders 243a and 243b, respectively. The air cylinders 243a and 243b are connected to the electromagnetic valve 28 shown in FIG. 10, and the movement of the shafts 242a and 242b is controlled by the electromagnetic valve 28 controlling the supply of air to the air cylinders 243a and 243b. .

  The movable portion 244 is connected to a servo motor 25 shown in FIG. 10 via a ball screw (not shown). As a result, when the servo motor 25 rotates, the entire holding unit 24 moves.

  In the above configuration, a transport method from receiving the wafer 22 from the previous process to placing it on the tray 23 will be described.

  First, the wafer 22 is transferred from the previous process by a transfer mechanism (not shown).

  Next, the solenoid valve 28 supplies air to the left and right air cylinders 243a and 243b under the control of the holding control unit 272 to move the shaft 242a in the left direction and move the shaft 242b in the right direction. Thereby, the clamp portions 241a and 241b sandwich the wafer 22.

  Since only a part of the outer peripheral portion of the wafer 22 is held by the clamp portions 241a and 241b, the portion near the center portion of the wafer 22 is lowered by its own weight while being clamped as shown in FIG. It is bent in the direction.

  Subsequently, under the control of the movement control unit 271 shown in FIG. 10, the holding unit 24 is moved upward to lift the wafer 22. Thereafter, the holding unit 24 is moved in the horizontal direction, and the holding unit 24 is stopped at a position immediately above the tray 23 as shown in FIG.

  Thereafter, the holding unit 24 is moved downward, and the movement of the holding unit 24 is stopped when the holding unit 24 is lowered to a preset position so that the wafer 22 is appropriately transferred as shown in FIG.

  Thereafter, the air cylinders 243a and 243b are driven to extend the left and right shafts 242a and 242b, and the clamp portions 241a and 241b move from directly below the outer peripheral portion of the wafer 22 to the outside of the wafer 22. As a result, the clamping of the wafer 22 by the clamp portions 241a and 241b is released, and the wafer 22 falls onto the tray 23.

  As described above, the transfer of the wafer 22 onto the tray 23 is completed.

  After the wafer 22 is transferred to the tray 23, the tray 23 is heated to 400 ° C. or more by a heater while the wafer 22 is placed, and then a gas as a material is supplied onto the wafer 22 so that the tray 23 The gas reacts with the thermal energy it has. As a result, a desired thin film is formed on the wafer 22.

JP 2004-327576 A (published November 18, 2004)

  However, the conventional technology as described above has a problem that the possibility of damaging the wafer increases when the wafer is thin.

  As shown in FIGS. 11 to 13, the wafer 22 clamped by the clamp portions 241 a and 241 b is bent downward by its own weight. The thinner the wafer, the greater the variation in the degree of warping (warping) of the wafer due to individual differences in thickness. For example, in a wafer having a thickness of about 0.1 mm, if the thickness varies by ± 10% due to a manufacturing error, the height of the lowest central portion of the clamped wafer varies by several mm depending on the degree of deflection.

  Assuming that there is no individual difference in the thickness of the wafer, the height of the central portion of the wafer 22 from the upper surface of the tray 23 when the clamp is released by appropriately setting the descending distance of the holding unit 24, The height can always be such that the wafer 22 is not damaged.

  However, when the thickness of the wafer is smaller than the set value due to a manufacturing error, the degree of bending of the clamped wafer 22 increases as shown in FIG. Therefore, there is a possibility that the central portion of the wafer 22 contacts the tray 23 while the wafer 22 is held while the holding unit 24 is being lowered.

  In this case, in the form in which the clamp portions 241a and 241b are mounted without fixing the wafer 22, after the wafer 22 floats from the clamp portions 241a and 241b, the outer peripheral portion of the wafer 22 strikes the clamp portions 241a and 241b again. It becomes. Therefore, the outer peripheral part of the wafer 22 is chipped. Furthermore, the position of the wafer 22 is shifted with respect to the clamp portions 241a and 241b.

  Further, in the form in which the clamp portions 241a and 241b hold the wafer 22 fixedly, when the central portion of the wafer 22 comes into contact with the tray 23, a force to bend the wafer 22 upward is applied. Therefore, a load is applied to the outer peripheral portion of the wafer 22 and the wafer 22 is cracked or chipped.

  Further, when the thickness of the wafer is larger than the set value due to a manufacturing error, the degree of bending of the wafer 22 in the clamped state becomes small as shown in FIG. Therefore, when the clamp is released on the tray 23, the height of the central portion of the wafer 22 with respect to the upper surface of the tray 23 becomes larger than an appropriate height.

  If the clamp is released in this state, there is a high possibility that the wafer 22 will be cracked or chipped by a drop impact. Even if no crack or chipping occurs, the position of the wafer 22 on the tray 23 is likely to be greatly deviated from the normal position, resulting in a failure in processing such as subsequent film formation or the wafer after the processing. May not be transported normally.

  For this reason, in the conventional technique, it is necessary to set the height at which the holding of the wafer 22 is released to be high so that the central portion of the wafer 22 does not come into contact with the tray 23 even when the deflection of the wafer 22 is large. is there. However, if the height at which the holding of the wafer 22 is released is set high, the distance between the lower end of the wafer 22 and the upper surface of the tray 23 at the time of releasing the holding becomes large when the degree of bending of the wafer 22 is small. The probability that the wafer 22 is damaged due to the impact of dropping increases.

  Furthermore, as described above, in the production of solar cells, since it is necessary to make the wafer thinner, individual differences in the degree of deflection of the held wafer increase. Therefore, when the conventional wafer transfer device is applied to the manufacture of solar cells, the probability of damaging the wafer is increased, and the manufacturing yield of solar cells is deteriorated.

  The present invention has been made to solve the above problems, and an object of the present invention is to provide a wafer transfer apparatus and a wafer transfer method that can transfer wafers having individual differences in thickness without damaging them.

  In order to solve the above-described problems, a wafer transfer apparatus according to the present invention is a wafer transfer apparatus that transfers a wafer and places the wafer on a mounting surface, the holding unit holding the wafer, and the holding unit A control unit for controlling movement of the wafer and holding of the wafer by the holding unit, a light emitting element having an emitting part for emitting light, a light receiving element having a light receiving part for receiving light emitted from the emitting part, and the light receiving element A determination unit that transmits a signal to the control unit according to the detected light intensity, and the emission unit and the light receiving unit are provided at a height of a first distance from the installation surface. When the intensity of the light received by the light receiving unit is changed by the lowest part of the wafer being blocked by the lowest part of the wafer with respect to the mounting surface immediately above the surface. The determination unit transmits a signal to the control unit, When the control unit receives the signal, the control unit lowers the holding unit by lowering the second distance shorter than the first distance, and after the stop, causes the holding unit to release the holding of the wafer. It is a feature.

  In order to solve the above problems, a wafer transfer method according to the present invention is a wafer transfer method for transferring a wafer and placing it on a mounting surface, wherein the holding step of holding the wafer by a holding unit; An emitting step for emitting light from the emitting portion of the light emitting element provided at a height of a first distance from the placement surface; and a placement surface provided at a height of the first distance from the placement surface. A light receiving step in which the light receiving portion of the light receiving element facing the light emitting portion across the position directly above the light receiving portion receives the light, and the emitted light is blocked by the lowest portion of the wafer with respect to the mounting surface. When the intensity of the light received by the light receiving portion is changed, the lowering / stopping step of stopping the holding portion by lowering the second distance shorter than the first distance from the position at the time of the change. And after the stop, the wafer It is characterized by having a release step for releasing the holding, the.

  According to the above configuration, the light emitting unit and the light receiving unit are provided at the height of the first distance from the mounting surface and face each other across the position directly above the mounting surface. When the distance in the vertical direction with respect to the mounting surface of the part reaches the first distance, the light emitted from the emitting unit is blocked by the wafer, and the intensity of the light received by the light receiving unit changes. Then, when the intensity of light received by the light receiving portion changes, the holding portion is stopped by lowering the second distance, and the holding of the wafer is released after the stop. Therefore, the height of the lowest portion of the wafer relative to the mounting surface when the wafer is released is always the first distance and the second distance regardless of the degree of bending of the held wafer. Equal to the difference. Therefore, by setting the first distance and the second distance so that the difference between the first distance and the second distance is not damaged when the wafer falls on the mounting surface, It can be mounted on the mounting surface without damaging it. Further, since the position of the wafer on the mounting surface does not greatly deviate from the desired position, the subsequent processing on the wafer and the transfer of the wafer after the processing can be performed normally.

  Therefore, it is possible to provide a wafer transfer apparatus and a wafer transfer method that can transfer wafers having individual differences in thickness without damaging them.

  In the wafer conveyance device according to the present invention, the light emitting element is preferably a semiconductor laser.

  According to said structure, since the laser beam which a semiconductor laser radiate | emits has high directivity, when a laser beam is interrupted | blocked by a wafer, the intensity | strength of the light which a light-receiving part receives will fall rapidly. Therefore, the determination unit can transmit a signal at a more accurate timing. Moreover, since the semiconductor laser is low-cost, the manufacturing cost of the wafer transfer device can be suppressed.

  In the wafer conveyance device according to the present invention, the light emitting element may be a light emitting diode.

  According to the above configuration, since the light emitting diode is a point light source that emits light having directivity, when the emitted light is blocked by the wafer, the intensity of the light received by the light receiving unit is rapidly reduced. Therefore, the determination unit can transmit a signal more accurately at the timing when the distance in the vertical direction with respect to the mounting surface of the lowest part of the wafer reaches the first distance.

  In the wafer transfer apparatus according to the present invention, it is preferable that the wafer is a silicon wafer, and a wavelength of light emitted from the light emitting element is 1.1 μm or less.

  According to the above configuration, the light emitted from the light-emitting element has a wavelength of 1.1 μm or less corresponding to the band gap of silicon, and thus is difficult to transmit through the silicon wafer. For this reason, when the light emitted from the light emitting element is blocked by the wafer, the intensity of the light received by the light receiving portion rapidly decreases. Therefore, the determination unit can transmit a signal more accurately at the timing when the distance in the vertical direction with respect to the mounting surface of the lowest part of the wafer reaches the first distance.

  In the wafer conveyance device according to the present invention, the light receiving element is preferably a photodiode.

  According to the above configuration, since the photodiode is a dot-shaped light receiving element, when the light emitted from the light emitting element is blocked by the wafer, the intensity of the light received by the light receiving unit is rapidly reduced. Therefore, the determination unit can transmit a signal more accurately at the timing when the distance in the vertical direction with respect to the mounting surface of the lowest part of the wafer reaches the first distance.

  In the wafer transfer apparatus according to the present invention, the difference between the first distance and the second distance is preferably 1 mm or less.

  According to said structure, the height with respect to the mounting surface of the lowest part of a wafer at the time of cancellation | release of holding | maintenance of a wafer can be 1 mm or less irrespective of the bending condition of the held wafer. Therefore, even if the wafer is thin, it can be placed on the placement surface without being damaged.

  The wafer transfer apparatus according to the present invention includes a servo motor connected to the holding unit, and when the determination unit transmits a signal to the control unit, the control unit sets in advance from the time of transmission. It is preferable to stop the rotation after rotating the servo motor by the rotation angle.

  According to the above configuration, by setting the rotation angle set in advance as the rotation angle at which the holding unit moves the second distance, the holding unit can be stopped by lowering the second distance.

  A solar cell manufacturing apparatus according to the present invention is a solar cell manufacturing apparatus including a wafer transfer device that transfers a wafer that has been processed in a previous process onto a mounting surface, It is characterized by including a wafer transfer device.

  In the manufacture of solar cells, thin wafers are used to reduce manufacturing costs. Therefore, individual differences in the degree of deflection of the wafer become significant. On the other hand, since the wafer transfer apparatus according to the present invention can transfer wafers having individual differences in thickness without damaging them, the wafer transfer apparatus can be suitably applied to prevent a decrease in manufacturing yield of solar cells.

  A control program for operating any one of the wafer transfer apparatuses, a control program for causing a computer to function as the control unit and the determination unit, and a computer-readable recording medium storing the control program Is also included in the technical scope of the present invention.

  As described above, the wafer transfer apparatus according to the present invention is a wafer transfer apparatus that transfers a wafer and places the wafer on a mounting surface, the holding unit holding the wafer, the movement of the holding unit, and the A control unit that controls the holding of the wafer by the holding unit, a light emitting element having an emitting unit that emits light, a light receiving element that has a light receiving unit that receives light emitted from the emitting unit, and light detected by the light receiving element A determination unit that transmits a signal to the control unit according to intensity, and the emission unit and the light receiving unit are provided at a height of a first distance from the mounting surface, and are directly above the mounting surface. When the intensity of light received by the light receiving unit is changed by the lowest part of the wafer being blocked by the lowest portion of the wafer with respect to the mounting surface, the determination unit A signal is transmitted to the control unit, and the control unit transmits the signal. When receiving, the holding portion is stopped by lowering the short second distance greater than the first distance, after the stop, a configuration for releasing the holding of the wafer to the holder.

  A wafer transfer method according to the present invention is a wafer transfer method for transferring a wafer and placing the wafer on a placement surface, a holding step for holding the wafer by a holding portion, and a first step from the placement surface described above. An emission step for emitting light from the emission part of the light emitting element provided at a height of a distance between the light emitting element and a position at a first distance from the placement surface, sandwiching a position directly above the placement surface. A light receiving step in which the light receiving portion of the light receiving element facing the light emitting portion receives the light, and the emitted light is blocked by the lowest portion of the wafer with respect to the mounting surface, and the light receiving portion receives the light. When the intensity of the light to be changed is changed, the holding unit lowers and stops the second distance shorter than the first distance from the position at the time of the change, and after the stop, Release screw for releasing the holding of the wafer Tsu has a flop, the.

  Therefore, it is possible to provide a wafer transfer apparatus and a wafer transfer method that can transfer wafers having individual differences in thickness without damaging them.

It is a block diagram showing a schematic structure of a wafer conveyance device concerning an embodiment of the present invention. It is a figure for demonstrating the specific structure of the holding part of the said wafer conveyance apparatus, and the installation position of a light emitting element and a light receiving element. It is a flowchart which shows the outline of the wafer conveyance method which concerns on embodiment of this invention. It is a figure which shows the state which has lowered | hung the holding | maintenance part toward the tray from directly above a tray in the state in which the holding | maintenance part hold | maintained the wafer. It is a figure which shows the state which the lower end of the wafer reached | attained the position of the 1st distance to the perpendicular direction from the mounting surface of a tray. It is a graph which shows the time change of the intensity | strength of the signal which a light receiving element outputs to a determination part. It is a figure which shows the state which the holding | maintenance part further lowered | hung the 2nd distance from the position where the distance of the perpendicular direction with respect to the tray of the lower end of a wafer is a 1st distance. It is a figure which shows the operation | movement which a holding part cancels | releases holding | maintenance of a wafer. It is a figure which shows the state which the conveyance to the tray of a wafer was completed. It is a block diagram which shows schematic structure of the conventional wafer conveyance apparatus. It is a figure which shows the specific structure of the holding part of the said conventional wafer conveyance apparatus. It is a figure which shows the state which has lowered | hung the holding | maintenance part toward the tray from directly above a tray in the state in which the holding | maintenance part hold | maintained the wafer. It is a figure which shows the state which the said holding | maintenance part fell to the position set beforehand, and stopped. It is a figure explaining the problem of a prior art, and is a figure which shows the state which the center part of the wafer contacted the tray in the state with which the wafer was hold | maintained. It is a figure explaining the problem of a prior art, and is a figure which shows operation | movement which cancels | releases holding | maintenance of a wafer in the state in which the lower end of a wafer is comparatively high from a tray.

  One embodiment of the present invention will be described below with reference to FIGS.

(Schematic configuration of wafer transfer device)
FIG. 1 is a block diagram showing a schematic configuration of a wafer transfer apparatus 1 according to the present embodiment.

  The wafer transfer device 1 is a device that transfers the wafer 2 received from the previous process and places it on the tray 3. The holding unit 4, the servo motor 5, the servo amplifier 6, the sequencer 7, the electromagnetic valve 8, and the light emitting element 9. And a light receiving element 10. The sequencer 7 controls the transfer of the wafer 2 and includes a movement control unit 71, a holding control unit 72, and a determination unit 73.

  The tray 3 is a mounting table for performing heat treatment or the like on the wafer 2, and the upper surface of the tray 3 corresponds to the mounting surface described in the claims. Moreover, both the movement control part 71 and the holding | maintenance control part 72 of the sequencer 7 are equivalent to the control part as described in a claim.

  The holding unit 4 includes a mechanism for holding the wafer 2 and is connected to a servo motor 5. A specific configuration example of the holding unit 4 will be described later with reference to FIG.

  The servo amplifier 6 supplies power to the servo motor 5 based on the control of the movement control unit 71. As the servo motor 5 rotates, the holding unit 4 moves in the vertical direction and the horizontal direction.

  The configuration of the wafer 2, the tray 3, the holding unit 4, the servo motor 5, the servo amplifier 6, and the electromagnetic valve 8 is the same as that of the wafer 22, tray 23, holding unit 24, servo of the conventional wafer transfer device 21 shown in FIG. The motor 25, the servo amplifier 26, and the electromagnetic valve 28 are the same.

  The movement control unit 71 transmits information such as the moving distance, moving direction, speed, and acceleration of the holding unit 4 to the servo amplifier 6, and the servo amplifier 6 supplies power to the servo motor 5 based on these information. Then, the servo motor 5 is rotated. The servo motor 5 feeds back the current position (rotation angle) to the servo amplifier 6, and the servo amplifier 6 returns an operation end signal or an alarm signal to the movement control unit 71 and the holding control unit 72. In this way, the movement control unit 71 controls the movement of the holding unit 4.

  The holding control unit 72 controls holding of the wafer 2 by the holding unit 4. More specifically, the holding controller 72 holds the wafer 2 by controlling the electromagnetic valves 8 that supply air to the air cylinders 43a and 43b shown in FIG. 2 and controlling the positions of the clamps 41a and 41b. And control the release of the hold.

  As will be described later, the determination unit 73 transmits a signal to the movement control unit 71 when the distance in the vertical direction with respect to the upper surface of the tray 3 at the lowest portion of the wafer 2 is the first distance. In other words, the lowest portion of the wafer 2 is the portion closest to the upper surface of the tray 3 of the wafer 2 and is expressed as “the lower end of the wafer 2” in the following description.

  The light emitting element 9 and the light receiving element 10 constitute a photoelectric sensor, and are provided at a predetermined position with a position immediately above the tray 3 interposed therebetween. The light emitting element 9 is composed of a semiconductor laser and emits laser light having high directivity toward the light receiving element 10. The light receiving element 10 includes a photodiode, receives the laser light from the light emitting element 9, and outputs a current signal corresponding to the intensity of the received laser light to the determination unit 73.

(Specific configuration of holding part)
Next, the configuration of the holding unit 4 and the installation positions of the light emitting element 9 and the light receiving element 10 will be described in more detail.

  FIG. 2 is a diagram for explaining a specific configuration of the holding unit 4 and the installation positions of the light emitting element 9 and the light receiving element 10.

  The holding part 4 includes clamp parts 41a and 41b, shafts 42a and 42b, air cylinders 43a and 43b, and a movable part 44. The clamp part 41a, the shaft 42a, the air cylinder 43a and the clamp part 41b, the shaft 42b, and the air cylinder 43b are arranged symmetrically.

  The left and right clamp portions 41 a and 41 b have an L-shaped cross section, and can hold two end portions that are symmetrical with respect to the center of the wafer 2. The clamp portions 41a and 41b are connected to the left and right shafts 42a and 42b, respectively, and the shafts 42a and 42b are movable in the left and right directions by the left and right air cylinders 43a and 43b, respectively.

  The electromagnetic valve 28 shown in FIG. 1 supplies air to the air cylinders 43 a and 43 b based on the control of the holding control unit 72. Further, the movable portion 44 is connected to the servo motor 5 shown in FIG. 1 via a ball screw (not shown).

  Accordingly, the movement control unit 71 shown in FIG. 1 controls the vertical and horizontal movements of the holding unit 4, and the holding control unit 72 controls the holding of the wafer 2 by the holding unit 4 and the release of the holding.

  When the holding unit 4 holds the wafer 2, the solenoid valve 28 supplies air to the left and right air cylinders 43 a and 43 b to move the shaft 42 a in the left direction and move the shaft 42 b in the right direction. Thereby, the clamp parts 41a and 41b pinch the wafer 2.

  Since only a part of the outer peripheral portion of the wafer 2 is held by the clamp portions 41a and 41b, as shown in FIG. 2, the portion close to the center portion of the wafer 2 is lowered by its own weight while being clamped. It is bent in the direction.

(Installation position of light emitting element and light receiving element)
As described above, the light emitting element 9 and the light receiving element 10 constitute a photoelectric sensor, and are provided at predetermined positions with the position immediately above the tray 3 being sandwiched therebetween.

  The light emitting element 9 is composed of a semiconductor laser and has an emission part 91 that emits a laser beam L1.

  The light receiving element 10 is composed of a photodiode and includes a light receiving unit 101 that receives the laser light L <b> 1 emitted from the emitting unit 91.

  The emitting portion 91 of the light emitting element 9 and the light receiving portion 101 of the light receiving element 10 are provided at a height of a first distance (distance D1) from the upper surface of the tray 3, and the wafer 2 having the mounting surface is placed thereon. It is opposed across the position immediately above the position where it is placed. In other words, the light emitting element 9 and the light receiving element 10 are provided so that the distance between the optical axis of the laser beam L1 emitted from the emitting portion 91 and the upper surface of the tray 3 is the distance D1.

  The light receiving element 10 is connected to the determination unit 73 shown in FIG. 1 and outputs a current signal corresponding to the intensity of the received laser beam L1 to the determination unit 73. The determination unit 73 transmits a signal to the movement control unit 71 based on the intensity of the laser light L1 received by the light receiving element 10.

(Wafer transfer method)
Next, a transport method for receiving the wafer 2 from the previous process and placing it on the tray 3 will be described.

  First, an outline of a method for transporting the wafer 2 will be described based on the flowchart of FIG.

  When the wafer 2 is transferred from the previous process by a transfer mechanism (not shown), the holding control unit 72 causes the holding unit 4 to hold the transferred wafer 2 (step S1, holding step). Subsequently, the movement control unit 71 moves the holding unit 4 in the horizontal direction to just above the tray 3 (step S2), and then lowers the holding unit 4 toward the tray 3 (step S3).

  Subsequently, the determination unit 73 determines whether or not the intensity of the laser light L1 received by the light receiving element 10 has started to decrease (step S4). If “Yes” in step S <b> 4, the determination unit 73 transmits a signal to the movement control unit 71.

  In this case, the movement control unit 71 stops the holding unit 4 by lowering the second distance (distance D2) shorter than the distance D1 from the position at the determined time (step S5, descent / stop step). ). After the stop, the holding control unit 72 causes the holding unit 4 to release the holding of the wafer 2 (step S6, release step). Thereby, the wafer 2 falls on the tray 3 (step S7), and the transfer of the wafer 2 onto the tray 3 is completed.

  Next, a method for transporting the wafer 2 will be specifically described with reference to FIGS.

  FIG. 4 is a diagram illustrating a state where the holding unit 4 is lowered from the position directly above the tray 3 toward the tray 3 in a state where the holding unit 4 holds the wafer 2 (step S3). In this state, the distance in the vertical direction with respect to the upper surface of the tray 3 at the lower end of the wafer 2 is larger than the distance D1, so that the laser light L1 emitted from the emitting portion 91 of the light emitting element 9 is received by the light receiving element 10 without being blocked. Incident on the part 101.

  FIG. 5 is a view showing a state where the lower end of the wafer 2 crosses the optical axis of the laser light L1 emitted from the emission part 91 of the light emitting element 9. In this state, since the lower end of the wafer 2 blocks the laser light L1 emitted from the emission part 91 of the light emitting element 9, the laser light L1 does not reach the light receiving part 101 of the light receiving element 10.

Specifically, as shown in the graph of FIG. 6, when the lower end of the wafer 2 begins to block the laser beam L1 at time t ₀ , the signal intensity output from the light receiving element 10 to the determination unit 73 rapidly decreases. It becomes zero. The determination unit 73 transmits a signal to the movement control unit 71, triggered by the signal strength starting to decrease (“YES” in step S4).

  Although the determination unit 73 transmits a signal to the movement control unit 71 triggered by the signal intensity from the light receiving element 10 starting to decrease, the determination unit 73 is not limited to this. For example, when the signal intensity from the light receiving element 10 decreases to a predetermined intensity (for example, half) or when the signal intensity becomes zero, the determination unit 73 transmits a signal to the movement control unit 71. Also good. Thus, in the present embodiment, the determination unit 73 transmits a signal to the movement control unit 71 based on the intensity of the laser light L1 received by the light receiving element 10.

  When the movement control unit 71 receives the signal from the determination unit 73, the holding unit 4 transmits information on the rotation angle set in advance of the servo motor 5 to the servo amplifier 6 so that the distance D2 is further lowered. The servo amplifier 6 supplies power to the servo motor 5, and after the servo motor 5 rotates by the rotation angle, stops supplying power to the servo motor 5 and transmits an operation end signal to the movement control unit 71. . Thereby, the movement of the holding | maintenance part 4 stops (step S5).

  FIG. 7 is a view showing a state in which the holding unit 4 is stopped by further lowering the distance D2 from the position where the distance in the vertical direction with respect to the upper surface of the tray 3 at the lower end of the wafer 2 is the distance D1. The distances D1 and D2 are set so that the difference between the distance D1 and the distance D2 is 1 mm. Therefore, regardless of how the wafer 2 is bent, in the state shown in FIG. 7, the height of the lower end of the wafer 2 relative to the upper surface of the tray 3 is 1 mm.

  From the viewpoint of reducing the impact on the wafer 2 when dropped, the smaller the difference between the distance D1 and the distance D2, the better. However, when the difference between the distance D1 and the distance D2 is extremely small, the lower end of the wafer 2 may come into contact with the tray 3 during the lowering due to the vibration of the wafer 2.

  When the servo amplifier 6 stops the holding unit 4 by lowering the distance D2, simultaneously with the stop, the servo amplifier 6 notifies the movement control unit 71 and the holding control unit 72 that the rotation operation of the servo motor 5 has been completed. Thereby, the holding control unit 72 instructs the holding unit 4 to release the holding of the wafer 2.

  Specifically, the holding controller 72 moves the air cylinders 43a and 43b to the air cylinders 43a and 43b so that the clamp part 41a moves to the right side and the clamp part 41b moves to the left side as shown in FIG. To supply. Accordingly, the holding of the wafer 2 by the holding unit 4 is released (step S6), and the wafer 2 falls on the tray 3 and is placed on the placement surface as shown in FIG. 9 (step S7). .

  In addition, after the wafer 2 is transferred to the tray 3, the wafer 2 is subjected to heat treatment or the like. Specifically, after the tray 2 is heated to 400 ° C. or more with a heater while the wafer 2 is placed, a gas as a material is supplied onto the wafer 2 and the gas reacts with the thermal energy of the tray 3. Let Thereby, a desired thin film is formed on the wafer 2.

(Function and effect)
As described above, in this embodiment, when the determination unit 73 transmits a signal to the movement control unit 71, that is, the distance in the vertical direction with respect to the upper surface of the tray 3 at the lower end of the wafer 2 held by the holding unit 4 is a distance. In the case of D1, the movement control unit 71 stops the holding unit 4 by lowering the distance D2 from the position at the time when the signal is transmitted, and after the stop, the holding control unit 72 causes the holding unit 4 to stop. The holding of the wafer 2 is released.

  For this reason, the height of the lower end of the wafer 2 relative to the upper surface of the tray 3 at the time when the wafer 2 is released is always the difference between the distance D1 and the distance D2, regardless of the degree of deflection of the held wafer 2. Will be equal. Therefore, by setting the distances D1 and D2 such that the difference between the distance D1 and the distance D2 is not damaged (preferably 1 mm or less) when the wafer 2 falls on the tray 3, the wafer 2 is It can be placed on the tray 3 without being damaged. That is, as in the conventional configuration shown in FIGS. 14 and 15, the lower end of the wafer comes into contact with the tray while the holding unit is being lowered, or damage to the wafer due to dropping the wafer onto the tray from a position that is too high is prevented. be able to. Further, since the position of the wafer on the mounting surface does not greatly deviate from the desired position, the subsequent processing on the wafer and the transfer of the wafer after the processing can be performed normally.

  Therefore, according to the present embodiment, a wafer having an individual difference in thickness can be transported without being damaged.

  In particular, in the manufacture of solar cells, since a thin wafer is used, individual differences in how the wafer bends become significant. Therefore, by using the wafer transfer apparatus according to this embodiment as the wafer transfer apparatus of the solar cell manufacturing apparatus including the wafer transfer apparatus that transfers the wafer that has been processed in the previous process onto the mounting surface, the solar cell The production yield can be prevented from decreasing.

  In this embodiment, since the position of the lower end of the wafer is detected by the photoelectric sensor, for example, the wafer is photographed with a camera and the position of the lower end of the wafer is detected from the image at a lower cost. A wafer transfer apparatus can be realized.

(Implementation of the present invention by software)
Each block of the wafer transfer apparatus 1 described above, in particular the movement control unit 71, the holding control unit 72, and the determination unit 73 may be configured by hardware logic, or realized by software using a CPU as follows. Also good.

  That is, the wafer transfer apparatus 1 includes a CPU (central processing unit) that executes instructions of a control program for realizing each function, a ROM (read only memory) that stores the program, and a RAM (random access memory) that expands the program. And a storage device (recording medium) such as a memory for storing the program and various data. An object of the present invention is a recording medium on which a program code (execution format program, intermediate code program, source program) of a control program of the wafer transfer apparatus 1 which is software for realizing the above-described functions is recorded so as to be readable by a computer. This can also be achieved by supplying the wafer transfer apparatus 1 and reading and executing the program code recorded on the recording medium by the computer (or CPU or MPU).

  Examples of the recording medium include a tape system such as a magnetic tape and a cassette tape, a magnetic disk such as a floppy (registered trademark) disk / hard disk, and an optical disk such as a CD-ROM / MO / MD / DVD / CD-R. Card system such as IC card, IC card (including memory card) / optical card, or semiconductor memory system such as mask ROM / EPROM / EEPROM / flash ROM.

  The wafer transfer apparatus 1 may be configured to be connectable to a communication network, and the program code may be supplied via the communication network. The communication network is not particularly limited. For example, the Internet, intranet, extranet, LAN, ISDN, VAN, CATV communication network, virtual private network, telephone line network, mobile communication network, satellite communication. A net or the like is available. Also, the transmission medium constituting the communication network is not particularly limited. For example, even in the case of wired such as IEEE 1394, USB, power line carrier, cable TV line, telephone line, ADSL line, etc., infrared rays such as IrDA and remote control, Bluetooth ( (Registered trademark), 802.11 wireless, HDR (high data rate), mobile phone network, satellite line, terrestrial digital network, and the like can also be used. The present invention can also be realized in the form of a computer data signal embedded in a carrier wave in which the program code is embodied by electronic transmission.

(Additional notes)
In the embodiment described above, the semiconductor laser is used as the light emitting element, but the present invention is not limited to this. For example, a light emitting diode that is a point light source may be used as the light emitting element.

  However, since the laser light emitted from the semiconductor laser has high directivity, when the laser light is blocked by the wafer, the intensity of the light received by the light receiving portion is rapidly reduced. For this reason, the distance in the vertical direction with respect to the mounting surface at the lower end of the wafer at the time when the determination unit transmits a signal can be substantially matched with the first distance on the order of 0.1 mm. Therefore, it is desirable to use a semiconductor laser as the light emitting element.

  In the above-described embodiment, the photodiode is used as the light receiving element. However, the light receiving element is not limited to the photodiode as long as the element can receive light and detect the intensity of the received light.

  In addition, it is desirable that the light emitted from the light emitting element does not easily pass through the material of the wafer. For example, when the wafer is a silicon wafer, the wavelength of the light emitted from the light emitting element is desirably 1.1 μm or less, which corresponds to the band gap of silicon.

  The distances D1 and D2 are not particularly limited as long as the difference between the distance D1 and the distance D2 is a small distance that does not cause damage when the wafer 2 falls on the tray 3. However, when the distances D1 and D2 are large, the size of the wafer transfer device increases, and thus the distances D1 and D2 are set to, for example, several mm to several tens mm.

  The present invention is not limited to the above-described embodiments, and various modifications can be made within the scope shown in the claims. That is, embodiments obtained by combining technical means appropriately modified within the scope of the claims are also included in the technical scope of the present invention.

  The present invention can also be expressed as follows.

  That is, the wafer transfer method according to the present invention includes a mechanism for clamping the wafer transferred from the previous step, transferring the wafer to the tray by releasing the clamp after transferring the wafer to the position immediately above the tray, In a solar cell manufacturing apparatus that performs film formation with a wafer placed on a tray, the release of the clamp is such that the output of a photoelectric sensor composed of a light-emitting element and a light-receiving element disposed facing each other in the horizontal direction passes through the wafer. It is characterized in that it is performed when the wafer is moved downward by a certain distance from the time point when changed by the above.

  Further, in the wafer transfer method according to the present invention, the means for moving the wafer downward by a certain distance is moved downward using a motor whose rotation angle can be controlled, such as a servo motor, and the photoelectric sensor It is characterized in that the rotation of the motor is stopped when it is detected that the angle has been rotated in advance from the time when the output changes.

  Further, a wafer transfer apparatus according to the present invention is a wafer transfer apparatus using the wafer transfer method described above.

  The present invention is particularly suitable for a solar cell manufacturing apparatus using a thin wafer.

DESCRIPTION OF SYMBOLS 1 Wafer transfer apparatus 2 Wafer 3 Tray 4 Holding part 5 Servo motor 6 Servo amplifier 7 Sequencer 8 Electromagnetic valve 9 Light emitting element 10 Light receiving element 41a Clamp part 41b Clamp part 42a Shaft 42b Shaft 43a Air cylinder 43b Air cylinder 44 Movable part 71 Movement control Part (control part)
72 Holding control unit (control unit)
73 determination unit 91 emission unit 101 light receiving unit D1 distance (first distance)
D2 distance (second distance)
L1 Laser light (light)

Claims (11)

A wafer transfer apparatus for transferring a wafer and placing it on a mounting surface,
A holding unit for holding the wafer;
A control unit for controlling movement of the holding unit and holding of the wafer by the holding unit;
A light emitting element having an emission part for emitting light;
A light-receiving element having a light-receiving unit that receives light emitted from the light-emitting unit, and a determination unit that transmits a signal to the control unit according to the intensity of light detected by the light-receiving element,
The emitting portion and the light receiving portion are provided at a height of a first distance from the placement surface, and face each other with a position directly above the placement surface,
The determination unit transmits a signal to the control unit when the emitted light is blocked by the lowest portion of the wafer with respect to the mounting surface and the intensity of the light received by the light receiving unit changes,
When the control unit receives the signal, the control unit lowers the holding unit by lowering the second distance shorter than the first distance, and after the stop, causes the holding unit to release the holding of the wafer. A wafer transfer device.   The wafer transfer apparatus according to claim 1, wherein the light emitting element is a semiconductor laser.   The wafer transfer apparatus according to claim 1, wherein the light emitting element is a light emitting diode.   The wafer transfer apparatus according to claim 1, wherein the wafer is a silicon wafer, and a wavelength of light emitted from the light emitting element is 1.1 μm or less.   The wafer transfer apparatus according to claim 1, wherein the light receiving element is a photodiode.   The wafer transfer apparatus according to claim 1, wherein a difference between the first distance and the second distance is 1 mm or less. Provided with a servo motor connected to the holding part,
When the determination unit transmits a signal to the control unit, the control unit stops the rotation after rotating the servo motor by a preset rotation angle from the time of the transmission. The wafer transfer apparatus according to any one of claims 1 to 6. A solar cell manufacturing apparatus including a wafer transfer device that transfers a wafer that has been processed in the previous step onto a mounting surface,
A solar cell manufacturing apparatus comprising the wafer transfer apparatus according to claim 1 as the wafer transfer apparatus.   A control program for operating the wafer transfer apparatus according to claim 1, wherein the control program causes a computer to function as the control unit and the determination unit.   A computer-readable recording medium on which the control program according to claim 9 is recorded. A wafer transfer method for transferring a wafer and placing it on a mounting surface,
A holding step of holding the wafer by a holding unit;
An emission step of emitting light from the emission portion of the light emitting element provided at a height of a first distance from the placement surface;
A light receiving step in which the light receiving portion of the light receiving element that is provided at a height of a first distance from the placement surface and faces the emitting portion across the position directly above the placement surface receives the light;
When the emitted light is blocked by the lowest part of the wafer with respect to the mounting surface and the intensity of the light received by the light receiving unit changes, the holding unit is moved away from the position at the time of the change. A descent / stop step for lowering and stopping a second distance shorter than the first distance;
And a release step of releasing the holding of the wafer after the stop.

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