JP4782544B2 - Laser processing equipment - Google Patents

Description

  The present invention relates to a laser processing apparatus that performs laser processing along streets formed on a workpiece such as a semiconductor wafer.

  In the semiconductor device manufacturing process, a plurality of regions are partitioned by dividing lines called streets arranged in a lattice pattern on the surface of a substantially wafer-shaped semiconductor wafer, and devices such as ICs, LSIs, etc. are partitioned in the partitioned regions. Form. Then, the semiconductor wafer is cut along the streets to divide the region in which the device is formed to manufacture individual semiconductor chips. In addition, optical device wafers in which light-receiving elements such as photodiodes and light-emitting elements such as laser diodes are stacked on the surface of the sapphire substrate are also divided into optical devices such as individual photodiodes and laser diodes by cutting along the streets. And widely used in electrical equipment.

As a method of dividing the wafer such as the semiconductor wafer or the optical device wafer described above along the street, a laser processing groove is formed by irradiating a pulse laser beam along the street formed on the wafer, and along the laser processing groove. A method of breaking is proposed. (For example, refer to Patent Document 1.)
JP-A-10-305420

  When laser processing a wafer such as a semiconductor wafer, the wafer is held on a chuck table in a state of being adhered to the surface of an adhesive tape mounted on an annular frame in order to facilitate handling of the wafer. Then, a laser beam is irradiated along the street of the wafer held on the chuck table. However, when irradiating a wafer stuck to the surface of the adhesive tape with a laser beam, if the laser beam irradiates off the wafer region or is irradiated through the wafer, the laser beam passes through the adhesive tape. The chuck table is irradiated and as a result, the chuck table is partially heated. When the chuck table is heated, the adhesive tape formed of a synthetic resin such as polyolefin or polyethylene is partially melted by heating the chuck table. As a result, there is a problem that the adhesive tape adheres to the chuck table, and the wafer adhered to the adhesive tape cannot be carried out of the chuck table.

  The present invention has been made in view of the above-mentioned facts, and its main technical problem is to provide a laser processing apparatus in which an adhesive tape to which a workpiece such as a wafer is attached is prevented from melting and adhering to a chuck table. Is to provide.

In order to solve the main technical problem, according to the present invention, a chuck table having a holding surface in which a suction hole for sucking and holding a wafer is formed , and a laser beam for irradiating the wafer held by the chuck table with a laser beam. In a laser processing apparatus comprising an irradiation means,
A protective sheet laying means provided with a protective sheet mounted on the chuck table and covering the holding surface ;
The protective sheet laying means comprises an unused roll around which an unused protective sheet having air permeability is wound, and a winding roll that winds up the protective sheet wound around the unused roll. The use roll and the take-up roll are arranged to face each other across the holding surface,
A laser processing apparatus is provided.

According to the present invention, since the protective sheet laying means provided with the protective sheet that is mounted on the chuck table and covers the holding surface is provided, the adhesive tape to which the workpiece is adhered is held on the chuck table via the protective sheet. Is done. Therefore, when the workpiece is overrun when irradiating the workpiece with a laser beam or when the workpiece is completely cut , the chuck table is heated and protected when the laser beam passes through the adhesive tape and the protective sheet and reaches the chuck table. Although the sheet may melt, the pressure-sensitive adhesive tape to which the wafer is attached does not melt. For this reason, the workpiece stuck to the adhesive tape can be easily carried out of the chuck table. Moreover, according to the present invention, the protective sheet laying means includes an unused roll around which an unused protective sheet having air permeability is wound, and a winding roll that winds up the protective sheet wound around the unused roll. Since the unused roll and the take-up roll are arranged facing each other across the holding surface, it is not necessary to replace the protective sheet each time, and the protective sheet can be replaced over a long period of time. It can be used without.

DESCRIPTION OF EMBODIMENTS Hereinafter, a preferred embodiment of a laser processing apparatus configured according to the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a perspective view of a laser processing apparatus constructed according to the present invention. A laser processing apparatus shown in FIG. 1 includes a stationary base 2, a chuck table mechanism 3 that is disposed on the stationary base 2 so as to be movable in a machining feed direction indicated by an arrow X, and holds a workpiece. The laser beam irradiation unit support mechanism 6 is movably arranged in an indexing direction indicated by an arrow Y perpendicular to the direction indicated by the arrow X in FIG. 2, and the laser beam unit support mechanism 6 moves in a focus position adjustment direction indicated by an arrow Z. And a laser beam irradiation unit 7 which can be arranged.

  The chuck table mechanism 3 includes a pair of guide rails 31, 31 arranged in parallel along the direction indicated by the arrow X on the stationary base 2, and the direction indicated by the arrow X on the guide rails 31, 31. A first sliding block 32 movably disposed, a second sliding block 33 movably disposed on the first sliding block 32 in a direction indicated by an arrow Y, and the second sliding block A cover table 35 supported by a cylindrical member 34 on the block 33 and a chuck table 4 as a workpiece holding means are provided.

  The first sliding block 32 is provided with a pair of guided grooves 321 and 321 fitted to the pair of guide rails 31 and 31 on the lower surface thereof, and along the direction indicated by the arrow Y on the upper surface thereof. A pair of guide rails 322 and 322 formed in parallel are provided. The first sliding block 32 configured as described above has the guided grooves 321 and 321 fitted into the pair of guide rails 31 and 31, thereby the direction indicated by the arrow X along the pair of guide rails 31 and 31. It is configured to be movable. The chuck table mechanism 3 in the illustrated embodiment includes a processing feed means 37 for moving the first sliding block 32 in the direction indicated by the arrow X along the pair of guide rails 31, 31. The processing feed means 37 includes a male screw rod 371 disposed in parallel between the pair of guide rails 31 and 31, and a drive source such as a pulse motor 372 for rotationally driving the male screw rod 371. One end of the male screw rod 371 is rotatably supported by a bearing block 373 fixed to the stationary base 2, and the other end is connected to the output shaft of the pulse motor 372 via a reduction gear (not shown). ing. The male screw rod 371 is screwed into a penetrating female screw hole formed in a female screw block (not shown) provided on the lower surface of the central portion of the first sliding block 32. Therefore, when the male screw rod 371 is driven to rotate forward and backward by the pulse motor 372, the first sliding block 32 is moved along the guide rails 31, 31 in the machining feed direction indicated by the arrow X.

  The second sliding block 33 is provided with a pair of guided grooves 331 and 331 which are fitted to a pair of guide rails 322 and 322 provided on the upper surface of the first sliding block 32 on the lower surface thereof. By fitting the guided grooves 331 and 331 to the pair of guide rails 322 and 322, the guided grooves 331 and 331 are configured to be movable in the direction indicated by the arrow Y. The chuck table mechanism 3 in the illustrated embodiment is a first for moving the second slide block 33 along the pair of guide rails 322 and 322 provided in the first slide block 32 in the direction indicated by the arrow Y. The indexing and feeding means 38 is provided. The first index feed means 38 includes a male screw rod 381 disposed in parallel between the pair of guide rails 322 and 322, and a drive source such as a pulse motor 382 for rotationally driving the male screw rod 381. It is out. One end of the male screw rod 381 is rotatably supported by a bearing block 383 fixed to the upper surface of the first sliding block 32, and the other end is connected to the output shaft of the pulse motor 382 via a reduction gear (not shown). Are connected. The male screw rod 381 is screwed into a penetrating female screw hole formed in a female screw block (not shown) provided on the lower surface of the central portion of the second sliding block 33. Therefore, when the male screw rod 381 is driven to rotate forward and reversely by the pulse motor 382, the second slide block 33 is moved along the guide rails 322 and 322 in the index feed direction indicated by the arrow Y.

Next, the chuck table 4 will be described with reference to FIGS.
The chuck table 4 shown in FIGS. 2 to 4 is rotatably supported by a cylindrical support cylinder 34 disposed on the upper surface of the second sliding block 33 via a bearing 340 as shown in FIG. ing. As shown in FIG. 3, the chuck table 4 includes a columnar main body 41 and a suction chuck 42 formed by a porous member made of porous ceramics or the like provided on the upper surface of the main body 41 and having numerous suction holes. It is made up of. The main body 41 is formed of a metal material such as stainless steel, and a circular fitting recess 411 is provided on the upper surface thereof. The fitting recess 411 is provided with an annular mounting shelf 412 on which the suction chuck 42 is mounted on the outer periphery of the bottom surface. The main body 41 is provided with a suction passage 413 that opens into the fitting recess 411, and the suction passage 413 communicates with a suction means (not shown). Accordingly, when a suction means (not shown) is operated, a negative pressure is applied to the fitting recess 411 through the suction passage 413. As a result, a negative pressure is applied to the holding surface 421 that is the upper surface of the suction chuck 42 provided with innumerable suction holes. I'm damned.

  An annular groove 415 is formed in the upper part of the main body 41 constituting the chuck table 4 as shown in FIG. The bases of the two clamps 43 and 43 are disposed in the annular groove 415, and the bases of the clamps 43 and 43 are attached to the main body 41 by appropriate fixing means. A cover table 35 is disposed at the upper end of the support cylinder 34. The lower end of the main body 41 of the chuck table 4 configured as described above is connected to a pulse motor (not shown) disposed in the cylindrical member 34 and is appropriately rotated by the pulse motor.

  As shown in FIGS. 2 and 4, the chuck table 4 configured as described above is provided with protective sheet laying means 5 including a protective sheet that covers the holding surface 421 of the suction chuck 42. The protective sheet laying means 5 includes a pair of support plates 51, 51 that are arranged to face each other at a predetermined interval, and an unused one that is rotatably supported at one end of the pair of support plates 51, 51. It comprises a roll 52, a winding roll 53 rotatably supported on the other end of the pair of support plates 51, 51, and a pulse motor 54 that rotates the winding roll 53. As shown in FIGS. 2 and 3, mounting members 55 and 55 are mounted on the inner surfaces of the pair of support plates 51 and 51 facing each other (in FIG. 2, one mounting plate 51 is mounted). Only one mounting member 55 is shown). As shown in FIG. 2, the attachment members 55, 55 are formed on an arc surface 551 corresponding to the outer peripheral surface of the main body 41 of the chuck table 4. Further, as shown in FIG. 3, the mounting members 55 and 55 are formed with two bolt insertion holes 552 in the longitudinal direction (only one bolt insertion hole 552 is shown in FIG. 3). On the other hand, two bolt insertion holes 511 are formed in the pair of support plates 51, 51 at positions corresponding to the screw holes 552 formed in the attachment members 55, 55 (FIG. 3 shows one bolt insertion hole. Only the hole 511 is shown). Accordingly, the bolt 56 is inserted into the bolt insertion hole 511 formed in the pair of support plates 51, 51 and the bolt insertion hole 552 formed in the attachment members 55, 55, and the screw hole formed in the main body 41 of the chuck table 4. The pair of support plates 51 and 51 are attached to the main body 41 of the chuck table 4 via attachment members 55 and 55 by being screwed to 416. Thus, the unused roll 52 and the take-up roll 53 rotatably supported by the pair of support plates 51, 51 attached to the main body 41 of the chuck table 4 sandwich the holding surface 421 of the suction chuck 42. Opposed to each other. An unused protective sheet 57 is wound around the unused roll 52, and the leading end portion of the protective sheet 57 is engaged with the winding roll 53. Therefore, by driving the pulse motor 54, the protective sheet 57 is wound around the winding roll 53, and the protective sheet 57 wound around the unused roll 52 is sent out. In the illustrated embodiment, the protective sheet 57 is a breathable sheet. As the sheet having air permeability, a polyethylene porous film “Sunmap LC-T” manufactured and sold by Nitto Denko Corporation can be used.

  Referring back to FIG. 1, the laser beam irradiation unit support mechanism 6 includes a pair of guide rails 61 and 61 disposed on the stationary base 2 in parallel along the direction indicated by the arrow Y, and the guide A movable support base 62 is provided on the rails 61 and 61 so as to be movable in the direction indicated by the arrow Y. The movable support base 62 includes a movement support portion 621 that is movably disposed on the guide rails 61, 61, and a mounting portion 622 that is attached to the movement support portion 621. The mounting portion 622 is provided with a pair of guide rails 623 and 623 extending in the direction indicated by the arrow Z on one side surface in parallel. The laser beam irradiation unit support mechanism 6 in the illustrated embodiment includes a second index feed means 63 for moving the movable support base 62 along the pair of guide rails 61, 61 in the direction indicated by the arrow Y. Yes. The second index feed means 63 includes a male screw rod 631 disposed in parallel between the pair of guide rails 61, 61, and a drive source such as a pulse motor 632 for rotating the male screw rod 631. It is out. One end of the male screw rod 631 is rotatably supported by a bearing block (not shown) fixed to the stationary base 2 and the other end is connected to the output shaft of the pulse motor 632 via a reduction gear (not shown). Has been. The male screw rod 631 is screwed into a female screw hole formed in a female screw block (not shown) provided on the lower surface of the central portion of the moving support portion 621 constituting the movable support base 62. Therefore, when the male screw rod 631 is driven to rotate forward and reversely by the pulse motor 632, the movable support base 62 is moved along the guide rails 61 and 61 in the index feed direction indicated by the arrow Y.

  The laser beam irradiation unit 7 in the illustrated embodiment includes a unit holder 71 and laser beam irradiation means 72 attached to the unit holder 71. The unit holder 71 is provided with a pair of guided grooves 711 and 711 slidably fitted to a pair of guide rails 623 and 623 provided in the mounting portion 622. By being fitted to the guide rails 623 and 623, the guide rails 623 and 623 are supported so as to be movable in the direction indicated by the arrow Z.

  The illustrated laser beam application means 72 includes a cylindrical casing 721 that is fixed to the unit holder 71 and extends substantially horizontally. As shown in FIG. 5, a pulse laser beam oscillation means 722 and a transmission optical system 723 are disposed in the casing 721. The pulse laser beam oscillating means 722 includes a pulse laser beam oscillator 722a composed of a YAG laser oscillator or a YVO4 laser oscillator, and a repetition frequency setting means 722b attached thereto. The transmission optical system 723 includes an appropriate optical element such as a beam splitter. A condenser 73 that collects the laser beam oscillated from the pulse laser beam oscillation means 722 and transmitted through the transmission optical system 723 is attached to the tip of the casing 721.

  Returning to FIG. 1, the description is continued. At the front end portion of the casing 721 constituting the laser beam irradiation means 72, an image pickup means 8 for detecting a processing region to be laser processed by the laser beam irradiation means 72 is disposed. . In the illustrated embodiment, the imaging unit 8 includes, in addition to a normal imaging device (CCD) that captures an image with visible light, an infrared illumination unit that irradiates a workpiece with infrared rays, and an infrared ray that is irradiated by the infrared illumination units. And an imaging device (infrared CCD) that outputs an electrical signal corresponding to the infrared rays captured by the optical system, and sends the captured image signal to a control means (not shown).

  The laser beam irradiation unit 7 in the illustrated embodiment includes a moving means 74 for moving the unit holder 71 along the pair of guide rails 623 and 623 in the direction indicated by the arrow Z. The moving means 74 includes a male screw rod (not shown) disposed between the pair of guide rails 623 and 623, and a drive source such as a pulse motor 742 for rotationally driving the male screw rod. By driving the male screw rod (not shown) by the motor 742 in the forward or reverse direction, the unit holder 71 and the laser beam irradiation means 72 are moved in the direction indicated by the arrow Z along the pair of guide rails 623 and 623. In the illustrated embodiment, the laser beam irradiation means 72 is moved upward by driving the pulse motor 742 forward, and the laser beam irradiation means 72 is moved downward by driving the pulse motor 742 in the reverse direction. ing.

The laser processing apparatus in the illustrated embodiment is configured as described above, and the operation thereof will be described below.
Here, a semiconductor wafer as a workpiece to be laser processed by the laser processing apparatus will be described with reference to FIG. A semiconductor wafer 10 shown in FIG. 6 is made of a silicon wafer, and a plurality of devices 101 are formed in a matrix on the surface 10a. Each device 101 is partitioned by streets 102 formed in a lattice shape. The semiconductor wafer 10 has a back surface attached to an adhesive tape 12 mounted on an annular frame 11 with the front surface 10a as the processing surface facing upward. When processing the semiconductor wafer 10 from the back side, the front surface 10 a of the semiconductor wafer 10 is stuck to the adhesive tape 12. As the adhesive tape 12, for example, a tape in which an acrylic resin adhesive material is laid about 5 μm thick on the surface of a synthetic resin sheet such as polyolefin or polyethylene having a thickness of 100 μm is used.

  In order to irradiate a laser beam along the street 102 of the semiconductor wafer 10 and to form a laser processing groove along the street 102, the semiconductor wafer adhered to the surface of the adhesive tape 12 attached to the annular frame 11 is used. 10 is placed on the chuck chuck 42 of the chuck table 4 positioned at the workpiece loading / unloading position shown in FIG. At this time, since the holding surface 421 which is the upper surface of the suction chuck 42 is covered with the protective sheet 57, the back surface (lower surface) of the adhesive tape 12 to which the semiconductor wafer 10 is adhered is the protective sheet 57 as shown in FIG. Placed on top. When a suction means (not shown) is operated, a negative pressure acts on the adhesive tape 12 through the suction chuck 42 having innumerable suction holes and the protective sheet 57 having air permeability, and the adhesive tape 12 to which the semiconductor wafer 10 is stuck. Is sucked and held by the holding surface 421 of the suction chuck 42. Next, the annular frame 11 to which the adhesive tape 12 is attached is fixed by the clamp 43.

  As described above, the chuck table 4 that sucks and holds the semiconductor wafer 10 is positioned immediately below the imaging unit 8 by the processing feed unit 37. When the chuck table 4 is positioned immediately below the image pickup means 8, an alignment operation for detecting a processing region to be laser-processed of the semiconductor wafer 10 is executed by the image pickup means 8 and a control means (not shown). That is, the imaging unit 8 and a control unit (not shown) align the street 102 formed in a predetermined direction of the semiconductor wafer 10 and the condenser 724 of the laser beam irradiation unit 72 that irradiates the laser beam along the street 102. Image processing such as pattern matching is performed to perform alignment of the laser beam irradiation position. The alignment of the laser beam irradiation position is similarly performed on the street 102 formed on the semiconductor wafer 10 and extending at right angles to the predetermined direction.

  As described above, when the street 102 formed on the semiconductor wafer 10 held on the chuck table 4 is detected and the alignment of the laser beam irradiation position is performed, the chuck table 4 is moved and the position shown in FIG. As shown in a), one end (the left end in FIG. 7A) of a predetermined division line 102 is positioned directly below the condenser 73. Then, while irradiating a pulse laser beam having a wavelength of, for example, 355 nm, which absorbs the silicon wafer from the condenser 73, the chuck table 4 is moved in the direction indicated by the arrow X1 in FIG. Move it. Then, as shown in FIG. 7B, when the irradiation position of the condenser 73 reaches the position of the other end of the street 102, the irradiation of the pulse laser beam is stopped and the movement of the chuck table 4 is stopped. As a result, a laser processing groove 110 is formed along the street 102 as shown in FIG. 7B (laser beam irradiation step). In this laser beam irradiation step, the condensing point P of the pulse laser beam is matched with the vicinity of the surface 10 a (upper surface) of the semiconductor wafer 10.

In the illustrated embodiment, the processing conditions in the laser beam irradiation step are set as follows.
Light source: LD excitation Q switch Nd: YVO4 laser Laser wavelength: 355 nm pulse laser Pulse output: 14 μJ
Condensing spot diameter: φ13μm
Repetition frequency: 100 kHz
Processing feed rate: 100 mm / sec

In the above-described laser beam irradiation step, a period from the state in which one end of the street 102 formed on the semiconductor wafer 10 is located immediately below the light collector 73 to the time in which the other end of the street 102 is located directly below the light collector 73. Although it is controlled so that a pulse laser beam is emitted from the condenser 73, the laser beam may be emitted by overrunning both ends of the street 102 of the semiconductor wafer 10. At this time, the laser beam passes through the adhesive tape 12 and the protective sheet 57 and reaches the chuck table 4. Further, even when the semiconductor wafer 10 is completely cut along the street 102 by irradiating the laser beam, the laser beam passes through the adhesive tape 12 and the protective sheet 57 and reaches the chuck table 4. When the laser beam reaches the chuck table 4 through the adhesive tape 12 and the protective sheet 57 in this way, the chuck table 4 may be heated and the protective sheet 57 may melt, but the adhesive tape 12 to which the wafer 10 is adhered melts. Never do.

  When the laser beam irradiation process is performed along the predetermined street 102 as described above, the chuck table 4 is indexed and fed by the interval of the street 102 in the direction indicated by the arrow Y in FIG. 1 (indexing process), and the laser beam irradiation process is performed. To implement. When the laser beam irradiation process and the indexing process are performed for all the streets 102 extending in a predetermined direction of the semiconductor wafer 10 in this manner, the chuck table 4 and thus the semiconductor wafer 2 held by the chuck table 4 are rotated 90 degrees. Then, by executing the laser beam irradiation step and the indexing step along each street 102 extending at right angles to the predetermined direction, the laser processing groove 110 can be formed along all the streets 102 of the semiconductor wafer 10. it can.

  When the laser processing grooves 110 are formed along all the streets 102 of the semiconductor wafer 10 as described above, the chuck table 4 is returned to the workpiece loading / unloading position shown in FIG. Is stopped and suction holding of the semiconductor wafer 10 is released. Then, by releasing the fixation of the annular frame 11 by the clamp 43, the semiconductor wafer 10 is conveyed to the next process while being held by the annular frame 11 via the adhesive tape 12. At this time, the adhesive tape 12 is stuck to the adhesive tape 12 because it does not melt as described above even when the laser beam irradiated by overrunning in the laser beam irradiation process or by completely cutting the semiconductor wafer heats the chuck table 4. The semiconductor wafer 10 can be easily carried out of the chuck table 4. If the protective sheet 57 deteriorates due to the irradiation of the laser beam and its function is lowered, the pulse motor 54 of the protective sheet laying means 5 is driven to rotate the winding roll 53 to wind the protective sheet 57 by a predetermined amount. As a result, the region of the protective sheet 57 that has previously covered the holding surface 421 of the chuck table 4 is taken up by the take-up roll 53, and the unused portion of the protective sheet 57 is sent out from the unused roll 52 to move the holding surface 421. cover. The winding operation of the protective sheet 57 may be automatically performed every predetermined operating time, or may be arbitrarily performed by the operator monitoring the protective sheet 57. In the above-described embodiment, an example in which the winding roll 53 is rotated by the pulse motor 54 has been described. However, the winding roll 53 may be manually rotated.

The perspective view of the laser processing apparatus comprised according to this invention. The perspective view of the chuck | zipper table and protection sheet laying means with which the laser processing apparatus shown in FIG. 1 is equipped. AA sectional drawing in FIG. BB sectional drawing in FIG. The block diagram which shows simply the structure of the laser beam irradiation means with which the laser processing apparatus shown in FIG. 1 is equipped. The perspective view which shows the state which affixed the semiconductor wafer as a to-be-processed object to the adhesive tape with which the cyclic | annular flame | frame was mounted | worn. Explanatory drawing of the laser beam irradiation process implemented by the laser processing apparatus shown in FIG.

Explanation of symbols

2: stationary base 3: chuck table mechanism 31, 31: a pair of guide rails 32: first sliding block 33: second sliding block 37: processing feeding means 38: first indexing feeding means 4: chuck table 41 : Chuck table body 42: Adsorption chuck 5: Protection sheet laying means 51, 51 A pair of support plates 52: Unused roll 53: Winding roll 54: Pulse motor 55: Mounting member 57: Protection sheet 6: Laser beam irradiation unit support Mechanisms 61, 61: A pair of guide rails 62: Movable support base 63: Second index feed means 7: Laser beam irradiation unit 71: Unit holder 72: Laser beam irradiation means 73: Condenser 8: Imaging means 10: Semiconductor wafer 11: annular frame 12: adhesive tape

Claims (1)

In a laser processing apparatus comprising: a chuck table having a holding surface in which a suction hole for sucking and holding a wafer is formed ; and a laser beam irradiation means for irradiating a wafer with a laser beam on the wafer held by the chuck table.
A protective sheet laying means provided with a protective sheet mounted on the chuck table and covering the holding surface ;
The protective sheet laying means comprises an unused roll around which an unused protective sheet having air permeability is wound, and a winding roll that winds up the protective sheet wound around the unused roll. The use roll and the take-up roll are arranged to face each other across the holding surface,
Laser processing equipment characterized by that.

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