JP2018129426A - Wafer processing method and adhesive tape - Google Patents

Abstract

PROBLEM TO BE SOLVED: To completely cut only a wafer by laser beam irradiation such that an adhesive tape adhered to the wafer is not completely cut.SOLUTION: In a wafer processing method for dividing a wafer W into individual chips by irradiating the wafer with a laser beam of a wavelength having an absorptive property, the wafer W is stuck to the adhesive tape T shielding irradiation with a laser beam, the adhesive tape T side is held on a chuck table to expose the wafer W, and the wafer W is divided while relatively moving the chuck table and the laser beam. The laser beam is shielded by the adhesive tape T, thereby preventing the adhesive tape T from being cut and preventing a problem in which the wafer W cannot be transferred afterwards and a chip cannot be picked up from occurring.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a wafer processing method in which a wafer is divided into individual chips by irradiating the wafer with a laser beam having a wavelength that is absorptive with respect to the wafer.

  A wafer in which a plurality of devices such as IC and LSI are defined by a division line and formed on the surface is divided into chips for each device by a cutting device, a laser processing device, etc., and various electronic devices such as mobile phones and personal computers Etc. are used.

  The cutting device is configured to divide the wafer into individual chips by cutting a cutting blade into the wafer division schedule line held on the chuck table, and an adhesive tape is attached to the back side of the wafer. Worn. Then, the wafer is completely cut by adjusting the cutting depth of the cutting blade and cutting the cutting blade until the adhesive tape is slightly cut.

JP-A-8-88202

  However, in the laser processing apparatus, if the output of the laser beam is too large, the wafer is completely cut and the adhesive tape is also cut, which makes it difficult to transport the wafer to the subsequent process. Further, if the adhesive tape is cut, there is a problem that the chip cannot be picked up from the adhesive tape.

  The present invention has been considered in view of such problems, and it is an object of the present invention to completely cut only the wafer and not completely cut the adhesive tape attached to the wafer by irradiation with a laser beam.

The present invention relates to a wafer processing method for irradiating a wafer with a laser beam having a wavelength that absorbs the wafer to divide the wafer into individual chips. It comprises at least an attaching step, a holding step of holding the adhesive tape side on the chuck table to expose the wafer, and a dividing step of dividing the wafer while relatively moving the chuck table and the laser beam.
In this wafer processing method, the adhesive tape is preferably composed of a glue layer and a sheet, and a metal powder is mixed in the glue layer or the sheet to shield the laser beam.
The metal fine powder preferably contains any of Al, Au, Cu, Fe, Ti, and Ni.

  The present invention also relates to an adhesive tape that is attached to a wafer when the wafer is divided into individual chips by irradiating the wafer with a laser beam having a wavelength that has an absorptivity to the wafer.

  In the present invention, an adhesive tape that shields the irradiation of the laser beam is attached to the wafer, and the wafer is individually irradiated by irradiating the wafer with a laser beam having a wavelength that absorbs the wafer while holding the adhesive tape side on the chuck table. Therefore, even if the wafer is completely cut and the laser beam reaches the adhesive tape, the adhesive tape can be prevented from being cut. Therefore, it is possible to prevent the subsequent problems that the wafer cannot be transported and the chip cannot be picked up.

It is a perspective view which shows the example of a laser processing apparatus. It is a block diagram which shows the example of a laser beam irradiation means. It is sectional drawing which shows the example of the structure of an adhesive tape. It is a perspective view which shows the state which laser-processes a wafer.

  A laser processing apparatus 1 shown in FIG. 1 is an apparatus for processing a wafer W by irradiating a wafer W held by a chuck table 2 with a laser beam irradiation means 3.

  The wafer W held on the chuck table 2 is configured by forming a plurality of devices D in an area defined by the division lines L on the front surface Wa, and an adhesive tape T is attached to the back surface Wb. A ring-shaped frame F is attached to the outer peripheral edge of the adhesive tape T. In this way, the wafer W is supported by the frame F via the adhesive tape T. Hereinafter, the wafer W supported by the frame F via the adhesive tape T is referred to as a wafer unit U.

  The chuck table 2 includes a suction portion 20 made of a porous member or the like that sucks a workpiece, a frame body 21 that supports the suction portion 20, a cover 22 disposed around the suction portion 20 and the frame body 21, Rotating means 23 is connected to the bottom surface side of the suction portion 20 and rotationally drives the suction portion 20 and the frame body 21. The suction unit 20 communicates with a suction source (not shown) and can cause suction to act on the holding surface 20a that is the exposed surface of the suction unit 20.

  The chuck table 2 is driven by the index feed means 4 and the machining feed means 5 and can move in the Y-axis direction and the X-axis direction.

  The index feeding means 4 includes a ball screw 40 having an axis in the Y-axis direction, a pair of guide rails 41 arranged in parallel to the ball screw 40, a motor 42 for rotating the ball screw 40, and an internal nut formed by the ball screw 40. The movable plate 43 is engaged with the guide rail 41 and is slidably contacted with the guide rail 41. When the motor 42 rotates the ball screw 40, the movable plate 43 is guided by the guide rail 41 and moved in the Y-axis direction. The chuck table 2 disposed on the movable plate 43 moves in the Y-axis direction as the movable plate 43 moves.

  The processing feed means 5 includes a ball screw 50 having an axis in the X-axis direction, a pair of guide rails 51 arranged in parallel to the ball screw 50, a motor 52 for rotating the ball screw 50, and an internal nut formed by the ball screw 50. The movable plate 53 is configured so that the bottom portion thereof is slidably contacted with the guide rail 51. When the motor 52 rotates the ball screw 50, the movable plate 53 is guided by the guide rail 51 along the X axis direction. The index feed means 4 and the chuck table 2 disposed on the movable plate 53 are configured to move in the X-axis direction as the movable plate 53 moves.

  Above the movement path of the chuck table 2, an alignment unit 6 that images the wafer W and detects a division line L to be processed is disposed. The alignment means 6 includes an imaging unit 60, and detects the planned division line L by performing image processing on an image captured and acquired by the imaging unit 60.

  Laser beam irradiation means 3 is disposed above the movement path of the chuck table 2. As shown in FIG. 2, the laser beam application means 3 collects a laser beam 30 that oscillates a laser beam, an attenuator 31 that adjusts the output of the laser beam, a mirror 32 that reflects the laser beam, and a laser beam reflected by the mirror 32 on the wafer. And a lens 33 that emits light. The mirror 32 and the lens 33 are disposed inside the irradiation head 34 shown in FIG.

  As shown in FIG. 2, the adhesive tape T constituting the wafer unit U shown in FIG. 1 includes a sheet 100 as a base material and a glue layer 101 formed on one surface of the sheet 100. ing. The sheet 100 is made of, for example, polyvinyl chloride. The glue layer 101 is made of, for example, an acrylic resin.

  In the adhesive layer 101, metal fine powder 102 is mixed. As the metal fine powder 102, for example, aluminum (Al), gold (Au), copper (Cu), iron (Fe), titanium (Ti), nickel (Ni) can be used.

  The metal fine powder 102 may be mixed in the sheet 100, or may be mixed in both the sheet 100 and the glue layer 101.

  In the following, a method for performing ablation processing along the division line L of the wafer W shown in FIG. As the wafer W, a silicon wafer is used. Although not shown, the surface Wa of the wafer W is covered with a protective film for protecting the device D.

  The wafer unit U shown in FIG. 1 is held on the chuck table 2. Specifically, the adhesive tape T side is sucked and held by the holding surface 20 a of the suction portion 20, and the frame F is fixed by the fixing clamp 24. Then, the wafer W is moved below the imaging unit 60 by the chuck table 2 being fed in the X-axis direction by the processing feed means 5. Then, the planned division line L to be processed is detected by the alignment means 6, and the detected division planned line L and the irradiation head 34 of the laser beam irradiation means 3 are aligned in the Y-axis direction.

Then, as shown in FIG. 4, the chuck table 2 is further sent in the same direction, and a laser beam LB having an absorptive wavelength is applied to the wafer W from the irradiation head 34, so that the division line L is irradiated. Along the ablation process. Here, the laser beam LB is irradiated, for example, under the following conditions.
Wavelength: 355nm
Average output: 3.0W
Repetition frequency: 20 kHz
Condensing spot diameter: φ10μm
Chuck table feed speed: 100 mm / sec

When the wafer W is irradiated with the laser beam LB under the above conditions, the processing groove G shown in FIG. 4 penetrating from the front surface Wa to the back surface Wb is formed, and the division line L is completely cut.
Further, the index feeding means 4 feeds the chuck table 3 in the Y-axis direction by the interval between the adjacent division lines L, and similarly irradiates the laser beam LB, whereby the next division line is ablated. By repeating the index feed and the laser beam irradiation in this manner, all the division lines L in the same direction are processed. Further, by performing the same processing after rotating the chuck table 2 by 90 degrees, all the division lines L are ablated in the vertical and horizontal directions to form the processing grooves G, and the wafer W is inserted into the chip for each device D. It is divided into.

  In the laser processing performed in this way, the laser beam applied to the wafer W reaches the adhesive tape T after completely cutting the wafer W, but the adhesive tape T is shielded from the irradiation of the laser beam LB. 3 is mixed, the laser beam LB does not reach the lower surface of the adhesive tape T. Therefore, even if the adhesive tape T is damaged by being irradiated with the laser beam, the damage does not penetrate the adhesive tape T, and the adhesive tape T is not completely cut.

  As described above, since the adhesive tape T is not completely cut, even after the wafer W is divided into chips for each device, the state where each chip is stuck to one adhesive tape T is maintained. . Therefore, it is possible to prevent problems that the wafer W cannot be transported or the chip cannot be picked up thereafter.

  In this embodiment, the laser beam is shielded by mixing fine metal powder into the adhesive tape T, but the shielding method is not limited to this.

  In the present embodiment, the adhesive tape T is attached to the back surface Wb of the wafer W and the laser beam is irradiated from the front surface Wa side. However, the adhesive tape T is attached to the front surface Wa of the wafer W, and the back surface Wb. You may irradiate a laser beam from the side.

1: Laser processing apparatus 2: Chuck table 20: Suction part 21: Frame body 22: Cover 23: Rotating means 24: Fixed clamp 3: Laser beam irradiation means 30: Laser oscillator 31: Attenuator 32: Mirror 33: Lens 34: Irradiation head 4: Index feed means 40: Ball screw 41: Guide rail 42: Motor 43: Movable plate 5: Processing feed means 50: Ball screw 51: Guide rail 52: Motor 53: Movable plate 6: Alignment means 60: Imaging unit U: Wafer unit W: Wafer Wa: Front surface L: Line to be divided D: Device Wb: Back surface T: Adhesive tape 100: Sheet 101: Adhesive layer 102: Fine metal powder

Claims (4)

A method of processing a wafer by irradiating a wafer with a laser beam having a wavelength that absorbs the wafer and dividing the wafer into individual chips,
An adhesive tape attaching process for attaching a wafer to an adhesive tape that shields irradiation of a laser beam;
A holding step of holding the adhesive tape side on the chuck table and exposing the wafer;
A dividing step of dividing the wafer while relatively moving the chuck table and the laser beam;
A method for processing a wafer comprising at least The wafer processing method according to claim 1, wherein the adhesive tape includes a glue layer and a sheet, and a metal fine powder is mixed into the glue layer or the sheet to shield a laser beam. The wafer processing method according to claim 2, wherein the fine metal powder includes any one of Al, Au, Cu, Fe, Ti, and Ni. An adhesive tape that is attached to the wafer when the wafer is divided into individual chips by irradiating the wafer with a laser beam having a wavelength that absorbs the wafer,
Adhesive tape that shields laser light irradiation.

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