JP5841738B2 - Wafer grinding method - Google Patents

Description

  The present invention relates to a method of grinding a back surface of a wafer in which a light emitting layer is laminated on the surface of a sapphire substrate and a chamfered portion is formed at least on the outer periphery on the front surface side.

  A wafer formed by laminating an n-type semiconductor layer and a p-type semiconductor layer on the surface of a sapphire substrate by epitaxial growth and forming a plurality of light-emitting devices in a region partitioned by the planned dividing lines is divided into the planned dividing lines by a laser processing apparatus. By being irradiated with laser light, it is divided into individual optical devices and used for lighting equipment, liquid crystal backlights, various electronic equipment, and the like (see, for example, Patent Document 1).

  About the wafer comprised in this way, in order to improve the brightness | luminance of an optical device, the back surface of a wafer is ground and it is thinned until the thickness of about 700 micrometers initially becomes about 100 micrometers.

  At the time of grinding the back surface of the wafer, the surface of the wafer is protected by adhering the surface of the wafer to a hard substrate formed of polyethylene terephthalate (PET) or the like via an acrylic adhesive or the like (for example, patent document) 2).

JP-A-10-305420 JP 2010-46744 A

  However, since the sapphire substrate has high hardness and the outer periphery on the front side of the wafer is chamfered, the back surface of the wafer is ground, and when the thickness reaches, for example, about 150 μm, the outer periphery of the wafer is chamfered. Since the portion flutters, there is a problem that cracks occur inside the wafer.

  The present invention has been considered in view of such a problem, and in the case of grinding the back surface of a wafer whose semiconductor layer is formed on the surface of the sapphire substrate and whose outer periphery is chamfered, it is intended to prevent internal cracking. Objective.

The present invention relates to a wafer grinding method for grinding a back surface of a wafer in which a light emitting layer is laminated on the surface of a sapphire substrate and a chamfered portion is formed at least on the outer periphery on the front surface side. A resin filling process for filling the gap between at least the hard substrate and the chamfered portion of the wafer with a resin, and after the resin is solidified, the hard substrate side is held on the wafer by holding the hard substrate side on a rotatable chuck table. to expose the back surface, at least composed of a back-grinding step of grinding the back surface is brought into contact with the back surface so as to pass the grinding wheel rotation center of the wafer by rotating the grinding wheel with the grinding wheel to the annular, the resin abrasive Grain is mixed in and prevents clogging of the grinding wheel in the back grinding process .

  In the back surface grinding process, the back surface of the wafer is ground up to the chamfered portion.

  In the present invention, the resin is filled in the gap between the hard substrate and the chamfered portion of the wafer, and the back surface of the wafer is ground in that state, so that the chamfered portion does not flutter and the inside of the wafer is prevented from cracking. can do.

  In addition, by mixing abrasive grains into the resin that fills the gap between the hard substrate and the chamfered portion of the wafer, the abrasive grains prevent clogging of the grinding stone because the resin prevents the resin from entering the grinding stone. Can be prevented.

It is a front view which shows a part of example of a wafer. It is a perspective view which shows an example of a wafer. It is a perspective view which shows the state which faced the surface of the wafer to the hard substrate. It is a perspective view which shows the state which affixed the wafer on the hard board | substrate. It is sectional drawing which shows schematically the state which filled the clearance gap between the hard substrate and the chamfering part of the surface of a wafer with resin. It is a perspective view which shows an example of a grinding device. It is a perspective view which shows the state which makes a chuck table hold | maintain a hard board | substrate. It is a perspective view which shows the state which grinds the back surface of a wafer. It is sectional drawing which shows schematically a part of wafer after the back surface is ground.

  A wafer 1 shown in FIG. 1 is formed by laminating a light emitting layer 11 on the surface of a sapphire substrate 10, and a chamfered portion 12 is formed at least on the outer periphery on the surface 1a side to prevent chipping. . In the example of FIG. 1, the chamfered portion 13 is also formed on the outer periphery of the back surface 1b. The wafer 1 has a thickness of, for example, 700 μm as a whole, and the chamfered portions 12 and 13 are chamfered, for example, by a thickness of 100 μm.

  As shown in FIG. 2, on the surface 1a of the wafer 1, division lines L are formed vertically and horizontally, and an optical device D is formed in a region defined by the division lines L. Below, the procedure which grind | polishes 1 back surface 1b comprised in this way and forms in desired thickness is demonstrated.

(1) Resin Filling Step As shown in FIG. 3, the surface 2 a of the hard substrate 2 and the surface 1 a of the wafer 1 face each other, and the wafer 1 is adhered on the hard substrate 2 as shown in FIG. 4. The hard substrate 2 is made of a material that has a hardness that can support the wafer 1 when the back surface 1b of the wafer 1 is ground and that is flexible and can be easily peeled off after grinding, such as polyethylene terephthalate (PET). To do.

  For example, an acrylic adhesive having a thickness of 5 μm is applied to the surface 2 a of the hard substrate 2, and the wafer 1 is fixed to the hard substrate 2 through the adhesive. The hard substrate 2 is formed to have a larger diameter than the wafer 1, and the peripheral edge of the surface 2a of the hard substrate 2 is exposed.

  With the wafer 1 fixed to the hard substrate 2, the resin 3 is filled in the gap between the hard substrate 2 and the chamfered portion 12 of the surface 1 a of the wafer 1 as shown in FIG. 5. As the resin 3, for example, epoxy resin or polybutadiene is used. The resin 3 desirably has a heat softening property in order to facilitate peeling from the wafer 1 later. In order to prevent clogging of the grinding wheel, alumina abrasive grains having a particle diameter of 1 μm are included in the resin 3 in a volume ratio of 30 to 40%. Green carborundum may be used instead of alumina.

(2) Back surface grinding step After the resin 3 is solidified, the back surface 1b of the wafer 1 fixed to the hard substrate 2 is ground. For grinding the back surface 1b, for example, a grinding device 4 shown in FIG. 6 can be used. The grinding apparatus 4 holds a workpiece and can rotate the chuck table 5, the grinding means 6 for grinding the workpiece held on the chuck table 5, and the grinding means 6 are ground and fed in the vertical direction. And a grinding feed means 7.

  The periphery of the chuck table 5 is covered with a cover 50, and a telescopic bellows 51 is connected to a side portion of the cover 50 in the front-rear direction. The chuck table 5 is configured to move in the front-rear direction with the expansion and contraction of the bellows 51.

  The grinding means 6 acts on the wafer 1 held on the chuck table 5 to perform grinding processing, a mount 61 that supports the grinding wheel 60, and a rotation that supports the mount 61 at the tip and extends in the vertical direction. A shaft 62, a housing 63 that rotatably supports the rotating shaft 62, and a drive unit 64 that rotationally drives the rotating shaft 62 are provided.

  The grinding wheel 60 is configured such that a grinding wheel 601 is fixed in an annular shape on the lower surface of a base 600. The base 600 is fixed to the mount 61 by screws. The grinding wheel 601 is constituted by solidifying diamond abrasive grains having a particle diameter of 20 to 30 μm with vitrified bonds.

  The grinding feed means 7 includes a ball screw 70 having a vertical axis, a pair of guide rails 71 arranged in parallel to the ball screw 70, a pulse motor 72 for rotating the ball screw 70, and a ball screw 70. And an elevating part 73 whose side part is in sliding contact with the guide rail 71 and is driven by the pulse motor 72 to rotate the ball screw 71. The elevating part 73 is guided by the guide rail 71 and is moved up and down. Since the support part 74 fixed to the raising / lowering part 73 is supporting the grinding means 6, it has the structure which the grinding means 6 also raises / lowers by raising / lowering of the raising / lowering part 73. FIG.

  In the grinding device 4 configured as described above, as shown in FIG. 7, the chuck table 5 holds the hard substrate 2 side and the back surface 1 b of the wafer 1 is exposed. Then, the chuck table 5 moves to the rear side of the apparatus, and the wafer 1 is positioned below the grinding means 6.

  Next, while rotating the chuck table 5 at, for example, 600 RPM, and rotating the grinding wheel 60 in the same direction as the chuck table 5 at, for example, 1000 RPM, the grinding means 6 is controlled at, for example, 1.0 μm / second by control by the grinding feed means 7. The back surface 1 b is ground by lowering at a feed rate and bringing the rotating grinding wheel 601 into contact with the back surface 1 b of the wafer 1. At this time, the grinding wheel 601 is controlled to pass through the rotation center of the wafer 1 as shown in FIG. During grinding, 4 l / min of grinding water is supplied to the contact portion between the grinding wheel 601 and the back surface 1b of the wafer 1.

  As shown in FIG. 9, the grinding surface 1b ′ is formed by grinding 600 μm from the back surface 1b, the grinding wheel 601 reaches the chamfered portion 12 of the front surface 1a, and when the thickness of the wafer 1 becomes 100 μm, the grinding feeding means 7 The grinding is finished by raising the grinding means 6.

  Since the resin 3 is filled in the gap between the chamfered portion 12 and the hard substrate 2, the chamfered portion 12 does not flutter during grinding. Therefore, it is possible to prevent cracks from occurring inside the wafer due to flapping of the chamfered portion 12.

  Further, the grinding wheel 601 also grinds the resin 3 in order to perform grinding up to the chamfered portion 12. Normally, clogging of the grinding wheel 601 is likely to occur when the resin is ground, but since the abrasive grains are mixed in the resin 3, the abrasive particles are prevented from entering the grinding wheel 601. Therefore, the grinding wheel 601 is not easily clogged.

1: Wafer 1a: Front surface 1b: Back surface L: Line to be divided D: Optical device 10: Sapphire substrate 11: Light emitting layer 12, 13: Chamfered portion 2: Hard substrate 2a: Front surface 3: Resin 4: Grinding device 5: Chuck table 50: Cover 51: Bellows 6: Grinding means 60: Grinding wheel 600: Base 601: Grinding wheel 61: Mount 62: Rotating shaft 63: Housing 64: Drive unit 7: Grinding feed means 70: Ball screw 71: Guide rail 72 : Pulse motor 73: Elevating part 74: Support part

Claims (2)

A wafer grinding method for grinding a back surface of a wafer in which a light emitting layer is laminated on a surface of a sapphire substrate and a chamfered portion is formed at least on the outer periphery on the surface side,
A resin filling step in which the surface of the wafer faces the surface of the hard substrate supporting the wafer, and at least a gap between the hard substrate and the chamfered portion of the wafer is filled with a resin;
After the resin is solidified, the hard substrate side is held on a rotatable chuck table to expose the back surface of the wafer, and a grinding wheel having a grinding wheel in an annular shape is rotated so that the center of rotation of the wafer is the grinding wheel. A back grinding step of grinding the back surface in contact with the back surface so as to pass through ,
A method for grinding a wafer, wherein abrasive grains are mixed in the resin, and clogging of the grinding wheel is prevented in the back grinding step . The wafer grinding method according to claim 1, wherein the back surface of the wafer is ground to the chamfered portion in the back surface grinding step.

Images