JP2011044474A - Grinding device for wafer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a grinding device for wafer that never causes a hard wafer such as a sapphire wafer to crack even when the hard wafer is ground to be processed thin. <P>SOLUTION: The grinding device 2 for wafer includes a chuck table 36 capable of rotating while holding the wafer stuck on an adhesive tape having an outer peripheral part mounted an annular frame, and a grinding means configured to rotatably support a grinding wheel having a grindstone 26 for grinding the wafer held by the chuck table. The chuck table includes a suction body 56 having a flat holding surface 58a adapted to suctionally hold the wafer on the adhesive tape and an inclined holding surface 58b such that an outer peripheral side formed on an outer peripheral side of the flat holding surface continuously to the flat holding surface is inclined downward, and a frame having a bottom part enclosing the outer periphery of the suction body except the flat holding surface and inclined holding surface, and also supporting a surface opposite to both the holding surfaces. The suction body is linked to a suction source through a suction path formed at the frame, the frame has a frame fixation part for fixing the annular frame, and a plurality of concentric circular grooves 60 are formed on the inclined holding surface of the suction body. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a wafer grinding apparatus suitable for grinding a hard wafer having a Mohs hardness of 9 or more, such as a sapphire wafer or a silicon carbide wafer.

  A sapphire wafer in which a nitride semiconductor layer such as gallium nitride is stacked on the surface, and an optical device is formed in each region defined by the planned division lines formed in a lattice pattern, is a laser beam along the planned division lines. The optical device is divided into individual optical devices by irradiation, and the divided optical devices are used for electronic devices such as a mobile phone and a digital camera (see, for example, Japanese Patent Application Laid-Open No. 2008-6492).

  Since sapphire wafers are formed by growing a nitride semiconductor layer on a sapphire substrate suitable for epitaxial layer growth, the sapphire substrate is an indispensable material for manufacturing optical devices. After the layers are stacked, the back surface of the sapphire substrate is ground and thinned by a grinding device in order to reduce the weight, size, and improve device characteristics of the electronic device (see, for example, Japanese Patent Application Laid-Open No. 2008-23693). .

JP 2008-6492 A JP 2008-23893 A

  However, when a protective tape made of an adhesive tape is attached to the surface of the sapphire wafer and the back surface of the sapphire wafer is ground to reduce its thickness to 100 μm or less, and further to 50 μm or less, there is a problem that the sapphire substrate is cracked. . Such a problem also occurs when grinding a hard brittle substrate such as a silicon carbide substrate (SiC substrate).

  Considering this cause, it can be inferred that one of the causes is that a large number of micro cracks are generated on the ground surface of the wafer and the substrate warps in a convex shape. When the substrate is warped, the wafer is dragged in the lateral direction during grinding, and the substrate is likely to be cracked.

  The present invention has been made in view of the above points, and the object of the present invention is to provide a wafer that does not cause cracks in a substrate even if a hard brittle substrate such as a sapphire substrate is ground and thinned. A grinding device is provided.

  According to the present invention, there is provided a grinding wheel having a chuck table that holds and rotates a wafer attached to an adhesive tape having an outer peripheral portion attached to an annular frame, and a grinding wheel that grinds the wafer held on the chuck table. A wafer grinding apparatus comprising a grinding means for rotatably supporting the chuck table, wherein the chuck table sucks and holds a wafer on the adhesive tape, and the flat holding surface is continuous with the flat holding surface. A suction body having an inclined holding surface formed on the outer peripheral side of the suction body, and an outer surface excluding the flat holding surface and the inclined holding surface of the suction body, and opposite surfaces of the two holding surfaces. A frame having a bottom portion to be supported, and the suction body communicates with a suction source through the suction path formed in the frame, and the frame is fixed to the frame to fix the annular frame. Has, wafer grinding apparatus in the inclined holding surface of the suction member, characterized in that a concentric plurality of circular grooves are formed is provided.

  According to the grinding apparatus of the present invention, the suction body of the chuck table has a flat holding surface for sucking and holding the wafer, and an inclined holding surface that is inclined downward from the outer periphery of the flat holding surface toward the frame body. Since a plurality of concentric circular grooves are formed on the surface, the adhesive tape between the wafer and the annular frame can be firmly sucked and held by the inclined holding surface, preventing the side slip of the wafer during grinding. The wafer can be ground without causing cracks in the wafer.

1 is an external perspective view of a grinding apparatus according to an embodiment of the present invention. It is a surface side perspective view of a sapphire wafer. It is a back surface side perspective view of a sapphire wafer in the state where a protective tape was stuck on the surface. It is a disassembled perspective view of a chuck table. It is a perspective view of a chuck table. It is a longitudinal cross-sectional view of a chuck table in a state where a sapphire wafer is sucked and held. It is a perspective view which shows the positional relationship of the chuck table and grinding wheel at the time of grinding.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is an external perspective view of a grinding apparatus 2 according to an embodiment of the present invention. Reference numeral 4 denotes a housing (base) of the grinding device 2, and a column 6 is erected on the rear side of the housing 4. A pair of guide rails 8 extending in the vertical direction is fixed to the column 6.

  A grinding unit (grinding means) 10 is mounted along the pair of guide rails 8 so as to be movable in the vertical direction. The grinding unit 10 includes a spindle housing 12 and a support portion 14 that holds the spindle housing 12, and the support portion 14 is attached to a moving base 16 that moves up and down along a pair of guide rails 8. Yes.

  The grinding unit 10 includes a spindle 18 rotatably accommodated in a spindle housing 12, a wheel mount 20 fixed to the tip of the spindle 18, and a plurality of grinding wheels that are screwed to the wheel mount 20 and arranged annularly. A grinding wheel 22 having an electric motor 24 for rotating the spindle 18 is included.

  The grinding apparatus 2 includes a grinding unit moving mechanism 32 including a ball screw 28 that moves the grinding unit 10 in the vertical direction along the pair of guide rails 8 and a pulse motor 30. When the pulse motor 30 is driven, the ball screw 28 rotates and the moving base 16 is moved in the vertical direction.

  A recess 4a is formed on the upper surface of the housing 4, and a chuck table mechanism 34 is disposed in the recess 4a. The chuck table mechanism 34 has a chuck table 36 and is moved in the Y-axis direction between a wafer attaching / detaching position A and a grinding position B facing the grinding unit 10 by a moving mechanism (not shown). 38 and 40 are bellows. On the front side of the housing 4, an operation panel 42 on which an operator of the grinding device 2 inputs grinding conditions and the like is disposed.

  Referring to FIG. 2, a perspective view of the sapphire wafer 11 before being ground to a predetermined thickness is shown. The sapphire wafer 11 is configured by laminating a gallium nitride layer (GaN layer) on a sapphire substrate, and a plurality of streets 13 are formed in a lattice shape on the surface 11a, and a plurality of sections partitioned by the plurality of streets 13 are formed. An optical device 15 such as an LED is formed in the region.

  The sapphire wafer 11 thus configured includes a device region 17 in which the optical device 15 is formed and an outer peripheral surplus region 19 that surrounds the device region 17. A notch 21 is formed on the outer periphery of the sapphire wafer 11 as a mark indicating the crystal orientation of the sapphire substrate.

  Prior to grinding, the surface 11a of the sapphire wafer 11 is stuck on an adhesive tape 46 having an outer peripheral portion attached to an annular frame 44 as shown in FIG. Accordingly, the front surface 11a of the sapphire wafer 11 is protected by the adhesive tape 46, and the back surface 11b is exposed.

  Referring to FIG. 4, an exploded perspective view of the chuck table 36 is shown. FIG. 5 is a perspective view of the chuck table 36. The chuck table 36 includes a frame 50 having a recess 54, and an annular permanent magnet 52 is attached to the upper surface of the outer periphery of the frame 50.

  A suction body 56 made of porous ceramics is fitted into the recess 54 of the frame body 50. As is apparent from the simultaneous reference to FIG. 6, the suction body 56 has a flat holding surface 58 a for sucking and holding the wafer 11 and an inclined holding surface 58 b that is inclined downward from the outer periphery of the flat holding surface 58 a toward the frame body 50. is doing. A plurality of circular grooves 60 formed concentrically are formed on the inclined holding surface 58b.

  The frame 50 is connected to the servo motor 62 via a cylindrical connecting part 64. The suction body 56 fitted in the concave portion 54 of the frame 50 is connected to the suction port 55 formed in the frame 50, the suction path formed in the cylindrical connecting portion 64, the rotary joint 66 and the pipe 68. The suction source 70 is connected.

  As shown in FIG. 6, when the sapphire wafer 11 supported by the annular frame 44 is mounted on the flat holding surface 58 a of the suction body 56 of the chuck table 36 and the suction source 70 is operated, the sapphire wafer 11 has the adhesive tape 46 attached thereto. The annular frame 44 is attracted by the permanent magnet 52 and pulled down and fixed.

  As a result, the adhesive tape 46 between the sapphire wafer 11 and the annular frame 44 is sucked and held by the inclined holding surface 58b, but since the plurality of circular grooves 60 are formed on the inclined holding surface 58b, the sapphire wafer 11 and the annular frame 44 can be firmly sucked and held.

  Hereinafter, a method for grinding the sapphire wafer 11 using the grinding apparatus 2 configured as described above will be described with reference to FIG. In FIG. 7, a wheel mount 20 is fixed to the tip of a spindle 18, and a grinding wheel 22 is detachably attached to the wheel mount 20 by a plurality of screws 25. The grinding wheel 22 is configured by adhering a plurality of grinding wheels 26 to a free end portion of an annular base 24.

  When the sapphire wafer 11 sucked and held by the chuck table 36 is positioned at a grinding position where the grinding wheel 26 of the grinding wheel 22 passes through the rotation axis of the chuck table 36 as shown in FIG. The grinding wheel 22 is rotated in the same direction as the chuck table 36, that is, in the direction of the arrow b, for example, 1000 rpm while rotating in the direction of 500 rpm, for example, and the grinding unit feed mechanism 32 is operated to move the grinding wheel 26 of the sapphire wafer 11. It is made to contact the back surface 11b.

  Then, the sapphire wafer 11 is ground by feeding the grinding wheel 22 downward by a predetermined amount at a predetermined grinding feed rate (for example, 0.1 μm / s). The sapphire wafer 11 is finished to a desired thickness (for example, 50 μm) while measuring the thickness of the sapphire wafer 11 with a contact-type or non-contact-type thickness gauge (not shown).

  As described above, a plurality of concentric circular grooves 60 are formed on the inclined holding surface 58b of the suction body 56 constituting the chuck table 36, and therefore, between the sapphire wafer 11 and the annular frame 44 during grinding. The adhesive tape 46 can be firmly sucked and held, and the sapphire wafer 11 can be thinly ground without preventing the sapphire wafer 11 from slipping and causing the sapphire wafer 11 to crack.

  The grinding device 2 of the embodiment of the present invention is not only suitable for grinding the sapphire wafer 11, but can be similarly applied to grinding a hard wafer having a Mohs hardness of 9 or more such as a silicon carbide wafer.

2 Grinding device 10 Grinding unit 11 Sapphire wafer 22 Grinding wheel 26 Grinding wheel 36 Chuck table 56 Suction body 58a Flat holding surface 58b Inclined holding surface 60 Circular groove

Claims (2)

A chuck table that holds and rotates a wafer attached to an adhesive tape whose outer peripheral portion is attached to an annular frame, and a grinding wheel having a grinding wheel for grinding the wafer held on the chuck table is rotatably supported. A wafer grinding device comprising a grinding means,
The chuck table has a flat holding surface that sucks and holds the wafer on the adhesive tape, and an inclined holding surface that is formed on the outer peripheral side of the flat holding surface and is inclined downward on the outer peripheral side of the flat holding surface. A suction body, and a frame body having a bottom portion that surrounds the outer periphery of the suction body excluding the flat holding surface and the inclined holding surface and supports the opposite surface of the both holding surfaces;
The suction body communicates with a suction source through the suction path formed in the frame body,
The frame has a frame fixing part for fixing the annular frame;
A wafer grinding apparatus, wherein a plurality of concentric circular grooves are formed on the inclined holding surface of the suction body.   2. The wafer grinding apparatus according to claim 1, wherein the wafer comprises a sapphire wafer.

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