JP2011040631A - Method of grinding rigid wafer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of grinding a rigid wafer in which the rigid wafer does not crack even when ground to be processed thin. <P>SOLUTION: The method of grinding the rigid wafer by a grinding device including a chuck table for holding the rigid wafer having a plurality of optical devices formed on a surface and a grinding means of grinding the rigid wafer held on the chuck table includes a wafer supporting step of closing an opening part of an annular frame having the opening part by sticking an adhesive tape on the annular frame while applying tension to the adhesive tape in a radial direction, and sticking a surface side of the rigid wafer on the adhesive tape to support the wafer with the annular frame, a wafer holding step of holding the wafer on the chuck table by bringing the adhesive tape side mounted on the annular frame into contact with a holding surface of the chuck table, and a grinding step of grinding an exposed surface of the wafer held on the chuck table. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method for grinding a hard wafer 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 grind a hard wafer that does not cause cracking of the substrate even if a hard brittle substrate such as a sapphire substrate is ground and thinned. Is to provide.

  According to the present invention, a method for grinding a hard wafer by a grinding apparatus comprising: a chuck table for holding a hard wafer having a plurality of optical devices formed on the surface; and a grinding means for grinding the hard wafer held on the chuck table. The adhesive tape is attached to an annular frame having an opening while applying a radial tension to the adhesive tape to close the opening, and the surface side of the hard wafer is attached to the adhesive tape. A wafer support step for supporting the wafer with the annular frame, a wafer holding step for holding the wafer with the chuck table by bringing the adhesive tape side mounted on the annular frame into contact with the holding surface of the chuck table, and And a grinding process for grinding an exposed surface of the wafer held on the chuck table. Grinding method is provided.

  Preferably, the hard wafer is composed of a sapphire wafer.

  According to the present invention, the wafer is stuck on the adhesive tape to which tension is applied in the radial direction, and the wafer is sucked and held by the chuck table via the adhesive tape to grind the back surface of the wafer. The adhesive tape is not twisted, warping of the wafer can be suppressed, and the wafer can be ground to a desired thickness.

1 is an external perspective view of a grinding apparatus suitable for carrying out the grinding method of the present invention. It is a surface side perspective view of a sapphire wafer. It is explanatory drawing of an adhesive tape sticking process. It is explanatory drawing of a wafer support process. It is a disassembled perspective view which shows a mode that the sapphire wafer supported by the annular frame is mounted in a chuck table. It is sectional drawing of the state which sucked and held the sapphire wafer with the chuck table. 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 shows an external perspective view of a grinding apparatus 2 suitable for carrying out the grinding method 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.

  FIG. 3 shows an explanatory diagram of the adhesive tape attaching process. The base material of the adhesive tape 46 is made of vinyl chloride, polyolefin, or the like, and a glue layer 47 is disposed on the surface thereof. In the adhesive tape adhering step of the present invention, the adhesive tape 46 is closed so as to close the opening 45 in the annular frame 44 having the opening 45 while applying tension to the adhesive tape 46 radially outward as indicated by an arrow A. Adhere. Therefore, a tension toward the radially outer side is applied to the adhesive tape 46 attached to the annular frame 44.

  Referring to FIG. 4, a perspective view showing a state where the surface 11 a of the sapphire wafer 11 is attached to the adhesive tape 46 attached to the annular frame 44 is shown. When the sapphire wafer 11 is attached to the adhesive tape 46, the sapphire wafer 11 is supported by the annular frame 44 through the adhesive tape 46.

  Referring to FIG. 5, there is shown a perspective view showing how the sapphire wafer 11 supported by the annular frame 44 is mounted on the chuck table 36. FIG. 6 shows the sapphire wafer 11 sucked and held by the chuck table 36. It is a longitudinal cross-sectional view of a state.

  The chuck table 36 includes a porous suction portion 48 formed of porous ceramics and the like, and a frame body 50 formed of metal surrounding the porous suction portion 48. An annular permanent magnet 52 is mounted on the outer peripheral surface of the frame 50.

  As best shown in FIG. 6, an inclined portion 54 whose outer peripheral side is inclined downward by a predetermined angle is formed between the porous suction portion 48 of the chuck table 36 and the annular permanent magnet 52 attached to the frame body 50. Has been. The porous suction portion 48 is connected to a suction source (not shown) via a suction path 56 formed in the frame body 50.

  Hereinafter, a method for grinding the sapphire wafer 11 using the grinding device 2 configured as described above will be described. First, the sapphire wafer 11 supported by the annular frame 44 as shown in FIG. 5 is mounted on the chuck table 36 moved to the wafer attachment / detachment position shown in FIG.

  FIG. 6 shows a longitudinal sectional view of the state in which the wafer 11 is attracted and held on the chuck table 36, but the annular frame 44 is attracted to the permanent magnet 52 and is held against the holding surface 48 a of the porous suction portion 48. As a result, the adhesive tape 46 is tensioned radially outward along the inclined portion 54.

  The adhesive tape 46 is originally attached to the annular frame 44 with a tension applied to the outside in the radial direction, and a tension is applied by pulling down the annular frame 44. Therefore, the sapphire wafer 11 applies a tension to the outside in the radial direction. In this state, it is sucked and held by the porous suction portion 48 via the adhesive tape 46.

  Referring to FIG. 7, a wheel mount 20 is fixed to the tip of the spindle 18, and a grinding wheel 22 is detachably attached to the wheel mount 20 with 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 the grinding position shown in FIG. 7, the grinding wheel 22 is rotated in the same direction as the chuck table 36 while rotating the chuck table 36 in the direction of arrow a at 500 rpm, for example. That is, while rotating in the arrow b direction at, for example, 1000 rpm, the grinding unit feeding mechanism 32 is operated to bring the grinding wheel 26 into contact with the back surface 11 b of the sapphire wafer 11.

  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 using a contact-type or non-contact-type thickness measurement gauge (not shown).

  According to the grinding method of the present embodiment, the back surface 11b of the sapphire wafer 11 is ground while applying a tension outward in the radial direction to the adhesive tape attached to the surface 11a of the sapphire wafer 11, so that the sapphire wafer 11 is Since the warp of the sapphire wafer 11 can be suppressed without twisting the adhesive tape 46 during grinding, the sapphire wafer 11 can be ground to a desired thickness.

  In the embodiment described above, an example in which the present invention is applied to grinding of a sapphire wafer has been described. However, the present invention is not limited to this, and similarly to a hard wafer having a Mohs hardness of 9 or more such as a silicon carbide wafer. Applicable.

2 Grinding device 10 Grinding unit 11 Sapphire wafer 22 Grinding wheel 26 Grinding wheel 36 Chuck table 44 Annular frame 46 Adhesive tape 48 Porous suction part 52 Permanent magnet 54 Inclined part

Claims (2)

A method for grinding a hard wafer by a grinding apparatus comprising: a chuck table for holding a hard wafer having a plurality of optical devices formed on a surface; and a grinding means for grinding the hard wafer held on the chuck table,
The adhesive tape is stuck to an annular frame having an opening while applying a radial tension to the adhesive tape to close the opening, and the surface side of a hard wafer is stuck on the adhesive tape to attach the wafer. A wafer support process for supporting with an annular frame;
A wafer holding step of holding the wafer by the chuck table by bringing the adhesive tape side mounted on the annular frame into contact with the holding surface of the chuck table;
A grinding step of grinding the exposed surface of the wafer held by the chuck table;
A method for grinding a hard wafer, comprising:   2. The method for grinding a hard wafer according to claim 1, wherein the hard wafer is composed of a sapphire wafer.

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