JP2011044475A - Grinder for wafer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a grinder for a wafer capable of preventing cracks from being generated, even if grinding a hard wafer, such as a sapphire wafer, which is to be worked thin. <P>SOLUTION: The grinder for the wafer includes a chuck table rotatable while holding the wafer, and a grinding means for rotatably supporting a grinding wheel having a grinding stone for grinding the wafer held by the chuck table; the chuck table includes a suction plate having a holding face for suction-holding the wafer, and a frame body for surrounding a portion other than the holding face of the suction plate; the chuck table is communicated with a suction source via a suction route formed in the frame body; the suction plate is formed of a porous ceramic exposed, on the holding face, with a plurality of pores and a partitioning wall for partitioning the pores; and an irregular shape is formed on an exposed face of the partitioning wall. <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 grind a 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 a device.

  According to the present invention, there is provided a wafer grinding apparatus comprising: a chuck table that holds and rotates a wafer; and a grinding means that rotatably supports a grinding wheel having a grinding wheel for grinding the wafer held on the chuck table. The chuck table includes a suction plate having a holding surface for sucking and holding the wafer, and a frame body that surrounds a portion other than the holding surface of the suction plate, and the chuck table includes a suction plate formed on the frame body. The suction plate communicates with a suction source through a path, and the suction plate is formed of porous ceramics with a plurality of pores and a partition wall separating the pores exposed on the holding surface, and unevenness is formed on the exposed surface of the partition wall. A wafer grinding apparatus is provided.

  Preferably, the unevenness formed on the exposed surface of the partition wall is formed with a height difference of at least 10 μm. These irregularities are formed by either sandblasting, water jet, or grindstone grinding.

  According to the grinding apparatus of the present invention, the suction plate constituting the chuck table is formed of porous ceramics, and the plurality of irregularities are formed on the exposed surface of the partition wall exposed on the holding surface of the suction plate. Side slip can be prevented, and 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 perspective view of a chuck table. FIG. 5A is a schematic diagram of the surface state of a conventional suction plate, and FIG. 5B is a schematic diagram of the surface state of the suction plate of the present invention. 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 protective tape 23 is attached to the surface 11a of the sapphire wafer 11 by a protective tape attaching process. Therefore, the front surface 11a of the sapphire wafer 11 is protected by the protective tape 23, and the back surface 11b is exposed as shown in FIG.

  Referring to FIG. 4, a perspective view of the chuck table 36 is shown. The chuck table 36 includes a frame body 46 made of a metal such as SUS, and a suction plate 48 fitted in a recess of the frame body 46. As shown in the enlarged view of the suction plate 48, the suction plate 48 is formed of porous ceramics in which a plurality of pores 49 and partition walls 51 that partition these pores 49 are exposed on the suction surface.

  The frame body 46 of the chuck table 36 is connected to a servo motor 52 through a cylindrical connecting portion 50. The suction plate 48 fitted in the recess of the frame body 46 includes a suction port formed in the frame body 46, a suction path formed in the cylindrical connecting portion 50, a rotary joint 54, and a duct 56. 58.

  As shown in FIG. 5A, a plurality of pores 49 and partition walls 51 that partition these pores 49 are exposed on the holding surface of the conventional suction plate 48, and the exposed surfaces of the partition walls 51 are substantially flat. Is formed. Thus, if the exposed surface of the partition wall 51 is formed to be substantially flat, there is a risk that the side slip of the wafer may occur during wafer grinding.

  Therefore, in the present invention, as shown in FIG. 5 (B), a plurality of irregularities 53 are supported on the exposed surface of the partition wall 51. The unevenness 53 can be formed by grinding the holding surface of the suction plate 48 with a grinding wheel having coarse abrasive grains. Alternatively, the unevenness 53 may be formed by hitting the holding surface of the suction plate 48 by sandblasting or by spraying a water jet that jets water mixed with abrasive grains onto the holding surface of the suction plate 48. Preferably, the unevenness 53 formed on the exposed surface of the partition wall 51 is formed with a height difference of at least 10 μm.

  Referring to FIG. 6, 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 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 the grinding position shown in FIG. 6, 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 direction of the arrow b 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 apparatus of the present embodiment, the suction plate 48 constituting the chuck table 36 is formed of porous ceramics, and the plurality of irregularities 53 are formed on the exposed surface of the partition wall 51 exposed on the holding surface of the suction plate 48. Since the resistance of the holding surface of the suction plate 48 increases during grinding and the sapphire wafer 11 can be prevented from slipping, the sapphire wafer 11 can be ground without causing cracks in the sapphire wafer 11.

  The grinding device 2 of the above-described embodiment 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 48 suction plate 49 pore 51 partition wall 53 uneven

Claims (4)

A wafer grinding apparatus comprising: a chuck table that holds a wafer and is rotatable; and a grinding means that rotatably supports a grinding wheel having a grinding wheel for grinding the wafer held on the chuck table.
The chuck table includes a suction plate having a holding surface for sucking and holding the wafer, and a frame body that surrounds other than the holding surface of the suction plate,
The chuck table is communicated to a suction source through a suction path formed in the frame,
The suction plate is formed of porous ceramics in which a plurality of pores and partition walls partitioning the pores are exposed on the holding surface, and an uneven surface is formed on the exposed surface of the partition wall. Grinding equipment.   2. The wafer grinding apparatus according to claim 1, wherein the irregularities are formed with a height difference of at least 10 [mu] m.   3. The wafer grinding apparatus according to claim 1, wherein the unevenness formed on the exposed surface of the partition wall is formed by sand blasting, water jet, or grinding of a grindstone.   The wafer grinding apparatus according to claim 1, wherein the wafer is composed of a sapphire wafer.

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