JP2012151410A - Grinding method of hard substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a grinding method for a hard substrate which can be ground without damaging the hard substrate.
A method for grinding a hard substrate, comprising: a holding step of holding a hard substrate on a holding surface of a chuck table; and a grinding wheel is operated from an upper surface of the hard substrate held on the chuck table by operating a grinding feed means. A grinding means positioning step for positioning the grinding means so that the grinding surface is slightly below, and a movement for rotating the grinding wheel and operating the positioning means to move the chuck table to the grinding position while rotating the chuck table. A grinding process for operating the grinding feed means to grind the hard substrate held on the chuck table at a predetermined grinding feed speed, and a grinding end detection for terminating the grinding when the hard substrate reaches a desired thickness And a process.
[Selection] Figure 5

Description

  The present invention relates to a method for grinding a hard substrate such as a sapphire substrate or a SiC substrate.

  A street in which a semiconductor layer (epitaxial layer) such as gallium nitride (GaN) is formed on the surface of a sapphire substrate, SiC substrate, etc., and a plurality of optical devices such as LEDs are formed in a lattice shape on the semiconductor layer (division planned line) Since the optical device wafer formed by dividing the optical device wafer is relatively high in Mohs hardness and difficult to divide by a cutting blade, it is divided into individual optical devices by laser beam irradiation. It is used for electric devices such as personal computers (see, for example, Japanese Patent Application Laid-Open No. 2008-6492).

  A sapphire substrate is suitable for the growth of epitaxial layers and is an indispensable material for manufacturing optical devices, but after the epitaxial layer has grown, it is necessary to reduce the weight and size of electrical equipment and improve the brightness of optical devices. Next, the back surface of the sapphire substrate is ground by a grinding device (for example, Japanese Patent Application Laid-Open No. 2008-23693).

  The grinding device is capable of rotating a grinding wheel having a holding surface for holding a workpiece and a rotatable chuck table, and a grinding wheel provided with an annular grinding wheel for grinding the workpiece held on the chuck table. It comprises at least grinding means for supporting and grinding feed means for moving the grinding means toward and away from the chuck table, so that a plate-like workpiece can be ground to a desired thickness.

JP 2008-6492 A JP 2008-23893 A

  However, since hard substrates such as sapphire substrates and SiC substrates have high Mohs hardness and the back surface is formed in a mirror surface, the grinding wheel with diamond abrasive grains as the main component does not allow sliding grinding on the back surface of the hard substrate, There is a problem that the hard substrate is damaged by the pressure of the grinding feed.

  This invention is made | formed in view of such a point, The place made into the objective is to provide the grinding method of the hard board | substrate which can be ground without damaging a hard board | substrate.

  According to the present invention, a rotatable chuck table having a holding surface for holding a workpiece, and a grinding wheel in which a grinding wheel for grinding the workpiece held on the chuck table is arranged in an annular shape can be rotated. Grinding means for supporting the workpiece, grinding water supply means for supplying grinding water, positioning means for positioning the chuck table at a loading / unloading position for loading / unloading the workpiece and a grinding position for grinding the workpiece, and the grinding By a grinding apparatus provided with grinding feed means for grinding and feeding the means relative to the chuck table to approach and separate, and thickness detecting means for detecting the thickness of the workpiece held on the chuck table, A method for grinding a hard substrate, comprising: a holding step for holding a hard substrate on a holding surface of the chuck table; A grinding means positioning step for positioning the grinding means so that the grinding surface of the grinding wheel is slightly below the upper surface of the hard substrate held by the bull, and the chuck is operated by rotating the grinding wheel and operating the positioning means A moving step of moving the chuck table to the grinding position while rotating the table, a grinding step of operating the grinding feed means to grind the hard substrate held by the chuck table at a predetermined grinding feed rate, There is provided a grinding method of a hard substrate, comprising: a grinding end detecting step of finishing grinding when the substrate reaches a desired thickness.

  According to the grinding method of the present invention, when grinding a hard substrate, the grinding means is positioned so that the grinding surface of the grinding wheel is slightly below the upper surface of the hard substrate held by the chuck table by operating the grinding feed means. Since the chuck table is moved to the grinding position while rotating the chuck table, the surface to be ground of the hard substrate is roughened by the grinding wheel. Therefore, the biting of the grinding wheel at the start of the grinding process becomes good, and grinding can be started without the grinding wheel sliding on the back surface of the hard substrate.

It is a perspective view of a grinding device suitable for carrying out the grinding method of the present invention. It is a perspective view of a chuck table unit and a chuck table feed mechanism. It is a perspective view which shows a mode that a protective tape is stuck on the surface of an optical device wafer. It is a disassembled perspective view which shows a holding process. It is a partial cross section side view which shows a grinding means positioning process. It is a partial cross section side view explaining a movement process. It is a partial cross section side view which shows a grinding process. It is a perspective view which shows a grinding process.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 shows a perspective view of a grinding apparatus 2 suitable for carrying out the grinding method of the present invention. The housing 4 of the grinding device 2 includes a base 6 and a column 8 rising vertically from the base 6.

  A pair of guide rails 12 and 14 extending in the vertical direction are fixed to the column 8. A grinding means (grinding unit) 16 is mounted along the pair of guide rails 12 and 14 so as to be movable in the vertical direction. The grinding unit 16 is attached to a moving base 18 that moves up and down along a pair of guide rails 12 and 14 via a support portion 20.

  The grinding unit 16 includes a spindle housing 22 attached to the support portion 20, a spindle 24 rotatably accommodated in the spindle housing 22, and a servo motor 26 that rotationally drives the spindle 24.

  As shown in FIG. 5, a mounter 28 is fixed to the tip of the spindle 24, and a grinding wheel 30 is screwed to the mounter 28. The grinding wheel 30 is configured by fixing a plurality of grinding wheels 34 in which diamond abrasive grains having a particle diameter of 5 to 10 μm are hardened by vitrified bonds to a free end portion of a wheel base 32.

  Grinding water is supplied to the grinding means (grinding unit) 16 via a hose 36. Preferably, pure water is used as the grinding water. As shown in FIGS. 5 to 7, the grinding water supplied from the hose 36 is supplied to the grinding water supply hole 38 formed in the spindle 24, the space 40 formed in the mounter 28, and the wheel base 32 of the grinding wheel 30. It is supplied to the wafer 11 held on the grinding wheel 34 and the chuck table 54 via the plurality of formed grinding water supply nozzles 42.

  Referring to FIG. 1 again, the grinding apparatus 2 includes a grinding unit feeding mechanism (grinding feeding means) 44 that moves the grinding unit 16 in the vertical direction along the pair of guide rails 12 and 14. The grinding unit feed mechanism 44 includes a ball screw 46 and a pulse motor 48 fixed to one end of the ball screw 46. When the pulse motor 48 is pulse-driven, the ball screw 46 rotates and the moving base 18 is moved in the vertical direction via the nut of the ball screw 46 fixed inside the moving base 18.

  A chuck table unit 50 is disposed in the recess 10 of the base 6. As shown in FIG. 2, the chuck table unit 50 includes a support base 52 and a chuck table 54 that is rotatably disposed on the support base 52. The chuck table unit 50 further includes a cover 56 having a hole through which the chuck table 54 is inserted.

  The chuck table 54 is moved in the Y-axis direction by a chuck table moving mechanism 58 between a loading / unloading position on the front side of the apparatus for loading / unloading the wafer 11 and a grinding position on the back side of the apparatus that receives the action of the grinding means 16. . The chuck table moving mechanism 58 includes a ball screw 60 and a pulse motor 64 connected to one end of a screw shaft 62 of the ball screw 60.

  When the pulse motor 64 is pulse-driven, the screw shaft 62 of the ball screw 60 rotates, and the support base 52 having a nut screwed to the screw shaft 62 moves in the front-rear direction (Y-axis direction) of the grinding device 2. Therefore, the chuck table 54 also moves in the Y-axis direction according to the rotation direction of the pulse motor 64.

  A thickness detecting means 94 for detecting the thickness of the wafer 11 held on the chuck table 54 is disposed adjacent to the chuck table 54. The detection needle (probe) 96 of the thickness detecting means 94 is rotated between a detection position that comes into contact with the grinding surface of the wafer 11 held on the chuck table 54 and a retreat position that is away from the chuck table 54.

  As shown in FIG. 1, the pair of guide rails 66 and 68 and the chuck table moving mechanism 58 shown in FIG. 2 are covered with bellows 70 and 72. That is, the front end portion of the bellows 70 is fixed to the front wall that defines the recess 10, and the rear end portion is fixed to the front end surface of the cover 56. Further, the rear end of the bellows 72 is fixed to the column 8, and the front end thereof is fixed to the rear end surface of the cover 56.

  The base 6 includes a first wafer cassette 74, a second wafer cassette 76, a wafer transfer robot 78, a wafer temporary table 80 having a plurality of positioning pins 81, a wafer carry-in means 82, and a wafer carry-out means. 84 and cleaning means 86 are disposed. Further, an operation means 88 is provided in front of the housing 4 for an operator to input grinding conditions and the like.

  A cleaning water spray nozzle 90 that cleans the chuck table 54 is provided at the approximate center of the base 6. The cleaning water jet nozzle 90 ejects cleaning water toward the wafer after grinding held by the chuck table 54 in a state where the chuck table 54 is positioned at the wafer loading / unloading position. The concave portion 10 of the base 6 is provided with a drain port 92 for draining the grinding water containing the grinding scraps of the wafer 11 ground by the grinding wheel 32.

  Referring to FIG. 3, a perspective view of an optical device wafer 11 which is a grinding object of the grinding method of the present invention is shown. The optical device wafer 11 is configured by laminating an epitaxial layer (semiconductor layer) 15 such as gallium nitride (GaN) on a sapphire substrate 13. The optical device wafer 11 has a front surface 11a on which an epitaxial layer 15 is stacked and a back surface 11b on which the sapphire substrate 13 is exposed.

  The sapphire substrate 13 before the grinding process has a thickness of 1300 μm, for example, and the epitaxial layer 15 has a thickness of 5 μm, for example. In the epitaxial layer 15, an optical device 19 such as an LED is partitioned and formed by dividing lines (streets) 17 formed in a lattice shape.

  Prior to grinding of the back surface of the optical device wafer 11, that is, grinding of the sapphire substrate 13, a protective tape 23 is applied to the surface 11 a of the optical device wafer 11 in order to protect the optical device 19 formed on the surface 11 a of the optical device wafer 11. Is pasted.

  Therefore, in the grinding method of the present invention, as shown in FIG. 4, the optical device wafer 11 is sucked and held by the holding surface 54a of the chuck table 54 positioned at the wafer loading / unloading position with the protective tape 23 facing down. Therefore, the sapphire substrate 13 is exposed in the held state.

  Next, the pulse motor 48 of the grinding unit feed mechanism 44 is driven, and as shown in FIG. 5, the grinding surface of the grinding wheel 34 is a slight distance h from the upper surface of the sapphire substrate 13 held on the chuck table 54, for example, 5 μm. A grinding means positioning step of positioning the grinding means 16 so as to be below is performed.

  Next, the chuck table moving mechanism 58 is actuated to move the chuck table 54 in the Y-axis direction while rotating the chuck table 54, and the moving step of positioning at the grinding position shown in FIG. 6 is performed. The feed rate of the chuck table 54 in this moving process is, for example, 200 mm / s. If the diameter of the optical device wafer 11 is 100 mm, the grinding position shown in FIG. 6 after the grinding wheel 34 contacts the outer periphery of the sapphire substrate 13. Will have 0.25 seconds to be sent.

  This moving step is performed while rotating the chuck table 54 in the direction of arrow a at 750 rpm and supplying grinding water while rotating the grinding wheel 30 in the direction of arrow b at 1300 rpm.

  After the grinding wheel 34 abuts the outer periphery of the sapphire substrate 13, the tip of the grinding wheel 34 bites into the surface of the sapphire substrate 13 while the chuck table 54 is sent to the grinding position shown in FIG. The chuck table 54 rotates about three times. Therefore, by implementing this moving process, the surface to be ground of the sapphire substrate 13 becomes rough.

  Next, as shown in FIG. 7, the detection needle 96 of the thickness detecting means 94 is rotated to the detection position to contact the sapphire substrate 13, and the chuck table 54 is rotated at 750 rpm in the direction of arrow a while supplying grinding water. While rotating the grinding wheel 30 in the direction of arrow b at 1300 rpm, the grinding unit feed mechanism 44 is driven to grind the grinding wheel 30 downward at a predetermined grinding feed speed, for example, 3 μm / s, while the grinding wheel 34 Then, the sapphire substrate 13 is ground.

  At the start of grinding, the back surface of the sapphire substrate 13 is roughened by the grinding wheel 34 by the moving process. Therefore, when the grinding stone 34 is brought into contact with the sapphire substrate 13 at a predetermined grinding feed speed, the biting becomes good, and the grinding wheel 34 Grinding is performed without sliding on the back surface of the sapphire substrate 13.

  The detection needle 96 of the thickness detection means 94 is brought into contact with the surface to be ground of the sapphire substrate 13 to perform grinding of the sapphire substrate 13, and the grinding is finished when the thickness of the optical device wafer 11 becomes 150 μm.

  When grinding the sapphire substrate 13, as shown in FIG. 8, a ground trace showing a pattern in which a large number of arcs are radially drawn on the back surface 11 b of the optical device wafer 11, that is, the surface to be ground of the sapphire substrate 13. 25 remains.

  In the above-described embodiment, the example in which the present invention is applied to grinding of the sapphire substrate 13 has been described. However, the present invention is not limited to this, and can be similarly applied to other hard substrates such as SiC substrates. is there.

  According to the embodiment described above, when grinding the sapphire substrate 13, the grinding unit feed mechanism 44 is operated so that the grinding surface of the grinding wheel 34 is slightly below the upper surface of the sapphire substrate 13 held on the chuck table 54. With the grinding means 16 positioned, the chuck table 54 is moved to the grinding position while rotating, so that the surface of the sapphire substrate 13 to be ground is roughened.

  Therefore, at the start of the grinding process that is carried out while feeding the grinding means 16 at a predetermined grinding feed speed, the grinding wheel 34 can be satisfactorily engaged with the sapphire substrate 13, and the grinding wheel 34 should slide on the back surface of the sapphire substrate 13. Thus, the sapphire substrate 13 can be ground.

2 Grinding device 11 Optical device wafer 13 Sapphire substrate 15 Epitaxial layer 16 Grinding unit 19 Optical device 30 Grinding wheel 34 Grinding wheel 54 Chuck table 94 Thickness detecting means

Claims (2)

Grinding means for rotatably supporting a grinding wheel in which a chuck table having a holding surface for holding a workpiece and rotatable and a grinding wheel for grinding the workpiece held on the chuck table are arranged in an annular shape. Grinding water supply means for supplying grinding water, positioning means for positioning the chuck table at a loading / unloading position for loading / unloading the workpiece and a grinding position for grinding the workpiece, and the grinding means for the chuck table A hard substrate is ground by a grinding apparatus comprising a grinding feed means for relatively approaching and moving away from the workpiece and a thickness detecting means for detecting the thickness of the workpiece held on the chuck table. A method of grinding a hard substrate,
A holding step of holding the hard substrate on the holding surface of the chuck table;
A grinding means positioning step of positioning the grinding means so that the grinding surface of the grinding wheel is slightly below the upper surface of the hard substrate held by the chuck table by operating the grinding feed means;
Rotating the grinding wheel and moving the chuck table to the grinding position while operating the positioning means and rotating the chuck table;
A grinding step of operating the grinding feed means to grind the hard substrate held on the chuck table at a predetermined grinding feed speed;
A grinding end detection step for finishing grinding when the hard substrate reaches a desired thickness;
A method for grinding a hard substrate, comprising:   The hard substrate grinding method according to claim 1, wherein the hard substrate is composed of a sapphire substrate or a SiC substrate.

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