JP2012223863A - Grinding method of hard substrate coated with metal film on surface - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a grinding method of a hard substrate by which the hard substrate coated with a metal film on a surface is ground, thereby the metal film is removed.SOLUTION: The grinding method of the hard substrate includes: a holding step of holding a rear face of the hard substrate to expose the metal film; a metal film grinding step of rotating a chuck table, feeding a grinding wheel to perform grinding while rotating the grinding wheel and grinding the metal film with which the surface of the hard substrate held on the chuck table has been coated; and a hard substrate grinding step of forming the hard substrate into a prescribed thickness by grinding continuously the hard substrate exposed by grinding the metal film. The metal film grinding step includes a separating step of separating the grinding wheel from the metal film when the load current value of a motor that drives the grinding wheel increases exceeding the prescribed value, and a contact step of grinding the metal film by bringing the grinding wheel into contact with the metal film again. The separation step and contact step are repeatedly performed to grind and remove the metal film.

Description

  The present invention relates to a method for grinding a hard substrate such as a SiC substrate having a metal film coated on its surface.

  SiC wafers, sapphire wafers, etc. on which a plurality of optical devices such as LEDs (light emitting diodes) and LDs (laser diodes) are formed on the front surface are ground to a predetermined thickness and then split into splitting devices such as laser processing devices Are divided into individual optical devices, and the divided optical devices are widely used in electrical devices such as television backlights, mobile phones, and personal computers.

  A grinding apparatus for grinding a back surface of a wafer includes a chuck table for holding a wafer, a grinding means for rotatably supporting a grinding wheel in which a grinding wheel for grinding the wafer held on the chuck table is annularly arranged, and grinding. A grinding feed means for bringing a grindstone into and out of contact with a wafer is generally configured, and the wafer can be ground to a desired thickness (see, for example, JP-A-2004-322247).

  By the way, a SiC wafer is disposed on a substrate having a diameter larger than that of the SiC wafer, and a hard substrate such as a SiC wafer in which a metal film such as titanium is coated on the surface of the SiC wafer is ground with a grinding wheel. There is a desire to grind the SiC wafer to such an extent that the metal film coated on the surface is removed and the metal film coated on the surface of the substrate is not reached.

JP 2004-322247 A

  However, when grinding a hard substrate such as a SiC wafer having such a metal film on the surface, the metal film is softened due to frictional heat, and accordingly, the grinding resistance increases and the grinding ability decreases, making grinding difficult. There is a problem of becoming.

  The present invention has been made in view of these points, and the object of the present invention is to remove a metal film by grinding a hard substrate such as SiC or sapphire whose surface is coated with a metal film, and further It is an object of the present invention to provide a hard substrate grinding method for grinding a substrate to a desired thickness.

  According to the present invention, there is provided a method of grinding a hard substrate having a surface coated with a metal film to a predetermined thickness, wherein the metal film is exposed by holding the back surface of the hard substrate with a chuck table of a grinding device. A holding step for rotating the chuck table holding the hard substrate, and positioning the grinding wheel so that the grinding wheel of the grinding wheel in which the grinding wheel is annularly disposed passes through the center of rotation of the chuck table. Grinding feed while rotating to grind the metal film coated on the surface of the hard substrate held by the chuck table, and subsequently grinding the hard substrate exposed by grinding the metal film A hard substrate grinding step for forming a hard substrate with a predetermined thickness, wherein the load current value of the motor that drives the grinding wheel exceeds a predetermined value. A separation step of separating the grinding wheel from the metal film when it rises, and a contact step of grinding the metal film by bringing the grinding wheel back into contact with the metal film, the separation step and the contact step A method of grinding a hard substrate is provided, wherein the metal film is removed by grinding.

  Preferably, the grinding feed rate of the grinding wheel is 0.3 μm / second, the hard substrate is made of a SiC substrate, and the metal film is made of a titanium film.

  According to the grinding method of the present invention, the metal film grinding step includes a separation step of separating the grinding wheel from the metal film when the load current value of the motor driving the grinding wheel exceeds a predetermined value, and the metal film A contact process of grinding the metal film by bringing the grinding wheel into contact again, and repeating the separation process and the contact process to grind the metal film and remove the metal film. The frictional heat between the metal film and the grinding wheel can be dissipated, whereby the problem that the metal film is softened and the grinding resistance increases and grinding becomes difficult can be solved.

It is a perspective view of a grinding device. FIG. 2A is a perspective view of a workpiece to which the grinding method of the present invention is applied, and FIG. 2B is a longitudinal sectional view thereof. It is a perspective view which shows a mode that a workpiece is suction-held with the chuck table of a grinding device. It is a perspective view explaining a metal film grinding process and a hard substrate grinding process. It is a flowchart of a metal film grinding process. It is a longitudinal cross-sectional view of the workpiece after completion | finish of grinding.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Referring to FIG. 1, an external perspective view of a grinding apparatus 2 suitable for carrying out the grinding method of the present invention is shown. Reference numeral 4 denotes a base of the grinding apparatus 2, and a column 6 is erected on the rear side of the base 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 motor 20 that rotationally drives the spindle 18, a wheel mount 22 fixed to the tip of the spindle 18, and a detachable attachment to the wheel mount 22. And a mounted grinding wheel 24.

  The grinding apparatus 2 includes a grinding unit feed mechanism 34 including a ball screw 30 and a pulse motor 32 that move the grinding unit 10 in the vertical direction along the pair of guide rails 8. When the pulse motor 32 is driven, the ball screw 30 rotates and the moving base 16 is moved in the vertical direction.

  A recess 4a is formed on the upper surface of the base 4, and a chuck table mechanism 36 is disposed in the recess 4a. The chuck table mechanism 36 has a chuck table 38 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). 40 and 42 are bellows. An operation panel 44 is provided on the front side of the base 4 so that an operator of the grinding apparatus 2 can input grinding conditions and the like.

  Referring to FIG. 2A, there is shown a perspective view of an example of a workpiece suitable for grinding by the grinding method of the present invention. FIG. 2B is a longitudinal sectional view thereof. The workpiece 11 is configured by laminating a SiC substrate 15 having a diameter smaller than that of the substrate 13 on the substrate 13. As is apparent from FIG. 2B, the workpiece 11 is formed on the surface of the SiC substrate 15 and the substrate 13. A titanium film having a thickness of about 10 μm is coated on the surface of the film. The substrate 13 is made of, for example, SiC.

  In the grinding method of this embodiment, the chuck table 38 is positioned at the wafer attachment / detachment position A, and the substrate 13 side of the workpiece 11 is sucked and held by the chuck table 38 as shown in FIG. .

  After the workpiece 11 is sucked and held by the chuck table 38 in this way, the chuck table 38 is moved in the Y-axis direction in FIG. At this grinding position B, the grinding wheel 24 and the workpiece 11 held on the chuck table 38 have a relationship as shown in FIG.

  In FIG. 4, a grinding wheel 24 is detachably attached to a wheel mount 22 fixed to the tip of a spindle 18 of the grinding unit 10 by a plurality of screws 31. The grinding wheel 24 is configured by arranging a plurality of grinding wheels 28 in an annular shape at a free end (lower end) of a wheel base 26.

  At the grinding position B, the grinding wheel 28 of the grinding wheel 24 is positioned so as to pass through the center of rotation of the chuck table 38, and as shown in FIG. 4, while the chuck table 38 is rotated in the direction indicated by the arrow a at, for example, 500 rpm, The grinding wheel 24 is rotated in the direction indicated by the arrow b at 1500 rpm, for example, and the grinding unit feeding mechanism 34 is driven to bring the grinding wheel 28 of the grinding wheel 24 into contact with the titanium film 17 coated on the SiC substrate 15 for grinding. Start.

  Referring to FIG. 5, a flowchart of the metal film grinding process of the embodiment of the present invention is shown. In step S10, the grinding wheel 28 is brought into contact with the titanium film 17 coated on the SiC substrate to start grinding, and the grinding wheel 24 is ground and fed downward at a predetermined grinding feed speed (for example, 0.3 μm / s) ( Step S11). The load current value of the motor 20 at this time is measured (step S12), and it is determined whether or not the load current value is 7A or less in step S13.

  Since the titanium film 17 on the SiC substrate 15 is difficult to grind, if the grinding is continued, the titanium film 17 softens and the grinding resistance increases. As the grinding resistance increases, the load current value of the motor 20 also increases. When the load current value becomes larger than 7A, the process proceeds to step S14 where the grinding wheel 28 is raised by 1.0 μm and separated from the titanium film 17 (separation process). ).

  After this separation step, the frictional heat between the titanium film 17 and the grinding wheel 28 is dissipated, and then the process proceeds to step S10 again to bring the grinding wheel 28 into contact with the titanium film 17 and start grinding. Since the grinding feed rate is 0.3 μm / s from when the grinding wheel 28 is raised to when grinding is started again, it takes about 4 seconds.

  Then, the titanium film 17 is ground while the grinding wheel 24 is ground and fed downward at a predetermined grinding feed rate (for example, 0.3 μm / s), and the load current value of the motor 20 is measured in step S12. Here, step S10 to step S12 are referred to as a contact process.

  Every time the load current value of the motor 20 becomes larger than 7A in the determination step of Step S13, the separation process of Step S14 and the contact process of Steps S10 to S12 are repeated to grind the titanium film 17. Then, the titanium film 17 on the SiC substrate 15 is removed.

  When titanium film 17 on SiC substrate 15 is removed, grinding of SiC substrate 15 is started. In grinding the SiC substrate 15, the load current value of the motor 20 is about 4 A and never larger than 7 A. Therefore, the SiC substrate 15 is fed while grinding the grinding wheel 24 at a predetermined grinding feed speed (for example, 0.3 μm / s). If it is determined in step S15 that the predetermined grinding amount has been reached, the grinding is terminated (step S16).

  FIG. 6 shows a longitudinal sectional view of the workpiece 11 after the metal film grinding step and the hard substrate grinding step. When the grinding is completed, the SiC substrate 15 on the substrate 13 is ground to a predetermined thickness, and the titanium film 17 on the substrate 13 remains without being ground.

  As a workpiece, a SiC substrate having a diameter of 10 cm and a thickness of 500 μm is disposed on a SiC substrate having a diameter of 15 cm and a thickness of 1 mm, and a titanium film is integrally formed on the surface of the substrate and the SiC substrate with a thickness of 5 to 10 μm. A coated workpiece was prepared, and the workpiece was ground under the following conditions.

Grinding wheel: Diamond abrasive grains with a particle diameter of φ20-30 μm are fixed with vitrified bond. Number of rotations of chuck table: 500 rpm
Grinding wheel speed: 1500rpm
Grinding feed rate: 0.3 μm / s
Grinding water: 4 liters / minute Load current value: The separation process is performed when the current exceeds 7 A (1.0 μm increase)

  When the workpiece described above was ground under the above-described grinding conditions, the titanium film on the SiC substrate could be removed, and the SiC substrate could be ground to a predetermined thickness of 100 μm.

  According to the grinding method of the above-described embodiment, the metal film grinding step includes a separation step of separating the grinding wheel 28 from the titanium film 17 when the load current value of the motor 20 that drives the grinding wheel 24 rises above 7A. Since the grinding wheel 28 is again brought into contact with the titanium film 17 and the titanium film is ground, the separation process and the contact process are repeatedly performed to remove the titanium film 17 by grinding. By the separation step, the frictional heat between the titanium film 17 and the grinding wheel 28 can be dissipated, and the problem that the titanium film 17 is softened to increase the grinding resistance and makes grinding difficult can be solved.

  In the above-described embodiment, the example in which the SiC substrate 15 is employed as the hard substrate and the titanium film 17 is coated on the SIC substrate as the metal film has been described. However, the grinding method of the present invention is limited to this special embodiment. However, the present invention can be similarly applied to grinding of other metal films other than a titanium film coated on another hard substrate such as a sapphire substrate.

2 Grinding device 10 Grinding unit 11 Work piece 13 Substrate 15 SiC substrate 17 Titanium film 24 Grinding wheel 28 Grinding wheel 38 Chuck table

Claims (3)

A hard substrate grinding method for grinding a hard substrate having a surface coated with a metal film to a predetermined thickness,
A holding step of holding the back surface of the hard substrate with a chuck table of a grinding apparatus to expose the metal film;
The chuck table holding the hard substrate is rotated, and the grinding wheel of the grinding wheel in which the grinding wheels are arranged in an annular shape is positioned so that it passes through the center of rotation of the chuck table, and the grinding wheel is rotated while the grinding wheel is rotated. A metal film grinding step of grinding the metal film coated on the surface of the hard substrate held by the chuck table;
A hard substrate grinding step of continuously grinding the hard substrate exposed by grinding the metal film to form the hard substrate to a predetermined thickness;
The metal film grinding step includes a separation step of separating the grinding wheel from the metal film when a load current value of a motor driving the grinding wheel exceeds a predetermined value, and the grinding wheel on the metal film. A contact step of re-contacting and grinding the metal film,
A method of grinding a hard substrate, characterized in that the metal film is ground and removed by repeatedly performing the separation step and the contact step.   The method for grinding a hard substrate according to claim 1, wherein a speed at which the grinding wheel is fed by grinding is 0.3 μm / second.   The method for grinding a hard substrate according to claim 1 or 2, wherein the hard substrate is composed of a SiC substrate, and the metal film is composed of a titanium film.

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