KR102117718B1 - Sapphire substrate processing method - Google Patents

Abstract

The present invention is a method for processing a sapphire substrate that can secure surface accuracy of a sapphire substrate having an A surface as a front and back surface, which has little useless cutting from a sapphire ingot, and has good fusion with a light emitting layer made of a gallium nitride compound semiconductor. The task is to provide.
A sapphire substrate processing method of grinding a sapphire substrate cut from an ingot of a sapphire and having a surface and a back surface formed by the A surface, and a holding process for holding a workpiece and holding one surface of the sapphire substrate on a rotatable chuck table. Including the grinding process of rotating the chuck table holding the sapphire substrate, and grinding the other surface of the sapphire substrate by contacting the grinding wheel with the other surface of the sapphire substrate while rotating the grinding wheel in which the grinding wheel is arranged in an annular shape. In the grinding step, a slurry in which diamond abrasive particles are mixed into a grinding portion by a grinding wheel is supplied as a grinding liquid.

Description

Processing method of sapphire substrate {SAPPHIRE SUBSTRATE PROCESSING METHOD}

The present invention relates to a method for processing a sapphire substrate, more specifically, to cut a sapphire substrate cut from an ingot of sapphire and having a surface and a back surface formed by the A surface.

In the optical device manufacturing process, a light emitting layer made of a gallium nitride compound semiconductor is stacked on the surface of a sapphire substrate, and optical devices such as light emitting diodes and laser diodes are formed in a plurality of regions partitioned by a plurality of streets formed in a lattice shape. , An optical device wafer. Then, by cutting the optical device wafer along the street, an area in which the optical device is formed is divided to manufacture individual optical devices.

The sapphire has a crystal structure having a crystal plane called an A plane, a C plane, and a R plane, and a sapphire substrate having an A plane, a C plane, and an R plane as front and rear surfaces is formed by a sapphire ingot cutting method. That is, the sapphire ingot has a conical shape close to a cylinder, and the bottom and top surfaces of the conical shape are A plane, the plane orthogonal to the A plane is C plane, and the plane inclined with respect to the C plane is R plane. When the core is cut toward the bottom and sliced, a sapphire substrate having an A surface as a front and back surface is formed, and when it is sliced by cutting away from the side of the truncated cone in a direction parallel to the A surface, a sapphire substrate having a C surface as a front and back surface is formed. , When the core is cut out from the direction orthogonal to the R surface, a sapphire substrate having the R surface as the front and back surfaces is formed. Since the A, C, and R surfaces have different crystal structures, it is preferable that a sapphire substrate corresponding to the crystal structure of the light-emitting layer to be stacked is appropriately selected.

In order to manufacture an optical device wafer, a light emitting layer is formed by laminating a surface of a sapphire substrate, but the sapphire substrate cut before laminating the light emitting layer is also flattened by grinding and grinding the surface and back surface by a grinding device (see, for example, Patent Document 1).

Patent Document 1: Japanese Patent Publication No. 2007-38357

Since the C-side of the sapphire has good grinding by a grinding device, a sapphire substrate having a C-side as a front and back surface is generally used as a substrate for an optical device wafer.

However, since the sapphire substrate having the C surface as the front and rear surfaces is sliced by cutting the conical sapphire ingot in a direction parallel to the A surface from the side surface, there is a problem that productivity is poor due to a lot of waste of the sapphire ingot. have.

On the other hand, since the sapphire substrate having the A surface as the front and back surfaces is sliced by cutting the core toward the bottom from the top surface of the conical sapphire ingot, as described above, there is little waste of the sapphire ingot and a light emitting layer made of a gallium nitride compound semiconductor Although it has the advantage of good fusion with, there is a problem in that surface precision cannot be secured due to defects when grinding the A surface with a grinding device.

The present invention has been made in view of the above facts, and the main technical problem of the sapphire substrate is a sapphire substrate, which has a small useless cut from the sapphire ingot, and has good A fusion with a light emitting layer made of a gallium nitride-based compound semiconductor. It is to provide a method for processing a sapphire substrate capable of securing surface precision.

In order to solve the above main technical problem, according to the present invention, as a processing method of a sapphire substrate that is cut from an ingot of sapphire and grinding a sapphire substrate having a surface and a back surface formed by the A surface,

A holding process for holding a workpiece and holding one surface of the sapphire substrate on a rotatable chuck table;

It includes a grinding process for rotating the chuck table holding the sapphire substrate, and grinding the other surface of the sapphire substrate by contacting the grinding wheel with the other surface of the sapphire substrate while rotating the grinding wheel in which the grinding wheel is arranged in an annular shape. ,

In the grinding step, there is provided a method for processing a sapphire substrate, characterized in that a slurry in which diamond abrasive grains are mixed is supplied as a grinding liquid to a grinding part by a grinding wheel.

The grinding wheel is composed of diamond abrasive particles having a particle diameter of 1 to 2 µm mixed with a bond agent, and the grinding liquid is composed of a slurry in which diamond abrasive particles having a particle diameter of 3 to 9 µm are mixed with pure water.

In the method for processing a sapphire substrate according to the present invention, the grinding wheel is rotated while rotating a chuck table holding one surface of the sapphire substrate having a surface and a back surface formed by the A surface, and rotating the grinding wheel in which the grinding wheels are arranged in an annular shape. In the grinding step of grinding the other side of the sapphire substrate by contacting the other side of the sapphire substrate, since the slurry containing diamond abrasive grains is supplied as a grinding liquid to the grinding portion by the grinding wheel, By the synergistic effect of polishing by supplying the slurry in which diamond abrasive grains are mixed with pure water to a grinding part by a grinding wheel, good surface precision can be obtained without generating defects on the surface to be polished, which is the A surface of the sapphire substrate.

1 is a perspective view of a grinding device for performing a grinding method for a sapphire substrate according to the present invention.
Fig. 2 is a perspective view seen from the lower side of a wheel mount constituting a grinding means provided in the grinding device shown in Fig. 1;
Fig. 3 is a perspective view of a grinding wheel mounted on the wheel mount shown in Fig. 2;
Fig. 4 is a sectional view showing a state in which the grinding wheel shown in Fig. 3 is attached to the wheel mount shown in Fig. 2;
5 is a perspective view of a sapphire substrate that is ground by the sapphire substrate grinding method according to the present invention.
Fig. 6 is a perspective view showing a state in which a substrate is attached to the back surface of the sapphire substrate shown in Fig. 5;
Fig. 7 is an explanatory view showing a grinding step performed by the grinding device shown in Fig. 1;
8 is an explanatory view showing a surface roughness measurement area of a sapphire substrate ground by the sapphire substrate grinding method according to the present invention.

Hereinafter, preferred embodiments of the method for processing a sapphire substrate according to the present invention will be described in more detail with reference to the accompanying drawings.

1 shows a perspective view of a grinding device for carrying out the method for processing a sapphire substrate according to the present invention. The grinding device 1 shown in Fig. 1 is provided with a device housing in which the whole is indicated by a number 2. The device housing 2 is provided with an elongated rectangular parallelepiped main part 21 and an upright wall 22 installed at the rear end (top right in FIG. 1) of the main part 21 and extending upwardly. Have On the front surface of the upright wall 22, a pair of guide rails 221 and 221 extending in the vertical direction are provided. The moving base 3 is slidably mounted on the pair of guide rails 221 and 221. The moving base 3 is provided with a pair of leg portions 31 and 31 extending in the vertical direction on both rear sides, and the pair of guide rails 221 is provided on the pair of leg portions 31 and 31. , 221) and guide grooves 311 and 311 slidably coupled to each other. As described above, a support portion 32 protruding forward is provided on the front surface of the moving base 3 slidably mounted on the pair of guide rails 221 and 221 installed on the upright wall 22. A spindle unit 4 as a grinding means is attached to the support portion 32.

The spindle unit 4 rotates the cylindrical spindle housing 41 mounted on the support part 32, the rotating spindle 42 rotatably arranged in the spindle housing 41, and the rotating spindle 42 A servo motor 43 as a driving source for driving is provided. In the rotating spindle 42 rotatably supported by the spindle housing 41, one end (lower end in FIG. 1) is disposed to protrude from the lower end of the spindle housing 41, and at one end (lower end in FIG. 1). The wheel mount 44 is installed. Then, the grinding wheel 5 is attached to the lower surface of the wheel mount 44.

The wheel mount 44 and the grinding wheel 5 will be described with reference to FIGS. 2 to 4.

2 shows a perspective view of the wheel mount 44 installed at the bottom of the rotating spindle 42, and FIG. 3 shows a perspective view of the grinding wheel 5 mounted on the lower surface of the wheel mount 44, and FIG. 4 A sectional view is shown in which the grinding wheel 5 shown in FIG. 3 is mounted on the lower surface of the wheel mount 44 shown in FIG. 2. The wheel mounts 44 shown in FIGS. 2 and 4 are formed in a circular shape and are integrally installed at the lower end of the rotating spindle 42. As shown in Fig. 2, four bolt insertion holes 441 are formed in the wheel mount 44 at a predetermined interval in the circumferential direction. Further, in the wheel mount 44, as shown in FIG. 4, a plurality of (eight in the illustrated embodiment) communication paths 422 communicating with the grinding fluid supply passage 421 formed at the shaft center of the rotating spindle 42 ) Is formed, and this communication path 422 is opened to the lower surface as shown in FIGS. 2 and 4. Moreover, the grinding liquid supply passage 421 formed in the shaft center of the rotating spindle 42 is connected to the grinding liquid supply means 40, as shown in FIG. The grinding liquid supply means 40 is adapted to supply a grinding liquid composed of a slurry in which diamond abrasive particles are mixed with pure water.

The grinding wheel 5 mounted on the wheel mount 44 configured as described above will be described with reference to FIGS. 3 and 4.

The grinding wheel 5 shown in FIGS. 3 and 4 includes an annular wheel base 51 and a plurality of grinding wheels 52 attached to the grinding wheel mounting portions of the outer circumference of the lower surface of the wheel base 51. Doing. The wheel base 51 is formed with four female screw holes 511 formed from the upper surface at positions corresponding to the plurality of bolt insertion holes 441 formed in the wheel mount 44. In addition, the grinding wheel 52 is constituted by mixing diamond abrasive particles having a particle diameter of 1 to 2 µm into a bonding agent, kneading them, shaping them into a predetermined shape, and firing them.

In order to attach the grinding wheel 5 configured as described above to the wheel mount 44, as shown in FIG. 4, the upper surface of the wheel base 51 of the grinding wheel 5 is pressed against the lower surface of the wheel mount 44. , A plurality of female screw holes 511 (see FIG. 3) formed in the wheel base 51 by inserting the fastening bolts 55 through the plurality of bolt insertion through holes 441 (see FIG. 2) formed in the wheel mount 44 ), The grinding wheel 5 can be attached to the lower surface of the wheel mount 44. In this way, the grinding liquid supply means 40 operates on the grinding portion of the grinding wheel 5 attached to the lower surface of the wheel mount 44 by mixing the diamond abrasive particles with pure water. The grinding liquid made of the slurry is supplied through the grinding liquid supply passage 421 formed on the rotating spindle 42 and the plurality of communication paths 422 formed on the wheel mount 44.

Returning to FIG. 1 and continuing the explanation, the grinding device 1 in the illustrated embodiment moves the spindle unit 4 up and down along the pair of guide rails 221 and 221 (chuck table to be described later) It is provided with a grinding transfer means (6) to move in a direction perpendicular to the holding surface of the. The grinding transfer means 6 is provided on the front side of the upright wall 22 and is provided with a male screw rod 61 extending in the vertical direction. The male screw rod 61 is rotatably supported by bearing members 62 and 63 whose upper and lower ends are attached to the upright wall 22. A pulse motor 64 as a driving source for rotationally driving the male screw rod 61 is disposed on the upper bearing member 62, and the output shaft of the pulse motor 64 is electrically connected to the male screw rod 61. A connection portion (not shown) protruding rearward from the center portion in the width direction is also formed on the rear surface of the moving base 3, and a through female screw hole (not shown) is formed in the connection portion, and the female screw hole is The male rod 61 is screwed. Therefore, when the pulse motor 64 rotates forward, the moving base 3 and the spindle unit 4 descend, that is, move forward, and when the pulse motor 64 rotates reversely, the moving base 3 and the spindle unit 4 move. Rise, ie retreat.

If the description continues with reference to FIG. 1, a chuck table mechanism 7 is disposed on the main portion 21 of the housing 2. The chuck table mechanism 7 includes a chuck table 71 as a workpiece holding means, a cover member 72 covering the circumference of the chuck table 71, and bellows means disposed before and after the cover member 72. (73 and 74). The chuck table 71 is rotated by a rotation drive mechanism (not shown), and is configured to hold and hold suction by operating a suction means (not shown) on the upper surface of the workpiece. In addition, the chuck table 71 is a grinding region facing the workpiece arrangement region 24 shown in Fig. 1 and a grinding wheel 5 constituting the grinding unit 4 by a chuck table moving means (not shown) ( 25). The bellows means 73 and 74 can be formed of a suitable material, such as cambus fabric. The front end of the bellows means 73 is fixed to the front wall of the main part 21, and the rear end is fixed to the front end surface of the cover member 72. Further, the front end of the bellows means 74 is fixed to the rear end face of the cover member 72, and the rear end is fixed to the front face of the upright wall 22 of the device housing 2. When the chuck table 71 moves in the direction indicated by the arrow 23a, the bellows means 73 is extended, the bellows means 74 contracts, and the chuck table 71 moves in the direction indicated by the arrow 23b. At this time, the bellows means 73 contracts and the bellows means 74 is extended.

The grinding device 1 shown in Figs. 1 to 4 is configured as described above, and is used when performing finish grinding described later.

5 shows a sapphire substrate processed by the processing method according to the present invention. The sapphire substrate 10 shown in FIG. 5 is composed of a sapphire substrate having the surface 10a and the back surface 10b as the A surface, and is formed to have a diameter of 150 mm and a thickness of 300 µm. The sapphire substrate 10 thus formed has one surface (the back surface 10b in the illustrated embodiment) attached to a substrate 11 made of a glass plate or the like as shown in FIG. 6 through wax.

In order to process the above-described sapphire substrate 10 to a predetermined thickness, first, rough grinding is performed. In this rough grinding operation, if the grinding fluid supply means 40 and the grinding wheel 52 of the grinding wheel 5 in the grinding device 1 shown in Figs. 1 to 4 are different, but the other configurations are substantially the same. Therefore, description will be given using the reference numerals used in the grinding device 1 shown in FIGS. 1 to 4. In addition, when performing rough grinding, the grinding liquid supply means 40 supplies grinding water made of pure water as in the prior art. In addition, the grinding wheel 52 of the grinding wheel 5 is formed by mixing diamond abrasive grains having a particle diameter of 10 to 15 µm into a resin bond, kneading them, molding them into a predetermined shape, and firing them.

In order to perform rough grinding of the sapphire substrate 10, as described above, the sapphire substrate 10 adhered to the substrate 11 is avoided in the same rough grinding apparatus as the grinding apparatus 1 shown in FIG. The substrate 11 side is arranged on the holding surface which is the upper surface of the chuck table 71 positioned in the work arrangement area 24. Then, the sapphire substrate 10 is sucked and maintained through the substrate 11 on the chuck table 71 by operating the suction means (not shown). In this way, if the sapphire substrate 10 is sucked and maintained through the substrate 11 on the chuck table 71, the chuck table 71 is operated by means of chuck table movement means (not shown) to indicate the chuck table 71 with arrows 23a. It is moved in the direction to give a position to the grinding region 25.

When the chuck table 71 is positioned in the grinding area 25 in this way, as shown in FIG. 7, the chuck table 71 is rotated at a rotation speed of 200 rpm in a predetermined direction, and the grinding wheel 5 is 800. While rotating at a rotational speed of rpm, the pulse motor 64 of the grinding conveying means 6 is driven in normal rotation to descend the grinding unit 4 at a speed of 0.1 µm / sec, and a plurality of grinding wheels of the grinding wheel 5 ( The grinding surface of 52) is brought into contact with the surface 10a (upper surface) of the sapphire substrate 10 held on the chuck table 71, and is transferred by a predetermined amount (100 µm). As a result, the sapphire substrate 10 held on the chuck table 71 is ground to 100 µm (rough grinding process).

In this coarse grinding process, the grinding part by the grinding wheel 52 of the grinding wheel 5 through the grinding water supply passage 421 formed in the rotating spindle 42 and the communication path 422 formed in the wheel mount 44. Is supplied with pure water.

The surface 10a of the sapphire substrate 10 subjected to the above-described rough grinding is subjected to finish grinding to increase the surface precision. This finish grinding process is performed using the grinding device 1 shown in FIGS. 1 to 4. That is, the grinding liquid supply means 40 supplies a grinding liquid made of a slurry in which diamond abrasive grains are mixed with pure water, and the grinding wheel 52 of the grinding wheel 5 has diamond grains having a particle diameter of 1 to 2 μm. It is constituted by incorporating the particles into a bonding agent, kneading them, molding them into a predetermined shape, and firing them. Hereinafter, an experimental example by the present inventor will be described.

[Experiment 1]

As described above, the sapphire substrate 10 subjected to rough grinding is placed on the holding surface, which is the upper surface of the chuck table 71, which is positioned in the workpiece arrangement area 24 of the grinding device 1 shown in FIG. On the substrate 11 side. Then, the sapphire substrate 10 is sucked and maintained through the substrate 11 on the chuck table 71 by operating a suction means (not shown). In this way, if the sapphire substrate 10 is sucked and maintained through the substrate 11 on the chuck table 71, the chuck table 71 is operated by means of a chuck table moving means (not shown) to indicate the chuck table 71 with an arrow 23a. It is moved in the direction to give a position to the grinding region 25.

When the chuck table 71 is positioned in the grinding region 25 in this way, the chuck table 71 is rotated at a rotation speed of 200 rpm in the direction indicated by the arrow 71a, as shown in FIG. (5) While rotating at a rotational speed of 800 rpm in the direction indicated by the arrow 5a, the pulse motor 64 of the grinding conveying means 6 is driven forward rotation to lower the grinding unit 4 at a speed of 0.1 µm / sec. And the grinding surfaces of the plurality of grinding wheels 52 of the grinding wheel 5 are brought into contact with the surface 10a (upper surface) of the sapphire substrate 10 held on the chuck table 71 by a predetermined amount (30 μm) Grinding feed. As a result, the sapphire substrate 10 held on the chuck table 71 is ground 30 µm (finishing grinding step). In this finishing grinding process, the grinding part by the grinding wheel 52 of the grinding wheel 5 is provided through the grinding water supply passage 421 formed in the rotating spindle 42 and the communication path 422 formed in the wheel mount 44. The slurry in which 5 g of diamond abrasive particles having a particle diameter of about 9 µm is mixed with 5 g per 1 liter of pure water is supplied at a rate of 5 liters (5 liters / minute) for 1 minute.

[Experiment 2 (Comparative Example)]

After the sapphire substrate 10 subjected to rough grinding as described above is maintained through the substrate 11 on the holding surface, which is the upper surface of the chuck table 71, in the same manner as in Experiment 1, the same as described above Finish (grinding liquid only) finish grinding. That is, the chuck table 71 positioned in the grinding area 25 is rotated at a rotational speed of 200 rpm in a predetermined direction, and the grinding wheel 5 is rotated at a rotational speed of 800 rpm while the grinding conveyance means 6 The pulse motor 64 is driven to rotate in a forward direction to lower the grinding unit 4 at a speed of 0.1 µm / sec, and the grinding surfaces of a plurality of grinding wheels 52 of the grinding wheel 5 are held on the chuck table 71. It is brought into contact with the surface 10a (top surface) of the sapphire substrate 10 and is transferred by grinding in a predetermined amount (30 µm). As a result, the sapphire substrate 10 held on the chuck table 71 is ground 30 µm (finish grinding process). In this finishing grinding process, the grinding part by the grinding wheel 52 of the grinding wheel 5 is provided through the grinding water supply passage 421 formed in the rotating spindle 42 and the communication path 422 formed in the wheel mount 44. Is supplied with pure water.

The surface 10a (top surface) of the sapphire substrate 10 subjected to the finish grinding process of the above-described Experiment 1 and Experiment 2 (Comparative Example) is roughened in the regions I, II, III, IV, and V shown in FIG. 8. As a result, the following results were obtained.

Measurement area I II III IV V

Surface roughness (Ra) of Experiment 1 0.031 0.017 0.044 0.038 0.019

Surface roughness of experiment 2 (Ra) 0.283 0.257 0.284 0.142 0.157

From the above experiment results, when using a slurry in which diamond abrasive particles are mixed with pure water as a grinding liquid as in Experiment 1, compared with the case where grinding water made of pure water is used as in Experiment 2 (Comparative Example), A surface of the sapphire substrate It can be seen that the surface roughness of (Ra) decreases to 1/10. This is due to the synergistic effect of polishing by supplying a slurry in which grinding by the grinding wheel 52 and diamond abrasive grains are mixed with pure water to the grinding unit by the grinding wheel 52. Therefore, by using a slurry in which diamond abrasive particles are mixed with pure water as a grinding liquid, since the surface precision of the sapphire substrate with the A surface as the front and rear surfaces can be secured, the A surface of the sapphire substrate can be used as the lamination surface of the light emitting layer. have. In addition, it can be seen that the diamond abrasive particles incorporated into the slurry supplied to the grinding portion by the grinding wheel 52 of the grinding wheel 5 are prone to grinding damage when a particle size of 10 µm or more is used. Therefore, the diamond abrasive particles mixed into the slurry supplied to the grinding portion by the grinding wheel 52 are larger than the particle diameters (1 to 2 µm) of the diamond abrasive particles constituting the grinding wheel 52 and grinding damage is likely to occur. It is preferable to set it to 3 to 9 mu m smaller than the particle diameter (10 mu m).

By carrying out the processing method of the sapphire substrate according to the present invention as described above, it becomes possible to use a sapphire substrate having an A surface as a front and back surface as a substrate for an optical device wafer, so that the sapphire ingot can be efficiently cut out. As the unit price goes down, optical devices such as LEDs can be manufactured at low cost. In addition, since the A-side of the sapphire substrate is a good crystal orientation for the growth of the light-emitting layer made of a gallium nitride compound semiconductor, the quality of optical devices such as LEDs is improved.

2: Device housing 3: Mobile base
4: Spindle unit 40: Grinding fluid supply means
41: spindle housing 42: rotating spindle
44: wheel mount 5: grinding wheel
51: wheel base 52: grinding wheel
6: Grinding conveying means 7: Chuck table mechanism
71: chuck table 10: sapphire substrate

Claims (2)

A method for processing a sapphire substrate, wherein the sapphire substrate is cut from the ingot of the sapphire and the surface and the back surface are formed by the A surface,
A holding process for holding a workpiece and holding one surface of the sapphire substrate on a rotatable chuck table,
The grinding process of rotating the chuck table holding the sapphire substrate, and grinding the other surface of the sapphire substrate by contacting the grinding wheel with the other surface of the sapphire substrate while rotating the grinding wheel in which a plurality of grinding wheels are arranged in an annular shape.
It includes,
The grinding process includes a rough grinding process and a finish grinding process performed after the rough grinding process,
The coarse grinding processing is performed while supplying grinding water made of pure water that does not contain abrasive particles,
The finishing grinding process uses a grinding stone composed of diamond abrasive particles having a particle diameter of 1 to 2 µm mixed with a bond agent, and a grinding liquid composed of a slurry in which diamond abrasive particles having a particle diameter of 3 to 9 µm are mixed with pure water. A method for processing a sapphire substrate, characterized in that it is carried out while being supplied. delete

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