JP7048335B2 - How to grind the holding surface - Google Patents

Description

The present invention relates to a grinding method for grinding a holding surface of a holding table.

A grinding device for grinding a wafer includes a holding table for holding the wafer and a grinding means for rotatably mounting a grinding wheel to which a grinding wheel for grinding the wafer held on the holding table is fixed. It can be ground to a predetermined thickness. After replacing the grinding wheel or holding table in the grinding device, self-grinding is performed to grind the holding surface with the grinding wheel in order to make the holding surface of the holding table parallel to the grinding surface of the grinding wheel (). For example, see Patent Document 1 below).

Japanese Unexamined Patent Publication No. 2014-237210

In the above self-grinding, since the grinding surface of the grinding wheel is brought into contact with the radius range of the holding table for grinding, the holding surface of the holding table is formed in a conical shape. When the wafer held by the holding table is thick, the wafer does not follow the shape of the holding surface, and a gap is created between the holding surface and the lower center of the wafer near the apex of the conical surface of the holding surface, and the center of the wafer is ground. There is a problem that it becomes too thin.

The present invention has been made in view of the above circumstances, and an object of the present invention is to enable the wafer to be held on a holding table so that the center of the wafer after grinding is not too thin.

The present invention provides a grinding device including a grinding means for rotating a grinding wheel in which a grinding wheel is arranged in an annular shape around the center of a grinding wheel and a holding means for rotating a holding table around the center of a holding surface for holding a wafer. A method for grinding a holding surface by using the grinding grind that passes through the center of the holding surface, wherein the grinding grind is a resin bond grindstone in which diamond abrasive grains are mixed with a resin bond and solidified. The axis of the center of the grinding wheel and the axis of the center of the holding table are relatively tilted so as to form the holding surface of a substantially conical surface having the center of the holding surface as an apex. The grinding surface of the grinding wheel is brought into contact with the outer periphery of the surface to the center of the holding surface, and when the grinding surface is in contact with the holding surface, the diamond abrasive grains exposed on the grinding surface are covered with the diamond abrasive grains. A grinding load larger than the elasticity of the resin bond is applied to grind the holding surface from the outer periphery of the holding surface toward the center of the holding surface, and the exposed grinding load is applied to the ground surface passing through the center of the holding surface. A flat recess is formed in the center of the holding surface by grinding the radial outer side from the center of the holding surface with the diamond abrasive grains that have not been formed .

It is preferable to use a grain size of 600 for the diamond abrasive grains.

In the method for grinding a holding surface according to the present invention, the grinding grind used for grinding the holding surface is a resin bond grindstone in which diamond abrasive grains are mixed with a resin bond and solidified, and the center of the holding surface is the apex. The axis at the center of the grinding wheel and the axis at the center of the holding table are relatively tilted so as to form the holding surface of the conical surface, from the outer periphery of the holding surface to the center of the holding surface. When the grinding surface of the grinding wheel is brought into contact with the grinding surface and the grinding surface is in contact with the holding surface, a grinding load is applied to the diamond abrasive grains exposed on the grinding surface to apply a grinding load to the holding surface from the outer periphery of the holding surface. The holding surface is ground toward the center of the holding surface, and the diamond abrasive grains that have passed through the center of the holding surface and are not subjected to the grinding load of the grinding surface grind the radial outer side from the center of the holding surface, so that the holding surface is held. A flat recess can be formed in the center of the surface. As a result, for example, when a thick wafer is held on a holding table, the wafer can be held without a gap on the holding surface having a recess formed in the center, so that the center of the wafer can be prevented from being excessively ground. , The wafer can be ground to a uniform thickness.

By using the grain size 600 as the diamond abrasive grains, the surface roughness of the holding surface can be satisfactorily finished.

It is sectional drawing which shows the structure of an example of a grinding apparatus partially. It is sectional drawing which shows the state of grinding a holding surface with a grinding wheel. It is explanatory drawing which shows the rotation locus of a grinding wheel, and explains the region which grinds the holding surface with a grinding wheel. It is a partial enlarged view which shows the state which the holding surface is ground with a grinding wheel from the outer periphery of the holding surface toward the center. It is a partial enlarged view which shows the state which the diamond abrasive grain is exposed from the grinding surface which passed through the center of a holding surface, and the region outside the radial direction from the center of a holding surface is ground. It is sectional drawing which shows the state of the holding table after being ground.

FIG. 1 is an example of a grinding device 1 used in the method for grinding a holding surface according to the present invention. The grinding device 1 is a holding means for rotating the holding table 21 around a rotating shaft 100 passing through the center of the grinding wheel 13 and a rotating shaft 200 passing through the center of the holding surface 24a for holding the wafer. It has at least 20.

The grinding means 10 includes a spindle 11 having a vertical axis, a grinding wheel 13 mounted on the lower end of the spindle 11 via a mount 12, and a plurality of grinding wheels arranged in an annular shape under the grinding wheel 13. It is equipped with 14. The grinding means 10 is connected to an elevating means 17 for raising and lowering the grinding means 10 in the vertical direction and a motor (not shown) for rotating the spindle 11.

The grinding wheel 14 is a resin bond grindstone in which diamond abrasive grains 16 are mixed with the resin bond 15 and solidified. The lower surface of the grinding wheel 14 is a grinding surface 14a that comes into contact with the object to be ground. The grinding wheel 14 is a rectangular parallelepiped, for example, by mixing diamond abrasive grains 16 into a resin bond 15, pressing the diamond abrasive grains 16 mixed in a predetermined mold, and then sintering the diamond abrasive grains 16 at a predetermined temperature for a predetermined time. Manufactured by solidifying into a shape.

Since the grinding wheel 14 shown in the present embodiment uses the resin bond 15 as the bonding material for solidifying the diamond abrasive grains 16, it is relatively softer than other bonding materials (for example, a vitrified bond or a metal bond) and grinds. When the holding surface 24a is ground with the grindstone 14, the surface roughness of the holding surface 24a can be satisfactorily finished. As the resin bond 15, for example, a phenol resin, an epoxy resin, or a polyimide resin can be used.

As the particle size of the diamond abrasive grains 16, it is preferable to use, for example, a particle size of 600 (average particle size of 20 μm). If the grain size of the diamond abrasive grains 16 is too small, the diamond abrasive grains 16 will not be exposed from the grinding surface 14a when the holding surface 24a is ground by the grinding wheel 14, and the holding surface 24a may be finished in a desired surface state. If the grain size of the diamond abrasive grains 16 is too large, the amount of protrusion of the diamond abrasive grains 16 from the ground surface 14a becomes large and the surface roughness of the holding surface 24a deteriorates. Therefore, as the grain size of the diamond abrasive grains 16, the above-mentioned grain size 600 is the most suitable, and according to the diamond abrasive grains 16, the surface roughness of the holding surface 24a can be satisfactorily finished.

The holding means 20 includes at least a holding table 21 for sucking and holding the wafer, and a motor 22 for rotating the rotating shaft 200 of the holding table 21. The holding table 21 includes a frame body 23 having a concave fitting groove 230 in the center, and a porous member 24 housed in the frame body 23. The frame body 23 is made of, for example, ceramics or the like. The porous member 24 is fitted into the fitting groove 230 of the frame body 23 to form a holding table 21.

The porous member 24 is formed in a disk shape and is made of a porous member such as porous ceramics. The upper surface of the porous member 24 is a holding surface 24a for holding the wafer. The holding surface 24a is formed to have a diameter of, for example, 300 mm. Further, the holding surface 24a of the porous member 24 is a substantially conical surface inclined from the center C of the holding surface 24a to the outer peripheral E of the holding surface 24a, and the center C shown in the figure is the apex of the substantially conical surface. .. The height difference between the center C and the outer circumference E of the holding surface 24a is formed to be, for example, about 30 μm. Although not shown, the holding means 20 is provided with tilt adjusting means for adjusting the tilt of the holding table 21.

Next, a method for grinding the holding surface 24a of the holding table 21 using the grinding device 1 will be described in detail. In the present embodiment, in order to hold the thick wafer on the holding surface 24a of the holding table 21, the holding surface 24a is ground in advance.

When starting grinding, as shown in FIG. 2, for example, by raising the outer peripheral right side of the holding table 21, the rotation axis 100 at the center of the grinding wheel 14 and the rotation axis at the center of the holding table 21 are raised by the inclination adjusting means. The grinding wheel 14 is adjusted so that the grinding surface 14a of the grinding wheel 14 is parallel to the surface from the apex (center C) of the conical surface of the holding surface 24a to the outer periphery E by tilting the 200 relative to a predetermined angle.

Next, the holding table 21 is rotated by the motor 22 in the direction of arrow A, for example. While lowering the grinding means 10 by the elevating means 17, the grinding means 10 rotates the grinding wheel 13 in the direction of arrow A, for example, by rotating the spindle 11, and grinds while pressing the holding surface 24a with the grinding wheel 14. ..

Here, as shown in FIG. 3, among the rotation loci of the grinding wheel 14 rotating in the direction of arrow A, an arcuate region (shown by a dotted line) in which the grinding wheel 14 actually contacts the holding surface 24a to perform grinding. Is the grinding area P1. During grinding of the holding surface 24a, the grinding wheel 14 always passes through the center C of the holding surface 24a, and the grinding surface 14a of the grinding wheel 14 comes into contact with the holding surface 24a in the grinding region P1 to grind the holding surface 24a.

As shown in FIG. 4, when the grinding surface 14a of the grinding wheel 14 is in contact with the holding surface 24a, the diamond abrasive grains 16 exposed from the grinding surface 14a are subjected to a grinding load from the outer circumference E of the holding surface 24a. Grinding can be performed toward the center C of the holding surface 24a. That is, when the grinding load acts on the diamond abrasive grains 16, the diamond abrasive grains 16 exposed from the grinding surface 14a of the grinding wheel 14 are embedded in the resin bond 15 and the protrusion amount of the diamond abrasive grains 16 is reduced and held. Since the surface 24a can be ground, the surface roughness can be satisfactorily finished. Further, in the grinding region P1 shown in FIG. 3, there is no gap between the grinding surface 14a and the holding surface 24a, and the state in which the diamond abrasive grains 16 are buried in the resin bond 15 is maintained.

On the other hand, when the grinding wheel 14 shown in FIG. 3 passes through the center C of the holding surface 24a, the grinding surface 14a of the grinding wheel 14 that has passed through the center C and the holding surface 24a are in a non-contact state. That is, when the grinding surface 14a of the grinding wheel 14 is not in contact with the holding surface 24a, as shown in FIG. 5, a gap is formed between the grinding surface 14a and the holding surface 24a, and the center C of the holding surface 24a is formed. The diamond abrasive grains 16 that have not received the grinding load of the grinding surface 14a that has passed through the above project from the resin bond 15 and are exposed from the grinding surface 14a. As shown in FIG. 6, a small region (for example, the central grinding region P2 shown in FIG. 3) outside the center C of the holding surface 24a is ground by the diamond abrasive grains 16 which are not subjected to the grinding load. A flat recess 25 is formed in the center of the surface 24a. The diameter indicated by the arrow of the recess 25 is, for example, a diameter of 30 mm. When the grinding of the holding surface 24a is completed, the wafer is held by the holding table 21 and the wafer is ground.

As described above, in the method for grinding the holding surface according to the present invention, the grinding grind 14 used is a resin bond grindstone in which diamond abrasive grains 16 are mixed with the resin bond 15 and solidified, and the center C of the holding surface 24a is formed. The rotation axis 100 at the center of the grinding wheel 13 and the rotation axis 200 at the center of the holding table 21 are relatively tilted so as to form the holding surface 24a of the substantially conical surface as the apex, and the holding surface from the outer periphery E of the holding surface 24a. When the grinding surface 14a of the grinding wheel 14 is in contact with the center C of the 24a and the grinding surface 14a is in contact with the holding surface 24a, the elasticity of the resin bond 15 is applied to the diamond abrasive grains 16 exposed on the grinding surface 14a. A larger grinding load is applied to embed the diamond abrasive grains 16 in the resin bond 15, and the holding surface 24a is formed from the outer periphery E of the holding surface 24a toward the center C of the holding surface 24a by the diamond abrasive grains 16 exposed on the grinding surface 14a. The diameter from the center C of the holding surface 24a due to the diamond abrasive grains 16 protruding from the inside of the resin bond 15 due to the elasticity of the resin bond 15 due to the grinding and not receiving the grinding load of the grinding surface 14a that has passed through the center C of the holding surface 24a. Since it is configured to grind the outside in the direction, a flat recess 25 can be formed in the center of the holding surface 24a.
In the holding table 21 in which the recessed portion 25 is formed in the center of the holding surface 24a, for example, when sucking and holding a thick wafer, the central portion of the wafer can be sucked and held in accordance with the recessed portion 25, so that the center of the holding surface 24a is held. There will be no gap between the wafer and the center of the wafer. Therefore, since the wafer can be held without a gap by the holding surface 24a, it is possible to prevent the center of the wafer from being excessively ground, and it is possible to grind the wafer to a uniform thickness.

1: Grinding device 10: Grinding means 11: Spindle 12: Mount 13: Grinding wheel 14: Grinding wheel 15: Resin bond 16: Diamond abrasive grains 17: Elevating means 20: Holding means 21: Holding table 22: Motor 23: Frame 24: Porous member 25: Recessed part

Claims (2)

Using a grinding device provided with a grinding means for rotating the center of the grinding wheel in which the grinding wheels are arranged in an annular shape around the center of the grinding wheel and a holding means for rotating the holding table around the center of the holding surface for holding the wafer. A method for grinding a holding surface by grinding the holding surface with the grinding wheel that passes through the center of the holding surface.
The grinding wheel is a resin bond grindstone in which diamond abrasive grains are mixed with a resin bond and solidified.
The outer circumference of the holding surface is tilted relatively between the axis at the center of the grinding wheel and the axis at the center of the holding table so as to form the holding surface of a substantially conical surface having the center of the holding surface as an apex. The grinding surface of the grinding wheel is brought into contact with the ground surface from the surface to the center of the holding surface.
When the grinding surface is in contact with the holding surface, a grinding load larger than the elasticity of the resin bond is applied to the diamond abrasive grains exposed on the grinding surface, and the center of the holding surface is applied from the outer periphery of the holding surface. By grinding the holding surface toward the center of the holding surface and grinding the radial outer side from the center of the holding surface with the diamond abrasive grains that have passed through the center of the holding surface and are not subjected to the surface grinding load on the ground surface. A method of grinding a holding surface that forms a flat recess in the center of the holding surface. The method for grinding a holding surface according to claim 1, wherein the diamond abrasive grains have a particle size of 600.

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