JPH0811061A - Grinding wheel for inner circumferential cutting edge slicing machine - Google Patents

Abstract

PURPOSE:To provide an inner circumferential cutting edge grinding wheel which can cut a wafer having a large outside diameter with a high yield while suppressing a warp within a tolerance without using any special device for forcibly suppressing deformation of the inner circumferential cutting edge grinding wheel during cutting. CONSTITUTION:An inner circumferential cutting edge slicing machine grinding wheel is provided with a base metal 2 made of a ringed plate having an inner circumference and an outer circumference concentric with each other, a ringed tension head 4 which clamps the outer circumference of the base metal 2 over the whole circumference from both front and back faces and applies tension in the direction from the center to the outer circumference so as to fix the base metal 2, and an inner circumferential cutting edge 3 containing an abrasive layer formed over its outer circumference in the inner circumference of the base metal 2. The thickness of the base metal 2 is one-5000th or less of its outside diameter, and a ratio of the inside diameter of the inner circumferential cutting edge 3 to the inside diameter of the tension head 4 is set from 0.25 to 0.33. In this way, workability and a cutting stroke are sufficiently secured, while rigidity of the inner circumferential cutting edge grinding wheel against cutting resistance is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a grindstone for an inner peripheral blade slicing machine used for thinly cutting a single crystal ingot or the like to obtain a wafer.

[0002]

2. Description of the Related Art Conventionally, in a cutting process for obtaining a thin wafer from an ingot such as silicon or gallium arsenide, an inner peripheral edge grinding wheel 1 as shown in FIGS.
The slicing machine to which is applied is used. The inner cutting edge grindstone 1 has a thin base metal 2 made of stainless steel or the like having a concentric inner circumference and an outer circumference, and nickel plating is applied to the inner circumference of the base metal 2 by sprinkling abrasive grains from diamond or the like. The base metal 2 is sandwiched between the end surface of the chuck body 5 and the end surface of the tension head 4, and is fixed by fastening with hexagon socket head cap screws 6. A pressing member 8 is fitted in a hole formed on the chuck body 5 side of the end surface of the tension head 4, and the hexagon socket set screw 7 is rotated to move the pressing member to a position near the outer periphery of the base metal 2. By pressing it against the concave portion formed on the end surface of the chuck body 5, a tension acting on the base metal 2 from the center to the outer peripheral direction is applied. The mechanism for applying the tension to the base metal 2 by the tension head 4 is shown clearly in FIG.

By using the inner peripheral blade grindstone 1, a thin plate-shaped wafer is cut from the ingot 9 shown in FIG. During the cutting process, cutting water is sprayed onto the inner peripheral blade 3 from the nozzle 10 fixed near the inner peripheral blade 3.

As the wafer diameter increases, it becomes more necessary to cut an ingot having a large diameter with high accuracy. It is necessary that the inner diameter of the inner peripheral blade 3 is larger than the outer diameter of the ingot 9, and in order to cut the wafer from the ingot 9, the distance from the inner peripheral edge of the base metal to the inner peripheral edge of the tension head 4. However, it must be at least larger than the outer diameter of the ingot 9. Furthermore, in order to improve the yield, it is desirable to make the cutting margin of the ingot as small as possible. Therefore, the thickness of the base metal 2 with respect to the nominal outer diameter of the base metal 2 is required to be smaller than 1/5000.

When attempting to cut the ingot 9 with an inner peripheral blade grindstone using such a thin base metal 2, as shown in FIG. 4 (a), the base metal 2 is cut in a state of being deformed in the rotation axis direction. As a result, the cut-off wafer 9a is warped. The base metal 2 is deformed in the rotation axis direction during the cutting process because when the base metal 2 becomes thin, as shown in FIG. 4B, the base metal 2 is buckled due to the cutting resistance R received from the ingot, and the inner circumference is reduced. Displacement δ ₁ in the rotation axis direction at the position of the blade 3
Is caused.

The size of the warp of the wafer 9a is shown in FIG.
As shown in, the distance from the plane formed by the outer peripheral edge of the wafer 9a to the central portion of the wafer 9a (x in FIG. 4C) is represented. The wafer 9a has a shape as shown in FIG. 4C because the cutting resistance R increases as the cutting length, that is, the length at which the inner peripheral blade 3 contacts the cut portion of the ingot 9 at each moment increases. This is because the cutting length becomes large and the cutting length becomes maximum at the time of cutting the vicinity of the central portion of the ingot 9.

The warp of the wafer 9a thus generated cannot be eliminated even in the subsequent lapping process. It is pressed between the upper and lower lapping machines, and it is processed in a straightened state, and its warp is
This is because if the straightening pressure is released after processing, it will return to the original value.

The demands on the flatness of the wafer have become more and more strict, and it has been extremely difficult to perform high-yield cutting with an inner peripheral grindstone using a thin base metal.

As a conventional technique for eliminating the warp of the wafer that goes through the above-mentioned cutting process, there is a method disclosed in Japanese Patent Laid-Open No. 5-318460. In the system used in this method, as shown in FIG. 9, a chuck body 12 is fixed to the upper end of a spindle 10,
Further, a motor (not shown) is provided at the lower end of the spindle 10.
Are connected so that the spindle 10 and the chuck body 12 are rotated. An inner peripheral edge of a donut-shaped blade is pulled up on the chuck body 12, an inner peripheral blade 16 is formed on the inner peripheral edge of the blade 14, and the outer peripheral edge of the blade is adjusted in tension by a tension applying mechanism of the chuck body 12. It is possible.

The upper end of the semiconductor ingot 18 is fixed to a work support base 21 and is movable in the XX direction shown in the drawing by a cutting feed mechanism 22. The work support base 21 is further operated by a work indexing mechanism 24. It is movable in the ZZ direction. The cutting feed mechanism 22 and the work indexing mechanism 24 are driven by a command signal from the control device 26.

A pair of non-contact type air pads 30, 30 and blade sensors 32, 32 are disposed on the upper surface of the blade 14, and the blade sensors 32, 32 serve as the blade 1.
4 deviation can be detected and the deviation of the blade 14 can be corrected by the air pads 30, 30. Further, the blade sensors 32, 32 are connected to the control device 26, and the control device 26 controls the air pressure adjusting device 36 to operate the air pads 30, 30.

Further, as another conventional technique for eliminating the warp of the wafer caused by the cutting process, the actual flat wafer 1-
There is one disclosed in Japanese Patent No. 138565. In the technique described in the publication, in order to reduce the cutting margin by thinning the wall thickness of the base metal to less than 1/5000 of the outer diameter of the inner peripheral edge grindstone used in the slicing machine for semiconductor wafers, a large size is required. A technique using an alloy having tensile strength as a material of a base metal is disclosed.

[0013]

The above-mentioned conventional techniques for eliminating the warp of the wafer caused by the cutting process have the following problems.

In the method disclosed in Japanese Patent Application No. 5-318460, the blade sensors 32, 32, the air pads 30, 30, the air pressure adjusting device 36, and the control device 26 are extremely large overhang in order to eliminate the warp of the wafer. However, there is a problem in that the cost of equipment for cutting and processing wafers increases.

Further, in the technique disclosed in Japanese Utility Model Laid-Open No. 1-138565, since the ratio of the inner diameter to the nominal outer diameter of the base metal of the inner peripheral grinding wheel is relatively large, the ingot to be cut is As the outer diameter increases,
There has been a problem that the problem of wafer warpage due to deformation due to buckling of the base metal cannot be solved sufficiently.

In order to solve the above-mentioned conventional problems, the present invention is focused on for the first time that the ratio of the inner diameter to the outer diameter of the base metal of the inner peripheral edge grinding wheel has a great influence on the rigidity of the inner peripheral edge grinding wheel at the time of cutting. However, by optimizing the inner-outer diameter ratio of the base metal of the inner-edge blade grindstone without using a special system, it is possible to suppress the warp of the wafer caused by the cutting process for the inner-edge blade slicing machine. The purpose is to provide a whetstone.

[0017]

A grindstone for an inner peripheral blade slicing machine according to the present invention, which solves the above-mentioned problems, includes a base metal made of an annular flat plate having a concentric inner circumference and an outer circumference, and an inner circumference of the base metal. And an inner peripheral blade including an abrasive grain layer formed over the entire circumference thereof. The outer periphery of the base metal is clamped and fixed by annular tension heads from the front and back sides over the entire periphery, and tension is applied from the center of rotation toward the outer periphery.

The feature of this grindstone for an inner peripheral blade slicing machine is that the thickness of the base metal is not more than 1/5000 of its outer diameter, and the ratio of the inner diameter of the inner peripheral blade to the inner diameter of the tension head is 0.25. It is above and 0.33 or less.

[0019]

According to the grindstone for the inner peripheral blade slicing machine of the present invention, the ratio of the inner diameter of the inner peripheral blade to the inner diameter of the tension head is 0.33 or less, and thus the thickness of the base metal is 5000 of the outer diameter. Even when a thin inner peripheral grindstone having a thickness of one-tenth or less is used, buckling deformation of the base metal caused by cutting resistance acting on the inner peripheral blade during cutting is suppressed. As a result, the warp of the wafer due to the deformation of the inner peripheral edge grindstone during the cutting process is suppressed within a desired allowable range.

Further, since the ratio of the inner diameter of the inner peripheral blade to the inner diameter of the tension head is 0.25 or more, the workability for setting the cut object in a cuttable state is kept good and sufficient. A cutting stroke is secured.

[0021]

An embodiment of the present invention will be described below with reference to the drawings.

In the present embodiment, as the inner peripheral blade grindstone,
The same shape as that shown in FIG. 1 described in the above conventional technique is used. Further, the manner of cutting the ingot 9 by the inner peripheral blade grindstone 1 and the mechanism for applying tension to the base metal 2 by the tension head 4 are the same as those of the conventional one shown in FIGS. 2 and 3.

As the cutting device used in the cutting method of this embodiment, the same device as the conventional one shown in FIG. 8 is used. However, in this embodiment, the deviation of the inner peripheral grindstone during the cutting process is used. Since the amount is suppressed to be relatively small, the air pad 30,
30, the blade sensors 32, 32, and the air pressure device 36 are not particularly necessary.

As shown in Table 1 below, in this embodiment, a gallium arsenide ingot for a wafer outer diameter of 3 inches is used as the material to be cut, and the thickness of the cut wafer is 0.7 mm. . Table 1 shows the material and size of the base metal 2 of the inner peripheral edge grindstone 1, the size of the tension head 3, and the thickness of the inner peripheral edge (abrasive layer).

[0025]

[Table 1]

As shown in Table 1 above, the base metal 2 is made of a stainless steel alloy having super tensile strength.
The ratio of the thickness T to the outer diameter D is 1/5000 or less.

As cutting conditions, the cutting speed is 5 to 3
0 mm / min, 1000 to 18 as the number of revolutions of the inner edge grinding wheel
Although it is possible to use a range of 00 rpm, in this example, as shown in Table 2 below, the cutting speed was 2
The case where the grinding wheel rotational speed is 1500 rpm at 0 mm / min is shown. Pure water was used as cutting water.

[0028]

[Table 2]

In the present embodiment, the base metal 2 is used as an index indicating the rigidity of the inner peripheral edge grindstone 1, that is, the degree of difficulty of deformation due to buckling due to cutting resistance. That is, Q measured by the contact displacement sensor 51 when a force of 300 g parallel to the rotation axis direction is applied to point P shown in FIG. The displacement amount δ _p of the point in the rotation axis direction was used. The displacement amount δ _p of the base metal was measured when the ratio of the inner diameter D _{1 of the} inner peripheral blade / the inner diameter D ₂ of the tension head was changed for each of the base metals A to C, and the results shown in FIG. 7 were obtained. . When the base metal having the same thickness is used from the wafer shown in FIG. 7, the ratio D ₁ / D
It can be seen that the smaller the value ₂ , the smaller the displacement amount δ _{p of the} base metal, and the greater the rigidity can be obtained.

In the present embodiment, the ratio D ₁ / D ₂ for each of the three types of base metals A to C having different thicknesses.
Was changed to four kinds of 0.40, 0.33, 0.30 and 0.25, and 20 wafers were cut for each, the warp x of the wafer was measured, and its average value and its standard value were measured. The deviation σ was calculated. The results are shown in Table 3 below.
And the graph of FIG.

[0031]

[Table 3]

The lower limit of the ratio D ₁ / D ₂ must be 0.25 or more for the following reason.

First, the inner diameter D ₁ of the inner peripheral blade must be larger than the outer diameter of the object to be cut because the object to be cut will enter inside. Further, the difference between the inner diameter saw within a radius D _1/2 and the radius D _2/2 tension head must be greater than the cutting stroke. Therefore, from the viewpoint of ensuring the longest cutting stroke, the ratio D ₁ / D ₂ is preferably about 1/3.

However, from the above consideration, in order to increase the rigidity of the inner peripheral blade grindstone, the smaller the inner peripheral blade inner diameter D ₁ is, the better. Further, in consideration of the actual size of the inner peripheral edge grinding wheel and the object to be cut, for example, an inner peripheral edge grinding wheel having a nominal outer diameter of 21.5 inches (tension head inner diameter D ₂ = 464 mm) is used for an ingot for a wafer outer diameter of 3 inches ( Cutting stroke including carbon base 83 mm, size of cut object 94 m
Considering workability when setting the inside of the inner peripheral blade of the object to be cut when performing the cutting of m), the inner peripheral blade inner diameter D ₁ needs to be about 110 mm or more.

Summing up the above, the ratio D ₁ / D ₂
It is necessary to secure a lower limit value of 0.25 or more, and as a result, the ratio D ₁ / D ₂ is 0.25 or more and 0.
By setting the value to 33 or less, the object of the present invention will be achieved.

The above description of the prior art will be made.
In the inner peripheral edge whetstone of Japanese Utility Model Publication No. 1-138565,
23.5 inches (597 mm) as outer diameter of gold, inner diameter
(D₁) Is 184 mm, and in that case
Tension head inner diameter D₂Is the radial direction of the tension head
Since the width is about 537 mm or less considering the width of the
₁/ D₂Exceeds 0.34. Therefore, in the publication
The object of the present invention cannot be achieved with a peripheral cutting wheel.

[0037]

As described above, according to the present invention, the workability and the workability can be improved by setting the ratio of the inner diameter of the inner peripheral blade of the grinding wheel to the inner diameter of the tension head to 0.25 or more and 0.33 or less. It is possible to provide an inner peripheral edge grindstone having high rigidity when using a thin base metal having a sufficient cutting stroke and a base metal thickness of 1/5000 or less of the outer diameter. As a result, it becomes possible to cut a wafer having a large outer diameter with a relatively small cutting margin, and suppress the magnitude of warpage and its variation within an allowable range. Therefore, it is possible to produce wafers having a large outer diameter with a high yield and at a relatively low cost without requiring a special device for forcibly suppressing the deformation of the inner peripheral edge grindstone.

[Brief description of drawings]

FIG. 1 (a) is a front view showing the shape of an inner peripheral edge grindstone commonly used in a conventional slicing machine and an embodiment of the present invention, and FIG. 1 (b) is a view showing a BB cross section thereof. .

FIG. 2 is a perspective view showing a state during cutting of an ingot by a conventional slicing machine and an inner peripheral blade grindstone in one embodiment of the present invention.

FIG. 3 is an enlarged partial cross-sectional perspective view for explaining a mechanism of applying tension to the base metal 2 by the tension head 4 in the inner peripheral blade grindstone shown in FIG.

4A is a partial cross-sectional view for explaining the relationship between the deformation of the base metal 2 of the inner peripheral edge grinding wheel and the warp of the wafer, and FIG. 4B is the cutting resistance R acting on the base metal 2 and the internal resistance. FIG. 3C is a partial cross-sectional view for explaining the relationship with the deviation amount δ ₁ of the peripheral blade 3, and FIG.

FIG. 5A is a partial perspective view for explaining a method of measuring the degree of rigidity of the inner peripheral edge grindstone in one embodiment of the present invention, and FIG. 5B is a partial sectional view of the same.

FIG. 6A is a stress σ _t in the circumferential direction of the base metal 2.
FIG. 3B is a diagram for explaining the meaning of, and FIG. 3B is a diagram showing the relationship between the position r from the rotation center of the base metal 2 and the stress σ _{t in the} circumferential direction.

FIG. 7 is a diagram showing the relationship between the inner peripheral blade inner diameter D ₁ / tension head inner diameter D ₂ and the base metal deviation amount δ _p for each of the base metals A to C measured in the example of the present invention. Is.

FIG. 8 shows the average value x− of each of the wafers and the respective average values x− of the wafers when the ratio D ₁ / D ₂ of each of the base metals A to C was changed to four types, which were measured in the example of the present invention. It is a figure which shows the relationship with standard deviation (sigma).

FIG. 9: Japanese Patent Laid-Open No. 5-3184 as prior art of the present invention
It is a figure which shows typically the system of the slicing machine disclosed by the 60th publication.

[Explanation of symbols]

 1 Inner peripheral blade whetstone 2 Base metal 3 Inner peripheral blade 4 Tension head

Claims (1)

[Claims] 1. A base metal comprising an annular flat plate having concentric inner and outer peripheries, and a tension that sandwiches the outer periphery of the base metal from the front and back sides over the entire circumference, and applies tension to the base metal from the center to the outer peripheral direction. Holding and fixing, an annular tension head, and an inner peripheral blade including an abrasive grain layer formed over the entire circumference on the inner circumference of the base metal, wherein the thickness of the base metal is A grindstone for an inner peripheral blade slicing machine having a diameter of 1 / 5,000 or less and a ratio of the inner diameter of the inner peripheral blade to the inner diameter of the tension head of 0.25 or more and 0.33 or less.