JP2002331518A - Method for cutting single crystal ingot - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method which can simply cut out a wafer having a main surface accurately parallel to a standard cross section formed in the end part of a columnar single crystal ingot. SOLUTION: In the method for simply cutting out the wafer having the main surface accurately parallel to the standard cross section 1a formed previously at least in one end part of the columnar single crystal ingot 1, the standard cross section 1a is cut accurately in advance to have a crystallographycally prescribed surface direction. A prescribed cleavage piece 6 is joined to the peripheral vicinity of the standard cross section 1a. The cleavage piece 6 has a completely flat cleavage surface as the first surface joined to the standard cross section 1a and the second completely flat cleavage surface crossing the first cleavage surface. The ridge between the first and second cleavage surfaces is set up to be parallel to a cut surface by a slicer or a wire saw 13.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for cutting a single crystal ingot, and more particularly to an improvement in a method for cutting a wafer from a columnar single crystal ingot such as a semiconductor or a dielectric.

[0002]

2. Description of the Related Art When a wafer is cut out from a columnar or prismatic single crystal ingot, an inner peripheral slicer, an outer peripheral slicer, a wire saw, and the like are generally used.

Incidentally, a wafer such as a semiconductor or a dielectric used for an electronic component is often required to have a specific crystallographic orientation on its main surface. For example, when each of a plurality of wafers cut out from one columnar single crystal ingot should have a specific principal plane orientation A, first, at one end of the columnar ingot, a reference cross section having the plane orientation A with high accuracy is obtained. Is formed.

When such a reference cross section is formed, generally, the crystal orientation of the ingot is obtained by X-ray diffraction,
Based on this, the plane orientation A at the end of the columnar ingot
The first section is formed by a slicer to produce Then, measurement is again performed by X-ray diffraction to confirm that the first cross section is correctly coincident with the plane orientation A. If the first cross section is shifted from the plane orientation A by an angle larger than a predetermined allowable amount. If so, the second section is formed again by the slicer so as to correct the deviation angle. Such an operation is repeated until the end surface of the columnar ingot becomes a reference cross section that matches the plane orientation A with a predetermined high accuracy.

After the reference section having the plane orientation A is formed at the end of the columnar ingot with high accuracy, a plurality of main sections having the main plane of the plane orientation A are formed by, for example, a multi-wire saw as shown in FIG. Wafers can be cut at the same time.

In the multi-wire saw shown in the schematic perspective view of FIG. 6, a columnar single crystal ingot 1 having a reference cross section 1 a having a plane orientation A is fixed to a fixing jig 3 via a carbon jig 2. I have. The carbon jig 2 is used to prevent and hold the wafer cut from the ingot 1 from falling. The fixing jig 3 is set on the turning stage 11. A plurality of wires 13 are wound around the head roller 12. These wires 13 are moved along the longitudinal direction of the wires themselves by the rotation of the head roller 12. As the wire 13, for example, a piano wire can be used. In the state shown in FIG. 6, the periphery of the reference cross section 1 a of the columnar ingot 1 is observed by the tool scope 14. The tool scope 14 has, for example, a magnification of about 40 times.

FIG. 7 shows a reference cross section 1 a of the columnar ingot 1.
From the front. Tool scope 14
Can be moved in parallel with the wire 13, and the upper periphery of the circular or elliptical reference cross section 1a is observed at the distance indicated by the broken line 14a. Then, the turning stage 11 is adjusted and turned so that the horizontal direction x in the reference cross section 1a and the longitudinal direction of the wire 13 are parallel. Thereafter, the ingot 1 is slowly lifted along the upward direction y in the reference cross section 1a together with the fixed rotating stage 11, and a plurality of wires 13 moving along the x direction cause the ingot 1 to move from the ingot 1 to the plurality of wires 13. The wafer will be cut out.

The surface of the wire 13 is provided with a cutting oil mixed with abrasive grains such as silicon carbide or diamond. The parallelism between the upward direction y in the reference section 1a and the rising direction of the ingot 1 is checked by applying a dial gauge to the upper and lower parts of the reference section 1a. Is corrected using

[0009]

In FIG. 7, when the upper periphery of the cross section 1a is observed by the tool scope 14 in order to set the x direction in the reference cross section 1a to be parallel to the direction of the wire 13, the upper periphery of the cross section is set. As the distance from the uppermost point in the left-right direction decreases, the height decreases, that is, the observation distance 14a changes. Therefore, if the tool scope 14 is focused on the uppermost point of the reference section 1a, the focus shifts as the distance from the tool scope 14 increases in the left-right direction, and the peripheral image of the section 1a appears blurred. For this reason, it is not easy to set the x direction in the cross section 1a to be parallel with the direction of the wire 13 with high precision while directly observing the periphery of the reference cross section 1a using the tool scope 14.

Under these circumstances, a method of cutting an ingot as illustrated in FIGS. 8 and 9 has been attempted. FIG. 8 is similar to FIG. 7, but in FIG. 8, the blade 4 of the cutter knife is joined at the upper part of the reference section 1a. FIG. 9 shows a state where the ingot 1 in FIG. 8 is viewed from the right side. As can be seen more clearly in this figure, the blade 4 of the cutter knife is joined by double-sided joining tape 5 to the upper part of the reference section 1a.

In the wafer cutting method using the cutter knife blade 4 as described above, as shown in FIG. 8, the height of the blade edge of the blade 4 does not change even if it is separated from the center in the left-right direction. The distance 14a does not change. That is,
Even if the focal point of the tool scope 14 is focused on the center of the cutting edge of the blade 4, the focal point does not shift significantly as the distance from the tool scope 14 increases. Therefore, in comparison with the case where the periphery of the reference section 1a is directly observed through the tool scope 14, the wafer cutting method using the blade 4 of the cutter knife can obtain a wafer having a principal surface closer to the plane orientation A. it can.

However, the blade 4 of the cutter knife is made by processing from a rolled thin steel plate,
The side surface to be joined to a is not necessarily a perfect plane. Further, since the double-sided bonding tape 5 is made of a soft polymer tape and an adhesive, if the pressing force at the time of bonding the blade 4 of the cutter knife is not uniform, the parallelism between the blade edge and the reference cross section 1a is obtained. May shift. Furthermore, when the cutting edge of the blade 4 is observed at a magnification of 40 times via the tool scope 14, the cutting edge is often seen with a fairly thick width with a halation. In such a case, it is not easy to accurately adjust the turning stage 11 so that the longitudinal direction of the cutting edge of the blade 4 is parallel to the wire 13. Furthermore, after the setting of the x direction in the reference section 1a is completed, when the cutter knife blade 4 and the double-sided bonding tape 5 are peeled off from the cross-section 1a, there is a danger of being hurt by the blade edge. It is often difficult to peel 5 off.

In view of the situation in the prior art as described above, according to the present invention, it is possible to easily cut a wafer having a main surface parallel to a reference cross section formed at the end of a columnar single crystal ingot with high accuracy. It is intended to provide a way.

[0014]

According to the present invention, a method for easily cutting a wafer having a main surface parallel to a reference cross-section formed at least at one end of a columnar single crystal ingot with high accuracy in a simple manner. In, the reference cross section is cut in advance with high precision so as to have a predetermined plane orientation crystallographically, a predetermined cleavage piece is joined near the periphery of the reference cross section, and the cleavage piece is joined to the reference cross section It has a completely flat cleavage plane as the first plane, and has a completely flat second cleavage plane that intersects the first cleavage plane, and a ridge where the first and second cleavage planes intersect is formed. It is characterized in that it is set so as to be parallel to a cut surface by a slicer or a wire saw.

Preferably, the cleavage pieces are joined on the reference cross section by the surface tension of the liquid. Preferably, the liquid is oil.

As the cleavage piece, a compound semiconductor can be preferably used. The first and second cleavage planes preferably intersect each other at a solid angle in the range of 45 to 135 degrees,
More preferably, they cross each other at a solid angle in the range of 85 to 95 degrees.

The ingot is fixed to the turning means via a predetermined jig, and a ridge at which the first and second cleavage planes intersect is observed by a cutting blade or a microscope which can be moved in parallel with the saw wire. Is preferably arranged within the movable range of the field of view of the microscope.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the schematic perspective view of FIG.
1 shows an embodiment of a method for cutting a single crystal ingot according to the present invention. The multi-wire saw shown in FIG. 1 is the same as that of FIG. 6, except that in FIG.
On the reference section 1a of the nP ingot 1, a thin rectangular parallelepiped cleavage piece 6 is joined by the surface tension of oil. The cleavage pieces 6 are formed of InP of the same material as the ingot 1. In general, many compound semiconductors such as GaAs and InP have good cleavage properties, and can be preferably used as a material of the cleavage pieces 6.

Since cleavage occurs along specific atomic planes regularly arranged in the crystal, the cleaved fracture surface can be flat in atomic order. Accordingly, the ridge formed by the intersection of the two cleavage planes has high accuracy linearity.

FIG. 2 schematically shows a state in which the cleavage piece 6 is observed through the tool scope 14 in the state of FIG. A horizontal line in the cross-hair frame 14b shown enlarged in the tool scope 14 is set in parallel with the longitudinal direction of the wire 13. Then, the turning stage 1 is set so that the ridge where the surface in contact with the reference section 1a and the narrow upper surface in the surface of the cleavage piece 6 intersect is parallel to the horizontal cross line.
The angle is adjusted by 1. Thereby, the reference cross section 1
The horizontal x-axis direction in a is exactly parallel to the longitudinal direction of the wire 13.

The top view of FIG. 3 and the corresponding side view of FIG. 4 illustrate the process of such angle adjustment. Referring to these figures, first, the tool scope 14 is
Is located at an arbitrary first position 141 close to one end.
Here, the focal point of the tool scope 14 is made to coincide with the upper surface F1 of the wire 13. Then, the horizontal line in the crosshair frame 14b and the side surface of the wire 13 are matched in the microscope visual field. Next, an arbitrary second position 1 near the other end of the cleavage piece 6
The tool scope 14 is moved in parallel to the wire 13 to 4II. Then, at the second position 14II, the tool scope 14 is turned so that the horizontal line in the cross hair frame 14b and the side surface of the wire 13 exactly match. Thereby, the crosshair frame 1 in the tool scope 14 is
The horizontal line in 4b and the wire 13 are set exactly in parallel.

Thereafter, the focal point of the tool scope 14 is made to coincide with the upper surface F2 of the cleavage piece 6. Then, by moving the tool scope 14 back and forth, the long side of the upper surface of the cleavage piece 6 is aligned with the horizontal line in the cross-hair frame 14b. Next, the tool scope 14 is returned parallel to the wire 13 near the first position 141 described above. Then, the swivel stage 11 on which the ingot 1 is installed is turned so that the long side of the upper surface of the cleavage piece 6 and the horizontal line in the cross-hair frame 14b exactly match again. by this,
This means that the horizontal x direction in the reference cross section 1a of the ingot 1 and the longitudinal direction of the wire 13 are set exactly parallel.

At the time of such angle adjustment, in the InP cleavage piece 6, the surface in contact with the reference section 1a and the narrow upper surface are orthogonal to each other and the upper surface becomes a horizontal plane. The tool scope 14 facilitates clear observation. This can further improve the accuracy of the cut plane orientation. In addition, in general, the solid angle formed by the surface in contact with the reference cross section 1a and the narrow upper surface in the surface of the cleavage piece 6 is preferably in the range of 45 to 135 degrees, and 85
More preferably, it is within the range of 95 degrees. Further, since the cleavage pieces 6 are joined by the surface tension of the oil, the joining and peeling of the cleavage pieces 6 with respect to the reference cross section 1a can be extremely easily performed.

According to the above embodiment, wafers were actually cut out from 14 columnar InP single crystal ingot samples of different lots. FIG. 5 shows a shift angle in the x direction between the main surface direction of the cut wafer and the plane direction of the reference cross section 1a.

That is, in the graph of FIG. 5, the horizontal axis represents the shift angle (degree) in the x direction, and the vertical axis represents the number of ingot samples. Statistical calculation was performed on the numerical value of the shift angle based on this graph, and the arithmetic mean error e
Was 0.009 degrees, and the standard deviation σ was 0.005 degrees. Therefore, assuming that the deviation angle in the x direction is managed by 3σ, the cutting method of the present invention is e + 3 in the x direction.
It has the ability to keep σ within the error range of 0.024 degrees.

For comparison, when the above-mentioned cutting method using the cutter knife was performed for the same number of samples, the arithmetic average error e was 0.025 degrees, and the standard deviation σ
Was 0.009 degrees. Therefore, if 3σ is managed in the cutting method of this comparative example, the cutting method has the ability to suppress the error to e + 3σ = 0.052 degrees in the x direction. As is apparent from the comparison between the comparative example and the above-described embodiment, it can be seen that the accuracy of the plane orientation of the wafer cut by the cutting method of the present invention can be significantly improved.

In the above embodiment, the surface tension of oil is used to join the cleavage pieces 6 to the reference cross section 1a.
Of course, the surface tension of water may be utilized if desired.

[Brief description of the drawings]

FIG. 1 is a schematic perspective view illustrating a method for cutting a single crystal ingot according to an embodiment of the present invention.

FIG. 2 is a top view showing a field of view of a tool scope in FIG. 1;

FIG. 3 is a top view illustrating a method of setting the parallelism between the horizontal direction of the reference cross section of the ingot and the saw wire.

FIG. 4 is a side view corresponding to FIG.

FIG. 5 is a graph showing angular accuracy in a method for cutting a single crystal ingot according to an embodiment of the present invention.

FIG. 6 is a schematic perspective view showing a conventional method for cutting a single crystal ingot.

FIG. 7 is a diagram showing a state in which a reference cross section of the ingot in FIG. 6 is viewed from the front.

FIG. 8 is a front view showing a cutting method attempted in the prior art.

9 is a diagram showing a state where the ingot in FIG. 8 is viewed from the right side.

[Explanation of symbols]

1 columnar single crystal ingot, 1a reference cross section, 2 carbon jig, 3 fixing jig, 4 cutter knife blade, 5
Double-sided adhesive tape, 6 cleavage pieces, 11 rotating stage, 1
2 Head roller, 13 wires, 14 tool scope, 14a line of sight through tool scope, 14b field of view of tool scope, 14I first position of tool scope, 14II second position of tool scope, F1
First focal plane of the tool scope, F2 Second focal plane of the tool scope.

Claims (7)

[Claims] 1. A method for easily cutting out a wafer having a principal surface parallel to a reference cross-section formed at least at one end of a columnar single crystal ingot with high precision, wherein the reference cross-section is crystallographic. Is cut in advance with high precision so as to have a predetermined plane orientation, and a predetermined cleavage piece is joined near the periphery of the reference cross section, and the cleavage piece is completely formed as a first surface to be joined to the reference cross section. And a second cleavage plane that is completely flat and intersects with the first cleavage plane, and the ridge where the first and second cleavage planes intersect is a cut plane by a slicer or a wire saw. A method for cutting a single crystal ingot, wherein the method is set so as to be parallel to the ingot. 2. The method for cutting a single crystal ingot according to claim 1, wherein the cleavage pieces are joined on the reference cross section by a surface tension of a liquid. 3. The method for cutting a single crystal ingot according to claim 2, wherein the liquid is oil. 4. The method for cutting a single crystal ingot according to claim 1, wherein the cleavage piece is made of a compound semiconductor. 5. The first and second cleavage planes are 45 to 135.
The method for cutting a single crystal ingot according to any one of claims 1 to 4, wherein the single crystal ingots intersect at a solid angle within a range of degrees. 6. The method for cutting a single crystal ingot according to claim 5, wherein the first and second cleavage planes cross each other at a solid angle within a range of 85 to 95 degrees. 7. The ingot is fixed to a turning means via a predetermined jig, and a ridge at which the first and second cleavage planes intersect is observed by a cutting blade or a microscope capable of moving in parallel with a saw wire. The method for cutting a single crystal ingot according to any one of claims 1 to 6, wherein a turning axis of the turning means is arranged within a movable range of a visual field of the microscope.