JPH08309737A - Method for working single-crystal ingot - Google Patents

Abstract

PURPOSE: To precisely cut out wafers with a desired orientation from an ingot of a single-crystal semiconductor or derivative. CONSTITUTION: In the state of a single-crystal ingot attached to the jig, an orientation D is measured in the face parallel to the end face of the jig, and the difference Z between D and the aimed orientation Q is obtained for securing the ingot to an angle-control device attached to the cutting table of a cutting machine in a condition of the ingot attached to the jig, then the angle control device is shifted by-Z so as to allow the direction intersecting to the base bottom of the cutting table to be an aimed face, thus, wafers are cut out by a cutting machine for cutting out objectives in the direction orthogonal to the cutting table.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for processing a single crystal ingot such as a semiconductor or a dielectric. The semiconductor of interest is a single crystal of Si, GaAs, InP or the like.
When a single crystal ingot produced by the Czochralski method or the Bridgman method is cut into thin wafers, it is necessary to accurately obtain the crystal orientation and cut the wafer having a desired orientation. For example, a (100) wafer or a (111) wafer may be processed so that its crystal plane is precisely parallel to the wafer surface. Further, a wafer having a surface inclined by a predetermined angle from (100) may be processed. In any case, it is necessary to determine the crystal orientation at the ingot stage and cut it. An inner peripheral blade slicer, an outer peripheral blade slicer, and a wire saw are used for cutting.

[0002]

2. Description of the Related Art Conventionally, the crystal orientation is determined by the time the ingot is attached to the attachment reference plane of the cutting machine, and the slice is sliced to obtain the desired orientation plane (hereinafter sometimes referred to as the cutting target plane or the desired orientation plane). It was fixed on the mounting reference surface of the cutting machine after the. In this case, the cutting direction may be parallel to the reference plane. When the ingot is cut by the wire saw, the traveling direction of the wire saw may be completely parallel to the reference plane. When using blades such as inner and outer blades, the surface of the blade is parallel to the reference plane of the cutting machine. The relationship between the movement of the blade and the cutting machine is simple. However, in this case, it takes time and trouble to cut the ingot and obtain a desired surface (target surface Q).

A method of obtaining the crystal orientation in the conventional method will be described. The ingot is attached to a jig of a carbon and fixed to a fixture of a cutting machine (for example, an inner peripheral blade slicer). This is Figure 1
Is the state shown in. 1 from the end surface of the ingot in this state
Cut out a piece of wafer. This is the procedure shown in FIG.
The reason why the jig is attached to the carbon jig is that when the ingot is cut into wafers, they are separated and do not fall. Even after the cutting, since the edge of the wafer is attached to the carbon jig, the state can be maintained as it is. It is common practice to secure the ingot to the carbon.

The crystal orientation W1 of this wafer is measured by X-ray diffraction. The deviation of the wafer surface orientation from the target surface orientation Q is calculated. It is good if there is no deviation. Remove from the cutting machine and start cutting the ingot by another cutting machine.

If there is a deviation, the angle adjuster of the cutting machine is adjusted so that the target surface Q is cut. In this state, the second wafer is cut out (FIG. 2). The crystal orientation W2 of this wafer is examined by X-ray diffraction. If the wafer surface is the target orientation plane Q, the wafer may be cut out in this state. However, if the wafer surface is not still the target surface Q, the angle adjuster is further adjusted to cut out the third wafer.

When the difference between the wafer azimuth plane W and the target azimuth plane Q is within the tolerance, the angle adjustment is finished. When this happens, the ingot is removed from the slicer. At this time, the end surface S of the ingot is the target surface Q.

The ingot is fixed on the cutting machine such that the end surface S of the removed ingot is parallel to the reference plane of the cutting machine (wire saw, etc.). This cutting machine cuts the object parallel to the reference plane. Therefore, this cuts out a wafer having a desired orientation plane. The first cutting machine for cutting the end face of the ingot into a desired orientation plane and the second cutting machine for cutting a large number of wafers are different machines. There are two methods for fixing the end surface of the ingot so that it is parallel to the reference surface.

One is the method shown in FIG. The adhesive 5 is applied on the fixing jig 3, the carbon jig 2 having the ingot 1 attached thereto is placed thereon, and the adhesive 5 is applied while pressing the end surface S of the ingot against the reference plane Z of the cutting machine. Let it harden. At this time, the angle adjuster supporting the fixing jig is appropriately tilted so that the end surface S becomes parallel to the reference surface Z.

Another method will be described with reference to FIG. The carbon jig 2 to which the ingot 1 is attached is fixed to the fixture 3. This is attached to the angle adjusting goniometer 4. The end surface S of the ingot and the reference surface Z may be parallel to each other. For this purpose, the distance between the end surface of the ingot and the reference surface is measured with a microscope at three locations. The goniometer is adjusted so that the distances D1, D2, and D3 at these three locations match. If D1 = D2 = D3, the ingot end surface S and the reference surface Z are parallel.

After the ingot is attached to the cutting machine in this way, the wafer is cut out with the wire saw, the inner peripheral blade slicer, the outer peripheral blade slicer, etc. as described above. Since the cutting plane is parallel to the reference plane, a wafer having a plane orientation equal to the desired orientation is cut out. The purpose of the present invention is to accurately determine the orientation of the ingot, and cutting the wafer is a subsequent step.

Wafer cutting is outside the scope of the present invention, but will be briefly described. The cutting by the wire saw is highly efficient because the wafer is cut out at once. In the wire saw, one endless wire is wound around three grooved rollers at regular intervals to reciprocate the wire. When the ingot is applied to a plurality of wires and translated, a large number of wafers are cut out at the same time. The present invention can be applied not only to the wire saw but also to the determination of the orientation at the time of cutting with the inner peripheral blade slicer.

Japanese Unexamined Patent Publication No. 1-177958 discloses a main
We have proposed a mechanism that can independently adjust the wire tension by controlling the speeds of the winding and winding rollers independently. JP-A-5-10
No. 4432 proposes a mechanism for reciprocating two or more wires because the conventional wire saw, which reciprocates one wire, wears the wires severely. Wear is reduced because multiple wires are used. Of course. Japanese Unexamined Patent Publication (Kokai) No. 3-208555 proposes an improvement of the mechanism for supplying the polishing liquid to the wire of the wire saw.

As described above, there are many improvements in the wire saw itself. The present invention is not an improvement on cutting machines such as wire saws. It relates to an orientation method for setting on a cutting machine. Therefore, there is no direct relation between these conventional examples and the present invention.

[0014]

In the conventional cutting method, the wafer is often cut out, the crystal orientation of the wafer is detected, the orientation of the ingot is adjusted, and the end face of the ingot is made into a plane having a desired orientation. Attach to. This has the following drawbacks.

Since the orientation is checked after the wafer is cut out for inspection, extra labor is required. Since it is necessary to cut out many wafers and examine the orientation, the material loss is large. It is difficult to set the end surface of the ingot in a desired orientation and fix it so as to be parallel to the contact surface (reference surface Z) of the cutting machine. Workers' skill and patience are required. Since there are many places where manual work is performed, the error is large.
The wafer surface orientation error does not fall below ± 0.2 °.

It is a first object of the invention to provide a method by which the orientation of a single crystal ingot can be determined without material loss. It is a second object of the present invention to provide a method capable of determining the orientation of a single crystal ingot without cutting the wafer. It is a third object of the present invention to provide a method for determining the orientation of an ingot that does not depend on the skill of the operator. It is a fourth object of the present invention to provide a method capable of determining the orientation of an ingot in a short time. A fifth object of the present invention is to provide a highly accurate ingot azimuth determination method.

[0017]

A method for processing a single crystal ingot according to the present invention is to attach the single crystal ingot to a jig,
This was fixed to a rectangular parallelepiped common jig having planes A, B, and C, and the orientation of the plane D of the ingot perpendicular to planes B and C of the common jig was determined by X-ray diffraction, and the cutting target plane Q Difference with Z
= D-Q, attach the ingot to the angle adjuster of the cutting machine with it attached to the rectangular parallelepiped jig, move the angle adjuster by -Z for the difference between the D plane and the Q plane, and move it to the base of the angle adjuster. The surface having a right angle is made to be the target cutting surface, and the ingot is cut at a right angle to the base of the angle adjuster, so that the wafer having the target surface is cut out.

[0018]

Several planes will be described below, but the plane X includes a specific plane X and all planes parallel thereto. In other words, only the orientation of the surface matters, the position of the surface does not matter.

A single crystal ingot 1 attached to a carbon jig as shown in FIG. 1 is fixed to a common jig 3 having a rectangular parallelepiped shape. This jig has a rectangular parallelepiped shape, and an end face A, a side face B, and a bottom face C are perpendicular to each other. The state becomes as shown in FIGS. Use this jig with the above-mentioned cutting machine (wire saw, inner blade slicer).
Etc.), the cutting machine cuts the ingot so that it becomes parallel to the plane perpendicular to both B and C planes, that is, A plane. I do not know what direction the end face of the ingot is.

Without cutting out a test wafer from the ingot, it is perpendicular to the B and C planes (that is, parallel to the A plane).
The orientation of the ingot surface D is measured by X-ray diffraction. The D surface represented by the broken line in FIG. 6 is the X-ray measurement surface. D side is D
It can be strictly defined for the ingot by ⊥B and D⊥C. The azimuth of plane D should be close to the target azimuth Q, but it is slightly different. Fix the ingot together with the common jig to the pedestal of the angle adjuster placed on the cutting table. That is, instead of placing the ingot directly on the cutting table, it is attached to the angle adjuster on the cutting table.

This is the state shown in FIG. An angle adjuster is placed on the cutting board of the cutting machine. The angle adjuster 6 has a pedestal 7 on the upper side and a base 8 on the lower side. The intermediate part is a biaxial adjusting part 9. A common jig is fitted into the U-shaped pedestal 7 and is fixed with bolts 10.

Let K be the upper surface of the cutting table. The bottom of the jig is C
The surface. The top surface of the pedestal of the angle adjuster is C, and the bottom surface of the base is K. In the conventional example, the jig 3 was directly fixed to the base without placing the angle adjuster. In this case, the plane K is parallel to the plane C, and the cutting is performed in the direction perpendicular to the plane K.
The target plane Q of the ingot had to be perpendicular to the plane C.

However, in the present invention, since the angle adjuster 6 is placed between the cutting table and the jig 3, the plane K does not have to be parallel to the plane C. The angle adjuster 6 can adjust the angles of two axes. A vertical direction Θ and a rotation direction Φ around the vertical axis. The crystal orientation of the D plane (plane orthogonal to the BC plane) of the ingot has been measured previously. The difference between the target cutting direction Q and the orientation of the D plane is calculated.

FIG. 8 shows the case where the angles Θ and Φ of the angle adjuster are both 0. In this case, since the jig bottom surface C and the pedestal bottom surface K are parallel to each other and the C surface and the D surface are at right angles, the D surface and the K surface are orthogonal to each other. It is D⊥K. The difference between the orthogonal plane D and the target plane Q, Z = D
-Calculate Q. This difference is actually a two-dimensional vector. The surface is represented by a unit vector of the normal line, and these differences are naturally two-dimensional vectors. Below, these parameters are two-dimensional quantities.

The angle adjuster is moved by -Z with a negative sign added to this difference. Then, the target plane Q becomes orthogonal to the K plane. FIG. 9 shows this state. C-plane and K-plane are not parallel, but differ by -Z. The cutting machine is the table surface K
Since the wafer is cut out in the direction orthogonal to, the wafer can be cut out along the target surface by cutting the ingot in this state.

According to the present invention, the angle adjuster is interposed, and the angle adjuster is displaced by an amount corresponding to the difference between the axis orthogonal plane D of the ingot and the target plane Q so that the target plane Q becomes parallel to the cutting plane. . Therefore, it is not necessary to cut out the wafer and detect the orientation. It is the measurement of the direction by non-destructive inspection. Therefore, it is possible to avoid the trouble of cutting the wafer and the loss of material. It is easy to measure the orientation of the plane D orthogonal to the axis. Moreover, the adjustment of the angle adjuster can be completed in a short time. No skill is required. Since the orientation of the ingot is not known from the wafer orientation after cutting the wafer, the orientation accuracy of the ingot is high.

[0027]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the description of FIGS. 7 to 9, details of the angle adjuster are omitted. This is a biaxial adjustable device, and any device that can be fixed to the cutting table of the cutting machine may be used. An example of the angle adjuster will be described with reference to FIGS.

In FIG. 10, the angle adjuster 6 includes an upper surface arc block 11, an intermediate arc block 12, and an
It is composed of an intermediate disk 13 and a base disk 14. The upper surface arc block 11 hits the pedestal 7 in FIGS. 7 to 9. Base disk 14
Corresponds to base 8.

The upper block 11 and the intermediate block 12 are
They are in contact with each other on an arc surface 17 having an axis in the horizontal direction. Both have guides 18 in a direction orthogonal to the axis of the arc surface.
Therefore, the upper surface block 11 and the intermediate block 12 are slidably fitted together. When the top block 11 moves along the guide, the tilt angle Θ of the top block changes. The tilt angle Θ can be seen by the scale 19 engraved along the arc surface. The tilt angle Θ can be changed by turning the Θ knob 16 provided on the side.

The intermediate block 12 has an intermediate disc 13 below it.
It is stuck to. The intermediate disc 13 rests on a base disc 14 and can rotate about a central axis. Φ
The knob 15 can change the rotation angle of the intermediate disk 13. Rotation angle Φ around the vertical axis of the intermediate disk 13
Can be seen on the scale 20. Given a reference plane,
Any surface can be represented by the future inclination Θ and rotation Φ.

FIG. 11 shows an initial state in which Θ = 0 and Φ = 0. When Θ = 0 and Φ = 0, the bottom surface K of the base and the bottom surface C of the ingot jig are parallel. The cutting machine cuts the object in a direction perpendicular to the basal plane K. Therefore, Θ = 0, Φ =
When 0, the cutting plane of the machine is parallel to the A side of the jig.
The surface. The crystal orientation of the D plane has already been verified. The target side is fixed from the beginning. The difference Z = D-Q between the two is immediately known. Then, when the angle adjuster is moved by -Z, the result is as shown in FIG. At this time, the target surface Q becomes perpendicular to the base surface K. That is, the cut surface coincides with the target surface Q.

Θ and Φ are two variables of the three-dimensional polar coordinate system. In the following description, Φ may be referred to as X and Θ may be referred to as Y. The present invention can be used for cutting Si, InP, and GaAs single crystal ingots. An example of applying the present invention to a GaAs ingot will be described.

The object is G grown in the <100> direction with a diameter of 76 mm (3 inches) and a length of 100 mm.
It is an aAs single crystal ingot. It was pulled up by the Czochralski method. Although it is a bell shape as it is, it is ground into a cylindrical shape to form a cylinder with a uniform diameter and a smooth end surface. The purpose is to cut this into (100) wafers.

Since it is grown in the <100> direction, a (100) wafer should be obtained by cutting at a right angle to the axial direction.
However, in reality, the axial direction is not exactly <100>.
There is a slight gap. Therefore, it is necessary to accurately determine the direction of the (100) plane.

According to the method of the present invention, a GaAs single crystal ingot is fixed to a carbon jig. Width 50m
It was fixed with an adhesive to a rectangular parallelepiped jig having m, a height of 10 mm and a length of 150 mm. The state shown in FIGS. 1, 5, and 6 is obtained. How much the orientation of the crystal plane D parallel to the end face A of the rectangular parallelepiped jig (common jig) deviates from the (100) plane was examined by an X-ray inspection apparatus.

As a result, it was found that the displacement was 1.24 ° in the X direction and 0.38 ° in the Y direction. That is, the difference from the target surface (100) Z = D-Q is ZX = 1.24 °,
ZY = 0.38 °. Where ZX is the X component of the difference, Z
Y is the Y component of the difference.

The carbon jig with ingot is removed from the X-ray inspection apparatus, and placed on the angle adjuster on the cutting table of the cutting machine and fixed. Adjust the angle adjuster in the X direction by -1.24 °,
Turn -0.38 ° in Y direction. As a result, the surface of the ingot that is perpendicular to the cutting table should match the target surface Q. Since this cutting machine is designed to cut an object on a surface perpendicular to the cutting table, it should cut an ingot along a target surface. The cutting machine can be of any kind,
A wire saw cutting machine is used here.

The wafer thus cut had a deviation from (100) of 0.01 ° in the X direction and 0.02 ° in the Y direction. The total deviation was only 0.023 °. Since the limit of the cutting error by the conventional method is 0.2 °, it is possible to perform highly accurate wafer cutting far exceeding the limit of the conventional method. It is an excellent invention.

Further, in the conventional method, the test wafer was cut out and the orientation was verified, so that the average thickness was 3 mm (about 72 mm).
The material of g) was wasted. 3 with a length of 100 mm
Since the loss was mm, the material loss was 3%. In the present invention, since the test wafer is not cut out, there is no waste of this amount. It is extremely effective because there is no material loss.

[0040]

According to the present invention, there is no material loss because it is not necessary to cut a test wafer in order to determine the cutting orientation of the ingot. All materials can be used effectively. This is because the orientation is tested nondestructively.

There is a more excellent effect than that. That is, it does not depend strongly on the skill of the worker and the perception. In the present invention, the orientation of the inner surface of the ingot parallel to the end surface A of the jig is determined by X-ray, but this does not require adjustment operation. No need for expert operation. Also, the measurement only needs to be done once. The measurement time can be short.

The best effect is that the accuracy is improved. Since the orientation of the ingot itself is inspected instead of inspecting the plane orientation of the wafer by cutting the wafer, the accuracy of orientation determination becomes extremely high. According to the present invention, an error that cannot be reduced to 0.2 ° or less in the conventional method can be reduced to 0.03 ° or less. 0.02 in some cases
Can be lowered below °.

[Brief description of drawings]

[Fig. 1] Attaching a single crystal ingot to a carbon jig,
Furthermore, the perspective view of the state which attached this to the jig of a rectangular parallelepiped.

FIG. 2 is a front view showing that a test wafer is obtained by cutting out an end portion of an ingot in a conventional example, and a plane orientation of the test wafer is measured.

[FIG. 3] In the conventional example, an adhesive is applied between the carbon jig and the rectangular parallelepiped jig, and the ingot cut so that the end surface becomes the target surface is pressed against the reference surface of the cutting machine to adjust the orientation. An explanatory sectional view showing deciding.

[Fig. 4] Fig. 4 shows an ingot fixed to a carbon jig in the conventional method, fixed to the jig, further placed on a table of a cutting machine, and the gap between the ingot end surface and the reference surface was measured at three points. FIG. 5 is an explanatory cross-sectional view showing fixing in parallel with each other.

FIG. 5 is a front view showing a state in which the single crystal ingot is fixed to a carbon jig and further fixed to the upper surface of the rectangular parallelepiped jig.

FIG. 6 is a side view showing a state in which a single crystal ingot is fixed to a carbon jig and the single jig is fixed to a rectangular parallelepiped jig.

FIG. 7 is a schematic front view of a state in which an ingot fixed to a rectangular parallelepiped jig is fixed on an angle adjuster of a cutting table of a cutting machine.

FIG. 8 is a side view showing the relationship among the ingot, the jig, the upper surface of the cutting table of the cutting machine, and the like when the angle adjuster is at Θ = 0 and Φ = 0.

FIG. 9 is a side view illustrating adjusting the angle adjuster on the cutting table so that the target surface is perpendicular to the surface K of the cutting table.

FIG. 10 is a perspective view showing a state where an ingot fixed to a jig is placed on an angle adjuster.

FIG. 11 is a side view showing the relationship among the ingot, the jig, the upper surface of the cutting table of the cutting machine, and the like when the angle adjuster is at Θ = 0 and Φ = 0.

FIG. 12 is a relationship between the ingot, the jig, and the cutting table of the cutting machine when the angle adjuster rotates in the X-axis and Y-axis directions and the target surface of the ingot is in a direction perpendicular to the surface of the cutting table. FIG.

[Explanation of symbols]

 1 Ingot 2 Carbon Jig 3 Fixing Jig (Common Jig) 4 Goniometer 5 Adhesive 6 Angle Adjuster 7 Pedestal 8 Base 9 Adjuster 10 Bolt 11 Top Arc Block 12 Middle Arc Block 13 Middle Disk 14 Base disk 15 Φ knob 16 Θ knob 17 Arc surface 18 Guide 19 Scale 20 Scale

Claims (1)

[Claims] 1. A columnar or prismatic single crystal ingot is attached to a jig, which is fixed to a rectangular parallelepiped common jig having orthogonal surfaces A, B, and C, and is attached to the common jig's B and C surfaces. The orientation of the right-angled ingot D plane is obtained by X-ray diffraction, the difference Z = D-Q from the target cutting plane Q is obtained, and the ingot is attached to the angle adjuster of the cutting machine while being attached to the rectangular parallelepiped jig to adjust the angle. The device is moved by the difference -Z between the D plane and the Q plane so that the plane perpendicular to the base of the angle adjuster becomes the target cutting plane Q, and the object is orthogonal to the base of the angle adjuster. By cutting the ingot with a cutting machine,
A method for processing a single crystal ingot, characterized in that a wafer having a target surface is cut out.