JPH0135800B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (A) Technical Field The present invention relates to a method for producing an OF surface of a compound semiconductor single crystal.

Compound semiconductors here refer to - group compound semiconductors, including GaAs, GaP, GaSb, InP,
Refers to InSb, InAs, etc.

Compound semiconductor wafers are used to create semiconductor lasers, light emitting diodes, FETs for high-speed calculations, and other products through wafer processing.

Compound semiconductor single crystals such as GaAs are (011),
(011), etc. become cleavage planes. A large number of equivalent devices are fabricated on a single wafer, which is then cut into individual elements. This is because cutting can be performed accurately by scribing along the cleavage plane.

The cleavage planes are orthogonal to each other, but there are also cleavage planes that are not orthogonal. Fabricating the wafer along a plane in which there are only orthogonal cleavage planes is convenient for fabricating a large number of repeating rectangular or square devices.

Therefore, (100) wafers are often used.

There are four cleavage planes perpendicular to the (100) plane in a (100) plane wafer, which can be expressed by an index of (0±1±1).

The wafer is cut into an arcuate shape at a point on its circumference to indicate one of the four cleavage planes. Since it follows the cleavage plane, it can be precisely excised. The arcuate cut portion on the circumference that curves the cleavage plane is called the orientation flat OF.

To make a (100) plane wafer, a single crystal is grown in the <100> direction by a pulling method (Czyochoralski method, CZ method). If the orientation of the seed crystal is <100>, the pulled crystal will be <100>
It becomes a single crystal parallel to the direction.

The pulled single crystal approximates a cylindrical shape, but
The upper part is the shoulder that continues to the seed crystal. The bottom is not flat, but protrudes downward.

This single crystal ingot is processed into the correct cylindrical shape by grinding the outer periphery and also grinding the shoulders and bottom.

Next, find the position where the orientation flat should be and grind the orientation flat.

A known method is used for the grinding device. For example, a rotating cup grindstone is applied to one generatrix of a single crystal ingot (generating line in the cleavage direction) and the single crystal ingot is fed in the axial direction to form a narrow flat portion in the axial direction.

(a) Prior Art Conventionally, the following methods have been used to find cleavage planes.

A single wafer is cut out from a cylindrical ingot. Labels are attached to the wafer so that the positions of the wafer and the remaining ingots correspond to each other.

Break this wafer. Since it splits along the cleavage plane, the cleavage plane can be identified by the cut end. By associating this broken wafer with the ingot, the cleavage plane of the ingot can be determined. 4 perpendicular to the (100) plane
You can know all the cleavage planes. This is because they form a 90° angle to each other.

In this way, when the wafer is actually split, the cleavage plane can be reliably found.

However, this method has the following drawbacks.

One is that one wafer is wasted.

The other problem is that it is time-consuming and complicated. This is because a wafer for testing is cut out, split, and the split pieces correspond to the original ingot.

There is another possibility of error. Test wafers are cut out from dozens of ingots, subjected to a cleavage test, and returned to the original ingot for matching, but since the ingots have the same diameter, there is a possibility of mistakes.

The present invention aims to solve these drawbacks.

(c) Method of the present invention In the present invention, wafers are not cut out for testing. Instead, they cut part of the end of a cylindrical ingot into a half-moon shape and break off the cut to find the cleavage plane.

FIG. 1 is a perspective view showing a state in which a cut 2 perpendicular to the axis is made at the end of a single crystal ingot 1.

The half-moon-shaped notch 2 is cut out by an inner circumferential slicer blade that slices the ingot 1. The ingot 1 has a cylindrical shape, and the end face has a (100) orientation.

As already mentioned, there are four cleavage planes perpendicular to the (100) plane (0±1±1). Among these, there is always a cleavage plane included in the half-moon-shaped cut.
An axial stress is then applied to the separated end 3 which is about to be separated from the main part of the ingot 1 by the cut 2. The stress may be applied impulsively or slowly.

The stress creates a bending moment in the separation end 3. The separation end 3 is sufficiently thin that it will break due to the bending moment. Since it breaks along the cleavage plane, the cleavage plane is exposed.

FIG. 2 is a perspective view of the ingot showing a state in which the separated end portion 3 is split along the cleavage plane. This cleavage plane 4 is called a reference cleavage plane.

FIG. 3 is a schematic perspective view of an OF processing machine according to the present invention.

A cylindrical single crystal ingot 1 is pressed and supported by ingot holding plates 5 on both end faces. The ingot presser plate 5 is connected to an angle adjustment mechanism 7 via a presser shaft 6. An ingot 1 whose both end surfaces are pressed and supported by an ingot presser 5
can be rotated in the circumferential direction and the angle can be adjusted.

The pressing mechanism is arbitrary, such as hydraulic pressure, pneumatic pressure, and screwing.

A grindstone 8 is placed on one side of the ingot 1.
is provided so as to be freely movable in the axial direction.

The grinding wheel 8 has a disc shape, and a rotating shaft 9 is seen from the rear.
It is designed to receive rotational force by. The rotating shaft 9 not only applies rotational force but also can be displaced in the front-back direction.

When the cup grindstone 8 is rotated, applied to the side of the ingot, and gradually moved in the axial direction, the ingot 1
The sides of the surface are cut into flat strips of the same width.

It is well known that OF processing is performed using a cutter grindstone.

In the present invention, the reference cleavage plane 4 is further used to strictly define the orientation of the ingot.

For this purpose, a light source with good directivity is provided above the ingot and illuminates the reference cleavage plane 4. Since the cleavage plane 4 is a mirror surface, the light is not reflected,
It is reflected in a fixed direction.

As the light source, gas lasers, semiconductor lasers, etc. are most suitable.

In this example, the light of the laser 11 is applied to the reference cleavage plane 4 of the ingot 1 through the pinhole 13 of the shielding plate 12. The reflected light returns to the pinhole 13 and enters the photodetector 18 via a half mirror or the like. When the output power of the photodetector is maximum, the light from the laser 11 and the reference cleavage plane 4 are at right angles.

The light of the laser 11 and the grindstone surface 10 of the cup grindstone are set in advance in parallel.

Adjust the orthogonal adjustment mechanism 7 while monitoring the output of the photodetector. When the light output reaches its maximum, the cup grindstone 8 is advanced by a certain distance and, while being rotated, the side surface of the ingot 1 is ground.

Among the cleavage planes perpendicular to the (100) plane, adjacent ones are orthogonal to each other. Since the laser beam and the grinding wheel surface 10 are parallel to each other, the reference cleavage plane 4 and
It is perpendicular to the grindstone surface 10.

A plane perpendicular to the reference cleavage plane 4 is also a cleavage plane. It can be seen that the grinding wheel surface 10 and the cleavage plane are parallel.
The grindstone moves parallel to the axis of the ingot 1. Therefore, the thin flat part cut by the grindstone 8 is one of the cleavage planes.

The orientation flat OF is a cleavage plane. Therefore, the orientation flat OF has been ground by the cup grindstone 8.

In this example, the sending light and the returning light from the laser 11 travel along the same path in opposite directions.
In this case, the positional relationship is simple because it is sufficient to make the laser beam and the grinding wheel surface 10 parallel.

However, the photodetector that detects the intensity of the returned light requires some ingenuity.

There is no need for the sending light and the returning light of the laser beam to travel back and forth along the same optical path.

As shown in FIG. 4, the laser 11 may be slightly tilted and the pinhole 13 and photodetector 18 may be slightly tilted to the opposite side. In this case, the center line 1 and the grindstone surface 10 may be set to be parallel to each other. The center line l is the normal to the reflective surface, that is, the reference cleavage surface 4. Since the center line l and the grindstone surface 10 are set to be parallel, the grindstone surface 10 is parallel to the cleavage plane.

In the example described here, the end faces are (100) planes and the cleavage planes are orthogonal to each other.

Depending on the orientation of the end face, the cleavage planes existing within the plane may not necessarily be perpendicular to each other. For example, if the end face orientation is (111), the cleavage planes are (110) and (01).
There are six faces: 1), (011), .... these are,
Forms a 60° angle.

In such a case, the OF surface cannot be properly ground by making the grindstone surface 10 parallel to the laser beam.
The grinding wheel surface 10 and the laser beam should form a 30° angle.

The angle between the laser beam and the grinding wheel surface must be appropriately determined depending on the surface orientation of the ingot.

(D) Effects According to the present invention, there is no need to cut out wafers from ingots, and therefore, there is no need to deal with wafers with different cleavage directions to correspond to a large number of ingots without making mistakes.

It saves time to bring out the OF side, and
There is less chance of error.

Furthermore, since the wafer and ingot are not separated, it has the advantage of high precision.

Silicon wafers and the like are made by conventional methods, and in the case of the conventional method of attaching OF to silicon ingots, the error was about 1 to 2 degrees.

In the present invention, the error can be reduced to about 0.1°.

[Brief explanation of drawings]

FIG. 1 is a perspective view of a cylindrical compound semiconductor single crystal ingot with a notch made near the end surface. FIG. 2 is a perspective view of the same ingot in which stress is applied to the cut portion and a portion is broken off to expose the cleavage surface. FIG. 3 is a perspective view of an OF processing machine for carrying out the OF surface extraction method of the present invention. FIG. 4 is a partial front view showing another embodiment in which the positions of the laser and the photodetector are changed. 1... Single crystal ingot, 2... Notch, 3
... Separation end, 4 ... Reference cleavage plane, 5 ... Ingot presser, 6 ... Presser shaft, 7 ... Orthogonal adjustment mechanism, 8 ... Cup grindstone, 9 ... Rotating shaft, 10 ...
Grinding wheel surface, 11... Laser, 12... Shielding plate, 13
...Pinhole, 18...Photodetector.

Claims (1)

[Claims] 1 After processing a compound semiconductor single crystal ingot 1 grown by the pulling method into a cylinder, a cut 2 is made perpendicular to the growth axis near the end face to form a thin separation end 3.
, and apply stress to the separated end 3 to create a standard cleavage plane 4.
The angle around the axis of the ingot 1 is adjusted by exposing the reference cleavage surface 4 to a light beam and detecting the reflected light with a photodetector, thereby forming a grindstone having a grindstone surface 10 that forms a constant angle with respect to the light beam. An orientation flat is created on the side of ingot 1 by parallel movement.
An OF surface production method for compound semiconductor single crystals, which is characterized by processing OF.