JPS61178491A - Method for pulling up single crystal - Google Patents

Abstract

PURPOSE:To make it possible to grow a single crystal of a Group III-V compound semiconductor having low or no dislocation in growing the single crystal of the Group III-V compound semiconductor, by adjusting the direction of the pulling up axis to <210> direction. CONSTITUTION:A Group III-V compound semiconductor is grown by the pulling up method. In the process, the direction of the pulling up axis is adjusted to <210> direction. The growing direction of the propagation dislocation from a seed crystal, i.e. [100] direction, is kept away from the pulling up axis. Therefore, the above-mentioned direction is fixed at a direction to make the dislocation 3 from the seed crystal go out to the surface of a crystal ingot 2 as shown in the sectional perspective view of the ingot 2 even if the dislocation 3 from the seed crystal is propagated in the direction [100] in the initial stage of growth. The <210> direction is set at the direction of the pulling axis. Thus, the <210> direction fixed at the pulling up and growth direction of the single crystal avoids the residual slip dislocation by the propagation of the dislocation from the seed crystal in the pulling up axis and thermal stress.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention provides a pulling method in which a seed crystal is immersed in a crucible containing a melt of raw material and then rotated to grow a ■-V group compound semiconductor single crystal. Regarding.

[Prior art]

High-speed logic devices and optical communication devices made of semiconductor crystals include m-v materials such as gallium arsenide (hereinafter referred to as GaAs) and indium phosphide (hereinafter referred to as InP).
Group compound semiconductor single crystals are used. These single crystals generally have linear lattice defects called dislocations of 103~
It is often contained at a density of about 10'/cm2, and when such a single crystal is used as a material for the above-mentioned elements, the operating threshold voltage may become non-uniform between elements, and the light It has been reported that the output may deteriorate. Therefore, m-v that does not contain such crystal defects
It is necessary to grow group compound semiconductor single crystals.

For example, for the purpose of reducing dislocations in a GaAs single crystal, indium (hereinafter I
By adding electrically neutral impurities such as Attempts have been made to obtain GaAs single crystals with low dislocation density or no dislocations by preventing dislocations from penetrating into the surface.

[Problems with conventional technology]

The pulling direction of these GaAs single crystals is often the HOO> direction as shown in Figure 4(a), and in that case,
Of the dislocations existing in the seed crystal 1, only the HOO> direction propagates as it is into the pulled grown single crystal ingot 2, resulting in the propagation from the seed crystal as shown in FIG. 4(b). Dislocation 3 is generated. Therefore, it is known that there are many dislocations perpendicular to the wafer surface near the center of a (100) wafer cut perpendicularly to the pulling axis (rotation axis).

As a result of analysis by X-ray topography, etc., these dislocations exist in the (110) plane that includes the pulling axis HOO>, and the direction of the Burgers vector is parallel to the H10) direction perpendicular to the dislocation line. , is also found to lie in the (110) plane containing the <100> pulling axis. In addition, Fig. 4(a) shows G grown by the pulling method.
A perspective view of an aAs single crystal ingot, FIG. 4(b) is a perspective view showing a cross section near the central axis of this ingot.

On the other hand, when pulling an m-v group compound semiconductor single crystal, dislocations are generally introduced from the surface of the growing ingot due to thermal stress into the interior while sliding on the (111) planes that exist, increasing the dislocation density. Something that happens frequently. Therefore, if the inclination of even one of these (111) planes with respect to the pulling axis becomes shallow, the probability that dislocations on this (111) plane will remain inside the ingot increases.

In the case of a <100> pulling axis, these four (111
) plane is (100>perpendicular to the pulling axis (10
0) plane, so the inclination between the (111) plane and the <100> pulling axis is not a problem, but
As mentioned above, since the (110) plane is parallel to the pulling axis, it has the disadvantage that propagation dislocations from the seed crystal as shown in FIG. 4(b) cannot be avoided.

[Purpose of the invention]

This invention eliminates the propagation of dislocations from such seed crystals from extending in the growth direction of the ingot;
111) To provide a method for growing a single crystal of a ■-v group compound semiconductor with low or no dislocations by pulling the single crystal in a direction such that none of its planes are parallel to the pulling direction. .

[Structure of the invention]

This invention is characterized in that when growing an m-v group compound semiconductor single crystal by a pulling method, the direction of the pulling axis is set to the <210> direction.

[Detailed explanation of the configuration]

The details of this invention will be explained below with reference to the drawings.

FIG. 3 is a conceptual diagram showing a unit cell of an m-v group compound semiconductor single crystal. The conventional pulling shaft explained in Fig. 4 is (10
0) direction, the propagating dislocation from the seed crystal is quadrilateral B
(011) plane of DHF or (011) of quadrilateral ACGE
) plane, and each Burgers vector is %(0
11) or %(011).

Therefore, in this invention, by making sure that the direction in which propagating dislocations from the seed crystal extend, that is, the (100) direction, does not become the pulling axis, it is possible to make it possible for dislocations 3 from the seed crystal to move in the (100) direction at the initial stage of growth. Even if it propagates, as shown in the cross-sectional perspective view of the ingot 2 in FIG. 1, the pulling axis is set to the 210〉 direction, which is such that it will eventually come out on the surface of the crystal ingot. There are many such directions other than the <210> direction (for example, the 3rd direction).
In the figure, even if the (110) direction is used as the pulling axis, the goal of dislocation from the seed crystal will be extracted to the ingot surface can be achieved, but in that case, the (111) direction of the triangular BGE
) plane or (111) plane of triangle CHF, (
A (111) plane parallel to the 11'O) direction exists, which is inappropriate for the reasons mentioned above.

Therefore, in this invention, (2
By setting the 210> direction represented by the 10) direction as the pulling growth direction of the single crystal, propagation of dislocations from the seed crystal in the pulling axis direction and residual slip dislocations due to thermal stress are avoided.

〔Example〕

After adding In into a GaAs melt and immersing a GaAs single crystal seed crystal, the direction of the pulling axis was set to <210
> direction and pulled up while rotating to grow an In-doped (In addition concentration: 5 x 1019 cm-3) GaAs single crystal ingot. Of this single crystal ingot,
A wafer is cut to have a (100) surface from a portion where the solidification rate is approximately 50%, and etch pits are exposed using a potassium hydroxide melt. After exposing the etch pits, the surface of the center of the wafer was photographed using an electron microscope. FIG. 2(a) shows the micrograph. For comparison, a similar electron micrograph is shown of a wafer of an In-doped GaAs single crystal ingot grown with the pulling axis in the HOO> direction and other conditions being exactly the same. As is clear from comparing these surface photographs, Figure 2 (b
According to the surface photograph of (100) wafer, there are dislocations propagating from the seed crystal in the central part of the (100) wafer, but as shown in Fig. 2 (
According to the surface photograph in a), there are no longer propagating dislocations from the seed crystal in the central part of the (100) wafer.

Thus, it has been found that the method of the present invention is effective in preventing dislocations from the seed crystal from propagating to the center of the (100) wafer.

This invention applies not only to the GaAs single crystal of the above embodiment, but also to
Of course, the present invention can also be applied to pulling other single crystals characterized by elongation of propagating dislocations in the H00> direction.

〔Effect of the invention〕

As is clear from the above explanation, according to the single crystal pulling method of the present invention, low dislocation or no dislocation m-v
It becomes possible to grow single crystals of group compound semiconductors.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional perspective view of a GaAs single crystal ingot near the central axis that has been pulled and grown in the <210> direction by the method of the present invention, and FIG. Solidification rate of GaAs single crystal ingot 50%
An electron micrograph showing the structure of the crystal in the central part of the (100) wafer cut from the vicinity, and a GaAs single crystal ingot pulled and grown in the <100> direction by the conventional method, cut from around 50% solidification rate. Ta (100)
FIG. 3 is an electron micrograph showing the structure of the crystal in the central part of the wafer. FIG. 3 is a diagram showing a unit cell explaining the crystallographic direction of this invention. FIG. FIG. 2 is a perspective view of a single crystal ingot and a cross-sectional perspective view of the vicinity of its central axis. 1... Seed crystal 2... Ingot 3... Propagating dislocation

Claims (1)

[Claims] (1) A method for pulling a single crystal, which is characterized in that when a III-V group compound semiconductor single crystal is grown by a pulling method, the direction of the pulling axis is the <210> direction.