JPH0380184A - Method for growing crystal - Google Patents

Abstract

PURPOSE:To substantially remove the axial dislocation propagating from a seed crystal and to obtain the semiconductor crystal having no crystal defects by specifying the bearings of the seed crystal at the time of growth of the semiconductor crystal by a melt pulling-up method. CONSTITUTION:The energy is minimized in the direction where the dislocation of + or -a/2[110] and + or -a/2[110] Burgers vector (b) coincides with the growth axis and, therefore, the dislocation propagates with the crystal growth and the axial dislocation is obtd. if the crystal growth direction is [001] as shown in Fig. The energy is minimized and the axial dislocation is obtd. in the direction where the dislocation of + or -a/2[101] and + or -a/2[101] Burgers vector (b) coincides with the growth axis if the growth direction is [101]. It is readable from Fig. that all the dislocations part furthest from the growth axis when the growth axis is inclined by about 14 deg. from [001], i.e., [104]. The axial dislocation is substantially removed in this way by setting the bearing of the seed crystal at <410>. The semiconductor crystal having no crystal defects is thus grown.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a crystal growth method using a melt pulling method.
In particular, the present invention relates to a growth method that prevents crystal defects from propagating from a seed crystal to a growing semiconductor crystal.

(Prior Art) Semiconductor wafers such as Si and GaAs are generally grown by a melt pulling method in which a seed crystal is attached to a melt in a crucible and pulled up while rotating. Conventionally, it has been known that a large number of dislocations remain in semiconductor crystals grown by this method. Currently, the technology to obtain completely dislocation-free Si crystals has been established, but GaAs and InP
Dislocations with a concentration of 104 to 105 cm remain in compound semiconductors such as 104 to 105 cm. Among these, the occurrence of slip dislocations due to thermal stress can be reduced by adding impurities, but they propagate straight from the seed crystal in the growth direction. Dislocations (on-axis dislocations) cannot be completely removed. Various methods have been tried to remove axial dislocations. For example, there is a method of escaping dislocations to the outside of the crystal by necking.
The axial displacement in the center remains and is not an essential solution. Also, Kuwamoto and Holmes (J, of Crystal Growth)
Volume 91, 1988, p. 567) is generally not 001
In addition to <111> and <441> pulling, it has been reported that axial dislocations still exist.

(Problems to be Solved by the Invention) The conventional crystal growth method described above has a drawback in that axial dislocations that propagate straight from the seed crystal in the growth direction cannot be completely removed.

An object of the present invention is to provide a method for growing semiconductor crystals that solves these conventional problems.

(Means for Solving the Problems) The present invention is a method for growing a semiconductor crystal by a melt pulling method, and is characterized in that the orientation of the seed crystal is <410>.

Furthermore, the present invention is characterized in that the orientation of the seed crystal is set in an arbitrary direction within the range between <001> and <101>, and necking is performed to the most appropriate length for the set orientation. .

(Example) Next, the present invention will be explained with reference to the drawings.

As a general rule, dislocations that propagate as the crystal grows grow in the direction that minimizes the energy of the dislocations. Therefore, by applying the above law to a slip system with a diamond-type structure such as a semiconductor crystal, we can calculate the energy of a dislocation having an arbitrary direction with respect to an arbitrary growth direction.
We found the position where they are minimum. FIG. 1 shows the position where the energy of each of six types of dislocations having Burgers vectors is minimum. The horizontal axis is the growth direction, which is shown as an elongation angle from [001]. The vertical axis is the direction of the dislocation line where the energy is minimum, and is shown as an elongation from the growth direction. According to Fig. 1, when the growth direction is [001], dislocations with Burgers vector b of ±a/2[110] and ±a/2[110] have the minimum energy in the direction that coincides with the growth axis, so , propagates as the crystal grows and becomes an axial dislocation. Moreover, when the growth direction is [101], Burgers vector b
The dislocations of ±a/2[101] and ±a/2[101] have the minimum energy in the direction that coincides with the growth axis, and become on-axis dislocations. The furthest distance of all dislocations from the growth axis is
It can be seen from FIG. 1 that when the growth axis is tilted approximately 14 degrees from [001], that is, [104].

As described above, by setting the orientation of the seed crystal to <410>, it is possible to essentially eliminate axial dislocations and grow a semiconductor crystal free of crystal defects.

Furthermore, if the seed crystal is oriented in any direction between [001] and [101], even the dislocation closest to the growth axis propagates at a certain angle from the crystal growth axis.

If the angle is A, then when the diameter of the seed crystal is D, D/1
All dislocations can be completely removed by necking with a length of anA. For example, if the growth direction is [10
2], then the dislocation closest to the growth axis is a dislocation with a Burgers vector b of x a/2 [101] according to FIG. 1, and the propagation direction of the dislocation can be read as approximately 9 degrees.

The diameter of the seed crystal is usually 2 to 3 mm, so D/1an
All dislocations from the seed crystal can be removed by necking for a length of A=3/jan9°=19 (mm).

As described above, by setting the orientation of the seed crystal in an arbitrary direction within the range between <001> and <101>, and performing necking to the most appropriate length for the set orientation, axial dislocations can be can be essentially removed, and semiconductor crystals without crystal defects can be grown.

(Effects of the Invention) As explained above, according to the present invention, axial dislocations propagated from a seed crystal are essentially removed in a semiconductor crystal grown by a melt pulling method, and a semiconductor crystal free of crystal defects is grown. can.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the relationship between the propagation direction of dislocations and the direction of crystal growth.

Claims (2)

[Claims] (1) A method for growing a semiconductor crystal by a melt pulling method, characterized in that the orientation of the seed crystal is <410>. (2) In growing semiconductor crystals by the melt pulling method, set the orientation of the seed crystal in an arbitrary direction in the range between <001> and <101>, and choose the most appropriate length for the set orientation. A crystal growth method characterized by necking.