JPH04199812A - Semiconductor crystal growth method - Google Patents

Abstract

PURPOSE:To make it possible to grow a compound semiconductor whose dislocation density is small on a semiconductor substrate by a method wherein, when the compound semiconductor in which lattice is not matched with the substrate is crystal-grown, an intermediate film whose dislocation propagation property is different is inserted into a growth film of the compound semiconductor. CONSTITUTION:A GaAs buffer layer 12 is grown on a Si substrate 11, and a dislocation 14 appears on a GaAs layer 13, which is grown by crystal-growing a GaAs layer 13 on the substrate 11 again due to the difference in the lattice constant, etc., from the substrate 11. Then, a Si film (intermediate film) 15 is grown on the GaAs layer 13 by lowering the temperature of the substrate 11. Finally, the GaAs layer 16 is grown by setting the temperature of the substrate 11 to 600 deg.C in a atmosphere of As. Thus, the Si film 15 has a dislocation propagation property differing from that of the GaAs layer 13 so that the dislocation occurred in the GaAs layer 13 will not be propagated to the GaAs layer 16, thereby making the GaAs layer 16 a high-quality crystal with less dislocation.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a semiconductor crystal growth method used for manufacturing semiconductor devices such as electronic devices and optical devices, and composite or integrated devices thereof.

[Prior Art] When considering optoelectronic integrated circuits and the like, a semiconductor material is required that allows the fabrication of optical devices and electronic devices on the same substrate. One way to obtain such a semiconductor material is to grow a compound semiconductor on a Si substrate.

Generally, when compound semiconductor crystals are grown on a Si substrate, due to differences in lattice constant and coefficient of thermal expansion between the Si substrate and the compound semiconductor, presence or absence of polarity, etc.
About m-2 dislocations are induced.

Since high quality semiconductor materials are desired for use in optical and electronic devices, efforts are being made to reduce dislocations.

Conventionally, the following methods are known as methods for reducing this dislocation.

(1) After crystal growth of a compound semiconductor thin film on a Si substrate, heat treatment is performed at a temperature higher than the growth temperature to thermally move the dislocations in the grown film, thereby creating a dislocation loop in which the Burgers vector is preserved. A method that reduces the dislocation density on the film surface by forming

(2) Interrupting the crystal growth of the compound semiconductor thin film and
After forming a strained superlattice such as Ga+-x As/GaAs, crystal growth of the compound semiconductor thin film is performed again to introduce a stress field into the compound semiconductor thin film and change the direction of dislocation lines toward the interface. A method of guiding dislocations to the side of the substrate and preventing dislocation tips from appearing on the film surface (strained superlattice insertion method).

(3) During crystal growth of a compound semiconductor thin film, the growth temperature is raised and lowered several times to control the movement of dislocations generated in the grown film, forming dislocation loops, and guiding dislocations to the side of the substrate. A method of reducing dislocation density on the surface of a grown film (
thermal cycle method).

Conventionally, the MBE method, MOCVD method, etc. have been used as crystal growth methods, and the above-mentioned methods have been appropriately combined with a so-called two-step growth method in which a low-temperature buffer layer is formed in the initial stage of growth to reduce dislocation density.

[Problems to be Solved by the Invention] However, the conventional method has the following problems.

In methods such as the Bost annealing method and the thermal cycle method, in which dislocations in the film are moved by thermal history to form dislocation loops or to escape to the side of the substrate, when the density of dislocations falls below a certain level, dislocations become 8 Since the probability of meeting is reduced, it is not possible to reduce dislocations by the mechanism described above. Currently, the lower limit is ~10 for GaAs films on Si substrates.
It is said to be about 6 cm-2.

In the strained superlattice insertion method, dislocations change their direction toward the interface due to the strain field at the interface. However, for example, I n
Considering the strained superlattices of GaAs and GaAs, the behavior of dislocations (propagation speed of dislocations, critical stress for dislocation generation) in both films is very similar, and dislocations are easily generated by fluctuations in the strain field. The propagation direction changes and heads toward the membrane surface. Therefore, even with this method, it is not possible to reduce the dislocation density beyond a certain level.

An object of the present invention is to provide a method for growing a compound semiconductor with a low dislocation density on a semiconductor substrate.

[Means for Solving the Problems] According to the present invention, in a semiconductor crystal growth method for crystal-growing a compound semiconductor having a lattice constant different from that of the semiconductor substrate on a semiconductor substrate, the compound semiconductor is grown on the semiconductor substrate. a first step of crystal-growing a semiconductor; a second step of forming a semiconductor thin film having a dislocation propagation property different from that of the compound semiconductor to a predetermined thickness or less on the compound semiconductor; A method for growing a semiconductor crystal is obtained, which further comprises a third step of growing the compound semiconductor again.

[Example] The present invention will be described in detail below with reference to the drawings.

FIG. 1 shows a process diagram of a semiconductor crystal growth method according to a first embodiment of the present invention.

First, the surface of the 5i (100) substrate 11 is cleaned by heat treatment or the like. Subsequently, the temperature of the Si (100) substrate 11 is raised to 250° C., and about 100 GaAs buffer layers 12 are grown on the Si substrate 11 as shown in FIG. 1(a). Then, the temperature of the substrate 11 is set to 600°C, and G
The aAs layer 13 is grown as a crystal.

Here, dislocations 14 have occurred in the grown GaAs layer 13 due to the difference in lattice constant, etc. with the substrate 11.

Next, the temperature of the substrate 11 is lowered to 250°C, and as shown in FIG.
As shown in , a Si film (intermediate film) is placed on the GaAs layer 13.
Grow 15. The thickness of this Si film 15 is several ML (
molecular layer), that is, below the critical film thickness. The critical film thickness herein refers to the film thickness at which internal stress due to lattice mismatch does not exceed the elastic limit.

Finally, the temperature of the substrate 11 was increased to 600°C in an As atmosphere.
℃, and a GaAs layer 16 is grown as shown in FIG. 1(C).

In this way, Si is formed between the GaAs layer 13 and the GaAs layer 16.
In the semiconductor material in which the layer 15 is inserted, the Si film 15 is Ga
Since the GaAs layer 13 has different dislocation propagation properties (propagation speed, critical stress, etc.) from the As layer 13, dislocations generated in the GaAs layer 13 are not propagated to the GaAs layer 16. Therefore, GaAs
The layer 16 becomes a high quality crystal with extremely few dislocations.

FIG. 2 shows a second embodiment.

In the second embodiment, the crystals of the GaAs layer 13 and the Si layer 15 are grown alternately to gradually block dislocations whose propagation cannot be blocked by the negative Si layer 15.

Although the above embodiment describes the method of forming a GaAs layer on a Si substrate, the method is not limited to this, and if it is a so-called lattice mismatched epitaxial system,
−■ group compound semiconductor, ■−■ group compound semiconductor, or
It may be a group (Ⅰ) compound semiconductor.

Further, the semiconductor growth method of the present invention can be combined with a conventional dislocation reduction method to further reduce dislocation density.

[Effects of the Invention] The present invention can achieve the following effects by inserting an intermediate film having different dislocation propagation properties into the grown compound semiconductor film when crystal-growing a compound semiconductor that is not lattice-matched with the substrate.
Dislocations generated in the compound semiconductor located below the intermediate film can be prevented from propagating to the compound semiconductor located above the intermediate film, and a high quality semiconductor material can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a process diagram for explaining a first embodiment of the present invention, and FIG. 2 is a structural diagram for explaining a second embodiment. 11...Si substrate, 12...GaAs buffer layer,
13-GaAs layer, 14-=dislocation, 15-3
i film, 16-G a As layer. Figure 1 Figure 2 (b) (C)

Claims (1)

[Scope of Claims] 1. A semiconductor crystal growth method for crystal-growing a compound semiconductor having a lattice constant different from that of the semiconductor substrate on a semiconductor substrate, comprising: a first step of crystal-growing the compound semiconductor on the semiconductor substrate; a second step of forming a semiconductor thin film having a dislocation propagation property different from that of the compound semiconductor on the compound semiconductor to a predetermined thickness or less; and crystallizing the compound semiconductor again on the semiconductor thin film. A method for growing a semiconductor crystal, the method comprising a third step of growing a semiconductor crystal. 2. The semiconductor crystal growth method according to claim 1, wherein a Si substrate is used as the semiconductor substrate, a III-V group compound semiconductor is used as the compound semiconductor, and a Si thin film is used as the semiconductor thin film. 3. It has a Si substrate, at least two III-V group compound semiconductor layers crystal-grown on the Si substrate, and a Si layer having a predetermined thickness or less sandwiched between the III-V group compound semiconductor layers. A semiconductor wafer characterized by: