JPH0263115A - Selective growth of thin film - Google Patents

Abstract

PURPOSE:To sharply reduce a lattice defect density at the upper part of a selective epitaxial growth layer by a method wherein a thin film is grown in such a way that a ratio of a height to a width of a groove satisfies a specific condition. CONSTITUTION:SiO2 12 with a film thickness of (h) is grown on a (100) Si substrate 11 by thermal oxidation; then, a square window part where a <110> direction is used as one side of a length (w) is formed in an SiO2 mask material by a dry etching operation. Then, the substrate is installed in a low-pressure MOCVD apparatus so as to obtain h>w tantheta; the surface of Si exposed on the bottom of the window part is cleaned in AsH3 which has been diluted by H2; then, GaAs 13 is grown selectively in the window part in an atomic-layer growth mode by using diethyl gallium chloride (DEGaA) and AsH3 as raw materials.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) This invention relates to a method for selectively growing thin films with low lattice defect density.

(Prior art) Up until now, epitaxial thin films with significantly different lattice constants from the substrate, such as GaAs thin films on Si substrates, have mainly been grown using metal organic chemical vapor deposition (MOCVD) and molecular beam epitaxial growth (MBE). This was done using a method called the stepwise growth method. In this method, a thin buffer layer is first grown at a low growth temperature. Misfit dislocations are introduced into the interface between the buffer layer and the substrate, the stress due to the difference in lattice constant between the epitaxial layer and the substrate is relaxed, and the lattice of the buffer layer returns to its original lattice.

Therefore, an epitaxial layer can be easily grown on this buffer layer during high temperature growth.

(Problem to be solved by the invention) However, the dislocation density of the epitaxial thin film grown in this way is 109~
It is very large at 108 cm-2. Some of these dislocations are ends of misfit dislocations, and others are caused by local stress concentration during growth.

To reduce the dislocation density in this epitaxial layer,
Attempts have been made to add a strained superlattice during epitaxial layer growth and to perform heat treatment after growth. However, even with such treatment, the dislocation density in the epitaxial layer is reduced to only about 10'cm-2 at most. Furthermore, adding a strained superlattice or applying heat treatment makes the manufacturing method of the epitaxial layer extremely complicated.

An object of the present invention is to provide a simple method for manufacturing an epitaxial thin film with a low dislocation density, which solves this problem.

(Means for Solving the Problems) The gist of the present invention is to selectively grow a thin film having a 111J plane as a dislocation slip plane on a groove portion by changing the ratio of the height h and width W of the groove to h> By setting wtan θ large enough to satisfy wtan θ (θ is the angle between the (111) plane and the normal to the substrate surface), the purpose is to suppress the propagation of lattice defects upward in the thin film.

(Function) Generally, most of the lattice defects in the heteroepitaxial layer occur near the interface and propagate upward. Lattice defects include the ends of misfit dislocations that occur at interfaces, slip dislocations that occur due to local stress concentration, and stacking faults. In zinc blend crystals, the slip plane of dislocations is the (111) plane, and the direction of the dislocation lines tends to be in the <110> direction. Therefore, in many cases, dislocations propagate diagonally upward in the <110> direction on the (111) plane in the epitaxial film, and rarely propagate upward parallel to the normal direction of the substrate. Further, stacking faults are always on the (111) plane.

Here, the height of the mask opening or groove is 51, the width is W,
Let θ be the angle between the substrate surface and the normal to the (111) plane. From what has been said above, in selective growth, if the height and width of the mask opening are made large enough to satisfy the condition h>wtanθ, most of the lattice defects generated near the interface will be in the (111) plane. It propagates diagonally upward, reaches the side of the mask material, and disappears there.

Therefore, the lattice defect density above the selective epitaxial growth layer can be significantly reduced.

In principle, the present invention is effective for crystals in which the (111) plane is a dislocation slip plane, and can be applied to various crystals of zinc blend type, diamond type, and face-centered cubic structure.

(Example) Hereinafter, a method for manufacturing a selective heteroepitaxial thin film will be explained with reference to an illustrated example.

(1) FIG. 1 is a sectional view of the main part of a sample for explaining an embodiment of the manufacturing method according to the present invention. (100) SiO□12 with a film thickness of 4 pm is formed by thermal oxidation on a Si substrate 11.
grew up. Next, by dry etching, the length W with the <110> direction as one side is 2.5p in the SiO2 mask material.
A square window portion of m was formed so that h>wtanθ. This substrate is mounted on a low pressure MOCVD equipment,
The exposed Si surface at the bottom of the window was cleaned in AsH3 diluted with H2 for 2 minutes at 900°C. Next, diethyl gallium chloride (DEGaCl) and AsH
GaAs13 was selectively grown in the window portion using a as a raw material in atomic layer growth mode. The substrate temperature was 600°C.

(2) FIG. 2 is a sectional view of the main part of a sample for explaining another embodiment. In this example, the GaAs growth method is described in Example (
This is the same as 1), but the method of forming the substrate is different. First, Si
The width of the square with one side in the <110> direction on 21 above is 4 pm.
1. A trench with a depth of 7 pm is formed by dry etching. Next, a 5t02 film 22 of 0.4 pm is grown by thermal oxidation, and only the SiO2 film at the bottom of the trench is removed by dry etching. In this trench, the embodiment (
GaAs23 was grown using the same method as in 1).

FIG. 3 is a diagram showing a comparison of cathodoluminescence between the thin film of the present invention produced as described above and a conventional example. That is, the emission intensity 31 of GaAs in the selectively grown portion by cathodoluminescence at 77°K is compared with 32 when GaAs is formed on the entire surface of a normal Si substrate.

In the cases of Examples (1) and (2), the emission intensity was about the same, and the intensity was about three times stronger than that in the case of full-surface growth.

Although GaAs was used in the above embodiments, GaAs
Other zinc blend crystals such as InPAIGa
It is also applicable to As diamond-type crystal Si, etc., and face-centered cubic structure At Ag. Also, the mask material is S.
It is not limited to the iO□ film, but may also be a SiNx film, a semiconductor material, or a metal material. The growth method is not limited to atomic layer epitaxial growth method, but also gas source molecular beam epitaxial growth method,
It can be applied to various growth methods such as sputtering.

(Effects of the Invention) As described above, the epitaxial thin film selectively grown by the present method has an increased emission intensity, which indicates that lattice defects are significantly reduced. Therefore, it is shown that according to the present invention, a heteroepitaxial film of extremely high quality can be grown.

It is also possible to grow an epitaxial film laterally on the SiO2 film using the selectively grown epitaxial layer as a seed.
An epitaxial film having the structure of a semiconductor l insulating film can be formed.

[Brief explanation of the drawing]

FIGS. 1 and 2 are diagrams showing the structure of a selected heteroepitaxial thin film to explain an embodiment of the growth method according to the present invention, and FIG. 3 is a diagram showing the results of cathodoluminescence to demonstrate the effects of this invention. FIG. 11, 21...Si substrate, 12,22...SiO2
Membrane, 13,23...GaA4゜

Claims (1)

[Claims] In a method for selectively growing a thin film having a {111} plane as a dislocation slip plane in a groove portion provided on a substrate, the width of the groove portion is w, the height is h, and the substrate surface and {111}
A method for selectively growing a thin film, characterized in that h>wtanθ, where θ is the angle formed by the normal to the surface.