JP2646973B2 - Method of forming semiconductor crystal surface - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a semiconductor crystal surface.

[0002]

2. Description of the Related Art In a (100) crystal surface of Si or Ge, domains in two directions are usually mixed on the surface at the same time. Conventionally, as a technique for artificially controlling this domain structure, a method of forming a single domain by inclining from the plane direction (100) is known.

[0003]

SUMMARY OF THE INVENTION In order to grow a compound semiconductor such as gallium arsenide (GaAs) on a (100) oriented semiconductor made of a single element such as silicon (Si) or germanium (Ge), the crystal must be grown. Due to the difference in structure, it is desirable to form a single domain on the substrate surface in order to suppress the generation of antiphase domains. On the other hand, the surface of a semiconductor crystal formed by a conventional method is inclined by 4 ° or more from the exact (001) crystal direction, so that the density of atomic layer steps on the surface increases. Therefore, when another substance is grown on such a surface, the step density at the interface is also increased. Interfaces with high step densities often adversely affect device characteristics. For example, if an insulating film such as a silicon oxide film is grown on the substrate at the same time, there is a problem that the step at the interface deteriorates the breakdown voltage of the device.

Further, when a gallium arsenide layer is grown on the silicon or germanium (100) substrate,
As disclosed in Japanese Patent Publication No. 2-36060, the surface is heated under an arsenic pressure in order to remove an oxide film of the first silicon or germanium substrate, and a gallium arsenide buffer layer is grown thereon at a low temperature of 450 ° C. A method is known in which gallium arsenide is grown thereon at a normal gallium arsenide layer growth temperature. However, in this method, the surface of the silicon or germanium substrate does not become a single domain. As a result, Applied Physics Letters
rs) 60 (5), 3 February 1992,
As shown in p. 616-618, the anti-phase domain enters the buffer layer.

It is an object of the present invention to unify the domain of the silicon or germanium (100) surface even when the inclination angle from the exact crystal plane is small.

[0006]

According to the present invention, there is provided a method of forming a semiconductor crystal surface, comprising the steps of: forming a silicon (Si) or germanium (Ge) crystal in which domains in two directions are mixed;
0) Arsenic (As) or antimony (Sb) of about one atomic layer is saturatedly adsorbed on the surface at a substrate temperature of 600 ° C. or more.

[0007]

[Action] Silicon (Si) or germanium (Ge)
(100) surface has a rearrangement structure peculiar to the surface of its atomic arrangement.
A stress is generated whose direction is opposite in the 1> direction and in a direction orthogonal to the 1> direction. In the actual (100) surface, domains in two orthogonal directions coexist, so that the anisotropic stress is canceled out as a whole and stabilized. On the surface of such a domain structure, the boundaries of the domain are steps of one atomic layer height. However, this (10
0) For the formation energy of the above surface steps, S _A
Than the sum of the formation energy type single atomic layer steps referred to as a step and S _B step, smaller for formation energy of diatomic layer step called D _B step. For this reason, on a surface having a large step density in which the orientation of the surface is greatly deviated from the (100) direction, this effect works preferentially, and the surface becomes a single domain composed of diatomic layer height steps.

Arsenic (A) is applied to the surface of silicon or germanium (100) in which the above-described two directions of domains are mixed.
When s) or antimony (Sb) is adsorbed, the direction of the anisotropic stress changes. This new stress is <0 in the surface.
The direction is the same in the 11> direction and the direction orthogonal thereto, and there is no stress relaxation effect due to the mixture of two orthogonal domains. Furthermore, the magnitude relation of the formation energy of the step on the adsorbed surface is qualitatively the same as before the adsorption. Therefore, by changing the surface to a stable structure, the surface can be made into a single domain composed of steps of a height of two atomic layers.

However, in the case of adsorption at a high substrate temperature at which arsenic or antimony evaporates, such as the oxide film removal temperature, described in Japanese Patent Publication No. 2-36060 described above,
The surface is not in thermodynamic equilibrium, its structure is different from the stable structure, and the surface domains are not unified.

[0010]

EXAMPLE First, a Si substrate tilted by 1 ° in the <011> direction from an accurate (100) plane was prepared, and the surface was cleaned by a normal method such as annealing in an ultra-high vacuum. As shown in FIG. 1, this clean surface was a double domain surface in which each domain was separated by a step of one atomic layer height. The arrow in the figure indicates the direction of the domain. This substrate was exposed to an arsenic atmosphere of about 1 × 60 ⁻⁶ Pa for 5 minutes in a molecular beam epitaxy apparatus while maintaining the substrate temperature at 600 ° C., so that one atomic layer of arsenic was saturatedly adsorbed on the surface. . This treatment resulted in a single domain surface as shown in FIG. In other words, the clean surface of FIG. 1 has two orthogonal domains (2 × 1 structure and 1 × 2 structure) that are bounded by a step of one atomic layer height, whereas the arsenic adsorbed surface has two domains (FIG. 2). , There is only one type of domain (2 × 1 domain) bounded by a step of a height of two atomic layers. Note that the 2 × 1 structure before adsorption is a 2 × 1 structure made of Si dimer, whereas that after adsorption is a 2 × 1 structure made of arsenic dimer.

In this embodiment, an example of Si and As has been described.
Si and Sb, Ge and As, and Ge and Sb may be used.

[0012]

As described above, according to the present invention, arsenic (As) or antimony (Sb) is deposited on the crystal surface of silicon (Si) or germanium (Ge) at a temperature at which these atoms do not evaporate. By adsorbing about one atomic layer and changing the stable domain structure on the surface, the domain on the surface can be unified.

By utilizing this surface, a single-domain compound semiconductor crystal such as gallium arsenide (GaAs) can be grown directly on the silicon or germanium (100) surface. When GaAs is grown on a substrate on which As or Sb is adsorbed, As is contained in GaAs.
There is a possibility that Sb or Sb may be diffused, but even if the same or different group V element is slightly mixed in the group III-V crystal, there is no problem in fabricating the device.

[Brief description of the drawings]

FIG. 1 is a diagram showing a domain structure of a clean surface of silicon.

FIG. 2 is a diagram showing a domain structure of a silicon surface on which arsenic is adsorbed.

Claims (2)

(57) [Claims] 1. A silicon (Si) or germanium (Ge) crystal (10) in which domains in two directions are mixed.
0) A method for forming a surface of a semiconductor crystal, wherein arsenic (As) or antimony (Sb) of about one atomic layer is saturatedly adsorbed on a surface at a substrate temperature of 600 ° C. or more. 2. A silicon (Si) or germanium (Ge) crystal (10) in which domains in two directions are mixed.
0) A method for forming a semiconductor crystal surface, wherein arsenic (As) or antimony (Sb) of about one atomic layer is saturatedly adsorbed on a surface by a molecular beam epitaxy method at a substrate temperature of 600 ° C. or more.