JPH0810675B2 - Semiconductor crystal growth method and apparatus for implementing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Outline] The present invention relates to a method for growing a semiconductor crystal and an apparatus for carrying out the method, in which a compound is provided in a growth preliminary chamber in a semiconductor crystal growing apparatus capable of performing a molecular beam epitaxial growth method. A semiconductor crystal substrate is set, and then a lamp in the growth preliminary chamber is flashed while irradiating a molecular beam of a substance that is easily desorbed among the materials forming the compound semiconductor crystal substrate to clean the surface of the compound semiconductor crystal substrate. A step of heating the compound semiconductor crystal substrate above a temperature at which it is easily desorbed and performing a heat treatment within a short time in which the surface of the compound semiconductor crystal substrate is not roughened, and then transferring the compound semiconductor crystal substrate to a growth chamber By subjecting a semiconductor crystal layer to epitaxial growth by molecular beam, and by providing an apparatus for carrying out such a technique. Compound to remove contaminants such as carbon from the semiconductor substrate surface, and is obtained by allowing the growing surface roughness less high-quality crystal.

[Industrial applications]

The present invention relates to a semiconductor crystal growth method incorporating a step of cleaning the surface of a compound semiconductor substrate and an improvement of an apparatus for carrying out the method.

[Conventional technology]

Generally, when manufacturing a compound semiconductor device, a compound semiconductor crystal layer is grown on a compound semiconductor substrate and an element is formed therein.

In recent years, in order to grow such a compound semiconductor crystal layer, molecular beam epitaxy has been used.
The xy: MBE) method is often applied.

In the apparatus for carrying out this MBE method, a growth prechamber is provided as a prechamber for the growth chamber, and a chemically pretreated GaAs substrate, for example, is grown before the actual crystal layer is grown. Contamination adhering to the surface of the GaAs substrate in the atmosphere by preheating to about 300 to 400 [° C] and further preheating to about 600 to 700 [° C] in the group V element atmosphere in the growth chamber. I try to remove things.

[Problems to be solved by the invention]

However, such means are not sufficient to remove contaminants, especially carbon-containing molecules such as hydrocarbons, and therefore, when a crystal layer is epitaxially grown on such a GaAs substrate, the substrate and the epitaxial growth are At the interface of the semiconductor crystal layer, for example, 10 ¹¹ [c
A level of about m ⁻² ] to 10 ¹² [cm ⁻² ] is generated,
This has various adverse effects on the semiconductor device such as the gating phenomenon.

To prevent this, it is recommended to heat the GaAs substrate in a high vacuum at a high temperature of 700 ° C or higher, but in such a case, group III element with high vapor pressure, that is, As, is desorbed and Has the drawback of becoming rough.

Figure 3 shows epitaxial growth according to the prior art
It shows a photomicrograph of the surface of the GaAs layer.

The sample used to obtain this micrograph was a GaAs substrate.
After heat treatment for 5 minutes at 750 ° C., a GaAs layer having a thickness of about 1 μm is grown on the heat treatment.

As can be seen from the figure, the surface of this GaAs layer is rough, which is not good.

The present invention removes hydrocarbons and other contaminants adhering to the surface of the substrate almost completely by heat treatment, yet prevents the surface of the substrate from becoming rough, and therefore,
A high-quality semiconductor crystal layer with few surface defects can be easily grown to obtain a semiconductor device with good characteristics.

[Means for solving problems]

An embodiment of the present invention will be described with reference to FIG. 1, which is a drawing for explaining the embodiment.

In the present invention, a compound semiconductor crystal substrate (for example, GaAs substrate 10) is set in a growth preliminary chamber (for example, growth preliminary chamber 2) in a semiconductor crystal growth apparatus capable of carrying out the molecular beam epitaxial growth method, and the compound semiconductor substrate is set. Of the materials forming the above, the lamp (eg, lamp 14) in the growth preparatory chamber is flashed while irradiating a molecular beam of a material (eg, As) which is easily desorbed, and the material which easily desorbs the surface of the compound semiconductor crystal substrate. At a temperature higher than the temperature at which
[° C.]) and heat treatment for a short time (for example, 10 [sec]) where the surface of the compound semiconductor crystal substrate is not roughened,
Then, the compound semiconductor substrate is transferred to a growth chamber (for example, growth chamber 6) and a required semiconductor crystal layer, for example, Ga
The As / AlGaAs crystal layer is grown by molecular beam epitaxy.

[Action]

By adopting the above means, the carbonaceous substances and other contaminants attached to the compound semiconductor substrate are surely removed, and the surface roughness is small, so that each semiconductor crystal layer formed thereon has few defects and is of good quality. Will be things.

〔Example〕

FIG. 1 shows an explanatory view of a main part of a semiconductor crystal growth apparatus for explaining one embodiment of the present invention.

In the figure, 1 is a substrate exchange chamber, 2 is a growth preparatory chamber, 3 is a substrate moving rod, 4 is a substrate holder, 5 is an As molecular beam source, 6 is a growth chamber, 7 is a substrate holder, 8 is an As molecular beam. Source, 9 is a Ga molecular beam source, 10 is a GaAs substrate, 11 is In solder, 12 and 13 are gate bulbs, 14 is a halogen lamp such as a halogen lamp capable of high-temperature and short-time heating, and 15 is reflection. Each shows a mirror. In addition, in the growth chamber 6 in this embodiment, an Al molecular beam source and a Si molecular beam source are provided in addition to the As molecular beam source 8 and the Ga molecular beam source 9, but each molecular beam source grows. Since it is provided rotationally symmetrically with respect to the center axis of the chamber 6, it does not appear in FIG. 1, which is a longitudinal sectional view.

Here, a GaAs layer and an AlGaAs layer or n on the GaAs substrate 10.
A case of growing a type AlGaAs layer will be described.

The GaAs substrate 10 is attached to a molybdenum (Mo) block for mounting a substrate by using In solder in the atmosphere, and then introduced into the substrate exchange chamber 1.

The inside of the substrate exchange chamber 1 is evacuated to about 10 ⁻⁷ [Torr] to 10 ⁻⁸ [Torr], and then the gate valve 12 is opened to transfer it to the growth preliminary chamber 2.

The inside of the growth preparatory chamber 2 is maintained at about 10 ⁻⁹ [Torr] so that the As molecular beam can be emitted from the As molecular beam source 5 toward the GaAs substrate 10. When the As molecular beam is emitted, the degree of vacuum in the growth preliminary chamber 2 is lowered to about 10 ⁻³ to 10 ⁻⁴ [Torr].

The GaAs substrate 10 is subjected to lamp heating with a temperature of 900 [° C.] and a time of 10 [seconds] while being irradiated with the As molecular beam from the As molecular beam source 5, and then is naturally cooled to about 30 ° C.
When the temperature reaches about 0 [° C.], it is transferred to the growth chamber 6.

In the growth chamber 6, the GaAs substrate 10 is heated again to bring the temperature to about 680 [° C.] to grow a GaAs / AlGaAs semiconductor crystal layer.

FIG. 2 shows a photomicrograph of the surface of the GaAs layer epitaxially grown in the above-described process.

The GaAs layer in this case has a thickness of about 1 [μm] as in the GaAs layer described with reference to FIG.

Comparing the GaAs layer shown in Fig. 2 and the GaAs layer shown in Fig. 3, there is no difference in the electrical characteristics between them, and the interface state density at the GaAs substrate-GaAs layer interface is sufficient. Although it is very low, it can be seen from the surface roughness of the conventional example shown in FIG. 3 that it is remarkably improved in the embodiment of the present invention shown in FIG.

〔The invention's effect〕

According to the present invention, when a compound semiconductor crystal layer is epitaxially grown on a compound semiconductor crystal substrate, in the growth preliminary chamber, a lamp is used while being exposed to a molecular beam of a substance that easily separates among the materials forming the compound semiconductor crystal substrate. It is designed to be flashed and heat treated at high temperature for a short time.

By adopting this configuration, it is possible to remove carbonaceous substances and other contaminants without causing surface roughness of the compound semiconductor crystal substrate, and as a result, the compound semiconductor crystal layer grown on the compound semiconductor crystal substrate also has surface roughness. There can be good quality.

[Brief description of drawings]

FIG. 1 is an explanatory view of a main part of one embodiment of the present invention, FIG. 2 is a micrograph showing a crystal structure on a surface of a wafer manufactured according to one embodiment of the present invention, and FIG. 3 is a conventional example. 3A and 3B are micrographs showing the structure of crystals on the surface of a wafer manufactured by the above method. In the figure, 1 is a substrate exchange chamber, 2 is a growth preparatory chamber, 3 is a substrate transfer rod, 4 is a substrate holder, 5 is an As molecular beam source, 6 is a growth chamber, 7 is a substrate holder, 8 is an As molecular beam. Source, 9 is a Ga molecular beam source, 10 is a GaAs substrate, 11 is In solder, 12 and 13 are gate bulbs, 14 is a lamp, and 15 is a reflector.

Claims (2)

[Claims] 1. A step of setting a compound semiconductor crystal substrate in a growth preliminary chamber in a semiconductor crystal growth apparatus capable of carrying out a molecular beam epitaxial growth method, and then removing the compound semiconductor crystal substrate from materials constituting the compound semiconductor crystal substrate. A lamp in the growth preliminary chamber is flashed while irradiating a molecular beam of a substance that is easily released, and the surface of the compound semiconductor crystal substrate is heated to a temperature higher than the temperature at which the substance that is easily released is released and the surface of the compound semiconductor crystal substrate. And a step of transferring the compound semiconductor crystal substrate to a growth chamber and growing a required semiconductor crystal layer by molecular beam epitaxy. Method for growing semiconductor crystal. 2. A holder for holding a compound semiconductor crystal substrate, a molecular beam source capable of irradiating the compound semiconductor crystal substrate with a substance that is easily detached as a molecular beam, and the surface of the compound semiconductor crystal substrate by flashing. A growth preparatory chamber provided with a lamp capable of being heated to a temperature higher than the temperature at which a substance that is easily desorbed is desorbed and capable of applying a short-time heat treatment that does not roughen the surface of the compound semiconductor crystal substrate; And a growth chamber that is connected to the chamber to grow a semiconductor crystal layer by molecular beam epitaxy.