JPH0927451A - Method for manufacturing compound semiconductor substrate - Google Patents

Abstract

(57) [Summary] (Modified) SOLUTION: A compound semiconductor substrate in which compound semiconductor thin films 13 and 14 are epitaxially grown by a two-step growth method after terminating dangling bonds a on a surface of a Si substrate 11 with hydrogen atoms 12a. 10. The manufacturing method of 10. [Effect] The first compound semiconductor thin film 1 is formed on the Si substrate 11.
When 3 grows, the surface of the first compound semiconductor thin film 13 is flattened, and surface roughness and dislocation are prevented from occurring in the second compound semiconductor thin film 14 epitaxially grown on the first compound semiconductor thin film 13. Therefore, the compound semiconductor substrate 10 having excellent crystallinity can be manufactured.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a compound semiconductor substrate, and more particularly to a method for manufacturing a compound semiconductor substrate used in, for example, optical or high speed electronic devices.

[0002]

2. Description of the Related Art In recent years, a compound semiconductor thin film, which is different from the compound semiconductor thin film, is epitaxially grown on a substrate, and a compound semiconductor substrate in which the respective advantages of the compound semiconductor thin film and the substrate can be utilized has been studied. For example, by epitaxially growing a GaAs thin film on a silicon (hereinafter referred to as Si) substrate, a compound semiconductor substrate having both mechanical strength of the Si substrate and high-speed response of the GaAs thin film has been manufactured. Compound semiconductor substrates obtained by various methods are applied to electronic devices, optical devices, and the like.

However, since Si and GaAs have different lattice constants, it has been difficult to directly epitaxially grow a GaAs thin film on a Si substrate. In order to deal with this problem, a two-step growth method has been proposed (Akiyama et al: Japanese Journal of Appli.
ed Physics; Vol.23 (1984), No.11, L843 to L845). This is because, at a relatively low temperature (first crystal growth temperature) of about 400 to 500 ° C., the first compound semiconductor thin film of GaAs or the like, which is close to an amorphous state of about 5 to 20 nm, is S-doped.
Grow on i substrate. Next, the temperature is raised to a relatively high temperature (second crystal growth temperature) of about 600 to 750 ° C. to single crystallize the first compound semiconductor thin film by solid phase growth, and on top of this, a second crystal such as GaAs is formed. This is a method of epitaxially growing the compound semiconductor thin film of No. 2 by a desired film thickness.

Prior to the two-step growth process, the S
The i substrate is subjected to a wet cleaning treatment using an HF aqueous solution, deionized water, etc. to remove the oxide film on the Si substrate, and the surface of the Si substrate is terminated by hydrogen to passivate it and is oxidized in the air. It is hard to be done, and pretreatment is performed to maintain a clean state. Then, the Si substrate is inserted into an epitaxial growth apparatus and heated to about 820 to 1000 ° C. in a hydrogen gas atmosphere to remove a thin oxide film formed on the Si substrate and form a double step structure. Pre-heat treatment is carried out (Mori et al: Appl. Phys. Lett .; Vol.63 (1993), N
o.14, p.1963 to p.1965).

[0005]

In the method of manufacturing a compound semiconductor substrate by the above two-step growth method, a compound semiconductor thin film can be epitaxially grown on a Si substrate. However, as shown in FIG. 4, in this manufacturing method, when the first compound semiconductor thin film 22 close to an amorphous state is grown on the Si substrate 21, the first compound semiconductor thin film 22 is formed in the vicinity of the interface 23 as in the conventional case. Compound semiconductor thin film 2
Strain energy (not shown) based on the difference between the lattice constants of 2 and the Si substrate 21 is likely to occur. Then, the first compound semiconductor thin film 22 takes a Stranski-Krastanov type growth mode, and the island-shaped crystal 22a easily grows from the initial stage of growth.
Further, when the temperature of the first crystal growth temperature is raised to the second crystal growth temperature and the island crystals 22a are solid-phase-grown and become single crystals due to the thermal effect, these agglomerate and form large island crystals (not shown). No)). Although not shown, when the second compound semiconductor thin film is further epitaxially grown on this island crystal, dislocations are generated in the vicinity of the junction between the island crystals,
Surface roughness occurs on the surface of the second compound semiconductor thin film, reflecting the concavo-convex shape of the surface of the associated island crystals.
With such a compound semiconductor substrate, a high electron mobility transistor (HEMT)
When an electronic device such as r) is formed, there is a problem that the mobility of the two-dimensional electron gas at the interface of the active layer is likely to decrease and the device characteristics are deteriorated.

Also in the manufacturing method in which the compound semiconductor thin film is epitaxially grown by the two-step growth method after the above-mentioned Si substrate is pretreated and preheated, the temperature of the preheat treatment is high and the two-step growth method is used. There was a problem similar to the case of the manufacturing method.

The present invention has been made in view of the above problems, and provides a method for producing a compound semiconductor substrate capable of epitaxially growing a compound semiconductor thin film having a flat surface and excellent crystallinity on a Si substrate. The purpose is to do.

[0008]

In order to achieve the above object, a method of manufacturing a compound semiconductor substrate according to the present invention is directed to a compound semiconductor substrate in which a compound semiconductor thin film having a lattice constant different from that of Si is epitaxially grown on a Si substrate. In the manufacturing method, the dangling bonds on the surface of the Si substrate are terminated with hydrogen atoms, and then a compound semiconductor thin film is epitaxially grown by a two-step growth method.

As described above, the high flatness at the surface of the second compound semiconductor thin film or at the interface between the second compound semiconductor thin film and the first compound semiconductor thin film has a good effect on the electron transfer of an electronic device such as HEMT. Therefore, in order to secure the flatness, it is necessary to prevent the generation of island crystals. After the dangling bonds 11b on the surface of the Si substrate 11 are terminated with hydrogen (H) atoms 12a (both of which are shown in FIG. 3), the first compound semiconductor thin film is formed on the dangling bonds 11b. Generation is suppressed, and this thin film can be grown while maintaining the surface of the first compound semiconductor thin film flat. As a result, it is possible to prevent the occurrence of dislocations in the vicinity of the association portion when these island crystals are grown, and the occurrence of surface roughness in the second compound semiconductor thin film when epitaxially grown on the island crystals. Become.

The behavior and action of the terminal hydrogen 12a have not been clarified at present, but when the first compound semiconductor thin film is formed on the Si substrate 11, the terminal hydrogen 12a constitutes the thin film. Since the compound molecules are sequentially substituted and segregated on the surface of the first compound semiconductor thin film, and the surface energy of the thin film can be reduced, the surface of the first compound semiconductor thin film is kept flat and the thin film is maintained. Are estimated to grow.

Further, the terminal surface of the hydrogen 12a is not easily oxidized even when exposed to the atmosphere and is stable. Therefore, the surface of the Si substrate 11 is maintained without being oxidized until the epitaxial growth step. . Further, the terminal hydrogen 12a is released / dissipated outward when the temperature is raised to the second crystal growth temperature, so that it does not remain in the first and second compound semiconductor thin films.

According to the method of manufacturing a compound semiconductor substrate having the above structure, the dangling bonds on the surface of the Si substrate are terminated with hydrogen atoms, and then the compound semiconductor thin film is epitaxially grown by the two-step growth method. When the first compound semiconductor thin film grows, the surface of the first compound semiconductor thin film is flattened. As a result,
It is possible to prevent surface roughness and dislocation from occurring in the second compound semiconductor thin film epitaxially grown on the first compound semiconductor thin film, and it is possible to manufacture a compound semiconductor substrate having excellent crystallinity.

The first crystal growth temperature in the two-step growth method is preferably 380 to 450 ° C., and more preferably 380 to 400 ° C. in order to prevent the desorption and diffusion of the terminal hydrogen atoms.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of a method for manufacturing a compound semiconductor substrate according to the present invention will be described below with reference to the drawings. FIG. 1 shows a method of manufacturing a compound semiconductor substrate according to the present invention.
FIG. 3 is a cross-sectional view schematically showing an example of a compound semiconductor substrate in which a compound semiconductor thin film is grown on a Si substrate, and FIG. 2 is a view showing a temperature sequence of a compound semiconductor substrate manufacturing method according to the example. is there. In the case of the compound semiconductor substrate manufacturing method according to the example, first, the Si substrate 11 is placed in an epitaxial growth apparatus (not shown) set to a predetermined vacuum degree.
Insert (Fig. 1) and preheat at about 900 ° C 15 (Fig. 2)
A thin natural oxide film on the Si substrate 11 (not shown)
Is removed, and the surface of the Si substrate 11 is set to a double step structure (not shown). Next, in the hydrogen termination processing step 16 (FIG. 2), the temperature of the Si substrate 11 is set to about 15
While setting the temperature to 0 ° C., H radicals generated by colliding and decomposing H ₂ gas with a tungsten filament heated to about 1500 ° C. or more are supplied into the apparatus set to a vacuum degree of 10 ⁻⁶ Torr or more, and this is supplied. Irradiate the surface of the Si substrate 11. Then, the dangling bond 11 on the surface Si11a
b (both FIG. 3) is H (hydrogen atom) 12a (FIGS. 1 and 3)
Terminated by Next, in the first crystal growth step 17 (FIG. 2), the Si substrate 11 is heated to the first crystal growth temperature (380 to 380).
The temperature is set to 450 ° C., and the first compound semiconductor thin film 13 (FIG. 1) is grown on the Si substrate 11 via H12a.
Then, the terminal end H12a moves upward while displacing the first compound molecule forming the thin film 13, and H1 is transferred onto the surface of the thin film 13.
2b (FIG. 1) is segregated and the surface of the thin film 13 is flattened. Second crystal growth step 18 (FIG. 2)
At the second crystal growth temperature (600
To 750 ° C.), and the second on the compound semiconductor thin film 13.
The compound semiconductor thin film 14 (FIG. 1) is grown. Then, the terminal hydrogen 12b is released / dissipated to the outside, and the compound semiconductor thin film 13 is solid-phase-grown due to the heat effect to be single-crystallized, and the flat compound semiconductor thin film 14 is epitaxially grown on the thin film 13 to form the compound semiconductor substrate. 10 are manufactured.

[0015]

EXAMPLES AND COMPARATIVE EXAMPLES Hereinafter, the results of examining the flatness and crystallinity of the compound semiconductor substrate 10 manufactured by the manufacturing method according to the example will be described. The experimental conditions were
The Si substrate 11 has a (001) plane orientation, and [11
The one tilted by 2 ° in the [0] direction was used. The Si substrate 11 was pretreated. That is, after removing the natural oxide film on the surface of the Si substrate 11 using a hydrofluoric acid-based etchant, a thin oxidation protection film was formed on the surface of the Si substrate 11 using a mixed aqueous solution of hydrochloric acid and hydrogen peroxide. As an epitaxial growth method, a molecular beam epitaxy method (MBE: Molecu
lar beam epitaxy) and solid Ga and As were used as compound semiconductor raw materials. In the first crystal growth step 17, the temperature is about 400 ° C. and the partial pressure ratio of As and Ga is about 1.
0, the growth rate is set to about 0.3 μm / h, and the GaAs film as the compound semiconductor thin film 13 is set to about 0.1 μm.
Was grown to a film thickness of Further, when the first crystal growth step 17 is transferred to the second crystal growth step 18, the Ga cell is closed, while the As cell (both not shown) is open.
Irradiated with flux. The second crystal growth step 1
In No. 8, the temperature was set to about 600 ° C., the partial pressure ratio of As and Ga was set to about 20, and the growth rate was set to about 1 μm / h.
A GaAs film as a compound semiconductor thin film of 3 was grown to a film thickness of about 3 μm. As a comparative example, a compound semiconductor substrate manufactured by the same method as that of the example except for the hydrogen termination treatment step 16 was selected.

The surface roughness of the GaAs films 13 and 14 was measured by an atomic force microscope (AFM), and the flatness was evaluated based on the standard deviation regarding the variation from the reference plane. The results are shown in Table 1 below.

[0017]

[Table 1]

As is apparent from Table 1, the GaAs film 13 is flattened (1.0 mm) by the method according to the embodiment, compared with the flatness of 2.5-3.0 nm by the method according to the comparative example.
.About.1.2 nm). Further, compared with the flatness of 5.0 to 6.0 nm in the method according to the comparative example, the GaAs film 14 is flatter (2.5 to 3.
0 nm).

Further, the crystallinity of the GaAs films 13 and 14 is determined by X
The results of evaluation by the half-width of the line 2 crystal diffraction peak are shown in Table 2 below.

[0020]

[Table 2]

As is clear from Table 2, the crystallinity of the method according to the example is superior to that of the comparative example.
The dislocation density in the GaAs films 13 and 14 is decreasing.

As is clear from the above results, in the method of manufacturing the compound semiconductor substrate according to the embodiment, the dangling bond 11a on the surface of the Si substrate 11 is terminated with hydrogen atoms 12a, and then the compound semiconductor thin film is formed by the two-step growth method. 13, 1
Since 4 is epitaxially grown, when the first compound semiconductor thin film 13 grows on the Si substrate 11, the surface of the first compound semiconductor thin film 13 is flattened. As a result, it is possible to prevent surface roughness and dislocation from occurring in the second compound semiconductor thin film 14 epitaxially grown on the first compound semiconductor thin film 13, and to manufacture the compound semiconductor substrate 10 having excellent crystallinity. You can

Although not shown, in the method of manufacturing a compound semiconductor substrate according to another embodiment, first, the Si substrate 11 (FIG. 1) is inserted into a normal thermal oxidation furnace, and preheated at about 1000 ° C. While forming an oxide film on the Si substrate 11,
The surface of the Si substrate 11 is set to have a double step structure (both not shown). Then, the Si substrate 11 is immersed in an HF (HF concentration is about 1 to 10%) aqueous solution for 1 to 5 minutes, and then subjected to a hydrogen termination treatment of cleaning with deionized water or the like, and Si
The oxide film on the substrate 11 is removed and the Si substrate 1
Terminate the surface of 1 with hydrogen. Thereafter, the compound semiconductor substrate is manufactured by epitaxially growing the first and second compound semiconductor thin films 13 and 14 (FIG. 1) on the Si substrate 11 by the two-step growth method shown in FIG.

In the method of manufacturing a compound semiconductor substrate according to another embodiment, after the Si substrate 11 is preheated at high temperature,
Since hydrogen termination treatment is performed, it is possible to obtain substantially the same effect as in the case of the method according to the embodiment shown in FIGS.

In each of the methods for manufacturing the compound semiconductor substrate according to the above-mentioned embodiments, the case where the solid source MBE method is used as the compound semiconductor raw material has been described, but it is possible to generate H radicals in an ultrahigh vacuum. In addition to the solid source, trimethylgallium (TMG),
A gas source of arsine (AsH ₃ ) may be used.

Further, in any of the methods for manufacturing a compound semiconductor substrate according to the above-described embodiments, the compound semiconductor thin film is formed of Ga.
Although the case of growing an As film has been described, InP,
It is also possible to grow a III-V group compound semiconductor thin film such as GaP or InAs.

[0027]

As described above in detail, in the method of manufacturing the compound semiconductor substrate according to the present invention, the compound semiconductor thin film is epitaxially grown by the two-step growth method after terminating the dangling bond on the Si substrate surface with hydrogen atoms. Therefore, when the first compound semiconductor thin film grows on the Si substrate, the surface of the first compound semiconductor thin film is flattened. As a result, it is possible to prevent surface roughness and dislocation from occurring in the second compound semiconductor thin film epitaxially grown on the first compound semiconductor thin film, and it is possible to manufacture a compound semiconductor substrate having excellent crystallinity. .

[Brief description of drawings]

FIG. 1 is a cross-sectional view schematically showing an example of a compound semiconductor substrate in which a compound semiconductor thin film is grown on a Si substrate by a compound semiconductor substrate manufacturing method according to the present invention.

FIG. 2 is a diagram showing a temperature sequence of a method for manufacturing a compound semiconductor substrate according to an example.

FIG. 3 is a schematic cross-sectional view shown for explaining a state where dangling bonds on the surface of a Si (100) substrate are terminated by hydrogen atoms by the method for manufacturing a compound semiconductor substrate according to the present invention.

FIG. 4 is a cross-sectional view schematically showing a compound semiconductor substrate in the process of growing a first compound semiconductor thin film on a Si substrate using a conventional method of manufacturing a compound semiconductor substrate by a two-step growth method. .

[Explanation of reference numerals] 10 compound semiconductor substrate 11 Si substrate 12a terminal hydrogen atom 13 first compound semiconductor thin film 14 second compound semiconductor thin film

Claims (1)

[Claims] 1. A method of manufacturing a compound semiconductor substrate in which a compound semiconductor thin film having a lattice constant different from that of Si is epitaxially grown on a Si substrate, wherein dangling bonds on the surface of the Si substrate are terminated with hydrogen atoms, and then two steps are performed. A method of manufacturing a compound semiconductor substrate, which comprises epitaxially growing a compound semiconductor thin film by a growth method.