JP3364696B2 - Method for producing group III-V compound thin film - 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 producing a group III-V compound thin film, and particularly to a group IV single crystal substrate.
The present invention relates to a method for manufacturing a III-V compound thin film.

[0002]

2. Description of the Related Art In order to fabricate an optoelectronic integrated circuit, Si
Attempts have been made to epitaxially grow III-V group compounds such as GaAs and InP on a group IV single crystal substrate such as Ge and Ge. This aims to complement each other's drawbacks by utilizing the advantages of both by the heterojunction between the III-V group compound and the group IV simple substance. However,
To date, no optoelectronic integrated circuit using such a heterojunction has been realized. This is because there is a large mismatch in the lattice constant and a difference in thermal expansion coefficient between the III-V group compound and the group IV simple substance, and in addition, the atoms constituting the group III-V compound and the group IV simple substance atom. III-V due to the presence of charge mismatch due to the difference in polarity at the junction with
This is because the crystallinity of the group compound thin film is significantly deteriorated.

Conventionally, when a group III-V compound thin film is formed on a group IV simple substance substrate, in order to suppress the generation of defects such as dislocations from the interface, a gap between the group IV simple substance substrate and the group III-V compound thin film is formed. It has been attempted to sandwich a buffer layer in the. For example, when a GaAs thin film is epitaxially grown on a Si substrate, the GaAs thin film is grown at a low temperature in the initial stage of growing the GaAs thin film, or a layered GaSe thin film having a film thickness of about 10 nm is sandwiched as a buffer layer. In addition, a so-called superlattice buffer layer (for example, In _x Ga _{1 -x} A) in which different III-V compound thin films are alternately stacked is used.
s / GaAs, AlGaAs / GaAs, etc. are alternately laminated every 10 layers and have a thickness of 50 nm).

Further, in order to bend or block dislocations generated at the interface, a superlattice buffer layer or a hard Si layer is sandwiched during the growth of the GaAs thin film to improve the crystallinity of the GaAs thin film thereafter. Is being attempted.

Further, it is also attempted to improve the crystallinity by performing a heat treatment at a high temperature of 800 ° C. to 900 ° C. after epitaxially growing a GaAs thin film on a Si substrate.

In general, the crystallinity is improved by combining the above-mentioned methods, that is, by sandwiching the superlattice buffer layer at the beginning or in the middle of the growth of the GaAs thin film, and performing a heat treatment after the growth. There is.

[0007]

However, no matter which method is used, the dislocation concentration in the GaAs thin film is 10 ⁶
There is a problem that it is very high at -10 ⁷ cm ^-2 .

Further, in the heat treatment step, the substrate on which the thin film is formed is taken out from the growth apparatus and the surface of the thin film is exposed to air, which is an important part of the light emitting element and the electronic element which are indispensable for optoelectronic integrated circuits and the like. There is a problem that the interface of the joint is contaminated. Note that it is possible to perform the heat treatment step in the growth apparatus, but in this case, there is a problem in that in the heat treatment at 700 ° C. or higher, a large number of defects occur because As atoms escape from GaAs.

Furthermore, when a superlattice buffer layer is used and a heat treatment is performed at 900 ° C. or higher, III--
There is a problem that mutual elements are diffused between group V compounds and the superlattice structure is broken.

An object of the present invention is to provide a method for forming a group III-V compound thin film having good crystallinity on a group IV simple substance substrate.

[0011]

According to the present invention, a thin film of a III-V group compound is crystal-grown on a single crystal substrate.
In the method for producing a group V compound thin film, the first step of epitaxially growing the group III-V compound and the step II
Than I-V group compound and the second step of growing a thin film of hard material with a high melting point, a thin film grown in the second step key
Third heat treatment as a cap material at a high temperature of 900 ° C or higher
And a fourth step of re-epitaxially growing the III-V group compound in this order, a method for producing a III-V group compound thin film is obtained.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. First, with reference to FIG. 1, a vapor phase growth apparatus (molecular beam epitaxy (MBE) apparatus) used in an embodiment of the present invention will be described. This vapor phase growth apparatus comprises a substrate preparation chamber 11 for introducing a substrate and a main M for growth.
BE device main body 12 and these are the gate valve 1
3 are connected to each other.

The substrate preparation chamber 11 is provided with a substrate holder receiver 14 with a heater and a transfer rod 15 for transporting the substrate. A turbo molecular pump 16 is connected to the substrate preparation chamber 11.

The main MBE apparatus main body 12 has a Knudsen cell 17 containing Ga raw material, a Knudsen cell 18 containing As, and a Knudsen cell 1 containing Si.
9, a substrate holder holder 20 with a heater, and a liquid nitrogen pipe 21 for cooling the inside of the main MBE device main body 12 are provided. An ion pump 22 is connected to the main MBE device body 12.

Next, using the above-mentioned apparatus, a Ga film was formed on the Si substrate.
An example of epitaxially growing an As thin film will be described with reference to FIG. It is assumed that the inside of the main MBE device main body 12 has been previously evacuated to the 10 ⁻¹⁰ Torr level.

First, the surface of the Si substrate 201 is etched with 30% hydrofluoric acid for 5 minutes to remove the oxide film and the contaminated layer formed on the surface. Next, the Si substrate 201 is set in the substrate holder 23, and the substrate holder 23 is loaded in the substrate holder holder 14 with a heater in the substrate preparation chamber 11.
Then, the inside of the substrate preparation chamber 11 is evacuated to the 10 ⁻⁸ Torr level by using the turbo molecular pump 16, and then the substrate is preheated at 400 ° C. for 30 minutes by the heater of the substrate holder holder 14 with a heater. By this heating, water and the like attached to the substrate holder 23 and the Si substrate 201 are removed.

Next, the gate valve 13 is opened, the substrate holder 23 is transported from the substrate preparation chamber 11 to the main MBE apparatus main body 12 by using the transfer rod 15, and set in the substrate holder holder 20 with a heater. Using the heater of the substrate holder holder with heater 20, the Si substrate 201 is gradually heated to 1100 ° C. and maintained for 20 minutes. By this heat treatment, contaminants attached to the Si substrate 201 are completely removed, and a clean surface is obtained. After that, the Si substrate 2
The temperature of 01 is lowered to 400 ° C., and GaAs is epitaxially grown.

Before performing the epitaxial growth of GaAs, for example, during the heat treatment, the Ga Knudsen cell 17 is 1000 ° C., the As Knudsen cell 18 is 278 ° C., and the Si Knudsen cell is 140 ° C.
Set to 0 ° C and prepare for irradiation of each molecular beam. Under this condition, the molecular beam intensity of Ga and Si is 1 × 10 ⁻⁷ Tor.
The molecular beam intensity of r and As is 1 × 10 ^-5 Torr, and GaA
The growth rate of s and Si is 1 μm / hour.

After the temperature of the Si substrate 201 has dropped to 400 ° C., the shutter of the As Knudsen cell 18 is opened and the surface of the Si substrate 201 is irradiated with As molecular beams.
Then, open the Knudsen cell 17 of Ga,
The epitaxial growth of s is started. The shutter of the Ga Knudsen cell 17 is open for 36 seconds and then closed. As a result, GaAs grows to 10 nm. Next, the substrate temperature is raised to 580 ° C., the shutter of the Ga Knudsen cell 17 is opened again, and the growth of GaAs is restarted. When GaAs is grown for 6 minutes, that is, 100 nm, the shutters of the Ga Knudsen cell 17 and the As Knudsen cell 18 are simultaneously closed. Thus, the GaAs thin film 202 is formed on the Si substrate 201.

Then, the shutter of the Si Knudsen cell 19 is opened. By closing the shutter after 3 seconds, the Si thin film 203 having a thickness of 1 nm is changed to the GaAs thin film 20.
2 is formed on. Here, the thickness of the Si film is set to 1 nm by Matthew et al., Journal of Crystal Growth 1974, Vol. 118, No. 27, p. 11
8 based on the critical film thickness of Si that does not generate dislocations.

Next, the temperature of the Si substrate 201 is raised to 900 ° C. or higher, for example, 950 ° C. After heat treatment for 1 minute,
The substrate temperature is lowered to 580 ° C again. At this time, Si
The thin film 203 acts as a cap material that can be placed in a high temperature heat treatment, prevents re-evaporation of atoms from the GaAs thin film 202, and can effectively improve the crystallinity of the GaAs thin film 202.

After that, the shutters of the As Knudsen cell 18 and the Ga Knudsen cell 17 are sequentially opened to regrow GaAs. In this embodiment, GaAs
Was grown for 54 minutes to form a 900 nm regrown GaAs thin film 204. Then, the Ga Knudsen cell is closed to complete the growth of GaAs. After that, when the temperature of the Si substrate 201 is lowered to 400 ° C. or lower, As
Close the shutter of the Knudsen cell.

The GaAs thin film (thickness: about 1 μm) thus obtained was obtained by the X-ray double crystal method (400) G.
The full width at half maximum of the rocking curve for aAs reflection was 200 seconds, and the dislocation density was 10 ⁵ cm ^-2 .

In the above embodiment, the case where GaAs is used as the III-V group compound has been described, but the present invention can be applied to other III-V group compounds. The thickness of the Si film in this case can be obtained from the lattice mismatch (4% in the case of GaAs and Si) based on the report of Matthew et al.

In the above embodiment, Si is used as a material having a higher melting point and being harder than the III-V group compound.
i, Mo, W, Ni, Cr, Fe and the like can also be used.

[0026]

According to the present invention, a thin film of a material that is harder and has a higher melting point than the III-V compound is formed during the epitaxial growth of the III-V compound.
It is possible to perform high temperature heat treatment at 900 ° C. or higher without exposing the grown III-V group compound thin film to the atmosphere.

Further, by setting the thickness of the thin film of a material having a higher melting point and harder than the III-V group compound to be equal to or less than the critical film thickness at which dislocation is not generated, the crystallinity is improved by the high heat treatment. Even if the III-V group compound is regrown on the compound, dislocations do not occur, and a regrown III-V group compound thin film having good crystallinity can be obtained.

[Brief description of drawings]

FIG. 1 is a schematic view of a vapor phase growth apparatus used in an embodiment of the present invention.

FIG. 2 is a III-V made according to one embodiment of the present invention.
It is a film structure figure of a group compound thin film.

[Explanation of symbols]

11 Board preparation room 12 Main MBE device body 13 Gate valve 14 Substrate holder holder with heater 15 Transfer rod 16 Turbo molecular pump 17 Knudsen cell 18 Knudsen cell 19 Knudsen cell 20 Substrate holder holder with heater 21 Liquid nitrogen piping 22 Ion pump 23 Board holder 201 Si substrate 202 GaAs thin film 203 Si thin film 204 GaAs thin film

Claims (4)

(57) [Claims] 1. A method for producing a III-V group compound thin film in which a thin film of a III-V group compound is crystal-grown on a single crystal substrate, the first step of epitaxially growing the III-V group compound, and the III-V group compound. a second step of growing a thin film of hard material with a high melting point than V compound, the second Engineering
The thin film that has grown up to about 900 ° C is used as a cap material.
A third step of performing heat treatment at a high temperature, and a fourth step of again epitaxially growing the group III-V compound, this
The method for producing a group III-V compound thin film, comprising: 2. The thin film of the III-V group compound according to claim 1 , wherein the thin film of a material having a higher melting point and a higher hardness than that of the III-V group compound has a predetermined film thickness or less. Production method. 3. A group III-V compound method of manufacturing a thin film according to claim 1 or 2 thin rigid material in the higher melting point than the III-V compound, characterized in that a Si thin film. 4. A said single crystal substrate is a Si substrate, producing a group III-V compound thin film according to claim 1, 2 or 3, wherein said group III-V compound is GaAs Method.