JPH11238683A - Manufacture of compound semiconductor film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable formation of a compound semiconductor film which exhibits high crystallinity and high surface flatness at low manufacturing cost. SOLUTION: This method for manufacturing a compound semiconductor film uses a hetero growth technique for forming a buffer layer on a Si substrate and growing a compound semiconductor. A buffer layer such as γ-Al2 O3 is formed on a Si substrate 1. A metal is preliminarily grown on the buffer layer 2 to form a preliminarily-grown layer 3. A desired compound semiconductor film 4 is formed on the preliminarily-grown layer 3 of the metal.

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 compound semiconductor film on a Si substrate, and more particularly, to a method for forming a compound semiconductor film having good crystallinity and surface flatness.

[0002]

2. Description of the Related Art At present, sapphire is mainly used as a substrate in nitride semiconductors represented by GaN, which are currently used as materials for blue light emitting LEDs (Jpn.
J. Appl. Phys. 30 (1991) L1998
Such). Si, SiC, M as substrates other than sapphire
Although the use of gO, GaAs, MgAl ₂ O ₄ , ZnO or the like has been reported, these substrates all use G
The lattice mismatch with aN is large, so that a better GaN film has not been produced as compared with a sapphire substrate.

On the other hand, in the epitaxial growth of an SOI structure in which Si is grown on an insulating substrate material, a γ-Al ₂ O ₃ film is grown on a Si single crystal substrate, and thereafter, the Si is grown.
Has been reported (Appl. Phy).
s. Lett. 67 (1995) 2200).

[0004]

Recently, there has been reported a method of growing γ-Al ₂ O ₃ on a Si single crystal substrate and thereafter growing a GaN film as a compound semiconductor film. (Appl. Phys. Lett.
72 (1998) 109).

However, the γ-Al
_{When a} compound semiconductor GaN film is formed on ₂ O ₃ , it is necessary to form a GaN film as a low-temperature buffer layer for preliminary growth before forming the GaN film. Therefore, there is a problem that the manufacturing process is complicated and the manufacturing cost is increased.

Further, when a GaN film is formed as a low-temperature buffer layer on such γ-Al ₂ O ₃ in advance, and then a GaN film is finally formed, the quality of the GaN film is, for example, 1.3 μm. When the X-ray rocking curve is measured at a film thickness of FWHM, the FWHM (Full Width of Half Maximum) is 32.
40 (arcsec) is bad and PL (Photo Lumi
Also, in the measurement of nescence, light emission from a deep level near 550 (nm) is strongly observed, so that a film having a quality that can be applied practically cannot be formed.

It is an object of the present invention to provide a method of manufacturing a compound semiconductor film capable of forming a compound semiconductor film having high crystallinity and good surface flatness at a low manufacturing cost.

[0008]

According to the present invention, there is provided a method for forming a compound semiconductor film on a Si substrate, comprising the steps of: forming a buffer layer made of an oxide on the Si substrate; Forming a pre-grown layer made of a metal as a pre-growth of the compound semiconductor film; and forming a desired compound semiconductor film on the pre-grown layer made of the metal, thereby forming a compound semiconductor film. And a method for producing the same.

Here, γ-Al _{2 is used} as the buffer layer.
O ₃ is formed, and as a pre-growth layer made of the metal, A
Preliminary growth can be performed using at least one of l, Ga, In, and a metal element constituting a growing compound semiconductor.

As the compound semiconductor film, AlN, Ga
N, InN, and mixed crystal compounds thereof can be grown.

[0011] Al can be used as the metal of the preliminary growth layer.

[0012] The thickness of the pre-growth layer can be substantially thinner than 30 Å.

[0013]

Embodiments of the present invention will be described below in detail with reference to the drawings.

First, an outline of a method for manufacturing a compound semiconductor film according to the present invention will be described based on the steps of FIG.

FIG. 1 shows a substrate used in the present invention.
A Si substrate 1 as shown in FIG.

Then, in the step of FIG.
Γ-Al ₂ O ₃ as a buffer layer 2 is formed on a substrate 1. The method for growing γ-Al ₂ O ₃ on the Si substrate 1 is not particularly limited. The buffer layer 2 is not limited to γ-Al ₂ O ₃ but may be another oxide layer.

As the growth method, for example, low pressure chemical vapor deposition (LPCVD), ultrahigh vacuum chemical vapor deposition (UHV-CVD), molecular beam epitaxy (MBE)
), A sputtering method, a laser MBE method, or the like. At this time, the thickness of the layer of γ-Al ₂ O ₃ is not particularly limited.
A range from 0.003 μm to 1 μm is practical.

Next, in the step of FIG.
On the buffer layer 2 made of l ₂ O ₃ , a preliminary growth layer 3 made of a metal is formed. Preliminary growth is performed by using at least one of Al, Ga, In, and a metal element constituting the compound semiconductor to be grown as a metal of the preliminary growth layer 3.

As a method for forming the preliminary growth layer 3, a metal organic chemical vapor deposition (MOCVD) method, a molecular beam epitaxy method (MBE method), an electron beam (EB) vapor deposition method, a sputtering method, or the like can be used. . Further, the thickness of the metal to be subjected to the preliminary growth is preferably 100 Å or less, more preferably 30 Å or less.

By performing such preliminary growth of the preliminary growth layer 3, the surface of γ-Al ₂ O ₃ , which was irregular at the atomic level in the conventional method, is stabilized by the metal element for preliminary growth. And uniformity.

Next, in the step of FIG. 1D, the Si substrate 1 including the pre-grown layer 3 is heated to a desired compound semiconductor growth temperature, and then the compound semiconductor is formed to a desired film thickness. Then, a compound semiconductor film 4 is formed.

As the compound semiconductor mentioned here, for example, AlN, GaN, InN, or a mixed crystal compound thereof can be used.

Since the surface of the substrate before the formation of the compound semiconductor film 4 is uniformly covered with the metal of the preliminary growth layer 3 in this manner, the two-dimensional nucleus growth of the compound semiconductor in the initial stage of growth. Easy to cause. For this reason, the crystallinity and flatness of the deposited compound semiconductor are significantly improved as compared with the conventional case where there is no preliminary growth of metal.

The method of forming the compound semiconductor film 4 is not particularly limited, but may be a metal organic chemical vapor deposition (MOCVD) method, a molecular beam epitaxy method (MBE).
Method), organometallic molecular beam epitaxy method (MOMBE)
Method, a sputtering method, a laser MBE method and the like. Through the above steps, a compound semiconductor thin film can be formed.

Here, the reason why the crystallinity and flatness are dramatically improved by forming the metal pre-growth layer 3 will be considered.

Normally, when γ-Al ₂ O ₃ or sapphire is used as a substrate, Al
It is not known which (aluminum) atom or O (oxygen) atom appears. When a compound semiconductor is grown on a substrate having such a surface morphology, it is expected that the initial growth morphology of the film will differ depending on the difference in atoms existing on the outermost surface. Thereby, for example, when oxygen atoms appear on the outermost surface, three-dimensional island-like growth occurs, and Al
When atoms appear, two-dimensional nuclear growth occurs as described above.

If three-dimensional growth occurs during the crystal growth process, the crystallinity and flatness of the surface will be deteriorated, for example, the boundary will become defective when the crystal nuclei are united.

Therefore, by performing pre-growth using a metal as in the present invention, the atoms on the outermost surface can be unified with the metal element, whereby the two-dimensional growth can be enhanced.
The effect is obtained. Since the pre-growth of the metal can change the arrangement of atoms on the outermost surface of the buffer layer 2 in this manner, the crystallinity and flatness of the surface can be improved.

Next, a specific example will be described.

(Embodiment 1) A first embodiment will be described.

First, γ-Al ₂ O ₃ as the buffer layer 2 is grown on the Si substrate 1. As the substrate, Si
In an MBE apparatus using a (111) substrate and using metal Al and N ₂ O as raw materials, a substrate temperature of 820 ° C., a Knudsen cell temperature of metal Al = 1100 ° C. (K-cell temperature; Knudsen cell temperature)
e), at a pressure of N ₂ O = 3 × 10 ⁻² Pa, a single crystal γ-A
I ₂ O ₃ was grown. A film thickness of about 5
0 Å (111) oriented single crystal γ-A
An l ₂ O ₃ film is formed.

Next, S grown on γ-Al ₂ O ₃
The temperature of the i-substrate 1 is lowered to room temperature, and the temperature of the Al Knudsen cell =
At 1050 ° C., an Al thin film
Grow at 20 Å at a growth rate of Å / sec.

Next, the substrate temperature was raised to 800 ° C., and in a gas source MBE apparatus using as a raw material N ₂ gas excited by metallic Ga and ECR plasma,
A GaN film of about 1000 Å is grown as the compound semiconductor film 4.

After the growth, when a reflection high-energy electron diffraction (RHEED) pattern was observed on the surface of the GaN film, a clear streak-like GaN pattern was observed. This indicates that the crystallinity and surface flatness of GaN are very good.

Further, the surface of the GaN film thus produced was subjected to AFM.
When observed with an (Atomic Force Microscope), the root mean square value (Rrms) of the roughness was 35 Å.

Further, the X-ray rocking curve of the manufactured GaN film was measured on the (0002) plane.
240 arcsec.

FIG. 2 shows the result of examining the PL spectrum of the grown GaN film at room temperature by excitation with a He-Cd laser. Only light emission due to an interband transition having a peak at 364.4 nm is clearly observed, confirming that the GaN film has good crystallinity.

(Comparative Example) Here, a comparative example of the first embodiment will be described.

As in the first embodiment, a (111) -oriented single crystal γ-Al ₂ O ₃ film is grown as a buffer layer 2 on a Si (111) substrate 1 by about 50 Å.

Thereafter, a GaN film was formed at a substrate temperature of 800 ° C. for about 10 minutes without the preliminary growth of Al as the preliminary growth layer 3.
Grow 00 Å.

After the growth, when a reflection high-energy electron diffraction (RHEED) pattern on the surface of the GaN film was observed, spot and ring-shaped GaN patterns were observed. This indicates that the crystallinity and surface flatness of GaN are worse than in the first embodiment.

When the surface of the produced GaN film was observed by AFM, the root-mean-square value (Rrms) of the roughness was 90%.
Angstrom.

Further, the X-ray rocking curve of the GaN film produced was measured on the (0002) plane.
010 arcsec.

FIG. 3 shows the result of examining the PL spectrum of the grown GaN film at room temperature by He-Cd laser excitation. In the case of the first embodiment, not only light emission due to the observed band-to-band transition but also light emission having a wide wavelength band near 470 nm is observed. This indicates that defect levels derived from nitrogen deficiency and the like are widely distributed in a region where the energy level of GaN is deep.

From the results shown in FIGS. 2 and 3, it can be seen that the crystallinity and flatness of the compound semiconductor film formed in the first embodiment are significantly improved as compared with the comparative example. Was confirmed.

(Embodiment 2) Next, a second embodiment will be described.

In this example, the pre-grown layer 3
Instead of the thin film, a Ga thin film is grown at 20 Å at a Ga Knudsen cell temperature of 850 ° C.

On the Si substrate 1 on which the Ga thin film has been formed, as the compound semiconductor film 4,
An aN film is grown.

After the growth, the reflection high-energy electron diffraction (RHEED) pattern on the surface of the GaN film was observed, and a clear streak-like GaN pattern was observed.

When the surface of the produced GaN film was observed by AFM, the root-mean-square value (Rrms) of the roughness was 40%.
Angstrom.

Further, the X-ray rocking curve of the manufactured GaN film was measured on the (0002) plane.
300 arcsec.

(Embodiment 3) Next, a third embodiment will be described.

In this embodiment, first, as in the first embodiment, a buffer layer 2 is formed on a Si (111) substrate.
A 0 Å single crystal γ-Al ₂ O ₃ film is formed. Subsequently, a 20 Å Al thin film is grown as the preliminary growth layer 3.

After that, as the compound semiconductor film 4, metal G
Using a and solid As as raw materials, a GaAs film of 1000 Å is grown at a substrate temperature of 630 ° C. in an MBE apparatus.

After the growth, when a reflection high-energy electron diffraction (RHEED) pattern on the surface of the GaAs film was observed, a clear streak-like GaAs pattern was observed. This indicates that GaAs has very good crystallinity and surface flatness.

Further, the surface of the GaAs film thus produced was subjected to AFM.
As a result, the root mean square value (Rrms) of the roughness was 1
It was 8 angstroms.

Further, the X-ray rocking curve of the GaAs film thus prepared was measured on the (111) plane.
20 arcsec.

(Embodiment 4) Next, a fourth embodiment will be described.

In this embodiment, first, as in the first embodiment, a buffer layer 2 is formed on a Si (111) substrate.
(111) oriented 50 Å single crystal γ-
An Al ₂ O ₃ film is formed.

Subsequently, the substrate was cooled to room temperature, and a 30 Å Al thin film (substrate A) and a 40 Å Al thin film were grown as preliminary growth layers 3 at an Al Knudsen cell temperature of 1050 ° C. (Substrate B).

Thereafter, each substrate is used as a compound semiconductor film 4 in a gas source MBE apparatus using metal Ga and N ₂ gas excited by ECR plasma as raw materials at a substrate temperature of 800 ° C. and a temperature of about 10 ° C.
A 00 angstrom GaN film is grown.

After the growth, the surface of the produced GaN film was changed to A
When observed by FM, the root mean square value of roughness (Rrms)
Was 38 Å for substrate A and 95 Å for substrate B.

When the X-ray rocking curve of the GaN film thus produced was measured on the (0002) plane, it was 1200 arcsec for the substrate A and 2100 arcsec for the substrate B.

From the above results, a good GaN film was obtained on the substrate A, but no effect of improving the crystallinity was recognized on the substrate B.

As a result, it was found that the thickness of the metal thin film to be subjected to the preliminary growth should desirably not exceed 30 angstroms.

(Application Example) Next, an application example will be described.

By using the method for manufacturing a compound semiconductor film of the present invention, a thick single crystal compound semiconductor can be grown on a Si substrate. In this case, using the steps described above,
By simply increasing the film formation time, a compound semiconductor layer having a large thickness can be easily formed.

By dissolving the Si substrate on which the thick compound semiconductor layer has been grown in this manner with a mixed solution of hydrofluoric acid and nitric acid, nitride of GaN or the like, which has conventionally been extremely difficult to manufacture, is formed. It is possible to obtain a single crystal substrate of a compound semiconductor. When a nitride-based compound semiconductor film is grown using this, an extremely high-quality film with a low defect density can be obtained because of homo-growth, and as a result, the reliability and lifetime of devices such as LEDs and LDs can be obtained. Can be dramatically increased.

[0069]

As described above, according to the present invention, when forming a compound semiconductor film on a Si substrate, first, a buffer layer such as γ-Al ₂ O ₃ is formed on the Si substrate, Al, Ga, In as a metal pre-growth layer on the layer
Pre-growth is performed using at least one of the metal elements constituting the compound semiconductor to be grown, and a desired compound semiconductor film is formed on the pre-grown layer. A compound semiconductor such as GaN having high crystallinity can be grown on a Si substrate with good flatness, and the manufacturing cost can be significantly reduced as compared with the case where a sapphire substrate is used. Accordingly, it becomes easy to make an optical resonator structure necessary for making a semiconductor laser by utilizing the cleavage of the Si substrate.

According to the present invention, a compound semiconductor and S
A device that takes advantage of the characteristics of each i
It can be formed monolithically on a substrate, and the entire circuit can be highly integrated and operated at high speed.

[Brief description of the drawings]

FIG. 1 is a process chart showing a method for manufacturing a compound semiconductor film according to the present invention.

FIG. 2 is a characteristic diagram showing a PL spectrum at room temperature of a GaN thin film formed according to the present invention.

FIG. 3 is a characteristic diagram showing a PL spectrum at room temperature of a GaN thin film when Al preliminary growth is not performed.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Si substrate 2 Buffer layer 3 Pre-growth layer 4 Compound semiconductor film

Claims (5)

[Claims] 1. A method for forming a compound semiconductor film on a Si substrate, comprising: forming a buffer layer made of an oxide on the Si substrate; and forming a pre-grown layer made of a metal on the buffer layer. A method for manufacturing a compound semiconductor film, comprising: a step of forming the compound semiconductor film as preliminary growth; and a step of forming a desired compound semiconductor film on the preliminary growth layer made of the metal. 2. A method according to claim 1, wherein γ-Al ₂ O ₃ is formed as the buffer layer, and Al, Ga, I
2. The method according to claim 1, wherein the preliminary growth is performed using at least one of n and a metal element constituting the compound semiconductor to be grown. 3. The method according to claim 1, wherein the compound semiconductor film is AlN, G,
3. The method for producing a compound semiconductor film according to claim 1, wherein aN, InN, and a mixed crystal compound thereof are grown. 4. The method of manufacturing a compound semiconductor film according to claim 1, wherein Al is used as a metal of said preliminary growth layer. 5. The pre-grown layer has a thickness of substantially 30.
5. The method for manufacturing a compound semiconductor film according to claim 1, wherein the thickness is smaller than Å.