JP3504851B2 - Method for manufacturing compound semiconductor film - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for forming a compound semiconductor film on a Si substrate, and a compound semiconductor film for forming a film having good crystallinity and surface flatness. And a method for producing the same. 2. Description of the Related Art At present, sapphire is mainly used as a substrate in a nitride semiconductor represented by GaN, which is currently used as a material for a blue light emitting LED (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 the 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 film of γ-Al ₂ O ₃ is grown on a Si single crystal substrate, and then the Si is grown.
Has been reported (Appl. Phy).
s. Lett. 67 (1995) 2200). Recently, there has been reported a method of growing γ-Al ₂ O ₃ on a Si single crystal substrate and then 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 as a low-temperature buffer layer is previously formed on such γ-Al ₂ O ₃ 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 was measured at a film thickness of FWHM, the FWHM (Full Width of Half Maximum) was 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, and it is not possible to produce a film of a sufficiently practical quality. SUMMARY OF THE INVENTION An object of the present invention is to provide a method for manufacturing a compound semiconductor film capable of forming a compound semiconductor film having high crystallinity and good surface flatness at a low manufacturing cost. SUMMARY OF THE INVENTION The present invention is a method for forming a compound semiconductor film on a Si substrate, the method comprising the steps of: grown _γ-Al 2 _{O 3} in the steps of forming a _γ-Al 2 _{O 3} film, Al, Ga, in, or is one or a compound semiconductor film grown formed among the elements constituting the selected The selected metal element is grown on the γ-Al ₂ O ₃ film on the Si substrate on which the γ-Al ₂ O ₃ film is grown and formed using the selected metal element, and is thinner than 30 Å. Forming a pre-growth layer, raising the temperature of the Si substrate on which the pre-growth layer has been grown to the growth temperature of the compound semiconductor film, and then forming AlN, GaN,
A method of growing a compound semiconductor film by growing InN and a mixed crystal compound thereof to provide a method of manufacturing a compound semiconductor film. 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. As a substrate used in the present invention, FIG.
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 γ-Al ₂ O ₃ layer is not particularly limited.
A range from 0.003 μm to 1 μm is practical. Next, in the step of FIG.
A pre-grown layer 3 made of metal is formed on the buffer layer 2 made of l ₂ O ₃ . 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 method (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. . The thickness of the metal to be pre-grown is 30 Å or less.
It is preferable that 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, after the Si substrate 1 including the pre-growth layer 3 is heated to a desired compound semiconductor growth temperature, 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 crystallinity and flatness are drastically 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 whether an (aluminum) atom or an 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,
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 degraded, 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 as described above, 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. The substrate is S
In a gas source MBE apparatus using an i (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 temp
erasure), N ₂ O pressure = 3 × 10 ⁻² Pa
Thus, a single crystal γ-Al ₂ O ₃ was grown. By growing for 60 minutes, a (111) -oriented single crystal γAl ₂ O ₃ film having a film thickness of about 50 Å 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 Al Knudsen cell temperature =
At 1050 ° C., an Al thin film
Grow 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 metal Ga and ECR plasma,
A GaN film of about 1000 Å is grown as the compound semiconductor film 4. 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. This indicates that the crystallinity and surface flatness of GaN are very good. Further, the surface of the GaN film thus prepared was subjected to AFM.
(Atomic Force Microscope), the root-mean-square value (Rrms) of the roughness was 35 Å. Further, the X-ray rocking curve of the produced 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 angstroms. After that, the GaN film was deposited 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, the reflection high-energy electron diffraction (RHEED) pattern on the surface of the GaN film was observed. As a result, 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 prepared 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 manufactured GaN film was measured on the (0002) plane.
010 arcsec. FIG. 3 shows a 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 remarkably 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, when the reflection high-energy electron diffraction (RHEED) pattern on the surface of the GaN film was observed, a clear streak-like GaN pattern was observed. When the surface of the prepared 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 pre-growth layer 3. Thereafter, as the compound semiconductor film 4, metal Ga and solid As are used as raw materials, and a gas source MB is used.
In the E device, a GaAs film of 1000 Å is grown at a substrate temperature of 630 ° C. 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 (Rrms) of 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 is cooled to room temperature, and a 30 Å Al thin film (substrate A) and a 40 Å Al thin film are 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
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 it is desirable that the thickness of the metal thin film to be subjected to the preliminary growth does not exceed 30 angstroms. (Application Example) Next, an application example will be described. By using the compound semiconductor film manufacturing method 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 as described above 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, reliability and lifetime of devices such as LEDs and LDs can be obtained. Can be dramatically increased. 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 buffer layer
Preliminary growth is performed by 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, so that it is inexpensive and mass-produced. A compound semiconductor such as GaN having high crystallinity can be grown with good flatness on a Si substrate, 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 features of
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. [Description of Signs] 1 Si substrate 2 Buffer layer 3 Pre-growth layer 4 Compound semiconductor film

Continuation of front page (56) References JP-A-9-134878 (JP, A) JP-A-9-36428 (JP, A) Wang, Wurtzite GaN epitaxy growth on a Si (001) substrate using γ-Al2O3 as an intermediary layer, Appl. Phys. Lett. U.S.A., January 5, 1998, 72 (1), p. 109-111 (58) Field surveyed (Int.Cl. ⁷ , DB name) H01L 21/203 H01L 21/205 H01L 33/00

Claims (1)

(57) A method for forming a compound semiconductor film on a Si substrate, the method comprising: setting the Si substrate at a predetermined film growth temperature;
Γ-Al ₂ O ₃ is grown on a Si substrate and γ-Al ₂ O
Step of forming _three films, Al, Ga, In, or a compound semiconductor film to be grown and formed
Selected from any one of the elements constituting
The γ-Al ₂ O ₃ film was grown and formed using an element .
On the Si substrate, on the γ-Al ₂ O ₃ film,
Grown metal element, thinner than 30 Å
Forming a pre-growth layer, and controlling the temperature of the Si substrate on which the pre-growth layer has been formed.
After raising the temperature to the growth temperature of the compound semiconductor film, Al
N, GaN, InN, and their mixed crystal compounds
And forming a compound semiconductor film. 2. A method for manufacturing a compound semiconductor film, comprising: