JPH0388324A - Method for forming compound semiconductor thin film - Google Patents

Abstract

PURPOSE:To obtain an optically pumped compound semiconductor thin film wherein a selecting ratio can be provided at high temperature and incorporation of impurities is less by using a compound incorporating cyclopentadienyl group or a substituted cyclopentadienyl group as an organic metal compound containing In. CONSTITUTION:As a compound containing indium, at least one kind of compound expressed by the formulas I-IV is used. In the formulas, R1 and R2 are same or different and express an alkyl group, a substituted alkyl group or halogen, and Cp expresses a cyclopentadienyl group or a substituted cyclopentadienyl group. At this time, the cyclopentadienyl group is decomposed in preference when the organic metal compound is decomposed. The formed cyclopentadiene is not incorporated into a thin film but exhausted. Thus, the amount of carbon impurities in the thin film can be reduced.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for forming a ■-■ group compound semiconductor thin film,
In particular, the present invention relates to the technical field of forming a partially thick or only partially grown semiconductor thin film by irradiating light onto a substrate to promote a thin film growth reaction when growing a thin film.

[Conventional technology]

■-V group compound semiconductor thin films, particularly those using indium as the group ■ element, have extremely wide application fields such as light-emitting devices, light-receiving devices, and high-speed transistors in the so-called long wavelength band around 1.5 μm. Along with this, the manufacturing process is also becoming more and more complicated. For example, when manufacturing a semiconductor laser, etc., first a thin film including an active layer is laminated on a semiconductor substrate, and then the thin film is taken out of the thin film forming apparatus into the air and processed into the required shape by means such as etching. However, the thin film has to be formed again, which poses the problem of requiring many complicated steps. One of the solutions is to selectively deposit GaAs on a portion of the semiconductor substrate using a metal organic pyrolysis (NOVPB) method, a metal organic molecular beam epitaxy (MOMBB) method, etc., which also uses exposure to ultraviolet rays. Techniques for forming semiconductor thin films are being studied (for example, Japanese Patent Application No. 3120/1983)
No. 94). In this method for forming a semiconductor thin film, in order to selectively grow the thin film preferentially in the necessary areas, the selection ratio, that is, the ratio of the thin film growth rate between the areas irradiated with light and the areas not irradiated with light, is increased or the thin film is not irradiated with light. It is necessary that no growth be allowed to occur in areas that are not irradiated.

Trimethylindium (TM
I) and triethylindium (TEI) are known.

[Problem to be solved by the invention]

However, when these raw materials were used, there were problems such as a low selectivity and a large amount of residual impurities presumed to be carbon. In addition, the temperature range where the selectivity can be obtained is 4.
The temperature is around 00°C, which is usually 100°C or more lower than the growth temperature of InP semiconductor thin films applicable to conventional devices.

For this reason, the photoluminescence intensity was 1710 or less than that of a thin film produced at a high temperature, and it was difficult to obtain a high-quality thin film that could be applied to devices.

An object of the present invention is to provide a method for forming a photoexcitable compound semiconductor thin film that can maintain a selectivity at higher temperatures and incorporates less impurities.

[Means to solve the problem]

To summarize the present invention, the present invention relates to a method for forming a compound semiconductor thin film, in which a compound containing indium and an element of group Vb of the periodic table of elements or a compound containing these are introduced into a reaction vessel and decomposed. In the method of forming a ■-V group compound semiconductor thin film on a substrate placed in the reaction vessel, the indium-containing compound has the following general formulas [A] to [D]: CA]R+R*InCpCB) Lln(CpL (C) In(Cp)s [D] InCp [wherein, R+ and R7 are the same or different, an alkyl group,
It is characterized by using at least one compound represented by a substituted alkyl group or halogen; Cp represents a sialkyl group, a substituted alkyl group, a substituted sialkyl group, or a substituted alkyl group.

Table 1 shows the specific names and physical property values of the compounds that can be used in the present invention, but the present invention is not limited to these compounds.

Table 1 Specific names of compounds When compound semiconductor thin films are created using these organometallic raw materials by organometallic vapor phase epitaxial growth (MOVPE method) or organometallic molecular beam epitaxial method (MOMBE method), compared to when conventional raw materials are used The present invention was completed based on the discovery that the quality of the thin film was improved by using the method, and the selectivity of growth by light irradiation was also significantly improved.

At present, it is not necessarily clear why this effect is obtained. However, due to the effects of commonly contained sialkyl groups, substituted alkyl groups, substituted sialkyl groups, substituted alkyl groups, etc., adsorption properties and thermal decomposition properties on the substrate differ, and the light absorption properties are generally those of TMI and TEI.
It is presumed that this is due to the fact that the decomposition properties due to light irradiation are improved because the wavelength is shifted to the longer wavelength side compared to .

Many of the raw material compounds used in the present invention are solid at room temperature, and many have low vapor pressures. Therefore, during actual use, measures such as heating the raw material storage tank and piping system are required. Raw materials that are liquid at room temperature can be introduced into the reaction vessel by bubbling as in the conventional method.

On the other hand, examples of group Vb elements of the periodic table of elements used in the present invention include nitrogen, phosphorus, arsenic, and antimony, and examples of compounds containing these include ammonia, arsine, phosphine, stibine, antimony trichloride, etc. .

In the method for forming a compound semiconductor thin film of the present invention, it is preferable to irradiate the substrate with ultraviolet light or visible light. Moreover, it is preferable that the ultraviolet light or visible light beam is a laser.

〔Example〕

Hereinafter, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited to these Examples.

Embodiment 1 FIG. 1 is a system diagram showing the configuration of an apparatus when the present invention is applied to the production of a single crystal thin film of an InP compound semiconductor by the laser-excited MOMBE method. In FIG. 1, reference numeral 1 is a substrate, 2 is a substrate heater 3 is an In compound cylinder, 4 and 7 are mass flow controllers, 5 is a gas cell, 6 is a phosphine cylinder, 8 is a cracking cell, 9 is an argon ion laser, 10 is a mirror, 11 is a laser beam, 12 is a view boat, 13 is a reaction vessel, 14 is an exhaust system, and 15 is a temperature controller.

(100) InP substrate 1 is placed on substrate heater 2 and kept at a constant temperature. The diethylsialkyl group and substituted alkylindium, which are In-based organometallic raw materials, are 1
It is introduced into the reaction vessel 13 from the cylinder 3 kept at 00° C. through the mass flow controller 4 and the gas cell 5 (flux: 5×10 4 ). Phosphine (10% diluted with hydrogen), which is a raw material for phosphorus, is introduced into the reaction vessel from cylinder 6 in the same way (flux: 10XIO-")
Since the pressure inside the reaction vessel is reduced to 10-'Torr,
Both the organometallic compound and phosphorus are irradiated onto the substrate as molecular beams. Argon ion laser (wavelength: 514.5nm)
) 9 is reflected by a mirror 10 and irradiated onto the substrate from a view port 12.

When grown for 1 hour at a substrate temperature of 450° C. and a laser power of 100 W/cd, an InP thin film with a thickness of 1.1 μm in the irradiated area and 0.6 μm in the non-irradiated area was obtained. The amount of carbon impurities in the thin film was determined by secondary ion mass spectrometry (SIMS) analysis and was found to be less than l Q l'l/cm3. Furthermore, the photoluminescence intensity at 77K was at the same level as that of a practically usable thin film.

Comparative Example 1 An InP thin film was formed in the same manner as in Example 1 except that TEI was used as the In-based organometallic compound.

The film thickness was 0.8 μm in the irradiated area and 0.6 μm in the non-irradiated area. The amount of carbon impurities was 3 x 10''/cm3, and photoluminescence measurements at 77K did not yield a measurable intensity spectrum.

Example 2 I was deposited on a (100) InP substrate using a M0VPE device.
An nP thin film was grown. As the phosphorus source, phosphine diluted with 10% hydrogen was used at a flow rate of 100 sccm, and as the indium source, 5 seconds of hydrogen was bubbled through diethylsialkyl group-substituted alkylindium at 120°C. The substrate temperature was 500 t, and argon ion laser (wavelength: 514.5 nm) with an intensity of 150 W/cj was irradiated. 0.8 μm at the laser irradiated area after 1 hour of growth
1. An InP film thickness of 0.4 μm was obtained in the non-irradiated area. Also? 7
The photoluminescence intensity at K was at the same level as a practically usable thin film.

Comparative Example 2 A thin InP spread was formed in the same manner as in Example 2 except that TMI (20 was kept warm) was used as the indium source. After 1 hour of growth, an InP thin film was obtained with a thickness of 0.6 μm in the laser irradiated area and 0.4 μm in the non-irradiated area. Moreover, no measurable intensity spectrum was obtained in photoluminescence measurement at 77K.

Examples 3 to 9 InP film thickness was formed in the same manner as in Example 1 except that the compounds shown in Table 2 below were used in place of the diethylsialkyl group and the substituted alkylindium. However, the cylinder heating temperature was the value shown in the table. Similar to Example 1, this result revealed that a larger contrast was obtained by laser irradiation compared to the conventional material. Further, the carbon impurity concentration was also 10'/cm3 or less in all cases.

〔Effect of the invention〕

As explained above, according to the method for forming a compound semiconductor thin film according to the present invention, as the organometallic compound containing In, a compound containing at least one sialkyl group, a substituted alkyl group, a substituted sialkyl group, or a substituted alkyl group is used. use. Therefore, when organometallic compounds are decomposed, sialkyl groups and substituted alkyl groups are preferentially decomposed, and the generated cyclopentadiene is exhausted without being incorporated into the thin film, reducing the amount of carbon impurities in the thin film. A significant reduction is possible. Moreover, these compounds have the advantage of improving photoselectivity during growth, since the light absorption wavelength shifts to the longer wavelength side compared to conventional compounds.

[Brief explanation of drawings]

FIG. 1 is a system diagram showing the configuration of an InP thin film forming apparatus used in the first embodiment of the present invention. 1. Substrate, 2... Substrate heater 3. In compound cylinder, 4 and 7. - Mass flow controller 5
・・Gas cell, 6・・Phosphine cylinder, 8・・Cracking cell, 9・ ◆Argon ion laser, 10
・・Mirror 11・Laser beam, 12・・View boat, 13・・Reaction vessel, 14・Exhaust system, 15・
・Temperature controller

Claims (1)

[Claims] 1. Introducing a compound containing indium, an element of group Vb of the periodic table of elements, or a compound containing these into a reaction vessel, decomposing them, and dissolving them onto a substrate placed in the reaction vessel.
- In the method for forming a group V compound semiconductor thin film, the indium-containing compound has the following general formulas [A] to [D
]: [A]R_1R_2InCp [B]R_1In(Cp)_2 [C]In(Cp)_3 [D]InCp [In the formula, R_1 and R_2 are the same or different, an alkyl group, a substituted alkyl group or a halogen, and Cp is a cyclo A method for forming a compound semiconductor thin film, the method comprising using at least one compound represented by the following formula: pentadienyl group or substituted cyclopentadienyl group.