JPS63224221A - Vapor phase epitaxy method - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a vapor phase epitaxial growth method for growing a thin film on the surface of a semiconductor substrate.

[Conventional technology] Conventionally, MO is one of the epitaxial growth methods.
A CVD method is known. For example, when growing GaAs on a semiconductor substrate, TMG or TEG is used as a raw material for Ga, and As H3 is usually used as a raw material for As.

When such raw material gas is introduced into a reaction chamber where a semiconductor substrate is set and GaAs is grown on the surface of the semiconductor substrate, the lower the temperature of the semiconductor substrate, the higher the density of Ga.
It is known that an As thin film is formed. However, when the temperature of the semiconductor substrate is, for example, 600° C. or lower, the thermal decomposition rate of the As H3 described above decreases, resulting in deterioration of crystallinity and decrease in mobility. In addition, P, which is a V-hydrogenide other than arsenic,
Similar problems exist with H3 and NH3.

In order to solve these problems, it is necessary to decompose As H3 by a method other than a thermal process, and one of the decomposition methods is plasma M using glow discharge.
OCVD method is known. It has been reported that the mobility of GaAs grown by this plasma MOCVD method does not decrease even if the temperature of the semiconductor substrate is 300°C.

However, when such a plasma MOCVD method is used, the growth layer is damaged by charged particles generated by glow discharge, and furthermore, the deposits on the reaction tube constituting the reaction chamber are damaged by the sputtering action. There are problems such as contamination with other materials, making it impossible to obtain a quality that can be used in the manufacturing process of ultra-high-speed devices.

[Problems to be Solved by the Invention] This invention has been made in view of the above points, and it is possible to effectively set the growth temperature to a low temperature, thereby suppressing the incorporation of impurities into the epitaxially grown film. Furthermore, it is an object of the present invention to provide a vapor phase epitaxial growth method that prevents redistribution of impurities and compositions due to thermal diffusion when producing a thin film multilayer structure.

[Means for Solving the Problems] That is, in the vapor phase epitaxial growth method according to the present invention, a raw material gas mixed with a sensitizer such as mercury is introduced into a reaction chamber in which a semiconductor substrate is set. At the same time, the sensitizer is irradiated with a light source such as a mercury lamp, which excites the sensitizer.

[Operation] By employing the above-mentioned means, the raw material gas mixed with the sensitizer is irradiated with excitation light in the reaction chamber, so that the sensitizer is excited. Sensitized photodecomposition occurs and an epitaxial film is formed on the semiconductor substrate. For example, when GaAs is grown on a semiconductor substrate by MOCVD, the minimum growth temperature is determined by the thermal decomposition temperature of As H3. Therefore, in order to lower the growth temperature of GaAs,
There is a need to decompose As H3 by means other than thermal processes.

In this invention, a photochemical reaction is used as a means to decompose As H3 at low temperature, but the peak value of light absorption of As H3 as a raw material is 183.
253.7 nm, which therefore accounts for most of the light from low-pressure mercury lamps, which are easily used as light sources.
light is not absorbed by As H3. Therefore, As H3 cannot be efficiently decomposed as it is.

Therefore, in this invention, a small amount of mercury as a sensitizer is added to As H3 as a raw material gas, and a mercury sensitizing chemical reaction is carried out using a low-pressure mercury lamp as an excitation light source. I'm doing it. And As H3
is decomposed effectively at low temperatures.

[Embodiments of the invention] Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

FIG. 1 shows the configuration of an apparatus for carrying out the vapor phase epitaxial growth method according to the present invention, in which a semiconductor substrate is supported by a substrate susceptor 12 inside a reaction tube 11 constituting a reaction chamber in which epitaxial growth is performed. 13 is set.

This reaction tube 11 is constructed in the shape of a sealed container, for example, by an organic metal material such as stainless steel or quartz, or a material having stable properties against As H3.

First and second gas introduction ports 14a and 14b are provided at one end of the reaction tube 11, and an outlet 15 is provided at the other end. A gas of A s H3 is introduced into the first gas inlet L4a, and a mercury reservoir 1G is set in the middle of the gas pipe that guides this gas. This mercury reservoir 1
B consists of a sealed container that stores mercury inside and is made of a material such as stainless steel or quartz that does not have reactivity with hydrogen or mercury. A pair of gas inlets and outlets lea and 16b are formed in this container, and the rAs H3+H2J gas is introduced into one of them, and the output gas from the other is introduced into the reaction tube ll from the first inlet 14a. It is something. That is, As H3 gas containing a trace amount of mercury is introduced into the reaction tube 11. TMG or TEG is introduced into the second input port 14b of the reaction tube 11 together with H2.

The mercury reservoir 16 is set in a bathtub of a constant temperature bath 17, and is set in such a state that the temperature of mercury in the mercury reservoir 16 easily becomes a predetermined mercury vapor.

An excitation light entrance window 18 is formed on the side wall of the reaction tube 11, corresponding to the position of the substrate susceptor 12.

This window 18 is made of a material such as fused silica, synthetic quartz, MgF2, etc. that can transmit ultraviolet light having a wavelength of 253.7 nm and a wavelength of 184.9 nm. The excitation light from the excitation light source 19 is irradiated onto the semiconductor substrate 13 inside the reaction tube 11 through the excitation light entrance window 18 . This excitation light source 19 has a wavelength of 253.7 nm.
Alternatively, it may be constituted by a low-pressure mercury lamp that generates at least one ultraviolet light of 184.9 nm.

That is, as H3 passes through the inside of the mercury reservoir 16 heated by the thermostatic chamber 17, the thermostatic chamber 1
Mercury vapor of about the saturated vapor pressure of mercury at the set temperature of 7 is mixed into the As H3 gas. The As H3 containing mercury passes through the gas pipe and enters the reaction tube 11 from the first inlet L4a, and is mixed with the machine metal from the second inlet 14b.

Further, the ultraviolet excitation light generated by the excitation light source 19 passes through the light entrance window 18 and enters the reaction tube 11, is absorbed by the mercury contained in the gas, and excites it.

When mercury excited to 1 collides with As H3, the energy obtained by absorption of ultraviolet light by mercury is transferred to As H3.

The energy of photons is 469.9 nm for ultraviolet light with a wavelength of 253.7 nm. 4KJ/mol, and light with a wavelength of 184.9nm is 643.9KJ/a+ol, both of which are the bond dissociation energy of As H3, 3 10, 6 KJ/m
ol (H2As-H bond), and therefore, As H3 decomposes due to energy transfer. Furthermore, mercury-sensitized decomposition of organic metals is also possible by a similar mechanism.

Group II metals (
Ga, A), etc.) and As react on the surface of the semiconductor substrate 13 heated by the substrate susceptor 12, and
This is a group compound semiconductor.

That is, in the epitaxial growth method as described above, thermal energy is not used to decompose the source gas. Therefore, the growth temperature is not limited by the thermal decomposition temperature of the raw material gas, and ideal low-temperature growth is possible.

FIG. 2 shows another embodiment, in which a rare gas for photosensitization is prepared from As H3 gas, mixed on a gas pipe, and introduced into the reaction tube 11. .

Incidentally, as the V group raw material used in this vapor phase evictional growth method, V hydrogen hydrides other than arsenic such as PH3 and NH3 may be used. Also, as a V group raw material, A
S (CH3) 3, As (C2H5) 3, P
(CH3) 3, P (C2Ha) s, Sb
Group V alkyl metals such as (CH3)3, Sb(C2Hs)s, etc. may also be used. Furthermore, As C no 3,
Group V halides such as sb cno3 and S bF3 may be used.

■As a source of elements, (CH3) 3Ga ・AS
(CH3)3, (CH3)3 In-PH3, etc. can be used for the -V group agua duct.

Although we have explained that a low-pressure mercury lamp is used as the excitation light [19], it is also possible to use a rare gas resonance lamp such as He, Ne 1Ar 1Kr %Xe, and mix these gases as a sensitizer into the source gas. It's okay. in this case,
Since the sensitizer is a gas at room temperature, piping for this rare gas can be set and used as in the embodiment shown in FIG. Also, it is better to use such a rare gas as the rear gas. in this case,
It is also necessary to use a material for the excitation light entrance window that transmits the ultraviolet light generated from such a rare gas resonance lamp.

[Effects of the Invention] As described above, in the vapor phase epitaxial growth method according to the present invention, the source gas can be decomposed at a low temperature, and epitaxial growth can be performed at a low substrate temperature. Therefore, a highly purified epitaxially grown film can be effectively obtained, and a grown film that can be effectively applied to, for example, ultrahigh-speed devices can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an apparatus for explaining a vapor phase epitaxial growth method according to one embodiment of the present invention, and FIG. 2 is a block diagram showing another embodiment of the present invention. 11... Reaction tube (reaction chamber), 12... Substrate susceptor, 13... Semiconductor substrate, 1B... Mercury reservoir, 17.
... Constant temperature chamber, 18 ... Excitation light entrance window, 19 ... Excitation light source.

Claims (3)

[Claims] (1) Introducing a raw material gas mixed with a sensitizer into a reaction chamber containing a semiconductor substrate on which an epitaxial film is to be formed, and irradiating the substrate in the reaction chamber with excitation light that excites the sensitizer. A vapor phase epitaxial growth method characterized in that an epitaxially grown film is formed by: (2) The vapor phase epitaxial growth method according to claim 1, wherein the epitaxially grown film is a III-V group compound. (3) Mercury is used as the sensitizer, and the excitation light source generates excitation light having a wavelength of at least one of 253.7 nm and 184.9 nm. vapor phase epitaxial growth method.