JP2739778B2 - Method for selective growth of group 3-5 compound semiconductor - 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 selectively growing a high-quality group III-V compound semiconductor at a low temperature.

[0002]

2. Description of the Related Art Selective epitaxial growth of a Group 3-5 compound semiconductor is performed by an optical device typified by a light emitting diode (LED) or a laser diode (LD), a field effect transistor (FET) or a heterogeneous device. It is extremely important for improving the performance of a high-speed device represented by a bipolar transistor (HBT). For example, in a GaAs FET, before the electrodes are formed, N
By growing a ⁺ -type contact layer, the parasitic resistance can be reduced. In the case of a BH laser in which the active region is embedded with a high-resistance AlGaAs layer, the drive current can be reduced. Further, the selective epitaxial growth technique is indispensable for element isolation and the like when integrating optical and high-speed devices on the same substrate to achieve high functionality.

The halogen transport method and the metal organic chemical vapor deposition method (M
Until the practical use of the OCVD method, the liquid phase growth method (LPE method) has been used exclusively as the selective epitaxial growth method. Recently, attention has been paid to a vapor phase growth method (VPE method) using a gas such as a metalorganic molecular beam epitaxial growth method (MO-MBE method) for growing in a high vacuum.

[0004] In addition to the selective growth, it is possible to grow a thin film structure necessary for improving device performance, and it is excellent in mass productivity.

[0005] Among the vapor phase growth methods using a group III organometallic compound as a raw material, a reduced pressure MOCVD method is particularly popular. Commercialization of the MO-MBE method for growing under high vacuum has begun.

In particular, the selectivity of the halogen transport method, which is a vapor phase growth method in a state closer to thermal equilibrium, is excellent. However, since it is difficult to grow a group III-V compound semiconductor containing Al as a constituent element, it is not often used. In the halogen transport method using a hot wall reaction tube, a reaction between Al and a quartz tube wall becomes a problem, and special measures such as coating the tube wall with carbon are required.

In the selective growth using a group III organometallic compound as a raw material, the group III organic metal is compared with the substrate crystal surface by SiO 2
₂ Utilizes the property of being difficult to disassemble on a mask. Therefore, triethyl gallium (TEG)
a) A raw material having a methyl group such as trimethylgallium (TMGa), which is more difficult to decompose, has superior selectivity and has a lower growth pressure than a material having an ethyl group such as a).
The selectivity improves as the surface diffusion length of the group 3 raw material on the O ₂ mask increases. Therefore, M grown under high vacuum
The O-MBE method provides better selectivity at lower temperatures.

An organometallic compound which is not a pure organic metal but has a bond with a group III atom and a halogen element, especially chlorine;
For example, diethyl gallium chloride (DEGaCl)
Is the best selectivity reported to date. This is considered to be because GaCl generated by the decomposition of DEGaCl is extremely stable and does not decompose on SiO ₂ . MOCV under reduced pressure at growth temperature 600 ℃
About APL (Applied
Physics Letters), vol. 54, n
o. 10, March, 1989, pp. L910-9
12

According to the experimental results of the present inventors, the growth temperature was 400 ° C.
It has been confirmed that there is selectivity in the entire temperature range up to and including the temperature at which DEGaCl can decompose and contribute to growth. Because it does not depend on the growth pressure, good selectivity is obtained, for example, even under atmospheric pressure.

[0010]

The problem in the above-described conventional selective growth technique using an organometallic compound having a bond of a group III element and a halogen element, for example, DEGaCl bonded to chlorine as a group III raw material will be considered.

When DEGaCl is used, it has selectivity in the entire temperature range of 400 ° C. or higher, at which DEGaCl decomposes and grows, and does not depend on the growth pressure. However, at a low temperature, there is a problem that a large amount of carbon is incorporated as an impurity. This is because decomposition of the raw material, that is, elimination of an ethyl group, is unlikely to occur at a low temperature, and carbon contained in the ethyl group is incorporated into a crystal. It is thought to be rare. Therefore, in order to obtain a high-purity film, it was necessary to grow at a relatively high temperature of 500 ° C. or more.

By the way, as long as the compound has a thermally stable Ga--Cl bond, there is no need to use an organic compound which causes the incorporation of carbon. For example, chlorogalane (GaH ₂ Cl) or dichlorogalane ( GaHC
l ₂ ), it is considered that the use of an inorganic compound such as GaCl ₃ can completely prevent the incorporation of carbon.

[0013] However GaH ₂ Cl and GaHCl ₂ is very unstable at room temperature, there is a big problem vapor pressure less like. On the other hand, since GaCl ₃ is stable and has a predetermined vapor pressure, it is considered that it can be transferred as a gas through the piping and switched by a valve to be supplied to the reaction vessel.

However, since GaCl ₃ has strong deliquescent and corrosive properties, it is extremely difficult to handle and cannot be used as a raw material for selective growth.

An object of the present invention is to solve the problems of the prior art and to provide a method for selectively growing a high-quality group III-V compound semiconductor at a low temperature.

[0016]

According to the method of the present invention for selectively growing a Group 3-5 compound semiconductor, a volatile complex compound comprising a Group 3 compound and a Group 5 compound and a Group 5 element or a Group 5 volatile compound are formed on a substrate. Supply on top. Here, the group III compound constituting the volatile complex compound is a hydrogen compound in which a group III element and a halogen element are directly bonded. Further, a nitrogen compound can be used as the group 5 compound constituting the volatile complex compound.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Generally, Group III atoms constituting a Group III compound have an empty p-electron orbit, and therefore these compounds work as an electron acceptor (Lewis acid). On the other hand, since the Group 5 atoms constituting the Group 5 compounds have a lone pair of electrons, these compounds function as electron donors (Lewis bases). As a result, the group 3 compound and the group 5 compound cause a so-called acid / base reaction. That is, the lone electron pair of the group V atom coordinates to the empty p-electron orbit of the group III atom to form a more stable complex.

A hydrogen compound in which a group 3 element and a halogen element are directly bonded, for example, GaH ₂ Cl having a Ga—Cl bond
And GaHCl ₂ have a problem that they are extremely unstable at room temperature. However, also in this case, if an appropriate group V compound is selected and reacted with these hydrogen compounds, a complex which is stable at room temperature and has an appropriate vapor pressure can be formed.
Such a complex is easily decomposed into a Group 3 hydrogen compound and a Group 5 compound at the growth temperature.

Here, if the Group 5 compound itself is stable and does not decompose, it can be considered that there is substantially no supply of the Group 5 element. Also, even if a group V organic compound is used, it does not become a carbon impurity source unless it is decomposed. 3
A group hydrogen compound, for example, GaH ₂ Cl is easily decomposed at the growth temperature, so that the above process ultimately results in Ga
Only -Cl can be supplied to the substrate surface.

As the Group V compound, a compound such as arsenic, phosphorus or nitrogen forms a stable complex with a Group 3 hydrogen compound. However, among them, nitrogen compounds having the smallest atomic number, for example, NH _3, and organic compounds, particularly, trimethylamine having a methyl group (TMN: N (CH ₃ ) ₃ ) and dimethylamine (DMNH: NH (CH ₃ ) ₂ ) ) Are the most thermally stable, and the resulting complex has a high vapor pressure.

Therefore, a volatile complex compound produced by a reaction between a Group III hydrogen compound having a Group III element-halogen element bond and a Group V nitrogen compound, for example, GaH ₂ Cl.TMN, is used as a Group 3 raw material to obtain a high-performance compound. A method of selectively growing a high quality Group 3-5 compound semiconductor at a lower temperature can be realized.

[0022]

An embodiment of the present invention will be described in detail with reference to the drawings.

GaAs (10) on which a SiO ₂ mask is formed
0) In order to grow GaAs on a substrate, a horizontal reduced pressure MOCVD apparatus shown in FIG. 1 was used.

A substrate crystal 3 was placed on a carbon susceptor 2 supported by a susceptor holder 4 in a reaction vessel 1. The susceptor 2 is heated by the high-frequency coil 8 on the outer periphery of the reaction vessel 1.

An exhaust device 6 and an exhaust pipe 7 are connected through a filter 5.

AsH ₃ gas cylinder 9, DEGaCl bubbler 10, GaH ₂ Cl.TMN bubbler 11 and H ₂ gas 12 serving as a carrier are connected as a gas introduction system, and a gas flow rate is controlled by a flow rate control device 13 and a valve 14.

GaAs substrate 3 for checking the selectivity
A SiO ₂ mask is formed on a part of the surface of the substrate.

GaAs was grown at a reaction tube pressure of 100 Torr and a temperature of 200 ° C. to 700 ° C. of the GaAs substrate 3 for 30 minutes with H _{2 serving} as a carrier gas being 9 l / min. A
The partial pressure of sH _{3 in} the reaction tube is 1 Torr, GaH ₂ Cl.T
The partial pressure of MN was 2 × 10 ⁻² Torr.

For comparison, an experiment using conventional DEGaCl instead of GaH ₂ Cl.TMN was also conducted. After the growth, the selectivity was evaluated by observation with an optical microscope. After removing the SiO ₂ mask, the thickness of the grown GaAs layer was measured with a step gauge.

FIG. 2 shows the temperature dependence of the growth rate of GaAs. In this temperature range, it is almost constant, and no GaAs is deposited on the SiO ₂ mask. It can be said that selective growth is possible.

On the other hand, when DEGaCl, which is a conventional raw material, was used, the growth rate was greatly reduced at 400 ° C. or lower as shown in FIG. It is considered that the decomposition rate of DEGaCl decreases at low temperatures.

GaH _{2 in} a temperature range of 200 ° C. to 700 ° C.
FIG. 3 shows the hole measurement data of the impurity density of the film grown using Cl.TMN and DEGaCl. The films grown using GaH ₂ Cl.TMN of this embodiment
0 showed ^{14 ~10 15} / cm ³ of the low concentration of N-type conductivity. On the other hand, a film grown using conventional DEGaCl exhibits P-type conduction at 500 ° C. or lower, and the impurity density increases at low temperatures. This P-type high-concentration impurity was confirmed to be carbon by SIMS measurement.

In this embodiment, by using GaH ₂ Cl.TMN as a Group 3 raw material, GaAs can be formed at a lower temperature.
s selective growth was realized. No uptake of carbon impurities was observed.

The group III Ga raw material is GaH ₂ Cl.
DMNH or the like can be used, and the present invention can be applied to the selective growth of GaP or GaSb in which the type of the group V element is changed, or the selective growth of a mixed crystal such as GaAsP. A
Similar effects can be obtained by selective growth of AlAs using lH ₂ I.TMN and AsH ₃ or selective growth of InP using InH ₂ Cl.TMN and PH ₃ . In addition, 3-
The present invention can be applied to selective growth of a group V compound semiconductor.

In this embodiment, a reduced pressure MO is used as a vapor phase growth apparatus.
Although a CVD apparatus was used, a similar result can be obtained with an atmospheric pressure MOCVD apparatus or a MOMBE apparatus that performs growth in a vacuum.

[0036]

According to the present invention, selectivity and a sufficient growth rate can be obtained at a low temperature, and high quality 3-
A low-temperature selective growth method for a group V compound semiconductor was realized.

[Brief description of the drawings]

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

FIG. 2 is a graph showing a relationship between a growth temperature and a growth rate using GaH ₂ Cl.TMN and DEGaCl.

FIG. 3 is a graph showing a relationship between a semiconductor film growth temperature and an impurity concentration.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Reaction container 2 Carbon susceptor 3 Substrate crystal 4 Susceptor holder 5 Filter 6 Exhaust device 7 Exhaust pipe 8 High frequency induction coil 9 AsH ₃ cylinder 10 DEGaCl bubbler 11 GaH ₂ Cl.TMN bubbler 12 Carrier H ₂ gas 13 Flow control device 14 Valve

Claims (2)

(57) [Claims] 1. A method for growing a Group 3-5 compound semiconductor, comprising supplying a volatile complex compound comprising a Group 3 compound and a Group 5 compound and a Group 5 element or a Group 5 volatile compound onto a substrate. Wherein the group III compound is a hydrogen compound in which a group III element and a halogen element are directly bonded. 2. The method for selectively growing a Group 3-5 compound semiconductor according to claim 1, wherein the Group 5 compound constituting the volatile complex compound is a nitrogen compound.