JPH04279023A - Method of selectively growing 3-5 compound semiconductor - Google Patents

Abstract

PURPOSE:To realize a low-temperature method for selectively growing a high- quality 3-5 compound semiconductor which does not take carbon impurities in its body by obtaining a selecting property and sufficiently high growing speed at a low temperature. CONSTITUTION:In this method for selectively growing 3-5 compound semiconductors which supplies a volatile complex compound composed of a gourp 3 compound and group 5 compound and a group 5 element or group 5 volatile compound onto a substrate, a hydrogen compound in which a group 3 element and halogen element are directly linked with each other is used for the group 3 compound constituting the valatile complex compound. In addition, a nitrogen compound can be used as the group 5 compound constituting the volatile complex compound.

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 Group 3-5 compound semiconductors of excellent quality at low temperatures.

0002

[Prior Art] Selective epitaxial growth of Group 3-5 compound semiconductors is used for optical devices such as light emitting diodes (LEDs) and laser diodes (LDs), as well as for field effect transistors (FETs) and heterogeneous devices. This is extremely important for improving the performance of high-speed devices such as bipolar transistors (HBTs). For example, in a GaAsFET, N is selectively applied only to the source and drain regions before electrode formation.
A + type contact layer can be grown to reduce parasitic resistance. Further, in a BH laser whose active region is buried with a high-resistance AlGaAs layer, the driving current can be reduced. Furthermore, selective epitaxial growth technology is indispensable for element isolation when integrating optical and high-speed devices on the same substrate and achieving higher functionality.

[0003] Halogen transport method and organometallic vapor phase epitaxy (M
Until the practical use of the OCVD method, the liquid phase epitaxy method (LPE method) was exclusively used as a selective epitaxial growth method. Recently, vapor phase epitaxy (VPE) using gas, such as metal organic molecular beam epitaxial growth (MO-MBE), which grows in a higher vacuum, has been attracting attention.

In addition to selective growth, it is possible to grow thin film structures necessary for improving device performance, and it has excellent mass productivity.

[0005] Among the vapor phase growth methods using group III organometallic compounds as raw materials, the low pressure MOCVD method is particularly popular. Practical use of the MO-MBE method, which performs growth under high vacuum, has begun.

[0006] Particularly, the selectivity of the halogen transport method, which is a vapor phase growth method in a state closer to thermal equilibrium, is excellent. However, because it is difficult to grow Group 3-5 compound semiconductors containing Al as a constituent element, they are not used much. In the halogen transport method using a hot wall reaction tube, the reaction between Al and the quartz tube wall becomes a problem, and special measures such as coating the tube wall with carbon are required.

In selective growth using a group 3 organometallic compound as a raw material, the group 3 organometal has a SiO
2. Utilizes the property that it is difficult to decompose on the mask. Therefore, triethylgallium (TE
Using a raw material with a methyl group such as trimethyl gallium (TMGa), which is more difficult to decompose, has better selectivity than a material with an ethyl group such as Ga), and has a lower growth pressure.
The longer the surface diffusion length of the Group 3 raw material on the iO2 mask, the better the selectivity. Therefore, the MO-MBE method, which performs growth under high vacuum, provides better selectivity at lower temperatures.

[0008] Organometallic compounds that are not pure organometallics but have bonds with group III atoms and halogen elements, especially chlorine;
For example, diethyl gallium chloride (DEGaCl)
The method using this method provides the best selectivity among the methods reported to date. This is thought to be because GaCl generated by decomposition of DEGaCl is extremely stable and does not decompose on SiO2. Depressurized MOCV at a growth temperature of 600℃ or higher
When applied to method D, APL (Applied
Physics Letters), vol. 54
, no. 10, March, 1989, pp. L910
~912 reported.

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

0010

Problems to be solved by the above conventional selective growth technique using an organometallic compound having a bond between a Group 3 element and a halogen element, such as DEGaCl bonded to chlorine, as a Group 3 raw material will be considered.

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

[0012] By the way, as long as the compound has a thermally stable Ga-Cl bond, there is no need to use an organic compound that causes carbon uptake.
It is considered that carbon uptake can be completely prevented by using inorganic compounds such as Cl2) or GaCl3.

However, GaH2 Cl and GaHCl2
has major problems, such as being extremely unstable at room temperature and having low vapor pressure. On the other hand, GaCl3 is stable and has a predetermined vapor pressure, so it is thought that it can be transported as a gas through piping and supplied to the reaction vessel by switching with a valve.

However, since GaCl3 has strong deliquescent and corrosive properties, it is extremely difficult to handle and could not 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 high quality Group 3-5 compound semiconductors at low temperatures.

[0016]

[Means for Solving the Problems] The method for selectively growing a Group 3-5 compound semiconductor of the present invention involves growing a volatile complex compound consisting of a Group 3 compound and a Group 5 compound and a Group 5 element or a Group 5 volatile compound on a substrate. feed on top. The Group 3 compound constituting the volatile complex compound is a hydrogen compound in which a Group 3 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]

[Operation] Generally, Group 3 atoms constituting Group 3 compounds have empty p-electron orbitals, and therefore these compounds function as electron acceptors (Lewis acids). On the other hand, since the Group 5 atoms constituting the Group 5 compounds have lone pairs of electrons, these compounds act as electron donors (Lewis bases). As a result, the Group 3 compound and the Group 5 compound undergo a so-called acid-base reaction. That is, the lone pair of electrons of the Group 5 atom coordinates with the vacant p-electron orbital of the Group 3 atom to form a more stable complex.

[0018] A hydrogen compound in which a Group 3 element and a halogen element are directly bonded, such as GaH2C having a Ga-Cl bond.
1 and GaHCl2 have a problem in that they are extremely unstable at room temperature. However, in this case as well, if a suitable Group 5 compound is selected and reacted with these hydrogen compounds, a complex that is stable at room temperature and has an appropriate vapor pressure can be formed. Such a complex easily decomposes 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 the Group 5 element is not substantially supplied. Furthermore, even if a Group 5 organic compound is used, it will not become a source of carbon impurities unless it is decomposed. On the other hand 3
Group hydrogen compounds, such as GaH2Cl, are easily decomposed at the growth temperature, so the above process ultimately produces G
Only a-Cl can be supplied to the substrate surface.

As Group 5 compounds, compounds such as arsenic, phosphorus, and nitrogen form stable complexes with Group 3 hydrogen compounds. However, among them, nitrogen compounds with the lowest atomic number, such as NH3, and organic compounds, especially trimethylamine (TMN:N(CH3)3), which has a methyl group, are
) and dimethylamine (DMNH:NH(CH3)2
) are the most thermally stable, and the resulting complex has a high vapor pressure.

[0021] Therefore, a volatile complex compound formed by the reaction of a group 3 hydrogen compound having a group 3 element-halogen element bond and a group 5 nitrogen compound, such as GaH2 Cl.TMN
It is possible to realize a method of selectively growing a high quality Group 3-5 compound semiconductor at a lower temperature by using the compound semiconductor as a Group 3 raw material.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail with reference to the drawings.

[0023] GaAs (1
00) In order to grow GaAs on a substrate, a horizontal low 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 a high frequency coil 8 around the outer periphery of the reaction vessel 1.

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

As a gas introduction system, AsH3 gas cylinder 9, DEGaCl bubbler 10, GaH2 Cl/TMN
A bubbler 11 and H2 gas 12 serving as a carrier are connected, and the gas flow rate is controlled by a flow rate control device 13 and a valve 14.

[0027] In order to examine the presence or absence of selectivity, the GaAs substrate 3
A SiO2 mask is formed on a part of the surface.

[0028] H2 as carrier gas is supplied at 9 l/min.
Then, GaAs was grown for 30 minutes at a reaction tube internal pressure of 100 Torr and a GaAs substrate 3 temperature of 200° C. to 700° C. The partial pressure in the reaction tube of AsH3 is 1 Torr, and the partial pressure of AsH3 is 1 Torr.
The partial pressure of l·TMN was set to 2×10 −2 Torr.

For comparison, an experiment was also conducted using conventional DEGaCl instead of GaH2Cl.TMN. After growth, selectivity was evaluated by optical microscopic observation. SiO2
After removing the mask, the thickness of the grown GaAs layer was measured using a step meter.

FIG. 2 shows the temperature dependence of the growth rate of GaAs. In this temperature range, the temperature is almost constant, and no GaAs precipitation is observed on the SiO2 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 decreased significantly at temperatures below 400° C., as shown in FIG. This is thought to be because the decomposition rate of DEGaCl decreases at low temperatures.

[0032] GaH2 in the temperature range of 200°C to 700°C
FIG. 3 shows Hall measurement data for the impurity density of films grown using Cl.TMN and DEGaCl. All the films grown using GaH2Cl.TMN in this example exhibited low concentration N-type conductivity of 1014 to 1015/cm3. On the other hand, a film grown using conventional DEGaCl exhibits P-type conductivity at temperatures below 500° C., and the impurity density increases as the temperature decreases. SIMS measurement confirmed that this highly concentrated P-type impurity was carbon.

In this example, GaH2Cl・TMN
By using Ga as a Group 3 raw material, Ga can be produced at lower temperatures.
Selective growth of As was achieved. No incorporation of carbon impurities was observed.

[0034] As the group III Ga raw material, GaH2Cl
- DMNH etc. can be used, and the present invention can also be applied to the selective growth of GaP and GaSb with different types of Group 5 elements, as well as the selective growth of mixed crystals such as GaAsP. Selective growth of AlAs using AlH2 I・TMN and AsH3 and I using InH2 Cl・TMN and PH3
A similar effect can be obtained by selective growth of nP. In addition, the present invention can be broadly applied to the selective growth of Group 3-5 compound semiconductors.

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

[0036]

Effects of the invention: High quality 3-5 that provides selectivity and sufficient growth rate at low temperatures and does not incorporate carbon impurities.
A low-temperature selective growth method for group compound semiconductors has been realized.

[Brief explanation of the drawing]

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

FIG. 2 is a graph showing the relationship between growth temperature and growth rate using GaH2Cl.TMN and DEGaCl.

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

[Explanation of symbols]

1 Reaction vessel 2 Carbon susceptor 3 Substrate crystal 4 Susceptor holder 5 Filter 6 Exhaust device 7 Exhaust pipe 8 High frequency induction coil 9 AsH3 cylinder 10 DEGaCl bubbler 11 GaH2 Cl/TMN bubbler 12
Carrier H2 Gas 13 Flow rate control device 14 Valve

Claims (2)

[Claims] 1. A method for growing a Group 3-5 compound semiconductor in which a volatile complex compound consisting of a Group 3 compound and a Group 5 compound and a Group 5 element or a Group 5 volatile compound are provided on a substrate, comprising: A selective growth method for a Group 3-5 compound semiconductor, characterized in that the Group 3 compound constituting the is a hydrogen compound in which a Group 3 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.