JPH02230722A - Vapor growth method of compound semiconductor - Google Patents

Abstract

PURPOSE:To realize the high purity ALE growth of chloride and a simple raw-material carrying method in an MO-ALE method by repeating a step wherein the chloride of a group III element which is obtained by the reaction of an organic metal compound and hydrogen chloride is carried into a substrate crystal region with a carrier gas and a step wherein a group V raw material is carried into said substrate crystal region. CONSTITUTION:As a group II organic metal raw material 11, Ga(CH3)3(TMG) is used. As a group V raw material 16, AsH3 is used. The mixed region of the TMG and the hydrogen chloride is heated to 650 deg.C. The region of a substrate crystal 15 is heated to 450 deg.C. the TMG and the hydrogen chloride gas 12 are mixed at the high temperature part in a reacting tube 13. The result is carried into the region of the substrate crystal 15 as GaCl with an H2 carrier gas. The GaCl is adsorbed in the upper part of the substrate crystal. Thereafter, the supply of the GaCl and HCl gas is stopped. Then, excessive chloride in the reacting tube is purged only with H2 gas. Then, AsH3 of the group V raw material gas 16 is fed into the reacting tube. A GaAs layer is grown by the reaction with the GaCl which is adsorbed in the substrate crystal. Thereafter, the excessive AsH3 is purged from the substrate region only with the H2 gas. The atomic layer epitaxy(ALE) growth advances by repeating these steps.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for vapor phase growth of compound semiconductors, and more specifically to atomic layer epitaxy (ALE).
ayer eplta
It must be related to a new ALE growth method that has both the characteristics of LE.

[Prior art and its problems] As an ALE growth method for -v group compound semiconductors, Ga
(, p) (chloride ALE method) and Ga (CH3) 3 (tri
A method (80-ALE method) using a group Ⅰ element organic metal such as -methylgal Iium (THG) has been attempted.

These methods will be briefly explained using drawings.

FIG. 2 is a schematic diagram of a GaAS chloride ALE growth apparatus using a two-chamber reaction tube based on the GaCl-^sH3-H2 system. In this method, a source port 22 for Ga metal is installed upstream of the upper reaction tube 21, and GaCf! is generated and transported to the substrate region by a hydrogen carrier gas. Meanwhile, AsH3 is introduced into the lower reaction tube 23. This gas is almost decomposed into As4 by the heat of the reaction tube before reaching the substrate region. The substrate crystal 24 moves between the two reaction tubes. In the figure, 26
2 shows the trajectory of the substrate holder 27.

According to this process, the substrate crystal surface becomes GaCJ2, As
The substrate is exposed alternately to four atmospheres, and one cycle of growth causes growth of one molecular layer of GaAs.

Characteristics of this chloride ALE method include the following points. First, GaCiJ has a wide substrate temperature, GaCJl
To form an extremely stable monolayer adsorption layer over a range of flow rates,
AL using organic metals, which will be described later in terms of single-molecular-layer growth
Easier to achieve results than E method. In general, this chloride AL
In Method E, impurities containing heavy metals are converted into evaporable chloride by the hydrogen chloride used as a raw material, making them difficult to incorporate into the crystal, and as a result, highly pure crystals are obtained.

On the other hand, it is necessary to react the group III element metal with hydrogen chloride, and even if the supply of hydrogen chloride is stopped, the generation of monochloride is immediate because α dissolved in the group III metal source gradually jumps out. The process of alternate supply of ALE cannot be performed simply by switching the gas. For this reason, there is a drawback that a complicated movement of the substrate crystal is required.

On the other hand, G by T}IG-As}13-82 system
A schematic diagram of the aAs ALE device is shown in FIG. In this method, the group (III) organic raw material 31 is transported to the reaction tube 33 with a hydrogen carrier gas using the vapor pressure controlled in the constant temperature bath 32, so there is no source in the reaction tube 33, such as a halogen transport method. Does not require space. ALE growth is valve 3
Using 7a-g, group II organic raw materials such as TMG 31
, AsH3, or other V group raw material gas 35, and purge H2 gas.

However, the problem with this method is that since the decomposition of the organometallic occurs very close to the substrate crystal 34, the decomposed hydrocarbons are adsorbed onto the growing surface, and as a result, a large amount of carbon is deposited inside the growing crystal. It is to be taken into account. For this reason, the grown crystal tends to be a p-type crystal with a high carrier concentration. In order to reduce the influence of carbon, it is necessary to strictly control the growth conditions, such as increasing the flow rate of the raw material gas. Further, the purification mechanism such as the halogen transport method does not work for impurities such as Si contained in the raw material gas, which is disadvantageous for obtaining high-purity crystals.

The present invention eliminates such drawbacks in the conventional ALE method, and achieves high purity growth of chloride ALE and }to-ALE.
The object of the present invention is to provide a method for vapor phase growth of compound semiconductors using a new and unprecedented ALE method, which combines the features of the LE method as a simple material transportation method.

[Means for Solving the Problems] The present invention provides a method for vapor phase growth of a compound semiconductor in which a group (III) element raw material and a group (III) element raw material are alternately supplied to a substrate crystal region in a reaction tube to grow epitaxial crystals on a substrate crystal. In the method, an organometallic compound containing a group (III) element is used as a group (III) element raw material, the organometallic compound and hydrogen chloride are reacted to form a chloride of the group (III) element, and then the chloride is applied to a crystal region of a substrate. A step of transporting, a step of substituting the substrate crystal region with a hydrogen carrier gas, a step of transporting the V group element base material to the substrate crystal region, and a step of substituting the substrate crystal region with a hydrogen carrier gas are sequentially carried out. This is a method for vapor phase growth of compound semiconductors characterized by repeated growth.

Compound semiconductors that can be grown by the method of the present invention include GaAs, InP, etc., as well as III-V compound semiconductors containing tertiary and quaternary elements;
It can also be applied to the growth of I-Vl group compound semiconductors.

[Function] FIG. 1 is a schematic diagram of an apparatus used to carry out the method of the present invention.Here, the function of the present invention will be explained by taking as an example GaAs ALE growth using TMG as the group Ⅰ organic material 11.

TMG is introduced into the reaction tube 13 together with hydrogen chloride 12.

The entire reaction tube 13 is heated by a resistance heating furnace 14.

1FIG immediately decomposes into Ga and methane in the reaction tube as shown in equation (1).

Ga (CH3) 3 + 3/2H2 ←Ga+
3CH4 ・(1) Ga decomposed here reacts with HC1 supplied at the same time to generate GacIl.

Ga+HCJ GaCj! +1/282
=・(2) This is carried by the hydrogen carrier gas to the downstream region of the substrate crystal 15, and Gaα is adsorbed onto the substrate crystal 15.

Here, THG and hydrogen chloride are supplied in approximately the same number of moles. If there is more T}IG, Ga will precipitate on the upstream side, and if there is more hydrogen chloride, excess hydrogen chloride will be transported downstream to the substrate crystal 15 region, causing inhibition of Gaα adsorption.

In the method of the present invention, if the supply of raw materials to the reaction tube is stopped by operating the valves 17a-i, the transport of chlorides such as GaCi to the substrate region can be stopped. Therefore,
In order to proceed with the ALE growth process, after adsorbing the chloride of the group III element onto the substrate crystal, the supply of the group III organic metal and Hα gas is stopped, and then the excess in the reaction tube is removed using only H2 gas. Do a chloride purge. Subsequently, AsH3, which is the Group 1 raw material gas 16, is supplied into the reaction tube, and a GaAs layer is grown by reaction with GaCl2 adsorbed on the substrate crystal. After this, again ■ Excess AS is removed from the substrate crystal region using only 2 gases.
Purge H3. ALE growth progresses by repeating these steps.

As described above, according to the present invention, by using the group (I) organic raw material and hydrogen chloride, it is possible to realize the ALE process by simply switching the gas while using the chloride of the group (I) element as the adsorbent. At the same time, the problem of group III metal source depletion in the chloride ALE method can be avoided, and
The decomposition reaction of group organic raw materials (reaction formula (1)) and the reaction with hydrogen chloride (reaction formula (2)) proceed satisfactorily even at temperatures of about 600 to 700°C. There is also no need to raise the source region to high temperatures. In addition, organic raw materials such as T}IQ are sufficiently decomposed due to the resistance heating method, and most of the hydrocarbons become methane and ethane, and the generation of higher-order hydrocarbons is extremely low.

In addition, radicals that are easily adsorbed onto the substrate surface are converted into stable ones while being transported downstream, and carbon contamination of the growing crystal as seen in the 80-ALE method is extremely small. As a result, a highly pure epitaxial crystal can be obtained.

[Embodiments] Next, embodiments of the present invention will be described in detail with reference to the drawings.

Example 1 Here, an example in which the present invention is applied to GaAs ALE will be described with reference to FIG. THG was used as the group (2) organic metal raw material H, and ASH3 was used as the group V raw material 16.

The reaction tube 13 is a horizontal quartz tube, and is heated by a resistance heating furnace 14.
The area where the group (Ⅰ) organic raw material and hydrogen chloride are mixed is heated to 650°C, and the substrate crystal 15 area is heated to 450°C.

The supply amount of TMG is controlled by the temperature control of the raw material container by the constant temperature bath 18 and the hydrogen carrier gas flow rate, and is controlled at a rate of 1 per minute.
It was set as XIO-4 mol. On the other hand, the flow rate of the hydrogen chloride 12 is controlled by the mass flow controller 19c, and the flow rate is the same as the group II organic raw material 11 < 1 x 10-4 IIlot/
It was supplied at min. Both are mixed in a high temperature section within the reaction tube 13 and transported as GaCfl to the substrate crystal 15 by H2 carrier gas. AsH3 is 5X1 from the introduction pipe 20
It is introduced into the reaction tube 13 at a rate of 0-4 mol/min. The total flow rate in the substrate crystal 15 region is 7 12 /mi
It is n.

As the substrate crystal 15, a GaAS (100) high resistance crystal was used. After setting the crystal substrate 15 in the reaction tube 13, the temperature is raised while supplying AsH3, and when a predetermined temperature is reached, the ALE process is started. The time for each step was as follows.

TMG + HCi supply: 1 second H2 purge: 3 seconds AsH3 supply: 2 seconds 112 purge: 3 seconds In this way, 1000 cycles of GaAs growth were performed with 9 seconds as one cycle. The growth rate converted to one cycle is 2. 8A 7 cycles, and it was found that single molecule growth was achieved. Further, as a result of photoluminescence measurement at 4.2K, a free exciton peak was clearly observed, and the light emission via the acceptor level due to carbon was extremely weak.

Example 2 Here, an example in which the present invention is applied to InP ALE will be described with reference to FIG. ■Group organometallic raw material 1
1 includes TEI ( triethylindium
:In(C2H5)3), P for group V raw material 16
I-13 was used. The reaction tube 13 is a horizontal quartz tube, and a resistance heating furnace 14 heats the area where the organic material 11 and the hydrogen chloride 12 are mixed to 650°C, and the area where the substrate crystal 15 is heated to 400°C.

The supply amount of Ding EI is controlled by controlling the temperature of the raw material container using the constant temperature bath 18 and the flow rate of the hydrogen carrier gas, and is controlled at a rate of 1 per minute.
It is supplied to the reaction tube 13 at a ratio of XIO-4 mol.

On the other hand, the flow rate of hydrogen chloride 12 is controlled by the mass flow controller 1.
Controlled by 9c, same as group Ⅰ organic raw material 11 < 1 x
It was supplied at a rate of 10-4 mol/min. Both are mixed in a high temperature section within the reaction tube 13 and transported as InrU to the substrate crystal 15 region by H2 carrier gas. PH3 is introduced into the reaction tube 13 from the introduction tube 20 at a rate of 5xlO-4 not/min. The total flow rate in the substrate crystal 15 region is 7 (2 2 /min).

As the substrate crystal 15, an InP (100) high resistance crystal was used. After setting the crystal substrate 15 in the reaction tube 13,
The temperature is raised while supplying PH3, and when a predetermined temperature is reached, the ALE process is started. The time for each step was as follows.

TEI + HIJ supply = 1 second ■ Purge by 2: 3 seconds PH3 supply = 2 seconds ■ Purge by 2: 3 seconds In this way, InP growth was performed for 1000 cycles with 9 seconds as one cycle. The growth rate converted to one cycle was 2.9 people/cycle, indicating that single molecule growth was achieved. Furthermore, as a result of photoluminescence measurement at 4.2K, a free exciton peak was clearly observed, and the light emission via the acceptor level due to carbon was extremely weak.

In addition, in this example, ALE growth examples of GaAs and InP are shown, but in addition to these, epitaxial growth of ■-V group compound semiconductors including ternary and quaternary elements, and more specifically, n-Vl group compound semiconductors are also possible. It is clear that this method can also be applied to the growth of semiconductors.

[Effects of the Invention] As explained above, according to the method of the present invention, the characteristics of high purity growth when using the chloride ALE method and the
A compound semiconductor vapor phase growth method using the ALE growth method that has both the features of the simple growth system of the E method is achieved.

[Brief explanation of the drawing]

FIG. 1 is a schematic block diagram of an example of a growth apparatus used to carry out the method of the present invention, FIG. 2 is a schematic block diagram of a chloride ALE apparatus in the prior art, and FIG.
FIG. 1 is a schematic configuration diagram of an O-ALE device. 11. 31...Group organic raw material 12...Hydrogen chloride (HCi)13. 33...Reaction tube 14
...Resistance heating furnace 15, 24. 34...Substrate crystal 16. 35... Group V raw material 17a-i, 3
7a-9...Valve 18. 32... Constant temperature chamber 19a-9, 36... Mass flow controller 20.
...Introduction tube 21...Upper reaction tube 22.
...Ga source boat 23...Lower reaction tube 26
...Trajectory of substrate holder movement 27...Substrate holder

Claims (1)

[Claims] (1) In a compound semiconductor vapor phase growth method in which a group III element raw material and a group V element raw material are alternately supplied to a substrate crystal region in a reaction tube to grow epitaxial crystals on a substrate crystal,
An organometallic compound containing a group III element is used as a group III element raw material, and the organometallic compound and hydrogen chloride are reacted.
After converting the group III element into a chloride, a step of transporting the chloride to the crystalline region of the substrate, a step of replacing the crystalline region of the substrate with a hydrogen carrier gas, and a step of transporting the group V element raw material to the crystalline region of the substrate. A method for vapor phase growth of a compound semiconductor, comprising sequentially repeating the steps of: and substituting the substrate crystal region with a hydrogen carrier gas.