JPS62205620A - Method and device for vapor growth - Google Patents

Abstract

PURPOSE:To decrease transient variation of semiconductor characteristics in the initial stage of growth, by depositing in advance a semiconductor consisting of the same elements as that in a semiconductor to be grown on a substrate on the inner wall of a reaction tube. CONSTITUTION:In order to grow a high-resistance GaAs layer 12, 14 and an N-type GaAs layer 16, a shield 7 is placed on the side of a gas introducing tube 3a. When a high-resistance A GaAs layer 13 and an N-type AlGaAs layer 15 are grown, the shield 7 is placed at the position of a susceptor. In this manner, a GaAs layer is deposited on the inner wall 1a of a reaction tube 1 during the growth of the high-resistance GaAs layer 12, while an AlGaAs layer is deposited on the inner wall 7a of the shield 7 during the growth of the high- resistance AlGaAs layer 13. Accordingly, a substrate 11 is covered with the inner wall 1a having the GaAs layer from the starting point of and during the growth of the high-resistance GaAs layer 14 and the N-type AlGaAs layer 16, and is covered with the inner wall 7a having the AlGaAs layer from the starting point of and during the growth of the N-type AlGaAs layer 15. In this manner, transient variation of the semiconductor characteristics in the initial stage of growth can be decreased substantially.

Description

[Detailed Description of the Invention] [Summary] In vapor phase growth in which a compound or mixed crystal semiconductor is grown in a reaction tube, by previously depositing a semiconductor made of the same element as the semiconductor to be grown on the inner wall of the reaction tube, This reduces transient changes in semiconductor properties during the initial stage of growth.

[Industrial application field]

The present invention relates to a vapor phase growth method for growing a compound or mixed crystal semiconductor in a reaction tube, and improvements to the apparatus.

Compound or mixed crystal semiconductors are used in various semiconductor devices by taking advantage of their properties, among which HEMT
(high electron mobility transistor), HBT (peterobibolar transistor), laser, superlattice structure, etc. utilize heterojunctions.

A heterojunction is formed by MH of crystal growth. It is desired that the semiconductor forming the semiconductor device has predetermined characteristics even in the heterojunction.

[Conventional technology]

FIG. 2 is a sectional side view of a main part of an example of a conventional apparatus for carrying out a conventional vapor phase growth method.

The apparatus shown in the figure is an apparatus for growing a compound or a mixed crystal semiconductor by the MOCVD (metal-organic chemical vapor deposition) method, and 1 is a reaction tube made of quartz glass in which the growth takes place, and 2 is a reaction tube for reaction g1. Lid to close the inlet/outlet, 3 is reaction tube 1
A gas introduction tube 4 introduces a reaction gas into the reaction tube 1, a gas exhaust tube 4 discharges the gas in the reaction tube 1, and a substrate S on which a semiconductor is to be grown is placed and placed at a predetermined position in the reaction tube 1. A carbon (graphite) $9 susceptor 6 is a high frequency coil provided on the outer periphery of the reaction tube 1 at the location where the susceptor 5 is disposed.

To grow the semiconductor, the susceptor 5 is heated by energizing the high-frequency coil 6 to raise the substrate S to a predetermined temperature, and the gas introduction tube 3 is heated.
This is done by introducing a reaction gas from the

The reaction gas contacts the heated substrate S, causes a chemical reaction, and grows a semiconductor on the substrate S.

An example of a semiconductor formed by the above-mentioned vapor phase growth is a multilayer semiconductor shown in a side cross-sectional view of FIG. 3, for example. This multilayer semiconductor is
It is used in the formation of HEMT.

In FIG. 3, 11 is a gallium arsenide (GaAs) substrate, 12 is a high-resistance GaAs layer, 13 is a high-resistance aluminum gallium arsenide (81GaAs) rfA, 14 is a high-resistance GaAsH115 is converted to n-type 1GaArJFf, ]6 is n type GaAsJW, high resistance GaAsFB14 and n-type A]GaAsB15 form a Peter junction between them, and the former is a two-dimensional electron gas (2DG
) formation layer, and the latter becomes an electron supply layer.

Each of the layers 12 to 16 is formed by sequentially growing on the substrate 11.

The reactive gases used for each eyebrow growth are as follows.

For the high resistance GaAs layers 12 and 14, a mixture of TMG [trimethylgallium, Ga(CH:+) 3 ) and arsine [ASH3], high resistance AIGaAsjf9
TMA () trimethylaluminum, Δ1 (
CH3) 3), TMG and arsine mixture, n-type A
A mixture of TMA, TMG, arsine, and monosilane [5i) (a) for lGaAs layer 15, n-type GaAs layer 1
6 is a mixture of TMG, arsine, and monosilane.

[Problem that the invention seeks to solve]

In HEMT, it is important that the carrier concentration at the heterojunction of the electron supply layer is sufficiently high.

However, in the multilayer semiconductor shown in FIG. 3 formed by the above method, as shown in the problem explanatory diagram of FIG.
It is observed that the carrier concentration decreases transiently in the initial stage of growth of type AlGaAs1t315. This is H
This causes deterioration of the characteristics of EMT.

Generally, in the vapor phase growth method described above, the vicinity of the susceptor 5 of the reaction tube 1 is heated by the propagation of heat from the susceptor 5. Therefore, when growing a semiconductor on the substrate S, the semiconductor made of the same element is also deposited on the inner wall 1a of the reaction tube 1.

Therefore, if we look at the growth of the n-type ^lGaAs layer 15, the deposit on the inner wall 1a at the start of growth is the same as the previous high-resistance G a A sf? Ga by t14 growth
As it grows, it becomes AlGaAs.

According to the experience of the inventor of the present application, it is thought that the transient change in semiconductor characteristics at the early stage of growth, such as the decrease in carrier concentration, is caused by the deposits on the inner wall 1a covering the susceptor 5.

[Means for solving problems]

The above problem can be solved by depositing a semiconductor made of the same element as the semiconductor on the inner wall of the reaction tube in advance when growing a compound or mixed crystal semiconductor in the reaction tube. Further, the problem is solved by using the vapor phase growth apparatus of the present invention, in which the reaction tube has a plurality of inner walls forming a multilayer structure, and the inner wall is configured to be movable in the axial direction of the reaction tube. Ru.

- [Operation] According to this method, the deposit on the inner wall of the reaction tube that covers the susceptor is a semiconductor made of the same element as the growing semiconductor even at the start of growth.

Therefore, the transient change in semiconductor characteristics at the early stage of growth described above is reduced.

When forming a multilayer semiconductor having a heterojunction, a semiconductor corresponding to each of the semiconductors to be grown is deposited on each of the plurality of inner walls of the vapor phase growth apparatus, and By selectively moving the susceptor, the deposit on the inner wall covering the susceptor can be made into a semiconductor made of the same element as the growing semiconductor even at the start of growth.

〔Example〕

FIG. 1 is a cross-sectional view (a) and (b) of a main part of an embodiment of a vapor phase growth apparatus according to the present invention for carrying out the method of the present invention. The same reference numerals indicate the same objects throughout the figures.

The apparatus shown in Fig. 1 is similar to the reaction tube 1 of the conventional apparatus shown in Fig. 2.
A movable shield 7 forming a second inner wall 7a is provided inside, and the conventional gas introduction pipe 3 is replaced with a gas introduction pipe 3a that is elongated in the direction of the susceptor 5.

The shielding body 7 is made of quartz glass, has a length slightly longer than the susceptor 5, and has an inverted gate-shaped cross section, and its moving direction is similar to that of the reaction tube 1.
When the susceptor 5 is located in the axial direction, the susceptor 5 is covered so as to be shielded from the inner wall 1a of the reaction tube 1.

Further, when the shield 7 is located on the side of the gas introduction pipe 3a, the tip of the gas introduction pipe 3a is positioned slightly to the right of the shield 7 in the figure.

The movement of the shield 7 is operated by a moving shaft 8, and the installation of the shaft 8 changes the conventional lid 2 to a lid 2a↓.

The method for forming the multi-I'5 semiconductor shown in FIG. 3 using this apparatus is the same as the conventional method described above, except for the addition of the operation of moving the shield 7.

That is, the high resistance GaAs layers 12 and 14 and the n-type GaAs
When growing J'516, the shield 7 is connected to the gas introduction pipe 3.
When growing lGaAs1' 513 and n-type AlGaAs layer 15 to a high resistance state on the a side, the shielding body 7 is located at the susceptor position.

Then, during the growth of high resistance GaAs #12, the reaction tube 1
GaAs is deposited on the inner wall 1a of , resulting in high resistance ^] GaAs1
'513, AlGaA was applied to the inner wall 7a of the shielding body 7 during the growth of
s is deposited.

Therefore, the substrate 11 consists of high resistance GaAs 114 and n-type GaA
During the growth of s1i16, the inner wall 1a coated with GaAs is exposed from the start of the growth, and 1GaAsj5'f1 becomes n-type.
During the growth of No. 5, it is covered with an inner wall 7a coated with AlGaAs from the start of growth.

From this, for example, when focusing on n-type AlGaAs1'515, which becomes an electron pick-up in HEMT, the transient decrease in carrier concentration at the early stage of growth as described in FIG. 4 is significantly reduced. According to confirmation by the inventor of the present application, the decrease is less than 1/10 of that in the conventional method.

In the above example, the semiconductors to be grown are GaAs and AlG.
2ftFn of aAs, but if it exceeds 2ftFn, the number of shielding bodies may be increased accordingly.

〔Effect of the invention〕

As explained above, according to the configuration of the present invention, in vapor phase growth for growing a compound or mixed crystal semiconductor in a reaction tube, it is possible to reduce transient changes in semiconductor properties in the early stage of growth, and to This has the effect of making it possible to prevent characteristic deterioration caused by such changes in the device.

[Brief explanation of drawings]

Fig. 1 is a side sectional view of the main part of an embodiment of the apparatus of the present invention for carrying out the method of the invention; Fig. 4 is a side cross-sectional view of an example of a multilayer semiconductor formed using vapor-phase sputum, and Fig. 4 is an explanatory diagram of problems in the conventional method. , 3.3a is a gas introduction pipe, 4 is a gas discharge pipe, 5 is a susceptor, 6 is a high frequency coil, 7
is a shield, 7a is an inner wall of 7, 8 is a moving shaft, S, 11 is a substrate, 12.14 is a high resistance GaAsff1.13 is a high resistance] GaAsJW, 1
5 is an n-type lGaAs layer, and 16 is an n-type GaAsN layer.

Claims (1)

[Claims] 1) Vapor phase growth characterized in that when growing a compound or mixed crystal semiconductor in a reaction tube, a semiconductor made of the same element as the semiconductor is previously deposited on the inner wall of the reaction tube. Method. 2) A reaction tube in which a compound or a mixed crystal semiconductor is grown has a plurality of inner walls forming a multilayer structure, and the inner wall is configured to be movable in the axial direction of the reaction tube. Vapor phase growth equipment.