JPS6353918A - Semiconductor crystal growth apparatus - Google Patents

Abstract

PURPOSE:To obtain uniform epitaxial layers by providing a jig for thermal decomposition of unreacted gas beneath a wafer susceptor in a quartz reaction tube. CONSTITUTION:After substrate crystals 3 are put on a wafer susceptor 2 and inserted into a quartz reaction tube 1 with a jig 6 for trapping As, both the wafer susceptor 2 and the jig 6 for trapping As are simultaneously induction- heated by an RF coil 4. After the wafer susceptor 2 is heated to the temperature for growth, mixed gas 5 of epitaxial growth material gas and carrier gas is supplied into the quartz reaction tube 1. The material gas is decomposed by heat on the crystals 3 and Al GaAs layers are made to grow by epitaxial growth. Moreover, as the same reaction occurs on the surface of the jig 6 for trapping As, Al GaAs is deposited.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides a method for obtaining a uniform epitaxial growth layer with good controllability in the pyrolytic vapor deposition method (MOCVD method) used for manufacturing compound semiconductor devices. The present invention relates to a semiconductor crystal growth apparatus.

[Conventional technology]

Conventionally, MOCVD is a method for obtaining an epitaxially grown layer of a compound semiconductor.

FIG. 2 is a diagram showing a schematic configuration of a reaction system portion of a conventional MOCVD apparatus. In this figure, 7 is a quartz reaction tube, 2 is a wafer susceptor, 3 is a substrate crystal made of a compound semiconductor such as GaAs, and 4 is the wafer susceptor 2.
An RF coil is used for induction heating, and 5 is a growth raw material gas.

Next, the operation of the MOCVD apparatus will be explained using an example in which epitaxial growth of an A1GaAs crystal is performed.

First, a substrate crystal 3 placed on a wafer susceptor 2 is placed in a quartz reaction tube 1, and then crystal growth is started.

The arrows in the figure indicate the flow direction of the growth raw material gas 5, which is a reactive gas, and indicate the direction in which AsH3, TMG (Trimet
hylgalliuz) and TMA (Trime
thylaluminun) as a raw material gas,
H2 gas is supplied into the quartz reaction tube 1 as a carrier gas. Further, the wafer susceptor 2 is heated to about 750'C by induction heating of the RF coil 4, and the above-mentioned A3 H3, TMG is heated on the substrate crystal 3.

TMA is thermally decomposed and an AIG aAs layer is epitaxially grown by the following reaction.

2ASH3+Ga (CH3)3 +AM (CH
3) 3+ (AuGa)As+6CHa The film thickness of the epitaxial growth layer is controlled by the concentration of the growth source gas 5, the flow rate of the carrier gas, and the gas introduction time.

After the reaction, the gas is led to the waste gas treatment device from the lower part of the quartz reaction tube 1, where dangerous and toxic gases, gases, and products are removed.

[Problem that the invention seeks to solve]

In the conventional MOCVD apparatus, as shown in FIG. 2, part of the unreacted gas becomes an upward current and is carried onto the substrate crystal 3.
Because epitaxial growth is performed by pyrolysis,
There is a problem that the epitaxially grown layer becomes non-uniform. Further, since most of the unreacted gas becomes waste gas and passes through the waste gas pipe, there is also the problem that As is deposited inside the waste gas pipe during long-term use.

This invention was made to solve the above-mentioned problems, and eliminates the accumulation of As inside the waste gas pipe.
An object of the present invention is to provide an MOCVD apparatus that can always grow a uniform epitaxial growth layer with good controllability.

[Failure to solve the problem]

The MOCVD apparatus according to the present invention is provided with a jig for thermally decomposing unreacted gas below a wafer susceptor that holds a substrate crystal inside a quartz reaction tube.

[Effect]

In this invention, As in the unreacted gas is trapped within the quartz reaction tube, resulting in the effect of lowering the A Sa degree in the waste gas.

Further, since most of the unreacted gas is thermally decomposed, the influence of upward air currents can be reduced, and a uniform epitaxial growth layer can be formed.

〔Example〕

An embodiment of the present invention will be described below with reference to FIG.

In Figure 1, the same symbols as in Figure 2 indicate the same things,
Reference numeral 6 denotes an As trap jig provided below the wafer susceptor 2, and its shape is processed into a step shape in order to efficiently deposit the As compound.

In order to accommodate the As trap jig 6, the quartz reaction tube 1 and the RF coil 4 are longer in shape than conventional ones, and the RF coil 4 allows the wafer susceptor 2 and the As trap jig 6 to be inserted. Both can be induction heated at the same time.

Next, a case where epitaxial growth on the substrate crystal 3 is performed using the MOCVD apparatus according to the present invention will be described.

First, the substrate crystal 3 is placed on the wafer susceptor 2, and the As
After putting it into the quartz reaction tube 1 together with the trapping jig 6, both the wafer susceptor 2 and the As trapping jig 6 are induction heated by the RF coil 4 at the same time. After heating the wafer susceptor 2 to the growth temperature, a mixture of epitaxial growth source gas (AsH3, TMG, TMA) 5 and carrier gas (H2) is supplied into the quartz reaction tube 1. On the substrate crystal 3, the growth raw material gas 5 is thermally decomposed into A.
An iGaAs layer is epitaxially grown and an As
A similar reaction also occurs on the surface of the trap jig 6, so that AJIGaAs is deposited.

In this way, by providing the jig 6 for As) wrapping, the As5 degree in the waste gas is reduced, and the amount of As deposited inside the waste gas pipe due to long-term use is significantly reduced compared to the conventional method. can be done.

Furthermore, since the unreacted gas is thermally decomposed on the surface of the As trapping jig 6, the influence of upward air currents is reduced, and uniform epitaxial growth can be achieved.

In addition, in the above embodiment, MOCV of A1GaAs-based crystal
Although method D has been described as an example, the present invention is not limited to this method, and has similar effects on crystal growth apparatuses in general using thermal decomposition reaction tubes and on other semiconductor materials.

Further, in the above embodiment, the induction heating method using the RF coil 4 was explained as an example, but other heating methods (resistance heating, lamp heating, etc.) can also have similar effects.

〔Effect of the invention〕

As explained above, in this invention, a jig for thermally decomposing unreacted gas is provided below the wafer susceptor inside the quartz reaction tube, so that the unreacted gas accumulates on this jig and flows into the waste gas pipe. As a result, a uniform epitaxially grown layer can be obtained since unreacted gases are no longer entrained on the substrate crystal as an upward current.

Furthermore, since the concentration of harmful gases contained in the waste gas can be lowered, there is no need for a conventional large-scale waste gas treatment device, and there is also the advantage that the device itself can be made smaller.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of the reaction system portion of an MOCVD apparatus showing an embodiment of the present invention, and FIG. 2 is a schematic diagram of the reaction system portion of a conventional MOCVD apparatus. In the figure, 1 is a quartz reaction tube, 2 is a wafer susceptor, and 3 is a wafer susceptor.
is a substrate crystal, 4 is an RF coil, 5 is a growth source gas, 6
AS) is a jig for wrapping. Note that the same reference numerals in each figure indicate the same or corresponding parts. Against Oiwa Ig Ig (2 outside)]] 1 Fig. 2 Fig. 2

Claims (1)

[Claims] In a pyrolytic vapor phase growth apparatus in which a substrate crystal placed on a wafer susceptor is placed in a quartz reaction tube, a reaction gas is introduced into the quartz reaction tube to form an epitaxial growth layer on the substrate crystal. A semiconductor crystal growth apparatus characterized in that a jig for thermally decomposing unreacted gas is provided below a wafer susceptor that holds a substrate crystal inside a reaction tube.