JPH03133123A - Organic metal vapor phase growth method - Google Patents

Abstract

PURPOSE:To enable a mixed crystal having excellent characteristics to be produced by a method wherein the mixed crystallization is performed by specifying the mutual feed ratio of organic compound gasses to homologous elements while sustaining the feed line of the organic compound of the elements of low composition ratios within the range of effective output of an MFC. CONSTITUTION:In order to produce a ternary or higher mixed crystal containing two homologous elements in a reactor by controlling the feeds of organic compound gasses to the reactor to the specific quantity by a mass flow controller MFC, the mutual feed ratio of the organic compound gasses to the homologous elements is specified but the feeds of these gasses are simultaneously increased more than the conventional feeds. Accordingly, the mixed crystallization can be performed assuming the output of MFC of the homologous elements in the low composition ratio as the value within the range of effective output of the MFC. Through these procedures, the precision in the reproducibility of the feed set up value can be enhanced thereby enabling the mixed crystal having excellent characteristics to be produced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a metal organic chemical vapor deposition method (hereinafter abbreviated as MOCVD method) for producing compound semiconductors and the like.

[Conventional technology]

In the MOCVD method, in the production of compound semiconductor crystals, a susceptor made of graphite or the like is installed in a reactor, a substrate is placed on the susceptor, an organic compound that is a component of the target crystal is supplied into the reactor, and high-frequency radiation is applied. A desired target crystal is grown by thermally decomposing these organic metals using a susceptor heated by a heating means such as a coil.

At this time, for example, when growing a compound semiconductor crystal such as GaAs, the growth rate is usually Ga or I? The rate is determined by the amount of supply.

In general, when growing the above-mentioned crystals, in order to maintain constant crystallinity, the growth rate must be maintained with good precision (constant).In other words, the supply amount of group (III) elements must be precisely controlled and kept constant. It won't happen.

By the way, AQGaAs and InGaA can be produced using the MOCVD method.
When growing compound semiconductor crystals such as s, group
The raw materials for a, AO, In) include trimethyl gallium (TMG), triethyl gallium (TEG),
Organic metals such as trimethylaluminum (TMA) and trimethylindium (TMI) are used, but
These are usually in liquid form. Therefore, in order to supply these raw materials to the reactor, these liquids are placed in a bubbler,
By supplying and bubbling a gas such as hydrogen or nitrogen into the raw material liquid in the bubbler, the organic metal is incorporated into this gas as saturated vapor, and this is carried out by supplying this gas to the reactor. ing.

Furthermore, as mentioned above, since it is necessary to precisely control the supply amount of Group III raw materials, the supply amount of hydrogen and other gases supplied to the bubbler is precisely controlled using a mass flow controller (hereinafter abbreviated as MFC). There is. MFC has made remarkable progress in both its response speed and the reproducibility of set values, and there are no problems at all in normal use.

However, in general, MFC is less than 5% of its maximum output and 95%
% or more, this was a problem because the reproducibility of the output was poor. Therefore, the effective output range for the reproducibility of set values is 5 to 95%.

For this reason, it is possible to control the output by increasing or decreasing the output by 5%, or by increasing or decreasing the output by 95%.
It was difficult to apply this method to gas lines that have to be controlled by raising and lowering it. Furthermore, since MFCs are expensive, it is economically disadvantageous to install multiple MFCs with different maximum outputs corresponding to different output ranges.

Next, MF when growing ternary or more mixed crystals by MOCVD method.
Looking at actual application examples of C, conventionally, for example, normal ACIG
In the case of aAs, the aluminum composition ratio varies depending on the device to be manufactured, but is generally in the range of 0.1 to 0.4.
In this range, the size of the MFC should be set so that the amount of bubbling gas to TMA, which is the raw material, is within the above effective output range of 5 to 95% when the output of TMG is constant. That's enough to deal with it.

However, in the epitaxial substrate of a heterojunction bipolar transistor (HBT), which has been attracting attention in recent years, the base layer has a composition that is gradually changed (i.e., X = 0 for AffgGa+-gAs crystal) in order to improve the device performance. −(), I) are essential.

Furthermore, in this case, X = 0.1 in the continuous emitter layer
Since an AQGaAs layer of −0.3 is also produced, the 10 composition must be changed within the range of 0≦X≦0.3.
Since the amount of bubbling gas that supplies the raw material TMA also needs to be changed significantly, the output of one MFC must be varied by 5% as described below. (low flow rate) was insufficiently controlled.

That is, the TM when manufacturing HBT by the conventional MOCVD method
MFC installed in G supply line and TMA supply line
Table 1 shows the output turn. As shown in the table, in order to fabricate the base layer AQ, Ga-, As(x = 0-(1,1) crystal under conditions that do not impair its crystallinity, the MFC output of TMA must be increased from 3% to Therefore, controlling a low output of 3 to 5% with one MFC is problematic as mentioned above, and furthermore, in general, MFC
Since there is a variation of about 1% in the output and a shift of the zero point, the reproducibility of the output of 3 to 5% was even worse.

Table 1 [Means for Solving the Problems] In view of this, the present invention has been made as a result of various studies. The present invention provides an organometallic vapor phase epitaxy method capable of obtaining mixed crystals with good properties.

That is, in the present invention, by controlling the amount of organic compound gas supplied to the reactor to a predetermined amount using a mass flow controller, a ternary or more mixed crystal containing two types of elements of the same group can be mixed at a predetermined composition ratio in the reactor. In the organometallic vapor phase epitaxy method for growing organic compounds of elements in the same group, the mutual supply ratio of organic compound gases of elements in the same group is kept constant, and by increasing the supply amount of these gases, organic compounds of elements with a small composition ratio among the elements in the same group can be grown. The mass flow controller of the supply line is operated within its effective output.

[Effect]

As described above, the present invention enables the production of a ternary or more mixed crystal containing two types of elements of the same group by the MOCVD method, when the composition ratio of these elements is small, and the supply line of the organic compound of this element is used. It is particularly effective when the output of the MFC must not be operated outside the effective output range. In other words, the mutual supply ratio of the organic compound gases of these homologous elements is kept constant, but at the same time the supply amount of these gases is increased. As a result, the output of the MFC of the same group element with a small composition ratio can be operated as a value within its effective output, which improves the accuracy of the reproducibility of the set value of the supply amount and produces mixed crystals with good characteristics. can get.

〔Example〕

Next, examples of the present invention will be described.

As shown in Table 2, in the fabrication of HBT, AO yo Ga+-+ As (x=0-
0.1) At the time of crystal production, by making the output of the MFC on the TMA supply side twice that of the conventional one (i.e. 6 to 40%), M
The output control range of the FC was always kept within 5% to 95% of the effective output of the device. The output of the MFC on the TMG supply side was also doubled compared to the conventional one so that the composition ratio of Ga and AQ would not change even if the amount of TMA supplied was doubled. Therefore, the base layer AQ, Ga
The growth rate of the +-jAs crystal has doubled compared to the conventional method.

In this way, since the output of any MFC was within the effective output of the apparatus, the reproducibility of the set value of the growth crystal composition was significantly improved.

After that, the emitter layer AQwGal, □, As (
x=0.1-0.3), the growth rate was returned to the conventional value as shown in Table 1, and the growth was performed under conditions favorable for crystallinity.

Table 2 Ru.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to control the composition over a wide range with one MFC in the MOCVD method, and it has remarkable effects such as improving device characteristics at low cost.

By increasing the growth rate of only the base layer in this way,
Although a decrease in crystallinity in the base layer may occur, judging from the characteristics of actually fabricated devices, the reproducibility of AQ composition control is more important than the decrease in crystallinity caused by changing the growth rate. Because the influence of was more significant, the characteristics improved overall.

Such a method of the present invention is applicable not only to A(71Gal-mAs but also to I nw Ga, -IAs, I n-
AO+-1As.

Claims (1)

[Claims] (1) By controlling the amount of organic compound gas supplied to the reactor to a predetermined amount using a mass flow controller, a ternary or more mixed crystal containing two types of elements of the same group is grown in the reactor at a predetermined composition ratio. In organometallic vapor phase epitaxy,
By keeping the mutual supply ratio of organic compound gases of these homologous elements constant and increasing the supply amount of these gases,
A metal organic vapor phase growth method characterized by operating a mass flow controller in a supply line for an organic compound of an element having a small composition ratio among homologous elements within its effective output.