JPH0318016A - Vapor growth apparatus for iii-v compound semiconductor crystal - Google Patents

Abstract

PURPOSE:To control the thickness and the composition of an epitaxial layer at the specified values with good reproducibility by adding a path which can keep the amount of supply of a group III raw material constant to an apparatus. CONSTITUTION:In a vapor growth apparatus, a path is provided between a flow control for a group III raw material gas and a reaction chamber. The path includes an amplifier and an analyzer and it provides feedback control to maintain a constant flow of the material gas. Namely, in the path between the flow control 8 and the reaction chamber 7, the amplifier 15 and the mass analyzer 16 operate to feed back the result of the gas analysis to the flow control 8. Therefore, the gas which is sent into the reaction chamber is sampled at any time by the operation of a valve, and the composition is analyzed. The result can be fed back immediately to the flow control for the group III raw material gas. Thus, the amount of supply of the group III raw material gas is kept always constant without fluctuating. The thickness and the composition of a grown crystal layer can be controlled at the specified values with good reproducibility.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an apparatus for vapor phase growth of crystals of m-v group compound semiconductors. [Prior Art] Ebitaxial crystal growth is one of the extremely important processes in producing compound semiconductor crystals used in semiconductor laser devices with fine structures. The epitaxial crystal growth method is the vapor phase growth method. The liquid phase growth method and the molecular beam epitaxy method are used, but with the vapor phase growth method, it is relatively easy to control the thickness of the vapor growth layer, the carrier concentration by adding impurities, or the composition. Because of these advantages, it has become widely used as a crystal growth method not only for two-element ■-V group compound semiconductor crystals such as GaAs and InP, but also for three-element or four-element compound semiconductor crystals. FIG. 2 is a schematic system diagram of a typical vapor phase growth apparatus for, for example, GaAs crystal. In FIG. 2, a bubbler 2 houses trimethyl gallium (hereinafter referred to as TMG) 1, an alkyl compound, which is a group II liquid raw material. TMCI is bubbled using the transport gas, and then arsine (AiHi) gas 5, H8, which is a hydride that becomes the group V raw material, is contained in gas cylinder 4.
The diluting gas is supplied to the reaction vessel 7 by opening the air valve 6. Each gas flow rate is determined by a flow rate controller 8. 9.
It is controlled by 10. Inside the reaction vessel 7, a crystal substrate 11 is placed on a susceptor 12, and the crystal growth temperature can be adjusted by a radio frequency (RF) coil l3 provided around the outer periphery of the reaction vessel 7. The raw material gas sent to the reaction vessel 7 causes a combination reaction on or near the substrate crystal 11 in the reaction vessel 7, and the crystal substrate 11
Ebitaxial growth on top. Excess gas is discharged to the outside through the air valve 14. Through the above process, the thickness of the epitaxial crystal layer and
As for the l1 precept, it is strongly dependent on the supply amount of TMGl, which is the raw material of group Ⅰ, so the amount of transport gas, vapor pressure, bubbling pressure, etc. are controlled by flow rate controller 8, constant temperature layer 3. This is controlled using a pressure adjustment needle (not shown). [Problems to be Solved by the Invention] However, when crystal lengthening of an m-v group compound semiconductor is performed using the vapor phase lengthening method, the following problems still occur. Even if the supply amount of the alkyl compound is controlled in the above manner, the amount of raw material supplied may decrease due to a drop in the liquid level of the bubbler 2 caused by a decrease in the amount of raw material, or it may occur due to the control accuracy of various adjustment needles. Short-term or long-term fluctuations in the thickness of the crystal growth layer and the strength of the crystal growth layer due to fluctuations in the amount of raw material supplied cannot be avoided, and this is undesirable as an apparatus for mass-producing compound semiconductor crystals.
The present invention has been made in view of the above points, and an object thereof is to reliably control the flow rate of the raw material gas and determine the supply amount of the raw material gas with good reproducibility, thereby increasing the thickness of the crystal growth layer. The purpose of this invention is to provide a vapor phase growth modification that can always maintain a stable state. [Means for Solving the Problem] In order to solve the above-mentioned problem 111111, m-v of the present invention
The gas phase lengthening device for group compound semiconductors is connected between the flow rate controller of the group II raw material gas used in this device system and the reaction vessel, and is capable of feedback to keep the flow rate of the group III raw material constant.
It has a path consisting of an amplifier and an analyzer. [Function] By arranging the apparatus of the present invention as described above, the gas sent to the reaction vessel is sampled at any time by the analyzer by operating the valve, and analyzed by the analyzer, and the results are sent to the flow rate controller for the group material gas. Since it is possible to immediately feed back the amount of Group I raw material gas, it is always kept constant and does not fluctuate, and the thickness of the crystal growth layer can be adjusted. It is possible to control parameters such as power to predetermined values with good reproducibility. [Examples] The present invention will be explained below based on Examples. FIG. 1 is a system diagram showing the vapor phase lengthening device for m-v group compound semiconductors of the present invention together with each component, and parts common to those in FIG. 2 are indicated by the same symbols. The difference between FIG. 1 and FIG. 2 is that in the reinstallation of the present invention, an amplifier 15 and a mass spectrometer 16 provided between the flow rate controller 8 and the reaction vessel 7 transmit the gas analysis results to the flow rate controller 8. It is important to have a route through which feedback can be provided. Next, the procedure for vapor phase growth of, for example, Ga^3 crystal using the apparatus shown in Fig. 1 will be described. H8 bubbles TMG 1 whose temperature is kept at -8℃ by constant temperature layer 3
GaA'a
However, before the crystal growth, the air valve 14 is
．． 6 are opened and closed, respectively, the flow rate setting value of the flow rate controller 8 is set to 15.0 cc/min, and TMG l is bubbled.・The air valve 17 belonging to the mass spectrometer 16 is opened, and a predetermined amount of gas is introduced. Sample. Then, the concentration of TMG 1 is measured using the mass spectrometer 16, and T
By feeding back to the flow rate controller 8 via the amplifier 10 so that the supply amount of MG1 is obtained,
Determine the true value of the flow rate of G1. After this, the crystal growth process begins, but at this time the valve operation is reversed and the air valves 14 and 6 are closed and opened, respectively. Here, the liquid level height of TMG 1 from the bottom of bubbler 2 is 100 m.
, 50 m, the GaAs obtained with each device is compared between the device of the present invention in which the flow rate controller 8 is fed with a feedbank so that the flow rate of TMCl is constant, and the conventional device in which this is not done. Table 1 shows the results of determining the crystal growth speed of . In both cases, the flow rate was 1t) The setting value for the 1st meter 8 was 15.0cc/min. Table 1 From Table 1, it can be seen that in the device of the present invention capable of feedback that controls the flow rate of TMG 1 at a constant level, the crystal growth rate of GaAs maintains an almost constant value without depending on the liquid level height of TMG 1. It can be seen that From the above, T
A decrease in the liquid level height of MG 1 means a decrease in the transport amount of TMG 1 due to bubbling, and when TMG 1 is used as a raw material, the GaAs crystal length chain is It can be seen that the thickness of the epitaxial growth layer gradually decreases along with this. From this point of view as well, it is clear that the feedback effect provided by the device of the present invention is effective. Here, as an example, we have shown the influence of changes in the liquid level height of TMG 1 on the crystal growth rate of GaAs.
Other mixed crystal compound semiconductors such as InGaAsP and InGaAjP systems also have problems such as fluctuations in crystal growth rate and changes in composition, and the use of the device of the present invention is effective for these problems as well. be. In addition, it goes without saying that the apparatus of the present invention works effectively against fluctuation factors in the raw material supply amount other than the raw material liquid level of group (I) elements. [Effects of the Invention] Conventionally, vapor phase growth equipment for Iff-V group compound semiconductors has been used for
Although the thickness of the obtained epitaxial growth layer was unstable, in the present invention, as described in the examples, a path was added to the equipment system that could keep the supply amount of the group (III) raw material constant9. By doing this, the thickness and strength of the ebitaxial stratum can be controlled to predetermined values with good reproducibility.

[Brief explanation of the drawing]

FIG. 1 is a system diagram showing the vapor phase growth apparatus of the present invention together with each component, and FIG. 1. It is a system diagram showing a conventional vapor phase growth apparatus along with each structural part. 1: TMG, 2: Bubbler 3: Tsunehachi layer, 4: Gas cylinder, 5: Arsine gas, 6.14.17: Air valve, 7: Reaction vessel,
a, 9, to: flow f controller, 1l two-substrate crystal, 12: susceptor, l3: high frequency coil, 15: amplifier, l6:
Mass spectrometer. Figure 1 Figure 2

Claims (1)

[Claims] 1) A group III element alkyl compound raw material and a group V element hydride raw material, whose flow rates are adjusted respectively, are supplied by a transport gas into a reaction vessel in which a substrate crystal is placed, and the III-V group compound is placed on the substrate crystal. An apparatus for vapor phase growth of a semiconductor, comprising an amplifier connected between a flow rate controller for the alkyl compound raw material of this apparatus system and the reaction vessel, and a mass spectrometer for measuring the concentration of the alkyl compound. A vapor phase growth apparatus for III-V compound semiconductor crystal, characterized in that it has a feedback path that keeps the supply amount of the alkyl compound raw material constant.