JPH0446096A - Vapor phase epitaxy - Google Patents

Abstract

PURPOSE:To obtain mixed crystal layers having a satisfactory surface state and high intrasurface uniformity by controlling the number of rotations of a rotary susceptor fitted to a vapor growth device and the flowrates of gaseous starting materials so as to satisfy specified conditions. CONSTITUTION:Semiconductor substrates 4 are set on a rotary susceptor 3 fitted to the inside of a reaction tube 2, the susceptor 3 is rotated by a rotating mechanism 7 and plural kinds of gaseous starting materials are fed into the tube 2 and brought into a reaction to grow compd. semiconductor layers on the substrates 4 by vapor phase epitaxy. In this epitaxy, the number or rotations of the susceptor 3 and the flow rates of the gaseous starting materials are controlled so that the thickness of semiconductor layers grown per one rotation of the susceptor 3 is regulated to that of termolecular layers or below.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to epitaxial growth technology and a method for controlling the rotation of a susceptor in a gas phase acid susceptor having a rotating susceptor. law)
This invention relates to a technique suitable for use in epitaxially growing a -V group compound semiconductor mixed crystal.

[Prior art] As epitaxial growth wave +ff1j of compound semiconductor, VPE method (vapor phase epitaxial growth method) and MOCV
D method and MBE method (molecular beam epitaxial method) are known. Among these, the MOCVD method has good film thickness controllability and is suitable for mass production, so it is used for epitaxial growth of m-V group compound semiconductor confusion.

FIG. 1 schematically shows a compound semiconductor vapor phase growth apparatus. That is, in this vapor phase growth apparatus, a plurality of raw material gases introduced into the reaction tube 2 by the manifold 1 are
It flows down toward a substrate 4 placed on a barrel-shaped susceptor 3, is thermally separated on the substrate heated by a high-frequency coil 5, and an epitaxial layer is grown on the substrate.

In the above vapor phase growth apparatus, it is difficult to uniformly control the concentration and flow of the flowing source gas throughout the reaction tube, and if the flow is non-uniform, it is difficult to obtain uniformity of the epitaxial layer. Therefore, a method has been proposed in which epitaxial growth is performed while rotating the support shaft 6 that supports the susceptor 3 using the rotation mechanism 7.

[Problems to be Solved by the Invention] However, while rotating the susceptor using the above vapor phase growth apparatus, the MOCVD method is used to grow m-v group compound semiconductor mixed crystals such as GaIn, AsP, and A Q Ga As. When the surface of the mixed crystal layer was grown, it was found that in some cases it was a good mirror surface and in other cases it was in a cloudy state when the surface of the mixed crystal layer was observed with an optical microscope.

The present invention has been made to solve the above-mentioned problems, and its purpose is to: Surface morphology (
An object of the present invention is to provide a vapor phase growth technique for obtaining a mixed crystal layer with a good surface condition and high in-plane uniformity.

[Means for Solving the Problems] The present inventors analyzed the causes of poor surface conditions of compound semiconductor mixed crystals grown by vapor phase epitaxial growth using the MOCVD method. As a result, it was found that even if the thickness of the mixed crystal is uniform, if the composition deviates significantly from the desired composition, the surface becomes cloudy and the surface morphology deteriorates.

The cause of this is that the concentration and flow rate of the raw material gas in the reaction tube change over time, and that the concentration distribution and flow state are different in each part of the reaction tube. It was concluded that the crystal composition changes in the growth direction (composition fluctuation) and varies between substrates and within the plane of the substrate.

Therefore, we conducted experiments to find growth conditions that minimize fluctuations and variations in the mixed crystal composition. As a result, if the flow rate of the raw material gas and the rotational speed of the susceptor are controlled so that the number of mixed crystal layers grown during one rotation of the susceptor is 3 or less molecular layers, the variation in the mixed crystal composition can be suppressed to less than 4%. I found out that it is possible.

This invention was made based on the above knowledge, and consists of placing a semiconductor substrate on a support stand placed inside a reaction tube and rotated by a rotation mechanism, and transferring a plurality of raw material scraps into the reaction tube while rotating the support stand. In a vapor phase epitaxial growth method in which a compound semiconductor layer is grown on the substrate by flowing and reacting, - the number of rotations of the support is controlled such that the number of semiconductor layers grown per one rotation of the support is 3 or less molecular layers; This proposal proposes controlling the flow rate of raw material gas.

[Operation] According to the above-mentioned means, only a few molecules of the mixed crystal layer are grown during one rotation of the susceptor, so even if there is a fluctuation in the composition in the growth direction, the migration of molecules adsorbed to the substrate is prevented. The fluctuation of the composition is alleviated, and
Each substrate or each part of the substrate is exposed to gas of the same concentration and flow, improving the uniformity of the composition of the mixed crystal layer and providing good surface morphology.

[Example 1] As shown in FIG. 1, a GaInAsP mixed crystal layer was repeatedly grown on an InP substrate using a vapor phase growth apparatus having an f2 configuration and changing the flow rate of the source gas and the rotational speed of the susceptor.

In the apparatus used, the inner diameter of the reaction tube 2 was 12 cm, and the diameter of the susceptor 3 (wafer mounting part) was 10 cm.

Three InP substrates 4 with a diameter of 2 inches are placed on the susceptor 3.
The high frequency coil 5 heats the substrate surface to 625°C, and the inside of the reaction tube is heated to 76 t using the vacuum pump 8.
triethylgallium, trimethylindium, and arsine (A, 5)-1 from manifold 1 while pulling to orr.
) and phosphine (PH,) at a desired composition ratio (χ
=0.28. The flow rate of each raw material gas is determined and flowed so that y=Q, 61), and a thickness of approximately 2 p, m is deposited on the substrate surface.
(7) G axl n, -xA 5yP-y mixed crystal layer was grown.

After the growth was completed, the substrate 4 was taken out from the reaction tube 2 and the mixed crystal layer on the surface was observed using an optical microscope. The results are shown in FIG.

In Figure 2, the horizontal axis represents the rotational speed of the susceptor 3, and the vertical axis represents the growth rate. The mixed crystal layer with good surface morphology is marked with an ○, and the surface morphology is poor. Each item is indicated by a Φ symbol.

From the figure, it can be seen that a mixed crystal layer having good surface morphology can be obtained when the growth rate per rotation of the susceptor is three molecular layers or less.

Further, for the samples indicated by symbols A, B, C, and D in FIG. 2, the composition of the mixed crystal layer was analyzed by photoluminescence and double-crystal X-ray diffraction, and the variations thereof were calculated.

The composition analysis was performed at a total of 17 points at 5M intervals from the center of the substrate along two orthogonal axes passing through the center of the substrate, and the deviation from the target composition ratio was calculated as a percentage for each of x and y. did. The results are shown in Table 1.

It can be seen from Table 1 that by setting the growth rate of the mixed crystal layer to 3 molecular layers or less per rotation of the susceptor, the in-plane variation in composition ratio can be suppressed to less than 4%.

In the above embodiment, GaIn is deposited on the In, P substrate.
Although the case where the AsP mixed crystal layer is epitaxially grown by the MOCVD method has been described, the present invention is not limited thereto, and when growing an AQGaAs mixed crystal layer on a GaAs substrate. It can be generally applied to epitaxial growth.

[Effects of the Invention] As explained above, the present invention has the following advantages:
In a vapor phase epitaxial growth method, a semiconductor substrate is placed on a support that is rotated by a rotation mechanism, and a plurality of raw material gases are caused to flow and react in a reaction tube while rotating the support to grow a compound semiconductor layer on the substrate. The number of rotations of the support and the flow rate of the raw material gas are controlled so that the number of semiconductor layers grown per one rotation of the support is 3 or less, so that the mixed crystal is grown during one rotation of the susceptor. Since only a few molecules of the layer are grown, even if there is a fluctuation in the composition in the growth direction, the fluctuation in the composition is alleviated by the migration of the molecules adsorbed to the substrate, and each substrate or each part of the substrate has the same concentration. By being exposed to the flowing gas, the uniformity of the composition of the mixed crystal layer is improved, resulting in the effect that good surface morphology can be obtained.

[Brief explanation of drawings]

Figure 1 is a schematic diagram showing an example of a vapor phase growth apparatus suitable for applying the method of the present invention, and Figure 2 is an MOC of a Ga1nAsP mixed crystal layer on an InP substrate.
It is a graph showing the correlation between the susceptor rotation speed and growth rate and the surface state of a mixed crystal layer when grown by the VD method.

Claims (1)

[Claims] (1) A semiconductor substrate is placed on a support stand placed in a reaction tube and rotated by a rotation mechanism, and while the support stand is rotated, a plurality of raw material gases are caused to flow into the reaction tube to react, and a compound semiconductor is placed on the substrate. In the vapor phase epitaxial growth method for growing a layer, the rotation speed of the support table and the flow rate of the source gas are controlled so that the semiconductor layer grown per one rotation of the support table is 3 molecular layers or less. Characteristic vapor phase epitaxial growth method.