JPH0316993A - Vapor-phase epitaxial growth of compound semiconductor - Google Patents

Abstract

PURPOSE:To grow an epitaxial layer on the whole surface uniformly and densely and to reduce surface roughness of growth layer in growing mixed crystal having a lattice constant different from that of substrate crystal in vapor phase on the substrate of compound semiconductor by using a substrate having specifically deviated plane orientation of surface. CONSTITUTION:A substrate 5 of compound semiconductor (e.g. GaAs substrate) having plane orientation of surface deviated 0.5-10 degrees in the direction from plane (100) to [001] or [010] is arranged at the downstream of a reaction tube 1. A boat 4 having stored a raw material 3 (e.g. gallium) is arranged at the upper stream of the reaction tube 1. Then the reaction tube 1 is heated by an electric furnace 2, other raw materials 8a (e.g. AsCl3) and 8b (e.g. PCl3) are transferred to the reaction tube 1, reacted with the raw material 3 and mixed crystal (e.g. GaAsP) having a lattice constant different from that of substrate crystal is subjected to vapor-phase epitaxial growth on the substrate 5 to obtain a growth layer of few crystal defects.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an epitaxial elongation technique on semiconductor wafers, and in particular to the method of elongating mixed crystals on compound semiconductor single crystal wafers having a zincblende crystal structure. This article relates to effective techniques for use in vapor phase growth.

[Prior Art] Conventionally, mixed crystal wafers such as GaAsP are
a On the A s substrate, hydride CVD method or active compound CvD method is applied.
The tb group-
In order to control the surface condition of the epitaxial growth layer during vapor phase growth of a wafer that serves as a substrate for a VB quaternary mixed crystal, a method has been proposed in which the longitudinal plane of the wafer is slightly tilted. (Unexamined Japanese Patent Publication No. 60-71599).

-However, when a mixed crystal epitaxial layer is grown on a compound semiconductor substrate, defects are likely to occur on the surface of the Kaincho layer due to the Sako mismatch. Therefore, a buffer layer whose composition ratio gradually changes is provided between the substrate and the mixed crystal epitaxial layer, but even if such a composition gradient layer is provided, surface defects cannot be completely eliminated.

[Problems to be Solved by the Invention] The above-mentioned prior invention solves the problem of surface roughness caused by a striped pattern called a crosshatch that appears on the surface of a grown layer during vapor phase elongation of a wafer that serves as a substrate for a quaternary mixed crystal wafer. The purpose is to reduce the surface roughness of the growth layer, and the appearance of the striped pattern itself indicates that the surface roughness of the growth layer is large.

This invention was made against the above background, and its purpose is to improve the surface of the grown layer when growing a mixed crystal epitaxial layer with different lattice constants on a compound semiconductor substrate. An object of the present invention is to provide a vapor phase epitaxial growth method that can reduce roughness.

[Means for Solving the Problems] In order to achieve the above-mentioned object 1), the present invention provides a technique for changing the surface orientation of the substrate surface when growing mixed crystal epitaxial layers with different lattice constants on a semi-quadram compound substrate. From the (100) plane [0
0 1] direction or [0 1 01 direction, or from a plane crystallographically equivalent to the (100) plane to the [00 direction] direction or the direction equivalent to the [0 1 0] direction regarding the (100) plane. A substrate deviated by 5 to 10 degrees was used, and a mixed crystal epitaxial layer was formed on the surface of the substrate.

Further, the direction of deviation of each of the above-mentioned surfaces is not limited to the designated direction, but may be any direction within ±30° of the designated direction.

[Function] The reason for the above method is that because the growth plane of the epitaxial layer is tilted, the edges of the element layers constituting the crystal lattice appear on the substrate surface in a step-like manner, and the epitaxial layer is elongated using these as seeds. Cheating. Moreover, since the inclination is set to 0.5 to 10 degrees, the epitaxial layer is uniformly and densely elongated over the entire surface, and defects are less likely to occur. In other words, the slope is 10"
If the slope exceeds 0.5°, there will be too many edges of the atomic layer to serve as seeds, resulting in a large number of various types of defects; if the slope is less than 0.5°, parts other than the edges of the atomic layer will randomly become seeds, causing Since the sites where . Furthermore, since the direction of deviation of the plane orientation is limited, the crosshatch on the surface of the epitaxial layer becomes weaker, and the surface roughness is reduced.

[Example] FIG. 1 shows an example of a vapor phase growth apparatus used in the vapor phase epitaxial growth method according to the present invention.

This vapor phase elongation device consists of a cylindrical quartz reaction tube 1 with both ends closed, and an electric furnace 2 that heats the reaction tube 1 from the outside. It is designed to control directional temperature distribution. When GaAsP is vapor-phase epitaxially elongated using this gas-phase elongation device, a raw material boat 4 containing gallium 3, which is a material source, is arranged on the upstream side (left side in the figure) in reaction v1, and A GaAs substrate 5 to be subjected to vapor phase elongation is placed.

On the other hand, a first gas introduction pipe 6a is connected to the upstream end of the reaction tube 1 to bypass the raw material boat 4 and supply gas upstream of the substrate 5. Further, at the upstream end of the reaction tube 1, there is a second gas introduction pipe 6b for supplying gas to the raw material boat 4, and a third gas conduit 4? A pipe 6c is connected.

In the middle of the gas introduction pipes 6b and 6c, there are bubblers 8a containing A s C n and PCQ:l, respectively.
8b is interposed. -H in the gas introduction pipes 6b and 6c
A.2 gas is introduced, and by blowing H2 gas into the bubblers 8a and 8b, A.2 gas is introduced. Id is set so that a mixed gas of s C Q and PGQ3 can be supplied into the reaction tube 1 using H2 as a carrier. Also, bubbler 8 a,'
8b was placed in a temperature-controllable constant-wet tank (as shown), and by controlling the temperature, the amount of evaporation of AsC and pcu3 was controlled.

Note that 7a, 7b, and 7c are mass flow controllers for controlling the flow rate, and 9 is an exhaust pipe connected to the downstream end of the reaction tube 1.

Figure 2 shows the temperature distribution on the reaction tube. The electric furnace 2 controls the temperature of the raw material boat section 4 to 870° C. and the humidity of the GaAs i & board 5 to 790° C. <fil1'.

Using the above apparatus, a GaAs substrate whose plane orientation is deviated by 2 degrees from the (100) plane in the [○OI] direction is set in the reaction tube 1, and then the mass flow controller 1 is placed in the mass flow controller 1. A at la 7b, 7c
The molar ratio of s C Q , and PCQ3 PC Qa/ (
P C Q3 + A s C Q3) from O to 0.38
GaAS substrate 5
After first lengthening a 3 μm GaAs buffer on top,
A 50 μm thick G a As P composition gradient layer was formed, and a G a S u . 6■Pa. A constant composition layer of a8 was grown to a thickness of 50 ILm.

FIG. 3(a) shows the results of measuring the surface roughness of the epitaxial growth layer of the wafer obtained by the above method. For comparison, the plane orientation of the substrate surface was determined by the same method (
100) Ga tilted 2 degrees in the [0 1 I] direction from the plane
Figure 3 (b) shows the measurement results of the surface roughness when the GaAsP epitaxial width is made to have a certain length on the As substrate.
).

From Figure 3, when using a substrate whose plane orientation is tilted from the (100) plane to the [OO■] direction, the surface roughness is approximately 30OA/
It can be seen that the surface roughness is considerably smaller than 90OA/200μm when a substrate tilted in the OII direction is used.

Furthermore, the direction of the deviation of the substrate surface is ( ]. O O )
Table 1 shows the results of determining the surface roughness as IFLL1 for G a As P epitaxial layers grown on substrates varying in angle from the surface within the range of [00■] ±45°.

From Table 1 above, the direction of deviation is ±30″ from the [OOI] direction.
If it is within this range, the surface roughness can be suppressed to 45OA/200μm (half of the conventional level) or less.

Note that even when the direction of deviation is other than the [0 0 I] direction, the same effect can be obtained as long as it is within the range of ±30'.

Further, the present invention can be used for ebitaxial lengthening of ternary and quaternary mixed crystals other than GaAsP.

[Effects of the Invention] As explained above, the present invention has the advantage that when growing a mixed crystal epitaxial layer having a different lattice constant from that of the substrate crystal on a compound semiconductor ~7 substrate, the plane orientation of the substrate surface is set to (100).
From the [00I] direction or [01.0] direction; or from a crystallographically equivalent plane to the (100') plane. (1.
Since we used a substrate that was deviated by 0.5 to 10 degrees in the [OOI] direction and the direction equivalent to the [0 1 0] direction with respect to the grows, crystal defects decrease, and
This has the effect of weakening the crosshatch on the surface of the oblong layer and reducing surface roughness.

[Brief explanation of drawings]

Fig. 1 is a longitudinal sectional front view showing an example of a vapor phase growth apparatus used in the vapor phase epitaxial growth method of compound semiconductors according to the present invention, Fig. 2 is a graph showing the temperature distribution of the reaction tube, and Fig. 3 (
a) is a graph showing the measurement results of the surface roughness of the epitaxial growth layer obtained by the method of the present invention, and FIG. 3(b) is a graph showing the surface roughness of the epitaxial growth layer obtained by the conventional method. These are graphs showing measurement results. 1...Reaction tube, 2...Electric furnace, 4...Raw material boat, 5...Substrate.

Claims (2)

[Claims] (1) When vapor-phase growing a mixed crystal with a different lattice constant from the substrate crystal on a compound semiconductor substrate, the surface orientation is (1).
A method for vapor phase epitaxial growth of a compound semiconductor, characterized in that a substrate is deviated by 0.5 to 10 degrees in the [00@1@] direction or the [010] direction from the 00) plane. (2) When vapor-phase growing a mixed crystal having a different lattice constant from that of the substrate crystal on a compound semiconductor substrate, use any substrate within a range of ±30° from each direction specified in claim 1 above. A method for vapor phase epitaxial growth of compound semiconductors, characterized by: