JPS6020509A - Liquid phase epitaxial growth method - Google Patents

Abstract

PURPOSE:To form a thin epitaxial growth layer at low cost by uniformly forming a polycrystalline layer having the same quality of material as an epitaxial growth substrate or the same quality of material as a semiconductor growing solution on the surface of a blank substrate not dissolved to the semiconductor growing solution and using the polycrystalline layer as a seed crystal. CONSTITUTION:A seed crystal board 10 is set at the predetermined position of a carbon board 3. Gallium arsenide and aluminum and a dopant are dissolved into gallium, and a semiconductor solution 4 is creeped under the seed crystal substrate 10 with a polycrystalline layer 12 consisting of gallium arsenide when the temperature of the semiconductor solution 4 is dropped to the saturation point or lower of a solute to a solvent. Consequently, the surface of the polycrystalline layer 12 has the same composition as the semiconductor solution. Since the deposition of aluminum gallium arsenide is generated to the polycrystalline layer 12 from the semiconductor solution 4 by slowly dropping the temperature of a furnace and the thickness of the deposition is thin, the semiconductor solution is equalized rapidly, and the degree of supersaturation is kept at a fixed value at all times. The thickness of a thin growth layer can be controlled by bringing a substrate 5 for epitaxial growth into contact with the semiconductor solution 4 under said state.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of the Invention] The present invention relates to a liquid phase epitaxial growth method, and more particularly to a liquid phase epitaxial growth method using an improved seed substrate for liquid phase epitaxial growth.

[Prior art]

Conventionally, a semiconductor substrate on which an epitaxial layer is formed by a liquid phase epitaxial growth method is used for manufacturing optical semiconductor devices. In these liquid phase epitaxial growths, it is necessary to grow a thin layer of about 0.1 μm with good reproducibility. That is, the growth rate of epitaxial growth must be controlled with good reproducibility.

In liquid phase epitaxial growth, the growth rate largely depends on the degree of supersaturation of the solute with respect to the solvent. One way to control the degree of supersaturation is to charge an amount of solute that exceeds the amount that dissolves in the solvent. There is a method of growing by keeping the seed crystal floating above the liquid, but this increases the degree of supersaturation, increases the initial growth rate of the epitaxial layer, and makes it difficult to obtain uniformity of the solution. ,
Forming thin and uniform epitaxial layers is difficult.

Another method is to contact the seed crystal with the semiconductor solution immediately before contacting the growth substrate with the semiconductor solution to reduce the initial supersaturation level, but it is difficult to obtain a thin epitaxial layer with a uniform composition. .

As a third method that has improved these problems, a method has been used in which a seed crystal is placed on top of a thin semiconductor solution to control the semiconductor solution.

1 to 3 are explanatory diagrams for explaining the third method. FIG. 1 shows a seed crystal substrate l used in this method, and a single crystal substrate having the same composition as the normal growth substrate is used.

As shown in FIG. 2, a semiconductor solution 4 having the composition of an epitaxial layer to be formed at a predetermined position of the carbon boat 3
If is disposed, and the seed crystal substrate 1 is disposed above in contact with the semiconductor solution. As a result, the degree of supersaturation of the semiconductor device 4 becomes a constant value after a certain period of time. Next, the temperature of the furnace is gradually lowered, and after a certain period of time, the carbon boat 3 is slid, the epitaxial growth substrate 5 is brought under the semiconductor solution 4 as shown in FIG. 3, and the temperature of the furnace is gradually lowered. As a result, a supersaturated epitaxial component is precipitated from the semiconductor solution 4 toward the seed crystal substrate l, and the degree of supersaturation of the semiconductor solution 4 is always kept at a constant value. By contacting! The thickness of the grown layer can be controlled as thin as about 70.1 μm.

However, as described above, the seed crystal substrate used in this growth method is the same single crystal substrate as the growth substrate. Once this seed crystal substrate has been subjected to the epitaxial process, it can be used only a few times after polishing and cleaning the surface. Moreover, since the epitaxial layers required for semiconductor devices usually need to be formed in multiple layers, many single-crystal substrates are required to manufacture one growth substrate, and since single-crystal substrates are very expensive, A drawback is that the unit cost of the substrate on which the epitaxially grown layer used for semiconductor devices is formed is extremely high.

[Purpose of the invention]

An object of the present invention is to provide a liquid phase epitaxial growth method that eliminates the above-mentioned drawbacks and can form a thin epitaxial growth layer at low cost.

[Structure of the Invention] The epitaxial growth method of the present invention includes a liquid phase method in which an epitaxial growth substrate is brought into contact with a semiconductor growth solution whose composition is controlled by bringing a seed crystal plate into contact with a molten semiconductor growth solution to form an epitaxial layer. In the epitaxial growth method, if the surface of the substrate is made of the same material as the epitaxial growth substrate and is not dissolved in the semiconductor growth solution, a polycrystalline layer made of the same material as the semiconductor growth solution is uniformly formed, and the polycrystalline WJ is used as a seed crystal. It can be used as i'/f.

[Explanation of Examples]

Next, there are cross-sectional views showing the non-inventive embodiment in the order of steps for reference to all the drawings. In this embodiment, a case will be described in which aluminum gallium arsenide is grown using gallium arsenide as a growth substrate.

FIG. 4 is a sectional view of a seed crystal plate used in the present invention. The material substrate 11 is a plate made of a material that does not dissolve in a semiconductor solution, for example silicon carbide, and has a thickness of approximately 1y+m.One surface of the material substrate 11 of C is made of a gallium arsenide film made of the same material as the epitaxial growth substrate. The polycrystalline layer forming the crystal layer 12 is, for example, ML) CV D (Me
tal Qrganic Chemical Vapor
By using a deposition method or the like, it can be formed relatively easily and uniformly with good reproducibility.

The polycrystalline layer 12 may be formed of the same material as the semiconductor solution used for epitaxial growth, in this embodiment aluminum gallium arsenide.

Next, as shown in FIG. 5, the seed crystal plate 1o is set at a predetermined position on the carbon boat 3. After dissolving gallium arsenide, aluminum, and a dopant into gallium and lowering the temperature to below the saturation point of the solute in the solvent, the semiconductor solution 4 is applied to a seed crystal substrate 1 having a polycrystalline layer 12 of gallium arsenide.
Slip it under 0. As a result, the seed crystal plate 10 will be in contact with the top of the thinly formed semiconductor solution 4. At this point, the semiconductor solution 4 is slightly supersaturated, so the polycrystalline gallium arsenide is transferred from the seed crystal substrate lO. However, no solution is released, and on the contrary, aluminum gallium arsenide is precipitated from the semiconductor solution 4 for each polycrystalline gallium arsenide 1 and 12. That is, the surface of the polycrystalline gallium arsenide layer 12 has the same composition as the semiconductor solution. If this state is maintained for a certain period of time, the degree of supersaturation of the semiconductor solution 94 becomes a constant value.

Next, as shown in FIG. 6, the temperature of the furnace is gradually lowered, and after a certain period of time, the carbon boat 3 is slid to move the epitaxial growth substrate 5 under the semiconductor solution 4.

During this time, by gradually lowering the temperature of the furnace, aluminum gallium arsenide is precipitated from the semiconductor solution 4 to the polycrystalline gallium arsenide layer 12, and since the thickness of the semiconductor solution 4 is thin, the semiconductor solution may be made uniform. To proceed quickly,
The degree of supersaturation of the semiconductor solution 4 is always maintained at a constant value. By bringing the epitaxial growth substrate 5 into contact with the semiconductor solution 4 in this state, a thin growth layer of about 0.1 μm can be grown! lI can be legged.

The material substrate of the seed crystal plate used in this example is mechanically stronger than the commonly used gallium arsenide substrate.
Further, the dimensions can be freely selected, and the polycrystalline layer can be easily removed by etching after the seed crystal plate used in this embodiment has been used for one growth. Furthermore, it is possible to deposit a large amount of polycrystalline layers on the material substrate at one time.

Therefore, by using the above seed crystal plate, liquid phase epitaxial growth can be performed at low cost and with good controllability.

In the above embodiments, a gallium arsenide-based material has been described, but similar effects can be obtained when an fnP-based material is used.

On the other hand, silicon carbide was used as a material that does not dissolve in solvents, but carbon and alumina were also used.

It is also possible to use silicon nitride or the like.

In addition to the above-mentioned MUCVD method, the polycrystalline layer of the substrate material or the growth material can be formed using MBE (Mole-cul-de-coupling method).
It is clear that the same effect can be obtained when the film is formed by a method such as ar beam epitaxy) or vapor deposition.

〔Effect of the invention〕

As explained above, according to the present invention, the degree of supersaturation of an epitaxially grown semiconductor solution can be easily controlled, the productivity is excellent, and a substrate on which an epitaxial layer is formed for an optical semiconductor device can be easily produced at a low production cost. I can do it.

[Brief explanation of the drawing]

They are sectional views shown in the order of steps for detailed explanation of the present invention. 1... Seed crystal plate, 3... Gallium arsenide seed crystal plate, 4... Semiconductor. Seikai FE, 5...
...Substrate for epitaxial growth, 10...Seed crystal plate, 11...Material substrate '1-12...
...polycrystalline layer, A

Claims (1)

[Claims] In a liquid phase epitaxial growth method in which an epitaxial growth substrate is brought into contact with a semiconductor growth solution whose composition is controlled by contacting a seed crystal plate with a molten semiconductor growth solution to form an epitaxial layer, a material substrate that does not dissolve in the semiconductor growth solution. A liquid phase epitaxial growth method, characterized in that a polycrystalline layer made of the same material as the epitaxial growth substrate or the semiconductor growth solution is uniformly formed on the surface, and the polycrystalline layer is used as a seed crystal plate.