JPS60144933A - Liquid phase growth apparatus - Google Patents

Abstract

PURPOSE:To realize uniform liquid phase epitaxial growth with good reproducibility by providing an engaging cover to a solution pot of solvent and attaching a source wafer in almost the same area as liquid pot at the lower part of cover. CONSTITUTION:An InP substrate 2 is placed on a slider 1 and a bath plate 3 is placed thereon. The measured source In 4 is put in the bath 5 and an InP sheet wafer 7 is inserted to the lower part of cover 6 and is engaged with the source 4. The source 4 melts and forms a film in the thickness determined by a predetermined value. A solute is saturated for solution by keeping the source to a constant temperature. When temperature is lowered at a constant rate, the solute starts to be precipitated on the wafer 7, excessive saturation degree in the solution 8, 9 becomes the maximum at the surface of slider 1, the excessive saturation degree is determined by transfer of solute in accordance with a gradent of concentration an it is proportional to the square of thickness of liquid at the slider surface. In this way, excessive saturation degree of In solution 8, 9 is adjusted at the slider surface and when a multi-layer epitaxial growth is realized on a substrate 2 by moving the slider under the steady state, the optimum condition of growth can be obtained and thereby reproducibility can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to an apparatus for growing a liquid phase epitaxial layer used in optical semiconductor devices and the like.

[Background of the invention]

Optical semiconductor devices are also at the stage of practical application, and there is a strong demand for stability, that is, uniformity and reproducibility of p1 liquid phase growth.

Conventionally, as a method to improve the uniformity and reproducibility of liquid phase growth, a seed wafer similar to the substrate is placed in a carbon port, and a solution with a uniform thickness is formed between the substrate and the seed wafer. In other words, an overseeding method was used. As a result, the degree of supersaturation of the solution is kept at an appropriate value and the thickness of the solution is also made uniform, so that a uniform growth layer can be obtained with good reproducibility. However, this method has the disadvantages that the carbon boat becomes messy and easily damaged, and has a short lifespan. It also has the disadvantages of instability due to the introduction of melt into the narrow gap between the substrate and the seed wafer. It has the disadvantage that the interval cannot be changed arbitrarily. Another method is to control the degree of supersaturation by adding an excess of source wafers to create a state where the seed wafer is on top of the solution. If the liquid thickness becomes uneven, a uniform growth layer cannot be obtained.

[Purpose of the invention]

An object of the invention is to provide an apparatus which has a simple structure and is capable of liquid phase epitaxial growth with good uniformity and reproducibility.

[Structure of the invention]

The present invention has a structure in which a fitting lid is attached to a solution reservoir containing a solvent, a source wafer having an area close to that of the solution reservoir is attached to the bottom of the lid, and the source wafer is in full contact with the solution. It is characterized by having the following.

In liquid phase growth, the saturation state of the solute in the solvent is one of the most important factors. Generally, when kept at Seki temperature,
The water remains close to saturation, and as the temperature begins to drop, it becomes supersaturated.

Constituent length is initiated by contacting the substrates in a supersaturated state. At this time, when the degree of supersaturation is low, the growth rate is low and it is easy to grow a thin layer, whereas when the degree of supersaturation is high, the growth rate is high and it is difficult to grow a thick layer. Further, the higher the degree of supersaturation, the less likely deformation of the processed shape provided on the substrate occurs.

〔Example〕

Next, embodiments of the invention will be described in detail with reference to the drawings. As an example, a case will be described in which an epitaxial layer of a double heterostructure with grooves buried therein is continuously grown in a liquid phase on an InP substrate with grooves dug therein.

That is, as shown in FIG. 1, a pre-treated lnP substrate 2 is placed at a predetermined position on a carbon slider plate 1.
and place the carbon bathtub plate 3.

A pre-weighed source such as ln4 is poured into a predetermined bathtub 5. Next, an lnP seed wafer 7 is inserted into the lower part of the carbon lid 6 that fits into the bathtub 5.
These are processed into various types. Pour over sauce 4. If you put it in a furnace in this state and raise the temperature, as shown in Figure 2,
■. Sauce 4 is melted to a liquid thickness determined by the lid of each sauce. By keeping the temperature in this state for a while, the seed wafer 7 of 9 Inl' is partially processed.

Dissolve in sauce 4. This shows that for the solvent In, the solute P
is almost saturated.

The thickness of the solution 8 in the first bath shown in FIG. 2 is 3 mm.

The liquid thickness of the solution 9 in the second bath is 2 mm, and each solution maintains a uniform thickness with the remaining seed wafer 7 placed thereon. In this state, the temperature of the furnace is lowered at a rate of 0.5°C/min. P in the In solution (8°9) exceeds the saturation point and becomes supersaturated.

■. P, which has become supersaturated in the solution 8.9, begins to precipitate on the seed wafer 7. Therefore, the degree of supersaturation near the seed wafer 7 becomes a very small value, and the further away from the seed wafer 7 the more the degree of supersaturation in the In solution 8.9 increases, reaching a maximum on the surface of the slider 1. This degree of supersaturation is determined by P
It is determined by the transport of the In solution, the temperature, the temperature, and the thickness of the In solution. If the rate of temperature drop is one foot, the degree of supersaturation on the surface of the slider 1 in the In solution of each bathtub is 8.9 mm. It is determined by the thickness of solutions 8 and 9. The degree of supersaturation at the liquid surface on the side opposite to the seed wafer 7 is proportional to the square of the liquid thickness. Therefore, ■ of the first bathtub. The supersaturation degree of solution 8 is ■ in the second bath. This is the 2.25th degree of supersaturation of solution 9.

That is, the growth of the first layer allows growth that preserves the groove shape provided in the substrate, and the growth of the second layer allows growth that controls the thickness of the thin active layer. I will omit the explanation after the third layer, but
■ in weighing the thickness of the In solution tailored to each purpose. It can be adjusted by the amount.

In this way, the degree of supersaturation on the surface of the slider 1 of the 1% In solution 8.9 is adjusted and brought to a steady state, and then the slider 1 is moved according to a predetermined program to place the substrate 2 under each bath. hold for a period of time. As a result,
A multilayer epitaxial layer is grown on the substrate 2.

As described above, by adjusting the degree of supersaturation of the In solution to an arbitrary value, the best conditions for growing each layer can be obtained, and the reproducibility of liquid phase growth can be improved.

In this example, InP/InGaA using In solution
Although we have described the growth of the sP system, Ga using a %Ga bath solution
It is clear that similar effects can be obtained with respect to the growth of the As1AIGaAs system.

[Brief explanation of drawings]

1 and 2 are diagrams showing one embodiment of the invention, in particular, FIG. 1 is a diagram showing a state where sauce is added at room temperature, and FIG.
The figure shows increasing the temperature■. This is a diagram showing the melted area. 1-1...Carbon slider plate, 2...
...Engineering nP board. 3... Bathtub board, 4... Engineering. Sauce, body...tub, 6...lid, 7...seed wafer, 8...first layer ■. solution, 9.
...Second layer ■. solution. h / Figure name? figure

Claims (1)

[Claims] A liquid phase growth apparatus characterized in that a lid that can be fitted into a solvent solution reservoir is provided, and a source wafer having an area close to the same as that of the solution reservoir is attached to the bottom of the lid.