JPS6288321A - Liquid growth method - Google Patents

Abstract

PURPOSE:To reduce oxidation of an element accommodated in a slide II and prevent oxidation of the solution in a slide I, by dropping the element in the slide II into the solution accumulator of the slide I by an overseed method before liquid phase growth, and performing liquid phase growth wherein the solution accumulator of the slide I and the growth substrate on a boat are made to coincide with each other. CONSTITUTION:When the whole of growth equipment is heated in a furnace is hydrogen atmosphere, solution 31 and Al grains are dissolved. When a slide II is transferred in the direction of the arrow in respect to a slide I, a thin film on the surface of the solution 31 (thin oxide film) is broken by the tip of a projection I, and Al grains 32 are dropped thereon. After the temperature is raised by a further heating, the slide I is transferred in the direction of the arrow with respect to a boat 10, and liquid phase growth is progressed while overlapping a GaAs substrate 1 and the solution 31. Element easy to be oxidized like Al, is mixed with the solution in a so short time that the oxidation is supressed and the crystal defect of growth layer is reduced. The crystal growth of compound semiconductor device of high quality is realized thereby.

Description

[Detailed Description of the Invention] [Summary] On top of the substrate holding boat and the slide I provided with the solution reservoir,
Using a liquid phase growth apparatus equipped with a slide II containing elements, the elements on slide ■ are dropped into the solution reservoir on slide I by the overseeding method before liquid phase growth, and then the solution reservoir on slide I and the boat are The liquid phase growth is performed by matching the growth substrate. This prevents oxidation of the solution on slide (2) by reducing the oxidation of the elements contained in slide (2).

[Industrial application field] The present invention relates to improvements in liquid phase growth methods.

Liquid phase epitaxial growth is known as one of the crystal growth methods for compound semiconductor devices, and it involves bringing a crystal growth substrate (wafer) into contact with a molten growth material, and epitaxially growing a crystal from the solution on the wafer contact surface. This is the way to do it.

In this method, the growth material is dissolved in a solvent as a solute, and during growth, the solute is supersaturated and the solute is epitaxially grown on the wafer surface. However, the solute also contains elements that are easily oxidized. A liquid phase growth method that takes care to suppress oxidation of elements as much as possible is desired.

[Prior Art] For example, a liquid phase growth method for heterojunction of a GaA115 layer 2 as shown in FIG. 3 on an insulating GaAs substrate 1 will be described with reference to FIG.

FIG. 4 shows a cross section of a conventional liquid phase growth apparatus, and the figure is a diagram showing an intermediate stage of the growth process. In the figure, 3 is a boat, 4
In the slide, a GaAs substrate 1 is housed in a boat 3, and a slide 4 has a liquid reservoir chamber 5, in which solute GaAs, AI, etc. are dissolved in a solvent GaO. A solution 22 is contained, and a GaAs seed 22' is placed on top of the solution. Note that 6 indicates a lid of the liquid storage chamber 5. Of course, the entire growth apparatus in this figure is heated in a heating furnace in a hydrogen atmosphere, and the crystal growth material is dissolved as a solution.

After maintaining the temperature at a constant temperature (for example, 800° C.), the slide 4 is slid in the direction of the arrow with respect to the boat 3, and the liquid reservoir chamber 5 is superimposed on the GaAs substrate 1.
A GaAs substrate 1 and a solution 22 are brought into contact with each other, and a GaAlAs layer 2 is deposited on the GaAs substrate 1 while the temperature is gradually lowered to perform epitaxial growth.

Now, in the above growth method, GaA1. An As seed 22' is held, and this is a seed that replenishes the solute as it gradually decreases from the solution when the solute is precipitated from the solution 22.

This method is called the overseeding method, and since the solute can be constantly replenished into the solution, an epitaxial layer with a desired composition can be grown by simply controlling the temperature accurately, without having to accurately weigh the solute first. In addition, the overseeding method allows easy control of film thickness and saturation, and allows growth even with a small amount of solution, so it has the advantage of suppressing abnormal edge growth at the edge of the growth substrate with a small amount of solution. It is something.

Incidentally, in the above embodiment, only one liquid reservoir chamber 5 is shown on the slide 4 for the sake of explanation, but normally, a plurality of liquid reservoir chambers are provided on the slide 4, and liquid phase growth is performed sequentially. .

[Problems to be solved by the invention] By the way, the overseeding method has many advantages as mentioned above, but if the solute contains an element that is easily oxidized,
The oxide forms in the solution (melt) and inhibits epitaxial growth.

For example, in the above example, AI (aluminum) is an element that is easily oxidized, and when a GaAlAs layer is grown in liquid phase by placing a GaAs seed with the same composition as the solute on a solution as described above, the oxide of A1 is GaAl generated and grown in solution
Crystal defects such as ungrown bits occur in the As layer. Conventionally, growth has been done by heating in a reducing hydrogen atmosphere and using graphite-based growth equipment materials to prevent the formation of such oxides, but since AI is an active element, it has not been possible to completely grow. It is not possible to eliminate the oxide.

The present invention proposes a liquid phase growth method for solving these problems and reducing crystal defects.

[Means for solving the problem] The problem is that the liquid phase growth apparatus has a boat that holds a growth substrate, a slide I that moves on the boat and contains a solution in a solution reservoir, and a slide It consists of a slide II that moves above and contains elements to be dropped into the solution reservoir, and a seed is placed on the solution, and before liquid phase growth,
A liquid phase growth method in which the slide II is moved to drop an element into the solution reservoir of slide I, and then the solution reservoir of slide II and the growth substrate of the boat are superimposed and liquid phase growth is performed on the growth substrate. solved by.

[Function] That is, in the present invention, an element that is easily oxidized is dropped into a solution immediately before liquid phase growth using an overseeding method in which a seed is placed on a solution. This will reduce the generation of oxides,
Crystal defects in the grown layer are reduced.

[Example] Hereinafter, embodiments will be described in detail with reference to the drawings.

FIG. 1 shows a cross-sectional view of the liquid phase growth apparatus according to the present invention, in which 10 is a boat, 11 is a slide I, 12 is a slide ■, 13 is a liquid reservoir chamber of slide I, and 14 is an element reservoir of slide The chamber 15 is a lid. In addition, a temporary frame 16 is fitted around the four circumferences of the element storage chamber 14, and a protruding end T is provided at the rear of the temporary frame.
is provided, and this protruding end T is connected to the liquid reservoir chamber 13 of the slide
It has a shape that protrudes to the inside.

The present invention uses such a liquid phase growth apparatus, and
~(Liquid phase growth is performed according to the process diagram shown in C1.

First, as shown in Fig. 2 (al), G in baud H, 0.
The aAs substrate 1 is accommodated, and a solution 31 (a solution of solute GaAs dissolved in a solvent GaO) is accommodated in the liquid reservoir chamber 13 of slide (2), and the GaAs substrate 1 and the solution 31 are placed at a separate position. Moreover, a GaAs seed 31 is placed on top of the solution 31.
This seed 311 has a frame shape with a hole in the center. Furthermore, the slide ■ is arranged with the element reservoir chamber 14 in front of the liquid reservoir chamber 13 as shown in the figure, and the protruding end T of the plate frame penetrates through the hole of the seed 31'' and enters the solution 31. A1 grains 32 are accommodated in the element storage chamber 14, and m15 is placed on top of the A1 grains 32.

With this arrangement, the entire growth apparatus is heated in a heating furnace in a hydrogen atmosphere to, for example, 700°C.
The solution 31 and the grains 32 are in a dissolved state. Then, at that temperature of 700°C, as shown in Figure 2 Tol,
Move slide II in the direction of the arrow relative to slide ■. Then, the thin film (
The thin oxide film) is broken and one grain 32 is dropped into it. FIG. 2 is a diagram showing this state.

Next, after further heating to 800°C, the temperature as shown in Fig. 2 (
As shown in C), the slide (2) is moved in the direction of the arrow with respect to the boat 10, and the GaAs substrate 1 and the solution 31 are superimposed to perform liquid phase growth.

As in the above example, the present invention involves mixing an easily oxidizable element such as AI into the solution for a short period of time to suppress its oxidation and reduce crystal defects in the grown layer. that way,
Crystal growth of even higher quality compound semiconductor devices becomes possible.

Although the above example uses 81 as an element that is easily oxidized, it goes without saying that it can be applied to other elements as well.

[Effects of the Invention] As is clear from the description of the embodiments above, the present invention can reduce crystal defects in the liquid phase epitaxial growth layer and significantly contribute to improving the quality of compound semiconductor devices. be.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of the liquid phase growth apparatus according to the present invention, FIG. , Fig. 4 is a process diagram of the conventional liquid phase growth method. In the figure, 1 is a GaAs substrate (growth substrate), 2 is a GaAlAs layer, 3.10 is a boat, and 4
is the slide, 5 and 13 are the liquid reservoir chamber, 6.15 is the lid, 11 is the slide I, 12 is the slide ■,
16 is a temporary frame, 22 and 31 are solutions, 22'
, 31' is a seed, and 32 is an element reservoir. Heta O, the figure in rxaH ha Sme'z+qtfh@th
3 Figure tL bundle is completed or failed, I2λ beam is shown
Figure 4

Claims (1)

[Claims] A boat in which a liquid phase growth device holds a growth substrate, and a slide that moves on the boat and contains a solution in a solution reservoir.
I and slide II, which moves on slide I and accommodates the elements to be dropped into the solution reservoir, and a seed is placed on the solution, and slide II is moved before liquid phase growth. Move and drop the element into the solution reservoir on slide I.
A liquid phase growth method characterized in that the solution reservoir of the slide I and the growth substrate of the boat are then superimposed to perform liquid phase growth on the growth substrate.