JPS599912A - Liquid phase crystal growth method - Google Patents

Abstract

PURPOSE:To uniformalize the thickness of the grown layer in a substrate surface by a method wherein the temperature of the substrate on the side where the solution begins to contact therewith is set lower than that on the side where it contacts therewith lastly in a sliding-type liquid phase crystal growth method. CONSTITUTION:A semiconductor substrate 1 formed of GaAs or so is fitted in a boat body 4, and a solution 2 of Ga and GaAs, etc. is put in a solution reservoir of a slide boat 3. Under such conditions that the solution 2 is heated up to 850 deg.C, held at that temperature for ca. 1hr and then cooled at a speed of 0.5 deg.C/min, the solution 2 is slid over the substrate 1 to make a growth. In this constitution, the temperature of the substrate 1 on the P side where the solution 2 is removed from the substrate 1 is set lower than that on the Q side where the solution 2 is slid to come into contact with the substrate, thereby to restrict lowering of the supersaturation degree of the solution 2 on the P side. Namely, the crystal is grown in the condition that the solution 2 has a temperature change with a gradient of 0.02 deg.C/mm. in the sliding direction. By so doing, it becomes possible to significantly uniformalize the thickness of the grown layer in the surface of the substrate 1.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a liquid phase crystal growth method, and in particular provides a liquid phase crystal growth method that makes the thickness of a grown layer uniform within the plane of a substrate.

When crystal growth is performed by liquid phase epitaxial growth, a substrate crystal and a solution are mounted on a board, and the solution is slid onto the substrate to perform growth. The so-called boat slide method is widely used.

This method allows continuous growth of multiple layers, and the growth layer can be easily made thin, so it is used for the production of semiconductor Lehli' crystals, etc. In this liquid phase epitaxial growth method, a growth solution is brought into a supersaturated state, and then the solution is slid onto a substrate and grown while being cooled to obtain a thin film layer. When the surface roughness of the substrate is large and the nulling distance of the solution is long, a large difference in the thickness of the grown layer occurs between the part where the solution first contacts the substrate and the part where the solution finally leaves the substrate after growth.

The present invention investigates the cause of the difference in the thickness of the grown layer, and eliminates the cause to make the thickness of the grown layer uniform within the plane of the substrate. When you think about it, the growth layer on the side of the substrate where the solution slides is thicker than the growth layer on the opposite side, near the edge of the substrate where the solution moves away. The reason for this is that growth occurs faster where a supersaturated solution comes into contact with the substrate, and on the other side, where the solution is moving away from the substrate, a less supersaturated solution comes into contact with the substrate. It is thought that this will slow down the growth.

In order to prevent such a phenomenon in which the crystal growth rate differs, it is necessary to suppress the decrease in the supersaturation degree of the solution. As shown in FIG. In the direction in which the solution 2 slides over the growth substrate 1, a temperature distribution is applied to the growth substrate 1 as shown in FIG. This method is characterized by controlling.

That is, in order to suppress the decrease in the degree of supersaturation of the solution on the P side where the solution 1 is removed from the crystal substrate 1 in FIG. 1, the temperature of the substrate is lowered on the Q side where the solution slides. . The temperature distribution of the crystal substrate 1 in the direction in which the solution slides is shown by the curve A1. in FIG. A2. As shown in A3, various distributions can be taken, and between both ends of the crystal substrate 1? Crystalline stones also take various values, but the optimal conditions are:
It is determined by the structure of the boat, the shape and amount of the solution, the shape of the substrate, etc.

In the following, a conventional case and an embodiment of the present invention will be specifically described using the GaAs0 solution + eye crystal growth method as an example.

A GaAs substrate 1 is mounted inside the boat body 4 shown in FIG. 1, a solution 2 made of Ga and GaAs is put into the solution reservoir of the slide boat 3, the temperature is raised to 850°C, and after holding for 1 hour, the temperature is increased to 0.5°C. C. Now cool down and slide the solution 2 onto the GaAs substrate 1 to perform growth. The width of the GaAs substrate 1 (the length of the substrate in the direction in which the solution 2 slides) is 16π
When the thickness of the grown layer was measured at a position 3 mm from both sides of the substrate at m, the thickness of the grown layer was 0.5 μm in both cases, and there was a large difference in thickness. On the other hand, when the width of the GaAs substrate 1 is set to 30 mm, the grown layer thickness is 0.3 μm and 0.7 μm at the position 3πm from both sides.
This resulted in a difference of 0.4 μm, resulting in variations in the thickness of the grown layer.

Next, the width of the GaAs substrate 1 was set to 3 om, and the same growth as described above was performed by changing the temperature in the sliding direction of the solution 2 at a gradient of 0.02° C. and 7 mm. That is, there is a temperature difference of 0.6°C between the temperature at Q11 where the solution 2 of the GaAs substrate 1 comes in the sliding direction and the opposite side (the P side where the solution slides and is removed from the substrate). Crystal growth was carried out according to an example of the present invention.

As a result, the thickness of the grown layer at a position 3 mytt from both sides was 0.6 μm and 0.6 μm, and the difference between them was very small. The thickness became uniform.

As explained above, the liquid phase crystal growth method of the present invention is an effective method for making the thickness of a grown layer uniform within the plane of a substrate in thin film growth, and has high industrial utility value.

[Brief explanation of drawings]

@1 Figure (2L) is a cross-sectional view of the growth boat used in the liquid phase crystal growth method of the present invention, Figure 1 (1)) is a diagram showing the temperature gradient of the growth boat shown in Figure 1 (2L), FIG. 2 is a diagram showing various temperature distribution states within the growth substrate. 1... GaAs substrate, 2... GaAs solution, 3... slide boat, 4... port body, 5... quartz rod. Name of agent: Patent attorney Toshio Nakao and one other person

Claims (1)

[Claims] A sliding liquid phase crystal growth method characterized in that the temperature of the substrate on the side that the solution comes into contact with at the end is lower than the temperature of the substrate on the side that the solution starts coming into contact with.