JPH03228898A - Crystal growing method - Google Patents

Abstract

PURPOSE:To improve crystallinity by setting the temp. in the aperture at the front end of a crucible higher than the temp. in the other part and setting the temp. in the other parts constant. CONSTITUTION:A crucible 2 contg. a material source Ga 3 is installed in a heat radiation preventive cylinder 1. This crucible is heated by a heater 4 for heating and is controlled to a prescribed temp. by a thermocouple 5. The temp. of the other material source As is similarly controlled another cell. A substrate to be grown is then set at a prescribed temp. and after the other conditions are attained, the shutters 6 of respective cells are opened to start crystal growth. The heater 4 near the aperture at the front end of the crucible 2 is wound more densely than in the other parts and is wound coarsely in the part lower than the part where the material source Ga 3 exists and, therefore, the temp. at this part is kept lower by 50 to 100 deg.C than in the front end part. Since the temp. from this material source Ga 3 to the lower part is kept constant, the surface of the evaporating liquid has the specified temp. in spite of a change in the volume of the raw material Ga 3 and the good-quality crystal is stably obtd. with good reproducibility even if the crystal is grown under specified conditions.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a crystal growth method using molecular beam epitaxy, and particularly to a cell for molecular beam epitaxy used for semiconductor crystal growth.

[Conventional technology]

Conventionally, in crystal growth using the single molecular beam epitaxy method, the raw material is supplied with PBN (PyrotitiC!).

For example, in the case of GaAs, Ga or A8
Al.

Generally, a predetermined crystal is epitaxially grown on a substrate by placing a doping material such as 2.2° or 81 as a doping material into each crucible and heating each crucible to an appropriate temperature to evaporate it.

Next, a Ga cell used for crystal growth of GaAs in molecular beam epitaxy, which is a conventional crystal growth method, will be described as an example.

FIG. 8 shows a cross-sectional view of the schematic structure of a conventional Ga cell.

In the figure, 90 is a Ga cell, and this Ga cell 10
A crucible 2 made by FBI etc. is placed inside a heat radiation prevention tube 1.
The material source Ga8(z
Put it in. The crucible 2 is heated by a heating heater 4,
The temperature is detected by a thermocouple 5 and adjusted to a predetermined temperature. Similarly, other necessary material sources such as A8 are set to predetermined conditions.1. After setting the temperature of the substrate to be grown and other conditions, the shutter 6 of the Ga cell 10 is opened, and the %Ga 8 evaporates. At the same time, the shutter 6 is also opened for the material sources needed for the pond, such as AB. In this way, GaAs crystals grow on the substrate.

At this time, the heater number one that heats crucible 2 is heated by the evaporated Ga.
8 adheres to the vicinity of the outlet of the crucible 2, and in order to prevent deterioration of crystallinity due to re-evaporation, the temperature of the vicinity of the outlet of the crucible 2 is made higher than other parts as shown in FIG. That is, a heating method with a structure called top heat was used.

[Problem to be solved by the invention]

Since the conventional crystal growth method was configured as described above, the heating of the crucible was concentrated at the tip, so the raw material GaI/
'iThere is a temperature difference between the upper and lower parts of the crucible, and the temperature of the crucible is controlled by a thermocouple installed at the bottom of the crucible, so even if growth is performed at the same general constant temperature, the amount of evaporation of the raw material Ga will be Since it is determined at the top of the liquid level, the material source Ga
As it is consumed, the actual temperature becomes lower and the amount of evaporation decreases, and the growth rate slows down even at the same general constant temperature.

Although not shown in the present invention, if the entire crucible is heated with a heater at regular intervals in order to keep the crucible temperature constant, the temperature near the opening at the tip of the crucible will be lower, and the evaporated Ga will be lowered. There has been a problem in that defects are likely to occur due to adhesion and re-evaporation, making it difficult to develop a high-quality crystal growth method.

This invention was made to solve the above-mentioned problems, and improves the way the heater is wound so that the temperature is constant from the center where the material source is at high temperature only to the bottom of the crucible near the tip opening. The object of the present invention is to obtain a crystal growth method that can stably obtain a crystal growth layer with a deviation of one inch.

[Means to solve the problem]

The crystal growth method according to this invention increases the temperature near the opening at the tip of the crucible, and changes the way the heater is wound so that the temperature in other parts from the center where the material source is located to the bottom remains low and constant. It is.

[Effect]

In the crystal growth method of this invention, the heater is wound tightly near the opening at the tip of the crucible, and the area where the material source is located at the bottom is made coarser than near the center, and the material source is kept at a constant temperature. Since the amount of evaporation is kept constant even if the amount changes, it is possible to perform stable crystal growth under constant conditions.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a cross-sectional view of a schematic structure of an implementation FRt of a cell for molecular beam epitaxy used for crystal growth of the present invention;
FIG. 2 is a curve diagram showing the temperature distribution of the crucible installed in the cell.

In this example, a case of a Ga cell in which a GaA11l crystal, which is an m-ma group compound semiconductor, is made will be explained.

In addition, in the drawings, the same reference numerals as those in the conventional device indicate the same components.

The structure of the cell is basically the same as the conventional one, but by improving the winding of the heater 4 in the crucible 8f, high quality crystals can be obtained with good reproducibility. In other words, the distance near the tip opening of Ruriho is about 8a! !
~ Volume 8, lower part, 5~6m+ to the bottom of the crucible
It is wound roughly at intervals to form a temperature distribution as shown in Figure 2. As a result, the molecular beam epitaxy cell 1 of this example
0 is configured.

To explain this operation, a crucible made of PBN etc.
//i It is installed in the heat radiation prevention cylinder l, and the material source Ga8'i is placed in the crucible B. The crucible g#'j is heated by the heater No. 1, its temperature is detected by the thermocouple, and the temperature is adjusted to a predetermined value.

Other material sources A8. The other cells are adjusted in the same way, and after setting the substrate (not shown) to a predetermined temperature and setting the other conditions, the shutter 6 of each cell is opened to start crystal growth.

At this time, the area near the tip opening of the crucible where the heater is first is wound more densely than other parts, and the lower part where the material source Ga 8 is located is more loosely wound.
kept low. In addition, since the temperature is kept constant below the material source Ga8, even if the amount of the material source Ga8 changes and decreases, the evaporated liquid level will remain at a constant temperature, so growth can be performed under constant conditions. It is possible to obtain stable, high-quality crystals with good reproducibility.

In addition, in the above example, the prescribed temperature distribution can be achieved by changing the way the heater is wound. A similar temperature distribution can also be obtained by keeping the winding method of the heater constant and reducing the diameter of the wire near the opening at the tip of the crucible.

〔Effect of the invention〕

As described above, according to the present invention, the tip of the crucible is wrapped tightly around the opening at the tip, and the other parts are wound loosely and kept at a constant temperature. There is no droplet adhesion, and the amount of evaporation does not change even if the amount of the material source decreases. Therefore, 4° ■: There is no re-evaporation at the tip of the crucible.

■: The growth rate can be kept constant.

This has the effect of improving crystallinity by preventing the contamination of impurities, and obtaining high-quality crystals with good reproducibility under constant conditions.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing the schematic structure of a G& cell showing an implementation IPII of the present invention, FIG. S is a curve diagram showing the temperature distribution of the crucible of the cell in FIG. 1, and FIG. 8 is a conventional Ga FIG. 4 is a sectional view showing the general structure of the cell, and FIG. 4 is a curve diagram showing the temperature distribution of the crucible of the cell shown in FIG. 8. In the figure, 1ri is a heat radiation prevention cylinder and 8 is a crucible. 8-Ga, 4 is a heating heater, 5 is a thermocouple. 6#: Indicates t-shutter. In addition, the same symbols in the figures indicate the same or equivalent parts.

Claims (1)

[Claims] A method for growing a crystal of GaAs or the like using molecular beam epitaxy, characterized in that the temperature of the opening at the tip of a crucible is made higher than other parts, and the temperature of the other parts is kept constant.