JPS62149121A - Crystal growth device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The field of industrial application is a crystal growth apparatus for epitaxially growing high-quality crystal thin films necessary for the production of electronic devices, optoelectronic devices, etc. on substrate crystals.

2. Description of the Related Art Conventionally, when producing high-performance semiconductor devices, one or more crystal thin film layers of the same type or different types have been epitaxially grown on a substrate crystal. Several methods are used for epitaxial growth, but the so-called liquid phase epitaxial growth method, which uses precipitation from a metal solvent, has been widely put into practical use because it can obtain high-quality crystals with relatively simple preparation. ing. This method will be described using an example in which gallium arsenide is grown. For example, gallium metal kept at a high temperature of 750° C. is saturated with arsenic atoms, this solution is brought into contact with a gallium arsenide crystal serving as a substrate, and the temperature is gradually lowered in this state. By doing so, excess arsenic in the molten gallium is precipitated on the substrate surface together with the gallium solvent, and precipitated as gallium arsenide crystals. By appropriately setting the material, composition, and growth temperature of the solvent and solute, not only gallium arsenide but also crystals of various compositions can be grown.

To epitaxially grow a crystal using the method described above, an apparatus as shown in FIG. 2 is used, for example. This is a conceptual diagram of an apparatus for continuously growing two types of epitaxial layers with different amounts of impurities, and a substrate crystal 21 is placed in a recess 22a formed on a slider 22 made of carbon. This slider 22 can be moved left and right in a boat 23 also made of carbon.

This boat 23 has a hole 24 called a melt reservoir in which a metal solvent, a solute raw material, and an added impurity source are accommodated. A cap 25 is provided at the entrance of this hole 24 to prevent evaporation of the solute during cooling or growth, or to prevent the substrate crystal surface from being thermally etched during equilibration during heating or growth. Covering with a crystal wafer of the same type is also carried out to prevent deterioration due to exposure to heat.

When the metal solution reaches equilibrium at a high temperature, the slider 22 is moved relative to the boat 23 to bring the substrate crystal 21 into contact with the metal solution 25a, and at the same time the overall temperature is gradually lowered. When the required first layer of 1 t thick is grown on the substrate crystal 21, the slider 22 is moved to bring the substrate crystal 21 into contact with the next metal solution 25b, and the second layer is grown. At this time, it is possible to grow even more layers by increasing the number of melt reservoirs.

On the other hand, another noteworthy method in the liquid phase epitaxial method is the temperature difference method.
toichiometry: stoichiometry)” Semiconductor Research 1
Volume 2, published by Kogyo Kenkyukai, p142~). In this method, a heater is further provided in the melt reservoir to create a temperature difference above and below the metal solution. In this case, there is an excess of raw material for the material to be deposited on top of the metal solution in the melt reservoir, which diffuses through the metal solution with a temperature difference and reaches the substrate crystal surface on the lower temperature side. , where it precipitates as an epitaxial crystal layer. This method is advantageous in that it is not necessary to lower the overall temperature as in the above method.

Problems to be Solved by the Invention However, in the first liquid phase epitaxial method, the temperature of the entire furnace must be changed at a constant rate, and the amount and temperature of the metal solution may cause precipitation. There are problems such as the hanging of the crystal, that is, the thickness is fixed, and the growth temperature changes, so in the case of multi-element growth, the composition also changes.

Although the second method solves the drawbacks of the first method, it not only complicates the configuration and handling, such as incorporating a heater into the reaction tube, but also makes it difficult to keep the atmosphere inside the reaction tube clean. Furthermore, there is a problem that the purity of the grown crystal is adversely affected.

The present invention solves the above-mentioned problems, and aims to provide a liquid phase epitaxial device that uses diffusion transport of solute due to temperature difference and does not impair the purity of the grown crystal.

In order to solve the above problems, the present invention provides a crystal growth apparatus for epitaxially growing a thin film on a substrate crystal using diffusion transport of a solute due to a temperature difference. The substrate crystal installation part and the metal solution reservoir are made of carbon, and are used as heating elements by high-frequency heating, and the substrate crystal installation part and the metal solution reservoir are made of carbon so that a temperature difference can be created between the substrate crystal installation part and the metal solution reservoir. A cooling means is provided to cool the installation part.

Effect With the above configuration, since the jig for the part where the crystal growth is performed is made of carbon, only that part can be heated to high temperature using high frequency heating method, and the heating system is not only simple, but also
Contamination from the surroundings can be minimized, and since the jig is provided with cooling means, the temperature distribution in the metal solution can also be varied over a wide range.

EXAMPLE An example of the present invention will be described below with reference to the drawings. FIG. 1 is a conceptual diagram of a crystal growth apparatus according to an embodiment of the present invention. In FIG. 1, 1 is a substrate crystal on which a crystalline US layer is epitaxially grown, 2 is a substrate crystal installation part (hereinafter referred to as the substrate installation part) in which a recess 2a is formed in which the substrate crystal 1 is installed, and 3 is a substrate crystal installation part (hereinafter referred to as the substrate installation part). A metal solution reservoir installed on the substrate installation part 2, which has a hole 4 in which a metal solution 5 is accommodated, and this metal solution reservoir 3 is equipped with a thermal lightning pair (not shown).
The metal solution 5 in the hole 4 comes into contact with the substrate crystal 1 in the recess 2a of the substrate installation part 2. Gallium was used as the metal solution 5, and gallium arsenide polycrystal was used as the raw material 5a. A substrate installation part 2 and a metal solution reservoir 3 where these crystal growths are performed.
is made of carbon, and the holding stand 7, which also serves as a T-sink and holds the substrate installation part 2, is hollow, and a quartz pipe 8 containing a thermal lightning pair (not shown) is placed in the center. There is. This pipe 8 is provided with multiple holes 8a through which cooling air or nitrogen can flow, thereby cooling the substrate installation section 2. Reference numeral 9 denotes a high-frequency coil placed on the side surface of the vertical quartz reaction tube 10. Since the substrate installation part 2 and the metal solution reservoir 3 are made of carbon, they absorb this high-frequency power and generate heat to supply electric power. Accordingly, the temperature of the metal solution 5 and the substrate crystal 1 can be controlled. Further, the reaction tube 10 is sealed by flanges 13 and 14 having a gas port 11 and an outlet 12, respectively, so that hydrogen gas H2 produced by vI is introduced from the inlet 11 and discharged from the outlet 12.

Next, its operation will be explained. After the inside of the reaction tube 10 has been sufficiently replaced with purified hydrogen H2, evacuation and hydrogen purge are repeated depending on the case, and power is supplied to the high frequency coil 9 to heat it. At this time, the substrate crystal 1 and the metal solution 5 are isolated. When the metal solution 5 reaches about 750° C., it is maintained for about 1 hour so that the As atoms of the solute are in equilibrium in the solution. Thereafter, the metal solution reservoir 3 is rotated to a position where the metal solution 5 and the substrate crystal 1 are in contact with each other.

Then, the temperature is maintained at 745° C. by flowing 1 liter of room temperature nitrogen gas per minute from the lower pipe 8.

Hold this state for 40 minutes, then rotate the metal solution reservoir 3 again, and the gold! / Separate the RWI liquid 5 and the substrate crystal 1,
Stop supplying high frequency power and cool down. After cooling, the crystal was taken out and the thickness of the grown layer was measured, and the growth of the gallium arsenide epitaxial layer was approximately 5 μm.

In this way, by using high-frequency heating as the heating method and using the gold FA solution reservoir and the substrate installation part made of carbon, they themselves generate heat and do not raise the surrounding temperature to a high temperature. Temperature difference liquid phase epitaxial growth can be easily performed by providing a separate cold W tank and combining partial cooling that creates a temperature gradient in the metal solution.

In this example, epitaxial growth of gallium arsenide has been described, but the present invention is not limited thereto, and can be applied to various compound semiconductors depending on the composition of the solution. Furthermore, multilayer growth is also possible by using a plurality of metal solutions depending on the design of the metal solution reservoir. Further, in this embodiment, a vertical reaction tube configuration has been described, but a horizontal configuration can also produce similar effects.

Effects of the Invention As described above, according to the present invention, a jig for liquid phase epitaxial growth is made of carbon, and the jig itself generates heat due to high frequency power, making use of the fact that other parts do not need to be heated to high temperatures. By combining with an appropriate partial cooling method, it is possible to perform fA differential liquid phase epitaxial growth in a simple manner, and since the structure is simple, cleaning is easy, and high purity crystals can be grown. It is possible to do so.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of a crystal growth apparatus according to an embodiment of the present invention, and FIG. 2 is a schematic diagram of a conventional one-stage apparatus. DESCRIPTION OF SYMBOLS 1... Substrate crystal, 2... Substrate installation part, 2a... Recessed part, 3... Metal solution reservoir, 4... Hole, 5... Metal solution, 6... Shaft, 7... ...Holding stand, 8...Pipe, 9
...High frequency coil, 10...Reaction tube

Claims (1)

[Claims] 1. A crystal growth apparatus that epitaxially grows a thin film on a substrate crystal using diffusive transport of solute due to temperature difference, which includes a substrate crystal installation part made of carbon in which the substrate crystal is installed in a recess, and a rotatable installation on the substrate crystal installation part. a metal solution reservoir made of carbon and housed so that the molten metal solution comes into contact with the substrate crystal in the recess through rotation; high-frequency heating means for heating the substrate crystal installation part and the metal solution reservoir; and the substrate crystal installation. A crystal growth apparatus comprising: cooling means for cooling the substrate crystal installation section and making it possible to set a temperature difference between the substrate crystal installation section and the metal solution reservoir.