JPH0215520B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a molecular beam crystal growth apparatus, and particularly to an improvement in the structure for supporting and heating a single crystal substrate on which a crystal is to be grown within the apparatus.

2. Description of the Related Art Substrates in which a required single crystal layer is epitaxially grown on a single crystal substrate are widely used in semiconductor devices and the like.

Various methods are used for epitaxial growth, but the molecular beam crystal growth method (MBE method) evaporates constituent elements and impurity elements of a single crystal layer from a cell in a high vacuum of about 10 ^-10 Torr. This is a method in which epitaxial growth is performed by irradiating the substrate in the form of a beam.

In the MBE method, the number of molecules of each element reaching the substrate is
It is uniquely determined by the geometry of the evaporation system and the evaporation source temperature. Therefore, it is possible to accurately control the crystal growth rate, the composition ratio of the mixed crystal, the amount of impurity doping, etc., and it is suitable for the most precise crystal growth such as a superlattice structure.

In order to epitaxially grow a good single crystal layer, the condition of the substrate on which it is grown is equally important, but conventional molecular beam crystal growth apparatuses are still inadequate in this respect.

[Conventional technology]

FIG. 2 shows a schematic diagram of an example of a conventionally most commonly used structure for holding and heating a substrate on which a single crystal layer of a compound is grown in a molecular beam crystal growth apparatus.

In the figure, 21 is a substrate supporter, 22 is a pin for fixing the substrate supporter 21, 23 is a heater,
24 is a heat reflecting plate, 25 is a thermocouple, and 26 is a rotation mechanism. The substrate support 21 is usually formed into a disk shape using a high melting point metal such as molybdenum (Mo), and has an appropriate amount of indium (In) 27 on its surface.
A substrate 11 on which a single crystal is grown is attached.

For example, when the substrate 11 is a gallium arsenide (GaAs) single crystal substrate and a single crystal layer of GaAs, aluminum gallium arsenide (AlGaAs), etc. is grown thereon, the substrate support 21, the indium (In) 27
The substrate 11 is heated, for example, to a temperature of about 680° C. to perform epitaxial growth as described above.

At this temperature, In27 diffuses into the GaAs substrate 11 to obtain adhesion, the substrate 11 is well fixed in vacuum, and the heat conduction between the substrate support 21 and the single crystal substrate 11 is good, resulting in temperature distribution. This has the advantage of being uniform.

However, during MBE growth for about one hour, the diffusion depth of this In reaches about 100 μm, and after epitaxial growth, the In layer 27 is melted and the substrate 1 is
1 was removed from the substrate support 21, and the part where In was diffused was removed by polishing together with the attached In.

In the above-mentioned conventional method, (a) not only the above-mentioned polishing step is required, but also (b) it is difficult to avoid contamination of the epitaxially grown single crystal layer in this polishing step. (c) It is inevitable that In will adhere to the periphery and surface of the substrate and growth layer, but it is impossible to selectively remove this from GaAs, and this adhered In will cause problems in later processes. It can also cause (d) evaporated
In enters the cell and is included in the beam and contaminates the growing single crystal. (e) Due to the difference in thermal expansion coefficient between the single crystal substrate and the substrate support, defects such as slip lines are likely to occur in the single crystal substrate. There are other problems.

In-free single crystal substrate support structures have been implemented for silicon (Si) substrates that suffer from the aforementioned problems. In this case, the substrate support exemplified above is made into an annular shape, and the Si substrate is directly heated from the back side.

However, for compound single crystal substrates such as GaAs, if the back side of the substrate is opened and heated, arsenic (As) etc. will evaporate and many defects will be generated from the back side of the single crystal substrate, so this structure cannot be applied. It's impossible.

Also known is a structure in which a disk-shaped substrate support similar to the substrate support 21 is used and a single crystal substrate is pressed against the disk-shaped substrate support. This structure prevents the compound from evaporating from the back side of the single-crystal substrate, but in order to achieve good temperature distribution on the single-crystal substrate surface and to obtain heat conduction between the substrate support and the single-crystal substrate, it is necessary to It is necessary to apply pressure, which causes distortion in the single crystal substrate, making it unsuitable for practical use.

[Problem that the invention seeks to solve]

As explained above, when performing epitaxial growth of a compound semiconductor layer using a conventional molecular beam crystal growth apparatus, problems such as contamination and crystal defects are unavoidable, and the structure for supporting and heating the substrate must be improved. There is a strong need to solve this problem.

[Means for solving problems]

The above-mentioned problem can be solved by the present invention, in which the back side of a single crystal substrate is brought into close contact with a substrate support member, the substrate is heated by a heat ray transmitted through the substrate support member, and a single crystal layer is epitaxially grown on the front surface of the substrate. This problem was solved by using a molecular beam crystal growth device. Note that the above-mentioned heat ray is a term for infrared rays that focuses on thermal effects, and is a concept well known to those skilled in the art.

[Effect]

In the molecular beam crystal growth apparatus of the present invention, the first
As shown in the figure, a single crystal substrate 11 on which a single crystal layer is grown
and the substrate support member 1 are stacked and brought into close contact with each other, and the substrate support member is mounted facing the heater 5.

The substrate support member 1 is made of a heat-resistant material that transmits thermal radiation or emits heat rays when heated, and is chemically stable under the environmental conditions during crystal growth. It is formed.

Heating to raise and maintain the single crystal substrate at the growth temperature is
In the conventional example, the substrate support member such as a Ta metal plate is heated first, and then the single crystal substrate is heated by heat conduction, whereas in the present invention, heating is performed by a hot ray that passes through the substrate support member. In addition to this, the substrate supporting member itself is heated and heated by radiated heat rays.

Therefore, the thermal resistance between the single crystal substrate and the substrate support member does not affect the heating of the single crystal substrate, and does not cause contamination or stress to the single crystal substrate and the grown single crystal layer as in the conventional example. Not at all. Further, evaporation and outward diffusion of atoms within the substrate crystal from the back surface are prevented by bringing the substrate into close contact with the substrate support member.

The materials for forming the substrate support member include:
Sapphire (Al ₂ O ₃ ), silicon (Si), quartz (SiO ₂ ), etc. are suitable.

〔Example〕

The present invention will be specifically explained below with reference to an example schematically shown in FIG.

In the figure, 1 is a substrate support member made of, for example, sapphire crystal, 2 is a substrate supporter, 3 is a stopper, 4 is a pin for fixing the substrate supporter 2, 5 is a heater, 6 is a heat reflection plate, and 7 is a Thermocouple 8 is a rotating mechanism.

A substrate 11 on which a single crystal is to be grown is inserted into an annular substrate support 2 together with a substrate support member 1, and is prevented from falling off by a stopper 3. Regarding the material of the substrate support 2, its attachment to the growth apparatus, etc., there is no need to particularly change the conventional method.

As the material of the substrate supporting member 1 according to the present invention, for example, sapphire crystal, silicon crystal, quartz, etc. can be used, but in particular, it is made into a substrate shape as in the above embodiment, and its surface is a crystal plane or a smooth surface close to this. Therefore, it is desirable that the single crystal be closely attached to the substrate 11 on which the single crystal is grown. Among the above-mentioned materials, sapphire crystal is particularly excellent in transmittance of thermal radiation, has good processing accuracy, and can easily obtain a smooth surface, so that good results can be obtained.

Although the heat source and the like can normally be used without changing, according to the present invention, since the substrate on which the single crystal is grown is directly heated, the effect of improving thermal efficiency can be obtained.

〔Effect of the invention〕

As explained above, according to the present invention, epitaxial growth by a molecular beam crystal growth method can be performed without causing contamination or crystal defects.

Furthermore, the present invention can be easily applied to conventionally used devices, and can be highly effective in promoting the practical use of compound semiconductor devices and the like.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing an embodiment of the present invention, and FIG. 2 is a schematic diagram showing a conventional example. In the figure, 1 is a substrate support member, 2 is a substrate supporter, 3 is a stopper, 4 is a fixing pin, 5 is a heater, 6 is a heat reflection plate, 7 is a thermocouple, 8 is a rotation mechanism,
11 is a substrate on which a single crystal is grown.

Claims (1)

[Scope of Claims] 1. An apparatus for epitaxially growing a compound semiconductor layer on the surface of a single crystal substrate by irradiation with molecular beams, comprising: a substrate support member that holds the single crystal substrate 11 with its back surface in close contact with the substrate support member; 1, the substrate support member is made of a material that transmits heat rays emitted from the heat source 5, and the heat source is disposed on the side of the substrate support member that does not bring the single crystal substrate into close contact with the substrate support member. Molecular beam crystal growth equipment.