JPH07288229A - Molecular-beam epitaxy apparatus - Google Patents

Abstract

PURPOSE:To grow a high-quality compound semiconductor epitaxial crystal on a substrate. CONSTITUTION:Shutters 9 and 10, movably supported between the closing positions and the opening positions of Knudsen cells 9 and 10, are selectively heated with external infrared-ray lamps 26 and 27. Thus, the attachment of growing raw material can be prevented, or the attached growing raw material can be evaporated again. Thus the closure of the openings of the Knudsen cells 7 and 8 and the defective opening/closing operations of the shutters caused by the falling of the attached material can be prevented. Thus, molecular beams are stabilized, and the excellent crystals are always obtained. It is not necessary to provide complicated wirings in a crystal growing chamber. Only a window is provided in the main body of a molecular-beam epitaxy apparatus. Therefore, the structure is not complicated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a molecular beam epitaxy apparatus for growing a compound semiconductor epitaxial crystal by supplying a growth material and a dopant gas to the surface of a substrate.

[0002]

2. Description of the Related Art A molecular beam epitaxy method (hereinafter abbreviated as MBE method in this specification) is generally known as one of epitaxial crystal growth methods for compound semiconductors.

In the above MBE method, a Knudsen cell (hereinafter, abbreviated as K cell in the present specification) which holds a substrate in a crystal growth chamber and is composed of a crucible and a heater provided at a position opposite to the substrate is held. Therefore, the growth raw material is irradiated onto the surface of the substrate as a molecular beam to grow crystals on the surface of the substrate. In addition, a p-type or n-type semiconductor crystal can be grown by introducing a dopant as needed.

Here, the K cell is opened upward and the substrate is set downward so that the fragments of the growth material solidified in other parts do not drop and adhere to the substrate, and the substrate is set downward so as to face downward. There is an MBE device that irradiates a molecular beam from the side. Further, in the MBE apparatus, a shutter that can be opened and closed is provided at the opening of the K cell so that the molecular beam is not accidentally irradiated toward the substrate surface.

However, when the crucible for closing the shutter of the K cell is heated, the shutter is irradiated with the molecular beam, and the growth raw material is deposited and deposited. When the shutter opens and closes, the attached matter comes into contact with the vicinity of the opening of the K cell,
There is a problem that it becomes difficult to smoothly perform the opening / closing operation, and in some cases, film formation cannot be performed. Further, if this deposit falls on the opening of the K cell, it is possible that the opening is blocked and a good molecular beam cannot be obtained, and the quality of the crystal is significantly deteriorated.

Therefore, there is an MBE device in which the entire device is obliquely arranged so that the opening of the K cell is not located directly below the shutter, but the problem that the opening and closing operation is defective due to the deposit on the shutter cannot be solved.

It is known that the above-mentioned problem that the growth material is attached to the shutter remarkably appears particularly in a molecular beam epitaxy apparatus for growing a II-VI group compound semiconductor epitaxial crystal.

[0008]

SUMMARY OF THE INVENTION The present invention has been made in view of the problems of the prior art as described above, and its main purpose is to grow a high-quality compound semiconductor epitaxial crystal on a substrate. It is an object of the present invention to provide a molecular beam epitaxy device which can be formed and does not cause a problem in the opening / closing operation of the shutter of the K cell.

[0009]

According to the present invention, there is provided a molecular beam epitaxy apparatus for growing a compound semiconductor epitaxial crystal by supplying a growth raw material and a dopant gas to a surface of a substrate in a crystal growth chamber. Between at least one Knudsen cell provided with a crucible for receiving a growth material inside and opening into the crystal growth chamber, and between a position that closes the opening of the Knudsen cell and a position that does not close the same. A shutter movably supported, a transparent window provided at a position facing the shutter from the outside, and an infrared lamp for irradiating the shutter with infrared rays from the outside through the window to heat the shutter. It is achieved by providing a molecular beam epitaxy apparatus characterized by having

[0010]

According to the above-mentioned structure, by heating the shutter from the outside by the infrared lamp, it is possible to prevent the growth raw material from adhering to the shutter or to re-evaporate the attached growth raw material.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a schematic sectional view showing a schematic structure of a molecular beam epitaxy apparatus (MBE apparatus) in a preferred embodiment to which the present invention is applied. This example is an MBE apparatus for growing an epitaxial crystal of zinc selenide (ZnSe) on a gallium arsenide (GaAs) substrate and introducing nitrogen (N) as a dopant to obtain a p-type crystal.

With the ultra-high vacuum exhaust device 2, 10 ^-7 to 10 ^-9
The substrate B is held by the holder 3 in the crystal growth chamber 1 capable of maintaining a high vacuum of about torr so that the processed surface faces downward. A heater 5 for heating the substrate is provided above the holder 3. Further, the disk-shaped main shutter 6 has a position where the film formation of the substrate B is started, that is, a position where the processed surface of the substrate B is not covered, and a position where film formation is stopped, that is, a position where the processed surface of the substrate B is covered. It is rotatably supported between the two, and the film formation can be selectively started / stopped by rotating the drive shaft 6a from the outside.

Two K cells 7 and 8 opening toward the substrate B are provided at a position in the lower part of the crystal growth chamber 1 which is substantially opposed to the substrate B. These K cells 7 and 8 have crucibles 7a and 8a opening toward the substrate B and heaters 7b and 8b for heating these crucibles 7a and 8a. Further, disk-shaped shutters 9 and 10 similar to the main shutter 6 are provided in the openings of the K cells 7 and 8 for the K cells.
The cells 7 and 8 are rotatably supported between a position that covers the openings and a position that does not cover the openings, and the drive shafts 9a and 10a are selectively rotated from the outside to selectively select the crucibles 7a,
Substrate B using the growth raw material received in 8a as a molecular beam
It is designed to irradiate to. Further, transparent windows 24 and 25 are provided in the side wall portion 1a of the crystal growth chamber 1 at positions facing the shutters 9 and 10 from the outside. Further window 2
Infrared lamps 26 and 27 connected to an external power source and a control unit (not shown) for heating the shutters 9 and 10 by irradiating the shutters 9 and 10 with infrared rays through windows 24 and 25 to the outside of the shutters 4 and 25. Is provided.

In addition to the K cells 7 and 8, a nitrogen plasma excitation cell device 11 is provided in the lower portion of the crystal growth chamber 1 at a position substantially facing the substrate B.

On the other hand, in the crystal growth chamber 1, there is provided a flux monitor 21 as a molecular beam intensity sensor consisting of a known BA type ionization vacuum gauge for measuring the intensity of each molecular beam from the degree of vacuum. .

The operating procedure of this embodiment will be described below. First, selenium (Se) is received in the crucible 7a and zinc (Zn) is received in the crucible 8a, the substrate B is held downward by the holder 3, and the inside of the crystal growth chamber 1 is evacuated by the ultrahigh vacuum exhaust device 2 to obtain 10 Maintain a high vacuum of about ^-7 to 10 ^-9 torr. Then, the substrate B is rotated and heated, and selenium and zinc are heated. At this time, each shutter 6,
9, 10, 11a are still closed. The shutters 9 and 10 are heated by the infrared lamps 26 and 27 to prevent selenium and zinc from adhering to the shutters 9 and 10, respectively.

Next, after a lapse of a predetermined time, the shutter 9 is first opened and closed, and the flux monitor 21 controls so that the selenium molecular beam is stabilized. Next, the shutter 10 is opened and closed, and the flux monitor 21 controls so that the zinc molecular beam is stabilized. At this time, it is advisable to control the molecular beams of selenium and zinc to be stable at an intensity of 1: 1. When each molecular beam stabilizes at an intensity of 1: 1, the flux monitor 21 is retracted to a position near the left wall surface in FIG. 1 where the molecular beam is not directly irradiated, both shutters 9 and 10 are closed, and shutter 11a is opened to open the excitation cell device. A high frequency is generated at 11 (5 W to 300 W), and nitrogen gas is supplied to the plasma generation chamber defined in the casing 12 at a flow rate in the range of 0.01 cc / min to 0.5 cc / min. Here, the magnetic field generated by the magnet 17 and the high frequency coil 1
A high-density nitrogen plasma is generated by the interaction with 9.

Thereafter, when the nitrogen plasma is stabilized, the shutters 9 and 10 are opened, and finally the shutter 6 is opened to open the substrate B.
It is possible to obtain a p-type crystal by introducing nitrogen as a dopant therein while growing an epitaxial crystal of zinc selenide on the surface of. With the p-type crystal thus formed, a carrier concentration of 1 × 10 ¹⁸ cm ⁻³ was obtained.

In the above embodiment, when the shutters 9 and 10 of the K cells 7 and 8 are closed, the infrared lamp 26,
27 is operated to heat the shutters 9 and 10 to prevent the growth material from adhering, but infrared rays are emitted from the infrared lamps 26 and 27 even when the shutters 9 and 10 are open. While the shutters 9 and 10 are open, the infrared lamps 26 and 27 are activated to operate the shutters 9 and 1, respectively.
It goes without saying that the same action and effect can be obtained by re-evaporating the growth material attached to 0. Also,
With such a structure, when the infrared lamps 26 and 27 are activated / deactivated to cause temperature fluctuations in the crystal growth chamber 1, the infrared lamps 26 and 27 are always kept activated during crystal growth. It is not affected by temperature.

On the other hand, in the present embodiment, the infrared lamps 26 and 27 are provided only on the shutters 9 and 10 of the K cells 9 and 10, respectively. It is also possible to prevent deposits from falling from the main shutter to the openings of the K cell and the excitation cell device.

Further, although zinc is used as the group II element and selenium is used as the group VI element in the above embodiment, any one of cadmium (Cd), zinc (Zn) and magnesium (Mg) as the group II element, VI I containing any one of sulfur (S), selenium (Se), tellurium (Te), and manganese (Mn) as a group element or any one of them.
The same effect can be obtained by using a group I-VI mixed crystal. Further, although a gallium arsenide (GaAs) substrate is used as a crystal growth substrate in the above-mentioned embodiment, an appropriate thin film crystal (for example, a gallium arsenide film epitaxially grown) is formed on a ZnSe, GaP or gallium arsenide (GaAs) substrate. It may be formed.

[0023]

As is apparent from the above description, according to the molecular beam epitaxy apparatus according to the present invention, a shutter movably supported between a position where the opening of the Knudsen cell is closed and a position where it is not closed is provided. By enabling selective heating by an external infrared lamp, it is possible to prevent the growth material from adhering to the shutter, or to re-evaporate the adhering growth material, and to open the Knudsen cell due to the fall of the adhered material. Since it is possible to prevent blockage and defective opening / closing operation of the shutter, the molecular beam becomes stable, and high-quality crystals can always be obtained. Further, since it is not necessary to provide a complicated wiring or the like in the crystal growth chamber, and only the window is provided in the main body of the molecular beam epitaxy apparatus, there is no fear that the structure becomes complicated.

[Brief description of drawings]

FIG. 1 is a schematic sectional view showing a schematic configuration of a molecular beam epitaxy apparatus in a preferred embodiment according to the present invention.

[Explanation of symbols]

 1 crystal growth chamber 2 ultra-high vacuum exhaust device 3 holder 5 heater 6 main shutter 6a drive shaft 7, 8 Knudsen cell 7a, 8a crucible 7b, 8b heater 9, 10 shutter 9a, 10a drive shaft 9b, 10b heat wire heater 11 excitation cell Device 11a Shutter 12 Casing 12a Orifice 13 Nitrogen gas supply port 14 Pipeline 15 Flow rate control device 16 Pressure reducing valve 17 Magnet 18 Nitrogen cylinder 19 High frequency coil 20 High frequency generator 21 Flux monitor 24, 25 Windows 26, 27 Infrared lamp

Claims (2)

[Claims] 1. A molecular beam epitaxy apparatus for growing a compound semiconductor epitaxial crystal by supplying a growth raw material and a dopant gas to a surface of a substrate in a crystal growth chamber, wherein the molecular beam epitaxy device has an opening inside the crystal growth chamber and an inside. At least one or more Knudsen cells provided with a crucible for receiving a growth material, a shutter movably supported between a position that closes the opening of the Knudsen cell and a position that does not close the opening, and the shutter from the outside. A molecular beam epitaxy apparatus comprising: a transparent window provided at a facing position; and an infrared lamp for heating the shutter by irradiating the shutter with infrared rays from the outside through the window. 2. The molecular beam epitaxy apparatus according to claim 1, wherein the growth raw material is composed of a group II element and a group VI element, and the compound semiconductor epitaxial crystal is composed of a II-VI group compound semiconductor epitaxial crystal. .