JPH05234916A - Molecular beam epitaxy equipment - Google Patents

Abstract

PURPOSE:To facilitate excitation of growth material, by using an excitation cell equipment together with a Knudsen cell, while this equipment has a casing which supplies gas to the inside and has an outlet of radicals, and a light source which optically decomposes the gas and supplies light having energy capable of excitation to the inside of the casing. CONSTITUTION:A first irradiation part 8a for irradiating the inside of an excitation cell equipment 4 with discharge light, and a second irradiation part 8b for irradiating the surface of a substrate B with discharge light are installed at the top part of a discharge tube 8. A light source 5 in the excitation cell equipment 4 is turned on, and ammonia gas is supplied to the inside of the excitation cell equipment 4 via a pipe channel 6 and a gas nozzle 6a, and nitrogen radicals are generated. Light is shed on the subtrate B from the second irradiation part 8b. Since said light has energy larger than that of zinc selenide, the crystal growth of zinc selenide on the substrate B surface is accelerated. Thereby growth material gas or dopant gas can be easily excitated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to at least one of a growth raw material and a dopant for growing a compound semiconductor epitaxial crystal by supplying one or a plurality of types of growth raw materials and a dopant to the surface of a substrate in a high vacuum. The present invention relates to a molecular beam epitaxy apparatus having such a molecular beam source.

[0002]

2. Description of the Related Art A molecular beam epitaxy method (hereinafter abbreviated as MBE method in the present specification) and a metal organic chemical vapor deposition method (hereinafter abbreviated as MOCVD method in the present specification) are mainly used for epitaxial crystal growth of a compound semiconductor. Are generally used.

On the other hand, Japanese Patent Application Laid-Open No. 62-88329 discloses
As an example of the II-VI group epitaxial crystal, an epitaxial crystal of zinc selenide (ZnSe) is grown on a gallium arsenide (GaAs) substrate, and arsenic (As), phosphorus (P), or nitrogen (N) is used as a dopant. Introduce p
Structures for obtaining mold crystals are disclosed. According to DePuydt et al. In the United States, a nitrogen radical beam is generated by an rf plasma cell by the MBE method at 10 ¹⁸ c.
A method of realizing nitrogen doping of m ⁻³ unit has been proposed (Appl. Phys. Lett. 57, 2127).
(1991)), which suggests that a low resistance p-type crystal can be obtained.

However, in order to generate the nitrogen radical beam by the rf plasma cell, the atmospheric pressure condition is set to 10 ^-1.
It is generally about 10 ^-2 torr, but M
The general application condition of the BE method is 10 ⁻⁷ to 10 ⁻¹⁰ torr.
Since it was a degree, the conditions did not match and it was not really realistic. Further, when a radical beam is generated by plasma, there is a concern that substances other than the dopants forming the cell may also be hit and diffused as contaminants into the epitaxial crystal, significantly deteriorating its quality.
Further, in the case of such an MBE device, the mean free path of radicals generated from the plasma cell is about several mm, and it is necessary to shorten the distance between the cell and the substrate. Therefore, the area of the substrate to be doped is increased. There were some problems that I couldn't do.

[0005]

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 easily excite a growth raw material or a dopant and to satisfy crystal growth conditions. Can be improved and the structure is simple.
It is to provide a BE device.

[0006]

According to the present invention, the above-mentioned object is to grow a compound semiconductor epitaxial crystal by supplying one or more kinds of growth raw materials and dopants to the surface of a substrate in a high vacuum. A molecular beam epitaxy apparatus having a molecular beam generation source of at least one of the growth raw material and the dopant, wherein either the growth raw material or the dopant is a gas, and the gas is supplied to the inside. A casing provided with an outlet for the radicals, a light source that photolytically decomposes the gas, and supplies light of excitable energy into the casing, and guides light from the light source to the substrate surface. To provide a molecular beam epitaxy device having an excitation cell device having means for activating a substrate surface. It is made. In particular, it is preferable to further include means for irradiating the surface of the substrate with an electron beam capable of activating the surface of the substrate, and means for detecting a crystal growth state from the electron beam reflected on the surface of the substrate.

[0007]

According to the above structure, the gas to be excited can be photoexcited without passing through the casing of the cell device without exciting unnecessary substances other than the target gas. In addition, by guiding and irradiating the substrate with light from a light source,
The substrate is activated during crystal growth, and crystal growth is promoted.
Further, the substrate surface is irradiated with an electron beam capable of activating the surface,
Further, by detecting the crystal growth state from the reflected electron beam, the crystal growth can be further promoted and the growth state can be managed.

[0008]

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 side sectional view of an MBE apparatus showing a first embodiment to which the present invention is applied. In this embodiment, zinc selenide (Zn) on a gallium arsenide (GaAs) substrate is used.
MBE for growing an epitaxial crystal of Se) and introducing nitrogen (N) as a dopant to obtain a p-type crystal
It is a device.

The reaction tube 1 has a rectangular cross section and extends in the vertical direction, and an intermediate portion of the internal passage 1a forms a reaction chamber 2. Further, a susceptor 3 for holding the substrate B downward and rotating it is provided in the upper portion of the reaction chamber 2. A resistance heater for heating the substrate B is attached to the susceptor 3 (not shown).

A Knudsen cell 11 for supplying the growth raw material as a molecular beam to the surface of the substrate B is provided at a lower position of the internal passage 1a in the figure. Further, at a position adjacent to the Knudsen cell 11, an excitation cell device 4 connected to an external ammonia gas supply source (not shown) is provided in order to supply nitrogen radicals as a dopant to the surface of the substrate B. ing.

As shown in FIG. 2, the excitation cell device 4 has a conical shape and is held so that its bottom surface faces the substrate B. A circular nitrogen radical outlet 4 a is provided on the bottom surface of the excitation cell device 4. Further, at a position facing the inside of the excitation cell device 4 from a part of the outlet 4a, there is sufficient energy to photolyze ammonia gas and generate nitrogen radicals (wavelength 120 nm to 190 nm).
A light source 5 for receiving the excitation light is received.

A gas nozzle 6a at the tip of the ammonia gas supply pipe 6 is provided so as to project into the excitation cell device 4 at a side end portion opposite to the bottom surface of the excitation cell device 4. The gas nozzle 6a has a large number of gas ejection ports on its peripheral surface. The outlet 4a is provided with a shutter 7 capable of selectively opening and closing the outlet so that the generated nitrogen radicals can be selectively supplied to the reaction chamber 2.

Here, the conical length L of the excitation cell device 4
Is 5 times or more the bottom surface diameter D, and the diameter S of the outlet 4a is 1/2 or less of the bottom surface diameter D. As a result, the excitation cell device 4 forms a so-called black body furnace, and the light source 5 is provided outside.
It is designed so that the light emitted from it does not leak. Further, the entire inner wall surface 4b of the cone is a mirror surface, and the light emitted from the light source 5 can be effectively used for generating nitrogen radicals.

Actually, the relationship among the conical length L of the excitation cell device 4, the bottom surface diameter D and the diameter S of the outlet 4a is that the pressure of the dopant gas, the flow velocity, the mean free path of the nitrogen radicals, the substrate B, and the like. It may be determined based on the relationship with the size of the diameter S.

The light source 5 comprises a discharge tube 8 in which a discharge gas is replaceably filled, and a microwave cavity for supplying a microwave to the discharge gas in the discharge tube 8 to generate discharge light. And a resonator 9, for example, JP-A-61-1
The discharge light generating device is similar to the device disclosed in Japanese Patent No. 2022. In addition, a first irradiation unit 8a for irradiating the discharge cell 8 with discharge light at the tip of the discharge tube 8 and a second irradiation unit 8b for irradiating the surface of the substrate B with discharge light.
And are provided.

A control unit 10 is connected to the gas supply unit (not shown) for the discharge tube 8 and the microwave cavity resonator 9 to control them. The control device 10 is connected to a discharge light intensity sensor 10a installed in the vicinity of the discharge tube 8, and based on the discharge light intensity detection value from the sensor 10a, the microwave generation amount and the discharge by the microwave cavity resonator 9 are generated. By adjusting the gas pressure and the like, the discharge light intensity is feedback-controlled.

Susceptor 3, ie substrate B and excitation cell device 4
An electron gun 12 as an electron beam irradiation source for obliquely irradiating the surface of the substrate B with an electron beam, and a sensor 13 capable of detecting the electron beam reflected on the surface of the substrate B are provided between and. .. The sensor 13 is a sensor for detecting a crystal growth state from an electron beam reflected on the surface of the substrate B.

Next, the operating procedure of this embodiment will be described. First, the gallium arsenide substrate B is held downward on the susceptor 3, and the substrate B is rotated and heated. At this time, the growth raw material is supplied to the substrate B from the Knudsen cell 11 as a molecular beam from the internal passage 1a. Further, the light source 5 of the excitation cell device 4 is turned on, and ammonia gas is supplied into the excitation cell device 4 through the pipe line 6 and the gas nozzle 6a.
Then, photoexcited nitrogen radicals are generated from this ammonia gas. At this time, the amount of nitrogen radicals supplied into the reaction chamber 5 can be appropriately controlled by feedback-controlling the intensity of the discharge light. Then, the shutter 7
By selectively opening and closing, nitrogen can be introduced as a dopant into the growing epitaxial crystal of zinc selenide.

On the other hand, both gases are supplied into the reaction chamber 2, and at the same time, light is irradiated from the second irradiation section toward the substrate B. Since this light has a higher energy than the band gap (band gap) of zinc selenide, the crystal growth of zinc selenide on the surface of the substrate B is promoted.

Further, an electron beam is emitted from the electron gun 12 toward the surface of the substrate B. As a result, the crystal growth is further promoted and the crystal growth state can be monitored by detecting the electron beam reflected on the surface of the substrate B by the sensor 13.

FIG. 3 is a view similar to FIG. 2 showing a second embodiment to which the present invention is applied. The configuration of this embodiment is almost first
The same parts as those in the first embodiment are designated by the same reference numerals, and detailed description thereof will be omitted.

The overall structure of this embodiment is substantially the same as that of the first embodiment, except that the excitation cell device 24 has a bottomed cylindrical shape, one bottom surface of which faces the substrate B and a circular nitrogen radical. An outlet 24a is provided. Further, at a position where the inside of the excitation cell device 24 is exposed from a part of the outlet 24a, the light source 2 including the discharge light generating device having the discharge tube 28 and the microwave cavity resonator 29 similar to those of the first embodiment.
5 are provided. Discharge tube 28 in this light source 25
Only the irradiation part 28a for irradiating the discharge cell device 24 with the discharge light is provided at the tip of the.

On the other hand, a gas nozzle 26a at the tip of the ammonia gas supply pipe 26 is provided on the other bottom surface opposite to the bottom surface.
Are provided so as to plunge into the excitation cell device 24. The entire inner wall surface 24b of the excitation cell device 24 is a mirror surface. As a result, a certain amount of light is transmitted to the wall surface 24.
It is reflected by b and is irradiated onto the substrate B through the outlet 24a. The other structure is the same as that of the first embodiment.

In each of the above embodiments, the excitation cell device has a conical shape or a cylindrical shape, but it may have a pyramid shape or a cylindrical shape having a polygonal cross section. Further, in each of the above-described embodiments, the entire inner wall surface of the excitation cell device or most of the inner wall surface is a mirror surface that totally reflects, but in reality, it may be a diffused surface that diffusely reflects. Furthermore, in each of the above-mentioned embodiments, the light source is constituted by the discharge light generator, but a normal D2 lamp or the like may be used.

[0026]

As is apparent from the above description, according to the molecular beam epitaxy apparatus of the present invention, a casing is provided with a gas inside and a radical outlet is provided, and By using a Knudsen cell together with an excitation cell device having a light source that photolyzes a gas and supplies light of excitable energy to the inside of the casing, it is possible to easily excite a growth source gas or a dopant gas, and other than that. There is no need to worry about exciting unnecessary substances. Further, by partially guiding the light from the light source to the surface of the substrate to activate the surface of the substrate, crystal growth is promoted, and a compound semiconductor epitaxial crystal can be grown early. In addition, by irradiating the surface of the substrate with an electron beam capable of activating the surface and detecting the crystal growth state from the reflected electron beam, the crystal growth can be further promoted and the growth state can be controlled.

[Brief description of drawings]

FIG. 1 is a side sectional view showing a first embodiment of the present invention.

FIG. 2 is an enlarged sectional view of a main part of FIG.

FIG. 3 is a side sectional view similar to FIG. 2, showing a second embodiment of the present invention.

[Explanation of symbols]

 1 Reaction Tube 1a Internal Passage 2 Reaction Chamber 3 Susceptor 4 Excitation Cell Device 4a Nitrogen Radical Outlet 4b Wall Surface 5 Light Source 5a First Irradiation Section 5b Second Irradiation Section 6 Pipeline 7 Shutter 8 Discharge Tube 9 Microwave Cavity Resonator 10 Control device 10a Strength sensor 11 Knudsen cell 12 Electron gun 13 Sensor 24 Excitation cell device 24a Nitrogen radical outlet 24b Wall surface 25 Light source 25a Irradiation part 26 Tube 26a Gas nozzle 28 Discharge tube 29 Microwave cavity resonator

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location H01L 21/26 8617-4M

Claims (9)

[Claims] 1. Generation of a molecular beam of at least one of the growth raw material and the dopant in order to grow a compound semiconductor epitaxial crystal by supplying one or a plurality of types of growth raw materials and the dopant to the surface of the substrate in a high vacuum. A molecular beam epitaxy apparatus having a source, wherein one of a growth raw material and a dopant is a gas, the casing is provided with the gas, and the radical outlet is provided, An excitation cell device comprising a light source that photolyzes a gas and supplies light having excitable energy to the inside of the casing, and means for guiding the light from the light source to the substrate surface to activate the substrate surface. A molecular beam epitaxy device characterized by having. 2. The apparatus further comprises means for irradiating the surface of the substrate with an electron beam capable of activating the surface of the substrate, and means for detecting a crystal growth state from the electron beam reflected on the surface of the substrate. The molecular beam epitaxy apparatus according to claim 1. 3. The light source comprises a discharge tube in which a discharge gas is replaceably filled, and a microwave cavity resonator for irradiating microwaves to generate discharge light in the discharge gas in the discharge tube. 3. The molecular beam epitaxy apparatus according to claim 1 or 2, which comprises a discharge light generator. 4. The black body furnace, wherein the light source has an irradiating unit for irradiating the inside of the casing and the surface of the substrate with light, and the casing prevents the light emitted from the light source into the casing from leaking to the outside. The molecular beam epitaxy apparatus according to any one of claims 1 to 3, wherein 5. The molecular beam epitaxy apparatus according to claim 4, wherein the black body furnace has any one of a cylindrical shape, a conical shape, and a pyramidal shape. 6. The method according to claim 1, wherein the casing has a shape that guides a part of the light emitted from the light source into the casing to the surface of the substrate. Molecular beam epitaxy equipment. 7. The molecular beam epitaxy apparatus according to claim 1, wherein an inner wall surface of the casing forms a mirror surface that reflects light emitted from the light source. 8. The dopant is a group V element simple substance,
The molecular beam epitaxy apparatus according to any one of claims 1 to 7, wherein the molecular beam epitaxy device comprises a member gas selected from a group V element compound and a group I element compound. 9. The molecular beam epitaxy apparatus according to claim 8, wherein the group V element is nitrogen, phosphorus, arsenic, and antimony, and the group I element compound is a lithium alkyl compound. .