JPH0350131A - Device for molecular-beam epitaxy - Google Patents

Abstract

PURPOSE:To improve the reproducibility, production efficiency and quality of an epitaxial film by charging a molecular-beam source material highly purified in an exclusive device or a molecular-beam source feeder into a molecular-beam source crucible of a reaction chamber without the material being brought into contact with air. CONSTITUTION:A discharge port 21 is opened, a treating crucible 15 charged with a molecular-beam source material 14 is set in a treating chamber 16, a vacuum valve 20 is opened to evacuate the chamber 16 to 10<-9>Torr, and then the material 14 is melted by a heater 17b. A valve 19a is opened to introduce gaseous H2 into the chamber 16, the valve 20 is simultaneously closed, a valve 19b is closed when the gaseous H2 pressure in the chamber 16 is increased above atmospheric pressure, the material 14 is heat-treated, and then the material 14 is cooled, solidified and highly purified. The valves 19a and 19b are then closed, the valve 20 is opened to evacuate the chamber 16 to the order of 10<-9>Torr, and then a molecular-beam source transter gate valve 7b is opened. An external magnet 22c is operated to insert the crucible 15 into a molecular-beam source crucible 1, a heater 8 is energized to heat the material 14 in the crucible 1 above its melting point, and the liquefied material 14 is dropped into the crucible 1 from a small hole 15a provided at the bottom of the crucible 15.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to improvements in molecular beam epitaxy equipment.

[Conventional technology]

Molecular beam epitaxy equipment is considered important as an epitaxial equipment for semiconductor devices that requires steep interfaces and high controllability of film thickness. The molecular beam epitaxy apparatus includes a bell jar 12 which is a reaction chamber, and a molecular beam source crucible 1 housed inside the bell jar 12. Substrate holder 3 for heating the substrate 2; and liquid nitrogen cooling traps 4a and 4b for adsorbing impurity gas, and a vacuum exhaust system 5 connected to the bell jar 12. leak valve 6
, and a substrate transfer gate valve 7a. The molecular beam source crucible 1 also has a heating heater 8. It is equipped with a thermocouple 9 and a heat radiation plate 10a, and has a structure that allows the temperature inside the crucible 1 to be controlled to a desired temperature. Further, a crucible flange 11 is attached to this molecular beam source crucible 1, and this crucible flange 11 is detachably attached to a crucible port flange 13 fixed to a bell jar 12.

In the conventional molecular beam epitaxy apparatus described above, when filling the molecular beam source crucible 1 with the molecular beam source material 14, nitrogen gas is introduced into the bell jar 12 from the leak valve 6 to break the vacuum and the molecular beam source crucible 1 is filled with the molecular beam source material 14. The crucible flange 11 was removed from the crucible port flange 13 to take it out into the atmosphere, and the molecular beam source material 14 was filled into the molecular beam source crucible 1 in the atmosphere.

[Problem that the invention seeks to solve]

Since the conventional molecular beam epitaxy apparatus is configured as described above, it has the following drawbacks.

(1) By breaking the vacuum, the molecular beam source crucible 1° substrate holder 3. Constituent members such as the liquid nitrogen cooling traps 4a and 4b are contaminated, which adversely affects the crystallinity and reproducibility of the epitaxial film.

(IF) Through the steps necessary before starting crystal growth again after breaking the vacuum, such as baking the bell jar 12 and vacuum heat treatment of the molecular beam source crucible 1 and the molecular beam source material 14,
The production efficiency is low because it requires a growth preparation period of about -weeks.

(III) Contaminants in the atmosphere of the molecular beam source material 14 cannot be completely removed by vacuum heat treatment alone, and this problem is particularly noticeable with oxides of group III elements, and furthermore, impurity gases grow during heat treatment. is released into a chamber where
These impair the crystallinity of the epitaxial film (and also cause defects on the surface of the epitaxial film).

The present invention was made to solve these conventional problems, and allows epitaxial growth without exposing the inside of the growth chamber to the atmosphere, improving the reproducibility and production efficiency of epitaxial films, and improving the quality of the epitaxial films. The purpose of the present invention is to provide a molecular beam epitaxy device that can greatly improve the performance.

[Means for solving problems]

The present invention uses a molecular beam epitaxy apparatus to prevent molecular beam source materials that have been highly purified through vacuum heat treatment or heat treatment in a hydrogen atmosphere from being exposed to the atmosphere using an airlock system (molecular beam source materials filled into a molecular beam source crucible). It is equipped with a processing device.

[Effect]

In the molecular beam epitaxy apparatus according to the present invention, the molecular beam source material is highly purified in advance in a dedicated device for highly purifying the molecular beam source material or in a molecular beam source supply device provided separately from the reaction chamber, Thereafter, it is filled into a molecular beam source crucible in a reaction chamber without being exposed to the atmosphere.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings, taking Ga as an example of the molecular beam source material.

1 and 2 show an embodiment of the present invention.

In the figure, the same reference numerals as in FIG. 3 indicate the same or equivalent parts, and 30 is a molecular beam source supply device, and the molecular beam source processing chamber 16, which is a closed container thereof, is connected to the bell jar 12 via the gate valve 7b. It is connected. 20 is a vacuum exhaust valve, 21
19 is a boat for taking out a crucible for molecular beam source processing; 19 is a gas supply device for supplying hydrogen gas into the processing chamber 16;
Consists of 9b.

In addition, a processing crucible 15 is provided in the molecular beam source processing chamber 16.
A PBN heating furnace 17a and a heating heater 17 are used to heat-treat the molecular beam source material 14 placed in the crucible 15.
b, a heating device 17 consisting of a heat radiation plate 17c, and a liquid nitrogen trap 4C for adsorbing gas released during heat treatment.

A small hole 15a is formed at the bottom of the processing crucible 15, and is used to allow the molecular beam source material 14 to fall into the molecular beam source crucible 1 when it is melted. .

Further, 22a is a moving rod for moving the processing crucible 15, which is connected to an internal magnet 22b, and this internal magnet 22b is magnetically coupled to an external magnet 22C to move the external magnet 22c. Crucible 1 for processing by
A crucible insertion device 22 for moving the crucible 5 is constructed.

Next, the operation will be explained.

First, in order to highly purify the molecular beam source material, open the take-out boat 21 and take out the processing crucible 15, fill it with Ga which is the molecular beam source material 14, and then
5 is set in the processing chamber 16 again. Then, the vacuum valve 20 is opened to evacuate the processing chamber 16 to a degree of vacuum on the order of 10-'torr, and after evacuation, current is applied to the temperature increasing heater 17b to raise the temperature of the evaporation source material Ga to about 950°C. Approximately 1
After a period of time has elapsed, the hydrogen introduction valve 19a is opened to introduce hydrogen gas into the processing chamber 16, and at the same time the vacuum exhaust valve 19a is opened.
Close 0. Then, when the hydrogen gas pressure in the molecular beam source processing chamber 16 becomes equal to or higher than atmospheric pressure, the hydrogen release valve 19b is opened.

After that, depending on the amount of Ga, for example, 2
Heat treatment is performed for 4 hours.

After a predetermined period of time has elapsed, the supply of electricity to the temperature increasing heater 17b is stopped and the evaporation source material Ga is cooled and solidified, thereby making the molecular beam source material 14 highly purified. Thereafter, the hydrogen-releasing pulp 19b is closed, and the hydrogen-introducing pulp 19a is also closed, and the evacuation valve 20 is opened again to evacuate the molecular beam source processing chamber 16 to a level of 10-9 torr.

Next, in order to fill the molecular beam source crucible 1 with the highly purified molecular beam source material 14, the process chamber 16 is evacuated, the molecular beam source transfer gate valve 7b is opened, and the external magnet 22c is opened.
The processing crucible 15 is inserted into the molecular beam source crucible 1 by operating the .

Then, by energizing the heating heater 18, the temperature inside the molecular beam source crucible 1 is raised to a temperature higher than the melting point of Ga. Then, the liquefied Ga falls from the small hole 15a provided at the bottom of the processing crucible 15, and is filled into the molecular beam source crucible 1 (see Fig. 2), and is processed by operating the filling diameter external magnet 22c. When the crucible 15 to be used is returned to the molecular beam source processing chamber 16 and the molecular beam source transfer gate pulp 7b is closed, filling with the molecular beam source material is completed.

In this way, in this example, the molecular beam source material is highly purified in advance in the sealed processing chamber 6 and is supplied into the molecular beam source crucible 1 without coming into contact with the atmosphere, so that the following effects can be achieved. There is.

(I) No atmosphere is introduced into Belljar 12,
Therefore, the components inside the bell jar 12 can be prevented from being contaminated, and the crystallinity of the epitaxial film can be improved.

There is no negative effect on reproducibility.

(n) The preparation steps required before restarting crystal growth can be significantly reduced, and production efficiency can be improved.

(III) The molecular beam source material is not contaminated with the atmosphere,
Furthermore, there is no need for heat treatment within the bell jar 12, and therefore, contaminants are not brought into the bell jar 12 and impurity gases are not released into the bell jar 12. can be prevented from occurring.

Although the above embodiments have been explained by taking Group (2) elements as an example, the present invention is not limited to the Group (2) elements, but all elements can be used. It will be filled as a solid without any oxidation.

Further, in the above embodiment, heat treatment was performed in a hydrogen atmosphere, but molecular beam source materials that do not require hydrogen treatment, such as As and P, may be highly purified by vacuum heating in the molecular beam source processing chamber 16. Further, the processing temperature may be set to a temperature at which the oxide of the molecular beam source material can be evaporated.

In addition, when filling the processing crucible 15 in the molecular beam source processing chamber 16 with highly purified molecular beam source material in advance, the molecular beam source processing chamber 16 is brought to a predetermined degree of vacuum after filling the molecular beam source. After evacuation, it may be introduced into the molecular beam source crucible 1 immediately without heat treatment.

Furthermore, the concept of the present invention is applicable not only to molecular beam epitaxy but also to high purity vapor deposition sources in vacuum evaporation, electron beam evaporation, sputtering evaporation, and the like.

〔Effect of the invention〕

As described above, according to the molecular beam epitaxy apparatus according to the present invention, since the molecular beam source processing apparatus is provided that fills highly purified molecular beam source material without exposing it to the atmosphere, the inside of the growth chamber is exposed to the atmosphere. This has the effect of making it possible to perform epitaxial growth without any problems, improving the reproducibility of epitaxial growth and mass productivity, and producing a high-quality epitaxial film with few surface defects.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a molecular beam epitaxy apparatus according to an embodiment of the present invention, FIG. 2 is a diagram showing the filling state of the molecular beam source material into a molecular beam source crucible, and FIG. 3 is a diagram showing a conventional molecular beam epitaxy apparatus. FIG. 2 is a cross-sectional view of the device. DESCRIPTION OF SYMBOLS 1... Molecular beam source crucible, 2... Substrate, 7b... Gate valve (open/close M), 12... Belljar (reaction chamber), 1
4... Molecular beam source material, 15... Processing crucible, 15
a...Small hole, 16...Molecular beam source processing chamber (closed container)
, 17... Heating device, 19... Atmospheric gas supply device, 22... Crucible insertion device, 30... Molecular beam source supply device.

Claims (1)

[Claims] (1) In a molecular beam epitaxy device in which a molecular beam substance from a molecular beam source crucible is grown as a crystal on a substrate in a reaction chamber, a boat is provided for transporting the substrate to the reaction chamber, and a boat is connected to the reaction chamber via a gate valve. a closed container arranged in the closed container and having a small hole at its bottom for the molecular beam source material that needs to be accommodated, melted, and dropped into the molecular beam source crucible; a processing crucible; an atmospheric gas supply device for supplying hydrogen gas into the sealed container; a heating device provided in the sealed container to heat the processing crucible; opening the gate valve to transfer the processing crucible to the molecular beam; A molecule comprising a crucible insertion device inserted into a source crucible, and a molecular beam source supply device that supplies molecular beam source material and the molecular beam source into the molecular beam source crucible without exposing the inside of the reaction chamber to the atmosphere. Line epitaxy equipment.