JPH1150963A - Getter pump and organic metal molecular beam epitaxial device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently exhaust organic metal molecules by arranging a hot cathode and an anode in the inside of a vacuum container, emitting thermion by electrification to the hot cathode and attaching gas molecules ionized by this thermion by moving them. SOLUTION: A hot cathode 31 and an anode 33 are arranged in the inside of a vacuum container 3, and an electric source Vf32 and an electric source Vc34 are respectively connected to them. Thereafter, thermion is emitted by heating the hot cathode 31 by an electric current supplied from the electric source Vf32, and molecules are ionized by colliding the emitted thermion against organic metal molecules. Additionally, at this time, favourably the two hot cathodes 31 processed in a mesh type are arranged at an opposite position with the anode 33 inbetween, and accordingly, even when the thermion emitted from the one hot cathode 31 passes the anode 33, it retrogresses by influence of an electric field formed by the other hot cathode 31, and as an electron moves for a long distance by repeating such a thing, ionization of the organic metal molecules is carried out.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a getter pump for efficiently capturing a raw material organometallic gas in a vacuum vessel used for forming a thin film of a III-V compound semiconductor, that is, by adsorbing the gas. The present invention relates to an apparatus for creating a high degree of vacuum and an organometallic molecular beam epitaxy apparatus equipped with this getter pump.

[0002]

2. Description of the Related Art An organometallic molecular beam epitaxy apparatus used for forming a thin film of a group III-V compound semiconductor is known from the group II.
Using an organic metal as a Group I raw material and a hydride gas as a Group V raw material,
This is an apparatus for supplying a group III and group V material and growing a group III-V compound semiconductor thin film. It is used especially for the growth of multiple quantum well structures, because high quality crystal thin films can be obtained by growing in a high vacuum, and the film thickness can be controlled to about the thickness of a monoatomic layer. . Further, when growing a mixed crystal containing two or more V groups, the composition ratio between the V groups can be controlled by the supply ratio of the source gas.
It is used when growing a mixed crystal containing P and As as group elements.

FIG. 6 shows an example of a conventional metalorganic molecular beam epitaxy apparatus. The substrate 1 crystal loaded in the vacuum vessel 3 is heated by the heater 2 and is maintained at a desired temperature. The organic metal of the group III raw material is filled in an organic metal bottle 7 and supplied to the vacuum vessel 3 via a flow rate controller 8 and a pipe 10a. The hydride gas of the group V raw material is filled in the hydride gas cylinder 6 and supplied to the vacuum vessel 3 via the flow control device 9 and the pipe 10b. The source gas is thermally decomposed on the substrate 1 and taken into the crystal. Unreacted gas is exhausted by the exhaust system 5. As the exhaust system 5, an oil diffusion pump, a turbo molecular pump, an oil rotary pump, a sputter ion pump, or the like is used.

[0004]

The organometallic gas supplied into the vacuum vessel 3 is thermally decomposed into a metal element and organic side chains. The metal element is taken into the crystal, and the organic side chain is quickly exhausted by the exhaust system 5. However, the supplied organometallic gas drifts in the vacuum vessel 3 with most of the gas being undecomposed. The organic metal gas has a property of repeatedly adsorbing and desorbing on the inner wall of the vacuum vessel 3 and is not easily exhausted. Therefore, there are problems such as that the degree of vacuum during the growth is increased, and that once the organometallic gas is supplied, the degree of vacuum does not rapidly decrease even after the supply is stopped.

[0005] A conventional typical vacuum pump, a sputter ion pump, is a vacuum pump utilizing the ionization phenomenon in a vacuum. The sputter ion pump is shown in FIG.
As shown in FIG. 1B, a honeycomb-shaped anode 13 and two flat cathodes 12 sandwiching the anode 13 are provided. The cathode 12 is made of titanium (Ti). The anode 13 has 3
A potential of ~ 7 kV is applied. Also, a magnetic field B is applied as shown. Electrons emitted from the cathode 12 due to the high voltage between the cathode 12 and the anode 13 reciprocate between the opposing cathodes 12 while helically moving due to the action of the magnetic field B, and can easily reach the anode 13. Can not. Therefore, the electrons travel an extremely long distance before reaching the anode 13. During this time, the electrons collide with gas molecules and ionize them. Positive ions generated by ionization are converted to cathode 12
Is accelerated towards the cathode 1 with thousands of volts of energy
2 and sputters (repels) titanium.
The sputtered titanium atoms adhere to the anode 13 and the inner wall constituting the pump to form an extremely clean titanium film.

[0006] Under such a discharge phenomenon, the sputter ion pump causes an exhaust action in the following two processes. One is a getter action of a clean titanium film, and the other is a phenomenon in which ionized gas molecules collide with the cathode 12 and enter the inside of the cathode 12 to be captured. Organometallic gas is
Since the molecular weight is large, it is difficult to exhaust with a sputter ion pump. The present invention has been made in view of the above-described problems of the related art,
An object of the present invention is to provide a getter pump capable of easily exhausting an organic metal gas and an organic metal molecular beam epitaxy apparatus using the getter pump.

[0007]

A getter pump according to the present invention comprises a hot cathode and an anode disposed in a vacuum vessel, a power supply for emitting thermoelectrons from the hot cathode, and gas molecules ionized by the thermoelectrons. And a power supply for applying an electric field for moving the gas between the hot cathode and the anode, so that ionized gas molecules are attached to the hot cathode.

Further, the getter pump of the present invention has an anode and at least two hot cathodes opposed to each other with the anode interposed therebetween, or a cylindrical hot cathode and an anode inside the hot cathode. It is arranged.

Further, the metalorganic molecular beam epitaxy apparatus of the present invention comprises a hot cathode and an anode disposed in a vacuum vessel, a power source for emitting thermoelectrons from the hot cathode, and gas molecules ionized by the thermoelectrons. And a power supply for applying an electric field for moving the gas between the hot cathode and the anode, and a getter pump for attaching ionized gas molecules to the hot cathode.

FIG. 1 is a conceptual diagram showing the basic structure of a getter pump according to the present invention. A hot cathode 31 and an anode 33 are arranged in a vacuum container. A power supply Vf32 for emitting thermoelectrons from the hot cathode 31, a hot cathode 31 and an anode 33;
A power supply Vc 34 for applying an electric field is connected between the two.
Usually, the getter pump is not used alone, but is used in combination with another exhaust system (not shown) such as an oil diffusion pump, a turbo-molecular pump, and an oil rotary pump.

The operation principle of the getter pump according to the present invention will be described. The hot cathode 31 is heated by a current supplied from the power supply Vf32 and emits thermoelectrons. The thermoelectrons emitted from the hot cathode 31 collide with surrounding organometallic molecules to ionize the molecules. Since the organometallic molecule is mainly positively charged, it moves to the cathode side by the electric field between the anode and the cathode. In the present embodiment, since the surface of the cathode is heated to form the hot cathode 31, the organometallic molecules attached to the hot cathode 31 are thermally decomposed, and the metal element having a low vapor pressure and the organic side having a high vapor pressure are removed. Breaks down into chains. The organic side chain having a high vapor pressure is desorbed, but the metal element having a low vapor pressure remains adsorbed on the surface of the hot cathode 31. The organic side chains are quickly exhausted by an exhaust system such as an oil diffusion pump, a turbo molecular pump, and an oil rotary pump.

[0012]

FIG. 2 is a view showing an embodiment of a getter pump according to the present invention, in which two hot cathodes 31 processed into a mesh shape are arranged at opposing positions sandwiching an anode 33. FIG. FIG. Since the hot cathodes 31 are arranged so as to face each other with the anode 33 interposed therebetween, the thermoelectrons emitted from one hot cathode 31 pass through the anode 33 and remain in the electric field formed by the other hot cathode 31 facing the other. Reversing under the influence. By repeating such a process, the electrons move over an extremely long distance, so that the organic metal molecules can be efficiently ionized. Therefore, the thermal decomposition of the organometallic molecules on the cathode side and the adhesion of the decomposed metal elements also increase. Further, by processing into a mesh shape, the area for adsorbing the thermally decomposed metal element can be made larger than that of a single-wire hot cathode.

FIG. 3 is a view showing a getter pump according to another embodiment using a cylindrical hot cathode 31 processed into a mesh. The anode 33 is disposed in the cylindrical hot cathode 31. The getter pump of FIG. 3 has the same effect as that described for the getter pump of FIG. Further, since the hot cathode 31 is processed into a mesh shape, organometallic molecules can easily enter the inside of the cylindrical hot cathode 31. Therefore, the organic metal molecules can be efficiently captured.

FIG. 4 is a configuration diagram of an organometallic molecular beam epitaxy apparatus 50 including the getter pump 30 of the present invention. The part surrounded by the dotted line is the getter pump 30.
The substrate 1 crystal loaded in the vacuum vessel 3 is heated by the heater 2 and is maintained at a desired temperature. The organic metal of the group III raw material is filled in an organic metal bottle 7 and supplied to the vacuum vessel 3 via a flow rate controller 8 and a pipe 10a.
The hydride gas of the group V raw material is filled in the hydride gas cylinder 6 and supplied to the vacuum vessel 3 via the flow control device 9 and the pipe 10b. Unreacted gas is exhausted by the exhaust system 5. As the exhaust system, an oil diffusion pump and an oil rotary pump are used. Although the organometallic molecular beam epitaxy apparatus 50 of the present invention includes the getter pump 30, the conventional organometallic molecular beam epitaxy apparatus 20 (FIG. 5)
And different. For this reason, there is an effect that the growth can be performed while maintaining the vacuum degree lower than before, and the vacuum degree is quickly reduced after the supply of the organic metal gas is stopped.

[0015]

The getter pump according to the present invention comprises a hot cathode and an anode disposed in a vacuum vessel, a power supply for emitting thermoelectrons from the hot cathode, and an electric field for moving gas molecules ionized by the thermoelectrons. Is provided between the hot cathode and the anode, and the ionized gas molecules are attached to the hot cathode, whereby the organometallic molecules can be efficiently exhausted. Further, the organometallic molecular beam epitaxy apparatus of the present invention includes a hot cathode and an anode disposed in a vacuum vessel, a power supply for emitting thermoelectrons from the hot cathode, and moving gas molecules ionized by the thermoelectrons. A power source for applying an electric field between the hot cathode and the anode is provided, and a getter pump configured to attach ionized gas molecules to the hot cathode is provided, thereby maintaining a lower vacuum than before. This has the effect that the growth can be performed as it is, and that the degree of vacuum immediately drops after the supply of the organometallic gas is stopped.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram showing a basic structure of a getter pump of the present invention.

FIG. 2 is a view showing one embodiment of a getter pump of the present invention.

FIG. 3 is a view showing another embodiment of the getter pump of the present invention.

FIG. 4 is a configuration diagram of an organometallic molecular beam epitaxy apparatus of the present invention.

FIG. 5 is a diagram showing a prior art sputter ion pump.

FIG. 6 is a diagram showing an example of a conventional organometallic molecular beam epitaxy apparatus.

[Description of Signs] 1 ... Substrate 2 ... Heater 3 ... Vacuum container 4 ... Gate valve 5 ... Exhaust system 6 ... Hydride gas cylinder 7 ... Organic metal bottle 8 ... Organic metal gas flow controller 9 ... Hydride gas flow controller 10 ... Piping a 11 ... Piping b 12 ... Cathode 13 ... Anode 20 ... Organic metal molecular beam epitaxy apparatus 30 ... Getter pump 31 ... Hot cathode 32 ... Power supply Vf 33 ... Anode 34 ... Power supply Vc 50 ... Organic metal molecular beam epitaxy apparatus

Claims (5)

[Claims] A hot cathode and an anode disposed in a vacuum vessel; a first power supply for emitting thermoelectrons from the hot cathode; and a second power supply for applying an electric field between the hot cathode and the anode. A getter pump configured to cause gas molecules in the vacuum vessel ionized by the thermoelectrons to adhere to the hot cathode. 2. The getter pump according to claim 1, wherein the vacuum vessel has an anode and at least two hot cathodes arranged with the anode interposed therebetween. 3. The getter pump according to claim 1, wherein a cylindrical hot cathode housed in said vacuum vessel and an anode are arranged inside said hot cathode. 4. The getter pump according to claim 1, wherein said hot cathode is a structure processed into a mesh shape. 5. An organic metal gas supply means for generating an organic metal gas and supplying the same to the vacuum vessel; a hydrogen gas supply means for generating a hydrogen gas and supplying the hydrogen gas to the vacuum vessel; An organometallic molecular beam epitaxy apparatus comprising: an exhaust system for discharging a reaction gas to the outside; and the getter pump according to claim 1.