JPH03167741A - Electron gun for medium vacuum - Google Patents

Abstract

PURPOSE:To stably use an electron gun for medium vacuum over a long period even under reaction gas atmosphere that causes bad effects on an electron supply element by providing an inactive gas supply means for keeping the electron emitting portion of the element in inactive gas atmosphere. CONSTITUTION:During supply of reaction gas to inside a reaction container 6, argon gas is supplied from a gas supply system 3 to around the filament 1 of an electron gun 7. Atmospheric gas (including the reaction gas and the argon gas) is continuously exhausted from inside the reaction container 6 through an exhaust system 8; the density distribution of the argon gas whose peak is located in a point around the filament 1 of the electron gun 2 is thereby formed inside the reaction container 6 whose pressure is kept constant during the above process. Therefore, the density of the reaction gas is at its minimum around the filament 1 and the possibility of the reaction gas making contact and reacting with the heated portion of the filament 1 is reduced. Normal emission of thermoelectrons by the filament 1 is thus maintained over a long period of time.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention provides a medium vacuum region (10-
The present invention relates to an electron gun suitable for use in chemical reaction processes at temperatures of up to 10 torr.

[Prior Art] In high vacuum electron guns used for applications such as electron beam melting and X-ray generation, electrons generated by an electron supply element such as a filament are accelerated at a high voltage of several kilovolts or more. When using an electron gun to excite ionize gas molecules or trigger gasification reactions, and to control chemical reactions in a medium-vacuum gas atmosphere, soft acceleration of less than V is required. . That is, the aim here is to avoid unnecessary decomposition or damage to the dregs molecules by high-energy electrons, and to obtain a reaction of controlled type and rate.

Generally, electron generation methods in electron guns include, in addition to thermionic emission from a heated substance, photoelectron emission by photoexcitation of a substance, field emission of electrons from a protrusion to which a high voltage is applied, and discharge gas plasma. There is a method of extracting electrons from the electron beam using an extraction voltage, but in the electron gun that performs the above-mentioned soft acceleration, a method using thermionic emission or photoelectron emission is adopted. This is because it is difficult to adjust electrons, which already have high or variable energy at the time of generation, to a uniform energy level of less than a dozen V due to field emission or discharge gas plasma.

FIG. r82 shows an example of an electron gun 2B that causes the filament 1 to emit thermionic electrons, and a process device that forms a thin film using the electron gun 2B. In this process equipment, the pressure of the reaction gas atmosphere is controlled in the medium vacuum region (lO-2~10
-'torr), the reaction gas molecules are
A thin film is formed by irradiating a low-energy electron beam of V to ionize it and mutually crosslinking it on the substrate 11.

In FIG. 2, the reaction vessel 6 includes an exhaust system 8 for exhausting the atmosphere, reaction residue, etc., and a reaction gas supply system 7 consisting of a reaction gas container, a flow rate regulator, piping, etc. for supplying the reaction gas. are connected. Prior to the start of the process, the atmosphere inside the reaction vessel 6 is brought to a high vacuum (10"-") by the exhaust system 8.
10-'torr), and then a reaction gas is supplied into the reaction vessel 6 by the reaction gas supply system 7. The pressure inside the reaction vessel 6 during the process depends on the balance between the exhaust characteristics of the exhaust system 8, the supply amount of the reaction gas supply system 7, and the reaction rate of the reaction gas, so the reaction gas is supplied by a control system (not shown). By adjusting the supply amount of the system 7, the inside of the reaction vessel 6 is maintained at a predetermined pressure in the medium vacuum region (10-2 to 10-'torr).

On the other hand, the electron gun 2B has a filament 1 made of tungsten.
, a conductive tube 2b, a grid 5, etc., and the filament 1 and the grid 5 are connected to a filament current power source 13 and an accelerating voltage power source 14 outside the reaction vessel 6, respectively.

Here, since a positive voltage is applied to the electron gun 2B containing the filament 1 by the accelerating voltage power supply 14, the thermoelectrons generated in the filament 1 fall through the electric field between the tube 2b and the grid 5. It stores kinetic energy and flies out in the direction of the arrow.

Now, the reaction vessel 6 maintained in a reaction gas atmosphere at a predetermined pressure
When an electron beam is irradiated from the electron gun 2B into the inside, the reactive gas molecules are excited and decomposed to form highly reactive active molecules. After the active molecules are deposited on the substrate 11, a crosslinking reaction is further progressed between the active molecules to form the thin film 12.

[Problems with the prior art] Since the interior of the reaction vessel 6 containing the electron gun 2B in the above process is filled with a reaction gas controlled to a predetermined pressure in a medium vacuum region, the filament 1 is oxidized and vaporized by unnecessary oxygen and moisture. In addition to this, deterioration of the filament 1 due to the reaction residue itself and process reaction by-products was considered a problem. That is, a film is formed on the surface of the filament 1 by the reactive gas, which directly prevents electron emission. Further, since the surface of the filament 1 is also sputtered by reactive gas ions, etc., the thermionic emission characteristics of the filament are greatly reduced by Y.

From the above, even if you choose an unreasonably low reaction gas pressure that is inconvenient for the process to ensure the lifetime of the electron gun, the filament's ability to emit thermionic electrons will be rapidly lost, making long-term operation unnecessary. It was impossible.

On the other hand, attempts have also been made to emit photoelectrons using photoelectric materials such as CdS as electron supply elements. However, a film (h) is formed on the surface of the photoelectric material due to the reaction gas and the emission of the light cage is inhibited, so long-term operation is similarly impossible.

As described above, when a conventional high-vacuum electron gun is used in a medium-vacuum reaction gas atmosphere, it is difficult to operate the electron gun stably for a long time, and this is a problem with the conventional technology. Ta.

[Object of the Invention] An object of the present invention is to provide an electron gun that can be stably used for a sufficiently long period of time even in a reactive gas atmosphere that adversely affects an electron supply element.

[Means for Solving the Problems] The electron gun for medium vacuum according to the present invention is equipped with an electron supply element that emits photoelectrons or thermionic electrons and is used in a medium vacuum atmosphere. It is equipped with an inert gas supply means for maintaining the discharge part in an inert gas atmosphere.

[Function] In the electron gun according to the present invention, the electron supply element produces relatively low-energy electrons by photoelectron emission or thermionic emission in a medium vacuum reaction or gas atmosphere. Here, the inert gas supply means supplies an inert gas around the electron emitting part of the electron supply element to reduce the partial pressure of the reactive gas in this part and prevent deterioration of the electron supply element.

As the inert gas mentioned here, a rare gas such as argon gas, nitrogen gas, hydrogen gas, or the like is used.

[Embodiments of the invention] Embodiments of the present invention will be described with reference to the drawings.

FIG. 1 shows a schematic configuration of a medium vacuum electron gun according to an embodiment of the present invention and a process device incorporating the gun. In this embodiment, a thin film is formed on the substrate 11 in the same way as in the conventional example, but at that time, argon gas is introduced and supplied from the gas supply system 3 into the cylinder 2a of the electron gun 2 to fill the filament 1. By blowing and removing the reactant gas from around the heated part, the
, the filament life is 1.

Here, members having the same configuration and function as those described in the conventional example are given the same reference numerals, and the description thereof will be omitted.

In FIG. 1, the electron gun 2 is composed of a tungsten filament 1, a conductive cylindrical tube 2a, a grid 5, etc., and includes a filament current power source 13 and an accelerating voltage power source 14.
It is supplied with electric power and generates thermoelectrons, which are accelerated and ejected.

On the other hand, the base portion of the electron gun 2 is provided with a gas supply port 3a for supplying argon gas into the cylinder 2a. Further, a gas supply system 3 including an argon gas container, a flow rate regulator, piping, etc. provided outside the closed container 6 is connected to the gas supply port 3a.

Here, the inert gas may be blown onto the filament 1 from any direction, but preferably from the opposite side from which electrons are emitted as shown in FIG. In addition, the shape of the shield 2a can be made into a shape other than cylindrical, but this may prevent the absorption of emitted electrons on the wall surface of the cylinder 2a, which occurs due to the disturbance of the flow of the inert gas, or the energy width of the emitted electrons. To prevent expansion, a cylindrical shape is desirable.

Now, in the process apparatus of this embodiment, during the period when the reaction gas is supplied into the reaction vessel 6, the electron gun 2 is supplied from the gas supply system 3.
Argon gas is supplied around the filament 1. On the other hand, the atmospheric gas (including reaction gas and argon gas) in the reaction vessel 6 is exhausted from the exhaust system 8 in a PJ 14 manner. An argon gas concentration distribution having a peak around the filament 1 of No. 2 is formed. Therefore, the concentration of the reactant gas is lowest around the filament 1, and the contact between the reactant gas and the heated part of the filament 1 and the chance of reaction are reduced, so that the filament 1 remains normal for a longer period of time than in the case of conventional electron guns. Thermionic emission can be maintained.

In addition, in the reaction apparatus of this embodiment, since the accelerating voltage is set to 20 V or less, ionization of argon gas molecules hardly occurs. Since scattering and absorption of the internal electron beam are suppressed, the output efficiency is improved and the electron beam output is increased.

In this embodiment, the inert gas was supplied using a cylinder, but the inert gas could also be supplied by heating an inert gas absorber or a solid source, or by heating the inert gas absorber or solid source. A similar effect can be expected by providing a decomposition mechanism or the like that decomposes the reactive gas to generate an inert gas on the exit side of the shield 2a.

[Effects of the Invention] In the medium vacuum electron gun according to the present invention, since the inert gas protects the electron emitting part of the electron supply element, when it is used in an atmospheric gas that is harmful to the electron supply element, it is It can operate more stably for a longer period of time than the example electron gun. Therefore, when using this electron gun to control chemical reactions, etc. in a medium-vacuum reaction gas atmosphere, it is possible to select an atmosphere gas pressure that is convenient for process progress without worrying about the effect on the electron supply element. Capable of carrying out long reaction processes.

Therefore, the range of applications of the process using an electron gun is expanded, for example, the process of forming a relatively thick capsule becomes possible. In addition, problems with the electron gun are reduced and the operating rate of the process equipment is improved, making it possible to improve the reliability of equipment incorporating the electron gun and reduce running costs.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing the general configuration of an electron gun and a chemical reaction process apparatus using the electron gun according to an embodiment of the present invention. FIG. 2 is a schematic diagram showing the general configuration of a conventional electron gun and a chemical reaction process device using the same. [Explanation of symbols of main parts] 1...Filament 2...Electron gun 3...Gas supply system 6...Reaction vessel 8...Exhaust system

Claims (1)

[Claims] In an electron gun used in a medium vacuum atmosphere and equipped with an electron supply element that emits photoelectrons or thermionic electrons, an inert gas for maintaining an electron emitting part of the element in an inert gas atmosphere. A medium vacuum electron gun characterized by being equipped with a supply means.