JPH0927294A - Ion pump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a smaller ion pump with higher exhaust performance by arranging a coaxial anode in a cylindrical casing and a cathode on an outer periphery to generate a radial electric field in the casing and a magnetic field in parallel thereto. SOLUTION: A coaxial anode 4 is arranged in a cylindrical casing 8 for an ion pump and a cathode 2 isolated therefrom is arranged on an outer periphery, both ends of the casing being open. A high voltage power supply 5 applies negative high voltage from a current guide terminal 6 to the cathode 2, and an anode 4 and the casing 8 are grounded. An electric field is radially formed between cylindrical faces of the coaxial anode 4 and the cathode 2 and a magnetic field is formed in a coil 3A in parallel to the axial direction of the anode 4 and the cathode 2. Discharge is caused between the cathode 2 and the anode 4 by the radial electric field and produced electrons are subjected to electromagnetic force in an orthogonal electromagnetic field to draw a trochoid track. In this way, an effective range of the electrons to cause ionization is greater, ionizing efficiency is increased and quick exhaust is realized.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ion pump, and more particularly to an ion pump which realizes a high vacuum condition required in the electronic industry such as semiconductor manufacturing, the material industry, or the accelerator field.

[0002]

2. Description of the Related Art High-vacuum technology is an indispensable basic technology in cutting-edge technical fields such as manufacturing of semiconductors, accelerators, and nuclear fusion. In recent years, in the production of quantum effect devices and new functional materials, or in the technology of operating atoms for each single atom, an extremely high degree of vacuum (10 ^-10 Pa or less) comparable to outer space has been required. There is. Further, in the field of elementary particle physics, unknown elementary particles have been discovered by collision experiments of particles accelerated to high energy, and a high degree of vacuum is also required in this field.

As a conventional technique, as means for realizing such a high vacuum space, a turbo molecular pump is used as a roughing pump, an ion pump, a sublimation pump or a combination thereof, or a cryopump is evacuated to high vacuum. It is used as a pump. Among them, the ion pump has conventionally used Penning discharge for ionization of gas.

4A and 4B show the structure of a conventional three-pole type ion pump. FIG. 4A is a front perspective view and FIG. 4B is a side view. Reference numeral 1 is a connection flange, 2 is a cathode, 3 is a magnet, and 4 is an anode. Reference numeral 5 is a high-voltage power supply, and 6 is a current introduction terminal for connecting the high-voltage power supply 5 and the cathode 2. The pump casing indicated by reference numeral 8 has a rectangular shape,
The cathode 2 is made of a getter material such as titanium, has a flat plate shape, and has a large number of voids 2A. Similarly, the anode 4 also has a thick flat plate shape, and has a large number of cylindrical voids 4A. In this example, the magnet 3 is a permanent magnet, and in FIG. 4A, the magnetic field is formed in a direction orthogonal to the flat plate-shaped cathode and anode (horizontal direction in the figure). Therefore, the electrons ionized by the electric field generated by the power source 5 between the cathode 2 and the anode 4 are, as shown by reference numeral 11 in FIG.
It reciprocates in and around the void 4A of the anode 4 along the magnetic field.

Therefore, the electrode structure composed of the cathode and the anode has a rectangular shape, and the pump casing has a rectangular shape accordingly. Therefore, there are the following problems.

The ion pump is usually directly connected to the vacuum container to be evacuated, and a vacuum flange is used for this connection. In the unlikely event that the discharge electrode fails and should be replaced, the structure must be such that the discharge electrode can pass through this vacuum flange. The vacuum flange is generally circular, whereas the casing of the ion pump is rectangular, so a useless space that does not contribute to the exhaust action is provided inside the pump, and the pump itself becomes large.

The exhaust action of a conventional ion pump is
It was done as follows. First, a discharge is generated by Penning discharge, and the electrons generated by the discharge reciprocate between the electrodes to ionize the gas in the space. As a result, the ionized gas becomes positive ions and is accelerated toward the cathode, and some ions collide with the cathode to sputter the atoms on the surface. Generally, the cathode of an ion pump is made of an active metal such as titanium, so the sputtered titanium atoms form an extremely clean and active monoatomic layer on the anode, the inner wall of the pump casing, etc. To capture. When the energy of cations is high, it penetrates into a place considerably deeper than the cathode surface. By these actions, the gas in the space is captured by the titanium layer formed on the casing surface,
Further, by being driven into the cathode, it is gradually exhausted. What is important for such exhaust action is to increase the flight distance of electrons to improve the ionization efficiency, but since Penning discharge uses a magnetic field parallel to the electric field, the effective range of electrons is limited to a narrow space. It can be increased only in the interior, and it is difficult to obtain a high pumping speed.

Further, the conventionally known ion pump is
As shown in FIG. 6, since it is a built-in type pump for accumulating and discharging the gas to be exhausted in the pump, it is attached to the vacuum container separately from the rough pumping systems 15, 16. Therefore, it is necessary to separately prepare a mounting flange on the vacuum container side, which is different from the roughing pump, which has been a cause of enlarging the entire vacuum exhaust system.

[0009]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances, and satisfies both the downsizing of the pump body and the improvement of the exhaust performance at the same time, and the connection to the ion pump and the roughing pump. It is an object of the present invention to provide an ion pump that can make a vacuum exhaust system compact.

[0010]

In order to achieve the above-mentioned object, the present invention has a cylindrical casing in which a cylindrical anode and a cylindrical cathode are arranged coaxially in the cylindrical casing, and the cylindrical cathode is arranged in the cylindrical casing. Further, it is characterized in that it is provided with a radial electric field generating means between the cylindrical cathode and the anode and the cylindrical surface of the casing, and a magnetic field generating means parallel to the axes of the cylindrical anode and the cathode.

Further, both ends of the cylindrical casing are opened, one is connected to a vacuum container to be evacuated, and the other is connectable to a vacuum pump for auxiliary evacuation.

Further, the ion pump is characterized by having a shutoff valve.

Further, a cooling pipe and a heater are provided on the outer peripheral surface of the pump casing.

[0014]

According to the first aspect of the invention, the electrons ionized between the cylindrical anode and the cylindrical cathode receive a force in the circumferential direction due to the electric field in the radial direction and the magnetic field in the axial direction, and draw a toroidal locus.
By performing so-called magnetron discharge, the flight distance of electrons can be lengthened and the ionization efficiency can be increased. As a result, the exhaust speed can be increased. In addition, since the cylindrical electrode and casing are used, the structure of the pump itself can be made compact without providing a wasteful space that does not contribute to the exhaust action, and the replacement of the discharge electrode during maintenance is easy. Is.

According to the second aspect of the present invention, both ends of the ion pump are opened so that the ion pump can be connected to the auxiliary exhaust system. It can be connected in series. As a result, conventionally, the vacuum container to be evacuated required a connection port for the ion pump, but this connection port is no longer required,
The overall size including the exhaust system can be reduced.

Further, according to the invention of claim 3, since the ion pump is provided with the shutoff valve, after rough evacuation by the auxiliary exhaust system,
It is possible to operate only the ion pump by disconnecting the auxiliary exhaust system. It is also possible to separate from the vacuum container side and perform gas discharge of the ion pump by an auxiliary exhaust system.

Further, according to the invention of claim 4, since the cooling pipe is provided on the outer peripheral surface of the pump casing, the pump casing can be cooled at the time of vacuum evacuation to improve the evacuation speed. Further, since the heater is provided, the ion pump can be easily heated and degassed.

[0018]

An embodiment of the present invention will be described below with reference to the accompanying drawings. In the drawings, the same reference numerals indicate the same or corresponding parts.

FIGS. 1A and 1B show the structure of an ion pump according to an embodiment of the present invention, FIG. 1A is a partial perspective view seen from the front, and FIG. 1B is a side view thereof. Is. In the ion pump of this embodiment, as shown in FIG. 1A, a cylindrical anode 4 and a cylindrical cathode 2 are arranged coaxially in a cylindrical pump casing 8. Both ends of the cylindrical casing 8 are provided with flanges 1A and 1B, respectively, and both ends of the casing 8 are open. Cylindrical cathode 2
Is made of a getter material such as titanium and has a large number of slit-shaped voids 2A. The cylindrical cathode 2 is arranged coaxially with the cylindrical anode 4 and the cylindrical casing 8 apart from each other by an insulator (not shown).

The high voltage power source 5 applies a negative high voltage from the current introducing terminal 6 to the cathode 2, and the anode 4 and the casing 8 are grounded. Therefore, a radial electric field is formed between the cylindrical surfaces of the coaxial anode 4 and cathode 2. Casing 8
The coil 3A arranged on the outer periphery of the coil forms a magnetic field parallel to the axial directions of the cylindrical anode 4 and the cathode 2. Also, the casing 8
A cooling pipe 9 and a heater 10 are respectively arranged on the outer periphery of the. The cooling pipe 9 is for cooling the pump casing 8 to improve the exhaust speed. The heater 10 is used for heating and degassing the ion pump by heating its inner wall surface via the pump casing 8.

FIG. 2 is a diagram for explaining the operation of this ion pump. As described above, a radial electric field is formed between the cylindrical anode 4 and the cylindrical cathode 2 by connecting the high voltage power supply 5 between the cathode 2 and the anode 4. The magnetic field is formed in the axial direction.

A radial electric field between the cylinders causes a discharge between the cathode 2 and the anode 4. The electrons generated by the discharge are accelerated toward the anode 4 on the cylindrical axis, but since there is a magnetic field in the axial direction, the orbit of the electrons is trochoidal as shown by the reference numeral 11 due to the electromagnetic force of the orthogonal electromagnetic field. Orbit. By adjusting the applied voltage and the magnetic flux density of the magnetic field so as to satisfy the critical condition expression, the electrons can continue to move without being trapped by the anode 4. As a result, the effective range of the electrons that collide with the gas in the space and cause ionization is lengthened, and the ionization efficiency is improved, so that the exhaust velocity can be increased. Further, at the time of exhaust, a coolant such as water is caused to flow through the cooling pipe 9 arranged on the outer peripheral surface of the casing to keep the inner surface of the pump casing 8 at a low temperature, so that the exhaust speed can be further increased.

FIG. 3 shows an example of the construction of the exhaust system, which is possible when the ion pump of the present invention is used.
One of the flanges of the ion pump 8 of the above embodiment is connected to the vacuum container 12 to be evacuated, and the other flange is connected to the turbo molecular pump 15 and the dry pump 16 via the shutoff valve 13. And the closing valve 13
May be provided in the casing 8 of the ion pump. Further, the shutoff valve 13 may be provided not only on the exhaust side of the ion pump but also on the intake side.

Since the ion pump cannot be started until the pressure becomes equal to or lower than a predetermined vacuum level, first, the turbo molecular pump 15 and the dry pump 16 in the auxiliary exhaust system are used for exhausting. At this time, the ion pump main body 8 is connected in series with the auxiliary exhaust system as shown in FIG. 3, and the turbo molecular pump 15 and the dry pump 16 of the auxiliary exhaust system exhaust the vacuum container 12 through the ion pump main body. During the auxiliary exhaust by the pump of the auxiliary exhaust system, the ion pump discharges the gas heated by the heater 9 and adsorbed inside the pump. After the pressure is reduced to a predetermined vacuum level in this auxiliary exhaust system, the heater 9 is turned off, the temperature of the casing of the ion pump is lowered, the valve 13 is closed, the high voltage power source is connected, and the ion pump is started.

Although an electromagnet coil is used as the magnetic field generating means in the above-described embodiment, it goes without saying that a permanent magnet may be used. Further, in the above-described embodiment, an example of the so-called three-pole structure in which the cathode and the anode are provided independently in the casing has been described. However, in an ion pump having a cylindrical discharge electrode in a cylindrical casing. It goes without saying that the gist of the present invention is applicable.

[0026]

According to the present invention as described above,
By using magnetron discharge, the shape becomes cylindrical compared to the conventional ion pump, and it is possible to improve maintenance and performance.

First, since the ion pump casing can be formed into a cylindrical shape, the space inside the pump can be effectively used, the pump itself can be downsized, and the discharge electrode fails and needs to be replaced. Good workability when doing. Furthermore, by providing a suction port and a discharge port on both sides of the cylindrical casing, it is possible to connect in series with the pump of the auxiliary exhaust system, eliminating the need for a mounting port for the ion pump in the vacuum container and thus the exhaust system as a whole. Can be made compact.

Further, in terms of performance, the effective range of electrons for ionizing gas by magnetron discharge can be made extremely long, so that ionization efficiency is increased and exhaust speed is increased. In addition, the efficiency of adsorbing titanium atoms and gas molecules on the inner surface of the casing can be increased by cooling the casing using the cooling pipe around the outer circumference of the ion pump casing, and the exhaust speed can be further increased.

[Brief description of drawings]

FIG. 1A is a front partial perspective view and FIG. 1B is a side view of an ion pump according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram of electron trajectories in the ion pump according to the embodiment of the present invention.

FIG. 3 is an explanatory diagram of an exhaust system according to an embodiment of the present invention.

FIG. 4 (A) is a front perspective view of a conventional ion pump,
And (B) side view.

FIG. 5 is an explanatory diagram of electron trajectories in a conventional ion pump.

FIG. 6 is an explanatory diagram of a conventional exhaust system.

[Explanation of symbols]

 1 Connection Flange 2 Cathode 3A Electromagnetic Coil 4 Anode 5 High Voltage Power Supply 6 Current Introduction Terminal 8 Pump Casing

Claims (4)

[Claims] 1. A cylindrical anode is coaxially arranged in a cylindrical casing, and a cylindrical cathode is arranged on the outer circumference thereof, and a radius between the cylindrical cathode and each of the cylindrical surfaces of the anode and the casing is arranged in the cylindrical casing. An ion pump comprising: a directional electric field generating means; and a magnetic field generating means parallel to the axes of the cylindrical anode and the cathode. 2. The structure is characterized in that both ends of the cylindrical casing are opened, one is connected to a vacuum container to be evacuated, and the other is connectable to a vacuum pump for auxiliary evacuation. 1. The ion pump according to 1. 3. The ion pump according to claim 2, wherein the ion pump includes a stop valve. 4. The ion pump according to claim 1, wherein a cooling pipe and a heater are provided on an outer peripheral surface of the pump casing.