JPH0955183A - Ionization type high vacuum auxiliary pump - Google Patents

Abstract

(57) Abstract: A high vacuum pump having a lower ultimate pressure than a general-purpose high vacuum pump and usable in a manufacturing process is obtained. SOLUTION: 1) A vacuum container provided between a vacuum chamber and a general-purpose high vacuum pump and communicating with each other, a filament for emitting thermoelectrons in order from the vacuum chamber side, and a through hole are provided in the vacuum container. An ionization type high vacuum auxiliary pump having a grid electrode for applying a positive potential and an ion collector electrode for applying a negative potential, and 2) a magnet for forming a magnetic field inside the vacuum container.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a practical high vacuum pump that can be used in a manufacturing process. Vacuum technology is one of the important factors in the manufacturing process of semiconductor devices, and it is a practical high vacuum pump that can be used in the manufacturing process in addition to a small-scale ultra-high vacuum pump used for experiments and physical property measurements. Realization of is desired.

[0002]

2. Description of the Related Art There are turbo molecular pumps, oil diffusion pumps, cryopumps, etc. as general-purpose high-vacuum pumps currently in use.
It is about 10 ^-7 to 10 ^-8 Torr. There are getter pumps and the like as pumps that can achieve lower ultimate pressure than these general-purpose pumps, but they are not practical for use in the manufacturing process.

[0003]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a high vacuum pump which has a lower ultimate pressure than the currently used high vacuum pump and which can be manufactured as a general-purpose pump.

[0004]

Means for Solving the Problems To solve the above problems, 1) a vacuum chamber communicating between a vacuum chamber and a general-purpose high vacuum pump, and a thermoelectron in the vacuum chamber in order from the vacuum chamber side. Ionization type high vacuum auxiliary pump having a filament for emitting electrons, a grid electrode having through holes for applying a positive potential, and an ion collector electrode for applying a negative potential, or 2) forming a magnetic field inside the vacuum container. It is achieved by the ionization type high vacuum auxiliary pump described in the above item 1, which has a magnet for

According to the present invention, a device (to be referred to as an ion booster pump here) for ionizing and collecting gas molecules is provided as an auxiliary pump before a general-purpose turbo molecular pump or cryopump.

An ion booster pump is a tungsten filament that generates thermoelectrons. A positive potential collector electrode that moves thermoelectrons (grid). A magnet for causing thermoelectrons to perform cyclotron motion. A negative potential electrode that collects ionized gas molecules (grid). Ion collector).

Next, the function of the ion booster pump will be described. Gas molecules are isobarically suspended in the vacuum chamber. The gas molecules are ionized by ionization, and these ions are collected in front of a general-purpose high vacuum pump using an ion collector. By collecting gas molecules in the previous stage of the general-purpose pump and increasing the gas pressure, the exhaust capacity of the pump, which had reached the limit of the ultimate pressure, is restored, and as a result, the degree of vacuum in the vacuum chamber is improved.

More specifically, according to the above items 1 to 4, the filament is heated in vacuum to a temperature at which electron emission occurs. The emitted thermoelectrons move toward the positive potential grid, and if gas molecules are present and collide with them, the gas molecules are ionized. The gas molecules ionized by the negative potential ion collector provided immediately before the general-purpose high vacuum pump can be collected before the general-purpose pump. As a result, the pressure in the vicinity of the intake port of the general-purpose high vacuum pump is increased, and the exhaust capacity of the general-purpose pump is restored.

Further, in order to improve the ionization rate of gas molecules, it is necessary to increase the number of thermoelectrons. For this reason, there is a method of increasing the filament current to increase the amount of thermionic emission, but this method shortens the life of the filament, and as a result, stops the pump and replaces the filament more frequently, resulting in poor efficiency. Therefore, a magnetic field is applied to the ion booster pump to cause the thermoelectrons to perform cyclotron motion, and the distance in which the thermoelectrons move is increased to increase the probability of collision with gas molecules.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION An ion booster pump is mounted between a vacuum chamber and a turbo molecular pump, as shown in FIG.

1A and 1B are explanatory views of the first embodiment.
FIG. 1 (A) is a sectional view and FIG. 1 (B) is a plan view. In the figure, 1 is a filament, 2 is a grid electrode, 3 is an ion collector electrode, and 4 is a magnet. A portion surrounded by a dotted line including these components shows an ion booster pump. In the figure, 5 is a vacuum chamber and 6 is a turbo molecular pump.

The turbo molecular pump in this example had a single unit exhaust capacity of 10 ^-7 Torr. Here, when the turbo molecular pump is operated and the degree of vacuum in the vacuum chamber reaches 10 ^-5 Torr, a current of 50 to 200 A is applied to filament 1 to emit thermoelectrons. The electrons are accelerated toward the grid electrode 2 by the magnetic field formed by the magnet 4 while performing cyclotron motion as shown in FIG. The electrons pass through the grid-shaped grid electrode 2 and are repelled by the ion collector electrode, which is a negative potential electrode. After reciprocating several times, the electrons are captured by the grid electrode. + For grid electrode
Apply a positive potential of 60 to +120 V. During the reciprocating motion of the electrons, the electrons collide with gas molecules within their range of motion,
Gas molecules are + ionized.

When a negative potential of −15 to −30 V is applied to the ion collector electrode 3, the ionized gas molecules are attracted to the negative potential and move to be collected near the ion collector electrode 3. Since the ion collector electrode 3 is located immediately before the turbo molecular pump 6, gas molecules are collected near the suction port of the turbo molecular pump and are exhausted by the turbo molecular pump.

As a result, the ultimate pressure is 10 ^-9 to 10 ^-10 Torr, which is 10 ^-7 to 10 ^-8 Torr in the case of a turbo molecular pump alone.
More improved. In the embodiment, the number of filaments of the ion booster pump is one, but it is possible to increase the ionization rate of gas molecules by using a plurality of filaments as in the embodiment 2 of FIG.

Further, in the embodiment, the filament is used for ionization of the ion booster pump, but high frequency (RF)
Ionization by a power source is also possible. The ion booster pump of the present invention does not need to be regenerated because it is exhausted by a general-purpose high vacuum pump in the next stage, rather than a so-called trapped pump that stores gas molecules like a getter pump.

FIG. 4 is an explanatory diagram of the third embodiment. In this example, if ionized gas molecules collide with the turbo molecular pump, the charging phenomenon may occur and the pump performance may be hindered. Therefore, the filament 1 is also provided below the ion collector electrode 3 to ionize it. Neutralize by supplying thermoelectrons to gas molecules.

[0017]

According to the present invention, the ultimate vacuum can be improved by simply adding an ion booster pump to a general-purpose high vacuum pump. In addition, unlike the getter pump, there is no need to perform regeneration (heat treatment for releasing the stored gas), the cyclotron motion of electrons by a magnetic field can extend the life of the filament, and can be used in a semiconductor device manufacturing process or the like. A high vacuum device was obtained.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a first embodiment of the present invention.

FIG. 2 is a schematic diagram illustrating the function of the present invention.

FIG. 3 is an explanatory diagram of a second embodiment of the present invention.

FIG. 4 is an explanatory diagram of a third embodiment of the present invention.

[Explanation of symbols]

 1 Filament 2 Grid electrode 3 Ion collector electrode 4 Magnet 5 Vacuum chamber 6 Turbo molecular pump

Claims (2)

[Claims] 1. A vacuum container provided between a vacuum chamber and a general-purpose high vacuum pump, which communicates with the vacuum chamber, a filament for emitting thermoelectrons in order from the vacuum chamber side, and a through hole. An ionization type high vacuum auxiliary pump characterized by having a grid electrode for applying a positive potential and an ion collector electrode for applying a negative potential. 2. The ionization type high vacuum auxiliary pump according to claim 1, further comprising a magnet for forming a magnetic field inside the vacuum container.