JPH024980B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a sputter ion pump, particularly to a triode ion pump having a novel structure.

An ion pump is a vacuum pump that can create an oil-free vacuum using cold cathode discharge in a magnetic field, and has the characteristic that it does not require high-temperature or cryogenic parts or mechanical movement, which raises the issue of vacuum quality. It is particularly useful in the field.

The initial drawbacks, such as the instability of pumping speed for rare gases such as helium and argon, were resolved with the development of triode ion pumps, and pumps with good operability became available.

FIG. 1 shows a cross-sectional view of a conventional ion pump.

Reference numeral 1 denotes an anode having a hollow portion 2 passing through it, 3 a set of two cathodes disposed close to and apart from both open ends of the anode 1 and having a shape that covers the openings, and 4 a collection electrode. be.

A magnetic field 5 is applied substantially parallel to the axis of the hollow portion 2 of the anode 1 to the entire hollow portion 2 by a magnetic field generator (not shown), and a discharge power supply is provided between the anode 1 and the cathode 3. 6 applies voltage Va. In this example, the anode 1 and the collector electrode 4 are grounded and the voltage at the cathode 3 is -Va.

The pumping action of the triode ion pump is explained as follows.

A group of high-energy, high-density electrons is formed in the hollow part 2 of the anode 1 by orthogonal electromagnetic fields, and the molecules that fly into the hollow part 2 are ionized and ions 7
The particles are accelerated and incident on the surface of the cathode 3 at high speed, sputtering atoms on the surface of the cathode 3, which is usually made of titanium.

The sputtered cathode surface material adheres to the surface of the collecting electrode 4, the adhering cathode surface material adsorbs gas molecules, the sputtered cathode surface material further adheres thereto, and the adsorbed gas molecules are transferred to the collecting electrode 4. For example, as shown at 4', it is embedded in the surface of.

This embedding of gas phase molecules into the solid phase is the exhaust action of the triode ion pump. In order to increase the pumping speed, the amount of cathode surface material sputtered from the cathode must be increased relative to the amount of gas ions formed by the discharge.

FIG. 2 is a diagram illustrating the sputtering amount of cathode surface material in the triode ion pump shown in FIG. 1.

The horizontal axis u in Figures 2a, b, and c represents the energy of ions incident on the cathode surface, and the vertical axis s in Figure 2a represents the energy of ions incident on the cathode surface.
is the sputtering ratio expressed as the number of atoms of the cathode material sputtered per one incident ion, and the vertical axis f in Fig. 2b is the energy of the incident ion, which is the energy u.
Above, the ion energy distribution function is defined as the number of ions less than u+du incident on the cathode surface per unit time is fdu, and the vertical axis fs in Figure 2c is the product of the distribution function f and the sputter ratio s, and f are both expressed as relative values.

In Figure 2b, the distribution function f is less than 0, eVa
(However, e represents unit charge) and above is zero,
Further, f is almost equal to zero below the acceleration energy eV _p due to the cathode drop V _p and in the range of the anode drop.

As shown in FIG. 2b, the distribution function f takes a non-zero value only when eV _p ≦u<eVa. The distribution function f is expressed as follows: When the energy u exceeds eV _p and u is a small value,
When the value of u is large, f becomes small.

Number of sputtered cathode materials per unit time Q
is given by Q=∫ ^eVa _eVp fsdu, and this integrand fs is shown in Figure 2c. As is clear from Fig. 2c, the energy u is required for the sputtering ratio s to take a large value.
Since the energy u at which the distribution function f takes a large value differs greatly, the amount of cathode material to be sputtered cannot be increased.

SUMMARY OF THE INVENTION A first object of the present invention is to provide an ion pump which increases the amount of cathode material sputtered and increases the pumping speed by using a configuration that does not disturb the discharge to a large extent. Furthermore, a second object of the present invention is to obtain a configuration that increases the life of such a novel triode ion pump.

The present invention achieves the first object by disposing a sputter electrode in the center of one of the cathodes, applying a negative potential to the cathode to the sputter electrode, and removing the sputter electrode from a vacuum. The second objective is achieved by making the sputter electrode's position variable, and the second objective is also achieved by making the getter material of the sputter electrode easily replaceable. This improves the achievement of the first objective by providing a cathode structure on the opposite side.

Examples of the present invention will be described below.

In the drawings, the same reference numerals indicate the same or corresponding parts.

3, 4, 5, and 6 are longitudinal sectional views of different embodiments of the present invention.

In these FIGS. 3 to 6, the anode 1 is a tube 8 forming a part of a vacuum container housing an ion pump.
It is electrically grounded through this tube 8.

Reference numeral 9 designates an externally insulated conductor column that fixes the relative position of a pair of cathodes 3 and electrically connects them. This cathode 3 is supported by a conductor column 10. The conductor column 10 is supported by a power supply terminal 11 and an insulating support member 12 so as to be insulated from the anode 1 and the vacuum container housing the ion pump. The voltage is applied to the cathode 3 through one of the lines.

A magnet 13 applies a magnetic field substantially parallel to the axis of the hollow part 2 of the anode 1 to the entire hollow part 2 of the anode 1. 14 is a through hole bored in the axis of the hollow part 2 of one anode 1 of the cathode 3; 15 is the through hole 1 of the cathode 3;
A sputter electrode 4 is insulated from the cathode 3 and extends through the hollow part 2 of the anode 1, and 16 is a sputter electrode that supports the sputter electrode 15 while being insulated from the anode 1, the cathode 3, and the vacuum vessel housing this ion pump. It is also a sputter electrode support body having a part of the power supply path to this sputter electrode 15.

The power supply path passes through the power supply terminal 17 and is connected to a sputter electrode power source (not shown), and a negative potential is applied to the sputter electrode 15 with respect to the cathode 3 .

In FIGS. 3 and 6, sputter electrode 1
5 is insulated and fixed to the cathode 3, and the portion extending into the hollow portion 2 of the anode 1, including the vicinity of its tip, is formed of a getter material.

In FIGS. 4 and 5, the sputter electrode support 16 has a chuck and is constructed so that the sputter electrode 15 made of getter material can be easily replaced.

In FIG. 5, the sputter electrode supports 16 that support the sputter electrodes 15 are screwed in opposite directions so that the position relative to the cathode 3 can be changed from outside the vacuum container housing the ion pump without disassembling the ion pump. The constructed sputter electrode 15 is supported by a linear motion introducing section 18 whose longitudinal position is adjustable.

In FIG. 6, reference numeral 19 is a stabilizing pin for stabilizing the discharge, which is placed on the axis of the hollow part 2 of the cathode 3 and anode 1 on the side facing the sputter electrode 15 and directed toward the sputter electrode 15. extending into contact;
By forming the conductive rod with a small sputtering ratio, the discharge can be kept stable even if the external dimensions of the sputtering electrode 15 are made larger.

The functions and effects of the present invention will be described with reference to the embodiments shown in FIGS. 3 to 6.

FIG. 7 is a diagram illustrating the amount of sputtering in the triode ion pump of the present invention, and is compared with the conventional diagram shown in FIG.

In the present invention, gas molecules ionized by the electron group formed in the hollow part 2 of the anode 1 collide with the sputter electrode 15 and sputter the getter material on its surface.

Sputtering ratio s to ion incident energy u
is the same as in FIG. 2a, as shown in FIG. 7a.

The potential of the anode 1 is zero, the cathode 3 is -Va as in the conventional case shown in FIG. 2, and the potential difference between the cathode 3 and the sputter electrode 15 is Vs.
The potential of 5 is -(Vs+Va), and the energy distribution function f of ions incident on the sputter electrode is as shown in FIG. 7b, and the energy distribution of ions incident on the conventional cathode shown in FIG. 2b is It takes the form of moving to the higher energy side than the function.

As a result, the integrand fs of the number Q of sputtered electrode material sputtered per unit time, Q=∫ ^e(Vs+Va) _e(Vs+Vp) fsdu, is as shown in Figure 7c. By taking a larger value than that shown in FIG. 2c, the amount of sputtered material can be increased compared to that in the conventional triode ion pump, and an ion pump with a high pumping speed can be realized.

When an ion pump is used at high pressure, it is desirable to extend its life. The wear and tear of the sputter electrode 15 is a factor that determines the life of the ion pump of the present invention, and the life can be extended by replenishing the sputter electrode 15 (FIG. 5) or replacing it (FIGS. 4 and 5). Another way to extend the life is to use a larger sputter electrode 15, but if the sputter electrode 15 is simply made larger, the sputter electrode 15 will be at a more negative potential with respect to the cathode 3, making the discharge unstable. This can be solved by adding a discharge stabilizing pin 19 (sixth
figure).

[Brief explanation of drawings]

Fig. 1 is a sectional view showing a conventional triode ion pump, Fig. 2 a, b, and c are diagrams explaining the sputtering amount of cathode surface material in the triode ion pump of Fig. 1, and Fig. 3 , FIG. 4, FIG. 5, and FIG. 6 are longitudinal sectional views of different embodiments of the present invention, and FIG. 7 a, b, and c are diagrams explaining the amount of sputtering in the triode ion pump of the present invention. It is. DESCRIPTION OF SYMBOLS 1... Anode, 2... Hollow part of the anode, 3... Cathode, 4... Collection electrode, 5... Magnetic field, 6... Discharge power source, 7... Ion, 8... Forms part of vacuum vessel Pipe, 9, 10... Conductor column, 11, 17... Power supply terminal, 12... Insulating support member, 13... Magnet, 14
...Through hole, 15...Sputter electrode, 16...Sputter electrode support, 18...Linear motion introduction part, 1
9...Stabilizing pin.

Claims (1)

[Scope of Claims] 1. An anode having a penetrating hollow portion, a set of two cathodes arranged spaced apart from and close to both open ends of the anode and having a shape that covers the openings; An ion pump comprising means for applying a voltage between the cathodes and means for generating a magnetic field that is substantially parallel to the axis of the hollow part of the anode and applied to the entire hollow part of the anode. A through hole is bored on one side on the axis of the hollow part of the anode,
A sputter electrode extending into the hollow part of the anode through the through hole is disposed insulated from one of the cathodes, and means for applying a negative potential to the cathode is provided to the sputter electrode, A triode ion pump characterized in that a portion of the sputter electrode extending into the hollow portion of the anode near the tip thereof is formed of a sputter material. 2. The triode ion pump according to claim 1, wherein the position of the sputter electrode relative to the cathode can be changed from outside the vacuum container housing the ion pump without disassembling the ion pump. . 3. The triode ion pump according to claim 1 or 2, wherein the sputter electrode is configured to be replaceable at least at a position containing the getter substance. 4. A rod made of a conductor having a small sputtering ratio is extended toward the sputtering electrode in a non-contact manner on the axis of the hollow part of the anode of the cathode on the side facing the sputtering electrode. A triode ion pump according to claim 1, 2, or 3.