JPH03293533A - Vacuum gauge - Google Patents

Abstract

PURPOSE:To achieve longer life with a shortened cathode sputtering by forming a cathode from a number of fine cold cathodes to stabilize discharge of the cold cathodes with the lowering of an applied voltage. CONSTITUTION:A cold cathode mechanism 50 is consisted of a polypolar elec tron releasing mechanism formed on a disc-shaped substrate 55, an emitter power source 542 and a acceleration power source 572. The substrate 55 has a polypolar electron releasing mechanism 58 formed outside along a circle and a polypolar electron releasing mechanism 59 inside, which are arranged concentrically. A diameter of the substrate 55 is almost equal to an inner diame ter of an anode electrode 31 and the polypolar electron releasing mechanism is arranged along a circle to match the shape of a cylinder of the anode elec trode 31. The polypolar electron releasing mechanism contains a number of fine cold cathodes formed by a microscopic pattern processing art. A number of emitters contained in the mechanism 58 are arranged along an electron releas ing surface 581 forming a cyndrical plane and a number of emitters contained in the mechanism 59 are arranged along an electron releasing surface 591 forming a cylindrical plane.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a vacuum gauge that utilizes the ionization phenomenon of gas.
In particular, it relates to a vacuum type in which a rotating electron current is generated in a space where an electric field and a magnetic field intersect, thereby increasing the ionization of gas (hereinafter referred to as the crossed electromagnetic field type).

[Prior Art] Vacuum gauges that utilize the ionization phenomenon of gas include those that have a hot cathode and those that do not. Vacuum gauges with a hot cathode are often used because of their high reliability, but they have the disadvantage that the hot cathode disturbs the vacuum system. In contrast, a vacuum gauge without a hot cathode is superior in that it does not disturb the vacuum system. There are many types of vacuum gauges of this type, but crossed electromagnetic variant vacuum gauges, such as Penning vacuum gauges and magnetron vacuum gauges, are the most commonly used.

[Problems to be Solved by the Invention] However, the crossed electromagnetic variant vacuum gauge has drawbacks such as the need to use high voltage and low reliability. The issue of reliability is related to the patent application filed by the applicant.
Most of the problems were solved by the vacuum gauge No. 39270. However, high voltage is still used, resulting in problems such as unstable cold cathode discharge and short cathode life due to cathode sputtering caused by positive ions.

[Purpose] The purpose of the present invention is to solve the above-mentioned drawbacks, and to provide (1) a vacuum gauge that can lower the applied voltage or provide high sensitivity with the same applied voltage; (2) provide stable cold cathode discharge. (3) A long-life vacuum gauge with less cathode sputtering; (4) A vacuum gauge that is safe and highly reliable because it does not use high voltage.

[Means for Solving the Problems] The present invention provides a microfabricated cold cathode emitter (for example,
The above objective could be achieved by applying NIKKEI MiCRODEVICES L989 November issue, page 149) to the cold cathode of a crossed electromagnetic variant vacuum gauge. That is, the vacuum gauge of the present invention is a crossed electromagnetic field type vacuum gauge, and is characterized in that the cathode is composed of a large number of minute cold cathodes formed on a substrate.

A microcold cathode is a cold cathode made using micropattern processing technology used in IC manufacturing processes. Therefore, a large number of minute cold cathodes can be formed on one substrate.

A large number of minute cold cathodes can be arranged along a circle on the substrate. In this case, they can be arranged along a plurality of concentric circles.

In this invention, the rotating electron current measuring means employed in the vacuum gauge of Japanese Patent Application No. 1-39270 mentioned above can be provided.

[Operation] The microcold cathode has a sharp tip, from which electrons are ejected by electric field radiation. The microcold cathode is, for example, 10μ
Since they can be arranged in the order of tens or tens of thousands with a pitch of m, even if the emitter overlap of one cold cathode is small, the total emitter current due to the large number of cold cathodes can be large, resulting in a stable Discharge becomes possible. The voltage applied between the minute cold cathode and the anode can be lower than that of conventional crossed electromagnetic variant vacuum gauges.

An example of the operation of this vacuum gauge is as follows. Electrons ejected from the tip of each cold minute cathode are accelerated by an accelerating electrode formed near the cold minute cathode, and then head toward the anode. A magnetic field that intersects with the electric field is formed near the anode, so the electrons undergo rotational motion under the influence of the magnetic field. When these rotating electrons collide with gas molecules inside the vacuum gauge, the gas molecules are ionized, and the positive ions generated at that time collect in the ion collector. By measuring this ion collector current, the pressure inside the vacuum gauge can be determined. Alternatively, the ion collector may be omitted and the anode current may be measured.

[Example code] Next, the present invention will be explained in detail using the drawings.

FIG. 1 is a longitudinal sectional view of an embodiment of the present invention. This vacuum gauge mainly includes a vacuum container 10 and this vacuum container 1.
0, an anode mechanism 30, an ion collector mechanism 40, and a cold cathode mechanism 50, which constitute a crossed electromagnetic field type cold cathode ionization vacuum gauge.

The vacuum vessel 10 consists of a cylindrical discharge tube 11, a connecting tube 12 for attaching to the vacuum chamber to be measured, and a stem portion 13 for penetrating and fixing various electrical connection terminals, and these are integrally formed. ing.

The magnetic field setting means 20 consists of two annular permanent magnets 21 and a yoke 23 between them. The magnetic field 22 created by the permanent magnet 21 is arranged along the center line 34 of the anode electrode 31 inside the anode electrode 31 . An annular recess is formed in the yoke 23, and the sensor coil 70 is accommodated in this recess.

This sensor coil 70 is for measuring a rotating electron current, which will be described later, and is wound with 2000 turns.

The magnetic field setting means includes a plurality of permanent magnets 2 as shown in FIG.
11 to 214 may be arranged such that the same magnetic poles face each other to form a spatially alternating magnetic field 221. A yoke 231 is located between the permanent magnets 211 to 214.
~233 is placed.

Returning to FIG. 1, the anode mechanism 30 includes a cylindrical anode electrode 3
1, a lead 32, and an anode power source 33. In this embodiment, the anode electrode 31 has a diameter of 26 mm and a length of 30 mm.
It is mm. The anode power supply 33 is for maintaining the anode electrode 31 at a predetermined voltage with respect to the ion collector and the cold cathode, and in the illustrated example, a DC power supply is used. The voltage applied to the anode electrode 31 is, for example, 200 to 300V. Note that when selecting a pressure measurement method in which the rotating electron current is measured using the above-described sensor coil 70, a DC power source and an AC power source connected in series are used as the anode power source 33.

The ion collector mechanism 40 includes a disk-shaped ion collector electrode 41, a lead 42, and an ammeter 43 that measures the ion collector current. Ion collector electrode 41 is grounded.

The cold cathode mechanism 50 includes a multipolar electron emission mechanism formed on a disk-shaped substrate 55, an emitter power source 542, and an acceleration power source 572. The emitter of the multipolar electron emission mechanism and the emitter power supply 542 are connected by a lead 543, and the acceleration electrode of the multipolar electron emission mechanism and the acceleration power supply 572 are connected by a lead wire 57.
3 and a lead 574.

FIG. 3 is a plan view of the substrate 55, which includes an outer multipolar electron emission mechanism 58 formed along a circular shape and an inner multipolar electron emission mechanism 59, which are arranged concentrically. . The diameter of the substrate 55 is approximately equal to the inner diameter of the anode electrode 31, and since the anode electrode 31 has a cylindrical shape, the multipolar electron emission mechanism is also arranged along a circle. The multipolar electron emission mechanism includes a large number of minute cold cathodes (hereinafter referred to as emitters) formed by a fine pattern processing technique. A large number of emitters included in the outer multipolar electron emission mechanism 58 have an electron emission surface 581 having a cylindrical surface.
The inner multipolar electron emission mechanism 59
A large number of emitters are arranged along an electron emitting surface 591 having a cylindrical surface.

4 is an enlarged vertical sectional view taken along the line TV-mV in FIG. 3, and FIG. 5 is a plan sectional view taken along the line V-v in FIG. 4. In FIGS. 4 and 5, a large number of emitters 54 with sharp tips are formed in a circular shape on a substrate 55, and a shield electrode 53 is formed on the upper surface of the emitters 54. A canopy 531 protrudes from the shield electrode 53. This shield electrode 53 prevents positive ions from entering the emitter 54. Therefore, the emitter 54 is not sputtered and the emitter 54 is not sputtered.
4 has a long lifespan. Further, an annular accelerating electrode base 575 is formed on the substrate 55, and a cylindrical accelerating electrode 57 stands on top of the annular accelerating electrode base 575. emitter 54, shield electrode 53,
Both the accelerating electrode base 575 and the accelerating electrode 57 are made of a conductive material. The accelerating electrode base 575 is formed on the substrate 55 with an insulator 56 in between.
It is insulated from The end of the accelerating electrode base 575 is a pad portion 576, and this pad portion 576 has a
A lead wire 571 made of gold wire is bonded. This lead wire 571 is connected to an acceleration power source 572 via a lead wire 573 and a lead 574 shown in FIG.

Electrons emitted from the tip of the emitter 54 by field emission are accelerated by the accelerating electrode 57 and then fly toward the anode electrode 31 in FIG.

That is, in FIGS. 4 and 5, electrons are first emitted in the direction of arrow 541. The electrons that have passed between the accelerating electrodes 57 are pulled by the electric field created by the anode electrode 31 and head upward in FIG. 4, and are influenced by the magnetic field 22 in FIG. 1 and fly in a spiral shape. .

When a multipolar electron emission mechanism is arranged as in this embodiment, electrons are emitted from the electron emission surface 581 in the direction of the arrow 52 in FIG.
That is, it is emitted toward the center of the substrate 55.

The emitter 54 is preferably made of a high melting point metal material such as molybdenum or tungsten, but any material with a small work function (that is, a high ability to emit cold cathode electrons by an electric field) may be used. It is also preferable to reduce the work function by providing an oxide film on the emitter surface.

The diameter of the substrate 55 is 10 to 25 mm. Electron emission surface 5
The diameter of 81.591 is not particularly limited, and the multipolar electron emission mechanisms 58.59 are not limited to two layers, but may be arranged concentrically in three or more layers. Emitters 54 can be arranged in the order of tens of thousands on the entire substrate, and the spacing between adjacent emitters 54 is about 10 μm. It is preferable to make the radius of curvature of the emitter tip as small as possible, and in the example, it was set to 0.1 μm or less. The spacing between adjacent accelerating electrodes 57 is also about 10 μm, similar to the emitter spacing, and the cylindrical accelerating electrode 57 has a diameter of 1 μm and a height of 2 to 3 μm. The distance from the tip of the emitter 54 to the electron emission surface 581 is 15 μm.

To form such micro-shaped emitters and accelerating electrodes, micropattern processing technology used in the IC manufacturing process is used. In other words, the film formation process, photoresist exposure and
A multipolar electron emission mechanism as shown in FIGS. 4 and 5 is formed by combining a patterning process using development, an etching process, and the like. By using this fine pattern processing technology, it is possible to stably mass-produce a large number of minute cold cathodes.

Next, the operation of this vacuum gauge will be explained.

This vacuum gauge is suitable for measuring pressures below 10-'Torr, so when that pressure is reached, each power source is activated.

For example, 300V is applied to the anode electrode 31 in FIG. 1, 10V is applied to the emitter 54 in FIG. 4, and 50V is applied to the accelerating electrode 57.
Apply. The strength of the magnetic field at the center of the anode electrode 31 is assumed to be 300 Gauss. The electrons emitted from the emitter 54 trace a trajectory as indicated by an arrow 541, and generate a discharge inside the anode electrode 31 similar to a normal crossed electromagnetic variant vacuum gauge. Positive ions generated by gas ionization are captured by the ion collector electrode 41, which has the lowest potential. The pressure can be determined by measuring the ion collector current at this time with the ammeter 43. For example, if the pressure is I
At 10-6 Torr, an ion collector current of 5×10-'A could be obtained. Since this vacuum gauge uses a multipolar electron emission mechanism that utilizes field radiation, the electron emission is stable and stable discharge was obtained. Also,
It is safe because it operates at a low voltage (usually 200 to 300 V), and there is little sputtering on the shield electrode 53 (almost no sputtering on the emitter 54), allowing long-life operation.

The operating conditions described above are just examples. Accelerating electrode 57
By reducing the distance between the emitter 54 and the emitter 54, the acceleration voltage can be further reduced.

If the eaves 531 of the shield electrode 53 are further extended to cover the accelerating electrode 57, the anode voltage may be higher. When increasing the anode voltage, it is desirable to also increase the magnetic field.

Next, returning to FIG. 1, the configuration related to the sensor coil 70 will be described. The two lead wires of the sensor coil 70 are
After passing through a bandpass filter 71, the signals are connected to each other to form a loop. Insert the ammeter 72 into this bulb. The bandpass filter 71 is for removing noise of a frequency different from the frequency of the alternating current applied to the anode electrode 31 from the output current of the sensor coil 70. To measure the rotating electron current using this sensor coil 70,
An anode voltage consisting of a DC component and an AC component is applied to the anode electrode 31 . The rotating electron current fluctuates due to this alternating current, and this fluctuation induces an alternating current in the sensor coil 70. This induced current is detected by an ammeter 72. Since the rate of variation of the rotating electron current is proportional to the intensity of the rotating electron current,
By determining the magnitude of the induced current in the sensor coil 70, the rotating electron current can be determined. Here, the sensitivity coefficient of the vacuum gauge is S, the ion collector current is Ic, and the rotating electron current! When r is the pressure inside the vacuum gauge, the pressure P inside the vacuum gauge can be determined by the following equation.

P-(1/S) (I c/I r) FIG. 6 is a longitudinal sectional view of another embodiment. The difference between this embodiment and the embodiment shown in FIG. 1 is that there is no ion collector and the cold cathode mechanism 50 is
There are two sets of anodes, the anode electrode 31 is not cylindrical but ring-shaped, and the magnetic field setting means 20 has a different shape. Components corresponding to the embodiment shown in FIG. 1 are given the same reference numerals.

The two cold cathode mechanisms 50 are arranged to face each other with the ring-shaped anode electrode 31 in between. As shown in FIG. 7, the magnetic field setting means 20 has two permanent magnets 21 fixed to both ends of a U-shaped yoke 23, with N and S poles facing each other. Therefore, in FIG. 6, the magnetic field 22 generated by the magnetic field setting means 20 extends along the center line of the ring-shaped anode electrode 31, and swells outward at the center of the anode electrode 31 (note that in FIG. In the embodiment, the magnetic field 22 bulges inward at the center of the anode electrode 31).
. In this embodiment, since there is no ion collector, the anode current is measured with an ammeter 35 with the anode electrode 31 at ground potential, and the pressure is determined based on this. cold cathode mechanism 50
A negative potential is applied to the emitter by the emitter power supply 542, and a higher potential than the emitter is applied to the acceleration electrode by the acceleration power supply 572.

In this embodiment, most of the positive ions generated by gas ionization eventually flow into the emitter of the cold cathode mechanism 50, while electrons flow into the anode electrode 31.

Therefore, measuring the anode current means measuring the discharge current.

This invention is not limited to the embodiments described above, but can be modified in many ways. The shape of the anode may be a rectangular tube instead of a cylinder. In that case, the electron emitting surface 581 in FIG.
．． 591 may be a square. Electron emission surface 581.5
The shape of 91 can be any shape, and a large number of electron emitting surfaces having a specific shape such as a circle may be arranged on the substrate. In short, it is sufficient if electrons can be emitted toward the anode electrode.

The direction of electron emission from the electron emission surface is indicated by arrow 52 in FIG.
, that is, toward the center of the circular board,
The emitter may be arranged so as to emit electrons toward the outer periphery of the circular substrate. The electron emission direction may be divided into a central direction and an outer peripheral direction for different electron emission surfaces. Also, 2
When there are a set of cold cathode mechanisms, one cold cathode mechanism may have its electron emission direction directed toward the center of the substrate, and the other cold cathode mechanism may have its electron emission direction directed toward the outer periphery of the substrate.

A desirable aspect of the electron emission direction is to emit electrons in the direction in which the lines of magnetic force inside the anode electrode bulge, which is desirable because the discharge intensity increases. In this regard, in the embodiment of FIG. 1, it is desirable that the electron emission direction 52 be directed toward the center of the substrate, and in the embodiment of FIG. 5, it is desirable that the electron emission direction 52 be directed toward the outer periphery of the substrate.

The shapes of the shield electrode 53; accelerating electrode 57 and emitter 54 can also be changed in various ways. For example, the shield electrode 53
Various changes can be made to the height of the eaves 531, the amount of protrusion of the eaves 531, the distance between the eaves 531 and the accelerating electrode 57, the height and shape of the accelerating electrodes 57, the shape of the tip of the emitter 54, and the like.

The vacuum vessel 10 can be of a so-called nude type, in which the discharge tube 11 and the connecting tube 12 are eliminated and only the stem portion 13 is left. In this case, elements of the vacuum gauge, such as an anode electrode or a cold cathode, are inserted into the vacuum system to be measured to measure pressure.

As the magnetic field setting means, an electromagnet may be used instead of a permanent magnet.

[Effects of the Invention] As explained above, the vacuum gauge of the present invention has a crossed electromagnetic field type vacuum gauge in which the cathode is formed of a large number of minute cold cathodes, and is therefore superior to the conventional crossed electromagnetic field type cold cathode ionization vacuum type. It has the following effects compared to:

(1) Discharge becomes stable.

(2) The voltage applied between the cathode and anode can be small. While conventional vacuum gauges require several kV, this invention requires only several hundred volts.

(3) Since the applied voltage is small, cathode sputtering by positive ions is reduced, resulting in a long life.

Also, if this vacuum gauge is equipped with a rotating electron current measuring means,
In addition to the above-mentioned effects, pressure measurement accuracy is improved and reliability is increased.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view of an embodiment of the present invention, FIG. 2 is a longitudinal sectional view of a modified example of the magnetic field setting means, FIG. 3 is a plan view of the substrate of the cold cathode mechanism, and FIG. FIG. 5 is a plan sectional view taken along the line ■-■ in FIG. 4, FIG. 6 is a vertical sectional view of another embodiment, and FIG. FIG. 7 is a perspective view of the magnetic field setting means of FIG. 6; 20...Magnetic field setting means 31...Anode electrode 41...Ion collector electrode 50...Cold cathode mechanism 54...Emitter 55...Substrate 57...Acceleration electrode 70...Sensor coil

Claims (4)

[Claims] (1) In a vacuum gauge having a cathode, an anode, and a magnetic field setting means for forming a magnetic field that intersects an electric field created by the cathode and the anode, the cathode is formed of a large number of minute particles formed on a substrate. A vacuum gauge characterized by consisting of a cold cathode. (2) The vacuum gauge according to claim 1, wherein the plurality of minute cold cathodes are arranged along a circle on the substrate. (3) The vacuum gauge according to claim 2, wherein the plurality of minute cold cathodes are arranged along a plurality of concentric circles. (4) The vacuum gauge according to claim 1, further comprising means for measuring a rotating electron current generated by the action of the electric field and the magnetic field.