JPH06109568A - Vacuum sensor - Google Patents

Abstract

PURPOSE:To measure absolute pressure within a wide range of gas with only a device and achieve miniaturization in simple structure in regard to a vacuum sensor for detecting an absolute pressure value from the change of an electrostatic capacity value. CONSTITUTION:Diaphragm electrodes 3-5 composed of pairs of opposed conductive thin films 3A-5A sandwiching inside spaces 3B-5B are arranged to fix their circumferential edges on a board 1. A plurality of the pairs of the diaphragm electrodes 3-5 composed of structure respectively different in the areas of the conductive thin films 3A-5A are electrically insulated and serially provided on the board 1 in a condition where the spaces 3B-5B between each diaphragm electrode 3-5 are mutually made to communicate and sealed in a high vacuum.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vacuum sensor for measuring pressure in a vacuum device, and more particularly to a vacuum sensor for detecting an absolute pressure value from a change in capacitance value.

[0002]

2. Description of the Related Art In recent years, in the process industry and the like, a vacuum sensor mounted on a vacuum device is required to have functions such as reliability and downsizing, and is used as a vacuum sensor for measuring the pressure inside the vacuum device. Conventionally, for example, a Pirani vacuum gauge is often used.

FIG. 5 shows a detection part of a Pirani vacuum gauge. A platinum filament 42 is stretched inside a vacuum container 41, and the filament 42 is electrically heated. Since the amount of gas molecules taking heat from the filament 42 changes due to the pressure change, electric power for keeping the filament 42 at a constant temperature is fed back to the detection circuit. The gas pressure is measured by this feedback amount.

FIG. 6 shows a detection part of a diaphragm vacuum gauge, in which a movable diaphragm electrode 52 of a metal thin film is provided in the center of an airtight container 51, a central fixed electrode 53 is provided in the central part, and an outer peripheral part is provided. Peripheral fixed electrodes 54 are provided so as to face and be close to the movable diaphragm electrode 52, respectively. The difference between the electrostatic capacitance between the central fixed electrode 53 and the movable diaphragm electrode 52 and the electrostatic capacitance between the outer peripheral fixed electrode 54 and the movable diaphragm electrode 52 is detected by the AC bridge circuit.

[0005]

However, the conventional Pirani vacuum gauge has a drawback in that the sensitivity changes due to the difference in the thermal conductivity of the gas, and it is necessary to calibrate each time depending on the gas to be measured.

Further, a metal filament 4 which is energized
There is also a problem that the output of the Pirani vacuum gauge changes during use in measuring the pressure of corrosive gas, etc., because 2 has a structure that directly contacts the gas to be measured.

On the other hand, in the diaphragm vacuum gauge, the output does not change depending on the type of gas unlike the Pirani vacuum gauge, and the pressure of corrosive gas can be measured by appropriately selecting the material of the movable diaphragm electrode 52. Although it becomes possible, in order to increase the pressure sensitivity, it is necessary to make the thickness of the movable diaphragm electrode 52 extremely thin to be about 10 microns or to have an area of several centimeters on each side.

If the thickness of the diaphragm electrode is extremely thin, it becomes difficult to process or fix it to the airtight container 51. If the area of the movable diaphragm electrode 52 is increased, the size of the entire device is increased and the dead space is increased. However, there are problems that it takes a long time to reach a predetermined degree of vacuum and the responsiveness to pressure change deteriorates.

Further, in order to increase the pressure sensitivity, it is necessary to make the movable diaphragm electrode 52 into a precision instrument in which the thickness of the movable diaphragm electrode 52 is processed to be very thin, but it is necessary to handle it with sufficient care, and it is necessary to handle it with an AC bridge circuit or the like. The vacuum gauge incorporating the signal processing circuit was large and very expensive.

Further, it is impossible to measure a wide range of vacuum pressure with one diaphragm, and when the vacuum measurement range is wide, a plurality of units are required and the dead space becomes large.

The present invention has been made to solve the above-mentioned problems, and an object thereof is to measure the absolute pressure of a wide range of gas with one device, and to achieve miniaturization with a simple structure. It is to provide a vacuum sensor.

[0012]

The invention according to claim 1 is
Diaphragm electrodes consisting of a pair of conductive thin films facing each other across an internal space are arranged with their peripheral edges fixed to a substrate, and a plurality of sets of diaphragm electrodes with the above-mentioned structures having different conductive thin film areas are provided for each diaphragm. It is characterized in that the spaces between the electrodes are communicated with each other and are electrically insulated from the substrate in a state of being sealed in a high vacuum.

A second aspect of the invention is characterized in that, in the first aspect of the invention, at least one of the plurality of diaphragm electrodes has a thick portion. The invention according to claim 3 is characterized in that, in the invention according to claim 1, the outer surface of the conductive thin film of the diaphragm electrode is covered with a corrosion resistant film.

[0014]

In the present invention, the diaphragm electrode having a large area of the conductive thin film measures a high vacuum region, and the diaphragm electrode having a small area of the conductive thin film measures a low vacuum region. .

Since a plurality of sets of diaphragm electrodes having the above-mentioned structure in which the areas of the conductive thin films are different are arranged on the substrate so that the spaces between the diaphragm electrodes communicate with each other at a plurality of positions, the diaphragm electrodes of the respective diaphragm electrodes are arranged. The spaces in between are kept at the same vacuum pressure at the same time.

[0016]

Embodiments of the present invention will be described below with reference to the drawings. 1 and 2 show a vacuum sensor according to an embodiment of the present invention.

In the figure, reference numeral 1 is a silicon substrate, and three sets of diaphragm electrodes 3, 4 and 5 are electrically insulated and fixed to one end side of the silicon substrate 1 via an insulating layer 2. Has been done. Each diaphragm electrode 3, 4,
5 is a pair of conductive thin films 3A, 3A, 4A, 4
A, 5A, 5A, and their peripheral edges are fixed to the silicon substrate 1 in a state where the internal space is sealed in a high vacuum.

The conductive thin films 3A, 4A, 5A of the three sets of diaphragm electrodes 3, 4, 5 have different areas, and the area Sa of the conductive thin film 3A> the area Sb of the conductive thin film 4A> the conductive thin film 4C. Area Sc.

A thick portion 1B is formed on the other end side of the silicon substrate 1. Inside the thick portion 1B, a pair of conductive thin films 6A, 6A is formed adjacent to the diaphragm electrode 5.
The reference electrode 6 is formed of, and the reference electrode 6 is insulated from the silicon substrate 1 through the insulating layers 2 and 2 in a state where the internal space 6B is sealed in a high vacuum, and the peripheral edges of the reference electrode 6 and the silicon substrate 1 are formed. It is fixed to.

Further, inside the thick portion 1B, a vacuum chamber 7 is formed adjacent to the reference electrode 6 and serving as a reference pressure when measuring the absolute pressure, and the getter material 7A is housed in the vacuum chamber 7. Has been done. The getter material 7A keeps the reference pressure in the vacuum chamber 7 at a high vacuum, and prevents the output of the vacuum sensor from changing due to the change in the reference pressure.

The space 3B of the diaphragm electrode 3 and the space 4B of the diaphragm electrode 4 communicate with each other through the first communication passage 8, and the space 4B of the diaphragm electrode 4 and the space 5B of the diaphragm electrode 5 form the second communication passage 9. Communicate with each other through. The space 5B in the diaphragm electrode 5 and the space 6B in the reference electrode 6 communicate with each other via the third communication passage 10, and the space 6B in the reference electrode 6 and the vacuum chamber 7 communicate with each other via the fourth communication passage 11. It is in communication. Therefore, the diaphragm electrode 3,
The spaces 3B, 4B and 5B of 4, 5 and the space 6B in the reference electrode 6 and the vacuum chamber 7 communicate with each other.

A fifth communication passage 12 is formed between the vacuum chamber 7 and the end surface on the other end side of the silicon substrate 1, and the middle of the fifth communication passage 12 is below the other end of the silicon substrate 1. It is closed by a sealing material 14 fitted in a sealing port 13 formed in the portion.

On the silicon substrate 1, terminals 15, 1 are provided.
5,15,15,15 are provided, and these terminal parts 1
5,15,15,15,15 and diaphragm electrode 3,
4, 5 are connected via a lead wire 16.

However, in this embodiment, when assembling the vacuum sensor, the gap between the upper and lower flat plate portions constituting the silicon substrate 1 is evacuated in the final step in a high vacuum to seal the vacuum sensor. The sealing member 13 is sealed by the stopper material 14. At this time, the getter material 7A is housed in the vacuum chamber 7 integrally formed in the silicon substrate 1 at the same time as the reference electrode 6, and the getter material 7A is housed in the silicon substrate 1. Diaphragm electrode 3,
Spaces 4 and 5 3B, 4B and 5B and a space 6 in the reference electrode 6
B and the vacuum chamber 7 are maintained in a high vacuum state.

In this state, the vacuum sensor is installed in the gas. When the pressure of the gas around the vacuum sensor is lowered, the conductive thin films 3A, 3A, 4A of the diaphragm electrodes 3, 4, 5 correspond to the change of the gas pressure.
The interval between 4A, 5A, and 5A becomes large, and the value of capacitance decreases.

The amount of displacement of each set of diaphragm electrodes 3, 4, 5 corresponding to the change in gas pressure is as long as the conductive thin films 3A, 4A, 5A of the diaphragm electrodes 3, 4, 5 have the same thickness. , Is proportional to the areas of the conductive thin films 3A, 4A, 5A, the diaphragm electrode 3 having a large area has a large change in the electrostatic capacitance value, and the diaphragm electrode 5 having a small area has a large change in the electrostatic capacitance value. Get smaller. The diaphragm electrode 4 is in the middle.

Therefore, the diaphragm electrode 3 having a large area
Thus, a region having a high degree of vacuum is measured, and a region having a low degree of vacuum is measured by the diaphragm electrode 5 having a small area. The diaphragm electrode 4 measures the vacuum region in the middle of the above range.

Then, the three sets of diaphragm electrodes 3, 4 having the above-mentioned structure in which the areas of the conductive thin films 3A, 4A, 5A are different from each other.
5, the diaphragm electrode 3, 4, 5 of each set over 3 places
Since the spaces 3B, 4B, 5B between them are arranged on the silicon substrate 1 so as to communicate with each other, the spaces 3B, 4B, 5B between the diaphragm electrodes 3, 4, 5 of each set are simultaneously maintained at the same vacuum pressure. To be done.

Since the outer portion of the reference electrode 6 is covered with the thick portion 1B of the silicon substrate 1, it is not deformed by the pressure of the gas around the reference electrode 6, and therefore,
The capacitance value of the reference electrode 6 does not change with pressure. Since the value of the capacitance in the reference electrode 6 changes only with the temperature (since the distance between the electrodes changes with the difference in the coefficient of thermal expansion of the constituent materials), this value (change amount due to temperature) is used as a reference. , Other diaphragm electrodes 3,
If the change in the value of the electrostatic capacitance between 4 and 5 (the change in the pressure + the change in the temperature) is measured and the change in the value of the electrostatic capacitance due to the temperature is canceled, the other diaphragm electrodes 3, 4,
The change in the capacitance value between 5 (the change in pressure only) is measured. That is, of the capacitances of the diaphragm electrodes 3, 4, and 5, the temperature compensation is performed by canceling out the capacitance due to temperature change.

According to the above construction, the conductive thin film 3
By arranging a plurality of sets of diaphragm electrodes 3, 4, 5 having appropriate areas A, 4A, 5A over a plurality of locations, the absolute pressure of a wide range of gas can be measured by one vacuum sensor.

Moreover, since the spaces 3B, 4B, 5B between the diaphragm electrodes 3, 4, 5 communicate with each other,
The structure of the device for creating a vacuum in those spaces 3B, 4B, 5B can be simplified. Therefore, the size of the vacuum sensor can be made compact with a few millimeters, and it is possible to make it ultra-compact compared to conventional vacuum sensors. Since the dead space can be reduced, the time required for exhausting the entire vacuum device can be shortened, and the response of the sensor to pressure changes can be accelerated.

As a result, it becomes possible to perform multipoint measurement and pressure distribution measurement inside the vacuum apparatus, and to enable more detailed process control and management. Further, it is easy to integrate the signal processing circuit around the sensing portion of the vacuum sensor by using the semiconductor integrated circuit technology.

Furthermore, since the spaces of the diaphragm electrodes 3, 4, 5 communicate with each other, the spaces 3B, 4B, 5
B is made into a high vacuum at the same time, and each diaphragm electrode
It is possible to eliminate the need to independently apply vacuum pressure to each space.

Although the number of diaphragm electrode sets is three in this embodiment, the number of sets is two or four.
It can be more than one. Further, a thick portion can be provided in at least one of the three sets of diaphragm electrodes 3, 4, 5. For example, as shown in FIG. 3, thick-walled portions 21 and 21 can be provided on the conductive thin films 5A and 5A of the diaphragm electrode 5 having the smallest area of the conductive thin film 5A. As a result, the displacement of the diaphragm electrode 5 due to the pressure change is suppressed, and the detection range of the absolute pressure of the diaphragm electrode 5 can be further expanded.

Further, as shown in FIG. 4, the conductive thin films 3A, 3A, 4 of the three diaphragm electrodes 3, 4, 5 are arranged.
The outer surface of each of A, 4A, 5A, and 5A may be covered with a corrosion-resistant coating 31. Thereby, the pressure of the corrosion resistant gas can be measured. As the corrosion resistant film 31 used here, for example, a polymer material, a noble metal or the like is used in correspondence with the corrosion resistant gas.

[0036]

As described above, according to the present invention,
By arranging a plurality of sets of diaphragm electrodes made of a conductive thin film having an appropriate area over a plurality of locations, it is possible to measure the absolute pressure of a wide range of gas with one vacuum sensor.

Moreover, since the spaces between the diaphragm electrodes of each set are communicated with each other, the structure of the device for evacuating those spaces can be simplified, and therefore the size of the vacuum sensor can be several millimeters. It is possible to reduce the dead space and speed up the exhaust speed and the response time by making it compact and making it more compact than the conventional vacuum sensor.

Further, since the spaces of the diaphragm electrodes are in communication with each other, it is possible to eliminate the need to simultaneously make the spaces into a high vacuum and to independently apply the vacuum pressure to the spaces of the diaphragm electrodes.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view of a vacuum sensor according to an embodiment of the present invention.

FIG. 2 is a plan view of the vacuum sensor.

FIG. 3 is a vertical sectional view showing a first modification of the vacuum sensor.

FIG. 4 is a vertical cross-sectional view showing a second modified example of the vacuum sensor.

FIG. 5 is a configuration diagram of a detection unit of a conventional Pirani vacuum gauge.

FIG. 6 is a configuration diagram of a detection unit of a conventional diaphragm vacuum gauge.

[Explanation of symbols]

 1 Silicon Substrate 3 Diaphragm Electrode 3A Conductive Thin Film 3B Space 4 Diaphragm Electrode 4A Conductive Thin Film 4B Space 5 Diaphragm Electrode 5A Conductive Thin Film 5B Space

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Masaki Moronuki 1-13-5 Kudankita, Chiyoda-ku, Tokyo 1-13-5 Riken Co., Ltd. (72) Inventor Koji Izumi 1-13-5, Kudankita, Chiyoda-ku, Tokyo In stock company Riken

Claims (3)

[Claims] 1. A plurality of sets of diaphragms of the above structure, wherein diaphragm electrodes made of a pair of conductive thin films facing each other with an internal space therebetween are arranged with their peripheral edges fixed to a substrate, and the conductive thin films have different areas. A vacuum sensor characterized in that electrodes are electrically insulated from a substrate in a state where spaces between respective diaphragm electrodes are communicated with each other and sealed in a high vacuum. 2. The vacuum sensor according to claim 1, wherein at least one of the plurality of diaphragm electrodes has a thick portion. 3. The vacuum sensor according to claim 1, wherein an outer surface of the conductive thin film of the diaphragm electrode is covered with a corrosion resistant film.