JPH085494A - Vacuum sensor - Google Patents

Abstract

PURPOSE:To provide a vacuum sensor which is simple in structure, small-sized, and besides can measure wide range of vacuum pressure with by itself by counterposing plural sets of diaphragm electrodes and conductive film electrodes with different areas thereby constituting a plurality of sensor capacitors. CONSTITUTION:Conductive diaphragm electrodes 14, 16 and 18 are made, possible to displace and besides in a body with the thick part of a board 4, below the hoes 8S, 10S, and 12S provided in the predetermined positions of a plate silicon board 4 and a second glass board 6. Moreover, conductive film electrodes 24, 26, and 28 with the same area as the electrodes 14, 16, and 18 are provided, in opposition to the electrodes 14, 16, and 18, at topside of the first glass board 2. And, these electrodes 24, 26, and 28 are led out through the conductive part of an island 40 and a field through part 22, and the vacuum degree can be measured from the change of capacitance between the electrodes 14, 16, and 18 and the electrodes 24, 26, and 28 caused accompanying the displacement of the electrodes 14, 16, and 18.

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 an improvement in a vacuum sensor for measuring an absolute pressure value from a change in a capacitance value. .

2. Description of the Related Art In the semiconductor process industry and the like, the demand for reliability and miniaturization of a vacuum sensor mounted on a vacuum device is increasing, and a vacuum sensor for measuring a pressure in a vacuum device, such as Pirani, is conventionally used. A vacuum gauge and a diaphragm type vacuum gauge are often used.

[0003]

2. Description of the Related Art FIG. 7 shows a detection section of a conventionally known Pirani vacuum gauge. As shown in FIG. 7, the detection unit includes an introduction unit 5 in which a platinum filament 52 is stretched inside a vacuum vessel 51 and arranged in a vacuum unit in a vacuum device.
3 are provided.

[0004] This detection unit operates as follows. That is, when the introduction section 53 of the Pirani vacuum gauge is arranged in the vacuum section in the vacuum apparatus and measures the pressure inside the vacuum apparatus, a predetermined current is supplied to the filament 52 of the detection section to heat the filament 52. The heat generated from the filament 52 is absorbed into the gas around the filament 52 by the heat conduction of the gas. The amount of heat absorbed by the gas molecules changes in accordance with the pressure of the gas surrounding the filament 52. Therefore, the filament 52
The power supplied to the filament 52 to keep the temperature of the filament 52 constant, or a signal representing the power, is fed back to the detection circuit and used to measure the gas pressure.

FIG. 8 shows a detecting section of a diaphragm type vacuum gauge. As shown in FIG. 8, a movable diaphragm electrode 62 made of a metal thin film is provided in the center of an airtight container 61 in this detection unit. A central fixed electrode 63 is provided at the center of the hermetic container 61, and an outer peripheral fixed electrode 64 is provided at an outer peripheral portion of the hermetic container 61 so as to face the movable diaphragm electrode 62. The center fixed electrode 63 and the movable diaphragm electrode 62 are connected between terminals to be measured of an AC bridge (not shown).

When measuring the pressure inside the vacuum device, the airtight space 61S in the airtight container 61 is communicated with the inside of the vacuum device via the vacuum introducing section 65. In this state, the pressure in the vacuum device is transmitted to the hermetic space of the diaphragm vacuum gauge via the vacuum introduction unit 65. The movable diaphragm electrode 62 is displaced according to the pressure. The displacement of the movable diaphragm electrode 62 causes the central fixed electrode 63
And the capacitance between the movable diaphragm electrode 62 and the movable diaphragm electrode 62 changes. The capacitance is measured by an AC bridge, and the measurement is used to represent the pressure of the vacuum device.

[0007]

Since the conventional Pirani vacuum gauge uses the thermal conductivity of gas, the sensitivity changes due to the difference in thermal conductivity of the gas. There is a need to do. Further, since the energized metal filament 52 is configured to directly contact the gas to be measured, a change in heat conduction occurs at the boundary between the filament 52 and the gas in pressure measurement of a corrosive gas or the like.
This causes the output of the Pirani gauge to change during use.

Further, in the diaphragm type vacuum gauge, the measured value does not change depending on the kind of gas unlike the Pirani vacuum gauge.
By appropriately selecting the material of the movable diaphragm electrode 62, the pressure of the corrosive gas can be measured.

However, in order to enhance the pressure sensitivity, it is necessary to make the thickness of the movable diaphragm electrode 62 as a very thin film of about 10 μm or to make an area of one side several centimeters.

[0010] When manufacturing a diaphragm vacuum gauge by reducing the thickness of the movable diaphragm electrode, the processing,
A technical problem that it becomes difficult to fix to the airtight container 61 newly occurs.

If the area of the movable diaphragm electrode 62 is to be increased, the size of the entire apparatus is increased, the dead space is increased, and it takes a long time to reach a predetermined degree of vacuum, or the pressure increases. Responsiveness to change is poor.

Further, in order to enhance the pressure sensitivity, it is necessary to use a precision instrument in which the thickness of the movable diaphragm electrode 62 is extremely thin. In addition to this, it is necessary to pay close attention to its handling. Further, a vacuum gauge incorporating a signal processing circuit such as an AC bridge becomes large and becomes a very expensive instrument.

Further, since the diaphragm type vacuum gauge utilizes the displacement of the movable diaphragm as described above, it is impossible to measure a wide range of vacuum pressure with one diaphragm. Therefore, in order to measure a wide range of vacuum pressure, it is necessary to provide a plurality of diaphragm vacuum gauges, which increases the dead space and increases the size of the diaphragm vacuum gauge.

The present invention has been made in view of such technical problems, and provides a vacuum sensor which has a simple structure, is small in size, and is capable of measuring a wide range of vacuum pressure with one unit. With that purpose.

[0015]

According to the present invention, a first substrate made of a conductive and moldable material and a second substrate made of an insulating and highly rigid material are provided. , First
A space formed apart from each other at each required position between the first substrate and the second substrate, an opening formed in the first substrate corresponding to each of the spaces, and each opening A conductive diaphragm electrode that has a different area for each opening and is displaced in accordance with the vacuum pressure applied to the opening, and the space on the second substrate. A conductive thin-film electrode disposed so as to face the conductive diaphragm electrode, and the first substrate and the second substrate in close contact with each other, and an opening is provided for each opening of the first substrate. A third substrate made of an insulating and high-rigidity material and a conductive lead-out portion drawn out to the outside for each conductive thin-film electrode, so that the spaces communicate with each other and are sealed in a high vacuum. From the capacitance between each conductive diaphragm electrode and the opposing conductive thin film electrode. And measuring the empty level.

According to a second aspect of the present invention, in the vacuum sensor according to the first or second aspect, at least one conductive diaphragm electrode is provided on a thick portion of the silicon substrate. I do.

According to a third aspect of the present invention, in the vacuum sensor according to the second or third aspect, the getter material is formed between the first substrate and the second and third substrates. The space between the first substrate and the second substrate communicates with the vacuum chamber.

[0018]

According to the first aspect of the present invention, a conductive diaphragm electrode having a different area and a conductive thin film electrode provided opposite to the conductive diaphragm electrode are provided for each required position of the first substrate and the second substrate. Since a sensor capacitor is formed and the degree of vacuum is detected by its capacitance, a single vacuum sensor can detect a wide range of absolute pressure with one vacuum sensor. Since the spaces of the sensor capacitors are connected to each other, a device for evacuating each space can be easily and compactly configured. Therefore,
It is possible to provide a vacuum sensor that is smaller and has a smaller dead space than a conventional vacuum sensor, requires less time for evacuation, and has a higher response speed. Further, since the spaces of the sensor capacitors are connected to each other, it is possible to eliminate the necessity of independently evacuating those spaces.

According to the second aspect of the present invention, since a reference sensor capacitor is provided, a function of compensating for a temperature change can be provided. According to the third aspect of the present invention, since the space of the sensor capacitor is communicated with the vacuum chamber containing the getter material, it is possible to maintain a high degree of vacuum in the space of the sensor capacitor.

[0020]

1 and 2 show one embodiment of the invention according to the first and second aspects. 1 is a plan view, and FIG. 2 is a sectional view taken along line II of FIG.

FIG. 2 shows a vacuum sensor having a laminated structure in which a first flat glass substrate 2, a flat silicon substrate 4, and a second flat glass substrate 6 are adhered to each other. At predetermined positions of the flat silicon substrate 4 and the second flat glass substrate 6, square holes having different sizes (claims 1 to 4).
Are formed in three holes. The three holes are referred to as 8G, 10G, 12G and 8S, 10S, 12S (see FIGS. 2 and 3). These holes 8S, 10
The conductive diaphragm electrodes 14, 16 and 18 are displaceable below the S and 12 S, respectively, and are integrally formed with the thick portion of the silicon substrate 4 by fine processing of the silicon substrate 4. The conductive diaphragm electrodes 14, 16, 18
Hereinafter, they are referred to as diaphragm electrodes 14, 16, and 18. The silicon substrate 4 is grounded. Silicon substrate 4
Need not necessarily be grounded. Diaphragm electrode 1
The areas of 4, 16, and 18 are determined so that the area becomes smaller as the reference number increases. The diaphragm electrodes 14, 16, 18 are connected to a terminal to be measured of a capacitance measuring circuit (for example, an AC bridge circuit) (not shown) via the silicon substrate 4.

When the vacuum sensor is placed in the device to be measured, holes 8G, 10G, 12G, and 8G formed in the glass substrate 6 are provided in close contact with the diaphragm electrodes 14, 16, 18 and the silicon substrate 4. When the gas pressure in the vacuum device to be measured enters the 8S, 10S, and 12S, the diaphragm electrodes 14, 16, 1, and 2 have a value corresponding to the gas pressure.
8 is a structural portion provided for displacing 8. The diaphragm electrodes 14, 16, 18 in the silicon substrate 4
Is cut out from the lower surface of the silicon substrate 4 by a predetermined thickness necessary to form a space. As described above, the space is formed as a sealed space, and when used as a vacuum pressure gauge, is a high vacuum space. In addition, in FIG. 2, the diaphragm electrodes 14, 16, and 18 are formed in a flat plate shape (see FIG. 4A), but are formed in a land bridge shape as shown in FIG. 4C. Is good. The difference is that the displacement of the diaphragm electrode is 2 in the case of FIG.
Although it can be approximated by the following equation (see FIG. 4B), in the case of FIG. 4C, it can be approximated by a linear equation (see FIG. 4D). FIG. 4B is more advantageous in value processing, and helps to simplify the processing.

A conductive thin-film electrode 24 having the same area as the diaphragm electrodes 14, 16, 18 is provided at a position on the upper surface of the first glass substrate 2 opposite to the space formed in this manner.
26 and 28 are provided to face the diaphragm electrodes 14, 16 and 18. These conductive thin film electrodes 24,
26 and 28 are conductive portions 4 of the island 40 as shown in FIG.
2, and a feed-through unit 2 for connecting to a terminal to be measured of a capacitance measuring circuit (for example, an AC bridge circuit)
2 (see FIGS. 2, 3 and 5), the diaphragm electrodes 14, 16, 18 and the conductive thin-film electrode 2, which are produced by the displacement of the diaphragm electrodes 14, 16, 18
It is configured so that the degree of vacuum can be measured from the change in capacitance between 4, 4, and 28. That is, each island 40 has a diffusion part 42 as shown in FIG.
Wiring 24 to conductive thin film electrodes 24, 26, 28 respectively
A, 26A, and 28A through the conductive thin film electrodes 24, 26,
28 (see FIG. 3). Therefore, the conductive thin film electrodes 24, 26, 28 are electrically connected to the diffusion portions 42 of the corresponding islands 40. Each of the islands 40 is tightly held between the flat glass substrate 2 and the flat glass substrate 6 by anodic bonding, and is electrically insulated from the silicon substrate 4. As shown in FIG. 3, the feed-through portion 22 is a structural portion for electrically extracting each of the diaphragm electrodes 24, 26, and 28. Lead lines are not shown.

The sealing space 15 between the diaphragm electrode 14 and the conductive thin-film electrode 24 and the sealing space 17 between the diaphragm electrode 16 and the conductive thin-film electrode 26 communicate with each other through a communication path 21. And the diaphragm electrode 16
The sealing space 17 between the conductive thin film electrode 26 and the sealing space 19 between the diaphragm electrode 18 and the conductive thin film electrode 28 communicates with each other through a communication path 23.

In addition, the diaphragm electrodes 14, 1
A reference electrode 30 for providing a reference capacitance with respect to the displacement of 6, 18 is provided on the thick portion 34 of the silicon substrate 4, and a conductive thin film electrode 32 is opposed to the reference electrode 30 by a first flat glass substrate. 2 is provided. This reference electrode 30
A notch cut out from the lower surface of the silicon substrate 4 in the thick portion 34 of the silicon substrate 4 adjacent to the diaphragm electrode 18 at the same position as the position where the diaphragm electrodes 14, 16, 18 are provided on the silicon substrate 4. It is provided in. The conductive thin-film electrode 32 is provided on the upper surface of the glass substrate 2. Therefore, a sealed space 33 is also formed between the reference electrode 30 and the conductive thin film electrode 32, and when used as a vacuum pressure gauge, it is a high vacuum space. The sealing space 33 is provided for the diaphragm electrode 18.
The sealing space 19 between the electrode and the conductive thin-film electrode 28 communicates with each other through a communication path 25.

A vacuum chamber 36 for supplying a vacuum pressure, which is a reference pressure in the measurement of the absolute pressure, to each of the sealed spaces 33, 19, 17, and 15 has a reference electrode inside the thick portion 34 of the silicon substrate 4. It is provided adjacent to 30 and communicates with the sealing space 33 via a communication passage (not shown). A getter material 38 is housed in the vacuum chamber 36. The getter member 38 is used to maintain the reference pressure in the vacuum chamber 36 at a high vacuum and prevent the output of the vacuum sensor from fluctuating due to the fluctuation of the reference pressure. As the getter material 38, _Zr
-AL-based alloy, using Z _r -V-F _e based alloy.

When assembling the vacuum sensor having such a structure, the silicon substrate 4 and the glass substrate 2 are placed in a high vacuum.
The space between the flat plate portions is evacuated and anodically bonded. Prior to the evacuation and anodic bonding, the first flat glass substrate 2 and the second After the getter material 38 is accommodated in the hollow portion of the silicon substrate 4 which is open to the flat glass substrate 2 side, the above-described sealing spaces 15, 17, 19, 33 A high vacuum is created, and the cutout acts as a vacuum chamber 36.

The operation of the vacuum sensor manufactured as described above will be described below. In order to measure a change in vacuum pressure in the device under test, the above-described vacuum sensor is installed in the device under test. The sealed spaces 15, 17, 1 of the vacuum sensor
9, and the sealing space 33 is communicated with the vacuum chamber 36 as described above, and is maintained in a high vacuum pressure state during the manufacture of the vacuum sensor, and the getter material 38 sealed in the vacuum chamber 36 at that time is The high vacuum pressure state is maintained by the operation.

Now, it is assumed that the vacuum pressure of the device to be measured has dropped. The diaphragm electrode 1 responds to the change in the vacuum pressure.
The distance between 4, 16 and 18 is increased, and the capacitance value between the diaphragm electrodes 14, 16 and 18 and the conductive thin film electrodes 24, 26 and 28 facing these electrodes is reduced. Regarding the decrease in capacitance, the amount of decrease in capacitance between the diaphragm electrode 14 and the conductive thin-film electrode 24 is the largest, and then, the amount of static capacitance generated between the diaphragm electrode 16 and the conductive thin-film electrode 26. The amount of decrease in capacitance is the next largest, and the amount of decrease in capacitance generated between the diaphragm electrode 18 and the conductive thin film electrode 28 is the smallest. These capacitances are directed to an AC bridge where they are measured and displayed as the value of the reduced pressure.

As described above, the amount of decrease in the capacitance is the same as that of the electrode 1.
The largest between electrodes 4 and 24, and the next largest is electrodes 16, 2
Among the six, the distance between the electrodes 18 and 28 is the least. Therefore, it is possible to measure the vacuum pressure in a region with a high degree of vacuum from the capacitance between the electrodes 14 and 24, and to measure the vacuum pressure in an intermediate pressure region from the capacitance between the electrodes 16 and 26. , The vacuum pressure in the pressure region having the lowest degree of vacuum can be measured from the capacitance between the electrodes 18 and 28.

In the measurement of such a vacuum pressure, temperature compensation for the measurement can be performed. That is, the reference electrode 3
Since 0 is provided in the thick portion 34 of the silicon substrate 4, the reference electrode 30 is not displaced by the surrounding gas pressure. Therefore, the reference electrode 30 and the conductive thin film electrode 32
Does not change with pressure.
Since the distance between the electrodes 30, 32 changes depending on the difference in the coefficient of thermal expansion of the constituent material to which the electrodes 30, 32 are attached,
The capacitance between the reference electrode 30 and the conductive thin film electrode 32 changes only with temperature. Therefore, the change in capacitance (the change due to pressure and the change due to temperature) between the diaphragm electrodes 14, 16, 18 and the conductive thin-film electrodes 24, 26, 28 opposed thereto are measured, and the reference electrode is measured. The diaphragm electrodes 14, 1 measured using a change in capacitance between the conductive film electrode 30 and the conductive thin film electrode 32 due to temperature.
6, 18 and conductive thin-film electrodes 24, 2 opposed thereto.
If the change in the capacitance due to the temperature between the diaphragm electrodes 6 and 28 is canceled out, the diaphragm electrodes 14 and 1 caused by the pressure change can be eliminated.
6, 18 and conductive thin-film electrodes 24, 2 opposed thereto.
Only the capacitance between 6 and 28 can be measured. As a result, temperature correction of the measurement can be performed.

As described above, a plurality of sets of diaphragm electrodes 14, 16, 18 having different areas and conductive thin-film electrodes 24,
With the configuration in which the pressure sensors 26 and 28 are opposed to each other, a wide range of absolute pressure can be measured with one vacuum sensor. Diaphragm electrode 1 enabling such measurement
Since the sealing spaces 15, 17, 19 between the conductive thin film electrodes 4, 16, 18 and the conductive thin film electrodes 24, 26, 28 are communicated with each other and communicated with the vacuum chamber 36, the sealing space 1
It is possible to simplify the structure of an apparatus for maintaining 5, 17, and 19 at a predetermined vacuum.

As a result, the size of the vacuum sensor can be made as small as several millimeters, and the size of the vacuum sensor can be made very small as compared with a conventional vacuum sensor. Due to such miniaturization, the exhaust amount of the vacuum device can be reduced, the time required for the exhaust can be reduced, and the response of the sensor to a pressure change can be increased. Also, multipoint measurement and pressure distribution measurement inside the vacuum apparatus can be performed, and more detailed process control and management can be performed.

Further, it is easy to integrate a signal processing circuit using semiconductor integrated circuit technology around an island portion for taking out a metal thin film electrode on a glass substrate of a vacuum sensor.
Further, since the sealing spaces 15, 17, and 19 are in communication with each other, it is possible to simultaneously apply a high vacuum to each of these sealing spaces, and each of the sealing spaces 15, 17, and 19 is independently evacuated. The need to do so can be eliminated.

In the above-described embodiment, three pairs of the diaphragm electrode and the conductive thin-film electrode are described. However, four or more pairs may be provided. Further, as shown in FIG. 6, by providing the diaphragm electrode 18 with a thick portion 35, the diaphragm electrode 1 can be subjected to a wide range of pressure changes.
8 can be actuated, and the detection range of the absolute pressure by the diaphragm electrode 18 can be expanded. FIG.
2 is the same as FIG. 2 except that a thick portion 35 is provided on the diaphragm electrode 18, and only the main reference numbers are given, but the reference numbers are also the same.

As in any of the above embodiments, the silicon substrate 4 does not necessarily have to be at a grounded potential.

[0037]

As described above, according to the present invention, a plurality of sensor capacitors are formed by arranging a plurality of sets of diaphragm electrodes and conductive thin-film electrodes having different areas so as to face each other. It can be measured by the number of vacuum sensors. Since the spaces of the sensor capacitors constituting the vacuum sensor are connected to each other, a device for evacuating each space can be simplified, and the vacuum sensor can be made compact to several millimeters. An ultra-small vacuum sensor with a small dead space can be provided as compared with a conventional vacuum sensor, and the exhaust speed and the response speed can be increased.

As described above, since the space of each sensor capacitor is configured to communicate with each other, there is no need to independently evacuate those spaces.

[Brief description of the drawings]

FIG. 1 is a diagram showing one embodiment of the invention described in claims 1 to 3;

FIG. 2 is a sectional view taken along line II of FIG.

FIG. 3 is an exploded view of the embodiment shown in FIGS. 1 and 2;

FIG. 4 is a diagram showing a structure of a diaphragm electrode and a displacement state thereof.

FIG. 5 is a diagram showing a structure for drawing a conductive thin film electrode through an island.

FIG. 6 is a diagram showing another embodiment of the invention described in claims 1 to 3;

FIG. 7 is a diagram showing a structure of a Pirani vacuum gauge.

FIG. 8 is a diagram showing a structure of a diaphragm type vacuum gauge.

[Explanation of symbols]

 2 First flat glass substrate 4 Flat silicon substrate 6 Second flat glass substrate 8G hole (opening) 10G hole (opening) 12G hole (opening) 8S hole (opening) 10S hole ( Opening portion) 12S hole (opening portion) 14 Diaphragm electrode 15 Space 16 Diaphragm electrode 17 Space 18 Diaphragm electrode 19 Space 22 Feed-through portion 24 Conductive thin film electrode 26 Conductive thin film electrode 28 Conductive thin film electrode 30 Reference electrode 32 Conductive Conductive thin film electrode 33 space 40 island 42 conductive part

Claims (3)

[Claims] 1. A first substrate made of a conductive and moldable material, a second substrate made of an insulating and highly rigid material, and a first substrate and a second substrate. A space formed apart from each other at each required position, an opening formed in the first substrate corresponding to each of the spaces, and a close contact with a periphery of each opening. A conductive diaphragm electrode having a different area for each opening, and being displaced in accordance with a vacuum pressure applied to the opening, and being arranged on the second substrate to face the conductive diaphragm electrode via the space. Conductive thin-film electrode, and the first substrate and the second substrate are in close contact with each other, and are provided with an opening for each opening of the first substrate. A third substrate made of a material, and a conductive lead portion drawn out to the outside for each conductive thin film electrode. Vacuum sensor, characterized in that the communicated each space together, measuring the degree of vacuum from the capacitance between the conductive thin film electrode facing the respective conductive diaphragm electrode sealed in a high vacuum. 2. The vacuum sensor according to claim 1, wherein at least one conductive diaphragm electrode is provided on a thick portion of the silicon substrate. 3. The vacuum sensor according to claim 1, wherein the first sensor is provided between a first substrate and second and third substrates, and the first sensor is disposed in a vacuum chamber containing a getter material. A vacuum sensor characterized by communicating a space between a substrate and a second substrate.