JP2002055008A - Vacuum sensor with built-in thin-film getter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce a space necessary for arranging a getter in the reference pressure chamber of a capacitance type vacuum sensor, simplify the structure of the vacuum sensor, reduce the size, simplify the production process, reduce the cost of production and to improve the yield. SOLUTION: In the capacitance type vacuum sensor, a diaphragm electrode having an elastic structure and a capacitance electrode of a stiff structure are faced to be arranged with a space inside; and when gas pressure is added on the diaphragm electrode from outside, the elastic structure of the diaphragm deforms and so the capacitance between the diaphragm electrode and the capacitance electrode varies. Using this principle, the gas pressure is measured. The vacuum sensor containing thin film getter is provided with the thin film getter on the wall surface facing the internal space given between the diaphragm electrode and the opposite capacitance electrode.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a capacitance type vacuum sensor, and more particularly to an internal space formed between a diaphragm electrode having an elastic structure and a capacitor electrode having a rigid structure. In order to maintain the inside of the reference pressure chamber at a high vacuum, the space required for disposing the gas absorbing material (getter material) disposed in the reference pressure chamber is significantly reduced, whereby the size is reduced and the manufacturing process is simplified. And a capacitance type vacuum sensor.

[0002]

2. Description of the Related Art In the process of manufacturing electronic parts and semiconductor products, a process of forming or etching a thin film in a vacuum apparatus is indispensable. At this time, the process usually proceeds while the pressure in the vacuum device is kept constant, but the pressure measuring means in the vacuum device during the process is a static pressure capable of accurately measuring the pressure regardless of the type of gas. Capacitive vacuum sensors are often used.

FIG. 3 shows a conventional example in which a capacitance type vacuum sensor is manufactured by a micromachine technique. In this conventional example, a structure is adopted in which an insulating substrate 13 such as glass is bonded to a rigid structure 11 such as silicon, and the reference pressure chamber 1 is formed in a space that is sandwiched and sealed therebetween. A capacitance electrode 5 is disposed on the upper surface of the insulating substrate 13 inside the reference pressure chamber 1, and an elastic structure 8 facing the capacitance electrode 5 is provided.
Is a diaphragm electrode 4.

Normally, the inside of the reference pressure chamber 1 is sealed with a high vacuum, and when the pressure in the region 3 communicating with the vacuum device 2 changes, the pressure difference between the reference pressure chamber 1 and the region 3 communicating with the vacuum device 2 changes. , The elastic structure 8 is displaced. As a result, the capacitance between the diaphragm electrode 4 and the capacitance electrode 5 changes, and the pressure in the region 3 communicating with the vacuum device 2 can be measured from the value.

[0005] In addition, the same phenomenon as the displacement of the elastic structure 8 due to a change in pressure in the region 3 communicating with the vacuum device 2 also occurs due to the influence of thermal expansion or the like caused by a temperature change.
As a result, since the capacitance of the diaphragm electrode 4 and the capacitance electrode 5 changes, a pressure error may occur. The capacitance change independent of the pressure due to the temperature change or the like is also detected in the capacitance between the correction electrode 10 facing the rigid structure 11 and the diaphragm electrode 4 (inversely, the correction electrode Since the capacitance 10 is not opposed to the elastic structure 8, it is difficult to detect a capacitance change caused by a pressure change.) The capacitance between the diaphragm electrode 4 and the capacitance electrode 5 is corrected by the capacitance. Thus, a change in capacitance due to factors other than pressure can be canceled out, and a more accurate pressure can be measured.

Here, since the sealing pressure inside the reference pressure chamber 1 is a reference pressure for measuring the pressure in the region 3 communicating with the vacuum device 2, a high vacuum is stably maintained for a long time. Need to keep. Therefore, a non-evaporable getter 6 is disposed inside the reference pressure chamber 1 to adsorb gas remaining inside the reference pressure chamber 1 or gas released from the wall surface of the reference pressure chamber 1 to solve this problem. Are dealing with.

The distance between the insulating substrate 13 and the diaphragm electrode 4 is usually several tens μm or less, while the thickness is several hundred μm in order to dispose the non-evaporable getter 6.
m grooves must be machined. Therefore, securing this space is a problem for miniaturization of the capacitance type vacuum sensor, and a manufacturing process for securing this space has conventionally been indispensable.

FIG. 4 shows a conventional example of a capacitance type vacuum sensor manufactured by a machining method. The capacitance type vacuum sensor shown in this example is provided with a reference pressure chamber 1 inside the sensor,
The reference pressure chamber 1 is partitioned by a region 3 communicating with the internal space of the vacuum device 2 and a diaphragm electrode 4 (the center of the diaphragm electrode 4 is a diaphragm-like elastic structure 8). The capacitance electrode 5 is arranged on the insulating substrate 13 so as to face the center of the diaphragm electrode 4, that is, the elastic structure 8. When there is a pressure difference between the reference pressure chamber 1 and the region 3 communicating with the vacuum device 2, the elastic structure 8 is displaced according to the pressure difference. Since the capacitance between the diaphragm electrode 4 and the capacitance electrode 5 is inversely proportional to the distance between them, this electric information is transmitted to the electric circuit 7 through the conductive wiring 9 and the change in the capacitance is converted into a change in voltage or current. Then, the pressure is output from the electric output terminal 12 to the outside of the vacuum sensor, and the pressure in the region 3 communicating with the vacuum device 2 is measured.

[0009] In the conventional example shown in FIG.
The correction electrode 10 disposed in the vicinity has a function of correcting a pressure measurement error caused by an environmental temperature or the like, similarly to the case of the capacitance type vacuum sensor manufactured by the micromachine technology described above.

Also, in the conventional example shown in FIG. 4, the pressure inside the reference pressure chamber 1 becomes a reference pressure for measuring the pressure in the region 3 communicating with the vacuum device 2, so that it is stable for a long time. It is necessary to maintain a high vacuum. Therefore, a non-evaporable getter 6 is disposed inside the reference pressure chamber 1 for the purpose of adsorbing the gas inside the reference pressure chamber 1.

However, in the case of a capacitance type vacuum sensor manufactured by machining, there is a problem that if fine processing is performed with high accuracy, the manufacturing cost increases. Therefore, as shown in FIG. 4, a hole is made in advance so as to penetrate both sides of the insulating substrate 13, and after the getter 6 is inserted into the hole, the hole cover 15 is attached to the hole opening of the insulating substrate 13 in a vacuum. To seal the inside of the reference pressure chamber 1 and then heat the getter to activate it.

Also in this case, it is necessary to process the insulating substrate 13 in order to secure a space for inserting the getter 6, and it is indispensable to perform a step of covering the hole cover 15 at a predetermined position in a vacuum. Become.

[0013]

In the capacitive vacuum sensor, the reference pressure chamber pressure inside the sensor and the gas pressure outside the sensor act on the diaphragm electrode. As a result, the diaphragm electrode is proportional to the difference between the two pressures. The elastic structure of the
The principle is that the pressure is measured by detecting the amount of deformation by the capacitance between the capacitance electrode and the diaphragm electrode.

Therefore, in order to accurately measure the gas pressure outside the sensor, the pressure in the reference pressure chamber inside the sensor needs to be stably maintained at a certain value. Normally, the inside of the reference pressure chamber is kept in a high vacuum, and the pressure of the gas is measured using this pressure as a zero reference.

As means for keeping the pressure inside the reference pressure chamber at a high vacuum at all times, a non-evaporable getter (NEG: non-ev) is used.
Applicable getters are often used. The non-evaporable getter has the function of pumping the gas molecules remaining in the periphery and diffusing it inside by heating once to high temperature and activating it (pumping action). Since the pumping action lasts for a long time, it is sealed. It is used to keep the pressure inside the space under high vacuum.

The size of the non-evaporable getter disposed in the reference pressure chamber of such a conventional capacitance type vacuum sensor is as small as about 1 mm and about 0.2 mm in thickness. Since the distance between the capacitance electrode and the diaphragm electrode inside the reference pressure chamber of the capacitance type vacuum sensor is at most about several tens of μm, in order to insert a non-evaporable getter into this reference pressure chamber, For example, a groove having an appropriate size is formed, and a non-evaporable getter is inserted therein.

However, in this case, the cost of the product increases due to an increase in the number of manufacturing steps and a decrease in the manufacturing yield that occur at the time of groove formation and getter sealing, and further, the groove communicates with the reference pressure chamber. The formation of the pressure chamber significantly increases the volume of the reference pressure chamber, and causes a problem that the pump action of the non-evaporable getter is reduced.

A non-evaporable getter to be inserted into a reference pressure chamber of a capacitance type vacuum sensor is also known from SAES Getters Co., Ltd. This is an alloy containing zirconium (Zr) as a main component. A getter material is deposited on a base material and has a thickness of about 0.2 mm or more and a size of about several mm is commercially available. When this non-evaporable getter is heated to several hundred degrees centigrade under a certain vacuum pressure, the protective film on the getter surface diffuses inside, a new active getter surface appears, and the gas molecules adsorbed on the surface diffuse inside the getter material. And is permanently fixed, ie a pumping action is obtained. However, when this non-evaporable getter is inserted into the reference pressure chamber of the capacitance type vacuum sensor, it is absolutely necessary to secure such a space. There is still a problem in simplifying the process and improving the manufacturing cost and yield of the vacuum sensor.

[0019]

SUMMARY OF THE INVENTION According to the present invention, there is provided a capacitance type vacuum sensor which is provided in an internal space (that is, a reference pressure chamber) sandwiched between a diaphragm electrode and a capacitance electrode which are opposed to each other. This problem has been solved by providing a getter as a thin film having a property of absorbing gas molecules on a wall surface facing the internal space formed as a reference pressure chamber.

That is, the vacuum sensor with a built-in thin film getter proposed by the present invention has a diaphragm electrode having an elastic structure and a capacitor electrode having a rigid structure which are spaced apart from each other and are arranged opposite to each other. The pressure of the gas is measured by utilizing the fact that the capacitance between the diaphragm electrode and the capacitance electrode changes due to the deformation of the elastic structure of the diaphragm electrode when a gas pressure is applied. In the capacitance type vacuum sensor according to the principle, a thin film-shaped getter is provided on a wall surface facing an internal space sandwiched between the diaphragm electrode and the capacitance electrode disposed opposite to each other. is there.

According to the thin film getter built-in type vacuum sensor of the present invention, the space for inserting the getter is formed by providing the getter material formed in a thin film on the wall surface facing the reference pressure chamber. Omit the manufacturing process,
Further, the getter can be arranged inside the reference pressure chamber as before without increasing the volume of the reference pressure chamber. Therefore, it is possible to provide a capacitance-type vacuum sensor smaller than the conventional one in a manufacturing process that is simpler than the conventional one, and to improve the manufacturing cost and yield of the vacuum sensor. Also, since the reference pressure chamber does not include an extra space for arranging the getter as in the related art, the volume of the reference pressure chamber can be made smaller than that of the conventional capacitive vacuum sensor. Reduce the exhaust load on the material,
An efficient pump action by the getter material can be exhibited.

In the vacuum sensor with a built-in thin film getter of the present invention, a technique for forming a getter material into a thin film is required, and several papers have already been published (for example, "Novel route to").
extreme vacuum: the non-ev
aporable getter thin film
coatings ", Benvenuti, J
. M. Caseneuv, P .; Chiggi
ato, F.A. . Cicira, A .; Escud
airo Santana, V .; Johanek
, V. Ruzinov, J .; Fraxeda
s, Vacuum 53, pp219-225 (1
999)).

As the getter material, titanium (Ti), zirconium (Zr), vanadium and the like having a property of absorbing gas molecules to perform a function of adsorbing and diffusing gas molecules therein (pump action) are used. (V),
Hafnium (Hf) or an alloy thereof, for example, a titanium-zirconium alloy, a titanium-zirconium-vanadium alloy, a hafnium-titanium alloy, or the like can be used. By subjecting them to sputtering and patterning using a photolithography technique or a metal mask in the same manner as in a normal semiconductor process, a thin film getter formed in a pattern can be provided on the wall surface facing the reference pressure chamber.

In the present invention, a thin film getter is provided on a wall surface facing an internal space (that is, a reference pressure chamber) sandwiched between a diaphragm electrode and a capacitance electrode of a capacitance type vacuum sensor which is arranged to face each other. In providing the thin film getter, the thin film getter can adopt any of a wall surface facing the internal space of the diaphragm electrode, a wall surface of a rigid structure facing the diaphragm electrode, or a structure provided on both of these wall surfaces.

However, the thin-film getter is formed of a substance having not only the property of absorbing gas molecules as described above but also a conductivity, and the thin-film getter is formed of a wall facing the diaphragm electrode (ie, a rigid structure). If the thin film getter is configured to have a capacity electrode or a correction electrode provided in the vicinity of the capacity electrode or a configuration having both of these functions, that is, the capacity electrode and / or the correction electrode If the electrode and the thin film getter are integrated, it is possible to provide a capacitance type vacuum sensor with a smaller number of manufacturing steps and a simpler structure.

In this case, titanium (Ti), zirconium (Zr), hafnium (Hf), or an alloy thereof can be used as a substance having a property of absorbing gas molecules and conductivity.

[0027]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of the present invention will be described with reference to FIGS.

The vacuum sensor with a built-in thin film getter according to the present invention shown in FIG. 1 is a capacitance type vacuum sensor manufactured by a micromachine technology to which a semiconductor manufacturing process technology is applied.

The vacuum sensor chip, that is, the insulating substrate 13 and the silicon substrate 14 shown in FIG.
1) are about several mm to several tens of mm in thickness, and about 1 mm in thickness.

The conductive wiring 9 is buried in the insulating substrate 13 (for example, the material is Pyrex glass of Corning or SDII glass of HOYA) whose thermal expansion coefficient is close to that of silicon so as to penetrate the upper and lower surfaces. The silicon substrate 14 is a silicon substrate having depressions formed on both sides. By bonding the insulating substrate 13 and the silicon substrate 14 in a vacuum atmosphere, the reference pressure chamber 1 formed therein forms a closed space with a gap of about 10 μm and is vacuum-sealed.

The basic structure of the vacuum sensor with a built-in thin film getter according to the present invention, the functions and functions exerted by the constituent elements are the same as those of the conventional capacitive vacuum sensor shown in FIG. Therefore, the same components as those of the conventional example shown in FIG. 3 are denoted by the same reference numerals, and description thereof will be omitted.

On the wall surface of the insulating substrate 13 facing the elastic structure 8 inside the reference pressure chamber 1, a capacitance electrode 5 is provided. In the vicinity of the capacitance electrode 5, this is also a conventional capacitance type vacuum. As in the case of the sensor, a correction electrode 10 that functions to correct a pressure measurement error due to a cause other than a change in pressure, such as an environmental temperature, is provided.

However, in the vacuum sensor with a built-in thin-film getter of the present invention shown in FIG. 1, these capacitance electrode 5 and correction electrode 10 have a property of absorbing gas molecules necessary for the getter material and are formed with electrodes. It is formed of a substance also having a conductivity necessary for the operation.

That is, in the embodiment shown in FIG. 1, the capacitance electrode 5 and the correction electrode 10 perform the necessary functions as electrodes, respectively, as in the case of the conventional electrostatic capacitance type vacuum sensor. The capacitance electrode and the correction electrode, which also function as a material, and the getter are formed as an integrated body.

The capacitance electrode 5 and the correction electrode 10 are in the form of a thin film having a thickness of about several μm and are formed of a titanium-zirconium alloy, a titanium-zirconia-vanadium alloy, a hafnium-titanium alloy or the like as a getter material. can do.

After forming and patterning these films, the insulating substrate 13 and the silicon substrate 14 are anodically bonded in a vacuum,
Subsequently, the getter material is activated by exposing it to a high temperature of 400 ° C. or more, adsorbing surrounding gas molecules and exerting a pumping action. Thus, the vacuum sensor with a built-in thin film getter of the present invention is obtained.

Conventionally, a non-evaporable getter (thickness of about several hundred μm) is inserted into a reference pressure chamber of a capacitance type vacuum sensor, that is, a non-evaporable getter in which a getter material is deposited on a base material. A mold getter (thickness of about several hundred μm) has been known.

However, according to the present invention, as described above,
A wall surface on which a getter material formed into a thin film having a thickness of about several μm faces the inside of the reference pressure chamber (in the embodiment shown in FIG. 1, a rigid structure opposed to the elastic structure 8, that is, a wall surface of the insulating substrate 13). ), It is sufficiently possible to dispose a getter inside the reference pressure chamber 1 having a gap of about 10 μm.

As a result, the structure of the vacuum sensor can be simplified, the size of the vacuum sensor can be reduced, and the manufacturing process can be simplified.

In the embodiment shown in FIG. 1, the capacitance electrode 5 and the correction electrode 10 having the same function and function as the capacitance electrode and the correction electrode in the conventional capacitance type vacuum sensor are formed integrally with the getter. Therefore, the structure of the vacuum sensor can be more effectively simplified, the size of the vacuum sensor can be reduced, and the manufacturing process can be simplified.

However, although not shown in FIG. 1, the thin film getter is not integrated with the capacitance electrode 5 and the correction electrode 10 and the wall surface facing the inside of the reference pressure chamber 1 (for example, the rigidity facing the elastic structure 8). Even if the thin film getter is provided on the wall of the structure, that is, the wall of the insulating substrate 13, the wall of the elastic structure 8 facing the inside of the reference pressure chamber 1, or both of them,
As described above, since it is formed to a thickness of about several μm,
The effects of the present invention are achieved in that the structure of the vacuum sensor is simplified, the size of the vacuum sensor is reduced, and the manufacturing process is simplified.

The vacuum sensor with a built-in thin film getter of the present invention shown in FIG. 2 is obtained by applying the present invention to a capacitance type vacuum sensor manufactured by machining. The basic structure, functions and functions exhibited by each component are the same as those of the conventional capacitive vacuum sensor shown in FIG. 4 manufactured by machining, so that the conventional example shown in FIG. The same reference numerals are given to the same components as those described above, and the description thereof will be omitted.

In the present embodiment, as in the case of the capacitance type vacuum sensor manufactured by applying the micromachine technology, instead of manufacturing the space for inserting the getter, a thin getter material having a thickness of about several μm is used. With a gap of tens of μm
It is provided inside a reference pressure chamber 1 of a degree.

In the example shown in FIG. 2, a thin film getter 16 having a thickness of several μm is formed on the insulating substrate 13 separately from the capacitor electrode 5 and the correction electrode 10. However, instead of this, the capacitance electrode 5 and the correction electrode 10 are formed of a thin film-like getter material having a thickness of several μm so that these electrodes have a getter function, thereby further simplifying the manufacturing process and the sensor structure. It is also possible to aim.

As described above, the preferred embodiments of the present invention have been described with reference to the accompanying drawings. However, the present invention is not limited to such embodiments, but has the technical scope understood from the description of the claims. It can be changed to various modes.

[0046]

According to the present invention, a space for inserting the getter into the reference pressure chamber is provided by forming a getter having a so-called pump effect in the form of a thin film in the reference pressure chamber inside the capacitive vacuum sensor. Since the manufacturing process for processing the space can be made unnecessary, the structure of the vacuum sensor can be simplified, the size of the vacuum sensor can be reduced, the manufacturing process can be simplified, the manufacturing cost can be reduced, and the manufacturing yield can be improved. Can be.

According to the vacuum sensor with a built-in thin film getter of the present invention, the volume inside the reference pressure chamber does not increase.
The space that must be exhausted by the getter is small, the load on the getter for exhausting gas molecules is reduced, and the inside of the reference pressure chamber can be efficiently exhausted.

Further, by forming a capacitor electrode and a correction electrode disposed inside the reference pressure chamber with a getter material and giving these electrodes a getter effect, the electrode forming step and the getter material arranging step can be performed together. And the manufacturing process can be further shortened.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a schematic configuration of a vacuum sensor with a built-in thin film getter of the present invention.

FIG. 2 is a diagram illustrating a schematic configuration of another vacuum sensor with a built-in thin film getter of the present invention.

FIG. 3 is a diagram illustrating a schematic configuration of a conventional electrostatic capacity type vacuum sensor.

FIG. 4 is a view for explaining a schematic configuration of another conventional capacitance vacuum sensor.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 reference pressure chamber 2 vacuum device 3 region communicating with vacuum device 4 diaphragm electrode 5 capacitance electrode 6 non-evaporable getter 7 electric circuit 8 elastic structure 9 conductive wiring 10 correction electrode 11 rigid structure 12 electric output terminal 13 insulating substrate 14 Silicon substrate 15 Hole lid 16 Thin film getter

Claims (3)

[Claims] A diaphragm electrode having an elastic structure and a capacitor electrode having a rigid structure are arranged so as to face each other with a space therebetween, and the elasticity of the diaphragm electrode is increased when gas pressure is applied to the diaphragm electrode from the outside. By the fact that the structure is deformed, utilizing the fact that the capacitance between the diaphragm electrode and the capacitance electrode changes, in a capacitance type vacuum sensor based on the principle of measuring the pressure of the gas,
A thin-film getter built-in type vacuum sensor, wherein a thin-film getter is provided on a wall surface facing an internal space sandwiched between the opposed diaphragm electrode and the capacitor electrode. 2. A thin film-like getter provided on a wall surface facing an internal space sandwiched between a diaphragm electrode and a capacitor electrode which are arranged opposite to each other, and is opposed to the diaphragm electrode by a substance having conductivity. Formed on the wall,
2. The vacuum sensor with a built-in thin film getter according to claim 1, wherein the thin film getter has a function of a capacitance electrode, a correction electrode provided near the capacitance electrode, or both of them. 3. A thin film-shaped getter provided on a wall surface facing an internal space sandwiched between a diaphragm electrode and a capacitor electrode disposed opposite to each other, is formed on a wall surface facing the internal space of the diaphragm electrode. The vacuum sensor with a built-in thin film getter according to claim 1, wherein: