JP2001356062A - Capacitive pressure sensor - Google Patents

Abstract

(57) [Summary] [Problem] To prevent the sensing sensitivity from changing even when the installation posture is changed. An electrode (1) is provided via a pedestal (4) on which a base (1) is supported via a plurality of support members (1b to 1d) and a first through hole penetrating the base (1), the support member (1d) and the pedestal (4).
a, the base 1 and the support member 1c.
And a second through hole penetrating through the pedestal 4,
A lead wire connected to the electrode 2a is provided, and the bottom of the base 1 facing the first diaphragm 2 forms a second diaphragm for receiving pressure.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a capacitive pressure sensor, and more particularly to a capacitive pressure sensor whose diaphragm and base are made of sapphire.

[0002]

2. Description of the Related Art In a capacitive pressure sensor, a fixed electrode formed on a base and a movable electrode formed on a diaphragm include:
A capacitance is formed by opposing each other, and a change in pressure is detected based on the change in capacitance. In addition, sapphire is often used for diaphragms and bases because of their excellent corrosion resistance and the like.

FIG. 3A is a plan view showing a conventional capacitive pressure sensor, and FIG. 3B is a sectional view taken along the line BB '.
As shown in these figures, a pressure sensor 110 includes a base 101 having a fixed electrode 101a provided in a concave portion, a movable electrode 102a, a reference electrode 102b, and pads 102c, 1c.
02d and 102e provided with a diaphragm 102;
It is composed of lead wires 103a and 103b connected to each pad and formed by solder.

[0004] The pressure sensor 110 thus configured
The diaphragm 102 bends according to the pressure difference between the outside of the sensor and the capacitance chamber, and the capacitance changes due to the change in the distance between the movable electrode 102a and the fixed electrode 101a, and the pressure is measured.

[0005]

However, in the conventional pressure sensor, since the diaphragm 102 is bent by its own weight, the distance between the electrodes (the fixed electrode 101a and the movable electrode 102a) varies depending on the installation posture of the sensor. As a result, there is a problem that the measurement sensitivity changes. That is, when the diaphragm 102 is directed vertically upward, the central portion of the diaphragm 102 bends downward and the distance between the electrodes is reduced. Conversely, when the diaphragm 102 is directed vertically downward,
Since the central portion bends downward, the distance between the electrodes becomes wide, and accurate measurement results cannot be obtained as it is. Therefore, conventionally, the measurement result cannot be used as it is, and it is necessary to perform correction according to the installation state of the sensor. An object of the present invention is to solve such a problem, and an object of the present invention is to provide a capacitive pressure sensor whose measurement sensitivity does not change even when the installation posture is changed.

[0006]

In order to achieve the above object, a capacitive pressure sensor according to the present invention comprises a first diaphragm for receiving pressure and a base joined to the first diaphragm. A capacitor having an enclosed space portion and having a first electrode provided on the first diaphragm side in the space portion and a second electrode provided on the base side in the space portion; In the pressure sensor, the pedestal on which the base is supported via a plurality of support members, and the base, the support member, and a first through-hole passing through the pedestal, the first electrode A first lead wire connected thereto, and a second lead wire connected to the second electrode via a second through hole penetrating the base, the support member and the pedestal, Facing the first diaphragm Bottom of the base constitutes a second diaphragm for pressure.

[0007] In another aspect, the present invention includes the following configuration. That is, the base is made of sapphire, silicon, glass, or diamond. In addition, a reference electrode is further provided near the first electrode or the second electrode.

[0008] Accordingly, the present invention having the above-described structure enables the first and second sensors to be mounted in accordance with the installation posture of the sensor.
Since the diaphragms are bent to the same extent in the same direction, it is possible to prevent the distance between the electrodes from being changed depending on the installation posture. Therefore, according to the present invention, the same measurement sensitivity can always be obtained irrespective of the installation location and the installation direction, and processing such as correcting the measurement result by calculation becomes unnecessary.

[0009]

Next, one embodiment of the present invention will be described with reference to the drawings. FIG. 1A is a plan view showing one embodiment of the present invention, and FIG.
FIG. 3 is a sectional view taken along line A ′. As shown in these figures, the pressure sensor 10 includes a base 1, a diaphragm 2 directly joined to the base, and four support members (support members 1b, 1 in the figures).
pedestal 4 joined to base 1 through c, 1d only)
It is composed of

The base 1 has a concave portion at the center on the main surface side, and a first movable electrode 1a is provided in the concave portion. On the back side of the base 1, support members 1b, 1c, and 1d in a columnar or rectangular parallelepiped shape are provided. This support member may be provided by processing the base 1, or may be provided by processing the pedestal 4.

The diaphragm 2 has a second movable electrode 2a on a surface opposite to a pressure receiving surface in contact with the process fluid,
Reference electrode 2b and pad 2c connected to movable electrode 2a
And a pad 2d connected to the reference electrode 2b, and a pad 2e connected to the fixed electrode 1a by soldering. Immediately below each pad, there are provided through-holes penetrating the base 1, the support members 1b, 1c, 1d and the pedestal 4. Three leads are formed by molten solder injected into these through-holes. Lines (only the lead wires 3a and 3b are shown in the figure) are formed. The other one through hole is used to introduce a reference pressure into the capacity chamber.

The bottom of the base 1 at a position facing the diaphragm 2 has the same thickness and area as those of the diaphragm 2 and constitutes a pressure receiving diaphragm. Therefore, in the pressure sensor 10 configured as described above, the bottom of the diaphragm 2 and the base 1 bends according to the pressure difference between the outside of the sensor and the capacity chamber, and the capacitance changes due to the change in the distance between the movable electrodes 1a and 2a. Changes and the pressure is measured. Since the bottom of the base 1 functions as a diaphragm as described above, when the attitude of the pressure sensor changes, the same degree of bending as the diaphragm 2 occurs. Therefore, the error caused by the deflection of the diaphragm is 2
This can be offset by the individual diaphragms, and a decrease in measurement sensitivity can be prevented. In addition, the pressure receiving area of this structure is twice as large as that of FIG. 3, so that the measurement sensitivity can be increased.

Here, the manufacturing process of the pressure sensor 10 will be described. FIG. 2 is a sectional view schematically showing a manufacturing process of the capacitive pressure sensor according to FIG. Here, three sapphire wafers are prepared, and each wafer is processed to separately form the diaphragm 2, the base 1, and the pedestal 4. First,
As shown in FIG. 1A, a plurality of movable electrodes 2a are formed on a sapphire wafer for forming the diaphragm 2. That is, a metal mask on which a pattern is formed for each sensor chip is mounted on the sapphire wafer, and then the movable electrode 2a and the pad 2 are formed by vapor deposition or the like.
c to 2f are formed.

Next, as shown in FIG.
The lead wire 3 is formed on the sapphire wafer for forming the
Through holes for inserting a, 3b, etc. are opened for each sensor chip. Next, a plurality of recesses are formed on the main surface side of the sapphire wafer by dry etching using Ar atoms for each sensor chip, and the back surface side is similarly dry-etched to form a support member 1b on a columnar or rectangular parallelepiped.
.About.1d, etc. are formed for each sensor chip. Next, a metal mask having a pattern formed for each sensor chip is placed on the concave side of the sapphire wafer, and then the movable electrode 1a is formed by vapor deposition or the like.

Next, as shown in FIG.
Are formed in the sapphire wafer for forming lead wires 3a and 3b for each sensor chip. Thereafter, the above three wafers are directly bonded, and then a solid solid solder (Sn-Ag solder) is placed in a through hole provided for each sensor chip and heated (for example, at 300 ° C.). The lead wires 3a and 3b are formed by the molten solder that has been melted and flowed into the through holes. Finally, the sensor chip is completed by dicing the bonded sapphire wafer using a diamond saw or the like.

The movable electrodes 1a and 2a and the reference electrode 2b are formed of, for example, a Pt / adhesion enhancing film. As the adhesion enhancing film, Ti, V, Cr, Nb, Zr, Hf, Ta or the like is used. The pads 2c to 2f are formed of, for example, Au / barrier film / adhesion enhancement film. Pt or the like is used as the barrier film, and Nb is used as the adhesion enhancing film.
Are used. Although not shown in FIG. 1, a total of four support members are provided for each of the pads 2c to 2f, and each of the pads 2c to 2e has a pedestal 4, a support member, and a base. A lead wire is connected through a through-hole opened at 1.

In the above, the case where sapphire is used as the material of the diaphragm and the base has been described, but the present invention is not limited to this. For example, a single crystal material such as silicon, glass, or diamond may be used. Further, the reference electrode is not an essential component, and may be added as needed. Therefore, the present invention includes a configuration using only two movable electrodes without using a reference electrode. Further, the number, shape and position of the support members are not limited to those described above. That is, if the bottom surface of the base 1 can function as a pressure-receiving diaphragm, it may be appropriately changed.

[0018]

As described above, in the present invention,
Since the first and second diaphragms bend in the same direction and to the same extent according to the installation position of the sensor, it is possible to prevent the distance between the electrodes from being changed by the installation position.
Therefore, according to the present invention, the same sensing sensitivity can always be obtained irrespective of the installation location and the installation direction, and processing such as correcting the measurement result by calculation becomes unnecessary.

[Brief description of the drawings]

FIG. 1A is a plan view showing one embodiment of the present invention, and FIG. 1B is a sectional view taken along line AA ′.

FIG. 2 is a cross-sectional view schematically showing a manufacturing process of the capacitive pressure sensor according to FIG.

FIG. 3A is a plan view showing a conventional example, and FIG.
It is a line sectional view.

[Explanation of symbols]

Reference Signs List 1 base, 1a movable electrode, 1b, 1c, 1d support member, 2 diaphragm, 2a movable electrode, 2b reference electrode, 2c, 2d, 2e, 2f pad, 3a, 3b electrode, 4 ... Base, 10 ... Pressure sensor.

Claims (3)

[Claims] 1. A space surrounded by a first diaphragm for receiving pressure and a base joined to the first diaphragm, and a second space provided on the side of the first diaphragm in the space. A capacitive electrode comprising: a first electrode; and a second electrode provided on the side of the base in the space, wherein: a base on which the base is supported via a plurality of support members; A first penetrating the base, the support member, and the base;
A first lead wire connected to the first electrode through a through hole, and a second lead wire penetrating the base, the support member, and the pedestal.
A second lead wire connected to the second electrode via a through hole of the base, and a bottom portion of the base facing the first diaphragm,
A capacitive pressure sensor comprising a second diaphragm for receiving pressure. 2. The capacitive pressure sensor according to claim 1, wherein the base is made of sapphire, silicon, glass, or diamond. 3. The capacitive pressure sensor according to claim 1, further comprising a reference electrode adjacent to the first electrode or the second electrode.