JP2002323395A - Capacitance-type sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a capacitance-type sensor capable of enhancing the sensitivity of the sensor without increasing the size of a diaphragm by providing the diaphragm and counter electrodes with rugged parts. SOLUTION: This capacitance-type sensor 1 is a capacitance-type sensor for measuring a physical quantity to be measured being the physical quantity of a measured object, based on the change in capacitance, and characterized in that, by forming a rugged part on the surface of the diaphragm 4 and a rugged part having a shape corresponding to the above-mentioned rugged part on each of the counter electrodes 9, the surface area of the diaphragm is increased to increase capacitance, thereby enhancing the sensitivity of the sensor.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a capacitance type sensor for measuring a physical quantity to be measured based on a change in capacitance, and particularly to improving the sensitivity of the sensor without increasing the size of the sensor. The present invention relates to a capacitance type sensor that can perform the above-described operations.

[0002]

2. Description of the Related Art As a conventional capacitance type pressure sensor,
There is a pressure sensor disclosed in Japanese Patent Application Laid-Open No. 10-82709. FIG. 5 shows the configuration of this pressure sensor.

[0003] As shown in FIG.
Reference numeral 1 denotes an elastically deformable diaphragm 102, upper glass 103, 104 anodically bonded to a thick portion of the diaphragm 102, and a central electrode 105 provided on the upper glass 103.

When pressure is applied to the pressure inlet 106, the pressure sensor 101 thus configured is elastically deformed so that the diaphragm 102 is curved, and the distance between the diaphragm 102 and the central electrode 105 is increased. Changes,
Thus, pressure measurement is performed.

The pressure sensor 101 is a so-called gauge pressure (differential pressure with respect to the atmospheric pressure when the atmospheric pressure is set to zero), and includes a diaphragm 102 and an upper glass 10.
The space between the holes 3 is open to the atmosphere through the through holes 107.

Here, the pressure sensor 101 as described above
In order to increase the sensitivity, it is conceivable that the surface area of the diaphragm 102 is increased or the distance between the central electrode 105 and the diaphragm 102 is reduced.

[0007]

However, reducing the distance between the center electrode 105 and the diaphragm 102 has a limit in terms of manufacturing accuracy. Therefore, in order to increase the sensitivity of the sensor, the surface area of the diaphragm must be increased. There was no choice.

However, when the surface area of the diaphragm is increased, there is a problem that the size of the sensor itself must be increased.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a capacitance type capable of increasing the surface area of a diaphragm and improving the sensitivity of a sensor without increasing the size of the sensor. It is to provide a sensor.

[0010]

In order to achieve the above object, a capacitance type sensor according to the first aspect of the present invention comprises:
A capacitance-type sensor that measures a physical quantity to be measured, which is a physical quantity to be measured, based on a change in capacitance. Irregularities of a shape corresponding to the irregularities of the diaphragm are formed, and the irregularities include a counter electrode arranged to face the irregularities of the diaphragm.

According to the first aspect of the present invention, the surface area of the diaphragm can be increased without increasing the size of the sensor, and the sensitivity of the sensor can be improved.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First, the configuration of a capacitance type sensor according to this embodiment will be described with reference to FIG. Here, the case of a pressure sensor will be described as an example.

As shown in FIG. 1, a capacitance type sensor 1
Is composed of a support substrate 3 provided with an upper pressure outlet 2, a silicon 5 provided with a diaphragm 4, and a support substrate 8 provided with a lower pressure inlet 7.
Is provided with a counter electrode 9 on a surface facing the diaphragm 4, and the counter electrode 9 and the diaphragm 4 are formed with irregularities, respectively.

The capacitance type sensor 1 having such a configuration is as follows.
When a measured pressure to be measured is introduced from the lower pressure inlet 7 and the diaphragm 4 is bent by the measured pressure, the distance between the counter electrode 9 and the diaphragm 4 changes, and the capacitance changes. This measures the measured pressure.

Here, the capacitance type sensor 1 of the present embodiment
FIG. 2 shows an enlarged view of the irregularities formed on the diaphragm 4 and the counter electrode 9.

FIG. 2A shows a pyramid-shaped convex portion, and FIG. 2B shows a pyramid-shaped concave portion.
The concave portion and the convex portion shown here may be formed on the diaphragm 4 or may be formed on the counter electrode 9, respectively. However, when a convex portion is formed on the diaphragm 4, a concave portion is formed on the counter electrode 9, or vice versa.

As described above, the shape of the unevenness of the diaphragm 4 and the shape of the unevenness of the counter electrode 9 are formed so as to correspond to each other.

By forming the irregularities as shown in FIG. 2 on the diaphragm 4 and the counter electrode 9, the surface area of the diaphragm 4 and the counter electrode 9 can be increased without increasing the size of the sensor. Thereby, the capacitance between the diaphragm 4 and the counter electrode 9 increases, so that the sensitivity of the sensor can be improved.

For example, when unevenness as shown in FIG. 2 is formed, a diaphragm having the same size and no unevenness is formed.
The surface area of the diaphragm can be increased 1.4 times or more.

Next, a method for manufacturing the above-described unevenness will be described with reference to FIG.

As shown in FIG. 3, the irregularities of the diaphragm 4 are formed by using the silicon anisotropic etching technique.
First, an oxide film 31 is formed on the silicon wafer 5 on which the diaphragm 4 is formed (FIG. 3A) (FIG. 3B), and an opening 32 is formed on the oxide film 31 by photolithography and oxide film etching (FIG. 3B). FIG.
c). At this time, the silicon surface is also slightly melted.

The opening 32 is filled with KOH
When anisotropic etching is performed using an anisotropic etchant such as HF, TMAH, or hydrazine, the silicon has a property that the <100> plane is fast and the <111> plane is slow. Such irregularities are formed (FIG. 3d). At this time, the angle formed by the plane orientation is about 54.7 °. After the unevenness is formed on the silicon wafer, the oxide film 31 is removed to complete the diaphragm 4 having the unevenness (FIG. 3E).

As shown in FIG. 4, a large number of sensor chips having such an uneven diaphragm can be formed from the surface of one silicon wafer. More than 300 sensor chips are made from a silicon wafer having a diameter of about 10 cm.

As described above, in the capacitance type sensor 1 of the present embodiment, since the surface area of the diaphragm is increased by forming irregularities on the diaphragm 4 and the counter electrode 9, the size of the sensor itself can be increased. Therefore, the sensitivity of the sensor can be improved.

In the above-described embodiment, the case of the pressure sensor has been described as an example of the capacitance type sensor. However, it is needless to say that the present invention can be applied to an acceleration sensor, a tilt angle sensor, and the like.

[0026]

As described above, according to the capacitance type sensor of the present invention, the sensitivity of the sensor can be improved without increasing the size of the diaphragm.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view and a perspective view showing a configuration of an embodiment of a capacitance type sensor according to the present invention.

FIG. 2 is an enlarged view showing an example of irregularities formed on the diaphragm shown in FIG.

FIG. 3 is a view for explaining a process for forming irregularities on the diaphragm shown in FIG. 1;

FIG. 4 is a diagram showing an example of the arrangement of sensor chips formed on a silicon wafer.

FIG. 5 is a sectional view and a perspective view showing a configuration of a conventional pressure sensor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Capacitance sensor 2 Upper pressure outlet 3,8 Support substrate 4,102 Diaphragm 5 Silicon 7 Lower pressure inlet 9 Counter electrode 31 Oxide film 32 Opening 101 Pressure sensor 103 Upper glass 104 Lower glass 105 Central electrode 106 Pressure Inlet 107 Through hole

Claims (1)

[Claims] 1. A capacitance type sensor for measuring a physical quantity to be measured, which is a physical quantity to be measured, based on a change in capacitance, wherein the sensor is deformed by the change in the physical quantity to be measured to form irregularities on the surface. A capacitance type sensor comprising: a formed diaphragm; and a concavo-convex shape having a shape corresponding to the concavo-convex shape of the diaphragm, and the concavo-convex shape includes a counter electrode arranged to face the concavo-convex shape of the diaphragm.