JPH06148016A - Capacitive pressure sensor - Google Patents

Abstract

PURPOSE:To provide a capacitive pressure sensor which can be employed for different media while facilitating the alteration of operating range. CONSTITUTION:A sensor chip 26a comprises a glass substrate 15a provided with fixed electrodes 14a and a silicon substrate 13a provided with a silicon diaphragm 11a opposing a fixed electrode 14a through a gap. The sensor chip 26a is placed in a sealed housing partially composed of a metal diaphragm 19a which deforms depending on the pressure and the housing is filled with a noncorrosive liquid 21a or inert gas. Operating range can be altered by simply altering the thickness of the metal diaphragm 19a and since pressure applied onto the metal diaphragm 10a is transmitted to the silicon diaphragm 11a through inert gas 21a, the sensor can be operated even in the liquid.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a capacitance type pressure sensor, and more particularly to a static pressure sensor in which electrodes are formed on a silicon substrate and a glass substrate respectively, and the surfaces of the electrodes are opposed to each other to bond the silicon substrate and the glass substrate. The present invention relates to a capacitance type pressure sensor.

[0002]

2. Description of the Related Art A pressure sensor shown in FIGS. 2A and 2B is generally known as an electrostatic capacitance type pressure sensor of this type.

First, referring to FIG. 2 (a), the illustrated pressure sensor is a so-called absolute pressure sensor, and a diaphragm portion 31 which deforms in response to pressure is formed on a silicon substrate 33a.
a is formed, and the fixed electrode 34a is formed on the glass substrate 35a.
Are formed. As shown in the figure, the silicon substrate 33a and the glass substrate 35a are joined together at a part thereof, whereby a cavity portion 32a is formed below the diaphragm portion 31a.

A sensor chip 46a is constituted by the silicon substrate 33a and the glass substrate 35a, and the sensor chip 46a is bonded onto the pedestal 37a by the glass substrate 35a. The pedestal 37a is provided with a lead terminal 36a, and the lead terminal 36a and the fixed electrode 34a are electrically connected by a lead wire 38a.

The sensor chip 46a is provided with a lateral hole 39a, by which the fixed electrode 34a is pulled out to the outside. Then, the cavity 32a and the sensor chip outside 4
The lateral hole 39a is sealed with a sealant 41a in order to isolate the lateral hole 39a from the side 0a. The pressure introducing hole 4 is formed in the pedestal 37a.
A cap 43a having 2a is arranged, and the pedestal 37a and the cap 43a are sealed by a hermetic seal.

In the illustrated pressure sensor for absolute pressure, when pressure is applied to the diaphragm portion 31a, the diaphragm portion 31a is deformed according to the magnitude of the pressure. Diaphragm part 31
Due to the deformation of a, the diaphragm portion 31a and the fixed electrode 3
The gap with 4a will change. here,
Between the diaphragm portion 31a and the fixed electrode 34a, C
= Ξ (A / d). In addition, C: capacitance,
ξ: permittivity of air, A: electrode area: d: gap between electrodes.

Therefore, the capacitance changes due to the change in the gap, and since there is a certain correlation between the pressure and the gap, it is possible to know the pressure by detecting the capacitance. it can.

The pressure sensor shown in FIG. 2 (b) is a so-called gauge pressure pressure sensor, and its basic structure is the same as that of the absolute pressure pressure sensor described with reference to FIG. 2 (a) (note that FIG. 2 (b)). 2A, the same reference numerals are assigned to the same constituent elements as those in FIG. 2A by changing the alphabet from a to b). The difference from the pressure sensor shown in FIG. 2A is that
This is that the glass substrate 35b forming the sensor chip 46b and the pedestal 37b on which the sensor chip 46b is arranged are provided with the through holes 44b and 45b for introducing the atmosphere. The operation of the pressure sensor shown in FIG. 2B is almost the same as the operation of the pressure sensor shown in FIG.

[0009]

In the conventional capacitance type pressure sensor, the medium for transmitting the pressure to be measured has a structure in which the medium directly contacts the diaphragm portion, the lead wire and the like. Is limited to non-corrosive gases and the like.

In addition, when manufacturing pressure sensors having different operating ranges, it is necessary to change the size and thickness of the diaphragm portion on the silicon substrate. Therefore, it is necessary to change the design and manufacturing process of the diaphragm portion, which not only increases the manufacturing time, but also increases the cost.

An object of the present invention is to provide a capacitance type pressure sensor whose medium for transmitting pressure to be measured is not limited to a non-corrosive gas, and whose specifications such as an operating range can be easily changed.

[0012]

According to the present invention, the diaphragm portion has a first substrate on which an electrode portion is formed and a second substrate on which a diaphragm portion that deforms in response to pressure is formed. And a sensor chip in which the first and second substrates are bonded so that the electrode section and the electrode section face each other with a gap therebetween, and the gap width is adjusted according to the pressure applied to the diaphragm section. In a capacitance type pressure sensor which is changed to detect the pressure by a change in capacitance between the diaphragm part and the electrode part due to a change in the gap width, the sensor chip is in a sealed casing. The sub-diaphragm portion that is arranged and part of the housing is deformed according to pressure, and the housing is filled with a non-corrosive liquid or an inert gas. Capacitive pressure sensor can be obtained.

[0013]

According to the present invention, a part of the sealed casing in which the sensor chip is arranged is composed of a diaphragm (sub-diaphragm), and the sealed casing is filled with a non-corrosive liquid or an inert gas. Therefore, when the pressure is detected, the pressure applied to the sub-diaphragm is transmitted through the diaphragm formed on the first substrate via the non-corrosive liquid or the inert gas, whereby the diaphragm portion and the electrode are The gap with the department will change.

As described above, since the double diaphragm structure is used, the pressure to be measured is not directly applied to the sensor chip, and therefore, it can be used in a liquid, for example. In addition, the operating range can be changed only by changing the thickness of the sub diaphragm, and the specification can be changed very easily.

[0015]

EXAMPLES The present invention will be described below with reference to examples.

First, an absolute pressure measuring pressure sensor to which the present invention is applied will be described with reference to FIG.

The silicon substrate 13a is formed with a silicon diaphragm 11a which deforms in response to pressure, and a cavity portion 12a is formed below the silicon diaphragm 12a. The fixed electrode 14a is formed on the glass substrate 15a, and the silicon substrate 13a and the glass substrate 15a are bonded to each other to form the sensor chip 26a. The sensor chip 26a is adhered onto the pedestal 17a, and the pedestal 17a is provided with the lead terminal 16a. The lead terminal 16a and the fixed electrode 14a are electrically connected by the lead wire 18a.

The sensor chip 26a is provided with a lateral hole 25a, by which the fixed electrode 34a is drawn out. After that, the lateral hole 25a is sealed with a sealant 22a in order to separate the cavity portion 12a from the outside of the sensor chip. The cap 20a is placed on the pedestal 17a.
And the pedestal 17a and the cap 20a are sealed by a hermetic seal. A hole is formed on the upper surface of the cap 20a, and this hole is made of a metal diaphragm 19 made of stainless steel or the like that deforms in response to pressure as shown in the figure.
It is blocked by a. A liquid such as silicone oil or an inert gas (hereinafter referred to as an encapsulating agent) is enclosed in the space defined by the pedestal 17a and the cap portion 20a.

In the above-mentioned pressure sensor, when pressure is applied to the metal diaphragm 19a, this applied pressure is transmitted to the silicon diaphragm 11a through the encapsulant, whereby the gap between the silicon diaphragm 11a and the fixed electrode 14a is generated. Therefore, the capacitance changes as described above.

The pressure sensor shown in FIG. 1 (b) is a cage pressure pressure sensor. The difference from the pressure sensor shown in FIG. 1 (a) is that the pedestal 17b has through holes 24b and 23 for introducing air into the atmosphere.
This is the point where b is formed. In FIG. 1B, the same reference numerals as those in FIG. 1A are used by changing the alphabet a in the reference numerals to b. Note that FIG.
Since the operation of the pressure sensor shown in (b) is almost the same as that of the pressure sensor shown in FIG. 1 (a), the description thereof is omitted here.

In the capacitance type pressure sensor according to the present invention,
By providing a metal diaphragm in the cap portion, that is, as a double diaphragm structure including a metal diaphragm in addition to the silicon diaphragm, a liquid such as silicon oil or an inert gas (sealing) is provided in the space defined by the pedestal and the cap portion. Since the stopper is sealed, the pressure to be measured is not directly applied to the sensor chip, and the pressure to be measured is transmitted to the sensor chip via the sealant. As a result, it can be used, for example, when measuring the pressure in a liquid.

In addition, the operating range can be changed only by changing the thickness of the metal diaphragm. That is, the pressure sensor having various operating ranges can be manufactured using the same sensor chip without changing the design and manufacturing process of the sensor chip itself. Also,
Since the sensor chip, the lead wire, and the like never touch the outside world, they have excellent environment resistance and can stably detect pressure for a long period of time.

[0023]

As described above, since the present invention uses the double diaphragm structure, it can be used even in a liquid and the like, and only by changing the thickness of the diaphragm formed in a part of the housing, that is, The operation range can be changed without changing the sensor chip itself, and the environment resistance and long-term stability can be improved.

[Brief description of drawings]

FIG. 1A is a diagram showing an embodiment of an electrostatic capacitance type pressure sensor for absolute pressure according to the present invention. (B) is a diagram showing an embodiment of the cage pressure electrostatic capacitance type pressure sensor according to the present invention.

FIG. 2A is a diagram showing a conventional absolute pressure capacitive pressure sensor. (B) is a figure which shows the conventional electrostatic capacitance type pressure sensor for cage pressures.

[Explanation of symbols]

 11a, 11b Silicon diaphragm 12a, 12b Cavity part 13a, 13b Silicon substrate 14a, 14b Fixed electrode 15a, 15b Glass substrate 16a, 16b Lead terminal 17a, 17b Pedestal 18a, 18b Lead wire 19a, 19b Metallic diaphragm 20a, 20b Cap Part 21a, 21b Liquid or inert gas 22a, 22b Sealant 23b, 24b Atmosphere introduction hole 25a, 25b Horizontal hole 26a, 26b Sensor chip

Claims (1)

[Claims] 1. A first substrate on which an electrode portion is formed, and a second substrate on which a diaphragm portion that deforms in response to pressure is formed, and a gap is formed between the diaphragm portion and the electrode portion. A sensor chip in which the first and second substrates are bonded so as to face each other,
Capacitance in which the gap width is changed according to the pressure applied to the diaphragm portion, and the pressure is detected by a change in the capacitance between the diaphragm portion and the electrode portion due to the change in the gap width. In the mold pressure sensor, the sensor chip is arranged in a sealed casing, and a part of the casing is composed of a sub-diaphragm portion that deforms in response to pressure. Capacitive pressure sensor characterized by being filled with gas.