JP2001264201A - Capacitance type pressure sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inexpensive capacitance type pressure sensor having little influence of a temperature, being excellent in a sensitivity characteristic and being excellent in mass productivity. SOLUTION: In this capacitance type pressure sensor, an insulating film A28 and an insulating film B31 of a multilayer structure formed on a fixed electrode 16 formed on a first base board 10 and a diaphragm part 13 of a second base board 11 are oppositely joined via a cavity part 14, and the fixed electrode 16 is formed on a shield layer 30.

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 for detecting the pressure of a fluid,
In particular, the present invention relates to a capacitance type pressure sensor including a sensor chip in which a fixed electrode formed on one substrate and a diaphragm portion serving as a movable electrode formed on the other substrate are opposed via a cavity.

[0002]

2. Description of the Related Art FIG. 3 is an external perspective view of a conventional capacitance type pressure sensor. FIG. 4 shows a cross-sectional view (AA cross section in FIG. 3).

A capacitance type pressure sensor will be described with reference to FIGS. In FIG. 4, a fixed electrode 16 is formed on a glass substrate 12 as a first substrate, and a diaphragm 13 which is deformed according to a pressure difference with a cavity 14 is formed on a silicon substrate 11 as a second substrate. Have been.

The silicon substrate 11 and the glass substrate 12
A part thereof is joined, whereby a cavity 14 is formed below the diaphragm 13. The sensor chip 15 composed of the bonded silicon substrate 11 and glass substrate 12 is
Glued on top.

The pedestal 23 has a through hole 20 for introducing atmospheric pressure.
Is provided, and a through hole 19 is formed in the glass substrate 12. Further, since the fixed electrode 16 is also provided with the through hole 26, the atmospheric pressure is introduced into the cavity 14.

On the pedestal 23, a lead terminal 24 formed at the time of molding is arranged, and the lead terminal 24 and the fixed electrode 16 are electrically connected by a lead wire 18. Similarly, the movable electrode formed on the diaphragm 13 is electrically connected to another lead terminal 24.

More specifically, the sensor chip 1
5 is provided with a lateral hole, whereby the fixed electrode 16 is electrically drawn out of the sensor chip 15. In order to isolate the cavity portion 14 from the pressure introduction portion to be measured in the outer region of the sensor chip 15, the above-mentioned side hole is formed by the sealant 1.
7 sealed.

The pedestal 23 and the cap 22 as a cover member provided with a pressure introducing hole 21 for introducing a measured pressure are sealed by ultrasonic welding or the like.

In such a capacitance type pressure sensor 25, when pressure is applied to the diaphragm 13, the pressure between the diaphragm 13 and the fixed electrode 16 constituting the movable electrode is changed according to the pressure difference between both surfaces of the diaphragm 13. The gap width between them changes.

At this time, the diaphragm 13 and the fixed electrode 1
6 is expressed by c = ζ (A / d).
Note that A is the electrode area, d is the gap width between the electrodes, and ζ is the dielectric constant of air.

Therefore, in inverse proportion to the gap width between the electrodes,
The capacitance will change. Furthermore, since there is a certain correlation between the pressure difference and the gap width between the electrodes,
The pressure can be known by detecting the capacitance c.

Next, the structure of the sensor chip and its manufacturing process will be described. FIG. 5 is a diagram showing the structure of a conventional sensor chip. FIG. 6 is a diagram showing an outline of a manufacturing process of a conventional sensor chip. Steps such as a mask and a protective film in the middle are omitted.

In FIGS. 5 and 6, a glass substrate 12 as a first substrate has a through-hole 19 for introducing atmospheric pressure which is close to the thermal expansion coefficient of the silicon substrate 11.
The fixed electrode 16 is formed on the glass substrate 12, and an insulating film 27 is formed on the fixed electrode 16 in some cases.

In the silicon substrate 11 as the second substrate, a cavity 14 is formed by etching.
Further, boron diffusion is performed from the side of the cavity section 14 as an etching stop when the diaphragm section 13 is formed in the subsequent step, and for using the diaphragm section 13 as a movable electrode.

Thereafter, an insulating film A28 is formed on the cavity 13 side of the diaphragm 13. Next, the glass substrate 12 and the silicon substrate 11 are bonded by anodic bonding, and the diaphragm portion 13 is formed by etching, thereby completing the sensor chip 15.

The above-described steps are performed in a state of a wafer in which a plurality of sensor chips are arranged on a plane in order to simultaneously produce a plurality of sensor chips. After the etching for forming the diaphragm, washing with water and drying in a vacuum oven are repeated to sufficiently clean the inside of the cavity.

Next, a wafer in which the plurality of sensor chips are connected in a plane is placed on an adhesive resin sheet, diced, and cut into individual sensor chips. Also, after dicing, washing and drying are performed to complete a sensor chip.

[0018]

In the case of the above-mentioned sensor chip for a capacitance type pressure sensor, the sensor chip is manufactured by anodically bonding a silicon substrate and a glass substrate to integrate them. However, with mass production, it is difficult to increase the diameter of the glass substrate (4 inches or more), and there is naturally a limit to cost reduction by increasing the diameter. further,
There is a problem that the processing cost for providing a through hole in the glass substrate to introduce the atmospheric pressure is high.

Further, there has been a problem in temperature characteristics that the diaphragm portion of the sensor chip is deformed due to temperature, and that the stray capacitance affects accuracy.

Accordingly, the present invention has been made to solve such a problem, and its object is to provide an inexpensive capacitive type which is less affected by temperature, has good sensitivity characteristics, and is excellent in mass productivity. It is to provide a pressure sensor.

[0021]

According to the present invention, a first substrate and a second substrate are composed of a silicon substrate, and fixed electrodes formed on the first substrate and diaphragm portions of the second substrate are provided. An electrostatic capacitance type in which the formed insulating films having a multilayer structure are joined so as to face each other via a cavity portion, and a fixed electrode is formed on a shield layer of a first substrate formed by boron diffusion. A pressure sensor is obtained.

That is, according to the present invention, the first substrate on which the fixed electrode is formed and the second substrate on which the diaphragm which also serves as the cavity and the movable electrode are formed face each other via the cavity. , Wherein the first substrate and the second substrate are formed of a silicon substrate.

Further, the present invention is the above-mentioned capacitance type pressure sensor, wherein a multilayered insulating film is formed on the surface of the diaphragm facing the fixed electrode.

Further, the present invention is the above-mentioned capacitance type pressure sensor, wherein a shield layer is formed on the surface of the second substrate.

Further, the present invention is the above-mentioned capacitance type pressure sensor, wherein said shield layer is formed by boron diffusion.

Further, the present invention is the above-mentioned capacitance type pressure sensor, wherein the shield layer is covered with an insulating film, and the fixed electrode is formed thereon.

According to the capacitive pressure sensor of the present invention, the first glass substrate is a silicon substrate, and the fixed electrode is provided on the shield layer formed on the surface of the silicon substrate. By using a sensor chip with a multi-layered insulating film formed on the diaphragm, sensitivity effects can be improved by minimizing the effects of temperature, and inexpensive static electricity can be obtained by improving mass productivity. A capacitance type pressure sensor can be provided.

[0028]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a structure of a sensor chip of a capacitance type pressure sensor according to an embodiment of the present invention. In FIG.
The outline of the manufacturing process of this sensor chip (the steps of a mask, a protective film and the like in the middle are omitted) is shown.

1 and 2, the first substrate (silicon substrate 10) has a through hole 19 for introducing atmospheric pressure formed by etching, and the surface of the silicon substrate 10 is diffused by boron to shield the surface. A layer 30 is formed, and an insulating film 29 is formed thereon. Further, a fixed electrode 16 is formed thereon, and an insulating film 27 is formed thereon as necessary.

A cavity 14 is formed in the second substrate (silicon substrate 11) by etching. In addition, boron diffusion is performed as an etching stop when the diaphragm portion 13 is formed by etching from the side of the cavity portion 14 in a later step, and for using the diaphragm portion 13 as a movable electrode.

Thereafter, an insulating film A28 and an insulating film B31 having different film materials are formed in a multilayer structure on the cavity portion 14 side of the diaphragm portion 13. Next, the first substrate and the second substrate are bonded by anodic bonding, and the diaphragm portion 13 is formed by etching to complete the sensor chip 35.

Note that the above-described steps are performed in a state of a wafer in which a plurality of sensor chips are arranged on a plane in order to simultaneously produce a plurality of sensor chips. After the etching for forming the diaphragm, washing with water and drying in a vacuum oven are repeated to sufficiently clean the inside of the cavity, and a wafer in which a plurality of sensor chips are arranged in a plane is attached to an adhesive resin sheet and diced. Thus, each of the sensor chips is separated into individual sensor chips. Also, after dicing, washing and drying are performed to complete a sensor chip.

In the sensor chip obtained in the above process, the first glass substrate is changed to a silicon substrate, a fixed electrode is formed on a shield layer, and a multi-layer insulating film is formed on the diaphragm of the second substrate. By forming the pressure sensor, it is possible to provide an inexpensive capacitance-type pressure sensor which relieves the stress of the diaphragm, is less affected by temperature, has good sensitivity characteristics, is excellent in mass productivity, and is inexpensive.

The conventional glass substrate as the first substrate is as follows:
After drilling with a laser or the like, polishing was necessary to remove burrs and the like from both sides. The silicon substrate can be manufactured by etching, and can be manufactured by a normal diffusion process. This allows
Mass productivity is improved. Therefore, by changing the first substrate to a silicon substrate, the cost of the material including the processing cost is reduced to about 1/10 or less.

Further, by forming the fixed electrode on the shield plate, it is possible for a sensor that senses a small change in capacitance (a change of about 0.1 pF at maximum for 2 pF) to be used.
It has become possible to greatly reduce the stray capacitance, which is a great enemy.

Further, by forming an insulating film having a multilayer structure on the diaphragm, the stress against temperature change is made uniform (the tensile stress film and the compressive stress film make the stress uniform), so that the stress on the diaphragm is relieved. , The effect of temperature can be minimized.

[0038]

As described above, according to the present invention, the first substrate is changed to a silicon substrate, the fixed electrode is formed on the shield layer, and the multilayer portion is formed on the diaphragm of the second substrate. By forming an insulating film having a structure, the influence of temperature is reduced by relaxing the stress of the diaphragm part, and it is possible to provide an inexpensive capacitance type pressure sensor excellent in sensitivity characteristics, excellent in mass productivity, and excellent in mass production. it can.

[Brief description of the drawings]

FIG. 1 is a diagram showing a structure of a sensor chip of a capacitance type pressure sensor according to an embodiment of the present invention.

FIG. 2 is a view schematically showing a manufacturing process of a sensor chip of the capacitance type pressure sensor according to the embodiment of the present invention.

FIG. 3 is an external perspective view of a conventional capacitance-type pressure sensor.

FIG. 4 is a sectional view taken along line AA of FIG. 3;

FIG. 5 is a diagram showing a structure of a sensor chip of a conventional capacitance type pressure sensor.

FIG. 6 is a diagram showing an outline of a manufacturing process of a sensor chip of a conventional capacitance type pressure sensor.

[Explanation of symbols]

 Reference Signs List 10 First substrate (silicon substrate) 11 Second substrate (silicon substrate) 12 First substrate (glass substrate) 13 Diaphragm part (movable electrode) 14 Cavity part 15 Sensor chip 16 Fixed electrode 17 Sealant 18 Lead wire 19, 20, 26 Through-hole 21 Pressure introducing hole 22 Cap part 23 Pedestal 24 Lead terminal 25 Capacitive pressure sensor 27 Insulating film 28 Insulating film A 29 Insulating film 30 Shield layer 31 Insulating film B 35 Sensor chip

Claims (5)

[Claims] 1. A first substrate having a fixed electrode formed thereon and a second substrate having a cavity portion and a diaphragm portion also serving as a movable electrode formed thereon are bonded to each other with the cavity portion interposed therebetween. A capacitance type pressure sensor having a sensor chip, wherein the first substrate and the second substrate are constituted by a silicon substrate. 2. The capacitance-type pressure sensor according to claim 1, wherein an insulating film having a multilayer structure is formed on a surface of the diaphragm portion facing the fixed electrode. 3. The capacitance type pressure sensor according to claim 1, wherein a shield layer is formed on a surface of the second substrate. 4. The capacitance type pressure sensor according to claim 3, wherein said shield layer is formed by boron diffusion. 5. The capacitance-type pressure sensor according to claim 4, wherein the shield layer is covered with an insulating film, and the fixed electrode is formed thereon.