JPH09257618A - Electro-static capacity type pressure sensor and production thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sensor which is less dependent on temperature and unnecessary for anode joining by constituting an insulating diaphragm film of insulating material containing silicon, aluminum and nitrogen. SOLUTION: A fixed electrode 40 containing p type or n type impurity of high concentration, a lead 41 and a connection terminal 42 are formed on the surface of a sensor substrate 30 of mono-crystal silicon to form a substrate protection film 50 on the region. A sacrifice film 60 for covering a pressure receiving region is formed thereon to form an insulating film 70 for covering it on the main surface of the substrate 30, a movable electrode 81 is formed in the pressure receiving region and a lead 82 and a connection terminal 83 are shaped with a semiconductor film 80 except for the pressure receiving region. The semiconductor film 80 is covered to form an insulating diaphragm film 90, a connection hole 110 reaching the terminal 83 by penetrating it is formed, and the electrode 81 is connected to an output terminal 120 via it. Here, the film 80 is constituted of at least material containing silicon, aluminum and nitrogen, and substantially equals to the thermal expansion coefficient of the substrate 30. Thus, a sensor of a small temperature coefficient of a zero point and sensitivity can be obtained.

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 in which a diaphragm is formed on the surface of a substrate by utilizing a silicon micromachining technique which is a combination of a semiconductor process technique and a special etching technique, and a method for manufacturing the same. Is.

[0002]

2. Description of the Related Art Conventionally, various pressure sensors have been known, and among them, there is a capacitance type pressure sensor in which a diaphragm is formed on the surface of a semiconductor substrate. FIG. 9 shows a cross-sectional structure of such a conventional capacitance type pressure sensor.

In this capacitance type pressure sensor, a silicon structure 10 having a diaphragm 11 functioning as a movable electrode and a glass substrate 20 having a fixed electrode 21 formed so as to face the diaphragm 11 are anode-contacted. It has a structure that is legally bonded. When the pressure P is applied from the direction indicated by the arrow in the figure, the diaphragm 11 is deformed accordingly, and the diaphragm 11 and the fixed electrode 21 are deformed.
Changes, and the capacitance of the capacitor formed by the diaphragm 11 and the fixed electrode 21 changes. Therefore,
The pressure P is detected by detecting this capacitance.

Here, the silicon structure 10 has (10
A (0) plane single crystal silicon substrate is used, and the diaphragm 11 is formed by anisotropically etching a part of the silicon structure 10. Generally, an aqueous solution of potassium hydroxide, an aqueous solution of tetramethylammonium hydroxide or the like is used as the etching solution. Further, the diaphragm 11 is treated so as to contain a p-type or n-type impurity in a high concentration in order to function as one movable electrode of the capacitor, so that a high conductivity characteristic is obtained.

Further, the glass substrate 20 is generally made of Pyrex glass, and the bonding surface side with the silicon structure 10 is etched to a desired depth so as to cover the diaphragm 11. Generally, a hydrofluoric acid-based solution is used as this etching solution. Further, a metal film is vapor-deposited on the etched surface 22 so as to face the diaphragm 11, and one fixed electrode 21 of the capacitor is formed by photoetching the metal film. As the metal film of the fixed electrode 21, for example, a laminated film in which titanium is formed and then aluminum is formed is used.

Then, the bonding surfaces of the silicon structure 10 and the glass substrate 20 formed as described above are overlapped and aligned with each other, and the silicon structure 10 is used as an anode and the glass substrate 20 as a cathode, for example, at 300.degree. Heat to 600
By applying a DC voltage of V, the silicon structure 1
0 and the glass substrate 20 are bonded to each other with good airtightness (anodic bonding) without using an adhesive or the like.

When this pressure sensor is used as an absolute pressure measuring type, when the silicon substrate 10 and the glass substrate 20 are anodically bonded, they are bonded while the ambient atmosphere is kept in a vacuum state. As a result, the space formed by etching the surface side of the silicon substrate 10 serves as a vacuum pressure reference chamber, the diaphragm bends in proportion to the applied absolute pressure, and this deflection changes the capacitance value. Therefore, the change in capacitance can be taken out as a pressure detection signal for the vacuum, and the absolute pressure applied to the diaphragm 11 can be measured.

In such a capacitance type sensor, the sensitivity can be increased by narrowing the gap between the pair of electrodes (counter electrodes) forming the capacitor. In addition, in principle, the sensitivity has no temperature dependence.

[0009]

However, in such a conventional capacitance type pressure sensor, the thermal expansion coefficient of the glass substrate 20 made of Pyrex glass is slightly smaller than that of the silicon structure 10 made of single crystal silicon. Therefore, when the ambient temperature changes, there is a problem that the thermal stress changes due to the difference in the coefficient of thermal expansion, and the temperature characteristics of the zero point and the sensitivity of the sensor deteriorate.
Further, the glass substrate 20 may be deformed by heating during anodic bonding, and the fixed electrode 21 formed on the glass substrate 20 may come into contact with the diaphragm 11 depending on the gap between the counter electrodes. In such a case, it does not function as a sensor. There was a problem.

The present invention has been made in view of the above conventional problems, and an object thereof is a capacitance type pressure sensor in which zero point and sensitivity have little temperature dependency and anodic bonding for assembling the sensor is unnecessary. It is to provide the manufacturing method.

[0011]

According to the present invention, a pressure reference chamber is provided on a fixed electrode formed on the main surface of a substrate, and an insulating film is formed on the main surface of the substrate so as to cover the pressure reference chamber. In a capacitance type pressure sensor in which a movable electrode made of a conductive film is formed in a pressure receiving region of a conductive diaphragm film, the insulating diaphragm film is made of an insulating material containing at least silicon, aluminum and nitrogen. And

The insulating diaphragm film is made of 10 to 40 atm% of silicon and 10 to 40 atm of aluminum.
In addition to containing m% and 30 to 50 atm% of nitrogen, the oxygen content is 25 atm% or less.

As described above, in the present invention, the insulating diaphragm film is made of an insulating material containing silicon, aluminum and nitrogen. Then, the thermal expansion coefficient of the insulating diaphragm film can be adjusted by adjusting the composition of the insulating diaphragm film (for example, adjusting the composition ratio as described above). Therefore, by setting the composition of the insulating diaphragm according to the thermal expansion coefficient of the substrate,
The thermal expansion coefficient of both can be made equal. Therefore, it is possible to solve the problem that the thermal stress changes due to the difference in the coefficient of thermal expansion, and the zero point of the sensor and the temperature characteristics of the sensitivity deteriorate.

Further, according to the present invention, a substrate having a fixed electrode formed on the main surface thereof and a substrate formed on the main surface of the substrate are separated from the main surface by a predetermined distance in a pressure receiving region to define a pressure reference chamber. A movable electrode composed of a first insulating diaphragm film, a conductive film formed in a pressure receiving region of the first insulating diaphragm film, and a main surface of the substrate coated so as to cover the movable electrode. A second insulating diaphragm film, the second insulating diaphragm film and the first insulating diaphragm film,
At least one opening formed through the insulating diaphragm film to reach the pressure reference chamber, and a sealing member for sealing the at least one opening to seal the pressure reference chamber. And are included.

Further, according to the present invention, the step of forming a fixed electrode on the main surface of the substrate, the step of forming a sacrificial film covering the pressure receiving region of the main surface of the substrate, and the step of forming the sacrificial film on the substrate are performed. A step of forming a first insulating diaphragm film on the main surface, a step of forming a movable electrode made of a conductive film in the first pressure receiving region, and a second step of covering the movable electrode.
The step of forming an insulating diaphragm film, and at least one etchant injection port is formed so as to penetrate the second insulating diaphragm film and the first insulating diaphragm film to reach the sacrificial film. Forming step, forming a pressure reference chamber by etching away the sacrificial film through the etching solution inlet, and the etching inlet so as to maintain the pressure reference chamber in a desired pressure state. And a step of sealing.

According to the capacitance type pressure sensor thus obtained, when pressure is applied to the sensor, the insulating diaphragm film is deformed by the pressure, and the movable electrode and
The fixed electrode distance changes. Then, the capacitance of the capacitor including the movable electrode and the fixed electrode changes according to the change in the distance. Therefore, the pressure can be detected by detecting the change in the capacitance. The pressure in the pressure reference chamber becomes the pressure of the atmosphere when the etching inlet is sealed. Therefore, if the etching inlet is sealed in a vacuum atmosphere, the reference pressure becomes a vacuum state, and the absolute pressure can be detected by this sensor.

According to the capacitance type pressure sensor of the present invention, the first insulating diaphragm film is formed on the sacrificial film, and then the sacrificial film is removed by etching. Therefore, anodic bonding or the like is not necessary to form the pressure reference chamber. Therefore, unlike the conventional case, the glass substrate is not deformed due to the anodic bonding.

As described above, according to the present invention, by using a thin film material having a coefficient of thermal expansion substantially equal to that of the substrate for the diaphragm, a zero point can be obtained as compared with a conventional product made of a material having a different coefficient of thermal expansion. , The temperature dependence of sensitivity is reduced.

Further, since the bonding for forming the pressure reference chamber is not necessary, there is no problem such as the deformation of the glass substrate at the time of anodic bonding as in the conventional product, and the sensor characteristics are stable.

The reference electrode is formed in the pressure receiving region of the first insulating diaphragm film so as to surround the movable electrode, and is formed in a part between the first insulating diaphragm film and the substrate. And a diaphragm fixing portion that restricts movement of the reference electrode.

As described above, by providing the reference electrode, the capacitance formed by the reference electrode can be formed in addition to the capacitance formed by the movable electrode. Therefore, the pressure can be detected according to the difference between the two capacities. The two electrodes are located at almost the same place, and by taking the difference between these capacities, the influence of temperature can be almost completely eliminated.

Further, this capacitance difference can be easily detected by a switched capacitor circuit or the like. Further, since the switched capacitor circuit can be easily formed by a normal semiconductor processing process, it can be easily formed on the same substrate. Therefore, the circuit portion can also be integrally formed on the same substrate.

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention (hereinafter referred to as embodiments) will be described below with reference to the drawings.

(Basic Structure) FIG. 1 is a plan view showing the structure of a basic structure of an electrostatic capacity type pressure sensor according to the present invention, and FIG. A cross-sectional explanatory view along the line B-C is shown. Also, in FIGS.
An enlarged view of the movable electrode connection hole and the fixed electrode connection hole is shown.

Substrate 30 of the capacitance type pressure sensor of the present invention
Is made of, for example, single crystal silicon, and p
A fixed electrode 40, a fixed electrode lead 41, and a fixed electrode connection terminal 42, which are processed so as to contain a high-concentration type or n-type impurity, are formed. Further, a substrate protective film 50 having etching resistance is formed on the entire surface of the substrate 30 as needed.

Then, on the surface of the substrate protective film 50,
A sacrificial film 60 having an isotropic etching property is formed so as to cover the pressure receiving region. The sacrificial film 6
0 is removed in the manufacturing process and is not present in the product. Further, a first insulating diaphragm film 70 is formed on the main surface of the substrate 30 so as to cover the sacrificial film 60 over the entire area thereof.

Further, the first insulating diaphragm film 70
The movable electrode 81 arranged in the pressure receiving area, the movable electrode lead 82 and the movable electrode connecting terminal 83 arranged outside the pressure receiving area are formed from the semiconductor film 80. For example,
When a polycrystalline silicon film is used for the semiconductor film 80, the semiconductor film 80 made of a polycrystalline silicon film is processed so as to contain a p-type or n-type impurity at a high concentration to obtain high conductivity characteristics.

Here, a feature of the present invention is that the insulating diaphragm film 70 is made of a material containing at least silicon, aluminum and nitrogen, and the coefficient of thermal expansion of the substrate 30 (3.68 × 10 ⁻⁶ / ° C.). Is almost equal to. For example, when single crystal silicon of (100) orientation is used for the substrate 30, the composition of the insulating diaphragm film 70 is 33 atm% of silicon, 17 atm% of aluminum, and 5 atm of nitrogen.
Set to 0 atm%. As a result, the coefficient of thermal expansion of the insulating diaphragm film 70 becomes substantially equal to that of the substrate 30 made of single crystal silicon with the (100) orientation, and thermal stress does not occur due to changes in the ambient temperature of the sensor as in the conventional case. Therefore,
It is possible to provide an electrostatic capacitance type pressure sensor having a zero point and a small temperature dependency of sensitivity. Note that by the said insulating diaphragm layer 70 to control the composition of the film (Change component ratio), the thermal expansion coefficient of 3.5 × 10 ^-6 /℃~4.1×10 ^-6 / ℃ You have what you have.

The semiconductor film 80 is preferably protected by an insulating film. Therefore, the second insulating diaphragm film 90 is formed so as to cover the semiconductor film 80. A movable electrode connection hole 110 that penetrates through the second insulating diaphragm film 90 and reaches the movable electrode connection terminal 83 is formed, and the movable electrode 81 is connected to the movable electrode output terminal 120 through the movable electrode connection hole 110. Has been done. An enlarged view of this portion is shown in FIG.

Further, as shown in FIG. 1, at the position opposite to the movable electrode connection port 110, the fixed electrode connection terminal is penetrated through the first insulating diaphragm film 70 and the second insulating diaphragm film 90. Fixed electrode connection hole 13 reaching 42
0 is formed. Then, the fixed electrode connection hole 13
The fixed electrode 40 is connected to the fixed electrode output terminal 140 via 0. The fixed electrode 40 extends between the fixed electrode connection terminals 42 via the fixed electrode lead 41. An enlarged view of this portion is shown in FIG.

At least one pressure receiving region of the capacitance type pressure sensor penetrates the first insulating diaphragm film 70 and the second insulating diaphragm film 90 and reaches the sacrificial film 60 at a predetermined position. Etching solution inlet 1
00 is formed in the opening, and the sacrificial film 60 originally formed is entirely removed by etching through the etching solution injection port 100.

That is, by removing all the sacrificial film 60, the pressure reference chamber 200 surrounded by the substrate 30 and the first insulating diaphragm film 70 is formed, and at the same time, the pressure reference chamber separated from the substrate 30 is formed. A movable diaphragm 400 composed of a first insulating diaphragm film 70, a semiconductor film 80, and a second insulating diaphragm film 90 located on the upper surface side of the chamber 200 is formed.

When this capacitance type pressure sensor is used as an absolute pressure measuring type, all of the etching solution injection port 100 is sealed with a sealing cap 300 in a vacuum atmosphere. As a result, the pressure reference chamber 200 is in a vacuum state, the movable diaphragm 400 bends in proportion to the applied absolute pressure, and this deflection changes the capacitance value between the fixed electrode 40 and the movable electrode 81. Therefore, the absolute pressure applied to the movable diaphragm 400 can be measured by extracting the change in capacitance as a pressure detection signal.

(Manufacturing Method) Next, an example of a method of manufacturing the capacitance type pressure sensor according to the present invention will be specifically described.

First, a fixed electrode 40, a fixed electrode lead 41 and a fixed electrode connection terminal 42 containing a high concentration of p-type or n-type impurities are formed on the surface of the substrate 30 made of single crystal silicon by ion implantation or thermal diffusion. . next,
A substrate protection film 50 having etching resistance is formed on the entire surface of the substrate 30 and a sacrificial film 60 having isotropic etching property is formed on the surface of the substrate protection film 50. Next, the peripheral portion of the pressure receiving region of the sacrificial film 60 is removed by etching.

Next, the first insulating diaphragm film 7 is formed so as to cover the sacrificial film 60 over the entire main surface of the substrate 30.
0 to form a coating. For example, (100) on the substrate 30
When single crystal silicon having an orientation is used, the composition of the insulating diaphragm film 70 is 33 atm% silicon, 17 atm% aluminum, and 50 atm% nitrogen. As a result, the coefficient of thermal expansion of the insulating diaphragm film 70 becomes substantially equal to that of the substrate 30 made of single crystal silicon of (100) orientation.

Next, the first insulating diaphragm film 7 is formed.
A semiconductor film 80 is formed by coating on the surface of 0. For example, when a polycrystalline silicon film is used for the semiconductor film 80, p-type or n-type impurities are contained at a high concentration by ion implantation or thermal diffusion and processed to obtain high conductivity characteristics.

Next, the movable electrode 81 formed in the pressure receiving area.
Then, the semiconductor film 80 around the movable electrode lead 82 and the movable electrode connection terminal 83 formed outside the pressure receiving region is removed by etching. Next, the second insulating diaphragm film 90 is formed so as to cover the semiconductor film 80 over the entire main surface of the substrate 30.
To form a coating.

Next, at a predetermined position of the pressure receiving region, at least one etching solution is poured so as to penetrate the first insulating diaphragm film 70 and the second insulating diaphragm film 90 to reach the sacrificial film 60. Form the inlet 100.

Then, the sacrificial film 60 is obtained by injecting the etching solution through the etching solution injection port 100.
Are completely removed by etching to form a pressure reference chamber 200 between the substrate 30 and the first insulating diaphragm film 70, the pressure reference chamber 200 having a size according to the shape and size of the sacrificial film 60. For example, when polycrystalline silicon is used for the sacrificial film 60, an ethylenediaminepyrocatechol (EPW) solution is used as an etching solution for removing the sacrificial film 60 by etching. Since the first and second insulating diaphragm films 70 and 90 located on the upper surface side of the pressure reference chamber 200 have etching resistance to the EPW solution, they are not removed by etching. As a result, the first insulating diaphragm film 70 and the semiconductor film 8 located on the upper surface side of the pressure reference chamber 200.
The laminated film including 0 and the second insulating diaphragm film 90 functions as the movable diaphragm 400.

Next, the movable electrode connecting hole 110 which penetrates the second insulating diaphragm film 90 to reach the movable electrode connecting terminal 82, the second insulating diaphragm film 90, the first insulating diaphragm film 70, and Fixed electrode connection hole 130 penetrating the substrate protective film 50 and reaching the fixed electrode connection terminal 42.
To form

Next, the entire surface of the substrate 30 is coated with aluminum to form the first wiring 150 and the second wiring 16.
Aluminum around the 0 region is removed by etching.
As a result, the movable electrode 81 is connected to the movable electrode output terminal 120 via the movable electrode connection hole 110 and the first wiring 150, and the fixed electrode 40 is fixed electrode via the fixed electrode connection hole 130 and the second wiring 160. It is connected to the output terminal 140.

Next, when using this capacitance type pressure sensor as an absolute pressure measurement type, in a vacuum atmosphere,
A sealing material made of an insulating material is formed to cover the entire surface of the substrate 30 so that the etching solution injection port 100 can be hermetically sealed. Finally, an unnecessary portion is removed by photoetching to form the sealing cap 300, and at the same time, the movable electrode output terminal 120 and the fixed electrode output terminal 140 are opened to obtain an absolute pressure measurement type electrostatic capacitance type pressure sensor. To be

(First Embodiment) Next, the capacitance type pressure sensor of the first embodiment will be described with reference to FIGS. 1 to 4 used in the explanation of the basic configuration example.

In the capacitance type pressure sensor of this embodiment, an n-type (100) orientation single crystal silicon substrate is used as the substrate 30.

First, boron is added as an impurity to the main surface of the single crystal silicon substrate 30 by an ion implantation method so as to be contained in a high concentration, diffused, and processed into a p-type semiconductor, and a fixed electrode 40 having a depth of 3 μm is formed. The fixed electrode lead 41 and the fixed electrode connection terminal 42 are formed. Next, a thermal oxide film having a thickness of 100 nm is formed on the entire surface of the single crystal silicon substrate 30 as a substrate protective film 50 having etching resistance.

Then, on the surface of the substrate protective film 50,
The sacrificial film 60 is formed so as to cover the pressure receiving region. The sacrificial film 60 is removed in a later process. In this embodiment, the sacrificial film 60 is made of polycrystalline silicon having a thickness of 200 nm formed by the low pressure CVD method. next,
On the main surface of the single crystal silicon substrate 30, the first insulating diaphragm film 7 is formed so as to cover the sacrificial film 60 over the entire area.
A thin film material composed of silicon, aluminum and nitrogen is formed to have a film thickness of 650 nm.

On the surface of the first insulating diaphragm film 70, a polycrystalline silicon film having a thickness of 2 is formed as a semiconductor film 80.
The film is formed to a thickness of 00 nm. Further, in the semiconductor film 80,
The movable electrode 81, the movable electrode lead 82, and the movable electrode connection terminal 83 are formed by photoetching. In the present embodiment, the polycrystalline silicon film used as the semiconductor film 80 is processed into a p-type semiconductor in which boron is added and diffused so as to be contained at a high concentration by an ion implantation method.

Further, silicon, aluminum, or the like is used as the second insulating diaphragm film 90 so as to cover the semiconductor film 80 over the entire main surface of the single crystal silicon substrate 30.
A thin film material composed of nitrogen is formed to a film thickness of 650 nm. In the present embodiment, the first insulating diaphragm film 70 and the second insulating diaphragm film 90 are made of silicon 33 atm%, aluminum 17 atm%, and nitrogen 50.
A thin film material having an atm% composition is used.

Then, the etching solution injection port 100 having a diameter of 5 μm, which penetrates the first insulating diaphragm film 70 and the second insulating diaphragm film 90 and reaches the sacrificial film 60, is photoetched at a predetermined position in the pressure receiving region. To form an opening. By injecting the etching solution through the formed etching solution injection port 100, the initially formed sacrificial film 60 is completely removed by etching, and the pressure reference chamber 2
A cavity that becomes 00 is formed.

In this embodiment, an ethylenediaminepyrocatechol (EPW) solution is used as the etching solution. At this time, the substrate protective film 50 located on the lower surface side of the pressure reference chamber 200, and the first and second protective film located on the upper surface side.
Since the insulating diaphragm films 70 and 90 have etching resistance against the EPW solution, they are not removed by etching. Therefore, the first insulating diaphragm film 70 and the semiconductor film 8 located on the upper surface side of the pressure reference chamber 200.
The laminated film including 0 and the second insulating diaphragm film 90 functions as the movable diaphragm 400.

Next, the movable electrode connecting hole 110 which penetrates the second insulating diaphragm film 90 and reaches the movable electrode connecting terminal 83, the second insulating diaphragm film 90, the first insulating diaphragm film 70 and Fixed electrode connection hole 130 penetrating the substrate protective film 50 and reaching the fixed electrode connection terminal 42.
To form an opening by photoetching.

Further, a first wiring 150 and a second wiring 160 are formed on a predetermined portion of the single crystal silicon substrate 30 on the second insulating diaphragm film 90. These wirings are formed by vacuum evaporation or sputtering covering the entire surface of the single crystal silicon substrate 30 with aluminum to a film thickness of 1 μm, and removing unnecessary portions of aluminum by photoetching. At this time, the movable electrode 81 is connected to the movable electrode output terminal 120 via the movable electrode connection hole 110 and the first wiring 150, and the fixed electrode 40 is fixed electrode via the fixed electrode connection hole 130 and the second wiring 160. It is connected to the output terminal 140 (see FIGS. 3 and 4).

Further, a sealing member including a sealing cap for the etching solution injection port 100 is formed on a predetermined portion of the single crystal silicon substrate 30. When forming this sealing member, first, by the plasma CVD method in a substantially vacuum state,
A sealing material made of a silicon nitride film is deposited on the entire surface of the single crystal silicon substrate 30 to a thickness such that the etching solution injection port 100 can be hermetically sealed. Then, unnecessary portions are removed by photoetching to form the sealing cap 300, and at the same time, a part of the movable electrode output terminal 120 and the fixed electrode output terminal 140 is opened. By doing so, the pressure reference chamber 200 is hermetically sealed while the inside of the pressure reference chamber 200 is kept in a vacuum state, and thus the movable diaphragm 40.
The absolute pressure applied to 0 can be measured.

In this embodiment, the movable diaphragm 400 has a diameter and a film thickness of 100 μm and 1.
It is as small as 5 μm and is formed accurately. This sensor has a capacitance change of 1 × 10 ^-14 F (farads) or more and an nonlinearity of ± 2% for an absolute pressure of 100 kPa.
F. S. In addition, in the temperature range of −30 to 100 ° C., the zero point and the temperature coefficient of sensitivity are ± 0.02% /
It was confirmed by experiments that it has excellent temperature characteristics of ℃ or less.

As described above, according to the capacitance type pressure sensor of this embodiment, it is possible to realize a capacitance type pressure sensor which is small in size and has a small zero point and a small temperature dependency of sensitivity. To be understood. In this embodiment, an n-type (100) -oriented single crystal silicon substrate is used as the substrate 30, and the first and second insulating diaphragm films 7 are used.
Silicon as 0, 90 atm% 33%, aluminum 1
A combination of thin film materials having a composition of 7 atm% and 50 atm% of nitrogen was used. However, the thin film material composed of silicon, aluminum, nitrogen and oxygen can control the coefficient of thermal expansion by changing the composition thereof in the film.

Table 1 shows the measurement results of the coefficient of thermal expansion of thin film materials having different compositions of silicon, aluminum, nitrogen and oxygen.

[0058]

[Table 1] Here, the sample No. The compositions of the thin film materials 1 to 8 were quantified by X-ray photoelectron spectroscopy. In addition, the coefficient of thermal expansion is the same as sample No. 1 on the single crystal silicon substrate. The thin film materials 1 to 8 were formed, and it was determined based on the amount of warpage of the single crystal silicon substrate due to temperature change.

[0059] Table As shown in 1, silicon, aluminum, nitrogen and scope of the oxygen thermal expansion coefficient of the formed thin film material in 3.5 × 10 ^-6 /℃~4.1×10 ^-6 / ℃ You can see that it can be controlled with. From this, 3.5 × 1
If the substrate has a coefficient of thermal expansion in the range of 0 ⁻⁶ / ° C. to 4.1 × 10 ⁻⁶ / ° C., the zero point can be obtained by changing the composition of the first and second insulating diaphragm films 70, 90. It can be seen that it is possible to realize an electrostatic capacitance type pressure sensor whose sensitivity is less dependent on temperature.

(Second Embodiment) Next, a preferred second embodiment of the present invention will be described. The members corresponding to those in the first embodiment are designated by the same reference numerals, and the description thereof will be omitted.

FIG. 5 is a plan view showing a second preferred embodiment of the capacitance type pressure sensor according to the present invention, and FIG.
FIG. 6 is a cross-sectional view taken along the line D-E of FIG. 5.

First, the fixed electrode 40, the fixed electrode lead 41 and the fixed electrode connection terminal 42 are formed on the main surface of the single crystal silicon substrate 30. In addition, a substrate protective film 50 made of a thermal oxide film having a thickness of 100 nm is formed so as to cover the entire surface of the single crystal silicon substrate 30. Then, a sacrificial film 60 made of polycrystalline silicon having a thickness of 200 nm is formed so as to cover the pressure receiving region on the substrate protective film 50, and then a region corresponding to the diaphragm fixing portion 170 of the sacrificial film 60 is formed.
Boron as an impurity is added and diffused by thermal diffusion or an ion implantation method to form a p-type semiconductor region having an impurity concentration of 1 × 10 ²⁰ / cm ³ or more. As a result, the region corresponding to the diaphragm fixing portion 170 has etching resistance, and the sacrificial film 60 in the region where impurities are not added or diffused is
Has isotropic etching characteristics. The sacrificial film 60 will be removed later.

Next, as in the first embodiment, the first insulating diaphragm film 70 and the semiconductor film 80 are formed. In the present embodiment, the semiconductor film 80 is photoetched to form the movable electrode 81, the movable electrode lead 82, the movable electrode connection terminal 83, the reference electrode 180, the reference electrode lead 181, and the reference electrode connection terminal 182. The movable electrode 81 has the diaphragm fixing portion 17 in the pressure receiving region.
0, and the reference electrode 180 is formed outside the diaphragm fixing portion 170 in the pressure receiving area. The movable electrode 81 and the reference electrode 180 are formed to have the same area.

Next, a second insulating diaphragm film 90 is formed so as to cover the semiconductor film 80 over the entire main surface of the single crystal silicon substrate 30, and an etching solution injection port 100 is opened. By injecting the ethylenediaminepyrocatechol (EPW) etching solution through the etching solution injection port 100, the sacrificial film 60 in the region which is not processed so as to have the etching resistance property is removed by etching, and the diaphragm fixing portion 170 and the pressure reference. Room 200
A cavity is formed. As a result, the outer region of the diaphragm fixing portion 170 in the pressure receiving region has high rigidity and becomes a region that is less likely to bend with respect to the measured pressure. The reference electrode 180 is formed in this region.

Next, the movable electrode connection hole 110 which penetrates the second insulating diaphragm film 90 to reach the movable electrode connection terminal 83, the reference electrode connection hole 185 which reaches the reference electrode connection terminal 182, and the second insulation. Permeable diaphragm film 90, first
Of the fixed electrode connection hole 1 reaching the fixed electrode connection terminal 42 through the insulating diaphragm film 70 and the substrate protection film 50 of
An opening 30 is formed by photoetching. Next, aluminum having a thickness of 1 μm is formed to cover the entire surface of the single crystal silicon substrate 30, and the first wiring 150, the second wiring 160, and the third wiring 190 are photoetched.
To form After that, as in the first embodiment, the sealing cap 300 is formed, and the movable electrode output terminal 120, the fixed electrode output terminal 140, and the reference electrode output terminal 183 are partially formed with openings.

Here, in this embodiment, the diameter is 15
A movable diaphragm 400 having a diameter of 100 μm and a film thickness of 1.5 μm is formed by supporting the diaphragm fixing portion 170 within a pressure receiving region of 0 μm. The movable electrode 81 and the fixed electrode 40 form a pressure detection capacitor Cx, and the reference electrode 180 and the fixed electrode 40 form a reference capacitor Cr. Therefore, since the pressure detection capacitor Cx and the reference capacitor Cr are made of the same material and are formed close to each other, the temperature characteristics are substantially equal.

There is a charge / discharge type switched capacitor circuit for converting the capacitance into a voltage as one of the methods for detecting the capacitance change. FIG. 7 shows a switched capacitor type capacitance detection circuit.

In this circuit, four switches SW1 to S
W4, and these four switches SW1 to SW4
Are switched by a clock signal having a frequency higher than a predetermined value. SW1 and SW2 are pressure detection capacitors Cx
And one end of the reference capacitor Cr are alternately connected to the ground or the power supply Vp. That is, one of the capacitors Cx or Cr is connected to the ground, and the other is connected to the power supply Vp.

The other ends of the pressure detection capacitor Cx and the reference capacitor Cr are connected to the negative input end of the operational amplifier. The positive input terminal is connected to the ground. A feedback capacitor Cf and a switch SW3 are connected in parallel between the output terminal and the negative input terminal of this operational amplifier. The output of the operational amplifier is connected to the output terminal via the switch SW4. The output end has a smoothing capacitor C whose other end is connected to the ground.
0 is connected. In the illustrated example, the switch S
When W1 is connected to the power supply Vp, SW2 is connected to ground, SW3 is on, SW4 is off,
When the switch SW2 is connected to the power source Vp,
SW1 is connected to ground, SW3 is off and SW4 is on.

In the switched capacitor circuit, Cx, Cr and Cf are substantially resistors due to switching,
The amplification factor of the operational amplifier is the capacitance on the input side (two capacitances C
Since x and Cr are alternately connected, it is determined by the ratio of this difference) and the capacitance on the feedback side. Therefore, if the output voltage of this switched capacitor circuit is E0, this E0 is
0 = Vp (Cx-Cr) / Cf, output voltage E
0 is proportional to the capacitance difference between the two capacitors Cx and Cr.
Therefore, by detecting the output voltage E0, the capacitance difference between the two capacitors Cx and Cr can be detected, and thus the applied pressure can be detected.

Therefore, as a result of connecting the sensor of the present embodiment to this switched capacitor type capacitance detection circuit and evaluating the sensor characteristics, the output characteristics are 100 kPa absolute pressure, the output voltage is 20 mV or more, and the non-linearity. Is -2% F.
S. The temperature characteristics are as follows, and the temperature coefficient of the zero point and sensitivity is ± 0.01% / ° C in the temperature range of -30 to 100 ° C.
It was confirmed by experiments that the following have excellent temperature characteristics.

As described above, in this embodiment, the reference electrode 180 is formed in the pressure receiving region so as to surround the movable electrode 81, and the diaphragm fixing portion 170 is provided at the boundary between the two.
As a result, the movable electrode 81 forms the pressure detection capacitor Cx, and the reference electrode 180 forms the reference capacitor Cr. And two capacitors C
A pressure change can be detected by detecting the capacitance difference between x and Cr. In particular, since two adjacent capacitors have almost the same temperature, the influence of temperature on the pressure detection value can be almost completely eliminated. Further, by providing the diaphragm fixing portion 170, the deformation of the reference electrode 180 due to the pressure can be prevented, and the capacitance difference between the two capacitors can be maintained sufficiently.

(Third Embodiment) FIG. 8 shows a third embodiment of the present invention.
The top view of the electrostatic capacity type pressure sensor concerning an embodiment is shown.

A feature of this embodiment is that the electrostatic capacitance type pressure sensor and the integrated capacitance detection circuit are integrated.

In the embodiment, the capacitance type pressure sensor 500 described in the second embodiment is formed at a predetermined position of the single crystal silicon substrate 30. Further, a circuit portion 600 is formed on the single crystal silicon substrate 30 by using a semiconductor manufacturing technique. The circuit unit 600 is composed of a switched capacitor type capacitance detection circuit that converts the above-mentioned capacitance change into a voltage.

Fixed electrode 4 of capacitance type pressure sensor 500
0, the movable electrode 81, and the reference electrode 180 are connected to the circuit section 600 via the fixed electrode output terminal 140, the movable electrode output terminal 120, and the reference electrode output terminal 183, respectively.

By integrating the circuit parts on the same substrate as described above, it is possible to manufacture a capacitance type pressure sensor which can obtain an electric output by one semiconductor processing process, and is integrated with the integrated circuit. The so-called integrated sensor can be obtained.

[0078]

As is apparent from the above description, the capacitance type pressure sensor of the present invention uses a thin film material having a coefficient of thermal expansion substantially equal to that of the substrate for the diaphragm.
The temperature dependence of sensitivity is small. In addition, the movable diaphragm can be formed with high accuracy by using the thin film forming technology of the semiconductor process and the sacrifice film etching technology, and it becomes easy to form a narrow gap between the opposing electrodes that form the capacitor. Miniaturization is possible. In addition, since all can be manufactured by processing one side of the substrate, it is extremely suitable for manufacturing a so-called integrated sensor integrated with an integrated circuit.

[Brief description of drawings]

FIG. 1 is a first electrostatic capacity type pressure sensor according to the present invention.
It is a top view showing an embodiment.

FIG. 2 is a cross-sectional view of the capacitance type pressure sensor shown in FIG.

3 is a cross-sectional view of a movable electrode portion of the capacitance type pressure sensor shown in FIG.

FIG. 4 is a cross-sectional view of a fixed electrode electrode portion of the capacitance type pressure sensor shown in FIG.

FIG. 5 is a second electrostatic capacity type pressure sensor according to the present invention.
It is a top view showing an embodiment.

6 is a sectional view of the capacitance type pressure sensor shown in FIG.

FIG. 7 is a circuit diagram showing a configuration of a capacitance detection circuit.

FIG. 8 is a third electrostatic capacity type pressure sensor according to the present invention.
It is a top view showing an embodiment.

FIG. 9 is a cross-sectional view of a conventional capacitance type pressure sensor.

[Explanation of symbols]

30 substrate, 40 fixed electrode, 60 sacrificial film, 70 insulating diaphragm film, 81 movable electrode, 200 pressure reference chamber, 300 sealing cap, 400 movable diaphragm.

Claims (7)

[Claims] 1. A pressure reference chamber is provided on a fixed electrode formed on a main surface of a substrate, and a pressure is applied to a pressure receiving region of an insulating diaphragm film formed on the main surface side of the substrate so as to cover the pressure reference chamber. In a capacitance type pressure sensor having a movable electrode made of a flexible film, the insulating diaphragm film is made of an insulating material containing at least silicon, aluminum and nitrogen. . 2. The insulating diaphragm film comprises 10 to 40 atm of silicon and 10 to 40 atm of aluminum.
%, Nitrogen 30 to 50 atm%, and the oxygen content is 25 atm% or less.
Capacitive pressure sensor according to. 3. A substrate having a main surface on which a fixed electrode is formed, and a first insulation formed on the main surface of the substrate and separated from the main surface by a predetermined distance in a pressure receiving region to define a pressure reference chamber. Conductive diaphragm film, a movable electrode formed of a conductive film formed in the pressure receiving region of the first insulating diaphragm film, and a second insulating film formed on the main surface of the substrate so as to cover the movable electrode. -Resistant diaphragm film, at least one opening formed to penetrate the second insulating diaphragm film and the first insulating diaphragm film to reach the pressure reference chamber, and the at least one opening And a sealing member which seals the pressure reference chamber, and a capacitance type pressure sensor. 4. The capacitance type pressure sensor according to claim 3, wherein the first and second insulating diaphragm films are made of a material containing at least silicon, aluminum and nitrogen. 5. The first and second insulating diaphragm films are made of 10 to 40 atm% silicon and 10 to 10 aluminum.
40 atm% and nitrogen 30 to 50 atm% are included,
The capacitance type pressure sensor according to claim 4, wherein the oxygen content is 25 atm% or less. 6. A reference electrode formed in a pressure receiving region of the first insulating diaphragm film so as to surround the movable electrode, and a part of the reference electrode formed between the first insulating diaphragm film and the substrate. The diaphragm pressure fixing part is included, The electrostatic capacity type pressure sensor as described in any one of Claims 3-5 characterized by the above-mentioned. 7. A step of forming a fixed electrode on a main surface of a substrate, a step of forming a sacrificial film covering a pressure receiving region of the main surface of the substrate, and a step of forming a sacrificial film on the main surface of the substrate so as to cover the sacrificial film. Forming a first insulating diaphragm film, forming a movable electrode made of a conductive film in the first pressure receiving region, and forming a second insulating diaphragm film so as to cover the movable electrode. And a step of penetrating the second insulating diaphragm film and the first insulating diaphragm film to reach the sacrificial film,
Forming at least one etching solution inlet, forming a pressure reference chamber by etching away the sacrificial film through the etching solution inlet, and forming the pressure reference chamber in a desired pressure state. And a step of sealing the etching inlet so as to hold the electrostatic pressure sensor.