JP2009002802A - Water sensor and dew condensation sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sensor that detects the adhesion of water with high sensitivity by a novel constitution. <P>SOLUTION: A pair of electrodes 20 and 21 constituted by covering electrode materials 10 and 11 with a protective film 12 are arranged on a substrate (a silicon substrate 1 and an insulating film 2) so as to be exposed to the atmosphere and a change in the capacitance between a pair of the electrodes 20 and 21 accompanied by the adhesion of water is detected. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a moisture sensor and a dew condensation sensor.

In the humidity sensor, a polymer material is used as a moisture sensitive material as disclosed in Patent Documents 1, 2, 3, and the like.
Japanese Patent Laid-Open No. 2002-5867 JP 2002-174609 A Japanese Patent Laid-Open No. 4-50757

  The use of a polymer material as a moisture-sensitive material has excellent characteristics such as good linearity of the sensor. However, when an existing humidity sensor is used as a wet sensor or a dew condensation sensor, the sensor eventually becomes a sensor. It is necessary to integrate with the part (electrode). That is, it is necessary to form the moisture sensitive material on the sensing part (on the electrode), and the manufacturing process becomes complicated.

  The present invention has been made under such a background, and an object of the present invention is to provide a sensor capable of detecting adhesion of water with high sensitivity with a novel configuration.

  In the invention according to claim 1, as a wet sensor, a pair of electrodes configured by covering an electrode material with a protective film is disposed on a substrate in a state where the electrodes are exposed to the atmosphere, The gist is that a change in capacitance between a pair of electrodes due to water adhesion is detected.

  According to the first aspect of the present invention, the pair of electrodes formed by covering the electrode material with the protective film is exposed to the atmosphere, and when water adheres to the water, the capacitance between the pair of electrodes becomes moisture sensitive. Compared with the case of using a material, the change is large (see FIG. 5), and this change in capacity is detected. In this way, it is possible to detect water adhesion due to moisture with high sensitivity without using a moisture sensitive material.

  In the invention according to claim 2, as a dew condensation sensor, a pair of electrodes configured by covering an electrode material with a protective film on a substrate are arranged in a state where the electrodes are exposed to the atmosphere, and water due to dew condensation is disposed. The gist is that a change in capacitance between a pair of electrodes accompanying the attachment is detected.

  According to the second aspect of the present invention, when a pair of electrodes formed by covering the electrode material with the protective film is exposed to the atmosphere, and water adheres due to condensation, the capacitance between the pair of electrodes becomes a moisture sensitive material. Compared with the case of using the change (see FIG. 5), this capacitance change is detected. In this way, water adhesion due to condensation can be detected with high sensitivity without using a moisture sensitive material.

  As described in claim 3, in the wet sensor according to claim 1, the protective film can be made of a silicon nitride film. Similarly, as described in claim 4, in the dew condensation sensor according to claim 2, the protective film can be made of a silicon nitride film.

  As described in claim 5, in the wet sensor according to claim 1 or 3, the electrode material can be made of a corrosion-resistant material. Similarly, as described in claim 6, in the dew condensation sensor according to claim 2 or 4, the electrode material can be made of a corrosion-resistant material.

  As described in the seventh, ninth, and eleventh aspects, the ruthenium-based material, platinum, and gold may be used as the corrosion-resistant material in the wet sensor according to the fifth aspect. Similarly, as described in claims 8, 10 and 12, in the dew condensation sensor according to claim 6, a ruthenium-based material, platinum, and gold may be used as the corrosion-resistant material.

DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, an embodiment of the invention will be described with reference to the drawings.
1 and 2 show the structure of the sensor in this embodiment. FIG. 1 shows a plan view of the sensor, and FIG. 2 shows a longitudinal section taken along line AA of FIG. This sensor is a sensor that detects water exposure and dew condensation. Specifically, as shown in FIGS. 3 and 4, it can detect that water W adheres when it is wet.

1 and 2, an insulating film 2 is formed on the upper surface of a silicon substrate 1, and this is used as a substrate in this embodiment. Alternatively, a ceramic substrate may be used. The insulating film 2 in FIG. 2 is a silicon oxide film (SiO ₂ ), which is a semiconductor insulating film.

  A pair of electrode materials 10 and 11 are formed on the silicon substrate 1 with a certain distance therebetween via an insulating film 2. The electrode materials 10 and 11 are made of a metal film and have a comb-teeth shape. The comb-like electrode members 10 and 11 are arranged to be engaged with each other in the same plane and are opposed to each other. By making the comb-teeth shape, the facing area can be increased and the electrode shape is excellent in miniaturization. Aluminum (Al), copper (Cu), titanium (Ti), silver (Ag), or the like is used as the material for the electrode materials 10 and 11.

Electrode materials (metal films) 10 and 11 are covered with a protective film 12 and subjected to corrosion resistance treatment. The protective film 12 is a silicon nitride film (Si ₃ N ₄ ), which is a semiconductor protective film. An electrode 20 having corrosion resistance is formed by covering the electrode material 10 with the protective film 12, and an electrode 21 having corrosion resistance is formed by covering the electrode material 11 with the protective film 12. Yes.

In this way, the pair of electrodes 20 and 21 having corrosion resistance are disposed on the substrates (1 and 2) in a state where they are exposed to the atmosphere.
Further, wide pad portions 13 and 14 are formed on the electrode materials 10 and 11, and the pad portions 13 and 14 are exposed from the protective film 12. A circuit portion (not shown) is electrically connected to the pad portions 13 and 14 through bonding wires, and a change in capacitance between the electrodes 20 and 21 is detected in the circuit portion. Specifically, as an example of the configuration of the circuit unit, a circuit configuration using a switched capacitor circuit (for example, FIG. 3 of Japanese Patent Laid-Open No. 2003-28824) or taking out a change in capacitance as a change in oscillation frequency. (For example, FIG. 4 of JP-A-62-17649) may be used.

  Then, as shown in FIGS. 3 and 4, the moisture (or condensation) can be detected from the capacitance change between the electrodes 20 and 21 due to the adhesion of the water W during the moisture (or condensation). That is, it is possible to detect a change in capacity between the pair of electrodes 20 and 21 due to adhesion of water due to moisture, or to detect a change in capacity between the pair of electrodes 20 and 21 due to adhesion of water due to condensation. .

  FIG. 5 shows sensor characteristics. In FIG. 5, the horizontal axis represents humidity 0 to 100 [% RH], water exposure, and dew condensation. In FIG. 5, the vertical axis represents the capacitance between the electrodes, specifically, the capacitance [pF] normalized at 0% RH.

  In FIG. 5, two types of samples are used as samples. The first sample has the sensor configuration of FIGS. 1 and 2 and is referred to as a “no polymer film” structure. The second sample has a sensor structure as a comparative example, and has a “with polymer film” configuration shown in FIGS.

  The sensor structure of the comparative example of FIGS. 6 and 7 correspond to a conventional humidity sensor, and a polymer moisture sensitive film 40 is formed on the protective film 12. That is, the polymer moisture sensitive film 40 having high hygroscopicity is disposed on the comb electrode materials 10 and 11 formed of a metal film via the protective film 12. 8 and 9 show a state in which water W adheres due to water.

On the other hand, in this embodiment (FIGS. 1 and 2), nothing is formed on the protective film 12, and the protective film 12 protecting the electrode materials 10 and 11 is exposed to the atmosphere.
Thus, in FIG. 5, in the case where the polymer moisture sensitive film 40 is formed as shown in FIGS. 6 and 7 (= there is a polymer film), as in this embodiment (FIGS. 1 and 2), The sensor characteristics with respect to humidity when no moisture sensitive film is formed (= no polymer film) are shown.

In addition, the electrode size used for obtaining the data of FIG. 5 is one in which the area of the comb electrode is about 50 times that of a normal one.
In FIG. 5, in the humidity region from 0% RH to 100% RH, the comb-tooth electrode that does not form a polymer film has a small change in capacitance value and is also difficult to use as a humidity sensor because there is no linearity. .

  On the other hand, the comb-teeth electrode on which the polymer film is formed has a linear capacitance change with respect to the relative humidity. However, when the comb electrode is wetted or dewed, the capacity change is much larger when the polymer film is not formed.

  The comb-teeth electrode type humidity sensor shown in FIGS. 6 and 7 uses a switched-capacitor type detection circuit because the capacitance change is as small as about 40 fF (femtofarad). If it demonstrates in FIG. 5, in the structure with a polymer film, it will change about 2 pF in the range of 0-100% RH, and will be 40 fF (= 2/50 * 1000) when converted into a normal electrode size. . On the other hand, in the present embodiment shown in FIGS. 1 and 2, since the sensitivity is very high for measuring the water exposure and the dew condensation state, the detection circuit can be simplified as a circuit configuration other than the switched capacitor method. If this is explained with reference to FIG. 5, in the “no polymer film” structure, a capacitance change of about 27 pF is obtained at the time of water exposure or condensation, and this is converted to a normal electrode size by about 0.5 pF (≈27 / 50). Therefore, a capacitance change of an order of magnitude different from that of the “with polymer film” structure can be obtained, and the detection circuit can be simplified as a circuit configuration other than the switched capacitor method.

As the electrode materials (metal films) 10 and 11 in FIGS. 1 and 2, a corrosion-resistant material (corrosion-resistant metal) may be used. Specifically, examples of the material (corrosion resistant material) of the electrode materials 10 and 11 include ruthenium-based materials such as chromium, Ru, and RuO ₂ and noble metals such as platinum (Pt) and gold (Au).

  As a method of using the sensor of the present embodiment, for example, it can be integrated in a part of an LSI and used instead of a submerged seal as in a mobile phone. That is, the submerged seal gradually changes color over time without being wet, but the wet sensor of this embodiment can detect water instantly only when it is wet without such a situation.

Although FIGS. 3 and 4 show the situation of being exposed to water, a large number of small water droplets adhere on the substrates (1, 2), that is, on the electrodes 20 and 21, during dew condensation.
According to the above embodiment, the following effects can be obtained.

  (A) As a wet sensor, a pair of electrodes 20 and 21 formed by covering electrode materials 10 and 11 with a protective film 12 on a substrate (silicon substrate 1 and insulating film 2) Are arranged in a state exposed to the atmosphere, and a change in capacitance between the pair of electrodes 20 and 21 due to the adhesion of water due to water is detected. As a dew condensation sensor, a pair of electrodes 20 and 21 configured by covering electrode materials 10 and 11 with a protective film 12 on a substrate (silicon substrate 1 and insulating film 2) are exposed to the atmosphere. In such a configuration, a change in capacitance between the pair of electrodes 20 and 21 due to the adhesion of water due to condensation is detected. As a result, the pair of electrodes 20 and 21 (the pair of electrodes 20 and 21 having corrosion resistance) configured by covering the electrode materials 10 and 11 with the protective film 12 are exposed to the atmosphere. When water adheres, the capacitance between the pair of electrodes 20 and 21 changes greatly compared to the case where a moisture sensitive material is used (see FIG. 5), and this capacitance change is detected. In this way, the adhesion of water due to moisture or condensation can be detected with high sensitivity without using a moisture sensitive material. In addition, since the capacitance changes greatly compared to the case where a moisture sensitive material is used, the detection circuit can be simplified. Furthermore, it is possible to provide a moisture / condensation sensor that can detect the moisture / condensation state without using a moisture-sensitive film made of a special polymer material or inorganic material. Thus, in the case where a humidity sensor having a conventional structure is used, forming the moisture sensitive material in the sensing portion increases the cost due to an extra manufacturing process, but in this embodiment, the moisture sensitive material It becomes easy to manufacture without forming.

  (B) If the protective film 12 is a silicon nitride film, it can be easily formed using semiconductor manufacturing technology. More specifically, an anticorrosion treatment is easily performed using a semiconductor process in which an insulating film 2 such as a silicon oxide film, electrode materials 10 and 11 such as an aluminum film, and a protective film 12 made of a silicon nitride film are sequentially laminated on the silicon substrate 1. Can be applied.

(C) When the electrode members 10 and 11 are made of a corrosion resistant material, the corrosion resistance of the electrode can be improved. In particular, when a ruthenium-based material (Ru, RuO ₂ ), platinum, or gold is used as the corrosion resistant material, the corrosion resistance is further improved.

  Note that the electrodes need only be opposed to each other in a plane. In FIGS. 1 and 2 and the like, comb-shaped electrodes are used as the electrodes. However, the shape of the electrodes is not limited to this and may be circular.

The top view of the sensor in this embodiment. The longitudinal cross-sectional view in the AA line of FIG. The top view which shows the adhesion state of the water at the time of the flooding in the sensor of embodiment. FIG. 4 is a longitudinal sectional view taken along line AA in FIG. 3. Sensor characteristic diagram. The top view of the sensor in a comparative example. The longitudinal cross-sectional view in the AA line of FIG. The top view which shows the adhesion state of the water at the time of flooding in the sensor of a comparative example. The longitudinal cross-sectional view in the AA line of FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Silicon substrate, 2 ... Insulating film, 10 ... Electrode material, 11 ... Electrode material, 12 ... Protective film, 20 ... Electrode, 21 ... Electrode.

Claims (12)

A pair of electrodes (20, 21) configured by covering the substrate (1, 2) with the electrode material (10, 11) by the protective film (12) is exposed to the atmosphere. The wet sensor is characterized by detecting a change in capacity between the pair of electrodes (20, 21) due to water adhering to the wet water. A pair of electrodes (20, 21) configured by covering the substrate (1, 2) with the electrode material (10, 11) by the protective film (12) is exposed to the atmosphere. The dew condensation sensor is characterized by detecting changes in the capacity between the pair of electrodes (20, 21) due to water adhering due to dew condensation. The wet sensor according to claim 1,
The wet sensor, wherein the protective film (12) is made of a silicon nitride film. The dew condensation sensor according to claim 2,
The dew condensation sensor, wherein the protective film (12) is made of a silicon nitride film. The wet sensor according to claim 1 or 3,
The wet sensor, wherein the electrode material (10, 11) is made of a corrosion-resistant material. The dew condensation sensor according to claim 2 or 4,
The dew sensor, wherein the electrode material (10, 11) is made of a corrosion resistant material. The wet sensor according to claim 5,
A wet sensor using a ruthenium-based material as the corrosion-resistant material. In the dew condensation sensor according to claim 6,
A dew condensation sensor using a ruthenium-based material as the corrosion-resistant material. The wet sensor according to claim 5,
A wet sensor, wherein platinum is used as the corrosion-resistant material. In the dew condensation sensor according to claim 6,
A dew condensation sensor using platinum as the corrosion resistant material. The wet sensor according to claim 5,
A wet sensor using gold as the corrosion-resistant material. In the dew condensation sensor according to claim 6,
A dew condensation sensor using gold as the corrosion resistant material.

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