JP3166290B2 - Gas sensor - Google Patents
Gas sensorInfo
- Publication number
- JP3166290B2 JP3166290B2 JP11076692A JP11076692A JP3166290B2 JP 3166290 B2 JP3166290 B2 JP 3166290B2 JP 11076692 A JP11076692 A JP 11076692A JP 11076692 A JP11076692 A JP 11076692A JP 3166290 B2 JP3166290 B2 JP 3166290B2
- Authority
- JP
- Japan
- Prior art keywords
- thin film
- gas
- gas sensor
- film
- metal oxide
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Fee Related
Links
Description
【０００１】[0001]
【産業上の利用分野】本発明は、ガスセンサに関する。
更に詳しくは、ガス感応膜として金属酸化物半導体薄膜
を用いたガスセンサに関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas sensor.
More specifically, the present invention relates to a gas sensor using a metal oxide semiconductor thin film as a gas-sensitive film.
【０００２】[0002]
【従来の技術】従来から、ガスセンサのガス感応膜とし
て、感度と選択性とにすぐれた酸化錫膜などの金属酸化
物半導体薄膜が用いられている。しかしながら、金属酸
化物半導体薄膜は、測定再現性が十分ではないという問
題点を有している。即ち、非動作時のセンサの保存状況
によって、測定時の初期値が変動する現象がみられる。2. Description of the Related Art Conventionally, a metal oxide semiconductor thin film such as a tin oxide film having excellent sensitivity and selectivity has been used as a gas sensitive film of a gas sensor. However, the metal oxide semiconductor thin film has a problem that measurement reproducibility is not sufficient. That is, there is a phenomenon in which the initial value at the time of measurement varies depending on the storage state of the sensor during non-operation.
【０００３】これ迄の検討から、その原因がセンサ保管
時の大気中湿度の影響によるものであることが分かって
いる。これは、大気中の水分が金属酸化物表面に水酸基
となって吸着あるいは結合することで、表面の荷電状態
を変化させているためと考えられる。しかも、このよう
な吸着水分は、センサの動作温度である約300〜400℃に
加熱しても容易に脱離せず、初期抵抗値のドリフト要因
となっている。[0003] From previous studies, it has been found that the cause is due to the influence of atmospheric humidity during storage of the sensor. This is considered to be because the moisture in the atmosphere is adsorbed or bonded to the surface of the metal oxide as a hydroxyl group, thereby changing the charge state of the surface. Moreover, such adsorbed moisture does not easily desorb even when heated to about 300 to 400 ° C., which is the operating temperature of the sensor, and causes a drift in the initial resistance value.
【０００４】このための対策としては、水分の吸着を防
ぐかあるいは吸着水分量をモニターすることで初期値を
補正するなどの方法が考えられるが、これらのいずれの
方法も従来の素子構造では実施が困難である。As a countermeasure for this, there are conceivable a method of preventing the adsorption of water or a method of correcting the initial value by monitoring the amount of water adsorbed, and any of these methods is implemented in the conventional element structure. Is difficult.
【０００５】[0005]
【発明が解決しようとする課題】本発明の目的は、ガス
感応膜として金属酸化物半導体薄膜を用いたガスセンサ
であって、吸着水分量をモニターし、初期値を補正する
ことが容易なものを提供することにある。An object of the present invention is to provide a gas sensor using a metal oxide semiconductor thin film as a gas-sensitive film, which can easily monitor the amount of adsorbed water and correct the initial value. To provide.
【０００６】[0006]
【課題を解決するための手段】かかる本発明の目的は、
絶縁性薄膜で被覆された水晶振動子の一方の面側に１組
の対向電極および金属酸化物半導体ガス感応膜を順次形
成させ、他方の面側に加熱用薄膜ヒータを形成させたガ
スセンサによって達成される。SUMMARY OF THE INVENTION The object of the present invention is as follows.
Achieved by a gas sensor in which a pair of counter electrodes and a metal oxide semiconductor gas-sensitive film are sequentially formed on one side of a quartz resonator covered with an insulating thin film, and a thin-film heater for heating is formed on the other side. Is done.
【０００７】水晶振動子としては、ATカット、共振周波
数6MHz以上のものが好んで用いられる。水晶振動子は、
表裏両面の水晶面の中央部分に銀電極が取付けられてお
り、それぞれの銀電極からリード線が引き出されている
ものを用いる。As the crystal oscillator, those having an AT cut and a resonance frequency of 6 MHz or more are preferably used. The crystal oscillator
A silver electrode is attached to the center part of the quartz surface on both front and back sides, and a lead wire is drawn out from each silver electrode.
【０００８】このような水晶振動子の表裏両面は、プラ
ズマCVD法などにより、厚さ約0.05〜3μmの絶縁性薄
膜、例えばSiO2、Si3N4などの薄膜で被覆されている。The front and back surfaces of such a crystal unit are coated with an insulating thin film having a thickness of about 0.05 to 3 μm, for example, a thin film of SiO 2 or Si 3 N 4 by a plasma CVD method or the like.
【０００９】絶縁性薄膜で被覆された水晶振動子の一方
の面側には、１組の対向電極および金属酸化物半導体ガ
ス感応膜が順次形成される。対向電極としては、一般に
くし形電極が用いられ、それは蒸着法、スパッタリング
法、イオンプレーティング法などにより、クロム(膜厚
約0.05〜0.1μm)および金(膜厚約0.1〜1μm)の積層電極
として一般に形成される。A pair of counter electrodes and a metal oxide semiconductor gas-sensitive film are sequentially formed on one surface side of the quartz resonator covered with the insulating thin film. As the counter electrode, a comb-shaped electrode is generally used, which is a laminated electrode of chromium (thickness of about 0.05 to 0.1 μm) and gold (thickness of about 0.1 to 1 μm) by a vapor deposition method, a sputtering method, an ion plating method, or the like. As a general rule.
【００１０】このような１組の対向電極を覆う金属酸化
物半導体ガス感応膜としては、膜厚が約10nm〜1μm程度
のSnO2、Fe2O3などの金属酸化物の半導体薄膜が用いら
れる。半導体薄膜の形成は、真空蒸着法、スパッタリン
グ法、イオンプレーティング法、プラズマCVD法などに
よりSnO2膜などを直接形成させる方法、金属Sn膜などを
形成させた後、熱処理して酸化する方法あるいはSnを含
む有機金属モノマーをプラズマ重合させてプラズマ重合
膜を形成させ、これを熱処理する方法(特開昭63-261148
号公報)などによって行われる。As a metal oxide semiconductor gas-sensitive film covering such a pair of counter electrodes, a semiconductor thin film of a metal oxide such as SnO 2 or Fe 2 O 3 having a thickness of about 10 nm to 1 μm is used. . The method of forming a semiconductor thin film is a method of directly forming an SnO 2 film or the like by a vacuum deposition method, a sputtering method, an ion plating method, a plasma CVD method, or the like, a method of forming a metal Sn film or the like, and then performing a heat treatment and oxidizing the method. A method of plasma-polymerizing an organometallic monomer containing Sn to form a plasma-polymerized film and heat-treating the film (JP-A-63-261148)
Gazette).
【００１１】絶縁性薄膜で被覆された水晶振動子の他方
の面側には、加熱用薄膜ヒータが形成される。薄膜ヒー
タは、金、白金、タングステンなどの高融点金属からペ
ースト法、真空蒸着法、スパッタリング法などにより、
約100nm〜1μm程度の膜厚で形成される。A heating thin film heater is formed on the other surface side of the crystal unit covered with the insulating thin film. Thin-film heaters are manufactured from high-melting metals such as gold, platinum, and tungsten by paste, vacuum evaporation, and sputtering.
It is formed with a thickness of about 100 nm to 1 μm.
【００１２】図１は、本発明に係るガスセンサの一態様
の表面図(a)、I-I線断面図(b)および裏面図(c)であり、
１は水晶振動子、２,２´はその銀電極、３,３´はそこ
からのリード線、４,４´は絶縁性薄膜、５,５´は対向
電極、６,６´はそこからのリード線、７はガス感応
膜、８は加熱用薄膜ヒータ、そして９,９´はそこから
のリード線である。FIG. 1 is a front view (a), a cross-sectional view taken along line II (b), and a rear view (c) of one embodiment of the gas sensor according to the present invention.
1 is a quartz oscillator, 2, 2 'is its silver electrode, 3, 3' is a lead wire from there, 4, 4 'is an insulating thin film, 5, 5' is a counter electrode, 6, 6 'is from there , 7 is a gas-sensitive film, 8 is a thin film heater for heating, and 9, 9 'are lead wires therefrom.
【００１３】[0013]
【作用】かかるガスセンサを用いての測定は、次のよう
にして行われる。通常のガス測定時には、水晶振動子と
しての発振は行わずに、水晶基板面の薄膜ヒータによ
り、基板を約300〜500℃の温度に加熱し、その反対面側
の対向電極により、ガス感応膜の抵抗値変化を検出す
る。非動作時、室温下においては大気中の水分の吸着が
生ずるため、水晶振動子を発振させ、その発振周波数を
測定する。このときの発振周波数は、質量付加効果によ
り吸着水分質量に応じて変化するため、この周波数変化
量から吸着水分量を求めることができる。The measurement using such a gas sensor is performed as follows. During normal gas measurement, the substrate is heated to a temperature of about 300 to 500 ° C by the thin film heater on the quartz substrate surface without oscillating as a quartz oscillator, and the gas-sensitive film is The change in the resistance value is detected. At the time of non-operation, at room temperature, moisture in the air is adsorbed. Therefore, the quartz oscillator is oscillated and its oscillation frequency is measured. Since the oscillation frequency at this time changes according to the mass of adsorbed water due to the mass addition effect, the amount of adsorbed water can be obtained from the frequency change amount.
【００１４】具体例を挙げると、例えば40%相対湿度の
空気中に24時間放置したとき(実線)と96時間放置した時
(点線)とでは、抵抗値に大きな差がみられるようになる
(図２)。従って、このときの水分吸着量と抵抗値変化と
の関係を予め求めておけば、ガス検出に際して、水晶振
動子の共振周波数変化から吸着水分量を測定することに
より、ガス検出時の抵抗値変化の内、水分吸着によるも
のと被検ガスとの反応によるものとを分けることが可能
となる。このようにして、抵抗の測定値から水分吸着に
よる変化分を差し引いた値を補正抵抗値として求めるこ
とができる。To be specific, for example, when left for 24 hours in air at 40% relative humidity (solid line) and when left for 96 hours
(Dotted line) shows a large difference in resistance value
(FIG. 2). Therefore, if the relationship between the amount of absorbed moisture and the change in resistance at this time is determined in advance, the change in resistance during gas detection can be determined by measuring the amount of absorbed moisture from the change in the resonance frequency of the quartz oscillator during gas detection. Of these, it is possible to distinguish between those due to moisture adsorption and those due to the reaction with the test gas. In this way, a value obtained by subtracting the change due to moisture adsorption from the measured resistance value can be obtained as the corrected resistance value.
【００１５】[0015]
【発明の効果】本発明に係るガスセンサは、飽和または
不飽和の炭化水素類、アルコ-ル類、一酸化炭素、水素
などの還元性ガス定量に用いられるが、その際ガス感応
膜たる金属酸化物半導体薄膜への吸着水分量を水晶振動
子の発振周波数の変化として検出することにより、ガス
感応膜の初期抵抗値の変動分を補正することが可能とな
り、ひいては測定再現性の向上が図られることになる。The gas sensor according to the present invention is used for the determination of reducing gases such as saturated or unsaturated hydrocarbons, alcohols, carbon monoxide, hydrogen and the like. By detecting the amount of water adsorbed on the semiconductor thin film as a change in the oscillation frequency of the crystal oscillator, it is possible to correct the variation in the initial resistance value of the gas-sensitive film, and thereby improve measurement reproducibility. Will be.
【００１６】[0016]
【実施例】次に、実施例について本発明を説明する。Next, the present invention will be described by way of examples.
【００１７】実施例 水晶振動子(ORION製品ATカット、10.170MHz)の表裏両面
に、プラズマCVD法により、SiO2絶縁性薄膜(膜厚約１μ
m)を形成させた。その一方の面側に、真空蒸着法により
Au(膜厚5000Å)／Cr(膜厚1000Å)積層電極を１組の対向
電極として形成させ、更にこれらの対向電極を覆うよう
に、プラズマCVD法により、SnO2半導体薄膜(膜厚3000
Å)を形成させた。また、他方の面側には、真空蒸着法
により、白金製加熱用薄膜ヒータ(膜厚約１μm)を形成
させた。EXAMPLE An SiO 2 insulating thin film (about 1 μm thick) was formed on both front and back surfaces of a crystal unit (ORION product AT cut, 10.170 MHz) by plasma CVD.
m) was formed. On one surface side, by vacuum evaporation method
An Au (thickness of 5000 mm) / Cr (thickness of 1000 mm) stacked electrode is formed as a set of counter electrodes, and a SnO 2 semiconductor thin film (thickness of 3000 mm) is formed by plasma CVD so as to cover these counter electrodes.
Å) was formed. On the other surface side, a platinum heating thin film heater (thickness: about 1 μm) was formed by a vacuum evaporation method.
【００１８】このようにして作製されたガスセンサを用
い、これを40%相対湿度の空気中に24時間放置したもの
と96時間放置したものとの抵抗値変化を測定し、補正抵
抗値を求めると、共に図３の曲線に示されるような結果
が得られた。このことは、このガスセンサによる補正に
より、放置雰囲気の湿度による影響が軽減されることを
示している。Using the gas sensor manufactured in this manner, the resistance change between the sensor left for 24 hours and the sensor left for 96 hours in the air at 40% relative humidity is measured, and the corrected resistance is calculated. , Both obtained the results shown in the curve of FIG. This indicates that the correction by the gas sensor reduces the influence of the humidity of the neglected atmosphere.
【図１】本発明に係るガスセンサの一態様の表面図
(a)、そのI-I線断面図(b)および裏面図(c)である。FIG. 1 is a surface view of one embodiment of a gas sensor according to the present invention.
(a), its II sectional drawing (b) and back view (c).
【図２】40%相対湿度の空気中に24時間(実線)または96
時間(点線)放置したときのメタンガス濃度と抵抗値との
関係を示すグラフである。Figure 2: 24 hours (solid line) or 96 hours in air at 40% relative humidity
5 is a graph showing a relationship between a methane gas concentration and a resistance value when left for a time (dotted line).
【図３】40%相対湿度の空気中に24時間または96時間放
置したときのメタンガス濃度と補正抵抗値との関係を示
すグラフである。FIG. 3 is a graph showing a relationship between a methane gas concentration and a corrected resistance value when left in air at 40% relative humidity for 24 hours or 96 hours.
【符号の説明】 １ 水晶振動子 ４ 絶縁性薄膜 ５ 対向電極 ７ ガス感応膜 ８ 加熱用薄膜ヒータ[Description of Signs] 1 Quartz crystal oscillator 4 Insulating thin film 5 Counter electrode 7 Gas sensitive film 8 Thin film heater for heating
───────────────────────────────────────────────────── フロントページの続き (58)調査した分野(Int.Cl.7，ＤＢ名) G01N 27/12 G01N 5/02 ──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. 7 , DB name) G01N 27/12 G01N 5/02
Claims (1)
方の面側に１組の対向電極および金属酸化物半導体ガス
感応膜を順次形成させ、他方の面側に加熱用薄膜ヒータ
を形成させてなるガスセンサ。1. A set of a counter electrode and a metal oxide semiconductor gas-sensitive film are sequentially formed on one surface of a quartz oscillator covered with an insulating thin film, and a heating thin film heater is formed on the other surface. A gas sensor.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP11076692A JP3166290B2 (en) | 1992-04-03 | 1992-04-03 | Gas sensor |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP11076692A JP3166290B2 (en) | 1992-04-03 | 1992-04-03 | Gas sensor |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH05281177A JPH05281177A (en) | 1993-10-29 |
| JP3166290B2 true JP3166290B2 (en) | 2001-05-14 |
Family
ID=14544041
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP11076692A Expired - Fee Related JP3166290B2 (en) | 1992-04-03 | 1992-04-03 | Gas sensor |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP3166290B2 (en) |
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| KR102049998B1 (en) | 2017-04-03 | 2019-11-28 | 국동훈 | Object Grasping Device, and Manufacturing Method for Object Grasping Device |
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|---|---|---|---|---|
| CA2549837A1 (en) * | 2003-11-13 | 2005-06-09 | Technische Universitat Clausthal | Sensor, sensor arrangement, and measuring method |
| WO2006006587A1 (en) * | 2004-07-12 | 2006-01-19 | Niigata University | Gas detection method and gas sensor |
| JP2009281786A (en) * | 2008-05-20 | 2009-12-03 | Nippon Dempa Kogyo Co Ltd | Piezoelectric sensor and sensing device |
| JP4685962B2 (en) * | 2010-06-02 | 2011-05-18 | 日本電波工業株式会社 | Piezoelectric sensor and sensing device |
| KR101355371B1 (en) * | 2012-05-29 | 2014-01-27 | 포항공과대학교 산학협력단 | Quartz Crystal Microbalance Sensors for Simultaneously Measurement of Electrical Properties and Mass Changes |
| JP5935706B2 (en) * | 2013-01-28 | 2016-06-15 | 富士通株式会社 | Environmental measuring apparatus and environmental measuring method |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR101862653B1 (en) | 2016-08-12 | 2018-05-31 | 최문수 | Holder for vehicle with variable spacer |
| KR102049998B1 (en) | 2017-04-03 | 2019-11-28 | 국동훈 | Object Grasping Device, and Manufacturing Method for Object Grasping Device |
Also Published As
| Publication number | Publication date |
|---|---|
| JPH05281177A (en) | 1993-10-29 |
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