JP3846313B2 - Gas sensor - Google Patents

Description

【００３７】
この（表１）から明らかなように、本発明１〜３は、白金のヒータ主薄膜１０と、白金薄膜より膜厚を薄くしてその下部に配置されたチタンもしくはジルコニウムもしくはクロムより選択した少なくとも１種材料を主成分とする金属ヒータ補助微薄膜１１とで構成された発熱体薄膜７であり、優れた耐久性を持つことがわかる。この優れた耐久性は、次の理由による。白金は展性および耐熱性に優れた材料で、チタンやジルコニウムさらにクロムは接合性に優れ良好な展性を持つ材料である。これらは積層されると良好に接合して展性を持つ発熱体薄膜７が得られ、この発熱体薄膜７は、絶縁性耐熱基板６や耐熱絶縁性薄膜８にも良好に接合する。通電すると、発熱体薄膜７は短時間に動作温度まで温度上昇して熱膨張し、その上下に配置された絶縁性耐熱基板６や耐熱絶縁性薄膜８も同時に温度上昇して熱膨張するが、絶縁性耐熱基板６や耐熱絶縁性薄膜８の熱膨張に、積層膜とした発熱体薄膜７は良好に追随して剥離や断線を生じることがないためである。
【００３８】
また、本発明１〜３は、その上部の耐熱ガス感受膜９が、耐熱絶縁性薄膜８の薄膜を介して発熱体薄膜７で発生した熱が効果的に伝達されるので、１０ミリ秒の通電で動作状態となって一酸化炭素ガス濃度が検知可能となり、その電力量は１４mＷ秒であった。また、硼珪酸系硝子や珪酸アルミナ系ガラスセラミックを絶縁性耐熱基板６や耐熱絶縁性薄膜８として用いたガスセンサでも、上記と同様に優れた耐久性を得られた。なお、ヒータ主薄膜１０は、少量のロジウムやパラジウム等が２０重量％以下で混合された白金の８０重量％以上を主成分とする白金系金属が有効であり、その膜厚は０．３〜１．０μmが適正であり、特に０．４〜０．７μmは最適であった。一方、チタンもしくはジルコニウムもしくはクロムからなる金属ヒータ補助微薄膜１１の膜厚は、５００〜２０Åが適正であり、特に３００〜３０Åは最適であった。
【００３９】
次に、絶縁性耐熱基板６および耐熱絶縁性薄膜８の材質を変化させ、本発明の効果の判定を行った。検討に使用した発熱体薄膜７は、下部に配置したクロムからなる金属ヒータ補助微薄膜１１と、上部に配置した白金からなるヒータ主薄膜１０の積層膜である。他は、前述と同じであり、耐熱絶縁性薄膜８の上部に前述の固体電解質型の耐熱ガス感受膜９を積層し、ガスセンサとしている。
【００４０】
本発明１の絶縁性耐熱基板６および耐熱絶縁性薄膜８は、石英硝子であり、転移温度は１０７５℃、熱膨張係数は０．５×１０^-6（１/deg）である。
【００４１】
本発明２の絶縁性耐熱基板６および耐熱絶縁性薄膜８は、珪酸９６％で硼酸４％の硼珪酸硝子であり、転移温度は８９０℃、熱膨張係数は０．８×１０^-6で（１/deg）である。
【００４２】
本発明３の絶縁性耐熱基板６および耐熱絶縁性薄膜８は、珪酸アルミナ系ガラスセラミック（結晶化硝子とも称する）である。その組成は、珪酸が６４％で、アルミナが１５％で、酸化チタンや酸化亜鉛等の金属酸化物が２１％の珪酸アルミナ系ガラスセラミックであり、転移温度は８８０℃、熱膨張係数は３．１×１０^-6で（１/deg）である。
【００４３】
従来例の絶縁性耐熱基板６および耐熱絶縁性薄膜８は、ソーダ石灰硝子であり、転移温度は６２０℃、熱膨張係数は５．２×１０^-6で（１/deg）である。
【００４４】
比較例は、絶縁性耐熱基板６をシリコンウエハーの表面に酸化珪素と窒化珪素とからなる絶縁微薄膜を形成した基板とし、耐熱絶縁性薄膜８を酸化珪素とアルミナを積層した。
【００４５】
その結果を（表２）に示す。発熱体薄膜７の抵抗変化率は、発熱体薄膜７に直流電圧電流を印加して動作温度４００℃まで１０ミリ秒で到達したのち、電源を切るＯＮ―ＯＦＦ試験を１０万回行った際の、実験前後の抵抗値より算出した値である。
【００４６】
【表２】

【００４７】
本発明１〜３の絶縁性耐熱基板６および耐熱絶縁性薄膜８は、石英硝子、硼珪酸系硝子、珪酸アルミナ系ガラスセラミックであり、これを用いたガスセンサの発熱体薄膜７は優れた耐久性を持つことがわかる。この優れた耐久性は、次の理由による。発熱体薄膜７を構成するクロムは、接合性に優れ良好な展性を持つ材料であり、これら材質の絶縁性耐熱基板６や耐熱絶縁性薄膜８にも良好に接合する。通電すると、発熱体薄膜７は短時間に動作温度まで温度上昇して熱膨張し、その上下に配置された絶縁性耐熱基板６や耐熱絶縁性薄膜８も同時に温度上昇して熱膨張するが、絶縁性耐熱基板６や耐熱絶縁性薄膜８の熱膨張に、この積層膜の発熱体薄膜７は良好に追随して剥離や断線を生じることがないためである。
【００４８】
また、本発明１〜３は、その上部の耐熱ガス感受膜９が、耐熱絶縁性薄膜８の薄膜を介して発熱体薄膜７で発生した熱が効果的に伝達されるので、１０ミリ秒の通電で動作状態となって一酸化炭素ガス濃度が検知可能となり、その電力量は１５〜２５mＷ秒と小さかった。なお、比較例として用いたシリコンウエハー系の基板は、耐熱性がせいぜい３００〜４００℃前後であり、センサ製造における６００℃の熱付与により、その表面に密着力の乏しい新たな酸化物を著しく生成させたため、パルス通電中に発熱体薄膜が剥離して断線した。
【００４９】
この構成の実施例において、発熱体薄膜７は、白金のヒータ主薄膜１０と、このヒータ主薄膜１０より薄くしてその下部に配置されたチタンもしくはジルコニウムの金属ヒータ補助微薄膜１１とで構成しても、上記と同様に優れた耐久性を得られた。さらに、絶縁性耐熱基板６は、アルミナやフォルステライトなどのセラミック板の上部に、石英硝子もしくは硼珪酸系硝子もしくは珪酸アルミナ系ガラスセラミックからなる硝子質の厚膜層（３０〜１００μm膜厚）を形成した基板を用いて良い。この絶縁性耐熱基板６と同じ硝子質材料の耐熱絶縁性薄膜８を用いたガスセンサは、その発熱体薄膜７が優れた耐久性を持ち、その電力量も１７〜２７mＷ秒と小さかった。
【００５０】
耐熱ガス感受膜９は、酸化スズや酸化鉄さらに酸化タングステンなどの金属酸化物半導体膜、固体電解質型が有効である。耐熱ガス感受膜９が固体電解質型の場合、酸素イオン導電性固体電解質薄膜１２は、酸化イットリウム３モル％と酸化ジルコニウム９７モル％の部分安定化ジルコニア体に代表される各種ジルコニア系酸素イオン導電性固体電解質やセリア系酸素イオン導電性固体電解質のスパッタ膜、蒸着膜、ゾルゲル膜が有効である。第１電極薄膜１３および第２電極薄膜１４は、白金などの貴金属もしくは酸素イオン導電性金属酸化物の通気性印刷膜およびスパッタ膜もしくは蒸着膜が有効である。酸化触媒膜１５は、結晶化硝子などの無機接着材に白金等の貴金属もしくは金属酸化物を混合させた通気性多孔質膜が有効である。
【００５１】
（実施例２）
実施例２は、絶縁性耐熱基板６および耐熱絶縁性薄膜８に用いる硝子の物性について検討した。硝子は、熱伝導率が非常に小さいので絶縁性耐熱基板６に使用すると、発熱体薄膜７で発生した熱が絶縁性耐熱基板６に僅かしか伝達されず、その多くが耐熱ガス感受膜９に伝達されので、動作温度４００℃まで少ない電力で到達でき、消費電力量を低減したガスセンサが実現できる利点が有る。また、硝子は、その材料組成の制約より熱膨張係数１０×１０^-6（１/deg）が現在の技術ではその製造可能な上限値であり、大部分の硝子はこの値以下の熱膨張係数を有する。一方、発熱体薄膜７は白金を主成分とするため、その熱膨張係数は１０×１０^-6（１/deg）である。発熱体薄膜７は発熱すると熱膨張するが、この発熱体薄膜７より熱膨張係数が小さい硝子からなる絶縁性耐熱基板６および耐熱絶縁性薄膜８は、僅かしか熱膨張せず、この結果、圧縮応力がかかるが、硝子には圧縮応力に非常に強い性質が有るので、これら材料は熱膨張に良好に追随して破損しない利点も有る。そこで、優れた耐久特性の発熱体薄膜７が得られる絶縁性耐熱基板６および耐熱絶縁性薄膜８の硝子組成について検討した。
【００５２】
検討は、珪酸の濃度を異ならせた絶縁性耐熱基板６および耐熱絶縁性薄膜８を用い、本発明の効果の判定を行った。検討に使用した発熱体薄膜７は、下部に配置したクロムからなる金属ヒータ補助微薄膜１１と、上部に配置した白金からなるヒータ主薄膜１０の積層膜である。他は、前述と同じであり、耐熱絶縁性薄膜８の上部に前述の固体電解質型の耐熱ガス感受膜９を積層し、ガスセンサとしている。
【００５３】
本発明１の絶縁性耐熱基板６および耐熱絶縁性薄膜８は、珪酸が９９．９９％の石英硝子であり、転移温度は１０７５℃、熱膨張係数は０．５×１０^-6（１/deg）である。
【００５４】
本発明２の絶縁性耐熱基板６および耐熱絶縁性薄膜８は、珪酸が９６％で硼酸が４％の硼珪酸硝子であり、転移温度は８９０℃、熱膨張係数は０．８×１０^-6で（１/deg）である。
【００５５】
本発明３の絶縁性耐熱基板６および耐熱絶縁性薄膜８は、珪酸が９０％で硼酸が４％で酸化カルシウム等の金属酸化物が６％の硼珪酸硝子であり、転移温度は８５０℃、熱膨張係数は１．６×１０^-6で（１/deg）である。
【００５６】
比較例の絶縁性耐熱基板６および耐熱絶縁性薄膜８は、珪酸が８７％で、硼酸が５％で、酸化カルシウム等の金属酸化物が８％の硼珪酸硝子であり、転移温度は７８０℃、熱膨張係数は２．６×１０^-6で（１/deg）である。
【００５７】
図２は、絶縁性耐熱基板６および耐熱絶縁性薄膜８として用いる硝子に含有される珪酸の濃度と、発熱体薄膜の抵抗変化率の関係を測定したものである。発熱体薄膜７の抵抗変化率は、実装ケースの端子に直流電圧電流を印加して発熱体薄膜１０を動作温度４００℃まで１０ミリ秒で上昇させたのち、電源を切るＯＮ―ＯＦＦ試験を１０万回行った際の抵抗変化率である。
【００５８】
図より明らかなように、発熱体薄膜７の抵抗変化率は、硝子に含有される珪酸の濃度が、９０％を境に変化することがわかる。本発明品は、硝子に含有される珪酸の濃度が９０％を越える絶縁性耐熱基板６および耐熱絶縁性薄膜８であるため、発熱体薄膜７は絶縁性耐熱基板６および耐熱絶縁性薄膜８に良好に接着し、優れた耐久特性が得られる。また、熱伝導率が非常に小さい硝子材の絶縁性耐熱基板６であるので、発熱体薄膜７で発生した熱は、絶縁性耐熱基板６に僅かしか伝達されず、その多くが耐熱ガス感受膜９に伝達される。そのため、動作温度まで少ない電力で到達でき、消費電力を一層低減したガスセンサが実現できた。またさらに、発熱体薄膜７は、消費電力が小さいので印加される電圧電流値が小さくなり、一層優れた耐久特性が得られる効果が生じた。
【００５９】
一方、硝子に含有される珪酸の濃度が９０％未満の絶縁性耐熱基板６および耐熱絶縁性薄膜８は、発熱体薄膜７が絶縁性耐熱基板６および耐熱絶縁性薄膜８に良好に接着しないため、幾分の耐久性低下が観察された。これは、珪酸の濃度が少ないため、耐久性の優れたヒータ膜を得るに最適な硝子組成が実現できていないためである。
【００６０】
なお、発熱体薄膜７として、白金系のヒータ主薄膜１０とその下部に少なくとも配置されたチタンやジルコニウムやクロムの金属ヒータ補助微薄膜１１を積層した構成を用いても、同様な効果が得られた。さらに、絶縁性耐熱基板６は、アルミナやフォルステライトなどのセラミック板の上部に、石英硝子もしくは硼珪酸系硝子からなる硝子質の厚膜層（３０〜１００μm膜厚）を形成した基板を用いて良い。この絶縁性耐熱基板６と同じ硝子質材料の耐熱絶縁性薄膜８を用いたガスセンサは、その発熱体薄膜７が優れた耐久性を持ち、その電力量も１７〜２２mＷ秒と小さかった。
【００６１】
（実施例３）
実施例３は、絶縁性耐熱基板６および耐熱絶縁性薄膜８に用いる珪酸アルミナ系ガラスセラミックの材料組成について検討した。珪酸アルミナ系ガラスセラミックは、熱伝導率が小さいので絶縁性耐熱基板６に使用すると、発熱体薄膜７で発生した熱が絶縁性耐熱基板６に僅かしか伝達されず、その多くが耐熱ガス感受膜９に伝達されので、動作温度４００℃まで少ない電力で到達でき、消費電力量を低減したガスセンサが実現できる利点が有る。また、珪酸アルミナ系ガラスセラミックは、その材料組成の制約より熱膨張係数１０×１０^-6（１/deg）が現在の技術ではその製造可能な上限値であり、大部分の珪酸アルミナ系ガラスセラミックはこの値以下の熱膨張係数を有する。一方、発熱体薄膜７は白金を主成分とするため、その熱膨張係数は１０×１０^-6（１/deg）である。発熱体薄膜７は発熱すると熱膨張するが、この発熱体薄膜７より熱膨張係数が小さい珪酸アルミナ系ガラスセラミックからなる絶縁性耐熱基板６および耐熱絶縁性薄膜８は、僅かしか熱膨張せず、この結果、圧縮応力がかかるが、珪酸アルミナ系ガラスセラミックには圧縮応力に強い性質が有るので、これら材料は熱膨張に良好に追随して破損しない利点も有る。そこで、この優れた効果の有る珪酸アルミナ系ガラスセラミックを実現するための組成について検討した。
【００６２】
検討は、珪酸およびアルミナの濃度を異ならせた絶縁性耐熱基板６および耐熱絶縁性薄膜８を用いて行った。検討に使用した発熱体薄膜７は、下部に配置したクロムからなる金属ヒータ補助微薄膜１１と、上部に配置した白金からなるヒータ主薄膜１０の積層膜である。他は、前述と同じであり、耐熱絶縁性薄膜８の上部に前述の固体電解質型の耐熱ガス感受膜９を積層し、ガスセンサとしている。検討に先だち、珪酸アルミナ系ガラスセラミックが良好な硝子物性を得るための、珪酸の含有量上限値と下限値、アルミナの含有量上限値と下限値を求めた。その結果、珪酸の含有量上限が８０％でアルミナの含有量上限が２０％であり、珪酸の含有量下限は６０％でアルミナの含有量下限が５％であることが判明した。また、この組成にすると、熱膨張係数が約２〜４×１０^-6（１/deg）と小さいので熱衝撃に優れるとともに、その転移温度も約８００℃以上と耐熱性にも優れることも判明した。そこで、検討はこの組成領域にて行なった。
【００６３】
本発明１の絶縁性耐熱基板６および耐熱絶縁性薄膜８は、珪酸が８０％でアルミナが２０％の珪酸アルミナ系ガラスセラミックであり、転移温度は９２０℃、熱膨張係数は１．８×１０^-6（１/deg）である。
【００６４】
本発明２の絶縁性耐熱基板６および耐熱絶縁性薄膜８は、珪酸が８０％でアルミナが５％で酸化チタン等の金属酸化物が１５％の珪酸アルミナ系ガラスセラミックであり、転移温度は９２０℃、熱膨張係数は３．６×１０^-6で（１/deg）である。
【００６５】
本発明３の絶縁性耐熱基板６および耐熱絶縁性薄膜８は、珪酸が６０％でアルミナが２０％で酸化チタンや酸化亜鉛等の金属酸化物が２０％の珪酸アルミナ系ガラスセラミックであり、転移温度は８８０℃、熱膨張係数は３．１×１０^-6で（１/deg）である。
【００６６】
本発明４の絶縁性耐熱基板６および耐熱絶縁性薄膜８は、珪酸が６０％で、アルミナが５％で、酸化チタン等の金属酸化物が３５％の珪酸アルミナ系ガラスセラミックであり、転移温度は８７０℃、熱膨張係数は３．６×１０^-6で（１/deg）である。
【００６７】
（表３）は、珪酸およびアルミナの濃度が異なる珪酸アルミナ系ガラスセラミックの絶縁性耐熱基板６および耐熱絶縁性薄膜８について、発熱体薄膜７の抵抗変化率を測定したものである。発熱体薄膜７の抵抗変化率は、実装ケースの端子に直流電圧電流を印加して発熱体薄膜７を動作温度４００℃まで１０ミリ秒で上昇させたのち、電源を切るＯＮ―ＯＦＦ試験を１０万回行った際の抵抗変化率である。
【００６８】
【表３】

【００６９】
（表３）より明らかなように、発熱体薄膜７の抵抗変化率は、珪酸を６０〜８０％でアルミナを５〜２０％を含有する珪酸アルミナ系ガラスセラミックとすることで、優れた耐久特性が得られることがわかる。
【００７０】
なお、発熱体薄膜７として、白金系のヒータ主薄膜１０とその下部に少なくとも配置されたチタンやジルコニウムやクロムの金属ヒータ補助微薄膜１１を積層した構成を用いても、同様な効果が得られた。またさらに、絶縁性耐熱基板６は、アルミナやフォルステライトなどのセラミック板の上部に、この組成の珪酸アルミナ系ガラスセラミックからなる硝子質の厚膜層（３０〜１００μm膜厚）を形成した基板を用いて良い。この絶縁性耐熱基板６と同じ硝子質材料の耐熱絶縁性薄膜８を用いたガスセンサは、その発熱体薄膜７が優れた耐久性を持ち、その電力量も２４〜２７mＷ秒と小さかった。
【００７１】
（実施例４）
前述の実施例１に記載したように、絶縁性耐熱基板６に珪酸１００％の石英硝子を用いると優れた耐久特性を持つことがわかる。そこで、実施例４は、絶縁性耐熱基板６に用いる石英硝子の組成について検討した。石英硝子は、珪酸（ＳｉＯ₂）を主成分とする硝子であるが、水酸基（ＯＨ基と称す）を微量含有する。そこで、水酸基の含有量を異ならした石英硝子の絶縁性耐熱基板６を用い、その影響の解析を行った。
【００７２】
検討は、水酸基の含有量を異ならした石英硝子の絶縁性耐熱基板６を用いその上部に、チタンからなる金属ヒータ補助微薄膜１１と白金からなるヒータ主薄膜１０を順々に積層して発熱体薄膜７とし、石英硝子からなる耐熱絶縁性薄膜８をさらに積層して焼成し、最後に、前述の固体電解質型の耐熱ガス感受膜９を積層したガスセンサで行った。
【００７３】
本発明１の絶縁性耐熱基板６は、０．０１wt％の水酸基を含有する石英硝子であり、その安全使用温度は１０５０℃である。
【００７４】
本発明２の絶縁性耐熱基板６は、０．０４wt％の水酸基を含有する石英硝子であり、その安全使用温度は１０００℃である。
【００７５】
本発明３の絶縁性耐熱基板６は、０．１２wt％の水酸基を含有する石英硝子であり、その安全使用温度は９５０℃である。
【００７６】
本発明４の絶縁性耐熱基板６は、０．２０wt％の水酸基を含有する石英硝子であり、その安全使用温度は９００℃である。
【００７７】
比較例２の絶縁性耐熱基板は、０．２５wt％の水酸基を含有する石英硝子であり、その安全使用温度は８００℃である。
【００７８】
図３は、石英硝子の水酸基の含有量を変化させ、発熱体薄膜７の抵抗変化率を測定したものであり、石英硝子の水酸基含有量と抵抗変化率の相関特性である。発熱体薄膜７の抵抗変化率は、実装ケースの端子に直流電圧電流を印加して発熱体薄膜７を動作温度４００℃まで２ミリ秒で到達させ、そののち８ミリ秒保持させ、電源を切るＯＮ―ＯＦＦ試験を１０万回行った際の抵抗変化率である。
【００７９】
ヒータの抵抗変化率は、石英硝子に含まれる水酸基が０．２０wt％を境に変化することがわかる。本発明品は、石英硝子に含まれる水酸基が０．２０wt％以下であるため、チタンの金属ヒータ補助微薄膜１１が石英硝子に良好に接着して一層優れた耐久特性が得られる。また、熱膨張係数が非常に小さい石英硝子を絶縁性耐熱基板６として使用しているので、発熱体薄膜７の発熱に起因する絶縁性耐熱基板６の熱膨張が小さくなり、これにともない発熱体薄膜７は絶縁性耐熱基板６に一層良好に接着して優れた耐久特性が得られる。さらに、熱伝導率が非常に小さい石英硝子の絶縁性耐熱基板６であるので、発熱体薄膜７で発生した熱は、絶縁性耐熱基板６に僅かしか伝達されず、その多くが耐熱ガス感受膜９に伝達される。そのため、動作温度まで少ない電力で到達でき、消費電力を一層低減したガスセンサが実現できる。また、発熱体薄膜７は、消費電力が小さいので印加される電圧電流値が小さくなり、一層優れた耐久特性が得られる効果が生じている。これに加え、石英硝子に含まれる水酸基が０．２０wt％以下であると、その上部に積層される耐熱絶縁性薄膜８の形成に、高温処理を施こすことができ、欠陥の少ない耐熱絶縁性薄膜８が生成されて優れた絶縁特性が確保できる。そのため、酸素イオン導電性固体電解質薄膜１２は、発熱体薄膜７の影響を受けることが少なく、適正動作温度４００℃で良好な酸素イオン導電性を発揮する。この効果により、酸素イオン導電性固体電解質薄膜１２や電極薄膜１３そして酸化触媒膜１５で構成される耐熱ガス感受膜９は、その下部に配置した発熱体薄膜７により短時間で加熱されて動作状態となり、極めて短時間に暖気される利点もある。
【００８０】
一方、石英硝子に含まれる水酸基が０．２０wt％を超えると、チタンの金属ヒータ補助微薄膜１１が石英硝子に接着しにくくなり、幾分の耐久性低下が観察された。
【００８１】
なお、発熱体薄膜７として、白金のヒータ主薄膜１０に、その下部もしくは上部に少なくとも配置されたチタンやジルコニウムやクロムの金属ヒータ補助微薄膜１１を積層した構成を用いても、同様な効果が得られた。
【００８２】
（実施例５）
実施例５は、絶縁性耐熱基板６の中心線表面粗さについて検討した。検討は、中心線表面粗さを変化させた石英硝子の絶縁性耐熱基板６の上部に、チタンからなる金属ヒータ補助微薄膜１１と白金からなるヒータ主薄膜１０を順々に積層して発熱体薄膜７とし、石英硝子からなる耐熱絶縁性薄膜８をさらに積層して焼成し、最後に、前述の固体電解質型の耐熱ガス感受膜９を積層したガスセンサで行った。
【００８３】
中心線表面粗さを変化させた絶縁性耐熱基板６を用いたガスセンサのＯＮ―ＯＦＦ通電試験を行い、発熱体薄膜７の抵抗変化率を測定した。図４は、中心線表面粗さと抵抗変化率の相関特性を整理した特性図である。発熱体薄膜７の抵抗変化率は、実装ケースの端子に直流電圧電流を印加して発熱体薄膜７を動作温度４００℃まで１０ミリ秒で到達させ、そののち電源を切るＯＮ―ＯＦＦ試験を１０万回行った際の抵抗変化率である。
【００８４】
図４から明らかなように、抵抗変化率は、中心線表面粗さが０．０５μmおよび１μmを境に大きく変化することがわかる。本発明品は、中心線表面粗さが０．０５〜１μmであるため、焼成により発熱体薄膜７が絶縁性耐熱基板６に良好に接着して優れた耐久特性が得られる。
【００８５】
一方、中心線表面粗さが０．０５μm未満および１μmを超える絶縁性耐熱基板６にすると、焼成しても発熱体薄膜７が絶縁性耐熱基板６に良好に接着せず幾分の耐久性低下が観察される。
【００８６】
上記結果は、絶縁性耐熱基板６として、硼珪酸系硝子もしくは珪酸アルミナ系ガラスセラミックの板を用いても、発熱体薄膜７は優れた耐久特性が得られる。または、アルミナやフォルステライトなどのセラミック板の上部に、石英硝子もしくは硼珪酸系硝子もしくは珪酸アルミナ系ガラスセラミックからなる硝子質の厚膜層（３０〜１００μm膜厚）を形成した基板を用いても、発熱体薄膜７は優れた耐久特性が得られることは言うまでもない。さらに、発熱体薄膜７として、白金のヒータ主薄膜１０に、その下部に少なくとも配置されたチタンやジルコニウムやクロムの金属ヒータ補助微薄膜１１を積層した構成を用いても、同様な効果が得られた。
【００８７】
（実施例６）
実施例６は、耐熱絶縁性薄膜８を構成する材料について検討した。
【００８８】
石英硝子は、前述に記載した様に、この組成の発熱体薄膜７より熱膨張係数が小さい特性を本来的に有している。そのため、石英硝子は、耐熱絶縁性薄膜８として用いると、発熱体薄膜７が発熱して熱膨張しても、極めて僅かしか熱膨張せず、石英硝子の持つ圧縮応力に非常に強い性質とかみ合って、熱膨張に良好に追随し、（表２）に記載した様に、優れた耐久特性を有する発熱体薄膜７が実現できる。
【００８９】
なお、上記結果は、発熱体薄膜７として、白金のヒータ主薄膜１０の下部に配置されたチタンやジルコニウムさらにクロムの金属ヒータ補助微薄膜１１を積層した構成を用いても、同様な効果が得られた。
【００９０】
（実施例７）
実施例７は、耐熱ガス感受膜９として固体電解質型ガス感受膜を用いる際の、酸素イオン導電性固体電解質薄膜１２の熱伝導率について検討した。
【００９１】
検討は、石英硝子の絶縁性耐熱基板６の上部に、チタンからなる金属ヒータ補助微薄膜１１と白金のヒータ主薄膜１０を順々に積層して発熱体薄膜７とし、石英硝子からなる耐熱絶縁性薄膜８をさらに積層して焼成したのち最後に、後述の固体電解質型の耐熱ガス感受膜９を積層したガスセンサで行った。
【００９２】
固体電解質型の耐熱ガス感受膜９は、酸素イオン導電性固体電解質薄膜１２と、その同一面に形成された通気性の第１電極薄膜１３および第２電極薄膜１４と、第１電極薄膜１３に積層した酸化触媒膜１５で構成される。第１電極薄膜１３および第２電極薄膜１４さらに酸化触媒膜１５は、次の２種類の材料を用いて検討を行なった。
【００９３】
材料（I）は、第１電極薄膜１３および第２電極薄膜１４が、白金をスパッタして形成した通気性の薄膜であり、熱膨張係数が９×１０^-6（１/deg）で熱伝導率が６９．５W/mKの物性値を持つ。酸化触媒膜１５は、白金触媒をシリカアルミナ系結晶化硝子の表面に担持させた通気性の多孔質膜であり、熱伝導率が１W/mKの物性値を持つ。
【００９４】
材料（II）は、第１電極薄膜１３および第２電極薄膜１４が、ペロブスカイト型金属酸化物であるランタンコバルト系複合酸化物を酸化ビスマスの３％と混合して厚膜印刷した通気性の薄膜である。酸化触媒膜１５は、白金触媒をアルミナ系結合材の表面に担持させた通気性の多孔質膜であり、熱伝導率が２５W/mKの物性値を持つ。
【００９５】
比較例１の酸素イオン導電性固体電解質薄膜は、セリウム添加のイットリウム系部分安定化ジルコニアであり、結晶粒径を微細化しているのでその熱伝導率は０．８W/mK、組成はＺｒＯ₂９６モル％とＹ₂Ｏ₃３モル％とＣｅＯ₂１モル％の固溶体である。
【００９６】
本発明１の酸素イオン導電性固体電解質薄膜１２は、スカンジウム添加のセリア系ジルコニアであり、結晶粒径を微細化しているのでその熱伝導率は１．０W/mK、組成はＺｒＯ₂９０モル％とＣｅＯ₂１０モル％とＳｃ₂Ｏ₃１０モル％の固溶体である。
【００９７】
本発明２の酸素イオン導電性固体電解質薄膜１２は、イットリウム系部分安定化ジルコニアであり、熱伝導率は３．０W/mKとなり、その組成はＺｒＯ₂９７モル％とＹ₂Ｏ₃３モル％の固溶体である。
【００９８】
本発明３の酸素イオン導電性固体電解質薄膜１２は、イットリウム系安定化ジルコニアであり、熱伝導率は５．０W/mKとなり、その組成はＺｒＯ₂９２モル％とＹ₂Ｏ₃８モル％の固溶体である。
【００９９】
本発明４の酸素イオン導電性固体電解質薄膜１２は、イットリアをドープしたセリア系材料であり、熱伝導率は６．５W/mKとなり、その組成は（ＣｅＯ₂）_1-0.7（ＹＯ_1.5）_0.3である。
【０１００】
本発明５の酸素イオン導電性固体電解質薄膜１２は、サマリウムをドープしたセリア系材料であり、熱伝導率は７．０W/mKとなり、組成は（ＣｅＯ₂）_0.8（ＳmＯ_1.5）_0.2である。
【０１０１】
比較例２の絶縁性耐熱基板は、イットリウム系酸化ビスマスであり、その熱伝導率は１０W/mK、組成はＢｉ₂Ｏ₃９６モル％とＹ₂Ｏ₃４モル％の固溶体である。
【０１０２】
熱伝導率が異なる酸素イオン導電性固体電解質薄膜を用いたガスセンサのＯＮ―ＯＦＦ通電試験を行い、発熱体薄膜７の抵抗変化率を測定した。図５は、酸素イオン導電性固体電解質薄膜１２の熱伝導率と抵抗変化率の相関特性を整理した特性図である。発熱体薄膜７の抵抗変化率は、実装ケースの端子に直流電圧電流を印加して発熱体薄膜６を動作温度４００℃まで１０ミリ秒で昇温させたのち、電源を切るＯＮ―ＯＦＦ試験を１０万回行った際の抵抗変化率である。
【０１０３】
図５から明らかなように、抵抗変化率は、酸素イオン導電性固体電解質薄膜１２の熱伝導率が１W/mK未満および７W/mKを越えると、大きく変化することがわかる。本発明品は、熱伝導率が１〜７W/mKであるため、酸素イオン導電性固体電解質薄膜１２が良好に放熱し、発熱体薄膜７はその温度上昇が抑制され優れた耐久特性が得られる。
【０１０４】
一方、熱伝導率が１W/mK未満であると、酸素イオン導電性固体電解質薄膜１２からの放熱が悪いため、発熱体薄膜７はその温度が上昇し幾分の耐久性低下が観察された。また、熱伝導率が７W/mKを越えると、酸素イオン導電性固体電解質薄膜１２からの放熱が良いため、発熱体薄膜７はその温度を保持しようと大きな電流が流れて幾分の耐久性低下が観察された。
【０１０５】
なお、上記結果は、発熱体薄膜７として、白金のヒータ主薄膜１０の下部に配置されたチタンやジルコニウムさらにクロムの金属ヒータ補助微薄膜１１を積層した構成を用いても、同様な効果が得られた。
【０１０６】
（実施例８）
実施例８は、耐熱ガス感受膜９として固体電解質型ガス感受膜を用いる際における、酸化触媒膜１５の熱伝導率について検討した。
【０１０７】
検討は、石英硝子の絶縁性耐熱基板６の上部に、チタンからなる金属ヒータ補助微薄膜１１と白金のヒータ主薄膜１０を順々に積層して発熱体薄膜７とし、石英硝子からなる耐熱絶縁性薄膜８をさらに積層して焼成したのち最後に、後述の固体電解質型の耐熱ガス感受膜９を積層したガスセンサで行った。固体電解質型の耐熱ガス感受膜９は、酸素イオン導電性固体電解質薄膜１２と、その同一面に形成された通気性の第１電極薄膜１３および第２電極薄膜１４と、第１電極薄膜１３に積層した酸化触媒膜１５で構成される。酸素イオン導電性固体電解質薄膜１２と、第１電極薄膜１３および第２電極薄膜１４は、次の２種類の材料を用いて検討を行なった。
【０１０８】
材料（I）は、酸素イオン導電性固体電解質薄膜１２が、イットリウム系安定化ジルコニアであり、熱伝導率は５W/mKで組成はＺｒＯ₂９２モル％とＹ₂Ｏ₃８モル％の固溶体である。第１電極薄膜１３および第２電極薄膜１４が、白金をスパッタして形成した通気性の薄膜であり、熱膨張係数が９×１０^-6（１/deg）で熱伝導率が６９．５W/mKの物性値を持つ。
【０１０９】
材料（II）は、酸素イオン導電性固体電解質薄膜１２が、サマリウムをドープしたセリア系材料であり、熱伝導率は７．０W/mKで組成は（ＣｅＯ₂）_0.8（ＳmＯ_1.5）_0.2である。第１電極薄膜１３および第２電極薄膜１４が、ペロブスカイト型金属酸化物であるランタンコバルト系複合酸化物を酸化ビスマスの３％と混合して厚膜印刷した通気性の薄膜である。
【０１１０】
比較例１の酸化触媒膜は、白金触媒をコージライト系結晶化硝子の表面に担持させた通気性の多孔質膜であり、熱伝導率が０．７W/mKの物性値を持つ。
【０１１１】
本発明１の酸化触媒膜１５は、白金ロジウム触媒をシリカアルミナ系結晶化硝子の表面に担持させた通気性の多孔質膜であり、熱伝導率が１．０W/mKの物性値を持つ。
【０１１２】
本発明２の酸化触媒膜１５は、白金パラジウム触媒をシリカアルミナ硼素系結晶化硝子の表面に担持させた通気性の多孔質膜であり、熱伝導率が２．５W/mKの物性値を持つ。
【０１１３】
本発明３の酸化触媒膜１５は、白金触媒をアルミナジルコニア系結合材の表面に担持させた通気性の多孔質膜であり、熱伝導率が７．０W/mKの物性値を持つ。
【０１１４】
本発明４の酸化触媒膜１５は、白金触媒をアルミナシリカ系結合材の表面に担持させた通気性の多孔質膜であり、熱伝導率が１２．５W/mKの物性値を持つ。
【０１１５】
本発明５の酸化触媒膜１５は、白金触媒をアルミナ系結合材の表面に担持させた通気性の多孔質膜であり、熱伝導率が２５W/mKの物性値を持つ。
【０１１６】
比較例２の酸化触媒膜１５は、白金触媒を炭化珪素系結合材の表面に担持させた通気性の多孔質膜であり、熱伝導率が４０W/mKの物性値を持つ。
【０１１７】
熱伝導率が異なる酸化触媒膜を用いたガスセンサのＯＮ―ＯＦＦ通電試験を行い、発熱体薄膜７の抵抗変化率を測定した。図６は、酸化触媒膜１５の熱伝導率と抵抗変化率の相関特性を整理した特性図である。発熱体薄膜７の抵抗変化率は、実装ケースの端子に直流電圧電流を印加して発熱体薄膜７を動作温度４００℃まで１０ミリ秒で到達させたのち、電源を切るＯＮ―ＯＦＦ試験を１０万回行った際の抵抗変化率である。
【０１１８】
図６から明らかなように、抵抗変化率は、酸化触媒膜１５の熱伝導率が１W/mK未満および２５W/mKを越えると、大きく変化することがわかる。本発明品は、熱伝導率が１〜２５W/mKであるため、酸化触媒膜１５が良好に放熱し、発熱体薄膜７はその温度上昇が抑制され優れた耐久特性が得られる。
【０１１９】
一方、熱伝導率が１W/mK未満であると、酸化触媒膜１５からの放熱が悪いため、発熱体薄膜７はその温度が上昇し幾分の耐久性低下が観察される。一方、熱伝導率が２５W/mKを越えると、酸化触媒膜１５からの放熱が良いため、発熱体薄膜７はその温度を保持しようと大きな電流が流れて幾分の耐久性低下が観察される。
【０１２０】
なお、上記結果は、発熱体薄膜７として、白金のヒータ主薄膜１０の下部に配置されたチタンやジルコニウムさらにクロムの金属ヒータ補助微薄膜１１を積層した構成を用いても、同様な効果が得られた。
【０１２１】
【発明の効果】
以上のように、本発明のガスセンサは、絶縁性耐熱基板の硝子質および耐熱絶縁性薄膜が、珪酸を主成分とする珪酸硝子、硼珪酸系硝子、または珪酸アルミナ系ガラスセラミックであるので、８００℃以上の耐熱性を有する材料となる。そのため、ガスセンサを構成する発熱体薄膜および耐熱ガス感受膜は、例えば８００℃以上といった高温焼成が可能となり、このことで焼成に関する制約が減少するので、簡単な製膜技術と品質管理技術を用いて製造できる。
【０１２２】
一方、チタン、ジルコニウム、またはクロムの金属ヒータ補助微薄膜は、接合性と展性に優れた材料であり、高温で焼成すると、ヒータ主材料である白金や絶縁性耐熱基板に良好に接合して展性を持つ発熱体薄膜が得られる。省電力実現のため大電力を短時間に印加すると、発熱体薄膜は短時間に動作温度まで温度上昇して熱膨張し、その上下に配置された絶縁性耐熱基板や耐熱絶縁性薄膜も同時に温度上昇して熱膨張するが、この積層型の発熱体薄膜は、この熱膨張に良好に追随して剥離を生じることがなく、優れた耐熱衝撃性を示し抵抗変化が発生しない。
【０１２３】
積層された耐熱ガス感受膜は、耐熱絶縁性薄膜の薄膜を介して発熱体薄膜で発生した熱が効果的に伝達され、短時間で動作状態となりガス濃度が検知可能となる。その際、絶縁性耐熱基板の表面に存在する硝子質は熱伝導率が非常に小さい材料であるので、発熱体薄膜で発生した熱は、絶縁性耐熱基板に僅かしか伝達されず、その多くが耐熱ガス感受膜に伝達される。そのため、動作温度まで少ない消費電力量で到達でき、消費電力量を低減したガスセンサが実現できる。
【０１２４】
さらに、発熱体薄膜は、消費電力が小さいので印加される電圧電流値が小さく、優れた耐久特性が得られる。また、絶縁性耐熱基板の硝子質および耐熱絶縁性薄膜は、応力に非常に強い性質を有する硝子材であるので発熱に起因する熱膨張に良好に追随し、このことで発熱体薄膜は、一層優れた耐久特性が得られる。これに加えて、ヒータの耐久性が優れているので、センサ動作温度が変化することがなくセンサ出力が長時間安定する利点や、ヒータの抵抗変化検知や抵抗変化に伴うセンサ出力の変化防止対策に纏わる制御回路が簡素化できる利点が有る。
【図面の簡単な説明】
【図１】本発明の実施例におけるガスセンサの断面図
【図２】同実施例における、硝子に含有される珪酸濃度と発熱体薄膜の抵抗変化率の特性図
【図３】同実施例における、石英硝子中の水酸基含有量と発熱体薄膜の抵抗変化率の特性図
【図４】同実施例における、絶縁性耐熱基板の中心線表面粗さと発熱体薄膜の抵抗変化率の特性図
【図５】同実施例における、酸素イオン導電性固体電解質薄膜の熱伝導率と発熱体薄膜の抵抗変化率の特性図
【図６】同実施例における、酸化触媒膜の熱伝導率と発熱体薄膜の抵抗変化率の特性図
【図７】従来のガスセンサの断面図
【符号の説明】
６ 絶縁性耐熱基板
７ 発熱体薄膜
８ 耐熱絶縁性薄膜
９ 耐熱ガス感受膜
１０ ヒータ主薄膜
１１ 金属ヒータ補助微薄膜
１２ 酸素イオン導電性固体電解質薄膜
１３ 第１電極薄膜
１４ 第２電極薄膜
１５ 酸化触媒膜[0001]
BACKGROUND OF THE INVENTION
The present invention is a gas sensor that detects the concentration of carbon monoxide and hydrocarbons in the atmosphere, and provides a power-saving gas sensor that is particularly excellent in durability and reliability.
[0002]
[Prior art]
Conventionally, various gas sensors that are sensitive to carbon monoxide have been proposed. An example of the configuration is as shown in FIG. A glass heat insulating layer 2 is provided on a non-glassy substrate 1 such as alumina, a film heater 3 such as ruthenium oxide is formed thereon, and an overcoat glass 4 is further laminated thereon, and a gas such as tin oxide is formed thereon. The sensitive portions 5 are sequentially stacked. As another example, a gas sensor having a structure in which a heater film such as ruthenium oxide or platinum and a gas sensitive part such as tin oxide is provided on one surface of a heat-resistant insulating substrate whose surface material is glassy is known. ing.
[0003]
  On the other hand, in the literature relating to the tin oxide gas sensor described in Sensors and Actuators B 65 (2000) 190-192, an oxide having a thickness of 470 nm is formed on the top of a metal silicon substrate wafer (hereinafter referred to as a silicon wafer) in order from the bottom. A thin insulating thin film made of silicon and silicon nitride with a thickness of 150 nm is formed, and further, a heater made of titanium metal with a thickness of 30 nm and platinum with a thickness of 240 nm is laminated on top of the thin insulating film.Are listed.
[0004]
[Problems to be solved by the invention]
In order to achieve power saving in gas sensors that operate at high temperatures such as 350 to 500 ° C, the size of the gas sensor is reduced as much as possible, and high power is applied to the built-in heater film in a short time to shorten the operating temperature. It is necessary to raise the temperature in time. However, the conventional gas sensor and its heater film have a problem of requiring complicated film forming technology and advanced quality control technology in order to achieve durability and reliability. This is because a large electric power value is supplied in the form of pulses, so the temperature of the gas sensitive part suddenly rises, and the gas sensor and its heater film are subjected to a large thermal shock due to this sudden rise in temperature. This is because the durability and reliability of the gas sensor and its heater film manufactured in (1) are lowered. For example, by combining conventional technologies, a heater film made of a laminated film of titanium or chromium and platinum is formed on the heat-resistant insulating substrate of general-purpose glass, and a general glass insulating thin film is formed on the heater film. Even if laminated, good durability cannot be obtained, and the resistance of the heater film increases. This is because when a heater film is formed by laminating titanium or chromium and platinum, the glass composition of the optimal heat-resistant insulating substrate and insulating thin film, as well as the optimal heater film firing, are required to improve the durability and reliability. This is because there are conditions. For this reason, when using conventional heat-resistant insulating glass substrates and insulating thin films, heater films are manufactured using complex film-forming technology so that optimum firing conditions are achieved, and the quality is controlled at a high level. If not managed by technology, the heater film could not have good durability.
[0005]
SUMMARY OF THE INVENTION An object of the present invention is to solve the above-described conventional problems and provide a gas sensor manufactured by using a simple film forming technique and a quality control technique as a small power saving type having excellent durability and reliability. Is.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, the gas sensor of the present invention comprises at least a heating element thin film, a heat-resistant insulating thin film, and a heat-resistant gas sensitive film in order from the bottom on an insulating heat-resistant substrate whose surface material is glassy. The glassy material of the insulating heat-resistant substrate and the heat-resistant insulating thin film are silicate glass, borosilicate glass, or silicate-alumina glass ceramic whose main component is silicic acid, and the heating element thin film is A heater main thin film mainly composed of platinum, and a metal heater auxiliary fine film mainly composed of at least one material selected from titanium, zirconium, or chromium which is thinner than the heater main thin film and is disposed below the heater main thin film. It is a thin film stack.
[0007]
Thereby, the gas sensor manufactured using simple film forming technology and quality control technology can be provided as a small power saving type with excellent durability and reliability.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
  The present inventionAt least the heating element thin film, the heat-resistant insulating thin film, and the heat-resistant gas-sensitive film are laminated in order from the bottom on the insulating heat-resistant substrate whose surface material is glassy, and the glass properties of the insulating heat-resistant substrate and The heat-resistant insulating thin film is a silicate glass, a borosilicate glass, or an alumina silicate glass ceramic mainly composed of silicic acid, and the heating element thin film is a heater main thin film mainly composed of platinum and the heater main film. The gas sensor is a laminated film of a metal heater auxiliary thin film whose main component is at least one material selected from titanium, zirconium, or chromium, which is thinner than the thin film and is disposed below the thin film.
[0009]
  Thus, the vitreous material and the heat-resistant insulating thin film of the insulating heat-resistant substrate are silicate glass, borosilicate glass, or silicate alumina glass ceramic mainly composed of silicic acid.800 ° CIt is a material having the above heat resistance. Therefore, the heating element thin film and the heat-resistant gas sensitive film constituting the gas sensor can be fired at a high temperature of, for example, 800 ° C. or higher, and can be manufactured using a simple film forming technique and quality control technique.
[0010]
On the other hand, the metal heater auxiliary fine thin film mainly composed of at least one material selected from titanium, zirconium and chromium is a material excellent in bondability and malleability, and when fired at a high temperature, the heater main material such as platinum or A heat generating thin film having excellent malleability can be obtained by bonding to an insulating heat-resistant substrate. When a large amount of power is applied in a short period of time to save power, the heating element thin film rises to the operating temperature in a short period of time and thermally expands, and the insulating heat-resistant substrates and heat-resistant insulating thin films placed above and below the temperature simultaneously The laminated heating element thin film follows the thermal expansion well and does not peel off, exhibits excellent thermal shock resistance, and does not cause a resistance change.
[0011]
In addition, since the glassy material on the surface of the insulating heat-resistant substrate is a material having a very low thermal conductivity, the heat generated in the heating element thin film is hardly transferred to the insulating heat-resistant substrate, and most of it is heat-resistant gas. It is transmitted to the sensitive film. Therefore, it is possible to achieve a gas sensor that can reach the operating temperature with low power consumption and reduce power consumption, and the heating element thin film has low power consumption, so the applied voltage / current value is small and excellent durability characteristics are obtained. It is done. In addition, since the glassy material and the heat-resistant insulating thin film of the insulating heat-resistant substrate are glass materials having a very strong property against stress, they follow the thermal expansion caused by heat generation well. Excellent durability characteristics can be obtained.
[0012]
In addition, because the heater has excellent durability, the sensor operating temperature does not change and the sensor output stabilizes for a long time, and the control is combined with the detection of the resistance change of the heater and the measures to prevent the sensor output from changing due to the resistance change. The circuit can be simplified.
[0013]
  Also,By virtue of the fact that the glassy material and heat-resistant insulating thin film of the insulating heat-resistant substrate are silicate glass or borosilicate glass containing at least 90% of silicic acid, the glassy material and heat-resistant insulating thin film of the insulating heat-resistant substrate are This composition has a low thermal expansion property and a very strong property against thermal shock. Therefore, the thermal expansion caused by heat generation can be followed well, whereby the heating element thin film can obtain further excellent durability characteristics.
[0014]
  Also,By virtue of the fact that the glassy material and the heat-resistant insulating thin film of the insulating heat-resistant substrate are made of silicate-alumina glass ceramic containing at least 60 to 80% silicic acid and 5 to 20% alumina, the glassy material of the insulating heat-resistant substrate With this composition, the glassy material on the surface of the insulating heat-resistant substrate has a low thermal expansion property and very strong resistance to stress. As a result, the heating element thin film can obtain more excellent durability characteristics.
[0015]
  Also,Since the insulating heat-resistant substrate is a quartz glass containing a hydroxyl group not exceeding 0.20 wt%, it is a quartz glass insulating heat-resistant substrate having a very low thermal conductivity. Only a small amount of heat is transferred to the insulating heat-resistant substrate, and most of it is transferred to the heat-resistant gas-sensitive film, so that it can reach the operating temperature with a very small amount of electric power, and a gas sensor with extremely reduced power consumption can be realized. In addition, quartz glass has a very small coefficient of thermal expansion, so that the thermal expansion of the insulating heat-resistant substrate is reduced. Accordingly, the heating element thin film adheres well to the insulating heat-resistant substrate and provides excellent durability characteristics. Furthermore, since the hydroxyl group contained in quartz glass does not exceed 0.20 wt%, the auxiliary thin film of titanium, zirconium, or chromium metal heater adheres better to the insulating heat-resistant substrate made of quartz glass. Excellent durability characteristics can be obtained. In addition, quartz glass has a very high transition temperature of 1075 ° C, so when used on an insulating heat-resistant substrate, the heating element thin film, heat-resistant insulating thin film, and heat-resistant gas sensitive film have fewer restrictions on the firing temperature. It can be formed by a simple manufacturing method.
[0016]
  Also,Since the insulating heat-resistant substrate has a center line surface roughness of 0.05 to 1 μm, the heating element thin film can be bonded more favorably and can follow the thermal expansion without causing peeling. Further excellent durability characteristics can be obtained.
[0017]
  Also,Since the heat-resistant insulating thin film is made of quartz glass, the heat-resistant insulating thin film is low in thermal expansion, resistant to thermal shock, and well follows thermal expansion due to heat generation. can get. In addition, quartz glass has a very high transition temperature of 1075 ° C, so when used on an insulating heat-resistant substrate, the heating element thin film, heat-resistant insulating thin film, and heat-resistant gas sensitive film have fewer restrictions on the firing temperature. It can be formed by a simple manufacturing method.
[0018]
  Also,The heat-resistant gas sensing film covers the oxygen ion conductive solid electrolyte thin film, the breathable first electrode thin film and the second electrode thin film disposed on the oxygen ion conductive solid electrolyte thin film, and the first electrode thin film. The oxygen ion conductive solid electrolyte thin film includes at least a laminated porous porous oxidation catalyst film, and the oxygen ion conductive solid electrolyte thin film is a material having a thermal conductivity of 1 to 7 W / mK. Works as a good heat dissipation thin film. For this reason, the heating element thin film is suppressed from rising in local temperature, and more excellent durability characteristics can be obtained.
[0019]
  Also,Since the oxidation catalyst film is mainly composed of a material having a thermal conductivity of 1 to 25 W / mK, the oxidation catalyst film works as a good heat dissipation thin film. For this reason, the heating element thin film is suppressed from rising in local temperature, and more excellent durability characteristics can be obtained.
[0020]
【Example】
Embodiments of the present invention will be described below with reference to the accompanying drawings.
[0021]
FIG. 1 shows a gas sensor according to an embodiment of the present invention. At least an exothermic thin film 7, a heat-resistant insulating thin film 8, and a heat-sensitive gas sensation are formed on an insulating heat-resistant substrate 6 whose surface material is glass. The film 9 is laminated in order from the bottom. The glassy material of the insulating heat-resistant substrate 6 and the heat-resistant insulating thin film 8 are silicate glass, borosilicate glass, or silicate alumina glass ceramic (also referred to as crystallized glass) mainly composed of silicic acid. The heating element thin film 7 is mainly composed of a heater main thin film 10 containing platinum as a main component and at least one material selected from titanium, zirconium, or chromium that is thinner than the heater main thin film 10 and is disposed below the heater main thin film 10. It is a laminated film of the metal heater auxiliary fine thin film 11 as a component.
[0022]
(Example 1)
The gas sensor of the present invention was prototyped and its effect was confirmed.
[0023]
The insulating heat-resistant substrate 6 is a plate having dimensions of 2 mm square × thickness 0.3 mm. The material is silicate glass, borosilicate glass, or silicate alumina glass ceramic.
[0024]
The heating element thin film 7 is composed of a laminated film of a metal heater auxiliary fine thin film 11 made of one kind of material of titanium, zirconium, or chromium disposed at a lower portion and a platinum heater main thin film 10 disposed thereon. It is formed using the method.
[0025]
The heat-resistant insulating thin film 8 is a thin film having a thickness of 2 μm formed by sputtering, and is laminated on the heating element thin film 6. The material is silicate glass, borosilicate glass, or silicate alumina glass ceramic.
[0026]
The heat-resistant gas sensitive film 9 was laminated on the oxygen ion conductive solid electrolyte thin film 12, the breathable first electrode thin film 13 and the second electrode thin film 14 formed on the same upper surface, and the first electrode thin film 13. It is composed of a ventilation porous oxidation catalyst film 15. The oxygen ion conductive solid electrolyte thin film 12 is a stabilized zirconia body which is a solid solution of 8 mol% of yttrium oxide and 92 mol% of zirconium oxide, and has a thickness of about 2 μm formed by sputtering and has a heat-resistant insulating thin film 8. Are stacked. Its physical property value is 10 × 10 thermal expansion coefficient.^-6(1 / deg) and thermal conductivity is 5 W / mK. The first electrode thin film 13 and the second electrode thin film 14 are platinum breathable porous thin films formed by sputtering platinum, and have a film thickness of about 0.5 μm on the same upper surface of the oxygen ion conductive solid electrolyte thin film 12. It is formed with. The oxidation catalyst film 15 is a breathable porous film in which a platinum catalyst is supported on the surface of crystallized glass, and is laminated on the first electrode thin film 13 with a film thickness of about 20 μm. Its physical property value is 9 × 10 thermal expansion coefficient.^-6(1 / deg) and the thermal conductivity is 2.5 W / mK.
[0027]
Finally, a platinum lead wire is connected to the heating element thin film 7 and the heat-resistant gas sensing film 9 and then completed in a mounting case. The heating element thin film 7 is electrically connected to a DC power source (not shown) through a connected platinum lead wire, and is heated by application of a voltage / current, and the heating element thin film 7 is heated to heat resistant gas. The sensor output emitted from the sensitive film 9 was measured with a voltmeter (not shown).
[0028]
The heat-resistant gas-sensitive film 9 having the above configuration is called a solid electrolyte type, and the detection mechanism of the carbon monoxide gas will be described. First, the gas sensor element is heated to 400 ° C. from the heating element thin film 7. On the surface of the oxidation catalyst film 15, the carbon monoxide gas reacts with the oxygen gas due to its catalytic action to become carbon dioxide gas and is not consumed. However, since the oxygen concentration is overwhelmingly high, the atmospheric concentration remains substantially the same. Thus, the first electrode thin film 13 is reached. On the other hand, on the surface of the other second electrode thin film 14, carbon monoxide gas and oxygen gas react with each other by the catalytic action to become carbon dioxide gas, and the oxygen gas concentration on the surface decreases. For this reason, paying attention to the oxygen concentration, the first electrode thin film 13 side has a higher concentration than the second electrode thin film 14, and the oxygen gas conducts oxygen ions from the first electrode thin film 13 side toward the second electrode thin film 14. The solid electrolyte electrolyte thin film 12 moves as oxygen ions, and an electromotive force is generated by this oxygen movement. This electromotive force is the sensor output, and a value approximately proportional to the logarithmic value of the carbon monoxide gas concentration is obtained.
[0029]
First, the effect of the present invention was determined by changing the material of the heating element thin film 7.
[0030]
The insulating heat-resistant substrate 6 and the heat-resistant insulating thin film 8 used for the examination are quartz glass. The physical property value is such that the thermal expansion coefficient is 0.5 × 10^-6(1 / deg), thermal conductivity is 1.7 W / mK, transition temperature is 1075 ° C., and softening point is 1580 ° C. Quartz glass is composed of 99.99% silicon oxide and less than 0.01% hydroxyl groups. The insulating heat-resistant substrate 6 has a surface polished to have a centerline surface roughness of 0.05 to 0.2 μm, and this material was used thereafter unless otherwise specified.
[0031]
The heating element thin film 7 according to the present invention includes a heater main thin film 10 made of platinum having a film thickness of 0.5 μm and a metal heater auxiliary thin film made of titanium having a film thickness of 0.005 μm disposed below the heater main thin film 10. 11.
[0032]
The heating element thin film 7 of the present invention 2 includes a heater main thin film 10 made of platinum having a film thickness of 0.5 μm and a metal heater auxiliary thin film made of zirconium having a film thickness of 0.005 μm disposed under the heater main thin film 10. 11.
[0033]
The heating element thin film 7 of the present invention 3 includes a heater main thin film 10 made of platinum having a film thickness of 0.5 μm and a metal heater auxiliary thin film made of chromium having a film thickness of 0.005 μm disposed below the heater main thin film 10. 11.
[0034]
The conventional heating element thin film is only a heater main thin film made of platinum having a thickness of 0.5 μm.
[0035]
The results are shown in (Table 1). The rate of change in resistance of the heating element thin film 7 was obtained when a DC voltage current was applied to the heating element thin film 7 to reach an operating temperature of 400 ° C. in 10 milliseconds, and then the ON / OFF test for turning off the power was conducted 100,000 times. The values calculated from the resistance values before and after the experiment.
[0036]
[Table 1]

[0037]
As is clear from this (Table 1), the present inventions 1 to 3 are the main heater thin film 10 of platinum, and at least selected from titanium, zirconium, or chromium disposed below the platinum thin film. It can be seen that the heating element thin film 7 is composed of the metal heater auxiliary fine thin film 11 mainly composed of one kind of material and has excellent durability. This excellent durability is due to the following reason. Platinum is a material with excellent malleability and heat resistance, and titanium, zirconium, and chromium are materials with excellent bondability and good malleability. When these layers are laminated, the heat generating thin film 7 having good malleability is obtained, and the heat generating thin film 7 is also well bonded to the insulating heat resistant substrate 6 and the heat resistant insulating thin film 8. When energized, the heating element thin film 7 rises to the operating temperature in a short time and thermally expands, and the insulating heat resistant substrate 6 and the heat resistant insulating thin film 8 disposed above and below the same simultaneously rise in temperature and thermally expand. This is because the heating element thin film 7 as a laminated film satisfactorily follows the thermal expansion of the insulating heat resistant substrate 6 and the heat resistant insulating thin film 8 and does not cause peeling or disconnection.
[0038]
Further, in the present invention 1 to 3, since the heat-resistant gas-sensitive film 9 on the upper part thereof effectively transfers the heat generated in the heating element thin film 7 through the thin film of the heat-resistant insulating thin film 8, 10 milliseconds The carbon monoxide gas concentration became detectable by energization, and the amount of power was 14 mW seconds. Further, even in a gas sensor using a borosilicate glass or an alumina silicate glass ceramic as the insulating heat-resistant substrate 6 or the heat-resistant insulating thin film 8, excellent durability similar to the above was obtained. The heater main thin film 10 is effectively made of a platinum-based metal whose main component is 80% by weight or more of platinum mixed with a small amount of rhodium, palladium or the like at 20% by weight or less. 1.0 μm is appropriate, and 0.4 to 0.7 μm is particularly optimal. On the other hand, the appropriate thickness of the metal heater auxiliary fine thin film 11 made of titanium, zirconium, or chromium is 500 to 20 mm, and particularly 300 to 30 mm is optimal.
[0039]
Next, the material of the insulating heat-resistant substrate 6 and the heat-resistant insulating thin film 8 was changed, and the effect of the present invention was determined. The heating element thin film 7 used for the examination is a laminated film of a metal heater auxiliary thin film 11 made of chromium arranged in the lower part and a heater main thin film 10 made of platinum arranged in the upper part. Others are the same as described above, and the above-described solid electrolyte type heat-resistant gas sensitive film 9 is laminated on the heat-resistant insulating thin film 8 to form a gas sensor.
[0040]
The insulating heat-resistant substrate 6 and the heat-resistant insulating thin film 8 of the present invention 1 are made of quartz glass, the transition temperature is 1075 ° C., and the thermal expansion coefficient is 0.5 × 10.^-6(1 / deg).
[0041]
The insulating heat-resistant substrate 6 and the heat-resistant insulating thin film 8 of the present invention 2 are borosilicate glass containing 96% silicic acid and 4% boric acid, having a transition temperature of 890 ° C. and a thermal expansion coefficient of 0.8 × 10.^-6(1 / deg).
[0042]
The insulating heat-resistant substrate 6 and the heat-resistant insulating thin film 8 of the present invention 3 are silicate alumina glass ceramics (also referred to as crystallized glass). Its composition is 64% silicic acid, 15% alumina, 21% metal oxide such as titanium oxide and zinc oxide, and a silicate-alumina glass ceramic with a transition temperature of 880 ° C. and a thermal expansion coefficient of 3. 1 × 10^-6(1 / deg).
[0043]
The insulating heat-resistant substrate 6 and the heat-resistant insulating thin film 8 of the conventional example are soda-lime glass, the transition temperature is 620 ° C., and the thermal expansion coefficient is 5.2 × 10.^-6(1 / deg).
[0044]
In the comparative example, the insulating heat-resistant substrate 6 was a substrate in which a thin insulating thin film made of silicon oxide and silicon nitride was formed on the surface of a silicon wafer, and the heat-resistant insulating thin film 8 was laminated with silicon oxide and alumina.
[0045]
The results are shown in (Table 2). The resistance change rate of the heating element thin film 7 is obtained when an ON-OFF test for turning off the power is performed 100,000 times after a DC voltage is applied to the heating element thin film 7 to reach an operating temperature of 400 ° C. in 10 milliseconds. The values calculated from the resistance values before and after the experiment.
[0046]
[Table 2]

[0047]
The heat-resistant insulating substrate 6 and the heat-resistant insulating thin film 8 of the present invention 1 to 3 are quartz glass, borosilicate glass, and silicate alumina glass ceramic, and the heating element thin film 7 of the gas sensor using the same is excellent in durability. You can see that This excellent durability is due to the following reason. Chromium constituting the heating element thin film 7 is a material having excellent bondability and good malleability, and is well bonded to the insulating heat-resistant substrate 6 and the heat-resistant insulating thin film 8 made of these materials. When energized, the heating element thin film 7 rises to the operating temperature in a short time and thermally expands, and the insulating heat resistant substrate 6 and the heat resistant insulating thin film 8 disposed above and below the same simultaneously rise in temperature and thermally expand. This is because the heating element thin film 7 of the laminated film follows the thermal expansion of the insulating heat resistant substrate 6 and the heat resistant insulating thin film 8 well and does not cause peeling or disconnection.
[0048]
Further, in the present invention 1 to 3, since the heat-resistant gas-sensitive film 9 on the upper part thereof effectively transfers the heat generated in the heating element thin film 7 through the thin film of the heat-resistant insulating thin film 8, 10 milliseconds The carbon monoxide gas concentration became detectable by energization, and the amount of power was as small as 15 to 25 mW seconds. The silicon wafer type substrate used as a comparative example has a heat resistance of about 300 to 400 ° C. at most, and by applying heat at 600 ° C. in sensor production, a new oxide with poor adhesion is remarkably generated on the surface. For this reason, the heating element thin film was peeled off and disconnected during pulse energization.
[0049]
In the embodiment of this configuration, the heating element thin film 7 is composed of a platinum heater main thin film 10 and a titanium or zirconium metal heater auxiliary fine thin film 11 which is thinner than the heater main thin film 10 and disposed below the heater main thin film 10. However, excellent durability was obtained as described above. Furthermore, the insulating heat-resistant substrate 6 has a glassy thick film layer (30 to 100 μm thickness) made of quartz glass, borosilicate glass, or silicate glass glass ceramic on the ceramic plate such as alumina or forsterite. A formed substrate may be used. In the gas sensor using the heat-resistant insulating thin film 8 made of the same glass material as the insulating heat-resistant substrate 6, the heating element thin film 7 has excellent durability and the electric energy is as small as 17 to 27 mW seconds.
[0050]
As the heat-resistant gas sensitive film 9, a metal oxide semiconductor film such as tin oxide, iron oxide or tungsten oxide, or a solid electrolyte type is effective. When the heat-resistant gas-sensitive film 9 is of a solid electrolyte type, the oxygen ion conductive solid electrolyte thin film 12 has various zirconia oxygen ion conductivity typified by a partially stabilized zirconia body of 3 mol% yttrium oxide and 97 mol% zirconium oxide. Sputtered films, vapor deposited films, and sol-gel films of solid electrolytes and ceria-based oxygen ion conductive solid electrolytes are effective. For the first electrode thin film 13 and the second electrode thin film 14, a gas-permeable printed film and a sputtered film or a vapor-deposited film of a noble metal such as platinum or an oxygen ion conductive metal oxide are effective. As the oxidation catalyst film 15, a breathable porous film in which a noble metal such as platinum or a metal oxide is mixed with an inorganic adhesive such as crystallized glass is effective.
[0051]
(Example 2)
In Example 2, the physical properties of glass used for the insulating heat-resistant substrate 6 and the heat-resistant insulating thin film 8 were examined. Since glass has a very low thermal conductivity, when it is used for the insulating heat-resistant substrate 6, only a small amount of heat generated in the heating element thin film 7 is transferred to the insulating heat-resistant substrate 6, and most of the heat is transferred to the heat-resistant gas sensitive film 9. Since it is transmitted, there is an advantage that a gas sensor that can reach an operating temperature of 400 ° C. with a small amount of electric power and can reduce power consumption can be realized. Glass has a coefficient of thermal expansion of 10 × 10 due to restrictions on its material composition.^-6(1 / deg) is the upper limit value that can be produced in the current technology, and most glass has a thermal expansion coefficient equal to or less than this value. On the other hand, since the heating element thin film 7 is mainly composed of platinum, its thermal expansion coefficient is 10 × 10.^-6(1 / deg). Although the heat generating thin film 7 is thermally expanded when heat is generated, the insulating heat resistant substrate 6 and the heat resistant insulating thin film 8 made of glass having a smaller coefficient of thermal expansion than the heat generating thin film 7 are slightly thermally expanded. Although stress is applied, since glass has a very strong property against compressive stress, these materials also have the advantage that they follow the thermal expansion well and do not break. Therefore, the glass composition of the insulating heat-resistant substrate 6 and the heat-resistant insulating thin film 8 from which the heat generating thin film 7 having excellent durability characteristics was obtained was examined.
[0052]
In the examination, the effect of the present invention was determined using the insulating heat-resistant substrate 6 and the heat-resistant insulating thin film 8 having different silicic acid concentrations. The heating element thin film 7 used for the examination is a laminated film of a metal heater auxiliary thin film 11 made of chromium arranged in the lower part and a heater main thin film 10 made of platinum arranged in the upper part. Others are the same as described above, and the above-described solid electrolyte type heat-resistant gas sensitive film 9 is laminated on the heat-resistant insulating thin film 8 to form a gas sensor.
[0053]
The insulating heat-resistant substrate 6 and the heat-resistant insulating thin film 8 of the present invention 1 are quartz glass having a silica content of 99.99%, a transition temperature of 1075 ° C., and a thermal expansion coefficient of 0.5 × 10.^-6(1 / deg).
[0054]
The insulating heat-resistant substrate 6 and the heat-resistant insulating thin film 8 of the present invention 2 are borosilicate glass containing 96% silicic acid and 4% boric acid, having a transition temperature of 890 ° C. and a thermal expansion coefficient of 0.8 × 10.^-6(1 / deg).
[0055]
The insulating heat-resistant substrate 6 and the heat-resistant insulating thin film 8 of the present invention 3 are borosilicate glass containing 90% silicic acid, 4% boric acid and 6% metal oxide such as calcium oxide, and the transition temperature is 850 ° C. The coefficient of thermal expansion is 1.6 × 10^-6(1 / deg).
[0056]
The insulating heat-resistant substrate 6 and the heat-resistant insulating thin film 8 of the comparative example are borosilicate glass containing 87% silicic acid, 5% boric acid, and 8% metal oxide such as calcium oxide, and the transition temperature is 780 ° C. The coefficient of thermal expansion is 2.6 × 10^-6(1 / deg).
[0057]
FIG. 2 shows the relationship between the concentration of silicic acid contained in the glass used as the insulating heat-resistant substrate 6 and the heat-resistant insulating thin film 8 and the resistance change rate of the heating element thin film. The resistance change rate of the heating element thin film 7 is determined by performing an ON-OFF test in which the power source thin film 10 is raised to an operating temperature of 400 ° C. in 10 milliseconds by applying a DC voltage current to the terminal of the mounting case and then turned off. It is the rate of resistance change when performed 10,000 times.
[0058]
As is apparent from the figure, the resistance change rate of the heating element thin film 7 changes with the concentration of silicic acid contained in the glass at 90%. Since the product of the present invention is the insulating heat resistant substrate 6 and the heat resistant insulating thin film 8 in which the concentration of silicic acid contained in the glass exceeds 90%, the heating element thin film 7 is replaced with the insulating heat resistant substrate 6 and the heat resistant insulating thin film 8. Adheres well and provides excellent durability characteristics. Further, since the insulating heat-resistant substrate 6 is made of a glass material having a very low thermal conductivity, only a small amount of heat generated in the heat generating thin film 7 is transferred to the insulating heat-resistant substrate 6, and most of the heat-resistant gas-sensitive film. 9 is transmitted. Therefore, a gas sensor that can reach the operating temperature with less power and further reduces power consumption has been realized. Furthermore, since the heating element thin film 7 has low power consumption, the applied voltage / current value is small, and the effect of obtaining more excellent durability characteristics is obtained.
[0059]
On the other hand, the insulating heat-resistant substrate 6 and the heat-resistant insulating thin film 8 in which the concentration of silicic acid contained in the glass is less than 90%, the heating element thin film 7 does not adhere well to the insulating heat-resistant substrate 6 and the heat-resistant insulating thin film 8. Some degradation in durability was observed. This is because the concentration of silicic acid is low, so that an optimum glass composition for obtaining a heater film with excellent durability cannot be realized.
[0060]
The same effect can be obtained by using a structure in which a platinum heater main thin film 10 and a metal heater auxiliary thin film 11 of titanium, zirconium, or chromium disposed at least under the platinum heater main film 10 are laminated as the heating element thin film 7. It was. Furthermore, the insulating heat-resistant substrate 6 is a substrate in which a glassy thick film layer (30 to 100 μm film thickness) made of quartz glass or borosilicate glass is formed on an upper part of a ceramic plate such as alumina or forsterite. good. In the gas sensor using the heat-resistant insulating thin film 8 made of the same glass material as the insulating heat-resistant substrate 6, the heating element thin film 7 has excellent durability and the electric energy is as small as 17 to 22 mW seconds.
[0061]
(Example 3)
In Example 3, the material composition of an alumina silicate glass ceramic used for the insulating heat-resistant substrate 6 and the heat-resistant insulating thin film 8 was examined. Since the silicate-alumina glass ceramic has a low thermal conductivity, when it is used for the insulating heat-resistant substrate 6, only a small amount of heat generated in the heating element thin film 7 is transferred to the insulating heat-resistant substrate 6, most of which is a heat-resistant gas sensitive film. Therefore, there is an advantage that a gas sensor that can reach an operating temperature of 400 ° C. with a small amount of electric power and can reduce power consumption can be realized. Silica-alumina-based glass ceramics have a thermal expansion coefficient of 10 × 10 due to restrictions on the material composition.^-6(1 / deg) is the upper limit value that can be produced in the current technology, and most silicate-alumina-based glass ceramics have a thermal expansion coefficient equal to or lower than this value. On the other hand, since the heating element thin film 7 is mainly composed of platinum, its thermal expansion coefficient is 10 × 10.^-6(1 / deg). The heat generating thin film 7 is thermally expanded when it generates heat, but the insulating heat resistant substrate 6 and the heat resistant insulating thin film 8 made of silicate-alumina-based glass ceramic having a smaller coefficient of thermal expansion than the heat generating thin film 7 are only slightly thermally expanded. As a result, although compressive stress is applied, the silicate-alumina glass ceramic has a strong property against compressive stress. Therefore, these materials have an advantage that they follow the thermal expansion well and do not break. Then, the composition for realizing the silicate-alumina glass ceramic having this excellent effect was examined.
[0062]
The examination was performed using the insulating heat-resistant substrate 6 and the heat-resistant insulating thin film 8 with different concentrations of silicic acid and alumina. The heating element thin film 7 used for the examination is a laminated film of a metal heater auxiliary thin film 11 made of chromium arranged in the lower part and a heater main thin film 10 made of platinum arranged in the upper part. Others are the same as described above, and the above-described solid electrolyte type heat-resistant gas sensitive film 9 is laminated on the heat-resistant insulating thin film 8 to form a gas sensor. Prior to the study, the upper limit and lower limit values of the silicic acid content and the upper limit value and lower limit value of the alumina content for obtaining good glass properties of the silicate alumina glass ceramic were determined. As a result, it was found that the upper limit of silicic acid content was 80%, the upper limit of alumina content was 20%, the lower limit of silicic acid content was 60%, and the lower limit of content of alumina was 5%. Also, with this composition, the thermal expansion coefficient is about 2-4 × 10^-6It was found that since it is small (1 / deg), it is excellent in thermal shock, and its transition temperature is about 800 ° C. or higher, and it is excellent in heat resistance. Therefore, the investigation was conducted in this composition region.
[0063]
The insulating heat-resistant substrate 6 and the heat-resistant insulating thin film 8 of the present invention 1 are silicate-alumina glass ceramics containing 80% silicic acid and 20% alumina, having a transition temperature of 920 ° C. and a thermal expansion coefficient of 1.8 × 10.^-6(1 / deg).
[0064]
The insulating heat-resistant substrate 6 and the heat-resistant insulating thin film 8 of the present invention 2 are silicate-alumina-based glass ceramics containing 80% silicic acid, 5% alumina, and 15% metal oxide such as titanium oxide, and have a transition temperature of 920. ° C, thermal expansion coefficient is 3.6 × 10^-6(1 / deg).
[0065]
The insulating heat-resistant substrate 6 and the heat-resistant insulating thin film 8 of the present invention 3 are silicate-alumina glass ceramics having 60% silicic acid, 20% alumina, and 20% metal oxide such as titanium oxide or zinc oxide. The temperature is 880 ° C., and the thermal expansion coefficient is 3.1 × 10^-6(1 / deg).
[0066]
The insulating heat-resistant substrate 6 and the heat-resistant insulating thin film 8 of the present invention 4 are a silicate-alumina glass ceramic having 60% silicic acid, 5% alumina, and 35% metal oxide such as titanium oxide, and has a transition temperature. Is 870 ° C. and thermal expansion coefficient is 3.6 × 10^-6(1 / deg).
[0067]
Table 3 shows the resistance change rate of the heating element thin film 7 for the insulating heat-resistant substrate 6 and the heat-resistant insulating thin film 8 of the silicate-alumina-based glass ceramic having different concentrations of silicic acid and alumina. The resistance change rate of the heating element thin film 7 is determined by applying an on-off test in which the power source thin film 7 is raised to an operating temperature of 400 ° C. in 10 milliseconds by applying a DC voltage current to the terminal of the mounting case and then turning off the power. It is the rate of resistance change when performed 10,000 times.
[0068]
[Table 3]

[0069]
As apparent from (Table 3), the resistance change rate of the heating element thin film 7 is excellent in durability characteristics by using a silicate-alumina glass ceramic containing 60 to 80% silicic acid and 5 to 20% alumina. It can be seen that
[0070]
The same effect can be obtained by using a structure in which a platinum heater main thin film 10 and a metal heater auxiliary thin film 11 of titanium, zirconium, or chromium disposed at least under the platinum heater main film 10 are laminated as the heating element thin film 7. It was. Furthermore, the insulating heat-resistant substrate 6 is a substrate in which a glassy thick film layer (30 to 100 μm film thickness) made of an alumina silicate glass ceramic having this composition is formed on a ceramic plate such as alumina or forsterite. May be used. In the gas sensor using the heat-resistant insulating thin film 8 made of the same glass material as the insulating heat-resistant substrate 6, the heating element thin film 7 has excellent durability and the electric energy is as small as 24 to 27 mW seconds.
[0071]
(Example 4)
As described in Example 1 above, it can be seen that when the insulating heat-resistant substrate 6 is made of silica glass of 100% silicic acid, it has excellent durability characteristics. Therefore, in Example 4, the composition of quartz glass used for the insulating heat-resistant substrate 6 was examined. Quartz glass is made of silicic acid (SiO₂), And contains a small amount of hydroxyl groups (referred to as OH groups). Therefore, the influence of the quartz glass insulating heat-resistant substrate 6 with different hydroxyl group contents was analyzed.
[0072]
In the examination, an insulating heat-resistant substrate 6 made of quartz glass with different hydroxyl group contents is used, and a metal heater auxiliary thin film 11 made of titanium and a heater main thin film 10 made of platinum are sequentially laminated on the upper portion of the heating element. A thin film 7 and a heat-resistant insulating thin film 8 made of quartz glass were further laminated and fired. Finally, the gas sensor was formed by laminating the above-mentioned solid electrolyte type heat-resistant gas sensitive film 9.
[0073]
The insulating heat-resistant substrate 6 of the present invention 1 is quartz glass containing 0.01 wt% of hydroxyl groups, and its safe use temperature is 1050 ° C.
[0074]
The insulating heat-resistant substrate 6 of the present invention 2 is quartz glass containing 0.04 wt% of hydroxyl groups, and its safe use temperature is 1000 ° C.
[0075]
The insulating heat-resistant substrate 6 of the present invention 3 is quartz glass containing 0.12 wt% of hydroxyl groups, and its safe use temperature is 950 ° C.
[0076]
The insulating heat-resistant substrate 6 of the present invention 4 is quartz glass containing 0.20 wt% of hydroxyl groups, and its safe use temperature is 900 ° C.
[0077]
The insulating heat-resistant substrate of Comparative Example 2 is quartz glass containing 0.25 wt% hydroxyl group, and its safe use temperature is 800 ° C.
[0078]
FIG. 3 shows the correlation characteristics between the hydroxyl group content of quartz glass and the resistance change rate when the resistance change rate of the heating element thin film 7 is measured by changing the hydroxyl group content of quartz glass. The resistance change rate of the heating element thin film 7 is such that a DC voltage current is applied to the terminals of the mounting case to cause the heating element thin film 7 to reach an operating temperature of 400 ° C. in 2 milliseconds, and then held for 8 milliseconds, and the power is turned off. This is the rate of resistance change when the ON-OFF test is conducted 100,000 times.
[0079]
It can be seen that the resistance change rate of the heater changes at 0.20 wt% of the hydroxyl group contained in the quartz glass. In the product of the present invention, since the hydroxyl group contained in the quartz glass is 0.20 wt% or less, the titanium metal heater auxiliary fine thin film 11 adheres well to the quartz glass, and further excellent durability characteristics can be obtained. In addition, since quartz glass having a very small thermal expansion coefficient is used as the insulating heat-resistant substrate 6, the thermal expansion of the insulating heat-resistant substrate 6 due to the heat generated by the heat-generating thin film 7 is reduced. The thin film 7 adheres more favorably to the insulating heat-resistant substrate 6 and provides excellent durability characteristics. Further, since the insulating heat-resistant substrate 6 is made of quartz glass having a very low thermal conductivity, the heat generated in the heat generating thin film 7 is hardly transferred to the insulating heat-resistant substrate 6, and most of the heat is generated in the heat-resistant gas sensitive film. 9 is transmitted. Therefore, it is possible to achieve a gas sensor that can reach the operating temperature with less power and further reduce power consumption. Further, since the heating element thin film 7 has low power consumption, the applied voltage / current value becomes small, and an effect of obtaining more excellent durability characteristics is produced. In addition to this, when the hydroxyl group contained in the quartz glass is 0.20 wt% or less, the formation of the heat-resistant insulating thin film 8 laminated thereon can be subjected to high-temperature treatment, and the heat-resistant insulating properties with few defects. The thin film 8 is produced and excellent insulating properties can be secured. Therefore, the oxygen ion conductive solid electrolyte thin film 12 is less affected by the heating element thin film 7 and exhibits good oxygen ion conductivity at an appropriate operating temperature of 400 ° C. Due to this effect, the heat-resistant gas-sensitive film 9 composed of the oxygen ion conductive solid electrolyte thin film 12, the electrode thin film 13 and the oxidation catalyst film 15 is heated in a short time by the heating element thin film 7 disposed below the heat-sensitive gas sensitive film 9. Therefore, there is an advantage that the air is warmed up in an extremely short time.
[0080]
On the other hand, when the hydroxyl group contained in the quartz glass exceeds 0.20 wt%, the titanium metal heater auxiliary fine thin film 11 becomes difficult to adhere to the quartz glass, and a slight decrease in durability was observed.
[0081]
The same effect can be obtained by using a structure in which the heater thin film 7 is formed by laminating a platinum heater main thin film 10 with a metal heater auxiliary thin film 11 of titanium, zirconium, or chrome disposed at least below or above the platinum heater main thin film 10. Obtained.
[0082]
(Example 5)
In Example 5, the center line surface roughness of the insulating heat-resistant substrate 6 was examined. The study was carried out by sequentially laminating a metal heater auxiliary thin film 11 made of titanium and a heater main thin film 10 made of platinum on the insulating heat-resistant substrate 6 made of quartz glass whose center line surface roughness was changed, in order. A thin film 7 and a heat-resistant insulating thin film 8 made of quartz glass were further laminated and fired. Finally, the gas sensor was formed by laminating the above-mentioned solid electrolyte type heat-resistant gas sensitive film 9.
[0083]
An ON-OFF energization test of the gas sensor using the insulating heat-resistant substrate 6 in which the center line surface roughness was changed was performed, and the resistance change rate of the heating element thin film 7 was measured. FIG. 4 is a characteristic diagram in which correlation characteristics between the center line surface roughness and the resistance change rate are arranged. The resistance change rate of the heating element thin film 7 is determined by applying a DC voltage current to the terminals of the mounting case to cause the heating element thin film 7 to reach an operating temperature of 400 ° C. in 10 milliseconds, and then turn ON / OFF the test to turn off the power. It is the rate of resistance change when performed 10,000 times.
[0084]
As can be seen from FIG. 4, the rate of resistance change greatly changes with the center line surface roughness being 0.05 μm and 1 μm as a boundary. Since the product of the present invention has a center line surface roughness of 0.05 to 1 μm, the heating element thin film 7 adheres well to the insulating heat-resistant substrate 6 by firing, and excellent durability characteristics are obtained.
[0085]
On the other hand, if the insulating heat-resistant substrate 6 has a center line surface roughness of less than 0.05 μm and more than 1 μm, the heating element thin film 7 does not adhere well to the insulating heat-resistant substrate 6 even when baked, resulting in a slight decrease in durability. Is observed.
[0086]
As a result, even when a borosilicate glass or an alumina silicate glass ceramic plate is used as the insulating heat-resistant substrate 6, the heating element thin film 7 can obtain excellent durability characteristics. Alternatively, a substrate in which a glassy thick film layer (30 to 100 μm thickness) made of quartz glass, borosilicate glass, or silicate glass glass ceramic is formed on the top of a ceramic plate such as alumina or forsterite. Needless to say, the heating element thin film 7 provides excellent durability characteristics. Further, the same effect can be obtained by using a structure in which the heater thin film 7 is formed by laminating a platinum heater main thin film 10 with a titanium, zirconium, or chromium metal heater auxiliary thin film 11 disposed at least below the platinum heater main thin film 10. It was.
[0087]
(Example 6)
In Example 6, the material constituting the heat-resistant insulating thin film 8 was examined.
[0088]
As described above, quartz glass inherently has a characteristic that the thermal expansion coefficient is smaller than that of the heating element thin film 7 having this composition. For this reason, when quartz glass is used as the heat-resistant insulating thin film 8, even if the heating element thin film 7 generates heat and thermally expands, the quartz glass expands very little, and is engaged with a property that is very strong against the compressive stress of quartz glass. Thus, as described in (Table 2), the heating element thin film 7 having excellent durability characteristics can be realized.
[0089]
The above results show that the same effect can be obtained even when the heating element thin film 7 is formed by laminating titanium, zirconium, and chromium metal heater auxiliary thin film 11 disposed below the platinum heater main thin film 10. It was.
[0090]
(Example 7)
Example 7 examined the thermal conductivity of the oxygen ion conductive solid electrolyte thin film 12 when a solid electrolyte type gas sensitive film was used as the heat resistant gas sensitive film 9.
[0091]
The examination was made by sequentially laminating a metal heater auxiliary thin film 11 made of titanium and a main heater thin film 10 of platinum on the insulating heat-resistant substrate 6 made of quartz glass in order to form a heating element thin film 7 and heat-resistant insulation made of quartz glass. The thin film 8 was further laminated and baked, and finally, a gas sensor in which a solid electrolyte type heat-resistant gas sensitive film 9 described later was laminated was used.
[0092]
The solid electrolyte type heat-resistant gas-sensitive film 9 includes an oxygen ion conductive solid electrolyte thin film 12, a breathable first electrode thin film 13 and second electrode thin film 14 formed on the same surface, and a first electrode thin film 13. It is composed of stacked oxidation catalyst films 15. The first electrode thin film 13 and the second electrode thin film 14 and the oxidation catalyst film 15 were examined using the following two types of materials.
[0093]
The material (I) is a breathable thin film formed by sputtering platinum on the first electrode thin film 13 and the second electrode thin film 14, and has a thermal expansion coefficient of 9 × 10.^-6(1 / deg) has a physical conductivity of 69.5 W / mK. The oxidation catalyst film 15 is a breathable porous film in which a platinum catalyst is supported on the surface of a silica-alumina crystallized glass, and has a physical conductivity value of 1 W / mK.
[0094]
The material (II) is a breathable thin film in which the first electrode thin film 13 and the second electrode thin film 14 are thickly printed by mixing lanthanum cobalt-based composite oxide, which is a perovskite-type metal oxide, with 3% of bismuth oxide. It is. The oxidation catalyst film 15 is a breathable porous film in which a platinum catalyst is supported on the surface of an alumina binder, and has a physical property value of thermal conductivity of 25 W / mK.
[0095]
The oxygen ion conductive solid electrolyte thin film of Comparative Example 1 is cerium-added yttrium-based partially stabilized zirconia, which has a finer crystal grain size, so its thermal conductivity is 0.8 W / mK, and its composition is ZrO.₂96 mol% and Y₂O_Three3 mol% and CeO₂It is a 1 mol% solid solution.
[0096]
The oxygen ion conductive solid electrolyte thin film 12 of the present invention 1 is scandium-added ceria-based zirconia, and since the crystal grain size is made finer, its thermal conductivity is 1.0 W / mK and the composition is ZrO.₂90 mol% and CeO₂10 mol% and Sc₂O_ThreeIt is a 10 mol% solid solution.
[0097]
The oxygen ion conductive solid electrolyte thin film 12 of the present invention 2 is yttrium-based partially stabilized zirconia, the thermal conductivity is 3.0 W / mK, and the composition is ZrO.₂97 mol% and Y₂O_ThreeIt is a 3 mol% solid solution.
[0098]
The oxygen ion conductive solid electrolyte thin film 12 of the present invention 3 is yttrium-based stabilized zirconia, has a thermal conductivity of 5.0 W / mK, and its composition is ZrO.₂92 mol% and Y₂O_ThreeIt is an 8 mol% solid solution.
[0099]
The oxygen ion conductive solid electrolyte thin film 12 of the present invention 4 is a ceria-based material doped with yttria, and its thermal conductivity is 6.5 W / mK, and its composition is (CeO₂)_1-0.7(YO_1.5)_0.3It is.
[0100]
The oxygen ion conductive solid electrolyte thin film 12 of the present invention 5 is a ceria-based material doped with samarium, the thermal conductivity is 7.0 W / mK, and the composition is (CeO₂)_0.8(SmO_1.5)_0.2It is.
[0101]
The insulating heat-resistant substrate of Comparative Example 2 is yttrium-based bismuth oxide, its thermal conductivity is 10 W / mK, and its composition is Bi.₂O_Three96 mol% and Y₂O_ThreeIt is a 4 mol% solid solution.
[0102]
The gas sensor using oxygen ion conductive solid electrolyte thin films with different thermal conductivities was subjected to an ON-OFF energization test, and the resistance change rate of the heating element thin film 7 was measured. FIG. 5 is a characteristic diagram in which correlation characteristics between the thermal conductivity and the resistance change rate of the oxygen ion conductive solid electrolyte thin film 12 are arranged. The resistance change rate of the heating element thin film 7 is determined by performing an ON-OFF test in which the heating element thin film 6 is heated to an operating temperature of 400 ° C. in 10 milliseconds in 10 milliseconds by applying a DC voltage current to the terminals of the mounting case. It is a resistance change rate when 100,000 times are performed.
[0103]
As is apparent from FIG. 5, it can be seen that the rate of change in resistance greatly changes when the thermal conductivity of the oxygen ion conductive solid electrolyte thin film 12 is less than 1 W / mK and exceeds 7 W / mK. Since the product of the present invention has a thermal conductivity of 1 to 7 W / mK, the oxygen ion conductive solid electrolyte thin film 12 radiates heat well, and the heating element thin film 7 is suppressed in temperature rise and has excellent durability characteristics. .
[0104]
On the other hand, when the thermal conductivity is less than 1 W / mK, the heat radiation from the oxygen ion conductive solid electrolyte thin film 12 is poor, so that the temperature of the heating element thin film 7 rises and a slight decrease in durability is observed. Also, if the thermal conductivity exceeds 7 W / mK, the heat radiation from the oxygen ion conductive solid electrolyte thin film 12 is good, so that a large current flows to maintain the temperature of the heating element thin film 7 and the durability decreases somewhat. Was observed.
[0105]
The above results show that the same effect can be obtained even when the heating element thin film 7 is formed by laminating titanium, zirconium, and chromium metal heater auxiliary thin film 11 disposed below the platinum heater main thin film 10. It was.
[0106]
(Example 8)
In Example 8, the thermal conductivity of the oxidation catalyst film 15 was examined when a solid electrolyte type gas sensitive film was used as the heat resistant gas sensitive film 9.
[0107]
The examination was made by sequentially laminating a metal heater auxiliary thin film 11 made of titanium and a main heater thin film 10 of platinum on the insulating heat-resistant substrate 6 made of quartz glass in order to form a heating element thin film 7 and heat-resistant insulation made of quartz glass. The thin film 8 was further laminated and baked, and finally, a gas sensor in which a solid electrolyte type heat-resistant gas sensitive film 9 described later was laminated was used. The solid electrolyte type heat-resistant gas-sensitive film 9 includes an oxygen ion conductive solid electrolyte thin film 12, a breathable first electrode thin film 13 and second electrode thin film 14 formed on the same surface, and a first electrode thin film 13. It is composed of stacked oxidation catalyst films 15. The oxygen ion conductive solid electrolyte thin film 12, the first electrode thin film 13, and the second electrode thin film 14 were studied using the following two types of materials.
[0108]
The material (I) is an oxygen ion conductive solid electrolyte thin film 12 made of yttrium-based stabilized zirconia, having a thermal conductivity of 5 W / mK and a composition of ZrO.₂92 mol% and Y₂O_ThreeIt is an 8 mol% solid solution. The first electrode thin film 13 and the second electrode thin film 14 are breathable thin films formed by sputtering platinum, and have a thermal expansion coefficient of 9 × 10.^-6(1 / deg) has a physical conductivity of 69.5 W / mK.
[0109]
Material (II) is a ceria-based material in which the oxygen ion conductive solid electrolyte thin film 12 is doped with samarium, the thermal conductivity is 7.0 W / mK, and the composition is (CeO₂)_0.8(SmO_1.5)_0.2It is. The first electrode thin film 13 and the second electrode thin film 14 are breathable thin films obtained by printing a thick film by mixing lanthanum cobalt-based composite oxide, which is a perovskite metal oxide, with 3% of bismuth oxide.
[0110]
The oxidation catalyst film of Comparative Example 1 is a breathable porous film in which a platinum catalyst is supported on the surface of cordierite crystallized glass, and has a physical property value of 0.7 W / mK.
[0111]
The oxidation catalyst film 15 of the present invention 1 is a breathable porous film in which a platinum rhodium catalyst is supported on the surface of a silica-alumina-based crystallized glass, and has a physical property value of 1.0 W / mK.
[0112]
The oxidation catalyst film 15 of the present invention 2 is a breathable porous film in which a platinum palladium catalyst is supported on the surface of a silica alumina boron-based crystallized glass, and has a physical property value of thermal conductivity of 2.5 W / mK. .
[0113]
The oxidation catalyst film 15 of the present invention 3 is a breathable porous film in which a platinum catalyst is supported on the surface of an alumina zirconia-based binder, and has a physical property value of 7.0 W / mK.
[0114]
The oxidation catalyst film 15 of the present invention 4 is a breathable porous film in which a platinum catalyst is supported on the surface of an alumina-silica binder, and has a physical property value of 12.5 W / mK.
[0115]
The oxidation catalyst film 15 of the present invention 5 is an air permeable porous film in which a platinum catalyst is supported on the surface of an alumina binder, and has a physical property value of 25 W / mK.
[0116]
The oxidation catalyst film 15 of Comparative Example 2 is a breathable porous film in which a platinum catalyst is supported on the surface of a silicon carbide-based binder, and has a physical property value of thermal conductivity of 40 W / mK.
[0117]
An ON-OFF energization test of gas sensors using oxidation catalyst films having different thermal conductivities was performed, and the resistance change rate of the heating element thin film 7 was measured. FIG. 6 is a characteristic diagram in which the correlation characteristics between the thermal conductivity and the resistance change rate of the oxidation catalyst film 15 are arranged. The resistance change rate of the heating element thin film 7 was determined by applying an ON-OFF test in which the power source thin film 7 was allowed to reach an operating temperature of 400 ° C. in 10 milliseconds by applying a DC voltage current to the terminal of the mounting case and then turned off. It is the rate of resistance change when performed 10,000 times.
[0118]
As is apparent from FIG. 6, it can be seen that the resistance change rate changes greatly when the thermal conductivity of the oxidation catalyst film 15 is less than 1 W / mK and more than 25 W / mK. Since the product of the present invention has a thermal conductivity of 1 to 25 W / mK, the oxidation catalyst film 15 dissipates heat well, and the heating element thin film 7 is suppressed from rising in temperature and has excellent durability characteristics.
[0119]
On the other hand, if the thermal conductivity is less than 1 W / mK, the heat dissipation from the oxidation catalyst film 15 is poor, so the temperature of the heating element thin film 7 rises and a slight decrease in durability is observed. On the other hand, if the thermal conductivity exceeds 25 W / mK, the heat radiation from the oxidation catalyst film 15 is good, so that a large current flows through the heating element thin film 7 to maintain its temperature, and a slight decrease in durability is observed. .
[0120]
The above results show that the same effect can be obtained even when the heating element thin film 7 is formed by laminating titanium, zirconium, and chromium metal heater auxiliary thin film 11 disposed below the platinum heater main thin film 10. It was.
[0121]
【The invention's effect】
  As aboveOf the present inventionIn the gas sensor, the glassy material and the heat-resistant insulating thin film of the insulating heat-resistant substrate are silicate glass, borosilicate glass, or silicate alumina glass ceramic whose main component is silicic acid.800 ° CIt becomes the material which has the above heat resistance. Therefore, the heating element thin film and the heat-resistant gas sensitive film constituting the gas sensor can be fired at a high temperature of, for example, 800 ° C. or more, and this reduces the restrictions on firing, so that simple film forming technology and quality control technology are used. Can be manufactured.
[0122]
On the other hand, titanium, zirconium, or chromium metal heater auxiliary thin film is a material with excellent bondability and malleability, and when fired at high temperature, it can bond well to platinum and insulating heat-resistant substrates as the main heater material. A malleable heating element thin film is obtained. When a large amount of power is applied in a short period of time to save power, the heating element thin film rises to the operating temperature in a short period of time and thermally expands, and the insulating heat-resistant substrates and heat-resistant insulating thin films placed above and below the temperature simultaneously The laminated heating element thin film follows the thermal expansion well and does not peel off, exhibits excellent thermal shock resistance, and does not cause a resistance change.
[0123]
The laminated heat-resistant gas sensitive film effectively transfers the heat generated in the heating element thin film through the heat-resistant insulating thin film, becomes an operating state in a short time, and can detect the gas concentration. At that time, since the vitreous material present on the surface of the insulating heat-resistant substrate is a material having a very low thermal conductivity, the heat generated in the heating element thin film is hardly transferred to the insulating heat-resistant substrate, most of which is It is transmitted to the heat-resistant gas sensitive film. Therefore, it is possible to achieve a gas sensor that can reach the operating temperature with a small amount of power consumption and that has a reduced power consumption.
[0124]
Furthermore, since the heating element thin film has low power consumption, the applied voltage / current value is small, and excellent durability characteristics can be obtained. In addition, the glassy material and the heat-resistant insulating thin film of the insulating heat-resistant substrate are glass materials having a very strong property against stress, so that they follow the thermal expansion caused by heat generation. Excellent durability characteristics can be obtained. In addition to this, the durability of the heater is excellent, so the sensor operating temperature does not change and the sensor output stabilizes for a long time, and the resistance change detection of the heater due to the resistance change detection and the resistance change prevention measures There is an advantage that the control circuit associated with can be simplified.
[Brief description of the drawings]
FIG. 1 is a sectional view of a gas sensor in an embodiment of the present invention.
FIG. 2 is a characteristic diagram of the concentration of silicic acid contained in the glass and the rate of change in resistance of the heating element thin film in the same example.
FIG. 3 is a characteristic diagram of the hydroxyl group content in quartz glass and the resistance change rate of the heating element thin film in the same example.
FIG. 4 is a characteristic diagram of the center line surface roughness of the insulating heat-resistant substrate and the resistance change rate of the heating element thin film in the same example.
FIG. 5 is a characteristic diagram of the thermal conductivity of the oxygen ion conductive solid electrolyte thin film and the resistance change rate of the heating element thin film in the same example.
FIG. 6 is a characteristic diagram of the thermal conductivity of the oxidation catalyst film and the resistance change rate of the heating element thin film in the same example.
FIG. 7 is a cross-sectional view of a conventional gas sensor
[Explanation of symbols]
6 Insulation heat-resistant substrate
7 Heating element thin film
8 Heat-resistant insulating thin film
9 Heat-resistant gas sensitive film
10 Heater main thin film
11 Metal heater auxiliary thin film
12 Oxygen ion conductive solid electrolyte thin film
13 First electrode thin film
14 Second electrode thin film
15 Oxidation catalyst membrane

Claims (6)

At least the heating element thin film, the heat-resistant insulating thin film, and the heat-resistant gas-sensitive film are laminated in order from the bottom on the insulating heat-resistant substrate whose surface material is glassy, and the glass properties of the insulating heat-resistant substrate and The heat-resistant insulating thin film is a silicate-alumina-based glass ceramic containing at least 60 to 80% silicic acid and 5 to 20% alumina, and the heating element thin film is a heater main thin film mainly composed of platinum and the heater A gas sensor which is a laminated film of a metal heater auxiliary fine thin film whose main component is at least one material selected from titanium, zirconium, or chromium, which is thinner than the main thin film and is disposed below the main thin film. At least a heating element thin film, a heat-resistant insulating thin film, and a heat-resistant gas-sensitive film are laminated in order from the bottom on the insulating heat-resistant substrate which is a quartz glass containing a hydroxyl group not exceeding 0.20 wt % . The glassy material of the insulating heat-resistant substrate and the heat-resistant insulating thin film are silicate glass, borosilicate glass, or silicate-alumina glass ceramic whose main component is silicic acid, and the heating element thin film is mainly composed of platinum. A heater main thin film having a thickness smaller than that of the heater main thin film, and a metal heater auxiliary fine thin film mainly composed of at least one material selected from titanium, zirconium, or chromium disposed below the heater main thin film. A gas sensor. The material of the surface with vitreous, on top of the insulating heat-resistant substrate center line surface roughness of 0.05～1Myu m, and at least the heating element thin film, sequentially and heat insulating thin, heat gas sensitive film from the bottom The insulating heat-resistant substrate glassy material and the heat-resistant insulating thin film are silicate glass, borosilicate glass, or silicate-alumina glass ceramic whose main component is silicic acid, and the heating element thin film is A heater main thin film mainly composed of platinum, and a metal heater auxiliary fine film mainly composed of at least one material selected from titanium, zirconium, or chromium which is thinner than the heater main thin film and is disposed below the heater main thin film. A gas sensor that is a thin film stack. At least an exothermic thin film , a heat-resistant insulating thin film made of quartz glass, and a heat-resistant gas-sensitive film are laminated in order from the bottom on the insulating heat-resistant substrate whose surface material is glassy, and the insulating heat-resistant substrate The glass material and the heat-resistant insulating thin film are silicate glass, borosilicate glass, or silicate-alumina glass ceramic whose main component is silicic acid, and the heating element thin film is a heater main thin film whose main component is platinum. A gas sensor which is a laminated film of a metal heater auxiliary thin film whose main component is at least one material selected from titanium, zirconium, or chromium, which is thinner than the heater main thin film and is disposed below the main film. At least the heating element thin film, the heat-resistant insulating thin film, and the heat-resistant gas-sensitive film are laminated in order from the bottom on the insulating heat-resistant substrate whose surface material is glassy, and the glass properties of the insulating heat-resistant substrate and The heat-resistant insulating thin film is a silicate glass, a borosilicate glass, or an alumina silicate glass ceramic mainly composed of silicic acid, and the heating element thin film is a heater main thin film mainly composed of platinum and the heater main film. titanium disposed thereunder by reducing the thickness from the thin film, zirconium or metallic heater auxiliary laminated film der fine film containing as a main component at least one material selected from chromium, is, the heat gas sensitive film The oxygen ion conductive solid electrolyte thin film, the breathable first electrode thin film and the second electrode thin film disposed on the oxygen ion conductive solid electrolyte thin film, and the first electrode thin film were laminated. Comprising at least a gas-porous oxide catalyst layer, the oxygen ion conductive solid electrolyte film is the thermal conductivity of the material of 1 to 7 W / mK gas sensor. The gas sensor according to claim 5 , wherein the oxidation catalyst film is mainly composed of a material having a thermal conductivity of 1 to 25 W / mK.

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