JP3608298B2 - Thermal infrared sensor and manufacturing method thereof - Google Patents

Thermal infrared sensor and manufacturing method thereof Download PDF

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JP3608298B2
JP3608298B2 JP17622596A JP17622596A JP3608298B2 JP 3608298 B2 JP3608298 B2 JP 3608298B2 JP 17622596 A JP17622596 A JP 17622596A JP 17622596 A JP17622596 A JP 17622596A JP 3608298 B2 JP3608298 B2 JP 3608298B2
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light receiving
thermal
infrared light
infrared sensor
insulating
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JPH1019671A (en
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徹 石津谷
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Nikon Corp
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J5/00—Radiation pyrometry, e.g. infrared or optical thermometry
    • G01J5/02—Constructional details
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J5/00—Radiation pyrometry, e.g. infrared or optical thermometry
    • G01J5/02—Constructional details
    • G01J5/0225—Shape of the cavity itself or of elements contained in or suspended over the cavity
    • G01J5/023—Particular leg structure or construction or shape; Nanotubes
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J5/00—Radiation pyrometry, e.g. infrared or optical thermometry
    • G01J5/02—Constructional details
    • G01J5/0225—Shape of the cavity itself or of elements contained in or suspended over the cavity
    • G01J5/0235—Spacers, e.g. for avoidance of stiction

Description

【０００１】
【発明の属する技術分野】
本発明は、熱型赤外線センサに関し、特にマイクロブリッジ構造の熱型赤外線センサ及びその製造方法に関する。
【０００２】
【従来の技術】
赤外線が入射する赤外線受光部と、該入射赤外線のフォトンエネルギーを吸収して温度が変化したときの上記赤外線受光部の物性値を示す電気信号を、半導体基板側に送るための配線部とで構成された熱型赤外線センサが公知である。
かかる熱型赤外線センサにあっては、入射赤外線の強さに応じて赤外線受光部の物性値（例えば、抵抗値）が応答よく変化する程、センサ感度が高くなる。
【０００３】
このため従来より、図９に示すように、赤外線受光部１１と半導体基板１との間の熱コンダクタンスを小さくするために、赤外線受光部１１と半導体基板１との間に空隙Ｍを設けるようにしたマイクロブリッジ構造の熱型赤外線センサ１０が提案されている。
この熱型赤外線センサ１０では、赤外線受光部１１に赤外線吸収層と熱電変換層（共に図示省略）が形成されると共に、当該赤外線受光部１１に連なる２つの橋梁部１４，１４によってその赤外線受光部１１が半導体基板１上に空隙Ｍを設けて配置されている。
【０００４】
この場合、橋梁部１４，１４は、図１０に示すように、その内部に配線層１４Ａが形成されており、赤外線受光部１１を支える機能のみならず当該配線層１４Ａによって熱電変換層（図示省略）を半導体基板１上の電極１Ａ，１Ａに電気的に接続させる機能を有する。
【０００５】
而して、上記橋梁部１４，１４は、赤外線受光部１１を支持するために（所定の強度を得るべく）、図１０に示すように、配線層（例えば、チタン膜）１４Ａを上下から保護層１４Ｂ，１４Ｃにて覆うようにしていた。
このような構造の熱型赤外線センサ１０は、赤外線受光部１１と半導体基板１との間に空隙Ｍが設けられているため、赤外線受光部を直付けするタイプの他の熱型赤外線センサ（図示省略）に比べて、赤外線受光部１１から半導体基板１への熱の伝導率が低くなりセンサ感度が向上する。
【０００６】
【発明が解決しようとする課題】
ところで、更にセンサ感度を高めるには、赤外線受光部１１と半導体基板１とを機械的に接続する橋梁部１４，１４の長さを長くし、又は、橋梁部１４の断面積を小さくして、当該赤外線受光部１１と半導体基板１との間の熱コンダクタンスを小さくすればよいことが知られている。
【０００７】
しかしながら、上記構造の熱型赤外線センサ１０では、上記のように橋梁部１４，１４で赤外線受光部１１を支持する必要があるために、当該橋梁部１４，１４を単に長くしたり、又、その断面積を小さくすることができず、センサの感度の向上が図れなかった。
本発明は、かかる事情に鑑みてなされたもので、赤外線受光部を半導体基板上に所定の空隙を設けつつ配置した熱型赤外線センサの、赤外線受光部と半導体基板との間の熱コンダクタンスを低下させて、センサ感度を向上させた熱型赤外線センサを提供することを目的とする。
【０００８】
【課題を解決するための手段】
上記目的を達成するため、請求項１に記載の発明は、半導体基板上に、入射した赤外線を熱エネルギーに変換し、該変換された熱エネルギーの大きさに応じて変化する物性値を電気的に読み出すための赤外線受光部と、上記赤外線受光部と上記半導体基板とを電気的に接続する配線が設けられた橋梁部と、上記赤外線受光部又は上記橋梁部の少なくとも一方を支持し、上記半導体基板とは異なる絶縁性物質からなる絶縁性脚部とを備えたものである。
【０００９】
又、請求項２に記載の発明は、上記絶縁性脚部を、有機物質にて形成したものである。
又、請求項３に記載の発明は、上記絶縁性脚部を、レジスト、ポリイミド樹脂、エナメル、セルロイドの何れかによって形成したものである。
又、請求項４に記載の発明は、上記橋梁部を、少なくとも配線層と絶縁層を含む２層構造若しくはそれ以上の多層構造としたものである。
【００１０】
又、請求項５に記載の発明は、上記絶縁層を、窒化シリコン膜で構成したものである。
又、請求項６に記載の発明は、請求項１から請求項５の何れかの熱型赤外線センサを作製するに当り、
半導体基板上に絶縁膜を形成し、該絶縁膜を上記絶縁性脚部の形状に合わせてエッチングし、
これに上記絶縁性脚部と、エッチング時の選択性が確保できる充填体を堆積させ、
該充填体を選択的にエッチングし、
その上面に少なくとも上記赤外線受光部若しくは橋梁部を構成する導電膜又は半導体膜を形成し、
これら導電膜又は半導体膜を当該赤外線受光部若しくは橋梁部の形状に合わせてエッチングし、
その後、上記充填体を除去して、
熱型赤外線センサを作製するものである。
【００１１】
（作用）
上記請求項１の発明によれば、橋梁部は赤外線受光部を支持する必要がなくなるため、当該絶縁性脚部を新たに設けたことによる熱コンダクタンスの上昇分より、橋梁部を長くし且つその断面積を小さくしたことによる熱コンダクタンスの低下分を大きくして、赤外線受光部と半導体基板との間の熱コンダクタンスを全体として低下させることができる。この場合、絶縁性脚部に関しては、その横断面積を、赤外線受光部を支持するのに必要な最小の大きさに決定すれば、赤外線受光部と半導体基板との間の熱コンダクタンスの上昇を最小限に抑えられる。又、橋梁部は、赤外線受光部を支持する必要がないため、配線としての機能さえあればよく、従って、その断面積を半導体製造技術において可能な限り小さくし、レイアウトの許す限りにおいてその長さを長くして、赤外線受光部と半導体基板との間の熱コンダクタンスを低下させることができる。又、橋梁部を絶縁性脚部によって支持する場合には、該橋梁部の全長を更に長くでき、この橋梁部の熱コンダクタンスを更に低下させることができる。
【００１２】
又、請求項２の発明によれば、絶縁性脚部の熱コンダクタンスが十分に小さくなり、又、橋梁部と半導体基板、及び赤外線受光部と半導体基板との間の絶縁も同時に達成できる。
又、請求項３の発明によれば、半導体製造技術等で一般的に用いられる材料で、当該絶縁性脚部が容易に作製できる。
【００１３】
又、請求項４の発明によれば、赤外線受光部を支持する強固さが要求されない橋梁部は、配線層の片面を保護するだけでよく、従来橋梁部の撓み防止に必要とされていた両面の保護層を必要としないので、当該橋梁部を簡単に作製できる。
又、請求項５の発明によれば、配線層の保護膜を容易に形成できる。
又、請求項６の発明によれば、一般的な半導体製造技術を、適宜組み合わせることで、従来より用いられている半導体製造装置で、容易に当該熱型赤外線センサを作製することができる。
【００１４】
【発明の実施の形態】
（第１の実施形態）
以下、本発明の第１の実施形態について、添付図面を参照して説明する。尚、この第１の実施形態は、請求項１から請求項６に対応する。
【００１５】
図１は第１の実施形態のマイクロブリッジ構造の熱型赤外線センサ２０を概念的に示す斜視図、図２は熱型赤外線センサ２０の橋梁部２４の構造を示す斜視図、図３及び図４は熱型赤外線センサ２０の製造工程を示す断面図、図５は熱型赤外線センサ２０の熱コンダクタンスを算出するための模式図である。
先ず、熱型赤外線センサ２０の構造の概略について、図１，図２を用いて説明する。
【００１６】
熱型赤外線センサ２０は、図１に示すように、赤外線受光部２１と、該赤外線受光部２１に連なる橋梁部２４，２４と、上記赤外線受光部２１を支持する第１の脚部２５，２５，２６，２６と、上記橋梁部２４，２４を支持する第２の脚部２７，２７とによって構成されている。
このうち赤外線受光部２１は、入射赤外線によるエネルギーを吸収する赤外線吸収層（図示省略）と、当該赤外線エネルギーの吸収に起因する温度上昇による物性値（例えば、抵抗値）の変化を検知するための熱電変換層（図示省略）とによって構成される。尚、この第１の実施形態では、赤外線受光部２１は、チタン膜とその上面を覆う窒化シリコン膜（図示省略）とからなり、これらチタン膜と窒化シリコン膜が、熱電変換層、赤外線吸収層（共に図示省略）を構成する。
【００１７】
尚、熱電変換層として膜厚が１０００Å以下の薄膜チタン膜を用いた場合は、当該膜が赤外線吸収層としての働きも併せもつため、赤外線受光部は、当該薄膜チタン膜による単一層で構成することもできる。
一方、橋梁部２４，２４は、図２に示すように、チタン膜からなる配線層２４Ａ及び窒化シリコン膜からなる保護層（絶縁層）２４Ｂの２層構造であり、この第１の実施形態では、詳細は後述するように、上記赤外線受光部２１を構成するチタン膜及び窒化シリコン膜と、同一の半導体製造工程において一体的に形成される。而して、配線層２４Ａは、赤外線受光部２１の熱電変換層（図示省略）と半導体基板１上の電極１Ａとを電気的に接続させ、入射赤外線のフォトンエネルギーによって上記赤外線受光部２１に温度変化が生じたときに、当該赤外線受光部２１の物性値の変化を、半導体基板１側で検出できるようになっている。
【００１８】
ところで、上記赤外線受光部２１は、図１に示すように、４つの第１の脚部２５，２５，２６，２６によって半導体基板１上方に空隙Ｍを空けて配置され、２つの橋梁部２４，２４は、その角部２４Ｃ，２４Ｃにおいて各々第２の脚部２７，２７で支持されている。
そして、第１の脚部２５，２５，２６，２６及び第２の脚部２７，２７は、共に、熱伝導率が低いレジスト（例えば、１．０×１０−３［Ｗ／ｃｍ・Ｋ］）によって形成されており、入射赤外線により温度上昇が生じる赤外線受光部２１から半導体基板１側に熱が伝わり難くなっている。因みに、第１の実施形態では、赤外線受光部２１は一辺が４０μｍ程度に作製され、上記第１，第２の脚部２５，２５，２６，２６，２７，２７は、この赤外線受光部２１を支持するのに充分な太さで、且つ、当該赤外線受光部２１と半導体基板１との熱の伝導が生じない空隙Ｍを確保するために必要な高さとなっている（例えば、横断面が直径１．０μｍで高さ２．０μｍ程度の円柱形状）。
【００１９】
一方で、上記橋梁部２４，２４は、上記赤外線受光部２１を支持する必要がないため、熱コンダクタンスが小さくなるように、半導体製造技術において可能な細さ（例えば、１．０μｍ程度）に設計され、しかも、その長さも長くなっている（図１に示す例では、一辺４０μｍの赤外線受光部２１の二辺に沿った長さで、約８０μｍ）。
【００２０】
次に、上記構成の熱型赤外線センサ２０の製造方法について、図３、図４を参照して説明する。尚、図３、図４は図１のＩＩＩ−ＩＩＩ線に沿った断面に対応する。
熱型赤外線センサ２０は概ね以下の手順に従って作製される。
（１）半導体基板１上に、例えば、ネガ形のレジスト３１を塗布し、これをマスク３８を使って上記第１，第２の脚部２５，２５，２６，２６，２７，２７の形状に露光する（図３（ａ））。
【００２１】
（２）被露光部を例えば、現像液にて除去して第１及び第２の脚部２５，２５，２６，２６，２７，２７を形成し、その上面に充填体として酸化シリコン膜３２をＣＶＤ法又は回転塗布法にて形成する（図３（ｂ））。
（３）上記酸化シリコン膜３２をプラズマエッチング法によりエッチングして、更に、橋梁部２４，２４に対応する傾斜部３２Ｃ（一点鎖線で示す）をウェットエッチングによるテーパーエッチング技術を利用して形成する（図３（ｃ））。
【００２２】
（４）上記エッチングされた酸化シリコン膜３２の上面に赤外線受光部２１の熱電変換層（図示省略）及び橋梁部２４，２４の配線層２４Ａを構成するチタン膜（金属膜）３３をスパッタ法や蒸着法等によって形成する。次いで、その上面に赤外線受光部２１の赤外線吸収層（図示省略）及び橋梁部２４，２４の保護膜２４Ｂを構成する窒化シリコン膜３４をＣＶＤ法又はスパッタ法にて形成する（図３（ｄ））。
【００２３】
（５）斯く形成したチタン膜３３及び窒化シリコン膜３４をホトリソグラフィ技術により作製されたマスクを用いて所望の形状にエッチングして、赤外線受光部２１及び橋梁部２４，２４を形成する（図４（ｅ））。
（６）上記赤外線受光部２１と半導体基板１との間にある酸化シリコン膜３２を、例えば、フッ酸系のエッチング液で除去して（ウェットエッチング）、空隙Ｍを設けた熱型赤外線センサ２０を得る（図４（ｆ）及び図１）。
【００２４】
次に、図５、図１１を参照しながら、上記第１及び第２の脚部２５，２５，２６，２６，２７，２７を設けたことによる赤外線受光部２１と半導体基板１との間の熱コンダクタンスの低減効果について、従来構造の熱型赤外線センサ１０の場合と比較して説明する。尚、図５は熱型赤外線センサ２０の熱コンダクタンスを算出するための模式図、図１１は従来の熱型赤外線センサ１０の熱コンダクタンスを算出するための模式図である。又、以下の説明では、２つの熱型赤外線センサ２０，１０は、その赤外線受光部２１，１１が共に、一辺がおよそ４０μｍの正方形とする。
【００２５】
ところで、熱コンダクタンス“Ｋ”は、一般に、次式（１）で与えられる。
Ｋ＝ｋ×Ｓ／Ｌ …（１）
ここで“ｋ”は物質によって定まる熱電導率、“Ｓ”は熱伝導経路の断面積、“Ｌ”は熱伝導経路の長さである。この算出式に基づいて、熱型赤外線センサ１０及び熱型赤外線センサ２０の各々の、赤外線受光部１１，２１と半導体基板１との間の熱コンダクタンスＫ１及びＫ２を求める。
【００２６】
因みに、赤外線受光部１１，２１と半導体基板１と間の熱コンダクタンスＫ１，Ｋ２は、その値が小さい程、熱型赤外線センサ１０，２０の感度が高くなる。
先ず、比較対象とする、従来の熱型赤外線センサ１０の赤外線受光部１１と半導体基板１との間の熱コンダクタンスＫ１を算出する。
ここでは熱型赤外線センサ１０の橋梁部１４，１４をチタン膜（Ｔｉ）と窒化シリコン膜（ＳｉＮ）とで構成した場合を考える。
【００２７】
前述したように、従来の熱型赤外線センサ１０は、その橋梁部１４，１４が、赤外線受光部１１を支持しなければならない。而して、一辺が４０μｍ程度の赤外線受光部１１を支持するのであれば、チタン膜（Ｔｉ）からなる配線層１４Ａは幅が１．５μｍ、厚さが７５０Åに形成され、窒化シリコン膜からなる上側の保護層（絶縁層）１４Ｂは幅が３．０μｍ、厚さが１５００Åに形成され、同じく窒化シリコン膜からなる下側の保護層１４Ｃは幅が３．０μｍ、高さが２０００Å程度に形成される。又、橋梁部１４，１４の長さは、赤外線受光部１１の一辺と略同じ４０μｍである。
【００２８】
ここで、チタン（Ｔｉ）の熱伝導率を０．２［Ｗ／ｃｍ・Ｋ］、窒化シリコン（ＳｉＮ）の熱伝導率を０．５５７［Ｗ／ｃｍ・Ｋ］とすると、橋梁部１４，１４の１つ当りの熱コンダクタンスＫ１１（図１１のＰ１−Ｐ２間の熱コンダクタンス）は、次式（２）によって得られる。

Figure 0003608298
而して、図９，図１１に示す従来の熱型赤外線センサ１０は、２つの橋梁部１４，１４でその赤外線受光部１１が半導体基板１上に支持されているので、赤外線受光部１１と半導体基板１との間の熱コンダクタンスＫ１は、次式（３）によって得られる。
【００２９】
Ｋ１＝２Ｋ１１＝３．０×１０−６［Ｗ／Ｋ］ …（３）
次に、熱型赤外線センサ２０の赤外線受光部２１と半導体基板１との間の熱コンダクタンスＫ２を算出する。
上記したように熱型赤外線センサ２０の赤外線受光部２１はレジストからなる第１，第２の脚部２５，２５，２６，２６，２７，２７によって支えられている。
【００３０】
一辺が４０μｍ程度の赤外線受光部２１を支持するのであれば、各々の脚部２５，２５，２６，２６，２７，２７は、直径が１．０μｍ程度、高さが２．０μｍ程度の円柱とすることができる。この場合、第１，第２の脚部２５，２５，２６，２６，２７，２７の１本当りの熱コンダクタンスＫ２１は、レジストの熱伝導率を１．０×１０−３［Ｗ／ｃｍ・Ｋ］とすると、次式（４）によって得られる。
【００３１】
Figure 0003608298
又、橋梁部２４の一辺（図５のＰ１−Ｐ２間、Ｐ２−Ｐ３間）当りの熱コンダクタンスＫ２２は以下のように求められる。
即ち、橋梁部２４は、配線層２４Ａと保護層２４Ｂの２層構造になっており、配線層２４Ａは、幅が１μｍ、膜厚が８００Åで、材質はチタン、又、保護層２４Ｂは、幅が１．０μｍ膜厚１０００Åで、材質は窒化シリコン（ＳｉＮ）とすることができる。又、橋梁部２４の一辺当りの長さは、上記従来の橋梁部１４と同じ４０μｍ程度である。チタンの熱伝導率を０．２［Ｗ／ｃｍ・Ｋ］、窒化シリコンの熱伝導率を０．５５７［Ｗ／ｃｍ・Ｋ］とすると、上記熱コンダクタンスＫ２２は、次式（５）によって得られる。
【００３２】
Figure 0003608298
前述した脚部（第１，第２の脚部２５，２６，２７）の１つ当たりの熱コンダクタンスＫ２１、及び当該橋梁部２４の一辺当りの熱コンダクタンスＫ２２を用いてＰ１−Ｐ３間の熱コンダクタンスＫ２３を求めると、該熱コンダクタンスＫ２３は、図５のＰ１−Ｐ２間の熱コンダクタンスと、Ｐ２点（角部２４Ｃに対応）を支える第２の脚部２７の熱コンダクタンスと、Ｐ２−Ｐ３間の熱コンダクタンスを合成したものであるから、次式（６）によって得られる。
【００３３】
Figure 0003608298
この熱コンダクタンスＫ２３はＰ１〜Ｐ３間の熱コンダクタンスであり、従来の熱型赤外線センサ１０における橋梁部１４の１つの熱コンダクタンスＫ１１に相当する値である。この値Ｋ２３と値Ｋ１１とを比較すると、前者は後者の１／１５程度になる。
【００３４】
このように、熱型赤外線センサ２０では、橋梁部２４と第２の脚部２７とを合わせても、熱型赤外線センサ１０の橋梁部１４に比べて格段に熱コンダクタンスを小さくすることができる。
而して、第１，第２の脚部２５，２５，２６，２６，２７，２７を用いて赤外線受光部２１と橋梁部２４とを、各々支持した場合の（図１に示す熱型赤外線センサ２０）当該赤外線受光部２１と半導体基板１との間の熱コンダクタンスＫ２は、次式（７）によって得られる。
【００３５】
Ｋ２＝４Ｋ２１＋２Ｋ２３＝３．５×１０−７［Ｗ／Ｋ］ …（７）
このように第１、第２の脚部２５，２５，２６，２６，２７，２７を用いた場合の熱コンダクタンスＫ２は、赤外線受光部１１，２１が略同じ大きさ（一辺が４０μｍ）の従来の熱型赤外線センサ１０の熱コンダクタンスＫ１の、およそ１／９となる。
【００３６】
以上のように、熱型赤外線センサ２０では、赤外線受光部２１が、当該脚部２５，２５，２６，２６で支えられているために、橋梁部２４，２４は、従来のようにその強度を強くする必要がなくなり、その断面積を小さくし、しかも半導体基板１上のレイアウトパターンが許す限りにおいて長くできるので、橋梁部２４，２４に係る上記熱コンダクタンスＫ２３を著しく低減することができる。
【００３７】
そして、赤外線受光部２１と半導体基板１との間に脚部２５，２５，２６，２６，２７，２７を配置することにより増加する熱コンダクタンスと、橋梁部２４，２４の断面積を小さくし、且つ、長くすることによって低減される熱コンダクタンスとを比較した場合、前者に対して後者を著しく大きくできるために、熱型赤外線センサ２０全体の熱コンダクタンスＫ２を大幅に低減できる。
【００３８】
図６は、脚部２８を用いて赤外線受光部２１若しくはこれに連なる橋梁部２４，２４を支持する変形例を示す説明図である。このうち（ａ）は２つの脚部２８，２８で赤外線受光部２１を支持した例、（ｂ）は脚部２８，２８で赤外線受光部２１及び橋梁部２４，２４の直線部を同時に支持した例、（ｃ）は２つの脚部２８，２８で赤外線受光部２１を支持し他の２つの脚部２８，２８で橋梁部２４，２４を支持した例、（ｄ）は橋梁部２４，２４を長く延ばし脚部２８，２８で当該橋梁部２４，２４と赤外線受光部２１を同時に支持した例、（ｅ）は脚部２８，２８で赤外線受光部２１及び橋梁部２４，２４の角部を同時に支持した例、（ｆ）は２つの脚部２８，２８で赤外線受光部２１を支持し他の４つの脚部２８，２８，２８，２８で長く延ばされた橋梁部（赤外線受光部２１の四辺の長さに相当）２４，２４を支持した例、（ｇ）は４つの脚部２８，２８，２８，２８で橋梁部２４，２４の８つの角部を支持した例、（ｈ）は葛籠状に形成された橋梁部２４，２４を４つの脚部２８，２８，２８，２８で支持した例を示す説明図である。
【００３９】
以上のものは何れも、脚部２８…の数を減らして当該熱コンダクタンスを低下するもの、及び／又は橋梁部２４，２４を細長く形成して当該熱コンダクタンスを低下させたものであり、これらの例によれば、熱コンダクタンスは更に低下し、熱型赤外線センサ２０の感度が更に向上する。
尚、この第１の実施形態では、第１及び第２の脚部２５，２５，２６，２６，２７，２７を熱伝導率の小さいレジストで形成した例を示したが、他の熱伝導率の小さい材質、例えば、ポリイミド樹脂、エナメル、セルロイド等の有機物質にて、これを形成してもよい。
【００４０】
又、上記実施形態では、橋梁部２４，２４の配線層２４Ａをチタンで構成する例を示したが、他の導体若しくは半導体（例えば、バナジウムオキサイド膜（ＶＯｘ））でこれを形成してもよい。
又、上記実施形態では、橋梁部２４，２４を、配線層２４Ａと保護層２４Ｂの２層構造としたが、３層構造以上にしてもよい。この場合、上記した実施形態では、橋梁部２４，２４を形成する際に、配線層２４Ａの上面に保護層２４Ｂを形成しているが、配線層２４Ａの上下に保護層を形成してもよい。反対に、配線層２４Ａを第２の脚部２７，２７で支持しているので、保護膜２４Ｂを省いても強度的には問題はない。
【００４１】
尚、熱型赤外線センサ２０の赤外線受光部２１の構造に関しては、例示した構造に限るものでなく、他のマイクロブリッジ構造の熱型赤外線センサに、本発明を適用できるのは、勿論である。
（第２の実施形態）
次に、本発明の第２の実施形態について説明する。尚、この第２の実施形態は、請求項１から請求項６に対応する。
【００４２】
熱型赤外線センサ４０では、図７に示すように、赤外線受光部４１が脚部４５によって支持されている。
尚、赤外線受光部４１、橋梁部４４の構造は、上記した第１の実施形態の赤外線受光部２１、橋梁部２４と同一の構成であり、その詳細な説明は省略する。
赤外線受光部４１は、図７に示すように、１つの円柱状の脚部４５によって半導体基板１上方に空隙Ｍを空けて配置されている。
【００４３】
この場合、脚部４５も、上記した第１の実施形態の脚部２５，２６，２７と同じように、熱伝導率が低いレジスト（例えば、１．０×１０−３［Ｗ／ｃｍ・Ｋ］）によって形成されている。このレジストで脚部４５を形成することによって、入射赤外線により温度上昇が生じる赤外線受光部４１から半導体基板１側に熱が伝わり難くなる。因みに、赤外線受光部４１の一辺が４０μｍ程度に作製されている場合には、脚部４５は、この赤外線受光部４１を支持するのに充分な太さで、且つ、当該赤外線受光部４１と半導体基板１との熱の伝導が生じない空隙Ｍを確保するために必要な高さとなっている（例えば、横断面が直径４．０μｍで高さ２．０μｍ程度の円柱形状）。
【００４４】
この場合、上記橋梁部４４，４４は、上記赤外線受光部４１を支持する必要がないため、熱コンダクタンスが小さくなるように、半導体製造技術において可能な細さ（例えば、１．０μｍ程度）に設計され、しかも、その長さも長くなっている（図７に示す例では、一辺４０μｍの赤外線受光部４１の二辺に沿った長さで、約８０μｍ）。
【００４５】
尚、上記構成の熱型赤外線センサ４０の製造方法は、上記した第１の実施形態の熱型赤外線センサ２０の製造方法と、脚部４５の形状のみが異なるものであって（図３（ａ）におけるマスク３８のパターンのみが異なる）、他の工程は略同一であり、その詳細な説明は省略する。
又、熱型赤外線センサ４０における熱コンダクタンスＫ３０は以下のような値になる。尚、ここでは、熱型赤外線センサ４０の赤外線受光部４１が、上記第１の実施形態の熱型赤外線センサ２０と同様に一辺がおよそ４０μｍの正方形とする。
【００４６】
上記したように熱型赤外線センサ４０の赤外線受光部４１はレジストからなる唯１つの脚部４５によって支えられている。
一辺が４０μｍ程度の赤外線受光部４１を支持するのであれば、脚部４５は、直径が４．０μｍ程度、高さが２．０μｍ程度の円柱とすることができる。この場合、１つの脚部４５の熱コンダクタンスＫ３１は、レジストの熱伝導率を１．０×１０−３［Ｗ／ｃｍ・Ｋ］とすると、次式（８）によって得られる。
【００４７】
Ｋ３１＝１．０×１０−３｛π×（２．０×１０−４）２／２×１０−４｝＝６．３×１０−７［Ｗ／Ｋ］ …（８）
又、橋梁部４４の一辺当りの熱コンダクタンスＫ３２は、第１の実施形態の熱コンダクタンスＫ２２と同じ値（１．８×１０−７［Ｗ／Ｋ］）となる。
従って、橋梁部４４の１本当りの熱コンダクタンスＫ３３は、Ｋ３２の半分の値（０．９×１０−７［Ｗ／Ｋ］）となる。
【００４８】
而して、脚部４５を用いて赤外線受光部４１を支持した場合の（図７に示す熱型赤外線センサ４０）当該赤外線受光部４１と半導体基板１との間の熱コンダクタンスＫ３は、次式（９）によって得られる。
Ｋ３＝Ｋ３１＋２Ｋ３３＝８．１×１０−７［Ｗ／Ｋ］ …（９）
このように１つの脚部４５を用いた場合の熱コンダクタンスＫ３は、赤外線受光部１１，４１が略同じ大きさ（一辺が４０μｍ）の従来の熱型赤外線センサ１０の熱コンダクタンスＫ１の、およそ１／４となる。
【００４９】
以上のように、熱型赤外線センサ４０では、赤外線受光部４１が、当該脚部４５で支えられているために、橋梁部４４，４４は、従来のようにその強度を強くする必要がなくなり、その断面積を小さくし、しかも半導体基板１上のレイアウトパターンが許す限りにおいて長くできるので、橋梁部４４，４４に係る上記熱コンダクタンスＫ３３を著しく低減することができる。
【００５０】
そして、赤外線受光部４１と半導体基板１との間に脚部４５を配置することにより増加する熱コンダクタンスと、橋梁部４４，４４の断面積を小さくし、且つ、長くすることによって低減される熱コンダクタンスとを比較した場合、前者に対して後者を著しく大きくできるために、熱型赤外線センサ４０全体の熱コンダクタンスＫ３を大幅に低減できる。
【００５１】
図８は、図７の円柱状の脚部４５に代えて、断面が十字状の脚部４６（図８（ａ））、中空の脚部４７（図８（ｂ））、断面がＣ型の脚部４８（図８（ｃ））、断面が長方形の脚部４９（図８（ｄ））を用いて赤外線受光部４１を支持する変形例を示す説明図である。
このような脚部４６，４７，４８，４９によれば、その断面積Ｓ１，Ｓ２，Ｓ３，Ｓ４をより小さくして当該脚部４６，４７，４８，４９の熱コンダクタンスを更に小さくして、赤外線受光部４１と半導体基板１との間の断熱効果を更に向上させることができ、熱型赤外線センサ４０の感度が更に向上する。
【００５２】
尚、これらの脚部４６，４７，４８，４９は、第１の実施形態の第１，第２の脚部２５，…，２７と置換して使用できるのは、勿論である。
尚、この第２の実施形態では脚部４５，４６，４７，４８，４９を、熱伝導率の小さいレジストで形成した例を示したが、他の熱伝導率の小さい材質、例えば、ポリイミド樹脂、エナメル、セルロイド等の有機物質にて、これを形成してもよい。
【００５３】
尚、熱型赤外線センサ４０の赤外線受光部４１の構造に関しては、例示した構造に限るものでなく、他のマイクロブリッジ構造の熱型赤外線センサに、本発明を適用できるのは、勿論である。
【００５４】
【発明の効果】
以上説明したように、請求項１の発明によれば、橋梁部は赤外線受光部を支持する必要がなくなるため、絶縁性脚部による熱コンダクタンスの上昇分と橋梁部の熱コンダクタンスの低下分とを調整して、全体として、熱型赤外線センサの熱コンダクタンスを低下させて、センサ感度の向上が図れる。この場合、絶縁性脚部はその横断面が、赤外線受光部を支持するに必要な最小の大きさに決定すれば、熱コンダクタンスの上昇が最小限に抑えられ、センサ感度の向上が図れる。又、橋梁部は、赤外線受光部を支持する必要がないため、配線としての機能があればよく、従って、その断面積を小さく且つ長さを長くして、熱コンダクタンスを低下させれば、センサ感度の更なる向上が図れる。又、橋梁部をも絶縁性脚部によって支持するのであれば、橋梁部の全長を更に長くでき、この橋梁部の熱コンダクタンスを更に低下させて、更なるセンサ感度の向上が図れる。
【００５５】
又、請求項２の発明によれば、絶縁性脚部の熱コンダクタンスが下がり、センサ感度の向上が図れる。
又、請求項３の発明によれば、半導体製造技術で一般的に用いられる材料で、絶縁性脚部が容易に形成できる。
又、請求項４の発明によれば、赤外線受光部を支持する強固さが要求されないため、橋梁部はその表面を絶縁するだけで、簡単に作製できる。
【００５６】
又、請求項５の発明によれば、容易に橋梁部の保護膜を形成できる。
又、請求項６の発明によれば、一般的に用いられている半導体製造装置で、センサ感度の高い熱型赤外線センサを容易に作製することができる。
【図面の簡単な説明】
【図１】第１の実施形態の熱型赤外線センサ２０を示す斜視図である。
【図２】
熱型赤外線センサ２０の橋梁部２４の構造を示す斜視図である。
【図３】熱型赤外線センサ２０の製造工程を示す断面図である。
【図４】熱型赤外線センサ２０の製造工程を示す断面図である。
【図５】熱コンダクタンスＫ２の算出のための熱型赤外線センサ２０の模式図である。
【図６】熱型赤外線センサ２０の橋梁部２４，２４の形状及び脚部２５，２５，２６，２６，２７，２７の配置を異ならせた変形例を示す説明図である。
【図７】第２の実施形態の熱型赤外線センサ４０を示す斜視図である。
【図８】熱型赤外線センサ４０の脚部の形状を異ならせた変形例を示す説明図である。
【図９】従来の熱型赤外線センサ１０を示す斜視図である。
【図１０】従来の熱型赤外線センサ１０の橋梁部１４の構造を示す斜視図である。
【図１１】熱コンダクタンスＫ１の算出のための従来の熱型赤外線センサ１０の模式図である。
【符号の説明】
１ 半導体基板
１Ａ 電極
２０，４０ 熱型赤外線センサ
２１，４１ 赤外線受光部
２４，４４ 橋梁部
２４Ａ 配線層
２４Ｂ 保護膜（絶縁膜）
２５，２６ 第１の脚部（絶縁性脚部）
２７ 第２の脚部（絶縁性脚部）
３１ レジスト
３２ 酸化シリコン膜（充填体）
３３ チタン膜
３４ 窒化シリコン膜
４５，４６，４７，４８，４９ 脚部[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a thermal infrared sensor, and more particularly to a thermal infrared sensor having a microbridge structure and a manufacturing method thereof.
[0002]
[Prior art]
Consists of an infrared light receiving unit on which infrared light is incident and a wiring unit for sending an electrical signal indicating the physical property value of the infrared light receiving unit when the temperature is changed by absorbing the photon energy of the incident infrared light to the semiconductor substrate side A thermal infrared sensor is known.
In such a thermal infrared sensor, the sensitivity of the sensor increases as the physical property value (for example, the resistance value) of the infrared light receiving portion changes in response to the intensity of incident infrared light.
[0003]
Therefore, conventionally, as shown in FIG. 9, a gap M is provided between the infrared light receiving unit 11 and the semiconductor substrate 1 in order to reduce the thermal conductance between the infrared light receiving unit 11 and the semiconductor substrate 1. A thermal infrared sensor 10 having a microbridge structure has been proposed.
In this thermal infrared sensor 10, an infrared absorption layer and a thermoelectric conversion layer (both not shown) are formed in the infrared light receiver 11, and the two infrared light receivers 14 and 14 are connected to the infrared light receiver 11. 11 is arranged on the semiconductor substrate 1 with a gap M provided.
[0004]
In this case, as shown in FIG. 10, the bridge portions 14, 14 have a wiring layer 14 </ b> A formed therein, and the thermoelectric conversion layer (not shown) is formed by the wiring layer 14 </ b> A as well as the function of supporting the infrared light receiving unit 11. ) Is electrically connected to the electrodes 1A and 1A on the semiconductor substrate 1.
[0005]
Thus, the bridge portions 14 and 14 protect the wiring layer (for example, titanium film) 14A from above and below as shown in FIG. 10 in order to support the infrared light receiving portion 11 (to obtain a predetermined strength). The layers 14B and 14C were covered.
Since the thermal infrared sensor 10 having such a structure is provided with a gap M between the infrared light receiving part 11 and the semiconductor substrate 1, another thermal infrared sensor of the type in which the infrared light receiving part is directly attached (illustrated). Compared to (omitted), the thermal conductivity from the infrared light receiving unit 11 to the semiconductor substrate 1 is lowered, and the sensor sensitivity is improved.
[0006]
[Problems to be solved by the invention]
By the way, in order to further increase the sensor sensitivity, the length of the bridge portions 14 and 14 that mechanically connect the infrared light receiving portion 11 and the semiconductor substrate 1 is increased, or the cross-sectional area of the bridge portion 14 is decreased, It is known that the thermal conductance between the infrared light receiving unit 11 and the semiconductor substrate 1 may be reduced.
[0007]
However, in the thermal infrared sensor 10 having the above structure, since the infrared light receiving unit 11 needs to be supported by the bridge units 14 and 14 as described above, the bridge units 14 and 14 are simply made longer, The cross-sectional area could not be reduced, and the sensitivity of the sensor could not be improved.
The present invention has been made in view of such circumstances, and the thermal conductance between the infrared light receiving part and the semiconductor substrate of the thermal infrared sensor in which the infrared light receiving part is arranged on the semiconductor substrate while providing a predetermined gap is reduced. An object of the present invention is to provide a thermal infrared sensor with improved sensor sensitivity.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, the invention according to claim 1 converts infrared rays incident on a semiconductor substrate into thermal energy, and electrically changes a physical property value that changes according to the magnitude of the converted thermal energy. An infrared light receiving unit for reading the light, and the infrared light receiving unit the above Supports at least one of the bridge portion provided with wiring for electrically connecting the semiconductor substrate and the infrared light receiving portion or the bridge portion. And an insulating material different from that of the semiconductor substrate. Insulating legs.
[0009]
According to a second aspect of the present invention, the insulating leg is formed of an organic material.
According to a third aspect of the present invention, the insulating leg is formed of any one of resist, polyimide resin, enamel, and celluloid.
According to a fourth aspect of the present invention, the bridge portion has a two-layer structure including at least a wiring layer and an insulating layer or a multilayer structure having more than that.
[0010]
According to a fifth aspect of the present invention, the insulating layer is composed of a silicon nitride film.
Further, the invention according to claim 6 provides a thermal infrared sensor according to any one of claims 1 to 5.
Forming an insulating film on the semiconductor substrate, etching the insulating film in accordance with the shape of the insulating legs,
The insulating legs and the filler that can ensure selectivity during etching are deposited on this,
Selectively etching the filler;
Forming a conductive film or a semiconductor film constituting at least the infrared light receiving part or the bridge part on the upper surface,
Etching these conductive film or semiconductor film according to the shape of the infrared light receiving part or bridge part,
Thereafter, the filler is removed,
A thermal infrared sensor is produced.
[0011]
(Function)
According to the first aspect of the present invention, since the bridge portion does not need to support the infrared light receiving portion, the bridge portion is made longer than the increase in thermal conductance caused by newly providing the insulating legs. The thermal conductance between the infrared light receiving part and the semiconductor substrate can be reduced as a whole by increasing the decrease in thermal conductance due to the reduced cross-sectional area. In this case, if the cross-sectional area of the insulating leg portion is determined to be the minimum size necessary to support the infrared light receiving portion, the increase in thermal conductance between the infrared light receiving portion and the semiconductor substrate is minimized. It can be suppressed to the limit. In addition, since the bridge portion does not need to support the infrared light receiving portion, it only needs to function as a wiring. Therefore, its cross-sectional area is made as small as possible in the semiconductor manufacturing technology, and its length is as long as the layout allows. The thermal conductance between the infrared light receiving part and the semiconductor substrate can be reduced by lengthening the length. Further, when the bridge portion is supported by the insulating legs, the entire length of the bridge portion can be further increased, and the thermal conductance of the bridge portion can be further reduced.
[0012]
According to the invention of claim 2, the thermal conductance of the insulating leg portion is sufficiently small, and insulation between the bridge portion and the semiconductor substrate and between the infrared light receiving portion and the semiconductor substrate can be achieved at the same time.
According to the invention of claim 3, the insulating leg portion can be easily manufactured with a material generally used in semiconductor manufacturing technology or the like.
[0013]
According to the invention of claim 4, the bridge portion that does not require the rigidity to support the infrared light receiving portion only needs to protect one side of the wiring layer, and both sides that are conventionally required for preventing the bending of the bridge portion. Therefore, the bridge portion can be easily manufactured.
According to the invention of claim 5, the protective film for the wiring layer can be easily formed.
According to the invention of claim 6, the thermal infrared sensor can be easily manufactured by a conventionally used semiconductor manufacturing apparatus by appropriately combining general semiconductor manufacturing techniques.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
(First embodiment)
DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, a first embodiment of the invention will be described with reference to the accompanying drawings. The first embodiment corresponds to claims 1 to 6.
[0015]
FIG. 1 is a perspective view conceptually showing a thermal infrared sensor 20 having a microbridge structure according to the first embodiment. FIG. 2 is a perspective view showing a structure of a bridge portion 24 of the thermal infrared sensor 20. FIGS. FIG. 5 is a cross-sectional view showing a manufacturing process of the thermal infrared sensor 20, and FIG. 5 is a schematic diagram for calculating the thermal conductance of the thermal infrared sensor 20.
First, the outline of the structure of the thermal infrared sensor 20 will be described with reference to FIGS.
[0016]
As shown in FIG. 1, the thermal infrared sensor 20 includes an infrared light receiver 21, bridge portions 24 and 24 connected to the infrared light receiver 21, and first legs 25 and 25 that support the infrared light receiver 21. , 26, 26 and second leg portions 27, 27 that support the bridge portions 24, 24.
Among these, the infrared light receiving unit 21 detects an infrared absorption layer (not shown) that absorbs energy by incident infrared rays, and changes in physical property values (for example, resistance values) due to temperature rise caused by absorption of the infrared energy. And a thermoelectric conversion layer (not shown). In the first embodiment, the infrared light receiving unit 21 is composed of a titanium film and a silicon nitride film (not shown) covering the upper surface thereof, and the titanium film and the silicon nitride film are composed of a thermoelectric conversion layer and an infrared absorption layer. (Both are not shown).
[0017]
When a thin film titanium film having a film thickness of 1000 mm or less is used as the thermoelectric conversion layer, the film also functions as an infrared absorption layer. Therefore, the infrared light receiving part is constituted by a single layer of the thin film titanium film. You can also.
On the other hand, as shown in FIG. 2, the bridge portions 24 and 24 have a two-layer structure of a wiring layer 24A made of a titanium film and a protective layer (insulating layer) 24B made of a silicon nitride film. As will be described later in detail, the titanium film and the silicon nitride film constituting the infrared light receiving unit 21 are integrally formed in the same semiconductor manufacturing process. Thus, the wiring layer 24A electrically connects the thermoelectric conversion layer (not shown) of the infrared light receiving unit 21 and the electrode 1A on the semiconductor substrate 1 to the infrared light receiving unit 21 by the photon energy of incident infrared rays. When the change occurs, the change in the physical property value of the infrared light receiving unit 21 can be detected on the semiconductor substrate 1 side.
[0018]
By the way, as shown in FIG. 1, the infrared light receiving unit 21 is arranged with a gap M above the semiconductor substrate 1 by four first leg portions 25, 25, 26, 26, and two bridge portions 24, 24 is supported by the second legs 27 and 27 at the corners 24C and 24C, respectively.
The first legs 25, 25, 26, 26 and the second legs 27, 27 are both resists having a low thermal conductivity (for example, 1.0 × 10 -3 [W / cm · K]), and it is difficult for heat to be transmitted from the infrared light receiving portion 21 where the temperature rises due to incident infrared rays to the semiconductor substrate 1 side. Incidentally, in the first embodiment, the infrared light receiving unit 21 is manufactured to have a side of about 40 μm, and the first and second leg portions 25, 25, 26, 26, 27, 27 have the infrared light receiving unit 21. It is thick enough to support and has a height required to secure a gap M that does not cause heat conduction between the infrared light receiving unit 21 and the semiconductor substrate 1 (for example, the cross section has a diameter). A cylindrical shape having a height of about 1.0 μm and a height of about 2.0 μm).
[0019]
On the other hand, since the bridge portions 24 and 24 do not need to support the infrared light receiving portion 21, the bridge portions 24 and 24 are designed to be as thin as possible in semiconductor manufacturing technology (for example, about 1.0 μm) so as to reduce thermal conductance. Moreover, the length is also long (in the example shown in FIG. 1, the length along the two sides of the infrared light receiving section 21 having a side of 40 μm is about 80 μm).
[0020]
Next, a method for manufacturing the thermal infrared sensor 20 having the above configuration will be described with reference to FIGS. 3 and 4 correspond to a cross section taken along line III-III in FIG.
The thermal infrared sensor 20 is generally manufactured according to the following procedure.
(1) On the semiconductor substrate 1, for example, a negative resist 31 is applied, and this is applied to the shape of the first and second legs 25, 25, 26, 26, 27, 27 using a mask 38. Exposure is performed (FIG. 3A).
[0021]
(2) The exposed portion is removed with, for example, a developer to form first and second leg portions 25, 25, 26, 26, 27, and 27, and a silicon oxide film 32 is formed on the upper surface thereof as a filler. It is formed by a CVD method or a spin coating method (FIG. 3B).
(3) The silicon oxide film 32 is etched by plasma etching, and an inclined portion 32C (indicated by a one-dot chain line) corresponding to the bridge portions 24 and 24 is formed by using a taper etching technique by wet etching ( FIG. 3 (c)).
[0022]
(4) A titanium film (metal film) 33 constituting the thermoelectric conversion layer (not shown) of the infrared light receiving portion 21 and the wiring layer 24A of the bridge portions 24, 24 is formed on the upper surface of the etched silicon oxide film 32 by sputtering or the like. It is formed by vapor deposition. Next, an infrared absorption layer (not shown) of the infrared light receiving unit 21 and a silicon nitride film 34 constituting the protective film 24B of the bridge portions 24 and 24 are formed on the upper surface by CVD or sputtering (FIG. 3D). ).
[0023]
(5) The thus formed titanium film 33 and silicon nitride film 34 are etched into a desired shape using a mask produced by a photolithography technique to form the infrared light receiving part 21 and the bridge parts 24 and 24 (FIG. 4). (E)).
(6) The thermal infrared sensor 20 in which the silicon oxide film 32 between the infrared light receiving portion 21 and the semiconductor substrate 1 is removed with, for example, a hydrofluoric acid-based etchant (wet etching) to provide a gap M. Is obtained (FIG. 4 (f) and FIG. 1).
[0024]
Next, with reference to FIGS. 5 and 11, between the infrared light receiving unit 21 and the semiconductor substrate 1 due to the provision of the first and second leg portions 25, 25, 26, 26, 27, 27. The effect of reducing the thermal conductance will be described in comparison with the case of the thermal infrared sensor 10 having a conventional structure. 5 is a schematic diagram for calculating the thermal conductance of the thermal infrared sensor 20, and FIG. 11 is a schematic diagram for calculating the thermal conductance of the conventional thermal infrared sensor 10. In the following description, it is assumed that the two thermal infrared sensors 20 and 10 have a square shape with both sides of the infrared light receiving portions 21 and 11 having a side of approximately 40 μm.
[0025]
Incidentally, the thermal conductance “K” is generally given by the following equation (1).
K = k × S / L (1)
Here, “k” is the thermal conductivity determined by the substance, “S” is the cross-sectional area of the heat conduction path, and “L” is the length of the heat conduction path. Based on this calculation formula, thermal conductances K1 and K2 between the infrared light receiving units 11 and 21 and the semiconductor substrate 1 of each of the thermal infrared sensor 10 and the thermal infrared sensor 20 are obtained.
[0026]
Incidentally, the thermal conductances K1 and K2 between the infrared light receiving units 11 and 21 and the semiconductor substrate 1 have higher sensitivity as the thermal infrared sensors 10 and 20 are smaller.
First, a thermal conductance K1 between the infrared light receiving unit 11 of the conventional thermal infrared sensor 10 and the semiconductor substrate 1 to be compared is calculated.
Here, a case is considered in which the bridge portions 14 of the thermal infrared sensor 10 are composed of a titanium film (Ti) and a silicon nitride film (SiN).
[0027]
As described above, in the conventional thermal infrared sensor 10, the bridge portions 14 and 14 must support the infrared light receiving unit 11. Thus, if the infrared light receiving unit 11 having a side of about 40 μm is supported, the wiring layer 14A made of a titanium film (Ti) is formed with a width of 1.5 μm, a thickness of 750 mm, and made of a silicon nitride film. The upper protective layer (insulating layer) 14B is formed with a width of 3.0 μm and a thickness of 1500 mm, and the lower protective layer 14C made of a silicon nitride film is formed with a width of 3.0 μm and a height of about 2000 mm. Is done. The length of the bridge portions 14 and 14 is 40 μm which is substantially the same as one side of the infrared light receiving portion 11.
[0028]
Here, assuming that the thermal conductivity of titanium (Ti) is 0.2 [W / cm · K] and the thermal conductivity of silicon nitride (SiN) is 0.557 [W / cm · K], the bridge portion 14, The thermal conductance K11 per 14 (the thermal conductance between P1 and P2 in FIG. 11) is obtained by the following equation (2).
Figure 0003608298
Thus, the conventional thermal infrared sensor 10 shown in FIGS. 9 and 11 has the two infrared light receiving portions 11 supported on the semiconductor substrate 1 by the two bridge portions 14 and 14. The thermal conductance K1 between the semiconductor substrate 1 and the semiconductor substrate 1 is obtained by the following equation (3).
[0029]
K1 = 2K11 = 3.0 × 10 -6 [W / K] (3)
Next, the thermal conductance K2 between the infrared light receiving unit 21 of the thermal infrared sensor 20 and the semiconductor substrate 1 is calculated.
As described above, the infrared light receiver 21 of the thermal infrared sensor 20 is supported by the first and second legs 25, 25, 26, 26, 27, and 27 made of resist.
[0030]
If the infrared light receiving unit 21 having a side of about 40 μm is supported, each leg 25, 25, 26, 26, 27, 27 is a cylinder having a diameter of about 1.0 μm and a height of about 2.0 μm. can do. In this case, the thermal conductance K21 per one of the first and second leg portions 25, 25, 26, 26, 27, 27 is 1.0 × 10. -3 When [W / cm · K], it is obtained by the following equation (4).
[0031]
Figure 0003608298
Further, the thermal conductance K22 per one side of the bridge portion 24 (between P1 and P2 and between P2 and P3 in FIG. 5) is obtained as follows.
That is, the bridge portion 24 has a two-layer structure of a wiring layer 24A and a protective layer 24B. The wiring layer 24A has a width of 1 μm and a film thickness of 800 mm, the material is titanium, and the protective layer 24B has a width. Can be made of silicon nitride (SiN). The length of one side of the bridge portion 24 is about 40 μm, which is the same as that of the conventional bridge portion 14. When the thermal conductivity of titanium is 0.2 [W / cm · K] and the thermal conductivity of silicon nitride is 0.557 [W / cm · K], the thermal conductance K22 is obtained by the following equation (5). It is done.
[0032]
Figure 0003608298
The thermal conductance between P1 and P3 using the thermal conductance K21 per one of the leg portions (first and second leg portions 25, 26, 27) and the thermal conductance K22 per side of the bridge portion 24 described above. When K23 is obtained, the thermal conductance K23 is calculated between the thermal conductance between P1 and P2 in FIG. 5, the thermal conductance of the second leg 27 that supports the point P2 (corresponding to the corner 24C), and between P2 and P3. Since thermal conductance is synthesized, it is obtained by the following equation (6).
[0033]
Figure 0003608298
The thermal conductance K23 is a thermal conductance between P1 and P3, and is a value corresponding to one thermal conductance K11 of the bridge portion 14 in the conventional thermal type infrared sensor 10. When this value K23 is compared with the value K11, the former is about 1/15 of the latter.
[0034]
As described above, in the thermal infrared sensor 20, even when the bridge portion 24 and the second leg portion 27 are combined, the thermal conductance can be remarkably reduced as compared with the bridge portion 14 of the thermal infrared sensor 10.
Thus, when the infrared light receiving portion 21 and the bridge portion 24 are respectively supported by using the first and second leg portions 25, 25, 26, 26, 27, and 27 (the thermal infrared ray shown in FIG. 1). Sensor 20) The thermal conductance K2 between the infrared light receiving unit 21 and the semiconductor substrate 1 is obtained by the following equation (7).
[0035]
K2 = 4K21 + 2K23 = 3.5 × 10 -7 [W / K] (7)
As described above, when the first and second legs 25, 25, 26, 26, 27, and 27 are used, the thermal conductance K2 of the infrared light receiving units 11 and 21 is substantially the same (one side is 40 μm). The thermal conductance K1 of the thermal infrared sensor 10 is about 1/9.
[0036]
As described above, in the thermal infrared sensor 20, since the infrared light receiving part 21 is supported by the leg parts 25, 25, 26, 26, the bridge parts 24, 24 have the strength as in the conventional case. Since the cross-sectional area can be reduced and the layout pattern on the semiconductor substrate 1 can be increased as long as the layout pattern permits, the thermal conductance K23 associated with the bridge portions 24 and 24 can be significantly reduced.
[0037]
Then, the thermal conductance which is increased by arranging the leg portions 25, 25, 26, 26, 27, 27 between the infrared light receiving portion 21 and the semiconductor substrate 1, and the cross-sectional area of the bridge portions 24, 24 are reduced. In addition, when the thermal conductance reduced by increasing the length is compared, the latter can be significantly increased with respect to the former, so that the thermal conductance K2 of the entire thermal infrared sensor 20 can be greatly reduced.
[0038]
FIG. 6 is an explanatory view showing a modification in which the infrared light receiving part 21 or the bridge parts 24, 24 connected to the infrared light receiving part 21 are supported by using the leg part 28. Among these, (a) is an example in which the infrared light receiving unit 21 is supported by two legs 28, 28, and (b) is a case in which the legs 28, 28 support the infrared light receiving unit 21 and the straight portions of the bridge portions 24, 24 simultaneously. Example, (c) is an example in which the infrared light receiving unit 21 is supported by two legs 28, 28 and the bridges 24, 24 are supported by the other two legs 28, 28, and (d) is the bridges 24, 24. (E) is an example in which the bridge portions 24 and 24 and the infrared light receiving portion 21 are simultaneously supported by the leg portions 28 and 28, and (e) shows the corner portions of the infrared light receiving portion 21 and the bridge portions 24 and 24 at the leg portions 28 and 28. In the example of supporting at the same time, (f) is a bridge portion (infrared light receiving portion 21) that supports the infrared light receiving portion 21 with two leg portions 28, 28 and is extended with the other four leg portions 28, 28, 28, 28. (G) is an example of supporting four legs 28, 28, An example in which the eight corners of the bridge portions 24, 24 are supported by 8, 28, and (h) is an example in which the bridge portions 24, 24 formed in a knot shape are supported by the four leg portions 28, 28, 28, 28. It is explanatory drawing which shows.
[0039]
In any of the above, the number of leg portions 28 is reduced to reduce the thermal conductance, and / or the bridge portions 24, 24 are elongated to reduce the thermal conductance. According to the example, the thermal conductance is further reduced, and the sensitivity of the thermal infrared sensor 20 is further improved.
In the first embodiment, the first and second legs 25, 25, 26, 26, 27, and 27 are formed of a resist having a low thermal conductivity. However, other thermal conductivity is shown. This material may be formed of a small material such as an organic material such as polyimide resin, enamel, or celluloid.
[0040]
In the above embodiment, an example in which the wiring layer 24A of the bridge portions 24 and 24 is made of titanium is shown. However, this may be formed of other conductors or semiconductors (for example, vanadium oxide film (VOx)). .
Moreover, in the said embodiment, although the bridge parts 24 and 24 were made into the two-layer structure of the wiring layer 24A and the protective layer 24B, you may make it more than a three-layer structure. In this case, in the above-described embodiment, when the bridge portions 24 and 24 are formed, the protective layer 24B is formed on the upper surface of the wiring layer 24A. However, the protective layers may be formed above and below the wiring layer 24A. . On the contrary, since the wiring layer 24A is supported by the second legs 27, 27, there is no problem in strength even if the protective film 24B is omitted.
[0041]
Note that the structure of the infrared light receiving unit 21 of the thermal infrared sensor 20 is not limited to the illustrated structure, and the present invention can of course be applied to other thermal infrared sensors having a microbridge structure.
(Second Embodiment)
Next, a second embodiment of the present invention will be described. The second embodiment corresponds to claims 1 to 6.
[0042]
In the thermal infrared sensor 40, as shown in FIG. 7, the infrared light receiving part 41 is supported by a leg part 45.
Note that the structures of the infrared light receiving section 41 and the bridge section 44 are the same as those of the infrared light receiving section 21 and the bridge section 24 of the first embodiment described above, and a detailed description thereof will be omitted.
As shown in FIG. 7, the infrared light receiving unit 41 is arranged with a gap M above the semiconductor substrate 1 by one columnar leg 45.
[0043]
In this case, the leg 45 is also a resist having a low thermal conductivity (for example, 1.0 × 10 10), like the legs 25, 26, and 27 of the first embodiment described above. -3 [W / cm · K]). By forming the leg portions 45 with this resist, it becomes difficult for heat to be transferred from the infrared light receiving portion 41 where the temperature rises due to incident infrared rays to the semiconductor substrate 1 side. Incidentally, when one side of the infrared light receiving unit 41 is formed to be about 40 μm, the leg portion 45 is thick enough to support the infrared light receiving unit 41, and the infrared light receiving unit 41 and the semiconductor. The height is necessary to secure a gap M in which heat conduction with the substrate 1 does not occur (for example, a columnar shape having a diameter of 4.0 μm and a height of about 2.0 μm).
[0044]
In this case, since the bridge portions 44 and 44 do not need to support the infrared light receiving portion 41, the bridge portions 44 and 44 are designed to be as thin as possible in the semiconductor manufacturing technology (for example, about 1.0 μm) so as to reduce the thermal conductance. Moreover, the length is also long (in the example shown in FIG. 7, the length along the two sides of the infrared light receiving section 41 having a side of 40 μm is about 80 μm).
[0045]
The manufacturing method of the thermal infrared sensor 40 having the above configuration is different from the manufacturing method of the thermal infrared sensor 20 of the first embodiment described above only in the shape of the leg 45 (FIG. 3A ) Only the pattern of the mask 38 is different), and other processes are substantially the same, and the detailed description thereof is omitted.
Further, the thermal conductance K30 in the thermal infrared sensor 40 has the following value. Here, it is assumed that the infrared light receiving portion 41 of the thermal infrared sensor 40 is a square having a side of approximately 40 μm, similar to the thermal infrared sensor 20 of the first embodiment.
[0046]
As described above, the infrared light receiving portion 41 of the thermal infrared sensor 40 is supported by only one leg portion 45 made of resist.
If the infrared light receiving part 41 having a side of about 40 μm is supported, the leg part 45 can be a cylinder having a diameter of about 4.0 μm and a height of about 2.0 μm. In this case, the thermal conductance K31 of one leg 45 has a thermal conductivity of 1.0 × 10 × 10. -3 When [W / cm · K], it is obtained by the following equation (8).
[0047]
K31 = 1.0 × 10 -3 {Π × (2.0 × 10 -4 ) 2 / 2 × 10 -4 } = 6.3 × 10 -7 [W / K] (8)
Further, the thermal conductance K32 per side of the bridge portion 44 is the same value (1.8 × 10 10) as the thermal conductance K22 of the first embodiment. -7 [W / K]).
Therefore, the thermal conductance K33 per one bridge portion 44 is half the value of K32 (0.9 × 10 -7 [W / K]).
[0048]
Thus, the thermal conductance K3 between the infrared light receiving unit 41 and the semiconductor substrate 1 when the infrared light receiving unit 41 is supported using the leg 45 (the thermal infrared sensor 40 shown in FIG. 7) is expressed by the following equation: It is obtained by (9).
K3 = K31 + 2K33 = 8.1 × 10 -7 [W / K] (9)
Thus, the thermal conductance K3 when using one leg 45 is approximately 1 of the thermal conductance K1 of the conventional thermal infrared sensor 10 in which the infrared light receiving portions 11 and 41 have substantially the same size (one side is 40 μm). / 4.
[0049]
As described above, in the thermal infrared sensor 40, since the infrared light receiving part 41 is supported by the leg part 45, the bridge parts 44 and 44 do not need to be increased in strength as in the related art. Since the cross-sectional area can be reduced and increased as long as the layout pattern on the semiconductor substrate 1 permits, the thermal conductance K33 associated with the bridge portions 44 and 44 can be significantly reduced.
[0050]
And the thermal conductance which increases by arrange | positioning the leg part 45 between the infrared rays light-receiving part 41 and the semiconductor substrate 1, and the heat | fever reduced by making the cross-sectional area of the bridge parts 44 and 44 small and lengthening. When the conductance is compared, the latter can be remarkably increased with respect to the former, so that the thermal conductance K3 of the entire thermal infrared sensor 40 can be greatly reduced.
[0051]
FIG. 8 shows a cross-shaped leg 46 (FIG. 8A), a hollow leg 47 (FIG. 8B), and a C-shaped section instead of the columnar leg 45 of FIG. It is explanatory drawing which shows the modification which supports the infrared rays light-receiving part 41 using the leg part 48 (FIG.8 (c)), and the leg part 49 (FIG.8 (d)) whose cross section is a rectangle.
According to such leg portions 46, 47, 48, 49, the cross-sectional areas S1, S2, S3, S4 are further reduced to further reduce the thermal conductance of the leg portions 46, 47, 48, 49, The heat insulation effect between the infrared light receiving unit 41 and the semiconductor substrate 1 can be further improved, and the sensitivity of the thermal infrared sensor 40 is further improved.
[0052]
Of course, these leg portions 46, 47, 48 and 49 can be used in place of the first and second leg portions 25,..., 27 of the first embodiment.
In the second embodiment, the legs 45, 46, 47, 48, and 49 are formed of a resist having a low thermal conductivity. However, other materials having a low thermal conductivity, such as a polyimide resin, are used. This may be formed of an organic substance such as enamel or celluloid.
[0053]
It should be noted that the structure of the infrared light receiving portion 41 of the thermal infrared sensor 40 is not limited to the illustrated structure, and the present invention can of course be applied to other thermal infrared sensors having a microbridge structure.
[0054]
【The invention's effect】
As described above, according to the invention of claim 1, since the bridge portion does not need to support the infrared light receiving portion, the increase in thermal conductance due to the insulating legs and the decrease in thermal conductance of the bridge portion are obtained. As a whole, the thermal conductance of the thermal infrared sensor is lowered and the sensor sensitivity can be improved. In this case, if the cross-section of the insulating leg is determined to be the minimum size required to support the infrared light receiving unit, the increase in thermal conductance can be minimized and the sensor sensitivity can be improved. Also, since the bridge portion does not need to support the infrared light receiving portion, it only needs to have a function as wiring. Therefore, if the cross-sectional area is reduced and the length is increased to reduce the thermal conductance, the sensor The sensitivity can be further improved. If the bridge portion is also supported by the insulating legs, the entire length of the bridge portion can be further increased, and the thermal conductance of the bridge portion can be further reduced to further improve the sensor sensitivity.
[0055]
According to the invention of claim 2, the thermal conductance of the insulating leg portion is lowered, and the sensor sensitivity can be improved.
According to the third aspect of the present invention, the insulating legs can be easily formed with a material generally used in semiconductor manufacturing technology.
According to the fourth aspect of the present invention, since the strength for supporting the infrared light receiving portion is not required, the bridge portion can be easily manufactured simply by insulating the surface thereof.
[0056]
According to the invention of claim 5, the protective film for the bridge portion can be easily formed.
According to the invention of claim 6, it is possible to easily manufacture a thermal infrared sensor having high sensor sensitivity with a generally used semiconductor manufacturing apparatus.
[Brief description of the drawings]
FIG. 1 is a perspective view showing a thermal infrared sensor 20 of a first embodiment.
[Figure 2]
2 is a perspective view showing a structure of a bridge portion 24 of a thermal infrared sensor 20. FIG.
3 is a cross-sectional view showing a manufacturing process of the thermal infrared sensor 20. FIG.
4 is a cross-sectional view showing a manufacturing process of the thermal infrared sensor 20. FIG.
FIG. 5 is a schematic diagram of a thermal infrared sensor 20 for calculating a thermal conductance K2.
FIG. 6 is an explanatory view showing a modification in which the shape of the bridge portions 24 and 24 of the thermal infrared sensor 20 and the arrangement of the leg portions 25, 25, 26, 26, 27, and 27 are different.
FIG. 7 is a perspective view showing a thermal type infrared sensor 40 of the second embodiment.
FIG. 8 is an explanatory view showing a modified example in which the shape of the leg portion of the thermal infrared sensor 40 is changed.
9 is a perspective view showing a conventional thermal infrared sensor 10. FIG.
10 is a perspective view showing a structure of a bridge portion 14 of a conventional thermal infrared sensor 10. FIG.
FIG. 11 is a schematic diagram of a conventional thermal infrared sensor 10 for calculating a thermal conductance K1.
[Explanation of symbols]
1 Semiconductor substrate
1A electrode
20, 40 Thermal infrared sensor
21, 41 Infrared detector
24,44 Bridge
24A wiring layer
24B Protective film (insulating film)
25, 26 First leg (insulating leg)
27 Second leg (insulating leg)
31 resist
32 Silicon oxide film (filler)
33 Titanium film
34 Silicon nitride film
45, 46, 47, 48, 49 Legs

Claims (6)

半導体基板上に、入射した赤外線を熱エネルギーに変換し、該変換された熱エネルギーの大きさに応じて変化する物性値を電気的に読み出すための赤外線受光部と、
上記赤外線受光部と上記半導体基板とを電気的に接続する配線が設けられた橋梁部と、
上記赤外線受光部又は上記橋梁部の少なくとも一方を支持し、上記半導体基板とは異なる絶縁性物質からなる絶縁性脚部と
を備えていることを特徴とする熱型赤外線センサ。Infrared light receiving unit for converting incident infrared rays into heat energy on a semiconductor substrate and electrically reading out physical property values that change according to the magnitude of the converted heat energy;
A bridge portion on which a wiring for electrically connecting the and the semiconductor substrate said infrared receiving portion is provided,
A thermal infrared sensor characterized by comprising at least one of the infrared light receiving portion or the bridge portion and an insulating leg portion made of an insulating material different from the semiconductor substrate . 上記絶縁性脚部は、有機物質にて形成されている
ことを特徴とする請求項１に記載の熱型赤外線センサ。2. The thermal infrared sensor according to claim 1, wherein the insulating legs are formed of an organic material. 上記絶縁性脚部は、レジスト、ポリイミド樹脂、エナメル、セルロイドの何れかによって形成されている
ことを特徴とする請求項２に記載の熱型赤外線センサ。3. The thermal infrared sensor according to claim 2, wherein the insulating legs are formed of any one of resist, polyimide resin, enamel, and celluloid. 上記橋梁部は、少なくとも配線層と絶縁層を含む２層構造若しくはそれ以上の多層構造をなしている
ことを特徴とする請求項１から請求項３の何れかに記載の熱型赤外線センサ。The thermal infrared sensor according to any one of claims 1 to 3, wherein the bridge portion has a two-layer structure including at least a wiring layer and an insulating layer or a multilayer structure of more than that. 上記絶縁層は、窒化シリコン膜で構成されている
ことを特徴とする請求項４に記載の熱型赤外線センサ。5. The thermal infrared sensor according to claim 4, wherein the insulating layer is made of a silicon nitride film. 半導体基板上に絶縁膜を形成し、
該絶縁膜を上記絶縁性脚部の形状に合わせてエッチングし、
これに上記絶縁性脚部と、エッチング時の選択性が確保できる充填体を堆積させ、
該充填体を選択的にエッチングし、
その上面に少なくとも上記赤外線受光部若しくは橋梁部を構成する導電膜又は半導体膜を形成し、
これら導電膜又は半導体膜を当該赤外線受光部若しくは橋梁部の形状に合わせてエッチングし、
その後、上記充填体を除去して、
請求項１から請求項５の何れかに記載の熱型赤外線センサを形成する
ことを特徴とする熱型赤外線センサの製造方法。Forming an insulating film on the semiconductor substrate;
Etching the insulating film according to the shape of the insulating legs,
The insulating legs and the filler that can ensure the selectivity during etching are deposited on this,
Selectively etching the filler;
Forming a conductive film or a semiconductor film constituting at least the infrared light receiving part or the bridge part on the upper surface,
Etching these conductive film or semiconductor film according to the shape of the infrared light receiving part or bridge part,
Thereafter, the filler is removed,
A method for manufacturing a thermal infrared sensor, comprising forming the thermal infrared sensor according to any one of claims 1 to 5.
JP17622596A 1996-07-05 1996-07-05 Thermal infrared sensor and manufacturing method thereof Expired - Fee Related JP3608298B2 (en)

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JPH11148861A (en) * 1997-09-09 1999-06-02 Honda Motor Co Ltd Microbidge structure
JP3003853B2 (en) 1997-09-09 2000-01-31 本田技研工業株式会社 Sensor with bridge structure
JP3109480B2 (en) * 1998-06-15 2000-11-13 日本電気株式会社 Thermal infrared detector
JP3460810B2 (en) 1999-07-26 2003-10-27 日本電気株式会社 Thermal infrared detector with thermal separation structure
JP2001153720A (en) 1999-11-30 2001-06-08 Nec Corp Heat type infrared detector
JP3672516B2 (en) * 2001-09-28 2005-07-20 株式会社東芝 Infrared sensor device and manufacturing method thereof
WO2005034248A1 (en) * 2003-10-09 2005-04-14 Ocas Corp. Bolometric infrared sensor having two layer structure and method for manufacturing the same
CN101248337B (en) 2005-08-17 2011-06-15 松下电工株式会社 Infrared sensor unit and its manufacturing method
KR100643708B1 (en) 2005-09-27 2006-11-10 한국과학기술원 Bolometer structure with high responsivity
JP4784399B2 (en) * 2006-05-29 2011-10-05 日産自動車株式会社 Infrared sensor and manufacturing method thereof
JP5644121B2 (en) * 2010-01-26 2014-12-24 セイコーエプソン株式会社 THERMAL TYPE PHOTODETECTOR, THERMAL TYPE PHOTODETECTOR, ELECTRONIC DEVICE, AND METHOD FOR PRODUCING THERMAL TYPE OPTICAL DETECTOR
KR101181248B1 (en) 2011-07-22 2012-09-11 한국과학기술원 Self-Protecting Infrared Bolometer
WO2016020993A1 (en) * 2014-08-06 2016-02-11 株式会社日立製作所 Infrared sensor and signal detection method
JP6529679B2 (en) * 2017-05-22 2019-06-12 三菱電機株式会社 Infrared imaging device, infrared imaging array, and method of manufacturing infrared imaging device
US20200249084A1 (en) * 2017-08-10 2020-08-06 Hamamatsu Photonics K.K. Light detector

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