JP3637665B2

JP3637665B2 - Pyroelectric infrared detector

Info

Publication number: JP3637665B2
Application number: JP00890296A
Authority: JP
Inventors: 努中西; 和司森杉; 文雄細見; 徳巳小谷; 幸治野村
Original assignee: Panasonic Corp; Matsushita Electric Industrial Co Ltd
Current assignee: Panasonic Corp; Panasonic Holdings Corp
Priority date: 1996-01-23
Filing date: 1996-01-23
Publication date: 2005-04-13
Anticipated expiration: 2016-01-23
Also published as: JPH09196765A

Description

【０００１】
【発明の属する技術分野】
本発明は焦電体を用いて赤外線を検出する焦電型赤外線検出素子に関するものである。
【０００２】
【従来の技術】
焦電型赤外線検出素子は、人体または物体の有無・位置・動作・温度等の情報を非接触で検出できる利点を活かして、電子レンジでの調理材の温度測定・エアコンでの室内温度制御あるいは自動照明コントロール・自動ドア・警報装置での人体検知などに利用されており、今後さらにその利用分野は拡大していくと見られている。
【０００３】
焦電型赤外線検出素子は強誘電体の焦電効果を利用したセンサで、強誘電体材料は一様に分極する性質を有し、一様に分極した状態では正および負の電荷を帯びている。大気中に放置された状態では、大気中の浮遊電荷と結合して電気的に中性状態を保っている。すべての物体は温度に応じた赤外線エネルギーを放出しており、物体から放出された赤外線エネルギーが焦電体で構成する赤外線検出素子の赤外線検出部に入射されると焦電体に温度変化が生じ、そのとき分極が変化することにより焦電体表面に電荷が誘起される。このとき誘起された電荷を電圧または電流として検出している。
【０００４】
以下に、従来の焦電型赤外線検出素子について説明する。
図８（ａ），（ｂ）は従来の焦電型赤外線検出素子の構成図を示すものである。図において焦電型赤外線検出素子は、８１は基板、８２ａ，８２ｂは電極、８３は焦電体薄膜、８４ａ，８４ｂは有機膜、８５は開口部の構成からなる。
【０００５】
以上のように構成された焦電型赤外線検出素子について、以下にその製造方法について説明する。まず基板８１として（１００）酸化マグネシウム（以下、（１００）ＭｇＯと略す）を用い、その上に焦電体薄膜８３としてランタンを添加したチタン酸鉛（以下、ＰＬＴと略す）をメタルマスクを用いて所定の形状に高周波マグネトロンスパッタ法によりエピタキシャル成長させる。次に層間絶縁膜として有機膜８４ａをフォトリソグラフィで所定の形状にパターニングし、エッチング形成する。そして、それら上部に電極８２ａとしてＮｉ−Ｃｒ合金薄膜を真空蒸着法で形成し、フォトリソグラフィおよび湿式エッチングで所定の形状にパターニング形成する。さらに、それら上部に保持体として有機膜８４ｂをフォトリソグラフィで所定の形状にパターニングし、エッチング形成する。続いて、焦電体薄膜８３を形成した（１００）ＭｇＯ基板面をレジストで保護し、焦電体薄膜８３の領域を裏面からエッチングし、開口部８５を形成する。最後に（１００）ＭｇＯ基板８１を取り除いた側に、電極８２ｂとしてＮｉ−Ｃｒ合金薄膜を真空蒸着法で形成し、フォトリソグラフィおよび湿式エッチングで所定の形状にパターニング形成する。
【０００６】
【発明が解決しようとする課題】
しかしながら上記従来の方法では、赤外線検出部での熱応答性を向上させて赤外線検出部の感度を良好にしようとした場合、赤外線検出部と全体を保持している（１００）ＭｇＯ基板８１との間隔を十分にとり、熱伝導を小さくして熱の逃げを最小限にする必要がある。このためには、開口部８５をより大きくする必要があるが、赤外線検出部を保持する有機膜８４ａ，８４ｂの内部応力の影響が強くなり、焦電体薄膜８３および電極８２ａ，８２ｂの断線・歪み・破壊を生じるという問題点を有していた。
【０００７】
また、有機膜８４ａ，８４ｂの内部応力での電極８２ａ，８２ｂの引き出し部の断線を避けるため、特に電極８２ｂの引き出し部のパターン幅を焦電体薄膜のパターン形状と同程度にしてあるので、電極の引き出し部から（１００）ＭｇＯ基板８１への熱の伝達量が大きくなっている。さらに赤外線検出部を保持する有機膜８４ｂは、赤外線検出部上層から基板にかけて一体構造になっているので、赤外線検出部に入射する赤外線エネルギは前記有機膜で熱エネルギとして吸収されると同時に、吸収された熱エネルギはこれを介して（１００）ＭｇＯ基板８１へ逃げてしまう。従ってこの構成では、赤外線検出部での熱吸収量が少なく、検出感度が十分に得られないといった問題点を有している。
【０００８】
本発明はこのような上記問題点を解決するものであり、感度・熱応答性に優れ、低コスト・小型化・集積化が可能で生産性に富んだ信頼性の高い焦電型赤外線検出素子を提供することを目的とするものである。
【０００９】
【課題を解決するための手段】
この目的を達成するために本発明の焦電型赤外線検出素子は、基板と、この基板上に設けられた第一の電極上に薄膜焦電体を形成しその上に、第一の電極の熱伝導率より小さな熱伝導率を有する材料からなる第二の電極を形成した赤外線検出部と、前記赤外線検出部が接する前記基板の表層部に設けた空洞と、前記赤外線検出部が前記基板で支えられるように設けた保持体とから構成される焦電型赤外線検出素子において、基板の空洞を形成していない同一表面上の領域に第一の電極材料と同一材料を用いて外部接続端子を設け、前記赤外線検出部と外部接続端子を電気的に接続する第一の電極の引き出し部の材料が第二の電極と同じ材料あるいは第一の電極の熱伝導率より小さな熱伝導率を有する材料のいずれかである焦電型赤外線検出素子としたものである。
【００１０】
この構成とすることにより、感度、熱応答性に優れた焦電型赤外線検出素子が得られる。
【００１１】
【発明の実施の形態】
本発明の請求項１に記載の発明は、基板と、この基板上に設けられた第一の電極上に薄膜焦電体を形成しその上に、第一の電極の熱伝導率より小さな熱伝導率を有する材料からなる第二の電極を形成した赤外線検出部と、前記赤外線検出部が接する前記基板の表層部に設けた空洞と、前記赤外線検出部が前記基板で支えられるように設けた保持体とから構成される焦電型赤外線検出素子において、基板の空洞を形成していない同一表面上の領域に第一の電極材料と同一材料を用いて外部接続端子を設け、前記赤外線検出部と外部接続端子を電気的に接続する第一の電極の引き出し部の材料が第二の電極と同じ材料あるいは第一の電極の熱伝導率より小さな熱伝導率を有する材料のいずれかである焦電型赤外線検出素子を構成し、この構成によって空洞が小さくできて引き出し部への歪を緩和し断線、破壊を抑制でき、基板への熱伝達を抑え感度、熱応答性の優れたものとすることができる。
【００１２】
請求項２に記載の発明は、第二の電極または第一の電極の引き出し部の材料がＴａ，Ｔｉ，Ｓｎ，Ａｌ−Ｃｕ合金、Ｎｉ−Ｃｒ合金、Ｃｕ−Ｎｉ合金、Ｃｕ−Ｓｎ合金、Ａｌ−Ｔｉ合金、またはＣｕ−Ｚｎ合金等のいずれかからなる請求項１記載の焦電型赤外線検出素子であり、基板への熱伝導を抑制することができる。
【００１３】
請求項３に記載の発明は、保持体は少なくとも５０％以上の領域に穴を備えかつその厚さが２μｍ以下の構成とした請求項１記載の焦電型赤外線検出素子であり、基板への熱伝導を抑制することができる。
【００１４】
請求項４に記載の発明は、１つの基板上に少なくとも２個以上のマトリックス状に構成された赤外線検出部の厚み方向の両端で発生した電気信号は、第二の電極と同一材料あるいは第一の電極の熱伝導率より小さな熱伝導率を有する材料のいずれかを用いた引き出し部を介して外部接続端子を引き出す構成とした請求項１記載の焦電型赤外線検出素子であり、基板への熱伝導を抑制し、集積度を高めるものである。
【００１５】
請求項５に記載の発明は、マトリックス状に構成された赤外線検出部どうしは第二の電極と同一材料あるいは第一の電極の熱伝導率より小さな熱伝導率を有する材料のいずれかを用いた引き出し部で電気的に接続された請求項１記載の焦電型赤外線検出素子であり、基板への熱伝導を抑制し、集積度を高めるものである。
【００１８】
以下、本発明の実施の形態について図面を参照しながら説明する。
（実施の形態１）
図１および図２は、本発明の第一の実施の形態における焦電型赤外線検出素子の構成を示す平面図および断面図である。図１および図２において、１１は基板、１２ａは第一の電極、１２ｂは第一の電極の引き出し部、１３は外部接続端子、１４は焦電体薄膜、１５ａは第二の電極、１５ｂは第二の電極の引き出し部、１６は層間絶縁膜、１７は赤外線検出部の保持体、１８は空洞である。
【００１９】
以上のように構成された焦電型赤外線検出素子について、以下にその製造方法について説明する。まず基板１１として（１００）酸化マグネシウム（以下、（１００）ＭｇＯと略す）を用い、前記（１００）ＭｇＯ基板１１上に第一の電極１２ａとして１５０ｎｍ程度の膜厚を有する白金（以下、Ｐｔと略す）薄膜をマグネトロンスパッタ法により、基板温度：６００℃、入射電力密度：０．１６Ｗ／ｃｍ²、スパッタガス雰囲気：Ａｒ／Ｏ₂＝２／１、ガス圧：１．０６Ｐａの成膜条件のもとエピタキシャル成長させる。
【００２０】
次にその上層に、焦電体薄膜１４としてＰｂＴｉＯ₃あるいはＰｂ_1-xＬａ_xＴｉ_1-x/4Ｏ₃等の焦電材料からなる薄膜を高周波マグネトロンスパッタ法により、基板温度：６００℃、入射電力密度：１．６Ｗ／ｃｍ²、スパッタガス雰囲気：Ａｒ／Ｏ₂＝９／１、ガス圧：１Ｐａの成膜条件のもとエピタキシャル成長させる。このとき（１００）ＭｇＯ基板１１と焦電体薄膜１４の熱膨張係数の差により、焦電体薄膜１４の結晶格子がキューリ点を境に歪み、基板面に対して垂直方向にＣ軸が伸びることにより一方向の自発分極が現れる。
【００２１】
次に焦電体薄膜１４をフォトリソグラフィおよび湿式エッチングで所定の形状にパターニング形成し、続いて第一の電極１２ａもフォトリソグラフィおよび乾式エッチングで所定の形状にパターニング形成する。このとき同時に、第一の電極の引き出し部１２ｂと外部接続端子１３をそれぞれパターニング形成し、外部接続端子１３の一方と第一の電極の引き出し部１２ｂを介して第一の電極１２ａとが電気的に接続している。
【００２２】
次に層間絶縁膜１６として感光性を有するポリイミド系樹脂を用いて、その前駆体をフォトリソグラフィで所定の形状にパターニングし、３００℃程度の温度雰囲気でイミド化を促進し、熱硬化させる。このとき、少なくとも焦電体薄膜１４と第二の電極１５ａが、直接電気的に接続できる領域と、それを除く部分の５０％以上の領域で穴を設けるパターニング形状とする。
【００２３】
次にそれら上層に第二の電極１５ａとして２０ｎｍ程度の膜厚を有するＮｉ−Ｃｒ合金薄膜をスパッタ法により、基板温度：１００℃、入射電力密度：０．５５Ｗ／ｃｍ²、スパッタガス雰囲気：Ａｒ、ガス圧：１Ｐａの成膜条件のもとで形成する。その後、フォトリソグラフィおよび湿式エッチングにより、所定の形状にパターニング形成する。このとき同時に、第二の電極１５ａの引き出し部１５ｂを第二の電極１５ａと電気的につながった状態にパターニング形成し、さらにもう一方の外部接続端子１３と電気的に接続する。
【００２４】
次に、保持体１７として感光性を有するポリイミド系樹脂を用いて、その前駆体をフォトリソグラフィで所定の形状にパターニングし、３００℃程度の温度雰囲気でイミド化を促進し、熱硬化させる。このとき、赤外線検出部にかかる部分を除く５０％以上の領域で穴を設けるパターニング形状とする。
【００２５】
最後に、赤外線検出部を同一表面上から（１００）ＭｇＯ基板１１の特定領域にフォトリソグラフィで作製したエッチング用保護マスクを介して空洞１８をエッチング形成する。このときのエッチング液として、濃度：１０％、液温：８０℃の燐酸を用いる。その結果、エッチング時間６０分のとき、空洞の大きさは水平方向：０．３ｍｍ、垂直方向０．０８ｍｍであることを確認している。
【００２６】
上記のように本実施の形態の焦電型赤外線検出素子の構成によれば、赤外線検出部が（１００）ＭｇＯ基板１１の表層部に設けた空洞１８上を５０％以上の領域で穴がパターニングされている多穴構造のポリイミド系樹脂の保持体１７を介して支持されているので、従来の焦電型赤外線検出素子の開口部に比べて非常に小さくなり、開口部の拡大に伴う赤外線検出部および電極の引き出し部への歪みを緩和できるので断線・破壊を抑制することができている。また入射赤外線エネルギに対して赤外線検出部の熱応答性の高速化が図れる。さらに赤外線検出部と基板１１上の外部接続端子との距離に対して十分に長い、具体的には２倍以上の長さの引き出し電極と保持体の多穴構造により、基板への熱伝導を十分に抑えられるので赤外線検出部での熱吸収量が増大し、検出感度を向上させることができる。加えて熱時定数が増大することにより、特に低速物体検知での大きな出力応答を得ることができる。
【００２７】
また、上記素子構成では、集積化・小型化が可能な信頼性の高い赤外線検出素子を実現できる。
【００２８】
本実施の形態では、第一の電極１２ａとして（１００）面にエピタキシャル成長したＰｔ薄膜を用いている。これは、焦電体薄膜１４および基板１１との格子整合性に優れているので、焦電体薄膜１４のＣ軸方向へのエピタキシャル成長を促進する効果がある。さらに化学的に非常に安定で、高温酸化雰囲気中でも熱酸化しないという特徴を有しているためである。第二の電極１５ａとしてＮｉ−Ｃｒ合金薄膜を用いているが、請求項５に挙げたいずれの材料を用いても本実施の形態と同様の効果が得られていることは確認している。さらに、本実施の形態では層間絶縁膜１６および保持体１７としてポリイミド系樹脂を使用したが、これに限るものではなく、１０¹⁰Ωｃｍ以上の体積抵抗率を有する膜で耐熱温度が高く信頼性に優れているものであれば、他の有機膜やガラス系無機膜でもかまわない。
【００２９】
（実施の形態２）
図３および図４は、本発明の第二の実施の形態における焦電型赤外線検出素子の構成を示す平面図および断面図である。図３および図４において、１１は基板、１２ａは第一の電極、１２ｂは第一の電極の引き出し部、１３は外部接続端子、１４は焦電体薄膜、１５ａは第二の電極、１５ｂは第二の電極の引き出し部、１６は層間絶縁膜、１７は赤外線検出部の保持体、１８は空洞である。
【００３０】
本発明の第二の実施の形態における焦電型赤外線検出素子の基本構成および基本的な製造方法は、本発明の第一の実施の形態で示したものと同様である。本発明の第一の実施の形態と異なるのは、第一の電極１２ａと外部接続端子１３との電気的接続方法である。本発明の第二の実施の形態では、第一の電極１２ａをフォトリソグラフィおよび乾式エッチングで所定の形状にパターニング形成するとき、第一の電極１２ａの引き出し部１２ｂとの接続パッドを設けるとともに、外部接続端子１３も同時形成しておく。
【００３１】
次に前記接続パッドと重なり合う層間絶縁膜１６の位置にスルーホールを形成する。そして第二の電極１５ａの形成と同時に、Ｎｉ−Ｃｒ合金薄膜を用いて第一の電極の引き出し部１２ｂを形成し、それを介して第二の電極１５ａと電気的に接続されていないもう一方の外部接続端子１３と第一の電極１２ａを電気的に接続する。
【００３２】
上記のように本実施の形態の焦電型赤外線検出素子の構成によれば、第一の電極１２ａの引き出し電極１２ｂを第一の電極材料の熱伝導率より小さい材料を用いることにより、基板への熱伝達を十分に抑えられるので赤外線検出部での熱吸収量が増大し、検出感度・熱時定数をさらに向上させることができる。また特に、低速物体検知での大きな出力応答を得ることができる。
【００３３】
本実施の形態では、上記引き出し電極１２ｂの材料を第二の電極１５ａの材料と同一のものを使用したが、これに限るものではなく、第一の電極材料より熱伝導率が小さくほどほどの電気伝導率があれば、他の単体金属や合金または低抵抗半導体でもかまわない。
【００３４】
（実施の形態３）
図５および図６は、本発明の第三の実施の形態における焦電型赤外線検出素子の構成を示す平面図および断面図である。図５および図６において、１１は基板、１２ａは第一の電極、１２ｂは第一の電極の引き出し部、１３は外部接続端子、１４は焦電体薄膜、１５ａは第二の電極、１５ｂは第二の電極の引き出し部、１６は層間絶縁膜、１７は赤外線検出部の保持体、１９は赤外線検出部と引き出し電極の保護膜、１８は空洞である。
【００３５】
本発明の第三の実施の形態における焦電型赤外線検出素子の基本構成および基本的な製造方法は、本発明の第一および第二の実施の形態で示したものと同様である。本発明の第一および第二の実施の形態と異なるのは、赤外線検出部を層間絶縁膜１６で保持し、赤外線検出部と引き出し電極の領域のみに保護膜１９を具備する点である。
【００３６】
上記のように本実施の形態の焦電型赤外線検出素子の構成によれば、赤外線検出部で吸収される熱エネルギが、保持体１７および層間絶縁膜１６を介して起こる基板１１への熱の逃げを最小限度に抑えることができるので赤外線検出部での熱吸収量が増大し、なお一層、検出感度を向上させることができる。加えて熱時定数が増大することにより、特に低速物体検知での大きな出力応答を得ることができる。
【００３７】
本実施の形態では層間絶縁膜１６および引き出し電極保護膜１９としてポリイミド系樹脂を使用したが、これに限るものではなく、１０¹⁰Ωｃｍ以上の体積抵抗率を有する膜で耐熱温度が高く信頼性に優れているものであれば、他の有機膜やガラス系無機膜でもかまわない。
【００３８】
（実施の形態４）
図７は、本発明の第四の実施の形態における焦電型赤外線検出素子の構成を示す平面図である。図７において、１１は基板、１２ａは第一の電極、１２ｂは第一の電極の引き出し部、１３は外部接続端子、１４は焦電体薄膜、１５ａは第二の電極、１５ｂは第二の電極の引き出し部、１６は層間絶縁膜、１７は赤外線検出部の保持体、１９は赤外線検出部と引き出し電極の保護膜、１８は空洞である。
【００３９】
本発明の第四の実施の形態における焦電型赤外線検出素子の基本構成および製造方法は、本発明の第一、第二および第三の実施の形態で示したものと同様である。本発明の前記実施の形態と異なるのは、赤外線検出部をマトリックス状に形成しているところで、赤外線検出部どうしが第二の電極１５ａと同一材料あるいは第一の電極１２ａの熱伝導率より低い材料を用いた引き出し電極で接続し、本発明の第三の実施の形態と同様に、赤外線検出部と引き出し電極上のみに保護膜１９を形成する点である。
【００４０】
上記のように本実施の形態の焦電型赤外線検出素子の構成によれば、保持体１７および引き出し電極を介して起こる赤外線検出部の間での熱クロストークを最小限抑えることができるので、各々の赤外線検出部での熱吸収量が増大し、検出感度および熱時定数を向上させることができる。これにより、近距離、中距離における物体の微弱な動きを検知できる高速・高出力マトリックス赤外線素子が実現できる。
【００４１】
本実施の形態では２行２列のマトリックス素子を使用したが、これに限るものではなく、多次元化していくことにより、さらに高分解能・高感度化が実現できるものである。
【００４２】
以上のように本発明によれば、基板と、この基板上に設けられた第一の電極上に薄膜焦電体を形成しその上に、第一の電極の熱伝導率より小さな熱伝統率を有する材料からなる第二の電極を形成した赤外線検出部と、前記赤外線検出部が接する前記基板の表層部に設けた空洞と、前記赤外線検出部が前記基板で支えられるように設けた保持体とから構成される焦電型赤外線検出素子において、基板の空洞を形成していない同一表面上の領域に第一の電極材料と同一材料を用いて外部接続端子を設け、前記赤外線検出部と外部接続端子を電気的に接続する第一の電極の引き出し部の材料が第二の電極と同じ材料あるいは第一の電極の熱伝導率より小さな熱伝導率を有する材料のいずれかである焦電型赤外線検出素子とすることにより、引き出し部または保持体を介して起こる基板あるいは隣接する赤外線検出部への熱エネルギの伝達を最小限抑えることができるので、赤外線検出部での熱吸収量が増大し、検出感度・熱時定数を向上させることができ、これにより高感度・高分解能を実現できるものである。
【図面の簡単な説明】
【図１】本発明の第一の実施の形態における焦電型赤外線検出素子の平面図
【図２】同焦電型赤外線検出素子の断面図
【図３】本発明の第二の実施の形態における焦電型赤外線検出素子の平面図
【図４】同焦電型赤外線検出素子の断面図
【図５】本発明の第三の実施の形態における焦電型赤外線検出素子の平面図
【図６】同焦電型赤外線検出素子の断面図
【図７】本発明の第四の実施の形態における焦電型赤外線検出素子の平面図
【図８】（ａ），（ｂ）は従来の焦電型赤外線検出素子の平面図と断面図
【符号の説明】
１１基板
１２ａ第一の電極
１２ｂ第一の電極の引き出し部
１３外部接続端子
１４焦電体薄膜
１５ａ第二の電極
１５ｂ第二の電極の引き出し部
１６層間絶縁膜
１７保持体
１８空洞[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a pyroelectric infrared detection element that detects infrared rays using a pyroelectric material.
[0002]
[Prior art]
Pyroelectric infrared detectors take advantage of the ability to detect the presence / absence / position / operation / temperature of a human body or object in a non-contact manner, measure the temperature of cooking materials with a microwave oven, control the indoor temperature with an air conditioner, or It is used to detect human bodies with automatic lighting control, automatic doors, and alarm devices, and its field of use is expected to expand in the future.
[0003]
A pyroelectric infrared detector is a sensor that uses the pyroelectric effect of a ferroelectric material. Ferroelectric materials have the property of being uniformly polarized, and in the uniformly polarized state, they have positive and negative charges. Yes. When left in the atmosphere, it is electrically neutralized by combining with floating charges in the atmosphere. All objects emit infrared energy according to temperature, and when the infrared energy emitted from the object is incident on the infrared detection part of the infrared detection element composed of the pyroelectric material, the temperature changes in the pyroelectric material. At that time, a change in polarization induces a charge on the pyroelectric surface. At this time, the induced charge is detected as voltage or current.
[0004]
A conventional pyroelectric infrared detection element will be described below.
FIGS. 8A and 8B show a configuration diagram of a conventional pyroelectric infrared detection element. In the figure, the pyroelectric infrared detecting element 81 has a substrate, 82a and 82b electrodes, 83 a pyroelectric thin film, 84a and 84b organic films, and 85 an opening.
[0005]
About the pyroelectric infrared detection element comprised as mentioned above, the manufacturing method is demonstrated below. First, (100) magnesium oxide (hereinafter abbreviated as (100) MgO) is used as the substrate 81, and lead titanate (hereinafter abbreviated as PLT) to which lanthanum is added as a pyroelectric thin film 83 is used as a metal mask. Then, it is epitaxially grown in a predetermined shape by high frequency magnetron sputtering. Next, the organic film 84a as an interlayer insulating film is patterned into a predetermined shape by photolithography and etched. Then, a Ni—Cr alloy thin film is formed as an electrode 82a on the upper portion by a vacuum vapor deposition method, and patterned into a predetermined shape by photolithography and wet etching. Further, an organic film 84b as a holding body is patterned into a predetermined shape by photolithography, and etched. Subsequently, the (100) MgO substrate surface on which the pyroelectric thin film 83 is formed is protected with a resist, and the region of the pyroelectric thin film 83 is etched from the back surface to form an opening 85. Finally, on the side from which the (100) MgO substrate 81 is removed, a Ni—Cr alloy thin film is formed as an electrode 82b by a vacuum deposition method, and patterned into a predetermined shape by photolithography and wet etching.
[0006]
[Problems to be solved by the invention]
However, in the conventional method described above, when the thermal response in the infrared detection unit is improved to improve the sensitivity of the infrared detection unit, the infrared detection unit and the entire (100) MgO substrate 81 that holds the entire infrared detection unit are used. There must be sufficient spacing to reduce heat conduction and minimize heat escape. For this purpose, it is necessary to make the opening 85 larger, but the influence of the internal stress of the organic films 84a and 84b holding the infrared detector becomes stronger, and the pyroelectric thin film 83 and the electrodes 82a and 82b are disconnected. It had the problem of causing distortion and destruction.
[0007]
Further, in order to avoid disconnection of the lead portions of the electrodes 82a and 82b due to internal stress of the organic films 84a and 84b, the pattern width of the lead portions of the electrode 82b is set to be substantially the same as the pattern shape of the pyroelectric thin film. The amount of heat transferred from the electrode lead portion to the (100) MgO substrate 81 is large. Further, since the organic film 84b holding the infrared detection unit is integrally formed from the upper layer of the infrared detection unit to the substrate, the infrared energy incident on the infrared detection unit is absorbed as heat energy by the organic film and absorbed at the same time. The thermal energy thus released escapes to the (100) MgO substrate 81 through this. Therefore, this configuration has a problem in that the amount of heat absorbed by the infrared detection unit is small and sufficient detection sensitivity cannot be obtained.
[0008]
The present invention solves the above-described problems, and is a highly reliable pyroelectric infrared detection element that is excellent in sensitivity and thermal response, is low in cost, downsized and integrated, and is rich in productivity. Is intended to provide.
[0009]
[Means for Solving the Problems]
In order to achieve this object, the pyroelectric infrared detecting element of the present invention forms a thin film pyroelectric body on a substrate and a first electrode provided on the substrate, and on the first electrode, An infrared detector formed with a second electrode made of a material having a thermal conductivity smaller than the thermal conductivity , a cavity provided in a surface layer portion of the substrate that is in contact with the infrared detector, and the infrared detector is the substrate In a pyroelectric infrared detecting element composed of a holding body provided to be supported, an external connection terminal is formed using the same material as the first electrode material in a region on the same surface where the cavity of the substrate is not formed. The material of the lead part of the first electrode for providing and electrically connecting the infrared detection part and the external connection terminal is the same material as the second electrode or a material having a thermal conductivity smaller than the thermal conductivity of the first electrode A pyroelectric infrared detector It is obtained by the.
[0010]
By adopting this configuration, a pyroelectric infrared detection element excellent in sensitivity and thermal response can be obtained.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
According to the first aspect of the present invention, a thin film pyroelectric material is formed on a substrate and a first electrode provided on the substrate, and a heat smaller than the thermal conductivity of the first electrode is formed thereon. An infrared detection unit having a second electrode made of a material having conductivity, a cavity provided in a surface layer portion of the substrate in contact with the infrared detection unit, and the infrared detection unit provided to be supported by the substrate In the pyroelectric infrared detection element constituted by the holding body, an external connection terminal is provided using the same material as the first electrode material in a region on the same surface where the cavity of the substrate is not formed, and the infrared detection unit The material of the lead-out portion of the first electrode that electrically connects the external connection terminal and the external connection terminal is either the same material as the second electrode or a material having a thermal conductivity smaller than that of the first electrode. An electric infrared detection element is constructed. Relaxation broken distortion of the lead portions made small cavity Te, destruction can be suppressed, sensitivity suppress heat transfer to the substrate, it is possible to improve the thermal response.
[0012]
In the invention according to claim 2, the material of the lead portion of the second electrode or the first electrode is Ta, Ti, Sn, Al-Cu alloy, Ni-Cr alloy, Cu-Ni alloy, Cu-Sn alloy, The pyroelectric infrared detection element according to claim 1, which is made of any one of an Al-Ti alloy and a Cu-Zn alloy, and can suppress heat conduction to the substrate .
[0013]
The invention according to claim 3 is the pyroelectric infrared detection element according to claim 1 , wherein the holding body has a hole in at least 50% of the area and the thickness is 2 μm or less. Heat conduction can be suppressed .
[0014]
According to a fourth aspect of the present invention, the electrical signals generated at both ends in the thickness direction of at least two infrared detectors configured in a matrix on one substrate are the same material as the second electrode or the first The pyroelectric infrared detection element according to claim 1, wherein the external connection terminal is drawn out through a lead-out portion using any one of materials having a thermal conductivity smaller than that of the electrode. It suppresses heat conduction and increases the degree of integration.
[0015]
In the invention described in claim 5, the infrared detectors configured in a matrix form use either the same material as the second electrode or a material having a thermal conductivity smaller than that of the first electrode. The pyroelectric infrared detection element according to claim 1, which is electrically connected by a lead-out portion, suppresses heat conduction to the substrate and increases the degree of integration.
[0018]
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
(Embodiment 1)
1 and 2 are a plan view and a cross-sectional view showing the configuration of the pyroelectric infrared detection element according to the first embodiment of the present invention. 1 and 2, 11 is a substrate, 12a is a first electrode, 12b is a lead portion of the first electrode, 13 is an external connection terminal, 14 is a pyroelectric thin film, 15a is a second electrode, and 15b is a second electrode. The lead-out portion of the second electrode, 16 is an interlayer insulating film, 17 is a holding body of the infrared detecting portion, and 18 is a cavity.
[0019]
About the pyroelectric infrared detection element comprised as mentioned above, the manufacturing method is demonstrated below. First, (100) magnesium oxide (hereinafter abbreviated as (100) MgO) is used as the substrate 11, and platinum (hereinafter referred to as Pt and Pt) having a thickness of about 150 nm as the first electrode 12 a on the (100) MgO substrate 11. (Omitted) The thin film was formed by magnetron sputtering with a substrate temperature of 600 ° C., an incident power density of 0.16 W / cm ² , a sputtering gas atmosphere: Ar / O ₂ = 2/1, and a gas pressure of 1.06 Pa. Originally grown epitaxially.
[0020]
Next, a thin film made of a pyroelectric material such as PbTiO ₃ or Pb _1-x La _x Ti _{1-x / 4} O ₃ as a pyroelectric thin film 14 is formed thereon by a high-frequency magnetron sputtering method as a substrate temperature: 600 ° C. Epitaxial growth is performed under the deposition conditions of incident power density: 1.6 W / cm ² , sputtering gas atmosphere: Ar / O ₂ = 9/1, and gas pressure: 1 Pa. At this time, due to the difference in thermal expansion coefficient between the (100) MgO substrate 11 and the pyroelectric thin film 14, the crystal lattice of the pyroelectric thin film 14 is distorted at the boundary of the Curie point, and the C axis extends in the direction perpendicular to the substrate surface. As a result, spontaneous polarization in one direction appears.
[0021]
Next, the pyroelectric thin film 14 is patterned and formed into a predetermined shape by photolithography and wet etching, and then the first electrode 12a is also patterned and formed into a predetermined shape by photolithography and dry etching. At the same time, the lead portion 12b of the first electrode and the external connection terminal 13 are formed by patterning, and the first electrode 12a is electrically connected to one of the external connection terminals 13 and the lead portion 12b of the first electrode. Connected to.
[0022]
Next, using a polyimide resin having photosensitivity as the interlayer insulating film 16, the precursor is patterned into a predetermined shape by photolithography, and imidization is promoted in a temperature atmosphere of about 300 ° C. to be thermally cured. At this time, at least the pyroelectric thin film 14 and the second electrode 15a have a patterning shape in which holes are provided in a region where the direct electrical connection is possible and a region of 50% or more of the portion excluding the region.
[0023]
Next, a Ni—Cr alloy thin film having a film thickness of about 20 nm as a second electrode 15a is formed on the upper layer by sputtering, substrate temperature: 100 ° C., incident power density: 0.55 W / cm ² , sputtering gas atmosphere: Ar The film is formed under a film forming condition of a gas pressure of 1 Pa. Thereafter, patterning is performed in a predetermined shape by photolithography and wet etching. At the same time, the lead portion 15b of the second electrode 15a is formed by patterning in a state of being electrically connected to the second electrode 15a, and further electrically connected to the other external connection terminal 13.
[0024]
Next, using a polyimide resin having photosensitivity as the holding body 17, the precursor is patterned into a predetermined shape by photolithography, imidization is promoted in a temperature atmosphere of about 300 ° C., and the resin is thermally cured. At this time, it is set as the patterning shape which provides a hole in 50% or more area | region except the part concerning an infrared detection part.
[0025]
Finally, the cavity 18 is formed by etching from the same surface on a specific region of the (100) MgO substrate 11 through a protective mask for etching produced by photolithography. As an etching solution at this time, phosphoric acid having a concentration of 10% and a liquid temperature of 80 ° C. is used. As a result, when the etching time is 60 minutes, the size of the cavity is confirmed to be 0.3 mm in the horizontal direction and 0.08 mm in the vertical direction.
[0026]
As described above, according to the configuration of the pyroelectric infrared detection element of the present embodiment, holes are patterned on the cavity 18 provided in the surface layer portion of the (100) MgO substrate 11 in a region of 50% or more. Is supported through a polyimide resin holder 17 having a multi-hole structure, which is much smaller than the opening of a conventional pyroelectric infrared detection element, and infrared detection associated with expansion of the opening Since the distortion to the part and the lead-out part of the electrode can be alleviated, disconnection / breakage can be suppressed. In addition, the thermal response of the infrared detector can be increased in speed with respect to incident infrared energy. Further, the heat conduction to the substrate is achieved by the multi-hole structure of the lead electrode and the holding body that is sufficiently long relative to the distance between the infrared detecting portion and the external connection terminal on the substrate 11, specifically, more than twice the length. Since it can be sufficiently suppressed, the amount of heat absorption in the infrared detection unit increases, and the detection sensitivity can be improved. In addition, since the thermal time constant increases, it is possible to obtain a large output response particularly when detecting a low-speed object.
[0027]
In addition, with the above element configuration, a highly reliable infrared detection element that can be integrated and miniaturized can be realized.
[0028]
In the present embodiment, a Pt thin film epitaxially grown on the (100) plane is used as the first electrode 12a. This is excellent in lattice matching with the pyroelectric thin film 14 and the substrate 11, and therefore has an effect of promoting epitaxial growth of the pyroelectric thin film 14 in the C-axis direction. Furthermore, it is chemically stable and has a feature that it is not thermally oxidized even in a high-temperature oxidizing atmosphere. Although a Ni—Cr alloy thin film is used as the second electrode 15a, it has been confirmed that the same effect as in the present embodiment can be obtained by using any of the materials recited in claim 5. Further, in this embodiment, polyimide resin is used as the interlayer insulating film 16 and the holding body 17, but the present invention is not limited to this, and a film having a volume resistivity of 10 ¹⁰ Ωcm or more has high heat resistance and high reliability. Other organic films or glass-based inorganic films may be used as long as they are excellent.
[0029]
(Embodiment 2)
3 and 4 are a plan view and a cross-sectional view showing the configuration of the pyroelectric infrared detection element according to the second embodiment of the present invention. 3 and 4, 11 is a substrate, 12a is a first electrode, 12b is a lead portion of the first electrode, 13 is an external connection terminal, 14 is a pyroelectric thin film, 15a is a second electrode, and 15b is a second electrode. The lead-out portion of the second electrode, 16 is an interlayer insulating film, 17 is a holding body of the infrared detecting portion, and 18 is a cavity.
[0030]
The basic configuration and the basic manufacturing method of the pyroelectric infrared detection element in the second embodiment of the present invention are the same as those shown in the first embodiment of the present invention. What is different from the first embodiment of the present invention is an electrical connection method between the first electrode 12 a and the external connection terminal 13. In the second embodiment of the present invention, when the first electrode 12a is patterned and formed into a predetermined shape by photolithography and dry etching, a connection pad to the lead portion 12b of the first electrode 12a is provided, and the external electrode The connection terminals 13 are also formed at the same time.
[0031]
Next, a through hole is formed at a position of the interlayer insulating film 16 overlapping with the connection pad. Simultaneously with the formation of the second electrode 15a, the lead portion 12b of the first electrode is formed using the Ni—Cr alloy thin film, and the other is not electrically connected to the second electrode 15a via the other portion. The external connection terminal 13 and the first electrode 12a are electrically connected.
[0032]
As described above, according to the configuration of the pyroelectric infrared detection element of the present embodiment, the lead electrode 12b of the first electrode 12a is made of a material having a thermal conductivity lower than that of the first electrode material. Therefore, the amount of heat absorbed by the infrared detection unit can be increased, and the detection sensitivity and thermal time constant can be further improved. In particular, a large output response in low-speed object detection can be obtained.
[0033]
In the present embodiment, the same material as that of the second electrode 15a is used as the material of the extraction electrode 12b. However, the present invention is not limited to this, and the electrical conductivity is lower than that of the first electrode material. Other conductive metals, alloys, or low resistance semiconductors may be used as long as they have conductivity.
[0034]
(Embodiment 3)
5 and 6 are a plan view and a cross-sectional view showing the configuration of the pyroelectric infrared detection element according to the third embodiment of the present invention. 5 and 6, 11 is a substrate, 12a is a first electrode, 12b is a lead portion of the first electrode, 13 is an external connection terminal, 14 is a pyroelectric thin film, 15a is a second electrode, and 15b is The lead portion of the second electrode, 16 is an interlayer insulating film, 17 is a holding body for the infrared detection portion, 19 is a protective film for the infrared detection portion and the lead electrode, and 18 is a cavity.
[0035]
The basic configuration and basic manufacturing method of the pyroelectric infrared detection element in the third embodiment of the present invention are the same as those shown in the first and second embodiments of the present invention. The difference from the first and second embodiments of the present invention is that the infrared detecting portion is held by the interlayer insulating film 16 and the protective film 19 is provided only in the region of the infrared detecting portion and the extraction electrode.
[0036]
As described above, according to the configuration of the pyroelectric infrared detection element of the present embodiment, the heat energy absorbed by the infrared detection unit is generated by the heat to the substrate 11 generated through the holding body 17 and the interlayer insulating film 16. Since escape can be suppressed to the minimum, the amount of heat absorption in the infrared detection unit increases, and the detection sensitivity can be further improved. In addition, since the thermal time constant increases, it is possible to obtain a large output response particularly when detecting a low-speed object.
[0037]
In the present embodiment using a polyimide resin as the interlayer insulating film 16 and the lead-out electrode protective film 19 is not limited to this, the heat resistance temperature at film reliable having a volume resistivity of more than 10 ¹⁰ [Omega] cm Other organic films or glass-based inorganic films may be used as long as they are excellent.
[0038]
(Embodiment 4)
FIG. 7 is a plan view showing a configuration of a pyroelectric infrared detection element according to the fourth embodiment of the present invention. In FIG. 7, 11 is a substrate, 12a is a first electrode, 12b is a lead portion of the first electrode, 13 is an external connection terminal, 14 is a pyroelectric thin film, 15a is a second electrode, and 15b is a second electrode. An electrode lead-out portion, 16 is an interlayer insulating film, 17 is an infrared detector holding body, 19 is an infrared detector and lead electrode protective film, and 18 is a cavity.
[0039]
The basic configuration and manufacturing method of the pyroelectric infrared detection element in the fourth embodiment of the present invention are the same as those shown in the first, second and third embodiments of the present invention. The difference from the above embodiment of the present invention is that the infrared detectors are formed in a matrix, and the infrared detectors are made of the same material as the second electrode 15a or the thermal conductivity of the first electrode 12a. The connection is made with an extraction electrode using a material, and the protective film 19 is formed only on the infrared detection portion and the extraction electrode, as in the third embodiment of the present invention.
[0040]
As described above, according to the configuration of the pyroelectric infrared detection element of the present embodiment, it is possible to minimize the thermal crosstalk between the infrared detection unit that occurs through the holding body 17 and the extraction electrode. The amount of heat absorption in each infrared detection unit increases, and detection sensitivity and thermal time constant can be improved. As a result, it is possible to realize a high-speed, high-power matrix infrared device that can detect a weak movement of an object at a short distance and a medium distance.
[0041]
In this embodiment, a matrix element of 2 rows and 2 columns is used, but the present invention is not limited to this, and higher resolution and higher sensitivity can be realized by increasing the number of dimensions.
[0042]
As described above, according to the present invention, a thin film pyroelectric body is formed on a substrate and a first electrode provided on the substrate, and a thermal tradition rate smaller than the thermal conductivity of the first electrode is formed thereon. An infrared detector formed with a second electrode made of a material having a cavity, a cavity provided in a surface layer portion of the substrate in contact with the infrared detector, and a holder provided so that the infrared detector is supported by the substrate In the pyroelectric infrared detecting element constituted by the above, an external connection terminal is provided by using the same material as the first electrode material in a region on the same surface where the cavity of the substrate is not formed, and the infrared detecting unit and the external The pyroelectric type in which the material of the lead portion of the first electrode that electrically connects the connection terminals is either the same material as the second electrode or a material having a thermal conductivity smaller than that of the first electrode with the infrared detector, drawers Or the substrate occurs via the holding member or can be suppressed minimum the transfer of heat energy to adjacent infrared detection section, the heat absorption amount of the infrared detection portion is increased, thereby improving the detection sensitivity and the thermal time constant Thus, high sensitivity and high resolution can be realized.
[Brief description of the drawings]
FIG. 1 is a plan view of a pyroelectric infrared detection element according to a first embodiment of the present invention. FIG. 2 is a cross-sectional view of the pyroelectric infrared detection element. FIG. 3 is a second embodiment of the present invention. FIG. 4 is a sectional view of the pyroelectric infrared detecting element in FIG. 5. FIG. 5 is a plan view of the pyroelectric infrared detecting element in the third embodiment of the present invention. FIG. 7 is a plan view of a pyroelectric infrared detection element according to a fourth embodiment of the present invention. FIGS. 8A and 8B are diagrams showing conventional pyroelectrics. Plane view and sectional view of the infrared detector
DESCRIPTION OF SYMBOLS 11 Board | substrate 12a 1st electrode 12b Leading part of 1st electrode 13 External connection terminal 14 Pyroelectric thin film 15a Second electrode 15b Leading part of 2nd electrode 16 Interlayer insulation film 17 Holder 18 Cavity

Claims

A thin film pyroelectric body is formed on a substrate and a first electrode provided on the substrate, and a second electrode made of a material having a thermal conductivity smaller than that of the first electrode is formed thereon. Pyroelectric infrared detection comprising a formed infrared detection unit, a cavity provided in a surface layer portion of the substrate in contact with the infrared detection unit, and a holder provided so that the infrared detection unit is supported by the substrate In the device, an external connection terminal is provided in the region on the same surface where the cavity of the substrate is not formed using the same material as the first electrode material, and the infrared detection unit and the external connection terminal are electrically connected to each other. A pyroelectric infrared detection element in which the material of the lead portion of the electrode is either the same material as the second electrode or a material having a thermal conductivity smaller than that of the first electrode.

The material of the lead portion of the second electrode or the first electrode is Ta, Ti, Sn, Al—Cu alloy, Ni—Cr alloy, Cu—Ni alloy, Cu—Sn alloy, Al—Ti alloy, or Cu—Zn. pyroelectric infrared detector of claim 1, wherein consisting of either alloy.

The pyroelectric infrared detection element according to claim 1, wherein the holding body has holes in at least 50% or more of the area and has a thickness of 2 μm or less.

Electrical signal generated across the thickness direction of at least two matrix infrared detector that is configured to a small than the thermal conductivity of the second electrode of the same material or the first electrode heat on one substrate The pyroelectric infrared detection element according to claim 1, wherein the external connection terminal is drawn out through a drawing portion using any one of materials having conductivity .

Infrared detectors configured in a matrix are electrically connected by a lead-out unit using either the same material as the second electrode or a material having a thermal conductivity smaller than that of the first electrode. The pyroelectric infrared detection element according to claim 1.