JP3931405B2

JP3931405B2 - Angular velocity sensor

Info

Publication number: JP3931405B2
Application number: JP33978997A
Authority: JP
Inventors: 健三田村
Original assignee: Nissan Motor Co Ltd
Current assignee: Nissan Motor Co Ltd
Priority date: 1997-04-10
Filing date: 1997-12-10
Publication date: 2007-06-13
Anticipated expiration: 2017-12-10
Also published as: DE19816203A1; DE19816203C2; JPH10339640A

Description

【０００１】
【発明の属する技術分野】
本発明は角速度を検出する角速度センサに関するものである。
【０００２】
【従来の技術】
近年、安全性や快適性向上のために多くの電子システムが車載されている。たとえば、車両のスピンを防止するシャシ制御システムや車両の現在位置を知るためのナビゲーションシステムなどは急速に需要が伸長している。これらシステムでは角速度を計測する角速度センサが重要な役割を果たす。それに伴いそれぞれのシステムに適用する角速度センサの高精度化とともに小型化と低コスト化とが求められる。このような要求に対して半導体を用いて角速度センサを実現する技術が知られている。
【０００３】
図２２は従来の半導体を用いた角速度センサ（たとえば、J. Bernstein et al. "Micromachined Comb-Drive Tuning Fork Rate Gyroscope", Digest IEEE/ASME Micro Electro Mechanical Systems (MEMS) Workshop, Florida, 1993, 143-148 に開示されている）を示す概略図、図２３は図２２のＡ−Ａ断面図である。図に示すように、基板６上に絶縁膜５が設けられ、基板６に固定部１、支持部２を介して振動質量３ａ、３ｂが設けられ、振動質量３ａ、３ｂの側面から延びた櫛歯電極と基板６に固定された櫛歯電極とで駆動電極４が構成され、固定部１、支持部２、振動質量３ａ、３ｂは多結晶シリコン薄膜を選択的にエッチングして作製されている。また、振動質量３ａ、３ｂの直下に検出電極７ａ、７ｂが設けられ、検出部は検出電極７ａ、７ｂを有している。
【０００４】
この角速度センサにおいては、図２４に示すように、共通電位の端子ａに対して端子ｂおよびｄに逆位相の駆動電圧Ｖ_bおよびＶ_dを印加すると、２つの振動質量３ａ、３ｂがそれぞれｘ方向の逆方向に駆動される。この状態で、角速度センサがｚ軸回りに回転して、ｚ軸方向に角速度Ωが入力すると、それぞれの振動質量３ａ、３ｂに対してｙ軸方向にコリオリ力が発生する。そして、振動質量３ａ、３ｂの質量をｍ、静電引力により駆動される振動質量３ａ、３ｂの速さをＶ_m(ｔ)とすると、コリオリ力Ｆｃ(ｔ)は次式で表される。なお、振動質量３ａ、３ｂはそれぞれ逆方向に駆動されるため、振動質量３ａ、３ｂに作用するコリオリ力Ｆｃ(ｔ)の符号は逆になる。
【０００５】
【数１】
Ｆｃ(ｔ)＝２・ｍ・Ｖ_m(ｔ)・Ω
このコリオリ力Ｆｃ(ｔ)による振動質量３ａ、３ｂのｙ方向の変位に応じて、振動質量３ａと検出電極４ａとの間の容量、振動質量３ｂと検出電極４ｂとの間の容量が変化するから、差動容量により角速度Ωを計測することができる。なお、（数１）式から明らかなように、コリオリ力Ｆｃ(ｔ)を大きくするには速さＶ_m(ｔ)を大きくすればよく、速さＶ_m(ｔ)を大きくするには真空中で共振周波数で振動質量３ａ、３ｂを駆動すればよい。
【０００６】
この角速度センサにおいては、極めて小型に製造することができるとともに、製造コストを安価にすることができる。
【０００７】
しかし、このような角速度センサにおいては、振動質量３ａ、３ｂを基板６の面と平行なｘ軸方向に駆動し、基板６の面と直角なｚ軸方向のコリオリ力を検出する構成となっているから、以下のような問題点がある。すなわち、支持部２のバネ定数は支持部２の断面形状つまり断面２次モーメントに依存する。そして、支持部２の断面を長方形として、支持部２の厚さをｔ、幅をｗとすると、基板６の主面に対して平行な方向の断面２次モーメントＩ_p、直角な方向の断面２次モーメントＩ_nは次式で表される。
【０００８】
【数２】
Ｉ_p＝ｗ・ｔ³／１２
【０００９】
【数３】
Ｉ_n＝ｗ³・ｔ／１２
そして、半導体製造技術においては幅ｗの加工精度はある程度確保することができるが、厚さｔを精度良く制御するのは困難であり、また断面２次モーメントＩ_pと断面２次モーメントＩ_nとの厚さｔに対する依存性は異なるから、検出軸（ｚ軸）方向および駆動軸（ｘ軸）方向の振動モード周波数を所定値に制御するのは困難である。また、構造パラメータへの依存性が異なるので、各々の振動モードの共振周波数の相対値の設定も不可能である。さらに、振動系を半導体で構成した場合、機械的調整は困難である。
【００１０】
図２５は従来の他の角速度センサ（特開平５−３１２５７６号公報）を示す概略図、図２６は図２５のＢ−Ｂ断面図である。図に示すように、シリコン基板２１上にパターニングされた酸化膜２０が形成され、シリコン基板２１に酸化膜２０を介してシリコン基板１９が接合され、シリコン基板１９に溝部１３が設けられ、溝部１３により構造体すなわち振動質量１５、第１支持部１４、第２支持部１０およびフレーム部１１が形成されている。そして、振動質量１５は第１支持部１４によって支持され、第１支持部１４の振動質量１５との接続部とは反対側の接続部はフレーム部１１に接続され、フレーム部１１は第２支持部１０によって支持され、フレーム部１１には静電引力で駆動を行なうための櫛歯電極８が構成され、振動質量１５のコリオリ力による変位を検出するために、第１支持部１４のフレーム部１１との接続部付近に２本平行に配置されたピエゾ抵抗９により抵抗ブリッジが構成され、または振動質量１５とフレーム部１１とに設けられた電極により検出電極１２が構成されている。なお、電気的配線の詳細は図面の簡略化のため省略した。
【００１１】
この角速度センサにおいては、櫛歯電極８に電圧を印加すると、第２支持部１０で支持されるフレーム部１１はｘ軸方向に静電引力により駆動される。この状態でシリコン基板２１の平面に垂直なｚ軸方向に角速度Ωで回転すると、（数１）式で表わされるコリオリ力がｙ軸方向に発生し、発生したコリオリ力による振動質量１５のｙ軸方向の変位はピエゾ抵抗９の抵抗差または検出電極１２の電気容量変化として検出することができる。
【００１２】
このような角速度センサにおいては、駆動軸（ｘ軸）および検出軸（ｙ軸）がともにシリコン基板２１の主面すなわち基板主面と平行な方向であるから、第１支持部１４、第２支持部１０の断面形状、特に構造体の厚さに対する駆動軸方向および検出軸方向の振動モード周波数の依存性は同等である。すなわち、製造バラツキにより厚さに設計値との偏差が生じた場合、駆動軸方向および検出軸方向のモード周波数の絶対値は変化するが、相対値は不変である。その結果、検出感度が製造バラツキに影響を受けにくいという効果が得られる。
【００１３】
【発明が解決しようとする課題】
しかし、図２５、図２６に示した角速度センサにおいては、一般的に角速度Ωの入力で発生するコリオリ力は重力加速度等と比べ微小な力であるから、ｙ軸方向の変位の高精度の検出が要求されるので、ピエゾ抵抗９での検出は実際上は不可能である。また、検出電極１２による静電容量の検出はピエゾ抵抗９での検出に比べより高感度であるが、検出電極１２による静電容量の検出にはある程度のベース容量（角速度の入力がない場合の検出電極の静電容量）を必要とし、そのベース容量からの変化を検出するが、検出電極１２は振動質量１５とフレーム部１１との側面にのみ形成されており、シリコン基板１９の厚さは通常最大数十μｍ程度であるから、充分なベース容量を確保できない。その結果、角速度Ωの高精度の検出が不可能である。
【００１４】
本発明は上述の課題を解決するためになされたもので、角速度を高精度に検出することができる角速度センサを提供することを目的とする。
【００１５】
【課題を解決するための手段】
この目的を達成するため、本発明においては、支持基板と、上記支持基板に固定された固定部と、上記固定部に弾性支持部を介して設けられた質量と、上記質量を振動する駆動手段と、上記質量の上記駆動手段による駆動方向と直角でかつ上記質量の面と平行な方向の変位を検出する検出手段とを有する角速度センサであって、上記質量の上記駆動方向と平行な側面に凹部を設け、上記検出手段として固定部に上記駆動方向を長さ方向として設けられた複数の第１の櫛歯電極と上記凹部内の上記質量部に上記駆動方向を長さ方向として設けられた複数の第２の櫛歯電極とを有するものを用いる。
【００１６】
この場合、上記弾性支持部は、上記支持基板に固定された固定部に上記駆動方向と直角の方向を長さ方向とする第１の弾性支持部を介して接続部を設け、上記接続部に上記駆動方向を長さ方向とする第２の弾性支持部を介して上記質量を設ける。
【００１７】
この場合、上記固定部に駆動方向が長さ方向でありかつ駆動方向と直角の方向に並んだ複数の固定梁の一端を接続し、上記固定梁の他端を固定梁接続部に接続し、上記第１の弾性支持部の上記接続部と接続された側とは反対側の端部を上記固定梁接続部に接続する。
【００１８】
また、上記駆動手段として上記固定部に上記駆動方向を長さ方向として設けられた複数の第３の櫛歯電極と上記接続部に上記駆動方向を長さ方向として設けられた複数の第４の櫛歯電極とを有するものを用いる。
【００１９】
また、上記第１、第２の弾性支持部の厚さを幅よりも大きくする。
【００２０】
また、上記支持基板の主面と平行に設けられかつ厚さが均一な板状部材を上記支持基板の主面と直角な方向に加工して上記固定部、上記第１の弾性支持部、上記接続部、上記第２の弾性支持部、上記質量を形成する。
【００２１】
また、上記第２の弾性支持部を上記質量のその重心から最も離れた部分に接続する。
【００２３】
この場合、上記接続部の各側部に２本の上記第１の弾性支持部を接続し、上記固定部に駆動方向が長さ方向でありかつ駆動方向と直角の方向に並んだ複数の第１、第２の固定梁の一端を接続し、上記第１の固定梁の他端を第１の固定梁接続部に接続し、上記第２の固定梁の他端を第２の固定梁接続部に接続し、一方の上記第１の弾性支持部の上記接続部と接続された側とは反対側の端部を上記第１の固定梁接続部に接続し、他方の上記第１の弾性支持部の上記接続部と接続された側とは反対側の端部を上記第２の固定梁接続部に接続する。
【００２４】
また、上記接続部の各側部に２本の上記第１の弾性支持部を接続し、上記固定部に駆動方向が長さ方向でありかつ駆動方向と直角の方向に並んだ複数の第１、第２の固定梁の一端を接続し、上記第１、第２の固定梁の他端を共通固定梁接続部に接続し、２本の上記第１の弾性支持部の上記接続部と接続された側とは反対側の端部を上記共通固定梁接続部に接続する。
【００２５】
これらの場合、上記第１の固定梁の一端を第１の固定部に接続し、上記第２の固定梁の一端を第２の固定部に接続する。
【００２６】
また、上記第２の弾性支持部の幅を上記第１の弾性支持部の幅よりも大きくする。
【００２７】
また、上記板状部材として半導体基板を用い、上記板状部材を半導体加工技術を用いて加工する。
【００２９】
【発明の効果】
本発明に係る角速度センサにおいては、質量の駆動方向と平行な側面に凹部を設け、凹部に第２の櫛歯電極を設けているから、質量のその面と直角な軸回りの慣性モーメントを抑制することができ、しかも第１、第２の櫛歯電極が質量の駆動に対して妨げとなることなく、剛性の許容範囲で第１、第２の櫛歯電極の長さを確保できるので、角速度を高精度に検出することができる。
【００３０】
また、支持基板に固定された固定部に駆動方向と直角の方向を長さ方向とする第１の弾性支持部を介して接続部を設け、接続部に駆動方向を長さ方向とする第２の弾性支持部を介して質量を設けたときには、駆動および検出を基板主面に平行な方向で行なうから、駆動方向および検出方向の振動モード周波数およびその相対値は基板主面内の構造体の平面構造に依存し、製造バラツキにより影響を受けにくく、安定した角速度の検出感度を得ることができる。
【００３１】
また、固定部に駆動方向が長さ方向でありかつ駆動方向と直角の方向に並んだ複数の固定梁の一端を接続し、固定梁の他端を固定梁接続部に接続し、第１の弾性支持部の接続部と接続された側とは反対側の端部を固定梁接続部に接続したときには、振動系を駆動したときに第１の弾性支持部に長さ方向の応力が生ずるのを抑制することができるから、駆動振動の非線形性を抑制することができ、また第１の弾性支持部の支持部の法線方向に対するねじり剛性が向上するから、振動系の法線方向のモード周波数の低下を回避することができるので、角速度をより高精度に検出することができる。
【００３２】
また、第１、第２の弾性支持部の厚さを幅よりも大きくしたときには、高精度検出に影響を及ぼす質量の面と直角な方向の振動モード周波数を駆動、検出モード周波数より高周波領域に設定可能であるから、前記モードの影響を抑制し、角速度をより高精度に検出することができる。
【００３３】
また、第２の弾性支持部を質量のその重心から最も離れた部分に接続したときには、質量の面と直角な方向の軸回りの回転に対する剛性が大きいから、回転モードの周波数を駆動、検出モード周波数に比べ充分高周波領域に設定することができるので、前記モードの影響を抑制し、角速度をより高精度に検出することができる。
【００３５】
また、接続部の各側部に２本の第１の弾性支持部を接続し、固定部に駆動方向が長さ方向でありかつ駆動方向と直角の方向に並んだ複数の第１、第２の固定梁の一端を接続し、第１の固定梁の他端を第１の固定梁接続部に接続し、第２の固定梁の他端を第２の固定梁接続部に接続し、一方の第１の弾性支持部の接続部と接続された側とは反対側の端部を第１の固定梁接続部に接続し、他方の第１の弾性支持部の接続部と接続された側とは反対側の端部を第２の固定梁接続部に接続したときには、振動系を駆動したときに第１の弾性支持部に長さ方向の応力が生ずるのを抑制することができるから、駆動振動の非線形性を抑制することができ、また第１の弾性支持部の支持部の法線方向に対するねじり剛性が向上するから、振動系の法線方向のモード周波数の低下を回避することができるので、角速度をより高精度に検出することができる。
【００３６】
また、接続部の各側部に２本の第１の弾性支持部を接続し、固定部に駆動方向が長さ方向でありかつ駆動方向と直角の方向に並んだ複数の第１、第２の固定梁の一端を接続し、第１、第２の固定梁の他端を共通固定梁接続部に接続し、２本の第１の弾性支持部の接続部と接続された側とは反対側の端部を共通固定梁接続部に接続したときには、振動系を駆動したときに第１の弾性支持部に長さ方向の応力が生ずるのを抑制することができるから、駆動振動の非線形性を抑制することができ、また第１の弾性支持部の支持部の法線方向に対するねじり剛性が向上するから、振動系の法線方向のモード周波数の低下を回避することができるので、角速度をより高精度に検出することができる。
【００３７】
また、第１の固定梁の一端を第１の固定部に接続し、第２の固定梁の一端を第２の固定部に接続したときには、駆動電圧に対する振動系の共通電位と検出信号に対する振動系の共通電位とが別の固定部にて外部信号処理回路に接続されるから、検出信号に対する駆動電圧の影響を抑制することができるので、角速度をより高精度に検出することができる。
【００３８】
また、第２の弾性支持部の幅を第１の弾性支持部の幅よりも大きくしたときには、高精度検出に影響を及ぼす質量の面と直角な方向の振動モード周波数を駆動、検出モード周波数より高周波領域に設定可能であるから、角速度をより高精度に検出することができる。
【００３９】
また、板状部材として半導体基板を用い、板状部材を半導体加工技術を用いて加工したときには、固定部、第１の弾性支持部、接続部、第２の弾性支持部、質量を容易に形成することができるから、製造コストが安価である。
【００４１】
【発明の実施の形態】
図１は本発明に係る角速度センサを示す概略平面図、図２は図１の概略Ｃ−Ｃ断面図、図３は図１の概略Ｄ−Ｄ断面図、図４は図１のＥ部詳細図である。図に示すように、板状部材である半導体基板３７に半導体支持基板３４の主面すなわち基板主面と直角な方向の溝３８が形成され、固定部２２、４１、接続部であるトラス２４、質量３２、第１、第２の弾性支持部２５、２７からなる構造体が設けられ、トラス２４、質量３２には小孔３５が多数配設され、半導体支持基板３４に絶縁膜３３を介して固定部２２、４１が接合されている。また、質量３２の駆動方向と平行な側面に四角形状の凹部３９が形成され、凹部３９のｘ軸方向の内壁にｘ軸方向が長手方向である第２の櫛歯電極３０が複数配設されている。また、固定部４１は半導体支持基板３４に固定され、固定部４１に櫛歯電極３０と同様の形状の第１の櫛歯電極３１が配設され、櫛歯電極３０の側面と櫛歯電極３１の側面とが対向しており、質量３２のｙ軸方向の変位を静電容量変化として検出する検出手段は櫛歯電極３０、櫛歯電極３１を有している。なお、図１においては入出力用パッド４２を図示したが、入出力用パッド４２に接続される信号処理回路は説明を簡単にするため省略する。
【００４２】
また、質量３２の重心から最も離れた部分すなわち最遠点近傍付近には第２の弾性支持部２７が接続され、弾性支持部２７はｘ軸方向が長手方向となっており、弾性支持部２７の厚さｔと幅ｗとの関係はｔ＞ｗとなっており、弾性支持部２７の基板主面と平行な方向の剛性より直角な方向の剛性の方が高くなっている。また、弾性支持部２７の長さは質量３２と櫛歯電極３０との合計質量で構成される振動系のｙ軸方向の共振周波数が所定値となるように設定されている。また、弾性支持部２７の質量３２とは反対側にトラス２４が接続され、質量３２は２つのトラス２４に接続されており、質量３２はトラス２４に対して両持梁構造で支持されている。
【００４３】
また、トラス２４のｘ軸方向の側面にはｘ軸が長手方向となる第４の櫛歯電極２９が配設され、固定部２２に櫛歯電極２９と同様の形状の第３の櫛歯電極２８が配設され、櫛歯電極２８の側面と櫛歯電極２９の側面とが対向しており、トラス２４および質量３２をｘ軸方向に静電引力を用いて駆動する駆動手段は櫛歯電極２８、櫛歯電極２９を有している。なお、図１においては入出力用パッド２３を図示したが、入出力用パッド２３に接続される信号処理回路は説明を簡単にするため省略する。
【００４４】
また、トラス２４のｙ軸方向の側面には第１の弾性支持部２５が接続され、弾性支持部２５はｙ軸方向が長手方向となっており、弾性支持部２５の厚さｔと幅ｗとの関係がｔ＞ｗとなっており、弾性支持部２５の基板主面に平行な方向の剛性より垂直方向の剛性の方が高くなっている。また、弾性支持部２５の長さは質量３２、トラス２４、弾性支持部２７および櫛歯電極２９、３０、３１の合計質量で構成される振動系のｘ軸方向の共振周波数が所定値となるように設定されている。また、弾性支持部２５のトラス２４とは反対側は固定部２２に接続され、弾性支持部２５が接続された固定部２２の弾性支持部２５の接続点近傍にはスリット溝２６が設けられ、各トラス２４は４本の弾性支持部２５に接続されており、固定部２２に対して両持梁構造で支持されている。
【００４５】
つぎに、図５により図１〜図４に示した角速度センサの製造方法を説明する。まず、図５(ａ)に示すように、半導体支持基板３４に絶縁膜３３を介して構造体となる半導体基板３７を接合したのち、所定の厚さまで研磨する。つぎに、図５(ｂ)に示すように、半導体基板３７の表面に構造に対応じたマスクパターン４０を形成する。つぎに、図５(ｃ)に示すように、半導体加工技術を用いて半導体基板３７に溝３８を作製し、構造体を形成する。この場合、溝３８の深さは絶縁膜３３まで達するようにする。つぎに、図５(ｄ)に示すように、トラス２４、質量３２、弾性支持部２５、２７からなる可動部となる半導体基板３７直下の絶縁膜３３を除去する。この場合、トラス２４、質量３２には小孔３５が多数配設されているから、絶縁膜３３を容易に除去することができる。なお、以上の説明では信号処理回路の作製プロセスについては簡略化のため説明を省いた。
【００４６】
図１〜図４に示した角速度センサにおいては、櫛歯電極２８、２９に電圧を印加することによりトラス２４および質量３２をｘ軸方向に駆動する。この場合、印加電圧の周波数は質量３２、トラス２４、弾性支持部２５、櫛歯電極２９〜３１で構成される振動系のｘ軸方向の共振周波数とし、より大きい振幅で駆動する。この駆動状態で基板主面に直角なｚ軸方向の角速度Ωが印加すると、ｙ軸方向に（数１）式で示したコリオリ力が生じる。この場合、弾性支持部２７で設定した共振周波数が駆動周波数と同一であれば、質量３２はｙ軸方向に共振振動を開始し、より大きなｙ軸方向変位として櫛歯電極３０、３１を有する検出手段の静電容量変化として検出される。このｙ軸方向の振幅は入力された角速度Ωに比例するため、ｙ軸方向の振幅から角速度Ωを検出することができる。
【００４７】
図１〜図４に示した角速度センサにおいては、図２５、図２６に示した従来の角速度センサと同様に、駆動および検出を基板主面に平行なｘ軸方向、ｙ軸方向で行なうから、駆動軸であるｘ軸の方向および検出軸であるｙ軸の方向の振動モード周波数およびその相対値は基板主面内の構造体の平面構造に依存し、製造バラツキにより影響を受けにくく、安定した角速度Ωの検出感度を得ることができる。また、櫛歯電極３０をその長手方向がｘ軸方向になるように配置してあるから、櫛歯電極３０が質量３２の駆動に対して妨げとなることなく、剛性の許容範囲で櫛歯電極３０の長さを確保できる。たとえば、２０μｍ厚の半導体基板３７で幅６μｍ、長さ３２０μｍの櫛歯電極３０を形成し、櫛歯電極３０を３００μｍの範囲でギャップ２μｍで櫛歯電極３１に対向させたとすると、１０Ｖ程度までは電圧が印加可能であり、この櫛歯電極３０、３１の対を３８対配設することにより、約１ｐＦの検出容量が確保できる。したがって、角速度Ωを高精度に検出することができる。また、質量３２の側面の一部に凹部３９を形成し、凹部３９の内側に櫛歯電極３０を複数配設しているから、櫛歯電極３０による可動体のｚ軸回りの慣性モーメントを抑制することができるので、角速度Ωをより高精度に検出することができる。また、弾性支持部２５、２７の厚さｔと幅ｗとの関係がｔ＞ｗとなっており、弾性支持部２５、２７の基板主面と平行な方向の剛性より直角な方向の剛性の方が高くなっているから、トラス２４のｙ軸回りの回転剛性が向上し、高精度検出に影響を及ぼす基板主面と直角なｚ軸方向の振動モード周波数を駆動、検出モード周波数より高周波領域に設定可能であるので、基板主面と直角な方向の振動を生じさせることなく角速度Ωを測定することができるため、角速度Ωをより高精度に検出することができる。また、弾性支持部２７が質量３２の重心から最遠点近傍付近に接続されているから、ｚ軸回りの回転に対する剛性が大きく、駆動および検出に悪影響をもたらす回転モードの周波数を駆動、検出モード周波数に比べ充分高周波領域に設定することができるので、ｚ軸回りの回転振動を生じさせることなく角速度Ωを測定することができるため、角速度Ωをより高精度に検出することができる。また、トラス２４を４本の弾性支持部２５によって固定部２２に接続しているから、高精度検出に影響を及ぼす基板主面と直角な方向の振動モード周波数を駆動、検出モード周波数より高周波領域に設定可能であるので、基板主面と直角な方向の振動を生じさせることなく角速度Ωを測定することができるため、角速度Ωをより高精度に検出することができる。また、半導体加工技術を用いて半導体基板３７に溝３８を作製して構造体を形成しているから、構造体を容易に形成することができるので、製造コストが安価である。また、固定部２２の弾性支持部２５の接続点近傍にはスリット溝２６が設けられているから、固定部２２からの応力の伝達を緩和することができるので、実装ストレス等による応力の影響を抑制できるため、安定した振動モード周波数を実現できる。その結果、角速度センサ感度の安定化が可能である。また、固定部２２、４１が可動体の外周部に配置されているから、基板主面内で固定部２２、４１に電気的な接続が可能であり、配線構造の簡素化が可能である。また、質量３２の両側に駆動手段を配置しているから、構造の対称性を確保することができ、また駆動振幅検出を行なうことができる。また、質量３２の中央部の両側に２列の検出手段を配置しているから、構造の対称性を確保することができ、また振幅を２つの静電容量の差動で変位を検出することができる。また、トラス２４のｙ軸方向のサイズを基板主面と直角な方向の剛性を確保できる範囲で長く設定できるから、駆動手段の櫛歯電極２８、２９を多数配設できるので、より大きい静電駆動力を得ることができる。以上述べたように、検出容量を確保すると同時に、安定した構造体の振動モードを実現できるから、角速度センサの感度の高精度化と安定化とを同時に実現することができる。
【００４８】
図６は本発明に係る他の角速度センサの質量部を示す概略図である。図に示すように、質量３２には基板主面と直角な方向の剛性が確保できる範囲で貫通孔３６が設けられている。なお、図面の簡略のため駆動手段、検出手段の図示を省略した。
【００４９】
この角速度センサにおいては、質量３２に貫通孔３６が設けられているから、軽量化することができる。その結果、設計共振振動数に対して支持部の剛性を抑えることができ、駆動振幅増加、発生コリオリ力に対する変位増大により高感度化が可能である。
【００５０】
図７〜図９に本発明に係る他の角速度センサの振動モードの具体例を示す。図に示すように、質量３２は凹部３９と貫通孔３６とを有する。なお、図面の簡略のため駆動手段、検出手段の図示を省略した。そして、図７はｘ軸方向の駆動モード、図８はｙ軸方向の検出モードであり、周波数はいずれも３．５ｋＨｚ程度である。また、図９はｚ軸回りの回転モードであり、周波数は３０ｋＨｚ程度であり、充分高い周波数に設定されている。
【００５１】
図１０は図７〜図９に示した角速度センサの構造体と同一の構造体の基板主面と直角な方向の振動モード例を示す図である。この振動モード周波数はおよそ７．５ｋＨｚであり、駆動、検出モード周波数（３．５ｋＨｚ）の２倍以上である。そして、周波数比は構造体の更なる厚膜化によりさらに増加する。
【００５２】
図１１は本発明に係る他の角速度センサを示す概略図である。図に示すように、凹部３９のｘ軸方向の内壁およびその内壁と相対する質量３２のｘ軸方向の外周部側壁に、ｘ軸方向が長手方向である櫛歯電極３０が複数配設されている。また、質量３２のｘ軸方向の外周部側壁の櫛歯電極３０に隣接する部分に弾性支持部２７が接続され、弾性支持部２７同士の間隔は櫛歯電極３０を外周部に配設したことにより増加した質量３２の慣性モーメントに対してｚ軸回りの回転剛性が確保できるように配置されている。
【００５３】
この角速度センサにおいては、櫛歯電極３０を質量３２の外周部側壁にも配設したから、より大きい検出容量が得られるので、角速度Ωをより高精度に検出することができる。また、櫛歯電極３０が質量３２の外周部にも配設されているから、質量３２のｙ軸方向のサイズを剛性の確保できる範囲で図１〜図４に示した角速度センサに比べ長くすることができる。
【００５４】
図１２は本発明に係る他の角速度センサの一部を示す概略図である。図に示すように、質量３２とトラス２４とを接続する弾性支持部２７の幅ｗ₁とトラス２４と固定部２２を接続する弾性支持部２５の幅ｗ₂との関係がｗ₁＞ｗ₂となるように設定してある。
【００５５】
この角速度センサの構造体の１次元近似モデルを図１３に示す。図において、ｋ₁は質量３２をトラス２４にて両持梁構造で支持する計４本の弾性支持部２７の基板主面と直角なｚ軸方向のバネ定数を表す。前述のように弾性支持部２７の幅はｗ₁である。また、ｍ₁は質量３２と櫛歯電極３０との質量合計である。また、ｋ₂はトラス２４を固定部２２にて両持梁構造で支持する計８本の弾性支持部２５の基板主面と直角なｚ軸方向のバネ定数を表す。前述のように弾性支持部２５の幅はｗ₂である。また、ｍ₂はトラス２４と櫛歯電極２９との質量合計である。そして、比γ＝ｗ₁／ｗ₂、比β＝ｍ₁／ｍ₂とすると、図１３に示す１次元２自由度振動系のｚ軸方向の１次振動モード周波数ω₁の２乗は次式で表される。
【００５６】
【数４】
ω₁ ²＝１／２［２＋γ²（β＋１）−√｛４＋γ⁴（β＋１）²｝］
図１４は１次モード周波数ω₁と比βとの関係を比γをパラメータとして示すグラフで、線ａ〜ｃはそれぞれ比γが０．５、１、２の場合を示す。図１４から明らかなように、γ＞１の方が１次振動モード周波数ω₁が大きくなる。したがって、γ＞１とすることによりすなわち弾性支持部２７の幅ｗ₁を弾性支持部２５の幅ｗ₂よりも大きくすることにより、高精度検出に影響を及ぼす基板主面と直角な方向の振動モード周波数を駆動、検出モード周波数より高周波領域に設定可能であるから、基板主面と直角な方向の振動を生じさせることなく角速度Ωを測定することができるので、角速度Ωを高精度に検出することができる。なお、この効果は構造体の更なる厚膜化によりさらに増大する。
【００５７】
図１５は本発明に係る他の角速度センサの一部を示す概略図である。図に示すように、トラス２４の各側部すなわち図１５紙面上下方向側の端部分に２本の第１の弾性支持部２５が接続され、第１、第２の固定部４６ａ、４６ｂが半導体支持基板３４に固定され、固定部４６ａに駆動軸であるｘ軸方向が長さ方向でありかつ検出軸であるｙ軸方向に並んだ２本の第１の固定梁４４ａの一端が接続され、固定部４６ｂにｘ軸方向が長さ方向でありかつｙ軸方向に並んだ２本の第２の固定梁４４ｂの一端が接続され、２本の固定梁４４ａの他端が第１の固定梁接続部４５ａに接続され、２本の固定梁４４ｂの他端が第２の固定梁接続部４５ｂに接続され、一方の弾性支持部２５のトラス２４と接続された側とは反対側の端部が固定梁接続部４５ａに接続され、他方の弾性支持部２５のトラス２４と接続された側とは反対側の端部が固定梁接続部４５ｂに接続され、固定梁接続部４５ａ、４５ｂ、固定梁４４ａ、４４ｂにより弾性支持部２５の片持梁構造の支持部が構成されている。
【００５８】
図１６は図１５に示した角速度センサの駆動検出時の等価回路を示す図である。図に示すように、駆動電圧が印加されるノード４７が信号処理回路２３に設けられ、櫛歯電極２８、２９で分布静電容量４８が構成され、トラス２４、弾性支持部２５、２７に電気抵抗４９が分布し、電気抵抗４９は固定部４６ａにて外部信号処理回路（図示せず）に接続され、電気抵抗４９に質量３２の抵抗５０が接続され、抵抗５０に櫛歯電極３０、３１で構成された静電容量５１が接続され、静電容量５１に入出力用パッド４２に設けられかつ静電容量５１の変化を検出するためのたノード５２が接続され、また電気抵抗４９は固定部４６ｂにて外部信号処理回路（図示せず）に接続されている。
【００５９】
この角速度センサにおいては、ノード４７に駆動電圧を印加すると、櫛歯電極２８、２９で構成される分布静電容量４８にて静電引力が発生し、振動系が駆動される。この場合、駆動電圧に対する振動系の共通電位は固定部４６ａにて外部信号処理回路に接続される。そして、角速度Ωの入力により発生する質量３２の変位は櫛歯電極３０、３１で構成された静電容量５１の変化として検出される。この場合、静電容量５１の変化は固定部４６ｂにて外部信号処理回路に接続される振動系の共通電位に対しノード５２において検出される。
【００６０】
このような角速度センサにおいては、弾性支持部２５のトラス２４と接続された側とは反対側の端部が固定梁接続部４５ａ、４５ｂ、固定梁４４ａ、４４ｂを介して固定部４６ａ、４６ｂに接続されているから、弾性支持部２５の支持部のｙ軸方向の剛性が小さいので、弾性支持部２５の固定梁接続部４５ａ、４５ｂ側端部が比較的自由にｙ軸方向に移動でき、振動系を駆動したときに弾性支持部２５に長さ方向の応力が生ずるのを抑制することができる。このため、櫛歯電極２８、２９で構成される分布静電容量４８にて発生する静電引力と質量３２のｘ軸方向の振幅とを比例させることができ、駆動振動の非線形性を抑制することができるから、より大きい振幅での質量３２の駆動が可能で、角速度Ωをより高精度に測定することができる。また、固定部４６ａ、４６ｂと固定梁接続部４５ａ、４５ｂとが２本の固定梁４４ａ、４４ｂによって接続されているから、弾性支持部２５の支持部の法線方向すなわち半導体支持基板３４と直角方向に対するねじり剛性が向上する。このため、振動系の法線方向のモード周波数の低下を回避することができるから、駆動モード、検出モードの周波数と法線方向モードの周波数との周波数弁別比を大きくすることができるので、角速度Ωをより高精度に測定することができる。また、駆動電圧に対する振動系の共通電位は固定部４６ａにて外部信号処理回路に接続され、また検出信号に対する振動系の共通電位は固定部４６ｂにて外部信号処理回路に接続されているから、検出信号に対する駆動電圧の影響を抑制することができるので、角速度Ωをより高精度に測定することができる。
【００６１】
図１７は分布静電容量４８にて発生する静電引力すなわち駆動力と質量３２の駆動方向の変位との関係を示すグラフであり、線ａは線形モデルを示し、線ｂは図１５に示した角速度センサの場合を示し、線ｃは第１の弾性支持部２５を直接固定部に接続した場合を示す。このグラフから明らかなように、図１５に示した角速度センサにおいては駆動振動の非線形性を確実に抑制することができる。
【００６２】
図１８〜図２０に図１５に示した角速度センサの固定梁４４ａ、４４ｂのｙ軸方向の剛性が弾性支持部２７のｙ軸方向の剛性の１０倍となるように、固定梁４４ａ、４４ｂの長さおよび幅を設定した場合の振動モードの具体例を示す。なお、図面の簡略のため駆動手段、検出手段の図示を省略した。そして、図１８はｘ軸方向の駆動モード（周波数ｆ＝３６９３Ｈｚ）、図１９はｙ軸方向の検出モード（周波数ｆ＝３６９１Ｈｚ）、図２０は法線方向モード（周波数ｆ＝５６６１Ｈｚ）であり、駆動モード、検出モードすなわち基本モードに対する法線方向モードの周波数弁別比は１．５３であり、この周波数弁別比は十分に大きい。
【００６３】
図２１は本発明に係る他の角速度センサの一部を示す概略図である。図に示すように、トラス２４の各側部に２本の弾性支持部２５が接続され、固定部４６ａにｘ軸方向が長さ方向でありかつｙ軸方向に並んだ２本の第１の固定梁４４ａの一端が接続され、固定部４６ｂにｘ軸方向が長さ方向でありかつｙ軸方向に並んだ２本の第２の固定梁４４ｂの一端が接続され、２本の固定梁４４ａおよび２本の固定梁４４ｂの他端が共通固定梁接続部５３に接続され、２本の第１の弾性支持部２５のトラス２４と接続された側とは反対側の端部が共通固定梁接続部５３に接続され、共通固定梁接続部５３、固定梁４４ａ、４４ｂにより弾性支持部２５の両持梁構造の支持部が構成されている。
【００６４】
この角速度センサにおいても、弾性支持部２５のトラス２４と接続された側とは反対側の端部が共通固定梁接続部５３、固定梁４４ａ、４４ｂを介して固定部４６ａ、４６ｂに接続されているから、弾性支持部２５の支持部のｙ軸方向の剛性が小さいので、櫛歯電極２８、２９にて発生する静電引力と質量３２のｙ軸方向の振幅とを比例させることができ、駆動振動の非線形性を抑制することができるため、角速度Ωをより高精度に測定することができる。また、固定部４６ａ、４６ｂと共通固定梁接続部５３とが２本の固定梁４４ａおよび２本の固定梁４４ｂによって接続されているから、弾性支持部２５の支持部の法線方向に対するねじり剛性が向上するので、振動系の法線方向のモード周波数の低下を回避することができるため、駆動モード、検出モードの周波数と法線方向モードの周波数との周波数弁別比を大きくすることができ、角速度Ωをより高精度に測定することができる。また、駆動電圧に対する振動系の共通電位は固定部４６ａにて外部信号処理回路に接続され、また検出信号に対する振動系の共通電位は固定部４６ｂにて外部信号処理回路に接続されているから、検出信号に対する駆動電圧の影響を抑制することができるので、角速度Ωをより高精度に測定することができる。
【００６５】
そして、図２１に示した角速度センサにおいて、固定梁４４ａ、４４ｂのｙ軸方向の剛性が弾性支持部２７のｙ軸方向の剛性の１００倍となるように、固定梁４４ａ、４４ｂの長さおよび幅を設定した場合には、駆動振動の非線形性の抑制の程度は図１７の線ｂで表される非線形性の抑制の程度とほぼ同じであり、またｘ軸方向の駆動モードの周波数ｆ＝３７１８Ｈｚであり、ｙ軸方向の検出モードの周波数ｆ＝３７１９Ｈｚであり、法線方向モードの周波数ｆ＝６２２３Ｈｚであって、駆動モード、検出モードすなわち基本モードに対する法線方向モードの周波数弁別比は１．６７であり、この周波数弁別比は十分に大きい。
【００６６】
なお、上述実施の形態においては、質量３２の両側に駆動手段を配置したが、質量３２の片側にのみ駆動手段を配置してもよい。また、上述実施の形態においては、質量３２の中央部の両側に２列の検出手段を配置したが、質量３２の中央部に１列の検出手段を配置してもよい。また、上述実施の形態においては、固定部２２、４１に入出力用パッド２３、４２を配置したが、固定部２２、４１に信号処理回路を配置してもよい。また、上述実施の形態においては、固定部４６ａに２本の第１の固定梁４４ａの一端を接続し、固定部４６ｂに２本の第２の固定梁４４ｂの一端を接続したが、固定部に３本以上の第１、第２の固定梁の一端を接続してもよい。
【図面の簡単な説明】
【図１】本発明に係る角速度センサを示す概略平面図である。
【図２】図１の概略Ｃ−Ｃの断面図である。
【図３】図１の概略Ｄ−Ｄの断面図である。
【図４】図１のＥ部詳細図である。
【図５】図１〜図４に示した角速度センサの製造方法の説明図である。
【図６】本発明に係る他の角速度センサの質量部を示す概略図である。
【図７】本発明に係る他の角速度センサの振動モードの具体例を示す図である。
【図８】本発明に係る他の角速度センサの振動モードの具体例を示す図である。
【図９】本発明に係る他の角速度センサの振動モードの具体例を示す図である。
【図１０】本発明に係る他の角速度センサの振動モードの具体例を示す図である。
【図１１】本発明に係る他の角速度センサを示す概略図である。
【図１２】本発明に係る他の角速度センサの一部を示す概略図である。
【図１３】図１２に示した角速度センサの構造体の１次元近似モデルを示す図である。
【図１４】１次モード周波数ω₁と比βとの関係を示すグラフである。
【図１５】本発明に係る他の角速度センサの一部を示す概略図である。
【図１６】図１５に示した角速度センサの駆動検出時の等価回路を示す図である。
【図１７】駆動力と質量の駆動方向の変位との関係を示すグラフである。
【図１８】図１５に示した角速度センサの振動モードの具体例を示す図である。
【図１９】図１５に示した角速度センサの振動モードの具体例を示す図である。
【図２０】図１５に示した角速度センサの振動モードの具体例を示す図である。
【図２１】本発明に係る他の角速度センサの一部を示す概略図である。
【図２２】従来の角速度センサを示す概略図である。
【図２３】図２２のＡ−Ａ断面図である。
【図２４】図２２、図２３に示した角速度センサの動作を説明するためのグラフである。
【図２５】従来の他の角速度センサを示す概略図である。
【図２６】図２５のＢ−Ｂ断面図である。
【符号の説明】
２２…固定部
２４…トラス
２５…第１の弾性支持部
２７…第２の弾性支持部
２８…第３の櫛歯電極
２９…第４の櫛歯電極
３０…第２の櫛歯電極
３１…第１の櫛歯電極
３２…質量
３４…半導体支持基板
３７…半導体基板
３９…凹部
４１…固定部
４４ａ…第１の固定梁
４４ｂ…第２の固定梁
４５ａ…第１の固定梁接続部
４５ｂ…第２の固定梁接続部
４６ａ…第１の固定部
４６ｂ…第２の固定部
５３…共通固定梁接続部[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an angular velocity sensor that detects an angular velocity.
[0002]
[Prior art]
In recent years, many electronic systems have been mounted on the vehicle to improve safety and comfort. For example, a demand for a chassis control system for preventing vehicle spin and a navigation system for knowing the current position of the vehicle is rapidly increasing. In these systems, an angular velocity sensor that measures the angular velocity plays an important role. Along with that, miniaturization and cost reduction as well as higher accuracy of the angular velocity sensor applied to each system are required. A technique for realizing an angular velocity sensor using a semiconductor for such a demand is known.
[0003]
FIG. 22 shows an angular velocity sensor using a conventional semiconductor (for example, J. Bernstein et al. “Micromachined Comb-Drive Tuning Fork Rate Gyroscope”, Digest IEEE / ASME Micro Electro Mechanical Systems (MEMS) Workshop, Florida, 1993, 143- FIG. 23 is a cross-sectional view taken along line AA of FIG. 22. As shown in the figure, an insulating film 5 is provided on a substrate 6, vibration masses 3a and 3b are provided on the substrate 6 via a fixing part 1 and a support part 2, and a comb extending from the side surface of the vibration masses 3a and 3b. The drive electrode 4 is composed of the tooth electrode and the comb electrode fixed to the substrate 6, and the fixed portion 1, the support portion 2, and the vibration masses 3a and 3b are made by selectively etching the polycrystalline silicon thin film. . Further, detection electrodes 7a and 7b are provided immediately below the vibration masses 3a and 3b, and the detection unit includes the detection electrodes 7a and 7b.
[0004]
In this angular velocity sensor, as shown in FIG. 24, the driving voltage V is in phase opposite to the terminals b and d with respect to the common potential terminal a._bAnd V_dIs applied, the two oscillating masses 3a and 3b are respectively driven in directions opposite to the x direction. In this state, when the angular velocity sensor rotates around the z-axis and the angular velocity Ω is input in the z-axis direction, Coriolis force is generated in the y-axis direction with respect to the respective vibration masses 3a and 3b. The mass of the vibrating masses 3a and 3b is m, and the speed of the vibrating masses 3a and 3b driven by electrostatic attraction is V._mIf (t), the Coriolis force Fc (t) is expressed by the following equation. Since the vibrating masses 3a and 3b are driven in opposite directions, the signs of the Coriolis forces Fc (t) acting on the vibrating masses 3a and 3b are reversed.
[0005]
[Expression 1]
Fc (t) = 2 · m · V_m(t) ・ Ω
The capacitance between the vibrating mass 3a and the detection electrode 4a and the capacitance between the vibrating mass 3b and the detection electrode 4b change according to the displacement of the vibrating masses 3a and 3b in the y direction due to the Coriolis force Fc (t). Therefore, the angular velocity Ω can be measured by the differential capacitance. As is clear from the equation (1), the speed V is required to increase the Coriolis force Fc (t)._mJust increase (t) and speed V_mIn order to increase (t), the vibrating masses 3a and 3b may be driven at a resonance frequency in a vacuum.
[0006]
This angular velocity sensor can be manufactured in a very small size, and the manufacturing cost can be reduced.
[0007]
However, in such an angular velocity sensor, the vibration masses 3a and 3b are driven in the x-axis direction parallel to the surface of the substrate 6 to detect the Coriolis force in the z-axis direction perpendicular to the surface of the substrate 6. Therefore, there are the following problems. That is, the spring constant of the support part 2 depends on the cross-sectional shape of the support part 2, that is, the moment of inertia of the cross section. Then, assuming that the cross section of the support portion 2 is a rectangle, the thickness of the support portion 2 is t, and the width is w, the cross sectional secondary moment I in a direction parallel to the main surface of the substrate 6 is obtained._p, Perpendicular moment I_nIs expressed by the following equation.
[0008]
[Expression 2]
I_p= W · t^Three/ 12
[0009]
[Equation 3]
I_n= W^Three・ T / 12
In the semiconductor manufacturing technology, the processing accuracy of the width w can be secured to some extent, but it is difficult to control the thickness t with high accuracy, and the secondary moment I_pAnd moment of inertia I_nTherefore, it is difficult to control the vibration mode frequency in the detection axis (z axis) direction and the drive axis (x axis) direction to a predetermined value. In addition, since the dependency on the structural parameter is different, it is impossible to set the relative value of the resonance frequency of each vibration mode. Furthermore, when the vibration system is made of a semiconductor, mechanical adjustment is difficult.
[0010]
FIG. 25 is a schematic view showing another conventional angular velocity sensor (Japanese Patent Laid-Open No. 5-312576), and FIG. 26 is a cross-sectional view taken along the line BB of FIG. As shown in the figure, a patterned oxide film 20 is formed on a silicon substrate 21, a silicon substrate 19 is bonded to the silicon substrate 21 via the oxide film 20, a groove 13 is provided in the silicon substrate 19, and a groove 13 Thus, the structure, that is, the vibration mass 15, the first support portion 14, the second support portion 10, and the frame portion 11 are formed. The vibration mass 15 is supported by the first support portion 14, the connection portion of the first support portion 14 opposite to the connection portion with the vibration mass 15 is connected to the frame portion 11, and the frame portion 11 is the second support portion. The comb portion electrode 8 is configured to be supported by the portion 10 and driven by electrostatic attraction on the frame portion 11, and the frame portion of the first support portion 14 is used to detect displacement due to the Coriolis force of the vibration mass 15. A resistance bridge is constituted by two piezoresistors 9 arranged in parallel in the vicinity of a connection portion with the eleventh electrode, or a detection electrode 12 is constituted by electrodes provided on the vibration mass 15 and the frame portion 11. The details of the electrical wiring are omitted for simplification of the drawing.
[0011]
In this angular velocity sensor, when a voltage is applied to the comb electrode 8, the frame portion 11 supported by the second support portion 10 is driven by electrostatic attraction in the x-axis direction. When rotating at an angular velocity Ω in the z-axis direction perpendicular to the plane of the silicon substrate 21 in this state, the Coriolis force expressed by the equation (1) is generated in the y-axis direction, and the y-axis of the vibration mass 15 due to the generated Coriolis force is generated. The displacement in the direction can be detected as a resistance difference of the piezoresistor 9 or a change in capacitance of the detection electrode 12.
[0012]
In such an angular velocity sensor, the drive axis (x axis) and the detection axis (y axis) are both in the direction parallel to the main surface of the silicon substrate 21, that is, the main surface of the substrate. The dependency of the vibration mode frequency in the drive axis direction and the detection axis direction on the cross-sectional shape of the portion 10, in particular, the thickness of the structure is the same. That is, when the thickness deviates from the design value due to manufacturing variations, the absolute values of the mode frequencies in the drive axis direction and the detection axis direction change, but the relative values remain unchanged. As a result, it is possible to obtain an effect that the detection sensitivity is hardly affected by manufacturing variations.
[0013]
[Problems to be solved by the invention]
However, in the angular velocity sensor shown in FIG. 25 and FIG. 26, the Coriolis force generated by the input of the angular velocity Ω is generally a minute force as compared with gravitational acceleration or the like. Therefore, detection by the piezoresistor 9 is practically impossible. Further, the detection of capacitance by the detection electrode 12 is more sensitive than the detection by the piezoresistor 9, but the detection of capacitance by the detection electrode 12 has a certain base capacitance (when there is no input of angular velocity). The detection electrode 12 is formed only on the side surfaces of the vibration mass 15 and the frame portion 11, and the thickness of the silicon substrate 19 is as follows. Usually, the maximum capacity is about several tens of μm, so that a sufficient base capacity cannot be secured. As a result, it is impossible to detect the angular velocity Ω with high accuracy.
[0014]
The present invention has been made to solve the above-described problems, and an object of the present invention is to provide an angular velocity sensor capable of detecting an angular velocity with high accuracy.
[0015]
[Means for Solving the Problems]
  In order to achieve this object, in the present invention, a support substrate, a fixed portion fixed to the support substrate, a mass provided on the fixed portion via an elastic support portion, and a driving means for vibrating the mass And an angular velocity sensor having a detecting means for detecting a displacement of the mass in a direction perpendicular to a driving direction of the mass by the driving means and parallel to the surface of the mass.Side surface parallel to the drive directionA plurality of first comb electrodes provided in the fixed portion as the length direction as the detection means and the mass portion in the recess as the length direction. In addition, one having a plurality of second comb electrodes is used.
[0016]
In this case, the elastic support portion is provided with a connection portion on the fixed portion fixed to the support substrate via a first elastic support portion whose length direction is a direction perpendicular to the drive direction, and the connection portion is provided with the connection portion. The mass is provided via a second elastic support portion whose length direction is the driving direction.
[0017]
In this case, one end of a plurality of fixed beams arranged in a direction perpendicular to the drive direction and the driving direction is connected to the fixed portion, and the other end of the fixed beam is connected to the fixed beam connecting portion, An end of the first elastic support portion opposite to the side connected to the connection portion is connected to the fixed beam connection portion.
[0018]
Further, as the driving means, a plurality of third comb electrodes provided in the fixed portion with the driving direction as the length direction and a plurality of fourth comb electrodes provided in the connection portion with the driving direction as the length direction. An electrode having a comb electrode is used.
[0019]
Further, the thickness of the first and second elastic support portions is made larger than the width.
[0020]
Further, a plate-like member provided in parallel with the main surface of the support substrate and having a uniform thickness is processed in a direction perpendicular to the main surface of the support substrate, so that the fixed portion, the first elastic support portion, The connecting portion, the second elastic support portion, and the mass are formed.
[0021]
Further, the second elastic support portion is connected to a portion of the mass farthest from the center of gravity.
[0023]
In this case, two first elastic support portions are connected to each side portion of the connection portion, and a plurality of first elastic support portions arranged in a direction perpendicular to the drive direction and having a drive direction in the length direction are connected to the fixed portion. 1. Connect one end of the second fixed beam, connect the other end of the first fixed beam to the first fixed beam connecting portion, and connect the other end of the second fixed beam to the second fixed beam. One end of the first elastic support part opposite to the side connected to the connection part is connected to the first fixed beam connection part, and the other first elastic support part is connected to the first elastic support part. The end of the support portion opposite to the side connected to the connection portion is connected to the second fixed beam connection portion.
[0024]
Further, two first elastic support portions are connected to each side portion of the connection portion, and a plurality of first elastic members are arranged such that the driving direction is a length direction and is perpendicular to the driving direction. , Connecting one end of the second fixed beam, connecting the other end of the first and second fixed beams to the common fixed beam connecting portion, and connecting to the connecting portions of the two first elastic support portions The end opposite to the formed side is connected to the common fixed beam connecting portion.
[0025]
In these cases, one end of the first fixed beam is connected to the first fixed portion, and one end of the second fixed beam is connected to the second fixed portion.
[0026]
The width of the second elastic support portion is made larger than the width of the first elastic support portion.
[0027]
Further, a semiconductor substrate is used as the plate member, and the plate member is processed using a semiconductor processing technique.
[0029]
【The invention's effect】
  In the angular velocity sensor according to the present invention, the massSide surface parallel to drive directionSince the concave portion is provided in the concave portion and the second comb-shaped electrode is provided in the concave portion, the moment of inertia around the axis perpendicular to the surface of the mass can be suppressed, and the first and second comb-shaped electrodes have the mass. Since the lengths of the first and second comb electrodes can be secured within an allowable range of rigidity without hindering the driving of the angular velocity, the angular velocity can be detected with high accuracy.
[0030]
In addition, a connection portion is provided on the fixed portion fixed to the support substrate via a first elastic support portion having a length direction perpendicular to the drive direction as a length direction, and the connection portion has a drive direction as a length direction. When the mass is provided via the elastic support portion, the driving and detection are performed in a direction parallel to the main surface of the substrate. Therefore, the vibration mode frequency in the driving direction and the detection direction and the relative values thereof are determined by the structure in the main surface of the substrate. Depending on the planar structure, it is not easily affected by manufacturing variations, and stable angular velocity detection sensitivity can be obtained.
[0031]
In addition, one end of a plurality of fixed beams whose driving direction is a length direction and aligned in a direction perpendicular to the driving direction is connected to the fixed portion, and the other end of the fixed beam is connected to the fixed beam connecting portion, When the end of the elastic support part opposite to the side connected to the connection part is connected to the fixed beam connection part, stress in the length direction is generated in the first elastic support part when the vibration system is driven. Since the non-linearity of the drive vibration can be suppressed and the torsional rigidity of the support portion of the first elastic support portion with respect to the normal direction is improved, the normal direction mode of the vibration system is improved. Since a decrease in frequency can be avoided, the angular velocity can be detected with higher accuracy.
[0032]
In addition, when the thickness of the first and second elastic support portions is made larger than the width, the vibration mode frequency in the direction perpendicular to the surface of the mass that affects high-accuracy detection is driven, and in a higher frequency region than the detection mode frequency. Since it can be set, the influence of the mode can be suppressed and the angular velocity can be detected with higher accuracy.
[0033]
In addition, when the second elastic support portion is connected to the portion of the mass farthest from its center of gravity, the rigidity with respect to rotation about the axis in the direction perpendicular to the surface of the mass is large. Since it can be set in a sufficiently high frequency region compared with the frequency, the influence of the mode can be suppressed and the angular velocity can be detected with higher accuracy.
[0035]
In addition, two first elastic support portions are connected to each side portion of the connection portion, and a plurality of first and second lines are arranged in a direction perpendicular to the drive direction with the drive direction being the length direction of the fixed portion. One end of the fixed beam is connected, the other end of the first fixed beam is connected to the first fixed beam connecting portion, the other end of the second fixed beam is connected to the second fixed beam connecting portion, The side opposite to the side connected to the connection portion of the first elastic support portion is connected to the first fixed beam connection portion, and the side connected to the connection portion of the other first elastic support portion When the opposite end to the second fixed beam connecting portion is connected, it is possible to suppress the occurrence of stress in the length direction in the first elastic support portion when the vibration system is driven. The nonlinearity of the drive vibration can be suppressed, and the torsional rigidity of the first elastic support portion with respect to the normal direction of the support portion is improved. It is possible to avoid a decrease in over de frequency, it is possible to detect the angular velocity with higher accuracy.
[0036]
In addition, two first elastic support portions are connected to each side portion of the connection portion, and a plurality of first and second lines are arranged in a direction perpendicular to the drive direction with the drive direction being the length direction of the fixed portion. One end of the fixed beam is connected, the other end of the first and second fixed beams is connected to the common fixed beam connecting portion, and opposite to the side connected to the connecting portion of the two first elastic support portions When the end portion on the side is connected to the common fixed beam connecting portion, it is possible to suppress the occurrence of stress in the length direction in the first elastic support portion when the vibration system is driven. Since the torsional rigidity in the normal direction of the support portion of the first elastic support portion is improved, a decrease in mode frequency in the normal direction of the vibration system can be avoided. It can be detected with higher accuracy.
[0037]
Further, when one end of the first fixed beam is connected to the first fixed portion and one end of the second fixed beam is connected to the second fixed portion, the vibration system generates a common potential of the vibration system with respect to the drive voltage and a vibration with respect to the detection signal. Since the common potential of the system is connected to the external signal processing circuit by another fixed portion, the influence of the drive voltage on the detection signal can be suppressed, so that the angular velocity can be detected with higher accuracy.
[0038]
Further, when the width of the second elastic support portion is made larger than the width of the first elastic support portion, the vibration mode frequency in the direction perpendicular to the surface of the mass that affects high-accuracy detection is driven. Since it can be set in the high frequency region, the angular velocity can be detected with higher accuracy.
[0039]
In addition, when a semiconductor substrate is used as the plate-like member and the plate-like member is processed using semiconductor processing technology, a fixed portion, a first elastic support portion, a connection portion, a second elastic support portion, and a mass are easily formed. Manufacturing cost is low.
[0041]
DETAILED DESCRIPTION OF THE INVENTION
  1 is a schematic plan view showing an angular velocity sensor according to the present invention, FIG. 2 is a schematic CC sectional view of FIG. 1, FIG. 3 is a schematic DD sectional view of FIG. 1, and FIG. FIG. As shown in the figure, a main surface of the semiconductor support substrate 34, that is, a groove perpendicular to the main surface of the substrate is formed in a semiconductor substrate 37 that is a plate-like member, and fixed portions 22 and 41, truss 24 that is a connection portion, A structure including a mass 32 and first and second elastic support portions 25 and 27 is provided. A large number of small holes 35 are provided in the truss 24 and the mass 32, and an insulating film 33 is provided on the semiconductor support substrate 34. The fixing parts 22 and 41 are joined. Also, the mass of 32Side surface parallel to drive directionA quadrangular recess 39 is formed on the inner wall of the recess 39, and a plurality of second comb electrodes 30 whose x-axis direction is the longitudinal direction are disposed on the inner wall in the x-axis direction. The fixing portion 41 is fixed to the semiconductor support substrate 34, and the first comb-teeth electrode 31 having the same shape as the comb-teeth electrode 30 is disposed on the fixing portion 41, and the side surfaces of the comb-teeth electrode 30 and the comb-teeth electrode 31 are arranged. The detection means for detecting the displacement of the mass 32 in the y-axis direction as a change in capacitance has a comb electrode 30 and a comb electrode 31. Although the input / output pad 42 is shown in FIG. 1, the signal processing circuit connected to the input / output pad 42 is omitted for the sake of simplicity.
[0042]
Further, the second elastic support portion 27 is connected to the portion farthest from the center of gravity of the mass 32, that is, near the farthest point, and the elastic support portion 27 has a longitudinal direction in the x-axis direction. The relationship between the thickness t and the width w is t> w, and the rigidity in the direction perpendicular to the rigidity in the direction parallel to the substrate main surface of the elastic support portion 27 is higher. Further, the length of the elastic support portion 27 is set so that the resonance frequency in the y-axis direction of the vibration system constituted by the total mass of the mass 32 and the comb electrode 30 becomes a predetermined value. Further, the truss 24 is connected to the opposite side of the mass 32 of the elastic support portion 27, the mass 32 is connected to the two trusses 24, and the mass 32 is supported with respect to the truss 24 by a double-supported beam structure. .
[0043]
Further, a fourth comb electrode 29 with the x axis extending in the longitudinal direction is disposed on the side surface of the truss 24 in the x axis direction, and a third comb electrode having the same shape as the comb electrode 29 is disposed on the fixing portion 22. 28, the side surface of the comb electrode 28 and the side surface of the comb electrode 29 are opposed to each other, and the driving means for driving the truss 24 and the mass 32 using electrostatic attraction in the x-axis direction is a comb electrode. 28. A comb-tooth electrode 29 is provided. Although the input / output pad 23 is shown in FIG. 1, the signal processing circuit connected to the input / output pad 23 is omitted for the sake of simplicity.
[0044]
In addition, a first elastic support portion 25 is connected to the side surface of the truss 24 in the y-axis direction. The elastic support portion 25 has a longitudinal direction in the y-axis direction. And t> w, and the rigidity in the vertical direction is higher than the rigidity in the direction parallel to the substrate main surface of the elastic support portion 25. The length of the elastic support portion 25 is a predetermined value of the resonance frequency in the x-axis direction of the vibration system configured by the total mass of the mass 32, the truss 24, the elastic support portion 27, and the comb-tooth electrodes 29, 30, and 31. Is set to Further, the opposite side of the elastic support portion 25 to the truss 24 is connected to the fixed portion 22, and a slit groove 26 is provided in the vicinity of the connection point of the elastic support portion 25 of the fixed portion 22 to which the elastic support portion 25 is connected, Each truss 24 is connected to four elastic support portions 25, and is supported with respect to the fixed portion 22 by a double-supported beam structure.
[0045]
Next, a method of manufacturing the angular velocity sensor shown in FIGS. 1 to 4 will be described with reference to FIG. First, as shown in FIG. 5A, a semiconductor substrate 37 that becomes a structure is bonded to a semiconductor support substrate 34 via an insulating film 33, and then polished to a predetermined thickness. Next, as shown in FIG. 5B, a mask pattern 40 corresponding to the structure is formed on the surface of the semiconductor substrate 37. Next, as shown in FIG. 5C, a groove 38 is formed in the semiconductor substrate 37 using a semiconductor processing technique to form a structure. In this case, the depth of the trench 38 reaches the insulating film 33. Next, as shown in FIG. 5D, the insulating film 33 immediately below the semiconductor substrate 37 which is a movable part including the truss 24, the mass 32, and the elastic support parts 25 and 27 is removed. In this case, since the truss 24 and the mass 32 are provided with a large number of small holes 35, the insulating film 33 can be easily removed. Note that in the above description, the manufacturing process of the signal processing circuit is omitted for the sake of brevity.
[0046]
In the angular velocity sensor shown in FIGS. 1 to 4, the truss 24 and the mass 32 are driven in the x-axis direction by applying a voltage to the comb electrodes 28 and 29. In this case, the frequency of the applied voltage is the resonance frequency in the x-axis direction of the vibration system composed of the mass 32, the truss 24, the elastic support portion 25, and the comb electrodes 29 to 31, and is driven with a larger amplitude. When an angular velocity Ω in the z-axis direction perpendicular to the main surface of the substrate is applied in this driving state, the Coriolis force expressed by the equation (1) is generated in the y-axis direction. In this case, if the resonance frequency set by the elastic support unit 27 is the same as the drive frequency, the mass 32 starts resonance vibration in the y-axis direction, and has the comb-shaped electrodes 30 and 31 as a larger displacement in the y-axis direction. It is detected as a change in capacitance of the means. Since the amplitude in the y-axis direction is proportional to the input angular velocity Ω, the angular velocity Ω can be detected from the amplitude in the y-axis direction.
[0047]
In the angular velocity sensor shown in FIGS. 1 to 4, as in the conventional angular velocity sensor shown in FIGS. 25 and 26, driving and detection are performed in the x-axis direction and the y-axis direction parallel to the substrate main surface. The vibration mode frequency in the x-axis direction that is the drive axis and the y-axis direction that is the detection axis and its relative value depend on the planar structure of the structure in the main surface of the substrate, and are less affected by manufacturing variations and stable. Detection sensitivity of angular velocity Ω can be obtained. Further, since the comb-shaped electrode 30 is arranged so that the longitudinal direction thereof is in the x-axis direction, the comb-shaped electrode 30 does not hinder the driving of the mass 32 and the comb-shaped electrode is within an allowable range of rigidity. A length of 30 can be secured. For example, if a comb electrode 30 having a width of 6 μm and a length of 320 μm is formed on a semiconductor substrate 37 having a thickness of 20 μm, and the comb electrode 30 is opposed to the comb electrode 31 with a gap of 2 μm within a range of 300 μm, up to about 10V A voltage can be applied, and by arranging 38 pairs of comb electrodes 30 and 31, a detection capacity of about 1 pF can be secured. Therefore, the angular velocity Ω can be detected with high accuracy. Further, since the concave portion 39 is formed on a part of the side surface of the mass 32 and a plurality of comb electrodes 30 are arranged inside the concave portion 39, the moment of inertia around the z axis of the movable body by the comb teeth electrode 30 is suppressed. Therefore, the angular velocity Ω can be detected with higher accuracy. Further, the relationship between the thickness t and the width w of the elastic support portions 25 and 27 is t> w, and the rigidity in the direction perpendicular to the rigidity in the direction parallel to the substrate main surface of the elastic support portions 25 and 27 is higher. Since the direction is higher, the rotational rigidity of the truss 24 around the y-axis is improved, and the vibration mode frequency in the z-axis direction perpendicular to the main surface of the substrate that affects high-accuracy detection is driven. Since the angular velocity Ω can be measured without causing vibration in a direction perpendicular to the main surface of the substrate, the angular velocity Ω can be detected with higher accuracy. In addition, since the elastic support portion 27 is connected in the vicinity of the farthest point from the center of gravity of the mass 32, the rigidity with respect to rotation around the z axis is large, and the rotational mode frequency that adversely affects driving and detection is driven and detected. Since it can be set in a sufficiently high frequency region as compared with the frequency, the angular velocity Ω can be measured without causing rotational vibration around the z axis, so that the angular velocity Ω can be detected with higher accuracy. Further, since the truss 24 is connected to the fixed portion 22 by the four elastic support portions 25, the vibration mode frequency in the direction perpendicular to the main surface of the substrate that affects high-accuracy detection is driven. Since the angular velocity Ω can be measured without causing vibration in a direction perpendicular to the main surface of the substrate, the angular velocity Ω can be detected with higher accuracy. In addition, since the structure is formed by forming the groove 38 in the semiconductor substrate 37 using a semiconductor processing technique, the structure can be easily formed, so that the manufacturing cost is low. Further, since the slit groove 26 is provided in the vicinity of the connection point of the elastic support portion 25 of the fixing portion 22, the transmission of stress from the fixing portion 22 can be relaxed. Since it can suppress, the stable vibration mode frequency is realizable. As a result, the angular velocity sensor sensitivity can be stabilized. Further, since the fixing portions 22 and 41 are disposed on the outer peripheral portion of the movable body, electrical connection to the fixing portions 22 and 41 is possible within the main surface of the substrate, and the wiring structure can be simplified. Further, since the driving means is arranged on both sides of the mass 32, the symmetry of the structure can be ensured and the driving amplitude can be detected. In addition, since two rows of detection means are arranged on both sides of the central portion of the mass 32, the symmetry of the structure can be ensured, and the displacement can be detected by the differential of the two capacitances. Can do. In addition, since the size of the truss 24 in the y-axis direction can be set long as long as the rigidity in the direction perpendicular to the main surface of the substrate can be secured, a large number of comb-tooth electrodes 28 and 29 can be provided. A driving force can be obtained. As described above, since a stable vibration mode of the structure can be realized while securing the detection capacity, it is possible to simultaneously achieve high accuracy and stabilization of the sensitivity of the angular velocity sensor.
[0048]
FIG. 6 is a schematic view showing a mass part of another angular velocity sensor according to the present invention. As shown in the figure, the mass 32 is provided with a through hole 36 within a range in which rigidity in a direction perpendicular to the main surface of the substrate can be secured. Note that the driving means and the detecting means are not shown for simplification of the drawing.
[0049]
In this angular velocity sensor, since the through hole 36 is provided in the mass 32, the weight can be reduced. As a result, the rigidity of the support portion can be suppressed with respect to the design resonance frequency, and high sensitivity can be achieved by increasing the drive amplitude and increasing the displacement with respect to the generated Coriolis force.
[0050]
7 to 9 show specific examples of vibration modes of other angular velocity sensors according to the present invention. As shown in the figure, the mass 32 has a recess 39 and a through hole 36. Note that the driving means and the detecting means are not shown for simplification of the drawing. FIG. 7 shows a drive mode in the x-axis direction, and FIG. 8 shows a detection mode in the y-axis direction. The frequency is about 3.5 kHz. FIG. 9 shows the rotation mode around the z axis, and the frequency is about 30 kHz, which is set to a sufficiently high frequency.
[0051]
FIG. 10 is a diagram showing an example of a vibration mode in a direction perpendicular to the substrate main surface of the same structure as the structure of the angular velocity sensor shown in FIGS. This vibration mode frequency is approximately 7.5 kHz, which is at least twice the drive and detection mode frequency (3.5 kHz). The frequency ratio is further increased by increasing the thickness of the structure.
[0052]
FIG. 11 is a schematic view showing another angular velocity sensor according to the present invention. As shown in the figure, a plurality of comb-shaped electrodes 30 whose longitudinal direction is the x-axis direction are arranged on the inner wall in the x-axis direction of the recess 39 and the outer peripheral side wall in the x-axis direction of the mass 32 facing the inner wall. Yes. Further, the elastic support portion 27 is connected to a portion of the mass 32 adjacent to the comb electrode 30 on the outer peripheral side wall in the x-axis direction, and the interval between the elastic support portions 27 is that the comb electrode 30 is disposed on the outer peripheral portion. The rotational rigidity around the z-axis can be secured with respect to the moment of inertia of the mass 32 increased by the above.
[0053]
In this angular velocity sensor, since the comb electrode 30 is also disposed on the outer peripheral side wall of the mass 32, a larger detection capacity can be obtained, so that the angular velocity Ω can be detected with higher accuracy. In addition, since the comb electrode 30 is also disposed on the outer periphery of the mass 32, the size of the mass 32 in the y-axis direction is made longer than the angular velocity sensor shown in FIGS. be able to.
[0054]
FIG. 12 is a schematic view showing a part of another angular velocity sensor according to the present invention. As shown in the figure, the width w of the elastic support 27 that connects the mass 32 and the truss 24.₁The width w of the elastic support portion 25 connecting the truss 24 and the fixing portion 22₂The relationship with₁> W₂It is set to become.
[0055]
A one-dimensional approximation model of the structure of this angular velocity sensor is shown in FIG. In the figure, k₁Represents a spring constant in the z-axis direction perpendicular to the main surface of the substrate of a total of four elastic support portions 27 that support the mass 32 by the truss 24 with a double-supported beam structure. As described above, the width of the elastic support 27 is w.₁It is. M₁Is the total mass of the mass 32 and the comb electrode 30. And k₂Represents a spring constant in the z-axis direction perpendicular to the main surface of the substrate of a total of eight elastic support portions 25 that support the truss 24 by the fixed portion 22 with a double-supported beam structure. As described above, the width of the elastic support portion 25 is w.₂It is. M₂Is the total mass of the truss 24 and the comb electrode 29. And the ratio γ = w₁/ W₂, Ratio β = m₁/ M₂Then, the primary vibration mode frequency ω in the z-axis direction of the one-dimensional two-degree-of-freedom vibration system shown in FIG.₁The square of is expressed by the following equation.
[0056]
[Expression 4]
ω₁ ²= 1/2 [2 + γ²(Β + 1) −√ {4 + γ^Four(Β + 1)²}]
FIG. 14 shows the primary mode frequency ω.₁Is a graph showing the relationship between the ratio γ and the ratio γ as a parameter. Lines a to c show cases where the ratio γ is 0.5, 1, and 2, respectively. As is apparent from FIG. 14, the primary vibration mode frequency ω is greater when γ> 1.₁Becomes larger. Therefore, by setting γ> 1, that is, the width w of the elastic support portion 27.₁The width w of the elastic support 25₂Since the vibration mode frequency in the direction perpendicular to the main surface of the substrate that affects high-precision detection can be driven and set to a higher frequency region than the detection mode frequency, the vibration in the direction perpendicular to the main surface of the substrate can be set. Since the angular velocity Ω can be measured without causing the angular velocity Ω, the angular velocity Ω can be detected with high accuracy. This effect is further increased by further increasing the thickness of the structure.
[0057]
FIG. 15 is a schematic view showing a part of another angular velocity sensor according to the present invention. As shown in the figure, two first elastic support portions 25 are connected to each side portion of the truss 24, that is, an end portion in the vertical direction of FIG. 15, and the first and second fixing portions 46a and 46b are semiconductors. One end of two first fixed beams 44a that are fixed to the support substrate 34 and are arranged in the length direction in the x-axis direction that is the drive shaft and in the y-axis direction that is the detection axis are connected to the fixed portion 46a. One end of two second fixed beams 44b whose length in the x-axis direction is parallel to the y-axis direction is connected to the fixed portion 46b, and the other end of the two fixed beams 44a is the first fixed beam. Connected to the connecting portion 45a, the other ends of the two fixed beams 44b are connected to the second fixed beam connecting portion 45b, and the end of one elastic support portion 25 opposite to the side connected to the truss 24 Is connected to the fixed beam connecting portion 45a, and the other elastic support portion 25 is connected to the truss 24. End of the pair side is connected to the fixed beam connecting portion 45b, fixed beam connecting portions 45a, 45b, fixed beam 44a, the supporting portion of the cantilevered structure of the elastic support portion 25 is constituted by 44b.
[0058]
FIG. 16 is a diagram showing an equivalent circuit when driving of the angular velocity sensor shown in FIG. 15 is detected. As shown in the figure, a node 47 to which a drive voltage is applied is provided in the signal processing circuit 23, and a distributed capacitance 48 is formed by the comb electrodes 28 and 29, and the truss 24 and the elastic support portions 25 and 27 are electrically connected. Resistors 49 are distributed, and the electrical resistors 49 are connected to an external signal processing circuit (not shown) at the fixed portion 46a. A resistor 50 having a mass 32 is connected to the electrical resistor 49, and the comb electrodes 30 and 31 are connected to the resistor 50. Is connected to the capacitance 51. A node 52 provided on the input / output pad 42 for detecting a change in the capacitance 51 is connected to the capacitance 51, and the electric resistance 49 is fixed. The unit 46b is connected to an external signal processing circuit (not shown).
[0059]
In this angular velocity sensor, when a driving voltage is applied to the node 47, an electrostatic attractive force is generated by the distributed capacitance 48 formed by the comb electrodes 28 and 29, and the vibration system is driven. In this case, the common potential of the vibration system with respect to the drive voltage is connected to the external signal processing circuit at the fixed portion 46a. The displacement of the mass 32 generated by the input of the angular velocity Ω is detected as a change in the capacitance 51 formed by the comb electrodes 30 and 31. In this case, the change in the capacitance 51 is detected at the node 52 with respect to the common potential of the vibration system connected to the external signal processing circuit at the fixed portion 46b.
[0060]
In such an angular velocity sensor, the end of the elastic support portion 25 opposite to the side connected to the truss 24 is connected to the fixed portions 46a and 46b via the fixed beam connecting portions 45a and 45b and the fixed beams 44a and 44b. Since it is connected, since the rigidity of the support part of the elastic support part 25 in the y-axis direction is small, the fixed beam connection part 45a, 45b side end part of the elastic support part 25 can move in the y-axis direction relatively freely, It is possible to suppress the occurrence of stress in the length direction in the elastic support portion 25 when the vibration system is driven. For this reason, the electrostatic attraction generated in the distributed capacitance 48 formed by the comb electrodes 28 and 29 can be proportional to the amplitude of the mass 32 in the x-axis direction, and the nonlinearity of the drive vibration is suppressed. Therefore, the mass 32 can be driven with a larger amplitude, and the angular velocity Ω can be measured with higher accuracy. Further, since the fixed portions 46a and 46b and the fixed beam connecting portions 45a and 45b are connected by the two fixed beams 44a and 44b, the normal direction of the support portion of the elastic support portion 25, that is, the right angle with the semiconductor support substrate 34. The torsional rigidity with respect to the direction is improved. For this reason, since it is possible to avoid a decrease in mode frequency in the normal direction of the vibration system, the frequency discrimination ratio between the frequency in the drive mode and the detection mode and the frequency in the normal direction mode can be increased, so the angular velocity Ω can be measured with higher accuracy. The common potential of the vibration system for the drive voltage is connected to the external signal processing circuit at the fixed portion 46a, and the common potential of the vibration system for the detection signal is connected to the external signal processing circuit at the fixed portion 46b. Since the influence of the drive voltage on the detection signal can be suppressed, the angular velocity Ω can be measured with higher accuracy.
[0061]
FIG. 17 is a graph showing the relationship between the electrostatic attractive force generated by the distributed capacitance 48, that is, the driving force, and the displacement of the mass 32 in the driving direction. The line a shows a linear model, and the line b shows in FIG. In the case of the angular velocity sensor, line c indicates the case where the first elastic support portion 25 is directly connected to the fixed portion. As is clear from this graph, in the angular velocity sensor shown in FIG. 15, the nonlinearity of the drive vibration can be reliably suppressed.
[0062]
18 to 20, the rigidity of the fixed beams 44a and 44b of the angular velocity sensor shown in FIG. 15 is 10 times the rigidity of the elastic support 27 in the y-axis direction. A specific example of the vibration mode when the length and width are set is shown. Note that the driving means and the detecting means are not shown for simplification of the drawing. 18 shows an x-axis direction drive mode (frequency f = 3693 Hz), FIG. 19 shows a y-axis direction detection mode (frequency f = 3691 Hz), and FIG. 20 shows a normal direction mode (frequency f = 5661 Hz). The frequency discrimination ratio in the normal mode with respect to the drive mode and the detection mode, that is, the basic mode is 1.53, and this frequency discrimination ratio is sufficiently large.
[0063]
FIG. 21 is a schematic view showing a part of another angular velocity sensor according to the present invention. As shown in the figure, two elastic support portions 25 are connected to each side portion of the truss 24, and the two first support portions 46a are arranged in the length direction in the x-axis direction and aligned in the y-axis direction. One end of the fixed beam 44a is connected, and one end of two second fixed beams 44b arranged in the length direction and aligned in the y-axis direction are connected to the fixed portion 46b, and the two fixed beams 44a are connected. The other ends of the two fixed beams 44b are connected to the common fixed beam connecting portion 53, and the end of the two first elastic support portions 25 opposite to the side connected to the truss 24 is the common fixed beam. Connected to the connecting portion 53, the common fixed beam connecting portion 53 and the fixed beams 44a and 44b constitute a support portion of the double-supported beam structure of the elastic support portion 25.
[0064]
Also in this angular velocity sensor, the end of the elastic support portion 25 opposite to the side connected to the truss 24 is connected to the fixed portions 46a and 46b via the common fixed beam connecting portion 53 and the fixed beams 44a and 44b. Therefore, since the rigidity of the support part of the elastic support part 25 in the y-axis direction is small, the electrostatic attractive force generated in the comb-tooth electrodes 28 and 29 and the amplitude of the mass 32 in the y-axis direction can be proportional to each other. Since the nonlinearity of the drive vibration can be suppressed, the angular velocity Ω can be measured with higher accuracy. Further, since the fixed portions 46a and 46b and the common fixed beam connecting portion 53 are connected by the two fixed beams 44a and the two fixed beams 44b, the torsional rigidity of the support portion of the elastic support portion 25 in the normal direction. Therefore, since it is possible to avoid a decrease in the mode frequency in the normal direction of the vibration system, the frequency discrimination ratio between the frequency in the drive mode, the detection mode and the frequency in the normal direction mode can be increased. The angular velocity Ω can be measured with higher accuracy. The common potential of the vibration system for the drive voltage is connected to the external signal processing circuit at the fixed portion 46a, and the common potential of the vibration system for the detection signal is connected to the external signal processing circuit at the fixed portion 46b. Since the influence of the drive voltage on the detection signal can be suppressed, the angular velocity Ω can be measured with higher accuracy.
[0065]
In the angular velocity sensor shown in FIG. 21, the lengths of the fixed beams 44a and 44b and the rigidity of the fixed beams 44a and 44b in the y-axis direction are 100 times the rigidity of the elastic support portion 27 in the y-axis direction. When the width is set, the degree of suppression of the nonlinearity of the drive vibration is substantially the same as the degree of suppression of the nonlinearity represented by the line b in FIG. 17, and the frequency f of the driving mode in the x-axis direction = The frequency f of the detection mode in the y-axis direction is 3718 Hz, the frequency f of the normal direction mode is f = 6223 Hz, and the frequency discrimination ratio of the normal direction mode to the drive mode, the detection mode, that is, the basic mode is 1. .67, and this frequency discrimination ratio is sufficiently large.
[0066]
In the above-described embodiment, the driving unit is arranged on both sides of the mass 32. However, the driving unit may be arranged only on one side of the mass 32. In the above-described embodiment, two rows of detection means are arranged on both sides of the central portion of the mass 32. However, one row of detection means may be arranged in the central portion of the mass 32. In the above-described embodiment, the input / output pads 23 and 42 are arranged in the fixing units 22 and 41. However, a signal processing circuit may be arranged in the fixing units 22 and 41. In the above-described embodiment, one end of the two first fixed beams 44a is connected to the fixed portion 46a, and one end of the two second fixed beams 44b is connected to the fixed portion 46b. One or more ends of three or more first and second fixed beams may be connected to each other.
[Brief description of the drawings]
FIG. 1 is a schematic plan view showing an angular velocity sensor according to the present invention.
2 is a cross-sectional view taken along the line CC in FIG.
FIG. 3 is a cross-sectional view taken along the line DD in FIG. 1;
FIG. 4 is a detailed view of a portion E in FIG.
FIG. 5 is an explanatory diagram of a method for manufacturing the angular velocity sensor shown in FIGS.
FIG. 6 is a schematic view showing a mass part of another angular velocity sensor according to the present invention.
FIG. 7 is a diagram showing a specific example of a vibration mode of another angular velocity sensor according to the present invention.
FIG. 8 is a diagram showing a specific example of a vibration mode of another angular velocity sensor according to the present invention.
FIG. 9 is a diagram showing a specific example of a vibration mode of another angular velocity sensor according to the present invention.
FIG. 10 is a diagram showing a specific example of a vibration mode of another angular velocity sensor according to the present invention.
FIG. 11 is a schematic view showing another angular velocity sensor according to the present invention.
FIG. 12 is a schematic view showing a part of another angular velocity sensor according to the present invention.
13 is a diagram showing a one-dimensional approximation model of the structure of the angular velocity sensor shown in FIG.
FIG. 14: First-order mode frequency ω₁And a ratio β.
FIG. 15 is a schematic view showing a part of another angular velocity sensor according to the present invention.
16 is a diagram showing an equivalent circuit when driving of the angular velocity sensor shown in FIG. 15 is detected.
FIG. 17 is a graph showing the relationship between driving force and mass displacement in the driving direction.
18 is a diagram showing a specific example of a vibration mode of the angular velocity sensor shown in FIG.
19 is a diagram showing a specific example of a vibration mode of the angular velocity sensor shown in FIG.
20 is a diagram showing a specific example of a vibration mode of the angular velocity sensor shown in FIG.
FIG. 21 is a schematic view showing a part of another angular velocity sensor according to the present invention.
FIG. 22 is a schematic view showing a conventional angular velocity sensor.
23 is a cross-sectional view taken along the line AA in FIG.
24 is a graph for explaining the operation of the angular velocity sensor shown in FIGS. 22 and 23. FIG.
FIG. 25 is a schematic view showing another conventional angular velocity sensor.
26 is a cross-sectional view taken along the line BB in FIG. 25. FIG.
[Explanation of symbols]
22 ... Fixing part
24 ... truss
25 ... 1st elastic support part
27. Second elastic support portion
28 ... Third comb electrode
29 ... Fourth comb electrode
30 ... Second comb electrode
31 ... 1st comb-tooth electrode
32 ... mass
34 ... Semiconductor support substrate
37 ... Semiconductor substrate
39 ... concave
41. Fixing part
44a ... 1st fixed beam
44b ... Second fixed beam
45a ... 1st fixed beam connection part
45b ... 2nd fixed beam connection part
46a ... 1st fixing | fixed part
46b ... 2nd fixing | fixed part
53 ... Common fixed beam connection

Claims

A support substrate, a fixed portion fixed to the support substrate, a mass provided on the fixed portion via an elastic support portion, a driving unit that vibrates the mass, and a driving direction of the mass by the driving unit; An angular velocity sensor having detection means for detecting displacement in a direction perpendicular to the direction parallel to the surface of the mass, wherein a concave portion is provided on a side surface parallel to the driving direction of the mass, and the fixing unit is used as the detection means. A plurality of first comb electrodes provided with the drive direction as a length direction; and a plurality of second comb electrodes provided with the drive direction as a length direction at the mass portion in the recess. An angular velocity sensor characterized by using an object.

The elastic support portion is provided with a connecting portion on a fixed portion fixed to the support substrate via a first elastic support portion whose length direction is a direction perpendicular to the driving direction, and the connecting portion has the driving direction. The angular velocity sensor according to claim 1, wherein the mass is provided via a second elastic support portion having a length direction of.

One end of a plurality of fixed beams whose driving direction is the length direction and arranged in a direction perpendicular to the driving direction is connected to the fixed portion, the other end of the fixed beam is connected to the fixed beam connecting portion, and the first portion The angular velocity sensor according to claim 2, wherein an end portion of the elastic support portion opposite to the side connected to the connection portion is connected to the fixed beam connection portion.

As the driving means, a plurality of third comb-teeth electrodes provided in the fixed portion with the driving direction as the length direction and a plurality of fourth comb teeth provided in the connection portion as the length direction of the driving direction. The angular velocity sensor according to claim 2, wherein an electrode having an electrode is used.

The angular velocity sensor according to claim 2, wherein the thickness of the first and second elastic support portions is larger than the width.

A plate-like member provided in parallel with the main surface of the support substrate and having a uniform thickness is processed in a direction perpendicular to the main surface of the support substrate to thereby fix the fixed portion, the first elastic support portion, and the connection portion. The angular velocity sensor according to claim 2, wherein the second elastic support portion and the mass are formed.

The angular velocity sensor according to claim 2, wherein the second elastic support portion is connected to a portion of the mass farthest from the center of gravity.

Two first elastic support portions are connected to each side portion of the connection portion, and a plurality of first and second lines arranged in a direction perpendicular to the drive direction in the length direction of the drive direction are connected to the fixed portion. One end of two fixed beams are connected, the other end of the first fixed beam is connected to the first fixed beam connecting portion, and the other end of the second fixed beam is connected to the second fixed beam connecting portion. And connecting one end of the first elastic support portion opposite to the side connected to the connection portion to the first fixed beam connection portion, and connecting the other end of the first elastic support portion to the first fixed beam connection portion. The angular velocity sensor according to claim 2 or 7 , wherein an end opposite to the side connected to the connection portion is connected to the second fixed beam connection portion.

Two first elastic support portions are connected to each side portion of the connection portion, and a plurality of first and second lines arranged in a direction perpendicular to the drive direction in the length direction of the drive direction are connected to the fixed portion. One end of the two fixed beams is connected, the other end of the first and second fixed beams is connected to the common fixed beam connecting portion, and connected to the connecting portion of the two first elastic support portions The angular velocity sensor according to claim 2, wherein an end opposite to the side is connected to the common fixed beam connecting portion.

The angular velocity sensor according to claim 8 or 9 , wherein one end of the first fixed beam is connected to the first fixed portion, and one end of the second fixed beam is connected to the second fixed portion. .

The angular velocity sensor according to claim 2 or 7 , wherein a width of the second elastic support portion is larger than a width of the first elastic support portion.

The angular velocity sensor according to claim 6, wherein a semiconductor substrate is used as the plate-like member, and the plate-like member is processed using a semiconductor processing technique.