JP4151959B2 - Vibrating mirror and manufacturing method thereof, optical writing device, and image forming apparatus - Google Patents

Description

【００１０】
ねじり梁支持型の振動ミラーは、一般に低エネルギーで大きな振れ角が得られるように、ミラー基板とねじり梁それぞれの材質、形状、寸法で決まってくる構造体の共振周波数を駆動周波数として設定しているが、以上の関係式からわかるように、ねじり梁寸法（c,t,L）とミラー基板寸法（a,b,t）並びに環境温度が振動ミラーの共振周波数に大きく影響してくる。したがって、駆動周波数を共振点に固定して振動ミラーを使用する場合に、寸法のばらつきや環境温度の変化により生じる共振点のずれによる振れ角の変動が大きいという問題がある。
【００１１】
このような問題点に鑑み、本出願人は、共振点外で安定した大きな振れ角で動作させることが可能な２段電極構造の振動ミラーの発明を特許出願している（特願2003-26528号、以下先願と記す）。この先願に係る発明の振動ミラーの一例について図１を参照し説明する。図１において、（ａ）は振動ミラーのミラー面と反対側から見た概略平面図、（ｂ）はＡ−Ａ' 線概略断面図、（ｃ）はミラー面側から見た概略平面図である。
【００１２】
図１において、101はミラー基板、102,103は一直線上にあるねじり梁、104は枠状支持部であり、ミラー基板101はその対向する２つの端部の中央部をねじり梁102,103を介して枠状支持部104に支持され、ねじり梁102,103をねじり回転軸として往復振動可能である。ミラー基板101のねじり梁102,103に支持されない対向した２つの端部105,106は櫛歯状に形成され、この櫛歯状の辺105,106と微小ギャップを隔てて噛み合う櫛歯状の第１の駆動電極107,108が枠状支持部104に形成されている。このようなミラー基板101、ねじり梁102,103及び駆動電極107,108を含む枠状支持部104からなる構造体は、第１の基板（例えば低抵抗の単結晶シリコン基板）から半導体プロセスによって一体的に作成される。ミラー基板101の一面に、反射率の高い金属膜からなるミラー面109が形成されている。
【００１３】
枠状支持部104には、それと略同一形状の枠状支持部111が絶縁層110を介して接合されている。この枠状支持部111には、第１の駆動電極107,108と同一の平面形状を有する櫛歯状の第２の駆動電極112,113が形成されている。このような第２の駆動電極112,113を含む枠状支持部111は、絶縁層110を介して前記第１の基板に接合された第２の基板（例えば低抵抗の単結晶シリコン基板）から半導体プロセスによって作成される。
【００１４】
枠状支持部104は、スリット120,121,122によって、ミラー基板101と電気的に導通した領域と第１の駆動電極107,108と電気的に導通した領域に絶縁分離され、それぞれの領域には金属薄膜からなる電極パッド123,124が形成されている。また、枠状支持部111は、スリット126,127,128,129によって、第２の駆動電極112と電気的に導通した領域と第２の駆動電極113と電気的に導通した領域とに絶縁分離され、それぞれの領域に金属薄膜からなる電極パッド130,131が形成されている。
【００１５】
この２段電極構造の振動ミラーは、ミラー基板101、ねじり梁102,103、枠状支持部104ならなる構造体の寸法などで決まる共振点外でも大きな振れ角で安定に駆動することができる。その駆動方法を次に説明する。
【００１６】
電極パッド１２３を接地しておく。すなわち、ミラー基板１０１を接地しておく。第１の駆動電極１０７，１０８の電極パッド１２４に電圧を印加すると、微小ギャップを介して噛み合っている第１の駆動電極１０７，１０８とミラー基板１０１の櫛歯状端部（可動電極）１０５，１０６の間に静電引力が働く。このとき、両電極間には厚さ方向に微小な位置ずれがあるため、両電極を最短距離とするようにミラー基板１０１に回転モーメントが発生する。このようにしてミラー基板１０１に微小変位が発生した後は、電極パッド１２３への電圧印加周期を振動ミラーの決まる共振周波数にあわせることでミラー基板１０１の振れ角を徐々に増大させていくことができる。可動電極が第１の駆動電極との最近接位置を通過した後、電極パッド１２３への電圧印加を停止し、次に可動電極が引き込まれる側の第２の駆動電極１１２又は１１３の電極パッド１３０又は１３１に電圧を印加することで、振れ角を増大させる方向への静電引力が作用し、振れ角をさらに増大させることができる。
【００１７】
図２に、ミラー基板１０１の振動と各駆動電極への電圧印加のタイミング関係を示す。（ａ）はミラー基板１０１の振動波形、（ｂ）は第１の駆動電極１０７，１０８への印加電圧波形、（ｃ）は第２の駆動電極１１２への印加電圧波形、（ｄ）は第２の駆動電極１１３への印加電圧波形を示す。各駆動電極による効率よく静電トルクが働くようにミラー基板１０１の振動と各駆動電極への印加電圧の位相関係を設定するのが望ましく、ここでは、第１の駆動電極１０７，１０８には０＜α1＜θ1の振れ角の範囲で電圧を印加し、第２の駆動電極１１２，１１３にはθ1＜α2＜θ2なる振れ角の範囲に電圧を印加するようにしている。
【００１８】
かかる２段電極構造の振動ミラーは、共振点外でも大きな振れ角でミラー基板を振動させることができる。共振点外では寸法ばらつきや環境温度変化による振れ角変化が共振点付近と比較して著しく小さいため、安定した振れ角でミラー基板を往復振動させることができる。
【００１９】
このような２段電極構造の振動ミラーにおいても、ミラー基板の慣性モーメントを小さくしつつ、その振動時の変形を抑えるために剛性を高めることが望まれる。しかし、ミラー基板そのもをエッチングにより肉抜きして凹部や補強部を形成する構成は前述したような問題がある。
【００２０】
よって、本発明の主たる目的は、上に述べたような問題がなく、かつ、製造プロセスを格別複雑化することもなく、さらに２段電極構造の場合に製造プロセスを変更することなく駆動電極の加工精度を向上する効果をも期待できる、ミラー基板の変形抑制のための新規な構造を有し、ビーム形状や共振周波数が安定した振動ミラーを提供することにある。本発明の他の目的は、そのような振動ミラーを用いた光書込装置及び画像形成装置を提供することにある。
【００２１】
【課題を解決するための手段】
請求項１の発明は、ミラー基板と、該ミラー基板の対向する２辺の中央部を支持する２本の梁と、前記ミラー基板を静電的に駆動するための駆動電極とを有し、前記ミラー基板が前記梁をねじり回転軸として往復振動する振動ミラーであって、前記ミラー基板が、そのミラー面が形成された面と反対側の面に形成された絶縁膜と、該絶縁膜上に形成された筋交い状の複数の補強用のリブとを有することを特徴とする振動ミラーである。
【００２２】
請求項２の発明は、ミラー基板と、２本の梁と、該梁を介して前記ミラー基板の対向する２辺の中央部を支持する枠状支持部と、前記ミラー基板の支持されない２辺に対向する前記枠状支持部の部位に形成された第１の駆動電極と、前記第１の枠状支持部に絶縁膜を介して接合された、前記第１の駆動電極と重なる第２の駆動電極とを有し、前記ミラー基板が、前記第１の駆動電極及び前記第２の駆動電極により静電的に駆動されることにより前記梁をねじり回転軸として往復振動する振動ミラーであって、前記ミラー基板は、そのミラー面が形成された面と反対側の面に形成された絶縁膜と、該絶縁膜上に形成された筋交い状の複数の補強用のリブとを有することを特徴とする振動ミラーである。
【００２６】
請求項３の発明は、請求項２の発明の振動ミラーにおいて、前記第１の駆動電極及び前記第２の駆動電極が櫛歯形状であり、前記リブの延長線上に前記第２の駆動電極の櫛歯部が位置することを特徴とするものである。
【００２７】
請求項４の発明は、請求項１乃至３のいずれか１項の発明の振動ミラーにおいて、前記リブの全体の重心位置と前記ミラー基板の重心位置とが面内方向で一致することを特徴とするものである。
【００２８】
請求項５の発明は、請求項１乃至４のいずれか１項の発明の振動ミラーにおいて、前記ミラー面が前記ミラー基板の周縁部を残して凹形に肉抜きされた面に形成されることを特徴とするものである。
【００２９】
請求項６の発明は、請求項１乃至５のいずれか１項の発明の振動ミラーの前記ミラー基板の振動空間を封止するための封止手段を有し、前記振動空間が減圧状態に封止されたことを特徴とする振動ミラーである。
【００３０】
請求項７の発明は、絶縁膜を介して接合された２枚の単結晶シリコン基板をエッチング加工することにより請求項１乃至５のいずれか１項の発明の振動ミラーを製造することを特徴とする振動ミラー製造方法である。
【００３１】
請求項８の発明は、請求項７の発明の振動ミラー製造方法において、前記リブの形成のためのエッチング加工がドライエッチングによりなされることを特徴とするものである。
【００３２】
請求項９の発明は、請求項１乃至６のいずれか１項の発明の振動ミラーと、前記振動ミラーのミラー基板のミラー面に光ビームを入射させる手段と、前記ミラー面で反射された光ビームを被走査面に結像させるための手段とを有することを特徴とする光書込装置である。
【００３３】
請求項１０の発明は、請求項１乃至６のいずれか１項の発明の振動ミラーと、像担持体と、記録信号によって変調された光ビームを前記振動ミラーのミラー基板のミラー面へ入射させるための手段と、前記ミラー面で反射された光ビームを前記像担持体に結像させるための手段と、該結像のための手段により光ビームが結像されることにより前記像担持体に形成された静電潜像をトナーで顕像化する現像手段と、該現像手段により顕像化されたトナー像を記録紙に転写する転写手段とを有することを特徴とする画像形成装置である。
【００３４】
【発明の実施の形態】
本発明による振動ミラーのミラー基板の変形を抑制するための構造は、図１及び図２に関連して説明した２段電極構造の振動ミラーへの適用する場合に特に好適であるため、２段電極構造の振動ミラーを例にして本発明の実施の形態を説明する。しかし、本発明は、駆動電極が１段のみの構造の振動ミラーに対しても同様に適用し得るものであることは、以下の説明から明らかであろう。したがって、本発明による１段電極構造の振動ミラーの実施例の提示は省略する。
【００３５】
［実施例１］
本発明の振動ミラーの一実施例の構成を図３に示す。図３の（ａ）は振動ミラーのミラー面と反対側から見た概略平面図、（ｂ）は振動ミラーのＢ−Ｂ’線概略断面図、（ｃ）は振動ミラーのミラー面側から見た概略平面図である。
【００３６】
図３において、200は第１の基板であり、これはミラー基板201、同軸上にある２本のねじり梁202,203、枠状支持部204からなり、ミラー基板201はその対向する２つの辺の中央部をねじり梁202,203を介して枠状支持部204に支持されている。ミラー基板201は、ねじり梁202,203をねじり回転軸として往復振動可能である。ミラー基板201のねじり梁202,203に支持されない対向した２つの辺には櫛歯状電極部（可動電極）206,207が形成されている。枠状支持部204には、櫛歯状電極部206,207と微小ギャップを隔てて噛み合う櫛歯状の第１の駆動電極208,209が形成されている。このような第１の基板200は、高精度の微細加工が可能で、弾性体として使用するうえで適度な剛性をもち、かつ、電極として使用可能な低抵抗の単結晶シリコン基板を、酸化膜をエッチングマスクとしてSF6ガスを用いた高密度プラズマエッチングにより貫通エッチングすることによって一体成形されている。
【００３７】
ミラー基板201の一面には、当該振動ミラーで使用される光に対して十分な反射率をもつ金属薄膜からなるミラー面205が形成されている。ミラー面205上に酸化防止のためのパッシベーション膜として絶縁膜が形成されてもよい。
【００３８】
第１の基板200に形成された各部の寸法は、必要とする共振周波数が得られるように設計される。ねじり梁202,203の幅は厚さとほぼ同じであることが望ましいが、多少変えることで共振周波数を調整可能である。また、ねじり梁202,203の長さも、所望の共振周波数となるように設定される。
【００３９】
枠状支持部204は、スリット210,211,212により、第１の駆動電極208,209と電気的に導通した領域とミラー基板201と電気的に導通した領域とに絶縁分離されている。絶縁分離された各領域には、表面の酸化膜をマスクエッチングで部分的に除去して低抵抗シリコン面を露出させ、スパッタ法でAl薄膜をマスク成膜することにより電極パッド213,214が形成されている。
【００４０】
第１の基板200のミラー面205と反対側の面に、絶縁膜220を介して接合された第２の基板221をドライエッチング加工することにより、絶縁膜220を介して枠状支持部204と重なる枠状支持部222と、ミラー基板201の裏面に絶縁膜220を介して配設されたリブ250が形成されている。枠状支持部222の内側端面には櫛歯状の第２の駆動電極223,224が形成されている。第２の駆動電極223,224は第１の駆動電極208,209と重なる位置関係にある。このような第２の基板221としては、高精度の微細加工が可能で、電極として使用可能な低抵抗の単結晶シリコン基板が用いられる。
【００４１】
枠状支持部222は、スリット225,226により、駆動電極223と電気的に導通した領域と駆動電極224と電気的に導通した領域とに絶縁分離され、その各領域には、表面の酸化膜をマスクエッチングで部分的に除去して低抵抗シリコン面を露出させ、スパッタ法でAl薄膜をマスク成膜することにより電極パッド229,230が形成されている。なお、電極パッド229,230及び電極パッド213,214の材料はAlに限定されるものではなく、十分な密着性とシリコンとの導通が得られればAu等の他の材料も選択可能であり、また、その成膜方法は真空蒸着法、イオンプレーティング法等の他の方法でもよい。
【００４２】
この実施例においては、リブ250は、図３（ｂ）に見られるように第２の基板221の厚さ相当の高さをもつ。図３（ｃ）に見られるように、リブ250はそれぞれ梁202,203と直交する方向に長く、梁202,203の方向に複数本が等間隔に並列配置されている。リブ250の間隔は駆動電極223,224の櫛歯の間隔と一致しており、各リブ250の延長線上に駆動電極223,224の対応した櫛歯が位置する。リブ250の全体の重心はミラー基板201の重心位置と面内方向で一致させており、これはミラー基板201の走査方向の振動を安定化するためである。
【００４３】
この実施例の振動ミラーは、図１に示した先願に係る発明の振動ミラーと同様の駆動方法によって駆動することができる。すなわち、ミラー基板の電極パッド213を接地し、図２の（ｂ）に示した駆動パルスを第１の駆動電極の電極パッド214に印加し、図２の（ｃ），（ｄ）に示した駆動パルスを第２の駆動電極の電極パッド229,230にそれぞれ印加することにより、図２の（ａ）に示したようにミラー基板を往復振動させることができる。
【００４４】
このように往復振動しているミラー基板201は、その慣性モーメントにより、特に梁202,203と直交する方向（ねじり回転軸と直交する方向）の変形が大きい。この方向について、ミラー基板201の裏面側に設けられたリブ250により剛性が増大するため、ミラー基板201の変形が効果的に抑えられ、したがって良好なビーム形状を得ることができる。そして、リブ250はミラー基板201とは絶縁膜220により絶縁されているため、ミラー基板201の可動電極206,207と駆動電極208,209,223,225の間の電界がリブ250によって格別影響されることがなく、したがってリブ250を設けたことがミラー基板201の挙動に悪影響を及ぼすことはない。
【００４５】
また、ミラー基板201の裏面の絶縁膜220上にリブ250を設ける構造は、先に触れたように、またより具体的に後述するように、第２の基板221を絶縁膜220までドライエッチングすることにより、容易に高い寸法精度のリブ250を形成することができ、しかも、この実施例のような２段電極構造の振動ミラーの場合、第２の駆動電極223,224と同じプロセスでリブ250を形成することができ製造プロセスが複雑化することもない。さらに大きなメリットとして、２段電極構造の振動ミラーの場合、以下の製造方法に関連して説明するように、ミラー基板201の裏面側にリブ250を設けることは、第２の駆動電極223,224の加工精度の向上、振動ミラーの製造歩留まりの向上にも寄与する。
【００４６】
次に、この実施例の振動ミラーの製造方法の一例について説明する。図４は製造工程を説明するための概略断面図である。
【００４７】
工程ａ： 板厚525μmの２枚のシリコン基板301,302を厚さ5000 の熱酸化膜303を介して直接接合したシリコンウェハを用意し、一方のシリコン基板301を板厚200μmまで、他方のシリコン基板302を板厚60μmまでそれぞれ研削、研磨した。シリコン基板301は第２の基板221として用いられるもので、シリコン基板302は第１の基板200として用いられるものである。なお、２枚のシリコン基板として、0.1Ω・ｃｍ以下の低抵抗の基板を用いた。また、シリコン基板の直接接合は、各シリコン基板の接合面をミラー面研磨して十分に洗浄した後、清浄かつ減圧雰囲気中で接合面を接触させ５００℃の温度で仮接合し、その後１１００℃の熱処理をすることにより本接合することにより行った。なお、仮接合を減圧中で行なうのは、接合面のボイドの発生を抑えるためである。
【００４８】
工程ｂ： シリコンウエハを熱酸化し、その全面に酸化膜304を１μmの厚さに形成した。
【００４９】
工程ｃ： 次に、シリコン基板302側の酸化膜304を、レジストマスクを用い、ドライエッチングにより、ミラー基板201、梁202,203、枠状支持部204、第１の駆動電極208,208、スリット210,211,212の形状にパターニングし酸化膜マスク305を形成した。なお、この説明においては、第２の駆動電極223,334のための電極パッド229,230をミラー面側に設けるために、その部分を開口させるようにパターニングした。
【００５０】
工程ｄ： 次に、パターニングした酸化膜マスク305をマスクとして、高密度プラズマエッチングにより、シリコン基板302を接合面の酸化膜303に達するまでエッチングした。このとき、界面の酸化膜303はシリコンに対して大きなエッチング選択比を持っているため酸化膜303に達したときにエッチングが停止した。第２の駆動電極223,224の電極パッドの引き出し部分のシリコンも除去され、その部分は絶縁膜303が露出している。
【００５１】
工程ｅ： 次に、シリコン基板301に形成された酸化膜304を、レジストマスクを用い、ドライエッチングにより、枠状支持部222、第２の駆動電極223,224、リブ250、スリット225,226の形状にパターニングして酸化膜マスク306を形成した。この際、両面アライナを用いて、シリコン基板302側に形成されたパターンに合わせて、シリコン基板301の表面にレジストマスクを形成し、パターニングした。
【００５２】
工程ｆ： この酸化膜マスク306を用い、高密度プラズマエッチングにより、シリコン基板301を接合面の酸化膜303に達するまでエッチングした。界面の酸化膜303はシリコンに対して大きなエッチング選択比を持っているため、酸化膜303に達したときにエッチングは確実に停止する。
【００５３】
このエッチングの際に、ミラー基板裏面にリブを設けることにより次のような効果を得られる。ドライエッチングでは、マスク開口が広い部分にはエッチングガスが入りやすいためエッチング速度が速く、マスク開口が狭い部分はエッチングガスが入りにくいためエッチング速度が遅くなる。ミラー基板裏面にリブを設けない場合、ミラー基板の部分と第２の駆動電極の部分とでマスク開口面積つまりエッチング面積が大きく違うためエッチングの進行が不均一になりやすい。これに対し、本発明の振動ミラーでは、ミラー基板裏面にリブを設けるため、エッチング面積の片寄りが少なくなるので、エッチングの進行が均一化される効果が得られる。特に、実施例１のように、リブの延長線上に第２の駆動電極の櫛歯が位置するようにリブを配置すると、第２の駆動電極の櫛歯のエッチング不足などを、より確実に防止することができるため、第２の駆動電極の加工精度が向上し、また、振動ミラーの製造歩留まりが向上する効果がある。
【００５４】
工程ｇ： 次に、基板全体をBHFウエットエッチング液にいれることで、酸化膜303の露出している部分（貫通させる部分及び電極パッド形成部）をエッチング除去した。
【００５５】
工程ｈ： 次に、電極パッド213,214としての金属薄膜307、電極パッド229,230としての金属薄膜309、及び、ミラー面205としての金属薄膜308を、メタルマスクを用いてスパッタ成膜し、振動ミラーを完成した。なお、前述したように、ここに示す製造工程例においては、第２の駆動電極223,224のための電極パッド229,230はミラー面側に形成されている。このように同じ側の面にすべての電極パッドを設ける構造は振動ミラーの実装に都合がよい。かかる構造の振動ミラーも本発明に包含されることは当然である。
【００５６】
［実施例２］
本発明の振動ミラーの他の実施例（請求項１，２に対応）を図５により説明する。図５の（ａ）は図３（ｂ）に対応した概略断面図、図５の（ｂ）は図３（ｃ）に対応した概略平面図であり、図３と同じ符号は同一部分又は対応部分を示す。
【００５７】
この実施例の振動ミラーにおいては、図５（ｂ）に見られるように、ミラー基板201の裏面に絶縁膜220を介して形成されるリブ250は筋交い状とされている。リブ250は、その全体の重心がミラー基板201の重心位置に面内方向で一致するように配列されている。これ以外の構成は前記実施例１の振動ミラーと同じであるので、その説明を省略する。また、この実施例の振動ミラーは、図４により説明した製造プロセスと同様のプロセスで製造できる。
【００５８】
この実施例の振動ミラーは、リブ250を筋交い状とすることにより、ミラー基板201の振動時に最も慣性モーメントによる変形が大きな梁202,203と直交する方向の変形を低減すると同時に、梁202,203と平行な方向の変形も低減することができる。図５（ｂ）では筋交い状のリブ250が２組配置された状態が示されているが、さらに多くの筋交い状リブ250を配置してもよく、そのようにすることにより変形低減の効果を高めることができる。また、この実施例においても、リブ250を設けることにより、第２の基板221のエッチング面積の偏りを減らす効果を得られることは明らかである。多数組の筋交い状リブ250を、その延長線上に第２の駆動電極223,224の櫛歯部が位置するように配置すると、第２の駆動電極の加工精度の向上と振動ミラーの製造歩留まりの向上に特に効果的である。
【００５９】
［実施例３］
本発明の振動ミラーの他の実施例を図６により説明する。図６の（ａ）は図３（ｂ）に対応した概略断面図、図６の（ｂ）は図３（ｃ）に対応した概略平面図であり、図３と同じ符号は同一部分又は対応部分を示す。
【００６０】
この実施例の振動ミラーにおいては、図６（ｂ）に見られるように、ミラー基板201の裏面に絶縁膜220を介して形成されるリブ250はハニカム状とされている。このリブ250は、その全体の重心がミラー基板201の重心位置に面内方向で一致するように配列されている。ハニカム状のリブ250の空隙部分は第２の駆動電極223,224の間隔とほぼ等しい寸法となっている。ここではハニカム状のリブ250は均等に配置されているが、リブ250の全体の重心がミラー基板201の重心位置に面内方向で一致するならば必ずしも均等配置でなくてもよい。枠状支持部222の駆動電極223,224が形成される領域はスリット260,261,262,263により絶縁分離されている。これ以外の構成は前記実施例１の振動ミラーと同じであるので、その説明を省略する。この実施例の振動ミラーは、図４により説明した製造プロセスと同様のプロセスで製造できる。
【００６１】
この実施例の振動ミラーは、ハニカム状のリブ250をミラー基板201の裏面に絶縁膜222を介して配列することで、ミラー基板201の振動時に最も慣性モーメントによる変形が大きな梁202,203と直交する方向の変形を効果的に低減させることができると同時に、それ以外の方向の変形も低減することができる。また、この実施例においても、リブ250を設けることにより、第２の基板221のエッチング面積の偏りを減らす効果を得られることは明らかである。
【００６２】
［実施例４］
本発明の振動ミラーの他の実施例を図７により説明する。図７は図３（ｂ）に対応した概略断面図である。
【００６３】
この実施例の振動ミラーにおいては、ミラー基板201のミラー面側が、その周辺部を残し略全面的に肉抜きされて凹形状とされ、その底面にミラー面205が形成されている。ミラー基板201の裏面側には、絶縁膜220を介して前記実施例１，２又は３と同様のリブ250形成されている。このリブ250が設けられているため、ミラー基板201を肉抜きして全体を薄くしても、ミラー基板201の必要な剛性を確保することができる。これ以外の構成は前記各実施例と同様であるので説明を省略する。
【００６４】
この実施例では、上に述べたようなミラー基板201の肉抜きによりミラー基板201の慣性モーメントが減少し、その分だけミラー基板201の振動時の変形がさらに生じにくくなる。また、ミラー面205の中心とミラー基板201の回転軸中心とのずれを小さくすることができ、例えば、ミラー基板201をその板厚の半分まで肉抜きするならば、ミラー面205の中心とミラー基板201の回転軸中心とを一致させることができる。
【００６５】
［実施例５］
図８は、本発明の振動ミラーの他の実施例を示す概略断面図である。この実施例の振動ミラーは、前記実施例１乃至４の振動ミラーの第１の基板200の枠状支持部204と第２の基板221の枠状支持部222に、パイレックスガラスかならなるカバー基板300とベース基板301をそれぞれ陽極接合し、ミラー基板201の振動空間307を減圧状態に封止したものである。このような減圧封止手段を有する振動ミラーは、ミラー基板201の振動空間の粘性抵抗が小さいため低い駆動電圧で大きな振れ角を安定に得ることができる。また、振動ミラー内部への塵芥などの侵入が阻止され、振動ミラーの信頼性が向上する。電極パッド213,214,229,230と外部との電気的接続は、カバー基板300及びベース基板301に設けられた貫通電極302〜305を通じてなされる。
【００６６】
なお、カバー基板300及びベース基板301の接合方法は陽極接合に限らないが、パイレックスガラスとシリコンとの陽極接合は長期安定な封止が可能である。また、カバー基板300は少なくとも光を通す窓部を有するならば、樹脂やセラミックスなどの材料から形成することも可能である。ベース基板301も樹脂やセラミックスなどの材料から形成することも可能である。また、封止手段として、振動ミラー全体を収容するような封止容器を用いることもできる。
【００６７】
［実施例６］
以上に説明した本発明の振動ミラーは、写真印刷方式のプリンタや複写機などの画像形成装置の光走査手段に好適である。図９は、本発明の振動ミラーを用いた画像形成装置の一例を説明するための概略構成図である。
【００６８】
図９において、801は光書込装置、802は光書込装置801の被走査面を提供する感光体ドラム（像担持体）である。光書込装置801は、記録信号によって変調された１本又は複数本のレーザビームで感光体ドラム802の表面（被走査面）を同ドラムの軸方向に走査するものである。感光体ドラム802は、矢印803方向に回転駆動され、帯電部804で帯電された表面に光書込装置801により光走査されることによって静電潜像を形成される。この静電潜像は現像部805でトナー像に顕像化され、このトナー像は転写部806で記録紙808に転写される。転写されたトナー像は定着部807によって記録紙808に定着される。感光体ドラム802の転写部806を通過した表面部分はクリーニング部809で残留トナーを除去される。なお、感光体ドラム802に代えてベルト状の感光体を用いる構成も可能であることは明らかである。また、トナー像を転写媒体に一旦転写し、この転写媒体からトナー像を記録紙に転写して定着させる構成とすることも可能である。
【００６９】
光書込装置801は、記録信号によって変調された１本又は複数本のレーザビームを発する光源部820と、前述したような本発明の振動ミラー821と、この振動ミラー821のミラー基板のミラー面に光源部820からのレーザビームを結像させるための結像光学系822と、ミラー面で反射された１本又は複数本のレーザビームを感光体ドラム802の表面（被走査面）に結像させるための走査光学系823から構成される。振動ミラー821は、その駆動のための集積回路824とともに回路基板825に実装された形で光書込装置801に組み込まれる。
【００７０】
このような構成の光書込装置801は、次のような利点を有する。本発明による振動ミラー821は、前述のようにミラー基板の変形が少なくビーム形状が安定しているため、安定したビームスポット径での書き込みが可能であるほか、回転多面鏡に比べ駆動のための消費電力が小さいため、画像形成装置の高画質化、省電力化に有利である。振動ミラー821のミラー基板の振動時の風切り音は回転多面鏡に比べ小さいため、画像形成装置の静粛性の改善に有利である。振動ミラー821は回転多面鏡に比べ設置スペースが圧倒的に少なくて済み、また、振動ミラー821の発熱量もわずかであるため、光書込装置801の小型化が容易であり、したがって画像形成装置の小型化に有利である。また、振動ミラーは高速の往復走査が可能であるため、画像記録速度の高速化が可能である。
【００７１】
なお、記録紙808の搬送機構、感光体ドラム802の駆動機構、現像部805、転写部806などの制御手段、光源部820の駆動系などは、従来の画像形成装置と同様でよいため図中省略されている。
【００７２】
【発明の効果】
（１）請求項１及び２の発明によれば、振動ミラーのミラー基板の振動時の変形がリブにより抑えられるため、安定したビーム形状を得ることができる。ミラー基板に形成された絶縁膜上にリブが形成される構造であるため、エッチング加工により容易に寸法精度の高いリブを形成することができる。リブはミラー基板とは絶縁されているため、リブを設けたことによりミラー基板の可動電極と駆動電極の間の電界に格別の影響はなく、ミラー基板の挙動に悪影響を及ぼすことはない。また、筋交い状の複数のリブによって、ミラー基板の振動時に慣性モーメントによる変形が最も大きな梁と直交する方向の変形を減らすと同時に、梁と平行な方向の変形も減らすことができるため、走査方向ばかりでなくそれと直交する方向についても安定したビーム形状を得ることができる。
（２）請求項２の発明によれば、２段電極構造の振動ミラーにおける第２の駆動電極を形成するためのエッチング工程において、同時にリブを形成することができるため、リブを設けることによる製造プロセスの変更は不要である。しかも、ミラー基板の裏面側にリブを設けるため、それを設けない場合に比べエッチング面積の偏りが減り、第２の駆動電極の加工精度が向上する。特に、請求項３の発明によれば、第２の駆動電極の櫛歯部から均一にエッチングを進行させることができるため、第２の駆動電極の櫛歯形状やエッチング速度のばらつきが小さくなり、共振周波数などのばらつきの少ない再現性のよい振動ミラーを得られる。
（３）請求項４の発明によれば、ミラー基板の走査方向の振動が安定するため安定したビーム形状が得られる。
（４）請求項５の発明によれば、ミラー基板の慣性モーメントが減少し、その分だけミラー基板の振動時の変形をさらに生じにくくなる。また、ミラー面の中心とミラー基板の回転軸中心とのずれを小さくし、さらには一致させることができる。
（５）請求項６の発明によれば、ミラー基板の振動空間の粘性抵抗が減り、低い駆動電圧で大きな振れ角を安定に得ることができる。また、振動ミラー内部への塵芥などの侵入が阻止され、振動ミラーの信頼性が向上する。
（６）請求項７の発明によれば、単純な製造プロセスで、加工精度が高く共振周波数などのばらつきの少ない請求項１乃至５の発明の振動ミラーを製造することができる。請求項８の発明によれば、リブの高精度の加工が可能であり、また、リブの形状の設計の自由度が広く最適化が容易になる。
（７）請求項９の発明によれば、安定したビームスポット径での書き込みが可能で、往復走査による高速書き込みが可能であり、消費電力が小さく、静粛性に優れたコンパクトな光書込装置を実現できる。
（８）請求項１０の発明によれば、高画質な画像形成を高速に行うことが可能で、消費電力が小さく静粛性も優れたコンパクトな画像形成装置を実現できる。
【図面の簡単な説明】
【図１】本出願人の先願に係る発明の２段電極構造の振動ミラーの一例を示す概略平面図及び概略断面図である。
【図２】２段電極構造の振動ミラーの駆動電圧波形及びミラー基板の振動波形を示す波形図である。
【図３】本発明の振動ミラーの一実施例を説明するための概略平面図及び概略断面図である。
【図４】図３に示した振動ミラーの製造工程説明図である。
【図５】本発明の振動ミラーの他の実施例を説明するための概略断面図及び概略平面図である。
【図６】本発明の振動ミラーの他の実施例を説明するための概略断面図及び概略平面図である。
【図７】本発明の振動ミラーの他の実施例を説明するための概略断面図である。
【図８】本発明の振動ミラーの他の実施例を説明するための概略断面図である。
【図９】本発明の光書込装置及び画像形成装置の一実施例を説明するための概略構成図である。
【符号の説明】
200 第１の基板
201 ミラー基板
202,203 ねじり梁
204 枠状支持部
206,207 可動電極
208,209 第１の駆動電極
123,214 電極パッド
220 絶縁膜
221 第２の基板
222 枠状支持部
223,224 第２の駆動電極
229,230 電極パッド
250 リブ
300 カバー基板
301 ベース基板
302〜305 貫通電極
801 光書込装置
821 振動ミラー
802 感光体ドラム
805 現像部
806 転写部[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a micro-optical system to which micromachining technology is applied, and more particularly to a torsion beam support type oscillating mirror driven by electrostatic force, and an optical writing apparatus and an image forming apparatus using the torsion beam support type oscillating mirror.
[0002]
[Prior art]
This type of vibrating mirror is promising for application to optical writing devices of image forming apparatuses such as digital copying machines and laser printers, and optical reading devices such as barcode readers and scanners.
[0003]
In this type of vibrating mirror (optical scanning device) described in Non-Patent Document 1, an electrode provided with a mirror substrate supported by two beams provided on the same straight line at a position facing the mirror substrate The two beams are caused to reciprocally vibrate with a torsional rotation axis by an electrostatic attractive force between them. This oscillating mirror created by micromachining technology has a simple structure compared to an optical scanning device configured to rotate a polygon mirror by a motor, and can be formed in a batch in a semiconductor process, making it easy to miniaturize. The manufacturing cost is low. In addition, since the polygon mirror uses a plurality of mirror surfaces, there is a problem of variation in accuracy for each mirror surface, but such a problem does not occur in a vibrating mirror having one mirror surface. Furthermore, the vibrating mirror can easily cope with high-speed scanning by reciprocating scanning.
[0004]
Further, in the oscillating mirror described in Non-Patent Document 2 and Non-Patent Document 3, in order to increase the deflection angle of the mirror substrate, a counter electrode is provided on the end surface of the mirror substrate so that the electrode does not overlap the oscillating region. These oscillating mirrors are driven by electrostatic attraction between a mirror substrate as a movable electrode made of silicon with a plate thickness of 20 μm and a fixed electrode facing the end surface of the mirror substrate with a small gap therebetween. It is formed at the site. In the oscillating mirror of Non-Patent Document 2, an initial moment for starting the vibration of the mirror substrate is obtained by utilizing the minute asymmetry of the structure generated in the formation process. The metal thin film electrode for activation is disposed on the surface orthogonal to the drive electrode.
[0005]
Further, in this type of oscillating mirror, Patent Document 1 discloses a structure in which a concave portion is formed by removing a mirror substrate in order to maintain rigidity while increasing a deflection angle of the mirror substrate.
[0006]
[Patent Document 1]
JP 2001-249300 A
[Non-Patent Document 1]
K.E.Petersen, "Silicon Tortional Scanning Mirror",
IBM Journal of Research and Development 24, (1980), pp.631-637
[Non-Patent Document 2]
Harald Schenk, "An Electrostatically Excited 2D-Micro-
Scanning-Mirror with an In-Plane configuration of the
Driving Electrodes ",
The 13th Annual International Workshop on MEMS 2000, (2000),
pp.473-478
[Non-Patent Document 3]
Harald Schenk et al, "A New Driving Principle for
Micromechanical Torsional Actuators ",
The 1999 ASME International Mechanical Engineering Congress
and Exposition, Nov.14-19,1999, pp.333-338
[0007]
[Problems to be solved by the invention]
In a oscillating mirror in which the mirror substrate reciprocally vibrates using the beam as a torsional rotation axis, it is effective for increasing the deflection angle of the mirror substrate and for high-speed driving to reduce the moment of inertia by reducing the mirror substrate. However, if the thickness of the mirror substrate is reduced in order to reduce the weight while maintaining the size required for the mirror substrate, the mirror substrate will be deformed during vibration and the flatness of the mirror surface cannot be maintained, and the mirror surface will be reflected. The cross-sectional shape and focal position of the light beam will fluctuate.
[0008]
As means for reducing the deformation of the mirror substrate while reducing the moment of inertia of the mirror substrate, a structure in which a recess is formed in the mirror substrate as described in Patent Document 1, or a patent application filed by the present applicant (Japanese Patent Application No. 2002). The structure of the oscillating mirror in which the reinforcing portion is formed on the back surface of the mirror substrate according to No. -216250) is effective. However, when a recess or a reinforcing portion is formed by etching on a mirror substrate made of single crystal silicon or the like, there is a problem in that it is difficult to increase the accuracy of the moment of inertia and resonance frequency of the mirror substrate due to variations in etching depth. In addition, since the mirror substrate also acts as a movable electrode, forming a concave portion or a reinforcing portion on the mirror substrate itself also complicates the shape of the movable electrode from an electrical viewpoint. There is a problem that the electric field between the (fixed electrode) is affected, and hence the behavior of the mirror substrate is also affected.
[0009]
The resonance frequency f of the oscillating mirror can be expressed by the following equation where k is the torsional elastic coefficient of the beam and I is the moment of inertia of the mirror substrate.
f = 1 / 2π√ (k / I)
The torsional elastic coefficient k can be expressed by the following equation where the beam width is c, the beam height is t, and the beam length is L. Where β is the cross-sectional shape factor, E is the Young's modulus, and ν is the Poisson's ratio.
k = βtc³E / L (1 + ν)
If the temperature coefficient of silicon is Δht, the Young's modulus E at temperature Tmt is
E = Eo (1-Δht * Tmt)
Given in.
The moment of inertia I of the mirror substrate can be expressed by the following equation where the mirror weight is M, the density is ρ, and the width, length, and thickness of the mirror substrate are b, a, and t, respectively.

[0010]
In general, torsion beam-supporting oscillating mirrors have a resonance frequency of the structure determined by the material, shape, and dimensions of the mirror substrate and torsion beam as the drive frequency so that a large deflection angle can be obtained with low energy. However, as can be seen from the above relational expression, the torsion beam dimensions (c, t, L), the mirror substrate dimensions (a, b, t) and the environmental temperature greatly affect the resonant frequency of the vibrating mirror. Therefore, when the vibration mirror is used with the drive frequency fixed at the resonance point, there is a problem that the fluctuation of the deflection angle due to the deviation of the resonance point caused by the variation in dimensions or the change in environmental temperature is large.
[0011]
In view of such problems, the present applicant has applied for a patent for the invention of a vibrating mirror having a two-stage electrode structure that can be operated with a stable large deflection angle outside the resonance point (Japanese Patent Application No. 2003-26528). No., hereinafter referred to as prior application). An example of the vibrating mirror of the invention according to the prior application will be described with reference to FIG. In FIG. 1, (a) is a schematic plan view seen from the side opposite to the mirror surface of the vibrating mirror, (b) is a schematic cross-sectional view taken along the line AA ′, and (c) is a schematic plan view seen from the mirror surface side. is there.
[0012]
  In FIG. 1, 101 is a mirror substrate, 102 and 103 are straight torsion beams, 104 is a frame-like support portion, and the mirror substrate 101 has a frame-like shape through two torsion beams 102 and 103 at its center. It is supported by the support portion 104 and can reciprocally vibrate with the torsion beams 102 and 103 as the torsional rotation shaft. To the torsion beams 102 and 103 of the mirror substrate 101supportThe two opposite end portions 105 and 106 that are not formed are formed in a comb-like shape, and comb-like first drive electrodes 107 and 108 that mesh with the comb-like sides 105 and 106 with a minute gap therebetween are formed on the frame-like support portion 104. Yes. Such a structure including the mirror substrate 101, the torsion beams 102 and 103, and the frame-like support portion 104 including the drive electrodes 107 and 108 is integrally formed from a first substrate (for example, a low-resistance single crystal silicon substrate) by a semiconductor process. The A mirror surface 109 made of a highly reflective metal film is formed on one surface of the mirror substrate 101.
[0013]
A frame-shaped support portion 111 having substantially the same shape as that of the frame-shaped support portion 104 is joined via an insulating layer 110. The frame-shaped support portion 111 is formed with comb-shaped second drive electrodes 112 and 113 having the same planar shape as the first drive electrodes 107 and 108. The frame-like support part 111 including the second drive electrodes 112 and 113 is used for a semiconductor process from a second substrate (for example, a low-resistance single crystal silicon substrate) bonded to the first substrate via the insulating layer 110. Created by.
[0014]
The frame-like support portion 104 is insulated and separated into a region electrically connected to the mirror substrate 101 and a region electrically connected to the first drive electrodes 107 and 108 by slits 120, 121, and 122, and each region is an electrode made of a metal thin film. Pads 123 and 124 are formed. Further, the frame-shaped support portion 111 is insulated and separated into a region electrically connected to the second drive electrode 112 and a region electrically connected to the second drive electrode 113 by the slits 126, 127, 128, and 129. Electrode pads 130 and 131 made of a metal thin film are formed.
[0015]
This oscillating mirror having a two-stage electrode structure can be driven stably with a large deflection angle even outside the resonance point determined by the dimensions of the structure consisting of the mirror substrate 101, the torsion beams 102 and 103, and the frame-like support 104. The driving method will be described next.
[0016]
The electrode pad 123 is grounded. That is, the mirror substrate 101 is grounded. When a voltage is applied to the electrode pads 124 of the first drive electrodes 107 and 108, the first drive electrodes 107 and 108 meshing with each other through a minute gap and the comb-like end portions (movable electrodes) 105 of the mirror substrate 101, An electrostatic attraction works during 106. At this time, since there is a slight positional shift in the thickness direction between the two electrodes, a rotational moment is generated in the mirror substrate 101 so as to make the both electrodes the shortest distance. After a minute displacement occurs in the mirror substrate 101 in this way, the deflection angle of the mirror substrate 101 can be gradually increased by adjusting the voltage application period to the electrode pad 123 to the resonance frequency determined by the vibration mirror. it can. After the movable electrode passes through the closest position with the first drive electrode, the voltage application to the electrode pad 123 is stopped, and then the electrode pad 130 of the second drive electrode 112 or 113 on the side where the movable electrode is drawn. Alternatively, by applying a voltage to 131, an electrostatic attractive force in the direction of increasing the deflection angle acts, and the deflection angle can be further increased.
[0017]
FIG. 2 shows the timing relationship between the vibration of the mirror substrate 101 and the voltage application to each drive electrode. (A) is a vibration waveform of the mirror substrate 101, (b) is a voltage waveform applied to the first drive electrodes 107 and 108, (c) is a voltage waveform applied to the second drive electrode 112, and (d) is a first voltage waveform. 2 shows voltage waveforms applied to two drive electrodes 113. It is desirable to set the phase relationship between the vibration of the mirror substrate 101 and the voltage applied to each drive electrode so that the electrostatic torque works efficiently by each drive electrode. Here, the first drive electrodes 107 and 108 are set to 0. A voltage is applied in the range of the swing angle of <α1 <θ1, and the voltage is applied to the second drive electrodes 112 and 113 in the range of the swing angle of θ1 <α2 <θ2.
[0018]
Such a vibrating mirror having a two-stage electrode structure can vibrate the mirror substrate with a large deflection angle even outside the resonance point. Outside the resonance point, the deflection angle change due to dimensional variations and environmental temperature changes is significantly smaller than that near the resonance point, so that the mirror substrate can be reciprocally oscillated with a stable deflection angle.
[0019]
Even in such a vibrating mirror having a two-stage electrode structure, it is desired to increase rigidity in order to reduce the moment of inertia of the mirror substrate and suppress deformation during vibration. However, the configuration in which the mirror substrate itself is thinned by etching to form the concave portion and the reinforcing portion has a problem as described above.
[0020]
Therefore, the main object of the present invention is that there is no problem as described above, the manufacturing process is not particularly complicated, and in the case of a two-stage electrode structure, the driving electrode is not changed. An object of the present invention is to provide a vibrating mirror having a novel structure for suppressing deformation of a mirror substrate, which can also be expected to improve the machining accuracy, and having a stable beam shape and resonance frequency. Another object of the present invention is to provide an optical writing apparatus and an image forming apparatus using such a vibrating mirror.
[0021]
[Means for Solving the Problems]
  The invention of claim 1 has a mirror substrate, two beams that support the central portions of two opposite sides of the mirror substrate, and a drive electrode for electrostatically driving the mirror substrate, The mirror substrate is a oscillating mirror that reciprocally vibrates with the beam as a torsional rotation axis, and the mirror substrate has an insulating film formed on a surface opposite to the surface on which the mirror surface is formed; Formed inMultiple bracesIt is a vibrating mirror characterized by having a reinforcing rib.
[0022]
  According to a second aspect of the present invention, there is provided a mirror substrate, two beams, a frame-shaped support portion that supports the central portion of two opposite sides of the mirror substrate via the beams, and two sides that are not supported by the mirror substrate. A first drive electrode formed at a portion of the frame-shaped support portion opposite to the first drive electrode, and a second drive electrode joined to the first frame-shaped support portion via an insulating film and overlapping the first drive electrode A oscillating mirror that reciprocally vibrates about the beam as a torsional rotation axis when the mirror substrate is electrostatically driven by the first driving electrode and the second driving electrode. The mirror substrate is formed on the insulating film formed on the surface opposite to the surface on which the mirror surface is formed, and on the insulating film.Multiple bracesIt is a vibrating mirror characterized by having a reinforcing rib.
[0026]
  Claim 3According to a second aspect of the present invention, in the oscillating mirror according to the second aspect, the first drive electrode and the second drive electrode are comb-shaped, and the comb-tooth portion of the second drive electrode is formed on the extension line of the rib. Is located.
[0027]
  Claim 4The invention ofClaims 1 to 3In the vibrating mirror according to any one of the above, the center of gravity position of the entire rib and the center of gravity of the mirror substrate coincide in the in-plane direction.
[0028]
  Claim 5The invention ofClaims 1 to 4The oscillating mirror according to any one of the above aspects is characterized in that the mirror surface is formed on a surface that is hollowed out in a concave shape leaving the peripheral edge of the mirror substrate.
[0029]
  Claim 6The invention ofClaims 1 to 5A vibrating mirror having sealing means for sealing the vibrating space of the mirror substrate of the vibrating mirror according to any one of the invention, wherein the vibrating space is sealed in a reduced pressure state. .
[0030]
  Claim 7According to the present invention, two single crystal silicon substrates bonded through an insulating film are etched.Claims 1 to 5A vibrating mirror manufacturing method, characterized in that the vibrating mirror according to any one of the inventions is manufactured.
[0031]
  Claim 8The invention ofClaim 7In the vibrating mirror manufacturing method according to the present invention, the etching process for forming the rib is performed by dry etching.
[0032]
  Claim 9The invention ofClaims 1 to 6The vibrating mirror according to any one of claims 1 to 3, means for causing a light beam to enter the mirror surface of a mirror substrate of the vibrating mirror, and means for forming an image of the light beam reflected by the mirror surface on a surface to be scanned And an optical writing device.
[0033]
  Claim 10The invention ofClaims 1 to 6Any one of the vibrating mirror according to the invention, the image carrier, means for causing a light beam modulated by a recording signal to enter the mirror surface of the mirror substrate of the vibrating mirror, and reflected by the mirror surface A means for forming an image of the light beam on the image carrier, and an electrostatic latent image formed on the image carrier by the light beam being imaged by the means for imaging is visualized with toner. An image forming apparatus comprising: developing means for converting the toner image; and transfer means for transferring the toner image visualized by the developing means to a recording sheet.
[0034]
DETAILED DESCRIPTION OF THE INVENTION
The structure for suppressing the deformation of the mirror substrate of the vibrating mirror according to the present invention is particularly suitable when applied to the vibrating mirror having the two-stage electrode structure described with reference to FIGS. An embodiment of the present invention will be described by taking a vibrating mirror having an electrode structure as an example. However, it will be apparent from the following description that the present invention can be similarly applied to a vibrating mirror having a structure with only one drive electrode. Accordingly, the description of the embodiment of the vibrating mirror having the one-stage electrode structure according to the present invention is omitted.
[0035]
[Example 1]
FIG. 3 shows the configuration of an embodiment of the vibrating mirror of the present invention. 3A is a schematic plan view seen from the side opposite to the mirror surface of the vibrating mirror, FIG. 3B is a schematic cross-sectional view taken along line BB ′ of the vibrating mirror, and FIG. 3C is a view seen from the mirror surface side of the vibrating mirror. FIG.
[0036]
In FIG. 3, reference numeral 200 denotes a first substrate, which is composed of a mirror substrate 201, two torsion beams 202, 203 on the same axis, and a frame-like support portion 204. The mirror substrate 201 is the center of two opposing sides. The part is supported by the frame-like support part 204 via the torsion beams 202 and 203. The mirror substrate 201 can reciprocate with the torsion beams 202 and 203 as the torsional rotation axis. Comb-like electrode portions (movable electrodes) 206 and 207 are formed on two opposing sides that are not supported by the torsion beams 202 and 203 of the mirror substrate 201. The frame-like support portion 204 is formed with comb-like first drive electrodes 208 and 209 that engage with the comb-like electrode portions 206 and 207 with a minute gap therebetween. Such a first substrate 200 is made of a low-resistance single crystal silicon substrate that can be finely processed with high precision, has an appropriate rigidity when used as an elastic body, and can be used as an electrode. Is integrally formed by performing through-etching by high-density plasma etching using SF6 gas as an etching mask.
[0037]
On one surface of the mirror substrate 201, a mirror surface 205 made of a metal thin film having a sufficient reflectance with respect to light used in the vibration mirror is formed. An insulating film may be formed on the mirror surface 205 as a passivation film for preventing oxidation.
[0038]
The dimensions of each part formed on the first substrate 200 are designed so as to obtain a required resonance frequency. The width of the torsion beams 202 and 203 is preferably substantially the same as the thickness, but the resonance frequency can be adjusted by slightly changing the width. Further, the lengths of the torsion beams 202 and 203 are also set to have a desired resonance frequency.
[0039]
The frame-like support portion 204 is insulated and separated into a region electrically connected to the first drive electrodes 208 and 209 and a region electrically connected to the mirror substrate 201 by the slits 210, 211, and 212. In each isolated region, electrode pads 213 and 214 are formed by partially removing the oxide film on the surface by mask etching to expose the low-resistance silicon surface, and forming the Al thin film as a mask by sputtering. Yes.
[0040]
By subjecting the second substrate 221 bonded to the surface opposite to the mirror surface 205 of the first substrate 200 via the insulating film 220 to dry etching, the frame-shaped support portion 204 Overlapping frame-shaped support portions 222 and ribs 250 disposed on the back surface of the mirror substrate 201 via an insulating film 220 are formed. Comb-shaped second drive electrodes 223 and 224 are formed on the inner end face of the frame-shaped support portion 222. The second drive electrodes 223 and 224 are in a positional relationship overlapping with the first drive electrodes 208 and 209. As such a second substrate 221, a low-resistance single crystal silicon substrate that can be processed with high precision and can be used as an electrode is used.
[0041]
The frame-shaped support part 222 is insulated and separated into a region electrically connected to the drive electrode 223 and a region electrically connected to the drive electrode 224 by the slits 225 and 226, and the surface oxide film is masked in each region. The electrode pads 229 and 230 are formed by partially removing by etching to expose the low-resistance silicon surface, and forming an Al thin film as a mask by sputtering. The material of the electrode pads 229 and 230 and the electrode pads 213 and 214 is not limited to Al, and other materials such as Au can be selected as long as sufficient adhesion and conduction with silicon can be obtained. The film method may be other methods such as a vacuum deposition method and an ion plating method.
[0042]
In this embodiment, the rib 250 has a height corresponding to the thickness of the second substrate 221 as seen in FIG. As shown in FIG. 3C, the ribs 250 are long in the direction orthogonal to the beams 202 and 203, respectively, and a plurality of ribs 250 are arranged in parallel in the direction of the beams 202 and 203 at equal intervals. The interval between the ribs 250 is the same as the interval between the comb teeth of the drive electrodes 223 and 224, and the corresponding comb teeth of the drive electrodes 223 and 224 are positioned on the extension lines of the ribs 250. The center of gravity of the entire rib 250 is aligned with the position of the center of gravity of the mirror substrate 201 in the in-plane direction, in order to stabilize the vibration of the mirror substrate 201 in the scanning direction.
[0043]
The oscillating mirror of this embodiment can be driven by the same driving method as the oscillating mirror of the invention according to the prior application shown in FIG. That is, the electrode pad 213 of the mirror substrate is grounded, and the drive pulse shown in FIG. 2B is applied to the electrode pad 214 of the first drive electrode, as shown in FIGS. 2C and 2D. By applying the drive pulse to the electrode pads 229 and 230 of the second drive electrode, respectively, the mirror substrate can be reciprocally oscillated as shown in FIG.
[0044]
The mirror substrate 201 that reciprocally vibrates in this manner is greatly deformed in the direction perpendicular to the beams 202 and 203 (the direction perpendicular to the torsional rotation axis) due to the moment of inertia. In this direction, the rigidity is increased by the rib 250 provided on the back surface side of the mirror substrate 201, so that the deformation of the mirror substrate 201 can be effectively suppressed, and thus a good beam shape can be obtained. Since the rib 250 is insulated from the mirror substrate 201 by the insulating film 220, the electric field between the movable electrodes 206, 207 and the drive electrodes 208, 209, 223, 225 of the mirror substrate 201 is not particularly affected by the rib 250. Providing this does not adversely affect the behavior of the mirror substrate 201.
[0045]
In addition, the structure in which the rib 250 is provided on the insulating film 220 on the back surface of the mirror substrate 201 is dry-etched to the insulating film 220 as described above and more specifically as described later. Therefore, the rib 250 with high dimensional accuracy can be easily formed. In the case of the vibrating mirror having the two-stage electrode structure as in this embodiment, the rib 250 is formed by the same process as the second drive electrodes 223 and 224. The manufacturing process is not complicated. As a further merit, in the case of a vibrating mirror having a two-stage electrode structure, providing a rib 250 on the back surface side of the mirror substrate 201 as described in connection with the following manufacturing method means that the second drive electrodes 223 and 224 are processed. Contributes to improved accuracy and improved manufacturing yield of vibrating mirrors.
[0046]
Next, an example of a method for manufacturing the vibrating mirror of this embodiment will be described. FIG. 4 is a schematic cross-sectional view for explaining the manufacturing process.
[0047]
Step a: A silicon wafer is prepared by directly bonding two silicon substrates 301 and 302 having a thickness of 525 μm via a thermal oxide film 303 having a thickness of 5000, and one silicon substrate 301 is reduced to a thickness of 200 μm, and the other silicon substrate 302 is prepared. Each was ground and polished to a plate thickness of 60 μm. The silicon substrate 301 is used as the second substrate 221, and the silicon substrate 302 is used as the first substrate 200. Note that a low resistance substrate of 0.1 Ω · cm or less was used as the two silicon substrates. In the direct bonding of the silicon substrates, the bonding surfaces of the silicon substrates are mirror-polished and sufficiently cleaned, and then the bonding surfaces are brought into contact with each other in a clean and low-pressure atmosphere, and then temporarily bonded at a temperature of 500 ° C., and then 1100 ° C. This was performed by performing the main bonding by performing the heat treatment. The reason why the temporary bonding is performed under reduced pressure is to suppress the generation of voids on the bonding surface.
[0048]
Step b: The silicon wafer was thermally oxidized to form an oxide film 304 with a thickness of 1 μm on the entire surface.
[0049]
Step c: Next, the oxide film 304 on the silicon substrate 302 side is formed into the shape of the mirror substrate 201, the beams 202 and 203, the frame support 204, the first drive electrodes 208 and 208, and the slits 210, 211, and 212 by dry etching using a resist mask. Patterning was performed to form an oxide film mask 305. In this description, in order to provide the electrode pads 229 and 230 for the second drive electrodes 223 and 334 on the mirror surface side, patterning is performed so that the portions are opened.
[0050]
Step d: Next, using the patterned oxide film mask 305 as a mask, the silicon substrate 302 was etched by high-density plasma etching until it reached the oxide film 303 on the bonding surface. At this time, since the oxide film 303 at the interface has a large etching selectivity with respect to silicon, the etching was stopped when the oxide film 303 was reached. The silicon in the lead pad portions of the second drive electrodes 223 and 224 is also removed, and the insulating film 303 is exposed in these portions.
[0051]
Step e: Next, the oxide film 304 formed on the silicon substrate 301 is patterned into the shape of the frame-shaped support portion 222, the second drive electrodes 223, 224, the ribs 250, and the slits 225, 226 by dry etching using a resist mask. Thus, an oxide film mask 306 was formed. At this time, a resist mask was formed on the surface of the silicon substrate 301 in accordance with the pattern formed on the silicon substrate 302 side using a double-sided aligner, and was patterned.
[0052]
Step f: Using this oxide film mask 306, the silicon substrate 301 was etched by high-density plasma etching until it reached the oxide film 303 on the bonding surface. Since the interface oxide film 303 has a large etching selection ratio with respect to silicon, the etching is surely stopped when the oxide film 303 is reached.
[0053]
In this etching, the following effects can be obtained by providing ribs on the back surface of the mirror substrate. In dry etching, an etching gas is likely to enter a portion where the mask opening is wide, so that the etching rate is high, and an etching gas is difficult to enter in a portion where the mask opening is narrow, so the etching rate is slow. In the case where no rib is provided on the rear surface of the mirror substrate, the mask opening area, that is, the etching area is greatly different between the mirror substrate portion and the second drive electrode portion, so that the etching progress tends to be non-uniform. On the other hand, in the oscillating mirror of the present invention, since the rib is provided on the rear surface of the mirror substrate, the deviation of the etching area is reduced, so that the effect of making the etching progress uniform can be obtained. In particular, when the ribs are arranged so that the comb teeth of the second drive electrode are positioned on the extended line of the ribs as in the first embodiment, insufficient etching of the comb teeth of the second drive electrode can be more reliably prevented. Therefore, the processing accuracy of the second drive electrode is improved, and the manufacturing yield of the vibrating mirror is improved.
[0054]
Step g: Next, the exposed portion of the oxide film 303 (the portion to be penetrated and the electrode pad forming portion) was etched away by placing the entire substrate in a BHF wet etching solution.
[0055]
Step h: Next, a metal thin film 307 as the electrode pads 213 and 214, a metal thin film 309 as the electrode pads 229 and 230, and a metal thin film 308 as the mirror surface 205 are formed by sputtering using a metal mask to complete a vibrating mirror. did. As described above, in the manufacturing process example shown here, the electrode pads 229 and 230 for the second drive electrodes 223 and 224 are formed on the mirror surface side. The structure in which all electrode pads are provided on the same side in this way is convenient for mounting a vibrating mirror. Naturally, the vibration mirror having such a structure is also included in the present invention.
[0056]
  [Example 2]
  Another embodiment of the vibrating mirror of the present invention(Corresponding to claims 1 and 2)Will be described with reference to FIG. 5A is a schematic cross-sectional view corresponding to FIG. 3B, FIG. 5B is a schematic plan view corresponding to FIG. 3C, and the same reference numerals as those in FIG. Indicates the part.
[0057]
In the oscillating mirror of this embodiment, as seen in FIG. 5B, the ribs 250 formed on the back surface of the mirror substrate 201 via the insulating film 220 are in the form of braces. The ribs 250 are arranged such that the center of gravity of the ribs 250 coincides with the position of the center of gravity of the mirror substrate 201 in the in-plane direction. Since the configuration other than this is the same as that of the vibrating mirror of the first embodiment, the description thereof is omitted. Further, the vibrating mirror of this embodiment can be manufactured by a process similar to the manufacturing process described with reference to FIG.
[0058]
In the vibrating mirror of this embodiment, the ribs 250 are brazed to reduce deformation in the direction orthogonal to the beams 202 and 203, which are most deformed by the moment of inertia when the mirror substrate 201 vibrates, and at the same time, in a direction parallel to the beams 202 and 203 The deformation of can also be reduced. Although FIG. 5B shows a state in which two sets of bracing ribs 250 are arranged, more bracing ribs 250 may be arranged, and by doing so, the effect of reducing deformation can be achieved. Can be increased. Also in this embodiment, it is obvious that the rib 250 can provide the effect of reducing the uneven etching area of the second substrate 221. If a large number of bracing ribs 250 are arranged so that the comb teeth of the second drive electrodes 223 and 224 are positioned on the extended line, the processing accuracy of the second drive electrodes and the manufacturing yield of the vibrating mirror can be improved. It is particularly effective.
[0059]
[Example 3]
Another embodiment of the vibrating mirror of the present invention will be described with reference to FIG. 6 (a) is a schematic sectional view corresponding to FIG. 3 (b), FIG. 6 (b) is a schematic plan view corresponding to FIG. 3 (c), and the same reference numerals as those in FIG. Indicates the part.
[0060]
In the oscillating mirror of this embodiment, as shown in FIG. 6B, the rib 250 formed on the back surface of the mirror substrate 201 via the insulating film 220 has a honeycomb shape. The ribs 250 are arranged so that the center of gravity of the ribs 250 coincides with the position of the center of gravity of the mirror substrate 201 in the in-plane direction. The gap portion of the honeycomb-shaped rib 250 has a size approximately equal to the distance between the second drive electrodes 223 and 224. Here, the honeycomb-like ribs 250 are arranged uniformly, but the ribs 250 need not necessarily be arranged uniformly if the center of gravity of the entire ribs 250 matches the center of gravity of the mirror substrate 201 in the in-plane direction. The region where the drive electrodes 223 and 224 of the frame-shaped support part 222 are formed is insulated and separated by slits 260, 261, 262 and 263. Since the configuration other than this is the same as that of the vibrating mirror of the first embodiment, the description thereof is omitted. The vibrating mirror of this embodiment can be manufactured by a process similar to the manufacturing process described with reference to FIG.
[0061]
In the vibrating mirror of this embodiment, the honeycomb-shaped rib 250 is arranged on the back surface of the mirror substrate 201 via the insulating film 222, so that the deformation due to the most moment of inertia during the vibration of the mirror substrate 201 is the direction orthogonal to the beams 202 and 203. Can be effectively reduced, and at the same time, deformation in other directions can also be reduced. Also in this embodiment, it is obvious that the rib 250 can provide the effect of reducing the uneven etching area of the second substrate 221.
[0062]
[Example 4]
Another embodiment of the vibrating mirror of the present invention will be described with reference to FIG. FIG. 7 is a schematic sectional view corresponding to FIG.
[0063]
In the oscillating mirror of this embodiment, the mirror surface side of the mirror substrate 201 is hollowed out substantially entirely, leaving the peripheral portion thereof, and has a mirror surface 205 formed on the bottom surface thereof. Ribs 250 similar to those in the first, second, or third embodiment are formed on the rear surface side of the mirror substrate 201 with an insulating film 220 interposed therebetween. Since the rib 250 is provided, the required rigidity of the mirror substrate 201 can be ensured even if the mirror substrate 201 is thinned and thinned. Since the configuration other than this is the same as that of each of the above embodiments, the description thereof is omitted.
[0064]
In this embodiment, the inertia moment of the mirror substrate 201 is reduced by the thinning of the mirror substrate 201 as described above, and the mirror substrate 201 is further less likely to be deformed by the corresponding amount. Further, the deviation between the center of the mirror surface 205 and the center of the rotation axis of the mirror substrate 201 can be reduced. For example, if the mirror substrate 201 is thinned to half the plate thickness, the center of the mirror surface 205 and the mirror The rotation axis center of the substrate 201 can be matched.
[0065]
[Example 5]
FIG. 8 is a schematic sectional view showing another embodiment of the vibrating mirror of the present invention. The vibrating mirror of this embodiment is a cover substrate made of Pyrex glass on the frame-shaped support portion 204 of the first substrate 200 and the frame-shaped support portion 222 of the second substrate 221 of the vibrating mirrors of the first to fourth embodiments. 300 and the base substrate 301 are respectively anodically bonded, and the vibration space 307 of the mirror substrate 201 is sealed in a reduced pressure state. Since the vibrating mirror having such a pressure reducing sealing means has a small viscous resistance in the vibrating space of the mirror substrate 201, a large deflection angle can be stably obtained with a low driving voltage. Also, dust and the like can be prevented from entering the inside of the vibrating mirror, and the reliability of the vibrating mirror is improved. The electrode pads 213, 214, 229 and 230 are electrically connected to the outside through through electrodes 302 to 305 provided on the cover substrate 300 and the base substrate 301.
[0066]
Note that the bonding method of the cover substrate 300 and the base substrate 301 is not limited to anodic bonding, but anodic bonding of Pyrex glass and silicon can be stably sealed for a long time. Further, the cover substrate 300 can be formed of a material such as resin or ceramics as long as it has at least a window portion through which light passes. The base substrate 301 can also be formed from a material such as resin or ceramics. Further, a sealing container that accommodates the entire vibration mirror can be used as the sealing means.
[0067]
[Example 6]
The vibrating mirror of the present invention described above is suitable for an optical scanning unit of an image forming apparatus such as a photographic printer or copying machine. FIG. 9 is a schematic configuration diagram for explaining an example of an image forming apparatus using the vibrating mirror of the present invention.
[0068]
In FIG. 9, reference numeral 801 denotes an optical writing device, and 802 denotes a photosensitive drum (image carrier) that provides a scanned surface of the optical writing device 801. The optical writing device 801 scans the surface (surface to be scanned) of the photosensitive drum 802 in the axial direction of the photosensitive drum 802 with one or a plurality of laser beams modulated by a recording signal. The photosensitive drum 802 is driven to rotate in the direction of an arrow 803, and an optical latent image is formed by optical scanning of the surface charged by the charging unit 804 by the optical writing device 801. The electrostatic latent image is visualized as a toner image by the developing unit 805, and the toner image is transferred to the recording paper 808 by the transfer unit 806. The transferred toner image is fixed on the recording paper 808 by the fixing unit 807. The cleaning unit 809 removes residual toner from the surface portion of the photosensitive drum 802 that has passed through the transfer unit 806. It is obvious that a belt-like photoconductor may be used instead of the photoconductor drum 802. It is also possible to adopt a configuration in which the toner image is once transferred to a transfer medium, and the toner image is transferred from the transfer medium to a recording sheet and fixed.
[0069]
The optical writing device 801 includes a light source unit 820 that emits one or a plurality of laser beams modulated by a recording signal, the vibration mirror 821 of the present invention as described above, and the mirror surface of the mirror substrate of the vibration mirror 821. An image forming optical system 822 for forming an image of the laser beam from the light source unit 820 and one or a plurality of laser beams reflected by the mirror surface are imaged on the surface (scanned surface) of the photosensitive drum 802. Scanning optical system 823. The vibration mirror 821 is incorporated in the optical writing device 801 in a form mounted on the circuit board 825 together with the integrated circuit 824 for driving the vibration mirror 821.
[0070]
The optical writing device 801 having such a configuration has the following advantages. As described above, the vibrating mirror 821 according to the present invention has less deformation of the mirror substrate and the beam shape is stable, so that writing with a stable beam spot diameter is possible, and moreover, it is more suitable for driving than a rotating polygon mirror. Since the power consumption is small, it is advantageous for improving the image quality and power saving of the image forming apparatus. Since the wind noise during vibration of the mirror substrate of the vibrating mirror 821 is smaller than that of the rotary polygon mirror, it is advantageous for improving the quietness of the image forming apparatus. The vibration mirror 821 requires much less installation space than the rotary polygon mirror, and the heat generation amount of the vibration mirror 821 is also small, so the optical writing device 801 can be easily downsized, and thus the image forming apparatus. This is advantageous for downsizing. In addition, since the vibrating mirror can perform high-speed reciprocating scanning, the image recording speed can be increased.
[0071]
Note that the conveyance mechanism for the recording paper 808, the driving mechanism for the photosensitive drum 802, the control means such as the developing unit 805 and the transfer unit 806, the driving system for the light source unit 820, and the like may be the same as those in the conventional image forming apparatus. It is omitted.
[0072]
【The invention's effect】
(1) Claims 1 and 2According to this invention, since the deformation | transformation at the time of the vibration of the mirror substrate of a vibration mirror is suppressed by a rib, the stable beam shape can be obtained. Since the rib is formed on the insulating film formed on the mirror substrate, the rib with high dimensional accuracy can be easily formed by etching. Since the rib is insulated from the mirror substrate, the provision of the rib has no particular effect on the electric field between the movable electrode and the drive electrode of the mirror substrate, and does not adversely affect the behavior of the mirror substrate.In addition, the plurality of bracing ribs can reduce deformation in the direction perpendicular to the beam that is most deformed by the moment of inertia when the mirror substrate vibrates, and at the same time reduce deformation in the direction parallel to the beam. It is possible to obtain a stable beam shape not only in the direction orthogonal thereto.
(2) According to the invention of claim 2, since the rib can be formed at the same time in the etching process for forming the second drive electrode in the vibrating mirror having the two-stage electrode structure, the manufacturing by providing the rib. No process changes are required. In addition, since the rib is provided on the back surface side of the mirror substrate, the etching area is less biased than when no rib is provided, and the processing accuracy of the second drive electrode is improved. In particular,Claim 3According to the invention, since the etching can be uniformly progressed from the comb-tooth portion of the second drive electrode, the variation in the comb-tooth shape and the etching rate of the second drive electrode is reduced, and the resonance frequency and the like are varied. A reproducible vibration mirror with less reproducibility
(3) Claim 4According to the invention, since the vibration in the scanning direction of the mirror substrate is stabilized, a stable beam shape can be obtained.
(4) Claim 5According to the invention, the moment of inertia of the mirror substrate is reduced, and accordingly, the mirror substrate is less likely to be deformed during vibration. Further, the deviation between the center of the mirror surface and the center of the rotation axis of the mirror substrate can be reduced and matched.
(5) Claim 6According to this invention, the viscous resistance of the vibration space of the mirror substrate is reduced, and a large deflection angle can be stably obtained with a low driving voltage. Also, dust and the like can be prevented from entering the inside of the vibrating mirror, and the reliability of the vibrating mirror is improved.
(6) Claim 7According to the invention, with a simple manufacturing process, the machining accuracy is high and the variation in the resonance frequency is small.Claims 1 to 5The oscillating mirror according to the invention can be manufactured.Claim 8According to this invention, it is possible to process the ribs with high accuracy, and it is easy to optimize with a wide degree of freedom in designing the shape of the ribs.
(7) Claim 9According to this invention, writing with a stable beam spot diameter is possible, high-speed writing by reciprocating scanning is possible, and a compact optical writing device with low power consumption and excellent quietness can be realized.
(8) Claim 10According to this invention, it is possible to form a high-quality image at high speed, and to realize a compact image forming apparatus with low power consumption and excellent quietness.
[Brief description of the drawings]
FIGS. 1A and 1B are a schematic plan view and a schematic cross-sectional view showing an example of a vibrating mirror having a two-stage electrode structure according to the invention of the present applicant.
FIG. 2 is a waveform diagram showing a driving voltage waveform of a vibrating mirror having a two-stage electrode structure and a vibrating waveform of a mirror substrate.
FIGS. 3A and 3B are a schematic plan view and a schematic cross-sectional view for explaining an embodiment of the vibrating mirror of the present invention. FIGS.
4 is an explanatory diagram of a manufacturing process of the vibrating mirror shown in FIG. 3;
FIGS. 5A and 5B are a schematic cross-sectional view and a schematic plan view for explaining another embodiment of the vibrating mirror of the present invention. FIGS.
FIGS. 6A and 6B are a schematic cross-sectional view and a schematic plan view for explaining another embodiment of the vibrating mirror of the present invention. FIGS.
FIG. 7 is a schematic cross-sectional view for explaining another embodiment of the vibrating mirror of the present invention.
FIG. 8 is a schematic cross-sectional view for explaining another embodiment of the vibrating mirror of the present invention.
FIG. 9 is a schematic configuration diagram for explaining one embodiment of an optical writing device and an image forming apparatus of the present invention.
[Explanation of symbols]
200 First substrate
201 mirror substrate
202,203 torsion beam
204 Frame support
206,207 Movable electrode
208,209 First drive electrode
123,214 electrode pads
220 Insulating film
221 Second substrate
222 Frame support
223,224 Second drive electrode
229,230 Electrode pad
250 ribs
300 Cover substrate
301 Base substrate
302 to 305 Through electrode
801 Optical writing device
821 Vibration mirror
802 Photosensitive drum
805 Development section
806 Transfer section

Claims (10)

A mirror substrate; two beams that support central portions of two opposite sides of the mirror substrate; and a drive electrode for electrostatically driving the mirror substrate. A vibrating mirror that reciprocally vibrates as a torsional rotation shaft, wherein the mirror substrate includes an insulating film formed on a surface opposite to a surface on which the mirror surface is formed, and a bracing formed on the insulating film . A vibrating mirror having a plurality of reinforcing ribs. A mirror substrate, two beams, a frame-like support portion that supports the central portion of two opposite sides of the mirror substrate via the beams, and the frame-like support that faces two unsupported sides of the mirror substrate A first drive electrode formed at a portion of the first portion and a second drive electrode joined to the first frame-like support portion via an insulating film and overlapping the first drive electrode, The mirror substrate is an oscillating mirror that reciprocally vibrates about the beam as a torsional rotation axis by being electrostatically driven by the first drive electrode and the second drive electrode, and the mirror substrate includes: An oscillating mirror comprising: an insulating film formed on a surface opposite to a surface on which a mirror surface is formed; and a plurality of reinforcing ribs formed on the insulating film. The said 1st drive electrode and the said 2nd drive electrode are comb-tooth shape, The comb-tooth part of the said 2nd drive electrode is located on the extension line of the said rib, The Claim 2 characterized by the above-mentioned. Vibration mirror. 4. The vibrating mirror according to claim 1, wherein the center of gravity of the entire rib and the center of gravity of the mirror substrate coincide with each other in an in-plane direction. 5. The vibrating mirror according to claim 1, wherein the mirror surface is formed on a surface that is hollowed in a concave shape leaving a peripheral edge of the mirror substrate. 6. The vibrating mirror according to claim 1, further comprising a sealing unit for sealing the vibration space of the mirror substrate, wherein the vibration space is sealed in a reduced pressure state. . 6. A vibrating mirror manufacturing method according to claim 1, wherein the vibrating mirror according to claim 1 is manufactured by etching two single crystal silicon substrates bonded via an insulating film. The method for manufacturing a vibrating mirror according to claim 7, wherein the etching process for forming the rib is performed by dry etching. 7. The vibrating mirror according to claim 1, means for causing a light beam to be incident on a mirror surface of a mirror substrate of the vibrating mirror, and a light beam reflected by the mirror surface is coupled to a surface to be scanned. And an optical writing device. 7. The oscillating mirror according to claim 1, an image carrier, means for causing a light beam modulated by a recording signal to enter a mirror surface of a mirror substrate of the oscillating mirror, and the mirror Means for forming an image of the light beam reflected by the surface on the image carrier, and an electrostatic latent image formed on the image carrier by the light beam being imaged by the means for image formation An image forming apparatus comprising: a developing unit that visualizes the toner image with toner; and a transfer unit that transfers the toner image visualized by the developing unit to a recording sheet.

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