JP3785663B2 - LIGHT MODULATION DEVICE, ITS MANUFACTURING METHOD, AND ELECTRONIC DEVICE USING THE LIGHT MODULATION DEVICE - Google Patents

Description

図１に示すガラス製電極基板２００は、中央領域に凹部２０２を有し、その周囲に立ち上げ部２０４を有する。立ち上げ部２０４の一辺は切り欠かれて電極取出口２０６とされ、この電極取出口２０６の外側には、凹部２０２と連続する電極取出板部２０８が形成されている。
【００６９】
このガラス製電極基板２００の凹部２０２には、Ｘ方向で隣り合う２つの微小ミラー２０２間のトーションバー１０４と対向する位置にて、凹部２０２より突出形成され、立ち上げ部２０４の天面と同じ高さを有する多数の支柱部２１０を有する。
【００７０】
さらに、ガラス製電極基板２００の凹部２０２及び電極取出板部２０８上には、配線パターン部２１２が形成されている。この配線パターン部２１２は、図２に示すように、トーションバー１０４を挟んだ両側の微小ミラー１０２の裏面と対向する位置に、それぞれ第１，第２のアドレス電極２１４，２１６を有する。そして、Ｙ方向に沿って配列された第１のアドレス電極２１４は第１の共通配線２１８に共通接続されている。同様に、Ｙ方向に沿って配設された第２のアドレス電極２１６は、第２の共通配線２２０に共通接続されている。
【００７１】
上記の構造を有するガラス製電極基板２００の上に、図１に示すようにして、シリコン製ミラー基板１００が陽極接合される。このとき、シリコン製ミラー基板１００のトーションバー１０４の両端部及び枠状部１０６と、ガラス製電極基板２００の立ち上げ部２０４とが接合される。さらに、シリコン製ミラー基板１００のトーションバー１０４の中間部と、ガラス製電極基板２００の支柱部２１０とが陽極接合される。さらにその後、シリコン製ミラー基板１００の枠状部１０６上に、カバーガラス基板３００が接合される。そして、枠状部１０６と連結されていた各々のトーションバー１０４の両端部が、枠状部１０６から切り離される位置にてダイシングされる。さらに、ガラス製電極基板２００の立ち上げ部２０４に切り欠き形成された電極取出口２０６を含む周縁部が、封止材により封止密閉され、第１実施例に係る光変調装置が完成する。ここで、光変調装置の内部を種々の方法により真空にすると、微小ミラーの駆動時に抵抗が少なく、応答動作の高速性、消費電力の低下が図られる。
【００７２】
光変調駆動原理の説明
微小ミラー１０２のＯＮ傾斜駆動の際には、図１に示すＸ方向に沿って配列された複数の微小ミラー１０２に対して、トーションバー１０４を介して同時に通電する。一方、これと同時に図１に示す第１，第２のアドレス電極２１４、２１６を一組として点順次又は線順次で駆動し、通電されるトーションバー１０４を、図１のＹ方向に向けて順次選択することで、マトリックス状に配列された微小ミラー１０２を所定のサイクルにてＯＮ傾斜駆動することができる。
【００７３】
一方、微小ミラー１０２をＯＦＦ傾斜駆動するには、第１，第２のアドレス電極２１４，２１６に加わる電圧の極性を、ＯＮ傾斜駆動時とは逆にすればよい。これにより、微小ミラー１０２はＯＮ傾斜駆動時とは逆の方向に傾斜駆動される。
【００７４】
光変調装置の製造方法の説明
第１実施例に係る光変調装置の製造方法について、図４及び図５を参照して説明する。まず、シリコン製ミラー基板１００の製造プロセスについて説明する。
【００７５】
（Ｉ）シリコン製ミラー基板１００の製造プロセス
（１）ドープ層を有するシリコン基板の形成工程
この工程では、図４（Ａ）に示すシリコン基板１１０の片面に、図４（Ｂ）に示すドープ層１１２を形成している。このために、シリコン基板１１０上に、例えばボロンドープ材をスピンコーティング法にて塗布する。このボロンドープ材は、有機溶剤の中にＢ₂Ｏ₃を混ぜたもので、例えば東京応化（株）のＰＢＦを用いることができる。このとき、ボロンドープ材の膜厚は、シリコン基板１１０のスピン回転条件及びボロンドープ材の粘度に依存して調整できる。
【００７６】
本実施例では、ボロンドープ材の粘度を５０〜１００ｃｐとし、スピン回転条件を変化させることで、ボロンドープ材の膜厚を０．５〜５．０μｍの範囲で変化させることができた。
【００７７】
このボロンドープ材のスピンコーティング後に、加熱炉にて１００〜１８０℃で２０〜４０分間加熱し、ボロンドープ材中の溶剤を蒸発させるとよい。本実施例では、１４０℃にて３０分間ベークを行った。さらに、４００〜８００℃の酸素雰囲気炉で１〜２時間焼成し、バインダーを除去する。本実施例では、６００℃で１時間の焼成を行った。その後の熱拡散工程は、窒素雰囲気中で８００〜１２００℃で４時間から１０時間かけて熱拡散が行われる。本実施例では、１１００℃にて６時間熱拡散工程を実施した。
【００７８】
この結果、ボロンドープ材中のボロン（Ｂ）がシリコン基板１１０の内部に熱拡散され、シリコン基板１１０の下面に、図４（Ｂ）に示すボロンドープ層１１２を形成することができた。この熱拡散工程での温度及び処理時間により、ボロンドープ層１１２の厚さを調整することができ、本実施例では１０００℃で６時間かけて熱拡散処理を行うことで、２〜３μｍのボロンドープ層１１２を形成することができた。
【００７９】
このとき、ボロンドープ１１２中のボロン濃度は、好ましくは１×１０¹⁸ａｔｍ／ｃｍ³以上であることが好ましい。こうすると、後述するシリコン基板１１０のエッチング工程において、このボロンドープ層１１２をエッチングストップ層として機能させることができる。
【００８０】
ボロンドープ層を形成するには、ボロン拡散板法を採用することもできる。このとき、シリコン基板のボロンドープしたい面を、例えばテクネグラス社製のボロンプラス板（商品名）を対向させて配置する。両者間の間隔は、０．５〜４．０ｍｍ、さらに好ましくは２．０〜３．０ｍｍとするとよい。この対向配置関係を維持したまま、加熱炉にて８００〜１２００℃、例えば１１００℃で、窒素流量３〜８リットル／ｍｉｎ例えば６リットル／ｍｉｎにて、１時〜６時間例えば２時間かけて熱拡散工程を実施してもよい。
【００８１】
さらに他の方法として、イオン注入法を採用してもよい。この時の加速エネルギーは２０〜５０ｋｅＶで、最適値は３５ｋｅＶである。また、加速電子の数を示すドーズ量は、２×１０¹⁸〜８×１０¹⁸個が適当で、望ましくは４×１０¹⁸個である。さらに、ビーム電流は１．５〜４．５ｍＡが適当で、望ましくは３．０ｍＡである。これらの条件でイオン打ち込みを行うと、０．５〜４μｍのボロンドープ層が形成できた。
【００８２】
（２）熱酸化工程
次に、ボロンドープ層１１２が形成されたシリコン基板１１０を熱酸化炉に搬入し、図４（Ｃ）に示すように、このシリコン基板１１０の周囲に熱酸化膜１１４を形成する。本実施例では、ウェット酸化法にて１０００℃の温度にて４時間かけて熱酸化処理を行うことで、１μｍの厚さの熱酸化膜１１４を形成した。このとき、ボロンドープ層１１２も熱酸化され、その表面にも熱酸化膜１１４が形成される。
【００８３】
（３）パターニング工程
次に、熱酸化膜１１４を有するシリコン基板１１０を、ホトリソグラフィ工程を実施することで、図４（Ｄ）に示すようにパターニングを行った。同図に示すとおり、シリコン基板１１０の表面側には、中心領域に窓を形成するための第１のマスク１１６をパターニングした。シリコン基板１１０のボロンドープ層１１２を有する下面は、図１〜３に示す微小ミラー１０２、トーションバー１０４、枠状部１０６及びスリット１０８などを形成するための第２のマスク１１８をパターニングした。このパターニングのために、熱酸化膜１１４の表面及び裏面にそれぞれレジスト塗布、露光及び現像を行った。現像工程後、緩衝フッ酸溶液を用いて所定領域の熱酸化膜（酸化シリコン膜）１１４を除去した。その後レジスト剥離を行うことでパターニング工程が終了する。このレジスト剥離は、例えば硫酸と過酸化水素水の混合液を８０℃にて加熱して使用することができる。
【００８４】
（４）シリコン基板１１０のエッチング工程
次に、図４（Ｅ）に示すように、シリコン基板１１０の上面側に形成された第１のマスク１１６を使用して、シリコン基板１１０をエッチングして除去した。このエッチング工程は、１〜４０重量％の濃度のＫＯＨ水溶液を用いて、シリコン基板１１０をウエットエッチングした。ＫＯＨ水溶液の濃度は、１０重量％前後が最適である。このエッチング工程の反応は、下記の反応式に従って行われる。
【００８５】
Ｓｉ＋２ＫＯＨ＋Ｈ₂Ｏ→Ｋ₂ＳｉＯ₃＋２Ｈ₂
ここで、図４（Ｅ）に示すように、シリコン基板１１０の表面１１０ａの結晶面方位を（１００）とすると、エッチングにより形成される側壁１１０ｂは５５℃の角度を持った傾斜壁となる。これに対して、表面１１０ａの結晶面方位を（１１０）とすると、側壁１１０ｂはほぼ垂直な壁とでき、異方性の高いエッチングを実現できる。こうすれば、より広い面積を光変調が可能な面とすることができる。
【００８６】
この場合のエッチング終点検出は、シリコン基板１１０の反応により生ずる水素気泡を観測し、水素気泡がなくなった時点を終点とすることができる。あるいは、ボロンドープ層１１２の不純物濃度を、１×１０¹⁸ａｔｍ／ｃｍ³以上とすることで、このボロンドープ層１１２をエッチングストップ層として機能させることができる。
【００８７】
なお、この工程で用いられるエッチング液としては、ＫＯＨ水溶液以外では、ＴＭＡＨ（テトラメチル水酸化アンモニウム）水溶液、ＥＰＤ（エチレンジアミン−ピロカテコール−ジアジン）水溶液またはヒドラジン水溶液などを使用することができる。
【００８８】
（５）ボロンドープ層１１２のエッチング工程
次に、図４（Ｆ）に示すように、熱酸化膜１１４の下面に形成された第２のマスク１１８を使用して、ボロンドープ層１１２をドライエッチングする。
【００８９】
このドライエッチングは、エッチング速度が速く量産に適したＲＩＥ（反応性イオンエッチング）を用いることが好ましい。このとき、処理ガスとして、ＣＦ₄を３０〜６０ｓｃｃｍ、Ｏ₂を３０〜６０ｓｃｃｍ導入し、１３．５６ＭＨｚの高周波電源のパワーを、４００〜８００Ｗ、特に最適地として６００Ｗに設定した。チャンバ内圧力は、好ましくは０．０５〜０．３０Ｔｏｒｒであり、本実施例では最適値である０．１５Ｔｏｒｒを採用した。本実施例では２μｍのボロンドープ層をエッチングするのに、１５〜３０分のエッチング時間を要した。
【００９０】
このボロンドープ層１１２をドライエッチングすることで、図１〜３に示す微小ミラー１０２、トーションバー１０４、枠状部１０６及びスリット１０８がそれぞれ形成される。
【００９１】
（６）熱酸化膜１１４の剥離工程
この熱酸化膜１１４は、（５）の工程の耐エッチングマスク材として使用された後に剥離される。剥離させる方法としては、例えば、（３）パターニング工程で説明したように、緩衝フッ酸溶液を用いることができる。また、１０％程度の希フッ酸溶液を用いても良い。この工程の実施例により、図４（Ｇ）に示すように、ボロンドープ層１１２で形成された枠状部１０６に、微小ミラー１０２、トーションバー１０４などが支持された状態を得ることができる。
【００９２】
（７）反射層１０２ａの蒸着工程
次に、ボロンドープ層１１２にて形成された微小ミラー１０２の表面に、例えばアルミニウム（Ａｌ）からなる反射層１０２ａを、例えば０．２〜２μｍの厚さにて蒸着する。反射層１０２ａの膜厚が上限を越えると、微小ミラー１０２の慣性モーメントが大きくなって、駆動時の応答速度が遅くなったり、傾斜駆動する際の駆動電圧が高くなる。上記膜厚範囲の下限を下回ると、ボロンドープ層１１２の全面に均一厚さで反射層１０２ａを形成することが困難となる。
【００９３】
このとき、微小ミラー１０２の表面以外の部分、すなわちトーションバー１０４にはＡｌが付着しないようにマスキングしてもよいが、本実施例のようにトーションバー１０４上にも反射層１０２ａを形成してもよい。枠状部１０６の表面に残存するシリコン基板１１０の天面は、その後ガラス製電極基板２００と陽極接合される領域であるため、この部分に陽極接合を妨げる異物が付着しないようにマスキングすることが重要である。
【００９４】
なお、反射層１０２ａの材質としては、可視光を効率よく反射できるものであればよく、例えば銀（Ａｇ）を用いることもできる。また、反射層１０２ａの形成工程は、必ずしも蒸着方法を用いるものに限らず、例えばスパッタを採用することもできる。
【００９５】
この反射層１０２ａの形成工程では、その下地材であるボロンドープ層１１２が平坦であるから、その上に形成される反射層１０２ａも平坦に形成することができる。これにより、反射層１０２ａに入射される光を、その入射角と等しい反射角にて反射させることができ、この光変調装置を用いて表示装置を構成した場合、コントラストを向上させることが可能となる。
【００９６】
以上の各工程の実施により、図１〜３に示すシリコン製ミラー基板１００が完成する。この後、図４（Ｉ）に示すように、シリコン製ミラー基板１００、ガラス製電極基板２００及びカバーガラス基板３００の接合が行われることになる。この接合工程を説明する前に、図５を参照して、ガラス製電極基板２００の製造プロセスについて説明する。
【００９７】
（ＩＩ）ガラス製電極基板２００の製造プロセス
図５（Ａ）に示すように、ガラス製電極基板２００のベースとなるガラス基板２３０は、後述する陽極接合を行うために、アルカリ金属例えばナトリウム（Ｎａ）を含有したガラス基板を用いている。この種のガラス基板２３０としては、ホウケイ酸ナトリウムガラスを用いることができ、例えばコーニング社製のパイレックスガラス（商品名）を用いることができる。特に、陽極接合時にガラス基板２３０を加熱するため、シリコンと熱膨張係数がほぼ等しいことを考慮すると、コーニング＃７７４０（商品名）が最適である。
【００９８】
以下、このガラス基板２３０を用いたガラス製電極基板２００の製造プロセスについて説明する。
【００９９】
（１）凹部２０２等のパターニング工程
ガラス基板２３０上へのレジスト塗布、露光及び現像工程を実施することで、図５（Ｂ）に示すように、ガラス基板２３０の表面に、レジストパターン部２３２を形成する。レジストパターン部２３２は、立ち上がり部２０４、支柱部２１０の相当箇所に形成される。
【０１００】
（２）凹部２０２等の形成のためのエッチング工程
このレジストパターン部２３２をマスクとして、ガラス基板２３０をフッ酸水溶液を用いてウエットエッチングする。これにより、図５（Ｃ）に示す凹部２０２の他、電極取出口２０６及び電極取出板部２０８も同時に形成される。この凹部２０２の深さは、処理時間及び温度などのエッチング条件を変更することで調整できる。
【０１０１】
この凹部２０２の深さは、微小ミラー１０２の振れ角を決める重要な要素であるため、上記のエッチング条件を調整して、ロット間で等しい深さの凹部２０２を形成する必要がある。
【０１０２】
（３）レジスト剥離工程
このレジスト剥離は、硫酸＋過酸化水素水の混合液を用いることで行うことができ、これにより図５（Ｄ）に示すように、ガラス基板２３０に形成された立ち上げ部２０４の天面から、レジストパターン部２３２を剥離させることができる。
【０１０３】
（４）配線パターン部２１２の形成工程
この配線パターン部２１２を、凹部２０２及び電極取出板部２０８上に形成するために、まず、図５（Ｅ）に示すように、ガラス基板２３０の全面に、例えばアルミニウム（Ａｌ）、銀（Ａｇ）、金（Ａｕ）又はＩＴＯにて代表される透明電極などを材質とする電極膜２３４を形成する。この電極膜２３４は、蒸着法、スパッタ法又はイオンプレーティング法等により形成することができる。その後、この電極膜２３４上に、ホトリソグラフィ工程を実施することでレジストパターン部２３６を形成する（図５（Ｆ）参照）。その後、このレジストパターン部２３６をマスクとして使用して、電極膜２３４をエッチングする。このエッチングは、ウエットエッチングにより実施できる。
【０１０４】
その後、図５（Ｇ）に示すように、配線パターン部２１２上のレジストパターン部２３６を剥離することで、ガラス製電極基板２００が完成する。このとき用いる剥離材は、電極膜２３４の材質により適宜選択される。電極膜２３４の材質をＩＴＯとすることもできる。この場合には、硫酸＋過酸化水素水の混合液からなる剥離液は、ＩＴＯ自体が溶解するため使用できないので、その代わりに有機溶剤系の剥離液を使用することができる。
【０１０５】
（ＩＩＩ）シリコン製ミラー基板１００とガラス製電極基板２００との陽極接合
図６に示すように、位置合わせ機構３１４上に搭載されたホットプレート３１０上にガラス製電極基板２００を載置し、その上にシリコン製ミラー基板１００を載置する。このとき、ガラス製電極基板２００に形成された第１，第２のアドレス電極２１４，２１６と、シリコン製ミラー基板１００に形成された微小ミラー１０２とが、それぞれ対向する位置に位置合わせする。この位置合わせは、上方より顕微鏡３１６にて観察しながら、位置合わせ機構３１４によりガラス製電極基板２００を二次元平面で移動させることで行われる。
【０１０６】
また、陽極接合の際に、基板１００、２００間にゴミなどの異物が混入していると、微小ミラー１０２と配線パターン部２１２とがショートし、不良品となってしまう。そこで、両基板１００、２００を接合する前に、異物混入の有無を確認する検査を行うことが重要である。この検査は、両基板１００、２００を重ね合わせる前に行うことができると共に、配線パターン部２１２を透明電極例えばＩＴＯにて形成した場合には、両基板を重ね合わせても、ガラス製電極基板２００の下側より顕微鏡にて観察して行うことができる。
【０１０７】
その後、シリコン製ミラー基板１００及びガラス製電極基板２００を直流電源３１２に接続する。シリコン製ミラー基板１００は電源３１２のプラス端子に、ガラス製電極基板２００は電源３１２のマイナス端子にそれぞれ接続される。そして、ホットプレート３１０により、ガラス製電極基板２００を２５０〜４５０℃、例えば３５０℃に加熱し、電源３１２より３００〜１０００Ｖ、例えば６００Ｖの電極を２〜３分間印加する。
【０１０８】
そうすると、ホットプレート３１０により加熱されることで、ガラス製電極基板２００中のＮａ（プラス）が移動しやすくなる。このＮａ（プラス）の移動により、ガラス製電極基板２００の接合面はマイナスに帯電し、シリコン製ミラー基板１００の接合面はプラスに帯電する。この結果、両接合面間には大きなクーロン力が作用し、界面で化学結合が生じて静電接合が行われることになる。これにより、シリコン製ミラー基板１００とガラス製電極基板２００とを強固に接合することができる。
【０１０９】
この陽極接合により、シリコン製ミラー基板１００のトーションバー１０４の両端部及び枠状部１０６が、ガラス製電極基板２００の立ち上げ部２０４と接合され、シリコン製ミラー基板１００のトーションバー１０４の中間部は、ガラス製電極基板２００の支柱部２１０と接合される。
【０１１０】
このように、シリコン製ミラー基板１００とガラス製電極基板２００とを陽極接合することで、接着剤を用いた場合のように、接着層の厚みを要することなく、両者を確実に接合できる。しかも、接着剤を用いた場合とは異なり、接着層の厚さがばらつくくこともないので、図３（Ｂ）に示す凹部深さＨをロット間でほぼ一定に設定することができる。この凹部深さＨは、微小ミラー１０２の振れ角θを決定するものであるが、陽極接合によりこの振れ角θをもロット間で均一に設定することが可能なる。
【０１１１】
カバーガラス基板３００を、ガラス製電極基板２００と同様にＮａを含有するガラス基板で構成すれば、シリコン製ミラー基板１００の枠状部１０６に対して、このカバーガラス基板３００を同様に陽極接合することができる。但し、シリコン製ミラー基板１００とカバーガラス基板３００との接合は、精度を要するものではないので、他の接合方法例えば接着剤を用いた接合方法を採用することもできる。
【０１１２】
（ＩＶ）封止、ダイシング及び配線工程
（１）封止工程
電極取出口２０６を封止材により封止して密閉する。こうすると、下記の（２）ダイシング工程にて、シリコン製ミラー基板１００およびガラス製電極基板２００の間に異物、水などが侵入することを防止できる。この結果、微小ミラー１０２と配線パターン部２１２とがショートすることを防止でき、処理の歩留まりを向上させることができる。また、下記の（２）ダイシング工程後には、光変調素子３３０の２つの側面に、図７（Ｂ）に示すようにトーションバー１０４の板厚分の微細な間隙２４０が生じるので、この微細な間隙２４０も同様にして封止することができる。
【０１１３】
（２）ダイシング工程
図７（Ａ）に示すように、上記のようにして得られる光変調素子３３０を複数個同時に、図４（Ａ）に示すシリコン基板１１０を構成する１枚のウェハ３２０上に形成することができる。このため、光変調素子３３０の完成後に、ウェハ３２０をダイシングして、個々の光変調素子３３０に分離している。このダイシング工程により、枠状部１０６に連結されていたトーションバー１０４の両端が切り離され、図１のＹ方向にて分離されて１本ずつ独立した電極として機能する。ダイシングにより分離された光変調素子３３０は図７（Ｂ）に示す通りである。
【０１１４】
（３）配線工程
その後、分離された光変調素子３３０を、図示しない基板上に固定し、配線を行う。図７（Ｂ）に示すように、電極取出板３０８上の配線パターン部２１２と、側面に露出するトーションバー１０４の端部とを、図示しない駆動回路に接続することで配線工程を実施する。こうして、光変調装置が完成する。
【０１１５】
（第２実施例）
次に、高密度実装が可能な光変調装置について、図８〜図１０を参照して説明する。
【０１１６】
高密度光変調装置の全体構成
この第２実施例に係る光変調装置は、図８及び図９に示すように、大別してシリコン製ミラー基板４００、ガラス製電極基板５００及びカバーガラス基板６００を有する。シリコン製ミラー基板４００とガラス製電極基板５００とは、第１実施例と同様に陽極接合される。シリコン製ミラー基板４００とカバーガラス基板６００との位置関係は、微小ミラーの振れ角には影響がないので、第１実施例と同様に、両基板４００、６００を陽極接合以外の例えば接着剤を用いて接合してもよい。
【０１１７】
このシリコン製ミラー基板４００は、図８のＸ方向及びＹ方向にてマトリクス状に配列された微小ミラー４０２と、Ｘ方向に配列された微小ミラー４０２を連結するトーションバー４０４と、このトーションバー４０４の端部を連結する枠状部４０６とを有する。トーションバー４０４が微小ミラー４０２と連結される連結部の周囲にはスリット４０８が形成されている。また、トーションバー４０４の一端４０４ａは、枠状部４０６に直接連結されているのに対し、その他端４０４ｂは、広い面積のミラー用電極４１０を介して枠状部４０６と連結されている。
【０１１８】
枠状部４０６の一辺には、アドレス電極取出口４１２が切り欠き形成されている。そして、多数の微小ミラー４０２が配列された領域と、アドレス電極取出口４１２とを仕切る仕切り部４１４が設けられている。
【０１１９】
このシリコン製ミラー基板４００は、シリコン基板上に複数同時に形成され、ダイシング工程の際には、図８に示すＡ〜Ｄの４箇所の位置に沿って、他のシリコン製ミラー基板と分離される。
【０１２０】
図８に示すガラス製電極基板５００は、中央領域に形成された凹部５０２と、その周囲にて立ち上げ形成された立ち上げ部５０４を有する。この凹部５０２には、シリコン製ミラー基板４００の仕切り部４１４と対向する位置に中間リブ５０６が設けられてる。さらに、凹部５０２には、図８のＸ方向にて隣接する２つの微小ミラー４０２，４０２の間に位置するトーションバー４０４と対向する位置に、支柱部５０８を有する。ガラス製電極基板５００の凹部５０２には、中間リブ５０６の両側にて、図８のＹ方向に沿って複数本の配線パターン部５１０が形成されている。この配線パターン部５１０は、トーションバー４０４を境にして微小ミラー４１２の２つの領域と対向する第１，第２のアドレス電極５１２，５１４を有する。図８のＹ方向に沿って配列された複数の第１のアドレス電極５１２は、第１の共通配線５１６に共通接続されている。同様に、図８のＹ方向に沿って配列された複数の第２のアドレス電極５１４は、第２の共通配線５１８に共通接続されいてる。そして、第１，第２の共通配線５１６，５１８の端部５１６ａ，５１８ａが、中間リブ５０６を越えた位置まで延在形成されている。
【０１２１】
なお、このガラス製電極基板５００も、一枚のガラス基板上に複数同時に形成され、その後一つの光変調素子に分離する際にダイシングされる。
【０１２２】
このガラス製電極基板５００をシリコン製ミラー基板４００と陽極接合した際には、第１，第２の共通配線５１６，５１８の各端部５１６ａ，５１８ａは、シリコン製ミラー基板４００に開口形成されたアドレス電極取出口４１２を介して露出される。なお、シリコン製ミラー基板４００とガラス製電極基板５００とが陽極接合された際には、第１実施例と同様に、シリコン製ミラー基板４００のトーションバー４０４の両端部４０４ａ，４０４ｂ及び枠状部４０６と、ガラス製電極基板５００の立ち上げ部５０４とが陽極接合される。また、シリコン製ミラー基板４００のトーションバー４０４の中間部が、ガラス製電極基板５００の支柱部５０８に陽極接合される。この第２実施例ではさらに、シリコン製ミラー基板４００の仕切り部４１４が、ガラス製電極基板５００の中間リブ５０６と陽極接合されるようになっている。
【０１２３】
図８に示すカバーガラス基板６００は、シリコン製ミラー基板４００に多数形成された微小ミラー４０２の配置領域と対向する位置に凹部６０２を有する。この凹部６０２の周縁には立ち上げ部６０４が形成されてる。製造プロセス上、複数のカバーガラス基板６００が１枚のガラス基板から形成されるようになっており、ガラス基板のダイシングにより図８に示す１つのカバーガラス基板６００が構成される。そして、立ち上げ部６０４の一辺６０４ａは、ダイシングされたトーションバー４０４の一端４０４ａと重合する位置に配置される。立ち上げ部６０４の前記一辺６０４ａと平行な他の一辺６０４ｂは、ダイシングされたトーションバー４０４の他端４０４ｂと重合する位置に配置される。この結果、シリコン製ミラー基板４００のミラー用電極４１０は外部に露出することになる。立ち上げ部６０４の前記各一辺６０４ａ，６０４ｂと直交する他の二辺６０４ｃ及び６０４ｄは、それぞれシリコン製ミラー基板４００の枠状部４０６と仕切り部４１４と重合する位置に配置される。
【０１２４】
この結果、図９に示すように、シリコン製ミラー基板４００に開口形成されているアドレス電極取出口４１２が外部に露出し、ガラス製電極基板５００上に形成された第１，第２の共通配線５１６，５１８への配線が可能となる。なお、この配線後は、アドレス電極取出口４１２は封止材により封止密閉される。また、上述のダイシング工程を実施すると、トーションバー４０４の一端４０４ａ及び他端４０４ｂが存在しない領域では、図９に示すように、ガラス製電極基板５００の立ち上げ部５０４と、カバーガラス基板６００の立ち上げ部６０４との間に、トーションバー４０４の厚み分だけの間隙５１１が生ずる。この間隙５１１も、上記と同様にして封止材により封止密閉される。
【０１２５】
光変調装置の製造プロセスについて
次に、図１０を参照して第２実施例に係る光変調装置の製造プロセスについて説明する。なお、ガラス製電極基板５００の製造プロセスは、図５に示すプロセスと実質的に同一プロセスを適用できる。カバーガラス基板６００は、凹部６０２をエッチング形成するために、図５（Ｂ）〜（Ｄ）のプロセスを適用すればよい。
【０１２６】
以下に、この第２実施例の光変調装置の製造プロセスに特有な点について説明する。
【０１２７】
（１）ボロンドープ層４２２の形成工程
図１０（Ａ）では、シリコン基板４２０の一面に、ボロンドープ層４２２が形成される。このボロンドープ層４２２の形成は、第１実施例と同様にして行われる。
【０１２８】
（２）基板４００，５００の陽極接合工程
この第２実施例に係る光変調装置の製造プロセスにて特有な点は、図１０（Ｂ）に示すように、ボロンドープ層４２２が形成されたシリコン基板４２０を、ガラス製電極基板５００と陽極接合している点である。
【０１２９】
この両基板４００，５００の陽極接合は、第１実施例と同様に、図６に示す装置を用いて実施される。すなわち、ホットプレート３１０上に載置されたガラス製電極基板５００を２５０〜４５０℃の範囲、例えば３５０℃まで加熱する。同時に、両基板４００，５００に直流電源３１２を接続し、ガラス製電極基板５００にはマイナス電圧を、シリコン製ミラー基板４００にはプラス電圧をそれぞれ印加する。こうすると、ガラス製電極基板５００中のＮａ（プラス）が移動し、ガラス製電極基板５００の接続合面がマイナスに帯電し、シリコン製ミラー基板４００の接合面がプラスに帯電し、両接合面間に大きなクーロン力が作用して静電接合される。
【０１３０】
この第２実施例に係る光変調装置が高密度実装に適している理由は、両基板４００，５００を陽極接合する際に、第１実施例のように既に形成された微小ミラーと配線パターン部との厳密な位置合わせを行わなくて済むからである。この厳密な位置合わせは、図１０（Ｅ）に示す反射層４０２ａのパターニングの際に必要となる。
【０１３１】
（３）シリコン基板４２０のウエットエッチング工程
次に、図１０（Ｃ）に示すように、ボロンドープ層４２２上に形成されたシリコン基板４２０を全面エッチングする。この時のウエットエッチングは、第１実施例と同じ例えば１０〜４０重量％の濃度のＫＯＨ水溶液を用い、第１実施例にて示したエッチング反応式従って、シリコンがエッチングされて除去される。エッチング終点検出はシリコン基板４２０の反応により生ずる水素気泡を観測し、水素気泡がなくなった時点を終点とすることができる。あるいは、ボロンドープ層４２２の不純物濃度を、１×１０¹⁸ａｔｍ／ｃｍ³以上とすることで、このボロンドープ層４２２をエッチングストップ層として機能させることができる。
【０１３２】
なお、ウエットエッチングに用いる水溶液は、ＫＯＨ水溶液に限らず、ＴＭＡＨ水溶液、ＥＰＤ水溶液あるいはヒドラジン水溶液などを使用することもできる。
【０１３３】
（４）反射層４０２ａの蒸着工程
次に、図１０（Ｄ）に示すように、ボロンドープ層４２２の全表面に、反射層４０２ａを形成する。この反射層４０２ａとしては、例えばアルミニウム（Ａｌ）を蒸着することで形成している。この反射層４０２ａの膜厚は、第１実施例と同様に０．２〜２μｍとすることができる。
【０１３４】
（５）反射層４０２ａのパターニング工程
次に、図１０（Ｅ）に示すように、一連のホトリソグラフィ工程を実施して、反射層４０２ａ上にレジストパターン部４２４を形成する。このレジストパターン部４２４は、図８に示すシリコン製ミラー基板４００に形成される微小ミラー４０２、トーションバー４０４、枠状部４０６、スリット４０８、ミラー用電極４１０、アドレス電極取出口４１２及び仕切り部４１４の形状と相応している。
【０１３５】
反射層４０２ａがアルミニウム（Ａｌ）で形成された場合には、燐酸と酢酸、硝酸の混合液を３０℃に加熱して、約３分間浸積してウエットエッチングを行うことができる。これにより、図１０（Ｅ）に示すように、反射層４０２ａのパターニングを行うことができる。
【０１３６】
このときに、両面アライメント装置を用いれば、０．５μｍの精度で、パターニングを行うことができる。すなわち、図１０（Ｅ）の下方より、すなわちガラス製電極基板５００の下方側より顕微鏡を介して配線パターン部５１０の位置を認識し、同時に、シリコン製ミラー基板４００の上方側からも顕微鏡にて観測を行う。そして、ガラス製電極基板５００に形成された配線パターン部５１０の認識位置を基準として、レジストパターン部４２４を形成するための露光工程を実施することができる。これにより、微小ミラー４０２などと相応する形状のレジストパターン４２４を、配線パターン部５１０の第１，第２のアドレス電極５１２，５１４と対向する位置に形成することができ、これにより実装密度が高まっても精度のよいパターニングを行うことが可能となる。
【０１３７】
また、両基板４００，５００の両極接合前に、その挟まれた空間に万一異物が混入していたとすると、これを除去することが極めて困難になる。この異物がガラス製電極基板５００の配線パターン部５１０と付着すると、微小ミラー４０２が傾斜駆動された際に、両者間にショートが生じ、不良となって歩留まりが低下してしまう。
【０１３８】
そこで、この第２実施例では、両基板４００，５００の陽極接合の前に、透明なガラス製電極基板５００側から光を照射し、異物の混入があるか否かを検査している。この際に、ガラス製電極基板５００に形成される配線パターン部５１０は、Ａｌ、Ａｇなどの金属に代えて、透明電極例えばＩＴＯとすることが好ましい。こうすると、ＩＴＯの表面に付着している異物をも検出可能となる。
【０１３９】
（６）ボロンドープ層４２２のドライエッチング工程
ボロンドープ層４２２をエッチングするには、ウエットエッチングよりもドライエッチングが適している。その理由は、ウェットエッチングではボロンドープ層４２２のエッチング、水洗、乾燥の一連の工程で、外部から異物が付着したり、乾燥しみが発生したりすることがあるが、ドライエッチングではそれがないからである。
【０１４０】
ボロンドープ層４２２をドライエッチングするには、レジストパターン部４２４を耐エッチングマスク材にしている。このドライエッチングは、第１実施例の図４（Ｆ）の工程と同じ条件で実施できる。
【０１４１】
（７）レジストパターン部４２４の剥離工程
このレジストパターン部４２４は、例えばＵＶアッシング装置により、ドライプロセスにてアッシングして除去することができる。
【０１４２】
（８）カバーガラス基板とシリコン製ミラー基板との接合工程
このカバーガラス基板６００は、第１実施例と同様に、精度の高い接合は不要であるため、陽極接合に代えて、接着剤による接合を行うこともできる。
【０１４３】
（９）封止工程
ダイシング時の水や異物の進入を防止するために、図９に示す電極取出し開口４１２を封止材で封止する。ダイシング後に生ずる図９に示す微細な間隙５１１も、後に同様にして封止される。
【０１４４】
（１０）ダイシング工程
上述した各工程は、複数個の光変調素子を構成するための基板４００，５００及び６００を複数組搭載できるシリコン基板あるいはガラス基板の状態で行われる。そしてカバーガラス基板６００の接合工程が終了した後に、一つ一つの光変調素子に分離するためのダイシングが行われる。このダイシングの際に、図８に示す位置Ａ〜Ｄの位置に沿って、基板４００，５００及び６００がそれぞれダイシングされることになる。これにより、組立中は相互に連結されていた複数本のトーションバー４０４がそれぞれ分離される。
【０１４５】
（１１）配線工程
最後に、分離された光変調素子のミラー電極４１０とアドレス電極５１２、５１４の端部５１２ａ、５１４ａを、図示しない駆動回路に接続して配線を行う。これにより、光変調装置が完成する。
【０１４６】
なお、上述の第１，第２実施例では、シリコン製ミラー基板とガラス製電極基板とを陽極接合した例を示したが、これに代えて他の接合方法を採用することもできる。他の例として、直接接合及び共晶接合を挙げることができる。
【０１４７】
直接接合は、ミラー基板及び電極基板を共にシリコン基板とした場合に利用できる。シリコン基板を良く洗浄し、シリコン基板の接合面の濡れ性を良好とした後に、例えば赤外線顕微鏡を用いて室温下で位置合わせ及び仮止めを行う。その後、仮止めされたシリコン基板を８００〜１２００℃、最適温度として１１００℃にて、窒素雰囲気中で１〜４時間熱処理することで、シリコン基板同士を直接接合することができる。ここで、シリコン基板の濡れ性が良好である時には、シリコン表面元素はＳｉ−Ｏ−Ｈの結合になっている。これを熱処理することにより、脱水反応が生じてＳｉ−Ｏ−Ｓｉの共有結合となり、シリコン基板同士が接合される。
【０１４８】
共晶接合は、電極基板の接合面をアルミニウム（Ａｌ）または金（Ａｕ）とした時に利用できる。これらの金属は、３００〜３５０℃と比較的低温で合金化し易い。例えば、Ａｕ膜を電極基板上にスパッタ法にて形成し、そのＡｕ膜表面にシリコン製ミラー基板を接触させ、３００〜４００℃で１〜２時間熱処理すると、接合界面のＡｕがＳｉ中に拡散してゆき、接合界面がなくなり接合される。
【０１４９】
このように、電極基板の材質としては、採択される接合法に応じて種々選択できる。ただし、接合が加熱下で行われる場合には、シリコンと熱膨張係数が近いことが好ましい。
【０１５０】
（第３実施例）
以下に示す第３実施例は、微小ミラー４０２と第１，２のアドレス電極５１２，５１４との間のショートを確実に防止できる構成を示している。図１１（Ａ）に示すように微小ミラー４０２が第１，第２のアドレス電極５１２，５１４と対向する側の面には、絶縁膜４１６が形成されている。こうすると、微小ミラー４０２と第１，第２のアドレス電極５１２，５１４との間に万一異物１０が存在したとしても、絶縁膜４１６によって、微小ミラー４０２と第１，第２のアドレス電極５１２，５１４との間のショートを防止できる。
【０１５１】
微小ミラー４０２の裏面側に絶縁膜４１６を形成すると、図１１（Ｂ）に示すように、第１，第２のアドレス電極５１２，５１４を微小ミラー４０２の傾動時の傾き角を決定するストッパーとして兼用することもできる。この種の絶縁膜は、例えば第１実施例に示す光変調装置の場合にあっては、図４（Ｇ）に示す熱酸化膜の剥離工程を省略することで実現できる。即ち、図４（Ｃ）にて形成した熱酸化膜１１４を、絶縁膜として兼用することができる。
【０１５２】
微小ミラー４０２と第１，第２のアドレス電極５１２，５１４との間のショートを防止するためには、第１，第２のアドレス電極５１２，５１４の表面に、絶縁をスパッタ装置等の成膜装置によって形成してもよい。
【０１５３】
微小ミラー４０２の裏面に絶縁膜４１６を形成した場合には、第１、第２のアドレス電極５１２、５１４の表面を粗面に形成するとよい。こうすると、微小ミラー４０２と接触する電極５１２、５１４の接触面積を少なくすることができる。粗面に形成しないと、微小ミラー４０２に形成された絶縁膜４１６に、ホットキャリアの帯電がおき、電極５１２、５１４への微小ミラー４０２の張り付きが生じてしまう。電極５１２、５１４の表面を粗面にするだけで、これらの弊害を防止できる。なお、この粗面は、好ましくは２００オングストローク以上の高さを持つ凸部を電極表面に形成することで実現できる。
【０１５４】
第１、第２のアドレス電極５１２、５１４の表面を粗面にするには、例えばスパッタ法による成膜時の条件を変えて粒径の大きなスパッタ粒子を用いて成膜するとよい。あるいは、蒸着法によって電極５１２、５１４を形成すると、その表面が粗面となる。
【０１５５】
あるいは、図５（Ｃ）に示す凹部２０２等の形成のためのエッチング工程において、エッチング条件を変えてエッチング面を粗面にすることにより、その上に形成されたＩＴＯ膜面を粗面にすることができる。
【０１５６】
微小ミラー４０２に形成された絶縁膜４１６と、電極５１２、５１４との接触面積を少なくするためには、図１２に示すように、微小ミラー４０２の両端側であって、絶縁膜４１６の一部を下方に突出させたマイクロピラミッド４１６ａを形成することもできる。このマイクロピラミッド４１６ａを形成するには、図１３（Ａ）〜（Ｃ）の工程を実施すればよい。まず、同図（Ａ）に示すように、絶縁膜４１６上に平坦な第１の酸化膜４３０を形成する。その後この第１の酸化膜４３０上であって、微小ミラー４０２の両端部の位置に、局所的に第２の酸化膜４３２を形成する。
【０１５７】
次に、この第１，第２の酸化膜４３０，４３２をエッチングする。こうすると、図１３（Ｂ）に示すように、エッチング速度が全面にて均一であるとすれば、中央領域の第１の酸化膜４３０が完全に除去された後も、その周縁領域の第１の酸化膜４３０が残存している。その後引き続きエッチングを進行させると、中央領域の絶縁膜４１６の表面のみがエッチングされ、その端部の絶縁膜４１６がエッチングされないことになる。
【０１５８】
そして、図１３（Ｃ）に示すように、その端部に残存している酸化膜を除去することで、微小ミラー４０２の両端に、絶縁膜４１６にて形成されたマイクロピラミッド４１６ａを形成することができる。
【０１５９】
第１，第２のアドレス電極５１２，５１４によって微小ミラー４０２の裏面に形成した絶縁膜４１６の帯電を防止するには、図１４に示すように、ガラス製電極基板５００の凹部５０２より突出する絶縁性ストッパ５３０を設けることでもよい。こうすると、微小ミラー４０２の傾斜駆動時であっても、その裏面側の絶縁膜４１６、第１，第２のアドレス電極５１２，５１４との距離を大きくとれることによって、帯電に伴う微小ミラー４０２の張り付きを防止できる。
【０１６０】
（第４実施例）
次に、第１実施例または第２実施例の光変調装置を用いて、プロジェクターを構成する実施例について、図１５〜図１７を参照して説明する。
【０１６１】
図１５は、１段の光変調装置７００を用いて、プロジェクターを構成した実施例を示している。同図に示す通り、プロジェクションランプ７０２から出射された白色光は、コンデンサレンズ７０４を介して回転式カラーフィルタ７０６に集光される。この回転式カラーフィルタ７０６は、Ｒ、Ｇ、Ｂの三色の色フィルターを有する。コンデンサレンズ７０４の集光位置に対して各色フィルターが回転配置されることで、順次異なる色の波長の光がフィルターを通過する。
【０１６２】
回転式カラーフィルタ７０６の「Ｒ」、「Ｇ」、「Ｂ」のフィルタを順次透過した光は、コンデンサレンズ７０８、反射ミラー７１０及びハーフプリズム７１２を経由して、光変調装置７００に入射することになる。この光変調装置７００では、外部からの映像信号に基づいて、上述した駆動法に従って、Ｘ方向（水平方向）の端から順次、微小ミラーを傾斜駆動させる走査を行い、かつ、Ｙ方向（垂直方向）に順次走査することで、マトリクス状に配列された各々の微小ミラーにて入射光を反射させる。これにより、微小ミラーが配置されたマトリクス状の各画素にて、階調に応じて変調された反射光を得ることができる。
【０１６３】
この反射光は、ハーフプリズム７１２を介して平行光としてプロジェクションレンズ７１４に入射され、このプロジェクションレンズ７１４を介してスクリーン７１６上にて拡大投影されることになる。
【０１６４】
ここで、本実施例の光変調装置７００は、偏光板を有することで光利用率の低い従来の液晶パネルと比べて、光利用効率は３倍以上あり、スクリーン７１６上に十分な明るさをもった画像を表示することが可能となる。
【０１６５】
しかも、微小ミラーの応答速度は２０μｓｅｃと、従来の液晶の３０ｍｓｅｃに比べて格段に速く、画像のちらつきをも防止することができる。さらには、従来の液晶パネルを利用する場には、光利用効率が低いため、「Ｒ」、「Ｇ」、「Ｂ」に対応して３枚の液晶パネルを必要としていたため、各軸方向でのアライメント調整が極めて煩雑であった。
【０１６６】
これに対して、本実施例の光変調装置７００を用いれば、図１５に示すように１段のみで十分な明るさを得られ、アライメント調整も極めて容易となる。
【０１６７】
なお、この光変調装置７００を、図１６，図１７に示すように、２段又は３段設けることもできる。図１６の場合、回転式カラーフィルタ７０７は「Ｇ」、「Ｂ」のフィルターを有し、２つの光変調装置７００の前段に２波長領域に分光する分光プリズム７１７が配置される。一方、図１７の場合には、回転式カラーフィルタは用いられず、３つの光変調装置７００の前段に３波長領域に分光する分光プリズム７１８が設けられる。こうして、光変調装置７００を、いずれか２色の波長に兼用し、あるいは各波長毎に独立して２段または３段配置することも可能である。こうすれば、より明るく鮮明な画像をスクリーン７１６上に投影することが可能となる。
【０１６８】
（第５実施例）
図１８は、本実施例の光変調装置７２０を、電子写真装置例えばレーザプリンタに適用した実施例を示している。この実施例では、光変調装置７２０が従来のポリゴンミラーの代用として用いらている。同図において、光変調装置７２０の複数の微小ミラー７２２は、レーザ光源７２４から出射されるレーザ光と平行な方向に沿って配列されている。
【０１６９】
図１８では、右側の端部に位置する微小ミラー７２２がＯＮ駆動された状態が示されており、この微小ミラー７２２のＯＮ駆動時に反射される反射光の進行方向前段には、感光ドラム７３０が配置されている。このとき、他の微小ミラーはＯＦＦ駆動であり、レーザ光を遮ることがない。
【０１７０】
感光ドラム７３０は、図１９に示すように例えば時計方向に回転可能となっている。この感光ドラム７３０の周囲には、露光ランプ７３２、現像装置７３４、転写装置７３６、クリーニング装置７３８、除電装置７４０がそれぞれ配置されている。図１８に示す光変調装置７２０の各々の微小ミラー７２２を、図の右側から左側に順番に走査すると、予め露光ランプ７３２にて一定電位に帯電された感光ドラム７３０の表面電位は、微小ミラー７２２により変調された反射光に基づいて電位が変わり、潜像が形成される。感光ドラム７３０の回転により、現像装置７３４により潜像にトナーが付着されて現像され、転写装置７３６によりそのトナーが記録媒体７４４側に転写される。この記録媒体７４４は、その後段に設けられた定着ローラ７４２にて定着が行われた後に排紙される。また、転写が終了した後は、感光ドラム７３０上に残存するトナーがクリーニング装置７３８により回収され、除電ランプ７４０により除電されて初期状態に戻る。
【０１７１】
このように、本実施例によれば、光変調装置７２０を従来のポリゴンミラーの代用として用いることができ、しかも光変調装置７２０は高密度実装が可能であってかつ応答速度が速いため、高い解像度の画像を記録媒体７４４上に記録することができる。
【０１７２】
（第６実施例）
この第６実施例は、本実施例の光変調装置を光スイッチングが可能な例えば光カードに適用した実施例を示している。図２０に示すように、絶縁基板７５０上には、任意の誘導電圧を生じされせることができる複数例えば１２個の誘導コイル７５２−１〜７５２−１２が設けられる。
【０１７３】
この絶縁基板７５０上の端部には本実施例の光変調装置７６０が配置されている。そして、各々の誘導コイル７５２−１〜７５２−１２は、光変調装置７６０に設けられた６個の微小ミラーとそれぞれ対向する第１，第２のアドレス電極に、配線パターン７５４を介して接続されている。
【０１７４】
この光カードからの光スイッチング信号を検出できるデバイスに、この光カードを挿入すると、絶縁基板７５０に形成された１２個の誘導コイル７５２−１〜７５２−１２とそれぞれ対応してデバイス側の１２個の誘導コイルが配置される。これに通電することで各々の誘導コイル７５２−１〜７５２−１２にて誘導電圧が生ずる。この誘導電圧に基づき、光変調装置７６０内の６個の微小ミラーを傾斜駆動させ、その反射光により変調された光スイッチング信号を得ることができる。
【０１７５】
ここで、この光変調装置７６０は極めて小型に形成することができるので、携帯用のカード内に十分収容することができる。しかも、この光カードは磁気の影響とは無関係であるので、カード内のデータが読みとられて犯罪に使用されることを防止できる。
【０１７６】
（第７実施例）
この第７実施例は、本発明に係る光変調装置７８０を露光装置に組み込み、露光される半導体ウェハ７７０の表面に、ロット番号その他のウェハ固有の情報を書き込むために用いている。
【０１７７】
ウェハ７７０が載置されるウェハ載置台７７２と対向して、その情報には露光のための光源７７４が設けられている。この光源７７４とウェハ載置台７７２との間には、光源７７４から出射された光を、所定のマスクパターン像として、ウェハ７７０上に縮小投影するレチクル７７６が設けられている。この露光装置に内蔵された光変調装置７８０は、光源７７４からの一部の光が入射される位置に配置され、微小ミラーがＯＮ駆動された際に、その反射光がウェハ７７０の所定の位置に入射するようになっている。
【０１７８】
ここで、露光装置の光源７７４の波長は、ｇ線、ｉ線、エキシマレーザと、素子の高密度化に従い短波長となっている。もしこのような短波長の光を、液晶を用いた光スイッチング素子にて変調しようとすれば、封入された液晶はすぐに劣化してしまう。
【０１７９】
本発明の光変調装置７８０は、微小ミラーにてこの短波長を反射するだけであるので、十分な耐久性を有する。
【０１８０】
このように、本発明の光変調装置７８０を用いれば、光源７７４からの短波長の露光用の光を兼用して、ウェハ７７０上にＩＤ情報などを記録することができ、別個に光源を設ける必要がなくなる。
【０１８１】
本発明に係る光変調装置は、上述の各種機器に応用されるものに限らず、光を階調変調するもの、あるいは単にＯＮ／ＯＦＦ変調する各種の機器に適用することが可能である。例えば、光変調装置の微小ミラーにて反射された光を直接目視できるように構成し、絵や文字などのキャラクターを表示する広告用の看板、あるいは時計表示などにも適用することが可能である。
【０１８２】
【図面の簡単な説明】
【図１】本発明の第１実施例に係る光変調装置の組立分解斜視図である。
【図２】図１に示す装置に用いられる微小ミラーの拡大斜視図である。
【図３】（Ａ）は微小ミラーの平面図、（Ｂ）は微小ミラーの側面図である。
【図４】（Ａ）〜（Ｉ）はそれぞれ、図１に示す光変調装置のシリコン製ミラー基板の製造プロセスを説明する概略断面図である。
【図５】（Ａ）〜（Ｇ）は、図１に示す光変調装置のガラス製電極基板の製造プロセスを示す概略断面図である。
【図６】図４（Ｉ）の陽極接合工程を説明するための概略説明図である。
【図７】（Ａ）は図１に示す複数の光変調装置が１枚のウエハ上から製造される状態を説明するための概略説明図、（Ｂ）はウエハから分離された一つの光変調装置の概略斜視図である。
【図８】本発明の第２実施例に係る光変調装置の組立分解斜視図である。
【図９】第２実施例に係る光変調装置の斜視図である。
【図１０】（Ａ）〜（Ｈ）はそれぞれ、図８に示す装置の製造プロセスを説明する概略断面図である。
【図１１】（Ａ）及び（Ｂ）はそれぞれ、微小ミラーの裏面に絶縁膜を形成した本発明の第３実施例を説明するための概略説明図である。
【図１２】微小ミラーの裏面に形成された絶縁膜の端部にマイクロピラミッドを設けた第３実施例の変形例を示す概略説明図である。
【図１３】（Ａ）〜（Ｃ）はそれぞれ、図１２に示すマイクロピラミッドを形成する工程を示す概略断面図である。
【図１４】ガラス製電極基板に絶縁性ストッパを設けた第３実施例の変形例を示す概略説明図である。
【図１５】１段の光変調装置を設けてプロジェクターを構成した本発明の第４実施例の概略説明図である。
【図１６】２段の光変調装置を設けてプロジェクターを構成した第４実施例の変形例を示す概略説明図である。
【図１７】３段の光変調装置を設けてプロジェクターを構成した第４実施例の変形例を示す概略説明図である。
【図１８】本発明の光変調装置をポリゴンミラーの代用として用いて電子写真装置を構成した本発明の第５実施例の概略説明図である。
【図１９】図１８に示す電子写真装置の感光体回りの構成を説明するための概略説明図である。
【図２０】光変調装置を光スイッチング装置としての光カードに適用した本発明の第６実施例を説明するための概略説明図である。
【図２１】光変調装置を露光装置に内蔵した本発明の第７実施例を説明するための概略説明図である。
【図２２】従来の光変調装置の組立分解斜視図である。
【図２３】従来の光変調装置の光変調動作を説明するための概略説明図である。
【図２４】（Ａ）〜（Ｈ）は、図２２に示す従来の光変調装置の製造プロセスを示し、下層の上に中間層を形成するプロセスの概略説明図である。
【図２５】（Ａ）〜（Ｆ）は、図２４で得られた中間層の上に上層を形成する従来のプロセスを示す概略説明図である。
【符号の説明】
１００，４００ シリコン製ミラー基板
１０２，４０２ 微小ミラー
２０２ａ，４０２ａ 反射層
１０４，４０４ トーションバー
１０６，４０６ 枠状部
１１０，４２０ シリコン基板
１１２，４２２ ドープ層
１１６ 第１マスク
１１８ 第２マスク
２００，５００ ガラス製電極基板
２０２，５０２ 凹部
２０４，５０４ 立ち上り部
２１０，５０８ 地中部
２１２，５１０ 配線パターン部
２１４，５１２ 第１のアドレス電極
２１６，５１４ 第２のアドレス電極
２１８，５１６ 第１の共通配線
２２０，５１８ 第２の共通配線
３００，６００ カバーガラス基板
３１０ ホットプレート
３１２ 直流電源
３２０，７７０ 半導体ウェハ
７００，７２０，７６０，７８０ 光変調装置
７０２，７１４ プロジェクションランプ
７０６ 回転式カラーフィルタ
７１２ ハーフプリズム
７１６ スクリーン
７２４ レーザ光源
７３０ 感光ドラム
７３４ 現像装置
７３６ 転写装置
７５０ 絶縁基板
７５２ 誘導コイル
７５４ 配線パターン
７７２ ウェハ載置台
７７４ 光源
７７６ レチクル[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a light modulation device including a micromirror and a method for manufacturing the same.
[0002]
[Background Art and Problems to be Solved by the Invention]
This type of light modulation device is disclosed in JP-A-4-230722, 5-188308, 5-196880, and the like. These improved structures are disclosed as DMD (Digital Micromirror Device) in the March 1994 issue of Nikkei Microdevice.
[0003]
As shown in FIG. 22, this DMD has a three-layer structure including an upper layer 800, an intermediate layer 810, and a lower layer 830.
[0004]
The upper layer 800 includes a mirror 802 and a mirror holding post 804 connected to the lower surface of the center portion. In the manufacturing process of the mirror 802, a recess 806 is formed at a position facing the mirror holding post 804.
[0005]
In the intermediate layer 810, a mirror holding plate 812 connected to the mirror holding post 804 is supported by hinges 814 on both sides so as to be tiltable. In order to secure an inclined drive space for the mirror holding plate 812, the hinge 814 has a hinge holding post 816 on its lower surface.
[0006]
The intermediate layer 810 further includes first and second address electrodes 818 and 820 on both sides of the hinge 814 and is supported by electrode holding posts 826, respectively. Further, a first mirror contact electrode 822 and a second mirror contact electrode 824 are provided on the outside thereof, and are respectively supported by electrode holding posts 826.
[0007]
The lower layer 830 includes four electrodes 832a to 832d to which the electrode holding posts 826 of the first and second address electrodes 818 and 820 are connected, and a common electrode 834 to which the first and second contact electrodes 822 and 824 are connected. have.
[0008]
In this DMD, a bias voltage Va is applied to the mirror 802 and the first and second mirror contact electrodes 822 and 824 as shown in FIG. For example, by applying a negative voltage to the first address electrode 818 and applying a positive voltage to the second address electrode 820, a Coulomb force acts between the mirror 802 and the first address electrode 818, and the mirror 802 can be driven to be inclined to the state of the one-dot chain line in FIG. By reversing the polarity of the voltage applied to the first and second address electrodes 818 and 820, tilt driving can be performed as shown by a two-dot chain line in FIG.
[0009]
When the mirror 802 is tilted as shown by the one-dot chain line in FIG. 23, the light is reflected toward the predetermined position. When the mirror 802 is tilted as shown by the two-dot chain line, the direction is different from the predetermined position. The light is reflected off. And 256 gradation display is possible by changing the switching time.
[0010]
It is assumed that the DMD shown in FIG. 22 can be manufactured according to the manufacturing process shown in FIGS. FIG. 24 shows a process of forming the intermediate layer 810 on the preformed lower layer 830, and FIG. 25 shows a process of forming the upper layer 800 on the intermediate layer 810 and forming a space between the layers. Yes.
[0011]
As shown in FIG. 24, a substrate 840 on which an SRAM is formed as a lower layer 830 is prepared. Next, as shown in FIG. 24B, a resist 842 is applied onto the substrate 840, and patterning is performed to form a pattern corresponding to the hinge holding post 816 and the electrode holding post 826 in the step of FIG. Do.
[0012]
Next, as shown in FIG. 24D, an aluminum (Al) film 844 is deposited on the surface of the resist 842 and the trench portion, and an Al oxide film 846 is formed on the surface as shown in FIG. To do.
[0013]
Further, after the deposition of the Al film 848 shown in FIG. 24F, a resist 850 is applied and patterned as shown in FIG. Thereafter, as shown in FIG. 24H, the Al film 848 is etched to form the mirror holding plate 812, the hinge 814, and the hinge holding post 816.
[0014]
Next, the upper layer 800 is formed by the process shown in FIG. For this purpose, a resist 852 is applied thickly as shown in FIG. 25A, and patterning is performed as shown in FIG. Further, after depositing an Al (aluminum) film 854 and forming an Al oxide film 856 on a part of its surface, the Al film 854 at the end is removed by etching, whereby a mirror 802 and a mirror holding post 804 are formed. (See FIGS. 26C to 26E).
[0015]
Finally, as shown in FIG. 25F, by removing the resists 842 and 852, a space is formed between the upper layer 800 and the intermediate layer 810, and between the intermediate layer 810 and the lower layer 830. A space is formed.
[0016]
However, the above process has a problem that the yield of DMD cannot be increased. One of the causes is the setting of the distance between the lower surface of the mirror 802 and the mirror contact electrodes 822 and 824, which is a factor for determining the tilt angle of the mirror 802, in the resist process shown in FIG. This is because it depends on the thickness of the resist 852.
[0017]
Normally, this type of resist is formed by a spin coating method, and even if it is difficult to increase the uniformity of the resist thickness, even if the thickness of the resist 852 is set to a constant value by the spin coating method, This is an extremely difficult technology.
[0018]
In addition, with the conventional spin coating method, it becomes difficult to ensure even in-plane uniformity of the resist film as the wafer area increases. This is almost impossible with semiconductor wafers. Accordingly, it is difficult to simultaneously form a large number of elements from a single semiconductor wafer, and the throughput is also reduced.
[0019]
Another problem is that in the resist removal process shown in FIG. 25F, it is difficult to completely remove the resist in the recessed area below the mirror 802 or the hinge 814. is there. If such foreign matter remains, the mirror 802 and the address electrodes 818 and 820 are short-circuited, the displacement of the mirror is prevented, or the mirror contact electrodes 822 and 824 and the address electrodes 818 and 820 are short-circuited. .
[0020]
Another problem of the DMD with the above structure is that a recess 806 is formed in the central region of the mirror 802. In the Al vapor deposition step of FIG. 25C, when Al is vapor deposited in the trench portion, the position facing the trench is necessarily depressed, and it cannot be prevented that the concave portion 806 is formed due to this depression.
[0021]
In the DMD having this three-layer structure, since the hinge 814 is not present on the same plane as the mirror 802, the opening area of the mirror 802 is increased, and the light utilization rate is increased.
[0022]
However, a concave portion 806 is formed at the center of the large-area mirror 802, and if such a concave portion 806 exists on the optical axis having a strong light intensity, the light utilization rate is reduced due to irregular reflection. Alternatively, a problem is pointed out that the irregularly reflected light is input as information of other pixels and the image quality is deteriorated. Even if the side wall of the recess 806 can be processed vertically, the effective light use area is reduced.
[0023]
Accordingly, an object of the present invention is to provide an optical modulation device including a micromirror that can be manufactured with a high yield and a method for manufacturing the same.
[0024]
Another object of the present invention is to provide a light modulation device including a minute mirror that can perform accurate light modulation control without causing irregular reflection on the surface of the minute mirror, and a method for manufacturing the same.
[0025]
[Means for Solving the Problems]
In the method of the present invention, a light modulating device having a micromirror is manufactured by bonding a conductive silicon mirror substrate and an electrode substrate. Here, the conductive silicon mirror substrate has a plurality of micromirrors arranged in a line or matrix, a torsion bar that connects the micromirrors in one direction, and both ends of the torsion bar. And a reflective layer is formed on at least one surface of the micromirror.
[0026]
The electrode substrate has a concave portion in a central region, a rising portion around the concave portion, a conductive layer formed at a position corresponding to each of the micro mirrors in the concave portion, and the micro mirrors are driven to be tilted by Coulomb force. An electrode group to be formed, and a column portion projecting from the recess at a position corresponding to the space between the two micromirrors adjacent in the one direction.
[0027]
In the step of bonding the silicon mirror substrate and the electrode substrate, at least an intermediate portion of the torsion bar of the silicon mirror substrate and the support column portion of the electrode substrate face each other.
[0028]
If it carries out like this, if the depth of the recessed part previously formed in a glass-made electrode board | substrate is formed accurately, the deflection angle of a micromirror can be set correctly between lots. In addition, the reflective layer formed on the surface of the micromirror can be made flat and can be formed on a surface without irregular reflection.
[0029]
In particular, when the electrode substrate is a glass electrode substrate containing an alkali metal such as Na, both substrates can be bonded by anodic bonding. This eliminates the need for an adhesive layer between the substrates, so that the deflection angle of the micromirror can be set more accurately between lots.
[0030]
Note that this bonding method is not limited to anodic bonding, and may be direct bonding, eutectic bonding, or the like. Details of each bonding method will be described later. Moreover, as a material of the electrode substrate, when the bonding step is performed under heating, it is preferable that the thermal expansion coefficient is close to that of silicon.
[0031]
The silicon mirror substrate may be formed with a frame-like portion in which both ends of the torsion bar are connected. In this case, both end portions and the frame-shaped portion of the torsion bar are joined to the rising portion of the electrode stranger. And after this joining, the process of cut | disconnecting the both ends of a torsion bar from a frame-shaped part is implemented.
[0032]
In this way, the mutual positional relationship of the plurality of torsion bars is maintained by the frame-like portion, and therefore, the mutual positional relationship can be maintained and bonded to the electrode substrate without positioning each one.
[0033]
Here, the step (a) of manufacturing the silicon mirror substrate includes:
Forming a doped layer by doping impurities in the silicon substrate;
Patterning a first mask for forming a window on one surface of the silicon substrate and a second mask for forming the plurality of micromirrors and the torsion bars on the other surface;
Etching the silicon substrate using the first mask until the doped layer is exposed;
Etching the doped layer using the second mask;
Removing the first and second masks and forming the micromirrors and torsion bars with the doped layer;
Forming the reflective layer on one side of the micromirror of the doped layer;
Can be implemented.
[0034]
According to another aspect of the method of the present invention, the bonding with the electrode substrate is performed in the state of the silicon substrate before the silicon mirror substrate is completed.
[0035]
In the electrode substrate, a conductive layer is formed at a position corresponding to each of the micromirrors in the concave portion in the central region, a rising portion around the concave portion, and the micromirrors, and the micromirrors are driven to tilt by Coulomb force. An electrode group, and a column portion that protrudes from the concave portion at a position corresponding to between the two micromirrors adjacent in one direction.
[0036]
Joined to this is a silicon substrate having a doped layer doped with impurities on one side. At this time, at least the support column portion of the electrode substrate is bonded to the dope layer.
[0037]
In this step, since a minute mirror or the like is not formed, alignment at the time of joining becomes easy.
[0038]
Thereafter, the silicon substrate is removed by etching, leaving only the doped layer, and a reflective layer is formed on the surface of the doped layer.
[0039]
Thereafter, an etching process of the doped layer is performed. At this time, a plurality of the micromirrors are formed at positions facing the electrode group. In addition, the micromirrors are connected in one direction, and a torsion bar joined to the support column between the two micromirrors adjacent in the one direction is formed.
[0040]
In consideration of the positional relationship with the electrode group previously formed on the electrode substrate at the time of patterning for this etching process, a micromirror can be formed with high accuracy with the accuracy of the photolithography process.
[0041]
This method facilitates alignment of the substrates at the time of bonding and can be formed after bonding, so that it is suitable for the case where the micromirrors are arranged at a high density.
[0042]
Note that the anodic bonding method can also be adopted in the above method, and a frame-like portion may be formed on a silicon mirror substrate.
[0043]
In the case of arranging micromirrors at high density, the electrode substrate is a transparent glass substrate, the position of the pattern of the electrode group is observed from the glass electrode substrate side, and the silicon electrode substrate is based on the pattern position. It is preferable to perform mask pattern alignment for the etching.
[0044]
In each of the above method inventions, the impurity concentration of the doped layer is 1 × 10¹⁸atm / cm^ThreeWith the above, the doped layer can be used as an etching stop layer when the silicon substrate is etched.
[0045]
In addition, as the step of forming the glass electrode substrate,
Masking the position corresponding to the raised portion and the column portion, etching a glass plate containing an alkali metal, and forming the concave portion of a predetermined depth;
Forming the electrode group on the bottom surface of the recess;
It is good to have. In this case, the depth of the recess that affects the deflection angle of the micromirror can be formed depending on the etching conditions.
[0046]
The electrode group is formed of a transparent electrode such as ITO (indium tin oxide),
The method may further include a step of inspecting from the glass electrode substrate side whether foreign matter is mixed between the glass electrode substrate to be bonded and the silicon mirror substrate. If this inspection is carried out before joining, the yield is improved, and even if it is carried out after joining, the cause of the defect that foreign matter is mixed in is easily found.
[0047]
The method may further include a step of bonding a transparent cover substrate on the silicon mirror substrate at a position that covers the silicon mirror substrate and does not interfere with the tilted micromirror.
[0048]
With this transparent cover substrate, it is possible to protect the element by preventing the entry of foreign matter that hinders the tilt drive of the micromirror.
[0049]
The device of the present invention is formed by joining a conductive silicon mirror substrate doped with impurities and an electrode substrate,
The silicon mirror substrate is
A plurality of micromirrors arranged in a line or matrix and having a reflective layer formed on one side;
A torsion bar that connects the micromirrors in one direction;
Have
The electrode substrate is
A recess in the central region;
The surrounding startup section,
An electrode group that is formed in the concave portion at a position corresponding to each of the micromirrors, and drives the micromirrors to be tilted by Coulomb force;
A column portion that protrudes from the recess at a position corresponding to the position between the two micromirrors adjacent in the one direction;
Have
At least an intermediate portion of the torsion bar of the silicon mirror substrate and the support column of the electrode substrate face each other, and the silicon mirror substrate and the electrode substrate are bonded. This bonding is also performed by anodic bonding, direct bonding or eutectic bonding.
[0050]
Here, the entire surface of the reflective layer formed on the micromirror is formed as a flat surface. Thereby, incident light can be reflected at a reflection angle equal to the incident angle.
[0051]
The electrode group is preferably formed of a transparent electrode such as ITO (Indium Tin Oxide). This is because the cause of the foreign matter contamination between the electrode group and the micromirror can be easily seen through the glass electrode substrate.
[0052]
An insulating film may be formed on the side of the micro mirror facing the electrode group. In this way, even if foreign matter is mixed in, it is possible to avoid a serious state of short circuit between the micromirror and the electrode group.
[0053]
More preferably, the surface of the electrode group facing the insulating film formed on the micromirror is formed to be a rough surface. The contact area between the insulating film and the electrode group is reduced, and sticking of the micromirror to the electrode group due to charging of the insulating film can be prevented.
[0054]
It is preferable that a convex portion having a height of 200 Å or more is provided on the surface of the electrode group to form the rough surface. Thereby, the surface roughness which can prevent sticking with a micromirror and an electrode group is securable. The upper limit of the height of the convex portion is G / 3 or less, where G is the gap between the micromirror and the electrode group when the micromirror is parallel to the electrode group. Thereby, the deflection angle of the micro mirror required for the function is secured at a minimum.
[0055]
In order to prevent sticking of the micromirror, an insulating protrusion may be formed on the insulating film at a position away from the torsion bar.
[0056]
As still another measure for preventing the sticking of the micromirror, the glass electrode substrate is formed so as to protrude from the bottom surface of the concave portion at a height lower than the top surface of the rising portion and the column portion, and the above-mentioned at the time of tilt driving. It is also possible to form an insulating stopper that abuts on the micromirror and determines the tilt angle.
[0057]
Various electronic devices can be configured using the light modulation device of the present invention.
[0058]
For example, a projection lamp, and a light modulation device that reflects light emitted from the projection lamp by tilt driving of a plurality of micromirrors arranged for each pixel to obtain reflected light modulated for each pixel, A projector can be configured by a projection lens that magnifies and projects the reflected light from the light modulation device toward the screen.
[0059]
Alternatively, the reflected light modulated while scanning in one direction by sequentially reflecting the photosensitive member on which the latent image is formed and the laser light from the laser light source by tilt driving of a plurality of micromirrors arranged in an array. Is emitted toward the photosensitive member to form the latent image, a developing device for developing the latent image formed on the photosensitive member, and the development on the photosensitive member is transferred onto a recording medium. An electrophotographic apparatus can be constituted by the transfer device.
[0060]
Furthermore, a plurality of induction coils in which the induction voltage is arbitrarily set, a light modulation device,
A wiring pattern for connecting each induction coil and the electrode group of the light modulation device, and driving each of the plurality of micromirrors in an inclined manner based on an induction voltage generated in each induction coil, An optical switch device that generates a desired optical signal by reflected light from a micromirror can be configured.
[0061]
Further, in an exposure apparatus that emits light from an exposure source to an object to be exposed through a mask and exposes the object to be exposed, the light from the exposure source is reflected by each micromirror, You may provide the light modulation apparatus which radiate | emits the modulated light to the said to-be-exposed body.
[0062]
This makes it possible to record ID information such as a lot number on an object to be exposed such as a semiconductor wafer by using an exposure process.
[0063]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of a light modulation device including a micromirror and a method for manufacturing the same according to the present invention will be described below with reference to the drawings.
[0064]
(First embodiment)
Structure explanation of light modulator
FIG. 1 is an exploded perspective view showing main components of the light modulation device according to the first embodiment. In this figure, the light modulation device is roughly divided into a silicon mirror substrate 100, a glass electrode substrate 200, and a cover glass substrate 300.
[0065]
The silicon mirror substrate 100 has a plurality of micromirrors 102 arranged on a matrix. Among the plurality of micromirrors 102, the micromirrors 102 arranged in one direction, for example, the X direction in FIG. 1 are connected by a torsion bar 104. Furthermore, a frame-like portion 106 is provided so as to surround an area where the plurality of micromirrors 102 are arranged. The frame portion 106 is connected to both ends of the plurality of torsion bars 104.
[0066]
As shown in the enlarged view of FIG. 2, the micromirror 102 has a slit 108 formed around the connection portion with the torsion bar 104. By forming the slits 108, the tilt drive of the micromirror 102 in the direction of the arrow shown in FIG. 2 is facilitated. Further, a reflective layer 102 a is formed on the surface of the micromirror 102. Then, when the micromirror 102 is tilted by driving to be described later, the reflection direction of light incident on the micromirror 102 changes. The light is modulated by controlling the time for reflecting the light in the predetermined reflection direction.
[0067]
Various dimensions of the micromirror 102 and the torsion bar 104 shown in FIGS. 2 and 3A and 3B are as follows.
[0068]

A glass electrode substrate 200 shown in FIG. 1 has a recess 202 in the central region, and has a raised portion 204 around it. One side of the rising portion 204 is cut away to form an electrode outlet 206, and an electrode extraction plate 208 that is continuous with the recess 202 is formed outside the electrode outlet 206.
[0069]
The concave portion 202 of the glass electrode substrate 200 is formed so as to protrude from the concave portion 202 at the position facing the torsion bar 104 between two micromirrors 202 adjacent in the X direction, and is the same as the top surface of the rising portion 204. It has a large number of pillars 210 having a height.
[0070]
Further, a wiring pattern portion 212 is formed on the concave portion 202 and the electrode extraction plate portion 208 of the glass electrode substrate 200. As shown in FIG. 2, the wiring pattern portion 212 has first and second address electrodes 214 and 216 at positions facing the back surfaces of the micromirrors 102 on both sides of the torsion bar 104, respectively. The first address electrodes 214 arranged along the Y direction are commonly connected to the first common wiring 218. Similarly, the second address electrodes 216 arranged along the Y direction are commonly connected to the second common wiring 220.
[0071]
On the glass electrode substrate 200 having the above structure, a silicon mirror substrate 100 is anodically bonded as shown in FIG. At this time, both ends of the torsion bar 104 of the silicon mirror substrate 100 and the frame-like portion 106 are joined to the rising portion 204 of the glass electrode substrate 200. Further, the intermediate portion of the torsion bar 104 of the silicon mirror substrate 100 and the support column portion 210 of the glass electrode substrate 200 are anodically bonded. Thereafter, the cover glass substrate 300 is bonded onto the frame-like portion 106 of the silicon mirror substrate 100. Then, both end portions of each torsion bar 104 connected to the frame-like portion 106 are diced at positions where they are separated from the frame-like portion 106. Further, the peripheral portion including the electrode outlet 206 cut out in the rising portion 204 of the glass electrode substrate 200 is hermetically sealed with a sealing material, and the light modulation device according to the first embodiment is completed. Here, when the inside of the light modulation device is evacuated by various methods, the resistance is small when the micromirror is driven, and the high-speed response operation and the power consumption are reduced.
[0072]
Explanation of optical modulation drive principle
When the micromirrors 102 are driven to be tilted ON, the plurality of micromirrors 102 arranged along the X direction shown in FIG. 1 are simultaneously energized via the torsion bar 104. Meanwhile, at the same time, the first and second address electrodes 214 and 216 shown in FIG. 1 are driven as a set in a dot-sequential or line-sequential manner, and the torsion bar 104 that is energized is sequentially directed in the Y direction in FIG. By selecting, the micromirrors 102 arranged in a matrix can be driven to tilt ON in a predetermined cycle.
[0073]
On the other hand, in order to drive the micro mirror 102 to be tilted OFF, the polarity of the voltage applied to the first and second address electrodes 214 and 216 may be reversed from that at the time of ON tilt driving. As a result, the micro mirror 102 is tilted in the direction opposite to that during ON tilt driving.
[0074]
Description of manufacturing method of light modulation device
A method of manufacturing the light modulation device according to the first embodiment will be described with reference to FIGS. First, a manufacturing process of the silicon mirror substrate 100 will be described.
[0075]
(I) Manufacturing process of mirror substrate 100 made of silicon
(1) Step of forming a silicon substrate having a doped layer
In this step, a doped layer 112 shown in FIG. 4B is formed on one surface of the silicon substrate 110 shown in FIG. For this purpose, for example, a boron doping material is applied on the silicon substrate 110 by a spin coating method. This boron dope is made of B in an organic solvent.₂O_ThreeFor example, PBF manufactured by Tokyo Ohka Co., Ltd. can be used. At this time, the film thickness of the boron dope material can be adjusted depending on the spin rotation conditions of the silicon substrate 110 and the viscosity of the boron dope material.
[0076]
In this example, the film thickness of the boron dope material could be changed in the range of 0.5 to 5.0 μm by changing the viscosity of the boron dope material to 50 to 100 cp and changing the spin rotation conditions.
[0077]
After spin coating of this boron dope material, it is good to heat at 100-180 degreeC for 20 to 40 minutes in a heating furnace, and to evaporate the solvent in a boron dope material. In this example, baking was performed at 140 ° C. for 30 minutes. Further, the binder is removed by baking in an oxygen atmosphere furnace at 400 to 800 ° C. for 1 to 2 hours. In this example, baking was performed at 600 ° C. for 1 hour. In the subsequent thermal diffusion step, thermal diffusion is performed in a nitrogen atmosphere at 800 to 1200 ° C. for 4 to 10 hours. In this example, the thermal diffusion process was performed at 1100 ° C. for 6 hours.
[0078]
As a result, boron (B) in the boron-doped material was thermally diffused inside the silicon substrate 110, and the boron-doped layer 112 shown in FIG. 4B could be formed on the lower surface of the silicon substrate 110. The thickness of the boron doped layer 112 can be adjusted by the temperature and the treatment time in this thermal diffusion process. In this embodiment, the thermal diffusion treatment is performed at 1000 ° C. for 6 hours, so that a boron doped layer of 2 to 3 μm is obtained. 112 could be formed.
[0079]
At this time, the boron concentration in the boron dope 112 is preferably 1 × 10 6.¹⁸atm / cm^ThreeThe above is preferable. In this case, the boron doped layer 112 can function as an etching stop layer in the etching process of the silicon substrate 110 described later.
[0080]
In order to form the boron doped layer, a boron diffusion plate method can also be employed. At this time, the surface of the silicon substrate to be doped with boron is disposed, for example, by facing a boron plus plate (trade name) manufactured by Techne Glass. The distance between the two may be 0.5 to 4.0 mm, more preferably 2.0 to 3.0 mm. While maintaining this opposing arrangement relationship, heat is applied in a heating furnace at 800 to 1200 ° C., for example, 1100 ° C., at a nitrogen flow rate of 3 to 8 liter / min, for example 6 liter / min, for 1 to 6 hours, for example, 2 hours. A diffusion step may be performed.
[0081]
As another method, an ion implantation method may be employed. The acceleration energy at this time is 20 to 50 keV, and the optimum value is 35 keV. The dose amount indicating the number of accelerated electrons is 2 × 10.¹⁸~ 8x10¹⁸Pieces are suitable, preferably 4 × 10¹⁸It is a piece. Further, the beam current is suitably 1.5 to 4.5 mA, desirably 3.0 mA. When ion implantation was performed under these conditions, a boron-doped layer of 0.5 to 4 μm could be formed.
[0082]
(2) Thermal oxidation process
Next, the silicon substrate 110 on which the boron doped layer 112 is formed is carried into a thermal oxidation furnace, and a thermal oxide film 114 is formed around the silicon substrate 110 as shown in FIG. In this embodiment, a thermal oxide film 114 having a thickness of 1 μm was formed by performing a thermal oxidation process at a temperature of 1000 ° C. for 4 hours by a wet oxidation method. At this time, the boron doped layer 112 is also thermally oxidized, and a thermal oxide film 114 is also formed on the surface thereof.
[0083]
(3) Patterning process
Next, the silicon substrate 110 having the thermal oxide film 114 was patterned by performing a photolithography process as shown in FIG. As shown in the figure, a first mask 116 for forming a window in the central region was patterned on the surface side of the silicon substrate 110. On the lower surface of the silicon substrate 110 having the boron doped layer 112, the second mask 118 for forming the micro mirror 102, the torsion bar 104, the frame portion 106, the slit 108 and the like shown in FIGS. For this patterning, resist coating, exposure, and development were performed on the front and back surfaces of the thermal oxide film 114, respectively. After the development step, the thermal oxide film (silicon oxide film) 114 in a predetermined region was removed using a buffered hydrofluoric acid solution. Thereafter, the patterning step is completed by removing the resist. This resist peeling can be used by heating a mixed solution of sulfuric acid and hydrogen peroxide water at 80 ° C., for example.
[0084]
(4) Etching process of silicon substrate 110
Next, as shown in FIG. 4E, the silicon substrate 110 was removed by etching using the first mask 116 formed on the upper surface side of the silicon substrate 110. In this etching step, the silicon substrate 110 was wet-etched using a KOH aqueous solution having a concentration of 1 to 40% by weight. The concentration of the KOH aqueous solution is optimally around 10% by weight. The reaction in this etching step is performed according to the following reaction formula.
[0085]
Si + 2KOH + H₂O → K₂SiO_Three+ 2H₂
Here, as shown in FIG. 4E, when the crystal plane orientation of the surface 110a of the silicon substrate 110 is (100), the side wall 110b formed by etching becomes an inclined wall having an angle of 55 ° C. On the other hand, when the crystal plane orientation of the surface 110a is (110), the side wall 110b can be a substantially vertical wall, and etching with high anisotropy can be realized. By so doing, a wider area can be made a surface capable of light modulation.
[0086]
In this case, the etching end point can be detected by observing hydrogen bubbles generated by the reaction of the silicon substrate 110 and setting the end point when the hydrogen bubbles disappear. Alternatively, the impurity concentration of the boron doped layer 112 is set to 1 × 10¹⁸atm / cm^ThreeBy setting it as the above, this boron dope layer 112 can be functioned as an etching stop layer.
[0087]
As an etching solution used in this step, a TMAH (tetramethylammonium hydroxide) aqueous solution, an EPD (ethylenediamine-pyrocatechol-diazine) aqueous solution, a hydrazine aqueous solution, or the like can be used other than the KOH aqueous solution.
[0088]
(5) Etching process of boron doped layer 112
Next, as shown in FIG. 4F, the boron doped layer 112 is dry etched using the second mask 118 formed on the lower surface of the thermal oxide film 114.
[0089]
For this dry etching, it is preferable to use RIE (reactive ion etching) which has a high etching rate and is suitable for mass production. At this time, as processing gas, CF_Four30-60 sccm, O₂30 to 60 sccm was introduced, and the power of the 13.56 MHz high-frequency power source was set to 400 to 800 W, particularly 600 W as the optimum location. The pressure in the chamber is preferably 0.05 to 0.30 Torr, and 0.15 Torr which is an optimum value is adopted in this embodiment. In this example, etching time of 15 to 30 minutes was required to etch the 2 μm boron doped layer.
[0090]
By dry etching the boron doped layer 112, the micro mirror 102, the torsion bar 104, the frame portion 106, and the slit 108 shown in FIGS.
[0091]
(6) Stripping process of the thermal oxide film 114
The thermal oxide film 114 is peeled off after being used as an etching resistant mask material in the step (5). As a peeling method, for example, as described in (3) patterning step, a buffered hydrofluoric acid solution can be used. Further, a dilute hydrofluoric acid solution of about 10% may be used. According to the embodiment of this step, as shown in FIG. 4G, it is possible to obtain a state in which the minute mirror 102, the torsion bar 104, and the like are supported on the frame-like portion 106 formed of the boron doped layer 112.
[0092]
(7) Deposition step of the reflective layer 102a
Next, a reflective layer 102a made of, for example, aluminum (Al) is deposited on the surface of the micromirror 102 formed of the boron-doped layer 112 with a thickness of, for example, 0.2 to 2 μm. When the film thickness of the reflective layer 102a exceeds the upper limit, the moment of inertia of the micromirror 102 increases, the response speed during driving becomes slow, and the driving voltage during tilt driving increases. Below the lower limit of the film thickness range, it is difficult to form the reflective layer 102a with a uniform thickness on the entire surface of the boron doped layer 112.
[0093]
At this time, the portion other than the surface of the micromirror 102, that is, the torsion bar 104 may be masked so that Al does not adhere to it, but a reflective layer 102a is also formed on the torsion bar 104 as in this embodiment. Also good. Since the top surface of the silicon substrate 110 remaining on the surface of the frame-like portion 106 is a region that is subsequently anodically bonded to the glass electrode substrate 200, masking may be performed so that foreign matter that prevents anodic bonding does not adhere to this portion. is important.
[0094]
In addition, as a material of the reflective layer 102a, what is necessary is just to be able to reflect visible light efficiently, for example, silver (Ag) can also be used. Moreover, the formation process of the reflective layer 102a is not necessarily limited to using a vapor deposition method, and for example, sputtering can be employed.
[0095]
In the step of forming the reflective layer 102a, the boron doped layer 112 as the base material is flat, and thus the reflective layer 102a formed thereon can be formed flat. Thereby, the light incident on the reflective layer 102a can be reflected at a reflection angle equal to the incident angle, and when a display device is configured using this light modulation device, the contrast can be improved. Become.
[0096]
By performing the above steps, the silicon mirror substrate 100 shown in FIGS. 1 to 3 is completed. Thereafter, as shown in FIG. 4I, the silicon mirror substrate 100, the glass electrode substrate 200, and the cover glass substrate 300 are bonded. Before describing this bonding step, a manufacturing process of the glass electrode substrate 200 will be described with reference to FIG.
[0097]
(II) Manufacturing process of glass electrode substrate 200
As shown in FIG. 5A, a glass substrate 230 serving as a base of the glass electrode substrate 200 uses a glass substrate containing an alkali metal such as sodium (Na) in order to perform anodic bonding described later. As this type of glass substrate 230, sodium borosilicate glass can be used. For example, Pyrex glass (trade name) manufactured by Corning Corporation can be used. In particular, Corning # 7740 (trade name) is optimal in consideration of the fact that the glass substrate 230 is heated at the time of anodic bonding and considering that the thermal expansion coefficient is substantially equal to that of silicon.
[0098]
Hereinafter, a manufacturing process of the glass electrode substrate 200 using the glass substrate 230 will be described.
[0099]
(1) Patterning process for the recess 202 and the like
By performing resist coating, exposure, and development steps on the glass substrate 230, a resist pattern portion 232 is formed on the surface of the glass substrate 230 as shown in FIG. The resist pattern portion 232 is formed at a corresponding portion of the rising portion 204 and the column portion 210.
[0100]
(2) Etching process for forming recesses 202 and the like
Using this resist pattern portion 232 as a mask, the glass substrate 230 is wet etched using a hydrofluoric acid aqueous solution. Thereby, in addition to the recess 202 shown in FIG. 5C, an electrode outlet 206 and an electrode extraction plate 208 are also formed at the same time. The depth of the recess 202 can be adjusted by changing etching conditions such as processing time and temperature.
[0101]
Since the depth of the recess 202 is an important factor for determining the deflection angle of the micromirror 102, it is necessary to adjust the etching conditions to form the recess 202 having the same depth between lots.
[0102]
(3) Resist stripping process
This resist peeling can be performed by using a mixed solution of sulfuric acid + hydrogen peroxide solution, and as a result, as shown in FIG. 5D, from the top surface of the rising portion 204 formed on the glass substrate 230. The resist pattern portion 232 can be peeled off.
[0103]
(4) Formation process of wiring pattern part 212
In order to form the wiring pattern portion 212 on the recess 202 and the electrode extraction plate portion 208, first, as shown in FIG. 5E, for example, aluminum (Al), silver (Ag) is formed on the entire surface of the glass substrate 230. ), An electrode film 234 made of a transparent electrode represented by gold (Au) or ITO is formed. The electrode film 234 can be formed by vapor deposition, sputtering, ion plating, or the like. Thereafter, a resist pattern portion 236 is formed on the electrode film 234 by performing a photolithography process (see FIG. 5F). Thereafter, the electrode film 234 is etched using the resist pattern portion 236 as a mask. This etching can be performed by wet etching.
[0104]
Thereafter, as shown in FIG. 5G, the resist pattern portion 236 on the wiring pattern portion 212 is peeled off, whereby the glass electrode substrate 200 is completed. The release material used at this time is appropriately selected depending on the material of the electrode film 234. The material of the electrode film 234 can also be ITO. In this case, a stripping solution composed of a mixed solution of sulfuric acid and hydrogen peroxide cannot be used because ITO itself dissolves, and an organic solvent-based stripping solution can be used instead.
[0105]
(III) Anodic bonding of the silicon mirror substrate 100 and the glass electrode substrate 200
As shown in FIG. 6, a glass electrode substrate 200 is placed on a hot plate 310 mounted on an alignment mechanism 314, and a silicon mirror substrate 100 is placed thereon. At this time, the first and second address electrodes 214 and 216 formed on the glass electrode substrate 200 and the micro mirror 102 formed on the silicon mirror substrate 100 are aligned at positions facing each other. This alignment is performed by moving the glass electrode substrate 200 in a two-dimensional plane by the alignment mechanism 314 while observing with a microscope 316 from above.
[0106]
In addition, if foreign substances such as dust are mixed between the substrates 100 and 200 during the anodic bonding, the micromirror 102 and the wiring pattern portion 212 are short-circuited, resulting in a defective product. Therefore, it is important to perform an inspection for confirming the presence or absence of foreign matter before the two substrates 100 and 200 are joined. This inspection can be performed before the substrates 100 and 200 are overlaid. When the wiring pattern portion 212 is formed of a transparent electrode such as ITO, the glass electrode substrate 200 can be used even if the substrates are overlaid. It can observe by observing with a microscope from the lower side.
[0107]
Thereafter, the silicon mirror substrate 100 and the glass electrode substrate 200 are connected to a DC power source 312. The silicon mirror substrate 100 is connected to the plus terminal of the power source 312, and the glass electrode substrate 200 is connected to the minus terminal of the power source 312. Then, the glass electrode substrate 200 is heated to 250 to 450 ° C., for example, 350 ° C. by the hot plate 310, and an electrode of 300 to 1000 V, for example, 600 V is applied from the power source 312 for 2 to 3 minutes.
[0108]
Then, Na (plus) in the glass electrode substrate 200 is easily moved by being heated by the hot plate 310. By this movement of Na (plus), the bonding surface of the glass electrode substrate 200 is negatively charged, and the bonding surface of the silicon mirror substrate 100 is positively charged. As a result, a large Coulomb force acts between both the joint surfaces, and chemical bonding occurs at the interface, and electrostatic bonding is performed. Thereby, the silicon mirror substrate 100 and the glass electrode substrate 200 can be firmly bonded.
[0109]
By this anodic bonding, both end portions of the torsion bar 104 of the silicon mirror substrate 100 and the frame-like portion 106 are bonded to the rising portion 204 of the glass electrode substrate 200, and an intermediate portion of the torsion bar 104 of the silicon mirror substrate 100. Is joined to the column part 210 of the electrode substrate 200 made of glass.
[0110]
Thus, by anodic bonding of the silicon mirror substrate 100 and the glass electrode substrate 200, both can be reliably bonded without requiring the thickness of the adhesive layer as in the case of using an adhesive. In addition, unlike the case where an adhesive is used, the thickness of the adhesive layer does not vary, so that the recess depth H shown in FIG. 3B can be set to be substantially constant between lots. The recess depth H determines the deflection angle θ of the micromirror 102, and the deflection angle θ can be set uniformly among lots by anodic bonding.
[0111]
If the cover glass substrate 300 is formed of a glass substrate containing Na similarly to the glass electrode substrate 200, the cover glass substrate 300 is similarly anodically bonded to the frame-like portion 106 of the silicon mirror substrate 100. be able to. However, since the bonding between the silicon mirror substrate 100 and the cover glass substrate 300 does not require accuracy, other bonding methods, for example, a bonding method using an adhesive may be employed.
[0112]
(IV) Sealing, dicing and wiring process
(1) Sealing process
The electrode outlet 206 is sealed with a sealing material. If it carries out like this, it can prevent that a foreign material, water, etc. penetrate | invade between the silicon | silicone mirror board | substrates 100 and the glass electrode board | substrates 200 at the following (2) dicing process. As a result, it is possible to prevent the micro mirror 102 and the wiring pattern portion 212 from being short-circuited, and to improve the processing yield. Further, after the following (2) dicing step, a minute gap 240 corresponding to the plate thickness of the torsion bar 104 is formed on the two side surfaces of the light modulation element 330 as shown in FIG. The gap 240 can be similarly sealed.
[0113]
(2) Dicing process
As shown in FIG. 7A, a plurality of light modulation elements 330 obtained as described above can be simultaneously formed on one wafer 320 constituting the silicon substrate 110 shown in FIG. it can. For this reason, after the light modulation element 330 is completed, the wafer 320 is diced and separated into individual light modulation elements 330. By this dicing process, both ends of the torsion bar 104 connected to the frame-like portion 106 are cut off and separated in the Y direction in FIG. 1 to function as independent electrodes one by one. The light modulation element 330 separated by dicing is as shown in FIG.
[0114]
(3) Wiring process
Thereafter, the separated light modulation element 330 is fixed on a substrate (not shown) and wiring is performed. As shown in FIG. 7B, the wiring process is performed by connecting the wiring pattern portion 212 on the electrode extraction plate 308 and the end portion of the torsion bar 104 exposed to the side surface to a drive circuit (not shown). Thus, the light modulation device is completed.
[0115]
(Second embodiment)
Next, an optical modulation device capable of high-density mounting will be described with reference to FIGS.
[0116]
Overall configuration of high-density optical modulator
As shown in FIGS. 8 and 9, the light modulation device according to the second embodiment is roughly divided into a silicon mirror substrate 400, a glass electrode substrate 500, and a cover glass substrate 600. The silicon mirror substrate 400 and the glass electrode substrate 500 are anodically bonded as in the first embodiment. Since the positional relationship between the silicon mirror substrate 400 and the cover glass substrate 600 does not affect the deflection angle of the micromirror, both the substrates 400 and 600 are bonded with, for example, an adhesive other than anodic bonding as in the first embodiment. And may be joined.
[0117]
The silicon mirror substrate 400 includes micromirrors 402 arranged in a matrix in the X and Y directions in FIG. 8, a torsion bar 404 that connects the micromirrors 402 arranged in the X direction, and the torsion bar 404. And a frame-like portion 406 for connecting the end portions of the two. A slit 408 is formed around the connecting portion where the torsion bar 404 is connected to the micromirror 402. One end 404a of the torsion bar 404 is directly connected to the frame-shaped portion 406, while the other end 404b is connected to the frame-shaped portion 406 via a mirror electrode 410 having a large area.
[0118]
An address electrode outlet 412 is cut out on one side of the frame-like portion 406. A partition portion 414 is provided to partition the area where a large number of micromirrors 402 are arranged from the address electrode outlet 412.
[0119]
A plurality of silicon mirror substrates 400 are simultaneously formed on the silicon substrate, and are separated from other silicon mirror substrates along the four positions A to D shown in FIG. 8 during the dicing process. .
[0120]
A glass electrode substrate 500 shown in FIG. 8 has a concave portion 502 formed in the central region and a raised portion 504 raised and formed around the concave portion 502. The recess 502 is provided with an intermediate rib 506 at a position facing the partition portion 414 of the silicon mirror substrate 400. Further, the recess 502 has a support column 508 at a position facing the torsion bar 404 positioned between the two micromirrors 402 and 402 adjacent in the X direction in FIG. A plurality of wiring pattern portions 510 are formed in the concave portion 502 of the glass electrode substrate 500 along the Y direction in FIG. 8 on both sides of the intermediate rib 506. The wiring pattern portion 510 includes first and second address electrodes 512 and 514 facing the two regions of the micromirror 412 with the torsion bar 404 as a boundary. The plurality of first address electrodes 512 arranged along the Y direction in FIG. 8 are commonly connected to the first common wiring 516. Similarly, the plurality of second address electrodes 514 arranged along the Y direction in FIG. 8 are commonly connected to the second common wiring 518. The end portions 516 a and 518 a of the first and second common wirings 516 and 518 are formed to extend to a position beyond the intermediate rib 506.
[0121]
A plurality of glass electrode substrates 500 are simultaneously formed on a single glass substrate and then diced when separated into one light modulation element.
[0122]
When the glass electrode substrate 500 was anodically bonded to the silicon mirror substrate 400, the end portions 516a and 518a of the first and second common wirings 516 and 518 were formed in the silicon mirror substrate 400 so as to have openings. It is exposed through the address electrode outlet 412. When the silicon mirror substrate 400 and the glass electrode substrate 500 are anodically bonded, as in the first embodiment, both end portions 404a and 404b of the torsion bar 404 of the silicon mirror substrate 400 and the frame-like portion. 406 and the rising portion 504 of the glass electrode substrate 500 are anodically bonded. Further, an intermediate portion of the torsion bar 404 of the silicon mirror substrate 400 is anodically bonded to the support column portion 508 of the glass electrode substrate 500. In the second embodiment, the partition portion 414 of the silicon mirror substrate 400 is further anodic bonded to the intermediate rib 506 of the glass electrode substrate 500.
[0123]
The cover glass substrate 600 shown in FIG. 8 has a recess 602 at a position facing the arrangement region of the micromirrors 402 formed in large numbers on the silicon mirror substrate 400. A rising portion 604 is formed on the periphery of the recess 602. In the manufacturing process, a plurality of cover glass substrates 600 are formed from a single glass substrate, and one cover glass substrate 600 shown in FIG. 8 is formed by dicing the glass substrate. Then, one side 604a of the rising portion 604 is disposed at a position where it overlaps with one end 404a of the diced torsion bar 404. The other side 604b parallel to the one side 604a of the rising portion 604 is disposed at a position where it overlaps with the other end 404b of the diced torsion bar 404. As a result, the mirror electrode 410 of the silicon mirror substrate 400 is exposed to the outside. The other two sides 604c and 604d orthogonal to the one sides 604a and 604b of the rising portion 604 are arranged at positions where they overlap with the frame-like portion 406 and the partition portion 414 of the silicon mirror substrate 400, respectively.
[0124]
As a result, as shown in FIG. 9, the address electrode outlet 412 formed in the silicon mirror substrate 400 is exposed to the outside, and the first and second common wirings formed on the glass electrode substrate 500 are exposed. Wiring to 516 and 518 is possible. After this wiring, the address electrode outlet 412 is sealed and sealed with a sealing material. Further, when the above-described dicing process is performed, in the region where the one end 404a and the other end 404b of the torsion bar 404 do not exist, as shown in FIG. 9, the rising portion 504 of the glass electrode substrate 500 and the cover glass substrate 600 A gap 511 corresponding to the thickness of the torsion bar 404 is formed between the raised portion 604 and the raised portion 604. This gap 511 is also hermetically sealed with a sealing material in the same manner as described above.
[0125]
Manufacturing process of light modulator
Next, a manufacturing process of the light modulation device according to the second embodiment will be described with reference to FIG. The manufacturing process of the glass electrode substrate 500 can be substantially the same as the process shown in FIG. For the cover glass substrate 600, the processes shown in FIGS. 5B to 5D may be applied in order to form the recess 602 by etching.
[0126]
In the following, points unique to the manufacturing process of the light modulation device of the second embodiment will be described.
[0127]
(1) Step of forming boron doped layer 422
In FIG. 10A, a boron doped layer 422 is formed on one surface of the silicon substrate 420. The boron doped layer 422 is formed in the same manner as in the first embodiment.
[0128]
(2) Anodic bonding process of substrates 400 and 500
A unique point in the manufacturing process of the light modulation device according to the second embodiment is that, as shown in FIG. 10B, a silicon substrate 420 on which a boron doped layer 422 is formed is anodic bonded to a glass electrode substrate 500. This is the point.
[0129]
The anodic bonding of the two substrates 400 and 500 is performed using the apparatus shown in FIG. 6 as in the first embodiment. That is, the glass electrode substrate 500 placed on the hot plate 310 is heated to a range of 250 to 450 ° C., for example, 350 ° C. At the same time, a DC power supply 312 is connected to both the substrates 400 and 500, and a minus voltage is applied to the glass electrode substrate 500 and a plus voltage is applied to the silicon mirror substrate 400, respectively. As a result, Na (plus) in the glass electrode substrate 500 moves, the connection surface of the glass electrode substrate 500 is negatively charged, the bonding surface of the silicon mirror substrate 400 is positively charged, and both bonding surfaces A large Coulomb force acts between them to effect electrostatic bonding.
[0130]
The reason why the light modulation device according to the second embodiment is suitable for high-density mounting is that when the two substrates 400 and 500 are anodically bonded, the micromirrors and wiring pattern portions already formed as in the first embodiment are used. This is because it is not necessary to perform the exact alignment with. This exact alignment is necessary when patterning the reflective layer 402a shown in FIG.
[0131]
(3) Wet etching process of silicon substrate 420
Next, as shown in FIG. 10C, the entire surface of the silicon substrate 420 formed on the boron doped layer 422 is etched. In this wet etching, the same KOH aqueous solution having a concentration of 10 to 40% by weight as in the first embodiment is used, and silicon is etched and removed according to the etching reaction equation shown in the first embodiment. In the etching end point detection, hydrogen bubbles generated by the reaction of the silicon substrate 420 are observed, and the end point of the hydrogen bubbles can be set as the end point. Alternatively, the impurity concentration of the boron-doped layer 422 is set to 1 × 10¹⁸atm / cm^ThreeBy setting it as the above, this boron dope layer 422 can be functioned as an etching stop layer.
[0132]
The aqueous solution used for wet etching is not limited to a KOH aqueous solution, and a TMAH aqueous solution, an EPD aqueous solution, a hydrazine aqueous solution, or the like can also be used.
[0133]
(4) Deposition step of the reflective layer 402a
Next, as illustrated in FIG. 10D, the reflective layer 402 a is formed on the entire surface of the boron doped layer 422. The reflective layer 402a is formed by evaporating aluminum (Al), for example. The thickness of the reflective layer 402a can be set to 0.2 to 2 μm as in the first embodiment.
[0134]
(5) Patterning process of the reflective layer 402a
Next, as shown in FIG. 10E, a series of photolithography steps are performed to form a resist pattern portion 424 on the reflective layer 402a. The resist pattern portion 424 includes a micro mirror 402, a torsion bar 404, a frame portion 406, a slit 408, a mirror electrode 410, an address electrode outlet 412 and a partition portion 414 formed on the silicon mirror substrate 400 shown in FIG. It corresponds to the shape.
[0135]
When the reflective layer 402a is formed of aluminum (Al), wet etching can be performed by heating a mixed solution of phosphoric acid, acetic acid, and nitric acid to 30 ° C. and immersing for about 3 minutes. Thereby, as shown in FIG. 10E, the reflective layer 402a can be patterned.
[0136]
At this time, if a double-sided alignment device is used, patterning can be performed with an accuracy of 0.5 μm. That is, the position of the wiring pattern portion 510 is recognized through the microscope from the lower side of FIG. 10E, that is, from the lower side of the glass electrode substrate 500, and at the same time from the upper side of the silicon mirror substrate 400 by the microscope. Observe. And the exposure process for forming the resist pattern part 424 can be implemented on the basis of the recognition position of the wiring pattern part 510 formed in the glass electrode substrate 500. As a result, the resist pattern 424 having a shape corresponding to the micromirror 402 or the like can be formed at positions facing the first and second address electrodes 512 and 514 of the wiring pattern portion 510, thereby increasing the mounting density. However, accurate patterning can be performed.
[0137]
Further, if foreign matter is mixed in the sandwiched space before the bipolar bonding of the two substrates 400 and 500, it is extremely difficult to remove this. If the foreign matter adheres to the wiring pattern portion 510 of the glass electrode substrate 500, when the micromirror 402 is driven to be tilted, a short circuit occurs between them, resulting in a defect and a decrease in yield.
[0138]
Therefore, in the second embodiment, before anodic bonding of the two substrates 400 and 500, light is irradiated from the transparent glass electrode substrate 500 side to inspect whether foreign matter is mixed. At this time, the wiring pattern portion 510 formed on the glass electrode substrate 500 is preferably a transparent electrode, for example, ITO, instead of a metal such as Al or Ag. In this way, it is possible to detect foreign matter adhering to the ITO surface.
[0139]
(6) Dry etching process of boron doped layer 422
For etching the boron doped layer 422, dry etching is more suitable than wet etching. The reason for this is that in the case of wet etching, foreign matter may adhere from the outside or dry spots may occur in the series of steps of etching, washing and drying the boron doped layer 422, but in dry etching there is no such thing. is there.
[0140]
In order to dry-etch the boron doped layer 422, the resist pattern portion 424 is used as an etching resistant mask material. This dry etching can be performed under the same conditions as in the step of FIG. 4F of the first embodiment.
[0141]
(7) Stripping process of resist pattern portion 424
The resist pattern portion 424 can be removed by ashing by a dry process using, for example, a UV ashing apparatus.
[0142]
(8) Joining process of cover glass substrate and silicon mirror substrate
Since the cover glass substrate 600 does not require highly accurate bonding as in the first embodiment, it can be bonded by an adhesive instead of anodic bonding.
[0143]
(9) Sealing process
In order to prevent water and foreign matter from entering during dicing, the electrode extraction opening 412 shown in FIG. 9 is sealed with a sealing material. A fine gap 511 shown in FIG. 9 generated after dicing is also sealed in the same manner.
[0144]
(10) Dicing process
Each process described above is performed in a state of a silicon substrate or a glass substrate on which a plurality of substrates 400, 500 and 600 for constituting a plurality of light modulation elements can be mounted. Then, after the bonding process of the cover glass substrate 600 is completed, dicing for separating into individual light modulation elements is performed. During this dicing, the substrates 400, 500 and 600 are diced along the positions A to D shown in FIG. As a result, the plurality of torsion bars 404 that are connected to each other during assembly are separated from each other.
[0145]
(11) Wiring process
Finally, the separated mirror electrode 410 of the light modulation element and the end portions 512a and 514a of the address electrodes 512 and 514 are connected to a drive circuit (not shown) for wiring. Thereby, the light modulation device is completed.
[0146]
In the first and second embodiments described above, an example in which the silicon mirror substrate and the glass electrode substrate are anodically bonded has been described, but other bonding methods may be employed instead. Other examples include direct bonding and eutectic bonding.
[0147]
Direct bonding can be used when the mirror substrate and the electrode substrate are both silicon substrates. After thoroughly cleaning the silicon substrate and improving the wettability of the bonded surface of the silicon substrate, alignment and temporary fixing are performed at room temperature using, for example, an infrared microscope. Then, the silicon substrates temporarily bonded can be directly bonded to each other by heat treatment in a nitrogen atmosphere at 800 to 1200 ° C. and 1100 ° C. as an optimum temperature for 1 to 4 hours. Here, when the wettability of the silicon substrate is good, the silicon surface element is a Si—O—H bond. By heat-treating this, a dehydration reaction occurs to form a Si—O—Si covalent bond, and the silicon substrates are bonded to each other.
[0148]
Eutectic bonding can be used when the bonding surface of the electrode substrate is made of aluminum (Al) or gold (Au). These metals are easily alloyed at a relatively low temperature of 300 to 350 ° C. For example, when an Au film is formed on an electrode substrate by sputtering, a silicon mirror substrate is brought into contact with the surface of the Au film, and heat treatment is performed at 300 to 400 ° C. for 1 to 2 hours, Au at the bonding interface diffuses into Si. As a result, the bonding interface disappears and bonding is performed.
[0149]
Thus, the material of the electrode substrate can be variously selected according to the joining method adopted. However, when bonding is performed under heating, it is preferable that the thermal expansion coefficient is close to that of silicon.
[0150]
(Third embodiment)
The third embodiment described below shows a configuration that can reliably prevent a short circuit between the micromirror 402 and the first and second address electrodes 512 and 514. As shown in FIG. 11A, an insulating film 416 is formed on the surface of the micromirror 402 facing the first and second address electrodes 512 and 514. In this case, even if the foreign material 10 exists between the micromirror 402 and the first and second address electrodes 512 and 514, the micromirror 402 and the first and second address electrodes 512 are formed by the insulating film 416. , 514 can be prevented from being short-circuited.
[0151]
When the insulating film 416 is formed on the back side of the micromirror 402, the first and second address electrodes 512 and 514 are used as stoppers for determining the tilt angle when the micromirror 402 is tilted, as shown in FIG. It can also be used. For example, in the case of the light modulation device shown in the first embodiment, this type of insulating film can be realized by omitting the thermal oxide film peeling step shown in FIG. That is, the thermal oxide film 114 formed in FIG. 4C can also be used as an insulating film.
[0152]
In order to prevent a short circuit between the micromirror 402 and the first and second address electrodes 512 and 514, insulation is formed on the surfaces of the first and second address electrodes 512 and 514 using a sputtering apparatus or the like. You may form by an apparatus.
[0153]
When the insulating film 416 is formed on the back surface of the micromirror 402, the surfaces of the first and second address electrodes 512 and 514 are preferably formed to be rough surfaces. Thus, the contact area of the electrodes 512 and 514 that are in contact with the micromirror 402 can be reduced. If it is not formed on the rough surface, hot carriers are charged in the insulating film 416 formed on the micromirror 402, and the micromirror 402 sticks to the electrodes 512 and 514. These problems can be prevented only by making the surfaces of the electrodes 512 and 514 rough. This rough surface can be realized by forming convex portions on the electrode surface, preferably having a height of 200 angstroms or more.
[0154]
In order to make the surfaces of the first and second address electrodes 512 and 514 rough, for example, film formation may be performed using sputtered particles having a large particle diameter by changing the conditions during film formation by sputtering. Alternatively, when the electrodes 512 and 514 are formed by a vapor deposition method, the surfaces become rough surfaces.
[0155]
Alternatively, in the etching process for forming the recesses 202 and the like shown in FIG. 5C, the etching condition is changed to make the etching surface rough, thereby making the ITO film surface formed thereon rough. be able to.
[0156]
In order to reduce the contact area between the insulating film 416 formed on the micromirror 402 and the electrodes 512 and 514, as shown in FIG. 12, on both ends of the micromirror 402 and a part of the insulating film 416. It is also possible to form a micropyramid 416a that protrudes downward. In order to form the micropyramid 416a, the steps shown in FIGS. 13A to 13C may be performed. First, a flat first oxide film 430 is formed over the insulating film 416 as shown in FIG. Thereafter, a second oxide film 432 is locally formed on the first oxide film 430 and at both end portions of the micromirror 402.
[0157]
Next, the first and second oxide films 430 and 432 are etched. In this case, as shown in FIG. 13B, if the etching rate is uniform over the entire surface, the first oxide film 430 in the peripheral region is completely removed even after the first oxide film 430 in the central region is completely removed. The oxide film 430 remains. Subsequently, when the etching is continued, only the surface of the insulating film 416 in the central region is etched, and the insulating film 416 at the end thereof is not etched.
[0158]
Then, as shown in FIG. 13C, the micro-pyramid 416a formed of the insulating film 416 is formed at both ends of the micromirror 402 by removing the oxide film remaining at the end portion. Can do.
[0159]
In order to prevent charging of the insulating film 416 formed on the back surface of the micromirror 402 by the first and second address electrodes 512 and 514, as shown in FIG. It is also possible to provide a property stopper 530. In this way, even when the micromirror 402 is tilted, the distance between the insulating film 416 on the back surface side and the first and second address electrodes 512 and 514 can be increased, so that the micromirror 402 is charged due to charging. Sticking can be prevented.
[0160]
(Fourth embodiment)
Next, an embodiment in which a projector is configured using the light modulation device of the first embodiment or the second embodiment will be described with reference to FIGS.
[0161]
FIG. 15 shows an embodiment in which a projector is configured using a one-stage light modulation device 700. As shown in the figure, the white light emitted from the projection lamp 702 is condensed on the rotary color filter 706 via the condenser lens 704. The rotary color filter 706 has three color filters of R, G, and B. By rotating each color filter with respect to the condensing position of the condenser lens 704, light of different color wavelengths sequentially passes through the filter.
[0162]
The light sequentially transmitted through the “R”, “G”, and “B” filters of the rotary color filter 706 is incident on the light modulation device 700 via the condenser lens 708, the reflection mirror 710, and the half prism 712. become. In this light modulation device 700, based on the video signal from the outside, according to the driving method described above, scanning is performed to tilt the micromirrors sequentially from the end in the X direction (horizontal direction), and the Y direction (vertical direction). ) Sequentially, the incident light is reflected by the micromirrors arranged in a matrix. Thereby, the reflected light modulated according to the gradation can be obtained in each of the matrix-like pixels in which the micromirrors are arranged.
[0163]
The reflected light is incident on the projection lens 714 as parallel light via the half prism 712, and is enlarged and projected on the screen 716 via the projection lens 714.
[0164]
Here, the light modulation device 700 of this embodiment has a polarizing plate and has a light utilization efficiency of three times or more compared with a conventional liquid crystal panel having a low light utilization rate, and has sufficient brightness on the screen 716. It is possible to display an image having the same.
[0165]
Moreover, the response speed of the micromirror is 20 μsec, which is much faster than the conventional liquid crystal of 30 msec, and can prevent image flickering. Furthermore, in the case of using a conventional liquid crystal panel, since the light use efficiency is low, three liquid crystal panels corresponding to “R”, “G”, and “B” are required. The alignment adjustment in was very complicated.
[0166]
On the other hand, if the light modulation device 700 of the present embodiment is used, sufficient brightness can be obtained with only one stage as shown in FIG. 15, and alignment adjustment becomes extremely easy.
[0167]
The light modulation device 700 can be provided in two or three stages as shown in FIGS. In the case of FIG. 16, the rotary color filter 707 has “G” and “B” filters, and a spectral prism 717 that splits into two wavelengths is disposed in front of the two light modulators 700. On the other hand, in the case of FIG. 17, a rotary color filter is not used, and a spectroscopic prism 718 that performs spectroscopy in a three-wavelength region is provided in front of the three light modulation devices 700. In this way, the light modulation device 700 can be used for any two colors of wavelengths, or can be arranged in two or three stages independently for each wavelength. In this way, a brighter and clearer image can be projected on the screen 716.
[0168]
(5th Example)
FIG. 18 shows an embodiment in which the light modulation device 720 of this embodiment is applied to an electrophotographic apparatus such as a laser printer. In this embodiment, the light modulation device 720 is used as a substitute for the conventional polygon mirror. In the figure, the plurality of micromirrors 722 of the light modulation device 720 are arranged along a direction parallel to the laser light emitted from the laser light source 724.
[0169]
FIG. 18 shows a state in which the minute mirror 722 located at the right end is ON-driven, and the photosensitive drum 730 is disposed in the preceding stage in the traveling direction of the reflected light reflected when the minute mirror 722 is ON-driven. Has been placed. At this time, the other micromirrors are OFF-driven and do not block the laser beam.
[0170]
As shown in FIG. 19, the photosensitive drum 730 can be rotated clockwise, for example. Around the photosensitive drum 730, an exposure lamp 732, a developing device 734, a transfer device 736, a cleaning device 738, and a charge eliminating device 740 are arranged. When the respective micromirrors 722 of the light modulation device 720 shown in FIG. 18 are scanned in order from the right side to the left side of the drawing, the surface potential of the photosensitive drum 730 charged in advance by the exposure lamp 732 to a constant potential becomes the micromirror 722. The potential changes based on the reflected light modulated by, and a latent image is formed. As the photosensitive drum 730 rotates, the developing device 734 attaches toner to the latent image and develops it, and the transfer device 736 transfers the toner to the recording medium 744 side. The recording medium 744 is discharged after being fixed by a fixing roller 742 provided at the subsequent stage. Further, after the transfer is completed, the toner remaining on the photosensitive drum 730 is collected by the cleaning device 738, and is neutralized by the neutralizing lamp 740 to return to the initial state.
[0171]
As described above, according to this embodiment, the light modulation device 720 can be used as a substitute for the conventional polygon mirror, and the light modulation device 720 can be mounted at high density and has a high response speed. A resolution image can be recorded on the recording medium 744.
[0172]
(Sixth embodiment)
The sixth embodiment shows an embodiment in which the light modulation device of this embodiment is applied to, for example, an optical card capable of optical switching. As shown in FIG. 20, on the insulating substrate 750, a plurality of, for example, twelve induction coils 752-1 to 752-12 capable of generating an arbitrary induced voltage are provided.
[0173]
The light modulation device 760 of this embodiment is disposed at the end on the insulating substrate 750. The induction coils 752-1 to 752-12 are connected to the first and second address electrodes respectively facing the six micromirrors provided in the light modulation device 760 via the wiring pattern 754. ing.
[0174]
When this optical card is inserted into a device that can detect an optical switching signal from this optical card, 12 devices on the device side correspond to the 12 induction coils 752-1 to 752-12 formed on the insulating substrate 750, respectively. Inductive coils are arranged. When this is energized, an induction voltage is generated in each induction coil 752-1 to 752-12. Based on this induced voltage, the six micromirrors in the light modulation device 760 can be tilted and an optical switching signal modulated by the reflected light can be obtained.
[0175]
Here, since the light modulation device 760 can be formed extremely small, it can be sufficiently accommodated in a portable card. In addition, since this optical card is unrelated to the influence of magnetism, data in the card can be prevented from being read and used for crimes.
[0176]
(Seventh embodiment)
In the seventh embodiment, a light modulation device 780 according to the present invention is incorporated in an exposure apparatus, and is used to write a lot number and other wafer-specific information on the surface of a semiconductor wafer 770 to be exposed.
[0177]
Opposing to the wafer mounting table 772 on which the wafer 770 is mounted, a light source 774 for exposure is provided for the information. A reticle 776 for reducing and projecting light emitted from the light source 774 as a predetermined mask pattern image on the wafer 770 is provided between the light source 774 and the wafer mounting table 772. The light modulation device 780 incorporated in the exposure apparatus is disposed at a position where a part of light from the light source 774 is incident, and when the micromirror is turned ON, the reflected light is a predetermined position on the wafer 770. It is made to enter.
[0178]
Here, the wavelength of the light source 774 of the exposure apparatus becomes shorter as the g-line, i-line, and excimer lasers and the density of elements increase. If such short-wavelength light is modulated by an optical switching element using liquid crystal, the sealed liquid crystal is quickly deteriorated.
[0179]
Since the light modulation device 780 of the present invention only reflects this short wavelength with a micromirror, it has sufficient durability.
[0180]
As described above, when the light modulation device 780 of the present invention is used, ID information and the like can be recorded on the wafer 770 by using the light for short wavelength exposure from the light source 774, and a light source is provided separately. There is no need.
[0181]
The light modulation device according to the present invention is not limited to those applied to the various devices described above, but can be applied to devices that perform gradation modulation of light or various devices that simply perform ON / OFF modulation. For example, the light reflected by the micromirror of the light modulation device can be directly viewed, and can be applied to advertising billboards for displaying characters such as pictures and characters, or clock displays. .
[0182]
[Brief description of the drawings]
FIG. 1 is an exploded perspective view of a light modulation device according to a first embodiment of the present invention.
FIG. 2 is an enlarged perspective view of a micromirror used in the apparatus shown in FIG.
3A is a plan view of a micromirror, and FIG. 3B is a side view of the micromirror.
4A to 4I are schematic cross-sectional views for explaining a manufacturing process of a silicon mirror substrate of the light modulation device shown in FIG.
5A to 5G are schematic cross-sectional views showing a manufacturing process of the glass electrode substrate of the light modulation device shown in FIG.
6 is a schematic explanatory view for explaining the anodic bonding step of FIG. 4 (I). FIG.
7A is a schematic explanatory diagram for explaining a state in which a plurality of light modulation devices shown in FIG. 1 are manufactured from one wafer, and FIG. 7B is one light modulation separated from the wafer. It is a schematic perspective view of an apparatus.
FIG. 8 is an exploded perspective view of an optical modulation device according to a second embodiment of the present invention.
FIG. 9 is a perspective view of a light modulation device according to a second embodiment.
10A to 10H are schematic cross-sectional views illustrating a manufacturing process of the apparatus shown in FIG.
FIGS. 11A and 11B are schematic explanatory views for explaining a third embodiment of the present invention in which an insulating film is formed on the back surface of a micromirror, respectively.
FIG. 12 is a schematic explanatory view showing a modification of the third embodiment in which a micropyramid is provided at an end portion of an insulating film formed on the back surface of a micromirror.
FIGS. 13A to 13C are schematic cross-sectional views showing steps of forming the micropyramid shown in FIG.
FIG. 14 is a schematic explanatory view showing a modification of the third embodiment in which an insulating stopper is provided on a glass electrode substrate.
FIG. 15 is a schematic explanatory diagram of a fourth embodiment of the present invention in which a projector is configured by providing a one-stage light modulation device.
FIG. 16 is a schematic explanatory diagram showing a modification of the fourth embodiment in which a projector is configured by providing a two-stage light modulation device.
FIG. 17 is a schematic explanatory diagram illustrating a modification of the fourth embodiment in which a projector is configured by providing a three-stage light modulation device.
FIG. 18 is a schematic explanatory diagram of a fifth embodiment of the present invention in which an electrophotographic apparatus is constructed using the light modulation device of the present invention as a substitute for a polygon mirror.
FIG. 19 is a schematic explanatory diagram for explaining a configuration around the photosensitive member of the electrophotographic apparatus shown in FIG. 18;
FIG. 20 is a schematic explanatory diagram for explaining a sixth embodiment of the present invention in which an optical modulation device is applied to an optical card as an optical switching device.
FIG. 21 is a schematic explanatory diagram for explaining a seventh embodiment of the present invention in which a light modulation device is built in an exposure apparatus;
FIG. 22 is an exploded perspective view of a conventional light modulation device.
FIG. 23 is a schematic explanatory diagram for explaining an optical modulation operation of a conventional optical modulation device.
24A to 24H show a manufacturing process of the conventional light modulation device shown in FIG. 22, and are schematic explanatory views of a process of forming an intermediate layer on a lower layer.
FIGS. 25A to 25F are schematic explanatory views showing a conventional process for forming an upper layer on the intermediate layer obtained in FIG. 24; FIGS.
[Explanation of symbols]
100,400 Mirror substrate made of silicon
102,402 micro mirror
202a, 402a Reflective layer
104,404 Torsion bar
106,406 Frame-shaped part
110,420 Silicon substrate
112,422 doped layer
116 First mask
118 Second mask
200,500 Glass electrode substrate
202,502 recess
204,504 Rising part
210,508 underground
212,510 Wiring pattern section
214, 512 First address electrode
216,514 Second address electrode
218, 516 First common wiring
220, 518 Second common wiring
300,600 Cover glass substrate
310 hot plate
312 DC power supply
320,770 Semiconductor wafer
700, 720, 760, 780 light modulator
702, 714 Projection lamp
706 Rotating color filter
712 half prism
716 screen
724 Laser light source
730 Photosensitive drum
734 Development Device
736 Transfer device
750 Insulating substrate
752 induction coil
754 Wiring pattern
772 Wafer mounting table
774 Light source
776 reticle

Claims (24)

In the manufacturing method of the light modulation device,
(A) a plurality of micromirrors arranged in a line or matrix;
A torsion bar that connects the plurality of micromirrors in one direction;
And forming a conductive silicon mirror substrate having a reflective layer formed on at least one surface of the micromirror, and
(B) a recess in the central region;
The surrounding startup section,
A conductive layer is formed at a position corresponding to each of the micromirrors in the recess, and an electrode group that tilts the micromirrors by Coulomb force;
A column portion that protrudes from the recess at a position corresponding to between the two micromirrors adjacent in the one direction;
Forming an electrode substrate having:
(C) at least an intermediate portion of the torsion bar of the silicon mirror substrate and the support portion of the electrode substrate are faced to join the silicon mirror substrate and the electrode substrate;
Have
The step (a) includes a step in which both ends of the torsion bar are connected and a frame-like portion surrounding a region where the micromirror is disposed is formed on the silicon mirror substrate,
The step (c) includes a step of joining the frame-like portion of the silicon mirror substrate and both end portions of the torsion bar and the rising portion of the electrode substrate,
A method for manufacturing an optical modulation device, comprising the step of separating both end portions of the torsion bar from the frame-shaped portion of the silicon mirror substrate after the step (c). In claim 1,
The step (a)
Forming a doped layer by doping impurities in the silicon substrate;
Patterning a first mask for forming a window on one surface of the silicon substrate, and a second mask for forming the plurality of micromirrors, the torsion bars, and the frame-shaped portion on the other surface;
Etching the silicon substrate using the first mask until the doped layer is exposed;
Etching the doped layer using the second mask;
Removing the first and second masks and forming the micromirrors, torsion bars and frame-like portions with the doped layer;
Forming the reflective layer on one side of the micromirror of the doped layer;
And forming the silicon mirror substrate. In the manufacturing method of the light modulation device provided with a plurality of micromirrors in one line or matrix,
(A) a recess in the central region;
The surrounding startup section,
A conductive layer is formed at a position corresponding to each of the micromirrors in the recess, and an electrode group that tilts the micromirrors by Coulomb force;
A strut portion that protrudes into the recess at a position corresponding to between the two micromirrors adjacent in one direction;
Forming an electrode substrate having:
(B) a step of bonding a silicon substrate on which a doped layer doped with impurities is formed on one side and the electrode substrate with at least the support portion of the electrode substrate facing the doped layer;
(C) etching and removing the silicon substrate leaving the doped layer;
(D) forming a reflective layer on the surface of the doped layer;
(E) etching the doped layer and the reflective layer;
Forming a plurality of the micromirrors at a position facing the electrode group;
The plurality of micromirrors are connected in the one direction, and are joined to the support column between two adjacent micromirrors in the one direction, and both ends thereof are joined to the rising portion or the support column. Forming a torsion bar,
Forming a silicon mirror substrate from the doped layer and the reflective layer;
Have
In the step (e), both ends of the torsion bar are connected, and a frame-like portion joined to the rising portion is formed on the silicon mirror substrate at a position surrounding the region where the micromirror is arranged. Including steps,
A method of manufacturing an optical modulation device, comprising the step of separating both end portions of the torsion bar from the frame-shaped portion of the silicon mirror substrate after the step (e). In claim 2 or 3,
The impurity concentration of the doped layer is 1 × 10 ¹⁸ atm / cm ³ or more,
A method of manufacturing a light modulation device, wherein the doped layer is used as an etching stop layer during etching of the silicon substrate. In claim 3,
The electrode substrate is formed of a glass electrode substrate having optical transparency,
A position of the pattern of the electrode group is observed from the glass electrode substrate side, and a mask pattern for etching in the step (e) is aligned based on the pattern position. Production method. In any one of Claims 1 thru | or 5,
The electrode substrate is formed of a glass electrode substrate containing an alkali metal,
An anodic bonding method is used as the bonding step. In claim 6,
Masking the position corresponding to the raised portion and the column portion, etching a glass plate containing an alkali metal, and forming the concave portion of a predetermined depth;
Forming the electrode group on the bottom surface of the recess;
The method for manufacturing a light modulation device is characterized in that the glass electrode substrate is formed. In any of claims 5 to 7,
Forming the electrode group with a transparent electrode;
A method for manufacturing a light modulation device, further comprising the step of inspecting from the glass electrode substrate side whether foreign matter is mixed between the glass electrode substrate and the silicon mirror substrate. In any one of Claims 1 thru | or 8.
The method of manufacturing a light modulation device, further comprising the step of forming an insulating film on the side of the micromirror facing the electrode group. In claim 9,
A method of manufacturing a light modulation device, comprising: forming a rough surface of the electrode group facing the insulating film formed on the micromirror. In claim 9,
A method of manufacturing a light modulation device, further comprising forming an insulating protrusion on the insulating film at a position away from the torsion bar. In claim 9,
Forms an insulating stopper that protrudes from the bottom surface of the concave portion of the electrode substrate at a height lower than the top surface of the rising portion and the column portion, and determines an inclination angle by abutting with the minute mirror during inclination driving. A method for manufacturing a light modulation device, further comprising the step of: In any one of Claims 1 to 12,
A light modulation device further comprising a step of bonding a transparent cover substrate on the silicon mirror substrate at a position that covers the silicon mirror substrate and does not interfere with the micromirror that is tilted. Production method. The conductive silicon mirror substrate doped with impurities and the electrode substrate are joined and integrated,
The silicon mirror substrate is
A plurality of micromirrors arranged in a line or matrix and having a reflective layer formed on one side;
A torsion bar that connects the plurality of micromirrors in one direction;
Have
The electrode substrate is
A recess in the central region;
The surrounding startup section,
An electrode group formed in a position corresponding to each of the micromirrors in the recess, and driving the micromirrors to be inclined by Coulomb force;
A strut portion formed to project into the recess at a position corresponding to between the two micromirrors adjacent in the one direction;
Have
At least an intermediate portion of the torsion bar of the silicon mirror substrate and the support portion of the electrode substrate face each other, and the silicon mirror substrate and the electrode substrate are bonded,
A square frame-like frame having first opposing two sides connected to both ends of the torsion bar in the manufacturing stage of the silicon mirror substrate and a second opposing two sides connecting the first opposing two sides The first opposed two sides are cut after the frame-shaped portion is bonded to the electrode substrate, and both ends of the torsion bar are exposed, and the second opposed two sides are connected to the electrode substrate. A light modulation device characterized in that it remains bonded. In claim 14,
The electrode substrate is formed of a glass electrode substrate containing an alkali metal,
The light modulation device, wherein the glass electrode substrate and the silicon mirror substrate are anodically bonded. In claim 14 or 15,
The light modulation device, wherein the entire surface of the reflection layer formed on the micromirror is formed as a flat surface that reflects incident light at a reflection angle equal to the incident angle. In any of claims 14 to 16,
The light modulation device, wherein the electrode group is formed of a transparent electrode. In any of claims 14 to 17,
An optical modulation device, wherein an insulating film is formed on a surface of the micromirror facing the electrode group. In claim 18,
The light modulation device characterized in that the surface of the electrode group facing the insulating film formed on the micromirror is formed to be a rough surface. In claim 19,
The light modulation device, wherein the surface of the electrode group is provided with a convex portion having a height of 200 angstroms or more to form the rough surface. In claim 18,
An optical modulation device, wherein an insulating protrusion is formed on the insulating film at a position away from the torsion bar. In claim 18,
An insulating stopper that protrudes from the bottom surface of the concave portion of the glass electrode substrate at a height lower than the top surface of the rising portion and the support column and determines the tilt angle by abutting against the micromirror during tilt driving An optical modulation device further comprising: 23. Any one of claims 14-22.
A light modulation device, characterized in that a transparent cover substrate is bonded onto the silicon mirror substrate at a position that covers the silicon mirror substrate and does not interfere with the micromirror that is tilted.   24. An electronic apparatus comprising the light modulation device according to claim 14.

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