JP2004212680A

JP2004212680A - Optical modulator array and method of manufacturing same

Info

Publication number: JP2004212680A
Application number: JP2002382580A
Authority: JP
Inventors: Koichi Kimura; 宏一木村; Fumihiko Mochizuki; 文彦望月
Original assignee: Fuji Photo Film Co Ltd
Current assignee: Fujifilm Holdings Corp
Priority date: 2002-12-27
Filing date: 2002-12-27
Publication date: 2004-07-29

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical modulator array in which the decrease in film and a residual stress of a movable transparent electrode due to a removing process of a sacrificial layer for making a gap are suppressed and the moving operation of the movable part is stably performed, and to provide a method of manufacturing the optical modulator array. <P>SOLUTION: The optical modulator array is composed by providing a transparent substrate 1, a substrate having a transparent electrode 2, and a movable part 8 which is furnished on the substrate with a gap 5, and composed of a flexible thin film having a transparent electrode 7 on the surface opposite to the substrate and a protective film 40 having a translucency and covering the transparent electrode 7, and arranging the optical modulators, which emit light emitted from a light source from the movable part 8 to the outside by moving the movable part 8 to the side of the substrate with an electrostatic force generated by applying a voltage between both transparent electrodes 2 and 7, in a two-dimensional matrix. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

【０００１】
【発明の属する技術分野】
本発明は、マイクロマシニングにより作製され、電気機械動作により光の透過率を変化させる光変調素子アレイ及びその製造方法に関するものである。
【０００２】
【従来の技術】
マイクロマシニングにより作製された可撓薄膜を可動部とし、これを静電気力により機械的動作させることで光変調を行う電気機械的な光変調素子が知られている（例えば、特許文献１参照）。図３はそのような光変調素子の一例を示す概略断面図であるが、光変調素子１０は、透光性を有する透明基板１に設けられた透明電極（以下、「固定透明電極」と呼ぶ）２の上に、支柱３を介して、透明基板１側より順に透明絶縁膜４、光拡散層６及び透明電極（以下、「可動透明電極」と呼ぶ）７を積層して構成される可動部８を備え、更に両透明電極２，７の間に電源９を接続して概略構成される。また、透明基板１の可動部８とは反対側の面（図では下方）には図示されない光源が配置されており、例えば紫外線等の光Ｌが照射される。
【０００３】
上記光変調素子１０において、光の変調は、固定透明電極２と可動部８とを離反又は接触させることによる導光拡散作用を利用する。即ち、固定透明電極２と可動透明電極７との間に電圧を印加しない状態（ＯＦＦ時）では同図（ａ）に示すように、透明基板１に入射した光Ｌは、透明基板１の屈折率と空隙部５である空気の屈折率との違いから、透明基板１の表裏面での屈折を繰り返しながら伝搬を続けるのみで、可動部８へと透過せず、遮光状態となる。一方、固定透明電極２と可動透明電極７との間に所定の電圧を印加すると（ＯＮ時）、同図（ｂ）に示すように、両透明電極間に静電気力が発生して可動部８が透明基板１に向かって撓み、透明絶縁膜４と固定透明電極２とが接触もしくは十分に接近する。それに伴い、光Ｌは透明基板１の界面から固定透明電極２を通じて透明絶縁膜４へと伝搬し、光拡散層６にて散乱された後、可動透明電極７を通じて外部に出射して導光状態となる。また、この状態から電圧の印加を停止すると、静電気力が作用しなくなり可動部８が弾性復帰して透明絶縁膜４が固定透明電極２から離反し、その結果光Ｌの透過が行われなくなり、遮光状態に戻る。
【０００４】
また、ファブリペロー干渉を利用した同様の光変調素子も知られている。ファブリペロー干渉では、二枚の平面が向かい合わせに平行に配置された状態において、入射光線は、反射と透過を繰り返して多数の光線に分割され、これらは互いに平行光となる。その中で透過光線は、無限遠において重なり合い干渉する。面の垂線入射光線とのなす角をθとすれば、隣り合う光線間の光路差は「ｘ＝ｎＤ・ｃｏｓθ（但し、ｎは二面間の屈折率、Ｄは間隔）」で与えられる。そして、光路差ｘが波長λの整数倍であれば透過線は互いに強め合い、半波長の奇数倍であれば互いに打ち消し合う。即ち、反射の際の位相変化がなければ、「２ｎＤ・ｃｏｓθ＝ｍλ」で透過光最大となり、「２ｎＤ・ｃｏｓθ＝（２ｍ＋１）λ／２」で透過光最小となる。但し、ｍは正整数である。従って、光路差ｘが所定の値となるように、両平面を接近または離反させてその間隔（Ｄ）を透過光最大となる間隔（Ｄｏｎ）または透過光最小となる間隔（Ｄｏｆｆ）に一致させることにより、遮光状態及び導光状態を制御することができる。
【０００５】
例えば、図４はこのようなファブリペロー干渉を利用した光変調素子である。以下、この光変調素子を「干渉型光変調素子」と呼び、それに伴い図３に示した光変調素子を「全反射型光変調素子」と呼ぶ。図３に示した全反射型光変調素子１０は、透明基板２１の固定透明電極２２上に誘電体ミラー（以下、「固定誘電体ミラー」と呼ぶ）３０を設け、透明絶縁膜２４及び可動透明電極２７を積層して構成される可動部２８に、更に透明絶縁膜２４の固定誘電体ミラー３０と対向する面に固定誘電体ミラー３０と同一の誘電体ミラー（以下、「可動誘電体ミラー」と呼ぶ）３１を付設して光変調素子２０が構成される。固定誘電体ミラー３０及び可動誘電体ミラー３１は、酸化シリコンや酸化チタン等の誘電体からなる薄膜を複数層に積層して形成され、両誘電体ミラー３０，３１の間隔２５は、電源２９からの導通が無い状態（ＯＦＦ時）で上記の透過光最小を満足する距離（Ｄｏｆｆ）となるように規定されている。また、光Ｌはコリメートされて透明基板２１に垂直に入射する。
【０００６】
この干渉型光変調素子２０では、ＯＦＦ時には同図（ａ）に示すように、両誘電体ミラー３０，３１は上記距離（Ｄｏｆｆ）で離間しており、光Ｌは透明基板２１と固定透明電極２２との界面で反射されて遮光状態となる。そして、ＯＮ時には同図（ｂ）に示すように、静電気力により可動部２８が透明基板２１側に撓んで両誘電体ミラー３０，３１の間隔が狭くなる。この間隔は、上記の透過光最大を満足する距離（Ｄｏｎ）であり、印加電圧を調節して透明絶縁膜２４に作用する静電気力と、透明絶縁膜２４の変形に伴って生じる復元力とをバランスさせることで適切に設定する。そして、可動部２８が撓むことにより、透明基板２１に入射した光Ｌは、固定誘電体ミラー３０から間隔２５を経て可動誘電体ミラー３１へと透過し、引き続き可動部２８を透過して可動透明電極２７から出射して導光状態となる。
【０００７】
以上のように、上記した各光変調素子１０，２０は静電気力の作用により可動部８，２８を変位させることにより、遮光状態及び導光状態を切り替えることができる。
【０００８】
また、図示は省略するが、上記の光変調素子１０，２０を２次元マトリクス状に配置した光変調素子アレイも実用化されている。
【特許文献１】
特開平１１−２５８５５８号公報
【０００９】
【発明が解決しようとする課題】
ところで、光変調素子１０，２０はマイクロマシングと呼ばれる方法より製造される。ここで、図３に示した全反射型光変調素子１０を例とし、図５を参照してその製造方法を説明する。尚、同図において断面Ａは図３に示した断面に一致し、断面Ｂは断面Ａと直交する方向における断面を示している。
【００１０】
先ず工程（ａ）に示すように、透明基板１の上に固定透明電極２を成膜し、次いで工程（ｂ）に示すように、固定透明電極２の上に犠牲層１５を成膜する。この犠牲層１５は空隙５を形成するために最終的に除去されるもので、例えばレジストや金属等を上記の透過光最小となる間隔（Ｄｏｆｆ）に一致する膜厚で成膜して得られる。次いで工程（ｃ）に示すように、マスク１６を用いて犠牲層１５を空隙５の形状に合わせてパターニングする。次いで工程（ｄ）に示すように、犠牲層１５と同一高さとなるように支柱３を形成する材料を設ける。次いで工程（ｅ）に示すように、可撓薄膜を構成する透明絶縁膜４、光拡散層６及び可動透明電極７を順次成膜する。次いで工程（ｆ）に示すように、マスク１７を用いて、犠牲層１５の上方位置にて可動透明電極７に所定間隔で複数の開口部１８を設ける。次いで工程（ｇ）に示すように、可動透明電極７をマスクとして、エッチングにより開口部１８から固定透明電極２に至る貫通孔１９を穿設する。そして、工程（ｈ）に示すように、犠牲層１５を除去して空隙５を形成し、複数の可動部８を得る。
【００１１】
上記工程（ｈ）において、犠牲層１５の除去は通常ドライエッチングにより行われ、可動透明電極７の上方から貫通孔１９を通じて、例えば酸素プラズマ等のエッチング媒体を犠牲層１５に作用させている。そのため、犠牲層１５の除去に伴って可動透明電極７もエッチングされ、膜減りして強度低下に陥ったり、応力が残留するなどして可動部８の変位動作に悪影響を及ぼす。
【００１２】
本発明は上記の状況に鑑みてなされたものであり、空隙を形成するための犠牲層の除去に伴う可動透明電極の膜減りや応力残留を抑え、可動部の変位動作を安定して行い得る光変調素子アレイを提供すること、並びに前記光変換素子アレイを得るための製造方法を提供することを目的とする。
【００１３】
【課題を解決するための手段】
上記目的を達成するために本発明は、透明電極を有する基板と、前記基板上に空隙を介在させて設けられ、基板とは反対側の面に透明電極を有する可撓薄膜からなる可動部とを備え、前記両透明電極との間に電圧を印加して静電気力により前記可動部を前記基板側に変位させることにより、光源からの光を前記基板及び前記可動部を透過させて外部に出射させる光変調素子を２次元マトリクス状に配列してなる光変調素子アレイにおいて、前記可動部の透明電極の表面に、透光性を有する保護膜が成膜されていることを特徴とする光変調素子アレイを提供する。
【００１４】
上記の光変調素子アレイでは、可動透明電極上に保護膜が成膜されているため、犠牲層除去のためのエッチングに対して可動透明電極が保護され、可動部の安定した変位動作を実現する。
【００１５】
また、本発明は、上記の光変調素子アレイを製造するために、
（ａ）前記基板上に犠牲層を形成し、
（ｂ）前記犠牲層を空隙の形状に形成し、
（ｃ）残存犠牲層及び前記基板の露出部分を覆うように、透明電極を最上層として前記可撓薄膜を構成する各層を積層し、
（ｄ）前記透明電極上に透光性を有する保護膜を形成し、
（ｅ）前記残存犠牲層の上方位置にて前記保護膜から前記基板に至る複数の貫通孔を穿設し、
（ｆ）残存保護膜をマスクとし、前記貫通孔を通じてエッチングにより前記残存犠牲層を除去する、
工程を含むことを特徴とする製造方法を提供する（以下、「第１の製造方法」と呼ぶ）。
【００１６】
同様の目的を達成するために本発明は、光源からの光に対して透光性を有し前記光を導入する透明基板と、透明電極とを有する基板と、前記基板上に空隙を介在させて設けられ、基板とは反対側の面に透明電極を有する可撓薄膜からなる可動部とを備え、前記両透明電極との間に電圧を印加して静電気力により前記可動部を前記基板側に変位させることにより、前記光源からの光を前記基板及び前記可動部を透過させて外部に出射させる光変調素子を２次元マトリクス状に配列してなる光変調素子アレイの製造方法において、
（ａ）前記基板上に犠牲層を形成し、
（ｂ）前記犠牲層を空隙の形状に形成し、
（ｃ）残存犠牲層及び前記基板の露出部分を覆うように、透明電極を最上層として前記可撓薄膜を構成する各層を積層し、
（ｄ）前記透明電極上に透光性を有する保護膜を形成し、
（ｅ）前記残存犠牲層の上方位置にて前記保護膜から前記基板に至る複数の貫通孔を穿設し、
（ｆ）残存保護膜をマスクとし、前記貫通孔を通じてエッチングにより前記残存犠牲層を除去し、
（ｇ）前記残存保護膜を除去する、
工程を含むことを特徴とする光変調素子アレイの製造方法を提供する（以下、「第２の製造方法」と呼ぶ）。
【００１７】
上記第２の製造方法によれば、犠牲層除去のためのエッチングを保護膜の存在下で行うために、可動透明電極の膜減りや応力残留が無く、安定した変位動作を行う可動部を有する光変調素子アレイが得られる。
【００１８】
同様の目的を達成するために本発明はまた、光源からの光に対して透光性を有し前記光を導入する透明基板と、透明電極とを有する基板と、前記基板上に空隙を介在させて設けられ、基板とは反対側の面に透明電極を有する可撓薄膜からなる可動部とを備え、前記両透明電極との間に電圧を印加して静電気力により前記可動部を前記基板側に変位させることにより、前記光源からの光を前記基板及び前記可動部を透過させて外部に出射させる光変調素子を２次元マトリクス状に配列してなる光変調素子アレイの製造方法において、
（ａ）前記基板上に犠牲層を形成し、
（ｂ）前記犠牲層を空隙の形状に形成し、
（ｃ）残存犠牲層及び前記基板の露出部分を覆うように、設計膜厚を超える膜厚を有する透明電極を最上層として前記可撓薄膜を構成する各層を積層し、
（ｄ）前記残存犠牲層の上方位置にて前記透明電極に複数の開口部を開口し、
（ｅ）前記透明電極の開口部から前記基板に至る複数の貫通孔をエッチングにより穿設し、
（ｆ）残存透明電極をマスクとし、前記貫通孔を通じてエッチングにより前記残存犠牲層を除去する、
工程を含むことを特徴とする光変調素子アレイの製造方法を提供する（以下、第３の製造方法）と呼ぶ）。
【００１９】
上記第３の製造方法によれば、可動透明電極を設計値よりも厚く成膜することにより、犠牲層除去のためのエッチングによる膜減り分を補償する。また、第１及び第２の製造方法における保護膜が不要であることから、保護膜の成膜、更には除去のための工程が無くなり、工程が簡素で、製造コストの低減にもなる。
【００２０】
【発明の実施の形態】
以下、本発明について図面を参照して説明する。
【００２１】
（第１の製造方法）
図１は本発明の第１の製造方法を示す断面図であり、従来の製造方法を示す図５に対応して示してある。先ず、工程（ａ）に示すように、透明基板１上に固定透明電極２を成膜する。透明基板１は、使用する照射光（例えば紫外線）に対して透過性を有する材料からなる平板であり、例えばガラス板を使用できる。また、固定透明電極２は、同じく照射光に対して透過性を有する導電性材料からなる薄膜であり、電子密度の高いＩＴＯ等の金属酸化物、非常に薄い金属（アルミニウム等）の膜、金属微粒子を透明絶縁体に分散した薄膜、又は高濃度ドープしたワイドバンドギャップ半導体等からなる薄膜を使用できる。
【００２２】
次いで工程（ｂ）に示すように、固定透明電極２の上に犠牲層１５を成膜する。この犠牲層１５は工程（ｈ）において空隙５を形成するために除去されるもので、例えばフォトレジストを使用でき、これを上記の透過光最小となる間隔（Ｄｏｆｆ）に一致する膜厚で成膜して得られる。また、金属膜とすることもできる。
【００２３】
次いで工程（ｃ）に示すように、マスク１６を用いて犠牲層１５を空隙５の形状に合わせてパターニングする。パターニング後、犠牲層１５の形状安定化のためにベーキングを施してもよい。
【００２４】
次いで工程（ｄ）に示すように、犠牲層１５と同一高さとなるように支柱３を形成する材料を設ける。尚、Ｂ断面において、この支柱３は、犠牲層１５の背後に存在する（工程（ｅ）、（ｆ）、（ｇ）においても同様）。また、この支柱３は省略することができ、その場合は、図示は省略するが、固定透明電極２の上に略アーチ状をなす透明絶縁膜４が直接載架した構造となる。
【００２５】
次いで工程（ｅ）に示すように、可撓薄膜を構成する透明絶縁膜４、光拡散層６及び可動透明電極７を順次成膜する。透明絶縁膜４は、透明基板１の屈折率と同程度もしくはそれ以上の屈折率を有する材料、例えばポリシリコン等の半導体、シリコン酸化物やシリコン窒化物等のセラミック材料、あるいは樹脂等からなる薄膜を使用できる。光拡散層６は、無機透明材料や有機透明材料の表面に凹凸を形成したもの、マイクロプリズム、マイクロレンズを形成したもの、無機多孔質材料や有機多孔質材料、又は屈折率の異なる微粒子を透明基材に分散したもの等で構成される。また、この光拡散層６は透明絶縁膜４と同一の材料を用いて一体に形成することができ、例えば窒化シリコン膜で透明絶縁膜４を形成し、その可動透明電極７側の表面に凹凸を形成することにより、拡散機能を持たせることができる。可動透明電極７は上記固定透明電極２と同一物とすることができる。
【００２６】
更に、可動透明電極７の上に保護膜４０が成膜される。この保護膜４０は、透光性を有し、犠牲層１５を除去するために使用されるエッチング媒体に対して化学的、物理的に耐性を有する材料で形成する。例えば、犠牲層１５をフォトレジストで形成した場合、工程（ｈ）において酸素プラズマエッチングが一般的に行われるため、保護膜４０として、透光性を有し、かつ酸素プラズマに耐性を有する無機の絶縁膜、金属酸化膜等の薄膜を使用する。
【００２７】
次いで工程（ｆ）に示すように、マスク１７を用いて、パターニングされた犠牲層１５の上方位置にて保護膜４０及び可動透明電極７に所定間隔で開口部１８を開口する。このパターニングは、例えば塩酸系の溶剤を用いたウエットエッチングが適当である。
【００２８】
次いで工程（ｇ）に示すように、保護膜３０及び可動透明電極７をマスクとしてエッチングし、開口部１８から固定透明電極２に至る複数の貫通孔１９を穿設する。このエッチングは、例えばＣＦ_４プラズマエッチングが適当である。
【００２９】
そして、工程（ｈ）に示すように、犠牲層１５を除去して空隙５を形成して可動部８を得ることにより、本発明の光変調素子アレイが完成する。犠牲層１５の除去方法は犠牲層１５の形成材料により異なり、例えば上記フォトレジストの場合には酸素プラズマエッチングが適当であり、また金属の場合は塩素系ガス又はフッ化炭素系ガスによるプラズマエッチング、あるいはウエットエッチングが好適に用いられる。ここで、酸素プラズマ等のエッチング媒体は上方から貫通孔１９を通じて犠牲層１５に作用するが、保護膜４０により可動透明電極７にはエッチング媒体が作用せず、膜減りを起こしたり、応力が残留することが無い。
【００３０】
この光変調素子アレイは、工程（ｈ）のＡ断面に示すように、可動透明電極７の上に保護膜４０が形成された構造となる。尚、実際には、犠牲層１５の除去に際して支柱３の露出部も若干エッチングされるため、図示されるように、支柱３は周側面が切削された形状となる。
【００３１】
（第２の製造方法）
本第２の製造方法は、図示は省略するが、上記第１の製造方法の工程（ｈ）の後に保護膜４０を除去する工程を付加して構成される。従って、第２の製造方法においても、第１の製造方法と同様に、犠牲層１５の除去に際して可動透明電極７がエッチングから保護される。但し、第１の製造方法では、工程（ｈ）において保護膜４０の表面が粗面化されることがあり、導光状態において可動透明電極７からの出射光がこの保護膜４０で散乱されて、極端な場合には解像度の低下や光量不足を招くことがある。そこで、犠牲層１５を除去した後に保護膜４０を取り除くことにより、このような不具合を解消することができる。尚、保護膜４０の除去方法は制限されるものではなく、例えばマスクにより貫通孔１９の開口部（１８）を覆い、ドライエッチングにより行うことができる。
【００３２】
（第３の製造方法）
本発明の第３の製造方法は、図５に示した従来の製造方法において、可動透明電極７を設計膜厚よりも厚く成膜して犠牲層除去のためのエッチングを行う。即ち、図２に示すように、工程（ａ）〜（ｄ）に従い、透明基板１の上に固定透明電極２及び犠牲層１５を積層した後、マスク１６を用いて犠牲層１５をパターニングする。
【００３３】
次いで工程（ｅ）に示すように、支柱３、透明絶縁膜４、光拡散層６及び可動透明電極７ａを順次成膜する。このとき、可動透明電極７ａの膜厚（Ｔａ）を設計膜厚よりも厚くする。光変調素子では、可動部の変位を安定かつ正確に行うように透明絶縁膜や光拡散層、可動透明電極のそれぞれの膜厚が設計されており、従来ではこの設計膜厚で可動透明電極を成膜している。しかし、犠牲層除去のためのエッチングに際して可動透明電極もエッチングされるため、最終的な可動透明電極は当初の設計膜厚よりも薄くなる。そこで、第３の製造方法では、可動透明電極７ａの膜厚（Ｔａ）を設計膜厚よりも厚くする。
【００３４】
尚、可動透明電極７ａの膜厚（Ｔａ）の設計膜厚からの増分は、電極材料や犠牲層除去のためのエッチング条件により適宜設定される。例えば、可動透明電極７ａとしてＩＴＯ膜を用い、犠牲層除去のために酸素プラズマエッチングを行う場合、可動透明電極７ａの膜厚（Ｔａ）を設計膜厚の１．１〜２倍程度とすることが好ましい。
【００３５】
次いで工程（ｆ）〜（ｈ）に示すように、固定透明電極７ａの開口部１８の開口及び貫通孔１９を穿設した後、犠牲層１５を除去する。犠牲層１５の除去に伴って可動透明電極７ａも減膜するが、上記の如くこの減膜分を考慮して可動透明電極７ａが成膜されているため、最終的な可動透明電極７ｂは従来の方法に比べて厚い膜厚（Ｔｂ）で残存する。
【００３６】
第３の製造方法によれば、上記した第１及び第２の製造方法における保護膜４０が不要であることから、保護膜４０の成膜、更には除去のための工程が無くなり、工程が簡素で、製造コストが低減される。
【００３７】
上記の第１〜第３の製造方法は、図４に示した干渉型光変調素子アレイにも適用できる。その場合、図示は諸略するが、両製造方法とも工程（ａ）の後に固定透明電極２の上に固定誘電体ミラーを形成する工程を追加し、更に工程（ｄ）の後に可動誘電体ミラ−を形成する工程を追加すればよい。
【００３８】
尚、上記の説明において、透明電極、犠牲層、透明絶縁膜、光拡散層、保護膜及び誘電体ミラーの形成方法に制限は無く、使用する材料に応じて適宜選択される。
【００３９】
【発明の効果】
以上説明したように、本発明によれば、可動透明電極上に保護膜を成膜して犠牲層除去のためのエッチング媒体から可動透明電極を防御するため、もしくは可動透明電極の膜厚を設計膜厚よりも厚く成膜して同様のエッチングによる減膜分を補償するため、従来に比べて可動透明電極が厚く、応力の残量も無く、可動部の変位動作を安定かつ確実に行い得る光変調素子アレイが得られる。
【図面の簡単な説明】
【図１】本発明に係る光変調素子アレイの第１の製造方法を工程別に示す断面図である。
【図２】本発明に係る光変調素子アレイの第３の製造方法を工程別に示す断面図である。
【図３】従来の光変調素子アレイの一例（全反射型）並びにその変調動作を示す断面図である。
【図４】従来の光変調素子アレイの他の例（干渉型）並びにその変調動作を示す断面図である。
【図５】図３に示す光変調素子アレイの製造方法を工程別に示す断面図である。
【符号の説明】
１透明基板
２固定透明電極
３支柱
４透明絶縁膜
５空隙
６光拡散層
７可動透明電極
８可動部
１８開口部
１９貫通孔
４０保護膜[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a light modulation element array that is manufactured by micromachining and changes light transmittance by electromechanical operation, and a method for manufacturing the same.
[0002]
[Prior art]
2. Description of the Related Art An electromechanical light modulation element that performs light modulation by using a flexible thin film manufactured by micromachining as a movable portion and mechanically operating the movable thin film by electrostatic force is known (for example, see Patent Document 1). FIG. 3 is a schematic cross-sectional view showing an example of such a light modulation element. The light modulation element 10 is a transparent electrode (hereinafter referred to as a “fixed transparent electrode”) provided on a transparent substrate 1 having translucency. ) Movable structure comprising a transparent insulating film 4, a light diffusion layer 6 and a transparent electrode (hereinafter referred to as “movable transparent electrode”) 7 stacked on the support 2 in order from the transparent substrate 1 side. A power source 9 is connected between the transparent electrodes 2 and 7 and is schematically configured. In addition, a light source (not shown) is disposed on the surface of the transparent substrate 1 opposite to the movable portion 8 (downward in the drawing), and is irradiated with light L such as ultraviolet rays.
[0003]
In the light modulation element 10, the light is modulated by utilizing a light guide diffusing action by separating or contacting the fixed transparent electrode 2 and the movable portion 8. That is, when no voltage is applied between the fixed transparent electrode 2 and the movable transparent electrode 7 (when OFF), the light L incident on the transparent substrate 1 is refracted by the transparent substrate 1 as shown in FIG. From the difference between the refractive index and the refractive index of the air that is the gap 5, the propagation is continued while repeating the refraction on the front and back surfaces of the transparent substrate 1. On the other hand, when a predetermined voltage is applied between the fixed transparent electrode 2 and the movable transparent electrode 7 (when ON), an electrostatic force is generated between the transparent electrodes as shown in FIG. Bends toward the transparent substrate 1, and the transparent insulating film 4 and the fixed transparent electrode 2 come into contact with each other or sufficiently approach each other. Accordingly, the light L propagates from the interface of the transparent substrate 1 to the transparent insulating film 4 through the fixed transparent electrode 2, is scattered by the light diffusion layer 6, and then exits to the outside through the movable transparent electrode 7 to be guided. It becomes. Further, when the application of voltage is stopped from this state, the electrostatic force does not act and the movable portion 8 is elastically restored, the transparent insulating film 4 is separated from the fixed transparent electrode 2, and as a result, the transmission of the light L is not performed. Return to shaded state.
[0004]
A similar light modulation element using Fabry-Perot interference is also known. In Fabry-Perot interference, in a state where two planes are arranged in parallel to face each other, an incident light beam is repeatedly reflected and transmitted to be divided into a large number of light beams, which become parallel light beams. Among them, the transmitted light overlaps and interferes at infinity. If the angle between the surface and the perpendicular incident light is θ, the optical path difference between adjacent light rays is given by “x = nD · cos θ (where n is the refractive index between the two surfaces, and D is the distance)”. If the optical path difference x is an integral multiple of the wavelength λ, the transmission lines reinforce each other, and if the optical path difference x is an odd multiple of the half wavelength, they cancel each other. That is, if there is no phase change at the time of reflection, the transmitted light is maximum at “2nD · cos θ = mλ” and the transmitted light is minimum at “2nD · cos θ = (2m + 1) λ / 2”. However, m is a positive integer. Accordingly, the two planes are moved closer or away so that the optical path difference x becomes a predetermined value, and the distance (D) is made equal to the distance (Don) that maximizes the transmitted light or the distance (Doff) that minimizes the transmitted light. Thus, the light shielding state and the light guiding state can be controlled.
[0005]
For example, FIG. 4 shows an optical modulation element using such Fabry-Perot interference. Hereinafter, this light modulation element will be referred to as an “interference light modulation element”, and the light modulation element shown in FIG. 3 will be referred to as a “total reflection light modulation element”. 3 includes a dielectric mirror (hereinafter referred to as “fixed dielectric mirror”) 30 on a fixed transparent electrode 22 of a transparent substrate 21, and includes a transparent insulating film 24 and a movable transparent film. The movable mirror 28 formed by laminating the electrodes 27 and the same dielectric mirror as the fixed dielectric mirror 30 (hereinafter referred to as “movable dielectric mirror”) on the surface of the transparent insulating film 24 facing the fixed dielectric mirror 30. The light modulation element 20 is configured by attaching 31. The fixed dielectric mirror 30 and the movable dielectric mirror 31 are formed by laminating a plurality of thin films made of a dielectric material such as silicon oxide or titanium oxide. An interval 25 between the dielectric mirrors 30 and 31 is determined from a power source 29. It is defined that the distance (Doff) satisfies the above-mentioned minimum transmitted light when there is no conduction (when OFF). The light L is collimated and enters the transparent substrate 21 perpendicularly.
[0006]
In this interference type light modulation element 20, when OFF, both dielectric mirrors 30, 31 are separated from each other by the distance (Doff), and the light L is transmitted from the transparent substrate 21 to the fixed transparent electrode. The light is reflected at the interface with the light 22 and is in a light shielding state. When ON, the movable portion 28 is bent toward the transparent substrate 21 due to electrostatic force, and the distance between the dielectric mirrors 30 and 31 is narrowed, as shown in FIG. This interval is a distance (Don) that satisfies the above-mentioned maximum transmitted light, and includes an electrostatic force that acts on the transparent insulating film 24 by adjusting the applied voltage and a restoring force that is generated as the transparent insulating film 24 is deformed. Set appropriately by balancing. Then, when the movable portion 28 is bent, the light L incident on the transparent substrate 21 is transmitted from the fixed dielectric mirror 30 to the movable dielectric mirror 31 via the interval 25 and subsequently transmitted through the movable portion 28 to be movable. The light exits from the transparent electrode 27 and enters a light guide state.
[0007]
As described above, the light modulation elements 10 and 20 described above can switch between the light shielding state and the light guiding state by displacing the movable parts 8 and 28 by the action of electrostatic force.
[0008]
Although not shown, a light modulation element array in which the light modulation elements 10 and 20 are arranged in a two-dimensional matrix has been put into practical use.
[Patent Document 1]
Japanese Patent Laid-Open No. 11-258558 [0009]
[Problems to be solved by the invention]
By the way, the light modulation elements 10 and 20 are manufactured by a method called micromachining. Here, taking the total reflection type light modulation element 10 shown in FIG. 3 as an example, a manufacturing method thereof will be described with reference to FIG. In addition, in the same figure, the cross section A corresponds to the cross section shown in FIG.
[0010]
First, as shown in the step (a), the fixed transparent electrode 2 is formed on the transparent substrate 1, and then the sacrificial layer 15 is formed on the fixed transparent electrode 2 as shown in the step (b). The sacrificial layer 15 is finally removed to form the void 5, and is obtained, for example, by depositing a resist, metal, or the like with a film thickness that matches the interval (Doff) that minimizes the transmitted light. . Next, as shown in step (c), the sacrificial layer 15 is patterned in accordance with the shape of the gap 5 using the mask 16. Next, as shown in step (d), a material for forming the column 3 is provided so as to be the same height as the sacrificial layer 15. Next, as shown in step (e), a transparent insulating film 4, a light diffusion layer 6 and a movable transparent electrode 7 constituting a flexible thin film are sequentially formed. Next, as shown in step (f), using the mask 17, a plurality of openings 18 are provided in the movable transparent electrode 7 at a predetermined interval above the sacrificial layer 15. Next, as shown in step (g), a through hole 19 extending from the opening 18 to the fixed transparent electrode 2 is formed by etching using the movable transparent electrode 7 as a mask. Then, as shown in the step (h), the sacrificial layer 15 is removed to form the gap 5 to obtain a plurality of movable parts 8.
[0011]
In the step (h), the sacrificial layer 15 is usually removed by dry etching, and an etching medium such as oxygen plasma is applied to the sacrificial layer 15 through the through hole 19 from above the movable transparent electrode 7. For this reason, the movable transparent electrode 7 is also etched along with the removal of the sacrificial layer 15, and the displacement of the movable portion 8 is adversely affected, for example, the film is reduced and the strength is lowered, or stress remains.
[0012]
The present invention has been made in view of the above situation, and can suppress the film loss and residual stress of the movable transparent electrode accompanying the removal of the sacrificial layer for forming the gap, and can stably perform the displacement operation of the movable part. It is an object of the present invention to provide a light modulation element array and a manufacturing method for obtaining the light conversion element array.
[0013]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides a substrate having a transparent electrode, a movable portion made of a flexible thin film provided on the substrate with a gap interposed therebetween and having a transparent electrode on the surface opposite to the substrate. And applying a voltage between the transparent electrodes and displacing the movable part to the substrate side by electrostatic force to transmit light from a light source through the substrate and the movable part to the outside. A light modulation element array in which light modulation elements to be arranged are arranged in a two-dimensional matrix, wherein a light-transmitting protective film is formed on the surface of the transparent electrode of the movable part. An element array is provided.
[0014]
In the above light modulation element array, since the protective film is formed on the movable transparent electrode, the movable transparent electrode is protected against etching for removing the sacrificial layer, and a stable displacement operation of the movable part is realized. .
[0015]
Further, the present invention provides the above light modulation element array,
(A) forming a sacrificial layer on the substrate;
(B) forming the sacrificial layer in the shape of a void;
(C) Laminate each layer constituting the flexible thin film with the transparent electrode as the uppermost layer so as to cover the remaining sacrificial layer and the exposed portion of the substrate,
(D) forming a translucent protective film on the transparent electrode;
(E) drilling a plurality of through holes from the protective film to the substrate at a position above the remaining sacrificial layer;
(F) Using the remaining protective film as a mask, the remaining sacrificial layer is removed by etching through the through hole.
A manufacturing method characterized by including a process is provided (hereinafter referred to as “first manufacturing method”).
[0016]
In order to achieve the same object, the present invention provides a transparent substrate that is transparent to light from a light source, introduces the light, a transparent electrode, and a gap on the substrate. And a movable portion made of a flexible thin film having a transparent electrode on the surface opposite to the substrate, and a voltage is applied between the transparent electrodes so that the movable portion is placed on the substrate side by electrostatic force. In the method of manufacturing a light modulation element array in which light modulation elements that transmit the light from the light source through the substrate and the movable part and emit the light to the outside are arranged in a two-dimensional matrix.
(A) forming a sacrificial layer on the substrate;
(B) forming the sacrificial layer in the shape of a void;
(C) Laminate each layer constituting the flexible thin film with the transparent electrode as the uppermost layer so as to cover the remaining sacrificial layer and the exposed portion of the substrate,
(D) forming a translucent protective film on the transparent electrode;
(E) drilling a plurality of through holes from the protective film to the substrate at a position above the remaining sacrificial layer;
(F) using the remaining protective film as a mask, removing the remaining sacrificial layer by etching through the through-hole,
(G) removing the remaining protective film;
A method of manufacturing a light modulation element array including a process is provided (hereinafter referred to as “second manufacturing method”).
[0017]
According to the second manufacturing method, since the etching for removing the sacrificial layer is performed in the presence of the protective film, the movable transparent electrode has no film reduction and no residual stress, and has a movable part that performs a stable displacement operation. A light modulation element array is obtained.
[0018]
In order to achieve the same object, the present invention also provides a transparent substrate that is transparent to light from a light source and that introduces the light, a transparent electrode, and a gap on the substrate. And a movable portion made of a flexible thin film having a transparent electrode on the surface opposite to the substrate, and a voltage is applied between the transparent electrodes so that the movable portion is placed on the substrate by electrostatic force. In the method of manufacturing a light modulation element array in which light modulation elements are arranged in a two-dimensional matrix by causing the light from the light source to pass through the substrate and the movable part and to be emitted to the outside by being displaced to the side.
(A) forming a sacrificial layer on the substrate;
(B) forming the sacrificial layer in the shape of a void;
(C) Laminate each layer constituting the flexible thin film with a transparent electrode having a film thickness exceeding the design film thickness as the uppermost layer so as to cover the remaining sacrificial layer and the exposed portion of the substrate;
(D) opening a plurality of openings in the transparent electrode at a position above the remaining sacrificial layer;
(E) Etching a plurality of through holes extending from the opening of the transparent electrode to the substrate;
(F) Using the remaining transparent electrode as a mask, the remaining sacrificial layer is removed by etching through the through hole.
A method of manufacturing an optical modulation element array including a process (hereinafter referred to as a third manufacturing method).
[0019]
According to the third manufacturing method, by forming the movable transparent electrode thicker than the design value, the film loss due to etching for removing the sacrificial layer is compensated. Further, since the protective film in the first and second manufacturing methods is unnecessary, there is no process for forming and removing the protective film, the process is simple, and the manufacturing cost is reduced.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
The present invention will be described below with reference to the drawings.
[0021]
(First manufacturing method)
FIG. 1 is a cross-sectional view showing a first manufacturing method of the present invention, corresponding to FIG. 5 showing a conventional manufacturing method. First, as shown in step (a), the fixed transparent electrode 2 is formed on the transparent substrate 1. The transparent substrate 1 is a flat plate made of a material that is transparent to irradiation light (for example, ultraviolet rays) to be used, and for example, a glass plate can be used. The fixed transparent electrode 2 is a thin film made of a conductive material that is also transmissive to irradiation light, and has a high electron density metal oxide such as ITO, a very thin metal (aluminum, etc.) film, metal A thin film in which fine particles are dispersed in a transparent insulator, or a thin film made of a wide band gap semiconductor or the like that is highly doped can be used.
[0022]
Next, as shown in step (b), a sacrificial layer 15 is formed on the fixed transparent electrode 2. The sacrificial layer 15 is removed in order to form the gap 5 in the step (h). For example, a photoresist can be used, and the sacrificial layer 15 is formed with a film thickness that matches the interval (Doff) that minimizes the transmitted light. Obtained by membrane. It can also be a metal film.
[0023]
Next, as shown in step (c), the sacrificial layer 15 is patterned in accordance with the shape of the gap 5 using the mask 16. After patterning, baking may be performed to stabilize the shape of the sacrificial layer 15.
[0024]
Next, as shown in step (d), a material for forming the column 3 is provided so as to be the same height as the sacrificial layer 15. In the cross section B, the support column 3 exists behind the sacrificial layer 15 (the same applies to the steps (e), (f), and (g)). Moreover, this support | pillar 3 can be abbreviate | omitted, In that case, although it abbreviate | omits illustration, it becomes the structure where the transparent insulating film 4 which makes a substantially arch shape on the fixed transparent electrode 2 was directly mounted.
[0025]
Next, as shown in step (e), a transparent insulating film 4, a light diffusion layer 6 and a movable transparent electrode 7 constituting a flexible thin film are sequentially formed. The transparent insulating film 4 is a thin film made of a material having a refractive index comparable to or higher than that of the transparent substrate 1, for example, a semiconductor such as polysilicon, a ceramic material such as silicon oxide or silicon nitride, or a resin. Can be used. The light diffusing layer 6 is made of a transparent inorganic or organic transparent material with irregularities formed thereon, a microprism, a microlens formed, an inorganic porous material or an organic porous material, or fine particles having different refractive indexes. It is composed of materials dispersed in a base material. The light diffusion layer 6 can be integrally formed using the same material as that of the transparent insulating film 4. For example, the transparent insulating film 4 is formed of a silicon nitride film, and the surface on the movable transparent electrode 7 side is uneven. By forming, a diffusion function can be provided. The movable transparent electrode 7 can be the same as the fixed transparent electrode 2.
[0026]
Further, a protective film 40 is formed on the movable transparent electrode 7. The protective film 40 is formed of a material having translucency and chemically and physically resistant to an etching medium used for removing the sacrificial layer 15. For example, when the sacrificial layer 15 is formed of a photoresist, oxygen plasma etching is generally performed in the step (h). Therefore, the protective film 40 is an inorganic material that is transparent and resistant to oxygen plasma. A thin film such as an insulating film or a metal oxide film is used.
[0027]
Next, as shown in step (f), using the mask 17, openings 18 are opened in the protective film 40 and the movable transparent electrode 7 at predetermined intervals above the patterned sacrificial layer 15. For this patterning, for example, wet etching using a hydrochloric acid solvent is suitable.
[0028]
Next, as shown in step (g), etching is performed using the protective film 30 and the movable transparent electrode 7 as a mask, and a plurality of through holes 19 extending from the opening 18 to the fixed transparent electrode 2 are formed. As this etching, for example, CF ₄ plasma etching is suitable.
[0029]
Then, as shown in the step (h), the sacrificial layer 15 is removed to form the gap 5 to obtain the movable portion 8, thereby completing the light modulation element array of the present invention. The removal method of the sacrificial layer 15 differs depending on the material for forming the sacrificial layer 15. For example, oxygen plasma etching is suitable for the above-described photoresist, and plasma etching with chlorine-based gas or fluorocarbon-based gas is used for metal. Alternatively, wet etching is preferably used. Here, an etching medium such as oxygen plasma acts on the sacrificial layer 15 from above through the through-hole 19, but the etching medium does not act on the movable transparent electrode 7 due to the protective film 40, causing film loss or residual stress. There is nothing to do.
[0030]
This light modulation element array has a structure in which a protective film 40 is formed on the movable transparent electrode 7 as shown in section A of step (h). Actually, since the exposed portion of the support column 3 is slightly etched when the sacrificial layer 15 is removed, the support column 3 has a shape in which the peripheral side surface is cut as shown in the figure.
[0031]
(Second manufacturing method)
Although not shown, the second manufacturing method is configured by adding a step of removing the protective film 40 after the step (h) of the first manufacturing method. Accordingly, also in the second manufacturing method, the movable transparent electrode 7 is protected from etching when the sacrificial layer 15 is removed, as in the first manufacturing method. However, in the first manufacturing method, the surface of the protective film 40 may be roughened in the step (h), and light emitted from the movable transparent electrode 7 is scattered by the protective film 40 in the light guide state. In extreme cases, the resolution may be reduced and the amount of light may be insufficient. Therefore, such a problem can be solved by removing the protective film 40 after removing the sacrificial layer 15. The method for removing the protective film 40 is not limited. For example, the opening (18) of the through hole 19 may be covered with a mask and dry etching may be performed.
[0032]
(Third production method)
The third manufacturing method of the present invention performs etching for removing the sacrificial layer by forming the movable transparent electrode 7 to be thicker than the designed film thickness in the conventional manufacturing method shown in FIG. That is, as shown in FIG. 2, after the fixed transparent electrode 2 and the sacrificial layer 15 are laminated on the transparent substrate 1 according to the steps (a) to (d), the sacrificial layer 15 is patterned using the mask 16.
[0033]
Next, as shown in step (e), the support column 3, the transparent insulating film 4, the light diffusion layer 6, and the movable transparent electrode 7a are sequentially formed. At this time, the film thickness (Ta) of the movable transparent electrode 7a is made larger than the designed film thickness. In the light modulation element, the thickness of each of the transparent insulating film, the light diffusion layer, and the movable transparent electrode is designed so that the movable part can be displaced stably and accurately. A film is being formed. However, since the movable transparent electrode is also etched during the etching for removing the sacrificial layer, the final movable transparent electrode becomes thinner than the original designed film thickness. Therefore, in the third manufacturing method, the film thickness (Ta) of the movable transparent electrode 7a is made larger than the designed film thickness.
[0034]
In addition, the increment from the design film thickness of the film thickness (Ta) of the movable transparent electrode 7a is appropriately set according to the etching conditions for removing the electrode material and the sacrificial layer. For example, when an ITO film is used as the movable transparent electrode 7a and oxygen plasma etching is performed to remove the sacrificial layer, the film thickness (Ta) of the movable transparent electrode 7a should be about 1.1 to 2 times the designed film thickness. Is preferred.
[0035]
Next, as shown in steps (f) to (h), after opening the opening 18 and the through hole 19 of the fixed transparent electrode 7a, the sacrificial layer 15 is removed. As the sacrificial layer 15 is removed, the movable transparent electrode 7a is also reduced in thickness. However, since the movable transparent electrode 7a is formed in consideration of the reduced thickness as described above, the final movable transparent electrode 7b is a conventional one. It remains with a thick film thickness (Tb) as compared with this method.
[0036]
According to the third manufacturing method, since the protective film 40 in the first and second manufacturing methods described above is unnecessary, the process for forming and further removing the protective film 40 is eliminated, and the process is simple. Thus, the manufacturing cost is reduced.
[0037]
The above first to third manufacturing methods can also be applied to the interference light modulation element array shown in FIG. In this case, although not shown in the drawings, both manufacturing methods include a step of forming a fixed dielectric mirror on the fixed transparent electrode 2 after the step (a), and a movable dielectric mirror after the step (d). What is necessary is just to add the process of forming-.
[0038]
In the above description, the method for forming the transparent electrode, the sacrificial layer, the transparent insulating film, the light diffusing layer, the protective film, and the dielectric mirror is not limited, and is appropriately selected according to the material used.
[0039]
【The invention's effect】
As described above, according to the present invention, a protective film is formed on the movable transparent electrode to protect the movable transparent electrode from the etching medium for removing the sacrificial layer, or the film thickness of the movable transparent electrode is designed. Since the film is thicker than the film thickness and compensates for the film thickness reduction caused by the same etching, the movable transparent electrode is thicker than before, there is no residual stress, and the movable part can be displaced stably and reliably. A light modulation element array is obtained.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing a first method of manufacturing a light modulation element array according to the present invention by process.
FIG. 2 is a cross-sectional view showing a third manufacturing method of the light modulation element array according to the present invention by process.
FIG. 3 is a cross-sectional view showing an example of a conventional light modulation element array (total reflection type) and a modulation operation thereof.
FIG. 4 is a cross-sectional view showing another example (interference type) of a conventional light modulation element array and its modulation operation.
5 is a cross-sectional view showing a method of manufacturing the light modulation element array shown in FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Transparent substrate 2 Fixed transparent electrode 3 Support | pillar 4 Transparent insulating film 5 Space | gap 6 Light diffusion layer 7 Movable transparent electrode 8 Movable part 18 Opening part 19 Through-hole 40 Protective film

Claims

A substrate having a transparent electrode;
A movable part made of a flexible thin film having a transparent electrode on the surface opposite to the substrate, provided with a gap on the substrate;
Light modulation that applies light between the transparent electrodes and displaces the movable part to the substrate side by electrostatic force to transmit light from the light source through the substrate and the movable part to the outside. In a light modulation element array in which elements are arranged in a two-dimensional matrix,
A light modulation element array, wherein a transparent protective film is formed on a surface of the transparent electrode of the movable part.

It is a manufacturing method of the light modulation element array according to claim 1,
(A) forming a sacrificial layer on the substrate;
(B) forming the sacrificial layer in the shape of a void;
(C) Laminate each layer constituting the flexible thin film with the transparent electrode as the uppermost layer so as to cover the remaining sacrificial layer and the exposed portion of the substrate,
(D) forming a translucent protective film on the transparent electrode;
(E) drilling a plurality of through holes from the protective film to the substrate at a position above the remaining sacrificial layer;
(F) Using the remaining protective film as a mask, the remaining sacrificial layer is removed by etching through the through hole.
The manufacturing method characterized by including a process.

A transparent substrate that is transparent to light from a light source and that introduces the light, a substrate having a transparent electrode, and a gap on the substrate, and is provided on a surface opposite to the substrate. A movable portion made of a flexible thin film having a transparent electrode, and by applying a voltage between the transparent electrodes and displacing the movable portion to the substrate side by electrostatic force, the light from the light source is In a method for manufacturing a light modulation element array in which light modulation elements that are transmitted through the substrate and the movable part and are emitted to the outside are arranged in a two-dimensional matrix,
(A) forming a sacrificial layer on the substrate;
(B) forming the sacrificial layer in the shape of a void;
(C) Laminate each layer constituting the flexible thin film with the transparent electrode as the uppermost layer so as to cover the remaining sacrificial layer and the exposed portion of the substrate,
(D) forming a translucent protective film on the transparent electrode;
(E) drilling a plurality of through holes from the protective film to the substrate at a position above the remaining sacrificial layer;
(F) using the remaining protective film as a mask, removing the remaining sacrificial layer by etching through the through-hole,
(G) removing the remaining protective film;
A method for manufacturing a light modulation element array, comprising: a step.

A transparent substrate that is transparent to light from a light source and that introduces the light, a substrate having a transparent electrode, and a gap on the substrate, and is provided on a surface opposite to the substrate. A movable portion made of a flexible thin film having a transparent electrode, and applying a voltage between the transparent electrodes to displace the movable portion to the substrate side by electrostatic force, thereby allowing light from the light source to In a method for manufacturing a light modulation element array in which light modulation elements that are transmitted through the substrate and the movable part and are emitted to the outside are arranged in a two-dimensional matrix,
(A) forming a sacrificial layer on the substrate;
(B) forming the sacrificial layer in the shape of a void;
(C) Laminate each layer constituting the flexible thin film with a transparent electrode having a film thickness exceeding the design film thickness as the uppermost layer so as to cover the remaining sacrificial layer and the exposed portion of the substrate;
(D) opening a plurality of openings in the transparent electrode at a position above the remaining sacrificial layer;
(E) Etching a plurality of through holes extending from the opening of the transparent electrode to the substrate;
(F) Using the remaining transparent electrode as a mask, the remaining sacrificial layer is removed by etching through the through hole.
A method for manufacturing a light modulation element array, comprising: a step.