JP4021053B2 - Semiconductor device - Google Patents

Description

【００３０】
表１から、誘電体多層膜の層数が多い程、反射率は高くなることが読み取れる。従って、反射率の高さを優先する場合は３組（６層）、好ましくは４組（８層）以上積層することが好ましい。
【００３１】
一方、製造コスト、歩留まりを優先する場合は、層数を可能な限り少なくすることが好ましい。また、誘電体多層膜を成膜後、コンタクトホールを形成するため、プロセス上、誘電体多層膜の総膜厚を薄くすることが望ましい。
【００３２】
また、層間絶縁膜１１２に低屈折率誘電体材料を用いた場合、層間絶縁膜１１２上に接して設けられた低屈折率誘電体膜１１４の有無に関係なく、反射率はほとんど変化しないという実験結果も得られた。従って、図２（Ａ）に一例を示したように、スイッチング素子を覆う層間絶縁膜２０１に低屈折率誘電体膜（ＳｉＯ₂ 、アクリル、ポリイミド等）を用いて、低屈折率誘電体膜２０２を一層省略し、層数を少なくする構成とすることが好ましい。
【００３３】
なお、本発明においては、反射膜に誘電体多層膜を用いる構成であれば、図１の構成に限定されない。例えば、透明性及び導電性を有する材料を用いて画素電極を設け、その上に誘電体多層膜を形成する構成としてもよいが、その場合、誘電体多層膜の膜厚を考慮する必要がある。なぜなら、誘電体多層膜の厚さ（総膜厚２μｍ以上）によっては、電圧損失が生じ、液晶のしきい値特性、応答速度等に影響を与えてしまう。従って、図１に示したように、入射光を反射する反射膜を誘電体多層膜で構成し、その上に透明性及び導電性を有する材料を用いて画素電極を設ける構成とすることが好ましい。なお、誘電体多層膜上に画素電極を設けた構成とした場合、多層、例えば１２層以上としても液晶のしきい値特性、応答速度等には全く影響がない。
【００３４】
上記画素電極１１３は、層間絶縁膜１１２及び誘電体多層膜を介してマトリクス状に配置され、且つ、薄膜トランジスタ等のスイッチング素子１１１に接続されている。画素電極は、透明性及び導電性を十分有する材料、例えばＩＴＯ（インディウム錫酸化物）やＳｎＯ₂ （酸化スズ）等で構成する。従って、図２（Ｂ）に示すように、画素電極２１５（ＩＴＯ：屈折率１．９８）を、入射光を反射する反射膜の一部とする構成とすると、層数を少なくすることができるため、好ましい。この場合、画素電極２１５の膜厚もλ／４膜となるように５０．５ｎｍ〜８８．４ｎｍの範囲で調節する。
【００３５】
また、本発明において、それぞれの誘電体膜の膜厚や材料を適宜変更して、選択的に反射波長を設定する構成とすることは容易である。
【００３６】
また、従来では、画素電極の隙間にブラックマスク等の遮光膜を形成し、スイッチング素子の光劣化を防止する必要があったが、本発明においては、画素電極の隙間の下方に設けられた誘電体多層膜が、斜め方向からの光に対して確実な遮光機能を果たす。
【００３７】
また、上記誘電体多層膜を形成する方法としては、スパッタリング法または真空蒸着法等が挙げられるが、本発明は特に限定されない。本発明においては、層間絶縁膜上または画素電極上に設ける誘電体多層膜の膜厚が均一に成膜されることが望ましい。
【００３８】
図１には、誘電体多層膜を４組、計８層で構成した例を示した。図１の構成では、従来の金属材料からなる反射電極と同程度の反射率が得られた。従って、誘電体多層膜の材料、膜厚、層数等を適宜変更すれば、例えば、５組（１０層）以上の誘電体多層膜を形成する構成とすれば、配向膜を積層した構成としても反射損失が少なく、容易に９０％以上の反射率が得られる。
【００３９】
本発明は、上記誘電体多層膜からなる反射膜を設けることにより、従来の構成（金属材料からなる画素電極を反射膜とする）と比較して、光の利用効率を向上させることができ、且つ、従来問題となっていた配向膜による反射率の低下を抑えることができる。本発明を用いると、９０％以上の反射率を得ることが可能となった。
【００４０】
【実施例】
〔実施例１〕
本実施例では本発明を利用して反射型ＬＣＤの画素マトリクス回路を作製する工程例を図３、４を用いて説明する。なお、本発明は反射膜に関する技術であるため、スイッチング素子構造、例えばＴＦＴ構造自体は本実施例に限定されるものではない。
【００４１】
まず、絶縁表面を有する基板３０１を用意する。基板としては、ガラス基板、石英基板、セラミックス基板、半導体基板を用いることができる。本実施例においてはガラス基板を用いた。次に、基板上に下地膜（図示しない）を設ける。下地膜は、酸化珪素膜、窒化珪素膜、窒化酸化珪素膜を１００〜３００ｎｍの膜厚で利用することができる。本実施例では、ＴＥＯＳを原料に用い、酸化珪素膜を２００ｎｍの膜厚に形成する。なお、石英基板のように十分平坦性を有しているなら、下地膜は特に設けなくともよい。
【００４２】
次に、基板または下地膜の上に活性層を形成する。活性層は膜厚が20〜100 nm（好ましくは25〜70nm）の結晶性半導体膜（代表的には結晶性珪素膜）で構成すれば良い。結晶性珪素膜の形成方法は公知の如何なる手段、例えば、レーザー結晶化、熱結晶化等を用いても良いが、本実施例では結晶化の際に結晶化を助長する触媒元素（ニッケル）を添加している。この技術については特開平7-130652号公報、特願平8-335152号等に詳細に記載されている。そして、その結晶性珪素膜を通常のフォトリソ工程でパターニングして膜厚５０ｎｍの活性層３０２〜３０４を得た。なお、本実施例では３つのＴＦＴのみ記載することになるが実際には１００万個以上のＴＦＴが画素マトリクス回路内に形成される。
【００４３】
次に、ゲイト絶縁膜３０５として150 nmの厚さの酸化珪素膜を形成した。ゲート絶縁膜３０５としては酸化珪素膜、窒化珪素膜、酸化窒化珪素膜またはこれらの積層膜を１００〜３００ｎｍの膜厚で用いることができる。その後、ゲイト絶縁膜上に0.2wt%のスカンジウムを含有させたターゲットを用いてアルミニウムを主成分とする膜（図示せず）を成膜し、パターニングによりゲイト電極の原型となる島状パターンを形成した。
【００４４】
本実施例では、ここで特開平7-135318号公報に記載された技術を利用した。なお、詳細は同公報を参考にすると良い。
【００４５】
まず、上記島状パターン上にパターニングで使用したレジストマスクを残したまま、３％のシュウ酸水溶液中で陽極酸化を行った。この時、白金電極を陰極として２〜３ｍＶの化成電流を流し、到達電圧は８Ｖとする。こうして、多孔質状の陽極酸化膜３０６〜３０８が形成された。
【００４６】
その後、レジストマスクを除去した後に３％の酒石酸のエチレングリコール溶液をアンモニア水で中和した溶液中で陽極酸化を行った。この時、化成電流は５〜６ｍＶとし、到達電圧は１００Ｖとすれば良い。こうして、緻密な陽極酸化膜３０９〜３１１が形成された。
【００４７】
そして、上記工程によってゲイト電極３１２〜３１４が画定した。なお、画素マトリクス回路ではゲイト電極の形成と同時に１ライン毎に各ゲイト電極を接続するゲイト線も形成されている。（図３（Ａ））
【００４８】
次に、陽極酸化膜３０６〜３１１及びゲイト電極３１２〜３１４をマスクとしてゲイト絶縁膜３０５をエッチングする。エッチングはＣＦ₄ ガスを用いたドライエッチング法により行った。これにより３１５〜３１７で示される様な形状のゲイト絶縁膜が形成された。
【００４９】
そして、陽極酸化膜３０６〜３０８をエッチングにより除去し、この状態で一導電性を付与する不純物イオンをイオン注入法またはプラズマドーピング法により添加する。この場合、画素マトリクス回路をＮ型ＴＦＴで構成するならばＰ（リン）イオンを、Ｐ型ＴＦＴで構成するならばＢ（ボロン）イオンを添加すれば良い。
【００５０】
なお、上記不純物イオンの添加工程は２度に分けて行う。１度目は８０ｋｅＶ程度の高加速電圧で行い、ゲイト絶縁膜３１５〜３１７の端部（突出部）の下に不純物イオンのピークがくる様に調節する。そして、２度目は５ｋｅＶ程度の低加速電圧で行い、ゲイト絶縁膜３１５〜３１７の端部（突出部）の下には不純物イオンが添加されない様に調節する。
【００５１】
こうしてＴＦＴのソース領域３１８〜３２０、ドレイン領域３２１〜３２３、低濃度不純物領域（ＬＤＤ領域とも呼ばれる）３２４〜３２６、チャネル形成領域３２７〜３２９が形成された。（図３（Ｂ））
【００５２】
この時、ソース／ドレイン領域は 300〜500 Ω／□のシート抵抗が得られる程度に不純物イオンを添加することが好ましい。また、低濃度不純物領域はＴＦＴの性能に合わせて最適化を行う必要がある。また、不純物イオンの添加工程が終了したら熱処理を行い、不純物イオンの活性化を行った。
【００５３】
次に、第１の層間絶縁膜３３０として酸化珪素膜を 400nmの厚さに形成し、その上にソース電極３３１〜３３３、ドレイン電極３３４〜３３６を形成した。（図３（Ｃ））また、第１の層間絶縁膜としては酸化珪素膜の他に酸化窒化珪素あるいは他の絶縁材料を使用することが可能である。
【００５４】
なお、本明細書では、図３（Ｃ）において、３４３で示される領域内に構成された素子をスイッチング素子（代表的にはＴＦＴ、ＭＩＭ素子でも良い）と呼ぶ。なお、本明細書中では、この後で形成される層間絶縁膜３３７や画素電極をスイッチング素子の構成には含まないものとする。
【００５５】
次に、第２の層間絶縁膜３３７として酸化珪素膜を 0.5〜1 μｍの厚さに形成する。また、第２の層間絶縁膜３３７として、酸化窒化珪素膜、有機性樹脂膜等を用いることも可能である。有機性樹脂膜としては、ポリイミド、ポリアミド、ポリイミドアミド、アクリル等を用いることができる。本実施例では、アクリル膜を1 μｍの厚さに成膜した。（図３（Ｄ））
【００５６】
なお、第２の層間絶縁膜３３７を形成した後、ＣＭＰ研磨等の平坦化処理を施す工程としてもよい。平坦化処理する際は、残存する凹凸部の高さ（山の頂上と谷の底の間の鉛直方向の距離）が後に形成される画素電極の厚さの１０％以内となる条件で行うことが好ましい。平坦化処理をすることで、後に形成する誘電体多層膜の膜厚を均一なものとすることができる。
【００５７】
そして、第２の層間絶縁膜３３７上に誘電体多層膜からなる反射膜を形成する。誘電体多層膜３４４は、低屈折率誘電体膜３４１と高屈折率誘電体膜３４２を、交互に数層〜数十層積層して形成する。なお、それぞれの膜厚は、必要とする反射波長帯の中心波長でλ／４膜となるように調節する必要がある。
【００５８】
上記誘電体多層膜３４４に用いる材料は、低屈折率誘電体膜３４１としてＳｉＯ₂ 、ＭｇＦ₂ 、Ｎａ₃ ＡｌＦ₆ 等を、また、高屈折率誘電体膜３４２としてＴｉＯ₂ 、ＺｒＯ₂ 、Ｔａ₂ Ｏ₅ 、ＺｎＳ、ＺｎＳｅ、ＺｎＴｅ、Ｓｉ、Ｇｅ、Ｙ₂ Ｏ₃ 、Ａｌ₂ Ｏ₃ 等を用いることができる。なお、それ以外の低屈折率誘電体材料として配向膜、アクリル、ポリイミド（屈折率１．５〜１．６）を用いることもできる。また、ＩＴＯ（屈折率１．９８）等の透明導電体膜を用いることもできる。
【００５９】
本実施例では、低屈折率誘電体膜３４１として、ＳｉＯ₂ （屈折率１．４３）、高屈折率誘電体膜３４２としてＴｉＯ₂ （屈折率２．２）を用いた。
【００６０】
可視光領域（４００ｎｍ＜λ＜７００ｎｍ）でλ／４膜となるように、誘電体多層膜の膜厚を調節する。上記可視光領域でλ／４膜となるような低屈折率誘電体膜（ＳｉＯ₂ ）の膜厚の範囲は、７０ｎｍ〜１２２ｎｍである。また、上記可視光領域でλ／４膜となるような高屈折率誘電体膜（ＴｉＯ₂ ）の膜厚の範囲は、４５．５ｎｍ〜７９．５ｎｍである。このような膜厚に調節すると、必要とする反射波長帯の光が干渉効果によって強め合い効率よく反射させることができる。本実施例では、誘電体多層膜は、膜厚７０ｎｍの低屈折率誘電体膜３４１と、膜厚５０ｎｍの高屈折率誘電体膜３４２の２層を１組とした時、４組、計８層（９６０ｎｍ）で構成した。（図４（Ａ））
【００６１】
なお、上記各誘電体膜の材料や膜厚に限定されないことは言うまでもなく、それぞれの誘電体膜の膜厚や材料を適宜変更して、選択的に反射波長を設定する構成とするもできる。
【００６２】
なお、本実施例においては、層間絶縁膜上に設ける誘電体多層膜の膜厚が均一に成膜されることが望ましいため、公知の方法である真空蒸着法を用いた。誘電体多層膜を形成する方法としては、本実施例に限定されることはなく、他の方法としては、スパッタリング法等が挙げられる。
【００６３】
次に、誘電体多層膜３４１、３４２および層間絶縁膜３３７をエッチングし、コンタクトホールの形成を行う。本実施例においては、酸溶液である１／１００に希釈したフッ化水素溶液を用いて誘電体多層膜をウェットエッチングした。（図４（Ｂ））
【００６４】
そして、透明性を有する導電性膜、本実施例ではＩＴＯ膜を 120nmの厚さに成膜し、パターニングにより画素電極３３８〜３４０を形成した。こうして図４（Ｃ）に示す状態が得られた。なお、従来では、画素電極の隙間にブラックマスク等の遮光膜を形成する必要があったが、本実施例においては、その必要はなく、画素電極の隙間の下方に設けられている誘電体多層膜が、斜め方向からの光に対しても確実な遮光機能を果たし、スイッチング素子の光劣化を防ぐ。
【００６５】
次に、配向膜を公知の方法、本実施例では、塗布法によって形成した。
【００６６】
以上の様にして、画素マトリクス回路が完成した。実際には画素ＴＦＴを駆動する駆動回路等も同一基板上に同時形成される。この様な基板は通常ＴＦＴ側基板またはアクティブマトリクス基板と呼ばれる。本明細書中ではアクティブマトリクス基板のことを第１の基板と呼ぶことにする。
【００６７】
第１の基板が完成したら、透明性基板に対向電極を形成した対向基板（本明細書中ではこの基板を第２の基板と呼ぶことにする）を貼り合わせ、それらの間に液晶層を挟持する。こうして、反射型ＬＣＤが完成する。
【００６８】
なお、このセル組み工程は公知の方法に従って行えば良い。また、液晶層に二色性色素を分散させたり、対向基板にカラーフィルターを設けたりすることも可能である。その様な液晶層の種類、カラーフィルターの有無等はどの様なモードで液晶を駆動するかによって変化するので実施者が適宜決定すれば良い。
【００６９】
上記作製工程によって得られた反射型ＬＣＤを図１に示す。図１は本実施例の簡略断面図である。
【００７０】
本実施例で作製された液晶表示パネルは、基板１１０と対向基板１１９の間で、基板１１０の上に、スイッチング素子１１１、層間絶縁膜１１２、画素電極１１３、低屈折率誘電体膜１１４、高屈折率誘電体膜１１５、配向膜１１６、液晶層１１７、配向膜１１６、対向電極１１８がそれぞれ順次設けられている。
【００７１】
なお、図１は、図３及び図４と対応しており、図１中の層間絶縁膜は図３中の第２の層間絶縁膜３３７と対応し、図１中の画素電極１１３は図３中の画素電極３３８〜３４０と対応し、図１中の低屈折率誘電体膜１１４は、図３中の３４１と対応し、図１中の高屈折率誘電体膜１１５は、図３中の３４２と対応している。
【００７２】
本実施例（誘電体多層膜＋配向膜）における反射率は、従来（金属薄膜＋配向膜）と同程度の反射率（８０〜９０％未満）が得られた。このように本実施例は、金属薄膜に代えて、誘電体多層膜が反射膜として十分使用可能であることを示した。従って、本実施例における誘電多層膜の層数、材料、膜厚等を適宜変更すれば、従来と比較して反射率を向上させることができる。例えば、誘電多層膜を５組（１０層）とすると計算上、９３．６％（表１参照）が得られ、６組（１２層）とすると計算上、９７．１％が得られる。なお、本実施例の構成において誘電多層膜の層数を増加させることは容易である。
【００７３】
また、本実施例では示さなかったが、対向基板と対向電極の間にカラーフィルターを配置した構成としてもよい。
【００７４】
〔実施例２〕
実施例１で示した作製工程では、８層からなる誘電体多層膜を形成した例を示した。本実施例では、第２の層間絶縁膜３３７として、低屈折率誘電体材料を用い、７層からなる誘電体多層膜を形成した例を以下に図２（Ａ）を用いて説明する。なお、途中（図３（Ｃ））までは実施例１に示した反射型ＬＣＤの作製工程と同一であるので、ここでは異なる点のみについて説明する。
【００７５】
まず、実施例１の作製工程と同一の方法を用いて、図３（Ｃ）の構成を得る。次に、ただし、第２の層間絶縁膜３３７として、低屈折率誘電体材料を用いる。本実施例では、層間絶縁膜２０１として、膜厚１μｍのアクリル膜を形成した。
【００７６】
なお、後に形成する誘電体多層膜を絶縁体として用いることが可能であるなら、ＣＭＰ等の平坦化処理を施し、層間絶縁膜２０１の膜厚を薄くする構成は、プロセス上、特にコンタクトホールを容易に形成しやすくなるため好ましい。
【００７７】
そして、本実施例では、層間絶縁膜２０１上に高屈折率誘電体膜（ＺｒＯ₂ ：膜厚５０ｎｍ）を形成した。その後、低屈折率誘電体膜（ＳｉＯ₂ ：膜厚７０ｎｍ）２０２と高屈折率誘電体膜２０３（ＺｒＯ₂ ：膜厚５０ｎｍ）の組を３組、計６層（７２０ｎｍ）形成した。可視光領域（４００ｎｍ＜λ＜７００ｎｍ）でλ／４膜となるように、それぞれ誘電体膜の膜厚を調節する。
【００７８】
本実施例では、低屈折率誘電体膜２０２として、ＳｉＯ₂ （屈折率１．４３、膜厚範囲は、７０ｎｍ〜１２２ｎｍ）、高屈折率誘電体膜２０１としてＺｒＯ₂ （屈折率２．０４、膜厚範囲は、４９ｎｍ〜８５．８ｎｍ）を用いた。
【００７９】
本実施例（ＳｉＯ₂ ）以外の低屈折率誘電体材料として、ＭｇＦ₂ 、Ｎａ₃ ＡｌＦ₆ 、配向膜、アクリル、またはポリイミド（屈折率１．５〜１．６）を用いることもできる。また、本実施例（ＺｒＯ₂ ）以外の高屈折率誘電体材料として、ＴｉＯ₂ 、Ｔａ₂ Ｏ₅ 、ＺｎＳ、ＺｎＳｅ、ＺｎＴｅ、Ｓｉ、Ｇｅ、Ｙ₂ Ｏ₃ 、Ａｌ₂ Ｏ₃ 等を用いることができる。
【００８０】
そして、実施例１と同様にコンタクトホールを形成し、透明性導電膜からなる画素電極２０５を形成した。本実施例における層間絶縁膜２０１は、低屈折率を有している。従って、実質的には、低屈折率誘電体膜と高屈折率誘電体膜の組を４組形成した場合（実施例１）と同程度の反射率を得ることができる。
【００８１】
その後、実施例１と同様に、配向膜２０６を形成し、第１の基板を作製した。（図２（Ａ））
【００８２】
このような構成とすることで、誘電体多層膜の層数及び総膜厚を削減し、実施例１と比較して容易にコンタクトホールの形成を行うことができた。
【００８３】
〔実施例３〕
実施例１で示した作製工程では、８層からなる誘電体多層膜を形成した例を示した。本実施例では、７層の誘電体多層膜を形成し、その上に高屈折率を有する材料として、画素電極を形成した例を以下に図２（Ｂ）を用いて説明する。なお、途中（図３（Ｃ））までは実施例１に示した反射型ＬＣＤの作製工程と同一であるので、ここでは異なる点のみについて説明する。
【００８４】
まず、実施例１の作製工程と同一の方法を用いて、図３（Ｃ）の構成を得る。
【００８５】
次に、第２の層間絶縁膜３３７上に低屈折率誘電体膜２１２と高屈折率誘電体膜２１３の組を３組、計６層成膜し、その上に低屈折率誘電体膜を１層成膜して誘電体多層膜２１４（７層）を形成した。
【００８６】
本実施例では、低屈折率誘電体膜（ＳｉＯ₂ ：膜厚７０ｎｍ）と高屈折率誘電体膜（ＴｉＯ₂ ：膜厚５０ｎｍ）の組を３組、計６層形成したが、本実施例の材料、膜厚、層数等に限定されないことは言うまでもない。ただし、効率よく反射率を得るためには、可視光領域（４００ｎｍ＜λ＜７００ｎｍ）でλ／４膜となるように、それぞれ誘電体膜の膜厚を調節することが好ましい。
【００８７】
そして、実施例１と同様にコンタクトホールを形成し、高屈折率を有した透明性導電膜からなる画素電極２１５（膜厚６０ｎｍ）を形成した。本実施例における透明性導電膜は、反射膜の一部として用いるため、可視光領域（４００ｎｍ＜λ＜７００ｎｍ）でλ／４膜となるように、画素電極の膜厚を５０．５ｎｍ〜８８．４ｎｍの範囲で調節することが好ましい。このような膜厚とすることで、実質的には、低屈折率誘電体膜と高屈折率誘電体膜の組を４組形成した場合（実施例１）と同程度の反射率を得ることができる。
【００８８】
その後、実施例１と同様に、配向膜２１６を形成し、第１の基板を作製した。（図２（Ｂ））
【００８９】
このような構成とすることで、誘電体多層膜の層数及び総膜厚を削減し、実施例１と比較して容易にコンタクトホールの形成を行うことができた。
【００９０】
なお、本実施例と実施例２と組合わせて、さらに層数を削減する構成とすることは容易である。この場合、層間絶縁膜と、６層の誘電体多層膜２１４と、画素電極２１５とで、実施例１と同程度の反射率を得ることができる。
【００９１】
〔実施例４〕
実施例１で示した作製工程では、８層からなる誘電体多層膜を形成した例を示した。本実施例では、画素電極と誘電体多層膜を用いて補助容量を形成する例を図５を用いて以下に説明する。なお、途中（図３（Ｃ））までは実施例１に示した反射型ＬＣＤの作製工程と同一であるので、ここでは異なる点のみについて説明する。
【００９２】
まず、実施例１の作製工程と同一の方法を用いて、図３（Ｃ）の構成を得る。
【００９３】
次に、層間絶縁膜上に低屈折率誘電体膜５０１と高屈折率誘電体膜５０２の組を３組、計６層成膜し、その上に低屈折率誘電体膜を１層成膜し、誘電体多層膜５００を形成した。
【００９４】
本実施例においては、次に、高屈折率を有する材料からなる共通電極５０３（第１の透明性導電膜）を形成し、パターニングを施す。さらに、低屈折率誘電体膜を１層形成する。そして、コンタクトホールを形成し、再度、高屈折率を有する材料からなる第２の透明性導電膜を形成し、パターニングを施して、画素電極５０４を形成した。なお、第１の透明性導電膜からなる共通電極５０３は、共通配線と接続する。
【００９５】
ただし、共通電極５０３（第１の透明性導電膜）の膜厚と、画素電極（第２の透明性導電膜）５０４の膜厚は、反射膜の一部として用いるため、可視光領域（４００ｎｍ＜λ＜７００ｎｍ）でλ／４膜となるように、５０．５〜８８．４ｎｍの範囲で調節することが好ましい。このような膜厚とすることで、実質的には、低屈折率誘電体膜と高屈折率誘電体膜の組を５組形成した場合と同程度の反射率９３．６％（計算上）を得ることができる。
【００９６】
その後、実施例１と同様に、配向膜５０６を形成し、第１の基板を作製した。（図５）
【００９７】
図５に示す構成とすることで、共通電極（第１の透明性導電膜）５０３と、低屈折率誘電体膜５０１と、画素電極（第２の透明性導電膜）５０４とで補助容量５０５を形成することができた。この補助容量は、実用上、十分な容量を得ることができた。
【００９８】
なお、本実施例と実施例２または実施例３と組み合わせることは容易である。
【００９９】
〔実施例５〕
実施例４で示した作製工程では、画素電極と誘電体多層膜を用いて補助容量を形成する例を示した。本実施例では、画素電極６０４と、低屈折率誘電体膜６０１と、透明性導電膜からなる共通電極６０２とを用いて補助容量６０５を形成する例（図６（Ａ）容量構成１）を以下に説明する。なお、途中（図３（Ｃ））までは実施例１に示した反射型ＬＣＤの作製工程と同一であるので、ここでは異なる点のみについて説明する。
【０１００】
まず、実施例１の作製工程と同一の方法を用いて、図３（Ｃ）の構成を得る。
【０１０１】
次に、第１の透明性導電膜からなる膜、例えばＩＴＯ膜を成膜し、パターニングして共通電極６０２を得た後、前記共通電極を覆って、低屈折率誘電体膜６０１を形成する。この工程を２回繰り返し、反射膜を形成する。
【０１０２】
次に、コンタクトホールを形成した。本実施例の構成において、コンタクトホール形成領域には層間絶縁膜と低屈折率誘電体膜６０１のみが積層されており、低屈折率誘電体膜を同一材料で構成した場合、エッチングを比較的容易に行うことができる。
【０１０３】
次に、高屈折率を有する材料からなる第２の透明性導電膜を成膜し、パターニングを施して、画素電極６０４を形成した。なお、共通電極６０２は、共通配線と接続する。
【０１０４】
ただし、共通電極６０２（第１の透明性導電膜）の膜厚と、画素電極（第２の透明性導電膜）６０４の膜厚は、反射膜の一部として用いるため、可視光領域（４００ｎｍ＜λ＜７００ｎｍ）でλ／４膜となるように５０．５〜８８．４ｎｍの範囲で調節することが好ましい。
【０１０５】
その後、実施例１と同様に、配向膜６０６を形成し、第１の基板を作製した。（図６（Ａ））
【０１０６】
図６（Ａ）に示す構成とすることで、共通電極６０２と、低屈折率誘電体膜６０１と、画素電極６０４とで補助容量６０５を形成することができた。なお、共通電極６０２は、フロ─ティング状態であっても容量が形成される。従って、低屈折率誘電体膜６０１を間に挟む共通電極６０２の間にも容量が形成される。なお、材料、膜の厚さ、積層数等を適宜変更することによって、補助容量６０５を自由に設計することができる。
【０１０７】
なお、本実施例と実施例２または実施例３と組み合わせることは容易である。
【０１０８】
〔実施例６〕
実施例５で示した作製工程では、画素電極と、低屈折率誘電体膜と、透明性導電膜からなる共通電極とを用いて補助容量を形成する例を示した。本実施例では、さらに大きな補助容量を形成する例（図６（Ｂ）容量構成２）を以下に説明する。なお、途中（図３（Ｃ））までは実施例１に示した反射型ＬＣＤの作製工程と同一であるので、ここでは異なる点のみについて説明する。
【０１０９】
まず、実施例１の作製工程と同一の方法を用いて、図３（Ｃ）の構成を得る。
【０１１０】
次に、第１の透明性導電膜からなる膜、例えばＩＴＯ膜を成膜し、パターニングして共通電極６１２を得た後、前記共通電極６１２を覆って、低屈折率誘電体膜６１１を形成する。
【０１１１】
次に、第１のコンタクトホールの形成を行い、透明性導電膜からなる容量電極６１３を形成し、スイッチング素子のドレイン電極と接続する。
【０１１２】
その後、前記容量電極６１３を覆って、低屈折率誘電体膜６１１を形成する。そして、再度、第１の透明性導電膜からなる膜、例えばＩＴＯ膜を成膜し、パターニングして共通電極６１２を得た後、前記共通電極を覆って、低屈折率誘電体膜６１１を形成する。
【０１１３】
次に、第２のコンタクトホールの形成を行い、透明性導電膜からなる画素電極６１４をパターニングによって形成し、容量電極６１３と接続する。
【０１１４】
なお、共通電極６１２は、共通配線と接続した。ただし、全ての共通電極を接続する必要はなく、適宜接続することが望ましい。
【０１１５】
上記工程とすることで得られる構成は、画素電極６１４と、低屈折率誘電体膜６１１と、共通電極６１２とで構成される補助容量と、容量電極６１３と、低屈折率誘電体膜６１１と、共通電極６１２とで構成される補助容量を形成することができる。
【０１１６】
このように、開口率を下げることなく補助容量を大きくとれるため、本実施例は、特に、小さな高精細パネルを用いるプロジェクタ装置に有効である。
【０１１７】
〔実施例７〕
本実施例では、アクティブマトリクス駆動を行うための半導体素子として、実施例１で示したＴＦＴとは異なる構造のＴＦＴを利用する場合の例について説明する。なお、本実施例で説明する構造のＴＦＴは実施例２〜６に対しても容易に適用することができる。
【０１１８】
実施例１〜６では代表的なトップゲイト型ＴＦＴであるコプレナー型ＴＦＴを一例として記載したが、ボトムゲイト型ＴＦＴであっても構わない。図７に示すのはボトムゲイト型ＴＦＴの代表例である逆スタガ型ＴＦＴを用いた例である。
【０１１９】
図７において、７０１はガラス基板、７０２、７０３はゲイト電極、７０４はゲイト絶縁膜、７０５、７０６は活性層である。活性層７０５、７０６は意図的に不純物を添加しない珪素膜で構成される。
【０１２０】
また、７０７、７０８はソース電極、７０９、７１０はドレイン電極であり、７１１、７１２はチャネルストッパー（またはエッチングストッパー）となる窒化珪素膜である。即ち、活性層７０５、７０６のうち、チャネルストッパー７１１、７１２の下に位置する領域が実質的にチャネル形成領域として機能する。
【０１２１】
以上までが逆スタガ型ＴＦＴの基本構造である。
【０１２２】
本実施例では、この様な逆スタガ型を有機性樹脂膜でなる層間絶縁膜７１３で覆って平坦化し、層間絶縁膜上に本発明の誘電体多層膜７１６（低屈折率誘電体膜７１７、高屈折率誘電体膜７１８）を形成し、その上に画素電極７１４、７１５を形成し、配向膜７１９を成膜する構成とする。
【０１２３】
また、次に本発明の半導体素子として絶縁ゲイト型電界効果トランジスタ（ＩＧＦＥＴ）を形成した場合の例について説明する。なお、ＩＧＦＥＴはＭＯＳＦＥＴとも呼ばれ、シリコンウェハー上に形成されたトランジスタを指す。
【０１２４】
図８において、８０１はガラス基板、８０２、８０３はソース領域、８０４、８０５はドレイン領域である。ソース／ドレイン領域はイオン注入で不純物を添加し、熱拡散させることで形成できる。なお、８０６は素子分離用の酸化物であり、通常のＬＯＣＯＳ技術を用いて形成できる。
【０１２５】
次に、８０７はゲイト絶縁膜、８０８、８０９はゲイト電極、８１０は第１の層間絶縁膜、８１１、８１２はソース電極、８１３、８１４はドレイン電極である。その上を第２の層間絶縁膜８１５で平坦化し、その平坦面上に本発明の誘電体多層膜８１８（低屈折率誘電体膜８１９、高屈折率誘電体膜８２０）を形成し、画素電極８１６、８１７を形成する。そして、配向膜８２１を成膜する。
【０１２６】
なお、本実施例で示したＩＧＦＥＴ、トップゲイト型またはボトムゲイト型ＴＦＴ以外にも、薄膜ダイオード、ＭＩＭ素子、バリスタ素子等を用いたアクティブマトリクスディスプレイに対しても本発明は適用できる。
【０１２７】
以上、本実施例に示した様に、本発明はあらゆる構造の半導体素子を用いた反射型ＬＣＤに対して適用可能である。
【０１２８】
〔実施例８〕 実施例１〜７に示した構成を含む第１の基板（素子形成側基板）を用いてＡＭＬＣＤを構成した場合の例について説明する。ここで本実施例のＡＭＬＣＤの外観を図９に示す。
【０１２９】
図９（Ａ）において、９０１はアクティブマトリクス基板であり、画素マトリクス回路９０２、ソース側駆動回路９０３、ゲート側駆動回路９０４が形成されている。駆動回路はＮ型ＴＦＴとＰ型ＴＦＴとを相補的に組み合わせたＣＭＯＳ回路で構成することが好ましい。また、９０５は対向基板である。
【０１３０】
図９（Ａ）に示すＡＭＬＣＤはアクティブマトリクス基板９０１と対向基板９０５とが端面を揃えて貼り合わされている。ただし、ある一部だけは対向基板９０５を取り除き、露出したアクティブマトリクス基板に対してＦＰＣ（フレキシブル・プリント・サーキット）９０６を接続してある。このＦＰＣ９０６によって外部信号を回路内部へと伝達する。
【０１３１】
また、ＦＰＣ９０６を取り付ける面を利用してＩＣチップ９０７、９０８が取り付けられている。これらのＩＣチップはビデオ信号の処理回路、タイミングパルス発生回路、γ補正回路、メモリ回路、演算回路など、様々な回路をシリコン基板上に形成して構成される。図９（Ａ）では２個取り付けられているが、１個でも良いし、さらに複数個であっても良い。
【０１３２】
また、図９（Ｂ）の様な構成もとりうる。図９（Ｂ）において図９（Ａ）と同一の部分は同じ符号を付してある。ここでは図９（Ａ）でＩＣチップが行っていた信号処理を、同一基板上にＴＦＴでもって形成されたロジック回路９０９によって行う例を示している。この場合、ロジック回路９０９も駆動回路９０３、９０４と同様にＣＭＯＳ回路を基本として構成される。
【０１３３】
また、カラーフィルターを用いてカラー表示を行っても良いし、ＥＣＢ（電界制御複屈折）モード、ＧＨ（ゲストホスト）モードなどで液晶を駆動し、カラーフィルターを用いない構成としても良い。
【０１３４】
〔実施例１０〕
本願発明の構成は、ＡＭＬＣＤ以外にも他の様々な電気光学装置や半導体回路に適用することができ、上記ＡＭＬＣＤ以外の電気光学装置として、単純マトリクス型駆動方式の液晶表示装置やＥＬ（エレクトロルミネッセンス）表示装置やイメージセンサ等が挙げられる。
【０１３５】
本実施例では、単純マトリクス型駆動方式の液晶表示装置に適用した場合の例を以下に示す。
【０１３６】
なお、一般的な単純マトリクス型液晶表示装置は、Ｘ方向のストライプ状電極を有する基板と、Ｙ方向のストライプ状電極を有する基板とが、液晶層を挟んでいる構造となっている。また、単純マトリクスでは、対向するＸ−Ｙ電極によって直接液晶に電圧を印加している。
【０１３７】
本実施例では、本発明をＳＴＮ反射型液晶パネルに応用した例を示す。ガラス基板（第１の基板）上には、誘電体多層膜からなる光反射膜、Ｘ方向のストライプ状の第１の透明電極、配向膜が設けられている。本実施例では、誘電体多層膜からなる光反射膜を透明電極の下方に設ける構成としたが特に限定されない。もう一方のガラス基板（第２の基板）上には、Ｙ方向のストライプ状の第２の透明電極、配向膜が設けられている。ガラス基板の配向膜が設けられた面を内側にして２枚のガラス基板を対向し、ガラス基板の間隔はセルギャップ保持部材によって確保して、この基板の隙間にＳＴＮ液晶が封止している。
【０１３８】
以下、本実施例の反射型液晶パネルの作製方法を説明する。まず、第１のガラス基板上に、誘電体多層膜からなる光反射膜を形成する。
【０１３９】
上記反射膜に用いる材料は、低屈折率誘電体膜としてＳｉＯ₂ 、ＭｇＦ₂ 、Ｎａ₃ ＡｌＦ₆ 等を用いることができる。なお、それ以外の低屈折率誘電体材料として配向膜、アクリル、ポリイミド（屈折率１．５〜１．６）を用いることもできる。また、高屈折率誘電体膜としてＴｉＯ₂ 、ＺｒＯ₂ 、Ｔａ₂ Ｏ₅ 、ＺｎＳ、ＺｎＳｅ、ＺｎＴｅ、Ｓｉ、Ｇｅ、Ｙ₂ Ｏ₃ 、Ａｌ₂ Ｏ₃ 等を用いることができる。また、それ以外の高屈折率を有する材料としてＩＴＯ（屈折率１．９８）等の透明導電体膜を用いることもできる。
【０１４０】
本実施例では、低屈折率誘電体膜として、ＳｉＯ₂ （屈折率１．４３）、高屈折率誘電体膜としてＴｉＯ₂ （屈折率２．２）を用いた。
【０１４１】
ただし、可視光領域（４００ｎｍ＜λ＜７００ｎｍ）でλ／４膜となるように、誘電体多層膜の膜厚を調節する。上記可視光領域でλ／４膜となるような低屈折率誘電体膜（ＳｉＯ₂ ）の膜厚の範囲は、７０ｎｍ〜１２２ｎｍである。また、上記可視光領域でλ／４膜となるような高屈折率誘電体膜（ＴｉＯ₂ ）の膜厚の範囲は、４５．５ｎｍ〜７９．５ｎｍである。このような膜厚に調節すると、必要とする反射波長帯の光が干渉効果によって強め合い効率よく反射させることができる。本実施例では、誘電体多層膜は、膜厚７０ｎｍの低屈折率誘電体膜と、膜厚５０ｎｍの高屈折率誘電体膜の２層を１組とした時、４組、計８層（９６０ｎｍ）で構成した。
【０１４２】
次に、第１の透明電極を形成する。本実施例では、ＩＴＯ膜を１００ｎｍ膜厚に成膜し、パターニングして、ストライプ状の透明電極を形成する。透明電極は紙面に垂直な方向に延在する構造となっている。
【０１４３】
次に、配向膜を形成する。配向膜材料にはポリイミド系の垂直配向膜を用いる。このポリイミド系の垂直配向膜をスピンコート法、フレキソ印刷法もしくはスクリーン印刷法によって第１の基板上に形成する。
【０１４４】
そして、もう一方のガラス基板（第２の基板）に対する処理を説明する。第２の基板上にカラーフィルタを形成し、次にカラーフィルタをアクリル樹脂、エポキシ樹脂からなる保護膜を形成する。本実施例では、保護膜を厚さ１μｍのアクリル樹脂で形成する。
【０１４５】
次に、ＩＴＯ（インディウム錫酸化物）やＳｎＯ₂（酸化スズ）等の透明導電膜でなる第２の透明電極を形成する。本実施例では、スパッタリング法によってＩＴＯ膜を成膜しパターニングして、ストライプ状の第２の透明電極を形成した。そして、ポリイミド系の垂直配向膜でなる配向膜を形成する。
【０１４６】
次に、第１の基板および第２の基板に設けられた配向膜それぞれにラビング処理を施す。ラビング方向は、基板の一つの対角線方向とし、かつ第１の基板と第２の基板を対向した状態で配向膜のラビング方向が直交するようにする。
【０１４７】
次に、一対の基板の一方に、セルギャップ材を形成し、基板を貼り合わせるためのシール材を塗布する。本実施例では、第２の基板側の周縁部に、紫外線硬化型樹脂でなるシール材を液晶注入口を残して塗布した。そして第１の基板と第２の基板を対向させて、セルギャップが一定にプレスし、この状態で紫外線を照射して、シール材を硬化させる。
【０１４８】
次に、液晶を液晶注入口より注入する。その後、液晶注入口に封止剤を塗布し、紫外線を照射することによって封止剤を硬化させ、液晶をセル内に完全に封止する。そして、第２の基板の背面に位相差板、偏光子、前方散乱板をそれぞれ設けた。以上の工程を経て、フルカラーＳＴＮ液晶パネルが完成した。
【０１４９】
なお、少なくとも誘電体多層膜からなる反射膜を有し、透明電極を有する単純マトリクス型駆動方式の液晶表示装置であれば、本実施例の構造及び作製工程に限定されないことはいうまでもない。
【０１５０】
〔実施例１０〕
実施例８に示したＡＭＬＣＤは、様々な電子機器のディスプレイとして利用される。なお、本実施例に挙げる電子機器とは、アクティブマトリクス型液晶表示装置を搭載した製品と定義する。
【０１５１】
その様な電子機器としては、ビデオカメラ、スチルカメラ、プロジェクター、プロジェクションＴＶ、ヘッドマウントディスプレイ、カーナビゲーション、パーソナルコンピュータ（ノート型を含む）、携帯情報端末（モバイルコンピュータ、携帯電話等）などが挙げられる。それらの一例を図１０に示す。
【０１５２】
図１０（Ａ）はモバイルコンピュータ（モービルコンピュータ）であり、本体２００１、カメラ部２００２、受像部２００３、操作スイッチ２００４、表示装置２００５で構成される。本願発明は受像部２００３、表示装置２００５等に適用できる。
【０１５３】
図１０（Ｂ）はヘッドマウントディスプレイであり、本体２１０１、表示装置２１０２、バンド部２１０３で構成される。本発明は表示装置２１０２に適用することができる。
【０１５４】
図１０（Ｃ）は携帯電話であり、本体２２０１、音声出力部２２０２、音声入力部２２０３、表示装置２２０４、操作スイッチ２２０５、アンテナ２２０６で構成される。本願発明は音声出力部２２０２、音声入力部２２０３、表示装置２２０４等に適用することができる。
【０１５５】
図１０（Ｄ）はビデオカメラであり、本体２３０１、表示装置２３０２、音声入力部２３０３、操作スイッチ２３０４、バッテリー２３０５、受像部２３０６で構成される。本願発明は表示装置２３０２、音声入力部２３０３、受像部２３０６に適用することができる。
【０１５６】
図１０（Ｅ）はリア型プロジェクターであり、本体２４０１、光源２４０２、表示装置２４０３、ミラー（偏光ビームスプリッタ等）２４０４、２４０５、スクリーン２４０６で構成される。本発明は表示装置２４０３に適用することができる。
【０１５７】
図１０（Ｆ）はフロント型プロジェクターであり、本体２５０１、光源２５０２、表示装置２５０３、光学系２５０４、スクリーン２５０５で構成される。本発明は表示装置２５０３に適用することができる。
【０１５８】
以上の様に、本発明の適用範囲は極めて広く、あらゆる分野の電子機器に適用することが可能である。また、他にも電光掲示盤、宣伝公告用ディスプレイなどにも活用することができる。
【０１５９】
【発明の効果】
本発明は、反射膜として誘電体多層膜を用い、材料、膜の厚さ、積層数等を適宜変更することによって、容易に反射率を９０％以上とすることができ、広い範囲の電子機器の液晶表示パネルとして適用できる。また、本発明の構成を用いることで、配向膜を積層した状態であっても９０〜１００％未満の反射率を得ることができる。
【０１６０】
特に、本発明の反射型液晶ＬＣＤは、誘電体多層膜を反射膜として、その上に透明性導電膜からなる画素電極を備えた構成とすることで、高い開口率を実現することができる。
【０１６１】
また、反射膜である誘電体多層膜を誘電体として、透明性導電膜からなる画素電極と透明性導電膜からなる共通電極とで容易に補助容量を形成することができる。
【０１６２】
本発明により、従来にない明るく、視認性の良い表示の液晶パネルを得ることができる。
【図面の簡単な説明】
【図１】 本発明の構成の一例を示す図（実施例１）
【図２】 本発明の構成の一例を示す図（実施例２、３）
【図３】 本実施例の作製工程の一例を示す図（実施例１）
【図４】 本実施例の作製工程の一例を示す図（実施例１）
【図５】 本発明の構成の一例を示す図（実施例４）
【図６】 本発明の構成の一例を示す図（実施例５）
【図７】 本発明の構成の一例を示す図（実施例７）
【図８】 本発明の構成の一例を示す図（実施例７）
【図９】 液晶パネルの外観図を示す図（実施例８）
【図１０】 本発明の応用製品の一例を説明するための図
【図１１】 従来例を示す図
【符号の説明】
１１０ 基板
１１１ スイッチング素子（ＴＦＴ）
１１２ 層間絶縁膜
１１３ 画素電極（透明性導電膜）
１１４ 低屈折率誘電体膜
１１５ 高屈折率誘電体膜
１１６ 配向膜
１１７ 液晶層
１１８ 対向電極
１１９ 対向基板
１２０ 入射光
１２１ 反射光[0001]
[Technical field to which the invention belongs]
The present invention relates to a configuration of an electric device such as a personal computer or a word processor, and more particularly to a liquid crystal display device (LCD) provided in the electric device and a method for manufacturing a reflective film in the liquid crystal display device. Further, the present invention can be applied to an electro-optical device having a liquid crystal display device.
[0002]
In this specification, “semiconductor device” refers to all devices that function by using a semiconductor. Therefore, the liquid crystal display device and the electro-optical device are also included in the category of the semiconductor device. However, in the specification, terms such as a liquid crystal display device and an electro-optical device are used differently for easy distinction.
[0003]
[Prior art]
A reflection type liquid crystal display device is generally known. The reflective liquid crystal display device has an advantage that it consumes less power than a transmissive liquid crystal display device because it does not use a backlight. Note that the demand for reflective liquid crystal display devices is increasing as a direct-view display for mobile computers and video cameras.
[0004]
FIG. 11 is a schematic diagram showing an example of a conventional configuration. In FIG. 11, between the substrate 10 and the counter substrate 17, a switching element 11 such as a thin film transistor, an interlayer insulating film 12, a pixel electrode 13, an alignment film 14, a liquid crystal layer 15, an alignment film 14, a counter electrode are arranged from the upper surface of the substrate 10. It is formed in the order of 16. Further, the incident light 20 is reflected by the pixel electrode, and reflected light 21 is generated. Since FIG. 11 is a schematic diagram, the entire structure is not shown, but a large number of switching elements and a large number of pixel electrodes are formed in a matrix on the surface of the substrate 10.
[0005]
The reflection-type liquid crystal display device uses an optical modulation action of liquid crystal to select a state in which incident light is reflected by the pixel electrode and output to the outside of the device, and a state in which incident light is not output to the outside of the device, By displaying bright and dark colors and combining them, image display is performed. Note that the pixel electrode is made of a metal material having high light reflectance such as aluminum and is electrically connected to a switching element such as a thin film transistor.
[0006]
When such a conventional configuration, that is, a configuration in which a pixel electrode made of a metal material having a high reflectance is used as a reflective film, the reflectance of light has a limit (for example, less than 92% with an aluminum electrode).
[0007]
[Problems to be solved by the invention]
Conventional reflective films (pixel electrodes made of a metal material) have insufficient light reflection and irregular reflection, and have a problem in brightness as a liquid crystal display device (particularly, a direct-view reflective liquid crystal panel).
[0008]
Further, conventionally, there has been a problem that the reflectance is lowered by forming an alignment film having a high refractive index on the reflective film (pixel electrode made of a metal material). For example, when an alignment film (refractive index 1.6) is provided on a vapor-deposited aluminum film (reflectance 91.6%), the calculated value is 87.4%, and the actual experimental result shows that the reflectivity is 85-86%. It had fallen to the extent. In addition, when silver is used as the metal material, the reflectance of the silver electrode is as high as 97.6%, but it is easily oxidized and difficult to use in the process.
[0009]
Accordingly, the invention disclosed in this specification solves the above problems and provides a structure of a novel liquid crystal display device including a reflective film that reflects incident light more efficiently than a conventional method and a manufacturing method thereof. The task is to do.
[0010]
[Means for Solving the Problems]
The first configuration of the present invention disclosed in this specification is as follows.
A switching element on the substrate;
A pixel electrode made of a transparent conductive film connected to the switching element;
A liquid crystal display device having a reflective film made of a dielectric multilayer film provided in contact with the pixel electrode.
[0011]
Furthermore, the second configuration is:
A liquid crystal display device comprising a pixel electrode on a substrate, a switching element connected to the pixel electrode, and a reflective film,
The pixel electrode is composed of a transparent conductive film,
The liquid crystal display device is characterized in that the reflective film made of a dielectric multilayer film is provided below the pixel electrode.
[0012]
Furthermore, the third configuration is
A liquid crystal display device comprising a pixel electrode on a substrate, a switching element connected to the pixel electrode, and a reflective film,
A capacitor is connected to the switching element,
The capacitor includes a common electrode made of a transparent conductive film, a dielectric film on the common electrode, and the pixel electrode made of a transparent conductive film on the dielectric film,
The liquid crystal display device is characterized in that the reflective film made of a dielectric multilayer film is provided below the common electrode.
[0013]
In the third configuration, the dielectric film is made of a low refractive index dielectric material,
The common electrode and the pixel electrode are made of a conductive material having a high refractive index.
[0014]
In each of the above structures, the liquid crystal display device includes a pixel electrode in which liquid crystal is sealed between a pair of substrates and arranged in a matrix on one substrate, a thin film transistor connected to the pixel electrode, and a reflective film It is characterized by being a liquid crystal display device provided with.
[0015]
Furthermore, the fourth configuration is
Forming a switching element on the substrate;
A liquid crystal display device comprising: a step of forming a reflective film made of a dielectric multilayer film above the switching element; and a step of forming a pixel electrode made of a transparent conductive film on the reflective film. Is the method.
[0016]
Furthermore, the fifth configuration is
Forming a switching element on the substrate;
Forming an interlayer insulating film covering the switching element;
Forming a common electrode made of a transparent conductive film on the interlayer insulating film;
Forming a reflective film made of a dielectric multilayer film on the common electrode;
Forming a pixel electrode made of a transparent conductive film on the reflective film, and forming an auxiliary capacitor made of the pixel electrode, the dielectric multilayer film, and the common electrode. This is a manufacturing method.
[0017]
In the fourth configuration or the fifth configuration, the step of forming the dielectric multilayer film is a step of forming using a sputtering method or a vacuum evaporation method.
[0018]
Furthermore, the sixth configuration is
Liquid crystal is sealed between a pair of substrates, a first transparent electrode on one substrate,
A liquid crystal display device comprising a second transparent electrode and a reflective film made of a dielectric multilayer film on the other substrate.
[0019]
In the sixth configuration, the first transparent electrode and the second transparent electrode are arranged in a stripe shape,
It is a liquid crystal display device of a simple matrix type drive system having a reflective film made of a dielectric multilayer film below the second transparent electrode.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a cross-sectional view schematically showing an example of the configuration of the present invention.
[0021]
The liquid crystal display panel of the present invention includes a switching element 111, an interlayer insulating film 112, a dielectric multilayer film (114, 115), a pixel electrode 113, and an alignment film 116 on the substrate 110 between the substrate 110 and the counter substrate 119. A liquid crystal layer 117, an alignment film 116, and a counter electrode 118 are sequentially provided.
[0022]
The first feature of the present invention is that the reflective film for reflecting incident light is formed of a dielectric multilayer film. This dielectric multilayer film is formed by alternately laminating several to several tens of low refractive index dielectric films and high refractive index dielectric films. The dielectric multilayer film used as the reflective film of the present invention also functions as a protective film that prevents deterioration due to light. In addition, since the reflective film of the present invention, that is, the dielectric multilayer film, has an insulating property, it also functions as an interlayer insulating film.
[0023]
The material used for the reflective film is SiO as the low refractive index dielectric film 114. ₂ , MgF ₂ , Na _Three AlF ₆ Etc. can be used. An alignment film, acrylic, polyimide (refractive index: 1.5 to 1.6) can also be used as other low refractive index dielectric materials. Further, as the high refractive index dielectric film 115, TiO ₂ , ZrO ₂ , Ta ₂ O _Five , ZnS, ZnSe, ZnTe, Si, Ge, Y ₂ O _Three , Al ₂ O _Three Etc. can be used. In addition, a transparent conductor film such as ITO (refractive index 1.98) can be used as another material having a high refractive index.
[0024]
However, in the present invention, since the dielectric multilayer film is used as the reflection film, it is necessary to adjust the film thickness of the dielectric multilayer film so as to be a λ / 4 film at the center wavelength of the required reflection wavelength band. . In this specification, the λ / 4 film refers to a film that satisfies the relationship of nd = λ / 4, where n is the refractive index, d is the film thickness, and λ is the center wavelength.
[0025]
For example, as a reflective film of the present invention, a low refractive index dielectric film (SiO ₂ When the refractive index is 1.43), the film thickness range of the λ / 4 film in the visible light region (400 nm <λ <700 nm) is 70 nm to 122 nm.
[0026]
In addition, as a reflective film of the present invention, a high refractive index dielectric film (TiO ₂ When the refractive index is 2.2), the film thickness range of the λ / 4 film in the visible light region (400 nm <λ <700 nm) is 45.5 nm to 79.5 nm.
[0027]
The dielectric multilayer film in which several layers of the low refractive index dielectric film and the high refractive index dielectric film are alternately laminated by adjusting the film thickness of the low refractive index dielectric film and the high refractive index dielectric film is Light is strengthened by the interference effect, the reflectance can be improved efficiently, and a wavelength region with a high reflectance can be obtained.
[0028]
As for the number of dielectric multilayer films, Table 1 shows the relationship between the number of dielectric multilayer films and the maximum reflectance when each dielectric multilayer film is a λ / 4 film. In the present specification, two layers having a lower refractive index dielectric film as a lower layer and a high refractive index dielectric film as an upper layer are referred to as one set.
[0029]
[Table 1]

[0030]
From Table 1, it can be seen that the reflectance increases as the number of layers of the dielectric multilayer film increases. Therefore, when priority is given to the high reflectance, it is preferable to stack 3 sets (6 layers), preferably 4 sets (8 layers) or more.
[0031]
On the other hand, when giving priority to manufacturing cost and yield, it is preferable to reduce the number of layers as much as possible. In addition, in order to form a contact hole after forming the dielectric multilayer film, it is desirable to reduce the total thickness of the dielectric multilayer film in the process.
[0032]
Further, when a low refractive index dielectric material is used for the interlayer insulating film 112, the reflectance hardly changes regardless of the presence or absence of the low refractive index dielectric film 114 provided in contact with the interlayer insulating film 112. Results were also obtained. Therefore, as shown in FIG. 2A, an interlayer insulating film 201 covering the switching element is formed on the low refractive index dielectric film (SiO 2). ₂ , Acrylic, polyimide, or the like), and the low-refractive-index dielectric film 202 is preferably omitted to reduce the number of layers.
[0033]
Note that the present invention is not limited to the configuration shown in FIG. 1 as long as it uses a dielectric multilayer film as the reflective film. For example, a pixel electrode may be provided using a material having transparency and conductivity, and a dielectric multilayer film may be formed thereon. In that case, it is necessary to consider the film thickness of the dielectric multilayer film. . This is because voltage loss occurs depending on the thickness of the dielectric multilayer film (total film thickness of 2 μm or more), which affects the threshold characteristics, response speed, etc. of the liquid crystal. Therefore, as shown in FIG. 1, it is preferable that the reflective film that reflects incident light is formed of a dielectric multilayer film, and a pixel electrode is provided thereon using a material having transparency and conductivity. . In the case where the pixel electrode is provided on the dielectric multilayer film, there is no influence on the threshold characteristics, response speed, etc. of the liquid crystal even when the number of layers is, for example, 12 or more.
[0034]
The pixel electrodes 113 are arranged in a matrix via an interlayer insulating film 112 and a dielectric multilayer film, and are connected to a switching element 111 such as a thin film transistor. The pixel electrode is made of a material having sufficient transparency and conductivity, such as ITO (indium tin oxide) or SnO. ₂ (Tin oxide) etc. Therefore, as shown in FIG. 2B, the number of layers can be reduced if the pixel electrode 215 (ITO: refractive index 1.98) is part of a reflective film that reflects incident light. Therefore, it is preferable. In this case, the thickness of the pixel electrode 215 is also adjusted in the range of 50.5 nm to 88.4 nm so as to be a λ / 4 film.
[0035]
In the present invention, it is easy to selectively set the reflection wavelength by appropriately changing the thickness and material of each dielectric film.
[0036]
Further, conventionally, it has been necessary to form a light-shielding film such as a black mask in the gap between the pixel electrodes to prevent light deterioration of the switching element. In the present invention, however, the dielectric provided below the gap between the pixel electrodes. The body multilayer film performs a reliable light shielding function against light from an oblique direction.
[0037]
Examples of the method for forming the dielectric multilayer film include a sputtering method and a vacuum deposition method, but the present invention is not particularly limited. In the present invention, it is desirable that the dielectric multilayer film provided on the interlayer insulating film or the pixel electrode is formed uniformly.
[0038]
FIG. 1 shows an example in which four sets of dielectric multilayer films are configured with a total of eight layers. In the configuration of FIG. 1, the same degree of reflectivity as that of a reflective electrode made of a conventional metal material was obtained. Therefore, if the material, film thickness, number of layers, etc. of the dielectric multilayer film are appropriately changed, for example, if a structure in which five or more sets (10 layers) of dielectric multilayer films are formed, a structure in which alignment films are stacked is used. In addition, there is little reflection loss, and a reflectance of 90% or more can be easily obtained.
[0039]
In the present invention, by providing the reflective film composed of the dielectric multilayer film, the light use efficiency can be improved as compared with the conventional configuration (the pixel electrode made of a metal material is a reflective film). In addition, it is possible to suppress a decrease in reflectance due to the alignment film, which has been a problem in the past. Using the present invention, a reflectance of 90% or more can be obtained.
[0040]
【Example】
[Example 1]
In this embodiment, an example of a process for manufacturing a pixel matrix circuit of a reflective LCD using the present invention will be described with reference to FIGS. In addition, since this invention is a technique regarding a reflecting film, a switching element structure, for example, TFT structure itself is not limited to a present Example.
[0041]
First, a substrate 301 having an insulating surface is prepared. As the substrate, a glass substrate, a quartz substrate, a ceramic substrate, or a semiconductor substrate can be used. In this example, a glass substrate was used. Next, a base film (not shown) is provided on the substrate. As the base film, a silicon oxide film, a silicon nitride film, or a silicon nitride oxide film can be used with a thickness of 100 to 300 nm. In this embodiment, TEOS is used as a raw material, and a silicon oxide film is formed to a thickness of 200 nm. Note that the base film is not necessarily provided as long as the quartz substrate has sufficient flatness.
[0042]
Next, an active layer is formed on the substrate or the base film. The active layer may be formed of a crystalline semiconductor film (typically a crystalline silicon film) having a thickness of 20 to 100 nm (preferably 25 to 70 nm). The crystalline silicon film may be formed by any known means, for example, laser crystallization, thermal crystallization, etc. In this embodiment, a catalyst element (nickel) that promotes crystallization is used in the crystallization. It is added. This technique is described in detail in Japanese Patent Application Laid-Open No. 7-130652 and Japanese Patent Application No. 8-335152. Then, the crystalline silicon film was patterned by a normal photolithography process to obtain active layers 302 to 304 having a thickness of 50 nm. Although only three TFTs are described in this embodiment, in reality, one million or more TFTs are formed in the pixel matrix circuit.
[0043]
Next, a 150 nm thick silicon oxide film was formed as the gate insulating film 305. As the gate insulating film 305, a silicon oxide film, a silicon nitride film, a silicon oxynitride film, or a stacked film thereof can be used with a thickness of 100 to 300 nm. After that, a film (not shown) containing aluminum as a main component is formed on the gate insulating film using a target containing 0.2 wt% scandium, and an island-shaped pattern that becomes a prototype of the gate electrode is formed by patterning. did.
[0044]
In this embodiment, the technique described in Japanese Patent Laid-Open No. 7-13518 is used here. For details, refer to the publication.
[0045]
First, anodic oxidation was performed in a 3% oxalic acid aqueous solution while leaving the resist mask used for patterning on the island pattern. At this time, a formation current of 2 to 3 mV is passed using the platinum electrode as a cathode, and the ultimate voltage is 8V. Thus, porous anodic oxide films 306 to 308 were formed.
[0046]
Then, after removing the resist mask, anodization was performed in a solution obtained by neutralizing an ethylene glycol solution of 3% tartaric acid with aqueous ammonia. At this time, the formation current may be 5 to 6 mV, and the ultimate voltage may be 100V. Thus, dense anodic oxide films 309 to 311 were formed.
[0047]
The gate electrodes 312 to 314 are defined by the above process. In the pixel matrix circuit, gate lines for connecting the gate electrodes are formed for each line simultaneously with the formation of the gate electrodes. (Fig. 3 (A))
[0048]
Next, the gate insulating film 305 is etched using the anodic oxide films 306 to 311 and the gate electrodes 312 to 314 as masks. Etching is CF _Four This was performed by a dry etching method using a gas. As a result, a gate insulating film having a shape as indicated by 315 to 317 was formed.
[0049]
Then, the anodic oxide films 306 to 308 are removed by etching, and impurity ions imparting one conductivity in this state are added by ion implantation or plasma doping. In this case, P (phosphorus) ions may be added if the pixel matrix circuit is composed of N-type TFTs, and B (boron) ions may be added if it is composed of P-type TFTs.
[0050]
Note that the impurity ion addition step is performed in two steps. The first is performed at a high acceleration voltage of about 80 keV, and is adjusted so that the peak of impurity ions comes under the end portions (protruding portions) of the gate insulating films 315 to 317. The second time is performed with a low acceleration voltage of about 5 keV, and adjustment is made so that impurity ions are not added under the end portions (protruding portions) of the gate insulating films 315 to 317.
[0051]
Thus, TFT source regions 318 to 320, drain regions 321 to 323, low-concentration impurity regions (also referred to as LDD regions) 324 to 326, and channel formation regions 327 to 329 were formed. (Fig. 3 (B))
[0052]
At this time, it is preferable to add impurity ions to the source / drain region to such an extent that a sheet resistance of 300 to 500 Ω / □ can be obtained. Further, the low concentration impurity region needs to be optimized in accordance with the performance of the TFT. Further, after the impurity ion addition step was completed, heat treatment was performed to activate the impurity ions.
[0053]
Next, a silicon oxide film having a thickness of 400 nm was formed as the first interlayer insulating film 330, and source electrodes 331 to 333 and drain electrodes 334 to 336 were formed thereon. (FIG. 3C) In addition to the silicon oxide film, silicon oxynitride or another insulating material can be used as the first interlayer insulating film.
[0054]
Note that in this specification, an element formed in the region indicated by 343 in FIG. 3C is referred to as a switching element (typically a TFT or an MIM element). Note that in this specification, the interlayer insulating film 337 and the pixel electrode formed later are not included in the configuration of the switching element.
[0055]
Next, a silicon oxide film is formed to a thickness of 0.5 to 1 μm as the second interlayer insulating film 337. In addition, as the second interlayer insulating film 337, a silicon oxynitride film, an organic resin film, or the like can be used. As the organic resin film, polyimide, polyamide, polyimide amide, acrylic, or the like can be used. In this example, an acrylic film was formed to a thickness of 1 μm. (Fig. 3 (D))
[0056]
Note that after the second interlayer insulating film 337 is formed, a planarization process such as CMP polishing may be performed. When performing the flattening process, the height of the remaining uneven part (the vertical distance between the top of the mountain and the bottom of the valley) should be within 10% of the thickness of the pixel electrode to be formed later. Is preferred. By performing the planarization treatment, the thickness of the dielectric multilayer film to be formed later can be made uniform.
[0057]
Then, a reflective film made of a dielectric multilayer film is formed on the second interlayer insulating film 337. The dielectric multilayer film 344 is formed by alternately stacking several to several tens of low refractive index dielectric films 341 and high refractive index dielectric films 342. Each film thickness must be adjusted so as to be a λ / 4 film at the center wavelength of the required reflection wavelength band.
[0058]
The material used for the dielectric multilayer film 344 is SiO as the low refractive index dielectric film 341. ₂ , MgF ₂ , Na _Three AlF ₆ Etc., and TiO as a high refractive index dielectric film 342 ₂ , ZrO ₂ , Ta ₂ O _Five , ZnS, ZnSe, ZnTe, Si, Ge, Y ₂ O _Three , Al ₂ O _Three Etc. can be used. An alignment film, acrylic, polyimide (refractive index: 1.5 to 1.6) can also be used as other low refractive index dielectric materials. A transparent conductor film such as ITO (refractive index 1.98) can also be used.
[0059]
In this embodiment, the low refractive index dielectric film 341 is made of SiO. ₂ (Refractive index 1.43), high refractive index dielectric film 342 as TiO ₂ (Refractive index 2.2) was used.
[0060]
The film thickness of the dielectric multilayer film is adjusted so as to be a λ / 4 film in the visible light region (400 nm <λ <700 nm). Low refractive index dielectric film (SiO2) that becomes a λ / 4 film in the visible light region ₂ ) Is in the range of 70 nm to 122 nm. In addition, a high refractive index dielectric film (TiO2) that becomes a λ / 4 film in the visible light region. ₂ ) Is in the range of 45.5 nm to 79.5 nm. By adjusting to such a film thickness, light in the required reflection wavelength band can be strengthened by the interference effect and reflected efficiently. In this embodiment, when the dielectric multilayer film is composed of two layers of a low-refractive index dielectric film 341 having a thickness of 70 nm and a high-refractive index dielectric film 342 having a thickness of 50 nm, a total of four sets are provided. It was composed of layers (960 nm). (Fig. 4 (A))
[0061]
Needless to say, it is not limited to the material and film thickness of each dielectric film, and the reflection wavelength can be selectively set by appropriately changing the film thickness and material of each dielectric film.
[0062]
In this example, since it is desirable that the dielectric multilayer film provided on the interlayer insulating film has a uniform film thickness, a vacuum deposition method which is a known method is used. The method for forming the dielectric multilayer film is not limited to this example, and other methods include sputtering.
[0063]
Next, the dielectric multilayer films 341 and 342 and the interlayer insulating film 337 are etched to form contact holes. In this example, the dielectric multilayer film was wet etched using a hydrogen fluoride solution diluted to 1/100 which is an acid solution. (Fig. 4 (B))
[0064]
A transparent conductive film, in this embodiment, an ITO film was formed to a thickness of 120 nm, and pixel electrodes 338 to 340 were formed by patterning. In this way, the state shown in FIG. 4C was obtained. Conventionally, it has been necessary to form a light-shielding film such as a black mask in the gap between the pixel electrodes. However, in this embodiment, this is not necessary, and a dielectric multilayer provided below the gap between the pixel electrodes. The film performs a reliable light shielding function against light from an oblique direction, and prevents light deterioration of the switching element.
[0065]
Next, the alignment film was formed by a known method, in this example, a coating method.
[0066]
The pixel matrix circuit was completed as described above. Actually, a drive circuit for driving the pixel TFT and the like are simultaneously formed on the same substrate. Such a substrate is usually called a TFT side substrate or an active matrix substrate. In this specification, the active matrix substrate is referred to as a first substrate.
[0067]
When the first substrate is completed, a counter substrate in which a counter electrode is formed on a transparent substrate (this substrate is referred to as a second substrate in this specification) is bonded, and a liquid crystal layer is sandwiched between them. To do. Thus, a reflective LCD is completed.
[0068]
This cell assembling step may be performed according to a known method. It is also possible to disperse a dichroic dye in the liquid crystal layer or provide a color filter on the counter substrate. The type of the liquid crystal layer, the presence / absence of the color filter, and the like vary depending on the mode in which the liquid crystal is driven, so that the practitioner may determine as appropriate.
[0069]
A reflective LCD obtained by the above manufacturing process is shown in FIG. FIG. 1 is a simplified cross-sectional view of this embodiment.
[0070]
The liquid crystal display panel manufactured in this example includes a switching element 111, an interlayer insulating film 112, a pixel electrode 113, a low refractive index dielectric film 114, a high height on the substrate 110 between the substrate 110 and the counter substrate 119. A refractive index dielectric film 115, an alignment film 116, a liquid crystal layer 117, an alignment film 116, and a counter electrode 118 are sequentially provided.
[0071]
1 corresponds to FIGS. 3 and 4, the interlayer insulating film in FIG. 1 corresponds to the second interlayer insulating film 337 in FIG. 3, and the pixel electrode 113 in FIG. 1 corresponds to the pixel electrodes 338 to 340 in FIG. 1, and the low refractive index dielectric film 114 in FIG. 1 corresponds to 341 in FIG. 3, and the high refractive index dielectric film 115 in FIG. 342.
[0072]
In this example (dielectric multilayer film + alignment film), the same reflectivity (80 to 90%) as that of the conventional (metal thin film + alignment film) was obtained. As described above, this example shows that a dielectric multilayer film can be sufficiently used as a reflective film instead of a metal thin film. Therefore, if the number of layers, material, film thickness, etc. of the dielectric multilayer film in this embodiment are appropriately changed, the reflectance can be improved as compared with the conventional case. For example, if the number of dielectric multilayer films is 5 sets (10 layers), 93.6% (see Table 1) is calculated, and if 6 sets (12 layers) are calculated, 97.1% is calculated. It should be noted that it is easy to increase the number of layers of the dielectric multilayer film in the configuration of this embodiment.
[0073]
Although not shown in this embodiment, a color filter may be arranged between the counter substrate and the counter electrode.
[0074]
[Example 2]
In the manufacturing process shown in Example 1, an example in which a dielectric multilayer film composed of eight layers was formed was shown. In this embodiment, an example in which a dielectric multilayer film composed of seven layers is formed as the second interlayer insulating film 337 using a low refractive index dielectric material will be described below with reference to FIG. Since the process up to the middle (FIG. 3C) is the same as the manufacturing process of the reflective LCD shown in Embodiment 1, only different points will be described here.
[0075]
First, the structure shown in FIG. 3C is obtained using the same method as the manufacturing process of Example 1. Next, however, a low refractive index dielectric material is used as the second interlayer insulating film 337. In this embodiment, an acrylic film having a thickness of 1 μm is formed as the interlayer insulating film 201.
[0076]
If a dielectric multilayer film to be formed later can be used as an insulator, a structure in which planarization processing such as CMP is performed and the film thickness of the interlayer insulating film 201 is thinned is particularly in contact holes. This is preferable because it can be easily formed.
[0077]
In this embodiment, a high refractive index dielectric film (ZrO) is formed on the interlayer insulating film 201. ₂ : Film thickness 50 nm). Then, a low refractive index dielectric film (SiO ₂ : Film thickness 70 nm) 202 and high refractive index dielectric film 203 (ZrO ₂ : Film thickness 50 nm), a total of 6 layers (720 nm) were formed. The thickness of each dielectric film is adjusted so that a λ / 4 film is obtained in the visible light region (400 nm <λ <700 nm).
[0078]
In this embodiment, the low refractive index dielectric film 202 is made of SiO. ₂ (Refractive index 1.43, film thickness range is 70 nm to 122 nm), high refractive index dielectric film 201 as ZrO ₂ (Refractive index 2.04, film thickness range 49 nm to 85.8 nm) was used.
[0079]
This example (SiO ₂ MgF as a low refractive index dielectric material other than ₂ , Na _Three AlF ₆ , Alignment film, acrylic, or polyimide (refractive index: 1.5 to 1.6) can also be used. In addition, this example (ZrO ₂ ) As a high refractive index dielectric material other than ₂ , Ta ₂ O _Five , ZnS, ZnSe, ZnTe, Si, Ge, Y ₂ O _Three , Al ₂ O _Three Etc. can be used.
[0080]
Then, contact holes were formed in the same manner as in Example 1 to form pixel electrodes 205 made of a transparent conductive film. The interlayer insulating film 201 in this embodiment has a low refractive index. Accordingly, substantially the same reflectivity as in the case where four pairs of low refractive index dielectric films and high refractive index dielectric films are formed (Example 1) can be obtained.
[0081]
Thereafter, in the same manner as in Example 1, an alignment film 206 was formed, and a first substrate was manufactured. (Fig. 2 (A))
[0082]
By adopting such a configuration, the number of dielectric multilayer films and the total film thickness were reduced, and contact holes could be easily formed as compared with Example 1.
[0083]
Example 3
In the manufacturing process shown in Example 1, an example in which a dielectric multilayer film composed of eight layers was formed was shown. In this embodiment, an example in which a seven-layer dielectric multilayer film is formed and a pixel electrode is formed thereon as a material having a high refractive index will be described below with reference to FIG. Since the process up to the middle (FIG. 3C) is the same as the manufacturing process of the reflective LCD shown in Embodiment 1, only different points will be described here.
[0084]
First, the structure shown in FIG. 3C is obtained using the same method as the manufacturing process of Example 1.
[0085]
Next, three pairs of a low refractive index dielectric film 212 and a high refractive index dielectric film 213 are formed on the second interlayer insulating film 337, for a total of six layers, and a low refractive index dielectric film is formed thereon. One layer was formed to form a dielectric multilayer film 214 (seven layers).
[0086]
In this embodiment, a low refractive index dielectric film (SiO ₂ : 70 nm film thickness) and high refractive index dielectric film (TiO) ₂ : Film thickness 50 nm), a total of 6 layers were formed, but it goes without saying that the present invention is not limited to the material, film thickness, number of layers, etc. However, in order to obtain the reflectance efficiently, it is preferable to adjust the thickness of each dielectric film so that the film becomes a λ / 4 film in the visible light region (400 nm <λ <700 nm).
[0087]
Then, contact holes were formed in the same manner as in Example 1 to form pixel electrodes 215 (film thickness 60 nm) made of a transparent conductive film having a high refractive index. Since the transparent conductive film in this example is used as a part of the reflective film, the film thickness of the pixel electrode is 50.5 nm to 88 so that the film becomes a λ / 4 film in the visible light region (400 nm <λ <700 nm). It is preferable to adjust within a range of 4 nm. With such a film thickness, substantially the same reflectivity as that obtained when four pairs of low refractive index dielectric films and high refractive index dielectric films are formed (Example 1) can be obtained. Can do.
[0088]
Thereafter, in the same manner as in Example 1, an alignment film 216 was formed, and a first substrate was manufactured. (Fig. 2 (B))
[0089]
By adopting such a configuration, the number of dielectric multilayer films and the total film thickness were reduced, and contact holes could be easily formed as compared with Example 1.
[0090]
It should be noted that it is easy to combine the present embodiment with the second embodiment to further reduce the number of layers. In this case, the interlayer insulating film, the six-layer dielectric multilayer film 214, and the pixel electrode 215 can obtain the same reflectance as that of the first embodiment.
[0091]
Example 4
In the manufacturing process shown in Example 1, an example in which a dielectric multilayer film composed of eight layers was formed was shown. In this embodiment, an example in which an auxiliary capacitor is formed using a pixel electrode and a dielectric multilayer film will be described below with reference to FIG. Since the process up to the middle (FIG. 3C) is the same as the manufacturing process of the reflective LCD shown in Embodiment 1, only different points will be described here.
[0092]
First, the structure shown in FIG. 3C is obtained using the same method as the manufacturing process of Example 1.
[0093]
Next, three pairs of low refractive index dielectric film 501 and high refractive index dielectric film 502 are formed on the interlayer insulating film, for a total of six layers, and one low refractive index dielectric film is formed thereon. Then, the dielectric multilayer film 500 was formed.
[0094]
In this embodiment, next, a common electrode 503 (first transparent conductive film) made of a material having a high refractive index is formed and patterned. Further, one layer of a low refractive index dielectric film is formed. Then, a contact hole was formed, a second transparent conductive film made of a material having a high refractive index was formed again, and patterning was performed to form a pixel electrode 504. Note that the common electrode 503 made of the first transparent conductive film is connected to a common wiring.
[0095]
However, the film thickness of the common electrode 503 (first transparent conductive film) and the film thickness of the pixel electrode (second transparent conductive film) 504 are used as part of the reflective film, so that the visible light region (400 nm) is used. It is preferable to adjust in the range of 50.5 to 88.4 nm so as to be a λ / 4 film at <λ <700 nm). By setting such a film thickness, the reflectivity is substantially 93.6% (calculated) which is substantially the same as the case where five sets of low refractive index dielectric films and high refractive index dielectric films are formed. Can be obtained.
[0096]
Thereafter, in the same manner as in Example 1, an alignment film 506 was formed, and a first substrate was manufactured. (Fig. 5)
[0097]
With the configuration illustrated in FIG. 5, the auxiliary capacitor 505 includes the common electrode (first transparent conductive film) 503, the low refractive index dielectric film 501, and the pixel electrode (second transparent conductive film) 504. Could be formed. As this auxiliary capacity, a practically sufficient capacity could be obtained.
[0098]
It is easy to combine the present embodiment with the second embodiment or the third embodiment.
[0099]
Example 5
In the manufacturing process shown in Example 4, an example in which an auxiliary capacitor is formed using a pixel electrode and a dielectric multilayer film is shown. In this embodiment, an example in which the auxiliary capacitor 605 is formed using the pixel electrode 604, the low refractive index dielectric film 601 and the common electrode 602 made of a transparent conductive film (capacitor configuration 1 in FIG. 6A). This will be described below. Since the process up to the middle (FIG. 3C) is the same as the manufacturing process of the reflective LCD shown in Embodiment 1, only different points will be described here.
[0100]
First, the structure shown in FIG. 3C is obtained using the same method as the manufacturing process of Example 1.
[0101]
Next, a film made of a first transparent conductive film, for example, an ITO film is formed and patterned to obtain the common electrode 602, and then the low refractive index dielectric film 601 is formed to cover the common electrode. . This process is repeated twice to form a reflective film.
[0102]
Next, contact holes were formed. In the configuration of this embodiment, only the interlayer insulating film and the low-refractive index dielectric film 601 are laminated in the contact hole forming region. When the low-refractive index dielectric film is made of the same material, etching is relatively easy. Can be done.
[0103]
Next, a second transparent conductive film made of a material having a high refractive index was formed and patterned to form a pixel electrode 604. Note that the common electrode 602 is connected to a common wiring.
[0104]
However, the thickness of the common electrode 602 (first transparent conductive film) and the thickness of the pixel electrode (second transparent conductive film) 604 are used as part of the reflective film, so that the visible light region (400 nm) is used. It is preferable to adjust in the range of 50.5 to 88.4 nm so as to be a λ / 4 film at <λ <700 nm.
[0105]
Thereafter, in the same manner as in Example 1, an alignment film 606 was formed, and a first substrate was manufactured. (Fig. 6 (A))
[0106]
With the configuration illustrated in FIG. 6A, the auxiliary capacitor 605 can be formed using the common electrode 602, the low refractive index dielectric film 601, and the pixel electrode 604. Note that the common electrode 602 forms a capacitance even in the floating state. Accordingly, a capacitance is also formed between the common electrodes 602 sandwiching the low refractive index dielectric film 601 therebetween. Note that the auxiliary capacitor 605 can be freely designed by appropriately changing the material, the thickness of the film, the number of stacked layers, and the like.
[0107]
It is easy to combine the present embodiment with the second embodiment or the third embodiment.
[0108]
Example 6
In the manufacturing process shown in Example 5, an example in which an auxiliary capacitor is formed using a pixel electrode, a low refractive index dielectric film, and a common electrode made of a transparent conductive film is shown. In this embodiment, an example in which a larger auxiliary capacitor is formed (capacitor configuration 2 in FIG. 6B) will be described below. Since the process up to the middle (FIG. 3C) is the same as the manufacturing process of the reflective LCD shown in Embodiment 1, only different points will be described here.
[0109]
First, the structure shown in FIG. 3C is obtained using the same method as the manufacturing process of Example 1.
[0110]
Next, a film made of the first transparent conductive film, for example, an ITO film is formed and patterned to obtain the common electrode 612, and then the low-refractive-index dielectric film 611 is formed to cover the common electrode 612. To do.
[0111]
Next, a first contact hole is formed, a capacitor electrode 613 made of a transparent conductive film is formed, and connected to the drain electrode of the switching element.
[0112]
Thereafter, a low refractive index dielectric film 611 is formed to cover the capacitor electrode 613. Then, a film made of the first transparent conductive film, for example, an ITO film is formed again and patterned to obtain the common electrode 612. Then, the low refractive index dielectric film 611 is formed to cover the common electrode. To do.
[0113]
Next, a second contact hole is formed, and a pixel electrode 614 made of a transparent conductive film is formed by patterning and connected to the capacitor electrode 613.
[0114]
Note that the common electrode 612 was connected to a common wiring. However, it is not necessary to connect all the common electrodes, and it is desirable to connect as appropriate.
[0115]
The structure obtained by the above steps is that an auxiliary capacitor including a pixel electrode 614, a low refractive index dielectric film 611, and a common electrode 612, a capacitive electrode 613, and a low refractive index dielectric film 611 A storage capacitor composed of the common electrode 612 can be formed.
[0116]
As described above, since the auxiliary capacity can be increased without reducing the aperture ratio, this embodiment is particularly effective for a projector apparatus using a small high-definition panel.
[0117]
Example 7
In this embodiment, an example in which a TFT having a structure different from the TFT shown in Embodiment 1 is used as a semiconductor element for performing active matrix driving will be described. The TFT having the structure described in this embodiment can be easily applied to Embodiments 2 to 6.
[0118]
In Examples 1 to 6, a typical top gate type TFT, which is a coplanar type TFT, is described as an example, but a bottom gate type TFT may be used. FIG. 7 shows an example using an inverted staggered TFT, which is a typical example of a bottom gate TFT.
[0119]
In FIG. 7, reference numeral 701 denotes a glass substrate, 702 and 703 are gate electrodes, 704 is a gate insulating film, and 705 and 706 are active layers. The active layers 705 and 706 are composed of silicon films to which impurities are not intentionally added.
[0120]
Reference numerals 707 and 708 denote source electrodes, reference numerals 709 and 710 denote drain electrodes, and reference numerals 711 and 712 denote silicon nitride films serving as channel stoppers (or etching stoppers). That is, in the active layers 705 and 706, a region located under the channel stoppers 711 and 712 substantially functions as a channel formation region.
[0121]
The above is the basic structure of the inverted staggered TFT.
[0122]
In this embodiment, such an inverted stagger type is covered and flattened with an interlayer insulating film 713 made of an organic resin film, and a dielectric multilayer film 716 (low refractive index dielectric film 717, of the present invention is formed on the interlayer insulating film. A high refractive index dielectric film 718) is formed, pixel electrodes 714 and 715 are formed thereon, and an alignment film 719 is formed.
[0123]
Next, an example in which an insulated gate field effect transistor (IGFET) is formed as the semiconductor element of the present invention will be described. The IGFET is also called a MOSFET and refers to a transistor formed on a silicon wafer.
[0124]
In FIG. 8, 801 is a glass substrate, 802 and 803 are source regions, and 804 and 805 are drain regions. The source / drain regions can be formed by adding impurities by ion implantation and thermally diffusing. Note that reference numeral 806 denotes an element isolation oxide, which can be formed using a normal LOCOS technique.
[0125]
Next, 807 is a gate insulating film, 808 and 809 are gate electrodes, 810 is a first interlayer insulating film, 811 and 812 are source electrodes, and 813 and 814 are drain electrodes. A dielectric interlayer film 818 (low refractive index dielectric film 819, high refractive index dielectric film 820) of the present invention is formed on the flat surface with a second interlayer insulating film 815, and a pixel electrode is formed. 816 and 817 are formed. Then, an alignment film 821 is formed.
[0126]
In addition to the IGFET, top gate type, or bottom gate type TFT shown in this embodiment, the present invention can be applied to an active matrix display using a thin film diode, an MIM element, a varistor element, or the like.
[0127]
As described above, as shown in this embodiment, the present invention can be applied to a reflection type LCD using semiconductor elements having any structure.
[0128]
[Example 8] An example in which an AMLCD is configured using a first substrate (element formation side substrate) including the configuration shown in Examples 1 to 7 will be described. Here, the appearance of the AMLCD of this embodiment is shown in FIG.
[0129]
In FIG. 9A, reference numeral 901 denotes an active matrix substrate, on which a pixel matrix circuit 902, a source side driver circuit 903, and a gate side driver circuit 904 are formed. The drive circuit is preferably composed of a CMOS circuit in which an N-type TFT and a P-type TFT are complementarily combined. Reference numeral 905 denotes a counter substrate.
[0130]
In the AMLCD shown in FIG. 9A, an active matrix substrate 901 and a counter substrate 905 are bonded with their end surfaces aligned. However, a part of the counter substrate 905 is removed, and an FPC (flexible printed circuit) 906 is connected to the exposed active matrix substrate. The FPC 906 transmits an external signal into the circuit.
[0131]
Further, IC chips 907 and 908 are attached using a surface to which the FPC 906 is attached. These IC chips are configured by forming various circuits on a silicon substrate, such as a video signal processing circuit, a timing pulse generation circuit, a γ correction circuit, a memory circuit, and an arithmetic circuit. Although two pieces are attached in FIG. 9A, one piece or a plurality of pieces may be provided.
[0132]
Further, a configuration as shown in FIG. 9B, the same portions as those in FIG. 9A are denoted by the same reference numerals. Here, an example is shown in which the signal processing performed by the IC chip in FIG. 9A is performed by a logic circuit 909 formed of TFTs on the same substrate. In this case, the logic circuit 909 is also configured based on a CMOS circuit in the same manner as the drive circuits 903 and 904.
[0133]
Further, color display may be performed using a color filter, or the liquid crystal may be driven in an ECB (electric field control birefringence) mode, a GH (guest host) mode, or the like, and the color filter may be used.
[0134]
Example 10
The configuration of the present invention can be applied to various other electro-optical devices and semiconductor circuits in addition to AMLCDs. As electro-optical devices other than the above AMLCDs, simple matrix type liquid crystal display devices and EL (electroluminescence) devices can be used. ) Display devices, image sensors, etc.
[0135]
In this embodiment, an example in which the present invention is applied to a simple matrix type liquid crystal display device will be described below.
[0136]
Note that a general simple matrix liquid crystal display device has a structure in which a substrate having an X-direction stripe electrode and a substrate having a Y-direction stripe electrode sandwich a liquid crystal layer. In the simple matrix, the voltage is directly applied to the liquid crystal by the opposing XY electrodes.
[0137]
In this embodiment, an example in which the present invention is applied to an STN reflective liquid crystal panel is shown. On the glass substrate (first substrate), a light reflection film made of a dielectric multilayer film, a first transparent electrode in the X-direction stripe shape, and an alignment film are provided. In this embodiment, the light reflecting film made of a dielectric multilayer film is provided below the transparent electrode, but is not particularly limited. On the other glass substrate (second substrate), a second transparent electrode in the Y direction and an alignment film are provided. The two glass substrates face each other with the surface on which the alignment film of the glass substrate is provided facing each other, and the gap between the glass substrates is secured by a cell gap holding member, and STN liquid crystal is sealed in the gap between the substrates. .
[0138]
Hereinafter, a method for manufacturing the reflective liquid crystal panel of this example will be described. First, a light reflecting film made of a dielectric multilayer film is formed on a first glass substrate.
[0139]
The material used for the reflective film is SiO as a low refractive index dielectric film. ₂ , MgF ₂ , Na _Three AlF ₆ Etc. can be used. An alignment film, acrylic, polyimide (refractive index: 1.5 to 1.6) can also be used as other low refractive index dielectric materials. Also, TiO as a high refractive index dielectric film ₂ , ZrO ₂ , Ta ₂ O _Five , ZnS, ZnSe, ZnTe, Si, Ge, Y ₂ O _Three , Al ₂ O _Three Etc. can be used. In addition, a transparent conductor film such as ITO (refractive index 1.98) can be used as another material having a high refractive index.
[0140]
In this embodiment, as the low refractive index dielectric film, SiO ₂ (Refractive index 1.43), TiO as a high refractive index dielectric film ₂ (Refractive index 2.2) was used.
[0141]
However, the film thickness of the dielectric multilayer film is adjusted so as to be a λ / 4 film in the visible light region (400 nm <λ <700 nm). Low refractive index dielectric film (SiO2) that becomes a λ / 4 film in the visible light region ₂ ) Is in the range of 70 nm to 122 nm. In addition, a high refractive index dielectric film (TiO2) that becomes a λ / 4 film in the visible light region. ₂ ) Is in the range of 45.5 nm to 79.5 nm. By adjusting to such a film thickness, light in the required reflection wavelength band can be strengthened by the interference effect and reflected efficiently. In this example, when the dielectric multilayer film is composed of two layers of a low-refractive index dielectric film having a film thickness of 70 nm and a high-refractive index dielectric film having a film thickness of 50 nm, four groups, a total of eight layers ( 960 nm).
[0142]
Next, a first transparent electrode is formed. In this embodiment, an ITO film is formed to a thickness of 100 nm and patterned to form a striped transparent electrode. The transparent electrode has a structure extending in a direction perpendicular to the paper surface.
[0143]
Next, an alignment film is formed. A polyimide-based vertical alignment film is used as the alignment film material. This polyimide vertical alignment film is formed on the first substrate by spin coating, flexographic printing, or screen printing.
[0144]
Then, processing for the other glass substrate (second substrate) will be described. A color filter is formed on the second substrate, and then a protective film made of an acrylic resin or an epoxy resin is formed on the color filter. In this embodiment, the protective film is formed of an acrylic resin having a thickness of 1 μm.
[0145]
Next, ITO (Indium Tin Oxide) and SnO ₂ A second transparent electrode made of a transparent conductive film such as (tin oxide) is formed. In this example, an ITO film was formed by sputtering and patterned to form a striped second transparent electrode. Then, an alignment film made of a polyimide-based vertical alignment film is formed.
[0146]
Next, a rubbing process is performed on each of the alignment films provided on the first substrate and the second substrate. The rubbing direction is one diagonal direction of the substrate, and the rubbing direction of the alignment film is orthogonal to the first substrate and the second substrate facing each other.
[0147]
Next, a cell gap material is formed on one of the pair of substrates, and a sealing material for bonding the substrates is applied. In this example, a sealing material made of an ultraviolet curable resin was applied to the peripheral portion on the second substrate side leaving the liquid crystal injection port. Then, the first substrate and the second substrate are made to face each other, the cell gap is pressed constant, and in this state, ultraviolet rays are irradiated to cure the sealing material.
[0148]
Next, liquid crystal is injected from the liquid crystal injection port. Thereafter, a sealant is applied to the liquid crystal injection port, and the sealant is cured by irradiating with ultraviolet rays to completely seal the liquid crystal in the cell. A retardation plate, a polarizer, and a forward scattering plate were provided on the back surface of the second substrate. Through the above steps, a full color STN liquid crystal panel was completed.
[0149]
Note that it is needless to say that the structure and the manufacturing process of this embodiment are not limited as long as the liquid crystal display device is a simple matrix type drive system having at least a reflective film made of a dielectric multilayer film and having a transparent electrode.
[0150]
Example 10
The AMLCD shown in the eighth embodiment is used as a display for various electronic devices. Note that the electronic device described in this embodiment is defined as a product on which an active matrix liquid crystal display device is mounted.
[0151]
Examples of such electronic devices include a video camera, a still camera, a projector, a projection TV, a head mounted display, a car navigation, a personal computer (including a notebook type), a portable information terminal (a mobile computer, a mobile phone, etc.). . An example of them is shown in FIG.
[0152]
FIG. 10A illustrates a mobile computer, which includes a main body 2001, a camera unit 2002, an image receiving unit 2003, an operation switch 2004, and a display device 2005. The present invention can be applied to the image receiving unit 2003, the display device 2005, and the like.
[0153]
FIG. 10B illustrates a head mounted display, which includes a main body 2101, a display device 2102, and a band portion 2103. The present invention can be applied to the display device 2102.
[0154]
FIG. 10C illustrates a mobile phone, which includes a main body 2201, an audio output unit 2202, an audio input unit 2203, a display device 2204, operation switches 2205, and an antenna 2206. The present invention can be applied to the audio output unit 2202, the audio input unit 2203, the display device 2204, and the like.
[0155]
FIG. 10D illustrates a video camera, which includes a main body 2301, a display device 2302, an audio input portion 2303, operation switches 2304, a battery 2305, and an image receiving portion 2306. The present invention can be applied to the display device 2302, the audio input unit 2303, and the image receiving unit 2306.
[0156]
FIG. 10E illustrates a rear projector, which includes a main body 2401, a light source 2402, a display device 2403, mirrors (such as a polarizing beam splitter) 2404 and 2405, and a screen 2406. The present invention can be applied to the display device 2403.
[0157]
FIG. 10F illustrates a front projector, which includes a main body 2501, a light source 2502, a display device 2503, an optical system 2504, and a screen 2505. The present invention can be applied to the display device 2503.
[0158]
As described above, the application range of the present invention is extremely wide and can be applied to electronic devices in various fields. In addition, it can also be used for electric billboards, advertising announcement displays, and the like.
[0159]
【The invention's effect】
In the present invention, a dielectric multilayer film is used as a reflective film, and the reflectivity can be easily increased to 90% or more by appropriately changing the material, the thickness of the film, the number of stacked layers, etc. It can be applied as a liquid crystal display panel. Further, by using the structure of the present invention, a reflectance of 90 to less than 100% can be obtained even in a state where alignment films are stacked.
[0160]
In particular, the reflective liquid crystal LCD of the present invention can achieve a high aperture ratio by using a dielectric multilayer film as a reflective film and a pixel electrode made of a transparent conductive film thereon.
[0161]
Further, an auxiliary capacitor can be easily formed with a pixel electrode made of a transparent conductive film and a common electrode made of a transparent conductive film, using the dielectric multilayer film as a reflective film as a dielectric.
[0162]
According to the present invention, an unprecedented bright liquid crystal panel with good visibility can be obtained.
[Brief description of the drawings]
FIG. 1 is a diagram showing an example of the configuration of the present invention (Example 1).
FIG. 2 is a diagram showing an example of the configuration of the present invention (Examples 2 and 3).
FIG. 3 is a diagram showing an example of a manufacturing process of this example (Example 1).
FIG. 4 is a diagram showing an example of a manufacturing process of this example (Example 1).
FIG. 5 is a diagram showing an example of the configuration of the present invention (Example 4).
FIG. 6 is a diagram showing an example of the configuration of the present invention (Example 5).
FIG. 7 is a diagram showing an example of the configuration of the present invention (Example 7).
FIG. 8 is a diagram showing an example of the configuration of the present invention (Example 7).
FIG. 9 is a diagram showing an external view of a liquid crystal panel (Example 8)
FIG. 10 is a diagram for explaining an example of an applied product of the present invention.
FIG. 11 is a diagram showing a conventional example
[Explanation of symbols]
110 substrates
111 Switching element (TFT)
112 Interlayer insulation film
113 Pixel electrode (transparent conductive film)
114 Low Refractive Index Dielectric Film
115 High Refractive Index Dielectric Film
116 Alignment film
117 Liquid crystal layer
118 Counter electrode
119 Counter substrate
120 Incident light
121 Reflected light

Claims (12)

A switching element formed on the substrate;
A reflective film comprising a dielectric multilayer film on the switching element ;
A pixel electrode made of a transparent conductive film formed on the reflective film and electrically connected to the switching element ;
The reflective film is configured such that a low refractive index dielectric film and a high refractive index dielectric film are alternately stacked , and the low refractive index dielectric film is in contact with the pixel electrode ,
The refractive index n and film thickness d of the low refractive index dielectric film and the high refractive index dielectric film satisfy nd = λ / 4, where λ is the center wavelength of the visible light wavelength band,
2. The semiconductor device according to claim 1, wherein the pixel electrode is made of ITO having a higher refractive index than the low refractive index dielectric film, and the film thickness of the pixel electrode is 50.5 to 88.4 nm . A switching element formed on the substrate;
A reflective film comprising a dielectric multilayer film on the switching element;
A common electrode made of a transparent conductive film formed on the reflective film;
A low refractive index dielectric film formed on the common electrode;
A pixel electrode made of a transparent conductive film formed on and in contact with the low refractive index dielectric film and electrically connected to the switching element;
  The reflective film is configured by alternately laminating the low refractive index dielectric film and the high refractive index dielectric film,
The refractive index n and film thickness d of the low refractive index dielectric film and the high refractive index dielectric film satisfy nd = λ / 4, where λ is the center wavelength of the visible light wavelength band,
The common electrode and the pixel electrode are made of ITO having a higher refractive index than the low refractive index dielectric film, and the film thickness of the pixel electrode is 50.5 nm to 88.4 nm. . In Claim 1 or 2, a material selected from SiO ₂ , MgF ₂ , Na ₃ AlF ₆ , acrylic and polyimide is used as the low refractive index dielectric film,
As the high refractive index dielectric film, a material selected from TiO ₂ , ZrO ₂ , Ta ₂ O ₅ , ZnS, ZnSe, ZnTe, Si, Ge, Y ₂ O ₃ , and Al ₂ O ₃ is used . A semiconductor device characterized by the above. A switching element formed on the substrate;
A reflective film comprising a dielectric multilayer film on the switching element;
A pixel electrode made of a transparent conductive film formed on the reflective film and electrically connected to the switching element;
The reflective film is configured such that a low refractive index dielectric film and a high refractive index dielectric film are alternately stacked, and the low refractive index dielectric film is in contact with the pixel electrode,
The low refractive index dielectric film has a thickness of 70 nm to 122 nm, the high refractive index dielectric film has a thickness of 45.5 nm to 79.5 nm, and the low refractive index dielectric film is made of SiO. ₂ The high refractive index dielectric film is TiO. ₂ And
2. The semiconductor device according to claim 1, wherein the pixel electrode is made of ITO having a higher refractive index than the low refractive index dielectric film, and the film thickness of the pixel electrode is 50.5 to 88.4 nm. 5. The semiconductor device according to claim 1, wherein the dielectric multilayer film is formed by a sputtering method or a vacuum evaporation method. A switching element formed on the substrate;
A reflective film composed of a multilayer film on the switching element;
A pixel electrode made of a first transparent conductive film formed on the reflective film and electrically connected to the switching element;
The reflective film is formed by alternately laminating a low refractive index dielectric film and a second transparent conductive film having a higher refractive index than the low refractive index dielectric film, and the pixel electrode has the low refractive index. The dielectric film is configured to contact,
The refractive index n and film thickness d of the low refractive index dielectric film and the second transparent conductive film satisfy nd = λ / 4, where λ is the center wavelength of the visible light wavelength band,
2. The semiconductor device according to claim 1, wherein the pixel electrode is made of ITO having a higher refractive index than the low refractive index dielectric film, and the film thickness of the pixel electrode is 50.5 to 88.4 nm. A switching element formed on the substrate;
A reflective film composed of a multilayer film on the switching element;
A pixel electrode made of a first transparent conductive film formed on the reflective film and electrically connected to the switching element;
  The reflective film is formed by alternately laminating a low refractive index dielectric film and a second transparent conductive film having a higher refractive index than the low refractive index dielectric film, and the pixel electrode has the low refractive index. The dielectric film is configured to contact,
The refractive index n and film thickness d of the low refractive index dielectric film satisfy nd = λ / 4, where λ is the center wavelength of the visible light wavelength band,
The pixel electrode is made of ITO having a higher refractive index than the low refractive index dielectric film, and the film thickness of the pixel electrode and the second transparent conductive film is 50.5 nm to 88.4 nm. A featured semiconductor device. 8. The semiconductor device according to claim 6, wherein the contact hole connecting the switching element and the pixel electrode is formed in a region where only the low refractive index dielectric film is laminated. 9. The semiconductor device according to claim 6, wherein a capacitor is formed using the low refractive index dielectric film, the second transparent conductive film, and the pixel electrode. In any one of claims 1 to 9, wherein the semiconductor device includes a second substrate, a liquid crystal sealed between said substrate and said second substrate, said pixel electrode is on the substrate The semiconductor device is arranged in a matrix. In any one of claims 1 to 10, as the switching element, a thin film transistor, a thin film diode, a semiconductor device which is characterized by using an MIM element or a varistor element. In any one of claims 1 to 11, as the substrate, a semiconductor device which is characterized by using a glass substrate, a quartz substrate, a ceramic substrate or a semiconductor substrate.

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