JP2004128374A6 - Light emitting device - Google Patents

Abstract

An object of the present invention is to provide a switching element capable of simultaneously shorting or opening three or more nodes and suppressing an area occupied by a substrate.
The switch element of the present invention includes an active layer, an insulating film in contact with the active layer, a gate electrode in contact with the insulating film, and three or more connection electrodes. The active layer has at least one channel formation region and three or more impurity-doped regions, and the connection electrode is in contact with one of the different impurity regions. An impurity region in contact with an arbitrary connection terminal is in contact with only one of the channel formation regions.
[Selection] Figure 1

Description

【０１９５】
（Ｍ．Ａ．Ｂａｌｄｏ， Ｄ．Ｆ．Ｏ’Ｂｒｉｅｎ， Ｙ．Ｙｏｕ， Ａ．Ｓｈｏｕｓｔｉｋｏｖ， Ｓ．Ｓｉｂｌｅｙ， Ｍ．Ｅ．Ｔｈｏｍｐｓｏｎ， Ｓ．Ｒ．Ｆｏｒｒｅｓｔ， Ｎａｔｕｒｅ ３９５ （１９９８） ｐ．１５１．）
【０１９６】
上記の論文により報告された有機発光材料（Ｐｔ錯体）の分子式を以下に示す。
【０１９７】
【化２】

【０１９８】
（Ｍ．Ａ．Ｂａｌｄｏ， Ｓ．Ｌａｍａｎｓｋｙ， Ｐ．Ｅ．Ｂｕｒｒｒｏｗｓ， Ｍ．Ｅ．Ｔｈｏｍｐｓｏｎ， Ｓ．Ｒ．Ｆｏｒｒｅｓｔ， Ａｐｐｌ．Ｐｈｙｓ．Ｌｅｔｔ．，７５ （１９９９） ｐ．４．） （Ｔ．Ｔｓｕｔｓｕｉ， Ｍ．−Ｊ．Ｙａｎｇ， Ｍ．Ｙａｈｉｒｏ， Ｋ．Ｎａｋａｍｕｒａ， Ｔ．Ｗａｔａｎａｂｅ， Ｔ．ｔｓｕｊｉ， Ｙ．Ｆｕｋｕｄａ， Ｔ．Ｗａｋｉｍｏｔｏ， Ｓ．Ｍａｙａｇｕｃｈｉ， Ｊｐｎ．Ａｐｐｌ．Ｐｈｙｓ．， ３８ （１２Ｂ） （１９９９） Ｌ１５０２．）
【０１９９】
上記の論文により報告された有機発光材料（Ｉｒ錯体）の分子式を以下に示す。
【０２００】
【化３】

【０２０１】
以上のように三重項励起子からの燐光発光を利用できれば原理的には一重項励起子からの蛍光発光を用いる場合より３〜４倍の高い外部発光量子効率の実現が可能となる。
【０２０２】
なお、本実施例の構成は、実施例１〜実施例５のいずれの構成とも自由に組み合わせて実施することが可能である。
【０２０３】
（実施例７）
本実施例では、本発明の発光装置外観について、図１３を用いて説明する。
【０２０４】
図１３は、トランジスタが形成された素子基板をシーリング材によって封止することによって形成された発光装置の上面図であり、図１３（Ｂ）は、図１３（Ａ）のＡ−Ａ’における断面図、図１３（Ｃ）は図１３（Ａ）のＢ−Ｂ’における断面図である。
【０２０５】
基板４００１上に設けられた画素部４００２と、信号線駆動回路４００３と、第１及び第２の走査線駆動回路４００４ａ、ｂとを囲むようにして、シール材４００９が設けられている。また画素部４００２と、信号線駆動回路４００３と、第１及び第２の走査線駆動回路４００４ａ、ｂとの上にシーリング材４００８が設けられている。よって画素部４００２と、信号線駆動回路４００３と、第１及び第２の走査線駆動回路４００４ａ、ｂとは、基板４００１とシール材４００９とシーリング材４００８とによって、充填材４２１０で密封されている。
【０２０６】
また基板４００１上に設けられた画素部４００２と、信号線駆動回路４００３と、第１及び第２の走査線駆動回路４００４ａ、ｂとは、複数のＴＦＴを有している。図１３（Ｂ）では代表的に、下地膜４０１０上に形成された、信号線駆動回路４００３に含まれる駆動ＴＦＴ（但し、ここではｎチャネル型ＴＦＴとｐチャネル型ＴＦＴを図示する）４２０１及び画素部４００２に含まれるトランジスタＴｒ１ ４２０２を図示した。
【０２０７】
本実施例では、駆動ＴＦＴ４２０１には公知の方法で作製されたｐチャネル型ＴＦＴまたはｎチャネル型ＴＦＴが用いられ、トランジスタＴｒ１ ４２０２には公知の方法で作製されたｎチャネル型ＴＦＴが用いられる。
【０２０８】
駆動ＴＦＴ４２０１及びトランジスタＴｒ１ ４２０２上には層間絶縁膜（平坦化膜）４３０１が形成され、その上にトランジスタＴｒ１ ４２０２のドレインと電気的に接続する画素電極（陽極）４２０３が形成される。画素電極４２０３としては仕事関数の大きい透明導電膜が用いられる。透明導電膜としては、酸化インジウムと酸化スズとの化合物、酸化インジウムと酸化亜鉛との化合物、酸化亜鉛、酸化スズまたは酸化インジウムを用いることができる。また、前記透明導電膜にガリウムを添加したものを用いても良い。
【０２０９】
そして、画素電極４２０３の上には絶縁膜４３０２が形成され、絶縁膜４３０２は画素電極４２０３の上に開口部が形成されている。この開口部において、画素電極４２０３の上には有機発光層４２０４が形成される。有機発光層４２０４は公知の有機発光材料または無機発光材料を用いることができる。また、有機発光材料には低分子系（モノマー系）材料と高分子系（ポリマー系）材料があるがどちらを用いても良い。
【０２１０】
有機発光層４２０４の形成方法は公知の蒸着技術もしくは塗布法技術を用いれば良い。また、有機発光層の構造は正孔注入層、正孔輸送層、発光層、電子輸送層または電子注入層を自由に組み合わせて積層構造または単層構造とすれば良い。
【０２１１】
有機発光層４２０４の上には遮光性を有する導電膜（代表的にはアルミニウム、銅もしくは銀を主成分とする導電膜またはそれらと他の導電膜との積層膜）からなる陰極４２０５が形成される。また、陰極４２０５と有機発光層４２０４の界面に存在する水分や酸素は極力排除しておくことが望ましい。従って、有機発光層４２０４を窒素または希ガス雰囲気で形成し、酸素や水分に触れさせないまま陰極４２０５を形成するといった工夫が必要である。本実施例ではマルチチャンバー方式（クラスターツール方式）の成膜装置を用いることで上述のような成膜を可能とする。そして陰極４２０５は所定の電圧が与えられている。
【０２１２】
以上のようにして、画素電極（陽極）４２０３、有機発光層４２０４及び陰極４２０５からなるＯＬＥＤ４３０３が形成される。そしてＯＬＥＤ４３０３を覆うように、絶縁膜４３０２上に保護膜４３０３が形成されている。保護膜４３０３は、ＯＬＥＤ４３０３に酸素や水分等が入り込むのを防ぐのに効果的である。
【０２１３】
４００５ａは電源線に接続された引き回し配線であり、トランジスタＴｒ１ ４２０２のソース領域に電気的に接続されている。引き回し配線４００５ａはシール材４００９と基板４００１との間を通り、異方導電性フィルム４３００を介してＦＰＣ４００６が有するＦＰＣ用配線４３０１に電気的に接続される。
【０２１４】
シーリング材４００８としては、ガラス材、金属材（代表的にはステンレス材）、セラミックス材、プラスチック材（プラスチックフィルムも含む）を用いることができる。プラスチック材としては、ＦＲＰ（Ｆｉｂｅｒｇｌａｓｓ−Ｒｅｉｎｆｏｒｃｅｄ Ｐｌａｓｔｉｃｓ）板、ＰＶＦ（ポリビニルフルオライド）フィルム、マイラーフィルム、ポリエステルフィルムまたはアクリル樹脂フィルムを用いることができる。また、アルミニウムホイルをＰＶＦフィルムやマイラーフィルムで挟んだ構造のシートを用いることもできる。
【０２１５】
但し、ＯＬＥＤからの光の放射方向がカバー材側に向かう場合にはカバー材は透明でなければならない。その場合には、ガラス板、プラスチック板、ポリエステルフィルムまたはアクリルフィルムのような透明物質を用いる。
【０２１６】
また、充填材４１０３としては窒素やアルゴンなどの不活性な気体の他に、紫外線硬化樹脂または熱硬化樹脂を用いることができ、ＰＶＣ（ポリビニルクロライド）、アクリル、ポリイミド、エポキシ樹脂、シリコーン樹脂、ＰＶＢ（ポリビニルブチラル）またはＥＶＡ（エチレンビニルアセテート）を用いることができる。本実施例では充填材として窒素を用いた。
【０２１７】
また充填材４１０３を吸湿性物質（好ましくは酸化バリウム）もしくは酸素を吸着しうる物質にさらしておくために、シーリング材４００８の基板４００１側の面に凹部４００７を設けて吸湿性物質または酸素を吸着しうる物質４２０７を配置する。そして、吸湿性物質または酸素を吸着しうる物質４２０７が飛び散らないように、凹部カバー材４２０８によって吸湿性物質または酸素を吸着しうる物質４２０７は凹部４００７に保持されている。なお凹部カバー材４２０８は目の細かいメッシュ状になっており、空気や水分は通し、吸湿性物質または酸素を吸着しうる物質４２０７は通さない構成になっている。吸湿性物質または酸素を吸着しうる物質４２０７を設けることで、ＯＬＥＤ４３０３の劣化を抑制できる。
【０２１８】
図１３（Ｃ）に示すように、画素電極４２０３が形成されると同時に、引き回し配線４００５ａ上に接するように導電性膜４２０３ａが形成される。
【０２１９】
また、異方導電性フィルム４３００は導電性フィラー４３００ａを有している。基板４００１とＦＰＣ４００６とを熱圧着することで、基板４００１上の導電性膜４２０３ａとＦＰＣ４００６上のＦＰＣ用配線４３０１とが、導電性フィラー４３００ａによって電気的に接続される。
【０２２０】
本実施例の構成は、実施例１〜実施例６に示した構成と自由に組み合わせて実施することが可能である。
【０２２１】
（実施例８）
ＯＬＥＤに用いられる有機発光材料は低分子系と高分子系に大別される。本発明の発光装置は、低分子系の有機発光材料でも高分子系の有機発光材料でも、どちらでも用いることができる。また、低分子系、高分子系いずれにも分類し難い材料、（例えば特願２００１−１６７５０８号等に記載されている材料）を用いても良い。
【０２２２】
低分子系の有機発光材料は、蒸着法により成膜される。したがって積層構造をとりやすく、ホール輸送層、電子輸送層などの機能が異なる膜を積層することで高効率化しやすい。もっとホール輸送層、電子輸送層等が必ずしも明確に存在せず、例えば特願２００１−０２０８１７号等に記載されているように、混合状態になった層が単数乃至複数層存在し、ＯＬＥＤの高寿命化、高発光効率化が図られていても良い。
【０２２３】
低分子系の有機発光材料としては、キノリノールを配位子としたアルミニウム錯体Ａｌｑ_３、トリフェニルアミン誘導体（ＴＰＤ）等が代表的に挙げられる。
【０２２４】
一方、高分子系の有機発光材料は低分子系に比べて物理的強度が高く、素子の耐久性が高い。また塗布により成膜することが可能であるので、素子の作製が比較的容易である。
【０２２５】
高分子系の有機発光材料を用いた発光素子の構造は、低分子系の有機発光材料を用いたときと基本的には同じであり、陰極／有機発光層／陽極となる。しかし、高分子系の有機発光材料を用いた有機発光層を形成する際には、低分子系の有機発光材料を用いたときのような積層構造を形成させることは難しく、知られている中では２層の積層構造が有名である。具体的には、陰極／発光層／正孔輸送層／陽極という構造である。なお、高分子系の有機発光材料を用いた発光素子の場合には、陰極材料としてＣａを用いることも可能である。
【０２２６】
なお、素子の発光色は、発光層を形成する材料で決まるため、これらを選択することで所望の発光を示す発光素子を形成することができる。発光層の形成に用いることができる高分子系の有機発光材料は、ポリパラフェニレンビニレン系、ポリパラフェニレン系、ポリチオフェン系、ポリフルオレン系が代表的に挙げられる。
【０２２７】
ポリパラフェニレンビニレン系には、ポリ（パラフェニレンビニレン） ［ＰＰＶ］ の誘導体、ポリ（２，５−ジアルコキシ−１，４−フェニレンビニレン） ［ＲＯ−ＰＰＶ］、ポリ（２−（２’−エチル−ヘキソキシ）−５−メトキシ−１，４−フェニレンビニレン）［ＭＥＨ−ＰＰＶ］、ポリ（２−（ジアルコキシフェニル）−１，４−フェニレンビニレン）［ＲＯＰｈ−ＰＰＶ］等が挙げられる。
【０２２８】
ポリパラフェニレン系には、ポリパラフェニレン［ＰＰＰ］の誘導体、ポリ（２，５−ジアルコキシ−１，４−フェニレン）［ＲＯ−ＰＰＰ］、ポリ（２，５−ジヘキソキシ−１，４−フェニレン）等が挙げられる。
【０２２９】
ポリチオフェン系には、ポリチオフェン［ＰＴ］の誘導体、ポリ（３−アルキルチオフェン）［ＰＡＴ］、ポリ（３−ヘキシルチオフェン）［ＰＨＴ］、ポリ（３−シクロヘキシルチオフェン）［ＰＣＨＴ］、ポリ（３−シクロヘキシル−４−メチルチオフェン）［ＰＣＨＭＴ］、ポリ（３，４−ジシクロヘキシルチオフェン）［ＰＤＣＨＴ］、ポリ［３−（４−オクチルフェニル）−チオフェン］［ＰＯＰＴ］、ポリ［３−（４−オクチルフェニル）−２，２ビチオフェン］［ＰＴＯＰＴ］等が挙げられる。
【０２３０】
ポリフルオレン系には、ポリフルオレン［ＰＦ］の誘導体、ポリ（９，９−ジアルキルフルオレン）［ＰＤＡＦ］、ポリ（９，９−ジオクチルフルオレン）［ＰＤＯＦ］等が挙げられる。
【０２３１】
なお、正孔輸送性の高分子系の有機発光材料を、陽極と発光性の高分子系有機発光材料の間に挟んで形成すると、陽極からの正孔注入性を向上させることができる。一般にアクセプター材料と共に水に溶解させたものをスピンコート法などで塗布する。また、有機溶媒には不溶であるため、上述した発光性の有機発光材料との積層が可能である。
【０２３２】
正孔輸送性の高分子系の有機発光材料としては、ＰＥＤＯＴとアクセプター材料としてのショウノウスルホン酸（ＣＳＡ）の混合物、ポリアニリン［ＰＡＮＩ］とアクセプター材料としてのポリスチレンスルホン酸［ＰＳＳ］の混合物等が挙げられる。
【０２３３】
なお、本実施例の構成は、実施例１〜実施例７のいずれの構成とも自由に組み合わせて実施することが可能である。
【０２３４】
（実施例９）
ＯＬＥＤを用いた発光装置は自発光型であるため、液晶ディスプレイに比べ、明るい場所での視認性に優れ、視野角が広い。従って、様々な電子機器の表示部に用いることができる。
【０２３５】
本発明の発光装置を用いた電子機器として、ビデオカメラ、デジタルカメラ、ゴーグル型ディスプレイ（ヘッドマウントディスプレイ）、ナビゲーションシステム、音響再生装置（カーオーディオ、オーディオコンポ等）、ノート型パーソナルコンピュータ、ゲーム機器、携帯情報端末（モバイルコンピュータ、携帯電話、携帯型ゲーム機または電子書籍等）、記録媒体を備えた画像再生装置（具体的にはＤｉｇｉｔａｌ Ｖｅｒｓａｔｉｌｅ Ｄｉｓｃ（ＤＶＤ）等の記録媒体を再生し、その画像を表示しうるディスプレイを備えた装置）などが挙げられる。特に、斜め方向から画面を見る機会が多い携帯情報端末は、視野角の広さが重要視されるため、発光装置を用いることが望ましい。それら電子機器の具体例を図１４に示す。
【０２３６】
図１４（Ａ）はＯＬＥＤ表示装置であり、筐体２００１、支持台２００２、表示部２００３、スピーカー部２００４、ビデオ入力端子２００５等を含む。本発明の発光装置は表示部２００３に用いることができる。発光装置は自発光型であるためバックライトが必要なく、液晶ディスプレイよりも薄い表示部とすることができる。なお、ＯＬＥＤ表示装置は、パソコン用、ＴＶ放送受信用、広告表示用などの全ての情報表示用表示装置が含まれる。
【０２３７】
図１４（Ｂ）はデジタルスチルカメラであり、本体２１０１、表示部２１０２、受像部２１０３、操作キー２１０４、外部接続ポート２１０５、シャッター２１０６等を含む。本発明の発光装置は表示部２１０２に用いることができる。
【０２３８】
図１４（Ｃ）はノート型パーソナルコンピュータであり、本体２２０１、筐体２２０２、表示部２２０３、キーボード２２０４、外部接続ポート２２０５、ポインティングマウス２２０６等を含む。本発明の発光装置は表示部２２０３に用いることができる。
【０２３９】
図１４（Ｄ）はモバイルコンピュータであり、本体２３０１、表示部２３０２、スイッチ２３０３、操作キー２３０４、赤外線ポート２３０５等を含む。本発明の発光装置は表示部２３０２に用いることができる。
【０２４０】
図１４（Ｅ）は記録媒体を備えた携帯型の画像再生装置（具体的にはＤＶＤ再生装置）であり、本体２４０１、筐体２４０２、表示部Ａ２４０３、表示部Ｂ２４０４、記録媒体（ＤＶＤ等）読み込み部２４０５、操作キー２４０６、スピーカー部２４０７等を含む。表示部Ａ２４０３は主として画像情報を表示し、表示部Ｂ２４０４は主として文字情報を表示するが、本発明の発光装置はこれら表示部Ａ、Ｂ２４０３、２４０４に用いることができる。なお、記録媒体を備えた画像再生装置には家庭用ゲーム機器なども含まれる。
【０２４１】
図１４（Ｆ）はゴーグル型ディスプレイ（ヘッドマウントディスプレイ）であり、本体２５０１、表示部２５０２、アーム部２５０３を含む。本発明の発光装置は表示部２５０２に用いることができる。
【０２４２】
図１４（Ｇ）はビデオカメラであり、本体２６０１、表示部２６０２、筐体２６０３、外部接続ポート２６０４、リモコン受信部２６０５、受像部２６０６、バッテリー２６０７、音声入力部２６０８、操作キー２６０９等を含む。本発明の発光装置は表示部２６０２に用いることができる。
【０２４３】
ここで図１４（Ｈ）は携帯電話であり、本体２７０１、筐体２７０２、表示部２７０３、音声入力部２７０４、音声出力部２７０５、操作キー２７０６、外部接続ポート２７０７、アンテナ２７０８等を含む。本発明の発光装置は表示部２７０３に用いることができる。なお、表示部２７０３は黒色の背景に白色の文字を表示することで携帯電話の消費電流を抑えることができる。
【０２４４】
なお、将来的に有機発光材料の発光輝度が高くなれば、出力した画像情報を含む光をレンズ等で拡大投影してフロント型若しくはリア型のプロジェクターに用いることも可能となる。
【０２４５】
また、上記電子機器はインターネットやＣＡＴＶ（ケーブルテレビ）などの電子通信回線を通じて配信された情報を表示することが多くなり、特に動画情報を表示する機会が増してきている。有機発光材料の応答速度は非常に高いため、発光装置は動画表示に好ましい。
【０２４６】
また、発光装置は発光している部分が電力を消費するため、発光部分が極力少なくなるように情報を表示することが望ましい。従って、携帯情報端末、特に携帯電話や音響再生装置のような文字情報を主とする表示部に発光装置を用いる場合には、非発光部分を背景として文字情報を発光部分で形成するように駆動することが望ましい。
【０２４７】
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用いることが可能である。また、本実施例の電子機器は実施例１〜８に示したいずれの構成の発光装置を用いても良い。
【０２４８】
【発明の効果】
本発明のスイッチ素子によって、スイッチ素子の面積を抑えることができ、画素を高精細化あるいは高機能化させることができる。
【０２４９】
また該スイッチ素子を用いた本発明の発光装置では、ＯＬＥＤに流れる電流を制御しているトランジスタＴｒ１の特性が画素間で異なっても、画素間においてＯＬＥＤに流れる電流の大きさに差が生じるのを防ぐことができ、輝度むらを抑えることができる。また画素回路の小面積化が行え、その結果開口率が上昇し、省電力化、発光装置の信頼性向上を図ることができる。
【０２５０】
さらに該スイッチ素子を用いた本発明の発光装置は、温度変化に左右されずに一定の輝度を得ることができる。また、カラー表示において、各色毎に異なる有機発光材料を有するＯＬＥＤを設けた場合でも、温度によって各色のＯＬＥＤの輝度がバラバラに変化して所望の色が得られないということを防ぐことができる。
【図面の簡単な説明】
【図１】本発明のトランジスタの構成を示す図。
【図２】本発明の発光装置のブロック図。
【図３】本発明の発光装置の画素の回路図。
【図４】走査線に入力される信号のタイミングチャート。
【図５】駆動における画素の概略図。
【図６】本発明のトランジスタの構成を示す図。
【図７】本発明のトランジスタの構成を示す図。
【図８】本発明のトランジスタの構成を示す図。
【図９】アナログ駆動法における信号線駆動回路の詳細図。
【図１０】走査線駆動回路のブロック図。
【図１１】本発明の発光装置の作製方法を示す図。
【図１２】本発明の発光装置の作製方法を示す図。
【図１３】本発明の発光装置の外観図及び断面図。
【図１４】本発明の発光装置を用いた電子機器の図。
【図１５】従来のトランジスタの回路図及び上面図。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a switch element formed using a semiconductor film. The present invention also relates to an OLED panel in which the switch element formed on a substrate and an organic light emitting element (OLED) are sealed between the substrate and a cover material. The present invention also relates to an OLED module in which an IC including a controller is mounted on the OLED panel. In this specification, the OLED panel and the OLED module are collectively referred to as a light emitting device.
[0002]
[Prior art]
In recent years, a technique for forming a thin film transistor (hereinafter referred to as TFT) on a substrate has greatly advanced, and application development to an active matrix display device has been advanced. In the active matrix display device, a TFT as a switching element is provided for each pixel, and an image is displayed by sequentially writing a video signal to each pixel. A TFT is an essential element for realizing an active matrix display device.
[0003]
The TFT also serves as a switch element having three terminals of a source electrode, a drain electrode, and a gate electrode. The electrical resistance between the source electrode and the drain electrode is controlled by the voltage applied to the gate electrode.
[0004]
[Problems to be solved by the invention]
By the way, in the active matrix display device, the demand for higher definition of pixels is increasing against the background of a rapid increase in display quality and display information amount and an increasing need for lightness, thinness, and smallness. In addition, there is a growing demand for higher functionality such as incorporating a memory into the pixel.
[0005]
However, even if the pixel is to have higher definition and higher functionality, the TFT provided in each pixel has a limit in reducing the size in consideration of securing the on-current amount and withstand voltage.
[0006]
However, when the ratio of the area of the TFT to the pixel cannot be reduced, in the case of a liquid crystal display device, the area through which light is transmitted in the pixel is reduced, and the apparent luminance is lowered. Also in the light emitting device, when the light emitted from the OLED is irradiated on the TFT side, the light from the OLED is blocked by the TFT, and the apparent luminance is lowered.
[0007]
Therefore, it is desirable to keep the number and area of TFTs provided in each pixel as small as possible.
[0008]
However, if the circuit configuration of each pixel is determined, it is usually not possible to simply reduce the number of TFTs. For example, as shown in FIG. 15A, when it is necessary to simultaneously short or open three nodes A, B, and C in each pixel, at least two TFTs 3001 in the case of a TFT that is a three-terminal switch element. 3002 and the number of TFTs cannot be reduced any more.
[0009]
In particular, in the case of an active matrix light-emitting device, compared to a liquid crystal display device that does not require a voltage signal writing switch, the number of TFTs provided in each pixel is generally large and the connection is complicated. It is difficult to keep the number down.
[0010]
In view of the above-described problems, an object of the present invention is to provide a switch element that can simultaneously short or open three or more nodes and can suppress the occupied area of the substrate. Another object is to provide an active matrix display device using the switch element.
[0011]
In addition, a problem in putting a light-emitting device into practical use has been a decrease in luminance of the OLED due to deterioration of the organic light-emitting material. Note that the OLED has a layer containing an organic compound (organic light emitting material) from which luminescence generated by applying an electric field is obtained (hereinafter referred to as an organic light emitting layer), an anode layer, and a cathode layer. ing. Luminescence in organic compounds includes light emission (fluorescence) when returning from the singlet excited state to the ground state and light emission (phosphorescence) when returning from the triplet excited state to the ground state. Any one of the above-described light emission may be used, or both light emission may be used.
[0012]
In this specification, all layers provided between the anode and the cathode of the OLED are defined as organic light emitting layers. Specifically, the organic light emitting layer includes a light emitting layer, a hole injection layer, an electron injection layer, a hole transport layer, an electron transport layer, and the like. Basically, the OLED has a structure in which an anode / light emitting layer / cathode is laminated in this order. In addition to this structure, the anode / hole injection layer / light emitting layer / cathode and the anode / hole injection layer / The light emitting layer / electron transport layer / cathode may be stacked in this order.
[0013]
Organic light-emitting materials are vulnerable to moisture, oxygen, light, and heat, and their deterioration is accelerated by these materials. Specifically, the speed of deterioration depends on the structure of the device that drives the light emitting device, the characteristics of the organic light emitting material, the electrode material, the conditions in the manufacturing process, the driving method of the light emitting device, and the like.
[0014]
Even if the voltage applied to the organic light emitting layer is constant, if the organic light emitting layer is deteriorated, the luminance of the OLED is lowered and the displayed image becomes unclear.
[0015]
In the case of displaying a color image using three types of OLEDs corresponding to R (red), G (green), and B (blue), the organic light emitting material constituting the organic light emitting layer corresponds to the OLED. It depends on the color. Therefore, the organic light emitting layer of the OLED may deteriorate at a different speed for each corresponding color. In this case, as the time passes, the brightness of the OLED varies from color to color, making it impossible to display a desired color on the light emitting device.
[0016]
In addition, the temperature of the organic light emitting layer depends on the outside air temperature, the heat generated by the OLED panel itself, etc., but in general, the value of the current flowing through the OLED varies depending on the temperature. Even if the voltage is constant, if the temperature of the organic light emitting layer increases, the current flowing through the OLED increases. Since the current flowing through the OLED and the luminance of the OLED are in a proportional relationship, the larger the current flowing through the OLED, the higher the luminance of the OLED. Thus, since the luminance of the OLED changes depending on the temperature of the organic light emitting layer, it is difficult to display a desired gradation, and the current consumption of the light emitting device increases as the temperature rises.
[0017]
Furthermore, in general, since the degree of change in flowing current due to temperature change differs depending on the type of organic light-emitting material, it is possible that the luminance of the OLED of each color varies with temperature in color display. If the luminance balance of each color is lost, a desired color cannot be displayed.
[0018]
In view of the foregoing, it is an object of the present invention to provide a light-emitting device capable of obtaining a certain luminance without being affected by deterioration of the organic light-emitting layer and temperature change, and capable of performing a desired color display. And
[0019]
[Means for Solving the Problems]
The present invention is a novel switch element having at least four terminals that can simultaneously short or open three or more nodes, and a light emitting device using the switch element.
[0020]
Specifically, the switch element includes an active layer, an insulating film in contact with the active layer, a gate electrode in contact with the insulating film, and three or more electrodes (hereinafter referred to as connection electrodes in this specification). is doing. The active layer has at least one channel forming region and three or more impurity doped regions, and the connection electrodes are in contact with one of the different impurity regions.
[0021]
The impurity region in contact with an arbitrary connection terminal is in contact with only one of the channel formation regions. Note that an impurity region having a low concentration may be sandwiched between an impurity region in contact with an arbitrary connection terminal and the one channel formation region. In other words, any two impurity regions in contact with the connection terminal do not sandwich the impurity region in contact with the other connection terminal.
[0022]
The gate electrode overlaps with the channel formation region with an insulating film interposed therebetween. By controlling the voltage applied to the gate electrode, the resistance between the connection electrodes can be controlled, and all the connection electrodes can be short-circuited or opened simultaneously.
[0023]
In the switching element of the present invention, a gate electrode may be provided between the substrate and the active layer, or an active layer may be provided between the gate electrode and the substrate.
[0024]
By using the above switch element, the area occupied by the pixel can be suppressed and the pixel aperture ratio can be increased and the function can be increased and the function can be increased as compared with the case where the switch circuit is configured by a plurality of TFTs. .
[0025]
In general, when the light is emitted while keeping the voltage applied to the OLED constant, and when the light is emitted while keeping the current flowing through the OLED constant, the latter reduces the decrease in luminance due to the deterioration of the OLED. be able to. In this specification, the current flowing through the OLED is referred to as an OLED current, and the voltage applied to the OLED is referred to as an OLED voltage. That is, by controlling the luminance of the OLED not by the voltage but by the current, a change in the emission luminance of the OLED due to the deterioration of the OLED can be suppressed.
[0026]
Therefore, it is preferable that each pixel is provided with the switch element of the present invention, and when the switch element is turned on, the drain current Id of the transistor that controls the current flowing through the OLED is controlled by the signal line driver circuit.
[0027]
When the drain current Id flows, a voltage is generated between the gate electrode and the source region of the transistor that controls the current flowing through the OLED. Then, while maintaining the voltage, the drain current of the transistor is caused to flow to the OLED through one or more circuit elements. Note that the transistor for controlling the current flowing through the OLED is operated in the saturation region.
[0028]
In the above configuration, the value of the current flowing through the OLED is controlled by the signal line driver circuit. Therefore, the current flowing through the OLED can be controlled to a desired value without being influenced by the difference in the characteristics of the transistors that control the current flowing through the OLED, the deterioration of the OLED, or the like.
[0029]
In the present invention, by configuring as described above using the switch element, it is possible to suppress a decrease in luminance of the OLED even when the organic light emitting layer is deteriorated, and as a result, a clear image can be displayed. In addition, in the case of a light emitting device for color display using OLEDs corresponding to each color, even if the organic light emitting layer of the OLED deteriorates at a different speed for each corresponding color, the balance of luminance of each color is prevented from being lost. A desired color can be displayed.
[0030]
Further, the OLED current can be controlled to a desired value even if the temperature of the organic light emitting layer depends on the outside air temperature, the heat generated by the OLED panel itself, or the like. Therefore, since the OLED current and the luminance of the OLED are proportional, it is possible to suppress the change in the luminance of the OLED, and it is possible to prevent the consumption current from increasing as the temperature rises. Further, in the case of a light emitting device for color display, since it is possible to suppress changes in the brightness of the OLEDs of each color without being influenced by temperature changes, it is possible to prevent the balance of the brightness of each color from being lost and display a desired color. can do.
[0031]
Furthermore, since the degree of change of the OLED current in the temperature change is generally different depending on the type of the organic light emitting material, the luminance of the OLED of each color may vary depending on the temperature in color display. However, in the light emitting device of the present invention, a desired luminance can be obtained without being influenced by a temperature change, so that it is possible to prevent the balance of the luminance of each color from being lost and display a desired color.
[0032]
Further, in a general light emitting device, since the wiring itself that supplies current to the OLED has a resistance, the potential of the light emitting device slightly drops depending on the length of the wiring. The drop in potential varies greatly depending on the image to be displayed. In particular, in a plurality of pixels to which current is supplied from the same wiring, when the ratio of pixels having a high number of gradations is increased, the current flowing through the wiring is increased, and a potential drop is noticeable. When the potential drops, the voltage applied to the OLED of each pixel decreases, so the current supplied to each pixel decreases. Therefore, even if an attempt is made to display a certain gradation in a certain pixel, if the number of gradations of other pixels to which current is supplied from the same wiring changes, the current supplied to the certain pixel is accordingly changed. As a result, the number of gradations also changes. However, in the light emitting device of the present invention, the current flowing through each OLED can be maintained at a desired value, so that the gradation can be prevented from changing due to a potential drop due to wiring resistance.
[0033]
Further, by using the switch element of the present invention, the ratio of the area of the transistor to each pixel can be suppressed.
[0034]
Note that in the light-emitting device of the present invention, the transistor used for the pixel may be a transistor formed using polycrystalline silicon or a thin film transistor using amorphous silicon. Further, a transistor using an organic semiconductor may be used.
[0035]
Note that the transistor provided in the pixel of the light-emitting device of the present invention may have a single-gate structure, or a double-gate structure or a multi-gate structure having a gate electrode higher than that.
[0036]
Note that the switch element of the present invention can be used not only for display devices but also for all semiconductor devices including integrated circuits.
[0037]
DETAILED DESCRIPTION OF THE INVENTION
(Embodiment 1)
The configuration of the switch element of the present invention will be described with reference to FIG. 1A is a top view of a transistor of the present invention, FIG. 1B corresponds to a cross-sectional view taken along a broken line AA ′ in FIG. 1A, and FIG. This corresponds to a cross-sectional view taken along broken line BB ′ in FIG.
[0038]
The transistor of the present invention includes an active layer 101, a gate insulating film 102 in contact with the active layer, and a gate electrode 103 in contact with the gate insulating film 102. The active layer 101 includes a channel formation region 104 and impurity regions 105, 106, and 107 to which an impurity imparting a conductivity type is added. The gate electrode 103 and the channel formation region 104 overlap with each other with the gate insulating film interposed therebetween.
[0039]
Impurity regions 105, 106, and 107 are in contact with channel formation region 104. Note that in this embodiment mode, all impurity regions are in contact with the channel formation region 104, but the present invention is not limited to this structure. A low-concentration impurity region (LDD region) having an impurity concentration lower than that of the impurity region may be provided between the impurity region and the channel formation region, or a region not added with an impurity that does not overlap with the gate electrode (offset region) ) May be provided.
[0040]
An insulating film 108 is formed on the gate insulating film 102 so as to cover the impurity regions 105, 106, and 107 of the active layer 101. Connection wirings 109, 110, and 111 connected to the impurity regions 105, 106, and 107 are formed through contact holes formed in the insulating film 108 and the gate insulating film 102. Note that although the gate insulating film 102 covers the impurity regions 105, 106, and 107 in FIG. 1, the present invention is not limited to this structure. The impurity regions 105, 106, and 107 are not necessarily covered by the gate insulating film 102 and may be exposed.
[0041]
In the switch element illustrated in FIG. 1, the resistance between the connection wirings 109, 110, and 111 is controlled by the voltage applied to the gate electrode 103.
[0042]
In the transistor in FIG. 1, three nodes, specifically, connection wirings 109, 110, and 111 can be connected simultaneously. In the present specification, the connection means an electrical connection unless otherwise specified.
[0043]
With the above structure, an area occupied by a transistor or the like to which a switch element is added can be suppressed, and the pixel can be made high definition or highly functional without reducing the aperture ratio of the pixel. On the other hand, when the connection of three nodes is controlled using a TFT, it is necessary to use two or more transistors.
[0044]
(Embodiment 2)
FIG. 2 is a block diagram showing the configuration of the OLED panel of the present invention. Reference numeral 200 denotes a pixel portion, and a plurality of pixels 201 are formed in a matrix. Reference numeral 202 denotes a signal line driving circuit, 203 denotes a first scanning line driving circuit, and 204 denotes a second scanning line driving circuit.
[0045]
In FIG. 2, the signal line driver circuit 202, the first scan line driver circuit 203, and the second scan line driver circuit 204 are formed over the same substrate as the pixel portion 200; however, the present invention is not limited to this structure. Even if the signal line driver circuit 202, the first scanning line driving circuit 203, and the second scanning line driving circuit 204 are formed on a different substrate from the pixel portion 200 and connected to the pixel portion 200 through a connector such as an FPC. good. In FIG. 2, the signal line driver circuit 202, the first scan line driver circuit 203, and the second scan line driver circuit 204 are provided one by one, but the present invention is not limited to this configuration. The number of the signal line driving circuit 202, the first scanning line driving circuit 203, and the second scanning line driving circuit 204 can be arbitrarily set by a designer.
[0046]
Although not shown in FIG. 2, the pixel unit 200 is provided with signal lines S1 to Sx, power supply lines V1 to Vx, first scanning lines G1 to Gy, and second scanning lines P1 to Py. Note that the number of signal lines and power supply lines is not necessarily the same. Further, the number of the first scanning lines and the number of the second scanning lines are not necessarily the same. Further, it is not always necessary to have all of these wirings, and other different wirings may be provided in addition to these wirings.
[0047]
The power supply lines V1 to Vx are kept at a predetermined voltage. Although FIG. 2 shows the structure of a light emitting device that displays a monochrome image, the present invention may be a light emitting device that displays a color image. In that case, the voltage levels of the power supply lines V1 to Vx need not be kept all the same, and may be changed for each corresponding color.
[0048]
Note that the voltage in this specification means a potential difference from the ground unless otherwise specified.
[0049]
FIG. 3 shows a detailed configuration example of the pixel 201 shown in FIG. 3 includes a signal line Si (one of S1 to Sx), a first scanning line Gj (one of G1 to Gy), and a second scanning line Pj (P1 to Py). 1) and a power supply line Vi (one of V1 to Vx).
[0050]
The pixel 201 includes the switch element Sw1 of the present invention, thin film transistors Tr1 and Tr2, an OLED 205, and a storage capacitor 206. The storage capacitor 206 is provided in order to more reliably maintain the voltage (gate voltage) between the gate electrode and the source region of the switch element Sw1, but it is not always necessary if the gate capacitance of Tr1 is sufficiently large.
[0051]
The switch element Sw1 of the present invention is a four-terminal thin film element that can control connection of three nodes with a voltage applied to a gate electrode. The gate electrode of the switch element Sw1 is connected to the first scanning line Gj. The three impurity regions of the switch element Sw1 are connected to the signal line Si, one to the gate electrode of the transistor Tr1, and one to the drain region of the transistor Tr1.
[0052]
Note that in this specification, in the case of an n-channel transistor, the voltage applied to the source region which is the impurity region is lower than the voltage applied to the drain region which is also the impurity region. In the case of a p-channel transistor, the voltage applied to the source region is higher than the voltage applied to the drain region.
[0053]
The gate electrode of the transistor Tr2 is connected to the second scanning line Pj. One of the source region and the drain region of the transistor Tr2 is connected to the drain region of the transistor Tr1, and the other is connected to the power supply line Vi.
[0054]
The source region of the transistor Tr1 is connected to the pixel electrode of the OLED 205. The OLED 205 has an anode and a cathode. In this specification, when the anode is used as a pixel electrode, the cathode is called a counter electrode, and when the cathode is used as a pixel electrode, the anode is called a counter electrode.
[0055]
One of the two electrodes of the storage capacitor 206 is connected to the gate electrode and the source region of the switch element Sw1.
[0056]
The voltage (power supply voltage) of the power supply line Vi is kept at a constant height. The voltage of the counter electrode is also maintained at a constant height.
[0057]
Although the present invention is not limited to the circuit of FIG. 3, if the circuit of FIG. 3 is assumed, Tr1 may be either an n-channel transistor or a p-channel transistor. However, when the anode is used as the pixel electrode and the cathode is used as the counter electrode, Tr1 is preferably an n-channel transistor. Conversely, when the anode is used as the counter electrode and the cathode is used as the pixel electrode, Tr1 is preferably a p-channel transistor.
[0058]
The switch elements Sw1 and Tr2 may be either n-channel transistors or p-channel transistors.
[0059]
Next, the operation of the above-described light emitting device of this embodiment will be described with reference to FIGS. The operation of the light-emitting device of the present invention can be described by dividing the writing period Ta and the display period Td for each pixel of each line. FIG. 4 shows a timing chart of the first and second scanning lines. A period during which the scan line is selected, in other words, a period in which all the transistors whose gate electrodes are connected to the scan line are in the ON state is indicated by ON. On the contrary, a period in which the scan line is not selected, in other words, a period in which all the transistors whose gate electrodes are connected to the scan line is in an OFF state is indicated by OFF. FIG. 5 is a diagram simply showing the pixel configuration in the writing period Ta and the display period Td.
[0060]
First, when the writing period Ta starts in the pixels on the first line, the first scanning line G1 is selected, and the switch element Sw1 is turned on. Since the second scanning line P1 is not selected, the transistor Tr2 is turned off.
[0061]
Then, currents Ic flow between the signal lines S1 to Sx and the counter electrode of the OLED 205 based on the video signal input to the signal line driver circuit 202, respectively. In this specification, the current Ic is referred to as a signal current.
[0062]
FIG. 5A shows a schematic diagram of the pixel 201 when the signal current Ic flows through the signal line Si in the writing period Ta. Reference numeral 210 denotes a terminal for connection with a power source for applying a voltage to the counter electrode. Reference numeral 211 denotes a constant current source included in the signal line driver circuit 202.
[0063]
Since the switch element Sw1 is on during the writing period, when the signal current Ic flows through the signal line Si, the current Id (drain current) flowing between the drain region and the source region of the switch element Sw1 has substantially the same value as the signal current Ic. Kept.
[0064]
In the writing period, the transistor Tr1 operates in the saturation region because the gate electrode and the drain region are connected. Therefore, the gate voltage is V _GS , Μ mobility, C ₀ Is the gate capacitance per unit area, W / L is the ratio of the channel width W to the channel length L of the channel formation region, V _TH Is a threshold value, the drain current Id of the transistor Tr1 is expressed by the following Equation 1.
[0065]
[Formula 1]
Id = μC ₀ W / L (V _GS -V _TH ) ² / 2
[0066]
In equation 1, μ, C ₀ , W / L, V _TH Are all fixed values determined by individual transistors. The drain current Id of the transistor Tr1 is maintained at the same magnitude as the signal current Ic by the constant current source 211. Therefore, as can be seen from Equation 1, the gate voltage V of the transistor Tr1 _GS Is determined by the value of the signal current Ic.
[0067]
The drain current Id of the transistor Tr1 flows to the OLED 205, and the OLED 205 emits light with a luminance corresponding to the magnitude of the current. The OLED 205 does not emit light when the drain current Id is as close as possible to 0 or is a reverse bias current.
[0068]
When the writing period Ta ends in the pixels on the first line, the selection of the first scanning line G1 ends. Then, the writing period Ta is started in the pixels on the second line, and the first scanning line G2 is selected. Therefore, the switch element Sw1 is turned on in the pixels on the second line. Since the second scanning line P2 is not selected, the transistor Tr2 is turned off.
[0069]
A signal current Ic flows between the signal lines S1 to Sx and the counter electrode of the OLED 205 based on the video signal input to the signal line driver circuit 202. Therefore, the current flowing through the OLED 205 is kept at the same magnitude as the signal current Ic, and the OLED 205 emits light with a luminance corresponding to the magnitude of the signal current Ic.
[0070]
Then, the writing period Ta ends for the pixels on the second line, and thereafter, similarly, the writing period Ta starts in order from the third line to the pixels on the y line, and the above-described operation is repeated.
[0071]
On the other hand, when the writing period Ta ends in the pixels on the first line, the display period Td starts next. When the display period Td is started, the second scanning line P1 is selected. Therefore, the transistor Tr2 is turned on in the pixels on the first line. Note that since the first scanning line G1 is not selected in the display period Td, the switch element Sw1 is turned off.
[0072]
FIG. 5B shows a schematic diagram of a pixel in the display period Td. Since the switch element Sw1 is off and the transistor Tr2 is on, the drain region of the transistor Tr1 is connected to the power supply line Vi, and a constant voltage (power supply voltage) is applied.
[0073]
Then, the transistor Tr1 has a voltage V determined in the writing period Ta. _GS Is held by the holding capacitor 206, and the drain current Id of the switch element Sw1 is maintained at the signal current Ic. Therefore, in the display period Td, as in the writing period Ta, the current flowing through the OLED 205 is maintained at the same magnitude as the signal current Ic. Therefore, in the display period Td, the OLED 205 emits light with the same luminance as the writing period Ta.
[0074]
When the display period Td ends for the pixels on the first line, the display period Td starts for the pixels on the second line. Then, like the pixels on the first line, the second scanning line P2 is selected, and the transistor Tr2 is turned on. Since the first scanning line G2 is not selected, the switch element Sw1 is turned off. Then, the OLED 205 emits light with the same luminance as the writing period.
[0075]
Then, the display period Td ends in the pixels on the second line, and thereafter, similarly, the display period Td starts in order from the third line to the pixels on the y line, and the above-described operation is repeated.
[0076]
When the writing period Ta and the display period Td are finished, one frame period is finished and one image is displayed. Then, the next frame period is started and the above-described operation is repeated again. The gradation of each pixel is determined by the magnitude of current flowing through the OLED 205 in the writing period Ta and the display period Td.
[0077]
With the above operation, even if the characteristics of the transistor Tr1 that controls the current flowing through the OLED differ from pixel to pixel, it is possible to prevent a significant variation in the magnitude of the current flowing through the OLED from pixel to pixel. Can be suppressed.
[0078]
Moreover, in this invention, even if an organic light emitting layer deteriorates with the said structure, the fall of the brightness | luminance of OLED can be suppressed, As a result, a clear image can be displayed. In the case of a light emitting device for color display using OLEDs corresponding to each color, even if the organic light emitting layer of the OLED deteriorates at a different speed for each corresponding color, the luminance balance of each color is prevented from being lost. Can display a desired color.
[0079]
Further, the OLED current can be controlled to a desired value even if the temperature of the organic light emitting layer depends on the outside air temperature, the heat generated by the OLED panel itself, or the like. Therefore, since the OLED current and the luminance of the OLED are proportional, it is possible to suppress the change in the luminance of the OLED, and it is possible to prevent the consumption current from increasing as the temperature rises. Further, in the case of a light emitting device for color display, since it is possible to suppress changes in the brightness of the OLEDs of each color without being influenced by temperature changes, it is possible to prevent the balance of the brightness of each color from being lost and display a desired color. can do.
[0080]
Furthermore, since the degree of change of the OLED current in the temperature change is generally different depending on the type of the organic light emitting material, the luminance of the OLED of each color may vary depending on the temperature in color display. However, in the light emitting device of the present invention, a desired luminance can be obtained without being influenced by a temperature change, so that it is possible to prevent the balance of the luminance of each color from being lost and display a desired color.
[0081]
Further, in the light emitting device of the present invention, the current flowing through each OLED can be maintained at a desired value, so that the gradation can be prevented from changing due to a potential drop due to wiring resistance.
[0082]
Further, by using the switch element of the present invention, the ratio of the area of the transistor to each pixel can be suppressed.
[0083]
Note that the organic light-emitting element used in this embodiment is a material in which a hole injection layer, an electron injection layer, a hole transport layer, an electron transport layer, or the like is an inorganic compound alone, or an organic compound is mixed with an inorganic compound. It can also take the form formed by. These layers may be partially mixed with each other.
[0084]
(Embodiment 3)
In the second embodiment, the case where the video signal is analog has been described. However, the video signal can be driven using a digital video signal.
[0085]
In the case of a time grayscale driving method (digital driving method) using a digital video signal, it is possible to display one image by repeatedly appearing a writing period Ta and a display period Td in one frame period. is there.
[0086]
For example, when an image is displayed by an n-bit video signal, at least n writing periods and n display periods are provided in one frame period. The n writing periods (Ta1 to Tan) and the n display periods (Td1 to Tdn) correspond to each bit of the video signal.
[0087]
Next to the writing period Tam (m is an arbitrary number from 1 to n), a display period corresponding to the same number of bits, in this case Tdm, appears. The writing period Ta and the display period Td are collectively called a subframe period SF. A subframe period having a writing period Tam and a display period Tdm corresponding to the m-th bit is SFm.
[0088]
The lengths of the subframe periods SF1 to SFn are SF1: SF2:...: SFn = 2 ⁰ : 2 ¹ : ...: 2 ^n-1 Meet.
[0089]
Whether or not to cause the OLED to emit light in each subframe period is selected by each bit of the digital video signal. Then, the number of gradations can be controlled by controlling the sum of the lengths of the display periods during which light is emitted during one frame period.
[0090]
Note that a subframe period having a long display period may be divided into several parts in order to improve image quality on display. A specific method of division is disclosed in Japanese Patent Application No. 2000-267164, and can be referred to.
[0091]
A period in which a reverse bias voltage is applied to the organic light emitting layer may be provided to extend the life of the organic light emitting layer.
[0092]
【Example】
Examples of the present invention will be described below.
[0093]
Example 1
In this embodiment, a transistor of the present invention having a so-called multi-gate structure in which two or more channel formation regions are provided between impurity regions connected to a connection wiring will be described. Note that in this embodiment, a transistor with a double gate structure in which two channel formation regions are provided between connection wirings is described; however, the present invention is not limited to the double gate structure, and a channel formation region is provided between connection wirings. Three or more multi-gate structures may be provided.
[0094]
The structure of the transistor of this example is described with reference to FIGS. 6A is a top view of the transistor of the present invention, FIG. 6B corresponds to a cross-sectional view taken along the broken line AA ′ in FIG. 6A, and FIG. This corresponds to a cross-sectional view taken along broken line BB ′ in FIG.
[0095]
The transistor of the present invention includes an active layer 301, a gate insulating film 302 in contact with the active layer, and gate electrodes 303a, 303b, and 303c in contact with the gate insulating film 302. The gate electrodes 303a, 303b, and 303c are electrically connected. In this embodiment, all the gate electrodes are part of the gate wiring 313. The active layer 301 includes channel formation regions 304a, 304b, and 304c and impurity regions 305, 306, 307, and 312 to which an impurity imparting a conductivity type is added.
[0096]
The gate electrode 303a and the channel formation region 304a overlap with the gate insulating film 302 interposed therebetween. The gate electrode 303b and the channel formation region 304b overlap with the gate insulating film 302 interposed therebetween. The gate electrode 303c and the channel formation region 304c overlap with the gate insulating film 302 interposed therebetween.
[0097]
Impurity regions 305, 306, and 307 are in contact with channel formation regions 304a, 304b, and 304c, respectively. The impurity region 312 is in contact with all the channel formation region formation regions 304a, 304b, and 304c. Accordingly, two channel formation regions 304a and 304b are provided between the impurity regions 305 and 306, and two channel formation regions 304b and 304c are provided between the impurity regions 306 and 307. Two channel formation regions 304 c and 304 a are provided between 307 and 305.
[0098]
In this embodiment, all the impurity regions are in contact with the channel formation regions, respectively, but the present invention is not limited to this configuration. A low-concentration impurity region (LDD region) having an impurity concentration lower than that of the impurity region may be provided between the impurity region and the channel formation region, or a region not added with an impurity that does not overlap with the gate electrode (offset region) ) May be provided.
[0099]
An insulating film 308 is formed on the gate insulating film 302 so as to cover the impurity regions 305, 306, and 307 of the active layer 301. Connection wirings 309, 310, and 311 connected to the impurity regions 305, 306, and 307 are formed through contact holes formed in the insulating film 308 and the gate insulating film 302, respectively. Note that although the gate insulating film 302 covers the impurity regions 305, 306, and 307 in FIG. 6, the present invention is not limited to this structure. The impurity regions 305, 306, and 307 are not necessarily covered by the gate insulating film 302, and may be exposed.
[0100]
In the switch element shown in FIG. 6, the resistance between the connection wirings 309, 310, and 311 is controlled by the voltage applied to the gate electrodes 303a, 303b, and 303c.
[0101]
The switch element in FIG. 6 can simultaneously connect three nodes, specifically, connection wirings 309, 310, and 311. In the present specification, the connection means an electrical connection unless otherwise specified.
[0102]
With the above structure, the area of the switch element can be suppressed, the area occupied by the switch element in the pixel can be suppressed, and the pixel can be made high definition. On the other hand, when the connection of the three nodes is controlled using a double-gate three-terminal transistor, for example, the connection is performed as shown in FIG. 15B. Also occupies a large area.
[0103]
Further, since the off-current can be reduced in the multi-gate structure as compared with the single-gate structure, it is more suitable for use as a switching element.
[0104]
(Example 2)
In this embodiment, a switching element of the present invention having five terminals, which can control connection of four nodes with a voltage applied to a gate electrode, will be described.
[0105]
The configuration of the switch element of the present invention will be described with reference to FIG. 7A is a top view of the transistor of the present invention, FIG. 7B corresponds to a cross-sectional view taken along the broken line AA ′ in FIG. 7A, and FIG. This corresponds to a cross-sectional view taken along broken line BB ′ in FIG.
[0106]
The transistor of this embodiment includes an active layer 501, a gate insulating film 502 in contact with the active layer, and a gate electrode 503 in contact with the gate insulating film 502. The active layer 501 includes a channel formation region 504 and impurity regions 505, 506, 507, and 508 to which an impurity imparting a conductivity type is added. The gate electrode 503 and the channel formation region 504 overlap with the gate insulating film interposed therebetween.
[0107]
The impurity regions 505, 506, 507, and 508 are in contact with the channel formation region 504, respectively. In this embodiment, all the impurity regions are in contact with the channel formation region 504 respectively, but the present invention is not limited to this structure. A low-concentration impurity region (LDD region) having an impurity concentration lower than that of the impurity region may be provided between the impurity region and the channel formation region, or a region not added with an impurity that does not overlap with the gate electrode (offset region) ) May be provided.
[0108]
An insulating film 509 is formed on the gate insulating film 502 so as to cover the impurity regions 505, 506, 507, and 508 of the active layer 501. Connection wirings 510, 511, 512, and 513 connected to the impurity regions 505, 506, 507, and 508 are formed through contact holes formed in the insulating film 509 and the gate insulating film 502. Note that although the gate insulating film 502 covers the impurity regions 505, 506, 507, and 508 in FIG. 7, the present invention is not limited to this structure. The impurity regions 505, 506, 507, and 508 are not necessarily covered by the gate insulating film 502, and may be exposed.
[0109]
In the switch element illustrated in FIG. 7, the resistance between the connection wirings 510, 511, 512, and 513 is controlled by the voltage applied to the gate electrode 503.
[0110]
7 can simultaneously connect four nodes, specifically, connection wirings 510, 511, 512, and 513. FIG. In the present specification, the connection means an electrical connection unless otherwise specified.
[0111]
With the above structure, the area of the switch element can be suppressed, the area occupied by the switch element in the pixel can be suppressed, and the pixel can be made high definition.
[0112]
Note that although a five-terminal transistor capable of controlling connection of four nodes has been described in this embodiment, the transistor of the present invention is not limited to four terminals or five terminals. It is possible to design a transistor in accordance with the number of nodes.
[0113]
Example 3
In this embodiment, a bottom-gate transistor of the present invention in which a gate electrode is formed between a substrate and an active layer will be described.
[0114]
A structure of the transistor of the present invention is described with reference to FIGS. 8A is a top view of the transistor of the present invention, FIG. 8B corresponds to a cross-sectional view taken along the broken line AA ′ in FIG. 8A, and FIG. This corresponds to a cross-sectional view taken along broken line BB ′ in FIG.
[0115]
The switch element of this embodiment includes a gate electrode 701, a gate insulating film 702 in contact with the gate electrode 701, and an active layer 703 in contact with the gate insulating film 702. The active layer 703 includes a channel formation region 704 and impurity regions 705, 706, and 707 to which an impurity imparting a conductivity type is added. The gate electrode 701 and the channel formation region 704 overlap with the gate insulating film 702 interposed therebetween. Note that reference numeral 708 denotes a mask used for forming a channel formation region, and is formed of an insulating film.
[0116]
The impurity regions 705, 706, and 707 are in contact with the channel formation region 704, respectively. In this embodiment, all the impurity regions are in contact with the channel formation region 704, but the present invention is not limited to this structure. A low-concentration impurity region (LDD region) having an impurity concentration lower than that of the impurity region may be provided between the impurity region and the channel formation region, or a region not added with an impurity that does not overlap with the gate electrode (offset region) ) May be provided.
[0117]
An insulating film 708 is formed so as to cover the impurity regions 705, 706, and 707 of the active layer 703. Connection wirings 709, 710, and 711 connected to the impurity regions 705, 706, and 707 are formed through contact holes formed in the insulating film 708.
[0118]
In the switch element illustrated in FIG. 8, the resistance between the connection wirings 709, 710, and 711 is controlled by the voltage applied to the gate electrode 701.
[0119]
The switch element in FIG. 8 can connect three nodes, specifically, connection wirings 709, 710, and 711 simultaneously. In the present specification, the connection means an electrical connection unless otherwise specified.
[0120]
With the above structure, the area of the switch element can be suppressed, the area occupied by the switch element in the pixel can be suppressed, and the pixel can be made high definition.
[0121]
Note that a multi-gate structure may be provided by providing two or more channel formation regions between the connection wirings.
[0122]
Example 4
In this embodiment, a structure of a driving circuit (a signal line driving circuit, a first scanning line driving circuit, and a second scanning line driving circuit) included in the light-emitting device of the present invention driven by an analog driving method will be described.
[0123]
FIG. 9A shows a block diagram of the signal line driver circuit 401 of this embodiment. Reference numeral 402 denotes a shift register, 403 denotes a buffer, 404 denotes a sampling circuit, and 405 denotes a current conversion circuit.
[0124]
A clock signal (CLK) and a start pulse signal (SP) are input to the shift register 402. When a clock signal (CLK) and a start pulse signal (SP) are input to the shift register 402, a timing signal is generated.
[0125]
The generated timing signal is amplified or buffer amplified in the buffer 403 and input to the sampling circuit 404. Note that a level shifter may be provided instead of the buffer to amplify the timing signal. Further, both a buffer and a level shifter may be provided.
[0126]
FIG. 9B illustrates specific structures of the sampling circuit 404 and the current conversion circuit 405. Note that the sampling circuit 404 is connected to the buffer 403 at a terminal 410.
[0127]
The sampling circuit 404 is provided with a plurality of switches 411. An analog video signal is input to the sampling circuit 404 from the video signal line 406, and the switch 411 samples the analog video signal in synchronization with the timing signal and inputs the analog video signal to the subsequent current conversion circuit 405. Note that in FIG. 9B, only the current conversion circuit connected to one of the switches 411 included in the sampling circuit 404 is illustrated as the current conversion circuit 405. However, in FIG. It is assumed that the current conversion circuit 405 as shown in FIG.
[0128]
In this embodiment, only one transistor is used for the switch 411. However, the switch 411 may be any switch that can sample an analog video signal in synchronization with the timing signal, and is not limited to the configuration of this embodiment.
[0129]
The sampled analog video signal is input to a current output circuit 412 included in the current conversion circuit 405. The current output circuit 412 outputs a current (signal current) having a value corresponding to the voltage of the input video signal. In FIG. 9, an amplifier and a transistor are used to form a current output circuit. However, the present invention is not limited to this configuration, and any circuit that can output a current corresponding to an input video signal can be used. It ’s fine.
[0130]
The signal current is input to a reset circuit 417 included in the current conversion circuit 405. The reset circuit 417 includes two analog switches 413 and 414, an inverter 416, and a power source 415.
[0131]
A reset signal (Res) is input to the analog switch 414, and a reset signal (Res) inverted by the inverter 416 is input to the analog switch 413. The analog switch 413 and the analog switch 414 operate in synchronization with the inverted reset signal and the reset signal, respectively, and when one is on, one is off.
[0132]
When the analog switch 413 is on, the signal current is input to the corresponding signal line. Conversely, when the analog switch 414 is on, the voltage of the power source 415 is applied to the signal line, and the signal line is reset. Note that the voltage of the power supply 415 is preferably almost the same as the voltage of the power supply line provided in the pixel, and the closer the current that flows to the signal line when the signal line is reset, the better. .
[0133]
Note that the signal line is desirably reset during the return period. However, if it is outside the period during which the image is displayed, it can be reset to a period other than the blanking period as necessary.
[0134]
Instead of the shift register, another circuit capable of selecting a signal line such as a decoder circuit may be used.
[0135]
Next, the configuration of the first scanning line driving circuit will be described.
[0136]
FIG. 10 is a block diagram showing a configuration of the first scanning line driving circuit 641. The first scan line driver circuit 641 includes a shift register 642 and a buffer 643, respectively. In some cases, a level shifter may be provided.
[0137]
In the first scan line driver circuit 641, the timing signal is generated by inputting the clock CLK and the start pulse signal SP to the shift register 642. The generated timing signal is buffered and amplified in the buffer 643 and supplied to the corresponding first scanning line.
[0138]
A gate electrode of a switch element Sw1 of pixels for one line is connected to the first scanning line. Since the switch elements Sw1 of the pixels for one line must be turned on all at once, a buffer 643 that can flow a large current is used.
[0139]
Instead of the shift register, another circuit that can select a scanning line such as a decoder circuit may be used.
[0140]
Further, the second scanning line driving circuit may have the same configuration as the first scanning line driving circuit.
[0141]
Note that the voltages of the first and second scanning lines may be controlled by a plurality of scanning line driving circuits corresponding to the respective scanning lines, or the voltages of several scanning lines or all the scanning lines may be controlled by one scanning. You may control by a line drive circuit.
[0142]
The signal line driver circuit and the scan line driver circuit for driving the light-emitting device of the present invention are not limited to the structures shown in this embodiment. The configuration of the present embodiment can be implemented by freely combining with the configurations shown in Embodiments 1 to 3.
[0143]
(Example 5)
An example of a method for manufacturing a light-emitting device of the present invention will be described with reference to FIGS. In this example, a method for manufacturing a light-emitting device having the pixel shown in FIGS. Here, representatively, the switch elements Sw1 and Tr1 are shown. Note that the transistor Tr2 is not particularly illustrated, but can be manufactured according to the manufacturing method of this embodiment.
[0144]
First, as shown in FIG. 11A, a silicon oxide film is formed on a substrate 5001 made of glass such as barium borosilicate glass represented by Corning # 7059 glass or # 1737 glass, or aluminoborosilicate glass. A base film 5002 made of an insulating film such as a silicon nitride film or a silicon oxynitride film is formed. For example, SiH by plasma CVD method ₄ , NH ₃ , N ₂ A silicon oxynitride film 5002a made of O is formed to 10 to 200 [nm] (preferably 50 to 100 [nm]), and similarly SiH ₄ , N ₂ A silicon oxynitride silicon nitride film 5002b formed from O is stacked to a thickness of 50 to 200 [nm] (preferably 100 to 150 [nm]). Although the base film 5002 is shown as a two-layer structure in this embodiment, it may be formed as a single-layer film of the insulating film or a structure in which two or more layers are stacked.
[0145]
The island-shaped semiconductor layers 5005 and 5006 are formed using a crystalline semiconductor film in which a semiconductor film having an amorphous structure is formed using a laser crystallization method or a known thermal crystallization method. The island-like semiconductor layers 5005 and 5006 are formed to a thickness of 25 to 80 [nm] (preferably 30 to 60 [nm]). There is no limitation on the material of the crystalline semiconductor film, but the crystalline semiconductor film is preferably formed of silicon or a silicon germanium (SiGe) alloy.
[0146]
When a crystalline semiconductor film is formed by laser crystallization, a pulse oscillation type or continuous emission type excimer laser, YAG laser, YVO ₄ Use a laser. In the case of using these lasers, it is preferable to use a method in which laser light emitted from a laser oscillator is linearly collected by an optical system and irradiated onto a semiconductor film. Crystallization conditions are appropriately selected by the practitioner. When an excimer laser is used, the pulse oscillation frequency is 300 [Hz], and the laser energy density is 100 to 400 [mJ / cm. ² ] (Typically 200 to 300 [mJ / cm ² ]). When a YAG laser is used, the second harmonic is used and the pulse oscillation frequency is set to 30 to 300 [kHz], and the laser energy density is set to 300 to 600 [mJ / cm. ² ] (Typically 350-500 [mJ / cm ² ]). Then, a laser beam condensed in a linear shape with a width of 100 to 1000 [μm], for example, 400 [μm] is irradiated over the entire surface of the substrate, and the superposition ratio (overlap ratio) of the linear laser light at this time is 50. ~ 90 [%].
[0147]
As the laser, a continuous wave or pulsed gas laser or solid-state laser can be used. There are excimer laser, Ar laser, Kr laser, etc. as gas laser, and YAG laser, YVO as solid laser. ₄ Laser, YLF laser, YAlO ₃ A laser, a glass laser, a ruby laser, an alexandride laser, a Ti: sapphire laser, and the like can be given. Solid lasers include YAG, YVO doped with Cr, Nd, Er, Ho, Ce, Co, Ti or Tm. ₄ , YLF, YAlO ₃ Lasers using crystals such as can also be used. The fundamental wave of the laser differs depending on the material to be doped, and laser light having a fundamental wave of around 1 μm can be obtained. The harmonic with respect to the fundamental wave can be obtained by using a nonlinear optical element.
[0148]
In crystallization of the amorphous semiconductor film, in order to obtain a crystal with a large grain size, it is preferable to apply a second to fourth harmonic of the fundamental wave using a solid-state laser capable of continuous oscillation. Typically, Nd: YVO ₄ It is desirable to apply the second harmonic (532 nm) or the third harmonic (355 nm) of the laser (fundamental wave 1064 nm). Specifically, continuous output YVO with an output of 10 W ₄ Laser light emitted from the laser is converted into a harmonic by a non-linear optical element. Also, YVO in the resonator ₄ There is also a method of emitting harmonics by inserting a crystal and a nonlinear optical element. Then, it is preferably formed into a rectangular or elliptical laser beam on the irradiation surface by an optical system, and irradiated to the object to be processed. The energy density at this time is 0.01 to 100 MW / cm. ² Degree (preferably 0.1-10 MW / cm ² )is required. Then, irradiation is performed by moving the semiconductor film relative to the laser light at a speed of about 10 to 2000 cm / s.
[0149]
Next, a gate insulating film 5007 is formed to cover the island-shaped semiconductor layers 5005 and 5006. The gate insulating film 5007 is formed of an insulating film containing silicon with a thickness of 40 to 150 [nm] by using a plasma CVD method or a sputtering method. In this embodiment, a silicon oxynitride film is formed with a thickness of 120 [nm]. Needless to say, the gate insulating film is not limited to such a silicon oxynitride film, and another insulating film containing silicon may be used as a single layer or a stacked structure. For example, in the case of using a silicon oxide film, TEOS (Tetraethyl Orthosilicate) and O ₂ And a reaction pressure of 40 [Pa], a substrate temperature of 300 to 400 [° C.], a high frequency (13.56 [MHz]), and a power density of 0.5 to 0.8 [W / cm]. ² ] Can be formed by discharging. The silicon oxide film thus produced can obtain good characteristics as a gate insulating film by subsequent thermal annealing at 400 to 500 [° C.].
[0150]
Then, a first conductive film 5008 and a second conductive film 5009 for forming a gate electrode are formed over the gate insulating film 5007. In this embodiment, the first conductive film 5008 is formed with Ta to a thickness of 50 to 100 [nm], and the second conductive film 5009 is formed with W to a thickness of 100 to 300 [nm].
[0151]
The Ta film is formed by sputtering, and a Ta target is sputtered with Ar. In this case, when an appropriate amount of Xe or Kr is added to Ar, the internal stress of the Ta film can be relieved and peeling of the film can be prevented. The resistivity of the α-phase Ta film is about 20 [μΩcm] and can be used for the gate electrode, but the resistivity of the β-phase Ta film is about 180 [μΩcm] and is used as the gate electrode. It is unsuitable. In order to form an α-phase Ta film, a tantalum nitride having a crystal structure close to that of the Ta α-phase is formed on a Ta base with a thickness of about 10 to 50 [nm]. It can be easily obtained.
[0152]
When forming a W film, it is formed by sputtering using W as a target. In addition, tungsten hexafluoride (WF ₆ It can also be formed by a thermal CVD method using In any case, it is necessary to reduce the resistance in order to use it as a gate electrode, and it is desirable that the resistivity of the W film be 20 [μΩcm] or less. Although the resistivity of the W film can be reduced by increasing the crystal grains, if the impurity element such as oxygen is large in W, the crystallization is hindered and the resistance is increased. Therefore, in the case of sputtering, a W target having a purity of 99.9999 or 99.99 [%] is used, and a W film is formed with sufficient consideration to prevent impurities from entering the gas phase during film formation. As a result, a resistivity of 9 to 20 [μΩcm] can be realized.
[0153]
Note that in this embodiment, the first conductive film 5008 is Ta and the second conductive film 5009 is W, but there is no particular limitation, and any of them is selected from Ta, W, Ti, Mo, Al, Cu, and the like. Or an alloy material or a compound material containing the element as a main component. Alternatively, a semiconductor film typified by a polycrystalline silicon film doped with an impurity element such as phosphorus may be used. As another example of a combination other than the present embodiment, a combination in which the first conductive film 5008 is formed of tantalum nitride (TaN) and the second conductive film 5009 is W is used. Is made of tantalum nitride (TaN), the second conductive film 5009 is made of Al, the first conductive film 5008 is made of tantalum nitride (TaN), and the second conductive film 5009 is made of Cu. Can be mentioned.
[0154]
Next, a resist mask 5010 is formed, and a first etching process is performed to form electrodes and wirings. In this embodiment, an ICP (Inductively Coupled Plasma) etching method is used, and CF is used as an etching gas. ₄ And Cl ₂ Then, 500 [W] RF (13.56 [MHz]) power is applied to the coil-type electrode at a pressure of 1 [Pa] to generate plasma. 100 [W] RF (13.56 [MHz]) power is also applied to the substrate side (sample stage), and a substantially negative self-bias voltage is applied. CF ₄ And Cl ₂ When W is mixed, the W film and the Ta film are etched to the same extent.
[0155]
Under the above etching conditions, by making the shape of the resist mask suitable, the end portions of the first conductive layer and the second conductive layer are tapered due to the effect of the bias voltage applied to the substrate side. The angle of the tapered portion is 15 to 45 °. In order to perform etching without leaving a residue on the gate insulating film, it is preferable to increase the etching time at a rate of about 10 to 20%. Since the selection ratio of the silicon oxynitride film to the W film is 2 to 4 (typically 3), the surface where the silicon oxynitride film is exposed is etched by about 20 to 50 [nm] by the overetching process. become. Thus, the first shape conductive layers 5013 and 5014 (the first conductive layers 5013a and 5014a and the second conductive layers 5013b and 5014b) formed of the first conductive layer and the second conductive layer by the first etching process. Form. At this time, in the gate insulating film 5007, regions that are not covered with the first shape conductive layers 5013 and 5014 are etched and thinned by about 20 to 50 [nm].
[0156]
Then, an impurity element imparting n-type is added by performing a first doping process. As a doping method, an ion doping method or an ion implantation method may be used. The condition of the ion doping method is a dose of 1 × 10 ¹³ ~ 5x10 ¹⁴ [Atoms / cm ² The acceleration voltage is set to 60 to 100 [keV]. As an impurity element imparting n-type, an element belonging to Group 15, typically phosphorus (P) or arsenic (As), is used here, but phosphorus (P) is used. In this case, the conductive layers 5013 and 5014 serve as a mask for the impurity element imparting n-type, and the first impurity regions 5017 and 5018 are formed in a self-aligning manner. The first impurity regions 5017 and 5018 have 1 × 10 ²⁰ ~ 1x10 ²¹ [Atoms / cm ³ An impurity element imparting n-type is added in a concentration range of (Fig. 11 (B))
[0157]
Next, as shown in FIG. 11C, a second etching process is performed without removing the resist mask. CF as etching gas ₄ And Cl ₂ And O ₂ Then, the W film is selectively etched. At this time, second shape conductive layers 5028 and 5029 (first conductive layers 5028a and 5029a and second conductive layers 5028b and 5029b) are formed by the second etching treatment. At this time, in the gate insulating film 5007, regions that are not covered with the second shape conductive layers 5028 and 5029 are further etched and thinned by about 20 to 50 [nm].
[0158]
CF of W film and Ta film ₄ And Cl ₂ The etching reaction by the mixed gas can be estimated from the generated radical or ion species and the vapor pressure of the reaction product. Comparing the vapor pressure of fluoride and chloride of W and Ta, WF, which is fluoride of W ₆ Is extremely high, other WCl ₅ , TaF ₅ , TaCl ₅ Are comparable. Therefore, CF ₄ And Cl ₂ With this mixed gas, both the W film and the Ta film are etched. However, an appropriate amount of O is added to this mixed gas. ₂ When CF is added ₄ And O ₂ Reacts to CO and F, and a large amount of F radicals or F ions are generated. As a result, the etching rate of the W film having a high fluoride vapor pressure is increased. On the other hand, the increase in etching rate of Ta is relatively small even when F increases. Further, since Ta is more easily oxidized than W, O ₂ When Ta is added, the surface of Ta is oxidized. Since the Ta oxide does not react with fluorine or chlorine, the etching rate of the Ta film further decreases. Therefore, it is possible to make a difference in the etching rate between the W film and the Ta film, and the etching rate of the W film can be made larger than that of the Ta film.
[0159]
Then, a second doping process is performed as shown in FIG. In this case, an impurity element imparting n-type conductivity is doped as a condition of a high acceleration voltage by lowering the dose than in the first doping process. For example, the acceleration voltage is set to 70 to 120 [keV], and 1 × 10 ¹³ [Atoms / cm ² A new impurity region is formed inside the first impurity region formed in the island-shaped semiconductor layer in FIG. 11B. Doping is performed using the second shape conductive layers 5028 and 5029 as masks against the impurity element so that the impurity element is also added to the lower regions of the first conductive layers 5028a and 5029a. Thus, third impurity regions 5034 and 5035 are formed. The concentration of phosphorus (P) added to the third impurity regions 5034 and 5035 has a gradual concentration gradient according to the film thickness of the tapered portions of the first conductive layers 5028a and 5029a. Note that, in the semiconductor layer overlapping the tapered portions of the first conductive layers 5028a and 5029a, although the impurity concentration slightly decreases inward from the end portions of the tapered portions of the first conductive layers 5028a and 5029a, the impurity concentration is almost reduced. The concentration is similar.
[0160]
Next, a third etching process is performed as shown in FIG. CHF as etching gas ₆ And using a reactive ion etching method (RIE method). By the third etching treatment, the tapered portions of the first conductive layers 5028a and 5029a are partially etched, so that a region where the first conductive layer overlaps with the semiconductor layer is reduced. By the third etching process, third-shaped conductive layers 5039 and 5040 (first conductive layers 5039a and 5040a and second conductive layers 5039b and 5040b) are formed. At this time, in the gate insulating film 5007, a region which is not covered with the third shape conductive layers 5039 and 5040 is further etched and thinned by about 20 to 50 [nm].
[0161]
By the third etching process, in the third impurity regions 5034 and 5035, the third impurity regions 5034a and 5035a overlapping with the first conductive layers 5039a and 5040a, the first impurity region, the third impurity region, Second impurity regions 5034b and 5035b are formed.
[0162]
Then, as shown in FIG. 12B, fourth impurity regions 5049 to 5054 having a conductivity type opposite to the first conductivity type are formed in the island-shaped semiconductor layer 5005 forming the p-channel TFT. Using the third shape conductive layer 5040b as a mask for the impurity element, an impurity region is formed in a self-aligning manner. At this time, the entire surface of the island-like semiconductor layer 5006 for forming the n-channel TFT is covered with a resist mask 5200. Phosphorus is added to the impurity regions 5049 to 5054 at different concentrations, but diborane (B ₂ H ₆ ), And the impurity concentration in each region is 2 × 10 ²⁰ ~ 2x10 ²¹ [Atoms / cm ³ ].
[0163]
Through the above steps, impurity regions are formed in each island-like semiconductor layer. The third shape conductive layers 5039 and 5040 overlapping with the island-shaped semiconductor layers function as gate electrodes.
[0164]
After removing the resist mask 5200, a process of activating the impurity element added to each island-like semiconductor layer is performed for the purpose of controlling the conductivity type. This step is performed by a thermal annealing method using a furnace annealing furnace. In addition, a laser annealing method or a rapid thermal annealing method (RTA method) can be applied. In the thermal annealing method, the oxygen concentration is 1 [ppm] or less, preferably 0.1 [ppm] or less in a nitrogen atmosphere of 400 to 700 [° C.], typically 500 to 600 [° C.], In this embodiment, heat treatment is performed at 500 [° C.] for 4 hours. However, if the wiring material used for the third shape conductive layers 5039 and 5040 is weak against heat, activation is performed after an interlayer insulating film (mainly composed of silicon) is formed to protect the wiring and the like. Preferably it is done.
[0165]
When activation is performed using a laser annealing method, the laser used for crystallization can be used. In the case of activation, the moving speed is the same as that of crystallization, and 0.01-100 MW / cm. ² Degree (preferably 0.01 to 10 MW / cm ² ) Energy density is required.
[0166]
Further, a heat treatment is performed at 300 to 450 [° C.] for 1 to 12 hours in an atmosphere containing 3 to 100% hydrogen to perform a step of hydrogenating the island-shaped semiconductor layer. This step is a step of terminating dangling bonds in the semiconductor layer with thermally excited hydrogen. As another means of hydrogenation, plasma hydrogenation (using hydrogen excited by plasma) may be performed.
[0167]
Next, as shown in FIG. 13C, a first interlayer insulating film 5055 is formed from a silicon oxynitride film to a thickness of 100 to 200 [nm]. A second interlayer insulating film 5056 made of an organic insulating material is formed thereon, and then contact holes are formed in the first interlayer insulating film 5055, the second interlayer insulating film 5056, and the gate insulating film 5007. After the wirings 5059 to 5062 are formed by patterning, the pixel electrode 5064 in contact with the connection wiring 5062 is formed by patterning.
[0168]
As the second interlayer insulating film 5056, a film made of an organic resin is used, and as the organic resin, polyimide, polyamide, acrylic, BCB (benzocyclobutene), or the like can be used. In particular, since the second interlayer insulating film 5056 has a strong meaning of flattening, acrylic having excellent flatness is preferable. In this embodiment, the acrylic film is formed with a film thickness that can sufficiently flatten the step formed by the TFT. Preferably, it may be 1-5 [μm] (more preferably 2-4 [μm]).
[0169]
The contact holes are formed by dry etching or wet etching, and contact holes reaching n-type impurity regions 5017 or p-type impurity regions 5049 and 5054 are formed.
[0170]
Further, as wirings (including connection wirings and signal lines) 5059 to 5062, a Ti film of 100 [nm], a Ti-containing aluminum film of 300 [nm], and a Ti film of 150 [nm] are continuously formed by sputtering 3 A layered film having a layer structure patterned into a desired shape is used. Of course, other conductive films may be used.
[0171]
In this example, an ITO film having a thickness of 110 [nm] was formed as the pixel electrode 5064 and patterned. A contact is made by arranging the pixel electrode 5064 so as to be in contact with and overlapping with the connection wiring 5062. Alternatively, a transparent conductive film in which indium oxide is mixed with 2 to 20% zinc oxide (ZnO) may be used. This pixel electrode 5064 becomes the anode of the OLED. (Fig. 12 (A))
[0172]
Next, as shown in FIG. 12D, an insulating film containing silicon (silicon oxide film in this embodiment) is formed to a thickness of 500 nm, and an opening is formed at a position corresponding to the pixel electrode 5064. Then, a third interlayer insulating film 5065 functioning as a bank is formed. When the opening is formed, a tapered sidewall can be easily formed by using a wet etching method. If the side wall of the opening is not sufficiently gentle, the deterioration of the organic light emitting layer due to the step becomes a significant problem, so care must be taken.
[0173]
Next, the organic light emitting layer 5066 and the cathode (MgAg electrode) 5067 are continuously formed by using a vacuum evaporation method without releasing to the atmosphere. The organic light emitting layer 5066 has a thickness of 80 to 200 [nm] (typically 100 to 120 [nm]), and the cathode 5067 has a thickness of 180 to 300 [nm] (typically 200 to 250 [nm]. nm]).
[0174]
In this step, the organic light emitting layer is sequentially formed on the pixel corresponding to red, the pixel corresponding to green, and the pixel corresponding to blue. However, since the organic light emitting layer has poor resistance to a solution, it must be formed for each color individually without using a photolithography technique. Therefore, it is preferable to use a metal mask to hide other than the desired pixels and to selectively form the organic light emitting layer only at necessary portions.
[0175]
That is, first, a mask that hides all pixels other than those corresponding to red is set, and an organic light emitting layer that emits red light is selectively formed using the mask. Next, a mask that hides all but the pixels corresponding to green is set, and an organic light emitting layer that emits green light is selectively formed using the mask. Next, similarly, a mask for hiding all but the pixels corresponding to blue is set, and a blue light emitting organic light emitting layer is selectively formed using the mask. Note that although all the different masks are described here, the same mask may be used.
[0176]
Here, a method of forming three types of OLEDs corresponding to RGB is used, but a method of combining a white light emitting OLED and a color filter, a blue or blue green light emitting OLED and a phosphor (fluorescent color conversion layer: CCM). ), A method of superimposing OLEDs corresponding to RGB using a transparent electrode as a cathode (counter electrode), or the like may be used.
[0177]
A known material can be used for the organic light emitting layer 5066. As the known material, it is preferable to use an organic material in consideration of the driving voltage. For example, a four-layer structure including a hole injection layer, a hole transport layer, a light emitting layer, and an electron injection layer may be used as the organic light emitting layer.
[0178]
Next, a cathode 5067 is formed using a metal mask. In this embodiment, MgAg is used as the cathode 5067, but the present invention is not limited to this. Other known materials may be used for the cathode 5067.
[0179]
Finally, a passivation film 5068 made of a silicon nitride film is formed to a thickness of 300 [nm]. By forming the passivation film 5068, the organic light emitting layer 5066 can be protected from moisture and the like, and the reliability of the OLED can be further improved.
[0180]
Thus, a light emitting device having a structure as shown in FIG. 12D is completed.
[0181]
By the way, the light emitting device of this embodiment can exhibit extremely high reliability and improve operating characteristics by arranging TFTs having an optimum structure not only in the pixel portion but also in the drive circuit portion. In addition, it is possible to increase the crystallinity by adding a metal catalyst such as Ni in the crystallization step. As a result, the drive frequency of the signal line driver circuit can be made 10 [MHz] or higher.
[0182]
First, a TFT having a structure that reduces hot carrier injection so as not to reduce the operating speed as much as possible is used as an n-channel TFT of a CMOS circuit that forms a drive circuit portion. Note that the driving circuit here includes a shift register, a buffer, a level shifter, a latch in line sequential driving, a transmission gate in dot sequential driving, and the like.
[0183]
In this embodiment, the active layer of the n-channel TFT has an overlap LDD region (L that overlaps the gate electrode with the source region, drain region, and gate insulating film interposed therebetween. _OV Region), an offset LDD region (L _OFF Region) and a channel formation region.
[0184]
In addition, since the p-channel TFT of the CMOS circuit is hardly concerned with deterioration due to hot carrier injection, it is not particularly necessary to provide an LDD region. Needless to say, it is possible to provide an LDD region as in the case of the n-channel TFT and take measures against hot carriers.
[0185]
In addition, when the driving circuit uses a CMOS circuit in which a current flows bidirectionally in the channel formation region, that is, a CMOS circuit in which the roles of the source region and the drain region are switched, an n-channel TFT that forms the CMOS circuit In this case, it is preferable to form the LDD region in such a manner that the channel formation region is sandwiched between both sides of the channel formation region. An example of this is a transmission gate used for dot sequential driving. In the case where a CMOS circuit that needs to keep off current as low as possible is used in the driver circuit, the n-channel TFT forming the CMOS circuit is _OV It is preferable to have a region. As such an example, there is a transmission gate used for dot sequential driving.
[0186]
In addition, when the state shown in FIG. 12D is actually completed, a protective film (laminate film, ultraviolet curable resin film, etc.) or a light-transmitting material having high hermeticity and low degassing so as not to be exposed to the outside air. It is preferable to package (enclose) with a sealing material. At that time, if the inside of the sealing material is made an inert atmosphere or a hygroscopic material (for example, barium oxide) is arranged inside, the reliability of the OLED is improved.
[0187]
In addition, when the airtightness is improved by processing such as packaging, a connector (flexible printed circuit: FPC) for connecting the terminal routed from the element or circuit formed on the substrate and the external signal terminal is attached. Completed as a product. In this specification, such a state that can be shipped is referred to as a light emitting device.
[0188]
Further, according to the steps shown in this embodiment, the number of photomasks necessary for manufacturing a light-emitting device can be suppressed. As a result, the process can be shortened, and the manufacturing cost can be reduced and the yield can be improved.
[0189]
The manufacturing method of the light-emitting device of the present invention is not limited to the manufacturing method described in this embodiment. The light emitting device of the present invention can be manufactured using a known method.
[0190]
This embodiment can be implemented by freely combining with Embodiments 1, 2, and 4.
[0191]
(Example 6)
In the present invention, by using an organic light emitting material that can utilize phosphorescence from triplet excitons for light emission, the external light emission quantum efficiency can be dramatically improved. Thereby, low power consumption, long life, and light weight of the OLED can be achieved.
[0192]
Here, a report of using triplet excitons to improve the external emission quantum efficiency is shown.
(T. Tsutsui, C. Adachi, S. Saito, Photochemical Processes in Organized Molecular Systems, ed. K. Honda, (Elsevier Sci. Pub., 19).
[0193]
The molecular formula of the organic light-emitting material (coumarin dye) reported by the above paper is shown below.
[0194]
[Chemical 1]

[0195]
(M. A. Baldo, D. F. O'Brien, Y. You, A. Shoustikov, S. Sibley, M. E. Thompson, S. R. Forrest, Nature 395 (1998) p. 151.)
[0196]
The molecular formula of the organic light-emitting material (Pt complex) reported by the above paper is shown below.
[0197]
[Chemical 2]

[0198]
(M. A. Baldo, S. Lamansky, P. E. Burrows, M. E. Thompson, S. R. Forrest, Appl. Phys. Lett., 75 (1999) p. 4.) (T. Tsutsui, M.-J. Yang, M. Yahiro, K. Nakamura, T. Watanabe, T. tsuji, Y. Fukuda, T. Wakimoto, S. Mayagi, Jpn. Appl. .)
[0199]
The molecular formula of the organic light-emitting material (Ir complex) reported by the above paper is shown below.
[0200]
[Chemical 3]

[0201]
As described above, if phosphorescence emission from triplet excitons can be used, in principle, it is possible to realize an external emission quantum efficiency that is 3 to 4 times higher than that in the case of using fluorescence emission from singlet excitons.
[0202]
In addition, the structure of a present Example can be implemented in combination with any structure of Example 1- Example 5 freely.
[0203]
(Example 7)
In this example, the appearance of a light emitting device of the present invention will be described with reference to FIG.
[0204]
FIG. 13 is a top view of a light-emitting device formed by sealing an element substrate over which a transistor is formed with a sealing material, and FIG. 13B is a cross-sectional view taken along a line AA ′ in FIG. FIG. 13C is a cross-sectional view taken along line BB ′ of FIG.
[0205]
A sealant 4009 is provided so as to surround the pixel portion 4002 provided over the substrate 4001, the signal line driver circuit 4003, and the first and second scan line driver circuits 4004a and 4004b. In addition, a sealing material 4008 is provided over the pixel portion 4002, the signal line driver circuit 4003, and the first and second scan line driver circuits 4004a and 4004b. Therefore, the pixel portion 4002, the signal line driver circuit 4003, and the first and second scan line driver circuits 4004a and 400b are sealed with a filler 4210 by the substrate 4001, the sealant 4009, and the sealing material 4008. .
[0206]
The pixel portion 4002, the signal line driver circuit 4003, and the first and second scan line driver circuits 4004a and 4004b provided over the substrate 4001 include a plurality of TFTs. In FIG. 13B, typically, a driving TFT (here, an n-channel TFT and a p-channel TFT are illustrated) 4201 included in the signal line driver circuit 4003 formed over the base film 4010 and a pixel The transistor Tr1 4202 included in the portion 4002 is illustrated.
[0207]
In this embodiment, a p-channel TFT or an n-channel TFT manufactured by a known method is used for the driving TFT 4201, and an n-channel TFT manufactured by a known method is used for the transistor Tr1 4202.
[0208]
An interlayer insulating film (planarization film) 4301 is formed over the driving TFT 4201 and the transistor Tr1 4202, and a pixel electrode (anode) 4203 electrically connected to the drain of the transistor Tr1 4202 is formed thereon. As the pixel electrode 4203, a transparent conductive film having a large work function is used. As the transparent conductive film, a compound of indium oxide and tin oxide, a compound of indium oxide and zinc oxide, zinc oxide, tin oxide, or indium oxide can be used. Moreover, you may use what added the gallium to the said transparent conductive film.
[0209]
An insulating film 4302 is formed over the pixel electrode 4203, and an opening is formed over the pixel electrode 4203 in the insulating film 4302. In this opening, an organic light emitting layer 4204 is formed on the pixel electrode 4203. A known organic light emitting material or inorganic light emitting material can be used for the organic light emitting layer 4204. The organic light emitting material includes a low molecular (monomer) material and a high molecular (polymer) material, either of which may be used.
[0210]
As a method for forming the organic light emitting layer 4204, a known vapor deposition technique or coating technique may be used. The structure of the organic light emitting layer may be a laminated structure or a single layer structure by freely combining a hole injection layer, a hole transport layer, a light emitting layer, an electron transport layer, or an electron injection layer.
[0211]
On the organic light emitting layer 4204, a cathode 4205 made of a light-shielding conductive film (typically a conductive film containing aluminum, copper or silver as a main component or a laminated film of these with another conductive film) is formed. The In addition, it is desirable to eliminate moisture and oxygen present at the interface between the cathode 4205 and the organic light emitting layer 4204 as much as possible. Therefore, it is necessary to devise a method in which the organic light emitting layer 4204 is formed in a nitrogen or rare gas atmosphere and the cathode 4205 is formed without being exposed to oxygen or moisture. In this embodiment, the above-described film formation is possible by using a multi-chamber type (cluster tool type) film formation apparatus. The cathode 4205 is given a predetermined voltage.
[0212]
As described above, the OLED 4303 including the pixel electrode (anode) 4203, the organic light emitting layer 4204, and the cathode 4205 is formed. A protective film 4303 is formed on the insulating film 4302 so as to cover the OLED 4303. The protective film 4303 is effective in preventing oxygen, moisture, and the like from entering the OLED 4303.
[0213]
Reference numeral 4005a denotes a lead wiring connected to the power supply line, which is electrically connected to the source region of the transistor Tr1 4202. The lead wiring 4005 a passes between the sealant 4009 and the substrate 4001 and is electrically connected to the FPC wiring 4301 included in the FPC 4006 through the anisotropic conductive film 4300.
[0214]
As the sealing material 4008, a glass material, a metal material (typically a stainless steel material), a ceramic material, or a plastic material (including a plastic film) can be used. As the plastic material, an FRP (Fiberglass-Reinforced Plastics) plate, a PVF (polyvinyl fluoride) film, a mylar film, a polyester film, or an acrylic resin film can be used. A sheet having a structure in which an aluminum foil is sandwiched between PVF films or mylar films can also be used.
[0215]
However, when the emission direction of light from the OLED is directed toward the cover material, the cover material must be transparent. In that case, a transparent material such as a glass plate, a plastic plate, a polyester film or an acrylic film is used.
[0216]
Further, as the filler 4103, in addition to an inert gas such as nitrogen or argon, an ultraviolet curable resin or a thermosetting resin can be used. PVC (polyvinyl chloride), acrylic, polyimide, epoxy resin, silicone resin, PVB (Polyvinyl butyral) or EVA (ethylene vinyl acetate) can be used. In this example, nitrogen was used as the filler.
[0217]
Further, in order to expose the filler 4103 to a hygroscopic substance (preferably barium oxide) or a substance capable of adsorbing oxygen, a recess 4007 is provided on the surface of the sealing material 4008 on the substrate 4001 side to adsorb the hygroscopic substance or oxygen. A possible substance 4207 is arranged. In order to prevent the hygroscopic substance or the substance 4207 capable of adsorbing oxygen from scattering, the concave part cover material 4208 holds the hygroscopic substance or the substance 4207 capable of adsorbing oxygen in the concave part 4007. Note that the concave cover material 4208 has a fine mesh shape, and is configured to allow air and moisture to pass therethrough but not a hygroscopic substance or a substance 4207 capable of adsorbing oxygen. By providing the hygroscopic substance or the substance 4207 capable of adsorbing oxygen, deterioration of the OLED 4303 can be suppressed.
[0218]
As shown in FIG. 13C, a conductive film 4203a is formed so as to be in contact with the lead wiring 4005a at the same time as the pixel electrode 4203 is formed.
[0219]
The anisotropic conductive film 4300 has a conductive filler 4300a. By thermally pressing the substrate 4001 and the FPC 4006, the conductive film 4203a on the substrate 4001 and the FPC wiring 4301 on the FPC 4006 are electrically connected by the conductive filler 4300a.
[0220]
The configuration of the present embodiment can be implemented by freely combining with the configurations shown in Embodiments 1 to 6.
[0221]
(Example 8)
Organic light-emitting materials used for OLEDs are roughly classified into low molecular weight systems and high molecular weight systems. The light emitting device of the present invention can be used with either a low molecular weight organic light emitting material or a high molecular weight organic light emitting material. Moreover, you may use the material (For example, material described in Japanese Patent Application No. 2001-167508 etc.) which cannot be classified into low molecular type and high molecular type.
[0222]
The low molecular weight organic light emitting material is formed by a vapor deposition method. Therefore, it is easy to take a laminated structure, and it is easy to increase efficiency by laminating films having different functions such as a hole transport layer and an electron transport layer. More hole transport layers, electron transport layers, etc. do not necessarily exist clearly. For example, as described in Japanese Patent Application No. 2001-020817, there are one or more layers in a mixed state. Life extension and high luminous efficiency may be achieved.
[0223]
Low molecular weight organic light-emitting materials include aluminum complex Alq with quinolinol as a ligand. ₃ And triphenylamine derivative (TPD).
[0224]
On the other hand, a high molecular organic light emitting material has higher physical strength and higher device durability than a low molecular material. In addition, since the film can be formed by coating, the device can be manufactured relatively easily.
[0225]
The structure of a light emitting element using a high molecular weight organic light emitting material is basically the same as that when a low molecular weight organic light emitting material is used, and is a cathode / organic light emitting layer / anode. However, when forming an organic light emitting layer using a high molecular weight organic light emitting material, it is difficult to form a laminated structure as in the case of using a low molecular weight organic light emitting material. The two-layer structure is famous. Specifically, the structure is cathode / light-emitting layer / hole transport layer / anode. In the case of a light emitting element using a polymer organic light emitting material, Ca can also be used as a cathode material.
[0226]
Note that since the light emission color of the element is determined by the material forming the light-emitting layer, a light-emitting element exhibiting desired light emission can be formed by selecting these. Typical examples of the polymer organic light emitting material that can be used for forming the light emitting layer include polyparaphenylene vinylene, polyparaphenylene, polythiophene, and polyfluorene.
[0227]
Examples of the polyparaphenylene vinylene include poly (paraphenylene vinylene) [PPV] derivatives, poly (2,5-dialkoxy-1,4-phenylene vinylene) [RO-PPV], poly (2- (2′- Ethyl-hexoxy) -5-methoxy-1,4-phenylenevinylene) [MEH-PPV], poly (2- (dialkoxyphenyl) -1,4-phenylenevinylene) [ROPh-PPV] and the like.
[0228]
Examples of polyparaphenylene include derivatives of polyparaphenylene [PPP], poly (2,5-dialkoxy-1,4-phenylene) [RO-PPP], poly (2,5-dihexoxy-1,4-phenylene). ) And the like.
[0229]
The polythiophene series includes polythiophene [PT] derivatives, poly (3-alkylthiophene) [PAT], poly (3-hexylthiophene) [PHT], poly (3-cyclohexylthiophene) [PCHT], poly (3-cyclohexyl). -4-methylthiophene) [PCHMT], poly (3,4-dicyclohexylthiophene) [PDCHT], poly [3- (4-octylphenyl) -thiophene] [POPT], poly [3- (4-octylphenyl) -2,2 bithiophene] [PTOPT] and the like.
[0230]
Examples of the polyfluorene series include polyfluorene [PF] derivatives, poly (9,9-dialkylfluorene) [PDAF], poly (9,9-dioctylfluorene) [PDOF], and the like.
[0231]
Note that when a hole-transporting polymer-based organic light-emitting material is sandwiched between an anode and a light-emitting polymer-based organic light-emitting material, hole injection properties from the anode can be improved. In general, an acceptor material dissolved in water is applied by spin coating or the like. In addition, since it is insoluble in an organic solvent, it can be stacked with the above-described light-emitting organic light-emitting material.
[0232]
Examples of the hole-transporting polymer organic light emitting material include a mixture of PEDOT and camphor sulfonic acid (CSA) as an acceptor material, a mixture of polyaniline [PANI] and polystyrene sulfonic acid [PSS] as an acceptor material, and the like. It is done.
[0233]
In addition, the structure of a present Example can be implemented in combination freely with any structure of Example 1-7.
[0234]
Example 9
Since a light emitting device using an OLED is a self-luminous type, it is superior in visibility in a bright place and has a wide viewing angle as compared with a liquid crystal display. Therefore, it can be used for display portions of various electronic devices.
[0235]
As an electronic device using the light emitting device of the present invention, a video camera, a digital camera, a goggle type display (head mounted display), a navigation system, a sound reproduction device (car audio, audio component, etc.), a notebook type personal computer, a game device, Play back a recording medium such as a portable information terminal (mobile computer, mobile phone, portable game machine or electronic book), an image playback device (specifically, Digital Versatile Disc (DVD)) equipped with a recording medium, A device having a display capable of displaying). In particular, since a wide viewing angle is important for a portable information terminal that often has an opportunity to see a screen from an oblique direction, it is desirable to use a light emitting device. Specific examples of these electronic devices are shown in FIGS.
[0236]
FIG. 14A illustrates an OLED display device which includes a housing 2001, a support base 2002, a display portion 2003, a speaker portion 2004, a video input terminal 2005, and the like. The light emitting device of the present invention can be used for the display portion 2003. Since the light-emitting device is a self-luminous type, a backlight is not necessary and a display portion thinner than a liquid crystal display can be obtained. The OLED display device includes all information display devices such as a personal computer, a TV broadcast receiver, and an advertisement display.
[0237]
FIG. 14B illustrates a digital still camera, which includes a main body 2101, a display portion 2102, an image receiving portion 2103, operation keys 2104, an external connection port 2105, a shutter 2106, and the like. The light emitting device of the present invention can be used for the display portion 2102.
[0238]
FIG. 14C illustrates a laptop personal computer, which includes a main body 2201, a housing 2202, a display portion 2203, a keyboard 2204, an external connection port 2205, a pointing mouse 2206, and the like. The light-emitting device of the present invention can be used for the display portion 2203.
[0239]
FIG. 14D illustrates a mobile computer, which includes a main body 2301, a display portion 2302, a switch 2303, operation keys 2304, an infrared port 2305, and the like. The light emitting device of the present invention can be used for the display portion 2302.
[0240]
FIG. 14E shows a portable image reproducing device (specifically, a DVD reproducing device) provided with a recording medium, which includes a main body 2401, a housing 2402, a display portion A2403, a display portion B2404, and a recording medium (DVD or the like). A reading unit 2405, operation keys 2406, a speaker unit 2407, and the like are included. Although the display portion A 2403 mainly displays image information and the display portion B 2404 mainly displays character information, the light-emitting device of the present invention can be used for the display portions A, B 2403, and 2404. Note that an image reproducing device provided with a recording medium includes a home game machine and the like.
[0241]
FIG. 14F illustrates a goggle type display (head mounted display), which includes a main body 2501, a display portion 2502, and an arm portion 2503. The light emitting device of the present invention can be used for the display portion 2502.
[0242]
FIG. 14G shows a video camera, which includes a main body 2601, a display portion 2602, a housing 2603, an external connection port 2604, a remote control receiving portion 2605, an image receiving portion 2606, a battery 2607, an audio input portion 2608, operation keys 2609, and the like. . The light-emitting device of the present invention can be used for the display portion 2602.
[0243]
Here, FIG. 14H shows a mobile phone, which includes a main body 2701, a housing 2702, a display portion 2703, an audio input portion 2704, an audio output portion 2705, operation keys 2706, an external connection port 2707, an antenna 2708, and the like. The light emitting device of the present invention can be used for the display portion 2703. Note that the display portion 2703 can suppress current consumption of the mobile phone by displaying white characters on a black background.
[0244]
If the light emission luminance of the organic light emitting material is increased in the future, the light including the output image information can be enlarged and projected by a lens or the like and used in a front type or rear type projector.
[0245]
In addition, the electronic devices often display information distributed through electronic communication lines such as the Internet and CATV (cable television), and in particular, opportunities to display moving image information are increasing. Since the organic light emitting material has a very high response speed, the light emitting device is preferable for displaying moving images.
[0246]
In addition, since the light emitting device consumes electric power in the light emitting device, it is desirable to display information so that the light emitting portion is minimized. Therefore, when a light emitting device is used for a display unit mainly including character information, such as a portable information terminal, particularly a mobile phone or a sound reproduction device, it is driven so that character information is formed by the light emitting part with the non-light emitting part as the background. It is desirable to do.
[0247]
As described above, the applicable range of the present invention is so wide that it can be used for electronic devices in various fields. In addition, the electronic device of this embodiment may use the light emitting device having any structure shown in Embodiments 1 to 8.
[0248]
【The invention's effect】
With the switch element of the present invention, the area of the switch element can be reduced, and the pixel can be made high definition or highly functional.
[0249]
Further, in the light emitting device of the present invention using the switch element, even if the characteristics of the transistor Tr1 that controls the current flowing through the OLED are different among the pixels, the magnitude of the current flowing through the OLED varies between the pixels. Can be prevented, and uneven brightness can be suppressed. Further, the area of the pixel circuit can be reduced, and as a result, the aperture ratio can be increased, so that power saving and the reliability of the light emitting device can be improved.
[0250]
Furthermore, the light-emitting device of the present invention using the switch element can obtain a certain luminance regardless of temperature change. Further, in color display, even when an OLED having a different organic light emitting material for each color is provided, it is possible to prevent a desired color from being obtained because the luminance of the OLED of each color varies with temperature.
[Brief description of the drawings]
FIG. 1 shows a structure of a transistor of the present invention.
FIG. 2 is a block diagram of a light emitting device of the present invention.
FIG. 3 is a circuit diagram of a pixel of the light emitting device of the present invention.
FIG. 4 is a timing chart of signals input to scanning lines.
FIG. 5 is a schematic diagram of a pixel in driving.
FIG 6 is a diagram showing a structure of a transistor of the present invention.
FIG. 7 illustrates a structure of a transistor of the present invention.
FIG. 8 illustrates a structure of a transistor of the present invention.
FIG. 9 is a detailed diagram of a signal line driver circuit in an analog driving method.
FIG. 10 is a block diagram of a scan line driver circuit.
11A to 11C illustrate a method for manufacturing a light-emitting device of the present invention.
12A to 12C illustrate a method for manufacturing a light-emitting device of the present invention.
13A and 13B are an external view and a cross-sectional view of a light-emitting device of the present invention.
14 is a diagram of an electronic device using the light-emitting device of the present invention. FIG.
15A and 15B are a circuit diagram and a top view of a conventional transistor.

Claims (2)

A light emitting device having a switch element, a first transistor, a second transistor, an organic light emitting element, a signal line, and a power line,
The switch element includes an active layer, a gate insulating film in contact with the active layer, and a gate electrode in contact with the gate insulating film,
The active layer has a channel formation region and three impurity regions,
The channel formation region and the gate electrode overlap with the gate insulating film interposed therebetween,
The three impurity regions are in contact with the channel formation region;
One of the three impurity regions is connected to the signal line, one is connected to a gate electrode of the first transistor, and one is connected to a drain region of the first transistor. And
One of the source region and the drain region of the second transistor is connected to the power supply line, and the other is connected to the drain region of the first transistor,
The light emitting device, wherein a source region of the first transistor is connected to a pixel electrode of the organic light emitting element. A light emitting device having a switch element, a first transistor, a second transistor, an organic light emitting element, a signal line, a power supply line, a first scanning line, and a second scanning line,
The switch element includes an active layer, a gate insulating film in contact with the active layer, and a gate electrode in contact with the gate insulating film,
The active layer has a channel formation region and three impurity regions,
The channel formation region and the gate electrode overlap with the gate insulating film interposed therebetween,
The three impurity regions are in contact with the channel formation region;
One of the three impurity regions is connected to the signal line, one is connected to a gate electrode of the first transistor, and one is connected to a drain region of the first transistor. And
A gate electrode of the switch element is connected to the first scanning line;
A gate electrode of the second transistor is connected to the second scanning line;
One of the source region and the drain region of the second transistor is connected to the power supply line, and the other is connected to the drain region of the first transistor,
The light emitting device, wherein a source region of the first transistor is connected to a pixel electrode of the organic light emitting element.

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