JP2004134508A - Vertical organic transistor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a highly integrated device or an organic device showing great flexibility as it is formed on a plastic board by manufacturing a device organic material independent of crystallinity even in a density increase of the device and fine processing of 0.1 μm or below. <P>SOLUTION: A vertical field-effect transistor three-terminal organic electronic device is manufactured. The device is equipped with, at least, a first and a second electrode formed on an optional board, a monomolecular film or a monomolecular cumulative film which contains a plurality of conductive conjugate bonded groups and polar functional groups is oriented nearly in parallel in the direction of a line drawn between the first and the second electrode, and a third electrode coming into direct or indirect contact with the polymerized monomolecular film or the polymerized monomolecular cumulative film. Even a low-molecular organic thin film or a high-molecular organic thin film other than the monomolecular film can be obtained. <P>COPYRIGHT: (C)2004,JPO

Description

【００３３】
次に、単分子膜を形成する部分を残してレジストパターンでカバー形成した絶縁性のガラス基板１を前記吸着液に浸漬して前記レジストパターン開口部に選択的に化学吸着を行い、さらに表面に残った未反応の前記物質をクロロフォルムで洗浄除去し、続いて前記レジストパターンを除去して、前記物質よりなる単分子膜２を選択的に形成した。このとき、レジスト開口部のガラス基板表面には活性水素を含む水酸基が多数存在するので、前記物質の−ＳｉＣｌ基が水酸基と脱塩酸反応を生じて基板表面に共有結合した（化２）で構成される単分子膜２が形成された（図２）。
【００３４】
【化２】

【００３５】
次に、液晶配向膜作製に使用するラビング装置３を使用し、レーヨン製ラビング布４（吉川加工（株）製：ＹＡ−２０−Ｒ）で、押し込み深さ０．３ｍｍ、ニップ幅１１．７ｍｍ、回転数１２００回転、テーブルスピード４０ｍｍ／ｓｅｃの条件で第１電極から第２電極に向かう方向と平行に縦方向にラビングした（図３）。このことにより、前記単分子膜を構成する化学吸着された分子（化２）は、ラビング方向に沿って配向された。
【００３６】
なお、ここでのラビング処理は単分子膜形成後に行ったが、単分子膜形成前、すなわち、基板表面を予め同様の条件でラビングし、その後、その表面に単分子膜を形成しても同様に配向した単分子膜が得られた。ただしこの場合、レジスト除去後、もう一度単分子膜形成後と同様にクロロフォルム洗浄を行い、さらにラビング方向と略平行に基板を立てながら引き上げて液切りを行うと、液切り方向と反対方向に配向し、より配向性に優れた単分子膜が得られた。
【００３７】
次に、基板の配向処理された化学吸着単分子膜２ａ上全面にニッケル薄膜を蒸着形成し、ホトリソ法を用いてギャップ間距離が１０ミクロンで長さが３０ミクロンの第１電極８を形成し、その後、ゲート絶縁膜を成膜して再度ニッケル薄膜を第２電極９として成膜し、最後にこれらの堆積した膜をドライエッチングでエッチングして形成した。このように、任意の基板上に形成された第１の電極と第２の電極と、前記第１の電極と第２の電極の間を接続する方向と略平行に配向させた複数の導電性共役結合基と光応答性の官能基を含む単分子膜または単分子累積膜を備えた３端子有機電子デバイスを製造した（図４）。
【００３８】
このデバイスでは、前記第１の電極と第２の電極間は、導電性のポリアセチレン結合基で接続されているので、電極間に数Ｖ電圧を印加すると、数ｍＡ電流（１Ｖで１００ｎＡ程度）が流れた。この値は、無配向で重合した場合のおよそ５０倍であった。
【００３９】
次に、前記状態で、前記電極間の単分子膜に紫外線（光１０）を照射すると、前記アゾ基がシス転移して、電流がほぼ０となった。またその後、可視光線（光１０）を照射すると、前記アゾ基がトランス転移して元の導電性が再現された（図５）。このような電極間の導電性の低下は、アゾ基の光異性化（トランス型からシス型への転移）により、単分子膜内の分子配向がひずみ、ポリアセチレン結合基の共役度が低下することにより生じるものと考えられる。
【００４０】
このように、光照射により、前記共役結合の共役度を制御して第１の電極と第２の電極間に流れる電流をスイッチング制御できた。
【００４１】
なお、ポリアセチレン基を導電性基として用いる場合、重合度が低いと抵抗が高くなる。すなわち、オン電流が低くなるが、その場合には電荷移動性の官能基を有するドーパント物質（例えば、アクセプタ分子としてハロゲンガスやルイス酸、ドナー分子としてアルカリ金属やアンモニウム塩）を表面に拡散する、すなわちドーピングすることで、オン電流を大きくできた。ちなみに、この被膜にヨウ素をドープした場合、１Ｖの電圧印加で０．２ｍＡの電流が流れた。
【００４２】
ここで、基板として金属などの導電性の基板を用いる場合には、導電性の基板表面に絶縁性の薄膜を介して単分子膜を形成しておけばよい。なお、このような構造では基板自体が帯電することがないので、デバイスの動作安定性が向上した。
【００４３】
また、より大きなオン電流を必要とする場合には、電極間距離を小さくするか、電極幅を広げればよい。さらに大きなオン電流を必要とする場合には、単分子膜を累積しておけばよい。
【００４４】
上記実施の形態１では、導電性の共役結合基の作製に触媒重合法を用いたが、電解重合、あるいは光や電子線、Ｘ線などのエネルギービーム照射により、同様の導電性の共役結合基を作製できた。また、導電性の共役結合基としてポリアセチレン基以外に、ポリジアセチレン基、ポリアセン基、ポリピロール基、ポリチェニレン基が利用できた。なお、触媒重合法には、重合性基として前記アセチレン基以外にピロール基、チェニレン基、ジアセチレン基等が適していた。
【００４５】
さらに、単分子膜または単分子累積膜の作製には、化学吸着法以外に、ラングミュアーブロジェット法を使用できた。また、単分子膜または単分子累積膜を重合して導電性の共役結合基を生成する工程の前に、第１及び第２電極を形成する工程を行うと、共役結合基の作製に際して、第１及び第２電極を電解重合に利用できた。すなわち、電解重合性の官能基としてピロール基またはチェニレン基を含む単分子膜または単分子累積膜を用い、第１及び第２電極の間に電流を流して第１及び第２電極間の薄膜を選択的に電解重合できた。さらにまた、ポリピロール基またはポリチェニレン基を含む単分子膜を形成した後、あるいは、ピロール基またはチェニレン基を含む単分子膜を形成した後、ピロール基またはチェニレン基を含む物質を溶かした有機溶媒中で、第１及び第２電極間に電流を流して、ポリピロール基またはポリチェニレン基を含む単分子膜表面にポリピロール基またはポリチェニレン基を含む被膜を形成すると導電領域の厚さを厚くできた。
【００４６】
また、重合性基としてエネルギービームにより重合する官能基であるアセチレン基やジアセチレン基等を含む単分子膜または単分子累積膜を用い、紫外線、遠紫外線、電子線またはＸ線等のエネルギービームを照射することで共役結合基を生成できた。
【００４７】
なお、使用する物質は、一般に（化３）で示される物質なら、本実施の形態１において同様に使用できた。
【００４８】
【化３】

【００４９】
ここで、
Ａは重合して導電性の共役結合基になる官能基
Ｂは光応答性の官能基
Ｄは基板表面の活性水素と反応する官能基
Ｅは水素、メチル基、エチル基、メトキシ基、エトキシ基、アルキル基等の他の官能基
ｍ、ｎは整数であり、ｍ＋ｎは２以上２５以下、特に１０〜２０が良かった。
【００５０】
ｐは１、２、または３である。
【００５１】
さらに詳しくは、（化４）〜（化７）で表される物質等が使用できた。
【００５２】
【化４】

【００５３】
【化５】

【００５４】
【化６】

【００５５】
【化７】

【００５６】
ここで、ｍ、ｎは整数であり、ｍ＋ｎは２以上２５以下である。
【００５７】
（実施の形態２）
例えば、予め、電解重合して導電性の共役結合基になるピロール基（Ｃ_４Ｈ_４Ｎ−）と有極性の官能基であるオキシカルボニル基（−ＯＣＯ−）と基板表面の活性水素（例えば、水酸基（−ＯＨ））と反応するクロロシリル基（−ＳｉＣｌ）を含む物質（化８）を用い、脱水したジメチルシリコーン系の有機溶媒で１％に薄めて化学吸着液を調製した。
【００５８】
【化８】

【００５９】
次に、絶縁性のポリイミド基板１１（あるいは導電性のメタル基板表面に絶縁性の薄膜、例えばシリカ被膜１２を介してでも良い）を用いて、その上に横方向選択線１３（第２電極にもなる）にゲート絶縁膜６のゲート長が１００ｎｍ（厚み）で幅が４０ミクロンになるようなスイッチング素子をドライエッチングで形成し、さらに前記Ａｌパターン（第１電極：ソース部、縦方向選択線１４）を形成し、７つの有機トランジスタを並べた（図６）。
【００６０】
次に、単分子膜を形成するために、前記吸着液に浸漬して前記絶縁膜に選択的に化学吸着を行い、さらに表面に残った未反応の前記物質をクロロフォルムで洗浄除去し、続いて前記レジストパターンを除去して、前記物質よりなる単分子膜１５を選択的に形成した（図７）。
【００６１】
このとき、用いた絶縁膜の側壁表面（シリカ被膜およびＡｌ_２Ｏ_３表面）には活性水素を含む水酸基が多数存在するので、前記物質の−ＳｉＣｌ基が水酸基と脱塩酸反応を生じて基板表面に共有結合した（化９）で示される分子で構成された単分子膜１５が形成された。
【００６２】
【化９】

【００６３】
その後、もう一度単分子膜形成後と同様にクロロフォルム洗浄を行い、さらに第１電極から第２電極に向かう方向と平行に基板を立てながら引き上げて液切りを行うと、第１電極から第２電極に向かって一次配向した単分子膜１５ａが得られた。
【００６４】
次に、アセトニトリル中で第１及び第２電極間に５Ｖ／ｃｍ程度の電界を印加し、電流を流して電解重合することで、導電性の共役結合基で第１電極１４及び第２電極１６間を接続するように生成した。このとき、重合された共役結合基は、電界方向に沿ってつながって行くので、完全に重合が終われば、第１及び第２電極は導電性の共役結合基１８で自己組織的に接続される（図１）。
【００６５】
最後に、第３の電極を基板側から取り出して、任意の基板上に形成された第１の電極と第２の電極と、前記第１の電極と第２の電極の間を接続する方向と略平行に配向させた複数の導電性共役結合基と有極性の官能基を含む単分子膜または単分子累積膜と、前記重合した単分子膜または単分子累積膜に直接または間接に接触した第３の電極を備えた３端子有機電子デバイスを製造した。
【００６６】
このデバイスでは、前記第１の電極と第２の電極間は、導電性のポリピロール結合基で接続されているので、ＢＦ⁻イオンをドープすると電極間に１Ｖの電圧を印加して１ｍＡ程度の電流が流れた。
【００６７】
次に、前記状態で、前記第３電極と第１電極の間に５Ｖの電圧を印加すると第１及び第２の電極間の電流がほぼ０となった。またその後、５Ｖの印加電圧を０Ｖにもどすと元の導電性が再現された。このような電極間の導電性の低下は、第３電極と第１電極の間に５Ｖの電圧を印加した際、有極性の官能基であるオキシカルボニル基（−ＯＣＯ−）の分極が進むことにより、単分子膜がひずみ、ポリピロール結合基の共役度が低下することにより生じるものと考えられる。
【００６８】
このように、第３の電極に電圧を印加することで、前記共役結合の共役度を制御して第１の電極と第２の電極間に流れる電流をスイッチング制御できた。
【００６９】
本実施の形態２において、第１電極から第２電極に向かう方向と平行に基板を立てながら引き上げて液切りを行った後、さらに第１電極から第２電極に向かう方向と平行方向に偏光した可視光１９を５００ｍＪ／ｃｍ^２程度照射すると、立てながら引き上げて液切りを行うだけに比べてさらに配向性に優れた単分子膜が得られた。また、このとき、偏光方向を第１電極から第２電極に向かう方向と４５°で交差する方向に設定して同様の照射を行うと、前記単分子膜を構成する分子は、当初の引き上げ方向から動き、前記偏光照射方向と略平行方向に配向した。すなわち、偏光照射を行うと、単分子膜を構成する分子が偏光方向に配向することが確認できた（図８）。
【００７０】
さらに、このように配向した状態で重合して共役結合基を生成すると、より導電性に優れた被膜を形成できた。
【００７１】
ここで、有極性の官能基が電界印加により分極するオキシカルボニル基であると、スイッチングを極めて高速で行えた。オキシカルボニル基以外に、カルボニル基等の官能基が使用できた。
【００７２】
さらにまた、導電性の共役結合基としてポリアセチレン基、ポリジアセチレン基、ポリアセン基、ポリピロール基、ポリチェニレン基が使用でき、導電度が高かった。
【００７３】
また、導電性の共役結合基を生成する物質として、電解重合性の官能基であるピロール基以外に、チェニレン基が利用できた。なお、重合方法を変えれば、アセチレン基、ジアセチレン基を含む物質も利用できた。
【００７４】
また、単分子膜または単分子累積膜の作製には、化学吸着法以外に、ラングミュアーブロジェット法が使用できた。
【００７５】
また、重合性基としてピロール基、チェニレン基、アセチレン基、ジアセチレン基等の触媒重合性の官能基を含む単分子膜または単分子累積膜を用いれば、触媒重合にて共役結合基を生成できた。また、重合性基としてアセチレン基、ジアセチレン基等のエネルギービームにより重合する官能基を含む単分子膜または単分子累積膜を用い、紫外線、遠紫外線、電子線またはＸ線等のエネルギービームを照射して共役結合基を生成することで有機電子デバイスを製造できた。
【００７６】
（実施の形態３）
従来の半導体装置に形成される薄膜トランジスタ（ＴＦＴ）は、非晶質シリコンを活性層とする構造が一般的であったが、非晶質シリコンＴＦＴはキャリア移動度が低く十分な動作特性を備えていないため、最近では有機ＴＦＴが注目されている。有機ＴＦＴは、非晶質シリコンＴＦＴに比べて製造コストが安く、動作特性にも優れており、画素スイッチング用としてだけでなく、周辺駆動回路のデバイスとして使用することも将来可能になると考えられている。そこで、今回発明した有機ＴＦＴの製造においては、室温プロセスで製造出来るので、基板に温度に弱いプラスティックを用いても問題ない。
【００７７】
有機ＴＦＴの一例を図４に示す。同図に示すように、絶縁性のガラス基板１に単分子膜２ａが形成され、この単分子膜２ａの上にドレイン電極９、ゲート絶縁膜６、ソース電極８が形成され、ゲート絶縁膜６の側壁に主になる有機半導体薄膜（活性層）２０が形成されている。この有機半導体薄膜２０とは、チャネル領域であり、ソース領域（第１電極８）・ドレイン領域（第２電極９）とを有している。
【００７８】
有機半導体薄膜２０はゲート絶縁膜６の側壁を覆ってチャネル領域となっているので、有機膜を用いたトランジスタの場合、特にソース・ドレイン領域に接続させるためのコンタクトホールを形成する必要もない。つまり、通常のトランジスタと違い、ソース、ドレイン電極と直接コンタクト（接触）できるようになっている。
【００７９】
ところが、多結晶シリコンＴＦＴなどを用いたＴＦＴでは、半導体薄膜中の結晶粒界に高密度のトラップ準位が存在し、このトラップを介してキャリアが移動する。このため、ゲート電圧Ｖ_ＧＳが負の領域においても、ゲート電圧Ｖ_ＧＳの絶対値の増加と共にドレイン電流Ｉ_Ｄが増加する。この現象は、オフ状態でのリーク電流であるオフ電流がゲート電圧依存性を有することを意味するものであり、トランジスタの特性としては好ましくない。また、オフ電流自体を更に低減させることも必要である。例えば、アクティブマトリックス型の液晶表示装置に使用される多結晶シリコンＴＦＴはゲート逆バイアス下で用いられるため、オフ電流が大きくなるとデータの保持特性が悪化するという問題が生じる。即ち、コンデンサに書き込まれたデータは、書き込み時間よりもはるかに長時間保持される必要があるが、コンデンサの静電容量が小さいため、ＴＦＴのオフ状態におけるオフ電流により、ドレインの電位（すなわち、コンデンサの電位）は急激にソースの電位に近づき、書き込まれたデータが正しく保持されなくなる。オフ電流の増大に伴う問題は、液晶表示装置だけの問題ではなく他の半導体装置においても生じ、例えば、通常のロジック回路においては静止電流の増加を招き、メモリ回路の場合は誤動作の原因となる。
【００８０】
そこで、オフ電流を低減するため、チャネル領域に不純物を導入してｐ⁻にすることも知られている。しかし、打ち込まれた不純物は比較的低濃度であることが要求されるのに対し、従来の低温プロセスにおいてはこのような濃度調整が難しく、実現は困難であった。また、同様の理由から閾値電圧Ｖｔｈの制御が十分に行われず、更には半導体薄膜が初期から不純物により汚染されている場合もあるため、大面積の絶縁基板上におけるＴＦＴの動作特性が不均一であるという問題を有していた。例えば、液晶表示装置の場合、閾値電圧Ｖｔｈがデプレッション側に振れるとオフ電流が増大して、画素の輝点欠陥になるという問題が生じる。
【００８１】
このような課題を解決した有機ＴＦＴの代表的な特性を図９に示す。同図は、ドレイン電圧Ｖ_ＤＳが４Ｖにおけるゲート電圧Ｖ_ＧＳに対するドレイン電流Ｉ_Ｄの関係を示すグラフである。ドレイン電流Ｉ_Ｄは、ゲート電圧Ｖ_ＧＳが０Ｖの近傍で最小値となり、ゲート電圧Ｖ_ＧＳが増加するにつれてドレイン電流Ｉ_Ｄも増加する。ゲート電圧Ｖ_ＧＳの値が正の領域におけるドレイン電流Ｉ_Ｄの増加は、トランジスタのオフ状態からオン状態への変化を意味するものであるから、電流の増加率はできる限り大きいことが望ましい。例えば、液晶表示装置に使用する場合、液晶の表示はコンデンサの電位により決定されるため、短時間にデータを書き込むことができるようにＴＦＴには十分な電流（オン電流）を流す必要がある。今回発明した縦型有機ＴＦＴの場合、半導体薄膜におけるキャリア移動度が大きくなっているため、十分なオン電流を供給できる点については特に問題がない。
【００８２】
このように、今回発明した縦型電界効果トランジスタである有機ＴＦＴは上記に示した多結晶シリコンＴＦＴでの問題を発生することなくよい動作を示した。
【００８３】
（実施の形態４）
近年において、有機ＥＬ素子を用いた表示装置が開発されている。有機ＥＬ素子を多数使用した有機ＥＬ素子装置をアクティブマトリックス回路により駆動する場合、各ＥＬのピクセル（画素）には、このピクセルに対して供給する電流を制御するための薄膜トランジスタ（ＴＦＴ）の如きＦＥＴ（電界効果トランジスタ）が一組ずつ接続されている。すなわち、有機ＥＬ素子に駆動電流を流すバイアス用のＴＦＴと、そのバイアス用ＴＦＴを選択すべきかを示すスイッチ用のＴＦＴが一組ずつ接続されている。
【００８４】
従来のアクティブマトリックス型の有機ＥＬ表示装置の回路図の一例を図１０に示す。この有機ＥＬ表示装置は、Ｘ方向信号線３０１−１、３０１−２・・・、Ｙ方向信号線３０２−１、３０２−２・・・電源Ｖｄｄ線３０３−１、３０３−２・・・、スイッチ用ＴＦＴトランジスタ３０４−１、３０４−２・・・、電流制御用ＴＦＴトランジスタ３０５−１、３０５−２・・・、有機ＥＬ素子３０６−１、３０６−２・・・、コンデンサ３０７−１、３０７−２・・・、Ｘ方向周辺駆動回路３０８、Ｙ方向周辺駆動回路３０９等により構成される。
【００８５】
Ｘ方向信号線３０１、Ｙ方向信号線３０２により画素が特定され、その画素においてスイッチ用ＴＦＴトランジスタ３０４がオンされてその信号保持用コンデンサ３０７に画像データが保持される。これにより、電流制御用のＴＦＴトランジスタ３０５がオンされ、電源Ｖｄｄ線３０３より有機ＥＬ素子３０６に画像データに応じたバイアス用の電流が流れ、これが発光する。
【００８６】
例えば、Ｘ方向信号線３０１−１に画像データに応じた信号が出力され、Ｙ方向信号線３０２−１にＹ方向走査信号が出力されると、これにより特定された画素のスイッチ用ＴＦＴトランジスタ３０４−１がオンになり、画像データに応じた信号により電流制御用ＴＦＴトランジスタ３０５−１が導通されて有機ＥＬ素子３０６−１に、この画像データに応じた発光電流が流れ、発光制御する。
【００８７】
このように、一画素毎に、薄膜型のＥＬ素子と、前記ＥＬ素子の発光制御用の電流制御用ＴＦＴトランジスタと、前記電流制御用ＴＦＴトランジスタのゲート電極に接続された信号保持用のコンデンサと、前記コンデンサへのデータ書き込み用のスイッチ用ＴＦＴトランジスタ等を有するアクティブマトリックス型ＥＬ画像表示装置において、ＥＬ素子の発光強度は、信号保持用のコンデンサに蓄積された電圧によって制御された発光電流制御用の非線形素子であるＴＦＴトランジスタに流れる電流で決定される（Ａ６６−ｉｎ　２０１ｐｉ　Ｅｌｅｃｔｒｏｌｕｍｉｎｅｓｃｅｎｔ　Ｄｉｓｐｌａｙ　Ｔ．ｐ．Ｂｒｏｄｙ、Ｆ．Ｃ．Ｌｕｏ、ｅｔ．ａｌ．、ＩＥＥＥ　Ｔｒａｎｓ．Ｅｌｅｃｔｒｏｎ　Ｄｅｖｉｃｅｓ、Ｖｏｌ．ＥＤ−２２、Ｎｏ．９、Ｓｅｐ．１９７５、ｐ７３９〜ｐ７４９参照）。
【００８８】
このとき使用される信号保持用のコンデンサの容量は微少な選択時間内で画素スイッチ用ＴＦＴトランジスタが十分に電荷を充電できる容量以下であり、またこの画素スイッチ用ＴＦＴトランジスタの非選択時のリーク電流が次の書き込み時間まで失わせる電荷により発生するコンデンサの保持電圧の低下が表示パネルの画像に悪影響を与えない容量以上であることが求められる。
【００８９】
アクティブマトリックスの表示装置は、その視認性から拡大投影を行う光学系を用いない場合は、４インチ以上の画角が要求される。このサイズの表示面をシリコン単結晶基板上に構成することは、現在の単結晶Ｓｉ基板の製作技術では１枚の単結晶基板から得られる枚数が非常に少ないため大変なコストがかかってしまう。
【００９０】
そこで、アクティブマトリックスの表示装置に、フレキシブル基板等の平面基板上に作成した有機膜半導体層を用いた本発明の縦型有機薄膜トランジスタ（ＴＦＴ）を使用することで上記のような問題が解決され、低コストで製作できるようになる。
【００９１】
また、平面基板上に形成される半導体層は大面積のものが比較的容易に成膜できることから、アモルファスＳｉ膜（以下、ａ−Ｓｉ膜という）を用いることが一般的である。しかし、ａ−Ｓｉ膜で形成されたＴＦＴは一方向に定常的に電流を流し続けると、閾値がドリフトして電流値が変わり、画質に変動が生ずる。しかも、ａ−Ｓｉ膜では移動度が小さいため高速応答でドライブできる電流にも限界があり、またＰチャネルの形成が困難なところより、小規模なＣＭＯＳ回路の構成さえも困難である。
【００９２】
そこで、本発明によれば平面基板上に形成される大面積の縦型有機半導体層を比較的容易に成膜できることから、アクティブマトリックス型有機ＥＬ画像表示装置の半導体層としては、比較的大面積化が容易でかつ高信頼性で移動度も高く、ＣＭＯＳ回路の形成も可能な有機膜を活性層として、かつ活性層に流れる電流を基板に垂直に流すように設計してあるため、基板面積に対して縦型電界効果トランジスタの占める割合が小さく済むために大面積に高解像度画素を持つ有機ＥＬディスプレイを作製することが可能となる。
【００９３】
【発明の効果】
以上のように、本発明によれば、
任意の基板上に形成された第１の電極と第２の電極と、前記第１の電極と第２の電極の間を接続する方向と略平行に配向させた複数の導電性共役結合基と有極性の官能基を含む単分子膜または単分子累積膜と、前記重合した単分子膜または単分子累積膜に直接または間接に接触した高性能な第３の電極を備えた高性能な縦型電界効果トランジスタ（３端子有機電子デバイス）を提供できる。また、単分子膜以外に低分子有機薄膜や高分子有機薄膜も提供できる。
【００９４】
これにより、低コストでかつ大面積に高解像度画素を持つ有機ＥＬディスプレイを作製することが可能となる。
【図面の簡単な説明】
【図１】本発明の実施の形態２における重合方法の一例図
【図２】本発明の実施の形態１において単分子膜を形成した状態を分子レベルまで拡大した断面概念図
【図３】本発明の実施の形態１においてラビングにより単分子膜を構成する分子を配向させる工程を説明する概念図
【図４】本発明の実施の形態１において完成されたデバイスを分子レベルまで拡大した断面概念図
【図５】本発明の実施の形態１における紫外線や可視光線をあてて有機膜を重合する工程図
【図６】本発明の実施の形態２において第３の電極を形成した状態を拡大した断面概念図（有機膜なし）
【図７】本発明の実施の形態２において第３の電極を形成した状態を拡大した断面概念図（有機膜あり）
【図８】本発明の実施の形態２において偏光照射により、単分子膜を構成する分子を配向させる工程を説明する断面概念図
【図９】従来の薄膜トランジスタのゲート電圧Ｖ_ＧＳとドレイン電流Ｉ_Ｄとの関係を示す図
【図１０】従来のアクティブマトリックス型の有機ＥＬ表示装置の回路図
【図１１】Ｓｉ系トランジスタを用いた従来例を示す図
【図１２】縦型Ｓｉ系トランジスタを用いた従来例を示す図
【符号の説明】
１　ガラス基板
２　アセチレン基とアゾ基を含む化学吸着単分子膜
２ａ　配向処理された化学吸着単分子膜
３　ラビング装置
４　ラビング布
５　導電性のポリアセチレン型共役結合基
６　ゲート絶縁膜
７　アゾ基
８　第１電極（ソース電極）
９　第２電極（ドレイン電極）
１０　スイッチング用に集光された光（紫外線、可視光線）
１１　ポリイミド基板
１２　シリカ被膜
１３　横方向選択線（第２電極）
１４　縦方向選択線（第１電極）
１５　ピロール基とオキシカルボニル基を含む単分子膜
１５ａ　配向処理された単分子膜
１６　第１電極
１７　第２電極
１８　導電性のポリピロール型共役結合基
１９　可視光
２０　活性層（有機半導体薄膜）
５１　シリコン基板
５２　ゲート絶縁膜
５３　フィールド酸化膜
５４　ゲート電極
５５　低濃度拡散層
５６　スペーサ
５７　ソース電極
５８　ドレイン電極
６１　シリコン基板
６２　シリコン柱
６３　酸化膜
６４　Ｎ＋ポリシリコン層
６４ａ　ゲート電極
６５　ドレイン電極
６６　ソース電極
３０１　Ｘ方向信号線
３０２　Ｙ方向信号線
３０３　電源Ｖｄｄ線
３０４　スイッチ用ＴＦＴトランジスタ
３０５　電流制御用ＴＦＴトランジスタ
３０６　有機ＥＬ素子
３０７　コンデンサ
３０８　Ｘ方向周辺駆動回路
３０９　Ｙ方向周辺駆動回路[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a vertical field effect transistor (organic electronic device) using a low molecular weight organic film, a high molecular weight organic film, and a coating containing a conductive conjugated group.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, an inorganic semiconductor material is used for an electronic device, as represented by a silicon crystal. At present, in a general metal oxide semiconductor (hereinafter abbreviated as MOS) type integrated circuit, a planar MOS transistor having a channel formed in the same direction (horizontal direction) as the direction of the surface of a semiconductor substrate is used. I have. In order to improve the degree of integration of an integrated circuit, it is necessary to reduce the area occupied by each element. In order to reduce the occupied area in the planar MOS transistor, it is necessary to shorten the channel length and the channel width. However, doing so causes many problems such as a short channel effect, deterioration due to hot carriers, and a reduction in current driving capability. Therefore, there is a limit to effectively reducing the occupied area by reducing the channel length and channel width.
[0003]
FIG. 11 is a manufacturing process diagram of a planar transistor having a normal LDD structure. Hereinafter, a method of manufacturing a planar transistor having an LDD structure will be described with reference to FIG.
[0004]
As shown in FIGS. 11A and 11B, a field oxide film 53, a gate insulating film 52, and a gate electrode 54 are formed on a silicon substrate 51 by a normal MOSFET manufacturing process.
[0005]
Next, as shown in FIG. 11C, a low concentration diffusion layer 55 is formed by ion implantation. Further, after forming the spacers 56 with the silicon oxide film, as shown in FIG. 11D, the source electrode 57 and the drain electrode 58 are formed by ion implantation. Thus, the low concentration diffusion layer 55 is provided at the source end and the drain end, so that the withstand voltage between the source and the drain is improved.
[0006]
However, as shown in FIG. 12, in the above conventional method for manufacturing a vertical transistor, the N + polysilicon layer 64 formed on the silicon pillar 62 is entirely etched to form the gate electrode 64a. Therefore, the gate electrode 64a in the obtained vertical transistor is formed in a very thin film shape on the side wall of the silicon pillar 62. For this reason, wiring must be performed to the gate electrode 64a having a very thin film, and there is a problem that it is extremely difficult to contact the gate electrode 64a. Further, the vertical transistor manufactured by the above-described conventional method of manufacturing a vertical transistor has a problem that the withstand voltage between the source and the drain is reduced as the channel length is reduced.
[0007]
Here, as one of the devices which realizes the above-described highly integrated and fully depleted device at once, there is a vertical transistor having a channel in a direction perpendicular to the semiconductor surface. This vertical transistor is manufactured by the following manufacturing process. Hereinafter, a method for manufacturing a conventional vertical transistor will be described with reference to FIG.
[0008]
As shown in FIGS. 12A and 12B, a silicon pillar 61 is formed by etching a silicon substrate 61 using an etching mask (not shown) formed by fine processing by photolithography. Next, as shown in FIG. 12C, after an oxide film 63 is formed on the silicon pillar 62 by thermal oxidation or vapor deposition, an N + polysilicon layer 64 is formed by vapor deposition.
[0009]
Then, the N + polysilicon layer 64 is entirely etched by a reactive ion etching (RIE) method, thereby forming a gate electrode 64a around the silicon pillar 62 as shown in FIG.
[0010]
Next, as shown in FIG. 12E, a drain electrode 65 and a source electrode 66 are formed by ion implantation. After that, a vertical transistor is formed by the same steps as those for manufacturing a normal MOS transistor. The vertical transistor manufactured in this manner has a feature that the vertical transistor occupies a small area because it is a vertical transistor, and that good characteristics can be obtained because the gate electrode 64a surrounds the periphery of the silicon pillar 62. (For example, see Patent Documents 1, 2, and 3).
[0011]
[Patent Document 1]
JP-A-5-129335
[Patent Document 2]
JP-A-5-21790
[Patent Document 3]
JP-A-9-45899
[0012]
[Problems to be solved by the invention]
On the other hand, SOI (semiconductor thin film on insulator) technology is one of the methods for solving the problems caused by miniaturization of integrated circuits as described above. In other words, the thickness of the SOI island (partially patterned island-shaped SOI) is made extremely thin to completely deplete the substrate, thereby suppressing the short channel effect and improving the characteristics. ing.
[0013]
However, in the above-described conventional method for manufacturing a vertical transistor, the formation of the silicon pillar 62 depends on an etching mask formed by fine processing by photolithography. The thickness cannot be reduced below a certain limit. Therefore, in the vertical transistor formed as described above, when a voltage is applied to the opposing gate electrodes 64a, a P-type silicon portion is formed between the depletion layers formed on both sides of the silicon pillar 62. There remains a problem that the silicon pillar 62 cannot be completely depleted and the original purpose cannot be achieved.
[0014]
Therefore, an object of the present invention is to provide a method of manufacturing a vertical transistor capable of manufacturing an ultrafine vertical transistor having high characteristics without being affected by the limitations of photolithography.
[0015]
The present invention provides a highly integrated device by manufacturing a device using an organic material which is not affected by crystallinity even if the device density is advanced and fine processing of 0.1 μm or less is performed. The purpose is to do. Another object is to provide an organic device having excellent flexibility by being formed on a plastic substrate. Further, by providing the organic film perpendicular to the in-plane direction of the flexible substrate, a load is not applied to the active layer even if the substrate is bent.
[0016]
[Means for Solving the Problems]
In order to achieve the above object, at least the first and second electrodes with an insulating film interposed therebetween are formed in a direction perpendicular to a substrate, and a doping step is performed by applying an organic film to a side wall of the insulating film. A vertical field-effect transistor not particularly required is provided.
[0017]
In particular, regarding the organic film,
Using a molecule containing a functional group that polymerizes to form a conductive conjugated bond group and a functional group that reacts with active hydrogen on the substrate surface, a monomolecular film or A step of forming a monomolecular cumulative film, a step of orienting the molecules constituting the monomolecular film, and a step of polymerizing a functional group that generates a conductive conjugated bonding group by polymerizing in the monomolecular film, An object of the present invention is to provide a monomolecular film or a monomolecular cumulative film containing a plurality of conductive conjugated groups oriented in a specific direction. Further, a general organic film such as pentacene or polyacene which is a low molecular weight system may be used as the organic film. In addition, there is no problem even if a polymer organic material is used.
[0018]
At this time, if the conductive conjugate group is a polyacetylene group, a polydiacetylene group, a polyacene group, a polypyrrole group, or a polychenylene group, a monomolecular film or a monomolecular cumulative film having excellent conductive anisotropy is obtained. Furthermore, a catalyst polymerization method, an electric field polymerization method, or an energy beam irradiation polymerization method is used in the step of polymerizing a functional group that generates a conjugated bonding group. At this time, when a monomolecular film or a monomolecular cumulative film containing a pyrrole group, a chenylene group, an acetylene group, or a diacetylene group is used as a functional group for forming a conjugated bond group, a conductive ultralong conjugate bond is formed by a catalytic polymerization method. Groups can be generated. In addition, when a monomolecular film or a monomolecular accumulation film containing a pyrrole group or a chenylene group is used, a conductive ultralong conjugated group can be generated by an electric field polymerization method. Furthermore, when a monomolecular film or a monomolecular accumulation film containing an acetylene group or a diacetylene group is used as a functional group for producing a conjugated bonding group, the polymerization method can be performed by energy beam irradiation polymerization such as X-ray, electron beam, or ultraviolet. An ultra-long conjugated conductive group can be formed.
[0019]
Further, a chemical adsorption method or a Langmuir-Blodgett method is used for producing a monomolecular film or a monomolecular accumulation film. In particular, a silane-based surfactant is used for producing a monomolecular film or a monomolecular cumulative film using a chemisorption method. Furthermore, if the step of forming the first and second electrodes is performed before the step of polymerizing the monomolecular film or the monomolecular cumulative film to generate a conductive conjugated bond group, these electrodes are formed by electropolymerization. And a current can flow between the first and second electrodes to generate a conductive conjugated group.
[0020]
As the electropolymerizable functional group, a pyrrole group or a chenylene group is convenient. At this time, after forming a monomolecular film containing a pyrrole group or a phenylene group, a current is applied between the first and second electrodes and the third electrode in an organic solvent in which a substance containing a pyrrole group or a phenylene group is dissolved. By flowing, a coating containing a polypyrrole group or a polyphenylene group is formed on the surface of the monomolecular film containing a polypyrrole group or a polyphenylene group. Further, a monomolecular film or a monomolecular cumulative film containing a functional group capable of catalytic polymerization such as a pyrrole group, a phenylene group, an acetylene group, or a diacetylene group is used as a polymerizable group, and a conjugated bond group is generated by catalytic polymerization. On the other hand, as a functional group polymerized by energy beam irradiation, a monomolecular film or a monomolecular cumulative film containing an acetylene group, a diacetylene group, or a polymerizable group is used, and an energy beam such as an ultraviolet ray, a far ultraviolet ray, an electron beam, or an X-ray is used. Irradiation produces conjugated groups.
[0021]
Further, at least a step of forming a third electrode on the surface of an insulating substrate or a conductive substrate via an insulating thin film, and a functional group that polymerizes to form a conductive conjugated group and a substrate. Using a molecule containing a functional group reactive with active hydrogen on the surface and a polar functional group, a monomolecular film or a monomolecular cumulative film is formed on the surface directly or through an insulating film so as to cover the electrode. A step of orienting the molecules constituting the monomolecular film, a step of polymerizing a functional group that forms a conductive conjugated group by polymerization in the monomolecular film, and a step of forming the first and second electrodes. By using the forming step, at least a first electrode and a second electrode formed on an arbitrary substrate are oriented substantially parallel to a direction in which the first electrode and the second electrode are connected to each other. Monolayer containing a plurality of conductive conjugated groups and polar functional groups or Providing a molecular accumulation film, the polymerized vertical field effect transistor having a third electrode in contact directly or indirectly to the monomolecular film or monomolecular built-up film (3 terminal organic electronic devices).
[0022]
At this time, a carbonyl group or an oxycarbonyl group which is polarized by application of an electric field is preferable as the polar functional group. In addition, the polymerized monomolecular film or monomolecular cumulative film is formed by electropolymerization, catalytic polymerization, or conductive polymerization such as polyacetylene group, polydiacetylene group, polyacene group, polypyrrole group, polyphenylene group, etc. When a conjugated bonding group is included, an organic device having excellent characteristics can be obtained.
[0023]
Further, a chemical adsorption method or a Langmuir-Blodgett method is used for producing a monomolecular film or a monomolecular accumulation film. In particular, a silane-based surfactant is used for producing a monomolecular film or a monomolecular cumulative film using a chemisorption method. Furthermore, if the step of forming the first and second electrodes is performed before the step of polymerizing the monomolecular film or the monomolecular cumulative film to generate a conductive conjugated bond group, these electrodes are formed by electropolymerization. And a current can flow between the first and second electrodes to generate a conductive conjugated group.
[0024]
As the electropolymerizable functional group, a pyrrole group or a chenylene group is convenient. At this time, after forming a monomolecular film containing a pyrrole group or a phenylene group, a current is applied between the first and second electrodes and the third electrode in an organic solvent in which a substance containing a pyrrole group or a phenylene group is dissolved. By flowing, a coating containing a polypyrrole group or a polyphenylene group is formed on the surface of the monomolecular film containing a polypyrrole group or a polyphenylene group. Further, a monomolecular film or a monomolecular cumulative film containing a functional group capable of catalytic polymerization such as a pyrrole group, a phenylene group, an acetylene group, or a diacetylene group is used as a polymerizable group, and a conjugated bond group is generated by catalytic polymerization. On the other hand, as a functional group polymerized by energy beam irradiation, a monomolecular film or a monomolecular cumulative film containing an acetylene group, a diacetylene group, or a polymerizable group is used, and an energy beam such as an ultraviolet ray, a far ultraviolet ray, an electron beam, or an X-ray is used. Irradiation produces conjugated groups.
[0025]
BEST MODE FOR CARRYING OUT THE INVENTION
First, an outline of a vertical field effect transistor according to an embodiment of the present invention will be described.
[0026]
First, an insulating substrate using at least a molecule containing a functional group that polymerizes to form a conductive conjugated group, a functional group that reacts with active hydrogen on the substrate surface, and a functional group that photoisomerizes, Alternatively, a step of forming a monomolecular film or a monomolecular cumulative film on the surface of the conductive substrate via an insulating thin film, a step of orienting the molecules constituting the monomolecular film, At least a first electrode formed on an arbitrary substrate and a second electrode formed on an arbitrary substrate are formed by using a step of polymerizing a molecular accumulation film to form a conductive conjugated bonding group and a step of forming a first and a second electrode. Monolayer or monomolecular film containing a plurality of conductive conjugated groups and photoresponsive functional groups oriented substantially parallel to the direction connecting the first electrode and the second electrode. Vertical field effect transistor (three-terminal organic electronic device) And elephants.
[0027]
In this device, the monomolecular film or the monomolecular cumulative film containing the conjugated bonding group formed by polymerization is irradiated with ultraviolet light or visible light while a voltage is applied between the first electrode and the second electrode. Thus, by controlling the degree of conjugation of the conjugate bond, the current flowing between the first electrode and the second electrode could be switching-controlled.
[0028]
Second, at least a step of forming a third electrode on the surface of an insulating substrate or a conductive substrate via an insulating thin film, and a functional group that polymerizes to form a conductive conjugated group. Using a molecule containing a functional group reactive with active hydrogen and a polar functional group on the surface of the base material, a monomolecular film or a monomolecular cumulative film is formed on the surface directly or through an insulating film so as to cover the electrode. Forming a monomolecular film, orienting molecules constituting the monomolecular film, polymerizing a functional group that forms a conductive conjugated group by polymerization in the monomolecular film, By using a step of forming an electrode, at least a first electrode and a second electrode formed on an arbitrary substrate and substantially parallel to a direction in which the first electrode and the second electrode are connected to each other. A monomolecular film containing a plurality of oriented conductive conjugated groups and polar functional groups or A monomolecular built-up film was produced three-terminal organic electronic device comprising a third electrode in contact directly or indirectly to the monomolecular film or monomolecular built-up film was the polymerization.
[0029]
In this device, with a voltage applied between the first electrode and the second electrode, a voltage is applied between the first electrode and the third electrode to control the degree of conjugation of the conjugate bond, Switching control of the current flowing between the first electrode and the second electrode could be performed.
[0030]
Hereinafter, specific embodiments will be described with reference to the drawings.
[0031]
(Embodiment 1)
For example, an acetylene group (—C≡C—C≡C—) that is polymerized in advance and becomes a conductive conjugate bond group, an azo group (—N = N—) that is a photoisomerizable functional group, and the activity of the substrate surface A substance containing a chlorosilyl group (—SiCl) that reacts with hydrogen (for example, hydroxyl group (—OH)) (Formula 1) was diluted to 1% with a dehydrated dimethyl silicone-based organic solvent to prepare a chemical adsorption solution.
[0032]
Embedded image

[0033]
Next, the insulating glass substrate 1 covered with the resist pattern except for a portion where a monomolecular film is formed is immersed in the adsorbing solution to selectively perform chemical adsorption on the opening of the resist pattern. The remaining unreacted substance was washed away with chloroform, and then the resist pattern was removed to selectively form the monomolecular film 2 made of the substance. At this time, since a large number of hydroxyl groups containing active hydrogen are present on the glass substrate surface at the resist opening, the -SiCl group of the substance causes a dehydrochlorination reaction with the hydroxyl group to form a covalent bond to the substrate surface (Formula 2). A monomolecular film 2 was formed (FIG. 2).
[0034]
Embedded image

[0035]
Next, using a rubbing device 3 used for producing a liquid crystal alignment film, a rubbing cloth 4 made of rayon (YA-20-R, manufactured by Yoshikawa Kako Co., Ltd.) was used, and the nip width was 0.3 mm and the nip width was 11.7 mm. Rubbing was performed in the vertical direction parallel to the direction from the first electrode to the second electrode under the conditions of 1200 rotations and a table speed of 40 mm / sec (FIG. 3). As a result, the chemically adsorbed molecules (Formula 2) constituting the monomolecular film were oriented along the rubbing direction.
[0036]
Note that the rubbing treatment here was performed after the formation of the monomolecular film, but before the formation of the monomolecular film, that is, the substrate surface was rubbed in advance under the same conditions, and thereafter, the same applies when the monomolecular film was formed on the surface. Thus, a monomolecular film oriented in was obtained. However, in this case, after the resist is removed, the chloroform cleaning is performed again in the same manner as after the formation of the monomolecular film, and further, the substrate is pulled up while standing up substantially in parallel with the rubbing direction, and the liquid is oriented in a direction opposite to the liquid draining direction. As a result, a monomolecular film having better orientation was obtained.
[0037]
Next, a nickel thin film is vapor-deposited on the entire surface of the chemically adsorbed monomolecular film 2a on which the substrate is oriented, and a first electrode 8 having a gap distance of 10 microns and a length of 30 microns is formed by photolithography. Thereafter, a gate insulating film was formed, a nickel thin film was formed again as the second electrode 9, and finally, these deposited films were formed by dry etching. As described above, the first electrode and the second electrode formed on an arbitrary substrate, and the plurality of conductive electrodes oriented substantially in parallel to the direction connecting the first electrode and the second electrode. A three-terminal organic electronic device including a monomolecular film or a monomolecular cumulative film containing a conjugated bond group and a photoresponsive functional group was manufactured (FIG. 4).
[0038]
In this device, the first electrode and the second electrode are connected by a conductive polyacetylene bonding group. Therefore, when a voltage of several V is applied between the electrodes, a current of several mA (about 100 nA at 1 V) is obtained. flowed. This value was about 50 times that in the case of non-oriented polymerization.
[0039]
Next, in this state, when the monomolecular film between the electrodes was irradiated with ultraviolet rays (light 10), the azo group was subjected to cis transition, and the current became almost zero. Further, after that, upon irradiation with visible light (light 10), the azo group was trans-transferred and the original conductivity was reproduced (FIG. 5). Such a decrease in conductivity between the electrodes is caused by the photoisomerization of the azo group (transformation from the trans-form to the cis-form), which causes the molecular orientation in the monomolecular film to be distorted and the degree of conjugation of the polyacetylene bonding group to decrease. It is thought to be caused by
[0040]
As described above, the switching of the current flowing between the first electrode and the second electrode could be controlled by controlling the degree of conjugation of the conjugate bond by light irradiation.
[0041]
When a polyacetylene group is used as the conductive group, the resistance increases when the degree of polymerization is low. That is, although the on-current is reduced, in that case, a dopant substance having a charge-transferring functional group (for example, a halogen gas or Lewis acid as an acceptor molecule, an alkali metal or ammonium salt as a donor molecule) diffuses to the surface, That is, the on-current can be increased by doping. Incidentally, when iodine was doped into this film, a current of 0.2 mA flowed when a voltage of 1 V was applied.
[0042]
Here, when a conductive substrate such as a metal is used as the substrate, a monomolecular film may be formed on the surface of the conductive substrate via an insulating thin film. In such a structure, the substrate itself is not charged, so that the operation stability of the device is improved.
[0043]
When a larger on-current is required, the distance between the electrodes may be reduced or the electrode width may be increased. If a larger on-current is required, the monomolecular films may be accumulated.
[0044]
In Embodiment 1 described above, the catalytic polymerization method is used for producing a conductive conjugated group. However, the same conductive conjugated group is formed by electrolytic polymerization or irradiation of an energy beam such as light, electron beam, or X-ray. Could be produced. Further, in addition to the polyacetylene group, a polydiacetylene group, a polyacetylene group, a polypyrrole group, and a polychenylene group could be used as the conductive conjugate bond group. In addition, a pyrrole group, a chenylene group, a diacetylene group, etc. other than the acetylene group were suitable as the polymerizable group for the catalytic polymerization method.
[0045]
In addition to the chemisorption method, the Langmuir-Blodgett method could be used to prepare a monomolecular film or a monomolecular cumulative film. In addition, when the step of forming the first and second electrodes is performed before the step of polymerizing the monomolecular film or the monomolecular cumulative film to generate a conductive conjugate bond group, The first and second electrodes were available for electrolytic polymerization. That is, a monomolecular film or a monomolecular cumulative film containing a pyrrole group or a chenylene group as an electropolymerizable functional group is used, and a current flows between the first and second electrodes to form a thin film between the first and second electrodes. Electrolytic polymerization could be selectively performed. Furthermore, after forming a monomolecular film containing a polypyrrole group or a polyphenylene group, or after forming a monomolecular film containing a pyrrole group or a phenylene group, in an organic solvent in which a substance containing a pyrrole group or a phenylene group is dissolved. When an electric current was passed between the first and second electrodes to form a film containing a polypyrrole group or a polyphenylene group on the surface of the monomolecular film containing a polypyrrole group or a polyphenylene group, the thickness of the conductive region could be increased.
[0046]
In addition, using a monomolecular film or a monomolecular accumulation film containing an acetylene group or a diacetylene group which is a functional group polymerized by an energy beam as a polymerizable group, an energy beam such as an ultraviolet ray, a far ultraviolet ray, an electron beam, or an X-ray is used. Irradiation produced a conjugated group.
[0047]
In addition, as the substance to be used, any substance generally represented by (Chemical Formula 3) can be used in the same manner in the first embodiment.
[0048]
Embedded image

[0049]
here,
A is a functional group that becomes a conductive conjugated group by polymerization
B is a photoresponsive functional group
D is a functional group that reacts with active hydrogen on the substrate surface
E is hydrogen, methyl, ethyl, methoxy, ethoxy, or another functional group such as an alkyl group
m and n are integers, and m + n is preferably 2 or more and 25 or less, particularly 10-20.
[0050]
p is 1, 2, or 3.
[0051]
More specifically, the substances represented by (Chem. 4) to (Chem. 7) could be used.
[0052]
Embedded image

[0053]
Embedded image

[0054]
Embedded image

[0055]
Embedded image

[0056]
Here, m and n are integers, and m + n is 2 or more and 25 or less.
[0057]
(Embodiment 2)
For example, a pyrrole group (C ₄ H ₄ N-), a substance containing a chlorocarbonyl group (—SiCl) that reacts with an oxycarbonyl group (—OCO—), which is a polar functional group, and active hydrogen (eg, hydroxyl group (—OH)) on the substrate surface (Chem. 8) Was diluted to 1% with a dehydrated dimethyl silicone-based organic solvent to prepare a chemically adsorbed liquid.
[0058]
Embedded image

[0059]
Next, an insulative polyimide substrate 11 (or an insulative thin film such as a silica coating 12 on the surface of a conductive metal substrate) may be used, and a horizontal selection line 13 (for the second electrode) may be formed thereon. A switching element having a gate length of 100 nm (thickness) and a width of 40 μm is formed by dry etching on the gate insulating film 6, and further, the Al pattern (first electrode: source portion, vertical selection line) is formed. 14), and seven organic transistors were arranged (FIG. 6).
[0060]
Next, in order to form a monomolecular film, the film is immersed in the adsorption solution to selectively chemically adsorb to the insulating film, and further, the unreacted substance remaining on the surface is washed and removed with chloroform. The resist pattern was removed to selectively form a monomolecular film 15 made of the substance (FIG. 7).
[0061]
At this time, the side wall surface (silica coating and Al ₂ O ₃ Since many hydroxyl groups containing active hydrogen are present on the surface), a single molecule composed of a molecule represented by (Chem. 9) in which the -SiCl group of the substance causes a dehydrochlorination reaction with the hydroxyl group and is covalently bonded to the substrate surface. The film 15 was formed.
[0062]
Embedded image

[0063]
After that, chloroform cleaning is again performed in the same manner as after the formation of the monomolecular film, and further, the substrate is pulled up while being parallel to the direction from the first electrode to the second electrode, and draining is performed. As a result, a monomolecular film 15a having a primary orientation was obtained.
[0064]
Next, an electric field of about 5 V / cm is applied between the first and second electrodes in acetonitrile, and a current is applied to perform electrolytic polymerization, whereby the first electrode 14 and the second electrode 16 are electrically conductively conjugated. Generated to connect between. At this time, the polymerized conjugated bond groups are connected along the direction of the electric field. Therefore, when the polymerization is completely completed, the first and second electrodes are connected in a self-organizing manner by the conductive conjugated bond groups 18. (FIG. 1).
[0065]
Finally, the third electrode is taken out from the substrate side, and a first electrode and a second electrode formed on an arbitrary substrate, a direction for connecting the first electrode and the second electrode, and A monomolecular film or a monomolecular cumulative film containing a plurality of conductive conjugated groups and polar functional groups oriented substantially parallel to each other, and A three-terminal organic electronic device with three electrodes was manufactured.
[0066]
In this device, since the first electrode and the second electrode are connected by a conductive polypyrrole bonding group, BF ⁻ When the ions were doped, a voltage of 1 V was applied between the electrodes, and a current of about 1 mA flowed.
[0067]
Next, in this state, when a voltage of 5 V was applied between the third electrode and the first electrode, the current between the first and second electrodes became almost zero. After that, when the applied voltage of 5 V was returned to 0 V, the original conductivity was reproduced. Such a decrease in conductivity between the electrodes is caused by the fact that when a voltage of 5 V is applied between the third electrode and the first electrode, the polarization of the oxycarbonyl group (—OCO—), which is a polar functional group, proceeds. It is considered that this is caused by distortion of the monomolecular film and reduction in the degree of conjugation of the polypyrrole binding group.
[0068]
As described above, by applying a voltage to the third electrode, the degree of conjugation of the conjugate bond was controlled, and switching of the current flowing between the first electrode and the second electrode could be controlled.
[0069]
In Embodiment 2, after the liquid is drained by raising the substrate while standing in parallel with the direction from the first electrode to the second electrode, the substrate is further polarized in the direction parallel to the direction from the first electrode to the second electrode. Visible light 19 at 500 mJ / cm ² When the irradiation was performed to a certain degree, a monomolecular film having more excellent orientation was obtained as compared with the case where the liquid was drained by lifting up while standing. Also, at this time, when the same irradiation is performed with the polarization direction set to a direction crossing the direction from the first electrode to the second electrode at 45 °, the molecules constituting the monomolecular film are moved in the initial pulling direction. , And oriented in a direction substantially parallel to the polarized light irradiation direction. That is, it was confirmed that when the polarized light irradiation was performed, the molecules constituting the monomolecular film were oriented in the polarization direction (FIG. 8).
[0070]
Furthermore, when polymerization was performed in such an oriented state to generate a conjugated bond group, a film having more excellent conductivity could be formed.
[0071]
Here, when the polar functional group was an oxycarbonyl group that was polarized by application of an electric field, switching could be performed at an extremely high speed. In addition to the oxycarbonyl group, functional groups such as a carbonyl group could be used.
[0072]
Furthermore, a polyacetylene group, a polydiacetylene group, a polyacene group, a polypyrrole group, and a polychenylene group could be used as the conductive conjugate bond group, and the conductivity was high.
[0073]
In addition, as a substance that generates a conductive conjugate bond group, a chenylene group could be used in addition to a pyrrole group, which is an electropolymerizable functional group. In addition, if the polymerization method was changed, a substance containing an acetylene group or a diacetylene group could be used.
[0074]
In addition to the chemisorption method, the Langmuir-Blodgett method could be used for producing a monomolecular film or a monomolecular accumulation film.
[0075]
If a monomolecular film or a monomolecular cumulative film containing a catalytic polymerizable functional group such as a pyrrole group, a phenylene group, an acetylene group, or a diacetylene group is used as the polymerizable group, a conjugated bond group can be generated by catalytic polymerization. Was. In addition, using a monomolecular film or a monomolecular accumulation film containing a functional group that is polymerized by an energy beam such as an acetylene group or a diacetylene group as a polymerizable group, and irradiating an energy beam such as an ultraviolet ray, a far ultraviolet ray, an electron beam, or an X-ray. As a result, an organic electronic device could be manufactured.
[0076]
(Embodiment 3)
A thin film transistor (TFT) formed in a conventional semiconductor device generally has a structure in which amorphous silicon is used as an active layer. However, an amorphous silicon TFT has low carrier mobility and sufficient operating characteristics. For this reason, organic TFTs have recently attracted attention. Organic TFTs are less expensive to manufacture and have better operating characteristics than amorphous silicon TFTs, and are expected to be used not only for pixel switching but also as peripheral drive circuit devices in the future. I have. Therefore, in the production of the organic TFT of the present invention, since it can be produced by a room temperature process, there is no problem even if a plastic which is weak in temperature is used for the substrate.
[0077]
FIG. 4 shows an example of the organic TFT. As shown in FIG. 1, a monomolecular film 2a is formed on an insulating glass substrate 1, and a drain electrode 9, a gate insulating film 6, and a source electrode 8 are formed on the monomolecular film 2a. The main organic semiconductor thin film (active layer) 20 is formed on the side wall of the substrate. The organic semiconductor thin film 20 is a channel region and has a source region (first electrode 8) and a drain region (second electrode 9).
[0078]
Since the organic semiconductor thin film 20 covers the side wall of the gate insulating film 6 and serves as a channel region, in the case of a transistor using an organic film, it is not necessary to particularly form a contact hole for connecting to a source / drain region. That is, unlike a normal transistor, it can directly contact (contact) the source and drain electrodes.
[0079]
However, in a TFT using a polycrystalline silicon TFT or the like, a high-density trap level exists at a crystal grain boundary in a semiconductor thin film, and carriers move through the trap. Therefore, the gate voltage V _GS Is negative, the gate voltage V _GS The drain current I with increasing absolute value of _D Increase. This phenomenon means that an off-state current, which is a leakage current in an off-state, has a gate voltage dependency, which is not preferable as a transistor characteristic. Further, it is necessary to further reduce the off-state current itself. For example, since a polycrystalline silicon TFT used for an active matrix type liquid crystal display device is used under a gate reverse bias, a problem arises that the data holding characteristic deteriorates when the off-current increases. That is, data written to the capacitor needs to be held for a much longer time than the writing time. However, since the capacitance of the capacitor is small, the off-state current in the off-state of the TFT causes the potential of the drain (ie, The potential of the capacitor rapidly approaches the potential of the source, and the written data cannot be held properly. The problem with an increase in off-state current occurs not only in a liquid crystal display device but also in other semiconductor devices. For example, a normal logic circuit causes an increase in quiescent current and a memory circuit causes a malfunction. .
[0080]
Therefore, in order to reduce the off-current, an impurity is introduced into the channel ⁻ It is also known that However, while the implanted impurity is required to have a relatively low concentration, such a concentration adjustment is difficult in a conventional low-temperature process, and it has been difficult to realize it. Further, for the same reason, the threshold voltage Vth is not sufficiently controlled, and furthermore, the semiconductor thin film may be contaminated with impurities from the beginning, so that the TFT has a non-uniform operating characteristic on a large-area insulating substrate. There was a problem that there is. For example, in the case of a liquid crystal display device, when the threshold voltage Vth shifts to the depletion side, the off-current increases, which causes a problem that a bright spot defect occurs in a pixel.
[0081]
FIG. 9 shows typical characteristics of an organic TFT that has solved such a problem. The figure shows the drain voltage V _DS Is the gate voltage V at 4V _GS Drain current I _D 6 is a graph showing the relationship of. Drain current I _D Is the gate voltage V _GS Becomes a minimum value near 0 V, and the gate voltage V _GS As the drain current I increases _D Also increase. Gate voltage V _GS Current I in a region where the value of _D Means a change from the off-state to the on-state of the transistor, and therefore it is desirable that the rate of increase of the current be as large as possible. For example, when used in a liquid crystal display device, a liquid crystal display is determined by the potential of a capacitor, so that a sufficient current (ON current) needs to flow through the TFT so that data can be written in a short time. In the case of the vertical organic TFT of the present invention, since the carrier mobility in the semiconductor thin film is large, there is no particular problem in that a sufficient on-current can be supplied.
[0082]
As described above, the organic TFT, which is the vertical field-effect transistor of the present invention, performed well without causing the above-described problems of the polycrystalline silicon TFT.
[0083]
(Embodiment 4)
In recent years, display devices using organic EL elements have been developed. When an organic EL device using a large number of organic EL devices is driven by an active matrix circuit, each pixel (pixel) of each EL has an FET such as a thin film transistor (TFT) for controlling a current supplied to the pixel. (Field effect transistors) are connected one by one. That is, a set of a bias TFT for flowing a drive current to the organic EL element and a set of switch TFTs indicating whether to select the bias TFT are connected.
[0084]
FIG. 10 shows an example of a circuit diagram of a conventional active matrix type organic EL display device. The organic EL display device includes X-direction signal lines 301-1 and 301-2,..., Y-direction signal lines 302-1 and 302-2,. .., Current control TFT transistors 305-1, 305-2,..., Organic EL elements 306-1, 306-2,. 307-2..., An X-direction peripheral drive circuit 308, a Y-direction peripheral drive circuit 309, and the like.
[0085]
A pixel is specified by the X-direction signal line 301 and the Y-direction signal line 302, the switching TFT transistor 304 is turned on in the pixel, and the image data is held in the signal holding capacitor 307. As a result, the current controlling TFT transistor 305 is turned on, a bias current corresponding to the image data flows from the power supply Vdd line 303 to the organic EL element 306, and this emits light.
[0086]
For example, when a signal corresponding to image data is output to the X-direction signal line 301-1 and a Y-direction scanning signal is output to the Y-direction signal line 302-1, the switching TFT transistor 304 of the pixel specified by this is output. -1 is turned on, the current control TFT transistor 305-1 is turned on by a signal corresponding to the image data, and a light emission current corresponding to the image data flows through the organic EL element 306-1 to control light emission.
[0087]
As described above, for each pixel, a thin film EL element, a current control TFT transistor for controlling light emission of the EL element, and a signal holding capacitor connected to the gate electrode of the current control TFT transistor are provided. In an active matrix EL image display apparatus having a switching TFT transistor for writing data to the capacitor, the emission intensity of the EL element is controlled by a voltage stored in a signal holding capacitor. (A66-in 201pi Electroluminescent Display Tp Bloody, FC Luo, et. Al., IEEE Trans. Electron Devices, Vol. ED-22, A66-in 201pi Electroluminescent Display T.P. No. , Sep.1975, see p739~p749).
[0088]
The capacity of the signal holding capacitor used at this time is equal to or less than the capacity of the pixel switch TFT transistor to sufficiently charge the electric charge within a minute selection time, and the leak current when the pixel switch TFT transistor is not selected is selected. However, it is required that the decrease in the holding voltage of the capacitor caused by the electric charge lost until the next writing time is equal to or larger than the capacity that does not adversely affect the image on the display panel.
[0089]
An active matrix display device requires an angle of view of 4 inches or more when not using an optical system that performs enlarged projection due to its visibility. When a display surface of this size is formed on a silicon single crystal substrate, the current technology for manufacturing a single crystal Si substrate requires a very small number of substrates to be obtained from one single crystal substrate, resulting in high costs.
[0090]
Therefore, the above-mentioned problem is solved by using a vertical organic thin film transistor (TFT) of the present invention using an organic film semiconductor layer formed on a flat substrate such as a flexible substrate in an active matrix display device. It can be manufactured at low cost.
[0091]
In addition, since a semiconductor layer formed over a flat substrate can be formed relatively easily with a large area, an amorphous Si film (hereinafter, referred to as an a-Si film) is generally used. However, when a current continuously flows in one direction in a TFT formed of an a-Si film, the threshold value drifts, the current value changes, and the image quality varies. In addition, since the mobility of the a-Si film is small, the current that can be driven with high-speed response is limited. Further, it is more difficult to form a small-scale CMOS circuit than to form a P-channel.
[0092]
Therefore, according to the present invention, since a large-sized vertical organic semiconductor layer formed on a flat substrate can be formed relatively easily, the semiconductor layer of an active matrix organic EL image display device has a relatively large area. Since the organic layer is designed to be easy to use, has high reliability, has high mobility, and can form a CMOS circuit as an active layer, and a current flowing through the active layer is designed to flow perpendicular to the substrate, the substrate area is increased. In contrast, the proportion occupied by the vertical field-effect transistor can be reduced, so that an organic EL display having high-resolution pixels in a large area can be manufactured.
[0093]
【The invention's effect】
As described above, according to the present invention,
A first electrode and a second electrode formed on an arbitrary substrate, and a plurality of conductive conjugate bonding groups oriented substantially parallel to a direction connecting the first electrode and the second electrode; A high-performance vertical type including a monomolecular film or a monomolecular accumulation film containing a polar functional group, and a high-performance third electrode directly or indirectly contacting the polymerized monomolecular film or the monomolecular accumulation film. Field effect transistors (three-terminal organic electronic devices) can be provided. In addition to the monomolecular film, a low molecular organic thin film and a high molecular organic thin film can be provided.
[0094]
This makes it possible to manufacture an organic EL display having high-resolution pixels in a large area at low cost.
[Brief description of the drawings]
FIG. 1 is an example of a polymerization method according to Embodiment 2 of the present invention.
FIG. 2 is a conceptual cross-sectional view of a state where a monomolecular film is formed in Embodiment 1 of the present invention, which is enlarged to a molecular level.
FIG. 3 is a conceptual diagram illustrating a process of aligning molecules constituting a monomolecular film by rubbing in Embodiment 1 of the present invention.
FIG. 4 is a conceptual cross-sectional view of the device completed in the first embodiment of the present invention, which is enlarged to a molecular level.
FIG. 5 is a process diagram of polymerizing an organic film by applying ultraviolet light or visible light according to the first embodiment of the present invention.
FIG. 6 is an enlarged conceptual sectional view showing a state in which a third electrode is formed in Embodiment 2 of the present invention (without an organic film);
FIG. 7 is an enlarged conceptual sectional view showing a state in which a third electrode is formed in Embodiment 2 of the present invention (with an organic film).
FIG. 8 is a conceptual cross-sectional view illustrating a step of orienting molecules constituting a monomolecular film by polarized light irradiation in Embodiment 2 of the present invention.
FIG. 9 shows a gate voltage V of a conventional thin film transistor. _GS And drain current I _D Diagram showing the relationship with
FIG. 10 is a circuit diagram of a conventional active matrix type organic EL display device.
FIG. 11 is a diagram showing a conventional example using a Si-based transistor.
FIG. 12 is a diagram showing a conventional example using a vertical Si-based transistor.
[Explanation of symbols]
1 Glass substrate
2 Chemisorption monolayers containing acetylene and azo groups
2a Oriented chemisorbed monolayer
3 Rubbing device
4 rubbing cloth
5 Conductive polyacetylene-type conjugated bonding group
6 Gate insulating film
7 azo group
8 1st electrode (source electrode)
9 Second electrode (drain electrode)
10. Light collected for switching (ultraviolet light, visible light)
11 Polyimide substrate
12 Silica coating
13 Horizontal selection line (second electrode)
14. Vertical selection line (first electrode)
15 Monolayers containing pyrrole and oxycarbonyl groups
15a Oriented monomolecular film
16 1st electrode
17 Second electrode
18 Conductive polypyrrole-type conjugated groups
19 Visible light
20 Active layer (organic semiconductor thin film)
51 Silicon substrate
52 Gate insulating film
53 Field oxide film
54 Gate electrode
55 Low concentration diffusion layer
56 Spacer
57 source electrode
58 Drain electrode
61 Silicon substrate
62 silicon pillar
63 oxide film
64 N + polysilicon layer
64a Gate electrode
65 Drain electrode
66 source electrode
301 X direction signal line
302 Y direction signal line
303 Power supply Vdd line
304 TFT transistor for switch
305 TFT transistor for current control
306 Organic EL device
307 Capacitor
308 X direction peripheral drive circuit
309 Y-direction peripheral drive circuit

Claims (12)

In a field-effect transistor having a first electrode and a second electrode on a substrate, an insulating film for insulating the first and second electrodes, and a third electrode in the insulating film.
The first electrode, the second electrode, and an insulating film for insulating the first and second electrodes are arranged in a thickness direction with respect to the substrate,
A vertical field effect transistor, wherein at least a part of the side wall of the insulating film is provided with an organic film as an active layer. The vertical field effect transistor according to claim 1, wherein a channel length of the vertical field effect transistor is a thickness of the insulating film. The vertical field-effect transistor according to claim 1, wherein the organic film is provided on at least a part of the insulating film. 4. The vertical field effect transistor according to claim 1, wherein the organic film as the active layer is a low molecular material. 5. The vertical field effect transistor according to claim 4, wherein a portion of the organic film serving as the active layer is an acene-based material such as pentacene, anthracene, and polyacene. 4. The vertical field effect transistor according to claim 1, wherein the organic film serving as the active layer is a polymer material. The organic film as the active layer has a conductive conjugated bonding group, and is a polyacetylene group, a polydiacetylene group, a polyacene group, a polypyrrole group, or a polychenylene group. A monomolecular film or a monomolecular cumulative film. The method for producing a coating film according to claim 7, wherein the step of polymerizing the functional group that forms the conjugated bond group uses a catalyst polymerization method, an electric field polymerization method, or an energy beam irradiation polymerization method. The method according to claim 8, wherein X-rays, electron beams, or ultraviolet rays are used in the energy beam irradiation polymerization method. In a field-effect transistor having a first electrode and a second electrode on a substrate, an insulating film for insulating the first and second electrodes, and a third electrode in the insulating film.
A vertical field effect transistor, wherein a direction of a current flowing through the organic film, which is an active layer provided between the first electrode and the second electrode, is perpendicular to a plane of the substrate. How it works. A plurality of vertical field-effect transistors provided at a plurality of first selection lines arranged on a substrate, a plurality of second selection lines, and an intersection of the first selection line and the second selection line; The vertical field-effect transistor has at least a first electrode, a second electrode, and a third electrode, and the second electrode and the third electrode are connected to the first selection line and the second selection electrode, respectively. In the array substrate connected to each line,
The first electrode, the second electrode, and an insulating film for insulating the first and second electrodes are vertically arranged with respect to the substrate;
An array substrate, wherein a plurality of vertical field-effect transistors each having at least an organic film on a part of the side wall of the insulating film are arranged in a matrix. A plurality of vertical field-effect transistors provided at a plurality of first selection lines arranged on a substrate, a plurality of second selection lines, and an intersection of the first selection line and the second selection line; The vertical field-effect transistor has at least a first electrode, a second electrode, and a third electrode, and the second electrode and the third electrode are connected to the first selection line and the second selection electrode, respectively. In the array substrate connected to each line,
The first electrode, the second electrode, and an insulating film for insulating the first and second electrodes are vertically arranged with respect to the substrate;
A method for operating an array substrate with a vertical field effect transistor, comprising a plurality of vertical field effect transistors arranged in a matrix, the vertical field effect transistors flowing current in a vertical direction of an organic film provided on a part of the insulating film side wall. .

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