JP4103530B2 - Thin film forming method and electronic device forming method - Google Patents

Description

【００１６】
【化２】

【００１７】
オリゴフェニレンの例としては、下記の（３）式で示されるｐ−ターフェニルが挙げられる。オリゴチオフェンの例としては、下記の（４）式で示されるターチオフェンが挙げられる。オリゴフェニレンの誘導体の例としては、下記の（５）式で示される４−アミノ−ｐ−ターフェニルが挙げられる。オリゴチオフェンの誘導体の例としては、下記の（６）式で示される2,2':5',2"−ターチオフェン−5,5"−ジカルボキシアルデヒドが挙げられる。
【００１８】
【化３】

【００１９】
【化４】

【００２０】
【化５】

【００２１】
【化６】

【００２２】
本発明の方法で使用可能な薄膜形成材料としては、また、下記の（７）式で示されるＡｌｑ３（キノリノール−アルミニウム錯体）が挙げられる。
【００２３】
【化７】

【００２４】
本発明はまた、本発明の方法で薄膜を形成する工程を有する電子デバイスの形成方法を提供する。
【００２５】
【発明の実施の形態】
以下、本発明の実施形態について説明する。
＜第１実施形態＞
前記化学式（３）で示される構造のターチオフェン（2,2':5',2"−ターチオフェン、薄膜形成材料）を、ドデシルベンゼン（溶媒）に、濃度が０．１重量％となるように溶解させて溶液を得た。ドデシルベンゼンの２０℃（吐出時の温度）での蒸気圧は１．３×１０^-3Ｐａ（１×１０^-5ｍｍＨｇ）である。
【００２６】
また、シリコン基板の表面に波長１７２ｎｍの紫外光を照射することにより、この表面を親液性（前記溶液によって濡れ易い性質）にした。このシリコン基板の表面に、前記溶液を、セイコーエプソン（株）製のインクジェット装置「ＭＪ−９３０Ｃ」を用い、１滴当たり２０ピコリットルの吐出量で吐出した。この吐出は２０℃の室内で行った。
【００２７】
このインクジェット装置のヘッドとしては、ノズルを１個備えたものを使用した。この吐出は、ヘッドのノズルと基板との距離を１ｍｍとし、１滴当たり２０ピコリットルの吐出量で、前記ヘッドを７０μｍずつ基板の１辺に沿って移動させながら、前記溶液を吐出することを１０回繰り返した。これにより、シリコン基板上に一直線に沿ってピッチ７０μｍで１０個の液滴が形成された。次に、この直線に平行であって７０μｍ離れた直線に沿って、７０μｍピッチで１０個の液滴を形成した。これを１０回繰り返すことによって、シリコン基板上にピッチ７０μｍで１０列×１０行の液滴を形成した。
【００２８】
次に、この状態で自然放置することにより、液滴から溶媒を乾燥させた。その際、形成された全ての液滴が移動せずに、各液滴形成位置に留まっていることが確認できた。そして、溶媒の蒸発後に、各液滴形成位置にターチオフェンからなる薄膜が形成された。ただし、このターチオフェン薄膜は結晶性薄膜ではなく、アモルファス状の薄膜であった。
【００２９】
次に、比較例用の溶液として、ドデシルベンゼンに代えて、２０℃（吐出時の温度）での蒸気圧が２６Ｐａ（０．２ｍｍＨｇ）である１，２，３，４−テトラメチルベンゼンを溶媒として用い、濃度０．１重量％のターチオフェン溶液を得た。この溶液を用いた以外は前記と同じ方法で、前記シリコン基板上にピッチ７０μｍで１０列×１０行の液滴を形成し、この状態で自然放置することにより、液滴から溶媒を乾燥させた。
【００３０】
その際、形成された１０列×１０行の液滴のうち、１列目の全ての行、１０列目の全ての行、および２〜９列目の１行目および１０行目の液滴が移動していることが確認された。つまり、外周に位置する部分の液滴が移動していた。
＜第２実施形態＞
前記化学式（７）で示される構造のＡｌｑ３（キノリノール−アルミニウム錯体；薄膜形成材料）を、２，３−ジヒドロベンゾフラン（溶媒）に、濃度が０．１重量％となるように溶解させて溶液を得た。２，３−ジヒドロベンゾフランの２５℃（吐出時の温度）での蒸気圧は１．３×１０² Ｐａ（１×１０^-1ｍｍＨｇ）である。
【００３１】
また、シリコン基板の表面に波長１７２ｎｍの紫外光を照射することにより、この表面を親液性（前記溶液によって濡れ易い性質）にした。このシリコン基板の表面に、前記溶液を、セイコーエプソン（株）製のインクジェット装置「ＭＪ−９３０Ｃ」を用い、１滴当たり２０ピコリットルの吐出量で吐出した。この吐出は２５℃の室内で行った。
【００３２】
このインクジェット装置のヘッドとしては、ノズルを１個備えたものを使用した。第１実施形態と同様にして、７０μｍ、２１０μｍ、２８０μｍ、３５０μｍ、４２０μｍ、５６０μｍの各ピッチで１０列×１０行の液滴を形成した。ヘッドのノズルと基板との距離は１ｍｍとした。
これにより、サンプルNo. １ではピッチ７０μｍで、サンプルNo. ２ではピッチ２１０μｍで、サンプルNo. ３ではピッチ２８０μｍで、サンプルNo. ４ではピッチ３５０μｍで、サンプルNo. ５ではピッチ４２０μｍで、サンプルNo. ６ではピッチ５６０μｍで、各シリコン基板上に１０列×１０行の液滴が形成された。
【００３３】
次に、各サンプルの基板をこの状態で自然放置することにより、液滴から溶媒を乾燥させた。その際、液滴がピッチ３５０μｍ以上で形成されたサンプルNo. ４〜６では、形成された全ての液滴が移動せずに、各液滴形成位置に留まっていることが確認できた。そして、溶媒の蒸発後に、各液滴形成位置にＡｌｑ３からなる薄膜が形成された。ただし、このＡｌｑ３薄膜は結晶性薄膜ではなく、アモルファス状の薄膜であった。
【００３４】
これに対して、液滴がピッチ２８０μｍ以下で形成されたサンプルNo. １〜３では、形成された１０列×１０行の液滴のうち、１列目の全ての行、１０列目の全ての行、および２〜９列目の１行目および１０行目の液滴が移動していることが確認された。つまり、外周に位置する部分の液滴が移動していた。
以上のことから、この実施形態では、３５０μｍ以上間隔を開けて隣り合う液滴の形成を行うことで、各液滴が隣の液滴から蒸発した溶媒（２，３−ジヒドロベンゾフラン）蒸気の影響を受けない状態となって、２，３−ジヒドロベンゾフランからなる気体の分圧が各液滴の周囲で均一になったと考えられる。
＜第３実施形態＞
第２実施形態と同じＡｌｑ３の２，３−ジヒドロベンゾフラン溶液からなる液滴を用い、以下の方法で液滴の形成を行った。この方法を図１を使用して説明する。
【００３５】
ノズルを１個有するヘッドを用い、図１の１−１、２−１、３−１、・・・３０−１（図１では１２−２までが表示されている）の順に移動させながら、前記溶液を吐出することにより、３５０μｍピッチで３列×１０行の液滴を形成した。次に、１−１の右隣の７０μｍ離れた位置に、１−２の液滴を形成し、順次２−２、３−２、・・・３０−２の順に移動させながら、前記溶液を吐出することにより、３５０μｍピッチで３列×１０行の液滴を形成した。
【００３６】
これを繰り返し、１−６〜３０−６の液滴形成までを行った後、１−１の下隣の７０μｍ離れた位置に、１−７の液滴を形成し、順次２−７、３−７、・・・３０−７の順に移動させながら、前記溶液を吐出することにより、３５０μｍピッチで３列×１０行の液滴を形成した。
以上のことを繰り返して、図１に１点鎖線で示す境界線で分割された３列×１０行の各領域に、それぞれ３６個の液滴を、縦横ともに７０μｍのピッチで形成した。その結果、基板面全体で、縦横ともに７０μｍピッチで３６×３０個の液滴が形成された。
【００３７】
また、この実施形態では、ヘッドの移動プログラムによって、各液滴が１〜６０秒毎に順次形成されるようにした。これにより、既に形成された液滴（第１の液滴）の７０μｍ離れた隣の位置に液滴（第２の液滴）を形成する際には、第１の液滴が乾燥した状態となっていた。
以上のように、この実施形態の方法では、同時またはほぼ同時に形成される液滴を、隣の液滴から蒸発した溶媒蒸気の影響を受けないピッチ３５０μｍで形成するとともに、既に形成された液滴が乾燥した状態となってからその隣の位置に液滴を形成している。そのため、各液滴に関して、２，３−ジヒドロベンゾフランからなる気体の分圧が液滴周囲で均一になって、形成された全ての液滴が移動せずに、各液滴形成位置に留まっていることが確認できた。
【００３８】
なお、既に形成された第１の液滴の隣の位置に対する第２の液滴の形成が、前記第１の液滴の乾燥後に行われるように、複数個の液滴の形成順序を設定する方法としては、例えば、この実施形態のように、基板面を複数の領域に分割して、或る領域に液滴を形成した次の液滴の形成は別の領域に対して行うことによって、各領域内で隣合う位置に対して時間を開けて液滴を形成する方法が挙げられる。
【００３９】
別の例としては、先ず、基板の四隅の位置に形成した後に、中心に形成し、次に四隅の間の位置・・・といった順序で、既に形成された第１の液滴の隣の位置に対する第２の液滴の形成が、前記第１の液滴の乾燥後に行われるようにしながら、生産性を考慮してインクジェットヘッドの全移動距離ができるだけ小さくなるように、形成順序を設定する方法が挙げられる。
【００４０】
全ての液滴が隣の液滴の乾燥後に形成されるようにでき、しかも生産性が良い方法については、液滴の配置と大きさ、および使用する溶媒の蒸気圧等に基づいてシミュレーションを行うことによって、最適な方法を設定することができる。＜第４実施形態＞
インクジェット法で結晶性薄膜を形成するためには、配置された液滴をなす溶液を過飽和状態にするとともに、前記液滴近傍での前記溶媒と同じ成分からなる気体の分圧を、当該液滴をなす溶液から溶媒が蒸発し難い第１の分圧（例えば、飽和蒸気圧と同じかほぼ同じ分圧）に制御することにより、前記液滴に結晶核を生成させ、前記結晶核の生成後に、前記液滴近傍での前記気体の分圧を、当該結晶核の結晶成長が更なる結晶核の生成よりも優先的に生じる第２の分圧（例えば、飽和蒸気圧の１／１０〜１／１００）となるまで低下させる必要がある。以下、このインクジェット法による結晶性薄膜の形成方法について説明する。
【００４１】
この結晶性薄膜の形成方法によれば、先ず、基板上に配置された直後の液滴をなす溶液が過飽和状態となることによって、結晶化に必要な結晶核が前記溶液内に生成される。次に、前記液滴近傍での前記気体（溶媒と同じ成分からなる気体）の分圧を、前記第１の分圧（液滴をなす溶液から溶媒が蒸発し難い高い分圧）から前記第２の分圧（既に生じた結晶核の結晶成長が、更なる結晶核の生成よりも優先的に生じる低い分圧）となるまで低下させることにより、結晶成長が始まる。
【００４２】
したがって、この方法において、例えば、前記液滴の配置をインクジェット法により所定パターンで行うことによって、パターン状の結晶性薄膜を基板上に容易に形成することができる。
ここで、液滴配置工程を例えばインクジェット法で行った場合のように、基板上に配置された液滴の体積が例えば２０ピコリットルと極少量である場合には、液滴近傍での前記気体（液滴をなす溶液の溶媒と同じ成分からなる気体）の分圧が低いと、溶媒が液滴から蒸発し易いため、液滴をなす溶液の濃度が急上昇して溶液の過飽和度も急激に高くなり、多数の結晶核が形成されて溶質が粉末化し易い。これに対して、前記結晶性薄膜の形成方法では、液滴配置直後の液滴近傍での前記気体の分圧を、前記第１の分圧（液滴をなす溶液から溶媒が蒸発し難い高い分圧）に制御することにより、液滴をなす溶液が比較的低い過飽和度の過飽和状態で安定する（すなわち、液滴をなす溶液の過飽和度の上昇度合いが穏やかになる）ため、少数（理想的には１個）の核が生成される。
【００４３】
また、単結晶の薄膜を形成するためには、１個の核が生成された後にこの核のみを結晶成長させ、他の核形成を生じさせないようにする必要があるが、液滴配置直後の液滴近傍での前記気体の分圧が高いままであると、更なる核が生成されることになる。これに対して、前記結晶性薄膜の形成方法では、結晶核の生成後に前記分圧を、既に生じた結晶核の結晶成長が更なる結晶核の生成よりも優先的に生じる低い分圧（第２の分圧）となるまで低下させることにより、更なる核生成を防止しながら結晶成長を促進している。
【００４４】
したがって、前記結晶性薄膜の形成方法においては、前記第１の分圧から第２の分圧への分圧低下を、前記溶液に少数（理想的には１個）の結晶核が生成した直後に急激に行うことによって、例えば、飽和蒸気圧と同じかほぼ同じ分圧である第１の分圧から、１．３Ｐａ（１０^-2torr）である第２の分圧まで、１〜１０秒間で低下させることことによって、液滴をなす溶液の過飽和度を急激に高くして、単結晶の結晶性薄膜を得ることができる。
【００４５】
前記結晶性薄膜の形成方法において、前記第１の分圧への分圧制御方法としては、▲１▼前記液滴の吐出間隔を調整する方法、▲２▼前記溶液の吐出量を調整する方法、▲３▼前記液滴配置工程前に、液滴が配置される位置の前記気体の分圧を調整する方法が挙げられる。
前記結晶性薄膜の形成方法において、前記分圧低下方法としては、▲１▼前記液滴近傍の雰囲気を減圧する方法、▲２▼前記液滴近傍の温度を上昇させる方法、▲３▼前記液滴近傍の雰囲気を不活性ガス雰囲気に置換する方法が挙げられる。なお、▲２▼の方法では前記気体の分圧低下が生じない場合（一連の工程を密閉空間で行う場合等）もあるが、その場合でも、温度上昇によって飽和蒸気圧が高くなり、液滴の溶媒が蒸発し易い状態となるため、前記気体の分圧低下が生じた場合と同じ作用（液滴をなす溶液の過飽和度を急激に高くする）が得られる。
【００４６】
さらに、前記結晶性薄膜の形成方法においては、前記溶液として、（１）吐出時に飽和状態となる量の薄膜形成材料を含有している溶液、または（２）吐出時に濃度が飽和濃度の１／１０以上飽和濃度未満となる量で、薄膜形成材料を含有している溶液、または（３）吐出時に過飽和状態となる量の薄膜形成材料を含有している溶液を使用することが好ましい。これにより、基板上に配置された液滴をなす溶液が、吐出された直後に過飽和状態となり易くなるため、結晶核の形成が確実に行われるようになる。
【００４７】
前記結晶性薄膜の形成方法で基板上に前記溶液の液滴を配置する際に、本発明の方法を採用して前記液滴に移動が生じないようにすることによって、基板上の所定位置に結晶性薄膜を形成することができる。
この第４実施形態は、前記結晶性薄膜の形成方法を行う際に、本発明の方法を適用した実施形態である。
【００４８】
図２に示す薄膜形成装置を使用して、前記シリコン基板に対する薄膜形成を行った。この装置は、密閉容器１と、この密閉容器１内に設置されたＸ−Ｙステージ２と、インクジェット装置のヘッド３と、密閉容器１内を減圧するためのポンプ６と配管７とで構成されている。ヘッド３は密閉容器１の上部に固定されており、このヘッド３内に外部から、前記溶液が供給されるように構成されている。ヘッド３とＸ−Ｙステージ２は、互いに向かい合う位置に配置されている。ポンプ６用の配管７は密閉容器１の底部に接続されている。
【００４９】
先ず、前記密閉容器（密閉空間）１内を２５℃に保持しながら、ターチオフェン（薄膜形成材料）をドデシルベンゼン（溶媒）に濃度が０．１重量％となるように溶解させ溶液を、第３実施形態と同じ方法で、前記シリコン基板上にインクジェット法により吐出した。ただし、第３実施形態では液滴の配置位置をヘッド３の移動により行っていたが、この実施形態ではＸ−Ｙステージ２の移動により行った。
【００５０】
２５℃（溶液吐出時の温度）でのドデシルベンゼンに対するターチオフェンの飽和濃度は１．０重量％である。したがって、このターチオフェン溶液は吐出時に飽和濃度の１／１０となっている。
この液滴形成を終了すると同時に、減圧ポンプ６を稼働させてこの密閉空間内を１．３Ｐａ（１０^-2torr）まで減圧し、この状態を６時間保持した。６時間後に密閉空間から取り出したシリコン基板１には、各液滴が形成された各位置に、２０μｍ×３０μｍの略長方形のターチオフェン薄膜（厚さ５０μｍ）が、略単結晶の状態で形成されていた。ターチオフェン単結晶薄膜は、有機半導体膜として好適に使用可能な機能性薄膜である。
【００５１】
この実施形態では、吐出時の溶液の濃度が飽和濃度の１／１０であるため、基板上に配置された直後に液滴をなす溶液が過飽和状態になり易い。また、１滴当たりの吐出量を２０ピコリットルとし、液滴をピッチ７０μｍで形成していることで、液滴周囲のドデシルベンゼン（溶媒と同じ成分）からなる気体の分圧が、液滴となっている溶液から２，３−ジヒドロベンゾフラン（溶媒）が蒸発し難い高い分圧となっている。これらのことから、液滴となっている溶液が比較的低い過飽和度の過飽和状態で安定して、少数の核形成がなされたと考えられる。
【００５２】
また、液滴形成を終了すると同時に密閉空間内の減圧を開始することによって、液滴近傍での溶媒蒸気の分圧が、少数の結晶核が形成された段階で急激に低下し、液滴となっている溶液の過飽和度が急激に高くなって、更なる結晶核の形成よりも結晶成長が優先的に生じる状態となり、この減圧状態を６時間保持することによって、結晶成長が促進されたと考えられる。
【００５３】
さらに、溶媒として低蒸気圧溶媒を使用しているため、形成された全ての液滴が移動せずに各液滴形成位置に留まって、基板上の液滴形成位置（所定位置）に結晶性薄膜が形成されたと考えられる。
なお、本実施形態では図２に示す薄膜形成装置を使用しているが、減圧をより確実に行うために、図２の薄膜形成装置のヘッド３とステージ２および配管７とを隔てる仕切り板を設けたものを使用してもよい。この仕切り板を設けることにより、密閉容器１内部のヘッド設置側は減圧させずに、ステージ設置側のみを減圧することができる。
＜第５実施形態＞
この第５実施形態も、第４実施形態と同様に、前記結晶性薄膜の形成方法を行う際に、本発明の方法を適用した実施形態である。
【００５４】
前記化学式（５）で示される構造の４−アミノ−ｐ−ターフェニル（薄膜形成材料）を、ジメチルホルムアミド（溶媒）に、濃度が１．０重量％となるように溶解させて溶液を得た。２５℃（溶液吐出時の温度）でのジメチルホルムアミドに対する４−アミノ−ｐ−ターフェニルの飽和濃度は１．０重量％である。したがって、この溶液は、吐出時に、４−アミノ−ｐ−ターフェニルが飽和状態となる。
【００５５】
この溶液を用いた以外は第４実施形態と同様にして、液滴形成を行った。
この液滴形成を終了すると同時に、減圧ポンプ６を稼働させてこの密閉空間内を１．３Ｐａ（１０^-2torr）まで減圧し、この状態を６時間保持した。６時間後に密閉空間から取り出したシリコン基板１には、各液滴が形成された各位置に、２０μｍ×３０μｍの略長方形の４−アミノ−ｐ−ターフェニル薄膜（厚さ５０μｍ）が、略単結晶の状態で形成されていた。４−アミノ−ｐ−ターフェニル結晶性薄膜は、各種電子デバイス用の半導体膜として好適に使用可能な機能性薄膜である。
【００５６】
この実施形態では、吐出時に溶液が飽和状態となるため、基板上に配置された直後に液滴をなす溶液が過飽和状態になり易いことと、第４実施形態と同様の作用によって、少数の核形成がなされたと考えられる。また、結晶成長についても、第４実施形態と同様の作用によって促進されたと考えられる。
＜第６実施形態＞
この第６実施形態も、第４実施形態と同様に、前記結晶性薄膜の形成方法を行う際に、本発明の方法を適用した実施形態である。
【００５７】
前記化学式（６）で示される構造の2,2':5',2"−ターチオフェン−5,5"−ジカルボキシアルデヒド（ターチオフェンの誘導体、薄膜形成材料）を、ジメチルホルムアミド（溶媒）に、濃度が１．０重量％となるように溶解させて溶液を得た。２５℃（溶液吐出時の温度）でのジメチルホルムアミドに対する前記誘導体の飽和濃度は１．０重量％である。したがって、この溶液は、吐出時に、前記誘導体が飽和状態となる。
【００５８】
この溶液を用いた以外は第４実施形態と同様にして、液滴形成を行った。
この液滴形成を終了すると同時に、減圧ポンプ６を稼働させてこの密閉空間内を１．３Ｐａ（１０^-2torr）まで減圧し、この状態を６時間保持した。６時間後に密閉空間から取り出したシリコン基板１には、各液滴が形成された各位置に、２０μｍ×３０μｍの略長方形の2,2':5',2"−ターチオフェン−5,5"−ジカルボキシアルデヒド薄膜（厚さ５０μｍ）が、略単結晶の状態で形成されていた。2,2':5',2"−ターチオフェン−5,5"−ジカルボキシアルデヒド結晶性薄膜は、各種電子デバイス用の半導体膜として好適に使用可能な機能性薄膜である。
【００５９】
この実施形態では、吐出時に溶液が飽和状態となるため、基板上に配置された直後に液滴をなす溶液が過飽和状態になり易いことと、第４実施形態と同様の作用によって、少数の核形成がなされたと考えられる。また、結晶成長についても、第４実施形態と同様の作用によって促進されたと考えられる。
なお、前記第４〜第６実施形態では、液滴形成を終了すると同時に密閉空間内の減圧を開始することによって、第１の分圧を第２の分圧に急激に低下させて、液滴をなす溶液の過飽和度を急激に高くして単結晶の結晶性薄膜を得ているが、前記減圧開始のタイミングは液滴形成の終了と同時に限定されるものではなく、他の条件等によって適切なタイミングで行うことができる。
【００６０】
本発明の形成方法により形成された結晶性薄膜は、各種電子デバイス（トランジスタ、ダイオード、キャパシタ、有機ＥＬ装置における発光層や正孔注入／輸送層等）用の半導体膜として好適に使用できる。また、本発明の方法で薄膜形成がなされた電子デバイスを備えた表示装置としては、液晶表示装置や有機ＥＬ表示装置等が挙げられる。これらの表示装置は、例えば、図３に示す各種電子機器に適用することができる。
【００６１】
図３（ａ）は、携帯電話の一例を示した斜視図である。図３（ａ）において、符号６００は携帯電話本体を示し、符号６０１は前記表示装置を用いた表示部を示している。
図３（ｂ）は、ワープロ、パソコンなどの携帯型情報処理装置の一例を示した斜視図である。図３（ｂ）において、符号７００は情報処理装置、符号７０１はキーボードなどの入力部、符号７０３は情報処理装置本体、符号７０２は前記表示装置を用いた表示部を示している。
【００６２】
図３（ｃ）は、腕時計型電子機器の一例を示した斜視図である。図３（ｃ）において、符号８００は時計本体を示し、符号８０１は前記表示装置を用いた表示部を示している。
図３（ａ）〜（ｃ）に示すそれぞれの電子機器は、前記実施形態の方法で形成された結晶性薄膜を半導体膜として使用した電子デバイスを備えた表示装置を表示部として備えたものであり、本発明の薄膜形成方法の特徴を有する。そのため、本発明の薄膜形成方法によれば、これらの電子機器の製造方法を容易にすることができる。
【００６３】
【発明の効果】
以上説明したように、本発明の方法によれば、低分子化合物の薄膜を基板上の所定位置に形成できるようになる。
また、本発明の方法を、インクジェット法によりパターン状の結晶性薄膜を形成する方法に適用することによって、結晶性薄膜がパターンに応じた基板上の所定位置に安定的に形成され易くなる。その結果、パターン状の結晶性薄膜を容易に形成できるようになる。
【図面の簡単な説明】
【図１】 第３実施形態で行った液滴の形成順序を説明する平面図である。
【図２】 第４〜第６実施形態で使用した薄膜形成装置を示す概略構成図である。
【図３】 本発明の方法で薄膜形成がなされた電子デバイスを備えた表示装置を有する電子機器の例を示す斜視図である。
【符号の説明】
１…密閉容器、２…Ｘ−Ｙステージ、３…ヘッド（インクジェット装置）、６…ポンプ、７…配管、１−１〜１−３６…液滴、２−１，２−２…液滴、３−１，３−２…液滴、４−１，４−２…液滴、５−１，５−２…液滴、６−１，６−２…液滴、７−１，７−２…液滴、８−１，８−２…液滴、９−１，９−２…液滴、１０−１，１０−２…液滴、１１−１，１１−２…液滴、１２−１，１２−２…液滴、６００…携帯電話本体、６０１…表示部、７００…情報処理装置、７０１…入力部、７０３…情報処理装置本体、７０２…表示部、８００…時計本体、８０１…表示部。[0001]
BACKGROUND OF THE INVENTION
The present invention provides a thin film on the substrate by discharging a solution in which a thin film forming material is dissolved in a solvent, arranging a plurality of droplets of the solution on the substrate, and evaporating the solvent from each droplet. The present invention relates to a method for forming a thin film.
[0002]
[Prior art]
Conventionally, a thin film formed by an inkjet method is a thin film made of a polymer compound. A thin film made of such a polymer compound is easily formed by placing a solution in which a polymer compound is dissolved in a solvent on a substrate by an ink jet method and then evaporating the solvent from the placed solution.
[0003]
The prior art document information related to the invention of this application includes the following.
[0004]
[Patent Document 1]
Japanese Patent Laid-Open No. 11-40358
[Patent Document 2]
Japanese Patent Laid-Open No. 11-54272
[0005]
[Problems to be solved by the invention]
However, using a low molecular weight compound that is not classified as a high molecular compound (hereinafter referred to as “low molecular compound”), even if an attempt is made to form a thin film by the same method as in the case of the above high molecular compound, No thin film is formed, and particles of low molecular weight compounds are deposited on the substrate. This is because even in a lyophilic substrate, the cohesive force between the low molecular compounds is much greater than the force with which the low molecular compound and the substrate are bonded.
[0006]
Thus, it can be said that a low molecular weight compound is a material with high crystallinity from the point that cohesion force is high. The high crystallinity is a great advantage in functions such as conductivity. Therefore, a method that can form a thin film of a low molecular compound is desired.
In addition, when a droplet is placed on a substrate by ejecting a solution by the inkjet method, the partial pressure of a gas composed of the same component as the solvent of the solution forming the droplet becomes non-uniform around the droplet. If so, the droplets are distorted, and the droplets easily move to the higher partial pressure. Such movement of droplets is particularly likely to occur when a solution of a low molecular compound having a weak binding force with the substrate is discharged. When the movement of the droplet occurs, it becomes difficult to form a thin film at a predetermined position on the substrate.
[0007]
For example, when a plurality of droplets are formed at a slight interval along a line, the partial pressure around the droplet formed at the end of the line is not adjacent to the droplet. It is non-uniform because it is low on the side and high on the side where the droplets are next. This is because the partial pressure of the gas is increased by the solvent vapor evaporated from the adjacent droplet on the side where the adjacent droplet exists around the droplet formed at the end of the line.
[0008]
On the other hand, in many electronic devices, a functional thin film is patterned and used. However, even if a crystalline organic thin film is formed by a vacuum deposition method or the like, unique conditions are necessary or the material used is limited. Or receive. Furthermore, since the organic thin film has low resist resistance, it is difficult to pattern by an ordinary patterning method including a photolithography process and an etching process.
[0009]
On the other hand, if a crystalline thin film can be formed by the inkjet method, formation of a patterned crystalline organic thin film, which has been difficult with the prior art, can be easily performed.
An object of the present invention is to provide a thin film forming method in which a plurality of droplets of a solution in which a thin film forming material is dissolved in a solvent are arranged on the substrate, and the solvent is evaporated from each droplet to form a thin film on the substrate. In this case, the partial pressure of the gas around the droplet formed on the substrate is made uniform to prevent the movement of the droplet as described above, and a low molecular compound thin film can be formed at a predetermined position on the substrate. And making it possible to easily form a patterned crystalline thin film (especially an organic thin film) by an ink jet method.
[0010]
[Means for Solving the Problems]
In order to solve the above-described problems, the present invention provides a method in which a plurality of droplets of the solution are disposed on a substrate by discharging a solution in which a thin film forming material is dissolved in a solvent by an inkjet method. In the method of forming a thin film on the substrate by evaporating a solvent, the thin film forming material is composed of oligophenylene, oligothiophene, or a derivative thereof, or Alq3 (quinolinol-aluminum complex). Vapor pressure at discharge is 1.3 × 10 ^-3 Pa (1 × 10 ^-Five mmHg) is used to prevent movement of the droplets by using a low vapor pressure solvent, so that the solution forming the droplets becomes supersaturated immediately after being placed on the substrate, and the liquid By controlling the partial pressure of the gas composed of the same component as the solvent in the vicinity of the droplet to a first partial pressure at which the solvent is difficult to evaporate from the solution forming the droplet, crystal nuclei are generated in the droplet, After the formation of the crystal nuclei, the partial pressure of the gas in the vicinity of the droplet is reduced until the crystal growth of the crystal nuclei becomes a second partial pressure that occurs preferentially over the generation of further crystal nuclei. A thin film forming method is provided.
[0011]
According to this method, since it is difficult for the solvent to evaporate from each of the droplets, even if the adjacent droplet is formed at a relatively close position, the influence of the solvent vapor in which each droplet evaporates from the adjacent droplet. It is difficult to receive. Therefore, even if the droplet is formed at the end of the line as described above, the droplet can be prevented from moving.
In addition, by discharging a solution in which the thin film forming material is dissolved in a solvent, a plurality of droplets of the solution are arranged on the substrate, and the solvent is evaporated from each droplet to form a thin film on the substrate. In this method, after the first droplet is formed, the second droplet is separated from the formation position of the first droplet by a predetermined distance (the influence of the solvent vapor evaporated from the first droplet is sufficiently negligible. There is a thin film forming method characterized in that the thin film is formed at positions separated by a large distance.
[0012]
According to this method, the second droplet is formed at a position not affected by the solvent vapor evaporated from the first droplet, so that the liquid formed at the end of the line as described above can be obtained. Even a droplet can be prevented from moving.
In addition, when the interval between adjacent droplets is shorter than a predetermined distance (a sufficient distance at which the influence of the solvent vapor evaporated from the first droplet can be ignored), the first droplet is placed at a certain position in this method. Then, the next second droplet is formed not on the adjacent droplet formation position, but on the position separated by the predetermined distance from the first droplet formation position. The droplet formation position can be accommodated by forming a droplet after the first droplet has dried.
[0013]
In addition, by discharging a solution in which the thin film forming material is dissolved in a solvent, a plurality of droplets of the solution are arranged on the substrate, and the solvent is evaporated from each droplet to form a thin film on the substrate. In this method, there is a thin film forming method characterized in that the second droplet is formed at a position adjacent to the first droplet after the first droplet is dried.
[0014]
According to this method, since the formation of the droplet (second droplet) formed later is performed after drying the droplet (first droplet) formed adjacently, each droplet is adjacent to the adjacent droplet. Less susceptible to solvent vapor evaporated from droplets. Therefore, even if the droplet is formed at the end of the line as described above, the droplet can be prevented from moving.
Thin film forming materials that can be used in the method of the present invention include oligophenylene or a derivative thereof, or oligothiophene or a derivative thereof. Oligophenylene is represented by the following formula (1), and oligothiophene is represented by the following formula (2). In each case, n is 2 or more. In any case, n is preferably 2 or more and 6 or less.
[0015]
[Chemical 1]

[0016]
[Chemical formula 2]

[0017]
Examples of oligophenylene include p-terphenyl represented by the following formula (3). Examples of oligothiophene include terthiophene represented by the following formula (4). Examples of oligophenylene derivatives include 4-amino-p-terphenyl represented by the following formula (5). Examples of oligothiophene derivatives include 2,2 ': 5', 2 "-terthiophene-5,5" -dicarboxaldehyde represented by the following formula (6).
[0018]
[Chemical 3]

[0019]
[Formula 4]

[0020]
[Chemical formula 5]

[0021]
[Chemical 6]

[0022]
Examples of the thin film forming material that can be used in the method of the present invention include Alq3 (quinolinol-aluminum complex) represented by the following formula (7).
[0023]
[Chemical 7]

[0024]
The present invention also provides a method for forming an electronic device having a step of forming a thin film by the method of the present invention.
[0025]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described.
<First Embodiment>
The concentration of terthiophene (2,2 ′: 5 ′, 2 ″ -terthiophene, a thin film forming material) having the structure represented by the chemical formula (3) is 0.1 wt% in dodecylbenzene (solvent). The vapor pressure of dodecylbenzene at 20 ° C. (temperature at discharge) was 1.3 × 10 ^-3 Pa (1 × 10 ^-Five mmHg).
[0026]
In addition, the surface of the silicon substrate was irradiated with ultraviolet light having a wavelength of 172 nm to make the surface lyophilic (properly wettable by the solution). The solution was discharged onto the surface of the silicon substrate at a discharge amount of 20 picoliters per drop using an ink jet apparatus “MJ-930C” manufactured by Seiko Epson Corporation. This discharge was performed in a room at 20 ° C.
[0027]
A head provided with one nozzle was used as the head of this ink jet apparatus. In this discharge, the distance between the nozzle of the head and the substrate is 1 mm, and the solution is discharged while the head is moved along one side of the substrate by 70 μm at a discharge amount of 20 picoliter per drop. Repeated 10 times. As a result, ten droplets were formed on the silicon substrate at a pitch of 70 μm along a straight line. Next, 10 droplets were formed at a pitch of 70 μm along a straight line parallel to the straight line and separated by 70 μm. By repeating this 10 times, droplets of 10 columns × 10 rows were formed on the silicon substrate at a pitch of 70 μm.
[0028]
Next, the solvent was dried from the liquid droplets by naturally leaving in this state. At that time, it was confirmed that all the formed droplets did not move and remained at each droplet formation position. After evaporation of the solvent, a thin film made of terthiophene was formed at each droplet formation position. However, this terthiophene thin film was not a crystalline thin film but an amorphous thin film.
[0029]
Next, instead of dodecylbenzene, 1,2,3,4-tetramethylbenzene having a vapor pressure of 26 Pa (0.2 mmHg) at 20 ° C. (temperature during discharge) was used as a solvent for the comparative example. To obtain a terthiophene solution having a concentration of 0.1% by weight. Except for using this solution, droplets of 10 columns × 10 rows were formed on the silicon substrate at a pitch of 70 μm by the same method as described above, and the solvent was dried from the droplets by naturally leaving in this state. .
[0030]
At that time, among the formed droplets of 10 columns × 10 rows, all of the first column, all of the 10th column, and the first and 10th droplets of the 2nd to 9th columns Was confirmed to be moving. In other words, the droplets in the portion located on the outer periphery have moved.
Second Embodiment
The Alq3 (quinolinol-aluminum complex; thin film forming material) having the structure represented by the chemical formula (7) is dissolved in 2,3-dihydrobenzofuran (solvent) so as to have a concentration of 0.1% by weight. Obtained. The vapor pressure of 2,3-dihydrobenzofuran at 25 ° C. (temperature at the time of discharge) is 1.3 × 10 ² Pa (1 × 10 ^-1 mmHg).
[0031]
In addition, the surface of the silicon substrate was irradiated with ultraviolet light having a wavelength of 172 nm to make the surface lyophilic (properly wettable by the solution). The solution was discharged onto the surface of the silicon substrate at a discharge amount of 20 picoliters per drop using an ink jet apparatus “MJ-930C” manufactured by Seiko Epson Corporation. This discharge was performed in a room at 25 ° C.
[0032]
A head provided with one nozzle was used as the head of this ink jet apparatus. Similarly to the first embodiment, 10 columns × 10 rows of droplets were formed at respective pitches of 70 μm, 210 μm, 280 μm, 350 μm, 420 μm, and 560 μm. The distance between the head nozzle and the substrate was 1 mm.
Thus, sample No. 1 has a pitch of 70 μm, sample No. 2 has a pitch of 210 μm, sample No. 3 has a pitch of 280 μm, sample No. 4 has a pitch of 350 μm, sample No. 5 has a pitch of 420 μm, sample No. In No. 6, droplets of 10 columns × 10 rows were formed on each silicon substrate at a pitch of 560 μm.
[0033]
Next, the substrate of each sample was allowed to stand in this state to dry the solvent from the droplets. At that time, in Sample Nos. 4 to 6 in which the droplets were formed at a pitch of 350 μm or more, it was confirmed that all the formed droplets did not move and remained at each droplet formation position. After evaporation of the solvent, a thin film made of Alq3 was formed at each droplet formation position. However, this Alq3 thin film was not a crystalline thin film but an amorphous thin film.
[0034]
On the other hand, in sample Nos. 1 to 3 in which the droplets were formed at a pitch of 280 μm or less, all of the first row and all the 10th columns among the formed 10 × 10 droplets It was confirmed that the liquid droplets in the first row and the 10th row in the 2nd and 9th columns were moving. In other words, the droplets in the portion located on the outer periphery have moved.
From the above, in this embodiment, by forming adjacent droplets at intervals of 350 μm or more, the influence of the solvent (2,3-dihydrobenzofuran) vapor in which each droplet evaporated from the adjacent droplet It is considered that the partial pressure of the gas composed of 2,3-dihydrobenzofuran became uniform around each droplet.
<Third Embodiment>
Droplets were formed by the following method using droplets made of the same Alq3 2,3-dihydrobenzofuran solution as in the second embodiment. This method will be described with reference to FIG.
[0035]
Using a head having one nozzle, moving it in the order of 1-1, 2-1, 3-1,... 30-1 (up to 12-2 in FIG. 1) in FIG. By discharging the solution, droplets of 3 columns × 10 rows were formed at a pitch of 350 μm. Next, a droplet of 1-2 is formed at a position 70 μm away to the right of 1-1, and the solution is moved while sequentially moving in the order of 2-2, 3-2,. By discharging, droplets of 3 columns × 10 rows were formed at a pitch of 350 μm.
[0036]
This process was repeated until the formation of droplets 1-6 to 30-6 was performed, and then 1-7 droplets were formed at positions 70 μm apart adjacent to the bottom of 1-1. While moving in the order of −7,... 30-7, the solution was discharged to form droplets of 3 columns × 10 rows at a pitch of 350 μm.
By repeating the above, 36 droplets were formed at a pitch of 70 μm both vertically and horizontally in each region of 3 columns × 10 rows divided by the boundary line shown by the one-dot chain line in FIG. As a result, 36 × 30 droplets were formed on the entire substrate surface at a pitch of 70 μm both vertically and horizontally.
[0037]
Further, in this embodiment, each droplet is sequentially formed every 1 to 60 seconds by the head moving program. As a result, when the droplet (second droplet) is formed at a position adjacent to the previously formed droplet (first droplet) by 70 μm, the first droplet is in a dry state. It was.
As described above, in the method of this embodiment, droplets formed simultaneously or almost simultaneously are formed with a pitch of 350 μm that is not affected by the solvent vapor evaporated from the adjacent droplets, and droplets that have already been formed. After the liquid becomes dry, droplets are formed at positions adjacent to it. Therefore, for each droplet, the partial pressure of the gas composed of 2,3-dihydrobenzofuran becomes uniform around the droplet, and all the formed droplets do not move and stay at each droplet formation position. It was confirmed that
[0038]
Note that the order of forming the plurality of droplets is set so that the second droplet is formed at the position adjacent to the already formed first droplet after the first droplet is dried. As a method, for example, as in this embodiment, the substrate surface is divided into a plurality of regions, and a droplet is formed in a certain region, and then the next droplet is formed on another region. There is a method in which droplets are formed with a time interval between adjacent positions in each region.
[0039]
As another example, first, the substrate is formed at the four corner positions, then formed at the center, and then the positions between the four corners. A method of setting the formation order so that the total movement distance of the ink-jet head becomes as small as possible in consideration of productivity while forming the second droplet with respect to the first droplet after the drying of the first droplet Is mentioned.
[0040]
For a method that enables all droplets to be formed after the adjacent droplets are dried and has good productivity, a simulation is performed based on the arrangement and size of the droplets and the vapor pressure of the solvent used. Thus, an optimal method can be set. <Fourth embodiment>
In order to form a crystalline thin film by the ink jet method, the solution forming the arranged droplet is supersaturated, and the partial pressure of the gas composed of the same component as the solvent in the vicinity of the droplet is changed to the droplet. The crystal nuclei are generated in the droplets by controlling to a first partial pressure at which the solvent does not easily evaporate from the solution forming the above (for example, a partial pressure equal to or approximately the same as the saturated vapor pressure). The partial pressure of the gas in the vicinity of the droplet is set to a second partial pressure (for example, 1/10 to 1 of the saturated vapor pressure) in which the crystal growth of the crystal nucleus preferentially occurs over the generation of a further crystal nucleus. / 100). Hereinafter, a method for forming a crystalline thin film by the ink jet method will be described.
[0041]
According to this method for forming a crystalline thin film, first, a solution forming a droplet immediately after being placed on a substrate is in a supersaturated state, thereby generating crystal nuclei necessary for crystallization in the solution. Next, the partial pressure of the gas (a gas composed of the same component as the solvent) in the vicinity of the droplet is changed from the first partial pressure (a high partial pressure at which the solvent hardly evaporates from the solution forming the droplet). Crystal growth begins by lowering to a partial pressure of 2 (the crystal growth of crystal nuclei already generated is a low partial pressure that occurs preferentially over the formation of further crystal nuclei).
[0042]
Therefore, in this method, for example, a patterned crystalline thin film can be easily formed on a substrate by arranging the droplets in a predetermined pattern by an ink jet method.
Here, when the volume of the droplet placed on the substrate is as small as 20 picoliters, for example, when the droplet placement step is performed by an ink jet method, the gas in the vicinity of the droplet is used. If the partial pressure of the gas (which consists of the same components as the solvent of the solution forming the droplet) is low, the solvent easily evaporates from the droplet, so the concentration of the solution forming the droplet increases rapidly and the supersaturation degree of the solution also increases rapidly. It becomes high and many crystal nuclei are formed, and the solute is easily powdered. In contrast, in the method for forming a crystalline thin film, the partial pressure of the gas in the vicinity of the droplet immediately after the droplet is placed is set to the first partial pressure (the solvent is difficult to evaporate from the solution forming the droplet). (Partial pressure), the solution forming the droplet stabilizes in a supersaturated state with a relatively low supersaturation (that is, the degree of increase in the supersaturation of the solution forming the droplet becomes mild), so a small number (ideal 1) is generated.
[0043]
In addition, in order to form a single crystal thin film, it is necessary to grow only this nucleus after one nucleus is generated and prevent other nucleation from occurring. If the partial pressure of the gas in the vicinity of the droplet remains high, further nuclei will be generated. On the other hand, in the method for forming a crystalline thin film, the partial pressure after the formation of crystal nuclei is set to a low partial pressure (first step) in which the crystal growth of the already formed crystal nuclei preferentially occurs over the generation of further crystal nuclei. 2), the crystal growth is promoted while preventing further nucleation.
[0044]
Therefore, in the method for forming the crystalline thin film, the partial pressure drop from the first partial pressure to the second partial pressure is performed immediately after a small number (ideally one) crystal nucleus is generated in the solution. For example, from the first partial pressure which is the same or substantially the same partial pressure as the saturated vapor pressure, ^-2 Torr) is decreased in 1 to 10 seconds until the second partial pressure is reached, whereby the degree of supersaturation of the solution forming the droplets can be rapidly increased to obtain a single crystal crystalline thin film.
[0045]
In the method of forming the crystalline thin film, the partial pressure control method to the first partial pressure includes (1) a method of adjusting the discharge interval of the droplets, and (2) a method of adjusting the discharge amount of the solution. (3) A method of adjusting the partial pressure of the gas at the position where the droplet is arranged before the droplet arranging step is mentioned.
In the method for forming the crystalline thin film, the partial pressure lowering method includes (1) a method of reducing the atmosphere in the vicinity of the droplet, (2) a method of increasing the temperature in the vicinity of the droplet, and (3) the liquid. A method of substituting the atmosphere in the vicinity of the droplets with an inert gas atmosphere can be mentioned. In the method (2), there is a case where the partial pressure of the gas does not decrease (such as when a series of steps are performed in a closed space). Therefore, the same action as when the partial pressure of the gas is reduced (the supersaturation degree of the solution forming the droplet is rapidly increased) can be obtained.
[0046]
Further, in the method for forming a crystalline thin film, as the solution, (1) a solution containing an amount of a thin film forming material that is saturated upon discharge, or (2) It is preferable to use a solution containing a thin film forming material in an amount that becomes 10 or more and less than a saturated concentration, or (3) a solution containing an amount of a thin film forming material that becomes supersaturated when discharged. As a result, the solution forming the droplets disposed on the substrate is likely to be supersaturated immediately after being discharged, so that the formation of crystal nuclei is reliably performed.
[0047]
When the droplet of the solution is disposed on the substrate by the method for forming the crystalline thin film, the method of the present invention is used to prevent the droplet from moving, so that the droplet is placed at a predetermined position on the substrate. A crystalline thin film can be formed.
The fourth embodiment is an embodiment in which the method of the present invention is applied when the method for forming a crystalline thin film is performed.
[0048]
A thin film was formed on the silicon substrate using the thin film forming apparatus shown in FIG. This apparatus is composed of a hermetic container 1, an XY stage 2 installed in the hermetic container 1, a head 3 of an ink jet apparatus, a pump 6 for reducing the pressure in the hermetic container 1, and a pipe 7. ing. The head 3 is fixed to the upper part of the hermetic container 1, and the solution is supplied into the head 3 from the outside. The head 3 and the XY stage 2 are disposed at positions facing each other. A pipe 7 for the pump 6 is connected to the bottom of the sealed container 1.
[0049]
First, while keeping the inside of the sealed container (sealed space) 1 at 25 ° C., terthiophene (thin film forming material) is dissolved in dodecylbenzene (solvent) so as to have a concentration of 0.1% by weight. In the same manner as in the third embodiment, the ink was ejected onto the silicon substrate by an inkjet method. However, in the third embodiment, the arrangement position of the droplet is performed by the movement of the head 3, but in this embodiment, it is performed by the movement of the XY stage 2.
[0050]
The saturation concentration of terthiophene with respect to dodecylbenzene at 25 ° C. (temperature at the time of solution discharge) is 1.0% by weight. Therefore, this terthiophene solution is 1/10 of the saturated concentration during ejection.
Simultaneously with the completion of the droplet formation, the decompression pump 6 is operated to move 1.3 Pa (10 ^-2 torr) and this state was maintained for 6 hours. On the silicon substrate 1 taken out of the sealed space after 6 hours, a 20 μm × 30 μm approximately rectangular terthiophene thin film (thickness 50 μm) is formed in a substantially single crystal state at each position where each droplet is formed. It was. The terthiophene single crystal thin film is a functional thin film that can be suitably used as an organic semiconductor film.
[0051]
In this embodiment, since the concentration of the solution at the time of ejection is 1/10 of the saturated concentration, the solution that forms droplets immediately after being placed on the substrate tends to be supersaturated. Moreover, the discharge amount per droplet is 20 picoliters, and the droplets are formed with a pitch of 70 μm, so that the partial pressure of the gas composed of dodecylbenzene (same component as the solvent) around the droplets The resulting solution has a high partial pressure at which 2,3-dihydrobenzofuran (solvent) hardly evaporates. From these facts, it is considered that the solution in the form of droplets was stably in a supersaturated state with a relatively low supersaturation level, and a small number of nuclei were formed.
[0052]
In addition, by starting the pressure reduction in the sealed space at the same time as the formation of the droplet, the partial pressure of the solvent vapor in the vicinity of the droplet is drastically reduced when a small number of crystal nuclei are formed. The supersaturation degree of the solution is rapidly increased, and crystal growth occurs preferentially over the formation of further crystal nuclei, and it is considered that the crystal growth was promoted by maintaining this reduced pressure state for 6 hours. It is done.
[0053]
Furthermore, since a low vapor pressure solvent is used as the solvent, all the formed droplets do not move and remain at each droplet formation position, and crystallinity at the droplet formation position (predetermined position) on the substrate. It is thought that a thin film was formed.
In this embodiment, the thin film forming apparatus shown in FIG. 2 is used. However, in order to perform decompression more reliably, a partition plate that separates the head 3 from the thin film forming apparatus in FIG. You may use what was provided. By providing this partition plate, only the stage installation side can be decompressed without depressurizing the head installation side inside the sealed container 1.
<Fifth Embodiment>
As in the fourth embodiment, the fifth embodiment is an embodiment to which the method of the present invention is applied when performing the method for forming a crystalline thin film.
[0054]
A solution was obtained by dissolving 4-amino-p-terphenyl (thin film forming material) having the structure represented by the chemical formula (5) in dimethylformamide (solvent) to a concentration of 1.0% by weight. . The saturated concentration of 4-amino-p-terphenyl with respect to dimethylformamide at 25 ° C. (temperature at the time of solution discharge) is 1.0% by weight. Therefore, when this solution is discharged, 4-amino-p-terphenyl is saturated.
[0055]
Droplets were formed in the same manner as in the fourth embodiment except that this solution was used.
Simultaneously with the completion of the droplet formation, the decompression pump 6 is operated to move 1.3 Pa (10 ^-2 torr) and this state was maintained for 6 hours. On the silicon substrate 1 taken out from the sealed space after 6 hours, a substantially rectangular 4-amino-p-terphenyl thin film (thickness: 50 μm) of 20 μm × 30 μm is formed at each position where each droplet is formed. It was formed in a crystalline state. The 4-amino-p-terphenyl crystalline thin film is a functional thin film that can be suitably used as a semiconductor film for various electronic devices.
[0056]
In this embodiment, since the solution becomes saturated at the time of ejection, the solution that forms droplets immediately after being placed on the substrate is likely to be supersaturated, and a small number of nuclei are obtained by the same operation as in the fourth embodiment. It is thought that the formation was made. Also, it is considered that the crystal growth was promoted by the same action as in the fourth embodiment.
<Sixth Embodiment>
As in the fourth embodiment, this sixth embodiment is also an embodiment to which the method of the present invention is applied when the method for forming a crystalline thin film is performed.
[0057]
2,2 ': 5', 2 "-terthiophene-5,5" -dicarboxaldehyde (terthiophene derivative, thin film forming material) having the structure represented by the chemical formula (6) is converted into dimethylformamide (solvent). The solution was obtained by dissolving to a concentration of 1.0% by weight. The saturated concentration of the derivative with respect to dimethylformamide at 25 ° C. (temperature at which the solution is discharged) is 1.0% by weight. Therefore, the derivative of the solution is saturated when discharged.
[0058]
Droplets were formed in the same manner as in the fourth embodiment except that this solution was used.
Simultaneously with the completion of the droplet formation, the decompression pump 6 is operated to move 1.3 Pa (10 ^-2 torr) and this state was maintained for 6 hours. 6 hours later, the silicon substrate 1 taken out of the sealed space has a 20 μm × 30 μm approximately rectangular 2,2 ′: 5 ′, 2 ”-terthiophene-5,5” at each position where each droplet is formed. -The dicarboxaldehyde thin film (50 micrometers in thickness) was formed in the state of a substantially single crystal. The 2,2 ': 5', 2 "-terthiophene-5,5" -dicarboxaldehyde crystalline thin film is a functional thin film that can be suitably used as a semiconductor film for various electronic devices.
[0059]
In this embodiment, since the solution becomes saturated at the time of ejection, the solution that forms droplets immediately after being placed on the substrate is likely to be supersaturated, and a small number of nuclei are obtained by the same operation as in the fourth embodiment. It is thought that the formation was made. Also, it is considered that the crystal growth was promoted by the same action as in the fourth embodiment.
In the fourth to sixth embodiments, the first partial pressure is drastically reduced to the second partial pressure by starting the pressure reduction in the sealed space at the same time as the formation of the liquid droplets is completed. Although the single crystal thin film is obtained by rapidly increasing the supersaturation degree of the solution forming the above, the timing of the decompression start is not limited at the same time as the end of the droplet formation, and may be appropriate depending on other conditions Can be done at any time.
[0060]
The crystalline thin film formed by the forming method of the present invention can be suitably used as a semiconductor film for various electronic devices (transistors, diodes, capacitors, light emitting layers and hole injection / transport layers in organic EL devices, etc.). In addition, examples of the display device including an electronic device in which a thin film is formed by the method of the present invention include a liquid crystal display device and an organic EL display device. These display devices can be applied to, for example, various electronic devices shown in FIG.
[0061]
FIG. 3A is a perspective view showing an example of a mobile phone. In FIG. 3A, reference numeral 600 indicates a mobile phone body, and reference numeral 601 indicates a display unit using the display device.
FIG. 3B is a perspective view showing an example of a portable information processing apparatus such as a word processor or a personal computer. 3B, reference numeral 700 denotes an information processing apparatus, reference numeral 701 denotes an input unit such as a keyboard, reference numeral 703 denotes an information processing apparatus main body, and reference numeral 702 denotes a display unit using the display device.
[0062]
FIG. 3C is a perspective view showing an example of a wristwatch type electronic device. In FIG. 3C, reference numeral 800 denotes a watch body, and reference numeral 801 denotes a display unit using the display device.
Each of the electronic devices shown in FIGS. 3A to 3C is provided with a display device including an electronic device using the crystalline thin film formed by the method of the embodiment as a semiconductor film as a display unit. There is a feature of the thin film forming method of the present invention. Therefore, according to the thin film forming method of the present invention, the manufacturing method of these electronic devices can be facilitated.
[0063]
【The invention's effect】
As described above, according to the method of the present invention, a thin film of a low molecular compound can be formed at a predetermined position on the substrate.
In addition, by applying the method of the present invention to a method of forming a patterned crystalline thin film by an ink jet method, the crystalline thin film is easily formed stably at a predetermined position on the substrate corresponding to the pattern. As a result, a patterned crystalline thin film can be easily formed.
[Brief description of the drawings]
FIG. 1 is a plan view for explaining a droplet formation order performed in a third embodiment.
FIG. 2 is a schematic configuration diagram showing a thin film forming apparatus used in the fourth to sixth embodiments.
FIG. 3 is a perspective view illustrating an example of an electronic apparatus having a display device including an electronic device on which a thin film is formed by the method of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Airtight container, 2 ... XY stage, 3 ... Head (inkjet apparatus), 6 ... Pump, 7 ... Piping, 1-1 to 1-36 ... Droplet, 2-1, 2-2 ... Droplet, 3-1, 3-2 ... droplet, 4-1, 4-2 ... droplet, 5-1, 5-2 ... droplet, 6-1, 6-2 ... droplet, 7-1, 7- 2 ... droplet, 8-1,8-2 ... droplet, 9-1,9-2 ... droplet, 10-1,10-2 ... droplet, 11-1,11-2 ... droplet, 12 -1,12-2 ... droplet, 600 ... mobile phone body, 601 ... display unit, 700 ... information processing device, 701 ... input unit, 703 ... information processing device body, 702 ... display unit, 800 ... clock body, 801 ... display section.

Claims (2)

By discharging a solution in which a thin film forming material is dissolved in a solvent by an ink jet method, a plurality of droplets of the solution are arranged on the substrate, and by evaporating the solvent from each droplet, a thin film is formed on the substrate. In the forming method,
The thin film forming material is composed of oligophenylene, oligothiophene, or a derivative thereof, or Alq3 (quinolinol-aluminum complex).
By using a low vapor pressure solvent having a vapor pressure at the time of discharge of 1.3 × 10 ⁻³ Pa (1 × 10 ⁻⁵ mmHg) or less as the solvent, the droplets are prevented from moving.
Immediately after the solution forming the droplet is placed on the substrate, a supersaturated state is obtained, and the partial pressure of the gas composed of the same component as the solvent in the vicinity of the droplet is changed from the solution forming the droplet to the solvent. Is controlled to a first partial pressure at which it is difficult to evaporate, thereby generating crystal nuclei in the droplets,
After the formation of the crystal nuclei, the partial pressure of the gas in the vicinity of the droplet is reduced until the crystal growth of the crystal nuclei becomes a second partial pressure that occurs preferentially over the generation of further crystal nuclei. A method for forming a thin film.   The formation method of an electronic device which has the process of forming a thin film with the method of Claim 1.

Images