JP3596007B2 - Method of forming single crystalline thin film - Google Patents

Description

【００７７】
表１に示されるように、本例では隙間（ｄ）が３ｍｍ以下であれば、単結晶性の強い薄膜が得られることが明らかになった。
【００７８】
例６
基材として厚さ０．１ｍｍ、幅５ｍｍのハステロイと呼ばれるＮｉ基合金テープを用い、図７に示すようなレーザアブレーション法を用いて、イットリア安定化ジルコニアおよび酸化マグネシウムの薄膜を各々個別に形成させた。
【００７９】
レーザアブレーション法において、基材温度は６５０〜７５０℃に設定し、酸素ガスの圧力は３０〜５００ｍＴｏｒｒに設定した。また、レーザとしてＫｒＦエキシマレーザ（波長２４８ｎｍ）を用い、レーザエネルギー密度は１．５〜３．３Ｊ／ｃｍ^２ 、レーザ繰返し周波数は１〜１００Ｈｚであった。また、基材５１とマスク５２の隙間（ｄ）は０．８ｍｍに設定した。
【００８０】
本例では、基材５１のマスク５２に覆われる部分と気相成長のための環境にさらされる部分との境界領域の移動速度が成膜に対してどのような影響を与えるかについて調べるため、マスク５２に対する基材５１の移動速度を０．１〜１．５ｃｍ／分の範囲で変化させて、基材全体にわたって厚み０．２μｍの薄膜を形成させた。
【００８１】
得られたイットリア安定化ジルコニア薄膜および酸化マグネシウム薄膜の各々における面内配向性について調査を行なった。
【００８２】
その結果、形成されたどちらの薄膜においても、テープ基材面に対して垂直に（１００）軸が配向し、基材面と平行の方向には薄膜結晶の成長端に沿って（０１０）軸が配向していた。
【００８３】
また、各薄膜における（０１０）面内配向の程度を比較するため、各結晶粒の相互の傾きが±５°以内である比率を求め、その結果を表２に示した。
【００８４】
【表２】

【００８５】
表２に示されるように、マスクに対するテープ基材の移動速度が１ｃｍ／分以上、すなわち、基材のマスクに覆われる部分と気相成長のための環境にさらされる部分との境界領域の移動速度が１ｃｍ／分以上であれば、良好な面内配向性を有する薄膜を得られることが明らかになった。
【００８６】
例７
例６と同様に、基材として厚さ０．１ｍｍ、幅５ｍｍのハステロイと呼ばれるＮｉ基合金テープを用い、まずマスクを設けない状態で基材上にイットリア安定化ジルコニア薄膜を形成させた。このようにして形成させた薄膜は、基材表面に（１００）軸および（１１１）軸が混在して垂直に立ったものであり、基材面内の方向においてランダムな配向を示した。
【００８７】
次に、基材上に形成したイットリア安定ジルコニア薄膜の上に、図７に示すようなレーザアブレーション法を用いて、Ｙ₁Ｂａ₂Ｃｕ₃Ｏ_X薄膜を形成させた。レーザアブレーション法において、基材温度は７００℃に設定し、酸素ガスの圧力は２００ｍＴｏｒｒに設定した。また、レーザとしてＫｒＦエキシマレーザ（波長２４８ｎｍ）を用い、レーザエネルギー密度は１．５〜３．３Ｊ／ｃｍ²、レーザ繰返し周波数は１〜１００Ｈｚであった。また、基材５１とマスク５２の隙間（ｄ）は１．０ｍｍに設定した。
【００８８】
本例では、基材５１のマスク５２に覆われる部分と気相成長のための環境にさらされる部分との境界領域の移動速度が成膜に対してどのような影響を与えるかについて調べるため、マスク５２に対する基材５１の移動速度を０．１〜２．０ｃｍ／分の範囲で変化させて、基材全体にわたって厚み１．０μｍの薄膜を形成させた。
【００８９】
得られたＹ_１ Ｂａ_２ Ｃｕ_３ Ｏ_Ｘ 薄膜における面内配向性について調査を行なった。
【００９０】
その結果、形成された薄膜は、基材表面にｃ軸が垂直に立ったものであり、薄膜結晶の成長端に沿ってａ軸およびｂ軸の配向性を強く示した。
【００９１】
また、薄膜における（０１０）面内配向の程度を比較するため、各結晶粒のａ軸の傾きが±５°以内である比率を求め、その結果を表３に示した。
【００９２】
【表３】

【００９３】
表３に示されるように、マスクに対するテープ基材の移動速度が１ｃｍ／分以上、すなわち、テープ基材のマスクに覆われる部分と気相成長のための環境にさらされる部分との境界領域の移動速度が１ｃｍ／分以上であれば、比率が９０％を上回り、良好な面内配向性を有する薄膜が得られることが明らかになった。
【００９４】
上述の例６，７からわかるように、基材のマスクに覆われる部分と気相成長のための環境にさらされる部分との境界領域の移動速度を１ｃｍ／分以上とすることでマスクと基材との間隔（ｄ）を３ｍｍ以下に設定しなくても、良好な面内配向性が実現できることが確認された。
【００９５】
例８
基材として厚さ０．１ｍｍ、幅５ｍｍのＮｉ−Ｃｒ合金テープを用い、例１と同様の製作プロセスにおいて反応性真空蒸着法により基材上に酸化マグネシウムの薄膜を形成させた。この場合、テープ先端より３．２ｃｍのところから単結晶性の強い酸化マグネシウム薄膜が形成された。
【００９６】
形成された薄膜において、テープ基材面に対して垂直に（１００）軸が配向し、基材面と平行の方向には（０１０）軸が角度４°の範囲内で一方向に配向していた。また、（００１）軸も（０１０）軸と同程度に配向していた。
【００９７】
例９
例８で作製された酸化マグネシウム薄膜上にＢｉ₂Ｓｒ₂Ｃａ₂Ｃｕ₃Ｏ_Xの薄膜をエキシマレーザアブレーション法により形成させた。レーザアブレーション法は、基材温度７２０℃、酸素ガス圧力１１０ｍＴｏｒｒ、基材の連続移動速度１．３ｍｍ／分、成膜速度０．１８μｍ／分の条件下で行なわれた。得られた薄膜は、テープ先端より３．８ｃｍのところから単結晶性の強い膜となり、かつｃ軸配向で、ａ軸およびｂ軸の各々の傾角は全長にわたって３．２°以内であった。
【００９８】
例１０
以上例１〜例９はテープ状の基材に薄膜を形成するものであったが、例１０では上述したような窓を有するマスクを用いて基材上の所定の領域に単結晶性薄膜を形成させた。
【００９９】
基材としてイットリア安定化ジルコニアの焼結体シート（５０×５０ｍｍ）を用い、マスクとして１０×１０ｍｍの正方形の窓が形成されたステンレス製マスク（１５０×１５０ｍｍ）を用いた。実施例３と同じ成膜条件下においてマスクと基材の隙間を０．２ｍｍとし、図２に示すようにしてマスクを連続的に移動させて基材面にＹ_１ Ｂａ_２ Ｃｕ_３ Ｏ_Ｘ 薄膜を形成させた。
【０１００】
このようにして形成させた膜では、ａおよびｂ軸が３°以内の傾角で配向することが明らかとなった。一方、ジルコニア基材は多結晶体であるため、マスクを用いずに基材上にそのまま薄膜を形成した場合、ｃ軸のみが配向した膜が得られ、ａおよびｂ軸は無配向であった。
【０１０１】
実施例１
基材として、厚み０．１ｍｍ、幅５ｍｍのＮｉ−Ｃｒ合金テープ上にイットリア安定化ジルコニア薄膜を形成し、さらにその上に銀の薄膜を０．３μｍの厚さで形成したものを用いた。
【０１０２】
このように銀薄膜が形成された基材上に、図８に示すようにしてＹ_１ Ｂａ_２ Ｃｕ_３ Ｏ_Ｘ 薄膜をエキシマレーザアブレーション法により形成した。図に示すように、銀薄膜６０を有する基材６１が、薄膜の形成環境にさらされる領域においてマスク６２の先端から１ｍｍまでの領域（図においてＦで示す）は、温度が７００℃に保持された。一方、マスク６２の先端より１ｍｍのところから３０℃／ｍｍの温度勾配が設定された。このような温度環境において、銀薄膜は上述したように固液境界を形成し、基材においてマスクで覆われる部分と薄膜の形成環境にさらされる部分との境界領域において図４に示されるような階段形状を有した。
【０１０３】
例２と同様にターゲット６４としてＹ系焼結体を用い、ターゲット６４にエキシマレーザ６５を照射することにより、プルーム６６を発生させ、プルーム６６中の化学種を基材６１上に堆積させた。基材６１の移動速度は５ｍｍ／分に設定され、成膜速度は０．４１μｍ／分に設定された。
【０１０４】
このようにして形成されたＹ_１ Ｂａ_２ Ｃｕ_３ Ｏ_Ｘ 膜は、テープ先端より３．５ｃｍのところから基材面内方向にａ軸およびｂ軸が揃い始め、それから２ｍの長さにわたって傾角が４°以内であることが確認された。
【０１０５】
実施例２
例８と同様に、まず、Ｎｉ−Ｃｒ合金テープ（厚さ０．１ｍｍ、幅５ｍｍ）上に酸化マグネシウムの薄膜を形成した。次に、酸化マグネシウムを形成した合金テープ上に実施例１と同様にして銀の薄膜を０．３μｍの厚さで形成した。
【０１０６】
次に、実施例１と同様にマスクを用いるプロセスにおいてエキシマレーザアブレーション法によりＢｉ₂Ｓｒ₂Ｃａ₂Ｃｕ₃Ｏ_Xの薄膜を基材に形成された酸化マグネシウム薄膜上に堆積させていった。形成されたＢｉ₂Ｓｒ₂Ｃａ₂Ｃｕ₃Ｏ_X薄膜は、テープの先端より４ｃｍのところから基材面内においてａおよびｂ軸が揃い始め、２ｍの長さにわたってその傾角が５°以内であった。
【０１０７】
実施例３
酸化マグネシウムの焼結基板（サイズ５０×５０×０．５ｍｍ）を用い、図９に示すように、基板７１のマスク７２の下から矢印の方向に移動させていくことにより、Ｙ₁Ｂａ₂Ｃｕ₃Ｏ_Xの薄膜を形成した。薄膜の形成にあたって、基板には予め厚さ０．５μｍの銀皮膜が形成されていた。また、温度分布および温度分布に対するマスクの位置は、実施例１と同様に設定した。実施例１と同様の成膜条件および移動条件下で、エキシマレーザアブレーション法によりＹ₁Ｂａ₂Ｃｕ₃Ｏ_X薄膜を形成した。得られた薄膜は、基板全面にわたってａおよびｂ軸を基板面内において揃えており、その傾角は３°以内であった。
【０１０８】
実施例４
図１０に示すように、Ｎｉ−Ｃｒ合金（厚み０．１ｍｍ、幅１０ｍｍ）からなる基材８１上に、配管８５が接続され、かつ先端部にスリット８２ａが形成されたマスク８２を設けた。マスク８２内は空洞になっており、配管８５から供給されるガスが、スリット８２ａから噴出されるようになっている。また、スリットの高さは０．２ｍｍ、幅はテープ状の基材と同じ１０ｍｍであった。
【０１０９】
このようにスリットを有するマスクを用い、上述した実施例と同様に基材を連続的に移動させながら、真空蒸着法によりイットリア安定化ジルコニア薄膜を堆積させた。成膜において、スリット８２ａからは酸素ガスが２ｃｃ／分の流速で基材の移動方向と同方向に流された。また、成膜室のガス圧力は４ｍＴｏｒｒに設定された。さらに、基材温度を７８０℃に設定し、４ｍｍ／分の速度で図１０に示す矢印の方向に基材を移動させながら、０．０５μｍ／分の速度で成膜が行なわれた。
【０１１０】
以上のようにして薄膜を形成した結果、テープの先端より２．８ｃｍのところからは全長１．８ｍにわたって（００１）配向（テープ面に垂直）となり、かつテープ上のガス流方向に（１１０）配向するイットリア安定化ジルコニア薄膜が得られた。このようにして軸配向したイットリア安定化ジルコニア薄膜は単結晶薄膜と言える。
【０１１１】
実施例５
実施例４と同じテープ状の基材を用い、マスクを用いずに配向性のないイットリア安定化ジルコニア薄膜を長さ１．５ｍにわたって基材上に予め形成した。次に、このようにして形成した薄膜上に、Ｙ₁Ｂａ₂Ｃｕ₃Ｏ_Xの薄膜を図１０に示すようにして形成させた。薄膜の形成において、基材温度を７００℃、スリットから流す酸素の流量を２０ｓｃｃｍ、成膜室のガス圧力を１５０ｍＴｏｒｒに設定した。また、テープ状の基材は、２．５ｃｍ／分の速度でエキシマレーザアブレーションにより成膜が行なわれた。
【０１１２】
以上の条件で形成されたＹ_１ Ｂａ_２ Ｃｕ_３ Ｏ_Ｘ 薄膜は、テープ先端から２５ｍｍまではｃ軸配向を示したが、テープ面内方向においてａおよびｂ軸に関しては無配向であった。しかしながら、２５ｍｍから１．４７５ｍの全長にわたってａ、ｂ軸が特定の方向に流されたガスの向きに揃い、かつその傾角が全長にわたって３°以内である薄膜が得られた。
【０１１３】
実施例６
実施例４と同様にして、Ｎｉ合金テープ上に酸化マグネシウムの薄膜を形成させた。このとき、テープの先端より２．８ｃｍのところからは全長１．８ｍにわたって（００１）配向（テープ面に垂直）であり、かつガス流方向に（１００）配向する酸化マグネシウム薄膜が得られた。
【０１１４】
実施例７
実施例４と同じテープ状の基材を用い、まず、その上に配向性のない酸化マグネシウム薄膜を通常の真空蒸着法で形成させた。
【０１１５】
次に、図１０に示すようにして、基材温度７２０℃、酸素流量３０ｓｃｃｍ、ガス圧力１１０ｍＴｏｒｒの条件下で、エキシマレーザアブレーション法により酸化マグネシウム薄膜上にＢｉ_２ Ｓｒ_２ Ｃａ_２ Ｃｕ_３ Ｏ_Ｘ 薄膜を形成した。薄膜形成において、テープ移動速度は１．８ｃｍ／分、成膜速度は１．１μｍ／分に設定された。
【０１１６】
以上のようにして形成された薄膜において、テープ先端より３．２ｃｍまでの部分はｃ軸配向（基材面に垂直）を示したが、テープ面方向において配向（ａおよびｂ軸）はランダムであった。しかしながら、テープ先端より３．２ｃｍのところから長さ１．２ｍにわたる部分に形成された膜は、ｃ軸配向とともにａおよびｂ軸がガス流方向に一致した配向を示し、その傾角は４°以内で一定であった。
【０１１７】
実施例８
５０×５０ｍｍの多結晶酸化マグネシウム焼結体を基板として用い、ガスノズルのスリット幅が５０ｍｍであるマスクにより基板を覆いながら、真空蒸着法によりＹ₁Ｂａ₂Ｃｕ₃Ｏ_X薄膜を形成した。薄膜形成は、基板温度７００℃、酸素ガス流量１０ｓｃｃｍ、ガス圧力１０ｍＴｏｒｒ、成膜速度０．０５μｍ／分、基板の移動速度０．５ｍｍ／分の条件下で行なわれた。
【０１１８】
このようにして形成された膜は、５０×５０ｍｍの領域のうち３０×５０ｍｍの領域において、ａ、ｂおよびｃ軸が揃った単結晶性の強いものであった。
【０１１９】
実施例９
本発明において、ノズルから特定の方向に流される酸素ガスの効果を確認するため、ガスノズルを用いて酸素ガスを一方向に流した場合とガスノズルを用いずに酸素ガスを供給した場合において、他の条件は実施例５と同一で実験を行なった。ガスノズルを用いて所定の方向に酸素ガスを用いた場合と、ガスノズルを用いずに任意の方向に酸素ガスを供給した場合においてそれぞれ５回ずつ実験を行なった結果を表４に示す。
【０１２０】
【表４】

【０１２１】
この実験結果を比較すると、ガスノズルを使用して酸素ガスを一方向に流すことにより、ａおよびｂ軸の傾角は減少し、得られる薄膜の単結晶性が強まったことが明らかになる。また、酸素ガスを一方向に流すことによって、ガスノズルを用いない場合よりも臨界電流密度を２〜５倍に増大させることができ、ガスノズル流によるさらなる効果が確認された。
【０１２２】
また、表４においてガスノズルを用いた場合、ａ、ｂ軸の平均的な方位は、ガスノズルから供給されたガスの方向、すなわちテープの長手方向とほぼ一致したのに対し、ガスノズルを用いない場合は、ａおよびｂ軸の平均的な方位とテープの長手方向はほとんど相関していなかった。このように本発明において特定の方向のガス流を用いれば、単結晶性薄膜を形成することができるだけでなく、単結晶性薄膜の結晶方位についても制御が可能になる。
【０１２３】
以上に示してきた例および実施例において、単結晶性の強い超電導体からなる薄膜を形成させた基材は、そのまま超電導線材として利用することができる。多結晶の酸化物超電導材料は、その粒界による電流の阻止という大きな問題を有しているが、単結晶性の強い膜は、粒界がより少ないため、より大きな電流容量を有するようになる。
【０１２４】
たとえば、例３、４および９において形成された超電導薄膜の臨界電流密度は、７７．３Ｋにおいてそれぞれ７．８×１０⁵ Ａ／ｃｍ² 、１．９５×１０⁶Ａ／ｃｍ² 、３．９×１０⁵ Ａ／ｃｍ² であった。また、実施例１および２において形成された超電導薄膜の臨界電流密度は、７７．３Ｋにおいてそれぞれ１．７０×１０⁶Ａ／ｃｍ² 、７．５×１０⁵ Ａ／ｃｍ² であった。さらに、実施例５および７において形成された超電導薄膜の臨界電流密度は、７７．３Ｋにおいてそれぞれ１．２８×１０⁶Ａ／ｃｍ² 、７．９×１０⁵ Ａ／ｃｍ²であった。これらの値は、多結晶からなる超電導薄膜の臨界電流密度より１〜２桁大きい値である。
【０１２５】
さらに、例１０、実施例３および８に示したように、本発明に従えば、大面積を有する領域に単結晶性薄膜を容易に形成することができる。
【０１２６】
【発明の効果】
以上説明したように、本発明によれば、基材の材質および結晶性等に依存することなく、基材上の所望する領域に単結晶性の強い薄膜を形成することができる。本発明では、従来用いられていた単結晶基板の代わりに、より安価でかつ所望の形状を有する基材上に単結晶性薄膜を形成させることができる。
【０１２７】
以上のような特質から、本発明は、Ｙ系、Ｂｉ系、Ｔｌ系等の酸化物高温超電導体について薄膜を形成する手法として極めて有用である。たとえば、本発明に従って、テープ状の金属基材上に単結晶性の強い超電導体薄膜を形成すれば、上述したように高い臨界電流密度を示す超電導線材を得ることができる。
【０１２８】
また、本発明によれば、基材上の任意の領域、特に大面積を有する領域に単結晶性薄膜を容易に形成することができるため、磁気シールドや高周波用部品として有効な薄膜を容易に得ることができる。
【０１２９】
またさらに、本発明は、たとえばジョセフソン結合を利用した超電導デバイスの薄膜形成に効果的である。たとえば、テープ状基材または大面積を有するウェハ上に本発明に従って単結晶性薄膜を形成することができる。本発明は、上述したように基材上の任意の領域に、または基材上のより大きな面積を有する領域に超電導体の単結晶性薄膜を形成できるものであるため、本発明に従って超電導体薄膜が形成された基材を切断してチップを得れば、大量の超電導デバイスを効率的に生産することができる。
【図面の簡単な説明】
【図１】薄膜形成プロセスの一例を模式的に示す斜視図である。
【図２】薄膜形成プロセスの他の例を示す平面図である。
【図３】本発明に従って金属薄膜が予め形成された基材上に単結晶性薄膜を形成させるプロセスを示す模式図である。
【図４】図３に示すプロセスにおいて、基材上に形成された金属薄膜の状態を拡大して示す断面図である。
【図５】本発明において、所定の方向にガスを流しながら単結晶性薄膜を形成するプロセスを説明するための斜視図である。
【図６】例１において単結晶性薄膜を形成するプロセス示す断面図である。
【図７】例２においてレーザアブレーションにより単結晶薄膜を形成する状態を示す模式図である。
【図８】本発明に従う実施例１において単結晶性薄膜を形成する状態を示す模式図である。
【図９】本発明に従う実施例３において、単結晶性薄膜の形成プロセスを示すための平面図である。
【図１０】本発明に従う実施例４において、単結晶性薄膜の形成プロセス示すための斜視図である。
【符号の説明】
１、１１、２１、３１、４１、５１、６１、８１ 基材
２、１２、２２、３２、４２、５２、６２、７２、８２ マスク
３ 気相
２０ 金属薄膜
５４、６４ ターゲット
５５、６５ レーザ
５６、６６ プルーム
６０ 銀皮膜
７１ 基板
８３ａ スリット
８４ 酸素ガス
８５ 配管[0001]
[Industrial applications]
The present invention relates to a method for forming a single-crystal thin film on a substrate, and more particularly, to a method for forming a single-crystal thin film made of an oxide material on a long substrate.
[0002]
[Prior art]
2. Description of the Related Art In a semiconductor device manufacturing technique, various methods for forming a semiconductor single crystal thin film include liquid phase epitaxy (LPE), metal organic chemical vapor deposition (MOCVD), molecular beam epitaxy (MBE), and ion beam epitaxy (IBE). Is adopted. These methods can form a high-quality single-crystal thin film, and are an indispensable technique in manufacturing a semiconductor device.
[0003]
In the field of superconductivity, the discovery of Y-based (90K), Bi-based (108K), and Tl-based (125K) oxide superconducting materials exhibiting a critical temperature higher than the liquid nitrogen temperature (77.3K) has led to the conversion of these materials to electrons. For application to devices, a method of forming a single crystal thin film has been studied. Then, it has been found that a technique such as a laser vapor deposition method and a reactive vapor deposition method is effective for forming a high-quality single crystal thin film of an oxide superconducting material.
[0004]
[Problems to be solved by the invention]
The conventional method for forming a single-crystal thin film described above utilizes epitaxy, that is, a phenomenon in which another type of crystal grows on a specific crystal plane with a certain orientation relationship. A thin film is formed on the surface.
[0005]
Since these conventional methods presuppose the use of a single-crystal substrate, in order to form a high-quality single-crystal thin film, it is extremely necessary to employ a single-crystal substrate having a similar lattice structure to the crystal structure of the thin film material. It was important.
[0006]
For this reason, in the above-mentioned conventional technology, a single crystal thin film can be formed only on a substrate made of a specific material, and the size of the single crystal thin film that can be formed is determined by the size of the substrate that can be adopted, and the desired A single crystal thin film having a size and a length could not be freely formed.
[0007]
On the other hand, in the field of semiconductor thin films, an amorphous substrate with a periodic groove cut in the surface is used, and crystal nuclei are generated in a selective orientation at the edge of the groove, thereby achieving single crystallization of the film deposited on the substrate. There is a graphoepitaxy technology to be used. According to this technique, for example, a single crystal thin film having excellent crystallinity of Si can be formed without using a single crystal substrate.
[0008]
However, even in graphoepitaxy, the size of a substrate on which a periodic groove can be formed is limited, so that a single-crystal thin film can be freely formed on a substrate having a desired size and length, as described above. It was difficult.
[0009]
An object of the present invention is to provide a method capable of forming a single crystal thin film having excellent crystallinity on a substrate without depending on the material and crystallinity of the substrate.
[0010]
A further object of the present invention is to provide a method capable of freely forming a single crystal thin film having excellent crystallinity on a substrate having a desired size.
[0011]
[Means for Solving the Problems]
The method for forming a monocrystalline thin film according to the present invention is a method for forming a thin film mainly composed of crystals having a specific orientation in a continuous region on a base material from a gas phase, and the base material includes A metal thin film is formed in advance, and a step of providing a mask to prevent the chemical species in the gas phase from adhering to the substrate, and moving the substrate relative to the mask In the continuous area of the base material to be crystal-grown, the portion covered by the mask is continuously fed to an environment for crystal growth, and the portion covered by the mask is A step of providing a temperature gradient by a temperature control mechanism such that a metal thin film on the base material forms a solid-liquid interface in a boundary region with a portion exposed to an environment for crystal growth; and By the border In which the metal thin film on the base material is evaporated, and the chemical species in the vapor phase are aligned with the corner of the tip of the metal thin film as an evaporation residue to generate nuclei and grow crystals. .
A method for forming a single-crystal thin film according to another aspect of the present invention is a method for forming a thin film mainly composed of crystals having a specific orientation in a continuous region on a substrate from a gas phase, Providing a mask so as to prevent the chemical species in the gas phase from adhering to the substrate; and moving the substrate relative to the mask to form the group to be crystal-grown. In a continuous region of the material, a step in which the portion covered by the mask is continuously sent to an environment for crystal growth, and by flowing a gas in a direction in which the base material is relatively moved, Providing a gas flow in the same direction as the relative movement direction of the substrate to a portion on the substrate sent to an environment for crystal growth, wherein the chemical species reacts with a gas in the gas flow. Crystal grows on the substrate in a specific orientation Including that the step.
Preferably, the chemical species in the gas phase is crystal-grown by a laser ablation method on the substrate sent out to the environment for crystal growth, and further, the substrate is moved relative to the mask. In moving the crystal, the boundary region between the portion covered with the mask and the portion exposed to the environment for crystal growth in a continuous region of the base material to be crystal-grown, It is sent to the environment at a moving speed of 1 cm / min or more.
Preferably, the single crystalline thin film is formed from an oxide superconducting material.
[0012]
In the present invention, the substrate may be of any material and shape. The material and shape of the base material may be appropriately determined according to the use of the material obtained by forming the single-crystal thin film and the film formation conditions and the like, but the method of the present invention is particularly applicable to a tape-like base material. It can be applied to form a single crystalline thin film on a longer substrate.
[0013]
In the present invention, the mask for covering the substrate is not particularly limited as long as it can prevent chemical species for vapor phase growth from adhering to the substrate, and the material and shape thereof are, A preferable material may be used as appropriate depending on the film formation conditions and the like.
[0014]
The mask must be provided to effectively prevent chemical species in the gas phase from flying onto the substrate. Therefore, when covering the substrate with the mask, it is necessary to prevent molecules and atoms for vapor phase growth from entering the gap between the mask and the substrate. For this reason, depending on the conditions for vapor phase growth, for example, when using a vapor deposition method or the like, the distance between the base material and the mask is preferably 3 mm or less.
[0015]
In the present invention, the substrate is moved relatively to the mask. That is, when the mask is fixed, the substrate is moved, and when the substrate is fixed, the mask is moved. Further, the mask and the substrate may be moved together.
[0016]
For example, if you want to form a monocrystalline thin film on a substrate using a tape-shaped substrate, fix the mask, and continuously feed the tape-shaped substrate into the gas phase to be grown through the mask I should go.
[0017]
Since the tape-shaped base material can be wound, the tape-shaped base material is unwound from the first reel, and while it is wound on the second reel, the tape-shaped base material is immersed in a gas phase to be grown through a mask. The substrate can be sent out, and a single crystalline thin film can be sequentially formed on the tape.
[0018]
Alternatively, the substrate may be covered with a mask having a window such as a slit, and chemical species in a gas phase may be attached to the substrate through the window. In this case, if the substrate or the mask is moved so that the window moves on the substrate, a single-crystal thin film can be formed on a portion of the substrate where the window passes.
[0019]
In the present invention, the environmental phase for crystal growth is a gas phase, and sputtering and vapor deposition can be used for the vapor phase growth of crystals.
[0020]
The vapor phase growth method preferably used in the present invention includes, for example, laser vapor deposition, reactive vapor deposition, metal organic chemical vapor deposition (MOCVD), molecular beam epitaxy (MBE), and ion beam epitaxy (IBE).
[0021]
Further, in the present invention, a thin film mainly composed of crystals having a specific orientation can be formed in a continuous region on a substrate from a gas phase by using a laser ablation method.
[0022]
In this case, when moving the base material relative to the mask, a continuous area of the base material to be crystal-grown includes a portion covered with the mask and a portion exposed to an environment for crystal growth. Is preferably sent to the environment for crystal growth at a moving speed of 1 cm / min or more.
[0023]
In this case, laser ablation is performed using a laser in a wavelength region of 650 to 750 ° C., an oxygen gas pressure of 30 to 500 mTorr, and 248 to 1060 nm, and a laser energy density of 1.5 to 3.3 J / cm.²More preferably, the reaction is performed under the following conditions.
[0024]
The speed at which the boundary region between the part covered by the mask and the part exposed to the environment for crystal growth is sent to the environment for crystal growth can be freely adjusted, for example, by changing the moving speed of the substrate relative to the mask. can do.
[0025]
For example, when it is desired to form a monocrystalline thin film on a base material using a tape-shaped base material, the tape-shaped base material is moved in the gas phase at a moving speed of 1 cm / min or more relative to a fixed mask. In this way, the single-crystal thin film can be sequentially formed on the tape-like substrate according to the method described above.
[0026]
In the present invention, a base material on which a metal thin film is formed in advance can also be used. in this case, BasisA temperature gradient is provided so that the metal thin film forms a solid-liquid boundary in a boundary region between a portion of the material covered by the mask and a portion exposed to the environment for crystal growth.Further, the metal thin film can be evaporated at the above-mentioned boundary region of the single crystalline thin film.
[0027]
This temperature gradient is such that the temperature decreases as the mask is provided from the vapor phase for crystal growth, and can be provided, for example, by adjusting the substrate temperature using a heater or cooling means. Such a temperature gradient can promote uniformity of the crystal orientation of the formed thin film.
[0028]
Further, in the present invention, by flowing gas in a direction in which the substrate is relatively moved,TieA gas flow in the same direction as the relative movement direction of the substrate can be applied to a portion sent to the environment for crystal growth.
[0029]
Such a gas flow can be generated, for example, by discharging gas from a slit-shaped hole provided at an end of the mask toward an environment for crystal growth.
[0030]
The directionality of the gas flow depends on the atmosphere for crystal growth, but is preferably maintained within a predetermined range in which crystal growth is performed. By using this gas flow, a single crystal thin film can be grown so that a specific crystal orientation is aligned with the gas flow direction.
[0031]
When a thin film composed of an oxide crystal is to be formed, oxygen gas can be preferably used as a gas.
[0032]
The method for forming a single-crystal thin film of the present invention described above is particularly applied as a method for forming a single-crystal thin film of an oxide superconductor on a substrate. As described above, oxide superconductors include Y-based materials such as Y-Ba-Cu-O, Bi-based materials such as Bi-Sr-Ca-Cu-O, and Tl-Bi-Sr-Ca-Cu-O and the like. Tl type and the like are included.
[0033]
In order to form a single crystalline thin film made of an oxide superconductor according to the present invention, for example, various deposition methods such as reactive deposition, laser ablation, MBE, CVD, ion plating, spray pyrolysis, flash plasma, and the like are used. Can be used.
[0034]
For example, when laser ablation is used to form a single-crystal thin film of an oxide superconductor, a Y-, Bi-, or Tl-based sintered target is irradiated with a laser to generate plasma, and this plasma is masked. By exposing the base material sent from below, a single crystalline thin film made of a superconductor can be formed.
[0035]
Conventionally, for forming a thin film of an oxide superconducting material, MgO, SrTiO₃, ZrO₂In the present invention, not only these materials but also MgO, SrTiO₃And ZrO₂Or the like, a yttria-stabilized zirconia sheet, a metal substrate such as a metal tape, or the like.
[0036]
When a single crystalline thin film of an oxide superconductor is formed according to the present invention, the gas flowing in the moving direction of the substrate is preferably oxygen gas as described above. The metal film formed on the base material in advance is preferably made of, for example, silver.
[0037]
[Action]
1 (a) to 1 (c), ThinIt is a perspective view which shows the process of film formation typically.
[0038]
FigureAs shown in FIG. 1A, a base material 1 is sent from one end thereof through a mask 2 to a vapor phase 3 for crystal growth. The direction of sending is the direction of arrow A shown in the figure.
[0039]
On the other hand, the chemical species existing in the gas phase 3 are deposited on the substrate 1 as shown by the arrow B in the figure. As shown in the figure, the chemical species in the gas phase do not adhere to the portion of the substrate 1 covered with the mask 2, while the chemical species adheres to the portion sent out from under the mask 2 into the gas phase. become. As described above, when the substrate 1 is continuously fed in the direction of arrow A, a thin film is continuously formed on the substrate.
[0040]
Next, a process of forming a single-crystal thin film by moving the substrate will be described. First, for the sake of explanation, it is assumed that the base material is sent out from a state in which one end of the base material slightly enters the gas phase. FIG. 1B shows a point in time when the base material is fed out from FIG. 1A. The region indicated by 1a in the substrate 1 is a region where the substrate was exposed to the gas phase before the movement of the substrate and did not undergo the movement from the bottom of the mask to the gas phase.
[0041]
In this region, the thin film formed on the surface of the base material is often in a crystal having a random orientation or in an amorphous state. Even when the thin film has a natural orientation, the crystal of the thin film orients a specific crystal axis in a normal direction on the surface of the substrate, but rarely achieves a specific orientation in the surface of the substrate.
[0042]
On the other hand, in the region that has undergone the movement between the region 1a and the mask 2, crystals having various orientations are formed in the initial portion 1b under the influence of the region that is not moved. Becomes dominant, and a region 1c having the same orientation is formed. In the figure, to schematically show such a state, the distribution state of the crystal orientation is represented by an arrow.
[0043]
This is because a crystal growth end is formed in a boundary region between a portion covered by a mask and a portion exposed to a gas phase in a substrate, and a crystal having the same orientation as the growth end on a substrate newly exposed by movement. Is thought to be due to the tendency to grow. Therefore, if a growth end having a specific crystal orientation can be reliably formed, a thin film having strong single crystallinity can be formed without being greatly affected by the material and crystal orientation of the base material.
[0044]
In this way, when the base material is further moved, a crystal having the same orientation as the region 1c grows further (FIG. 1C). As described above, once the specific oriented grains are formed, regardless of the material and crystal orientation of the base material, the crystal grains having the specific orientation are continuously formed due to the continuous movement of the base material and the effect of the mask. To be formed on the substrate.
[0045]
In the method described above, if a tape-shaped base material is used and the base material is moved from one end of the tape in the longitudinal direction, a single-crystal thin film can be formed in the longitudinal direction of the base material.
[0046]
Also, LesIn a method for forming a thin film mainly composed of crystals having a specific orientation in a continuous region on a substrate from a gas phase using a laser ablation method, the substrate is moved relative to a mask. In performing the crystal growth, the boundary region between the portion covered with the mask and the portion exposed to the environment for crystal growth in the continuous region of the substrate on which the crystal growth is to be performed is 1 cm / min or more in the environment for crystal growth. A thin film with strong single crystallinity, with little effect on the size of the distance between the mask and the substrate, on a substrate that is newly exposed to the environment for crystal growth. Can be formed.
[0047]
This is because the boundary region between the portion covered with the mask during the vapor phase growth and the portion exposed to the environment for crystal growth is sent to the environment for crystal growth at a moving speed of 1 cm / min or more, so that the mask and The time period in which the boundary region comes into contact with molecules and atoms for vapor phase growth entrained in a small space with the substrate is shortened, and the boundary region on the substrate has a sharp crystal having a specific crystal orientation. Since the growing edge of the crystal is more reliably formed, as a result, a crystal grain having a specific crystal orientation is more likely to be formed on the substrate that is newly exposed to the environment for crystal growth. it is conceivable that.
[0048]
According to the above-described method, as shown in the following examples, even when the distance between the mask and the substrate is set to be larger than 3 mm, a single-crystal thin film having a uniform crystal orientation is formed on the substrate. Will be able to
[0049]
As shown in FIG. 2, when a mask 12 having a window 12 a is formed on a base material 11 and vapor deposition or the like is performed on the mask 12, a thin film can be formed only on the window 12 a in the base material 11. . If the base material 11 or the mask 12 is continuously moved in this state, a thin film can be formed in the area 11a (indicated by a dashed line in FIG. 1) in which the window 12a has moved.
[0050]
Also in this case, since the effects of the continuous movement and the mask as described above are provided, a single-crystal thin film can be formed in the region 11a. By using such a mask, a single-crystal thin film can be formed in an arbitrary region on the substrate.
[0051]
Further, as shown in FIG. 3, a substrate 21 on which the metal thin film 20 is formed in advance is used, and a boundary region between a portion of the substrate 21 covered with the mask 22 and a portion exposed to the gas phase 23 (C in FIG. 3). (Shown), a single crystal thin film can be formed by providing a temperature gradient. The temperature gradient can be set, for example, by a heater 24 provided below the base material.
[0052]
The metal thin film has a solid-liquid boundary in the boundary region C due to the set temperature gradient. The state of the solid-liquid boundary is shown in FIG. As shown in the figure, the metal thin film 20 having a predetermined thickness remains in the portion 21a covered by the mask 23, but in the boundary region C, the metal thin film is melted to form a solid-liquid boundary, and at a high temperature. The metal forming the thin film evaporates from the portion.
[0053]
As a result, the film in the boundary region C is eroded, and has a step shape. Such a state can be observed with an electron microscope. For example, when a silver thin film is formed on a substrate, a staircase is formed in a shape corresponding to the contour line of the temperature, and the height of one staircase is about 100 mm and the width of the terrace is about 1000 mm. It became clear by observation.
[0054]
When a mask is provided so that a film formation region is interrupted in a region where a step is formed, that is, a crystal growth end is formed, a chemical species deposited from a gas phase has an orientation at a corner of the step. Nuclei will be generated together. Then, when the base material is continuously moved in the direction of the arrow shown in FIG. 3, the metal thin film always has a step formed in the area where the temperature gradient is provided. And grow. As a result, a single-crystal thin film is continuously formed.
[0055]
As described above, the formation of a thin film having such a temperature gradient is performed when a single-crystal thin film is formed in the longitudinal direction of the tape-shaped base material, or when a mask having a window is provided to an arbitrary region of the base material. It can be applied when forming a crystalline thin film.
[0056]
In the present invention, the base material is moved as described above, and the gas 34 is moved from the end 32a of the mask 32 in the moving direction of the base material 31 (indicated by an arrow D in the figure) as shown in FIG. By flowing, a crystal having a specific orientation can be grown in a region of the base material 31 where the directionality of the gas flow is maintained.
[0057]
It is considered that the region where the direction of the gas flow is maintained is limited to a very narrow range. However, once a thin film having a uniform orientation is formed in this region, the region where the direction of the gas flow is lost (for example, the gas flow direction). Even if the film is formed at a portion remote from the ejection port), the film can be formed according to the orientation of the base film formed according to the gas flow. Therefore, even when a thick film is formed, a crystal having a specific orientation can be grown by aligning the orientation on a base whose orientation is controlled by the gas flow.
[0058]
Thus, the gas flow acts to form crystal nuclei having a specific orientation. If the region covered by the mask is successively exposed to the gas phase by continuously moving the base material, the thin film is grown so that the orientation is aligned with the crystal whose orientation is controlled by the gas flow as described above. Go on. In this manner, a single-crystal thin film having a uniform crystal orientation can be formed on a substrate.
[0059]
As described above, a thin film for generating such a gas flow may be formed by forming a single-crystal thin film in the longitudinal direction of a tape-shaped base material or by providing a mask having a window on an arbitrary region of the base material. It can be applied when forming a crystalline thin film.
[0060]
【Example】
An example1
Using a Ni-Cr alloy tape having a thickness of 0.1 mm and a width of 5 mm as a base material, a mask 42 was fixed on the base material 41 with a gap (d) of 0.1 mm as shown in FIG.
[0061]
In order to form a thin film of yttria-stabilized zirconia on a Ni alloy tape, a reactive vacuum deposition method was used. Oxygen was used as a reaction gas, and the gas pressure was set to 3 mTorr. The temperature of the substrate was set at 750 ° C.
[0062]
As described above, a thin film of yttria-stabilized zirconia was vacuum-deposited while continuously moving the substrate 41 in the direction of arrow E in FIG. 6 at a speed of 2 mm / min.
[0063]
At this time, a non-oriented yttria-stabilized zirconia thin film was formed in a portion up to 5.2 cm from the tape tip, and subsequently in a portion extending 3.8 cm, the (100) axis was oriented perpendicular to the substrate surface. An axis-oriented film was formed, and subsequently, the (010) axis and the (001) axis were strongly oriented in the substrate surface, and a yttria-stabilized zirconia thin film having a uniform orientation within a tilt angle of 5 ° was formed. X-ray diffraction confirmed that this orientation (biaxial orientation) was realized over a length of 3 m.
[0064]
In addition, as long as the conditions for vacuum deposition and the condition for continuous movement of the base material are stable and the mask is fixedly provided, strong biaxial orientation, that is, a monocrystalline thin film Was expected to be obtained.
[0065]
An example2
An exampleUsing the same Ni—Cr alloy tape as in Example 1, a thin film of yttria-stabilized zirconia was formed by laser ablation.
[0066]
Laser ablation is performed as shown in FIG. 7, and a laser 55 is applied to the Y-based sintered body target 54 to generate a plume 56 as shown in FIG. The chemical species in the plume 56 were deposited on the base material 51 which was continuously fed out of the substrate. In laser ablation, the temperature of the substrate was set at 650 to 750 ° C., and the pressure of oxygen gas was set at 30 to 500 mTorr. Further, a KrF excimer laser (wavelength 248 nm) is used as a laser, and the laser energy density is 1.5 to 3.3 J / cm.²And the laser repetition frequency was 1 Hz to 100 Hz. The gap (d) between the substrate 51 and the mask 53 was set to 0.1 mm.
[0067]
As described above, even when laser ablation was used, a yttria-stabilized zirconia thin film having strong single crystallinity could be formed over a length of 2 m from 12.5 cm from the tape-shaped base end.
[0068]
An example3
An exampleFirst, a yttria-stabilized zirconia thin film was formed on the substrate using the same substrate as in Example 1 without a mask. The thin film thus formed stood vertically with the (100) axis and the (111) axis mixed on the surface of the substrate, and exhibited a random orientation in the direction within the substrate surface.
[0069]
Next, on the yttria-stabilized zirconia thin film formed on the base material, a laser ablation method as shown in FIG.₁Ba_TwoCu_ThreeO_XThin filmThe shapeI made it. In the laser ablation method, the pressure of the oxygen gas was set to 200 mTorr, the substrate temperature was set to 700 ° C., and the film formation rate was set to 1.5 μm / min. In addition, laserIs an exampleThe substrate was continuously moved at a speed of 18 mm / min using an excimer laser in₁Ba_TwoCu_ThreeO_XA thin film was continuously formed.
[0070]
The thin film thus formed becomes a c-axis oriented film over the entire length of the tape, and the orientation of the a and b axes becomes strong at 5.6 cm from the leading end of the tape, and the orientation is increased over a length of 1.4 m. It was confirmed that it was within 4 °.
[0071]
An example4
An exampleThe tape-shaped substrate 1m having the yttria-stabilized zirconia thin film having a strong single crystal property prepared in 2 was prepared. Next, the substrate temperature was set to 700 ° C., the oxygen gas pressure was set to 200 mTorr, the film forming speed was set to 1.5 μm / min, and the substrate moving speed was set to 18 mm / min by laser ablation using a mask in the same manner as in Example 3. And Y₁ Ba_Two Cu_Three O_XA thin film was formed.
[0072]
In this case, a c-axis oriented film having strong single crystallinity was formed at a position 8 mm from the tip of the tape, and the orientation of this film in the in-plane direction of the base material was extremely good, being within 2 °.
[0073]
On the other hand, for comparison, Y without a mask was₁Ba₂Cu₃O_XWas formed, but the orientation in the in-plane direction of the substrate was 4 ° or more. It was clarified that a thin film having strong single crystallinity can be obtained by providing a mask and forming a thin film in this manner.
[0074]
An example5
An exampleIn FIG. 4, the gap (d) between the tape-shaped base material and the mask was 0.1 mm. In order to examine the effect of this gap on film formation, the gap value (d) was set between 0.1 mm and 5 mm. Change and other conditionsIs an exampleY in the same way as 4₁ Ba_Two Cu_Three O_XA thin film was formed.
[0075]
As a result, for each value of the gap, a tilt angle indicating the orientation in the in-plane direction of the base material as shown in Table 1 was obtained.
[0076]
[Table 1]

[0077]
As shown in Table 1,This exampleIt was found that if the gap (d) was 3 mm or less, a thin film having strong single crystallinity could be obtained.
[0078]
An example6
Using a Ni-based alloy tape called Hastelloy having a thickness of 0.1 mm and a width of 5 mm as a base material, thin films of yttria-stabilized zirconia and magnesium oxide were individually formed using a laser ablation method as shown in FIG. Was.
[0079]
In the laser ablation method, the substrate temperature was set at 650 to 750 ° C., and the pressure of oxygen gas was set at 30 to 500 mTorr. A KrF excimer laser (wavelength 248 nm) is used as a laser, and the laser energy density is 1.5 to 3.3 J / cm.²And the laser repetition frequency was 1 to 100 Hz. The gap (d) between the substrate 51 and the mask 52 was set to 0.8 mm.
[0080]
This exampleIn order to investigate how the movement speed of the boundary region between the portion covered with the mask 52 of the base material 51 and the portion exposed to the environment for vapor phase growth affects the film formation, The moving speed of the substrate 51 with respect to the substrate was changed in the range of 0.1 to 1.5 cm / min to form a thin film having a thickness of 0.2 μm over the entire substrate.
[0081]
The in-plane orientation of each of the obtained yttria-stabilized zirconia thin film and magnesium oxide thin film was investigated.
[0082]
As a result, in either of the formed thin films, the (100) axis is oriented perpendicular to the tape substrate surface, and the (010) axis is oriented parallel to the substrate surface along the growth edge of the thin film crystal. Was oriented.
[0083]
Further, in order to compare the degree of in-plane (010) orientation in each thin film, a ratio in which the mutual inclination of each crystal grain was within ± 5 ° was obtained. The result is shown in Table 2.
[0084]
[Table 2]

[0085]
As shown in Table 2, the movement speed of the tape substrate with respect to the mask is 1 cm / min or more, that is, the movement of the boundary region between the portion of the substrate covered with the mask and the portion exposed to the environment for vapor phase growth. It has been found that when the speed is 1 cm / min or more, a thin film having good in-plane orientation can be obtained.
[0086]
An example7
An exampleAs in the case of No. 6, a Ni-based alloy tape called Hastelloy having a thickness of 0.1 mm and a width of 5 mm was used as a substrate, and a yttria-stabilized zirconia thin film was first formed on the substrate without providing a mask. The thin film thus formed was one in which the (100) axis and the (111) axis were mixed and stood vertically on the surface of the substrate, and exhibited a random orientation in the direction within the substrate surface.
[0087]
Next, on the yttria-stable zirconia thin film formed on the base material, the laser ablation method as shown in FIG.₁Ba_TwoCu_ThreeO_XThin filmThe shapeI made it. In the laser ablation method, the substrate temperature was set at 700 ° C., and the pressure of oxygen gas was set at 200 mTorr. Further, a KrF excimer laser (wavelength 248 nm) is used as a laser, and the laser energy density is 1.5 to 3.3 J / cm.^TwoAnd the laser repetition frequency was 1 to 100 Hz. The gap (d) between the substrate 51 and the mask 52 was set to 1.0 mm.
[0088]
This exampleIn order to investigate how the moving speed of the boundary region between the portion of the base material 51 covered by the mask 52 and the portion exposed to the environment for vapor phase growth affects the film formation, The moving speed of the base material 51 with respect to the range of 0.1 to 2.0 cm / min was changed to form a thin film having a thickness of 1.0 μm over the entire base material.
[0089]
Y obtained₁Ba₂Cu₃O_XThe in-plane orientation of the thin film was investigated.
[0090]
As a result, the formed thin film had the c-axis standing perpendicular to the substrate surface, and showed strong orientation of the a-axis and the b-axis along the growth edge of the thin-film crystal.
[0091]
Further, in order to compare the degree of (010) in-plane orientation in the thin film, a ratio in which the inclination of the a-axis of each crystal grain was within ± 5 ° was obtained. The result is shown in Table 3.
[0092]
[Table 3]

[0093]
As shown in Table 3, the moving speed of the tape substrate with respect to the mask is 1 cm / min or more, that is, the boundary region between the portion of the tape substrate covered with the mask and the portion exposed to the environment for vapor phase growth. When the moving speed is 1 cm / min or more, the ratio exceeds 90%, and it is clear that a thin film having good in-plane orientation can be obtained.
[0094]
AboveExampleAs can be seen from FIGS. 6 and 7, the movement speed of the boundary region between the portion of the base material covered with the mask and the portion exposed to the environment for vapor phase growth is set to 1 cm / min or more, whereby the mask and the base material can be separated. It was confirmed that good in-plane orientation could be achieved without setting the interval (d) to 3 mm or less.
[0095]
An example8
Using Ni-Cr alloy tape of thickness 0.1mm and width 5mm as base material, ExampleA thin film of magnesium oxide was formed on a substrate by a reactive vacuum deposition method in the same manufacturing process as in Example 1. In this case, a magnesium oxide thin film having strong single crystallinity was formed at 3.2 cm from the tip of the tape.
[0096]
In the formed thin film, the (100) axis is oriented perpendicular to the tape substrate surface, and the (010) axis is oriented in one direction in a direction parallel to the substrate surface within an angle of 4 °. Was. Also, the (001) axis was oriented to the same degree as the (010) axis.
[0097]
An example9
An exampleBi on the magnesium oxide thin film prepared in_TwoSr_TwoCa_TwoCu_ThreeO_XWas formed by an excimer laser ablation method. The laser ablation method was performed under the conditions of a substrate temperature of 720 ° C., an oxygen gas pressure of 110 mTorr, a continuous moving speed of the substrate of 1.3 mm / min, and a film forming speed of 0.18 μm / min. The obtained thin film was a film having strong single crystallinity at 3.8 cm from the tape tip, was c-axis oriented, and the inclination angles of the a-axis and b-axis were within 3.2 ° over the entire length.
[0098]
An example10
Less thanExample1~ ExampleNo. 9 was for forming a thin film on a tape-shaped base material., ExampleIn No. 10, a single-crystal thin film was formed in a predetermined region on the substrate using the mask having the above-described window.
[0099]
A sintered sheet (50 × 50 mm) of yttria-stabilized zirconia was used as a base material, and a stainless steel mask (150 × 150 mm) having a 10 × 10 mm square window was used as a mask. Under the same film forming conditions as in Example 3, the gap between the mask and the base material was set to 0.2 mm, and the mask was continuously moved as shown in FIG.₁Ba₂Cu₃O_XA thin film was formed.
[0100]
In the film thus formed, it was found that the a and b axes are oriented at an inclination angle of 3 ° or less. On the other hand, since the zirconia base material is a polycrystalline material, when a thin film was formed on the base material without using a mask, a film in which only the c axis was oriented was obtained, and the a and b axes were not oriented. .
[0101]
Example1
As the base material, a yttria-stabilized zirconia thin film was formed on a Ni-Cr alloy tape having a thickness of 0.1 mm and a width of 5 mm, and a silver thin film having a thickness of 0.3 µm was further formed thereon.
[0102]
On the substrate on which the silver thin film was formed in this manner, Y was formed as shown in FIG.₁Ba₂Cu₃O_XThin films were formed by excimer laser ablation. As shown in the figure, in a region where the base material 61 having the silver thin film 60 is exposed to the environment for forming the thin film, a region (indicated by F in the drawing) up to 1 mm from the tip of the mask 62 is maintained at 700 ° C. Was. On the other hand, a temperature gradient of 30 ° C./mm was set from 1 mm from the tip of the mask 62. In such a temperature environment, the silver thin film forms a solid-liquid boundary as described above, and as shown in FIG. 4 in the boundary region between the portion of the substrate covered with the mask and the portion exposed to the environment in which the thin film is formed. It had a step shape.
[0103]
An exampleA Y-type sintered body was used as the target 64 in the same manner as in Example 2, and a plume 66 was generated by irradiating the target 64 with an excimer laser 65, and the chemical species in the plume 66 were deposited on the substrate 61. The moving speed of the substrate 61 was set to 5 mm / min, and the film forming speed was set to 0.41 μm / min.
[0104]
The Y thus formed₁Ba₂Cu₃O_XThe a-axis and b-axis of the film began to be aligned in the in-plane direction of the substrate from 3.5 cm from the tape tip, and it was confirmed that the inclination angle was within 4 ° over a length of 2 m.
[0105]
Example2
An exampleSimilarly to 8, a thin film of magnesium oxide was first formed on a Ni-Cr alloy tape (thickness 0.1 mm, width 5 mm). Next, the example was performed on an alloy tape on which magnesium oxide was formed.1In the same manner as in the above, a silver thin film was formed with a thickness of 0.3 μm.
[0106]
Next, the embodiment1In a process using a mask in the same manner as in_TwoSr_TwoCa_TwoCu_ThreeO_XWas deposited on the magnesium oxide thin film formed on the substrate. Bi formed_TwoSr_TwoCa_TwoCu_ThreeO_XThe a and b axes of the thin film began to be aligned within 4 cm from the tape tip in the plane of the base material, and the inclination angle was within 5 ° over a length of 2 m.
[0107]
Example3
By using a sintered substrate of magnesium oxide (size 50 × 50 × 0.5 mm) and moving it from the bottom of the mask 72 of the substrate 71 in the direction of the arrow as shown in FIG.₁Ba_TwoCu_ThreeO_XWas formed. In forming the thin film, a silver film having a thickness of 0.5 μm was previously formed on the substrate. The temperature distribution and the position of the mask with respect to the temperature distribution1The settings were the same as in. Example1Under the same film forming conditions and moving conditions as those of₁Ba_TwoCu_ThreeO_XA thin film was formed. In the obtained thin film, the a and b axes were aligned in the substrate surface over the entire surface of the substrate, and the inclination angle was within 3 °.
[0108]
Example4
As shown in FIG. 10, a mask 82 connected to a pipe 85 and having a slit 82a formed at a tip was provided on a substrate 81 made of a Ni—Cr alloy (thickness 0.1 mm, width 10 mm). The inside of the mask 82 is hollow, and the gas supplied from the pipe 85 is ejected from the slit 82a. The height of the slit was 0.2 mm and the width was 10 mm, which was the same as that of the tape-shaped substrate.
[0109]
Using the mask having the slits as described above, the yttria-stabilized zirconia thin film was deposited by the vacuum deposition method while continuously moving the substrate in the same manner as in the above-described embodiment. In the film formation, oxygen gas was flowed from the slit 82a at a flow rate of 2 cc / min in the same direction as the moving direction of the substrate. The gas pressure in the film forming chamber was set at 4 mTorr. Furthermore, the substrate temperature was set to 780 ° C., and the film was formed at a speed of 0.05 μm / min while moving the substrate in the direction of the arrow shown in FIG. 10 at a speed of 4 mm / min.
[0110]
As a result of forming a thin film as described above, the film becomes (001) oriented (perpendicular to the tape surface) over a total length of 1.8 m from 2.8 cm from the tip of the tape, and (110) in the gas flow direction on the tape. An oriented yttria-stabilized zirconia thin film was obtained. The yttria-stabilized zirconia thin film axially oriented in this way can be said to be a single crystal thin film.
[0111]
Example5
Example4Using the same tape-shaped substrate as in Example 1, a yttria-stabilized zirconia thin film having no orientation was formed in advance over the substrate over a length of 1.5 m without using a mask. Next, on the thin film thus formed, Y₁Ba_TwoCu_ThreeO_XWas formed as shown in FIG. In forming the thin film, the substrate temperature was set at 700 ° C., the flow rate of oxygen flowing from the slit was set at 20 sccm, and the gas pressure of the film formation chamber was set at 150 mTorr. The tape-shaped substrate was formed by excimer laser ablation at a rate of 2.5 cm / min.
[0112]
Y formed under the above conditions₁Ba₂Cu₃O_XThe thin film showed c-axis orientation up to 25 mm from the tape tip, but was non-oriented with respect to the a and b axes in the tape plane direction. However, a thin film was obtained in which the a and b axes were aligned with the direction of the gas flowing in a specific direction over the entire length from 25 mm to 1.475 m, and the inclination angle was within 3 ° over the entire length.
[0113]
Example6
Example4In the same manner as in the above, a thin film of magnesium oxide was formed on the Ni alloy tape. At this time, a magnesium oxide thin film having a (001) orientation (perpendicular to the tape surface) and a (100) orientation in the gas flow direction was obtained over a total length of 1.8 m from 2.8 cm from the tip of the tape.
[0114]
Example7
Example4First, a magnesium oxide thin film having no orientation was formed thereon by a usual vacuum evaporation method using the same tape-shaped substrate as that described above.
[0115]
Next, as shown in FIG. 10, under the conditions of a substrate temperature of 720 ° C., an oxygen flow rate of 30 sccm, and a gas pressure of 110 mTorr, a Bi layer was formed on the magnesium oxide thin film by excimer laser ablation.₂Sr₂Ca₂Cu₃O_XA thin film was formed. In forming the thin film, the tape moving speed was set at 1.8 cm / min, and the film forming speed was set at 1.1 μm / min.
[0116]
In the thin film formed as described above, the portion from the tape tip to 3.2 cm showed c-axis orientation (perpendicular to the substrate surface), but the orientation (a and b axes) was random in the tape surface direction. there were. However, the film formed in a portion extending from 3.2 cm from the tape tip to 1.2 m in length shows the c-axis orientation and the orientations where the a and b axes coincide with the gas flow direction, and the inclination angle is within 4 °. Was constant.
[0117]
Example8
A 50 × 50 mm polycrystalline magnesium oxide sintered body was used as a substrate, and Y was formed by vacuum evaporation while covering the substrate with a mask having a gas nozzle having a slit width of 50 mm.₁Ba_TwoCu_ThreeO_XA thin film was formed. The thin film was formed under the conditions of a substrate temperature of 700 ° C., an oxygen gas flow rate of 10 sccm, a gas pressure of 10 mTorr, a film forming speed of 0.05 μm / min, and a substrate moving speed of 0.5 mm / min.
[0118]
The film thus formed had a strong single crystallinity in which the a, b, and c axes were aligned in a 30 × 50 mm region of a 50 × 50 mm region.
[0119]
Example9
In the present invention, in order to confirm the effect of oxygen gas flowing in a specific direction from the nozzle, when oxygen gas is flowed in one direction using a gas nozzle and when oxygen gas is supplied without using a gas nozzle, Conditions are examples5An experiment was performed in the same manner as described above. Table 4 shows the results of experiments performed five times each in the case where oxygen gas was used in a predetermined direction using a gas nozzle and in the case where oxygen gas was supplied in an arbitrary direction without using a gas nozzle.
[0120]
[Table 4]

[0121]
Comparing the experimental results, it is clear that by flowing oxygen gas in one direction using a gas nozzle, the inclination angles of the a and b axes are reduced and the obtained thin film has increased single crystallinity. In addition, by flowing oxygen gas in one direction, the critical current density could be increased 2 to 5 times as compared with the case where the gas nozzle was not used, and a further effect by the gas nozzle flow was confirmed.
[0122]
In addition, when the gas nozzle is used in Table 4, the average azimuths of the a and b axes almost coincide with the direction of the gas supplied from the gas nozzle, that is, the longitudinal direction of the tape, whereas when the gas nozzle is not used, The average orientation of the a, b and b axes hardly correlated with the longitudinal direction of the tape. As described above, when a gas flow in a specific direction is used in the present invention, not only can a single-crystal thin film be formed, but also the crystal orientation of the single-crystal thin film can be controlled.
[0123]
Has been shown aboveExamples andIn the embodiment, the base material on which the thin film made of the superconductor having a strong single crystal property is formed can be used as a superconducting wire as it is. Polycrystalline oxide superconducting materials have the major problem of blocking current due to their grain boundaries, but films with strong single crystallinity have greater current carrying capacity due to fewer grain boundaries .
[0124]
For example, ExampleThe critical current densities of the superconducting thin films formed in 3, 4 and 9 were 7.8 × 10 3 at 77.3K, respectively.^Five A / cm^Two , 1.95 × 10⁶A / cm^Two 3.9 × 10^Five A / cm^Two Met. Also, the embodiment1and2The critical current density of the superconducting thin film formed at 1.73 × 10 was 1.70 × 10⁶A / cm^Two , 7.5 × 10^Five A / cm^Two Met. Further, the embodiment5and7The critical current density of the superconducting thin film formed at 1.73 × 10 was 1.28 × 10⁶A / cm^Two , 7.9 × 10^Five A / cm^TwoMet. These values are one to two orders of magnitude larger than the critical current density of the polycrystalline superconducting thin film.
[0125]
further, Example10,Example 3and8As described above, according to the present invention, a single-crystal thin film can be easily formed in a region having a large area.
[0126]
【The invention's effect】
As described above, according to the present invention, it is possible to form a thin film having strong single crystallinity in a desired region on a substrate, without depending on the material, crystallinity, and the like of the substrate. According to the present invention, a single-crystal thin film can be formed on a base material having a desired shape at a lower cost, instead of a conventionally used single-crystal substrate.
[0127]
From the above-described characteristics, the present invention is extremely useful as a technique for forming a thin film on a high-temperature superconductor such as a Y-based, Bi-based, or Tl-based oxide. For example, when a superconducting thin film having strong single crystallinity is formed on a tape-shaped metal substrate according to the present invention, a superconducting wire having a high critical current density can be obtained as described above.
[0128]
Further, according to the present invention, since a single-crystal thin film can be easily formed in an arbitrary region on a substrate, particularly in a region having a large area, a thin film effective as a magnetic shield or a high-frequency component can be easily formed. Obtainable.
[0129]
Further, the present invention is effective for forming a thin film of a superconducting device using, for example, Josephson coupling. For example, a monocrystalline thin film can be formed on a tape-shaped substrate or a wafer having a large area according to the present invention. Since the present invention is capable of forming a single-crystal thin film of a superconductor in an arbitrary region on the substrate as described above or in a region having a larger area on the substrate, the superconductor thin film according to the present invention If a chip is obtained by cutting the substrate on which is formed, a large amount of superconducting devices can be efficiently produced.
[Brief description of the drawings]
FIG.ThinIt is a perspective view which shows an example of a film formation process typically.
FIG. 2ThinIt is a top view which shows the other example of a film formation process.
FIG. 3 is a schematic view showing a process for forming a single-crystal thin film on a substrate on which a metal thin film has been formed in advance according to the present invention.
FIG. 4 is an enlarged cross-sectional view showing a state of a metal thin film formed on a base material in the process shown in FIG.
FIG. 5 is a perspective view for explaining a process of forming a single-crystal thin film while flowing gas in a predetermined direction in the present invention.
FIG. 6An example1 is a cross-sectional view illustrating a process for forming a single-crystal thin film in FIG.
FIG. 7An exampleFIG. 2 is a schematic diagram showing a state where a single crystal thin film is formed by laser ablation in FIG.
FIG. 8 shows an embodiment according to the present invention.1FIG. 3 is a schematic view showing a state in which a single-crystal thin film is formed in FIG.
FIG. 9 shows an embodiment according to the invention.35 is a plan view for illustrating a process of forming a single-crystal thin film in FIG.
FIG. 10 shows an embodiment according to the present invention.4FIG. 3 is a perspective view for illustrating a formation process of a single-crystal thin film.
[Explanation of symbols]
1, 11, 21, 31, 41, 51, 61, 81 Base material
2, 12, 22, 32, 42, 52, 62, 72, 82 Mask
3 gas phase
20 Metal thin film
54, 64 targets
55, 65 laser
56, 66 plume
60 silver coating
71 Substrate
83a slit
84 Oxygen gas
85 Piping

Claims (4)

A method for forming a thin film mainly composed of crystals having a specific orientation in a continuous region on a substrate from a gas phase, wherein a metal thin film is formed on the substrate in advance,
A step of Ru provided a mask so as to prevent the chemical species of the gas phase from adhering to the substrate,
Continuous said substrate by going moved relative to the mask, in the contiguous area of the substrate to be grown, the portion covered with the mask in the environment for crystal growth a manner the delivered Ru process, in the boundary region between the portion which is exposed to the environment for the partial crystal growth covered by the mask, so that the metal thin film on said substrate to form a solid-liquid interface temperature A process in which a temperature gradient is provided by an adjusting mechanism,
Evaporating the metal thin film on the substrate in the boundary region by the temperature gradient,
A method of forming a single-crystal thin film, wherein the chemical species in the gaseous phase are aligned and aligned with the corner of the tip of the metal thin film as a residue of evaporation to grow a crystal. A method for forming a thin film mainly composed of crystals having a specific orientation in a continuous region on a substrate from a gas phase,
A step of Ru provided a mask so as to prevent the chemical species of the gas phase from adhering to the substrate,
Continuous said substrate by going moved relative to the mask, in the contiguous area of the substrate to be grown, the portion covered with the mask in the environment for crystal growth a step of Ru is to sent out,
By flowing a gas in a direction in which the base material is relatively moved , a portion of the base material sent to the environment for crystal growth has a gas in the same direction as the relative movement direction of the base material. and the step of providing a flow,
A method in which the chemical species reacts with a gas in the gas flow to grow a crystal on the substrate in a specific orientation . The chemical species in the gas phase are crystal-grown by the laser ablation method on the substrate sent to the environment for crystal growth, and further move the substrate relative to the mask. In the process, the boundary region between the portion covered with the mask and the portion exposed to the environment for crystal growth in a continuous region of the base material on which the crystal is to be grown is 1 cm in the environment for crystal growth. 3. The method for forming a single-crystal thin film according to claim 1, wherein the film is fed at a moving speed of not less than / min . The method for forming a single-crystal thin film according to claim 1 , wherein the single-crystal thin film is formed from an oxide superconducting material .

Images