JP4363877B2 - Photovoltaic device and manufacturing method thereof - Google Patents

Description

上記表１を参照して、６つの光起電力装置のｎ型単結晶シリコン基板とノンドープ非晶質シリコン膜との界面の水素原子面密度を、それぞれ、約５．３×１０¹³ｃｍ^-2、約１．２×１０¹⁴ｃｍ^-2、約２．５×１０¹⁴ｃｍ^-2、約１．９×１０¹⁵ｃｍ^-2（上記第１実施形態に対応するもの）、約２．１×１０¹⁶ｃｍ^-2および約１．３×１０¹⁷ｃｍ^-2とした。ｎ型単結晶シリコン基板とノンドープ非晶質シリコン膜との界面の水素原子面密度は、上記した製造プロセスにおいて、ｎ型単結晶シリコン基板の上面を水素処理する際の水素ガスの流量を制御することにより制御される。なお、水素原子面密度が約５．３×１０¹³ｃｍ^-2の場合の光起電力装置では、水素処理は行われていない。この水素原子面密度が約５．３×１０¹³ｃｍ^-2の場合の水素原子は、ノンドープ非晶質シリコン膜の形成時に、原料ガスであるシラン（ＳｉＨ₄）中に含まれていた水素がｎ型単結晶シリコン基板とノンドープ非晶質シリコン膜との界面に導入されたものであると考えられる。
【００４２】
上記表１および図６を参照して、水素原子面密度が約１．２×１０¹⁴ｃｍ^-2〜約２．１×１０¹⁶ｃｍ^-2の場合の開放電圧Ｖ_OCは、約０．６７１Ｖ〜約０．７０８Ｖとなり、水素処理を行わなかった水素原子面密度が約５．３×１０¹³ｃｍ^-2の場合の開放電圧Ｖ_OC（約０．６６５Ｖ）よりも向上することが判明した。また、水素原子面密度が約１．２×１０¹⁴ｃｍ^-2〜約２．１×１０¹⁶ｃｍ^-2の場合の曲線因子Ｆ．Ｆは、約０．７５７〜約０．７６５となり、水素処理を行わなかった水素原子面密度が約５．３×１０¹³ｃｍ^-2の場合の曲線因子Ｆ．Ｆ（約０．７３１）よりもより１に近づくことが判明した。また、水素原子面密度が約１．２×１０¹⁴ｃｍ^-2〜約２．１×１０¹⁶ｃｍ^-2の場合のセル出力Ｐ_maxは、約１．８７５Ｗ〜約２．０１６Ｗとなり、水素処理を行わなかった水素原子面密度が約５．３×１０¹³ｃｍ^-2の場合のセル出力Ｐ_max（約１．８１Ｗ）よりも向上することが判明した。これにより、水素処理を行った場合で、かつ、水素原子面密度が約１．２×１０¹⁴ｃｍ^-2〜約２．１×１０¹⁶ｃｍ^-2の範囲では、水素原子により結晶欠陥が不活性化されると考えられる。
【００４３】
その一方、水素処理を行った場合でも、水素原子面密度が約１．３×１０¹⁷ｃｍ^-2と高すぎる場合には、開放電圧Ｖ_OCが約０．６４８Ｖ、および、セル出力Ｐ_maxが約１．７７７Ｗとなり、水素処理を行わなかった水素原子面密度が約５．３×１０¹³ｃｍ^-2の場合よりも、開放電圧Ｖ_OCおよびセル出力Ｐ_maxが低下することが判明した。これは、水素処理時に、水素原子の量が多くなることに起因して水素のイオンエネルギが増加し、その結果、水素イオンがｎ型単結晶シリコン基板の表面に照射されて欠陥が発生したためであると考えられる。
【００４４】
上記表１および図６の結果より、ｎ型単結晶シリコン基板とノンドープ非晶質シリコン膜との界面の水素原子面密度が約１．２×１０¹⁴ｃｍ^-2以上約２．１×１０¹⁶ｃｍ^-2以下の場合に、開放電圧Ｖ_OC、曲線因子Ｆ．Ｆおよびセル出力Ｐ_maxを向上させることができる。したがって、上記した第１実施形態では、ｎ型単結晶シリコン基板１とノンドープ非晶質シリコン膜２ａとの界面の水素原子面密度を約１．９×１０¹⁵ｃｍ^-2に設定しているので、開放電圧Ｖ_OC、曲線因子Ｆ．Ｆおよびセル出力Ｐ_maxを向上させることができる。
【００４５】
（第２実施形態）
この第２実施形態では、上記第１実施形態と異なり、欠陥を不活性化するために、フッ素原子をｎ型単結晶シリコン基板中、ノンドープ非晶質シリコン膜中、および、ｎ型単結晶シリコン基板とノンドープ非晶質シリコン膜との界面近傍に導入した場合の例について説明する。すなわち、この第２実施形態による光起電力装置では、製造プロセスの最初にｎ型単結晶シリコン基板を洗浄する工程中に、ｎ型単結晶シリコン基板をフッ酸で処理することによってフッ素原子を導入する。
【００４６】
具体的には、この第２実施形態では、ｎ型単結晶シリコン基板を洗浄する工程において、ｎ型単結晶シリコン基板の表面に対して、フッ酸（ＨＦ／Ｈ₂Ｏ）（約３ｍｏｌ／ｌ〜約１０ｍｏｌ／ｌのＨＦ含有量、室温）による処理を行った後、Ｈ₂Ｏリンス（室温、約１０秒〜約１０分）を行う。これにより、ｎ型単結晶シリコン基板の表面に、Ｈ₂Ｏリンスによって除去されなかったフッ酸の残留分が残る。なお、上記したフッ酸（ＨＦ／Ｈ₂Ｏ）の濃度およびＨ₂Ｏリンスのリンス時間を変化させることにより、導入されるフッ素原子の量を制御することができる。たとえば、フッ酸の濃度を大きくすれば、導入されるフッ素原子の量は多くなる。また、Ｈ₂Ｏリンスのリンス時間を短くすれば、フッ酸の残留分が多くなるので、導入されるフッ素原子の量は多くなる。
【００４７】
また、この第２実施形態では、上記第１実施形態のようなｎ型単結晶シリコン基板の表面の水素処理を行わない。なお、第２実施形態のこれら以外の部分の構造および製造プロセスは、上記第１実施形態と同様である。
【００４８】
第２実施形態では、上記のようなフッ酸処理およびＨ₂Ｏリンスによって、ｎ型単結晶シリコン基板とノンドープ非晶質シリコン膜との界面に、ｎ型単結晶シリコン基板の上面近傍の結晶欠陥を不活性化することが可能な量のフッ素原子（フッ素原子面密度：約１．５×１０¹²ｃｍ^-2）が導入される。また、ｎ型単結晶シリコン基板とノンドープ非晶質シリコン膜との界面に導入されたフッ素原子が、ｎ型単結晶シリコン基板中およびノンドープ非晶質シリコン膜中に拡散することにより、ｎ型単結晶シリコン基板中およびノンドープ非晶質シリコン膜中にフッ素原子が導入される。
【００４９】
図７には、第２実施形態による光起電力装置および比較例による光起電力装置のＳＩＭＳにより測定したｎ型単結晶シリコン基板の上面近傍のフッ素原子の濃度プロファイル図が示されている。このフッ素原子（Ｆ）の濃度プロファイルの測定には、Ｐｈｙｓｉｃａｌ ｅｌｅｃｔｒｏｎｉｃ Ｉｎｃｏｒｐｏｒａｔｉｏｎ製のＳＩＭＳ（ＡＤＥＰＴ １０１０）を用いた。このときの測定条件は、照射イオン種：Ｃｓ⁺イオン、イオン照射エネルギー：１ｋｅＶ、照射角度：６０°、検出二次イオン種：Ｆ^-イオン、リファレンス二次イオン種：Ｓｉ^-イオンであった。なお、ＳＩＭＳによる測定では、光起電力装置にＣｓ⁺イオンを照射して、たたき出された二次イオン（Ｆ^-イオンおよびＳｉ^-イオン）の数を測定するとともに、Ｓｉ^-イオンの数［Ｓｉ^-］に対するＦ^-イオンの数［Ｆ^-］の比（［Ｆ^-］／［Ｓｉ^-］、ただし、［Ｓｉ^-］＝５．０×１０²²／ｃｍ³）を計算することにより、フッ素原子の濃度が求められる。
【００５０】
ここで、第２実施形態による光起電力装置では、上記した約３ｍｏｌ／ｌ〜約１０ｍｏｌ／ｌのＨＦ含有量で室温でのフッ酸処理および約１０秒〜約１０分間の室温でのＨ₂Ｏリンスを行った後、基板温度を約１７０℃に保持した状態で、シラン（ＳｉＨ₄）ガスを約４０ｓｃｃｍの流量で、かつ、約４０Ｐａの圧力で導入するとともに、約８．３３ｍＷ／ｃｍ²の電力を供給することにより、ｎ型単結晶シリコン基板の上面上に、約５ｎｍ〜約２０ｎｍの厚みを有するノンドープ非晶質シリコン膜を形成した。つまり、この第２実施形態では、ノンドープ非晶質シリコン膜の形成前にフッ素の導入を行うとともに、ノンドープ非晶質シリコン膜の形成中はフッ素の導入を行っていない。その一方、比較例による光起電力装置では、上記した約３ｍｏｌ／ｌ〜約１０ｍｏｌ／ｌのＨＦ含有量で室温でのフッ酸処理および約１０秒〜約１０分間の室温でのＨ₂Ｏリンスを行った後、基板温度を約１７０℃に保持した状態で、フッ素（Ｆ）／シラン（ＳｉＨ₄）（ＳｉＨ₄ガスに対するＦの濃度：約０．２％で一定に保持）ガスを約４０ｓｃｃｍの流量で、かつ、約４０Ｐａの圧力で導入するとともに、約８．３３ｍＷ／ｃｍ²の電力を供給することにより、ｎ型単結晶シリコン基板の上面上に、約５ｎｍ〜約２０ｎｍの厚みを有するノンドープ非晶質シリコン膜を形成した。すなわち、比較例では、ノンドープ非晶質シリコン膜の形成前のみならず、ノンドープ非晶質シリコン膜の形成中もフッ素を導入している。これ以外は、上記第２実施形態と同様にして比較例による光起電力装置を作製した。
【００５１】
図７を参照して、第２実施形態では、フッ素原子濃度のピークがｎ型単結晶シリコン基板とノンドープ非晶質シリコン膜との界面近傍に位置しており、そのピーク濃度は、約１．０×１０¹⁹ｃｍ^-3であることがわかる。また、この第２実施形態では、上記第１実施形態と同様に、ＳＩＭＳ測定データの測定条件依存性を排除するために、ｎ型単結晶シリコン基板とノンドープ非晶質シリコン膜との界面のフッ素原子の量を、フッ素原子のピーク濃度を深さ方向に積分した面密度で規定する。すなわち、ｎ型単結晶シリコン基板とノンドープ非晶質シリコン膜との界面のフッ素原子面密度は、図７中の破線で示した曲線の積分値（図７中の斜線部の面積）であり、約１．５×１０¹²ｃｍ^-2である。
【００５２】
また、比較例では、ｎ型単結晶シリコン基板中からｎ型単結晶シリコン基板とノンドープ非晶質シリコン膜との界面近傍にかけての領域では、第２実施形態と同様のフッ素原子の濃度プロファイルを示すことがわかる。その一方、比較例では、第２実施形態と異なり、ｎ型単結晶シリコン基板とノンドープ非晶質シリコン膜との界面近傍に、フッ素原子の濃度ピークを有していない。具体的には、比較例による光起電力装置は、ｎ型単結晶シリコン基板とノンドープ非晶質シリコン膜との界面からノンドープ非晶質シリコン膜中にかけての領域では、ほぼ一定で、かつ、第２実施形態よりも大きなフッ素原子濃度（約１．０×１０¹⁹ｃｍ^-3）を有する。
【００５３】
第２実施形態において、図７に示すような濃度プロファイルが得られたのは、ｎ型単結晶シリコン基板表面のフッ酸処理によってｎ型単結晶シリコン基板とノンドープ非晶質シリコン膜との界面近傍にフッ素原子の局所的に多い領域が形成されたためであると考えられる。これに対して、比較例において、図７に示すような濃度プロファイルが得られたのは、フッ酸処理に加えて、所定の割合でフッ素が混合されたフッ素／シランガスを用いてノンドープ非晶質シリコン膜を形成したことにより、ノンドープ非晶質シリコン膜の厚み方向に渡って、ほぼ均一な量で、かつ、第２実施形態よりも多くのフッ素原子が導入されたことによると考えられる。
【００５４】
第２実施形態では、上記のように、ｎ型単結晶シリコン基板およびノンドープ非晶質シリコン膜に、欠陥を不活性化することが可能なフッ素原子を導入することによって、導入されたフッ素原子がｎ型単結晶シリコン基板中およびノンドープ非晶質シリコン膜中の欠陥であるシリコン原子のダングリングボンドと結合することにより、ダングリングボンドを不活性化することができる。これにより、ｎ型単結晶シリコン基板中およびノンドープ非晶質シリコン膜中の欠陥を低減することができるので、欠陥にキャリアが捕獲されるのを抑制することができる。このため、ｎ型単結晶シリコン基板中およびノンドープ非晶質シリコン膜中でキャリアが再結合するのを抑制することができる。また、導入されたフッ素原子の濃度のピーク（ピーク濃度：約１．０×１０¹⁹ｃｍ^-3）がｎ型単結晶シリコン基板とノンドープ非晶質シリコン膜との界面近傍に位置するとともに、ｎ型単結晶シリコン基板とノンドープ非晶質シリコン膜との界面のフッ素原子面密度を約１．５×１０¹²ｃｍ^-2にすることによって、ｎ型単結晶シリコン基板とノンドープ非晶質シリコン膜との界面のフッ素原子の量が増加するので、その増加したフッ素原子によりｎ型単結晶シリコン基板の上面近傍の結晶欠陥であるダングリングボンドを終端して不活性化することができる。これにより、ｎ型単結晶シリコン基板の上面近傍において、結晶欠陥を低減することができるので、結晶欠陥にキャリアが捕獲されるのを抑制することができる。このため、ｎ型単結晶シリコン基板の上面近傍でキャリアが再結合するのを抑制することができる。このように、ｎ型単結晶シリコン基板中、ノンドープ非晶質シリコン膜中およびｎ型単結晶シリコン基板の上面近傍でキャリアが再結合するのを抑制することができるので、光起電力装置の出力特性を向上させることができる。
【００５５】
また、第２実施形態では、比較例と異なり、ｎ型単結晶シリコン基板とノンドープ非晶質シリコン膜との界面近傍にフッ素原子の濃度のピークが位置するように構成することによって、ｎ型単結晶シリコン基板とノンドープ非晶質シリコン膜との界面近傍のフッ素原子の量よりも、ノンドープ非晶質シリコン膜中のフッ素原子の量が多くなるのを抑制することができる。これにより、ノンドープ非晶質シリコン膜中に多くのフッ素原子が導入されることに起因してノンドープ非晶質シリコン膜の緻密さなどの膜特性が低下するのを抑制することができる。このため、ノンドープ非晶質シリコン膜の膜特性の低下に起因して光起電力装置の出力特性が低下するのを抑制することができる。
【００５６】
また、第２実施形態では、導入されたフッ素原子がシリコン原子のダングリングボンドと結合するので、シリコン原子の配位数が低減される。これにより、シリコン原子の柔軟性が増大するので、結晶欠陥であるシリコン原子のダングリングボンドが新たに発生するのを抑制することができる。
【００５７】
次に、上記した第２実施形態による効果を確認するために光起電力装置の出力特性を実際に測定した実験について説明する。具体的には、図７の第２実施形態のようなフッ素原子の濃度プロファイルを有する光起電力装置（実施例１）、および、図７の比較例のようなフッ素原子の濃度プロファイルを有する光起電力装置（比較例１）の出力特性（開放電圧Ｖ_oc、短絡電流Ｉ_sc、曲線因子Ｆ．Ｆおよびセル出力Ｐ_max）を測定した。そして、実施例１に対する比較例１の開放電圧Ｖ_oc、短絡電流Ｉ_sc、曲線因子Ｆ．Ｆおよびセル出力Ｐ_maxのそれぞれの比を計算した。その結果を以下の表２に示す。
【００５８】
【表２】

上記表２を参照して、実施例１に対する比較例１の出力特性の比（開放電圧Ｖ_oc：０．９９５、短絡電流Ｉ_sc：１．００１、曲線因子Ｆ．Ｆ：０．９９３およびセル出力Ｐ_max：０．９８９）は、短絡電流Ｉ_scを除いて、１より小さいことがわかる。これにより、実施例１では、比較例１と比べて、短絡電流Ｉ_sc以外の出力特性（開放電圧Ｖ_oc、曲線因子Ｆ．Ｆおよびセル出力Ｐ_max）が向上することがわかる。これは、比較例１では、実施例１と比べて、ノンドープ非晶質シリコン膜中により多くのフッ素原子が導入されているため、ノンドープ非晶質シリコン膜の緻密さなどの膜特性が低下したことにより出力特性が低下したことによると考えられる。
【００５９】
次に、ｎ型単結晶シリコン基板とノンドープ非晶質シリコン膜との界面のフッ素原子面密度の違いによる光起電力装置のセル出力Ｐ_maxを調べるために、フッ素原子面密度がそれぞれ異なる光起電力装置のセル出力Ｐ_maxを測定した。その測定結果について、図８を参照して説明する。なお、図８では、各光起電力装置のセル出力Ｐ_maxをフッ素原子面密度が１．０×１０¹²ｃｍ^-2のときのセル出力Ｐ_maxで規格化した値をセル出力の規格値として示している。
【００６０】
図８を参照して、ｎ型単結晶シリコン基板とノンドープ非晶質シリコン膜との界面でのフッ素原子面密度が１．０×１０⁹ｃｍ^-2から大きくなるのに従って、セル出力が大きくなるとともに、フッ素原子面密度が１．０×１０¹²ｃｍ^-2付近でセル出力が最大となることがわかる。また、フッ素原子面密度が１．０×１０¹²ｃｍ^-2を超えると、セル出力が小さくなっていくことがわかる。フッ素原子面密度が１．０×１０¹²ｃｍ^-2付近までの範囲でセル出力が大きくなったのは、ｎ型単結晶シリコン基板とノンドープ非晶質シリコン膜との界面のフッ素原子の増加に伴ってｎ型単結晶シリコン基板の上面近傍の結晶欠陥であるシリコン原子のダングリングボンドがより不活性化されることに起因すると考えられる。また、フッ素原子面密度が１．０×１０¹²ｃｍ^-2付近を超えるとセル出力が小さくなっていくのは、ｎ型単結晶シリコン基板とノンドープ非晶質シリコン膜との界面に導入されたフッ素原子の量が過剰となることに起因すると考えられる。具体的には、フッ素原子（Ｆ）の量が過剰になると結合エネルギー（結合力）の小さいＦ−Ｆ結合が発生するため、そのＦ−Ｆ結合が切れることに起因してｎ型単結晶シリコン基板の上面近傍の結晶欠陥であるダングリングボンドが増加するためであると考えられる。
【００６１】
また、図８を参照して、フッ素原子面密度が１．０×１０¹⁰ｃｍ^-2以上１．０×１０¹⁴ｃｍ^-2以下の範囲では、セル出力の規格値が０．８以上になることがわかる。フッ素原子面密度がこの範囲の光起電力装置では、良好な出力特性が得られることが本願発明者により確認されている。また、フッ素原子面密度が５．０×１０¹⁰ｃｍ^-2以上２．０×１０¹³ｃｍ^-2以下の範囲では、セル出力の規格値が０．９以上になることがわかる。フッ素原子面密度がこの範囲の光起電力装置では、より良好な出力特性が得られることが本願発明者により確認されている。
【００６２】
なお、今回開示された実施形態は、すべての点で例示であって制限的なものではないと考えられるべきである。本発明の範囲は、上記した実施形態の説明ではなく特許請求の範囲によって示され、さらに特許請求の範囲と均等の意味および範囲内でのすべての変更が含まれる。
【００６３】
たとえば、上記実施形態では、ｎ型単結晶シリコン基板１の上面上に、実質的に真性なノンドープ非晶質シリコン膜２ａを介してｐ型非晶質シリコン膜２ｂを形成するようにしたが、本発明はこれに限らず、ｐ型単結晶シリコン基板の上面上に、実質的に真性なノンドープ非晶質シリコン膜を介してｎ型非晶質シリコン膜を形成するようにしてもよい。
【００６４】
また、上記実施形態では、ｎ型単結晶シリコン基板１の裏面上に、非晶質シリコン膜１２（ノンドープ非晶質シリコン膜１２ａおよびｎ型非晶質シリコン膜１２ｂ）が形成されたＢＳＦ構造を有するようにしたが、本発明はこれに限らず、ｎ型単結晶シリコン基板の裏面上に、ｎ側の非晶質シリコン膜を形成せずに、裏面電極を形成するようにしてもよい。
【００６５】
また、上記実施形態では、ｐ側の膜形成を先に行うようにしたが、本発明はこれに限らず、ｎ側の膜形成を先に行うようにしてもよい。
【００６６】
また、上記実施形態では、ｎ型単結晶シリコン基板１とｐ型非晶質シリコン膜２ｂ（ｎ型非晶質シリコン膜１２ｂ）との間に、実質的に真性なノンドープ非晶質シリコン膜２ａ（ノンドープ非晶質シリコン膜１２ａ）を形成するようにしたが、本発明はこれに限らず、第１導電型の結晶系半導体と第２導電型の非晶質半導体膜との間に、実質的に真性なノンドープ非晶質シリコン膜を形成しなくてもよい。
【００６７】
また、上記実施形態では、ｎ型単結晶シリコン基板の上面近傍、ｎ型単結晶シリコン基板中およびノンドープ非晶質シリコン膜中の欠陥を不活性化するための不純物として、水素原子およびフッ素原子を導入した例について説明したが、本発明はこれに限らず、他の原子を導入してもよい。たとえば、塩素原子などを導入しても同様の効果を得ることができる。
【００６８】
また、上記実施形態では、本発明を光起電力装置のｐ側（表側）に適用した例について説明したが、本発明はこれに限らず、ｎ側（裏側）に適用した場合にも同様の効果を得ることができる。
【図面の簡単な説明】
【図１】本発明の第１実施形態による光起電力装置の構造を示した断面図である。
【図２】図１に示した第１実施形態による光起電力装置のｎ型単結晶シリコン基板１の上面近傍の水素原子の濃度プロファイル図である。
【図３】図１に示した第１実施形態による光起電力装置の製造プロセスを説明するための断面図である。
【図４】図１に示した第１実施形態による光起電力装置の製造プロセスを説明するための断面図である。
【図５】図１に示した第１実施形態による光起電力装置の製造プロセスを説明するための断面図である。
【図６】水素原子面密度とセル出力Ｐ_maxとの関係を示したグラフである。
【図７】本発明の第２実施形態による光起電力装置および比較例による光起電力装置のＳＩＭＳにより測定したｎ型単結晶シリコン基板の上面近傍のフッ素原子の濃度プロファイル図である。
【図８】ｎ型単結晶シリコン基板とノンドープ非晶質シリコン膜との界面のフッ素原子面密度とセル出力との関係を示した図である。
【符号の説明】
１ ｎ型単結晶シリコン基板（結晶系半導体）
２、１２ 非晶質シリコン膜
２ａ、１２ａ ノンドープ非晶質シリコン膜（非晶質半導体膜、第１非晶質半導体膜）
２ｂ ｐ型非晶質シリコン膜（非晶質半導体膜、第２非晶質半導体膜）
１２ｂ ｎ型非晶質シリコン膜（非晶質半導体膜、第２非晶質半導体膜）[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a photovoltaic device and a manufacturing method thereof, and more particularly to a photovoltaic device in which an amorphous semiconductor film is formed on a crystalline semiconductor and a manufacturing method thereof.
[0002]
[Prior art]
Conventionally, in a photovoltaic device in which a pn junction is formed by forming an amorphous silicon film of a second conductivity type on the surface of a crystal silicon substrate of a first conductivity type, the crystal system of the first conductivity type A technique is known in which junction characteristics are improved by inserting a substantially intrinsic amorphous silicon film between a silicon substrate and a second conductivity type amorphous silicon film (for example, Patent Document 1). reference). In Patent Document 1, a substantially intrinsic amorphous silicon film and a p-type amorphous silicon film are sequentially formed on an n-type single crystal silicon substrate, and an n-type single crystal silicon substrate is formed. And a photovoltaic device in which boron is introduced between the substantially intrinsic amorphous silicon film. In this Patent Document 1, since a substantially intrinsic non-doped amorphous silicon film is formed on an n-type single crystal silicon substrate at a low temperature of about 200 ° C. or lower using a plasma CVD method, about 800 Unlike the case of forming a pn junction by diffusing p-type impurities from the surface of an n-type single crystal silicon substrate using a thermal diffusion method at a high temperature of ℃ or higher, thermal damage can be suppressed, and p Interdiffusion between the n-type impurity and the n-type impurity can be suppressed. As a result, good bonding characteristics can be obtained.
[0003]
[Patent Document 1]
JP 2001-345463 A
[Problems to be solved by the invention]
However, in the photovoltaic device disclosed in Patent Document 1, sufficient measures are not taken to reduce (inactivate) dangling bonds, which are crystal defects near the surface of the single crystal silicon substrate. . For this reason, there is an inconvenience that carriers are captured by dangling bonds which are crystal defects near the surface of the single crystal silicon substrate. In this case, since carriers disappear due to recombination near the surface of the single crystal silicon substrate, there is a problem that output characteristics of the photovoltaic device deteriorate. For this reason, it has been difficult to improve the output characteristics of the photovoltaic device.
[0004]
The present invention has been made to solve the above-described problems, and one object of the present invention is to improve output characteristics by reducing crystal defects near the surface of a crystalline semiconductor. It is to provide a possible photovoltaic device.
[0005]
Another object of the present invention is to provide a photovoltaic device capable of improving output characteristics by reducing defects in a crystalline semiconductor and an amorphous semiconductor film.
[0006]
Still another object of the present invention is to provide a method of manufacturing a photovoltaic device capable of improving output characteristics by reducing crystal defects near the surface of a crystalline semiconductor.
[0007]
[Means for Solving the Problems and Effects of the Invention]
To achieve the above object, a photovoltaic device according to a first aspect of the present invention includes a crystalline semiconductor, and an amorphous semiconductor film formed on the surface of the crystalline semiconductor, The hydrogen atom concentration at the interface with the amorphous semiconductor film is higher than the hydrogen atom concentration in the amorphous semiconductor film. The crystalline semiconductor in the present invention is a broad concept including a crystalline semiconductor substrate and a thin film polycrystalline semiconductor formed on the substrate. In addition, the amorphous semiconductor in the present invention is a broad concept including a microcrystalline semiconductor.
[0008]
In the photovoltaic device according to the first aspect, as described above, the hydrogen atom concentration at the interface between the crystalline semiconductor and the amorphous semiconductor film is made higher than the hydrogen atom concentration in the amorphous semiconductor film. As a result, the amount of hydrogen atoms at the interface between the crystalline semiconductor and the amorphous semiconductor film increases, so that the increased hydrogen atoms terminate dangling bonds of silicon atoms, which are crystal defects near the surface of the crystalline semiconductor. Can be inactivated. Thereby, crystal defects near the surface of the crystalline semiconductor can be reduced, so that carriers can be prevented from being captured by the crystal defects. As a result, the recombination of carriers near the surface of the crystalline semiconductor can be suppressed, so that the output characteristics of the photovoltaic device can be improved. In addition, since the dangling bonds of silicon atoms are terminated by hydrogen atoms, the coordination number of silicon atoms is reduced. As a result, the flexibility of the silicon atoms is increased, so that new generation of dangling bonds of silicon atoms that are crystal defects can be suppressed.
[0009]
In the photovoltaic device according to the first aspect, preferably, the interface between the crystalline semiconductor and the amorphous semiconductor film has an amount capable of inactivating crystal defects in the vicinity of the surface of the crystalline semiconductor. Hydrogen atoms have been introduced. With this configuration, dangling bonds that are crystal defects in the vicinity of the surface of the crystalline semiconductor can be easily deactivated, so that dangling bonds that are crystal defects in the vicinity of the surface of the crystalline semiconductor can be easily obtained. Can be reduced.
[0010]
In the photovoltaic device according to the first aspect, preferably, the hydrogen atom surface density at the interface between the crystalline semiconductor and the amorphous semiconductor film is 1.2 × 10 6. ¹⁴ cm ^-2 2.1 × 10 or more ¹⁶ cm ^-2 It is as follows. With this configuration, the amount of hydrogen atoms at the interface between the crystalline semiconductor and the amorphous semiconductor film can be easily inactivated, and dangling bonds that are crystal defects near the surface of the crystalline semiconductor can be inactivated. It can be as much as possible.
[0011]
In the photovoltaic device according to the first aspect, preferably, the hydrogen atom concentration at the interface between the crystalline semiconductor and the amorphous semiconductor film is higher than the hydrogen atom concentration in the crystalline semiconductor, and the crystalline semiconductor The hydrogen atom concentration therein is lower than the hydrogen atom concentration in the amorphous semiconductor film. With this configuration, the amount of hydrogen atoms at the interface between the crystalline semiconductor and the amorphous semiconductor film increases, so that the increased hydrogen atoms cause crystal defects near the surface of the crystalline semiconductor with a low hydrogen concentration. Can be inactivated.
[0012]
In the photovoltaic device according to the first aspect, preferably, the amorphous semiconductor film includes a substantially intrinsic first amorphous semiconductor film formed on a surface of the crystalline semiconductor, and a first amorphous semiconductor film. And a first conductive type second amorphous semiconductor film formed on the surface of the porous semiconductor film. According to this structure, the substantially intrinsic first amorphous semiconductor film can alleviate the lattice mismatch between the crystalline semiconductor and the second amorphous semiconductor film, thereby improving the junction characteristics. be able to.
[0013]
A photovoltaic device according to a second aspect of the present invention includes a crystalline semiconductor and an amorphous semiconductor film formed on the surface of the crystalline semiconductor. The crystalline semiconductor and the amorphous semiconductor film include: Impurities capable of inactivating defects are introduced, and the impurity concentration peak is located in the vicinity of the interface between the crystalline semiconductor and the amorphous semiconductor film.
[0014]
In the photovoltaic device according to the second aspect, as described above, the introduced impurities are introduced into the crystalline semiconductor and the amorphous semiconductor film by introducing impurities capable of inactivating defects. A dangling bond can be inactivated by bonding with a dangling bond of a silicon atom which is a defect in a crystalline semiconductor and an amorphous semiconductor film. Accordingly, defects in the crystalline semiconductor and the amorphous semiconductor film can be reduced, so that carriers can be prevented from being captured by the defects. For this reason, recombination of carriers in the crystalline semiconductor and the amorphous semiconductor film can be suppressed. In addition, since the concentration peak of the introduced impurity is located in the vicinity of the interface between the crystalline semiconductor and the amorphous semiconductor film, the amount of impurities at the interface between the crystalline semiconductor and the amorphous semiconductor film increases. The increased impurities can terminate and inactivate dangling bonds, which are crystal defects near the surface of the crystalline semiconductor. Thereby, crystal defects can be reduced in the vicinity of the surface of the crystalline semiconductor, so that carriers can be suppressed from being captured by the crystal defects. For this reason, it can suppress that a carrier recombines near the surface of a crystalline semiconductor. As described above, since recombination of carriers in the crystalline semiconductor, in the amorphous semiconductor film, and in the vicinity of the surface of the crystalline semiconductor can be suppressed, the output characteristics of the photovoltaic device can be improved. . In addition, since the impurity concentration peak is located near the interface between the crystalline semiconductor and the amorphous semiconductor film, the amount of impurities near the interface between the crystalline semiconductor and the amorphous semiconductor film is more An increase in the amount of impurities in the semiconductor film can be suppressed. Thus, deterioration of film characteristics such as the denseness of the amorphous semiconductor film due to the introduction of many impurities into the amorphous semiconductor film can be suppressed. For this reason, it can suppress that the output characteristic of a photovoltaic device falls by the fall of the film | membrane characteristic of an amorphous semiconductor film. Further, since the introduced impurities are bonded to dangling bonds of silicon atoms, the coordination number of silicon atoms is reduced. As a result, the flexibility of the silicon atoms is increased, so that new generation of dangling bonds of silicon atoms that are crystal defects can be suppressed.
[0015]
In the photovoltaic device according to the second aspect, preferably, the impurity is either a hydrogen atom or a fluorine atom. By using such atoms, dangling bonds of silicon atoms, which are defects in the crystalline semiconductor, the amorphous semiconductor film, and the vicinity of the surface of the crystalline semiconductor can be easily inactivated. Thereby, the output characteristic of a photovoltaic device can be improved easily. This point has been confirmed by the experiments of the present inventors.
[0016]
In this case, preferably, an amount of fluorine atoms capable of inactivating crystal defects in the vicinity of the surface of the crystalline semiconductor is introduced into the interface between the crystalline semiconductor and the amorphous semiconductor film. With this configuration, dangling bonds that are crystal defects in the vicinity of the surface of the crystalline semiconductor can be easily deactivated, so that dangling bonds that are crystal defects in the vicinity of the surface of the crystalline semiconductor can be easily obtained. Can be reduced.
[0017]
In this case, the fluorine atom surface density at the interface between the crystalline semiconductor and the amorphous semiconductor film is preferably 1 × 10 5. ^Ten cm ^-2 1 × 10 or more ¹⁴ cm ^-2 It is as follows. With this configuration, the amount of fluorine atoms at the interface between the crystalline semiconductor and the amorphous semiconductor film can be easily inactivated, and dangling bonds that are crystal defects near the surface of the crystalline semiconductor can be inactivated. It can be as much as possible.
[0018]
In this case, the fluorine atom surface density at the interface between the crystalline semiconductor and the amorphous semiconductor film is preferably 5 × 10 5. ^Ten cm ^-2 2 × 10 or more ¹³ cm ^-2 It is as follows. With this configuration, dangling bonds that are crystal defects in the vicinity of the surface of the crystalline semiconductor can be further inactivated.
[0019]
A method for manufacturing a photovoltaic device according to a third aspect of the present invention includes a step of hydrogen-treating a surface of a crystalline semiconductor with hydrogen gas at a predetermined flow rate, and thereafter, without performing gas replacement by high vacuum evacuation. And a step of forming an amorphous semiconductor film on the surface of the crystalline semiconductor. Here, the replacement of gas by high vacuum evacuation means that the replacement of gas is performed at a degree of vacuum of about 1 Pa or less, for example.
[0020]
In the method for manufacturing a photovoltaic device according to the third aspect, as described above, after the surface of the crystalline semiconductor is subjected to hydrogen treatment with hydrogen gas at a predetermined flow rate, without replacing the gas by high vacuum exhaust, By forming an amorphous semiconductor film on the surface of the crystalline semiconductor, hydrogen atoms adsorbed in an unstable state near the surface of the crystalline semiconductor can be prevented from being removed by high vacuum exhaust. it can. In this case, since the state in which the amount of hydrogen atoms at the interface between the crystalline semiconductor and the amorphous semiconductor film is increased is maintained, the increased hydrogen atoms cause the silicon atoms that are crystal defects near the surface of the crystalline semiconductor to Dangling bonds can be terminated and deactivated. Thereby, crystal defects near the surface of the crystalline semiconductor can be reduced, so that carriers can be prevented from being captured by the crystal defects. As a result, the recombination of carriers near the surface of the crystalline semiconductor can be suppressed, so that the output characteristics of the photovoltaic device can be improved. In addition, since the dangling bonds of silicon atoms are terminated by hydrogen atoms, the coordination number of silicon atoms is reduced. As a result, the flexibility of the silicon atoms is increased, so that new generation of dangling bonds of silicon atoms that are crystal defects can be suppressed.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0022]
(First embodiment)
FIG. 1 is a sectional view showing the structure of a photovoltaic device according to a first embodiment of the present invention. First, the structure of the photovoltaic device according to the first embodiment will be described with reference to FIG.
[0023]
In the photovoltaic device according to the first embodiment, as shown in FIG. 1, an amorphous silicon film 2 having a thickness of about 70 nm to about 100 nm is formed on the upper surface of a hydrogen-treated n-type single crystal silicon substrate 1. A surface electrode 3 made of ITO (indium tin oxide) and a collecting electrode 4 made of silver having a thickness of several tens of μm are sequentially formed. The amorphous silicon film 2 includes a substantially intrinsic non-doped amorphous silicon film 2a having a thickness of about 5 nm to about 20 nm formed on the upper surface of the n-type single crystal silicon substrate 1, and a non-doped amorphous silicon. The p-type amorphous silicon film 2b doped with boron (B) having a thickness of about 3 nm to about 10 nm formed on the film 2a. The n-type single crystal silicon substrate 1 is an example of the “crystal semiconductor” in the present invention. The non-doped amorphous silicon film 2a is an example of the “amorphous semiconductor film” and “first amorphous semiconductor film” in the present invention, and the p-type amorphous silicon film 2b is “ It is an example of “amorphous semiconductor film” and “second amorphous semiconductor film”.
[0024]
Further, on the back surface of the n-type single crystal silicon substrate 1 subjected to the hydrogen treatment, the amorphous silicon film 12 has a thickness of about 70 nm to about 100 nm in order from the side closer to the back surface of the n-type single crystal silicon substrate 1. A back electrode 13 made of ITO and a collecting electrode 14 made of silver having a thickness of several tens of μm are formed. The amorphous silicon film 12 includes a substantially intrinsic non-doped amorphous silicon film 12a having a thickness of about 5 nm to about 40 nm formed on the back surface of the n-type single crystal silicon substrate 1, and non-doped amorphous silicon. The n-type amorphous silicon film 12b doped with phosphorus (P) having a thickness of about 5 nm to about 40 nm formed on the back surface of the film 12a. The non-doped amorphous silicon film 12a, the n-type amorphous silicon film 12b, and the back electrode 13 form a so-called BSF (Back Surface Field) structure. The non-doped amorphous silicon film 12a is an example of the “amorphous semiconductor film” and the “first amorphous semiconductor film” in the present invention, and the n-type amorphous silicon film 12b is “ It is an example of “amorphous semiconductor film” and “second amorphous semiconductor film”.
[0025]
Here, in the first embodiment, it is possible to inactivate crystal defects near the upper surface of the n-type single crystal silicon substrate 1 at the interface between the n-type single crystal silicon substrate 1 and the non-doped amorphous silicon film 2a. A large amount of hydrogen atoms has been introduced. Hereinafter, this point will be described in detail.
[0026]
FIG. 2 is a concentration profile diagram of hydrogen atoms in the vicinity of the upper surface of the n-type single crystal silicon substrate 1 of the photovoltaic device according to the first embodiment shown in FIG. Note that the solid line in FIG. 2 is a concentration profile of hydrogen atoms measured by SIMS (Secondary Ion Mass Spectrometer). The broken line in FIG. 2 is a curve obtained by fitting the hydrogen atom concentration at the interface between the n-type single crystal silicon substrate 1 and the non-doped amorphous silicon film 2a with a normal function (Gaussian function). For measurement of the concentration profile of the hydrogen atom (H), SIMS (ADEPT 1010) manufactured by Physical electronic Corporation was used. The measurement conditions at this time are irradiation ion species: Cs ⁺ Ion, ion irradiation energy: 1 keV, irradiation angle: 60 °, detected secondary ion species: H ^- Ion, reference secondary ion species: Si ^- It was an ion. In addition, in the measurement by SIMS, Cs ⁺ Secondary ions (H ^- Ion and Si ^- The number of ions) and Si ^- Number of ions [Si ^- ] For H ^- Number of ions [H ^- ] Ratio ([H ^- ] / [Si ^- ] However, [Si ^- ] = 5.0 × 10 ^{twenty two} / Cm ^Three ) To obtain the hydrogen atom concentration.
[0027]
Referring to the solid line (SIMS measurement data) in FIG. 2, in the first embodiment, the hydrogen atom concentration at the interface between the n-type single crystal silicon substrate 1 and the non-doped amorphous silicon film 2a is n-type single crystal silicon. It can be seen that the hydrogen atom concentration in the substrate 1 and the hydrogen atom concentration in the non-doped amorphous silicon film 2a are higher. That is, the peak concentration of hydrogen atoms is located at the interface between the n-type single crystal silicon substrate 1 and the non-doped amorphous silicon film 2a, and the peak concentration is about 6.0 × 10. ^{twenty one} cm ^-3 It is.
[0028]
Here, when the impurity concentration in a very thin region such as the interface between the n-type single crystal silicon substrate 1 and the non-doped amorphous silicon film 2a is measured by SIMS, the measured value depends on the measurement conditions and the measurement apparatus. It has been known. For example, under measurement conditions with a low resolution in the depth direction, the peak concentration value decreases and the full width at half maximum increases. On the other hand, under measurement conditions with a high resolution in the depth direction, the peak concentration value increases and the half-value width decreases. Further, when the resolution of the measuring apparatus is low, the peak density value is lowered and the half-value width is widened. On the other hand, when the resolution of the measuring device is high, the peak density value increases and the half-value width decreases. For this reason, in the first embodiment, in order to eliminate the dependence of the SIMS measurement data on the measurement conditions, the peak concentration of hydrogen atoms at the interface between the n-type single crystal silicon substrate 1 and the non-doped amorphous silicon film 2a is set to a depth. It is specified by the surface density integrated in the vertical direction. That is, the hydrogen atom surface density at the interface between the n-type single crystal silicon substrate 1 and the non-doped amorphous silicon film 2a is the integral value of the curve indicated by the broken line in FIG. 2 (the area of the hatched portion in FIG. 2). Yes, about 1.9 x 10 ¹⁵ cm ^-2 It becomes.
[0029]
3-5 is sectional drawing for demonstrating the manufacturing process of the photovoltaic apparatus by 1st Embodiment shown in FIG. Next, a manufacturing process of the photovoltaic device according to the first embodiment will be described with reference to FIGS. 1 and 3 to 5.
[0030]
First, as shown in FIG. 3, after the cleaned n-type single crystal silicon substrate 1 is placed in a vacuum chamber (not shown), the n-type single crystal silicon substrate 1 is removed under a temperature condition of about 200 ° C. or lower. By heating, moisture adhering to the surface of the n-type single crystal silicon substrate 1 is removed as much as possible. Thereby, it is suppressed that the oxygen in the water | moisture content adhering to the surface of the n-type single crystal silicon substrate 1 couple | bonds with a silicon | silicone, and becomes a crystal defect.
[0031]
Next, with the substrate temperature maintained at about 170 ° C., hydrogen (H ₂ ) Introducing gas and about 3mW / cm ² ~ About 30mW / cm ² The upper surface of the n-type single crystal silicon substrate 1 is subjected to hydrogen treatment by supplying the above power. At this time, in the first embodiment, the upper surface of the n-type single crystal silicon substrate 1 is cleaned by introducing hydrogen gas at a flow rate of about 500 sccm to about 2000 sccm and a pressure of about 50 Pa to about 200 Pa. In the vicinity of the upper surface of the n-type single crystal silicon substrate 1, an amount of hydrogen atoms capable of inactivating crystal defects on the upper surface of the n-type single crystal silicon substrate 1 is adsorbed.
[0032]
Thereafter, in the first embodiment, an n-type single crystal is used by plasma CVD as shown in FIG. 4 without performing gas replacement by high vacuum exhaust (exhaust at a degree of vacuum of about 1 Pa or less). On the upper surface of the silicon substrate 1, a non-doped amorphous silicon film 2a is formed. Specifically, with the substrate temperature maintained at about 170 ° C., silane (SiH _Four ) The gas is introduced at a flow rate of about 40 sccm and a pressure of about 40 Pa, and about 8.33 mW / cm ² The non-doped amorphous silicon film 2a having a thickness of about 5 nm to about 20 nm is formed on the upper surface of the n-type single crystal silicon substrate 1 by supplying the above power. In this case, at the interface between the n-type single crystal silicon substrate 1 and the non-doped amorphous silicon film 2a, an amount of hydrogen atoms capable of inactivating crystal defects in the vicinity of the upper surface of the n-type single crystal silicon substrate 1 (Hydrogen atom surface density: about 1.9 × 10 ¹⁵ cm ^-2 ) Is introduced.
[0033]
In the process of forming the non-doped amorphous silicon film 2a, if the gas is replaced by high vacuum exhaust after the hydrogen treatment, the hydrogen atom surface density is lowered. In particular, if high vacuum evacuation is performed for about 1 minute or more, the hydrogen atom surface density becomes substantially the same as the case where hydrogen treatment is not performed. This is because hydrogen atoms supplied to the upper surface of the n-type single crystal silicon substrate 1 by hydrogen treatment are not necessarily implanted into the n-type single crystal silicon substrate 1 to form a stable covalent bond. This suggests an unstable state adsorbed on the upper surface of the single crystal silicon substrate 1 and in the vicinity thereof. Therefore, in the control of the hydrogen atom surface density at the interface between the n-type single crystal silicon substrate 1 and the non-doped amorphous silicon film 2a, the upper surface of the n-type single crystal silicon substrate 1 is subjected to hydrogen treatment and then subjected to high vacuum evacuation. It is important to continuously form the non-doped amorphous silicon film 2a without replacing the gas by.
[0034]
Subsequently, while maintaining the substrate temperature at about 170 ° C., SiH _Four Gas flow rate: about 40 sccm, hydrogen gas flow rate: 0 to about 100 sccm, diborane (B ₂ H ₆ ) / H ₂ (H ₂ Against B ₂ H ₆ Gas concentration: about 2%) Gas flow rate: about 40 sccm, pressure: about 40 Pa, and power density: about 8.33 mW / cm ² Under the conditions, a p-type amorphous silicon film 2b doped with boron (B) having a thickness of about 3 nm to about 10 nm is formed on the non-doped amorphous silicon film 2a.
[0035]
Next, as shown in FIG. 5, a surface electrode 3 made of ITO (indium tin oxide) having a thickness of about 70 nm to about 100 nm is formed on the upper surface of the p-type amorphous silicon film 2b by sputtering. Form. Thereafter, the collector electrode 4 made of silver having a thickness of several tens of μm is formed in a predetermined region on the surface electrode 3 by using a screen printing method.
[0036]
Next, the same hydrogen treatment as the above-described hydrogen treatment of the upper surface of the n-type single crystal silicon substrate 1 is performed on the back surface of the n-type single crystal silicon substrate 1. However, hydrogen gas in this case is introduced at a flow rate of about 100 sccm and a pressure of about 50 Pa.
[0037]
Thereafter, as shown in FIG. 1, a non-doped amorphous silicon film 12a is formed on the back surface of the n-type single crystal silicon substrate 1 by using a plasma CVD method. Specifically, with the substrate temperature maintained at about 170 ° C., SiH _Four The gas is introduced at a flow rate of about 40 sccm and a pressure of about 40 Pa, and about 8.33 mW / cm. ² Is supplied to form a non-doped amorphous silicon film 12a having a thickness of about 5 nm to about 40 nm on the back surface of the n-type single crystal silicon substrate 1. Subsequently, while maintaining the substrate temperature at about 170 ° C., SiH _Four Gas flow rate: about 40 sccm, hydrogen gas flow rate: 0 to about 100 sccm, phosphine (PH _Three ) / H ₂ (H ₂ PH against _Three Concentration: about 1%) Gas flow rate: about 40 sccm, pressure: about 40 Pa, and power density: 8.33 mW / cm ² Under the conditions, an n-type amorphous silicon film 12b doped with phosphorus (P) having a thickness of about 5 nm to about 40 nm is formed on the back surface of the non-doped amorphous silicon film 12a.
[0038]
Finally, a sputtering method is used to form a back electrode 13 made of ITO having a thickness of about 70 nm to about 100 nm on the back surface of the n-type amorphous silicon film 12b. A collector electrode 14 made of silver having a thickness of several tens of μm is formed. In this way, the photovoltaic device according to the first embodiment shown in FIG. 1 is formed.
[0039]
In the first embodiment, as described above, the hydrogen atom concentration (about 6 × 10 6) at the interface between the n-type single crystal silicon substrate 1 and the non-doped amorphous silicon film 2a. ^{twenty one} cm ^-3 ) Higher than the hydrogen atom concentration in the non-doped amorphous silicon film 2a, and the hydrogen atom surface density at the interface between the n-type single crystal silicon substrate 1 and the non-doped amorphous silicon film 2a is about 1.9. × 10 ¹⁵ cm ^-2 As a result, the amount of hydrogen atoms at the interface between the n-type single crystal silicon substrate 1 and the non-doped amorphous silicon film 2a is larger than the amount of hydrogen atoms in the non-doped amorphous silicon film 2a. The increased hydrogen atoms can terminate and inactivate dangling bonds of silicon atoms that are crystal defects near the upper surface of the n-type single crystal silicon substrate 1. Thereby, crystal defects near the upper surface of the n-type single crystal silicon substrate 1 can be reduced, so that carriers can be prevented from being captured by the crystal defects. As a result, since recombination of carriers near the upper surface of the n-type single crystal silicon substrate 1 can be suppressed, the output characteristics of the photovoltaic device can be improved. In addition, since the dangling bonds of silicon atoms are terminated by hydrogen atoms, the coordination number of silicon atoms is reduced. As a result, the flexibility of the silicon atoms is increased, so that new generation of dangling bonds of silicon atoms that are crystal defects can be suppressed.
[0040]
Next, an experiment conducted to confirm the effect of introducing hydrogen atoms into the interface between the n-type single crystal silicon substrate 1 and the non-doped amorphous silicon film 2a will be described. Specifically, in order to investigate the characteristics of the photovoltaic device due to the difference in hydrogen atom surface density at the interface between the n-type single crystal silicon substrate and the non-doped amorphous silicon film, six light beams having different hydrogen atom surface densities are used. Open-circuit voltage V of electromotive force device _OC , Short circuit current I _SC , Fill factor F. F and cell output P _max Was measured. The results are shown in Table 1 below, and the hydrogen atom surface density and cell output P in Table 1 are shown. _max FIG. 6 shows the relationship. The open circuit voltage V in Table 1 _OC Is a voltage measured by connecting a voltmeter between the front electrode and the back electrode, which is generated when light is applied to the photovoltaic device, and is an output voltage value when no current flows. is there. In addition, the short circuit current I _SC Is a current measured by applying an ammeter between the front electrode and the back electrode of the photovoltaic device when light is applied to the photovoltaic device, and the output current when there is no load Value. Cell output P _max Is the voltage V when maximum load is obtained by changing the load resistance when the load resistance is connected to the photovoltaic device. _m And current I _m Is the product of Also, the fill factor F.I. F is the cell output P _max Open circuit voltage V _OC And short circuit current I _SC The product of this curve factor F. The closer the value of F is to 1, the better the current-voltage characteristics of the photovoltaic device.
[0041]
[Table 1]

Referring to Table 1 above, the hydrogen atom surface density at the interface between the n-type single crystal silicon substrate and the non-doped amorphous silicon film of each of the six photovoltaic devices is about 5.3 × 10 5 respectively. ¹³ cm ^-2 About 1.2 × 10 ¹⁴ cm ^-2 Approx.2.5 × 10 ¹⁴ cm ^-2 1.9 × 10 ¹⁵ cm ^-2 (Corresponding to the first embodiment), about 2.1 × 10 ¹⁶ cm ^-2 And about 1.3 × 10 ¹⁷ cm ^-2 It was. The hydrogen atom surface density at the interface between the n-type single crystal silicon substrate and the non-doped amorphous silicon film controls the flow rate of hydrogen gas when the upper surface of the n-type single crystal silicon substrate is subjected to hydrogen treatment in the manufacturing process described above. It is controlled by. The hydrogen atom surface density is about 5.3 × 10. ¹³ cm ^-2 In the photovoltaic device in this case, hydrogen treatment is not performed. This hydrogen atom areal density is about 5.3 × 10 ¹³ cm ^-2 In this case, hydrogen atoms are converted into silane (SiH), which is a source gas, when the non-doped amorphous silicon film is formed. _Four It is considered that the hydrogen contained in is introduced into the interface between the n-type single crystal silicon substrate and the non-doped amorphous silicon film.
[0042]
Referring to Table 1 and FIG. 6, the hydrogen atom surface density is about 1.2 × 10 ¹⁴ cm ^-2 ~ About 2.1 × 10 ¹⁶ cm ^-2 Open circuit voltage V _OC Is about 0.671 V to about 0.708 V, and the hydrogen atom surface density without hydrogen treatment is about 5.3 × 10 ¹³ cm ^-2 Open circuit voltage V _OC It was found to be better than (about 0.665V). The hydrogen atom surface density is about 1.2 × 10 ¹⁴ cm ^-2 ~ About 2.1 × 10 ¹⁶ cm ^-2 Fill factor F. F is about 0.757 to about 0.765, and the hydrogen atom surface density without hydrogen treatment is about 5.3 × 10 5. ¹³ cm ^-2 Fill factor F. It was found to be closer to 1 than F (about 0.731). The hydrogen atom surface density is about 1.2 × 10 ¹⁴ cm ^-2 ~ About 2.1 × 10 ¹⁶ cm ^-2 Cell output P for _max Is about 1.875 W to about 2.016 W, and the hydrogen atom surface density without hydrogen treatment is about 5.3 × 10 ¹³ cm ^-2 Cell output P for _max It was found to be better than (about 1.81 W). As a result, when hydrogen treatment is performed, the hydrogen atom surface density is about 1.2 × 10 10. ¹⁴ cm ^-2 ~ About 2.1 × 10 ¹⁶ cm ^-2 In this range, it is considered that crystal defects are inactivated by hydrogen atoms.
[0043]
On the other hand, even when hydrogen treatment is performed, the hydrogen atom surface density is about 1.3 × 10 ¹⁷ cm ^-2 If it is too high, the open circuit voltage V _OC Is about 0.648V and cell output P _max Is about 1.777 W, and the hydrogen atom surface density without hydrogen treatment is about 5.3 × 10 ¹³ cm ^-2 Open circuit voltage V than _OC And cell output P _max Turned out to be lower. This is because during hydrogen treatment, the hydrogen ion energy increases due to an increase in the amount of hydrogen atoms, and as a result, the surface of the n-type single crystal silicon substrate is irradiated with hydrogen ions, resulting in defects. It is believed that there is.
[0044]
From the results shown in Table 1 and FIG. 6, the hydrogen atom surface density at the interface between the n-type single crystal silicon substrate and the non-doped amorphous silicon film is about 1.2 × 10 ¹⁴ cm ^-2 About 2.1 × 10 ¹⁶ cm ^-2 Open voltage V in the following cases _OC , Fill factor F. F and cell output P _max Can be improved. Therefore, in the first embodiment described above, the hydrogen atom surface density at the interface between the n-type single crystal silicon substrate 1 and the non-doped amorphous silicon film 2a is about 1.9 × 10. ¹⁵ cm ^-2 Open voltage V _OC , Fill factor F. F and cell output P _max Can be improved.
[0045]
(Second Embodiment)
In the second embodiment, unlike the first embodiment, in order to inactivate defects, fluorine atoms are introduced into an n-type single crystal silicon substrate, a non-doped amorphous silicon film, and an n-type single crystal silicon. An example in the case of introducing near the interface between the substrate and the non-doped amorphous silicon film will be described. That is, in the photovoltaic device according to the second embodiment, fluorine atoms are introduced by treating the n-type single crystal silicon substrate with hydrofluoric acid during the process of cleaning the n-type single crystal silicon substrate at the beginning of the manufacturing process. To do.
[0046]
Specifically, in the second embodiment, in the step of cleaning the n-type single crystal silicon substrate, hydrofluoric acid (HF / H) is applied to the surface of the n-type single crystal silicon substrate. ₂ O) (about 3 mol / l to about 10 mol / l HF content, room temperature) followed by H ₂ Perform O rinse (room temperature, about 10 seconds to about 10 minutes). As a result, the surface of the n-type single crystal silicon substrate is subjected to H ₂ There remains a residue of hydrofluoric acid that was not removed by O-rinsing. The hydrofluoric acid (HF / H ₂ O) concentration and H ₂ By changing the rinsing time of O-rinsing, the amount of fluorine atoms introduced can be controlled. For example, if the concentration of hydrofluoric acid is increased, the amount of fluorine atoms introduced increases. H ₂ If the rinsing time for O-rinsing is shortened, the residual amount of hydrofluoric acid increases, so the amount of fluorine atoms introduced increases.
[0047]
Further, in the second embodiment, the hydrogen treatment of the surface of the n-type single crystal silicon substrate as in the first embodiment is not performed. The structure and manufacturing process of other parts of the second embodiment are the same as those of the first embodiment.
[0048]
In the second embodiment, the hydrofluoric acid treatment and H ₂ An amount of fluorine atoms (fluorine atoms) capable of inactivating crystal defects near the upper surface of the n-type single crystal silicon substrate at the interface between the n-type single crystal silicon substrate and the non-doped amorphous silicon film by O rinsing. Surface density: about 1.5 × 10 ¹² cm ^-2 ) Is introduced. Further, the fluorine atoms introduced at the interface between the n-type single crystal silicon substrate and the non-doped amorphous silicon film diffuse into the n-type single crystal silicon substrate and the non-doped amorphous silicon film, whereby the n-type single crystal Fluorine atoms are introduced into the crystalline silicon substrate and the non-doped amorphous silicon film.
[0049]
FIG. 7 shows a concentration profile diagram of fluorine atoms in the vicinity of the upper surface of the n-type single crystal silicon substrate measured by SIMS of the photovoltaic device according to the second embodiment and the photovoltaic device according to the comparative example. For the measurement of the fluorine atom (F) concentration profile, SIMS (ADEPT 1010) manufactured by Physical electronic Corporation was used. The measurement conditions at this time are irradiation ion species: Cs ⁺ Ion, ion irradiation energy: 1 keV, irradiation angle: 60 °, detection secondary ion species: F ^- Ion, reference secondary ion species: Si ^- It was an ion. In addition, in the measurement by SIMS, Cs ⁺ Secondary ions (F ^- Ion and Si ^- The number of ions) and Si ^- Number of ions [Si ^- ] For ^- Number of ions [F ^- ] Ratio ([F ^- ] / [Si ^- ] However, [Si ^- ] = 5.0 × 10 ^{twenty two} / Cm ^Three ) To obtain the concentration of fluorine atoms.
[0050]
Here, in the photovoltaic device according to the second embodiment, hydrofluoric acid treatment at room temperature with the HF content of about 3 mol / l to about 10 mol / l and H at room temperature for about 10 seconds to about 10 minutes. ₂ After performing the O rinse, in a state where the substrate temperature is maintained at about 170 ° C., silane (SiH _Four ) The gas is introduced at a flow rate of about 40 sccm and a pressure of about 40 Pa, and about 8.33 mW / cm ² The non-doped amorphous silicon film having a thickness of about 5 nm to about 20 nm was formed on the upper surface of the n-type single crystal silicon substrate. That is, in the second embodiment, fluorine is introduced before the formation of the non-doped amorphous silicon film, and fluorine is not introduced during the formation of the non-doped amorphous silicon film. On the other hand, in the photovoltaic device according to the comparative example, the hydrofluoric acid treatment at the room temperature with the HF content of about 3 mol / l to about 10 mol / l and the H at room temperature for about 10 seconds to about 10 minutes. ₂ After O-rinsing, fluorine (F) / silane (SiH) with the substrate temperature maintained at about 170 ° C. _Four ) (SiH _Four The concentration of F with respect to the gas: kept constant at about 0.2%) The gas was introduced at a flow rate of about 40 sccm and a pressure of about 40 Pa, and about 8.33 mW / cm ² The non-doped amorphous silicon film having a thickness of about 5 nm to about 20 nm was formed on the upper surface of the n-type single crystal silicon substrate. That is, in the comparative example, fluorine is introduced not only before the formation of the non-doped amorphous silicon film but also during the formation of the non-doped amorphous silicon film. Except for this, a photovoltaic device according to a comparative example was produced in the same manner as in the second embodiment.
[0051]
Referring to FIG. 7, in the second embodiment, the fluorine atom concentration peak is located in the vicinity of the interface between the n-type single crystal silicon substrate and the non-doped amorphous silicon film, and the peak concentration is about 1. 0x10 ¹⁹ cm ^-3 It can be seen that it is. In the second embodiment, as in the first embodiment, fluorine at the interface between the n-type single crystal silicon substrate and the non-doped amorphous silicon film is removed in order to eliminate the dependency of the SIMS measurement data on the measurement conditions. The amount of atoms is defined by the surface density obtained by integrating the peak concentration of fluorine atoms in the depth direction. That is, the fluorine atom surface density at the interface between the n-type single crystal silicon substrate and the non-doped amorphous silicon film is an integral value of the curve indicated by the broken line in FIG. 7 (the area of the hatched portion in FIG. 7). 1.5 × 10 ¹² cm ^-2 It is.
[0052]
Further, in the comparative example, in the region from the n-type single crystal silicon substrate to the vicinity of the interface between the n-type single crystal silicon substrate and the non-doped amorphous silicon film, the same fluorine atom concentration profile as in the second embodiment is shown. I understand that. On the other hand, unlike the second embodiment, the comparative example does not have a fluorine atom concentration peak near the interface between the n-type single crystal silicon substrate and the non-doped amorphous silicon film. Specifically, the photovoltaic device according to the comparative example is substantially constant in the region from the interface between the n-type single crystal silicon substrate and the non-doped amorphous silicon film to the non-doped amorphous silicon film, and the first Fluorine atom concentration larger than that of the second embodiment (about 1.0 × 10 ¹⁹ cm ^-3 ).
[0053]
In the second embodiment, the concentration profile as shown in FIG. 7 is obtained in the vicinity of the interface between the n-type single crystal silicon substrate and the non-doped amorphous silicon film by hydrofluoric acid treatment of the n-type single crystal silicon substrate surface. This is probably because a region having a large amount of fluorine atoms was formed. On the other hand, in the comparative example, the concentration profile as shown in FIG. 7 was obtained because non-doped amorphous using fluorine / silane gas mixed with fluorine at a predetermined ratio in addition to hydrofluoric acid treatment. It is considered that the formation of the silicon film resulted in the introduction of more fluorine atoms in a substantially uniform amount than in the second embodiment over the thickness direction of the non-doped amorphous silicon film.
[0054]
In the second embodiment, as described above, the introduced fluorine atoms are introduced into the n-type single crystal silicon substrate and the non-doped amorphous silicon film by introducing fluorine atoms capable of inactivating defects. The dangling bonds can be inactivated by bonding with dangling bonds of silicon atoms which are defects in the n-type single crystal silicon substrate and the non-doped amorphous silicon film. Thereby, defects in the n-type single crystal silicon substrate and the non-doped amorphous silicon film can be reduced, so that carriers can be prevented from being captured by the defects. For this reason, it is possible to suppress recombination of carriers in the n-type single crystal silicon substrate and in the non-doped amorphous silicon film. Moreover, the peak of the concentration of the introduced fluorine atom (peak concentration: about 1.0 × 10 ¹⁹ cm ^-3 ) Is located in the vicinity of the interface between the n-type single crystal silicon substrate and the non-doped amorphous silicon film, and the fluorine atom surface density at the interface between the n-type single crystal silicon substrate and the non-doped amorphous silicon film is about 1.5. × 10 ¹² cm ^-2 Since the amount of fluorine atoms at the interface between the n-type single crystal silicon substrate and the non-doped amorphous silicon film increases, the increased fluorine atoms cause crystal defects near the upper surface of the n-type single crystal silicon substrate. Some dangling bonds can be terminated and deactivated. Thereby, since crystal defects can be reduced in the vicinity of the upper surface of the n-type single crystal silicon substrate, carriers can be prevented from being captured by the crystal defects. For this reason, it is possible to suppress recombination of carriers in the vicinity of the upper surface of the n-type single crystal silicon substrate. In this manner, since recombination of carriers in the n-type single crystal silicon substrate, in the non-doped amorphous silicon film, and in the vicinity of the upper surface of the n-type single crystal silicon substrate can be suppressed, the output of the photovoltaic device Characteristics can be improved.
[0055]
Also, in the second embodiment, unlike the comparative example, the n-type single crystal is configured so that the peak of the fluorine atom concentration is located in the vicinity of the interface between the n-type single crystal silicon substrate and the non-doped amorphous silicon film. It can be suppressed that the amount of fluorine atoms in the non-doped amorphous silicon film is larger than the amount of fluorine atoms in the vicinity of the interface between the crystalline silicon substrate and the non-doped amorphous silicon film. Thereby, it is possible to suppress deterioration of film characteristics such as the denseness of the non-doped amorphous silicon film due to the introduction of many fluorine atoms into the non-doped amorphous silicon film. For this reason, it can suppress that the output characteristic of a photovoltaic device falls by the fall of the film | membrane characteristic of a non-doped amorphous silicon film.
[0056]
In the second embodiment, since the introduced fluorine atom is bonded to the dangling bond of the silicon atom, the coordination number of the silicon atom is reduced. As a result, the flexibility of the silicon atoms is increased, so that new generation of dangling bonds of silicon atoms that are crystal defects can be suppressed.
[0057]
Next, an experiment for actually measuring the output characteristics of the photovoltaic device in order to confirm the effect of the second embodiment will be described. Specifically, a photovoltaic device (Example 1) having a fluorine atom concentration profile as in the second embodiment of FIG. 7 and light having a fluorine atom concentration profile as in the comparative example of FIG. Output characteristics of the electromotive force device (Comparative Example 1) (open voltage V _oc , Short circuit current I _sc , Fill factor F. F and cell output P _max ) Was measured. And the open circuit voltage V of the comparative example 1 with respect to Example 1 _oc , Short circuit current I _sc , Fill factor F. F and cell output P _max The ratio of each was calculated. The results are shown in Table 2 below.
[0058]
[Table 2]

Referring to Table 2 above, the ratio of the output characteristics of Comparative Example 1 to Example 1 (open-circuit voltage V _oc : 0.995, short circuit current I _sc : 1.001, fill factor F.I. F: 0.993 and cell output P _max : 0.989) is the short circuit current I _sc It can be seen that it is smaller than 1 except for. Thereby, in Example 1, compared with the comparative example 1, the short circuit current I _sc Output characteristics (open voltage V _oc , Fill factor F. F and cell output P _max ) Is improved. This is because in Comparative Example 1, compared with Example 1, since more fluorine atoms were introduced into the non-doped amorphous silicon film, film characteristics such as the denseness of the non-doped amorphous silicon film were deteriorated. This is thought to be due to the fact that the output characteristics deteriorated.
[0059]
Next, the cell output P of the photovoltaic device due to the difference in fluorine atom surface density at the interface between the n-type single crystal silicon substrate and the non-doped amorphous silicon film. _max Cell output P of photovoltaic devices having different fluorine atom surface densities _max Was measured. The measurement result will be described with reference to FIG. In FIG. 8, the cell output P of each photovoltaic device _max The fluorine atom surface density is 1.0 × 10 ¹² cm ^-2 Cell output P when _max The value normalized by (1) is shown as the standard value of the cell output.
[0060]
Referring to FIG. 8, the fluorine atom surface density at the interface between the n-type single crystal silicon substrate and the non-doped amorphous silicon film is 1.0 × 10 6. ⁹ cm ^-2 As the cell voltage increases, the cell output increases and the fluorine atom surface density is 1.0 × 10 6. ¹² cm ^-2 It can be seen that the cell output becomes maximum in the vicinity. Also, the fluorine atom surface density is 1.0 × 10 ¹² cm ^-2 It can be seen that the cell output decreases when the value exceeds. Fluorine atom surface density is 1.0 × 10 ¹² cm ^-2 The cell output increased up to the vicinity up to the crystal defects near the top surface of the n-type single crystal silicon substrate with the increase of fluorine atoms at the interface between the n-type single crystal silicon substrate and the non-doped amorphous silicon film. This is probably because the dangling bonds of silicon atoms are more inactivated. Also, the fluorine atom surface density is 1.0 × 10 ¹² cm ^-2 It is considered that the cell output becomes smaller beyond the vicinity because the amount of fluorine atoms introduced into the interface between the n-type single crystal silicon substrate and the non-doped amorphous silicon film becomes excessive. Specifically, when the amount of fluorine atoms (F) becomes excessive, FF bonds having a small binding energy (bonding force) are generated. Therefore, the n-type single crystal silicon is caused by the breakage of the FF bonds. This is presumably because dangling bonds, which are crystal defects near the top surface of the substrate, increase.
[0061]
Further, referring to FIG. 8, the fluorine atom surface density is 1.0 × 10 6. ^Ten cm ^-2 1.0 × 10 or more ¹⁴ cm ^-2 It can be seen that the standard value of the cell output is 0.8 or more in the following range. It has been confirmed by the present inventor that good output characteristics can be obtained with a photovoltaic device having a fluorine atom surface density in this range. The fluorine atom surface density is 5.0 × 10. ^Ten cm ^-2 2.0 × 10 or more ¹³ cm ^-2 In the following range, it can be seen that the standard value of the cell output is 0.9 or more. It has been confirmed by the present inventor that a better output characteristic can be obtained in a photovoltaic device having a fluorine atom surface density in this range.
[0062]
The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is shown not by the above description of the embodiments but by the scope of claims for patent, and further includes all modifications within the meaning and scope equivalent to the scope of claims for patent.
[0063]
For example, in the above embodiment, the p-type amorphous silicon film 2b is formed on the upper surface of the n-type single crystal silicon substrate 1 via the substantially intrinsic non-doped amorphous silicon film 2a. The present invention is not limited to this, and an n-type amorphous silicon film may be formed on the upper surface of a p-type single crystal silicon substrate via a substantially intrinsic non-doped amorphous silicon film.
[0064]
In the above embodiment, the BSF structure in which the amorphous silicon film 12 (non-doped amorphous silicon film 12a and n-type amorphous silicon film 12b) is formed on the back surface of the n-type single crystal silicon substrate 1 is used. However, the present invention is not limited to this, and the back electrode may be formed on the back surface of the n-type single crystal silicon substrate without forming the n-side amorphous silicon film.
[0065]
In the above embodiment, the p-side film formation is performed first. However, the present invention is not limited to this, and the n-side film formation may be performed first.
[0066]
In the above embodiment, a substantially intrinsic non-doped amorphous silicon film 2a is interposed between the n-type single crystal silicon substrate 1 and the p-type amorphous silicon film 2b (n-type amorphous silicon film 12b). (Non-doped amorphous silicon film 12a) is formed. However, the present invention is not limited to this, and a substantial gap is formed between the first conductive type crystalline semiconductor and the second conductive type amorphous semiconductor film. Therefore, it is not necessary to form an intrinsically non-doped amorphous silicon film.
[0067]
In the above embodiment, hydrogen atoms and fluorine atoms are used as impurities for inactivating defects in the vicinity of the upper surface of the n-type single crystal silicon substrate, in the n-type single crystal silicon substrate, and in the non-doped amorphous silicon film. Although the introduced example has been described, the present invention is not limited to this, and other atoms may be introduced. For example, the same effect can be obtained even when chlorine atoms are introduced.
[0068]
Moreover, although the said embodiment demonstrated the example which applied this invention to the p side (front side) of a photovoltaic apparatus, this invention is not restricted to this, The same is applicable when it applies to the n side (back side). An effect can be obtained.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing the structure of a photovoltaic device according to a first embodiment of the present invention.
2 is a concentration profile diagram of hydrogen atoms in the vicinity of the upper surface of the n-type single crystal silicon substrate 1 of the photovoltaic device according to the first embodiment shown in FIG. 1;
3 is a cross-sectional view for explaining a manufacturing process of the photovoltaic device according to the first embodiment shown in FIG. 1; FIG.
4 is a cross-sectional view for explaining a manufacturing process of the photovoltaic device according to the first embodiment shown in FIG. 1; FIG.
5 is a cross-sectional view for explaining a manufacturing process for the photovoltaic device according to the first embodiment shown in FIG. 1; FIG.
Fig. 6 Hydrogen atom surface density and cell output P _max It is the graph which showed the relationship.
FIG. 7 is a concentration profile diagram of fluorine atoms in the vicinity of the upper surface of an n-type single crystal silicon substrate measured by SIMS of the photovoltaic device according to the second embodiment of the present invention and the photovoltaic device according to the comparative example.
FIG. 8 is a diagram showing the relationship between the fluorine atom surface density at the interface between the n-type single crystal silicon substrate and the non-doped amorphous silicon film and the cell output.
[Explanation of symbols]
1 n-type single crystal silicon substrate (crystalline semiconductor)
2,12 Amorphous silicon film
2a, 12a Non-doped amorphous silicon film (amorphous semiconductor film, first amorphous semiconductor film)
2b p-type amorphous silicon film (amorphous semiconductor film, second amorphous semiconductor film)
12b n-type amorphous silicon film (amorphous semiconductor film, second amorphous semiconductor film)

Claims (3)

A first conductivity type crystalline semiconductor;
A substantially intrinsic first amorphous semiconductor film having a thickness of about 5 nm to about 20 nm formed on the surface of the crystalline semiconductor;
A second conductivity type second amorphous semiconductor film formed on the first amorphous semiconductor film,
Fluorine atoms, to have a peak local concentration near the interface between the crystalline semiconductor and the first amorphous semiconductor film, the in the crystalline semiconductor and the first amorphous semiconductor film each interface Introduced in the vicinity,
A photovoltaic device , wherein a fluorine atom plane density at an interface between the crystalline semiconductor and the first amorphous semiconductor film is 1 × 10 ¹⁰ cm ⁻² or more and 1 × 10 ¹⁴ cm ⁻² or less . Fluorine atom concentration at the interface between the crystalline semiconductor and the first amorphous semiconductor film is 5 × ^{10 10 cm -2} or more 2 × ¹⁰ 13 ^{cm -2} or less, photoelectromotive according to claim 1 Power equipment. A step have rows surface treatment with hydrofluoric acid is carried out followed H _{2 O} rinse with respect to the surface of the crystalline semiconductor wafer of a first conductivity type,
Forming a substantially intrinsic first amorphous semiconductor film having a thickness of about 5 nm to about 20 nm on the surface of the crystalline semiconductor wafer subjected to H ₂ O rinsing ;
Forming a second amorphous semiconductor film of a second conductivity type on the first amorphous semiconductor film ,
In the step of rinsing with H ₂ O, a fluorine atom surface density at an interface between the crystalline semiconductor wafer and the first amorphous semiconductor film is 1 × 10 ¹⁰ cm ⁻² or more and 1 × 10 ¹⁴ cm ⁻² or less. Thus, a method for manufacturing a photovoltaic device , wherein fluorine atoms are allowed to remain on the surface of the crystalline semiconductor wafer .

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