JP3548404B2 - Method for manufacturing zinc oxide thin film, method for manufacturing semiconductor element substrate, and method for manufacturing photovoltaic element - Google Patents

Description

【００８４】
これから以下のことがわかる。
（１）超音波を使用することにより異常成長を減少できる。
（２）超音波を使用することにより２０ミクロン以上の異常成長を無くすことができる。
（３） 約５ｍＡ／ｃｍ^２では超音波のＯＮ、ＯＦＦに関係なく０．０７５ｍｏｌ／ｌでｃ軸配向がくずれる。
【００８５】
（実施例２）
図１の装置で、印加電流密度を約５ｍＡ／ｃｍ^２で一定とし、溶液の硝酸亜鉛濃度を０．２ｍｏｌ／ｌ、溶液温度を８５℃にして超音波の周波数を１０ｋＨｚから１３０ｋＨｚまで変化させて酸化亜鉛薄膜の液相堆積を行なった。溶液堆積後のサンプルをＳＥＭを使用して、異常成長の数を１０ｍｍ×１０ｍｍの範囲で数を数えた。
【００８６】
その結果を表２に示す。
【００８７】
【表２】

【００８８】
これから超音波周波数２０ｋＨｚから１００ｋＨｚの範囲で特に異常成長の数を減少できることが分かる。
【００８９】
また、比較例１で作成したサンプルと、実施例２で作成したサンプルを基板ごと折り曲げ剥離試験を行なった。比較例１で作成したサンプルは折り曲げ部分で剥離が始まり、曲げ戻しでほとんど剥離してしまった。実施例２で作成した超音波周波数２０ｋＨｚから１００ｋＨｚまでのサンプルは、１８０度の角度で折り曲げても剥離は観察されなかった。また実施例２で作成した超音波周波数１０ｋＨｚ、１１０ｋＨｚ、１２０ｋＨｚ、１３０ｋＨｚのサンプルは、１８０度の角度で折り曲げた時剥離は観察されなかったが、長さ１ｍｍ程度の亀裂が観察できた。
【００９０】
以上の結果から、超音波を使用した系で密着性の高いことが確認された。さらに超音波周波数２０ｋＨｚから１００ｋＨｚの範囲では密着性が最も強いことが確認できた。
【００９１】
（実施例３）
図１の装置で、印加電流密度を１．０ｍＡ／ｃｍ^２、２．０ｍＡ／ｃｍ^２、５．０ｍＡ／ｃｍ^２、７．０ｍＡ／ｃｍ^２、１０．０ｍＡ／ｃｍ^２、１５ｍＡ／ｃｍ^２、に対して、硝酸亜鉛濃度を０．０２５ｍｏｌ／ｌ、０．０５ｍｏｌ／ｌ、０．０７５ｍｏｌ／ｌ、０．１ｍｏｌ／ｌ、０．１５ｍｏｌ／ｌ、０．２ｍｏｌ／ｌ、０．３ｍｏｌ／ｌ、０．５ｍｏｌ／ｌに変化させ液温を８５℃程度で液相堆積を行なった。
【００９２】
液相堆積後のサンプルをＸ線回折により配向性とその傾きを測定した。〈１０１〉が強く出る場合と、〈００２〉すなわちｃ軸が強く出る場合の典型例をそれぞれ図８及び９に示す。結果を表３に示す。
【００９３】
【表３】

【００９４】
これから、超音波が存在し、硝酸亜鉛濃度０．０５ｍｏｌ／ｌ以上で、ｃ軸配向がくずれることがあることが分かる。
【００９５】
（実施例４）
１の装置で、硝酸亜鉛濃度０．０２５ｍｏｌ／ｌ、０．０７５ｍｏｌ／ｌ、０．２０ｍｏｌ／ｌの系で印加電流密度を１．０ｍＡ／ｃｍ^２、３．０ｍＡ／ｃｍ^２、５．０ｍＡ／ｃｍ^２、１０．０ｍＡ／ｃｍ^２、に変化させ、さらに溶液温度を３０℃、４０℃、５０℃、６０℃、７０℃、８０℃、９０℃に変化させ、酸化亜鉛薄膜の液相堆積液相堆積可能域を確認した。
【００９６】
その結果を表４に示す。
【００９７】
【表４】

【００９８】
これから、超音波の存在下では、硝酸亜鉛濃度に関係なく６０℃以上で酸化亜鉛が液相堆積しうることが分かる。
【００９９】
（実施例５及び比較例２）
図１の装置で、印加電流密度を約５．０ｍＡ／ｃｍ^２で一定とし、溶液の硝酸亜鉛濃度を０．０２５ｍｏｌ／ｌ、０．２ｍｏｌ／ｌに対して液温を７０℃、８０℃、９０℃に変化させ、超音波ＯＮにし、負側の導電性基体２０３の前処理無しの系（比較例２）と、前処理として導電性基体２０３を液温と同一温度に前加熱する系（実施例５）にて１分間酸化亜鉛薄膜の液相堆積を行なった。
【０１００】
液相堆積後のサンプルをＳＥＭを使用して、２０ミクロン以下３ミクロン以上の異常成長の数を１０ｍｍ×１０ｍｍの範囲で数を数えた。
【０１０１】
その結果を表５に示す。
【０１０２】
【表５】

【０１０３】
これから、前処理として導電性基体を液相堆積液温と同一温度に前加熱することにより異常成長が減少することが分かる。
【０１０４】
（実施例７〜１２及び比較例３）
本発明の酸化亜鉛薄膜を光起電力素子へ適用した。ステンレス基板（５０×５０×０．１５ｍｍ）上にアルミニウム（厚さ０．２μｍ）をスパッタ法で形成した基板に、図１の装置で酸化亜鉛薄膜を形成した。
【０１０５】
溶液は硝酸亜鉛の水溶液とし、１００ｍｌに２ｇの割合でサッカロースを加え、硝酸亜鉛濃度は０．０２５ｍｏｌ／ｌ、液温は８５℃、印加電流は１０ｍＡ／ｄｍとした。液相堆積中は周波数１０、４０、７０、１００、又は１３０ｋＨＺの超音波振動を与えた。これらを実施例７から１１と呼ぶ。
【０１０６】
また、硝酸亜鉛濃度を０．２ｍｏｌ／ｌとしたほかは実施例８と同様の条件で実施例１２を作成した。図１の装置の負極の電極１０３に用いる基体を前処理として、液相堆積温度と同じ８５℃に加熱した純水に、セッティング直前までの１０分間浸漬し、硝酸亜鉛濃度を０．２ｍｏｌ／ｌとする以外は実施例８と同じ条件で実施例１３を作成した。いずれも３分の反応で約１ミクロンの酸化亜鉛薄膜が堆積した。
【０１０７】
ＳＥＭ像では実施例７から１１の酸化亜鉛層は０．１ミクロン以下の微細な結晶粒からなり、Ｘ線回折ではＣ軸配向が確認でき、最も強度の強いピークが〈００２〉であった。一方実施例１２，１３の酸化亜鉛層は約０．７ミクロンの結晶粒からなり、Ｘ線回折ではＣ軸配向が確認でき、最も強度の強いピークが〈１０１〉であった。いずれの例もＳＥＭ観察範囲１０ｍｍ×１０ｍｍの中で、２０ミクロン以上の異常成長は確認されなかった。
【０１０８】
この後、半導体層としてＣＶＤ法により、ｎ型非晶質シリコン（ａ−Ｓｉ）を２００Å、ｉ型非晶質シリコン（ａ−Ｓｉ）を２０００Å、ｐ型微結晶シリコン（ｍｃ−Ｓｉ）を１４０Åの順に堆積した。さらに酸素雰囲気の加熱蒸着でＩＴＯを６５０Å蒸着し、反射防止効果のある上部電極としての透明導電膜とした。この上に銀によるグリッドを加熱蒸着により堆積して上部取り出し電極とし、素子とした。
【０１０９】
比較例３として、超音波振動を与えなかったほかは実施例８と同じ条件で光起電力素子を作成した。
【０１１０】
比較例３を１として、初期特性の相対比較と、温湿度劣化試験後の変換効率の低下率を表６に示す。
【０１１１】
【表６】

【０１１２】
比較例３の変換効率の低下が大きいのは、多数の異常成長部から剥離現象が発生し、酸化亜鉛薄膜と半導体部界面の密着性が低下し抵抗が増大したため変換効率を低下させたと考えられる。
【０１１３】
（実施例１４及び１５）
図３に示す装置で、長尺のステンレス基板（支持体ロール：３０ｃｍ×３００ｍ×０．１２ｍｍ）上に酸化亜鉛薄膜を形成し、光起電力素子を作成した。ただし送り出しロールと温水槽の間には、脱脂槽、水洗槽、蝕刻槽、水洗槽、金属層形成槽、水洗槽が設けられている。それぞれの槽内には、支持体ロールの搬送経路をコントロールするためのローラが設けられている。支持体ロールのプロセススピードは２００ｃｍ／ｍｉｎとした。支持体ロールに係わっている張力は５０ｋｇｆとした。張力は巻き取りローラーに組み込まれた張力調整クラッチによって制御される。
【０１１４】
まずオイルで防錆 された支持体ロールは脱脂槽にてオイル分を脱脂される。脱脂浴は、水１ｌ中に硫酸６０ｍｌと塩酸（３７％塩化水素（以下同様））７０ｍｌを含んでなる水溶液である。温度は室温とする。しかるのち搬送ローラーを経て、水洗槽に搬送される。水洗シャワーにて水洗が十分に行なわれる。水量は最低毎分２ｌであることが好ましい。
【０１１５】
次に支持体ロールは、搬送ローラーを経て、酸性蝕刻槽に搬送される。蝕刻液はフッ酸（４６％フッ酸化水素、以下同様）３、酢酸１（モル比）を混合した物である。温度は室温とする。
【０１１６】
更に脱脂浴後の水洗槽と同様の水洗槽に搬送される。次工程の金属層形成浴がアルカリ性であるから、弱アルカリのシャワーとすることも可能である。
【０１１７】
支持体ロールは搬送ローラーを経て、金属層形成槽５１４にてめっきによる金属層を形成する。金属層形成槽の浴は水１ｌ中に、ピロ燐酸銅８０ｇ、ピロ燐酸カリウム３００ｇ、アンモニア水（比重０．８８）６ｍｌ、硝酸カリウム１０ｇからなる。５０℃乃至６０℃で制御する。ｐＨは８．２乃至８．８の範囲に入るようにする。陽極には銅板を用いる。本装置にては支持体ロールが接地電位とされているので、陽極の銅板での電流を読んで層形成を制御する。本例では電流密度３Ａ／ｄｍ^２とした。また、層形成速度は６０Å／ｓｅｃであり、金属形成浴中で形成された金属層の層厚は４０００Åであった。
【０１１８】
その後水洗槽で水洗されたのち、支持体ロールは搬送ローラーを経て、純水温度８５℃に保たれた温水槽を経て、充分に前加熱されたのち、酸化亜鉛層形成槽５２３（長さ２ｍ，幅０．５ｍ，高さ０．５ｍ）に搬送さる。
【０１１９】
実施例１４での酸化亜鉛形成浴は、水１ｌ中に硝酸亜鉛・６水塩３０ｇ、サッカロース２０ｇを含む。実施例１５での浴は水１ｌ中に硝酸亜鉛・６水塩２０ｇ、デキストリン０．０２ｇを含む。その外は同様である。
【０１２０】
基板には超音波振動子（４０ｋＨｚ）（１５ｃｍ×１５ｃｍ）による超音波印加がなされている。液温は８５℃の温度に保たれており、ｐＨは５．９乃至６．４に保持される。対向電極（３０ｃｍ×３０ｃｍ）は表面をバフ研磨した亜鉛が用いられる。この亜鉛対向電極に流す電流密度は５Ａ／ｄｍ２とした。また、形成速度は３０Å／ｓｅｃであり、酸化亜鉛層形成浴中で形成された、酸化亜鉛層の膜厚は１ミクロンであった。
【０１２１】
その後、水洗槽で水洗された後支持体ロールは搬送ローラーを経て乾燥炉に送られる。乾燥炉は不図示の温風ノズルと赤外線ヒーターからなっており、温風は溌水も同時に行なう。温風ノズルからの温風は８０℃に制御し、赤外線ヒーターは２００℃で制御した。
【０１２２】
このようにして乾燥工程を経た支持体ローラーは支持体上に、金属層、酸化亜鉛層、を形成した物として巻き上げローラーに巻き取られる。
【０１２３】
金属層形成槽は空気撹拌（バブリング）とし、酸化亜鉛層形成槽は本発明による超音波撹拌とした。またいずれも、ガラス電極を用いた温度補正を内蔵したｐＨ計にて常時浴のｐＨモニターし、金属層形成槽ではアンモニアを追加し、酸化亜鉛層形成槽では適時硝酸亜鉛を追加して浴のｐＨを制御した。
【０１２４】
続いて、ｐｉｎ構造を３つ有するトリプルセルをＣＶＤ法で形成した。順に、ａ−Ｓｉ（ｎ型）層２０ｎｍ，ａ−ＳｉＧｅ（ｉ型）層１１０ｎｍ，μｃ−Ｓｉ（ｐ型）層１０ｎｍ，ａ−Ｓｉ（ｎ型）層１０ｎｍ，ａ−ＳｉＧｅ（ｉ型）層１１０ｎｍ，μｃ−Ｓｉ（ｐ型）層１０ｎｍ，ａ−Ｓｉ（ｎ型）層１０ｎｍ，ａ−Ｓｉ（ｉ型）層１００ｎｍ，μｃ−Ｓｉ（ｐ型）層１０ｎｍ，を形成した。さらにＩＴＯ（厚さ６０ｎｍ）をスパッタで形成し、最後にＡｇペーストで集電電極を形成した。
【０１２５】
また、金属層をめっき法の代わりにＤＣマグネトロンスパッタ法で形成した（銅４０００Å）ほかは、実施例１４と同様に光起電力素子を作成したものを実施例１６とした。
【０１２６】
また、酸化亜鉛層形成時に超音波使用しないほかは実施例１４と同様に光起電力素子を作成したものを比較例４とした。
【０１２７】
前述と同様に比較例４との相対比較した結果を以下に示す。
【０１２８】
【表７】

【０１２９】
（実施例１７及び比較例５）
図２に示す装置で、表８に示すように硝酸亜鉛濃度ある範囲で変化させて全部で２０の酸化亜鉛薄膜を形成したものを実施例１７とした。また、振動体に振動を与えずに膜形成を行った以外は実施例１７と全く同様に、酸化亜鉛薄膜を形成したものを比較例５とした。
【０１３０】
（実施例１８及び比較例６）
図４に示す装置を用いて、表８に示すように硝酸亜鉛濃度ある範囲で変化させて全部で２０の酸化亜鉛薄膜を長尺ステンレス基板上に作成したものを実施例１８とした。実施例１８で基板に振動を与えなかったものを比較例６とした。
【０１３１】
（実施例１９及び比較例７，８）
図４に示す装置を用いて、表８に示すように硝酸亜鉛濃度ある範囲で変化させて全部で２０の酸化亜鉛薄膜を長尺ステンレス基板上に作成したものを実施例１９とした。ただし、図６ｂに示すように磁性回転ベルトと対向する位置の溶液中に磁石を配した。また、酸化亜鉛薄膜形成槽のあとに水洗槽を設けた。また、垂直方向の振動は超音波振動子を使用した。実施例１９で基板に振動を与えなかったものを比較例７とした。
【０１３２】
対向磁石の効果を確かめるために、対向磁石を配置しなかったほかは実施例１９と同様に酸化亜鉛薄膜を作成したものを比較例８とした。なお、後述する評価においては、比較例６と対比した。
【０１３３】
（実施例２０及び比較例９）
図１０に示す装置を用いて、表８に示すように硝酸亜鉛濃度ある範囲で変化させて２層の酸化亜鉛薄膜を長尺ステンレス基板上に作成したものを実施例２０とした。図１０に示す装置は洗浄槽１００１、第１の酸化亜鉛形成槽１０１０、第２の酸化亜鉛形成槽１０１７、及び洗浄槽１０２３を備えている。洗浄槽１００１及び１０２３は超音波振動体を溶液中に有しており効率的な洗浄を可能にする。第１及び第２の酸化亜鉛形成槽の溶液成分、電流密度、及び溶液温度は表８に示すように異なっている。また、基板に振動を与えなかったこと以外は実施例２０同様としたものを比較例９とした。
【０１３４】
（実施例２１及び参考例１）
図４の装置を用いて、表８に示すように水溶液温度をある範囲で変化させて２０の酸化亜鉛薄膜を長尺ステンレス基板上に作成したものを実施例２１とした。ただし装置は対向磁石を備えている。このうち水溶液温度５０度以下で形成したサンプルを参考例１と呼ぶ。
【０１３５】
（実施例２２及び参考例２）
図４の装置を用いて、表８に示すように硝酸亜鉛濃度をある範囲で変化させて２０の酸化亜鉛薄膜を長尺ステンレス基板上に作成したものを実施例２２とした。ただし装置は対向磁石を備えている。また、ステンレス基板には予めＡｇを２０００Åスパッタ法により形成しておく。また、酸化亜鉛薄膜形成槽のあとに水洗槽を設けた。このうち硝酸亜鉛濃度が０．００１ｍｏｌ／ｌ以下で形成したサンプルを参考例２と呼ぶ。
【０１３６】
（実施例２３及び参考例３，参考例４）
図４の装置を用いて、表８に示すように電流密度をある範囲で変化させて２０の酸化亜鉛薄膜を長尺ステンレス基板上に作成したものを実施例２３とした。ただし装置は対向磁石を備えている。また、ステンレス基板には予めＡｇを２０００Åスパッタ法により形成しておく。また、酸化亜鉛薄膜形成槽のあとに水洗槽を設けた。このうち電流密度が７ｍＡ／ｄｍ^２で形成したサンプルを参考例３、１２Ａ／ｄｍ^２で形成したサンプルを参考例４と呼ぶ。
【０１３７】
（実施例２４及び参考例５，参考例６）
酸化亜鉛薄膜形成槽の前に水洗槽を有する図４の装置を用いて、水洗層の温度を２０度から９５度の範囲で変化させて２０の酸化亜鉛薄膜を長尺ステンレス基板上に作成したものを実施例２４とした。ただし装置は対向磁石を備えている。このうち、水洗槽の温度が酸化亜鉛形成槽の温度２３℃で形成したサンプルを参考例５、９５℃で形成したサンプルを参考例６と呼ぶ。
【０１３８】
（実施例２５及び比較例１０）
図４の装置を用いて、表８に示すように酸化亜鉛形成槽の水溶液温度をある範囲で変化させて２０の酸化亜鉛薄膜を長尺ステンレス基板上に作成したものを実施例２５とした。ただし装置は対向磁石を備えている。また、ステンレス基板には予めＡｇを２０００Åスパッタ法により形成しておく。実施例２５で基板に振動を与えなかったものを比較例１０とした。
【０１３９】
【表８】

【０１４０】
酸化亜鉛薄膜の評価
表面観察は光学顕微鏡を用いて、ステンレス基板の中央部分の１ｃｍ×１ｃｍの面積の中に直径１０μｍ以上の異常成長が何個存在するか観察した。（ 異常成長観察）
【０１４１】
また、電子顕微鏡（ＳＥＭ）観察により、５μｍ×５μｍの範囲の中で酸化亜鉛の結晶 （ウルツ鉱型 ）粒径を測定し（結晶粒径観察）、粒径のばらつきを調べた（ 結晶粒径ばらつき観察）。
【０１４２】
また、それぞれの酸化亜鉛薄膜の形成された基板の一部上に碁盤目テープ法により格子状に１ｍｍ間隔で１０本づつの切り傷をつけ、１００個のます目をつける。セロハン粘着テープを貼りつけ、充分に付着した後に瞬間的に引きはがし、剥れた部分の面積を求めることで導電性基板と酸化亜鉛薄膜との密着性の評価を行ない、次にその基板を環境試験箱に入れ温度８５℃、湿度８５％の条件で１００時間保持し、再び前回と同様の方法で密着性の評価を行った。（密着性試験）
【０１４３】
いずれの実施例においても、ほとんど異常成長が見られなかったのに対して、比較例及び参考例においては異常成長が認められた。表９に実施例の酸化亜鉛薄膜を基準にした時の、それぞれに対応する比較例及び参考例の結晶粒の粒径、粒径のばらつき、及び密着性を相対値で示した。実施例の結晶粒は比較例及び参考例に比べてばらつきが小さく、粒径が大きく、また実施例の酸化亜鉛薄膜は成膜直後及び高温多湿劣化試験後においても密着性が優れている事が分かる。
【０１４４】
【表９】

【０１４５】
光起電力素子の作製と評価
実施例１７から２５の酸化亜鉛薄膜の成膜後、それぞれにＣＶＤ法でｐｉｎ接合を形成し、透明電極、集電電極を形成し、図７に示すような光起電力素子を作成した。
【０１４６】
全ての素子（２０個）についてそれぞれ２５個のサブセルに分けた後、暗所でー１．０Ｖの逆バイアス電圧をかけた状態でシャント抵抗を測定した。シャント抵抗の基準値を４×１０^４Ωｃｍ^２とし、歩留りを調べた。
【０１４７】
さらに続いて酸化亜鉛薄膜の密着性試験と全く同様の方法を用いて光起電力素子の密着性試験、初期特性（光導電特性）、高温高湿度逆バイアス試験（ＨＨＲＢ）劣化の試験を行なった。
【０１４８】
初期特性は、ソーラーシュミレーター（ＡＭ１．５ １００ｍＷ／ｃｍ２ 表面温度２５℃）を用いて光電変換効率を測定した。ＨＨＲＢ試験は、環境試験箱に入れ温度８５℃、湿度８５％、逆バイアス電圧０．８Ｖの条件で１００時間保持した後、同じく光電変換効率を調べた。
【０１４９】
実施例１７から２５の酸化亜鉛薄膜を使用した光起電力素子を、それぞれに対応する比較例及び参考例を基準とした時の、歩留まり、密着性、初期光電変換効率、ＨＨＲＢ試験後の光電変換効率についての相対評価を表９に示す。本発明の酸化亜鉛薄膜を使用した光起電力素子は優れた特性を有することがわかる。
【０１５０】
【発明の効果】
本発明の酸化亜鉛薄膜製造方法によれば、真空プロセスが不要であるため、大幅に作成コストを低減する。また、歩留が高く、均一性、密着性に優れた酸化亜鉛薄膜の製造が可能になる。特に結晶粒が２０ミクロン以上に異常成長することを抑制する。
【０１５１】
また、本発明の方法で形成された酸化亜鉛薄膜を有する光起電力素子は、作成コストを大幅に低減し、かつ歩留が高く、均一性や耐環境性を向上することができる。
【図面の簡単な説明】
【図１】超音波振動子を使用した酸化亜鉛製造装置を示す模式図。
【図２】（ａ）は振動体を使用した酸化亜鉛製造装置を示す模式図、（ｂ）はその振動体電源を示す模式図。
【図３】超音波振動子を使用した酸化亜鉛薄膜の連続製造装置を示す模式図。
【図４】振動体を使用した酸化亜鉛薄膜の連続製造装置を示す模式図。
【図５】磁性回転ベルトの詳細を示す模式図。
【図６】ａは基板近傍の磁力線を示す模式図。ｂは対向磁石を配置した場合の基板近傍の磁力線を示す模式図。
【図７】本発明の方法で形成された酸化亜鉛薄膜を光起電力素子に応用した例を示す模式図。
【図８】硝酸亜鉛濃度が低濃度で作成された酸化亜鉛層のＸ線回折強度を示すチャート。
【図９】硝酸亜鉛濃度が高濃度で作成された酸化亜鉛層のＸ線回折強度を示すチャート。
【図１０】２層の酸化亜鉛層の連続製造装置を示す模式図。
【符号の説明】
１０１ 耐腐食性容器
１０２ 水溶液
１０３ 導電性基体
１０４ 対向電極
１０５ 電源
１０６ 負荷抵抗
１０７ 射出口
１０８ 吸入口
１０９ 吸入溶液パイプ
１１０ 射出溶液パイプ
１１１ 溶液循環ポンプ
１１２ 超音波振動子
１１３ 超音波発振器
１１４ ヒーター
１１５ 温度計
１１６ 熱電対
２１２ 振動体
２１３ 振動体電源
３０２ 送り出しロール
３０３ 巻き取りロール
３０５ 温水槽
３０８ 酸化亜鉛形成槽
３１３ 水洗槽
３１５ 乾燥炉
４０５ 振動体
４０６ 振動体電源
４１２ 送り出しロール
４１３ 巻き取りロール
７０１ 支持体
７０２ 金属層
７０２ 酸化亜鉛層
７０４ 半導体層
７０５ 透明導電層
７０６ 集電電極
１００１ 洗浄槽１
１０１０ 第１の酸化亜鉛形成槽
１０１７ 第２の酸化亜鉛形成槽
１０１４、１０２１ 振動体
１０１５、１０２２ 振動体電源
１０１６ 対向磁石
１０２３ 洗浄槽２
１０２５ 乾燥炉
１０２８ 磁性回転ベルト[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for producing a zinc oxide thin film by liquid phase growth, a method for producing a semiconductor element substrate using the same, and a method for producing a photovoltaic element.
[0002]
[Prior art]
Conventionally, it has been known to provide a reflective layer made of metal or the like on the back surface of a semiconductor layer in order to improve the collection efficiency at a long wavelength of a photovoltaic element. In addition, by providing a transparent conductive layer having irregularities between the reflective layer and the semiconductor layer, it is possible to obtain an optical confinement effect of extending an optical path length of reflected light and an effect of suppressing an excessive current from flowing during a shunt. Is known to be. ZnO formed by a sputtering method is widely used for the transparent conductive layer.
[0003]
For example, "Light Confinement Effect in a-SiGe Solar Cell on 29p-MF-22 Stainless Steel Substrate" (Autumn 1990), Proceedings of the 51st Annual Conference of the Japan Society of Applied Physics p747, or "P-IA-15a-SiC / a-Si / a-SiGe Multi-Bandgap Stacked Solar Cells With Bandgap Profiling, "Sannomiya et al. , Technical Digest of the International PVSEC-5, Kyoto, Japan, p381, 1990, describe that a combination of a reflective layer and a zinc oxide layer has increased the short-circuit current due to the light confinement effect.
[0004]
On the other hand, "Electrolyte Optimization for Cathodic Growth of Zinc Oxide Films" IZAKI and T.I. Omi J. et al. Electrochem. Soc. , Vol. 143, March 1996, L53 and JP-A-8-217443 report methods of forming a zinc oxide thin film by electrolysis from an aqueous solution containing zinc ions and nitrate ions.
[0005]
[Problems to be solved by the invention]
However, the conventional optical confinement layer is generally formed by a vacuum deposition method using resistance heating or an electron beam, a sputtering method, an ion plating method, a CVD method, or the like. For this reason, there are problems such as a high production labor for a target material, a need for a vacuum process, a large depreciation cost of a vacuum apparatus, and a low efficiency of material use. Therefore, the cost of a photovoltaic element using these technologies is extremely high, and this is a great barrier for industrial application of solar cells.
[0006]
In addition, a zinc oxide thin film formed by electrolysis from an aqueous solution containing zinc ions and acetate ions can be formed at low cost, but has the following problems.
[0007]
(1) In particular, when the current density is increased or the concentration of the solution is increased, abnormal growth in the form of needles, spheres, resins, etc. exceeding micron order easily occurs on the deposition. When the zinc oxide thin film is used as a part of the photovoltaic device, it is considered that such abnormal growth causes a shunt path of the photovoltaic device.
[0008]
Although the cause of the abnormal projection growth is not clear, it is considered that the electric field partially concentrated depending on the uneven shape of the substrate surface due to the use of electrodeposition, and zinc oxide was abnormally grown in the concentrated portion. In the case of forming a zinc oxide thin film, almost no gas is generated at the cathode (substrate). However, when the temperature of the aqueous solution is 50 ° C. or higher, dissolved air appears as fine bubbles, Pit is generated by adhering to the vicinity, and a depression is generated on the surface of the zinc oxide thin film. As a result, it is considered that a difference was generated in the electric field and abnormal growth was formed. Furthermore, when a high-concentration solution is used, zinc hydroxide is formed even when the electrolytic conditions are adjusted, and after the fine film is deposited on the substrate, abnormal growth starts using the film as a nucleus. It is thought that it will be done.
[0009]
The crystal grain size is considered to be caused by high-speed formation, and it is thought that the zinc oxide particles adsorbed on the crystal surface accumulate before sufficient surface diffusion is performed, so that the grain size becomes small. Increasing the temperature of the aqueous solution increases the surface diffusion, but may cause abnormal growth as described above.
[0010]
(2) The size of zinc oxide crystal grains tends to vary, and there is a problem in uniformity when the area is increased.
[0011]
(3) When applied to a photovoltaic element, adhesion to the conductive substrate and / or adhesion to a semiconductor formed on the zinc oxide layer was poor.
[0012]
(4) Only a thin film having a smooth film thickness is formed, and a method for forming a deposited film having an uneven shape having an optical confinement effect has not been found.
[0013]
The present invention provides a manufacturing method that stabilizes the formation of a zinc oxide thin film by electrodeposition and has excellent adhesion to a semiconductor layer. In particular, it is a zinc oxide thin film suitable for application to a light confinement layer of a photovoltaic element.
[0014]
[Means for Solving the Problems]
Means for solving the above-mentioned problem is that a current is passed between a conductive substrate immersed in an aqueous solution containing at least nitrate ions and zinc ions and an electrode immersed in the solution, By forming a zinc oxide thin film on the conductive substrate by vibrating the substrate.
[0015]
This suppresses abnormal growth of the zinc oxide thin film. In addition, due to the violent vibration, the ion concentration distribution in the solution near the surface of the substrate is sufficiently stirred, and the surface diffusion of the adsorbed particles on the film forming surface is activated, so that the oxidation with more uniform and large crystal grain size is achieved. This makes it possible to form a zinc thin film.
[0016]
Further, by preventing the abnormal growth, the peeling of the film starting from the abnormal growth can be suppressed, and the adhesion between the conductive substrate and the zinc oxide thin film is improved. In application to a photoelectric conversion element, adhesion to a semiconductor layer deposited on a zinc oxide thin film can also be improved. In particular, when a long substrate is used, the film is wound into a roll after film formation, so that the adhesion between the film and the substrate or between the films is important. The improvement in the adhesion improves the production yield of the photovoltaic device.
[0017]
As a method of applying vibration to the substrate, there are a method of applying vibration through an aqueous solution from a position distant from the substrate, and a method of directly contacting the vibrator with the substrate.
[0018]
Specifically, there is a method in which an ultrasonic vibrator is arranged at a position distant from the substrate and the substrate is vibrated through an aqueous solution.
[0019]
The high-speed stirring action by ultrasonic vibration has a large effect by cavitation generated by ultrasonic waves. Vibration by the ultrasonic vibrator has an effect that the solution concentration in the vicinity of the reaction becomes uniform in a range where the cavitation intensity from 20 kHz to 100 kHz is strong. In particular, abnormal growth of crystal grains larger than 20 microns can be suppressed.
[0020]
As a method of directly contacting the vibrating body with the substrate, for example, there is a method of transmitting the power of a motor to the substrate through a crank. When the substrate is long, a part of the rotating belt-shaped vibrator is brought into close contact with the back surface of the long substrate, and is vibrated by the same method while moving in the same direction as the substrate.
[0021]
By bringing the rotating belt into close contact, the conductive substrate can be efficiently vibrated and the ions on the substrate surface can be sufficiently stirred. In addition, by vibrating the vibrating body while moving in the same direction as the long substrate, vibration can be efficiently transmitted to the substrate without causing scratches between the substrate and the vibrating body due to friction. In addition, the suppression of the occurrence of scratches improves the production yield in the process of forming the photoelectric conversion element in a later step.
[0022]
It is preferable that the vibrating body is a rotating belt including a ferromagnetic body partially magnetized. This allows the whole or part of the vibrating body to be ferromagnetic rather than just pressing the vibrating body against a tensioned substrate when the vibrating body is moved in the same direction as the transport direction by bringing the vibrating body into close contact with the long substrate. In the case of a body, vibration can be more efficiently propagated from the vibrating body. In addition, by using a rotating belt-like ferromagnetic material, when forming a plurality of layers by passing a plurality of solutions through the substrate, once the long substrate is taken out of the solution tank, the film forming surface is brought into contact with the roller. It is possible to change the direction without causing a change in the direction and to adhere to the ferromagnetic material, so that the long substrate can be wound with high tension, and the coil can be easily handled in the process after the formation of the conductive oxide film. To do.
[0023]
Further, a magnetic body may be provided on the side facing the substrate so that the magnetic field lines are perpendicular to the conductive substrate. When the magnetic field lines of the ferromagnetic material are perpendicular to the substrate, the movement of ions in the electric field solution becomes uniform over the entire width direction of the conductive substrate, forming an oxide conductive film with excellent film quality uniformity. Is possible. The uniformity of the film quality has an effect of making the photoelectric conversion efficiency of the photoelectric conversion element formed on the zinc oxide thin film uniform.
[0024]
The vibration of the vibrating body is in the range of a frequency of 1 Hz to 100 kHz, a vibration width of 1 μm to 100 mm, and an average moving speed of 10 m / sec or less.
[0025]
A first zinc nitrate aqueous solution tank having at least a first zinc nitrate aqueous solution and a first vibrator, and a second zinc nitrate aqueous solution tank having a second zinc nitrate aqueous solution and a second vibrator; Forming the zinc oxide thin film on the conductive substrate with the first and second vibrators having different frequencies and / or vibration directions has the following effects.
[0026]
By laminating a plurality of conductive oxide films, a zinc oxide thin film is deposited on the first layer under the condition of forming a layer having a large surface irregularity having excellent optical properties. By reforming by covering or slightly gently laminating the second layer, the production yield of the element can be improved without lowering the optical and electrical performance.
[0027]
Alternatively, a dense but flat zinc oxide layer is formed on the first layer, and then a second layer having thin irregularities is formed, so that the production yield of the element can be reduced without deteriorating the optical and electrical performance. It can be improved.
[0028]
Alternatively, a zinc oxide layer having a desired shape is formed by forming a dense but flat zinc oxide layer on the first layer, and then forming a second layer under conditions that produce thin pits, and then etching the outermost surface. By using a thin film, it is possible to improve the production yield of the device without deteriorating the optical and optical performances, and to improve the durability and weather resistance of the device. Here, a preferable range of the surface roughness Ra of the second layer is 0.001 to 2 μm.
[0029]
The concentration of zinc nitrate is preferably 0.05 to 1.0 mol / l. By setting the zinc nitrate concentration to 0.05 mol / l or more, the peak with the highest intensity in X-ray diffraction changes from (002) to (101). At this time, the surface shape of the zinc oxide changes from a flat state to an uneven state, and becomes a shape suitable for application to a light confinement layer of a photovoltaic element. When the content is less than 0.05 mol / l, the zinc oxide film may not be deposited, and metallic zinc may be deposited. If the concentration is higher than 1 mol / l, abnormal growth is likely to occur.
[0030]
The current density applied to the aqueous solution is 10 mA / dm²More than 10A / dm²It is desirable that: Below this range, it is difficult to deposit a zinc oxide thin film. Above this range, abnormal growth tends to occur.
[0031]
The temperature range in which the liquid phase can be deposited in the preparation of a zinc oxide thin film is 50 ° C. or higher under atmospheric pressure, and a stable zinc oxide reaction is performed by maintaining the temperature of the aqueous solution at 50 ° C. or higher.
[0032]
Pre-heating the conductive substrate to within ± 5 ° C of the solution temperature as a pretreatment eliminates abnormal growth due to temperature unevenness on the surface of the conductive substrate immediately after the start of liquid phase deposition, and stabilizes the liquid phase deposition reaction Can be started.
[0033]
It is preferable to add a carbohydrate to the aqueous solution. Carbohydrates function as a buffer to generate hydrogen and suppress a rise in the pH of the solution. By this action, the reaction is carried out stably and the crystal grain size is adjusted.
[0034]
Examples of the carbohydrate include glucose, saccharose, cellulose, starch and the like.
[0035]
BEST MODE FOR CARRYING OUT THE INVENTION
Equipment for manufacturing zinc oxide thin films
FIG. 1 shows an example of an apparatus for producing a zinc oxide thin film of the present invention. Reference numeral 101 denotes a corrosion-resistant container, which holds an aqueous solution 102 containing nitrate ions, zinc ions, and carbohydrates. In order to obtain a desired zinc oxide thin film, the concentrations of nitrate ions and zinc ions are preferably in the range of 0.05 mol / l to 1.0 mol / l.
[0036]
The source of nitrate ion and zinc ion is not particularly limited, and zinc nitrate, which is a source of both ions, or a water-soluble nitrate such as ammonium nitrate, which is a source of nitrate ion, and zinc ion May be a mixture of zinc salts such as zinc sulfate, which is a supply source of zinc.
[0037]
Reference numeral 103 denotes a conductive base, which is a cathode. Reference numeral 104 denotes a counter electrode, which can use platinum, carbon, or the like in addition to zinc, which is a metal to be deposited in a liquid phase. The counter electrode 104 is an anode. The base 103 serving as a cathode and the counter electrode 104 serving as an anode are connected to a power supply 105 via a load resistor 106 so that a substantially constant current flows. In order to obtain a desired zinc oxide thin film, the current density is desirably in the range of 10 mA / dm to 10 A / dm.
[0038]
Reference numeral 112 denotes an ultrasonic vibrator, which imparts vibration by transmitting ultrasonic waves generated by the ultrasonic oscillator 113 to the conductive base 103 via the aqueous solution 102. The frequency is preferably 20 kHz or more and 100 kHz or less.
[0039]
FIG. 2 shows a case where vibration is directly applied to the substrate. By bringing the vibrating body 212 into contact with the conductive substrate 203, reciprocating motion in the vertical and horizontal directions can be given. This vibration may be such that a driving part is provided in a vibrating body and converted into motion in each direction by a gear and a crank, or a vibrating part including a driving part may be provided on the vibrating body power supply 213 side. . FIG. 2B shows an example of the driving method. At the same time as applying a vertical vibration to the substrate to another motor 254 by a crank 253 connected to the motor 251 inside the vibrating body power supply 213, the motor 254 generates a horizontal vibration to the substrate through the crank 255. The vibration is transmitted to the vibration plate 257 through the vibration transmission shaft 256. The diaphragm itself may be made of an ultrasonic vibrator. The vibrating body power supply 213 may be arranged in the corrosion-resistant container 201.
[0040]
Further, it is desirable that the vibration frequency is 1 Hz to 100 kHz in each direction, the vibration width is 1 μm to 100 mm, and the average moving speed is 10 m / sec or less.
[0041]
In particular, when the above-described ultrasonic vibrator is used, the amplitude is as narrow as several μm, and ion agitation on the conductive substrate becomes effective due to the cavitation effect, but the pitch of the standing wave is coarse, so that the agitation is uneven. May be possible. Therefore, a vibrating body having different resonance frequencies f1 and f2 is prepared, and the vibrating body is further vibrated at frequencies f1 ± Δf and f2 ± Δf slightly shifted from the respective vibrating bodies, or the frequency is swept by a certain width. Alternatively, modulation is applied so that oscillation does not always occur at a constant frequency. Thus, it is possible to continuously change the position of cavitation, to suppress the occurrence of unevenness, and to form a uniform and large-diameter film.
[0042]
Further, in order to reduce the layer formation unevenness by stirring the solution and increase the layer formation speed to improve the efficiency, the solution suction port 108, the solution ejection port 107, the solution circulation pump 111, the suction solution pipe 109, the injection solution pipe 110 And a solution circulation system comprising: In a small-scale apparatus, a magnetic stirrer can be used instead of such a solution circulation system.
[0043]
Further, it is desirable to control the temperature of the aqueous solution while monitoring the temperature using a heater 114 and a thermometer such as a thermocouple 115. In order to obtain a desired zinc oxide thin film, the liquid temperature of the aqueous solution is desirably 50 ° C. or higher. Further, it is preferable that the temperature of the substrate is previously set at a liquid temperature of ± 5 ° C., and it is more preferable that the temperature of the substrate is the same as the liquid temperature.
[0044]
After the deposition of the first zinc oxide thin film, the conditions may be changed and a second zinc oxide thin film may be subsequently deposited.
[0045]
In addition, carbohydrates such as monosaccharides such as glucose (glucose) and fructose (fructose), disaccharides such as maltose (maltose) and saccharose (sucrose), and polysaccharides such as dextrin and starch are added to the aqueous solution. In addition, abnormal growth of crystals can be further suppressed.
[0046]
The amount of carbohydrate in the aqueous solution is preferably in the range of 0.001 g / l to 300 g / l, and more preferably in order to obtain a zinc oxide thin film having no abnormal growth and excellent in uniformity and adhesion. Desirably, it is in the range of 0.005 g / l to 100 g / l, and most preferably in the range of 0.01 g / l to 60 g / l.
[0047]
Continuous manufacturing equipment
The apparatus shown in FIGS. 3 and 4 is an apparatus capable of continuously forming a zinc oxide layer on the surface of a flexible long sheet-shaped conductive substrate from an aqueous solution.
[0048]
FIG. 3 shows a case in which the substrate is vibrated by an ultrasonic vibrator. An insulating tape (not shown) for preventing the deposition of the zinc oxide thin film is attached to the back surface of the conductive substrate 301. Reference numeral 302 denotes a delivery roll that winds the conductive substrate 301 in a roll shape, and reference numeral 303 denotes a winding roll that winds the conductive substrate. The conductive substrate is wound by the winding roll 303 via many transport rolls 304. To go. The diameter of each roll needs to be determined according to the material of the conductive substrate in order to prevent plastic deformation of the substrate.
[0049]
A hot water tank 305 for heating the conductive substrate is connected to a circulation system including a filter for removing dust, and a heater is provided inside the hot water tank.
[0050]
A liquid deposition tank 308 for forming a zinc oxide layer is connected to a circulation system (not shown) that also has a filter for removing dust, and a counter electrode 310 and a heater (not shown) are provided inside the liquid deposition tank. A constant current power supply 312 is connected to the outside. The circulation device has a system for monitoring the solution concentration and adding the solution as needed.
[0051]
An ultrasonic oscillator 305 is provided at the bottom of the zinc oxide forming tank 308, and is connected to an ultrasonic oscillator 306.
[0052]
A washing tank 313 is connected to a circulating system (not shown) which also has a filter for removing dust. After passing through a water-washing shower 314, it is dried with hot air in a drying oven 315 and wound up on a winding roll 303.
[0053]
FIG. 4 shows a case where the vibrating body is in direct contact with the substrate. Reference numeral 401 denotes a zinc oxide forming tank which holds an aqueous solution 402 containing nitrate ions, zinc ions, and carbohydrates. Reference numeral 403 denotes a conductive long substrate which is a cathode. Reference numeral 404 denotes a zinc anode, which serves as a counter electrode. The counter electrode 404 serving as an anode is connected to a power supply 407, and is set so that a substantially constant current flows. In addition, a heater 409 is provided at the bottom of the corrosion-resistant solution layer 401 to keep the temperature of the solution constant, and the temperature is adjusted by a heater power supply 410 by a thermometer 414 so as to reach a desired constant temperature. Further, in order to reduce the layer formation unevenness by stirring the solution and increase the layer formation speed to improve the efficiency, a solution circulation system including a solution circulation pump 411 and a solution pipe is used, and the solution is circulated through the flow path in the figure. By doing so, the effect is enhanced. A stirrer may be used in order to prevent a temperature difference due to convection due to heater heating.
[0054]
The vibrating body 405 has a belt shape, and contacts the back surface of the conductive substrate 403 to give a reciprocating motion in a direction perpendicular to the substrate and in a direction parallel to the substrate. If the vibrating body 405 is in a stationary state at the time of winding, a vertical scratch is likely to occur on the back surface of the substrate, which may be a fatal defect when a device is formed later. Therefore, the vibrating body 405 is in the form of a rotating belt so as to move in the solution at the same speed as the conductive long substrate, and transmits vibration to the substrate while pressing the conductive long substrate to float. Things. Alternatively, the belt may have magnetism and may be transported while attracting the substrate by magnetic force.
[0055]
FIG. 5 shows a magnetic rotating belt (ferromagnetic rotating belt). The magnetic rotating belt 50 is made of a corrosion-resistant rubber such as silicon rubber, fluorine rubber, urethane rubber, nitrile rubber, styrene rubber, butyl rubber, or the like as a binder, and magnetized ferromagnetic material in the rubber, such as tungsten steel. A rotating belt is formed by binding a hardening magnet, a precipitation hardening magnet such as alnico, a rare earth cobalt magnet, an oxide magnet, and the like.
[0056]
As shown in the figure, the ferromagnetic rotating belt 501 has grooves formed by the width and thickness of the conductive long substrate 502, and has a structure without deviation. Since one surface of the conductive substrate is in contact with the magnetic rotating belt, the zinc oxide thin film 504 can be formed only on one surface. In addition, the ferromagnetic rotating belt has a sufficient width and strength, and the transport direction can be changed without deforming the substrate by the end support rollers 503 and without contacting the rollers. Although the end support roller 503 is used in two places, one or more end support rollers 503 may be used.
[0057]
FIGS. 6a and 6b show the state of the magnetic lines of force provided by the ferromagnetic rotating belt. FIG. 6A shows the lines of magnetic force when no ferromagnetic material is provided below the solution tank, and the density of the lines of magnetic force is increased in the width direction of the substrate even though the width of the ferromagnetic rotating belt 601 is larger than the width of the conductive substrate 602. On the other hand, there is a difference between the central portion and the end portion. As a result, ions in the solution to which an electric field is applied are also affected, and the film thickness becomes uneven. On the other hand, in the case of FIG. 6B in which a counter magnet 603 made of a ferromagnetic material is installed in the lower part of the solution tank, the lines of magnetic force of the conductive substrate 602 are almost parallel, and it is possible to form a uniform film without affecting the film thickness and film quality. it can.
[0058]
Before and after the apparatus shown in FIG. 4, a hot water tank, a washing tank and a drying furnace as described above may be provided. Further, a plurality of zinc oxide forming tanks may be arranged. In this case, the single belt-shaped vibrator is configured to pass through a plurality of tanks.
[0059]
(Substrate)
The substrate used in the present invention has a base made of various magnetic or non-magnetic metal supports. Among them, stainless steel plates, steel plates, copper plates, brass plates, aluminum plates and the like are relatively inexpensive and suitable. Alternatively, a substrate in which a metal layer such as Al is formed on a resin by sputtering or the like may be used.
[0060]
Such a metal plate or a substrate having a metal layer may be cut into a fixed shape, or may be used in a long sheet-like shape depending on the plate thickness. In this case, since it can be wound in a coil shape, it is suitable for continuous production, and storage and transportation become easy. Further, depending on the application, a crystal substrate such as silicon, a glass, ceramics, or resin plate can be used.
[0061]
The surface of the support may be polished, but may be used as it is when the finish is good such as a stainless steel plate subjected to a bright annealing treatment. Further, the substrate may be appropriately roughened so that the zinc oxide layer formed thereon has a desired uneven shape.
[0062]
Application to photovoltaic devices
FIG. 7 is a schematic cross-sectional view of a photovoltaic element to which the zinc oxide thin film formed by the method of the present invention is applied. In the figure, 701 is a support, 702 is a metal layer, 703 is a zinc oxide layer formed by the method of the present invention, 704 is a semiconductor layer, 705 is a transparent conductive layer, and 706 is a current collecting electrode.
[0063]
The zinc oxide layer 703 may be a stack of a plurality of layers having different grain sizes and different orientations of crystal axes.
[0064]
At this time, if the support 701 and / or the metal layer 702 and / or the zinc oxide layer 703 and / or the semiconductor layer 704 are formed to be uneven enough to bend the light path, the optical path is tilted, It is expected that the optical path length passing through the layer 303 will be extended and the absorption will be increased. The increase in absorption due to the extension of the optical path length is so small that it hardly causes any problem in a layer almost transparent to light, but the region where absorption is present to some extent, that is, the wavelength of light is a wavelength near the absorption edge of the substance. Becomes exponential. Since the zinc oxide layer 703 which is a transparent layer is transparent to visible light to near infrared light, light of 600 nm to 1200 nm is absorbed in the semiconductor layer 303.
[0065]
Although the metal layer 702 is not essential, a substrate made of a material having low reflectivity as it is, such as stainless steel or a steel plate, or a support made of a material having low conductivity as it is, such as glass or ceramics, has a silver layer thereon. It is preferable to provide a metal layer having a high reflectance such as copper, gold, or aluminum. When aluminum is used for the metal layer, an extremely thin transparent conductive film layer may be formed on the metal layer in order to prevent aluminum from dissolving in the aqueous solution.
[0066]
(Semiconductor layer)
Examples of a material of the semiconductor layer 704 include a pn junction, a pin junction, a Schottky junction, and a hetero junction. Examples of the semiconductor material include hydrogenated amorphous silicon, hydrogenated amorphous silicon germanium, and hydrogenated amorphous silicon. Silicon carbide, microcrystalline silicon, polycrystalline silicon, or the like can be used.
[0067]
In particular, amorphous or microcrystalline Si, C, Ge, or an alloy thereof is suitable for continuous formation on a long substrate. At the same time, hydrogen and / or halogen atoms are contained. The preferred content is 0.1 to 40 atomic%. Further, oxygen, nitrogen and the like may be contained. These impurity concentrations are 5 × 10¹⁹Atom cm^-3The following is desirable. Further, a p-type semiconductor contains a group III element, and an n-type semiconductor contains a group V element.
[0068]
In the case of a stack cell having a plurality of pin junctions, it is preferable that the band gap of the i-type semiconductor layer having the pin junction near the light incident side is wide and the band gap is narrow as the farther the pin junction is. Further, it is preferable that the band gap has a minimum value closer to the p-layer than the center of the film thickness in the i-layer.
[0069]
As the doped layer on the light incident side, a crystalline semiconductor with little light absorption or a semiconductor with a wide band gap is suitable.
[0070]
In order to form the above semiconductor layer, a microwave (MW) plasma CVD method, a VHF plasma CVD method, or a radio frequency (RF) plasma CVD method is suitable.
[0071]
The source gas suitable for depositing the group IV and group IV alloy amorphous semiconductor layer suitable for the photovoltaic device of the present invention is SiH₄, Si₂H₆And the like. A gasizable compound containing a silicon atom, such as a silicon atom, and a gasizable compound containing a germanium atom, such as GeH4, are mainly used.
[0072]
Further, a gasizable compound containing carbon, nitrogen, oxygen and the like may be used in combination.
[0073]
B is used as a dopant gas for forming a p-type layer.₂H₆, BF₃Are used.
[0074]
PH as a dopant gas for forming an n-type layer₃, PF₃Are used.
[0075]
In particular, when depositing a layer having a small light absorption or a wide band gap such as a microcrystalline or polycrystalline semiconductor or SiC, the dilution rate of the source gas with hydrogen gas is increased, and the microwave power or RF power is relatively high power. It is preferred to introduce
[0076]
(Transparent electrode)
The transparent electrode 705 can also function as an antireflection film by appropriately setting its film thickness.
[0077]
The transparent electrode 107 is made of ITO, ZnO, InO₃Is formed using a method such as evaporation, CVD, spraying, spin-on, or dipping. These compounds may contain a substance that changes electric conductivity.
[0078]
(Collecting electrode)
The current collecting electrode 706 is provided to improve current collecting efficiency. Examples of the manufacturing method include a method of forming a metal of an electrode pattern by sputtering using a mask, a method of printing a conductive paste or a solder paste, and a method of fixing a metal wire with a conductive paste.
[0079]
Note that protective layers may be formed on both surfaces of the photovoltaic element 100 as necessary. At the same time, a reinforcing material such as a steel plate may be used in combination.
[0080]
【Example】
(Example 1 and Comparative Example 1)
Using the apparatus of FIG. 1, a zinc oxide thin film (1.2 μm thick) was formed on a stainless steel substrate (50 × 50 × 0.15 mm). The applied current density is about 5 mA / cm²And the zinc nitrate concentration of the solution was adjusted to 0.025 mol / l, 0.05 mol / l, 0.075 mol / l, 0.1 mol / l, 0.15 mol / l, 0.2 mol / l, 0.3 mol / l The liquid temperature was set to 85 ° C. for 0.5 mol / l. A zinc plate (50 × 50 × 1 mm) was used as a counter electrode. A case where an ultrasonic wave (40 kHz) was applied (Example 1) and a case where no ultrasonic wave was applied (Comparative Example 1) were prepared.
[0081]
The sample after the liquid phase deposition was counted for the number of abnormal growth in the range of 10 mm × 10 mm using SEM. Each sample was measured by X-ray diffraction.
[0082]
Table 1 shows the results.
[0083]
[Table 1]

[0084]
From this, the following can be understood.
(1) Abnormal growth can be reduced by using ultrasonic waves.
(2) By using ultrasonic waves, abnormal growth of 20 microns or more can be eliminated.
(3) About 5mA / cm²In this case, the c-axis orientation is lost at 0.075 mol / l regardless of ON / OFF of the ultrasonic wave.
[0085]
(Example 2)
In the apparatus of FIG. 1, the applied current density is about 5 mA / cm.², The zinc nitrate concentration of the solution was 0.2 mol / l, the solution temperature was 85 ° C., and the ultrasonic frequency was changed from 10 kHz to 130 kHz to perform liquid phase deposition of the zinc oxide thin film. The number of abnormal growths of the sample after the solution deposition was counted in the range of 10 mm × 10 mm using SEM.
[0086]
Table 2 shows the results.
[0087]
[Table 2]

[0088]
From this, it can be seen that the number of abnormal growth can be particularly reduced in the ultrasonic frequency range of 20 kHz to 100 kHz.
[0089]
Further, the sample prepared in Comparative Example 1 and the sample prepared in Example 2 were subjected to a bending and peeling test together with the substrate. The sample prepared in Comparative Example 1 started peeling at the bent portion, and almost peeled off when bent back. In the sample having an ultrasonic frequency of 20 kHz to 100 kHz prepared in Example 2, no peeling was observed even when bent at an angle of 180 degrees. In the samples of ultrasonic frequencies 10 kHz, 110 kHz, 120 kHz, and 130 kHz created in Example 2, no peeling was observed when bent at an angle of 180 degrees, but cracks of about 1 mm in length could be observed.
[0090]
From the above results, it was confirmed that the system using ultrasonic waves had high adhesion. Further, it was confirmed that the adhesiveness was the strongest in the range of the ultrasonic frequency of 20 kHz to 100 kHz.
[0091]
(Example 3)
In the apparatus of FIG. 1, the applied current density was set to 1.0 mA / cm.², 2.0 mA / cm², 5.0 mA / cm², 7.0 mA / cm², 10.0 mA / cm², 15mA / cm², The zinc nitrate concentration was 0.025 mol / l, 0.05 mol / l, 0.075 mol / l, 0.1 mol / l, 0.15 mol / l, 0.2 mol / l, 0.3 mol / l , 0.5 mol / l, and liquid phase deposition was performed at a liquid temperature of about 85 ° C.
[0092]
The orientation and inclination of the sample after the liquid phase deposition were measured by X-ray diffraction. FIGS. 8 and 9 show typical examples of the case where <101> appears strongly and the case where <002>, ie, the c-axis appears strongly. Table 3 shows the results.
[0093]
[Table 3]

[0094]
From this, it can be understood that the presence of ultrasonic waves and the zinc nitrate concentration of 0.05 mol / l or more may cause the c-axis orientation to be lost.
[0095]
(Example 4)
1, the applied current density was set to 1.0 mA / cm in a system having a zinc nitrate concentration of 0.025 mol / l, 0.075 mol / l, and 0.20 mol / l.²3.0mA / cm², 5.0 mA / cm², 10.0 mA / cm², And the solution temperature was further changed to 30 ° C., 40 ° C., 50 ° C., 60 ° C., 70 ° C., 80 ° C., and 90 ° C., and a liquid deposition area of the zinc oxide thin film was confirmed.
[0096]
Table 4 shows the results.
[0097]
[Table 4]

[0098]
This indicates that in the presence of ultrasonic waves, zinc oxide can be deposited in a liquid phase at 60 ° C. or higher regardless of the zinc nitrate concentration.
[0099]
(Example 5 and Comparative Example 2)
In the apparatus of FIG. 1, the applied current density was set to about 5.0 mA / cm.²The solution temperature was changed to 70 ° C., 80 ° C., 90 ° C. with respect to the zinc nitrate concentration of the solution of 0.025 mol / l and 0.2 mol / l, the ultrasonic wave was turned on, and the negative conductive substrate was turned on. Liquid phase deposition of a zinc oxide thin film was performed for 1 minute in a system without pretreatment 203 (Comparative Example 2) and a system in which the conductive substrate 203 was preheated to the same temperature as the liquid temperature (Example 5) as pretreatment. Was.
[0100]
The number of abnormal growths of 20 μm or less and 3 μm or more of the sample after the liquid phase deposition was counted in a range of 10 mm × 10 mm using SEM.
[0101]
Table 5 shows the results.
[0102]
[Table 5]

[0103]
From this, it is understood that abnormal growth is reduced by preheating the conductive substrate to the same temperature as the liquid deposition liquid temperature as the pretreatment.
[0104]
(Examples 7 to 12 and Comparative Example 3)
The zinc oxide thin film of the present invention was applied to a photovoltaic device. A zinc oxide thin film was formed on a stainless steel substrate (50 × 50 × 0.15 mm) formed by sputtering aluminum (thickness: 0.2 μm) by the apparatus shown in FIG.
[0105]
The solution was an aqueous solution of zinc nitrate, and saccharose was added at a ratio of 2 g to 100 ml. The zinc nitrate concentration was 0.025 mol / l, the liquid temperature was 85 ° C., and the applied current was 10 mA / dm. During the liquid phase deposition, ultrasonic vibration at a frequency of 10, 40, 70, 100, or 130 kHz was applied. These are called Examples 7 to 11.
[0106]
Example 12 was made under the same conditions as in Example 8, except that the zinc nitrate concentration was 0.2 mol / l. As a pretreatment, the substrate used for the negative electrode 103 of the apparatus in FIG. 1 was immersed in pure water heated to 85 ° C., which is the same as the liquid deposition temperature, for 10 minutes immediately before setting, and the zinc nitrate concentration was set to 0.2 mol / l. Example 13 was made under the same conditions as Example 8 except that the above conditions were satisfied. In each case, a zinc oxide thin film of about 1 micron was deposited by the reaction for 3 minutes.
[0107]
In the SEM images, the zinc oxide layers of Examples 7 to 11 consisted of fine crystal grains of 0.1 μm or less, and the C-axis orientation was confirmed by X-ray diffraction, with the strongest peak being <002>. On the other hand, the zinc oxide layers of Examples 12 and 13 consisted of crystal grains of about 0.7 μm, and the C-axis orientation was confirmed by X-ray diffraction, and the strongest peak was <101>. In each case, abnormal growth of 20 μm or more was not confirmed in the SEM observation range of 10 mm × 10 mm.
[0108]
Thereafter, n-type amorphous silicon (a-Si) is deposited at 200 °, i-type amorphous silicon (a-Si) is deposited at 2000 °, and p-type microcrystalline silicon (mc-Si) is deposited at 140 ° by a CVD method as a semiconductor layer. In this order. Further, ITO was vapor deposited at 650 ° by heating vapor deposition in an oxygen atmosphere to form a transparent conductive film as an upper electrode having an antireflection effect. A silver grid was deposited thereon by heating and vapor deposition to form an upper extraction electrode, thereby forming an element.
[0109]
As Comparative Example 3, a photovoltaic element was prepared under the same conditions as in Example 8 except that no ultrasonic vibration was applied.
[0110]
Table 6 shows the relative comparison of the initial characteristics and the decrease rate of the conversion efficiency after the temperature / humidity deterioration test, with Comparative Example 3 as 1.
[0111]
[Table 6]

[0112]
It is considered that the large decrease in the conversion efficiency of Comparative Example 3 was caused by the separation phenomenon occurring from a large number of abnormally grown portions, the adhesion between the zinc oxide thin film and the semiconductor portion being reduced, and the resistance being increased, thereby lowering the conversion efficiency. .
[0113]
(Examples 14 and 15)
With the apparatus shown in FIG. 3, a zinc oxide thin film was formed on a long stainless steel substrate (support roll: 30 cm × 300 m × 0.12 mm) to produce a photovoltaic element. However, a degreasing tank, a washing tank, an etching tank, a washing tank, a metal layer forming tank, and a washing tank are provided between the delivery roll and the hot water tank. Rollers for controlling the transport path of the support roll are provided in each tank. The process speed of the support roll was 200 cm / min. The tension related to the support roll was 50 kgf. Tension is controlled by a tension adjustment clutch built into the take-up roller.
[0114]
First, the support roll rust-proofed with oil is degreased in a degreasing tank. The degreasing bath is an aqueous solution comprising 60 ml of sulfuric acid and 70 ml of hydrochloric acid (37% hydrogen chloride (the same applies hereinafter)) in 1 liter of water. The temperature is room temperature. After that, it is transported to the washing tank via the transport roller. Washing is sufficiently performed in the washing shower. Preferably, the amount of water is at least 2 l / min.
[0115]
Next, the support roll is transported to an acidic etching tank via a transport roller. The etching solution is a mixture of 3 hydrofluoric acid (46% hydrogen hydrofluoride, the same applies hereinafter) and 1 acetic acid (molar ratio). The temperature is room temperature.
[0116]
Furthermore, it is conveyed to the same washing tank as the washing tank after a degreasing bath. Since the metal layer forming bath in the next step is alkaline, it is possible to use a weak alkaline shower.
[0117]
The support roll forms a metal layer by plating in a metal layer forming tank 514 via a transport roller. The bath of the metal layer forming tank is composed of 80 g of copper pyrophosphate, 300 g of potassium pyrophosphate, 6 ml of aqueous ammonia (specific gravity 0.88), and 10 g of potassium nitrate in 1 liter of water. Control at 50 ° C to 60 ° C. The pH should be in the range 8.2 to 8.8. A copper plate is used for the anode. In this apparatus, since the support roll is set to the ground potential, the current is read from the anode copper plate to control the layer formation. In this example, the current density is 3 A / dm²And The layer formation rate was 60 ° / sec, and the thickness of the metal layer formed in the metal forming bath was 4000 °.
[0118]
Then, after being washed in a washing tank, the support roll passes through a conveying roller, passes through a warm water tank maintained at a pure water temperature of 85 ° C., is sufficiently preheated, and then is subjected to a zinc oxide layer forming tank 523 (length 2 m). , Width 0.5 m, height 0.5 m).
[0119]
The zinc oxide forming bath in Example 14 contains 30 g of zinc nitrate hexahydrate and 20 g of saccharose in 1 liter of water. The bath in Example 15 contains 20 g of zinc nitrate hexahydrate and 0.02 g of dextrin per liter of water. Others are the same.
[0120]
Ultrasonic waves are applied to the substrate by an ultrasonic oscillator (40 kHz) (15 cm × 15 cm). The liquid temperature is maintained at 85 ° C., and the pH is maintained at 5.9 to 6.4. As the counter electrode (30 cm × 30 cm), zinc whose surface is buffed is used. The current density applied to the zinc counter electrode was 5 A / dm2. The formation rate was 30 ° / sec, and the thickness of the zinc oxide layer formed in the zinc oxide layer forming bath was 1 μm.
[0121]
Then, after being washed in a washing tank, the support roll is sent to a drying oven via a transport roller. The drying furnace includes a hot air nozzle (not shown) and an infrared heater, and the hot air simultaneously repels water. The hot air from the hot air nozzle was controlled at 80 ° C, and the infrared heater was controlled at 200 ° C.
[0122]
The support roller that has undergone the drying process in this manner is wound on a take-up roller as a product having a metal layer and a zinc oxide layer formed on the support.
[0123]
The metal layer forming tank was air-stirred (bubbling), and the zinc oxide layer-forming tank was ultrasonically stirred according to the present invention. In each case, the pH of the bath was constantly monitored by a pH meter with a built-in temperature correction using a glass electrode, ammonia was added in the metal layer forming tank, and zinc nitrate was added in a timely manner in the zinc oxide layer forming tank. The pH was controlled.
[0124]
Subsequently, triple cells having three pin structures were formed by the CVD method. A-Si (n-type) layer 20 nm, a-SiGe (i-type) layer 110 nm, μc-Si (p-type) layer 10 nm, a-Si (n-type) layer 10 nm, a-SiGe (i-type) layer 110 nm, 10 μm of a μc-Si (p-type) layer, 10 nm of an a-Si (n-type) layer, 100 nm of an a-Si (i-type) layer, and 10 nm of a μc-Si (p-type) layer. Further, ITO (thickness: 60 nm) was formed by sputtering, and finally, a current collecting electrode was formed by an Ag paste.
[0125]
A photovoltaic element was prepared in the same manner as in Example 14, except that the metal layer was formed by DC magnetron sputtering instead of plating (copper: 4000 ４).
[0126]
A photovoltaic element was produced in the same manner as in Example 14 except that no ultrasonic wave was used when forming the zinc oxide layer.
[0127]
The result of relative comparison with Comparative Example 4 as described above is shown below.
[0128]
[Table 7]

[0129]
(Example 17 and Comparative Example 5)
The apparatus shown in FIG. 2 was used to form a total of 20 zinc oxide thin films by changing the zinc nitrate concentration within a certain range as shown in Table 8 to obtain Example 17. In addition, Comparative Example 5 was obtained in which a zinc oxide thin film was formed in the same manner as in Example 17 except that the film was formed without applying vibration to the vibrator.
[0130]
(Example 18 and Comparative Example 6)
As shown in Table 8, a total of 20 zinc oxide thin films were formed on a long stainless steel substrate by changing the zinc nitrate concentration within a certain range as shown in Table 8 using the apparatus shown in FIG. Comparative Example 6 was obtained by applying no vibration to the substrate in Example 18.
[0131]
(Example 19 and Comparative Examples 7, 8)
As shown in Table 8, a total of 20 zinc oxide thin films were formed on a long stainless steel substrate using the apparatus shown in FIG. However, as shown in FIG. 6b, a magnet was arranged in the solution at a position facing the magnetic rotating belt. A washing tank was provided after the zinc oxide thin film forming tank. In addition, an ultrasonic vibrator was used for vertical vibration. Comparative Example 7 was obtained by applying no vibration to the substrate in Example 19.
[0132]
In order to confirm the effect of the opposing magnet, a zinc oxide thin film was prepared in the same manner as in Example 19 except that the opposing magnet was not arranged, and Comparative Example 8 was used. In the evaluation described below, comparison was made with Comparative Example 6.
[0133]
(Example 20 and Comparative Example 9)
Example 20 A two-layer zinc oxide thin film was formed on a long stainless steel substrate by using the apparatus shown in FIG. 10 and changing the zinc nitrate concentration within a certain range as shown in Table 8. The apparatus shown in FIG. 10 includes a cleaning tank 1001, a first zinc oxide forming tank 1010, a second zinc oxide forming tank 1017, and a cleaning tank 1023. The cleaning tanks 1001 and 1023 have an ultrasonic vibrator in the solution and enable efficient cleaning. The solution components, current densities, and solution temperatures of the first and second zinc oxide forming tanks are different as shown in Table 8. Comparative Example 9 was the same as Example 20 except that no vibration was applied to the substrate.
[0134]
(Example 21 and Reference Example 1)
As shown in Table 8, using the apparatus of FIG. 4 and changing the temperature of the aqueous solution within a certain range, a zinc oxide thin film of 20 was formed on a long stainless steel substrate. However, the device is provided with a counter magnet. Among them, a sample formed at an aqueous solution temperature of 50 ° C. or lower is referred to as Reference Example 1.
[0135]
(Example 22 and Reference Example 2)
As shown in Table 8, a zinc oxide thin film of 20 was formed on a long stainless steel substrate by changing the zinc nitrate concentration within a certain range as shown in Table 8 using the apparatus of FIG. However, the device is provided with a counter magnet. Ag is formed on the stainless steel substrate in advance by a 2000 ° sputtering method. A washing tank was provided after the zinc oxide thin film forming tank. Among them, a sample formed with a zinc nitrate concentration of 0.001 mol / l or less is referred to as Reference Example 2.
[0136]
(Example 23 and Reference Examples 3 and 4)
As shown in Table 8, a zinc oxide thin film of 20 was formed on a long stainless steel substrate by changing the current density within a certain range as shown in Table 8 using the apparatus of FIG. However, the device is provided with a counter magnet. Ag is formed on the stainless steel substrate in advance by a 2000 ° sputtering method. A washing tank was provided after the zinc oxide thin film forming tank. Among them, the current density is 7 mA / dm²Reference Example 3, 12 A / dm²The sample formed in Example 2 is referred to as Reference Example 4.
[0137]
(Example 24 and Reference Examples 5 and 6)
Using the apparatus shown in FIG. 4 having a washing tank in front of the zinc oxide thin film forming tank, 20 zinc oxide thin films were formed on a long stainless steel substrate by changing the temperature of the washing layer in the range of 20 to 95 degrees. This was designated as Example 24. However, the device is provided with a counter magnet. Among these, a sample formed at a temperature of the washing tank of 23 ° C. in the zinc oxide forming tank is referred to as Reference Example 5, and a sample formed at 95 ° C. is referred to as Reference Example 6.
[0138]
(Example 25 and Comparative Example 10)
As shown in Table 8, a zinc oxide thin film of 20 was formed on a long stainless steel substrate by changing the temperature of the aqueous solution in the zinc oxide forming tank within a certain range as shown in Table 8 using the apparatus of FIG. However, the device is provided with a counter magnet. Ag is formed on the stainless steel substrate in advance by a 2000 ° sputtering method. In Example 25, no vibration was applied to the substrate.
[0139]
[Table 8]

[0140]
Evaluation of zinc oxide thin film
Surface observation was performed using an optical microscope to observe how many abnormal growths having a diameter of 10 μm or more existed in a 1 cm × 1 cm area at the center of the stainless steel substrate. (Observation of abnormal growth)
[0141]
In addition, by observation with an electron microscope (SEM), the crystal grain size (wurtzite type) of zinc oxide was measured within a range of 5 μm × 5 μm (observation of crystal grain size), and the variation of the grain size was examined. Variation observation).
[0142]
Also, 10 cuts are made in a grid pattern at intervals of 1 mm on a part of the substrate on which the respective zinc oxide thin films are formed, and 100 squares are formed. Adhere the cellophane adhesive tape, peel it off momentarily after it is sufficiently adhered, evaluate the adhesion between the conductive substrate and the zinc oxide thin film by calculating the area of the peeled part, and then put the substrate on the environment. It was put in a test box, kept at a temperature of 85 ° C. and a humidity of 85% for 100 hours, and the adhesion was evaluated again by the same method as the previous time. (Adhesion test)
[0143]
In each of the examples, almost no abnormal growth was observed, whereas in the comparative example and the reference example, abnormal growth was observed. Table 9 shows relative values of the crystal grain size, the variation in the grain size, and the adhesion of the corresponding comparative example and reference example based on the zinc oxide thin film of the example. The crystal grains of the examples have smaller variations and larger particle diameters than the comparative examples and the reference examples, and the zinc oxide thin film of the examples has excellent adhesion immediately after film formation and after the high-temperature and high-humidity deterioration test. I understand.
[0144]
[Table 9]

[0145]
Fabrication and evaluation of photovoltaic devices
After forming the zinc oxide thin films of Examples 17 to 25, pin junctions were formed on each of them by a CVD method, transparent electrodes and current collecting electrodes were formed, and a photovoltaic element as shown in FIG. 7 was produced.
[0146]
After dividing all the devices (20 devices) into 25 subcells, the shunt resistance was measured while applying a reverse bias voltage of -1.0 V in a dark place. The reference value of the shunt resistor is 4 × 10⁴Ωcm²Then, the yield was checked.
[0147]
Subsequently, the adhesion test, initial characteristics (photoconductive characteristics), and high temperature / high humidity reverse bias test (HHRB) deterioration tests of the photovoltaic element were performed using exactly the same method as the adhesion test of the zinc oxide thin film. .
[0148]
For the initial characteristics, the photoelectric conversion efficiency was measured using a solar simulator (AM1.5 100 mW / cm2, surface temperature 25 ° C). In the HHRB test, the sample was put in an environmental test box, kept at a temperature of 85 ° C., a humidity of 85%, and a reverse bias voltage of 0.8 V for 100 hours, and then the photoelectric conversion efficiency was examined.
[0149]
The yield, adhesion, initial photoelectric conversion efficiency, and photoelectric conversion after the HHRB test were performed on the photovoltaic devices using the zinc oxide thin films of Examples 17 to 25, based on the corresponding comparative examples and reference examples. Table 9 shows the relative evaluation of efficiency. It can be seen that the photovoltaic device using the zinc oxide thin film of the present invention has excellent characteristics.
[0150]
【The invention's effect】
According to the method for producing a zinc oxide thin film of the present invention, a vacuum process is unnecessary, and thus the production cost is greatly reduced. In addition, it is possible to produce a zinc oxide thin film having a high yield and excellent uniformity and adhesion. In particular, it suppresses abnormal growth of crystal grains of 20 microns or more.
[0151]
Further, the photovoltaic device having the zinc oxide thin film formed by the method of the present invention can significantly reduce the production cost, increase the yield, and improve the uniformity and environmental resistance.
[Brief description of the drawings]
FIG. 1 is a schematic view showing a zinc oxide producing apparatus using an ultrasonic transducer.
FIG. 2A is a schematic diagram showing a zinc oxide manufacturing apparatus using a vibrating body, and FIG. 2B is a schematic diagram showing a vibrating body power supply.
FIG. 3 is a schematic diagram showing an apparatus for continuously producing a zinc oxide thin film using an ultrasonic vibrator.
FIG. 4 is a schematic view showing a continuous manufacturing apparatus of a zinc oxide thin film using a vibrator.
FIG. 5 is a schematic diagram showing details of a magnetic rotating belt.
FIG. 6A is a schematic diagram illustrating magnetic lines of force near a substrate. b is a schematic diagram showing magnetic lines of force near the substrate when the opposing magnet is arranged.
FIG. 7 is a schematic view showing an example in which a zinc oxide thin film formed by the method of the present invention is applied to a photovoltaic element.
FIG. 8 is a chart showing the X-ray diffraction intensity of a zinc oxide layer formed at a low zinc nitrate concentration.
FIG. 9 is a chart showing the X-ray diffraction intensity of a zinc oxide layer formed at a high zinc nitrate concentration.
FIG. 10 is a schematic view showing an apparatus for continuously manufacturing two zinc oxide layers.
[Explanation of symbols]
101 Corrosion-resistant container
102 aqueous solution
103 conductive substrate
104 Counter electrode
105 power supply
106 Load resistance
107 injection port
108 suction port
109 Inhalation solution pipe
110 Injection solution pipe
111 Solution circulation pump
112 ultrasonic transducer
113 Ultrasonic oscillator
114 heater
115 thermometer
116 thermocouple
212 vibrator
213 vibrator power supply
302 Delivery roll
303 take-up roll
305 Hot water tank
308 Zinc oxide forming tank
313 Rinse tank
315 drying oven
405 vibrator
406 vibrator power supply
412 Delivery roll
413 Take-up roll
701 Support
702 metal layer
702 Zinc oxide layer
704 semiconductor layer
705 transparent conductive layer
706 current collecting electrode
1001 Cleaning tank 1
1010 First zinc oxide forming tank
1017 Second zinc oxide forming tank
1014, 1021 vibrator
1015, 1022 Oscillator power supply
1016 Opposite magnet
1023 Cleaning tank 2
1025 drying oven
1028 Magnetic rotating belt

Claims (67)

A current is passed between the conductive substrate immersed in an aqueous solution containing at least nitrate ions and zinc ions, and the electrode immersed in the solution, and the conductive substrate is vibrated at the same time, whereby a zinc oxide thin film is formed. Is formed on the conductive substrate. 2. The method according to claim 1, wherein the vibration is transmitted from an ultrasonic vibrator to the conductive substrate via the aqueous solution. 2. The method according to claim 1, wherein the vibration is transmitted by bringing a vibrator into contact with the conductive substrate. 3. The method according to claim 2, wherein a vibration frequency of the ultrasonic vibrator is in a range of 20 kHz to 100 kHz. 4. The method according to claim 3, wherein a vibration frequency of the vibrator is in a range of 1 Hz to 100 kHz. 4. The method according to claim 3, wherein an amplitude of the vibrator is in a range of 1 μm to 100 mm. The method according to claim 1, wherein a frequency slightly different from the frequency of the vibration is applied to the substrate. 2. The method according to claim 1, wherein the vibration is a vibration in a horizontal direction and a vertical direction of the conductive substrate. 2. The method according to claim 1, wherein the conductive substrate is a long substrate. 10. The zinc oxide according to claim 9, wherein a part of a rotating belt is brought into close contact with one surface of the conductive substrate, and a vibrator is brought into contact with the rotating belt while moving the rotating belt in the same direction as the substrate. Manufacturing method of thin film. The method for producing a zinc oxide thin film according to claim 10, wherein the rotating belt has magnetism. The method for producing a zinc oxide thin film according to claim 11, wherein a magnetic body is disposed at a position facing the rotating belt having magnetism. The zinc oxide thin film according to claim 11, wherein the rotating belt is a magnetic material dispersed in at least one selected from silicone rubber, fluorine rubber, urethane rubber, nitrile rubber, styrene rubber, and butyl rubber. Manufacturing method. The method for producing a zinc oxide thin film according to claim 10, wherein the rotating belt has a concave portion for inserting the conductive substrate. The method for producing a zinc oxide thin film according to claim 1, wherein the temperature of the aqueous solution is higher than 50C. 2. The method for producing a zinc oxide thin film according to claim 1, wherein the concentration of zinc nitrate in the aqueous solution is 0.05 mol / l or more and 1.0 mol / l or less. ^{2. The} method for producing a zinc oxide thin film according to claim 1, wherein the current density at which the current flows is 10 mA / dm ² or more and 10 A / dm ² or less. The method for producing a zinc oxide thin film according to claim 1, wherein the temperature of the aqueous solution is set within ± 5 ° C before immersing the conductive substrate in the aqueous solution. 2. The method according to claim 1, wherein the conductive substrate has a metal layer formed on a support. 2. The method for producing a zinc oxide thin film according to claim 1, wherein said zinc oxide thin film comprises at least a first zinc oxide thin film and a second zinc oxide thin film. The plurality of zinc oxide thin films are formed under different conditions at least one of a concentration of the aqueous solution, a current density, a temperature of the aqueous solution, a vibration frequency, an amplitude, and a vibration direction of the substrate. Item 21. The method for producing a zinc oxide thin film according to Item 20. The method for producing a zinc oxide thin film according to claim 1, wherein the aqueous solution contains a carbohydrate. A current is passed between the conductive substrate immersed in an aqueous solution containing at least nitrate ions and zinc ions, and the electrode immersed in the solution, and the conductive substrate is vibrated at the same time, whereby a zinc oxide thin film is formed. Forming a semiconductor layer on the conductive substrate, and forming a semiconductor layer. 24. The method for manufacturing a photovoltaic device according to claim 23, wherein the vibration transmits vibration by an ultrasonic vibrator to the conductive substrate via the aqueous solution. The method according to claim 23, wherein the vibration is transmitted by bringing a vibrator into contact with the conductive substrate. The method according to claim 24, wherein a vibration frequency of the ultrasonic vibrator is in a range of 20 kHz to 100 kHz. 26. The method according to claim 25, wherein a vibration frequency of the vibrator is in a range of 1 Hz to 100 kHz. 26. The method according to claim 25, wherein an amplitude of the vibrator is in a range of 1 [mu] m to 100 mm. The method according to claim 23, wherein a frequency slightly different from the frequency of the vibration is applied to the substrate. The method according to claim 23, wherein the vibration is a vibration in a horizontal direction and a vertical direction of the conductive substrate. 24. The method according to claim 23, wherein the conductive substrate is a long substrate. 32. The photovoltaic device according to claim 31, wherein a part of a rotating belt is brought into close contact with one surface of the conductive substrate, and a vibrator is brought into contact with the rotating belt while moving the rotating belt in the same direction as the substrate. A method for manufacturing a power element . 33. The method according to claim 32, wherein the rotating belt has magnetism. The method for manufacturing a photovoltaic element according to claim 33, wherein a magnetic body is disposed at a position facing the rotating belt having magnetism. The photovoltaic device according to claim 33, wherein the rotating belt is made by dispersing a magnetic material in at least one selected from silicone rubber, fluorine rubber, urethane rubber, nitrile rubber, styrene rubber, and butyl rubber. Device manufacturing method. 33. The method according to claim 32, wherein the rotating belt has a concave portion into which the conductive substrate is inserted. The method according to claim 23, wherein the temperature of the aqueous solution is higher than 50C. The method for manufacturing a photovoltaic device according to claim 23, wherein the concentration of zinc nitrate in the aqueous solution is 0.05 mol / l or more and 1.0 mol / l or less. 24. The method for manufacturing a photovoltaic device according to claim 23, wherein the current density to be applied is 10 mA / dm ² or more and 10 A / dm ² or less. 24. The method for manufacturing a photovoltaic device according to claim 23, wherein the temperature of the aqueous solution is set within ± 5 [deg.] C. before dipping the conductive substrate in the aqueous solution. 24. The method according to claim 23, wherein the conductive substrate is formed by forming a metal layer on a support. 24. The method according to claim 23, wherein the zinc oxide thin film comprises at least a first zinc oxide thin film and a second zinc oxide thin film. The plurality of zinc oxide thin films are formed under different conditions at least one of a concentration of the aqueous solution, a current density, a temperature of the aqueous solution, a vibration frequency, an amplitude, and a vibration direction of the substrate. Item 43. The method for producing a photovoltaic device according to Item 42. The method for manufacturing a photovoltaic device according to claim 23, wherein the aqueous solution contains a carbohydrate. 24. The method according to claim 23, wherein the semiconductor layer is a non-single-crystal silicon semiconductor. A current is passed between the conductive substrate immersed in an aqueous solution containing at least nitrate ions and zinc ions, and the electrode immersed in the solution, and the conductive substrate is vibrated at the same time, whereby a zinc oxide thin film is formed. Is formed on the conductive substrate. 47. The method according to claim 46, wherein the vibration is transmitted from the ultrasonic vibrator to the conductive substrate via the aqueous solution. 47. The method according to claim 46, wherein the vibration is transmitted by bringing a vibrator into contact with the conductive substrate. 48. The method according to claim 47, wherein a vibration frequency of the ultrasonic vibrator is in a range of 20 kHz to 100 kHz. 49. The method according to claim 48, wherein a vibration frequency of the vibrator is in a range of 1 Hz to 100 kHz. 49. The method according to claim 48, wherein the amplitude of the vibrator is in a range of 1 [mu] m to 100 mm. 47. The method according to claim 46, wherein a frequency slightly different from the frequency of the vibration is applied to the substrate. 47. The method according to claim 46, wherein the vibration is a horizontal and vertical vibration of the conductive substrate. 47. The method according to claim 46, wherein the conductive substrate is a long substrate. 55. The semiconductor device according to claim 54, wherein a part of a rotating belt is brought into close contact with one surface of the conductive substrate, and a vibrator is brought into contact with the rotating belt while moving the rotating belt in the same direction as the substrate. Substrate manufacturing method. The method according to claim 55, wherein the rotating belt has magnetism. 57. The method according to claim 56, wherein a magnetic body is disposed at a position facing the rotating belt having magnetism. 57. The semiconductor device substrate according to claim 56, wherein the rotating belt is made by dispersing a magnetic material in at least one selected from silicon rubber, fluorine rubber, urethane rubber, nitrile rubber, styrene rubber, and butyl rubber. Manufacturing method. The method according to claim 55, wherein the rotating belt has a recess for fitting the conductive substrate. 47. The method according to claim 46, wherein the temperature of the aqueous solution is higher than 50C. 47. The method according to claim 46, wherein the zinc nitrate concentration of the aqueous solution is 0.05 mol / l or more and 1.0 mol / l or less. The method for manufacturing a semiconductor element substrate according to claim 46, wherein the current density to be applied is 10 mA / dm ² or more and 10 A / dm ² or less. 47. The method for manufacturing a semiconductor element substrate according to claim 46, wherein the temperature of the aqueous solution is set within ± 5 [deg.] C. before immersing the conductive substrate in the aqueous solution. 47. The method according to claim 46, wherein the conductive substrate is formed by forming a metal layer on a support. 47. The method according to claim 46, wherein the zinc oxide thin film comprises at least a first zinc oxide thin film and a second zinc oxide thin film. The plurality of zinc oxide thin films are formed under different conditions at least one of a concentration of the aqueous solution, a current density, a temperature of the aqueous solution, a vibration frequency, an amplitude, and a vibration direction of the substrate. Item 65. The method for manufacturing a semiconductor element substrate according to Item 65. The method for manufacturing a semiconductor device substrate according to claim 46, wherein a carbohydrate is contained in the aqueous solution.

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