JP3554314B2 - Deposition film formation method - Google Patents

Description

【０１０９】
成膜容器８０１内の圧力が安定したところで、各導波管８１２、各マイクロ波アプリケータ８１１を介して、不図示のマイクロ波電源より周波数２．４５ＧＨｚのマイクロ波を成膜容器８０１内に導入した。この結果、成膜空間８０２の各小成膜空間８１０内でマイクロ波グロー放電が生起し、プラズマが発生した。次に、基板送り出し容器（不図示）から基板巻取り容器（不図示）の方向に向け、すなわち図１の図示矢印方向に、基板８０４の移動を開始した。このときの移動速度は、１００ｃｍ／ｍｉｎであった。１０分間にわたり、基板８０４を連続的に移動させつつ基板８０４の上に、ｉ型のａ−ＳｉＧｅ：Ｈからなる堆積膜の形成を行なった。堆積膜の形成が終了したら、基板８０３を冷却させて堆積膜形成装置８９１から取り出した。
【０１１０】
この実験例１で形成された堆積膜について膜厚分布を測定したところ、基板８０４の幅方向および長手方法に関し、膜厚のばらつきは５％以内に収まっていた。堆積膜の形成速度を算出したところ、平均９５Å／ｓｅｃであった。
【０１１１】
次に、基板８０４の、この実験例１でａ−ＳｉＧｅ：Ｈからなる堆積膜が形成された部分について、任意に６ヶ所を選んで切りだし、２次イオン質量分析計（ＳＩＭＳ）（ＣＡＭＥＣＡ社製、ｉｍｆ−３型）を用い、深さ方向の元素分布を測定した。その結果、図１０に示した深さ方向分布が得られ、図７（ｃ）に示したのと同様のバンドギャッププロファイルとなっていることがわかった。また、金属中水素分析計（堀場製作所製、ＥＭＧＡ−１１００型）を用いて、堆積膜中の全水素を定量したところ、１６±２原子％であった。なお、図１０において、横軸は時間で表されているが、２次イオン質量分析においては、経過時間と深さが比例するので、図１０の横軸を表面からの深さと考えて差し支えない。
【０１１２】
（実験例２）
上述の実験例１に用いた堆積膜形成装置８９１の７つの小成膜空間８１０を分離する壁８０９の開孔率を２５％として、原料ガスの相互拡散をある程度可能とした。その他の装置構成は実験例１と変えずに、実験例１と同様の条件にて基板８０４上に堆積膜を形成した。
【０１１３】
この実験例２で形成された堆積膜について、その膜厚の分布のばらつきを調べたところ、５％以内に収まっており、また、堆積膜の形成速度は平均８０Å／ｓｅｃであると算出された。次に、実験例８−１と同様に、この実験例８−２でａ−ＳｉＧｅ：Ｈからなる堆積膜が形成された部分について、任意に６ヶ所を選んで切りだし、深さ方向の元素分布を測定した。その結果、図１１に示した深さ方向分布が得られ、図８（ｃ）に示したのと同様のバンドギャッププロファイルとなっていることがわかった。隣接する小成膜空間で形成される堆積膜のバンドギャップのつながりは連続的となった。また、堆積膜中の全水素を定量したところ、１４±２原子％であった。
【０１１４】
（実験例３）
実験例２と同様にゲートガスを供給し、表２に示す条件で、基板８０４上にｉ型のａ−ＳｉＣ：Ｈからなる堆積膜を連続的に形成した。このとき、基板８０４の移動速度を９５ｃｍ／ｍｉｎとした。また、成膜容器８０１の内圧は、堆積膜の形成中、１２ｍＴｏｒｒに保持するようにした。
【０１１５】
【表２】

【０１１６】
堆積膜の形成が終了した後、この実験例３で形成された堆積膜について、その膜厚の分布のばらつきを調べたところ、５％以内に収まっており、また、堆積膜の形成速度は平均８０Å／ｓｅｃであると算出された。また、実験例１と同様に、この実験例３でａ−ＳｉＣ：Ｈからなる堆積膜が形成された部分について、任意に６ヶ所を選んで切りだし、深さ方向の元素分布を測定した。その結果、図１２に示した深さ方向分布が得られ、図８（ｂ）に示したのと同様のバンドギャッププロファイルとなっていることがわかった。また、堆積膜中の全水素を定量したところ、１４±２原子％であった。
【０１１７】
（実験例４）
実験例２と同様にして、表３に示す条件で、基板８０４上に、不純物としてＢを含むａ−Ｓｉ：Ｈからなる堆積膜を連続的に形成した。このとき、基板８０４の移動速度を９５ｃｍ／ｍｉｎとした。また、堆積膜の形成中、成膜容器８０１の内圧を５ｍＴｏｒｒに保持するようにした。
【０１１８】
【表３】

【０１１９】
堆積膜の形成が終了した後、この実験例４で形成された堆積膜について、その膜厚の分布のばらつきを調べたところ、５％以内に収まっており、また、堆積膜の形成速度は平均１１０Å／ｓｅｃであると算出された。実験例１と同様に、この実験例４でａ−Ｓｉ：Ｈからなる堆積膜が形成された部分について、任意に６ヶ所を選んで切りだし、深さ方向の元素分布を測定した。その結果、図１３に示した深さ方向分布が得られ、図９（ｂ）に示したのと同様のフェルミレベルプロファイルとなっていることがわかった。また、堆積膜中の全水素を定量したところ、１８±２原子％であった。
【０１２０】
（実験例５）
図６に示す連続堆積膜形成装置８５０を用い、図１７（ａ）に示した層構成のアモルファスシリコン系太陽電池を作製した。堆積膜形成装置８９１内の成膜空間８０２は７つの小成膜空間８１０に分割し、小成膜空間８１０を分離する壁は開口のない板とした。このアモルファスシリコン太陽電池は、単一のｐｉｎ接合を有し、ｉ型半導体層４０４におけるバンドギャッププロファイルは図８（ｃ）に示したものとなっている。
【０１２１】
まず、上述の実験例１で使用したのと同様の、ＳＵＳ４３０ＢＡからなる帯状の基板８０４を、不図示の連続スパッタ装置に装着し、Ａｇ電極（Ａｇ純度：９９．９９％）をターゲットとして、基板８０４の上に厚さ１０００ÅのＡｇ薄膜をスパッタ蒸着した、さらに、ＺｎＯ（ＺｎＯ純度：９９．９９９％）電極をターゲットとして厚さ１．２μｍのＺｎＯ薄膜をＡｇ薄膜の上にスパッタ蒸着し、基板８０４の上に下部電極９０２を形成した。
【０１２２】
次に、下部電極９０２の形成された基板８０４を、基板送り出し容器８５１に装着し、第１の不純物層形成用真空容器８５２、堆積膜形成装置８９１、第２の不純物層形成用真空容器８５３を介し、基板巻取り容器８５４まで通した。そして、基板８０４がたるまないようにその張力を調整し、実験例１と同様に、各不純物層形成用真空容器８５２，８５３、堆積膜形成装置８９１、基板送り出し容器８５１、基板巻取り容器８５４を５×１０^−６Ｔｏｒｒまで排気した。
【０１２３】
続いて、基板８０４を基板送り出し容器８５１から基板巻取り容器８５４に向けて連続的に移動させながら、この基板８０４の上に、第１の不純物層形成用真空容器８５２でｎ型半導体層９０３を、堆積膜形成装置８９１でｉ型半導体層９０４を、第２の不純物層形成用真空容器８５３でｐ型半導体層９０５を順次形成するようにした。ｎ型半導体層９０３とｐ型半導体層９０５の形成の条件は、表４に示すとおりであり、ｉ型半導体層９０４の形成条件は、実験例８−１においてｉ型ａ−ＳｉＧｅ：Ｈからなる堆積層を形成する場合と同じにした。各半導体層９０３〜９０５の形成は、各不純物層形成用真空容器８５２，８５３の内部と堆積膜形成装置８９１の内部でマイクロ波グロー放電を生起させ、グロー放電によるプラズマが安定したら、基板８０４を移動速度９５ｃｍ／ｍｉｎで移動させることにより行なった。なお、各不純物層形成用真空容器８５２，８５３内において、マイクロ波グロー放電が発生している領域の、基板８０４の移動方向の長さを表４の成膜領域の長さの欄に示した。
【０１２４】
【表４】

基板８０４の全長（２００ｍ）のすべてにわたって、各半導体層９０３〜９０５が形成されたら、基板８０４を冷却させてから連続堆積膜形成装置８５０から取り出し、ｐ型半導体層９０５の上に、さらに、透明電極９０６と集電電極９０７とを形成し、帯状の太陽電池を完成させた。
【０１２５】
次に、連続モジュール化装置（不図示）を用いて、作製した太陽電池を、大きさが３６ｃｍ×２０ｃｍの多数の太陽電池モジュールに加工した。作製した太陽電池モジュールについて、ＡＭ値が１．５でエネルギー密度１００ｍｗ／ｃｍ^２の疑似太陽光を用いて特性評価を行なったところ、光電変換効率で７．０％以上が得られ、また各太陽電池モジュール間の特性のばらつきも５％以内に収まった。また、作製した太陽電池モジュールの中から２個を抜き取り、連続２００回の繰り返し曲げ試験を行なったところ、試験後においても特性が劣化することはなく、堆積膜の剥離などの現象も認められたかった。上述のＡＭ値が１．５でエネルギー密度１００ｍｗ／ｃｍ^２の疑似太陽光に連続して５００時間照射したのちにおいても、光電変換効率の変動は、初期値に対して１０．０％以内に収まっていた。
【０１２６】
この太陽電池モジュールを接続することにより、出力２．５ｋＷの電力供給システムを作製することができた。
【０１２７】
（実験例６）
上述の実験例５に用いた連続堆積膜形成装置８５０において、堆積膜形成装置８９１の７つの小成膜空間８１０を分離する壁８０９の開孔率を２５％として、原料ガスの相互拡散をある程度可能とした。ｉ型半導体層９０４を実験例２と同様の条件で堆積させること以外は実験例５と同様にして太陽電池を作成し、太陽電池モジュールに加工した。なお、ｉ型半導体層９０４は図８（ｃ）に示すようなバンドギャッププロファイルとなっている。
【０１２８】
そして、作製した太陽電池モジュールについて、実験例５と同様の特性の評価を行なったところ、光電変換効率で８．０％以上が得られ、さらに各太陽電池モジュール間の特性のばらつきも５％以内に収まっていた。また、連続２００回の繰り返し曲げ試験後においても、特性の劣化は認められず、堆積膜の剥離も起こらなかった。さらに、連続５００時間の疑似太陽光照射ののちも、光電変換効率の変動は、初期値に対して８．５％以内に収まっていた。この太陽電池モジュールを使用することにより、出力５ｋＷの電力供給システムを作製することができた。
【０１２９】
（実験例７）
実験例５，６においては、ｉ型半導体層９０４としてａ−ＳｉＧｅ：Ｈ堆積膜を用いたが、ここではａ−ＳｉＧｅ：Ｈのかわりにａ−ＳｉＣ：Ｈを用いて太陽電池を作製し、太陽電池モジュールに加工した。このｉ型半導体層９０４を実験例３と同様の条件で堆積させる以外は実験例５と同様にした。なお、このｉ型半導体層９０４は、図８（ｂ）に示すようなバンドギャッププロファイルとなっている。
【０１３０】
そして、作製した太陽電池モジュールについて、実験例５と同様の特性の評価を行なったところ、光電変換効率で７．２％以上が得られ、さらに各太陽電池モジュール間の特性のばらつきも５％以内に収まっていた。また、連続２００回の繰り返し曲げ試験後においても、特性の劣化は認められず、堆積膜の剥離も起こらなかった。さらに、連続５００時間の疑似太陽光照射ののちも、光電変換効率の変動は、初期値に対して８．５％以内に収まっていた。この太陽電池モジュールを使用することにより、出力５ｋＷの電力供給システムを作製することができた。
【０１３１】
（実験例８）
実験例５，６においては、ｉ型半導体層９０４としてａ−ＳｉＧｅ：Ｈ堆積膜を用いたが、ここではａ−ＳｉＧｅ：Ｈのかわりにａ−Ｓｉ：Ｈを用いて太陽電池を作製し、太陽電池モジュールに加工した。このｉ型半導体層９０４を実験例４と同様の条件で堆積させる以外は実験例５と同様にした。なお、このｉ型半導体層９０４は、図９（ｂ）に示すようなフェルミレベルプロファイルとなっている。
【０１３２】
そして、作製した太陽電池モジュールについて、実験例５と同様の特性の評価を行なったところ、光電変換効率で８．４％以上が得られ、さらに各太陽電池モジュール間の特性のばらつきも５％以内に収まっていた。また、連続２００回の繰り返し曲げ試験後においても、特性の劣化は認められず、堆積膜の剥離も起こらなかった。さらに、連続５００時間の疑似太陽光照射ののちも、光電変換効率の変動は、初期値に対して８．５％以内に収まっていた。この太陽電池モジュールを使用することにより、出力２．５ｋＷの電力供給システムを作製することができた。
【０１３３】
（実験例９）
図１７（ｃ）に示す、２組のｐｉｎ接合を積層した構成のアモルファスシリコン系太陽電池を作製し、太陽電池モジュールに加工した。作製にあたっては、２組のｐｉｎ接合を形成できるように、図６に示す連続堆積膜形成装置８５０の第２の不純物層形成用真空容器８５３と基板巻取り容器８５４との間に、この連続堆積膜形成装置８５０の第１の不純物層形成用真空容器８５２、堆積膜形成装置８９１、第２の不純物層形成用真空容器８５３を順次直列に接続したものを挿入した構成の装置を用いた。
【０１３４】
帯状の基板８０４としては、実験例１で使用したものと同様のものを使用し、２組のｐｉｎ接合のうち、光の入射側から遠い方の第１のｐｉｎ接合９１１は、上述の実験例６でのｐｉｎ接合と同じ条件で形成し、光の入射側に近い方の第２のｐｉｎ接合９１２は、実験例８−８のｐｉｎ接合と同じ条件で形成した。第１および第２のｐｉｎ接合９１１，９１２の形成後、実験例６と同様の工程により、太陽電池モジュールとした。
【０１３５】
作製した太陽電池モジュールについて、実験例５と同様の特性の評価を行なったところ、光電変換効率で１１．０％以上が得られ、さらに各太陽電池モジュール間の特性のばらつきも５％以内に収まっていた。また、連続２００回の繰り返し曲げ試験後においても、特性の劣化は認められず、堆積膜の剥離も起こらなかった。さらに、連続５００時間の疑似太陽光の照射ののちの光電変換効率の変化率は７．５％以内に収まっていた。この太陽電池モジュールを使用することにより、出力２．５ｋＷの電力供給システムを作製することができた。
【０１３６】
（実験例１０）
図１７（ｃ）に示す、２組のｐｉｎ接合を積層した構成のアモルファスシリコン系太陽電池を作製し、太陽電池モジュールに加工した。作製にあたっては、第１のｐｉｎ接合９１１を上述の実験例８でのｐｉｎ接合と同じ条件で形成し、第２のｐｉｎ接合９１２をは実験例７のｐｉｎ接合と同じ条件で形成したこと以外は、実験例９と同様にした。
【０１３７】
作製した太陽電池モジュールについて、実験例５と同様の特性の評価を行なったところ、光電変換効率で１０．５％以上が得られ、さらに各太陽電池モジュール間の特性のばらつきも５％以内に収まっていた。また、連続２００回の繰り返し曲げ試験後においても、特性の劣化は認められず、堆積膜の剥離も起こらなかった。さらに、連続５００時間の疑似太陽光の照射ののちの光電変換効率の変化率は７．５％以内に収まっていた。この太陽電池モジュールを使用することにより、出力２．５ｋＷの電力供給システムを作製することができた。
【０１３８】
（実験例１１）
図１７（ｄ）に示す、３組のｐｉｎ接合を積層した構成のアモルファスシリコン系太陽電池を作製し、太陽電池モジュールに加工した。作製にあたっては、３組のｐｉｎ接合を形成できるように、図６に示す連続堆積膜形成装置８５０の第２の不純物層形成用真空容器８５３と基板巻取り容器８５４との間に、この連続堆積膜形成装置８５０の第１の不純物層形成用真空容器８５２、堆積膜形成装置８９１、第２の不純物層形成用真空容器８５３、第１の不純物層形成用真空容器８５２、堆積膜形成装置８９１、第２の不純物層形成用真空容器８５３を順次直列に接続したものを挿入した構成の装置を用いた。
【０１３９】
基板８０４としては、実験例１で使用したのと同様のものを使用し、３組のｐｉｎ接合のうち、光の入射側から遠い方の第１のｐｉｎ接合９１１は、上述の実験例６でのｐｉｎ接合と同じ条件で形成し、第２のｐｉｎ接合９１２は、実験例８のｐｉｎ接合と同じ条件で形成し、光の入射側に位置する第３のｐｉｎ接合９１３は、実験例７のｐｉｎ接合と同じ条件で形成した。各ｐｉｎ接合９１１〜９１３の形成後、実験例６と同様の工程により、太陽電池モジュールとした。
【０１４０】
作製した太陽電池モジュールについて、実験例５と同様の特性の評価を行なったところ、光電変換効率で１２．０％以上が得られ、さらに各太陽電池モジュール間の特性のばらつきも５％以内に収まっていた。また、連続２００回の繰り返し曲げ試験後においても、特性の劣化は認められず、堆積膜の剥離も起こらなかった。さらに、連続５００時間の疑似太陽光の照射ののちの光電変換効率の変化率は７％以内に収まっていた。この太陽電池モジュールを使用することにより、出力２．５ｋＷの電力供給システムを作製することができた。
【０１４１】
以上、本発明の実施例について、主として、アモルファスシリコン系太陽電池を作製する場合について説明してきたが、本発明は、アモルファスシリコン系太陽電池以外の、大面積あるいは長尺であることが要求される薄膜半導体素子を形成する場合にも、好適に用いられるものである。このような薄膜半導体素子として、例えば、液晶ディスプレイの画素を駆動するための薄膜トランジスタ（ＴＦＴ）や、密着型イメージセンサ用の光電変換素子、スイッチング素子などが挙げられる。これら薄膜半導体素子は画像入出力装置の主要な部品として使用されることが多く、本発明を実施することにより、これら薄膜半導体素子を高品質で均一性よく量産できることとなり、画像入出力装置がさらに広く普及することが期待されている。
【０１４２】
【発明の効果】
以上説明したように本発明は、移動成膜式マイクロ波プラズマＣＶＤ法において、壁で分離された複数の小成膜空間によって成膜空間を構成し、組成制御を行なうことにより、大面積の組成制御された機能性堆積膜を連続して再現性よく形成でき、また、大面積のプラズマの制御性、安定性が向上して、大面積にわたって一様なプラズマを生起することが可能となり、膜厚方向で組成の一様な堆積膜の形成を容易に行なえるようになるという効果がある。また、連続して移動する帯状の部材上に、任意のバンドギャッププロファイルを有する機能性堆積膜を連続して形成できるようになるという効果がある。
【図面の簡単な説明】
【図１】本発明の一実施例での堆積膜形成装置の構成を示す模式断面図である。
【図２】図１の堆積膜形成装置の成膜容器の構成を示す要部破断斜視図である。
【図３】図１とは別の構成の成膜容器を示す要部破断斜視図である。
【図４】本発明の一実施例の堆積膜形成方法の実施に使用される成膜容器を示す要部破断斜視図である。

【図５】さらに別の構成の成膜容器を示す要部破断斜視図である。
【図６】図１の装置を組み込んだ連続堆積膜形成装置の構成を示す図である。
【図７】（ａ）〜（ｃ）はｉ型半導体層のバンドギャッププロファイルを示す図である。
【図８】（ａ）〜（ｃ）はｉ型半導体層のバンドギャッププロファイルを示す図である。
【図９】（ａ），（ｂ）はｉ型半導体層のフェルミレベルプロファイルを示す図である。
【図１０】２次イオン質量分析の結果を示す特性図である。
【図１１】２次イオン質量分析の結果を示す特性図である。
【図１２】２次イオン質量分析の結果を示す特性図である。
【図１３】２次イオン質量分析の結果を示す特性図である。
【図１４】従来のマイクロ波プラズマＣＶＤ装置の構成を示す模式断面図である。
【図１５】従来の移動成膜式マイクロ波プラズマＣＶＤ装置の構成を示す模式断面図である。
【図１６】従来のマイクロ波プラズマＣＶＤ装置におけるバイアス電界のかかり方を示す模式図である。
【図１７】（ａ）〜（ｄ）はそれぞれ太陽電池の構成を示す概略断面図である。
【図１８】（ａ）〜（ｄ）はｉ型半導体層のバンドギャッププロファイルを示す図である。
【図１９】（ａ）〜（ｄ）はｉ型半導体層のフェルミレベルプロファイルを示す図である。
【符号の説明】
８００ 真空容器
８０１，８０１ａ，８０１ｂ，８０１ｃ 成膜容器
８０２ 成膜空間
８０３，８０５ ガスゲート
８０４ 基板
８０９ 壁
８１０ 小成膜空間
８１１ マイクロ波アプリケータ
８１２ 導波管
８１４ 原料ガス供給手段
８１５ 原料ガス供給管
８２０ バイアス電極
８５０ 連続堆積膜形成装置
８５１ 基板送り出し容器
８５２ 第１の不純物層形成用真空容器
８５３ 第２の不純物層形成用真空容器
８５４ 基板巻取り容器
８９１ 堆積膜形成装置[0001]
[Industrial applications]
The present invention relates to a method for forming a deposited film by a plasma CVD method, and more particularly, to a method for forming a deposited film in which various functional deposited films are continuously formed on a large-area substrate.
[0002]
[Prior art]
In recent years, demand for electric power has been rapidly increasing worldwide, and electric power production has become active. In accordance with this, environmental pollution and global warming problems associated with thermal power generation and nuclear power generation have become apparent. Under these circumstances, solar cell power generation using sunlight does not cause problems of environmental pollution or global warming, and there is little uneven distribution of solar resources. ing.
[0003]
By the way, in order to put solar cell power generation to practical use, it is required that a solar cell to be used has sufficiently high photoelectric conversion efficiency, excellent characteristics and stability, and is suitable for mass production. In addition, a large-area solar cell is required in view of the power generation scale. For this reason, an amorphous silicon formed by depositing a semiconductor thin film such as amorphous silicon on a relatively inexpensive substrate such as a glass or metal sheet by decomposing a readily available source gas such as silane by glow discharge. Silicon-based solar cells have been proposed. This amorphous silicon-based solar cell has attracted attention as being superior in mass productivity and low in cost as compared with a solar cell manufactured from single crystal silicon or the like, and various proposals have been made on a manufacturing method thereof.
[0004]
In photovoltaic power generation, unit cells of a photovoltaic cell are often connected in series or parallel to form a unit to obtain a desired current and voltage, and each unit module is required to be free from disconnection or short circuit. Further, it is required that variations in output voltage and output current between unit modules are small. Therefore, at least at the stage of manufacturing the unit module, uniformity of the characteristics of the semiconductor layer itself, which is the largest factor for determining the characteristics, is required. In addition, in order to simplify the module design and simplify the module assembling process, it is necessary to be able to form a semiconductor deposition film having excellent characteristics over a large area, thereby increasing the mass productivity of solar cells and reducing production costs. Will be greatly reduced.
[0005]
Semiconductor layers, which are important components of a solar cell, include semiconductor junctions such as a pn junction and a pin junction. These semiconductor junctions are formed by sequentially stacking semiconductor layers having different conductivity types or a semiconductor having a certain conductivity type. The layers are formed by ion implantation or thermal diffusion of dopants of different conductivity types. In the production of the above amorphous silicon solar cell, phosphine (PH₃) And diborane (B₂H₆) Is mixed with a silane gas or the like as a main source gas, and the mixed source gas is decomposed by glow discharge to obtain a semiconductor film having a desired conductivity type. It is known that a semiconductor junction can be easily obtained by sequentially laminating and forming these semiconductor films on a substrate. Therefore, when fabricating an amorphous silicon-based solar cell, it is common to provide an independent film formation chamber corresponding to each semiconductor layer and form each semiconductor layer in this film formation chamber.
[0006]
As a method for forming a deposited film by a plasma CVD method suitable for manufacturing such an amorphous silicon-based solar cell, US Pat. No. 4,400,409 discloses a method using a roll-to-roll method. I have. In this deposition film forming method, a plurality of glow discharge regions are provided, a long strip-shaped substrate is arranged along a path in which the substrate sequentially passes through each glow discharge region, and a semiconductor layer of a required conductivity type is provided. Is formed in each glow discharge region, and the belt-shaped substrate is continuously transported in the longitudinal direction. Thereby, a solar cell having a desired semiconductor junction can be continuously formed. In this deposition film forming method, in order to prevent the dopant gas used in each glow discharge region from diffusing and mixing into other glow discharge regions, each glow discharge region is separated by a slit-shaped separation passage called a gas gate. Are separated from each other, and furthermore, Ar, H₂The flow of scavenging gas is formed. With such a configuration, the method of forming a deposited film by the roll-to-roll method is suitable for manufacturing a semiconductor element such as a solar cell.
[0007]
On the other hand, as an attempt to improve the photoelectric conversion efficiency of an amorphous silicon solar cell, a-SiGe: H, a-SiGe: F, a-SiGe: H: F, a-SiC: H, a-SiC: F , A-SiC: H: F or the like, when an i-type (intrinsic) semiconductor layer is used as the i-type (intrinsic) semiconductor layer, the forbidden body width (band gap: E_g ^opt) Is continuously and appropriately changed in the film thickness direction, so that the open-circuit voltage (V_oc) And fill factor (FF) have been found to be greatly improved (20th IEEE PVSC, 1988, " et al.).
[0008]
Also, for semiconductor devices, electrophotographic photosensitive devices, image input line sensors, imaging devices and other various electronic elements, or optical elements, amorphous semiconductors such as hydrogen and / or halogen (fluorine, chlorine, etc.) Have been proposed, and some of them have been put to practical use. Such a deposited film is generally formed by a plasma CVD method. That is, it is formed by a method of decomposing a raw material gas by direct current, high frequency or microwave glow discharge and forming a thin film deposition film on a substrate made of a material such as glass, quartz, heat-resistant synthetic resin film, stainless steel, and aluminum. Have been.
[0009]
Here, the plasma CVD method will be described in more detail. The plasma CVD method is a method in which energy such as electromagnetic waves is applied to a specific substance and discharged to make the specific substance a chemically active radical, and furthermore, the radical is brought into contact with a substrate or a substrate to form a deposited film on the substrate. Refers to a method of forming The plasma CVD apparatus is an apparatus designed and manufactured for performing the plasma CVD method.
[0010]
Conventionally, a plasma CVD apparatus includes a film forming chamber which is a vacuum vessel having a film forming gas inlet and an exhaust port, gas supply means for supplying a film forming gas to the film forming chamber through the film forming gas inlet, Gas exhaust means for exhausting a film forming gas in the film forming chamber through a film forming gas exhaust port, energy supplying means for supplying energy such as electromagnetic waves for dissociating the film forming gas supplied to the film forming chamber, And a substrate transfer means for transferring a substrate for film formation into the film formation chamber.
[0011]
By the way, the plasma CVD method relies on the strong activity of radicals, and a desired deposited film is formed by appropriately selecting the radical generation density and the substrate temperature. In order to increase the density and to form a uniform deposited film over a large area, it is necessary to select plasma conditions for generating radicals uniformly and in a large amount over a large area.
[0012]
Conventionally, a high frequency (RF) of 13.56 MHz has been used as energy for dissociating a film forming gas. However, in recent years, by using a microwave of 2.45 GHz having a shorter wavelength, high-density plasma has been generated. Since plasma can be efficiently produced and the deposition film formation rate can be improved in the plasma CVD method, a plasma CVD method using microwaves has been attracting attention, and many plasma CVD apparatuses have been proposed for the purpose. I have. For example, various microwave plasma CVD apparatuses have been proposed on amorphous silicon (hereinafter, referred to as “a-Si”) as an element material used for various electronic elements and optical elements as described above on a desired substrate.
[0013]
For example, JP-B-58-49295, JP-B-59-43991, and JP-B-62-36240 disclose a technique in which a gas pipe is penetrated or brought into contact with a rectangular or coaxial waveguide to generate plasma. Have been. As this type of device, the one shown in FIG. 14 can be mentioned as a typical one. This apparatus generally comprises a vacuum system, an exhaust system, and a microwave introduction system.
[0014]
In FIG. 14, the vacuum system includes a reaction vessel 981 and a microwave-permeable tube 983 (for example, a quartz tube) having an inner diameter of about 40 mm and a window connected through a gas transport tube 982. The tube 983 (or window) is connected to the first gas introduction tube 982 and is orthogonal to the microwave waveguide 984 at the same time. A second gas introduction pipe (not shown) is connected to the inside of the reaction container 981, and a gas (for example, silane gas) introduced from the second gas introduction pipe is constituted by an exhaust pipe 985 and a pump 986. Exhaust system. In this device, gas (oxygen gas or nitrogen gas) introduced from the first gas introduction pipe 982 is dissociated by microwave power supplied from a microwave power supply 987. When discharging with microwave power, the sliding short-circuit plate (plunger) 988 can be moved to match the microwave input impedance. The radicals in the plasma thus generated react with silane gas or the like introduced through the second gas introduction pipe, and SiO 2 is deposited on the substrate 989.₂Thus, a film of SiN or SiN is formed. Further, with this apparatus, a photoconductive material or a photovoltaic material can be formed at a high deposition rate of several tens of Å / sec.
[0015]
U.S. Pat. No. 4,517,223 and U.S. Pat. No. 4,545,518 disclose a method of depositing a thin film on a small-area substrate in a microwave glow discharge plasma under a low pressure. In this method, since the process is performed under a low pressure, not only the high-quality deposited film can be obtained by preventing the polymerization of the active species which causes the deterioration of the film characteristics, but also the powder of polysilane or the like in the plasma can be obtained. It is said that generation can be suppressed and the deposition rate can be dramatically improved. On the other hand, US Pat. No. 4,729,341 discloses a low-pressure microwave plasma for depositing and forming a photoconductive semiconductor thin film on a large-area cylindrical substrate by a high-power process using a pair of radiation-type waveguide applicators. A CVD method and apparatus are disclosed.
[0016]
In order to form a uniform deposition on a large area without using a microwave plasma CVD method, a uniform plasma must be generated and maintained by controlling the microwave power and the spatial density (concentration) distribution of the source gas. Must. Further, in the roll-to-roll system, that is, the substrate moving film forming system, in order to have a composition distribution in the thickness direction of the deposited film, it is necessary to control the plasma to have a spatial composition distribution.
[0017]
In order to generate and maintain such plasma, a plurality of microwave introduction means are provided in a reaction vessel (deposited film forming vessel), and the energy distribution of microwaves radiated from the microwave introduction means to the reaction vessel is controlled. Alternatively, the concentration distribution of the raw material gas in the reaction vessel is adjusted by providing a plurality of gas supply means.
[0018]
In order to maintain a homogeneous plasma over a long period of time, it is necessary to keep the microwave energy supplied to the reaction vessel constant. As a method of keeping the microwave energy constant, the traveling wave energy and the reflected wave energy of the microwave are respectively monitored, and the effective supply energy is obtained by subtracting the reflected wave energy from the traveling wave energy. There is a method of performing control so that is constant. However, since the monitoring of the traveling wave and the reflected wave is performed on the waveguide on the way from the microwave power supply to the reaction vessel, there is a problem that the actual energy supplied to the reaction vessel cannot be accurately obtained. On the other hand, there is a method in which plasma parameters in a reaction vessel are monitored by a probe, and microwave energy from a microwave power supply is controlled so that each parameter value becomes constant. However, in a large-area microwave plasma CVD apparatus having a plurality of microwave introduction means, it is difficult to monitor plasma over a large area and maintain uniform plasma due to mutual interference of microwaves.
[0019]
There have been proposed various moving film forming type microwave plasma CVD devices that combine the above-described known plasma CVD method and the substrate moving film forming method of forming a film while moving a substrate. Is as shown in FIG.
[0020]
In FIG. 15, three film-forming containers 951 to 953 connected in series via slit-shaped openings 954 and 955 each have a vacuum-tight structure. Each of the slit-shaped openings 954 and 955 is provided with a gate gas introducing means (not shown) for injecting an inert gas in order to suppress mixing of source gases between the film forming vessels 951 to 953. Specific examples of the slit-shaped openings 954 and 955 include a gas gate described in U.S. Patent Application No. 204,493. A long strip-shaped substrate 956 is arranged so as to penetrate these film-forming containers 951 to 953 and the slit-shaped openings 954 and 955. The substrate 956 can be continuously conveyed in the longitudinal direction, is unreeled from an unwinding roller 957 provided in the unwinding chamber 974, and is wound by a winding roller 958 provided in the winding chamber 975. It has become. The feeding chamber 974 and the winding chamber 975 communicate with the exhaust devices 977 and 977, respectively.
[0021]
Each of the film forming containers 951 to 953 communicates with exhaust devices 971 to 973 through exhaust ports 968 to 970, respectively. Further, each of the film forming containers 951 to 953 is provided with lamp heaters 959 to 961 for heating the substrate 956 and dielectric windows 965 to 967. Each of the dielectric windows 965 to 967 is formed of a material capable of efficiently transmitting microwave power into the film forming container and maintaining vacuum tightness, such as quartz glass and alumina ceramics. A waveguide (not shown), which is a microwave transmission path and is mainly made of metal, is connected to the outside of the film forming container of the dielectric windows 965 to 967, and the microwave is transmitted through a matching isolator (not shown). It is connected to a power supply (not shown). Further, source gas supply pipes 962 and 963 are provided in the two film deposition vessels 951 and 953 on the left and right in the figure, and a bias for applying a bias voltage which also serves as the source gas supply pipe is provided in the film deposition vessel 952 at the center in the figure. A voltage application rod 964 is provided.
[0022]
Formation of a deposited film by such a conventional microwave plasma CVD apparatus is performed as follows. That is, the insides of the film forming containers 951 to 953 are evacuated by the exhaust devices 971 to 973, respectively, and adjusted to a desired pressure. Next, the lamp heaters 959 to 961 are energized to heat and maintain the temperature of the substrate 956 at a temperature suitable for film deposition. At this time, the substrate 956 is being conveyed at a suitable speed from the feeding roller 957 to the winding roller 958. In the case of forming a photovoltaic element having a pin structure, for example, via a bias voltage applying rod 964 also serving as the source gas supply pipes 962 and 963 and the source gas supply pipe, silane (SiH₄) Gas and diborane (B₂H₆Silane gas such as silane gas, phosphine (PH)₃A) A gas mixture or the like is introduced into the film forming containers 951 to 953, and an appropriate DC bias voltage is applied by a bias applying rod 964. At the same time, a microwave power supply (not shown) is operated to generate microwaves having a frequency of 500 MHz or more, preferably 2.45 GHz, and the microwaves are passed through waveguides (not shown) to dielectric windows 965 to 967. Through the film forming containers 951 to 953 respectively. Thus, the source gases in the film forming containers 951 to 953 are excited by microwave energy and dissociated, and a p-type semiconductor layer, an i-type semiconductor layer, and an n-type semiconductor layer are sequentially formed on the surface of the substrate 956. Will be.
[0023]
[Problems to be solved by the invention]
However, in the above-described conventional method for forming a deposited film, it is difficult and costly to form a large number of deposited films continuously and stably on a large-area substrate such as an electrophotographic photosensitive member or a solar cell. It was. There is also a problem that it is difficult to uniformly form a large-area deposited film whose composition continuously changes in the thickness direction.
[0024]
That is, as described above, the control method for keeping the microwave energy constant is insufficient, and it is difficult to uniformly form a large amount of deposited film.
[0025]
When a member having a large area such that one side exceeds 300 mm is prepared, the capacity of the reaction vessel (film formation vessel) is approximately 10 liters or more. In this reaction vessel, silane or germane (GeH₄) And the like, when the pressure is set to 5 to 20 mTorr to generate glow discharge, the required microwave power is about 2 to 4 kW. In order to facilitate the generation of glow discharge, it has been proposed to provide a mechanism for generating an arc discharge for ignition in a reaction vessel (JP-A-59-158323). However, in this case, a new problem arises in that the arc discharge electrode is sputtered and mixed as an impurity into the deposited film, thereby deteriorating the electrical characteristics of the deposited film. As another method for facilitating the generation of glow discharge, a method of causing electron cyclotron resonance (ECR) by interaction of a magnetic field and a microwave is generally known (Japanese Patent Publication No. 63-67332). In order to form a uniform magnetic field over a large area with a diameter of 150 mm or more, enormous equipment costs were required, and the cost was extremely insufficient.
[0026]
Further, in the above-described roll-to-roll deposition film formation method, since the deposition film is formed while continuously moving the belt-like substrate, the deposition is performed while the substrate passes through the glow discharge region. Therefore, the thickness of the deposited film can be controlled relatively easily by the deposition speed and the passing speed of the glow discharge region. On the other hand, in order to provide a composition distribution in the film thickness direction, since the substrate is continuously moving, it is necessary to provide a film forming atmosphere in the glow discharge region with a distribution in the moving direction of the substrate. However, it is difficult to provide such a distribution with good reproducibility for a film forming atmosphere such as the composition and pressure of the source gas or the energy density of glow discharge. Even in a deposited film forming method in which a substrate is fixed, no distribution is given to the film forming atmosphere because the uniformity of the deposited film is impaired.
[0027]
When forming an amorphous deposition film such as a-Si, it is known that the characteristics of the deposition film may be improved by applying an electric field by a bias voltage to the substrate in addition to the microwave power. However, an optimum bias application method in a moving film formation type microwave plasma CVD apparatus has not been found. FIG. 16 is a schematic diagram showing how a bias electric field is applied in a conventional device. Here, a bias applying rod 942 extending parallel to the surface of the band-shaped substrate 941 and perpendicular to the longitudinal direction of the substrate 941 is provided substantially at the center of the film forming container 943. Arrows in the figure indicate electric fields. As is clear from this figure, the magnitude of the electric field applied to the substrate 941 changes between the vicinity of the end of the film formation container 943 (section L in the drawing) and other places. The applied electric field will change. In particular, the DC bias is extremely applied to the substrate immediately before entering the film forming container 943 and immediately before exiting the film forming container 943 (when the substrate is in the illustrated section L), as compared with the substrate substantially at the center of the film forming container 941. Will be weakened. Thus, the characteristics of the deposited film formed near the end of the film forming container 941 are inferior to the characteristics of the deposited film formed in the central portion of the film forming container 941. For example, when forming an i-layer while applying a bias voltage to form a pin-type photovoltaic element, the characteristics are poor at the interface between the p-layer and the i-layer or at the interface between the i-layer and the n-layer. An i-layer will be deposited, and the characteristics as a photovoltaic element will be greatly reduced.
[0028]
In the case of plasma generated by microwaves, it is possible to control the plasma potential by applying a bias voltage to the plasma. At this time, there are various problems to be solved.
[0029]
Specifically, by applying a bias voltage to the microwave plasma, a deposited film of a desired quality can be formed over a relatively large area, but the bias current due to the application of the bias voltage causes And the stability of the bias current greatly affects the characteristics of the deposited film. For example, in a roll-to-roll deposition film formation method using microwave plasma, while continuously moving a belt-like substrate constituting one surface of a film formation container, a deposition film having a desired film thickness is formed on this substrate. On the other hand, a large amount of deposited film adheres to the inner wall of the fixed film forming container while being formed on the upper side. As a result, for example, when a bias voltage is applied by a bias application rod or the like, the state of the wall into which the bias current flows, that is, the conductivity is constant on the moving substrate, but is large on the wall constituting the film forming container. It changes. In this state, if the microwave energy and the bias voltage supplied to the film forming container are constant, the bias current value becomes apparently constant, but the bias current flowing into the substrate actually increases, and the film forming container The bias current flowing into the wall of the device is reduced. Therefore, the film quality of the film deposited on the substrate greatly changes with the change of the bias current, and it is difficult to continuously form a deposited film having constant characteristics with good reproducibility.
[0030]
In the above-described roll-to-roll deposition film forming method, a slit-shaped hole is provided in a film-forming container surrounding the plasma region in order to allow the band-shaped substrate to pass through the microwave plasma region. Through. For this reason, a gap is formed between the substrate and the film formation container at the hole, and microwave plasma or raw material gas itself easily leaks through the gap, and it is difficult to stably maintain the film forming atmosphere.
[0031]
An object of the present invention is to provide a method for forming a deposited film capable of forming a deposited film of high quality continuously on a large-area substrate with no variation in characteristics and stably with good reproducibility. In addition to a deposited film whose composition does not change in the film thickness direction, a deposited film having a composition distribution in the film thickness direction can be formed stably with good reproducibility without variation in characteristics. Is the purpose.
[0032]
[Means for Solving the Problems]
In the method of forming a deposited film of the present invention, a raw material gas for forming a deposited film is introduced into a columnar deposition space in which the substrate is one surface of a side wall while continuously moving the belt-shaped substrate in the longitudinal direction, and at the same time, In the method for forming a deposited film, microwave energy is introduced into the deposition space to generate microwave plasma in the deposition space, and a deposited film is formed on a surface of the substrate on the deposition space side. Membrane space, Inter-diffusion of source gas for deposition film formationThe plurality of small deposition spaces are separated by walls, and the composition is controlled to form the deposited film.
[0033]
[Action]
In the present invention, the film formation space in which the deposited film is formed on the substrate is divided into a plurality of small film formation spaces. Plasma can be generated by introducing wave energy. Therefore, favorable film forming conditions for forming deposited films having different compositions can be set for each small film forming space. If the deposition conditions in the small deposition space are set so that the composition of the deposited film gradually changes with respect to the moving direction of the belt-shaped substrate, the substrate moves continuously and the deposited film is also formed and grown continuously. As a result, the composition of the deposited film formed on the substrate changes stepwise in the film thickness direction.
[0034]
When an appropriate opening is provided on the wall separating the adjacent small film formation spaces so as to allow the permeation of the source gas, the material gas and plasma mutually diffuse between the adjacent small film formation spaces, and the moving strip-shaped substrate is moved. The composition of the deposited film formed thereon is such that the above-mentioned step-shaped change portions are smoothly connected. If the opening ratio of the opening provided in the wall is too large, mutual diffusion becomes severe and it becomes impossible to maintain good film forming conditions in each small film forming space. In addition, when the aperture ratio is reduced, mutual diffusion is reduced, and the composition change in the film thickness direction shows a clearer step change. When it is necessary to make the composition change smooth, it is also effective to increase the number of small film formation spaces obtained by dividing the film formation space.
[0035]
These small film formation spaces are provided with source gas discharge means for introducing a source gas for forming a deposited film. The source gas release means is provided with a gas release hole for releasing the source gas into the small film formation space. The shape of the gas discharge holes may be any shape such as a slit shape, a circular shape, an elliptical shape, a sponge shape, a mesh shape, and the number of the gas discharge holes may be any number. It is necessary to devise the source gas so that the formation speed and film quality of the deposited film are uniform in the width direction and the movement direction of the substrate in the film space.
[0036]
Further, in these small film formation spaces, a source gas exhaust means for exhausting the source gas is provided. The source gas exhaust means is provided with a gas exhaust hole for sucking the source gas. The shape of this gas exhaust hole may be any shape such as a slit shape, a circular shape, an elliptical shape, a sponge shape, a mesh shape, and the number of gas exhaust holes may be any number. It must be devised so that the gas is exhausted uniformly in the direction. The opening area of the gas exhaust hole should be small so that the microwave energy does not leak from the gas exhaust hole to the outside. The width of the opening is preferably １ ／ or less, more preferably 1/20 or less of the wavelength of the microwave.
[0037]
Further, each of the small film formation spaces is provided with a microwave introducing means for introducing microwave energy into the small film formation space. It is preferable that the microwave energy is radiated and propagated in a direction parallel to the band-shaped substrate and in a lateral width direction of the substrate from a surface of the columnar small deposition space which is perpendicular to the substrate surface. This microwave energy is transmitted from the microwave power source to the microwave introducing means via the waveguide, and is transmitted through the microwave transmitting member (dielectric window) provided at the tip of the microwave introducing means, and is reduced. Radiated and propagated in the film formation space. The microwave permeable member is for hermetically separating the inside of the waveguide under atmospheric pressure from the film formation space under reduced pressure.
[0038]
A heater is provided in the vacuum vessel in which the film-forming space is formed so as to face the film-forming space across the substrate in order to adjust the temperature of the band-shaped substrate passing through the film-forming space. It is preferable that the amount of heat generated by the heater can be independently adjusted for each of the small film formation spaces so that the temperature of the substrate can be set independently for each of the small film formation spaces. In general, a film forming container that substantially defines a film forming space is provided in a vacuum container. Discharge energy or plasma is supplied from a slit-shaped opening through which a substrate passes through the film forming container. In order to prevent leakage, the opening area in these portions should be as small as possible. The narrow width of the opening is preferably １ ／ or less, more preferably 1/20 or less of the wavelength of the microwave. Further, an electromagnetic shielding material may be used.
[0039]
<< Example of deposited film formed by the method of the present invention >>
The present invention has been described above. Here, an example of a deposited film formed by the deposited film forming method of the present invention will be described.
[0040]
Representative examples of such a deposited film include a group IV semiconductor thin film such as Si, Ge, and C and a film containing a valence electron controlling element. In addition, group IV alloy semiconductor thin films such as SiGe, SiC, GeC, SiSn, GeSn, and SnC; group III-V compound semiconductor thin films such as GaAs, GaP, GaSb, InP, and InAs; ZnSe, ZnS, ZnTe, CdS, and CdSe II-VI compound semiconductor thin films such as CdTe and CdTe, CuAlS₂, CuAlSe₂, CuAlTe₂, CuInS₂, CuInSe₂, CuInTe₂, CuGaS₂, CuGaSe₂, CuGaTe, AgInSe₂, AgInTe₂I-III-VI compound semiconductor thin film such as ZnSiP₂, ZnGeAs₂, CdSiAs₂, CdSnP₂II-IV-V compound semiconductor thin film such as Cu₂O, TiO₂, In₂O₃, SnO₂, ZnO, CdO, Bi₂O₃, CdSnO₄Oxide semiconductor thin films, and those containing a valence electron controlling element for controlling valence electrons in these semiconductor thin films. Of course, these thin film semiconductors may be any of amorphous, polycrystalline, microcrystalline, and single crystalline. Further, as an example of a deposited film in which the composition is changed in the film thickness direction, the content of hydrogen and / or fluorine is changed in an amorphous semiconductor such as a-Si: H or a-Si: H: F. Things.
[0041]
The raw material gas for forming the deposited film used for forming the deposited film is introduced into the film formation space by appropriately adjusting the mixing ratio thereof according to the desired composition of the deposited film.
[0042]
The compound containing a Group IV element of the periodic table, which is preferably used for forming the above-described Group IV semiconductor or Group IV alloy semiconductor thin film, includes a Si atom, a Ge atom, a C atom, a Sn atom, and a Pb atom. A compound, specifically, SiH₄, Si₂H₆, Si₃H₈, Si₃H₆, Si₄H₈, Si₅H₁₀Silane compounds such as SiF₄, (SiF₂)₅, (SiF₂)₆, (SiF₂)₄, Si₂F₆, Si₃F₈, SiHF₃, SiH₂F₂, Si₂H₂F₄, Si₂H₃F₃, SiCl₄, (SiCl₂)₅, SiBr₄, (SiBr₂)₅, Si₂Cl₆, Si₂Br₆, SiHCl₃, SiHBr₃, SiHI₃, Si₂Cl₃F₃Halogenated silane compounds such as GeH₄, Ge₂H₆Such as germane compounds, GeF₄, (GeF₂)₅, (GeF₂)₆, (GeF₂)₄, Ge₂F₆, Ge₃F₈, GeHF₃, GeH₂F₂, Ge₂H₂F₄, Ge₂H₃F₃, GeCl₄, (GeCl₂)₅, GeBr₄, (GeBr₂)₅, Ge₂Cl₆, Ge₂Br₆, GeHCl₃, GeHBr₃, GeHI₃, Ge₂Cl₃F₃Such as halogenated germanium compounds, CH₄, C₂H₆, C₃H₈Methane column hydrocarbons such as C₂H₄, C₃H₆Ethylene chain hydrocarbons such as C₆H₆Cyclic hydrocarbons such as CF₄, (CF₂)₅, (CF₂)₆, (CF₂)₄, C₂F₆, C₃F₈, CHF₃, CH₂F₂, CCl₄, (CCl₂)₅, CBr₄, (CBr₂)₅, C₂Cl₆, C₂Br₆, CHCl₃, CHI₃, C₂Cl₃F₃Halogenated carbon compounds such as SnH₄, Sn (CH₃)₄Tin compounds such as Pb (CH₃)₄, Pb (C₂H₅)₆And the like. These compounds may be used alone or in combination of two or more.
[0043]
The valence electron controlling agent used for controlling the valence electrons of the above-mentioned group IV semiconductor or group IV alloy semiconductor includes, as a p-type impurity, a group III element of the periodic table, for example, B, Al, Ga, Preferable examples include In and Tl, and preferable examples of the n-type impurity include elements belonging to Group V of the periodic table, such as N, P, As, Sb, and Bi. Particularly, B, Ga, P, Sb, etc. are optimal. The amount of the impurity to be doped is appropriately determined according to the required electrical and optical characteristics. As such a raw material for impurity introduction, a substance that is in a gas state at normal temperature and normal pressure or that can be easily gasified at least under film forming conditions is employed. As a starting material for introducing such impurities, specifically, PH₃, P₂H₄, PF₃, PF₅, PCl₃, AsH₃, AsF₃, AsF₅, AsCl₃, SbH₃, SbF₅, BiH₃, BF₃, BCl₃, BBr₃, B₂H₆, B₄H₁₀, B₅H₉, B₅H₁₁, B₆H₁₀, B₆H₁₂, AlCl₃And the like. The compounds containing the above impurity elements may be used alone or in combination of two or more.
[0044]
As the compound containing a Group II element of the periodic table, which is used for forming the above-described II-VI compound semiconductor, specifically, Zn (CH₃)₂, Zn (C₂H₅)₂, Zn (OCH₃)₂, Zn (OC₂H₅)₂, Cd (CH₃)₂, Cd (C₂H₅)₂, Cd (C₃H₇)₂, Cd (C₄H₉)₂, Hg (CH₃)₂, Hg (C₂H₅)₂, Hg (C₆H₅)₂, Hg [C≡ (C₆H₅)]₂And the like. Compounds containing Group VI elements of the periodic table include, specifically, NO, N₂O, CO₂, CO, H₂S, SCl₂, S₂Cl₂, SOCl₂, SeH₂, SeCl₂, Se₂Br₂, Se (CH₃)₂, Se (C₂H₅)₂, TeH₂, Te (CH₃)₂, Te (C₂H₅)₂And the like. Of course, these raw materials can be used alone or in combination of two or more.
[0045]
As a valence electron controlling agent used for controlling the valence electrons of the II-VI group compound semiconductor, a compound containing an element of the periodic table I, III, IV or V can be mentioned as an effective one. Specifically, the compound containing a group I element is LiC₃H₇, Li (sec-C₄H₉), Li₂S, Li₃N and the like are preferred. Compounds containing a group III element include BX₃, B₂H₆, B₄H₁₀, B₅H₉, B₅H₁₁, B₆H₁₀, B (CH₃)₃, B (C₂H₅)₃, B₆H₁₂, AlX₃, Al (CH₃)₂Cl, Al (CH₃)₃, Al (OCH₃)₃, Al (CH₃) Cl₂, Al (C₂H₅)₃, Al (OC₂H₅)₃, Al (CH₃)₃Cl₃, Al (i-C₄H₉)₃, Al (i-C₃H₇)₃, Al (C₃H₇)₃, Al (OC₄H₉)₃, GaX₃, Ga (OCH₃)₃, Ga (OC₂H₅)₃, Ga (OC₃H₇)₃, Ga (OC₄H₉)₃, Ga (CH₃)₃, Ga₂H₆, GaH (C₂H₅)₂, Ga (OC₂H₅) (C₂H₅)₂, In (CH₃)₃, In (C₃H₇)₃, In (C₄H₉)₃And a compound containing a group V element is NH.₃, HN₃, N₂H₅N₃, N₂H₄, NH₄N₃, PX₃, P (OCH₃)₃, P (OC₂H₅)₃, P (OC₃H₇)₃, P (OC₄H₉)₃, P (CH₃)₃, P (C₂H₅)₃, P (C₃H₇)₃, P (C₄H₉)₃, P (SCN)₃, P₂H₄, PH₃, AsH₃, AsX₃, As (OCH₃)₃, As (OC₂H₅)₃, As (OC₃H₇)₃, As (OC₄H₉)₃, As (CH₃)₃, As (C₂H₅)₃, As (C₆H₅)₃, SbX₃, Sb (OCH₃)₃, Sb (OC₂H₅)₃, Sb (OC₃H₇)₃, Sb (OC₄H₉)₃, Sb (CH₃)₃, Sb (C₃H₇)₃, Sb (C₄H₉)₃And the like. X represents a halogen element (F, Cl, Br, I). Of course, these raw materials may be used alone or in combination of two or more. Further, as the compound containing a group IV element, the compounds described above can be used.
[0046]
As the compound containing a Group III element of the periodic table used for forming the above-described Group III-V compound semiconductor, a compound containing a Group III element used for controlling valence electrons of a Group II-VI compound semiconductor is used. As the compound containing a Group V element of the periodic table, the compound containing a Group V element used for controlling a valence electron of a II-VI compound semiconductor can be used as it is. The same can be used as it is. Of course, these raw materials may be used alone or in combination of two or more.
[0047]
As the valence electron controlling agent used for controlling the valence electrons of the group III-V compound semiconductor, compounds containing elements of groups II, IV and VI of the periodic table can be cited as effective ones. As such a compound, a compound containing the above-described group II element, a compound containing the above-described group IV element, and a compound containing the above-described group VI element can be used.
[0048]
Each of the above-mentioned source gases is a rare gas such as He, Ne, Ar, Kr, Xe, or H.₂, HF, HCl or the like, and may be introduced into the deposited film forming apparatus. Further, the rare gas or the diluent gas may be introduced into the deposition film forming apparatus independently of the source gas.
[0049]
Further, when forming a deposited film of these semiconductor thin films, N is used as a characteristic improving gas for changing the band gap width of the deposited film.₂, NH₃Molecules containing a nitrogen atom, such as O₂, NO₂Molecules containing oxygen atoms, such as CH₄, C₂H₆, C₂H₄, C₂H₂, C₃H₈Such as hydrocarbons, SiF₄, Si₂F₆, GeF₄And a mixed gas thereof.
[0050]
In the present invention, it is possible to form a composition distribution controlled in the thickness direction of the deposited film. However, by controlling the composition in the semiconductor thin film described above, it is possible to control the forbidden band width, the valence electron, and the refractive index. Control, crystal control, and the like are performed. By forming a deposited film whose composition is controlled in the thickness direction on a belt-shaped substrate, a large-area thin-film semiconductor device having excellent electrical, optical, and mechanical characteristics can be manufactured. That is, by changing the forbidden band width and / or the valence electron density in the film thickness direction of the deposited semiconductor layer, the mobility of carriers is increased, and the recombination of carriers at the semiconductor interface is prevented, so that electrical connection is prevented. The characteristics are improved. Further, by continuously changing the refractive index, an optically non-reflective surface can be obtained, and the light transmittance into the semiconductor layer can be improved. Further, by changing the hydrogen content and the like, a structural change can be given, the internal stress is reduced, and a deposited film having high adhesion to the substrate can be formed.
[0051]
The substrate on which the deposited film is formed in the present invention is not particularly limited in its material, but may be, for example, Al, Cr, Mo, Au, In, Nb, Te, V, Ti, Pt, Pd, or the like. Metals, alloys thereof, stainless steel, synthetic resins such as polycarbonates whose surfaces are subjected to conductive treatment, glass, ceramics, paper and the like are usually used.
[0052]
《Configuration example of solar cell》
An example of a semiconductor device suitably manufactured using the deposited film forming method and the deposited film forming apparatus of the present invention is a photovoltaic element, that is, a solar cell. A typical amorphous silicon solar cell having such a layer structure will be described with reference to FIGS.
[0053]
In the solar cell shown in FIG. 17A, a lower electrode 902, an n-type semiconductor layer 903, an i-type semiconductor layer 904, a p-type semiconductor layer 905, and a transparent electrode 906 are sequentially stacked on a substrate 901, and the substrate is further transparent. The structure is such that a grid-like current collecting electrode 907 is formed on the electrode 906. This solar cell is based on the assumption that light enters from the transparent electrode 906 side. Note that the lower electrode 902 is an electrode opposed to the transparent electrode 906 with the semiconductor layers 903 to 905 interposed therebetween.
[0054]
In the solar cell shown in FIG. 17B, the substrate 901 is translucent and light enters from the side of the substrate 901, and the transparent electrode 906 and the p-type A semiconductor layer 905, an i-type semiconductor layer 904, an n-type semiconductor layer 903, and a lower electrode 902 are sequentially stacked.
[0055]
Although each of the above solar cells has only one set of pin junctions, two sets of pin junctions are stacked to improve the utilization efficiency of incident light. FIG. 17C shows a configuration of a solar cell having two sets of pin junctions (a so-called tandem type solar cell). The solar cell includes a substrate 901, a lower electrode 902, and a first pin junction. 911, a second pin junction 912, a transparent electrode 906, and a collecting electrode 907 are sequentially stacked. Light enters from the transparent electrode 906 side. Each of the pin junctions 911 and 912 has, of course, a structure in which an n-type semiconductor layer 903, an i-type semiconductor layer 904, and a p-type semiconductor layer 905 are stacked. The i-type semiconductor layer 904 is used to improve photoelectric conversion efficiency. Then, the band gap and the film thickness are made different depending on each of the first and second pin junctions 911 and 912.
[0056]
Furthermore, in order to improve the photoelectric conversion efficiency, three sets of pin junctions are stacked. FIG. 17D shows a configuration of a solar cell having three sets of pin junctions (so-called triple type solar cell). This solar cell has a lower electrode 902 and a first pin junction on a substrate 901. 911, a second pin junction 912, a third pin junction 913, a transparent electrode 906, and a current collecting electrode 907 are sequentially stacked. Light enters from the transparent electrode 906 side. Also in this solar cell, in order to improve the photoelectric conversion efficiency, the band gap and the film thickness of the i-type semiconductor layer 904 are made different in each of the pin junctions 911 to 913.
[0057]
Next, details of each component of the above-described solar cell will be described. In each of the solar cells shown in FIGS. 17A to 17D, when the n-type semiconductor layer 903 and the p-type semiconductor layer 905 are compared, the p-type semiconductor layer 905 is located on the light incident side. However, a layer configuration in which the n-type semiconductor layer 903 is located on the light incident side is also possible.
[0058]
First, the substrate 901 will be described.
[0059]
The substrate 901 used in this solar cell is preferably made of a material that can be easily bent and can form a curved shape, and may be conductive or electrically insulating. The substrate 901 may be light-transmitting or non-light-transmitting. However, when light is incident from the substrate 901 side, the substrate 901 needs to be light-transmitting. It is. Specifically, a belt-like substrate as used in each embodiment of the present invention can be mentioned. By using a belt-shaped substrate, a solar cell can be continuously formed on a substrate by the method and apparatus of the present invention, and the weight and strength of the solar cell can be improved, and the space for transportation can be reduced.
[0060]
Next, an electrode for extracting electric power from the solar cell will be described.
[0061]
In this solar cell, an appropriate electrode is selectively used depending on its configuration. As the electrodes, a lower electrode 902, a transparent electrode 906, and a collecting electrode 907 can be given. (However, the transparent electrode 906 here refers to the one provided on the light incident side, and the lower electrode 902 refers to the one provided opposite the transparent electrode 906 with the semiconductor layers 903 to 905 interposed therebetween. It will be shown.)
These electrodes will be described in detail below.
[0062]
(I) Lower electrode 902
The lower electrode 902 has a different surface on which light for generating photovoltaic light is irradiated depending on whether the material of the substrate 901 is translucent or not (for example, the substrate 901 is made of a non-translucent material such as a metal). In the case of a material, light is irradiated from the transparent electrode 906 side as shown in FIG. 17A.)
[0063]
Specifically, in the case of a layer configuration as shown in FIGS. 17A, 17C and 17D, a lower electrode is provided between the substrate 901 and the n-type semiconductor layer 903 as an electrode for extracting current. 902 are provided. Note that when the substrate 901 is conductive, the substrate 901 can also serve as the lower electrode 902, so that the lower electrode 902 can be omitted. However, when the sheet resistance is high even if the substrate 901 is conductive, the lower part is used as a low-resistance electrode for extracting current or for the purpose of increasing the reflectivity on the surface of the support and effectively utilizing incident light. An electrode 902 may be provided.
[0064]
In the case of FIG. 17B, a light-transmitting substrate 901 is used, and light enters from the substrate 901 side. Therefore, the lower electrode 902 is connected to the substrate 901 for current extraction and light reflection. The semiconductor layers 903 to 905 are provided so as to face the semiconductor layer 901.
[0065]
Examples of the material for the lower electrode 902 include metals such as Ag, Au, Pt, Ni, Cr, Cu, Al, Ti, Zn, Mo, and W and alloys thereof. It is formed by beam evaporation, sputtering, or the like. Further, care must be taken that the formed metal thin film does not become a resistance component with respect to the output of the solar cell, and the sheet resistance of the lower electrode 902 is preferably 50Ω or less, more preferably 10Ω or less. Is desirable.
[0066]
A diffusion preventing layer (not shown) such as conductive zinc oxide may be provided between the lower electrode 902 and the n-type semiconductor layer 903. The effect of the diffusion preventing layer is to prevent the metal element forming the lower electrode 902 from diffusing into the n-type semiconductor layer 903 and to provide a slight resistance value to each of the semiconductor layers 903 to 905. To prevent a short circuit between the lower electrode 902 and the transparent electrode 906 due to a defect such as a pinhole generated in the device, and to confine incident light in a solar cell by generating multiple interference by a thin film. be able to.
[0067]
(Ii) Transparent electrode 906
The transparent electrode 906 desirably has a light transmittance of 85% or more in order to efficiently absorb light from the sun, a white fluorescent lamp, or the like in each of the semiconductor layers 903 to 905. The sheet resistance is desirably 100Ω or less so as not to become a resistance component with respect to the output of the solar cell. As a material having such characteristics, SnO 2₂, In₂O₃, ZnO, CdO, Cd₂SnO₄, ITO (In₂O₃+ SnO₂), And metal thin films formed of a metal such as Au, Al, Cu, etc. in an extremely thin and translucent state. The transparent electrode is laminated on the p-type semiconductor layer 905 in the solar cell shown in FIGS. 17A, 17C and 17D, and on the substrate 901 in the solar cell shown in FIG. Since they are laminated, it is necessary to select one having good mutual adhesion. As a method for forming the transparent electrode 906, a resistance heating evaporation method, an electron beam heating evaporation method, a sputtering method, a spray method, or the like can be used, and is appropriately selected as desired.
[0068]
(Iii) Current collecting electrode 907
The current collecting electrode 907 is provided in a grid on the transparent electrode 906 for the purpose of effectively reducing the surface resistance of the transparent electrode 906. Examples of the material of the current collecting electrode 907 include a thin film of a metal such as Ag, Cr, Ni, Al, Ag, Au, Ti, Pt, Cu, Mo, W, or an alloy thereof. These thin films can be used by being laminated. The shape and area of the semiconductor layers 903 to 905 are appropriately designed so that a sufficient amount of light enters the semiconductor layers 903 to 905.
[0069]
For example, it is desirable that the shape is uniformly spread on the light receiving surface of the solar cell, and that the area is preferably 15% or less, more preferably 10% or less with respect to the light receiving area. Further, the sheet resistance value is preferably 50Ω or less, more preferably 10Ω or less.
[0070]
Next, the n-type semiconductor layer 903, the i-type semiconductor layer 904, and the p-type semiconductor layer 905 will be described.
[0071]
(I) i-type semiconductor layer 904
Semiconductor materials constituting the i-type semiconductor layer 904 include a-Si: H, a-Si: F, a-Si: H: F, a-SiC: H, a-SiC: F, and a-SiC: H : F, a-SiGe: H, a-SiGe: F, a-SiGe: H: F, poly-Si: H, poly-Si: F, poly-Si: H: F and other Group IV semiconductor materials and IV Group alloy-based semiconductor materials. In addition, a group II-VI compound semiconductor material, a group III-V compound semiconductor material, and the like can be given.
[0072]
In the i-type semiconductor layer 904, the band gap is changed by changing the composition in the film thickness direction for the purpose of improving the photoelectric conversion efficiency and the like. FIGS. 18A to 18D show specific examples of changes in band gap (band gap profile) in the i-type semiconductor layer 904. The mark → in the figure indicates the light incident side.
[0073]
The band gap profile shown in FIG. 18A has a constant band gap in the i-type semiconductor layer 904. The band gap profile shown in FIG. 18B is of a type in which the band gap on the light incident side of the i-type semiconductor layer 904 is narrow and the band gap gradually widens. By setting the shape of the band gap in this way, it is effective to improve a fill factor (FF). The band gap profile shown in FIG. 18C is of a type in which the band gap on the light incident side is wide and the band gap gradually narrows, and the open-circuit voltage (V_oc) Is effective for improvement. The band gap profile shown in FIG. 18 (d) is of a type in which the band gap on the light incident side is wide, the band gap is narrowed relatively steeply, and spreads again. ) Can be combined to obtain both effects simultaneously. To change the band gap as described above, different semiconductors may be combined. For example, a-Si: H (E_g ^opt= 1.72 eV) and a-SiGe: H (E_g ^opt(1.45 eV), an i-type semiconductor layer 904 having a band gap profile shown in FIG. 18D can be manufactured. Also, a-SiC: H (E_g ^opt= 2.05 eV) and a-Si: H (E_g ^opt= 1.72 eV), an i-type semiconductor layer 904 having a band gap profile shown in FIG. 18C can be manufactured.
[0074]
In addition, by changing the concentration of an impurity added to the i-type semiconductor layer 904 in a small thickness direction in the film thickness direction, the Fermi level of the i-type semiconductor layer 904 can be changed while the conductivity type remains i-type. . FIG. 19A shows a specific example of how the Fermi level changes (Fermi level profile) in the i-type semiconductor layer 904 whose band gap profile is shown in FIG. 18A (that is, the band gap does not change). To (d). The mark → in the figure indicates the light incident side.
[0075]
FIG. 19A is a Fermi level profile of the i-type semiconductor layer 904 to which no impurity is added. On the other hand, the one shown in FIG. 19B is of a type in which the Fermi level on the light incident side is closer to the valence band and the Fermi level is gradually closer to the conduction band. This is effective in preventing the occurrence of the carrier and improving the traveling performance of the carrier. FIG. 19C shows a type in which the Fermi level gradually approaches the valence band from the light incident side. When an n-type semiconductor layer is provided on the light incident side, the structure shown in FIG. The same effect as in the case b) is obtained. FIG. 19D shows a type in which the Fermi level changes from the valence band to the conduction band almost continuously from the light incident side. These illustrate the case where the band gap is constant. However, in the case of the band gap profiles shown in FIGS. 18B to 18D, the Fermi level can be similarly controlled.
[0076]
By appropriately designing the band gap profile and the Fermi level profile, a solar cell with high photoelectric conversion efficiency can be manufactured. In particular, the control of the bandgap profile and the Fermi level profile is desirably applied to the i-type semiconductor layer 904 of a so-called tandem-type or triple-type solar cell shown in FIGS. 17C and 17D. .
[0077]
(Ii) p-type semiconductor layer 905 and n-type semiconductor layer 903
The p-type semiconductor layer 905 or the n-type semiconductor layer 903 can be obtained by doping a semiconductor material constituting the above-described i-type semiconductor layer 904 with a valence control agent by a known method.
[0078]
【Example】
Next, embodiments of the present invention will be described with reference to the drawings.
[0079]
FIG. 1 is a schematic diagram showing a configuration of a deposited film forming apparatus used for carrying out a deposited film forming method according to one embodiment of the present invention, and FIG. 2 is a three-dimensional view showing a main internal configuration. . The deposited film forming apparatus 891 shown in FIG. 1 and FIG. 2 includes a substantially rectangular parallelepiped metal vacuum container 800 and a film forming container 801 provided in the vacuum container.
[0080]
The long strip-shaped substrate 804 on which the deposited film is formed is introduced into the vacuum container 800 via a gas gate 803 attached to the left side of the vacuum container 800 in the drawing, that is, the side wall on the loading side, and is introduced into the film forming container 801. The gas passes through the film formation space 802, passes through a gas gate 805 attached to the right side of the vacuum container 800 in the drawing, that is, the side wall on the carry-out side, and is discharged to the outside of the vacuum container 800.
[0081]
Gate gas supply pipes 806 and 807 for supplying a gate gas are connected to the gas gates 803 and 805, respectively. The substrate 804 is continuously moved from a substrate delivery container (not shown) connected to the carry-in side gas gate 803 to a substrate take-up container (not shown) connected to the carry-out gas gate 805. Has become. Further, an exhaust pipe 808 for directly exhausting the inside of the vacuum vessel 800 is attached to the vacuum vessel 800, and the exhaust pipe 808 is connected to an exhaust means (not shown) such as a vacuum pump via a valve 808a. .
[0082]
The film formation container 801 has a columnar structure made of a conductive member, and the substrate 804 forms a part of a wall surface forming the film formation container 801. A film formation space 802 which is a space where plasma is substantially formed is formed in a film formation container 801 in contact with a substrate 804. The film formation space 802 is divided into a plurality of small film formation spaces 810 by a metal wall (that is, a separation wall or a partition wall) 809 provided in a direction perpendicular to the substrate 804 and in the width direction. In each small film formation space 810, a microwave applicator 811 is attached from the side surface of the film formation container 801 perpendicular to the substrate 804 so as to be arranged in the moving direction of the substrate 804. Each microwave applicator 811 radiates and transmits microwave energy into the film formation space 802, and the other end of the waveguide 812 having one end connected to a microwave power source (not shown) is connected to each other. Have been.
[0083]
In the film forming container 801, the raw material gas is exhausted from an exhaust surface 819 that is perpendicular to the band-shaped substrate 804 penetrating the film forming container 801 and faces the microwave applicator 811. The exhaust surface 819 is formed of a mesh or a punching board to prevent microwave energy from leaking.
[0084]
The film forming container 801 is provided with a rod-shaped source gas releasing means 814 extending in parallel with the substrate 804 and in the width direction of the substrate 804. On the surface of the raw material gas releasing means 814, a number of gas releasing holes for releasing the raw material gas are provided. The source gas discharging means 814 is connected to one end of a source gas supply pipe 815 connected to a source gas supply source (not shown) such as a gas cylinder or a mass flow controller via an insulating insulator 821 outside the film forming container 801. . At least one source gas releasing means 814 is provided in each of the small film forming spaces 810 so that a source gas for forming a deposited film is supplied. The source gas releasing means 814 is made of metal and also serves as a bias electrode for applying a DC or AC bias voltage. A DC or AC bias can be applied from a bias power supply (not shown) external to the vacuum vessel 800 to the source gas releasing means 814 via a bias supply line 822 to also serve as a bias electrode. .
[0085]
A large number of infrared lamp heaters 816 and a lamp house 817 for efficiently concentrating radiant heat from these infrared lamp heaters 816 on the substrate 804 are provided on the opposite side of the film forming space 802 with the band-shaped substrate 804 interposed therebetween. Is provided. A thermocouple 818 for monitoring the temperature of the substrate 804 heated by the infrared lamp heater 816 is provided so as to be in contact with the substrate 804.
[0086]
Next, the operation of the deposited film forming apparatus 891 will be described.
[0087]
First, from the substrate delivery container (not shown) connected to the carry-in side gas gate 803 to the substrate take-up container (not shown) connected to the carry-out gas gate 805 so as to pass through the deposited film forming apparatus 891. For example, a band-shaped substrate 804 made of, for example, SUS403BA is stretched, and the inside of the vacuum chamber 801 and the film forming space 802 are exhausted through an exhaust pipe 808. When the pressure reaches a predetermined degree of vacuum, a gate gas is supplied to each of the gas gates 803 and 805 from each of the gate gas supply pipes 806 and 807. The gate gas is mainly exhausted from an exhaust pipe 808 attached to the vacuum vessel 801.
[0088]
Next, a substrate feeding means (not shown) provided in a substrate feeding container (not shown) and a substrate winding means (not shown) provided in a substrate winding container (not shown) are operated, The substrate 804 is continuously moved from the substrate delivery container toward the substrate take-up container. Then, the substrate 804 is heated to a predetermined temperature by operating the infrared lamp heater 816 while monitoring the output of the thermocouple 818. The source gas is supplied from each source gas supply pipe 815 to the source gas discharging means 814 and discharged into each small film formation space 810. Each source gas supplied to each source gas release means 814 contains a plurality of types of substances serving as the source of the deposited film.
[0089]
Next, microwave power was supplied from a microwave power supply to each microwave applicator 811 via each waveguide 812 to generate a microwave glow discharge in the film formation space 802. Until the discharge occurs, the substrate 804 and other wall surfaces forming the film forming container 802 serve as microwave reflectors, so that microwave energy can be efficiently accumulated in the film forming space 802 and discharge can be easily generated. Can be. After the occurrence of the discharge, a bias voltage of, for example, +90 V DC is applied to the source gas discharging means 814.
[0090]
By the above operation, the source gas is decomposed in the film forming space 802, and a deposited film is formed on the substrate 804 which is moving continuously. In this deposited film forming apparatus 891, in each small film forming space 810, the conditions for forming the deposited film can be changed by appropriately selecting the type, supply amount, microwave power, bias voltage, and pressure of the source gas. . As a result, a composition distribution occurs in the thickness direction in the deposited film formed on the substrate 804 that is moving continuously. By adjusting the aperture ratio of the wall 809 (partition plate) separating each small film formation space 810, the inclination angle of the composition generated in the film thickness direction can be changed.
[0091]
A deposition film forming apparatus to which a method for continuously forming a large-area functional deposition film by separating a deposition space into small deposition spaces is not limited to that shown in FIGS. 3 to 5 show examples of a film forming container of another deposited film forming apparatus.
[0092]
In FIG. 3, the gas in the film forming container 801a is exhausted from the rear wall 819a of the film forming container 801a. Further, a source gas releasing means and a bias electrode are separately provided for each small film formation space. That is, the source gas releasing means 813 is provided on the bottom wall of the film forming vessel 801a, and the source gas is discharged from each of the source gas releasing means 813 into each of the small film forming spaces 810 through many small openings. On the other hand, the bias electrode 820 is a rod-shaped member extending in parallel with the substrate 804 and in the width direction of the substrate 804, and is attached to the film forming container 801a.
[0093]
FIG. 4 shows a film forming container 801b used for performing the deposited film forming method according to one embodiment of the present invention,In the film forming container 801b shown in FIG. 4, a microwave applicator 811 is installed in the film forming container 801b in parallel with the band-shaped substrate 804 and opposed to the width direction of the substrate 804. Source gas releasing means 814 also serving as a bias electrode is provided on the central axis of the opposed microwave applicator 811 in parallel with the substrate 804. The raw material gas in the small film formation space 810 is discharged outside from the wall surfaces 819b at both ends in the moving direction of the substrate 804 of the film formation container 801b. Further, a wall 809 separating each small film formation space 810 is formed by a punching board, so that gas can be diffused into both adjacent small film formation spaces.
[0094]
The film forming container 801c shown in FIG. 5 is different from the film forming container 801b shown in FIG. 4 in that the exhaust direction of the source gas in each small film forming space 810 is set to the bottom surface of the film forming container 801c facing the substrate 804. It is. Therefore, many small openings are provided on the bottom wall of the film forming container 801c.
[0095]
Next, a continuous deposited film forming apparatus 850 incorporating the deposited film forming apparatus 891 shown in FIG. 1 will be described with reference to FIG.
[0096]
This continuous deposited film forming apparatus 850 is suitable for forming a semiconductor element having a pin junction on a strip-shaped substrate 804, and includes a substrate sending container 851, a first impurity forming vacuum container 852, and a deposited film forming device. An apparatus 891, a second impurity-forming vacuum vessel 853, and a substrate take-up vessel 854 are connected in series by four gas gates 861, 803, 805, and 862. Gate gas supply pipes 863, 806, 807, and 864 for supplying a gate gas are connected to the gas gates 861, 803, 805, and 862, respectively.
[0097]
The substrate sending container 851 is for storing the substrate 804 and sending it out toward the substrate winding container 854, and is provided with a bobbin 865 around which the substrate 804 is wound. An exhaust pipe 866 connected to an exhaust unit (not shown) is attached to the substrate delivery container 851, and a throttle valve 867 for controlling the pressure in the substrate delivery container 851 is provided in the middle of the exhaust pipe 866. Has been. Further, the substrate delivery container 851 is provided with a pressure gauge 868, a heater 869 for heating the substrate 804, and a transport roller 870 for supporting and transporting the substrate 804. The bobbin 865 is connected to a substrate delivery mechanism (not shown) for delivering the substrate 804.
[0098]
The first and second vacuum chambers 852 and 853 for forming an impurity layer have the same structure and form a p-type or n-type semiconductor layer. Exhaust pipes 871 and 872 connected to exhaust means (not shown) are attached to each of the impurity layer forming vacuum vessels 852 and 853. In the middle of the exhaust pipes 871 and 872, impurity layer forming vacuum vessels 852 and 853 are provided. Are provided with throttle valves 873 and 874 for controlling the internal pressure. Each of the vacuum chambers 852 and 853 for forming an impurity layer is a continuous deposition film forming apparatus using a microwave plasma CVD method, and inside thereof, rectangular parallelepiped film forming vessels 875 and 876 are provided, respectively. The film forming containers 875 and 876 are the same as the film forming container in the above-described deposited film forming apparatus 891 except that they are not divided into small film forming spaces, and generate plasma in the internal film forming space. Then, a deposited film is formed on the moving substrate 804. In the film forming containers 875 and 876, source gas releasing means 877 and 878 for introducing a source gas for forming a deposited film and microwave applicators 879 and 880 for introducing microwave energy are provided. . Further, heaters 881 and 882 for heating the substrate 804 during formation of the deposited film and transport rollers 825 for transporting the substrate 804 are provided in the vacuum vessels 852 and 853 for forming the impurity layers.
[0099]
In the deposited film forming apparatus 891, a film forming space 802 is divided into seven small film forming spaces 810. The substrate winding container 854 is for winding the substrate 804 on which the deposited film is formed, and has the same configuration as the substrate unloading container 851. However, a bobbin 883 is connected to a substrate winding mechanism (not shown) for winding the band-shaped substrate 804.
[0100]
Next, the operation of the continuous deposited film forming apparatus 850 will be described focusing on the case of forming a semiconductor element having a pin junction.
[0101]
First, the substrate 804 is stretched from the substrate delivery container 851 to the substrate take-up container 854 with a tension so as not to sag, in a catenary curve shape. The back surface of the stretched substrate 805 is in contact with the transport roller 825 installed in each vacuum vessel (the surface on which the deposited film is not formed). Subsequently, the substrate delivery container 851, each impurity forming vacuum container 852, 853, the deposited film forming apparatus 891, and the substrate take-up container 854 are evacuated. When a predetermined degree of vacuum is reached, each of the gas gates 861, 803, 805, 862 is exhausted. Is supplied with a gate gas.
[0102]
Next, a source gas for forming a p-type or n-type semiconductor layer is supplied to each of the impurity layer forming vacuum vessels 302 and 303, and a deposition film forming apparatus 891 for forming an i-type semiconductor layer. The raw material gas is supplied, and microwave power is further supplied to the vacuum chambers 852 and 853 for forming the impurity layers and the deposition film forming apparatus 891, and the movement of the substrate 804 from the substrate delivery container 851 toward the substrate winding container 854 is started. As a result, plasma is generated in each of the vacuum chambers 852 and 853 for forming an impurity layer and the deposited film forming apparatus 891, and a deposited film is formed on the substrate 804. The substrate 804 has a pin junction on the substrate 804 because it is continuously moved with the first vacuum chamber 852 for forming an impurity layer, the deposition film forming apparatus 891, and the vacuum chamber 853 for forming a second impurity layer. A semiconductor element will be formed. At this time, in the deposited film forming apparatus 891, since the composition distribution can be provided in the thickness direction of the deposited film as described above, in the formed semiconductor element, the composition is distributed in the thickness direction of the i-type semiconductor layer. For example, the band gap and the Fermi level can be changed.
[0103]
Next, the results of an experiment performed on the present example will be described with specific numerical values. Each of the experimental examples described here is applied to the formation of the amorphous silicon-based solar cell or the amorphous silicon semiconductor film which is a component of the solar cell described in the above-mentioned “action” section with reference to FIGS. This is an application of the deposited film forming method of the embodiment. Here, the band gap profile or the Fermi level profile of the i-type semiconductor layer will be described in more detail. It is desirable that these profiles change continuously and smoothly as shown in FIG. 18 or FIG. However, the optimum conditions for forming the deposited film (eg, gas mixture ratio, microwave power, pressure, substrate temperature, etc.) also change with respect to changes in the band gap or Fermi level of the deposited film. It is not easy to continuously control the band gap profile and the Fermi level profile while maintaining the following. In this embodiment, by dividing the film formation space into a plurality of small film formation spaces, these band gaps are approximately stepped as shown in FIGS. 7A to 7C and 9A. And change the Fermi level.
[0104]
It is also possible to cause the interdiffusion of the source gas through the wall separating the small film formation space, whereby the band gap and the Fermi level steps can be maintained while maintaining good conditions for forming the deposited film. As shown in FIGS. 8 (a) to 8 (c) and FIG. 9 (b), it is possible to smoothly connect the shape change portions.
[0105]
(Experimental example 1)
Using the deposited film forming apparatus 891 shown in FIG. 1, a substrate delivery container (not shown) and a substrate take-up container (not shown) were connected to the carry-in side gas gate 803 and the carry-out side gas gate 805, respectively. Each of the substrate feeding container and the substrate winding container is provided with a substrate feeding mechanism (not shown) for feeding out a band-shaped substrate and a substrate winding mechanism (not shown) for winding a band-shaped substrate. However, the film forming space of the deposited film forming apparatus 891 was divided into seven small film forming spaces 810. The wall 809 separating the small film formation space 810 was a plate having no opening so that mutual diffusion of the source gas did not occur.
[0106]
First, a belt-like substrate 804 (width 20 cm × length 200 m × thickness 0.125 mm) made of stainless steel (SUS304BA) is sufficiently degreased and washed, and a bobbin (not shown) around which the substrate 804 is wound in a substrate delivery container. After mounting, the substrate 804 was passed through the gas gate 803 on the carry-in side, the film forming container 801 and the gas gate 805 on the carry-out side to the substrate winding container, and the tension was adjusted so that the substrate 804 did not sag. Then, each of the substrate delivery container (not shown), the vacuum container 800, the film formation container 801, and the substrate take-up container (not shown) is roughed by a mechanical booster pump / rotary pump (not shown), and an oil diffusion pump (not shown). 5 × 10^-6Evacuation was performed to a high vacuum of Torr or less. Thereafter, while the infrared lamp heater 816 was turned on and the output of the thermocouple 818 was monitored, temperature control was performed so that the surface temperature of the substrate 804 became 300 ° C., and heating and degassing were performed.
[0107]
When the degassing is sufficiently performed, the source gas for forming a deposited film is discharged from each gas releasing means 814 while operating an oil diffusion pump (not shown) connected to the exhaust pipe 808 under the conditions shown in Table 1. It was introduced into each small film formation container 810. At the same time, the gate gas is supplied from the gate gas supply pipes 806 and 807 to the gas gates 803 and 805 at a flow rate of 300 sccm.₂A gas is supplied, and the gate gas is exhausted through an exhaust pipe 808 directly connected to the vacuum container 800, a substrate sending container (not shown), and a substrate winding container (not shown). In this state, the pressure in the film forming container 801 was maintained at 6 mTorr.
[0108]
[Table 1]

[0109]
When the pressure in the film forming container 801 is stabilized, a microwave having a frequency of 2.45 GHz is introduced into the film forming container 801 from each of the waveguides 812 and each of the microwave applicators 811 from a microwave power supply (not shown). did. As a result, microwave glow discharge was generated in each small film formation space 810 of the film formation space 802, and plasma was generated. Next, the movement of the substrate 804 was started from the substrate unloading container (not shown) toward the substrate winding container (not shown), that is, in the direction of the arrow shown in FIG. The moving speed at this time was 100 cm / min. Over a period of 10 minutes, a deposition film made of i-type a-SiGe: H was formed on the substrate 804 while continuously moving the substrate 804. After the formation of the deposited film was completed, the substrate 803 was cooled and taken out of the deposited film forming apparatus 891.
[0110]
When the film thickness distribution of the deposited film formed in Experimental Example 1 was measured, the variation in the film thickness was within 5% with respect to the width direction and the longitudinal direction of the substrate 804. The calculated formation rate of the deposited film was 95 ° / sec on average.
[0111]
Next, a portion of the substrate 804 where the deposited film made of a-SiGe: H was formed in Experimental Example 1 was arbitrarily selected and cut out, and a secondary ion mass spectrometer (SIMS) (CAMECA) was used. , Imf-3 type), and the element distribution in the depth direction was measured. As a result, the distribution in the depth direction shown in FIG. 10 was obtained, and it was found that the band gap profile was the same as that shown in FIG. 7C. The total hydrogen in the deposited film was determined using a hydrogen-in-metal analyzer (Model EMGA-1100, manufactured by HORIBA, Ltd.) and found to be 16 ± 2 atomic%. In FIG. 10, the horizontal axis is represented by time. However, in secondary ion mass spectrometry, the elapsed time is proportional to the depth. Therefore, the horizontal axis in FIG. 10 may be considered as the depth from the surface. .
[0112]
(Experimental example 2)
The opening ratio of the wall 809 separating the seven small film-forming spaces 810 of the deposited film forming apparatus 891 used in the above-mentioned Experimental Example 1 was set to 25%, so that mutual diffusion of the source gas was possible to some extent. The deposited film was formed on the substrate 804 under the same conditions as in Experimental Example 1 without changing the other device configuration.
[0113]
The variation in the distribution of the film thickness of the deposited film formed in Experimental Example 2 was examined. The variation was within 5%, and the deposition film formation speed was calculated to be 80 ° / sec on average. . Next, in the same manner as in Experimental Example 8-1, six portions were arbitrarily selected from the portion where the deposited film made of a-SiGe: H was formed in Experimental Example 8-2, and the element in the depth direction was cut out. The distribution was measured. As a result, the distribution in the depth direction shown in FIG. 11 was obtained, and it was found that the band gap profile was similar to that shown in FIG. The connection of the band gap of the deposited film formed in the adjacent small film formation space became continuous. When the total hydrogen in the deposited film was quantified, it was 14 ± 2 atomic%.
[0114]
(Experimental example 3)
A gate gas was supplied in the same manner as in Experimental Example 2, and a deposited film made of i-type a-SiC: H was continuously formed on the substrate 804 under the conditions shown in Table 2. At this time, the moving speed of the substrate 804 was 95 cm / min. The internal pressure of the film forming container 801 was kept at 12 mTorr during the formation of the deposited film.
[0115]
[Table 2]

[0116]
After the formation of the deposited film was completed, the variation in the distribution of the film thickness of the deposited film formed in Experimental Example 3 was examined. The variation was within 5%. It was calculated to be 80 ° / sec. In the same manner as in Experimental Example 1, six portions were arbitrarily selected from the portion where the deposited film made of a-SiC: H was formed in Experimental Example 3, and the element distribution in the depth direction was measured. As a result, the distribution in the depth direction shown in FIG. 12 was obtained, and it was found that the band gap profile was the same as that shown in FIG. 8B. When the total hydrogen in the deposited film was quantified, it was 14 ± 2 atomic%.
[0117]
(Experimental example 4)
In the same manner as in Experimental Example 2, a deposited film of a-Si: H containing B as an impurity was continuously formed on the substrate 804 under the conditions shown in Table 3. At this time, the moving speed of the substrate 804 was 95 cm / min. During the formation of the deposited film, the internal pressure of the film forming container 801 was maintained at 5 mTorr.
[0118]
[Table 3]

[0119]
After the formation of the deposited film was completed, the variation in the distribution of the film thickness of the deposited film formed in Experimental Example 4 was examined. The variation was within 5%. It was calculated to be 110 ° / sec. As in Experimental Example 1, six portions were arbitrarily selected from the portion where the deposited film made of a-Si: H was formed in Experimental Example 4, and the element distribution in the depth direction was measured. As a result, the distribution in the depth direction shown in FIG. 13 was obtained, and it was found that the Fermi level profile was similar to that shown in FIG. 9B. When the total hydrogen in the deposited film was determined, it was 18 ± 2 atomic%.
[0120]
(Experimental example 5)
Using the continuous deposited film forming apparatus 850 shown in FIG. 6, an amorphous silicon solar cell having the layer configuration shown in FIG. 17A was manufactured. The film formation space 802 in the deposition film forming apparatus 891 was divided into seven small film formation spaces 810, and the walls separating the small film formation spaces 810 were plates without openings. This amorphous silicon solar cell has a single pin junction, and the band gap profile in the i-type semiconductor layer 404 is as shown in FIG.
[0121]
First, a strip-shaped substrate 804 made of SUS430BA similar to that used in the above-described Experimental Example 1 was mounted on a continuous sputtering device (not shown), and a target was an Ag electrode (Ag purity: 99.99%). An Ag thin film having a thickness of 1000 ° was sputter-deposited on 804, and a 1.2 μm thick ZnO thin film was sputter-deposited on the Ag thin film using a ZnO (ZnO purity: 99.999%) electrode as a target. A lower electrode 902 was formed on 804.
[0122]
Next, the substrate 804 on which the lower electrode 902 is formed is mounted on a substrate delivery container 851, and a first impurity layer forming vacuum container 852, a deposited film forming apparatus 891, and a second impurity layer forming vacuum container 853 are mounted. Through the substrate winding container 854. Then, the tension of the substrate 804 is adjusted so that the substrate 804 does not sag, and the vacuum containers 852 and 853 for forming the impurity layers, the deposition film forming apparatus 891, the substrate delivery container 851, and the substrate take-up container 854 are arranged in the same manner as in Experimental Example 1. 5 × 10^-6Evacuated to Torr.
[0123]
Subsequently, while continuously moving the substrate 804 from the substrate unloading container 851 toward the substrate winding container 854, the n-type semiconductor layer 903 is formed on the substrate 804 by the first vacuum container 852 for forming an impurity layer. Then, the i-type semiconductor layer 904 is formed sequentially by the deposition film forming apparatus 891, and the p-type semiconductor layer 905 is formed sequentially by the second impurity layer forming vacuum chamber 853. The conditions for forming the n-type semiconductor layer 903 and the p-type semiconductor layer 905 are as shown in Table 4, and the conditions for forming the i-type semiconductor layer 904 include i-type a-SiGe: H in Experimental Example 8-1. It was the same as when forming the deposited layer. The semiconductor layers 903 to 905 are formed by generating microwave glow discharge inside the vacuum chambers 852 and 853 for forming impurity layers and inside the deposition film forming apparatus 891, and when the plasma by the glow discharge is stabilized, the substrate 804 is formed. This was performed by moving at a moving speed of 95 cm / min. In each of the impurity layer forming vacuum vessels 852 and 853, the length of the region in which the microwave glow discharge is generated in the moving direction of the substrate 804 is shown in the column of the length of the film formation region in Table 4. .
[0124]
[Table 4]

When the semiconductor layers 903 to 905 are formed over the entire length (200 m) of the substrate 804, the substrate 804 is cooled, taken out of the continuous deposition film forming apparatus 850, and further placed on the p-type semiconductor layer 905. The electrode 906 and the current collecting electrode 907 were formed to complete a belt-shaped solar cell.
[0125]
Next, using a continuous modularization apparatus (not shown), the produced solar cell was processed into a large number of solar cell modules having a size of 36 cm × 20 cm. For the manufactured solar cell module, the AM value was 1.5 and the energy density was 100 mw / cm.²When the characteristics were evaluated using pseudo sunlight, the photoelectric conversion efficiency was 7.0% or more, and the variation in characteristics among the solar cell modules was within 5%. In addition, when two of the fabricated solar cell modules were extracted and subjected to a continuous bending test of 200 times, the characteristics did not deteriorate even after the test, and phenomena such as peeling of the deposited film were not observed. Was. When the above-mentioned AM value is 1.5 and the energy density is 100 mw / cm²After 500 hours of continuous irradiation with the pseudo sunlight, the fluctuation of the photoelectric conversion efficiency was within 10.0% of the initial value.
[0126]
By connecting this solar cell module, a power supply system with an output of 2.5 kW could be manufactured.
[0127]
(Experimental example 6)
In the continuous deposited film forming apparatus 850 used in the above-described Experimental Example 5, the porosity of the wall 809 separating the seven small film forming spaces 810 of the deposited film forming apparatus 891 is set to 25%, and the mutual diffusion of the raw material gas is made to some extent Made it possible. A solar cell was prepared and processed into a solar cell module in the same manner as in Experimental Example 5, except that the i-type semiconductor layer 904 was deposited under the same conditions as in Experimental Example 2. Note that the i-type semiconductor layer 904 has a band gap profile as shown in FIG.
[0128]
Then, when the same characteristics as in Experimental Example 5 were evaluated for the manufactured solar cell module, a photoelectric conversion efficiency of 8.0% or more was obtained, and the variation in characteristics between the respective solar cell modules was also within 5%. It was in. Further, even after the continuous bending test of 200 times, no deterioration of the characteristics was observed, and no peeling of the deposited film occurred. Furthermore, even after 500 hours of continuous pseudo-sunlight irradiation, the variation in photoelectric conversion efficiency was within 8.5% of the initial value. By using this solar cell module, a power supply system with an output of 5 kW could be manufactured.
[0129]
(Experimental example 7)
In Experimental Examples 5 and 6, an a-SiGe: H deposition film was used as the i-type semiconductor layer 904. Here, a solar cell was manufactured using a-SiC: H instead of a-SiGe: H. Processed into a solar cell module. The procedure was the same as in Experimental Example 5 except that the i-type semiconductor layer 904 was deposited under the same conditions as in Experimental Example 3. The i-type semiconductor layer 904 has a band gap profile as shown in FIG.
[0130]
When the same characteristics as those of Experimental Example 5 were evaluated for the manufactured solar cell module, a photoelectric conversion efficiency of 7.2% or more was obtained, and the variation in characteristics between the respective solar cell modules was also within 5%. It was in. Further, even after the continuous bending test of 200 times, no deterioration of the characteristics was observed, and no peeling of the deposited film occurred. Furthermore, even after 500 hours of continuous pseudo-sunlight irradiation, the variation in photoelectric conversion efficiency was within 8.5% of the initial value. By using this solar cell module, a power supply system with an output of 5 kW could be manufactured.
[0131]
(Experimental example 8)
In Experimental Examples 5 and 6, an a-SiGe: H deposited film was used as the i-type semiconductor layer 904. Here, instead of a-SiGe: H, a solar cell was manufactured using a-Si: H. Processed into a solar cell module. The procedure was the same as in Experimental Example 5 except that the i-type semiconductor layer 904 was deposited under the same conditions as in Experimental Example 4. The i-type semiconductor layer 904 has a Fermi level profile as shown in FIG.
[0132]
Then, the same characteristics as in Experimental Example 5 were evaluated for the manufactured solar cell module. As a result, a photoelectric conversion efficiency of 8.4% or more was obtained, and the variation in characteristics between the respective solar cell modules was also within 5%. It was in. Further, even after the continuous bending test of 200 times, no deterioration of the characteristics was observed, and no peeling of the deposited film occurred. Furthermore, even after 500 hours of continuous pseudo-sunlight irradiation, the variation in photoelectric conversion efficiency was within 8.5% of the initial value. By using this solar cell module, a power supply system with an output of 2.5 kW could be manufactured.
[0133]
(Experimental example 9)
An amorphous silicon solar cell having a configuration in which two sets of pin junctions are stacked as shown in FIG. 17C was manufactured and processed into a solar cell module. At the time of fabrication, the continuous deposition film is formed between the second impurity layer forming vacuum container 853 and the substrate winding container 854 of the continuous deposition film forming apparatus 850 shown in FIG. 6 so that two sets of pin junctions can be formed. An apparatus having a structure in which a first vacuum layer 852 for forming an impurity layer, a deposited film forming apparatus 891, and a vacuum chamber 853 for forming a second impurity layer 853 of the film forming apparatus 850 were sequentially connected in series was used.
[0134]
As the band-shaped substrate 804, the same one as that used in Experimental Example 1 is used. Of the two sets of pin junctions, the first pin junction 911 that is farther from the light incident side is the same as the above-described experimental example. 6, and the second pin junction 912 closer to the light incident side was formed under the same conditions as the pin junction of Experimental Examples 8-8. After the formation of the first and second pin junctions 911 and 912, a solar cell module was obtained through the same steps as in Experimental Example 6.
[0135]
When the same characteristics as in Experimental Example 5 were evaluated for the manufactured solar cell module, a photoelectric conversion efficiency of 11.0% or more was obtained, and the variation in characteristics between the respective solar cell modules was within 5%. I was Further, even after the continuous bending test of 200 times, no deterioration of the characteristics was observed, and no peeling of the deposited film occurred. Furthermore, the rate of change in photoelectric conversion efficiency after 500 hours of continuous irradiation with pseudo-sunlight was within 7.5%. By using this solar cell module, a power supply system with an output of 2.5 kW could be manufactured.
[0136]
(Experimental example 10)
An amorphous silicon solar cell having a configuration in which two sets of pin junctions are stacked as shown in FIG. 17C was manufactured and processed into a solar cell module. In the fabrication, except that the first pin junction 911 was formed under the same conditions as the pin junction in the above-described Experimental Example 8, and the second pin junction 912 was formed under the same conditions as the pin junction in the Experimental Example 7. The same as in Experimental Example 9.
[0137]
When the same characteristics as in Experimental Example 5 were evaluated for the manufactured solar cell module, a photoelectric conversion efficiency of 10.5% or more was obtained, and the variation in characteristics between the respective solar cell modules was within 5%. I was Further, even after the continuous bending test of 200 times, no deterioration of the characteristics was observed, and no peeling of the deposited film occurred. Furthermore, the rate of change in photoelectric conversion efficiency after 500 hours of continuous irradiation with pseudo-sunlight was within 7.5%. By using this solar cell module, a power supply system with an output of 2.5 kW could be manufactured.
[0138]
(Experimental example 11)
An amorphous silicon solar cell having a configuration in which three sets of pin junctions are stacked as shown in FIG. 17D was manufactured and processed into a solar cell module. In order to form three continuous pin junctions, the continuous deposition film is formed between the second impurity layer forming vacuum container 853 and the substrate winding container 854 of the continuous deposition film forming apparatus 850 shown in FIG. A first impurity layer forming vacuum vessel 852, a deposited film forming apparatus 891, a second impurity layer forming vacuum vessel 853, a first impurity layer forming vacuum vessel 852, a deposited film forming apparatus 891, of the film forming apparatus 850; An apparatus having a configuration in which a vacuum vessel 853 for forming a second impurity layer 853 was sequentially connected in series was used.
[0139]
As the substrate 804, the same one as that used in Experimental Example 1 is used. Among the three pin junctions, the first pin junction 911 farther from the light incident side is used in Experimental Example 6 described above. The second pin junction 912 is formed under the same conditions as the pin junction of Experimental Example 8, and the third pin junction 913 positioned on the light incident side is formed under the same conditions as those of Experimental Example 8. It was formed under the same conditions as the pin junction. After the formation of each of the pin junctions 911 to 913, a solar cell module was obtained through the same steps as in Experimental Example 6.
[0140]
When the same characteristics as in Experimental Example 5 were evaluated for the manufactured solar cell module, a photoelectric conversion efficiency of 12.0% or more was obtained, and the variation in characteristics between the respective solar cell modules was within 5%. I was Further, even after the continuous bending test of 200 times, no deterioration of the characteristics was observed, and no peeling of the deposited film occurred. Furthermore, the rate of change of the photoelectric conversion efficiency after the irradiation of pseudo sunlight for 500 hours was within 7%. By using this solar cell module, a power supply system with an output of 2.5 kW could be manufactured.
[0141]
As mentioned above, although the example of the present invention was mainly explained about the case where an amorphous silicon solar cell is manufactured, the present invention is required to have a large area or a long shape other than the amorphous silicon solar cell. It is preferably used also when forming a thin film semiconductor element. Examples of such a thin film semiconductor element include a thin film transistor (TFT) for driving a pixel of a liquid crystal display, a photoelectric conversion element for a contact image sensor, and a switching element. These thin-film semiconductor elements are often used as main components of an image input / output device, and by implementing the present invention, these thin-film semiconductor elements can be mass-produced with high quality and uniformity. It is expected to spread widely.
[0142]
【The invention's effect】
As described above, according to the present invention, in a moving film forming type microwave plasma CVD method, a film forming space is constituted by a plurality of small film forming spaces separated by a wall, and composition control is performed, thereby forming a large area composition. A controlled functional deposition film can be formed continuously and with good reproducibility, and the controllability and stability of large-area plasma are improved, making it possible to generate uniform plasma over a large area. There is an effect that a deposited film having a uniform composition in the thickness direction can be easily formed. Further, there is an effect that a functional deposition film having an arbitrary band gap profile can be continuously formed on a belt-shaped member that moves continuously.
[Brief description of the drawings]
FIG. 1 is a schematic sectional view showing a configuration of a deposited film forming apparatus according to an embodiment of the present invention.
FIG. 2 is a fragmentary perspective view showing a configuration of a film forming container of the deposited film forming apparatus of FIG. 1;
FIG. 3 is a fragmentary perspective view showing a film forming container having a configuration different from that of FIG. 1;
FIG. 4Used for carrying out the deposited film forming method of one embodiment of the present invention.FIG. 2 is a fragmentary perspective view showing a film forming container.

FIG. 5 is a fragmentary perspective view showing a film forming container having still another configuration.
FIG. 6 is a view showing a configuration of a continuous deposition film forming apparatus incorporating the apparatus of FIG. 1;
FIGS. 7A to 7C are diagrams showing band gap profiles of an i-type semiconductor layer.
FIGS. 8A to 8C are diagrams showing band gap profiles of an i-type semiconductor layer.
FIGS. 9A and 9B are diagrams showing Fermi level profiles of an i-type semiconductor layer.
FIG. 10 is a characteristic diagram showing a result of secondary ion mass spectrometry.
FIG. 11 is a characteristic diagram showing a result of secondary ion mass spectrometry.
FIG. 12 is a characteristic diagram showing a result of secondary ion mass spectrometry.
FIG. 13 is a characteristic diagram showing a result of secondary ion mass spectrometry.
FIG. 14 is a schematic sectional view showing a configuration of a conventional microwave plasma CVD apparatus.
FIG. 15 is a schematic sectional view showing a configuration of a conventional moving film formation type microwave plasma CVD apparatus.
FIG. 16 is a schematic diagram showing how a bias electric field is applied in a conventional microwave plasma CVD apparatus.
FIGS. 17A to 17D are schematic cross-sectional views each showing a configuration of a solar cell.
FIGS. 18A to 18D are diagrams showing band gap profiles of an i-type semiconductor layer.
FIGS. 19A to 19D are diagrams showing Fermi level profiles of an i-type semiconductor layer.
[Explanation of symbols]
800 Vacuum container
801, 801a, 801b, 801c Deposition container
802 deposition space
803,805 gas gate
804 substrate
809 wall
810 Small film formation space
811 Microwave applicator
812 Waveguide
814 Source gas supply means
815 Source gas supply pipe
820 bias electrode
850 Continuous deposited film forming equipment
851 substrate delivery container
852 Vacuum container for forming first impurity layer
853 Vacuum container for forming second impurity layer
854 substrate winding container
891 deposited film forming equipment

Claims (2)

While continuously moving the belt-shaped substrate in the longitudinal direction, a source gas for depositing a film is introduced into a columnar film-forming space in which the substrate is one surface of a side wall, and simultaneously, microwave energy is supplied to the film-forming space. Introducing a microwave plasma in the film-forming space by being introduced, and forming a deposited film on the surface of the substrate on the film-forming space side, a deposition film forming method,
The film forming space is constituted by a plurality of small film forming spaces separated by a wall capable of mutually diffusing a source gas for forming a deposited film, and forming the deposited film by controlling the composition. A method for forming a deposited film. 2. The method according to claim 1, wherein the intensity of the microwave energy introduced into each of the small film formation spaces and the composition of the deposited film forming source gas are independently controlled for each of the small film formation spaces.

Images