JP3970840B2 - Semiconductor manufacturing method and apparatus - Google Patents

Description

上記の表より、例えば、光電子法は、大型化への適用性に劣るが、オゾンレスでクリーンな負イオンであることから酸化抑制効果に優れており、また放射線照射法は、大型化・小型化への適用性およい負イオン発生量に優れるが、安全性に課題があることが分かる。本発明においては、上述の各種負イオン発生法の有利性及び課題点を考慮し、用途、求められる性能等に応じて適宜好ましい負イオン発生法を採用することができる。
上記の負イオン発生法のうち、放電法で負イオンを発生させた後に加湿を行なったり、或いは水破砕法によって負イオンを発生させる場合には、形成される負イオンの粒径が他の方式に比べて大きいことが分かった。例えば、光電子法による場合や、放電法で加湿を行わない場合などでは、形成される負イオンの粒径は１ｎｍ程度であるが、放電法で負イオンを発生させた後に加湿を行う場合や、水破砕法によって負イオンを発生させる場合に形成される負イオンの粒径は３〜５ｎｍ程度である。そして、本発明者らの研究により、負イオンの粒径が大きいほど、本発明の基板の酸化抑制に効果的であることが分かった。この原因の詳細は不明であるが、次のように考えられる。即ち、負イオンは、中心分子（例えば、酸素分子）がマイナスの電荷を有し、その周りに水分子が吸着（付着）するが、この吸着水分子の数がある程度多い方が、基板の酸化抑制により大きな効果を発揮する。従って、用途、装置の規模、要求される仕様によっては、加湿を伴う放電法或いは水破砕法による負イオン発生法が好ましく用いられる。
本発明においては、このようにして調整された負イオン富化気体に基板を暴露しながら基板の処理を行うのであるが、その際、負イオン富化気体の利用先、即ち基板の処理領域の方向に正電極を設置して、負イオンを電界中で引き寄せるとより基板の酸化抑制に効果的である。これは、負イオンは移動速度が速く、装置の形状や構造等によっては消費が多いためである。
本発明においては、上記のように負イオンを発生させて負イオン富化気体を形成するのであるが、気体中に汚染物質が含まれていると、発生した負イオンが汚染物質によって消費されてしまう。例えば、微粒子状物質が気体中に存在すると、発生した負イオンの電荷がこの微粒子に移行して荷電粒子が形成されるために、負イオンが消費される。このために、基板の酸化抑制のために有効活用されるべき負イオンの濃度が減少してしまう。また、半導体基板は、微粒子や化学汚染物質の存在によって汚染が顕著に生じ、歩留まり低下が激しくなることが知られている。更に、Ｃｌ_２などのような酸性ガスが気体中に残留していると、そのような気体に対して負イオン発生を行うと、Ｃｌ_２などが核になった負イオンも形成されるが、このような負イオンは酸化力を有していると考えられるため、本発明の「基板の酸化の抑制」という目的には合致しない。よって、このような化学汚染物質を十分に除去した後に、負イオン発生処理を行うことが望ましい。
このような観点から、本発明においては、予め微粒子及びイオン成分、無機物、有機物のような化学的汚染物質の除去を行った気体を、上述の負イオン発生装置に通して負イオンを発生させることが好ましい。具体的には、本発明においては、負イオン発生装置に供給する気体は、微粒子濃度が、クラス（気体１ｆｔ^３中の粒子個数、基準粒径０．１μｍ）１００以下、好ましくは１０以下、より好ましくは１以下；イオン成分濃度が、１０μｇ／ｍ^３以下、好ましくは５μｇ／ｍ^３以下、より好ましくは２μｇ／ｍ^３以下；有機物濃度が、１０μｇ／ｍ^３以下、好ましくは５μｇ／ｍ^３以下、より好ましくは２μｇ／ｍ^３以下であることが好ましい。なお、ここで「イオン成分」とは、ＮＯ_ｘ、ＳＯ_ｘ、ＨＣｌ、ＨＦ、Ｃｌ_２、Ｆ_２、ＨＢｒ、Ｂｒ_２のような酸性ガス、並びに、アンモニア、アミンのようなアルカリ性ガスなどを指す。
以上に説明したように、本発明においては、負イオン発生装置に供給する気体を予め汚染物質除去処理にかけることが好ましい。本発明において、負イオン発生の前段処理として行うことのできる汚染物質除去処理は、大きく分けて微粒子除去処理と化学的汚染物質除去処理とに分けられる。それぞれについて以下に説明する。
Ｂ．微粒子除去処理
本発明において負イオン発生処理にかける気体は、予め微粒子をクラス１００以下、好ましくは１０以下、より好ましくは１以下まで捕集することが好ましく、この清浄度を達成できるものであれば、当該技術において公知の微粒子除去手段を用いることができる。本発明において用いることのできる微粒子除去手段としては、例えば、フィルタを用いる方法や、本発明者らが別に提案している光電子を用いる方法などを挙げることができる。
Ｂ−１：フィルタによる微粒子除去手段
本発明において微粒子除去手段として用いることのできるフィルタとしては、ＵＬＰＡフィルタ、ＨＥＰＡフィルタ、中性能フィルタ、静電フィルタなどの当該技術において周知のフィルタを挙げることができ、これらの１種或いは複数を組み合わせて用いることができる。
Ｂ−２：光電子による微粒子除去手段
本手段は、本発明者らが、別に、特公平６−７４９０９号、特公平７−１２１３６９号、特公平８−２１１号、特公平８−２２３９３号、特許２６２３２９０号等において提案している光電子を用いて微粒子の除去を行う方法であえる。本方法は、上述した光電子を用いて負イオンを発生させる方法と同様にして、負イオンを発生させ、発生させた負イオンにより微粒子を荷電させ、荷電微粒子を電極等を用いて捕集・除去するものである。即ち、本発明において用いることのできる光電子による微粒子除去手段は、光電子放出材、紫外線源、電極材、荷電微粒子捕集材により構成される。光電子放出材、紫外線源、電極材としては、上記の光電子による負イオン発生方法において述べた各種材料を用いることができる。
荷電微粒子の捕集材としては、通常の荷電装置における集塵板、集塵電極等、各種電極材や静電フィルタ方式のものを一般的に用いることができるが、スチールウール電極、タングステンウール電極のようなウール状構造のものも有効に用いることができる。また、エレクトレット材も好適に使用できる。
光電子放出材、電極材、荷電微粒子捕集材の好適な組み合わせは、被清浄空間の形状、構造、要求される性能、経済性などに応じて適宜定めることができる。例えば、光電子放出材と電極の位置と形状は、紫外線源を囲み、紫外線源、光電子放出材、電極材及び荷電微粒子捕集材を一体化することができ、紫外線源から放出された紫外線を有効に利用することができ、且つ光電子の放出と光電子による微粒子の荷電・捕集を効果的に行うことができるように、形状、効果、経済性等を考慮して適宜定めることができる。例えば、棒状若しくは円筒状の紫外線ランプを紫外線源として用いる場合には、紫外線がランプの円周方向に放射状に放出され、この円周方向の放射状の紫外線を光電子放出材にできるだけ多く照射すれば、光電子の放出量が多くなる。従って、紫外線ランプに対向して円周方向に光電子放出材を配置し、その対向面に光電子放出用の電極を設置することが好ましい。
Ｃ．イオン成分、化学的汚染物質の除去
上述したように、本発明において負イオン発生処理にかける気体は、予め、Ｃｌ_２、ＮＯ_ｘ、ＳＯ_ｘのような酸性ガス、アンモニアのようなアルカリ性ガスなどのイオン成分や、無機物、有機物などの化学的汚染物質を除去することが好ましく、具体的には、イオン成分濃度を１０μｇ／ｍ^３以下、好ましくは５μｇ／ｍ^３以下、より好ましくは２μｇ／ｍ^３以下；有機物濃度を１０μｇ／ｍ^３以下、好ましくは５μｇ／ｍ^３以下、より好ましくは２μｇ／ｍ^３以下とすることが好ましい。このような汚染物質除去手段としては当該技術において周知の方法を使用することができ、例えば、吸着材による方法、光触媒による方法などを使用することができる。以下、それぞれの方法について説明する。
Ｃ−１：吸着材による化学的汚染物質の除去手段
本発明において、吸着材による化学的汚染物質の除去手段は、負イオン富化気体を生成させる際に、処理気体中のＮＯ_ｘ、ＳＯ_ｘ、ＨＣｌ、ＨＦ、Ｃｌ_２、Ｆ_２、ＨＢｒ、Ｂｒ_２のような酸性ガス、並びに、アンモニア、アミンのようなアルカリ性ガスを捕集・除去するものであり、吸着材としては、上記の各種酸性・アルカリ性ガスを低濃度まで効率よく吸着する材料であればよい。このような吸着材としては、シリカゲル、ゼオライト、アルミナ、活性炭、イオン交換繊維などが知られており、この中で、活性炭及びイオン交換繊維が効果的であることから本発明において好ましく用いることができる。特に、イオン交換繊維は、化学反応によって汚染物質を低濃度まで捕集することができ、到達クリーン度が高いので、用途によっては好ましく用いることができる。また、活性炭としては、捕集成分に応じて、適宜、酸やアルカリを添着した添着活性炭を用いることができる。
上記吸着材の形状は、適宜の形状で用いることができるが、一般に、繊維状、ハニカム状の形状が、圧力損失が少ないので好ましい。
イオン交換繊維は、天然繊維又は合成繊維或いはこれらの混合体等の支持体表面に、陽イオン交換体若しくは陰イオン交換体或いは陽イオン交換基と陰イオン交換基を併有するイオン交換体を支持させたもので、支持方法としては、繊維状の支持体に直接イオン交換体を支持させてもよく、或いは、繊維から形成された織物状、編物状若しくは植毛状の基材にイオン交換体を支持させてもよい。本発明において用いることのできるイオン交換繊維としては、グラフト重合法、特に放射線グラフト重合法を利用して製造したイオン交換繊維が好適に用いられる。これは、放射線グラフト重合法によれば、種々の材質及び形状の素材を利用してイオン交換繊維を形成することができるからである。
上記天然繊維としては、羊毛、絹等を適用することができ、合成繊維としては、炭化水素系重合体を素材とするもの、含フッ素系重合体を素材とするもの、或いはポリビニルアルコール、ポリアミド、ポリエステル、ポリアクリロニトリル、セルロース、酢酸セルロースなどを適用することができる。上記炭化水素系重合体としては、ポリエチレン、ポリプロピレン、ポリイソブチレン、ポリブテン等の脂肪族系重合体、ポリスチレン、ポリα−メチルスチレン等の芳香族系重合体、ポリビニルシクロヘキサン等の脂環式系重合体、或いはこれらの共重合体が用いられる。また、上記含フッ素系重合体としては、ポリ四フッ化エチレン、ポリフッ化ビニリデン、エチレン−四フッ化エチレン共重合体、四フッ化エチレン−六フッ化プロピレン共重合体、フッ化ビニリデン−六フッ化プロピレン共重合体等が用いられる。いずれの素材に関しても、イオン交換体用の支持体としては、ガス流との接触面積が大きく、抵抗が小さい形状で、容易にグラフト化を行うことができ、機械的強度が大で、繊維くずの脱落及び発生が少なく、熱の影響が小さい材料であれば好適であり、使用用途、経済性、効果等を考慮して、当業者が適宜に選択できるが、通常はポリエチレンやポリエチレンとポリプロピレンとの複合材が一般的に好ましく用いられる。
これらの素材に導入することのできるイオン交換体としては、特に限定されることなく、種々のカチオン交換体又はアニオン交換体を使用することができる。例えば、カルボキシル基、スルホン酸基、リン酸基、フェノール性水酸基などのカチオン交換基含有体；第一級〜第三級アミノ基及び第四級アンモニウム基などのアニオン交換基含有体；或いは上記カチオン交換基及びアニオン交換基の両方を併有するイオン交換体などを使用することができる。具体的には、上記繊維素材上に、例えば、アクリル酸、メタクリル酸、ビニルベンゼンスルホン酸、スチレン、ハロメチルスチレン、アシルオキシスチレン、ヒドロキシスチレン、アミノスチレン等のスチレン化合物、ビニルピリジン、２−メチル−５−ビニルピリジン、２−メチル−５−ビニルイミダゾール、アクリロニトリルなどをグラフト重合させた後、必要に応じて硫酸クロルスルホン酸、スルホン酸などを反応させることにより、カチオン交換基又はアニオン交換基を有する繊維状イオン交換体が得られる。また、上記のモノマーを、ジビニルベンゼン、トリビニルベンゼン、ブタジエン、エチレングリコール、ジビニルエーテル、エチレングリコールジメタクリレートなどの２個以上の二重結合を有するモノマーの共存下で繊維上にグラフト重合させてもよい。
本発明において化学汚染物質用吸着材として好ましく用いられるイオン交換繊維の繊維径は、１〜１０００μｍ、好ましくは５〜２００μｍであり、繊維の種類、用途などに応じて適宜定めることができる、また、イオン交換繊維におけるカチオン交換基とアニオン交換基の種類及び導入量は、処理対象気体中の被除去成分の種類や濃度によって定めることができる。例えば、気体中の被除去成分を予め測定・評価し、それに見合うイオン交換基の種類及び量を用いればよい。例えば、アルカリ性ガスを除去したい場合にはカチオン交換基を有するもの、酸性ガスを除去したい場合にはアニオン交換基を有するもの、両者が混合した気体を処理する場合にはカチオンとアニオンの両方の交換基を有する繊維を用いることができる。
イオン交換繊維への気体の流し方としては、フィルタ状のイオン交換繊維に気体を直交して流すと効果的である。イオン交換繊維へ気体を流す流速は、予備試験を行って適宜定めることができるが、イオン交換繊維はガス成分の除去速度が速いので、通常ＳＶ（空間速度）として１，０００〜１００，０００（ｈ^−１）程度で気体を流すことができる。イオン交換繊維としては、本発明者らが先に提案したような、放射線グラフト重合法を利用して製造したものを用いると、特に効果が高いので好ましく、適宜用いることができる（特公平５−９１２３号、特公平５−６７２３５号、特公平５−４３４２２号、特公平６−２４６２６号等）。放射線グラフト重合によってイオン交換基を繊維素材（支持体）に導入すると、支持体への放射線の照射が奥部まで均一になされるため、イオン交換体が広い面積に高密度で強固に付加されるので、イオン交換容量が大きくなる。したがって、低濃度のガス成分も、速い速度で高効率に除去することができる。また、放射線グラフト重合によるイオン交換繊維の製造は、製品に近い形状の素材を用いて製造を行うことができること、室温で製造できること、気相中で製造を行うことができること、グラフト率を大きくとることができること、不純物の少ない吸着フィルタが形成されること、などの利点がある。このため、放射線グラフト重合法を利用して製造したイオン交換繊維は、ガス成分の吸着機能を果たす部分であるイオン交換体が均一に且つ高密度で大量に付加するので、ガス成分の吸着速度が速く、吸着量が多い。更には圧力損失の少ないフィルタ材料を形成することができる。
また、要求される仕様によっては、ガラス及びフッ素樹脂により形成される吸着材、例えばフッ素樹脂をバインダーとしたガラス繊維フィルタも、本発明における化学汚染物質除去用吸着材として好適に使用することができる。かかるフィルタは、ガス状の有機物と、粒子状物質の同時除去に効果的である（特許２５８２８０６号）。
Ｃ−２：光触媒を用いる化学的汚染物質の除去手段
光触媒を用いて気体中の化学汚染物質を除去する手段は、除去すべき気体成分がフタル酸エステルのような有機物（Ｈ．Ｃ．）を含む場合に好適である。ＤＯＰなどのフタル酸エステルのような高分子量Ｈ．Ｃ．は、基板表面に吸着すると、酸化膜耐圧性の劣化、即ち信頼性の低下など、生産性及び歩留まりの低下をもたらすので、除去が必要である。
光触媒としては、光照射によって励起され、Ｈ．Ｃ．を分解してＣＯ_２やＨ_２Ｏなどのような基板に対して安定な形態に変換できるものであれば、任意のものを用いることができる。通常、光触媒としては、半導体材料が効果的であり、容易に入手することができ、加工性もよいことから、本発明において好ましく用いられる。効果や経済性を考慮すると、Ｓｅ、Ｇｅ、Ｓｉ、Ｔｉ、Ｚｎ、Ｃｕ、Ａｌ、Ｓｎ、Ｇａ、Ｉｎ、Ｐ、Ａｓ、Ｓｂ、Ｃ、Ｃｄ、Ｓ、Ｔｅ、Ｎｉ、Ｆｅ、Ｃｏ、Ａｇ、Ｍｏ、Ｓｒ、Ｗ、Ｃｒ、Ｂａ、Ｐｂのいずれか、又はこれらの化合物若しくは合金或いは酸化物が好ましく、これらは単独で若しくは二種類以上を複合して用いることができる。
例えば、元素としては、Ｓｉ、Ｇｅ、Ｓｅ、化合物としては、ＡｌＰ、ＡｌＡｇ、ＧａＰ、ＡｌＳｂ、ＧａＡｓ、ＩｎＰ、ＧａＳｂ、ＩｎＡｓ、ＩｎＳｂ、ＣｄＳ、ＣｄＳｅ、ＺｎＳ、ＭｏＳ_２、ＷＴｅ_２、Ｃｒ_２Ｔｅ_３、ＭｏＴｅ、Ｃｕ_２Ｓ、ＷＳ_２などが挙げられ、酸化物としては、ＴｉＯ_２、Ｂｉ_２Ｏ_３、ＣｕＯ、Ｃｕ_２Ｏ、ＺｎＯ、ＭｏＯ_３、ＩｎＯ_３、Ａｇ_２Ｏ、ＰｂＯ、ＳｒＴｉＯ_３、ＢａＴｉＯ_３、Ｃｏ_３Ｏ_４、Ｆｅ_２Ｏ_３、ＮｉＯなどが挙げられる。また、適用先によっては、金属材を焼成して、金属材表面に光触媒を形成することができる。例えば、Ｔｉ材を１０００℃で焼成し、その表面にＴｉＯ_２を形成することにより光触媒を製造することができる（特開平１１−９０２３６号）。また、上記の光触媒材料に、Ｐｔ、Ａｇ、Ｐｄ、ＲｕＯ_２、Ｃｏ_３Ｏ_４のような物質を添加して使用すると、光触媒によるＨ．Ｃ．分解作用が促進されるので好ましい。これらの添加剤は一種又は複数種を組み合わせて用いることができる。添加量は、通常、光触媒に対して０．０１〜１０重量％であり、添加物質の種類や要求される性能などにより予備実験を行って適正濃度を適宜選択することができる。また、添加剤の添加方法としては、含浸法、光還元法、スパッタ蒸着法、混練法などの修理の技法を用いることができる。
光触媒の設置形態は、被処理気体の流れる空間中への固定化、気体が流れる流路の壁面への固定化などによることができ、或いは、気体が流れる空間中に浮遊させて用いることもできる。光触媒の固定化は、光触媒を、板状、綿状、線状、ファイバー状、網状、ハニカム状、膜状、シート状或いは繊維状などの適宜の材料にコーティングしたり、或いはこれらの材料で包み込むか若しくは挟み込んでユニット内に固定してもよい。例えば、任意の光触媒材料を、セラミック、金属、フッ素樹脂、ガラス材などに対して、ゾル−ゲル法、焼結法、蒸着法、スパッタリング法などの周知の付加手段を適宜用いて固定化することができる。光触媒を固定化する材料としては、一般に、繊維状、網状、ハニカム状の形状が、圧力損失が少ないので好ましい。例えば、ガラス繊維へＴｉＯ_２をゾル−ゲル法によって付加したものや、光透過性線状物品の表面に光触媒を付加したもの（特開平７−２５６０８９号）などを、本発明における気体中の化学汚染物質除去用手段として用いることができる。
本発明において、光触媒に光照射を行う光源としては、光触媒への光照射によって光触媒が光触媒作用を奏することのできるものであればいずれでもよく、周知の光源を用いることができる。即ち、光触媒作用によるＨ．Ｃ．の分解は、光触媒の種類により定められる光吸収波長域の光を光触媒に照射しながら被処理気体を光触媒に接触させることによって行うことができる。
各種光触媒材料の主たる光吸収波長域は次の通りである。
Ｓｉ：＜１，１００（ｎｍ）；Ｇｅ：＜１，８２５（ｎｍ）；Ｓｅ：＜５９０（ｎｍ）；ＡｌＡｓ：＜５１７（ｎｍ）；ＡｌＳｂ：＜８２７（ｎｍ）；ＧａＡｓ：＜８８６（ｎｍ）；ＩｎＰ：＜９９２（ｎｍ）；ＩｎＳｂ：＜６，８８８（ｎｍ）；ＩｎＡｓ：＜３，７５７（ｎｍ）；ＣｄＳ：＜５２０（ｎｍ）；ＣｄＳｅ：＜７３０（ｎｍ）；ＭｏＳ_２：＜５８５（ｎｍ）；ＺｎＳ：＜３３５（ｎｍ）；ＴｉＯ_２：＜４１５（ｎｍ）；ＺｎＯ：＜４００（ｎｍ）；Ｃｕ_２Ｏ：＜６２５（ｎｍ）；ＰｂＯ：＜５４０（ｎｍ）；Ｂｉ_２Ｏ_３：＜３９０（ｎｍ）。
光触媒への照射を行うために用いる光源は、光触媒の光吸収域の波長を持つものであればよく、周知のものを適宜使用することができ、例えば、太陽光、紫外線ランプなどを用いることができる。紫外線源としては、通常、水銀灯、水素放電管、キセノン放電管、ライマン放電管などを適宜使用することができる。光源の具体的な形態としては、殺菌ランプ、ブラックライト、蛍光ケミカルランプ、ＵＶ−Ｂ紫外線ランプ、キセノンランプなどを用いることができる。この中で、殺菌ランプ（主波長２５４ｎｍ）は、光触媒への有効照射光量を強くすることができるので光触媒作用が強くなること、オゾンレスであること、簡単に取り付けができること、安価で保守・管理・維持が容易であること、性能が高いこと、などの理由で特に好ましく用いることができる。光触媒への照射量は、一般に０．０５〜５０ｍＷ／ｃｍ^２であり、０．１〜１０ｍＷ／ｃｍ^２が好ましい。
Ｈ．Ｃ．は、吸着材、例えば活性炭の使用によっても捕集することができるが、吸着材を使用した場合には、吸着容量と破過の問題がある。即ち、発生ガス濃度が高いと、短時間で吸着容量が飽和するので、交換などの手間がかかり、また、破過による捕集物流出による二次汚染の問題がある。これに対して、光触媒はＨ．Ｃ．の堆積がなく、長時間安定してＨ．Ｃ．を分解することができるので、本発明において、Ｈ．Ｃ．などの化学汚染物質の除去手段として極めて好ましく用いることができる。
次に、本発明において、負イオンの生成に重要な水分濃度について説明する。
気体中の水分は、本発明の負イオン生成メカニズムにおいて重要な役割をなす。従って、気体中の水分濃度を制御することによって、基板の酸化抑制に効果的な負イオンが効率よく得られる。
特に光電子法及び放電法による負イオンの生成メカニズムは、発生した電子が電子親和性の大きい水分子や酸素分子との電子付着又はクラスタリングによって、Ｏ_２ ⁻（Ｈ_２Ｏ）_ｎ、Ｏ⁻（Ｈ_２Ｏ）_ｎ、ＯＨ⁻（Ｈ_２Ｏ）_ｎなどの負イオンクラスタを形成することによると考えられる。これらの反応を次に示す。
Ｏ_２ ＋ ｅ⁻ → Ｏ_２ ⁻
Ｏ_２ ⁻ ＋ Ｈ_２Ｏ → Ｏ_２ ⁻（Ｈ_２Ｏ）
・
・
・
Ｏ_２ ⁻（Ｈ_２Ｏ）_ｎ−１ ＋ Ｈ_２Ｏ → Ｏ_２ ⁻（Ｈ_２Ｏ）_ｎ
上記の式から分かるように、電子により電荷を受けた水分は負イオンとなる。従って、気体中の水分濃度に対応した電子供給がある場合には水分濃度の制御は不要である。しかしながら、発生電子の濃度が少ない場合には、ウエハにとって有害な所謂酸化作用を有する水分が放出されることになり、ウエハに悪影響を及ぼす。このような有害水分の存在は、雰囲気に曝露したウエハ表面の酸化状態、例えば自然酸化膜の形成状況などを調べることによって把握することができる。このようにして有害な水分の存在が検出される場合には、適宜の濃度まで除湿を行うことが好ましい。有害水分除去を目的とした除湿の場合には、気体の相対湿度を４５±５％程度まで、好ましくは３０％以下、より好ましくは２０％以下まで除湿することが好ましい。気体の除湿は周知の方法を適宜用いることができ、本発明においては一般に負イオン発生の前に行うことが好ましい。
本発明で用いることのできる除湿手段としては、冷却式、吸着式、吸収式、圧縮式、膜分離式などの周知の方式のものを使用することができ、本発明の適用分や、装置の規模、形状、使用条件、例えば大気圧下か加圧下かなどの条件によって適宜予備試験を行い、上記の１種類又は２種類以上を組み合わせて用いることができる。なお、除湿手段は、通常、数ヶ月〜半年以上の長期間に亘って安定した除湿性能が維持されるものを用いることが好ましく、特に、冷却式、吸着式又は膜分離式のものが簡易で効果的である。冷却式の除湿手段としては、電子除湿方式、冷却コイル方式などがコンパクト構造で効果的なことから好ましく、また吸着式の除湿手段としては、除湿と除湿器自体の再生を行いながら長期間連続して除湿する方式（固定式、回転式）が簡易で効果的であることから好ましい。吸着式除湿手段において用いることのできる除湿材料としては、シリカゲル、ゼオライト、活性炭、活性アルミナ、過塩素酸マグネシウム、塩化カルシウム、アルミナ架橋粘土多孔体、構造状活性炭、多孔質リン酸アルミニウムなどを挙げることができる。なお、アルミナ架橋粘土多孔体とは、層状ケイ酸塩層間の交換性カチオンをアルミニウムを含む多核金属水酸化イオンで交換し、これを加熱脱水したものである。また、構造状活性炭とは、ポリビニルホルマールを炭化処理し、８５０℃以下の温度で賦活して得られるものである。多孔質リン酸アルミニウムは、所謂モレキュラーシーブと称されるもので、水酸化アルミニウム、ベーマイト、擬ベーマイトなどのアルミナ水和物とリン酸とを、トリプロピルアミンのような有機塩基などの熱解離性テンプレート剤を用いて反応させて得られるものである。
また、水破砕による負イオン発生法においては、水破砕（噴霧）により所謂水ミストが生成するので、エリミネータ、加熱コイルなどの周知の除湿手段を用いて有害な水分を除去することが必要である。
上記の除湿は、通常、気体中の電子量が空間で測定した電流値として０．１ＰＡ以下の場合に行うが、逆にこの値が０．１ＰＡ以上である場合には、気体への加湿を行ってより多くの水分子が付加した負イオンを生成させることが好ましい。加湿は、水分のヒーターによる加熱、気化、超音波による噴霧、膜による供給など、当該技術において周知の手段によって行うことができる。なお、加湿によって気体に水分を添加する場合には、負イオン生成に関与しなかった余剰の水分は、上記のようにエリミネータや加熱コイル等の除湿手段によって除去することが好ましい。
上述のように、適宜加湿手段及び除湿手段を適用して、適正な水分濃度で酸化抑制に効果的な負イオン富化気体を形成することができる。即ち、水分濃度を適正に制御することにより、適正な量の水分を負イオン源として有効に利用することができる。
なお、負イオンを発生させて負イオン富化気体を形成するための気体として、Ｎ_２やＡｒのような不活性気体を用いることができるが、これらの不活性気体は一般に乾燥しており、このままでは負イオン発生を効率的に行うことができないので、上記の加湿手段によって水分の添加を行うことが好ましい。どの程度の量の水分添加を行うかについては、負イオン発生法、要求される仕様等により適宜予備試験を行って定めることができる。
次に、本発明に係る半導体製造装置の幾つかの具体的態様を図面を参照しながら説明する。
図１は、半導体工場（クリーンルーム、クラス１０，０００）における半導体基板上での特定プロセス工程を示す。本発明は、図１に示す各特定プロセス処理において適用することができる。即ち、本発明に係る半導体製造装置は、以下に説明するような負イオン富化気体調整装置と、該装置によって調整された負イオン富化気体を図１に示される各種特定プロセス工程の半導体処理装置において基板表面に供給する供給手段とによって構成される。例えば、以下に説明する「負イオン富化気体調整装置」と「調整された負イオン富化気体を基板表面に供給する供給手段」とを備えた装置を、図１に示す「基板の清浄化と乾燥」の工程で用いることのできる「気体を基板に吹き付けて基板表面を空気洗浄及び乾燥する装置」と組み合わせることにより、基板の酸化を抑制しながら基板の清浄化・乾燥を行うことができる。
図２には、吸着材による化学汚染物質除去手段とフィルタによる微粒子除去手段とからなる清浄気体調整装置と、放電法による負イオン発生装置とにより構成される、本発明の一態様に係る負イオン富化気体調整装置の概略構成図を示す。かかる装置により、クラス１０以下で、化学汚染成分が含まれない負イオン富化空気（負イオン数１００，０００個／ｍＬ以上）が調整される。図１に示す各特定プロセス処理を、半導体基板表面に本実施例で調整された負イオン富化空気を曝露しながら行うことにより、半導体基板の汚染防止が図られる。
図２に示す負イオン富化空気調整装置Ａは、クリーンルーム空気送気のためのファン２０、クリーンルーム空気中の化学汚染物除去のための吸着材（イオン交換繊維及び活性炭）２１、クリーンルーム空気（クラス１０，０００）中の微粒子及びファン２０から発生する微粒子を除去するための除塵フィルタ（ＵＬＰＡフィルタ）２２、負イオンを発生するための放電部（コロナ放電）２３、放電部２３から発生するＯ_３を除去するためのＯ_３分解・除去材２４により構成される。図中、２５−１は、ファン２０によって負イオン富化気体調整装置Ａに導入される空気の流れを示し、２５−２は負イオン富化気体調整装置Ａによって調整された負イオン富化気体の流れを示し、２６は負イオンを示す。図２の放電部２３において、２３−１は針状の放電電極、２３−２は対向電極を示す。
図２に示す負イオン富化気体調整装置Ａによれば、ファンによって導入されるクリーンルーム空気（微粒子濃度がクラス１０，０００で、負イオン濃度は１００個／ｍＬ以下である）が、まず、化学汚染物除去吸着材２１及び微粒子除去フィルタ２２を通って、微粒子濃度がクラス１０以下、イオン成分濃度及び有機物濃度がいずれも２μｇ／ｍ^３以下に清浄化される。次に、放電法による負イオン発生装置２３によって負イオンの発生が行われ、発生したオゾンをオゾン分解・除去材２４によって除去することにより、負イオン濃度が１００，０００個／ｍＬ以上、微粒子濃度がクラス１０以下、イオン成分濃度及び有機物濃度がいずれも２μｇ／ｍ^３以下、オゾン濃度が０．０１ｐｐｍ以下のクリーンな負イオン富化気体が提供される。この負イオン富化気体を、図１の各種プロセス工程において基板曝露用の気体として用いることにより、基板の酸化抑制と共に、微粒子汚染と化学汚染が防止された半導体製造処理を行うことができる。
図３は、吸着材／微粒子除去フィルタによる清浄気体調整装置と、光電子法による負イオン発生装置とにより構成される、本発明の他の態様に係る負イオン富化気体調整装置の概略構成図を示す。図３において、図２と同様の構成部材については、同じ参照番号で示し、説明を省略する。
図３に示す負イオン富化空気調整装置Ａは、化学汚染物除去吸着材２１と、微粒子除去フィルタ２２とにより構成される清浄化装置と、光電子放出材２７、紫外線ランプ２８、電場形成用電極２９により構成される負イオン発生装置とを具備する。図３に示す負イオン富化気体調整装置Ａによれば、ファンによって導入されるクリーンルーム空気が、化学汚染物除去吸着材２１及び微粒子除去フィルタ２２を通って、微粒子濃度がクラス１０以下、イオン成分濃度及び有機物濃度がいずれも２μｇ／ｍ^３以下に清浄化された後、負イオン発生装置に導入され、ここで光電子放出材２７に紫外線を照射することによって光電子が放出される。これによって、負イオン濃度が１０，０００個／ｍＬ以上、微粒子濃度がクラス１０以下、イオン成分濃度及び有機物濃度がいずれも２μｇ／ｍ^３以下のクリーンな負イオン富化気体が提供される。なお、光電子法によればオゾンの発生がないので、図２に示されるようなオゾン除去材は通常は必要ない。図３の負イオン富化気体調整装置Ａによって調整された負イオン富化気体を、図１の各種プロセス工程において基板曝露用の気体として用いることにより、基板の酸化抑制と共に、微粒子汚染と化学汚染が防止された半導体製造処理を行うことができる。
図４は、吸着材による化学汚染物質除去手段と光電子法による微粒子除去手段とからなる清浄気体調整装置と、図３と同様の光電子法による負イオン発生装置とにより構成される、本発明の他の態様に係る負イオン富化気体調整装置の概略構成図を示す。図４において、図３と同様の構成部材については同じ参照番号で示す。
図４に示す負イオン富化気体調整装置Ａは、化学汚染物除去吸着材２１と；光電子放出材４１、紫外線ランプ４２、電場形成用電極４３及び荷電微粒子捕集材４４により構成される微粒子除去手段；とからなる清浄気体調整装置と、光電子放出材２７、紫外線ランプ２８、電場形成用電極２９により構成される負イオン発生装置とを具備する。図４に示す負イオン富化気体調整装置Ａによれば、ファンによって導入されるクリーンルーム空気は、まず化学汚染物除去吸着材２１を通って、気体中の化学汚染物質が除去される。次に気体は、光電子法による微粒子除去手段に導入され、ここで光電子放出材４１に紫外線が照射されることによって光電子が発生され、この光電子によって負イオンが発生する。そして発生した負イオンにより、気体中の微粒子が荷電する。荷電した微粒子は、後段の荷電微粒子捕集材４４によって捕集・除去される。この結果、微粒子濃度がクラス１００以下、イオン成分濃度及び有機物濃度がいずれも２μｇ／ｍ^３以下に清浄化された気体が形成され、この清浄気体が負イオン発生装置に導入され、ここで光電子放出材２７に紫外線を照射することによって光電子が放出される。これによって、負イオン濃度が５，０００個／ｍＬ以上、微粒子濃度がクラス１００以下、イオン成分濃度及び有機物濃度がいずれも２μｇ／ｍ^３以下のクリーンな負イオン富化気体が提供される。図４の負イオン富化気体調整装置Ａによって調整された負イオン富化気体を、図１の各種プロセス工程において基板曝露用の気体として用いることにより、基板の酸化抑制と共に、微粒子汚染と化学汚染が防止された半導体製造処理を行うことができる。
図５は、吸着材／微粒子除去フィルタによる清浄気体調整装置と、水破砕法による負イオン発生装置とにより構成される、本発明の他の態様に係る負イオン富化気体調整装置の概略構成図を示す。図５において、図２と同様の構成部材については、同じ参照番号で示し、説明を省略する。
図５に示す負イオン富化空気調整装置Ａは、化学汚染物除去吸着材２１と、微粒子除去フィルタ２２とにより構成される清浄化装置と、水破砕ノズル３３、余剰水除去用エリミネータ３４、水供給用水槽３１により構成される負イオン発生装置とを具備する。図５に示す負イオン富化気体調整装置Ａによれば、ファンによって導入されるクリーンルーム空気が、化学汚染物除去吸着材２１及び微粒子除去フィルタ２２を通って、微粒子濃度がクラス１０以下、イオン成分濃度及び有機物濃度がいずれも２μｇ／ｍ^３以下に清浄化された後、負イオン発生装置に導入され、ここで、水供給用水槽３１の水を熱交換器３２を経由して水破砕ノズル３３から高圧で噴霧することによって負イオンが形成される。形成された負イオン富化気体は、余剰の水分を含んでいるので、エリミネータ３４によって余剰水分を除去し、再熱ヒーター３５によって所望の温度に加熱される。これによって、負イオン濃度が２００，０００個／ｍＬ〜３００，０００個／ｍＬ、微粒子濃度がクラス１０以下、イオン成分濃度及び有機物濃度がいずれも２μｇ／ｍ^３以下のクリーンな負イオン富化気体が提供される。エリミネータ３４で捕集された余剰の水分は、水供給用水槽３１に収容され、水破砕ノズル３３で再利用される。なお、上述したように、光電子法によればオゾンの発生がないので、図２に示されるようなオゾン除去材は通常は必要ない。図３の負イオン富化気体調整装置Ａによって調整された負イオン富化気体を、図１の各種プロセス工程において基板曝露用の気体として用いることにより、基板の酸化抑制と共に、微粒子汚染と化学汚染が防止された半導体製造処理を行うことができる。
なお、水破砕による負イオン発生法においては、条件によって負イオンと共に１０〜２０％程度の正イオンが発生する場合がある。通常は、水破砕法によれば大量の負イオンが発生するので、２０％程度の正イオンが発生しても負イオンによって中和されるので特に正イオン除去手段は必要ないが、場合によっては、再熱ヒーター３５の更に下流に負電極を配置して、正イオンを捕集・除去することが望ましい場合がある。
図６は、吸着材／微粒子除去フィルタによる清浄気体調整装置と、Ｘ線照射による負イオン発生装置とにより構成される、本発明の他の態様に係る負イオン富化気体調整装置の概略構成図を示す。図６において、図２と同様の構成部材については、同じ参照番号で示し、説明を省略する。
図６に示す負イオン富化空気調整装置Ａは、化学汚染物除去吸着材２１と、微粒子除去フィルタ２２とにより構成される清浄化装置と、極微弱Ｘ線（軟Ｘ線：波長０．２〜０．３ｎｍ）発生装置３６により構成される負イオン発生装置とを具備する。図６に示す負イオン富化気体調整装置Ａによれば、ファンによって導入されるクリーンルーム空気が、化学汚染物除去吸着材２１及び微粒子除去フィルタ２２を通って、微粒子濃度がクラス１０以下、イオン成分濃度及び有機物濃度がいずれも２μｇ／ｍ^３以下に清浄化された後、負イオン発生装置に導入され、ここで気体にＸ線を照射することにより、気体分子がイオン化して負イオンが発生する。図６中、ＢはＸ線照射によるガス分子のイオン化部を示す。気体にＸ線を照射すると、負イオンと正イオンとが生成するが、正イオンは負電極３７によって除去される。これによって、負イオン濃度が１００，０００個／ｍＬ以上、微粒子濃度がクラス１０以下、イオン成分濃度及び有機物濃度がいずれも２μｇ／ｍ^３以下のクリーンな負イオン富化気体が提供される。図６の負イオン富化気体調整装置Ａによって調整された負イオン富化気体を、図１の各種プロセス工程において基板曝露用の気体として用いることにより、基板の酸化抑制と共に、微粒子汚染と化学汚染が防止された半導体製造処理を行うことができる。
なお、気体にＸ線を照射して負イオンを発生させる際に、照射条件等によって微量のオゾンが発生する場合がある。このようにオゾンが発生する恐れがある場合には、図７に示すように、正イオン除去用の負電極３７の更に下流に、オゾン分解・除去材２４を配置して、極微量のオゾンが発生しても分解除去できるようにすることが好ましい。これにより、負イオン濃度が１００，０００個／ｍＬ以上、微粒子濃度がクラス１０以下、イオン成分濃度及び有機物濃度がいずれも２μｇ／ｍ^３以下で、且つオゾン濃度が０．０１ｐｐｍ以下のクリーンな負イオン富化気体が提供され、この気体を図１の各種プロセス工程において基板曝露用の気体として用いることにより、基板の酸化抑制と共に、微粒子汚染と化学汚染が防止された半導体製造処理を行うことができる。
実施例
図２〜７に示す本発明の各種態様に係る負イオン富化気体調整装置を用いて負イオン富化気体を調整した。各装置は以下の構成のものを用いた。
▲１▼負イオン富化気体調整装置１：図２に示す構成の装置（サイズ約３０Ｌ）
−吸着材２０：イオン交換繊維：活性炭（１：１）の混床材
−除塵フィルタ２１：ＵＬＰＡフィルタ
−放電部：３０ｋＶを電極間に印加
−Ｏ_３分解・除去材：ＭｎＯ_２／ＴｉＯ_２−Ｃ
▲２▼負イオン富化気体調整装置２：図３に示す構成の装置（サイズ約３０Ｌ）
−吸着材２０及び除塵フィルタ２１は上記▲１▼と同じ
−紫外線ランプ２８：殺菌灯（４Ｗ）
−光電子放出材２７：ＴｉＯ_２上にＡｕを薄膜状に被覆したもの
−電極２９：ＳＵＳ製の網状電極を図３のようにランプ上方に設置した；電界１０Ｖ／ｃｍ
▲３▼負イオン富化気体調整装置３：図４に示す構成の装置（サイズ約４０Ｌ）
−吸着材２０は上記▲１▼と同じ
−光電子放出材２７及び４１、紫外線ランプ２８及び４２、電極２９及び４３は上記▲２▼と同じ
−荷電微粒子捕集材：板状Ｃｕ−Ｚｎ；
▲４▼負イオン富化気体調整装置４：図５に示す構成の装置（サイズ約２００Ｌ）
−吸着材２０及びフィルタ２１は上記▲１▼と同じ
−水噴霧装置：水破砕ノズル３３にイオン交換水３Ｌ／ｍｉｎを水圧３５０ｋＰａ、水空気比（Ｌ／Ｇ）＝１で供給して噴霧した
−再熱ヒーター：再熱コイルで生成水滴を気化した
▲５▼負イオン富化気体調整装置５：図６に示す構成の装置（サイズ約３０Ｌ）
−吸着材２０及びフィルタ２１は上記▲１▼と同じ
−Ｘ線発生装置３６：波長０．２〜０．３ｎｍ；
−負電極３７：板状Ｃｕ−Ｚｎ；
上記の負イオン富化気体調整装置１〜３、５に、クリーンルーム空気（微粒子濃度クラス１０，０００、有機物濃度１００〜１２０μｇ／ｍ^３、ＮＨ_３濃度１５〜２０μｇ／ｍ^３）を流速３Ｌ／ｍｉｎで供給した。また、上記の負イオン富化気体調整装置４には、同様のクリーンルーム空気を流速３０Ｌ／ｍｉｎで供給した。負イオン富化気体調整装置１〜５のそれぞれから得られた空気の性状を下表２に示す。

なお、装置▲１▼により得られた負イオン富化気体中のＯ_３濃度は、０．０１ｐｐｍ以下であった。
上記の負イオン富化気体調整装置１〜５で得られた負イオン富化気体を、Ｓｉウエハ表面に曝露して、酸化膜の生成状況を観察した。Ｓｉウエハとして、高分解能ＸＰＳ：Ｓｃｉｅｎｔａ製、ＥＳＣＡ３００型を用い、ＲＣＡで洗浄した後、ＨＦ（０．０５％）処理を行って純水リンス、乾燥したものをウエハ試料として用いた。このウエハ試料の表面に、上記の負イオン富化気体調整装置１〜５で得られた負イオン富化気体を流速３Ｌ／ｍｉｎで吹きつけて、所定時間経過後に、試料表面に形成された酸化膜の膜厚を測定した。結果を下表３に示す。また、比較例として、クリーンルーム空気をそのまま用いて、同じウエハ試料の表面に曝露した。結果を同様に下表３に示す。

次に、負イオン富化気体調整装置１を用い、処理条件を変化させることによって調整気体中の負イオンの濃度を約５００、約１，０００、約３，０００、約５，０００、約１０，０００、約３０，０００、約５０，０００個／ｍＬに調整し、同様にウエハ試料表面への暴露（暴露時間１２時間）して、酸化膜生成抑制に効果的な負イオンの濃度を調べた。負イオン濃度が１，０００個／ｍＬ以上で酸化膜厚が＜０．１Åであり効果が認められ、５，０００個／ｍＬ以上で＜０．０５Åであり顕著な効果が認められた。また１０，０００個／ｍＬ以上で＜０．０２Åであり特に顕著な効果が認められた。
産業上の利用の可能性
以上の知見により、本発明によれば次のような効果を奏することができることが認められた。
（１）半導体製造工程の空間中に負イオン富化気体を供給することによって、基板の酸化を抑制しながら基板の各種加工を行うことができる。
（２）負イオン富化気体を調整するに当たって、微粒子や化学汚染物質を除去することによって、微粒子、化学成分を含まないクリーンな負イオン富化気体が得られるので、汚染に対して安定な（汚染防止機能を有する）気体が調整される。
（３）負イオン富化気体を調整するに当たって、微粒子や化学汚染物質を除去した気体を用いることにより、発生した負イオンが微粒子などの汚染物質によって消費されてしまうのを防ぐことができる。
（４）現在においては、基板の汚染原因は主として微粒子や化学汚染物によるものであるが、今後はこれらの汚染物に加えて基板表面の酸化抑制が重要になる。本発明によれば、基板表面の酸化抑制作用をも併せ持つ清浄気体が得られる。
（５）本発明の適用先の装置規模、求められる負イオン発生量、求められる酸化抑制効果などの要求される仕様により、好適な負イオン発生方法を選択することができる（表１参照）ので、より実用上状的な汚染防止用気体を提供することができる。
【図面の簡単な説明】
図１は、半導体工場（クリーンルーム）における半導体基板上での特定処理の内容を示す工程図である。
図２は、本発明において用いる負イオン富化気体を得るための装置の一例を示す概略構成図である。
図３は、本発明において用いる負イオン富化気体を得るための装置の他の例を示す概略構成図である。
図４は、本発明において用いる負イオン富化気体を得るための装置の他の例を示す概略構成図である。
図５は、本発明において用いる負イオン富化気体を得るための装置の他の例を示す概略構成図である。
図６は、本発明において用いる負イオン富化気体を得るための装置の他の例を示す概略構成図である。
図７は、本発明において用いる負イオン富化気体を得るための装置の他の例を示す概略構成図である。
図８は、従来の半導体工場（クリーンルーム）において汎用されている空気清浄システムを示す概略構成図である。Technical field
The present invention relates to semiconductor manufacturing, and more particularly, to a semiconductor manufacturing method and apparatus in advanced industries such as semiconductors and liquid crystals.
Background art
Semiconductor manufacturing is usually performed in a space called an “clean room” in which the air environment is adjusted, and air cleaning in a work environment is extremely important. A conventional air cleaning technique in a semiconductor factory (clean room) will be described with reference to FIG.
In FIG. 8, the outside air 1 first passes through the prefilter 2, where coarse particles are removed, and then the temperature and humidity are adjusted in the air conditioner 3, and dust is removed by the medium performance filter 4. Next, fine particles are removed by the HEPA filter 6 installed on the ceiling of the clean room 5. By such an air cleaning device, the fine particle concentration class 10,000 is maintained in the clean room. In FIG. 8, reference numerals 7-1 and 7-2 denote fans, and arrows indicate the flow of air.
The conventional air cleaning in the clean room is intended to remove particulates, and thus is configured as shown in FIG. 8, but this configuration is effective for removing particulates, but it is effective for removing gaseous harmful components. Has no effect.
By the way, in recent years, in the semiconductor industry, the quality and precision of products have been increasing, and along with this, fine particles (particulate matter) are naturally involved as gaseous contaminants. It was.
However, the conventional clean room dust removal filter (eg, HEPA filter, ULPA filter, etc.) as shown in FIG. 8 can remove only fine particles, and gaseous harmful components from the outside air are not removed but introduced into the clean room. End up. Examples of such gaseous harmful components include hydrocarbons (HC) resulting from, for example, automobile exhaust gas, degassing (gas generation) from polymer resin products widely used as consumer products, and the like. Called gas, NH₃And basic (alkaline) gases such as amines.
Of these, hydrocarbons (HC) cause contamination even at extremely low concentrations in normal air (room air and outside air) as gaseous harmful components, and thus must be completely removed. Recently, degassing of clean room components, production equipment, and polymer resins used as tools has become a problem as a source of hydrocarbons (HC).
These gaseous substances are also problematic when they are generated during work in a clean room. That is, in the normal clean room, in addition to the gaseous substance introduced from the outside air as a cause of the generation of gaseous substances (those that cannot be removed by the clean room particulate removal filter and are introduced into the clean room from the outside air). Since the gaseous substance generated in the clean room is added, the gaseous substance in the clean room has a higher concentration than the outside air, and the possibility of contaminating the semiconductor substrate is increased.
When the particulate contaminants adhere to the surface of the semiconductor substrate, the circuit (pattern) on the substrate surface is disconnected or short-circuited, resulting in a defect. Further, when gaseous harmful components, particularly hydrocarbons (HC) adhere to the surface of the semiconductor substrate, the contact angle is increased, and for example, the affinity (compatibility) between the substrate and the resist is adversely affected. If the affinity between the substrate and the resist deteriorates, the film thickness of the resist and the adhesion between the substrate and the resist are adversely affected. In addition, hydrocarbons (HC) also have a problem of causing a breakdown voltage deterioration (reduction in reliability) of the oxide film on the surface of the semiconductor substrate. The contact angle is a contact angle of wetting with water and is an index indicating the degree of contamination of the substrate surface. That is, when hydrophobic (oil-based) contaminants adhere to the substrate surface, the surface repels water and becomes difficult to get wet. Then, the contact angle with water droplets on the substrate surface increases. Therefore, when the contact angle is large, the degree of contamination is high, and when the contact angle is small, the degree of contamination is low. NH₃Causes the formation of ammonium salt and the like, and causes clouding (defective resolution) in the semiconductor substrate.
For these reasons, the above-mentioned gaseous pollutants as well as fine particles lower the productivity (yield) of semiconductor products.
In particular, the above-mentioned gaseous substances as gaseous harmful components are generated due to the above-mentioned causes of occurrence, and recently, since the circulation of clean room air is increased from the viewpoint of energy saving, the concentration of gaseous substances in the clean room Is concentrated and has a considerably higher concentration than the outside air, and adheres to the substrate and contaminates its surface.
As countermeasures against these contaminations, the present inventors have proposed methods for cleaning various spaces using photoelectrons and photocatalysts.
For example, as a method for removing particulate matter by photoelectrons, the methods described in Japanese Patent Publication No. 3-5859, Japanese Patent Publication No. 6-74909, Japanese Patent Publication No. 8-211, and Japanese Patent Publication No. 7-121367. Can be mentioned. Examples of the method for removing gaseous harmful components using a photocatalyst include the methods described in Japanese Patent Nos. 2863419 and 2991963. Furthermore, as a method for simultaneously removing fine particles and gaseous substances by using a photoelectron and a photocatalyst together, a method described in Japanese Patent No. 2623290 may be mentioned.
By the way, if the quality of semiconductor products is improved (microfabricated products) in the future, the pattern on the wafer surface will be limited by the current Al wiring, so it will be converted to Cu wiring in the future. In other words, with the reduction of wiring and design rules in future ultra-large scale integrated circuits (ULSI), the current Al wiring and SiO₂In the combination of insulating films, the wiring delay time becomes long, so it will be necessary in the future to shorten the delay time using Cu wiring and a low dielectric constant interlayer insulating film (Low-K). In this case, the Cu material is more susceptible to oxidation than conventional Al and W. In other words, in the past, it was sufficient to pay attention only to the removal of fine particles in the semiconductor manufacturing environment. However, in the future, control of gaseous substances, especially substances that oxidize the wafer surface (wiring surface and interface) will become important. Come.
As substances that promote the oxidation of the wafer surface, moisture and organic substances (HC) in clean room air can be considered, and moisture is present in the clean room air in an amount of about 45 to 50% (RH). Control is difficult. This is because a person is working in a clean room, and if moisture in the air is reduced too much, it may adversely affect the health of the worker.
For this reason, moisture and H. C. The emergence of a new method for controlling (suppressing) the oxidation of the wafer surface by controlling the substance including the material is desired.
In view of the above circumstances, the present invention controls the oxidation of the wafer surface with simple means, and can comprehensively control the contaminants that promote the oxidation and the contaminants that reduce the yield of the wafer. It is an object to provide a manufacturing method and apparatus.
Disclosure of the invention
In order to solve the above problems, the present invention provides a semiconductor characterized in that a semiconductor substrate is processed while using a negative ion-enriched gas obtained by a negative ion generator to suppress oxidation of the substrate surface in a semiconductor manufacturing process. A manufacturing method is provided.
That is, one embodiment of the present invention relates to a method for manufacturing a semiconductor, in which a substrate is processed while a negative ion-enriched gas is exposed to the substrate surface. In the present invention, the negative ion-enriched gas is preferably adjusted by passing a clean gas from which fine particles and / or chemical contaminants have been removed in advance through a negative ion generator. Here, examples of the chemical contaminant include one or more selected from the group consisting of ionic components, inorganic substances, and organic substances. In the present invention, the negative ion enriched gas has a fine particle concentration of class 100 or less and an ion component concentration of 10 μg / m.³Hereinafter, the organic substance concentration is 10 μg / m.³It is preferable to adjust the following gas through a negative ion generator.
In another aspect of the present invention, a gas flow path for passing a gas to be treated; a gas cleaning device disposed in an upstream portion of the gas flow channel; and a negative ion generator disposed in a downstream portion And a supply means for supplying the obtained negative ion-enriched gas to the substrate surface. A semiconductor manufacturing apparatus is provided.
BEST MODE FOR CARRYING OUT THE INVENTION
The present invention has a high degree of cleanliness (that is, a very low concentration of fine particles and chemical contaminants) and a large amount of negative ions during various processing operations of a substrate in any step of a semiconductor manufacturing process in a clean room. By treating the substrate while exposing the substrate to a gas containing it (ie, a negative ion-enriched gas), the oxidation of the substrate during the treatment is suppressed, thereby improving the yield of semiconductor products and withstanding the demand for higher performance. It has been found that a semiconductor product can be manufactured and has been completed.
The negative ion-enriched gas adjustment method according to the method of the present invention is divided into stages of negative ion generation and gas purification before negative ion generation. Each will be described below.
A. Negative ion generation method
The inventors' studies have confirmed that exposure of the negative ion enriched gas to the substrate suppresses oxidation of the substrate surface. Here, the “negative ion” is a substance in which electrons are attached to an electrophilic substance such as oxygen. For example, an oxygen molecule having one or more water molecules added to a negatively charged oxygen molecule.₂ ⁻(H₂O)_nIt refers to small ions such as hydrate ions. Furthermore, CO₃ ⁻(H₂O)_n, NO₂ ⁻(H₂O)_nCO such as_x ⁻, NO_x ⁻Can be considered as “negative ions” according to the present invention. The concentration of negative ions sufficient to suppress the oxidation of the substrate surface varies depending on the application / type of semiconductor, performance required for the semiconductor, coexisting substances, etc., but is generally 1,000 / mL or more, preferably 5 5,000 / mL or more, more preferably 10,000 / mL or more, and even more preferably 50,000 / mL or more. A suitable negative ion concentration can be determined by conducting a preliminary test as appropriate according to the use / type of semiconductor, required performance, coexisting substances, and the like. The reason why the oxidation of the substrate surface is suppressed by the negative ion-enriched gas is not yet well understood, but it is presumably because the negative ions give a reducing action to the surface of the substrate.
In addition, the density | concentration of the negative ion in gas can be measured by flowing ion in an electric field and measuring the electrical mobility of the ion. As such a negative ion concentration measuring device in the gas, a product name: Air ion counter Model 83-1001B manufactured by Dan Kagaku is commercially available.
Examples of means for generating negative ions include a method using photoelectrons proposed by the present inventors (Japanese Patent Publication No. 8-10616, Japanese Patent No. 3139951), a method using electric discharge, a method using water fragmentation, a method using radiation irradiation, and the like. It is done. Hereinafter, various negative ion generation methods will be described.
A-1: Method for generating negative ions by photoelectrons
In the negative ion generation method by photoelectrons, photoelectrons are generated by irradiating the photoelectron emitting material from an ultraviolet light source such as an ultraviolet lamp in the presence of an electric field, and negative ions are formed by the photoelectrons. It is. At this time, an electric field can be formed by disposing an electrode (positive electrode) on the opposite side of the photoelectron emitting material (negative electrode), whereby the generation of photoelectrons from the photoelectron emitting material can be accelerated. Therefore, a negative ion generator using photoelectrons is composed of a photoelectron emitting material, an ultraviolet ray generation source such as an ultraviolet lamp, and an electric field setting electrode in some cases. As supply gas, in addition to air, N₂An inert gas such as can also be used.
Any photoelectron emitting material may be used as long as it emits photoelectrons upon irradiation with ultraviolet rays, and a material having a small photoelectric work function is preferable. From the aspect of effect and economy, Ba, Sr, Ca, Y, Gd, La, Ce, Nd, Th, Pr, Be, Zr, Fe, Ni, Zn, Cu, Ag, Pt, Cd, Pb, Al, Any of C, Mg, Au, In, Bi, Nb, Si, Ti, Ta, U, B, Eu, Sn, P, and W, or a compound, alloy, or mixture thereof is preferable. These may be used alone or in combination of two or more. As the composite material, a physical composite material such as amalgam can also be used.
Examples of the compounds of the above elements include oxides, borides, and carbides. Examples of oxides include BaO, SrO, CaO, and Y.₂O₃, Gd₂O₃, Nd₂O₃, ThO₂, ZrO₂, Fe₂O₃, ZnO, CuO, Ag₂O, La₂O₃, PtO, PbO, Al₂O₃, MgO, In₂O₃, BiO, NbO, BeO and the like, and as the boride, YB₆, GdB₆, LaB₅, CeB₆, EuB₆, PrB₆, ZrB₂Examples of the carbide include UC, ZrC, TaC, TiC, NbC, and WC. The alloys of the above elements include brass, bronze, phosphor bronze, an alloy of Ag and Mg (Mg = 2 to 20 wt%), an alloy of Cu and Be (Be = 1 to 10 wt%), Ba and Al. An alloy of Ag and Mg, an alloy of Cu and Be, and an alloy of Ba and Al can be preferably used. The oxide of the element can also be obtained by heating only the metal surface in the air or oxidizing it with a chemical. Further, by heating the metal or alloy material of the above element before use to form an oxide layer on the surface, a stable oxide layer can be formed over a long period of time, and this can be used as a photoelectron emitting material. For example, by treating an alloy of Mg and Ag in water vapor at a temperature of 300 ° C. to 400 ° C., an oxide film can be formed on the surface, and such an oxide film is stable over a long period of time. It can be used as a photoelectron emitting material for a long time.
Further, another substance can be added to the substance that emits photoelectrons. As an example of this, for example, a material that can emit photoelectrons is added to an ultraviolet light transmissive material such as glass (Japanese Patent Publication No. 7-93098, Japanese Patent Application Laid-Open No. 4-243540).
Also, the photoelectron emitting material is TiO₂It can also be integrated with a photocatalyst such as JP-A-9-294919. In this form, the photocatalyst can remove substances that adversely affect the photoelectron emission material, so that the photoelectron emission material can be stabilized for a long period of time, and coexisting gaseous pollutants can be removed. It is preferable depending on the required performance.
The shape of the photoelectron emitting material can be appropriately selected according to the transmission form of the negative ion generating gas and the type of apparatus, such as a plate shape, a pleat shape, and a net shape. Among these, if a gas is allowed to pass from the back surface to the surface of the reticulated photoelectron emitting material using a reticulated photoelectron emitting material, negative ions can be generated without forming an electric field. preferable. Further, when an irradiation source and a photoelectron emission material, which will be described later, are integrated, the photoelectron emission device becomes compact, so that it can be preferably used depending on the type of device to be applied. This can be done, for example, by adding a photoelectron emitting material to the surface of the ultraviolet lamp.
The irradiation source for emitting photoelectrons from the photoelectron emitting material may be anything as long as it emits photoelectrons from the photoelectron emitting material by irradiation, but generally ultraviolet rays or radiation is preferable (Japanese Patent No. 2623290, Japanese Patent Publication No. 6-74910). Ultraviolet rays are particularly preferable because they are simple and can be used safely.
The ultraviolet ray source that can be used may be any type as long as the photoelectron emitting material emits photoelectrons upon irradiation, and a mercury lamp, for example, a sterilizing lamp, is preferably used from the viewpoint of compactness.
The electric field when photoelectrons are emitted under an electric field is preferably 0.1 V / cm to 1 kV / cm, and can be determined by appropriately conducting preliminary tests depending on the form and structure of the apparatus. The electrode material used for forming the electric field may be any material as long as it does not generate impurities from the electrode material and photoelectrons are effectively generated by the installation of the photoelectron emitting material. The material is SUS material, Cu-Zn. Examples of the shape include a linear shape, a rod shape, a net shape, and a plate shape. By installing these electrode materials so that an electric field is formed in the vicinity of the photoelectron emitting material, photoelectrons can be emitted under an electric field.
A-2: Method for generating negative ions by discharge
In the discharge method, electrons are emitted by discharging in a gas, and negative ions are generated by the electrons. An apparatus constituted by a discharge electrode and a counter electrode is used.
As discharge methods for generating negative ions, methods well known in the art such as corona discharge, glow discharge, arc discharge, spark discharge, creeping discharge, pulse discharge, high frequency discharge, laser discharge, trigger discharge, plasma discharge, etc. Can be used. Among these, creeping discharge and pulse discharge are preferable depending on the application destination in terms of downsizing the apparatus because the concentration of generated negative ions is high. Corona discharge is preferable in terms of simplicity, operability, and effects.
A-3: Method for generating negative ions by water fragmentation
The negative ion generation method by water crushing generates negative ions by the Leonard effect by crushing water. For example, negative ions are generated by spray charging of droplets generated when water is sprayed into the air. be able to. The mechanism of negative ion generation by the Leonard effect is considered as follows. Water molecules are polar molecules that are electrically positively and negatively polarized, and the positive side is oriented outward on the water surface (orientation dipole). Since many negative ions are attracted to the oriented dipole, an electric double layer is formed. When energy such as high pressure is applied to this portion, negatively charged air is formed. That is, since the water surface is positive, the air adjacent to it is negative, and when high pressure is applied to the water to make it finer, negatively ionized air is generated. Next, if necessary, this air is vaporized and evaporated to remove excess coexisting moisture, so that air enriched with negative ions is formed.
A-4: Method for generating negative ions by irradiation
In the radiation irradiation method, negative ions are generated by irradiating air with radiation. As the radiation that can be used in the method, any radiation may be used as long as ions are generated by the radiation source. X-ray irradiation method, α-ray irradiation method, γ-ray irradiation method, β-ray irradiation method Etc. can be used. Among these, from the viewpoint of operability, the X-ray irradiation method, the α-ray irradiation method, and the γ-ray irradiation method are preferable, and the X-ray irradiation method is particularly preferable. The X-ray irradiation method uses ions obtained by irradiating gas molecules with X-rays. Usually, an accelerating electron beam is irradiated onto a metal target, and the obtained X-rays collide with gas molecules to air. The molecule is ionized.
The ionization by soft X-rays that are particularly preferably used in the method of the present invention is considered to be the following mechanism. Air molecules absorb irradiation X-rays, that is, photons (wavelength 0.2 to 0.3 nm) and ionize, that is, photoionize. Since the ionized electrons have high kinetic energy, they are ionized by collision with neutral electrons and molecules. A large amount of ions are generated by the continuous occurrence of ionization due to the electron avalanche phenomenon. Since the ions generated here are both positive ions and negative ions, a gas enriched only with negative ions can be obtained by removing the positive ions with an appropriate well-known means such as an electrode plate.
The photon energy of soft X-rays preferably used in this method is several KeV to 10 KeV or less, which is about 1/10 of the energy of hard X-rays used in X-rays or the like, but can be entered by workers. A shield device is required when irradiation is performed in a sensitive area. The shielding can be performed using, for example, a metal plate having a thickness of about 1 mm or a plastic (for example, vinyl chloride) plate having a thickness of about 2 to 3 mm.
Also by the α-ray irradiation method or the γ-ray irradiation method, a large amount of ions are generated by the same high kinetic energy as described above, and a gas enriched only with negative ions can be obtained by performing the above-described treatment. Note that radioactive materials such as cobalt 60 and cesium 137 can be used as the γ-ray source.
When negative ions are generated by the above discharge method or radiation irradiation method, particularly X-ray irradiation method, ozone (O₃) May occur at the same time. Since ozone is a substance that promotes oxidation of the substrate surface, it must be removed from the gas. In the application of the present invention, it is desirable that the ozone concentration in the gas is 0.1 ppm or less, preferably 0.01 ppm or less, more preferably 1 ppb or less. Therefore, in the discharge method or the radiation irradiation method, for example, O which becomes a generation source of ozone.₂Inert gases such as N₂Is preferably used as a gas, or the formed negative ion-enriched gas is preferably subjected to ozone removal treatment. Further, when gas is humidified after generation of negative ions, decomposition of ozone is promoted by humidification, which may be preferable depending on applications or required specifications.
As a method for removing the generated ozone from the negative ion-enriched gas, the gas after the generation of negative ions is replaced with a well-known O 2.₃Treatment with a treating agent can be mentioned. Well-known O that can be used for this purpose₃Examples of the treating agent include a Mn-based catalyst. O which can be used in the present invention₃As the treating agent, a material and shape having a small decrease in generated negative ions coexisting in the gas is preferable. For example, a manganese dioxide catalyst formed into a honeycomb shape or a net shape, for example, MnO.₂/ TiO₂-C, MnO₂/ ZrO—C or the like can be used.
Table 1 below shows the characteristics of each negative ion generation method. The symbols in the table are relative comparisons for each method, meaning that ○ is good and Δ is slightly inferior.

From the above table, for example, the photoelectron method is inferior in applicability to enlargement, but it is ozone-less and clean negative ion, so it has excellent oxidation suppression effect, and the radiation irradiation method is upsized and downsized Although it is excellent in the negative ion generation amount with good applicability to, it is understood that there is a problem in safety. In the present invention, in consideration of the advantages and problems of the various negative ion generation methods described above, a preferable negative ion generation method can be appropriately employed depending on the application, required performance, and the like.
Among the negative ion generation methods described above, when negative ions are generated by the discharge method and humidification is performed, or when negative ions are generated by the water crushing method, the particle size of the negative ions formed is different from the other methods. It was found to be larger than For example, when the photoelectron method is used or when humidification is not performed by the discharge method, the particle size of the formed negative ions is about 1 nm, but when the negative ions are generated by the discharge method and humidification is performed, When negative ions are generated by the water crushing method, the particle size of the negative ions formed is about 3 to 5 nm. The inventors' research has shown that the larger the negative ion particle size, the more effective the suppression of oxidation of the substrate of the present invention. Although the details of the cause are unknown, it is considered as follows. That is, in the negative ions, the central molecule (for example, oxygen molecule) has a negative charge, and water molecules are adsorbed (attached) around it. The more the number of adsorbed water molecules, the more the substrate is oxidized. Great effect by suppression. Therefore, depending on the application, the scale of the apparatus, and the required specifications, a negative ion generation method using a discharge method with humidification or a water crushing method is preferably used.
In the present invention, the substrate is processed while exposing the substrate to the negative ion-enriched gas thus adjusted. At that time, the application destination of the negative ion-enriched gas, that is, the processing region of the substrate is used. Placing a positive electrode in the direction and attracting negative ions in an electric field is more effective in suppressing oxidation of the substrate. This is because negative ions move at high speed and are consumed depending on the shape and structure of the apparatus.
In the present invention, as described above, negative ions are generated to form a negative ion-enriched gas. However, if contaminants are contained in the gas, the generated negative ions are consumed by the contaminants. End up. For example, when a particulate material is present in the gas, the generated negative ions are transferred to the fine particles to form charged particles, so that negative ions are consumed. For this reason, the density | concentration of the negative ion which should be utilized effectively for the oxidation suppression of a board | substrate will reduce. Further, it is known that the semiconductor substrate is significantly contaminated by the presence of fine particles and chemical contaminants, and the yield is severely lowered. In addition, Cl₂If an acidic gas such as the above remains in the gas, if negative ions are generated for such a gas, Cl₂However, since such negative ions are considered to have an oxidizing power, they do not meet the purpose of “suppression of substrate oxidation” of the present invention. Therefore, it is desirable to perform a negative ion generation process after sufficiently removing such chemical contaminants.
From such a point of view, in the present invention, a gas from which chemical contaminants such as fine particles and ionic components, inorganic substances, and organic substances have been previously removed is passed through the negative ion generator to generate negative ions. Is preferred. Specifically, in the present invention, the gas supplied to the negative ion generator has a fine particle concentration of class (gas 1 ft.³The number of particles in it, the standard particle size 0.1 μm) 100 or less, preferably 10 or less, more preferably 1 or less; the ion component concentration is 10 μg / m³Or less, preferably 5 μg / m³Or less, more preferably 2 μg / m³Below: Organic concentration is 10 μg / m³Or less, preferably 5 μg / m³Or less, more preferably 2 μg / m³The following is preferable. Here, “ion component” means NO._x, SO_x, HCl, HF, Cl₂, F₂, HBr, Br₂As well as alkaline gases such as ammonia and amines.
As described above, in the present invention, it is preferable to subject the gas supplied to the negative ion generator to the contaminant removal process in advance. In the present invention, the contaminant removal process that can be performed as a pre-stage process for generating negative ions is roughly divided into a fine particle removal process and a chemical contaminant removal process. Each will be described below.
B. Particulate removal processing
In the present invention, the gas to be subjected to the negative ion generation treatment preferably collects fine particles in advance up to class 100 or less, preferably 10 or less, more preferably 1 or less, as long as this cleanliness can be achieved. Known fine particle removing means can be used. Examples of the particulate removing means that can be used in the present invention include a method using a filter and a method using photoelectrons separately proposed by the present inventors.
B-1: Particulate removal means using a filter
Examples of filters that can be used as particulate removing means in the present invention include filters well known in the art such as ULPA filters, HEPA filters, medium performance filters, electrostatic filters, and the like, or a combination of one or more of these. Can be used.
B-2: Particulate removal means by photoelectrons
This means is the photoelectron proposed by the present inventors separately in Japanese Patent Publication No. 6-74909, Japanese Patent Publication No. 7-121369, Japanese Patent Publication No. 8-211, Japanese Patent Publication No. 8-22393, Japanese Patent No. 2623290, etc. A method of removing fine particles using This method is similar to the method of generating negative ions using photoelectrons as described above, generating negative ions, charging the fine particles with the generated negative ions, and collecting and removing the charged fine particles using an electrode or the like. To do. That is, the photoelectron particulate removing means that can be used in the present invention is constituted by a photoelectron emitting material, an ultraviolet ray source, an electrode material, and a charged particulate collection material. As the photoelectron emitting material, the ultraviolet light source, and the electrode material, various materials described in the above method for generating negative ions by photoelectrons can be used.
As the collecting material for charged fine particles, various electrode materials and electrostatic filter type materials such as a dust collecting plate and a dust collecting electrode in a normal charging device can be generally used. Those having a wool-like structure can also be used effectively. Moreover, an electret material can also be used conveniently.
A suitable combination of the photoelectron emitting material, the electrode material, and the charged particulate collection material can be appropriately determined according to the shape, structure, required performance, economy, and the like of the space to be cleaned. For example, the position and shape of the photoelectron emitting material and the electrode surround the ultraviolet light source, and the ultraviolet light source, the photoelectron emitting material, the electrode material and the charged particle collecting material can be integrated, and the ultraviolet light emitted from the ultraviolet light source is effective. It can be appropriately determined in consideration of the shape, effect, economy, etc. so that the photoelectrons can be emitted and the fine particles can be charged and collected effectively by the photoelectrons. For example, when a rod-shaped or cylindrical ultraviolet lamp is used as the ultraviolet light source, the ultraviolet light is emitted radially in the circumferential direction of the lamp, and if the circumferential ultraviolet radiation is irradiated to the photoelectron emitting material as much as possible, The amount of photoelectrons emitted increases. Accordingly, it is preferable that a photoelectron emitting material is disposed in the circumferential direction facing the ultraviolet lamp, and an electrode for photoelectron emission is disposed on the facing surface.
C. Removal of ionic components and chemical contaminants
As described above, in the present invention, the gas to be subjected to the negative ion generation treatment is previously Cl.₂, NO_x, SO_xIt is preferable to remove ionic components such as acidic gases such as alkaline gases such as ammonia, and chemical contaminants such as inorganic and organic substances. Specifically, the concentration of ionic components is 10 μg / m 2.³Or less, preferably 5 μg / m³Or less, more preferably 2 μg / m³Below: Organic concentration is 10 μg / m³Or less, preferably 5 μg / m³Or less, more preferably 2 μg / m³The following is preferable. As such contaminant removal means, a method well known in the art can be used. For example, a method using an adsorbent, a method using a photocatalyst, or the like can be used. Hereinafter, each method will be described.
C-1: Means for removing chemical contaminants by adsorbent
In the present invention, the means for removing chemical pollutants by the adsorbent is the NO ion in the process gas when the negative ion enriched gas is generated._x, SO_x, HCl, HF, Cl₂, F₂, HBr, Br₂As an adsorbent, the adsorbent is a material that can adsorb various acid / alkaline gases to low concentrations efficiently. Good. As such an adsorbent, silica gel, zeolite, alumina, activated carbon, ion exchange fiber, and the like are known. Among these, activated carbon and ion exchange fiber are effective, and therefore can be preferably used in the present invention. . In particular, the ion exchange fiber can collect contaminants to a low concentration by a chemical reaction and has a high degree of cleanliness, so that it can be preferably used depending on the application. Moreover, as the activated carbon, an impregnated activated carbon impregnated with an acid or an alkali can be used as appropriate according to the collected components.
The adsorbent can be used in an appropriate shape, but generally, a fibrous or honeycomb shape is preferable because of a small pressure loss.
The ion exchange fiber is made by supporting a cation exchanger, an anion exchanger, or an ion exchanger having both a cation exchange group and an anion exchange group on the surface of a support such as natural fiber, synthetic fiber or a mixture thereof. As a support method, the ion exchanger may be supported directly on a fibrous support, or the ion exchanger is supported on a woven, knitted or flocked substrate formed from fibers. You may let them. As the ion exchange fiber that can be used in the present invention, an ion exchange fiber produced by using a graft polymerization method, particularly a radiation graft polymerization method, is preferably used. This is because according to the radiation graft polymerization method, ion exchange fibers can be formed using materials of various materials and shapes.
As said natural fiber, wool, silk, etc. can be applied, and as a synthetic fiber, what uses a hydrocarbon polymer as a raw material, what uses a fluorine-containing polymer as a raw material, or polyvinyl alcohol, polyamide, Polyester, polyacrylonitrile, cellulose, cellulose acetate and the like can be applied. Examples of the hydrocarbon polymer include aliphatic polymers such as polyethylene, polypropylene, polyisobutylene, and polybutene, aromatic polymers such as polystyrene and poly α-methylstyrene, and alicyclic polymers such as polyvinylcyclohexane. Alternatively, these copolymers are used. Examples of the fluorine-containing polymer include polytetrafluoroethylene, polyvinylidene fluoride, ethylene-tetrafluoroethylene copolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and vinylidene fluoride-6-fluoride. Propylene copolymer or the like is used. For any material, the support for the ion exchanger has a large contact area with the gas flow, a shape with low resistance, can be easily grafted, has high mechanical strength, and is free from fiber waste. It is suitable if it is a material that has little dropout and generation and is less affected by heat, and can be appropriately selected by those skilled in the art in consideration of the intended use, economy, effects, etc. These composite materials are generally preferably used.
The ion exchanger that can be introduced into these materials is not particularly limited, and various cation exchangers or anion exchangers can be used. For example, a cation exchange group-containing product such as a carboxyl group, a sulfonic acid group, a phosphoric acid group, or a phenolic hydroxyl group; an anion exchange group-containing product such as a primary to tertiary amino group or a quaternary ammonium group; or the above cation An ion exchanger having both an exchange group and an anion exchange group can be used. Specifically, on the fiber material, for example, acrylic acid, methacrylic acid, vinylbenzenesulfonic acid, styrene, halomethylstyrene, acyloxystyrene, hydroxystyrene, aminostyrene, and other styrene compounds, vinylpyridine, 2-methyl- After graft polymerization of 5-vinylpyridine, 2-methyl-5-vinylimidazole, acrylonitrile, etc., and having a cation exchange group or anion exchange group by reacting with chlorosulfonic acid sulfate, sulfonic acid, etc. as required A fibrous ion exchanger is obtained. Further, the above monomer may be graft-polymerized on a fiber in the presence of a monomer having two or more double bonds such as divinylbenzene, trivinylbenzene, butadiene, ethylene glycol, divinyl ether, and ethylene glycol dimethacrylate. Good.
In the present invention, the fiber diameter of the ion exchange fiber preferably used as the adsorbent for chemical contaminants is 1-1000 μm, preferably 5-200 μm, and can be appropriately determined according to the type of fiber, use, etc. The kind and introduction amount of the cation exchange group and the anion exchange group in the ion exchange fiber can be determined by the kind and concentration of the component to be removed in the gas to be treated. For example, the component to be removed in the gas may be measured and evaluated in advance, and the type and amount of ion exchange group corresponding to it may be used. For example, if you want to remove the alkaline gas, you have a cation exchange group, if you want to remove the acid gas, have an anion exchange group, and if you want to treat a mixed gas, exchange both cation and anion. A fiber having a group can be used.
As a method of flowing the gas to the ion exchange fiber, it is effective to flow the gas orthogonally to the filter-like ion exchange fiber. The flow rate at which the gas flows to the ion exchange fiber can be determined as appropriate by conducting a preliminary test. However, since the ion exchange fiber has a high gas component removal rate, the SV (space velocity) is usually 1,000 to 100,000 (space velocity). h^-1) Gas can be flowed to the extent. As the ion-exchange fiber, it is preferable to use an ion-exchange fiber produced by using the radiation graft polymerization method as proposed previously by the present inventors because it is particularly effective and can be used as appropriate (Japanese Patent Publication No. 5). No. 9123, Japanese Patent Publication No. 5-67235, Japanese Patent Publication No. 5-43422, Japanese Patent Publication No. 6-24626, etc.). When ion exchange groups are introduced into the fiber material (support) by radiation graft polymerization, the support is uniformly irradiated with radiation to the back, so that the ion exchanger is firmly and densely added to a large area. Therefore, the ion exchange capacity is increased. Therefore, low concentration gas components can also be removed with high efficiency at a high speed. In addition, the production of ion exchange fibers by radiation graft polymerization can be performed using a material having a shape close to that of the product, can be manufactured at room temperature, can be manufactured in the gas phase, and has a large graft ratio. There are advantages such as being capable of forming an adsorption filter with less impurities. For this reason, the ion exchange fiber produced by using the radiation graft polymerization method is uniformly and densely added in large quantities with the ion exchanger, which is a part that performs the adsorption function of the gas component. Fast and large amount of adsorption. Furthermore, a filter material with little pressure loss can be formed.
Depending on the required specifications, an adsorbent formed of glass and fluororesin, for example, a glass fiber filter using fluororesin as a binder, can also be suitably used as the adsorbent for removing chemical contaminants in the present invention. . Such a filter is effective for simultaneous removal of gaseous organic substances and particulate substances (Japanese Patent No. 2582806).
C-2: Means for removing chemical contaminants using a photocatalyst
The means for removing chemical contaminants in the gas using a photocatalyst is suitable when the gas component to be removed contains an organic substance (HC) such as a phthalate ester. High molecular weight H.P. such as phthalate such as DOP C. When adsorbed on the surface of the substrate, the oxide film pressure resistance is deteriorated, that is, the reliability and the yield are reduced, so that the removal is necessary.
As a photocatalyst, it is excited by light irradiation, and H.P. C. Decomposes CO₂And H₂Any material can be used as long as it can be converted into a stable form with respect to a substrate such as O. Usually, as a photocatalyst, a semiconductor material is effective, can be easily obtained, and has good processability, so that it is preferably used in the present invention. In consideration of the effect and economy, Se, Ge, Si, Ti, Zn, Cu, Al, Sn, Ga, In, P, As, Sb, C, Cd, S, Te, Ni, Fe, Co, Ag, Any of Mo, Sr, W, Cr, Ba, and Pb, or a compound, alloy, or oxide thereof is preferable, and these can be used alone or in combination of two or more.
For example, the elements are Si, Ge, Se, and the compounds are AlP, AlAg, GaP, AlSb, GaAs, InP, GaSb, InAs, InSb, CdS, CdSe, ZnS, MoS.₂, WTe₂, Cr₂Te₃, MoTe, Cu₂S, WS₂As the oxide, TiO₂, Bi₂O₃, CuO, Cu₂O, ZnO, MoO₃, InO₃, Ag₂O, PbO, SrTiO₃, BaTiO₃, Co₃O₄, Fe₂O₃And NiO. Further, depending on the application destination, the photocatalyst can be formed on the surface of the metal material by firing the metal material. For example, a Ti material is fired at 1000 ° C., and TiO is formed on the surface thereof.₂By forming the photocatalyst, a photocatalyst can be produced (Japanese Patent Laid-Open No. 11-90236). Moreover, Pt, Ag, Pd, RuO₂, Co₃O₄When a substance such as is added and used, the photocatalytic H.P. C. This is preferable because the decomposition action is promoted. These additives can be used alone or in combination. The addition amount is usually 0.01 to 10% by weight with respect to the photocatalyst, and an appropriate concentration can be appropriately selected by conducting a preliminary experiment depending on the kind of the additive substance and the required performance. In addition, as a method for adding the additive, repair techniques such as an impregnation method, a photoreduction method, a sputter deposition method, and a kneading method can be used.
The installation form of the photocatalyst can be fixed in the space in which the gas to be treated flows, fixed on the wall surface of the flow path through which the gas flows, or can be suspended in the space in which the gas flows. . For immobilization of the photocatalyst, the photocatalyst is coated or wrapped with an appropriate material such as a plate, cotton, wire, fiber, net, honeycomb, film, sheet or fiber. Alternatively, it may be sandwiched and fixed in the unit. For example, an arbitrary photocatalyst material is fixed to a ceramic, metal, fluororesin, glass material, or the like by appropriately using known addition means such as a sol-gel method, a sintering method, a vapor deposition method, and a sputtering method. Can do. As a material for immobilizing the photocatalyst, a fiber shape, a net shape, or a honeycomb shape is generally preferable because of a small pressure loss. For example, glass fiber with TiO₂Or the like added with a sol-gel method or a photocatalyst added to the surface of a light-transmitting linear article (Japanese Patent Laid-Open No. 7-256089) is used as a means for removing chemical contaminants in a gas in the present invention. be able to.
In the present invention, the light source for irradiating the photocatalyst may be any light source as long as the photocatalyst can exhibit a photocatalytic action by irradiating the photocatalyst with light, and a known light source can be used. That is, H.P. C. The decomposition can be performed by bringing the gas to be treated into contact with the photocatalyst while irradiating the photocatalyst with light in the light absorption wavelength range determined by the type of photocatalyst.
The main light absorption wavelength ranges of various photocatalytic materials are as follows.
Si: <1,100 (nm); Ge: <1,825 (nm); Se: <590 (nm); AlAs: <517 (nm); AlSb: <827 (nm); GaAs: <886 (nm) InP: <992 (nm); InSb: <6,888 (nm); InAs: <3,757 (nm); CdS: <520 (nm); CdSe: <730 (nm); MoS₂: <585 (nm); ZnS: <335 (nm); TiO₂: <415 (nm); ZnO: <400 (nm); Cu₂O: <625 (nm); PbO: <540 (nm); Bi₂O₃: <390 (nm).
The light source used for irradiating the photocatalyst is not particularly limited as long as it has a wavelength in the light absorption region of the photocatalyst, and a known light source can be used as appropriate. For example, sunlight, an ultraviolet lamp, or the like can be used. it can. As the ultraviolet light source, a mercury lamp, a hydrogen discharge tube, a xenon discharge tube, a Lyman discharge tube, or the like can be used as appropriate. As a specific form of the light source, a sterilizing lamp, a black light, a fluorescent chemical lamp, a UV-B ultraviolet lamp, a xenon lamp, or the like can be used. Among them, the sterilizing lamp (main wavelength 254 nm) can increase the effective irradiation light amount to the photocatalyst, so that the photocatalytic action becomes strong, it is ozone-free, it can be easily installed, and it is inexpensive, maintenance, management, It can be particularly preferably used because it is easy to maintain and has high performance. The irradiation amount to the photocatalyst is generally 0.05 to 50 mW / cm.²0.1 to 10 mW / cm²Is preferred.
H. C. Can also be collected by the use of an adsorbent, such as activated carbon, but there are problems of adsorption capacity and breakthrough when using an adsorbent. That is, if the generated gas concentration is high, the adsorption capacity is saturated in a short time, so that it takes time and effort for replacement, and there is a problem of secondary contamination due to the outflow of collected matter due to breakthrough. In contrast, the photocatalyst is H.264. C. No accumulation of H. and stable for a long time. C. In the present invention, H. can be decomposed. C. It can be used very preferably as a means for removing chemical contaminants such as.
Next, in the present invention, the moisture concentration important for the generation of negative ions will be described.
Moisture in the gas plays an important role in the negative ion generation mechanism of the present invention. Therefore, by controlling the moisture concentration in the gas, negative ions effective for suppressing oxidation of the substrate can be obtained efficiently.
In particular, the generation mechanism of negative ions by the photoelectron method and the discharge method is based on the fact that the generated electrons are attached to water molecules or oxygen molecules having a high electron affinity or are clustered by clustering.₂ ⁻(H₂O)_n, O⁻(H₂O)_n, OH⁻(H₂O)_nThis is thought to be due to the formation of negative ion clusters. These reactions are shown below.
O₂  + E⁻  → O₂ ⁻
O₂ ⁻  + H₂O → O₂ ⁻(H₂O)
・
・
・
O₂ ⁻(H₂O)_n-1  + H₂O → O₂ ⁻(H₂O)_n
As can be seen from the above formula, the moisture that has been charged by electrons becomes negative ions. Therefore, when there is an electron supply corresponding to the moisture concentration in the gas, it is not necessary to control the moisture concentration. However, when the concentration of generated electrons is low, moisture having a so-called oxidizing action harmful to the wafer is released, which adversely affects the wafer. The presence of such harmful moisture can be grasped by examining the oxidation state of the wafer surface exposed to the atmosphere, for example, the formation state of a natural oxide film. When the presence of harmful moisture is detected in this way, it is preferable to perform dehumidification to an appropriate concentration. In the case of dehumidification for the purpose of removing harmful moisture, it is preferable to dehumidify the relative humidity of the gas to about 45 ± 5%, preferably 30% or less, more preferably 20% or less. A known method can be appropriately used for dehumidification of the gas, and in the present invention, it is generally preferable to perform it before the generation of negative ions.
As a dehumidifying means that can be used in the present invention, a known method such as a cooling type, an adsorption type, an absorption type, a compression type, a membrane separation type, etc. can be used. Preliminary tests can be performed as appropriate depending on the scale, shape, and usage conditions such as atmospheric pressure or pressure, and one or more of the above can be used in combination. In addition, it is preferable to use a dehumidifying means that normally maintains a stable dehumidifying performance over a long period of several months to half a year or more, especially a cooling type, adsorption type or membrane separation type is simple. It is effective. As the cooling-type dehumidifying means, an electronic dehumidifying system, a cooling coil system, etc. are preferable because they are effective with a compact structure. The dehumidifying method (fixed type, rotary type) is preferable because it is simple and effective. Examples of dehumidifying materials that can be used in the adsorption-type dehumidifying means include silica gel, zeolite, activated carbon, activated alumina, magnesium perchlorate, calcium chloride, porous alumina cross-linked clay, structured activated carbon, and porous aluminum phosphate. Can do. The porous alumina cross-linked clay is obtained by exchanging exchangeable cations between layered silicate layers with polynuclear metal hydroxide ions containing aluminum, and heat-dehydrating them. The structural activated carbon is obtained by carbonizing polyvinyl formal and activating it at a temperature of 850 ° C. or lower. Porous aluminum phosphate is a so-called molecular sieve, and heat dissociation of alumina hydrate such as aluminum hydroxide, boehmite and pseudoboehmite and phosphoric acid, organic base such as tripropylamine, etc. It is obtained by reacting using a template agent.
Further, in the negative ion generation method by water crushing, so-called water mist is generated by water crushing (spraying), so it is necessary to remove harmful water using a known dehumidifying means such as an eliminator and a heating coil. .
The above dehumidification is usually performed when the amount of electrons in the gas is 0.1 PA or less as a current value measured in space. Conversely, if this value is 0.1 PA or more, the gas is humidified. It is preferred to generate a negative ion to which more water molecules have been added. Humidification can be performed by means well known in the art, such as heating with a water heater, vaporization, spraying with ultrasonic waves, or supply with a film. In addition, when adding moisture to the gas by humidification, it is preferable to remove excess moisture that was not involved in negative ion generation by a dehumidifying means such as an eliminator or a heating coil as described above.
As described above, a negative ion-enriched gas effective for suppressing oxidation can be formed with an appropriate moisture concentration by appropriately applying humidifying means and dehumidifying means. That is, by appropriately controlling the moisture concentration, an appropriate amount of moisture can be effectively used as a negative ion source.
As a gas for generating negative ions to form a negative ion-enriched gas, N₂Inert gases such as Ar and Ar can be used. However, since these inert gases are generally dry and negative ions cannot be generated efficiently as they are, moisture can be added by the humidifying means described above. It is preferable to carry out. The amount of water to be added can be determined by conducting a preliminary test as appropriate according to the negative ion generation method, required specifications, and the like.
Next, some specific embodiments of the semiconductor manufacturing apparatus according to the present invention will be described with reference to the drawings.
FIG. 1 shows specific process steps on a semiconductor substrate in a semiconductor factory (clean room, class 10,000). The present invention can be applied to each specific process shown in FIG. That is, the semiconductor manufacturing apparatus according to the present invention includes a negative ion-enriched gas adjusting device as described below, and a semiconductor process in various specific process steps shown in FIG. It is comprised by the supply means supplied to the substrate surface in an apparatus. For example, an apparatus including a “negative ion-enriched gas adjusting device” and a “supplying means for supplying the adjusted negative ion-enriched gas to the substrate surface” described below is shown in FIG. In combination with an “apparatus that blows gas onto the substrate and cleans and dries the surface of the substrate with air” that can be used in the process of “and drying”, the substrate can be cleaned and dried while suppressing oxidation of the substrate. .
FIG. 2 shows a negative ion according to an embodiment of the present invention, which is composed of a clean gas adjusting device composed of a chemical contaminant removing means using an adsorbent and a fine particle removing means using a filter, and a negative ion generator using a discharge method. The schematic block diagram of an enriched gas adjustment apparatus is shown. With such an apparatus, negative ion-enriched air (number of negative ions of 100,000 / mL or more) that is class 10 or less and does not contain chemical contaminants is adjusted. By performing each specific process shown in FIG. 1 while exposing the negative ion-enriched air adjusted in the present embodiment to the surface of the semiconductor substrate, contamination of the semiconductor substrate can be prevented.
A negative ion enriched air conditioning apparatus A shown in FIG. 2 includes a fan 20 for supplying clean room air, an adsorbent (ion exchange fiber and activated carbon) 21 for removing chemical contaminants in the clean room air, and clean room air (class). 10,000) and a dust removing filter (ULPA filter) 22 for removing fine particles generated from the fan 20, a discharge part (corona discharge) 23 for generating negative ions, and an O generated from the discharge part 23₃O to remove₃It is constituted by the decomposition / removal material 24. In the figure, reference numeral 25-1 denotes a flow of air introduced into the negative ion-enriched gas adjusting device A by the fan 20, and reference numeral 25-2 denotes a negative ion-enriched gas adjusted by the negative ion-enriched gas adjusting device A. 26 represents negative ions. In the discharge part 23 of FIG. 2, 23-1 shows a needle-like discharge electrode and 23-2 shows a counter electrode.
According to the negative ion enriched gas adjusting apparatus A shown in FIG. 2, clean room air (fine particle concentration is class 10,000, negative ion concentration is 100 / mL or less) introduced by a fan is Passing through the contaminant removal adsorbent 21 and the particulate removal filter 22, the particulate concentration is class 10 or less, and both the ionic component concentration and the organic matter concentration are 2 μg / m.³The following is cleaned. Next, negative ions are generated by the negative ion generator 23 using a discharge method, and the generated ozone is removed by the ozone decomposition / removal material 24, so that the negative ion concentration is 100,000 particles / mL or more and the fine particle concentration. Class 10 or less, both ionic component concentration and organic substance concentration are 2 μg / m³Hereinafter, a clean negative ion enriched gas having an ozone concentration of 0.01 ppm or less is provided. By using this negative ion-enriched gas as a substrate exposure gas in the various process steps of FIG. 1, it is possible to perform a semiconductor manufacturing process in which fine particle contamination and chemical contamination are prevented while suppressing oxidation of the substrate.
FIG. 3 is a schematic configuration diagram of a negative ion-enriched gas adjusting device according to another aspect of the present invention, which includes a clean gas adjusting device using an adsorbent / particulate removal filter and a negative ion generator using a photoelectron method. Show. 3, the same components as those in FIG. 2 are denoted by the same reference numerals, and description thereof is omitted.
A negative ion-enriched air conditioning apparatus A shown in FIG. 3 includes a cleaning device including a chemical contaminant removal adsorbent 21 and a particulate removal filter 22, a photoelectron emission material 27, an ultraviolet lamp 28, and an electric field forming electrode. 29, a negative ion generator. According to the negative ion-enriched gas control apparatus A shown in FIG. 3, clean room air introduced by a fan passes through the chemical contaminant removal adsorbent 21 and the particulate removal filter 22 and has a particulate concentration of class 10 or less and an ionic component. Concentration and organic matter concentration are both 2 μg / m³After being cleaned below, it is introduced into a negative ion generator, where photoelectrons are emitted by irradiating the photoelectron emission material 27 with ultraviolet rays. As a result, the negative ion concentration is 10,000 ions / mL or more, the fine particle concentration is class 10 or less, and the ion component concentration and the organic substance concentration are both 2 μg / m.³The following clean negative ion enriched gas is provided: In addition, since there is no generation | occurrence | production of ozone according to a photoelectron method, an ozone removal material as shown in FIG. 2 is not normally required. The negative ion-enriched gas adjusted by the negative ion-enriched gas adjusting device A in FIG. 3 is used as a gas for substrate exposure in various process steps in FIG. Thus, the semiconductor manufacturing process can be performed.
FIG. 4 shows another embodiment of the present invention, which is composed of a clean gas adjusting device comprising a chemical contaminant removing means using an adsorbent and a fine particle removing means using a photoelectron method, and a negative ion generator using a photoelectron method similar to that shown in FIG. The schematic block diagram of the negative ion enriched gas adjustment apparatus which concerns on the aspect of is shown. In FIG. 4, the same components as those in FIG. 3 are denoted by the same reference numerals.
The negative ion-enriched gas adjusting device A shown in FIG. 4 includes a chemical contaminant removal adsorbent 21; a particulate removal composed of a photoelectron emission material 41, an ultraviolet lamp 42, an electric field forming electrode 43, and a charged particulate collection material 44. And a negative ion generator comprising a photoelectron emitting material 27, an ultraviolet lamp 28, and an electric field forming electrode 29. According to the negative ion enriched gas adjusting apparatus A shown in FIG. 4, the clean room air introduced by the fan first passes through the chemical contaminant removal adsorbent 21 to remove chemical contaminants in the gas. Next, the gas is introduced into the fine particle removing means by the photoelectron method, where the photoelectron emitting material 41 is irradiated with ultraviolet rays to generate photoelectrons, and the photoelectrons generate negative ions. Fine particles in the gas are charged by the generated negative ions. The charged fine particles are collected and removed by the charged fine particle collecting material 44 in the subsequent stage. As a result, the fine particle concentration is class 100 or less, and the ionic component concentration and the organic substance concentration are both 2 μg / m.³A purified gas is formed below, and this clean gas is introduced into the negative ion generator, where photoelectrons are emitted by irradiating the photoelectron emitting material 27 with ultraviolet rays. As a result, the negative ion concentration is 5,000 / mL or more, the fine particle concentration is class 100 or less, and the ionic component concentration and the organic substance concentration are both 2 μg / m.³The following clean negative ion enriched gas is provided: The negative ion-enriched gas adjusted by the negative ion-enriched gas adjusting device A of FIG. 4 is used as a gas for substrate exposure in various process steps of FIG. Thus, the semiconductor manufacturing process can be performed.
FIG. 5 is a schematic configuration diagram of a negative ion-enriched gas adjusting device according to another aspect of the present invention, which includes a clean gas adjusting device using an adsorbent / particulate removal filter and a negative ion generating device using a water crushing method. Indicates. 5, the same components as those in FIG. 2 are denoted by the same reference numerals, and description thereof is omitted.
The negative ion-enriched air conditioning apparatus A shown in FIG. 5 includes a cleaning device including a chemical contaminant removal adsorbent 21 and a particulate removal filter 22, a water crushing nozzle 33, an excess water removal eliminator 34, and water. And a negative ion generator configured by a water tank 31 for supply. According to the negative ion-enriched gas control apparatus A shown in FIG. 5, clean room air introduced by a fan passes through the chemical contaminant removal adsorbent 21 and the particulate removal filter 22 and has a particulate concentration of class 10 or less and an ionic component. Concentration and organic matter concentration are both 2 μg / m³After being purified below, it is introduced into a negative ion generator, where negative ions are formed by spraying the water in the water supply tank 31 through the heat exchanger 32 from the water crushing nozzle 33 at a high pressure. Is done. Since the formed negative ion-enriched gas contains excess moisture, the excess moisture is removed by the eliminator 34 and heated to a desired temperature by the reheat heater 35. As a result, the negative ion concentration is 200,000 / mL to 300,000 / mL, the fine particle concentration is class 10 or less, and the ion component concentration and the organic substance concentration are both 2 μg / m.³The following clean negative ion enriched gas is provided: Excess water collected by the eliminator 34 is accommodated in the water supply water tank 31 and reused by the water crushing nozzle 33. As described above, since ozone is not generated according to the photoelectron method, an ozone removing material as shown in FIG. 2 is usually not necessary. The negative ion-enriched gas adjusted by the negative ion-enriched gas adjusting device A in FIG. 3 is used as a gas for substrate exposure in various process steps in FIG. Thus, the semiconductor manufacturing process can be performed.
In the negative ion generation method by water crushing, about 10 to 20% of positive ions may be generated together with the negative ions depending on conditions. Normally, a large amount of negative ions are generated according to the water crushing method, so even if about 20% of positive ions are generated, they are neutralized by negative ions, so there is no need for positive ion removal means. It may be desirable to place a negative electrode further downstream of the reheat heater 35 to collect and remove positive ions.
FIG. 6 is a schematic configuration diagram of a negative ion-enriched gas adjusting device according to another aspect of the present invention, which includes a clean gas adjusting device using an adsorbent / particulate removal filter and a negative ion generating device using X-ray irradiation. Indicates. In FIG. 6, the same components as those in FIG. 2 are denoted by the same reference numerals, and description thereof is omitted.
The negative ion-enriched air conditioning apparatus A shown in FIG. 6 includes a cleaning device including a chemical contaminant removal adsorbent 21 and a particulate removal filter 22 and extremely weak X-rays (soft X-rays: wavelength 0.2). -0.3 nm) a negative ion generator constituted by the generator 36. According to the negative ion-enriched gas control apparatus A shown in FIG. 6, the clean room air introduced by the fan passes through the chemical contaminant removal adsorbent 21 and the particulate removal filter 22, and the particulate concentration is class 10 or less. Concentration and organic matter concentration are both 2 μg / m³After being purified below, it is introduced into a negative ion generator, where the gas molecules are ionized to generate negative ions by irradiating the gas with X-rays. In FIG. 6, B shows the ionization part of the gas molecule by X-ray irradiation. When the gas is irradiated with X-rays, negative ions and positive ions are generated, but the positive ions are removed by the negative electrode 37. As a result, the negative ion concentration is 100,000 ions / mL or more, the fine particle concentration is class 10 or less, and both the ion component concentration and the organic substance concentration are 2 μg / m.³The following clean negative ion enriched gas is provided: The negative ion-enriched gas adjusted by the negative ion-enriched gas adjusting device A of FIG. 6 is used as a gas for substrate exposure in various process steps of FIG. Thus, the semiconductor manufacturing process can be performed.
Note that when a gas is irradiated with X-rays to generate negative ions, a small amount of ozone may be generated depending on the irradiation conditions. When ozone may be generated in this way, as shown in FIG. 7, an ozone decomposition / removal material 24 is disposed further downstream of the negative electrode 37 for removing positive ions, so that a very small amount of ozone is generated. Even if it occurs, it is preferable that it can be decomposed and removed. As a result, the negative ion concentration is 100,000 ions / mL or more, the fine particle concentration is class 10 or less, and the ion component concentration and the organic substance concentration are both 2 μg / m.³A clean negative ion-enriched gas having an ozone concentration of 0.01 ppm or less is provided below, and this gas is used as a gas for substrate exposure in various process steps of FIG. A semiconductor manufacturing process in which contamination and chemical contamination are prevented can be performed.
Example
The negative ion enriched gas was adjusted using the negative ion enriched gas adjusting device according to various aspects of the present invention shown in FIGS. Each device has the following configuration.
(1) Negative ion-enriched gas adjusting device 1: Device having the configuration shown in FIG. 2 (size: about 30 L)
Adsorbent 20: ion exchange fiber: mixed bed material of activated carbon (1: 1)
-Dust removal filter 21: ULPA filter
-Discharge part: 30 kV is applied between electrodes
-O₃Decomposition / removal material: MnO₂/ TiO₂-C
(2) Negative ion enriched gas adjusting device 2: Device having the configuration shown in FIG. 3 (size: about 30 L)
-Adsorbent 20 and dust filter 21 are the same as in (1) above.
-UV lamp 28: germicidal lamp (4W)
-Photoelectron emitting material 27: TiO₂An Au film coated on top
-Electrode 29: A mesh electrode made of SUS was installed above the lamp as shown in Fig. 3; an electric field of 10 V / cm
(3) Negative ion enriched gas adjusting device 3: Device having the configuration shown in FIG. 4 (size: about 40 L)
-Adsorbent 20 is the same as (1) above
-Photoelectron emitting materials 27 and 41, ultraviolet lamps 28 and 42, and electrodes 29 and 43 are the same as in (2) above.
-Charged particulate collection material: plate-like Cu-Zn;
(4) Negative ion enriched gas adjusting device 4: Device having the configuration shown in FIG. 5 (size: about 200 L)
-Adsorbent 20 and filter 21 are the same as in (1) above
-Water spraying device: The water crushing nozzle 33 was sprayed with 3 L / min of ion-exchanged water supplied at a water pressure of 350 kPa and a water-air ratio (L / G) = 1.
-Reheat heater: Generated water droplets were vaporized by the reheat coil.
(5) Negative ion enriched gas adjusting device 5: device having the configuration shown in FIG. 6 (size: about 30 L)
-Adsorbent 20 and filter 21 are the same as in (1) above
-X-ray generator 36: wavelength 0.2-0.3nm;
-Negative electrode 37: plate-like Cu-Zn;
In the negative ion enriched gas regulators 1 to 3 and 5 above, clean room air (fine particle concentration class 10,000, organic matter concentration 100 to 120 μg / m³, NH₃Concentration 15-20 μg / m³) At a flow rate of 3 L / min. In addition, the same clean room air was supplied to the negative ion enriched gas adjusting device 4 at a flow rate of 30 L / min. The properties of the air obtained from each of the negative ion enriched gas adjusting devices 1 to 5 are shown in Table 2 below.

In addition, O in the negative ion enriched gas obtained by the apparatus (1).₃The concentration was 0.01 ppm or less.
The negative ion-enriched gas obtained by the negative ion-enriched gas adjusting devices 1 to 5 was exposed to the Si wafer surface, and the generation state of the oxide film was observed. As a Si wafer, a high resolution XPS: made by Scienta, ESCA300 type was used, and after cleaning with RCA, HF (0.05%) treatment was performed and pure water rinsed and dried were used as wafer samples. The negative ion-enriched gas obtained by the negative ion-enriched gas adjusting devices 1 to 5 is blown onto the surface of the wafer sample at a flow rate of 3 L / min. After a predetermined time has elapsed, the oxidation formed on the sample surface The film thickness was measured. The results are shown in Table 3 below. As a comparative example, the same wafer sample surface was exposed using clean room air as it was. The results are also shown in Table 3 below.

Next, the concentration of negative ions in the adjusted gas is changed to about 500, about 1,000, about 3,000, about 5,000, about 10 by changing the processing conditions using the negative ion enriched gas adjusting device 1. , 30,000, about 30,000, adjusted to about 50,000 / mL, and similarly exposed to the wafer sample surface (exposure time 12 hours) to examine the negative ion concentration effective in suppressing the formation of oxide film. It was. The effect was recognized when the negative ion concentration was 1,000 ions / mL or more and the oxide film thickness was <0.1 mm, and when it was 5,000 ions / mL or more, the effect was recognized as <0.05 mm. Further, it was <0.02 kg at 10,000 pieces / mL or more, and a particularly remarkable effect was recognized.
Industrial applicability
From the above knowledge, it was confirmed that the present invention can provide the following effects.
(1) By supplying the negative ion-enriched gas into the space of the semiconductor manufacturing process, various processing of the substrate can be performed while suppressing oxidation of the substrate.
(2) In adjusting the negative ion enriched gas, by removing fine particles and chemical contaminants, a clean negative ion enriched gas free of fine particles and chemical components can be obtained. The gas (having a pollution prevention function) is adjusted.
(3) In adjusting the negative ion enriched gas, it is possible to prevent the generated negative ions from being consumed by contaminants such as fine particles by using a gas from which fine particles and chemical contaminants have been removed.
(4) At present, the cause of contamination of the substrate is mainly due to fine particles and chemical contaminants, but in the future, in addition to these contaminants, it is important to suppress oxidation of the substrate surface. According to the present invention, it is possible to obtain a clean gas having an effect of suppressing oxidation of the substrate surface.
(5) A suitable negative ion generation method can be selected according to required specifications such as the device scale to which the present invention is applied, the amount of negative ion generation required, and the required oxidation suppression effect (see Table 1). Thus, it is possible to provide a more practical state of the pollution-preventing gas.
[Brief description of the drawings]
FIG. 1 is a process diagram showing the contents of specific processing on a semiconductor substrate in a semiconductor factory (clean room).
FIG. 2 is a schematic configuration diagram showing an example of an apparatus for obtaining a negative ion-enriched gas used in the present invention.
FIG. 3 is a schematic configuration diagram showing another example of an apparatus for obtaining a negative ion-enriched gas used in the present invention.
FIG. 4 is a schematic configuration diagram showing another example of an apparatus for obtaining a negative ion-enriched gas used in the present invention.
FIG. 5 is a schematic configuration diagram showing another example of an apparatus for obtaining a negative ion-enriched gas used in the present invention.
FIG. 6 is a schematic configuration diagram showing another example of an apparatus for obtaining a negative ion-enriched gas used in the present invention.
FIG. 7 is a schematic configuration diagram showing another example of an apparatus for obtaining a negative ion-enriched gas used in the present invention.
FIG. 8 is a schematic configuration diagram showing an air cleaning system widely used in a conventional semiconductor factory (clean room).

Claims (4)

Depositing a resist layer on the substrate as a substrate treatment while exposing a negative ion enriched gas having a negative ion concentration of 10,000 ions / mL or more and an organic substance concentration of 2 μg / m ³ or less to the substrate surface; A method for manufacturing a semiconductor, comprising performing at least one of polishing, plating on a substrate, cleaning and drying of the substrate. 2. The semiconductor manufacturing method according to claim 1, wherein the negative ion-enriched gas is adjusted by passing a clean gas from which fine particles and / or chemical contaminants have been removed through a negative ion generator. 3. The method of manufacturing a semiconductor according to claim 2, wherein the chemical contaminant is one or more selected from the group consisting of an ionic component, an inorganic substance, and an organic substance. The negative ion-enriched gas is adjusted by passing a gas having a fine particle concentration of class 100 or less, an ion component concentration of 10 μg / m ³ or less, and an organic substance concentration of 10 μg / m ³ or less through a negative ion generator. A method for manufacturing a semiconductor according to claim 2 or 3.

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