JP3630533B2 - Synthetic silica glass large plate for high output vacuum ultraviolet ray and method for producing the same - Google Patents
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Description
【０００１】
【産業上の利用分野】
本発明は、高出力真空紫外線用合成シリカガラス大型板材およびその製造方法、さらに詳しくは１６０〜２００ｎｍの波長域の高出力紫外線、特にエキシマレーザー、エキシマランプ等の高出力真空紫外線を用いるドライ洗浄、光ＣＶＤの照射装置のウインドウとして用いる合成石英ガラス大型ウインドウに関する。
【０００２】
【従来技術】
現在、シリコン半導体素子の製造方法における洗浄処理手段として真空紫外線を使用したドライ洗浄装置が開発されつつあり、その光源として波長１６０〜２００ｎｍのＡｒＦエキシマレーザ（１９３ｎｍ）、Ｘｅ２エキシマレーザ（１７２ｎｍ）、ＡｒＣｌエキシマレーザ（１７５ｎｍ）、Ｘｅ２エキシマランプ（１７２ｎｍ）、ＡｒＣｌエキシマランプ（１７５ｎｍ）等が考えられている。前記ドライ洗浄装置にはウインドウ用として大型のガラス板材を必要とするが、市販の窓用ガラスで前記ウインドウを形成すると、ドライ洗浄装置で放射する紫外線が短波長、高出力のため照射エネルギーが水銀ランプやＣＷレーザー等に比べて大きく、大きなダメージを受け使用不能となる。そこで前記高出力真空紫外線に対してもダメージの少ないシリカガラスでウインドウを形成することが検討されたが、従来の大型のシリカガラスは、高純度珪素化合物を酸水素火炎中に導入し加水分解で得たガラス微粒子をターゲット上に直接堆積するダイレクト法、又は高純度珪素化合物を酸水素火炎で加水分解しで得た白色不透明スート体を電気炉内で真空雰囲気下で透明固体化するＶＡＤ法によって合成シリカガラスインゴットを形成し、それをグラファイト型枠を用いて真空電気炉で加熱プレス成型し、薄層板状に切断、研磨して製造されるところから、製造可能な板材の大きさに限界があった。さらに、前者のダイレクト法で得たシリカガラス板材は、ＯＨ基含有量が４００〜１０００ｗｔｐｐｍと多く、長時間の高出力真空紫外線の照射でダメージが生じソラリゼーションにより光透過率が低下し、さらにインゴットが層状に形成されるところからＯＨ基含有量が板材の中心部と外縁部とで１００〜４００ｗｔｐｐｍの変動幅ができ、真空紫外線の透過率や耐紫外線性が板材中で不均一となり、ドライ洗浄装置等のウインドウ用としては満足できるものではなかった。また、後者のＶＡＤ法で得たシリカガラス板材は、ＯＨ基含有量が１００〜４００ｗｔｐｐｍと前記ダイレクト法に比べて少なく、かつＯＨ基の変動幅も５０〜２００ｗｔｐｐｍと少ないが、それでも依然としてＯＨ基含有量とＯＨ基濃度変動幅が大きく、真空紫外線の透過率や耐紫外線性が板材中で不均一となり大きな障害となっていた。そのため前記高出力真空紫外線に対してダメージが少なく、かつ透過率が高く、しかもそれらの均一性にも優れた大型のシリカガラス板材の開発が熱望されていた。
【０００３】
【発明が解決しようとする課題】
こうした現状に鑑み、本発明者等は、鋭意研究を続けた結果、大型シリカガラス板材のＯＨ基濃度を５〜３００ｗｔｐｐｍ、１ｃｍ当たりのＯＨ基濃度変動幅（ΔＯＨ／ｃｍ）を１０ｗｔｐｐｍ以下とすることで１６０〜２００ｎｍの波長域の高出力真空紫外線であっても安定で、しかも透過率の高いシリカガラス大型板材が得られることを見出し、本発明を完成したものである。すなわち
【０００４】
本発明は、１６０〜２００ｎｍの波長域の高出力真空紫外線に対して初期透過率が高く、耐久性、およびそれらの均一性に優れたシリカガラス大型板材を提供することを目的とする。
【０００６】
【課題を解決するための手段】
上記目的を達成する本発明は、高純度の合成シリカガラスからなり１６０〜２００ｎｍの波長域で使用する高出力真空紫外線用合成シリカガラス大型板材において、該合成シリカガラス大型板材が縦３００×横３００ｍｍ〜縦１，０００×横１，０００ｍｍで、肉厚が２〜８ｍｍの大型板材であって、そのＯＨ基濃度が５〜３００ｗｔｐｐｍ、平板面の１ｃｍ当たりのＯＨ基濃度変動幅（ΔＯＨ／ｃｍ）が１０ｗｔｐｐｍ以下であることを特徴とする高出力真空紫外線用合成シリカガラスウインドウに係る。
【０００７】
本発明の大型合成シリカガラス板材は、高出力真空紫外線に対して安定した高純度の合成シリカガラス板材であるが、前記高出力真空紫外線とはＡｒＦエキシマレーザ（１９３ｎｍ）、Ｘｅ２エキシマレーザ（１７２ｎｍ）、ＡｒＣｌエキシマレーザ（１７５ｎｍ）、Ｘｅ２エキシマランプ（１７２ｎｍ）、ＡｒＣｌエキシマランプ（１７５ｎｍ）等の波長１６０〜２００ｎｍの紫外線をいう。また前記高純度とは、シリカガラス板材中のＬｉ、Ｎａ、Ｋ等のアルカリ金属元素及びＭｇ、Ｃａ等のアルカリ土類金属元素濃度がそれぞれ１０ｗｔｐｐｂ以下、Ｔｉ、Ｃｒ、Ｍｎ、Ｆｅ等の遷移金属元素濃度がそれぞれ１ｗｔｐｐｂ以下、Ｃｏ、Ｎｉ、Ｃｕ等の遷移金属元素濃度がそれぞれ０．１ｗｔｐｐｂ以下であることをいう。本発明の大型合成シリカガラス板材中のアルカリ金属元素及びアルカリ土類金属元素濃度が前記範囲を超えるとシリカガラスの再結晶化が促進されクリストバライトを生成し易くなり、白色失透することが起る。また遷移金属元素濃度が前記範囲を超えると、紫外線を吸収し紫外線吸収端を長波長側にシフトさせ透過率の低下を招き好ましくない。
【０００８】
本発明の合成シリカガラス大型板材は上記に加えてＯＨ基濃度が５〜３００ｗｔｐｐｍ、１ｃｍ当たりのＯＨ基濃度変動幅（ΔＯＨ／ｃｍ）が１０ｗｔｐｐｍ以下であることを必須とする。一般に、ＯＨ基はシリカガラス網目構造において構造の終端部になるが、このＯＨ基が適量シリカガラス中に含まれていると網目構造内の内部歪みが除去され、Ｓｉ−Ｏ−Ｓｉの結合角度が安定値に近づきＳｉ−Ｏの平均結合エネルギーが上昇するといわれている。ところが、ＯＨ基はシリカガラスの紫外線吸収端を長波長側にシフトさせる作用があり、高濃度に含まれると透過率を低下させることになる。そこで、本発明の合成シリカガラス大型板材ではＯＨ基濃度を５〜３００ｗｔｐｐｍの範囲とする。特に波長１６０〜１８０ｎｍの高出力真空紫外線用として使用する場合にはＯＨ基濃度を５〜１００ｗｔｐｐｍとするのが好ましい。また、ＯＨ基濃度が不均一であると、透過率、絶対屈折率等に板材の位置によってムラが生じ、結果的に初期特性が悪化する。そこで本発明の合成シリカガラス大型板材では１ｃｍ当たりのＯＨ基濃度変動幅（ΔＯＨ／ｃｍ）を１０ｗｔｐｐｍ以下とする。さらに、板材全体のＯＨ基濃度変動幅（ΔＯＨ）を５０ｗｔｐｐｍ以下とするのが好ましい。
【０００９】
上記に加えて、本発明の合成シリカガラス板材は含有する水素分子濃度を１×１０１７〜１×１０２０分子／ｃｍ３の範囲に設定する。前記濃度の水素分子を含有することでＥ’センター吸収帯の生成が抑制され透過率の低下が起りにくくなる。さらに水分子濃度を１×１０１７以下とすると、水分子に起因する紫外線吸収端の長波長側ヘのシフトが抑制できて好適である。ただし、ここでいう水分子とは、Ｓｉに結合したＯＨ基ではなく、シリカガラス網目構造の隙間に溶存する分子をいう。
【００１０】
さらに、本発明の合成シリカガラス板材は含有する塩素元素含有量を５０ｗｔｐｐｍ以下とするのがよい。塩素元素により形成するＳｉ−Ｃｌは２１０ｎｍの吸収帯、いわゆるＥ’センター吸収帯生成のプリカーサとなるが、前記範囲内であればプリカーサの生成が抑えられ透過率の低下が抑制できる。
【００１１】
本発明の合成シリカガラス大型板材は以下の製造方法で製造される。すなわち
【００１２】
（ｉ）合成シリカガラスシリンダーの製造
蒸留等の手段で超高純度化したＳｉＣｌ４、ＨＳｉＣｌ３、（ＣＨ３）２ＳｉＣｌ２、ＣＨ３ＳｉＣｌ３、ＣＨ３Ｓｉ（ＯＣＨ３）３、ＨＳｉ（ＯＣＨ３）３、Ｓｉ（ＯＣＨ３）４などの珪素化合物、好ましくはＣＨ３Ｓｉ（ＯＣＨ３）３、ＨＳｉ（ＯＣＨ３）３、Ｓｉ（ＯＣＨ３）４の塩素を含まない珪素化合物を酸水素ガスまたはプロパンガスを使い火炎加水分解して、例えば特開平４−２６０６１８号公報、米国特許第５，６０９，６６６号明細書等に記載の作成方法でバーナースイングにより軸方向のＯＨ基濃度を均一にしながら棒状ターゲット上に白色不透明の大型スート体を形成する。前記大型スート体の形成において電気炉内の温度と時間と真空度によってＯＨ基濃度を調整する。次いで、同じ電気炉内で真空雰囲気下、１５００〜１７００℃に加熱、溶融して気泡のない外径８０〜２００ｍｍ、肉厚２０〜７０ｍｍ程度のシリンダー状合成シリカガラス体とする。前記合成シリカガラスの製造方法を本発明ではスート再溶融法という。
【００１３】
（ｉｉ）合成シリカガラス大型板材の製造
上記大型シリンダー状合成シリカガラス体の内圧をＮ２ガスで調整しながら加熱し、管引きで外径２００〜４００ｍｍ、肉厚３〜１０ｍｍ程度の大型チューブに成型する。得られた大型チューブの管軸方向に所定幅にわたって切り込みを入れ、該切り込み部の内側と外側から管軸方向全幅にわたって、管周方向に帯状バーナーで順次加熱軟化しながら、管の接線方向に引っ張って図１のように管開き処理で平板化し合成シリカガラス大型板材とする。図１において、１はシリカガラスチューブ、２は板材の引張る方向、３は加熱手段、４は切込み部を示す。得られた合成シリカガラス大型板材を電気炉内で歪み除去処理し、エッチング洗浄、熱処理したのち、鏡面研磨して寸法３００×３００ｍｍ角〜１０００×１０００ｍｍ角、肉厚２〜８ｍｍの合成シリカガラス大型板材に仕上げる。得られた大型板材は、ＯＨ基濃度が調整された軸方向が板面となるところから平板面のＯＨ基濃度変動幅は１ｃｍ当たり１０ｗｔｐｐｍ以下と均一になる。その一方で、チューブの径方向にあった大きなＯＨ基濃度変動幅は、大型板材の厚さ方向の変動幅となる。板材は肉厚２〜８ｍｍと薄い上に、ＯＨ基濃度が均一に漸増または漸減しているところから高出力真空紫外線の透過率と、それによるソラリゼーションの程度にムラが少なく板面方向に均一な特性を有する。
【００１４】
【発明の実施の態様】
次に具体例に基づいて本発明を詳細に説明するが、本発明はそれにより限定されるものではない。
【００１５】
【実施例】
実施例１〜６
（１）合成シリカガラスシリンダーの作成
蒸留精製して得た超高純度のＣＨ３Ｓｉ（ＯＣＨ３）３ガスを合計１５０リットル／分と固定し、酸素ガス合計及び水素ガス合計を各々１０〜１００リットル／分、３０〜３００リットル／分の範囲の割合で複数のバーナーに供給し、バーナーをスイングさせながら特開平４−２６０６１８号公報に記載のように外付け法でＯＨ基含有量が数１００ｗｔｐｐｍの白色大型スート体に形成した。前記大型スート体を円筒型高純度グラファイトヒーターを内装したステンレススチール製電気炉内に設置し、電気炉内を約１０３Ｐａ以下の真空度にするとともに約６００〜９００℃の範囲の所定温度にて加熱処理し、ＯＨ基濃度の調整を行った。ＯＨ基濃度は処理時の真空度、温度及び時間を調整してコントロールした。次いで電気炉中、真空下で約１５００〜１７００℃に加熱・再溶融して外径１５０ｍｍ、厚さ４０ｍｍの合成シリカガラスシリンダーを作成した。
【００１６】
（２）シリカガラスチューブの製造
上記シリカガラスシリンダーの内圧を窒素ガスで調整しながら、グラファイトヒーターを通して加熱し、横型管引きで直径２５０ｍｍ、長さ１６００ｍｍ、厚さ７ｍｍの大型シリカガラスチューブを製造した。
【００１７】
（３）合成シリカガラス大型板材の製造
得られた大型シリカガラスチューブ１を図１に示すように軸方向に所定幅にわたって切り込み５を入れ、切込み部の内側と外側から管軸方向全幅にわたって、管周方向に帯状バーナー３で順次１８００〜２０００℃に加熱軟化させながら、管の接線方向に引っ張って平板化し６７０×６００×厚さ７ｍｍの合成シリカガラス大型板材に成型した。前記合成シリカガラス大型板材を電気炉内、１１５０℃で３０分間アニール処理して歪みを除去したのち、５％ＨＦで３０分間のエッチング洗浄を行い、さらに板材の上下に高純度カーボンシートを敷いて汚染を防ぎつつ、板材の外側にシリカガラス板を挟み、上から重しをのせて、電気炉中、１２００℃で２時間加熱加圧した。得られた大型板材の両面を鏡面研磨し、６５０×５５０×厚さ５ｍｍの合成シリカガラス大型板材に仕上げた。
【００１８】
次いで、実施例１〜３の試料については１気圧、水素ガス雰囲気下で６００℃、３時間のアニール処理を行い、実施例４では１００気圧、水素ガス雰囲気下で６００℃、３時間のアニール処理を行って水素分子のドープを行った。得られた実施例１〜４の試料および前記水素ドープ処理をしない実施例５、６の試料について、ＯＨ基濃度、１ｃｍ当たりのＯＨ基濃度変動幅（ΔＯＨ／ｃｍ）、板材全体におけるＯＨ基濃度変動幅（ΔＯＨ）、水素分子濃度、水分子濃度、塩素元素含有量、Ｘｅ２エキシマランプ及びＡｒＦエキシマレーザ照射に対する透過率の測定を行い、それらの結果を表１に示した。
【００１９】
【表１】
また、実施例５、６の合成シリカガラス大型板材について不純物元素濃度を測定し、その結果を表２に示す。
【００２１】
【表２】
【００２２】
比較例１〜４
比較例１、２では、実施例１で使用した高純度珪素化合物を原料として白色スート体を形成し、塩素ガス雰囲気下、電気炉内で脱水処理を施し、さらに真空雰囲気下で透明固体化して合成シリカガラスシリンダーを作成し（スート法）、横型管引きで大型合成シリカガラスチューブとした後、管開きし、プレス成型、鏡面研磨を行って、６５０×５５０×厚さ５ｍｍの合成シリカガラス大型板材を得た。比較例２では前記合成シリカガラス大型板材をさらに水素ガス雰囲気下でアニール処理を施し水素分子のドープを行った。該大型合成シリカガラス板材のＯＨ基濃度、１ｃｍ当たりのＯＨ基濃度変動幅（ΔＯＨ／ｃｍ）、板材全体におけるＯＨ基濃度変動幅（ΔＯＨ）、水素分子濃度、水分子濃度、塩素元素含有量、Ｘｅ２エキシマランプ及びＡｒＦエキシマレーザ照射に対する透過率の測定を行い、その結果を表３に示す。
【００２４】
比較例３では、超高純度ＳｉＣｌ４を原料として、酸水素火炎加水分解法のダイレクト法でインゴットの製造を行い、比較例４では前記原料を酸水素火炎加水分解法のＶＡＤ法でインゴットの形成を行ったのち、グラファイト型枠を用いて真空電気炉内で加熱プレス成型し、薄層板状に切断し、鏡面研磨によって合成シリカガラス大型板材を製造した。得られた各試料について、ＯＨ基濃度、１ｃｍ当たりのＯＨ基濃度変動幅（ΔＯＨ／ｃｍ）、板材全体におけるＯＨ基濃度変動幅（ΔＯＨ）、水素分子濃度、水分子濃度、塩素元素含有量、Ｘｅ２エキシマランプ及びＡｒＦエキシマレーザ照射に対する透過率の測定を行い、その結果を表３に示す。
【００２５】
【表３】
上記実施例及び比較例の各物性値の測定法は下記の方法による。
【００２７】
（ｉ）ＯＨ基濃度の測定法
Ｄ．Ｍ． ＤＯＤＤ ａｎｄ Ｄ．Ｂ． ＦＲＡＳＥＲ，Ｏｐｔｉｃａｌ ｄｅｔｅｒｍｉｎａｔｉｏｎ ｏｆ ＯＨ ｉｎ ｆｕｓｅｄ ｓｉｌｉｃａ，Ｊｏｕｒｎａｌ ｏｆ Ａｐｐｌｉｅｄ Ｐｈｙｓｉｃｓ，Ｖｏｌ．３７（１９６６）ｐ．３９１１文献記載の測定法。
【００２８】
（ｉｉ）ＯＨ基濃度変動幅の測定法
６５０×５５０×厚さ５ｍｍのシリカガラス大型板材において、面板の対角線方向に１０ｍｍ間隔にて８５点のＯＨ基濃度測定を行う。隣同志の２点のＯＨ基濃度値より１ｃｍ当たりのＯＨ基濃度変動幅（ΔＯＨ／ｃｍ）を、８５点のＯＨ基濃度の最大と最小値から板材全体におけるＯＨ基濃度変動幅（ΔＯＨ）を計算する測定法。
【００２９】
（ｉｉｉ）水素分子濃度の測定法。
Ｖ．Ｋ．ＫＨＯＴＩＭＣＨＥＮＫＯ、ｅｔ ａｌ．， Ｄｅｔｅｒｍｉｎ‐ ｉｎｇ ｔｈｅ ｃｏｎｔｅｎｔ ｏｆ ｈｙｄｒｏｇｅｎ ｄｉｓｓｏｌｖｅｄ ｉｎ ｑｕａｒｔｚ ｇｌａｓｓ ｕｓｉｎｇ ｔｈｅ ｍｅｔｈｏｄｓ ｏｆＲａｍａｎ ｓｃａｔｔｅｒｉｎｇ ａｎｄ ｍａｓｓ ｓｐｅｃｔｒｏｍｅｔｒｙ， Ｊｏｕｒｎａｌ ｏｆ Ａｐｐｌｉｅｄ Ｓｐｅｃｔｒｏｓｃｏｐｙ， Ｖｏｌ．４６， Ｎｏ．６，（１９８７） ｐｐ６３２〜６３５文献記載の測定法。
【００３０】
（ｉｖ）水分子濃度の測定法。
Ｙ．ＭＯＲＩＭＯＴＯ，ｅｔ ａｌ．， Ａｎａｌｙｓｉｓ ｏｆ ｇａｓ ｒｅｌｅａｓｅ ｆｒｏｍ ｖｉｔｒｅｏｕｓ ｓｉｌｉｃａ， Ｊｏｕｒｎａｌ ｏｆ Ｎｏｎ−Ｃｒｙｓｔａｌｌｉｎｅ Ｓｏｌｉｄｓ， １３９（１９９２）３５〜４６文献記載の測定法。
【００３１】
（ｖ）塩素濃度の測定法。
ＨＦ水溶液により分解後、ＡｇＮＯ３添加による比濁法による測定法。
【００３２】
（ｖｉ）シリカガラス中の不純物測定
Ｎａ、Ｋ、Ｍｇ、Ｃａ、Ｔｉ、Ｆｅは原子吸光光度法による測定法、Ｌｉ、Ｓｒ、Ｃｒ、Ｍｎ、Ｃｏ、Ｎｉ、Ｃｕはプラズマ質量分析法により測定（ＩＣＰ−ＭＳ法）。
【００３３】
（ｖｉｉ）ＡｒＦエキシマレーザ照射前後の１９３ｎｍの透過率の測定法
サイズ３０×２０×厚さ５ｍｍ、両面鏡面研磨仕上したサンプルに波長
１９３ｎｍ、波長半値幅３ｎｍ、パルス寿命半値幅１７ｎｓｅｃ、エネルギー密度５０ｍＪ／ｃｍ２／ｓｈｏｔ、周波数１００Ｈｚで照射ショット数１×１０６ｓｈｏｔｓのレーザ照射した時の１９３ｎｍでの透過率を測定する測定法。
【００３４】
（ｖｉｉｉ）Ｘｅ２エキシマランプ照射前後の波長１７２ｎｍの透過率の測定法サイズφ４０×厚さ５ｍｍ、両面鏡面研磨仕上したサンプルに波長１７２ｎｍ、波長半値幅１４ｎｍ、平均ランプエネルギー密度７ｍＷ／ｃｍ２で２１日間照射した時の１７２ｎｍでの透過率を測定する測定法。
【００３５】
〈評価〉
上記表１、３から明らかなように本発明の合成シリカガラス大型板材は、耐エキシマ光性およびその均一性に優れている。特に、実施例１、２、４については、ＯＨ基濃度が低くＨ２分子濃度が高いため、より耐エキシマ光性に優れている。
【００３６】
一方、比較例１、２の合成シリカガラス大型板材は、初期特性と耐エキシマ光性に劣り、比較例３、４の合成シリカガラス大型板材は、耐エキシマ光性に劣る上にＯＨ基濃度変動幅が大きく、透過率に分布があり不均一となっている。
【００３７】
【発明の効果】
本発明の合成シリカガラス大型板材は、１６０〜２００ｎｍの波長域の高出力真空紫外線に対して優れた初期透過率を示すとともに耐久性、それらの均一性に優れ、高出力真空紫外線を用いたドライ洗浄装置のウインドウ材として有用である。
【図面の簡単な説明】
【図１】本発明の製造方法における管開き成型の概略図である。
【符号の説明】
１ シリカガラスチューブ
２ 板材を引張る方向
３ 加熱手段
５ 切込み部[0001]
[Industrial application fields]
The present invention relates to a synthetic silica glass large plate for high-power vacuum ultraviolet rays and a method for producing the same, and more specifically, dry cleaning using high-power ultraviolet rays having a wavelength range of 160 to 200 nm, particularly high-power vacuum ultraviolet rays such as excimer lasers and excimer lamps, The present invention relates to a synthetic quartz glass large-sized window used as a window of a photo-CVD irradiation apparatus.
[0002]
[Prior art]
Currently, a dry cleaning apparatus using vacuum ultraviolet rays is being developed as a cleaning processing means in a method of manufacturing a silicon semiconductor element, and an ArF excimer laser (193 nm) having a wavelength of 160 to 200 nm, an Xe 2 excimer laser (172 nm), ArCl excimer laser (175 nm), Xe 2 excimer lamp (172 nm), ArCl excimer lamp (175 nm) and the like are considered. The dry cleaning device requires a large glass plate for the window, but when the window is made of commercially available window glass, the ultraviolet radiation emitted by the dry cleaning device is short wavelength, and the irradiation energy is mercury because of high output. Larger than lamps and CW lasers, it becomes damaged and becomes unusable. Therefore, it has been studied to form a window with silica glass that is less damaged against the high-power vacuum ultraviolet rays. However, conventional large silica glass introduces a high-purity silicon compound into an oxyhydrogen flame so that it can be hydrolyzed. By the direct method of directly depositing the obtained glass fine particles on the target or the VAD method of transparently solidifying a white opaque soot body obtained by hydrolyzing a high purity silicon compound with an oxyhydrogen flame in a vacuum atmosphere in an electric furnace A synthetic silica glass ingot is formed, heated and press-molded in a vacuum electric furnace using a graphite mold, cut into a thin plate, and polished. was there. Furthermore, the silica glass plate material obtained by the former direct method has a high OH group content of 400 to 1000 wtppm, damage is caused by irradiation with high-power vacuum ultraviolet rays for a long time, and light transmittance is lowered by solarization. Since it is formed in a layer shape, the OH group content can vary from 100 to 400 wtppm at the center and outer edge of the plate material, and the vacuum ultraviolet light transmittance and UV resistance are non-uniform in the plate material. It was not satisfactory for a window such as. In addition, the silica glass plate material obtained by the latter VAD method has an OH group content of 100 to 400 wtppm, which is smaller than that of the direct method, and the fluctuation range of the OH group is as small as 50 to 200 wtppm. The amount of variation in the amount and OH group concentration was large, and the transmittance and ultraviolet resistance of vacuum ultraviolet rays were not uniform in the plate material, which was a major obstacle. Therefore, development of a large-sized silica glass plate material with little damage to the high-power vacuum ultraviolet rays, high transmittance, and excellent uniformity thereof has been eagerly desired.
[0003]
[Problems to be solved by the invention]
In view of the current situation, the present inventors have conducted intensive research, and as a result, the OH group concentration of the large silica glass plate material is set to 5 to 300 wtppm, and the OH group concentration fluctuation range (ΔOH / cm) per cm is set to 10 wtppm or less. The present inventors have found that a large silica glass plate material that is stable and has high transmittance can be obtained even with high-power vacuum ultraviolet rays in the wavelength range of 160 to 200 nm. That is, [0004]
An object of the present invention is to provide a large-sized silica glass plate material having high initial transmittance with respect to high-power vacuum ultraviolet rays in a wavelength range of 160 to 200 nm, excellent durability, and uniformity thereof.
[0006]
[Means for Solving the Problems]
The present invention that achieves the above object is a synthetic silica glass large plate for high-power vacuum ultraviolet rays made of high-purity synthetic silica glass and used in a wavelength range of 160 to 200 nm, wherein the synthetic silica glass large plate is 300 × 300 mm wide. ~ Large plate with a height of 1,000 x 1000 mm and a thickness of 2 to 8 mm, the OH group concentration is 5 to 300 wtppm, and the fluctuation range of OH group concentration per cm of the flat plate surface (ΔOH / cm) Is a synthetic silica glass window for high-power vacuum ultraviolet rays characterized by being 10 wtppm or less.
[0007]
The large-sized synthetic silica glass plate of the present invention is a high-purity synthetic silica glass plate that is stable against high-power vacuum ultraviolet rays. The high-power vacuum ultraviolet rays are ArF excimer laser (193 nm), Xe 2 excimer laser (172 nm). ), ArCl excimer laser (175 nm), Xe 2 excimer lamp (172 nm), ArCl excimer lamp (175 nm), and the like. The high purity means that the concentration of alkali metal elements such as Li, Na and K and alkaline earth metal elements such as Mg and Ca in the silica glass plate is 10 wtppb or less, and transition metals such as Ti, Cr, Mn and Fe. The element concentration is 1 wtppb or less, and the concentration of transition metal elements such as Co, Ni, and Cu is 0.1 wtppb or less. When the alkali metal element and alkaline earth metal element concentration in the large-sized synthetic silica glass plate of the present invention exceeds the above range, recrystallization of silica glass is promoted and cristobalite is easily generated, and white devitrification occurs. . On the other hand, if the transition metal element concentration exceeds the above range, it absorbs ultraviolet rays and shifts the ultraviolet absorption edge to the longer wavelength side, leading to a decrease in transmittance, which is not preferable.
[0008]
In addition to the above, the synthetic silica glass large plate of the present invention must have an OH group concentration of 5 to 300 wtppm and an OH group concentration fluctuation range (ΔOH / cm) per cm of 10 wtppm or less. In general, the OH group is the terminal part of the structure in the silica glass network structure. If an appropriate amount of the OH group is contained in the silica glass, the internal strain in the network structure is removed, and the bonding angle of Si—O—Si. However, it is said that the average bond energy of Si—O increases as the value approaches a stable value. However, the OH group has an action of shifting the ultraviolet absorption edge of the silica glass to the long wavelength side, and when it is contained in a high concentration, the transmittance is lowered. Therefore, in the synthetic silica glass large plate of the present invention, the OH group concentration is in the range of 5 to 300 wtppm. In particular, when used for high-power vacuum ultraviolet rays having a wavelength of 160 to 180 nm, the OH group concentration is preferably 5 to 100 wtppm. Further, if the OH group concentration is not uniform, the transmittance, the absolute refractive index and the like are uneven depending on the position of the plate material, and as a result, the initial characteristics are deteriorated. Therefore, in the synthetic silica glass large plate of the present invention, the fluctuation range of OH group concentration per 1 cm (ΔOH / cm) is set to 10 wtppm or less. Furthermore, it is preferable that the OH group concentration fluctuation range (ΔOH) of the entire plate material is 50 wtppm or less.
[0009]
In addition to the above, the concentration of hydrogen molecules contained in the synthetic silica glass plate material of the present invention is set in the range of 1 × 10 17 to 1 × 10 20 molecules / cm 3 . By containing the hydrogen molecule at the above concentration, the generation of the E ′ center absorption band is suppressed, and the transmittance is less likely to decrease. Furthermore, when the water molecule concentration is 1 × 10 17 or less, the shift of the ultraviolet absorption edge to the long wavelength side caused by water molecules can be suppressed, which is preferable. However, the water molecule referred to here is not an OH group bonded to Si but a molecule dissolved in a gap in a silica glass network structure.
[0010]
Furthermore, the synthetic silica glass plate material of the present invention preferably contains a chlorine element content of 50 wtppm or less. Si—Cl formed by chlorine element serves as a precursor for generating a 210 nm absorption band, so-called E ′ center absorption band, but if it is within the above range, the generation of the precursor can be suppressed and the decrease in transmittance can be suppressed.
[0011]
The synthetic silica glass large plate of the present invention is produced by the following production method. That is, [0012]
(I) Production of synthetic silica glass cylinder SiCl 4 , HSiCl 3 , (CH 3 ) 2 SiCl 2 , CH 3 SiCl 3 , CH 3 Si (OCH 3 ) 3 , HSi (OCH) purified by means such as distillation 3 ) 3 and a silicon compound such as Si (OCH 3 ) 4 , preferably a silicon compound containing no chlorine such as CH 3 Si (OCH 3 ) 3 , HSi (OCH 3 ) 3 , and Si (OCH 3 ) 4 oxyhydrogen gas Alternatively, flame hydrolysis is performed using propane gas, and the OH group concentration in the axial direction is made uniform by a burner swing by a preparation method described in, for example, JP-A-4-260618, US Pat. No. 5,609,666. On the other hand, a white opaque large soot body is formed on the rod-shaped target. In the formation of the large soot body, the OH group concentration is adjusted according to the temperature, time, and degree of vacuum in the electric furnace. Subsequently, it is heated and melted at 1500 to 1700 ° C. in a vacuum atmosphere in the same electric furnace to obtain a cylindrical synthetic silica glass body having an outer diameter of 80 to 200 mm and a wall thickness of about 20 to 70 mm without bubbles. In the present invention, the method for producing the synthetic silica glass is referred to as a soot remelting method.
[0013]
(Ii) Manufacture of synthetic silica glass large plate material The large cylindrical synthetic silica glass body is heated while adjusting the internal pressure with N 2 gas, and is pulled into a large tube having an outer diameter of 200 to 400 mm and a wall thickness of about 3 to 10 mm. Mold. The resulting large tube is cut in a predetermined width in the tube axis direction, and pulled in the tangential direction of the tube while heating and softening with a strip burner in the tube circumferential direction from the inside and outside of the cut portion to the entire width in the tube axis direction. As shown in FIG. 1, it is flattened by a tube opening process to obtain a large synthetic silica glass plate. In FIG. 1, 1 is a silica glass tube, 2 is the direction in which the plate is pulled, 3 is a heating means, and 4 is a notch. The obtained synthetic silica glass large plate is subjected to strain removal treatment in an electric furnace, etched and heat-treated, and then mirror polished to have a size of 300 × 300 mm square to 1000 × 1000 mm square and a thickness of 2 to 8 mm. Finish the board. The obtained large plate has a flat OH group concentration fluctuation range of 10 wtppm or less per cm since the axial direction in which the OH group concentration is adjusted becomes the plate surface. On the other hand, the large fluctuation range of the OH group concentration in the radial direction of the tube is the fluctuation width in the thickness direction of the large plate. The plate material is thin with a thickness of 2 to 8 mm, and the OH group concentration is gradually increased or decreased uniformly. Therefore, the transmittance of the high-power vacuum ultraviolet ray and the degree of solarization caused thereby are less uneven and uniform in the plate surface direction. Has characteristics.
[0014]
BEST MODE FOR CARRYING OUT THE INVENTION
Next, the present invention will be described in detail based on specific examples, but the present invention is not limited thereto.
[0015]
【Example】
Examples 1-6
(1) Preparation of synthetic silica glass cylinder Ultra high purity CH 3 Si (OCH 3 ) 3 gas obtained by distillation purification was fixed at a total of 150 liters / minute, and the total of oxygen gas and total of hydrogen gas were 10 to 100 respectively. Liter / minute, supplied to a plurality of burners at a rate in the range of 30 to 300 liter / minute, and the OH group content is several hundred wtppm by an external method as described in JP-A-4-260618 while swinging the burner. The white large soot body was formed. The large soot body is installed in a stainless steel electric furnace equipped with a cylindrical high-purity graphite heater, and the electric furnace is evacuated to about 10 3 Pa or less and at a predetermined temperature in the range of about 600 to 900 ° C. The OH group concentration was adjusted by heat treatment. The OH group concentration was controlled by adjusting the degree of vacuum, temperature and time during processing. Subsequently, it was heated and remelted at about 1500 to 1700 ° C. under vacuum in an electric furnace to produce a synthetic silica glass cylinder having an outer diameter of 150 mm and a thickness of 40 mm.
[0016]
(2) Manufacture of silica glass tube While adjusting the internal pressure of the silica glass cylinder with nitrogen gas, it was heated through a graphite heater, and a large silica glass tube having a diameter of 250 mm, a length of 1600 mm, and a thickness of 7 mm was manufactured by horizontal tube drawing. .
[0017]
(3) Manufacture of synthetic silica glass large plate material The large
[0018]
Next, the samples of Examples 1 to 3 were annealed at 1 atm and hydrogen gas atmosphere at 600 ° C. for 3 hours, and in Example 4 at 100 atm and hydrogen gas atmosphere at 600 ° C. for 3 hours. To dope hydrogen molecules. For the obtained samples of Examples 1 to 4 and the samples of Examples 5 and 6 that were not subjected to the hydrogen doping treatment, the OH group concentration, the OH group concentration fluctuation width per cm (ΔOH / cm), the OH group concentration in the whole plate material The fluctuation width (ΔOH), hydrogen molecule concentration, water molecule concentration, chlorine element content, transmittance for Xe 2 excimer lamp and ArF excimer laser irradiation were measured, and the results are shown in Table 1.
[0019]
[Table 1]
Further, impurity element concentrations were measured for the synthetic silica glass large plate materials of Examples 5 and 6, and the results are shown in Table 2.
[0021]
[Table 2]
[0022]
Comparative Examples 1-4
In Comparative Examples 1 and 2, a white soot body is formed using the high-purity silicon compound used in Example 1 as a raw material, dehydrated in an electric furnace in a chlorine gas atmosphere, and further transparently solidified in a vacuum atmosphere. Create a synthetic silica glass cylinder (soot method) and make a large synthetic silica glass tube by horizontal tube drawing, then open the tube, press mold, and mirror polish, 650 x 550 x 5 mm thick synthetic silica glass A board was obtained. In Comparative Example 2, the synthetic silica glass large plate was further annealed in a hydrogen gas atmosphere to dope hydrogen molecules. OH group concentration of the large synthetic silica glass plate, OH group concentration fluctuation width per 1 cm (ΔOH / cm), OH group concentration fluctuation width (ΔOH) of the whole plate material, hydrogen molecule concentration, water molecule concentration, chlorine element content, The transmittance for Xe 2 excimer lamp and ArF excimer laser irradiation was measured, and the results are shown in Table 3.
[0024]
In Comparative Example 3, an ingot was produced by using an ultra-high purity SiCl 4 as a raw material by the direct method of the oxyhydrogen flame hydrolysis method, and in Comparative Example 4, the ingot was formed by the VAD method of the oxyhydrogen flame hydrolysis method. After performing this, it was hot press molded in a vacuum electric furnace using a graphite mold, cut into a thin layer plate, and a synthetic silica glass large plate was produced by mirror polishing. For each sample obtained, OH group concentration, OH group concentration fluctuation width per 1 cm (ΔOH / cm), OH group concentration fluctuation width (ΔOH) in the whole plate material, hydrogen molecule concentration, water molecule concentration, chlorine element content, The transmittance for Xe 2 excimer lamp and ArF excimer laser irradiation was measured, and the results are shown in Table 3.
[0025]
[Table 3]
The measuring method of each physical property value in the above Examples and Comparative Examples is as follows.
[0027]
(I) OH group concentration measurement method M.M. DODD and D.D. B. FRASER, Optical determination of OH in fused silica, Journal of Applied Physics, Vol. 37 (1966) p. Measurement method described in 3911 literature.
[0028]
(Ii) Measuring method of OH group concentration fluctuation width In a large silica glass plate of 650 × 550 × 5 mm thickness, 85 points of OH group concentration are measured at 10 mm intervals in the diagonal direction of the face plate. The OH group concentration fluctuation range per 1 cm (ΔOH / cm) from the two OH group concentration values of neighboring neighbors, and the OH group concentration fluctuation range (ΔOH) of the entire plate from the maximum and minimum values of the OH group concentration at 85 points. The measurement method to calculate.
[0029]
(Iii) Measuring method of hydrogen molecule concentration.
V. K. KHOTIMCHENKO, et al. , Determining the content of hydrodissolved in quartz glass using the methods of Raman scattering and mass spectrometry in Journal of Vaporization. 46, no. 6, (1987) pp 632-635.
[0030]
(Iv) Measuring method of water molecule concentration.
Y. MORIMOTO, et al. , Analysis of Gas Release from Vitreous Silica, Journal of Non-Crystalline Solids, 139 (1992) 35-46.
[0031]
(V) Measuring method of chlorine concentration.
Measurement method by turbidimetric method with AgNO 3 addition after decomposition with HF aqueous solution.
[0032]
(Vi) Impurity measurement in silica glass Na, K, Mg, Ca, Ti, Fe are measured by atomic absorption photometry, Li, Sr, Cr, Mn, Co, Ni, Cu are measured by plasma mass spectrometry ( ICP-MS method).
[0033]
(Vii) Measurement method of transmittance at 193 nm before and after irradiation with ArF excimer laser Size 30 × 20 × thickness 5 mm, double-sided mirror finished sample, wavelength 193 nm, wavelength half width 3 nm, pulse lifetime half width 17 nsec, energy density 50 mJ / A measurement method for measuring the transmittance at 193 nm when the laser irradiation with the number of irradiation shots of 1 × 10 6 shots is performed at cm 2 / shot and the frequency of 100 Hz.
[0034]
(Viii) Measuring method of transmittance at wavelength 172 nm before and after Xe 2 excimer lamp irradiation Size φ40 × thickness 5 mm, double-sided mirror-finished sample, wavelength 172 nm, wavelength half width 14 nm, average
[0035]
<Evaluation>
As is apparent from Tables 1 and 3, the synthetic silica glass large plate of the present invention is excellent in excimer light resistance and uniformity. In particular, Examples 1, 2, and 4 are more excellent in excimer light resistance because the OH group concentration is low and the H 2 molecule concentration is high.
[0036]
On the other hand, the synthetic silica glass large plate materials of Comparative Examples 1 and 2 are inferior in initial characteristics and excimer light resistance, and the synthetic silica glass large plate materials in Comparative Examples 3 and 4 are inferior in excimer light resistance and change in OH group concentration. The width is large and the transmittance is distributed and non-uniform.
[0037]
【The invention's effect】
The synthetic silica glass large plate of the present invention exhibits excellent initial transmittance with respect to high-power vacuum ultraviolet rays in the wavelength range of 160 to 200 nm, is excellent in durability and uniformity thereof, and is dry using high-power vacuum ultraviolet rays. It is useful as a window material for cleaning devices .
[Brief description of the drawings]
FIG. 1 is a schematic view of tube opening molding in the production method of the present invention.
[Explanation of symbols]
DESCRIPTION OF
Claims (4)
Priority Applications (5)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP22445097A JP3630533B2 (en) | 1997-08-07 | 1997-08-07 | Synthetic silica glass large plate for high output vacuum ultraviolet ray and method for producing the same |
| US09/214,894 US6143676A (en) | 1997-05-20 | 1998-05-20 | Synthetic silica glass used with uv-rays and method producing the same |
| EP98928299A EP0917523B1 (en) | 1997-05-20 | 1998-05-20 | Synthetic silica glass used with uv-rays and method producing the same |
| PCT/EP1998/002965 WO1998052879A1 (en) | 1997-05-20 | 1998-05-20 | Synthetic silica glass used with uv-rays and method producing the same |
| DE69816758T DE69816758T2 (en) | 1997-05-20 | 1998-05-20 | SYNTHETIC QUARTZ GLASS FOR USE IN UV RADIATION AND METHOD FOR THE PRODUCTION THEREOF |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP22445097A JP3630533B2 (en) | 1997-08-07 | 1997-08-07 | Synthetic silica glass large plate for high output vacuum ultraviolet ray and method for producing the same |
Related Child Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP2004265100A Division JP4111940B2 (en) | 2004-09-13 | 2004-09-13 | Method for producing synthetic silica glass large plate for high output vacuum ultraviolet light |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH1160264A JPH1160264A (en) | 1999-03-02 |
| JP3630533B2 true JP3630533B2 (en) | 2005-03-16 |
Family
ID=16813971
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP22445097A Expired - Lifetime JP3630533B2 (en) | 1997-05-20 | 1997-08-07 | Synthetic silica glass large plate for high output vacuum ultraviolet ray and method for producing the same |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP3630533B2 (en) |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2002097036A (en) * | 2000-09-21 | 2002-04-02 | Photoscience Japan Corp | Vitreous silica for short wavelength ultraviolet ray, discharge lamp using it, the container, and ultraviolet ray radiation device |
| JP2005298323A (en) * | 2004-03-18 | 2005-10-27 | Shinetsu Quartz Prod Co Ltd | Large size synthetic quartz glass plate for excimer uv lamp device |
| US20070059533A1 (en) * | 2005-09-12 | 2007-03-15 | Burdette Steven R | Thermal reflow of glass and fused silica body |
| DE102006043368B4 (en) * | 2005-09-16 | 2019-01-10 | Corning Inc. | Synthetic silicic acid glass and process for producing the same |
-
1997
- 1997-08-07 JP JP22445097A patent/JP3630533B2/en not_active Expired - Lifetime
Also Published As
| Publication number | Publication date |
|---|---|
| JPH1160264A (en) | 1999-03-02 |
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