JP4447246B2 - Method for producing quartz glass - Google Patents
Method for producing quartz glass Download PDFInfo
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- JP4447246B2 JP4447246B2 JP2003166466A JP2003166466A JP4447246B2 JP 4447246 B2 JP4447246 B2 JP 4447246B2 JP 2003166466 A JP2003166466 A JP 2003166466A JP 2003166466 A JP2003166466 A JP 2003166466A JP 4447246 B2 JP4447246 B2 JP 4447246B2
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- quartz glass
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Classifications
-
- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
- C03B19/00—Other methods of shaping glass
- C03B19/14—Other methods of shaping glass by gas- or vapour- phase reaction processes
- C03B19/1453—Thermal after-treatment of the shaped article, e.g. dehydrating, consolidating, sintering
-
- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
- C03B2201/00—Type of glass produced
- C03B2201/06—Doped silica-based glasses
- C03B2201/08—Doped silica-based glasses doped with boron or fluorine or other refractive index decreasing dopant
- C03B2201/12—Doped silica-based glasses doped with boron or fluorine or other refractive index decreasing dopant doped with fluorine
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Physics & Mathematics (AREA)
- Thermal Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Manufacturing & Machinery (AREA)
- Materials Engineering (AREA)
- Organic Chemistry (AREA)
- Glass Compositions (AREA)
- Lasers (AREA)
- Glass Melting And Manufacturing (AREA)
- Surface Treatment Of Glass (AREA)
Description
【0001】
【発明の属する技術分野】
本発明は、エキシマレーザ等の紫外域の高出力レーザ光を利用する光学装置に使用され、耐紫外線特性に優れた石英ガラスの製造方法に関するものである。
【0002】
【従来の技術】
紫外線、特に真空紫外と呼ばれる波長200nm以下のArFエキシマレーザ光(193nm)、F2エキシマレーザ光(157nm)に耐性の高いガラスとして、石英ガラスにF(フッ素)をドープしたガラスが使用される。
【0003】
このガラスは主に、VAD法で作製したスート(微粒子成形体)をF含有化合物を含む雰囲気で処理した後、加熱焼結して透明ガラス化するが、その際、一旦形成されたSi−F結合の一部が再び解離してF2 分子とSi−Si結合を形成することが知られている(例えば、特許文献1を参照)。
【0004】
Si−Si結合は163nmに吸収帯を持つため、F2エキシマレーザ光透過率低下の要因となる。またSi−Si結合は容易に上記エキシマレーザ光により解離してSi・(E’センター)を生成するが、Si・は210nm帯に吸収を持つため、ArFエキシマレーザ光透過率低下の要因となる。また、エキシマレーザを照射した際に切断されて透過率低下の原因となるのは上記Si−Si結合以外にもSi−O−O−Si結合や歪んだSi−O−Si結合、原料に含まれる塩素に由来するSi−Cl結合等がある。
【0005】
焼結後のガラスに関して、紫外線耐性を向上させる処理方法としては、アニール処理が一般に行われる(例えば、特許文献2を参照)。アニール処理により仮想温度を低下させることにより、三員環、四員環等の歪んだSi−O−Si結合を低減してSi−O−Siネットワークの平均結合角を広げて、紫外光に対して安定な構造とするものであるが、あくまで平均的、統計的な処理方法であり、その有効性には限界がある。
【0006】
また、特許文献3には、純粋シリカガラスに対して、紫外線照射後、または紫外線照射と同時に熱処理することにより、耐紫外線性を付与する手法が開示されているが、紫外線照射により切断されたSi−O−Si結合を、熱処理により再結合させることを目的としたものであり、Si−Si結合やSi−O−O−Si結合に対しては効果が小さい。
【0007】
特許文献4及び特許文献5には、合成石英ガラス部材に波長260nm以下の連続紫外線を照射して193nmの紫外透過率を改善する手法が開示されているが、これは不純物としてNaを含有する場合に、紫外透過率を改善する手段として有効なもので、耐紫外特性の改善を対象とするものではない。
【0008】
紫外線透過率低下を防止する手段としては、他にH2分子をガラスの中に溶存させる手段が用いられるが(特許文献6及び特許文献7)、これらは弱い結合を事前に補修するわけではなく、エキシマレーザ照射により生成するSi・やSi−O・等の吸収を持つ欠陥種を、吸収を持たないSi−H、Si−OHに変換して透過率低下を防止するものである。しかしSi−Hは強い結合ではないので再びレーザ光により解離して欠陥種となりやすい。この手法はArFエキシマレーザには有効であるが、F2エキシマレーザに対してはかならずしも有効ではない。
【0009】
【特許文献1】
特開2001−72428号公報
【特許文献2】
特開平10−67526号公報
【特許文献3】
特開2000−86258号公報
【特許文献4】
特開2000−258601号公報
【特許文献5】
特開2000−143258号公報
【特許文献6】
特開平3−88742号公報
【特許文献7】
特開平10−324538号公報
【0010】
【発明が解決しようとする課題】
本発明は上記事情に鑑みてなされたもので、長時間にわたる紫外線照射による透過率の低下が少ない、耐紫外線特性に優れた石英ガラスの製造方法を提供することを目的とする。
【0011】
【課題を解決するための手段】
本発明の請求項1に係る石英ガラスの製造方法は、フッ素濃度が100wtppm〜10000wtppmである石英ガラスを用い、該石英ガラスに主波長が200nmより短い真空紫外光を照射する第一の光学処理工程と、前記石英ガラスを400℃以上徐冷点以下の温度に1時間以上保持して加熱する熱処理工程とを備え、前記第一の光学処理工程に次いで前記熱処理工程を行う、又は、前記第一の光学処理工程とともに前記熱処理工程を行う石英ガラスの製造方法であって、前記熱処理工程を行うためにマイクロ波を用いることを特徴としている。
【0012】
本発明の請求項2に係る石英ガラスの製造方法は、フッ素濃度が100wtppm〜10000wtppmである石英ガラスを用い、該石英ガラスに主波長が200nmより短い真空紫外光を照射する第一の光学処理工程と、前記石英ガラスを400℃以上徐冷点以下の温度に1時間以上保持して加熱する熱処理工程とを備え、前記第一の光学処理工程に次いで前記熱処理工程を行う、又は、前記第一の光学処理工程とともに前記熱処理工程を行う石英ガラスの製造方法であって、前記第一の光学処理工程及び/又は前記熱処理工程とともに、前記石英ガラスに主波長が200nm以上350nm以下の紫外光を照射する第二の光学処理工程を行うことを特徴としている。
【0013】
本発明の請求項3に係る石英ガラスの製造方法は、請求項2に記載の石英ガラスの製造方法において、前記第二の光学処理工程を行う光源として、水銀ランプ、LD励起YAGレーザ又はKrFエキシマレーザを用いることを特徴としている。
【0015】
第一の光学処理工程では、フッ素濃度を100wtppm〜10000wtppmとした石英ガラスに主波長が200nmより短い真空紫外光を照射することにより、Si−Si結合等のガラス中の弱い結合を切断する。
【0016】
次いで、第一の光学処理工程を経た石英ガラスに対し、400℃以上徐冷点以下の温度に1時間以上保持して加熱する熱処理工程を施すことで、石英ガラスを徐冷点以下の高温状態とし、溶存F2 で切断された結合を補修する。
【0017】
前記第一の光学処理工程に次いで前記熱処理工程を行う、又は、前記第一の光学処理工程とともに前記熱処理工程を行うことにより、上記作用が得られる。したがって、本発明に係る石英ガラスの製造方法は、上述した優れた耐紫外線特性を有する石英ガラスの安定した製造に寄与する。
【0018】
前記第一の光学処理工程を行う光源としてArFエキシマレーザ、F2エキシマレーザ又はXeエキシマランプが好適に用いられる。前記熱処理工程を行うためにはマイクロ波が好ましい。
【0019】
上述した石英ガラスの製造方法は、前記第一の光学処理工程及び/又は前記熱処理工程とともに、前記石英ガラスに主波長が200nm以上350nm以下の紫外光を照射する第二の光学処理工程を行うことが好ましい。
【0020】
上記第二の光学処理工程を加えると、F2 分子が吸収をもつ波長である288nm付近の紫外線を照射することにより、Fラジカルがより生成されるので、上述した補修効果を向上させることができる。特に、高温処理と同時に行えば、より一層その効果を高くすることができるので望ましい。
【0021】
前記第二の光学処理工程を行う光源としては、水銀ランプ、LD励起YAGレーザ又はKrFエキシマレーザが好ましい。
【0022】
【発明の実施の形態】
以下、実施の形態に基づいて本発明を詳しく説明する。
本発明に係る石英ガラスは、フッ素を100wtppm〜10000wtppmの範囲で含有する石英ガラスであり、Si−Si結合のうち、紫外線により切断された状態にある自由端(ダングリングボンド)が、加熱または加熱と紫外線照射により溶存フッ素(F)で補修され、Si−F結合をなしている。
【0023】
本発明では、フッ素を含有する石英ガラスが用いられるが、その含有量は100wtppm〜10000wtppmが好ましい。フッ素含有量が100wtppmより少ない場合は、溶存するF2 分子が著しく少なくなるためにFラジカルによる補修も殆ど行われなくなることから芳しくない。一方、10000wtppmより多い場合は、紫外線により切断される結合が著しく多くなり補修が間に合わなくなることから好ましくない。
【0024】
あらかじめフッ素を上記範囲内の一定の割合で含有する石英ガラスであれば、この一定の割合で存在するF2分子、または積極的にガラス中に溶存させたF2分子を利用することにより、あらかじめエキシマレーザ等で切断した弱い結合をFで補修しておくことが可能となるので、上記構成によれば、優れた耐エキシマレーザ特性を有する石英ガラスが得られる。Si−F結合はSi−O結合よりも強く、ArF、F 2 エキシマレーザ光でも切断されにくいので、このような処理を施された石英ガラスは、特にエキシマレーザ照射時の初期の透過率低下を抑制する高い能力を備えることが可能となる。
【0025】
上記構成からなる石英ガラスの代表的な作製手順は、以下の通りである。
1)VAD法等で作製したスートをフッ素含有化合物を含む雰囲気中で加熱、焼結してF2の溶存したフッ素ドープ石英ガラスを作製する。
2)作製した石英ガラス体を切断、研磨した板状とする。
3)ArF、F2エキシマレーザまたはXeエキシマランプ等の紫外光を一定の強度で一定の時間、上記石英ガラスに照射して、Si−Si結合等のガラス中の弱い結合を切断する。
【0026】
4)上記操作と同時か、その後にガラスを徐冷点以下の高温に加熱し、溶存F2で切断された結合を補修する。高温にすることにより、実際に補修の作用を担うFラジカルが発生しやすくなり、Fラジカルが切断位置に容易に移動できるようになる。徐冷点以上の高温にしてしまうと、補修により形成されたSi−F結合や、既に形成されていたSi−F結合の一部が再び解離してF2分子とSi−Si結合を形成しやすくなる。また、一旦切断した三員環、四員環等の歪んだSi−O−Si結合も再形成されてしまう。
【0027】
5)高温処理する際、F2分子が吸収を持つ288nm付近の紫外線を同時に照射した方が、Fラジカルがより生成しやすくなるため、補修の効果が高い。光源としては、新たな欠陥を生成しない強度の水銀ランプ(254nm)、LD励起YAGレーザ(266nm)、KrFエキシマレーザ(248nm)等が好適に使用される。
【0028】
【実施例】
〔試験例1〕
VAD法によって得た石英ガラスのスートを、0.01%〜30%SiF4と残部Heからなる雰囲気中に、800℃〜1100℃で、5hr〜80hr保持した後、1380℃〜1460℃で、2hr〜5hrの焼結処理を施すという前処理を行うことにより、平均F濃度が50〜12000wtppmの範囲で異なる透明ガラス体(この前処理を施したものを試料1αと呼ぶ。)を得た。
【0029】
次に、平均F濃度が異なる試料1αに対して、10mJ/cm2 /shotのArFエキシマレーザ(193nm)を1×106 回照射後、100%He雰囲気中に700℃で8hr保持という後処理を行った。この後処理を施したものを試料1βと呼ぶ。
【0030】
上記の平均F濃度が異なる試料1βに対し、80mJ/cm2 /shotのArFエキシマレーザ(193nm)を200Hzの繰り返し周波数で1×106 回照射し、照射前後でのArFエキシマレーザ透過率変化を測定した。その結果を表1に示す。
【0031】
【表1】
【0032】
(A1) 表1から、平均F濃度が100wtppm〜10000wtppmの範囲にある試料1βであれば、レーザ照射後の透過率低下を1.0%以下に抑制できることが分かった。
【0033】
〔試験例2〕
VAD法によって得た石英ガラスのスートを、0.1%SiF4、99.9%He雰囲気中に1000℃で20hr保持した後、1400℃で2hrの焼結処理を施すという前処理を行うことにより、平均F濃度が4200wtppmの透明ガラス体(この前処理を施したものを試料2αと呼ぶ。)を得た。この透明ガラス体を切断、研磨して厚さ20mm、直径100mmの円盤を複数枚作製した。
【0034】
次に、上記切断、研磨された試料2αに対して、以下の異なる条件からなる後処理を施し、3種類の試料2βa、試料2βb、試料2βcを作製した。
【0035】
試料2βa[サンプルA]の後処理条件とは、10mJ/cm2 /shotのArFエキシマレーザ(193nm)を1×106 回照射した後、100%He雰囲気中に700℃で8hr保持するものである。
【0036】
試料2βb[サンプルB]の後処理条件とは、10mJ/cm2 /shotのArFエキシマレーザ(193nm)を1×106 回照射した後、100%He雰囲気中、マイクロ波(28GHz)により700℃で8hr保持するものである。
【0037】
試料2βc[サンプルC]の後処理条件とは、10mJ/cm2 /shotのArFエキシマレーザ(193nm)を1×106 回照射した後、100%He雰囲気中700℃で8hr保持し、これと同時に水銀ランプを1mW/cm2 の照度で全面に照射するものである。
【0038】
(比較例1)
上記後処理の効果を確認するため、本例では試料2βd[サンプルD]として、上述した試料2βaの後処理を行わなかったもの採用した。
【0039】
上記4種類の試料2βに対し、80mJ/cm2 /shotのArFエキシマレーザ(193nm)を200Hzの繰り返し周波数で1×106 回照射し、照射前後でのArFエキシマレーザ透過率変化を測定した。その結果を表2に示す。
【0040】
【表2】
【0041】
表2から、以下の点が明らかとなった。
(B1)後処理として、ArFエキシマレーザを照射した後、熱処理または熱処理と紫外線照射両方を施すことにより、試料の透過率低下の度合いが減少する(試料2βa,試料2βb,試料2βc)。
【0042】
(B2)特に熱処理と紫外線照射両方を施した試料の透過率低下の度合いは、著しく減少する(試料2βc)。
【0043】
(B3)マイクロ波による加熱は、通常の抵抗過熱炉による加熱よりも効果が大きい(試料2βb)が、これはマイクロ波の持ついわゆる非熱的効果により、欠陥の補修が効率的に行われるためと考えられる。
【0044】
〔試験例3〕
VAD法によって得た石英ガラスのスートを、0.01%SiF4、99.99%He雰囲気中に1000℃で20hr保持した後、100%He雰囲気中において1440℃で2hrの焼結処理を施すという前処理を行うことにより、平均F濃度が1800wtppmの透明ガラス体(この前処理を施したものを試料3αと呼ぶ。)を得た。この透明ガラス体を切断、研磨して厚さ20mm、直径100mmの円盤を複数枚作製した。
【0045】
次に、この切断、研磨した試料3αに対して、以下の異なる条件からなる後処理を施し、4種類の試料3βa、試料3βb、試料3βc、試料3βdを作製した。さらに、各々の後処理を行った後、全ての試料は、100%、0.81MPaのH2 雰囲気中において、500℃で120hr保持して試料内部にH2 を溶存させた。
【0046】
試料3βa[サンプルE]の後処理条件とは、5mW/cm2 /shotのXeエキシマランプ(172nm)を48hr照射した後、100%He雰囲気中に700℃で8hr保持するものである。
【0047】
試料3βb[サンプルF]の後処理条件とは、5mW/cm2 /shotのXeエキシマランプ(172nm)を48hr照射中、100%He雰囲気中に500℃で保持するものである。
【0048】
試料3βc[サンプルG]の後処理条件とは、5mW/cm2 /shotのXeエキシマランプ(172nm)を48hr照射した後、100%He雰囲気中に700℃で8hr保持し、これと同時に水銀ランプを1mW/cm2 の照度で全面に照射するものである。
【0049】
試料3βd[サンプルH]の後処理条件とは、5mW/cm2 /shotのXeエキシマランプ(172nm)を48hr照射中、100%He雰囲気中に500℃で保持し、これと同時に水銀ランプを1mW/cm2 の照度で全面に照射するものである。
【0050】
(比較例2)
上記後処理の効果を確認するため、本例では試料3βe[サンプルI]として、上述した試料3βaの後処理を行わなかったもの採用した。
【0051】
上記5種類の試料3βに対し、80mJ/cm2 /shotのArFエキシマレーザ(193nm)を200Hzの繰り返し周波数で1×106 回照射し、照射前後でのArFエキシマレーザ透過率変化を測定した。その結果を表3に示す。
【0052】
【表3】
【0053】
表3から、以下の点が明らかとなった。
(C1)後処理として、Xeエキシマランプを照射した後または照射中に、熱処理または熱処理と紫外線照射両方を施すことにより、試料の透過率低下の度合いが減少する(試料3βa,試料3βb,試料3βc,試料3βd)。
【0054】
(C2)後処理を行った後に施した試料内部へのH2 溶存処理により、全ての試料における透過率低下の度合いはさらに減少する(試料3βa,試料3βb,試料3βc,3βd)。
【0055】
(C3)特に熱処理と紫外線照射両方を同時に施した試料の透過率低下の度合いは、著しく減少する(試料3βc,試料3βd)。
【0056】
(比較例3)
上述したフッ素をドープした試料における前処理および後処理の効果を確認するため、本例では前処理においてフッ素をドープしない試料を作製した。
すなわち、VAD法によって得た石英ガラスのスートを、100%He雰囲気中において1480℃で2hrの焼結処理を施し、フッ素がドープされていない透明ガラス体(この前処理を施したものを試料4αと呼ぶ。)を得た。この透明ガラス体を切断、研磨して厚さ20mm、直径100mmの円盤を複数枚作製した。
【0057】
次に、この切断、研磨した試料4αに対して、以下の異なる条件からなる後処理を施し、3種類の試料4βa、試料4βb、試料4βcを作製した。
【0058】
試料4βa[サンプルJ]は、後処理を行わなかったものであり、後処理の効果を確認するために用いた。
【0059】
試料4βb[サンプルK]の後処理条件とは、10mJ/cm2 /shotのArFエキシマレーザ(193nm)を1×106 回照射した後、100%He雰囲気中に700℃で8hr保持するものである。
【0060】
試料4βc[サンプルL]の後処理条件とは、10mJ/cm2 /shotのArFエキシマレーザ(193nm)を1×106 回照射した後、100%He雰囲気中に700℃で8hr保持し、これと同時に水銀ランプを1mW/cm2 の照度で全面に照射するものである。
【0061】
上記3種類の試料4βに対し、80mJ/cm2 /shotのArFエキシマレーザ(193nm)を200Hzの繰り返し周波数で1×106 回照射し、照射前後でのArFエキシマレーザ透過率変化を測定した。その結果を表4に示す。
【0062】
【表4】
【0063】
表4から、以下の点が明らかとなった。
(D1)後処理を全く行わない場合(4βa)よりは後処理を行った方(4βb)が、前処理の効果が見られる。
【0064】
(D2)しかしながら、後処理として、ArFエキシマレーザを照射した後、熱処理を施しても、フッ素をドープしない試料に対してはその効果は殆ど発揮されない(試料4βb)。
【0065】
(D3)また、熱処理と紫外線照射両方を同時に施しても、フッ素をドープしない試料に対してはその効果は認められない(試料4βc)。
【0066】
(D4)よって、表4の結果より、Fドープしない試料では、ArFエキシマレーザを照射後に熱処理または熱処理と紫外線照射両方を施しても効果が小さいことが分かった。
【0067】
【発明の効果】
以上説明したように、本発明に係る石英ガラスの製造方法は、フッ素ドープ石英ガラスにおいて、紫外線により一旦切断したSi−Si結合等のガラス中の弱い結合を、加熱または加熱と紫外線照射により溶存F2で補修してより強い結合であるSi−Fに変換することにより、処理前よりも耐紫外線特性に優れているので、この製造方法によって作製された材料を例えば窓材として用いることにより、真空紫外に発振波長を有するレーザの長期信頼性の向上に寄与する。
【0068】
本発明に係る石英ガラスの製造方法において、フッ素濃度が100wtppm〜10000wtppmである石英ガラスを用い、該石英ガラスに主波長が200nmより短い真空紫外光を照射する第一の光学処理工程と、前記石英ガラスを400℃以上徐冷点以下の温度に1時間以上保持して加熱する熱処理工程とを備え、前記第一の光学処理工程に次いで前記熱処理工程を行う、又は、前記第一の光学処理工程とともに前記熱処理工程を行うことにより、長時間にわたる紫外線照射による透過率の低下が少ない、耐紫外線特性に優れた石英ガラスを安定して作製できる。
【0069】
そして、本発明の請求項1に係る石英ガラスの製造方法は、上記熱処理をマイクロ波で行うことにより、マイクロ波による非熱的作用により、効率的な耐紫外線特性をさらに向上させることができる。
【0070】
さらに、本発明の請求項2に係る石英ガラスの製造方法は、前記第一の光学処理工程及び/又は前記熱処理工程とともに、前記石英ガラスに主波長が200nm以上350nm以下の紫外光を照射する第二の光学処理工程を行うことにより、一段と高い耐紫外線特性が確立できる。
【0071】
よって、本発明に係る製造方法は、優れた量産性を実現するとともに、高品質でかつ長寿命である石英ガラスの安定した提供に貢献する。[0001]
BACKGROUND OF THE INVENTION
The present invention is used in an optical device utilizing a high output laser light of ultraviolet region such as an excimer laser, a method of manufacturing a superior quartz glass ultraviolet resistance.
[0002]
[Prior art]
As a glass having high resistance to ultraviolet light, particularly ArF excimer laser light (193 nm) and F2 excimer laser light (157 nm), which is called vacuum ultraviolet light, a glass in which F (fluorine) is doped into quartz glass is used.
[0003]
This glass is mainly treated with a soot (fine particle compact) produced by the VAD method in an atmosphere containing an F-containing compound and then sintered by heating to form a transparent glass. At that time, once formed Si-F It is known that part of the bonds are dissociated again to form F 2 molecules and Si—Si bonds (see, for example, Patent Document 1).
[0004]
Since the Si—Si bond has an absorption band at 163 nm, it causes a decrease in F2 excimer laser light transmittance. The Si—Si bond is easily dissociated by the excimer laser beam to generate Si · (E ′ center). However, since Si · has absorption in the 210 nm band, it causes a decrease in the transmittance of the ArF excimer laser beam. . In addition to the Si-Si bond, it is cut when the excimer laser is irradiated and the transmittance is reduced. In addition to the Si-Si bond, the Si-O-O-Si bond and the distorted Si-O-Si bond are included in the raw material. Si-Cl bond derived from chlorine.
[0005]
An annealing process is generally performed as a processing method for improving the ultraviolet resistance of the sintered glass (see, for example, Patent Document 2). By reducing the fictive temperature by annealing treatment, the strained Si-O-Si bonds such as three-membered rings and four-membered rings are reduced, and the average bond angle of the Si-O-Si network is widened. The structure is stable and stable, but it is an average and statistical processing method, and its effectiveness is limited.
[0006]
Patent Document 3 discloses a method of imparting ultraviolet resistance to pure silica glass by heat treatment after ultraviolet irradiation or simultaneously with ultraviolet irradiation, but Si C cut by ultraviolet irradiation is disclosed. This is intended to recombine —O—Si bonds by heat treatment, and has little effect on Si—Si bonds and Si—O—O—Si bonds.
[0007]
Patent Document 4 and Patent Document 5 disclose a method for improving the 193 nm ultraviolet transmittance by irradiating a synthetic quartz glass member with continuous ultraviolet light having a wavelength of 260 nm or less, which includes Na as an impurity. In addition, it is effective as a means for improving the ultraviolet transmittance, and is not intended to improve the ultraviolet resistance.
[0008]
As a means for preventing a decrease in ultraviolet transmittance, other means for dissolving H2 molecules in glass are used (Patent Document 6 and Patent Document 7), but these do not repair weak bonds in advance, A defect type having absorption such as Si. Or Si-O. Produced by excimer laser irradiation is converted to Si-H or Si-OH having no absorption to prevent a decrease in transmittance. However, since Si—H is not a strong bond, it is easily dissociated by laser light and becomes a defect species. This method is effective for an ArF excimer laser, but is not always effective for an F2 excimer laser.
[0009]
[Patent Document 1]
Japanese Patent Laid-Open No. 2001-72428 [Patent Document 2]
Japanese Patent Laid-Open No. 10-67526 [Patent Document 3]
JP 2000-86258 A [Patent Document 4]
JP 2000-258601 A [Patent Document 5]
JP 2000-143258 A [Patent Document 6]
JP-A-3-88742 [Patent Document 7]
Japanese Patent Laid-Open No. 10-324538
[Problems to be solved by the invention]
The present invention has been made in view of the above circumstances, reduction in transmittance due to ultraviolet irradiation for a long time is small, and an object thereof is to provide a method for producing superior quartz glass ultraviolet resistance.
[0011]
[Means for Solving the Problems]
The method for producing quartz glass according to claim 1 of the present invention uses a quartz glass having a fluorine concentration of 100 wtppm to 10000 wtppm, and irradiates the quartz glass with vacuum ultraviolet light having a dominant wavelength shorter than 200 nm. And a heat treatment step of heating the quartz glass at a temperature of 400 ° C. or more and an annealing point for 1 hour or more, and performing the heat treatment step after the first optical treatment step, or the first A method for producing quartz glass that performs the heat treatment step together with the optical treatment step, wherein microwaves are used to perform the heat treatment step.
[0012]
The method for producing quartz glass according to claim 2 of the present invention uses a quartz glass having a fluorine concentration of 100 wtppm to 10000 wtppm, and irradiates the quartz glass with vacuum ultraviolet light having a dominant wavelength shorter than 200 nm. And a heat treatment step of heating the quartz glass at a temperature of 400 ° C. or more and an annealing point for 1 hour or more, and performing the heat treatment step after the first optical treatment step, or the first A method for producing quartz glass in which the heat treatment step is performed together with the optical treatment step, wherein the quartz glass is irradiated with ultraviolet light having a dominant wavelength of 200 nm or more and 350 nm or less together with the first optical treatment step and / or the heat treatment step. The second optical processing step is performed.
[0013]
The method for producing quartz glass according to claim 3 of the present invention is the method for producing quartz glass according to claim 2, wherein a mercury lamp, an LD-excited YAG laser, or a KrF excimer is used as a light source for performing the second optical processing step. It is characterized by using a laser.
[0015]
In the first optical treatment process, weak bonds in the glass such as Si-Si bonds are cut by irradiating quartz glass having a fluorine concentration of 100 wtppm to 10000 wtppm with vacuum ultraviolet light having a dominant wavelength shorter than 200 nm.
[0016]
Next, the quartz glass that has undergone the first optical processing step is subjected to a heat treatment step in which the quartz glass is heated at a temperature of 400 ° C. or higher and below the annealing point for 1 hour or more, so that the quartz glass is in a high temperature state below the annealing point. And repair the bond cleaved with dissolved F 2 .
[0017]
The said effect | action is acquired by performing the said heat processing process following a said 1st optical processing process, or performing the said heat processing process with a said 1st optical processing process. Therefore, the method for producing quartz glass according to the present invention contributes to the stable production of quartz glass having the above-described excellent ultraviolet resistance.
[0018]
An ArF excimer laser, F2 excimer laser, or Xe excimer lamp is preferably used as a light source for performing the first optical processing step. Microwave is preferred for performing the heat treatment step.
[0019]
The method for producing quartz glass described above includes performing the second optical processing step of irradiating the quartz glass with ultraviolet light having a principal wavelength of 200 nm to 350 nm in addition to the first optical processing step and / or the heat treatment step. Is preferred.
[0020]
When the second optical processing step is added, F radicals are generated more by irradiating ultraviolet rays around 288 nm, which is the wavelength at which the F 2 molecule has absorption, so that the above-described repair effect can be improved. . In particular, it is desirable to perform it at the same time as the high temperature treatment because the effect can be further enhanced.
[0021]
As a light source for performing the second optical processing step, a mercury lamp, an LD excitation YAG laser, or a KrF excimer laser is preferable.
[0022]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail based on embodiments.
The quartz glass according to the present invention is a quartz glass containing fluorine in a range of 100 wtppm to 10000 wtppm, and a free end (dangling bond) in a state cut by ultraviolet rays among Si-Si bonds is heated or heated. And repaired with dissolved fluorine (F) by ultraviolet irradiation to form a Si-F bond.
[0023]
In the present invention, quartz glass containing fluorine is used, but the content is preferably 100 wtppm to 10000 wtppm. When the fluorine content is less than 100 wtppm, the amount of dissolved F 2 molecules is remarkably reduced, so that repair by F radicals is hardly performed, which is not good. On the other hand, when it is more than 10000 wtppm, the number of bonds that are cut by ultraviolet rays is remarkably increased, and repair is not completed in time.
[0024]
Advance if fluorine quartz glass containing at a constant rate within the above range, by using the F 2 molecule or F 2 molecules actively is dissolved in the glass, in a proportion of this constant, pre Since weak bonds cut with an excimer laser or the like can be repaired with F, according to the above configuration, quartz glass having excellent excimer laser resistance can be obtained. Since the Si-F bond is stronger than the Si-O bond and is difficult to be cut by ArF or F 2 excimer laser light, the quartz glass treated in this way has an initial decrease in transmittance particularly during excimer laser irradiation. It is possible to have a high ability to suppress.
[0025]
A typical procedure for producing quartz glass having the above-described configuration is as follows.
1) A soot produced by the VAD method or the like is heated and sintered in an atmosphere containing a fluorine-containing compound to produce a fluorine-doped quartz glass in which F2 is dissolved.
2) The produced quartz glass body is cut and polished into a plate shape.
3) The quartz glass is irradiated with ultraviolet light such as ArF, F2 excimer laser or Xe excimer lamp at a constant intensity for a certain time to break weak bonds in the glass such as Si-Si bond.
[0026]
4) At the same time as the above operation, or after that, the glass is heated to a high temperature below the annealing point to repair the bond cut by dissolved F2. By increasing the temperature, F radicals that are actually responsible for repairing are easily generated, and the F radicals can easily move to the cutting position. If the temperature is higher than the annealing point, the Si-F bond formed by the repair or a part of the Si-F bond that has already been formed is dissociated again to easily form the Si-Si bond with the F2 molecule. Become. In addition, a distorted Si—O—Si bond such as a three-membered ring or a four-membered ring once broken is also re-formed.
[0027]
5) When high-temperature treatment is performed, irradiation with ultraviolet rays near 288 nm, in which F2 molecules are absorbed, is more effective for repair because F radicals are more easily generated. As the light source, a mercury lamp (254 nm) having an intensity that does not generate a new defect, an LD excitation YAG laser (266 nm), a KrF excimer laser (248 nm), or the like is preferably used.
[0028]
【Example】
[Test Example 1]
The quartz glass soot obtained by the VAD method is held at 800 ° C. to 1100 ° C. for 5 hours to 80 hours in an atmosphere composed of 0.01% to 30% SiF 4 and the balance He, and then at 1380 ° C. to 1460 ° C. By performing a pretreatment of performing a sintering treatment for 2 hr to 5 hr, transparent glass bodies having different average F concentrations in the range of 50 to 12000 wtppm (referred to as sample 1α) were obtained.
[0029]
Next, after the sample 1α having a different average F concentration is irradiated with 10 mJ / cm 2 / shot ArF excimer laser (193 nm) 1 × 10 6 times, post-treatment is performed in a 100% He atmosphere at 700 ° C. for 8 hours. Went. This post-treated sample is referred to as sample 1β.
[0030]
The sample 1β having a different average F concentration is irradiated with 80 mJ / cm 2 / shot ArF excimer laser (193 nm) 1 × 10 6 times at a repetition frequency of 200 Hz, and the ArF excimer laser transmittance change before and after irradiation is measured. It was measured. The results are shown in Table 1.
[0031]
[Table 1]
[0032]
(A1) From Table 1, it was found that if the sample 1β has an average F concentration in the range of 100 wtppm to 10000 wtppm, the transmittance decrease after laser irradiation can be suppressed to 1.0% or less.
[0033]
[Test Example 2]
Pretreatment of quartz glass soot obtained by the VAD method in a 0.1% SiF 4 , 99.9% He atmosphere at 1000 ° C. for 20 hours, followed by sintering for 2 hours at 1400 ° C. Thus, a transparent glass body having an average F concentration of 4200 wtppm (this pre-treated one is referred to as sample 2α) was obtained. The transparent glass body was cut and polished to produce a plurality of disks having a thickness of 20 mm and a diameter of 100 mm.
[0034]
Next, the cut and polished sample 2α was subjected to post-processing under the following different conditions to produce three types of sample 2βa, sample 2βb, and sample 2βc.
[0035]
The post-treatment conditions of sample 2βa [sample A] are those in which an ArF excimer laser (193 nm) of 10 mJ / cm 2 / shot is irradiated 1 × 10 6 times and then held at 700 ° C. for 8 hours in a 100% He atmosphere. is there.
[0036]
The post-treatment conditions for sample 2βb [sample B] are: 10 mJ / cm 2 / shot ArF excimer laser (193 nm) irradiated 1 × 10 6 times, and then 100 ° C. by microwave (28 GHz) in a 100% He atmosphere. Is held for 8 hours.
[0037]
The post-treatment conditions for sample 2βc [sample C] are: ArF excimer laser (193 nm) of 10 mJ / cm 2 / shot is irradiated 1 × 10 6 times, then held at 700 ° C. in 100% He atmosphere for 8 hours. At the same time, a mercury lamp is irradiated on the entire surface with an illuminance of 1 mW / cm 2 .
[0038]
(Comparative Example 1)
In order to confirm the effect of the post-treatment, in this example, the sample 2βd [sample D] that was not subjected to the post-treatment of the sample 2βa was adopted.
[0039]
The four types of samples 2β were irradiated with 80 mJ / cm 2 / shot ArF excimer laser (193 nm) 1 × 10 6 times at a repetition frequency of 200 Hz, and the change in ArF excimer laser transmittance before and after irradiation was measured. The results are shown in Table 2.
[0040]
[Table 2]
[0041]
From Table 2, the following points became clear.
As post-processing (B1), after irradiation with ArF excimer laser, by applying both heat treatment or heat treatment and the ultraviolet irradiation, the degree of decrease transmittance of the sample decreases (sample 2Betaei, sample 2Betabi, sample 2βc).
[0042]
(B2) In particular, the degree of decrease in the transmittance of the sample subjected to both heat treatment and ultraviolet irradiation is remarkably reduced (sample 2βc).
[0043]
(B3) Microwave heating is more effective than normal resistance heating furnace (sample 2βb), because defects are efficiently repaired by the so-called non-thermal effect of microwaves. it is conceivable that.
[0044]
[Test Example 3]
The quartz glass soot obtained by the VAD method is held in a 0.01% SiF 4 , 99.99% He atmosphere at 1000 ° C. for 20 hours, and then subjected to a sintering treatment in a 100% He atmosphere at 1440 ° C. for 2 hours. By performing the pretreatment, a transparent glass body having an average F concentration of 1800 wtppm was obtained (referred to as sample 3α). The transparent glass body was cut and polished to produce a plurality of disks having a thickness of 20 mm and a diameter of 100 mm.
[0045]
Next, the cut and polished sample 3α was subjected to post-processing under the following different conditions to prepare four types of samples 3βa, 3βb, 3βc, and 3βd. Further, after each post-treatment, all the samples were held at 500 ° C. for 120 hours in a 100%, 0.81 MPa H 2 atmosphere to dissolve H 2 in the samples.
[0046]
The post-treatment conditions for sample 3βa [sample E] are those in which a 5 mW / cm 2 / shot Xe excimer lamp (172 nm) is irradiated for 48 hours and then held in a 100% He atmosphere at 700 ° C. for 8 hours.
[0047]
The post-treatment conditions for sample 3βb [sample F] are those in which a 5 mW / cm 2 / shot Xe excimer lamp (172 nm) is held at 500 ° C. in a 100% He atmosphere during irradiation for 48 hours.
[0048]
The post-treatment conditions of sample 3βc [sample G] are that a 5 mW / cm 2 / shot Xe excimer lamp (172 nm) was irradiated for 48 hours and then held in a 100% He atmosphere at 700 ° C. for 8 hours, and at the same time, a mercury lamp Is irradiated on the entire surface with an illuminance of 1 mW / cm 2 .
[0049]
The post-treatment conditions for sample 3βd [sample H] are: a 5 mW / cm 2 / shot Xe excimer lamp (172 nm) is held at 500 ° C. in a 100% He atmosphere during irradiation for 48 hr, and at the same time, a mercury lamp is 1 mW. The whole surface is irradiated with an illuminance of / cm 2 .
[0050]
(Comparative Example 2)
In order to confirm the effect of the post-treatment, in this example, the sample 3βe [sample I] that was not subjected to the post-treatment of the sample 3βa was adopted.
[0051]
The above five kinds of samples 3β were irradiated with 80 mJ / cm 2 / shot ArF excimer laser (193 nm) 1 × 10 6 times at a repetition frequency of 200 Hz, and the change in ArF excimer laser transmittance before and after irradiation was measured. The results are shown in Table 3.
[0052]
[Table 3]
[0053]
From Table 3, the following points became clear.
(C1) as later processing, or during irradiation after irradiation with Xe excimer lamp, by applying both heat treatment or heat treatment and the ultraviolet irradiation, the degree of decrease transmittance of the sample decreases (sample 3Betaei, sample 3Betabi, sample 3βc Sample 3βd).
[0054]
(C2) The degree of decrease in the transmittance in all the samples is further reduced by the H 2 dissolution treatment performed inside the samples after the post-treatment (sample 3βa, sample 3βb, sample 3βc, 3βd).
[0055]
(C3) In particular, the degree of decrease in the transmittance of the sample subjected to both the heat treatment and the ultraviolet irradiation is remarkably reduced (sample 3 β c , sample 3 βd).
[0056]
(Comparative Example 3)
In order to confirm the effect of the pretreatment and posttreatment on the fluorine-doped sample described above, a sample not doped with fluorine in the pretreatment was prepared in this example.
That is, the soot of quartz glass obtained by the VAD method was subjected to a sintering treatment at 1480 ° C. for 2 hours in a 100% He atmosphere, and a transparent glass body not doped with fluorine (the sample 4α was subjected to this pretreatment). Called). The transparent glass body was cut and polished to produce a plurality of disks having a thickness of 20 mm and a diameter of 100 mm.
[0057]
Next, the cut and polished sample 4α was subjected to post-processing under the following different conditions to produce three types of samples 4βa, 4βb, and 4βc.
[0058]
Sample 4βa [Sample J] was not subjected to post-processing, and was used to confirm the effect of post-processing.
[0059]
The post-treatment conditions of sample 4βb [sample K] are those in which an ArF excimer laser (193 nm) of 10 mJ / cm 2 / shot is irradiated 1 × 10 6 times and then held in a 100% He atmosphere at 700 ° C. for 8 hours. is there.
[0060]
The post-treatment conditions of sample 4βc [sample L] are: ArF excimer laser (193 nm) of 10 mJ / cm 2 / shot is irradiated 1 × 10 6 times, then held in a 100% He atmosphere at 700 ° C. for 8 hours. At the same time, a mercury lamp is irradiated on the entire surface with an illuminance of 1 mW / cm 2 .
[0061]
The three types of samples 4β were irradiated with 80 mJ / cm 2 / shot ArF excimer laser (193 nm) 1 × 10 6 times at a repetition frequency of 200 Hz, and the change in ArF excimer laser transmittance before and after irradiation was measured. The results are shown in Table 4.
[0062]
[Table 4]
[0063]
From Table 4, the following points became clear.
(D1) The effect of the pre-processing is seen when the post-processing is performed (4βb) rather than the case where no post-processing is performed (4βa).
[0064]
(D2), however, as a post-treatment, after irradiation with ArF excimer laser, be subjected to heat treatment, the effect is hardly exerted against no fluorine doped sample (Sample 4βb).
[0065]
(D3) Further, even when both heat treatment and ultraviolet irradiation are performed simultaneously, the effect is not recognized for a sample not doped with fluorine (sample 4βc).
[0066]
(D4) Therefore, from the results in Table 4, it was found that in the sample not doped with F, the effect was small even if heat treatment or both heat treatment and ultraviolet irradiation were performed after irradiation with ArF excimer laser.
[0067]
【The invention's effect】
As described above, in the method for producing quartz glass according to the present invention, in fluorine-doped quartz glass, weak bonds in glass such as Si—Si bonds once cut by ultraviolet rays are dissolved by heating or heating and ultraviolet irradiation. By repairing with 2 and converting to Si-F, which is a stronger bond, it has better UV resistance than before processing. Therefore, by using the material produced by this manufacturing method as a window material, for example, vacuum This contributes to improving the long-term reliability of lasers having an oscillation wavelength in the ultraviolet.
[0068]
In the method for manufacturing a quartz glass according to the present invention, a quartz glass fluorine concentration is 100Wtppm~10000wtppm, the first optical processing steps dominant wavelength quartz glass is irradiated with short vacuum ultraviolet light from 200 nm, the quartz A heat treatment step of heating the glass at a temperature not lower than 400 ° C. and not higher than the annealing point for 1 hour or longer, and performing the heat treatment step subsequent to the first optical treatment step, or the first optical treatment step At the same time, by performing the heat treatment step, it is possible to stably produce quartz glass having excellent ultraviolet resistance characteristics and little reduction in transmittance due to ultraviolet irradiation over a long period of time.
[0069]
And the manufacturing method of the quartz glass which concerns on Claim 1 of this invention can further improve an efficient ultraviolet-ray-proof characteristic by the nonthermal action by a microwave by performing the said heat processing with a microwave.
[0070]
Furthermore, in the method for producing quartz glass according to claim 2 of the present invention, the quartz glass is irradiated with ultraviolet light having a dominant wavelength of 200 nm or more and 350 nm or less together with the first optical treatment step and / or the heat treatment step. By performing the second optical processing step, it is possible to establish much higher UV resistance.
[0071]
Therefore, the manufacturing method according to the present invention contributes to the stable provision of high-quality and long-life quartz glass while realizing excellent mass productivity.
Claims (3)
前記熱処理工程を行うためにマイクロ波を用いることを特徴とする石英ガラスの製造方法。 A first optical processing step of using quartz glass having a fluorine concentration of 100 wtppm to 10000 wtppm, and irradiating the quartz glass with vacuum ultraviolet light having a dominant wavelength shorter than 200 nm; And a heat treatment step of holding and heating for 1 hour or more, and performing the heat treatment step subsequent to the first optical treatment step, or performing the heat treatment step together with the first optical treatment step. Because
Method for manufacturing a silica glass, which comprises using microwave in order to perform the heat treatment process.
前記第一の光学処理工程及び/又は前記熱処理工程とともに、前記石英ガラスに主波長が200nm以上350nm以下の紫外光を照射する第二の光学処理工程を行うことを特徴とする石英ガラスの製造方法。 A first optical processing step of using quartz glass having a fluorine concentration of 100 wtppm to 10000 wtppm, and irradiating the quartz glass with vacuum ultraviolet light having a dominant wavelength shorter than 200 nm; And a heat treatment step of holding and heating for 1 hour or more, and performing the heat treatment step subsequent to the first optical treatment step, or performing the heat treatment step together with the first optical treatment step. Because
Together with the first optical processing step and / or the heat treatment step, the method for manufacturing a silica glass which is characterized in that the second optical processing steps main wavelength to the quartz glass is irradiated with 350nm in the ultraviolet light over 200nm .
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DE102018211234A1 (en) * | 2018-07-06 | 2020-01-09 | Carl Zeiss Smt Gmbh | Substrate for a reflective optical element |
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