JP4256955B2 - High purity transparent quartz glass and method for producing the same - Google Patents
High purity transparent quartz glass and method for producing the same Download PDFInfo
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- JP4256955B2 JP4256955B2 JP25357698A JP25357698A JP4256955B2 JP 4256955 B2 JP4256955 B2 JP 4256955B2 JP 25357698 A JP25357698 A JP 25357698A JP 25357698 A JP25357698 A JP 25357698A JP 4256955 B2 JP4256955 B2 JP 4256955B2
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- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
- C03B19/00—Other methods of shaping glass
- C03B19/06—Other methods of shaping glass by sintering, e.g. by cold isostatic pressing of powders and subsequent sintering, by hot pressing of powders, by sintering slurries or dispersions not undergoing a liquid phase reaction
-
- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
- C03B19/00—Other methods of shaping glass
- C03B19/06—Other methods of shaping glass by sintering, e.g. by cold isostatic pressing of powders and subsequent sintering, by hot pressing of powders, by sintering slurries or dispersions not undergoing a liquid phase reaction
- C03B19/066—Other methods of shaping glass by sintering, e.g. by cold isostatic pressing of powders and subsequent sintering, by hot pressing of powders, by sintering slurries or dispersions not undergoing a liquid phase reaction for the production of quartz or fused silica articles
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- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
- C03B20/00—Processes specially adapted for the production of quartz or fused silica articles, not otherwise provided for
Description
【０００１】
【発明の属する技術分野】
本発明はＦｅ、Ｎａ、Ｋの各不純物含有量が０．０１〜０．３ｐｐｍの範囲にあり、ＯＨ基含有量が０〜３ｐｐｍの範囲にあり、かつ含有されるＦｅ不純物のうち価数状態が＋０の金属鉄含有量が０．１ｐｐｍ以下であり、９００〜１４００℃の温度に２０時間以上保持しても、可視短波長域の透過率が低下せず、波長４００ｎｍでの吸光係数が０．００９以上にならず、着色が認められないことを特徴とする高純度透明石英ガラス及びその形状の一つである高純度透明石英ガラスリング、並びにそれらの高純度透明石英ガラスの製造方法に関する。
【０００２】
これらの高純度透明石英ガラスは半導体用耐熱治具及び各種フランジ類、炉心管部品などに応用できる。
【０００３】
【従来の技術】
近年、半導体集積回路の集積度はますます上昇し、それらの半導体集積回路の性能に悪影響を与えるナトリウム元素またはカリウム元素を不純物として含まない石英ガラスが、半導体製造用治具の材料として求められている。例えば特開昭５９−１２９４２１では半導体熱処理用部材中のＮａ、Ｋ、Ｌｉをそれぞれ０．０５ｐｐｍ以下としている。また同様に半導体の性質に悪影響を与える鉄元素の不純物濃度も減少させることが求められてきている。例えば、特開平８−１６５１３４、特開平８−１７５８４０では石英ガラス中の鉄元素含有量が０．８ｐｐｍ未満であるとしている。
【０００４】
しかし、半導体製造用治具の材料としての透明石英ガラスに求められている性質はその純度ばかりではない。半導体集積回路基板用ウェハー径は年々大きくなってきており、それに伴って半導体熱処理用石英ガラス製治具の大きさも大きくなってきている。従って半導体熱処理用石英ガラス製治具の材料には高温における高い粘性も要求させる。一般に高温において高い粘性を持つ透明石英ガラスは天然の結晶質石英粉末を溶融することによって作成されている。
【０００５】
石英ガラスリングの製造方法としては、耐熱金属から構成されたリング状空間に結晶質石英粉末を充填し、１７００℃以上に加熱溶融して石英ガラスリングを製造する方法が既に特公昭３５−７９１に記載されており、また、最近、特開平９−２０２６３１、特開平９−２０２６３２及び特開平９−１８３６２３には、黒鉛材からなる容器とシリカ粉末の接触面に石英ガラスを介在させ、加熱溶融して石英ガラスを製造する方法が開示されている。
【０００６】
【発明が解決しようとする課題】
天然石英粉末を溶融するのに耐熱性金属容器やカーボン製容器を用いた場合、高温で容器を酸化損傷しないようにするために容器のまわりの雰囲気を真空としている。この場合に黒鉛質モールドに普通グレードの黒鉛質を用いると溶融された透明石英ガラスが褐色に着色するという問題が起きた。また、溶融直後には着色していなくても、これらの透明石英ガラスを、製品とするための融着等の加工を行なった後に９００〜１４００℃の温度で２０時間程度、熱歪を取るためのアニール処理を行なうと、アニール処理後に透明石英ガラスが褐色に着色しているという問題が起きた。着色を起こした透明石英ガラスは製品としての価値を失い問題である。透明石英ガラスが着色を起こすか、起こさないかは必ずしも透明石英ガラス中の不純物濃度と一対一で対応せず、原因が完全に明らかになっていたわけではなかった。
【０００７】
また、特公昭３５−７９１では、モールドとして、耐熱金属であるＭｏを用いているが、この方法ではＭｏが高温酸化を受け、ガスとして得られる石英ガラスに侵入して汚染するという問題があった。
【０００８】
また、モールドとして黒鉛材を用いた場合、ＣとＳｉＯ2との高温反応によってモールドと石英ガラスが融着し、相互に損傷したり、融着を避け得た場合でもモールドの耐久性は著しく低い等の問題があった。更に、一般の黒鉛材には１ｐｐｍを遥かに越えるＦｅやＣａなどが含まれており、これらの不純物が高温でガス化し、ガラスに侵入し高純度が保てないという問題もあった。 特開平９−２０２６３１、特開平９−２０２６３２及び特開平９−１８３６２３に開示されている黒鉛材からなる容器とシリカ粉末の接触面に石英ガラスを介在させることにより、上記の問題を解決する方法が開示されている。しかし、この方法は介在させる石英ガラスの加工製造に手間を要し、かつ、石英ガラスは高価であるため、経済性に優れた方法とは言い難い。
【０００９】
【課題を解決するための手段】
本発明者らは上記課題を解決するため鋭意検討した結果、黒鉛モールドとシリカ粉末の間に多孔質黒鉛層を介在させ、モールドとシリカガラスの融着を防ぐと伴に、用いる原料粉末及び黒鉛材料を高純度にすることにより、Ｆｅ、Ｎａ、Ｋの各不純物含有量が０．０１〜０．３ｐｐｍの範囲にあり、ＯＨ基含有量が０〜３ｐｐｍの範囲にあり、かつ含有させるＦｅ不純物のうち、価数が＋０の金属鉄含有量が０．１ｐｐｍ以下であり、９００〜１４００℃の温度に２０時間以上保持しても、可視短波長域の透過率が低下せず、波長４００ｎｍでの吸光係数が０．００９以上にならないという極めて優れた透明性維持特性を有しており、半導体用耐熱治具及び各種フランジ類、炉心管部品などに好適に適用が可能である。すなわち本願発明は、透明石英ガラス中のＦｅ、Ｎａ、Ｋの各不純物含有量が０．０１〜０．３ｐｐｍの範囲にあり、かつ含有されるＦｅ不純物のうち価数が＋０の金属鉄の含有量が０．１ｐｐｍ以下であり、９００〜１４００℃の温度に２０時間以上保持しても、可視短波長域の透過率が低下せず、波長４００ｎｍでの吸光係数が０．００９以上にならず、着色が認められないことを特徴とする透明石英ガラス及びその製造方法として黒鉛質モールドから構成された空間にシリカ粉末を充填し、１７００℃以上に加熱溶融して透明石英ガラスを得る方法において、黒鉛質モールドとシリカ粉末の接触面に嵩密度０．１〜１．５ｇ／ｃｍ3であり、Ｎａ，Ｋ，Ｆｅ及びＴｉの各不純物が１ｐｐｍ以下の高純度黒鉛からなる多孔質層を介在させ、加熱溶融する方法に関する。
【００１０】
以下、本願発明をさらに詳細に説明する。
【００１１】
本発明にかかる透明石英ガラスの製造方法について述べる。まず、Ｆｅ、Ｎａ、Ｋの各不純物含有量が０．３ｐｐｍ以下の高純度結晶質石英、または高純度非晶質シリカ粉末を高純度合成石英ガラス製の容器に入れ、雰囲気を制御できる電気炉内に設置する。電気炉内に酸素割合を増加させた酸化ガスを流す。酸化ガスの組成は特に規定はしないが、例えば酸素と窒素の割合が１：１の気体や純酸素ガスとする。電気炉内の温度を８００〜１０００℃に昇温し２〜４時間保持した後に炉中で冷却する。
【００１２】
次に、塩素等を用いてＦｅ、Ｎａ、Ｋ、Ｔｉの各不純物が１ｐｐｍ以下になるように高純度化した黒鉛質モールドを用い、この黒鉛質モールドの内側の空間に先ほど酸化雰囲気中で熱処理を行った高純度結晶質石英、または高純度非晶質シリカ粉末を充填する。ただし、粉末を充填する前に黒鉛質モールドと粉末の接触面の間に嵩密度０．１〜１．５ｇ／ｃｍ3、Ｎａ、Ｋ、Ｆｅ、Ｔｉの各不純物が１ｐｐｍ以下の高純度黒鉛からなる多孔質層を介在させる。この多孔質の役割は３つある。第１点は、モールド黒鉛と石英又はシリカ粉末との直接反応によるモールドの損耗を防ぐことであり、第２点は、モールド黒鉛と得られた石英ガラスの熱膨張差のため、冷却過程でモールドの破損を緩和材として防ぐことであり、第３点は、多孔質層黒鉛自身と石英又はシリカ粉末との高温反応で発生するガスを系外に効率よく逃がし、ガス滞留によるガラス内気泡の発生を防ぐことである。嵩密度０．１〜１．５ｇ／ｃｍ3の高純度黒鉛からなる多孔質層としては、高純度処理した黒鉛フェルト、黒鉛シート、黒鉛粉末を堆積したものなどを用いることができる。黒鉛フェルトとしては、カーボン繊維を成形織物とした、嵩密度０．１〜０．４ｇ／ｃｍ3のものが市販されており、厚さ２〜１０ｍｍのものを用いることが好ましい。
【００１３】
黒鉛シートとしては、カーボン繊維を成形織物とした、嵩密度０．８〜１．２ｇ／ｃｍ3のものが市販されており、厚さ２〜１０ｍｍのものを用いることが好ましい。黒鉛粉末としては、粒度０．１〜１ｍｍの高純度処理したものが好ましい。黒鉛フェルト、黒鉛シート、黒鉛粉末堆積物は、いずれも伸縮性と通気性を有するものであり、モールドの破損を防止すると同時に、発生ガスの逃散路を与える役割を果たす。黒鉛フェルトは黒鉛シートに比較して、伸縮性及び通気性とも優れた物であり、上記役割を果たすにはより適している。しかし、ＳｉＯ2との反応による消失量は多く、接触するガラス面の平坦部が保てないという欠点がある。一方、黒鉛シートはＳｉＯ2との反応による消失量は少なく、また、面が平滑であるため、ガラス面の平坦度を出すに適している。従って、これら多孔質材料は、その適性により、使い分けることが好ましい。例えば、好適な構成として、得られる石英ガラスの内外側面には黒鉛フェルト、石英ガラスの底面には黒鉛シートとするものが挙げられる。
【００１４】
黒鉛質モールド全体を電気炉内に設置し、電気炉内を減圧する。電気炉内を１７００℃以上の温度で加熱し、黒鉛質モールド内の高純度結晶質石英、または高純度非晶質シリカ粉末を溶融する。黒鉛質モールド内から取り出した透明石英ガラスの分析方法は特には規定しないが、透明石英ガラスをフッ化水素酸で処理した後にＩＣＰ測定もしくは原子吸光光度法によって行なった。本発明にかかる透明石英ガラスのＦｅ、Ｎａ、Ｋの各不純物濃度は０．０１〜０．３ｐｐｍの範囲であった。
【００１５】
透明石英ガラス中のＯＨ基の濃度は、透明石英ガラスから１０ｍｍの厚さの両面を光学研磨した試料を作成し、赤外吸収スペクトル中に現れる吸収から算出した。次に算出式を示す。透明石英ガラス中のＯＨ基の濃度をＡ［ｐｐｍ］、波長２．５μｍにおける試料の透過率をＩ1［％］、波長２．７３μｍにおける試料の透過率をＩ2［％］とする。Ａ［ｐｐｍ］＝０．０１・ｌｏｇ10（Ｉ1［％］／Ｉ2［％］）上式においてＯＨ濃度を算出した。試料中のＯＨ基濃度は０〜３ｐｐｍであった。
【００１６】
透明石英ガラス中のＦｅの価数はＥＳＲスペクトルの観察によって決定した。ＥＳＲスペクトルの測定法についてはとくには限定しないが、例えば次のように行なった。透明石英ガラスから７ｍｍ×７ｍｍ×１０ｍｍの直方体の試料を切り出す。試料の重量は約１ｇである。この試料についてＥＳＲスペクトルを測定した。ＥＳＲスペクトル中にはｇ＝２近傍に大きな吸収が、ｇ＝４．２近傍に小さな吸収が観測された。
【００１７】
ｇ＝２近傍の吸収が透明石英ガラス中の価数＋０の金属鉄からの強磁性共鳴による吸収であることをGriscom らとＦｒｉｔｓｃｈらが同定した(D. L. Griscom, E. J. Friebele and D. B. Shinn, J. Appl. Phys. 50(3) 2402-2404 (1979), E. Fritsch and G. Clas, Non-Cryst. Solid.)。ｇ＝４．２近傍の吸収は透明石英ガラス中の価数＋３の鉄イオンによる吸収であると同定された（D. R. Uhlmann and N. J. Kreidl, Glass Science and Technology, Academic Press, inc., (1990) Chapter 3）。
【００１８】
価数＋０の金属鉄の定量方法についてさらに詳しく述べる。Ｆｅ元素の含有量が０．０１ｐｐｍ以下である合成シリカ粉末を超純水中に分散し、その中へＦｅＣｌ3をＦｅ重量換算で０．１、０．２、０．５、０．７、１、５、１０ｐｐｍ添加する。これらのスラリーを８０℃の温度において良く攪拌した後に水を蒸発させて取り除く。得られた粉末を水素気流中、４００〜８００℃の温度で４時間程度熱処理することによって、粉末中のＦｅを価数＋０の金属鉄に還元する。
【００１９】
これらの粉末のＥＳＲスペクトルを測定し、ｇ＝２近傍に現われる強磁性共鳴吸収の積分強度を計測して価数＋０の金属鉄含有量と積分強度の検量線を作成する。この検量線を用いて透明石英ガラス中の価数＋０の金属鉄の量を定量化した。積分強度の定量化のための一次標準試料としてＴＥＭＰＯＬ（4-Hydroxy-2,2,6,6-tetramethyl-piperidine-oxyl ）のベンゼン溶液を用い、二次標準試料としてルビー結晶（Ｃｒ+3を含むα−Ａｌ2Ｏ3）を用いた。
【００２０】
我々の作成した透明石英ガラスはＥＳＲスペクトルを使っての解析の結果、透明石英ガラス中のＦｅ不純物のうち、価数が＋０の金属鉄の含有量が０．１ｐｐｍ以下であることが判明した。さらに、透明石英ガラス中に価数が＋０の金属鉄が０．２ｐｐｍより多く含まれる場合はその透明石英ガラスは、後に述べる９００〜１４００℃での再加熱によって着色を起こすこともわかった。我々の作成した透明石英ガラスを９００〜１４００℃の温度に２０時間以上保持したが、可視−紫外スペクトル中の可視短波長域での透過率は低下せず、波長４００ｎｍでの吸光係数は０．００９以下であり、着色は認められなかった。
【００２１】
以下実施例によって、本発明をさらに説明するが、本発明は実施例に限定されるものではない。
【００２２】
【実施例】
実施例１
表１に示した高純度の天然水晶粉を原料に用いた。この原料粉末６．４ｋｇを外枠直径４１０ｍｍ、内枠直径３８０ｍｍ、深さ７５ｍｍのリング状空間を持つ高純度黒鉛質モールド内に充填する。外枠の内壁には厚さ５ｍｍの高純度黒鉛質フェルトを張り、内枠の外壁には厚さ２mmの高純度黒鉛質フェルトを張る。リング状空間の底には厚さ０．４ｍｍの高純度黒鉛質シートを敷いた。高純度黒鉛質フェルトおよび高純度黒鉛質シートの純度も表１に示した。
【００２３】
透明石英ガラス化条件としては、真空中で室温から１６００℃まで５℃／分で昇温し、その後１６００℃から１８５０℃まで２℃／分で昇温する。１８５０℃において真空中１５分間加熱した後、圧力１．７ｋｇｆ／ｃｍ2の窒素雰囲気中で５分間加熱する。その後炉冷する。
【００２４】
作成した透明石英ガラスを湿式により組成分析した結果を表１の下段に示す。Ｆｅ、Ｎａ、Ｋの各不純物濃度が０．０１〜０．３ｐｐｍの範囲にあることがわかった。
【００２５】
【表１】
透明石英ガラスから厚さ１０ｍｍの試験片を切り出し、両面を光学研磨し、赤外吸収スペクトルを測定した。波長２．５μｍにおける透過率は８７．５％であり、波長２．７３μｍにおける透過率は８６．０％であり、これらから算出される透明石英ガラス中のＯＨ基濃度は０．７５ｐｐｍである。
【００２７】
透明石英ガラスを空気中、１１５０℃の温度に６６時間保持した。１１５０℃に６６時間保持した後の透明石英ガラスは目視観察でも着色は認められない。図１および図２に可視光吸収スペクトルを示した。この可視光吸収スペクトル中で、波長４００ｎｍにおける吸収係数は０．００３であった。
【００２８】
作成した直後と、空気中１１５０℃で６６時間保持したあとの両方の透明石英ガラスから、７ｍｍ×７ｍｍ×１０ｍｍの直方体試料を切り出し、ＥＳＲスペクトルを測定した。ｇ＝２近傍に観測された共鳴吸収の積分強度から算出された、透明石英ガラス中の価数＋０の金属鉄の濃度は０．１ｐｐｍ以下だった。
【００２９】
比較例１
以下の表２に示した純度の天然水晶粉末を原料に用いる。
【００３０】
【表２】
この原料粉末２．３ｋｇを、外枠直径２５５ｍｍ、内枠直径１００ｍｍ、深さ４７．５ｍｍのリング状空間を持つ黒鉛質モールド内に充填する。外枠の内壁には厚さ５ｍｍの黒鉛質フェルトを張り、内枠の外壁には厚さ５ｍｍの黒鉛質フェルトを張る。リング状空間の底には厚さ０．４ｍｍの黒鉛質シートを敷く。黒鉛質フェルトおよび黒鉛質シートの純度も表２に示す。
【００３２】
透明石英ガラス化条件としては、真空中で室温から１６００℃まで５℃／分で昇温し、その後１６００℃から１８５０℃まで２℃／分で昇温する。１８５０℃において真空中１５分間加熱した後、圧力１．７ｋｇｆ／ｃｍ2の窒素雰囲気中で５分間加熱し、その後炉冷する。
【００３３】
作成した透明石英ガラスを湿式による組成分析をした結果を表２の下段に示す。透明石英ガラスから厚さ１０ｍｍの試料片を切出し、両面を光学研磨し、赤外吸収スペクトルを測定した。波長２．５μｍにおける透過率は８６．６％であり、波長２．７３μｍにおける透過率は８５．４％であり、これから算出される透明石英ガラス中のＯＨ基濃度は０．６２ｐｐｍである。
【００３４】
この透明石英ガラスを空気中、１１５０℃の温度に２０時間保持した。１１５０℃に２０時間保持した後の透明石英ガラスは目視観察で着色が認められた。図１に可視光吸収スペクトルを示す。この可視光吸収スペクトル中で波長４００ｎｍにおける吸収係数は０．２９８であった。
【００３５】
空気中１１５０℃で２０時間保持した後の着色を起こした透明石英ガラスから７ｍｍ×７ｍｍ×１０ｍｍの直方体の試料を切り出し、ＥＳＲスペクトルを測定した。ｇ＝２近傍にはブロードで大きな共鳴吸収ピークが観測された。ピークの積分強度から算出された透明石英ガラス中の価数＋０の金属鉄の濃度は４ｐｐｍだった。
【００３６】
比較例２
以下の表３に示した純度の天然水晶粉末を原料に用いた。
【００３７】
【表３】
この原料粉末２．３ｋｇを外枠直径２５５ｍｍ、内枠直径１００ｍｍ、深さ４７．５ｍｍのリング状空間を持つ高純度黒鉛質モールド内に充填する。外枠の内壁には厚さ５ｍｍの高純度黒鉛質フェルトを張り、内枠の外壁には厚さ２mmの高純度黒鉛質フェルトを張る。リング状空間の底には厚さ０．４ｍｍの高純度黒鉛質シートを敷いた。高純度黒鉛質フェルトおよび高純度黒鉛質シートの純度も表３に示した。
【００３９】
透明石英ガラス化条件としては、真空中で室温から１６００℃まで５℃／分で昇温し、その後１６００℃から１８５０℃まで２℃／分で昇温する。１８５０℃において真空中１５分間加熱した後、圧力１．７ｋｇｆ／ｃｍ2の窒素雰囲気中で５分間加熱する。その後炉冷する。
【００４０】
作成した透明石英ガラスを湿式により組成分析した結果を表３の下段に示す。Ｆｅ、Ｎａ、Ｋの各不純物濃度が０．０１〜０．３ｐｐｍの範囲にあることがわかった。
【００４１】
透明石英ガラスから厚さ１０ｍｍの試験片を切り出し、両面を光学研磨し、赤外吸収スペクトルを測定した。波長２．５μｍにおける透過率は８８．５％であり、波長２．７３μｍにおける透過率は８５．４％であり、これらから算出される透明石英ガラス中のＯＨ基濃度は１．５ｐｐｍである。
【００４２】
透明石英ガラスを空気中、１３００℃の温度で２０時間保持した。１３００℃に２０時間保持した後の透明石英ガラスは目視観察で軽い着色が認められた。図２中に可視光吸収スペクトルを示す。この可視光吸収スペクトル中で、波長４００ｎｍにおける吸収係数は０．０１２であった。空気中１３００℃で２０時間保持した後の着色を起こした透明石英ガラスから７ｍｍ×７ｍｍ×１０ｍｍの直方体の試料を切り出し、ＥＳＲスペクトルを測定した。ｇ＝２近傍にはブロードな共鳴吸収ピークが観測された。ピークの積分強度から算出された透明石英ガラス中の価数＋０の金属鉄の濃度は０．２ｐｐｍだった。
【００４３】
実施例２
石英ガラスリングの製造実験に用いた黒鉛モールド／黒鉛多孔質層／石英粉末の構成の内、数種類を図３に示す。
【００４４】
実験に用いた石英粉末、高純度黒鉛モールド、高純度黒鉛フェルト、高純度黒鉛シート及び高純度黒鉛粉末の純度をそれぞれ表４〜８に示す。
【００４５】
【表４】
【表５】
【表６】
【表７】
【表８】
密度１．７ｇ／ｃｍ3の高純度黒鉛からなる、図３（ａ）〜（ｃ）に示した形状のモールド（リング外径４００ｍｍ、内径２４０ｍｍ、高さ７０ｍｍ）を用意した。図３の（ａ）の場合、モールド底面、内側面及び外側面すべてに厚さ５ｍｍ、嵩密度０．２ｇ／ｃｍ3の高純度黒鉛フェルトを設置し、結晶質石英粉末（平均粒径０．２ｍｍ）を高さ５０ｍｍになるように充填し、上面に同様のフェルトを被せた後、高純度黒鉛荷重リング（高さ５０ｍｍ）を載せた。図３の（ｂ）の場合、モールド底面に厚さ０．４ｍｍ、嵩密度１．０ｇ／ｃｍ3の高純度黒鉛シートを敷く以外は、（ａ）と同様の構成とした。また図３の（ｃ）の場合、フェルトの設置は（ａ）と同様にしたが、荷重リングは乗せず、高純度黒鉛外周リングをモールド枠に取り付けた。
【００５１】
以上の３種類をカーボン抵抗加熱電気炉に入れ、真空に排気した状態で室温から１８５０℃まで８時間で昇温し、３０分間保持した後、真空解除し、窒素を導入し放冷した。
【００５２】
得られた３種類の透明石英ガラスリングの形状及びサイズを図４に示すが、３種類とも気泡が少ない透明石英ガラスリングが得られ、特に、（ｂ）では底面の平坦度がよい透明石英ガラスリングが得られ、また、（ｃ）では外周に段差のあるフランジ形状のリングが得られた。
【００５３】
得られた３種類の透明石英ガラスリングの不純物の分析結果を以下の表９に示すが、原料の純度がほぼ保たれていることが判った。
【００５４】
【表９】
【発明の効果】
本発明の方法によって得られた透明石英ガラスは、高純度であり、ＯＨ濃度が低いために高温での粘性が高く、半導体製造用治具の材料として優れた特性を有している。また価数状態＋０の金属鉄の濃度を０．１ｐｐｍ以下に抑えることにより、９００〜１４００℃の温度での長時間の再加熱によっても着色を起こさない特徴を持ち、有用な半導体熱処理用透明石英ガラス部材を供することができる。
【００５６】
また、本発明の方法によって得られた透明石英ガラスリングは、高純度であり、また外径３００〜５５０ｍｍ、高さ１００ｍｍ程度の大型サイズが可能である。従来行われていた石英ガラスブロックから機械加工する方法と比較すると、極めて材料収率が優れた方法であり、高純度黒鉛モールドの耐久性も向上し、経済的にも有利な方法となる。特に、半導体製造に使用される石英ガラス治工具類、例えば反応管のフランジ、エッチング装置の反応室ライナー、枚葉式装置部品として有用となる。
【図面の簡単な説明】
【図１】実施例１と比較例１での可視吸収スペクトルの比較を示す図である。
【図２】実施例１と比較例２での可視吸収スペクトルの比較を示す図である。
【図３】実施例２で使用した黒鉛モールド、黒鉛多孔質層、石英粉末の構成の内、３種類の断面構造を示す。
【符号の説明】
▲１▼：高純度黒鉛モールド
▲２▼：高純度黒鉛荷重
▲３▼：石英原料粉末
▲４▼：高純度黒鉛フェルト
▲５▼：高純度黒鉛シート
▲６▼：高純度黒鉛外周リング
【図４】実施例２で得られた透明石英ガラスリングの形状及びサイズを示す。[0001]
BACKGROUND OF THE INVENTION
The present invention has Fe, Na and K impurity contents in the range of 0.01 to 0.3 ppm, OH group content in the range of 0 to 3 ppm, and valence state among Fe impurities contained +0 is a metal iron content of 0.1 ppm or less, and even when kept at a temperature of 900 to 1400 ° C. for 20 hours or more, the transmittance in the visible short wavelength region does not decrease, and the extinction coefficient at a wavelength of 400 nm is 0. The present invention relates to a high-purity transparent quartz glass characterized in that it is not 0.009 or higher and coloring is not recognized, a high-purity transparent quartz glass ring which is one of its shapes, and a method for producing these high-purity transparent quartz glasses.
[0002]
These high-purity transparent quartz glass can be applied to heat-resistant jigs for semiconductors, various flanges, and core tube parts.
[0003]
[Prior art]
In recent years, the degree of integration of semiconductor integrated circuits has increased, and quartz glass that does not contain sodium element or potassium element as an impurity, which adversely affects the performance of these semiconductor integrated circuits, has been demanded as a material for semiconductor manufacturing jigs. Yes. For example, in Japanese Patent Laid-Open No. 59-129421, Na, K, and Li in the semiconductor heat treatment member are each 0.05 ppm or less. Similarly, it has been required to reduce the impurity concentration of the iron element that adversely affects the properties of the semiconductor. For example, JP-A-8-165134 and JP-A-8-175840 assume that the content of iron element in quartz glass is less than 0.8 ppm.
[0004]
However, the properties required of transparent quartz glass as a material for semiconductor manufacturing jigs are not limited to its purity. The diameter of a wafer for a semiconductor integrated circuit substrate is increasing year by year, and accordingly, the size of a quartz glass jig for semiconductor heat treatment is also increasing. Accordingly, the quartz glass jig for semiconductor heat treatment is required to have a high viscosity at a high temperature. In general, transparent quartz glass having high viscosity at high temperature is produced by melting natural crystalline quartz powder.
[0005]
As a method for producing a quartz glass ring, a method for producing a quartz glass ring by filling a crystalline quartz powder in a ring-shaped space composed of a heat-resistant metal and heating and melting it to 1700 ° C. or higher has already been disclosed in Japanese Patent Publication No. 35-791. Recently, JP-A-9-202631, JP-A-9-202632, and JP-A-9-183623 have quartz glass interposed between the contact surface of a container made of a graphite material and silica powder, and are heated and melted. A method for producing quartz glass is disclosed.
[0006]
[Problems to be solved by the invention]
When a refractory metal container or a carbon container is used to melt the natural quartz powder, the atmosphere around the container is evacuated to prevent oxidative damage to the container at a high temperature. In this case, when ordinary grade graphite was used for the graphite mold, there was a problem that the molten transparent quartz glass was colored brown. Further, even if the transparent quartz glass is not colored immediately after melting, it takes thermal strain at a temperature of 900 to 1400 [deg.] C. for about 20 hours after processing such as fusion for making the product into a product. When the annealing process was performed, there was a problem that the transparent quartz glass was colored brown after the annealing process. Colored transparent quartz glass loses its value as a product and is a problem. Whether the transparent quartz glass is colored or not does not necessarily correspond one-to-one with the impurity concentration in the transparent quartz glass, and the cause has not been completely clarified.
[0007]
In Japanese Examined Patent Publication No. 35-791, Mo, which is a heat-resistant metal, is used as a mold. However, this method has a problem that Mo undergoes high-temperature oxidation and enters and contaminates quartz glass obtained as a gas. .
[0008]
Further, when a graphite material is used as a mold, the mold and the quartz glass are fused by a high temperature reaction between C and SiO 2, and even when the mutual damage or the fusion can be avoided, the durability of the mold is extremely low. There was a problem such as. Further, general graphite materials contain Fe, Ca, and the like far exceeding 1 ppm, and there is a problem that these impurities gasify at a high temperature and enter the glass and cannot maintain high purity. A method for solving the above problem by interposing quartz glass between the contact surface of silica powder and a container made of a graphite material disclosed in JP-A-9-202631, JP-A-9-202632 and JP-A-9-183623. It is disclosed. However, this method requires time and effort for processing and manufacturing the intercalated quartz glass, and the quartz glass is expensive, so it is difficult to say that it is an economical method.
[0009]
[Means for Solving the Problems]
As a result of intensive investigations to solve the above problems, the present inventors have intervened a porous graphite layer between the graphite mold and the silica powder to prevent fusion between the mold and the silica glass, and used raw material powder and graphite. Fe impurities contained in Fe, Na and K impurities in the range of 0.01 to 0.3 ppm, OH group content in the range of 0 to 3 ppm and contained by making the material highly pure Among them, the content of metallic iron having a valence of +0 is 0.1 ppm or less, and even when kept at a temperature of 900 to 1400 ° C. for 20 hours or more, the transmittance in the visible short wavelength region does not decrease, and the wavelength is 400 nm. It has an extremely excellent transparency maintaining characteristic that its extinction coefficient does not become 0.009 or more, and can be suitably applied to heat-resistant jigs for semiconductors, various flanges, core tube parts, and the like. That is, according to the present invention, the content of Fe, Na, and K impurities in the transparent quartz glass is in the range of 0.01 to 0.3 ppm, and the content of metallic iron having a valence of +0 among the Fe impurities contained Even if the amount is 0.1 ppm or less and kept at a temperature of 900 to 1400 ° C. for 20 hours or more, the transmittance in the visible short wavelength region does not decrease, and the extinction coefficient at a wavelength of 400 nm does not become 0.009 or more. In a method for obtaining transparent quartz glass by filling silica powder into a space composed of a graphite mold as a transparent quartz glass characterized in that coloring is not recognized and a method for producing the transparent quartz glass, and heating and melting to 1700 ° C. or higher. a bulk density of 0.1 to 1.5 g / cm 3 on the contact surface of the graphite mold and the silica powder, by interposing a porous layer Na, K, each impurity of Fe and Ti consisting of high-purity graphite 1ppm It relates to a method of heating and melting.
[0010]
Hereinafter, the present invention will be described in more detail.
[0011]
The manufacturing method of the transparent quartz glass concerning this invention is described. First, an electric furnace capable of controlling the atmosphere by placing high-purity crystalline quartz having a content of impurities of Fe, Na, and K of 0.3 ppm or less or a high-purity amorphous silica powder in a container made of high-purity synthetic quartz glass Install in. An oxidizing gas with an increased oxygen ratio is allowed to flow into the electric furnace. Although the composition of the oxidizing gas is not particularly defined, for example, a gas having a ratio of oxygen to nitrogen of 1: 1 or pure oxygen gas is used. The temperature in the electric furnace is raised to 800 to 1000 ° C. and held for 2 to 4 hours, and then cooled in the furnace.
[0012]
Next, a graphite mold purified with chlorine or the like so that each impurity of Fe, Na, K, Ti is 1 ppm or less is used, and heat treatment is performed in an oxidizing atmosphere in the space inside the graphite mold. The high-purity crystalline quartz or high-purity amorphous silica powder subjected to the above is filled. However, before filling the powder, high purity graphite having a bulk density of 0.1 to 1.5 g / cm 3 and Na, K, Fe, and Ti impurities of 1 ppm or less between the graphite mold and the contact surface of the powder. A porous layer is interposed. This porous role has three roles. The first point is to prevent wear of the mold due to the direct reaction between the mold graphite and quartz or silica powder, and the second point is due to the difference in thermal expansion between the mold graphite and the obtained quartz glass. The third point is to prevent the gas generated by the high-temperature reaction between the porous graphite itself and quartz or silica powder from escaping outside the system, and to generate bubbles in the glass due to gas retention. Is to prevent. As the porous layer made of high-purity graphite having a bulk density of 0.1 to 1.5 g / cm 3 , graphite felt, graphite sheet, and graphite powder deposited on a high-purity treatment can be used. As the graphite felt, those having a bulk density of 0.1 to 0.4 g / cm 3 made of carbon fiber as a molded fabric are commercially available, and those having a thickness of 2 to 10 mm are preferably used.
[0013]
As the graphite sheet, those having a bulk density of 0.8 to 1.2 g / cm 3 made of carbon fiber as a molded fabric are commercially available, and those having a thickness of 2 to 10 mm are preferably used. As the graphite powder, a high-purity treated particle having a particle size of 0.1 to 1 mm is preferable. The graphite felt, the graphite sheet, and the graphite powder deposit are all stretchable and breathable, and prevent the mold from being damaged, and at the same time provide a escape path for the generated gas. Graphite felt is superior in both stretchability and air permeability as compared with graphite sheet, and is more suitable for the above-mentioned role. However, the amount of disappearance due to the reaction with SiO 2 is large, and there is a drawback that the flat part of the glass surface in contact cannot be maintained. On the other hand, the graphite sheet has a small amount of disappearance due to the reaction with SiO 2 and has a smooth surface, which is suitable for obtaining flatness of the glass surface. Therefore, these porous materials are preferably used properly depending on their suitability. For example, as a suitable configuration, a graphite felt is used for the inner and outer surfaces of the obtained quartz glass, and a graphite sheet is used for the bottom surface of the quartz glass.
[0014]
The entire graphite mold is placed in an electric furnace, and the pressure in the electric furnace is reduced. The inside of the electric furnace is heated at a temperature of 1700 ° C. or higher to melt the high purity crystalline quartz or the high purity amorphous silica powder in the graphite mold. The method for analyzing the transparent quartz glass taken out from the graphite mold is not particularly specified, but the transparent quartz glass was treated with hydrofluoric acid and then subjected to ICP measurement or atomic absorption spectrophotometry. Each impurity concentration of Fe, Na, and K in the transparent quartz glass according to the present invention was in the range of 0.01 to 0.3 ppm.
[0015]
The concentration of OH groups in the transparent quartz glass was calculated from the absorption appearing in the infrared absorption spectrum by preparing a sample obtained by optically polishing both sides of the transparent quartz glass with a thickness of 10 mm. Next, a calculation formula is shown. The concentration of OH groups in the transparent quartz glass is A [ppm], the transmittance of the sample at a wavelength of 2.5 μm is I 1 [%], and the transmittance of the sample at a wavelength of 2.73 μm is I 2 [%]. A [ppm] = 0.01 · log 10 (I 1 [%] / I 2 [%]) The OH concentration was calculated in the above equation. The OH group concentration in the sample was 0 to 3 ppm.
[0016]
The valence of Fe in the transparent quartz glass was determined by observation of the ESR spectrum. The method for measuring the ESR spectrum is not particularly limited, but for example, it was performed as follows. A rectangular solid sample of 7 mm × 7 mm × 10 mm is cut out from the transparent quartz glass. The weight of the sample is about 1 g. The ESR spectrum was measured for this sample. In the ESR spectrum, a large absorption was observed near g = 2 and a small absorption was observed near g = 4.2.
[0017]
Griscom et al. and Fritsch et al. identified that absorption near g = 2 is due to ferromagnetic resonance from valence + 0 metallic iron in transparent quartz glass (DL Griscom, EJ Friebele and DB Shinn, J. Appl Phys. 50 ( 3) 2402-2404 (1979), E. Fritsch and G. Clas, Non-Cryst. Solid. Absorption near g = 4.2 has been identified as absorption by valence +3 iron ions in transparent quartz glass (DR Uhlmann and NJ Kreidl, Glass Science and Technology, Academic Press, inc., (1990) Chapter. 3).
[0018]
The method for determining the valence +0 metallic iron will be described in more detail. Synthetic silica powder having a content of Fe element of 0.01 ppm or less is dispersed in ultrapure water, and FeCl 3 is converted into Fe in terms of Fe weight in terms of 0.1, 0.2, 0.5, 0.7, Add 1, 5, 10 ppm. These slurries are thoroughly stirred at a temperature of 80 ° C., and then water is removed by evaporation. The obtained powder is heat-treated at a temperature of 400 to 800 ° C. for about 4 hours in a hydrogen stream, thereby reducing Fe in the powder to metallic iron having a valence of +0.
[0019]
The ESR spectrum of these powders is measured, and the integrated intensity of the ferromagnetic resonance absorption that appears in the vicinity of g = 2 is measured to create a calibration curve of the metal iron content of valence +0 and the integrated intensity. Using this calibration curve, the amount of valence + 0 metallic iron in the transparent quartz glass was quantified. A benzene solution of TEMPOL (4-Hydroxy-2,2,6,6-tetramethyl-piperidine-oxyl) is used as the primary standard sample for quantifying the integrated intensity, and ruby crystals (Cr +3 are used as the secondary standard sample. Containing α-Al 2 O 3 ).
[0020]
As a result of analysis using the ESR spectrum, it was found that the content of metallic iron having a valence of +0 among the Fe impurities in the transparent quartz glass was 0.1 ppm or less. Further, it was also found that when the transparent quartz glass contains more than 0.2 ppm of metallic iron having a valence of +0, the transparent quartz glass is colored by reheating at 900 to 1400 ° C. described later. Although the transparent quartz glass prepared by us was held at a temperature of 900 to 1400 ° C. for 20 hours or more, the transmittance in the visible short wavelength region in the visible-ultraviolet spectrum did not decrease, and the extinction coefficient at a wavelength of 400 nm was 0. 009 or less, and no coloring was observed.
[0021]
EXAMPLES The present invention will be further described below with reference to examples, but the present invention is not limited to the examples.
[0022]
【Example】
Example 1
The high purity natural crystal powder shown in Table 1 was used as a raw material. 6.4 kg of this raw material powder is filled into a high purity graphite mold having a ring-shaped space having an outer frame diameter of 410 mm, an inner frame diameter of 380 mm, and a depth of 75 mm. A high purity graphite felt having a thickness of 5 mm is stretched on the inner wall of the outer frame, and a high purity graphite felt having a thickness of 2 mm is stretched on the outer wall of the inner frame. A high-purity graphite sheet having a thickness of 0.4 mm was laid on the bottom of the ring-shaped space. The purity of the high purity graphite felt and the high purity graphite sheet is also shown in Table 1.
[0023]
As transparent quartz vitrification conditions, the temperature is raised from room temperature to 1600 ° C. in vacuum at 5 ° C./min, and then from 1600 ° C. to 1850 ° C. at 2 ° C./min. After heating in vacuum at 1850 ° C. for 15 minutes, heating is performed in a nitrogen atmosphere at a pressure of 1.7 kgf / cm 2 for 5 minutes. Then cool the furnace.
[0024]
The results of the composition analysis of the prepared transparent quartz glass by a wet method are shown in the lower part of Table 1. It was found that the impurity concentrations of Fe, Na, and K are in the range of 0.01 to 0.3 ppm.
[0025]
[Table 1]
A test piece having a thickness of 10 mm was cut out from the transparent quartz glass, both surfaces were optically polished, and an infrared absorption spectrum was measured. The transmittance at a wavelength of 2.5 μm is 87.5%, the transmittance at a wavelength of 2.73 μm is 86.0%, and the OH group concentration in the transparent quartz glass calculated from these is 0.75 ppm.
[0027]
The transparent quartz glass was kept in air at a temperature of 1150 ° C. for 66 hours. The transparent quartz glass after being held at 1150 ° C. for 66 hours is not colored even by visual observation. The visible light absorption spectrum is shown in FIGS. In this visible light absorption spectrum, the absorption coefficient at a wavelength of 400 nm was 0.003.
[0028]
A 7 mm × 7 mm × 10 mm rectangular parallelepiped sample was cut out from both transparent quartz glasses immediately after the preparation and after being held at 1150 ° C. in air for 66 hours, and an ESR spectrum was measured. The concentration of valence + 0 metallic iron in the transparent quartz glass calculated from the integrated intensity of resonance absorption observed near g = 2 was 0.1 ppm or less.
[0029]
Comparative Example 1
Natural quartz powder having the purity shown in Table 2 below is used as a raw material.
[0030]
[Table 2]
2.3 kg of this raw material powder is filled into a graphite mold having a ring-shaped space having an outer frame diameter of 255 mm, an inner frame diameter of 100 mm, and a depth of 47.5 mm. A graphite felt having a thickness of 5 mm is stretched on the inner wall of the outer frame, and a graphite felt having a thickness of 5 mm is stretched on the outer wall of the inner frame. A graphite sheet having a thickness of 0.4 mm is laid on the bottom of the ring-shaped space. Table 2 also shows the purity of the graphite felt and the graphite sheet.
[0032]
As transparent quartz vitrification conditions, the temperature is raised from room temperature to 1600 ° C. in vacuum at 5 ° C./min, and then from 1600 ° C. to 1850 ° C. at 2 ° C./min. After heating in vacuum at 1850 ° C. for 15 minutes, heating is performed in a nitrogen atmosphere at a pressure of 1.7 kgf / cm 2 for 5 minutes, followed by furnace cooling.
[0033]
The results of a wet composition analysis of the produced transparent quartz glass are shown in the lower part of Table 2. A sample piece having a thickness of 10 mm was cut out from transparent quartz glass, both surfaces were optically polished, and an infrared absorption spectrum was measured. The transmittance at a wavelength of 2.5 μm is 86.6%, the transmittance at a wavelength of 2.73 μm is 85.4%, and the OH group concentration in the transparent quartz glass calculated from this is 0.62 ppm.
[0034]
This transparent quartz glass was kept in air at a temperature of 1150 ° C. for 20 hours. The transparent quartz glass after being held at 1150 ° C. for 20 hours was colored by visual observation. FIG. 1 shows a visible light absorption spectrum. In this visible light absorption spectrum, the absorption coefficient at a wavelength of 400 nm was 0.298.
[0035]
A 7 mm × 7 mm × 10 mm rectangular parallelepiped sample was cut out from the transparent quartz glass that had been colored after being held at 1150 ° C. for 20 hours in air, and the ESR spectrum was measured. In the vicinity of g = 2, a broad and large resonance absorption peak was observed. The concentration of the valence + 0 metallic iron in the transparent quartz glass calculated from the integrated intensity of the peak was 4 ppm.
[0036]
Comparative Example 2
Natural quartz powder having the purity shown in Table 3 below was used as a raw material.
[0037]
[Table 3]
2.3 kg of this raw material powder is filled into a high purity graphite mold having a ring-shaped space having an outer frame diameter of 255 mm, an inner frame diameter of 100 mm, and a depth of 47.5 mm. A high purity graphite felt having a thickness of 5 mm is stretched on the inner wall of the outer frame, and a high purity graphite felt having a thickness of 2 mm is stretched on the outer wall of the inner frame. A high-purity graphite sheet having a thickness of 0.4 mm was laid on the bottom of the ring-shaped space. Table 3 also shows the purity of the high purity graphite felt and the high purity graphite sheet.
[0039]
As transparent quartz vitrification conditions, the temperature is raised from room temperature to 1600 ° C. in vacuum at 5 ° C./min, and then from 1600 ° C. to 1850 ° C. at 2 ° C./min. After heating in vacuum at 1850 ° C. for 15 minutes, heating is performed in a nitrogen atmosphere at a pressure of 1.7 kgf / cm 2 for 5 minutes. Then cool the furnace.
[0040]
The results of the composition analysis of the prepared transparent quartz glass by a wet method are shown in the lower part of Table 3. It was found that the impurity concentrations of Fe, Na, and K are in the range of 0.01 to 0.3 ppm.
[0041]
A test piece having a thickness of 10 mm was cut out from the transparent quartz glass, both surfaces were optically polished, and an infrared absorption spectrum was measured. The transmittance at a wavelength of 2.5 μm is 88.5%, the transmittance at a wavelength of 2.73 μm is 85.4%, and the OH group concentration in the transparent quartz glass calculated from these is 1.5 ppm.
[0042]
The transparent quartz glass was kept in air at a temperature of 1300 ° C. for 20 hours. The transparent quartz glass after being held at 1300 ° C. for 20 hours was lightly colored by visual observation. A visible light absorption spectrum is shown in FIG. In this visible light absorption spectrum, the absorption coefficient at a wavelength of 400 nm was 0.012. A 7 mm × 7 mm × 10 mm rectangular parallelepiped sample was cut out from the transparent quartz glass that had been colored after being held at 1300 ° C. for 20 hours in air, and the ESR spectrum was measured. A broad resonance absorption peak was observed in the vicinity of g = 2. The concentration of the valence + 0 metallic iron in the transparent quartz glass calculated from the integrated intensity of the peak was 0.2 ppm.
[0043]
Example 2
FIG. 3 shows several types of the composition of the graphite mold / graphite porous layer / quartz powder used in the production experiment of the quartz glass ring.
[0044]
Tables 4 to 8 show the purity of the quartz powder, high purity graphite mold, high purity graphite felt, high purity graphite sheet, and high purity graphite powder used in the experiment, respectively.
[0045]
[Table 4]
[Table 5]
[Table 6]
[Table 7]
[Table 8]
A mold (ring
[0051]
The above three types were placed in a carbon resistance heating electric furnace, heated from room temperature to 1850 ° C. in 8 hours in a state of being evacuated, held for 30 minutes, then released from the vacuum, introduced with nitrogen, and allowed to cool.
[0052]
The shapes and sizes of the three types of transparent quartz glass rings obtained are shown in FIG. 4, and all three types of transparent quartz glass rings with few bubbles are obtained. In particular, in FIG. A ring was obtained, and in (c), a flange-shaped ring having a step on the outer periphery was obtained.
[0053]
The analysis results of the impurities of the three types of transparent quartz glass rings obtained are shown in Table 9 below, and it was found that the purity of the raw materials was almost maintained.
[0054]
[Table 9]
【The invention's effect】
The transparent quartz glass obtained by the method of the present invention has a high purity, a low OH concentration, a high viscosity at a high temperature, and excellent properties as a material for semiconductor manufacturing jigs. Moreover, by suppressing the concentration of metallic iron in the valence state +0 to 0.1 ppm or less, it has a feature that it does not cause coloration even when it is reheated for a long time at a temperature of 900 to 1400 ° C. A glass member can be provided.
[0056]
Moreover, the transparent quartz glass ring obtained by the method of the present invention has high purity, and can have a large size with an outer diameter of 300 to 550 mm and a height of about 100 mm. Compared with a conventional method of machining from a quartz glass block, the method has an extremely excellent material yield, and the durability of the high-purity graphite mold is improved, which is an economically advantageous method. In particular, it becomes useful as quartz glass jigs and tools used in semiconductor manufacturing, for example, a flange of a reaction tube, a reaction chamber liner of an etching apparatus, and a single wafer type apparatus part.
[Brief description of the drawings]
FIG. 1 is a diagram showing a comparison of visible absorption spectra in Example 1 and Comparative Example 1. FIG.
2 is a diagram showing a comparison of visible absorption spectra in Example 1 and Comparative Example 2. FIG.
3 shows three types of cross-sectional structures among the graphite mold, graphite porous layer, and quartz powder used in Example 2. FIG.
[Explanation of symbols]
(1): High purity graphite mold (2): High purity graphite load (3): Quartz raw material powder (4): High purity graphite felt (5): High purity graphite sheet (6): High purity graphite outer ring [Figure] 4 shows the shape and size of the transparent quartz glass ring obtained in Example 2.
Claims (6)
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP25357698A JP4256955B2 (en) | 1997-12-03 | 1998-09-08 | High purity transparent quartz glass and method for producing the same |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP33276497 | 1997-12-03 | ||
| JP9-332764 | 1997-12-03 | ||
| JP25357698A JP4256955B2 (en) | 1997-12-03 | 1998-09-08 | High purity transparent quartz glass and method for producing the same |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH11228166A JPH11228166A (en) | 1999-08-24 |
| JP4256955B2 true JP4256955B2 (en) | 2009-04-22 |
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| JP25357698A Expired - Fee Related JP4256955B2 (en) | 1997-12-03 | 1998-09-08 | High purity transparent quartz glass and method for producing the same |
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| EP2042622A4 (en) | 2006-07-14 | 2014-06-11 | Toyo Tanso Co | Protective sheet for crucible and crucible device using the same |
| JP4388041B2 (en) | 2006-07-31 | 2009-12-24 | 東洋炭素株式会社 | Release sheet and usage of release sheet |
| US20140152914A1 (en) * | 2012-11-30 | 2014-06-05 | Corning Incorporated | Low-Fe Glass for IR Touch Screen Applications |
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