JP4424824B2

JP4424824B2 - Method for producing quartz glass crucible

Info

Publication number: JP4424824B2
Application number: JP2000160736A
Authority: JP
Inventors: 正徳福井; 光一鈴木; 貴宏佐藤
Original assignee: Japan Super Quartz Corp
Current assignee: Japan Super Quartz Corp
Priority date: 2000-05-30
Filing date: 2000-05-30
Publication date: 2010-03-03
Anticipated expiration: 2020-05-30
Also published as: JP2001342029A

Description

【０００１】
【発明の属する技術分野】
本発明は、内表面に凹凸や汚れがなく、かつ内表面層に微細気泡や異物を実質的に含有しない高品質の石英ガラスルツボに関する。本発明の石英ガラスルツボはシリコン単結晶引き上げ用のルツボとして好適である。
【０００２】
【従来の技術】
シリコン融液からシリコン単結晶を引き上げるシリコン単結晶の製造方法において、シリコン融液を入れた石英ガラスルツボはシリコンの融点以上に加熱されており、シリコン融液に接するルツボ内表面層に気泡や異物が含まれていたり、あるいは内表面に凹凸があったり汚れが付着していると、これがシリコン融液と反応してクリストバライト等の局部的な結晶を生じ、引き上げられるシリコンの単結晶化率を低下させる原因の一つになる。従って、石英ルツボの内側層は可能な限り表面が滑らかで汚れがなく、内表面層に気泡や異物を含まない透明層として形成されている。
【０００３】
しかし、従来の石英ガラスルツボは、内側透明層全体(約０.５〜３.５mm厚)の気泡量は少なくても、内表面に接する極く薄い表面層(内表面層：内表面から約０.５mm厚)に肉眼では識別し難い微細気泡が多数含まれている場合がある。回転モールド法によって石英ガラスルツボを製造した場合、内表面層は最初に石英粉が溶融して溶融層の被膜となる部分であるために、この部分に微細気泡が取り込まれると石英溶融層を減圧しても微細気泡を外部に吸引して除去することが難しく、この部分に微細気泡が残留しやすいと云う問題がある。
【０００４】
この内表面層に含まれる気泡は透明な微細気泡であるために肉眼で見出すことが難しい。顕微鏡を用いれば検出できるが、通常の顕微鏡による検出方法では試料を切り出す必要があり、出荷製品の検査には適しない。また、顕微鏡の画像をモニターで観察する検査方法によれば観察試料を切り出す必要はないが、視野が限定されるためにルツボ全体を観察するのに適さない。また、この方法はルツボ内表面の汚れや凹凸を観察するのが難しく、気泡や異物などを検出してもこれを直ちに除去できない。さらに、システムの構成に費用が嵩むなどの問題がある。
【０００５】
【発明の解決課題】
本発明は従来の石英ガラスルツボにおける上記問題を解決したものであり、石英ガラスルツボについて、その内表面層に含まれる微細気泡や異物、または内表面の凹凸や内表面に付着した汚染物質を容易に検出して除去した高品質の石英ガラスルツボを提供するものである。
【０００６】
【課題を解決する手段】
すなわち、本発明は、（１）ルツボ内表面を赤熱温度以上および軟化温度未満に加熱すると加熱領域に輝点が生じる石英ガラスルツボについて、ルツボ外表面を軟化温度より低く維持する一方、ルツボの内表面をアーク炎によって軟化温度以上に加熱して再溶融させ、輝点を除去したことを特徴とする再溶融石英ガラスルツボに関する。
【０００７】
本発明の石英ガラスルツボの具体的な例は、（２）ルツボ内表面を８００℃〜１５００℃以下に加熱すると加熱領域に輝点が生じる石英ガラスルツボについて、ルツボ外表面を１５００℃以下に維持する一方、ルツボの内表面をアーク炎によって１８５０℃〜２４００℃に加熱して再溶融させ、輝点を除去した再溶融石英ガラスルツボである。
【０００８】
本発明の上記石英ガラスルツボは、（３）ルツボ外表面を冷気にさらして外表面の温度を１４００℃以下に維持しつつ、ルツボの内表面を加熱して再溶融させ、輝点を除去した再溶融石英ガラスルツボ、（４）ルツボ内表面を８００℃〜１５００℃以下に加熱すると加熱領域に輝点が生じる石英ガラスルツボについて、ルツボ内表面をサンドブラスト処理し、次いで、ルツボ外表面を１５００℃以下に維持する一方、ルツボの内表面をアーク炎によって１７００℃(軟化温度以上)〜２４００℃に加熱して再溶融させ、輝点を除去した再溶融石英ガラスルツボを含む。
【０００９】
本発明の石英ガラスルツボは、石英ガラスルツボの内表面を一定温度に加熱して内表面に浮かび上がる輝点を観察すると云う極めて簡単な非破壊検査方法によってルツボ内表面の凹凸や汚れ、あるいは内表面層に含まれる微細気泡や異物を検出し、アーク炎によって内表面層を再溶融することによって、これらを除去した高品質のルツボである。この微細気泡や異物は検出後の再溶融ないしサンドブラスト処理によって容易に除去されるので、高品質の石英ガラスルツボを低コストで得ることができる。また、この石英ガラスルツボは内表面の凹凸や汚れがなく、また内表面層に微細気泡や異物を実質的に含まないので、シリコン単結晶の引き上げに用いることにより、優れた単結晶収率を得ることができる。
【００１０】
【発明の実施の形態】
以下、本発明を実施形態に基づいて詳細に説明する。
本発明の石英ガラスルツボは、ルツボ内表面を赤熱温度以上および軟化温度未満に加熱すると加熱領域に輝点が生じる石英ガラスルツボについて、ルツボ外表面を軟化温度より低く維持する一方、ルツボの内表面をアーク炎によって軟化温度以上に加熱して再溶融させ、輝点を除去したことを特徴とする再溶融石英ガラスルツボである。
【００１１】
再溶融に用いる石英ガラスルツボの製造方法は限定されない。回転モールド法や他の方法によって製造された石英ガラスルツボを広く用いることができる。加熱手段はアーク炎を用いることができる。アーク炎は酸水素バーナなどの加熱手段よりもルツボ内表面を比較的広く加熱することができるので効率が良い。
【００１２】
輝点観察時の石英ガラスルツボ内表面の加熱温度は、石英ガラスの赤熱温度以上および軟化温度(軟化点)未満である。赤熱温度とは石英ガラスルツボの加熱部分が赤色を呈し始める温度を云い、概ね８００℃である。加熱部分が赤熱しないと微細気泡や異物による輝点が観察されない。一方、加熱温度が石英ガラスの軟化温度(約１７００℃)を超えるとルツボが変形して凹凸を生じるので好ましくない。輝点を明瞭に判別するには１５００℃以下が適当であり、１４００℃以下が好ましい。１５００℃を超えるとルツボ表面の輝点とその周囲が同じ明るさになるので輝点を判別し難くなる。表面温度は赤外線温度計などによって測定すると良い。
【００１３】
ルツボ内表面を石英ガラスの赤熱温度以上および軟化温度未満、好ましくは８００℃〜１５００℃に加熱すると、ルツボの内表面層に微細気泡が含まれているものや、ルツボ内表面に凹凸が存在しているものは、この部分の屈折率が周囲と異なるために光が反射して周囲より明るい輝点として観察される。また、ルツボ内表面層に異物が含まれていたり、内表面に汚染物質が付着していると、石英ガラスより放射率が高いものは周囲よりも明るく光って観察される。従って、この輝点によって内表面の凹凸や汚れ、あるいは内表面層に含まれる微細気泡や異物の存在を判断することができる。なお、大部分の異物や汚染物質の放射率は石英ガラスより大きいので輝点として観察されるものが多い。
【００１４】
次に、加熱領域に輝点が生じたものについて、ルツボ外表面の温度を軟化温度未満に維持する一方、アーク炎を用いてルツボの内表面層を軟化温度以上に加熱し、再溶融させて輝点を除去する。ルツボ外表面の温度がその軟化温度より高い状態で内表面層を再溶融するとルツボが変形する虞がある。具体的には、ルツボ外表面を例えば１５００℃以下、好ましくは１４００℃以下に維持し、ルツボ内表面を１８５０℃〜２４００℃、好ましくは２０００℃〜２３５０℃に加熱して再溶融させる。ルツボ外表面と内表面の温度を以上の範囲に制御することにより、ルツボの内表面層を再溶融してもルツボが変形しない。
【００１５】
このような温度に制御するには、ルツボ内表面の加熱を急速に行い、外表面が高温になる前に内表面の温度を高くするのが好ましい。具体的には、加熱開始後約１分程度で、内表面温度を２０００℃以上に高め、加熱後３分以内に再溶融を終えると良い。
【００１６】
なお、再溶融の際、モールドを使用せずにルツボ外表面を冷気にさらしてルツボの放熱を促せば、ルツボ外表面の温度を１５００℃以下、好ましくは１４００℃以下に抑制することができる。
【００１７】
ルツボの内表面層を再溶融することにより、この部分に含まれている微細気泡は内表面に押し出されて弾け、そのピンホールが溶融した石英ガラスによって充填され、実質的に気泡を含有しない石英ガラス層になる。また表面の凹凸は消滅して平滑になり、異物は揮発して除去される。
【００１８】
アーク炎によってルツボ内表面を１８５０℃〜２４００℃に加熱して再溶融するには、アーク炎の熱量を１５０〜２５００W/cm²、好ましくは、４００〜２２００W/cm²とすれば良い。
【００１９】
加熱試験によって輝点が生じたものについて、内表面層の再溶融に先立ち、ルツボ内表面をサンドブラスト処理することにより再溶融処理の負担を軽減することができる。サンドブラスト処理を行うことにより、微細気泡や異物を含有する部分が削り落とされるので再溶融時間を短縮することができる。サンドブラスト処理は例えば、２〜７kg/cm²の高圧空気でシリカ粒子を吹き付けて行う。
【００２０】
輝点が観察された石英ガラスルツボについて以上の再溶融処理を施すことによって輝点を除去し、実質的に輝点を含まない石英ガラスルツボを得る。なお、輝点の個数が１０個/cm²以下、好ましくは３個/cm²以下であれば、失透テストにおいて、ルツボの失透面積を抑えることができ、高い平均単結晶化率を達成することができる。具体的には、輝点の個数が１０個/cm²以下のルツボは、アルゴン雰囲気５〜２０Torr、加熱温度１５００±５０℃、２０〜５０hrの加熱条件下において、内表面の失透面積を面積率で概ね３０％以下に抑えることができ、このルツボを用いてシリコン単結晶を引き上げたときに平均で７０％程度の単結晶化率を得ることができる。また、輝点の個数が３個/cm²以下のルツボは実質的に内表面の失透を生ぜず、平均で７７％程度の高い単結晶化率を得ることができる。なお、本発明においてルツボ内表面に凹凸や汚れがなく、内表面層に微細気泡や異物が実質的に含まれていないとは輝点の個数が好ましくは３個/cm²以下であることを云う。また、本発明の再溶融加熱はルツボ内表面の全体に適用しても良く、また輝点が存在する部分について局部的に適用しても良い。
【００２１】
【実施例】
回転モールド法によって口径２２インチの石英ガラスルツボ(内側透明層:２mm、外周側不透明層:１０mm)を複数個製造した。この石英ガラスルツボについて、石英バーナを用い、その内表面を酸水素炎によって約１１００℃に加熱して輝点の個数を検査した。次いで、アーク炎を用い表１の条件下でルツボ内表面層を再溶融した。この再溶融したルツボについて形状に変化がないか検査した。さらに、この再溶融ルツボを電気加熱炉に入れ、２０Torrのアルゴン雰囲気下、１５００℃の一定温度で２４時間加熱することにより失透試験を行った。また、他の再溶融したルツボを用いてシリコン単結晶の引き上げを行い、単結晶化率を求めた。この結果を表１に示した。
【００２２】
【表１】

【００２３】
【発明の効果】
本発明の石英ガラスルツボは、ルツボ内表面を一定温度に加熱して輝点を検出し、さらにルツボ内表面を軟化温度以上に加熱して内表面層に含まれる微細気泡や異物を除去したルツボであり、内表面層に微細気泡や異物を実質的に含まないので、シリコン単結晶引き上げの際に高い単結晶収率を得ることができる。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a high-quality quartz glass crucible that is free from irregularities and dirt on the inner surface and that does not substantially contain fine bubbles or foreign substances in the inner surface layer. The quartz glass crucible of the present invention is suitable as a crucible for pulling a silicon single crystal.
[0002]
[Prior art]
In a silicon single crystal manufacturing method for pulling a silicon single crystal from a silicon melt, the quartz glass crucible containing the silicon melt is heated to a temperature higher than the melting point of silicon, and bubbles and foreign substances are formed on the inner surface layer of the crucible in contact with the silicon melt. If there is stagnation, or the inner surface is uneven or has dirt, it reacts with the silicon melt to produce local crystals such as cristobalite, reducing the single crystallization rate of the silicon that is pulled up. One of the causes. Accordingly, the inner layer of the quartz crucible is formed as a transparent layer that is as smooth as possible and free from contamination, and the inner surface layer does not contain bubbles or foreign matters.
[0003]
However, the conventional quartz glass crucible has a very thin surface layer (inner surface layer: approximately from the inner surface) in contact with the inner surface even though the amount of bubbles in the entire inner transparent layer (approximately 0.5 to 3.5 mm thick) is small. 0.5 mm thick) may contain many fine bubbles that are difficult to identify with the naked eye. When a quartz glass crucible is manufactured by the rotary mold method, the inner surface layer is the part where the quartz powder is first melted to form the film of the molten layer. However, it is difficult to suck and remove the fine bubbles to the outside, and there is a problem that the fine bubbles are likely to remain in this portion.
[0004]
Since the bubbles contained in the inner surface layer are transparent fine bubbles, it is difficult to find them with the naked eye. Although it can be detected by using a microscope, it is necessary to cut out a sample by a normal detection method using a microscope, which is not suitable for inspection of shipped products. Further, according to the inspection method for observing the image of the microscope with the monitor, it is not necessary to cut out the observation sample, but since the field of view is limited, it is not suitable for observing the entire crucible. Also, this method makes it difficult to observe dirt and irregularities on the inner surface of the crucible, and even if bubbles or foreign substances are detected, they cannot be removed immediately. Furthermore, there is a problem that the cost of the system configuration increases.
[0005]
[Problem to be Solved by the Invention]
The present invention solves the above-mentioned problems in the conventional quartz glass crucible, and the quartz glass crucible easily removes fine bubbles and foreign matters contained in the inner surface layer, or irregularities on the inner surface and contaminants attached to the inner surface. The present invention provides a high-quality quartz glass crucible that has been detected and removed.
[0006]
[Means for solving the problems]
That is, the present invention provides (1) a quartz glass crucible in which a bright spot is generated in a heating region when the inner surface of the crucible is heated to a temperature higher than the red heat temperature and lower than the softening temperature, while the outer surface of the crucible is kept lower than the softening temperature. The present invention relates to a remelted silica glass crucible characterized in that the surface is heated to a softening temperature or higher by an arc flame and remelted to remove bright spots.
[0007]
Specific examples of the silica glass crucible of the present invention are as follows: (2) Maintaining the outer surface of the crucible at 1500 ° C. or less for the silica glass crucible that generates a bright spot in the heating region when the inner surface of the crucible is heated to 800 ° C. to 1500 ° C. or less. On the other hand, it is a remelted silica glass crucible in which the inner surface of the crucible is remelted by heating to 1850 ° C. to 2400 ° C. with an arc flame to remove the bright spots.
[0008]
The quartz glass crucible of the present invention has (3) the outer surface of the crucible exposed to cold to maintain the outer surface temperature at 1400 ° C. or less, and the inner surface of the crucible is heated to remelt to remove the bright spots. Remelted silica glass crucible (4) For a silica glass crucible in which a bright spot is generated in the heating region when the inner surface of the crucible is heated to 800 ° C. to 1500 ° C. or less, the inner surface of the crucible is sandblasted, and then the outer surface of the crucible is 1500 ° C. While maintaining below, the inner surface of the crucible is remelted by heating to 1700 ° C. (softening temperature or higher) to 2400 ° C. with an arc flame to remove a bright spot, and includes a remelted silica glass crucible.
[0009]
The quartz glass crucible of the present invention has a very simple non-destructive inspection method in which the inner surface of the quartz glass crucible is heated to a certain temperature and the bright spots floating on the inner surface are observed. It is a high-quality crucible in which fine bubbles and foreign matters contained in the surface layer are detected and these are removed by remelting the inner surface layer with an arc flame. Since these fine bubbles and foreign substances are easily removed by remelting or sandblasting after detection, a high-quality quartz glass crucible can be obtained at low cost. In addition, this quartz glass crucible has no irregularities or dirt on the inner surface, and the inner surface layer does not substantially contain fine bubbles or foreign substances. Obtainable.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail based on embodiments.
The quartz glass crucible of the present invention maintains the outer surface of the crucible lower than the softening temperature while the inner surface of the crucible is maintained at a lower temperature than the softening temperature. This is a remelted silica glass crucible characterized in that a bright spot is removed by heating to a softening temperature or higher with an arc flame and remelting.
[0011]
The manufacturing method of the quartz glass crucible used for remelting is not limited. Quartz glass crucibles manufactured by the rotary mold method or other methods can be widely used. An arc flame can be used as the heating means. The arc flame is more efficient than the heating means such as an oxyhydrogen burner because the inner surface of the crucible can be heated relatively widely.
[0012]
The heating temperature of the inner surface of the quartz glass crucible at the time of observation of the bright spot is not less than the red hot temperature and less than the softening temperature (softening point) of the quartz glass. The red heat temperature is a temperature at which the heated portion of the quartz glass crucible starts to appear red, and is generally 800 ° C. If the heated part is not red hot, bright spots due to fine bubbles and foreign matters are not observed. On the other hand, when the heating temperature exceeds the softening temperature of quartz glass (about 1700 ° C.), the crucible is deformed to form irregularities, which is not preferable. In order to clearly distinguish the bright spot, 1500 ° C. or lower is appropriate, and 1400 ° C. or lower is preferable. If the temperature exceeds 1500 ° C., the bright spot on the surface of the crucible and the surrounding area have the same brightness, so that it is difficult to distinguish the bright spot. The surface temperature may be measured with an infrared thermometer.
[0013]
When the inner surface of the crucible is heated to a temperature above the red temperature of the quartz glass and below the softening temperature, preferably 800 ° C. to 1500 ° C., the inner surface layer of the crucible contains fine bubbles, or there are irregularities on the inner surface of the crucible. In this case, since the refractive index of this portion is different from that of the surrounding area, the light is reflected and observed as a bright spot brighter than the surrounding area. In addition, if the inner surface layer of the crucible contains foreign substances or if contaminants are attached to the inner surface, those having an emissivity higher than that of quartz glass are observed brighter than the surroundings. Therefore, it is possible to determine the presence or absence of irregularities and dirt on the inner surface or the presence of fine bubbles or foreign substances contained in the inner surface layer by this bright spot. It should be noted that the emissivity of most foreign substances and contaminants is larger than that of quartz glass, and thus is often observed as a bright spot.
[0014]
Next, for those with bright spots in the heating region, the temperature of the outer surface of the crucible is maintained below the softening temperature, while the inner surface layer of the crucible is heated to the softening temperature or higher using an arc flame and remelted. Remove bright spots. If the inner surface layer is remelted in a state where the temperature of the outer surface of the crucible is higher than its softening temperature, the crucible may be deformed. Specifically, the outer surface of the crucible is maintained at, for example, 1500 ° C. or lower, preferably 1400 ° C. or lower, and the inner surface of the crucible is heated to 1850 ° C. to 2400 ° C., preferably 2000 ° C. to 2350 ° C., and remelted. By controlling the temperature of the outer surface and inner surface of the crucible within the above range, the crucible will not be deformed even if the inner surface layer of the crucible is remelted.
[0015]
In order to control to such a temperature, it is preferable to rapidly heat the inner surface of the crucible and raise the temperature of the inner surface before the outer surface becomes hot. Specifically, about 1 minute after the start of heating, the inner surface temperature is increased to 2000 ° C. or higher, and the remelting is finished within 3 minutes after the heating.
[0016]
Note that the temperature of the outer surface of the crucible can be suppressed to 1500 ° C. or lower, preferably 1400 ° C. or lower by exposing the outer surface of the crucible to cold air without reusing the mold to promote heat dissipation of the crucible.
[0017]
By remelting the inner surface layer of the crucible, the fine bubbles contained in this part are pushed out and blown to the inner surface, and the pinholes are filled with the molten quartz glass and are substantially free of bubbles. Become a glass layer. Further, the unevenness on the surface disappears and becomes smooth, and the foreign matter is volatilized and removed.
[0018]
To re-melted by heating the inner surface of the crucible to 1850 ° C. 2400 ° C. by the arc flame, 150~2500W / cm ² the heat of the arc flame, preferably, may be a 400~2200W / cm ^2.
[0019]
For those in which bright spots are generated by the heating test, the burden of the remelting process can be reduced by sandblasting the inner surface of the crucible prior to the remelting of the inner surface layer. By performing the sand blasting process, the portion containing fine bubbles and foreign matters is scraped off, so that the remelting time can be shortened. For example, the sandblast treatment is performed by spraying silica particles with high-pressure air of ^{2 to} 7 kg / cm ² .
[0020]
The quartz glass crucible in which the bright spot is observed is subjected to the above remelting process to remove the bright spot, thereby obtaining a quartz glass crucible that does not substantially contain the bright spot. If the number of bright spots is 10 / cm ² or less, preferably 3 / cm ² or less, the devitrification area of the crucible can be suppressed and a high average single crystallization rate is achieved in the devitrification test. can do. Specifically, a crucible having a number of bright spots of 10 pieces / cm ² or less has an area of devitrification on the inner surface under heating conditions of 5 to 20 Torr of argon atmosphere, heating temperature of 1500 ± 50 ° C. and 20 to 50 hours. When the silicon single crystal is pulled up using this crucible, an average single crystallization rate of about 70% can be obtained. The number of bright spots 3 / cm ² or less of the crucible not occur devitrification substantially inner surface, it is possible to obtain a high as 77% at an average single crystallization rate. In the present invention, the fact that the inner surface of the crucible is free of irregularities and dirt and that the inner surface layer is substantially free of fine bubbles and foreign matters means that the number of bright spots is preferably 3 / cm ² or less. say. Further, the remelting heating of the present invention may be applied to the entire inner surface of the crucible, or may be applied locally to a portion where a bright spot exists.
[0021]
【Example】
A plurality of quartz glass crucibles (inner transparent layer: 2 mm, outer peripheral opaque layer: 10 mm) having a diameter of 22 inches were produced by the rotary molding method. With respect to this quartz glass crucible, a quartz burner was used, and the inner surface thereof was heated to about 1100 ° C. with an oxyhydrogen flame to examine the number of bright spots. Next, the inner surface layer of the crucible was remelted using an arc flame under the conditions shown in Table 1. The remelted crucible was inspected for changes in shape. Further, the remelted crucible was placed in an electric heating furnace and subjected to a devitrification test by heating at a constant temperature of 1500 ° C. for 24 hours in an argon atmosphere of 20 Torr. In addition, the silicon single crystal was pulled using another remelted crucible to determine the single crystallization rate. The results are shown in Table 1.
[0022]
[Table 1]

[0023]
【The invention's effect】
The quartz glass crucible of the present invention is a crucible in which the inner surface of the crucible is heated to a constant temperature to detect a bright spot, and further, the inner surface of the crucible is heated to a softening temperature or higher to remove fine bubbles and foreign matters contained in the inner surface layer. In addition, since the inner surface layer does not substantially contain fine bubbles or foreign substances, a high single crystal yield can be obtained when pulling up the silicon single crystal.

Claims

Heat the crucible inner surface to above the red heat temperature and below the softening temperature , determine whether or not a bright spot is generated in the heating area, and for the quartz glass crucible in which the bright spot is generated in the heating area, the outer surface of the crucible is lower than the softening temperature. A method for producing a silica glass crucible, characterized in that the inner surface of the crucible is heated above the softening temperature by an arc flame to be remelted and the bright spots are removed.

The inner surface of the crucible is heated to 800 ° C. to 1500 ° C., it is determined whether or not a bright spot is generated in the heating region, and the outer surface of the crucible is maintained at 1500 ° C. or less for the quartz glass crucible in which the bright region is generated. On the other hand, the method for producing a quartz glass crucible according to claim 1, wherein the inner surface of the crucible is remelted by heating to 1850 ° C to 2400 ° C by an arc flame to remove a bright spot.

3. The method for producing a quartz glass crucible according to claim 2, wherein the outer surface of the crucible is exposed to cold to maintain the temperature of the outer surface at 1400 ° C. or less, and the inner surface of the crucible is heated to remelt to remove bright spots.

The method for producing a quartz glass crucible according to claim 2 or 3, wherein the inner surface of the crucible is heated to 2000 ° C to 2350 ° C by an arc flame and remelted to remove a bright spot .

The method for producing a quartz glass crucible according to any one of claims 1 to 4, wherein the inner surface of the crucible is sandblasted prior to remelting of the inner surface of the crucible .