JP5912903B2 - Silica glass crucible for pulling silicon single crystal and method for producing the same - Google Patents
Silica glass crucible for pulling silicon single crystal and method for producing the same Download PDFInfo
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- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 title claims description 79
- 229910052710 silicon Inorganic materials 0.000 title claims description 37
- 239000010703 silicon Substances 0.000 title claims description 37
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 title claims description 36
- 239000013078 crystal Substances 0.000 title claims description 31
- 238000004519 manufacturing process Methods 0.000 title claims description 13
- 239000002994 raw material Substances 0.000 claims description 22
- 239000010453 quartz Substances 0.000 claims description 19
- 239000000843 powder Substances 0.000 claims description 17
- 238000000034 method Methods 0.000 claims description 14
- 239000007864 aqueous solution Substances 0.000 claims description 9
- IIPYXGDZVMZOAP-UHFFFAOYSA-N lithium nitrate Chemical compound [Li+].[O-][N+]([O-])=O IIPYXGDZVMZOAP-UHFFFAOYSA-N 0.000 claims description 8
- 238000002844 melting Methods 0.000 claims description 6
- 230000008018 melting Effects 0.000 claims description 6
- XNDZQQSKSQTQQD-UHFFFAOYSA-N 3-methylcyclohex-2-en-1-ol Chemical compound CC1=CC(O)CCC1 XNDZQQSKSQTQQD-UHFFFAOYSA-N 0.000 claims description 3
- 238000002425 crystallisation Methods 0.000 description 26
- 230000008025 crystallization Effects 0.000 description 26
- 239000011734 sodium Substances 0.000 description 12
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 8
- 229910052700 potassium Inorganic materials 0.000 description 7
- 229910052708 sodium Inorganic materials 0.000 description 7
- 238000001816 cooling Methods 0.000 description 6
- 238000004031 devitrification Methods 0.000 description 6
- 229910052782 aluminium Inorganic materials 0.000 description 5
- 229910052744 lithium Inorganic materials 0.000 description 5
- 230000001737 promoting effect Effects 0.000 description 5
- 230000009471 action Effects 0.000 description 4
- 229910052783 alkali metal Inorganic materials 0.000 description 4
- 150000001340 alkali metals Chemical class 0.000 description 4
- 239000000463 material Substances 0.000 description 4
- 239000000470 constituent Substances 0.000 description 3
- 238000011109 contamination Methods 0.000 description 3
- 230000007423 decrease Effects 0.000 description 3
- 238000000465 moulding Methods 0.000 description 3
- 238000006467 substitution reaction Methods 0.000 description 3
- 229910002651 NO3 Inorganic materials 0.000 description 2
- NHNBFGGVMKEFGY-UHFFFAOYSA-N Nitrate Chemical compound [O-][N+]([O-])=O NHNBFGGVMKEFGY-UHFFFAOYSA-N 0.000 description 2
- 150000001768 cations Chemical class 0.000 description 2
- 238000001035 drying Methods 0.000 description 2
- 238000011156 evaluation Methods 0.000 description 2
- 238000010438 heat treatment Methods 0.000 description 2
- 229910052751 metal Inorganic materials 0.000 description 2
- 239000002184 metal Substances 0.000 description 2
- 239000000377 silicon dioxide Substances 0.000 description 2
- 239000000243 solution Substances 0.000 description 2
- BNGXYYYYKUGPPF-UHFFFAOYSA-M (3-methylphenyl)methyl-triphenylphosphanium;chloride Chemical compound [Cl-].CC1=CC=CC(C[P+](C=2C=CC=CC=2)(C=2C=CC=CC=2)C=2C=CC=CC=2)=C1 BNGXYYYYKUGPPF-UHFFFAOYSA-M 0.000 description 1
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 1
- DGAQECJNVWCQMB-PUAWFVPOSA-M Ilexoside XXIX Chemical compound C[C@@H]1CC[C@@]2(CC[C@@]3(C(=CC[C@H]4[C@]3(CC[C@@H]5[C@@]4(CC[C@@H](C5(C)C)OS(=O)(=O)[O-])C)C)[C@@H]2[C@]1(C)O)C)C(=O)O[C@H]6[C@@H]([C@H]([C@@H]([C@H](O6)CO)O)O)O.[Na+] DGAQECJNVWCQMB-PUAWFVPOSA-M 0.000 description 1
- 229910013553 LiNO Inorganic materials 0.000 description 1
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 description 1
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 description 1
- ZLMJMSJWJFRBEC-UHFFFAOYSA-N Potassium Chemical compound [K] ZLMJMSJWJFRBEC-UHFFFAOYSA-N 0.000 description 1
- 239000000654 additive Substances 0.000 description 1
- 230000000996 additive effect Effects 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 239000012141 concentrate Substances 0.000 description 1
- 229910052802 copper Inorganic materials 0.000 description 1
- 239000010949 copper Substances 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000010828 elution Methods 0.000 description 1
- 230000004927 fusion Effects 0.000 description 1
- 239000011521 glass Substances 0.000 description 1
- 230000003301 hydrolyzing effect Effects 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 230000002401 inhibitory effect Effects 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 239000000155 melt Substances 0.000 description 1
- 229910021421 monocrystalline silicon Inorganic materials 0.000 description 1
- 229910017604 nitric acid Inorganic materials 0.000 description 1
- 230000002093 peripheral effect Effects 0.000 description 1
- 239000011591 potassium Substances 0.000 description 1
- 230000008569 process Effects 0.000 description 1
- 238000000746 purification Methods 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- -1 silicon alkoxide Chemical class 0.000 description 1
- 230000001629 suppression Effects 0.000 description 1
- 229920002994 synthetic fiber Polymers 0.000 description 1
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- Crystals, And After-Treatments Of Crystals (AREA)
- Glass Melting And Manufacturing (AREA)
- Glass Compositions (AREA)
Description
本発明は、チョクラルスキー法（以下、ＣＺ法と言う。）によりシリコン単結晶を引上げる際に用いられる、原料シリコン融液を収容するための石英ガラスルツボ及びその製造方法に関する。 The present invention relates to a quartz glass crucible for containing a raw material silicon melt used when pulling up a silicon single crystal by the Czochralski method (hereinafter referred to as CZ method) and a method for producing the same.
シリコン単結晶の製造においては、ＣＺ法が広く用いられている。この方法は、ルツボ内に収容された原料シリコン融液の表面に種結晶を接触させ、ルツボを回転させるとともに、前記種結晶を反対方向に回転させながら上方へ引上げることにより、種結晶の下端に単結晶インゴットを育成していくものである。
上記方法において、シリコン融液を収容するためのルツボには、一般に、内層が、高純度の合成石英ガラスの透明層からなり、外層が、内層よりも純度が低く、安価な、天然石英ガラスの不透明層からなる石英ガラスルツボが用いられている。
The CZ method is widely used in the production of silicon single crystals. In this method, the seed crystal is brought into contact with the surface of the raw material silicon melt contained in the crucible, the crucible is rotated, and the seed crystal is pulled upward while rotating the seed crystal in the opposite direction. Single crystal ingots are nurtured.
In the above method, the crucible for containing the silicon melt generally has an inner layer made of a transparent layer of high-purity synthetic quartz glass, and the outer layer is made of natural quartz glass, which is less expensive and cheaper than the inner layer. A quartz glass crucible made of an opaque layer is used.
近年、シリコン単結晶製造の効率化のため、引上げるシリコン単結晶の大口径化が進み、これに伴い、シリコン単結晶の製造に要する時間も長くなり、ルツボの使用時間、すなわち、加熱時間も長くなり、ルツボは長時間にわたって高温下に曝されるようになっている。このため、ルツボを構成する石英ガラスの粘度が低下し、ルツボが変形を生じやすくなることが懸念される。
また、シリコン単結晶の大口径化に伴い、使用される原料シリコン融液も増量し、ルツボ自体のサイズも大きくなるため、ルツボに対する重量負荷が大きくなり、しかも、原料シリコン融液の湯面振動も大きくなる。
In recent years, in order to increase the efficiency of silicon single crystal production, the diameter of the silicon single crystal to be pulled up has increased, and accordingly, the time required for the production of the silicon single crystal has become longer, and the usage time of the crucible, that is, the heating time has also increased. Increasingly, crucibles are exposed to high temperatures for extended periods of time. For this reason, there is a concern that the viscosity of the quartz glass constituting the crucible decreases and the crucible tends to be deformed.
In addition, as the diameter of the silicon single crystal is increased, the amount of raw material silicon melt used is increased and the size of the crucible itself is increased, so that the weight load on the crucible increases and the surface vibration of the raw material silicon melt melts. Also grows.
したがって、石英ガラスルツボ、特に、大型のルツボにあっては、高温下においても変形せず、かつ、収容される原料シリコン融液の湯面振動を抑制することができる強度が求められている。 Accordingly, quartz glass crucibles, particularly large crucibles, are required to have a strength that does not deform even at high temperatures and can suppress the surface vibration of the raw material silicon melt to be accommodated.
これに対しては、高温下でのルツボの変形抑制するために、石英原料粉にアルミニウム（Ａｌ）を添加することにより、石英ガラスの粘度を高めることが知られている。
例えば、特許文献１には、所定濃度のＡｌと該Ａｌ濃度の２％以上の濃度のリチウム（Ｌｉ）を含有した石英粉を用いて外周部分を製造したルツボが記載されている。該特許文献１によれば、このルツボは、石英粉中のＡｌ含有量が多いほど石英ガラスの粘性が高くなり、高温下での形状安定性が向上し、一方で、Ｌｉによって、Ａｌによる電気抵抗の増加分を打ち消して、高電圧印加によりアルカリ金属や銅を外表面部分に濃集させて除去する電解精製効果を高めることができるとされている。
On the other hand, it is known to increase the viscosity of quartz glass by adding aluminum (Al) to quartz raw material powder in order to suppress deformation of the crucible at high temperature.
For example, Patent Document 1 describes a crucible in which an outer peripheral portion is manufactured using quartz powder containing Al having a predetermined concentration and lithium (Li) having a concentration of 2% or more of the Al concentration. According to Patent Document 1, as the crucible has a higher Al content in the quartz powder, the viscosity of the quartz glass increases and the shape stability at high temperature is improved. It is said that the increase in resistance can be canceled and the effect of electrolytic purification that concentrates and removes alkali metal and copper on the outer surface portion by applying a high voltage can be enhanced.
しかしながら、Ａｌは、石英ガラスの結晶化を促進する作用があるため、石英ガラス中の含有濃度が高い場合、ルツボ使用時の高温下において、ルツボの結晶化が急速に進行し、厚い結晶層が形成され、特に、底部の湾曲部において、冷却時にルツボにクラックが生じ、湯漏れを招くおそれがある。
また、Ｌｉ濃度が高い場合、結晶構造において、シリコン（Ｓｉ）の位置に同型置換したＡｌが電荷拘束される割合が低下し、この部分が結晶化の起点となりやすいため、過剰な結晶化が誘発され、この場合も、ルツボが脆くなり、クラックの発生や湯漏れを招くおそれがある。
However, since Al has an action of promoting crystallization of quartz glass, when the concentration in the quartz glass is high, crystallization of the crucible proceeds rapidly at a high temperature when the crucible is used, and a thick crystal layer is formed. In particular, the crucible cracks at the time of cooling in the curved portion at the bottom, and there is a risk of causing hot water leakage.
In addition, when the Li concentration is high, the proportion of charge constrained by isomorphous substitution at the silicon (Si) position in the crystal structure decreases, and this portion is likely to be the starting point of crystallization, so excessive crystallization is induced. In this case, too, the crucible becomes brittle, and there is a risk of causing cracks and leaking hot water.
したがって、ルツボの強度の向上を図るためには、結晶化を過度に促進することなく、石英ガラスの粘度を高めることが望ましい。 Therefore, in order to improve the strength of the crucible, it is desirable to increase the viscosity of the quartz glass without excessively promoting crystallization.
本発明は、上記技術的課題を解決するためになされたものであり、石英ガラスを適度に結晶化させることにより、ルツボの変形及びクラックの発生を抑制し、大型化した場合においても、シリコン融液を安定的に保持し得るシリコン単結晶引上げ用石英ガラスルツボ及びその製造方法を提供することを目的とするものである。 The present invention has been made in order to solve the above technical problems, and by appropriately crystallizing quartz glass, deformation of the crucible and generation of cracks are suppressed, and even when the size is increased, silicon fusion is achieved. It is an object of the present invention to provide a quartz glass crucible for pulling up a silicon single crystal that can stably hold a liquid and a method for producing the same.
本発明に係るシリコン単結晶引上げ用石英ガラスルツボは、Ａｌ濃度が８．８〜１５ｗｔｐｐｍ、ナトリウム（Ｎａ）濃度が０．１ｗｔｐｐｍ未満、カリウム（Ｋ）濃度が０．２ｗｔｐｐｍ未満、Ｌｉ濃度が０．３〜０．８ｗｔｐｐｍであり、かつ、ＡｌのＬｉに対するモル濃度比が７．５以下である石英ガラス原料からなる外層を備えていることを特徴とする。
このように、所定量のＡｌ及びＬｉを含む石英ガラスでルツボ外層を形成することにより、優れた強度特性を有するルツボが得られる。
The silica glass crucible for pulling a silicon single crystal according to the present invention has an Al concentration of 8.8 to 15 wtppm, a sodium (Na) concentration of less than 0.1 wtppm, a potassium (K) concentration of less than 0.2 wtppm, and a Li concentration of 0.8. An outer layer made of a quartz glass raw material having a molar concentration ratio of Al to Li of 3 to 0.8 wtppm and not more than 7.5 is provided.
Thus, the crucible which has the outstanding intensity | strength characteristic is obtained by forming a crucible outer layer with the quartz glass containing predetermined amount Al and Li.
また、本発明に係るシリコン単結晶引上げ用石英ガラスルツボの製造方法は、前記シリコン単結晶引上げ用石英ガラスルツボの製造方法において、前記石英ガラス中のＡｌ濃度及びＬｉ濃度は、溶融して前記石英ガラスとするために用いられる石英原料粉中のＡｌ成分又はＬｉ成分の少なくともいずれかを添加することにより調整されることを特徴とする。
Ａｌ成分又はＬｉ成分の添加により、適度に結晶化が促進される所望のＡｌ濃度及びＬｉ濃度の石英ガラスを容易に調整することができる。
The method for producing a quartz glass crucible for pulling a silicon single crystal according to the present invention is the method for producing a quartz glass crucible for pulling a silicon single crystal, wherein the Al concentration and the Li concentration in the quartz glass are melted and the quartz glass crucible is melted. It is characterized by being adjusted by adding at least one of an Al component or a Li component in a quartz raw material powder used for forming glass.
By adding the Al component or the Li component, it is possible to easily adjust the quartz glass having a desired Al concentration and Li concentration that can be appropriately accelerated in crystallization.
前記製造方法においては、前記Ａｌ濃度は硝酸アルミニウム九水和物水溶液の添加により、前記Ｌｉ濃度は硝酸リチウム水溶液の添加により、それぞれ調整されることが好ましい。
このような硝酸塩の水溶液を用いることにより、Ａｌ成分及びＬｉ成分を石英原料粉中に均一かつ容易に添加することができる。
In the manufacturing method, the Al concentration is preferably adjusted by adding an aqueous aluminum nitrate nonahydrate solution, and the Li concentration is adjusted by adding an aqueous lithium nitrate solution.
By using such an aqueous solution of nitrate, the Al component and the Li component can be uniformly and easily added to the quartz raw material powder.
本発明に係るシリコン単結晶引上げ用石英ガラスルツボによれば、ルツボ使用時の高温下においても変形せず、収容されるシリコン融液の湯面振動を抑制することができ、かつ、冷却時におけるクラックの発生や湯漏れ等も抑制することができ、優れた強度特性が得られる。
さらに、本発明は、石英ガラスルツボの大型化にも対応し得るものであり、シリコン単結晶引上げの効率向上に寄与し得る。
According to the silica glass crucible for pulling up a silicon single crystal according to the present invention, it is not deformed even under high temperature when the crucible is used, it is possible to suppress the molten metal surface vibration of the contained silicon melt, and at the time of cooling. Generation of cracks and leakage of hot water can be suppressed, and excellent strength characteristics can be obtained.
Furthermore, the present invention can cope with an increase in the size of a quartz glass crucible, and can contribute to an improvement in the efficiency of pulling a silicon single crystal.
以下、本発明をより詳細に説明する。
本発明に係るシリコン単結晶引上げ用石英ガラスルツボは、Ａｌ濃度が８．８〜１５ｗｔｐｐｍ、Ｎａ濃度が０．１ｗｔｐｐｍ未満、Ｋ濃度が０．２ｗｔｐｐｍ未満、Ｌｉ濃度が０．３〜０．８ｗｔｐｐｍであり、かつ、ＡｌのＬｉに対するモル濃度比が７．５以下である石英ガラスからなる外層を備えているものである。
すなわち、本発明に係る石英ガラスルツボは、外層を構成する石英ガラス中のＡｌ濃度及びＬｉ濃度が所定量であることを特徴とするものである。
このような石英ガラスで外層を形成することにより、高温下においても変形せず、また、冷却時における体積変化によるクラックの発生や湯漏れを生じることのない優れた強度特性を有するルツボを得ることができる。
Hereinafter, the present invention will be described in more detail.
The silica glass crucible for pulling a silicon single crystal according to the present invention has an Al concentration of 8.8 to 15 wtppm, an Na concentration of less than 0.1 wtppm, a K concentration of less than 0.2 wtppm, and an Li concentration of 0.3 to 0.8 wtppm. And an outer layer made of quartz glass having a molar concentration ratio of Al to Li of 7.5 or less.
That is, the quartz glass crucible according to the present invention is characterized in that the Al concentration and the Li concentration in the quartz glass constituting the outer layer are predetermined amounts.
By forming an outer layer of such quartz glass, a crucible having excellent strength characteristics that does not deform even at high temperatures and does not cause cracks or leak due to volume changes during cooling is obtained. Can do.
本発明においては、ルツボ外層の石英ガラス中のＡｌ濃度を８．８〜１５ｗｔｐｐｍとする。
上述したように、Ａｌは、石英ガラスの結晶化促進作用を有しており、石英ガラス中に上記範囲内の濃度で含まれていることにより、Ｌｉ濃度との適度なバランスでの相互作用によって、外層が過度に結晶化することなく、適度な結晶化の進行を維持することにより、ルツボの強度の向上を図ることができる。
In the present invention, the Al concentration in the silica glass of the outer crucible layer is set to 8.8 to 15 wtppm.
As described above, Al has an action of promoting crystallization of quartz glass, and since it is contained in the quartz glass at a concentration within the above range, it interacts with an appropriate balance with the Li concentration. The strength of the crucible can be improved by maintaining an appropriate progress of crystallization without excessively crystallizing the outer layer.
前記石英ガラス中のＮａ濃度は０．１ｗｔｐｐｍ未満、Ｋ濃度は０．２ｗｔｐｐｍ未満とする。
ＮａもＫも、石英ガラスの結晶化促進作用を有しているが、１価の陽イオンとなるアルカリ金属であり、Ｓｉとの親和性等の観点から、２価又は３価の陽イオンとなりやすいＡｌよりも結晶化促進作用が過激であり、これらの濃度調整によって結晶化の程度を制御することは難しい。また、Ｎａ及びＫは、引上げるシリコン単結晶に対する重大な汚染源となりやすいアルカリ金属であるため、ルツボの構成材料中に含まれていないことが好ましい。
したがって、Ｎａ及びＫは、前記石英ガラス中の濃度はできる限り低く抑えることが好ましい。
The Na concentration in the quartz glass is less than 0.1 wtppm, and the K concentration is less than 0.2 wtppm.
Both Na and K have an action to promote crystallization of quartz glass, but they are alkali metals that become monovalent cations and become divalent or trivalent cations from the viewpoint of affinity with Si and the like. The action of promoting crystallization is more extreme than that of easy Al, and it is difficult to control the degree of crystallization by adjusting these concentrations. Moreover, since Na and K are alkali metals which are likely to become a significant contamination source for the silicon single crystal to be pulled up, it is preferable that Na and K are not contained in the constituent material of the crucible.
Therefore, it is preferable that Na and K have a concentration in the quartz glass as low as possible.
また、前記石英ガラス中のＬｉ濃度は０．３〜０．８ｗｔｐｐｍとする。
Ｌｉは、結晶化抑制作用を有するため、Ａｌによる結晶化促進作用を適度に抑制する調整剤としての役割を果たすものとして石英ガラス中に含有させる。
ただし、Ｌｉは、ＮａやＫと同様に、引上げるシリコン単結晶に対する重大な汚染源となりやすいアルカリ金属であるため、ルツボの構成材料中に多く含まれることは好ましくなく、上記濃度範囲内に抑える。
The Li concentration in the quartz glass is 0.3 to 0.8 wtppm.
Since Li has a crystallization inhibitory action, Li is contained in quartz glass as a function of a regulator that moderately suppresses the crystallization promoting action by Al.
However, Li, like Na and K, is an alkali metal that is likely to become a serious source of contamination for the silicon single crystal to be pulled up. Therefore, it is not preferable that Li is contained in the constituent material of the crucible.
さらに、前記石英ガラス中のＡｌとＬｉの濃度は、ＡｌのＬｉに対するモル濃度比（Ａｌ／Ｌｉモル濃度比）が７．５以下となるように調整する。
Ａｌは、結晶構造において、Ｓｉの位置に同型置換した際、正電荷が不足した状態となる。Ｌｉは、この部分に取り込まれやすく、Ａｌは電荷拘束される。この電荷拘束された原子ペアは結晶化の起点とはならない。
Ａｌ／Ｌｉモル濃度比が大きい場合、相対的にＬｉ濃度が小さく、Ｓｉ位置に同型置換したＡｌが電荷拘束される割合が低下し、その部分が結晶化の起点となりやすい。そして、Ａｌ／Ｌｉモル濃度比が大きくなるにつれて、結晶化の起点となる核である点失透の個数が増加し、結晶化が過度に促進される。特に、Ａｌ／Ｌｉモル濃度比が７．５を超えると、結晶化がルツボ内層にまで伸展し、特に、底部の湾曲部において、冷却時の体積変化によりルツボにクラックが生じたり、さらには、湯漏れが起きたりするおそれがある。
したがって、Ａｌ／Ｌｉモル濃度比を７．５以下とすることにより、電荷拘束されずに存在するＡｌを低減し、点失透の発生を抑制し、適度な結晶化の進行を維持させる。
Furthermore, the concentration of Al and Li in the quartz glass is adjusted so that the molar concentration ratio of Al to Li (Al / Li molar concentration ratio) is 7.5 or less.
Al is in a state where the positive charge is insufficient when the same type substitution is made at the Si position in the crystal structure. Li is easily taken into this part, and Al is charge-constrained. This charge-constrained atomic pair is not the starting point for crystallization.
When the Al / Li molar concentration ratio is large, the Li concentration is relatively small, and the proportion of charge constrained by Al having the same type substitution at the Si position decreases, and this portion tends to be the starting point of crystallization. As the Al / Li molar concentration ratio increases, the number of point devitrifications, which are nuclei that are the starting points of crystallization, increases, and crystallization is promoted excessively. In particular, when the Al / Li molar concentration ratio exceeds 7.5, crystallization extends to the inner layer of the crucible, and in particular, in the curved portion at the bottom, cracks occur in the crucible due to volume change during cooling, There is a risk of leaking water.
Therefore, by setting the Al / Li molar concentration ratio to 7.5 or less, Al existing without charge restriction is reduced, the occurrence of point devitrification is suppressed, and the progress of moderate crystallization is maintained.
前記Ａｌ濃度及びＬｉ濃度は、石英原料粉中に元々含まれているＡｌ及びＬｉの濃度をＩＣＰ発光分析法等にて測定し、それぞれ所定の濃度範囲及びＡｌ／Ｌｉモル濃度比となるように、必要に応じて、Ａｌ成分又は／及びＬｉ成分を添加して濃度調整する。
石英原料粉中の元々のＡｌ濃度又はＬｉ濃度が、前記石英ガラス中の所定濃度範囲内である場合には、Ａｌ／Ｌｉモル濃度比を考慮して、Ａｌ成分又はＬｉ成分の一方のみを添加すればよい。
なお、前記Ｎａ濃度及びＫ濃度はできる限り低いことが好ましいため、石英原料粉中に元々含まれているＮａ及びＫの濃度が、前記石英ガラス中の濃度範囲を超えている場合には、公知の方法により予め精製しておく必要がある。
The Al concentration and the Li concentration are determined by measuring the concentrations of Al and Li originally contained in the quartz raw material powder by an ICP emission analysis method or the like, so that a predetermined concentration range and an Al / Li molar concentration ratio are obtained, respectively. If necessary, the concentration is adjusted by adding an Al component or / and a Li component.
When the original Al concentration or Li concentration in the quartz raw material powder is within the predetermined concentration range in the quartz glass, only one of the Al component or Li component is added in consideration of the Al / Li molar concentration ratio. do it.
Since the Na concentration and the K concentration are preferably as low as possible, when the concentration of Na and K originally contained in the quartz raw material powder exceeds the concentration range in the quartz glass, it is known. It is necessary to purify in advance by this method.
前記Ａｌ成分は、硝酸アルミニウム九水和物（Ａｌ(ＮＯ3)3・９Ｈ2Ｏ）の水溶液として、また、前記Ｌｉ成分は、硝酸リチウム（ＬｉＮＯ3）の水溶液として、石英原料粉にそれぞれ添加されることが好ましい。
各水溶液は石英原料粉の量に応じて、できるだけ均一に添加することができるように適宜濃度調整し、石英原料粉に均一に添加した後、これを乾燥して、再度粉末化して使用することが好ましい。
このような硝酸塩の水溶液の添加によれば、Ａｌ及びＬｉの濃度調整を均一かつ容易に行うことができる。また、過剰の水分及び硝酸分は、乾燥、加熱により容易に除去することができ、取扱い容易である。
The Al component is added to the quartz raw material powder as an aqueous solution of aluminum nitrate nonahydrate (Al (NO 3 ) 3 · 9H 2 O), and the Li component is added as an aqueous solution of lithium nitrate (LiNO 3 ). It is preferred that
The concentration of each aqueous solution should be adjusted appropriately so that it can be added as uniformly as possible according to the amount of the quartz raw material powder, added uniformly to the quartz raw material powder, then dried and powdered again Is preferred.
By adding such an aqueous solution of nitrate, the concentration of Al and Li can be adjusted uniformly and easily. Excess water and nitric acid can be easily removed by drying and heating, and is easy to handle.
なお、前記石英原料粉は、合成石英及び天然石英のいずれを用いてもよいが、ルツボ外層の不透明層の構成材料であるため、低コスト化の観点からは、内層よりも純度が低く、安価である天然石英がより好適に用いられる。
一方、ルツボ内層は、ルツボの構成材料に起因する単結晶シリコンの不純物汚染や原料シリコン融液の湯面振動の抑制等の観点から、通常、シリコンアルコキシドの加水分解等により得られる高純度の合成シリカ原料により形成される合成石英ガラスからなる透明層とする。
The quartz raw material powder may be either synthetic quartz or natural quartz. However, since it is a constituent material of the opaque layer of the outer layer of the crucible, the purity is lower than the inner layer and is inexpensive from the viewpoint of cost reduction. The natural quartz is more preferably used.
On the other hand, the inner layer of the crucible is a high-purity synthetic material usually obtained by hydrolyzing silicon alkoxide, etc., from the viewpoint of impurity contamination of single crystal silicon caused by the material constituting the crucible and suppression of surface vibration of the raw silicon melt. A transparent layer made of synthetic quartz glass formed of a silica raw material is used.
前記内層及び外層を含むルツボ全体の厚さは、ルツボの強度や重量等を考慮して、１０〜２３ｍｍ程度であることが好ましい。通常は１５ｍｍ程度とする。
また、前記外層の厚さは、特に限定されるものではないが、同様の観点から、９〜１８ｍｍ程度であることが好ましい。
一方、前記内層は、溶出によりルツボ内表面にルツボ外層が露出したり、シリコン融液の湯面振動を生じさせたりしない程度の厚さとする必要があり、このような観点から、１〜５ｍｍ程度であることが好ましい。
The thickness of the entire crucible including the inner layer and the outer layer is preferably about 10 to 23 mm in consideration of the strength and weight of the crucible. Usually about 15 mm.
The thickness of the outer layer is not particularly limited, but is preferably about 9 to 18 mm from the same viewpoint.
On the other hand, the inner layer needs to have such a thickness that the outer layer of the crucible is not exposed on the inner surface of the crucible due to elution or the molten metal surface of the silicon melt is not generated. From this viewpoint, about 1 to 5 mm. It is preferable that
本発明に係る石英ガラスルツボの製造方法は、上記のように、外層の形成に使用する石英原料粉中の添加物を濃度調整して配合すること以外は、特に限定されるものではなく、公知の工程により製造することができる。一般的には、回転モールド法及びアーク溶融法により製造される。
具体的には、回転するルツボ成形用型内に、外層を構成するための石英原料粉を所定の層厚さで装填し、その内側に内層を構成するための合成シリカ原料粉を所定厚さで装填して、成形する。そして、この中にアーク電極を挿入し、減圧アーク溶融にてガラス化することにより、本発明に係る石英ガラスルツボを製造することができる。
なお、外層形成後、火炎溶融法により内層を直接堆積させて形成することもできる。
The method for producing the quartz glass crucible according to the present invention is not particularly limited as described above, except that the additive in the quartz raw material powder used for forming the outer layer is adjusted in concentration and blended. It can be manufactured by the process. Generally, it is manufactured by a rotary molding method and an arc melting method.
Specifically, in a rotating crucible molding die, a quartz raw material powder for constituting the outer layer is loaded with a predetermined layer thickness, and a synthetic silica raw material powder for constituting the inner layer is placed on the inner side thereof with a predetermined thickness. Load with and mold. And the quartz glass crucible which concerns on this invention can be manufactured by inserting an arc electrode in this and vitrifying by low pressure arc melting.
In addition, after forming the outer layer, the inner layer can be directly deposited by a flame melting method.
以下、本発明を実施例に基づきさらに具体的に説明するが、本発明は下記の実施例により制限されるものではない。
回転モールド法及びアーク溶融法により、ルツボ内層が厚さ２ｍｍの合成石英ガラスからなり、ルツボ外層が厚さ１４ｍｍの天然石英ガラスからなる外径３２インチ、高さ４５０ｍｍの石英ガラスルツボを作製した。
ルツボ外層を構成するための天然石英原料粉は、Ｎａ濃度０．１ｗｔｐｐｍ未満、Ｋ濃度０．２ｗｔｐｐｍ未満とし、また、０．１〜０．９ｗｔ％の範囲の濃度で適宜調製した硝酸アルミニウム九水和物水溶液及び硝酸リチウム水溶液を添加して均一に分散させて乾燥させることにより、Ａｌ濃度８．８〜１５ｗｔｐｐｍ、Ｌｉ濃度０．３〜０．８ｗｔｐｐｍとなるように調整した。
また、前記アーク溶融は、約２０００℃で１時間未満で行った。
EXAMPLES Hereinafter, although this invention is demonstrated more concretely based on an Example, this invention is not restrict | limited by the following Example.
A quartz glass crucible having an outer diameter of 32 inches and a height of 450 mm, in which the inner layer of the crucible is made of synthetic quartz glass having a thickness of 2 mm and the outer layer of the crucible is made of natural quartz glass having a thickness of 14 mm, was produced by a rotary molding method and an arc melting method.
The natural quartz raw material powder for constituting the crucible outer layer has a Na concentration of less than 0.1 wtppm, a K concentration of less than 0.2 wtppm, and an aluminum nitrate nine water appropriately prepared at a concentration in the range of 0.1 to 0.9 wt%. By adding a hydrate aqueous solution and a lithium nitrate aqueous solution, and uniformly dispersing and drying, the Al concentration was adjusted to 8.8 to 15 wtppm, and the Li concentration was adjusted to 0.3 to 0.8 wtppm.
The arc melting was performed at about 2000 ° C. for less than 1 hour.
（評価１）
前記ルツボ外層から、１０ｍｍ×１０ｍｍ×４０ｍｍのサンプルを切り出し、大気中で１５００℃で１００時間熱処理し、発生した点失透を目視にて観察し、その個数をカウントすることにより、結晶化の評価を行った。
(Evaluation 1)
A 10 mm × 10 mm × 40 mm sample was cut out from the outer layer of the crucible, heat treated at 1500 ° C. for 100 hours in the air, the generated point devitrification was observed visually, and the number of the samples was evaluated to evaluate crystallization. Went.
その結果、ルツボ外層を構成する天然石英ガラス中のＡｌ／Ｌｉモル濃度比が１０以上の場合は、点失透が４０個以上となる場合もあるのに対して、Ａｌ／Ｌｉモル濃度比が７．５以下の場合、点失透は２０個以下であり、Ａｌ／Ｌｉモル濃度比が小さいほど、点失透の個数は少ないことが確認された。 As a result, when the Al / Li molar concentration ratio in the natural quartz glass constituting the crucible outer layer is 10 or more, the point devitrification may be 40 or more, whereas the Al / Li molar concentration ratio is In the case of 7.5 or less, the number of point devitrification was 20 or less, and it was confirmed that the smaller the Al / Li molar concentration ratio, the smaller the number of point devitrification.
（評価２）
作製した石英ガラスルツボを、カーボンルツボに嵌め込んでセットし、ルツボ外周からヒータ加熱して、ルツボ内で約３００ｋｇの原料シリコンを溶融させ、ＣＺ法により、直径１２インチのシリコン単結晶の引上げを行った。
そして、シリコン単結晶引上げ後のルツボの表面状態の観察及び結晶化の評価を行った。
(Evaluation 2)
The produced quartz glass crucible is fitted into a carbon crucible and set, and the heater is heated from the outer periphery of the crucible to melt about 300 kg of raw silicon in the crucible, and a 12-inch diameter silicon single crystal is pulled by the CZ method. went.
Then, the surface state of the crucible after the pulling of the silicon single crystal was observed and the crystallization was evaluated.
その結果、ルツボ外層を構成する天然石英ガラス中のＡｌ／Ｌｉモル濃度比が７．５以下の場合、評価した２０個のルツボはいずれも、シリコン単結晶引上げに問題なく使用することができ、そのうちの１６個（８０％）については、内層への結晶化の伸展も見られなかった。
一方、前記Ａｌ／Ｌｉモル濃度比が７．５を超える場合は、９．０以下であれば、２０個中１３個（６５％）のルツボは、内層への結晶化の伸展が見られたが、シリコン単結晶引上げにおける使用上の問題はなかった。しかしながら、７個のルツボは、結晶化が過度に進行し、内層への結晶化の伸展も多く、冷却時に湯漏れが発生又は発生するおそれがある状態であった。
さらに、前記前記Ａｌ／Ｌｉモル濃度比が９．０を超える場合は、２０個中１８個（９０％）のルツボが、結晶化が過度に進行し、内層への結晶化の伸展も多く、冷却時に湯漏れが発生又は発生するおそれがある状態であった。
As a result, when the Al / Li molar concentration ratio in the natural quartz glass constituting the crucible outer layer is 7.5 or less, any of the evaluated 20 crucibles can be used without any problem for pulling up the silicon single crystal, In 16 of them (80%), no crystallization extension to the inner layer was observed.
On the other hand, when the Al / Li molar concentration ratio exceeds 7.5, if it is 9.0 or less, 13 out of 20 crucibles (65%) showed crystallization extension to the inner layer. However, there was no problem in use in pulling the silicon single crystal. However, the seven crucibles were in a state where the crystallization progressed excessively, the crystallization spread to the inner layer was much, and there was a possibility that hot water leakage might occur during cooling.
Further, when the Al / Li molar concentration ratio exceeds 9.0, 18 of 20 crucibles (90%) are excessively crystallized, and the extension of crystallization to the inner layer is also large. It was in a state where hot water leakage occurred or might occur during cooling.
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