JP6459987B2 - Method for producing silicon single crystal - Google Patents
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- JP6459987B2 JP6459987B2 JP2016002766A JP2016002766A JP6459987B2 JP 6459987 B2 JP6459987 B2 JP 6459987B2 JP 2016002766 A JP2016002766 A JP 2016002766A JP 2016002766 A JP2016002766 A JP 2016002766A JP 6459987 B2 JP6459987 B2 JP 6459987B2
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- 239000013078 crystal Substances 0.000 title claims description 201
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 title claims description 127
- 229910052710 silicon Inorganic materials 0.000 title claims description 127
- 239000010703 silicon Substances 0.000 title claims description 127
- 238000004519 manufacturing process Methods 0.000 title claims description 53
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 232
- 229910052757 nitrogen Inorganic materials 0.000 claims description 106
- 238000000034 method Methods 0.000 claims description 77
- 239000002994 raw material Substances 0.000 claims description 18
- 238000010438 heat treatment Methods 0.000 claims description 14
- 230000006698 induction Effects 0.000 claims description 14
- 208000028659 discharge Diseases 0.000 description 23
- 229910001873 dinitrogen Inorganic materials 0.000 description 20
- 239000007789 gas Substances 0.000 description 18
- 230000007547 defect Effects 0.000 description 17
- 239000002019 doping agent Substances 0.000 description 16
- 239000000155 melt Substances 0.000 description 15
- 238000002844 melting Methods 0.000 description 11
- 230000008018 melting Effects 0.000 description 11
- 230000000052 comparative effect Effects 0.000 description 10
- 230000001965 increasing effect Effects 0.000 description 10
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 8
- 235000012431 wafers Nutrition 0.000 description 6
- 239000002244 precipitate Substances 0.000 description 5
- 239000004065 semiconductor Substances 0.000 description 5
- 229910052786 argon Inorganic materials 0.000 description 4
- 230000015572 biosynthetic process Effects 0.000 description 4
- 230000007704 transition Effects 0.000 description 4
- 238000002425 crystallisation Methods 0.000 description 3
- 230000008025 crystallization Effects 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- 239000011261 inert gas Substances 0.000 description 3
- 238000005204 segregation Methods 0.000 description 3
- 238000004804 winding Methods 0.000 description 3
- ZOXJGFHDIHLPTG-UHFFFAOYSA-N Boron Chemical compound [B] ZOXJGFHDIHLPTG-UHFFFAOYSA-N 0.000 description 2
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 description 2
- 229910052796 boron Inorganic materials 0.000 description 2
- 230000007423 decrease Effects 0.000 description 2
- 230000003247 decreasing effect Effects 0.000 description 2
- 239000012535 impurity Substances 0.000 description 2
- 239000011810 insulating material Substances 0.000 description 2
- 150000004767 nitrides Chemical class 0.000 description 2
- QJGQUHMNIGDVPM-UHFFFAOYSA-N nitrogen group Chemical group [N] QJGQUHMNIGDVPM-UHFFFAOYSA-N 0.000 description 2
- 238000010899 nucleation Methods 0.000 description 2
- 229910052698 phosphorus Inorganic materials 0.000 description 2
- 239000011574 phosphorus Substances 0.000 description 2
- 238000000926 separation method Methods 0.000 description 2
- 239000000758 substrate Substances 0.000 description 2
- -1 as described above Substances 0.000 description 1
- 238000004090 dissolution Methods 0.000 description 1
- 230000002708 enhancing effect Effects 0.000 description 1
- 238000005530 etching Methods 0.000 description 1
- 238000012423 maintenance Methods 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 238000002156 mixing Methods 0.000 description 1
- 230000002265 prevention Effects 0.000 description 1
- 239000000047 product Substances 0.000 description 1
- 230000009257 reactivity Effects 0.000 description 1
- 238000007711 solidification Methods 0.000 description 1
- 230000008023 solidification Effects 0.000 description 1
- 238000005507 spraying Methods 0.000 description 1
- 238000004857 zone melting Methods 0.000 description 1
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Description
本発明は、ＦＺ法（フローティングゾーン法又は浮遊帯溶融法）による半導体単結晶の製造方法に関する。 The present invention relates to a method for producing a semiconductor single crystal by FZ method (floating zone method or floating zone melting method).
ＦＺ法は、例えば、現在半導体素子として最も多く使用されているシリコン単結晶等の半導体単結晶の製造方法の一つとして使用される。通常、シリコン単結晶に所望の抵抗率を与えるためにはＮ型或いはＰ型の不純物ドーピングが必要である。ＦＺ法においては、ドーパントガスを溶融帯に吹き付けるガスドーピング法が知られている（非特許文献１参照）。 The FZ method is used, for example, as one method for manufacturing a semiconductor single crystal such as a silicon single crystal that is most frequently used as a semiconductor element. Usually, in order to give a desired resistivity to a silicon single crystal, N-type or P-type impurity doping is required. In the FZ method, a gas doping method in which a dopant gas is sprayed onto a melting zone is known (see Non-Patent Document 1).
ドーパントガスとして、例えばＮ型ドーパントであるＰ（リン）のドーピングにはＰＨ３等が、Ｐ型ドーパントであるＢ（ホウ素）のドーピングにはＢ２Ｈ６等が用いられる。シリコン単結晶の抵抗率は、これらＮ型ドーパントとＰ型ドーパントの結晶中の濃度差により変化するが、通常の結晶製造においてＮ型ドーパントのみ、或いはＰ型ドーパントのみをドーピングする場合には、抵抗率はドーパント添加量が増加するにつれて低くなる。 As the dopant gas, for example, PH 3 or the like is used for doping P (phosphorus) which is an N-type dopant, and B 2 H 6 or the like is used for doping B (boron) which is a P-type dopant. The resistivity of the silicon single crystal varies depending on the concentration difference in the crystals of the N-type dopant and the P-type dopant. However, in the case of doping only the N-type dopant or only the P-type dopant in normal crystal production, the resistivity is reduced. The rate decreases with increasing dopant loading.
所望の抵抗率のシリコン単結晶を得るためには、原料の抵抗率と所望の抵抗率を基に算出されたドーパント添加量が適正に保たれる必要がある。供給されるドーパントガスの濃度や流量等を調整することによりドーパント添加量を適正に保ちつつＦＺ法により単結晶を成長させることで、所望の抵抗率を持つシリコン単結晶を得ることができる。 In order to obtain a silicon single crystal having a desired resistivity, it is necessary to appropriately maintain the dopant addition amount calculated based on the resistivity of the raw material and the desired resistivity. A silicon single crystal having a desired resistivity can be obtained by growing the single crystal by the FZ method while adjusting the concentration and flow rate of the supplied dopant gas to keep the dopant addition amount appropriate.
半導体デバイスの生産性等の観点から、使用されるシリコンウェーハの直径は段々と拡大してきた経緯があり、ウェーハの原料とするシリコン単結晶の直径も拡大してきた。製造するシリコン単結晶の直径が拡大することにより必要とする供給電力も増大し、シリコン単結晶製造中に高周波誘導加熱コイルにかかる電圧も高電圧となる。しかしこのように供給電力増大、高周波誘導加熱コイルへの印加電圧増加の状況下では、コイルスリット部、或いはコイルと原料や付帯設備の間等、炉内で放電が発生してシリコン単結晶製造を妨げることになる。 From the viewpoint of the productivity of semiconductor devices, etc., the diameter of silicon wafers used has gradually increased, and the diameter of silicon single crystals used as raw materials for wafers has also increased. The required power supply increases as the diameter of the silicon single crystal to be produced increases, and the voltage applied to the high-frequency induction heating coil during the production of the silicon single crystal also becomes a high voltage. However, under the circumstances where the supply power is increased and the voltage applied to the high frequency induction heating coil is increased in this way, discharge is generated in the furnace such as the coil slit part or between the coil and the raw material or incidental equipment, thereby producing a silicon single crystal. Will interfere.
ＦＺ装置内でのシリコン単結晶製造中の放電防止対策として、製造中の雰囲気に窒素ガスを混合する方法が開示されている（例えば、特許文献１参照）。雰囲気中に窒素ガスを加えることによって放電開始電圧を高め、高周波誘導加熱コイルの放電現象を制御する。 As a measure for preventing discharge during the production of a silicon single crystal in an FZ apparatus, a method of mixing nitrogen gas into the atmosphere during production is disclosed (for example, see Patent Document 1). By adding nitrogen gas to the atmosphere, the discharge start voltage is increased and the discharge phenomenon of the high frequency induction heating coil is controlled.
また、高周波誘導加熱コイルの放電を防止する方法としては、コイルのスリット部での放電を防止する目的でスリット空隙部に絶縁部材を挿入する方法（例えば、特許文献２参照）、スリット空隙部に窒素ガスを吹き付ける方法（例えば、特許文献３参照）、高周波誘導加熱コイルの外巻き部と内巻き部の間で発生する放電を防止するために外巻き部を絶縁性部材で被覆する方法（例えば、特許文献４参照）、高周波誘導加熱コイルとその周囲の部材或いは原料棒や単結晶の間に絶縁部材を配置する方法（例えば、特許文献５参照）、高周波誘導加熱コイルの表面に絶縁性材料を被覆する方法（例えば、特許文献６参照）、などが開示されている。 Moreover, as a method of preventing discharge of the high frequency induction heating coil, a method of inserting an insulating member into the slit gap for the purpose of preventing discharge at the slit of the coil (for example, see Patent Document 2), A method of spraying nitrogen gas (see, for example, Patent Document 3), a method of covering the outer winding portion with an insulating member in order to prevent discharge generated between the outer winding portion and the inner winding portion of the high-frequency induction heating coil (for example, , Patent Document 4), a method of disposing an insulating member between a high-frequency induction heating coil and its surrounding members, a raw material rod or a single crystal (see, for example, Patent Document 5), an insulating material on the surface of the high-frequency induction heating coil And the like (see, for example, Patent Document 6).
一方、ＦＺ法によって製造されるシリコン単結晶及びシリコン単結晶を材料とするシリコンウェーハの品質の観点からは、シリコンウェーハの強度増強や結晶欠陥発生抑制の効果を得るために、シリコン単結晶へ窒素を導入することが好ましい。 On the other hand, from the viewpoint of the quality of silicon single crystals produced by the FZ method and silicon wafers made of silicon single crystals, nitrogen is added to silicon single crystals in order to obtain the effects of enhancing the strength of silicon wafers and suppressing the generation of crystal defects. Is preferably introduced.
結晶欠陥については、例えば特許文献１に記述されるように結晶中へ窒素添加することで、エッチングデプレッションを防止することができる。また、特にシリコン単結晶の直胴部初期において過剰な格子間シリコンが生じることに起因する積層欠陥の発生も、結晶中窒素濃度を高めることで抑制することができる。
For crystal defects, for example, as described in
前述のように、ＦＺ法によるシリコン単結晶製造中の放電発生防止のためには様々な方法が提案されているが、特許文献３や特許文献５のような方法を取る場合付帯設備の追加などで装置は複雑になりがちで、シリコン単結晶取得率の低下やメンテナンス頻度増加のデメリットが生ずる。特許文献３の方法で窒素ガスを吹き付ける部分は必然的に溶融メルト近傍になるが、前述のようにドーパントガスも同様の部分に吹き付けるため、ＦＺ単結晶の抵抗率制御に支障をきたす恐れがある。
As described above, various methods have been proposed to prevent the occurrence of electric discharge during the production of a silicon single crystal by the FZ method. However, when the methods such as
また特許文献４や特許文献６のように絶縁性素材被覆の方法では、新たな素材をシリコン単結晶製造中の炉内に投入することになるのでシリコン単結晶中への不純物導入の危険性が高まる。 Moreover, in the method of covering an insulating material as in Patent Document 4 and Patent Document 6, since a new material is put into a furnace during the production of a silicon single crystal, there is a risk of introducing impurities into the silicon single crystal. Rise.
更に放電防止をより確実にするためには、ＦＺ単結晶製造雰囲気中への窒素ガス添加を行うことが望ましく、結晶欠陥発生防止も考慮すると必須と考えられる。このため、他の対策を行ったとしても、併用してシリコン単結晶製造雰囲気中への窒素ガス添加も行うことが望ましい。 In order to further prevent discharge, it is desirable to add nitrogen gas to the FZ single crystal manufacturing atmosphere, and it is considered essential in consideration of prevention of crystal defects. For this reason, even if other measures are taken, it is desirable to add nitrogen gas into the silicon single crystal manufacturing atmosphere in combination.
シリコン単結晶に導入される窒素濃度は偏析の影響で、結晶成長方向で一定ではなく成長とともに増加する。製造したシリコン単結晶中の窒素濃度が過剰に高い場合は、当該結晶から作製した半導体基板でデバイス製造する時に、デバイス製造プロセスによっては窒素析出物の発生などで所望の特性が得られない場合がある。すなわち、製造結晶内で品質不適合部分が発生することとなり歩留が下がってしまうため、結晶内での窒素濃度の差を低減することが望ましい。 The concentration of nitrogen introduced into the silicon single crystal is not constant in the crystal growth direction but increases with growth due to the effect of segregation. When the nitrogen concentration in the manufactured silicon single crystal is excessively high, when manufacturing a device with a semiconductor substrate manufactured from the crystal, depending on the device manufacturing process, desired characteristics may not be obtained due to generation of nitrogen precipitates, etc. is there. That is, a nonconforming part is produced in the manufactured crystal and the yield is lowered, so it is desirable to reduce the difference in nitrogen concentration in the crystal.
ただし、単純に単結晶の製造の初期から炉内雰囲気中の窒素濃度を減らすだけでは放電トラブルのリスクが伴う。また、特にシリコン単結晶の直胴初期では、逆に一定以上の窒素濃度としなければ積層欠陥の発生リスクが生ずる。 However, simply reducing the nitrogen concentration in the furnace atmosphere from the beginning of the production of the single crystal involves the risk of discharge trouble. Also, particularly in the initial stage of the straight body of a silicon single crystal, the risk of stacking faults arises unless the nitrogen concentration exceeds a certain level.
本発明は前述のような問題に鑑みてなされたもので、炉内での放電の発生を防止し、結晶欠陥の発生を抑制し、かつ、直胴後半部の窒素濃度の過剰な増大も抑制できるＦＺ法によるシリコン単結晶の製造方法を提供することを目的とする。 The present invention has been made in view of the above-mentioned problems, prevents the occurrence of discharge in the furnace, suppresses the generation of crystal defects, and suppresses the excessive increase in the nitrogen concentration in the latter half of the straight body. An object of the present invention is to provide a method for producing a silicon single crystal by FZ method.
上記目的を達成するために、本発明は、シリコン原料結晶を回転させながら、該シリコン原料結晶を誘導加熱コイルにより部分的に加熱溶融して溶融帯を形成し、該溶融帯を前記シリコン原料結晶の一端部から他端部へ移動させてシリコン単結晶を成長させるＦＺ法によるシリコン単結晶の製造方法であって、窒素を含む雰囲気下で、前記シリコン単結晶を所望の直径まで拡げながら成長させるコーン工程と、前記シリコン単結晶が前記所望の直径に達した後に、前記窒素を含む雰囲気中の窒素濃度を減少させて、前記直径を前記所望の直径に維持しつつ前記シリコン単結晶を成長させる直胴工程とを有することを特徴とするシリコン単結晶の製造方法を提供する。 In order to achieve the above object, the present invention provides a silicon raw material crystal that is partially heated and melted by an induction heating coil while rotating the silicon raw material crystal to form a molten zone. A method of manufacturing a silicon single crystal by an FZ method in which a silicon single crystal is grown by moving from one end to the other end of the substrate, and growing the silicon single crystal while expanding it to a desired diameter in an atmosphere containing nitrogen A cone process, and after the silicon single crystal reaches the desired diameter, the nitrogen concentration in the nitrogen-containing atmosphere is reduced to grow the silicon single crystal while maintaining the diameter at the desired diameter. A method for producing a silicon single crystal comprising a straight body process is provided.
コーン工程では窒素濃度を高く維持し、直胴工程で雰囲気中の窒素濃度を下げることで、誘導加熱コイルからの放電を確実に防止でき、さらに、直胴部における結晶欠陥の発生を確実に抑制できる。また、直胴工程において、雰囲気中の窒素濃度を減少させて、直胴部を成長させることで、直胴後半部の窒素濃度が大きくなり過ぎず、適切な範囲内となり、デバイス製造プロセス等における窒素析出物の発生を抑制することができる。また、このような方法であれば、雰囲気以外のシリコン単結晶の製造条件を大幅に変更する必要もない。 By maintaining a high nitrogen concentration in the cone process and lowering the nitrogen concentration in the atmosphere in the straight cylinder process, it is possible to reliably prevent discharge from the induction heating coil and to further suppress the occurrence of crystal defects in the straight cylinder section. it can. In addition, in the straight body process, by reducing the nitrogen concentration in the atmosphere and growing the straight body portion, the nitrogen concentration in the latter half of the straight body does not become too large and falls within an appropriate range. Generation of nitrogen precipitates can be suppressed. Also, with such a method, it is not necessary to significantly change the silicon single crystal manufacturing conditions other than the atmosphere.
このとき、前記直胴工程開始時点に形成される前記シリコン単結晶の直胴部の結晶中窒素濃度を２×１０１４ａｔｏｍｓ／ｃｍ３以上とすることが好ましい。 At this time, it is preferable that the nitrogen concentration in the crystal of the straight body portion of the silicon single crystal formed at the start of the straight body step is 2 × 10 14 atoms / cm 3 or more.
直胴工程開始時点での結晶中窒素濃度を、２×１０１４ａｔｏｍｓ／ｃｍ３以上とすることで直胴前半部における結晶欠陥の発生をより確実に防止することができる。 By setting the nitrogen concentration in the crystal at the start of the straight cylinder process to 2 × 10 14 atoms / cm 3 or more, the occurrence of crystal defects in the first half of the straight cylinder can be more reliably prevented.
またこのとき、前記直胴工程において、前記シリコン単結晶の直胴部のテール側の結晶中窒素濃度が２×１０１５ａｔｏｍｓ／ｃｍ３以下となるように前記窒素を含む雰囲気中の窒素濃度を減少させて、前記シリコン単結晶を成長させることができる。 Further, at this time, in the straight body step, the nitrogen concentration in the atmosphere containing nitrogen is set so that the nitrogen concentration in the crystal on the tail side of the straight body portion of the silicon single crystal is 2 × 10 15 atoms / cm 3 or less. The silicon single crystal can be grown in a reduced manner.
直胴部のテール側の窒素濃度が２×１０１５ａｔｏｍｓ／ｃｍ３以下となるように、雰囲気中の窒素濃度を減少させることで、直胴後半部の窒素濃度を適切な範囲内により確実に抑えることができ、窒素析出物の発生をより確実に防止することができる。 By reducing the nitrogen concentration in the atmosphere so that the nitrogen concentration on the tail side of the straight barrel portion is 2 × 10 15 atoms / cm 3 or less, the nitrogen concentration in the latter half portion of the straight barrel portion is more reliably within an appropriate range. It can suppress, and generation | occurrence | production of a nitrogen precipitate can be prevented more reliably.
このとき、前記シリコン単結晶の直径を１５０ｍｍ以上とすることができる。 At this time, the diameter of the silicon single crystal can be 150 mm or more.
直径が１５０ｍｍ以上の大直径のシリコン単結晶の製造に本発明は好適に適応できる。 The present invention can be suitably applied to the production of a large-diameter silicon single crystal having a diameter of 150 mm or more.
本発明のＦＺ法によるシリコン単結晶の製造方法であれば、炉内での放電の発生を防止し、結晶欠陥の発生を抑制し、かつ、直胴後半部の窒素濃度の過剰な増大も抑制できる。 The method for producing a silicon single crystal by the FZ method of the present invention prevents the occurrence of discharge in the furnace, suppresses the generation of crystal defects, and suppresses the excessive increase in the nitrogen concentration in the latter half of the straight body. it can.
以下、本発明について実施の形態を説明するが、本発明はこれに限定されるものではない。 Hereinafter, although an embodiment is described about the present invention, the present invention is not limited to this.
本発明者等は、ＦＺ法によるシリコン単結晶の製造において、単結晶製造条件を大幅に変更せず、かつ、従来と比べてシリコン単結晶の後半部まで結晶中窒素濃度の値が適切な範囲内となるシリコン単結晶を取得するために鋭意検討を重ねた。 In the manufacture of a silicon single crystal by the FZ method, the present inventors have not significantly changed the single crystal manufacturing conditions, and the nitrogen concentration in the crystal is within an appropriate range up to the latter half of the silicon single crystal compared to the conventional case. In order to obtain an inner silicon single crystal, intensive studies were repeated.
シリコン単結晶へ導入される窒素はまず溶融メルトに溶け込み、メルト中の窒素の一部が凝固の際に単結晶に導入されるものであるが、シリコン単結晶へ導入されなかった分の窒素は溶融メルト中に残留する偏析現象が生じる。シリコン単結晶の成長は放電発生防止のため依然として窒素を含む炉内雰囲気中で継続されるため、シリコン単結晶の成長中の溶融帯のメルトへの窒素の溶け込みも継続される。このため、結晶成長の後半になるにつれて、シリコン単結晶の窒素濃度は直線的に増加してしまう。 The nitrogen introduced into the silicon single crystal is first dissolved in the melt, and part of the nitrogen in the melt is introduced into the single crystal during solidification, but the amount of nitrogen not introduced into the silicon single crystal is A segregation phenomenon remaining in the melt occurs. Since the growth of the silicon single crystal is continued in the furnace atmosphere containing nitrogen in order to prevent the occurrence of electric discharge, the dissolution of nitrogen into the melt in the melting zone during the growth of the silicon single crystal is also continued. For this reason, the nitrogen concentration of the silicon single crystal increases linearly in the latter half of the crystal growth.
この状態への対策として、窒素を含む炉内雰囲気中下でシリコン単結晶の直径を徐々に拡大させるコーン部の形成を行い、所望の直径になってから炉内雰囲気中の窒素濃度を減少させつつ直胴部を成長させることで、直胴前半部における結晶欠陥の発生を抑制し、かつ、直胴後半部の結晶中窒素濃度の過剰な増大も抑制することができることを知見し、本発明を完成させた。 As a countermeasure against this condition, a cone portion is formed that gradually expands the diameter of the silicon single crystal in a furnace atmosphere containing nitrogen, and the nitrogen concentration in the furnace atmosphere is reduced after the desired diameter is reached. It has been found that by growing the straight body portion, the occurrence of crystal defects in the first half of the straight body can be suppressed, and an excessive increase in the nitrogen concentration in the crystal in the second half of the straight body can also be suppressed, and the present invention. Was completed.
まず、本発明のシリコン単結晶の製造方法で用いることができるＦＺ法による単結晶製造装置（ＦＺ単結晶製造装置）について、図１を参照して説明する。図１に示すように、ＦＺ単結晶製造装置１は、チャンバー１１を有しており、該チャンバー１１内には、回転可能な上軸１２および下軸１３が設けられている。上軸１２にはシリコン原料結晶１４として所定の直径のシリコン棒が取り付けられ、また下軸１３には種結晶１５が取り付けられる。またチャンバー１１内には、シリコン原料結晶１４を溶融するための誘導加熱コイル１６や、ガスドーピングの際に、シリコン原料結晶１４が溶融された溶融帯１８にドーパントガスを噴出するためのドープノズル２０が配置されている。
First, a single crystal manufacturing apparatus (FZ single crystal manufacturing apparatus) by the FZ method that can be used in the method for manufacturing a silicon single crystal of the present invention will be described with reference to FIG. As shown in FIG. 1, the FZ single
さらに、チャンバー１１はガス供給装置２１を備えており、その炉内雰囲気中にベースとなる不活性ガス（窒素ガス以外）、及び窒素ガスを供給することができる。ガス供給装置はシリコン単結晶の成長中のベースの不活性ガス及び窒素ガスの供給量を調整する機能を有するものとできる。
Further, the
次に、本発明のシリコン単結晶の製造方法について、図１のようなＦＺ単結晶製造装置１を用いる場合を例にして説明する。図２に示すように、本発明のシリコン単結晶の製造方法は、種付け工程、絞り工程、コーン工程、直胴工程、テール工程、切り離し工程を有する。
Next, a method for manufacturing a silicon single crystal according to the present invention will be described using an example of using an FZ single
（種付け工程）
まず、図１のＦＺ単結晶製造装置１の炉内雰囲気を、ガス供給装置２１により窒素を含む雰囲気とし、シリコン原料結晶１４の先端を誘導加熱コイル１６で溶融した後、種結晶１５に融着させる。
(Seeding process)
First, the atmosphere in the furnace of the FZ single
（絞り工程）
次に、絞り１７を形成することにより無転位化し、上軸１２及び下軸１３を回転させながら下降させ、溶融帯１８をシリコン原料結晶１４に対して相対的に移動させながらシリコン単結晶１９を成長させる。
(Drawing process)
Next, dislocation is eliminated by forming the
（コーン工程）
次に、窒素を含む雰囲気下で、シリコン単結晶１９を所望の直径まで徐々に拡げながら成長させる（コーン部２２の形成）。
(Cone process)
Next, the silicon
（直胴工程）
シリコン単結晶１９が所望の直径に達した後に、窒素を含む雰囲気中の窒素濃度を減少させて、直径を所望の直径に維持しつつシリコン単結晶１９の直胴部２３を成長させる（直胴部２３の形成）。本発明において、雰囲気中の窒素濃度を減少させるとは、コーン工程における雰囲気中の窒素濃度より、直胴工程における雰囲気中の窒素濃度が低くなる時間が有ればよいことを意味している。例えば、直胴工程の開始時から雰囲気中の窒素濃度は徐々に減少させても良いし、段階的に減少させても良い。なお、炉内雰囲気の窒素濃度を下げる方法としては、窒素ガス流量を減らす方法やベースガスとなる不活性ガスの流量を上げる方法がある。
(Straight cylinder process)
After the silicon
コーン工程では窒素濃度を高く維持し、直胴工程で雰囲気中の窒素濃度を下げることで、誘導加熱コイルからの放電を確実に防止でき、かつ、直胴部における結晶欠陥の発生を確実に抑制できる窒素濃度で直胴部の形成を始めることができる。また、直胴工程における雰囲気中の窒素濃度を、コーン工程における雰囲気中の窒素濃度よりも小さくして、直胴部を成長させることで、直胴後半部の結晶中窒素濃度が大きくなり過ぎず、適切な範囲内となる。これにより、デバイス製造プロセス等におけるウェーハの窒素析出物の発生を抑制することができる。また、このような方法であれば、雰囲気以外のシリコン単結晶の製造条件を大幅に変更する必要もない。 By maintaining a high nitrogen concentration in the cone process and lowering the nitrogen concentration in the atmosphere in the straight cylinder process, discharge from the induction heating coil can be reliably prevented, and the occurrence of crystal defects in the straight cylinder part is reliably suppressed. Formation of the straight body portion can be started at a nitrogen concentration that can be achieved. In addition, the nitrogen concentration in the crystal in the latter half of the straight cylinder does not become too high by growing the straight cylinder part by making the nitrogen concentration in the atmosphere in the straight cylinder process smaller than the nitrogen concentration in the atmosphere in the cone process. Within the appropriate range. Thereby, generation | occurrence | production of the nitrogen precipitate of a wafer in a device manufacturing process etc. can be suppressed. Also, with such a method, it is not necessary to significantly change the silicon single crystal manufacturing conditions other than the atmosphere.
また、シリコン単結晶１９の直胴部の初期の結晶欠陥顕在化を確実に防止するために、直胴工程を開始する際に結晶中窒素濃度を一定値以上とすることが好ましい。特に、直胴工程開始時点に形成されるシリコン単結晶１９の直胴部の結晶中窒素濃度を２×１０１４ａｔｏｍｓ／ｃｍ３以上とすることが好ましい。このようにすれば、直径２００ｍｍ以上の大直径ＦＺ単結晶を成長させる場合等にも、直胴部の初期の結晶欠陥の発生をより確実に抑制できる。
Further, in order to surely prevent the occurrence of initial crystal defects in the straight body portion of the silicon
また、直胴工程において、シリコン単結晶の直胴部のテール側の結晶中窒素濃度が２×１０１５ａｔｏｍｓ／ｃｍ３以下となるように窒素を含む雰囲気中の窒素濃度を減少させて、シリコン単結晶を成長させることが好ましい。これにより、直胴部の後半部の結晶中窒素濃度が高くなり過ぎることが無く、デバイス製造プロセスにおいては窒素析出物の発生などが起きにくく、所望の特性のウェーハが得られる。また、不具合の発生する窒素濃度はデバイス製造プロセスの内容で変わるものであるため、適用されるデバイス製造プロセスによって結晶中窒素濃度の目標を、例えば上記のように２×１０１５ａｔｏｍｓ／ｃｍ３以下等と定めても良いし、他の結晶中窒素濃度を目標に定めても良い。 Further, in the straight body process, the nitrogen concentration in the atmosphere containing nitrogen is reduced so that the nitrogen concentration in the crystal on the tail side of the straight body portion of the silicon single crystal is 2 × 10 15 atoms / cm 3 or less. It is preferable to grow a single crystal. As a result, the nitrogen concentration in the crystal in the latter half of the straight body does not become excessively high, and the generation of nitrogen precipitates hardly occurs in the device manufacturing process, and a wafer having desired characteristics can be obtained. Further, since the nitrogen concentration at which defects occur varies depending on the contents of the device manufacturing process, the target of the nitrogen concentration in the crystal is, for example, 2 × 10 15 atoms / cm 3 or less as described above depending on the device manufacturing process to be applied. Or other nitrogen concentrations in crystals may be set as targets.
このとき、ドープノズル２０からリン又はホウ素等を含むドーパントガスを溶融帯１８に噴射してドーパントを供給し、所望の抵抗率を持つシリコン単結晶１９としても良い。
At this time, a dopant gas containing phosphorus or boron may be sprayed from the
（テール工程）
所望の長さの直胴部を形成した後、溶融帯１８をシリコン原料結晶１４の上端まで移動させて原料の供給を止めてシリコン単結晶１９の直径を縮小させる（テールの形成）。
(Tail process)
After forming the straight body portion of a desired length, the
（切り離し工程）
次に、シリコン単結晶１９をシリコン原料結晶１４から切り離す。以上のようにして、ＦＺ法によりシリコン単結晶を製造できる。
(Separation process)
Next, the silicon
上記のような本発明のシリコン単結晶の製造方法は、直径１５０ｍｍ以上のシリコン単結晶の製造に好適に使用することができる。 The method for producing a silicon single crystal of the present invention as described above can be suitably used for producing a silicon single crystal having a diameter of 150 mm or more.
ここで、シリコン単結晶への窒素の導入プロセスについて詳細に考える。シリコン単結晶へは、主に溶融帯のメルトに溶け込んだ窒素が、更にメルトからシリコン単結晶に導入されるが、この時、溶融帯のメルトへ溶け込む窒素は雰囲気中に含まれる窒素ガスが由来となる。溶け込みの際、窒素はメルトとの反応性が乏しいため、窒素ガスから直接メルトに溶け込むのではなく、高温となったシリコン原料結晶と窒素ガスが反応してシリコン原料結晶の表面に窒化物を形成した後、シリコン原料結晶の溶解とともにメルト内へ窒素が溶解するものと考えられる。この時、結晶成長条件が同一であれば、炉内雰囲気の窒素濃度が高い方が窒化物の形成量も高くなり、即ち、結晶中窒素濃度も高くなる。 Here, the process of introducing nitrogen into the silicon single crystal will be considered in detail. Nitrogen dissolved in the melt in the melting zone is mainly introduced into the silicon single crystal, and then the nitrogen from the melt is introduced into the silicon single crystal. At this time, nitrogen dissolved in the melt in the melting zone is derived from the nitrogen gas contained in the atmosphere. It becomes. At the time of melting, nitrogen has poor reactivity with the melt, so it does not melt directly from the nitrogen gas into the melt, but the silicon raw material crystal that has become hot reacts with the nitrogen gas to form a nitride on the surface of the silicon raw material crystal Then, it is considered that nitrogen dissolves into the melt as the silicon raw material crystal dissolves. At this time, if the crystal growth conditions are the same, the higher the nitrogen concentration in the furnace atmosphere, the higher the amount of nitride formed, that is, the higher the nitrogen concentration in the crystal.
シリコンに対する窒素の偏析係数は７×１０−４と小さいため、シリコン単結晶成長の際に導入される窒素はメルト中のごく一部で、大部分はメルトに残留する。更に、放電防止目的で炉内雰囲気中に窒素ガスを添加し、窒素含有雰囲気中でシリコン単結晶製造を行うため、単結晶成長中は継続して窒素がメルトへと供給される。この結果、メルト中の窒素濃度は結晶成長が進むにつれて増加し、即ち、結晶中窒素濃度も結晶成長後半に向けて増加し続ける。 Since the segregation coefficient of nitrogen with respect to silicon is as small as 7 × 10 −4 , nitrogen introduced during the growth of the silicon single crystal is a small part of the melt, and most of it remains in the melt. Further, nitrogen gas is added to the furnace atmosphere for the purpose of preventing discharge, and the silicon single crystal is produced in the nitrogen-containing atmosphere. Therefore, nitrogen is continuously supplied to the melt during the growth of the single crystal. As a result, the nitrogen concentration in the melt increases as the crystal growth proceeds, that is, the nitrogen concentration in the crystal continues to increase toward the latter half of the crystal growth.
また、単結晶直径を拡大していくコーン工程で単結晶直径を所望の値まで拡大した後に、結晶直径を所定値に維持したまま結晶成長を続ける直胴工程に移行していく中で、シリコン単結晶製造中の発振器回路への投入電力は、単結晶直径の拡大とともに急激に増大し直胴工程後はほぼ一定で推移する。 In addition, after expanding the single crystal diameter to the desired value in the cone process that expands the single crystal diameter, the process proceeds to the straight body process where the crystal growth continues while maintaining the crystal diameter at a predetermined value. The power input to the oscillator circuit during the manufacture of the single crystal increases rapidly as the diameter of the single crystal increases, and remains almost constant after the straight body process.
このため、放電発生防止の観点からは、直胴工程に入って以降は炉内窒素濃度を増加させ続ける必要はなく、むしろ放電が発生しない範囲である限り炉内窒素濃度を減少させることができる。 For this reason, from the viewpoint of preventing the occurrence of discharge, it is not necessary to continue increasing the furnace nitrogen concentration after entering the straight cylinder process, but rather the furnace nitrogen concentration can be reduced as long as it is within the range where no discharge occurs. .
よって、シリコン単結晶成長中に窒素ガス流量を徐々に又は段階的に減少させる等して、炉内窒素濃度を低減させて結晶製造することで、結晶後半で窒素濃度を低減させたシリコン単結晶を取得することが可能となる。 Therefore, a silicon single crystal in which the nitrogen concentration is reduced in the latter half of the crystal by manufacturing the crystal by reducing the nitrogen concentration in the furnace by gradually or gradually reducing the nitrogen gas flow rate during the growth of the silicon single crystal. Can be obtained.
以下、本発明の実施例及び比較例を示して本発明をより具体的に説明するが、本発明はこの実施例に限定されるものではない。 EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples of the present invention, but the present invention is not limited to these examples.
（実施例）
図２に示すような本発明のシリコン単結晶の製造方法に従って、ＦＺ法による直径８インチ（約２００ｍｍ）のシリコン単結晶の製造を行った。このとき、炉内条件を炉内圧０．２ＭＰａ、炉内への雰囲気ガスの導入量をアルゴンガス流量５５Ｌ／ｍｉｎ、窒素ガス流量１７０ｃｃ／ｍｉｎとして、シリコン単結晶の製造を開始した。そして、コーン工程から直胴工程への移行直後から、アルゴンガス流量及び窒素ガス流量を徐々に変更し、最終的にアルゴンガス流量１１０Ｌ／ｍｉｎ、窒素ガス流量９０ｃｃ／ｍｉｎまで変更して長さ７０ｃｍのシリコン単結晶を取得した。即ち、直胴工程において、図３に示すように、徐々に雰囲気中の窒素濃度を減少させながら、シリコン単結晶を成長させた。なお、図３はシリコン単結晶の直胴部の長さに対する炉内の窒素濃度の変化を示している。
(Example)
According to the method for manufacturing a silicon single crystal of the present invention as shown in FIG. 2, a silicon single crystal having a diameter of 8 inches (about 200 mm) was manufactured by the FZ method. At this time, the production of the silicon single crystal was started with the furnace conditions set to a furnace pressure of 0.2 MPa, the atmosphere gas introduced into the furnace at an argon gas flow rate of 55 L / min, and a nitrogen gas flow rate of 170 cc / min. Then, immediately after the transition from the cone process to the straight body process, the argon gas flow rate and the nitrogen gas flow rate are gradually changed, and finally the argon gas flow rate is 110 L / min and the nitrogen gas flow rate is 90 cc / min, and the length is 70 cm. A silicon single crystal was obtained. That is, in the straight body process, as shown in FIG. 3, a silicon single crystal was grown while gradually reducing the nitrogen concentration in the atmosphere. FIG. 3 shows a change in the nitrogen concentration in the furnace with respect to the length of the straight body portion of the silicon single crystal.
その結果、図４に示すように、取得結晶の窒素濃度は直胴部の全ての部分で２×１０１５ａｔｏｍｓ／ｃｍ３未満であり、直胴後半部においても窒素濃度が高くなり過ぎることは無かった。また、結晶欠陥の発生も見られず、炉内放電も発生しなかった。 As a result, as shown in FIG. 4, the nitrogen concentration of the acquired crystal is less than 2 × 10 15 atoms / cm 3 in all portions of the straight body, and the nitrogen concentration is not too high in the latter half of the straight body. There was no. In addition, no crystal defects were observed, and no in-furnace discharge occurred.
このように、本発明のシリコン単結晶の製造方法であれば、炉内での放電の発生を防止し、結晶欠陥の発生を抑制し、かつ、直胴後半部の結晶中窒素濃度の過剰な増大も抑制できることが確認できた。 Thus, according to the method for producing a silicon single crystal of the present invention, the occurrence of discharge in the furnace is prevented, the occurrence of crystal defects is suppressed, and the nitrogen concentration in the crystal in the latter half of the straight body is excessive. It was confirmed that the increase could be suppressed.
（比較例１）
直胴工程において、炉内雰囲気の窒素濃度を減少させなかったこと以外、実施例と同様な条件でシリコン単結晶を製造した。即ち、炉内条件を終始、炉内圧０．２ＭＰａ、アルゴンガス流量５５Ｌ／ｍｉｎ、窒素ガス流量１７０ｃｃ／ｍｉｎとし、長さ７０ｃｍのシリコン単結晶を取得した。この時の直胴部の長さに対する炉内窒素濃度を図５に示す。
(Comparative Example 1)
In the straight body process, a silicon single crystal was produced under the same conditions as in the examples except that the nitrogen concentration in the furnace atmosphere was not reduced. That is, a silicon single crystal having a length of 70 cm was obtained from the beginning of the furnace conditions, with the furnace pressure set to 0.2 MPa, the argon gas flow rate 55 L / min, and the nitrogen gas flow rate 170 cc / min. FIG. 5 shows the in-furnace nitrogen concentration with respect to the length of the straight body at this time.
その結果、図６に示すように、この時の結晶中窒素濃度は直胴部のテール側で２．５×１０１５ａｔｏｍｓ／ｃｍ３を超えてしまった。このように、比較例１では、実施例に比べて、特に直胴後半部における結晶中窒素濃度が大幅に増加する結果となった。 As a result, as shown in FIG. 6, the nitrogen concentration in the crystal at this time exceeded 2.5 × 10 15 atoms / cm 3 on the tail side of the straight body portion. As described above, in Comparative Example 1, the nitrogen concentration in the crystal in the latter half part of the straight body was significantly increased as compared with the Example.
（比較例２）
窒素ガス流量のみ８０ｃｃ／ｍｉｎとしたこと以外、比較例１と同じ炉内条件でＦＺ法による８インチ（約２００ｍｍ）のシリコン単結晶製造を行った。１回目は直胴１５ｃｍ程度で放電が起こってしまったので、シリコン単結晶の製造を中止した。このように、シリコン単結晶を所望の長さで製造できなかった。
(Comparative Example 2)
An 8-inch (about 200 mm) silicon single crystal was manufactured by the FZ method under the same in-furnace conditions as in Comparative Example 1 except that only the nitrogen gas flow rate was 80 cc / min. At the first time, discharge occurred in a straight cylinder of about 15 cm, and the production of the silicon single crystal was stopped. Thus, a silicon single crystal could not be produced with a desired length.
また、再度同条件で結晶製造を行ったところ、長さ７０ｃｍの結晶を取得できた。この時の直胴部の長さに対する炉内窒素濃度を図７に示す。 Moreover, when the crystal was manufactured again under the same conditions, a crystal having a length of 70 cm was obtained. FIG. 7 shows the nitrogen concentration in the furnace with respect to the length of the straight body at this time.
その結果、図８に示すように、この時の取得結晶の窒素濃度は１．３×１０１５ａｔｏｍｓ／ｃｍ３以下であったが、直胴５ｃｍまで結晶欠陥が発生し、この部分が製品に使用できなかった。 As a result, as shown in FIG. 8, the nitrogen concentration of the acquired crystal at this time was 1.3 × 10 15 atoms / cm 3 or less, but crystal defects occurred up to a straight cylinder of 5 cm, and this portion was added to the product. Could not be used.
このように、比較例２では、雰囲気中の窒素濃度を直胴工程から減少させず、最初から小さくしため、放電及び結晶欠陥が発生してしまった。これにより、雰囲気中の窒素濃度は、本発明のように、直胴工程で減少させることで放電を防止でき、かつ、結晶欠陥の発生も抑制できることが分かった。 As described above, in Comparative Example 2, discharge and crystal defects occurred because the nitrogen concentration in the atmosphere was not reduced from the straight body process but was reduced from the beginning. Thereby, it turned out that discharge can be prevented and generation | occurrence | production of a crystal defect can also be suppressed by reducing the nitrogen concentration in atmosphere by a straight body process like this invention.
なお、本発明は、上記実施形態に限定されるものではない。上記実施形態は例示であり、本発明の特許請求の範囲に記載された技術的思想と実質的に同一な構成を有し、同様な作用効果を奏するものは、いかなるものであっても本発明の技術的範囲に包含される。 The present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, and the present invention has any configuration that has substantially the same configuration as the technical idea described in the claims of the present invention and that exhibits the same effects. Are included in the technical scope.
１…ＦＺ単結晶製造装置、 １１…チャンバー、 １２…上軸、 １３…下軸、
１４…シリコン原料結晶、 １５…種結晶、 １６…誘導加熱コイル、 １７…絞り、
１８…溶融帯、 １９…シリコン単結晶、 ２０…ドープノズル、
２１…ガス供給装置、 ２２…コーン部、 ２３…直胴部。
DESCRIPTION OF
14 ... Silicon raw material crystal, 15 ... Seed crystal, 16 ... Induction heating coil, 17 ... Drawing,
18 ... melting zone, 19 ... silicon single crystal, 20 ... dope nozzle,
21 ... Gas supply device, 22 ... Cone part, 23 ... Straight trunk part.
Claims (3)
窒素を含む雰囲気下で、前記シリコン単結晶を所望の直径まで拡げながら成長させるコーン工程と、
前記シリコン単結晶が前記所望の直径に達した後に、前記窒素を含む雰囲気中の窒素濃度を減少させて、前記直径を前記所望の直径に維持しつつ前記シリコン単結晶を成長させる直胴工程と
を有し、
前記シリコン単結晶の直径を１５０ｍｍ以上とすることを特徴とするシリコン単結晶の製造方法。 While rotating the silicon raw material crystal, the silicon raw material crystal is partially heated and melted by an induction heating coil to form a molten zone, and the molten zone is moved from one end to the other end of the silicon raw material crystal to form silicon. A method for producing a silicon single crystal by FZ method for growing a single crystal,
A cone process in which the silicon single crystal is grown while expanding to a desired diameter under an atmosphere containing nitrogen; and
A straight cylinder step of growing the silicon single crystal while reducing the nitrogen concentration in the atmosphere containing nitrogen and maintaining the diameter at the desired diameter after the silicon single crystal has reached the desired diameter; I have a,
A silicon single crystal manufacturing method, wherein the diameter of the silicon single crystal is 150 mm or more .
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