JP3132412B2 - Single crystal pulling method - Google Patents
Single crystal pulling methodInfo
- Publication number
- JP3132412B2 JP3132412B2 JP09088218A JP8821897A JP3132412B2 JP 3132412 B2 JP3132412 B2 JP 3132412B2 JP 09088218 A JP09088218 A JP 09088218A JP 8821897 A JP8821897 A JP 8821897A JP 3132412 B2 JP3132412 B2 JP 3132412B2
- Authority
- JP
- Japan
- Prior art keywords
- magnetic field
- melt
- single crystal
- crucible
- crystal
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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- Crystals, And After-Treatments Of Crystals (AREA)
Description
【0001】[0001]
【発明の属する技術分野】本発明は、回転引き上げによ
る単結晶成長方法、すなわち半導体材料として使用され
るシリコン単結晶の製造方法に関するものである。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for growing a single crystal by rotation pulling, that is, a method for producing a silicon single crystal used as a semiconductor material.
【0002】[0002]
【従来の技術】半導体材料に用いられるシリコンの単結
晶の製造手段として、回転引き上げ法すなわちチョクラ
ルスキー法(CZ法)は、種々の改善改良が加えられ、
工業的量産の場で広く活用されている。2. Description of the Related Art The rotational pulling method, that is, the Czochralski method (CZ method), as a means for producing a single crystal of silicon used for a semiconductor material, has various improvements and improvements.
Widely used in industrial mass production.
【0003】図1は、CZ法による単結晶製造装置の原
理を、模式的に示したものである。ここで、原料となる
シリコンは、有底円筒形の石英るつぼの中に溶融状態に
あり、単結晶をその底面が溶融シリコン液の表面と接し
た状態にして回転させ、底面に凝固成長する速度にあわ
せて上方に引き上げ、成長させて所要寸法の単結晶を得
る。溶融液を入れる石英るつぼは、有底円筒状の外側支
持用黒鉛るつぼの内側に嵌合されており、このるつぼ
は、全体を中心軸の周りに回転させることができ、さら
に上下に移動させることができる。るつぼの中心軸上方
には、中心軸の周りに回転でき、そして上方に引き上げ
可能なワイヤからなる引き上げ装置が付いている。るつ
ぼの外側には、加熱用の電熱ヒーター、およびさらに外
側に保温材が同心円状に配置され、これら全体は外気を
遮断できるチャンバー内に設置されて、CZ法の回転引
き上げ装置が構成されている。FIG. 1 schematically shows the principle of an apparatus for producing a single crystal by the CZ method. Here, silicon as a raw material is in a molten state in a cylindrical quartz crucible with a bottom, and the single crystal is rotated with its bottom surface in contact with the surface of the molten silicon liquid, and the rate of solidification growth on the bottom surface And a single crystal having a required size is obtained by growing the crystal. The quartz crucible for holding the melt is fitted inside the bottomed cylindrical outer supporting graphite crucible, and the whole crucible can be rotated around the central axis and moved up and down. Can be. Above the central axis of the crucible is a lifting device consisting of a wire that can rotate about the central axis and can be raised upward. On the outside of the crucible, an electric heater for heating, and further on the outside, a heat insulating material are arranged concentrically, all of which are installed in a chamber capable of shutting off outside air, and constitute a rotary pulling device of the CZ method. .
【0004】この装置による通常の単結晶製造方法は、
まず、原料となる高純度の多結晶シリコンを所要量るつ
ぼ内に装荷し、減圧下アルゴンなどの不活性雰囲気中で
電熱ヒーターにより高温に加熱し溶融する。溶融液の表
面温度を調整後、引き上げ装置の先端に取り付けた種結
晶を溶融液表面に接触させ、回転しつつ引き上げること
によりまず細長いネック部を形成させる。次に引き上げ
速度および温度を調節して所定の直径の定径部まで増径
させ、その後は結晶成長にあわせて回転させつつ上方に
引き上げることによって一定径の単結晶を成長させる。
所定重量に達した単結晶は、定径部から結晶直径を次第
に細くしていき、最後に直径をゼロにして溶融液から切
り離す。[0004] A usual method for producing a single crystal using this apparatus is as follows.
First, a required amount of high-purity polycrystalline silicon as a raw material is loaded in a crucible, and is heated to a high temperature by an electric heater and melted in an inert atmosphere such as argon under reduced pressure. After adjusting the surface temperature of the melt, the seed crystal attached to the tip of the pulling device is brought into contact with the surface of the melt, and is pulled up while rotating to first form an elongated neck portion. Next, the pulling speed and temperature are adjusted to increase the diameter to a constant diameter portion having a predetermined diameter, and thereafter, the single crystal having a constant diameter is grown by pulling upward while rotating in accordance with the crystal growth.
The single crystal that has reached the predetermined weight is gradually reduced in crystal diameter from the constant diameter portion, and finally has a diameter of zero to be separated from the melt.
【0005】このようなCZ法は、空孔や転位など結晶
欠陥ができるだけ少なく、均質なそして大型の単結晶を
安定して製造するための、様々な工夫がなされている。
例えば、引き上げる結晶を中心軸周りにゆっくり回転さ
せ、同時に溶融液を満たしたるつぼも結晶とは逆方向に
回転させたり、引き上げにワイヤを用いたり、炉内雰囲
気を不活性ガスの減圧下として発生するSiOガスを排
除したりすることなどである。[0005] In the CZ method, various contrivances have been made to stably produce a uniform and large single crystal having as few crystal defects as possible such as vacancies and dislocations.
For example, slowly rotate the crystal to be pulled around the central axis, and at the same time rotate the crucible filled with the melt in the opposite direction to the crystal, use a wire for pulling, or generate a furnace atmosphere under reduced pressure of inert gas. Or to eliminate the SiO gas.
【0006】半導体用シリコン単結晶としては、結晶欠
陥のないことに加えて、さらに不純物の偏析のないこと
もきわめて重要である。とくに不純物の一つである酸素
は、多すぎると結晶の欠陥の原因となる。しかし、ウエ
ハからデバイスを作製する過程において、熱処理による
歪みを抑止し、欠陥のない正常な表面を作り出すため
に、一定レベルの含有が必要である。また、単結晶には
シリコンウエハの電気抵抗率や電導型を定めるため、特
定の不純物元素(ドーパント)を添加する必要があり、
この不純物も、偏析することなく単結晶全体に均一に分
布していなければならない。It is very important for a silicon single crystal for a semiconductor to have no crystal defects and no segregation of impurities. In particular, oxygen, which is one of the impurities, causes crystal defects if it is too much. However, in the process of manufacturing a device from a wafer, a certain level of inclusion is required to suppress distortion due to heat treatment and to create a normal surface without defects. In addition, it is necessary to add a specific impurity element (dopant) to the single crystal in order to determine the electrical resistivity and conductivity type of the silicon wafer,
These impurities must also be uniformly distributed throughout the single crystal without segregation.
【0007】酸素は、主としてるつぼに用いる石英から
溶けだして溶融液中の濃度が高くなる一方、シリコンの
溶融点以上の温度ではSiOガスの蒸気圧が高いため、
減圧下の溶融液表面から排除される。溶融液中の酸素は
拡散によって移動するものもあるが、多くは溶融液の熱
対流に乗って移動する。大きな熱対流は、るつぼ表面を
洗い、溶融液表面に上昇した後、引き上げられつつある
単結晶と溶融液との界面に達するものである。この場
合、るつぼ表面から供給される酸素量、表面で失われる
酸素量、および結晶に取り込まれる酸素量がバランスす
れば、成長方向に均一な酸素濃度分布を有する単結晶が
得られる。しかしながら現実には、結晶やるつぼの回転
に伴う層流、あるいは表層のマランゴニ対流などの影響
を受け、熱対流を定常的かつ均一にするのは容易ではな
い。このため、酸素の均一な濃度分布の単結晶を得るの
は困難であり、結晶の酸素レベルが、要望する範囲を外
れていたりする。Oxygen is mainly melted from quartz used for a crucible to increase its concentration in a melt, while at a temperature higher than the melting point of silicon, the vapor pressure of SiO gas is high.
Excluded from the melt surface under reduced pressure. Although oxygen in the melt moves by diffusion, most of the oxygen moves by heat convection of the melt. The large heat convection is that the surface of the crucible is washed, rises to the surface of the melt, and then reaches the interface between the single crystal being pulled and the melt. In this case, if the amount of oxygen supplied from the crucible surface, the amount of oxygen lost on the surface, and the amount of oxygen taken into the crystal are balanced, a single crystal having a uniform oxygen concentration distribution in the growth direction can be obtained. However, in reality, it is not easy to make the thermal convection steady and uniform due to the influence of the laminar flow accompanying the rotation of the crystal or the crucible, or the Marangoni convection of the surface layer. For this reason, it is difficult to obtain a single crystal having a uniform concentration distribution of oxygen, and the oxygen level of the crystal may be out of a desired range.
【0008】結晶中の酸素の量を制御し、さらに濃度分
布を均一にするため、例えば、特開昭56-104791号公報
や特開昭56-45889号公報に提示されたように、るつぼ内
の溶融液に磁場を印加する方法がある。これは、磁場に
垂直な方向に移動する導体は、生じた誘導電流により、
逆向きの力(ローレンツ力)を受けるという原理を利用
している。るつぼに対し横から水平方向の磁場を印加す
れば、熱対流の上下方向の移動が妨げられて、るつぼ側
壁の表面に沿う流れを抑制するため酸素の混入を抑止で
き、水平方向の流れは拘束されないので、融液表面から
の酸素排除は十分に行われ、結晶に取り込まれる酸素量
を低減できるというものである。[0008] In order to control the amount of oxygen in the crystal and to make the concentration distribution uniform, for example, as disclosed in JP-A-56-104791 and JP-A-56-45889, There is a method of applying a magnetic field to the melt. This is because the conductor moving in the direction perpendicular to the magnetic field, due to the induced current generated,
It utilizes the principle of receiving the opposite force (Lorentz force). When a horizontal magnetic field is applied to the crucible from the side, the vertical movement of the heat convection is hindered, and the flow along the surface of the crucible side wall is suppressed, so that the mixing of oxygen can be suppressed, and the horizontal flow is restricted. Therefore, oxygen is sufficiently removed from the melt surface, and the amount of oxygen taken into the crystal can be reduced.
【0009】水平方向に磁場を印加する方法の他、例え
ば、特開昭57-149894号公報には結晶の引き上げ方向す
なわち垂直方向の磁場を印加する方法が開示され、さら
に特公平8-22797号公報には、垂直の磁場を溶融液表面
位置において、引き上げの中心軸周りが強く、るつぼ壁
近傍ではほぼ0の分布とする発明が提示されている。ま
た、特公平2-12920公報には、るつぼの上下に同極対向
磁石をおき、溶融液に対し軸対象的かつ放射状のカスプ
磁場を作り、単結晶引き上げをおこなう方法が提示され
ている。In addition to the method of applying a magnetic field in the horizontal direction, for example, JP-A-57-149894 discloses a method of applying a magnetic field in a crystal pulling direction, that is, a vertical direction. The gazette discloses an invention in which a vertical magnetic field has a strong distribution around the center axis of the pulling up at the surface of the melt and a distribution of almost 0 near the crucible wall. Japanese Patent Publication No. 2-12920 discloses a method in which magnets of the same polarity are placed above and below a crucible, an axially symmetrical cusp magnetic field is generated in the melt, and a single crystal is pulled.
【0010】このような磁場の印加は、溶融液の攪拌を
抑制するものであり、酸素のように、るつぼ壁からの混
入と溶融液表面からの排出といった、るつぼ内の特定の
場所により生じる現象が異なる場合には効果的に活用で
きる。しかしながら、温度の均一化や、ドーパントなど
不純物の濃度分布の均一化には、必ずしも有効に作用す
るとは限らない。The application of such a magnetic field suppresses the agitation of the melt, and, like oxygen, a phenomenon caused by a specific place in the crucible, such as mixing from the crucible wall and discharge from the melt surface. If they are different, they can be used effectively. However, it does not always work effectively to make the temperature uniform and the concentration distribution of impurities such as dopants uniform.
【0011】ドーパントとなる不純物元素は、液相と固
相が共存する場合、固相中の濃度(CS)と、液相中の
濃度(CL)とは異なっていて、その濃度比は温度と液
相中濃度が定まれば、平衡状態では一定値を示す。現実
の単結晶引き上げでは、平衡状態とは多少ずれがある
が、通常、シリコンに用いられるドーパントの場合、そ
の実効偏析係数KE=(CS/CL)は1よりも小さい。
すなわち、成長する単結晶中の濃度は溶融液中の濃度よ
りも低い。このため、結晶が成長し、溶融液が減少して
いくにつれて、溶融液中のドーパント分の濃度が増加し
ていき、成長させた結晶の後方になるほどドーパント濃
度が増すという傾向がある。必要とする電気的特性を具
備する単結晶部分をより多く採取するには、ドーパント
の成長方向に沿った濃度変化をできるだけ小さくする必
要がある。水平方向に磁場を印加する方法は、酸素濃度
の低減や特定濃度範囲への制御に有効であり、不純物濃
度分布の均一化にも効果があるとされているが、凝固時
の偏析によるドーパントの成長方向に沿った濃度変化は
避けがたい。また、回転引き上げ軸に対しては非対称で
あることから、回転周期性の不純物のミクロ的不均一性
があるとも言われている。When a liquid phase and a solid phase coexist, the impurity element serving as a dopant is different from the concentration in the solid phase (C S ) and the concentration in the liquid phase (C L ), and the concentration ratio is different. If the temperature and the concentration in the liquid phase are determined, they show a constant value in the equilibrium state. In actual single crystal pulling, there is a slight deviation from the equilibrium state. However, in the case of a dopant used for silicon, the effective segregation coefficient K E = (C S / C L ) is usually smaller than 1.
That is, the concentration in the growing single crystal is lower than the concentration in the melt. For this reason, as the crystal grows and the melt decreases, the concentration of the dopant in the melt tends to increase, and the dopant concentration tends to increase toward the rear of the grown crystal. In order to collect more single crystal portions having the required electrical characteristics, it is necessary to minimize the change in concentration of the dopant along the growth direction. The method of applying a magnetic field in the horizontal direction is effective for reducing the oxygen concentration and controlling to a specific concentration range, and is also said to be effective for uniformizing the impurity concentration distribution. A change in concentration along the growth direction is unavoidable. Further, it is said that there is a micro-uniformity of the impurity having the periodicity of rotation because it is asymmetric with respect to the rotation pulling shaft.
【0012】垂直方向の磁場を印加する方法は、るつぼ
側壁に沿った対流やるつぼ底からの上下流の抑止作用が
小さく、その上溶融液表面での水平方向の流動が拘束さ
れて酸素が排出された溶融液の結晶成長界面への流入が
抑止されるため、酸素濃度が高くなり、また得られた結
晶の酸素濃度の均一性もよくない。しかし、結晶成長面
近傍の結晶の回転による溶融液流動が抑制されるので、
実効偏析係数が1により近づくという効果が得られ、こ
のためにドーパントの成長方向に沿った濃度変化が小さ
くなって、目標抵抗率を満足する部分が増し、歩留まり
が向上する。In the method of applying a vertical magnetic field, the convection along the crucible side wall and the effect of suppressing the upstream and downstream from the bottom of the crucible are small, and the horizontal flow on the surface of the melt is restrained and oxygen is discharged. Since the flow of the melt into the crystal growth interface is suppressed, the oxygen concentration increases, and the uniformity of the oxygen concentration of the obtained crystal is not good. However, since the melt flow due to the rotation of the crystal near the crystal growth surface is suppressed,
The effect that the effective segregation coefficient is closer to 1 is obtained, so that the change in the concentration of the dopant in the growth direction is small, the portion satisfying the target resistivity is increased, and the yield is improved.
【0013】カスプ磁場を印加する方法は、溶融液面近
傍における垂直方向の磁場を零に近づけて、溶融液の流
動は拘束しないと同時に、るつぼ壁に沿った熱対流など
流動を拘束しようとするものであり、酸素の低減と、結
晶回転の効果が十分生かされる。しかしながら、ドーパ
ントの成長方向に沿った濃度変化は磁場を印加しないC
Z法と同程度と思われる。In the method of applying a cusp magnetic field, the magnetic field in the vertical direction near the surface of the melt is brought close to zero so that the flow of the melt is not restricted, and at the same time, the flow such as thermal convection along the crucible wall is restricted. Therefore, the effects of oxygen reduction and crystal rotation can be fully utilized. However, the concentration change along the growth direction of the dopant is caused by the C
It seems to be comparable to the Z method.
【0014】[0014]
【発明が解決しようとする課題】引き上げ結晶中の酸素
濃度の制御を主眼とした磁場印加による結晶成長法は、
以上にその主要例を説明したように、いくつかの方法が
あり、それぞれ特徴をもっている。本発明の課題とする
ところは、単結晶の品質改善のための磁場印加法を活用
し、健全かつ均質な単結晶を歩留まりよく、かつより速
い速度で引き上げる方法を提供することにある。引き上
げ速度の高速化により生産性が向上し、高品質の単結晶
をより低コストで製造することが可能になる。The crystal growth method by applying a magnetic field with the primary purpose of controlling the oxygen concentration in the pulled crystal is as follows.
As described above, there are several methods, each of which has its own characteristics. It is an object of the present invention to provide a method for pulling up a healthy and uniform single crystal at a higher yield at a higher speed by utilizing a magnetic field application method for improving the quality of the single crystal. By increasing the pulling speed, productivity is improved, and high-quality single crystals can be manufactured at lower cost.
【0015】[0015]
【課題を解決するための手段】本発明者らは、単結晶の
品質の健全性を失うことなく、歩留まりを向上させ、そ
の引き上げ速度を増大させるための手段の検討をおこな
った。まず引き上げ速度の増加には、溶融液の温度を下
げる必要がある。ところが溶融液の温度を下げていく
と、結晶の非軸対称的な成長を誘発し、変形した単結晶
となりやすい。同時に、溶融液の表面で微細な結晶の晶
出を生じるようになり、健全な単結晶の引き上げを困難
にする。Means for Solving the Problems The present inventors have studied means for improving the yield and increasing the pulling speed without losing the soundness of the quality of the single crystal. First, to increase the pulling speed, it is necessary to lower the temperature of the melt. However, when the temperature of the melt is lowered, non-axially symmetric growth of the crystal is induced, and the crystal tends to be deformed. At the same time, fine crystals are crystallized on the surface of the melt, which makes it difficult to pull up a healthy single crystal.
【0016】これらの問題に対し、中央部にある単結晶
の成長界面近傍の温度は、成長速度を増すために低くす
るが、溶融液表面では、るつぼ壁に近づくほど高くなる
ような温度勾配を付けることによって対処できることが
確認された。るつぼ壁に囲まれた円盤状の溶融液の表面
において、周辺近傍の温度を高くし、中央部の温度を低
くする温度勾配は、昇温途中の過程では生じさせること
ができる。しかしながら、るつぼの外側からの入熱によ
り溶融液の温度が上昇し、さらに表面での熱対流等があ
るので、結晶の引き上げ期間を通じて中央部の温度を一
定に保ちつつ温度勾配を確保するという、安定した定常
状態を維持することは容易ではないと考えられた。In order to solve these problems, the temperature near the growth interface of the single crystal at the center is lowered to increase the growth rate, but the temperature gradient on the surface of the melt becomes higher as it approaches the crucible wall. It was confirmed that it could be dealt with by attaching. On the surface of the disk-shaped molten liquid surrounded by the crucible wall, a temperature gradient that increases the temperature in the vicinity of the periphery and lowers the temperature in the center can be generated in the process of increasing the temperature. However, the temperature of the melt rises due to heat input from the outside of the crucible, and there is further heat convection at the surface, so that the temperature gradient is secured while keeping the temperature in the center constant throughout the crystal pulling period. Maintaining a stable steady state was not considered easy.
【0017】CZ法にて、磁場印加の目的は対流の抑制
にある。対流を抑制すれば溶融液中での熱の伝達は伝導
が主体となり、温度勾配を大きくし得る。そこで、とく
に水平方向の溶融液流動を抑止できる、垂直磁場印加の
活用を検討することにした。その結果、垂直磁場印加に
より、溶融液の表面温度について、中央部が低くしかも
一定の温度に維持しつつ周辺のるつぼ壁に近い部分ほど
温度を高くなる温度勾配が実現できることが明らかにな
った。これは溶融液の水平方向の対流が抑止され、るつ
ぼの外周近くに設置されたヒーターからの熱の伝達が、
伝導主体になったためと考えられた。In the CZ method, the purpose of applying a magnetic field is to suppress convection. If convection is suppressed, heat transfer in the melt is mainly conducted, and the temperature gradient can be increased. Therefore, the use of a vertical magnetic field application, which can suppress the melt flow in the horizontal direction, was studied. As a result, it has been clarified that, by applying a vertical magnetic field, a temperature gradient can be realized in which the temperature near the peripheral crucible wall becomes higher while maintaining the surface temperature of the melt at a low and constant temperature at the central portion. This is because the horizontal convection of the melt is suppressed, and the heat transfer from the heater installed near the outer periphery of the crucible,
It was thought that it became the main body of conduction.
【0018】さらに垂直磁場の印加は、ドーパントなど
不純物の結晶成長方向の濃度分布を均一にする効果があ
る。これは垂直磁界によって、結晶回転に基づく水平方
向の溶融液の流動が拘束され、固化に伴って不純物が濃
化した成長界面近傍の溶融液が容易に排除されず、垂直
磁場のない場合に比較して実効偏析係数が、大幅に1に
近づくためである。その結果として、結晶成長方向の抵
抗率変化が小さくなり、所要の抵抗率範囲に入る部分の
歩留まりが向上する。Further, the application of the vertical magnetic field has the effect of making the concentration distribution of impurities such as dopants in the crystal growth direction uniform. This is because the vertical magnetic field restricts the flow of the melt in the horizontal direction due to the rotation of the crystal, and the melt near the growth interface where impurities are concentrated due to solidification is not easily removed. This is because the effective segregation coefficient approaches 1 significantly. As a result, a change in resistivity in the crystal growth direction is reduced, and the yield in a portion falling within a required resistivity range is improved.
【0019】このように垂直磁界の印加は、引き上げ速
度を増加できる条件を実現させ、しかも抵抗率均一化に
よる歩留まりを改善させるので、生産性の大幅向上に有
意である。しかしながら、結晶中の酸素濃度が、通常の
磁場を印加しないCZ法よりも高くなる傾向にあり、酸
素およびドーパントなどの不純物濃度が成長方向に直角
の結晶断面内での均一性がよくないと言う難点がある。
そこで、垂直磁場印加の特徴を生かし、その上で酸素の
濃度が制御でき、さらにドーパントなどの結晶断面内で
の均一性を向上させる方法を種々検討した。As described above, application of the vertical magnetic field realizes a condition capable of increasing the pulling speed, and also improves the yield by making the resistivity uniform, which is significant for significantly improving the productivity. However, the oxygen concentration in the crystal tends to be higher than in the CZ method in which a normal magnetic field is not applied, and the concentration of impurities such as oxygen and dopant is not uniform in a crystal cross section perpendicular to the growth direction. There are difficulties.
Therefore, various methods for utilizing the characteristics of the application of the perpendicular magnetic field, controlling the oxygen concentration on the basis of the characteristics, and improving the uniformity of the dopant or the like in the crystal cross section have been studied.
【0020】その結果、垂直磁場を印加するためのコイ
ルとは別に、溶融液面の上方に引き上げ軸と同一軸のコ
イルを設置し、そこに電流を流して逆方向の磁場を発生
させることが、きわめて効果的であることが明らかにな
った。この場合、溶融液の表面において、垂直方向の磁
場成分を中央部が小さく、るつぼ壁に近い周辺部が高く
なるような磁場の状態にする。それによって、酸素の濃
度の制御が可能となり、酸素やドーパントの断面内の均
一性を向上させることができたのである。As a result, apart from the coil for applying the vertical magnetic field, a coil having the same axis as the pull-up axis may be installed above the surface of the melt, and a current may be passed through the coil to generate a magnetic field in the opposite direction. Proved to be extremely effective. In this case, on the surface of the melt, the magnetic field component in the vertical direction is set to a magnetic field state such that the central portion is small and the peripheral portion near the crucible wall is high. As a result, the oxygen concentration can be controlled, and the uniformity of oxygen and the dopant in the cross section can be improved.
【0021】垂直磁場の中で、溶融液面の位置における
中央部、すなわち単結晶の成長界面とその近傍の磁場垂
直成分を小さくし、周辺を高くするように逆磁場を印加
する場合、液面の周辺および全溶融液の大部分は垂直磁
場に支配されており、引き上げ速度増加に好ましく、抵
抗率均一化が可能という効果もある程度維持される。そ
の上で、成長界面とその近傍において溶融液の水平方向
の流動が容易になるので、酸素の低減、およびドーパン
トなど不純物の成長界面での均一化がおこなわれたため
と考えられた。In a vertical magnetic field, when a reverse magnetic field is applied so as to reduce the vertical component of the magnetic field in the central portion at the position of the melt surface, that is, the growth interface of the single crystal and its vicinity, and to increase the periphery, And the majority of the entire melt is governed by the vertical magnetic field, which is preferable for increasing the pulling speed, and the effect of making the resistivity uniform can be maintained to some extent. In addition, it is considered that the flow of the molten liquid in the horizontal direction becomes easy at the growth interface and in the vicinity thereof, so that oxygen was reduced and impurities such as dopants were made uniform at the growth interface.
【0022】以上のように本発明の要旨は、磁場発生用
のコイルの磁化方向を中心軸と一致させて垂直方向に磁
場を印可するCZ法による単結晶製造装置において、溶
融液面より上方に引き上げ軸と同軸の別コイルを配置し
逆方向の磁場を発生させることにより、溶融液表面にお
ける磁場の垂直成分の強さ分布を、るつぼ中心付近の溶
融液の固液界面近傍は低く、るつぼ壁周辺は高くするこ
とを特徴とする、単結晶引き上げ方法である。As described above, the gist of the present invention is to provide a single crystal manufacturing apparatus by a CZ method in which a magnetic field is applied in the vertical direction while the magnetization direction of a coil for generating a magnetic field coincides with the central axis. By arranging another coil coaxial with the lifting axis and generating a magnetic field in the opposite direction, the strength distribution of the vertical component of the magnetic field on the melt surface is reduced near the solid-liquid interface of the melt near the crucible center, and the crucible wall This is a single crystal pulling method characterized by making the periphery high.
【0023】この方法によりCZ法にてシリコンの単結
晶の引き上げをおこなえば、成長方向に直角の断面にお
ける酸素やドーパントなどの不純物の濃度分布が均一
で、成長方向の抵抗率の変動も少ない結晶を、従来より
も高速で製造することが可能である。When a silicon single crystal is pulled by the CZ method by this method, a crystal having a uniform concentration distribution of impurities such as oxygen and dopant in a cross section perpendicular to the growth direction and a small variation in resistivity in the growth direction is obtained. Can be manufactured at a higher speed than before.
【0024】[0024]
【発明の実施の形態】本発明の方法は、垂直方向磁場印
加によるCZ法を基本とする。シリコン単結晶引き上げ
の際の溶融液に対し、垂直方向の磁場を印加する方法
は、1個又は複数の磁場発生用の円筒状に巻かれたコイ
ルを、その中心軸を単結晶引き上げの回転軸又はるつぼ
回転軸と一致させ、るつぼ位置ないしはるつぼを中心と
する上下位置に配置し、直流電流を流して磁場を発生さ
せる。複数のコイルの場合はいずれのコイルも磁化方向
が一致するように電流を流す。DESCRIPTION OF THE PREFERRED EMBODIMENTS The method of the present invention is based on the CZ method by applying a vertical magnetic field. The method of applying a magnetic field in the vertical direction to the melt at the time of pulling a silicon single crystal is such that one or a plurality of cylindrically wound coils for generating a magnetic field are rotated around the center axis of the single crystal pulling axis. Alternatively, it is arranged at the crucible position or at a vertical position with the crucible as the center so as to coincide with the crucible rotation axis, and a direct current is passed to generate a magnetic field. In the case of a plurality of coils, the current flows so that the magnetization directions of all the coils match.
【0025】図2は、本発明の実施形態の一例を示す模
式図である。この図を用いて本発明の方法を説明する。
るつぼの上方および下方に設置されたコイル6aおよびコ
イル6bに同一方向の磁場が発生するように電流を流せ
ば、両コイルの間に、中心軸に平行で、かつ中心軸に直
角な断面における磁束密度の比較的均一な磁場が発生す
る。この状態で溶融液を入れたるつぼおよび得られた単
結晶を回転しつつ引き上げ成長させるのが、垂直方向磁
場印加によるCZ法である。これに対し本発明では、垂
直磁場を発生させるコイルとは別に、溶融液上方の垂直
磁場の域内に同一の中心軸を持つコイル12を配置し、周
囲とは逆の磁場を発生させる。FIG. 2 is a schematic view showing an example of the embodiment of the present invention. The method of the present invention will be described with reference to FIG.
If an electric current is applied so that a magnetic field in the same direction is generated in the coils 6a and 6b installed above and below the crucible, the magnetic flux between the coils in a cross section parallel to the central axis and perpendicular to the central axis is generated. A relatively uniform density magnetic field is generated. In this state, the crucible containing the melt and the obtained single crystal are pulled up while rotating, and the CZ method by applying a vertical magnetic field. On the other hand, in the present invention, a coil 12 having the same central axis is arranged in the vertical magnetic field region above the melt, separately from the coil that generates the vertical magnetic field, and generates a magnetic field opposite to the surroundings.
【0026】コイル12により発生させる逆磁場の強さ
は、磁場の垂直成分が溶融液の液面の位置において、中
央部が低く、周辺のるつぼ壁に近づくほど高くなるよう
にする。磁場の垂直成分の分布状態は、コイル12の位
置、大きさおよび発生させる逆磁場と、元になる垂直磁
場強さとの関係により、様々に変化するので、それらを
調整し、中央部が低く周辺部が高くなるようにしなけれ
ばならない。液面位置の垂直磁場をこのように設定する
ことにより、溶融液の大部分は垂直磁場が印加された状
態が維持される。これにより溶融液表面にてるつぼ壁近
傍の温度が高く、中央部は低くでき、溶融液温度を低く
しても単結晶の変形や微細結晶の析出が抑止されるの
で、引き上げ速度の増加が可能である。一方、引き上げ
単結晶の周辺の融液表面、および成長界面近傍は磁場の
垂直成分が低く、結晶の回転による溶融液の流動によ
り、脱酸素がおこなわれると共に酸素やドーパントなど
の成長方向直角断面の均一化が実現できる。The strength of the reverse magnetic field generated by the coil 12 is such that the vertical component of the magnetic field is lower at the center of the liquid surface of the melt and higher as it approaches the peripheral crucible wall. The distribution state of the vertical component of the magnetic field varies in various ways depending on the relationship between the position, the size of the coil 12, the generated reverse magnetic field, and the strength of the original vertical magnetic field. Parts must be high. By setting the vertical magnetic field at the liquid surface position in this way, the state where the vertical magnetic field is applied is maintained for most of the melt. As a result, the temperature near the crucible wall on the melt surface can be high, and the center can be lowered. Even if the melt temperature is lowered, deformation of single crystals and precipitation of fine crystals are suppressed, so the pulling speed can be increased. It is. On the other hand, the surface of the melt around the pulled single crystal and the vicinity of the growth interface have a low perpendicular component of the magnetic field, and the flow of the melt due to the rotation of the crystal causes deoxidation and the cross section perpendicular to the growth direction of oxygen and dopants. Uniformization can be realized.
【0027】[0027]
【実施例】図2に模式的に示した装置にて、16インチφ
のるつぼを用い、チャージ量70kgとし、ドーパントとし
てPを添加して目標抵抗値が10Ωcmの、径が6インチ
φ、長さ1300mmの単結晶を引き上げ育成をおこなった。
その際、通常の磁場の無いCZ法の場合、垂直磁場を印
加した場合、および本発明の垂直磁場に溶融液上方から
逆磁場をかけ、液面中央部の垂直磁場を周囲より低くし
た場合、の三者を比較した。FIG. 2 shows a schematic diagram of the apparatus shown in FIG.
Using a crucible, a charge amount was set to 70 kg, P was added as a dopant, and a single crystal having a target resistance value of 10 Ωcm, a diameter of 6 inches and a length of 1300 mm was pulled up and grown.
At that time, in the case of the CZ method without a normal magnetic field, when a vertical magnetic field is applied, and when a reverse magnetic field is applied to the vertical magnetic field of the present invention from above the melt, and the vertical magnetic field at the center of the liquid surface is lower than the surroundings, Were compared.
【0028】垂直磁場による引き上げの場合は、図2に
おいてコイル6aおよび6bにより磁場を印加した。コイル
巻線の中心位置の直径は600mmで、溶融液面に対し6aは4
00mm上方、6bは400mm下方に設置した。本発明の方法の
場合、さらにコイル12により逆の磁場を導入するが、そ
のコイル巻線の中心位置は、直径が400mmで、コイル6a
と同一平面に配置した。励磁電流を調節して逆方向の磁
場を印加することにより、垂直方向の磁場の溶融液表面
における分布を変えることができる。まず、磁場を印加
しない通常のCZ法にて、単結晶引き上げ条件を選定し
た。結晶回転を15rpm、逆方向のるつぼ回転を5rpmと
し、健全な単結晶が得られる限界の引き上げ速度を求
め、そのときの条件を基準とした。垂直磁場をコイル6a
および6bにより印加した場合の引き上げ試験は、溶融液
の表面温度を放射温度計により計測して、るつぼ壁近傍
の温度は磁場印加のない場合と同等の温度とし、単結晶
近傍の温度を低下させて、引き上げ速度の増加を検討し
た。その結果、強さ0.2Tの垂直磁場印加により、るつ
ぼ壁近傍の温度に対し、単結晶近傍の温度を5〜10℃低
くすることが可能になり、引き上げ速度を磁場のない場
合の2倍に増加しても、十分健全な単結晶が得られるこ
とが確認された。In the case of lifting by a vertical magnetic field, a magnetic field was applied by the coils 6a and 6b in FIG. The diameter of the center position of the coil winding is 600 mm, and 6a is 4
00b was set above and 6b was set below 400mm. In the case of the method of the present invention, a reverse magnetic field is further introduced by the coil 12, but the center position of the coil winding is 400 mm in diameter and the coil 6a
And arranged on the same plane. By adjusting the exciting current and applying a magnetic field in the opposite direction, the distribution of the magnetic field in the vertical direction on the melt surface can be changed. First, single crystal pulling conditions were selected by a normal CZ method without applying a magnetic field. The crystal rotation was 15 rpm, and the crucible rotation in the reverse direction was 5 rpm, and the limit pulling speed at which a sound single crystal was obtained was determined, and the conditions at that time were used as a reference. Vertical magnetic field coil 6a
In the pull-up test when applying by 6b and 6b, the surface temperature of the melt was measured with a radiation thermometer, the temperature near the crucible wall was set to the same temperature as when no magnetic field was applied, and the temperature near the single crystal was reduced. Then, the increase in the lifting speed was considered. As a result, by applying a vertical magnetic field of 0.2 T in intensity, it becomes possible to lower the temperature near the single crystal by 5 to 10 ° C with respect to the temperature near the crucible wall, and to double the pulling speed as compared to the case without a magnetic field. It was confirmed that a sufficiently healthy single crystal could be obtained even if the number increased.
【0029】次に、本発明の垂直磁場をコイル6aおよび
6bにより印加し、かつコイル12により逆方向の磁場を導
入し、溶融液表面位置における垂直磁場の強さを、るつ
ぼ中央部にて0.002T、周辺部にて0.2Tとした。この状
態にて、垂直磁場のみの場合と同等の表面の温度勾配が
得られることがわかったので、垂直磁場のみの場合と同
様、引き上げ速度を磁場のない場合の2倍として成長を
おこなわせ、十分健全な単結晶の得られることを確認し
た。Next, the vertical magnetic field of the present invention is applied to the coils 6a and 6a.
The magnetic field was applied by 6b and a reverse magnetic field was introduced by the coil 12, and the strength of the vertical magnetic field at the surface of the melt was set to 0.002T at the center of the crucible and 0.2T at the periphery. In this state, it was found that the same surface temperature gradient as in the case of only the vertical magnetic field was obtained, so that the growth was performed with the pulling speed twice that in the case without the magnetic field, as in the case of the vertical magnetic field only, It was confirmed that a sufficiently sound single crystal was obtained.
【0030】表1にこれら3種の引き上げ方法による単
結晶の調査結果を示す。これらの数値は、得られた単結
晶の中央部で調査したものであり、通常のCZ法による
場合は6回、垂直磁場印加の場合は2回、本発明の方法
による場合は6回、それぞれ繰り返しおこなった結果の
平均値である。Table 1 shows the results of examination of single crystals by these three methods of pulling. These numerical values were obtained by investigating the central part of the obtained single crystal, and were obtained six times in the case of the usual CZ method, twice in the case of applying a vertical magnetic field, and six times in the case of the method of the present invention. This is the average value of the results of the repetition.
【0031】[0031]
【表1】 [Table 1]
【0032】これからわかるように、本発明の方法によ
れば従来のCZ法による場合に比較し、引き上げ速度が
2倍になっても十分健全な単結晶が得られ、酸素量のレ
ベルおよび酸素含有量の面内均一性はほぼ同等である。
さらに、ドーパントとして添加したPの実効偏析係数を
見ると、30%以上大きくなっており、抵抗値の歩留まり
が改善されている。As can be seen, the method of the present invention can provide a sufficiently sound single crystal even when the pulling speed is doubled, as compared with the case of the conventional CZ method. The in-plane uniformity of the quantities is approximately equal.
Further, looking at the effective segregation coefficient of P added as a dopant, the effective segregation coefficient is increased by 30% or more, and the yield of the resistance value is improved.
【0033】[0033]
【発明の効果】本発明の方法によれば、均一性のすぐれ
た健全な単結晶を、より高速でかつ歩留まりよく製造す
ることができる。According to the method of the present invention, a sound single crystal with excellent uniformity can be manufactured at a higher speed and with a higher yield.
【図面の簡単な説明】[Brief description of the drawings]
【図1】通常の回転引き上げ法(CZ法)による単結晶
製造装置の断面を、模式的に示した図である。FIG. 1 is a diagram schematically showing a cross section of a single crystal manufacturing apparatus by a normal rotation pulling method (CZ method).
【図2】本発明の方法を実施する単結晶製造装置の断面
を、模式的に示した図である。FIG. 2 is a diagram schematically showing a cross section of a single crystal manufacturing apparatus for performing the method of the present invention.
1a…るつぼ(石英部分)、1b…るつぼ(黒鉛部分)、2
…ヒータ、3…種結晶、4…溶融液、5…結晶、6a…垂直
磁場印加用コイル(上方)、6b…垂直磁場印加用コイル
(下方)、7…引き上げ用ワイヤ、8…チャンバ、9…プ
ルチャンバ、10…保温材、11…るつぼ支持軸、12…逆磁
場印加用コイル1a… Crucible (quartz part), 1b… Crucible (graphite part), 2
... heater, 3 ... seed crystal, 4 ... melt, 5 ... crystal, 6a ... vertical magnetic field applying coil (upper), 6b ... vertical magnetic field applying coil (lower), 7 ... pulling wire, 8 ... chamber, 9 ... Pull chamber, 10 ... Insulation material, 11 ... Crucible support shaft, 12 ... Coil for applying reverse magnetic field
───────────────────────────────────────────────────── フロントページの続き (58)調査した分野(Int.Cl.7,DB名) C30B 1/00 - 35/00 ──────────────────────────────────────────────────続 き Continuation of front page (58) Field surveyed (Int.Cl. 7 , DB name) C30B 1/00-35/00
Claims (1)
一致させて垂直方向に磁場を印可するCZ法による単結
晶製造装置において、溶融液面より上方に引き上げ軸と
同軸の別コイルを配置し逆方向の磁場を発生させること
により、溶融液表面における磁場の垂直成分の強さ分布
を、るつぼ中心付近の溶融液の固液界面近傍は低く、る
つぼ壁周辺は高くすることを特徴とする、単結晶引き上
げ方法。An apparatus for manufacturing a single crystal by a CZ method in which a magnetization direction of a coil for generating a magnetic field is made coincident with a central axis and a magnetic field is applied in a vertical direction, another coil coaxial with an axis is pulled up above a melt surface. By arranging and generating a magnetic field in the opposite direction, the strength distribution of the vertical component of the magnetic field at the melt surface is low near the solid-liquid interface of the melt near the center of the crucible and high near the crucible wall. A single crystal pulling method.
Priority Applications (1)
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JP09088218A JP3132412B2 (en) | 1997-04-07 | 1997-04-07 | Single crystal pulling method |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP09088218A JP3132412B2 (en) | 1997-04-07 | 1997-04-07 | Single crystal pulling method |
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Publication Number | Publication Date |
---|---|
JPH10287488A JPH10287488A (en) | 1998-10-27 |
JP3132412B2 true JP3132412B2 (en) | 2001-02-05 |
Family
ID=13936759
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JP09088218A Expired - Fee Related JP3132412B2 (en) | 1997-04-07 | 1997-04-07 | Single crystal pulling method |
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JP4725752B2 (en) * | 2008-05-09 | 2011-07-13 | 信越半導体株式会社 | Single crystal manufacturing method |
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