JP3986029B2 - Silicon single crystal pulling method - Google Patents
Silicon single crystal pulling method Download PDFInfo
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- JP3986029B2 JP3986029B2 JP36757697A JP36757697A JP3986029B2 JP 3986029 B2 JP3986029 B2 JP 3986029B2 JP 36757697 A JP36757697 A JP 36757697A JP 36757697 A JP36757697 A JP 36757697A JP 3986029 B2 JP3986029 B2 JP 3986029B2
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- quartz crucible
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Description
【０００１】
【発明の属する技術分野】
本発明は、ＣＺ法によるシリコン単結晶引き上げ方法、更に詳しくは、結晶長さ方向の酸素濃度均一化による歩留まり改善及び単結晶化率の改善を図るシリコン単結晶引き上げ方法に関するものである。
【０００２】
【従来の技術】
従来から使用されてきたシリコン単結晶引き上げ用の石英ルツボは、図６に示す様にルツボの底部が２つの円で構成される平底型であった。
また特開昭５７−３８３９８号公報に示される石英ルツボでは、開口部から底部にかけて、側部をテーパ状にしてシリコン単結晶に取り込まれる酸素濃度のコントロールを行うようにしている。
【０００３】
【発明が解決しようとする課題】
従来の平底型石英ルツボを用いる方法では、シリコン単結晶を引き上げるにつれ、シリコン融液と石英ルツボの接触面積が減っていくがシリコン融液の表面積は変わらないから酸素の蒸発面積は一定となり、結晶に取り込まれる酸素が減って行き、結果的に結晶長さ方向で所望の酸素濃度を有する部位の取得率が低下して歩留まりが悪いという問題があった。
というのは、基本的に単結晶中の酸素濃度は、
（１）シリコン融液と石英ルツボの接触した部分より酸素が溶けだし
（２）シリコン融液表面から酸素がＳｉＯとして蒸発する。
つまり、結晶へは（１）−（２）の分が取り込まれるのである。
そして、結晶への酸素濃度を上げようとすれば石英ルツボからの酸素の溶け出しを多くしなければならない為融液中に石英の破片が放出される可能性が増大し、この石英破片が成長中の単結晶の固液界面に付着して、単結晶に転位を発生させ多結晶化し、単結晶化率が悪くなるという問題があった。
特に直径５５０ｍｍ以上の大きさの石英ルツボの場合に顕著であった。即ち、石英ルツボの大型化に伴い石英ルツボを取り囲むカーボン部材も大きくなってくる。大型化すると熱の損失が大きくなる為大きなヒーターパワーをかける必要があり、石英ルツボにかかる熱負荷が大きくなり、上述の如く単結晶に転位を発生させる確率が高くなり、単結晶化率が悪くなるのである。
ここで、単結晶化率とは、Ｎ回の結晶引上げプロセスの試行で、所定の直径及び長さの結晶が完全に単結晶で成長した回数がＭの場合、（Ｍ／Ｎ）×１００％＝単結晶化率と定義する。
【０００４】
また、特開昭５７−３８３９８号公報に示される様なテーパ状石英ルツボでは、直径５５０ｍｍ以上の大型の石英ルツボをこの様な複雑な形状に再現性良く生産することは、現実的には困難である。また、シリコン単結晶の直径制御を行うにも、形状が複雑な為困難さが伴っていた。本発明は、上記問題を解消し、結晶長さ方向の酸素濃度均一化による歩留まりの向上及び単結晶化率の改善を図るシリコン単結晶の引き上げ方法を提供することを目的とするものである。
【０００５】
【課題を解決するための手段】
上記目的を達成するために、本発明のシリコン単結晶引き上げ方法においては、直径２００ｍｍ以上のシリコン単結晶を、直径５５０ｍｍ以上の石英ルツボから引き上げるに際して、底の形状が半球である石英ルツボを使用して引き上げる方法を採用するものである。
【０００６】
また、素材溶解後の融液深さは、半球部のＲ以下であることが好ましい。
【０００７】
【発明の実施の形態】
本発明では、石英ルツボの形状を丸底型としている為、単結晶を引き上げるにつれ、シリコン融液が減り石英ルツボとシリコン融液の接触面積が減っていってもシリコンの蒸発面積も減っていく為、単結晶の長さ方向の酸素濃度はほぼ一定となり歩留まり改善が図られる。
また、同一酸素濃度を狙う場合、平底型石英ルツボに比べて丸底型石英ルツボは、シリコンの蒸発面積が小さい分石英ルツボからの酸素の溶け出しを少なく出来る為石英ルツボの溶損を少なく出来、従って石英破片放出に伴う単結晶への転位の発生も減り、よって単結晶化率の向上が図られる。
【０００８】
特に直径５５０ｍｍ以上の石英ルツボでは石英ルツボの大型化に伴い熱負荷がより多くかかる為単結晶化率が悪くなっていた。しかし、丸底型石英ルツボでは石英ルツボからの酸素の溶け出しを少なく出来る為、石英ルツボの溶損（負荷）を少なく出来、従って石英破片放出に伴う単結晶への転位の発生も減り、単結晶化率の向上が図られる。
【０００９】
本発明に用いる半球状ルツボであれば特開昭５７−３８３９８号公報に示されるテーパ状石英ルツボより制作も容易である。
また、素材溶解後の融液深さを、半球部のＲ以下とすることにより、引き上げ初期から蒸発面積が減少し始める為、結晶トップ部では平底型の場合よりも、酸素濃度を低く、結晶後半では酸素濃度を高く出来、容易に酸素濃度分布を単結晶の長さ方向で均一化出来る。
【００１０】
【実施例】
以下本発明の実施例を図面を参酌し乍ら説明する。
図１は本発明実施例の丸底型石英ルツボの断面図、図６は従来の平底型石英ルツボの断面図であり、図１及び図６にそれぞれ示す数値はその単位はｍｍである。
上記図１及び図６にそれぞれ示す形状、大きさの石英ルツボで直径２００ シリコン単結晶の引き上げを行った場合の、単結晶固化率に対するシリコン融液と石英ルツボとの接触面積の変化を図２に、単結晶固化率に対する蒸発面積（シリコン融液表面積）の変化を図３に、それぞれ示すが、これらの図から明らかな如く、平底型石英ルツボと丸底型石英ルツボは、シリコン融液と石英ルツボとの接触面積はほぼ同等であるが、シリコン融液の蒸発面積は丸底型石英ルツボの方がある範囲の固化率のところでかなり小さくなっている。
【００１１】
図４に固化率に対する接触面積／蒸発面積を、また図５に引上げ結晶長に対する酸素濃度をそれぞれ示す。これら図４及び図５から明らかな如く、単結晶を引き上げるにつれシリコン融液が減り接触面積が減っていき石英ルツボから入って来る酸素が減っても、平底型ルツボに比べて丸底型ルツボは、酸素の蒸発面積が減り酸素の蒸発も減る為、単結晶の長さ方向の酸素濃度は略一定となっている。
なお単結晶化率は、上記実施例において、丸底型石英ルツボの場合は９５％であったのに対し、従来の平底型石英ルツボの場合には８７％であった。
また、比較の為に、直径１５０ｍｍのシリコン単結晶を図1 に示すのと相似形で直径４６０ｍｍの丸底型石英ルツボから引き上げた場合と、同じく図６に示すのと相似形で直径４６０ｍｍの平底型石英ルツボから引き上げた場合における単結晶化率を比較すると、それぞれ９３％及び９５％であった。すなわち、引き上げ単結晶、使用する石英ルツボのそれぞれの径が２００ｍｍ、５５０ｍｍを越えると丸底ルツボの効果が発揮されてくる。
【００１２】
【発明の効果】
以上詳述した如く、本発明方法によれば、石英ルツボの底の形状を半球としたので、単結晶を引き上げるにつれ酸素の蒸発も減り、単結晶の長さ方向の酸素濃度を均一化出来る為歩留まりが向上出来るという効果を奏する。そしてこの事は素材溶融後の融液深さを、半球部のＲ以下にすることにより、より一層効果的である。
【００１３】
また、本発明によれば、単結晶化率も従来の平底型石英ルツボの場合に比べて高くなり、その事は上述の如く直径１５０ｍｍ程度のシリコン単結晶を引き上げる場合には丸底型石英ルツボと平底型石英ルツボにおいてあまり変わらなかったのが、本発明の様に直径２００ｍｍ以上のシリコン単結晶引き上げにあっては、その差異が顕著になると共に、用いる丸底型石英ルツボがテーパ状石英ルツボに比べて形状が簡単なので大型のルツボでも容易に生産できる。
また、本発明によれば、石英ルツボ底がヒ−ターから徐々に離れる為、たとえば図７に示したように、ルツボ底の温度を低めに、しかも均一に保つことが可能な為、石英の劣化が少なく、その事も単結晶化率の向上につながるという効果もある。
【図面の簡単な説明】
【図１】本発明方法で用いる丸底型石英ルツボの断面図である。
【図２】丸底型石英ルツボと平底型石英ルツボの単結晶固化率に応じた接触面積の変化を示すグラフである。
【図３】丸底型石英ルツボと平底型石英ルツボの単結晶固化率に応じた蒸発面積の変化を示すグラフである。
【図４】丸底型石英ルツボと平底型石英ルツボの単結晶固化率に対する接触面積／蒸発面積の変化を示すグラフである。
【図５】丸底型石英ルツボと平底型石英ルツボの引き上げ結晶長に応じた酸素濃度の変化を示すグラフである。
【図６】従来の平底型石英ルツボの断面図である。
【図７】ルツボ断面方向の温度分布を示す図である。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a silicon single crystal pulling method by a CZ method, and more particularly to a silicon single crystal pulling method for improving yield and improving a single crystallization rate by uniforming oxygen concentration in the crystal length direction.
[0002]
[Prior art]
A conventionally used quartz crucible for pulling up a silicon single crystal is a flat-bottom type in which the bottom of the crucible is composed of two circles as shown in FIG.
In the quartz crucible disclosed in Japanese Patent Application Laid-Open No. 57-38398, the oxygen concentration taken into the silicon single crystal is controlled by tapering the side from the opening to the bottom.
[0003]
[Problems to be solved by the invention]
In the conventional method using a flat bottom type quartz crucible, as the silicon single crystal is pulled up, the contact area between the silicon melt and the quartz crucible decreases, but the surface area of the silicon melt does not change, so the oxygen evaporation area is constant, As a result, the amount of oxygen taken in decreases, and as a result, there is a problem in that the yield is poor because the acquisition rate of a portion having a desired oxygen concentration in the crystal length direction decreases.
Because basically the oxygen concentration in the single crystal is
(1) Oxygen begins to dissolve from the contact portion between the silicon melt and the quartz crucible. (2) Oxygen evaporates as SiO from the surface of the silicon melt.
That is, (1)-(2) is taken into the crystal.
If the oxygen concentration in the crystal is increased, the amount of oxygen dissolved out from the quartz crucible must be increased, increasing the possibility of quartz fragments being released into the melt, and this quartz fragment grows. There is a problem that the single crystal is attached to the solid-liquid interface, and dislocations are generated in the single crystal to be polycrystallized, and the single crystallization rate is deteriorated.
This was particularly remarkable in the case of a quartz crucible having a diameter of 550 mm or more. That is, as the size of the quartz crucible increases, the carbon member surrounding the quartz crucible also increases. When the size is increased, heat loss increases, so it is necessary to apply a large heater power, the heat load applied to the quartz crucible increases, the probability of generating dislocations in the single crystal increases as described above, and the single crystallization rate is poor. It becomes.
Here, the single crystallization rate is (M / N) × 100% when the number of times that a crystal having a predetermined diameter and length is completely grown as a single crystal is M in trials of N crystal pulling processes. = Defined as single crystallization rate.
[0004]
In addition, with a tapered quartz crucible as disclosed in JP-A-57-38398, it is practically difficult to produce a large quartz crucible having a diameter of 550 mm or more in such a complicated shape with good reproducibility. It is. Also, controlling the diameter of a silicon single crystal has been difficult due to its complicated shape. An object of the present invention is to provide a method for pulling up a silicon single crystal that solves the above-described problems and improves the yield and the single crystallization rate by making the oxygen concentration uniform in the crystal length direction.
[0005]
[Means for Solving the Problems]
In order to achieve the above object, the silicon single crystal pulling method of the present invention uses a quartz crucible whose bottom shape is a hemisphere when pulling a silicon single crystal having a diameter of 200 mm or more from a quartz crucible having a diameter of 550 mm or more. The method of pulling up is adopted.
[0006]
Moreover, it is preferable that the melt depth after melt | dissolving a raw material is below R of a hemisphere part.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
In the present invention, since the shape of the quartz crucible is a round bottom, as the single crystal is pulled up, the silicon melt is reduced, and even if the contact area between the quartz crucible and the silicon melt is reduced, the silicon evaporation area is also reduced. Therefore, the oxygen concentration in the length direction of the single crystal is almost constant, and the yield is improved.
In addition, when aiming at the same oxygen concentration, the round bottom quartz crucible can reduce the melting of the quartz crucible because the silicon evaporating area is smaller and the oxygen elution from the quartz crucible can be reduced. Therefore, the occurrence of dislocations to the single crystal accompanying the release of quartz fragments is reduced, and the single crystallization rate can be improved.
[0008]
In particular, in a quartz crucible having a diameter of 550 mm or more, the heat load is increased as the size of the quartz crucible is increased, so that the single crystallization rate is deteriorated. However, in the round bottom type quartz crucible, the melting of oxygen from the quartz crucible can be reduced, so that the melting loss (load) of the quartz crucible can be reduced. The crystallization rate can be improved.
[0009]
The hemispherical crucible used in the present invention is easier to manufacture than the tapered quartz crucible disclosed in JP-A-57-38398.
Further, by setting the melt depth after melting the material to be equal to or less than R of the hemispherical portion, the evaporation area starts to decrease from the initial stage of pulling up. In the second half, the oxygen concentration can be increased, and the oxygen concentration distribution can be easily made uniform in the length direction of the single crystal.
[0010]
【Example】
Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a sectional view of a round bottom type quartz crucible according to an embodiment of the present invention. FIG. 6 is a sectional view of a conventional flat bottom type quartz crucible, and the numerical values shown in FIG. 1 and FIG.
Changes in the contact area between the silicon melt and the quartz crucible with respect to the single crystal solidification rate when a silicon single crystal having a diameter of 200 is pulled with a quartz crucible having the shape and size shown in FIGS. 1 and 6, respectively. FIG. 3 shows changes in the evaporation area (silicon melt surface area) with respect to the single crystal solidification rate. As is clear from these figures, the flat-bottom quartz crucible and the round-bottom quartz crucible are composed of silicon melt and The contact area with the quartz crucible is almost the same, but the evaporation area of the silicon melt is considerably smaller at the solidification rate within a certain range of the round bottom quartz crucible.
[0011]
FIG. 4 shows the contact area / evaporation area with respect to the solidification rate, and FIG. 5 shows the oxygen concentration with respect to the pulled crystal length. As is clear from FIGS. 4 and 5, as the single crystal is pulled up, the silicon melt decreases, the contact area decreases, and even if the oxygen coming from the quartz crucible decreases, the round bottom crucible is less than the flat bottom crucible. Since the oxygen evaporation area is reduced and the oxygen evaporation is also reduced, the oxygen concentration in the longitudinal direction of the single crystal is substantially constant.
In the above examples, the single crystallization rate was 95% in the case of the round bottom type quartz crucible, whereas it was 87% in the case of the conventional flat bottom type quartz crucible.
For comparison, a silicon single crystal having a diameter of 150 mm is similar to that shown in FIG. 1 and pulled up from a round-bottom quartz crucible having a diameter of 460 mm, and similar to that shown in FIG. 6 and having a diameter of 460 mm. When compared with the single crystallization rate when pulled up from the flat bottom type quartz crucible, they were 93% and 95%, respectively. That is, when the diameters of the pulled single crystal and the quartz crucible used exceed 200 mm and 550 mm, the effect of the round bottom crucible is exhibited.
[0012]
【The invention's effect】
As described above in detail, according to the method of the present invention, since the bottom shape of the quartz crucible is a hemisphere, the evaporation of oxygen is reduced as the single crystal is pulled up, and the oxygen concentration in the longitudinal direction of the single crystal can be made uniform. There is an effect that the yield can be improved. This is even more effective by making the melt depth after melting the material less than or equal to R of the hemisphere.
[0013]
In addition, according to the present invention, the single crystallization rate is also higher than in the case of the conventional flat bottom type quartz crucible, which means that when pulling up a silicon single crystal having a diameter of about 150 mm as described above, a round bottom type quartz crucible. The difference between the flat bottom type quartz crucible and the flat bottom type quartz crucible is that when the silicon single crystal having a diameter of 200 mm or more is pulled as in the present invention, the difference becomes remarkable, and the round bottom type quartz crucible used is a tapered quartz crucible. Compared to, the shape is simple and even large crucibles can be produced easily.
Further, according to the present invention, since the quartz crucible bottom is gradually separated from the heater, for example, as shown in FIG. 7, the temperature of the crucible bottom can be kept low and uniform. There is little deterioration, and this also has the effect of leading to an improvement in the single crystallization rate.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a round bottom quartz crucible used in the method of the present invention.
FIG. 2 is a graph showing a change in contact area according to a single crystal solidification rate of a round bottom type quartz crucible and a flat bottom type quartz crucible.
FIG. 3 is a graph showing a change in evaporation area according to a single crystal solidification rate of a round bottom quartz crucible and a flat bottom quartz crucible.
FIG. 4 is a graph showing changes in contact area / evaporation area with respect to a single crystal solidification rate of a round bottom quartz crucible and a flat bottom quartz crucible.
FIG. 5 is a graph showing a change in oxygen concentration according to a pulling crystal length of a round bottom quartz crucible and a flat bottom quartz crucible.
FIG. 6 is a cross-sectional view of a conventional flat bottom quartz crucible.
FIG. 7 is a diagram showing a temperature distribution in a cross-sectional direction of the crucible.
Claims (1)
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP36757697A JP3986029B2 (en) | 1997-12-26 | 1997-12-26 | Silicon single crystal pulling method |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP36757697A JP3986029B2 (en) | 1997-12-26 | 1997-12-26 | Silicon single crystal pulling method |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH11199368A JPH11199368A (en) | 1999-07-27 |
| JP3986029B2 true JP3986029B2 (en) | 2007-10-03 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP36757697A Expired - Lifetime JP3986029B2 (en) | 1997-12-26 | 1997-12-26 | Silicon single crystal pulling method |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE602004029057D1 (en) * | 2003-05-30 | 2010-10-21 | Heraeus Quarzglas | QUARTZ GLASS LEVER FOR PULLING SILICON INCREDIENT |
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| Publication number | Publication date |
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| JPH11199368A (en) | 1999-07-27 |
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