JP5121760B2 - Method of pulling a silicon single crystal - Google Patents
Method of pulling a silicon single crystal Download PDFInfo
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- JP5121760B2 JP5121760B2 JP2009063628A JP2009063628A JP5121760B2 JP 5121760 B2 JP5121760 B2 JP 5121760B2 JP 2009063628 A JP2009063628 A JP 2009063628A JP 2009063628 A JP2009063628 A JP 2009063628A JP 5121760 B2 JP5121760 B2 JP 5121760B2
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- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 title claims description 106
- 229910052710 silicon Inorganic materials 0.000 title claims description 106
- 239000010703 silicon Substances 0.000 title claims description 106
- 239000013078 crystal Substances 0.000 title claims description 37
- 238000000034 method Methods 0.000 title claims description 12
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 144
- 239000010453 quartz Substances 0.000 claims description 64
- 230000002093 peripheral effect Effects 0.000 claims description 33
- 239000007788 liquid Substances 0.000 claims description 32
- 238000002844 melting Methods 0.000 claims description 8
- 230000008018 melting Effects 0.000 claims description 8
- 229910021420 polycrystalline silicon Inorganic materials 0.000 claims description 8
- 239000012535 impurity Substances 0.000 claims description 7
- 238000010438 heat treatment Methods 0.000 claims description 6
- 239000000843 powder Substances 0.000 claims description 6
- 239000002994 raw material Substances 0.000 claims description 5
- 239000004065 semiconductor Substances 0.000 claims description 4
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 13
- 238000002425 crystallisation Methods 0.000 description 13
- 230000008025 crystallization Effects 0.000 description 13
- 239000001301 oxygen Substances 0.000 description 13
- 229910052760 oxygen Inorganic materials 0.000 description 13
- 238000004519 manufacturing process Methods 0.000 description 4
- 239000000203 mixture Substances 0.000 description 3
- 230000007423 decrease Effects 0.000 description 2
- 239000002184 metal Substances 0.000 description 2
- 238000004090 dissolution Methods 0.000 description 1
- 230000003628 erosive effect Effects 0.000 description 1
- 239000007789 gas Substances 0.000 description 1
- 239000012466 permeate Substances 0.000 description 1
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- Crystals, And After-Treatments Of Crystals (AREA)
Description
本発明は、シリコン単結晶の引き上げに用いる石英ルツボにおいて、ルツボ内周面に対するシリコン融液面の接触角を所定角度以上に調整することによって単結晶化率を高めた石英ルツボに関する。 The present invention relates to a quartz crucible used for pulling up a silicon single crystal and having a single crystallization rate increased by adjusting a contact angle of a silicon melt surface with respect to the inner peripheral surface of the crucible to a predetermined angle or more.
半導体シリコン単結晶は、一般に原料の多結晶シリコンを加熱溶融したシリコン融液から単結晶を引き上げる方法によって製造されており、この多結晶シリコンを溶融するために石英ガラスルツボが用いられている。この石英ルツボは天然石英粉や合成石英粉を原料として製造されており、例えば、ルツボ外周部は機械的強度を高めるために天然石英を用い、ルツボ内周部はシリコン単結晶の純度を高めるために合成石英粉を用いた石英ルツボが従来から用いられている。この内周側の合成石英ガラス層は実質的に無気泡の透明層であり、また引き上げ時の溶損を考慮して概ね１ｍｍ以上の層厚に形成されている（特許文献１）。このようなルツボ内周部が合成石英ガラス層によって形成された石英ルツボによれば不純物量が極めて少ない高抵抗のシリコン単結晶を引き上げることができる。 A semiconductor silicon single crystal is generally manufactured by a method of pulling up a single crystal from a silicon melt obtained by heating and melting polycrystalline silicon as a raw material, and a quartz glass crucible is used to melt the polycrystalline silicon. This quartz crucible is manufactured using natural quartz powder or synthetic quartz powder as the raw material. For example, the outer periphery of the crucible uses natural quartz to increase the mechanical strength, and the inner periphery of the crucible increases the purity of the silicon single crystal. Conventionally, a quartz crucible using synthetic quartz powder has been used. The synthetic quartz glass layer on the inner peripheral side is a substantially bubble-free transparent layer, and is formed with a layer thickness of approximately 1 mm or more in consideration of melting damage during pulling (Patent Document 1). A quartz crucible having such a crucible inner periphery formed of a synthetic quartz glass layer can pull up a high-resistance silicon single crystal with an extremely small amount of impurities.
一方、図１に示すように、ルツボ内周面とシリコン融液の液面が接触する部分において（Ａ）の部分は、石英ガラス面とシリコン融液および雰囲気ガスの三相界面部分（固体−液体−気体）であり、（Ａ）より下側の部分よりも石英ガラスの溶解速度が大きいので液中の酸素濃度が高い。従って、この（Ａ）部分の体積が大きいと熱対流によってシリコン融液全体に運ばれる酸素量が多くなり、シリコン単結晶の酸素濃度が高くなる。 On the other hand, as shown in FIG. 1, in the portion where the inner peripheral surface of the crucible and the surface of the silicon melt are in contact with each other, the portion (A) is a three-phase interface portion (solid- (Liquid-Gas), and the dissolution rate of quartz glass is higher than that of the portion below (A), so the oxygen concentration in the liquid is high. Therefore, if the volume of the portion (A) is large, the amount of oxygen carried to the entire silicon melt by thermal convection increases, and the oxygen concentration of the silicon single crystal increases.
本発明は、内周面部分が合成石英ガラス層によって形成された石英ルツボにおいて、従来の上記課題を解消したものであって、上記合成石英ガラス層表面に接触するシリコン融液面の接触角を所定角度以上に大きく保つことができるようにして、シリコン単結晶の酸素濃度を低く抑えるようにした石英ガラスルツボを提供することを目的とする。 The present invention eliminates the above-mentioned conventional problems in a quartz crucible having an inner peripheral surface portion formed of a synthetic quartz glass layer, and provides a contact angle of a silicon melt surface that contacts the surface of the synthetic quartz glass layer. An object of the present invention is to provide a quartz glass crucible that can be kept large at a predetermined angle or more so as to keep the oxygen concentration of the silicon single crystal low.
本発明のシリコン単結晶の引き上げを行う方法は、原料の多結晶シリコンを加熱溶融したシリコン融液から半導体シリコン単結晶を引き上げる方法において、
多結晶シリコンを溶融するための石英ガラスルツボが、ルツボ外周部に天然石英を用いルツボ内周部に合成石英粉を用いた石英ルツボとされ、ルツボ内周面の底部およびコーナー部が天然石英ガラスからなり、ルツボ内周面のコーナー部より上側部分が１ｍｍ以上の層厚に形成された合成石英ガラス層からなるとともに、引き上げ開始時のシリコン融液の液面レベルから液面下１０〜１５ｃｍまでの範囲に相当する内周面部分が層厚０．１ｍｍ〜０．５ｍｍの透明な合成石英ガラスからなる接触角調整層によって形成されており、該接触角調整層表面に対する上記シリコン融液液面の接触角が８０°以上として引き上げることを特徴とする。
本発明のシリコン単結晶の引き上げを行う方法は、原料の多結晶シリコンを加熱溶融したシリコン融液から半導体シリコン単結晶を引き上げる方法において、
多結晶シリコンを溶融するための石英ガラスルツボが、ルツボ外周部に天然石英を用いルツボ内周部に合成石英粉を用いた石英ルツボとされ、ルツボ内周面の底部およびコーナー部が１ｍｍ以上の層厚に形成された合成石英ガラスからなり、ルツボ内周面のコーナー部より上側部分が１ｍｍ以上の層厚に形成された合成石英ガラス層からなるとともに、引き上げ開始時のシリコン融液の液面レベルから液面下１０〜１５ｃｍまでの範囲に相当する内周面部分が層厚０．１ｍｍ〜０．５ｍｍの透明な合成石英ガラスからなる接触角調整層によって形成されており、該接触角調整層表面に対する上記シリコン融液液面の接触角が８０°以上として引き上げることを特徴とする。
本発明は、前記石英ガラスルツボにおける天然石英の不純物量がＮａ；０．０８ｐｐｍ、Ｋ；０．０８ｐｐｍ、Ｌｉ；０．１ｐｐｍ、Ａｌ；８．０ｐｐｍとされ、前記合成石英の不純物量がＮａ；０．０５ｐｐｍ、Ｋ；０．０３ｐｐｍ、Ｌｉ；０．０３ｐｐｍ、Ａｌ；１．０ｐｐｍとされることができる。
また以下の構成からなるシリコン単結晶引き上げ用石英ルツボとその製造方法および引き上げ方法に関することもできる。
The method of pulling up a silicon single crystal of the present invention is a method of pulling up a semiconductor silicon single crystal from a silicon melt obtained by heating and melting polycrystalline silicon as a raw material.
The quartz glass crucible for melting polycrystalline silicon is a quartz crucible using natural quartz for the outer periphery of the crucible and synthetic quartz powder for the inner periphery of the crucible. And a synthetic quartz glass layer having a thickness of 1 mm or more above the corner portion of the inner peripheral surface of the crucible, and from the liquid level of the silicon melt at the start of pulling up to 10-15 cm below the liquid level The inner peripheral surface portion corresponding to the range is formed by a contact angle adjusting layer made of transparent synthetic quartz glass having a layer thickness of 0.1 mm to 0.5 mm, and the silicon melt liquid surface with respect to the contact angle adjusting layer surface The contact angle is raised to 80 ° or more.
The method of pulling up a silicon single crystal of the present invention is a method of pulling up a semiconductor silicon single crystal from a silicon melt obtained by heating and melting polycrystalline silicon as a raw material.
A quartz glass crucible for melting polycrystalline silicon is a quartz crucible in which natural quartz is used for the outer peripheral part of the crucible and synthetic quartz powder is used for the inner peripheral part of the crucible. It consists of a synthetic quartz glass formed with a layer thickness, and is composed of a synthetic quartz glass layer formed with a layer thickness of 1 mm or more above the corner of the inner peripheral surface of the crucible, and the silicon melt liquid level at the start of pulling The inner peripheral surface portion corresponding to the range from the level to 10-15 cm below the liquid surface is formed by a contact angle adjusting layer made of transparent synthetic quartz glass having a layer thickness of 0.1 mm to 0.5 mm, and the contact angle adjustment The contact angle of the silicon melt surface with respect to the surface of the layer is raised to 80 ° or more, which is characterized by being raised.
In the present invention, the amount of impurities of natural quartz in the quartz glass crucible is Na; 0.08 ppm, K: 0.08 ppm, Li: 0.1 ppm, Al; 8.0 ppm, and the amount of impurities of the synthetic quartz is Na; 0.05 ppm, K; 0.03 ppm, Li; 0.03 ppm, Al; 1.0 ppm.
Further, the present invention can also relate to a quartz crucible for pulling a silicon single crystal having the following configuration, a manufacturing method thereof and a pulling method.
（１）シリコン単結晶の引き上げに用いる石英ルツボであって、ルツボ内周面の少なくともシリコン融液の液面に接する部分が透明な合成石英ガラス層によって形成されており、該合成石英ガラス層表面に対する上記液面の接触角が８０°以上であることを特徴とする石英ルツボ。
（２）引き上げ開始時のシリコン融液の液面レベルから液面下１０〜１５ｃｍまでの範囲に相当する内周面部分が透明な合成石英ガラス層によって形成されており、該合成石英ガラス層表面に対する上記液面の接触角が８０°以上である上記（１）に記載する石英ルツボ。
（３）シリコン単結晶の引き上げに用いる石英ルツボであって、ルツボ内周面の少なくともシリコン融液の液面に接する部分が透明な合成石英ガラス層によって形成されており、該合成石英ガラス層の層厚が１ｍｍ未満であることを特徴とする石英ルツボ。
（４）引き上げ開始時のシリコン融液の液面レベルから液面下１０〜１５ｃｍまでの範囲に相当する内周面部分が透明な合成石英ガラス層によって形成されており、該合成石英ガラス層の層厚が１ｍｍ未満である上記（３）に記載する石英ルツボ。
（５）シリコン単結晶の引き上げに用いる石英ルツボであって、ルツボ内周面の少なくともシリコン融液の液面に接する部分が透明な合成石英ガラス層によって形成されており、この合成石英ガラス層表面に対するシリコン融液面の接触角を８０°以上に保つように合成石英ガラス層の層厚を定めることを特徴とする石英ルツボの製造方法。
（６）上記（１）〜（５）の何れかに記載する石英ルツボを用いてシリコン単結晶の引き上げを行う方法。
(1) A quartz crucible used for pulling up a silicon single crystal, wherein at least a portion of the inner peripheral surface of the crucible that is in contact with the silicon melt surface is formed by a transparent synthetic quartz glass layer, and the surface of the synthetic quartz glass layer A quartz crucible, wherein the liquid surface has a contact angle of 80 ° or more.
(2) The inner peripheral surface portion corresponding to the range from the liquid level of the silicon melt at the start of pulling up to 10-15 cm below the liquid surface is formed of a transparent synthetic quartz glass layer, and the surface of the synthetic quartz glass layer The quartz crucible as described in (1) above, wherein the liquid surface has a contact angle of 80 ° or more.
(3) A quartz crucible used for pulling up a silicon single crystal, wherein at least a portion of the inner peripheral surface of the crucible that is in contact with the liquid surface of the silicon melt is formed by a transparent synthetic quartz glass layer. A quartz crucible having a layer thickness of less than 1 mm.
(4) The inner peripheral surface portion corresponding to a range from the liquid level of the silicon melt at the start of pulling up to 10 to 15 cm below the liquid surface is formed by a transparent synthetic quartz glass layer. The quartz crucible described in (3) above, wherein the layer thickness is less than 1 mm.
(5) A quartz crucible used for pulling up a silicon single crystal, and at least a portion of the inner peripheral surface of the crucible that is in contact with the liquid surface of the silicon melt is formed by a transparent synthetic quartz glass layer. A method for producing a quartz crucible, characterized in that a layer thickness of a synthetic quartz glass layer is determined so as to keep a contact angle of a silicon melt surface to 80 ° or more.
(6) A method of pulling up a silicon single crystal using the quartz crucible described in any one of (1) to (5) above.
本発明の石英ガラスルツボは、内周面が合成石英ガラス層によって形成された石英ルツボにおいて、合成石英ガラス層表面に対するシリコン融液面の接触角が大きいので、三相界面部分の体積が少なく、従ってシリコン単結晶の酸素濃度を低く抑えることができる。また、この接触角を大きくすることによってシリコン単結晶の結晶化率を高めることができる。 In the quartz glass crucible of the present invention, the quartz crucible whose inner peripheral surface is formed by the synthetic quartz glass layer has a large contact angle of the silicon melt surface to the surface of the synthetic quartz glass layer, so the volume of the three-phase interface portion is small, Therefore, the oxygen concentration of the silicon single crystal can be kept low. Moreover, the crystallization rate of the silicon single crystal can be increased by increasing the contact angle.
本発明の石英ルツボは、シリコン単結晶の引き上げに用いる石英ルツボであって、ルツボ内周面の少なくともシリコン融液の液面に接する部分が透明な合成石英ガラス層によって形成されており、この合成石英ガラス層表面に対するシリコン融液面の接触角が所定角度以上であることを特徴とする石英ルツボである。具体的には、例えば、上記合成石英ガラス層表面に対するシリコン融液面の接触角が８０°以上であることを特徴とする石英ルツボである。 The quartz crucible of the present invention is a quartz crucible used for pulling up a silicon single crystal, and at least a portion of the inner peripheral surface of the crucible that is in contact with the liquid surface of the silicon melt is formed by a transparent synthetic quartz glass layer. The quartz crucible is characterized in that the contact angle of the silicon melt surface with the quartz glass layer surface is a predetermined angle or more. Specifically, for example, the quartz crucible is characterized in that the contact angle of the silicon melt surface with respect to the surface of the synthetic quartz glass layer is 80 ° or more.
図１に示すように、シリコン単結晶引き上げ時において、ルツボ内周面のシリコン融液の液面が接触する部分は、石英ガラス面とシリコン融液および空気の三相界面部分（固体−液体−気体）であり、このシリコン融液の液面が接触する石英ガラスの種類によって、石英ガラス面に対するシリコン融液面の接触角θが大きく異なる。即ち、シリコン融液に対して合成石英ガラス層表面は濡れ性が大きいので、図１に示すように、シリコン融液が合成石英ガラス層表面に接触する液面が合成石英ガラス層表面に沿って上側に這い上がった状態になる。従って、シリコン融液面の合成石英ガラス層表面に対する接触角θが小さくなる。一方、天然石英層表面は濡れ性が小さい。このため図２に示すように、シリコン融液の接触液面が天然石英層表面に沿って浸透した状態にはならず、従って、天然石英ガラス層表面に対するシリコン融液面の接触角θは大きくなり、ほぼ直角に近い角度になる。 As shown in FIG. 1, when the silicon single crystal is pulled, the portion of the inner peripheral surface of the crucible where the liquid surface of the silicon melt comes into contact is the three-phase interface portion between the quartz glass surface and the silicon melt and air (solid-liquid- The contact angle θ of the silicon melt surface with respect to the quartz glass surface varies greatly depending on the type of quartz glass with which the liquid surface of the silicon melt contacts. That is, since the surface of the synthetic quartz glass layer has a high wettability with respect to the silicon melt, as shown in FIG. 1, the liquid surface where the silicon melt contacts the surface of the synthetic quartz glass layer is along the surface of the synthetic quartz glass layer. It will crawl up. Accordingly, the contact angle θ of the silicon melt surface with the synthetic quartz glass layer surface is reduced. On the other hand, the natural quartz layer surface has low wettability. Therefore, as shown in FIG. 2, the contact surface of the silicon melt does not permeate along the surface of the natural quartz layer. Therefore, the contact angle θ of the silicon melt surface with respect to the surface of the natural quartz glass layer is large. Thus, the angle is almost a right angle.
本発明者等の研究によれば、シリコン融液面の合成石英ガラス層表面に対する接触角θが大きいほど上記三相界面部分の体積が小さくなるので、シリコン単結晶の酸素濃度を低く抑えることができ、さらに天然石英の場合を除き、この接触角θが大きいほどシリコン単結晶の単結晶化率が向上することが見い出された。 According to the study by the present inventors, the volume of the three-phase interface portion decreases as the contact angle θ of the silicon melt surface with the synthetic quartz glass layer surface increases, so that the oxygen concentration of the silicon single crystal can be kept low. In addition, except for the case of natural quartz, it has been found that the single crystallization rate of the silicon single crystal increases as the contact angle θ increases.
具体的には、引き上げ条件等にもよるが、例えば、接触角θが概ね８０°以上であればシリコン単結晶の酸素濃度が低く、かつ８５％以上の単結晶化率を得ることができ、好ましくは接触角θが８５°以上であれば、９０％以上の高い単結晶化率を得ることができる。一方、この接触角θが小さく、例えば３５°〜５０°であると、シリコン単結晶の酸素濃度が高くなり、単結晶化率も６０％以下である。 Specifically, depending on the pulling conditions and the like, for example, if the contact angle θ is approximately 80 ° or more, the oxygen concentration of the silicon single crystal is low, and a single crystallization ratio of 85% or more can be obtained. Preferably, when the contact angle θ is 85 ° or more, a high single crystallization ratio of 90% or more can be obtained. On the other hand, when the contact angle θ is small, for example, 35 ° to 50 °, the oxygen concentration of the silicon single crystal is high, and the single crystallization rate is 60% or less.
なお、天然石英層表面はシリコン融液に対して濡れ性が小さいのでシリコン融液面の接触角は大きく、概ね９０°前後であるが、合成石英よりも不純物量が多いので、上記接触角θが大きくてもシリコン単結晶の単結晶化率は低く、概ね６０％程度である。従って、シリコン単結晶の単結晶化率を向上するには、シリコン融液に接するルツボ内周面を合成石英ガラス層によって形成し、かつ合成石英ガラス層表面に接触するシリコン融液の接触角を８０°以上、好ましくは８５°以上になるように形成するのが良い。 Since the natural quartz layer surface has low wettability with respect to the silicon melt, the contact angle of the silicon melt surface is large and is approximately 90 °. However, since the amount of impurities is larger than that of synthetic quartz, the contact angle θ Is large, the single crystallization rate of the silicon single crystal is low, approximately 60%. Therefore, in order to improve the single crystallization rate of the silicon single crystal, the inner peripheral surface of the crucible in contact with the silicon melt is formed by the synthetic quartz glass layer, and the contact angle of the silicon melt in contact with the surface of the synthetic quartz glass layer is increased. It is good to form so that it may become 80 degrees or more, preferably 85 degrees or more.
さらに、本発明者の研究によれば、ルツボ内表面部分の合成石英ガラス層表面に対するシリコン融液面の接触角θは、この液面が接触している合成石英ガラス層の層厚に応じて異なることが見い出された。すなわち、合成石英ガラス層表面に接触するシリコン融液の接触角θはシリコン融液の組成によっても異なるが、概ね、上記接触角θはこのシリコン融液が接触する合成石英ガラス層の層厚が薄いほど大きい。後述の実施例に示すように、合成石英ガラス層の層厚によってシリコン融液の接触角θが大きく異なることが見い出される。この結果、引き上げられたシリコン単結晶の酸素濃度も相違している。 Furthermore, according to the study of the present inventor, the contact angle θ of the silicon melt surface with respect to the surface of the synthetic quartz glass layer on the inner surface portion of the crucible depends on the layer thickness of the synthetic quartz glass layer with which the liquid surface is in contact. Different things were found. That is, the contact angle θ of the silicon melt contacting the surface of the synthetic quartz glass layer varies depending on the composition of the silicon melt, but the contact angle θ is generally the thickness of the synthetic quartz glass layer contacting the silicon melt. The thinner it is, the bigger it is. As shown in the examples described later, it is found that the contact angle θ of the silicon melt varies greatly depending on the layer thickness of the synthetic quartz glass layer. As a result, the oxygen concentration of the pulled silicon single crystal is also different.
後述の実施例において、合成石英ガラス層の層厚０．９ｍｍに対してシリコン融液の接触角θは８３°であり、合成石英ガラス層の層厚が薄いほど上記接触角θが大きく、例えば合成石英ガラス層厚０．２ｍｍにおいて上記接触角θは８８°である。この結果に基づいて、本発明の石英ルツボは、一例として、ルツボ内周面の少なくともシリコン融液の液面に接する部分が透明な合成石英ガラス層によって形成された石英ルツボにおいて、該合成石英ガラス層の層厚が１ｍｍ未満、好ましくは０．５ｍｍ以下であることを特徴とするものである。 In the examples described later, the contact angle θ of the silicon melt is 83 ° with respect to the layer thickness of 0.9 mm of the synthetic quartz glass layer, and the contact angle θ increases as the layer thickness of the synthetic quartz glass layer decreases. The contact angle θ is 88 ° when the synthetic quartz glass layer thickness is 0.2 mm. Based on this result, the quartz crucible of the present invention is, for example, a quartz crucible in which at least a portion of the inner peripheral surface of the crucible that is in contact with the liquid surface of the silicon melt is formed by a transparent synthetic quartz glass layer. The layer thickness is less than 1 mm, preferably 0.5 mm or less.
先に述べたように、合成石英ガラス層表面に対するシリコン融液の接触角は、シリコン融液の組成、すなわち微量成分の含有によって上記接触角θが変化するので、シリコン融液の組成に応じて、この接触角θが８０°以上になるように合成石英ガラス層の層厚を定めれば良い。本発明はこの接触角θが８０°以上になるようにシリコン融液の液面に接触する合成石英ガラス層の層厚を定める製造方法を含む。また、本発明はこの接触角θが８０°以上になるような合成石英ガラス層の層厚を有する石英ルツボを用いる引き上げ方法を含む。なお、ルツボ内周面の合成石英ガラス層はシリコン融液によって溶損するので、少なくとも０．１ｍｍ程度の層厚を有するものが好ましい。 As described above, the contact angle of the silicon melt with respect to the surface of the synthetic quartz glass layer varies depending on the composition of the silicon melt, that is, the contact angle θ depending on the inclusion of a trace component. The thickness of the synthetic quartz glass layer may be determined so that the contact angle θ is 80 ° or more. The present invention includes a manufacturing method for determining the layer thickness of the synthetic quartz glass layer in contact with the surface of the silicon melt so that the contact angle θ is 80 ° or more. The present invention also includes a pulling method using a quartz crucible having a layer thickness of the synthetic quartz glass layer such that the contact angle θ is 80 ° or more. Since the synthetic quartz glass layer on the inner peripheral surface of the crucible is melted by the silicon melt, it is preferable to have a layer thickness of at least about 0.1 mm.
また、上記接触角θはシリコン融液の粘度の影響を受け、粘度が低くなる高温時において、天然石英と合成石英とに対する接触角θの差が大きい。シリコン単結晶引き上げにおいて高温になるのは一般に引き上げ初期である。そこで、少なくとも引き上げ初期の液面位置付近のルツボ内周面を合成石英ガラス層によって形成し、シリコン融液の接触角が８０°以上になるようにすればよい。具体的には、引き上げ開始時のシリコン融液の液面に対して僅かに上側の位置、例えば数ｃｍ上側の位置から液面下１０〜１５ｃｍまでの範囲に相当する内周面部分を透明な合成石英ガラス層によって形成し、該合成石英ガラス層表面に対する上記液面の接触角が８０°以上になるようにすれば良い。なお、引き上げ開始時のシリコン融液の液面に対して僅かに上側の位置を便宜上、引き上げ開始時のシリコン融液の液面レベルと云う。 The contact angle θ is affected by the viscosity of the silicon melt, and the difference in the contact angle θ between natural quartz and synthetic quartz is large at high temperatures when the viscosity is low. In general, a silicon single crystal is pulled at a high temperature in the initial stage. Therefore, at least the inner peripheral surface of the crucible in the vicinity of the initial liquid surface position may be formed of a synthetic quartz glass layer so that the contact angle of the silicon melt is 80 ° or more. Specifically, the inner peripheral surface portion corresponding to a position slightly above the liquid level of the silicon melt at the start of pulling, for example, a range from several cm above to 10-15 cm below the liquid level is transparent. What is necessary is just to make it form with a synthetic quartz glass layer, and the contact angle of the said liquid level with respect to this synthetic quartz glass layer surface may be set to 80 degrees or more. For convenience, the position slightly above the liquid level of the silicon melt at the start of pulling is referred to as the liquid level of the silicon melt at the start of pulling.
引き上げ開始時のシリコン融液の液面レベルからその下側１０〜１５ｃｍまでの範囲に相当する内周面部分が透明な合成石英ガラス層によって形成されており、該合成石英ガラス層表面に対する上記液面の接触角が８０°以上である石英ルツボとしては、例えば、シリコン融液の組成にもよるが、引き上げ開始時のシリコン融液の液面レベルからその下側１０〜１５ｃｍまでの範囲に相当する部分の合成石英ガラス層の層厚が１ｍｍ未満、好ましくは０．５ｍｍ以下の石英ルツボであればよい。なお、引き上げ時の湯面は次第に下側に移るので、ルツボ内周面の引き上げ初期の湯面付近はシリコン融液との接触時間が短く、溶損量は比較的少ないので、合成石英ガラス層の層厚を薄くすることができる。 The inner peripheral surface portion corresponding to the range from the level of the silicon melt at the start of pulling up to the lower side of 10 to 15 cm is formed by a transparent synthetic quartz glass layer, and the liquid is applied to the surface of the synthetic quartz glass layer. The quartz crucible having a surface contact angle of 80 ° or more corresponds to, for example, the range from the silicon melt level at the start of pulling up to the lower 10 to 15 cm depending on the composition of the silicon melt. A quartz crucible having a layer thickness of less than 1 mm, preferably 0.5 mm or less, may be used for the synthetic quartz glass layer. Since the molten metal surface at the time of pulling gradually moves downward, the vicinity of the molten metal surface on the inner surface of the crucible is short in contact time with the silicon melt, and the amount of erosion loss is relatively small. The layer thickness can be reduced.
以上のように本発明の石英ルツボは、ルツボ内周面の少なくともシリコン融液の液面に接する部分が透明な合成石英ガラス層によって形成されており、該合成石英ガラス層表面に対する上記液面の接触角が８０°以上であることを特徴とするものであり、ルツボ内表面部分の全体を合成石英ガラス層によって形成したものでもよく、あるいは、引き上げ開始時のシリコン融液の液面レベルからその下側１０〜１５ｃｍまでの範囲に相当する部分の合成石英ガラス層によって形成したものでもよい。 As described above, in the quartz crucible of the present invention, at least a portion of the inner peripheral surface of the crucible that is in contact with the liquid surface of the silicon melt is formed by the transparent synthetic quartz glass layer, and the liquid surface with respect to the surface of the synthetic quartz glass layer is formed. The contact angle is 80 ° or more, and the entire inner surface portion of the crucible may be formed of a synthetic quartz glass layer, or from the level of the silicon melt at the start of pulling It may be formed by a portion of the synthetic quartz glass layer corresponding to the range of 10-15 cm on the lower side.
なお、ルツボのコーナー部および底部では天然石英ガラスでも合成石英ガラスでもシリコン融液が接触する三相界面の体積は小さくなり、両者間の有意差はなくなるので、何れの石英を用いてもよい。また、ルツボのコーナー部および底部の内周面に合成石英ガラスを用いた場合には、その層厚についても同様である。 Note that any quartz may be used because the volume of the three-phase interface with which the silicon melt is in contact with both the natural quartz glass and the synthetic quartz glass becomes small at the corner and bottom of the crucible, and there is no significant difference between the two. When synthetic quartz glass is used for the inner peripheral surface of the corner and bottom of the crucible, the same applies to the layer thickness.
本発明に係る上記石英ルツボを得るには、石英ルツボの製造方法において、ルツボ内周面の少なくともシリコン融液の液面に接する部分を透明な合成石英ガラス層によって形成し、該合成石英ガラス層表面に対するシリコン融液面の接触角が所定範囲、例えば８０°以上になるように合成石英ガラス層の層厚を定めれば良い。 In order to obtain the quartz crucible according to the present invention, in the quartz crucible manufacturing method, at least a portion of the inner peripheral surface of the crucible that is in contact with the liquid surface of the silicon melt is formed by a transparent synthetic quartz glass layer, and the synthetic quartz glass layer What is necessary is just to determine the layer thickness of the synthetic quartz glass layer so that the contact angle of the silicon melt surface with respect to the surface is within a predetermined range, for example, 80 ° or more.
本発明に係る上記石英ルツボを用いてシリコン単結晶の引き上げを行うことによって、酸素濃度が低いシリコン単結晶を得ることができ、またその単結晶化率も向上する。本発明の範囲はこの上記石英ルツボを用いてシリコン単結晶の引き上げを行う態様も含む。 By pulling up the silicon single crystal using the quartz crucible according to the present invention, a silicon single crystal having a low oxygen concentration can be obtained, and the single crystallization rate is also improved. The scope of the present invention includes an embodiment in which the silicon single crystal is pulled using the quartz crucible.
本発明を実施例によって具体的に示す。
内周面（コーナー部より上側部分）の合成石英ガラス層の層厚が異なる石英ガラスルツボを用い、シリコン単結晶の引き上げを行い、ルツボ内表面に対するシリコン融液面の接触角θ、シリコン単結晶の酸素濃度、単結晶化率を測定した。この結果を表１に示した。なお、使用した天然石英と合成石英の不純物量を表２に示した。また、接触角θは図３に示す装置を用いて測定した。この測定装置は図示するように、加熱炉１の内部に石英ルツボ２が収納されており、該ルツボ２の周りにヒータ３が設置されており、側方に温度センサー４が設けられている。ルツボ内周面に対するシリコン融液面の接触角θは通孔５を通じて測定器６によって計測される。
The present invention is specifically illustrated by examples.
Using a quartz glass crucible with a different thickness of the synthetic quartz glass layer on the inner peripheral surface (upper corner), the silicon single crystal is pulled up, the contact angle θ of the silicon melt surface with respect to the inner surface of the crucible, the silicon single crystal The oxygen concentration and the single crystallization rate were measured. The results are shown in Table 1. Table 2 shows the amount of impurities of natural quartz and synthetic quartz used. The contact angle θ was measured using the apparatus shown in FIG. As shown in the figure, a
表１に示すように、合成石英ガラス層の層厚が０．９ｍｍ以下のものは、シリコン融液面の接触角θが８３°以上であって、酸素濃度１．２Ｅ１８以下、および単結晶化率８７％以上である。一方、合成石英ガラス層の層厚が１．０ｍｍ以上のものは、シリコン融液面の接触角θが５１°以下と小さく、従って酸素濃度３．５Ｅ１８以上であり、単結晶化率は５９％以下である。なお、ルツボ内表面を天然石英によって形成した石英ルツボはシリコン融液面の接触角は大きく８９°であるが、単結晶化率は低く６０％である。 As shown in Table 1, when the synthetic quartz glass layer has a layer thickness of 0.9 mm or less, the contact angle θ of the silicon melt surface is 83 ° or more, the oxygen concentration is 1.2E18 or less, and single crystallization is performed. The rate is 87% or more. On the other hand, when the synthetic quartz glass layer has a thickness of 1.0 mm or more, the contact angle θ of the silicon melt surface is as small as 51 ° or less, and therefore the oxygen concentration is 3.5E18 or more, and the single crystallization rate is 59%. It is as follows. In addition, the quartz crucible in which the inner surface of the crucible is made of natural quartz has a large contact angle of the silicon melt surface of 89 °, but the single crystallization rate is low and 60%.
θ…接触角、１…加熱炉、２…石英ルツボ、３…ヒータ、４…温度センサー、５…通孔、６…測定器 θ: contact angle, 1 ... heating furnace, 2 ... quartz crucible, 3 ... heater, 4 ... temperature sensor, 5 ... through hole, 6 ... measuring instrument
Claims (2)
多結晶シリコンを溶融するための石英ガラスルツボが、ルツボ外周部に天然石英を用いルツボ内周部に合成石英粉を用いた石英ルツボとされ、ルツボ内周面の底部およびコーナー部が１ｍｍ以上の層厚に形成された合成石英ガラスからなり、ルツボ内周面のコーナー部より上側部分が１ｍｍ以上の層厚に形成された合成石英ガラス層からなるとともに、引き上げ開始時のシリコン融液の液面レベルから液面下１０〜１５ｃｍまでの範囲に相当する内周面部分が層厚０．１ｍｍ以上１ｍｍ未満の透明な合成石英ガラスからなる接触角調整層によって形成されており、該接触角調整層表面に対する上記シリコン融液液面の接触角が８０°以上として引き上げることを特徴とするシリコン単結晶の引き上げを行う方法。 In a method of pulling up a semiconductor silicon single crystal from a silicon melt obtained by heating and melting polycrystalline silicon as a raw material,
A quartz glass crucible for melting polycrystalline silicon is a quartz crucible in which natural quartz is used for the outer peripheral part of the crucible and synthetic quartz powder is used for the inner peripheral part of the crucible. It consists of a synthetic quartz glass formed with a layer thickness, and is composed of a synthetic quartz glass layer formed with a layer thickness of 1 mm or more above the corner of the inner peripheral surface of the crucible, and the silicon melt liquid level at the start of pulling The inner peripheral surface portion corresponding to a range from the level to 10-15 cm below the liquid surface is formed by a contact angle adjusting layer made of transparent synthetic quartz glass having a layer thickness of 0.1 mm or more and less than 1 mm, and the contact angle adjusting layer A method for pulling up a silicon single crystal, wherein the contact angle of the silicon melt surface with respect to the surface is raised to 80 ° or more.
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