WO2015083327A1 - Method for growing silicon single crystal - Google Patents
Method for growing silicon single crystal Download PDFInfo
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- WO2015083327A1 WO2015083327A1 PCT/JP2014/005723 JP2014005723W WO2015083327A1 WO 2015083327 A1 WO2015083327 A1 WO 2015083327A1 JP 2014005723 W JP2014005723 W JP 2014005723W WO 2015083327 A1 WO2015083327 A1 WO 2015083327A1
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- C—CHEMISTRY; METALLURGY
- C30—CRYSTAL GROWTH
- C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
- C30B15/00—Single-crystal growth by pulling from a melt, e.g. Czochralski method
- C30B15/20—Controlling or regulating
- C30B15/203—Controlling or regulating the relationship of pull rate (v) to axial thermal gradient (G)
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- C—CHEMISTRY; METALLURGY
- C30—CRYSTAL GROWTH
- C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
- C30B15/00—Single-crystal growth by pulling from a melt, e.g. Czochralski method
- C30B15/20—Controlling or regulating
- C30B15/206—Controlling or regulating the thermal history of growing the ingot
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- C—CHEMISTRY; METALLURGY
- C30—CRYSTAL GROWTH
- C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
- C30B29/00—Single crystals or homogeneous polycrystalline material with defined structure characterised by the material or by their shape
- C30B29/02—Elements
- C30B29/06—Silicon
Definitions
- the present invention relates to a method for growing a silicon single crystal by the Czochralski method (hereinafter referred to as “CZ method”).
- CZ method a method for growing defect-free crystals that do not generate point defects such as infrared scatterer defects and dislocation clusters such as LD (Interstitial-type Large Dislocation).
- a seed crystal is immersed in a silicon raw material melt stored in a quartz crucible in a chamber maintained in an inert gas atmosphere under reduced pressure, and the immersed seed crystal is gradually added. Pull up. Thereby, a silicon single crystal is grown continuously with the lower end of the seed crystal.
- FIG. 1 is a schematic diagram for explaining a situation where various defects occur based on the Boronkov theory.
- the pulling speed is V (mm / min)
- the temperature gradient in the pulling axis direction near the solid-liquid interface between the raw material melt in the crucible and the ingot (silicon single crystal) is G. (° C./mm)
- the ratio V / G is taken on the horizontal axis
- the concentration of vacancy-type point defects and the density of interstitial silicon type point defects are taken on the same vertical axis.
- the relationship with the defect concentration is schematically represented. It is explained that there is a boundary between a region where a vacancy type point defect occurs and a region where an interstitial silicon type point defect occurs, and that boundary is determined by V / G.
- the vacancy-type point defect originates from vacancies lacking silicon atoms constituting the crystal lattice, and a representative example of the aggregate of the vacancy-type point defects is COP.
- Interstitial silicon type point defects originate from interstitial silicon in which silicon atoms enter between crystal lattices, and LD is a representative example of an aggregate of interstitial silicon type point defects.
- V / G When V / G is in the range of (V / G) 1 to (V / G) 2 , a defect-free region in which neither a vacancy-type point defect nor an interstitial silicon-type point defect exists as an aggregate in a single crystal [ P] appears and neither COP nor LD defect including OSF occurs.
- region [V] (V / G is in the range of (V / G) 2 to (V / G) 3 ) adjacent to the defect-free region [P] there is an OSF region that forms an OSF nucleus.
- the defect-free region [P] is divided into a region [P V ] adjacent to the OSF region and a region [P I] adjacent to the region [ I ]. That is, in the defect-free region [P], when V / G is in the range of the critical point to (V / G) 2 , a region [P V ] in which vacant point defects that do not become aggregates predominately appear. In the range of V / G from (V / G) 1 to the critical point, a region [P I ] in which interstitial silicon point defects that do not become aggregates predominately appear.
- FIG. 2 is a schematic diagram showing the relationship between the pulling rate and the defect distribution during single crystal growth.
- a silicon single crystal is grown while gradually lowering the pulling speed V, and the grown single crystal is cut along the central axis (pulling axis) to form a plate-shaped specimen.
- the result of having observed the plate-shaped test piece by the X-ray topograph method after making Cu adhere and heat-treating is shown.
- V / G is generated in the hot zone, and aggregates of interstitial silicon type point defects are generated over the entire surface.
- the first critical point (V / G) is not higher than 1 and the second critical point (V / G) 2 is not higher than the second critical point (V / G) where no agglomeration of vacancy-type point defects is generated.
- the temperature gradient G in the pulling axis direction in the vicinity of the solid-liquid interface depends on the size of the hot zone in the vicinity of the solid-liquid interface, so that the hot zone is appropriately designed in advance prior to single crystal growth.
- the hot zone is composed of a water-cooled body arranged so as to surround the growing single crystal and a heat shield arranged so as to surround the outer peripheral surface and the lower end surface of the water-cooled body.
- the management indicators in designing the hot zone, and the temperature gradient G c of the pulling axis direction of the center portion of the single crystal, the temperature gradient G e in the pulling axis direction of the outer peripheral portion of the single crystal is used.
- the difference ⁇ G ( G e ⁇ ) between the temperature gradient G c at the center of the single crystal and the temperature gradient G e at the outer periphery of the single crystal.
- G c is set to be within 0.5 ° C./mm.
- Patent Document 2 the diameter is the subject of development over the single crystal 300 mm, taking into account the effect of the stress in the single crystal, the single crystal center portion of the pulling axis direction of the temperature gradient G c and the single A technique is disclosed in which a ratio G c / G e with the temperature gradient G e in the pulling axis direction of the crystal outer peripheral portion (hereinafter also referred to as “temperature gradient ratio”) is larger than 1.8.
- the technique disclosed in Patent Document 2 does not always provide a perfect defect-free crystal even though the effect of stress in the single crystal is taken into consideration. This is considered to be due to the influence of the stress distribution in the plane perpendicular to the pulling axis direction in the single crystal.
- JP 11-79889 A Japanese Patent No. 4819833
- the present invention has been made in view of the above problems, and in consideration of the in-plane distribution of stress acting on a single crystal during single crystal growth, grows defect-free crystals including large diameters with high accuracy.
- An object of the present invention is to provide a method for growing a silicon single crystal.
- the present inventors paid attention to the stress acting on the single crystal at the time of growing the single crystal, and conducted intensive studies by conducting a numerical analysis taking this stress into consideration. As a result, the following knowledge was obtained.
- FIG. 3 is a diagram showing the relationship between the stress ⁇ mean acting on the single crystal and the critical V / G.
- the stress distribution in the plane perpendicular to the pulling axis direction of the single crystal has regularity. If the stress in the center of the single crystal is determined, the stress distribution in the plane is the distance R in the radial direction from the center of the single crystal. Can be expressed as a function of Furthermore, by determining the stress at the center of the single crystal and determining the size of the gap between the lower end of the heat shield surrounding the single crystal and the liquid surface of the raw material melt in the quartz crucible, From the stress distribution, it is possible to grasp the optimum temperature gradient distribution G ideal (R) for growing defect-free crystals.
- the optimum temperature gradient distribution G ideal (R) as a management index, it becomes possible to perform an appropriate dimension design of the hot zone, and the optimum temperature gradient distribution G ideal (R) is used as a reference.
- the management range of the actual temperature gradient distribution Greal (R) it becomes possible to grow a defect-free crystal with high accuracy.
- the method for growing a silicon single crystal of the present invention includes: A method of pulling up and growing a silicon single crystal from a raw material melt in a crucible placed in a chamber by a CZ method, Using a single crystal growth apparatus in which a water-cooled body surrounding the single crystal being grown is arranged, and a heat shield surrounding the outer peripheral surface and the lower end surface of the water-cooled body is arranged,
- a single crystal having a radius of R max (mm) is grown
- G real (R ) an actual temperature gradient in the pulling axis direction at the position of the radius R (mm) from the center of the single crystal
- G ideal (R) is the optimum temperature gradient in the pulling axis direction at the radius R from the center of the single crystal
- the following equation (A) is satisfied within the range of 0 ⁇ R ⁇ R max ⁇ 35 (mm):
- the single crystal is pulled
- G ideal (R) is represented by the following formula (a).
- G ideal (R) [(0.1789 + 0.0012 ⁇ ⁇ mean (0)) / (0.1789 + 0.0012 ⁇ ⁇ mean (x))] ⁇ G real (0) (a)
- x R / R max
- ⁇ mean (0) and ⁇ mean (x) are represented by the following formula (b) and formula (c), respectively.
- ⁇ mean (0) ⁇ b 1 ⁇ G real (0) + b 2 (b)
- ⁇ mean (x) [n (x) ⁇ ( ⁇ mean (0) ⁇ mean (0.75)) ⁇ (N ⁇ ⁇ mean (0) ⁇ mean (0.75))] / (1 ⁇ N) ... (c)
- N 0.30827
- ⁇ mean (0.75) and n (x) are represented by the following formula (d) and formula (e), respectively.
- GAP is the distance (mm) between the lower end of the heat shield and the liquid surface of the raw material melt.
- the defect-free crystal is accurately measured. It becomes possible to train well.
- FIG. 1 is a schematic diagram for explaining a situation in which various defects occur based on the Boronkov theory.
- FIG. 2 is a schematic diagram showing the relationship between the pulling rate and the defect distribution during single crystal growth.
- FIG. 3 is a diagram showing the relationship between the average stress ⁇ mean acting in the single crystal and the critical V / G.
- FIG. 4 is a diagram showing the relationship between the in-plane average stress ⁇ mean (0) at the center of the single crystal and the temperature gradient G (0) at the center of the single crystal.
- FIG. 4 (a) shows a single crystal having a diameter of 300 mm.
- FIG. 5B shows the case of a single crystal having a diameter of 450 mm.
- FIG. 5 is a diagram showing the relationship between the relative radius r from the center of the single crystal and the in-plane average stress ⁇ mean (r) in the case of growing a single crystal having a diameter of 300 mm.
- FIG. 7B shows the case where the size of the liquid surface gap is 70 mm
- FIG. 7C shows the case where the size of the liquid surface gap is 90 mm.
- FIG. 6 is a diagram showing the relationship between the relative radius r from the center of the single crystal and the in-plane average stress ⁇ mean (r) in the case of growing a single crystal having a diameter of 450 mm.
- FIG. 60 mm shows the size of the surface gap 60 mm
- FIG. 5B shows the case where the size of the liquid surface gap is 90 mm
- FIG. 5C shows the case where the size of the liquid surface gap is 120 mm
- FIG. 7 is a diagram showing the relationship between the size of the liquid level Gap and the average stress ⁇ mean (0.75).
- FIG. 7A shows the case of a single crystal having a diameter of 300 mm
- FIG. The case of a single crystal of 450 mm is shown.
- FIG. 8 is a diagram showing the relationship between the relative radius r from the center of the single crystal and the standardized average stress n (r).
- FIG. 9 is a diagram showing the relationship between the relative radius r from the center of the single crystal and the optimum temperature gradient G ideal , where FIG.
- FIG. 10 is a diagram schematically showing a configuration of a single crystal growing apparatus to which the silicon single crystal growing method of the present invention can be applied.
- V is the pulling speed when growing a single crystal (unit: mm / min)
- G is the temperature gradient in the pulling axis direction near the solid-liquid interface of the single crystal (unit: ° C). / Mm)
- critical V / G the ratio of V to G (hereinafter also referred to as “critical V / G”) from which defect-free crystals are obtained is ⁇ .
- the critical V / G can be defined by the following equation (1) if the effect of stress acting on the single crystal during single crystal growth is introduced.
- the vicinity of the solid-liquid interface of the single crystal means that the temperature of the single crystal is in the range from the melting point to 1350 ° C.
- ⁇ ⁇ mean ⁇ 0 + ⁇ ⁇ ⁇ mean ...
- the stress in the crystal represents the critical V / G when the sigma mean.
- ⁇ 0 is a constant indicating the critical V / G when the stress in the crystal is zero.
- ⁇ is a stress coefficient
- ⁇ mean is an average stress (unit: MPa) in the single crystal.
- MPa average stress
- the single crystal having a diameter of 300 mm herein refers to a product (silicon wafer) having a diameter of 300 mm, specifically, a single crystal having a diameter of 300.5 to 330 mm when grown.
- a single crystal having a diameter of 450 mm means a product (silicon wafer) having a diameter of 450 mm, specifically, a single crystal having a diameter of 450.5 to 480 mm when grown.
- the average stress ⁇ mean is equivalent to the stress that causes the volume change of the single crystal during growth, and can be grasped by numerical analysis.
- the circumferential direction The vertical components ⁇ rr , ⁇ ⁇ , and ⁇ zz of the stress acting on each of the three planes, the plane along and the plane orthogonal to the pulling-up axis direction, are extracted, and these are totaled and divided by three.
- the positive mean stress ⁇ mean means tensile stress
- the negative means compressive stress.
- Equation (1) represents the relationship between the critical V / G in one dimension and the average stress ⁇ mean , but in order to grow a defect-free crystal, the in-plane perpendicular to the pulling axis direction of the single crystal It is necessary to think in.
- V / G (r) The ratio of V to G (r) from which defect-free crystals can be obtained (hereinafter also referred to as “critical V / G (r)”, expressed numerically as “(V / G (r)) cri ”) is a stress effect.
- V / G (r)) cri ⁇ 0 + ⁇ ⁇ ⁇ mean (r) (2)
- ⁇ mean (r) is an average stress (unit: MPa) at the position of the relative radius r from the center of the single crystal, and the distribution of the average stress in a plane orthogonal to the pulling axis direction of the single crystal. Indicates.
- the temperature gradient G (r) indicates the distribution of the temperature gradient in a plane orthogonal to the pulling axis direction of the single crystal
- the distribution of the optimal temperature gradient G (r) for growing a defect-free crystal I want to ask.
- the regularity of the distribution of the average stress ⁇ mean (r) in the plane is unknown.
- the control condition cannot be determined. Become.
- the size of the gap (hereinafter also referred to as “liquid level gap”) between the lower end of the heat shield surrounding the single crystal and the liquid level of the raw material melt in the quartz crucible is set. changed.
- the height in the pulling axis direction from the liquid surface of the raw material melt to the center of the solid-liquid interface (hereinafter also referred to as “interface height”) was changed.
- the average stress was calculated.
- FIG. 4 is a diagram showing the relationship between the in-plane average stress ⁇ mean (0) at the center of the single crystal and the temperature gradient G (0) at the center of the single crystal.
- FIG. 4 (a) shows a single crystal having a diameter of 300 mm.
- FIG. 5B shows the case of a single crystal having a diameter of 450 mm. This figure is obtained from the above analysis results. From the figure, the average stress ⁇ mean (0) at the center of the single crystal is proportional to the temperature gradient G (0) at the center of the single crystal regardless of the interface height, and the following equation (3) It was found that there was a correlation expressed.
- ⁇ mean (0) ⁇ b 1 ⁇ G (0) + b 2 (3)
- b 1 and b 2 are constants obtained by linear approximation from the calculated value of the in-plane average stress ⁇ mean (0) and the calculated value of the temperature gradient G (0) at the center of the single crystal, respectively.
- the liquid surface gap size is set to three values of 60 mm, 90 mm, and 120 mm, and in each case, the height of the interface is 8 types at intervals of 5 mm at 0 to 35 mm.
- the in-plane average stress ⁇ mean (r) at the position of the relative radius r from the center of the single crystal was calculated.
- FIG. 5 is a diagram showing the relationship between the relative radius r from the center of the single crystal and the in-plane average stress ⁇ mean (r) in the case of growing a single crystal having a diameter of 300 mm.
- FIG. 7B shows the case where the size of the liquid surface gap is 70 mm
- FIG. 7C shows the case where the size of the liquid surface gap is 90 mm.
- FIG. 6 is a diagram showing the relationship between the relative radius r from the center of the single crystal and the in-plane average stress ⁇ mean (r) in the case of growing a single crystal having a diameter of 450 mm.
- FIG. 5B shows the case where the size of the liquid surface gap is 90 mm
- FIG. 5C shows the case where the size of the liquid surface gap is 120 mm.
- FIG. 7 is a diagram showing the relationship between the size of the liquid level Gap and the average stress ⁇ mean (0.75).
- FIG. 7A shows the case of a single crystal having a diameter of 300 mm, and FIG. The case of a single crystal of 450 mm is shown. From the figure, it was found that the relationship between the size of the liquid level gap (GAP, unit: mm) and the average stress ⁇ mean (0.75) (unit: MPa) is expressed by the following equation (4). . That is, it was found that ⁇ mean (0.75) is determined if the size of the liquid level Gap is determined.
- ⁇ mean (0.75) d 1 ⁇ GAP ⁇ d 2 (4)
- ⁇ mean (r) The in-plane average stress ⁇ mean (r) described above was standardized as n (r) in the following equation (5).
- ⁇ mean (0) is the in-plane average stress at the center of the single crystal
- ⁇ mean (1) is the in-plane average stress at the outer periphery of the single crystal.
- n (r) [ ⁇ mean (r) ⁇ mean (1)] / [ ⁇ mean (0) ⁇ mean (1)] (5)
- FIG. 8 is a diagram showing the relationship between the relative radius r from the center of the single crystal and the standardized average stress n (r).
- the diameter of the single crystal is 300 mm and 450 mm
- the size of the liquid surface gap and the interface height are variously changed and calculated from the in-plane average stress ⁇ mean (r) under each change condition. Normalized mean stress n (r) was plotted. From the figure, it was found that the standardized average stress n (r) does not depend on the diameter of the single crystal, the size of the liquid surface gap, and the interface height.
- the in-plane average stress ⁇ mean (r) has regularity, and the in-plane average stress ⁇ mean (0) at the center of the single crystal and the in-plane average stress ⁇ mean (1) at the outer periphery of the single crystal are known.
- the distribution of the in-plane average stress ⁇ mean (r) can be grasped from the above equation (5).
- N 0.30827
- r 0.75 into the equation (5)
- the following equation (7) is obtained as an equation representing P (1).
- ⁇ mean (1) [ ⁇ mean (0.75) ⁇ N ⁇ ⁇ mean (0)] / [1-N] (7)
- ⁇ mean (r) can be obtained as ⁇ mean (1) in the above equation (3) and ⁇ mean (0.75) in the above equation (4).
- n (r) in the above formula (6) and the constant N can be expressed by the following formula (8).
- V / G (r) ⁇ 0 + ⁇ ⁇ ⁇ mean (r) (2)
- G ideal (r) [( ⁇ 0 + ⁇ ⁇ ⁇ mean (0)) / ( ⁇ 0 + ⁇ ⁇ ⁇ mean (r))] ⁇ G (0) (9)
- G ideal (R) [(0.1789 + 0.0012 ⁇ ⁇ mean (0)) / (0.1789 + 0.0012 ⁇ ⁇ mean (x))] ⁇ G real (0) (a)
- x R / R max
- G real (0) is an actual temperature gradient in the pulling axis direction at the center of the single crystal.
- ⁇ mean (0) and ⁇ mean (x) are expressed by the following formulas (b) and (c).
- the expressions (b) and (c) are the same as the expressions (3) and (8), respectively.
- ⁇ mean (0) is an average stress at the center of the single crystal, and may be a value obtained by equation (b) or may be a value obtained by another method.
- N 0.30827
- ⁇ mean (0.75) and n (x) are represented by the following formulas (d) and (e).
- FIG. 9 is a diagram showing the relationship between the relative radius r from the center of the single crystal and the optimum temperature gradient G ideal , where FIG. 9A shows the case of a single crystal having a diameter of 300 mm, and FIG. The cases of single crystals are shown respectively.
- the horizontal axis is r (R / R max ).
- the temperature gradient Greal (0) at the center of the single crystal is 1.5 ° C / mm, 2.0 ° C / mm, 2.5 ° C / mm, 3.0 ° C / mm and 3.5 ° C. / Mm and the size of the liquid level gap is 60 mm, 80 mm and 100 mm.
- the optimum temperature gradient can be grasped by determining the size of the temperature gradient G real (0) and the liquid level Gap.
- the distribution of the average stress ⁇ mean (r) in the plane perpendicular to the pulling axis direction of the single crystal is regular, and the distribution of the in-plane average stress ⁇ mean (r) is in the center of the single crystal.
- the temperature gradient G real (0) of the single crystal central portion or the stress ⁇ mean (0) of the single crystal central portion and the liquid level gap are determined in consideration of the effect of stress that affects the occurrence of point defects. This makes it possible to grasp the distribution of the temperature gradient G ideal (R) that is optimal for growing defect-free crystals.
- FIG. 8 is a diagram schematically showing a configuration of a single crystal growth apparatus to which the silicon single crystal growth method of the present invention can be applied.
- the single crystal growing apparatus is configured with a chamber 1 as an outer shell, and a crucible 2 is disposed at the center thereof.
- the crucible 2 has a double structure composed of an inner quartz crucible 2a and an outer graphite crucible 2b, and is fixed to the upper end of a support shaft 3 that can be rotated and lifted.
- a resistance heating type heater 4 surrounding the crucible 2 is disposed outside the crucible 2, and a heat insulating material 5 is disposed outside the crucible 2 along the inner surface of the chamber 1.
- a pulling shaft 6 such as a wire that is coaxial with the support shaft 3 and rotates in a reverse direction or the same direction at a predetermined speed is disposed.
- a seed crystal 7 is attached to the lower end of the pulling shaft 6.
- a cylindrical water-cooled body 11 surrounding the silicon single crystal 8 being grown is disposed above the raw material melt 9 in the crucible 2.
- the water-cooled body 11 is made of, for example, a metal having good thermal conductivity such as copper, and is forcibly cooled by cooling water that is circulated inside. This water-cooled body 11 plays a role of accelerating the cooling of the growing single crystal 8 and controlling the temperature gradient in the pulling axis direction of the single crystal central portion and the single crystal outer peripheral portion.
- a cylindrical heat shield 10 is arranged so as to surround the outer peripheral surface and the lower end surface of the water-cooled body 11.
- the heat shield 10 shields high temperature radiant heat from the raw material melt 9 in the crucible 2, the heater 4, and the side wall of the crucible 2 from the growing single crystal 8, and a solid-liquid interface that is a crystal growth interface. In the vicinity of, the diffusion of heat to the low-temperature water-cooled body 11 is suppressed, and the temperature gradient in the pulling axis direction of the single crystal central part and the single crystal outer peripheral part is controlled with the water-cooled body 11.
- a gas inlet 12 for introducing an inert gas such as Ar gas into the chamber 1 is provided in the upper part of the chamber 1.
- An exhaust port 13 for sucking and discharging the gas in the chamber 1 by driving a vacuum pump (not shown) is provided below the chamber 1.
- the inert gas introduced into the chamber 1 from the gas inlet 12 descends between the growing single crystal 8 and the water-cooled body 11, and the lower end of the heat shield 10 and the liquid level of the raw material melt 9 are reduced. After passing through the gap (liquid level gap), it flows toward the outside of the heat shield 10 and further to the outside of the crucible 2, and then descends outside the crucible 2 and is discharged from the exhaust port 13.
- solid material such as polycrystalline silicon filled in the crucible 2 is used for the heater 4 while the chamber 1 is maintained in an inert gas atmosphere under reduced pressure.
- the raw material melt 9 is formed by melting by heating.
- the pulling shaft 6 is lowered, the seed crystal 7 is immersed in the raw material melt 9, and the crucible 2 and the pulling shaft 6 are rotated in a predetermined direction while the pulling shaft 6 is gradually pulled up to grow a single crystal 8 connected to the seed crystal 7.
- the method for growing a silicon single crystal of the present invention is extremely useful for growing a large-diameter defect-free crystal in which various point defects such as OSF, COP, and LD do not occur.
Abstract
Description
CZ法によりチャンバ内に配置したルツボ内の原料融液からシリコン単結晶を引き上げて育成する方法であって、
育成中の単結晶を囲繞する水冷体を配置するとともに、この水冷体の外周面および下端面を包囲する熱遮蔽体を配置した単結晶育成装置を用い、
半径がRmax(mm)の単結晶の育成時に、単結晶の固液界面近傍にて、単結晶の中心から半径R(mm)の位置における実際の引き上げ軸方向の温度勾配をGreal(R)、単結晶の中心から半径Rの位置における引き上げ軸方向の最適温度勾配をGideal(R)とした場合、0<R<Rmax-35(mm)の範囲で、下記(A)式を満足する条件で単結晶の引き上げを行うことを特徴とする。
|Greal(R)-Gideal(R)|/Greal(R)<0.08 …(A)
上記(A)式中、Gideal(R)は下記(a)式で表される。
Gideal(R)=[(0.1789+0.0012×σmean(0))/(0.1789+0.0012×σmean(x))]×Greal(0) …(a)
上記(a)式中、x=R/Rmaxであり、σmean(0)およびσmean(x)は、それぞれ下記(b)式および(c)式で表される。
σmean(0)=-b1×Greal(0)+b2 …(b)
σmean(x)=[n(x)×(σmean(0)-σmean(0.75))-(N×σmean(0)-σmean(0.75))]/(1-N) …(c)
上記(c)式中、N=0.30827であり、σmean(0.75)およびn(x)は、それぞれ下記(d)式および(e)式で表される。
σmean(0.75)=d1×GAP-d2 …(d)
n(x)=0.959x3-2.0014x2+0.0393x+1 …(e)
上記(d)式中、GAPは前記熱遮蔽体の下端と前記原料融液の液面との間隔(mm)である。 The present invention has been completed based on the above findings, and the gist thereof is the following method for growing a silicon single crystal. That is, the method for growing a silicon single crystal of the present invention includes:
A method of pulling up and growing a silicon single crystal from a raw material melt in a crucible placed in a chamber by a CZ method,
Using a single crystal growth apparatus in which a water-cooled body surrounding the single crystal being grown is arranged, and a heat shield surrounding the outer peripheral surface and the lower end surface of the water-cooled body is arranged,
When a single crystal having a radius of R max (mm) is grown, an actual temperature gradient in the pulling axis direction at the position of the radius R (mm) from the center of the single crystal is expressed as G real (R ), Where G ideal (R) is the optimum temperature gradient in the pulling axis direction at the radius R from the center of the single crystal, the following equation (A) is satisfied within the range of 0 <R <R max −35 (mm): The single crystal is pulled under satisfying conditions.
| G real (R) −G ideal (R) | / G real (R) <0.08 (A)
In the above formula (A), G ideal (R) is represented by the following formula (a).
G ideal (R) = [(0.1789 + 0.0012 × σ mean (0)) / (0.1789 + 0.0012 × σ mean (x))] × G real (0) (a)
In the above formula (a), x = R / R max , and σ mean (0) and σ mean (x) are represented by the following formula (b) and formula (c), respectively.
σ mean (0) = − b 1 × G real (0) + b 2 (b)
σ mean (x) = [n (x) × (σ mean (0) −σ mean (0.75)) − (N × σ mean (0) −σ mean (0.75))] / (1− N) ... (c)
In the above formula (c), N = 0.30827, and σ mean (0.75) and n (x) are represented by the following formula (d) and formula (e), respectively.
σ mean (0.75) = d 1 × GAP−d 2 (d)
n (x) = 0.959x 3 -2.0014x 2 + 0.0393x + 1 (e)
In the above formula (d), GAP is the distance (mm) between the lower end of the heat shield and the liquid surface of the raw material melt.
|Greal(R)-Gideal(R)|/Greal(R)<0.05 …(B) In the growth method described above, it is preferable to pull up the single crystal under the condition that satisfies the following formula (B).
| G real (R) −G ideal (R) | / G real (R) <0.05 (B)
単結晶を育成するときの引き上げ速度をV(単位:mm/min)、単結晶の固液界面近傍における引き上げ軸方向の温度勾配をG(単位:℃/mm)とし、無欠陥結晶が得られるVとGの比(以下、「臨界V/G」ともいう。)をξとする。臨界V/Gは、単結晶育成時に単結晶中に作用する応力の効果を導入すれば、下記の(1)式で定義することができる。ここでいう単結晶の固液界面近傍とは、単結晶の温度が融点から1350℃までの範囲のことをいう。
ξσmean=ξ0+α×σmean …(1) 1. Expression of critical V / G in which stress effect is introduced V is the pulling speed when growing a single crystal (unit: mm / min), and G is the temperature gradient in the pulling axis direction near the solid-liquid interface of the single crystal (unit: ° C). / Mm), and the ratio of V to G (hereinafter also referred to as “critical V / G”) from which defect-free crystals are obtained is ξ. The critical V / G can be defined by the following equation (1) if the effect of stress acting on the single crystal during single crystal growth is introduced. Here, the vicinity of the solid-liquid interface of the single crystal means that the temperature of the single crystal is in the range from the melting point to 1350 ° C.
ξ σmean = ξ 0 + α × σ mean ... (1)
単結晶を育成するときの引き上げ速度をV(単位:mm/min)とする。また、育成する単結晶の半径をRmax(単位:mm)とし、単結晶の中心から半径R(単位:mm)の位置での固液界面近傍における引き上げ軸方向の温度勾配をG(r)(単位:℃/mm)とする。ここで、r=R/Rmaxであり、rを相対半径と呼ぶ。r=0は単結晶の中心を意味し、r=1はR=Rmaxであるため単結晶の外周を意味する。 2. Extension of the critical V / G formula introducing the stress effect to the in-plane distribution of the single crystal The pulling speed when growing the single crystal is V (unit: mm / min). Also, the radius of the single crystal to be grown is R max (unit: mm), and the temperature gradient in the pulling axis direction near the solid-liquid interface at the radius R (unit: mm) from the center of the single crystal is G (r). (Unit: ° C./mm). Here, r = R / R max , and r is called a relative radius. r = 0 means the center of the single crystal, and r = 1 means the outer periphery of the single crystal because R = R max .
(V/G(r))cri=ξ0+α×σmean(r) …(2) The ratio of V to G (r) from which defect-free crystals can be obtained (hereinafter also referred to as “critical V / G (r)”, expressed numerically as “(V / G (r)) cri ”) is a stress effect. Can be defined by the following formula (2) according to the above formula (1). Again, ξ 0 is 0.1789 and α is 0.0012. These values are the same regardless of whether a single crystal having a diameter of 300 mm is a growth target or a single crystal having a diameter of 450 mm. This is because these values do not depend on the diameter of the single crystal to be grown.
(V / G (r)) cri = ξ 0 + α × σ mean (r) (2)
単結晶中心部の温度勾配G(0)と単結晶中心部の面内平均応力σmean(0)の関係を検討した。この検討は、以下のように行った。直径が300mmの単結晶、または450mmの単結晶を育成する場合を前提にし、まずホットゾーンの条件を種々変更した総合伝熱解析により、各ホットゾーン条件での単結晶表面の輻射熱を算出し、次いで算出された各ホットゾーン条件での輻射熱と、種々変更した固液界面形状を境界条件として、各境界条件での単結晶内の温度を再計算した。ここで、ホットゾーンの条件変更としては、単結晶を包囲する熱遮蔽体の下端と石英ルツボ内の原料融液の液面との隙間(以下、「液面Gap」ともいう)の大きさを変更した。また、固液界面形状の条件変更としては、原料融液の液面から固液界面の中心部までの引き上げ軸方向の高さ(以下、「界面高さ」ともいう)を変更した。そして、各条件について、再計算によって得られた単結晶内温度の分布に基づき、平均応力の計算を実施した。 2-1. Relationship between Temperature Gradient and Average Stress in Single Crystal Center The relationship between the temperature gradient G (0) in the center of the single crystal and the in-plane average stress σ mean (0) in the center of the single crystal was examined. This examination was performed as follows. Based on the assumption that a single crystal with a diameter of 300 mm or a single crystal with a diameter of 450 mm is grown, first, the radiant heat of the surface of the single crystal under each hot zone condition is calculated by comprehensive heat transfer analysis with various changes in the hot zone conditions. Next, the temperature in the single crystal under each boundary condition was recalculated using the calculated radiant heat under each hot zone condition and variously changed solid-liquid interface shapes as boundary conditions. Here, as the hot zone condition change, the size of the gap (hereinafter also referred to as “liquid level gap”) between the lower end of the heat shield surrounding the single crystal and the liquid level of the raw material melt in the quartz crucible is set. changed. In addition, as a change in the condition of the solid-liquid interface shape, the height in the pulling axis direction from the liquid surface of the raw material melt to the center of the solid-liquid interface (hereinafter also referred to as “interface height”) was changed. And about each condition, based on the distribution of the temperature in a single crystal obtained by recalculation, the average stress was calculated.
σmean(0)=-b1×G(0)+b2 …(3)
ここで、b1およびb2はそれぞれ面内平均応力σmean(0)の計算値および単結晶中心部の温度勾配G(0)の計算値から一次近似で得られる定数である。直径300mmの単結晶では、b1=17.2、b2=40.8であり、厳密には、b1=17.211、b2=40.826である。直径450mmの単結晶では、b1=27.5、b2=44.7であり、厳密には、b1=27.548、b2=44.713である。 FIG. 4 is a diagram showing the relationship between the in-plane average stress σ mean (0) at the center of the single crystal and the temperature gradient G (0) at the center of the single crystal. FIG. 4 (a) shows a single crystal having a diameter of 300 mm. FIG. 5B shows the case of a single crystal having a diameter of 450 mm. This figure is obtained from the above analysis results. From the figure, the average stress σ mean (0) at the center of the single crystal is proportional to the temperature gradient G (0) at the center of the single crystal regardless of the interface height, and the following equation (3) It was found that there was a correlation expressed.
σ mean (0) = − b 1 × G (0) + b 2 (3)
Here, b 1 and b 2 are constants obtained by linear approximation from the calculated value of the in-plane average stress σ mean (0) and the calculated value of the temperature gradient G (0) at the center of the single crystal, respectively. In a single crystal having a diameter of 300 mm, b 1 = 17.2 and b 2 = 40.8, and strictly speaking, b 1 = 17.211 and b 2 = 40.826. In a single crystal having a diameter of 450 mm, b 1 = 27.5 and b 2 = 44.7, and strictly speaking, b 1 = 27.548 and b 2 = 44.713.
引き続き、上記の数値解析により、面内平均応力σmean(r)の規則性について検討した。直径300mmの単結晶については、液面Gapの大きさを、40mm、70mmおよび90mmの3種類の値に設定し、それぞれの場合について界面高さを0~25mmにおいて5mm間隔で6種類の高さに設定し、単結晶の中心から相対半径rの位置での面内平均応力σmean(r)を算出した。直径450mmの単結晶については、液面Gapの大きさを、60mm、90mmおよび120mmの3種類の値に設定し、それぞれの場合について界面高さを0~35mmにおいて5mm間隔で8種類の高さに設定し、単結晶の中心から相対半径rの位置での面内平均応力σmean(r)を算出した。 2-2. Regularity of in-plane average stress σ mean (r) (Part 1)
Subsequently, the regularity of the in-plane average stress σ mean (r) was examined by the above numerical analysis. For a single crystal with a diameter of 300 mm, the size of the liquid level gap is set to three values of 40 mm, 70 mm, and 90 mm, and in each case, the height of the interface is 6 types at 5 mm intervals at 0 to 25 mm. The in-plane average stress σ mean (r) at the position of the relative radius r from the center of the single crystal was calculated. For a single crystal having a diameter of 450 mm, the liquid surface gap size is set to three values of 60 mm, 90 mm, and 120 mm, and in each case, the height of the interface is 8 types at intervals of 5 mm at 0 to 35 mm. The in-plane average stress σ mean (r) at the position of the relative radius r from the center of the single crystal was calculated.
σmean(0.75)=d1×GAP-d2 …(4)
ここで、d1およびd2はそれぞれ、各々の液面Gapの大きさと単結晶の中心からの相対半径r=0.75の位置における平均応力σmean(0.75)の計算値から一次近似で得られる定数である。直径300mmの単結晶では、d1=0.108、d2=11.3であり、厳密には、d1=0.1084、d2=11.333である。直径450mmの単結晶では、d1=0.081、d2=11.2であり、厳密には、d1=0.0808、d2=11.233である。 FIG. 7 is a diagram showing the relationship between the size of the liquid level Gap and the average stress σ mean (0.75). FIG. 7A shows the case of a single crystal having a diameter of 300 mm, and FIG. The case of a single crystal of 450 mm is shown. From the figure, it was found that the relationship between the size of the liquid level gap (GAP, unit: mm) and the average stress σ mean (0.75) (unit: MPa) is expressed by the following equation (4). . That is, it was found that σ mean (0.75) is determined if the size of the liquid level Gap is determined.
σ mean (0.75) = d 1 × GAP−d 2 (4)
Here, d 1 and d 2 are first-order approximations from the calculated values of the average stress σ mean (0.75) at the position of the relative radius r = 0.75 from the size of each liquid level Gap and the center of the single crystal, respectively. Is a constant obtained by In a single crystal having a diameter of 300 mm, d 1 = 0.108 and d 2 = 11.3, and strictly speaking, d 1 = 0.1008 and d 2 = 11.333. In a single crystal having a diameter of 450 mm, d 1 = 0.081 and d 2 = 11.2, and strictly speaking, d 1 = 0.0808 and d 2 = 11233.
さらに、面内平均応力σmean(r)の規則性について検討した。ここでは、面内平均応力σmean(r)の形状が、液面Gapの大きさまたは界面高さに依存するか否かについて検討した。 2-3. Regularity of in-plane average stress σ mean (r) (2)
Furthermore, the regularity of the in-plane average stress σ mean (r) was examined. Here, it was examined whether or not the shape of the in-plane average stress σ mean (r) depends on the size of the liquid level Gap or the interface height.
n(r)=[σmean(r)-σmean(1)]/[σmean(0)-σmean(1)] …(5) The in-plane average stress σ mean (r) described above was standardized as n (r) in the following equation (5). In formula (5), σ mean (0) is the in-plane average stress at the center of the single crystal, and σ mean (1) is the in-plane average stress at the outer periphery of the single crystal.
n (r) = [σ mean (r) −σ mean (1)] / [σ mean (0) −σ mean (1)] (5)
n(r)=0.959r3-2.0014r2+0.0393r+1 …(6) FIG. 8 is a diagram showing the relationship between the relative radius r from the center of the single crystal and the standardized average stress n (r). In the figure, when the diameter of the single crystal is 300 mm and 450 mm, the size of the liquid surface gap and the interface height are variously changed and calculated from the in-plane average stress σ mean (r) under each change condition. Normalized mean stress n (r) was plotted. From the figure, it was found that the standardized average stress n (r) does not depend on the diameter of the single crystal, the size of the liquid surface gap, and the interface height. n (r) can be expressed by the following equation (6) from the results shown in FIG.
n (r) = 0.959r 3 -2.0014r 2 + 0.0393r + 1 (6)
以上の検討により、再掲する下記(3)式、(4)式および(6)式が得られた。また、検討の際に、下記(5)式を用いた。
σmean(0)=-b1×G(0)+b2 …(3)
σmean(0.75)=d1×GAP-d2 …(4)
n(r)=0.959r3-2.0014r2+0.0393r+1 …(6)
n(r)=[σmean(r)-σmean(1)]/[σmean(0)-σmean(1)] …(5)
ここで、直径が300mmの単結晶を育成する場合、上記(3)式中、b1=17.2、b2=40.8であり、上記(4)式中、d1=0.108、d2=11.3である。また、直径が450mmの単結晶を育成する場合、上記(3)式中、b1=27.5、b2=44.7であり、上記(4)式中、d1=0.081、d2=11.2である。 3. Derivation of distribution of optimum temperature gradient G ideal (r) The following expressions (3), (4), and (6) are obtained by the above examination. In the study, the following formula (5) was used.
σ mean (0) = − b 1 × G (0) + b 2 (3)
σ mean (0.75) = d 1 × GAP−d 2 (4)
n (r) = 0.959r 3 -2.0014r 2 + 0.0393r + 1 (6)
n (r) = [σ mean (r) −σ mean (1)] / [σ mean (0) −σ mean (1)] (5)
Here, when growing a single crystal having a diameter of 300 mm, b 1 = 17.2 and b 2 = 40.8 in the above formula (3), and d 1 = 0.108 in the above formula (4). , D 2 = 11.3. When a single crystal having a diameter of 450 mm is grown, in the above formula (3), b 1 = 27.5 and b 2 = 44.7, and in the above formula (4), d 1 = 0.081, d 2 = 11.2.
σmean(1)=[σmean(0.75)-N×σmean(0)]/[1-N] …(7) From equation (6), n (0.75) can be calculated as a constant N (= 0.30827). By using this constant N and substituting r = 0.75 into the equation (5), the following equation (7) is obtained as an equation representing P (1).
σ mean (1) = [σ mean (0.75) −N × σ mean (0)] / [1-N] (7)
σmean(r)=n(r)[σmean(0)-σmean(1)]+σmean(1)
=[n(r)×(σmean(0)-σmean(0.75))-(N×σmean(0)-σmean(0.75))]/(1-N) …(8) Furthermore, by modifying the above equation (5), σ mean (r) can be obtained as σ mean (1) in the above equation (3) and σ mean (0.75) in the above equation (4). And n (r) in the above formula (6) and the constant N can be expressed by the following formula (8).
σ mean (r) = n (r) [σ mean (0) −σ mean (1)] + σ mean (1)
= [N (r) × (σ mean (0) −σ mean (0.75)) − (N × σ mean (0) −σ mean (0.75))] / (1-N) (8) )
(V/G(r))cri=ξ0+α×σmean(r) …(2) Incidentally, as described above, the critical V / G (r) is expressed by the following equation (2).
(V / G (r)) cri = ξ 0 + α × σ mean (r) (2)
Gideal(r)=[(ξ0+α×σmean(0))/(ξ0+α×σmean(r))]×G(0) …(9) V can be regarded as a constant. Therefore, the optimum temperature gradient G ideal (r) for growing defect-free crystals can be expressed by the following equation (9) using G (0) where r = 0 in the equation (2).
G ideal (r) = [(ξ 0 + α × σ mean (0)) / (ξ 0 + α × σ mean (r))] × G (0) (9)
直径が300mmまたは450mmの単結晶を育成対象とする場合、ξ0は0.1789であり、αは0.0012であることから、これらの値を上記式(9)に代入して、単結晶の中心から半径R(単位:mm)の位置における引き上げ軸方向の最適温度勾配Gideal(R)(単位:MPa)は下記(a)式で表される。
Gideal(R)=[(0.1789+0.0012×σmean(0))/(0.1789+0.0012×σmean(x))]×Greal(0) …(a)
(a)式中、x=R/Rmaxであり、Greal(0)は、単結晶の中心における実際の引き上げ軸方向の温度勾配である。σmean(0)、σmean(x)は、下記(b)式および(c)式で表される。(b)式および(c)式は、それぞれ上記(3)式および(8)式と同じ式である。σmean(0)は、単結晶の中心における平均応力であり、(b)式で求めた値としてもよいし、他の方法で求めた値としてもよい。
σmean(0)=-b1×Greal(0)+b2 …(b)
σmean(x)=[n(x)×(σmean(0)-σmean(0.75))-(N×σmean(0)-σmean(0.75))]/(1-N) …(c)
直径が300mmの単結晶を育成する場合、上記(b)式中、b1=17.2、b2=40.8である。また、直径が450mmの単結晶を育成する場合、上記(b)式中、b1=27.5、b2=44.7である。(c)式中、N=0.30827であり、σmean(0.75)およびn(x)は下記(d)式および(e)式で表される。(d)式および(e)式は、それぞれ上記(4)式および(6)式と同じ式である。
σmean(0.75)=d1×GAP-d2 …(d)
n(x)=0.959x3-2.0014x2+0.0393x+1 …(e)
上記(d)式中、GAPは液面Gapの大きさ(単位:mm)である。直径が300mmの単結晶を育成する場合、d1=0.108、d2=11.3である。また、直径が450mmの単結晶を育成する場合、d1=0.081、d2=11.2である。 4). Condition of temperature gradient during single crystal growth When a single crystal having a diameter of 300 mm or 450 mm is to be grown, ξ 0 is 0.1789 and α is 0.0012. Substituting into 9), the optimum temperature gradient G ideal (R) (unit: MPa) in the pulling axis direction at a radius R (unit: mm) from the center of the single crystal is expressed by the following equation (a).
G ideal (R) = [(0.1789 + 0.0012 × σ mean (0)) / (0.1789 + 0.0012 × σ mean (x))] × G real (0) (a)
In the formula (a), x = R / R max , and G real (0) is an actual temperature gradient in the pulling axis direction at the center of the single crystal. σ mean (0) and σ mean (x) are expressed by the following formulas (b) and (c). The expressions (b) and (c) are the same as the expressions (3) and (8), respectively. σ mean (0) is an average stress at the center of the single crystal, and may be a value obtained by equation (b) or may be a value obtained by another method.
σ mean (0) = − b 1 × G real (0) + b 2 (b)
σ mean (x) = [n (x) × (σ mean (0) −σ mean (0.75)) − (N × σ mean (0) −σ mean (0.75))] / (1− N) ... (c)
When growing a single crystal having a diameter of 300 mm, b 1 = 17.2 and b 2 = 40.8 in the formula (b). When a single crystal having a diameter of 450 mm is grown, b 1 = 27.5 and b 2 = 44.7 in the above formula (b). In the formula (c), N = 0.30827, and σ mean (0.75) and n (x) are represented by the following formulas (d) and (e). The expressions (d) and (e) are the same as the expressions (4) and (6), respectively.
σ mean (0.75) = d 1 × GAP−d 2 (d)
n (x) = 0.959x 3 -2.0014x 2 + 0.0393x + 1 (e)
In the formula (d), GAP is the size (unit: mm) of the liquid level Gap. When growing a single crystal having a diameter of 300 mm, d 1 = 0.108 and d 2 = 11.3. When growing a single crystal having a diameter of 450 mm, d 1 = 0.081 and d 2 = 11.2.
|Greal(R)-Gideal(R)|/Greal(R)<0.08 …(A)
ここで、Greal(R)は、単結晶の中心から半径R(mm)の位置における実際の引き上げ軸方向の温度勾配である。 When growing a single crystal having a radius R max (mm), the following equation (A) is satisfied within the range of 35 mm or more from the outer periphery, that is, in the range of 0 <R <R max −35 (mm). The single crystal is pulled up. Thereby, it becomes possible to grow a defect-free single crystal with high accuracy.
| G real (R) −G ideal (R) | / G real (R) <0.08 (A)
Here, G real (R) is a temperature gradient in the actual pulling axis direction at a position of radius R (mm) from the center of the single crystal.
|Greal(R)-Gideal(R)|/Greal(R)<0.05 …(B) Moreover, in order to grow a single crystal without defect single crystals with higher accuracy, it is preferable to pull up the single crystal under conditions that satisfy the following formula (B).
| G real (R) −G ideal (R) | / G real (R) <0.05 (B)
図8は、本発明のシリコン単結晶の育成方法を適用できる単結晶育成装置の構成を模式的に示す図である。同図に示すように、単結晶育成装置は、その外郭をチャンバ1で構成され、その中心部にルツボ2が配置されている。ルツボ2は、内側の石英ルツボ2aと、外側の黒鉛ルツボ2bとから構成される二重構造であり、回転および昇降が可能な支持軸3の上端部に固定されている。 5. Silicon Single Crystal Growth FIG. 8 is a diagram schematically showing a configuration of a single crystal growth apparatus to which the silicon single crystal growth method of the present invention can be applied. As shown in the figure, the single crystal growing apparatus is configured with a
2b:黒鉛ルツボ、 3:支持軸、 4:ヒータ、 5:断熱材、
6:引き上げ軸、 7:種結晶、 8:シリコン単結晶、
9:原料融液、 10:熱遮蔽体、 11:水冷体、
12:ガス導入口、 13:排気口 1: chamber, 2: crucible, 2a: quartz crucible,
2b: graphite crucible, 3: support shaft, 4: heater, 5: heat insulating material,
6: Lifting shaft, 7: Seed crystal, 8: Silicon single crystal,
9: Raw material melt, 10: Thermal shield, 11: Water-cooled body,
12: Gas introduction port, 13: Exhaust port
Claims (4)
- チョクラルスキー法によりチャンバ内に配置したルツボ内の原料融液からシリコン単結晶を引き上げて育成する方法であって、
育成中の単結晶を囲繞する水冷体を配置するとともに、この水冷体の外周面および下端面を包囲する熱遮蔽体を配置した単結晶育成装置を用い、
半径がRmax(mm)の単結晶の育成時に、単結晶の固液界面近傍にて、単結晶の中心から半径R(mm)の位置における実際の引き上げ軸方向の温度勾配をGreal(R)、単結晶の中心から半径Rの位置における引き上げ軸方向の最適温度勾配をGideal(R)とした場合、0<R<Rmax-35(mm)の範囲で、下記(A)式を満足する条件で単結晶の引き上げを行う、シリコン単結晶の育成方法。
|Greal(R)-Gideal(R)|/Greal(R)<0.08 …(A)
上記(A)式中、Gideal(R)は下記(a)式で表される。
Gideal(R)=[(0.1789+0.0012×σmean(0))/(0.1789+0.0012×σmean(x))]×Greal(0) …(a)
上記(a)式中、x=R/Rmaxであり、σmean(0)およびσmean(x)は、それぞれ下記(b)式および(c)式で表される。
σmean(0)=-b1×Greal(0)+b2 …(b)
σmean(x)=[n(x)×(σmean(0)-σmean(0.75))-(N×σmean(0)-σmean(0.75))]/(1-N) …(c)
上記(c)式中、N=0.30827であり、σmean(0.75)およびn(x)は、それぞれ下記(d)式および(e)式で表される。
σmean(0.75)=d1×GAP-d2 …(d)
n(x)=0.959x3-2.0014x2+0.0393x+1 …(e)
上記(d)式中、GAPは前記熱遮蔽体の下端と前記原料融液の液面との間隔(mm)である。 A method for growing a silicon single crystal from a raw material melt in a crucible placed in a chamber by the Czochralski method,
Using a single crystal growth apparatus in which a water-cooled body surrounding the single crystal being grown is arranged, and a heat shield surrounding the outer peripheral surface and the lower end surface of the water-cooled body is arranged,
When a single crystal having a radius of R max (mm) is grown, an actual temperature gradient in the pulling axis direction at the position of the radius R (mm) from the center of the single crystal is expressed as G real (R ), Where G ideal (R) is the optimum temperature gradient in the pulling axis direction at the radius R from the center of the single crystal, the following equation (A) is satisfied within the range of 0 <R <R max −35 (mm): A method for growing a silicon single crystal, which pulls up the single crystal under satisfying conditions.
| G real (R) −G ideal (R) | / G real (R) <0.08 (A)
In the above formula (A), G ideal (R) is represented by the following formula (a).
G ideal (R) = [(0.1789 + 0.0012 × σ mean (0)) / (0.1789 + 0.0012 × σ mean (x))] × G real (0) (a)
In the above formula (a), x = R / R max , and σ mean (0) and σ mean (x) are represented by the following formula (b) and formula (c), respectively.
σ mean (0) = − b 1 × G real (0) + b 2 (b)
σ mean (x) = [n (x) × (σ mean (0) −σ mean (0.75)) − (N × σ mean (0) −σ mean (0.75))] / (1− N) ... (c)
In the above formula (c), N = 0.30827, and σ mean (0.75) and n (x) are represented by the following formula (d) and formula (e), respectively.
σ mean (0.75) = d 1 × GAP−d 2 (d)
n (x) = 0.959x 3 -2.0014x 2 + 0.0393x + 1 (e)
In the above formula (d), GAP is the distance (mm) between the lower end of the heat shield and the liquid surface of the raw material melt. - 下記(B)式を満足する条件で単結晶の引き上げを行う、請求項1に記載のシリコン単結晶の育成方法。
|Greal(R)-Gideal(R)|/Greal(R)<0.05 …(B) The method for growing a silicon single crystal according to claim 1, wherein the single crystal is pulled under conditions satisfying the following formula (B).
| G real (R) −G ideal (R) | / G real (R) <0.05 (B) - 直径が300mmの単結晶を育成する場合、上記(b)式中、b1=17.2、b2=40.8、上記(d)式中、d1=0.108、d2=11.3である、請求項1または2に記載のシリコン単結晶の育成方法。 When growing a single crystal having a diameter of 300 mm, in the above formula (b), b 1 = 17.2, b 2 = 40.8, in the above formula (d), d 1 = 0.108, d 2 = 11 3. The method for growing a silicon single crystal according to claim 1, which is .3.
- 直径が450mmの単結晶を育成する場合、上記(b)式中、b1=27.5、b2=44.7、上記(d)式中、d1=0.081、d2=11.2である、請求項1または2に記載のシリコン単結晶の育成方法。 When growing a single crystal having a diameter of 450 mm, in the above formula (b), b 1 = 27.5, b 2 = 44.7, in the above formula (d), d 1 = 0.081, d 2 = 11 The method for growing a silicon single crystal according to claim 1 or 2, wherein.
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