WO2023007830A1 - シリコン単結晶の製造方法及び単結晶引上装置 - Google Patents

シリコン単結晶の製造方法及び単結晶引上装置 Download PDF

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Publication number
WO2023007830A1
WO2023007830A1 PCT/JP2022/012659 JP2022012659W WO2023007830A1 WO 2023007830 A1 WO2023007830 A1 WO 2023007830A1 JP 2022012659 W JP2022012659 W JP 2022012659W WO 2023007830 A1 WO2023007830 A1 WO 2023007830A1
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Prior art keywords
single crystal
dopant
silicon
silicon single
silicon melt
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PCT/JP2022/012659
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English (en)
French (fr)
Japanese (ja)
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真吾 成松
高志 石川
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グローバルウェーハズ・ジャパン株式会社
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Priority to DE112022003764.4T priority Critical patent/DE112022003764T5/de
Publication of WO2023007830A1 publication Critical patent/WO2023007830A1/ja

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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
    • 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
    • C30B15/02—Single-crystal growth by pulling from a melt, e.g. Czochralski method adding crystallising materials or reactants forming it in situ to the melt
    • C30B15/04—Single-crystal growth by pulling from a melt, e.g. Czochralski method adding crystallising materials or reactants forming it in situ to the melt adding doping materials, e.g. for n-p-junction

Definitions

  • the present invention relates to a silicon single crystal manufacturing method and single crystal pulling apparatus, and more particularly to a silicon single crystal manufacturing method and single crystal pulling apparatus capable of keeping the resistivity along the axial direction within a standard range.
  • a silicon single crystal is grown by the Czochralski method (CZ method) by filling a quartz crucible placed in a chamber with polysilicon as a raw material and heating the polysilicon with a heater provided around the quartz crucible. It is melted to form a silicon melt. After that, a seed crystal (seed) attached to a seed chuck is immersed in the silicon melt, and the seed chuck is pulled up while rotating the seed chuck and the quartz crucible in the same direction or in the opposite direction.
  • CZ method Czochralski method
  • the silicon single crystals manufactured by such CZ method are used as semiconductor materials.
  • the resistivity of the grown silicon single crystal is adjusted by a dopant added to the silicon melt. Dopants are classified into n-type and p-type, and P (phosphorus) is often used as a dopant for growing an n-type crystal.
  • Patent Document 1 discloses a method of adding a main dopant and a sub-dopant having a polarity opposite to that of the main dopant and having a smaller segregation coefficient before crystal pulling (that is, counter-doping). is disclosed.
  • the decrease in resistivity due to the primary dopant is offset by the secondary dopant, making it possible to improve the resistivity distribution in the axial direction of the single crystal.
  • the most frequently used dopant in the production of n-type single crystals is phosphorus (P), which has a segregation coefficient of about 0.35.
  • Boron (B) which is widely used, has a segregation coefficient of about 0.8, which is larger than that of phosphorus (P), and the above technique cannot be used as it is.
  • Patent Document 2 discloses a method of continuously adding boron (B) as a secondary dopant to phosphorus (P) as a main dopant during single crystal pulling.
  • boron (B) as a secondary dopant
  • P phosphorus
  • B boron
  • the invention disclosed in Patent Document 3 has a sub-dopant thin rod and a main dopant thin rod in the chamber, and during the growth of the straight body part, Intermittently, the secondary dopant thin rod is pushed into the silicon melt, and when dislocations are formed, the silicon single crystal is remelted, and before pulling up, the main dopant thin rod is pushed into the silicon melt to remove the main dopant. is disclosed.
  • Patent Document 3 describes that granular dopants may be introduced into the melt instead of using the structure in which the thin dopant rods are pushed into the melt as described above.
  • the granular dopant is introduced into the melt, and if the granular dopant is simply introduced into the melt, there is a risk that the melt surface will ripple and dislocations will occur. There was a problem.
  • An object of the present invention is to introduce a sub-dopant during the pulling of a silicon single crystal to perform counter-doping for controlling resistivity in the axial direction. It is an object of the present invention to provide a method for producing a silicon single crystal that can supply a main dopant with the same configuration and make the concentration of the main dopant insufficient even when remelting is performed by dislocation. That is, regardless of the presence or absence of dislocations in the silicon single crystal, the resistivity along the axial direction can be controlled with high accuracy, and the yield can be improved. The purpose is to provide an apparatus.
  • a method for producing a silicon single crystal according to the present invention which has been devised to solve the above problems, forms a silicon melt in a crucible by heating a heater in a chamber, and grows a silicon single crystal by the Czochralski method.
  • a method for producing a silicon single crystal comprising the steps of: adding a main dopant to the silicon melt when forming the silicon melt in the crucible; and in the step of growing the silicon single crystal, continuously or intermittently adding a secondary dopant having a conductivity type opposite to that of the primary dopant to the silicon melt;
  • a step of conveying one or more chip-shaped dopants into the chamber by means of a pushing rod that can move back and forth with respect to the chamber Alternatively, a plurality of chip-shaped dopants are dropped into a funnel-shaped jig, and the chip-shaped dopants are introduced into the silicon melt through a narrow tube provided in the funnel-shaped jig.
  • the step of growing the silicon single crystal if the silicon single crystal is dislocated after the step of adding the sub-dopant to the silicon melt, the dislocated silicon single crystal is melted again. adding a chip-shaped dopant of the main dopant to the silicon melt using the pushing rod and the funnel-shaped jig; regrowing a silicon single crystal from the silicon melt; Preferably, the step of regrowing the single crystal further comprises continuously or intermittently adding a secondary dopant having a conductivity type opposite to that of the primary dopant to the silicon melt.
  • the step of applying a horizontal magnetic field to the silicon melt in the crucible is provided, and during the step of growing the silicon single crystal, the main dopant is opposite to the main dopant.
  • the dopant dropping position in the horizontal magnetic field is defined as 45° to 135° and 225° to 315° when the magnetic field application direction is defined as 0°. It is desirable to
  • chip-shaped sub-dopants having a conductivity type opposite to that of the main dopant are continuously or intermittently added.
  • the resistivity along the axial direction of the silicon single crystal can be kept within the standard range.
  • the chip-shaped dopant is added to the silicon melt, the chip-shaped dopant is pinpointed and dropped onto the exact position of the melt surface via a funnel-shaped jig arranged in the chamber. It is possible to suppress the occurrence of dislocations due to dopant injection without affecting the flow of the dopant.
  • the funnel-shaped jig is configured to receive the chip-shaped dopant conveyed by the pushing rod, the chip-shaped dopant is supplied to the funnel-shaped jig by free fall, and passes through the thin tube portion in a vigorous state. It falls on the melt surface of the silicon melt. Therefore, the dopant can be added to the silicon melt without clogging the narrow tube portion of the funnel-shaped jig.
  • the dopant can be added during the growth of the silicon single crystal, it can be realized with a relatively simple configuration, and the necessary amount of dopant can be added for each chip, so that the resistivity can be controlled accurately. can be
  • a single crystal pulling apparatus which has been made to solve the above-mentioned problems, forms a silicon melt in a crucible placed in a chamber heated by a heater, and processes silicon by the Czochralski method.
  • a shielding shield arranged to surround a silicon single crystal grown above the crucible, a conical portion attached to the shielding shield and opening upward, and the conical portion
  • a funnel-shaped jig consisting of a narrow tube extending downward from the lower top of the funnel-shaped jig, and one or more chip-shaped dopants placed on the tip end of the funnel-shaped jig. and a push rod to be introduced into the opening, wherein the chip-shaped dopant introduced into the opening of the conical portion of the funnel-shaped jig falls into the silicon melt through the narrow tube of the funnel-shaped jig.
  • the tip of the pushing rod is formed in the shape of a spoon and that the pushing rod is rotatable about its axis.
  • a horizontal magnetic field applying means for applying a horizontal magnetic field to the silicon melt in the crucible is provided. It is desirable that they are arranged in the regions of degrees to 135 degrees and 225 degrees to 315 degrees.
  • the chip-shaped sub-dopant having a conductivity type opposite to that of the main dopant is continuously or intermittently added.
  • the resistivity along the axial direction of the silicon single crystal can be kept within the standard range.
  • the chip-shaped dopant is added to the silicon melt, the chip-shaped dopant is pinpointed and dropped onto the exact position of the melt surface via a funnel-shaped jig arranged in the chamber. It is possible to suppress the occurrence of dislocations due to adhering to the crystal during growth riding on the flow of .
  • the funnel-shaped jig is configured to receive the chip-shaped dopant conveyed by the pushing rod, the chip-shaped dopant is supplied to the funnel-shaped jig by free fall, and passes through the thin tube portion in a vigorous state. It falls on the melt surface of the silicon melt. Therefore, the dopant can be added to the silicon melt without clogging the narrow tube portion of the funnel-shaped jig.
  • the dopant can be added during the growth of the silicon single crystal, it can be realized with a relatively simple configuration, and the necessary amount of dopant can be added for each chip, so that the resistivity can be controlled accurately. can be
  • the sub-dopant when a sub-dopant is introduced during the pulling of a silicon single crystal to perform counter-doping for controlling the resistivity in the axial direction, the sub-dopant can be supplied with a relatively simple configuration, and the crystal can be improved. Even when re-melting is performed by dislocation, the main dopant can be supplied with the same configuration to make the concentration of the main dopant insufficient. As a result, the resistivity along the axial direction can be accurately controlled regardless of the presence or absence of dislocations in the silicon single crystal, and the yield can be improved.
  • FIG. 1 is a cross-sectional view of a single crystal pulling apparatus in which the method for producing a silicon single crystal according to the present invention is carried out.
  • 2(a) and 2(b) are cross-sectional views showing a partially enlarged single crystal pulling apparatus of FIG.
  • FIG. 3 is a plan view showing the flow direction of the surface of the melt due to the influence of the horizontal magnetic field.
  • FIG. 4 is a flowchart of the method for manufacturing a silicon single crystal according to the present invention.
  • FIG. 5 is a flow chart following the flow chart of FIG.
  • FIG. 6 is a graph showing the results of Experiment 1 of the example.
  • FIG. 1 is a cross-sectional view of a single crystal pulling apparatus in which the method for producing a silicon single crystal according to the present invention is carried out.
  • This single crystal pulling apparatus 1 comprises a furnace body 10 formed by stacking a pull chamber 10b on a cylindrical main chamber 10a. and a quartz glass crucible 3 held by the carbon crucible 2 (hereinafter simply referred to as crucible 3).
  • the crucible 3 is rotatable around the vertical axis together with the rotation of the carbon crucible 2 .
  • a rotary drive unit 14 such as a rotary motor that rotates the carbon crucible 2 about a vertical axis and an elevation drive unit 15 that moves the carbon crucible 2 up and down are provided below the carbon crucible 2.
  • a rotation drive control section 14a is connected to the rotation drive section 14, and an elevation drive control section 15a is connected to the elevation drive section 15. As shown in FIG.
  • the single crystal pulling apparatus 1 also includes a side heater 4 that melts the semiconductor raw material (raw polysilicon) loaded in the crucible 3 to form a silicon melt M (hereinafter simply referred to as melt M), a side heater 4 that uses resistance heating, A pulling mechanism 9 is provided for winding up the wire 6 and pulling up the single crystal C to be grown. A seed crystal P is attached to the tip of the wire 6 of the pulling mechanism 9 .
  • a side heater 4 that melts the semiconductor raw material (raw polysilicon) loaded in the crucible 3 to form a silicon melt M (hereinafter simply referred to as melt M)
  • melt M silicon melt M
  • a pulling mechanism 9 is provided for winding up the wire 6 and pulling up the single crystal C to be grown.
  • a seed crystal P is attached to the tip of the wire 6 of the pulling mechanism 9 .
  • a heater control section 4a for controlling the amount of power supplied is connected to the side heater 4, and a rotational drive control section 9a for controlling the rotational drive of the lifting mechanism 9 is connected.
  • a magnetic field applying electromagnetic coil 8 horizontal magnetic field applying means
  • a horizontal magnetic field of predetermined strength 1000 to 4000 Gauss
  • the magnetic field applying electromagnetic coil 8 is connected to an electromagnetic coil control section 8a for controlling its operation. That is, in the present embodiment, a magnetic field applied CZ method (MCZ method) is performed in which a horizontal magnetic field is applied to the melt M to grow a single crystal. It is designed to stabilize crystallization.
  • a radiation shield 7 surrounding the single crystal C is arranged above the melt M formed in the crucible 3 .
  • the radiation shield 7 has openings at the top and bottom, shields the single crystal C during growth from excess radiation heat from the side heater 4 and the molten liquid M, and rectifies the gas flow in the furnace. .
  • the gap between the lower end of the radiation shield 7 and the melt surface M1 is controlled so as to maintain a predetermined distance constant (for example, 50 mm) depending on the desired properties of the single crystal to be grown.
  • the single crystal pulling apparatus 1 also includes an optical measurement sensor 16 such as a CCD camera for measuring the diameter of the silicon single crystal.
  • An optical measurement sensor 16 such as a CCD camera for measuring the diameter of the silicon single crystal.
  • a small window 10a1 for observation is provided in the upper surface of the main chamber 10a, and the change in position of the solid-liquid interface is detected from the outside of the small window 10a1. From the measured single crystal diameter and crystal length, the solidification rate represented by the weight of the single crystal/the weight of the initial silicon raw material is obtained, and the resistivity of the crystal is estimated.
  • a single crystal has a dopant concentration distribution in its length direction (vertical direction during pulling).
  • the dopant concentration distribution Cs when the solidification rate of silicon is g is represented by the following equation (1).
  • Cs k ⁇ C 0 ⁇ (1 ⁇ g) k ⁇ 1 (1)
  • k is the equilibrium segregation coefficient
  • C0 is the initial dopant concentration in the silicon melt.
  • the equilibrium segregation coefficient of boron (B), which is most commonly used as a p-type dopant, is 0.0. 8
  • the equilibrium segregation coefficient of phosphorus (P), which is most commonly used as an n-type dopant, is 0.35.
  • the relationship between the dopant concentration and the solidification rate in the growth of the silicon single crystal is obtained, and the dopant concentration is adjusted from this relationship so that the resistivity of the single crystal falls within the desired range.
  • the single crystal pulling apparatus 1 also includes a dopant supply jig 17 for supplying the melt M with dopants in the form of chips.
  • An opening 10a2 is provided in the upper surface of the main chamber 10a, and the lower end of a tubular rod portion 18 of a dopant supply jig 17 is connected to the opening 10a2.
  • a pushing rod 19 having a spoon-shaped tip is provided in the tube rod-shaped portion 18 so as to be able to advance and retreat in the axial direction.
  • a piston rod 20 is inserted into the push rod 19 , and the push rod 19 is configured to move forward and backward along the piston rod 20 when an air cylinder 21 is driven.
  • a gate valve 22 is provided in the cylinder pipe rod-shaped portion 18, and by opening the gate valve 22, the push rod 19 can advance and enter into the main chamber 10a.
  • An air cylinder driving portion 21a is connected to the air cylinder 21. As shown in FIG.
  • the pushing rod 19 is for supplying the chip-shaped dopant Dp to the silicon melt M.
  • the tip of the pushing rod 19 is provided with a spoon portion 19a. 1 to 10 chip-like dopants Dp can be placed on the spoon portion 19a.
  • the piston rod 20 and the pushing rod 19 are rotatable about their axes by a rotary drive unit 25. When the pushing rod 19 rotates about its axis, the dopant chips Dp placed on the spoon portion 19a move downward. Configured for free fall.
  • a rotation drive control section 25 a is connected to the rotation drive section 25 .
  • the dopant supply jig 17 has a funnel-shaped jig 23 made of quartz glass attached to the radiation shield 7 .
  • the funnel-shaped jig 23 has an open conical portion 23a and a thin tube portion 23b extending like a leg from the tip (lower top) of the conical portion 23a.
  • the opening 23a1 of the conical portion 23a is arranged to open upward, and when the pushing rod 19 is inserted most deeply into the main chamber 19a, the opening of the conical portion 23a is directly below the spoon portion 19a. 23a1 is to be located.
  • the opening diameter of the conical portion 23a is formed to be, for example, 50 mm to 100 mm so as to receive all the dopant chips Dp dropped from the spoon portion 19a without overflowing.
  • it is formed to be 10 mm to 15 mm so that it can pass through without clogging.
  • the distance d1 between the tip (lower end) of the thin tube portion 23b and the melt surface M1 is, for example, 5 mm to 50 mm so as not to adversely affect the state of the melt surface M1 as the radiation shield 7 moves up and down.
  • it is controlled to be between 20 mm and 30 mm.
  • the position of the tip of the narrow tube portion 23b is located at least at a distance of d2 (for example, a distance of 1/10 of the crystal diameter) or more from the outer surface of the single crystal C in the radial direction.
  • d2 for example, a distance of 1/10 of the crystal diameter
  • the position of the tip of the narrow tube portion 23b is located at least at a distance of d2 (for example, a distance of 1/10 of the crystal diameter) or more from the outer surface of the single crystal C in the radial direction.
  • the tip position of the thin tube portion 23b is arranged.
  • the flow direction on the melt surface changes, and in the direction perpendicular to the magnetic field application direction (0° direction), the outward flow from the crystal toward the quartz crucible is dominant. target.
  • the direction in which the magnetic field is applied there is a flow that is partially directed inward. In the former, the dropped dopant chips ride on the outward flow and melt while the dopant diffuses, so it is possible to create sufficient time for the added dopant to reach the solid-liquid interface. .
  • the dopant drop positions in the horizontal magnetic field are preferably in the regions of 45° to 135° and 225° to 315°. Note that this is not the case under no magnetic field and cusp magnetic field conditions because there is no inward surface flow around the entire circumference.
  • a dopant supply opening 18a that can be opened and closed for supplying the tip-shaped dopant Dp to the spoon portion 19a. That is, in a state where the gate valve 22 is closed, the spoon portion 19a is arranged at the height position of the dopant supply opening portion 18a, and the dopant tip Dp is 1 to 10% from the dopant supply opening portion 18a to the spoon portion 19a. are placed individually.
  • the dopant supply opening 18a is closed, the gate valve 22 is opened, and the push rod 19 is driven by the air cylinder 21 from the tip side to the main opening 10a2. It is adapted to enter the chamber 10a.
  • the spoon portion 19a is in a state where the chip-shaped dopant Dp is placed thereon, and when the spoon portion 19a is positioned directly above the opening 23a1 of the conical portion 23a, the rotation is driven.
  • the pushing rod 19 is rotated about its axis by the portion 25, and the chip-like dopant Dp falls from the spoon portion 19a to the funnel-like jig 23 as shown in FIG. 2(b).
  • the chip-shaped dopant Dp introduced into the melt M is a silicon single crystal with a thickness of 500 ⁇ m or more and 1000 ⁇ m or less sliced from each of the silicon single crystal containing the sub-dopant or the silicon single crystal containing the main dopant.
  • a silicon single crystal used as the dopant tip Dp is measured for resistivity and processed to a desired size. The dopant concentration can be calculated from the resistivity to control the amount of dopant added by the weight of the chip.
  • the tip-shaped dopant Dp must have a minimum weight so as not to be discharged out of the chamber by the inert gas passing directly above the melt surface M1 when it is introduced into the melt surface M1. Therefore, the surface area per chip is desirably 4 mm 2 or more. However, if the size of the chip is too large, it will take a long time to melt and the risk of sticking to the growing single crystal will increase, so 25 mm 2 or less is desirable. Similarly, the thickness of the chip is desirably 500 ⁇ m or more and 1000 ⁇ m or less from the viewpoint of weight and ease of dissolution.
  • the single crystal pulling apparatus 1 includes a computer 11 having a storage device 11a and an arithmetic control device 11b, and includes a rotation drive control section 14a, an elevation drive control section 15a, an electromagnetic coil control section 8a, and a rotation drive control section 9a.
  • the measurement sensor 16, the air cylinder drive section 21a, and the rotation drive control section 25a are each connected to the arithmetic control unit 11b.
  • the pulling is performed as follows. That is, first, the crucible 3 is loaded with raw polysilicon (for example, 150 kg) and silicon chips for dopant addition, and the crystal growth process is started based on the program stored in the storage device 11a of the computer 11.
  • raw polysilicon for example, 150 kg
  • silicon chips for dopant addition for example, silicon chips for dopant addition
  • the crystal growth process is started based on the program stored in the storage device 11a of the computer 11.
  • FIG. When manufacturing an n-type silicon single crystal, a silicon chip containing P (phosphorus) is used as a main dopant.
  • the inside of the furnace body 10 is made into a predetermined atmosphere (mainly an inert gas such as argon gas).
  • a furnace atmosphere is formed with a furnace pressure of 60 to 110 torr and an argon gas flow rate of 40 to 110 l/min.
  • the raw material polysilicon and the main dopant charged in the crucible 3 are melted by heating by the side heater 4 to form a molten liquid.
  • M step S1 in FIG. 4
  • silicon chips for dopant addition may be introduced into the crucible 3 while the raw material polysilicon is being melted.
  • a predetermined current is passed through the magnetic field applying electromagnetic coil 8, and a horizontal magnetic field is started to be applied with a magnetic flux density (for example, 3000 Gauss) set within the range of 1000 to 4000 Gauss in the melt M (step in FIG. 4 S2).
  • the pulling conditions are adjusted with parameters such as the power supplied to the side heater 4, the pulling speed, and the strength of the applied magnetic field, and the seed crystal P starts rotating around the axis at a predetermined rotational speed.
  • the direction of rotation is opposite to the direction of rotation of the crucible 3 .
  • the wire 6 is lowered to bring the seed crystal P into contact with the melt M, and after the tip of the seed crystal P is melted, necking is performed to form a neck portion P1.
  • the single crystal pulling process is started. That is, the crystal diameter is gradually expanded to form the shoulder portion C1, and the process shifts to the step of forming the straight body portion C2 as the product portion (step S3 in FIG. 4).
  • the computer 11 obtains the solidification rate of the silicon single crystal using the measurement result of the measurement sensor 16, and estimates the resistivity of the pulled single crystal based on this (see FIG. 4). step S4).
  • B boron
  • step S8 is added to the melt surface M1 as a secondary dopant having a conductivity type opposite to that of the main dopant.
  • the resistivity decreases. is added while adjusting the doping amount of the auxiliary dopant to an appropriate amount.
  • the auxiliary dopant is added each time the estimated resistance value is, for example, the lower limit + 1% of the lower limit (50.5 ⁇ in this case) or less. should be added.
  • the target resistance value is, for example, 1% of the upper limit value - the upper limit value (59.4 ⁇ in this case)
  • the chip-shaped dopant Dp may be added so that the resistance value approaches this value.
  • the dopant supply opening 18a is opened in the dopant supply jig 17, and 1 to 10 dopant chips Dp containing B (boron) are placed on the spoon 19a. Then, after the dopant supply opening 18a is closed and the gas in the cylinder tube rod-shaped portion 18 is replaced by a sub-pump (not shown), the gate valve 22 is opened and the push rod 19 is driven by the air cylinder 21. enters into the main chamber 10a from the opening 10a2 from the tip side. At this time, the dopant chip Dp is placed on the spoon portion 19a.
  • the resistivity along the axial direction of the single crystal C is maintained within the standard range.
  • the chip-shaped dopant Dp is supplied to the melt surface M1 via the funnel-shaped jig 23, it can be accurately pinpointed to a preset position on the melt surface M1.
  • by pinpointing the chip-shaped dopant Dp it is possible to suppress the generation of dislocations caused by adhering to the growing crystal along the flow of the melt surface.
  • single crystal growth is continued, and when the single crystal is pulled up to a desired length without dislocations, single crystal growth is completed (steps S6 and S7 in FIG. 4). That is, when the straight body portion C2 is formed to a predetermined length, the process shifts to the final tail portion step. and the melt M are separated to produce a silicon single crystal.
  • step S6 in FIG. 4 if dislocation occurs during the growth of the single crystal (step S6 in FIG. 4), and the solidification rate of the single crystal grown so far has not reached a specified value (step S9 in FIG. 5), the crystal is remelted. (step S10 in FIG. 5).
  • step S10 in FIG. 5 After the remelting, an amount of P (phosphorus) chip dopant Dp as the main dopant based on the solidification rate of the remelted single crystal is added to the melt surface M1 using the dopant supply jig 17 (FIG. 5 step S11). Thereby, the phosphorus concentration in the melt M can be sufficiently supplemented. After that, the process returns to step S2 in FIG. 4, and the single crystal C is pulled again.
  • the conductivity type opposite to that of the main dopant is continuously or intermittently
  • a chip-shaped sub-dopant (boron) having to the silicon melt the resistivity along the axial direction of the silicon single crystal C can be kept within the standard range.
  • the chip-shaped dopant Dp is added to the silicon melt M
  • the chip-shaped dopant is pinpointed and dropped to an accurate position on the melt surface M1 via a funnel-shaped jig arranged in the chamber. It is possible to suppress the occurrence of dislocations caused by adhering to the growing crystal while riding on the melt surface flow.
  • the funnel-shaped jig 23 is configured such that one or a plurality of chip-shaped dopants Dp placed on the spoon portion 19a at the tip of the pushing rod 19 is put into the funnel-shaped jig 23, the chip-shaped dopant Dp is dropped into the funnel-shaped jig by free fall. 23, and drops onto the melt surface M1 of the silicon melt M through the narrow tube portion 23b in a vigorous state. Therefore, the dopant can be added to the silicon melt M without clogging the narrow tube portion 23 b of the funnel-shaped jig 23 .
  • the structure for adding a dopant during the growth of the silicon single crystal C can be realized with a relatively simple structure, and the necessary amount of dopant can be added for each chip, so that the resistivity can be accurately controlled. can be made possible.
  • a horizontal magnetic field is applied to the silicon melt, but the present invention is not limited to a horizontal magnetic field, and may be a cusp magnetic field or a non-magnetic field. can be applied.
  • Experiment 1 In Experiment 1, 135 kg of silicon raw material was filled in a quartz crucible, and phosphorus was added as a main dopant and melted. Further, the distance between the radiation shield and the melt surface was set to 50 mm, the furnace pressure was 65 torr, argon gas was flowed at a flow rate of 90 l/min, and the strength of the horizontal magnetic field was set to 3000 Gauss.
  • the single crystal was grown at a crucible rotation speed of 0.5 rpm, a crystal rotation speed of 10.0 rpm (in the opposite direction to the crucible rotation), and a pulling rate of 0.55 mm/min, aiming at a crystal diameter of 200 mm.
  • the resistivity standard was set to 60 to 50 ⁇ cm, and the target resistivity at the start of the straight body portion was set to 59 ⁇ m.
  • Example 1 In Example 1, the single crystal was grown according to the present embodiment described above. The introduction timing and input amount including the auxiliary dopant were calculated from the solidification rate of the crystal, the phosphorus concentration in the melt, and the boron concentration in the chip. When the resistivity standard lower limit was approached, a tip-shaped dopant (secondary dopant) containing a desired boron concentration was set on the spoon portion at the tip of the push rod. After the gate valve was released, the tip of the spoon was brought close to a height of 10 mm from the upper opening of the funnel-shaped jig, and the spoon portion was rotated to introduce the chip-shaped dopant into the funnel-shaped jig.
  • secondary dopant secondary dopant
  • FIG. 6 shows changes in resistivity in the crystal growth direction. As shown in FIG. 6, the resistivity, which had decreased to near the lower limit of the specification, could be raised to near the upper limit of the specification each time counter-doping was repeated. As a result, it was confirmed that the resistivity yield can be significantly increased even for products with a narrow resistivity.
  • Comparative example 1 In Comparative Example 1, no auxiliary dopant was added during the growth of the silicon single crystal. Other conditions are the same as in Example 1. The results of Comparative Example 1 are shown in FIG. As shown in FIG. 6, when the secondary dopant is not added as in Comparative Example 1, as the solidification rate increases, the resistivity decreases along the axial direction, confirming that it is out of the standard. bottom.
  • Example 2 In Experiment 2, pulling was started under the same pulling conditions as in Example 1, and when counter-doping (addition of secondary dopants) was performed twice, the growth of the straight body was interrupted and the crystal was remelted. . Then, after remelting, the shortage of phosphorus atoms due to the boron added by the counter doping was added by chip-like silicon of the main dopant. After that, the pulling of the silicon single crystal was started, and the resistivity at the start of forming the straight body portion was estimated.
  • Examples 2 to 4 were carried out under the same conditions, and the resistivity at the start of the straight body portion before the suspension of pulling (before remelting) and the resistivity at the start of forming the straight body portion after remelting were estimated, verified.
  • the results of Examples 2-4 are shown in Table 1. As shown in Table 1, the resistivity was within the standard range before and after remelting, and the resistivity at the start of the straight body portion could be stabilized.
  • Example 3 In Experiment 3, in a horizontal magnetic field 3D computer simulation, a single crystal was pulled under the same conditions as in Example 1, and the flow direction of the melt surface during pulling was verified. In addition, as pulling conditions, the flow on the surface of the melt was observed for single crystals with diameters of 200 mm, 300 mm, and 450 mm. As a result, the flow direction on the surface of the melt changes at any of the above crystal diameters, and in the direction perpendicular to the magnetic field application direction (0° direction), the flow is outward from the crystal toward the quartz crucible. became dominant. On the other hand, in the direction in which the magnetic field was applied, there was a partial inward flow.
  • the dopant drop position in the horizontal magnetic field is preferably in the regions of 45° to 135° and 225° to 315° when the magnetic field application direction is defined as 0°. .

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