WO2019107190A1 - Silicon single crystal, method for producing same, and silicon wafer - Google Patents

Silicon single crystal, method for producing same, and silicon wafer Download PDF

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Publication number
WO2019107190A1
WO2019107190A1 PCT/JP2018/042522 JP2018042522W WO2019107190A1 WO 2019107190 A1 WO2019107190 A1 WO 2019107190A1 JP 2018042522 W JP2018042522 W JP 2018042522W WO 2019107190 A1 WO2019107190 A1 WO 2019107190A1
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single crystal
silicon
silicon single
crystal
oxygen concentration
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PCT/JP2018/042522
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French (fr)
Japanese (ja)
Inventor
貴光 豊竹
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株式会社Sumco
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Priority to JP2019557153A priority Critical patent/JP6958632B2/en
Priority to CN201880077304.4A priority patent/CN111615569A/en
Priority to DE112018006080.2T priority patent/DE112018006080T5/en
Publication of WO2019107190A1 publication Critical patent/WO2019107190A1/en

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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
    • C30B15/30—Mechanisms for rotating or moving either the melt or the crystal
    • C30B15/305—Stirring of the melt
    • 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
    • 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
    • C30B30/00—Production of single crystals or homogeneous polycrystalline material with defined structure characterised by the action of electric or magnetic fields, wave energy or other specific physical conditions
    • C30B30/04—Production of single crystals or homogeneous polycrystalline material with defined structure characterised by the action of electric or magnetic fields, wave energy or other specific physical conditions using magnetic fields

Definitions

  • the present invention relates to a silicon single crystal, a method of manufacturing the same, and a silicon wafer, and more particularly to a method of manufacturing a silicon single crystal by a magnetic field applied CZ (MCZ) method and a silicon single crystal and a silicon wafer manufactured thereby.
  • MCZ magnetic field applied CZ
  • a silicon single crystal having a low interstitial oxygen concentration is preferably used as a silicon wafer for power semiconductors centering on an IGBT (Gate Insulated Bipolar Transistor).
  • IGBT Insulated Bipolar Transistor
  • the FZ method which does not use a quartz crucible serving as a source of oxygen is often used, but in order to improve mass productivity, the CZ method (Czochralski method) should be used. Is also being considered.
  • the MCZ method As one of the CZ methods for producing a silicon single crystal with a low oxygen concentration, the MCZ method is known which pulls up a silicon single crystal while applying a magnetic field. According to the MCZ method, melt convection can be suppressed, and dissolution of oxygen into the silicon melt due to erosion of the quartz crucible can be suppressed to reduce the oxygen concentration in the silicon single crystal.
  • the horizontal magnetic field strength is 2000 G (Gauss) or more
  • the rotation number of the quartz crucible is 1.5 rpm or less
  • the crystal rotation number is 7.0 rpm or less. It is described that a single crystal having an interstitial oxygen concentration of 6 ⁇ 10 17 atoms / cm 3 or less is grown by using a crystal pulling rate that makes dislocation cluster defects free.
  • Patent Document 2 a step of melting polycrystalline silicon in a crucible contained in a vacuum chamber to form a melt, a step of forming a cusp magnetic field in the vacuum chamber, and immersing a seed crystal in the melt And pulling the seed crystals from the melt to form a silicon single crystal ingot having a diameter of greater than about 150 mm, wherein the plurality of process parameters are such that the silicon ingot has an oxygen concentration less than about 5 ppma. It is described to adjust simultaneously.
  • the plurality of process parameters include crucible sidewall temperature, migration of silicon monoxide (SiO) from crucible to single crystal, and evaporation rate of SiO from the melt, with a crucible rotation rate of 1.3 to 2.2 rpm.
  • the crystal rotation speed is 8 to 14 rpm, and the magnetic field strength of the edge of the single crystal at the solid-liquid interface is 0.02 to 0.05 T (Tesla).
  • Patent Document 2 sets the crucible rotation speed to 1.3 to 2.2 rpm and the crystal rotation speed to 8 to 14 rpm, when the manufacturing conditions are actually applied, the oxygen concentration and There is a problem that the in-plane distribution of resistivity is not uniform.
  • an object of the present invention is to provide a silicon single crystal according to the Czochralski method to which a cusp magnetic field can be applied which can produce a silicon single crystal having a low oxygen concentration and high uniformity of in-plane distribution of oxygen concentration and resistivity. It is to provide a manufacturing method of Another object of the present invention is to provide a silicon single crystal and a silicon wafer having a low oxygen concentration and a high uniformity of in-plane distribution of oxygen concentration and resistivity.
  • the inventor of the present invention has conducted intensive studies on factors that change the in-plane distribution of oxygen concentration and resistivity in a silicon single crystal. As a result, when pulling up a single crystal while applying a cusp magnetic field, the single crystal is rotated at high speed. It has been found that the uniformity of the in-plane distribution of the oxygen concentration and the resistivity can be enhanced without causing an increase in the oxygen concentration or crystal deformation (dislocation) even if it is carried out. Generally, in order to produce a silicon single crystal with low oxygen concentration, it is necessary to slow the crystal rotation, but the in-plane uniformity of oxygen concentration is degraded. However, it becomes clear that even if the crystal rotation is made faster by using a cusp magnetic field, a silicon single crystal with low oxygen concentration can be obtained, and the in-plane distribution of oxygen concentration and resistivity is also stabilized. It is.
  • the present invention is based on such technical knowledge, and the method for producing a silicon single crystal according to the present invention is a method for producing a silicon single crystal by the Czochralski method for pulling up a silicon single crystal from a silicon melt while applying a cusp magnetic field.
  • the manufacturing method is characterized in that a crystal rotation speed when pulling up the silicon single crystal while rotating is 17 rpm or more and 19 rpm or less.
  • the rotational speed of the quartz crucible holding the silicon melt is preferably 4.5 rpm or more and 8.5 rpm or less.
  • the magnetic field strength of the cusp magnetic field is preferably 500 to 700 G, and the magnetic field center position in the vertical direction is preferably in the range of +40 mm to ⁇ 26 mm with respect to the liquid level position of the silicon melt. According to this condition, it is possible to enhance the uniformity of the in-plane distribution of the oxygen concentration and the resistivity in the single crystal.
  • the silicon single crystal according to the present invention has an oxygen concentration of 1 ⁇ 10 17 atoms / cm 3 or more and 8 ⁇ 10 17 atoms / cm 3 or less, and ROG (Radial Oxygen Gradient: ROG) in the crystal cross section orthogonal to the crystal growth direction.
  • the oxygen concentration gradient is 15% or less, and the RRG (Radial Resistivity Gradient) in the crystal cross section is 5% or less.
  • the silicon wafer according to the present invention has an oxygen concentration of 1 ⁇ 10 17 atoms / cm 3 or more and 8 ⁇ 10 17 atoms / cm 3 or less, an ROG of 15% or less, and an RRG of 5% or less. It is characterized by According to the present invention, a silicon wafer suitable as a substrate material of a power semiconductor can be provided.
  • the present invention it is possible to provide a method for producing a silicon single crystal having a low oxygen concentration and a high uniformity of in-plane distribution of oxygen concentration and resistivity. Further, according to the present invention, it is possible to provide a silicon single crystal and a silicon wafer which have a low oxygen concentration and high uniformity of in-plane distribution of oxygen concentration and resistivity.
  • FIG. 1 is a side cross-sectional view schematically showing the configuration of a single crystal production apparatus according to an embodiment of the present invention.
  • FIG. 2 is a flowchart illustrating a method of manufacturing a silicon single crystal according to the embodiment of the present invention.
  • FIG. 3 is a schematic cross-sectional view showing the shape of a silicon single crystal ingot.
  • FIG. 4 is a graph showing ROG of a silicon wafer sample according to Example 1 (CUSP).
  • FIG. 5 is a graph showing RRG of a silicon wafer sample according to Example 1 (CUSP).
  • FIG. 6 is a graph showing ROG of a silicon wafer sample according to Example 2 (CUSP).
  • FIG. 7 is a graph showing ROG of a silicon wafer sample according to Example 3 (CUSP).
  • FIG. 1 is a side cross-sectional view schematically showing the configuration of a single crystal production apparatus according to an embodiment of the present invention.
  • FIG. 2 is a flowchart illustrating a method of manufacturing a
  • FIG. 8 is a graph showing ROG of a silicon wafer sample according to Example 4 (CUSP).
  • FIG. 9 is a graph showing ROG of a silicon wafer sample according to Example 5 (CUSP).
  • FIG. 10 is a graph showing ROG of a silicon wafer sample according to Comparative Example 1 (CUSP).
  • FIG. 11 is a graph showing ROG of a silicon wafer sample according to Comparative Example 2 (HMCZ).
  • FIG. 12 is a graph showing RRG of a silicon wafer sample according to Comparative Example 2 (HMCZ).
  • FIG. 13 is a graph showing RRG of a silicon wafer sample according to Comparative Example 3 (FZ).
  • FIG. 1 is a side cross-sectional view schematically showing the configuration of a single crystal production apparatus according to an embodiment of the present invention.
  • the single crystal production apparatus 1 includes a chamber 10 (CZ furnace), a quartz crucible 11 holding a silicon melt 2 in the chamber 10, and a graphite susceptor 12 holding the quartz crucible 11. , A rotating shaft 13 supporting the susceptor 12, a shaft drive mechanism 14 for rotating and elevating the rotating shaft 13, a heater 15 disposed around the susceptor 12, an outer side of the heater 15 and an inner surface of the chamber 10. A heat insulating material 16 disposed along with the heat shield 17 disposed above the quartz crucible 11, and a single crystal pulling wire 18 disposed above the quartz crucible 11 and coaxial with the rotating shaft 13. And a wire winding mechanism 19 disposed above the chamber 10.
  • CZ furnace CZ furnace
  • quartz crucible 11 holding a silicon melt 2 in the chamber 10
  • a graphite susceptor 12 holding the quartz crucible 11.
  • a rotating shaft 13 supporting the susceptor 12
  • a shaft drive mechanism 14 for rotating and elevating the rotating shaft 13
  • a heater 15 disposed around the susceptor 12, an
  • the single crystal manufacturing apparatus 1 further includes a magnetic field generator 21 disposed outside the chamber 10, a CCD camera 22 for imaging the inside of the chamber 10, and an image processing unit 23 for processing an image captured by the CCD camera 22.
  • the control unit 24 controls the shaft drive mechanism 14, the heater 15, and the wire winding mechanism 19 based on the output of the image processing unit 23.
  • the chamber 10 is composed of a main chamber 10a and an elongated cylindrical pull chamber 10b connected to the upper opening of the main chamber 10a.
  • the quartz crucible 11, the susceptor 12, the heater 15 and the heat shield 17 are main chambers It is provided in 10a.
  • the pull chamber 10 b is provided with a gas inlet 10 c for introducing an inert gas (purge gas) such as argon gas into the chamber 10, and a gas for discharging the inert gas is provided at the lower part of the main chamber 10 a.
  • An outlet 10d is provided.
  • an observation window 10e is provided in the upper part of the main chamber 10a, and the growth state (solid-liquid interface) of the silicon single crystal 3 can be observed from the observation window 10e.
  • the quartz crucible 11 is a container made of quartz glass having a cylindrical side wall and a curved bottom.
  • the susceptor 12 closely contacts the outer surface of the quartz crucible 11 and holds the quartz crucible 11 so as to wrap the quartz crucible 11 in order to maintain the shape of the quartz crucible 11 softened by heating.
  • the quartz crucible 11 and the susceptor 12 constitute a double-structured crucible for supporting the silicon melt in the chamber 10.
  • the susceptor 12 is fixed to the upper end of a rotating shaft 13 extending in the vertical direction. Further, the lower end portion of the rotating shaft 13 is connected to a shaft driving mechanism 14 provided on the outside of the chamber 10 through the center of the bottom portion of the chamber 10.
  • the susceptor 12, the rotating shaft 13 and the shaft driving mechanism 14 constitute a rotating mechanism and an elevating mechanism of the quartz crucible 11.
  • the heater 15 is used to melt the silicon raw material filled in the quartz crucible 11 and maintain the molten state.
  • the heater 15 is a resistance heating heater made of carbon, and is a substantially cylindrical member provided so as to surround the entire circumference of the quartz crucible 11 in the susceptor 12. Furthermore, the outside of the heater 15 is surrounded by the heat insulating material 16, which enhances the heat retention in the chamber 10.
  • the thermal shield 17 suppresses the temperature fluctuation of the silicon melt 2 to form an appropriate hot zone in the vicinity of the solid-liquid interface, and prevents the heating of the silicon single crystal 3 by the radiant heat from the heater 15 and the quartz crucible 11.
  • the heat shield 17 is a cylindrical member made of graphite which covers the region above the silicon melt 2 except the pulling path of the silicon single crystal 3.
  • a circular opening larger than the diameter of the silicon single crystal 3 is formed at the center of the lower end of the heat shield 17, and a pulling path of the silicon single crystal 3 is secured. As illustrated, the silicon single crystal 3 is pulled upward through the opening of the thermal shield 17.
  • the diameter of the opening of the heat shield 17 is smaller than the diameter of the quartz crucible 11 and the lower end of the heat shield 17 is located inside the quartz crucible 11, so the rim upper end of the quartz crucible 11 is from the lower end of the heat shield 17 Even if the temperature is raised to the upper side, the heat shield 17 does not interfere with the quartz crucible 11.
  • the silicon melt is raised by raising the quartz crucible 11 so that the gap between the melt surface and the heat shield 17 becomes constant. While suppressing the temperature fluctuation of the liquid 2, it is possible to control the evaporation amount of SiO gas from the silicon melt 2 by making the flow velocity of the gas flowing near the melt surface constant. Therefore, the stability of the crystal defect distribution, the oxygen concentration distribution, the resistivity distribution and the like in the pulling axis direction of the single crystal can be improved.
  • FIG. 1 shows a state in which the silicon single crystal 3 in the process of being grown is hung on the wire 18.
  • a gas inlet 10c for introducing an inert gas into the chamber 10 is provided at the top of the pull chamber 10b, and a gas exhaust for evacuating the inert gas in the chamber 10 is provided at the bottom of the main chamber 10a.
  • An outlet 10d is provided.
  • the inert gas is introduced into the chamber 10 from the gas inlet 10c, and the introduction amount is controlled by a valve. Further, since the inert gas in the sealed chamber 10 is exhausted from the gas outlet 10 d to the outside of the chamber 10, the SiO gas or CO gas generated in the chamber 10 is recovered to keep the inside of the chamber 10 clean. Is possible.
  • a vacuum pump is connected to the gas discharge port 10d through a pipe, and the flow rate is controlled by a valve while suctioning the inert gas in the chamber 10 by the vacuum pump. Is maintained at a constant reduced pressure.
  • the magnetic field generation device 21 is configured using an upper coil 21a and a lower coil 21b opposed in the vertical direction, and generates a cusp magnetic field in the chamber 10 by supplying currents in opposite directions to the pair of magnetic field generation coils. .
  • “•” indicates the flow of current coming out of the paper
  • “x” indicates the flow of current going into the paper.
  • the cusp magnetic field is axisymmetric with respect to the pulling axis, and the magnetic fields cancel each other at the magnetic field center point, and the magnetic field strength in the vertical direction becomes zero.
  • a vertical magnetic field is present, and a radially directed horizontal magnetic field is formed.
  • the magnetic field center position of the cusp magnetic field be in the vicinity of the liquid surface of the silicon melt 2 and be set in the range of +40 mm to ⁇ 26 mm with respect to the liquid surface position.
  • the magnetic field strength of the cusp magnetic field is preferably 500 to 700 G.
  • the magnetic field strength is less than 500 G, it is difficult to pull up a silicon single crystal with a low oxygen concentration of 8 ⁇ 10 17 atoms / cm 3 or less. Further, it is difficult to stably output a magnetic field strength exceeding 700 G in the existing magnetic field generator, and it is desirable from the viewpoint of power consumption that the magnetic field strength is as low as possible.
  • the value of the magnetic field strength of the cusp magnetic field described in the present application is the center position of the magnetic field in the vertical direction and the side wall position of the quartz crucible in the horizontal direction.
  • the direction of the magnetic field lines is one direction, so there is an effect of suppressing convection in the direction orthogonal to the magnetic field lines, but convection in the direction parallel to the magnetic field lines can not be suppressed.
  • the direction of the magnetic lines of force is radial, and has symmetry in a plan view centering on the pulling axis, so that melt convection in the circumferential direction in the quartz crucible 11 can be suppressed. Therefore, it is possible to suppress the elution of oxygen from the quartz crucible 11 and reduce the oxygen concentration in the silicon single crystal.
  • An observation window 10e for observing the inside is provided above the main chamber 10a, and the CCD camera 22 is disposed outside the observation window 10e.
  • the CCD camera 22 captures an image of the boundary between the silicon single crystal 3 and the silicon melt 2 seen through the opening of the thermal shield 17 from the observation window 10e.
  • the CCD camera 22 is connected to the image processing unit 23, the photographed image is processed by the image processing unit 23, and the processing result is used by the control unit 24 to control the crystal pulling condition.
  • FIG. 2 is a flowchart illustrating a method of manufacturing a silicon single crystal according to the embodiment of the present invention.
  • FIG. 3 is a schematic cross-sectional view showing the shape of a silicon single crystal ingot.
  • the silicon raw material in the quartz crucible 11 is heated to generate the silicon melt 2 (step S11). Thereafter, the seed crystal attached to the tip of the wire 18 is lowered to be deposited on the silicon melt 2 (step S12).
  • the seed crystal is gradually pulled to carry out a single crystal pulling step of growing a single crystal.
  • the shoulder portion growing step (step S14) for forming 3b, and in the body portion growing step (step S15) for forming the body portion 3c (straight body portion with the crystal diameter kept constant) the crystal diameter gradually decreased
  • the tail portion growing step (step S16) for forming the tail portion 3d is sequentially performed, and the single crystal is finally separated from the melt surface to complete the tail portion growing step.
  • the silicon single crystal ingot 3 having the neck portion 3a, the shoulder portion 3b, the body portion 3c, and the tail portion 3d is completed in order from the upper end (top) to the lower end (bottom) of the single crystal.
  • the control unit 24 controls pulling conditions such as the pulling speed of the wire 18 and the power of the heater 15 so that the diameter of the silicon single crystal 3 becomes the target diameter. Further, the control unit 24 controls the height position of the quartz crucible 11 so that the distance between the melt surface and the heat shield 17 becomes constant.
  • the rotational speed of the silicon single crystal 3 is set in the range of 17 to 19 rpm. If the crystal rotational speed is less than 17 rpm, the uniformity of the in-plane distribution of the oxygen concentration can not be improved, and if it is greater than 19 rpm, not only the oxygen concentration in the crystal increases but also the crystal If the axis is deviated, the single crystal is easily deformed in a spiral shape due to eccentric rotation, and when the crystal is subjected to outer diameter grinding after crystal pulling up, a defective portion in which the crystal diameter is smaller than the wafer diameter is generated. Another problem is that it becomes easy to have dislocations due to crystal deformation.
  • the rotational speed of the quartz crucible 11 is preferably 4.5 to 8.5 rpm.
  • the rotation speed of the quartz crucible 11 is smaller than 4.5 rpm, the in-plane distribution of the oxygen concentration and the resistivity is deteriorated.
  • the rotation speed of the quartz crucible 11 is larger than 8.5 rpm, the amount of erosion of the quartz crucible is increased, and the oxygen concentration in the silicon melt becomes very high.
  • the oxygen concentration of the body portion 3c of the silicon single crystal 3 is 1 ⁇ 10 17 atoms / cm 3 to 8 ⁇ 10 17 atoms / cm 3 , and is within the crystal cross section orthogonal to the crystal growth direction.
  • ROG is 15% or less
  • RRG in the crystal cross section is 5% or less.
  • a silicon wafer cut out from this silicon single crystal 3 and processed has the same quality. That is, a silicon wafer having an oxygen concentration of 1 ⁇ 10 17 atoms / cm 3 or more and 8 ⁇ 10 17 atoms / cm 3 or less, an ROG of 15% or less, and an RRG of 5% or less can be obtained.
  • the oxygen concentrations specified in this specification are all measured values by FTIR (Fourier Transform Infrared Spectroscopy) specified in ASTM F-121 (1979).
  • resistance value is a measured value by the four-point probe method.
  • the oxygen concentration is low by pulling the single crystal while rotating at a high speed of 17 to 19 rpm in the Czochralski method applying a cusp magnetic field.
  • the single crystal production apparatus 1 shown in FIG. 1 is used as an example, but the detailed configuration of the single crystal production apparatus is not particularly limited, and various ones may be used. Can.
  • Example 1 In pulling up silicon single crystals for 200 mm diameter wafers by Czochralski method using Cusp (CUSP) magnetic field, the influence of cusp magnetic field and crystal rotational speed on in-plane distribution of oxygen concentration and resistivity was evaluated.
  • the magnetic field strength of the cusp magnetic field was set to 600 G, and the magnetic field center position was set to a position 40 mm above the liquid level position of the silicon melt.
  • the crucible rotation speed was 6 rpm, and the crystal rotation speed was 18 rpm.
  • the pulled three silicon single crystal ingots were processed to prepare a total of six silicon wafer samples each having a diameter of 200 mm.
  • the in-plane distribution of the oxygen concentration of the silicon wafer sample was measured.
  • the oxygen concentration was measured at a pitch of 5 mm in the radial direction from the center of the wafer. Since it is not possible to measure the oxygen concentration at the outermost periphery of the wafer, the measurement range of the oxygen concentration in the wafer plane is the range from the center of the wafer to 95 mm in the radial direction (measurement exclusion width of wafer periphery: 5 mm) .
  • the ROG Ring Oxygen Gradient
  • the in-plane distribution of the resistivity of the silicon wafer sample was measured.
  • the resistivity was measured by the four probe method at a pitch of 2 mm in the radial direction from the center of the wafer. Since the resistivity of the outermost periphery of the wafer can not be measured, the measurement range of resistivity within the wafer surface is the range from the center of the wafer to 96 mm in the radial direction (measurement exclusion width of wafer outer periphery: 4 mm) .
  • RRG Ring Resistivity Gradient
  • the formula for calculating RRG is as follows.
  • RRG (%) ⁇ ( ⁇ Max - ⁇ Min ) / ⁇ Min ⁇ ⁇ 100
  • FIG. 4 is a graph showing the oxygen concentration distribution of a silicon wafer sample. As shown in the drawing, the oxygen concentration in the surface of each wafer sample was 3 ⁇ 10 17 atoms / cm 3 or less, and the ROG was 7.1 to 14.8%.
  • FIG. 5 is a graph showing the resistivity distribution of a silicon wafer sample. As shown, the in-plane resistivity distribution of all silicon wafers was 3.5 to 4.9%.
  • Example 2 After pulling up a silicon single crystal under the same conditions as Example 1 except that the crystal rotation speed was 17 rpm, the oxygen concentration distribution and ROG of the silicon wafer sample obtained by processing this were the same as Example 1 I asked for. As a result, as shown in FIG. 6, the oxygen concentration in the wafer plane was 3 ⁇ 10 17 atoms / cm 3 or less, and the ROG was about 12.3%.
  • Example 3 After pulling up a silicon single crystal under the same conditions as Example 1 except that the crystal rotation speed was 19 rpm, the oxygen concentration distribution and ROG of the silicon wafer sample obtained by processing this were the same as Example 1 I asked for. As a result, as shown in FIG. 7, the oxygen concentration in the wafer surface was 3 ⁇ 10 17 atoms / cm 3 or less, and the ROG was about 7.5%.
  • Example 4 Silicon obtained by processing a silicon single crystal after pulling up a silicon single crystal under the same conditions as Example 1 except that the central position of the cusp magnetic field was set 7 mm above the liquid level position of the silicon melt.
  • the oxygen concentration distribution and ROG of the wafer sample were determined under the same conditions as in Example 1. As a result, as shown in FIG. 8, the oxygen concentration in the wafer plane was 4.3 ⁇ 10 17 atoms / cm 3 or less, and the ROG was 5.9 to 11.7%.
  • Example 5 Silicon obtained by processing a silicon single crystal after pulling up a silicon single crystal under the same conditions as Example 1 except that the center position of the cusp magnetic field was set to a position 26 mm downward from the liquid level position of the silicon melt
  • the oxygen concentration distribution and ROG of the wafer sample were determined under the same conditions as in Example 1.
  • the oxygen concentration in the wafer surface was 5.3 ⁇ 10 17 atoms / cm 3 or less, and the ROG was 3.0 to 10.4%.
  • Comparative Example 1 After pulling up a silicon single crystal under the same conditions as Example 1 except that the crystal rotational speed was changed to 9 rpm, the oxygen concentration distribution and ROG of the silicon wafer sample obtained by processing this were the same as Example 1 I asked for. As a result, as shown in FIG. 10, the oxygen concentration in the wafer surface is 5.7 ⁇ 10 17 atoms / cm 3 or less, the ROG is 84.8 to 135.1%, and the in-plane uniformity of the oxygen concentration is It was very bad.
  • Comparative Example 2 The silicon single crystal was pulled up by the HMCZ method applying a horizontal magnetic field. The crystal rotation speed at this time was 5 rpm. Thereafter, the in-plane distribution of oxygen concentration and resistivity of a silicon wafer sample obtained by processing a silicon single crystal was determined under the same conditions as in Example 1. As a result, as shown in FIG. 11, although the oxygen concentration in the wafer surface became 3.1 ⁇ 10 17 atoms / cm 3 or less, the ROG became 57.3 to 83.4%, and the in-plane of the oxygen concentration became The uniformity was bad. Further, as shown in FIG. 12, RRG was 3.2 to 5.8%, and the in-plane uniformity of the resistivity was good.
  • Comparative Example 3 After producing a silicon single crystal for a wafer of 200 mm in diameter by the FZ method, the in-plane distribution of resistivity of a 200 mm diameter silicon wafer sample obtained by processing this was determined under the same conditions as in Example 1. As a result, as shown in FIG. 13, RRG was 7.7 to 11.9%, and the in-plane uniformity of resistivity was worse than that of Example 1.
  • the oxygen concentration in the silicon single crystal can be made 8 ⁇ 10 17 atoms / cm 3 or less by setting the crystal rotation speed to 17 to 19 rpm in pulling up the silicon single crystal by the Czochralski method using the cusp magnetic field. It can be seen that RRG and RRG are also smaller.

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Abstract

[Problem] To provide a method for producing a silicon single crystal having a low oxygen concentration and high uniformity of in-plane distributions of oxygen concentration and resistivity, and a silicon wafer. [Solution] A method for producing a silicon single crystal by the MCZ method, said method involving drawing up a silicon single crystal 3 from a silicon melt 2 in a quartz crucible 11 while applying a cusp magnetic field, wherein the crystal rotary speed when the silicon single crystal 3 is being drawn up while being rotated is 17-19 rpm. The oxygen concentration of the silicon single crystal 3 drawn up in this manner is from 1 × 1017atoms/cm3 to 8 ×1017atoms/cm3, ROG within a crystal cross-section orthogonal to the crystal growth direction is 15% or less, and RRG within the crystal cross-section is 5% or less.

Description

シリコン単結晶及びその製造方法並びにシリコンウェーハSilicon single crystal, method of manufacturing the same, and silicon wafer
　本発明は、シリコン単結晶及びその製造方法並びにシリコンウェーハに関し、特に、ＭＣＺ（Magnetic field applied CZ）法によるシリコン単結晶の製造方法とこれにより製造されるシリコン単結晶及びシリコンウェーハに関する。 The present invention relates to a silicon single crystal, a method of manufacturing the same, and a silicon wafer, and more particularly to a method of manufacturing a silicon single crystal by a magnetic field applied CZ (MCZ) method and a silicon single crystal and a silicon wafer manufactured thereby.
　ＩＧＢＴ（Gate Insulated Bipolar Transistor）を中心としたパワー半導体向けのシリコンウェーハには格子間酸素濃度が低いシリコン単結晶が好ましく用いられている。そのようなシリコン単結晶の製造には、酸素の供給源となる石英ルツボを用いないＦＺ法が用いられることが多いが、量産性を向上させるためＣＺ法（チョクラルスキー法）により製造することも検討されている。 A silicon single crystal having a low interstitial oxygen concentration is preferably used as a silicon wafer for power semiconductors centering on an IGBT (Gate Insulated Bipolar Transistor). In order to produce such silicon single crystals, the FZ method which does not use a quartz crucible serving as a source of oxygen is often used, but in order to improve mass productivity, the CZ method (Czochralski method) should be used. Is also being considered.
　低酸素濃度のシリコン単結晶を製造するＣＺ法の一つとして、磁場を印加しながらシリコン単結晶を引き上げるＭＣＺ法が知られている。ＭＣＺ法によれば、融液対流を抑制することができ、石英ルツボの溶損によるシリコン融液中への酸素の溶け込みを抑制してシリコン単結晶中の酸素濃度を低減することができる。例えば特許文献１には、水平磁場又はカスプ磁場を用いるＭＣＺ法において、水平磁場強度を２０００Ｇ（ガウス）以上、石英ルツボの回転数を１．５ｒｐｍ以下、結晶回転数７．０ｒｐｍ以下とし、単結晶が転位クラスタ欠陥フリーとなる結晶引き上げ速度とすることで、格子間酸素濃度が６×１０１７ａｔｏｍｓ／ｃｍ３以下の単結晶を育成することが記載されている。 As one of the CZ methods for producing a silicon single crystal with a low oxygen concentration, the MCZ method is known which pulls up a silicon single crystal while applying a magnetic field. According to the MCZ method, melt convection can be suppressed, and dissolution of oxygen into the silicon melt due to erosion of the quartz crucible can be suppressed to reduce the oxygen concentration in the silicon single crystal. For example, in Patent Document 1, in the MCZ method using a horizontal magnetic field or a cusp magnetic field, the horizontal magnetic field strength is 2000 G (Gauss) or more, the rotation number of the quartz crucible is 1.5 rpm or less, and the crystal rotation number is 7.0 rpm or less. It is described that a single crystal having an interstitial oxygen concentration of 6 × 10 17 atoms / cm 3 or less is grown by using a crystal pulling rate that makes dislocation cluster defects free.
　また特許文献２には、真空チャンバーに含まれる坩堝中で多結晶シリコンを溶融させて融液を形成する工程と、真空チャンバーの中にカスプ磁場を形成する工程と、種結晶を融液に浸漬する工程と、融液から種結晶を引き出して約１５０ｍｍより大きな直径を有するシリコン単結晶インゴットを形成する工程とを有し、シリコンインゴットが約５ｐｐｍａより低い酸素濃度を有するように複数のプロセスパラメータを同時に調整することが記載されている。複数のプロセスパラメータは、坩堝の側壁温度、坩堝から単結晶への一酸化ケイ素（ＳｉＯ）の移動、および融液からのＳｉＯの蒸発速度を含み、ルツボ回転速度を１．３～２．２ｒｐｍ、結晶回転速度を８～１４ｒｐｍ、固液界面における単結晶のエッジの磁場強度を０．０２～０．０５Ｔ（テスラ）としている。 Further, in Patent Document 2, a step of melting polycrystalline silicon in a crucible contained in a vacuum chamber to form a melt, a step of forming a cusp magnetic field in the vacuum chamber, and immersing a seed crystal in the melt And pulling the seed crystals from the melt to form a silicon single crystal ingot having a diameter of greater than about 150 mm, wherein the plurality of process parameters are such that the silicon ingot has an oxygen concentration less than about 5 ppma. It is described to adjust simultaneously. The plurality of process parameters include crucible sidewall temperature, migration of silicon monoxide (SiO) from crucible to single crystal, and evaporation rate of SiO from the melt, with a crucible rotation rate of 1.3 to 2.2 rpm. The crystal rotation speed is 8 to 14 rpm, and the magnetic field strength of the edge of the single crystal at the solid-liquid interface is 0.02 to 0.05 T (Tesla).
特開２０１０－２２２２４１号公報JP, 2010-222241, A 特表２０１６－５１９０４９号公報JP 2016-519049 gazette
　しかしながら、水平磁場を印加しながらシリコン単結晶を引き上げるＨＭＣＺ法では、シリコン単結晶の低酸素化を図ることができるが、酸素濃度や抵抗率の面内均一性が問題となる。例えば、特許文献１に記載された従来の製造方法は、ルツボ回転速度を１．５ｒｐｍ以下、結晶回転速度を７ｒｐｍ以下としているが、その製造条件を実際に適用すると、酸素濃度及び抵抗率の面内分布が均一にならないという問題がある。また、特許文献２に記載された従来の製造方法は、ルツボ回転速度を１．３～２．２ｒｐｍ、結晶回転速度を８～１４ｒｐｍとしているが、その製造条件を実際に適用すると、酸素濃度及び抵抗率の面内分布が均一にならないという問題がある。 However, in the HMCZ method of pulling up a silicon single crystal while applying a horizontal magnetic field, it is possible to reduce oxygen of the silicon single crystal, but the in-plane uniformity of oxygen concentration and resistivity becomes a problem. For example, although the conventional manufacturing method described in Patent Document 1 sets the crucible rotation speed to 1.5 rpm or less and the crystal rotation speed to 7 rpm or less, when the manufacturing conditions are actually applied, the oxygen concentration and the resistivity There is a problem that the internal distribution is not uniform. Moreover, although the conventional manufacturing method described in Patent Document 2 sets the crucible rotation speed to 1.3 to 2.2 rpm and the crystal rotation speed to 8 to 14 rpm, when the manufacturing conditions are actually applied, the oxygen concentration and There is a problem that the in-plane distribution of resistivity is not uniform.
　したがって、本発明の目的は、酸素濃度が低く、酸素濃度及び抵抗率の面内分布の均一性が高いシリコン単結晶を製造することが可能なカスプ磁場を印加したチョクラルスキー法によるシリコン単結晶の製造方法を提供することにある。また本発明は、酸素濃度が低く、酸素濃度及び抵抗率の面内分布の均一性が高いシリコン単結晶並びにシリコンウェーハを提供することにある。 Therefore, an object of the present invention is to provide a silicon single crystal according to the Czochralski method to which a cusp magnetic field can be applied which can produce a silicon single crystal having a low oxygen concentration and high uniformity of in-plane distribution of oxygen concentration and resistivity. It is to provide a manufacturing method of Another object of the present invention is to provide a silicon single crystal and a silicon wafer having a low oxygen concentration and a high uniformity of in-plane distribution of oxygen concentration and resistivity.
　本願発明者は、シリコン単結晶中の酸素濃度や抵抗率の面内分布を変化させる要因について鋭意研究を重ねた結果、カスプ磁場を印加しながら単結晶を引き上げる場合には、単結晶を高速回転させても酸素濃度の増加や結晶変形（有転位化）を招くことなく、酸素濃度及び抵抗率の面内分布の均一性を高めることができることを見出した。通常、低酸素濃度のシリコン単結晶を製造するためには結晶回転を遅くする必要があるが、酸素濃度の面内均一性が悪くなる。しかし、カスプ磁場を用いることで結晶回転を速くしても低酸素濃度のシリコン単結晶が得られ、酸素濃度及び抵抗率の面内分布も安定することが明らかとなり、本発明をなし得たものである。 The inventor of the present invention has conducted intensive studies on factors that change the in-plane distribution of oxygen concentration and resistivity in a silicon single crystal. As a result, when pulling up a single crystal while applying a cusp magnetic field, the single crystal is rotated at high speed. It has been found that the uniformity of the in-plane distribution of the oxygen concentration and the resistivity can be enhanced without causing an increase in the oxygen concentration or crystal deformation (dislocation) even if it is carried out. Generally, in order to produce a silicon single crystal with low oxygen concentration, it is necessary to slow the crystal rotation, but the in-plane uniformity of oxygen concentration is degraded. However, it becomes clear that even if the crystal rotation is made faster by using a cusp magnetic field, a silicon single crystal with low oxygen concentration can be obtained, and the in-plane distribution of oxygen concentration and resistivity is also stabilized. It is.
　本発明はこのような技術的知見に基づくものであり、本発明によるシリコン単結晶の製造方法は、カスプ磁場を印加しながらシリコン融液からシリコン単結晶を引き上げるチョクラルスキー法によるシリコン単結晶の製造方法であって、前記シリコン単結晶を回転させながら引き上げる際の結晶回転速度が１７ｒｐｍ以上１９ｒｐｍ以下であることを特徴とする。 The present invention is based on such technical knowledge, and the method for producing a silicon single crystal according to the present invention is a method for producing a silicon single crystal by the Czochralski method for pulling up a silicon single crystal from a silicon melt while applying a cusp magnetic field. The manufacturing method is characterized in that a crystal rotation speed when pulling up the silicon single crystal while rotating is 17 rpm or more and 19 rpm or less.
　本発明において、前記シリコン融液を保持する石英ルツボの回転速度は４．５ｒｐｍ以上８．５ｒｐｍ以下であることが好ましい。また、前記カスプ磁場の磁場強度は５００～７００Ｇであり、垂直方向の磁場中心位置は前記シリコン融液の液面位置に対し＋４０ｍｍから－２６ｍｍまでの範囲であることが好ましい。この条件によれば、単結晶中の酸素濃度及び抵抗率の面内分布の均一性を高めることができる。 In the present invention, the rotational speed of the quartz crucible holding the silicon melt is preferably 4.5 rpm or more and 8.5 rpm or less. The magnetic field strength of the cusp magnetic field is preferably 500 to 700 G, and the magnetic field center position in the vertical direction is preferably in the range of +40 mm to −26 mm with respect to the liquid level position of the silicon melt. According to this condition, it is possible to enhance the uniformity of the in-plane distribution of the oxygen concentration and the resistivity in the single crystal.
　また、本発明によるシリコン単結晶は、酸素濃度が１×１０１７atoms/cm3以上８×１０１７atoms/cm3以下であり、結晶成長方向と直交する結晶断面内のＲＯＧ（Radial Oxygen Gradient：酸素濃度勾配）が１５％以下であり、前記結晶断面内のＲＲＧ（Radial Resistivity Gradient：抵抗率勾配）が５％以下であることを特徴とする。本発明によれば、パワー半導体向けのシリコンウェーハの材料として好適な酸素濃度が低いシリコン単結晶を提供することができる。 The silicon single crystal according to the present invention has an oxygen concentration of 1 × 10 17 atoms / cm 3 or more and 8 × 10 17 atoms / cm 3 or less, and ROG (Radial Oxygen Gradient: ROG) in the crystal cross section orthogonal to the crystal growth direction. The oxygen concentration gradient is 15% or less, and the RRG (Radial Resistivity Gradient) in the crystal cross section is 5% or less. According to the present invention, it is possible to provide a silicon single crystal with a low oxygen concentration, which is suitable as a material of a silicon wafer for power semiconductors.
　さらにまた、本発明によるシリコンウェーハは、酸素濃度が１×１０１７atoms/cm3以上８×１０１７atoms/cm3以下であり、ＲＯＧが１５％以下であり、ＲＲＧが５％以下であることを特徴とする。本発明によれば、パワー半導体の基板材料として好適なシリコンウェーハを提供することができる。 Furthermore, the silicon wafer according to the present invention has an oxygen concentration of 1 × 10 17 atoms / cm 3 or more and 8 × 10 17 atoms / cm 3 or less, an ROG of 15% or less, and an RRG of 5% or less. It is characterized by According to the present invention, a silicon wafer suitable as a substrate material of a power semiconductor can be provided.
　本発明によれば、酸素濃度が低く、酸素濃度及び抵抗率の面内分布の均一性が高いシリコン単結晶の製造方法を提供することができる。また本発明によれば、酸素濃度が低く、酸素濃度及び抵抗率の面内分布の均一性が高いシリコン単結晶並びにシリコンウェーハを提供することができる。 According to the present invention, it is possible to provide a method for producing a silicon single crystal having a low oxygen concentration and a high uniformity of in-plane distribution of oxygen concentration and resistivity. Further, according to the present invention, it is possible to provide a silicon single crystal and a silicon wafer which have a low oxygen concentration and high uniformity of in-plane distribution of oxygen concentration and resistivity.
図１は、本発明の実施の形態による単結晶製造装置の構成を概略的に示す側面断面図である。FIG. 1 is a side cross-sectional view schematically showing the configuration of a single crystal production apparatus according to an embodiment of the present invention. 図２は、本発明の実施の形態によるシリコン単結晶の製造方法を説明するフローチャートである。FIG. 2 is a flowchart illustrating a method of manufacturing a silicon single crystal according to the embodiment of the present invention. 図３は、シリコン単結晶インゴットの形状を示す略断面図である。FIG. 3 is a schematic cross-sectional view showing the shape of a silicon single crystal ingot. 図４は、実施例１（ＣＵＳＰ）によるシリコンウェーハサンプルのＲＯＧを示すグラフである。FIG. 4 is a graph showing ROG of a silicon wafer sample according to Example 1 (CUSP). 図５は、実施例１（ＣＵＳＰ）によるシリコンウェーハサンプルのＲＲＧを示すグラフである。FIG. 5 is a graph showing RRG of a silicon wafer sample according to Example 1 (CUSP). 図６は、実施例２（ＣＵＳＰ）によるシリコンウェーハサンプルのＲＯＧを示すグラフである。FIG. 6 is a graph showing ROG of a silicon wafer sample according to Example 2 (CUSP). 図７は、実施例３（ＣＵＳＰ）によるシリコンウェーハサンプルのＲＯＧを示すグラフである。FIG. 7 is a graph showing ROG of a silicon wafer sample according to Example 3 (CUSP). 図８は、実施例４（ＣＵＳＰ）によるシリコンウェーハサンプルのＲＯＧを示すグラフである。FIG. 8 is a graph showing ROG of a silicon wafer sample according to Example 4 (CUSP). 図９は、実施例５（ＣＵＳＰ）によるシリコンウェーハサンプルのＲＯＧを示すグラフである。FIG. 9 is a graph showing ROG of a silicon wafer sample according to Example 5 (CUSP). 図１０は、比較例１（ＣＵＳＰ）によるシリコンウェーハサンプルのＲＯＧを示すグラフである。FIG. 10 is a graph showing ROG of a silicon wafer sample according to Comparative Example 1 (CUSP). 図１１は、比較例２（ＨＭＣＺ）によるシリコンウェーハサンプルのＲＯＧを示すグラフである。FIG. 11 is a graph showing ROG of a silicon wafer sample according to Comparative Example 2 (HMCZ). 図１２は、比較例２（ＨＭＣＺ）によるシリコンウェーハサンプルのＲＲＧを示すグラフである。FIG. 12 is a graph showing RRG of a silicon wafer sample according to Comparative Example 2 (HMCZ). 図１３は、比較例３（ＦＺ）によるシリコンウェーハサンプルのＲＲＧを示すグラフである。FIG. 13 is a graph showing RRG of a silicon wafer sample according to Comparative Example 3 (FZ).
　以下、添付図面を参照しながら、本発明の好ましい実施の形態について詳細に説明する。 Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.
　図１は、本発明の実施の形態による単結晶製造装置の構成を概略的に示す側面断面図である。 FIG. 1 is a side cross-sectional view schematically showing the configuration of a single crystal production apparatus according to an embodiment of the present invention.
　図１に示すように、単結晶製造装置１は、チャンバー１０（ＣＺ炉）と、チャンバー１０内においてシリコン融液２を保持する石英ルツボ１１と、石英ルツボ１１を保持するグラファイト製のサセプタ１２と、サセプタ１２を支持する回転シャフト１３と、回転シャフト１３を回転及び昇降駆動するシャフト駆動機構１４と、サセプタ１２の周囲に配置されたヒーター１５と、ヒーター１５の外側であってチャンバー１０の内面に沿って配置された断熱材１６と、石英ルツボ１１の上方に配置された熱遮蔽体１７と、石英ルツボ１１の上方であって回転シャフト１３と同軸上に配置された単結晶引き上げ用のワイヤー１８と、チャンバー１０の上方に配置されたワイヤー巻き取り機構１９とを備えている。 As shown in FIG. 1, the single crystal production apparatus 1 includes a chamber 10 (CZ furnace), a quartz crucible 11 holding a silicon melt 2 in the chamber 10, and a graphite susceptor 12 holding the quartz crucible 11. , A rotating shaft 13 supporting the susceptor 12, a shaft drive mechanism 14 for rotating and elevating the rotating shaft 13, a heater 15 disposed around the susceptor 12, an outer side of the heater 15 and an inner surface of the chamber 10. A heat insulating material 16 disposed along with the heat shield 17 disposed above the quartz crucible 11, and a single crystal pulling wire 18 disposed above the quartz crucible 11 and coaxial with the rotating shaft 13. And a wire winding mechanism 19 disposed above the chamber 10.
　また単結晶製造装置１は、チャンバー１０の外側に配置された磁場発生装置２１と、チャンバー１０内を撮影するＣＣＤカメラ２２と、ＣＣＤカメラ２２で撮影された画像を処理する画像処理部２３と、画像処理部２３の出力に基づいてシャフト駆動機構１４、ヒーター１５及びワイヤー巻き取り機構１９を制御する制御部２４とを備えている。 The single crystal manufacturing apparatus 1 further includes a magnetic field generator 21 disposed outside the chamber 10, a CCD camera 22 for imaging the inside of the chamber 10, and an image processing unit 23 for processing an image captured by the CCD camera 22. The control unit 24 controls the shaft drive mechanism 14, the heater 15, and the wire winding mechanism 19 based on the output of the image processing unit 23.
　チャンバー１０は、メインチャンバー１０ａと、メインチャンバー１０ａの上部開口に連結された細長い円筒状のプルチャンバー１０ｂとで構成されており、石英ルツボ１１、サセプタ１２、ヒーター１５及び熱遮蔽体１７はメインチャンバー１０ａ内に設けられている。プルチャンバー１０ｂにはチャンバー１０内にアルゴンガス等の不活性ガス（パージガス）を導入するためのガス導入口１０ｃが設けられており、メインチャンバー１０ａの下部には不活性ガスを排出するためのガス排出口１０ｄが設けられている。また、メインチャンバー１０ａの上部には覗き窓１０ｅが設けられており、シリコン単結晶３の育成状況（固液界面）を覗き窓１０ｅから観察可能である。 The chamber 10 is composed of a main chamber 10a and an elongated cylindrical pull chamber 10b connected to the upper opening of the main chamber 10a. The quartz crucible 11, the susceptor 12, the heater 15 and the heat shield 17 are main chambers It is provided in 10a. The pull chamber 10 b is provided with a gas inlet 10 c for introducing an inert gas (purge gas) such as argon gas into the chamber 10, and a gas for discharging the inert gas is provided at the lower part of the main chamber 10 a. An outlet 10d is provided. Further, an observation window 10e is provided in the upper part of the main chamber 10a, and the growth state (solid-liquid interface) of the silicon single crystal 3 can be observed from the observation window 10e.
　石英ルツボ１１は、円筒状の側壁部と湾曲した底部とを有する石英ガラス製の容器である。サセプタ１２は、加熱によって軟化した石英ルツボ１１の形状を維持するため、石英ルツボ１１の外表面に密着して石英ルツボ１１を包むように保持する。石英ルツボ１１及びサセプタ１２はチャンバー１０内においてシリコン融液を支持する二重構造のルツボを構成している。 The quartz crucible 11 is a container made of quartz glass having a cylindrical side wall and a curved bottom. The susceptor 12 closely contacts the outer surface of the quartz crucible 11 and holds the quartz crucible 11 so as to wrap the quartz crucible 11 in order to maintain the shape of the quartz crucible 11 softened by heating. The quartz crucible 11 and the susceptor 12 constitute a double-structured crucible for supporting the silicon melt in the chamber 10.
　サセプタ１２は鉛直方向に延びる回転シャフト１３の上端部に固定されている。また回転シャフト１３の下端部はチャンバー１０の底部中央を貫通してチャンバー１０の外側に設けられたシャフト駆動機構１４に接続されている。サセプタ１２、回転シャフト１３及びシャフト駆動機構１４は石英ルツボ１１の回転機構及び昇降機構を構成している。 The susceptor 12 is fixed to the upper end of a rotating shaft 13 extending in the vertical direction. Further, the lower end portion of the rotating shaft 13 is connected to a shaft driving mechanism 14 provided on the outside of the chamber 10 through the center of the bottom portion of the chamber 10. The susceptor 12, the rotating shaft 13 and the shaft driving mechanism 14 constitute a rotating mechanism and an elevating mechanism of the quartz crucible 11.
　ヒーター１５は、石英ルツボ１１内に充填されたシリコン原料を溶融して溶融状態を維持するために用いられる。ヒーター１５はカーボン製の抵抗加熱式ヒーターであり、サセプタ１２内の石英ルツボ１１の全周を取り囲むように設けられた略円筒状の部材である。さらにヒーター１５の外側は断熱材１６に取り囲まれており、これによりチャンバー１０内の保温性が高められている。 The heater 15 is used to melt the silicon raw material filled in the quartz crucible 11 and maintain the molten state. The heater 15 is a resistance heating heater made of carbon, and is a substantially cylindrical member provided so as to surround the entire circumference of the quartz crucible 11 in the susceptor 12. Furthermore, the outside of the heater 15 is surrounded by the heat insulating material 16, which enhances the heat retention in the chamber 10.
　熱遮蔽体１７は、シリコン融液２の温度変動を抑制して固液界面付近に適切なホットゾーンを形成するとともに、ヒーター１５及び石英ルツボ１１からの輻射熱によるシリコン単結晶３の加熱を防止するために設けられている。熱遮蔽体１７は、シリコン単結晶３の引き上げ経路を除いたシリコン融液２の上方の領域を覆うグラファイト製の円筒部材である。 The thermal shield 17 suppresses the temperature fluctuation of the silicon melt 2 to form an appropriate hot zone in the vicinity of the solid-liquid interface, and prevents the heating of the silicon single crystal 3 by the radiant heat from the heater 15 and the quartz crucible 11. Provided for The heat shield 17 is a cylindrical member made of graphite which covers the region above the silicon melt 2 except the pulling path of the silicon single crystal 3.
　熱遮蔽体１７の下端中央にはシリコン単結晶３の直径よりも大きな円形の開口が形成されており、シリコン単結晶３の引き上げ経路が確保されている。図示のように、シリコン単結晶３は熱遮蔽体１７の開口を通過して上方に引き上げられる。熱遮蔽体１７の開口の直径は石英ルツボ１１の口径よりも小さく、熱遮蔽体１７の下端部は石英ルツボ１１の内側に位置するので、石英ルツボ１１のリム上端を熱遮蔽体１７の下端よりも上方まで上昇させても熱遮蔽体１７が石英ルツボ１１と干渉することはない。 A circular opening larger than the diameter of the silicon single crystal 3 is formed at the center of the lower end of the heat shield 17, and a pulling path of the silicon single crystal 3 is secured. As illustrated, the silicon single crystal 3 is pulled upward through the opening of the thermal shield 17. The diameter of the opening of the heat shield 17 is smaller than the diameter of the quartz crucible 11 and the lower end of the heat shield 17 is located inside the quartz crucible 11, so the rim upper end of the quartz crucible 11 is from the lower end of the heat shield 17 Even if the temperature is raised to the upper side, the heat shield 17 does not interfere with the quartz crucible 11.
　シリコン単結晶３の成長と共に石英ルツボ１１内の融液量は減少するが、融液面と熱遮蔽体１７との間のギャップが一定になるように石英ルツボ１１を上昇させることにより、シリコン融液２の温度変動を抑制すると共に、融液面近傍を流れるガスの流速を一定にしてシリコン融液２からのＳｉＯガスの蒸発量を制御することができる。したがって、単結晶の引き上げ軸方向の結晶欠陥分布、酸素濃度分布、抵抗率分布等の安定性を向上させることができる。 Although the amount of melt in the quartz crucible 11 decreases with the growth of the silicon single crystal 3, the silicon melt is raised by raising the quartz crucible 11 so that the gap between the melt surface and the heat shield 17 becomes constant. While suppressing the temperature fluctuation of the liquid 2, it is possible to control the evaporation amount of SiO gas from the silicon melt 2 by making the flow velocity of the gas flowing near the melt surface constant. Therefore, the stability of the crystal defect distribution, the oxygen concentration distribution, the resistivity distribution and the like in the pulling axis direction of the single crystal can be improved.
　石英ルツボ１１の上方には、シリコン単結晶３の引き上げ軸であるワイヤー１８と、ワイヤー１８を巻き取るワイヤー巻き取り機構１９が設けられている。ワイヤー巻き取り機構１９はワイヤー１８と共に単結晶を回転させる機能を有している。ワイヤー巻き取り機構１９はプルチャンバー１０ｂの上方に配置されており、ワイヤー１８はワイヤー巻き取り機構１９からプルチャンバー１０ｂ内を通って下方に延びており、ワイヤー１８の先端部はメインチャンバー１０ａの内部空間まで達している。図１には、育成途中のシリコン単結晶３がワイヤー１８に吊設された状態が示されている。単結晶の引き上げ時には種結晶をシリコン融液２に浸漬し、石英ルツボ１１と種結晶をそれぞれ回転させながらワイヤー１８を徐々に引き上げることにより単結晶を成長させる。 Above the quartz crucible 11, a wire 18 which is a pulling shaft of the silicon single crystal 3 and a wire winding mechanism 19 for winding the wire 18 are provided. The wire winding mechanism 19 has a function of rotating the single crystal together with the wire 18. The wire take-up mechanism 19 is disposed above the pull chamber 10b, and the wire 18 extends downward from the wire take-up mechanism 19 through the pull chamber 10b, and the tip of the wire 18 is the inside of the main chamber 10a. It has reached space. FIG. 1 shows a state in which the silicon single crystal 3 in the process of being grown is hung on the wire 18. When pulling the single crystal, the seed crystal is immersed in the silicon melt 2 and the single crystal is grown by gradually pulling the wire 18 while rotating the quartz crucible 11 and the seed crystal.
　プルチャンバー１０ｂの上部にはチャンバー１０内に不活性ガスを導入するためのガス導入口１０ｃが設けられており、メインチャンバー１０ａの底部にはチャンバー１０内の不活性ガスを排気するためのガス排出口１０ｄが設けられている。不活性ガスはガス導入口１０ｃからチャンバー１０内に導入され、その導入量はバルブにより制御される。また密閉されたチャンバー１０内の不活性ガスはガス排出口１０ｄからチャンバー１０の外部へ排気されるので、チャンバー１０内で発生するＳｉＯガスやＣＯガスを回収してチャンバー１０内を清浄に保つことが可能となる。図示していないが、ガス排出口１０ｄには配管を介して真空ポンプが接続されており、真空ポンプでチャンバー１０内の不活性ガスを吸引しながらバルブでその流量を制御することでチャンバー１０内は一定の減圧状態に保たれている。 A gas inlet 10c for introducing an inert gas into the chamber 10 is provided at the top of the pull chamber 10b, and a gas exhaust for evacuating the inert gas in the chamber 10 is provided at the bottom of the main chamber 10a. An outlet 10d is provided. The inert gas is introduced into the chamber 10 from the gas inlet 10c, and the introduction amount is controlled by a valve. Further, since the inert gas in the sealed chamber 10 is exhausted from the gas outlet 10 d to the outside of the chamber 10, the SiO gas or CO gas generated in the chamber 10 is recovered to keep the inside of the chamber 10 clean. Is possible. Although not shown, a vacuum pump is connected to the gas discharge port 10d through a pipe, and the flow rate is controlled by a valve while suctioning the inert gas in the chamber 10 by the vacuum pump. Is maintained at a constant reduced pressure.
　磁場発生装置２１は上下方向に対向する上部コイル２１ａ及び下部コイル２１ｂを用いて構成されており、一対の磁場発生用コイルにそれぞれ逆向きの電流を流すことによってチャンバー１０内にカスプ磁場を発生させる。図中では、「・」は紙面から出てくる電流の流れを示し、「×」は紙面に入っていく電流の流れを示している。 The magnetic field generation device 21 is configured using an upper coil 21a and a lower coil 21b opposed in the vertical direction, and generates a cusp magnetic field in the chamber 10 by supplying currents in opposite directions to the pair of magnetic field generation coils. . In the figure, “•” indicates the flow of current coming out of the paper, and “x” indicates the flow of current going into the paper.
　カスプ磁場は引き上げ軸に対して軸対称であり、磁場中心点では互いの磁界が打ち消し合って垂直方向の磁場強度はゼロとなる。磁場中心点から外れた位置では垂直方向の磁場は存在し、半径方向に向かう水平磁場が形成される。またカスプ磁場の磁場中心位置はシリコン融液２の液面近傍であり、液面位置に対し＋４０ｍｍから－２６ｍｍまでの範囲に設定されることが好ましい。このように、シリコン融液にカスプ磁場を印加することで磁力線に直交する方向の融液対流を抑制することができる。 The cusp magnetic field is axisymmetric with respect to the pulling axis, and the magnetic fields cancel each other at the magnetic field center point, and the magnetic field strength in the vertical direction becomes zero. At a position deviating from the magnetic field center point, a vertical magnetic field is present, and a radially directed horizontal magnetic field is formed. Further, it is preferable that the magnetic field center position of the cusp magnetic field be in the vicinity of the liquid surface of the silicon melt 2 and be set in the range of +40 mm to −26 mm with respect to the liquid surface position. Thus, by applying a cusp magnetic field to the silicon melt, melt convection in the direction orthogonal to the magnetic lines of force can be suppressed.
　カスプ磁場の磁場強度は５００～７００Ｇであることが好ましい。磁場強度が５００Ｇよりも小さい場合には８×１０１７atoms/cm3以下低酸素濃度のシリコン単結晶を引き上げることが難しくなるからである。また既存の磁場発生装置では７００Ｇを超える磁場強度を安定的に出力することが難しく、消費電力の観点からもできるだけ低い磁場強度が望ましいからである。本願に記載のカスプ磁場の磁場強度の値は、垂直方向には磁場中心位置で、水平方向には石英ルツボの側壁位置である。 The magnetic field strength of the cusp magnetic field is preferably 500 to 700 G. When the magnetic field strength is less than 500 G, it is difficult to pull up a silicon single crystal with a low oxygen concentration of 8 × 10 17 atoms / cm 3 or less. Further, it is difficult to stably output a magnetic field strength exceeding 700 G in the existing magnetic field generator, and it is desirable from the viewpoint of power consumption that the magnetic field strength is as low as possible. The value of the magnetic field strength of the cusp magnetic field described in the present application is the center position of the magnetic field in the vertical direction and the side wall position of the quartz crucible in the horizontal direction.
　水平磁場を印加するＨＭＣＺ法の場合、磁力線の方向は一方向であるため、磁力線と直交する方向の対流を抑制する効果はあるが、磁力線と平行な方向の対流を抑制することはできない。一方、カスプ磁場の場合、磁力線の方向は放射状であり、引き上げ軸を中心に平面視で対称性を有するため、石英ルツボ１１内の周方向の融液対流を抑制することができる。したがって、石英ルツボ１１からの酸素の溶出を抑えてシリコン単結晶中の酸素濃度を低減することが可能となる。 In the case of the HMCZ method in which a horizontal magnetic field is applied, the direction of the magnetic field lines is one direction, so there is an effect of suppressing convection in the direction orthogonal to the magnetic field lines, but convection in the direction parallel to the magnetic field lines can not be suppressed. On the other hand, in the case of the cusp magnetic field, the direction of the magnetic lines of force is radial, and has symmetry in a plan view centering on the pulling axis, so that melt convection in the circumferential direction in the quartz crucible 11 can be suppressed. Therefore, it is possible to suppress the elution of oxygen from the quartz crucible 11 and reduce the oxygen concentration in the silicon single crystal.
　メインチャンバー１０ａの上部には内部を観察するための覗き窓１０ｅが設けられており、ＣＣＤカメラ２２は覗き窓１０ｅの外側に設置されている。単結晶引き上げ工程中、ＣＣＤカメラ２２は覗き窓１０ｅから熱遮蔽体１７の開口を通して見えるシリコン単結晶３とシリコン融液２との境界部の画像を撮影する。ＣＣＤカメラ２２は画像処理部２３に接続されており、撮影画像は画像処理部２３で処理され、処理結果は制御部２４において結晶引き上げ条件の制御に用いられる。 An observation window 10e for observing the inside is provided above the main chamber 10a, and the CCD camera 22 is disposed outside the observation window 10e. During the single crystal pulling process, the CCD camera 22 captures an image of the boundary between the silicon single crystal 3 and the silicon melt 2 seen through the opening of the thermal shield 17 from the observation window 10e. The CCD camera 22 is connected to the image processing unit 23, the photographed image is processed by the image processing unit 23, and the processing result is used by the control unit 24 to control the crystal pulling condition.
　図２は、本発明の実施の形態によるシリコン単結晶の製造方法を説明するフローチャートである。また、図３は、シリコン単結晶インゴットの形状を示す略断面図である。 FIG. 2 is a flowchart illustrating a method of manufacturing a silicon single crystal according to the embodiment of the present invention. FIG. 3 is a schematic cross-sectional view showing the shape of a silicon single crystal ingot.
　図２及び図３示すように、シリコン単結晶３の製造では、石英ルツボ１１内のシリコン原料を加熱してシリコン融液２を生成する（ステップＳ１１）。その後、ワイヤー１８の先端部に取り付けられた種結晶を降下させてシリコン融液２に着液させる（ステップＳ１２）。 As shown in FIGS. 2 and 3, in the production of the silicon single crystal 3, the silicon raw material in the quartz crucible 11 is heated to generate the silicon melt 2 (step S11). Thereafter, the seed crystal attached to the tip of the wire 18 is lowered to be deposited on the silicon melt 2 (step S12).
　次に、シリコン融液２との接触状態を維持しながら種結晶を徐々に引き上げて単結晶を育成する単結晶の引き上げ工程を実施する。単結晶の引き上げ工程では、無転位化のために結晶直径が細く絞られたネック部３ａを形成するネッキング工程（ステップＳ１３）と、規定の直径を得るために結晶直径が徐々に増加したショルダー部３ｂを形成するショルダー部育成工程（ステップＳ１４）と、結晶直径が一定に維持されたボディー部３ｃ（直胴部）を形成するボディー部育成工程（ステップＳ１５）と、結晶直径が徐々に減少したテール部３ｄを形成するテール部育成工程（ステップＳ１６）が順に実施され、単結晶が融液面から最終的に切り離されることによりテール部育成工程が終了する。以上により、単結晶の上端（トップ）から下端（ボトム）に向かって順に、ネック部３ａ、ショルダー部３ｂ、ボディー部３ｃ、及びテール部３ｄを有するシリコン単結晶インゴット３が完成する。 Next, while maintaining the state of contact with the silicon melt 2, the seed crystal is gradually pulled to carry out a single crystal pulling step of growing a single crystal. In the single crystal pulling step, a necking step (step S13) of forming a neck portion 3a in which the crystal diameter is narrowed to reduce dislocations for no dislocation, and a shoulder portion in which the crystal diameter gradually increases to obtain a prescribed diameter In the shoulder portion growing step (step S14) for forming 3b, and in the body portion growing step (step S15) for forming the body portion 3c (straight body portion with the crystal diameter kept constant), the crystal diameter gradually decreased The tail portion growing step (step S16) for forming the tail portion 3d is sequentially performed, and the single crystal is finally separated from the melt surface to complete the tail portion growing step. Thus, the silicon single crystal ingot 3 having the neck portion 3a, the shoulder portion 3b, the body portion 3c, and the tail portion 3d is completed in order from the upper end (top) to the lower end (bottom) of the single crystal.
　単結晶の引き上げ工程中は、シリコン単結晶３の直径及びシリコン融液２の液面位置を制御するため、ＣＣＤカメラ２２でシリコン単結晶３とシリコン融液２との境界部の画像を撮影し、撮影画像から固液界面における単結晶の直径及び融液面と熱遮蔽体１７との間隔（ギャップ）を算出する。制御部２４は、シリコン単結晶３の直径が目標直径となるようにワイヤー１８の引き上げ速度、ヒーター１５のパワー等の引き上げ条件を制御する。また制御部２４は、融液面と熱遮蔽体１７との間隔が一定となるように石英ルツボ１１の高さ位置を制御する。 During the single crystal pulling process, in order to control the diameter of the silicon single crystal 3 and the liquid level position of the silicon melt 2, an image of the boundary between the silicon single crystal 3 and the silicon melt 2 is taken with a CCD camera 22. From the photographed image, the diameter of the single crystal at the solid-liquid interface and the distance (gap) between the melt surface and the heat shield 17 are calculated. The control unit 24 controls pulling conditions such as the pulling speed of the wire 18 and the power of the heater 15 so that the diameter of the silicon single crystal 3 becomes the target diameter. Further, the control unit 24 controls the height position of the quartz crucible 11 so that the distance between the melt surface and the heat shield 17 becomes constant.
　本実施形態において、シリコン単結晶３の回転速度は１７～１９ｒｐｍの範囲内に設定される。結晶回転速度が１７ｒｐｍより小さい場合には、酸素濃度の面内分布の均一性を高めることができないからであり、また１９ｒｐｍよりも大きい場合には結晶中の酸素濃度が高くなるだけでなく、結晶軸芯がずれていると偏心回転によって単結晶がスパイラル状に変形しやすく、結晶引上後に結晶を外径研削した際に、結晶直径がウェーハ直径未満となる不良箇所が発生するからである。また、結晶変形にともない有転位化しやすくなることも問題である。 In the present embodiment, the rotational speed of the silicon single crystal 3 is set in the range of 17 to 19 rpm. If the crystal rotational speed is less than 17 rpm, the uniformity of the in-plane distribution of the oxygen concentration can not be improved, and if it is greater than 19 rpm, not only the oxygen concentration in the crystal increases but also the crystal If the axis is deviated, the single crystal is easily deformed in a spiral shape due to eccentric rotation, and when the crystal is subjected to outer diameter grinding after crystal pulling up, a defective portion in which the crystal diameter is smaller than the wafer diameter is generated. Another problem is that it becomes easy to have dislocations due to crystal deformation.
　結晶引き上げ中、石英ルツボ１１の回転速度は４．５～８．５ｒｐｍであることが好ましい。石英ルツボ１１の回転速度が４．５ｒｐｍよりも小さい場合には、酸素濃度及び抵抗率の面内分布が悪化するからである。石英ルツボ１１の回転速度が８．５ｒｐｍよりも大きい場合には、石英ルツボの溶損量が増加してシリコン融液中の酸素濃度が非常に高くなるからである。 During crystal pulling, the rotational speed of the quartz crucible 11 is preferably 4.5 to 8.5 rpm. When the rotation speed of the quartz crucible 11 is smaller than 4.5 rpm, the in-plane distribution of the oxygen concentration and the resistivity is deteriorated. When the rotation speed of the quartz crucible 11 is larger than 8.5 rpm, the amount of erosion of the quartz crucible is increased, and the oxygen concentration in the silicon melt becomes very high.
　以上の結晶引き上げ条件下でシリコン単結晶を引き上げる場合、シリコン単結晶の格子間酸素濃度を低くすることができるだけでなく、単結晶の外周部での酸素濃度の低下を抑制することができ、酸素濃度の面内分布の均一化を実現することができる。 When pulling up a silicon single crystal under the above crystal pulling conditions, it is possible not only to lower the interstitial oxygen concentration of the silicon single crystal but also to suppress the decrease in oxygen concentration at the outer peripheral portion of the single crystal. A uniform in-plane distribution of concentration can be realized.
　こうして引き上げられたシリコン単結晶３（図３参照）のボディー部３ｃの酸素濃度は１×１０１７atoms/cm3～８×１０１７atoms/cm3となり、結晶成長方向と直交する結晶断面内のＲＯＧは１５％以下となり、結晶断面内のＲＲＧは５％以下となる。さらに、このシリコン単結晶３から切り出して加工されたシリコンウェーハも同様の品質となる。すなわち、酸素濃度が１×１０１７atoms/cm3以上８×１０１７atoms/cm3以下であり、ＲＯＧが１５％以下であり、ＲＲＧが５％以下であるシリコンウェーハを得ることができる。なお本明細書中に規定する酸素濃度はすべてASTM F-121(1979)に規格されたＦＴＩＲ（Fourier Transform Infrared Spectroscopy：フーリエ変換赤外分光法）による測定値である。また抵抗値は四探針法による測定値である。 The oxygen concentration of the body portion 3c of the silicon single crystal 3 (see FIG. 3) thus pulled is 1 × 10 17 atoms / cm 3 to 8 × 10 17 atoms / cm 3 , and is within the crystal cross section orthogonal to the crystal growth direction. ROG is 15% or less, and RRG in the crystal cross section is 5% or less. Furthermore, a silicon wafer cut out from this silicon single crystal 3 and processed has the same quality. That is, a silicon wafer having an oxygen concentration of 1 × 10 17 atoms / cm 3 or more and 8 × 10 17 atoms / cm 3 or less, an ROG of 15% or less, and an RRG of 5% or less can be obtained. The oxygen concentrations specified in this specification are all measured values by FTIR (Fourier Transform Infrared Spectroscopy) specified in ASTM F-121 (1979). Moreover, resistance value is a measured value by the four-point probe method.
　以上説明したように、本実施形態によるシリコン単結晶の製造方法は、カスプ磁場を印加するチョクラルスキー法において単結晶を１７～１９ｒｐｍの回転速度で高速回転させながら引き上げることにより、酸素濃度が低く且つ酸素濃度及び抵抗率の面内分布ができるだけ均一なシリコン単結晶を製造することができる。したがって、ＩＧＢＴ用低酸素シリコンウェーハをＦＺ法ではなくＣＺ法により製造することができ、量産性を向上させることができる。 As described above, in the method of manufacturing a silicon single crystal according to the present embodiment, the oxygen concentration is low by pulling the single crystal while rotating at a high speed of 17 to 19 rpm in the Czochralski method applying a cusp magnetic field. In addition, it is possible to produce a silicon single crystal in which the in-plane distribution of oxygen concentration and resistivity is as uniform as possible. Therefore, the low oxygen silicon wafer for IGBT can be manufactured not by FZ method but by CZ method, and mass productivity can be improved.
　以上、本発明の好ましい実施形態について説明したが、本発明は、上記の実施形態に限定されることなく、本発明の主旨を逸脱しない範囲で種々の変更が可能であり、それらも本発明の範囲内に包含されるものであることはいうまでもない。 Although the preferred embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention. It is needless to say that they are included in the scope.
　例えば、上記実施形態においては、図１に示した単結晶製造装置１を用いる場合を例に挙げたが、単結晶製造装置の詳細な構成は特に限定されず、様々な構成のものを用いることができる。 For example, in the above embodiment, the single crystal production apparatus 1 shown in FIG. 1 is used as an example, but the detailed configuration of the single crystal production apparatus is not particularly limited, and various ones may be used. Can.
＜実施例１＞
　カスプ（ＣＵＳＰ）磁場を用いたチョクラルスキー法による直径２００ｍｍウェーハ用のシリコン単結晶の引き上げにおいて、カスプ磁場及び結晶回転速度が酸素濃度及び抵抗率の面内分布に与える影響を評価した。結晶引き上げ工程では、カスプ磁場の磁場強度を６００Ｇとし、磁場中心位置をシリコン融液の液面位置から上方に４０ｍｍの位置に設定した。またルツボ回転速度を６ｒｐｍとし、結晶回転速度を１８ｒｐｍとした。その後、引き上げられた３本のシリコン単結晶インゴットを加工して直径２００ｍｍのシリコンウェーハのサンプルを２枚ずつ、合計６枚用意した。 Example 1
In pulling up silicon single crystals for 200 mm diameter wafers by Czochralski method using Cusp (CUSP) magnetic field, the influence of cusp magnetic field and crystal rotational speed on in-plane distribution of oxygen concentration and resistivity was evaluated. In the crystal pulling process, the magnetic field strength of the cusp magnetic field was set to 600 G, and the magnetic field center position was set to a position 40 mm above the liquid level position of the silicon melt. The crucible rotation speed was 6 rpm, and the crystal rotation speed was 18 rpm. Thereafter, the pulled three silicon single crystal ingots were processed to prepare a total of six silicon wafer samples each having a diameter of 200 mm.
　次に、シリコンウェーハサンプルの酸素濃度の面内分布を測定した。酸素濃度はウェーハの中心から径方向に５ｍｍピッチで測定した。ウェーハの最外周部の酸素濃度を測定することはできないため、酸素濃度のウェーハ面内の測定範囲を、ウェーハの中心から径方向９５ｍｍまでの範囲とした（ウェーハ外周部の測定除外幅：５ｍｍ）。さらに酸素濃度の測定結果からシリコンウェーハのＲＯＧ（Radial Oxygen Gradient：径方向酸素濃度分布）を求めた。測定範囲内における酸素濃度の最大値をＤMax、最小値をＤMinとするとき、ＲＯＧの計算式は次のようになる。
　ＲＯＧ（％）＝｛（ＤMax－ＤMin）／ＤMin｝×１００ Next, the in-plane distribution of the oxygen concentration of the silicon wafer sample was measured. The oxygen concentration was measured at a pitch of 5 mm in the radial direction from the center of the wafer. Since it is not possible to measure the oxygen concentration at the outermost periphery of the wafer, the measurement range of the oxygen concentration in the wafer plane is the range from the center of the wafer to 95 mm in the radial direction (measurement exclusion width of wafer periphery: 5 mm) . Further, the ROG (Radial Oxygen Gradient) of the silicon wafer was determined from the measurement result of the oxygen concentration. Assuming that the maximum value of oxygen concentration in the measurement range is D Max and the minimum value is D Min , the formula for calculating ROG is as follows.
ROG (%) = {(D Max- D Min ) / D Min } x 100
　次に、シリコンウェーハサンプルの抵抗率の面内分布を測定した。抵抗率はウェーハの中心から径方向に２ｍｍピッチで四探針法により測定した。ウェーハの最外周部の抵抗率を測定することはできないため、抵抗率のウェーハ面内の測定範囲を、ウェーハの中心から径方向９６ｍｍまでの範囲とした（ウェーハ外周部の測定除外幅：４ｍｍ）。さらに抵抗率の測定結果からシリコンウェーハのＲＲＧ（Radial Resistivity Gradient：径方向抵抗率分布）を求めた。測定範囲内における抵抗率の最大値をρMax、最小値をρMinとするとき、ＲＲＧの計算式は次のようになる。
　ＲＲＧ（％）＝｛（ρMax－ρMin）／ρMin｝×１００ Next, the in-plane distribution of the resistivity of the silicon wafer sample was measured. The resistivity was measured by the four probe method at a pitch of 2 mm in the radial direction from the center of the wafer. Since the resistivity of the outermost periphery of the wafer can not be measured, the measurement range of resistivity within the wafer surface is the range from the center of the wafer to 96 mm in the radial direction (measurement exclusion width of wafer outer periphery: 4 mm) . Further, RRG (Radial Resistivity Gradient) of the silicon wafer was determined from the measurement result of the resistivity. Assuming that the maximum value of resistivity in the measurement range is Max Max and the minimum value is Min Min , the formula for calculating RRG is as follows.
RRG (%) = {(ρ Max -ρ Min ) / ρ Min } × 100
　図４は、シリコンウェーハサンプルの酸素濃度分布を示すグラフである。図示のように、いずれのウェーハサンプルも面内の酸素濃度は３×１０１７atoms/cm3以下となり、ＲＯＧは７．１～１４．８％となった。 FIG. 4 is a graph showing the oxygen concentration distribution of a silicon wafer sample. As shown in the drawing, the oxygen concentration in the surface of each wafer sample was 3 × 10 17 atoms / cm 3 or less, and the ROG was 7.1 to 14.8%.
　図５は、シリコンウェーハサンプルの抵抗率分布を示すグラフである。図示のように、いずれのシリコンウェーハも面内の抵抗率分布は３．５～４．９％となった。 FIG. 5 is a graph showing the resistivity distribution of a silicon wafer sample. As shown, the in-plane resistivity distribution of all silicon wafers was 3.5 to 4.9%.
＜実施例２＞
　結晶回転速度を１７ｒｐｍにした点以外は実施例１と同一条件下でシリコン単結晶を引き上げた後、これを加工して得られたシリコンウェーハサンプルの酸素濃度分布及びＲＯＧを実施例１と同条件で求めた。その結果、図６に示すように、ウェーハ面内の酸素濃度は３×１０１７atoms/cm3以下となり、ＲＯＧは約１２．３％となった。 Example 2
After pulling up a silicon single crystal under the same conditions as Example 1 except that the crystal rotation speed was 17 rpm, the oxygen concentration distribution and ROG of the silicon wafer sample obtained by processing this were the same as Example 1 I asked for. As a result, as shown in FIG. 6, the oxygen concentration in the wafer plane was 3 × 10 17 atoms / cm 3 or less, and the ROG was about 12.3%.
＜実施例３＞
　結晶回転速度を１９ｒｐｍにした点以外は実施例１と同一条件下でシリコン単結晶を引き上げた後、これを加工して得られたシリコンウェーハサンプルの酸素濃度分布及びＲＯＧを実施例１と同条件で求めた。その結果、図７に示すように、ウェーハ面内の酸素濃度は３×１０１７atoms/cm3以下となり、ＲＯＧは約７．５％となった。 Example 3
After pulling up a silicon single crystal under the same conditions as Example 1 except that the crystal rotation speed was 19 rpm, the oxygen concentration distribution and ROG of the silicon wafer sample obtained by processing this were the same as Example 1 I asked for. As a result, as shown in FIG. 7, the oxygen concentration in the wafer surface was 3 × 10 17 atoms / cm 3 or less, and the ROG was about 7.5%.
＜実施例４＞
　カスプ磁場の中心位置をシリコン融液の液面位置から上方に７ｍｍの位置に設定した点以外は実施例１と同一条件下でシリコン単結晶を引き上げた後、これを加工して得られたシリコンウェーハサンプルの酸素濃度分布及びＲＯＧを実施例１と同条件で求めた。その結果、図８に示すように、ウェーハ面内の酸素濃度は４．３×１０１７atoms/cm3以下となり、ＲＯＧは５．９～１１．７％となった。 Example 4
Silicon obtained by processing a silicon single crystal after pulling up a silicon single crystal under the same conditions as Example 1 except that the central position of the cusp magnetic field was set 7 mm above the liquid level position of the silicon melt. The oxygen concentration distribution and ROG of the wafer sample were determined under the same conditions as in Example 1. As a result, as shown in FIG. 8, the oxygen concentration in the wafer plane was 4.3 × 10 17 atoms / cm 3 or less, and the ROG was 5.9 to 11.7%.
＜実施例５＞
　カスプ磁場の中心位置をシリコン融液の液面位置から下方に２６ｍｍの位置に設定した点以外は実施例１と同一条件下でシリコン単結晶を引き上げた後、これを加工して得られたシリコンウェーハサンプルの酸素濃度分布及びＲＯＧを実施例１と同条件で求めた。その結果、図９に示すように、ウェーハ面内の酸素濃度は５．３×１０１７atoms/cm3以下となり、ＲＯＧは３．０～１０．４％となった。 Example 5
Silicon obtained by processing a silicon single crystal after pulling up a silicon single crystal under the same conditions as Example 1 except that the center position of the cusp magnetic field was set to a position 26 mm downward from the liquid level position of the silicon melt The oxygen concentration distribution and ROG of the wafer sample were determined under the same conditions as in Example 1. As a result, as shown in FIG. 9, the oxygen concentration in the wafer surface was 5.3 × 10 17 atoms / cm 3 or less, and the ROG was 3.0 to 10.4%.
＜比較例１＞
　結晶回転速度を９ｒｐｍにした点以外は実施例１と同一条件下でシリコン単結晶を引き上げた後、これを加工して得られたシリコンウェーハサンプルの酸素濃度分布及びＲＯＧを実施例１と同条件で求めた。その結果、図１０に示すように、ウェーハ面内の酸素濃度は５．７×１０１７atoms/cm3以下となり、ＲＯＧは８４．８～１３５．１％となり、酸素濃度の面内均一性は非常に悪かった。 Comparative Example 1
After pulling up a silicon single crystal under the same conditions as Example 1 except that the crystal rotational speed was changed to 9 rpm, the oxygen concentration distribution and ROG of the silicon wafer sample obtained by processing this were the same as Example 1 I asked for. As a result, as shown in FIG. 10, the oxygen concentration in the wafer surface is 5.7 × 10 17 atoms / cm 3 or less, the ROG is 84.8 to 135.1%, and the in-plane uniformity of the oxygen concentration is It was very bad.
＜比較例２＞
　水平磁場を印加するＨＭＣＺ法によりシリコン単結晶を引き上げた。このときの結晶回転速度は５ｒｐｍとした。その後、シリコン単結晶を加工して得られたシリコンウェーハサンプルの酸素濃度及び抵抗率の面内分布を実施例１と同条件で求めた。その結果、図１１に示すように、ウェーハ面内の酸素濃度は３．１×１０１７atoms/cm3以下となったが、ＲＯＧは５７．３～８３．４％となり、酸素濃度の面内均一性は悪かった。また図１２に示すように、ＲＲＧは３．２～５．８％となり、抵抗率の面内均一性は良好であった。 Comparative Example 2
The silicon single crystal was pulled up by the HMCZ method applying a horizontal magnetic field. The crystal rotation speed at this time was 5 rpm. Thereafter, the in-plane distribution of oxygen concentration and resistivity of a silicon wafer sample obtained by processing a silicon single crystal was determined under the same conditions as in Example 1. As a result, as shown in FIG. 11, although the oxygen concentration in the wafer surface became 3.1 × 10 17 atoms / cm 3 or less, the ROG became 57.3 to 83.4%, and the in-plane of the oxygen concentration became The uniformity was bad. Further, as shown in FIG. 12, RRG was 3.2 to 5.8%, and the in-plane uniformity of the resistivity was good.
＜比較例３＞
　ＦＺ法により直径２００ｍｍウェーハ用のシリコン単結晶を製造した後、これを加工して得られた直径２００ｍｍシリコンウェーハサンプルの抵抗率の面内分布を実施例１と同条件で求めた。その結果、図１３に示すように、ＲＲＧは７．７～１１．９％となり、抵抗率の面内均一性は実施例１よりも悪かった。 Comparative Example 3
After producing a silicon single crystal for a wafer of 200 mm in diameter by the FZ method, the in-plane distribution of resistivity of a 200 mm diameter silicon wafer sample obtained by processing this was determined under the same conditions as in Example 1. As a result, as shown in FIG. 13, RRG was 7.7 to 11.9%, and the in-plane uniformity of resistivity was worse than that of Example 1.
　以上の結果から、カスプ磁場を用いたチョクラルスキー法によるシリコン単結晶の引き上げにおいて結晶回転速度１７～１９ｒｐｍとすることにより、シリコン単結晶中の酸素濃度を８×１０１７atoms/cm3以下にすることができ、ＲＲＧ及びＲＲＧも小さくなることが分かった。 From the above results, the oxygen concentration in the silicon single crystal can be made 8 × 10 17 atoms / cm 3 or less by setting the crystal rotation speed to 17 to 19 rpm in pulling up the silicon single crystal by the Czochralski method using the cusp magnetic field. It can be seen that RRG and RRG are also smaller.
１　　単結晶製造装置
２　　シリコン融液
３　　シリコン単結晶（インゴット）
３ａ　　ネック部
３ｂ　　ショルダー部
３ｃ　　ボディー部
３ｄ　　テール部
１０　　チャンバー
１０ａ　　メインチャンバー
１０ｂ　　プルチャンバー
１０ｃ　　ガス導入口
１０ｄ　　ガス排出口
１０ｅ　　覗き窓
１１　　石英ルツボ
１２　　サセプタ
１３　　回転シャフト
１４　　シャフト駆動機構
１５　　ヒーター
１６　　断熱材
１７　　熱遮蔽体
１８　　ワイヤー
１９　　ワイヤー巻き取り機構
２１　　磁場発生装置
２１ａ　　上部コイル（磁場発生用コイル）
２１ｂ　　下部コイル（磁場発生用コイル）
２２　　カメラ
２３　　画像処理部
２４　　制御部 1 Single Crystal Production Equipment 2 Silicon Melt 3 Silicon Single Crystal (Ingot)
3a Neck part 3b Shoulder part 3c Body part 3d Tail part 10 Chamber 10a Main chamber 10b Pull chamber 10c Gas inlet 10d Gas outlet 10e Penetration window 11 Quartz crucible 12 Susceptor 13 Rotatable shaft 14 Shaft drive mechanism 15 Heater 16 Heat insulation material 17 Thermal Shield 18 Wire 19 Wire winding mechanism 21 Magnetic field generator 21a Upper coil (coil for magnetic field generation)
21b Lower coil (magnetic field generation coil)
22 camera 23 image processing unit 24 control unit

Claims (5)

  1. 　カスプ磁場を印加しながらシリコン融液からシリコン単結晶を引き上げるチョクラルスキー法によるシリコン単結晶の製造方法であって、
    　前記シリコン単結晶を回転させながら引き上げる際の結晶回転速度が１７ｒｐｍ以上１９ｒｐｍ以下であることを特徴とするシリコン単結晶の製造方法。     A method for producing a silicon single crystal by the Czochralski method, wherein a silicon single crystal is pulled up from a silicon melt while applying a cusp magnetic field,
    The method for producing a silicon single crystal, wherein a crystal rotation speed at the time of pulling up while rotating the silicon single crystal is 17 rpm or more and 19 rpm or less.
  2. 　前記シリコン融液を保持する石英ルツボの回転速度が４．５ｒｐｍ以上８．５ｒｐｍ以下である、請求項１に記載のシリコン単結晶の製造方法。 The method for producing a silicon single crystal according to claim 1, wherein a rotation speed of the quartz crucible holding the silicon melt is 4.5 rpm or more and 8.5 rpm or less.
  3. 　前記カスプ磁場の磁場強度が５００～７００Ｇであり、垂直方向の磁場中心位置が前記シリコン融液の液面位置に対し＋４０ｍｍから－２６ｍｍの範囲である、請求項１又は２に記載のシリコン単結晶の製造方法。 The silicon single crystal according to claim 1 or 2, wherein the magnetic field strength of the cusp magnetic field is 500 to 700 G, and the magnetic field center position in the vertical direction is in the range of +40 mm to -26 mm with respect to the liquid level position of the silicon melt. Manufacturing method.
  4. 　酸素濃度が１×１０１７atoms/cm3以上８×１０１７atoms/cm3以下であり、
    　結晶成長方向と直交する結晶断面内のＲＯＧが１５％以下であり、
    　前記結晶断面内のＲＲＧが５％以下であることを特徴とするシリコン単結晶。     The oxygen concentration is 1 × 10 17 atoms / cm 3 or more and 8 × 10 17 atoms / cm 3 or less,
    ROG in the crystal cross section orthogonal to the crystal growth direction is 15% or less,
    A silicon single crystal characterized in that RRG in the crystal cross section is 5% or less.
  5. 　酸素濃度が１×１０１７atoms/cm3以上８×１０１７atoms/cm3以下であり、
    　ＲＯＧが１５％以下であり、
    　ＲＲＧが５％以下であることを特徴とするシリコンウェーハ。     The oxygen concentration is 1 × 10 17 atoms / cm 3 or more and 8 × 10 17 atoms / cm 3 or less,
    ROG is less than 15%,
    A silicon wafer characterized in that RRG is 5% or less.
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