Method for producing an n-type silicon single crystal, n-type silicon single crystal ingot, silicon wafer and epitaxial silicon wafer

Abstract

Method for producing an n-type silicon single crystal, wherein a silicon single crystal is grown from a silicon melt containing a major dopant in the form of red phosphorus, and the silicon single crystal is grown according to a Czochralski process, wherein the silicon single crystal comprises a diameter of a straight body that lies in the range of 201 mm to 230 mm, and The silicon single crystal, part of which has a specific electrical resistance in the range of 0.5 mΩcm to 0.7 mΩcm, is grown using a quartz crucible whose inner diameter is in the range of 2.1 to 2.3 times the diameter of the straight body of the silicon single crystal.

Description

TECHNICAL FIELD

[0001] The present invention relates to methods for producing an n-type silicon single crystal, ingots of an n-type silicon single crystal, silicon wafers, and epitaxial silicon wafers. STATE OF THE ART

[0002] In recent years, mobile devices such as mobile phones have become widely used. Such devices require high portability and long-term usability. Accordingly, efforts have been made to increase the capacity of the mobile device's built-in battery and reduce the mobile device's power consumption.

[0003] In order to reduce the energy consumption of the mobile device itself, it is necessary to reduce the energy consumption of a semiconductor component built into the mobile device.

[0004] For example, because a low-voltage power MOSFET (metal oxide semiconductor field-effect transistor) used in an electrical power device for a mobile device has a certain internal electrical resistance in an on-state, the low-voltage power MOSFET itself consumes electrical energy depending on the electric current flowing through the low-voltage power MOSFET.

[0005] Accordingly, the power consumption of the mobile device can be reduced if the internal resistance of the low-voltage power MOSFET in the on-state can be reduced. Against this background, there is a strong demand for an n-type silicon single crystal with low electrical resistivity (hereinafter referred to as low resistivity) to reduce the internal resistance of the low-voltage power MOSFET in the on-state.

[0006] For a typical method for producing single-crystal silicon according to the Czochralski process, Patent Literature 1 discloses that the inner diameter of a quartz crucible is preferably three times the diameter (diameter of the straight body) of the silicon single crystal, and that with this arrangement, the silicon single crystal can be stably pulled up even if the diameter of the silicon single crystal is large.

[0007] Examples of dopants that can reduce the resistivity of a silicon wafer are red phosphorus and arsenic. Patent Literature 2 discloses the use of red phosphorus as a dopant for low resistivity.

[0008] Furthermore, Patent Literature 3 discloses the use of arsenic as a dopant for low resistivity. LITERATURE LIST

[0009] Patent Literature 4 describes processes for producing highly doped n-type silicon single crystals using the Czochralski process. These processes are intended to further reduce the frequency of macroscopic voids in silicon single crystals without affecting the other crystal properties. Phosphorus, arsenic, and antimony are mentioned as dopants. The examples describe silicon wafers with crystal diameters of 104 to 154 mm. Antimony or arsenic are used as dopants.

[0010] Patent Literature 5 relates to another Czochralski method for producing n-type silicon single crystals with low resistivity. In an experiment, using red phosphorus as a dopant, a resistivity of 1.0 mΩcm was obtained at the top end of the straight body of a 200 mm diameter single crystal. Using arsenic as a dopant, a resistivity of 2.0 mΩcm or less at the top end of the straight body was reported. PATENT LITERATURE Patent literature 1 JP 2009-292684 A Patent literature 2 Japanese patent JP 5 890 587 B2 Patent literature 3 JP 2011-44505 A Patent literature 4 DE 10 2010 007 460 A1 Patent literature 5 JP 2016-121032 A (and US 2017 / 0327966 A1) SUMMARY OF THE INVENTION TASK(S) TO BE SOLVED BY THE INVENTION

[0011] However, when the above technique described in Patent Literature 1 is used to pull up n-type silicon single crystal with low resistivity, an n-type dopant (e.g., red phosphorus and arsenic), which is a volatile dopant, evaporates during the pulling up of the silicon single crystal, thus reducing the yield of the silicon single crystal with the desired low resistivity and causing the occurrence of dislocations in the silicon single crystal due to an increase in the added amount of the n-type dopant.

[0012] According to the disclosure of Patent Literature 2, a low-resistivity silicon wafer can be manufactured using red phosphorus as a dopant. However, the example only shows a silicon wafer with a diameter of 200 mm.

[0013] Furthermore, according to the disclosure of Patent Literature 3, a low-resistivity silicon wafer can be manufactured using arsenic as a dopant. However, the example only shows a silicon wafer with a diameter of 150 mm.

[0014] It is an object of the invention to provide a method for producing an n-type silicon single crystal which can avoid a reduction in the yield of the silicon single crystal and prevent the occurrence of dislocations in the silicon single crystal, an ingot of the n-type silicon single crystal, a silicon wafer having a diameter of 200 mm or more, and an epitaxial silicon wafer. MEANS FOR SOLVING THE TASK(S)

[0015] According to one aspect of the invention, there is provided a manufacturing method for an n-type silicon single crystal (for monocrystalline silicon) by pulling up a silicon single crystal from a silicon melt containing a main dopant in the form of red phosphorus, and growing the silicon single crystal according to a Czochralski process. In this process, the silicon single crystal, a portion of which has an electrical resistivity falling within a range of 0.5 mΩcm to 0.7 mΩcm, is pulled up using a quartz crucible whose inner diameter is in a range of 2.1 times to 2.3 times relative to a diameter of the straight body of the silicon single crystal. The diameter of the straight body of the silicon single crystal is in a range of 201 mm to 230 mm.

[0016] In the present application, the diameter of the straight body refers to a diameter of a part of the pulled-up silicon single crystal from which a silicon wafer is cut out, the diameter being controlled to be substantially constant.

[0017] According to the above aspect of the invention, the free surface area of ​​the melt in the quartz crucible can be reduced by using the quartz crucible whose inner diameter is in the range of 2.1 to 2.3 times the diameter of the straight body of the silicon single crystal. Accordingly, the evaporation of red phosphorus as a dopant in the melt can be prevented, thus avoiding a reduction in the yield of a part in the low-resistivity silicon single crystal.

[0018] In addition, because preventing the evaporation of red phosphorus results in avoiding the addition of large amounts of red phosphorus at the beginning of pulling up, the occurrence of dislocations in the silicon single crystal can be prevented.

[0019] In other words, according to the above aspect of the invention, by preventing the evaporation of red phosphorus in the melt while preventing dislocations in the silicon single crystal due to high concentration of red phosphorus at the beginning of pulling up the silicon single crystal, the concentration of red phosphorus in the melt can be increased according to the progress of pulling up, so that the silicon single crystal with low resistivity can be obtained.

[0020] In the above embodiment, the diameter of the straight body of the silicon single crystal is in a range of 201 mm to 230 mm and the inner diameter of the quartz crucible is in a range of 2.1 times to 2.3 times relative to the diameter of the straight body of the silicon single crystal.

[0021] Because the evaporation of red phosphorus can be prevented when the silicon single crystal has a straight body diameter within a range of 201 mm to 230 mm, the above functions and effects can be obtained when the inner diameter of the quartz crucible is within the above range.

[0022] In the above embodiment, the specific electrical resistance of the part of the silicon single crystal is in a range of 0.5 mΩcm to 0.7 mΩcm. Even in the above range of electrical resistivity, the pulled-up silicon single crystal can be dislocation-free by setting the inner diameter of the quartz crucible to a range of 2.1 times to 2.3 times relative to the diameter of the straight body of the silicon single crystal.

[0023] According to a further aspect, the present invention relates to a method for producing an n-type silicon single crystal according to claim 2. In this embodiment, the diameter of the straight body of the silicon single crystal is in a range of 301 mm to 330 mm and the inner diameter of the quartz crucible is in a range of 1.7 times to 2.0 times, relative to the diameter of the straight body of the silicon single crystal.

[0024] Because the evaporation of red phosphorus can be prevented when the silicon single crystal has a straight body diameter in the range of 301 mm to 330 mm, the above functions and effects can be obtained when the inner diameter of the quartz crucible is within the above range.

[0025] In the embodiment of the method according to claim 2, the specific electrical resistance of the part of the silicon single crystal is in a range from 0.8 mΩcm to 1.0 mΩcm.

[0026] Even in the above range of electrical resistivity, the pulled-up silicon single crystal can be dislocation-free by setting the inner diameter of the quartz crucible to fall within a range of 1.7 times to 2.0 times relative to the diameter of the straight body of the silicon single crystal.

[0027] According to another aspect of the invention, there is provided a manufacturing method for an n-type silicon single crystal (for monocrystalline silicon) by pulling up a silicon single crystal from a silicon melt containing arsenic as a main dopant, and growing the silicon single crystal according to a Czochralski process, in which the silicon single crystal is pulled up using a quartz crucible whose inner diameter is in a range of 1.7 times to 2.0 times relative to the diameter of the straight body of the silicon single crystal, in which a part of the silicon single crystal has an electrical resistivity in a range of 1.7 mΩcm to 2.0 mΩcm, and the diameter of the straight body of the silicon single crystal is in a range of 301 mm to 330 mm. Also according to the above aspect of the invention, the same functions and effects as those described above can be achieved.

[0028] Specifically, according to the above aspect of the invention, by preventing the evaporation of arsenic in the melt while preventing dislocations in the silicon single crystal due to high concentration of arsenic at the beginning of pulling up the silicon single crystal, the concentration of arsenic in the melt can be increased in accordance with the progress of pulling up, so that the silicon single crystal having low resistivity can be obtained.

[0029] In the above embodiment, the silicon single crystal is preferably pulled up using a pulling device whose furnace internal pressure is set in a range of 40 kPa to 80 kPa.

[0030] In this embodiment, the evaporation of red phosphorus and arsenic can be prevented by setting the internal pressure of the pull-up device to 40 kPa or more. On the other hand, by setting the internal pressure of the furnace to 80 kPa or less, the occurrence of dislocations caused by the concentration of the dopant in the silicon melt due to dopant segregation can be prevented.

[0031] In the above embodiment, when pulling up the silicon single crystal, a magnetic field with a magnetic field strength in the range of 0.2 T to 0.4 T is preferably applied to the silicon melt in the quartz crucible. Because the application of the magnetic field with the magnetic field strength in the range of 0.2 T to 0.4 T can prevent the in-plane fluctuation of the silicon single crystal during pulling up, the silicon single crystal can be reliably pulled up without causing dislocations.

[0032] According to another aspect of the invention, an ingot of n-type silicon single crystal contains a main dopant in the form of red phosphorus, wherein the ingot has a straight body diameter ranging from 301 mm to 330 mm, and a portion of the ingot has a specific electrical resistivity ranging from 0.8 mΩcm to 1.0 mΩcm. The ingot can be produced by the method according to claim 2.

[0033] According to another aspect of the invention, a silicon wafer is cut out from the ingot of the n-type silicon single crystal according to the above aspect of the invention, and the silicon wafer has a specific electrical resistance in the range of 0.8 mΩcm to 1.0 mΩcm and has a diameter of 300 mm.

[0034] According to another aspect of the invention, an epitaxial silicon wafer has an epitaxial film formed on a surface of the silicon wafer according to the above aspect of the invention.

[0035] According to the above aspects of the invention, the ingot of the silicon single crystal containing red phosphorus as a dopant and having an unusually large diameter of 300 mm and a low resistivity, the low resistivity silicon wafer, and the low resistivity epitaxial silicon wafer can be obtained.

[0036] According to another aspect of the invention, an ingot of n-type silicon single crystal contains a main dopant in the form of arsenic, wherein the ingot has a straight body diameter ranging from 301 mm to 330 mm and a portion of the ingot has a specific electrical resistivity ranging from 1.7 mΩcm to 2.0 mΩcm. The ingot can be produced by the method according to claim 3.

[0037] According to another aspect of the invention, a silicon wafer is cut out from the ingot of the n-type silicon single crystal according to the above aspect of the invention, and the silicon wafer has an electrical resistivity ranging from 1.7 mΩcm to 2.0 mΩcm and has a diameter of 300 mm. According to another aspect of the invention, an epitaxial silicon wafer has an epitaxial film formed on a surface of the silicon wafer according to the above aspect of the invention.

[0038] According to the above aspects of the invention, the silicon single crystal ingot containing arsenic as a dopant and having an unusually large diameter of 300 mm and a low resistivity, the low resistivity silicon wafer, and the low resistivity epitaxial silicon wafer can be obtained. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 schematically illustrates an exemplary structure of a silicon single crystal pulling apparatus according to an exemplary embodiment of the invention. Fig. Figure 2 is a graph showing a relationship between a straight body length and the resistivity in silicon single crystal (the diameter of the straight body is in the range of 201 mm to 230 mm) in examples using red phosphorus as a dopant. Fig. 3 is a graph showing a relationship between a length of the straight body and the resistivity in the silicon single crystal (the diameter of the straight body is in the range of 201 mm to 230 mm) in other examples using red phosphorus as a dopant. Fig. Figure 4 is a graph showing a relationship between a length of the straight body and the resistivity in the silicon single crystal (the diameter of the straight body is in the range of 301 mm to 330 mm) in examples using red phosphorus as a dopant. Fig. Figure 5 is a graph showing a relationship between a length of the straight body and the resistivity in the silicon single crystal (the diameter of the straight body is in the range of 301 mm to 330 mm) in examples with arsenic as a dopant. DESCRIPTION OF EMBODIMENTS[1] Structure of the pull-up device 1 for single-crystal silicon

[0039] Fig. Figure 1 schematically shows an exemplary structure of a pull-up apparatus 1 for single-crystal silicon. A method for producing single-crystal silicon according to an exemplary embodiment of the invention is applicable to the pull-up apparatus 1. The pull-up apparatus 1, which pulls up silicon single crystal (single-crystal silicon) 10 according to the Czochralski process, includes a chamber 2 defining an outer body and a crucible 3 arranged in the center of the chamber 2.

[0040] The crucible 3, which has a double structure formed of an inner quartz crucible 3A and an outer graphite crucible 3B, is fixed to an upper end of a support shaft 4 which is rotatable and vertically movable.

[0041] The inner diameter of the inner quartz crucible 3A of the crucible 3 is set to be in a range of 1.7 times to 3.2 times relative to the diameter of the straight body of the pulled-up silicon single crystal 10.

[0042] Specifically, when the diameter of the straight body of the silicon single crystal 10 is in a range of 201 mm to 230 mm, the inner diameter of the quartz crucible 3A is preferably in a range of 2.1 times to 2.3 times relative to the diameter of the straight body of the silicon single crystal 10. When the diameter of the straight body of the silicon single crystal 10 is in a range of 301 mm to 330 mm, the inner diameter of the quartz crucible 3A is preferably in a range of 1.7 times to 2.0 times relative to the diameter of the straight body of the silicon single crystal 10.

[0043] Because a larger inner diameter of the crucible 3 than the above inner diameter increases the expansion of a heat shield plate 12 and an opening diameter of the chamber 2, there is a possibility that evaporated dopant adheres to a furnace body and causes foreign substances to adhere to the silicon single crystal 10, resulting in the occurrence of dislocations.

[0044] Because a gap between the silicon single crystal 10 and the quartz crucible 3A can be reduced by setting the inner diameter of the crucible 3 to the above range, the evaporation of the dopant (e.g., red phosphorus and arsenic) can be reduced and the occurrence of dislocations in the starting region of the straight body caused by the segregation phenomenon of the dopant can be prevented.

[0045] A resistance heater 5 is provided on the outside of the crucible 3 so as to surround the crucible 3. A thermal insulation material 6 is provided on the outside of the heater 5 and along an inner surface of the chamber 2. The heater 5 is not necessarily in the form of a single body, but may also be in the form of separate bodies (ie, upper body and lower body), each of which can independently adjust a temperature.

[0046] A pulling shaft 7 (e.g., a wire) rotatable at a predetermined speed coaxially with the support shaft 4 and in a direction opposite or the same as the direction of the support shaft 4 is provided above the crucible 3. A seed crystal 8 is attached to a lower end of the pulling shaft 7.

[0047] A cylindrical water-cooled body surrounding the silicon single crystal 10 during growth may be provided above a silicon melt 9 in the chamber 2.

[0048] The water-cooled body, made of a metal with excellent thermal conductivity (e.g., copper), is forced-cooled by cooling water circulating inside the water-cooled body. The water-cooled body promotes the cooling of the silicon single crystal 10 during growth, thus controlling a temperature gradient between a central region of the silicon single crystal 10 and a peripheral region of the silicon single crystal 10 toward the pull shaft.

[0049] The cylindrical heat shield plate 12 is arranged in the chamber 2.

[0050] The heat shield plate 12 shields the silicon single crystal 10 during its growth from high-temperature radiant heat from the silicon melt 9 in the crucible 3, the heater 5, and a side wall of the crucible 3. Near a solid-liquid interface (crystal growth interface), the heat shield plate 12 also prevents heat diffusion to the outside and controls the temperature gradient of the central region of the silicon single crystal 10 and the peripheral region of the silicon single crystal 10 toward the pull shaft.

[0051] A gas inlet 13 for supplying inert gas (e.g., Ar gas) into the chamber 2 is provided at an upper part of the chamber 2. A gas outlet 14 through which the gas in the chamber 2 is sucked and discharged when a vacuum pump (not shown) is driven is provided at a lower part of the chamber 2.

[0052] The inert gas supplied through the gas inlet 13 into the chamber 2 flows downward between the growing silicon single crystal 10 and the heat shield plate 12, flows through a gap (liquid surface gap) between the lower end of the heat shield plate 12 and the liquid surface of the silicon melt 9, toward the outside of the heat shield plate 12, further the outside of the crucible 3, and then flows downward along the outside of the crucible 3 to be discharged through the outlet 14.

[0053] For the growth of the silicon single crystal 10 using the above growth apparatus, while maintaining the interior of the chamber 2 under an inert gas atmosphere and reduced pressure, a solid material (e.g., polycrystalline silicon) filled in the crucible 3 is heated by the heater 5 to melt it, thereby forming the silicon melt 9. After the silicon melt 9 is formed in the crucible 3, the pulling shaft 7 is lowered to immerse the seed crystal 8 into the silicon melt 9. While the crucible 3 and the pulling shaft 7 are rotated in predetermined directions, the pulling shaft 7 is gradually pulled up, and thereby the silicon single crystal 10 grows continuously with the seed crystal 8. [2] Process for producing single-crystal silicon

[0054] When the silicon single crystal 10 (ie, an n-type silicon single crystal according to the exemplary embodiment) is manufactured using the above pulling-up apparatus 1, red phosphorus or arsenic is added as the main dopant to the silicon melt 9 at the beginning of the pulling-up or as needed during the pulling-up, whereby the silicon single crystal 10 can be manufactured. When red phosphorus or arsenic is used as the main dopant, red phosphorus or arsenic accounts for 50 mass% or more of the n-type dopant. However, another dopant may be further added.

[0055] When pulling up an ingot of silicon single crystal 10 with a straight body diameter ranging from 201 mm to 230 mm, when the dopant is red phosphorus, the resistivity of the silicon single crystal 10 at a starting point of the straight body is controlled to fall within a range of 0.8 mΩcm to 1.05 mΩcm. Subsequently, the resistivity of the silicon single crystal 10 continuously decreases with the growth of the silicon single crystal 10 by pulling up the silicon single crystal 10, and thereby finally obtaining the silicon single crystal 10 with the resistivity ranging from 0.5 mΩcm to 0.7 mΩcm.

[0056] When pulling up the silicon single crystal ingot 10 with the diameter of the straight body ranging from 301 mm to 330 mm, when the dopant is red phosphorus, the resistivity of the silicon single crystal 10 at the starting point of the straight body is controlled to fall within a range of 1.2 mΩcm to 1.7 mΩcm. Subsequently, as the silicon single crystal 10 grows, the resistivity of the silicon single crystal 10 decreases continuously by pulling up the silicon single crystal 10, and thereby finally obtaining the silicon single crystal 10 whose resistivity in a part of the ingot ranges from 0.8 mΩcm to 1.0 mΩcm.

[0057] When pulling up the silicon single crystal ingot 10 with the diameter of the straight body ranging from 301 mm to 330 mm, when the dopant is arsenic, the resistivity of the silicon single crystal 10 at the starting point of the straight body is controlled to fall within a range of 2.5 mΩcm to 3.1 mΩcm. Subsequently, the resistivity of the silicon single crystal 10 continuously decreases with the growth of the silicon single crystal 10 by pulling up the silicon single crystal 10, and thereby finally obtaining the silicon single crystal 10 whose resistivity at the part of the ingot is in a range of 1.7 mΩcm to 2.0 mΩcm.

[0058] The ingot of the silicon single crystal 10 according to the exemplary embodiment can be pulled up under conventional pulling-up conditions. To increase the concentration of the dopant (e.g., red phosphorus and arsenic) in the silicon melt 9 within the crucible 3, for example, the added amount of the dopant is changed during the pulling-up, the segregation phenomenon during the pulling-up is used to increase the dopant concentration, and / or the amount of inert gas supplied to the chamber 2 is changed to prevent evaporation of the dopant, which leads to a change in the internal pressure of the chamber 2.

[0059] Specifically, in order to reduce the evaporation of the dopant and increase the dopant concentration in the silicon melt 9 in the crucible 3 in the first half of pulling up the straight body of the silicon single crystal 10, an Ar flow rate is set to fall within a range of 50 l / min to 150 l / min, and the internal pressure of the furnace is set to fall within a range of 40 kPa to 80 kPa.

[0060] On the other hand, in order to increase the dopant concentration in the silicon melt 9 in the crucible 3 at a later stage when pulling up the straight body of the silicon single crystal 10 by increasing the evaporation of the dopant and balancing the dopant concentration with the concentrated dopant concentration caused by segregation of the dopant as the growth of the silicon single crystal 10 progresses, the Ar flow rate is set to fall within a range of 50 l / min to 200 l / min, and the internal pressure of the furnace is set to fall within a range of 20 kPa to 80 kPa, preferably 30 kPa to 40 kPa.

[0061] Furthermore, when pulling up the silicon single crystal 10, it is preferable to apply a magnetic field with a magnetic field strength ranging from 0.2 T to 0.4 T. Applying the magnetic field can prevent the silicon single crystal 10 being pulled up from causing melt flow and can reduce temperature unevenness and turbulence phenomena in the melt, so that the silicon single crystal 10 can be reliably pulled up without causing dislocations.

[0062] When the heater 5 is in the form of an upper heater and a lower heater that can independently adjust a temperature, when pulling up the silicon single crystal 10, the value of the ratio of a heating amount of the lower heater to a heating amount of the upper heater is preferably in a range of 1 to 4.

[0063] When the ratio is less than 1, in other words, when the heating intensity of the lower heater is lower than the heating intensity of the upper heater, a convection flow of the silicon melt from the bottom of the crucible 3 toward below the solid-liquid interface becomes not strong enough to weaken the temperature-unstable convection flow of the liquid from the surface of the dopant-added silicon melt 9 to the silicon single crystal, so that the occurrence of dislocations caused by the temperature unstable cannot be prevented.

[0064] On the other hand, when the ratio of heating intensity exceeds 4, a heat load acting on the lower part of the crucible is increased, so that there is a possibility that deformation of the crucible 3 and exfoliation of quartz from the crucible 3 occur.

[0065] When forming the shoulder of the silicon single crystal 10, it is preferable to pull up the silicon single crystal 10 in such a way as to avoid the occurrence of a remelting region with a large height (e.g., 200 µm or more). The remelting region refers to a region in which the silicon single crystal 10, which has solidified after being pulled up from the silicon melt 9, melts again and becomes liquid during the pulling up.

[0066] Specifically, during shoulder formation, the silicon single crystal 10 is initially pulled up while the crucible 3 is rotated at a rotation speed ranging from 16 rpm to 30 rpm. Subsequently, when the diameter of the shoulder becomes equal to or more than half the diameter of the straight body of the silicon single crystal 10, the rotation speed of the crucible 3 is gradually reduced to a range of 4 rpm to 12 rpm.

[0067] When the silicon single crystal 10 is initially pulled up at a rotation speed exceeding 30 rpm when forming the shoulder, the operation of the pull-up device 1 is not stabilized, so that the shoulder is most likely to be deformed.

[0068] Furthermore, when the diameter of the shoulder becomes equal to or larger than half the diameter of the straight body of the silicon single crystal 10, and when the rotation speed of the crucible 3 is less than 4 rpm, the silicon melt 9 with the added dopant is not stabilized, so that dislocations are most likely to occur.

[0069] On the other hand, when the rotation speed of the crucible 3 exceeds 12 rpm, in-plane fluctuations of the oxygen density and the resistivity of the silicon single crystal 10 increase, and stable crystal quality cannot be achieved.

[0070] In forming the straight body of the silicon single crystal 10, it is preferable to pull up the silicon single crystal 10 in a manner that avoids the occurrence of the reflow region having a large height (e.g., 200 μm or more). Specifically, in forming the straight body, the silicon single crystal 10 is initially pulled up while rotating the crucible 3 at a rotation speed ranging from 9 rpm to 30 rpm. Then, when the straight body of the silicon single crystal 10 has been pulled up by a length ranging from 50 mm to 200 mm, the rotation speed of the crucible 3 is changed to a range from 0.1 rpm to 7 rpm.

[0071] When the silicon single crystal 10 is pulled up at a rotation speed exceeding 30 rpm at the beginning of the formation of the straight body, the operation of the pull-up device 1 is not stabilized, so that the straight body is most likely to be deformed.

[0072] Furthermore, when the straight body is pulled up at a rotation speed of the crucible 3 of less than 0.1 rpm in a range of 50 mm to 200 mm from a starting point of the straight body, the silicon melt 9 with added dopant is not stabilized, so that dislocations are most likely to occur.

[0073] However, when the rotation speed of the crucible 3 exceeds 7 rpm, fluctuations in the oxygen density and electrical resistivity within the plane of the silicon single crystal 10 increase and cause unstable crystal quality.

[0074] When the dopant is red phosphorus, a part close to a tail of the silicon single crystal 10 pulled up with the pull-up device 1 and having a straight body diameter ranging from 201 mm to 230 mm provides the silicon single crystal 10 in the form of an ingot having a resistivity ranging from 0.5 mΩcm to 0.7 mΩcm.

[0075] After the periphery of the silicon single crystal ingot 10 is ground to obtain an ingot with a straight body diameter of 200 mm, the ingot is cut into a silicon wafer using a wire saw or the like. The resulting silicon wafer is lapped and polished to obtain a silicon wafer with a resistivity of 0.5 mΩcm to 0.7 mΩcm and a diameter of 200 mm.

[0076] Furthermore, after the silicon wafer is processed, an epitaxial film is formed on a surface of the silicon wafer, thus producing an epitaxial silicon wafer with a diameter of 200 mm for delivery to a customer.

[0077] When the dopant is red phosphorus, a part near the tail of the silicon single crystal 10 having a straight body diameter in the range of 301 mm to 330 mm provides the silicon single crystal 10 in the form of an ingot having a resistivity in the range of 0.8 mΩcm to 1.0 mΩcm.

[0078] After grinding the periphery of the silicon single crystal ingot 10 to obtain an ingot with a straight body diameter of 300 mm, the ingot is cut into a silicon wafer using a wire saw or the like. The resulting silicon wafer is lapped and polished to obtain a silicon wafer with a resistivity ranging from 0.8 mΩcm to 1.0 mΩcm and a diameter of 300 mm.

[0079] Furthermore, after processing the silicon wafer, an epitaxial growth film is formed on a surface of the silicon wafer, thus producing an epitaxial silicon wafer with a diameter of 300 mm for delivery to a customer.

[0080] When the dopant is arsenic, a part close to a tail of the silicon single crystal 10 having a straight body diameter in the range of 301 mm to 330 mm provides the silicon single crystal 10 in the form of an ingot having a resistivity in the range of 1.7 mΩcm to 2.0 mΩcm.

[0081] After grinding the periphery of the silicon single crystal ingot 10 to obtain an ingot with a straight body diameter of 300 mm, the ingot is cut into a silicon wafer using a wire saw or the like. The resulting silicon wafer is lapped and polished to obtain a silicon wafer with a diameter of 300 mm.

[0082] Furthermore, after the silicon wafer is processed, an epitaxial film is formed on a surface of the silicon wafer, thus producing an epitaxial silicon wafer with a diameter of 300 mm for delivery to a customer. EXAMPLES

[0083] Next, examples of the invention will be described. It should be understood that the scope of the invention is not limited to the examples shown below, but includes other embodiments as long as the object of the invention can be achieved.

[0084] [1] Ingot of silicon single crystal 10 with a diameter of the straight body in the range of 201 mm to 230 mm

[0085] When pulling up the silicon single crystal 10 having a straight body diameter (hereinafter sometimes referred to as crystal diameter) in the range of 201 mm to 230 mm, the resistivity of the silicon single crystal 10 at the starting point of the straight body (ie, end point of the shoulder) was controlled to be in a range of 0.8 mΩcm to 1.05 mΩcm. The ratio of the inner diameter of the crucible 3 to the crystal diameter (=[inner diameter of the crucible 3] / (crystal diameter]) was set to fall within a range of 2.1 to 2.3 in the examples and within a range of 2.6 to 3.0 in the comparative examples and reference examples. The filling amount was set to a range of 80 kg to 180 kg. The pulling-up speed was set to a range of 0.3 mm / min to 1.0 mm / min. The crystal rotation speed was set to a range of 9 rpm to 17 rpm.The rotation speed of crucible 3 was set to a range of 0.2 rpm to 22 rpm.

[0086] Furthermore, in the first half of the straight body of the silicon single crystal 10, the argon flow rate was set to a range of 50 l / min to 150 l / min, and the internal furnace pressure was set to a range of 40 kPa to 80 kPa. In the latter half of the straight body of the silicon single crystal 10, the argon flow rate was set to a range of 50 l / min to 200 l / min, and the internal furnace pressure was set to a range of 20 kPa to 80 kPa.

[0087] [1-1] Specific resistance in the range of 0.6 mΩcm to 0.7 mΩcm.

[0088] The inner diameter of the quartz crucible 3A was changed relative to the diameter of the straight body of the silicon single crystal 10. The red phosphorus-doped silicon single crystal 10 was pulled up while controlling the resistivity using several measures: specifically, the addition of red phosphorus as a dopant; the Ar flow rate; the internal furnace pressure; the height of the heat shield plate 12 from the liquid surface; the pulling-up speed of the silicon single crystal 10; and a combination thereof. The results are shown in Table 1 and Fig. 2. A crucible diameter of 24" corresponds to 60.96 cm. 22" corresponds to 55.88 cm. 18" corresponds to 45.72 cm. In the following description, the 0% point of the straight body length refers to the starting point of the straight body of the silicon single crystal 10, and the 100% point of the straight body length refers to a starting point of the tail of the silicon single crystal 10. The pass length of the straight body refers to a value obtained by dividing a length of a region of the straight body that has a satisfactory resistivity (within a desired resistivity range) and is dislocation-free by the total length of the straight body.The dislocation-free success rate refers to the rate of the number of attempts that successfully led to a dislocation-free state when pulling up the silicon single crystal 10, relative to the number of attempts for pulling up the silicon single crystal 10.

[0089] When comparing Comparative Examples 1 and 2 (Comparison 1 and 2) with Examples 1 to 3, Examples 1 to 3 obviously show a higher success rate of dislocation-free formation and thus an increase in crystal yield, so that it is found that a part of the silicon single crystal ingot 10 can have a larger region with a specific resistance in the range of 0.6 mΩcm to 0.7 mΩcm. Accordingly, when the dopant is red phosphorus and the silicon single crystal ingot 10 is manufactured with the target specific resistance in the range of 0.6 mΩcm to 0.7 mΩcm, it is found that the inner diameter of the quartz crucible 3A is preferably in the range of 2.1 times to 2.3 times relative to the diameter of the straight body of the silicon single crystal 10. [1-2] Specific resistance in the range of 0.5 mΩcm to 0.6 mΩcm

[0090] It was investigated in a part of the ingot of the silicon single crystal 10 with the diameter of the straight body in the range of 201 mm to 230 mm how the inner diameter of the quartz crucible 3A exerts an influence on the specific resistance, which falls in a range of 0.5 mΩcm to 0.6 mΩcm.

[0091] Specifically, resistivity control by controlling the Ar flow rate, the internal pressure of the furnace, and the pull-up speed is a two-way control of preventing evaporation and promoting evaporation. Evaporation is prevented on the silicon single crystal 10 from the tip end of the crystal to a portion with a resistivity equal to or less than a desired value. Furthermore, when the resistivity falls within a desired range, resistivity control is changed to promoting evaporation to eliminate the effects of segregation. In a range of 0.5 mΩcm to 0.6 mΩcm relative to the target value, which ranges from 0.6 mΩcm to 0.7 mΩcm, the duration of evaporation prevention is long until the later time of pulling up the silicon single crystal (just before the resistivity reaches 0.6 mΩcm).

[0092] Results are shown in Table 2 and Fig. 3. A crucible diameter of 24" corresponds to 60.96 cm. 22" corresponds to 55.88 cm. 18" corresponds to 45.72 cm.

[0093] In Reference Examples 1 and 2 (References 1 and 2), the crystal survival length was 0%, indicating that a portion of the silicon single crystal ingot 10 could not achieve the target resistivity in the range of 0.5 mΩcm to 0.6 mΩcm. In contrast, in Examples 4 to 6, it was confirmed that the crystal survival length was obtained in a portion of the silicon single crystal ingot 10 whose resistivity fell within the target resistivity range. Accordingly, when the dopant was red phosphorus and the ingot of the silicon single crystal 10 with the target resistivity in the range of 0.5 mΩcm to 0.6 mΩcm was prepared, it was confirmed that the inner diameter of the quartz crucible 3A was also preferably in the range of 2.1 times to 2.3 times relative to the diameter of the straight body of the silicon single crystal 10.

[0094] In particular, Example 7 shows that the resistivity drops sharply as the pulling-up of the silicon single crystal 10 progresses. The resistivity of the silicon single crystal 10 at the starting point of the straight body becomes 1.05 mΩcm, and the resistivity of the silicon single crystal 10 at 20% of the length of the straight body becomes a relatively high value to prevent dislocation. Then, by sharply reducing the resistivity, the silicon single crystal 10 with the target resistivity in the range of 0.5 mΩcm to 0.6 mΩcm or 0.7 mΩcm can be obtained with high yield. When the resistivity of the silicon single crystal at the starting point of the straight body exceeds 1.05 mΩcm, the length of the straight body with the target resistivity in the range of 0.5 mΩcm to 0.6 mΩcm is very short, resulting in a low yield.

[0095] As shown in Example 8, by setting the resistivity of the silicon single crystal at the starting point of the straight body to 0.8 mΩcm, the occurrence of dislocations in the silicon single crystal can be prevented, and a part of the straight body whose target resistivity is in the range of 0.5 mΩcm to 0.6 mΩcm can account for 35% of the entire straight body, and a part of the straight body whose target resistivity is in the range of 0.5 mΩcm to 0.7 mΩcm can account for 70% of the entire straight body, which is extremely high. It should be noted that when the resistivity of the silicon single crystal at the starting point of the straight body was set to 0.75 mΩcm, which is lower than 0.8 mΩcm, discocations often occurred in the silicon single crystal until reaching 20% ​​of the length of the straight body and hindered the growth of the silicon single crystal. [2] Ingot of silicon single crystal 10 with a diameter of the straight body in the range of 301 mm to 330 mm

[0096] A silicon single crystal 10 with a crystal diameter in the range of 301 mm to 330 mm was pulled up.

[0097] In the examples and comparative examples (comparisons), the ratio of the inner diameter of the crucible 3 to the crystal diameter (=[inner diameter of the crucible 3] / [crystal diameter]) was set to fall within a range of 1.7 to 2.0 in the examples and 2.5 to 2.6 in the comparative examples. The feed amount was set to a range of 80 kg to 250 kg. The pull-up speed was set to a range of 0.3 mm / min to 1.0 mm / min. The crystal rotation speed was set to a range of 5 rpm to 17 rpm. The rotation speed of the crucible 3 was set to a range of 0.2 rpm to 22 rpm.

[0098] Furthermore, in the first half of the straight body of the silicon single crystal 10, the argon gas flow rate was set to a range of 50 l / min to 150 l / min, and the furnace internal pressure was set to a range of 40 kPa to 80 kPa. In the latter half of the straight body of the silicon single crystal 10, the argon flow rate was set to a range of 50 l / min to 200 l / min, and the furnace internal pressure was set to a range of 20 kPa to 80 kPa. [2-1] With red phosphorus as dopant (from 0.8 mΩcm to 1.0 mΩcm)

[0099] Using red phosphorus as a dopant, when pulling up the silicon single crystal 10 with a crystal diameter in the range of 301 mm to 330 mm, the resistivity of the silicon single crystal 10 at the starting point of the straight body (ie, end point of the shoulder) was controlled to a range of 1.2 mΩcm to 1.7 mΩcm.

[0100] For the silicon single crystal 10 with the straight body diameter in the range of 301 mm to 330 mm, the inner diameter of the quartz crucible 3A was changed in the same manner as above relative to the straight body diameter of the silicon single crystal 10, and while controlling the resistivity by adding red phosphorus as a dopant according to several measures, the red phosphorus-doped silicon single crystal 10 was pulled up. The results are shown in Table 3 and Fig. 4. A crucible diameter of 32" corresponds to 81.28 cm. 36" corresponds to 91.44 cm. 24" corresponds to 60.96 cm. 26" corresponds to 66.04 cm. 22" corresponds to 55.88 cm.

[0101] In Comparative Examples 3 and 4 (Comparison 3 and 4), the pulled silicon single crystal was not dislocation-free. Fig. Figure 4 shows the measurement results of the resistivity of the silicon single crystal with dislocation in dashed lines. However, a resistivity of 1.0 mΩcm or less was not obtained.

[0102] In contrast, in Examples 9 to 12, a dislocation-free success rate of 20% or more was obtained, and the crystal survival length was from 7% to 50%. This demonstrated that a portion of the silicon single crystal ingot 10 could have a specific resistance in the range of 0.8 mΩcm to 1.0 mΩcm. Accordingly, when the silicon single crystal ingot 10 with the target specific resistance in the range of 0.8 mΩcm to 1.0 mΩcm was prepared using red phosphorus as a dopant, it was found sufficient that at least the inner diameter of the quartz crucible 3A was set to a range of 1.7 to 2.0 times the diameter of the straight body of the silicon single crystal 10. [2-2] With arsenic as dopant (from 1.7 mΩcm to 2.0 mΩcm)

[0103] For the silicon single crystal 10 having the straight body diameter in the range of 301 mm to 330 mm, in the same manner as above, the inner diameter of the quartz crucible 3A was changed relative to the straight body diameter of the silicon single crystal 10, and while controlling the resistivity by adding arsenic as the dopant according to the several measures, the arsenic-doped silicon single crystal 10 was pulled up.

[0104] The resistivity of the silicon single crystal 10 at the starting point of the straight body (ie, the end point of the shoulder) was controlled within a range of 2.5 mΩcm to 3.1 mΩcm. The results are shown in Table 4 and Fig. 5. A crucible diameter of 32" corresponds to 81.28 cm. 36" corresponds to 91.44 cm. 24" corresponds to 60.96 cm. 26" corresponds to 66.04 cm. 22" corresponds to 55.88 cm.

[0105] In Comparative Examples 5 and 6 (Comparison 5 and 6), the pulled silicon single crystal was not dislocation-free. Fig. Figure 5 shows the measurement results of the resistivity of the silicon single crystal with dislocations with dashed lines. However, a resistivity of 2.0 mΩcm or less was not obtained.

[0106] In Examples 13 to 16, a dislocation-free success rate of 10% or more was obtained, and the crystal survival length was from 13% to 61%. This demonstrated that a portion of the silicon single crystal ingot 10 could have a specific resistance in the range of 1.7 mΩcm to 2.0 mΩcm. Accordingly, when manufacturing the silicon single crystal ingot 10 with a target specific resistance in the range of 1.7 mΩcm to 2.0 mΩcm using arsenic as a dopant, it was found sufficient that at least the inner diameter of the quartz crucible 3A was set to a range of 1.7 times to 2.0 times relative to the diameter of the straight body of the silicon single crystal 10. EXPLANATION OF REFERENCE SYMBOLS

[0107] 1...pulling device, 2...chamber, 3...crucible, 3A...quartz crucible, 3B...graphite crucible, 4...supporting shaft, 5...heater, 6...heat insulation material, 7...pulling shaft, 8...seed crystal, 9...silicon melt, 10...single crystal silicon (monocrystalline silicon), 12...heat shield plate, 13...gas inlet, 14...exhaust outlet.

Claims

[1] A method for producing an n-type silicon single crystal, comprising pulling up a silicon single crystal from a silicon melt containing a main dopant in the form of red phosphorus, and growing the silicon single crystal according to a Czochralski process in which the silicon single crystal comprises a diameter of a straight body which is in a range of 201 mm to 230 mm, and the silicon single crystal, a part of which has a specific electrical resistance ranging from 0.5 mΩcm to 0.7 mΩcm, is pulled up using a quartz crucible whose inner diameter is in a range of 2.1 times to 2.3 times relative to the diameter of the straight body of the silicon single crystal. [2] A method for producing an n-type silicon single crystal, comprising pulling up a silicon single crystal from a silicon melt containing a main dopant in the form of red phosphorus, and growing the silicon single crystal according to a Czochralski process in which the silicon single crystal comprises a diameter of a straight body which is in a range of 301 mm to 330 mm, and the silicon single crystal, a part of which has a specific electrical resistance ranging from 0.8 mΩcm to 1.0 mΩcm, is pulled up using a quartz crucible whose inner diameter is in a range from 1.7 times to 2.0 times relative to the diameter of the straight body of the silicon single crystal. [3] A method for producing an n-type silicon single crystal, which comprises pulling up a silicon single crystal from a silicon melt containing a main dopant in the form of arsenic, and growing the silicon single crystal according to a Czochralski process, in which the silicon single crystal is pulled up using a quartz crucible whose inner diameter is in a range of 1.7 times to 2.0 times relative to a diameter of the straight body of the silicon single crystal, in which a part of the silicon single crystal has an electrical resistivity in a range of 1.7 mΩcm to 2.0 mΩcm, and the diameter of the straight body of the silicon single crystal is in a range of 301 mm to 330 mm. [4] A method for producing the n-type silicon single crystal according to any one of claims 1 to 3, wherein the silicon single crystal is pulled up using a pulling-up device whose furnace internal pressure is set in a range of 40 kPa to 80 kPa. [5] A method for producing the n-type silicon single crystal according to any one of claims 1 to 4, wherein, when pulling up the silicon single crystal, a magnetic field having a magnetic field strength in a range of 0.2 T to 0.4 T is applied to the silicon melt in the quartz crucible. [6] Ingot of an n-type silicon single crystal containing a main dopant in the form of red phosphorus, where the ingot has a straight body diameter in a range of 301 mm to 330 mm, and a part of the ingot has a specific electrical resistance in a range of 0.8 mΩcm to 1.0 mΩcm, and wherein the ingot is obtainable by a process according to claim 2. [7] A silicon wafer cut from the ingot of the n-type silicon single crystal according to claim 6, wherein the silicon wafer has an electrical resistivity in a range of 0.8 mΩcm to 1.0 mΩcm and has a diameter of 300 mm. [8] An epitaxial silicon wafer comprising an epitaxial film formed on a surface of the silicon wafer according to claim 7. [9] Ingot of an n-type silicon single crystal containing a main dopant in the form of arsenic, where the ingot has a straight body diameter in a range of 301 mm to 330 mm, and a part of the ingot has a specific electrical resistance in a range of 1.7 mΩcm to 2.0 mΩcm and wherein the ingot is obtainable by a process according to claim 3. [10] A silicon wafer cut from the n-type silicon single crystal ingot according to claim 9, wherein the silicon wafer has an electrical resistivity ranging from 1.7 mΩcm to 2.0 mΩcm and has a diameter of 300 mm. [11] An epitaxial silicon wafer comprising an epitaxial film formed on a surface of the silicon wafer according to claim 10.

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