Process for producing a silicon single crystal

Abstract

A method for producing a phosphorus-doped silicon single crystal, which comprises pulling the phosphorus-doped silicon single crystal from a phosphorus-doped silicon melt by the magnetic field applying Czochralski (MCZ) method, wherein the phosphorus is doped in such a way that a phosphorus concentration of the phosphorus-doped silicon single crystal is 2×10 16 atoms / cm 3 or more, and a horizontal magnetic field with a central magnetic field strength of 0.2 Tesla (2,000 Gauss) or more is applied to the silicon melt, wherein the measures for controlling the uptake of oxygen into the phosphorus-doped silicon single crystal include controlling the rotation of the crystal axis, the single crystal growth rate, the flow rate of an inert gas, the furnace pressure, or the design of the heating chamber structure so that, during the production of the phosphorus-doped silicon single crystal, the oxygen concentration is adjusted to a value of 1.6×10 18 atoms / cm 3 (ASTM'79) or above over the entire length of the entire body of the single crystal.

Description

TECHNICAL FIELD

[0001] The present invention relates to a method for producing a phosphorus-doped silicon single crystal by the MCZ method. STATE OF THE ART

[0002] A silicon single crystal, primarily produced by the Czochralski (CZ) process, is sliced ​​into silicon wafers to be used as substrates for semiconductor devices such as memory or image sensors. This silicon single crystal produced by the CZ process contains oxygen atoms. During device fabrication using silicon wafers sliced ​​from such a silicon single crystal, silicon atoms and oxygen atoms combine to form oxide precipitates and bulk microdefects (BMD).

[0003] These oxide precipitates and BMD are known to create an intrinsic gettering (IG) capability to trap impurity atoms, such as heavy metal atoms, within wafers, thereby improving device properties. Wafers with a larger amount of oxide precipitates or a higher BMD density in their bulk enable the achievement of high-performance devices with high reliability.

[0004] In recent years, there has been a demand for radiation-resistant semiconductor devices using phosphorus-doped silicon wafers. The use of high-oxygen substrates for such devices enables a significant improvement in device properties.

[0005] In the production of a single crystal, an oxygen concentration is controlled during its growth to be incorporated in the crystal at a high concentration in order to impart useful IG capability and high oxygen concentration to these semiconductor devices.

[0006] There is also a growing demand for various wafers: polished wafers obtained by performing mirror polishing on the silicon wafers cut from a silicon single crystal prepared in the manner described above; annealed wafers obtained from the polished wafers subjected to an annealing process to suppress defects in their surface layer or to form an intrinsic gettering (IG) layer in their bulk; epitaxial wafers each having a formed epitaxial layer; and SOI wafers.

[0007] Since these wafers are subjected to multi-device processes, factors exist that impair electrical properties: metallic impurities penetrate device regions during these processes. The penetration of radial rays or cosmic rays into device regions leads to ionization. Accordingly, it is a fundamental problem to further develop a technique to prevent the spread of harmful impurities, such as a non-uniform image for an image sensor, or to neutralize ionization caused by radial rays or cosmic rays for a radiation-resistant device. A technique for growing a single crystal, particularly one doped with phosphorus and having a high oxygen concentration of 1.6×10 18 atoms / cm 3 (ASTM'79) or more is required for use in some image sensors and radiation resistance devices.

[0008] US 2005 / 0 263 062 A1 relates to a single crystal produced by a single crystal pulling process. In the single crystal pulling process, the interval of stripes formed in the single crystal due to a temperature fluctuation of the crystal melt at the time of crystal growth is controlled.

[0009] US 2011 / 0 056 428 A1 describes a method for producing a silicon single crystal with comparatively low resistance. The method comprises producing the silicon single crystal by controlling the height of a solid-liquid interface when the silicon single crystal is pulled.

[0010] GB 1 524 604 A relates to a process for producing single-crystal silicon rods. The process is carried out under reduced pressure and in a protective gas atmosphere, with the protective gas flowing into the pulling chamber of the single crystal during the pulling process through a tube that at least partially surrounds the pulling shaft and the growing silicon rod.

[0011] JP 2005 - 314 143 A describes a process for producing a silicon single crystal in an argon-shielding gas atmosphere using the Czochralski process. In this process, a silicon raw material is melted at a pressure of 13.3 to 40.0 kPa. LITERATURE LISTPATENT LITERATURE Patent Document 1: Japanese Patent JP 4 953 386 B2 Patent Document 2: Japanese Unexamined Patent Publication (Kokai) JP 2008-189 523 A Patent Document 3: US Patent Application No. US 2005 / 0 263 062 A1 Patent Document 4: US Patent Application No. US 2011 / 0 056 428 A1 Patent Document 5: British Patent Application No. GB ​​1 524 604 A Patent Document 6: Japanese Patent Application No. JP 2005 - 314 143 A SUMMARY OF THE INVENTION TECHNICAL PROBLEM

[0012] Patent Documents 1 and 2 propose a method for adjusting the oxygen concentration of a silicon single crystal to a high concentration, but do not describe a method for adjusting this oxygen concentration to 1.6×10 18 atoms / cm 3 (ASTM'79) or more. It is not easy to limit the oxygen concentration along the entire length of a straight body of a single crystal to 1.6×10 18 atoms / cm 3 (ASTM'79) or more. It is particularly difficult to control the oxygen concentration to 1.6×10 18 atoms / cm 3(ASTM'79) or more because the amount of melt is reduced and a contact area between the wall of a quartz crucible and the melt is also reduced.

[0013] The present invention has been developed in view of the problems described above. It is an object of the present invention to provide a method for producing a silicon single crystal that is heavily doped with phosphorus and has an oxygen concentration of 1.6×10 18 atoms / cm 3 (ASTM'79) or more. SOLUTION TO THE PROBLEM

[0014] To achieve this object, the present invention provides a method for producing a phosphorus-doped silicon single crystal according to claim 1. The method includes pulling the phosphorus-doped silicon single crystal from a phosphorus-doped silicon melt by the magnetic field applying Czochralski (MCZ) method, wherein the phosphorus is doped such that a phosphorus concentration of the phosphorus-doped silicon single crystal is 2×10 16 atoms / cm 3 or more, and a horizontal magnetic field with a central magnetic field strength of 0.2 Tesla (2,000 Gauss) or more is applied to the silicon melt, so that the phosphorus-doped silicon single crystal to be produced has an oxygen concentration of 1.6×10 18 atoms / cm 3 (ASTM'79) or more.

[0015] This process can produce a silicon single crystal that is heavily doped with phosphorus and has an oxygen concentration of 1.6×1018 atoms / cm 3 (ASTM'79) or more. In particular, the process can achieve a high oxygen concentration over essentially the entire length of a straight body of the crystal.

[0016] The step of pulling the phosphorus-doped silicon single crystal preferably includes setting a pressure of an interior of a furnace in a single crystal pulling apparatus for use in pulling the phosphorus-doped silicon single crystal to 100 hPa or more.

[0017] In this way, the process can produce a phosphorus-doped silicon single crystal with a higher oxygen concentration over essentially the entire length of the straight body of the crystal. ADVANTAGEOUS EFFECTS OF THE INVENTION

[0018] The present invention enables the production of a silicon single crystal that is heavily doped with phosphorus and has an oxygen concentration of 1.6×10 18 atoms / cm 3(ASTM'79) or more, as described above. In particular, the invention can achieve a silicon single crystal that is heavily doped with phosphorus and has a high oxygen concentration over substantially the entire length of the straight body of the crystal. Furthermore, high-quality silicon wafers with excellent electrical properties can be obtained from this heavily doped with phosphorus. These wafers can form a very high density of the BMD layer within their bulk through a device process and, depending on the application, eliminate factors in hindering electrical properties. In this way, these wafers can be suitably used for, for example, memories, image sensors, and substrates for semiconductor devices with radiation resistance. BRIEF DESCRIPTION OF THE DRAWINGS Fig.1 is a schematic diagram showing an example of a single crystal pulling apparatus that can be used in the present invention; Fig. 2 is a graph showing the distribution of oxygen concentration (ASTM'79) of a phosphorus-doped silicon single crystal in the example of the invention with respect to positions in that crystal; and Fig. Figure 3 is a graph showing the oxygen concentration distribution (ASTM'79) of a phosphorus-doped silicon single crystal in Comparative Example with respect to positions in this crystal. DESCRIPTION OF EMBODIMENTS

[0019] When producing a silicon single crystal, it is difficult to keep the oxygen concentration over the entire length of the straight body of this single crystal at 1.6×10 18 atoms / cm 3(ASTM'79) or more, as previously described. A pulling technique of a silicon single crystal, which is particularly heavily doped with phosphorus and has an oxygen concentration of 1.6×10 18 atoms / cm 3 (ASTM'79) or more along the entire length of this straight body is to be developed for use in some image sensors and radiation-resistant devices.

[0020] The inventors of the present invention considered this problem in detail and consequently found that a process of applying a horizontal magnetic field in the production of a heavily phosphorus-doped silicon single crystal enables this produced phosphorus-doped silicon single crystal to have a high oxygen concentration substantially over the entire length of its straight body, thereby completing the invention.

[0021] The invention is directed to a method for producing a phosphorus-doped silicon single crystal, which involves pulling the phosphorus-doped silicon single crystal from a phosphorus-doped silicon melt by applying a magnetic field using the Czochralski (MCZ) method. The phosphorus is doped such that a phosphorus concentration of the phosphorus-doped silicon single crystal is 2×10 16 atoms / cm 3 or more, and a horizontal magnetic field with a central magnetic field strength of 0.2 Tesla (2,000 Gauss) or more is applied to the silicon melt, so that the phosphorus-doped silicon single crystal to be produced has an oxygen concentration of 1.6×10 8 atoms / cm 3 (ASTM'79) or more.

[0022] An embodiment of the present invention will be specifically described below with reference to the drawings, but the present invention is not limited to this embodiment.

[0023] Fig. Figure 1 is a schematic diagram showing an example of a single crystal pulling apparatus that can be used in the method for producing a phosphorus-doped silicon single crystal according to the present invention. This embodiment of the invention will be described below based on Fig. 1 described.

[0024] The single crystal pulling apparatus used in the invention has a main chamber 1 and a pulling chamber 2. Inside this main chamber 1, a quartz crucible 4 for holding a raw material melt 3 and a graphite crucible 5 for supporting the quartz crucible 4 are provided. These crucibles are held by a support device 6 arranged on a support arm 7. A heater 8 is arranged outside the crucibles. A heat insulating material 9 is arranged outside this heater along the inner wall of the main chamber. A lower heat insulating material 10 may also be provided if necessary. A cooling cylinder 14 for cooling a pulled phosphorus-doped silicon single crystal 11 and a cylindrical gas flow guide cylinder 12 made of graphite with a heat insulating plate 13 at its lower end for restricting radiant heat from the raw material melt 3 and the heater 8 are arranged above the crucibles.

[0025] In addition, heat can be prevented from being removed from an upper part of the main chamber 1 by taking countermeasures: widening the distance between a lower part of the gas flow guide cylinder 12 and the surface of the raw material melt or moving the center of heat generation by operating the heater 8 except for heat insulating an upper part of the cooling cylinder 14.

[0026] In the invention, the silicon single crystal is pulled by the magnetic field applying CZ (MCZ) method while applying a horizontal magnetic field. Therefore, the single crystal pulling apparatus used in the invention is provided with a magnet 15 to apply the horizontal magnetic field outside the main chamber 1. The MCZ method has various magnetic field configurations, such as a vertical magnetic field, a horizontal magnetic field, or a cusp magnetic field, and can control the oxygen concentration according to configurations such as the distribution of lines of magnetic force or a magnetic field strength.

[0027] Convection of the raw material melt 3 without a magnetic field achieves the transport of a large amount of oxygen within the melt, thereby increasing the amount of oxygen transported to a surface portion of the melt. This increase in the amount of oxygen transported to the surface portion of the melt significantly increases the amount of oxygen to be evaporated, making it easy to reduce the oxygen in the melt. In contrast, the MCZ, especially using a horizontal magnetic field, reduces the amount of oxygen transported to the surface portion of the melt and the amount of oxygen to be evaporated when the raw material melt 3 is in a strong magnetic field, thereby enabling the control of the amount of oxygen in the melt.

[0028] When the method for producing a phosphorus-doped silicon single crystal according to the present invention is carried out using the single crystal pulling apparatus of this type, polycrystalline silicon, a raw material of a silicon single crystal, is loaded into the quartz crucible 4. At this time, phosphorus is added as a dopant to determine the n-type resistivity of a substrate. In addition to this dopant for controlling the resistivity, the melt may also be doped with nitrogen or carbon depending on the application. After the raw material is loaded into the quartz crucible 4, an inert gas such as argon gas is introduced through a gas inlet (not shown) arranged in the pulling chamber 2 and discharged through a gas outlet (not shown) by operating a vacuum pump (not shown), so that the interior is placed in an inert gas atmosphere.The raw material is then heated and melted by the heating device 8, which is arranged to surround the graphite crucible 5, to obtain the raw material melt 3. After the raw material is melted, a single crystal seed is immersed in the raw material melt 3 and pulled while rotating to grow an ingot of the phosphorus-doped silicon single crystal 11.

[0029] During single crystal pulling, the inner surface of the quartz crucible 4 on the melting side is heated to high temperatures by the heater 8 and gradually melted, thereby dissolving oxygen into the raw material melt 3. Although most of the dissolved oxygen evaporates from the melt surface to form SiO vapor, the other oxygen is absorbed in a very small amount into the phosphorus-doped silicon single crystal 11 to be grown.

[0030] Important considerations in incorporating oxygen into the phosphorus-doped silicon single crystal 11 at a high concentration are the rotation of a crystal axis and the support arm 7 of the single crystal pulling apparatus (i.e., rotation of the grown crystal and the crucibles), a single crystal growth rate, the control of a furnace pressure and a flow rate of an inert gas such as an argon gas, a proper design of a heating chamber structure including the heating device 8, etc.

[0031] This embodiment of the invention uses simulation software, FEMAG, for numerical thermal analysis to calculate the optimal structure of the heating space 1 provided in the main chamber, the optimal conditions, for example, the positional relationship between the raw material melting surface and the center of heat generation, and the conditions for the convection of the inert gas in the main chamber 1 (Reference: F.Dupret, P.Nicodeme, Y.Ryckmans, P.Wouters and MJ Crochet, Int.J. Heat Mass Transfer 33, 1849 (1990)).

[0032] In the invention, a phosphorus dopant is introduced into the melt so that the phosphorus concentration of the phosphorus-doped silicon single crystal 11 2×10 16 atoms / cm 3or more. The amount of this phosphorus dopant only needs to be equal to or less than the solubility limit. This range of phosphorus concentration in the phosphorus-doped silicon single crystal 11 enables wafers to have a resistivity of 0.2 Ωcm or less. The phosphorus-doped silicon single crystal 11 with a phosphorus concentration of 2×10 16 atoms / cm 3 or more and a straight body with an oxygen concentration of 2×10 18 atoms / cm 3 (ASTM '79) or more along the entire length of the straight body can be used for recently required devices, such as semiconductor devices with radiation resistance. This oxygen concentration only needs to be equal to or less than the solubility limit.

[0033] The dopant can be introduced when the polycrystalline silicon is loaded into the quartz crucible 4, or after this polycrystalline silicon has been completely melted by the heater 8. An alloy of silicon crystal and phosphorus or red phosphorus can be used as the dopant.

[0034] Since phosphorus is a volatile element, a high concentration of the phosphorus dopant increases its vapor pressure but reduces the vapor pressure of SiO. Reducing the oxygen to be evaporated in SiO inhibits a decrease in the oxygen concentration in the raw material melt 3, thereby increasing the amount of oxygen absorbed into the interior of the phosphorus-doped silicon single crystal 11. In other words, a high concentration of the phosphorus dopant facilitates the absorption of oxygen into the crystal. The amount of phosphorus and SiO to be evaporated can also be controlled, for example, by the flow rate of the inert gas or the adjustment of the furnace pressure.

[0035] When the single crystal is pulled in the invention, a horizontal magnetic field is applied to the raw material melt 3 by the magnet 15, so that the central magnetic field strength is 0.2 Tesla (2,000 Gauss) or more. If the strength of the applied horizontal magnetic field is less than 0.2 Tesla (2,000 Gauss), the convection of the raw material melt 3 is insufficiently inhibited and the evaporation of SiO is slightly inhibited; a phosphorus-doped silicon single crystal with an oxygen concentration of 1.6×10 18 atoms / cm 3 (ASTM'79) or more cannot be achieved. The strength of the applied horizontal magnetic field is preferably in the range of 0.3 Tesla (3,000 Gauss) to 0.5 Tesla (5,000 Gauss).

[0036] When pulling the phosphorus-doped silicon single crystal 11, the pressure inside the furnace in the single crystal pulling apparatus is preferably set to 100 hPa or more. This furnace pressure range inhibits the evaporation of SiO, enabling the production of a phosphorus-doped silicon single crystal with a higher oxygen concentration throughout substantially the entire length of its straight body. However, the interior of the furnace is preferably under reduced pressure to facilitate the removal of SiO from the furnace; this reduced pressure is preferably 1013.25 hPa (1 atm) or less, more preferably 600 hPa or less.

[0037] Wafers sliced ​​from the phosphorus-doped silicon single crystal 11 produced by the method of the present invention can be used as mirror-polished wafers in a device process after these sliced ​​wafers are subjected to only one mirror-polishing process. Alternatively, these mirror-polished wafers can be subjected to various processes: annealing, ion implantation, the production process of epitaxial wafers by growing an epitaxial layer on their surface, or the production process of SOI wafers by using these mirror-polished wafers as raw material.

[0038] The invention can be used without being limited to the crystal orientation, etc., of a silicon single crystal to be produced.

[0039] In this way, the invention can produce a silicon single crystal that is heavily doped with phosphorus and has an oxygen concentration of 1.6×10 18 atoms / cm 3(ASTM'79) or more. In particular, the invention can provide a silicon single crystal that is heavily doped with phosphorus and has a high oxygen concentration along substantially the entire length of its straight body. Furthermore, high-quality silicon wafers with excellent electrical properties can be obtained from this heavily doped with phosphorus. These wafers can form a very high density BMD layer within their bulk through a device process and eliminate factors inhibiting electrical properties depending on the application. Thus, these wafers can be suitably used for, for example, memories, image sensors, and substrates for semiconductor devices with radiation resistance. EXAMPLE

[0040] The present invention will be described in more detail below with reference to examples and comparative examples, but the invention is not limited to these examples. (Example 1)

[0041] Raw material of 360 kg of polycrystalline silicon was loaded into a 32-inch (800 mm) diameter quartz crucible located in the main chamber of a single-crystal puller. This raw material was heated and melted with a heater. A phosphorus dopant was introduced to adjust the resistivity so that the phosphorus concentration of the shoulder of a single crystal to be pulled was 2.5 × 10 16 atoms / cm 3 The phosphorus concentration of the straight body of the single crystal was 2.5×10 16 atoms / cm 3or more along its entire length. The furnace pressure of the single-crystal pulling apparatus was 150 hPa during single-crystal pulling. The n-type silicon single crystal was grown to a diameter of 300 mm and a straight-body length of 140 cm, while a horizontal magnetic field with a central magnetic field strength of 0.3 Tesla (3,000 Gauss) was applied by the MCZ method.

[0042] Wafers were grown from the silicon single crystal at positions 0, 20, 40, 60, 80, 100, 120, and 140 cm from its shoulder as samples. The oxygen concentrations of these wafers at these positions, measured by FT-IR, are shown in Table 1 below.

[0035] (Table 1) EXAMPLE 1 POSITION IN CRYSTALcm OXYGEN CONCENTRATION (ASTM'79) x 10 18 atoms / cm 3 0 1,66 20 1,65 40 1,64 60 1,66 80 1,69 100 1,70 120 1,72 140 1,73

[0043] As shown in Table 1, the oxygen concentration of the silicon single crystal prepared under the conditions of Example 1 was in the range of 1.64 x10 18 atoms / cm3 up to 1.73 x10 18 atoms / cm 3 (ASTM'79).

[0036] (Example 2)

[0044] Raw material of 360 kg of polycrystalline silicon was loaded into a 32-inch (800 mm) diameter quartz crucible located in the main chamber of a single-crystal puller as in Example 1. This raw material was heated and melted with a heater. A phosphorus dopant was introduced to adjust the resistivity so that the phosphorus concentration of the shoulder of a single crystal to be pulled was 2.5 × 10 16 atoms / cm 3 The phosphorus concentration of the straight body of the single crystal was 2.5×10 16 atoms / cm 3or more along its entire length. The furnace pressure of the single crystal pulling apparatus was 150 hPa during single crystal pulling. The n-type silicon single crystal was grown to have a diameter of 300 mm and a straight body length of 140 cm while applying a horizontal magnetic field with a central magnetic field strength of 0.22 Tesla (2,200 Gauss) by the MCZ method. Other conditions were the same as in Example 1 for pulling this single crystal. Wafers were prepared as samples from the silicon single crystal pulled at positions of 0, 20, 40, 60, 80, 100, 120, and 140 cm from its shoulder. The oxygen concentration of these wafers at these positions, measured by FT-IR, is shown below in Table 2.

[0037] (Table 2) EXAMPLE 2 POSITION IN CRYSTALcm OXYGEN CONCENTRATION (ASTM'79) x 10 18 atoms / cm 3 0 1,64 20 1,62 40 1,62 60 1,65 80 1,65 100 1,65 120 1,66 140 1,68

[0045] As shown in Table 2, the oxygen concentration of the silicon single crystal prepared under the conditions of Example 2 was in the range of 1.62 x10 18 atoms / cm 3 up to 1.68 x10 18 atoms / cm 3 (ASTM'79).

[0038] (Example 3)

[0046] Raw material of 360 kg of polycrystalline silicon was loaded into a 32-inch (800 mm) diameter quartz crucible located in the main chamber of a single-crystal puller as in Example 1. This raw material was heated and melted with a heater. A phosphorus dopant was introduced to adjust the resistivity so that the phosphorus concentration of the shoulder of a single crystal to be pulled was 2.5 × 10 16 atoms / cm 3 The phosphorus concentration of the straight body of the single crystal was 2.5×10 16 atoms / cm 3or more along its entire length. The furnace pressure of the single-crystal pulling apparatus was 80 hPa during single-crystal pulling. The n-type silicon single crystal was grown to a diameter of 300 mm and a straight-body length of 140 cm, while a horizontal magnetic field with a central magnetic field strength of 0.3 Tesla (3,000 Gauss) was applied by the MCZ method. The other conditions were the same as those in Example 1 for single-crystal pulling.

[0047] Wafers were grown from the silicon single crystal at positions 0, 20, 40, 60, 80, 100, 120, and 140 cm from its shoulder as samples. The oxygen concentrations of these wafers at these positions, measured by FT-IR, are shown below in Table 3.

[0039] (Table 3) EXAMPLE 3 POSITION IN CRYSTALcm OXYGEN CONCENTRATION (ASTM'79) x 10 18 atoms / cm 3 0 1,62 20 1,61 40 1,60 60 1,62 80 1,62 100 1,62 120 1,63 140 1,64

[0048] As shown in Table 3, the oxygen concentration of the silicon single crystal prepared under the conditions of Example 3 was in the range of 1.60×10 18 atoms / cm 3 up to 1.64×10 18 atoms / cm 3 (ASTM'79).

[0040] (Comparative Example 1)

[0049] Raw material of 360 kg of polycrystalline silicon was loaded into a 32-inch (800 mm) diameter quartz crucible located in the main chamber of a single-crystal puller as in Example 1. This raw material was heated and melted with a heater. A phosphorus dopant was introduced to adjust the resistivity so that the phosphorus concentration of the rear end of a single crystal to be pulled was 1.1 × 10 16 atoms / cm 3 The phosphorus concentration of the straight body of the single crystal was 1.1×10 16 atoms / cm 3or less along its entire length. The furnace pressure of the single-crystal pulling apparatus was 150 hPa during single-crystal pulling. The n-type silicon single crystal was grown to a diameter of 300 mm and a straight-body length of 140 cm, while a horizontal magnetic field with a central magnetic field strength of 0.3 Tesla (3,000 Gauss) was applied by the MCZ method. The other conditions were the same as those in Example 1 for single-crystal pulling.

[0050] Wafers were grown from the silicon single crystal at positions 0, 20, 40, 60, 80, 100, 120, and 140 cm from its shoulder as samples. The oxygen concentrations of these wafers at these positions, measured by FT-IR, are shown below in Table 4.

[0041] (Table 4) COMPARISON EXAMPLE 1 POSITION IN CRYSTALcm OXYGEN CONCENTRATION (ASTM'79) x 10 18 atoms / cm 3 0 1,43 20 1,42 40 1,41 60 1,42 80 1,44 100 1,46 120 1,46 140 1,42

[0051] As shown in Table 4, the oxygen concentration of the silicon single crystal prepared under the conditions of Comparative Example 1 was in the range of 1.41×10 18 atoms / cm 3 up to 1.46×10 18 atoms / cm 3 (ASTM'79).

[0042] (Comparative Example 2)

[0052] Raw material of 360 kg of polycrystalline silicon was loaded into a 32-inch (800 mm) diameter quartz crucible located in the main chamber of a single-crystal puller as in Example 1. This raw material was heated and melted with a heater. A phosphorus dopant was introduced to adjust the resistivity so that the phosphorus concentration of the shoulder of a single crystal to be pulled was 2.5 × 10 16 atoms / cm 3 The phosphorus concentration of the straight body of the single crystal was 2.5×10 16 atoms / cm 3or more along its entire length. The furnace pressure of the single-crystal pulling apparatus was 150 hPa during single-crystal pulling. The n-type silicon single crystal was grown to a diameter of 300 mm and a straight-body length of 140 cm, while a horizontal magnetic field with a central magnetic field strength of 0.15 Tesla (1,500 Gauss) was applied by the MCZ method. The other conditions were the same as those in Example 1 for single-crystal pulling.

[0053] Wafers were grown from the silicon single crystal at positions 0, 20, 40, 60, 80, 100, 120, and 140 cm from its shoulder as samples. The oxygen concentrations of these wafers at these positions, measured by FT-IR, are shown below in Table 5.

[0043] (Table 5) COMPARISON EXAMPLE 2 POSITION IN CRYSTALcm OXYGEN CONCENTRATION (ASTM'79) x 10 18 atoms / cm 3 0 1,47 20 1,46 40 1,45 60 1,46 80 1,48 100 1,49 120 1,50 140 1,47

[0054] As shown in Table 5, the oxygen concentration of the silicon single crystal prepared under the conditions of Comparative Example 2 was in the range of 1.45×10 18 atoms / cm 3 up to 1.50×10 18 atoms / cm 3 (ASTM'79).

[0044] (Comparative Example 3)

[0055] Raw material of 360 kg of polycrystalline silicon was loaded into a 32-inch (800 mm) diameter quartz crucible located in the main chamber of a single-crystal puller as in Example 1. This raw material was heated and melted with a heater. A phosphorus dopant was introduced to adjust the resistivity so that the phosphorus concentration of the rear end of a single crystal to be pulled was 1.1 × 10 16 atoms / cm 3 The phosphorus concentration of the straight body of the single crystal was 1.1×10 16 atoms / cm 3or less along its entire length. The furnace pressure of the single-crystal pulling apparatus was 150 hPa during single-crystal pulling. The n-type silicon single crystal was grown to a diameter of 300 mm and a straight-body length of 140 cm, while a horizontal magnetic field with a central magnetic field strength of 0.1 Tesla (1,000 Gauss) was applied by the MCZ method. Other conditions were the same as those in Example 1 for single-crystal pulling.

[0056] Wafers were grown from the silicon single crystal at positions 0, 20, 40, 60, 80, 100, 120, and 140 cm from its shoulder as samples. The oxygen concentrations of these wafers at these positions, measured by FT-IR, are shown below in Table 6.

[0045] (Table 6) COMPARISON EXAMPLE 3 POSITION IN CRYSTALcm OXYGEN CONCENTRATION (ASTM'79) x 10 18 atoms / cm 3 0 1,39 20 1,34 40 1,33 60 1,34 80 1,34 100 1,35 120 1,34 140 1,33

[0057] As shown in Table 6, the oxygen concentration of the silicon single crystal prepared under the conditions of Comparative Example 3 was in the range of 1.33×10 18 atoms / cm 3 up to 1.39×10 18 atoms / cm 3 (ASTM'79).

[0046] (Comparative Example 4)

[0058] Raw material of 360 kg of polycrystalline silicon was loaded into a 32-inch (800 mm) diameter quartz crucible located in the main chamber of a single-crystal puller as in Example 1. This raw material was heated and melted with a heater. A phosphorus dopant was introduced to adjust the resistivity so that the phosphorus concentration of the shoulder of a single crystal to be pulled was 2.5 × 10 16 atoms / cm 3 The phosphorus concentration of the straight body of the single crystal was 2.5×10 16 atoms / cm 3or more along its entire length. The furnace pressure of the single-crystal pulling apparatus was 150 hPa during single-crystal pulling. The n-type silicon single crystal was grown to a diameter of 300 mm and a straight-body length of 140 cm while no magnetic field was applied (0 gauss).

[0059] Wafers were formed from the silicon single crystal grown at positions 0, 20, 40, 60, 80, 100, 120, and 140 cm from its shoulder as samples. The oxygen concentrations of these wafers at these positions, measured by FT-IR, are shown below in Table 7.

[0047] (Table 7) COMPARISON EXAMPLE 4 POSITION IN CRYSTALcm OXYGEN CONCENTRATION (ASTM'79) x 10 18 atoms / cm 3 0 1,34 20 1,27 40 1,26 60 1,26 80 1,24 100 1,22 120 1,18 140 1,16

[0060] As shown in Table 7, the oxygen concentration of the silicon single crystal prepared under the conditions of Comparative Example 4 was in the range of 1.16×10 18 atoms / cm 3 up to 1.34×10 18 atoms / cm 3 (ASTM'79).

[0061] Fig. Figure 2 shows a graph of all oxygen concentrations (ASTM'79) measured at the positions in the crystal in Examples 1 to 3 of the invention. Fig. Figure 3 shows a graph of all oxygen concentrations (ASTM'79) measured at the positions in the crystal in Comparative Examples 1 to 4.

[0062] As shown by the graphs in Fig. 2 and Fig. 3, Examples 1 to 3 show that the straight body of the single crystal has an oxygen concentration of 1.6×10 18 atoms / cm 3 (ASTM'79) or more at all positions. Comparative Examples 1 to 4 were carried out under the following conditions: the single crystal had a phosphorus concentration of less than 2×10 16 atoms / cm 3 , the applied horizontal magnetic field was less than 0.2 Tesla (2,000 Gauss); the single crystal had a phosphorus concentration of less than 2×10 16 atoms / cm 3and the applied horizontal magnetic field was less than 0.2 Tesla (2,000 Gauss); and no magnetic field was applied. All these comparative examples have shown that the straight body of the single crystal has an oxygen concentration of less than 1.6×10 18 atoms / cm 3 in all positions.

[0063] The results described above showed that the method for producing a phosphorus-doped silicon single crystal according to the invention produced a phosphorus-doped silicon single crystal with an oxygen concentration of 1.6 x10 18 atoms / cm 3 (ASTM'79) or more over substantially the entire length of the straight body of the single crystal.

[0064] Please note that the present invention is not limited to the above embodiment. This embodiment is merely an example.

Claims

[1] A method for producing a phosphorus-doped silicon single crystal, which comprises pulling the phosphorus-doped silicon single crystal from a phosphorus-doped silicon melt by the magnetic field applying Czochralski (MCZ) method, wherein the phosphorus is doped in such a way that a phosphorus concentration of the phosphorus-doped silicon single crystal is 2×10 16 atoms / cm 3 or more, and a horizontal magnetic field with a central magnetic field strength of 0.2 Tesla (2,000 Gauss) or more is applied to the silicon melt, wherein the measures for controlling the uptake of oxygen into the phosphorus-doped silicon single crystal include controlling the rotation of the crystal axis, the single crystal growth rate, the flow rate of an inert gas, the furnace pressure, or the design of the heating chamber structure so that, during the production of the phosphorus-doped silicon single crystal, the oxygen concentration is adjusted to a value of 1.6×10 18 atoms / cm 3 (ASTM'79) or above over the entire length of the entire body of the single crystal. [2] The method according to claim 1, wherein the step of pulling the phosphorus-doped silicon single crystal includes setting a pressure of an inside of a furnace in a single crystal pulling apparatus for use in pulling the phosphorus-doped silicon single crystal to 100 hPa or more.

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