Silicon single crystal, process for its production, and silicon wafer

Abstract

A method for producing a silicon single crystal with an approximate diameter of 200 mm using the Czochralski method, wherein the method includes growing a silicon single crystal from a silicon melt while a Cusp magnetic field is applied, characterized in that the rotational speed of the crystal during the growing of the silicon single crystal under rotation is set to 17 rpm or more and 19 rpm or less, the rotational speed of a quartz crucible holding the silicon molten metal is set to 4.5 rpm or more and 8.5 rpm or less, the magnetic field strength of the Cusp magnetic field is set to 0.05 T to 0.07 T, and The central position of the magnetic field in the vertical direction is set to a range of +7 mm to +40 mm, relative to the position of the liquid surface of the silicon melt.

Description

[Technical field]

[0001] The present invention relates to a silicon single crystal, a method for producing the same, and a silicon wafer, and more particularly to a method for producing a silicon single crystal using an MCZ (magnetic field applied CZ) method, and to a silicon single crystal and a silicon wafer produced thereby. [State of the art]

[0002] A silicon single crystal with a low concentration of interstitial oxygen is preferred for a silicon wafer for power semiconductors, which mainly include an IGBT (Gate Insulated Bipolar Transistor). Although such a silicon single crystal is often manufactured using an FZ process that does not use a quartz crucible, which serves as an oxygen source, the CZ (Czochralski) process is also being considered to improve mass production.

[0003] As one of the CZ methods for producing a silicon single crystal with a low oxygen concentration, an MCZ method is known, in which a silicon single crystal is pulled up while a magnetic field is applied. According to the MCZ method, convection of the melt can be suppressed, and thereby the dissolution of oxygen in the silicon melt due to erosion of the quartz crucible can be suppressed, and the oxygen concentration in the silicon single crystal can be reduced. For example, Patent Document 1 describes an MCZ method configured to use a horizontal magnetic field or a cusp magnetic field. In this MCZ method, a single crystal with an interstitial oxygen concentration of 6 × 10 17 atoms / cm 3or less under the conditions that the strength of the horizontal magnetic field is 2,000 G (Gauss) or more, i.e. 0.2 T (Tesla) or more, the rotation speed of the quartz crucible is 1.5 rpm or less, the rotation speed of the crystal is 7.0 rpm or less, and the pulling speed of the silicon single crystal is adjusted so that the silicon single crystal becomes free of dislocation cluster defects.

[0004] Patent Document 2 further describes a method including the steps of forming a melt by melting polycrystalline silicon in a crucible installed in a vacuum chamber, forming a cusp magnetic field in the vacuum chamber, immersing a seed crystal in the melt, and forming a silicon single-crystal ingot with a diameter greater than about 150 mm while pulling the seed crystal up from the melt. In this method, several process parameters are simultaneously adjusted so that the silicon ingot has an oxygen concentration of less than about 5 ppma.The process parameters include the temperature of the side wall of the crucible, the transfer of silicon monoxide (SiO) from the crucible to the single crystal, and an evaporation rate of SiO from the melt, and the rotation speed of the crucible is set to a range of about 1.3 rpm to 2.2 rpm, the rotation speed of the crystal to a range of about 8 rpm to 14 rpm, and the strength of the magnetic field at the edge of a melt-solid interface is set to a range of about 0.02 T (Tesla) to 0.05 T.

[0005] Patent Document 3 describes CZ processes for producing silicon single crystals using a cusp magnetic field with a flux density of 0.02 T to 0.09 T. The center of the magnetic field lies on the pulling axis between the surface of the melt and half the depth of the melt. The rotation speed of the single crystal can be between 15 rpm and 23 rpm. The rotation speed of the crucible is not more than 5 rpm. In the examples of Patent Document 3, silicon single crystals with an approximate diameter of 200 mm are produced. [Citation list][Patent documents] [Patent Document 1] JP 2010-222241A [Patent Document 2] JP 2016-519049A [Patent Document 3] US 6,458,204 B1 [Summary of the invention][Problem to be solved by the invention]

[0006] In the HMCZ method for pulling a silicon single crystal while applying a horizontal magnetic field, a reduction in the oxygen concentration of the silicon single crystal can be achieved, but the in-plane uniformity of the oxygen concentration or resistivity becomes problematic. For example, in the conventional manufacturing method described in Patent Document 1, the crucible rotation speed is 1.5 rpm or less, and the crystal rotation speed is 7 rpm or less. However, the practical application of the above manufacturing conditions may cause a problem in that the in-plane distributions of the oxygen concentration and resistivity are not uniform.Similarly, in the conventional manufacturing method described in Patent Document 2, the rotation speed of the crucible is 1.3 rpm to 2.2 rpm, and the rotation speed of the crystal is 8 rpm to 14 rpm; however, the practical application of the above manufacturing conditions may cause a problem that the in-plane distributions of oxygen concentration and resistivity are not uniform.

[0007] Accordingly, an object of the present invention is to provide a method for producing a silicon single crystal using a Czochralski method configured to apply a cusp magnetic field, which can produce a silicon single crystal having a low oxygen concentration and high uniformity of the in-plane oxygen concentration and resistivity distributions. Another object of the present invention is to provide a silicon single crystal and a silicon wafer having a low oxygen concentration and high uniformity of the in-plane oxygen concentration and resistivity distributions. [Means of solving the problem]

[0008] The inventor has intensively investigated the factors that cause changes in the oxygen concentration distribution or in-plane resistivity in a silicon single crystal. As a result, he found that by pulling up a single crystal while subjected to a cusp magnetic field, it is possible to improve the uniformity of the oxygen concentration and in-plane resistivity distributions without causing an increase in oxygen concentration and crystal deformation (dislocation), even when the single crystal is rotated at high speed. Generally, to produce a silicon single crystal with a low oxygen concentration, the rotation speed of the crystal must be low; however, the low rotation speed may reduce the uniformity of the oxygen concentration in-plane.However, it became clear that the use of a cusp magnetic field allows to obtain a silicon single crystal with a low oxygen concentration, and in-plane distributions of oxygen concentration and resistivity to be stabilized even with a high rotation speed of the crystal, and thus the present invention was made.

[0009] The present invention is based on the above finding, and a method for producing a silicon single crystal according to the present invention is a method using a Czochralski method, which includes pulling a silicon single crystal from a silicon melt while applying a cusp magnetic field, wherein the rotation speed of the crystal during the process of pulling the silicon single crystal while rotating is set to 17 rpm or more and 19 rpm or less. The silicon single crystal produced by the method of the present invention has an approximate diameter of 200 mm.

[0010] In the present invention, the rotation speed of the quartz crucible holding the silicon melt is set to 4.5 rpm or more and 8.5 rpm or less. Furthermore, the magnetic field strength of the cusp magnetic field is set to 0.05 T to 0.07 T (500 G to 700 G), and the center position of the magnetic field in the vertical direction is set within a range of +7 mm to +40 mm relative to the position of the liquid surface of the silicon melt. Under the above conditions, it is possible to improve the uniformity of the oxygen concentration distribution and the in-plane resistivity in the single crystal.

[0011] Furthermore, a silicon single crystal according to the present invention is characterized in that the oxygen concentration according to ASTM F-121 (1979) is 1 × 10 17 atoms / cm 3 or more and 8 × 10 17 atoms / cm 3or less, ROG (Radial Oxygen Gradient) in a crystal cross-section perpendicular to a growth direction of the crystal is 15% or less, and RRG (Radial Resistivity Gradient) in the crystal cross-section is 5% or less. The silicon single crystal of the present invention has an approximate diameter of 200 mm. According to the present invention, a silicon single crystal with a low oxygen concentration suitable for a material of a silicon wafer for a power semiconductor can be provided.

[0012] A silicon wafer according to the invention is characterized in that its oxygen concentration according to ASTM F-121 (1979) is 1 × 10 17 atoms / cm 3 or more and 8 × 10 17 atoms / cm 3or less, ROG is 15% or less, and RRG is 5% or less. The silicon wafer according to the invention has a diameter of 200 mm. According to the present invention, a silicon wafer suitable for a substrate material for a power semiconductor can be provided. [Advantageous effects of the invention]

[0013] According to the present invention, a method for producing a silicon single crystal with an approximate diameter of 200 mm, a low oxygen concentration, and high uniformity of the oxygen concentration and resistivity distributions in-plane can be provided. Furthermore, the present invention can provide a silicon single crystal with an approximate diameter of 200 mm and a silicon wafer with a diameter of 200 mm that have a low oxygen concentration and high uniformity of the oxygen concentration and resistivity distributions in-plane. [Brief description of the drawings] Fig. 1 is a cross-sectional side view schematically illustrating the configuration of a single crystal manufacturing apparatus according to the embodiment of the present invention. Fig. 2 is a flowchart for explaining a method for producing a silicon single crystal according to an embodiment of the present invention. Fig. Figure 3 is a schematic cross-sectional view illustrating the shape of a silicon single crystal ingot. Fig. Figure 4 is a graph showing the ROG of the silicon wafer specimens according to Example 1 (CUSP). Fig. Figure 5 is a graph showing the RRG of the silicon wafer specimens according to Example 1 (CUSP). Fig. Figure 6 is a graph showing the ROG of the silicon wafer specimens according to Example 2 (CUSP). Fig. Figure 7 is a graph showing the ROG of the silicon wafer specimens according to Example 3 (CUSP). Fig. Figure 8 is a graph showing the ROG of the silicon wafer specimens according to Example 4 (CUSP). Fig. Figure 9 is a graph showing the ROG of the silicon wafer specimens according to Example 5 (CUSP). Fig. Figure 10 is a graph showing the ROG of the silicon wafer specimens according to Comparative Example 1 (CUSP). Fig. Figure 11 is a graph showing the ROG of the silicon wafer specimens according to Comparative Example 2 (HMCZ). Fig. Figure 12 is a graph showing the RRG of the silicon wafer specimens according to Comparative Example 2 (HMCZ). Fig. Figure 13 is a graph showing the RRG of the silicon wafer specimens according to Comparative Example 3 (FZ). [Way to carry out the invention]

[0014] Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.

[0015] Fig. 1 is a cross-sectional side view schematically illustrating the configuration of a single crystal manufacturing apparatus according to the embodiment of the present invention.

[0016] As in Fig. 1, a single crystal manufacturing apparatus 1 includes a chamber 10 (CZ furnace), a quartz crucible 11 holding a silicon melt 2 in the chamber 10, a graphite susceptor 12 holding the quartz crucible 11, a rotary shaft 13 supporting the susceptor 12, a shaft drive mechanism 14 rotating and elevating the rotary source 13, a heater 15 arranged around the susceptor 12, a heat insulating material 16 arranged outside the heater 15 and along the inner surface of the chamber 10, a heat shielding body 17 arranged above the quartz crucible 11, a single crystal pulling-up wire 18 arranged above the quartz crucible 11 so as to be coaxial with the rotary shaft 13, and a wire winding mechanism 19 arranged at the upper portion of the chamber 10 is arranged.

[0017] The single crystal manufacturing apparatus 1 further includes a magnetic field generator 21 arranged outside the chamber 10, a CCD camera 22 that images the interior of the chamber 10, an image processing unit 23 that processes an image captured by the CCD camera 22, and a control unit 24 that controls the shaft drive mechanism 14, the heater 15, and the wire winding mechanism 19 based on the output from the image processing unit 23.

[0018] The chamber 10 consists of a main chamber 10a and an elongated cylindrical pulling chamber 10b connected to an upper opening of the main chamber 10a. The quartz crucible 11, the susceptor 12, the heater 15, and the heat shield 17 are mounted inside the main chamber 10a. A gas inlet 10c for supplying an inert gas (purge gas), such as argon gas, into the chamber 10 is formed in the pulling chamber 10b, and a gas outlet 10d for discharging the inert gas is formed at the bottom of the main chamber 10a. Furthermore, an observation window 10e is formed at the upper portion of the main chamber 10a to allow observation of a growth state (solid-liquid interface) of the silicon single crystal 3 therethrough.

[0019] The quartz crucible 11 is a vessel made of quartz glass with a cylindrical side wall and a rounded bottom. The susceptor 12 is in tight contact with the outer surface of the quartz crucible 11 and covers and holds the quartz crucible 11, thereby maintaining the shape of the quartz crucible 11 softened by heating. The quartz crucible 11 and the susceptor 12 form a dual-structure crucible that supports the silicon melt in the chamber 10.

[0020] The susceptor 12 is attached to the upper end of the vertically extending rotating shaft 13. The lower end of the rotating shaft 13 passes through the center of the bottom of the chamber 10 and is connected to the shaft drive mechanism 14 located outside the chamber 10. The susceptor 12, the rotating shaft 13, and the shaft drive mechanism 14 form a rotation and lifting mechanism for the quartz crucible 11.

[0021] The heater 15 is used to melt a silicon source material filled in the quartz crucible 11 and maintain its molten state. The heater 15 is a resistance heater made of carbon and is a substantially cylindrical component mounted to surround the entire circumference of the quartz crucible 11 in the susceptor 12. The heater 15 is surrounded by the thermal insulation material 16, and this can increase the heat retention capacity within the chamber 10.

[0022] The heat shielding body 17 forms a suitable hot zone around the solid-liquid interface by suppressing a change in the temperature of the silicon melt 2 and prevents the silicon single crystal 3 from being heated by radiant heat from the heater 15 and the quartz crucible 11. The heat shielding body 17 is a cylindrical member made of graphite that covers an area above the silicon melt 2, excluding the pull-up path for the silicon single crystal 3.

[0023] A circular opening with a diameter larger than that of the silicon single crystal 3 is formed in the center of the lower end of the heat-shielding body 17, thereby ensuring the pulling-up path for the silicon single crystal 3. As illustrated, the silicon single crystal 3 is pulled up and passes through the opening of the heat-shielding body 17. The diameter of the opening of the heat-shielding body 17 is smaller than the opening diameter of the quartz crucible 11, and the lower end portion of the heat-shielding body 17 is located inside the quartz crucible 11, so that even if the rim at the upper end of the quartz crucible 11 is raised and higher than the lower end of the heat-shielding body 17, the heat-shielding body 17 does not interfere with the quartz crucible 11.

[0024] The amount of melt in the quartz crucible 11 decreases with the growth of the silicon single crystal 3; however, by raising the quartz crucible 11 so that the gap between the melt surface and the heat shielding body 17 remains constant, it is possible to suppress the temperature change of the silicon melt 2 and keep the flow rate of gas flowing near the melt constant, thereby controlling the evaporation amount of SiO gas from the silicon melt 2. Thus, the stability of the distribution of crystal defects, the distribution of oxygen concentration, the distribution of resistivity, etc., in the direction of the pull-up wave of the single crystal can be improved.

[0025] The wire 18, which serves as a pulling shaft for the silicon single crystal 3, and the wire winding mechanism 19, which winds the wire 18, are provided above the quartz crucible 11. The wire winding mechanism 19 functions to rotate the single crystal along with the wire 18. The wire winding mechanism 19 is provided at the upper portion of the pulling chamber 10b. The wire 18 extends downward from the wire winding mechanism 19 and passes through the pulling chamber 10b until its front end reaches the interior of the main chamber 10a. Fig. Figure 1 illustrates a state in which the silicon single crystal 3 is suspended from the wire 18 during growth. During the single crystal pulling, a seed crystal is immersed in the silicon melt 2, and the wire 18 is gradually pulled up while rotating the quartz crucible 11 and the seed crystal, thus growing the single crystal.

[0026] The gas inlet 10c for supplying inert gas into the chamber 10 is formed at the upper portion of the pulling chamber 10b, and the gas outlet 10d for discharging the inert gas from the chamber 10 is formed at the bottom of the main chamber 10a. The inert gas is supplied into the chamber 10 through the gas inlet 10c, and the amount of inert gas to be supplied is controlled by a valve. The inert gas in the sealed chamber 10 is discharged from the chamber 10 through the gas outlet 10d, making it possible to collect SiO gas or CO gas generated in the chamber 10 and thereby keep the interior of the chamber 10 clean.Although not illustrated, a vacuum pump is connected to the gas outlet 10d via a pipe, and the inside of the chamber 10 is kept in a certain reduced pressure state by controlling the flow rate of the inert gas using the valve while exhausting the inert gas in the chamber 10 with the vacuum pump.

[0027] The magnetic field generator 21 is formed of upper and lower coils 21a and 21b arranged vertically opposite to each other, and supplies currents of opposite directions to the pair of magnetic field generating coils to generate a cusp magnetic field in the chamber 10. In the drawing, "•" denotes a current flow coming out of the paper plane, and "×" denotes a current flow going into the paper plane.

[0028] The cusp magnetic field is symmetrical with respect to the pull-up wave, and their magnetic fields cancel each other at the center of the magnetic field, making the vertical magnetic field strength zero. The vertical magnetic field exists at an off-center position and forms a horizontal magnetic field oriented in the radial direction. The cusp magnetic field center is located near the liquid surface of the silicon melt 2 and is set in the range of +7 mm to +40 mm relative to the liquid surface position. By applying the cusp magnetic field to the silicon melt in this way, it is possible to suppress melt convection in a direction perpendicular to magnetic field lines.

[0029] The magnetic field strength of the cusp magnetic field is 0.05 T to 0.07 T (500 G to 700 G). If the magnetic field strength is lower than 0.05 T (500 G), it is difficult to grow a silicon single crystal with an oxygen concentration as low as 8 × 10 17 atoms / cm 3 Furthermore, it is difficult for existing magnetic field generators to stably output a magnetic field strength exceeding 0.07 T (700 G), and a magnetic field strength as low as possible is also desired from the perspective of energy consumption. The magnetic field strength value of the cusp magnetic field described in the present invention is a value at the center of the magnetic field in the vertical direction and at the side wall of the quartz crucible in the horizontal direction.

[0030] In the HMCZ method, which is configured to apply a horizontal magnetic field, the magnetic lines of force are aligned in one direction, so that although there is an effect of suppressing convection in a direction perpendicular to the magnetic lines of force, convection in a direction parallel to the magnetic lines of force cannot be suppressed. On the other hand, the cusp magnetic field has magnetic lines of force aligned radially and is symmetrical with respect to the pull-up wave in plan view, which enables the suppression of convection of the melt in the circumferential direction within the quartz crucible 11. Thus, it is possible to suppress the elution of oxygen from the quartz crucible 11 and thereby reduce the oxygen concentration in the silicon single crystal.

[0031] The observation window 10e for observing the interior of the chamber 10 is provided at the upper portion of the main chamber 10a, and the CCD camera 22 is installed outside the observation window 10e. During single-crystal pulling, the CCD camera 22 captures an image of the boundary between the silicon single crystal 3 and the silicon melt 2, which is visible through the observation window 10e and the opening 17a of the heat shield body 17. The CCD camera 22 is connected to the image processing unit 23. The captured image is processed in the image processing unit 23, and the processing result is supplied to the control unit 24 and used to control the pulling conditions.

[0032] Fig. 2 is a flowchart for explaining a method for producing a silicon single crystal according to an embodiment of the present invention. Fig. Figure 3 is a schematic cross-sectional view illustrating the shape of a silicon single crystal ingot.

[0033] As in the Fig. 2 and Fig. As illustrated in Figure 3, in the manufacturing process for the silicon single crystal 3, a silicon source material is heated in the quartz crucible 11 to produce the silicon melt 2 (step S11). Thereafter, a seed crystal attached to the front end portion of the wire 18 is lowered to immerse itself in the silicon melt 2 (step S12).

[0034] Then, a single crystal pulling-up process is performed in which the seed crystal is gradually pulled up while in contact with the silicon melt 2, and thus the single crystal grows. In the single crystal pulling-up process, a neck formation step (step S13) in which a neck portion 3a whose crystal diameter is reduced to prevent dislocation is formed, a shoulder portion growth step (step S14) in which a shoulder portion 3b whose crystal diameter is gradually increased to a predetermined diameter is formed, a body portion growth step (step S15) in which a body portion 3c whose crystal diameter is kept constant is formed, and a tail portion growth step (step S16) in which a tail portion 3d whose crystal diameter is gradually reduced is formed are performed in sequence.Finally, the single crystal is separated from the melt surface, and the tail section growth step is completed. Through the above steps, the silicon single crystal ingot 3 is completed, which includes the neck section 3a, the shoulder section 3b, the body section 3c, and the tail section 3d in this order from the top (head) of the single crystal to the bottom (bottom).

[0035] During the single-crystal pulling-up process, in order to control the diameter of the silicon single crystal 3 and the position of the liquid level of the silicon melt 2, an image of the portion at the boundary between the silicon single crystal 3 and the silicon melt 2 is captured with the CCD camera 22, and the diameter of the single crystal at the solid-liquid interface and the distance (gap) between the melt surface and the heat-shielding body 17 are calculated based on the captured image. The control unit 24 controls the pulling-up conditions, such as the pulling-up 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. Furthermore, the control unit 24 controls the height position of the quartz crucible 11 so as to keep the distance between the melt surface and the heat-shielding body 17 constant.

[0036] In the present embodiment, the rotation speed of the silicon single crystal 3 is set in the range of 17 rpm to 19 rpm. If the crystal rotation speed is lower than 17 rpm, the in-plane uniformity of the oxygen concentration cannot be improved. On the other hand, if the crystal rotation speed is higher than 19 rpm, the oxygen concentration in the crystal becomes high, and in addition, if the crystal axis deviates, there is a possibility that the single crystal will be deformed into a spiral shape due to eccentric rotation, which may generate an irregular portion in which the crystal diameter is smaller than the wafer diameter when grinding the outer diameter of the pulled crystal. Furthermore, it is also problematic that dislocation is likely to occur with the crystal deformation.

[0037] The rotation speed of the quartz crucible 11 during crystal pulling is 4.5 rpm to 8.5 rpm. If the rotation speed of the quartz crucible 11 is lower than 4.5 rpm, the uniformity of the oxygen concentration and resistivity distributions in the plane deteriorates. If the rotation speed of the quartz crucible 11 is higher than 8.5 rpm, the erosion loss of the quartz crucible increases, significantly increasing the oxygen concentration in the silicon melt.

[0038] When the silicon single crystal is pulled under the crystal pulling conditions described above, it is possible not only to reduce the concentration of interstitial oxygen of the silicon single crystal, but also to suppress a reduction in the oxygen concentration at the outer periphery of the single crystal, whereby the in-plane oxygen concentration distribution can be made uniform.

[0039] The oxygen concentration of the body portion 3c of the thus grown silicon single crystal 3 (see Fig. 3) is 1 × 10 17 atoms / cm 3 up to 8 × 10 17 atoms / cm 3 , the ROG in the crystal cross-section perpendicular to the crystal growth direction is 15% or less, and the RRG in the crystal cross-section is 5% or less. Furthermore, a silicon wafer obtained by cutting from the silicon single crystal 3 and subsequent processing has the same quality. That is, it is possible to obtain a silicon wafer having an oxygen concentration of 1 × 10 17 atoms / cm 3 or more and 8 × 10 17 atoms / cm 3or less; an ROG of 15% or less; and an RRG of 5% or less. All oxygen concentrations defined in this application are measured values ​​obtained using FTIR (Fourier Transform Infrared Spectroscopy) (ASTM F-121 (1979)). Furthermore, the resistivity values ​​are measured values ​​obtained using a four-probe method.

[0040] As described above, in the silicon single crystal manufacturing method according to the present invention as specified in claim 1, the single crystal is pulled while rotating at a high rotation speed of 17 rpm to 19 rpm according to the Czochralski method configured to utilize the action of a cusp magnetic field. This allows a silicon single crystal with a low oxygen concentration and the highest possible uniformity of the oxygen concentration and resistivity distributions to be manufactured. Consequently, it is possible to manufacture a low-oxygen silicon wafer for IGBT not only by the FZ method but also by the CZ method, thus enabling an improvement in mass production.

[0041] While the preferred embodiment of the present invention has been explained above, the present invention is not limited to it, and various modifications can be made to the embodiments without departing from the scope of the present invention, and it is understood that such modifications are also included in the scope of the invention.

[0042] For example, although the Fig. 1 is used in the above embodiment, the detailed configuration of the single crystal manufacturing apparatus is not particularly limited but may take various forms. [Examples]<Beispiel 1>

[0043] During the Czochralski method for pulling a silicon single crystal for a 200 mm diameter wafer using a cusp magnetic field, the influence of the cusp magnetic field and the rotation speed of the crystal on the oxygen concentration and in-plane resistivity distributions was evaluated. During the crystal pulling process, the magnetic field strength of the cusp magnetic field was set to 0.06 T (600 G), and the center of the magnetic field was set to a position 40 mm above the liquid surface of the silicon melt. Furthermore, the crucible rotation speed was set to 6 rpm and the crystal rotation speed to 18 rpm. Three pulled silicon single crystal ingots were then processed, and a total of six silicon wafer specimens were prepared (two silicon wafer specimens for each ingot).

[0044] Then, the in-plane oxygen concentration distribution in each of the silicon wafer specimens was measured. The oxygen concentration was measured at a distance of 5 mm in the radial direction from the center of the wafer. Because it was not possible to measure the oxygen concentration at the outermost peripheral part of the wafer, the in-plane oxygen concentration measurement was performed from the center of the wafer to a position 95 mm radially from the center (the area excluded from measurement at the outer peripheral part of the wafer was 5 mm). Furthermore, the ROG (Radial Oxygen Gradient) of the silicon wafer was calculated from the oxygen concentration measurement results. Assuming that the maximum value of the oxygen concentration was within the measurement range D Max and its minimum value D Min ROG can be calculated as follows: ROG(%)={(DMax−DMin) / DMin}×100

[0045] Then, the in-plane resistivity distribution of each silicon wafer sample was measured. The resistivity was measured using a four-probe method at a distance of 2 mm radially from the wafer center. Because it was not possible to measure the resistivity at the outermost peripheral part of the wafer, the in-plane resistivity measurement was performed from the wafer center to a position 96 mm radially from the center (the area excluded from measurement at the outer peripheral part of the wafer was 4 mm). Furthermore, the RRG (Radial Resistivity Gradient) of the silicon wafer was calculated from the resistivity measurement results. Assume the maximum resistivity value within the measurement range is ρ. Maxand its minimum value ρ Min RRG can be calculated as follows: RRG(%)={(ρMax−ρMin) / ρMin}×100

[0046] Fig. Figure 4 is a graph illustrating the oxygen concentration distributions of the silicon wafer specimens. As shown, the in-plane oxygen concentration in all wafer specimens was 3 × 10 17 atoms / cm 3 or less and the ROG 7.1% to 14.8%.

[0047] Fig. Figure 5 is a graph illustrating the resistivity distributions of the silicon wafer samples. As shown, the in-plane resistivity distribution in all wafer samples was 3.5% to 4.9%. <Beispiel 2>

[0048] Silicon single crystals were pulled under the same conditions as in Example 1, except that the rotation speed of the crystal was set to 17 rpm, and then the oxygen concentration and ROG of each of the silicon wafer specimens obtained by processing the pulled silicon single crystal ingots were determined under the same conditions as in Example 1. As a result, as shown in Fig. 6, the oxygen concentration in the wafer plane is 3 × 10 17 atoms / cm 3 or less and the ROG about 12.3%. <Beispiel 3>

[0049] Silicon single crystals were pulled under the same conditions as in Example 1, except that the rotation speed of the crystal was set to 19 rpm, and then the oxygen concentration and ROG of each of the silicon wafer specimens obtained by processing the pulled silicon single crystal ingots were examined under the same conditions as in Example 1. As a result, as shown in Fig. 7, the oxygen concentration in the wafer plane is 3 × 10 17 atoms / cm 3 or less and the ROG about 7.5%. <Beispiel 4>

[0050] Silicon single crystals were pulled under the same conditions as in Example 1, except that the center of the cusp magnetic field was set at a position 7 mm above the position of the liquid surface of the silicon melt, and then the oxygen concentration and ROG of each of the silicon wafer specimens obtained by processing the pulled silicon single crystal ingots 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 is 4.3 × 10 17 atoms / cm 3 or less and the ROG was 5.9% to 11.7%. <Beispiel 5>

[0051] The manufacturing method of Example 5 does not fall within the scope of claim 1. Silicon single crystals were grown under the same conditions as in Example 1, except that the center of the cusp magnetic field was set at a position 26 mm below the position of the liquid surface of the silicon melt, and then the oxygen concentration and ROG of each of the silicon wafer specimens obtained by processing the pulled silicon single crystal ingots were determined under the same conditions as in Example 1. As a result, as shown in Fig. 9, the oxygen concentration in the wafer plane is 5.3 × 10 17 atoms / cm 3 or less and the ROG was 3.0% to 10.4%. <Vergleichsbeispiel 1>

[0052] Silicon single crystals were pulled under the same conditions as in Example 1, except that the rotation speed of the crystal was set to 9 rpm, and then the oxygen concentration and ROG of each of the silicon wafer specimens obtained by processing the pulled silicon single crystal ingots were determined under the same conditions as in Example 1. As a result, as shown in Fig. 10, the oxygen concentration in the wafer plane is 5.7 × 10 17 atoms / cm 3 or less, and the ROG was approximately 84.8% to 135.1%. Thus, the uniformity of the oxygen concentration within the plane was very poor. <Vergleichsbeispiel 2>

[0053] Silicon single crystals were pulled up using a HMCZ configured to apply a horizontal magnetic field. The rotation speed of the crystal was set at 5 rpm. Then, the oxygen concentration and in-plane resistivity distributions of each of the silicon wafer specimens obtained by processing the pulled silicon single crystal ingots were determined under the same conditions as in Example 1. As a result, Fig. 11, although the oxygen concentration in the wafer plane is 3.1 × 10 17 atoms / cm 3 or less, the ROG was 57.3% to 83.4%. Thus, the uniformity of the oxygen concentration within the plane was poor. Furthermore, as shown in Fig. As illustrated in Figure 12, the RRG was 3.2% to 5.8%. Thus, the in-plane resistivity uniformity was good. <Vergleichsbeispiel 3>

[0054] After producing silicon single crystals for wafers with a diameter of 200 mm using an FZ method, the in-plane resistivity distribution was determined for each of the silicon wafer specimens, each having a diameter of 200 mm and obtained by processing the produced silicon single crystal ingots, under the same conditions as in Example 1. As in Fig. As illustrated in Figure 13, the RRG was 7.7% to 11.9%. Thus, the in-plane resistivity uniformity was worse than that of Example 1.

[0055] The above results show that by adjusting the rotation speed of the crystal in the pulling process of the silicon single crystal by the Czochralski method, which was arranged to use the cusp magnetic field, to 17 rpm to 19 rpm, it is possible to increase the oxygen concentration in the silicon single crystal to 8 × 1017 atoms / cm 3 or less, resulting in a reduction in both ROG and RRG. [List of reference symbols] 1 single crystal production device 2 silicon melt 3 Silicon single crystal (ingot) 3a Neck section 3b shoulder section 3c Body section 3D tail section 10 chambers 10a Main Chamber 10b Drawing chamber 10c Gas inlet 10d Gas outlet 10th observation window 11 quartz crucibles 12 Susceptor 13 Rotating shaft 14 Shaft drive mechanism 15 Heating 16 Thermal insulation material 17 Heat shielding body 18 wire 19 Wire winding mechanism 21 Magnetic field generator 21a Upper coil (coil for generating a magnetic field) 21b Lower coil (coil for generating a magnetic field) 22 Camera 23 Image processing unit 24 Control unit

Claims

[1] A method for producing a silicon single crystal having an approximate diameter of 200 mm by the Czochralski method, the method including pulling up a silicon single crystal from a silicon melt while applying a cusp magnetic field, characterized by , that the rotation speed of the crystal during the pulling up of the silicon single crystal under rotation is set to 17 rpm or more and 19 rpm or less, the rotation speed of a quartz crucible holding the silicon melt is set to 4.5 rpm or more and 8.5 rpm or less, the magnetic field strength of the cusp magnetic field is set to 0.05 T to 0.07 T, and the central position of the magnetic field in the vertical direction is set to a range of +7 mm to +40 mm, relative to the position of the liquid surface of the silicon melt. [2] Silicon single crystal with an approximate diameter of 200 mm, characterized by that its oxygen concentration according to ASTM F-121 (1979) is 1 × 10 17 atoms / cm 3 or more and 8 × 10 17 atoms / cm 3 or less, its radial oxygen gradient ROG in a crystal cross section perpendicular to a crystal growth direction is 15% or less, and its radial resistivity gradient RRG in the crystal cross section is 5% or less. [3] Silicon wafers with a diameter of 200 mm, characterized by that its oxygen concentration according to ASTM F-121 (1979) is 1 × 10 17 atoms / cm 3 or more and 8 × 10 17 atoms / cm 3 or less, its Radial Oxygen Gradient ROG is 15% or less, and its Radial Resistivity Gradient RRG is 5% or less.

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