JPWO2019107190A1 - Silicon single crystal and its manufacturing method and silicon wafer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a silicon single crystal having a low oxygen concentration and a high uniformity of in-plane distribution of oxygen concentration and resistivity, and a silicon wafer. SOLUTION: This is a method for producing a silicon single crystal by the MCZ method in which a silicon single crystal 3 is pulled up from a silicon melt 2 in a quartz crucible 11 while applying a cusp magnetic field, and when the silicon single crystal 3 is pulled up while rotating. The crystal rotation speed is 17 rpm or more and 19 rpm or less. The oxygen concentration of the silicon single crystal 3 thus pulled up is 1 × 1017 atoms / cm3 or more and 8 × 1017 atoms / cm3 or less, the ROG in the crystal cross section orthogonal to the crystal growth direction is 15% or less, and the RRG in the crystal cross section. Is less than 5%. [Selection diagram] Fig. 1

Description

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 by the MCZ (Magnetic field applied CZ) method and a silicon single crystal and a silicon wafer produced by the method.

A silicon single crystal having a low interstitial oxygen concentration is preferably used for a silicon wafer for a power semiconductor centered on an IGBT (Gate Insulated Bipolar Transistor). The FZ method, which does not use a quartz crucible as an oxygen supply source, is often used to produce such a silicon single crystal, but it should be produced by the CZ method (Czochralski method) in order to improve mass productivity. Is also being considered.

As one of the CZ methods for producing a silicon single crystal having a low oxygen concentration, an MCZ method for pulling up a silicon single crystal while applying a magnetic field is known. According to the MCZ method, the melt convection can be suppressed, the dissolution of oxygen into the silicon melt due to the melting damage of the quartz crucible can be suppressed, and the oxygen concentration in the silicon single crystal can be reduced. For example, Patent Document 1 states that in the MCZ method using a horizontal magnetic field or a cusp magnetic field, the horizontal magnetic field strength is 2000 G (Gauss) or more, the rotation speed of a quartz rut is 1.5 rpm or less, and the crystal rotation speed is 7.0 rpm or less, and a single crystal. It is described that a single crystal having an interstitial oxygen concentration of 6 × 10 ¹⁷ atoms / cm ³ or less is grown by setting the crystal pulling rate to be free of rearrangement cluster defects.

Further, Patent Document 2 describes a step of melting polycrystalline silicon in a chamber included in a vacuum chamber to form a melt, a step of forming a cusp magnetic field in the vacuum chamber, and a step of immersing a seed crystal in the melt. A plurality of process parameters are set so that the silicon ingot has an oxygen concentration lower than about 5 ppma, which comprises a step of drawing out a seed crystal from the melt to form a silicon single crystal ingot having a diameter larger than about 150 mm. It is stated that adjustments are made at the same time. Multiple process parameters include crucible sidewall temperature, silicon monoxide (SiO) transfer from the crucible to the single crystal, and the rate of SiO evaporation from the melt, with a crucible rotation speed of 1.3-2.2 rpm. The crystal rotation speed is 8 to 14 rpm, and the magnetic field strength of the edge of the single crystal at the solid-liquid interface is 0.02 to 0.05 T (tesla).

JP-A-2010-222241 Special Table 2016-519049

However, in the HMCZ method in which the silicon single crystal is pulled up while applying a horizontal magnetic field, it is possible to reduce the oxygen content of the silicon single crystal, but the in-plane uniformity of the oxygen concentration and the resistivity becomes a problem. 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, but when the manufacturing conditions are actually applied, the oxygen concentration and the resistivity are improved. There is a problem that the internal distribution is not uniform. Further, in the conventional manufacturing method described in Patent Document 2, the crucible rotation speed is 1.3 to 2.2 rpm and the crystal rotation speed is 8 to 14 rpm, but when the manufacturing conditions are actually applied, the oxygen concentration and the oxygen concentration and There is a problem that the in-plane distribution of resistivity is not uniform.

Therefore, an object of the present invention is a silicon single crystal by the Czochralski method to which a cusp magnetic field is applied, which enables the production of a silicon single crystal having a low oxygen concentration and a high uniformity of in-plane distribution of oxygen concentration and resistivity. Is to provide a manufacturing method for. Another object of the present invention is to provide a silicon single crystal and a silicon wafer having a low oxygen concentration and a high uniformity of in-plane distribution of oxygen concentration and resistivity.

As a result of intensive studies on factors that change the in-plane distribution of oxygen concentration and resistivity in a silicon single crystal, the inventor of the present application rotates the single crystal at high speed when the single crystal is pulled up while applying a cusp magnetic field. It was found that the uniformity of the in-plane distribution of the oxygen concentration and the resistivity can be improved without causing an increase in the oxygen concentration or crystal deformation (dislocation). Normally, in order to produce a silicon single crystal having a low oxygen concentration, it is necessary to slow down the crystal rotation, but the in-plane uniformity of the oxygen concentration deteriorates. However, it has been clarified that a silicon single crystal having a low oxygen concentration can be obtained by using a cusp magnetic field even if the crystal rotation is accelerated, and the in-plane distribution of the oxygen concentration and the resistivity is stable, and the present invention can be achieved. Is.

The present invention is based on such technical knowledge, and the method for producing a silicon single crystal according to the present invention is a method for producing a silicon single crystal by a Czochralski method in which a silicon single crystal is pulled up from a silicon melt while applying a cusp magnetic field. It is a manufacturing method, characterized in that the crystal rotation speed at the time of pulling up the silicon single crystal while rotating is 17 rpm or more and 19 rpm or less.

In the present invention, the rotation speed of the quartz crucible holding the silicon melt is preferably 4.5 rpm or more and 8.5 rpm or less. Further, the magnetic field strength of the cusp magnetic field is preferably 500 to 700 G, and the magnetic field center position in the vertical direction is preferably in the range of +40 mm to −26 mm with respect to the liquid level position of the silicon melt. According to this condition, the uniformity of the in-plane distribution of oxygen concentration and resistivity in the single crystal can be improved.

Further, the silicon single crystal according to the present invention has an oxygen concentration of 1 × 10 ¹⁷ atoms / cm ³ or more and 8 × 10 ¹⁷ atoms / cm ³ or less, and ROG (Radial Oxygen Gradient:) in the crystal cross section orthogonal to the crystal growth direction. The oxygen concentration gradient) is 15% or less, and the RRG (Radial Resistivity Gradient) in the crystal cross section is 5% or less. According to the present invention, it is possible to provide a silicon single crystal having a low oxygen concentration, which is suitable as a material for a silicon wafer for a power semiconductor.

Furthermore, the silicon wafer according to the present invention has an oxygen concentration of 1 × 10 ¹⁷ atoms / cm ³ or more and 8 × 10 ¹⁷ atoms / cm ³ or less, a ROG of 15% or less, and an RRG of 5% or less. It is characterized by. According to the present invention, it is possible to provide a silicon wafer suitable as a substrate material for a power semiconductor.

According to the present invention, it is possible to provide a method for producing a silicon single crystal having a low oxygen concentration and a high uniformity of in-plane distribution of oxygen concentration and resistivity. Further, according to the present invention, it is possible to provide a silicon single crystal and a silicon wafer having a low oxygen concentration and a high uniformity of in-plane distribution of oxygen concentration and resistivity.

FIG. 1 is a side sectional view schematically showing a configuration of a single crystal manufacturing apparatus according to an embodiment of the present invention. FIG. 2 is a flowchart illustrating a method for producing a silicon single crystal according to an embodiment of the present invention. FIG. 3 is a schematic cross-sectional view showing the shape of a silicon single crystal ingot. FIG. 4 is a graph showing ROG of a silicon wafer sample according to Example 1 (CUSP). FIG. 5 is a graph showing the RRG of a silicon wafer sample according to Example 1 (CUSP). FIG. 6 is a graph showing ROG of a silicon wafer sample according to Example 2 (CUSP). FIG. 7 is a graph showing ROG of a silicon wafer sample according to Example 3 (CUSP). FIG. 8 is a graph showing ROG of a silicon wafer sample according to Example 4 (CUSP). FIG. 9 is a graph showing ROG of a silicon wafer sample according to Example 5 (CUSP). FIG. 10 is a graph showing ROG of a silicon wafer sample according to Comparative Example 1 (CUSP). FIG. 11 is a graph showing ROG of a silicon wafer sample according to Comparative Example 2 (HMCZ). FIG. 12 is a graph showing the RRG of a silicon wafer sample according to Comparative Example 2 (HMCZ). FIG. 13 is a graph showing the RRG of the silicon wafer sample according to Comparative Example 3 (FZ).

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a side sectional view schematically showing a configuration of a single crystal manufacturing apparatus according to an embodiment of the present invention.

As shown in FIG. 1, the single crystal manufacturing apparatus 1 includes a chamber 10 (CZ furnace), a quartz crucible 11 that holds the silicon melt 2 in the chamber 10, and a graphite susceptor 12 that holds the quartz crucible 11. , A rotary shaft 13 that supports the susceptor 12, a shaft drive mechanism 14 that rotates and lifts the rotary shaft 13, a heater 15 arranged around the susceptor 12, and an outer surface of the heater 15 and an inner surface of the chamber 10. A heat insulating material 16 arranged along the line, a heat shield 17 arranged above the quartz crucible 11, and a wire 18 for pulling up a single crystal arranged above the quartz crucible 11 and coaxially with the rotating shaft 13. And a wire winding mechanism 19 arranged above the chamber 10.

Further, the single crystal manufacturing apparatus 1 includes a magnetic field generator 21 arranged outside the chamber 10, a CCD camera 22 for photographing the inside of the chamber 10, an image processing unit 23 for processing an image captured by the CCD camera 22, and the like. It includes a shaft drive mechanism 14, a heater 15, and a control unit 24 that controls a wire winding mechanism 19 based on the output of the image processing unit 23.

The chamber 10 is composed of a main chamber 10a and an elongated cylindrical pull chamber 10b connected to the upper opening of the main chamber 10a, and the quartz crucible 11, the susceptor 12, the heater 15 and the heat shield 17 are the main chambers. It is provided in 10a. The pull chamber 10b is provided with a gas introduction port 10c for introducing an inert gas (purge gas) such as argon gas into the chamber 10, and a gas for discharging the inert gas is provided in the lower part of the main chamber 10a. A discharge port 10d is provided. Further, a viewing window 10e is provided above the main chamber 10a, and the growing state (solid-liquid interface) of the silicon single crystal 3 can be observed from the viewing window 10e.

The quartz crucible 11 is a quartz glass container having a cylindrical side wall portion and a curved bottom portion. In order to maintain the shape of the quartz crucible 11 softened by heating, the susceptor 12 is held in close contact with the outer surface of the quartz crucible 11 so as to wrap the quartz crucible 11. The quartz crucible 11 and the susceptor 12 form a double-structured crucible that supports the silicon melt in the chamber 10.

The susceptor 12 is fixed to the upper end of the rotating shaft 13 extending in the vertical direction. The lower end of the rotating shaft 13 penetrates the center of the bottom of the chamber 10 and is connected to a shaft drive mechanism 14 provided on the outside of the chamber 10. The susceptor 12, the rotary shaft 13, and the shaft drive mechanism 14 constitute a rotary mechanism and an elevating mechanism of the quartz crucible 11.

The heater 15 is used to melt the silicon raw material filled in the quartz crucible 11 and maintain the molten state. The heater 15 is a carbon resistance heating type heater, and is a substantially cylindrical member provided so as to surround the entire circumference of the quartz crucible 11 in the susceptor 12. Further, the outside of the heater 15 is surrounded by the heat insulating material 16, which enhances the heat retention in the chamber 10.

The heat shield 17 suppresses the temperature fluctuation of the silicon melt 2 to form an appropriate hot zone near the solid-liquid interface, and prevents the silicon single crystal 3 from being heated by the radiant heat from the heater 15 and the quartz crucible 11. It is provided for the purpose. The heat shield 17 is a cylindrical member made of graphite that covers the region above the silicon melt 2 excluding the pulling path of the silicon single crystal 3.

A circular opening larger than the diameter of the silicon single crystal 3 is formed in the center of the lower end of the heat shield 17, and a pull-up path for the silicon single crystal 3 is secured. As shown, the silicon single crystal 3 passes through the opening of the heat shield 17 and is pulled upward. The diameter of the opening of the heat shield 17 is smaller than the diameter of the quartz crucible 11, and the lower end of the heat shield 17 is located inside the quartz crucible 11, so that the upper end of the rim of the quartz crucible 11 is from the lower end of the heat shield 17. The heat shield 17 does not interfere with the quartz crucible 11 even if it is raised upward.

Although the amount of melt in the quartz crucible 11 decreases with the growth of the silicon single crystal 3, the silicon melt is formed by raising the quartz crucible 11 so that the gap between the melt surface and the heat shield 17 becomes constant. It is possible to suppress the temperature fluctuation of the liquid 2 and control the evaporation amount of the SiO gas from the silicon melt 2 by keeping the flow velocity of the gas flowing near the melting surface constant. Therefore, it is possible to improve the stability of the crystal defect distribution, the oxygen concentration distribution, the resistivity distribution, etc. in the pulling axis direction of the single crystal.

Above the quartz crucible 11, a wire 18 which is a pulling shaft of the silicon single crystal 3 and a wire winding mechanism 19 for winding the wire 18 are provided. The wire winding mechanism 19 has a function of rotating a single crystal together with the wire 18. The wire winding mechanism 19 is arranged above the pull chamber 10b, the wire 18 extends downward from the wire winding mechanism 19 through the inside of the pull chamber 10b, and the tip of the wire 18 is inside the main chamber 10a. It has reached the space. FIG. 1 shows a state in which the silicon single crystal 3 being grown is suspended from the wire 18. When pulling up the single crystal, the seed crystal is immersed in the silicon melt 2, and the single crystal is grown by gradually pulling up the wire 18 while rotating the quartz crucible 11 and the seed crystal, respectively.

A gas introduction port 10c for introducing an inert gas into the chamber 10 is provided in the upper part of the pull chamber 10b, and a gas exhaust for exhausting the inert gas in the chamber 10 is provided in the bottom of the main chamber 10a. An exit 10d is provided. The inert gas is introduced into the chamber 10 from the gas introduction port 10c, and the introduction amount thereof is controlled by a valve. Further, since the inert gas in the closed chamber 10 is exhausted from the gas discharge port 10d to the outside of the chamber 10, the SiO gas and CO gas generated in the chamber 10 should be recovered to keep the inside of the chamber 10 clean. Is possible. Although not shown, a vacuum pump is connected to the gas discharge port 10d via a pipe, and the inside of the chamber 10 is controlled by controlling the flow rate with a valve while sucking the inert gas in the chamber 10 with the vacuum pump. Is kept at a constant depressurized state.

The magnetic field generator 21 is configured by using an upper coil 21a and a lower coil 21b that face each other in the vertical direction, and generates a cusp magnetic field in the chamber 10 by passing a current in opposite directions to each of the pair of magnetic field generating coils. .. In the figure, "・" indicates the current flow coming out of the paper surface, and "x" indicates the current flow entering the paper surface.

The cusp magnetic field is axially symmetric with respect to the pulling axis, and at the center of the magnetic field, the magnetic fields cancel each other out and the magnetic field strength in the vertical direction becomes zero. A vertical magnetic field exists at a position deviating from the magnetic field center point, and a horizontal magnetic field is formed in the radial direction. The magnetic field center position of the cusp magnetic field is near the liquid level of the silicon melt 2, and is preferably set in the range of +40 mm to −26 mm with respect to the liquid level position. In this way, by applying the cusp magnetic field to the silicon melt, it is possible to suppress the melt convection in the direction orthogonal to the magnetic field lines.

The magnetic field strength of the cusp magnetic field is preferably 500 to 700 G. This is because when the magnetic field strength is smaller than 500 G, it becomes difficult to pull up a silicon single crystal having a low oxygen concentration of 8 × 10 ¹⁷ atoms / cm ³ or less. Further, it is difficult for the existing magnetic field generator to stably output a magnetic field strength exceeding 700 G, and it is desirable that the magnetic field strength is as low as possible from the viewpoint of power consumption. The value of the magnetic field strength of the cusp magnetic field described in the present application is the position of the magnetic field center in the vertical direction and the position of the side wall of the quartz rut in the horizontal direction.

In the case of the HMCZ method in which a horizontal magnetic field is applied, since the direction of the magnetic field lines is one direction, there is an effect of suppressing convection in the direction orthogonal to the magnetic field lines, but it is not possible to suppress convection in the direction parallel to the magnetic force lines. On the other hand, in the case of a cusp magnetic field, the directions of the magnetic field lines are radial and have symmetry in a plan view about the pulling axis, so that it is possible to suppress the convection of melt in the circumferential direction in the quartz crucible 11. Therefore, it is possible to suppress the elution of oxygen from the quartz crucible 11 and reduce the oxygen concentration in the silicon single crystal.

A viewing window 10e for observing the inside is provided in the upper part of the main chamber 10a, and the CCD camera 22 is installed outside the viewing window 10e. During the single crystal pulling process, the CCD camera 22 takes an image of the boundary between the silicon single crystal 3 and the silicon melt 2 which can be seen through the opening of the heat shield 17 through the viewing window 10e. The CCD camera 22 is connected to the image processing unit 23, the captured image is processed by the image processing unit 23, and the processing result is used by the control unit 24 to control the crystal pulling condition.

FIG. 2 is a flowchart illustrating a method for producing a silicon single crystal according to an embodiment of the present invention. Further, FIG. 3 is a schematic cross-sectional view showing the shape of the silicon single crystal ingot.

As shown in FIGS. 2 and 3, in the production of the silicon single crystal 3, the silicon raw material in the quartz crucible 11 is heated to generate the silicon melt 2 (step S11). Then, the seed crystal attached to the tip of the wire 18 is lowered and landed on the silicon melt 2 (step S12).

Next, a single crystal pulling step is carried out in which the seed crystal is gradually pulled up while maintaining the contact state with the silicon melt 2 to grow the single crystal. In the single crystal pulling step, a necking step (step S13) of forming a neck portion 3a in which the crystal diameter is narrowed for non-dislocation, and a shoulder portion in which the crystal diameter is gradually increased in order to obtain a specified diameter. The crystal diameter gradually decreased in the shoulder part growing step (step S14) for forming 3b and the body part growing step (step S15) for forming the body part 3c (straight body part) in which the crystal diameter was kept constant. The tail portion growing step (step S16) for forming the tail portion 3d is carried out in order, and the tail portion growing step is completed when the single crystal is finally separated from the melt surface. As described above, the silicon single crystal ingot 3 having the neck portion 3a, the shoulder portion 3b, the body portion 3c, and the tail portion 3d is completed in this order from the upper end (top) to the lower end (bottom) of the single crystal.

During the single crystal pulling process, in order to control the diameter of the silicon single crystal 3 and the liquid level position of the silicon melt 2, the CCD camera 22 takes an image of the boundary between the silicon single crystal 3 and the silicon melt 2. , The diameter of the single crystal at the solid-liquid interface and the distance (gap) between the melt surface and the heat shield 17 are calculated from the photographed image. The control unit 24 controls the pulling conditions such as the pulling speed of the wire 18 and the power of the heater 15 so that the diameter of the silicon single crystal 3 becomes the target diameter. Further, the control unit 24 controls the height position of the quartz crucible 11 so that the distance between the melt surface and the heat shield 17 is constant.

In the present embodiment, the rotation speed of the silicon single crystal 3 is set in the range of 17 to 19 rpm. This is because when the crystal rotation speed is less than 17 rpm, the uniformity of the in-plane distribution of the oxygen concentration cannot be improved, and when it is higher than 19 rpm, not only the oxygen concentration in the crystal increases but also the crystal This is because if the axis is deviated, the single crystal is easily deformed into a spiral shape due to eccentric rotation, and when the crystal is ground to an outer diameter after the crystal is pulled up, a defective portion where the crystal diameter is less than the wafer diameter occurs. Another problem is that dislocations are likely to occur with crystal deformation.

During crystal pulling, the rotation speed of the quartz crucible 11 is preferably 4.5 to 8.5 rpm. This is because when the rotation speed of the quartz crucible 11 is smaller than 4.5 rpm, the in-plane distribution of the oxygen concentration and the resistivity deteriorates. This is because when the rotation speed of the quartz crucible 11 is higher than 8.5 rpm, the amount of melt damage of the quartz crucible increases and the oxygen concentration in the silicon melt becomes very high.

When the silicon single crystal is pulled up under the above crystal pulling conditions, not only the interstitial oxygen concentration of the silicon single crystal can be lowered, but also the decrease of the oxygen concentration at the outer peripheral portion of the single crystal can be suppressed, and oxygen can be pulled up. It is possible to realize uniform distribution of the concentration in the plane.

The oxygen concentration of the body portion 3c of the silicon single crystal 3 (see FIG. 3) pulled up in this way is 1 × 10 ¹⁷ atoms / cm ³ to 8 × 10 ¹⁷ atoms / cm ³ , which is within the crystal cross section orthogonal to the crystal growth direction. The ROG is 15% or less, and the RRG in the crystal cross section is 5% or less. Further, a silicon wafer cut out from the silicon single crystal 3 and processed has the same quality. That is, a silicon wafer having an oxygen concentration of 1 × 10 ¹⁷ atoms / cm ³ or more and 8 × 10 ¹⁷ atoms / cm ³ or less, a ROG of 15% or less, and an RRG of 5% or less can be obtained. All the oxygen concentrations specified in this specification are measured values by FTIR (Fourier Transform Infrared Spectroscopy) specified in ASTM F-121 (1979). The resistance value is a value measured by the four-probe method.

As described above, in the method for producing a silicon single crystal according to the present embodiment, the oxygen concentration is low by pulling up the single crystal while rotating it at a high speed of 17 to 19 rpm in the Czochralski method in which a cusp magnetic field is applied. Moreover, it is possible to produce a silicon single crystal in which the in-plane distribution of oxygen concentration and resistivity is as uniform as possible. Therefore, the low oxygen silicon wafer for IGBT can be manufactured by the CZ method instead of the FZ method, and mass productivity can be improved.

Although the preferred embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and various modifications can be made without departing from the gist of the present invention, and these are also the present invention. It goes without saying that it is included in the range.

For example, in the above embodiment, the case where the single crystal manufacturing apparatus 1 shown in FIG. 1 is used is given as an example, but the detailed configuration of the single crystal manufacturing apparatus is not particularly limited, and various configurations may be used. Can be done.

<Example 1>
In pulling up a silicon single crystal for a wafer with a diameter of 200 mm by the Czochralski method using a CUSP magnetic field, the effects of the cusp magnetic field and crystal rotation speed on the in-plane distribution of oxygen concentration and resistance were evaluated. In the crystal pulling step, the magnetic field strength of the cusp magnetic field was set to 600 G, and the magnetic field center position was set to a position 40 mm above the liquid level position of the silicon melt. The crucible rotation speed was 6 rpm, and the crystal rotation speed was 18 rpm. After that, the three pulled-up silicon single crystal ingots were processed to prepare two samples of silicon wafers having a diameter of 200 mm, for a total of six samples.

Next, the in-plane distribution of oxygen concentration in the silicon wafer sample was measured. The oxygen concentration was measured at a pitch of 5 mm in the radial direction from the center of the wafer. Since it is not possible to measure the oxygen concentration at the outermost periphery of the wafer, the measurement range of the oxygen concentration within the wafer surface was set to the range from the center of the wafer to 95 mm in the radial direction (measurement exclusion width at the outer periphery of the wafer: 5 mm). .. Furthermore, the ROG (Radial Oxygen Gradient: radial oxygen concentration distribution) of the silicon wafer was obtained from the measurement result of the oxygen concentration. When the maximum value of oxygen concentration in the measurement range is D _Max and the minimum value is D _Min , the formula for calculating ROG is as follows.
ROG (%) = {(D _Max −D _Min ) / D _Min } × 100

Next, the in-plane distribution of the resistivity of the silicon wafer sample was measured. The resistivity was measured by the four-probe method at a pitch of 2 mm in the radial direction from the center of the wafer. Since it is not possible to measure the resistivity at the outermost periphery of the wafer, the resistivity measurement range within the wafer surface was set to the range from the center of the wafer to 96 mm in the radial direction (measurement exclusion width of the outer periphery of the wafer: 4 mm). .. Further, the RRG (Radial Resistivity Gradient: Radial Resistivity Gradient) of the silicon wafer was obtained from the measurement result of the resistivity. When the maximum value of the resistivity in the measurement range is ρ _Max and the minimum value is ρ _Min , the calculation formula of RRG is as follows.
RRG (%) = {(ρ _Max −ρ _Min ) / ρ _Min } × 100

FIG. 4 is a graph showing the oxygen concentration distribution of the silicon wafer sample. As shown in the figure, the in-plane oxygen concentration of each wafer sample was 3 × 10 ¹⁷ atoms / cm ³ or less, and the ROG was 7.1 to 14.8%.

FIG. 5 is a graph showing the resistivity distribution of the silicon wafer sample. As shown in the figure, the in-plane resistivity distribution of each silicon wafer was 3.5 to 4.9%.

<Example 2>
After pulling up the silicon single crystal under the same conditions as in Example 1 except that the crystal rotation speed was set to 17 rpm, the oxygen concentration distribution and ROG of the silicon wafer sample obtained by processing this were the same conditions as in Example 1. I asked for it. As a result, as shown in FIG. 6, the oxygen concentration in the wafer surface was 3 × 10 ¹⁷ atoms / cm ³ or less, and the ROG was about 12.3%.

<Example 3>
After pulling up the silicon single crystal under the same conditions as in Example 1 except that the crystal rotation speed was set to 19 rpm, the oxygen concentration distribution and ROG of the silicon wafer sample obtained by processing this were the same conditions as in Example 1. I asked for it. As a result, as shown in FIG. 7, the oxygen concentration in the wafer surface was 3 × 10 ¹⁷ atoms / cm ³ or less, and the ROG was about 7.5%.

<Example 4>
Silicon obtained by pulling up a silicon single crystal under the same conditions as in Example 1 except that the central position of the cusp magnetic field was set to a position 7 mm above the liquid level position of the silicon melt, and then processing the silicon single crystal. The oxygen concentration distribution and ROG of the wafer sample were determined under the same conditions as in Example 1. As a result, as shown in FIG. 8, the oxygen concentration in the wafer surface was 4.3 × 10 ¹⁷ atoms / cm ³ or less, and the ROG was 5.9 to 11.7%.

<Example 5>
Silicon obtained by pulling up a silicon single crystal under the same conditions as in Example 1 except that the central position of the cusp magnetic field was set to a position 26 mm below the liquid level position of the silicon melt, and then processing the silicon single crystal. The oxygen concentration distribution and ROG of the wafer sample were determined under the same conditions as in Example 1. As a result, as shown in FIG. 9, the oxygen concentration in the wafer surface was 5.3 × 10 ¹⁷ atoms / cm ³ or less, and the ROG was 3.0 to 10.4%.

<Comparative example 1>
After pulling up the silicon single crystal under the same conditions as in Example 1 except that the crystal rotation speed was set to 9 rpm, the oxygen concentration distribution and ROG of the silicon wafer sample obtained by processing this were the same conditions as in Example 1. I asked for it. As a result, as shown in FIG. 10, the oxygen concentration in the wafer surface was 5.7 × 10 ¹⁷ atoms / cm ³ or less, the ROG was 84.8 to 135.1%, and the in-plane uniformity of the oxygen concentration was It was very bad.

<Comparative example 2>
The silicon single crystal was pulled up by the HMCZ method in which a horizontal magnetic field was applied. The crystal rotation speed at this time was 5 rpm. Then, the in-plane distribution of the oxygen concentration and the resistivity of the silicon wafer sample obtained by processing the silicon single crystal was determined under the same conditions as in Example 1. As a result, as shown in FIG. 11, the oxygen concentration in the wafer surface was 3.1 × 10 ¹⁷ atoms / cm ³ or less, but the ROG was 57.3 to 83.4%, and the oxygen concentration was in-plane. The uniformity was poor. Further, as shown in FIG. 12, the RRG was 3.2 to 5.8%, and the in-plane uniformity of the resistivity was good.

<Comparative example 3>
After producing a silicon single crystal for a wafer having a diameter of 200 mm by the FZ method, the in-plane distribution of the resistivity of a silicon wafer sample having a diameter of 200 mm obtained by processing the single crystal was determined under the same conditions as in Example 1. As a result, as shown in FIG. 13, the RRG was 7.7 to 11.9%, and the in-plane uniformity of the resistivity was worse than that of Example 1.

From the above results, the oxygen concentration in the silicon single crystal was reduced to 8 × 10 ¹⁷ atoms / cm ³ or less by setting the crystal rotation speed to 17 to 19 rpm in the pulling up of the silicon single crystal by the Czochralski method using the cusp magnetic field. It was found that RRG and RRG were also reduced.

1 Single crystal manufacturing equipment 2 Silicon melt 3 Silicon single crystal (ingot)
3a Neck 3b Shoulder 3c Body 3d Tail 10 Chamber 10a Main chamber 10b Pull chamber 10c Gas inlet 10d Gas outlet 10e Peephole 11 Quartz rut 12 Suceptor 13 Rotating shaft 14 Shaft drive mechanism 15 Heater 16 Insulation 17 Heat Shield 18 Wire 19 Wire winding mechanism 21 Magnetic field generator 21a Upper coil (magnetic field generation coil)
21b Lower coil (magnetic field generation coil)
22 Camera 23 Image processing unit 24 Control unit

Claims (5)

A method for producing a silicon single crystal by the Czochralski method in which a silicon single crystal is pulled up from a silicon melt while applying a cusp magnetic field.
A method for producing a silicon single crystal, wherein the crystal rotation speed when pulling up the silicon single crystal while rotating it is 17 rpm or more and 19 rpm or less. The method for producing a silicon single crystal according to claim 1, wherein the rotation speed of the quartz crucible holding the silicon melt is 4.5 rpm or more and 8.5 rpm or less. The silicon single crystal according to claim 1 or 2, wherein the magnetic field strength of the cusp magnetic field is 500 to 700 G, and the magnetic field center position in the vertical direction is in the range of +40 mm to −26 mm with respect to the liquid level position of the silicon melt. Manufacturing method. Oxygen concentration is 1 × 10 ¹⁷ atoms / cm ³ or more and 8 × 10 ¹⁷ atoms / cm ³ or less.
ROG in the crystal cross section orthogonal to the crystal growth direction is 15% or less.
A silicon single crystal having an RRG of 5% or less in the crystal cross section. Oxygen concentration is 1 × 10 ¹⁷ atoms / cm ³ or more and 8 × 10 ¹⁷ atoms / cm ³ or less.
ROG is 15% or less,
A silicon wafer having an RRG of 5% or less.