Method for manufacturing silicon single crystal and method for manufacturing silicon wafer

Abstract

To provide production methods that enable the production of silicon monocrystal and silicon wafers having stable oxygen levels by allowing the orientation of convection of silicon melt to be stably controlled.SOLUTION: A production method for silicon monocrystal comprises: a resistance value-setting step (S2) for setting a first resistance value that is the resistance value of a first power supply unit and a second resistance value that is the resistance value of a second power supply unit; a silicon melt-heating step (S3) for heating silicon melt in a quartz crucible in the absence of a magnetic field; a horizontal magnetic field-applying step (S4) for applying a horizontal magnetic field to the silicon melt in the quartz crucible; and a pulling-up step (S6) for pulling up silicon monocrystal from the silicon melt. In the resistance value-setting step, the first and second resistance values are measured, and if the resistance ratio of the first and second resistance values is less than a determination value, at least one of the first and second resistance values is adjusted, and the resistance values are measured again and compared with the determination value, and if the resistance ratio is not less than the determination value, the resistance value-setting step is ended.SELECTED DRAWING: Figure 9

Description

[Technical field]

[0001] The present invention relates to a method for producing a silicon single crystal and a method for producing a silicon wafer. [Background technology]

[0002] A manufacturing method called the Czochralski method (hereinafter abbreviated as the "CZ method") is used to manufacture silicon single crystals. In a manufacturing method using this CZ method, when a horizontal magnetic field is applied from the outside, the silicon melt initially forms either a right-handed vortex or a left-handed vortex with respect to the direction of the applied magnetic field. The direction of the vortex is random, and the oxygen concentration taken into the crystal varies depending on the direction of the vortex and the environment inside the furnace. In order to obtain silicon single crystals with a stable oxygen concentration, it is important to control the convection pattern of the silicon melt during pulling. For this reason, various studies have been conducted on methods for controlling the convection pattern of the silicon melt in the crucible (see, for example, Patent Document 1).

[0003] In the method for controlling the convection pattern of silicon melt described in Patent Document 1, when the crucible is viewed vertically from above, an imaginary line is set that is parallel to the magnetic field line at the center of the horizontal magnetic field and passes through the center of the surface of the silicon melt, and the silicon melt is heated using heating parts with different heating capacities on either side of this imaginary line, and a horizontal magnetic field is applied to fix the direction of convection in a cross section perpendicular to the magnetic field. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2019 / 167989 Summary of the Invention [Problem to be solved by the invention]

[0005] Even if the method for controlling the convection pattern of silicon melt described in Patent Document 1 is adopted, when silicon single crystals are actually produced, the environment inside the furnace changes due to deterioration over time of the components inside the furnace, so there is a possibility that the convection cannot be stably controlled. As a result, it becomes impossible to produce silicon single crystals with a stable oxygen concentration, and the quality of silicon wafers cut from the silicon single crystals may also deteriorate.

[0006] An object of the present invention is to provide a method for producing a silicon single crystal and a method for producing a silicon wafer, which are capable of stably controlling the direction of convection in a silicon melt and capable of producing a silicon single crystal and a silicon wafer having a stable oxygen concentration. [Means for solving the problem]

[0007] The present invention is a method for producing a silicon single crystal, which involves pulling up a silicon single crystal from a silicon melt in a quartz crucible heated by a heating device, the heating device comprising a heat generating unit arranged around the quartz crucible and a power supply unit for supplying power to the heat generating unit, the power supply unit comprising a first power supply unit arranged in the first heating region and a second power supply unit arranged in the second heating region when the heating device is divided into a first heating region and a second heating region by a central magnetic field line of a horizontal magnetic field passing through a central axis of the quartz crucible when viewed vertically from above the quartz crucible, and the method includes a resistance value setting step of setting a first resistance value which is a resistance value of the first power supply unit and a second resistance value which is a resistance value of the second power supply unit, a silicon melt heating step of heating the silicon melt in the quartz crucible in a magnetic field-free state, and a silicon melt heating step of heating the silicon melt in the quartz crucible in a magnetic field-free state. The method includes a horizontal magnetic field application step of applying a horizontal magnetic field to a silicon melt, and a pulling step of pulling up a silicon single crystal from the silicon melt, and the resistance value setting step includes a measurement step of measuring the first resistance value and the second resistance value, a determination step of determining whether a resistance ratio, which is a value obtained by dividing a higher resistance value of the first resistance value and the second resistance value by a lower resistance value, is equal to or higher than a predetermined determination value, and an adjustment step of adjusting at least one of the first resistance value and the second resistance value when it is determined in the determination step that the resistance ratio is less than the determination value, and is characterized in that if it is determined in the determination step that the resistance ratio is less than the determination value, the determination step is performed again after performing the adjustment step and the measurement step, and if it is determined in the determination step that the resistance ratio is equal to or higher than the determination value, the resistance value setting step is terminated.

[0008] In the method for producing a silicon single crystal of the present invention, the resistance value setting step is preferably performed every time the pulling step is performed a predetermined number of times.

[0009] In the method for producing a silicon single crystal of the present invention, the predetermined number of times is preferably 1 time or more and 50 times or less.

[0010] In the method for producing a silicon single crystal of the present invention, the judgment value is preferably 1.2 or more.

[0011] In the method for producing a silicon single crystal of the present invention, it is preferable that the measurement process includes a first measurement process of measuring a combined resistance of the heat generation portion and the power supply portion, a second measurement process of measuring a combined resistance of the heat generation portion, and a resistance value calculation process of determining the first resistance value and the second resistance value based on the measured resistance values.

[0012] In the silicon single crystal manufacturing method of the present invention, it is preferable that each of the power supply units has a terminal formed integrally with the heat generating unit and an electrode having one end connected to the terminal and the other end connected to a power source, and that the adjustment process includes a resistance value reduction process of reducing the resistance value of the power supply unit by placing a conductive sheet between the terminal and the electrode.

[0013] In the silicon single crystal manufacturing method of the present invention, it is preferable that each of the power supply units has a terminal connected to the heat generating unit and an electrode having one end connected to the terminal and the other end connected to a power source, and the adjustment process includes a resistance increasing process for roughening the contact surface between the terminal and the electrode to increase the resistance value of the power supply unit.

[0014] In the method for producing a silicon single crystal of the present invention, each of the power supply units has a terminal connected to the heat generating unit and an electrode having one end connected to the terminal and the other end connected to a power source, and a plate-shaped electrical resistance adjustment member is interposed between the terminal and the electrode, and the adjustment process preferably adjusts the resistance value by making the number or thickness dimension of the electrical resistance adjustment members interposed between the terminal and the electrode of the first power supply unit different from the number or thickness dimension of the electrical resistance adjustment members interposed between the terminal and the electrode of the second power supply unit.

[0015] The method for producing a silicon wafer of the present invention is characterized in that a silicon wafer is produced by slicing a silicon single crystal pulled by a method for producing a silicon single crystal. Effect of the Invention

[0016] According to the present invention, the direction of convection in a silicon melt can be stably controlled, and silicon single crystals and silicon wafers having a stable oxygen concentration can be produced. [Brief description of the drawings]

[0017] [Figure 1] 1 is a vertical sectional view showing a schematic configuration of a silicon single crystal manufacturing apparatus according to an embodiment of the present invention. [Diagram 2] 1 is a perspective view showing a main part of a heating device according to an embodiment of the present invention. [Diagram 3] FIG. 2 is a plan view showing a heating device and a magnetic field application unit according to the embodiment of the present invention. [Figure 4] 1 is a schematic diagram showing a configuration of a heating device according to an embodiment of the present invention and a state in which a horizontal magnetic field is applied; [Diagram 5] FIG. 2 is a schematic diagram showing an arrangement of a temperature measuring unit according to an embodiment of the present invention. [Figure 6] 1A and 1B are schematic diagrams illustrating a connection structure between a terminal and an electrode according to an embodiment of the present invention, in which (A) is a partially cutaway front view, and (B) is a plan view of a conductive sheet. [Figure 7] FIG. 2 is an equivalent circuit diagram of a heating device according to an embodiment of the present invention. [Figure 8] FIG. 2 is a block diagram showing a control device of the silicon single crystal manufacturing apparatus according to the embodiment of the present invention. [Figure 9] 1 is a flowchart for explaining an example of a method for producing a silicon single crystal according to an embodiment of the present invention. [Figure 10] 10 is a flowchart showing a resistance value setting step in FIG. 9. [Figure 11] 11 is a flowchart showing the measurement steps in FIG. 10. [Figure 12] 11 is a flowchart showing the adjustment process in FIG. 10. [Figure 13] 10 is a flowchart showing a silicon melt heating step in FIG. 9. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] [Silicon single crystal manufacturing equipment] FIG. 1 is a vertical cross-sectional view showing a schematic configuration of a silicon single crystal manufacturing apparatus 1 that can be applied to a silicon single crystal manufacturing method according to an embodiment of the present invention. The silicon single crystal manufacturing apparatus 1 is an apparatus for pulling up a silicon single crystal SM by the CZ method, and is comprised of a chamber 2 forming an outer shell, a crucible 3 disposed in the center of the chamber 2, and a crucible of 3 and a heating device 4 arranged around the periphery. The crucible 3 has a double structure consisting of an outer graphite crucible 3A and an inner quartz crucible 3B, and silicon melt M (raw material melt) is contained in the quartz crucible 3B. The graphite crucible 3A and the quartz crucible 3B are cylindrical containers with bottoms, and are circular in plan view when viewed vertically from above. The crucible 3 is fixed to the upper end of a support shaft 5 that can rotate and rise and fall.

[0019] 2, the heating device 4 is a graphite heater formed in a substantially cylindrical shape and disposed around the crucible 3, and will be described in detail later. As shown in FIG. 1, a heat insulating material 6 is provided on the outside of the heating device 4 along the inner surface of the chamber 2.

[0020] A pulling shaft 7 is disposed coaxially with the support shaft 5 above the crucible 3. The pulling shaft 7 is formed of a wire or the like, and rotates at a predetermined speed in the same direction or in the opposite direction to the rotation direction of the support shaft 5. A seed crystal SC is attached to the lower end of this pulling shaft 7.

[0021] In the chamber 2, a cylindrical heat shield 8 is disposed above the silicon melt M in the crucible 3 to surround the silicon single crystal SM being grown. The thermal shield 8 blocks the silicon single crystal SM being grown from radiant heat from the silicon melt M in the crucible 3 and from radiant heat from the heating device 4 and the side walls of the crucible 3, and also suppresses the diffusion of heat to the outside in the vicinity of the solid-liquid interface, which is the crystal growth interface, and plays a role in controlling the temperature gradient in the direction of the pulling axis 7 at the center and outer periphery of the silicon single crystal SM.

[0022] A gas inlet 9 is provided at the top of the chamber 2 to introduce an inert gas such as argon gas into the chamber 2. An exhaust port 10 is provided at the bottom of the chamber 2 to suck and exhaust gas from within the chamber 2 by driving a vacuum pump (not shown). The inert gas introduced into the chamber 2 from the gas inlet 9 flows down between the silicon single crystal SM being grown and the thermal shield 8, passes through the gap between the lower end of the thermal shield 8 and the liquid surface of the silicon melt M, and then flows toward the outside of the thermal shield 8 and then toward the outside of the crucible 3, and then flows down outside the crucible 3 and is exhausted through the exhaust port 10.

[0023] The silicon single crystal manufacturing apparatus 1 includes a magnetic field application unit 14 shown in FIG. 3, and a temperature measurement unit 15 shown in FIGS. The magnetic field applying unit 14 includes a first magnetic body 14A and a second magnetic body 14B each of which is made up of an electromagnetic coil. The first magnetic body 14A and the second magnetic body 14B are provided so as to face each other with the crucible 3 interposed therebetween outside the chamber 2. In the example of FIG. 3, the magnetic field applying unit 14 applies a horizontal magnetic field so that, in a plan view seen from above in the vertical direction, the magnetic field center line (the central magnetic field line of the horizontal magnetic field) passing through the coil central axis intersects with the cylindrical heating unit 30 and the central axis CA of the crucible 3, and is in a direction from the second magnetic body 14B toward the first magnetic body 14A (the upward direction indicated by the arrow ML in FIG. 3, the direction from the front to the back of the paper in FIG. 1). However, the magnetic field center line does not necessarily pass through the intersection CS of the central axis CA of the crucible 3 on the melt surface of the silicon melt M. In other words, the height position of the magnetic field center line is not particularly limited, and may be inside or outside the silicon melt M according to the quality of the silicon single crystal SM. 5, the central axis of the crucible 3 is defined as CA, the surface of the silicon melt M in the crucible 3 as S, and the center of the surface S as CS. Then, as shown in FIG. 3, in a plan view of the crucible 3 and the heating device 4 viewed vertically from above, an imaginary line along the magnetic field center line intersecting with the central axis CA of the crucible 3 is defined as VL. Therefore, the imaginary line VL is a line that passes through the central axis CA of the crucible 3 and follows the arrow ML from the second magnetic body 14B toward the first magnetic body 14A.

[0024] The temperature measuring unit 15 measures the temperatures of the first measuring point P1 and the second measuring point P2 as shown in FIG. 1, FIG. 4, and FIG. 5. The radial positions of the first measuring point P1 and the second measuring point P2 are between the outer peripheral surface of the silicon single crystal SM to be grown and the inner peripheral surface of the opening of the thermal shield 8 as shown in FIG. 1, and preferably the intermediate positions. In this embodiment, the first measuring point P1 and the second measuring point P2 are set at positions that are point-symmetric with respect to the center CS of the surface S. As will be described later, the direction of convection of the silicon melt M can be confirmed by measuring the temperatures of the measuring points P1 and P2. For example, when the direction of convection of the silicon melt M is fixed to a right-handed direction in FIG. 4, that is, a right vortex, due to heating of the silicon melt M by the heating device 4, the measured temperature of the first measuring point P1 is higher than the measured temperature of the second measuring point P2. Furthermore, when the direction of convection of the silicon melt M is fixed to the left, i.e., a left vortex, by heating the silicon melt M by the heating device 4, the measured temperature at the first measurement point P1 is lower than the measured temperature at the second measurement point P2. Note that Fig. 4 shows an example in which the ascending flow is fixed to the left side of the crucible 3 and the descending flow is fixed to the right side of the crucible 3, and the direction of convection of the silicon melt M is fixed to the right, i.e., a right vortex.

[0025] As shown in FIGS. 1 and 5, the temperature measuring unit 15 includes a pair of reflecting units 15A and a pair of radiation thermometers 15B. The reflecting section 15A is installed inside the chamber 2. As shown in Fig. 5, the reflecting section 15A is preferably installed such that the distance (height) K from the lower end of the reflecting section 15A to the surface S of the silicon melt M is 600 mm or more and 5000 mm or less. In addition, the reflecting section 15A is preferably installed such that the angle θf between the reflecting surface 15C and the horizontal plane F is 40° or more and 50° or less.

[0026] With the configuration described above, the sum of the incidence angle θ1 and the reflection angle θ2 of the radiant light L emitted vertically upward from the first measurement point P1 and the second measurement point P2 with respect to the reflector 15A is equal to or greater than 80° and equal to or less than 100°. From the viewpoint of heat resistance, it is preferable to use, as the reflector 15A, a silicon mirror having one surface mirror-polished to form the reflecting surface 15C.

[0027] The radiation thermometer 15B is installed outside the chamber 2. The radiation thermometer 15B receives radiant light L incident through a quartz window 2A (see FIG. 1) provided in the chamber 2, and measures the temperatures of the first measurement point P1 and the second measurement point P2 in a non-contact manner.

[0028] [Heating device] As shown in FIGS. 2 and 3, the heating device 4 includes a heat generating section 30 and 2n (n is an integer of 2 or more) power supply sections 20A, 20B, 20C, and 20D, four in this embodiment, that supply power to the heat generating section 30. The heat generating part 30 is a cylindrical graphite heater, formed with a uniform thickness all around the circumference, and has a plurality of upper slits 31 extending downward from the upper end and a plurality of lower slits 32 extending upward from the lower end formed in the circumferential direction. The upper slits 31 and the lower slits 32 have the same slit width dimension and the same cutting depth in the vertical direction. The interval between the upper slits 31 and the lower slits 32 is also the same all around the circumference of the heat generating part 30.

[0029] 3, the heat generating part 30 is virtually divided into two parts, left and right, in a plan view by a virtual line VL passing through a central axis CA of the heat generating part 30. Therefore, the heating device 4 has a first heating region 4A located on the left side of the virtual line VL in FIG. 3, and a second heating region 4B located on the right side of the virtual line VL. The first heating region 4A and the second heating region 4B have the same total number of upper slits 31 and lower slits 32. In the example of FIG. 2 and FIG. 3, four upper slits 31 and six lower slits 32 are formed in the first heating region 4A, and the total number of the upper slits 31 and lower slits 32 is 10. Four upper slits 31 and six lower slits 32 are formed in the second heating region 4B, and the total number of the upper slits 31 and lower slits 32 is 10. Note that the two lower slits 32 that overlap on the virtual line VL straddle the first heating region 4A and the second heating region 4B, and therefore are counted as 0.5 in the number included in each of the heating regions 4A and 4B. Since there are two lower slits 32 that span the heating regions 4A and 4B, 0.5×2=1 lower slit 32 that spans the heating regions 4A and 4B is disposed in each of the heating regions 4A and 4B.

[0030] As shown in Fig. 2, the power supply units 20A to 20D include four terminals 21A, 21B, 21C, and 21D, four electrodes 22A, 22B, 22C, and 22D, and four nuts 23A to 23D. As shown in Fig. 3, the power supply units 20A to 20D are arranged at 90 degree intervals along the circumferential direction of the heat generating unit 30, and in this embodiment, the power supply units 20A and 20B arranged in the first heating region 4A constitute a first power supply unit, and the power supply units 20C and 20D arranged in the second heating region 4B constitute a second power supply unit. Terminals 21A-21D extend downward from the lower end of a portion of heat generating portion 30 defined by two lower slits 32, and are formed integrally with heat generating portion 30. Terminals 21A-21D also include connection portions 211A-211D bent at a right angle from the lower end toward the inside, and through holes 212A-212D are formed in connection portions 211A-211D. Therefore, the heating device 4 of this embodiment is a heater element Department The heater is configured using a graphite heater in which a cylindrical heat generating portion 30, which is the heater body, and terminals 21A to 21D, which are heater legs, are integrally molded.

[0031] Heat generating portion 30 is partitioned into zigzag-shaped first meandering portion 33A to fourth meandering portion 33D by forming upper slits 31 and lower slits 32, and these first meandering portion 33A to fourth meandering portion 33D constitute four heater elements. That is, two upper slits 31 and three lower slits 32 are alternately formed between terminals 21A and 21B to form a first meandering portion 33A. Similarly, two upper slits 31 and three lower slits 32 are alternately formed between terminals 21B and 21C to form a second meandering portion 33B. Between terminal 21C and terminal 21D, two upper slits 31 and three lower slits 32 are alternately formed to form a third meandering portion 33C. Between terminal 21D and terminal 21A, two upper slits 31 and three lower slits 32 are alternately formed to form a fourth meandering portion 33D.

[0032] The electrodes 22A to 22D are rod-shaped electrodes made of carbon, one end of which is connected to the terminals 21A to 21D, and the other end of which is connected to a power source. The connection structure between the terminal 21A and the electrode 22A will be described with reference to FIG. As shown in Fig. 6(A), the electrode 22A is configured to include a main body portion 221A and an insertion portion 223A protruding upward from an upper surface 222A of the main body portion 221A. The main body portion 221A is formed in a cylindrical shape, and the upper end side is expanded in diameter. The insertion portion 223A is formed in a cylindrical shape, and the diameter is smaller than that of the main body portion 221A. A male screw 224A is formed on the outer periphery of the insertion portion 223A. Although not shown in the figure, the electrodes 22B to 22D are also formed in the same manner as the electrode 22A.

[0033] The insertion portion 223A of the electrode 22A is inserted into a through hole 212A formed in the connection portion 211A of the terminal 21A, and the terminal 21A and the upper end of the electrode 22A are connected by screwing a male screw 224A protruding from the upper surface 213A of the connection portion 211A into a carbon nut 23A. The electrical resistance of the power supply unit 20A when the terminal 21A and the electrode 22A are connected increases or decreases depending on the contact resistance between the terminal 21A and the electrode 22A. For example, when the upper surface 222A of the electrode 22A and the lower surface 214A of the connection part 211A are directly contacted, the contact resistance increases when the contact area is reduced due to the surface roughness of the contact surface. On the other hand, as shown in FIG. 6(A), when the conductive sheet 24 is disposed between the upper surface 222A of the electrode 22A and the lower surface 214A of the connection part 211A, the conductive sheet 24 adheres closely to the lower surface 214A and the upper surface 222A, increasing the contact area, so that the contact resistance between the terminal 21A and the electrode 22A decreases compared to when the conductive sheet 24 is not disposed. As shown in FIG. 6(B), the conductive sheet 24 is a disk-shaped sheet material having a hole into which the insertion part 223A is inserted, and is formed of, for example, a carbon-based fiber material. The conductive sheet 24 may be disposed between the upper surface 213A of the connection part 211A and the nut 23A, in addition to between the lower surface 214A of the connection part 211A and the upper surface 222A of the electrode 22A. On the other hand, when the conductive sheet 24 is disposed on either the lower surface 214A side or the upper surface 213A side of the connection part 211A, it is preferable to dispose the conductive sheet 24 between the lower surface 214A of the connection part 211A and the upper surface 222A of the electrode 22A, as shown in Fig. 6(A). This is because disposing the conductive sheet 24 between the electrode 22A connected to the power source and the terminal 21A formed integrally with the heat generating part 30 can effectively reduce the contact resistance.

[0034] The connection structure between each of the electrodes 22B-22D and the corresponding terminals 21B-21D is the same as the connection structure between the electrode 22A and the terminal 21A. The conductive sheet 24 is arranged when it is necessary to reduce the contact resistance between each of the electrodes 22B-22D and the terminals 21B-21D, and is not arranged when it is not necessary to reduce the contact resistance.

[0035] FIG. 7 is an equivalent circuit diagram of the heating device 4. In FIG. 7, V is a voltage value applied to the heating device 4. RA, RB, RC, and RD are resistance values ​​of the first meandering portion 33A to the fourth meandering portion 33D, respectively. R α is the contact resistance between the terminal 21A and the electrode 22A. Similarly, R β is the contact resistance between the terminal 21B and the electrode 22B, R γ is the contact resistance between the terminal 21C and the electrode 22C, R δ is the contact resistance value between terminal 21D and electrode 22D. In Fig. 7, arrow ML indicates the direction in which the horizontal magnetic field is applied.

[0036] Heat generating portion 30, terminals 21A-21D and electrodes 22A-22D are made of graphite. Generally, graphite has low ductility, so there is contact resistance at the contact portion between each of terminals 21A-21D and corresponding electrodes 22A-22D. In Fig. 7, the resistance value of each of electrodes 22A-22D is ignored. This is because electrodes 22A-22D are generally short, and a current-carrying cable with an extremely low resistance value is used between each of electrodes 22A-22D and voltage application portion 43 (see Fig. 8) described later.

[0037] By making the resistance distribution of the power supply units 20A-20D non-uniform, it is possible to control the convection behavior of the silicon melt during the magnetic field application process, and to grow high-quality silicon single crystals with little variation in oxygen concentration. That is, the resistance of the heat generating unit 30, i.e., the graphite heater element unit, is highly dependent on the processing accuracy (thickness and length) of the heater, and the resistance variation is 1% or less. Also, the resistances RA, RB, RC, and RD of the heat generating unit 30 are calculated by multiplying the contact resistance R α、 R β、 R γ , R δ is significantly larger than the contact resistance R α、 R β、 R γ , R δEven if these are set non-uniformly, there is almost no change in the current values ​​flowing through the resistors RA, RB, RC, and RD of the heating part 30. Therefore, the heat distribution of the heating part 30 is almost the same in the first heating area 4A and the second heating area 4B, and the effect on the convection behavior of the silicon melt can be ignored. Therefore, the resistance distribution of the power supply units 20A to 20D, more specifically, the contact resistance R α、 R β and the contact resistance R of the second power supply unit (power supply units 20C and 20D) disposed in the second heating region 4B. γ , R δ By making the second resistance value R2, which is the sum of the contact resistance R α、 R β、 R γ , R δ This makes it possible to make the heat generation distribution by the graphite heater unbalanced, and fixes the heat generation distribution of the graphite heater, i.e., the direction of the convection of the silicon melt. For example, when the first resistance value R1 is made larger than the second resistance value R2, the amount of heat generated in the first heating area 4A becomes larger than that in the second heating area 4B, and the left side of the crucible 3 in FIG. 1 is heated more, and the upward flow on the left side becomes dominant. As a result, the convection of the silicon melt rotates in the clockwise direction with respect to the application direction of the horizontal magnetic field, and a right-handed vortex is formed. On the other hand, when the second resistance value R2 is larger than the first resistance value R1, the upward flow on the right side of the crucible 3 in FIG. 1 becomes dominant, and a left-handed vortex is formed.

[0038] In other words, since the heat generation distribution of the heat generating portion 30 is almost the same in the first heating region 4A and the second heating region 4B, the imbalance in the heat generation distribution can be controlled by controlling the magnitude of the first resistance value R1 and the second resistance value R2 of the power supply unit, and the desired vortex direction can be controlled. In addition, the environment inside the chamber 2 is constantly changing due to the deterioration of the carbon members used over time, and the contact resistance R α、 R β、 R γ , R δThe contact resistance R changes due to deterioration over time of the terminals 21A to 21D, the electrodes 22A to 22D, etc. α、 R β、 R γ , R δ When the contact resistance changes, the heat distribution in the first heating region 4A and the second heating region 4B also changes, affecting the stability of the convection direction of the silicon melt, which results in a variation in the oxygen concentration. Therefore, in this embodiment, as described later, the contact resistance is measured every time the pulling of the silicon single crystal is repeated a predetermined number of times, and if there is a change that affects the convection direction of the silicon melt, the contact resistance is adjusted, so that the vortex direction can be fixed even if the pulling of the silicon single crystal is repeated. As a result, the variation in the amount of oxygen supplied to the crystal growth interface from the quartz crucible 3B between batches is reduced, and silicon single crystals having a stable oxygen concentration can be obtained. Since crystals having a desired oxygen concentration in the crystal growth axis direction can be grown, the crystal yield is improved.

[0039] In this embodiment, the resistance ratio, which is the value obtained by dividing the higher resistance value of the first resistance value R1 and the second resistance value R2 by the lower resistance value, is adjusted to be equal to or greater than a predetermined judgment value, specifically, equal to or greater than 1.2. For example, if the contact surfaces of the connection parts 211A and 211B and the electrodes 22A and 22B are roughened by mechanical polishing, the sum of the contact resistances of the power supply parts 20A and 20B (R α +R β On the other hand, when the conductive sheet 24 is interposed between the contact surfaces of the connection parts 211C, 211D and the electrodes 22C, 22D, the sum of the contact resistances of the power supply parts 20C, 20D (R γ +R δ Therefore, if R1>R2, the first resistance R1 is increased and the second resistance R2 is decreased so that R1 / R2>1.2.<R2であれば、R2 / R1> To achieve 1.2, the first resistance value R1 can be adjusted to be lowered and the second resistance value R2 can be adjusted to be higher.

[0040] As shown in FIG. 8, the silicon single crystal manufacturing apparatus 1 includes a control device 41, a magnetic field application unit 14, a radiation thermometer 15B, a memory unit 42, a voltage application unit 43, a resistance value measurement unit 44, and a display unit 45. The memory unit 42 stores pulling conditions under which the oxygen concentration of the silicon single crystal SM becomes a desired value, such as the flow rate of the inert gas, the pressure inside the chamber 2, the rotation speed of the crucible 3, and the like, as well as the contact resistance R α , R β , R γ , R δ The adjustment rules, for example, the selection of the power supply units 20A to 20D to be adjusted, the arrangement of the conductive sheet 24, and the selection of an adjustment method such as mechanical polishing of the contact surface, are determined based on the contact resistance R α , R β , R γ , R δ Rules for setting the temperature according to the measured values ​​are stored. The voltage application unit 43 is controlled by the control device 41 and applies a predetermined voltage to the heating device 4 . The resistance value measuring unit 44 measures each resistance value of the heating device 4, and is configured, for example, by a resistance meter that measures resistance by a four-terminal method. The resistance value measuring unit 44 is configured so that an operator measures the resistance value by contacting a probe with a measurement point of the heating device 4, and outputs the measurement data to the control device 41. The measured value may be input by the operator using an input device such as a keyboard or touch panel provided on the control device 41. The display unit 45 is configured with a liquid crystal display or the like, and displays various information and work instructions to the worker.

[0041] The control device 41 includes a convection pattern control unit 410 , a pull-up control unit 420 , and a resistance value setting unit 430 . The convection pattern control unit 410 controls the voltage application unit 43 to heat the silicon melt M using the heating device 4, and controls the magnetic field application unit 14 to apply a horizontal magnetic field, thereby fixing the direction of convection in the cross section perpendicular to the magnetic field. After the convection pattern control unit 410 fixes the convection direction, the pulling control unit 420 controls the pulling of the silicon single crystal SM.

[0042] The resistance value setting section 430 includes a resistance value measurement control section 431 , a resistance value calculation section 432 , a resistance ratio determination section 433 , and a resistance value adjustment section 434 . The resistance value measurement control section 431 measures each resistance value of the heating device 4 using the resistance value measuring section 44 . The resistance value calculation unit 432 calculates the contact resistance R α , R β , R γ , R δ These are used to calculate the first resistance value R1 and the second resistance value R2. The resistance ratio determination unit 433 obtains the resistance ratio between the first resistance value R1 and the second resistance value R2, and determines whether the resistance ratio is equal to or greater than a determination value. When the resistance ratio determination unit 433 determines that the resistance ratio is equal to or greater than the determination value, the resistance value adjustment unit 434 displays on the display unit 45 that adjustment of the contact resistance is not required. When the resistance ratio determination unit 433 determines that the resistance ratio is less than the determination value, the resistance value adjustment unit 434 adjusts the contact resistance R calculated by the resistance value measurement control unit 431. α , R β , R γ , R δ Based on the value of and the adjustment rule stored in memory unit 42, the target of contact resistance adjustment among power supply units 20A to 20D is selected, an adjustment method is determined, and work instructions for the adjustment are displayed on display unit 45.

[0043] [Method of manufacturing silicon single crystals] Next, the method for producing a silicon single crystal according to this embodiment will be described with reference to the flow charts shown in FIGS. FIG. 9 is a flowchart showing one batch process for producing one silicon single crystal, FIG. 10 is a flowchart showing the resistance value setting process in FIG. 9, FIG. 11 is a flowchart showing the measurement process in FIG. 10, FIG. 12 is a flowchart showing the adjustment process in FIG. 10, and FIG. 13 is a flowchart showing the silicon melt heating process in FIG. 9. 9, pulling conditions (e.g., the flow rate of the inert gas, the furnace pressure of the chamber 2, the rotation speed of the crucible 3, etc.) that will give a desired oxygen concentration in the silicon single crystal SM are determined in advance as predetermined conditions and stored in the storage unit 42. Note that the oxygen concentration in the predetermined conditions may be the oxygen concentration values ​​at multiple locations in the longitudinal direction of the straight body portion that constitutes the silicon single crystal SM, or may be the average value of the multiple locations. Also, a predetermined number of times, which is an interval for executing the resistance value setting process, is stored in the storage unit 42. The predetermined number of times sets the timing for executing the process for setting the resistance value of the contact resistance of each of the power supply units 20A-20D. This predetermined number of times can be set, for example, by experimentally determining the number of times that the resistance ratio of the first resistance value R1 and the second resistance value R2 changes to less than the determination value due to deterioration over time of carbon members such as the terminals 21A-21D and the electrodes 22A-22D, and in this embodiment, it is set in the range of 1 time to 50 times.

[0044] When the control device 41 starts the manufacturing process of a silicon single crystal, it first determines whether the number of times the pulling process has been performed is a predetermined number (step S1), as shown in Fig. 9. If the predetermined number is 30 times, the control device 41 determines YES in step S1 every time the pulling process is performed 30 times.

[0045] If the answer to step S1 is YES, the control device 41 executes a resistance value setting step (step S2). The resistance value setting step S2 is also executed when the silicon single crystal manufacturing apparatus 1 is installed, when the heating device 4 is maintained, and the like. When the control device 41 starts the resistance value setting step S2, as shown in FIG. 10, the resistance value measurement control unit 431 of the resistance value setting unit 430 executes a measurement step of measuring the resistance value (step S21). After executing the measurement step S21, the resistance value measurement control unit 431 executes a first measurement step of measuring the combined resistance of the heat generating unit 30 and the power supply units 20A to 20D (step S211) as shown in FIG. 11. In the first measurement step, the resistance value measurement unit 44 measures the combined resistance between the electrodes 22A and 22B. At this time, the operator measures the combined resistance between the electrodes 22A and 22B by bringing the probe of the resistance value measurement unit 44 into contact with a position where the combined resistance between the electrodes 22A and 22B can be measured, for example, a metal terminal portion that connects the electrodes 22A and 22B to a current-carrying cable. By performing a similar operation, resistance value measuring section 44 successively measures the combined resistance between electrodes 22B and 22C, the combined resistance between electrodes 22C and 22D, and the combined resistance between electrodes 22D and 22A.

[0046] Next, the resistance value measurement control section 431 executes a second measurement step of measuring the combined resistance of the heat generating section 30 (step S212). In the second measurement step, the resistance value measurement section 44 measures the combined resistance between the terminals 21A and 21B. Similarly, the combined resistance between the terminals 21B and 21C, the combined resistance between the terminals 21C and 21D, and the combined resistance between the terminals 21D and 21A are successively measured. At this time, the operator measures the combined resistance by bringing the probe of the resistance value measurement section 44 into contact with the same surface and the same height position of each of the terminals 21A to 21D. This is because the measured combined resistance changes depending on the position where the probe is contacted. As a result of the above, the resistance values ​​shown in FIG.

[0047] Next, the resistance value calculation unit 432 calculates the contact resistance R using the measured combined resistance data, as shown in FIG. α , R β , R γ , R δCalculate it, and further execute a resistance value calculation step of calculating a first resistance value R1 and a second resistance value R2 (step S213). That is, based on the eight - variable simultaneous equations set according to the circuit diagram in FIG. 7 and the eight resistance values measured in the first measurement step S211 and the second measurement step S212, the resistance value calculation unit 432 calculates the contact resistance R α , R β , R γ , R δ . Then, the resistance value calculation unit 432 calculates the first resistance value R1 = R α + R β、 and the second resistance value R2 = R γ + R δ . Thus, the measurement step S21 ends.

[0048] Next, as shown in FIG. 10, when the measurement step S21 ends, the resistance ratio determination unit 433 of the resistance value setting unit 430 determines whether the resistance ratio calculated based on the first resistance value R1 and the second resistance value R2 calculated in the resistance value calculation step S213 is equal to or greater than the determination value (step S22). The resistance ratio is obtained by dividing the higher resistance value by the lower resistance value. When R1 ≥ R2, it is calculated as R1 / R2, and when R1 < R2, it is calculated as R2 / R1. Note that the determination value is stored in the storage unit 42 of the single - crystal silicon manufacturing apparatus 1. For example, in the single - crystal silicon manufacturing apparatus 1, experiments are conducted to set different resistance ratios and determine whether the convection direction of the silicon melt is fixed. The value of the resistance ratio at which the convection direction is fixed is set as the determination value. In this embodiment, the determination value is set to "1.2".

[0049] When the control device 41 determines NO in step S22, it executes an adjustment step of adjusting the resistance value by the resistance value adjustment unit 434 (step S23). When the resistance value adjustment unit 434 executes the adjustment step S23, as shown in FIG. 12, the contact resistances R α , R β , R γ , R δBased on the adjustment rules stored in the memory unit 42, an adjustment target is selected for which the contact resistance is reduced by placing a conductive sheet 24 or the contact resistance is increased by roughening the surface by mechanical polishing (step S231). Next, the resistance value adjusting unit 434 determines whether or not the selected adjustment target is a target for decreasing the resistance value (step S232). When the result of the determination in step S232 is YES, the resistance value adjusting unit 434 executes a resistance value lowering step (step S233). In the resistance value lowering step S233, the resistance value adjusting unit 434 displays, on the display unit 45, a work instruction to interpose the conductive sheet 24 for the power supply unit selected from the power supply units 20A to 20D as a target for which the resistance value is to be lowered. In accordance with the work instruction, the worker places the conductive sheet 24 between the terminal and the electrode of the selected power supply unit to lower the contact resistance. On the other hand, when the result of the determination in step S232 is NO, the resistance value adjusting unit 434 executes a resistance value increasing step (step S234). In the resistance value increasing step S234, the resistance value adjusting unit 434 displays, on the display unit 45, a work instruction to roughen the surface by mechanical polishing for the power supply unit selected from the power supply units 20A to 20D as a target for increasing the resistance value. The worker mechanically polishes the contact surface between the terminal and the electrode of the selected power supply unit in accordance with the work instruction to increase the contact resistance. After executing steps S233 and S234, the resistance value adjustment unit 434 determines whether or not there is another power supply unit to be adjusted (step S235). If the resistance value adjustment unit 434 determines YES in step S235, it returns to step S231 and executes the processes of steps S231 to S235 again. If the resistance value adjustment unit 434 determines NO in step S235, it ends the adjustment process S23.

[0050] The adjustment rule by the resistance value adjusting unit 434 is set so that the resistance value decreasing step S233 of arranging the conductive sheet 24 is executed with priority over the resistance value increasing step S234. This is because arranging the conductive sheet 24 is an easier task than mechanical polishing. Therefore, when the resistance ratio of the first resistance value R1 and the second resistance value R2 is less than the judgment value, the resistance value adjusting unit 434 gives an instruction to prioritize the task of decreasing the contact resistance with a smaller resistance value. For example, when R1>R2 and R1 / R2<1.2, the resistance value adjusting unit 434 adjusts the second resistance value R2, that is, the contact resistance R γ , R δ If it is determined that the resistance ratio can be increased to or above the judgment value by decreasing only one of the contact resistance R γ , R δ Among them, the power supply units 20C and 20D having high resistance are instructed to insert a conductive sheet 24 therebetween to reduce the resistance. γ , R δ If it is determined that the resistance ratio can be made equal to or greater than the judgment value by reducing both of the resistance ratio and the conductive sheet 24, the resistance value adjustment unit 434 instructs both of the power supply units 20C and 20D to insert the conductive sheet 24 to reduce the resistance value. The memory unit 42 stores the amount of change in contact resistance before and after the conductive sheet 24 is placed based on past experimental data. For example, when the contact resistance is relatively high, it is highly likely that the contact surface is roughened and the contact area between the terminal and the electrode is small. Therefore, the amount of decrease in resistance value when the conductive sheet 24 is placed is relatively large. On the other hand, when the contact resistance is relatively low, it is highly likely that the contact area between the terminal and the electrode is also large, and the amount of decrease in resistance value when the conductive sheet 24 is placed is smaller than when the contact resistance is high. Therefore, the resistance value adjustment unit 434 can estimate the amount of decrease when the conductive sheet 24 is placed based on the measured contact resistance value, and based on the estimation, it is determined whether the conductive sheet 24 is placed only on one of the power supply units or on both.

[0051] Furthermore, the resistance value adjusting unit 434 adjusts the second resistance value R2, that is, the contact resistance R γ , R δIf it is determined that the resistance ratio cannot be increased to the judgment value or more by only decreasing the second resistance value R2, the resistance value adjustment unit 434 instructs the operation of increasing the first resistance value R1 in addition to the operation of decreasing the second resistance value R2. α , R β If it is determined that the resistance ratio can be increased to or above the judgment value by increasing only one of the contact resistance R α , R β The power supply units 20A and 20B having the lowest resistance are mechanically polished to increase their resistance. α , R β If it is determined that the resistance ratio can be made equal to or greater than the judgment value by increasing both of the power supply units 20A and 20B, an instruction is given to mechanically polish both of the power supply units 20A and 20B to increase their resistance values. The worker adjusts the contact resistance of power supply units 20A to 20D based on the work instruction from resistance value adjustment unit 434 displayed on display unit 45, and inputs to control device 41 that the adjustment is completed.

[0052] When step S23 ends, the control device 41 executes the measurement step S21 and the determination step S22 again, as shown in FIG. 10, and determines again whether or not the resistance ratio has become equal to or greater than the determination value. If the determination in step S22 is NO, the control device 41 repeats the adjustment step S23, the measurement step S21, and the determination step S22 until the determination in the determination step of step S22 is YES. If the determination in step S22 is YES, control device 41 determines that the contact resistances of power supply units 20A to 20D have been appropriately adjusted, ends the resistance value setting process in step S2, and returns to the process in FIG.

[0053] As shown in FIG. 9, when the controller 41 judges NO in step S1, that is, when it is not the timing to set the resistance value, or when the resistance value setting process of step S2 is completed, the controller 41 executes a heating process of the silicon melt by the convection pattern control unit 410 (step S3). In the silicon melt heating process S3, as shown in FIG. 13, the convection pattern control unit 410 maintains an inert gas atmosphere under reduced pressure within the chamber 2 in a magnetic field-free state, rotates the crucible 3, and operates the heating device 4 via the voltage application unit 43 to melt the solid raw material such as polycrystalline silicon filled in the crucible 3 and generate silicon melt M (step S31).

[0054] At this time, the convection pattern control unit 410 applies the same voltage to the first heating region 4A and the second heating region 4B using the voltage application unit 43. At this time, if the first resistance value R1 is 1.2 times or more the second resistance value R2, the first power supply unit (power supply units 20A, 20B) becomes hotter than the second power supply unit (power supply units 20C, 20D) due to Joule heating, and the left side (first heating region 4A side) of the silicon melt M is heated to a higher temperature than the right side (second heating region 4B side). Then, the convection pattern control unit 410 controls the heating so that the temperature of the silicon melt M is 1415°C or higher and 1500°C or lower.

[0055] The silicon melt M generated in step S31 convects due to the influence of heat and the rotation of the crucible 3. Therefore, the convection pattern control unit 410 judges whether the vortex of the silicon melt M rotates periodically or not. Specifically, the convection pattern control unit 410 checks the change over time (temperature transition) of the temperature at the first measurement point P1 or the second measurement point P2 in the temperature measurement unit 15, and judges whether the periodic fluctuation width, which is the fluctuation width of the maximum and minimum values ​​of the periodically fluctuating measured temperature, is within a predetermined temperature range (predetermined range) (step S32). By the process of step S32, the stability of the vortex of the silicon melt M rotating periodically can be determined.

[0056] In this step S32, if the convection pattern control unit 410 determines that the periodic fluctuation width is not within a predetermined range, that is, that the vortex is not rotating periodically, it adjusts the heating temperature of the silicon melt M (step S33) and performs the processing of step S32 after a predetermined time has elapsed.

[0057] On the other hand, in step S32, when it is determined that the periodic fluctuation width is within the predetermined range and the vortex is rotating stably and periodically, the convection pattern control unit 410 controls the heating of the silicon melt. temperature After the process of step S3 is completed, the convection pattern control unit 410 continues heating the silicon melt by the voltage application unit 43.

[0058] 9, after the step S3 is completed, the control device 41 executes a horizontal magnetic field application step (step S4) of applying a horizontal magnetic field of 0.2 Tesla or more and 0.6 Tesla or less to the silicon melt M by controlling the magnetic field application unit 14 via the convection pattern control unit 410. The convection direction of the silicon melt M is fixed by the process of step S4. Next, the convection pattern control unit 410 executes a convection direction confirmation step of confirming the temperature difference between the first measurement point P1 and the second measurement point P2 in the temperature measurement unit 15 and confirming whether the convection direction is clockwise or counterclockwise (step S5).

[0059] Thereafter, the pulling control unit 420 performs a pulling process in which the seed crystal SC is immersed in the silicon melt M while continuing to apply a horizontal magnetic field of 0.2 Tesla or more and 0.6 Tesla or less based on predetermined conditions, and then the silicon single crystal SM having a straight body portion with a desired oxygen concentration is pulled up (step S6). In addition, the process of confirming the periodic fluctuation width in step S32, the process of adjusting the heating temperature in step S33, the process of starting the application of the horizontal magnetic field in step S4, the process of confirming the convection direction by measuring the temperature in step S5, and the process of lifting up in step S6 may be performed by an operator.

[0060] The straight body portion constituting the silicon single crystal SM pulled using the above-described method for producing a silicon single crystal is cut into silicon wafers using a wire saw or the like. Next, the cut silicon wafers are subjected to a lapping step and a polishing step to obtain silicon wafers. This process corresponds to the method for producing a silicon wafer of the present invention.

[0061] [Actions and Effects of the Embodiments] According to this embodiment, the resistance value setting step of step S2 is executed every time the pulling-up step S6 is executed a predetermined number of times, and the contact resistance R α , R β and the contact resistance R of the power supply units 20C and 20D arranged in the second heating region 4B. γ , R δ The resistance ratio to the second resistance value R2, which is the sum of these, is set to be equal to or greater than the judgment value of 1.2, so that the heat generation amount of the power supply units 20A and 20B in the first heating area 4A can be made larger than the heat generation amount of the power supply units 20C and 20D in the second heating area 4B. Therefore, regardless of the symmetry of the structure of the silicon single crystal manufacturing apparatus 1, it is possible to easily fix the direction of convection of the silicon melt M in one direction in the cross section perpendicular to the magnetic field. By fixing the convection of the silicon melt M in one direction, it is possible to suppress the variation in oxygen concentration for each silicon single crystal SM. This makes it possible to suppress the variation in quality and productivity of silicon single crystals between furnaces and between batches. In particular, the contact resistance between the terminals 21A-21D constituting each power supply unit 20A-20D and the electrodes 22A-22D is reduced by interposing a conductive sheet 24 between them, or the contact resistance is increased by roughening the contact surfaces by mechanical polishing, so that the resistance ratio of the first resistance value R1 and the second resistance value R2 is set to a value equal to or greater than the determination value. By using such a simple method, the variation in oxygen concentration for each silicon single crystal SM can be suppressed.

[0062] According to this embodiment, the resistance value setting step S2 is performed every time the pulling step S6 is performed a predetermined number of times, so even if deterioration over time occurs in the terminals 21A-21D or the electrodes 22A-22D, the contact resistance of each of the power supply units 20A-20D can be measured and adjusted periodically, and the direction of convection of the silicon melt M can be fixed. This makes it possible to improve the yield of silicon single crystals. In addition, since the predetermined number of times, which is the interval for performing the resistance value setting step, is set to 1 time or more and 50 times or less, the contact resistance can be adjusted at an appropriate interval according to the silicon single crystal manufacturing apparatus 1. For example, if the predetermined number of times is set to 1 time, the contact resistance can be measured every time the silicon single crystal SM is pulled up, and if necessary, the contact resistance can be adjusted at that time, so that the direction of convection of the silicon melt M can be reliably fixed and the yield of silicon single crystals can be improved. Furthermore, if the predetermined number of times is set to 50 times, the contact resistance can be measured and adjusted in accordance with, for example, the timing for replacing parts with short life in the silicon single crystal manufacturing apparatus 1, so that the yield of silicon single crystals can be improved without reducing the manufacturing efficiency of silicon single crystals. Note that the actual predetermined number of times can be determined optimally by experimentation depending on the configuration of the silicon single crystal manufacturing apparatus 1, such as the type of crystal and the shape of the hot zone.

[0063] According to this embodiment, since the contact resistance between the terminals 21A-21D and the electrodes 22A-22D is adjusted, no special processing is required for the heating device 4, and a commercially available product can be used, thereby reducing costs. In addition, the heating device 4 can be one that is symmetrical in shape and has a uniform thickness, and has a simple structure and high durability.

[0064] Furthermore, according to this embodiment, in the resistance value setting process of step S2, the control device 41 measures the first resistance value R1 and the second resistance value R2, and determines whether the resistance ratio is a judgment value. less than In this case, the target for resistance value adjustment and the adjustment method are proposed based on the measured contact resistance, so that the worker can adjust the resistance value easily and in a short time. In the measurement step S21, the combined resistance of the heat generating unit 30 and the power supply units 20A-20D is measured in the first measurement step S211, and the combined resistance of the heat generating unit 30 is measured in the second measurement step S212, so that the contact resistance can be measured correctly without disassembling the heating device 4. Furthermore, since the resistance value measuring unit 44 is composed of a four-terminal resistance meter, each combined resistance can be measured with high accuracy, and the contact resistance calculated based on the measured values ​​can also be calculated with high accuracy.

[0065] [Variations] Although an embodiment of the present invention has been described in detail above with reference to the drawings, the specific configuration is not limited to this embodiment, and various improvements and design changes that do not deviate from the gist of the present invention are also included in the present invention.

[0066] For example, the predetermined number of times of the pulling process, which sets the interval for executing the resistance value setting process, is not limited to 1 or more and 50 or less. For example, when the number of times of execution of the pulling process at which the resistance ratio of the first resistance value R1 and the second resistance value R2 falls below the judgment value is experimented in the silicon single crystal manufacturing apparatus 1, if the resistance ratio falls below the judgment value on average 60 times, the predetermined number may be set to 60. In other words, the predetermined number may be set by actually experimenting according to the type of silicon single crystal manufacturing apparatus 1 used for manufacturing the silicon single crystal.

[0067] Furthermore, the resistance value setting step is not limited to being performed every time the pulling step is performed a predetermined number of times, and may be performed when a parameter capable of estimating a change in the resistance ratio satisfies a condition. For example, if a correlation can be found between the time from the start of heating by the heating device 4 until the first measurement point P1 and the second measurement point P2 measured by the radiation thermometer 15B reach a predetermined temperature and the resistance ratio, the resistance value setting step may be performed when the time until the predetermined temperature is reached satisfies a predetermined condition.

[0068] The judgment value for judging the resistance ratio is not limited to "1.2" and may be set to a value obtained by experiment. For example, if the resistance ratio at which the convection direction of the silicon melt M is fixed is "1.25" as a result of experiment, the judgment value may also be set to "1.25". In other words, since the resistance ratio at which the convection direction of the silicon melt M is fixed also depends on other factors that affect the heat generation distribution in the first heating region 4A and the second heating region 4B, such as the type of silicon single crystal manufactured by the silicon single crystal manufacturing apparatus 1, the shape of the hot zone, and the configuration of the heat generating unit 30, it is preferable to obtain it by experiment for each silicon single crystal manufacturing apparatus 1, and the judgment value may be set according to the value of the experimental result. In addition, when the heat generation distribution of the heating device 4 and the convection of the silicon melt M can be simulated, the judgment value may be set according to the simulation result without performing an experiment. Furthermore, the judgment value for judging the resistance ratio may be set to a value equal to or greater than the value obtained by experiment or simulation. For example, if the value obtained by experiment is "1.2", the judgment value may be set to a larger value such as "1.2 or greater". By setting the judgment value to a larger value, the difference in the amount of heat generated in each of the heating regions 4A and 4B can be increased, and the direction of convection of the silicon melt M can be further stabilized.

[0069] The judgment value for judging the resistance ratio may be changed according to the number of times the pulling process of the silicon single crystal is performed. For example, when the resistance value setting step is performed every 10 times, the judgment value when the pulling process is performed 10 times may be "1.2", the judgment value when the pulling process is performed 20 times may be "1.22", and the judgment value when the pulling process is performed 30 times may be "1.24". Changing the judgment value in this way is effective, for example, when the thermal environment in the hot zone of the silicon single crystal manufacturing apparatus 1 is affected by the deterioration of parts over time, and the direction of convection of the silicon melt M cannot be fixed unless the resistance ratio between the first resistance value R1 and the second resistance value R2 is further increased.

[0070] In the above embodiment, the power supply units 20A to 20D are arranged at positions symmetrical with respect to the virtual line VL, but the present invention is not limited thereto. That is, in the above embodiment, the cross angle between the virtual line VL and the line connecting the power supply units 20A to 20D and the central axis CA of the heating device 4 is set to 45 degrees, but for example, the power supply units 20A and 20C may be arranged so that the cross angle between the virtual line VL and the line connecting the central axis CA and the power supply units 20B and 20D and the central axis CA is 30 degrees, and the cross angle between the virtual line VL and the line connecting the virtual line VL and the power supply units 20B and 20D and the central axis CA is 60 degrees. That is, in order to make the heat distribution of the heat generation unit 30 constant, the power supply units 20A to 20D are arranged at 90 degree intervals in the circumferential direction of the heat generation unit 30, and further, the power supply units 20A and 20B as the first power supply units are arranged in the first heating area 4A, and the power supply units 20C and 20D as the second power supply units are arranged in the second heating area 4B.

[0071] In the above embodiment, the conductive sheet 24 is disposed in the resistance value decreasing step S233, and the surfaces of the terminals 21A-21D and the electrodes 22A-22D are roughened by mechanical polishing in the resistance value increasing step S234, but the resistance value may be decreased or increased by other methods. For example, the resistance value may be adjusted by inserting plate-shaped electrical resistance adjusting members made of carbon-based fiber material or the like between the terminals 21A-21D and the electrodes 22A-22D and adjusting the number of inserted members. That is, by making the total number of electrical resistance adjusting members inserted in the power supply units 20A and 20B, which are the first power supply units, greater than the total number of electrical resistance adjusting members inserted in the power supply units 20C and 20D, which are the second power supply units, the first resistance value R1 can be made higher than the second resistance value R2, and by changing the ratio of the total number of the members, the resistance ratio of the first resistance value R1 and the second resistance value R2 can also be changed. In addition, the electrical resistance adjustment member may be a thick disk-shaped sheet made of porous carbon, which is a member that can intentionally increase resistance, and the first resistance value R1 and the second resistance value R2 may be adjusted by changing the thickness dimension of the disk-shaped sheet inserted in the power supply units 20A and 20B and the thickness dimension of the disk-shaped sheet inserted in the power supply units 20C and 20D. In other words, the first resistance value R1 and the second resistance value R2 may be adjusted by changing the number of electrical resistance adjustment members inserted in the first power supply unit and the thickness dimension of the electrical resistance adjustment members inserted in the second power supply unit to make the resistance values ​​of each electrical resistance adjustment member different.

[0072] As a method for changing the resistance values ​​of the first resistance value R1 and the second resistance value R2, for example, a method for adjusting the fastening force of the nuts 23A-23D used when connecting the electrodes 22A-22D to the terminals 21A-21D may be used. For example, by increasing the fastening force of the nuts 23A-23D, the contact area between the terminals 21A-21D and the electrodes 22A-22D increases, so that the contact resistance can be reduced. In this case, by disposing the conductive sheet 24 and increasing the fastening force of the nuts 23A-23D, the contact resistance can be further reduced. On the other hand, when the fastening force of nuts 23A-23D is weakened, the contact area between terminals 21A-21D and electrodes 22A-22D is reduced, and the contact resistance can be increased. In this case, if the contact surface is roughened by mechanical polishing and the fastening force of nuts 23A-23D is weakened, the contact resistance can be further increased. Furthermore, the contact resistance may be changed by combining adjustment of the tightening force of the nut with adjustments made by the positioning of the conductive sheet 24 or mechanical polishing.

[0073] In addition, while the above embodiment has four power supply units 20A to 20D, the number of power supply units may be six or eight, etc., as long as the first heating area 4A and the second heating area 4B are provided with the same number of power supply units. EXAMPLES

[0074] Next, examples of the present invention will be described, but the present invention is not limited to the examples.

[0075] Seven silicon single crystal manufacturing apparatuses 1 of the embodiment, each having the same furnace structure, were prepared, numbered #1 to #7. 7The power supply unit 20A has four power supply units 20A to 20D, and the contact resistance of the power supply units 20A to 20D is measured by a resistance value measuring unit 44 using the principle of the four-terminal method. Specifically, a constant current was applied between electrodes 22A and 22B, the voltage between electrodes 22A and 22B was measured, and the combined resistance between electrodes 22A and 22B was measured. In a similar manner, the combined resistance between electrodes 22B and 22C, the combined resistance between electrodes 22C and 22D, and the combined resistance between electrodes 22D and 22A were each measured. Next, a constant current was similarly applied between electrodes 22A and 22B, the voltage between terminals 21A and 21B was measured, and the combined resistance between terminals 21A and 21B was measured. Using a similar method, the combined resistance between terminals 21B and 21C, the combined resistance between terminals 21C and 21D, and the combined resistance between terminals 21D and 21A were each measured. The control device 41 uses the eight combined resistance values ​​measured by the resistance value measuring unit 44 to calculate the resistance value shown in FIG. 7 The contact resistances R of the four power supply units 20A to 20D are calculated by solving the simultaneous equations set based on the equivalent circuit. α , R β , R γ , R δ was calculated. The amount of heat generated by the power supply units 20A to 20D is related to the contact resistance R and the current I flowing through the resistance, and is expressed as W=RI 2 Therefore, the resistance distribution of the power supply units 20A-20D can be regarded as equivalent to the heat generation distribution of the power supply units 20A-20D. On the other hand, the resistance of each of the heat generation units 30 depends greatly on the processing accuracy (thickness and length) of the heater, and the variation in resistance is 1% or less. Therefore, the influence of the heat generation distribution of the heat generation unit 30 on the fixing behavior of the convection of the silicon melt can be ignored. Therefore, the resistance distribution of the power supply units 20A-20D determines the heat generation distribution of the heating device 4 used for crystal growth, and this heat generation distribution determines the fixing state of the convection direction of the silicon melt. Table 1 shows the contact resistances of the power supply units 20A to 20D in each of the silicon single crystal manufacturing apparatuses 1 of #1 to #7 before performing the resistance value setting process, the first resistance value R1 and the second resistance value R2, the resistance ratio of the first resistance value R1 and the second resistance value R2, the direction of convection of the silicon melt, that is, the direction of the vortex, the vortex fixation rate, and the results of the crystal yield.

[0076] [Table 1]

[0077] In Table 1, the first resistance value R1 is the sum of the contact resistances of the first heating region 4A, that is, R1 = R α +R β And the second resistance value R2 is the sum of the contact resistances of the second heating region 4B, that is, R2 = R γ +R δ And the resistance ratio is obtained as R1 / R2 if R1 > R2, and R2 / R1 if R1 < R2. The direction of the vortex is such that when the probability that the left side in the figure 4 becomes an upward flow and the right side becomes a downward flow, resulting in a rightward vortex is 95% or more, it is denoted as "right"; conversely, when the probability of a leftward vortex is 95% or more, it is denoted as "left"; when the probability of a rightward vortex is 65% or more and less than 95%, it is denoted as "right dominant"; when the probability of a leftward vortex is 65% or more and less than 95%, it is denoted as "left dominant"; when it does not meet the above conditions, that is, when the probability of a rightward or leftward vortex does not change much, it is denoted as "left·right". The vortex fixation rate indicates the ratio at which the direction of the vortex is fixed to be leftward or rightward when growing 100 silicon single crystals in each of the seven silicon single crystal manufacturing apparatuses 1. The crystal yield indicates the ratio of the number of silicon single crystals that meet the product standards with preset variations in oxygen concentration, diameter variations, etc. when growing 100 silicon single crystals in each of the seven silicon single crystal manufacturing apparatuses 1.

[0078] From the results in Table 1, #1 and #5, in which the resistance ratio of the first resistance value R1 to the second resistance value R2 is large, 1.20 or more, had a vortex fixation rate of 100% and a high crystal yield of 100%. In addition, it was confirmed that the direction of the vortex is determined by the magnitude of the first resistance value R1 and the second resistance value R2, which are the sum of the contact resistances of the first heating area 4A and the second heating area 4B. On the other hand, #2, #6, and #7, in which the ratio of the first resistance value R1 to the second resistance value R2 is in the range of 1.00 or more and 1.10 or less, had a vortex fixation rate of 50 to 60%, the direction of the vortex was random, and the crystal yield was low. #3 and #4, in which the ratio of the first resistance value R1 to the second resistance value R2 is in the range of more than 1.10 and less than 1.20, did not completely fix the direction of the vortex, and the crystal yield was lower than #1 and #5. From the results in Table 1, it was found that in this embodiment, the ratio of the first resistance value R1 to the second resistance value R2, which allows the direction of convection to be controlled, needs to be 1.20 or more.

[0079] Next, based on the results of Table 1, the judgment value was set to 1.2, and the contact resistances of some of the power supply units 20A to 20D were changed to adjust the resistance ratio of the first resistance value R1 to the second resistance value R2 to be equal to or greater than the judgment value. The results are shown in Table 2.

[0080] [Table 2]

[0081] Table 2 shows the resistance values ​​after adjusting some of the contact resistances in Table 1. That is, in #2 and #3, the contact resistance R δ In #4, the contact resistance R was reduced by sandwiching the conductive sheet 24 between the power supply unit 20B. β was reduced. In #6, the contact resistance R α However, this alone did not make the ratio 1.2 or more, so mechanical polishing was performed on the power supply unit 20C, which has the lower contact resistance, to reduce the contact resistance R γ Increased. In #7, the contact resistance R δ Furthermore, the power supply parts 20A and 20B are mechanically polished to reduce the contact resistance R α , R β Increased. The reason why the conductive sheet 24 is sandwiched and adjusted first is that the positioning of the conductive sheet 24 can be performed in a shorter time than mechanical polishing. ~23D On the other hand, mechanical polishing requires polishing work, which takes longer and also poses the risk of discharge during the crystal growth process (when high power load is applied).

[0082] Table 2 shows the results of data collection after growing 100 silicon single crystals with the resistance ratio of the first resistance value R1 and the second resistance value R2 set to a judgment value of 1.2 or more in all silicon single crystal manufacturing apparatuses 1 #1 to #7. As shown in Table 2, the fixation rate of the vortex direction of the silicon melt was improved to 100%, and the crystal yield was also greatly improved to 100%. Furthermore, in the process after the vortex direction was fixed, the phenomenon of the vortex reversal during the growth of the silicon single crystal was not confirmed.

[0083] [evaluation] From the above results, it has been confirmed that by adjusting the contact resistance between terminals 21A-21D and electrodes 22A-22D of power supply units 20A-20D and setting the resistance ratio between a first resistance value R1, which is the sum of the contact resistance of power supply units 20A, 20B in the first heating region 4A, and a second resistance value R2, which is the sum of the contact resistance of power supply units 20C, 20D in the second heating region 4B, to be equal to or greater than a judgment value, it is possible to completely fix the direction of convection of the silicon melt and improve the yield of silicon single crystals. In addition, in the first heating area 4A or the second heating area 4B, the upward flow of the silicon melt becomes dominant in the area where the sum of the contact resistance is large, and the direction of the vortex of the convection current is determined. In other words, by controlling the magnitude of the contact resistance, it is possible to create an opportunity to determine the direction of the vortex. Furthermore, in the silicon single crystal manufacturing apparatus 1 of the embodiment, it was found that the resistance ratio at which the direction of convection of the silicon melt can be controlled is "1.2" or more, and therefore the judgment value should be set to "1.2". It was also found that, as a means for controlling the contact resistance of the power supply units 20A-20D, it is effective to reduce the resistance by sandwiching the conductive sheet 24 between the contact surfaces, or to increase the resistance by roughening the contact surfaces by mechanical polishing. Furthermore, it was found that the method for adjusting the contact resistance value does not require processing of the heat generating unit 30, and can be adjusted at the work site, making it extremely useful. [Explanation of symbols]

[0084] Reference Signs List 1...silicon single crystal manufacturing apparatus, 2...chamber, 2A...quartz window, 3...crucible, 3A...graphite crucible, 3B...quartz crucible, 4...heating device, 4A...first heating area, 4B...second heating area, 5...support shaft, 6...insulating material, 7...pulling shaft, 8...thermal shield, 9...gas inlet, 10...exhaust port, 14...magnetic field application section, 14A...first magnetic body, 14B...second magnetic body, 15...temperature measurement section, 15A...reflection section, 15B...radiation temperature Total, 15C...reflecting surface, 20A...power supply unit, 20B...power supply unit, 20C...power supply unit, 20D...power supply unit, 21A...terminal, 21B...terminal, 21C...terminal, 21D...terminal, 22A...electrode, 22B...electrode, 22C...electrode, 22D...electrode, 23A...nut, 23B...nut, 23C...nut, 23D...nut, 24...conductive sheet, 30...heat generating unit, 31...upper slit, 32...lower slit, 33A...first snake 21A...connection portion, 211B...connection portion, 211C...connection portion, 211D...connection portion, 212A...through hole, 212B...through hole, 212C...through hole, 212D...through hole, 213A...upper surface, 214A...lower surface, 221A...main body portion, 222A...upper surface, 2 23A...insertion portion, 224A...male screw, 410...convection pattern control portion, 420...pull-up control portion, 430...resistance value setting portion, 431...resistance value measurement control portion, 432...resistance value calculation portion, 433...resistance ratio determination portion, 434...resistance value adjustment portion, CA...center axis, CS...center, F...horizontal plane, L...radiant light, M...silicon melt, ML...arrow, P1...first measurement point, P2...second measurement point, R1...first resistance value, R2...second resistance value, R α …Contact resistance, R β …Contact resistance, R γ …Contact resistance, R δ ...contact resistance, S...surface, SC...seed crystal, SM...silicon single crystal, VL...virtual line, W...heat generation amount, θ1...incident angle, θ2...reflection angle, θf...angle.

Claims

1. A method for producing a silicon single crystal, comprising: pulling a silicon single crystal from a silicon melt in a quartz crucible heated by a heating device, The heating device includes a heat generating unit disposed around the quartz crucible and a power supply unit that supplies power to the heat generating unit, When the heating device is divided into a first heating region and a second heating region by a central magnetic field line of a horizontal magnetic field passing through a central axis of the quartz crucible when viewed vertically from above the quartz crucible, the power supply unit includes a first power supply unit disposed in the first heating region and a second power supply unit disposed in the second heating region; a resistance value setting step of setting a first resistance value which is a resistance value of the first power supply unit and a second resistance value which is a resistance value of the second power supply unit; a silicon melt heating step of heating the silicon melt in the quartz crucible in a magnetic field-free state; a horizontal magnetic field application step of applying a horizontal magnetic field to the silicon melt in the quartz crucible; A pulling step of pulling a silicon single crystal from the silicon melt, The resistance value setting step includes: a measuring step of measuring the first resistance value and the second resistance value; a determination step of determining whether a resistance ratio, which is a value obtained by dividing a higher resistance value of the first resistance value and a lower resistance value of the second resistance value, is 1.2 or more; and an adjustment step of adjusting at least one of the first resistance value and the second resistance value when the resistance ratio is determined to be less than 1.2 in the determination step, When the resistance ratio is determined to be less than 1.2 in the determination step, the determination step is performed again after the adjustment step and the measurement step are performed; When it is determined in the determination step that the resistance ratio is 1.2 or more, the resistance value setting step is terminated. A method for producing silicon single crystals.

2. The method for producing a silicon single crystal according to claim 1, The resistance value setting step is performed every time the pulling step is performed a predetermined number of times. A method for producing silicon single crystals.

3. The method for producing a silicon single crystal according to claim 2, The predetermined number of times is 1 or more and 50 or less. A method for producing silicon single crystals.

4. The method for producing a silicon single crystal according to any one of claims 1 to 3, The measuring step includes: a first measurement step of measuring a combined resistance of the heat generating unit and the power supply unit; A second measurement step of measuring a combined resistance of the heat generating portion; and a resistance value calculation step of determining the first resistance value and the second resistance value based on the measured resistance values. A method for producing silicon single crystals.

5. The method for producing a silicon single crystal according to any one of claims 1 to 4, Each of the power supply units has a terminal formed integrally with the heat generating unit, and an electrode having one end connected to the terminal and the other end connected to a power source, The adjustment step includes a resistance value reducing step of reducing a resistance value of the power supply unit by disposing a conductive sheet between the terminal and the electrode. A method for producing silicon single crystals.

6. The method for producing a silicon single crystal according to any one of claims 1 to 5, Each of the power supply units has a terminal connected to the heat generating unit, and an electrode having one end connected to the terminal and the other end connected to a power source, The adjustment step includes a resistance increasing step of increasing the resistance of the power supply unit by roughening the contact surfaces of the terminal and the electrode. A method for producing silicon single crystals.

7. The method for producing a silicon single crystal according to any one of claims 1 to 6, Each of the power supply units has a terminal connected to the heat generating unit, and an electrode having one end connected to the terminal and the other end connected to a power source, A plate-shaped electrical resistance adjusting member is interposed between the terminal and the electrode, The adjustment step adjusts the resistance value by making the number or thickness of the electrical resistance adjustment members interposed between the terminals and the electrodes of the first power supply unit different from the number or thickness of the electrical resistance adjustment members interposed between the terminals and the electrodes of the second power supply unit. A method for producing silicon single crystals.

8. A method for producing a silicon wafer, comprising: producing a silicon wafer by slicing a silicon single crystal pulled by the method for producing a silicon single crystal according to any one of claims 1 to 7.

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