Dopant addition device, dopant addition method, and method for producing silicon single crystal

Abstract

This invention provides a dopant addition device capable of suppressing the differential crystallization of silicon single crystals. The dopant addition device of this invention is a dopant addition device for adding volatile dopant to molten silicon, comprising: a dopant receiving portion and an outer cylinder; wherein the dopant receiving portion is configured to receive the dopant and release dopant gas generated by the sublimation of the dopant; the outer cylinder comprises: an outer cylinder body forming a cylinder with an open lower end, having the dopant receiving portion inside, and allowing the dopant gas to flow out from the lower end and be blown into the molten silicon; and a shielding plate protruding from the outer cylinder body in the form of a flange; the shielding plate is positioned above the lower end of the shield that surrounds the silicon single crystals pulled upward from the molten silicon when the dopant is added.

Description

Technical Field

[0001] The present invention relates to a dopant adding device, a dopant adding method and a method for manufacturing a silicon single crystal. Prior Art

[0002] Conventional methods for adding volatile dopants to silicon melts during the manufacture of silicon single crystals include, for example, sublimating the dopant to generate dopant gas, and then blowing the dopant gas into the silicon melt (see, for example, Patent Documents 1 and 2).

[0003] The doping device disclosed in Figures 1 and 2 of Patent Document 1 comprises a container body comprising a container body and a release tube, and an outer cylindrical body containing the container body and having an opening at its lower end. When the doping device is lowered to near the surface of a silicon melt, solid arsenic (dopant) contained in the container body sublimates due to the radiant heat of the silicon melt, generating arsenic gas (dopant gas). When the dopant gas is released from the lower end of the release tube and blown into the silicon melt, a portion of the dopant contained in the dopant gas dissolves in the silicon melt, thereby adding the dopant to the silicon melt. Meanwhile, a portion of the dopant that does not dissolve in the silicon melt becomes dopant vapor. Furthermore, the remaining dopant that does not dissolve in the silicon melt reacts with the silicon melt to form amorphous vapor. A downward gas flow occurs outside the outer cylinder, while an upward gas flow occurs near the sides of the outer cylinder. If dopant vapor and amorphous vapor (hereinafter collectively referred to as "vapor") rise with this upward gas flow, they may adhere to the interior of the silicon single crystal production apparatus and solidify. If this solidified material falls into the silicon melt, the silicon single crystal may undergo dislocation.

[0004] On the other hand, FIG. 3 (A) and FIG. 3 (B) of Patent Document 1 disclose that, in order to increase the contact area between the dopant gas and the surface of the silicon melt, a skirt member extending outward is provided at the lower end of the outer cylinder. The doping device disclosed in FIG5 of Patent Document 2 comprises an inner tube and an outer cylinder, each having the same functions as the container and outer cylinder of Patent Document 1. Heat shields extending outward from the side of the outer cylinder are provided to prevent radiant heat from the silicon melt from reaching the container containing the dopant. The skirt member of Patent Document 1 or the heat shielding plate of Patent Document 2, although not having the above-mentioned original function, may be able to suppress the rising of steam near the outer cylinder or the side surface of the outer cylinder. [Prior technical literature] [Patent Document]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2001-342094 [Patent Document 2] Japanese Patent Application Laid-Open No. 2008-024547 Summary of the Invention

[0006] (Problems that the invention aims to solve) However, the configuration described in Figure 5 of Patent Document 2, because the heat shield is positioned below the shield's lower end during dopant addition, the vapor velocity flowing between the heat shield and the silicon melt accelerates, potentially causing waving in the silicon melt. In this case, the silicon melt adheres to the shield and solidifies. If this solidified material falls into the silicon melt, it could potentially cause dislocation of the silicon single crystal. Furthermore, Patent Document 1 does not disclose the positional relationship between the skirt member and the shield. As mentioned above, when dopants are added, the vapor flowing between the skirt member and the silicon melt causes the silicon melt to wave, causing the silicon melt to adhere to the shield and solidify. If the solidified material falls into the silicon melt, there is a possibility of causing heterogeneity of the silicon single crystal.

[0007] The object of the present invention is to provide: a dopant addition device, a dopant addition method, and a method for manufacturing a silicon single crystal that can suppress the occurrence of dislocation in a silicon single crystal.

[0008] (Technical means to solve the problem) The dopant addition device of the present invention is a dopant addition device for adding volatile dopants to a silicon melt, and is provided with: a dopant storage portion and an outer cylinder; the dopant storage portion is configured to store the dopant and release the dopant gas generated by the sublimation of the dopant; the outer cylinder is provided with: an outer cylinder body with an open lower end, the dopant storage portion being provided inside, and allowing the dopant gas to flow out from the lower end and be blown into the silicon melt; and a shielding plate protruding from the outer cylinder body in a flange shape; the shielding plate is arranged to be located above the lower end of the shield that surrounds the silicon single crystal pulled up from the silicon melt when the dopant is added.

[0009] The dopant adding device of the present invention is preferably configured such that the outer cylinder is formed into a cylindrical shape with an open lower end; the shielding plate is formed into a circular plate shape, and when the dopant is added, it is located above the lower end of the cylindrical or conical trapezoidal shielding plate, and the void ratio R obtained by the following formula (1) is less than 69%; R(%)=(A 2-(B+2×C) 2) / A 2×100… (1) A: Inner diameter of the lower end of the shield B: The outer diameter of the above-mentioned outer cylinder body C: The distance between the side of the outer cylinder and the protruding front end of the shielding plate when viewing the outer cylinder from above the dopant adding device

[0010] In the dopant adding device of the present invention, the shielding plate is preferably configured so that the void ratio R reaches 49% or more.

[0011] The dopant addition method of the present invention is a dopant addition method for adding a volatile dopant to a silicon melt. In a shield surrounding a silicon single crystal pulled from the silicon melt, while an inert gas is flowing downward, the dopant addition device is lowered such that the shield plate is positioned above the lower end of the shield, thereby adding the dopant to the silicon melt.

[0012] In the dopant adding method of the present invention, it is preferred to use the dopant adding device having a circular plate-shaped shielding plate provided at the lower end of the outer cylinder body, and to add the dopant to the silicon melt when the distance from the lower end of the outer cylinder to the surface of the silicon melt is greater than 30 mm.

[0013] In the dopant adding method of the present invention, the dopant is preferably added to the silicon melt when the distance between the lower end of the outer cylinder and the surface of the silicon melt is less than 60 mm.

[0014] The method for manufacturing silicon single crystal of the present invention is to pull up silicon single crystal from silicon melt to which volatile dopants are added by the above-mentioned dopant adding method. Simple diagram description

[0015] Figure 1 is a schematic diagram showing the schematic configuration of an embodiment of a silicon single crystal manufacturing apparatus; Figure 2 is a schematic diagram of the structure of the dopant adding device according to the embodiment, (A) is a longitudinal sectional view, (B) is a cross-sectional view along the IIB-IIB line in (A); Figure 3 is an explanatory diagram of the dopant adding step performed by the dopant adding apparatus according to the embodiment; FIG4 is an explanatory diagram of a dopant addition step performed using a dopant addition apparatus without a shielding plate; and FIG5 is a diagram showing the relationship between the presence or absence of a shielding plate in the dopant adding device, the gas flow between the outer cylinder body and the shield of the dopant adding device, and the void ratio in Experimental Example 1 of the embodiment. Implementation Method

[0016] [Implementation form] <Structure of Silicon Single Crystal Manufacturing Apparatus> First, the structure of a silicon single crystal production apparatus according to an embodiment of the present invention will be described. The silicon single crystal production apparatus 1 shown in FIG1 uses the Czochralski method to produce silicon single crystals (SM) doped with volatile dopants. Examples of volatile dopants include arsenic and red phosphorus. The silicon single crystal production apparatus 1 includes a processing chamber 11, a crucible 12, a heater 13, a heat-insulating tube 14, a shield 15, and a rectifying unit 16.

[0017] The processing chamber 11 comprises a main processing chamber 111 formed in a cylindrical shape with a bottom; a top processing chamber 112 formed in a slightly conical trapezoidal cylindrical shape, with its lower end connected to the upper end of the main processing chamber 111; and a cylindrical pulling chamber 113, with its lower end connected to the upper end of the top processing chamber 112. The main processing chamber 111 houses the crucible 12, heater 13, heat-insulating tube 14, shield 15, and rectifying section 16. A gas inlet 113A is provided at the top of the pulling chamber 113 for introducing an inert gas Gf, such as argon (Ar), into the processing chamber 11. A gas exhaust port 111A is provided at the bottom of the main processing chamber 111 for exhausting the internal gas Gn within the processing chamber 11, driven by a vacuum pump (not shown).

[0018] The crucible 12 is disposed in the main processing chamber 111 and stores silicon melt MD to which volatile dopants have been added. The crucible 12 is fixed to the upper end of a support shaft 121 that can rotate and rise and fall. Above the crucible 12, a pull-up shaft 17 is disposed coaxially with the support shaft 121. The pull-up shaft 17 is formed of a metal wire or the like, and a seed crystal SC is attached to its lower end.

[0019] The heater 13 is cylindrical and is disposed so as to surround the crucible 12. The heater 13 melts the silicon raw material in the crucible 12 by generating heat. The heat-insulating tube 14 is formed in a cylindrical shape and is arranged to surround the heater 13 . Shield 15 is formed of a carbon material into a roughly cylindrical shape, but may also be formed into a roughly conical trapezoidal cylindrical shape with a smaller diameter at the top than at the bottom. The top of shield 15 is supported by a plurality of shield support members 114 within main processing chamber 111. Shield 15 is positioned to surround silicon single crystal SM being pulled from silicon melt MD, thereby blocking radiant heat from heater 13 toward silicon single crystal SM. The rectifying section 16 comprises an upper rectifying tube 161 and a lower rectifying tube 162. The upper rectifying tube 161 is formed cylindrically from a carbon material and extends downward from the lower end of the pulling chamber 113, surrounding the silicon single crystal SM being pulled. The lower rectifying tube 162 is formed cylindrically from quartz and extends upward from the lower end of the shield 15, surrounding the silicon single crystal SM being pulled, with its upper end receiving the lower end of the upper rectifying tube 161.

[0020] <Composition of dopant adding device> Next, the structure of a dopant adding device for adding a volatile dopant to the silicon melt MD stored in the crucible 12 of the silicon single crystal production apparatus 1 will be described. The dopant adding device 2 shown in FIG. 2(A) and FIG. 2(B) comprises: a dopant receiving portion 21, an outer cylinder 22, and a supporting portion 23.

[0021] The dopant storage section 21 is formed of quartz in a bottomed cylindrical shape with an open top and a closed bottom. As indicated by the two-dot chain line, the dopant storage section 21 is filled with a solid dopant (hereinafter referred to as "solid dopant") D. The dopant gas Gd generated by the sublimation of the solid dopant D is released through the top opening. Alternatively, the opening for releasing the dopant gas Gd may be provided on the side of the dopant storage section 21.

[0022] The outer cylinder 22 includes an outer cylinder body 221 and a shielding plate 222 , each of which is formed of quartz. The outer cylinder body 221 is formed in a bottomed cylindrical shape with an open lower end and a closed upper end. A dopant receiving portion 21 is provided inside the outer cylinder body 221. Dopant gas Gd released from the dopant receiving portion 21 flows out from the lower end and is blown into the silicon melt MD. The shielding plate 222 is formed as a circular plate protruding from the lower end of the outer cylinder body 221 in a flange-like manner in a direction perpendicular to the central axis of the outer cylinder body 221. Specifically, when the shielding plate 222 is positioned horizontally with respect to the vertical direction relative to the central axis of the outer cylinder body 221, it forms a circular plate protruding horizontally from the outer cylinder body 221.

[0023] The support portion 23 comprises four supported members 231 and four receiving members 232, each formed of carbon material. The supported members 231 are circumferentially spaced evenly on the outer surface of the impurity receiving portion 21. The receiving members 232 are circumferentially spaced evenly on the inner surface of the outer cylinder body 221. Each supported member 231 fits into a groove formed on each receiving member 232, thereby supporting the dopant receiving portion 21 within the outer tube 22. Dopant gas Gd released from the dopant receiving portion 21 passes through the space between the dopant receiving portion 21 and the outer tube body 221, where neither the supported member 231 nor the receiving member 232 is present, and then flows out from the lower end of the outer tube 22.

[0024] The dopant addition device 2 constructed as described above is disposed within the processing chamber 11 such that, when dopants are added to the silicon melt MD, the central axes of the outer cylinder body 221 and the shield 15 overlap, as shown in FIG3 , and the shield plate 222 is positioned above the lower end of the shield 15. The distance H between the lower end of the outer cylinder 22 and the surface of the silicon melt MD (hereinafter also referred to as the "outer cylinder-melt distance") is 30 mm or greater and 60 mm or less. The shield plate 222 of the dopant addition device 2 is positioned such that, when the dopant addition device 2 is disposed, the void ratio R obtained by the following equation (1) is 49% or greater and 69% or less. R(%)=(A 2-(B+2×C) 2) / A 2×100… (1) A: Inner diameter of the lower end of shield 15 B: outer diameter of outer cylinder body 221 C: When viewing the outer cylinder 22 from above, the distance from the side of the outer cylinder body 221 to the protruding front end of the shielding plate 222

[0025] <Method for Manufacturing Silicon Single Crystal> Next, a method for manufacturing silicon single crystal SM is described. The method for manufacturing silicon single crystal SM includes: a silicon melt generation step, a dopant addition step, and a pull-up step.

[0026] In the silicon melt generation step, inert gas Gf is introduced into the processing chamber 11 through the gas inlet 113A, and the flow rate of the inert gas Gf and the furnace pressure in the processing chamber 11 are controlled to a predetermined state. Then, the heater 13 is heated to melt the silicon raw material in the crucible 12 to generate silicon melt MD.

[0027] The dopant adding step includes the dopant adding method of the present invention, using the dopant adding device 2 to add volatile dopants to the silicon melt MD generated in the silicon melt generating step. Here, in order to explain the reason for providing the shielding plate 222 in the dopant adding device 2, the dopant adding steps performed when the dopant adding device 3 is used, as shown in FIG. 4 , in which the shielding plate 222 is not provided in the outer cylinder body 221.

[0028] The dopant addition step using dopant addition device 3 is performed by lowering dopant addition device 3, mounted on pull-up shaft 17, to the position shown in FIG4 , while the inert gas Gf flow rate and furnace pressure downward within processing chamber 11 are controlled at predetermined conditions. The height position of the lower end of outer cylinder body 221 of dopant addition device 3 relative to the lower end of shield 15 is the same as the height position of the lower end of outer cylinder body 221 of dopant addition device 2 shown in FIG3 . Solid dopant D contained in dopant container 21 is sublimated by radiant heat from molten silicon liquid MD to form dopant gas Gd. Dopant gas Gd is blown into molten silicon liquid MD from a position away from molten silicon liquid MD through the upper opening of dopant container 21, the space between dopant container 21 and outer cylinder body 221, and the lower opening of outer cylinder body 221.

[0029] When dopant gas Gd is blown into silicon melt MD, dopant is added to silicon melt MD as described above, generating dopant vapor Vd and amorphous vapor Va (hereinafter collectively referred to as "vapor Vd, Va"). Then, in the area between outer cylinder body 221 and shield 15 (rectifier 16), an upward gas flow is generated in the area near outer cylinder body 221, and a downward gas flow is generated in the area near shield 15.

[0030] Part of the vapors Vd and Va flow with the downward gas flow and the inert gas Gf between the lower end of the shield 15 and the silicon melt Md, and between the side of the shield 15 and the crucible 12, and are then discharged from the processing chamber 11 in the form of internal gas Gn. Meanwhile, the remaining vapors Vd and Va may adhere to the rectifying section 16 and the pulling chamber 113 and solidify along with the upward gas flow. If this solidified material falls into the silicon melt MD, the silicon single crystal SM may undergo dislocation. In order to suppress the occurrence of dislocation in the silicon single crystal SM, a dopant adding device 2 provided with a shielding plate 222 is used in the dopant adding step.

[0031] The dopant addition process using the dopant addition apparatus 2 involves lowering the dopant addition apparatus 2 to the position shown in FIG3 (i.e., where the outer cylinder-melt distance H is greater than 30 mm and less than 60 mm) and allowing it to rest. Dopants are then added to the silicon melt MD by blowing dopant gas Gd into the silicon melt MD. At this point, upward vapor flows Vd and Va are generated. However, these vapors are suppressed from rising by the shielding plate 222 and do not flow between the outer cylinder body 221 and the shield 15. Instead, they flow away from the center of the dopant addition apparatus 2 between the silicon melt MD and the shielding plate 222. These vapors then merge with the downwardly flowing inert gas Gf and are exhausted from the processing chamber 11 as the internal gas Gn as described above. If all the solid dopants D in the dopant receiving portion 21 have sublimated and a predetermined time has passed, the dopant adding device 2 is raised and taken out of the processing chamber 11 .

[0032] As described above, by suppressing the rise of vapors Vd and Va using shielding plate 222, the occurrence of dislocation in silicon single crystal SM caused by the solidification of vapors Vd and Va falling off can be suppressed. Furthermore, by suppressing the rise of vapors Vd and Va, the amount of dopants dissolved in silicon melt MD can be reduced, thereby increasing the probability of obtaining silicon single crystal SM with the desired resistivity. In particular, by providing shielding plate 222 with a void ratio R of 69% or less, the rise of vapors Vd and Va can be reliably suppressed. Furthermore, by providing shielding plate 222 with a void ratio R of 49% or greater, even if dopant addition apparatus 2 were to shake, shielding plate 222 would be prevented from colliding with shield 15 and rectifying section 16.

[0033] Furthermore, dopants are added to the molten silicon liquid MD while the shielding plate 222 is positioned above the lower end of the shield 15. Therefore, compared to the case where the shielding plate 222 is positioned below the lower end of the shield 15, the flow rates of vapor Vd and Va flowing between the shielding plate 222 and the molten silicon liquid MD can be slowed, thereby suppressing waving in the molten silicon liquid MD. Consequently, the molten silicon liquid MD can be prevented from adhering to the shield 15 and solidifying, thereby preventing the solidified material from falling off and causing differential dislocation of the silicon single crystal SM.

[0034] Furthermore, when the distance H between the outer cylinder and the melt reaches 30 mm or more, dopants are added to the silicon melt MD. Here, when the distance H between the outer cylinder and the melt is less than 30 mm, the dopant sublimation rate due to radiant heat from the silicon melt MD is too rapid. Consequently, as the surface of the silicon melt MD cools, a large amount of dopant residue may form between the dopant adding device 2 and the silicon melt MD. This dopant residue will dissolve to some extent in the silicon melt MD. However, if some of the dopant residue remains undissolved on the surface of the silicon melt MD, it may cause heterogeneity in the silicon single crystal SM. In this embodiment, by adding a dopant to the silicon melt MD while the outer cylinder-melt distance H is at least 30 mm, the dopant sublimation rate can be suppressed. As a result, the formation of dopant residues can be suppressed, and the occurrence of dislocation in the silicon single crystal SM caused by these dopant residues can be suppressed.

[0035] Furthermore, in a state where the outer cylinder-melt distance H is 60 mm or less, a dopant is added to the silicon melt MD. Here, when the outer cylinder-melt distance H exceeds 60 mm, the dopant addition device 2 is too far away from the silicon melt MD. Therefore, the temperature of the dopant gas generated and rising within the dopant receiving portion 21 may fall below its sublimation temperature, and there is a possibility that the dopant gas may return to the dopant receiving portion 21 in a solid state. As a result, the amount of dopant added to the silicon melt MD may decrease, potentially preventing the production of a silicon single crystal SM with the desired resistivity. According to this embodiment, by adding dopants to silicon melt MD while the outer tube melt distance H is 60 mm or less, the temperature of the dopant gas generated within dopant receiving portion 21 can be prevented from exceeding the sublimation temperature, thereby suppressing excessive sublimation speed. Consequently, the likelihood of obtaining silicon single crystal SM having the desired resistivity is increased.

[0036] In the pulling step, the pulling shaft 17 is lowered to immerse the seed crystal SC in the silicon melt MD to which the dopant has been added, and the crucible 12 and the pulling shaft 17 are rotated in a predetermined direction while the seed crystal SC is pulled upward, thereby pulling up the silicon single crystal SM.

[0037] [Example of Change] The above is a detailed description of the embodiment of the present invention with reference to the drawings. However, the specific structure is not limited to the embodiment, and various improvements and design changes made without departing from the scope of the present invention are included in the present invention.

[0038] The void ratio R of the shielding plate 222 may be greater than 69% or less than 49%. Alternatively, dopants may be added to the silicon melt MD when the distance H between the outer cylinder and the melt exceeds 60 mm or is less than 30 mm.

[0039] Although the dopant receiving portion 21 and the outer cylinder 22 are made of quartz, at least one of them may be formed of a material other than quartz, such as SiC, C, or other ceramics. Although the outer cylinder body 221 is exemplified as a cylindrical outer cylinder with a bottom, the outer cylinder body 221 may also be in a shape other than a cylinder, such as a square cylinder with a bottom, a conical trapezoidal cylinder, or the like. Although the shielding plate 222 is shown as protruding from the lower end of the outer tube body 221 in a flange shape, the protruding position of the shielding plate 222 can also be a predetermined distance above the lower end of the outer tube body 221. Although the shielding plate 222 is shown as protruding in a direction perpendicular to the central axis of the outer cylinder body 221, the shielding plate 222 may protrude in an inclined direction relative to the central axis of the outer cylinder body 221, that is, in an obliquely upward or obliquely downward direction. [Example]

[0040] Next, the present invention will be described with reference to the embodiments.

[0041] [Experimental Example 1] Experimental Example 1 was a simulation conducted to investigate the relationship between the presence or absence of a shield plate in a dopant addition system, as well as the gas flow between the outer cylinder and the shield, and the porosity. In Experimental Example 1 and Experimental Examples 2, 3, and 4 described below, the dopant was arsenic, and the diameter of the silicon single crystal SM being produced was 300 mm.

[0042] <Experimental Methods> (Comparative Example 1) The silicon single crystal production apparatus of Comparative Example 1 was set as the silicon single crystal production apparatus 1 shown in Figure 1 . Furthermore, the dopant addition apparatus was set as the dopant addition apparatus 3 shown in Figure 4 , which does not include the shielding plate 222 . The outer cylinder body 221 and shield 15 of the dopant addition apparatus 3 were configured to achieve a void ratio R of 89%. Furthermore, the parameter values were set as follows. Distance between outer cylinder and melt H: 60mm Downward inert gas Gf flow rate: 0.69m / s Then, the gas flow at the position corresponding to each void ratio R between the outer cylinder body 221 and the shield 15 is calculated.

[0043] (Example 1) The silicon single crystal production apparatus of Example 1 was configured as the same silicon single crystal production apparatus 1 as in Comparative Example 1. The dopant addition apparatus of Example 1 was configured as the dopant addition apparatus 2, shown in Figure 3, equipped with an annular plate-shaped shielding plate 222. The protrusion dimension of the shielding plate 222 from the outer edge of the outer cylinder body 221 was set to a size that resulted in a void ratio R of 49%. Furthermore, the various parameter values were set to the same values as in Comparative Example 1. Then, the gas flow at the position corresponding to each void ratio R between the outer cylinder body 221 and the shield 15 is calculated.

[0044] <Experimental Results and Evaluation> In Figure 5 , the calculation results for Comparative Example 1 are indicated by the dashed line, while the calculation results for Example 1 are indicated by the solid line. In Figure 5 , positive gas flow rates indicate that the gas is flowing upward through the space between outer cylinder body 221 and shield 15 . Negative gas flow rates indicate that the gas is not flowing through the space between outer cylinder body 221 and shield 15 , but is flowing from below shield 15 toward the space between crucible 12 and shield 15 . In Comparative Example 1, upward gas flow occurred at locations where the void ratio R exceeded 69%, but no upward gas flow occurred at locations below 69%, resulting in downward gas flow. On the other hand, in Example 1, no gas flow occurred at locations where the void ratio R exceeded 49% on the shielding plate 222, but downward gas flow occurred at locations below 49%. These results confirm that by providing the shielding plate 222 in the dopant addition device 2 with a void ratio R of 69% or less, it is possible to suppress the upward flow of gas between the outer cylinder body 221 and the shield 15. By suppressing this upward flow of gas, the rise of vapors Vd and Va is suppressed, and it is speculated that this can also suppress the occurrence of dislocation in the silicon single crystal SM caused by the solidified products of vapors Vd and Va.

[0045] [Experimental Example 2] Experimental Example 2 was conducted to investigate the relationship between the presence or absence of a shielding plate in the dopant addition device and the occurrence of heterogeneity in silicon single crystals.

[0046] <Experimental Methods> (Comparative Example 2) The silicon single crystal manufacturing apparatus and dopant addition apparatus of Comparative Example 2 were prepared with the same configurations as those of Comparative Example 1 (the dopant addition apparatus 3 was not equipped with the shielding plate 222). The parameter values were set as follows. Distance between outer cylinder and melt H: 60mm Downward inert gas Gf flow rate: 0.69m / s Then, 46 (pulled) silicon single crystals SM were produced using the same method as the silicon single crystal SM production method of the aforementioned embodiment. During the pulling of the silicon single crystal SM, the occurrence of dislocation was confirmed using an image of the silicon single crystal SM. If dislocation was observed, the pulling of the silicon single crystal SM was stopped, and the silicon single crystal SM was melted in silicon melt MD and then melted back. The pulling and melting of the silicon single crystal SM were repeated until a silicon single crystal SM without dislocation was produced.

[0047] (Example 2) The dopant addition apparatus of Example 2 is a dopant addition apparatus 2 having the same shape as that of Example 1 (a dopant addition apparatus 2 having a shielding plate 222 with a void ratio R of 49%). Then, using the same silicon single crystal manufacturing apparatus 1 and manufacturing method as in Comparative Example 2, 18 silicon single crystals SM were pulled up.

[0048] <Experimental Results and Evaluation> The average number of occurrences of differential shifting in Comparative Example 2 and Example 2 (the average number of occurrences of differential shifting until one pull-up is completed) is shown in Table 1.

[0049] [Table 1] Average number of occurrences of differential Manufacturing quantity Comparative Example 2 2.1 46 Example 2 1.4 18

[0050] As shown in Table 1, the average number of occurrences of the related differential arrangement is 2.1 times for Comparative Example 2 and 1.4 times for Example 2. These results confirm that the occurrence of dislocation can be suppressed by using the dopant adding device 2 that can suppress the upward gas flow between the outer cylinder body 221 and the shield 15 to manufacture silicon single crystal SM.

[0051] [Experimental Example 3] Experimental Example 3 was conducted to investigate the relationship between the presence or absence of a shielding plate in the dopant addition device and the resistivity of silicon single crystal.

[0052] <Experimental Methods> (Comparative Example 3) The silicon single crystal manufacturing apparatus and dopant addition apparatus of Comparative Example 3 are prepared by preparing a silicon single crystal manufacturing apparatus 1 and a dopant addition apparatus 3 having the same shapes as those of Comparative Example 2. Then, using the same manufacturing conditions and manufacturing method as in Comparative Example 2, six silicon single crystal SMs were pulled up so that the target resistivity at a predetermined position of the straight tube portion became 2.5 mΩ·cm.

[0053] (Example 3) The silicon single crystal manufacturing apparatus and dopant adding apparatus of the third embodiment are prepared by preparing a silicon single crystal manufacturing apparatus 1 and a dopant adding apparatus 2 of the same shape as those of the second embodiment. Then, using the same manufacturing conditions and manufacturing method as Comparative Example 3, three silicon single crystal SMs with the same target resistivity as Comparative Example 3 at predetermined positions of the straight tube portion were pulled up.

[0054] <Experimental Results and Evaluation> The resistivity, average resistivity, and the difference between the average resistivity and the target resistivity of each silicon single crystal SM of Comparative Example 3 and Example 3 are shown in Table 2.

[0055] [Table 2] Average resistivity (mΩ·cm) The average resistivity and Target resistivity difference (mΩ·cm) Resistivity (mΩ·cm) Comparative Example 3 2.610 0.110 2.65 2.61 2.57 2.65 2.61 2.57 Example 3 2.517 0.017 2.48 2.53 2.54

[0056] As shown in Table 2, the difference between the average resistivity of Example 3 and the target resistivity is smaller than that of Comparative Example 3. These results confirm that by suppressing the rise of vapors Vd and Va by the shielding plate 222 , the reduction in the amount of dopants dissolved in the silicon melt MD can be suppressed, and silicon single crystal SM having a desired resistivity can be obtained.

[0057] [Experimental Example 4] Experimental Example 4 was conducted to investigate the relationship between the distance between the outer tube melt and the occurrence of differential dislocation of silicon single crystals.

[0058] <Experimental Methods> (Comparative Example 4) The silicon single crystal manufacturing apparatus and dopant addition apparatus of Comparative Example 4 are prepared by preparing a silicon single crystal manufacturing apparatus 1 and a dopant addition apparatus 2 having the same shapes as those of Example 2. Then, except that the distance H between the outer cylinder melts is set to 1 mm, the rest is the same as the manufacturing method of Example 2 to pull up three silicon single crystals SM.

[0059] (Examples 4-1, 4-2, 4-3) As shown in Table 2, in Examples 4-1, 4-2, and 4-3, the distance H between the outer cylinder melt was set to 30 mm, 55 mm, and 60 mm, respectively. The rest of the examples used the same silicon single crystal manufacturing apparatus, dopant addition apparatus, and manufacturing method as those in Comparative Example 4, and pulled up 2, 2, and 3 silicon single crystal SMs, respectively.

[0060] <Experimental Results and Evaluation> The number of dislocations and the average number of dislocations occurring in each silicon single crystal SM of Comparative Example 4 and Examples 4-1, 4-2, and 4-3 are shown in Table 3.

[0061] [Table 3] Distance between outer cylinder and melt H (mm) Average number of differential occurrences Number of differential displacements Comparative Example 4 1 3.3 4 3 3 Example 4-1 30 2.5 2 3 Example 4-2 55 1.5 2 1 Example 4-3 60 1 1 1 1

[0062] As shown in Table 3, the average number of occurrences of differential displacement decreases as the distance H between the outer tube melt increases. These results confirm that by setting the outer cylinder melt distance H to 30 mm or more, the waving of the silicon melt MD can be suppressed, and the occurrence of dislocation of the silicon single crystal SM caused by the silicon melt MD adhering to the shield 15 and solidifying can be suppressed.

[0063] 1: Silicon single crystal manufacturing equipment 2: Dopant adding device 11: Processing Room 12: Crucible 13: Heater 14: Insulation tube 15: Shield 16: Rectification unit 17: Pull-up shaft 21: Dopant Containment Department 22:Outer cylinder 23: Support 111: Main processing room 111A: Gas exhaust port 112: Top processing chamber 113: Lifting Room 113A: Gas inlet 114: Shielding support member 121: Support shaft 161: Upper rectifier tube 162: Lower rectifier 221:Outer cylinder body 222: Shielding plate 231: Supported member 232: Connecting components D: Solid-state dopant Gd: dopant gas Gf: inert gas H: Distance between outer cylinder and melt MD: Silicon melt SC: Seed crystallization SM: Silicon Single Crystal Va: amorphous vapor Vd: dopant vapor

Claims

1. A method for adding a dopant, comprising adding a volatile dopant to a molten silicon, wherein, within a shield surrounding a silicon single crystal drawn from the molten silicon, and under a state of downward flow of inert gas, a dopant adding device is lowered such that the shield is positioned above the lower end of the shield to add the dopant to the molten silicon, wherein the dopant adding device is a dopant adding device for adding the volatile dopant to the molten silicon, comprising: a dopant receiving portion and an outer cylinder; the dopant receiving portion is configured to receive the dopant and release dopant gas generated by the sublimation of the dopant; the outer cylinder comprises: an outer cylinder body which is formed into a cylinder with an open lower end, having the dopant receiving portion inside, and allowing the dopant gas to flow out from the lower end of the outer cylinder body and be blown into the molten silicon; and the shielding plate which protrudes from the outer cylinder body as a flange; The shielding plate is positioned above the lower end of the shield that surrounds the silicon monocrystal pulled up from the silicon melt when the dopant is added, and the porosity R obtained by the following formula (1) is less than 69%; R(%)=(A2-(B+2×C)2) / A2×100 …… (1) A: Inner diameter of the lower end of the shield B: Outer diameter of the outer cylinder body C: Distance between the side of the outer cylinder body and the protruding front end of the shielding plate when viewed from above the dopant adding device.

2. As in request item 1, the method for adding dopant, wherein, Using the dopant addition device which has a circular plate-shaped shielding plate at the lower end of the outer cylinder body, the dopant is added to the silicon melt when the distance from the lower end of the outer cylinder to the surface of the silicon melt is 30 mm or more.

3. As in request item 2, the method for adding the dopant, wherein, The dopant is added to the molten silicon when the distance between the lower end of the outer cylinder and the surface of the molten silicon is less than 60 mm.

4. As in request item 1, the method for adding dopant, wherein, The aforementioned shielding plate is configured such that the porosity R reaches 49% or more.

5. A method for manufacturing silicon single crystals, comprising pulling silicon single crystals upward from a silicon melt in which volatile dopants have been added by the dopant addition method of claim 1.

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