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

Abstract

This dopant addition device for adding a volatile dopant to a silicon melt comprises a dopant accommodation part and an outer cylinder, wherein: the dopant accommodation part is configured to accommodate the dopant and emit a dopant gas generated by sublimation of the dopant; the outer cylinder includes an outer cylinder body that is formed in a cylindrical shape with an open lower end, has therein the dopant accommodation part, and causes the dopant gas to flow out from the lower end and blows the dopant gas onto the silicon melt, and a shielding plate that projects in a flange shape from the outer cylinder body; and the shielding plate is provided so as to be positioned above the lower end of a shield surrounding a silicon single crystal to be pulled up from the silicon melt when adding the dopant.

Description

DOPANT ADDING APPARATUS, DOPANT ADDING METHOD, AND SILICON SINGLE CRYSTAL MANUFACTURING METHOD

[0001] The present invention relates to a dopant addition device, a dopant addition method, and a silicon single crystal manufacturing method.

[0002] Conventionally, when producing silicon single crystals, a method of adding a volatile dopant to a silicon melt is known in which the dopant is sublimated to generate a dopant gas, and the dopant gas is sprayed onto the silicon melt (see, for example, Patent Documents 1 and 2).

[0003] 1 and 2 of Patent Document 1 disclose a doping device comprising a container body having a container body main body and a discharge tube, and an outer cylinder body that houses the container body and has an open lower end. When the doping device is lowered to near the surface of the silicon melt, solid arsenic (dopant) contained in the container body sublimes 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 discharge tube and sprayed onto the silicon melt, a portion of the dopant contained in the dopant gas dissolves in the silicon melt, adding the dopant to the silicon melt. Meanwhile, a portion of the dopant that does not dissolve in the silicon melt becomes dopant vapor. The remaining portion of the dopant that does not dissolve in the silicon melt reacts with the silicon melt to become amorphous vapor. While a downward gas flow occurs outside the outer cylinder, an upward gas flow occurs near the side of the outer cylinder. When the dopant vapor and amorphous vapor (hereinafter collectively referred to as "vapor") rise due to this upward gas flow, they may adhere to the inside of the silicon single crystal manufacturing equipment and solidify. If this solidified material falls into the silicon melt, there is a risk of dislocations occurring in the silicon single crystal.

[0004] On the other hand, Figures 3(A) and 3(B) of Patent Document 1 disclose a configuration in which an outwardly extending skirt member is provided at the lower end of an outer cylinder to increase the contact area between the dopant gas and the silicon melt surface. Figure 5 of Patent Document 2 discloses a doping device including an inner tube and an outer cylinder having the same functions as the container body and outer cylinder of Patent Document 1, respectively. A heat shield plate extending outward is provided on the side of the outer cylinder to prevent radiant heat from the silicon melt from irradiating the container section containing the dopant. Although the skirt member of Patent Document 1 or the heat shield plate of Patent Document 2 do not have the original function described above, they may be able to suppress the rise of vapor near the outer cylinder or the side of the outer cylinder.

[0005] JP 2001-342094 A JP 2008-024547 A

[0006] However, in the configuration shown in Fig. 5 of Patent Document 2, the heat shield is positioned below the lower end of the shield during dopant addition, which increases the flow rate of vapor flowing between the heat shield and the silicon melt, potentially causing rippling of the silicon melt. In this case, if the silicon melt adheres to the shield and solidifies, and this solidified material falls into the silicon melt, there is a risk of dislocations in the silicon single crystal. Furthermore, Patent Document 1 does not disclose the positional relationship between the skirt member and the shield. However, as described above, if the vapor flowing between the skirt member and the silicon melt during dopant addition causes rippling of the silicon melt, and the silicon melt adheres to the shield and solidifies, and this solidified material falls into the silicon melt, there is a risk of dislocations in the silicon single crystal.

[0007] An object of the present invention is to provide a dopant addition device, a dopant addition method, and a silicon single crystal manufacturing method that can suppress the formation of dislocations in the silicon single crystal.

[0008] The dopant addition device of the present invention is a dopant addition device that adds a volatile dopant to a silicon melt, and includes a dopant storage section and an outer cylinder. The dopant storage section is configured to store the dopant and to release dopant gas generated by sublimation of the dopant. The outer cylinder is formed in a cylindrical shape with an open lower end and has the dopant storage section provided inside. The outer cylinder also includes an outer cylinder main body that causes the dopant gas to flow out from the lower end and spray it onto the silicon melt, and a shielding plate that protrudes in a brim-like shape from the outer cylinder main body. The shielding plate is positioned above the lower end of a shield that surrounds the silicon single crystal pulled up from the silicon melt when the dopant is added.

[0009] In the dopant adding device of the present invention, it is preferable that the outer cylinder body is formed in a cylindrical shape with the lower end open, the shielding plate is formed in an annular plate shape, and is positioned above the lower end of the cylindrical or truncated conical shield when adding the dopant, and is provided so that the porosity R obtained from the following formula (1) is 69% or less. ２ -(B + 2 × C) ２ ) / A ２ × 100 (1) A: inner diameter of the lower end of the shield B: outer diameter of the outer cylinder body C: distance from the side surface of the outer cylinder body to the protruding tip of the shielding plate when the outer cylinder is viewed from above the dopant addition device

[0010] In the dopant addition device of the present invention, the shielding plate is preferably provided so that the void ratio R is 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 which the dopant is added to the silicon melt by lowering the above-mentioned dopant addition device so that the shielding plate is positioned above the lower end of the shield while an inert gas is flowing downward within a shield surrounding a silicon single crystal being pulled up from the silicon melt.

[0012] In the dopant addition method of the present invention, it is preferable to add the dopant to the silicon melt using the dopant addition device in which the annular plate-shaped shielding plate is provided at the lower end of the outer cylinder body, with the distance from the lower end of the outer cylinder to the surface of the silicon melt being 30 mm or more.

[0013] In the dopant adding method of the present invention, it is preferable that the dopant is added to the silicon melt in a state where the distance from the lower end of the outer cylinder to the surface of the silicon melt is 60 mm or less.

[0014] In the method for producing a silicon single crystal of the present invention, a silicon single crystal is pulled from a silicon melt to which a volatile dopant has been added by the above-described dopant addition method.

[0015] 2A is a schematic diagram showing the general configuration of a silicon single crystal manufacturing apparatus according to an embodiment. FIG. 2B is a longitudinal sectional view showing the general configuration of a dopant addition device according to an embodiment. FIG. 2C is a transverse sectional view taken along line IIB-IIB of FIG. 2A. FIG. 2D is an explanatory diagram of a dopant addition process using a dopant addition device according to an embodiment. FIG. 2E is an explanatory diagram of a dopant addition process using a dopant addition device not provided with a shielding plate. FIG. 2F is a graph showing the relationship between the presence or absence of a shielding plate in the dopant addition device, the gas flow between the outer cylinder body and the shield of the dopant addition device, and the porosity in Experimental Example 1 of the embodiment.

[0016] [Embodiment] <Configuration of Silicon Single Crystal Manufacturing Apparatus> First, the configuration of a silicon single crystal manufacturing apparatus according to one embodiment of the present invention will be described. The silicon single crystal manufacturing apparatus 1 shown in Figure 1 uses the Czochralski method to manufacture silicon single crystals SM doped with a volatile dopant. Examples of volatile dopants include arsenic and red phosphorus. The silicon single crystal manufacturing apparatus 1 includes a chamber 11, a crucible 12, a heater 13, a heat-retaining tube 14, a shield 15, and a rectifier 16.

[0017] The chamber 11 includes a main chamber 111 formed in a cylindrical shape with a bottom, a top chamber 112 formed in a generally truncated cone shape with its lower end connected to the upper end of the main chamber 111, and a pull chamber 113 formed in a cylindrical shape with its lower end connected to the upper end of the top chamber 112. The main chamber 111 accommodates a crucible 12, a heater 13, a heat-retaining tube 14, a shield 15, and a flow rectifier 16. A gas inlet 113A is provided at the top of the pull chamber 113, through which an inert gas Gf, such as argon (Ar) gas, is introduced into the chamber 11. A gas outlet 111A is provided at the bottom of the main chamber 111, through which an internal gas Gn in the chamber 11 is discharged by driving a vacuum pump (not shown).

[0018] The crucible 12 is disposed in the main chamber 111 and stores a silicon melt MD to which a volatile dopant has been added. The crucible 12 is fixed to the upper end of a support shaft 121 that is rotatable and movable up and down. A pulling shaft 17 is disposed above the crucible 12 and coaxially with the support shaft 121. The pulling shaft 17 is formed of a wire or the like, and a seed crystal SC is attached to the lower end thereof.

[0019] The heater 13 is cylindrical and disposed so as to surround the crucible 12. The heater 13 generates heat to melt the silicon raw material in the crucible 12. The heat-retaining cylinder 14 is cylindrical and disposed so as to surround the heater 13. The shield 15 is generally cylindrical and made of a carbon material, but may also be formed in a generally truncated cone shape with a larger diameter at the top end than at the bottom end. The upper end of the shield 15 is supported by the main chamber 111 via multiple shield support members 114. The shield 15 is disposed so as to surround the silicon single crystal SM being pulled from the silicon melt MD, and blocks radiant heat from the heater 13 to the silicon single crystal SM. The rectifying unit 16 includes an upper rectifying cylinder 161 and a lower rectifying cylinder 162. The upper flow straightening cylinder 161 is cylindrically formed from a carbon material, extends downward from the lower end of the pull chamber 113, and is disposed so as to surround the silicon single crystal SM being pulled. The lower flow straightening cylinder 162 is cylindrically formed from quartz, extends upward from the lower end of the shield 15, and is disposed so as to surround the silicon single crystal SM being pulled, and the lower end of the upper flow straightening cylinder 161 is accommodated in the upper end.

[0020] <Configuration of Dopant Addition Apparatus> Next, a description will be given of the configuration of a dopant addition apparatus that adds a volatile dopant to the silicon melt MD stored in the crucible 12 of the silicon single crystal manufacturing apparatus 1. The dopant addition apparatus 2 shown in Figures 2A and 2B includes a dopant accommodation unit 21, an outer cylinder 22, and a support unit 23.

[0021] The dopant accommodation unit 21 is formed of quartz in the shape of a cylinder with an open top end and a closed bottom end. As indicated by the two-dot chain line, the dopant accommodation unit 21 is filled with a solid dopant (hereinafter, sometimes referred to as a "solid dopant") D, and is configured to release a dopant gas Gd generated by sublimation of the solid dopant D from the opening at the top end. The opening for releasing the dopant gas Gd may be provided on a side surface of the dopant accommodation unit 21.

[0022] The outer cylinder 22 includes an outer cylinder main body 221 and a shielding plate 222, each made of quartz. The outer cylinder main body 221 is formed in a cylindrical shape with an open lower end and a closed upper end. The dopant accommodating section 21 is provided inside the outer cylinder main body 221, and the dopant gas Gd released from the dopant accommodating section 21 flows out from the lower end and is sprayed onto the silicon melt MD. The shielding plate 222 is formed in a ring-like plate shape that protrudes from the lower end of the outer cylinder main body 221 in a direction perpendicular to the central axis of the outer cylinder main body 221. In other words, when the outer cylinder 22 is positioned so that the central axis of the outer cylinder main body 221 is horizontal to the vertical direction, the shielding plate 222 is formed in a ring-like plate shape that protrudes horizontally from the outer cylinder main body 221.

[0023] The support portion 23 includes four supported members 231 and four receiving members 232, each made of a carbon material. The supported members 231 are provided on the outer peripheral surface of the dopant accommodating portion 21 at equal intervals along the circumferential direction thereof. The receiving members 232 are provided on the inner peripheral surface of the outer cylinder body 221 at equal intervals along the circumferential direction thereof. The supported members 231 fit into grooves formed on the upper surface of the receiving members 232, thereby supporting the dopant accommodating portion 21 within the outer cylinder 22. The dopant gas Gd released from the dopant accommodating portion 21 passes through a space between the dopant accommodating portion 21 and the outer cylinder body 221 where the supported members 231 and the receiving members 232 are not located, and flows out from the lower end of the outer cylinder 22.

[0024] The dopant adding device 2 configured as described above is disposed in the chamber 11 so that, when dopant is added to the silicon melt MD, the central axes of the outer cylinder body 221 and the shield 15 overlap, the shielding plate 222 is positioned above the lower end of the shield 15, and the distance H from the lower end of the outer cylinder 22 to the surface of the silicon melt MD (hereinafter sometimes referred to as the "outer cylinder-melt distance") is 30 mm to 60 mm, as shown in Figure 3. The shielding plate 222 of the dopant adding device 2 is disposed so that, with the dopant adding device 2 disposed in this manner, the porosity R obtained from the following formula (1) is 49% to 69%. R (%) = (A ２ -(B + 2 × C) ２) / A ２ ×100 (1) A: inner diameter of the lower end of the shield 15 B: outer diameter of the outer cylinder body 221 C: distance from the side surface of the outer cylinder body 221 to the protruding tip of the shielding plate 222 when the outer cylinder 22 is viewed from above the dopant addition device

[0025] <Method for Producing Silicon Single Crystal> Next, a method for producing a silicon single crystal SM will be described. The method for producing a silicon single crystal SM includes a silicon melt producing step, a dopant adding step, and a pulling step.

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

[0027] The dopant adding step includes the dopant adding method of the present invention, and adds a volatile dopant to the silicon melt MD generated in the silicon melt generating step using the dopant adding device 2. Here, to explain the reason for providing the shielding plate 222 in the dopant adding device 2, the dopant adding step will be described in the case of using a dopant adding device 3 in which the shielding plate 222 is not provided on the outer cylinder main body 221, as shown in Figure 4.

[0028] In the dopant addition process using the dopant addition device 3, the dopant addition device 3 attached to the pulling shaft 17 is lowered to the position shown in FIG. 4 while the flow rate of the inert gas Gf downward within the chamber 11 and the furnace pressure are controlled to predetermined states. The height position of the lower end of the outer cylinder body 221 of the dopant addition device 3 relative to the lower end of the shield 15 is the same as the height position of the lower end of the outer cylinder body 221 of the dopant addition device 2 shown in FIG. 3. The solid dopant D loaded in the dopant accommodation unit 21 is sublimated by the radiant heat of the silicon melt MD to become dopant gas Gd. The dopant gas Gd is sprayed onto the silicon melt MD from a position separated from the silicon melt MD through the opening at the upper end of the dopant accommodation unit 21, the space between the dopant accommodation unit 21 and the outer cylinder body 221, and the opening at the lower end of the outer cylinder body 221.

[0029] When the dopant gas Gd is sprayed onto the silicon melt MD, as described above, the dopant is added to the silicon melt MD, and dopant vapor Vd and amorphous vapor Va (hereinafter, these may be collectively referred to as "vapors Vd, Va") are generated. Then, in the region between the outer cylinder main body 221 and the shield 15 (flow rectifying portion 16), an upward gas flow is generated in the region on the outer cylinder main body 221 side, and a downward gas flow is generated in the region on the shield 15 side.

[0030] A portion of the vapors Vd and Va flows, along with the downward gas flow, between the lower end of the shield 15 and the silicon melt MD, and between the side surface of the shield 15 and the crucible 12, together with the inert gas Gf, and is discharged from the chamber 11 as the internal gas Gn. Meanwhile, the remainder of the vapors Vd and Va rises along with the upward gas flow, and may adhere to the rectifying section 16 or the pull chamber 113 and solidify. If this solidified material falls into the silicon melt MD, there is a risk of dislocations occurring in the silicon single crystal SM. In order to suppress the occurrence of dislocations in the silicon single crystal SM, a dopant addition device 2 provided with a shielding plate 222 is used in the dopant addition step.

[0031] In the dopant addition process using the dopant addition device 2, the dopant addition device 2 is lowered to the position shown in FIG. 3 , i.e., a position where the outer cylinder-to-melt distance H is 30 mm to 60 mm, and then stopped. The dopant is added to the silicon melt MD by spraying dopant gas Gd onto the silicon melt MD. At this time, upward flows of vapors Vd and Va are generated. However, the upward movement of the vapors Vd and Va is suppressed by the shield plate 222. Instead of flowing between the outer cylinder body 221 and the shield 15, the vapors Vd and Va flow between the silicon melt MD and the shield plate 222, away from the center of the dopant addition device 2. The vapors Vd and Va then merge with the downward flowing inert gas Gf and are discharged from the chamber 11 as the internal gas Gn, as described above. After all of the solid dopant D in the dopant accommodation section 21 has sublimated and a predetermined time has elapsed, the dopant addition device 2 is raised and removed from the chamber 11.

[0032] As described above, by suppressing the increase in the vapors Vd and Va using the shielding plate 222, dislocations in the silicon single crystal SM due to the falling of solidified vapors Vd and Va can be suppressed. Furthermore, suppressing the increase in the vapors Vd and Va can suppress a decrease in the amount of dopant dissolved in the silicon melt MD, thereby increasing the possibility of obtaining a silicon single crystal SM having the desired resistivity. In particular, because the shielding plate 222 is provided so that the porosity R is 69% or less, the increase in the vapors Vd and Va can be reliably suppressed. Furthermore, because the shielding plate 222 is provided so that the porosity R is 49% or more, the shielding plate 222 can be prevented from colliding with the shield 15 or the rectifying unit 16 even if the dopant addition device 2 shakes.

[0033] Furthermore, the dopant is added to the silicon melt MD in a state in which the shielding plate 222 is positioned above the lower end of the shield 15. Therefore, compared to when the shielding plate 222 is positioned below the lower end of the shield 15, the flow rate of the vapors Vd and Va flowing between the shielding plate 222 and the silicon melt MD can be slowed down, and rippling of the silicon melt MD can be suppressed. Therefore, the silicon melt MD can be suppressed from adhering to the shield 15 and solidifying, and dislocations in the silicon single crystal SM caused by the falling of the solidified material can be suppressed.

[0034] Furthermore, the dopant is added to the silicon melt MD when the outer-melt-to-outer-cylinder distance H is 30 mm or more. If the outer-melt-to-outer-cylinder distance H is less than 30 mm, the dopant sublimation rate becomes too fast due to the radiant heat of the silicon melt MD, which may result in a large amount of dopant residue being generated between the dopant addition device 2 and the silicon melt MD when the surface of the silicon melt MD is cooled. This residue dissolves to some extent in the silicon melt MD. However, if some of the residue does not dissolve and remains on the surface of the silicon melt MD, this residue may cause dislocations in the silicon single crystal SM. By adding the dopant to the silicon melt MD when the outer-melt-to-outer-cylinder distance H is 30 mm or more, as in this embodiment, the dopant sublimation rate can be prevented from becoming too fast. As a result, the generation of dopant residue can be suppressed, and dislocations in the silicon single crystal SM caused by this residue can be suppressed.

[0035] Furthermore, the dopant is added to the silicon melt MD when the outer-melt-to-outer-cylinder distance H is 60 mm or less. If the outer-melt-to-outer-cylinder distance H exceeds 60 mm, the dopant addition device 2 is too far from the silicon melt MD, causing the temperature of the dopant gas generated and elevated in the dopant accommodation unit 21 to fall below the sublimation temperature, potentially resulting in the dopant returning to the dopant accommodation unit 21 in the form of a solid dopant. As a result, the amount of dopant added to the silicon melt MD may be reduced, potentially preventing a silicon single crystal SM having the desired resistivity from being obtained. By adding the dopant to the silicon melt MD when the outer-melt-to-outer-cylinder distance H is 60 mm or less, the temperature of the dopant gas generated and elevated in the dopant accommodation unit 21 may be prevented from rising too high above the sublimation temperature, preventing the sublimation rate from becoming too fast. As a result, the likelihood of obtaining a silicon single crystal SM having the desired resistivity may be increased.

[0036] In the pulling process, 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 seed crystal SC is pulled up while rotating the crucible 12 and the pulling shaft 17 in a predetermined direction, thereby pulling up the silicon single crystal SM.

[0037] [Modifications] Although an embodiment of the present invention has been described above in detail 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.

[0038] The shielding plate 222 may be formed so that the porosity R exceeds 69% or may be formed so that the porosity R is less than 49%. A dopant may be added to the silicon melt MD when the outer cylinder-to-melt distance H exceeds 60 mm or is less than 30 mm.

[0039] While the dopant accommodating portion 21 and the outer cylinder 22 are illustrated as being made of quartz, at least one of them may be formed of a material other than quartz, such as SiC, C, or other ceramics. While the outer cylinder body 221 is illustrated as being cylindrical with a bottom, the outer cylinder body 221 may have a shape other than a cylinder, such as a rectangular cylinder with a bottom or a truncated cone. While the shielding plate 222 protruding like a brim from the lower end of the outer cylinder body 221 is illustrated, the protruding position of the shielding plate 222 may be a predetermined distance above the lower end of the outer cylinder body 221. While the shielding plate 222 protruding in a direction perpendicular to the central axis of the outer cylinder body 221 is illustrated, the protruding direction of the shielding plate 222 may be inclined relative to the central axis of the outer cylinder body 221, i.e., diagonally upward or diagonally downward.

[0040] Next, examples of the present invention will be described, but the present invention is not limited to these examples.

[0041] [Experimental Example 1] In Experimental Example 1, a simulation was performed to examine the relationship between the presence or absence of a shield plate in the dopant addition device, the gas flow between the outer cylinder body and the shield of the dopant addition device, and the porosity. In this 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 to be produced was 300 mm.

[0042] <Experimental Method> (Comparative Example 1) As the silicon single crystal manufacturing apparatus of Comparative Example 1, a silicon single crystal manufacturing apparatus 1 as shown in Fig. 1 was set. Furthermore, as the dopant addition apparatus, a dopant addition apparatus 3 without a shielding plate 222 as shown in Fig. 4 was set. The shapes of the outer cylinder body 221 and the shield 15 of the dopant addition apparatus 3 were set to have a porosity R of 89%. Furthermore, the values ​​of each parameter were set as follows: - Outer cylinder-to-melt distance H: 60 mm - Downward flow rate of inert gas Gf: 0.69 m / s Then, the gas flow at positions corresponding to each porosity R between the outer cylinder body 221 and the shield 15 was calculated.

[0043] Example 1 The silicon single crystal manufacturing apparatus of Example 1 was the same as that of Comparative Example 1. As the dopant addition apparatus of Example 1, a dopant addition apparatus 2 equipped with a shielding plate 222 in the shape of an annular plate, as shown in FIG. 3, was set. The protrusion dimension of the shielding plate 222 from the outer edge of the outer cylinder main body 221 was set to a size that would result in a porosity R of 49%. In addition, the values ​​of each parameter were set to the same values ​​as those of Comparative Example 1. Then, the gas flow at positions corresponding to each porosity R between the outer cylinder main body 221 and the shield 15 was calculated.

[0044] <Experimental Results and Evaluation> The calculation results for Comparative Example 1 are shown by dotted lines in Figure 5, and the calculation results for Example 1 are shown by solid lines. In Figure 5, a positive value for the gas flow rate indicates that the gas flows upward between the outer cylinder body 221 and the shield 15, while a negative value indicates that the gas does not pass between the outer cylinder body 221 and the shield 15 but flows from below the shield 15 to between the crucible 12 and the shield 15. In Comparative Example 1, an upward gas flow occurred at positions where the porosity R exceeded 69%, and a downward gas flow occurred at positions where the porosity R was 69% or less. On the other hand, in Example 1, no gas flow occurred at positions where the porosity R exceeded 49% where the shield plate 222 was present, and a downward gas flow occurred at positions where the porosity R was 49% or less. From these results, it was confirmed that by providing the shielding plate 222 in the dopant addition device 2 so that the porosity R is 69% or less, it is possible to suppress the upward flow of gas between the outer cylinder main body 221 and the shield 15. Since such an upward flow of gas can be suppressed, it is thought that the increase in the vapors Vd and Va can be suppressed, and dislocations in the silicon single crystal SM due to the solidification of the vapors Vd and Va can be suppressed.

[0045] [Experimental Example 2] In Experimental Example 2, an experiment was conducted to examine the relationship between the presence or absence of a shielding plate in a dopant addition device and the occurrence of dislocations in silicon single crystals.

[0046] <Experimental Method> (Comparative Example 2) As the silicon single crystal manufacturing apparatus and dopant addition apparatus of Comparative Example 2, a silicon single crystal manufacturing apparatus 1 and a dopant addition apparatus 3 (dopant addition apparatus 3 without a shielding plate 222) having the same configuration as those of Comparative Example 1 were prepared. The values ​​of each parameter were set as follows: Outer cylinder-melt distance H: 60 mm Downward flow rate of inert gas Gf: 0.69 m / s Then, 46 silicon single crystals SM were manufactured (pulled) using the same method as the silicon single crystal SM manufacturing method of the above embodiment. During the pulling of the silicon single crystal SM, the occurrence of dislocations was confirmed by photographing images of the silicon single crystal SM. If dislocations occurred, the pulling of the silicon single crystal SM was stopped and melt-back was performed, in which the silicon single crystal SM was dissolved in the silicon melt MD. Thereafter, the pulling and melt-back of the silicon single crystal SM were repeated until a silicon single crystal SM without dislocations was produced.

[0047] (Example 2) As a dopant addition device of Example 2, a dopant addition device 2 (a dopant addition device 2 provided with a shielding plate 222 such that the porosity R was 49%) having the same shape as that of Example 1 was prepared. Then, using the same silicon single crystal manufacturing apparatus 1 and manufacturing method as those of Comparative Example 2, 18 silicon single crystals SM were pulled.

[0048] <Experimental Results and Evaluation> Table 1 shows the average number of times dislocations occurred in Comparative Example 2 and Example 2 (average number of times dislocations occurred until one piece was completely pulled).

[0049]

[0050] As shown in Table 1, the average number of dislocations occurring was 2.1 in Comparative Example 2, while it was 1.4 in Example 2. From these results, it was confirmed that the occurrence of dislocations can be suppressed by producing silicon single crystal SM using a dopant addition device 2 that can suppress the upward gas flow between the outer cylinder body 221 and the shield 15.

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

[0052] <Experimental Method> (Comparative Example 3) As a silicon single crystal manufacturing apparatus and a dopant addition apparatus of Comparative Example 3, a silicon single crystal manufacturing apparatus 1 and a dopant addition apparatus 3 having the same shapes as those of Comparative Example 2 were prepared. Then, using the same manufacturing conditions and manufacturing method as those of Comparative Example 2, six silicon single crystals SM were pulled so that the target resistivity at a predetermined position of the straight body portion was 2.5 mΩ cm.

[0053] Example 3 As a silicon single crystal manufacturing apparatus and a dopant addition apparatus of Example 3, a silicon single crystal manufacturing apparatus 1 and a dopant addition apparatus 2 having the same shapes as those of Example 2 were prepared. Then, using the same manufacturing conditions and manufacturing method as those of Comparative Example 3, three silicon single crystals SM having the same target resistivity at a predetermined position of the straight body portion as those of Comparative Example 3 were pulled.

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

[0055]

[0056] As shown in Table 2, the difference between the average resistivity and the target resistivity in Example 3 was smaller than that in Comparative Example 3. From these results, it was confirmed that the increase in vapors Vd and Va was suppressed by the shielding plate 222, thereby suppressing the decrease in the amount of dopant dissolved in the silicon melt MD, and that a silicon single crystal SM having the desired resistivity could be obtained.

[0057] Experimental Example 4 In Experimental Example 4, an experiment was conducted to examine the relationship between the outer cylinder-melt distance and the occurrence of dislocations in silicon single crystals.

[0058] <Experimental Method> (Comparative Example 4) As a silicon single crystal manufacturing apparatus and a dopant addition apparatus of Comparative Example 4, a silicon single crystal manufacturing apparatus 1 and a dopant addition apparatus 2 having the same shapes as those of Example 2 were prepared. Then, three silicon single crystals SM were pulled using the same manufacturing method as in Example 2, except that the outer cylinder-to-melt distance H was set to 1 mm.

[0059] (Examples 4-1, 4-2, 4-3) As shown in Table 3, in Examples 4-1, 4-2, and 4-3, two, two, and three silicon single crystals SM were pulled, respectively, using the same silicon single crystal manufacturing apparatus, dopant addition apparatus, and manufacturing method as in Comparative Example 4, except that the outer cylinder-to-melt distance H was set to 30 mm, 55 mm, and 60 mm, respectively.

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

[0061]

[0062] As shown in Table 3, the average occurrence of dislocations decreased as the outer cylinder-melt distance H increased. From these results, it was confirmed that by setting the outer cylinder-melt distance H to 30 mm or more, it is possible to suppress rippling of the silicon melt MD and to suppress the occurrence of dislocations in the silicon single crystal SM that occurs when the silicon melt MD adheres to the shield 15 and solidifies.

[0063] 2...dopant addition device, 15...shield, 21...dopant storage section, 22...outer cylinder, 221...outer cylinder main body, 222...shielding plate, Gd...dopant gas, Gf...inert gas, MD...silicon melt, SM...silicon single crystal.

Claims

1. A dopant adding device for adding a volatile dopant to a silicon melt, comprising: a dopant accommodating section; and an outer cylinder, wherein the dopant accommodating section is configured to accommodate the dopant and to release a dopant gas generated when the dopant sublimes, and the outer cylinder is formed in a cylindrical shape with an open lower end, and the dopant accommodating section is provided inside, and the outer cylinder comprises: an outer cylinder main body that causes the dopant gas to flow out from the lower end and spray it onto the silicon melt, and a shielding plate that protrudes like a brim from the outer cylinder main body, and wherein the shielding plate is provided so as to be positioned above the lower end of a shield that surrounds a silicon single crystal pulled up from the silicon melt when the dopant is added.

2. A dopant adding device according to claim 1, wherein the outer cylinder body is formed in a cylindrical shape with the lower end open, and the shielding plate is formed in an annular plate shape and is positioned above the lower end of the cylindrical or truncated conical shield when the dopant is added, and is provided so that the void ratio R obtained from the following formula (1) is 69% or less. R(%)=(A ２ -(B+2×C) ２ ) / A ２ ×100 ... (1) A: inner diameter of the lower end of the shield B: outer diameter of the outer cylinder body C: distance from the side surface of the outer cylinder body to the protruding tip of the shielding plate when the outer cylinder is viewed from above the dopant addition device 3. A dopant adding device as described in claim 2, wherein the shielding plate is provided so that the void ratio R is 49% or more.

4. A dopant addition method for adding a volatile dopant to a silicon melt, comprising: flowing an inert gas downward within a shield surrounding a silicon single crystal being pulled up from the silicon melt; and lowering a dopant addition device as described in any one of claims 1 to 3 so that the shielding plate is positioned above the lower end of the shield, thereby adding the dopant to the silicon melt.

5. A dopant adding method as described in claim 4, comprising the steps of: adding the dopant to the silicon melt using the dopant adding device in which the annular shielding plate is provided at the lower end of the outer tube body, with the distance from the lower end of the outer tube to the surface of the silicon melt being 30 mm or more.

6. A method for adding a dopant according to claim 5, wherein the dopant is added to the silicon melt in a state where the distance from the lower end of the outer cylinder to the surface of the silicon melt is 60 mm or less.

7. A method for producing a silicon single crystal, comprising pulling a silicon single crystal from a silicon melt to which a volatile dopant has been added by the dopant addition method according to claim 4.

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