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

Abstract

To provide a dopant addition device capable of preventing a silicon single crystal from being dislocated.SOLUTION: A dopant addition device for adding a volatile dopant to a silicon melt includes a dopant storage part and an outer cylinder. The dopant storage part is constituted so as to store the dopant and discharge dopant gas generated by sublimating the dopant. The outer cylinder includes: an outer cylinder main body formed in a cylindrical shape having an open lower end, including the dopant storage part in the inside and capable of discharging the dopant gas from the lower end to spray the dopant gas on the silicon melt; and a shield plate projected in a flange shape from the outer cylinder main body. The shield plate is provided so as to be positioned above the lower end of a shield surrounding a silicon single crystal pulled up from the silicon melt when adding the dopant.SELECTED DRAWING: Figure 3

Description

Technical Field

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

Background Art

[0002] Conventionally, in manufacturing a silicon single crystal, as a method of adding a volatile dopant to a silicon melt, a method 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] FIGS. 1 and 2 of Patent Document 1 disclose a doping device including a container body having a container body main body and a discharge pipe, and an outer cylindrical body that houses the container body and has an opening at the lower end surface. When the doping device is lowered to near the surface of the silicon melt, solid arsenic (dopant) accommodated in the container body main body sublimates due to the radiant heat of the silicon melt to generate arsenic gas (dopant gas). When the dopant gas is discharged from the lower end of the discharge pipe and sprayed onto the silicon melt, a part of the dopant contained in the dopant gas dissolves in the silicon melt, and the dopant is added to the silicon melt. On the other hand, a part of the dopant that did not melt in the silicon melt becomes a dopant vapor. Further, the remaining part of the dopant that did not melt in the silicon melt reacts with the silicon melt to become an amorphous vapor. Although a downward gas flow is generated outside the outer cylindrical body, an upward gas flow is generated near the side surface of the outer cylindrical body. When the dopant vapor and the amorphous vapor (hereinafter sometimes collectively referred to as "vapor") rise along with this upward gas flow, they may adhere to the inside of the silicon single crystal manufacturing apparatus and solidify. If this solidified material falls onto the silicon melt, the silicon single crystal may be dislocated.

[0004] On the other hand, Patent Document 1 discloses a configuration in which a skirt member extending outward is provided at the lower end of the outer cylinder in order to increase the contact area between the dopant gas and the surface of the silicon melt. FIG. 5 of Patent Document 2 discloses a doping apparatus including an inner tube and an outer tube having the same functions as the container body and the outer cylinder of Patent Document 1, respectively. A heat shield plate extending outward is provided on the side surface of the outer tube to prevent irradiation of radiant heat of the silicon melt to the accommodation portion for accommodating the dopant. Although the skirt member of Patent Document 1 or the heat shield plate of Patent Document 2 is not the original function described above, it may be possible to suppress the rise of the paper in the vicinity of the side surface of the outer cylinder or the outer tube.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, in the configuration described in FIG. 5 of Patent Document 2, since the heat shield plate is located below the lower end of the shield at the time of adding the dopant, the flow velocity of the vapor flowing between the heat shield plate and the silicon melt becomes high, and the silicon melt may be wavy. In this case, if the silicon melt adheres to the shield and solidifies, and this solidified product falls onto the silicon melt, there is a risk that the silicon single crystal may be dislocated. Further, although Patent Document 1 does not disclose the positional relationship between the skirt member and the shield, as described above, when the dopant is added, the silicon melt is wavy due to the vapor flowing between the skirt member and the silicon melt, and the silicon melt adheres to the shield and solidifies. If this solidified product falls onto the silicon melt, there is a risk that the silicon single crystal may be dislocated.

[0007] An 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 generation of dislocations in the silicon single crystal.

Means for Solving the Problems

[0008] The dopant addition device of the present invention is a dopant addition device for adding a volatile dopant to a silicon melt, and includes a dopant storage part and an outer cylinder. The dopant storage part stores the dopant and is configured 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 the dopant storage part is provided inside. The outer cylinder includes an outer cylinder body configured to allow the dopant gas to flow out from the lower end and spray onto the silicon melt, and a shielding plate protruding in a flange shape from the outer cylinder body. The shielding plate is provided so as to be located above the lower end of a shield surrounding a silicon single crystal pulled up from the silicon melt when adding the dopant.

[0009] In the dopant addition device of the present invention, the outer cylinder body is formed in a cylindrical shape with an open lower end, the shielding plate is formed in an annular plate shape, and when adding the dopant, it is located above the lower end of the shield having a cylindrical or frustum-shaped cylinder, and is preferably provided so that the porosity 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 viewing the outer cylinder 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 porosity 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, and in a state where an inert gas is flowing downward in a shield surrounding a silicon single crystal pulled up from the silicon melt, the above-described dopant addition device is lowered so that the shielding plate is positioned above the lower end of the shield, whereby the dopant is added to the silicon melt.

[0012] In the dopant addition method of the present invention, using the dopant addition device in which the annular plate-shaped shielding plate is provided at the lower end of the outer cylinder body, 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 30 mm or more. This is preferable.

[0013] In the dopant addition 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] The method for producing a silicon single crystal of the present invention pulls up a silicon single crystal from a silicon melt to which a volatile dopant has been added by the above-described dopant addition method.

Brief Description of the Drawings

[0015]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Mode for Carrying Out the Invention

[0016] [Embodiment] <Configuration of Silicon Single Crystal Manufacturing Apparatus> First, the configuration of a silicon single crystal manufacturing apparatus according to an embodiment of the present invention will be described. The silicon single crystal manufacturing apparatus 1 shown in FIG. 1 manufactures a silicon single crystal SM to which a volatile dopant is added using the Czochralski method. Examples of the volatile dopant include arsenic and red phosphorus. The silicon single crystal manufacturing apparatus 1 includes a chamber 11, a crucible 12, a heater 13, a heat insulating cylinder 14, a shield 15, and a rectifying unit 16.

[0017] The chamber 11 includes a main chamber 111 formed in a bottomed cylindrical shape, a top chamber 112 formed in a substantially frustum-shaped cylindrical shape and having its lower end connected to the upper end of the main chamber 111, and a pull chamber 113 formed in a cylindrical shape and having its lower end connected to the upper end of the top chamber 112. The main chamber 111 houses the crucible 12, the heater 13, the heat insulating cylinder 14, the shield 15, and the rectifying unit 16. At the upper part of the pull chamber 113, a gas inlet 113A for introducing an inert gas Gf such as argon (Ar) gas into the chamber 11 is provided. At the lower part of the main chamber 111, a gas outlet 111A for discharging the internal gas Gn in the chamber 11 is provided 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 is added. The crucible 12 is fixed to the upper end portion of a support shaft 121 that can rotate and move up and down. Above the crucible 12, a pulling shaft 17 is disposed 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 formed in a cylindrical shape and is arranged to surround the crucible 12. By generating heat, the heater 13 melts the silicon raw material in the crucible 12. The heat-insulating cylinder 14 is formed in a cylindrical shape and is arranged to surround the heater 13. The shield 15 is formed in a substantially cylindrical shape from a carbon material, but may be formed in a substantially frustum-shaped cylindrical shape with the diameter of the upper end smaller than that of the lower end. The upper end portion of the shield 15 is supported by the main chamber 111 via a plurality of shield support members 114. The shield 15 is arranged to surround the silicon single crystal SM being pulled up from the silicon melt MD and blocks the radiant heat from the heater 13 to the silicon single crystal SM. The rectifying section 16 includes an upper rectifying cylinder 161 and a lower rectifying cylinder 162. The upper rectifying cylinder 161 is formed in a cylindrical shape from a carbon material, extends downward from a portion on the lower end side of the pull chamber 113, and is arranged to surround the silicon single crystal SM being pulled up. The lower rectifying cylinder 162 is formed in a cylindrical shape from quartz, extends upward from a portion on the lower end side of the shield 15, and is arranged to surround the silicon single crystal SM being pulled up and to accommodate the lower end side portion of the upper rectifying cylinder 161 on the upper end side.

[0020] <Configuration of Dopant Addition Device> Next, the configuration of a dopant addition device that adds a volatile dopant to the silicon melt MD stored in the crucible 12 of the silicon single crystal manufacturing apparatus 1 will be described. The dopant addition device 2 shown in FIGS. 2(A) and 2(B) includes a dopant storage section 21, an outer cylinder 22, and a support section 23.

[0021] The dopant storage part 21 is formed in a bottomed cylindrical shape with an open upper end and a closed lower end made of quartz. As shown by the two-dot chain line, the dopant storage part 21 is loaded with a solid dopant (hereinafter sometimes referred to as "solid dopant") D inside, and is configured to release dopant gas Gd generated by sublimation of the solid dopant D from the upper opening. Note that the opening for releasing the dopant gas Gd may be provided on the side surface of the dopant storage part 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 bottomed cylindrical shape with an open lower end and a closed upper end. The outer cylinder main body 221 is provided with the dopant storage part 21 inside, and the dopant gas Gd released from the dopant storage part 21 is caused to flow out from its lower end and sprayed onto the silicon melt MD. The shielding plate 222 is formed in an annular plate shape protruding in a flange shape in a direction orthogonal to the central axis of the outer cylinder main body 221 from the lower end of the outer cylinder main body 221. That is, the shielding plate 222 is formed in an annular plate shape protruding in the horizontal direction from the outer cylinder main body 221 when the outer cylinder 22 is arranged such that the central axis of the outer cylinder main body 221 is horizontal with respect to the vertical direction.

[0023] The support part 23 includes four supported members 231 and receiving members 232 each made of a carbon material. Each supported member 231 is provided at equal intervals along the circumferential direction on the outer peripheral surface of the dopant storage part 21. Each receiving member 232 is provided at equal intervals along the circumferential direction on the inner peripheral surface of the outer cylinder main body 221. By fitting each supported member 231 into a groove formed on the upper surface of each receiving member 232, the dopant storage part 21 is supported inside the outer cylinder 22. The dopant gas Gd released from the dopant storage part 21 passes through the space where the supported members 231 and the receiving members 232 are not located between the dopant storage part 21 and the outer cylinder main body 221, and flows out from the lower end of the outer cylinder 22.

[0024] When adding a dopant to the silicon melt MD, as shown in FIG. 3, the dopant adding device 2 configured as described above is arranged in the chamber 11 such that the central axes of the outer cylinder main 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 "distance between the outer cylinder and the melt") is 30 mm or more and 60 mm or less. The shielding plate 222 of the dopant adding device 2 is provided such that the porosity R obtained from the following formula (1) is 49% or more and 69% or less in the state where the dopant adding device 2 is arranged as described above. 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 main body 221 C: Distance from the side surface of the outer cylinder main body 221 to the protruding tip of the shielding plate 222 when viewing the outer cylinder 22 from above the dopant adding device

[0025] <Method for manufacturing a silicon single crystal> Next, a method for manufacturing a silicon single crystal SM will be described. The method for manufacturing a silicon single crystal SM includes a silicon melt generation step, a dopant addition step, and a pulling-up step.

[0026] In the silicon melt generation 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 in the chamber 11 and the furnace internal pressure are controlled to a predetermined state. 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 addition step includes the dopant addition method of the present invention, and a volatile dopant is added to the silicon melt MD generated in the silicon melt generation step using the dopant adding device 2. Here, in order to explain the reason for providing the shielding plate 222 in the dopant addition device 2, the dopant addition process in the case of using a dopant addition device 3 in which the shielding plate 222 is not provided on the outer cylinder body 221 as shown in FIG. 4 will be described.

[0028] In the dopant addition process using the dopant addition device 3, with the flow rate of the inert gas Gf downward in the chamber 11 and the furnace pressure controlled to a predetermined state, the dopant addition device 3 attached to the lifting shaft 17 is lowered to the position shown in FIG. 4. The height position of the lower end of the outer cylinder body 221 of the dopant addition device 3 with respect 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 storage portion 21 sublimates due to the radiant heat of the silicon melt MD and becomes a dopant gas Gd. The dopant gas Gd is sprayed onto the silicon melt MD from a position away from the silicon melt MD through the opening at the upper end of the dopant storage portion 21, the space between the dopant storage portion 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 at the same time, a dopant vapor Vd and an amorphous vapor Va (hereinafter sometimes collectively referred to as "vapor Vd,Va") are generated. Then, in the region between the outer cylinder body 221 and the shield 15 (straightening portion 16), an upward gas flow occurs in the region on the outer cylinder body 221 side, and a downward gas flow occurs in the region on the shield 15 side.

[0030] A part of the vapor Vd,Va flows with the downward gas flow together with the inert gas Gf 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, and is discharged from the chamber 11 as the internal gas Gn. On the other hand, 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 drops onto the silicon melt MD, there is a risk that the silicon single crystal SM will become dislocated. In order to suppress such dislocation of 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 step using the dopant addition device 2, the dopant addition device 2 is lowered to the position shown in FIG. 3, that is, the position where the distance H between the outer cylinder and the melt is 30 mm or more and 60 mm or less, and is stationary, and the dopant gas Gd is sprayed onto the silicon melt MD to add the dopant to the silicon melt MD. At this time, an upward flow of vapors Vd and Va occurs, but the vapors Vd and Va are suppressed from rising by the shielding plate 222 and flow between the silicon melt MD and the shielding plate 222 away from the center of the dopant addition device 2 without flowing between the outer cylinder main body 221 and the shield 15. Then, it merges with the inert gas Gf flowing downward and is discharged from the chamber 11 as the internal gas Gn as described above. When all the solid dopant D in the dopant storage section 21 has sublimated and a predetermined time has elapsed, the dopant addition device 2 is raised and taken out of the chamber 11.

[0032] As described above, by suppressing the rise of the vapors Vd and Va by the shielding plate 222, it is possible to suppress the dislocation of the silicon single crystal SM caused by the fall of the solidified product of the vapors Vd and Va. In addition, since the rise of the vapors Vd and Va can be suppressed, it is possible to suppress a decrease in the melting amount of the dopant in the silicon melt MD, and the possibility of obtaining a silicon single crystal SM having a desired resistivity can be increased. In particular, since the shielding plate 222 is provided so that the porosity R is 69% or less, the rise of the vapors Vd and Va can be surely suppressed. In addition, since the shielding plate 222 is provided so that the porosity R is 49% or more, even if the dopant addition device 2 sways, it is possible to prevent the shielding plate 222 from colliding with the shield 15 or the rectifying section 16.

[0033] Also, while the shielding plate 222 is positioned above the lower end of the shield 15, a dopant is added to the silicon melt MD. Therefore, compared with the case where the shielding plate 222 is positioned below the lower end of the shield 15, the flow velocity of the vapors Vd, Va flowing between the shielding plate 222 and the silicon melt MD can be slowed down, and the undulation of the silicon melt MD can be suppressed. Accordingly, it is possible to suppress the adhesion and solidification of the silicon melt MD to the shield 15, and it is possible to suppress the dislocation of the silicon single crystal SM caused by the fall of the solidified product.

[0034] Also, while the distance H between the outer cylinder and the melt is 30 mm or more, a dopant is added to the silicon melt MD. Here, when the distance H between the outer cylinder and the melt is less than 30 mm, the sublimation rate of the dopant becomes too fast due to the radiant heat of the silicon melt MD. Therefore, when the surface of the silicon melt MD is cooled, there is a risk of generating a large amount of dopant residue between the dopant adding device 2 and the silicon melt MD. Such residue dissolves in the silicon melt MD to some extent. However, if a part of the residue remains on the surface of the silicon melt MD without dissolving, the silicon single crystal SM may be dislocated due to this residue. As in the present embodiment, by adding a dopant to the silicon melt MD while the distance H between the outer cylinder and the melt is 30 mm or more, it is possible to suppress the sublimation rate of the dopant from becoming too fast. As a result, the generation of dopant residue can be suppressed, and the dislocation of the silicon single crystal SM caused by this residue can be suppressed.

[0035] Also, while the distance H between the outer cylinder and the melt is 60 mm or less, a dopant is added to the silicon melt MD. Here, when the distance H between the outer cylinder and the melt exceeds 60 mm, the dopant addition device 2 is too far away from the silicon melt MD. As a result, the temperature of the dopant gas generated and rising in the dopant storage portion 21 becomes lower than the sublimation temperature, and there is a possibility that it will return to the dopant storage portion 21 in the state of solid dopant. Consequently, the amount of dopant added to the silicon melt MD may decrease, and there is a possibility that a silicon single crystal SM having a desired resistivity cannot be obtained. As in this embodiment, by adding a dopant to the silicon melt MD in a state where the distance H between the outer cylinder and the melt is 60 mm or less, it is possible to suppress the temperature of the dopant gas generated and rising in the dopant storage portion 21 from becoming too high above the sublimation temperature, and it is possible to suppress the sublimation rate from becoming too fast. As a result, the possibility of obtaining a silicon single crystal SM having a desired resistivity can be increased.

[0036] In the pulling-up process, the pulling-up 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-up shaft 17 in a predetermined direction, thereby pulling up the silicon single crystal SM.

[0037] [Modification Example] As described above, the embodiments of the present invention have been described in detail with reference to the drawings. However, the specific configuration is not limited to this embodiment, and various improvements and design changes within the scope not departing 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 to be less than 49%. The dopant may be added to the silicon melt MD in a state where the distance H between the outer cylinder and the melt exceeds 60 mm or is less than 30 mm.

[0039] Although the dopant storage portion 21 and the outer cylinder 22 made of quartz have been exemplified, at least one of them may be formed of a material other than quartz such as SiC, C, or other ceramics. Although a bottomed cylindrical outer cylinder body 221 has been exemplified, the outer cylinder body 221 may have a shape other than a cylindrical shape such as a bottomed rectangular tube shape or a truncated cone tube shape. Although a shielding plate 222 protruding in a flange shape from the lower end of the outer cylinder body 221 has been exemplified, the position where the shielding plate 222 protrudes may be at a predetermined distance above the lower end of the outer cylinder body 221. Although a shielding plate 222 protruding in a direction orthogonal to the central axis of the outer cylinder body 221 has been exemplified, the direction in which the shielding plate 222 protrudes may be a direction inclined with respect to the central axis of the outer cylinder body 221, that is, an obliquely upward direction or an obliquely downward direction.

Example

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

[0041] [Experimental Example 1] As Experimental Example 1, a simulation was conducted to examine 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 this Experimental Example 1 and Experimental Examples 2, 3, and 4 described later, the dopant is arsenic, and the diameter of the silicon single crystal SM to be manufactured is 300 mm.

[0042] <Experimental Method> (Comparative Example 1) As a silicon single crystal manufacturing apparatus of Comparative Example 1, a silicon single crystal manufacturing apparatus 1 as shown in FIG. 1 was set. Further, as a dopant addition device, a dopant addition device 3 not provided with 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 device 3 were set to a shape with a porosity R of 89%. Also, the values of each parameter were set as follows. · Distance H between the outer cylinder and the melt: 60 mm · Flow velocity of the inert gas Gf downward: 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) As the silicon single crystal manufacturing apparatus of Example 1, the same silicon single crystal manufacturing apparatus 1 as that of Comparative Example 1 was set. As the dopant adding apparatus of Example 1, as shown in FIG. 3, a dopant adding apparatus 2 having an annular plate-shaped shielding plate 222 was set. The protruding dimension from the outer edge of the outer cylinder main body 221 of the shielding plate 222 was set to a size such that the porosity R was 49%. Also, the values of each parameter were set to the same values as those of Comparative Example 1. Then, the gas flow at the position 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 of Comparative Example 1 are shown by a dotted line in FIG. 5, and the calculation results of Example 1 are shown by a solid line. In FIG. 5, when the gas flow velocity is a positive value, it indicates that the gas flows upward through between the outer cylinder main body 221 and the shield 15, and when it is a negative value, it indicates that the gas does not flow through between the outer cylinder main body 221 and the shield 15 and flows from below the shield 15 into the space 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 without an upward gas flow 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 shielding 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 to the dopant adding apparatus 2 so that the porosity R becomes 69% or less, the upward gas flow between the outer cylinder main body 221 and the shield 15 can be suppressed. Since such an upward gas flow can be suppressed, it is considered that the rise of the vapors Vd, Va can be suppressed and the dislocation generation in the silicon single crystal SM due to the solidified products of the vapors Vd, Va can be suppressed.

[0045] [Experimental Example 2] As Experimental Example 2, an experiment was conducted to investigate the relationship between the presence or absence of a shielding plate in the dopant adding apparatus and the occurrence of dislocation generation in the silicon single crystal.

[0046] <Experimental method> (Comparative Example 2) As the silicon single crystal manufacturing apparatus and the dopant addition apparatus of Comparative Example 2, a silicon single crystal manufacturing apparatus 1 and a dopant addition apparatus 3 having the same shape as those of Comparative Example 1 (the dopant addition apparatus 3 not provided with the shielding plate 222) were prepared. Further, the values of each parameter were set as follows. · Distance H between the outer cylinder and the melt: 60 mm · Flow rate of the inert gas Gf downward: 0.69 m / s Then, 46 silicon single crystals SM were manufactured (pulled up) by the same method as the method for manufacturing the silicon single crystal SM of the above embodiment. During the pulling up of the silicon single crystal SM, the occurrence status of the dislocation was confirmed by the photographed image of the silicon single crystal SM. When the dislocation occurred, the pulling up of the silicon single crystal SM was stopped, and a melt back was performed to melt the silicon single crystal SM into the silicon melt MD. Thereafter, the pulling up and the melt back of the silicon single crystal SM were repeated until a silicon single crystal SM without the occurrence of the dislocation was manufactured.

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

[0048] <Experimental results and evaluation> Table 1 shows the average values of the number of occurrences of the dislocation in Comparative Example 2 and Example 2 (the average number of occurrences of the dislocation until the completion of the pulling up of one single crystal).

[0049]

Table 1

[0050] As shown in Table 1, the average number of occurrences of the dislocation was 2.1 times in Comparative Example 2, whereas it was 1.4 times in Example 2. From these results, it was confirmed that the generation of dislocations can be suppressed by manufacturing a silicon single crystal SM using the dopant addition device 2 capable of suppressing the upward gas flow between the outer cylinder main body 221 and the shield 15.

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

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

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

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

[0055]

Table 2

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

[0057] [Experimental Example 4] As Experimental Example 4, an experiment was conducted to examine the relationship between the distance between the outer cylinder melts and the occurrence status of dislocations in the silicon single crystal.

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

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

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

[0061]

Table 3

[0062] As shown in Table 3, the average number of occurrences of dislocations decreased as the distance H between the outer cylinder melts increased. From these results, it was confirmed that by setting the distance H between the outer cylinder and the melt to 30 mm or more, the undulation of the silicon melt MD can be suppressed, and the dislocation of the silicon single crystal SM caused by the adhesion and solidification of the silicon melt MD to the shield 15 can be suppressed.

Explanation of symbols

[0063] 2... Dopant addition device, 15... Shield, 21... Dopant storage section, 22... Outer cylinder, 221... Outer cylinder body, 222... Shielding plate, Gd... Dopant gas, Gf... Inert gas, MD... Silicon melt, SM... Silicon single crystal.

Claims

1. A dopant addition device for adding a volatile dopant to a silicon melt, comprising a dopant storage part and an outer cylinder, wherein the dopant storage part is configured to store the dopant and release dopant gas generated by sublimation of the dopant, and the outer cylinder is formed in a cylindrical shape with an open lower end, has the dopant storage part provided therein, and includes an outer cylinder body configured to allow the dopant gas to flow out from the lower end and spray it onto the silicon melt, and a shielding plate protruding in a flange shape from the outer cylinder body, wherein the shielding plate is provided above the lower end of a shield surrounding a silicon single crystal pulled up from the silicon melt when adding the dopant.

2. The dopant addition device according to claim 1, wherein the outer cylinder body is formed in a cylindrical shape with an open lower end, the shielding plate is formed in an annular plate shape, is located above the lower end of the shield which is cylindrical or frustum-shaped when adding the dopant, and is provided such that the porosity R obtained from the following formula (1) is 69% or less. 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 viewing the outer cylinder from above the dopant addition device

3. R (%) = (A ２ - (B + 2 × C) ２ ) / A ２ × 100 … (1) The dopant addition device according to claim 2, wherein the shielding plate is provided such that the porosity 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 in a shield surrounding a silicon single crystal pulled up from the silicon melt, and lowering the dopant addition device according to any one of claims 1 to 3 so that the shielding plate is located above the lower end of the shield, thereby adding the dopant to the silicon melt.

5. The dopant addition method according to claim 4, 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 30 mm or more, using the dopant addition device in which the annular plate-shaped shielding plate is provided at the lower end of the outer cylinder body.

6. ​ ​ ​ ​ ​ ​ ​ In the dopant addition method according to claim 5, A dopant addition method in which 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, in which a silicon single crystal is pulled up from a silicon melt to which a volatile dopant has been added by the dopant addition method according to claim 4.

Images