Thermal field system for improving oxygen content of heavily antimony-doped silicon single crystal, single crystal furnace and crystal pulling method

Abstract

A thermal field system, a single crystal furnace and a crystal pulling method for increasing the oxygen content of a heavily antimony-doped silicon single crystal relate to the technical field of heavily antimony-doped silicon single crystal pulling, and comprise a heater, a thermal field assembly, a thermal insulation layer assembly, a crucible bottom thermal insulation assembly and a reflection thermal insulation assembly, the inner screen and the outer screen are coaxially arranged, the bottom ends of the inner screen and the outer screen can stretch into the quartz crucible, the heater is sleeved with the annular inner container, the inner screen is gradually reduced from top to bottom, the top end of the outer screen is in lap joint with the top end of the inner screen, and the bottom end of the outer screen is bent towards the inner screen to form a bent part; one end, far away from the outer screen, of the bending part is lapped with the bottom end of the inner screen, so that a closed annular cavity is formed between the outer screen and the inner screen; the bottom end of the annular inner container is flush with the heater and connected with the inner wall of the furnace body through a supporting ring, so that a containing space is formed between the annular inner container and the inner wall of the furnace body. The thermal insulation layer assembly comprises a side thermal insulation layer located in the containing space and a lower thermal insulation layer located below the supporting ring. The oxygen content in the silicon single crystal is increased.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of heavy-doped antimony silicon single crystal drawing, in particular to a hot field system for improving the oxygen content of heavy-doped antimony silicon single crystal, a single crystal furnace and a crystal drawing method. BACKGROUND

[0002] Oxygen is an inherent element in Czochralski silicon single crystal, and its main source is the dissolution reaction of high-temperature silicon melt and quartz crucible. More than 90% of the oxygen obtained by the dissolution reaction will volatilize, and the remaining oxygen will enter the silicon crystal. The oxygen content in the silicon crystal will affect the performance of the device. Specifically, 1) the oxygen precipitates formed based on oxygen can be used to absorb heavy metal impurities on the surface of the silicon wafer; 2) the transmission of oxygen during the crystal drawing process will affect the transmission of doped elements and other impurity elements, thereby affecting the resistivity and uniformity of the silicon wafer; 3) the oxygen content in the silicon crystal is related to the formation of internal micro-defects in the silicon crystal; 4) the oxygen in the silicon crystal can increase the strength of the silicon crystal. Therefore, the silicon single crystal prepared by the Czochralski method needs to have a certain oxygen content.

[0003] The oxygen content of heavy-doped antimony silicon single crystal is about 40% lower than that of conventional silicon single crystal, and the main reasons are as follows: 1) antimony atoms change the surface tension of the silicon melt, affecting the dissolution rate of oxygen at the quartz crucible wall; 2) antimony atoms change the convection mode of the silicon melt, reducing the effective contact between the melt and the quartz crucible; 3) antimony has high volatility, forming a barrier on the surface of the silicon melt that hinders oxygen transmission; 4) antimony is incorporated into the silicon single crystal lattice, changing the oxygen solubility. The reduction of oxygen content in heavy-doped antimony silicon single crystal directly affects the performance of the device (such as internal gettering efficiency and resistivity uniformity), therefore, it is necessary to increase the oxygen content in heavy-doped antimony silicon single crystal.

[0004] In the prior art, CN109576779A provides a production process and production equipment for improving the oxygen content of heavy-doped antimony silicon single crystal. In the production of the crystal, a quartz ring is added to the polycrystalline silicon material as an additive material to increase the oxygen content in the heavy-doped antimony silicon single crystal. However, special anti-floating structures need to be considered during the quartz ring addition process, making the production equipment more complex. CN208844225U provides heavy-doped antimony single crystal high-oxygen-content high-lifetime hot field components, which increase the temperature at the position of the solution liquid surface by adding a heat preservation ring, which is beneficial to the complete release of oxygen in the materializing crucible, thereby increasing the oxygen entering the silicon single crystal. This method of increasing oxygen content only increases the melting temperature by increasing the heat preservation performance, thereby increasing the oxygen content of the melt during the materializing process. However, in the actual crystal drawing process, the volatilization of oxygen and the longitudinal temperature gradient will both affect the oxygen content in the silicon single crystal. SUMMARY

[0005] The application aims to provide a thermal field system for increasing the oxygen content of heavily doped antimony silicon single crystal, a single crystal furnace and a crystal pulling method.

[0006] To achieve the above-mentioned purpose, the application adopts the following specific scheme: a thermal field system for increasing the oxygen content of heavily doped antimony silicon single crystal, comprising a heater, a thermal field assembly, a heat preservation layer assembly, a crucible bottom heat preservation assembly and a reflective heat preservation assembly, the thermal field assembly comprises an inner screen and an outer screen coaxially arranged and capable of extending into a quartz crucible at the bottom end, and an annular inner container arranged outside the heater, the inner screen gradually shrinks in diameter from top to bottom, the top end of the outer screen is overlapped with the top end of the inner screen, the bottom end of the outer screen is bent to form a bent part towards the inner screen, and the end of the bent part away from the outer screen is overlapped with the bottom end of the inner screen, so as to form a closed annular cavity between the outer screen and the inner screen; the bottom end of the annular inner container is flush with the heater and connected with the inner wall of the furnace body through a support ring, so as to form an accommodation space between the annular inner container and the inner wall of the furnace body; the heat preservation layer assembly comprises a side heat preservation layer located in the accommodation space and a lower heat preservation layer located below the support ring, the side heat preservation layer comprises an upper heat preservation layer and a middle heat preservation layer distributed along the height thereof; the crucible bottom heat preservation assembly comprises an annular heat preservation layer arranged in the crucible bottom support pin; the reflective heat preservation assembly comprises two reflective screens coaxial with the support shaft and distributed along the height of the support shaft, and the two reflective screens are filled with heat preservation material.

[0007] As an optimization scheme of the above-mentioned thermal field system for increasing the oxygen content of heavily doped antimony silicon single crystal, the top end of the middle heat preservation layer is flush with the top end of the heater, and the bottom end of the middle heat preservation layer is flush with the bottom end of the heater.

[0008] As another optimization scheme of the above-mentioned thermal field system for increasing the oxygen content of heavily doped antimony silicon single crystal, the thickness of the middle heat preservation layer is 10-30mm greater than the thickness of the upper heat preservation layer.

[0009] A single crystal furnace, wherein the single crystal furnace is provided with the above-mentioned thermal field system.

[0010] As an optimization scheme of the above-mentioned single crystal furnace, the crucible bottom support pin is provided with an annular groove with an opening facing upward, a graphite crucible bottom is supported above the crucible bottom support pin, and the lower surface of the graphite crucible bottom can block the opening of the annular groove to form an accommodation cavity for accommodating the annular heat preservation layer.

[0011] A method for improving the oxygen content of heavily antimony-doped silicon single crystals, based on the above-mentioned single crystal furnace, comprising a melting process, a doping process, a stabilizing process, a seeding process, a shoulder growth process, a shoulder conversion process, an equal diameter process and a finishing process, characterized in that: the melting process comprises a melting stage and a stabilizing stage, in the melting stage, the quartz crucible is completely inside the heater, the power of the heater is first increased at a rate of 20 kW per 10 min to 60 kW, and then gradually increased to the maximum power of 85-95 kW at a rate of 1 kW / min, and then the maximum power is maintained until the material collapses, then the heater power is increased by 5 kW for 10-20 min, and then restored to the maximum power for 10-20 min, and the cycle is repeated until the end of the melting process; in the stabilizing stage, the power of the heater is 15-20 kW lower than the maximum power, the furnace pressure is 40-50 torr, and the argon flow rate is 60-70 slpm.

[0012] As an optimization of the above-mentioned method for improving the oxygen content of heavily antimony-doped silicon single crystals: in the equal diameter process, the crystal rotation is 18 rpm, the argon flow rate is 40-50 slpm, and the furnace pressure is 70-80 torr.

[0013] As another optimization of the above-mentioned method for improving the oxygen content of heavily antimony-doped silicon single crystals: the equal diameter process is divided into three stages, namely the first stage, the second stage and the third stage; the crucible rotation in the first stage is 15 rpm, the crucible rotation in the second stage is 14 rpm, and the crucible rotation in the third stage is 12 rpm.

[0014] As another optimization of the above-mentioned method for improving the oxygen content of heavily antimony-doped silicon single crystals: during the equal diameter process, the liquid level is increased from 25 mm to 35 mm, and the pulling rate is reduced from 75 mm / hr to 40 mm / hr.

[0015] As another optimization of the above-mentioned method for improving the oxygen content of heavily antimony-doped silicon single crystals: in the seeding process, the crystal rotation is 18 rpm, and the crucible rotation is increased from 10 rpm to 15 rpm.

[0016] Compared with the prior art, the present application has the following advantages: The present invention provides a thermal field system, single crystal furnace, and crystal pulling method for increasing the oxygen content of heavily antimony-doped silicon single crystals. The thermal field system includes a heater, a thermal field assembly, a crucible bottom insulation assembly, a reflective insulation assembly, and an insulation layer assembly. The thermal field assembly not only improves radiative heat transfer from the silicon single crystal surface, increasing the crystal pulling speed, reducing oxygen volatilization, and accelerating oxygen incorporation into the crystal, but also increases the radial temperature gradient, thereby enhancing oxygen transport at the edge of the silicon single crystal and facilitating oxygen incorporation into the silicon single crystal. The thermal field assembly can suppress oxygen volatilization within the molten silicon, allowing more oxygen to have a higher solid solubility during both the melting process and the crystal pulling process. The crucible bottom insulation assembly, the reflective insulation assembly, and the insulation layer assembly enhance diffusion and convection from the oxygen-rich zone at the bottom of the quartz crucible toward the molten silicon, thereby increasing the amount of oxygen entering the silicon single crystal. Specifically, the thermal field system, combined with the crystal pulling method, ensures efficient diffusion of the oxygen-rich zone at the bottom of the crucible to the silicon single crystal growth interface, suppresses oxygen volatilization, and stabilizes the growth interface, thereby increasing the oxygen content of the heavily antimony-doped silicon single crystal. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is the single crystal furnace of the present invention.

[0018] Figure 2 It is the structure of the heater.

[0019] Figure 3 It is a structural diagram of the crucible bottom insulation component.

[0020] Figure 4 These are the oxygen content measurement results of four silicon single crystals in Examples 3-5 and the comparative example.

[0021] Figure numerals: 1. furnace body, 2. thermal field assembly, 201. inner screen, 202. outer screen, 203. annular liner, 204. cover plate, 205. top screen, 3. accommodating space, 4. insulation layer assembly, 401. upper insulation layer, 402. middle insulation layer, 403. lower insulation layer, 404. bottom insulation layer, 5. annular cavity, 6. quartz crucible, 7. graphite crucible, 8. heater, 801. wide part, 802. narrow part, 803. gap, 804. connecting ear, 9. graphite crucible bottom, 10. crucible bottom support pin, 1001. groove, 11. annular insulation layer, 12. reflective insulation assembly, 13. support shaft, 14. support ring. DETAILED DESCRIPTION

[0022] The technical solution of the present invention is further elaborated in detail below in conjunction with specific embodiments. Parts not described and disclosed in detail in the following embodiments of the present invention should be understood as existing technologies known or should be known to those skilled in the art.

[0023] Example 1 The application discloses a thermal field system for improving oxygen content of heavy-antimony-doped silicon single crystal, which comprises a heater 8, a thermal field assembly 2, a heat preservation layer assembly 4, a crucible bottom heat preservation assembly and a reflective heat preservation assembly 12. Figure 1 As shown in the figure, the inner screen 201 is gradually reduced in diameter from top to bottom, and the diameter of the top end of the inner screen 201 is larger than that of the bottom end of the inner screen 201; the top end of the outer screen 202 is overlapped with the top end of the inner screen 201, and the bottom end of the outer screen 202 is bent to form a bent part towards the inner screen 201, and the end of the bent part away from the outer screen 202 is overlapped with the bottom end of the inner screen 201, so that a closed annular cavity 5 is formed between the outer screen 202 and the inner screen 201, and the annular cavity 5 has a structure of being narrow at the top and wide at the bottom. The top end of the annular inner liner 203 is located below the top end of the furnace body 1, the bottom end of the annular inner liner 203 is flush with the heater 8 and is connected with the inner wall of the furnace body through a support ring 14, so that a containing space 3 is formed between the annular inner liner 203 and the inner wall of the furnace body; in the embodiment, the annular inner liner 203 has a segmented structure, comprising an upper half segment and a lower half segment, and the bottom end of the upper half segment is overlapped with the top end of the lower half segment; the bottom end of the lower half segment is overlapped with the upper surface of the support ring 14, and the support ring 14 is fixedly connected with the inner wall of the furnace body. The top end of the annular inner liner 203 is provided with a top screen 205, the top ends of the inner screen 201 and the outer screen 202 are both bent towards the outside to form overlapping parts, the overlapping part of the outer screen 202 is overlapped with the top screen 205, and the overlapping part of the inner screen 201 is overlapped with the overlapping part of the outer screen 202; a cover plate 204 is arranged above the annular inner liner 203, the inner edge of the cover plate 204 is in contact with the top screen 205, the outer edge of the cover plate 204 is in contact with the inner wall of the furnace body 1, a containing space 3 in communication with the annular space is formed between the cover plate 204 and the top screen 205, and the containing space 3 is filled with a top heat preservation layer.

[0024] The above-mentioned thermal field assembly 2 can protect the continuously growing silicon single crystal from the influence of heat radiation of the crucible wall, improve the radiation heat transfer of the surface of the silicon single crystal, increase the crystal pulling rate, improve the radial temperature gradient, and further improve the oxygen transmission of the edge of the silicon single crystal, so that the oxygen can enter the silicon single crystal; the arrangement of the thermal field assembly 2 reduces the loss of radiation heat from the molten silicon, and the structure of the thermal field assembly 2 can gather the gas control pressure, so that the volatilization of oxygen in the molten silicon is inhibited, and more oxygen has a high solid solubility in the molten material and the crystal pulling process.

[0025] In the embodiment, the heater 8 provides energy for pulling the silicon single crystal, and the heater 8 is formed by winding graphite resistance wires, and the heater 8 follows R=ρ·L / S and P=I 2R, where R is the heater resistance, ρ represents the material of heater 8, L is the length of the graphite strips in heater 8, S is the cross-sectional area of ​​the graphite strips in heater 8, P is the output power, and I is the input current. Heater 8 is formed by a winding graphite strip and is divided into a wide portion 801 located at the top and a narrow portion 802 located at the bottom. Within narrow portion 802, there is a gap 803 between adjacent graphite strips. The height of narrow portion 802 accounts for 1 / 2-2 / 3 of the total height of heater 8. This shifts the heating center downward, lowering the temperature at the solid-liquid growth interface, increasing the axial silicon single crystal growth gradient, and increasing the crystal pulling speed, to a certain extent compensating for the reduction in axial temperature gradient caused by thermal field assembly 2. In this embodiment, heater 8 is connected to the electrode via connecting ears 804.

[0026] The insulation layer assembly 4 includes side insulation layers located within the accommodating space 3 and a lower insulation layer 403 located below the support ring 14. The side insulation layer includes an upper insulation layer 401 and a middle insulation layer 402 distributed along its height. The top of the middle insulation layer 402 is flush with the top of the heater 8, and the bottom of the middle insulation layer 402 is flush with the bottom of the heater 8. The middle insulation layer 402 is 10-30 mm thicker than the upper insulation layer 401. The inner wall of the upper insulation layer 401 contacts the outer wall of the annular inner liner 203, and the outer wall of the upper insulation layer 401 is spaced a certain distance from the inner wall of the furnace body 1. In this embodiment, a bottom insulation layer 404 is provided at the bottom of the furnace body to increase thermal insulation and reduce heat loss.

[0027] The crucible bottom insulation assembly includes an annular insulation layer 11 disposed within a crucible bottom support pin 10. The crucible bottom support pin 10 is a tray structure with an upward-facing annular groove 1001. The graphite crucible bottom 9 is supported on the crucible bottom support pin 10, and the lower surface of the graphite crucible bottom 9 is capable of blocking the opening of the annular groove 1001, forming a closed accommodating cavity for the annular insulation layer 11. The annular insulation layer 11 is filled within the accommodating cavity. The extension of the crucible bottom support pin 10 is aligned with the graphite crucible bottom 9, ensuring that the annular insulation layer 11 is completely enclosed. This not only increases the crucible bottom's thermal insulation but also prevents the diffusion of impurities in the annular insulation layer 11.

[0028] The reflective insulation assembly 12 comprises two circular, plate-like reflective screens coaxial with and distributed along the support shaft 13. Their edges are flush with the edges of the graphite crucible 7 and are fixedly mounted to the outer wall of the support shaft 13. Insulating material is placed between the two reflective screens, raising the temperature at the bottom of the quartz crucible 6 and accelerating upward convection and diffusion from the oxygen-rich region at the bottom.

[0029] Example 2 A single crystal furnace is provided with the thermal field system described in Example 1.

[0030] Example 3 A method for improving the oxygen content of heavily antimony-doped silicon single crystals, which is based on the single crystal furnace described in Example 2, the furnace table type is CG6000, the charging amount is 60 kg, and the heavily doped <100> silicon single crystal is drawn, and the target resistivity is 0.02 Ω·cm. The crystal pulling method comprises a melting process, a doping process, a stabilizing process, a seeding process, a shoulder growing process, a necking process, a constant diameter process and a finishing process, specifically: After thermal field calcination and cleaning, assemble according to the single crystal furnace described in Example 2, the height of the heater is 498 mm, the height of the narrow part is 330 mm, the height of the heater is greater than the height of the quartz crucible; the distance between the upper reflection screen of the reflection heat preservation assembly and the bottom end of the heater is 50 mm, in this embodiment, the quartz crucible uses a bottom-thickened uncoated crucible, which increases the reaction time of molten silicon with the quartz crucible, and the bottom thickening ensures the structural strength of the bottom, and always keeps the oxygen content of the bottom of the quartz crucible sufficient; the middle heat preservation layer is 20 mm thicker than the upper heat preservation layer. Thermal field calcination and cleaning are prior art known or should be known to those skilled in the art, and will not be described here.

[0031] Charging and furnace assembly, after leak detection is qualified, pressure is applied, which is prior art known or should be known to those skilled in the art, and will not be described here, it should be noted that the pressure process of this embodiment does not set automatic control of furnace pressure, and the argon flow is 100 slpm.

[0032] Melting process: including melting stage and stabilizing stage, in the melting stage, the quartz crucible is completely inside the heater, and the bottom of the quartz crucible is in the narrow part of the heater, the power of the heater is first increased at a rate of 20 kW per 10 min to 60 kW, and then gradually increased to the maximum power of 85 kW at a rate of 1 kW / min, and kept at the maximum power until the material collapses, then the heater power is increased by 5 kW for 10 min, and then restored to the maximum power for 10 min, and the cycle is repeated until the end of the melting stage, the cycle not only ensures the safety of the quartz crucible, but also improves the oxygen solubility in combination with the thermal field system; at the same time, the contact part of the molten silicon and the quartz crucible continues to dissolve, increasing the precipitation of oxygen. In the stabilizing stage, the heater power is 15 kW lower than the maximum power, the furnace pressure is 40 torr, and the argon flow is 60 slpm. When the material collapses, there is molten silicon at the bottom of the crucible, and increasing the heater power increases the reaction degree of the bottom molten silicon and the quartz crucible. In the melting process, the power of the heater in the stabilizing stage is called the stabilizing power, if silicon boiling occurs during the process, the power is quickly turned off, and the heater power is restored to the stabilizing power after cooling for 3-5 min.

[0033] Doping process: antimony is doped according to the target resistivity through the quartz bell.

[0034] Stabilization process: After the doping is completed, the inner screen and the outer screen are lowered to stabilize the molten silicon for 2h to meet the seeding requirement.

[0035] Seeding, shoulder forming and shoulder turning, at this stage, the crystal rotation is 18 rpm, and the crucible rotation is gradually increased from 10 rpm to 15 rpm, and the crucible rotation value is kept at 15 rpm after the shoulder turning to enter the constant diameter stage, while the furnace pressure is continuously increased to 80 torr to provide a stable premise for the constant diameter crystal pulling process.

[0036] Constant diameter process: the crystal rotation is 18 rpm, the argon flow is 40 slpm, and the furnace pressure is 70 torr, the meniscus distance is increased from 25 mm to 35 mm, and the crystal pulling rate is reduced from 75 mm / hr to 40 mm / hr. The constant diameter process is divided into three stages, namely the first stage, the second stage and the third stage. Specifically, the process of growing silicon single crystal from 0 to 200 mm is the first stage, the process from 200 mm to 800 mm is the second stage, and the process from 800 mm to the end is the third stage. The crucible rotation of the first stage is 15 rpm, the crucible rotation of the second stage is 14 rpm, and the crucible rotation of the third stage is 12 rpm. High furnace pressure control is adopted in the constant diameter process to suppress the volatilization of the dopant antimony and oxygen. The crucible rotation is gradually reduced in this process. The reason is that the first stage has a large melt depth. High crucible rotation is not only conducive to the reaction between molten silicon and quartz crucible, but also can inhibit the natural convection of molten silicon to a certain extent in cooperation with the crystal rotation to ensure the stability of the growth interface. The crucible rotation is gradually reduced backward, because the melt depth is reduced. The centrifugal effect caused by too high crucible rotation will make the oxygen near the crucible difficult to move to the interface. In the constant diameter process, the meniscus distance is gradually increased with the decrease of the melt depth, so that the oxygen-rich zone at the bottom of the crucible is always located or close to the narrow part below the heater during the process, and maintains a close distance with the reflective heat preservation assembly, which is beneficial to the diffusion of the oxygen-rich zone at the bottom to the interface. The high pulling rate in the first stage is based on the assembly of the upper heat preservation layer and the middle heat preservation layer, which increases the growth gradient of the silicon single crystal, is conducive to high pulling rate crystal pulling, and can make more oxygen enter the melt; the pulling rate is gradually reduced, which is also based on the decrease of the melt depth and the further increase of the system temperature, and the pulling rate needs to be reduced to meet the stable growth of the system, but at this time, the increase of the system temperature increases the precipitation of oxygen, so the oxygen content entering the crystal is also ensured.

[0037] End process: the pulling rate is increased to 60-70 mm / hr to gradually reduce the crystal diameter, and finally the crystal diameter is in contact with the melt tip, and then the crystal is lifted off the liquid surface, the main purpose is to inhibit the generation and migration of dislocations, and affect the output of the constant diameter main product. The obtained silicon single crystal is segmented, and the oxygen content is measured by GFA (gas fusion analysis method) at the segmentation position. The longitudinal distribution results are shown in Table 1.

[0038] Example 4 A method for improving the oxygen content of heavily antimony-doped silicon single crystals, which is based on the single crystal furnace described in Example 2, the furnace table type is CG6000, the charging amount is 60 kg, and the heavily doped <100> silicon single crystal is drawn, and the target resistivity is 0.02 Ω·cm. The crystal drawing method comprises a melting process, a doping process, a stabilizing process, a seeding process, a shoulder forming process, a shoulder turning process, an equal diameter process and a finishing process, specifically: After thermal field calcination and cleaning, assemble according to the single crystal furnace described in Example 2, the height of the heater is 498 mm, the height of the narrow part is 330 mm, the height of the heater is greater than the height of the quartz crucible; the distance between the upper reflecting screen in the reflecting heat preservation assembly and the bottom end of the heater is 80 mm, in this embodiment, the quartz crucible uses a bottom-thickened uncoated crucible, and the middle heat preservation layer is 20 mm thicker than the upper heat preservation layer. Thermal field calcination and cleaning are prior art known or should be known to those skilled in the art, and will not be described here.

[0039] After charging and furnace assembly, perform pressure treatment after passing the vacuum leak detection, which is prior art known or should be known to those skilled in the art, and will not be described here. It should be noted that the pressure treatment process in this embodiment does not set the automatic control of the furnace pressure, and the argon flow is 100 slpm.

[0040] Melting process: including material melting stage and stabilizing stage, in the material melting stage, the quartz crucible is completely inside the heater, and the bottom of the quartz crucible is in the narrow part of the heater, the power of the heater is first increased at a rate of 20 kW per 10 min to 60 kW, and then gradually increased to the maximum power of 95 kW at a rate of 1 kW / min, and then the power of the heater is increased by 5 kW for 20 min, and then restored to the maximum power for 20 min, and the cycle is repeated until the end of the material melting stage. In the stabilizing stage, the power of the heater is 20 kW lower than the maximum power, the furnace pressure is 50 torr, and the argon flow is 70 slpm.

[0041] Doping process: doping of antimony according to the target resistivity through the quartz bell.

[0042] Stabilizing process: after completing the doping, the inner screen and the outer screen are lowered, and the molten silicon is stabilized for 2 h to meet the seeding requirements.

[0043] Seeding, shoulder forming and shoulder turning, in this stage, the crystal rotation is 18 rpm, and the crucible rotation is gradually increased from 10 rpm to 15 rpm, and after the shoulder turning, the crucible rotation value is kept at 15 rpm to enter the equal diameter process, while the furnace pressure is continuously increased to 80 torr to provide a stable premise for the equal diameter crystal drawing process.

[0044] Constant diameter process: the crystal rotation is 18 rpm, the argon flow is 50 slpm, the furnace pressure is 80 torr, the liquid level is increased from 25 mm to 35 mm, and the crystal pulling rate is decreased from 75 mm / hr to 40 mm / hr. The constant diameter process is divided into three stages, namely the first stage, the second stage and the third stage. Specifically, the process of growing silicon single crystal from 0 to 200 mm is the first stage, the process from 200 mm to 800 mm is the second stage, and the process from 800 mm to the end is the third stage. The crucible rotation in the first stage is 15 rpm, the crucible rotation in the second stage is 14 rpm, and the crucible rotation in the third stage is 12 rpm.

[0045] Finishing process: the pulling rate is increased to 60-70 mm / hr, so that the crystal diameter gradually decreases, and finally reaches the contact with the melt tip. Then it is lifted off the liquid surface, the main purpose is to suppress the generation and migration of dislocations, and affect the output of the constant diameter main product. The obtained silicon single crystal is segmented, and the oxygen content is measured by GFA (gas fusion analysis method) at the segmentation position. The longitudinal distribution results are shown in Table 1.

[0046] Example 5 A method for improving the oxygen content of heavily doped antimony silicon single crystal, which is based on the single crystal furnace described in Example 2, the furnace table type is CG6000, the charging amount is 60 kg, and the heavily doped <100> crystal direction silicon single crystal is pulled, and the target resistivity is 0.02 Ω·cm. The crystal pulling method includes a melting process, a doping process, a stabilizing process, a seeding process, a shoulder process, a shoulder rotation process, a constant diameter process and a finishing process, specifically: After heat field calcination and cleaning, the single crystal furnace described in Example 2 is assembled, the height of the heater is 498 mm, the height of the narrow part is 330 mm, the height of the heater is greater than the height of the quartz crucible; the distance between the reflection screen at the top of the reflection and insulation assembly and the bottom end of the heater is 70 mm. In this embodiment, the quartz crucible uses a bottom-thickened uncoated crucible, and the middle insulation layer is 20 mm thicker than the upper insulation layer. Heat field calcination and cleaning are prior art known or should be known to those skilled in the art, and will not be described here.

[0047] Charging and furnace assembly, after leak detection is qualified, pressure is applied, this process is prior art known or should be known to those skilled in the art, and will not be described here. It should be noted that the pressure process in this embodiment does not set the automatic control of the furnace pressure, and the argon flow is 100 slpm.

[0048] Melting process: including melting stage and stabilization stage, in the melting stage, the quartz crucible is completely inside the heater, and the bottom of the quartz crucible is in the narrow part of the heater, the power of the heater is first increased to 60 kW at a rate of 20 kW per 10 min, and then gradually increased to the maximum power of 90 kW at a rate of 1 kW / min, and then the maximum power is kept until the material collapses, then the heater power is increased by 5 kW for 15 min, and then the maximum power is restored for 15 min, and the cycle is repeated until the end of the melting stage. In the stabilization stage, the power of the heater is 18 kW lower than the maximum power, the furnace pressure is 45 torr, and the argon flow rate is 65 slpm.

[0049] Doping process: doping of antimony by quartz bell according to the target resistivity.

[0050] Stabilization process: after the doping is completed, the inner and outer screens are lowered to stabilize the molten silicon for 2 hours to meet the crystal pulling requirements.

[0051] Crystal pulling, shoulder opening and shoulder turning, in this stage, the crystal rotation is 18 rpm, and the crucible rotation is gradually increased from 10 rpm to 15 rpm, and after the shoulder turning, the crucible rotation value remains 15 rpm to enter the constant diameter, and at the same time, the furnace pressure is continuously increased to 80 torr to provide a stable premise for the constant diameter crystal pulling process.

[0052] Constant diameter process: the crystal rotation is 18 rpm, the argon flow rate is 45 slpm, and the furnace pressure is 75 torr, the liquid port distance is increased from 25 mm to 35 mm, and the crystal pulling rate is reduced from 75 mm / hr to 40 mm / hr. The constant diameter process is divided into three stages, namely the first stage, the second stage and the third stage. Specifically, the silicon single crystal growth from 0 growth to 200 mm is the first stage, from 200 mm to 800 mm is the second stage, and from 800 mm to the end is the third stage, and the crucible rotation of the first stage is 15 rpm, the crucible rotation of the second stage is 14 rpm, and the crucible rotation of the third stage is 12 rpm.

[0053] End process: the pulling rate is increased to 60-70 mm / hr, so that the crystal diameter gradually decreases, and finally reaches the contact with the melt tip, and then the liquid surface is lifted, the main purpose is to suppress the generation and migration of dislocations, and affect the output of the constant diameter main product. The obtained silicon single crystal is segmented, and the oxygen content is measured by GFA (gas fusion analysis method) at the segmentation position, and the longitudinal distribution result is shown in Table 1.

[0054] Comparative example The furnace table type is CG6000, the charging amount is 60 kg, and the heavily doped <100> crystal direction silicon single crystal is pulled, and the target resistivity is 0.02 Ω·cm. The crystal pulling method includes melting process, doping process, stabilization process, crystal pulling process, shoulder opening process, shoulder turning process, constant diameter process and end process, specifically: After the hot field calcination and cleaning, the height of the heater is 495 mm, the height of the wide part and the narrow part is consistent, the quartz crucible adopts a conventional coating crucible and the thickness is consistent.

[0055] After loading and furnace assembling, and after the vacuum leak detection is qualified, pressure is applied, which is a prior art known or should be known by those skilled in the art, and will not be described here. It should be noted that the furnace pressure automatic control is not set during the pressure process of the present embodiment, and the argon flow is 100 slpm.

[0056] Melting process: in this process, the heater power is gradually increased to the maximum material power, the maximum material power is maintained until the melting is completed, and then the heater power is gradually reduced to the stable power, and the furnace pressure is 40-50 torr and the argon flow is 60-70 slpm.

[0057] Doping process, stabilization process, seed crystal introduction process, shoulder forming process and shoulder turning process are the same as the corresponding processes in Example 3.

[0058] Constant diameter process: the crystal is turned to 18 rpm, the argon flow is 40-50 slpm, the furnace pressure is 70-80 torr, the liquid port is always 25 mm, the crystal pulling rate is reduced from 65 mm / hr to 30 mm / hr, and the crucible is turned to 15 rpm.

[0059] The finishing process is the same as the finishing process in Example 3.

[0060] Four silicon single crystals are pulled by the above method, and the four silicon single crystals are segmented respectively, and the oxygen content is measured by GFA (gas phase fusion analysis method) at the segmentation position, and the longitudinal distribution results are shown in Table 1. In Table 1, Comparative Example-1, Comparative Example-2, Comparative Example-3 and Comparative Example-4 are four silicon single crystals pulled by the comparative examples.

[0061] Table 1 Oxygen content measurement results of four silicon single crystals of Examples 3-5 and Comparative Examples Silicon single crystal 0 mm 300 mm 600 mm 900 mm 1200 mm Example 3 16.73% 13.69% 11.55% 10.01% 7.82% Example 4 16.10% 12.92% 11.78% 10.17% 7.72% Example 5 16.36% 13.47% 11.31% 9.84% 7.68% Mean value 16.40% 13.36% 11.55% 10.01% 7.74% Comparative Example -1 13.16% 10.21% 9.21% 7.67% 7.28% Comparative Example -2 13.07% 10.29% 8.98% 7.98% 7.18% Comparative Example -3 13.14% 10.19% 9.24% 7.84% 6.82% Comparative Example -4 13.23% 9.44% 8.86% 7.78% 7.37% Mean value 13.15% 10.03% 9.07% 7.82% 7.16% The above description of the disclosed embodiments enables a person skilled in the art to implement or use the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A thermal field system for increasing the oxygen content of heavily antimony-doped silicon single crystals, characterized by: The invention comprises a heater (8), a heat field assembly (2), an insulation layer assembly (4), a crucible bottom insulation assembly and a reflective insulation assembly (12), wherein the heat field assembly (2) comprises an inner screen (201) and an outer screen (202) which are coaxially arranged and whose bottom end can be extended into the quartz crucible (6), and an annular inner liner (203) which is sleeved on the outer side of the heater (8), wherein the inner screen (201) gradually decreases in diameter from top to bottom, the top end of the outer screen (202) overlaps with the top end of the inner screen (201), and the outer screen ( The bottom end of the outer screen (202) is bent toward the inner screen (201) to form a bent portion, and one end of the bent portion away from the outer screen (202) overlaps with the bottom end of the inner screen (201), so that a closed annular cavity (5) is formed between the outer screen (202) and the inner screen (201); the bottom end of the annular inner liner (203) is flush with the heater (8) and is connected to the inner wall of the furnace body (1) through the support ring (14), so that a holding space (3) is formed between the annular inner liner (203) and the inner wall of the furnace body (1); The insulation layer assembly (4) comprises a side insulation layer located in the accommodating space (3) and a lower insulation layer (403) located below the support ring (14), wherein the side insulation layer comprises an upper insulation layer (401) and a middle insulation layer (402) distributed along its height; The crucible bottom insulation component includes an annular insulation layer (11) arranged in the crucible bottom support pin (10); the reflective insulation component (12) includes two reflective screens coaxial with the support shaft (13) and distributed at a height along the support shaft (13), and the space between the two reflective screens is filled with insulation material.

2. A thermal field system for increasing the oxygen content of heavily antimony-doped silicon single crystals according to claim 1, characterized in that: The top end of the middle thermal insulation layer (402) is flush with the top end of the heater (8), and the bottom end of the middle thermal insulation layer (402) is flush with the bottom end of the heater (8).

3. The thermal field system for increasing the oxygen content of heavily antimony-doped silicon single crystal according to claim 1, characterized in that: The thickness of the middle insulation layer (402) is 10-30 mm greater than the thickness of the upper insulation layer (401).

4. A single crystal furnace, characterized in that: A thermal field system according to any one of claims 1 to 3 is provided in the single crystal furnace.

5. A single crystal furnace according to claim 4, characterized in that: The crucible bottom support pin (10) is provided with an annular groove (1001) with an opening facing upwards, and a graphite crucible bottom (9) is supported above the crucible bottom support pin (10), and the lower surface of the graphite crucible bottom (9) can block the opening of the annular groove (1001), thereby forming an accommodating cavity for accommodating the annular thermal insulation layer (11).

6. A method for increasing the oxygen content of heavily antimony-doped silicon single crystals, the method being based on the single crystal furnace according to any one of claims 4 to 5, comprising a melting step, a doping step, a stabilization step, a seeding step, a shoulder release step, a shoulder rotation step, a diameter equalization step, and a finishing step, wherein: The melting process includes a melting stage and a stabilization stage. During the melting stage, the quartz crucible is completely inside the heater, and the power of the heater is first increased by 20kW every 10 minutes to 60kW, and then gradually increased at a rate of 1kW / min to a maximum power of 85-95kW, maintaining the maximum power until the material collapses. Then, the heater power is increased by 5kW for 10-20 minutes, and then restored to the maximum power for 10-20 minutes, and this cycle is repeated until the melting process is completed; during the stabilization stage, the heater power is 15-20kW lower than the maximum power, the furnace pressure is 40-50torr, and the argon flow rate is 60-70slpm.

7. The method for increasing the oxygen content of heavily antimony-doped silicon single crystal according to claim 6, wherein: In the equal diameter process, the crystal rotation is 18 rpm, the argon flow rate is 40-50 slpm, and the furnace pressure is 70-80 torr.

8. The method for increasing the oxygen content of heavily antimony-doped silicon single crystal according to claim 7, wherein: The equal diameter process is divided into three stages, namely the first stage, the second stage and the third stage; the crucible in the first stage is rotated at 15 rpm, the crucible in the second stage is rotated at 14 rpm, and the crucible in the third stage is rotated at 12 rpm.

9. The method for increasing the oxygen content of heavily antimony-doped silicon single crystal according to claim 7, wherein: During the equal diameter process, the liquid nozzle distance increased from 25 mm to 35 mm, and the crystal pulling rate decreased from 75 mm / hr to 40 mm / hr.

10. The crystal pulling method for increasing the oxygen content of heavily antimony-doped silicon single crystal according to claim 6, characterized in that: During the seeding process, the crystal rotation speed was 18 rpm and the crucible rotation speed was increased from 10 rpm to 15 rpm.

Images