Single crystal furnace and single crystal silicon rod annealing method

Abstract

The present invention provides a single crystal furnace and a single crystal silicon rod annealing method, the single crystal furnace comprises: a main chamber comprising a furnace body and a throat structure located above the furnace body which are connected with each other, and the furnace body is used for forming a single crystal silicon rod; the auxiliary chamber is mounted above the throat structure; the flow guide cover is arranged in the main chamber and located at the throat structure, the flow guide cover comprises a cover body, and the cover body is provided with a middle flow channel allowing the silicon single crystal rod to penetrate through and an annular flow channel surrounding the middle flow channel; the throat structure is provided with an inlet which is communicated with an inlet of the annular flow channel so as to introduce a first fluid into the annular flow channel; an inlet of the middle flow channel is communicated with the auxiliary chamber so as to receive a second fluid introduced from the auxiliary chamber; and an outlet of the annular flow channel is communicated with an outlet of the middle flow channel, so that the first fluid and the second fluid are converged to cool the monocrystalline silicon rod, and the problem that the minority carrier lifetime of monocrystalline silicon is easily shortened by a monocrystalline silicon annealing process in the prior art is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of single-crystal silicon production, and more particularly, to a single-crystal furnace and a method for annealing a single-crystal silicon rod. Background Art

[0002] As an important basic material for the modern semiconductor industry, the quality of single-crystal silicon plays a crucial role in the performance and reliability of various electronic devices. The minority carrier lifetime is one of the key indicators for measuring the quality of single-crystal silicon and directly affects the electrical properties of silicon materials.

[0003] In the process of preparing single-crystal silicon, the annealing process is a crucial link, which directly affects the minority carrier lifetime of single-crystal silicon. The current single-crystal silicon annealing process is to first take out the single-crystal silicon rod from the single-crystal furnace, then cut it into silicon wafers, and finally perform annealing. There are still limitations in improving the minority carrier lifetime. One of the main reasons is that during the annealing process, it is difficult to ensure the uniformity of the thermal field, resulting in uneven diffusion of silicon atoms and uneven distribution of impurities such as oxygen, thus affecting the minority carrier lifetime, which limits the improvement of the quality of single-crystal silicon.

[0004] The above information disclosed in the background art section is only used to enhance the understanding of the background art of the technology described in this article. Therefore, the background art may contain certain information that is not prior art known to those skilled in the art in this country. Summary of the Invention

[0005] The main object of the present invention is to provide a single-crystal furnace and a method for annealing a single-crystal silicon rod to solve the problem that the existing single-crystal silicon annealing process is likely to reduce the minority carrier lifetime of single-crystal silicon.

[0006] To achieve the above object, according to one aspect of the present invention, there is provided a single-crystal furnace, comprising: a main chamber including a furnace body and a throat structure located above the furnace body, the furnace body being used for forming a single-crystal silicon rod; a secondary chamber installed above the throat structure; a flow guide cover disposed in the main chamber and located at the throat structure, the flow guide cover including a cover body, the cover body being provided with an intermediate flow channel through which the single-crystal silicon rod passes and an annular flow channel disposed around the intermediate flow channel; wherein, at the throat structure, there is a through inlet communicating with the inlet of the annular flow channel to introduce a first fluid into the annular flow channel; the inlet of the intermediate flow channel communicates with the secondary chamber to receive a second fluid introduced from the secondary chamber; the outlet of the annular flow channel communicates with the outlet of the intermediate flow channel so that the first fluid and the second fluid converge to cool the single-crystal silicon rod.

[0007] Further, the inlet and outlet of the intermediate flow channel are the fluid inlet and fluid outlet respectively. The fluid inlet is located above the fluid outlet, and the single crystal rod can pass through from the fluid outlet to the fluid inlet; both ends of the annular flow channel are closed; the cover body is further provided with: an inlet hole, which is arranged at a position on the outer peripheral surface of the cover body close to the fluid inlet and communicated with the annular flow channel to serve as the inlet of the annular flow channel for introducing the first fluid into the annular flow channel; a plurality of diversion holes, which are arranged at intervals at a position on the inner wall surface of the cover body close to the fluid outlet and are all communicated with the annular flow channel to serve as the outlet of the annular flow channel for spraying the first fluid to a position on the intermediate flow channel close to the fluid outlet.

[0008] Further, the cover body includes a hollow cylindrical section and a hollow frustum section that are sequentially connected along its own center line. The inner diameter of the hollow frustum section gradually increases in the direction away from the hollow cylindrical section; wherein, the fluid inlet is located at one end of the hollow cylindrical section away from the hollow frustum section, the fluid outlet is located at one end of the hollow frustum section away from the hollow cylindrical section, the inlet hole is located on the hollow cylindrical section, and the diversion holes are located on the hollow frustum section.

[0009] Further, the cover body includes a first annular end plate, a second annular end plate, a cylindrical inner wall and a cylindrical outer wall. The first annular end plate and the second annular end plate are arranged at intervals along the center line of the cover body, and the cylindrical inner wall and the cylindrical outer wall are sequentially sleeved along the direction away from the center line of the cover body; the first end of the cylindrical inner wall and the first end of the cylindrical outer wall are respectively connected to the inner side and the outer side of the first annular end plate, and the second end of the cylindrical inner wall and the second end of the cylindrical outer wall are respectively connected to the inner side and the outer side of the second annular end plate; wherein, the intermediate flow channel is located inside the cylindrical inner wall, the annular flow channel is located between the cylindrical inner wall and the cylindrical outer wall, the inlet hole is located on the cylindrical outer wall, and the diversion holes are located on the cylindrical inner wall.

[0010] Further, the plurality of diversion holes are divided into a plurality of diversion hole groups, and the plurality of diversion hole groups are arranged at intervals around the center line of the cover body. Each diversion hole group includes: one diversion hole; or at least two diversion holes, and the at least two diversion holes are arranged at intervals in sequence along the extending direction of the cover body.

[0011] Further, the single crystal furnace further includes a ventilation connecting piece. The first end of the ventilation connecting piece is arranged in the ventilation inlet, and the second end of the ventilation connecting piece is inserted into the annular flow channel through the inlet hole; the ventilation connecting piece is a hollow cylindrical structure with external threads arranged on its outer peripheral surface, and at least one of the ventilation inlet and the inlet hole is a threaded hole threadedly connected with the external threads; the first end of the ventilation connecting piece is open and the second end is closed, and a side opening is further opened on the outer peripheral surface of the second end of the ventilation connecting piece. Both ends of the side opening are communicated with the inner hole of the ventilation connecting piece and the annular flow channel respectively.

[0012] Further, the single crystal furnace further includes a temperature detection component. The detection probe of the temperature detection component is arranged at a position close to the fluid outlet of the intermediate flow channel for detecting the temperature at the position close to the fluid outlet of the intermediate flow channel, so as to adjust the flow rate of the first fluid at the inlet and / or adjust the speed of lifting the single crystal rod upward according to the detection result of the temperature detection component.

[0013] According to another aspect of the present invention, there is provided a method for annealing a single crystal rod, which is applicable to the above-mentioned single crystal furnace. The method for annealing a single crystal rod includes: after the growth of the single crystal rod in the main chamber of the single crystal furnace is completed, introducing a first fluid into the annular flow channel of the flow guide cover through the inlet of the single crystal furnace, and introducing a second fluid into the intermediate flow channel of the flow guide cover through the upper end of the auxiliary chamber of the single crystal furnace; lifting the single crystal rod upward so that the single crystal rod gradually passes through the intermediate flow channel.

[0014] Further, the flow rate of the first fluid at the inlet is 60 L / min to 80 L / min; and / or the flow rate of the second fluid at the upper end of the auxiliary chamber is 25 L / min to 35 L / min; and / or the speed of lifting the single crystal rod upward is 60 mm / h to 80 mm / h; and / or the first fluid includes argon; and / or the second fluid includes argon.

[0015] Further, the method for annealing a single crystal rod further includes: detecting the temperature at the position close to the fluid outlet of the intermediate flow channel, so as to adjust the flow rate of the first fluid at the inlet and / or adjust the speed of lifting the single crystal rod upward according to the detection result.

[0016] Applying the technical solution of the present invention, the single crystal furnace of the present invention includes: a main chamber, including a furnace body connected to a throat structure above the furnace body, and the furnace body is used to form a single crystal rod; a secondary chamber, installed above the throat structure; a flow guide cover, arranged in the main chamber and located at the throat structure, the flow guide cover includes a cover body, and the cover body is provided with an intermediate flow channel for the single crystal rod to pass through and an annular flow channel arranged around the intermediate flow channel; wherein, a through inlet communicating with the inlet of the annular flow channel to introduce a first fluid into the annular flow channel is arranged at the throat structure; the inlet of the intermediate flow channel communicates with the secondary chamber to receive a second fluid introduced from the secondary chamber; the outlet of the annular flow channel communicates with the outlet of the intermediate flow channel, so that the first fluid and the second fluid converge to cool the single crystal rod. In this way, in the single crystal furnace of the present invention, the argon gas that all enters the furnace from the top of the secondary chamber in the prior art is changed to a part entering the annular flow channel of the flow guide cover from the throat structure, and the other part entering the intermediate flow channel of the flow guide cover from the top of the secondary chamber, guiding the argon gas to be evenly distributed in the single crystal furnace, thereby optimizing the uniformity of the thermal field distribution in the single crystal furnace, changing the thermal history of the single crystal rod in the single crystal furnace, so that the single crystal rod can reach the optimal annealing temperature and annealing time, realizing uniform cooling of the surface temperature of the single crystal rod, reducing the crystal defects of the single crystal rod caused by uneven temperature, making the temperature control of the single crystal rod during the annealing process more precise, reducing the formation of oxygen precipitation and defects, etc., significantly improving the minority carrier lifetime and quality of the single crystal rod, solving the problem that the single crystal annealing process in the prior art is easy to reduce the minority carrier lifetime of the single crystal, and being able to effectively improve the production efficiency and product yield of the single crystal rod. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The accompanying drawings forming a part of this specification are used to provide a further understanding of the present invention. The schematic embodiments and descriptions thereof of the present invention are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0018] Figure 1 The front view of the cover body showing an embodiment of the flow guide cover of the single crystal furnace according to the present invention is shown;

[0019] Figure 2 It shows Figure 1 The sectional view of the shown cover body along the A-A direction is shown;

[0020] Figure 3 It shows Figure 1 The structural schematic diagram of the shown cover body is shown;

[0021] Figure 4 The structural schematic diagram of the fastener showing an embodiment of the flow guide cover of the single crystal furnace according to the present invention is shown;

[0022] Figure 5 The structural schematic diagram showing an embodiment of the single crystal furnace according to the present invention is shown;

[0023] Figure 6 shows Figure 5 a front view of the single crystal furnace shown;

[0024] Figure 7 shows Figure 6 a sectional view of the single crystal furnace shown along the B - B direction;

[0025] Figure 8 shows Figure 7 a partially enlarged view at position C of the single crystal furnace shown;

[0026] Figure 9 shows Figure 8 a schematic structural view of the gas - passing connecting piece of the single crystal furnace shown;

[0027] Figure 10 shows Figure 9 a sectional view of the gas - passing connecting piece of the single crystal furnace shown;

[0028] Figure 11 shows Figure 7 a schematic stage view of each part inside the single crystal furnace matching each stage of oxygen precipitation formation;

[0029] Figure 12 shows a flowchart of an embodiment of the single - crystal silicon rod annealing method according to the present invention.

[0030] Among them, the above - mentioned drawings include the following reference numerals:

[0031] 1. Deflector; 10. Housing; 11. Intermediate flow channel; 111. Fluid inlet; 112. Fluid outlet; 12. Annular flow channel; 121. Inlet hole; 122. Deflection hole; 13. Hollow cylindrical section; 14. Hollow frustum section; 15. First annular end plate; 16. Second annular end plate; 17. Cylindrical inner wall; 18. Cylindrical outer wall; 19. Fixing hole;

[0032] 2. Fastener;

[0033] 3. Main chamber; 31. Furnace body; 32. Throat structure; 33. Inlet;

[0034] 4. Auxiliary chamber;

[0035] 5. Single - crystal silicon rod;

[0036] 6. Gas - passing connecting piece; 60. Intermediate hole; 61. Side opening. Detailed implementation manners

[0037] It should be noted that, without conflict, the embodiments and features in the embodiments of the present invention can be combined with each other. The present invention will be described in detail below with reference to the drawings and in combination with the embodiments.

[0038] The present invention will be further described in detail below in conjunction with specific embodiments, and these embodiments should not be construed as limiting the scope of the present invention claimed.

[0039] As Figures 1 to 9 shown, the present invention provides a single crystal furnace, comprising: a main chamber 3, including a furnace body 31 connected thereto and a throat structure 32 located above the furnace body 31, wherein a single crystal rod 5 is formed within the furnace body 31; a sub-chamber 4, installed above the throat structure 32; a flow guiding cover 1, disposed within the main chamber 3 and at the throat structure 32, the flow guiding cover 1 including a cover body 10, and an intermediate flow channel 11 for the single crystal rod 5 to pass through and an annular flow channel 12 disposed around the intermediate flow channel 11 are provided on the cover body 10; wherein, a through inlet 33 communicating with the inlet of the annular flow channel 12 to introduce a first fluid into the annular flow channel 12 is provided at the throat structure 32; the inlet of the intermediate flow channel 11 communicates with the sub-chamber 4 to receive a second fluid introduced from the sub-chamber 4; the outlet of the annular flow channel 12 communicates with the outlet of the intermediate flow channel 11, so that the first fluid and the second fluid converge to cool the single crystal rod 5.

[0040] In this way, in the single crystal furnace of the present invention, part of the argon gas that was all introduced into the furnace from the top of the sub-chamber 4 in the prior art is changed to enter the annular flow channel 12 of the flow guiding cover 1 from the throat structure 32, and the other part enters the intermediate flow channel 11 of the flow guiding cover 1 from the top of the sub-chamber 4, guiding the argon gas to be evenly distributed within the single crystal furnace, thereby optimizing the uniformity of the thermal field distribution within the single crystal furnace, changing the thermal history of the single crystal rod 5 within the single crystal furnace, so that the single crystal rod 5 can reach the optimal annealing temperature and annealing time, achieving uniform cooling of the surface temperature of the single crystal rod 5, reducing crystal defects of the single crystal rod 5 caused by uneven temperature, making the temperature control of the single crystal rod 5 during the annealing process more precise, reducing the formation of oxygen precipitation and defects, significantly improving the minority carrier lifetime and quality of the single crystal rod 5, solving the problem that the single crystal annealing process in the prior art is prone to reducing the minority carrier lifetime of single crystal, and being able to effectively improve the production efficiency and product yield of the single crystal rod 5.

[0041] As Figure 2 shown, M is the first fluid and N is the second fluid.

[0042] The drawbacks of the annealing method of single crystal in the prior art are that the sealing and heat preservation of the annealing equipment of single crystal in the prior art are poor, and the contamination of impurities such as oxygen in metal and air will cause an increase in recombination centers. Through actual research and testing, the following Table 1 is obtained. When the Fe contamination concentration rises from 1*10^12 cm^-3 to 1*10^13 cm^-3, the minority carrier lifetime of single crystal will drop sharply from 120 μs to 20 μs.

[0043]

[0044]

[0045] In the annealing process of single-crystal silicon in the prior art, the cooling rate is too fast, usually 10°C / min to 20°C / min, resulting in excessive thermal stress and causing dislocation defects. Through actual testing of single-crystal silicon, the following Table 2 can be obtained. When the cooling rate is increased from 5°C / min to 15°C / min, the dislocation density of single-crystal silicon rises from 1×10^4 cm^-2 to 5×10^5 cm^-2, and the minority carrier lifetime decreases by 50% (from 150 μs to 75 μs).

[0046]

[0047] The following Table 3 shows the comparison between the single-crystal silicon annealing process in the prior art and the single-crystal silicon annealing process of the present invention. Combining Tables 1 to 3, it can be seen that compared with the single-crystal silicon annealing process in the prior art, the single-crystal silicon rod annealing method used in the single-crystal furnace of the present invention has a higher annealing temperature, a slower cooling rate, a lower oxygen content, and a smaller oxygen precipitation density. This effectively improves the minority carrier lifetime of the annealed single-crystal silicon rod, thus solving the problem that the single-crystal silicon annealing process in the prior art is prone to reducing the minority carrier lifetime of single-crystal silicon, and can effectively improve the production efficiency and product yield of single-crystal silicon rods.

[0048]

[0049]

[0050] In the single-crystal furnace of the present invention, the first fluid and the second fluid together form the argon gas used in the single-crystal furnace. Among them, the first fluid can account for 60% to 100% of the overall argon gas.

[0051] For example, the first fluid accounts for 80% of the overall argon gas, and the second fluid accounts for 20% of the overall argon gas.

[0052] Specifically, single-crystal silicon is initially grown from a liquid state to a solid state at the crystal-forming liquid level in the furnace body 31. The temperature here is relatively high, about 1420°C. A negative pressure pipeline is provided at the bottom of the furnace body 31, which is connected to a vacuum pump and continuously pumps air during the crystal pulling process to form a negative pressure state in the furnace body 31, so that the argon gas introduced from the upper end of the auxiliary chamber 4 can quickly take away volatiles such as Sio. Actual experiments have shown that the greater the gas flow rate on the liquid surface, the faster the volatiles are taken away and the lower the oxygen content. The part of the furnace body 31 close to the throat structure 32 is the furnace cover. If the diversion cover 1 is not provided, the flow pattern of the argon gas flowing in from the upper end of the auxiliary chamber 4 will form a vortex and the air flow will disperse when passing through the furnace cover, and the gas pressure will also decrease accordingly. Since the auxiliary chamber 4 is about seven meters high, the temperature of the argon gas flowing down from the upper part of the auxiliary chamber 4 to reach the throat structure 32 is already the same as the temperature in the furnace body 31, and the effect of quickly cooling the single-crystal silicon rod 5 cannot be achieved.

[0053] Among them, the structure diagram of the single-crystal silicon rod 5 in the drawings of the present invention is only a schematic representation of the position of the single-crystal silicon rod 5 and does not represent the actual situation during the production of the single-crystal silicon rod 5. The single-crystal silicon rod 5 in the drawings of the present invention is nearly two meters long. Due to the difference in the temperature field distribution in the single-crystal furnace, the temperatures of the upper end, middle part, lower end, and the growing part of the single-crystal silicon rod 5 at this time are all different.

[0054] The manufacturing material of the flow guide cover 1 of the present invention may include metals such as 316 stainless steel or molybdenum.

[0055] As Figures 2 to 4 shown, the inlet and outlet of the middle flow channel 11 are the fluid inlet 111 and the fluid outlet 112 respectively. The fluid inlet 111 is located above the fluid outlet 112, and the single-crystal silicon rod 5 can pass through from the fluid outlet 112 to the fluid inlet 111; both ends of the annular flow channel 12 are closed; the cover body 10 is further provided with: an inlet flow hole 121, which is arranged at a position on the outer peripheral surface of the cover body 10 close to the fluid inlet 111 and communicates with the annular flow channel 12 to serve as the inlet of the annular flow channel 12 to introduce the first fluid into the annular flow channel 12; a plurality of diversion holes 122, which are arranged at intervals at a position on the inner wall surface of the cover body 10 close to the fluid outlet 112 and all communicate with the annular flow channel 12 to serve as the outlet of the annular flow channel 12 to spray the first fluid to a position on the middle flow channel 11 close to the fluid outlet 112, so that the first fluid is evenly sprayed onto the surface of the single-crystal silicon rod 5, realizing uniform cooling of the surface temperature of the single-crystal silicon rod 5, thereby optimizing the thermal field distribution in the single-crystal furnace, changing the thermal history of the single-crystal silicon rod 5, thereby reducing the generation of oxygen precipitation and improving the minority carrier lifetime of the single-crystal silicon rod 5.

[0056] As Figures 2 to 4 shown, the cover body 10 includes a hollow cylindrical section 13 and a hollow frustum section 14 connected in sequence along its own center line. The inner diameter of the hollow frustum section 14 gradually increases in the direction away from the hollow cylindrical section 13; among them, the fluid inlet 111 is located at one end of the hollow cylindrical section 13 away from the hollow frustum section 14, the fluid outlet 112 is located at one end of the hollow frustum section 14 away from the hollow cylindrical section 13, the inlet flow hole 121 is located on the hollow cylindrical section 13, and the diversion holes 122 are located on the hollow frustum section 14. In this way, by using the gradually changing inner diameter of the hollow frustum section 14, the distribution and guiding of the first fluid and the second fluid are optimized, so that the cooling effect of the first fluid and the second fluid on the surface of the single-crystal silicon rod 5 is more uniform, and the local overheating phenomenon of the single-crystal silicon rod 5 during annealing can be significantly reduced, and the uniformity and quality of the crystal of the single-crystal silicon rod 5 are further improved.

[0057] As Figures 2 to 4As shown, the cover body 10 includes a first annular end plate 15, a second annular end plate 16, a cylindrical inner wall 17 and a cylindrical outer wall 18. The first annular end plate 15 and the second annular end plate 16 are arranged at intervals along the center line of the cover body 10. The cylindrical inner wall 17 and the cylindrical outer wall 18 are sleeved in sequence along the direction away from the center line of the cover body 10. The first end of the cylindrical inner wall 17 and the first end of the cylindrical outer wall 18 are respectively connected to the inner side and the outer side of the first annular end plate 15. The second end of the cylindrical inner wall 17 and the second end of the cylindrical outer wall 18 are respectively connected to the inner side and the outer side of the second annular end plate 16. Among them, the intermediate flow channel 11 is located inside the cylindrical inner wall 17, the annular flow channel 12 is located between the cylindrical inner wall 17 and the cylindrical outer wall 18, the inlet holes 121 are located on the cylindrical outer wall 18, and the diversion holes 122 are located on the cylindrical inner wall 17. In this way, through the supporting action of the first annular end plate 15 and the second annular end plate 16, and the double-flow-channel design formed by the cylindrical inner wall 17 and the cylindrical outer wall 18, the precise guiding and uniform distribution of the first fluid and the second fluid are realized, the cooling efficiency of the single crystal silicon rod 5 is improved, and the thermal stress is reduced.

[0058] Among them, the number of the inlet holes 121 is multiple, and the multiple inlet holes 121 are arranged at intervals around the center line of the cover body 10; and / or the aperture of the diversion holes 122 is 2.5 mm to 3.5 mm. In this way, by arranging multiple inlet holes 121, the uniform distribution of the first fluid in the diversion cover 1 can be realized, and the phenomenon of local overheating or overcooling of the single crystal silicon rod 5 can be avoided. The aperture of the diversion holes 122 is designed to be 2.5 mm to 3.5 mm, which can control the injection speed and injection pressure of the first fluid, and ensure that the cooling effect of the first fluid on the surface of the single crystal silicon rod 5 reaches the optimum.

[0059] Specifically, the number of the inlet holes 121 is two, and the two inlet holes 121 are symmetrically arranged about the center line of the cover body 10.

[0060] Optionally, the aperture of the diversion holes 122 is 3 mm.

[0061] As Figures 2 to 4 shown, the multiple diversion holes 122 are divided into multiple diversion hole groups, and the multiple diversion hole groups are arranged at intervals around the center line of the cover body 10. Each diversion hole group includes: one diversion hole 122; or at least two diversion holes 122, and the at least two diversion holes 122 are arranged at intervals in sequence along the extending direction of the cover body 10.

[0062] Specifically, the multiple diversion holes 122 are divided into multiple diversion hole groups, and the multiple diversion hole groups are arranged at intervals around the center line of the cover body 10. Each diversion hole group includes four diversion holes 122, and at least two diversion holes 122 are arranged at intervals in sequence along the extending direction of the hollow frustum section 14 of the cover body 10.

[0063] By grouping the diversion holes 122, the present invention can achieve more precise control over the injection direction and injection speed of the first fluid, thereby optimizing the thermal field distribution in the single crystal furnace, reducing crystal defects in the single crystal rod 5, improving the crystal quality of the single crystal rod 5, and ensuring that the temperature distribution of the single crystal rod 5 reaches the optimal state during the annealing process.

[0064] As Figure 5 shown, the diversion hood 1 further includes a fastener 2. The hood body 10 is provided with fixing holes 19 for cooperating with the fastener 2. The fixing holes 19 are threaded through holes. The fastener 2 is threadedly connected to the fixing holes 19, and one end of the fastener 2 passes through the fixing holes 19 and abuts against the component to be installed, so as to fix the hood body 10 on the component to be installed, ensuring the stable fixation of the diversion hood 1 in the single crystal furnace and avoiding affecting the thermal field distribution and cooling effect of the single crystal rod 5 due to the displacement of the diversion hood 1 under the action of high temperature and air flow.

[0065] Specifically, the number of the fasteners 2 is multiple, and the number of the fixing holes 19 is also multiple. The multiple fixing holes 19 are arranged at intervals around the center line of the hood body 10, and the multiple fasteners 2 are arranged in one-to-one correspondence with the multiple fixing holes 19. Through the cooperation of the multiple fasteners 2 and the multiple fixing holes 19, the fixing effect of the diversion hood 1 is further enhanced, ensuring the stability and reliability of the diversion hood 1 under the action of high temperature and air flow, making the position of the diversion hood 1 in the single crystal furnace more stable, reducing the problem of uneven thermal field caused by the displacement of the diversion hood 1, improving the stability and repeatability of the annealing process of the single crystal rod 5, and ensuring the consistency of the annealing effect of the single crystal rod 5.

[0066] Optionally, the component to be installed is a throat structure 32, and one end of the fastener 2 passes through the fixing hole 19 and abuts against the inner wall surface of the throat structure 32. The fastener 2 is a solid structure to ensure that the diversion hood 1 does not leak air at the fixing holes 19.

[0067] As Figure 8 and Figure 9 shown, the single crystal furnace further includes an air vent connecting member 6. The first end of the air vent connecting member 6 is arranged in the air inlet 33, and the second end of the air vent connecting member 6 is inserted into the annular flow channel 12 through the inlet hole 121. The air vent connecting member 6 is a hollow cylindrical structure with external threads on its outer peripheral surface. At least one of the air inlet 33 and the inlet hole 121 is a threaded hole threadedly connected to the external threads. The first end of the air vent connecting member 6 is open and the second end is closed. A side opening 61 is further formed on the outer peripheral surface of the second end of the air vent connecting member 6, and both ends of the side opening 61 are communicated with the inner hole of the air vent connecting member 6 and the annular flow channel 12 respectively.

[0068] The ventilation connection member 6 of the present invention can not only provide a stable and accurate fluid inlet channel, but also ensure the sealing and guiding of the flow of the first fluid, realize the control of the injection direction and injection speed of the first fluid, ensure that the first fluid can quickly and stably enter the annular flow channel 12 from the inlet 33, thereby improving the cooling effect on the single crystal silicon rod 5, making the temperature control of the single crystal silicon rod 5 more stable and uniform during the annealing process, reducing the crystal defects of the single crystal silicon rod 5, and improving the electrical properties of the crystal of the single crystal silicon rod 5.

[0069] As Figure 10 shown, the ventilation connection member 6 of the present invention includes a middle hole 60 with an open first end and a closed second end, and a side opening 61 provided on the side of the middle hole 60 and communicating with the middle hole 60. The first end of the middle hole 60 is used to communicate with the inlet 33, and the side opening 61 is used to communicate with the annular flow channel 12.

[0070] The single crystal furnace of the present invention further includes a temperature detection component. The detection probe of the temperature detection component is arranged at a position close to the fluid outlet 112 of the middle flow channel 11 to detect the temperature at a position close to the fluid outlet 112 of the middle flow channel 11, so as to adjust the flow rate of the first fluid at the inlet 33 and / or adjust the speed of lifting the single crystal silicon rod 5 upward according to the detection result of the temperature detection component, in order to achieve the optimal ratio of the annealing temperature and annealing time of the single crystal silicon rod 5, minimize the generation of oxygen precipitation, ensure that the temperature control during the annealing process of the single crystal silicon rod 5 reaches the optimal state, achieve the best cooling effect on the single crystal silicon rod 5, reduce the crystal defects of the single crystal silicon rod 5, and improve the electrical properties of the crystal of the single crystal silicon rod 5.

[0071] The technical effects of the single crystal furnace of the present invention are as follows:

[0072] (1) Improve temperature uniformity

[0073] a. Precise temperature control: The flow guide cover optimizes the heat radiation and air flow path, making the temperature distribution in the single crystal furnace more uniform, avoiding local overheating or overcooling, and ensuring that the single crystal silicon rod is uniformly heated during the entire annealing process.

[0074] b. Reduce thermal stress: The uniform temperature gradient can reduce the internal stress in the crystal caused by thermal expansion and contraction, thereby reducing the formation of lattice defects (such as dislocations and vacancies).

[0075] (2) Improve annealing efficiency

[0076] Shorten the process time: The flow guide cover accelerates the heat transfer and convection, enabling the single crystal silicon rod to quickly reach the critical temperature required for annealing and stably maintain it, shortening the overall process cycle.

[0077] (3) Reduce crystal defects

[0078] a. Suppress abnormal recrystallization: A uniform temperature field avoids non-equilibrium phase transitions caused by local rapid cooling or heating, reducing secondary defects (such as twins and stacking faults).

[0079] b. Improve crystal integrity: A stable thermal environment helps the single-crystal silicon rod maintain an ordered structure and enhances optoelectronic properties (such as minority carrier lifetime).

[0080] (4) Protect the furnace body and silicon wafers

[0081] a. Reduce thermal pollution: The purification environment inside the single-crystal furnace during crystal pulling is the best (high-temperature purification, vacuum, inert gas protection), and the flow guide cover isolates the high-temperature area from contacting the furnace wall, delaying the material aging of the furnace body of the single-crystal furnace.

[0082] b. Reduce particulate deposition: Directed gas flow control can reduce the probability of dust adhering to the surface of single-crystal silicon, avoiding the generation of microdefects.

[0083] (5) Reduce the risk of process fluctuations

[0084] a. Enhanced stability: The flow guide cover can block the interference of external gas flows (such as turbulence caused by the vibration of the vacuum pump), reducing the impact of process parameter fluctuations on the annealing result.

[0085] b. Good repeatability: The consistency between different batches is improved, which is beneficial to the yield control during large-scale production of single-crystal silicon rods.

[0086] (6) Meet the requirements of new processes

[0087] It can be compatible with large-size single-crystal silicon rods: As the demand for silicon wafers with a diameter of 210 mm or more in the photovoltaic industry increases, the setting of the flow guide cover can optimize the thermal management of large-size single-crystal silicon rods and solve the problem of edge heat dissipation.

[0088] As Figure 12 shown, the present invention also provides a method for annealing a single-crystal silicon rod, which is applicable to the above-mentioned single-crystal furnace. The method for annealing a single-crystal silicon rod includes: after the single-crystal silicon rod 5 in the main chamber 3 of the single-crystal furnace grows to completion, a first fluid is introduced into the annular flow channel 12 of the flow guide cover 1 through the inlet 33 of the single-crystal furnace, and a second fluid is introduced into the middle flow channel 11 of the flow guide cover 1 through the upper end of the auxiliary chamber 4 of the single-crystal furnace; the single-crystal silicon rod 5 is lifted upward so that the single-crystal silicon rod 5 gradually passes through the middle flow channel 11.

[0089] The annealing method of the single-crystal silicon rod of the present invention realizes uniform cooling of the surface temperature of the single-crystal silicon rod 5 by precisely controlling the flow directions of the first fluid and the second fluid, as well as the speed of lifting the single-crystal silicon rod 5 upward, thereby optimizing the thermal field distribution in the single-crystal furnace, reducing the crystal defects of the single-crystal silicon rod 5, making the temperature control of the single-crystal silicon rod 5 during the annealing process more precise, and significantly improving the uniformity and electrical properties of the crystal of the single-crystal silicon rod 5.

[0090] Specifically, the flow rate of the first fluid at the inlet 33 is 60 L / min to 80 L / min; and / or the flow rate of the second fluid at the upper end of the auxiliary chamber 4 is 25 L / min to 35 L / min; and / or the speed of lifting the single-crystal silicon rod 5 upward is 60 mm / h to 80 mm / h; and / or the first fluid includes argon; and / or the second fluid includes argon.

[0091] In this way, by adjusting the flow rates of the first fluid and the second fluid and the speed of lifting the single-crystal silicon rod 5 upward, etc., the cooling rate of the single-crystal silicon rod 5 during the annealing process can be precisely controlled, thereby optimizing the heat distribution of the thermal field of the single-crystal silicon rod 5 and reducing the crystal defects of the single-crystal silicon rod 5.

[0092] As Figure 12 shown, the annealing method of the single-crystal silicon rod of the present invention further includes: detecting the temperature at a position near the fluid outlet 112 of the intermediate channel 11, so as to adjust the flow rate of the first fluid at the inlet 33 and / or adjust the speed of lifting the single-crystal silicon rod 5 upward according to the detection result.

[0093] In this way, by real-time monitoring of the temperature at the position near the fluid outlet 112 of the intermediate channel 11, the flow rate of the first fluid at the inlet 33 and the speed of lifting the single-crystal silicon rod 5 upward can be adjusted in a timely manner, which can ensure that the temperature control of the single-crystal silicon rod 5 during the annealing process reaches the optimal state, achieve the best cooling effect of the single-crystal silicon rod 5, reduce the crystal defects of the single-crystal silicon rod 5, and improve the electrical properties of the crystal.

[0094] In an embodiment of the annealing method of the single-crystal silicon rod of the present invention, after the initial furnace start-up, the inlet 33 at the throat structure 32 equipped with the flow guide cover 1 can be opened simultaneously, so that the argon gas at the inlet 33 flows into the annular flow channel 12 at a flow rate of 70 L / min, and the argon gas at the top of the auxiliary chamber 4 flows into the middle flow channel 11 at a flow rate of 30 L / min. The argon gas introduced at the inlet 33 is evenly blown onto the surface of the single-crystal silicon rod 5 through the annular flow channel 12 of the flow guide cover 1. At this time, since most of the argon gas is directly blown in from the inlet 33, it can quickly take away the temperature on the surface of the single-crystal silicon rod 5 by using its own temperature after being blown onto the surface of the single-crystal silicon rod 5 over a short distance, thereby forming a certain temperature difference at the throat structure 32, corresponding to the oxygen precipitation temperature, to reduce its generation, and thus reduce its influence on the minority carrier lifetime of the single-crystal silicon rod 5 and improve the minority carrier lifetime of the single-crystal silicon rod 5. The argon gas introduced at the top of the auxiliary chamber 4 is mainly used to prevent the argon gas introduced at the inlet 33 from failing to exert a vertically downward pressure on a small part of the oxides, and is used to assist the argon gas introduced at the throat structure 32 to exert a certain downward pressure on the floating oxides.

[0095] The setting principle in the single-crystal furnace of the present invention is as follows:

[0096] (1) The principle of oxygen precipitation generation is as follows: During the entire process of oxygen precipitation generation, only the oxygen dissolution and growth stages can be regulated using the existing conditions of the current single-crystal furnace. The oxygen dissolution stage can be controlled by the oxygen reduction process at the head of the single-crystal silicon rod, and the growth stage can reduce the oxygen precipitation generation time by changing the thermal history of the single-crystal silicon rod in the single-crystal furnace, thereby reducing the generation of oxygen precipitation.

[0097] (2) As Figure 11 shown is the stage schematic diagram of the matching between each part in the single-crystal furnace and each stage of oxygen precipitation generation. In Figure 10 it, S1 represents the nucleation stage, where the gas flow temperature is high, reaching the initial conditions for annealing; S2 represents the growth stage, where the initial cooling degree of the gas flow is high, the supercooling degree increases, and the annealing enters the medium stage; S3 represents the precipitation stage, where the cooling degree of the gas flow is the largest and the supercooling degree at the top is the largest.

[0098] (3) The principle of reducing oxygen precipitation in the single-crystal furnace of the present invention is as follows: As previously known, the minority carrier lifetime is an important indicator for measuring the quality of single crystals. Among the factors affecting the minority carrier lifetime, oxygen precipitation is a relatively important factor. Both the single-crystal furnace and the annealing method of the single-crystal silicon rod of the present invention reduce the generation of oxygen precipitation by changing the thermal history of the single-crystal silicon rod 5 in the single-crystal furnace (including the high-temperature annealing process), thereby improving the minority carrier lifetime. Among them, when the single-crystal silicon undergoes high-temperature annealing, the arrangement structure of its internal atoms will change from the following two aspects:

[0099] a. Principle of diffusion driving force: At high temperatures, silicon atoms have a higher diffusion ability, and high temperatures increase the diffusion coefficient of oxygen atoms in single-crystalline silicon in the silicon crystal. Oxygen atoms will diffuse towards defect regions or the surface in the silicon crystal. For example, at high temperatures of 1000°C to 1200°C, oxygen atoms can move rapidly, diffusing from regions where oxygen precipitates might originally form to the crystal surface or other low-concentration regions. In the single-crystal furnaces in the prior art, due to the absence of a flow guide cover, more oxygen precipitates grow in the single-crystalline silicon here (reasons include inappropriate temperature, short cooling time, and long oxygen precipitate growth time, etc.).

[0100] b. Change in solid solubility: As the temperature rises, the solid solubility of oxygen in silicon changes. At high temperatures, the solid solubility of oxygen in silicon increases, and oxygen atoms that were originally supersaturated and might form oxygen precipitates can dissolve more in the silicon crystal, thus reducing the chance of oxygen precipitate formation.

[0101] From the above description, it can be seen that the above embodiments of the present invention achieve the following technical effects:

[0102] The single-crystal furnace of the present invention includes: a main chamber 3, including a furnace body 31 connected to a throat structure 32 located above the furnace body 31, and the furnace body 31 is used to form a single-crystalline silicon rod 5; a secondary chamber 4 installed above the throat structure 32; a flow guide cover 1 disposed in the main chamber 3 and located at the throat structure 32, and the flow guide cover 1 includes a cover body 10, and an intermediate flow channel 11 for the single-crystalline silicon rod 5 to pass through and an annular flow channel 12 surrounding the intermediate flow channel 11 are provided on the cover body 10; wherein, a through inlet 33 communicating with the inlet of the annular flow channel 12 to introduce a first fluid into the annular flow channel 12 is provided at the throat structure 32; the inlet of the intermediate flow channel 11 communicates with the secondary chamber 4 to receive a second fluid introduced from the secondary chamber 4; the outlet of the annular flow channel 12 communicates with the outlet of the intermediate flow channel 11 so that the first fluid and the second fluid converge to cool the single-crystalline silicon rod 5. In this way, the single-crystal furnace of the present invention changes the argon gas that was all introduced into the furnace from the top of the secondary chamber 4 in the prior art to part of it entering the annular flow channel 12 of the flow guide cover 1 from the throat structure 32 and the other part entering the intermediate flow channel 11 of the flow guide cover 1 from the top of the secondary chamber 4, guiding the argon gas to be evenly distributed in the single-crystal furnace, thereby optimizing the uniformity of the thermal field distribution in the single-crystal furnace, changing the thermal history of the single-crystalline silicon rod 5 in the single-crystal furnace, so that the single-crystalline silicon rod 5 can reach the optimal annealing temperature and annealing time, achieving uniform cooling of the surface temperature of the single-crystalline silicon rod 5, reducing crystal defects of the single-crystalline silicon rod 5 caused by uneven temperature, making the temperature control of the single-crystalline silicon rod 5 during the annealing process more precise, reducing the formation of oxygen precipitates and defects, etc., significantly improving the minority carrier lifetime and quality of the single-crystalline silicon rod 5, solving the problem that the single-crystalline silicon annealing process in the prior art is likely to reduce the minority carrier lifetime of single-crystalline silicon, and being able to effectively improve the production efficiency and product yield of the single-crystalline silicon rod 5.

[0103] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A single crystal furnace, characterized in that, Comprising: A main chamber (3), including a furnace body (31) connected thereto and a throat structure (32) located above the furnace body (31), wherein the furnace body (31) is for forming a single crystal silicon rod (5); An auxiliary chamber (4), installed above the throat structure (32); A flow guiding cover (1), disposed in the main chamber (3) and at the throat structure (32), the flow guiding cover (1) including a cover body (10), and a middle flow channel (11) for the single crystal silicon rod (5) to pass through and an annular flow channel (12) disposed around the middle flow channel (11) are provided on the cover body (10); Wherein, a through inlet (33) communicating with an inlet of the annular flow channel (12) to introduce a first fluid into the annular flow channel (12) is provided at the throat structure (32); an inlet of the middle flow channel (11) communicates with the auxiliary chamber (4) to receive a second fluid introduced from the auxiliary chamber (4); an outlet of the annular flow channel (12) communicates with an outlet of the middle flow channel (11) so that the first fluid and the second fluid converge to cool the single crystal silicon rod (5).

2. The single crystal furnace according to claim 1, characterized in that, An inlet and an outlet of the middle flow channel (11) are respectively a fluid inlet (111) and a fluid outlet (112), the fluid inlet (111) is located above the fluid outlet (112), and the single crystal silicon rod (5) can pass through from the fluid outlet (112) to the fluid inlet (111); both ends of the annular flow channel (12) are closed; further provided on the cover body (10) are: An inlet flow hole (121), disposed at a position on the outer peripheral surface of the cover body (10) close to the fluid inlet (111) and communicating with the annular flow channel (12), serving as an inlet of the annular flow channel (12) to introduce the first fluid into the annular flow channel (12); A plurality of flow guiding holes (122), spacedly disposed at a position on the inner wall surface of the cover body (10) close to the fluid outlet (112) and all communicating with the annular flow channel (12), serving as an outlet of the annular flow channel (12) to spray the first fluid to a position on the middle flow channel (11) close to the fluid outlet (112).

3. The single crystal furnace according to claim 2, wherein, The cover body (10) includes a hollow cylindrical section (13) and a hollow frustum section (14) sequentially connected along its own central axis, and the inner diameter of the hollow frustum section (14) gradually increases in a direction away from the hollow cylindrical section (13); wherein, the fluid inlet (111) is located at one end of the hollow cylindrical section (13) away from the hollow frustum section (14), the fluid outlet (112) is located at one end of the hollow frustum section (14) away from the hollow cylindrical section (13), the inlet flow hole (121) is located on the hollow cylindrical section (13), and the flow guiding holes (122) are located on the hollow frustum section (14).

4. The single crystal furnace according to claim 2 or 3, characterized in that The cover body (10) includes a first annular end plate (15), a second annular end plate (16), a cylindrical inner wall (17) and a cylindrical outer wall (18). The first annular end plate (15) and the second annular end plate (16) are arranged at intervals along the central axis of the cover body (10). The cylindrical inner wall (17) and the cylindrical outer wall (18) are sleeved in sequence along the direction away from the central axis of the cover body (10). The first end of the cylindrical inner wall (17) and the first end of the cylindrical outer wall (18) are respectively connected to the inner side and the outer side of the first annular end plate (15). The second end of the cylindrical inner wall (17) and the second end of the cylindrical outer wall (18) are respectively connected to the inner side and the outer side of the second annular end plate (16). Wherein, the intermediate flow channel (11) is located inside the cylindrical inner wall (17), the annular flow channel (12) is located between the cylindrical inner wall (17) and the cylindrical outer wall (18), the inlet hole (121) is located on the cylindrical outer wall (18), and the diversion hole (122) is located on the cylindrical inner wall (17).

5. The single crystal furnace according to claim 2, wherein, The multiple diversion holes (122) are divided into multiple diversion hole groups, and the multiple diversion hole groups are arranged at intervals around the central axis of the cover body (10). Each of the diversion hole groups includes: one of the diversion holes (122); or at least two of the diversion holes (122), and the at least two diversion holes (122) are arranged at intervals in sequence along the extending direction of the cover body (10).

6. The single crystal furnace according to claim 2, wherein the single crystal furnace further includes a ventilation connecting member (6). The first end of the ventilation connecting member (6) is arranged in the ventilation inlet (33), and the second end of the ventilation connecting member (6) is inserted into the annular flow channel (12) through the inlet hole (121); the ventilation connecting member (6) is a hollow cylindrical structure with external threads provided on its outer peripheral surface, and at least one of the ventilation inlet (33) and the inlet hole (121) is a threaded hole threadedly connected to the external threads; the first end of the ventilation connecting member (6) is open and the second end is closed. A side opening (61) is further formed on the outer peripheral surface of the second end of the ventilation connecting member (6), and both ends of the side opening (61) are respectively communicated with the inner hole of the ventilation connecting member (6) and the annular flow channel (12).

7. The single crystal furnace according to claim 2, wherein, The single crystal furnace further includes a temperature detection component. The detection probe of the temperature detection component is arranged at a position close to the fluid outlet (112) of the intermediate flow channel (11) to detect the temperature at the position close to the fluid outlet (112) of the intermediate flow channel (11), so as to adjust the flow rate of the first fluid at the ventilation inlet (33) and / or adjust the speed of lifting the single crystal rod (5) upward according to the detection result of the temperature detection component.

8. A method for annealing a single crystal silicon rod, characterized in that, Applicable to the single crystal furnace according to any one of claims 1 to 7, the method for annealing a single crystal rod includes: After the single-crystal silicon rod (5) in the main chamber (3) of the single-crystal furnace is grown, the first fluid is introduced into the annular flow channel (12) of the flow guide cover (1) through the inlet (33) of the single-crystal furnace, and the second fluid is introduced into the middle flow channel (11) of the flow guide cover (1) through the upper end of the auxiliary chamber (4) of the single-crystal furnace; Lift the single-crystal silicon rod (5) upward so that the single-crystal silicon rod (5) gradually passes through the middle flow channel (11).

9. The method for annealing a single-crystal silicon rod according to claim 8, wherein, the flow rate of the first fluid at the inlet (33) is 60 L / min to 80 L / min; and / or the flow rate of the second fluid at the upper end of the auxiliary chamber (4) is 25 L / min to 35 L / min; and / or the speed of lifting the single-crystal silicon rod (5) upward is 60 mm / h to 80 mm / h; and / or the first fluid includes argon; and / or the second fluid includes argon.

10. The annealing method of the single-crystal silicon rod according to claim 8, wherein, The method for annealing a single-crystal silicon rod further includes: detecting the temperature at a position near the fluid outlet (112) of the middle flow channel (11) to adjust the flow rate of the first fluid at the inlet (33) and / or adjust the speed of lifting the single-crystal silicon rod (5) upward according to the detection result.

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