Crystal pulling method for czochralski polycrystalline silicon rod and polycrystalline silicon rod

Abstract

The invention provides a crystal pulling method of a czochralski polycrystalline silicon rod and the polycrystalline silicon rod, and belongs to the technical field of polycrystalline silicon production. Comprising a charging procedure, a material melting procedure, a stabilizing procedure, a temperature testing procedure, a welding procedure, an equal-diameter procedure, an ending procedure, a cooling procedure and a furnace cleaning procedure, a special polycrystalline seed crystal is used for crystal pulling, the diameter of the outer circle of the bottom of the special polycrystalline seed crystal is consistent with the diameter of a pulled polycrystalline silicon rod, and the bottom surface of the special polycrystalline seed crystal is a convex arc surface. According to the method, the polycrystalline silicon rod is drawn by adopting a czochralski method, so that the purity of the polycrystalline silicon rod is improved from 6N to 7N, a silicon part with higher requirements can be met, and then the special polycrystalline seed crystal is matched with a new crystal pulling process, so that on one hand, the processes of seeding, shouldering and shoulder rotating can be omitted in the process method, the crystal pulling process period is shortened, and the crystal pulling efficiency is improved; on the other hand, bad crystal flowers at the head and the tail can be reduced, the back-cutting rate of the bad crystal flowers is reduced, and the crystal pulling yield is improved, so that the material utilization rate is improved by more than 35%.

Description

Technical Field

[0001] The present invention relates to the technical field of polycrystalline silicon rod production, and in particular to a crystal pulling method for a CZ-pulled polycrystalline silicon rod and a polycrystalline silicon rod. Background Art

[0002] At present, semiconductor materials are mainly based on silicon, and silicon-based semiconductor materials have more than 90% of the market share. As a semiconductor material, CZ polysilicon rods, especially as components related to etching machines, are trusted by silicon component customers because of their high purity and mechanical properties. As the market demand for the diameter of single crystal silicon rods gradually increases, the demand for the diameter of CZ polysilicon rods is also increasing, from the original 10 inches to more than 14 inches.

[0003] Conventional methods for producing polycrystalline silicon rods are roughly divided into two categories. One category uses a polycrystalline ingot furnace to produce polycrystalline silicon ingots, which are then processed into polycrystalline materials. However, the disadvantage of the polycrystalline materials produced by this method is that the purity of the material does not meet customer requirements. At the same time, the crystal growth situation cannot be seen during the growth process, and the polycrystalline crystal flowers cannot be confirmed. The other category uses a single crystal furnace to pull polycrystalline silicon rods. Its process flow is similar to the method of pulling single crystal silicon rods by the Czochralski method. Both mainly include furnace dismantling, loading, melting, temperature adjustment, crystal seeding, shoulder release, shoulder rotation, equal diameter, tailing, furnace shutdown and other processes. The single crystal furnace Czochralski method can meet the customer's requirements for purity, but the output polycrystalline material has a high scrap rate due to bad crystal flowers, especially the large difference in the size of the crystal flowers at the head / tail, and there are many recuts, and sometimes even half of the equal diameter length is cut off, which seriously affects production efficiency and cost. Since the polycrystalline products required by customers are high-purity and uniform crystal flower polycrystalline sheet materials, tube materials and rod materials. Therefore, it is necessary to provide a crystal pulling process for polycrystalline silicon rods that can simultaneously meet the requirements of high purity and uniform crystal flowers. Summary of the invention

[0004] In view of this, the present invention provides a crystal pulling method for a CZ-pulled polycrystalline silicon rod and a polycrystalline silicon rod, so that the produced polycrystalline silicon rod can simultaneously meet the requirements of high purity and uniform crystal flower.

[0005] The technical solution adopted by the present invention to solve its technical problem is: A method for pulling a polycrystalline silicon rod by vertical pulling includes a charging process, a material chemical process, a stabilization process, a temperature test process, a welding process, a diameter equalization process, a finishing process, a cooling process and a furnace cleaning process, and a special polycrystalline seed crystal is used for crystal pulling, the diameter of the bottom outer circle of the special polycrystalline seed crystal is consistent with the diameter of the polycrystalline silicon rod to be pulled, and the bottom surface of the special polycrystalline seed crystal is a convex arc surface. By using a special polycrystalline seed crystal with a corresponding crystal pulling process, the process method can omit the crystal seeding, shoulder release, and shoulder rotation processes, shorten the crystal pulling process cycle, and improve the crystal pulling efficiency; it can also reduce the head and tail crystal flower defects, reduce the crystal flower defect back-cutting rate, and improve the crystal pulling yield, thereby increasing the material utilization rate by more than 35%.

[0006] Preferably, in the temperature test process, the special polycrystalline seed crystal is preheated, and after the preheating is completed, the special polycrystalline seed crystal is lowered at a pulling speed of 5-15 mm / min, and the edge of the special polycrystalline seed crystal is observed to contact the liquid surface for temperature test. By fully preheating the special polycrystalline seed crystal, the seed crystal is prevented from being cracked by thermal shock when it is close to the liquid surface, thereby affecting the growth quality of the polycrystalline silicon rod.

[0007] Preferably, the preheating of the special polycrystalline seed crystal includes: controlling the special polycrystalline seed crystal to descend, so that the special polycrystalline seed crystal stays at the upper position of the heat shield for preheating for 30-60 minutes, then descending to the middle position of the heat shield for preheating for 30-60 minutes, and finally descending to 20-35 mm above the liquid surface at a speed of 5-30 mm / min for preheating for 60-90 minutes. By preheating the special polycrystalline seed crystal in sections, the temperature of the seed crystal can be controlled to be close to the temperature of the liquid surface, thereby preventing the seed crystal from being cracked by thermal shock when it is close to the liquid surface.

[0008] Preferably, when the crystal pulling method is used for the first time, in the temperature test process, a conventional single crystal seed crystal is first used to test the temperature to determine the center temperature and power, and then the special multi-crystalline seed crystal is replaced for preheating and temperature test. By determining the center temperature and power by a conventional single crystal seed crystal, the temperature test point can be determined more quickly, thereby improving the crystal pulling efficiency.

[0009] Preferably, in the welding process, the welding time is 60-150 minutes. A longer welding time can make the special polycrystalline seed crystal completely welded, which is convenient for the subsequent equal diameter process.

[0010] Preferably, in the equal diameter process, the average pulling speed is set at 0.3-0.6 mm / min, the equal diameter crystal rotation is set at 4-8 rpm, the equal diameter crucible rotation is set at 8-12 rpm, the argon flow rate is set at 100-130 slm, and the pressure is set at 1.5-3 kPa. By adopting appropriate pulling speed, crystal rotation, crucible rotation, argon flow rate and pressure, it is conducive to the uniform growth of crystal flowers.

[0011] Preferably, the finishing process starts when the remaining material in the pot is 35-50kg to ensure the uniformity of the crystal flowers at the end.

[0012] Preferably, in the cooling process, the power is reduced to 0 kW and the pressure is reduced to 50-80 slm within 2-3 hours after entering the cooling process, and flow pressure cooling is performed.

[0013] Preferably, the special polycrystalline seed crystal is fixed to the pulling mechanism by a special seed crystal tooling, and the special seed crystal tooling includes a seed crystal rope hook, a polycrystalline weight, a polycrystalline seed crystal tooling, and a polycrystalline seed crystal anti-drop protection cover. The polycrystalline seed crystal tooling and the clamping part of the special polycrystalline seed crystal are jacketed to connect the special polycrystalline seed crystal to the special seed crystal tooling to prevent the special polycrystalline seed crystal from falling during the crystal pulling process.

[0014] A polycrystalline silicon rod is pulled by the above-mentioned direct-pull polycrystalline silicon rod crystal pulling method.

[0015] Compared with the prior art, the present invention has the following beneficial effects: The present invention firstly adopts the Czochralski method to pull polycrystalline silicon rods to increase their purity from 6N to 7N, which can meet the silicon components with higher requirements. Secondly, the use of special polycrystalline seed crystals in combination with the crystal pulling process of the present invention can, on the one hand, omit the seeding, shoulder release, and shoulder rotation steps in the process method, shorten the crystal pulling process cycle, and improve the crystal pulling efficiency. On the other hand, it can reduce the defective crystal flowers at the head and tail, reduce the defective crystal flower re-cutting rate, and improve the crystal pulling yield, thereby increasing the material utilization rate by more than 35%. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 The present invention is a process flow chart of the crystal pulling method for directly pulling polycrystalline silicon rods.

[0017] Figure 2 It is a schematic structural diagram of the special polycrystalline seed crystal of the present invention.

[0018] Figure 3 This is a diagram showing the coordination of the special seed crystal tooling and the special polycrystalline seed crystal of the present invention.

[0019] Figure 4 It is the equal diameter process curve diagram of the present invention.

[0020] Figure 5 This is a process flow chart for the comparative example.

[0021] Figure 6 FIG. 4 is a cross-sectional view of a polycrystalline silicon rod pulled by the method of the embodiment.

[0022] Figure 7 This is a cross-sectional view of a polycrystalline silicon rod pulled by a comparative example method.

[0023] Figure 8 It is a comparison chart of the direct pulling yield of the embodiment and the comparative example.

[0024] Fig. 9 It is a comparison chart of the defective re-cutting rate of the crystal flower of the embodiment and the comparative example.

[0025] In the figure: 1: special polycrystalline seed crystal, 2: seed crystal rope hook, 3: polycrystalline weight, 4: polycrystalline seed crystal tooling, 5: polycrystalline seed crystal anti-drop protection cover, 6: bottom outer circle of special polycrystalline seed crystal, 7: clamping part, 8: polycrystalline seed crystal welding arc surface. DETAILED DESCRIPTION

[0026] The technical solutions and technical effects of the embodiments of the present invention are further described in detail below in conjunction with the accompanying drawings of the present invention.

[0027] Please also see Figure 1 and Figure 2 A method for pulling a polycrystalline silicon rod by pulling a crystal includes a charging process, a material processing process, a stabilization process, a temperature test process, a welding process, a diameter equalization process, a finishing process, a cooling process and a furnace cleaning process, and a special polycrystalline seed crystal is used for crystal pulling. The diameter of the outer circle 6 of the bottom of the special polycrystalline seed crystal is consistent with the diameter of the polycrystalline silicon rod to be pulled, and the bottom surface of the special polycrystalline seed crystal is a convex arc surface, that is, Figure 2 The polycrystalline seed crystal is shown welded to an arc surface 8.

[0028] Since the diameter of the crystal does not increase uniformly during the shouldering stage, it increases slowly at the beginning and then quickly accelerates. This change in diameter has an important impact on the formation of the crystal flower and the quality of the crystal. If the diameter change during the shouldering stage is not properly controlled, defects may appear inside the crystal, thus affecting the uniformity and quality of the crystal flower. And the shoulder rotation operation also needs to be precisely controlled to ensure that the growth rate of the crystal in all directions remains consistent to avoid crystal defects caused by uneven growth rates. If the shoulder rotation operation is improper, irregular growth lines may appear in the crystal flower, affecting the appearance and performance of the crystal.

[0029] The special polycrystalline seed crystal used in the present invention has a bottom outer diameter consistent with the diameter of the polycrystalline silicon rod to be pulled, so it is not necessary to expand the diameter of the seed crystal through the shoulder release process to achieve the same diameter as the polycrystalline silicon rod to be pulled, thereby eliminating the seed crystal, shoulder release, and shoulder rotation processes in the process method, shortening the crystal pulling process cycle and improving the crystal pulling efficiency; on the other hand, it can reduce the impact of shoulder release and shoulder rotation on lateral growth, eliminate the defective crystal flower at the head position, and improve the material utilization rate. In addition, the bottom of the special polycrystalline seed crystal of the present invention adopts a convex arc surface, which can prevent the seed crystal from breaking when the bottom contacts the liquid surface, and ensure the growth quality of the polycrystalline silicon rod. Therefore, the present invention firstly uses the direct pulling method to pull the polycrystalline silicon rod to increase its purity from 6N to 7N, which can meet the silicon components with higher requirements. Secondly, the special polycrystalline seed crystal is used in combination with the crystal pulling process of the present invention to reduce the defective crystal flower at the head and tail, reduce the defective crystal flower re-cutting rate, and improve the crystal pulling yield, thereby increasing the material utilization rate by more than 35%.

[0030] In some embodiments, the special polycrystalline seed crystal of the present invention is made of a polycrystalline silicon rod with uniform crystal flowers and low impurities, so as to ensure that the crystal flowers at the head of the drawn polycrystalline silicon rod are uniform. When the equal diameter process is performed later, the crystal flowers in the horizontal direction of the polycrystalline silicon rod when it grows longitudinally are consistent with the crystal flowers of the special polycrystalline seed crystal, and are always evenly distributed. In addition, the bottom of the special polycrystalline seed crystal of the present invention adopts a convex arc surface. Due to the relationship between the radial temperature gradient, the center temperature is the lowest and the surrounding temperature is high. If the bottom of the seed crystal is a plane, the middle of the seed crystal is cool, and the surrounding temperature suddenly rises, causing the seed crystal to be easily broken due to thermal expansion and contraction. Therefore, the bottom of the special polycrystalline seed crystal of the present invention adopts a convex arc surface. In the welding process, the arc surface of the seed crystal can be gradually melted, gradually from the center to both sides, so that the seed crystal is heated evenly and prevents large surfaces from directly contacting and breaking.

[0031] Further, please also see Figure 2 and Figure 3 The special polycrystalline seed crystal 1 is fixed to the pulling mechanism by a special seed crystal tool. The special seed crystal tool includes a seed crystal rope hook 2, a polycrystalline weight 3, a polycrystalline seed crystal tool 4, and a polycrystalline seed crystal anti-drop protection sleeve 5. The polycrystalline seed crystal tool 4 is clamped with the clamping part 7 of the special polycrystalline seed crystal to connect the special polycrystalline seed crystal 1 with the special seed crystal tool. Specifically, the polycrystalline seed crystal tool 4 is clamped in the clamping part 7 of the special polycrystalline seed crystal, and the polycrystalline seed crystal anti-drop protection sleeve 5 is set at the connection between the polycrystalline seed crystal tool 4 and the clamping part 7 to fix the polycrystalline seed crystal tool 4, further strengthen the fixation between the special polycrystalline seed crystal 1 and the special seed crystal tool, and prevent the special polycrystalline seed crystal from falling during the crystal pulling process.

[0032] Furthermore, when the crystal pulling method is used for the first time, in the temperature test process, a conventional single crystal seed crystal temperature test is first used to determine the center temperature and power, and then replaced with a special polycrystalline seed crystal for preheating and temperature test. Since it is difficult to find the temperature test point when the crystal pulling method of the present invention is used to pull a polycrystalline silicon rod for the first time, it is necessary to use a conventional single crystal seed crystal temperature test to determine the center temperature and power after the silicon material is melted and stabilized, and then replace the special polycrystalline seed crystal. When the crystal pulling method of the present invention is used again after the first use, the special polycrystalline seed crystal can be directly used for temperature test, and the conventional single crystal seed crystal temperature test is no longer used.

[0033] Furthermore, in the temperature test process, the special polycrystalline seed crystal is preheated, and after the preheating is completed, the special polycrystalline seed crystal is lowered at a pulling speed of 5-15mm / min, and the edge of the special polycrystalline seed crystal is observed to contact the liquid surface for temperature test. The special polycrystalline seed crystal of the present invention has a large heating area and volume, and is a polycrystalline material, so it needs to be fully preheated to make the temperature of the special polycrystalline seed crystal uniform, and reduce the temperature difference between the seed crystal and the molten silicon, thereby reducing the thermal stress generated in the seed crystal when the seed crystal contacts the molten silicon, and preventing the seed crystal from being cracked by thermal shock when it is close to the liquid surface.

[0034] Furthermore, preheating the special polycrystalline seed crystal includes: controlling the special polycrystalline seed crystal to descend, so that the special polycrystalline seed crystal stays at the upper position of the heat screen for preheating for 30-60 minutes, then descending to the middle position of the heat screen for preheating for 30-60 minutes, and finally descending to 20-35mm above the liquid surface at a speed of 5-30mm / min for preheating for 60-90 minutes. Specifically, since the internal temperature of the seed crystal is difficult to collect, but in order to ensure that the difference between the seed crystal temperature and the liquid surface temperature is small when the seed crystal is close to the liquid surface, a segmented preheating method is adopted, which can control the temperature of the seed crystal to be close to the temperature of the liquid surface. Among them, the manual state is adopted when controlling the descent of the special polycrystalline seed crystal, and the operating handle descends the special polycrystalline seed crystal. 20-35mm above the liquid surface can be observed and determined by the edge of the seed crystal being about 10-35mm away from the liquid surface.

[0035] Furthermore, in the welding process, the welding time is 60-150 minutes. Because the contact area between the special polycrystalline seed crystal and the silicon liquid surface is large, and the radial temperature gradient, in which the radial temperature gradient of the melt is mainly determined by the heaters on all sides, the center temperature is low, and the temperature is higher as it goes outward, so that the temperature of the special polycrystalline seed crystal from the inside to the outside surface is different, and the internal welding time of the special polycrystalline seed crystal is longer than the surface welding time, so in order to ensure that the special polycrystalline seed crystal is completely welded, the welding time should be as long as possible. After complete welding, the deviation of the radial temperature gradient can be reduced, that is, the deviation from the center to the edge of the seed crystal, and the convex arc surface at the bottom of the special polycrystalline seed crystal can be cut into a plane, which is convenient for the equal diameter process.

[0036] Furthermore, in the equal diameter process, the average pulling speed is set at 0.3-0.6mm / min, the equal diameter crystal rotation is set at 4-8rpm, the equal diameter crucible rotation is set at 8-12rpm, the argon flow rate is set at 100-130slm, and the pressure is set at 1.5-3kpa. After welding, the equal diameter process begins. During the equal diameter process, the crystal flower must be consistent with the crystal flower of the special multi-crystalline seed crystal. Figure 4 The temperature and pulling speed curve of the equal diameter process shown in the figure adjusts the temperature parameters and controls the average pulling speed in the range of 0.3-0.6mm / min to prevent the high pulling speed from affecting the uniformity of the crystal flower. The equal diameter crystal rotation is set to 4-8rpm. Properly reducing the crystal rotation can reduce the thermal convection of the silicon liquid and make the solid-liquid interface tend to be stable. The equal diameter crucible rotation is set to 8-12rpm. Appropriately large crucible rotation stirring makes the impurity distribution more uniform and improves the radial temperature distribution, which is more conducive to the uniform growth of the crystal flower. The argon flow rate is set to 100-130slm and the pressure is set to 1.5-3kpa. During the equal diameter process, keep an eye on the window to understand the crystal growth situation and the longitudinal distribution of the crystal flower.

[0037] Furthermore, the finishing process starts when the remaining material in the pot is 35-50kg. Because the shape of the finishing directly affects the uniformity of the tail crystal flower, but the diameter camera at the time of finishing cannot be captured and can only be determined by the change in weight and length, so the finishing time is determined according to the remaining material at the bottom of the pot. The present invention starts the finishing process when the remaining material in the pot is 35-50kg, and in order to ensure the uniformity of the tail crystal flower, the temperature and pulling speed are controlled to ensure that the length of the finishing is greater than or equal to the diameter of the pulled polysilicon rod, and the cross section is less than 100mm.

[0038] Furthermore, in the cooling process, the power is reduced to 0kw and the pressure is reduced to 50-80slm within 2-3 hours after entering the cooling process, and flow pressure cooling is performed.

[0039] A polycrystalline silicon rod is pulled by the above-mentioned direct-pull polycrystalline silicon rod crystal pulling method. Example

[0040] The equipment used in the embodiment is a CZ single crystal furnace, and the thermal field structure is selected as a 28-inch thermal field, and its thermal field structure mainly includes: inner and outer guide tubes, graphite crucibles, main heaters, bottom heaters, insulation barrels, soft felt, bottom insulation materials and other components, and the feed amount is 300-350kg. Figure 1 The process flow shown in FIG. 1 is used to pull the crystal. The crystal pulling parameters refer to the parameters in the above specific implementation mode. The crystal pulling process adopts the following method: Figure 2 and Figure 3 The special polycrystalline seed crystal and special seed crystal tooling shown are used to pull the crystal rod to obtain a polycrystalline silicon rod.

[0041] Comparative Example The equipment, thermal field structure and feeding amount used in the comparative example are the same as those in the embodiment. Figure 5 The process flow shown is used for crystal pulling. During the crystal pulling process, conventional seed crystals are used to pull crystal rods to obtain polycrystalline silicon rods.

[0042] The cross section of the polycrystalline silicon rod pulled by the embodiment is as follows: Figure 6 As shown; the cross section of the polycrystalline silicon rod pulled by comparison is as follows Figure 7 It can be seen that the polycrystalline silicon rods pulled by the crystal pulling method of the present invention and the special polycrystalline seed crystals have uniform polycrystalline flowers, while the polycrystalline silicon rods pulled by the comparative example have poor polycrystalline flowers.

[0043] The yields of the polycrystalline silicon rods pulled by the embodiment and the comparative example were calculated respectively, and the following results were obtained: Figure 8The comparison diagram is shown. The yield refers to the ratio of the successfully pulled single crystal silicon rods to the input high-purity polycrystalline silicon raw materials during the crystal pulling process. It can be seen that the polycrystalline silicon rods pulled in the comparative example are affected by the material properties and the seed crystal, and the crystal pulling yield is about 65%. Compared with the polycrystalline silicon rods pulled in the comparative example, the polycrystalline silicon rods pulled in the embodiment increase the crystal pulling yield by more than 9%.

[0044] Furthermore, the defective re-cutting rates of the polycrystalline silicon rods pulled in the embodiment and the comparative example were calculated respectively, and the following results were obtained: Fig. 9 As shown in the comparison diagram. It can be seen that the head and tail defective crystal flower re-cutting rate of the polycrystalline silicon rod drawn by the comparative example is high, because the defective crystal flower re-cuts about 30% of the material in the processing stage, and the re-cut part is scrapped or melted back, so that the utilization rate of the polycrystalline material is not high. The polycrystalline silicon rod drawn by the embodiment can reduce the re-cutting rate of the head crystal flower defect to 1.2%, almost eliminating the head crystal flower defect, and at the same time can reduce the re-cutting rate of the tail crystal flower defect to 4.6%, thereby increasing the utilization rate of the polycrystalline material by more than 35%.

[0045] What is disclosed above is only a preferred embodiment of the present invention, which certainly cannot be used to limit the scope of rights of the present invention. A person skilled in the art can understand that all or part of the processes of the above embodiments and equivalent changes made according to the claims of the present invention still fall within the scope of the invention.

Claims

1. A method for pulling a polycrystalline silicon rod by pulling a polycrystalline silicon rod, characterized in that: The process includes a loading process, a chemical process, a stabilization process, a temperature testing process, a welding process, a diameter equalization process, a finishing process, a cooling process and a furnace cleaning process, and uses a special polycrystalline seed crystal for crystal pulling. The outer diameter of the bottom of the special polycrystalline seed crystal is consistent with the diameter of the pulled polycrystalline silicon rod, and the bottom surface of the special polycrystalline seed crystal is a convex arc surface.

2. The method for pulling a polycrystalline silicon rod according to claim 1, characterized in that: In the temperature testing process, the special polycrystalline seed crystal is preheated, and after the preheating is completed, the special polycrystalline seed crystal is lowered at a pulling speed of 5-15 mm / min to observe the position where the edge of the special polycrystalline seed crystal contacts the liquid surface for temperature testing.

3. The method for pulling a CZ-pull polycrystalline silicon rod according to claim 2, characterized in that: The preheating of the special polycrystalline seed crystal includes: controlling the special polycrystalline seed crystal to descend so that the special polycrystalline seed crystal stays at the upper position of the heat shield for preheating for 30-60 minutes, then descending to the middle position of the heat shield for preheating for 30-60 minutes, and finally descending at a speed of 5-30 mm / min to 20-35 mm above the liquid surface for preheating for 60-90 minutes.

4. The method for pulling a CZ-pull polycrystalline silicon rod according to claim 3, characterized in that: When the crystal pulling method is used for the first time, in the temperature testing process, a conventional single crystal seed crystal is first used to test the temperature to determine the center temperature and power, and then replaced with the special multi-crystalline seed crystal for preheating and temperature testing.

5. The method for pulling a CZ-pull polycrystalline silicon rod according to claim 1, characterized in that: In the welding process, the welding time is 60-150 minutes.

6. The method for pulling a CZ-pull polycrystalline silicon rod according to claim 1, characterized in that: In the equal-diameter process, the average pulling speed is set at 0.3-0.6 mm / min, the equal-diameter crystal rotation is set at 4-8 rpm, the equal-diameter crucible rotation is set at 8-12 rpm, the argon flow rate is set at 100-130 slm, and the pressure is set at 1.5-3 kPa.

7. The method for pulling a polycrystalline silicon rod according to claim 1, characterized in that: When the remaining material in the pot is 35-50kg, the finishing process begins.

8. The method for pulling a CZ-pull polycrystalline silicon rod according to claim 1, characterized in that: In the cooling process, the power is reduced to 0kw and the pressure is reduced to 50-80slm within 2-3 hours after entering the cooling process, and flow pressure cooling is performed.

9. The method for pulling a CZ-pull polycrystalline silicon rod according to any one of claims 1 to 8, characterized in that: The special polycrystalline seed crystal is fixed to the pulling mechanism by a special seed crystal tooling, and the special seed crystal tooling includes a seed crystal rope hook, a polycrystalline weight, a polycrystalline seed crystal tooling, and a polycrystalline seed crystal anti-detachment protective cover. The polycrystalline seed crystal tooling and the clamping part of the special polycrystalline seed crystal are clamped to connect the special polycrystalline seed crystal to the special seed crystal tooling.

10. A polycrystalline silicon rod, characterized in that: The polycrystalline silicon rod is pulled by the crystal pulling method of any one of claims 1 to 9.

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