Method for reducing axial resistivity attenuation of N-type silicon single crystal rod

Abstract

The invention relates to the technical field of crystal pulling methods of single crystal silicon rods, in particular to a method for reducing axial resistivity attenuation of an N-type single crystal silicon rod, which comprises the stages of preparation work, stabilization, seeding, shouldering, shoulder rotation, equal diameter and ending. The adsorption tool is placed on the inner wall of the guide cylinder and close to the molten silicon liquid level, small holes are formed in the surface, the surface area is increased, and the phosphorus atom adsorption rate in the environment is increased; through adsorption of the adsorption tool, the growth environment of the crystal is not changed, the dislocation generation probability in the crystal is reduced, meanwhile, phosphorus atoms are stably adsorbed, the phosphorus atoms in the environment cannot enter the crystal in the crystal growth process, and therefore the problem that the tail resistance is low is solved. And the effect of effectively controlling the axial resistivity is achieved on the whole.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of single crystal silicon rod pulling method, and particularly relates to a method for reducing axial resistivity attenuation of N-type single crystal silicon rod. BACKGROUND

[0002] Most of the single crystal silicon rods are manufactured by the Czochralski method, also known as the Czochralski method. The method is driven by the principle of condensation crystallization of the melt. At the interface between the solid and the liquid, the phase change from liquid to solid is generated due to the temperature drop of the melt. In the method, the polycrystalline silicon melt is placed in a quartz crucible and heated to melt the polycrystalline silicon melt in the quartz crucible. Then, through the processes of crystal pulling, necking, shoulder setting, constant diameter and tailing, the single crystal silicon rod without dislocation is finally pulled.

[0003] At present, the first generation of semiconductor phosphorus-doped single crystal silicon rods are pulled by the Czochralski method, and the axial resistivity attenuation can only be slowed down by adjusting the furnace pressure or the crucible rotation ratio. In order to more effectively control the resistivity attenuation, the product delivery rate is improved within the same resistivity range. Through the control of argon flow and furnace pressure, the control accuracy of the throttle valve and the stability of the vacuum pump are required to a certain extent. At the same time, changing the argon flow and the furnace pressure will directly affect the crystal growth and increase the probability of dislocation. Through the improvement of the crucible rotation ratio, when the crucible rotation ratio is too large, the crystal will produce arc, liquid surface will shake and other adverse conditions. SUMMARY

[0004] The purpose of the present application is to overcome the shortcomings in the prior art and provide a method for reducing the axial resistivity attenuation of N-type single crystal silicon rod.

[0005] The present application is implemented by the following technical solutions: A method for reducing the axial resistivity attenuation of N-type single crystal silicon rod, including preparation, stabilization, crystal pulling, shoulder setting, shoulder rotation, constant diameter and tailing stages; the specific steps are as follows: S1: preparation, including S11. raw material preparation: preparing polycrystalline silicon material and dopant, and using ultra-high purity solar-grade or electronic-grade polycrystalline silicon blocks / particles for the polycrystalline silicon material; S12. Quartz crucible preparation: using high-purity, non-polluted transparent quartz crucible; S13. Absorption tool placement, the absorption tool is placed on the inner wall of the flow guide cylinder, close to the molten silicon liquid surface, for improving the phosphorus atom absorption rate in the environment.

[0006] In an embodiment of the present application, S2: vacuum pumping and gas charging, including S21. vacuum pumping: closing the furnace chamber and starting the vacuum pump to pump the pressure in the furnace to a lower vacuum degree; S22. Inert gas filling: high purity argon is filled into the furnace body and maintained at a proper positive pressure.

[0007] In an embodiment of the present application, S3: melting includes S31. Heating: starting the heater, slowly increasing the power, and heating the quartz crucible and the silicon material inside; S32. Holding the melting temperature: after the temperature exceeds the melting point of silicon, the temperature is maintained until all the solid silicon material is completely melted into bright red molten silicon liquid with mirror surface reflection; S33. Stabilization: after the silicon material is completely melted, a period of time is required for stabilization; at the same time, the melt is made more uniform by rotating the quartz crucible and the seed crystal shaft.

[0008] In an embodiment of the present application, S4: seeding includes S41. Temperature reduction and seed lowering: the temperature of the melt is adjusted to a superheat state slightly higher than the melting point, and then the rotating seed crystal is slowly lowered until the tip is immersed into the surface of the silicon melt; S42. Fusion: by controlling the temperature reduction rate, the part of the seed crystal in contact with the melt is also slightly melted, and then by controlling the temperature increase, the fusion of the seed crystal and the melt is achieved; S43. Fine neck pulling: after the seed crystal and the melt are fused, the crystal is pulled upward at a relatively fast speed while the seed crystal is rotated.

[0009] In an embodiment of the present application, S5: shoulder formation includes, S51. Shoulder formation: after the fine neck grows to a sufficient length, the diameter of the crystal is gradually increased from the fine neck to form a conical shoulder by gradually reducing the pulling speed and accurately controlling the temperature; S52. Shoulder turning: when the diameter of the crystal increases to close to the target diameter, the next step is started.

[0010] In an embodiment of the present application, S6: constant diameter growth includes S61. Diameter control: the shape of the crystal and the meniscus of the melt is monitored in real time by a diameter measuring instrument based on a CCD camera or a laser.

[0011] In an embodiment of the present application, S7: end includes S71. Start of the end: when the crystal grows to a predetermined length, or the remaining molten silicon in the crucible is about 10-20%, the end stage is entered; S72. Process: by significantly increasing the pulling speed and simultaneously increasing the temperature, the diameter of the crystal is rapidly reduced, and finally a sharp conical tail is formed; S8: Cooling and taking out includes, S81. Crystal bar cooling: after the growth is completed, the crystal bar is pulled to the upper cooling area of the furnace chamber; S82. Furnace chamber cooling and cavitation: Stop argon gas filling after the crystal rod and furnace components have cooled to a safe temperature; S83. Remove the crystal rod: Open the furnace chamber and remove the complete single crystal silicon rod; S84. Post-processing: Using a diamond wire saw or external cylindrical grinder, the seed crystal, shoulder, and tail end of the crystal rod are removed, and the cylindrical surface is ground and polished to obtain a silicon ingot with accurate dimensions and a smooth surface, in preparation for subsequent slicing.

[0012] In one embodiment of this application, the adsorption fixture includes a fixture body, the inner wall of which is provided with a plurality of micropores, thereby further increasing the structural area of ​​the adsorption fixture.

[0013] In one embodiment of this application, the adsorption fixture includes a fixture body II, the inner wall of which is provided with a plurality of micropores II; at the same time, a plurality of protrusions are provided between each row of micropores II on the inner side of the fixture body II; the combination of protrusions and micropores II further increases the structural area of ​​the adsorption fixture.

[0014] In one embodiment of this application, the adsorption fixture includes a fixture body three, the inner wall of which is provided with a plurality of micropores three; at the same time, a strip plate is provided between each row of micropores three inside the fixture body three; each strip plate is provided with a plurality of micropores four; the combination of the strip plate and the micropores one further increases the structural area of ​​the adsorption fixture.

[0015] The beneficial effects of this application are: 1. The material of the adsorption tool is calcium-based oxide ceramic. Properties: calcium oxide has a NaCl-type crystal structure, a density of 0.08~3.40 g / cm3, a melting point of 2570℃, and thermodynamic stability.

[0016] 2. At high temperatures (>1200℃), calcium oxide (CaO) reacts with phosphorus vapor (P4 or P2) to form stable phosphates, which are adsorbed on the surface of the adsorption tool: 3 CaO + P4 → Ca3(PO4)2. This type of reaction can effectively convert gaseous phosphorus into solid compounds, reducing its diffusion into the silicon melt. By using an adsorption fixture, the crystal growth environment is not altered, the probability of dislocation formation in the crystal is reduced, and phosphorus atoms are stably adsorbed, preventing phosphorus atoms from the environment from re-entering the crystal during crystal growth, thereby improving the low tail resistance problem. Overall, this achieves effective control of axial resistivity. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the heater structure of this application; Figure 2 This is a schematic diagram of the tooling structure of this application; Figure 3 This is a schematic diagram of the tooling body two structure of this application; Figure 4 This is a schematic diagram of the three-dimensional structure of the tooling body in this application.

[0018] Reference numerals: 1. Heater; 11. Furnace body; 12. Insulation layer; 13. Quartz crucible; 131. Crucible connecting rod; 14. Heating zone; 15. Guide tube; 2. Adsorption fixture; 21. Fixture body one; 211. Micropore one; 22. Fixture body two; 221. Micropore two; 222. Protrusion; 23. Fixture body three; 231. Micropore three; 232. Strip plate; 233. Micropore four. Detailed Implementation

[0019] To enable those skilled in the art to better understand the technical solutions in this application, the technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0020] It should be noted that when a component is referred to as being "fixed to" or "set on" another component, it can be directly on or indirectly set on the other component; when a component is referred to as being "connected to" another component, it can be directly connected to or indirectly connected to the other component.

[0021] It should be understood that the terms "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", and "outer" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or component referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0022] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" or "several" means two or more, unless otherwise explicitly specified.

[0023] It should be noted that the structures, proportions, sizes, etc., shown in the accompanying drawings of this specification are only for the purpose of assisting those skilled in the art in understanding and reading the content disclosed in the specification, and are not intended to limit the conditions under which this application can be implemented. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in the proportions, or adjustments to the size should still fall within the scope of the technical content disclosed in this application, provided that they do not affect the effects and purposes that this application can produce. Example

[0024] Please refer to Figures 1-4 As shown, this application proposes a method for reducing the axial resistivity decay of N-type single-crystal silicon rods, including preparation, stabilization, crystal pulling, shoulder formation, shoulder rotation, equal diameter setting, and finishing stages; the specific steps are as follows: S1: Preparations S11. Raw material preparation: Prepare polysilicon material and dopants. Use ultra-high purity solar-grade or electronic-grade polysilicon blocks / particles.

[0025] The dopant used is phosphorus as the n-type dopant. It can be in the form of a high-phosphorus doped master alloy: a pre-drawn silicon rod containing a high concentration of phosphorus, with precise composition and easy control. Doping amount calculation: Based on the target resistivity, the segregation coefficient of phosphorus in silicon, and the total mass of the silicon material, the required mass of dopant is precisely calculated. This is one of the most critical calculations, directly determining the resistivity of the finished silicon.

[0026] S12. Quartz Crucible Preparation: Use a high-purity, uncontaminated, transparent quartz crucible. It is the only container capable of withstanding high-temperature molten silicon without introducing excessive impurities.

[0027] S13. Placement of adsorption fixture 2: The adsorption fixture 2 is placed on the inner wall of the guide tube, close to the surface of the molten silicon.

[0028] S2: Vacuuming and Inflating S21. Vacuuming: Close the furnace chamber and start the vacuum pump to evacuate the furnace to a low vacuum level. The purpose is to remove oxygen and moisture from the furnace to prevent silicon from being oxidized (forming silicon dioxide) at high temperatures.

[0029] S22. Induction of Inert Gas: High-purity argon gas is introduced into furnace body 11 and maintained at a suitable positive pressure. The role of argon gas is: as a protective gas to prevent residual oxidizing gases from reacting with silicon; and as a carrier gas to carry reaction byproducts and volatile dopants (phosphorus) out of the furnace.

[0030] S3: Melting S31. Heating: Start heater 1 and slowly increase the power to heat the quartz crucible 13 and the silicon material inside. The heating process needs to be slow and controlled to prevent the silicon material from cracking or impacting the wall of the quartz crucible 13 due to thermal stress.

[0031] S32. Heat preservation and melting: After the temperature exceeds the melting point of silicon, maintain the temperature until all solid silicon material is completely melted into a bright red molten silicon liquid with a mirror-like surface.

[0032] S33. Stabilization: After the silicon material is completely melted, it needs to be kept at a constant temperature for a period of time (approximately 30-60 minutes) to ensure that the melt temperature is uniform and stable, and to allow volatile impurities and bubbles to escape fully. At the same time, the rotation of the quartz crucible 13 and the seed crystal axis makes the melt flow more uniform.

[0033] S4: seeding S41. Cooling and Seed Crystal Lowering: Adjust the melt temperature to a superheated state slightly above the melting point. Then, slowly lower the rotating seed crystal until its tip is immersed (or slightly in contact) with the surface of the silicon melt.

[0034] S42. Welding: By precisely controlling the cooling rate, the part of the seed crystal in contact with the melt is slightly melted. Then, by controlling the heating, a perfect "fusion" between the seed crystal and the melt is achieved. This step ensures that the crystal structure of the seed crystal can grow epitaxially.

[0035] S43. Neck Pulling: After the seed crystal is fused with the melt, it is pulled upwards at a relatively fast speed while the seed crystal is rotated. This will pull out a "neck" with a diameter slightly thinner than the seed crystal.

[0036] The above method utilizes the "necking" property of crystals to remove crystal defects such as dislocations caused by thermal shock when the seed crystal comes into contact with the melt, thus achieving "dislocation-free" growth. This is a key step in the Czochralski method for growing perfect single crystals.

[0037] S5: Shoulder relaxation and shoulder rotation S51. Shoulder Formation: After the neck has grown to a sufficient length (ensuring that defects are eliminated), the crystal diameter is gradually increased from the neck by gradually reducing the pulling speed and precisely controlling the temperature, forming a conical "shoulder".

[0038] S52. Shoulder Turning: When the crystal diameter increases to near the target diameter, proceed to the next step.

[0039] S6: Constant Diameter Growth S61. Diameter Control: This is the main stage of crystal growth. A sophisticated automatic control system (usually a diameter measuring instrument based on a CCD camera or laser) monitors the shape of the crystal and the meniscus of the melt in real time.

[0040] Specifically, the system compares the measured diameter with a set value. If the diameter is too large, the pulling speed is increased or the heater power is increased; if the diameter is too small, the pulling speed is decreased or the power is decreased. Through this dynamic and continuous feedback control, the crystal is kept growing at an extremely constant diameter.

[0041] S7: Finishing Touches S71. Beginning the finishing stage: When the crystal grows to the predetermined length, or when about 10-20% of the molten silicon remains in the crucible, the finishing stage begins.

[0042] S72. Process: By significantly increasing the pulling speed and simultaneously raising the temperature, the diameter of the crystal is rapidly reduced, ultimately forming a pointed, conical tail. This prevents dislocations from forming due to thermal stress when the crystal leaves the liquid surface, as these dislocations could propagate in the back and destroy the already grown single crystal.

[0043] S8: Cooling and Removal S81. Crystal Ingot Cooling: After growth is complete, the crystal ingot is pulled to the upper cooling zone of the furnace chamber and cooled to room temperature at a very slow, controlled rate under an argon atmosphere (this may take tens of hours). Rapid cooling will generate huge thermal stress, causing the crystal ingot to deform or generate dislocations.

[0044] S82. Furnace Chamber Cooling and Venting: After the crystal rod and furnace components have cooled to a safe temperature, stop the argon gas filling and restore the furnace chamber to atmospheric pressure (“venting”).

[0045] S83. Remove the crystal rod: Open the furnace chamber and remove the complete single crystal silicon rod.

[0046] S84. Post-processing: Using a diamond wire saw or external cylindrical grinder, the seed crystal, shoulder, and tail end of the crystal rod are removed, and the cylindrical surface is ground and polished to obtain a silicon ingot with accurate dimensions and a smooth surface, in preparation for subsequent slicing (making silicon wafers).

[0047] Example 2: This example is an improvement on Example 1; The heater 1 includes a furnace body 11, an insulation layer 12 is provided on the inner wall of the furnace body 11, a quartz crucible 13 is provided at the bottom center of the insulation layer 12, and a crucible connecting rod 131 is provided below the quartz crucible 13; the crucible connecting rod 131 can move the bottom of the heater 1 up and down; the area between the quartz crucible 13 and the insulation layer 12 is a heating zone 14; a guide tube 15 is provided on the top of the insulation layer 12; an adsorption fixture 2 is provided at the top center of the guide tube 15; the shape of the adsorption fixture 2 matches the clearance groove on the top of the guide tube 15; by placing the adsorption fixture 2 on the top inner wall of the guide tube 15, close to the surface of the molten silicon, the adsorption rate of phosphorus atoms in the environment is improved.

[0048] The material of the adsorption fixture 2 is calcium-based oxide ceramic. Its properties are: calcium oxide has a NaCl-type crystal structure, a density of 0.08~3.40 g / cm3, a melting point of 2570℃, and thermodynamic stability, and can be used at high temperatures (2000℃).

[0049] At high temperatures (>1200℃), calcium oxide (CaO) reacts with phosphorus vapor (P4 or P2) to form stable phosphate, which is adsorbed on the surface of adsorption fixture 2: 3 CaO + P4 → Ca3(PO4)2. This type of reaction can effectively convert gaseous phosphorus into solid compounds, reducing its diffusion into the silicon melt. Advantages: Adsorption using adsorption fixture 2 does not alter the crystal growth environment, reduces the probability of dislocation formation in the crystal, and stabilizes the adsorbed phosphorus atoms, preventing phosphorus atoms from the environment from re-entering the crystal during crystal growth, thereby improving the low tail resistance problem. Overall, this achieves effective control of axial resistivity.

[0050] Example 3: This example is an improvement on Example 2; As one possible implementation, in order to further improve the adsorption rate of phosphorus atoms in the environment, the adsorption fixture 2 includes a fixture body 21, and the inner wall of the fixture body 21 is provided with a plurality of micropores 211; the structural area of ​​the adsorption fixture 2 is further increased, thereby improving the adsorption capacity of phosphorus atoms in the environment.

[0051] Example 4: This example is an improvement on Example 2; To further improve the adsorption rate of phosphorus atoms in the environment, the adsorption fixture 2 includes a fixture body 22, the inner wall of which is provided with a plurality of micropores 221; at the same time, a plurality of protrusions 222 are provided between each row of micropores 221 on the inner side of the fixture body 22; through the combination of protrusions 222 and micropores 221, the structural area of ​​the adsorption fixture 2 is further increased, thereby improving the adsorption capacity of phosphorus atoms in the environment.

[0052] Example 5: This example is an improvement on Example 2; As one possible implementation, in order to further improve the adsorption rate of phosphorus atoms in the environment, the adsorption fixture 2 includes a fixture body 23, the inner wall of which is provided with a plurality of micropores 231; at the same time, a strip plate 232 is provided between each row of micropores 231 on the inner side of the fixture body 23; each strip plate 232 is provided with a plurality of micropores 233; through the combination of the strip plate 232 and the micropores 211, the structural area of ​​the adsorption fixture 2 is further increased, thereby improving the adsorption capacity of phosphorus atoms in the environment.

[0053] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for reducing the axial resistivity decay of an N-type single-crystal silicon rod, comprising preparation, stabilization, crystal pulling, shoulder formation, shoulder rotation, equal diameter setting, and finishing stages; the specific steps are as follows: characterized in that... ， S1: Preparation work includes, S11. Raw material preparation: Prepare polysilicon material and dopants. Use ultra-high purity solar-grade or electronic-grade polysilicon blocks / particles for polysilicon material. S12. Quartz crucible preparation: Use a high-purity, uncontaminated transparent quartz crucible; S13. Placement of adsorption fixture (2): The adsorption fixture (2) is placed on the inner wall of the guide tube, close to the surface of the molten silicon, to improve the adsorption rate of phosphorus atoms in the environment.

2. The method for reducing the axial resistivity decay of an N-type single-crystal silicon rod according to claim 1, characterized in that, S2: Vacuuming and gas filling include, S21. Vacuuming: Close the furnace chamber, start the vacuum pump, and pump the pressure inside the furnace to a low vacuum level; S22. Fill with inert gas: Fill the furnace body (11) with high-purity argon gas and maintain it at a suitable positive pressure.

3. The method for reducing the axial resistivity decay of an N-type single-crystal silicon rod according to claim 2, characterized in that, S3: Melting includes, S31. Heating: Start the heater (1), slowly increase the power, and heat the quartz crucible (13) and the silicon material inside; S32. Heat preservation and melting: After the temperature exceeds the melting point of silicon, maintain the temperature until all solid silicon material is completely melted into a bright red molten silicon liquid with a mirror-like surface; S33. Stabilization: After the silicon material is completely melted, it needs to be kept for a period of time; at the same time, the flow of the melt is made more uniform by rotating the quartz crucible (13) and the seed crystal axis.

4. The method for reducing the axial resistivity decay of an N-type single-crystal silicon rod according to claim 1, characterized in that, S4: Seeding includes S41. Cooling and lowering the seed crystal: Adjust the melt temperature to a superheated state slightly above the melting point, and then slowly lower the rotating seed crystal until its tip is immersed in the surface of the silicon melt. S42. Welding: By controlling the cooling rate, the part of the seed crystal in contact with the melt is also slightly melted, and then by controlling the heating, the seed crystal and the melt are fused together; S43. Neck Removal: After the seed crystal is fused with the melt, it is pulled upwards at a relatively fast speed while the seed crystal is rotated.

5. The method for reducing the axial resistivity decay of an N-type single-crystal silicon rod according to claim 1, characterized in that, S5: Shoulder relaxation and shoulder rotation include, S51. Shoulder Formation: After the neck has grown to a sufficient length, the crystal diameter is gradually increased from the neck by gradually reducing the pulling speed and precisely controlling the temperature, forming a conical shoulder. S52. Shoulder Turning: When the crystal diameter increases to near the target diameter, proceed to the next step.

6. The method for reducing the axial resistivity decay of an N-type single-crystal silicon rod according to claim 1, characterized in that, S6: Constant diameter growth includes, S61. Diameter control: Real-time monitoring of the shape of the crystal and melt meniscus using a diameter measuring instrument based on a CCD camera or laser.

7. The method for reducing the axial resistivity decay of an N-type single-crystal silicon rod according to claim 5, characterized in that, S7: The finishing process includes, S71. Beginning of finishing: When the crystal grows to the predetermined length, or when about 10-20% of the molten silicon remains in the crucible, the finishing stage begins; S72. Process: By significantly increasing the pulling speed and simultaneously raising the temperature, the diameter of the crystal is rapidly reduced, ultimately forming a pointed, conical tail. S8: Cooling and removal include, S81. Crystal rod cooling: After growth is completed, the crystal rod is pulled to the upper cooling zone of the furnace chamber; S82. Furnace chamber cooling and cavitation: Stop argon gas filling after the crystal rod and furnace components have cooled to a safe temperature; S83. Remove the crystal rod: Open the furnace chamber and remove the complete single crystal silicon rod; S84. Post-processing: Using a diamond wire saw or external cylindrical grinder, the seed crystal, shoulder, and tail end of the crystal rod are removed, and the cylindrical surface is ground and polished to obtain a silicon ingot with accurate dimensions and a smooth surface, in preparation for subsequent slicing.

8. The method for reducing the axial resistivity decay of an N-type single-crystal silicon rod according to claim 1, characterized in that, The adsorption fixture (2) includes a fixture body (21), and the inner wall of the fixture body (21) is provided with a plurality of micropores (211); further increasing the structural area of ​​the adsorption fixture (2).

9. The method for reducing the axial resistivity decay of an N-type single-crystal silicon rod according to claim 8, characterized in that, The adsorption fixture (2) includes a fixture body (22), and a plurality of micropores (221) are provided on the inner wall of the fixture body (22). At the same time, a plurality of protrusions (222) are provided between each row of micropores (221) on the inner side of the fixture body (22). The structural area of ​​the adsorption fixture (2) is further increased by the combination of protrusions (222) and micropores (221).

10. The method for reducing the axial resistivity decay of an N-type single-crystal silicon rod according to claim 1, characterized in that, The adsorption fixture (2) includes a fixture body (23), and a plurality of micropores (231) are provided on the inner wall of the fixture body (23). At the same time, a strip (232) is provided between each row of micropores (231) on the inner side of the fixture body (23). A plurality of micropores (233) are provided on each strip (232). The structural area of ​​the adsorption fixture (2) is further increased by the combination of the strip (232) and the micropores (211).

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