Method for drawing multiple 6 inch heavily doped boules using a 24 inch hot field

Abstract

The application provides a method for drawing multiple 6-inch heavy-doped crystal rods by using a 24-inch hot field, relates to the technical field of small-size single crystal silicon rod drawing, and first sets the crystal rod drawing speed, the crystal rotation speed and the crucible rotation speed of different isodiametric lengths in the preset isodiametric process in the MCZ process of the 24-inch hot field; wherein, the crystal rod drawing speed setting value is 0.68mm / min-1.3mm / min, the crystal rotation speed setting value is 12rpm-16rpm, and the crucible rotation speed setting value is 0.5rpm-4rpm; then, multiple crystal rods are drawn according to the preset crystal rod drawing speed, the crystal rotation speed and the crucible rotation speed of different isodiametric lengths in the isodiametric crystal drawing process; in the MCZ process, the complex thermal convection in the hot field is inhibited through the cooperation of the'strong magnetic field, low drawing speed, specific crystal rotation speed and crucible rotation speed ratio', the doping uniformity is good, and then the head and tail resistivity consistency of the drawn crystal rods is good and the fluctuation range is small.

Description

Technical Field

[0001] This invention belongs to the field of small-size single-crystal silicon ingot pulling technology, specifically involving a method for pulling multiple 6-inch heavily doped ingots using a 24-inch hot field. Background Technology

[0002] The magnetic field Czochralski method is the mainstream technology for preparing high-quality, especially heavily doped semiconductor silicon single crystals. By applying a magnetic field, the thermal convection of the melt can be effectively suppressed, thereby significantly improving the oxygen content, resistivity uniformity and defect distribution of the crystal.

[0003] The traditional (Magnetic-field applied Czochralski method, MCZ) process typically adopts a "one furnace, one ingot" production mode. For 6-inch heavily doped crystal rods, if a 24-inch or even larger hot field is used, the raw materials, argon gas, and electricity consumed in a single crystal pulling process are enormous, but only one crystal rod is produced. This results in high production costs for a single crystal rod, low economies of scale, and an inability to meet the market's urgent demand for low-cost heavily doped silicon materials.

[0004] To reduce the cost of pulling small-sized crystal rods in a large hot field, multiple small-sized crystal rods can be pulled in a large hot field. However, there are serious technical challenges in the pulling process. The addition of heavily doped elements will significantly change the physical properties of molten silicon (such as segregation coefficient, evaporation rate, and melt convection intensity). In the same large hot field, there is complex thermal convection between the melt and the liquid, which will lead to uncontrolled doping uniformity. It is difficult for the resistivity distribution between the head and tail of a single crystal rod to be consistent, and the fluctuation range is large, resulting in the pulled crystal rods not meeting the requirements. Summary of the Invention

[0005] In view of this, the present invention develops a method for drawing multiple 6-inch heavily doped crystal rods using a 24-inch hot field, which can reduce resistivity fluctuations between the beginning and end of a single crystal rod and improve the yield of 6-inch crystal rods.

[0006] A method for pulling multiple 6-inch heavily doped crystal rods using a 24-inch hot field includes the following steps:

[0007] S1: In the MCZ process based on a 24-inch hot zone, preset the crystal pulling speed, crystal rotation speed, and crucible rotation speed for different diameter lengths during the constant diameter process;

[0008] Wherein: the crystal rod pulling speed is set to 0.68mm / min-1.3mm / min, the crystal rotation speed is set to 12rpm or 16rpm, and the crucible rotation speed is set to 0.5rpm-4rpm; the magnetic field is a Cusp type magnetic field with a magnetic field strength of 3000GS or higher.

[0009] S1 specifically includes the following steps:

[0010] S11: When drawing the first length of equal diameter starting from equal diameter, the set value of the crystal rod pulling speed gradually decreases, or the set value of the crystal rod pulling speed first gradually decreases and then remains stable, the crystal rotation speed remains stable, and the crucible rotation speed first decreases and then remains stable.

[0011] S12: When drawing a second length of equal diameter from a first length of equal diameter, the set value of the crystal rod pulling speed first gradually decreases and then remains stable, or the set value of the crystal rod pulling speed first decreases and then remains stable and then decreases again, or the set value of the crystal rod pulling speed remains stable, the crystal rotation speed remains stable, and the crucible rotation speed remains stable.

[0012] S13: When the constant diameter drawing from the second constant diameter length ends, the set value of the crystal rod drawing speed first decreases, and then remains stable, or remains stable, the crystal rotation speed remains stable, and the crucible rotation speed remains stable.

[0013] The constant diameter start, constant diameter first length, constant diameter second length, and constant diameter end constitute a continuous constant diameter stage. The constant diameter first length is 300mm-600mm, and the constant diameter second length is 800mm-1000mm.

[0014] S2: During the constant diameter crystal pulling process, multiple crystal rods are pulled according to the preset constant diameter length crystal rod pulling speed, crystal rotation speed and crucible rotation speed to suppress complex thermal convection, avoid doping uniformity loss of control, and systematically reduce oxygen introduction and transport efficiency.

[0015] The process of pulling multiple crystal rods is as follows: After the first crystal rod is pulled out by the process of material preparation, stabilization, crystal pulling, shoulder formation, equal diameter formation, tail formation, and cooling, the remaining silicon material in the crucible in the 24-inch hot zone is used to continuously pull the next crystal rod. Specifically, the next crystal rod is obtained by the process of crystal pulling, shoulder formation, equal diameter formation, tail formation, and cooling.

[0016] Preferably, in step S1, the fluctuation range of the crystal rod pulling speed is set to 0.6 mm / min - 1.8 mm / min.

[0017] Preferably, in S11, the range of "the crystal rod pulling speed setting value gradually decreases" is 0.9 mm / min-1.2 mm / min, and the range of "the crucible rotation speed first decreases and then remains stable" is 0.5 rpm-1 rpm;

[0018] In S13, the range of "the crystal rod pulling speed setting value first decreases and then remains stable" is 0.7 mm / min to 1.3 mm / min.

[0019] Preferably, in S11, the range of "the crystal rod pulling speed setting value gradually decreases" is 0.9 mm / min-1.3 mm / min, and the range of "the crucible rotation speed first decreases and then remains stable" is 1 rpm-3 rpm;

[0020] In S13, the range of "the crystal rod pulling speed setting value first decreases and then remains stable" is 0.68 mm / min to 0.9 mm / min.

[0021] Preferably, in S11, the range of "the crystal rod pulling speed setting value gradually decreases" is 0.7 mm / min-1.3 mm / min, and the range of "the crucible rotation speed first decreases and then remains stable" is 2 rpm-4 rpm;

[0022] In S13, the range of "the crystal rod pulling speed is guaranteed to be stable and unchanged" is 0.7 mm / min.

[0023] Preferably, in step S1, the furnace pressure and argon flow rate for different equal diameter stages need to be preset, wherein the furnace pressure is 10KPa-25KPa and the argon flow rate is 100slm-150slm.

[0024] Preferably, in step S1, the furnace pressure and argon flow rate for different equal diameter stages need to be preset, wherein the furnace pressure is 10KPa-25KPa and the argon flow rate is 120slm-150slm.

[0025] Preferably, in step S1, the furnace pressure and argon flow rate for different equal diameter stages are preset, wherein the furnace pressure is 15KPa-22KPa and the argon flow rate is 100slm-120slm.

[0026] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0027] This invention provides a method for pulling multiple 6-inch heavily doped crystal rods using a 24-inch hot zone. First, in the MCZ process using a 24-inch hot zone, the pulling speed, crystal rotation speed, and crucible rotation speed for different diameter lengths during the constant-diameter process are preset. Specifically, the crystal pulling speed is set to 0.68 mm / min-1.3 mm / min, the crystal rotation speed is set to 12 rpm-16 rpm, and the crucible rotation speed is set to 0.5 rpm-4 rpm. Then, during the constant-diameter crystal pulling process, multiple crystal rods are pulled according to the preset pulling speed, crystal rotation speed, and crucible rotation speed for different diameter lengths. In the MCZ process, the synergistic effect of "strong magnetic field, low pulling speed, and a specific ratio of crystal rotation speed to crucible rotation speed" suppresses complex thermal convection within the hot zone, resulting in good doping uniformity and excellent consistency in resistivity at the head and tail of the pulled crystal rods with minimal fluctuation. Furthermore, this synergistic process, while suppressing convection, forms a stable and suppressed oxygen volatilization interface layer on the melt surface, systematically reducing oxygen transport from molten silicon into the crystal and lowering the oxygen content. Attached Figure Description

[0028] Figure 1 These are resistivity comparison diagrams of the pulled crystal rods from Examples 1 to 3 and Comparative Example 1.

[0029] Figure 2 This is a comparison chart of the oxygen content of the pulled crystal rods in Examples 1 to 3 and Comparative Example 1.

[0030] Figure 3 This is an in-plane distribution diagram of Res in a crystal rod pulled in Example 3.

[0031] Figure 4 This is an in-plane distribution diagram of the Oi plane of the crystal rod pulled in Example 3.

[0032] Figure 5 This is the in-plane distribution diagram of Res in a pull-out crystal rod of the comparative example.

[0033] Figure 6 This is the in-plane Oi distribution diagram of the pull-out crystal rod of the comparative example.

[0034] In the picture: Figures 3 to 6 From left to right, the images are: 0mm section of equal diameter head, 300mm section of equal diameter, 600mm section of equal diameter, 900mm section of equal diameter, 1200mm section of equal diameter, 1400mm section of equal diameter, and 1700mm section of equal diameter tail. Detailed Implementation

[0035] 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 of this application. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0036] The embodiments in this application are applied to the scenario of controlling the constant diameter stage during crystal pulling using the magnetron Czochralski (MCZ) method in a single crystal furnace.

[0037] This invention provides a method for pulling multiple 6-inch heavily doped crystal rods using a 24-inch hot zone, comprising the following steps:

[0038] S1: In the MCZ process based on a 24-inch hot zone, preset the crystal pulling speed, crystal rotation speed, and crucible rotation speed for different diameter lengths during the constant diameter process;

[0039] Wherein: the crystal rod pulling speed is set to 0.68mm / min-1.3mm / min, the crystal rotation speed is set to 12rpm or 16rpm, the crucible rotation speed is set to 0.5rpm-4rpm; the magnetic field is a hook-shaped magnetic field (Cusp type magnetic field) with a magnetic field strength of 3000GS or higher;

[0040] S1 specifically includes the following steps:

[0041] S11: When drawing the first length of equal diameter starting from equal diameter, the set value of the crystal rod pulling speed gradually decreases, or the set value of the crystal rod pulling speed first gradually decreases and then remains stable, the crystal rotation speed remains stable, and the crucible rotation speed first decreases and then remains stable.

[0042] S12: When drawing a second length of equal diameter from a first length of equal diameter, the set value of the crystal rod pulling speed first gradually decreases and then remains stable, or the set value of the crystal rod pulling speed first decreases and then remains stable and then decreases again, or the set value of the crystal rod pulling speed remains stable, the crystal rotation speed remains stable, and the crucible rotation speed remains stable.

[0043] S13: When the constant diameter drawing from the second constant diameter length ends, the set value of the crystal rod drawing speed first decreases, and then remains stable, or remains stable, the crystal rotation speed remains stable, and the crucible rotation speed remains stable.

[0044] The constant diameter start, constant diameter first length, constant diameter second length, and constant diameter end constitute a continuous constant diameter stage. The constant diameter first length is 300mm-600mm, and the constant diameter second length is 800mm-1000mm.

[0045] S2: During the constant diameter crystal pulling process, multiple crystal rods are pulled according to the preset constant diameter length crystal rod pulling speed, crystal rotation speed and crucible rotation speed to suppress complex thermal convection, avoid doping uniformity loss of control, and systematically reduce oxygen introduction and transport efficiency.

[0046] The process of pulling multiple crystal rods is as follows: After the first crystal rod is pulled out by the process of material preparation, stabilization, crystal pulling, shoulder formation, equal diameter formation, tail formation, and cooling, the remaining silicon material in the crucible in the 24-inch hot zone is used to continuously pull the next crystal rod. Specifically, the next crystal rod is obtained by the process of crystal pulling, shoulder formation, equal diameter formation, tail formation, and cooling.

[0047] Furthermore, in S1, the fluctuation range of the crystal rod pulling speed is set to 0.6 mm / min-1.8 mm / min to avoid excessive fluctuations in the crystal rod pulling speed setting value, so as to control the shape of the crystallization interface and stabilize the crystal growth process.

[0048] Furthermore, after the diameter reaches 200mm, the fluctuation range of the crystal rod pulling speed is ±0.1mm / min of the crystal rod pulling speed setting value.

[0049] Under the premise of stable crystal growth, a stable and gentle flow field is formed on the surface of the melt by using a strong magnetic field environment and a predetermined ratio of crystal rotation speed to crucible rotation speed, which promotes uniform doping and facilitates the steady-state volatilization of oxygen.

[0050] Furthermore, in S11, the range of "the crystal rod pulling speed setting value gradually decreases" is 0.9 mm / min-1.2 mm / min, and the range of "the crucible rotation speed first decreases and then stabilizes" is 0.5 rpm-1 rpm;

[0051] In S13, the range of "the crystal rod pulling speed setting value first decreases and then remains stable" is 0.7 mm / min to 1.3 mm / min.

[0052] Furthermore, in S11, the range of "the crystal rod pulling speed setting value gradually decreases" is 0.9 mm / min-1.3 mm / min, and the range of "the crucible rotation speed first decreases and then stabilizes" is 1 rpm-3 rpm;

[0053] In S13, the range of "the crystal rod pulling speed setting value first decreases and then remains stable" is 0.68 mm / min to 0.9 mm / min.

[0054] Furthermore, in S11, the range of "the crystal rod pulling speed setting value gradually decreases" is 0.7mm / min-1.3mm / min, and the range of "the crucible rotation speed first decreases and then stabilizes" is 2rpm-4rpm;

[0055] In S13, the range of "the crystal rod pulling speed is guaranteed to be stable and unchanged" is 0.7 mm / min.

[0056] Furthermore, in S1, it is also necessary to preset the furnace pressure and argon flow rate for different equal diameter stages, wherein the furnace pressure is 10KPa-25KPa and the argon flow rate is 100slm-150slm.

[0057] Furthermore, in S1, it is also necessary to preset the furnace pressure and argon flow rate for different equal diameter stages, wherein the furnace pressure is 10KPa-25KPa and the argon flow rate is 120slm-150slm.

[0058] Furthermore, in S1, it is also necessary to preset the furnace pressure and argon flow rate for different equal diameter stages, wherein the furnace pressure is 15KPa-22KPa and the argon flow rate is 100slm-120slm.

[0059] The present invention will now be further described through the following embodiments.

[0060] Examples 1-3:

[0061] Two 6-inch heavily arsenic-doped (As) strands were simultaneously drawn in a 24-inch MCZ hot zone. <100> Crystal rods, with a feed amount of 160kg.

[0062] First, prepare the hot zone and load the material. Inside the 24-inch master crucible (graphite crucible), precisely install the quartz crucible and add 160 kg of material into it. Then, install the hot zone assembly.

[0063] After evacuating, filling, and sealing the furnace chamber with the melted material, a high vacuum is created, followed by filling with high-purity argon gas to the set pressure of 15 kPa. The main heater is started, and the polycrystalline silicon in the quartz crucible is completely melted according to the program. After stabilization, an accurately measured amount of arsenic dopant is added according to the target resistivity. The magnetic field is then activated and raised to the target magnetic field strength of 3000 Gauss.

[0064] The seed crystal is lowered to bring it into contact with the molten surface through seeding, necking, and shoulder formation. Seeding and necking processes are performed simultaneously to eliminate dislocations. Under magnetic field suppression and independent temperature control, shoulder formation is carried out simultaneously to gradually increase the crystal diameter to the target value of 156 mm.

[0065] In the constant diameter growth process, the settings for the ingot pulling speed, upper limit (SL) of the ingot pulling speed, lower limit of the ingot pulling speed (SL), crystal rotation speed, crucible rotation speed, furnace pressure, and argon flow rate are shown in Tables 1, 2, 3, 4, and 5. Constant diameter pulling is performed according to Tables 1, 2, 3, 4, and 5. When the ingot reaches the predetermined length of 1700 mm for rod A (the first ingot), a finishing operation is performed simultaneously, gradually reducing the diameter until it separates from the melt. The temperature is slowly lowered according to the program, and the magnetic field is turned off. After the furnace temperature drops to the specified range, the furnace chamber is opened, and the 6-inch heavily doped single crystal ingot that has completed its growth is removed.

[0066] After the A rod is pulled, the B rod is pulled, shoulder is formed, equal diameter is achieved, and the end is finished according to the above process. After the B rod is pulled, the entire 24-inch hot zone multi-rod pulling is completed.

[0067] Table 1

[0068]

[0069] Table 2

[0070]

[0071] Table 3

[0072]

[0073] Table 4

[0074]

[0075] Table 5

[0076]

[0077] Comparative Example 1:

[0078] In the existing technology, drawing a 6-inch heavy arsenic (As) doped bar <100> Crystal rods are typically drawn using the CZ method within an 18-inch hot zone, with a feed weight of 65 kg.

[0079] The settings for the ingot pulling speed, upper limit, lower limit, crystal rotation speed, crucible rotation speed, furnace pressure, and argon flow rate during the constant diameter process are shown in Table 6. Constant diameter pulling was performed according to Table 6. No magnetic field was applied during the pulling process, and the other steps were the same as in Example 1, resulting in an 18-inch thermally pulled ingot.

[0080] Table 6

[0081]

[0082] The resistivity of the A-bars and B-bars drawn in Examples 1-3, and the 18-inch hot-field drawn ingots drawn in the comparative example, were measured using a four-probe resistivity meter. Specifically, equal-diameter portions of the ingots were divided into ingots. Samples approximately 1.8 mm thick were taken from the beginning and end of each ingot. The end faces were ground, cleaned, flattened, and free of oxide layers. Four equally spaced metal probes were vertically pressed onto the sample surface. A constant DC current I was passed through the two outer probes, and the voltage drop V between the two inner probes was measured. The resistivity ρ was calculated using the formula: ρ = 2πs * (V / I). Multiple measurements were taken at the center and symmetrical positions on each end face, and the average was taken to evaluate radial uniformity. Figure 1 Resistivity (Res) comparison chart.

[0083] The oxygen content of the A-bars (Examples A and B) and the 18-inch hot-field pulled ingot (comparative example) from Examples 1-3 was determined using an inert gas melting-infrared absorption method. Specifically, the samples were heated and melted in a graphite crucible under a high temperature and an inert atmosphere (helium). All forms of oxygen in the samples (including interstitial oxygen, oxygen precipitates, surface oxide layers, etc.) reacted with the carbon in the graphite crucible to generate CO. The released CO gas was carried by a carrier gas into a precisely calibrated nondispersive infrared detection cell. By measuring the infrared absorption intensity at the characteristic absorption peak of CO, the total oxygen content (Oi) in the sample could be calculated. Figure 2 Oi comparison chart.

[0084] Depend on Figure 1 It can be seen that the present invention uses a 24-inch hot zone to pull multiple crystal rods, and the resistivity of the crystal rods can reach the level of the prior art (Comparative Example 1). Among them, after multi-parameter coordination in Example 3, the resistivity fluctuation range between the head and tail of a single crystal rod is the smallest, and is better than that of Comparative Example 1; Figure 2 It is known that the invention can draw multiple crystal rods through a 24-inch hot field, and the oxygen content of the crystal rods can reach the level of the prior art (Comparative Example 1). Among them, after the multi-parameter coordination in Examples 2 and 3, the oxygen content of a single crystal rod is lower than that in Example 1. Moreover, compared with Comparative Example 1, the oxygen content of Examples 2 and 3 is lower than that in Comparative Example 1, which can meet the requirement of lower oxygen content.

[0085] The crystal rods obtained in Example 3 and Comparative Example 1 were tested again using the resistivity and oxygen content detection methods described above. The in-plane resistivity distribution was calculated using the method described above (ρ...). a -ρ c ) / ρ c *100; ρ c ρ is the average resistivity at the center point, calculated using the second order. a : Represents resistivity from edge / distance from edge; the in-plane oxygen content distribution is calculated as (Nc-Ne) / Nc*100; NC Ne represents the average test value at the center point, and Ne represents the average test value at the edge points. The in-plane distribution maps of Res and Oi in Example 3 are obtained, and the in-plane distribution maps of Res and Oi in Comparative Example 1 are shown below. Figure 3 , 4 As shown in Figures 5 and 6.

[0086] Figure 3 , Figure 5 The shades of color in the medium represent resistivity; darker shades indicate higher resistivity, and colors that are closer together indicate better uniformity. Figure 3 It can be seen that the resistivity uniformity of multiple crystal rods pulled in Embodiment 3 of the present invention is better than that of the traditional comparative example 1;

[0087] Figure 4 , Figure 6 The shades of color represent the concentration of oxygen; the darker the color, the higher the oxygen concentration. Figure 6 In the traditional 18-inch single-strand pull wafer, there are many sudden blue areas (low oxygen areas) at the edge of the wafer. The excessively wide low oxygen areas at the edges will weaken the defect control capability of the edge chip. However, the oxygen concentration uniformity of Embodiment 3 of the present invention is better than that of the traditional comparative example 1.

[0088] Therefore, through the above-mentioned resistivity and oxygen content detection, it was found that the present invention achieves a significant reduction in oxygen content. While achieving multi-strand pulling, through the synergistic mechanism of "strong magnetic field suppressing convection + low pulling speed and thin boundary layer + crucible rotation ratio," the oxygen introduction and transport efficiency are systematically reduced, resulting in a 18%-30% reduction in oxygen content in the obtained heavily doped rods compared to the traditional single-strand pulling method. Figure 2 The resistivity of the crystal in this invention consistently reaches the low-oxygen index. Simultaneously, the resistivity level decreases more gradually than in Comparative Example 1, with minimal fluctuations at the head and tail of the crystal rod, resulting in high resistivity uniformity. Therefore, the resistivity uniformity of the crystal in this invention (…) Figure 3 ) and Oi uniformity ( Figure 4 Overall, it is superior to the traditional single-strand drawing level of Comparative Example 1. Figure 5 , 6 Production efficiency is improved, overall yield is increased, and energy consumption, gas consumption, and labor costs per crystal rod are significantly reduced. Suitable for demanding, heavily doped products: providing a mass production solution for applications such as logic circuits and advanced memories that require heavily doped, low-oxygen, and highly uniform substrates.

[0089] The above-disclosed embodiments are merely preferred embodiments of the present invention and should not be construed as limiting the scope of the invention. Those skilled in the art will understand that implementing all or part of the above-described embodiments and making equivalent changes in accordance with the claims of the present invention are still within the scope of the invention.

Claims

1. A method for drawing multiple 6-inch heavily doped crystal rods using a 24-inch hot field, characterized in that, Includes the following steps: S1: In the MCZ process based on a 24-inch hot zone, preset the crystal pulling speed, crystal rotation speed, and crucible rotation speed for different diameter lengths during the constant diameter process; Wherein: the crystal rod pulling speed is set to 0.68mm / min-1.3mm / min, the crystal rotation speed is set to 12rpm or 16rpm, and the crucible rotation speed is set to 0.5rpm-4rpm; the magnetic field is a Cusp type magnetic field with a magnetic field strength of 3000GS or higher. S1 specifically includes the following steps: S11: When drawing the first length of equal diameter starting from equal diameter, the set value of the crystal rod pulling speed gradually decreases, the crystal rotation speed remains stable, and the crucible rotation speed first decreases and then remains stable; the range of "the set value of the crystal rod pulling speed gradually decreases" is 0.9mm / min-1.2mm / min, and the range of "the crucible rotation speed first decreases and then remains stable" is 0.5rpm-1rpm; S12: When drawing a second length of equal diameter from a first length of equal diameter, the set value of the crystal rod drawing speed remains stable, the crystal rotation speed remains stable, and the crucible rotation speed remains stable. S13: When the equal diameter drawing process ends from the second equal diameter length, the set value of the crystal rod pulling speed first decreases and then remains stable, the crystal rotation speed remains stable, and the crucible rotation speed remains stable; the range of "the set value of the crystal rod pulling speed first decreases and then remains stable" is 0.7mm / min-0.9mm / min; The constant diameter start, constant diameter first length, constant diameter second length, and constant diameter end constitute a continuous constant diameter stage. The constant diameter first length is 300mm-600mm, and the constant diameter second length is 800mm-1000mm. S2: During the constant diameter crystal pulling process, multiple crystal rods are pulled according to the preset pulling speed, crystal rotation speed and crucible rotation speed of different constant diameter lengths to suppress complex thermal convection and avoid loss of doping uniformity. At the same time, the introduction and transport efficiency of oxygen are systematically reduced. Moreover, the resistivity, resistivity uniformity, oxygen content and oxygen content uniformity of multiple crystal rods pulled by the 24-inch hot field can reach the level of a single crystal rod pulled by the 18-inch hot field. The process of pulling multiple crystal rods is as follows: After the first crystal rod is pulled out by the process of material preparation, stabilization, crystal pulling, shoulder formation, equal diameter formation, tail formation, and cooling, the remaining silicon material in the crucible in the 24-inch hot zone is used to continuously pull the next crystal rod. Specifically, the next crystal rod is obtained by the process of crystal pulling, shoulder formation, equal diameter formation, tail formation, and cooling.

2. The method for drawing multiple 6-inch heavily doped crystal rods using a 24-inch hot field as described in claim 1, characterized in that, In step S1, it is also necessary to preset the furnace pressure and argon flow rate for different equal diameter stages, wherein the furnace pressure is 10kPa-25kPa and the argon flow rate is 100slm-150slm.

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