A method for growing a silicon ingot

Abstract

The application relates to the technical field of photovoltaic monocrystalline silicon preparation, in particular to a silicon rod growing method. The silicon rod growing method provided by the application comprises the following steps: S1, using a zone melting method to prepare a monocrystalline silicon base rod; the monocrystalline silicon base rod is sequentially subjected to ion doping and annealing, a first doping area is formed at the head and tail of the monocrystalline silicon base rod, and a primary mother alloy rod is obtained; S2, the primary mother alloy rod is cut into a silicon core, the silicon core is uniformly mixed with high-purity intrinsic polycrystalline silicon fragments, and a secondary doping material is obtained; S3, high-purity intrinsic polycrystalline silicon blocks are laid in a main crucible, and then the secondary doping material is laid on the surface of the high-purity intrinsic polycrystalline silicon blocks; and then heating and crystal growth are sequentially performed. The method realizes high uniform distribution of the dopant in the molten silicon body, introduces less impurities, and can meet the requirements of the BC battery on high uniformity of the monocrystalline silicon resistivity, low oxygen content and high minority carrier lifetime.

Description

Technical Field

[0001] This invention relates to the field of photovoltaic monocrystalline silicon preparation technology, and in particular to a method for growing silicon rods. Background Technology

[0002] Back-contact (BC) cells have become a leading technology in the industry due to their lack of front-side grid lines and high conversion efficiency. BC cells have a complex structure, with all electrodes located on the back side, achieved through precision processes such as laser grooving and photolithography. This places the following demands on the quality of the silicon substrate: Extremely high resistivity uniformity: BC cells form staggered P- and N-regions on the back side. Any macroscopic or microscopic resistivity non-uniformity in the silicon substrate will lead to degradation of PN junction characteristics, resulting in a decrease in fill factor and open-circuit voltage. Extremely low oxygen content: The BC cell fabrication process involves multiple high-temperature processes. Excessive oxygen content will lead to the thermal donor effect, causing resistivity drift and the formation of oxygen deposits, which become recombination centers, reducing lifetime. Extremely high minority carrier lifetime: Requires extremely low density of metallic impurities and defects in the silicon substrate.

[0003] In Czochralski-grown single-crystal silicon, resistivity is typically controlled by doping with elements such as boron for P-type single-crystal silicon and phosphorus for N-type single-crystal silicon. However, traditional doping processes have the following problems: Master alloy method: A highly doped master alloy is pre-formed with dopants (such as boron or phosphorus) and polycrystalline silicon outside the crucible before being placed into the main crucible. This method is simple, but the initial dopant concentration is high, and insufficient diffusion and convection in the molten silicon can easily lead to uneven axial resistivity. In addition, the master alloy itself may introduce additional oxygen and metallic impurities.

[0004] Feeding method / Pad method: The bulk dopant is directly mixed with the polycrystalline silicon raw material and loaded into the crucible. This method also suffers from uneven distribution, and in the early stages of melting, the local concentration is too high, causing the components to become too cold and affecting crystal formation.

[0005] Gas phase doping method: By introducing a gas containing dopant (such as B2H6, PH3) into the furnace, although the uniformity is good, the safety is poor (highly toxic and explosive), the equipment sealing requirements are extremely high, and the gas may participate in the thermal field chemical reaction, introducing complex pollution.

[0006] Therefore, developing a process that can achieve precise, uniform, and clean doping is a key bottleneck for the mass production of monocrystalline silicon for BC batteries.

[0007] In view of this, the present invention is hereby proposed. Summary of the Invention

[0008] The purpose of this invention is to provide a method for growing silicon rods, which achieves a highly uniform distribution of dopants in molten silicon, introduces fewer impurities, and meets the requirements of BC cells for high uniformity of resistivity, low oxygen content and high minority carrier lifetime of single crystal silicon.

[0009] In order to achieve the above-mentioned objectives of the present invention, the following technical solution is adopted: This invention provides a method for growing silicon rods into crystals, comprising the following steps: S1. A single-crystal silicon-based rod is prepared by zone melting method; the single-crystal silicon-based rod is subjected to ion doping and annealing in sequence to form a first doped region at both ends of the single-crystal silicon-based rod, thereby obtaining a primary master alloy rod. S2. Cut the primary master alloy rod into silicon cores, and mix the silicon cores with high-purity intrinsic polycrystalline silicon fragments to obtain secondary doped material; S3. Lay high-purity intrinsic polycrystalline silicon ingots in the main crucible, and then lay the secondary dopant on the surface of the high-purity intrinsic polycrystalline silicon ingots; then perform heating and crystal growth in sequence.

[0010] Furthermore, in step S1, the resistivity of the single-crystal silicon-based rod is >1000Ω·cm; And / or, the monocrystalline silicon substrate includes an N-type monocrystalline silicon substrate or a P-type monocrystalline silicon substrate.

[0011] Furthermore, in step S1, the ion doping method includes transmutation doping or ion implantation.

[0012] Further, in step S1, the resistivity of the first doped region is 1 / 10 to 1 / 5 of the target resistivity of the silicon rod.

[0013] Furthermore, in step S1, the length of the first doped region is 5% to 15% of the total length of the single-crystal silicon rod.

[0014] Further, in step S2, the diameter of the silicon core is 1 / 50 to 1 / 20 of the inner diameter of the main crucible, and the length-to-diameter ratio of the silicon core is (3~10):1.

[0015] Further, in step S2, the mass ratio of the silicon core to the high-purity intrinsic polycrystalline silicon fragment is (2~3):(7~8).

[0016] Further, in step S3, the mass ratio of the high-purity intrinsic polycrystalline silicon block material to the secondary doped material is (6~7):(3~4).

[0017] Furthermore, in step S3, before laying the secondary dopant, the process further includes: chemically cleaning the secondary dopant.

[0018] Furthermore, in step S3, the crystal growth includes: performing crystal growth under a magnetic field.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows: The silicon rod growth method of the present invention combines multi-stage dilution with layered loading to achieve highly uniform distribution of dopants in the molten silicon, thereby achieving precise, uniform, and clean doping; it can meet the requirements of BC cells for high uniformity of single-crystal silicon resistivity, low oxygen content, and high minority carrier lifetime. Detailed Implementation

[0020] The technical solution of the present invention will be clearly and completely described below with reference to specific embodiments. However, those skilled in the art will understand that the embodiments described below are some embodiments of the present invention, but not all embodiments, and are only used to illustrate the present invention, and should not be regarded as limiting the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall be followed. Where the manufacturers of reagents or instruments are not specified, they are all conventional products that can be purchased commercially.

[0021] In some embodiments of the present invention, a method for growing silicon rods is provided, comprising the following steps: S1. Single-crystal silicon rods are prepared by zone melting method; the single-crystal silicon rods are sequentially ion-doped and annealed to form the first doped region at both ends of the single-crystal silicon rods, thus obtaining a primary master alloy rod. S2. Cut the primary master alloy rod into silicon cores and mix the silicon cores with high-purity intrinsic polycrystalline silicon fragments to obtain secondary doped material. S3. Lay high-purity intrinsic polycrystalline silicon ingots in the main crucible, and then lay secondary dopants on the surface of the high-purity intrinsic polycrystalline silicon ingots; then proceed with heating and crystal growth in sequence.

[0022] The doping method of the present invention is a doping method for single crystal silicon rods used in Czochralski (CBS) cell growth; it can achieve precise, uniform, and clean doping; and meet the requirements of CBS cells for high uniformity of single crystal silicon resistivity, low oxygen content, and high minority carrier lifetime.

[0023] This invention achieves highly uniform distribution of dopants in molten silicon through a combination of multi-stage dilution and layered loading, resulting in high resistivity uniformity, high purity, and minimal introduction of impurities; and high safety with a safe and controllable process.

[0024] The silicon rod growth method of this invention significantly improves resistivity uniformity. Through a two-stage dilution process of primary master alloy rod and secondary dopant, local oversaturation of the dopant in the initial melt is avoided, allowing sufficient space and time for uniform distribution through melt convection. The dopant is uniformly distributed in the main material in the form of fine silicon cores, providing multiple uniformly distributed dopant sources from the beginning of melting, fundamentally solving the problem of macroscopic uneven distribution. The initial dopant concentration is precisely controlled and uniformly distributed, resulting in a more stable effective segregation effect and improved axial resistivity uniformity.

[0025] The silicon rod growth method of the present invention improves the purity of single-crystal silicon; the single-crystal silicon rod is prepared by crucibleless zone melting, which fundamentally eliminates oxygen pollution caused by quartz crucibles and ensures the purity of dopants; the whole process avoids the use of external master alloys or bulk dopants, significantly reducing the risk of introducing metal impurities and oxygen due to foreign materials, and providing a guarantee for obtaining high minority carrier lifetime.

[0026] The silicon rod crystal growth method of the present invention is safe and controllable, and operates entirely with solid silicon material, avoiding the highly toxic and explosive gas phase doping method. The process is highly safe, has low equipment requirements, and is easy to implement and promote on existing production lines. By adjusting the doping concentration of the primary master alloy rod and the proportion of silicon core added in the secondary dopant, the resistivity of the monocrystalline silicon finally used in BC cells can be precisely and flexibly controlled.

[0027] In some embodiments of the present invention, in step S1, the resistivity of the single-crystal silicon substrate is >1000 Ω·cm; typically, but not limitingly, for example, the resistivity of the single-crystal silicon substrate is 1010 Ω·cm, 1020 Ω·cm, 1050 Ω·cm, 1100 Ω·cm, 1200 Ω·cm, and any value between any two of these.

[0028] In some embodiments of the present invention, in step S1, the single-crystal silicon substrate rod includes an N-type single-crystal silicon substrate rod or a P-type single-crystal silicon substrate rod.

[0029] In some embodiments of the present invention, in step S1, a zone melting method is used to prepare a single-crystal silicon-based rod in an environment free from crucible contamination.

[0030] In some embodiments of the present invention, in step S1, the ion doping method includes transmutation doping or ion implantation.

[0031] This invention uses the zone melting method to prepare single-crystal silicon rods, and only at the head and tail ends of the single-crystal silicon rods are neutron transmutation doping or ion implantation and annealing to form low-resistivity regions with specific resistivity; this is an ultra-clean, quantitative and localized method for preparing the source material.

[0032] In some embodiments of the present invention, in step S1, the resistivity of the first doped region is 1 / 10 to 1 / 5 of the target resistivity of the silicon rod; typically, but not limitingly, for example, the resistivity of the first doped region is 1 / 10, 1 / 9, 1 / 8, 1 / 7, 1 / 6, 1 / 5 of the target resistivity of the silicon rod, and any value between any two thereof.

[0033] In some embodiments of the present invention, in step S1, the length of the first doped region is 5% to 15% of the total length of the single-crystal silicon substrate rod; typically, but not limitingly, for example, the length of the first doped region is 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15% of the total length of the single-crystal silicon substrate rod, and any value between any two of these.

[0034] By locally doping the head and tail ends of a single-crystal silicon-based rod, a primary master alloy rod is formed with low-resistivity regions at the head and tail and high-resistivity regions in the middle.

[0035] In some embodiments of the present invention, in step S2, the primary master alloy rod is cut into silicon cores of equal diameter.

[0036] In some embodiments of the present invention, in step S2, the diameter of the silicon core is 1 / 50 to 1 / 20 of the inner diameter of the main crucible, and the aspect ratio (length to diameter ratio) of the silicon core is (3 to 10):1; typically, but not limitingly, for example, the diameter of the silicon core is 1 / 50, 1 / 45, 1 / 40, 1 / 35, 1 / 30, 1 / 25, 1 / 20 of the inner diameter of the main crucible, and any value between any two thereof; the aspect ratio of the silicon core can be 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, and any value between any two thereof.

[0037] The diameter of the silicon core is 1 / 50 to 1 / 20 of the inner diameter of the main crucible, which ensures that the silicon core is fully and uniformly heated by the high-frequency electromagnetic field, and the resulting suspended molten zone is more stable and less prone to breakage or dripping; the length-to-diameter ratio of the silicon core is (3~10):1, which takes into account both production efficiency (growing a longer crystal in one step) and process control difficulty (too long a crystal can easily lead to swaying and uneven thermal field).

[0038] In some embodiments of the present invention, in step S2, the mass ratio of silicon core to high-purity intrinsic polycrystalline silicon fragments is (2~3):(7~8); the mass ratio of silicon core to high-purity intrinsic polycrystalline silicon fragments can be 2:8, 2.5:7.5, 3:8, and any value between any two of them.

[0039] The primary master alloy rod was cut into small silicon cores with a length-to-diameter ratio of (3~10):1 and mixed with high-purity intrinsic polycrystalline silicon fragments, realizing the morphological transformation of the dopant from blocky to distributed point-like.

[0040] In some embodiments of the present invention, in step S3, the mass ratio of high-purity intrinsic polycrystalline silicon ingot to secondary dopant is (6~7):(3~4); typically, but not limitingly, for example, the mass ratio of high-purity intrinsic polycrystalline silicon ingot to secondary dopant can be 6:4, 6.5:3.5, 7:3 and any value between any two of them.

[0041] In some embodiments of the present invention, in steps S2 and S3, the high-purity intrinsic polycrystalline silicon fragments are 9N (electronic grade) high-purity intrinsic polycrystalline silicon fragments.

[0042] In some embodiments of the present invention, step S3, before laying the secondary dopant, further includes: chemically cleaning the secondary dopant; preferably, the secondary dopant is crushed or cut into blocks or rods; and then chemically cleaned; more preferably, the chemical cleaning includes the RCA cleaning method.

[0043] Layered loading is performed in the main crucible, ensuring the cleanliness of the materials entering the crucible and precisely controlling the feeding structure. Secondary dopants are chemically cleaned (e.g., by RCA cleaning) to thoroughly remove surface oxides and metallic impurities, and then dried for later use. The main crucible is loaded in layers, with high-purity intrinsic polycrystalline silicon blocks in the lower layer (bottom) and the cleaned secondary dopants in the upper layer (top). The advantages of this structure are: during melting, the lower layer of high-purity silicon melts first, forming a molten pool, which "suspends" and "buffers" the upper layer of secondary dopants, preventing high-concentration dopants from directly contacting the crucible wall and causing localized contamination or erosion. At the same time, it facilitates the stable diffusion of dopants through natural convection.

[0044] In some embodiments of the present invention, in step S3, crystal growth includes: crystal growth under a magnetic field; preferably, crystal growth includes crystal growth using the Czochralski method; preferably, during crystal growth, the crucible rotation speed is 1~5 rpm (e.g., 1 rpm, 2 rpm, 3 rpm, 4 rpm, 5 rpm), the crystal and the crucible rotate in opposite directions (the rotation direction of the seed crystal and the growing crystal is opposite to the rotation direction of the crucible), and the magnetic field strength is 0.2~0.5T (2000~5000 Gauss).

[0045] The crystal growth stage of this invention incorporates special control into the conventional crystal pulling process, and crystal growth is carried out under a magnetic field, which ensures the final quality.

[0046] Applying a magnetic field can further suppress the violent flow of the melt boundary layer, ensuring uniform melting of the melt (which is beneficial for uniform doping) while significantly reducing the dissolution of the quartz crucible, thus meeting the stringent low-oxygen requirements of the BC battery back contact structure.

[0047] In some embodiments of the present invention, step S3 includes heating as follows: after the laying is completed, the furnace is evacuated to a vacuum, and then high-purity argon is introduced as a protective atmosphere, and then heated until it is completely melted to obtain molten silicon; preferably, the heating system is started and a graphite heater is used to heat the main crucible.

[0048] Multi-stage melting and doping diffusion: As the temperature rises, the lower layer of high-purity intrinsic polycrystalline silicon melts first, forming a molten silicon pool; the upper layer of secondary dopant gradually penetrates the molten pool and melts. Due to the uniformity of the secondary dopant itself, the dopant can diffuse throughout the melt with a relatively gentle concentration gradient. This process has a shorter and more uniform diffusion path than directly adding small pieces of high-concentration dopant (such as borosilicate alloy). By adjusting the thermal field and holding time, it is ensured that the dopant achieves a highly uniform distribution before crystal growth begins.

[0049] In some embodiments of the present invention, crystal growth includes: crystal pulling, shoulder formation, constant diameter growth, and finishing; the present invention does not strictly limit the crystal pulling, shoulder formation, constant diameter growth, and finishing, and adopts conventional standard crystal pulling, shoulder formation, constant diameter growth, and finishing processes; preferably, after crystal growth, a silicon rod is obtained.

[0050] The silicon rod crystal growth method of this invention comprises the following process flow: preparing a primary master alloy rod with low-resistivity regions at both ends; cutting the primary master alloy rod into silicon cores and mixing them with high-purity intrinsic polycrystalline silicon fragments to form a secondary dopant; performing layered loading in a main crucible; and performing crystal growth under a magnetic field. This method constructs a globally optimized scheme from the source to the process and then to the result, rather than improving a single step; it provides a process for preparing single-crystal silicon materials with high uniformity and high purity for BC batteries; it achieves high resistivity uniformity, low oxygen content, and high minority carrier lifetime; the axial resistivity fluctuation range is within ±5%, the radial resistivity fluctuation is <5%, the oxygen content is <6 ppma, and the minority carrier lifetime can reach hundreds of microseconds or even milliseconds.

[0051] Mechanism for achieving high resistivity uniformity: Secondary dopant has already achieved initial homogenization of the dopant during the prefabrication stage; during the growth stage, the extremely stable solid-liquid interface shape and melt convection state ensure that the segregation coefficient of the dopant (boron or phosphorus) in the crystal remains constant. This is the basis for achieving a gradual change in axial resistivity and a uniform radial resistivity distribution in the crystal.

[0052] The mechanism for achieving high minority carrier lifetime involves using clean secondary doped materials and high-purity intrinsic polycrystalline silicon to reduce heavy metal impurities to extremely low levels. A stable thermal field and growth interface prevent excessive thermal stress, thereby suppressing the generation of defects such as dislocations and interstitial atomic clusters. Successfully controlled low oxygen content is crucial, as oxygen and its thermal donor effect are key factors affecting minority carrier lifetime. Through this synergistic control, the minority carrier lifetime of the silicon rod can ultimately reach hundreds of microseconds or even milliseconds, meeting the requirements of high-efficiency BC solar cells.

[0053] Example 1 The method for growing silicon rods provided in this embodiment includes the following steps: S1. P-type single-crystal silicon rods are prepared by zone melting method. The resistivity of the single-crystal silicon rods is >1000Ω·cm, the diameter is 100mm, and the length is 1000mm. By neutron transmutation doping and annealing, a first doped region with a length of 100 mm (10% of the total length) is formed at both ends of a P-type single crystal silicon rod. The resistivity of the first doped region is 0.125 Ω·cm (1 / 8 of the target resistivity of the silicon rod), thus obtaining a first-level master alloy rod. S2. Cut the primary master alloy rod into silicon cores with a diameter of 20mm and a length of 120mm. The diameter of the silicon core is 1 / 35 of the inner diameter of the main crucible (700mm), and the length-to-diameter ratio of the silicon core is 6:1. The silicon cores described above, in a mass ratio of 2.5:7.5, were mixed with high-purity intrinsic polycrystalline silicon fragments (9N, electronic grade) to obtain secondary doped material. S3. Cut the secondary dopant into blocks and then perform chemical cleaning using the RCA cleaning method; 78 kg of high-purity intrinsic polycrystalline silicon block material (9N, electronic grade) was laid in the main crucible, and then 42 kg of secondary dopant was laid on the surface of the high-purity intrinsic polycrystalline silicon block material; the mass ratio of high-purity intrinsic polycrystalline silicon block material to secondary dopant was 6.5:3.5. After the laying is completed, the vacuum is drawn, and then high-purity argon is filled in as a protective atmosphere. The heating system is started, and the main crucible is heated with a graphite heater (1520~1540℃, 20~22h). After complete melting, molten silicon is obtained. The molten silicon is grown into a crystal under a magnetic field (Czochralski method). The crucible rotates at a speed of 2 rpm, the crystal rotates in the opposite direction to the crucible, and the magnetic field strength is 0.3T. Crystal growth includes crystal introduction, shoulder formation, constant diameter growth, and tailing to obtain a silicon rod.

[0054] Example 2 The method for growing silicon rods provided in this embodiment includes the following steps: S1. N-type single-crystal silicon rods are prepared by zone melting method. The resistivity of the single-crystal silicon rods is >1000Ω·cm, the diameter is 100mm, and the length is 1000mm. By ion implantation and annealing, a first doped region with a length of 50 mm (5% of the total length) is formed at both ends of an N-type single crystal silicon rod. The resistivity of the first doped region is 0.1 Ω·cm (1 / 10 of the target resistivity of the silicon rod), thus obtaining a first-level master alloy rod. S2. Cut the primary master alloy rod into silicon cores with a diameter of 14mm and a length of 42mm. The diameter of the silicon core is 1 / 50 of the inner diameter of the main crucible (700mm), and the length-to-diameter ratio of the silicon core is 3:1. The silicon cores described above, in a mass ratio of 2:8, were mixed with high-purity intrinsic polycrystalline silicon fragments (9N, electronic grade) to obtain secondary doped material. S3. Cut the secondary dopant into blocks and then perform chemical cleaning using the RCA cleaning method; 72 kg of high-purity intrinsic polycrystalline silicon block material (9N, electronic grade) was laid in the main crucible, and then 48 kg of secondary dopant was laid on the surface of the high-purity intrinsic polycrystalline silicon block material; the mass ratio of high-purity intrinsic polycrystalline silicon block material to secondary dopant was 6:4. After the laying is completed, the vacuum is drawn, and then high-purity argon is filled in as a protective atmosphere. The heating system is started, and the main crucible is heated with a graphite heater (1520~1540℃, 20~22h). After complete melting, molten silicon is obtained. The molten silicon is grown into a crystal under a magnetic field (Czochralski method). The crucible rotates at 3 rpm, the crystal rotates in the opposite direction to the crucible, and the magnetic field strength is 0.4T. Crystal growth includes crystal introduction, shoulder formation, constant diameter growth, and tailing to obtain a silicon rod.

[0055] Example 3 The method for growing silicon rods provided in this embodiment includes the following steps: S1. N-type single-crystal silicon rods are prepared by zone melting method. The resistivity of the single-crystal silicon rods is >1000Ω·cm, the diameter is 100mm, and the length is 1000mm. By ion implantation and annealing, a first doped region with a length of 150 mm (15% of the total length) is formed at both ends of an N-type single crystal silicon rod. The resistivity of the first doped region is 0.2 Ω·cm (1 / 5 of the target resistivity of the silicon rod), thus obtaining a first-level master alloy rod. S2. Cut the primary master alloy rod into silicon cores with a diameter of 35mm and a length of 350mm. The diameter of the silicon core is 1 / 20 of the inner diameter of the main crucible (700mm), and the length-to-diameter ratio of the silicon core is 10:1. The silicon cores described above, in a mass ratio of 3:7, were mixed with high-purity intrinsic polycrystalline silicon fragments (9N, electronic grade) to obtain secondary doped material. S3. Cut the secondary dopant into blocks and then perform chemical cleaning using the RCA cleaning method; 84 kg of high-purity intrinsic polycrystalline silicon block material (9N, electronic grade) was laid in the main crucible, and then 36 kg of secondary dopant was laid on the surface of the high-purity intrinsic polycrystalline silicon block material; the mass ratio of high-purity intrinsic polycrystalline silicon block material to secondary dopant was 7:3. After the laying is completed, the vacuum is drawn, and then high-purity argon is filled in as a protective atmosphere. The heating system is started, and the main crucible is heated with a graphite heater (1520~1540℃, 20~22h). After complete melting, molten silicon is obtained. The molten silicon is grown into a crystal under a magnetic field (Czochralski method). The crucible rotates at a speed of 4 rpm, the crystal rotates in the opposite direction to the crucible, and the magnetic field strength is 0.4 T. Crystal growth includes crystal introduction, shoulder formation, constant diameter growth, and tailing to obtain a silicon rod.

[0056] Tests showed that the axial resistivity fluctuation of the silicon rods prepared in Examples 1-3 was within ±5%, the radial resistivity fluctuation was <5%, the oxygen content was <6 ppma (detected using Fourier transform infrared spectroscopy), and the minority carrier lifetime could reach hundreds of microseconds or even milliseconds (680~1250 μs).

[0057] The resistivity testing methods are as follows: Axial resistivity is measured by equidistant slices along the crystal axis using the straight-line four-probe method (GB / T 1551-2021) to measure the resistivity at the center point; radial resistivity is measured at 9 points along the diameter direction using the extended resistance probe method, according to GB / T 11073-2007 standard. Minority carrier lifetime: The testing method involves sampling at the same locations, performing standard surface passivation treatment, and then measuring using the microwave photoconductivity attenuation method (μ-PCD), conforming to GB / T 42907-2023 standard.

[0058] Although the present invention has been illustrated and described with specific embodiments, it should be understood that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; those skilled in the art should understand that modifications can be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein, without departing from the spirit and scope of the present invention; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention; therefore, this means that all such substitutions and modifications that fall within the scope of the present invention are included in the appended claims.

Claims

1. A method for growing silicon rods, characterized in that, Includes the following steps: S1. A single-crystal silicon-based rod is prepared by zone melting method; the single-crystal silicon-based rod is subjected to ion doping and annealing in sequence to form a first doped region at both ends of the single-crystal silicon-based rod, thereby obtaining a primary master alloy rod. S2. Cut the primary master alloy rod into silicon cores, and mix the silicon cores with high-purity intrinsic polycrystalline silicon fragments to obtain secondary doped material; S3. Lay high-purity intrinsic polycrystalline silicon ingots in the main crucible, and then lay the secondary dopant on the surface of the high-purity intrinsic polycrystalline silicon ingots; then perform heating and crystal growth in sequence.

2. The method for growing silicon rods according to claim 1, characterized in that, In step S1, the resistivity of the single-crystal silicon rod is >1000Ω·cm; And / or, the monocrystalline silicon substrate includes an N-type monocrystalline silicon substrate or a P-type monocrystalline silicon substrate.

3. The method for growing silicon rods according to claim 1, characterized in that, In step S1, the ion doping method includes transmutation doping or ion implantation.

4. The method for growing silicon rods according to claim 3, characterized in that, In step S1, the resistivity of the first doped region is 1 / 10 to 1 / 5 of the target resistivity of the silicon rod.

5. The method for growing silicon rods according to claim 4, characterized in that, In step S1, the length of the first doped region is 5% to 15% of the total length of the single-crystal silicon rod.

6. The method for growing silicon rods according to claim 5, characterized in that, In step S2, the diameter of the silicon core is 1 / 50 to 1 / 20 of the inner diameter of the main crucible, and the length-to-diameter ratio of the silicon core is (3~10):

1.

7. The method for growing silicon rods according to claim 5, characterized in that, In step S2, the mass ratio of the silicon core to the high-purity intrinsic polycrystalline silicon fragment is (2~3):(7~8).

8. The method for growing silicon rods according to claim 5, characterized in that, In step S3, the mass ratio of the high-purity intrinsic polycrystalline silicon block to the secondary doped material is (6~7):(3~4).

9. The method for growing silicon rods according to claim 5, characterized in that, In step S3, before laying the secondary dopant, the process further includes chemically cleaning the secondary dopant.

10. The method for growing silicon rods according to claim 5, characterized in that, In step S3, the crystal growth includes: performing crystal growth under a magnetic field.