Monocrystalline silicon rod and production method and production equipment thereof

Abstract

The invention provides a silicon single crystal rod and a production method and equipment thereof. The production method of the silicon single crystal rod comprises the following steps: S1, paving a polycrystalline silicon material at the bottom of a quartz crucible of a single crystal furnace; s2, a polycrystalline silicon protection wall is arranged in the quartz crucible, the polycrystalline silicon protection wall is a cylindrical wall body with the two axial ends communicated, and the outer diameter of the polycrystalline silicon protection wall is matched with the inner diameter of the quartz crucible; s3, filling the polycrystalline silicon protection wall with a polycrystalline silicon material; s4, heating the quartz crucible through a single crystal furnace to melt the polycrystalline silicon material into a silicon melt; and S5, carrying out Czochralski single crystal growth on the silicon melt in the polycrystalline silicon protection wall to obtain a single crystal silicon rod. The polycrystalline silicon material is filled in the internal space of the polycrystalline silicon protection wall and the bottom of the crucible below the polycrystalline silicon protection wall. After melting, the periphery of the silicon melt is surrounded by the polycrystalline silicon protection wall, so that physical isolation between the silicon melt and the side wall of the quartz crucible is realized, the most important oxygen introduction source is greatly reduced, and the quality of the obtained silicon single crystal rod is improved.

Description

Technical Field

[0001] This application relates to the field of monocrystalline silicon rod production, specifically a monocrystalline silicon rod and its production method and equipment. Background Technology

[0002] With the photovoltaic industry trending towards higher photoelectric conversion efficiency, the quality of monocrystalline silicon wafers has become one of the key limiting factors. Among them, the oxygen content in monocrystalline silicon wafers is one of the core key parameters affecting the electrical performance of the wafers and the final cell efficiency. Excessive oxygen content can form oxygen-related recombination centers, which may generate defects in subsequent thermal processes, significantly reducing minority carrier lifetime and thus impairing the cell's conversion efficiency.

[0003] Currently, the Czochralski method is the mainstream technology for preparing monocrystalline silicon. Studies have shown that oxygen impurities in monocrystalline silicon grown using this method primarily originate from the quartz crucible, which serves as the melting vessel. The main component of the quartz crucible is silicon dioxide. During prolonged high-temperature processing, the molten silicon continuously contacts the inner wall of the quartz crucible, resulting in chemical reactions and physical erosion. Under these conditions, oxygen elements in the quartz crucible continuously dissolve and migrate into the silicon melt. As the crystal grows, these oxygen atoms are captured by the growing crystal lattice, ultimately leading to a persistently high oxygen content in the crystallized material. This makes it difficult to meet the increasingly stringent requirements for low oxygen content in silicon wafer raw materials for high-efficiency solar cell modules. Therefore, effectively suppressing or reducing oxygen contamination from the quartz crucible within the existing Czochralski process framework has become a key technological bottleneck for improving the quality of photovoltaic monocrystalline silicon materials and ultimately driving breakthroughs in cell efficiency. Summary of the Invention

[0004] To address the aforementioned technical problems, this application provides a method for producing single-crystal silicon rods, the detailed technical solution of which is as follows: A method for producing single-crystal silicon rods includes the following steps: S1. Lay polycrystalline silicon material at the bottom of the quartz crucible in the single crystal furnace; S2. Place the polycrystalline silicon protective wall inside the quartz crucible. The polycrystalline silicon protective wall is a cylindrical wall that runs through both ends of the axis. The outer diameter of the polycrystalline silicon protective wall is matched with the inner diameter of the quartz crucible. S3. Fill the polysilicon material into the polysilicon wall; S4. The quartz crucible is heated by a single crystal furnace, so that the polycrystalline silicon material is melted into silicon melt. S5. Perform Czochralski single crystal growth on the silicon melt inside the polycrystalline silicon wall to obtain a single crystal silicon rod.

[0005] The monocrystalline silicon rod production process of this application involves setting a cylindrical polycrystalline silicon protective wall inside a quartz crucible, with the outer wall of the polycrystalline silicon protective wall close to the inner wall of the quartz crucible. During loading, polycrystalline silicon material is filled into the internal space of the polycrystalline silicon protective wall and the bottom of the crucible below. After melting, the silicon melt is surrounded by the polycrystalline silicon protective wall, thereby achieving physical isolation between the silicon melt and the sidewall of the quartz crucible. This significantly reduces the most important source of oxygen introduction and improves the quality of the obtained monocrystalline silicon rod.

[0006] In some embodiments, the outer diameter of the polycrystalline silicon retainer is 2 mm to 3 mm smaller than the inner diameter of the quartz crucible, and the wall thickness of the polycrystalline silicon retainer is 10 mm to 15 mm.

[0007] The outer diameter of the polycrystalline silicon retainer is set to be 2mm to 3mm smaller than the inner diameter of the quartz crucible, allowing for deformation of the quartz crucible and facilitating the smooth placement of the polycrystalline silicon retainer into the quartz crucible. The wall thickness of the polycrystalline silicon retainer is set to 10mm to 15mm to ensure that after all the polycrystalline silicon material filled within the retainer melts into the silicon melt, the retainer has not yet melted through, thus ensuring physical isolation between the silicon melt and the sidewall of the quartz crucible.

[0008] In some embodiments, the purity of the polycrystalline silicon wall is not less than 99.9999%.

[0009] When the polycrystalline silicon material filled within the polycrystalline silicon retainer is melted into molten silicon, the polycrystalline silicon retainer also partially melts and merges into the molten silicon. Therefore, the purity of the polycrystalline silicon retainer must be high enough to avoid reducing the purity of the molten silicon.

[0010] In some embodiments, in step S3, the amount of polysilicon material filled into the polysilicon retainer is set such that the liquid level of the molten silicon is lower than the top opening of the polysilicon retainer.

[0011] To prevent molten silicon from overflowing the polycrystalline silicon retaining wall.

[0012] In some embodiments, the single crystal furnace has a bottom heater located below the quartz crucible and a main heater located around the quartz crucible; in step S4, heating the quartz crucible by the single crystal furnace includes: Start the bottom heater and the main heater, and control the heating power ratio of the bottom heater and the main heater to be (2.5~3.5):2 during startup; Monitor the melting state of polysilicon material inside the polysilicon wall. As the solid-liquid ratio of solid polysilicon material to molten silicon in the quartz crucible decreases, dynamically adjust the heating power of the bottom heater and the main heater to create a temperature gradient in the quartz crucible where the lower temperature is higher than the upper temperature. When the polysilicon material inside the polysilicon wall is completely melted, the heating power ratio of the bottom heater and the main heater is controlled to be the same as the heating power ratio at startup, so that the polysilicon material inside the polysilicon wall remains in a molten state.

[0013] By controlling the heating temperatures of the bottom heater and the bottom heater, an axial temperature gradient of "high temperature at the bottom and low temperature at the top" can be formed and maintained. This ensures that the silicon material melts from the bottom of the quartz crucible upwards and from the inside of the polycrystalline silicon retainer to the sidewall. This prevents the polycrystalline silicon retainer from melting or being melted through before the internal silicon material due to excessive temperature. As a result, when the polycrystalline silicon material inside the polycrystalline silicon retainer is completely melted, the polycrystalline silicon retainer can still physically isolate the silicon melt from the sidewall of the quartz crucible.

[0014] In addition, the temperature gradient formed by preferential heating at the bottom is conducive to the upward transfer of heat, which accelerates the overall melting process of polycrystalline silicon material inside the polycrystalline silicon wall. At the same time, it creates disturbance, stirs the silicon melt, promotes the uniform distribution of temperature and dopants, and creates an extremely stable initial melt environment for subsequent single crystal growth.

[0015] In some embodiments, the heating power of the bottom heater and the main heater is adjusted according to the solid-liquid ratio as shown in the table below (Table 1): Table 1: .

[0016] A convenient gradient adjustment strategy for the heating power of the bottom heater and the main heater is provided to ensure that the polycrystalline silicon wall remains intact even after all the polycrystalline silicon material filled within it has melted into silicon melt. This also ensures a stable initial melt environment for subsequent single crystal growth.

[0017] In some embodiments, in step S4, while heating the quartz crucible in a single-crystal furnace, the single-crystal silicon rod production method further includes controlling the quartz crucible to rotate at a speed of 1-3 rpm.

[0018] By controlling the quartz crucible to rotate at a speed of 1-3 rpm during the melting process, the silicon melt can be further stirred, promoting the uniform distribution of temperature and dopant.

[0019] In some embodiments, the polycrystalline silicon retainer is obtained by cutting and cleaning a hollow cylindrical polycrystalline silicon ingot that has been scrapped due to internal wall cracks.

[0020] By processing discarded hollow cylindrical polycrystalline silicon ingots (with internal wall cracks) into polycrystalline silicon wall protectors, waste is turned into treasure, realizing the recycling of waste materials and reducing the raw material cost of polycrystalline silicon wall protectors.

[0021] This application also provides a single-crystal silicon rod production apparatus for implementing the single-crystal silicon rod production method described in any of the above claims, the single-crystal silicon rod production apparatus comprising: Quartz crucible; The cylindrical polycrystalline protective wall has an outer diameter that matches the inner diameter of the quartz crucible; A single crystal furnace, which contains a bottom heater and a main heater that can be independently temperature controlled; The control system is configured to execute the heating power control program described above.

[0022] The monocrystalline silicon rod production equipment provided in this application is used to produce monocrystalline silicon rods. During loading, polycrystalline silicon material is filled into the internal space of the polycrystalline silicon protective wall and the bottom of the crucible below. After melting, the silicon melt is surrounded by the polycrystalline silicon protective wall, thereby achieving physical isolation between the silicon melt and the sidewall of the quartz crucible. This significantly reduces the most important source of oxygen introduction and improves the quality of the obtained monocrystalline silicon rods.

[0023] This application also provides a single-crystal silicon rod, which is prepared by the single-crystal silicon rod production method described in any of the above claims. Attached Figure Description

[0024] Figure 1 This is a flowchart illustrating the process of producing single-crystal silicon rods according to this application. Detailed Implementation

[0025] To make the above-mentioned objects, features, and advantages of this application more apparent and understandable, the application will be further described in detail below with reference to the accompanying drawings and specific embodiments. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this application. Rather, they are merely examples of apparatuses and methods consistent with some aspects of this application as detailed in the appended claims.

[0026] In this specification, for ease of description and consistent understanding, the relative positional relationships of the components will be defined with reference to the directions shown in the accompanying drawings. For example, the use of directional terms such as "upper," "lower," "top," and "bottom" is generally based on the layout of the drawings. It should be understood that these directional terms are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application.

[0027] Currently, in the process of preparing monocrystalline silicon using the Czochralski method, oxygen in the quartz crucible continuously dissolves and migrates into the silicon melt, resulting in a high oxygen content in the pulled monocrystalline silicon rod, which cannot meet the stringent requirements of high-efficiency battery modules for low oxygen content in silicon wafer raw materials.

[0028] In view of this, the first aspect of this application provides a method for producing single-crystal silicon rods, comprising the following steps: S1. Lay polycrystalline silicon material at the bottom of the quartz crucible in the single crystal furnace.

[0029] S2. Place the polycrystalline silicon protective wall inside the quartz crucible. The polycrystalline silicon protective wall is a cylindrical wall that runs through both ends of the axial direction. The outer diameter of the polycrystalline silicon protective wall is matched with the inner diameter of the quartz crucible.

[0030] S3. Fill the polycrystalline silicon material into the polycrystalline silicon wall.

[0031] S4. The quartz crucible is heated by a single crystal furnace, so that the polycrystalline silicon material is melted into silicon melt.

[0032] S5. Perform Czochralski single crystal growth on the silicon melt inside the polycrystalline silicon wall to obtain a single crystal silicon rod.

[0033] The monocrystalline silicon rod production process of this application involves setting a cylindrical polycrystalline silicon protective wall inside a quartz crucible, with the outer wall of the polycrystalline silicon protective wall close to the inner wall of the quartz crucible. During loading, polycrystalline silicon material is filled into the internal space of the polycrystalline silicon protective wall and the bottom of the crucible below. After melting, the silicon melt is surrounded by the polycrystalline silicon protective wall, thereby achieving physical isolation between the silicon melt and the sidewall of the quartz crucible, significantly reducing the most important source of oxygen introduction and improving the quality of the obtained monocrystalline silicon rod.

[0034] In an optional embodiment, the outer diameter of the polycrystalline silicon retainer is 2mm to 3mm smaller than the inner diameter of the quartz crucible. For example, the outer diameter of the polycrystalline silicon retainer is 2mm, 2.1mm, 2.2mm, ..., 2.9mm or 3mm smaller than the inner diameter of the quartz crucible. Controlling the outer diameter of the polycrystalline silicon retainer to be 2mm to 3mm smaller than the inner diameter of the quartz crucible helps to smoothly place the polycrystalline silicon retainer into the quartz crucible, and also allows for thermal deformation of the quartz crucible during melting.

[0035] Since the inner wall material of the polycrystalline silicon retainer partially melts and merges into the molten silicon when heated, to prevent the polycrystalline silicon retainer from melting through and losing its ability to physically isolate the molten silicon from the sidewall of the quartz crucible, in an optional embodiment, the wall thickness of the polycrystalline silicon retainer is set to 10mm to 15mm, for example, 10mm, 11mm, ... 15mm. Furthermore, to prevent the polycrystalline silicon retainer material that merges into the molten silicon after melting from affecting the purity of the molten silicon, in an optional embodiment, the purity of the polycrystalline silicon retainer is not less than 99.9999%.

[0036] In order to prevent the silicon melt from overflowing from the top of the polycrystalline silicon retainer, in an optional embodiment, in step S3, the filling amount of polycrystalline silicon material filled into the polycrystalline silicon retainer is set such that the liquid level of the molten silicon is lower than the top opening of the polycrystalline silicon retainer.

[0037] In an optional embodiment, the single crystal furnace has a bottom heater located below the quartz crucible and a main heater located around the quartz crucible.

[0038] In step S4, heating the quartz crucible using a single-crystal furnace includes: Start the bottom heater and the main heater, and control the heating power ratio of the bottom heater and the main heater to be (2.5~3.5):2 during startup; Monitor the melting state of polysilicon material inside the polysilicon wall. As the solid-liquid ratio of solid polysilicon material to molten silicon in the quartz crucible decreases, dynamically adjust the heating power of the bottom heater and the main heater to create a temperature gradient in the quartz crucible where the lower temperature is higher than the upper temperature. When the polysilicon material inside the polysilicon wall is completely melted, the heating power ratio of the bottom heater and the main heater is controlled to be the same as the heating power ratio at startup, so that the polysilicon material inside the polysilicon wall remains in a molten state.

[0039] By controlling the heating temperatures of the bottom heater and the bottom heater, an axial temperature gradient of "high temperature at the bottom and low temperature at the top" can be formed and maintained. This ensures that the silicon material melts from the bottom of the quartz crucible upwards and from the inside of the polycrystalline silicon retainer to the sidewall. This prevents the polycrystalline silicon retainer from melting or being melted through before the internal silicon material due to excessive temperature. As a result, when the polycrystalline silicon material inside the polycrystalline silicon retainer is completely melted, the polycrystalline silicon retainer still maintains its structural integrity, thereby implementing physical isolation between the silicon melt and the sidewall of the quartz crucible.

[0040] In addition, the temperature gradient formed by preferential heating at the bottom facilitates the upward transfer of heat, thereby accelerating the overall melting process of the polycrystalline silicon material within the polycrystalline silicon wall and simultaneously creating disturbances to stir the silicon melt, promoting the uniform distribution of temperature and dopants, and creating an extremely stable initial melt environment for subsequent single crystal growth.

[0041] In an optional implementation, during the melting stage, the heating power of the bottom heater and the main heater can be adjusted synchronously according to the solid-liquid ratio as shown in Table 1 below: Table 1: .

[0042] By referencing the quantitative correspondence between the solid-liquid ratio, the heating power of the bottom heater and the main heater in the reference table, it is possible to conveniently and precisely control the heating power of the bottom heater and the main heater during the melting process, effectively protecting the sidewalls of the polycrystalline silicon retainer, suppressing its melt-through, and ensuring that an extremely stable initial melt environment is created for subsequent single crystal growth.

[0043] As can be seen from the table, after the polycrystalline silicon material inside the polycrystalline silicon wall is completely melted, the heating power of the bottom heater and the main heater is stabilized at 55 kW and 35 kW respectively, so that the silicon melt remains in a molten state, ensuring the subsequent Czochralski single crystal growth effect.

[0044] During the melting process, AI vision-assisted technology can be used to monitor the melting state of the polycrystalline silicon material inside the polycrystalline silicon wall and obtain the solid-liquid ratio.

[0045] It should be noted that the specific heating power values ​​provided in Table 1 are merely a preferred embodiment for illustrating the principles of this application and are not intended to limit this application.

[0046] Therefore, in other embodiments, the control of heating power can follow the following principles, rather than adhering to the specific figures in the table: The heating power of both the bottom heater and the main heater is dynamically adjusted as the solid-liquid ratio decreases.

[0047] In the early stages of melting (when the solid-liquid ratio is high), a high heating power ratio of bottom / main heater (e.g., close to 3.5:2) is maintained to establish a strong bottom-up temperature gradient; as melting progresses, this heating power ratio can be gradually reduced (e.g., close to 2.5:2) to accommodate changes in the melt level and thermal field distribution.

[0048] The ultimate goal of adjusting the heating power is to maintain a stable temperature field at the polycrystalline silicon wall that allows for melting from bottom to top and from the inside out, meaning that the temperature of the lower and inner parts of the polycrystalline silicon wall is higher than that of the upper and outer parts.

[0049] As long as the inventive concept of "forming and maintaining a specific dynamic temperature gradient at the polycrystalline silicon wall by coordinating the heating power of the bottom heater and the main heater" is adopted, regardless of how the specific heating power value is adjusted, it should be covered within the protection scope of this application.

[0050] In an optional embodiment, the polycrystalline silicon wall protector is obtained by cutting and cleaning hollow cylindrical polycrystalline silicon ingots that are scrapped due to internal wall cracks. Processing scrapped hollow cylindrical polycrystalline silicon ingots (with internal wall cracks) into polycrystalline silicon wall protectors turns waste into treasure, realizes the recycling of waste materials, and reduces the raw material cost of polycrystalline silicon wall protectors.

[0051] During the heating process, the polycrystalline silicon wall material will melt from the inside out, and the thickness will continuously decrease. In order to ensure that the remaining polycrystalline silicon wall material can effectively physically isolate the silicon melt from the side wall of the quartz crucible, the outer wall of the selected scrapped hollow cylindrical polycrystalline silicon ingot must not have obvious cracks.

[0052] Of course, in other alternative implementations, entirely new polycrystalline silicon insulators can also be prepared, for example, by centrifugal casting or machining. The centrifugal casting process is roughly as follows: high-purity polycrystalline silicon is melted in a special crucible, and then the molten silicon is poured into a high-speed rotating cylindrical mold. Under centrifugal force, the melt adheres tightly to the inner wall of the mold, solidifies, and directly yields a hollow cylindrical ingot. This ingot is then annealed, machined (e.g., turning of the inner and outer walls), and cleaned. The machining process is roughly as follows: a solid polycrystalline silicon ingot is first prepared, then the outer circle is cut and large holes are drilled using a diamond wire saw or internal circular slicing machine. Finally, precision machining such as grinding and lapping is used to obtain a hollow cylinder of the required size.

[0053] In an optional embodiment, in step S4, while heating the quartz crucible in the single crystal furnace, the single crystal silicon rod production method further includes controlling the quartz crucible to rotate at a speed of 1-3 rpm.

[0054] Controlling the rotation of the quartz crucible during the melting process can further stir the silicon melt, promote the uniform distribution of temperature and dopants, and create an extremely stable initial melt environment for subsequent single crystal growth.

[0055] Step S5, which involves Czochralski single-crystal growth of the silicon melt within the polycrystalline silicon wall, can be implemented using existing mature Czochralski single-crystal technology, which generally includes the following steps: Seed crystal: The rotating seed crystal descends into the molten silicon within the polycrystalline silicon wall; Necking: Pulling up the seed crystal to grow a narrow neck with a diameter smaller than the seed crystal in order to eliminate dislocations; Shoulder formation: Gradually reduce the pulling speed of the seed crystal and / or reduce the temperature of the silicon melt, so that the diameter of the crystal gradually increases from the narrow neck to the target diameter; Constant diameter growth: Maintaining a constant crystal diameter, the main body of a single crystal silicon ingot is grown by coordinating the pulling speed and the temperature of the silicon melt; Final stage: In the final stage of growth, gradually increase the pulling speed and / or increase the temperature of the silicon melt to gradually reduce the crystal diameter until it separates from the melt, thus completing the single crystal growth.

[0056] The specific process parameters for each step can be set according to actual needs.

[0057] A second aspect of this application provides a single-crystal silicon rod production apparatus for implementing the single-crystal silicon rod production method in any of the above embodiments. The single-crystal silicon rod production apparatus includes: Quartz crucible; The cylindrical polycrystalline silicon protective wall has an outer diameter that matches the inner diameter of the quartz crucible; A single crystal furnace, which contains a bottom heater and a main heater that can be independently temperature controlled; The control system is configured to execute the heating power control program described above. Specifically, by writing the heating power gradient control strategy (e.g., the control strategy in the table) of the bottom heater and the main heater in Example 2 into an executable heating power control program, the control system executes the heating power control program to implement gradient temperature control of the bottom heater and the main heater.

[0058] The monocrystalline silicon rod production equipment provided in this application is used to produce monocrystalline silicon rods. During loading, polycrystalline silicon material is filled into the internal space of the polycrystalline silicon protective wall and the bottom of the crucible below. After melting, the silicon melt is surrounded by the polycrystalline silicon protective wall, thereby achieving physical isolation between the silicon melt and the sidewall of the quartz crucible. This significantly reduces the most important source of oxygen introduction and improves the quality of the obtained monocrystalline silicon rods.

[0059] By controlling the heating power of the bottom heater and the bottom heater, an axial temperature gradient of "high temperature at the bottom and low temperature at the top" can be formed and maintained. This ensures that the silicon material melts from the bottom of the quartz crucible upwards and from the inside of the polycrystalline silicon retainer to the sidewall. This prevents the polycrystalline silicon retainer from melting or being melted through before the internal silicon material due to excessive temperature. Thus, when the polycrystalline silicon material inside the polycrystalline silicon retainer is completely melted, the polycrystalline silicon retainer can still physically isolate the silicon melt from the sidewall of the quartz crucible.

[0060] In addition, the temperature gradient formed by preferential heating at the bottom is conducive to the upward transfer of heat, which accelerates the overall melting process of polycrystalline silicon material inside the polycrystalline silicon wall. At the same time, it creates disturbance, stirs the silicon melt, promotes the uniform distribution of temperature and dopants, and creates an extremely stable initial melt environment for subsequent single crystal growth.

[0061] A third aspect of this application also provides a single-crystal silicon rod, which is prepared by the single-crystal silicon rod production method of any of the above embodiments.

[0062] The present application will be further illustrated by the following examples. Unless otherwise specified, the polysilicon material and polysilicon wall coverings in the examples are commercially available, and the single crystal furnace equipment is manufactured by the applicant (this type of equipment is available on the market).

[0063] Example 1: The single crystal furnace used in the single crystal silicon rod production method of this embodiment is a type 1600 single crystal furnace. The single crystal furnace includes a quartz crucible, a bottom heater located on the lower side of the quartz crucible, and a main heater located around the periphery of the quartz crucible. The quartz crucible is 36 inches in size, with an inner diameter of 875 mm.

[0064] S1. Lay polycrystalline silicon material with a particle size of 1mm to 25mm at the bottom of the quartz crucible of the single crystal furnace.

[0065] S2. Place the polycrystalline silicon protective wall inside the quartz crucible. The polycrystalline silicon protective wall is a cylindrical wall that runs through both ends of the axial direction. The thickness of the polycrystalline silicon protective wall is 15mm. The outer diameter of the polycrystalline silicon protective wall is 2mm smaller than the inner diameter of the quartz crucible. The purity of the polycrystalline silicon protective wall is 99.9999%.

[0066] S3. Fill the polycrystalline silicon material into the polycrystalline silicon wall, totaling 600 kg.

[0067] S4. The quartz crucible is heated by a single crystal furnace, so that the polycrystalline silicon material is melted into silicon melt.

[0068] Start the bottom heater and the main heater, and control the heating power ratio of the bottom heater and the main heater to be 1.25 at startup; use AI vision-assisted technology to monitor the melting state of the polycrystalline silicon material in the polycrystalline silicon wall; as the solid-liquid ratio of the solid polycrystalline silicon material to the molten silicon liquid in the quartz crucible decreases, dynamically adjust the heating power of the bottom heater and the main heater to form a temperature gradient in the quartz crucible where the lower temperature is higher than the upper temperature. When the polycrystalline silicon material inside the polycrystalline silicon wall is completely melted, the heating power ratio of the bottom heater and the main heater is controlled to be the same as the heating power ratio at startup (i.e., the heating power ratio of the bottom heater and the main heater is 1.25) so that the polycrystalline silicon material inside the polycrystalline silicon wall remains in a molten state.

[0069] S5. Perform Czochralski single crystal growth on the silicon melt inside the polycrystalline silicon wall to obtain a single crystal silicon rod.

[0070] Example 2: This embodiment provides a method for producing single-crystal silicon rods, which differs from Embodiment 1 in that: In Example 2, the thickness of the polycrystalline silicon protective wall is 10 mm. In step S4, the heating power ratio of the bottom heater and the main heater is controlled to be 1.75 during startup.

[0071] Example 3: This embodiment provides a method for producing single-crystal silicon rods, which differs from Embodiment 1 in that: In Example 3, the thickness of the polycrystalline silicon protective wall is 12mm. In step S4, the heating power ratio of the bottom heater and the main heater is controlled to be 1.5 during startup.

[0072] Comparative Example 1 This comparative example provides a method for producing single-crystal silicon rods, which differs from Example 1 in that: Comparative Example 1 does not use polycrystalline silicon wall protection.

[0073] Comparative Example 2 This comparative example provides a method for producing single-crystal silicon rods, which differs from Example 1 in that: In Comparative Example 2, in step S4, the heating power ratio of the bottom heater and the main heater is controlled to be 1.2 during startup.

[0074] Comparative Example 3 This comparative example provides a method for producing single-crystal silicon rods, which differs from Example 1 in that: In Comparative Example 3, in step S4, the heating power ratio of the bottom heater and the main heater is controlled to be 1.8 during startup.

[0075] Comparative Example 4 This comparative example provides a method for producing single-crystal silicon rods, which differs from Example 1 in that: The thickness of the polycrystalline silicon sheath used in Comparative Example 4 is 9 mm.

[0076] Test case Melting time statistics: The PLC control system built into the single crystal furnace is used, which is linked with parameters such as heating power, vacuum degree, and argon flow rate. The timer starts automatically when melting starts and stops automatically when full melting is determined (such as when the temperature is stable and the liquid surface brightness meets the standard). The melting time in Examples 1-3 and Comparative Examples 1-4 is recorded.

[0077] Test samples: The single-crystal silicon rods prepared in Examples 1-3 and Comparative Examples 1-4 were used as samples for testing.

[0078] For each of the above single-crystal silicon rods, samples were taken from the head of the rod with equal diameter, and thin sheet samples 1, 2, and 3 with a thickness of 0.5 mm to 2 mmd were cut out respectively without damage or stress.

[0079] Infrared absorption spectra of each thin-film sample were acquired using a BRUKER HYPERION Vertex 70 FTIR spectrometer. Oxygen content was calculated using Lambert-Beer's law, expressed in ppm (parts per million). The average oxygen content of thin-film sample 1, sample 2, and sample 3 at the head of each single-crystal silicon rod with the same diameter was taken as the oxygen content result for that single-crystal silicon rod.

[0080] The test and record results are shown in Table 2.

[0081] Table 2:

[0082] As shown in Table 2, in Comparative Example 1, no polycrystalline silicon wall protector was used, resulting in a short melting time but a high oxygen content. In Comparative Example 2, the bottom-applied power ratio was too small, leading to an excessively long melting time and high oxygen content. In Comparative Example 3, the bottom-applied power ratio was too large, reducing the melting time, but oxygen diffused from the bottom of the crucible into the molten silicon, resulting in an excessively high oxygen content. In Comparative Example 4, the polycrystalline silicon wall protector used was relatively thin, gradually melting and collapsing during the melting process, offering limited protection and resulting in an excessively high oxygen content.

[0083] This application provides a sufficiently detailed and specific description. Those skilled in the art should understand that the descriptions in the embodiments are merely exemplary, and all changes made without departing from the true spirit and scope of this application should fall within its protection scope. The scope of protection claimed in this application is defined by the claims, not by the above descriptions in the embodiments. Without contradiction, some optional components in one embodiment can also be used in another embodiment, and some preferred structures of the same component in one embodiment are also applicable to another embodiment. Furthermore, there may be slight differences in the wording of the names of certain components in different embodiments; these slight differences will not affect the understanding of the technical solution of the present invention by those skilled in the art.

Claims

1. A method for producing single-crystal silicon rods, characterized in that, The method for producing single-crystal silicon rods includes the following steps: S1. Lay polycrystalline silicon material at the bottom of the quartz crucible in the single crystal furnace; S2. Place the polycrystalline silicon protective wall inside the quartz crucible, wherein the polycrystalline silicon protective wall is a cylindrical wall that extends through both ends in the axial direction, and the outer diameter of the polycrystalline silicon protective wall is adapted to the inner diameter of the quartz crucible. S3. Fill the polycrystalline silicon material into the polycrystalline silicon retaining wall; S4. The quartz crucible is heated by a single crystal furnace, so that the polycrystalline silicon material is melted into a silicon melt; S5. Perform Czochralski single crystal growth on the silicon melt inside the polycrystalline silicon wall to obtain a single crystal silicon rod.

2. The method for producing single-crystal silicon rods as described in claim 1, characterized in that, The outer diameter of the polycrystalline silicon protective wall is 2mm to 3mm smaller than the inner diameter of the quartz crucible, and the wall thickness of the polycrystalline silicon protective wall is 10mm to 15mm.

3. The method for producing single-crystal silicon rods as described in claim 1, characterized in that, The purity of the polycrystalline silicon wall is not less than 99.9999%.

4. The method for producing single-crystal silicon rods as described in claim 1, characterized in that, In step S3, the amount of polycrystalline silicon material filled into the polycrystalline silicon retaining wall is set such that the liquid level of the molten silicon is lower than the top opening of the polycrystalline silicon retaining wall.

5. The method for producing single-crystal silicon rods as described in claim 1, characterized in that, The single crystal furnace has a bottom heater located on the lower side of the quartz crucible and a main heater located on the periphery of the quartz crucible; In step S4, heating the quartz crucible using a single-crystal furnace includes: Start the bottom heater and the main heater, and control the heating power ratio of the bottom heater and the main heater to be (2.5~3.5):2 during startup; The melting state of the polycrystalline silicon material inside the polycrystalline silicon wall is monitored. As the solid-liquid ratio of the solid polycrystalline silicon material to the molten silicon liquid in the quartz crucible decreases, the heating power of the bottom heater and the main heater is dynamically adjusted to form a temperature gradient in the quartz crucible where the lower temperature is higher than the upper temperature. When the polycrystalline silicon material inside the polycrystalline silicon wall is completely melted, the heating power ratio of the bottom heater and the main heater is controlled to be the same as the heating power ratio at startup, so that the polycrystalline silicon material inside the polycrystalline silicon wall remains in a molten state.

6. The method for producing single-crystal silicon rods as described in claim 5, characterized in that: The heating power of the bottom heater and the main heater is adjusted according to the solid-liquid ratio as shown in the table below: 。 7. The method for producing single-crystal silicon rods as described in claim 4, characterized in that, In step S4, while heating the quartz crucible in a single-crystal furnace, the single-crystal silicon rod production method further includes controlling the quartz crucible to rotate at a speed of 1-3 rpm.

8. The method for producing single-crystal silicon rods as described in claim 1, characterized in that: The polycrystalline silicon protective wall is made by cutting and cleaning hollow cylindrical polycrystalline silicon ingots that were scrapped due to internal wall cracks.

9. A single-crystal silicon rod production equipment, characterized in that, For implementing the method for producing monocrystalline silicon rods according to any one of claims 1 to 8, the monocrystalline silicon rod production equipment comprises: Quartz crucible; The cylindrical polycrystalline silicon protective wall has an outer diameter that matches the inner diameter of the quartz crucible; A single crystal furnace, which contains a bottom heater and a main heater that can be independently temperature controlled; The control system is configured to execute the heating power control program of claim 5 or claim 6.

10. A single-crystal silicon rod, characterized in that, The single-crystal silicon rod is prepared by the single-crystal silicon rod production method according to any one of claims 1 to 8.

Images