Crystal bar manufacturing method, single crystal furnace and silicon wafer

Abstract

The invention relates to the field of photovoltaic technology, and provides a manufacturing method of a crystal bar, a single crystal furnace and a silicon wafer, and the single crystal furnace comprises a main furnace chamber, an auxiliary furnace chamber, a plasma doping device and a controller. The main furnace chamber is provided with a first chamber; the auxiliary furnace chamber is provided with a second chamber, the second chamber is communicated with the first chamber, and the second chamber is used for accommodating a crystal bar which completes a crystal pulling process in the main furnace chamber; the plasma doping device is arranged on the auxiliary furnace chamber and is configured to convert a dopant into plasma, and the plasma is introduced into the second chamber, so that the plasma is doped into the crystal bar; the controller is connected with the plasma doping device and is configured to control the working state of the plasma doping device, and the embodiment of the invention is at least beneficial to improving the uniformity of the resistivity of the crystal bar.

Description

TECHNICAL FIELD

[0001] Embodiments of the present disclosure relate to the technical field of photovoltaic technology, and particularly relate to a method for manufacturing a crystal bar, a single crystal furnace, and a silicon wafer. BACKGROUND

[0002] A crystal bar is an important raw material for manufacturing photovoltaic cell panels and semiconductor devices. In recent years, with the rapid expansion of the photovoltaic market and technological progress, the production capacity and quality of crystal bars have been significantly improved. The maturity of technologies such as the Czochralski (CZ) method and the floating zone method (FZ method) ensures the purity and crystallization quality of the crystal bar, thereby improving the conversion efficiency of solar cells and the performance of semiconductor devices.

[0003] In order to improve the quality of the crystal bar, the crystal bar is usually doped. The current commonly used doping techniques mainly include the co-melting method and the doping method. The co-melting method mainly puts high-purity solid dopants and polycrystalline silicon raw materials into a quartz crucible at the same time in the charging process of the crystal bar prepared by the Czochralski method, and the doping concentration can be adjusted by changing the proportion of the solid dopants; in the process of preparing the crystal bar, the quartz crucible needs to be continuously rotated to ensure uniform distribution of the dopants in the silicon melt. The doping method is to add high-purity solid dopants into the silicon melt after the polycrystalline silicon raw material is melted, which is more suitable for some dopants with a large evaporation coefficient.

[0004] However, the current prepared crystal bar still has the problem of poor doping uniformity, which makes it difficult to meet the standard for the resistance uniformity of the prepared crystal bar, and affects the quality of the crystal bar. SUMMARY

[0005] Embodiments of the present disclosure provide a method for manufacturing a crystal bar, a single crystal furnace, and a silicon wafer, which at least facilitate to improve the uniformity of the resistivity of the crystal bar.

[0006] According to some embodiments of the present disclosure, in one aspect, a single crystal furnace is provided, comprising: a main furnace chamber having a first chamber; a secondary furnace chamber having a second chamber, the second chamber being in communication with the first chamber, the second chamber being configured to accommodate a crystal bar that has completed a crystal pulling process in the main furnace chamber; a plasma doping device disposed on the secondary furnace chamber and configured to convert a dopant into plasma and introduce the plasma into the second chamber so as to dope the plasma into the crystal bar; and a controller connected to the plasma doping device and configured to control an operating state of the plasma doping device.

[0007] In some embodiments, the single crystal furnace further comprises a temperature detector configured to acquire a temperature of the crystal bar; and the controller acquires the temperature and controls the plasma doping device to work to dope the plasma into the crystal bar when the temperature reaches a preset temperature.

[0008] In some embodiments, the single crystal furnace further comprises a cooling device configured to provide cooling gas into the second chamber to reduce the temperature of the crystal bar; and the controller controls the cooling device to stop providing the cooling gas when the temperature reduces to the preset temperature.

[0009] In some embodiments, the plasma doping device comprises a plasma generator located at a side of the second chamber away from the first chamber, configured to receive the dopant and plasmaize the dopant to form the plasma; and an excitation source configured to provide an excitation voltage to move the plasma to the surface of the crystal bar and dope into the crystal bar.

[0010] According to some embodiments of the present disclosure, another aspect of the present disclosure further provides a method for manufacturing a crystal bar, applied to the single crystal furnace as described in the above embodiment, comprising: pulling the crystal bar, which has completed a crystal pulling process in the main furnace chamber, into the second chamber; and providing plasma into the second chamber to dope the plasma into the crystal bar.

[0011] In some embodiments, before the step of providing the plasma into the second chamber, the method further comprises: acquiring a temperature of the crystal bar; providing cooling gas into the second chamber to cool the crystal bar when the temperature is higher than a preset temperature; and stopping providing the cooling gas and performing the step of providing the plasma when the temperature reduces to the preset temperature.

[0012] In some embodiments, the step of providing the plasma into the second chamber to dope the plasma into the crystal bar comprises: applying an excitation voltage to the plasma at a first voltage and a first pulse frequency to move the plasma to the surface of the crystal bar and dope into the crystal bar in a first doping period; and applying an excitation voltage to the plasma at a second voltage and a second pulse frequency to move the plasma to the surface of the crystal bar and dope into the crystal bar in a second doping period; wherein the second doping period is a period after the first doping period, and the second voltage is less than the first voltage, and the second pulse frequency is less than the first pulse frequency.

[0013] In some embodiments, the manufacturing method further comprises: during the first transition period, decreasing the voltage value of the excitation voltage from the first voltage to the second voltage at a first rate, and decreasing the pulse frequency of the excitation voltage from the first pulse frequency to the second pulse frequency at a second rate; during the second transition period, decreasing the voltage value of the excitation voltage from the second voltage to the third voltage at a third rate, and decreasing the pulse frequency of the excitation voltage from the second pulse frequency to the third pulse frequency at a fourth rate; wherein the first doping period, the first transition period, the second doping period, and the second transition period are consecutive periods.

[0014] In some embodiments, the manufacturing method further comprises: during the first doping period and the second doping period, introducing a cooling gas into the second chamber to cool the crystal bar.

[0015] According to some embodiments of the present disclosure, a further aspect of the embodiments of the present disclosure further provides a silicon wafer, which is cut from a crystal bar obtained by using the single crystal furnace according to the above embodiments, or is cut from a crystal bar obtained by using the manufacturing method of the crystal bar according to the above embodiments; wherein the axial resistivity deviation of the silicon wafer is 10% to 15%, and the radial resistivity deviation of the silicon wafer is 8% to 14%.

[0016] The technical solutions provided by the embodiments of the present disclosure have at least the following advantages:

[0017] According to the embodiments of the present disclosure, after the crystal pulling in the main furnace chamber is completed, the crystal bar is transferred to the auxiliary furnace chamber for plasma doping, so that the doping process is completely separated from the crystal growth stage, and the axial concentration gradient problem caused by the different segregation coefficients of the dopant in the melt and the crystal is avoided. At the same time, the large-area uniform doping capability of the plasma significantly improves the consistency of the resistivity of the crystal bar. The prepared crystal bar has excellent electrical uniformity, which can effectively improve the conversion efficiency and product yield of the solar cell. BRIEF DESCRIPTION OF DRAWINGS

[0018] One or more embodiments are illustrated by way of example in the drawings that are for illustrative purposes only, and not for the purposes of limiting the embodiments, unless otherwise specifically stated herein, the drawings in the accompanying drawings are not to scale; in order to more clearly illustrate the technical solutions in the embodiments of the present disclosure or in the prior art, a brief introduction will be given to the drawings needed in the embodiments. Obviously, the drawings described below are only some embodiments of the present disclosure, and those skilled in the art can obtain other drawings according to these drawings without creative labor.

[0019] Fig. 1 A partial cross-sectional structure schematic diagram of the single crystal furnace provided by the embodiments of the present disclosure;

[0020] Fig. 2 A connection diagram of a controller in a single crystal furnace provided by an embodiment of the present disclosure is shown in FIG. 1.

[0021] Fig. 3 A process flow chart corresponding to the method for manufacturing a crystal bar provided by an embodiment of the present disclosure is shown in FIG. 2.

[0022] Legend of reference signs:

[0023] A crystal bar 10, a secondary furnace chamber 11, a plasma doping device 12, a controller 13, a second chamber 111, a temperature detector 14, a cooling device 15, a plasma generator 121, an excitation source 122, and a vacuum system 16. DETAILED DESCRIPTION

[0024] Traditional doping processes are usually performed during the growth of a crystal bar, which is affected by the segregation effect of dopants. Specifically, the segregation coefficients of dopants (such as boron, phosphorus, etc.) in the crystal and the melt are different, resulting in uneven concentration distribution of the dopants during the growth of the crystal bar, and further resulting in difficulty in meeting the standard of the resistance uniformity of the prepared crystal bar, which affects the quality of the crystal bar.

[0025] For example, referring to Table 1, Table 1 shows the resistivity distribution of a current N-type phosphorus-doped crystal bar. Due to the low segregation coefficient of phosphorus, the doping concentration at the tail of the crystal bar is significantly higher than that at the head, resulting in a significant gradient change in the resistivity of the crystal bar from the head to the tail. This phenomenon not only affects the axial resistance uniformity of the crystal bar, but also may cause inconsistency in the radial resistivity, ultimately resulting in difficulty in meeting the standard requirements of the overall electrical performance of the crystal bar.

[0026] Table 1

[0027]

[0028]

[0029] At least to solve or improve the above technical problems, the present disclosure provides a method for manufacturing a crystal bar, a single crystal furnace, and a silicon wafer. By transferring the crystal bar to a secondary furnace chamber for plasma doping after the crystal bar is drawn, the doping process is completely separated from the crystal growth stage, avoiding the axial concentration gradient problem caused by the different segregation coefficients of dopants in the melt and the crystal, which is at least beneficial to improve the uniformity of the resistivity of the crystal bar.

[0030] In the description of the embodiments of the disclosure, the technical terms "first", "second", and the like are only used to distinguish different objects, and cannot be understood as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features. In the description of the embodiments of the disclosure, the meaning of "multiple" is more than two, unless otherwise explicitly and specifically limited. Similarly, "multiple groups" means more than two groups (including two groups), and "multiple pieces" means more than two pieces (including two pieces).

[0031] Reference herein to "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment of the disclosure. The appearance of the phrase in various places in the specification does not necessarily all refer to the same embodiment, nor is it necessarily independent or alternative embodiments to each other. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0032] In the description of the embodiments of the disclosure, the term "and / or" is only a description of the association relationship of the associated objects, which means that there can be three relationships, for example, A and / or B, which can mean: A exists, A and B exist, and B exists. In addition, the character " / " in this paper generally means that the front and rear associated objects are a "or" relationship.

[0033] In the description of the embodiments of the disclosure, the technical terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the embodiments of the disclosure and simplifying the description, and therefore cannot be understood as indicating or implying that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the embodiments of the disclosure. For example, if the device or element in the drawing is inverted, the element described as "below" or "under" or "under" or "bottom" of the other element or feature will be oriented "above" or "top" of the other element or feature. Therefore, the term "below" can cover both upward and downward orientations depending on the context in which the term is used, which will be apparent to those skilled in the art. The material can be oriented in other ways (e.g., rotated 90 degrees, inverted, flipped), and the spatial relative descriptions used herein can be interpreted accordingly.

[0034] In the description of the embodiments of the present disclosure, unless specifically defined and limited otherwise, the terms "mount", "connected", "connection", "fixed", and similar terms are to be construed as broadest possible terms, for example, can be fixed connection, can be detachable connection, or integral; can be mechanical connection, can be electrical connection; can be direct connection, can be indirect connection through intermediate medium, or can be internal connection of two elements or interaction relationship between two elements. For those skilled in the art, the specific meanings of the above terms in the embodiments of the present disclosure can be understood according to the specific circumstances.

[0035] In the corresponding drawings of the embodiments of the present disclosure, the thickness and area of the layers are exaggerated for better understanding and ease of description. In addition, when it is described that one component is "formed substantially" on another component, it means that the component is not formed on the entire surface (or front surface) of the other component, nor is it formed on a part of the edge of the entire surface.

[0036] In the description of the embodiments of the present disclosure, when a certain component "includes" another component, unless otherwise stated, other components are not excluded, and other components can also be further included. The first component is formed or disposed above or on the first component, or the second component is formed or disposed on the surface of the first component, or the second component is formed or disposed on the side of the first component. It can include an embodiment in which the first component and the second component are in direct contact, and can also include an embodiment in which additional components can be included between the first component and the second component, so that the first component and the second component can not be in direct contact. For the sake of simplicity and clarity, various components can be arbitrarily drawn in different proportions. In the drawings, some layers / components can be omitted for simplicity. Unless otherwise specified, the second component formed or disposed on the surface of the first component means that the first component is in direct contact with the second component. Among them, the "component" mentioned above can refer to layers, films, regions, parts, structures, etc.

[0037] The terms used in the description of various embodiments described herein are only used to describe specific embodiments, and are not intended to be limiting. As used in the description of various embodiments and the appended claims, "the component" is also intended to include the plural form, unless the context clearly indicates otherwise. Among them, the components include layers, films, regions, or plates, etc.

[0038] The embodiments of the present disclosure will be described in detail below with reference to the accompanying drawings. However, those skilled in the art can understand that in the embodiments of the present disclosure, many technical details are proposed in order to enable the reader to better understand the present disclosure. However, the technical solutions claimed by the present disclosure can be implemented even without these technical details and various changes and modifications based on the following embodiments.

[0039] Reference Figs. 1-2The single crystal furnace comprises a main furnace chamber (not shown in the figure), a secondary furnace chamber 11, a plasma doping device 12, and a controller 13. The main furnace chamber has a first chamber (not shown in the figure); the secondary furnace chamber 11 has a second chamber 111, which is in communication with the first chamber and is used to accommodate the crystal bar 10 for which the crystal pulling process is completed in the main furnace chamber; the plasma doping device 12 is arranged on the secondary furnace chamber 11 and is configured to convert a dopant into plasma and introduce the plasma into the second chamber 111 so as to dope the crystal bar 10 with the plasma; and the controller 13 is connected with the plasma doping device 12 and is configured to control the working state of the plasma doping device 12.

[0040] The single crystal furnace 1 is used to form a crystal bar and complete the doping process of the crystal bar. Specifically, the crystal bar is formed in the main furnace chamber, that is, raw materials are put into a boiler in the main furnace chamber, and then the crystal bar is formed through processes such as seeding, shoulder setting, shoulder turning, constant diameter, and tailing. After that, the doping process of the crystal bar is completed in the secondary furnace chamber 11.

[0041] The second chamber 111 is in communication with the first chamber through a controllable isolation valve or passage. After the crystal bar is completed, it can be smoothly moved from the first chamber into the second chamber 111 through a pulling mechanism or a transfer device. The second chamber 111 is used to accommodate the crystal bar for which the crystal pulling process is completed but has not been doped, and provides a dedicated space for subsequent plasma doping. The second chamber 111 can independently control the atmosphere, pressure, and temperature to adapt to the requirements of the plasma doping process.

[0042] The plasma doping device 12 can be integrated into the gas inlet end or the sidewall of the second chamber 111, and is used to perform the plasma doping process under the regulation of the controller 13. The controller 13 can stepwise, independently, and accurately regulate the entire doping process. Specifically, the controller 13 can control the plasma generation process and the plasma injection / doping process respectively, for example, the controller 13 can independently control the plasma generation, the doping gas flow, the injection time, the chamber pressure, and the doping depth, and other key parameters, so as to realize high-precision control of the doping process.

[0043] The single crystal furnace provided by the embodiments of the present disclosure places the doping process after the crystal growth stage by arranging the secondary furnace chamber and the plasma doping device, thereby breaking away from the limitation of the dopant segregation effect, significantly improving the axial and radial uniformity of the resistivity of the crystal bar, and further improving the conversion efficiency and product yield of the solar cell. In addition, the working state of the plasma doping device is accurately regulated by the controller, so as to realize high-precision control of the doping process.

[0044] The embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings.

[0045] In some embodiments, the single crystal furnace further comprises a temperature detector 14 configured to acquire the temperature of the crystal bar; and a controller 13 configured to acquire the temperature and control the plasma doping device 12 to dope the crystal bar when the temperature reaches a preset temperature.

[0046] The temperature detector 14 can be arranged in the auxiliary furnace chamber to acquire the surface or overall temperature information of the crystal bar in real time or at a fixed time.

[0047] The preset temperature can be set according to the type of dopant, the thermal stability of the crystal bar material such as silicon, and the plasma doping process window, for example, can be set to a specific value such as 800°C, 600°C or room temperature, to ensure that the crystal bar is doped in a suitable thermal state, avoiding uncontrolled ion diffusion at high temperature or damage accumulation at low temperature.

[0048] The controller 13 determines whether the doping start condition is met based on the real-time temperature data fed back by the temperature detector 14, and outputs a control signal to start the plasma doping device 12 when the condition is met, to introduce the dopant plasma into the second chamber 111 to achieve controllable doping of the crystal bar.

[0049] Through the cooperation of the above structure and control logic, the embodiment realizes temperature-triggered automatic start and stop of the doping process. This design not only ensures that the doping process is carried out after the crystal bar is cooled to the target temperature, effectively avoiding uneven doping distribution or lattice damage caused by high temperature, but also improves the automation level and batch consistency of the process. Especially for applications that require precise shallow doping at low temperature (such as substrates for high-efficiency solar cells), this temperature control mechanism can significantly improve doping accuracy and uniformity of the electrical properties of the crystal bar, further improving the conversion efficiency and reliability of solar cells.

[0050] In some embodiments, the single crystal furnace further comprises a cooling device 15 configured to provide cooling gas into the second chamber 111 to reduce the temperature of the crystal bar; wherein the controller 13 controls the cooling device 15 to stop supplying cooling gas when the temperature decreases to a preset temperature.

[0051] In some embodiments, the cooling device 15 is connected to the second chamber 111 to supply cooling gas (such as inert gas such as nitrogen, argon, etc.) into the second chamber 111 containing the crystal bar to accelerate the cooling process of the crystal bar from high temperature to the preset temperature. The cooling device 15 is electrically connected to the controller 13, and the controller 13 controls the cooling device 15 to stop supplying cooling gas when it is detected that the temperature decreases to the preset temperature, thereby realizing closed-loop control of the cooling process.

[0052] Specifically, the cooling device includes a gas pipeline, a flow regulating valve, and a nozzle structure. The cooling gas enters the second chamber 111 after being accurately controlled, and removes the heat on the surface of the crystal bar through forced convection. The controller 13 dynamically adjusts the on-off and flow of the cooling gas based on the real-time temperature signal fed back by the temperature detector 14. When the temperature reaches the preset temperature, the cooling gas supply is immediately turned off to prevent overcooling or temperature fluctuations and ensure process stability.

[0053] Through the above design, the embodiment realizes precise and automatic control of the crystal bar cooling process. On the one hand, by actively introducing cooling gas, the waiting time of the crystal bar from the high-temperature crystal pulling state to the suitable temperature for doping is significantly shortened, and the overall operation efficiency of the equipment is improved. On the other hand, combined with real-time temperature feedback and closed-loop regulation of the controller 13, the temperature lag and unevenness caused by natural cooling are avoided, ensuring that each doping is carried out under consistent thermal conditions, improving the repeatability and controllability of the doping concentration and depth, and helping to further improve the consistency of the crystal bar resistivity and the photoelectric conversion efficiency of the solar cell.

[0054] In some embodiments, the plasma doping device 12 includes a plasma generator 121 located on the side of the second chamber 111 away from the first chamber, for receiving a dopant and plasmaizing the dopant to form a plasma; and an excitation source 122 for providing an excitation voltage to move the plasma to the surface of the crystal bar and dope into the crystal bar.

[0055] The plasma generator 121 is configured to receive an externally input dopant and ionize it into a high-activity plasma; and the excitation source 122 is electrically connected to the plasma generator 121 for applying a directional excitation voltage to drive the plasma to move towards the surface of the crystal bar and achieve doping.

[0056] Specifically, the dopant is introduced into the plasma generator 121 through a gas delivery system and ionized under the action of radio frequency (RF) or microwave energy to generate a high-activity plasma containing active doping atoms, free radicals, and electrons. Subsequently, the excitation source 122 applies a directional electric field to enable the charged active doping atoms to obtain sufficient kinetic energy, thereby driving the charged active doping atoms to migrate directionally towards the crystal bar, penetrate the surface of the crystal bar, and embed into the crystal lattice to complete the doping process.

[0057] The dopant is not limited to a single gas form and can include a gaseous or volatile precursor containing a doping element that can be vaporized and ionized. The doping elements include phosphorus (P), boron (B), arsenic (As), antimony (Sb), etc. commonly used in semiconductors, and their corresponding precursors include PH3 (phosphine), B2H6 (diborane), AsH3 (arsine), etc.

[0058] The plasma generator 121 is arranged on the side away from the first chamber, which can avoid the influence of the high temperature of the main furnace chamber on the stability of the plasma; in combination with the directional electric field provided by the excitation source 122, the transmission efficiency and distribution uniformity of the plasma are significantly improved.

[0059] In some embodiments, the controller 13 is further configured to control the excitation source 122 to excite the voltage value of the excitation voltage to be the first voltage and the excitation voltage to have the first pulse frequency in the first doping period, and control the excitation source 122 to excite the voltage value of the excitation voltage to be the second voltage and the excitation voltage to have the second pulse frequency in the second doping period, wherein the second doping period is a period after the first doping period, and the second voltage is less than the first voltage, and the second pulse frequency is less than the first pulse frequency.

[0060] Specifically, the first doping period corresponds to the initial doping stage, and the controller 13 controls the excitation source 122 to apply a higher first voltage and a higher first pulse frequency to generate a stronger electric field strength and ion acceleration capability, so as to promote the active doping atoms in the plasma to obtain sufficient energy to penetrate the surface layer of the crystal bar and be injected into the central region inside the crystal bar, realize the doping of the center of the crystal bar, and ensure that the entire crystal bar has sufficient doping concentration, thereby improving the overall carrier concentration. Subsequently, in the second doping period, the controller 13 switches to a lower second voltage and a lower second pulse frequency to reduce the ion injection energy, so that the doping process is mainly concentrated in the surface and near-surface region of the crystal bar, and the doping of the surface of the crystal bar is realized. Low-energy injection can form a thin and uniform doping layer on the surface of the crystal bar, which plays a passivation role, reduces the carrier recombination loss caused by the surface state, and improves the minority carrier lifetime; and the injection energy is low, which will not cause excessive damage to the surface of the crystal bar or introduce new defects, thereby maintaining good surface quality.

[0061] The duration of the first doping period may be, for example, 10 min; and the duration of the second doping period may be, for example, 10 min.

[0062] Through the above-mentioned phased voltage and frequency regulation strategy, the embodiment realizes spatially selective doping: the high-energy stage is used to realize deep doping of the central region of the crystal bar to ensure the uniformity of the bulk resistance; and the low-energy stage is used to realize mild doping of the surface of the crystal bar to optimize the surface electrical properties and reduce the introduction of defects. The embodiment not only overcomes the limitation of the traditional single-parameter doping that is difficult to balance depth and surface quality, but also significantly improves the flexibility and controllability of the doping process. The step-by-step doping strategy helps to build a more reasonable carrier distribution gradient, improve the minority carrier lifetime and open-circuit voltage, and thus improve the battery conversion efficiency and product consistency.

[0063] In some embodiments, the controller is further configured to control the excitation source to decrease the voltage value of the excitation source from the first voltage to the second voltage at a first rate and decrease the pulse frequency of the excitation source from the first pulse frequency to the second pulse frequency at a second rate during the first transition period; control the excitation source to decrease the voltage value of the excitation source from the second voltage to the third voltage at a third rate and decrease the pulse frequency of the excitation source from the second pulse frequency to the third pulse frequency at a fourth rate during the second transition period; wherein the first doping period, the first transition period, the second doping period and the second transition period are continuous periods.

[0064] Specifically, the above four periods constitute a continuous doping sequence, and there are two optional time relationships between the first transition period and the first doping period, and between the second transition period and the second doping period:

[0065] Case one: the transition period partially overlaps with the doping period.

[0066] At the same time when the first doping period starts, the excitation voltage and the pulse frequency start to decrease at the preset rate. That is, the first transition period completely coincides with the initial stage of the first doping period, and the energy parameters enter the smooth decay process at the initial stage of the high-energy injection. Similarly, the second transition period also overlaps with the second doping period from the starting time, and the excitation parameters gradually decrease to the third voltage and the third pulse frequency at the beginning of the second doping stage. In this doping mode, the energy starts to decrease gradually from the initial injection, which is suitable for application scenarios requiring continuous gradient doping profile, can effectively avoid the sudden change of carrier concentration, form a smooth doping distribution, and is beneficial to the construction of ideal built-in electric field structure.

[0067] Case two: the transition period is contained in the doping period.

[0068] In a constant high-energy stage after the start of the first doping period, the excitation voltage and the pulse frequency remain unchanged at the first voltage and the first pulse frequency; after a period of time, the controller 13 starts the first transition period, so that the excitation voltage and the pulse frequency start to decrease at the first rate and the second rate. That is, the first transition period is contained in the first doping period. Similarly, the second transition period is also started after a period of time after the start of the second doping period, that is, the second transition period is contained in the second doping period. In this doping mode, a constant high-energy injection is maintained first to ensure sufficient doping in the central region, and then the energy is gradually reduced into the transition stage, which is suitable for the preparation of P-type or N-type substrates with higher requirements for central doping depth.

[0069] The above two cases can be flexibly selected according to the type of crystal bar material (such as N-type silicon doped with at least one of phosphorus, arsenic, antimony or bismuth, or P-type silicon doped with at least one of boron, gallium or indium), the target doping depth, the type of doping element and the process window, which significantly improves the process adaptability and control flexibility.

[0070] The scheme provided by the embodiments of the present disclosure not only avoids the problems of lattice stress concentration, surface damage and uneven doping caused by traditional step voltage switching, but also realizes continuous and gradient doping distribution from the center to the surface of the crystal bar through fine adjustment in the time dimension. The scheme is particularly suitable for the preparation of crystal bars for high-efficiency solar cells, and helps to improve the minority carrier lifetime, reduce the series resistance, improve the open-circuit voltage and the fill factor, and finally significantly enhance the photoelectric conversion efficiency of the solar cell.

[0071] In some embodiments, the single crystal furnace further comprises a cooling device 15 configured to provide cooling gas into the second chamber 111 to reduce the temperature of the crystal bar; and the controller 13 is further configured to control the cooling device 15 to provide cooling gas into the second chamber 111 during the first doping period and the second doping period.

[0072] In some embodiments, the sub-chamber 11 comprises a cooling pipeline through which the cooling device 15 can provide cooling gas into the sub-chamber 11 to reduce the temperature of the crystal bar.

[0073] The cooling gas can be an inert gas such as argon or nitrogen.

[0074] The controller 13 keeps the cooling gas continuously flowing during the entire first doping period and the subsequent second doping period. The cooling gas can carry away the heat generated during the plasma doping process due to ion bombardment, electric field discharge, etc., to prevent the local temperature of the crystal bar from rising too high. The flow rate, temperature and flow mode of the cooling gas can be dynamically adjusted according to the size and material type of the crystal bar to ensure that the crystal bar is always within the preset temperature range during doping.

[0075] During high-energy plasma injection, the kinetic energy of ions is converted into heat energy, which can easily cause the temperature of the crystal bar to rise, possibly leading to uncontrolled diffusion of dopants, lattice damage or uneven doping. By continuously supplying cooling gas during the two doping periods, the temperature rise is effectively suppressed, the thermal field stability is maintained, and the axial and radial uniformity of the doping concentration is ensured. In addition, a stable temperature environment is also conducive to the stability of the plasma state. The present embodiment helps to improve the resistivity consistency of the crystal bar.

[0076] In some embodiments, the plasma doping device 12 further comprises a concentration detector (not shown in the figure) configured to detect the concentration of the plasma formed by the plasma generator; and the controller 13 is further configured to obtain the concentration and, in the case that the concentration is lower than a preset concentration, control the plasma generator 121 to continue to form plasma to increase the concentration until the concentration is the same as the preset concentration.

[0077] The concentration detector can adopt optical emission spectrometer (OES), mass spectrometer (MS) or Langmuir probe, etc. to measure the density of target doping element ions (such as P + , B + ) or characteristic active groups (such as PH3 + , B2H6 + ) in the plasma in a non-invasive or in-situ manner.

[0078] When the controller 13 receives the real-time concentration value from the concentration detector, it compares the real-time concentration value with the preset concentration value. If the real-time concentration value is lower than the preset concentration value, the controller drives the plasma generator 121 to continuously work to improve the ionization efficiency until the concentration reaches the standard. Once the concentration reaches the set range, the controller 13 controls the plasma generator 121 to stop working.

[0079] The scheme ensures that the concentration of active doping particles in the plasma is always at an ideal level through real-time detection and feedback adjustment, thereby ensuring the uniformity and repeatability of the ion implantation flux. Especially in the doping process of long crystal rods or large-diameter crystal rods, the closed-loop system can effectively suppress the axial doping gradient deviation caused by the decay or uneven distribution of the plasma, and significantly improve the consistency of the crystal rod resistivity.

[0080] In some embodiments, the single crystal furnace further comprises a vacuum system 16 connected with the controller 13 and the secondary furnace chamber 11. Under the control of the controller 13, the vacuum system 16 can adjust the vacuum degree in the secondary furnace chamber 11 to provide a vacuum environment for ion implantation.

[0081] The single crystal furnace provided by the embodiments of the present disclosure places the doping process after the crystal growth stage by setting the secondary furnace chamber and the plasma doping device, thereby breaking away from the limitation of the dopant segregation effect, significantly improving the axial and radial uniformity of the crystal rod resistivity, and further improving the conversion efficiency and product yield of the solar cell. Moreover, the controller accurately controls the working state of the plasma doping device, realizing high-precision control of the doping process. In addition, by setting the temperature detector and the cooling device, the temperature of the crystal rod can be monitored in real time, and cooling gas can be provided into the second chamber to reduce the temperature of the crystal rod to a preset temperature, which is conducive to effectively avoiding uneven doping distribution or lattice damage caused by high temperature, and improving the automation degree and batch consistency of the process. Furthermore, by setting the concentration detector to detect and feedback adjust the concentration of the plasma in the plasma generator in real time, the concentration of active doping particles in the plasma is ensured to be always at an ideal level, and the consistency of the crystal rod resistivity is significantly improved.

[0082] According to some embodiments of the present disclosure, another aspect of the embodiments of the present disclosure further provides a method for manufacturing a crystal bar using the single crystal furnace of any of the preceding embodiments. The method for manufacturing a crystal bar provided by the embodiments of the present disclosure will be described below. It should be noted that the same or corresponding parts as the preceding embodiments will not be described here again.

[0083] With reference to Fig. 3 The method for manufacturing a crystal bar provided by the embodiments of the present disclosure at least includes the following steps:

[0084] S1: pulling the crystal bar completing the crystal pulling process in the main furnace chamber into the second chamber.

[0085] S2: introducing plasma into the second chamber to dope the crystal bar with the plasma.

[0086] The second chamber is an independent processing chamber isolated from the main furnace chamber; after high-temperature crystal pulling, the crystal bar is transferred to the second chamber by the pulling mechanism and receives plasma doping treatment at a suitable temperature.

[0087] Specifically, in step S1, after the crystal bar completes single crystal growth in the main furnace chamber, it is slowly pulled into the second chamber from the high-temperature growth environment by the pulling device. The transfer process is carried out under the protection of an inert atmosphere (such as argon or nitrogen) to avoid oxidation or contamination of the crystal bar surface. After the crystal bar enters the second chamber, its temperature is cooled to a suitable doping range, and enters the doping stage.

[0088] In step S2, the dopant is introduced into the plasma generator of the second chamber, and ionized to form a plasma containing active doping ions under the action of radio frequency or microwave energy; the excitation source applies a directional electric field to drive the charged particles in the plasma to migrate to the surface of the crystal bar, and injects the crystal bar at a suitable energy to achieve doping. The controller can adjust the gas flow, plasma power, excitation voltage and doping time to control the doping concentration and depth.

[0089] Through the above method, the present embodiment realizes the spatial and temporal separation of crystal growth and doping process. Traditional crystal pulling and doping rely on the segregation effect of dopants in the melt, which easily leads to uneven axial resistivity (large head-tail difference). The present scheme independently performs plasma doping after crystal pulling, avoiding the problems of dopant volatilization, segregation and concentration gradient in high-temperature melt, significantly improving the uniformity and repeatability of doping. At the same time, plasma doping has the advantages of controllable energy, rapid response and suitability for multiple doping elements, which can flexibly adapt to the preparation needs of N-type or P-type crystal bars, and is helpful to obtain substrate materials with high consistency of resistivity and excellent surface quality, and to improve the conversion efficiency and yield of solar cells.

[0090] In some embodiments, before the plasma is introduced into the second chamber, the manufacturing method further comprises: obtaining the temperature of the crystal bar; in the case that the temperature is higher than a preset temperature, introducing cooling gas into the second chamber to cool the crystal bar; in the case that the temperature is reduced to the preset temperature, stopping the introduction of the cooling gas and performing the step of introducing the plasma.

[0091] Specifically, the temperature of the crystal bar surface or the axial multiple points is monitored in real time by the temperature detector arranged in the auxiliary furnace chamber, and the data is fed back to the controller. The preset temperature is a process threshold set according to the doping type, for example, for phosphorus doping, the preset temperature can be set to 500-600℃; for boron doping, it can be set to 550-650℃, to ensure that the crystal bar is in a thermodynamic window suitable for doping reaction. When the detected temperature is higher than the threshold, the controller starts the cooling device to introduce cooling gas (such as nitrogen, argon) into the second chamber to remove heat through forced convection, achieving rapid and uniform cooling. Once the temperature is reduced to the preset range, the controller closes the cooling gas supply.

[0092] Through the above design, the embodiment realizes the precise and automatic control of the cooling process of the crystal bar. On the one hand, by actively introducing cooling gas, the waiting time of the crystal bar from the high-temperature crystal pulling state to the suitable doping temperature is significantly shortened, and the overall operation efficiency of the equipment is improved; on the other hand, combined with the real-time temperature feedback and the closed-loop adjustment of the controller, the temperature hysteresis and non-uniformity caused by natural cooling are avoided, ensuring that each doping is carried out under consistent thermal conditions, improving the repeatability and controllability of the doping concentration and depth, and helping to further improve the consistency of the crystal bar resistivity and the photoelectric conversion efficiency of the solar cell.

[0093] In some embodiments, the introduction of the plasma into the second chamber to dope the crystal bar with the plasma comprises: in a first doping period, applying an excitation voltage to the plasma at a first voltage and a first pulse frequency to make the plasma move to the surface of the crystal bar and dope into the crystal bar; in a second doping period, applying an excitation voltage to the plasma at a second voltage and a second pulse frequency to make the plasma move to the surface of the crystal bar and dope into the crystal bar; wherein the second doping period is a period after the first doping period, and the second voltage is less than the first voltage, and the second pulse frequency is less than the first pulse frequency.

[0094] Specifically, the first doping period corresponds to an initial doping stage, the controller controls the excitation source to apply a higher first voltage and a higher first pulse frequency, so as to generate a stronger electric field intensity and ion acceleration capability, so as to promote the active doping atoms in the plasma to obtain sufficient energy to penetrate the surface layer of the crystal bar and be injected into the central region inside the crystal bar, so as to realize the doping of the center of the crystal bar, and ensure that the entire crystal bar has sufficient doping concentration in the volume, so as to improve the overall carrier concentration. Subsequently, the excitation source is switched to a lower second voltage and a lower second pulse frequency, so as to reduce the ion implantation energy, so that the doping process is mainly concentrated in the surface and near-surface region of the crystal bar, so as to realize the doping of the surface of the crystal bar. Low-energy implantation can form a thin and uniform doping layer on the surface of the crystal bar, which plays a passivation role, reduces the carrier recombination loss caused by the surface state, and improves the minority carrier lifetime; and the implantation energy is low, which will not cause excessive damage to the surface of the crystal bar or introduce new defects, so as to maintain good surface quality.

[0095] The specific values of the first voltage and the second voltage, the pulse frequency parameters, and the durations of the first doping period and the second doping period can be set according to a preset program, a crystal bar type (such as N-type or P-type), a target resistivity, and the like, so as to realize fully automated multi-stage doping control.

[0096] Through the above-mentioned phased voltage and frequency regulation strategy, the embodiment realizes spatially selective doping: the high-energy stage is used to realize deep doping of the central region of the crystal bar, so as to ensure the bulk resistivity uniformity; and the low-energy stage is used to realize mild doping of the surface of the crystal bar, so as to optimize the surface electrical properties and reduce defect introduction. This method not only overcomes the limitation of the traditional single-parameter doping that is difficult to balance depth and surface quality, but also significantly improves the flexibility and controllability of the doping process. The step-by-step doping strategy helps to build a more reasonable carrier distribution gradient, improve the minority carrier lifetime and open-circuit voltage, and thus improve the battery conversion efficiency and product consistency.

[0097] In some embodiments, the manufacturing method further includes: in the first transition period, reducing the voltage value of the excitation voltage from the first voltage to the second voltage at a first rate, and reducing the pulse frequency of the excitation voltage from the first pulse frequency to the second pulse frequency at a second rate; in the second transition period, reducing the voltage value of the excitation voltage from the second voltage to the third voltage at a third rate, and reducing the pulse frequency of the excitation voltage from the second pulse frequency to the third pulse frequency at a fourth rate; wherein the first doping period, the first transition period, the second doping period, and the second transition period are consecutive periods.

[0098] Specifically, the above-mentioned four periods constitute a continuous doping time sequence, and the first transition period and the first doping period, and the second transition period and the second doping period have two kinds of optional time relationships:

[0099] Case 1: The transition period partially overlaps with the doping period.

[0100] At the same time when the first doping period starts, the excitation voltage and the pulse frequency start to decrease at a preset rate. That is, the first transition period completely overlaps with the initial stage of the first doping period, and the energy parameters enter the smooth decay process at the initial stage of high-energy injection. Similarly, the second transition period also overlaps with the initial stage of the second doping period, and the excitation parameters gradually decrease to the third voltage and the third pulse frequency at the beginning of the second doping stage. In this doping mode, the energy starts to decrease gradually from the initial injection, which is suitable for application scenarios that require continuous gradient doping profiles, can effectively avoid the sudden change of carrier concentration, form a smooth doping distribution, and is beneficial to the construction of an ideal built-in electric field structure.

[0101] Case 2: The transition period is contained in the doping period.

[0102] In a constant high-energy stage after the start of the first doping period, the excitation voltage and the pulse frequency remain unchanged at the first voltage and the first pulse frequency; after a period of time, the controller 13 starts the first transition period, so that the excitation voltage and the pulse frequency start to decrease at the first rate and the second rate. That is, the first transition period is contained in the first doping period. Similarly, the second transition period is also started after a period of time after the start of the second doping period, that is, the second transition period is contained in the second doping period. In this doping mode, a constant high-energy injection is maintained for a period of time to ensure sufficient doping in the central region, and then the energy is gradually reduced into the transition stage, which is suitable for the preparation of P-type or N-type substrates with higher central doping depth requirements.

[0103] The above two cases can be flexibly selected according to the type of crystal bar material (such as N-type or P-type silicon), the target doping depth, the type of doping element (such as boron, phosphorus), and the process window, which significantly improves the process adaptability and control flexibility.

[0104] The scheme provided by the embodiments of the present disclosure not only avoids the problems of lattice stress concentration, surface damage and uneven doping caused by the traditional step voltage switching, but also realizes a continuous and gradient doping distribution from the center of the crystal bar to the surface through fine adjustment in the time dimension. It is especially suitable for the preparation of crystal bars for high-efficiency solar cells, which helps to improve the minority carrier lifetime, reduce the series resistance, increase the open-circuit voltage and the fill factor, and ultimately significantly enhance the photoelectric conversion efficiency of the solar cell.

[0105] In some embodiments, the manufacturing method further comprises: introducing cooling gas into the second chamber to cool the crystal bar during the first doping period and the second doping period.

[0106] In some embodiments, the auxiliary furnace chamber comprises a cooling pipeline and a cooling device, and the cooling device can reduce the temperature of the crystal bar by providing cooling gas into the auxiliary furnace chamber through the cooling pipeline.

[0107] The cooling gas can be an inert gas such as argon or nitrogen.

[0108] The cooling gas is continuously supplied during the entire first doping period and the subsequent second doping period. The cooling gas can take away the heat generated by ion bombardment, electric field discharge and the like during the plasma doping process, preventing the local temperature of the crystal rod from rising too high. The flow rate, temperature and supply mode of the cooling gas can be dynamically adjusted according to the size and material type of the crystal rod to ensure that the crystal rod is always within the preset temperature range during doping.

[0109] During high-energy plasma injection, the kinetic energy of ions is converted into heat energy, which can easily cause the temperature of the crystal rod to rise, possibly leading to uncontrolled diffusion of dopants, lattice damage or uneven doping. By continuously supplying cooling gas during the two doping periods, the temperature rise is effectively suppressed, the thermal field stability is maintained, and the axial and radial uniformity of the doping concentration is ensured. In addition, a stable temperature environment is also conducive to the stability of the plasma state. The present embodiment helps to improve the resistivity consistency of the crystal rod.

[0110] In some embodiments, before the plasma is supplied into the second chamber, the manufacturing method further comprises: detecting the concentration of the plasma formed by the plasma generator; in the case that the concentration is lower than a preset concentration, controlling the plasma generator to continue forming plasma to increase the concentration until the concentration is the same as the preset concentration; wherein the preset concentration is determined according to the diameter of the crystal rod and the target resistivity.

[0111] Specifically, after obtaining the real-time concentration value in the plasma generator, it is compared with the preset concentration: if the real-time concentration is lower than the preset value, the controller drives the plasma generator to continue working to improve the ionization efficiency until the concentration meets the standard; once the concentration reaches the set range, the controller controls the plasma generator to stop working.

[0112] The concentration of the plasma is a key factor affecting the doping effect. The higher the concentration of the plasma, the lower the resistance of the crystal rod; the lower the concentration of the plasma, the higher the resistance of the crystal rod. The diameter of the crystal rod and the target resistivity are key factors affecting the setting of the preset concentration during the plasma doping process. Among them, the larger the diameter of the crystal rod, the larger its surface area, and more plasma is needed to cover the surface for uniform doping. If the concentration of the plasma is too low, it is easy to lead to insufficient doping, so the preset concentration needs to be increased to ensure the uniformity of doping. At the same time, the lower the target resistivity (i.e. the heavier the doping degree), the higher the carrier concentration is required, which corresponds to the need to introduce more plasma to meet the process requirements of doping depth and dose, and to ensure the consistency and controllability of the electrical properties of the crystal rod.

[0113] The scheme ensures that the concentration of active doping particles in the plasma is always at an ideal level through real-time detection and feedback adjustment, thereby ensuring the uniformity of the plasma injection flux. Especially in the doping process of long crystal rods or large-diameter crystal rods, the axial doping gradient deviation caused by plasma decay or uneven distribution can be effectively inhibited, and the consistency of the crystal rod resistivity is significantly improved.

[0114] In some embodiments, the weight of the dopant required for doping the crystal rod can be calculated according to the target resistivity and the weight of the crystal rod, and the formula is as follows:

[0115]

[0116] Wherein, C1 is the doping concentration corresponding to the target resistivity of the crystal, C2 is the impurity concentration in the master alloy, K is the segregation coefficient of the dopant, a is the weight of the crystal rod, and M is the weight of the master alloy.

[0117] Wherein, the master alloy refers to a binary alloy composed of the dopant and Si (or other semiconductor materials). Since the amount of doping elements is small, calculation errors may occur. The error can be reduced by forming a compound containing the doping element to amplify the equivalent, and then reducing the error. The compound can be a master alloy.

[0118] In some embodiments, the plasma flow P required for the first doping period and the second doping period can be calculated according to the length of the crystal rod and the diameter of the crystal rod, and the formula is as follows:

[0119]

[0120] Wherein, Cm is the plasma concentration, N A is the Avogadro constant, r is the radius of the crystal rod, h is the length of the crystal rod, and t is the stage time.

[0121] In some embodiments, the first voltage is 50kv-80kv, for example, it can be 50kv, 51kv, 52kv, 53kv, 54kv, 55kv, 56kv, 57kv, 58kv, 59kv, 60kv, 61kv, 62kv, 63kv, 64kv, 65kv, 66kv, 67kv, 68kv, 69kv, 70kv, 71kv, 72kv, 73kv, 74kv, 75kv, 76kv, 77kv, 78kv, 79kv or 80kv, etc.; the first pulse frequency is 400hz-500hz, for example, it can be 400hz, 410hz, 420hz, 430hz, 440hz, 450hz, 460hz, 470hz, 480hz, 490hz or 500hz, etc.

[0122] It can be understood that the excitation voltage value is different, the energy given to the doped plasma is also different, which leads to different doping effects. If the excitation voltage is too low (for example, the first voltage is less than 50kv), the ion energy is insufficient, it is difficult to penetrate the surface oxide layer or achieve deep doping, which will cause uneven doping, uneven distribution of crystal bar resistance and other problems; if the excitation voltage is too high (for example, the first voltage is greater than 80kv), the ion kinetic energy is too large, which is easy to cause local over-injection, especially at the edge of the crystal bar or the place where the curvature changes, resulting in uneven axial or radial doping, and may cause arc discharge or local breakdown, destroy the uniformity of the plasma. By setting the first voltage in the range of 50kv-80kv, it is ensured that the plasma can penetrate the surface layer of the crystal bar, be injected into the central region or deep region of the crystal bar, and realize deep doping, thereby significantly improving the overall carrier concentration.

[0123] The pulse frequency is the pulse modulation frequency of the excitation voltage, which controls the periodic application rhythm of the electric field to maintain the stability of the plasma and adjust the plasma flux. The first pulse frequency is set in the medium-high frequency range of 400hz-500hz, which can maintain the stable and continuous ionization state of the plasma, and ensure the continuous supply of high-density active particles. The combination of this voltage and frequency works together to form a high-flux, high-energy doping environment, which is suitable for process scenarios with high requirements for doping depth and overall carrier concentration.

[0124] In some embodiments, the second voltage is 20kv-50kv, for example, it can be 20kv, 21kv, 22kv, 23kv, 24kv, 25kv, 26kv, 27kv, 28kv, 29kv, 30kv, 31kv, 32kv, 33kv, 34kv, 35kv, 36kv, 37kv, 38kv, 39kv, 40kv, 41kv, 42kv, 43kv, 44kv, 45kv, 46kv, 47kv, 48kv, 49kv or 50kv, etc.; the second pulse frequency is 200hz-400hz, for example, it can be 200hz, 210hz, 220hz, 230hz, 240hz, 250hz, 260hz, 270hz, 280hz, 290hz, 300hz, 310hz, 320hz, 330hz, 340hz, 350hz, 360hz, 370hz, 380hz, 390hz or 400hz, etc.

[0125] Specifically, the second voltage range is significantly lower than the first voltage, so that the kinetic energy of the ions is reduced, the implantation depth is shallower, and the main effect is on the surface layer to the subsurface layer of the crystal bar; the second pulse frequency range is in the medium frequency band, which can maintain the basic ionization state of the plasma and allow a certain cooling interval between each pulse cycle, which is conducive to heat release and reduces lattice damage or amorphization caused by continuous high-energy injection. This parameter combination is suitable for light doping or surface modification, which can optimize the surface electrical conductivity and suppress defect generation. By using this medium and low energy parameter range, controlled doping and damage suppression of the surface region of the crystal bar are realized, avoiding over-doping or structural damage on the surface, and improving the surface passivation quality; at the same time, a certain doping flux is still maintained to ensure that the surface carrier concentration meets the subsequent electrode contact requirements.

[0126] In some embodiments, the flow rate of the cooling gas into the second chamber during the first doping period and the second doping period is 75 lpm-85 lpm, for example, it can be 75 lpm, 76 lpm, 77 lpm, 78 lpm, 79 lpm, 80 lpm, 81 lpm, 82 lpm, 83 lpm, 84 lpm or 85 lpm, etc.

[0127] Setting the cooling gas flow rate to 75 lpm-85 lpm can ensure sufficient cooling capacity while avoiding excessive gas flow causing pressure fluctuations or plasma disturbance in the chamber.

[0128] The method for manufacturing a crystal bar provided by the embodiments of the present disclosure realizes the spatial and temporal separation of the crystal growth and doping processes. The present scheme independently performs plasma doping after crystal pulling, avoiding problems such as dopant volatilization, segregation and concentration gradient in the high-temperature melt, and significantly improving the uniformity and repeatability of doping. At the same time, plasma doping has the advantages of controllable energy, rapid response, and suitability for multiple doping elements, and can be flexibly adapted to the preparation requirements of N-type or P-type crystal bars, which helps to obtain substrate materials with high consistency in resistivity and excellent surface quality, and improves the conversion efficiency and yield of solar cells. In addition, by using the stage voltage and frequency regulation strategy, the present embodiment realizes spatially selective doping: high-energy stage is used to realize deep doping in the central region of the crystal bar to ensure uniform bulk resistance; low-energy stage is used to realize mild doping on the surface of the crystal bar to optimize the surface electrical properties and reduce defect introduction. Further, in combination with real-time temperature regulation, the crystal bar is ensured to be always within the preset temperature range during doping; and by adjusting the plasma concentration, the concentration of active doping particles in the plasma is always kept at an ideal level, thereby ensuring the uniformity of the plasma implantation flux.

[0129] According to some embodiments of the present disclosure, the present disclosure further provides a crystal bar in yet another aspect, which is formed by using the single crystal furnace of any of the above embodiments, or formed by using the method for manufacturing the crystal bar of any of the above embodiments. The crystal bar provided by the embodiments of the present disclosure will be described below. It should be noted that the same or corresponding parts as the above embodiments will not be described herein.

[0130] The crystal bar can be a single crystal silicon bar.

[0131] In the process of manufacturing semiconductor devices, the four-probe method is a commonly used method for measuring the resistivity of materials. In some embodiments of the present disclosure, the four-probe method can be used to measure the axial resistivity of the crystal bar.

[0132] Specifically, under room temperature conditions, four probes arranged at equal intervals are placed along the length direction of the crystal bar (i.e. the crystal growth direction) and in contact with the surface of the crystal bar. Among them, the outer two probes are connected to a constant current source for injecting a constant current into the crystal bar: the current flows in from one outer probe and flows out from the other outer probe after being conducted through the crystal bar; the inner two probes are connected to a voltmeter for measuring the voltage drop between the two points. According to the measured voltage value and the injected current value, combined with the probe spacing and the cross-sectional area of the crystal bar, the axial resistivity of the crystal bar at that position is calculated. Exemplarily, the calculation formula of the axial resistivity P1 of the crystal bar can be:

[0133]

[0134] Wherein, V is the measured voltage value, I is the injected current value, A is the cross-sectional area of the crystal bar, and L is the spacing between the outer two probes, i.e. the length through which the current flows.

[0135] Similarly, the radial resistivity of the crystal bar can be measured by the four-probe method. Illustratively, a silicon wafer cut from the crystal bar is provided as a test sample; a polar coordinate system is established on the surface of the silicon wafer with the geometric center as the origin, and 9 sampling points are arranged at three typical radial positions to comprehensively characterize the resistivity distribution of the cross section of the crystal bar. The specific layout is as follows: 1 sampling point is arranged in the central region (r = 0 mm, r represents the distance from the sampling point to the geometric center of the silicon wafer); 4 sampling points are uniformly distributed along two mutually perpendicular main diameters in the middle region (r = R / 2, R is the effective radius of the silicon wafer), and the azimuth angles are 0°, 90°, 180° and 270°, respectively; 4 sampling points are symmetrically arranged along the above-mentioned directions in the edge vicinity region (r = R-20 mm), and the azimuth angles are 45°, 135°, 225° and 315°, respectively, which is about 20 mm away from the edge, which can effectively avoid the interference of the edge effect and ensure that the measurement results reflect the electrical properties of the crystal bar; the resistivity of the 9 sampling points is measured by using the four-probe detector, and is recorded as p1, p2, p3, p4, p5, p6, p7, p8 and p9; the average value of the resistivity of the 9 sampling points is calculated to obtain the radial resistivity of the crystal bar.

[0136] Illustratively, the calculation formula of the radial resistivity P2 of the crystal bar is as follows:

[0137]

[0138] Illustratively, referring to Table 2, Table 2 shows the resistivity data of the crystal bar provided by the embodiments of the present disclosure. The results show that the resistivity uniformity of the crystal bar is significantly improved. Among them, the axial resistivity deviation of the crystal bar is controlled within 10% to 15%; the radial resistivity deviation is controlled within 8% to 14%, which meets the requirements of high-efficiency semiconductor devices on material electrical consistency.

[0139] Table 2

[0140]

[0141] According to some embodiments of the present disclosure, the silicon wafer is cut from the crystal bar obtained by using any of the above-mentioned embodiments of the single crystal furnace, or is cut from the crystal bar obtained by using the manufacturing method of the crystal bar according to any of the above-mentioned embodiments. The silicon wafer provided by the embodiments of the present disclosure will be described below. It should be noted that the same or corresponding parts as the above-mentioned embodiments will not be described here.

[0142] It can be understood that the resistivity of the silicon wafer is consistent with the resistivity of the crystal bar, i.e., the axial resistivity deviation of the silicon wafer is 10% to 15%, and the radial resistivity deviation of the silicon wafer is 8% to 14%.

[0143] The silicon wafer can be used to manufacture solar cells.

[0144] The silicon wafer provided by the embodiments of the present disclosure has an actual photoelectric conversion efficiency improved by 0.03% compared with the prior art.

[0145] According to some embodiments of the present disclosure, the embodiments of the present disclosure still provide a solar cell prepared from the silicon wafer of the above-mentioned embodiment. The solar cell provided by the embodiments of the present disclosure will be described below. It should be noted that the same or corresponding parts as the foregoing embodiments will not be described herein.

[0146] The solar cell can be a TOPCON cell (Tunnel Oxide Passivated Contact), a BC cell (Back Contact), an HJT cell (Heterojunction Technology), or the like.

[0147] Those skilled in the art can understand that the above-mentioned embodiments are specific embodiments for implementing the present disclosure, and in actual application, various changes can be made in form and details without departing from the spirit and scope of the present disclosure. Any person skilled in the art can make various modifications and changes without departing from the spirit and scope of the present disclosure, and therefore the protection scope of the present disclosure should be limited by the scope defined in the claims.

Claims

1. A single crystal furnace characterized by comprising: The single crystal furnace comprises: a main furnace chamber having a first chamber; a sub-furnace chamber having a second chamber, the second chamber being in communication with the first chamber, the second chamber being configured to accommodate a crystal rod on which a crystal pulling process is performed in the main furnace chamber; a plasma doping device disposed on the sub-furnace chamber, the plasma doping device being configured to convert a dopant into plasma and to introduce the plasma into the second chamber so as to dope the crystal rod with the plasma; a controller connected to the plasma doping device, the controller being configured to control an operating state of the plasma doping device.

2. The single crystal furnace of claim 1, wherein The single crystal furnace further comprises: a temperature detector configured to obtain a temperature of the crystal rod; the controller obtains the temperature and controls the plasma doping device to operate when the temperature reaches a preset temperature so as to dope the crystal rod with the plasma.

3. The single crystal furnace of claim 2, wherein The single crystal furnace further comprises: a cooling device configured to supply cooling gas into the second chamber so as to reduce the temperature of the crystal rod; wherein the controller controls the cooling device to stop supplying the cooling gas when the temperature is reduced to the preset temperature.

4. The single crystal furnace of claim 1, wherein The plasma doping device comprises: a plasma generator located on a side of the second chamber away from the first chamber, the plasma generator being configured to receive the dopant and to plasmaize the dopant so as to form the plasma; an excitation source configured to provide an excitation voltage so as to move the plasma to a surface of the crystal rod and to dope the crystal rod with the plasma.

5. A method of manufacturing a crystal bar, applied to the single crystal furnace according to any one of claims 1 to 4, characterized by, The method comprises: pulling a crystal rod on which a crystal pulling process is performed in the main furnace chamber into the second chamber; introducing plasma into the second chamber so as to dope the crystal rod with the plasma.

6. The production method according to claim 5, wherein Before the step of introducing the plasma into the second chamber, the method further comprises: obtaining a temperature of the crystal rod; supplying cooling gas into the second chamber to cool the crystal rod when the temperature is higher than a preset temperature; stopping the supply of the cooling gas and performing the step of introducing the plasma when the temperature is reduced to the preset temperature.

7. The production method according to claim 5, wherein The step of introducing the plasma into the second chamber so as to dope the crystal rod with the plasma comprises: applying an excitation voltage to the plasma at a first voltage and a first pulse frequency during a first doping period so as to move the plasma to the surface of the crystal rod and to dope the crystal rod with the plasma; applying an excitation voltage to the plasma at a second voltage and a second pulse frequency during a second doping period so as to move the plasma to the surface of the crystal rod and to dope the crystal rod with the plasma; wherein the second doping period is a period after the first doping period, and the second voltage is less than the first voltage, and the second pulse frequency is less than the first pulse frequency.

8. The manufacturing method according to claim 7, wherein The method further comprises: during the first transition period, decreasing the voltage value of the excitation voltage from the first voltage to the second voltage at a first rate, and decreasing the pulse frequency of the excitation voltage from the first pulse frequency to the second pulse frequency at a second rate; In the second transition period, the voltage value of the excitation voltage is decreased from the second voltage to the third voltage at a third rate, and the pulse frequency of the excitation voltage is decreased from the second pulse frequency to the third pulse frequency at a fourth rate. The first doping period, the first transition period, the second doping period and the second transition period are continuous periods.

9. The production method according to claim 7, wherein The manufacturing method further comprises: During the first doping period and the second doping period, cooling gas is introduced into the second chamber to cool the crystal bar.

10. A silicon wafer, characterized by, The silicon wafer is cut from the crystal bar obtained by the single crystal furnace of any one of claims 1 to 4, or cut from the crystal bar obtained by the manufacturing method of any one of claims 5 to 9; wherein the axial resistivity deviation of the silicon wafer is 10% to 15%, and the radial resistivity deviation of the silicon wafer is 8% to 14%.

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