A Czochralski silicon ingot and a method of manufacturing the same

Abstract

The present application relates to a kind of straight pull single crystal silicon immersion type doping device and doping method.The immersion type doping device is set with a straight pull single crystal furnace, comprising: cup, top has a first cavity with upper end open to hold dopant, and its sidewall is provided with several side spoilers and is opened with several first through holes close to cup bottom, and its bottom wall is provided with several bottom fairing and is opened with several second through holes;Cover, bottom has a second cavity with lower end open and at least partially set on the upper end of the cup to cooperate with the first cavity composition material chamber, and its upper portion has at least one connecting hole for loading in the straight pull single crystal furnace;Wherein, the cup and the cover can be detachably connected to form the doping device.The present application realizes the stable, controllable release of dopant, promotes the uniform mixing of liquefied dopant in silicon melt, avoids furnace contamination, and greatly improves the preparation quality of heavily doped single crystal silicon.

Description

Technical Field

[0001] This invention relates to the field of semiconductor material preparation technology, specifically to a Czochralski single-crystal silicon immersion doping device and doping method. Background Technology

[0002] Heavily doped Czochralski-grown single-crystal silicon is an indispensable basic material for manufacturing power devices, and its electrical properties, such as resistivity, need to be controlled through precise doping processes. During the growth of single-crystal silicon, impurity elements such as boron, phosphorus, arsenic, or antimony need to be introduced into the silicon melt to achieve the doping target.

[0003] Current doping technologies are mainly divided into two categories: solid-phase doping and gas-phase doping. Solid-phase doping involves pre-mixing the dopant into the silicon material and then melting it. The operation process is simple, but secondary doping cannot be carried out. Gas-phase doping uses a special device to vaporize the dopant and then enter the silicon melt. Although it supports secondary doping, it suffers from serious dopant volatilization loss and insufficient precision in doping concentration control.

[0004] Currently, commonly used methods in the preparation of heavily doped Czochralski single-crystal silicon include "umbrella" doping (e.g., patent CN1337476A), bell jar doping (e.g., patent CN113549994A), funnel doping (e.g., patent CN115044965A), and container doping (e.g., patent CN112941617A). With the continuous growth in demand for heavily doped single-crystal silicon substrates for power devices and the significant increase in single-doping amounts (often reaching kilogram levels), the above methods have revealed problems in actual production: during the doping process, a large amount of vaporized dopant will disorderly escape into the furnace interior, causing severe contamination of the furnace cover and sub-chamber surfaces. This not only significantly reduces the effective utilization rate of the dopant but also causes uneven doping distribution within the silicon melt, ultimately affecting the stability of single-crystal growth, hindering the single-crystal pulling process, and making it difficult to meet the production requirements of high-precision semiconductor materials.

[0005] To this end, we propose a Czochralski single-crystal silicon immersion doping device and doping method. Summary of the Invention

[0006] This application provides a Czochralski single-crystal silicon immersion doping device and doping method to at least solve the problems of furnace contamination, low doping efficiency, and uneven doping caused by large volatilization during the doping process in commonly used doping methods in the prior art.

[0007] In a first aspect, this application provides a Czochralski single-crystal silicon immersion doping apparatus, wherein the immersion doping apparatus is configured in conjunction with a Czochralski single-crystal furnace, and includes: The cup body has a first cavity with an open top for holding dopants, and its side walls are provided with several side baffles and several first through holes near the bottom of the cup body. Its bottom wall is provided with several bottom guide plates and several second through holes. The cover has a bottom opening and is at least partially fitted onto the upper end of the cup to form a second cavity that cooperates with the first cavity to form a material chamber, and has at least one connection hole on its upper part for loading inside the Czochralski single crystal furnace; wherein the cup and the cover are detachably connected to form the doping device.

[0008] In the above technical solution, the cup body is the main structure of the doping device, and its interior forms a first cavity for directly holding the dopant to be doped. Specifically, the first cavity is designed as a container cavity with a cylindrical inner wall, and its bottom is flat or slightly conical to facilitate the filling and concentration of the dopant. The cover body is a component used in conjunction with the cup body, and its bottom has a second cavity, which, together with the first cavity of the cup body, forms a sealed material chamber. The material chamber stores the dopant during the doping process. A first through-hole is opened on the side wall of the cup body near the bottom to break the vacuum in the material chamber when the doping device is lifted, preventing the heated molten silicon from being siphoned into the material chamber. A second through-hole is opened on the bottom wall of the cup body, serving as the main channel for the release of the dopant into the molten silicon after heating and liquefaction; its number is set according to the dopant release requirements. When the doping device is immersed in molten silicon, the side baffles and bottom guide plates, in conjunction with the crucible's rotation, agitate the molten silicon, guiding its flow and promoting uniform mixing of the dopant. Finally, the detachable connection between the cup and the lid facilitates the filling of the material chamber with dopant before each doping cycle and the cleaning and maintenance of the doping device after doping is complete.

[0009] The Czochralski single-crystal silicon immersion doping device of this application, through the detachable connection between the cup and the lid, facilitates the filling and cleaning of dopant in the material chamber, and also isolates the dopant from most of the space inside the single-crystal furnace, greatly reducing the volatilization area and loss of dopant at high temperatures, improving the accuracy of doping amount, and reducing the risk of furnace contamination. After doping, the first through-hole allows air to enter when the doping device is raised, breaking the pressure difference inside and outside the doping device and effectively preventing the silicon melt from being sucked into the cup due to the siphon effect. The second through-hole serves as a channel for the dopant to be released into the silicon melt after being heated and liquefied. When the doping device is immersed in the silicon melt, the dopant melts in the sealed cup and slowly exchanges with the silicon melt through the second through-hole, avoiding the violent reaction and splashing that may be caused when the solid dopant directly contacts the high-temperature silicon melt. When the silicon melt rotates with the crucible, the side baffle and the bottom guide plate disturb the silicon melt and guide the melt flow, realizing the stable and controllable release of the dopant, promoting the uniform mixing of the liquefied dopant in the silicon melt, and achieving high doping efficiency. This solves the problems of furnace contamination, low doping efficiency, and uneven doping caused by the large amount of dopant volatilization in the traditional doping process, thus improving the preparation quality of Czochralski single crystal silicon.

[0010] Optionally, a plurality of external flanges are formed on the outer wall of the first cavity, and a plurality of annular grooves that match and lock with the external flanges are formed on the inner wall of the second cavity. The outer flange is axially limited within the annular groove by axial movement and circumferential rotation, thereby locking the cup body and the lid body together.

[0011] In the aforementioned technical solution, the outer flange is a protruding structure located on the outer wall of the first cavity of the cup body, serving as a physical locking point for engagement with the annular groove on the lid. It can be understood that the outer flange consists of multiple circumferentially spaced arc-shaped protrusions. Furthermore, the cross-sectional shape of the outer flange is rectangular or trapezoidal, etc., to provide different levels of engagement and anti-detachment strength. In the technical solution of this application, a specific locking structure of outer flange and annular groove is introduced between the cup body and the lid body, employing an axial movement and circumferential rotation engagement method to achieve a firm connection and axial limitation between the cup body and the lid body. This ensures the strength and stability of the connection, avoiding connection failure due to loosening in high-temperature and high-pressure doping environments. Because the connection is tighter and more reliable, the leakage of dopant volatiles is significantly reduced, thereby lowering the risk of furnace contamination and ultimately improving doping efficiency and doping uniformity.

[0012] Optionally, the annular groove includes an upper annular inner flange, a plurality of lower arc-shaped inner flanges, and a locking groove formed between the upper annular inner flange and the lower arc-shaped inner flanges; Wherein, one of the free ends of the lower arc-shaped inner flange is formed with a boss portion facing the upper annular inner flange to lock the outer flange, and the outer flange is engaged in the locking groove by axial movement and circumferential rotation and cooperates with the boss portion for axial positioning. In the above technical solution, the annular groove serves as a structure for achieving a detachable connection between two components, securing them through shape fit and friction. Specifically, the upper annular inner flange, acting as the top or upper limiting structure of the annular groove, provides initial axial guidance and upper support for the outer flange entering the groove, preventing it from being pushed upwards during engagement. The lower arc-shaped inner flange is the lower structure of the annular groove, opposite to the upper annular inner flange, together forming a locking groove. The upper annular inner flange and the lower arc-shaped inner flange together define the axial range of the locking groove and provide axial lower limiting and support after the outer flange is rotated into place. Simultaneously, the boss provides additional axial locking after the outer flange is rotated into place, preventing axial loosening or detachment of the outer flange due to thermal expansion and contraction, vibration, or other factors during doping, ensuring a stable connection. The outer flange moves axially first, allowing the component to enter the preset engagement position. Then, the circumferential rotation utilizes the shape matching between the outer flange and the annular groove to ultimately achieve a tight mechanical lock, which greatly improves the firmness and stability of the connection between the cup body and the lid body, and reduces the risk of furnace contamination.

[0013] It is understood that, in addition to the flange and slot mating method described in this application, the annular slot can also be mated with the outer flange to achieve locking through various conventional methods such as elastic deformation snapping and threaded engagement.

[0014] In one example, there are two lower arc-shaped inner flanges, both of which are fan-shaped at 45° to 90° and are symmetrically and evenly distributed circumferentially.

[0015] In the above technical solution, the lower arc-shaped inner flange is designed as two, arranged in a fan shape and symmetrically and evenly distributed circumferentially. For example, it can be designed as two 60° fan shapes, spaced 120° apart; or two 90° fan shapes, spaced 90° apart, thereby providing multiple evenly distributed support points to disperse the stress during engagement. At the same time, the fan-shaped structure design also provides operating space for the rotational engagement of the outer flange while ensuring sufficient contact area.

[0016] Optionally, several of the side spoilers are arranged axially along the outer side wall of the cup and distributed in a ring array; Several bottom guide plates are arranged radially outward from the center of the outer bottom wall of the cup and distributed in a ring array. The bottom guide plates are arc-shaped.

[0017] In the above technical solution, when the dopant is released from the second through-hole of the cup and enters the silicon melt, the side baffle and the bottom guide plate can provide lateral and radial guidance, respectively, to promote the uniform diffusion of the dopant in the silicon melt. Simultaneously, the arc-shaped bottom guide plate conforms to hydrodynamic characteristics, reducing the resistance of the silicon melt and preventing the formation of dead zones or unnecessary turbulence near the bottom guide plate, thereby promoting smooth and uniform diffusion of the dopant. The combined effect of the side baffle and the bottom guide plate can more effectively guide the liquid dopant released from the through-hole to disperse rapidly and uniformly in the silicon melt, significantly improving doping efficiency and uniformity while reducing the risk of furnace contamination.

[0018] Furthermore, in a preferred embodiment of this application, the geometric dimensions and spatial arrangement of the side spoiler and the bottom guide vane are quantitatively matched and designed: The number of bottom guide plates is 8, each of which is arc-shaped with an arc radius of 85mm, an arc length of 102.74mm, and an axial height of 5mm protruding outward from the bottom of the cup. The bottom guide plates are arranged in a radially divergent ring array along the center of the outer bottom wall of the cup, and the circumferential distribution angle between two adjacent bottom guide plates is 45°. The upper inner edge of the bottom guide plate is fixedly connected to the outer bottom wall of the cup.

[0019] The number of side spoilers is always 8. Each side spoiler is arranged axially along the outer wall of the cup body in a circular array. In the axial direction, the extension direction of each side spoiler is parallel to the axis of the cup body, and its axial length is 60mm. In the radial direction, the side spoiler protrudes outward from the outer wall of the cup body to a radial height of 5mm, and its circumferential width is 5mm. The side spoiler has a symmetrical outer chamfer on the side away from the outer wall of the cup body, and the diameter of the outer chamfer is 2mm. Each side spoiler is also circumferentially and equally spaced at 45 degrees along the outer periphery of the cup body.

[0020] In terms of spatial arrangement, each of the side spoilers is connected to the outside of the cup body, and in the radial circumferential projection, each of the side spoilers is precisely distributed in the middle of two adjacent bottom guide plates, so that the side spoilers and the bottom guide plates form a three-dimensional staggered spoiler structure that is complementary and staggered by 22.5 degrees in space.

[0021] In the above technical solution, eight side baffles and eight bottom arc-shaped guide plates are arranged circumferentially at a staggered 22.5° angle. With the crucible rotating, the side baffles parallel to the axial direction generate a downward axial pumping force, which then flows into the bottom guide plates with an 85mm arc radius and a 102.74mm arc length. The smooth curvature pushes the high-density liquid dopant released from the second through-hole radially. This three-dimensional forced shear convection breaks the melt dead zone, achieving instantaneous microscopic uniform mixing and improving the radial resistivity uniformity of the single crystal head. At the same time, the 85mm arc radius of the bottom guide plates and the 2mm diameter chamfer on the outer side of the side baffles form a low-flow-resistance linear surface, which promotes a smooth transition of the silicon melt in the high-temperature flow field, eliminates the transient high-pressure eddy current zone that is easily caused by abrupt right-angle edges, avoids instantaneous overheating and boiling of the dopant caused by local heat accumulation due to eddy current damping, eliminates violent vaporization and splashing, significantly improves the dopant yield, and eliminates furnace contamination. In addition, the two sets of baffles are arranged in a staggered and complementary manner at a 45° angle, and the protrusion height of each is limited to 5mm. When the device is suspended and immersed in the high-temperature melt and subjected to the thermal shock of a kilogram-level load as it rotates with the crucible, this three-dimensional staggered phase layout can evenly distribute the rotational shear torque and thermal stress on the outer wall of the cup, eliminating the pain point of cracking and falling off at the root of the traditional single baffle due to excessive torque, and ensuring a long working life.

[0022] In one example, the diameter of the cup body is 190mm~210mm, the height is 140mm~160mm, the wall thickness of the lid and the cup body is 5mm~7mm, the radial width of the outer flange is 8mm~12mm, the radial thickness of the upper annular inner flange and the lower arc-shaped inner flange is 5mm~7mm, the thickness of the side spoiler and the bottom guide plate is 5mm, the diameter of the first through hole is 10mm~20mm, and the diameter of the second through hole is 4mm~8mm; Furthermore, the number of the first through holes is four, and the number of the second through holes is 100 to 300, which are evenly distributed at the bottom of the cup body.

[0023] The assembly gap between the second cavity and the outer diameter of the cup body is 7mm~9mm; the distance between the first through hole and the bottom of the cup body is 100mm~120mm.

[0024] The above technical solution optimizes the diameter, number, and distribution of the first and second through holes to address issues such as high dopant volatilization, low doping efficiency, uneven doping during dopant release, and the siphoning of the silicon melt into the material chamber during dopant lifting after dopant release. Specifically, the diameter range of the second through hole is limited to balance dopant release efficiency and volatilization control. If the diameter is too small, dopant release may be hindered or blocked; if the diameter is too large, dopant volatilization may be too rapid, making precise control of the release rate difficult. The number of first through holes is limited to four to prevent blockage of a single hole from disrupting the vacuum within the material chamber. The four first through holes are arranged in a uniform ring array on the sidewall of the cup. The number of second through holes is limited to 100-300 and uniformly distributed to ensure that the dopant enters the silicon melt in a more dispersed and uniform manner, avoiding excessively high local concentrations and improving doping uniformity. The arrangement of 100 to 300 second through holes can be set to be uniformly distributed in a concentric circle array on the bottom wall of the cup, or the arrangement can be optimized according to the guiding path of the bottom guide plate to maximize the uniform release of dopant.

[0025] The assembly gap of 7mm~9mm effectively balances the dimensional changes caused by thermal expansion, ensuring the stability and sealing of the device at high temperatures and reducing the unexpected volatilization of dopants, ultimately lowering the risk of furnace contamination. Simultaneously, the setting of the second through-hole being 100mm~120mm from the bottom of the cup, combined with the control of the immersion liquid level of the doping device, prevents the silicon molten liquid from submerging the second through-hole during doping. At this point, the dopant can be released precisely and uniformly at a preset, relatively stable liquid level depth, improving doping efficiency.

[0026] In a preferred embodiment of this application, the diameter, number, and spatial arrangement matrix of the second through holes at the bottom of the cup body were quantitatively matched and designed: the diameter of the second through holes was fixed at 5 mm, and the number was fixed at 224. At the bottom of the cup body, the second through holes were uniformly distributed in a concentric circle array, and their specific spatial arrangement followed the geometric tessellation principle of "equal radial step size and equal linear density increasing series". The specific distribution matrix of the second through hole diameter and the number of concentric circle holes is shown in Table 1: Table 1. Distribution matrix of diameter of the second through hole (203) and number of concentric holes The technical advantages of the above-mentioned quantitative design of the second through-hole diameter, number, and distribution matrix are as follows: Firstly, the diameter of the second through hole is set to 5mm. The particle size of the high-purity arsenic powder, red phosphorus powder, antimony powder, etc. used is generally controlled to be above 3mm (or controlled by pre-screening). This can effectively intercept unmelted solid particles during the solid charging and lifting head lowering stage (before contact with the melt), preventing them from falling into the silicon melt prematurely due to gravity and causing violent liquid splashing and vaporization. At the same time, 5mm is the minimum critical aperture that the dopant can flow out smoothly after being heated and liquefied, under the combined force of melt capillary force and gravity. This avoids liquid dopant from sticking to the quartz orifice or becoming blocked due to surface tension caused by the aperture being too small.

[0027] Secondly, the number of second through holes is set to 224, and these holes are evenly distributed in concentric circles at the bottom of the doping cup. Through a strict fluid density quantization design of "equal radial step size and equal linear density increment", the total number of openings is precisely balanced to 224, achieving isotropic distribution at the microscopic level at the bottom of the 200mm diameter cup. The evenly distributed 224 holes prevent the dopant from being concentrated in a single area. Combined with the arc-shaped bottom guide plates arranged in a divergent pattern on the outer bottom wall to cut the melt and guide the flow field, the liquid dopant flowing out is rapidly diluted by the low-concentration silicon melt brought by the crucible rotation the moment it enters the melt. This mechanism eliminates the violent boiling and splashing caused by excessively high local concentrations, thereby minimizing the amount of vaporization and volatilization and effectively protecting the cleanliness of the furnace environment.

[0028] Optionally, both the lid and the cup are made of high-purity quartz material.

[0029] In the aforementioned technical solution, high-purity quartz material is silicon dioxide (SiO2) material with extremely high purity. Its impurity content is typically below parts per million (ppm) or even parts per billion (ppb). It possesses excellent high-temperature resistance, a high melting point, and a high softening point, enabling it to maintain structural stability without deformation or decomposition at high temperatures. Furthermore, high-purity quartz material exhibits excellent chemical inertness, making it resistant to reaction with most chemical substances. Especially at high temperatures, the cap and cup maintain structural stability, releasing no impurities and avoiding chemical reactions with dopants or molten silicon, thus preventing the introduction of impurities and maintaining the cleanliness of the doping environment.

[0030] Optionally, the dopant is any one of high-purity arsenic powder, red phosphorus powder, and antimony powder.

[0031] In the above technical solution, high-purity arsenic powder is used as a dopant. Its characteristics are that it has a relatively stable thermal decomposition temperature and controllable vapor pressure. Under high temperature environment, its vaporization rate is relatively stable and it is not easy to volatilize in large quantities instantly. This helps to reduce the loss of dopant before entering the silicon melt and reduce the adhesion and contamination of the furnace wall. Red phosphorus powder is an allotrope of phosphorus. As a dopant, it exhibits controlled sublimation or vaporization behavior within a specific temperature range. Compared with other forms of phosphorus, it has higher thermal stability and can avoid the problems of reduced doping efficiency and furnace contamination caused by excessively rapid volatilization during the doping process. Antimony powder is a dopant with low vapor pressure and excellent thermal stability. At the growth temperature of Czochralski single crystal silicon, antimony has low volatility, which makes its presence in the material chamber more stable and can be released in a more uniform and sustained manner, thereby effectively suppressing excessive volatilization of dopant and furnace contamination. Furthermore, the dopant can be any one of the above-mentioned dopants or any combination thereof, allowing for flexible adjustment of the doping scheme based on the resistivity, conductivity type, and specific application requirements of the target single-crystal silicon. By selecting a single dopant or a combination thereof, the volatilization behavior of the dopant can be effectively controlled while meeting specific electrical performance requirements, thereby optimizing the efficiency and cleanliness of the doping process.

[0032] Secondly, this application provides a Czochralski single-crystal silicon immersion doping method, which uses the immersion doping device of the first aspect described above. The immersion doping device is used in conjunction with a Czochralski single-crystal furnace. The Czochralski single-crystal furnace includes at least a main furnace chamber, a secondary chamber disposed above the main furnace chamber, and an isolation valve disposed between the main furnace chamber and the secondary chamber. A crucible is provided in the lower part of the inner cavity of the main furnace chamber, and the crucible contains molten silicon containing polysiliconizing material. A weight that can be lowered into the main furnace chamber is suspended in the upper part of the inner cavity of the secondary chamber by a lifting head. The method is characterized by including the following steps: S1. After the polysiliconized material in the crucible is heated and melted into a silicon melt, the isolation valve is closed and the secondary chamber is restored to normal pressure and then opened. S2. Place a predetermined amount of dopant into the first cavity of the cup body and lock the top cover to assemble it into a doping device for carrying materials. S3. The doping device carrying the material is suspended below the weight and sent into the auxiliary chamber. The auxiliary chamber is closed and lowered to the same pressure as the main furnace chamber. The isolation valve is opened and the material carrying doping device is slowly lowered into the main furnace chamber to a position 400mm~500mm above the surface of the silicon melt. S4. Adjust the furnace pressure of the main furnace chamber to 180~250 torr, the argon flow rate to 80~150 L / min, the heater power to 45KW~50KW crystal-driving power, the crucible position to 0, and the crucible rotation speed to 1~5 rpm. Here, 0 means that the upper edge of the crucible is flush with the upper edge of the heater in the main furnace chamber. S5. Driven by the lifting head, the doping device carrying the material is lowered at a speed of 300~500 mm / min to the second through hole, immersing it 10mm~20mm below the surface of the silicon melt, and maintained for 5~15min; the dopant is heated and melted into liquid in the first cavity, and released through the second through hole. The crucible rotates in conjunction with the side baffle and the bottom guide plate to guide the release path, and the liquid dopant is quickly and evenly dispersed into the silicon melt; S6. After the dopant is released, the doping device is raised to 100mm-200mm above the surface of the silicon melt at a speed of 300-500mm / min, left to stand for 5-10 minutes, and then raised to the sub-chamber and the isolation valve is closed. S7. Adjust the furnace pressure in the main furnace chamber to 30~80 torr, the argon flow rate to 40~80 L / min, and the crucible rotation speed to 8~15 rpm. Doping is complete.

[0033] In the above technical solution, by synergistically combining a sealed material chamber with precise process parameter control, dopant volatilization can be reduced and the uniform dispersion of liquefied dopant in the silicon melt can be promoted. Specifically, the isolation valve can isolate the main furnace chamber environment, thereby preventing volatiles from diffusing into the secondary chamber and causing contamination to the secondary chamber and the lifting head; the upper cover and the cup body form a sealed material chamber, reducing dopant volatilization loss during transportation and the initial stage; furthermore, by adjusting the furnace pressure, argon flow rate, heater power, crucible position and rotation speed to a specific range, the thermal field and airflow conditions are optimized to create a stable environment for doping; at the same time, the device is lowered at a specific speed to immerse the second through hole below the melt surface, and the crucible rotation, combined with the side baffle and bottom guide plate to guide the release path, ensures rapid and uniform dispersion of liquefied dopant; in addition, raising the doping device and letting it stand still can break the vacuum state of the material chamber, preventing residue and contamination caused by silicon melt siphoning. The above technical solution achieves efficient and uniform doping of dopants, avoids furnace contamination, and significantly improves the preparation quality of heavily doped single crystal silicon.

[0034] Understandably, during the heating process, a small portion of the dopant will inevitably vaporize into a gaseous state under heated conditions and escape through several first through holes. This escaped gaseous dopant can be adjusted by the flow rate of argon gas purging into the upper part of the main furnace chamber. The flowing argon gas carries this escaped gaseous dopant downwards to the upper part of the silicon melt surface, simultaneously coordinating with the silicon melt doping process to avoid furnace contamination and precisely control the doping dosage.

[0035] Optionally, in step S6, the first through hole is used to break the vacuum in the material chamber when the doping device is lifted, so as to prevent the silicon melt from being siphoned into the material chamber.

[0036] In the above technical solution, the first through-hole is located on the side wall of the cup body. Its main function is to act as a gas channel during the lifting of the doping device, allowing gases from the external environment (such as the inert gas argon in a Czochralski single crystal furnace) to enter the material chamber. When the doping device is lifted from the surface of the silicon melt, if a negative pressure (vacuum) forms inside the material chamber, the external atmospheric pressure or the furnace pressure will push the silicon melt upward into the chamber, forming a siphon effect. The presence of the first through-hole can timely introduce gas, balance the pressure difference between the inside and outside of the chamber, break the vacuum state inside the chamber, and ultimately ensure the cleanliness of the doping process.

[0037] Compared with related technologies, the Czochralski single-crystal silicon immersion doping device and doping method provided in this application have at least the following technical advantages: In the doping device, the detachable connection between the cup and the lid facilitates the filling and cleaning of the dopant in the material chamber, while also isolating the dopant from most of the space inside the single crystal furnace. This significantly reduces the volatilization area and loss of the dopant at high temperatures, improves the accuracy of the doping amount, and reduces the risk of furnace contamination. After doping, the first through-hole allows air to enter when the doping device is lifted, breaking the pressure difference between the inside and outside of the doping device and effectively preventing the silicon melt from being sucked into the cup due to the siphon effect. The second through-hole serves as a channel for the dopant to be released into the silicon melt after liquefaction due to heating. When the doping device is immersed in the silicon melt, the dopant melts in the sealed cup and slowly exchanges with the silicon melt through the second through-hole, avoiding the violent reaction and splashing that may occur when the solid dopant directly contacts the high-temperature silicon melt. When the silicon melt rotates with the crucible, the side baffles and bottom guide plates disturb the silicon melt and guide its flow, achieving a stable and controllable release of the dopant and promoting the uniform mixing of the liquefied dopant in the silicon melt.

[0038] In terms of doping methods, by synergistically combining a sealed material chamber with precise process parameter control, dopant volatilization is effectively reduced and uniform dispersion of liquefied dopant in the silicon melt is promoted. The isolation valve prevents contamination caused by the diffusion of volatiles into the secondary chamber. By adjusting furnace pressure, argon flow rate, heater power, crucible position, and rotation speed to specific ranges, the thermal field and airflow conditions are optimized, creating a stable environment for doping. Simultaneously, the doping device is lowered at a specific speed to immerse the second through-hole below the melt surface. Combined with crucible rotation and the guidance of side baffles and bottom guide plates to direct the release path, efficient and uniform dispersion of the dopant is ultimately achieved, furnace contamination is avoided, and the preparation quality of heavily doped monocrystalline silicon is significantly improved.

[0039] Details of one or more embodiments of this application are set forth in the following drawings and description to make other features, objects and advantages of this application more readily apparent. Attached Figure Description

[0040] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0041] Figure 1 This is a schematic diagram of a Czochralski single-crystal silicon immersion doping device according to an exemplary embodiment.

[0042] Figure 2 This is one of the exploded views of a Czochralski single-crystal silicon immersion doping device according to an exemplary embodiment.

[0043] Figure 3 This is the second exploded view of a Czochralski single-crystal silicon immersion doping device according to an exemplary embodiment.

[0044] Figure 4 This is a cross-sectional view of a Czochralski single crystal furnace according to an exemplary embodiment.

[0045] Figure 5 This is a resistivity comparison diagram based on an exemplary embodiment and a comparative example of crystal pulling.

[0046] Figure 6 This is a photograph of volatiles on the furnace cover and isolation valve after dismantling, according to an exemplary embodiment.

[0047] Figure 7 The images are photographs of volatiles on the furnace cover and isolation valve after dismantling, as shown in the comparative example.

[0048] Explanation of reference numerals in the attached figures: Cover body 10; Cover top 101; Connecting hole 102; Upper annular inner flange 103; Lower arc-shaped inner flange 104; Boss portion 1041; Locking groove 105; Cup body 20; outer flange 201; first through hole 202; second through hole 203; side spoiler 204; bottom guide plate 205; Czochralski single crystal furnace 30; crucible 300; main furnace chamber 301; auxiliary chamber 302; isolation valve 303; lifting head 304; counterweight 305. Detailed Implementation

[0049] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0050] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for 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. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0051] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0052] Example This application provides a method for doping Czochralski single-crystal silicon, which uses a Czochralski single-crystal silicon immersion doping device, which is used in conjunction with a Czochralski single-crystal furnace 30. Figure 1 This is a schematic diagram of a Czochralski single-crystal silicon immersion doping device according to an exemplary embodiment. Figure 2 This is one of the exploded views of a Czochralski single-crystal silicon immersion doping device according to an exemplary embodiment. Figure 3 This is the second exploded view of a Czochralski single-crystal silicon immersion doping device according to an exemplary embodiment. Figure 4 This is a cross-sectional view of a Czochralski single crystal furnace according to an exemplary embodiment. (Refer to...) Figures 1-4 The doping method includes the following steps: S1. A Czochralski single crystal furnace 30 with pressure and airflow control functions is adopted, and the thermal field system is adapted to 8-inch 200mm single crystal growth. High-purity polycrystalline silicon raw material is loaded into a quartz crucible 300 and heated to melt into a stable silicon melt. After closing the isolation valve 303 and filling the secondary chamber 302 with high-purity argon gas to atmospheric pressure, the secondary chamber 302 is opened. S2. Prepare a high-purity arsenic (As) block as a dopant. The amount is calculated to be 1100 grams based on the target resistivity and is placed into the first cavity of the cup body 20. Then, insert the outer flange 201 of the cup body 20 into the annular groove of the cover body 10 through axial insertion and rotate it circumferentially by a certain angle so that the cup body 20 and the cover body 10 are reliably engaged, and assemble it into a doping device for carrying materials.

[0053] In this embodiment, the doping device is made of high-purity quartz. Its cup body 20 has a diameter of 210mm and a height of 160mm. The wall thickness of the cover body 10 and the cup body 20 is 7mm. The top wall of the cover body 10 is formed with a top cover 101. A connecting hole 102 is provided in the center of the top cover 101. The assembly gap between the inner diameter of the cover body 10 and the outer diameter of the cup body 20 is 7mm. The radial width of the outer flange 201 is 12mm. The radial thickness of the upper annular inner flange 103 and the lower arc-shaped inner flange 104 is 7mm. The bottom of the cup body 20 has 224 second channels, each 5mm in diameter, evenly distributed in a concentric array. Hole 203 is spatially arranged according to the geometric tessellation principle of "equal radial step size and equal linear density increasing series". The distribution matrix is ​​as follows: 1 hole in the center; 8 holes in the first ring with a diameter of 30mm; 16 holes in the second ring with a diameter of 55mm; 24 holes in the third ring with a diameter of 80mm; 32 holes in the fourth ring with a diameter of 105mm; 40 holes in the fifth ring with a diameter of 130mm; 48 holes in the sixth ring with a diameter of 155mm; and 56 holes in the seventh ring with a diameter of 180mm. Four first through holes 202 with a diameter of 8mm are evenly opened on the side wall of the cup body 20. The distance between the first through holes 202 and the cup body is... The distance between the bottom of the cup body 20 is 120mm. The sidewall of the cup body 20 has eight side spoilers 204, each arranged axially along the outer sidewall of the cup body 20 in a circular array. The axial length of each spoiler is 60mm, the radial height protruding outward from the outer sidewall of the cup body 20 is 5mm, and the circumferential width is 5mm. A symmetrical outer chamfer with a diameter of 2mm is formed on the side away from the outer sidewall of the cup body 20. The side spoilers 204 are evenly spaced and proportionally distributed at a 45° circumferential angle along the outer periphery of the cup body 20. The bottom wall of the cup body 20 has eight bottom guide vanes 205, each... It is arc-shaped with a radius of 85mm and an arc length of 102.74mm. The axial height protruding outward from the bottom of the cup body 20 is 5mm. Each bottom guide plate 205 is arranged in a radially divergent ring array along the center of the outer bottom wall of the cup body 20. The circumferential distribution angle between two adjacent bottom guide plates 205 is 45°. In terms of spatial arrangement, each side spoiler 204 is precisely distributed in the center of two adjacent bottom guide plates 205 in the radial circumferential projection, so that the side spoilers 204 and the bottom guide plates 205 form a three-dimensional staggered spoiler structure with a complementary phase of 22.5° in space.

[0054] S3. The doping device carrying the material is suspended below the weight 305 through the connection hole 102 and sent into the secondary chamber 302. The secondary chamber 302 is closed and lowered to the same pressure as the main furnace chamber 301. The isolation valve 303 is opened and driven by the lifting head 304, the doping device carrying the material is slowly lowered to a position 400mm above the surface of the silicon melt in the main furnace chamber 301. S4. Adjust the process parameters of the Czochralski single crystal furnace 30 to the doping preparation state: adjust the furnace pressure of the main furnace chamber 301 to stabilize at 200 torr, set the argon flow rate to 100 L / min, adjust the heater power to 47.5KW crystal pulling power, set the crucible 300 position to 0, and start the crucible 300 to slowly rotate at a rate of 3 rpm. The 0 position is the optimal initial position for matching the thermal field of the crucible 300 with the main furnace chamber 301. S5. Driven by the lifting head 304, the doping device is lowered at a speed of 400 mm / min until the second through-hole 203 of the doping device is immersed 15 mm below the surface of the silicon melt, and maintained for 8 minutes. The dopant is heated and melted in the first cavity and released through the first through-hole 202 and the second through-hole 203. During this period, high-purity arsenic As is heated and melted into a liquid state. Driven by the slow rotation of the crucible 300 at a speed of 3 rpm, the silicon melt is generated to flow. With the help of the side baffle 204 and the bottom guide plate 205 to guide the release path, the liquid arsenic is rapidly and uniformly dispersed throughout the silicon melt.

[0055] S6. After confirming the complete release of the arsenic dopant, raise the doping device at a speed of 400 mm / min until its bottom is approximately 150 mm above the surface of the molten silicon. Let it stand for 5 minutes to allow the molten silicon adhering to the outer wall of the doping device to drip off completely. Simultaneously, the first through-hole 202 on the side wall of the cup 20 effectively breaks the vacuum, preventing the molten silicon from being siphoned into the material chamber. Then, fully pull the doping device into the sub-chamber 302 and close the isolation valve 303. After filling the sub-chamber 303 to atmospheric pressure, open and remove the doping device for cleaning, ready for future use.

[0056] S7. Simultaneously, the process parameters of the Czochralski single crystal furnace 30 were adjusted to the crystal pulling stage: the furnace pressure in the main furnace chamber 301 was adjusted to 50 torr, the argon flow rate was adjusted to 60 L / min, and the crucible rotation speed was increased to 12 rpm. Subsequently, the normal crystal pulling, shoulder formation, constant diameter growth, and finishing processes were performed, and finally, an 8-inch heavily doped arsenic single crystal was successfully pulled.

[0057] The 8-inch heavily arsenic-doped single crystal prepared in this embodiment underwent multi-point resistivity testing at different heights on the pulled 8-inch heavily arsenic-doped single crystal. The resistivity at the top was 0.0031 Ω·cm. -1 The tail resistivity is 0.0022 Ω·cm -1 This achieved the quality requirements for heavily doped semiconductor-grade single-crystal silicon. The entire doping process effectively avoided the large-scale volatilization of arsenic, eliminated silicon melt splashing, and prevented siphoning, significantly improving production safety and single-crystal production quality.

[0058] Comparative Example This comparative example uses the same single crystal furnace, silicon material, target single crystal, and high-purity arsenic (As) blocks of the same quality and type as those in the aforementioned embodiments. The difference between this comparative example and the embodiments is that it employs a traditional non-immersion liquid-surface bell-type doping method, using a bell-type doping device, to illustrate the beneficial effects of the present invention. The bell-type doping device and doping method are described in Chinese Patent Publication No. CN113549994A, entitled "Doping Device and Method for Czochralski Silicon Single Crystals," and its structure will not be repeated here.

[0059] The Czochralski single crystal furnace 30, high-purity polycrystalline silicon raw materials, and dopants are exactly the same as those in the previous embodiments; the doping device adopts a traditional high-purity quartz bell jar with an open bottom structure and no second through hole 203, side baffle 204, or bottom guide plate 205 design.

[0060] The material is melted in the single crystal furnace, and the auxiliary chamber is operated at atmospheric pressure; arsenic blocks of the same mass are placed in the bell jar; then, the bell jar is suspended below the lifting head by a weight.

[0061] S1. The steps are exactly the same as those in the previous embodiment. High-purity polycrystalline silicon raw material is loaded into a quartz crucible 300 and heated to melt into a stable silicon melt. After closing the isolation valve 303 and filling the secondary chamber 302 with high-purity argon gas to atmospheric pressure, the secondary chamber 302 is opened. S2. Prepare high-purity arsenic (As) blocks as dopant. The amount is calculated based on the target resistivity and determined to be 1100 grams. These blocks are then placed inside a bell jar to form a bell jar doping device for carrying the material.

[0062] S3. Suspend the bell-shaped doping device carrying the material under the weight 305 and send it into the auxiliary chamber 302. Close the auxiliary chamber 302 and lower it to the same pressure as the main furnace chamber 301. Open the isolation valve 303 and drive the lifting head 304 to slowly lower the bell-shaped doping device carrying the material into the main furnace chamber 301, so that its lower edge is 20mm away from the surface of the silicon melt. S4. Adjust the process parameters of the Czochralski single crystal furnace 30 to the doping preparation state: adjust the furnace pressure of the main furnace chamber 301 to stabilize at 150 torr, set the argon flow rate to 80 L / min, adjust the heater power to 47.5KW crystal pulling power, set the crucible 300 position to position 0, and set the crucible 300 rotation speed to 0 rpm. Among them, position 0 is the optimal initial position for matching the thermal field between the crucible 300 and the main furnace chamber 301. S5. Keep the doping device in the bell jar 20mm above the surface of the molten silicon and continue heating for 5 minutes. During this process, the high-purity arsenic (As) is heated by radiant heat inside the bell jar and rapidly sublimates to form arsenic vapor. The arsenic vapor escapes from the bottom opening of the bell jar and enters the surface of the molten silicon below for doping mainly through gas phase diffusion and the action of airflow in the furnace.

[0063] S6. After confirming that the arsenic dopant has been completely released and sublimated, raise the doping device at a speed of 400 mm / min until it is fully pulled into the sub-chamber 302, and close the isolation valve 303. After purging the sub-chamber 303 to atmospheric pressure, open and remove the doping device for cleaning in preparation for the next use.

[0064] S7. Simultaneously, the process parameters of the Czochralski single crystal furnace 30 were adjusted to the crystal pulling stage: the furnace pressure in the main furnace chamber 301 was adjusted to 50 torr, the argon flow rate was adjusted to 60 L / min, and the crucible rotation speed was increased to 12 rpm. Subsequently, the normal crystal pulling, shoulder formation, constant diameter growth, and finishing processes were performed, and finally, an 8-inch heavily doped arsenic single crystal was successfully pulled.

[0065] The comparative example also produced an 8-inch heavily arsenic-doped single crystal. Resistivity tests were conducted at multiple points at different heights on the produced 8-inch heavily arsenic-doped single crystal, and the resistivity at the top was 0.0035 Ω·cm. -1 The tail resistivity is 0.0025 Ω·cm -1 The resistivity at the head of the single crystal is higher than the design value; specific values ​​are shown in Table 2. Table 2. Resistivity test results of 8-inch heavily arsenic-doped single crystal at different heights at multiple points. Construct a resistivity comparison chart based on the data in Table 2. Figure 5 This is a resistivity comparison diagram of crystal pulling according to an exemplary embodiment and a comparative example. Refer to Table 2 and Appendix. Figure 5 Under the same amount of dopant, the resistivity of the embodiments of the present invention is lower than that of the comparative example, indicating that the doping device and doping method of the embodiments of the present invention have higher doping efficiency. In contrast, in the doping device and doping method of the comparative example, a large amount of arsenic vapor was not effectively captured by the silicon melt at high temperature, which not only resulted in low actual utilization of the dopant, but also caused the head resistivity of the single crystal to be higher than the design value.

[0066] Figure 6 This is a photograph of volatiles on the furnace cover and isolation valve after dismantling, according to an exemplary embodiment. Figure 7 These are photographs of volatiles on the furnace cover and isolation valve after dismantling, shown in a comparative example. (See attached image.) Figure 6 and Figure 7Under the same dopant conditions, compared to the furnace cover and isolation valve plate of the comparative example, the embodiments of the present invention exhibit a cleaner surface at similar crystal pulling times. This demonstrates that the doping device and doping method of the present invention can effectively prevent dopant volatilization during the doping process. In contrast, the bell jar in the comparative example was not immersed in the melt, and a large amount of arsenic vapor failed to be effectively captured by the silicon melt at high temperatures. Instead, it volatilized and condensed on the furnace cover, heater, and main furnace chamber walls at lower temperatures. This not only resulted in low actual dopant utilization but also caused the resistivity of the single crystal head to exceed the design value, further severely polluting the furnace environment.

[0067] By directly comparing the examples and comparative examples, it is fully demonstrated that the immersion doping device and method provided by the present invention have outstanding advantages such as high dopant utilization, reduced furnace pollution, significantly improved doping uniformity, and enhanced single crystal quality and process stability.

[0068] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0069] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A Czochralski single-crystal silicon immersion doping apparatus, wherein the immersion doping apparatus is configured in conjunction with a Czochralski single-crystal furnace, characterized in that, include: The cup body has a first cavity with an open top for holding dopants, and its side walls are provided with several side baffles and several first through holes near the bottom of the cup body. Its bottom wall is provided with several bottom guide plates and several second through holes. The cover has a bottom opening and is at least partially fitted onto the upper end of the cup to form a second cavity that cooperates with the first cavity to form a material chamber, and has at least one connection hole on its upper part for loading inside the Czochralski single crystal furnace; wherein the cup and the cover are detachably connected to form the doping device.

2. The immersion doping device according to claim 1, characterized in that, The outer wall of the first cavity is formed with a plurality of external flanges, and the inner wall of the second cavity is formed with a plurality of annular grooves that match and lock with the external flanges. The outer flange is axially limited within the annular groove by axial movement and circumferential rotation, thereby locking the cup body and the lid body together.

3. The immersion doping device according to claim 2, characterized in that, The annular groove includes an upper annular inner flange, several lower arc-shaped inner flanges, and a locking groove formed between the upper annular inner flange and the lower arc-shaped inner flanges. One of the free ends of the lower arc-shaped inner flange is formed with a boss portion facing the upper annular inner flange to lock the outer flange. The outer flange is engaged in the locking groove by axial movement and circumferential rotation and cooperates with the boss portion for axial positioning.

4. The immersion doping device according to claim 1, characterized in that, Several of the side spoilers are arranged axially along the outer side wall of the cup and distributed in a ring array; Several bottom guide plates are arranged radially outward from the center of the outer bottom wall of the cup and distributed in a ring array. The bottom guide plates are arc-shaped.

5. The doping apparatus according to claim 1, characterized in that, The diameter of the first through hole is 10mm~20mm, and the diameter of the second through hole is 4mm~8mm.

6. The immersion doping device according to claim 1, characterized in that, The assembly gap between the second cavity and the outer diameter of the cup body is 7mm~9mm; The distance between the first through hole and the bottom of the cup body is 100mm~120mm.

7. The immersion doping device according to claim 1, characterized in that, Both the lid and the cup are made of high-purity quartz material.

8. The immersion doping device according to claim 1, characterized in that, The dopant is any one of high-purity arsenic powder, red phosphorus powder, and antimony powder.

9. A method for immersion doping of Czochralski single-crystal silicon, using the immersion doping apparatus of any one of claims 1-8, wherein the immersion doping apparatus is used in conjunction with a Czochralski single-crystal furnace, the Czochralski single-crystal furnace comprising at least a main furnace chamber, a secondary chamber disposed above the main furnace chamber, and an isolation valve disposed between the main furnace chamber and the secondary chamber, a crucible is provided in the lower part of the inner cavity of the main furnace chamber, the crucible containing molten silicon containing polysilicon, and a weight that can be lowered into the main furnace chamber is suspended in the upper part of the inner cavity of the secondary chamber by a lifting head, characterized in that... Includes the following steps: S1. After the polysiliconized material in the crucible is heated and melted into a silicon melt, the isolation valve is closed and the secondary chamber is restored to normal pressure and then opened. S2. Place a predetermined amount of dopant into the first cavity of the cup body and lock the top cover to assemble it into a doping device for carrying materials. S3. The doping device carrying the material is suspended below the weight and sent into the auxiliary chamber. The auxiliary chamber is closed and lowered to the same pressure as the main furnace chamber. The isolation valve is opened and the material carrying doping device is slowly lowered into the main furnace chamber to a position 400mm~500mm above the surface of the silicon melt. S4. Adjust the furnace pressure of the main furnace chamber to 180~250 torr, the argon flow rate to 80~150 L / min, the heater power to 45KW~50KW crystal-driving power, the crucible position to 0, and the crucible rotation speed to 1~5 rpm. Here, 0 is the position where the upper edge of the crucible is flush with the upper edge of the heater in the main furnace chamber. S5. Driven by the lifting head, the doping device carrying the material is lowered at a speed of 300~500 mm / min until it is submerged in the second through hole of the doping device to a depth of 10 mm~20 mm below the surface of the silicon melt, and maintained for 5~15 min; the dopant is heated and melted into liquid in the first cavity, and released through the second through hole. The crucible rotates in conjunction with the side baffle and the bottom guide plate to guide the release path, and the liquid dopant is quickly and evenly dispersed into the silicon melt; S6. After the dopant is released, the doping device is raised to 100mm-200mm above the surface of the silicon melt at a speed of 300-500mm / min, left to stand for 5-10 minutes, and then raised to the sub-chamber and the isolation valve is closed. S7. Adjust the furnace pressure in the main furnace chamber to 30~80 torr, the argon flow rate to 40~80 L / min, and the crucible rotation speed to 8~15 rpm. Doping is complete.

10. The doping method according to claim 9, characterized in that, In step S6, the first through hole is used to break the vacuum in the material chamber when the doping device is lifted, so as to prevent the silicon melt from being siphoned into the material chamber.

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