Spliced diffusion furnace pipe and diffusion furnace

Abstract

The spliced diffusion furnace pipe comprises a long-barrel-shaped furnace pipe outer wall and a furnace pipe body which is arranged in the furnace pipe outer wall and formed by splicing a plurality of heating pipes in the length direction of the furnace pipe outer wall, and the furnace pipe body comprises at least one first heating pipe and a second heating pipe which is located at the head end and / or the tail end and is adjacent to a furnace door. The first heating tube comprises a metal heating wire used for heating an inner cavity of the heating tube, the second heating tube comprises at least one group of electrode rod windings used for heating the inner cavity of the heating tube, and the electrode rod windings are silicon carbide rods or silicon molybdenum rods. According to the technical scheme, the spliced furnace pipe structure is designed, the silicon carbide rod or the silicon molybdenum rod is adopted at the opening for heating, the silicon carbide rod and the silicon molybdenum rod are ceramic heating bodies, the surface load can be designed to be very high and is about 10w / cm < 2 >, and a formed oxidation film is easier to resist stripping, so that the service life is greatly prolonged when the silicon carbide rod or the silicon molybdenum rod is used at the opening of the furnace pipe.

Description

Technical Field

[0001] The utility model belongs to the field of diffusion furnaces, and in particular relates to a spliced ​​diffusion furnace furnace core and a diffusion furnace. Background Art

[0002] The diffusion furnace is one of the important process equipment in the front process of the semiconductor production line. It is used for diffusion, oxidation, annealing, alloying and sintering in industries such as large-scale integrated circuits, discrete devices, power electronics, optoelectronic devices and optical fibers.

[0003] In the production of TOPCon batteries, diffusion furnaces are used for boron diffusion and phosphorus diffusion of silicon wafers. The working temperature of boron diffusion is about 1050 degrees, and the working temperature of phosphorus diffusion is about 900 degrees. The operating temperature of the boron diffusion furnace is too high, and the operating conditions are rapid cooling and heating. If the furnace wire is a metal heating wire, after it is heated to a high temperature, an oxide film of several tens of microns will form on the surface of the furnace wire, which can protect the metal wire from oxidation. However, since the silicon wafer needs to be quickly cooled to 600-700 degrees after ion diffusion and then the silicon wafer is taken out from the furnace door, the furnace is mainly damaged by the inner metal heating wire at the inlet and outlet of the furnace door. The surface load of the metal heating wire generally cannot exceed 1.5w / cm 2 The oxide film on the furnace wire is easy to peel off, and then the silicon wafer is installed and rapidly heated to 1050 degrees. The heating work is repeated six times a day, resulting in repeated formation and peeling of the oxide film of the metal heating wire in the inner tank of the furnace door. The metal heating wire is continuously consumed, thereby greatly shortening the life of the metal heating wire, resulting in the furnace life of only about 10 months. In addition, during the repeated formation and peeling of the oxide film, the metal heating wire is continuously consumed, the heating efficiency becomes lower, resulting in lower diffusion efficiency, affecting the product quality of silicon wafer production.

[0004] Therefore, the market demands to design a diffusion furnace core with long service life, low maintenance cost, high diffusion efficiency and high product quality. Utility Model Content

[0005] The technical problem to be solved by the utility model is to provide a spliced ​​diffusion furnace liner.

[0006] In order to solve the above technical problems, the technical solution adopted by the utility model is: a spliced ​​diffusion furnace furnace, including a furnace outer wall in the shape of a long cylinder, a plurality of heating tubes arranged in the furnace outer wall and spliced ​​into a furnace body along the length direction of the furnace outer wall, the furnace body including at least one first heating tube, a second heating tube located at the head end and / or the tail end and adjacent to the furnace door, the first heating tube including a metal heating wire for heating the inner cavity of the tube, the second heating tube including at least one group of electrode rod windings for heating the inner cavity of the tube, the electrode rod windings are silicon carbon rods or silicon molybdenum rods. The furnace is designed to be a spliced ​​furnace structure, and silicon carbon rods or silicon molybdenum rods are used for heating at the opening. Silicon carbon rods and silicon molybdenum rods are ceramic heating elements, and the surface load can be designed to be very high, for example, 10w / cm 2 , and the oxide film formed on the surface is more resistant to peeling. Therefore, after the temperature at the furnace opening is heated to 1050 degrees and then quickly cooled to 600-700 degrees, the oxide film produced on the surface of the silicon carbon rod and silicon molybdenum rod is not easy to peel off, so that the surface oxide film can protect the silicon carbon rod and silicon molybdenum rod from being oxidized. Therefore, the use of silicon carbon rods or silicon molybdenum rods at the furnace opening greatly extends the service life, while ensuring the stable and efficient diffusion of boron and the product quality of the battery silicon wafer.

[0007] In some embodiments, the second heating tube includes a second thermal insulation tube body and a stable structure capable of stably winding at least one group of electrode rods in the second thermal insulation tube body.

[0008] In some embodiments, the second thermal insulation tube body is a tubular body formed by wrapping at least one layer of high temperature resistant fiber blanket around at least one group of electrode rod windings; or, the second thermal insulation tube body is a tubular body formed by vacuum adsorption of high temperature resistant fiber material.

[0009] In some embodiments, the stabilizing structure includes a plurality of ceramic positioning parts integrally formed on the inner wall of the second insulation tube body by vacuum adsorption; or, the stabilizing structure includes at least two groups of positioning hoops suitable for the electrode rod winding whose rod body at least partially extends along the center line direction of the furnace, each group of the positioning hoops includes a ceramic ring and a plurality of ceramic positioning parts passed through the ceramic ring; or, the stabilizing structure includes at least two groups of positioning strips suitable for the electrode rod winding whose rod body at least partially extends spirally along the length direction of the furnace, each group of positioning strips includes a ceramic positioning rod and a plurality of ceramic positioning parts passed through the ceramic positioning rod; each of the ceramic positioning parts has a positioning groove for interlocking or hooking the electrode rod winding rod body for positioning.

[0010] In certain embodiments, the second thermal insulation pipe body is a tubular body wrapped by an alumina fiber blanket of at least one thickness, and the wall thickness of the tubular body is 35 mm-55 mm.

[0011] In some embodiments, the first heating tube includes a first thermal insulation tube body formed by vacuum adsorption of high temperature resistant fibers, and the metal heating wire is integrally formed during the vacuum adsorption process and embedded in the inner wall of the first thermal insulation tube body.

[0012] In some embodiments, the second heating tube has multiple groups of electrode rod windings evenly distributed along the inner circle of the tube. By controlling the temperatures of the electrode rod windings separately, the inner cavity of the second heating tube can have multiple temperature zones.

[0013] In certain embodiments, the spliced ​​diffusion furnace furnace further includes furnace door frames fixed to both ends of the furnace outer wall, and the first heating tube and the second heating tube are spliced ​​between the two furnace door frames.

[0014] The technical problem to be solved by the utility model is to provide a diffusion furnace.

[0015] In order to solve the above technical problems, the technical solution adopted by the utility model is: a diffusion furnace including the spliced ​​diffusion furnace furnace core described in any one of the embodiments, and also including a furnace box body, and the furnace core is located in the furnace box body.

[0016] The scope of the utility model is not limited to the technical solutions formed by the specific combination of the above technical features, but also includes other technical solutions formed by any combination of the above technical features or their equivalent features. For example, the above features are replaced with the technical features with similar functions disclosed in this application (but not limited to) by each other.

[0017] Due to the application of the above technical solution, the utility model has the following advantages compared with the prior art:

[0018] 1. The furnace of the diffusion furnace of the utility model is designed as a spliced ​​furnace structure, and silicon carbon rods or silicon molybdenum rods are used for heating at the opening. Silicon carbon rods and silicon molybdenum rods are ceramic heating elements, and the surface load can be designed to be very high, such as 10w / cm 2 , and the oxide film formed on the surface is more resistant to peeling. Therefore, after the temperature at the furnace opening is heated to 1050 degrees and then quickly cooled to 600-700 degrees, the oxide film on the surface of the silicon carbon rod and silicon molybdenum rod is not easy to peel off, so that the surface oxide film can protect the silicon carbon rod and silicon molybdenum rod from being oxidized. Therefore, the use of silicon carbon rods or silicon molybdenum rods at the furnace opening greatly prolongs the service life, while ensuring the stable and efficient diffusion of boron, and ensuring the product quality of silicon wafers;

[0019] 2. The metal heating wire is used in the middle section of the furnace. This assembly heating method can extend the service life while reducing the cost as much as possible, which is cost-effective;

[0020] 3. The electrode rod winding is firmly secured by snapping or hooking with the ceramic positioning piece, which is easy to disassemble and assemble, and convenient for subsequent maintenance;

[0021] 4. After the electrode rod winding is stabilized by cooperating with the ceramic positioning piece, at least one layer of high temperature resistant fiber blanket is wrapped on the electrode rod winding to form a second insulation tube body, which makes installation more convenient and simple;

[0022] 5. The setting of the furnace door frame makes the first heating tube and the second heating tube axially fixed and will not shift. The structure is simple, no additional fixing mechanism is required, and it is convenient to disassemble and assemble each heating tube during subsequent maintenance. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a schematic diagram of the structure of the utility model;

[0024] Figure 2 for Figure 1 AA cross-sectional diagram (Example 1);

[0025] Figure 3 is a schematic diagram of the three-dimensional structure of the second heating tube (embodiment 1);

[0026] Figure 4 This is a schematic diagram of the three-dimensional structure of the second heating tube (Example 2);

[0027] Figure 5 This is a schematic diagram of the structure of a ceramic positioning member (Example 2);

[0028] Among them: 1. furnace outer wall; 2. first heating tube; 3. second heating tube; 4. electrode rod winding; 5. ceramic positioning piece; 51. positioning groove; 52. mounting hole; 6. second insulation tube body. DETAILED DESCRIPTION

[0029] The utility model is further described in detail below in conjunction with the accompanying drawings.

[0030] A diffusion furnace comprises a spliced ​​diffusion furnace core and a furnace box, wherein the furnace core is located in the furnace box.

[0031] During the boron diffusion process, the temperature needs to be controlled at 1050°C. The reason is that at high temperatures, the diffusion rate of boron atoms in silicon increases significantly. 1050°C provides a high enough temperature for boron atoms to quickly diffuse into the silicon lattice to form a uniform doping layer. This high diffusion rate is particularly important in industrial production, which can improve production efficiency and reduce process time.

[0032] At 1050°C, boron atoms can effectively enter the surface of silicon wafers to form a doping layer with uniform depth and concentration, which is crucial to the performance of solar cells because a uniform doping layer can ensure the uniformity of the electric field inside the battery, thereby improving the carrier collection efficiency. Under high temperature conditions, boron diffusion can form a thin silicon oxide (SiO2) layer on the surface of the silicon wafer, which plays a role in surface passivation and reduces surface recombination, which helps to improve the open circuit voltage (Voc) and overall efficiency of the battery.

[0033] The high temperature of 1050℃ enables boron atoms to embed deeper into the surface of the silicon wafer, forming a low-resistance P-type contact area. This low-resistance contact area is crucial to reducing the series resistance (Rs) and helps to improve the fill factor (FF) and efficiency of solar cells.

[0034] Boron diffusion at high temperature can also help repair some lattice defects in silicon wafers, improving the crystal quality and electrical properties of silicon wafers, which is very important for the manufacture of high-efficiency solar cells.

[0035] Diffusion at 1050°C can be coordinated with other high-temperature processes (such as oxidation and metallization) to optimize the thermal budget of the entire solar cell manufacturing process. This means that efficient diffusion can be maintained while avoiding excessive thermal stress and deformation of the silicon wafer.

[0036] Figure 1 The utility model shows the structure of the spliced ​​diffusion furnace, which includes a long cylindrical furnace outer wall 1, a furnace door frame fixed to both ends of the furnace outer wall 1, and a furnace body formed by splicing a plurality of heating tubes arranged in the furnace outer wall 1 along the length direction of the furnace outer wall 1.

[0037] The furnace body includes four first heating tubes 2 spliced ​​along the length direction and second heating tubes 3 located at the head end and the tail end and adjacent to the furnace door. The first heating tube 2 and the second heating tube 3 are both cylindrical. The first heating tube 2 and the second heating tube 3 are spliced ​​between the two furnace door frames. The positions of the two furnace door frames are fixed to achieve axial positioning of the first heating tube 2 and the second heating tube 3.

[0038] The length of the first heating tube 2 is 580mm-590mm, and the length of the second heating tube 3 is 400mm-500mm. In this embodiment, the length of the first heating tube 2 is 585mm, the length of the second heating tube 3 is 450mm, plus the furnace door frames at the outermost ends for installing the furnace door, the entire furnace is 3390mm long, which is suitable for sintering products with longer lengths.

[0039] The traditional one-piece long cylindrical furnace requires multiple metal heating wires of more than 3 meters to be embedded in the furnace wall. The opening and closing of the furnace doors at both ends leads to rapid heat dissipation, which requires high-intensity heating. The service life of the metal heating wire is generally about half a year. Since the metal heating wire is a whole piece, replacement requires replacement of the entire metal heating wire, and the maintenance and replacement cost is high. This embodiment adopts the structure of a spliced ​​diffusion furnace furnace. Subsequent maintenance does not require overall disassembly and repair or replacement, but only requires repair of damaged or replacement of one section, and the maintenance cost is low.

[0040] like Figure 1 , 2 As shown, the first heating tube 2 is equipped with a metal heating wire for heating the tube cavity, and the second heating tube 3 is equipped with an electrode rod winding 4 for heating the tube cavity. The electrode rod winding 4 is a silicon carbon rod or a silicon molybdenum rod. The silicon carbon rod or the silicon molybdenum rod has a strong heating capacity, and the surface load can be designed to be very high, about 10w / cm 2 , and the formed oxide film is more resistant to peeling and has a long service life. The first heating tube 2 still uses a metal heating wire because the middle section is not easy to dissipate heat and has a good thermal insulation effect. The metal heating wire does not need to be frequently switched between 600°C and 1050°C, and its service life can be more than one year. The price of silicon-molybdenum rods or silicon-carbon rods is high, and the price of metal heating wires is low. This assembly method ensures heat input while reducing costs as much as possible, and has a high cost-effectiveness ratio.

[0041] The electrode rod winding 4 is a regular U-shaped multi-bend winding, having multiple parallel sections of rods extending along the center line of the heating tube. All rods are evenly distributed in the circumferential direction of the center line of the heating tube. The electrode rod winding 4 has multiple groups, and multiple groups of electrode rod windings 4 form a heating tube body. By controlling the temperature of the electrode rod winding 4 separately, the cavity of the heating tube body can have multiple temperature zones. The heating of the multiple temperature zones is controlled separately, and products requiring heating at different temperatures can be sintered.

[0042] Embodiment 1: Figure 3 As shown, the second heating tube 3 has a rigid tubular body formed by vacuum adsorption of high temperature resistant fiber material, namely the second heat preservation tube body 6. Figure 3 As shown, the second heating tube 3 also has a ceramic positioning piece 5 integrally formed on the inner wall of the second insulation tube body 6 through a vacuum adsorption process. In this embodiment, the ceramic positioning piece 5 includes a ceramic rod integrally formed on the inner wall of the second insulation tube body 6 and a ceramic clamp fixed on the ceramic rod through a mounting hole 52. Positioning grooves 51 for interlocking and positioning the rod bodies of the electrode rod winding 4 are provided on both sides of the ceramic clamp. In this embodiment, the length direction of the positioning groove 51 is consistent with the length direction of the second insulation tube body 6, the length direction of the mounting hole 52 is consistent with the radial direction of the second insulation tube body 6, and the direction of the ceramic rod is perpendicular to the cross-section of the second insulation tube body 6.

[0043] Each electrode rod winding 4 is inserted into the positioning grooves 51 of multiple ceramic clamps from top to bottom. The multiple ceramic clamps can be aligned or staggered in the vertical direction to ensure that each rod is inserted into the positioning groove 51.

[0044] Embodiment 2: Figure 4 As shown, in this embodiment, the electrode rod winding 4 is also a regular U-shaped multi-bend winding. Different from the first embodiment, the ceramic positioning member 5 in this embodiment has no fixed relationship with the second thermal insulation tube body 6. In this embodiment, the ceramic positioning member 5 includes a ceramic clamping block, and positioning grooves 51 are provided on both sides of the ceramic clamping block. Figure 5 As shown, the ceramic clamp block is also provided with a mounting hole 52, and the extension direction of the mounting hole 52 is consistent with the extension direction of the positioning groove 51, and both are consistent with the length direction of the second insulation tube body 6. In this embodiment, the ceramic clamp blocks are strung together by multiple ceramic positioning rods, and the positioning grooves 51 of the ceramic clamp blocks are aligned. Then, the rod body of the electrode rod winding 4 is buckled into the positioning groove 51 of the ceramic clamp block, and the installation of the electrode rod winding 4 is completed. Then, at least one layer of high-temperature resistant alumina fiber blanket is tightly wrapped on the electrode rod winding 4 to form the second insulation tube body 6. The electrode rod winding 4 and the positioning rod form a skeleton of the high-temperature resistant alumina fiber blanket. The alumina fiber blanket tightens the electrode rod winding 4 and the positioning rod and stably arranges them in the second heating tube 3.

[0045] Embodiment three (not shown): In this embodiment, the electrode rod winding 4 is also a regular U-shaped multi-bend winding, and the second heating tube 3 has a rigid tubular body formed by vacuum adsorption of high-temperature resistant fiber material, namely the second thermal insulation tube body 6. What is different from Embodiment one is that in this embodiment, a ceramic hook is integrally formed on the inner wall of the second thermal insulation tube body 6 through a vacuum adsorption process, and the rod body of the electrode rod winding 4 is hooked with the ceramic hook so that the electrode rod winding 4 is stably arranged on the inner wall of the second thermal insulation tube body 6.

[0046] Embodiment 4 (not shown): In this embodiment, the electrode rod winding 4 is also a regular U-shaped multi-bend winding, and the second heating tube 3 is provided with at least two groups of positioning hoops, each group of the positioning hoops includes a ceramic ring and a plurality of ceramic clamping blocks inserted on the ceramic ring, and a positioning groove 51 is provided on each ceramic clamping block, and the positioning grooves 51 of two adjacent ceramic clamping blocks match to form a clamping groove that can clamp the rod body of the electrode rod winding 4, the circumferential direction of the ceramic ring is consistent with the circumferential direction of the inner wall of the second heating tube 3, and the positioning groove 51 is perpendicular to the surface where the ceramic ring is located. After the electrode rod winding 4 is buckled into the positioning groove 51 and stabilized, at least one layer of high-temperature resistant alumina fiber blanket is tightly wrapped on the electrode rod winding 4 to form a second thermal insulation tube body 6, the electrode rod winding 4 and the ceramic ring form a skeleton of the high-temperature resistant alumina fiber blanket, and the alumina fiber blanket tightens the electrode rod winding 4 and the ceramic ring and stably arranges them in the second heating tube 3.

[0047] Embodiment 4 (not shown): In this embodiment, the electrode rod winding 4 is a winding that extends spirally and uniformly along the length direction of the furnace. In this embodiment, the ceramic positioning member 5 includes a ceramic clamping block and a ceramic positioning rod passing through a plurality of ceramic clamping blocks. The length direction of the ceramic positioning rod is consistent with the length direction of the furnace. The positioning grooves 51 of each two adjacent ceramic clamping blocks match to form a clamping groove that can clamp the rod body of the electrode rod winding 4. The ceramic clamping blocks are distributed along the length direction of the furnace. After the electrode rod winding 4 is buckled into the positioning groove 51 for stabilization, at least one layer of high-temperature resistant alumina fiber blanket is tightly wrapped on the electrode rod winding 4 to form a second thermal insulation tube body 6.

[0048] The spliced ​​diffusion furnace also includes furnace door frames fixed at both ends of the furnace outer wall 1, and the first heating tube 2 and the second heating tube 3 are spliced ​​between the two furnace door frames.

[0049] The length of the second heating tube 3 is in a ratio relationship with the length of the first heating tube 2. In this embodiment, the ratio of the length of the second heating tube 3 to the length of the first heating tube 2 can be obtained by a heat balance method.

[0050] The energy input of the diffusion furnace is mainly heat, which comes from the heating of the metal heating wire on the first heating tube 2 and the heating of the electrode rod winding 4 on the second heating tube 3. The heat formula of the metal heating wire is: t, where S1 represents the cross-sectional area of ​​the metal heating wire, represents the resistivity of the metal heating wire, L1 represents the length of the metal heating wire, t represents the heating time, and the heating heat formula of the electrode rod winding is: , where S2 represents the cross-sectional area of ​​the electrode rod winding, represents the resistivity of the electrode winding, L2 represents the length of the electrode winding, assuming S1=S2, and the two electric heating elements need to provide the same amount of heat per unit time, then L1:L2= : .

[0051] However, when the furnace door on the second heating tube at both ends of the diffusion furnace is opened, the high-temperature gas in the furnace comes into contact with the outside normal temperature atmosphere, and a large amount of heat in the diffusion furnace will be lost. Therefore, the electrode rod winding on the second heating tube not only needs to ensure that the temperature maintained by the electrode rod winding of the second heating tube is consistent with the temperature maintained by the metal heating wire of the first heating tube when the furnace door is closed, but also needs to ensure that when the furnace door is opened, the lost heat is quickly replenished and the temperature of the second heating tube is continuously maintained. That is, the length of the electrode rod winding needs to be set according to the length of the metal heating wire, so that the length of the electrode rod winding is within a range that can quickly replenish heat to maintain the temperature without being too long and wasteful.

[0052] When the diffusion furnace is turned on, the heat dissipated is calculated as , where k is the comprehensive heat transfer coefficient, the unit is w / (℃×m^2). The size of k can be found in materials such as "Heat Transfer" and "Industrial Furnace Design Manual" and will not be elaborated here. S is the cross-sectional area of ​​the second heating tube, T0 is the initial temperature in the second heating tube, and T1 is the initial temperature in the second heating tube after the door is opened for heat dissipation. Both temperatures can be obtained by measurement.

[0053] Therefore, the electrode rod winding must not only be able to provide the same amount of heat as the metal heating wire, but also provide the dissipated heat according to the principle of thermal balance, that is, the electrode rod winding needs to provide Q2+Q s ,but , that is, the length ratio between the electrode rod winding and the metal heating wire is obtained, and the furnace in this embodiment can be manufactured according to this length ratio.

[0054] The working principle of TOPCon (Tunneling Oxide Passivation Contact) diffusion furnace mainly involves the preparation of tunneling oxide layer and polysilicon layer to achieve high-efficiency solar cells.

[0055] This process can be divided into several key steps.

[0056] 1. Cleaning and pretreatment: Before diffusion, the silicon wafer needs to be cleaned to remove impurities and contaminants on the surface. Common cleaning methods include wet chemical cleaning and plasma cleaning.

[0057] 2. Formation of tunneling oxide layer: After the silicon wafer is cleaned, an extremely thin tunneling oxide layer (usually 1.5-2nm) is formed on the surface of the silicon wafer by thermal oxidation or chemical vapor deposition (CVD). This oxide layer plays an electrical isolation and passivation role in subsequent processes, helping to reduce the recombination loss of charge carriers.

[0058] 3. Deposition of polysilicon layer: After the tunnel oxide layer is formed, the silicon wafer is placed in a diffusion furnace for doping diffusion. The diffusion furnace is filled with doping source gas (such as phosphorus source gas POCI3) and the doping elements (such as phosphorus) are diffused into the surface of the silicon wafer at high temperature (usually 800-1000°C) to form a highly doped N-type or P-type polysilicon layer with a thickness of 60-100 nanometers. This layer can further passivate the charge carriers, thereby improving the efficiency of the battery. Commonly used deposition methods include low-pressure chemical vapor deposition (LPCVD), plasma enhanced chemical vapor deposition (PECVD) and physical vapor deposition (PVD). Among them, LPCVD has become the mainstream due to its mature technology (Inkpv).

[0059] 4. Preparation of the front surface passivation layer: A layer of aluminum oxide film is deposited on the front surface of the silicon wafer to provide additional passivation effect. Then a silicon nitride layer is deposited to protect the aluminum oxide film and enhance the anti-reflection effect (Inkpv).

[0060] 5. Diffusion process: After doping diffusion, the silicon wafer will continue to undergo drive-in diffusion and annealing processes. This step uses high-temperature treatment to make the distribution of doping elements in the silicon wafer more uniform, repair lattice defects generated during high-temperature diffusion, and improve the electrical performance of the silicon wafer. Doping elements such as phosphorus or boron are diffused into the silicon wafer through a high-temperature diffusion process to form a PN junction, which is the core part of the photovoltaic cell. In TOPCon technology, selective emitter (SE) technology is usually used to optimize cell performance through high-concentration and low-concentration doping (Solar Panel Solution).

[0061] 6. Post-processing: including cleaning, etching and passivation steps to remove surface impurities and optimize surface properties. For example, hydrofluoric acid (HF) cleaning is used to remove the oxide layer on the surface of the silicon wafer, and alkaline solution is used to polish the surface of the silicon wafer to improve reflectivity and surface flatness (Solar Panel Solution).

[0062] 7. Sintering and electrode formation: Sintering at high temperature to form a good ohmic contact, and then forming the electrode (Inkpv) by screen printing or laser transfer printing technology.

[0063] The above embodiments are only for illustrating the technical concept and features of the utility model, and their purpose is to enable people familiar with the technology to understand the content of the utility model and implement it accordingly, and they cannot be used to limit the protection scope of the utility model. Any equivalent changes or modifications made according to the spirit of the utility model should be included in the protection scope of the utility model.

Claims

1. A spliced ​​diffusion furnace, characterized in that: The invention comprises a furnace outer wall (1) in the form of a long tube, a furnace body formed by a plurality of heating tubes arranged in the furnace outer wall (1) and spliced ​​along the length direction of the furnace outer wall (1), the furnace body comprising at least one first heating tube (2), and a second heating tube (3) located at the head end and / or the tail end and adjacent to the furnace door, the first heating tube (2) comprising a metal heating wire for heating the inner cavity of the tube, the second heating tube (3) comprising at least one group of electrode rod windings (4) for heating the inner cavity of the tube, the electrode rod windings (4) being silicon carbon rods or silicon molybdenum rods.

2. The spliced ​​diffusion furnace according to claim 1, characterized in that: The second heating tube (3) comprises a second thermal insulation tube body and a stable structure capable of stably placing at least one set of electrode rod windings (4) inside the second thermal insulation tube body.

3. The spliced ​​diffusion furnace according to claim 2, characterized in that: The second thermal insulation tube body is a tubular body formed by at least one layer of high temperature resistant fiber blanket wrapped around at least one group of electrode rod windings (4); or, the second thermal insulation tube body is a tubular body formed by vacuum adsorption of high temperature resistant fiber material.

4. The spliced ​​diffusion furnace according to claim 3 is characterized in that: The stable structure comprises a plurality of ceramic positioning members (5) integrally formed on the inner wall of the second thermal insulation tube body by vacuum adsorption; or, the stable structure comprises at least two groups of positioning hoops suitable for the electrode rod winding (4) whose rod body at least partially extends along the center line direction of the furnace, each group of the positioning hoops comprises a ceramic ring and a plurality of ceramic positioning members (5) worn on the ceramic ring; or, the stable structure comprises at least two groups of positioning strips suitable for the electrode rod winding (4) whose rod body at least partially extends spirally along the length direction of the furnace, each group of positioning strips comprises a ceramic positioning rod and a plurality of ceramic positioning members (5) worn on the ceramic positioning rod; each of the ceramic positioning members (5) has a positioning groove for interlocking or hooking the rod body of the electrode rod winding (4) to position it.

5. The spliced ​​diffusion furnace according to claim 3 is characterized in that: The second thermal insulation pipe body is a tubular body wrapped by an alumina fiber blanket of at least one thickness, and the wall thickness of the tubular body is 35mm-55mm.

6. The spliced ​​diffusion furnace according to claim 1, characterized in that: The first heating tube (2) comprises a first thermal insulation tube body formed by vacuum adsorption of high temperature resistant fibers, and the metal heating wire is integrally formed during the vacuum adsorption process and embedded on the inner wall of the first thermal insulation tube body.

7. The spliced ​​diffusion furnace according to claim 1, characterized in that: The second heating tube (3) has a plurality of groups of electrode rod windings (4) evenly distributed along the inner circle of the tube. By controlling the temperatures of the electrode rod windings (4) respectively, the inner cavity of the second heating tube (3) can have a plurality of temperature zones.

8. The spliced ​​diffusion furnace according to claim 1, characterized in that: The spliced ​​diffusion furnace furnace also includes furnace door frames fixed to both ends of the furnace outer wall (1), and the first heating tube (2) and the second heating tube (3) are spliced ​​between the two furnace door frames.

9. A diffusion furnace comprising the spliced ​​diffusion furnace core according to any one of claims 1 to 8, characterized in that: It also includes a furnace box, in which the furnace core is located.

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