Boron diffusion furnace for silicon wafer

Abstract

The boron diffusion furnace comprises a furnace body, a furnace door, a bearing assembly and a flow equalizing plate set, and the bearing assembly is arranged in a furnace cavity of the furnace body; the flow equalizing plate set comprises a first flow equalizing plate close to the air inlet pipe and a second flow equalizing plate close to the bearing assembly, a through hole and a plurality of first through grooves are formed in the first flow equalizing plate in a penetrating mode, and the air outlet pipe penetrates through the through hole; the second flow equalizing plate is rotationally connected with the inner wall of the furnace cavity of the furnace body, a sliding groove and a plurality of second through grooves are formed in the second flow equalizing plate in a penetrating mode, and the air outlet pipe is slidably connected with the sliding groove. Therefore, the flow field distribution can be improved by introducing the pore-adjustable flow equalizing plate group, the uniform distribution of gas in the furnace body is realized, the doped gas carried by the gas can be uniformly deposited on the surface of a silicon wafer, and meanwhile, the furnace tube is maintained in a low-pressure state and is matched with the gas flowing at a constant speed, so that the uniformity of the silicon wafer is improved. And the diffusion uniformity of the silicon wafers at the front, middle and rear positions in the quartz boat is further improved, so that the square resistance of the silicon wafers is reduced, and the electric efficiency is improved.

Description

Technical Field

[0001] The present application relates to the technical field of photovoltaic cell equipment manufacturing, and in particular to a boron diffusion furnace for silicon wafers. Background Art

[0002] Crystalline silicon cells, as solar cells made of single crystal silicon technology, have been widely used in many fields due to their excellent conversion efficiency and outstanding stability. In the fine manufacturing process of solar photovoltaic cells, silicon wafers undergo a series of precision processes such as texturing, diffusion, etching, coating and printing. Among them, the diffusion step is particularly critical, which directly affects the quality of the PN junction and becomes one of the core factors that determine the performance of solar cells.

[0003] Boron diffusion is the process of depositing boron atoms in a boron source on the surface of a silicon wafer in the form of boron trioxide at high temperature. The boron atoms diffuse into the phosphorus-containing solar silicon wafer to form a PN junction. Boron diffusion is usually carried out in a diffusion furnace. This process is usually completed in a professional diffusion furnace to ensure high efficiency and precision.

[0004] At present, as attached Figure 8 As shown, the silicon wafers in the boron diffusion furnace are mainly inserted vertically, which has a low output. In order to increase the hourly output of a single machine, the insertion method is changed from vertical to horizontal layout, and the single-tube wafer capacity is increased from the original 1,200 wafers to 2,400 wafers, greatly enhancing the hourly output capacity of the single machine.

[0005] However, in actual application, the square resistance of the silicon wafers at the head and tail ends of the quartz boat fluctuates greatly, and the uniformity of the square resistance within the wafer is poor, which will affect the uniformity of the silicon wafer diffusion in the entire furnace tube, and then cause the PN junction of the same cell to have different depths, directly affecting the normal distribution of the electrical performance parameters of the solar cell, and ultimately leading to a decrease in the electrical efficiency of the cell. Summary of the invention

[0006] The present application aims to solve one of the technical problems in the related art at least to some extent.

[0007] To this end, one purpose of the present application is to propose a boron diffusion furnace for silicon wafers. By introducing a flow balancing plate group with adjustable pores, the flow field distribution can be improved, and the uniform distribution of gas inside the furnace body is achieved, so that the doping gas carried by the gas can be evenly deposited on the surface of the silicon wafer. At the same time, the furnace tube is maintained in a low-pressure state, and the uniform flow of gas further improves the uniformity of the diffusion of silicon wafers at the front, middle and rear positions in the quartz boat, thereby reducing the square resistance of the silicon wafer and improving the electrical efficiency.

[0008] To achieve the above-mentioned objectives, the first embodiment of the present application proposes a boron diffusion furnace for silicon wafers, comprising a furnace body, a furnace door, a bearing assembly and a flow equalizing plate group, wherein a furnace mouth is provided at one end of the furnace body, and the furnace door is arranged at the furnace mouth; the bearing assembly is arranged inside the furnace cavity of the furnace body, and a plurality of silicon wafers with horizontal insertion are arranged on the bearing assembly; the other end of the furnace body is connected to an air inlet pipe, and an air outlet pipe is arranged inside the furnace body, and the air outlet pipe is arranged through the tail of the furnace body; the flow equalizing plate group is arranged between the air inlet pipe and the bearing assembly, and the flow equalizing plate group includes a first flow equalizing plate arranged near the air inlet pipe and a second flow equalizing plate arranged near the bearing assembly, wherein a through hole and a plurality of first through grooves are penetrated on the first flow equalizing plate, and the air outlet pipe is arranged through the through hole; the second flow equalizing plate is rotatably connected to the inner wall of the furnace cavity of the furnace body, a slide groove and a plurality of second through grooves are penetrated on the second flow equalizing plate, and the air outlet pipe is slidably connected to the slide groove.

[0009] The boron diffusion furnace for silicon wafers in the embodiment of the present application can improve the flow field distribution by introducing a flow balancing plate group with adjustable pores, thereby achieving uniform distribution of gas inside the furnace body, so that the doping gas carried by the gas can be uniformly deposited on the surface of the silicon wafer. At the same time, the furnace tube is maintained in a low-pressure state, and the uniform flow of gas further improves the uniformity of diffusion of silicon wafers at the front, middle and rear positions in the quartz boat, thereby reducing the square resistance of the silicon wafer and improving the electrical efficiency.

[0010] In addition, the boron diffusion furnace for silicon wafers proposed in the present application may also have the following additional technical features: In one embodiment of the present application, the supporting assembly includes two silicon carbide paddles, a quartz boat support and a plurality of quartz boats, wherein two first card slots are respectively provided on two opposite end plates of the quartz boat support, and the two first card slots are respectively arranged to fit with two right-angle edges of the corresponding silicon carbide paddles; the plurality of quartz boats are evenly distributed inside the quartz boat support, and a plurality of silicon wafers are horizontally stacked on each of the quartz boats.

[0011] In one embodiment of the present application, the quartz boat includes an upper plate, a lower plate, a plurality of support rods and two mounting plates, wherein the plurality of support rods are respectively arranged between the upper plate and the lower plate; the two mounting plates are symmetrically installed on the support rods, and the upper surface of the side plate of the quartz boat support is provided with a plurality of second card grooves, and the two mounting plates are respectively engaged in the second card grooves of the corresponding side plates.

[0012] In one embodiment of the present application, both the first through groove and the second through groove are arc-shaped grooves, and the first through groove and the second through groove are arranged correspondingly.

[0013] Additional aspects and advantages of the present application will be given in part in the description below, and in part will become apparent from the description below, or will be learned through the practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The above and / or additional aspects and advantages of the present application will become apparent and easily understood from the following description of the embodiments in conjunction with the accompanying drawings, in which: Figure 1 A schematic diagram of the internal structure of a boron diffusion furnace for a silicon wafer according to an embodiment of the present application; Figure 2 This is a schematic structural diagram of a first current equalizing plate in a boron diffusion furnace for silicon wafers according to an embodiment of the present application; Figure 3 This is a schematic structural diagram of a second current balancing plate in a boron diffusion furnace for silicon wafers according to an embodiment of the present application; Figure 4 This is a schematic diagram of the structure of a quartz boat support and a quartz boat in a boron diffusion furnace for silicon wafers according to an embodiment of the present application; Figure 5 This is a schematic diagram of the structure of a quartz boat support in a boron diffusion furnace for silicon wafers according to an embodiment of the present application; Figure 6 This is a schematic diagram of the structure of a quartz boat in a boron diffusion furnace for silicon wafers according to an embodiment of the present application; Figure 7 This is a schematic structural diagram of three types of pass areas in a boron diffusion furnace for a silicon wafer according to an embodiment of the present application; Figure 8 This is a schematic diagram of the structure of vertically inserting a silicon wafer in a boron diffusion furnace of a silicon wafer according to an embodiment of the present application.

[0015] As shown in the figure: 1. furnace body; 2. furnace door; 3. bearing assembly; 4. flow equalizing plate group; 5. air inlet pipe; 6. air outlet pipe; 30. silicon carbide paddle; 31. quartz boat support; 32. quartz boat; 310. first card slot; 311. second card slot; 320. upper plate; 321. lower plate; 322. support rod; 323. mounting plate; 40. first flow equalizing plate; 41. second flow equalizing plate; 400. through hole; 401. first through slot; 410. slide slot; 411. second through slot. DETAILED DESCRIPTION

[0016] Embodiments of the present application are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements with the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present application, and should not be construed as limitations on the present application. On the contrary, the embodiments of the present application include all changes, modifications and equivalents that fall within the spirit and connotation of the appended claims.

[0017] The boron diffusion furnace for silicon wafers according to an embodiment of the present application is described below with reference to the accompanying drawings.

[0018] like Figures 1 to 7 As shown, the boron diffusion furnace for silicon wafers according to the embodiment of the present application may include a furnace body 1 , a furnace door 2 , a bearing assembly 3 and a current equalizing plate group 4 .

[0019] Among them, a furnace mouth is provided at one end of the furnace body 1, a furnace door 2 is arranged at the furnace mouth, a supporting component 3 is arranged inside the furnace cavity of the furnace body 1, and a plurality of silicon wafers inserted in a horizontal manner are arranged on the supporting component 3, an air inlet pipe 5 is connected to the other end of the furnace body 1, an air outlet pipe 6 is arranged inside the furnace body 1, and the air outlet pipe 6 runs through the tail of the furnace body 1.

[0020] In an embodiment of the present application, the furnace body 1 is a horizontal furnace. Since the furnace door 2 is usually heavy, a switch device (not shown in the figure) for opening or closing the furnace door 2 is provided on the furnace door 2, wherein the switch device may include a forward motor, through which the furnace door 2 can be brought into contact with or separated from the furnace body 1.

[0021] Furthermore, the air inlet pipe 5 and the furnace body 1 are located on the same axis, and the air inlet pipe 5 is convenient for introducing oxygen and a boron source into the furnace body 1 , and the air outlet pipe 6 is used to discharge waste gas generated after the boron reaction.

[0022] The flow equalizing plate group 4 is arranged between the air inlet pipe 5 and the supporting component 3, and the flow equalizing plate group 4 may include a first flow equalizing plate 40 arranged near the air inlet pipe 5 and a second flow equalizing plate 41 arranged near the supporting component 3, wherein the first flow equalizing plate 40 is penetrated by a through hole 400 and a plurality of first through grooves 401, the air outlet pipe 6 is penetrated by the through hole 400, the second flow equalizing plate 41 is rotatably connected to the inner wall of the furnace cavity of the furnace body 1, the second flow equalizing plate 41 is penetrated by a slide groove 410 and a plurality of second through grooves 411, and the air outlet pipe 6 is slidably connected to the slide groove 410.

[0023] It should be noted that the first current equalizing plate 40 and the second current equalizing plate 41 are coaxially arranged circular plate structures. The first current equalizing plate 40 is fixedly arranged inside the furnace body 1, and the second current equalizing plate 41 is rotatably arranged inside the furnace body 1, and the first current equalizing plate 40 and the second current equalizing plate 41 are arranged in close proximity. By rotating the second current equalizing plate 41, the size of the overlapping area between the first through groove 401 and the second through groove 411 can be adjusted, thereby adjusting the speed of the gas (oxygen and boron source) passing through the current equalizing plate group 4.

[0024] Furthermore, the thickness of the first current equalizing plate 40 and the second current equalizing plate 41 and the number of the first through slots 401 and the second through slots 411 can be customized according to the actual production requirements, and are not specifically limited in this application.

[0025] In the embodiments of the present application, the diffusion process of crystalline silicon solar cells includes 10 processes: entering the boat, constant temperature and pressure reduction, low-pressure oxidation, low-temperature and low-pressure deposition, heating, high-temperature and low-pressure advancement, pressure increase, normal pressure oxidation, cooling and exiting the boat. The factors affecting the results of the diffusion process are mainly concentrated in the two processes of low-temperature and low-pressure deposition and high-temperature and low-pressure advancement. The temperature, air pressure and gas flow in these two processes affect the size of the diffusion square resistance, the uniformity of the square resistance, and the depth of the junction, thereby affecting the photoelectric conversion efficiency of the solar cell. In the present application, by adding the first current equalizing plate 40 and the second current equalizing plate 41, the gas can be uniformly introduced into the interior of the furnace body 1, which is beneficial to the uniformity of the diffusion, so that the depth of the junction is uniform, thereby improving the electrical efficiency of the battery cell.

[0026] Furthermore, if Figure 2 and Figure 3 As shown, the first through slot 401 and the second through slot 411 are both arc-shaped slots, and the first through slot 401 and the second through slot 411 are correspondingly arranged.

[0027] In an embodiment of the present application, the first through slot 401 and the second through slot 411 are arranged in correspondence, which means that the distance between the first through slot 401 and the center of the first current equalizing plate 40 is the same as the distance between the second through slot 411 and the center of the second current equalizing plate 41. When the second through slot 411 is completely overlapped with the first through slot 401, the area allowed to pass through is the largest. When the second through slot 411 is completely overlapped with the first through slot 401, the first through slot 401 and the second through slot 411 will be blocked by each other, thereby adjusting the passing area.

[0028] Specifically, after oxygen and boron source are introduced into the interior of the furnace body 1 through the air inlet pipe 5, the oxygen and boron source will pass through the first through groove 401 and the second through groove 411 and evenly enter the interior of the furnace body 1, so that the doping gas carried by the gas is evenly deposited on the surface of the silicon wafer. At the same time, the furnace body 1 is in a low-pressure state, and the uniform gas speed can better ensure the uniformity of the diffusion of the silicon wafers in the front, middle and rear of the quartz boat, thereby reducing the square resistance of the silicon wafer and improving the electrical efficiency.

[0029] Furthermore, by rotating the second flow equalizing plate 41 , the size of the overlapping area (the area through which gas is allowed to pass) between the second through slot 411 and the first through slot 401 can be adjusted, thereby adjusting the gas flow rate, which is beneficial to the uniformity of silicon wafer diffusion.

[0030] In order to further clarify the above embodiment, in one embodiment of the present application, Figure 1 , Figure 4 and Figure 5As shown, the supporting assembly 3 may include two silicon carbide paddles 30, a quartz boat support 31 and a plurality of quartz boats 32, wherein two first card slots 310 are respectively provided on two opposite end plates of the quartz boat support 31, and the two first card slots 310 are respectively arranged to fit with two right-angle edges of the corresponding silicon carbide paddles 30, and the plurality of quartz boats 32 are evenly distributed inside the quartz boat support 31, and a plurality of silicon wafers are horizontally stacked on each quartz boat 32.

[0031] In an embodiment of the present application, the silicon carbide paddle 30, which may also be referred to as a silicon carbide cantilever paddle or a silicon carbide cantilever beam, is a silicon carbide ceramic product sintered at a high temperature of about 1800°C and used in the photovoltaic and semiconductor industries. The silicon carbide paddle 30 provides support for the quartz boat support 31 and multiple quartz boats 32, and one end of the silicon carbide paddle 30 is connected to a driving device (not shown in the figure), through which the supporting assembly 3 can be delivered into the interior of the furnace body 1.

[0032] Furthermore, if Figure 6 As shown, the quartz boat 32 may include an upper plate 320, a lower plate 321, a plurality of support rods 322 and two mounting plates 323, wherein the plurality of support rods 322 are respectively arranged between the upper plate 320 and the lower plate 321, and the two mounting plates 323 are symmetrically mounted on the support rods 322, and a plurality of second card grooves 311 are provided on the upper surface of the side plate of the quartz boat support 31, and the two mounting plates 323 are respectively engaged in the second card grooves 311 of the corresponding side plates.

[0033] In the embodiment of the present application, the quartz boat 32 is used to carry the silicon wafer. The quartz boat 32 has excellent thermal stability and can work stably in a high temperature and high pressure environment. The quartz boat 32 usually uses high-purity quartz ore or quartz sand as raw material, and obtains fine quartz powder after grinding, washing and other treatments. Then, the quartz powder is evenly mixed with the required dopant in a certain proportion, and the mixed powder is formed into a blank by high-temperature sintering or melt molding. Finally, the blank is mechanically processed and finely processed to obtain the final quartz boat 32.

[0034] In summary, the boron diffusion furnace for silicon wafers in the embodiment of the present application can improve the flow field distribution by introducing a flow balancing plate group with adjustable pores, thereby achieving uniform distribution of gas inside the furnace body, so that the doping gas carried by the gas can be evenly deposited on the surface of the silicon wafer. At the same time, the furnace tube is maintained in a low-pressure state, and the uniform flow of gas further improves the uniformity of diffusion of silicon wafers at the front, middle and rear positions in the quartz boat, thereby reducing the square resistance of the silicon wafer and improving the electrical efficiency.

[0035] In the description of this specification, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of this application, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0036] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0037] Although the embodiments of the present application have been shown and described above, it can be understood that the above embodiments are exemplary and cannot be understood as limitations on the present application. Ordinary technicians in this field can change, modify, replace and deform the above embodiments within the scope of the present application.

Claims

1. A boron diffusion furnace for silicon wafers, characterized in that: It includes a furnace body, a furnace door, a bearing assembly and a flow plate group, wherein: A furnace opening is provided at one end of the furnace body, and the furnace door is arranged at the furnace opening; The bearing assembly is arranged inside the furnace cavity of the furnace body, and a plurality of silicon wafers inserted in a horizontal manner are arranged on the bearing assembly; The other end of the furnace body is connected to an air inlet pipe, and the interior of the furnace body is provided with an air outlet pipe, and the air outlet pipe runs through the tail of the furnace body; The flow balancing plate group is arranged between the air intake pipe and the bearing assembly, and the flow balancing plate group includes a first flow balancing plate arranged near the air intake pipe and a second flow balancing plate arranged near the bearing assembly, wherein: The first flow equalizing plate is provided with a through hole and a plurality of first through grooves, and the air outlet pipe is provided through the through hole; The second flow equalizing plate is rotatably connected to the inner wall of the furnace chamber of the furnace body, a slide groove and a plurality of second through grooves are penetrated through the second flow equalizing plate, and the air outlet pipe is slidably connected to the slide groove.

2. The boron diffusion furnace for silicon wafers according to claim 1, characterized in that: The bearing assembly includes two silicon carbide paddles, a quartz boat support and a plurality of quartz boats, wherein: Two first card slots are respectively arranged on two opposite end plates of the quartz boat support, and the two first card slots are respectively arranged to fit with two right-angle edges of the corresponding silicon carbide paddle; The plurality of quartz boats are evenly distributed inside the quartz boat holder, and a plurality of silicon wafers are horizontally stacked on each of the quartz boats.

3. The boron diffusion furnace for silicon wafers according to claim 2, characterized in that: The quartz boat comprises an upper plate, a lower plate, a plurality of support rods and two mounting plates, wherein: A plurality of support rods are respectively arranged between the upper plate and the lower plate; The two mounting plates are symmetrically mounted on the support rod, a plurality of second slots are provided on the upper surface of the side plate of the quartz boat support, and the two mounting plates are respectively engaged in the second slots of the corresponding side plate.

4. The boron diffusion furnace for silicon wafers according to claim 1, characterized in that: The first through slot and the second through slot are both arc-shaped slots, and the first through slot and the second through slot are correspondingly arranged.

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