Preparation method and equipment of battery emitter
By depositing multiple borosilicate glass layers in a boron-oxygen integrated machine and introducing protective gas during the cooling process, combined with the formation of a boron oxide layer, the problem of the silicon wafer edge temperature being higher than the center was solved, achieving uniform distribution of boron impurities and improving battery performance.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- LAPLACE RENEWABLE ENERGY TECH CO LTD
- Filing Date
- 2025-12-31
- Publication Date
- 2026-04-17
AI Technical Summary
In boron-oxygen integrated circuits, the temperature at the edge of the silicon wafer is higher than that at the center, resulting in uneven distribution of boron impurities, which affects battery performance, including low PL brightness, short minority carrier lifetime, and high dark saturation current, thereby reducing battery efficiency.
By depositing multiple borosilicate glass layers under heating conditions and introducing a protective gas during continuous cooling, boron atoms are pushed into the silicon wafer. Combined with the formation of a boron oxide layer, the uniformity of boron impurity distribution is controlled, and oxidation reactions on the silicon wafer surface are avoided.
It improves PL brightness and minority carrier lifetime, reduces dark saturation current, improves open-circuit voltage and fill factor, and enhances battery efficiency.
Smart Images
Figure CN121888730A_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of semiconductor or photovoltaic material processing, specifically to a method and apparatus for preparing a battery emitter. Background Technology
[0002] The boron-oxygen integrated process combines the boron diffusion and post-oxidation processes of TopCon solar cells. By eliminating the front-side laser selective emitter (SE) process and merging the boron diffusion and post-oxidation processes into a single step, it reduces heating and cooling times and process turnaround time, significantly increasing production capacity. This boron-oxygen integrated process has become the mainstream technology for the fabrication of front-side emitters in TopCon solar cells.
[0003] In the boron diffusion process, a borosilicate glass layer is first deposited on the surface of the silicon wafer, and then boron atoms in the borosilicate glass layer are pushed into the silicon wafer to form the emitter. Because the heating wire of the boron-oxygen integrated furnace is arranged around the outer wall of the furnace tube, under the continuous heat output of the heating wire, some heat is first transferred to the edge of the silicon wafer, and then diffuses from the edge to the center. Therefore, the temperature at the edge of the silicon wafer is consistently higher than the temperature at the center, causing boron atoms to push into the edge of the silicon wafer more quickly, resulting in more boron impurities being doped at the edge. Due to the significant difference in boron impurity distribution between the center and edge of the silicon wafer, a noticeable darkening of the edges appears in the photoluminescence (PL) image, resulting in lower PL brightness, shorter minority carrier lifetime, and higher dark saturation current (J0). This also significantly affects cell performance parameters such as open-circuit voltage and fill factor, leading to lower cell efficiency. Summary of the Invention
[0004] To address the aforementioned technical problems, this application is proposed. Embodiments of this application provide a method and apparatus for preparing a battery emitter.
[0005] In a first aspect, one embodiment of this application provides a method for preparing a battery emitter, used to prepare an emitter on an N-type silicon wafer, wherein the N-type silicon wafer is placed in a process chamber of a process cavity, the method comprising: depositing a borosilicate glass layer on one side of the N-type silicon wafer in a first direction under heating conditions; and introducing a protective gas into the process chamber under continuous cooling conditions, so that boron atoms in the borosilicate glass layer are pushed into the portion of the N-type silicon wafer near the borosilicate glass layer, so that the portion of the N-type silicon wafer near the borosilicate glass layer becomes the emitter of the N-type silicon wafer, wherein the protective gas does not react with the N-type silicon wafer and the borosilicate glass layer.
[0006] In some embodiments, the borosilicate glass layer includes a plurality of sub-borosilicate glass layers; wherein, under heating conditions, depositing a borosilicate glass layer on one side of an N-type silicon wafer in a first direction includes: under heating conditions, sequentially depositing a plurality of sub-borosilicate glass layers on one side of an N-type silicon wafer in a first direction, wherein, except for the first deposition of a sub-borosilicate glass layer, the first deposition temperature of each deposition of a sub-borosilicate glass layer is higher than the first deposition temperature of the previous deposition of a sub-borosilicate glass layer.
[0007] In some embodiments, except for the first deposition of the sub-borosilicate glass layer, the first deposition temperature of each subsequent deposition of the sub-borosilicate glass layer is higher than the first deposition temperature of the previous deposition of the sub-borosilicate glass layer by a preset temperature rise temperature, which is in the range of 10 °C to 15 °C.
[0008] In some embodiments, except for the last deposition of a sub-borosilicate glass layer, the heating rate ranges from 3 °C / min to 4.5 °C / min when increasing the preset heating temperature after each deposition of a sub-borosilicate glass layer.
[0009] In some embodiments, after each deposition of a borosilicate glass layer, the method further includes purging and evacuating the process chamber.
[0010] In some embodiments, under heating conditions, a plurality of sub-borosilicate glass layers are sequentially deposited on one side of an N-type silicon wafer in a first direction, including: under heating conditions, introducing boron trichloride, oxygen, and nitrogen into a process chamber, and sequentially depositing three sub-borosilicate glass layers on one side of an N-type silicon wafer in a first direction; wherein the flow rate of boron trichloride is 120-180 sccm, the flow rate of oxygen is 400-600 sccm, the flow rate of nitrogen is 2500-4000 sccm, the pressure is 100-150 mBar, and the process time for each sub-borosilicate glass layer deposition is 140 s.
[0011] In some embodiments, after a protective gas is introduced into the process chamber under continuous cooling conditions to push boron atoms in the borosilicate glass layer into the portion of the N-type silicon wafer near the borosilicate glass layer, the method further includes: introducing oxygen into the process chamber to form a precipitated boron oxide layer on the side of the borosilicate glass layer away from the N-type silicon wafer.
[0012] In some embodiments, the boron oxide layer includes three sub-boron oxide layers; wherein, introducing oxygen into the process chamber to form a precipitated boron oxide layer on the side of the borosilicate glass layer away from the N-type silicon wafer includes: introducing oxygen into the process chamber; forming a first sub-boron oxide layer on the side of the borosilicate glass layer away from the N-type silicon wafer under continuous heating conditions; forming a second sub-boron oxide layer on the side of the first sub-boron oxide layer away from the N-type silicon wafer under isothermal conditions; and forming a third sub-boron oxide layer on the side of the second sub-boron oxide layer away from the N-type silicon wafer under continuous cooling conditions.
[0013] In some embodiments, before depositing a borosilicate glass layer on one side of an N-type silicon wafer in a first direction under heating conditions, the method further includes: introducing oxygen into a process chamber at a preset calcination temperature, and / or introducing boron trichloride and oxygen into the process chamber at a preset saturation temperature; placing a test silicon wafer into the process chamber; depositing a test borosilicate glass layer on one side of the test silicon wafer in a first direction under heating conditions; and introducing a protective gas into the process chamber under continuous cooling conditions to push boron atoms in the test borosilicate glass layer into the portion of the test silicon wafer near the test borosilicate glass layer, so that the portion of the test silicon wafer near the test borosilicate glass layer becomes the emitter of the test silicon wafer.
[0014] Secondly, one embodiment of this application provides a battery emitter fabrication apparatus, comprising: a process chamber having a process cavity, wherein an N-type silicon wafer is placed in the process cavity; and a heating assembly configured to heat the process cavity; wherein the heating assembly is capable of heating the process cavity to a heating condition to deposit a borosilicate glass layer on one side of the N-type silicon wafer in a first direction, and, when the heating assembly stops heating, the process cavity is capable of continuously cooling down, and the process cavity is capable of receiving a protective gas to push boron atoms in the borosilicate glass layer into the portion of the N-type silicon wafer near the borosilicate glass layer, so that the portion of the N-type silicon wafer near the borosilicate glass layer becomes the emitter of the N-type silicon wafer, and the protective gas does not react with the N-type silicon wafer and the borosilicate glass layer.
[0015] The method and equipment for preparing the battery emitter proposed in this application involve heating the N-type silicon wafer during the deposition of the borosilicate glass layer. This results in the edge temperature of the N-type silicon wafer being higher than the center temperature. The boron push-junction process is then performed under continuous cooling conditions. Since some heat from the center of the N-type silicon wafer needs to be transferred outwards through the edge, the cooling rate at the edge is faster than at the center. This reduces the temperature difference between the edge and center, making the rate at which boron atoms push to the edge and center of the N-type silicon wafer more similar. This reduces the difference in boron impurity distribution between the edge and center, resulting in a more uniform junction depth. Consequently, the darkened areas at the edges of the photoluminescence (PL) image are reduced, improving PL brightness and minority carrier lifetime, reducing dark saturation current, and improving battery performance parameters such as open-circuit voltage and fill factor, thus increasing battery efficiency. In particular, when depositing the borosilicate glass layer using boron trichloride, the reactivity of boron trichloride is much greater than that of boron tribromide. It readily undergoes homogeneous nucleation in the gas phase, but remains on the surface of the silicon wafer. In subsequent processes, the nuclei tend to propagate locally, leading to uneven boron diffusion. By introducing a protective gas into the process chamber, the protective gas can remove the crystal nuclei generated by homogeneous nucleation, reducing the probability of excessive local doping on the surface of the N-type silicon wafer. Furthermore, the protective gas does not react with the N-type silicon wafer and the borosilicate glass layer, thus pausing the growth of the borosilicate glass during the subsequent cooling process. At this point, no additional boron atoms are supplied to the N-type silicon wafer; instead, boron atoms diffuse into the wafer interior through the self-diffusion of boron atoms already deposited on the N-type silicon wafer, thereby precisely controlling the junction depth. Attached Figure Description
[0016] The above and other objects, features, and advantages of this application will become more apparent from the more detailed description of the embodiments of this application in conjunction with the accompanying drawings. The drawings are provided to further illustrate the embodiments of this application and form part of the specification. They are used together with the embodiments of this application to explain this application and do not constitute a limitation thereof. In the drawings, the same reference numerals generally represent the same components or steps.
[0017] Figure 1 The diagram shown is a flowchart illustrating a method for preparing a battery emitter according to an exemplary embodiment of this application.
[0018] Figure 2 The diagram shown is a flowchart illustrating a method for depositing a borosilicate glass layer according to an exemplary embodiment of this application.
[0019] Figure 3 The diagram shown is a schematic flowchart of a processing method after each deposition of a borosilicate glass layer provided in an exemplary embodiment of this application.
[0020] Figure 4The diagram shown is a flowchart illustrating a specific method for depositing a borosilicate glass layer according to an exemplary embodiment of this application.
[0021] Figure 5 The diagram shown is a flowchart illustrating a method for forming a boron oxide layer according to an exemplary embodiment of this application.
[0022] Figure 6 The diagram shown is a flowchart illustrating a method for forming a sub-boron oxide layer according to an exemplary embodiment of this application.
[0023] Figure 7 The diagram shown is a flowchart illustrating a pretreatment method prior to the boron diffusion process provided in an exemplary embodiment of this application.
[0024] Figure 8 The diagram shown is a schematic diagram of the structure of a battery emitter fabrication apparatus provided in an exemplary embodiment of this application.
[0025] Figure 9 The diagram shown is a schematic diagram of the structure of an N-type silicon wafer after the preparation of a borosilicate glass layer and a boron oxide layer, according to an exemplary embodiment of this application.
[0026] Figure 10 The image shown is a PL detection image of multiple N-type silicon wafers fabricated using a traditional battery emitter fabrication method.
[0027] Figure 11 The image shown is a PL detection image of multiple N-type silicon wafers prepared by a specific method for preparing a battery emitter according to an exemplary embodiment of this application.
[0028] Figure 12 The image shown is a PL detection image of multiple N-type silicon wafers prepared by another specific method for preparing a battery emitter according to an exemplary embodiment of this application.
[0029] Figure label: 800. Equipment for preparing the emitter of a battery; 801. Process chamber; 8011. Process room; 802. Heating assembly; 900. N-type silicon wafer; 901. Borosilicate glass layer; 9011. First sub-borosilicate glass layer; 9012. Second sub-borosilicate glass layer; 9013. Third sub-borosilicate glass layer; 902. Boron oxide layer; 9021. First sub-boron oxide layer; 9022. Second sub-boron oxide layer; 9023. Third sub-boron oxide layer. Detailed Implementation
[0030] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.
[0031] Figure 1 The diagram shown is a schematic flowchart of a method for preparing a battery emitter according to an exemplary embodiment of this application. Figure 9 The diagram shown is a schematic diagram of the structure of an N-type silicon wafer after the preparation of a borosilicate glass layer and a boron oxide layer, according to an exemplary embodiment of this application.
[0032] like Figure 1 and Figure 9 As shown, this application embodiment provides a method for preparing a battery emitter, used to prepare an emitter on an N-type silicon wafer 900. The N-type silicon wafer 900 is placed in the process chamber 8011 of the process cavity 801. The method for preparing the battery emitter includes the following steps 101 to 102.
[0033] Step 101: Under heating conditions, deposit a borosilicate glass layer on one side of the N-type silicon wafer in the first direction.
[0034] For example, a borosilicate glass layer 901 may be deposited on one side of an N-type silicon wafer in a first direction at a fixed temperature, such as at 855 °C; or, multiple sub-borosilicate glass layers may be deposited in stages at multiple different temperatures, the multiple sub-borosilicate glass layers forming a complete borosilicate glass layer 901, as detailed below.
[0035] For example, gases such as boron trichloride, oxygen, and nitrogen can be introduced into the process chamber 8011 to deposit a borosilicate glass layer 901 on one side of the N-type silicon wafer 900 in the first direction.
[0036] Step 102: Under continuous cooling conditions, a protective gas is introduced into the process chamber to push boron atoms in the borosilicate glass layer into the part of the N-type silicon wafer near the borosilicate glass layer, so that the part of the N-type silicon wafer near the borosilicate glass layer becomes the emitter of the N-type silicon wafer.
[0037] The protective gas does not react with the N-type silicon wafer 900 and the borosilicate glass layer 901. For example, the protective gas can be nitrogen or an inert gas (such as argon).
[0038] For example, the flow rate of nitrogen is 3000 sccm.
[0039] For example, the continuous cooling condition can be achieved by stopping heating and allowing the N-type silicon wafer 900 to cool down naturally.
[0040] In the above embodiments, since the N-type silicon wafer 900 undergoes a heating process during the deposition of the borosilicate glass layer 901, the edge temperature of the N-type silicon wafer 900 is higher than the center temperature. At this time, the boron push-junction process is carried out under continuous cooling conditions. Since some of the heat in the center of the N-type silicon wafer 900 needs to be transferred outward through the edge of the N-type silicon wafer 900, the cooling rate of the edge of the N-type silicon wafer 900 is faster than that of the center. This reduces the temperature difference between the edge and center of the N-type silicon wafer 900, making the speed at which boron atoms push to the edge and center of the N-type silicon wafer more similar. This reduces the difference in boron impurity distribution between the edge and center of the N-type silicon wafer, making the junction depth more uniform. As a result, the darkened part at the edge of the PL image is reduced, the PL brightness and minority carrier lifetime are improved, the dark saturation current is reduced, and the battery performance parameters such as open circuit voltage and fill factor are improved, thereby increasing the battery efficiency. In addition, by introducing a protective gas into the process chamber 8011, the surface of the N-type silicon wafer 900 will not undergo oxidation reaction or will undergo very little oxidation reaction, thereby pausing the growth of borosilicate glass on the surface of the N-type silicon wafer 900. At this time, the protective gas no longer provides additional boron atoms to the N-type silicon wafer 900. Boron atoms are doped into the interior of the silicon wafer through the self-diffusion (lattice diffusion) of the boron atoms that have been deposited on the N-type silicon wafer 900, thereby precisely controlling the junction depth.
[0041] Figure 2 The diagram shown is a flowchart illustrating a method for depositing a borosilicate glass layer according to an exemplary embodiment of this application.
[0042] In some embodiments, the borosilicate glass layer 901 includes a plurality of sub-borosilicate glass layers. Specifically, in step 101, i.e., when depositing the borosilicate glass layer 901 on one side of the N-type silicon wafer 900 in the first direction under heating conditions, as... Figure 2 and Figure 9 As shown, the following steps 201 can be performed.
[0043] Step 201: Under heating conditions, a plurality of sub-borosilicate glass layers are sequentially deposited on one side of the N-type silicon wafer in the first direction.
[0044] Except for the first deposition of the borosilicate glass layer, the first deposition temperature of each deposition of the borosilicate glass layer is higher than the first deposition temperature of the previous deposition of the borosilicate glass layer.
[0045] For example, the number of borosilicate glass layers may be two, three, or four.
[0046] For example, if the number of sub-borosilicate glass layers is 3, a first sub-borosilicate glass layer 9011 can be deposited on one side of the N-type silicon wafer 900 in the first direction at a first preset temperature. Then, the first preset temperature is raised to a second preset temperature. At the second preset temperature, a second sub-borosilicate glass layer 9012 is deposited on the side of the first sub-borosilicate glass layer 9011 away from the N-type silicon wafer 900. Finally, the second preset temperature is raised to a third preset temperature, and a third sub-borosilicate glass layer 9013 is deposited on the side of the second sub-borosilicate glass layer 9012 away from the N-type silicon wafer 900.
[0047] It is understandable that the continuous cooling condition in step 102 can be based on the initial deposition temperature during the final deposition of the borosilicate glass layer, such as continuously cooling from 885 ℃ to 860 ℃. In the above embodiments, since there is a time for isothermal deposition of each sub-borosilicate glass layer during deposition, as in the previous example, after the temperature rises to the first preset temperature, the N-type silicon wafer 900 is heated at the first preset temperature for a period of time; after the temperature rises to the second preset temperature, the N-type silicon wafer 900 is heated at the second preset temperature for a period of time; and after the temperature rises to the third preset temperature, the N-type silicon wafer 900 is heated at the third preset temperature for a period of time. Therefore, compared with the traditional method of heating the N-type silicon wafer 900 to a high temperature at once, resulting in a large temperature difference between the edge and center of the N-type silicon wafer 900, this embodiment provides time to reduce the temperature difference between the edge and center of the N-type silicon wafer 900 during each isothermal heating process, thereby reducing the deposition rate difference of the sub-borosilicate glass layers between the edge and center of the N-type silicon wafer 900, making the thickness of the borosilicate glass layer 901 more uniform. In the subsequent boron push-bonding step (step 102), boron atoms can be uniformly supplied during the diffusion process, thereby improving the uniformity of the sheet resistance of the solar cell. Furthermore, at the process temperature in step 201, boron atoms can be initially pushed into the interior of the N-type silicon wafer 900. Specifically, except for the deposition of the first sub-borosilicate glass layer 9011, boron atoms can be pushed into the interior of the N-type silicon wafer 900 in small quantities each time a sub-borosilicate glass layer is deposited.
[0048] In some embodiments, except for the first deposition of the sub-borosilicate glass layer, the first deposition temperature of each subsequent deposition of the sub-borosilicate glass layer is higher than the first deposition temperature of the previous deposition of the sub-borosilicate glass layer by a preset temperature rise temperature, which is in the range of 10 °C to 15 °C.
[0049] For example, the first deposition temperature for the first deposition of the borosilicate glass layer is in the range of 800 ℃ to 880 ℃, such as 800 ℃, 820 ℃, 840 ℃, 860 ℃ or 880 ℃.
[0050] For example, the preset heating temperature is 10 ℃, 11 ℃, 12 ℃, 13 ℃, 14 ℃ or 15 ℃.
[0051] In the above embodiments, by gradually increasing the first deposition temperature when depositing each layer of borosilicate glass with a smaller preset heating temperature, the N-type silicon wafer 900 can be heated slowly, reducing the temperature difference between the edge and center of the N-type silicon wafer 900, thereby obtaining a borosilicate glass layer 901 with uniform thickness.
[0052] In some embodiments, except for the last deposition of a sub-borosilicate glass layer, the heating rate ranges from 3 °C / min to 4.5 °C / min when increasing the preset heating temperature after each deposition of a sub-borosilicate glass layer.
[0053] For example, the heating rate is 3 °C / min, 3.5 °C / min, 4 °C / min, or 4.5 °C / min. In the above embodiments, by increasing the temperature of the N-type silicon wafer 900 at a slower heating rate, the temperature difference between the edge and center of the N-type silicon wafer 900 can be reduced, thereby obtaining a borosilicate glass layer 901 with uniform thickness.
[0054] Figure 3 The diagram shown is a schematic flowchart of a processing method after each deposition of a borosilicate glass layer provided in an exemplary embodiment of this application.
[0055] In some embodiments, after each deposition of a borosilicate glass layer, such as Figure 3 As shown, the following steps 301 can also be performed.
[0056] Step 301: Purge and evacuate the process chamber.
[0057] For example, if the N-type silicon wafer 900 is placed in a quartz boat, and the quartz boat is supported by a paddle structure extending into the process chamber 8011, then when purging the process chamber 8011, the inner wall of the process chamber, the paddle structure, and the quartz boat can all be purged.
[0058] If a complete borosilicate glass layer 901 is continuously deposited under high-temperature conditions, the boron atom concentration inside the process chamber 8011 will gradually increase. Since the edge temperature of the N-type silicon wafer 900 is higher than the center temperature, excessively thick borosilicate glass will be deposited at the edge. In the above embodiment, purging and evacuating the process chamber 8011 after each deposition of the sub-borosilicate glass layer can reduce the boron concentration inside the process chamber 8011, thereby reducing the deposition rate of the sub-borosilicate glass layer, reducing the difference in the deposition rate of sub-borosilicate glass between the edge and center of the N-type silicon wafer 900, and making the thickness of the deposited sub-borosilicate glass layer more uniform.
[0059] Figure 4The diagram shown is a flowchart illustrating a specific method for depositing a borosilicate glass layer according to an exemplary embodiment of this application.
[0060] In some embodiments, during step 201, i.e., when multiple sub-borosilicate glass layers are sequentially deposited on one side of the N-type silicon wafer 900 in the first direction under heating conditions, such as Figure 4 and Figure 9 As shown, the following steps 401 can be performed.
[0061] Step 401: Under heating conditions, boron trichloride, oxygen and nitrogen are introduced into the process chamber, and three sub-borosilicate glass layers are sequentially deposited on one side of the N-type silicon wafer in the first direction.
[0062] In some embodiments, during step 401, the flow rate of boron trichloride is 120-180 sccm, the flow rate of oxygen is 400-600 sccm, the flow rate of nitrogen is 2500-4000 sccm, the pressure is 100-150 mBar, and the process time for each deposition of a borosilicate glass layer is 140 s.
[0063] In the above embodiments, by reducing the oxygen flow rate and increasing the boron trichloride concentration, the deposition speed can be increased while maintaining the uniformity of the silicon wafer deposition. Furthermore, reducing the oxygen flow rate lowers the overall gas flow rate, making the gas within the process chamber more stable and less prone to localized turbulence, which could lead to differences in deposition thickness between turbulent areas and other areas. Controlling the oxygen flow rate to 3-4 times that of boron trichloride ensures a stable and saturated reaction for the thermal decomposition and oxidative deposition of boron trichloride to form borosilicate glass, thus helping to control the uniformity of boron doping on the silicon wafer surface.
[0064] Figure 5 The diagram shown is a flowchart illustrating a method for forming a boron oxide layer according to an exemplary embodiment of this application.
[0065] In some embodiments, after step 102, i.e., under continuous cooling conditions, a protective gas is introduced into the process chamber 8011 to push boron atoms in the borosilicate glass layer 901 into the portion of the N-type silicon wafer 900 near the borosilicate glass layer 901, such as... Figure 5 As shown, the following steps 501 can also be performed.
[0066] Step 501: Introduce oxygen into the process chamber to form a boron oxide layer on the side of the borosilicate glass layer away from the N-type silicon wafer.
[0067] For example, the thickness of the boron oxide layer 902 is 100 nm.
[0068] For example, in an oxygen atmosphere, the temperature can be raised to 1040 °C to cause a borosilicate glass layer 901 to precipitate a boron oxide layer 902 on the side away from the N-type silicon wafer 900.
[0069] In the above embodiments, by raising the temperature, a thin layer of molten BSG appears on the surface of the borosilicate glass layer 901. Boron in the molten BSG combines with external oxygen to generate boron oxide, which gradually grows to form a boron oxide layer 902. During this process, as boron atoms react with oxygen, the thickness of the boron oxide layer 902 gradually increases, and the boron atom concentration in the borosilicate glass layer 901 decreases. The borosilicate glass layer 901 absorbs boron atoms from the N-type silicon wafer 900. When the borosilicate glass layer 901 absorbs boron atoms from the N-type silicon wafer 900, it starts absorbing from the high-concentration region (the boron atoms in this region can also be called boron impurities), thereby further distributing the boron atoms doped in the N-type silicon wafer 900, making the boron doping within the N-type silicon wafer 900 more uniform.
[0070] Step 501 can optimize the impurity distribution, significantly reduce the concentration of boron atoms in the junction region, and also have a slight boron atom pushing effect.
[0071] Figure 6 The diagram shown is a flowchart illustrating a method for forming a sub-boron oxide layer according to an exemplary embodiment of this application.
[0072] In some embodiments, the boron oxide layer 902 comprises three sub-boron oxide layers; wherein, in step 501, i.e., when oxygen is introduced into the process chamber 8011 and the boron oxide layer 902 is formed on the side of the borosilicate glass layer 901 away from the N-type silicon wafer 900, as... Figure 6 and Figure 9 As shown, the following steps 601 to 604 can be performed, wherein step 602 is referred to as oxidation treatment after heating, step 603 is referred to as oxidation treatment after constant temperature, and step 604 is referred to as oxidation treatment after cooling.
[0073] Step 601: Introduce oxygen into the process chamber.
[0074] Step 602: Under continuous heating conditions, a first sub-boron oxide layer is formed on the side of the borosilicate glass layer away from the N-type silicon wafer.
[0075] Specifically, step 602 can be based on the temperature after step 102 is completed, and the temperature can be continuously increased to a fourth preset temperature (e.g., from 860 ℃ to 1040 ℃), and a first sub-boron oxide layer 9021 is formed during the continuous heating process.
[0076] For example, the oxygen flow rate in step 602 is 20,000 sccm.
[0077] Step 603: Under constant temperature conditions, a second sub-boron oxide layer is formed on the side of the first sub-boron oxide layer away from the N-type silicon wafer.
[0078] Specifically, step 603 can maintain a fourth preset temperature (e.g., 1040 °C) to form the second sub-boron oxide layer 9022 at a constant temperature.
[0079] For example, the oxygen flow rate in step 603 is 25,000 sccm.
[0080] Step 604: Under continuous cooling conditions, a third sub-boron oxide layer is formed on the side of the second sub-boron oxide layer away from the N-type silicon wafer.
[0081] Specifically, step 604 may involve continuously cooling from a fourth preset temperature to a fifth preset temperature (e.g., continuously cooling from 1040 ℃ to 850 ℃), and forming a third sub-boron oxide layer 9023 during the continuous cooling process.
[0082] For example, the oxygen flow rate in step 604 is 20,000 sccm.
[0083] In the above embodiments, when forming the borosilicate layer under heating and constant temperature conditions, the surface of the borosilicate glass layer 901 can be partially melted at high temperature, which facilitates the transfer of boron atoms, especially the reaction and combination of boron atoms and oxygen molecules. Maintaining the partial melting of the surface of the borosilicate glass layer 901 under constant temperature conditions also helps to maintain the diffusion activity of boron atoms.
[0084] Figure 7 The diagram shown is a flowchart illustrating a pretreatment method prior to the boron diffusion process provided in an exemplary embodiment of this application.
[0085] In some embodiments, prior to step 101, i.e., before depositing a borosilicate glass layer 901 on one side of the N-type silicon wafer 900 in the first direction under heating conditions, such as Figure 7 As shown, steps 701 to 704 can also be performed.
[0086] Step 701: At a preset calcination temperature, oxygen is introduced into the process chamber, and / or, at a preset saturation temperature, boron trichloride and oxygen are introduced into the process chamber.
[0087] Specifically, by introducing oxygen into the process chamber 8011 at a preset calcination temperature (e.g., above 1000 °C) (hereinafter referred to as the calcination process), carbon-related impurities within the process chamber 8011 can be removed. By introducing a low flow rate of boron trichloride and oxygen into the process chamber 8011 at a preset saturation temperature (hereinafter referred to as the saturation process), boron atoms can be saturated and adsorbed onto the inner wall of the process chamber 801 and the surfaces of components such as the paddle structure. This prevents boron atoms from failing to effectively deposit onto the surface of the N-type silicon wafer 900 during step 101. Simultaneously, the chlorine gas generated from the decomposition of boron trichloride has a strong and effective binding and removal effect on metal ions within the process chamber 8011, preventing contamination of the N-type silicon wafer 900.
[0088] For example, for a process chamber 801 that has not been used for a long time (e.g., more than 2 hours), or for a process chamber 801 that has not undergone the battery emitter preparation method in the aforementioned embodiments, multiple rounds (e.g., 3 rounds) of calcination process can be performed, and multiple rounds (e.g., 5 rounds) of saturation process can be performed after the calcination process; for a process chamber 801 that has not been used for a short time (e.g., 2 hours or less), only one round of saturation process can be performed.
[0089] Step 702: Place the test silicon wafer into the process chamber.
[0090] Step 703: Under heating conditions, deposit a test borosilicate glass layer on one side of the test silicon wafer in the first direction.
[0091] The method for depositing the borosilicate glass layer in step 703 is the same as the method for depositing the borosilicate glass layer 901 on the N-type silicon wafer 900 in the aforementioned embodiment, and can be referred to the aforementioned embodiment.
[0092] Step 704: Under continuous cooling conditions, a protective gas is introduced into the process chamber to push boron atoms in the test borosilicate glass layer into the part of the test silicon wafer near the test borosilicate glass layer, so that the part of the test silicon wafer near the test borosilicate glass layer becomes the emitter of the test silicon wafer.
[0093] The boron atom push-bonding method used in step 704 is the same as the boron atom push-bonding method for the N-type silicon wafer 900 in the aforementioned embodiments, and can be referred to the aforementioned embodiments.
[0094] Specifically, through step 704, before mass-producing emitters on N-type silicon wafers 900, emitter fabrication can be performed on test silicon wafers. By testing relevant data (such as PL images) of the test silicon wafers, it can be determined whether the current state of the process chamber 801 will affect the fabrication of the battery emitters.
[0095] In some embodiments, since the quartz boat can absorb moisture in the air, it can be placed in the process chamber 8011 or other furnace tubes for drying before step 702 to avoid moisture interfering with the testing of the silicon wafer.
[0096] In summary, the traditional methods for preparing battery emitters and the specific methods for preparing the two battery emitters provided in this application are shown in Tables 1 to 3 below. The test results of the N-type silicon wafer 900 prepared according to these three battery emitter preparation methods are shown in Tables 4 to 6 below. The difference between Table 1 and Table 2 is that in Table 1, a complete borosilicate glass layer 901 is directly deposited at 855 °C, and boron atom push-bonding is performed under isothermal conditions of 900 °C. In Table 2, a first sub-borosilicate glass layer 9011 is deposited at 855 °C, a second sub-borosilicate glass layer 9012 is deposited at 870 °C, and a third sub-borosilicate glass layer 9013 is deposited at 885 °C, and boron push-bonding is performed under cooling conditions of 885 °C to 860 °C. The difference between Table 2 and Table 3 is that in Table 2, the oxygen flow rate during the deposition of each sub-borosilicate glass layer is 520 sccm, while in Table 3, the oxygen flow rates during the deposition of the first sub-borosilicate glass layer 9011, the second sub-borosilicate glass layer 9012, and the third sub-borosilicate glass layer 9013 are 2000 sccm, 3000 sccm, and 4000 sccm, respectively. In Tables 4-6, Implied_Voc_ refers to the open-circuit voltage, Implied_FF_ refers to the fill factor, Lifetime_ refers to the minority carrier lifetime, and J0 / 2_ refers to the dark saturation current.
[0097] Table 1. Parameters of Traditional Battery Emitter Fabrication Methods Table 2. Parameter table of a specific preparation method of a battery emitter provided in the embodiments of this application. Table 3. Parameter table of another specific preparation method of battery emitter provided in the embodiments of this application. Table 4 Test results of traditional battery emitter fabrication methods Table 5. Test results of a specific preparation method for a battery emitter provided in the embodiments of this application. Table 6 Test Results of Another Specific Preparation Method of Battery Emitter Provided in the Embodiments of this Application Figure 10The image shown is a PL (Photonic Photovoltaic Detection) image of multiple N-type silicon wafers fabricated using a traditional cell emitter fabrication method. Figure 11 The image shown is a PL detection image of multiple N-type silicon wafers prepared by a specific method for preparing a battery emitter according to an exemplary embodiment of this application. Figure 12 The image shown is a PL detection image of multiple N-type silicon wafers prepared by another specific method for preparing a battery emitter according to an exemplary embodiment of this application. According to... Figures 10-12 It can be seen that the PL detection images of the N-type silicon wafers prepared according to the two specific preparation methods of the battery emitter provided in the embodiments of this application have higher brightness and less blackened edges.
[0098] According to Tables 1-6 and Figures 10-12 It can be seen that, compared to directly forming a complete borosilicate glass layer 901 at a fixed temperature and performing boron push-junction under isothermal conditions, the present application embodiment prepares three sub-borosilicate glass layers at three successively increasing temperatures and performs boron push-junction under cooling conditions. This can improve the open-circuit voltage, fill factor, minority carrier lifetime, and PL brightness, reduce the dark saturation current, and show no significant difference in intra-sheet resistance and inter-sheet uniformity compared to traditional battery emitter preparation methods. Furthermore, the finished battery cell exhibits superior electrical performance and efficiency compared to cells prepared using traditional battery emitter preparation methods. Therefore, the battery emitter preparation method provided in this application embodiment can significantly improve the passivation effect, thereby greatly improving battery efficiency and has broad application prospects. Comparing the processes in Tables 1 and 3, and the corresponding test results in Tables 4 and 6, it can be seen that controlling the oxygen flow rate and boron trichloride flow rate ratio at a lower level is actually beneficial to the uniformity of boron atom doping.
[0099] Figure 8 The diagram shown is a schematic diagram of the structure of a battery emitter fabrication apparatus provided in an exemplary embodiment of this application.
[0100] Based on the same concept, such as Figure 8As shown in the illustration, this application also provides a battery emitter fabrication apparatus 800, which includes a process chamber 801 and a heating assembly 802. The process chamber 801 has a process cavity 8011, in which an N-type silicon wafer 900 is placed. The heating assembly 802 is configured to heat the process cavity 8011. The heating component 802 can heat the process chamber 8011 to the heating condition to deposit a borosilicate glass layer 901 on one side of the N-type silicon wafer 900 in the first direction. When the heating component 802 stops heating, the process chamber 8011 can continuously cool down and receive a protective gas, which pushes boron atoms in the borosilicate glass layer 901 into the portion of the N-type silicon wafer 900 near the borosilicate glass layer 901, so that the portion of the N-type silicon wafer 900 near the borosilicate glass layer 901 becomes the emitter of the N-type silicon wafer 900. The protective gas does not react with the N-type silicon wafer 900 and the borosilicate glass layer 901.
[0101] For example, the heating assembly 802 includes a heating wire.
[0102] For example, such as Figure 8 As shown, the heating assembly 802 is arranged around the process cavity 801.
[0103] Since the battery emitter preparation equipment 800 is the implementation equipment corresponding to the battery emitter preparation method, the battery emitter preparation equipment 800 includes all the technical features and technical effects of the battery emitter preparation method, and will not be repeated here.
[0104] The basic principles of this application have been described above with reference to specific embodiments. However, it should be noted that the advantages, benefits, and effects mentioned in this application are merely examples and not limitations, and should not be considered as essential features of each embodiment of this application. Furthermore, the specific details disclosed above are for illustrative and facilitative purposes only, and are not limitations. These details do not limit the application to the necessity of employing the aforementioned specific details for implementation.
[0105] The block diagrams of devices, apparatuses, devices, and systems involved in this application are merely illustrative examples and are not intended to require or imply that they must be connected, arranged, or configured in the manner shown in the block diagrams. As those skilled in the art will recognize, these devices, apparatuses, devices, and systems can be connected, arranged, and configured in any manner. Words such as “comprising,” “including,” “having,” etc., are open-ended terms meaning “including but not limited to,” and are used interchangeably with them. The terms “or” and “and” as used herein refer to the terms “and / or,” and are used interchangeably with them unless the context clearly indicates otherwise. The term “such as” as used herein refers to the phrase “such as but not limited to,” and is used interchangeably with it.
[0106] It should also be noted that in the apparatus, equipment, and methods of this application, the components or steps can be disassembled and / or recombined. These disassemblies and / or recombinations should be considered as equivalent solutions of this application.
[0107] The above description of the disclosed aspects is provided to enable any person skilled in the art to make or use this application. Various modifications to these aspects will be readily apparent to those skilled in the art, and the general principles defined herein can be applied to other aspects without departing from the scope of this application. Therefore, this application is not intended to be limited to the aspects shown herein, but rather to be accorded the widest scope consistent with the principles and novel features disclosed herein.
[0108] The above description has been given for purposes of illustration and description. Furthermore, this description is not intended to limit the embodiments of this application to the forms disclosed herein. Although numerous exemplary aspects and embodiments have been discussed above, those skilled in the art will recognize certain variations, modifications, alterations, additions, and sub-combinations thereof.
Claims
1. A method for preparing a battery emitter, characterized in that, The method for fabricating emitters on an N-type silicon wafer, wherein the N-type silicon wafer is placed within a process chamber of a process cavity, includes: Under heating conditions, a borosilicate glass layer is deposited on one side of the N-type silicon wafer in the first direction; Under continuous cooling conditions, a protective gas is introduced into the process chamber, causing boron atoms in the borosilicate glass layer to be pushed into the portion of the N-type silicon wafer near the borosilicate glass layer, so that the portion of the N-type silicon wafer near the borosilicate glass layer becomes the emitter of the N-type silicon wafer, wherein the protective gas does not react with the N-type silicon wafer and the borosilicate glass layer.
2. The method for preparing the battery emitter according to claim 1, characterized in that, The borosilicate glass layer includes multiple sub-borosilicate glass layers; The step of depositing a borosilicate glass layer on one side of the N-type silicon wafer in a first direction under heating conditions includes: Under the heating conditions, a plurality of sub-borosilicate glass layers are sequentially deposited on one side of the N-type silicon wafer in the first direction, wherein, except for the first deposition of the sub-borosilicate glass layer, the first deposition temperature of each deposition of the sub-borosilicate glass layer is higher than the first deposition temperature of the previous deposition of the sub-borosilicate glass layer.
3. The method for preparing the battery emitter according to claim 2, characterized in that, Except for the first deposition of the sub-borosilicate glass layer, the first deposition temperature of each deposition of the sub-borosilicate glass layer is higher than the first deposition temperature of the previous deposition of the sub-borosilicate glass layer by a preset temperature rise temperature, which is in the range of 10 ℃ to 15 ℃.
4. The method for preparing the battery emitter according to claim 3, characterized in that, Except for the final deposition of the sub-borosilicate glass layer, the heating rate range for each subsequent deposition of the sub-borosilicate glass layer when increasing the preset heating temperature is 3 ℃ / min to 4.5 ℃ / min.
5. The method for preparing a battery emitter according to any one of claims 2 to 4, characterized in that, After each deposition of the sub-borosilicate glass layer, the method further includes: The process chamber is purged and evacuated.
6. The method for preparing a battery emitter according to any one of claims 2 to 4, characterized in that, Under the heating conditions, the deposition of a plurality of sub-borosilicate glass layers sequentially on one side of the N-type silicon wafer in the first direction includes: Under the heating conditions, boron trichloride, oxygen and nitrogen are introduced into the process chamber, and three sub-borosilicate glass layers are sequentially deposited on one side of the N-type silicon wafer in the first direction. The flow rate of boron trichloride is 120-180 sccm, the flow rate of oxygen is 400-600 sccm, the flow rate of nitrogen is 2500-4000 sccm, the pressure is 100-150 mBar, and the process time for each deposition of the borosilicate glass layer is 140 s.
7. The method for preparing the battery emitter according to any one of claims 1 to 4, characterized in that, Under the continuous cooling condition, after introducing a protective gas into the process chamber to push boron atoms in the borosilicate glass layer into the portion of the N-type silicon wafer near the borosilicate glass layer, the method further includes: Oxygen is introduced into the process chamber to form a boron oxide layer on the side of the borosilicate glass layer away from the N-type silicon wafer.
8. The method for preparing the battery emitter according to claim 7, characterized in that, The boron oxide layer comprises three sub-boron oxide layers; The step of introducing oxygen into the process chamber to form a boron oxide layer on the side of the borosilicate glass layer away from the N-type silicon wafer includes: Oxygen is introduced into the process chamber; Under continuous heating conditions, a first sub-boron oxide layer is formed on the side of the borosilicate glass layer away from the N-type silicon wafer; Under constant temperature conditions, a second layer of the sub-boron oxide layer is formed on the side of the first sub-boron oxide layer away from the N-type silicon wafer; Under continuous cooling conditions, a third layer of the sub-boron oxide layer is formed on the side of the second sub-boron oxide layer away from the N-type silicon wafer.
9. The method for preparing a battery emitter according to any one of claims 1 to 4, characterized in that, The method further includes, prior to depositing a borosilicate glass layer on one side of the N-type silicon wafer in the first direction under heated conditions: At a preset calcination temperature, oxygen is introduced into the process chamber, and / or, at a preset saturation temperature, boron trichloride and oxygen are introduced into the process chamber; The test silicon wafer is placed into the process chamber; Under the heating conditions, a test borosilicate glass layer is deposited on one side of the test silicon wafer in the first direction; Under the continuous cooling condition, the protective gas is introduced into the process chamber, causing boron atoms in the test borosilicate glass layer to be pushed into the portion of the test silicon wafer near the test borosilicate glass layer, so that the portion of the test silicon wafer near the test borosilicate glass layer becomes the emitter of the test silicon wafer.
10. An apparatus for preparing a battery emitter, characterized in that, include: A process chamber, wherein an N-type silicon wafer is placed in the process chamber; A heating assembly is configured to heat the process chamber; The heating assembly is capable of heating the process chamber to a heating condition to deposit a borosilicate glass layer on one side of the N-type silicon wafer in a first direction. Furthermore, when the heating assembly stops heating, the process chamber is capable of continuous cooling, and the process chamber is capable of receiving a protective gas that pushes boron atoms in the borosilicate glass layer into the portion of the N-type silicon wafer near the borosilicate glass layer, making the portion of the N-type silicon wafer near the borosilicate glass layer the emitter of the N-type silicon wafer. The protective gas does not react with the N-type silicon wafer or the borosilicate glass layer.