Preparation method of tunneling oxide layer and preparation method of TOPCon battery
By performing three-oxidation in ALD equipment, a high-density tunneling oxide layer was prepared, which solved the problems of low density and serious winding in the prior art, and significantly improved the performance of TOPCon solar cells.
Patent Information
- Application Number
- CN202311431618.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2023-10-31
- Publication Date
- 2025-05-02
AI Technical Summary
In the prior art, when preparing the tunneling oxide layer of TOPCon solar cells, the density is low and the winding phenomenon is serious, which affects the energy conversion efficiency and product yield of the battery.
ALD method of triple oxidation is used to form a high-density tunneling oxide layer through the oxidation process under different conditions. During the first oxidation, the temperature of the ALD equipment is low, forming a loose and uniform surface layer; during the second oxidation, the temperature, pressure and ozone flow rate are increased to enhance the oxidation depth; during the third oxidation, the temperature is further increased, the pressure and ozone flow rate are reduced, and the density is improved.
The high density of the tunneled oxide layer is achieved, the winding phenomenon is reduced, and the energy conversion efficiency and product yield of TOPCon solar cells are significantly improved.
Smart Images
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Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of electronic industry, and in particular to a method for preparing a tunneling oxide layer and a method for preparing a TOPCon battery. Background Art
[0002] In TOPCon solar cells, the tunneling oxide layer is usually prepared by LPCVD, PECVD or ALD. When the tunneling oxide layer is prepared by LPCVD, wrap-around plating will occur, which has a great impact on the yield and has low production capacity. When the tunneling oxide layer is prepared by PECVD, although the deposition speed is fast and the wrap-around is slight, the density of the prepared tunneling oxide layer is low, which not only affects the passivation effect, but also affects the open circuit voltage of the TOPCon solar cell. When the tunneling oxide layer is prepared by ALD, SiCl4 or SiH4 is required, both of which are toxic and explosive gases, and high requirements are placed on equipment safety. Summary of the invention
[0003] Based on this, it is necessary to provide a method for preparing a tunneling oxide layer and a method for preparing a TOPCon battery to address the above problems. The tunneling oxide layer prepared by the method for preparing the tunneling oxide layer has high density and slight wrapping, which can effectively improve the energy conversion efficiency and product yield of the TOPCon solar cell.
[0004] The present invention discloses a method for preparing a tunneling oxide layer, comprising the following steps:
[0005] The silicon wafer is placed in the ALD equipment and ozone and nitrogen are circulated to perform the first oxidation;
[0006] Increasing the temperature and pressure of the ALD equipment, and increasing the flow rate of ozone, circulate ozone and nitrogen to perform a second oxidation, wherein the number of cycles of the second oxidation is greater than the number of cycles of the first oxidation, and the single time length of ozone introduction during the second oxidation process is greater than the single time length of ozone introduction during the first oxidation process; and
[0007] The temperature of the ALD device is increased, the pressure inside the ALD device is reduced, and the flow rate of ozone is increased, and ozone and nitrogen are circulated to perform a third oxidation to form a tunneling oxide layer, wherein the number of cycles of the third oxidation is less than the number of cycles of the second oxidation, and the single time of ozone introduction during the third oxidation process is less than the single time of ozone introduction during the second oxidation process.
[0008] In one embodiment, during the first oxidation step, the temperature of the ALD device is 150° C.-200° C.;
[0009] In the step of performing the second oxidation, the temperature of the ALD equipment is 180° C.-280° C.;
[0010] During the third oxidation step, the temperature of the ALD equipment is 200°C-300°C.
[0011] In one embodiment, during the first oxidation step, the pressure of the ALD equipment is 1 Torr-20 Torr;
[0012] In the step of performing the second oxidation, the pressure of the ALD equipment is 5 Torr-30 Torr;
[0013] During the third oxidation step, the pressure of the ALD equipment is 1 Torr-20 Torr.
[0014] In one embodiment, in the first oxidation step, the ozone flow rate is 500 sccm-2000 sccm, and the single introduction time is 5 seconds-25 seconds;
[0015] In the second oxidation step, the ozone flow rate is 1000 sccm-6500 sccm, and the single introduction time is 6 seconds-26 seconds;
[0016] In the third oxidation step, the ozone flow rate is 1500sccm-7000sccm, and the single introduction time is 5 seconds-25 seconds.
[0017] In one embodiment, during the first oxidation, the second oxidation or the third oxidation step, the temperature, the pressure and the ozone flow rate of the ALD device remain unchanged during the cycle.
[0018] In one embodiment, in the first oxidation step, the flow rate of nitrogen is 5000 sccm-15000 sccm, and the single introduction time is 1 second-20 seconds;
[0019] In the second oxidation step, the flow rate of nitrogen is 5000sccm-15000sccm, and the single introduction time is 1 second-20 seconds;
[0020] In the third oxidation step, the flow rate of nitrogen is 5000sccm-15000sccm, and the single introduction time is 1 second-20 seconds.
[0021] In one embodiment, in the first oxidation step, ozone is first introduced and then nitrogen is introduced during the cycle, with one ozone and one nitrogen introduction as one cycle, the number of cycles is 3-20 times, and the time interval between two adjacent cycles is less than or equal to 15 seconds;
[0022] In the step of performing the second oxidation, ozone is first introduced and then nitrogen is introduced during the cycle, with one ozone and one nitrogen introduction as one cycle, the number of cycles is 5-45 times, and the time interval between two adjacent cycles is less than or equal to 15 seconds;
[0023] In the step of the third oxidation, ozone is introduced first and then nitrogen is introduced during the cycle, with one ozone and one nitrogen introduction as one cycle, the number of cycles is 5-45 times, and the time interval between two adjacent cycles is less than or equal to 15 seconds.
[0024] In one embodiment, after the first oxidation is completed, the second oxidation is started within 60 seconds; after the second oxidation is completed, the third oxidation is started within 90 seconds.
[0025] In one embodiment, the thickness of the tunnel oxide layer is 1.2 nm-2.5 nm.
[0026] The present invention also discloses a method for preparing a TOPCon battery, wherein the method for preparing the tunneling oxide layer comprises the method for preparing the tunneling oxide layer.
[0027] The preparation method of the tunneling oxide layer provided by the present invention includes three oxidations under different conditions. First, in the first oxidation step, the temperature of the ALD equipment is low, and the surface layer formed is loose and uniform, so that the ozone can penetrate the surface layer well for further oxidation during the second oxidation and the third oxidation process; secondly, in the second oxidation step, the temperature, pressure, and ozone flow of the ALD equipment are increased, the single introduction time is the longest, and the number of cycles is the largest, so that the ozone can penetrate the surface layer well and the thickness of the tunneling oxide layer is greatly improved; finally, in the third oxidation step, the temperature of the ALD equipment is further increased, and the single introduction time of ozone is reduced, which can improve the density of the tunneling oxide layer while avoiding the decrease in the uniformity of the tunneling oxide layer; the above three oxidations cooperate with each other, so that the prepared tunneling oxide layer has the characteristics of high density; in addition, since the plate-type method is used for preparation, the plating is slight; in summary, when the preparation method of the TOPCon battery includes the preparation method of the tunneling oxide layer as described above, the energy conversion efficiency and product yield of the TOPCon solar cell can be effectively improved. DETAILED DESCRIPTION
[0028] For ease of understanding of the present invention, the present invention will be described in more detail below. However, it should be understood that the present invention can be implemented in many different forms and is not limited to the embodiments or examples described herein. On the contrary, the purpose of providing these embodiments or examples is to make the understanding of the disclosure of the present invention more thorough and comprehensive.
[0029] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those generally understood by those skilled in the art of the present invention. The terms used herein in the specification of the present invention are only for the purpose of describing specific implementation methods or embodiments, and are not intended to limit the present invention. The optional scope of the term "and / or" used herein includes any one of two or more related listed items, and also includes any and all combinations of related listed items, and the combinations include any two related listed items, any more related listed items, or all related listed items.
[0030] The present invention provides a method for preparing a tunneling oxide layer, comprising the following steps:
[0031] S10, placing the silicon wafer in the ALD equipment, circulating ozone and nitrogen to perform the first oxidation;
[0032] S20, increasing the temperature and pressure of the ALD equipment, and increasing the flow rate of ozone, circulating ozone and nitrogen to perform a second oxidation, wherein the number of cycles of the second oxidation is greater than the number of cycles of the first oxidation, and the single introduction time of ozone during the second oxidation process is greater than the single introduction time of ozone during the first oxidation process; and
[0033] S30, increasing the temperature of the ALD equipment, reducing the pressure inside the ALD equipment, and increasing the flow rate of ozone, circulating ozone and nitrogen to perform a third oxidation to form a tunneling oxide layer, wherein the number of cycles of the third oxidation is less than the number of cycles of the second oxidation, and the single introduction time of ozone during the third oxidation process is less than the single introduction time of ozone during the second oxidation process.
[0034] The method for preparing the tunneling oxide layer provided by the present invention comprises three oxidations under different conditions:
[0035] First, in step S10, the temperature of the ALD equipment for the first oxidation is low, and the surface layer formed is loose and uniform, so that ozone can penetrate the surface layer well during the second oxidation and the third oxidation process to further oxidize.
[0036] In one embodiment, during the first oxidation step, the temperature of the ALD equipment is 150°C-200°C, including but not limited to 150°C, 160°C, 170°C, 180°C, 190°C or 200°C, so that the film formation rate is low and a more uniform and loose surface layer is formed; preferably, the temperature of the ALD equipment is 160°C-200°C.
[0037] In one embodiment, during the first oxidation step, the pressure of the ALD equipment is 1 Torr-20 Torr, including but not limited to 1 Torr, 5 Torr, 10 Torr, 15 Torr or 20 Torr. Preferably, the pressure of the ALD equipment is 3 Torr-10 Torr.
[0038] In one embodiment, in the first oxidation step, the ozone flow rate is 500sccm-2000sccm, including but not limited to 500sccm, 750sccm, 1000sccm, 1250sccm, 1500sccm, 1750sccm or 2000sccm, and the single introduction time is 5 seconds to 25 seconds; preferably, the ozone flow rate is 1200sccm-1800sccm, and the single introduction time is 5 seconds to 25 seconds.
[0039] The introduction of nitrogen gas can clean the chamber. In one embodiment, during the first oxidation step, the flow rate of nitrogen gas is 5000sccm-15000sccm, including but not limited to 5000sccm, 7500sccm, 10000sccm, 12500sccm or 15000sccm, and the single introduction time is 1 second to 20 seconds.
[0040] In one embodiment, in the first oxidation step, ozone is introduced first and then nitrogen is introduced during the cycle, with one ozone and one nitrogen introduction as one cycle, and the number of cycles is 3-20 times, including but not limited to 3 times, 5 times, 7 times, 9 times, 11 times, 13 times, 15 times, 17 times, 19 times or 20 times, preferably, the cycle is 5-13 times.
[0041] In one embodiment, in the step of performing the first oxidation, the time interval between two adjacent cycles is less than or equal to 15 seconds.
[0042] It should be noted that in the first oxidation step, the temperature, pressure and ozone flow rate of the ALD equipment may remain unchanged during the cycle, or may be adjusted within the above range. For example, during the cycle, the temperature, pressure and ozone flow rate of the ALD equipment may increase, decrease, increase first and then decrease, or decrease first and then increase. In order to improve the uniformity of the thickness of the tunneling oxide layer, it is preferred that the temperature, pressure and ozone flow rate of the ALD equipment remain unchanged during the cycle.
[0043] In one embodiment, after the first oxidation is completed, the second oxidation is started within 60 seconds.
[0044] Secondly, in the second oxidation step, the temperature, pressure and ozone flow of the ALD equipment are increased, the single entry time is the longest, and the number of cycles is the largest, so that ozone can penetrate the surface layer well and the thickness of the tunnel oxide layer is greatly improved.
[0045] In step S20, during the second oxidation step, the temperature of the ALD equipment is 180°C-280°C, including but not limited to 180°C, 190°C, 200°C, 210°C, 220°C, 230°C, 240°C, 250°C, 260°C, 270°C or 280°C; preferably, the temperature of the ALD equipment is 230°C-280°C.
[0046] In the second oxidation step, the pressure of the ALD equipment is 5 Torr-30 Torr, including but not limited to 5 Torr, 10 Torr, 15 Torr, 20 Torr, 25 Torr or 30 Torr; preferably, the pressure of the ALD equipment is 5 Torr-20 Torr.
[0047] In the second oxidation step, the ozone flow rate is 1000sccm-6500sccm, including but not limited to 1000sccm, 2000sccm, 3000sccm, 4000sccm, 5000sccm, 6000sccm or 6500sccm, and the single introduction time is 6 seconds to 26 seconds; preferably, the ozone flow rate is 4000sccm-5000sccm, and the single introduction time is 6 seconds to 26 seconds.
[0048] In the second oxidation step, the flow rate of nitrogen is 5000sccm-15000sccm, including but not limited to 5000sccm, 7500sccm, 10000sccm, 12500sccm or 15000sccm, and the single introduction time is 1 second to 20 seconds.
[0049] In the step of the second oxidation, ozone is introduced first and then nitrogen is introduced during the cycle, with one ozone and one nitrogen introduction as one cycle, and the cycle is 5-45 times, including but not limited to 5 times, 10 times, 15 times, 20 times, 25 times, 30 times, 35 times, 40 times or 45 times, and the number of cycles is 15-40 times.
[0050] In one embodiment, the time interval between two adjacent cycles is less than or equal to 15 seconds.
[0051] It should be noted that in the step of the second oxidation, the temperature, pressure and ozone flow rate of the ALD equipment may remain unchanged during the cycle, or may be adjusted within the above range. For example, during the cycle, the temperature, pressure and ozone flow rate of the ALD equipment may increase, decrease, increase first and then decrease, or decrease first and then increase. In order to improve the uniformity of the thickness of the tunneling oxide layer, it is preferred that the temperature, pressure and ozone flow rate of the ALD equipment remain unchanged during the cycle.
[0052] In one embodiment, after the second oxidation is completed, the third oxidation is started within 90 seconds.
[0053] Finally, in the third oxidation step, the temperature of the ALD equipment is further increased and the single ozone introduction time is reduced, which can improve the density of the tunneling oxide layer while avoiding the decrease in the uniformity of the tunneling oxide layer.
[0054] In the step of performing the third oxidation, the temperature of the ALD equipment is 200°C-300°C, including but not limited to 200°C, 220°C, 240°C, 260°C, 280°C or 300°C. Preferably, the temperature of the ALD equipment is 250°C-300°C.
[0055] During the third oxidation step, the pressure of the ALD equipment is 1 Torr-20 Torr, including but not limited to 1 Torr, 5 Torr, 10 Torr, 15 Torr or 20 Torr. Preferably, the pressure of the ALD equipment is 5 Torr-15 Torr.
[0056] In the step of the third oxidation, the ozone flow rate is 1500sccm-7000sccm, including but not limited to 1500sccm, 2500sccm, 3500sccm, 4500sccm, 5500sccm, 6500sccm or 7000sccm, and the single introduction time is 5 seconds to 25 seconds; preferably, the ozone flow rate is 5000sccm-7000sccm, and the single introduction time is 5 seconds to 25 seconds.
[0057] In the step of performing the third oxidation, the flow rate of nitrogen is 5000sccm-15000sccm, including but not limited to 5000sccm, 7500sccm, 10000sccm, 12500sccm or 15000sccm, and the single introduction time is 1 second to 20 seconds.
[0058] In the step of the third oxidation, ozone is introduced first and then nitrogen is introduced during the cycle, with one ozone and one nitrogen introduction as one cycle, and the cycle is 3-20 times, including but not limited to 3 times, 5 times, 7 times, 9 times, 11 times, 13 times, 15 times, 17 times, 19 times or 20 times, preferably, 5-13 times.
[0059] In one embodiment, the time interval between two adjacent cycles is less than or equal to 15 seconds.
[0060] It should be noted that in the step of the third oxidation, the temperature, pressure and ozone flow rate of the ALD equipment may remain unchanged during the cycle, or may be adjusted within the above range. For example, during the cycle, the temperature, pressure and ozone flow rate of the ALD equipment may increase, decrease, increase first and then decrease, or decrease first and then increase. In order to improve the uniformity of the thickness of the tunneling oxide layer, it is preferred that the temperature, pressure and ozone flow rate of the ALD equipment remain unchanged during the cycle.
[0061] In one embodiment, the thickness of the tunnel oxide layer is 1.2 nm-2.5 nm.
[0062] The above three oxidation processes cooperate with each other, so that the prepared tunnel oxide layer has the characteristics of high density; in addition, since the plate-type method is used for preparation, the wrapping plating is slight.
[0063] The present invention also discloses a method for preparing a TOPCon battery, and the method for preparing the TOPCon battery includes the method for preparing the tunneling oxide layer as described above.
[0064] When the preparation method of the TOPCon cell includes the preparation method of the tunnel oxide layer as described above, the energy conversion efficiency and product yield of the TOPCon solar cell can be effectively improved.
[0065] In one embodiment, the preparation method comprises the following steps:
[0066] The silicon wafer is textured on both sides to form a pyramid-shaped light-trapping structure.
[0067] Boron diffusion is performed on the front side of the silicon wafer to prepare a PN junction. Specifically, low-pressure diffusion can be used for boron diffusion. During the boron diffusion process, boron chloride reacts with oxygen to generate boron trioxide. Boron trioxide reacts with silicon to generate silicon oxide and boron element. Boron trioxide and silicon oxide are mixed and precipitated on the front side of the silicon wafer to form borosilicate glass (BSG). The precipitated boron atoms diffuse into the silicon to form a BSG layer on the silicon surface.
[0068] The borosilicate glass on the back and edge of the silicon wafer is removed; specifically, a water film is first used to cover and protect the borosilicate glass, and then an HF solution is used as an etching solution to remove the borosilicate glass formed on the edge and back of the silicon wafer.
[0069] The back side of the silicon wafer is polished; specifically, the back side of the silicon wafer can be polished by alkali washing.
[0070] The tunneling oxide layer is formed on the back side of the silicon wafer by using the tunneling oxide layer preparation method of the present invention.
[0071] A polycrystalline silicon layer is formed on the surface of the tunnel oxide layer away from the silicon wafer; specifically, a phosphorus-doped amorphous silicon film is first deposited by PECVD, and then an annealing treatment is performed to further crystallize the amorphous silicon in the amorphous silicon film and convert it into a polycrystalline silicon layer; in one embodiment, the amorphous silicon film is 80nm-160nm; the annealing step is performed in a nitrogen atmosphere at 700℃-950℃.
[0072] An aluminum oxide layer and a silicon nitride layer are sequentially formed on the front side of the silicon wafer. In one embodiment, the silicon nitride layer is deposited by PECVD, and the thickness of the silicon nitride layer is 60nm-90nm.
[0073] A passivation film is formed on the surface of the doped polysilicon layer away from the tunnel oxide layer; in one embodiment, the passivation film is a silicon nitride layer, which is deposited by PECVD and has a thickness of 50nm-200nm.
[0074] Electrodes are formed on the front and back sides of the silicon wafer.
[0075] Hereinafter, the preparation method of the tunnel oxide layer and the preparation method of the TOPCon battery will be further described through the following specific examples.
[0076] Example 1
[0077] The silicon wafer was placed in an ALD device at 180°C and a pressure of 5 Torr, and ozone was introduced at a flow rate of 1500 sccm for 10 seconds, followed by nitrogen at a flow rate of 10,000 sccm for 5 seconds. This cycle was repeated 8 times to complete the first oxidation.
[0078] The temperature of the ALD equipment was adjusted to 250°C, and the pressure was adjusted to 10 Torr. After introducing ozone at a flow rate of 4500 sccm for 20 seconds, 10000 sccm of nitrogen was introduced for 10 seconds. This cycle was repeated 35 times to complete the second oxidation.
[0079] The temperature of the ALD equipment was adjusted to 280°C, and the pressure was adjusted to 12 Torr. After introducing ozone at a flow rate of 6500 sccm for 10 seconds, 10000 sccm of nitrogen was introduced for 10 seconds. After 10 cycles, the third oxidation was completed to form a tunneling oxide layer with a thickness of 1.6 nm.
[0080] Comparative Example 1
[0081] Comparative Example 1 is carried out with reference to Example 1, except that the order of the three oxidations is adjusted to first carry out the second oxidation, then carry out the first oxidation, and finally carry out the third oxidation, and the thickness of the tunneling oxide layer is 1.6 nm.
[0082] Comparative Example 2
[0083] Comparative Example 2 was carried out with reference to Example 1, except that the order of the three oxidations was adjusted to first carry out the third oxidation, then the first oxidation, and finally the second oxidation, and the thickness of the tunneling oxide layer was 1.65 nm.
[0084] Comparative Example 3
[0085] Comparative Example 3 is carried out with reference to Example 1, except that the order of the three oxidations is adjusted to first carry out the first oxidation, then the third oxidation, and finally the second oxidation, and the thickness of the tunneling oxide layer is 1.62 nm.
[0086] Comparative Example 4
[0087] Comparative Example 4 is carried out with reference to Example 1, except that the first oxidation is not performed, the second oxidation is performed directly, and then the third oxidation is performed, and the thickness of the tunneling oxide layer is 1.55 nm.
[0088] Comparative Example 5
[0089] Comparative Example 5 was carried out with reference to Example 1, except that the second oxidation was not performed, and the first oxidation was performed directly, and then the third oxidation was performed, and the thickness of the tunneling oxide layer was 1.15 nm.
[0090] Comparative Example 6
[0091] Comparative Example 6 was carried out with reference to Example 1, except that the third oxidation was not performed, and the first oxidation was performed directly, and then the second oxidation was performed, and the thickness of the tunneling oxide layer was 1.35 nm.
[0092] Comparative Example 7
[0093] Comparative Example 7 was carried out with reference to Example 1, except that the first and second oxidations were not performed, and the third oxidation was performed directly, and the thickness of the tunneling oxide layer was 0.8 nm.
[0094] Comparative Example 8
[0095] Comparative Example 8 was carried out with reference to Example 1, except that it was carried out only under the first oxidation condition, and the number of cycles was the sum of the number of cycles of the three oxidations in the example.
[0096] Comparative Example 9
[0097] Comparative Example 9 was carried out with reference to Example 1, except that it was carried out only under the second oxidation conditions, and the number of cycles was the sum of the number of cycles of the three oxidations in the example.
[0098] Comparative Example 10
[0099] Comparative Example 10 is carried out with reference to Example 1, except that the number of cycles of the first oxidation is greater than the number of cycles of the second oxidation, and the number of cycles of the second oxidation is greater than the number of cycles of the third oxidation.
[0100] Comparative Example 11
[0101] Comparative Example 11 is carried out with reference to Example 1, except that the number of cycles of the first oxidation is less than the number of cycles of the second oxidation, and the number of cycles of the second oxidation is less than the number of cycles of the third oxidation.
[0102] Example 2
[0103] The silicon wafer was placed in an ALD device at 160°C and a pressure of 3 Torr, and ozone was introduced at a flow rate of 1200 sccm for 10 seconds, followed by nitrogen at a flow rate of 5000 sccm for 5 seconds. This cycle was repeated 5 times to complete the first oxidation.
[0104] The temperature of the ALD equipment was adjusted to 230°C, and the pressure was adjusted to 5 Torr. After introducing ozone at a flow rate of 4000 sccm for 20 seconds, 5000 sccm nitrogen was introduced for 10 seconds. This cycle was repeated 15 times to complete the second oxidation.
[0105] The temperature of the ALD equipment was adjusted to 250°C, and the pressure was adjusted to 5 Torr. After passing ozone at a flow rate of 5000 sccm for 10 seconds, 5000 sccm of nitrogen was passed for 10 seconds. After 10 cycles, the third oxidation was completed to form a tunneling oxide layer with a thickness of 1.5 nm.
[0106] Example 3
[0107] The silicon wafer was placed in an ALD device at 200°C and 10 Torr pressure, and ozone was introduced at a flow rate of 1800 sccm for 10 seconds, followed by nitrogen at a flow rate of 15000 sccm for 5 seconds. This cycle was repeated 13 times to complete the first oxidation.
[0108] The temperature of the ALD equipment was adjusted to 280°C, and the pressure was adjusted to 20 Torr. After 5000 sccm of ozone was introduced for 26 seconds, 15000 sccm of nitrogen was introduced for 10 seconds. This cycle was repeated 40 times to complete the second oxidation.
[0109] The temperature of the ALD equipment was adjusted to 300°C, and the pressure was adjusted to 15 Torr. After introducing ozone at a flow rate of 7000 sccm for 25 seconds, 15000 sccm of nitrogen was introduced for 10 seconds. After 10 cycles, the third oxidation was completed to form a tunneling oxide layer with a thickness of 2.1 nm.
[0110] Test Example 1
[0111] The tunnel oxide layers prepared in Examples 1-3 and Comparative Examples 1-5 were cleaned with hydrofluoric acid having a concentration of 1% until the tunnel oxide layers were completely cleaned. The cleaning time is shown in Table 1.
[0112] Table 1
[0113]
[0114]
[0115] The tunneling oxide layer preparation method obtained in Examples 1-3 and Comparative Examples 1-11 was applied to the preparation of N-type TOPCon cells, and N-type TOPCon cells containing tunneling oxide layers corresponding to Example 1 and Comparative Examples 1-5 were obtained respectively. The performance of the cells was tested using the same test method. In this example, the data was normalized. The parameters of the N-type passivated contact cell obtained in Example 1 were all 1, and the parameter data of Examples 2-3 and Comparative Examples 1-5 were the ratios of the parameters to Example 1. The test results are shown in Table 2 below.
[0116] Table 2
[0117]
[0118]
[0119] It can be seen from Table 1 and Table 2 that the preparation method of the tunneling oxide layer provided by the present invention can improve the compactness of the tunneling oxide layer, thereby effectively improving the energy conversion efficiency and product yield of the TOPCon solar cell.
[0120] All possible combinations of the various technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.
[0121] The above-mentioned embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.
Claims
1. A method for preparing a tunneling oxide layer, characterized in that: The following steps are involved: The silicon wafer is placed in the ALD equipment and ozone and nitrogen are circulated to perform the first oxidation; Increasing the temperature and pressure of the ALD equipment, and increasing the flow rate of ozone, circulate ozone and nitrogen to perform a second oxidation, wherein the number of cycles of the second oxidation is greater than the number of cycles of the first oxidation, and the single time length of ozone introduction during the second oxidation process is greater than the single time length of ozone introduction during the first oxidation process; and The temperature of the ALD device is increased, the pressure inside the ALD device is reduced, and the flow rate of ozone is increased, and ozone and nitrogen are circulated to perform a third oxidation to form a tunneling oxide layer, wherein the number of cycles of the third oxidation is less than the number of cycles of the second oxidation, and the single time of ozone introduction during the third oxidation process is less than the single time of ozone introduction during the second oxidation process.
2. The method for preparing a tunneling oxide layer according to claim 1, characterized in that: In the step of performing the first oxidation, the temperature of the ALD equipment is 150° C.-200° C.; In the step of performing the second oxidation, the temperature of the ALD equipment is 180° C.-280° C.; During the third oxidation step, the temperature of the ALD equipment is 200°C-300°C.
3. The method for preparing a tunneling oxide layer according to claim 1, characterized in that: In the first oxidation step, the pressure of the ALD equipment is 1 Torr-20 Torr; In the step of performing the second oxidation, the pressure of the ALD equipment is 5 Torr-30 Torr; During the third oxidation step, the pressure of the ALD equipment is 1 Torr-20 Torr.
4. The method for preparing a tunneling oxide layer according to claim 1, characterized in that: In the first oxidation step, the ozone flow rate is 500 sccm-2000 sccm, and the single introduction time is 5 seconds-25 seconds; In the second oxidation step, the ozone flow rate is 1000 sccm-6500 sccm, and the single introduction time is 6 seconds-26 seconds; In the third oxidation step, the ozone flow rate is 1500sccm-7000sccm, and the single introduction time is 5 seconds-25 seconds.
5. The method for preparing a tunneling oxide layer according to claim 1, characterized in that: During the first oxidation, the second oxidation or the third oxidation step, the temperature, the pressure and the ozone flow rate of the ALD equipment remain unchanged during the cycle.
6. The method for preparing a tunneling oxide layer according to claim 1, characterized in that: In the first oxidation step, the flow rate of nitrogen is 5000sccm-15000sccm, and the single introduction time is 1 second-20 seconds; In the second oxidation step, the flow rate of nitrogen is 5000sccm-15000sccm, and the single introduction time is 1 second-20 seconds; In the third oxidation step, the flow rate of nitrogen is 5000sccm-15000sccm, and the single introduction time is 1 second-20 seconds.
7. The method for preparing a tunneling oxide layer according to claim 1, characterized in that: In the first oxidation step, ozone is first introduced and then nitrogen is introduced during the cycle, with one ozone and one nitrogen introduction as one cycle, the number of cycles is 3-20 times, and the time interval between two adjacent cycles is less than or equal to 15 seconds; In the step of performing the second oxidation, ozone is first introduced and then nitrogen is introduced during the cycle, with one ozone and one nitrogen introduction as one cycle, the number of cycles is 5-45 times, and the time interval between two adjacent cycles is less than or equal to 15 seconds; In the step of the third oxidation, ozone is introduced first and then nitrogen is introduced during the cycle, with one ozone and one nitrogen introduction as one cycle, the number of cycles is 5-45 times, and the time interval between two adjacent cycles is less than or equal to 15 seconds.
8. The method for preparing a tunneling oxide layer according to claim 1, characterized in that: After the first oxidation is completed, the second oxidation is started within 60 seconds; after the second oxidation is completed, the third oxidation is started within 90 seconds.
9. The method for preparing a tunneling oxide layer according to any one of claims 1 to 8, characterized in that: The thickness of the tunnel oxide layer is 1.2nm-2.5nm.
10. A method for preparing a TOPCon battery, characterized in that: The preparation method includes the preparation method of the tunneling oxide layer according to any one of claims 1 to 9.