Method for preparing laminated solar aluminum oxide film based on PECVD (plasma enhanced chemical vapor deposition) and PE-ALD (polyethylene-atomic layer deposition) processes

Abstract

The invention discloses a method for preparing a laminated solar aluminum oxide film based on PECVD (Plasma Enhanced Chemical Vapor Deposition) and PE-ALD (Poly Ethylene-Atomic Layer Deposition) processes, and relates to a method for preparing a solar aluminum oxide film, which comprises the following steps of: treating an interface by laughing gas plasma, depositing a silicon oxide layer of about 1-2nm, and depositing an aluminum oxide layer of 2-3nm by using a PE-ALD process. The method comprises the following steps: depositing a silicon oxide layer with the thickness of about 1-2nm by using a plasma enhanced chemical vapor deposition (PECVD) process instead of laughing gas and silane plasmas, depositing an aluminum oxide layer with the thickness of 4-5nm by using a PECVD process, and finally performing plasma bombardment treatment on the aluminum oxide layer by using laughing gas and hydrogen to form a denser aluminum oxide film layer; when each film layer is deposited, the power, the duty ratio, the plasma action time and the plasma frequency of a radio frequency power supply are not limited; the geometric dimension, specification and shape of the silicon wafer are not limited; the material and the shape of the silicon wafer bearing device, such as the shape and the size of a graphite boat, are not limited. And the field passivation and chemical passivation effects are greatly improved, so that the conversion efficiency of the cell is improved.

Description

Technical Field

[0001] The present invention relates to a method for preparing a solar aluminum oxide film, and particularly to a method for preparing a laminated solar aluminum oxide film based on PECVD and PE-ALD processes. Background Art

[0002] Depositing an aluminum oxide passivation film on the front side of a solar cell can provide high field-effect passivation and relatively high chemical passivation. Currently, the mainstream in the industry chooses the ALD process to deposit the Al2O3 passivation film. The advantages are good film formation compactness and good passivation effect. The disadvantages are that the ALD equipment requires a relatively long process time, and when depositing a film layer exceeding 4 nm, it is easy to produce overplating in large-sized wafers of 210 mm×210 mm.

[0003] In actual battery production, in order to take into account the silicon nitride passivation film deposited by the subsequent PECVD process, the silicon wafer also needs to be switched from the ALD equipment chamber to the PECVD equipment chamber, which greatly increases the operation complexity and production rhythm. And the aluminum oxide passivation film deposited by the PECVD process is one of the options that can replace this intermediate operation. Due to the relatively poor film formation compactness of the aluminum oxide film deposited by the PECVD process compared with the ALD process, the negative fixed charge density at the interface is relatively low, which will in turn lead to a decrease in the passivation effect of the Al2O3 passivation film. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for preparing a laminated solar aluminum oxide film based on PECVD and PE-ALD processes. In this method, a 1-2 nm thin tunneling silicon oxide layer is formed at the interface of the Si substrate treated by N2O plasma at the bottom layer, and then a 2-3 nm thick aluminum oxide thin film is deposited by the PE-ALD process. The next layer is a 1-2 nm SiOx interface formed by N2O+SiH4 plasma treatment, and the top layer is a 4-5 nm thick aluminum oxide thin film deposited by the PECVD process. Finally, this interface is treated by N2O+H2 plasma. This laminated aluminum oxide structure greatly improves the field passivation and chemical passivation effects and improves the conversion efficiency of the battery.

[0005] The purpose of the present invention is achieved by the following technical solutions: A method for preparing a laminated aluminum oxide film layer based on PECVD process and PE-ALD process, comprising the following steps: S1. Place the silicon substrate in the tube PECVD deposition chamber, and perform vacuum pumping, leak detection, temperature and pressure adjustment on the chamber; S2. Continuously introduce nitrous oxide to perform plasma interface treatment on the surface of the silicon wafer to construct the first layer of thin tunneling silicon oxide film; S3. Construct the second layer of alumina film: Evacuate the air, and in the form of heating and evaporating with argon carrying the source, deposit gaseous TMA on the surface of the silicon wafer. Subsequently, introduce argon to purge away the excess TMA, then turn on the radio frequency power while introducing N2O, react with the previously deposited TMA, form an Al2O3 film on the surface of the silicon wafer, and finally introduce argon again to purge away the excess N2O and TMA groups; repeat the above process to obtain the second layer of alumina film. S4. Construct the third layer of silicon oxide film: Evacuate the air, continuously introduce nitrous oxide and silane, and form a silicon oxide film under the discharge of the radio frequency power supply. S5. Construct the fourth layer of alumina film: Evacuate the air, pre-ventilate, and after a short temperature rise, introduce gaseous TMA and N2O under the discharge environment of the radio frequency power supply to deposit and form the fourth layer of alumina film. S6. Evacuate the air, pre-ventilate, continuously introduce nitrous oxide and ammonia to perform plasma interface treatment on the surface of the silicon wafer. And, in S6, the amounts of nitrous oxide and ammonia introduced are higher than those in S2, and the amount of TMA gas introduced in S5 is higher than that in S3.

[0006] S7. Evacuate the air, clean and purge the remaining gas in the reaction chamber of the furnace tube, and back-pressurize the chamber with nitrogen to obtain a laminated alumina film layer. In an embodiment of the present invention, in S2, the amount of nitrous oxide introduced is 5000 SCCM, the time is 18 s, and the radio frequency power is 4500 W.

[0007] In an embodiment of the present invention, in S3, the amount of TMA gas introduced is 500 mg / min, and the time is 10 - 15 s.

[0008] In an embodiment of the present invention, in S3, the amount of nitrous oxide introduced is 3000 SCCM / min, the time is 15 s, and the radio frequency power is 5000 W.

[0009] In an embodiment of the present invention, in S3, the amount of argon introduced is 5000 SCCM / min, and the time is 10 s.

[0010] In an embodiment of the present invention, in S3, the number of repetitions is 10 - 15 times.

[0011] In an embodiment of the present invention, in S4, the amount of silane introduced is 850 SCCM / min. The amount of nitrous oxide is 5500 SCCM / min, the time is 10 s, and the radio frequency power is 7500 W.

[0012] In an embodiment of the present invention, in S5, the amount of TMA gas introduced is 1500 mg / min, the amount of N2O is 5500 SCCM / min, the time is 160 s, and the radio frequency power supply power is 6000 W.

[0013] In one embodiment of the present invention, in S6, the amounts of nitrous oxide and ammonia introduced are both 6000 SCCM, the time is 18 s, and the radio frequency power is 5500 W.

[0014] In one embodiment of the present invention, in S7, the amount of nitrogen used for purging is 10000 SCCM / min, and the time is 30 s. In one embodiment of the present invention, the temperature and pressure adjustment treatment in S1 refers to a pressure adjustment value of 175 Pa to 180 Pa and a temperature adjustment value of 250 to 290 °C.

[0015] In one embodiment of the present invention, a method for preparing a laminated alumina film layer based on the PECVD process and the PE-ALD process specifically includes the following steps: S1: Place the substrate silicon wafer in a high-temperature furnace tube (reaction chamber), and perform nitrogen atmosphere preheating, vacuum pumping, leak detection, and heating treatments on the reaction chamber. The pressure is 175 Pa to 180 Pa, and the temperature is 250 °C to 290 °C.

[0016] S2: Continuously introduce nitrous oxide into the reaction chamber. After 10 s, turn on the radio frequency power supply to perform interface treatment on the surface of the silicon substrate. The radio frequency power supply frequency is 40 KHZ, the power is 4500 W, and the discharge time is 18 s.

[0017] S3. Construct the second layer of alumina film: Introduce TMA (trimethylaluminum) vapor into the chamber to cover the entire surface of the silicon substrate. The amount of TMA is 500 mg / min, and the time is 10 - 15 s; then introduce an inert gas, argon or nitrogen, to purge away the excess TMA. The argon flow rate is 5000 SCCM / min, and the time is 10 s. S4. Then introduce nitrous oxide or oxygen, and use the radio frequency power supply to decompose it into plasma to react with the TMA on the surface of the silicon wafer. The amount of nitrous oxide or oxygen is 3000 SCCM / min, the radio frequency power supply frequency is 40 KHZ, the power is 5000 W, the duty cycle is 4:300 / ms, and the time is 15 s. S5. Finally, introduce argon to purge away the residual plasma. The amount of argon introduced is 3000 SCCM, and the time is 10 s. Repeat the above process 10 - 15 times. S6. Construct the silicon oxide film: Continuously introduce silane and nitrous oxide into the reaction chamber. The temperature in the chamber is 300 - 320 °C, the pressure is 200 Pa, the amount of silane introduced is 850 SCCM / min, the amount of nitrous oxide introduced is 5500 SCCM / min. After 15 s, turn on the radio frequency power supply. The radio frequency power supply frequency is 40 KHZ, the power is 7500 W, the duty cycle is 4:80 / ms, and the discharge time is 20 s. S7. Construct the fourth layer of alumina film: Continuously introduce gaseous trimethylaluminum (TMA) and nitrous oxide into the reaction chamber. The temperature in the chamber is 310 - 320 °C, the pressure is 190 Pa, the amount of gaseous TMA introduced is 1500 mg / min, and the amount of nitrous oxide introduced is 5500 SCCM / min. After 10 s, turn on the radio frequency power supply. The radio frequency power supply frequency is 40 KHZ, the power is 6000 W, the duty cycle is 4:280 / ms, and the discharge time is 160 s; S8. Construct the fifth layer for interface treatment: Continuously introduce nitrous oxide and hydrogen into the reaction chamber. The temperature in the chamber is 340 - 360 °C, the pressure is 180 Pa, and the amounts of nitrous oxide and ammonia introduced are both 6000 SCCM / min. After 18 s, turn on the radio frequency power supply. The radio frequency power supply frequency is 40 KHZ, the power is 5500 W, the duty cycle is 4:60 / ms, and the discharge time is 300 s; S9: Evacuate the chamber and purge the remaining gas in the chamber. The amount of nitrogen purging introduced is 10000 SCCM / min, and the time is 30 s; Backpressure the chamber with nitrogen. The amount of nitrogen at normal pressure introduced is 50000 SCCM / min, and the time is 200 s. Take out the wafer to complete the process.

[0018] The present invention prepares a laminated alumina film with a high negative charge density based on the above method.

[0019] The present invention also provides the application of the above laminated alumina film layer in the battery field.

[0020] The present invention also provides a battery manufacturing process, including the following steps: Clean the original silicon wafer with deionized water, and then perform alkaline texturing to prepare a textured surface; Boron diffusion on the front side of the battery to prepare a PN junction; Use laser SE for secondary doping concentration promotion to remove the surface borosilicate glass, alkaline polish the back side to prepare a tunneling oxide layer and a phosphorus-doped amorphous layer; Anneal to form a phosphorus-doped polycrystalline layer; Remove the surface phosphosilicate glass; Clean the silicon wafer; Prepare the front Al2O3 film according to the above method to enhance the field passivation and chemical passivation effects; Prepare silicon nitride films on the front and back sides; Screen-print electrodes, sinter, and test.

[0021] The present invention also provides a battery product obtained based on the above battery manufacturing process.

[0022] The beneficial effects of the present invention: The process of the present invention has been verified through a large number of maturations. The front passivation quality of the battery wafer has a relative advantage. Due to the gain in Jsc (short-circuit current density) and Voc (open-circuit voltage), the conversion efficiency of the battery is improved.

[0023] The process advantages of the present invention include: Cost Advantage: The existing method uses an ALD device to deposit Al2O3, but subsequent silicon nitride requires a PECVD device for deposition. During the preparation of the battery, the price will be increased by the price of an additional ALD device. The process of the present invention is based on the PECVD device platform and uses the PECVD device to complete the entire battery preparation process, which has a cost advantage over the additional ALD device. Product Performance Advantage: The alumina thin film obtained based on the process of the present invention, although the film density is slightly looser than that of the ALD device, the high-quality field passivation brought by the high negative charge density reduces the gap with the alumina passivation thin film deposited by the ALD device.

[0024] Principle Explanation of the Present Invention: Nitrous oxide is used for interface treatment at the bottom layer. The silicon atoms in the thin tunneling oxide layer SiOx formed are in a tetrahedral structure, which will promote the formation of excess tetrahedral configuration AlO4 in the Al2O3 film deposited as the capping layer. - This will generate a high density of negative charges. Since the film density of the alumina film deposited by the PE-ALD method is already good enough, a silicon oxide film layer as thin as 1-2 nm is sufficient to generate a high density of negative charges. In the subsequent third layer, a 1-2 nm SiOx layer is deposited by the PECVD method. This layer can promote the generation of a higher density of negative charges in the Al2O3 deposited by the PECVD method. Since the film density of the alumina film deposited by the PECVD method is slightly poor, it still needs to be deposited on the 1-2 nm SiOx layer to form an Al2O3 film layer with a higher negative charge density of 4-5 nm. Finally, nitrous oxide and hydrogen are simultaneously ionized to treat the interface. The purpose of the treatment is still to improve the film density of the Al2O3 film deposited by the PECVD method. During the plasma action process, the ionization of a large amount of nitrous oxide will cause the O-H bond to break, increasing the ratio of O-Al-O bonds, which helps to reduce oxygen vacancy defects and form more oxygen interstitials. At the same time, a large amount of hydrogen generated by the ionization of hydrogen will penetrate to the surface of Al2O3 and the Al2O3 / C-Si(n) interface along with the hydrogen released by the breakage of the O-H bond. The stacked alumina structure of the present invention greatly improves the field passivation and chemical passivation effects, thereby improving the conversion efficiency of the battery. Description of the Drawings

[0025] Figure 1 It is the battery structure diagram of Comparative Example 1 / 2; Figure 2 It is the battery structure diagram of the alumina stacked structure of Example 5. Detailed Implementation Manner

[0026] Table 1 shows the process flow of preparing the stacked alumina film layer based on the PECVD process and the PE-ALD process of the present invention.

[0027] Table 2 shows the I-V performance test results of the Al2O3 thin film batteries deposited in each example.

[0028] Comparative Example 1 An alumina single-layer film process deposited by PECVD process includes the following steps: S1: Place the silicon substrate on the graphite boat, send it into the furnace tube reaction chamber, preheat the reaction chamber, evacuate, leak-check, and perform a temperature-raising treatment in a nitrogen atmosphere; S2: Evacuate, raise the temperature to 315 °C, introduce TMA gas at 1660 SCCM / min and nitrous oxide at 5500 SCCM / min for 25 s, and keep the pressure constant at 190 Pa; S3: Turn on the RF power supply, with the RF power supply frequency of 40 KHZ, the RF power supply power of 6000 W, the RF power supply duty cycle of 4:280 / ms, and the turn-on time of 169 s; S4: Evacuate and introduce argon to purge the remaining gas in the reaction chamber, with the argon flow rate of 5000 SCCM / min for 30 s; S5: Backpressure the chamber with nitrogen, with the nitrogen introduction amount of 50000 SCCM / min for 200 s, take the wafer, complete the process, and obtain the Al2O3 passivation film layer.

[0029] Example 2 Referring to Comparative Example 1, add a step of depositing silicon oxide before S2, and keep other steps unchanged.

[0030] S1: Place the silicon substrate on the graphite boat, send it into the furnace tube reaction chamber, preheat the reaction chamber, evacuate, leak-check, and perform a temperature-raising treatment in a nitrogen atmosphere; S2: Continuously introduce nitrous oxide and silane into the reaction chamber, with the amount of nitrous oxide being 5500 SCCM / min and the amount of silane being 850 SCCM / min for 20 s. Then turn on the RF power supply to perform an interface treatment of plasma bombardment on the surface of the silicon substrate. The RF power supply frequency is 40 KHZ, the power of the RF power supply is 7500 W, the duty cycle of the RF power supply is 4:80 / ms, and the discharge time of the RF power supply is 20 s.

[0031] S3: Evacuate, raise the temperature to 315 °C, introduce TMA gas at 1660 SCCM / min and nitrous oxide at 5500 SCCM / min for 25 s, and keep the pressure constant at 190 Pa; S4: Turn on the RF power supply, with the RF power supply frequency of 40 KHZ, the RF power supply power of 6000 W, the RF power supply duty cycle of 4:280 / ms, and the turn-on time of 169 s; S5: Evacuate the chamber, purge the remaining gas in the reaction chamber with argon, with an argon flow rate of 5000 SCCM / min for 30 s; S6: Backpressure the chamber with nitrogen, with a nitrogen flow rate of 50000 SCCM / min for 200 s, take out the wafer, complete the process, and obtain the Al2O3 passivation film layer.

[0032] Example 3 Refer to Example 2, add an interface treatment step after S5, and keep other steps unchanged.

[0033] S1: Place the silicon substrate on the graphite boat, send it into the reaction chamber of the furnace tube, preheat, evacuate, leak-check the reaction chamber, and perform a temperature increase treatment in a nitrogen atmosphere; S2: Continuously introduce nitrous oxide and silane into the reaction chamber, with a nitrous oxide flow rate of 5500 SCCM / min and a silane flow rate of 850 SCCM / min for 20 s. Then turn on the RF power supply to perform an interface treatment of plasma bombardment on the surface of the silicon substrate. The RF power supply frequency is 40 KHZ, the power of the RF power supply is 7500 W, the duty cycle of the RF power supply is 4:80 / ms, and the discharge time of the RF power supply is 20 s; S3: Evacuate the chamber, heat up to 315 °C, introduce TMA gas at 1660 SCCM / min and nitrous oxide at 5500 SCCM / min for 25 s, and keep the pressure constant at 190 Pa; S4: Turn on the RF power supply, with an RF power supply frequency of 40 KHZ, an RF power supply power of 6000 W, an RF power supply duty cycle of 4:280 / ms, and turn it on for 169 s; S5: Evacuate the chamber, purge the remaining gas in the reaction chamber with argon, with an argon flow rate of 5000 SCCM / min for 30 s; S6: Evacuate the chamber, heat up to 350 °C, introduce nitrous oxide and hydrogen into the reaction chamber, with a nitrous oxide flow rate of 5000 SCCM / min and a hydrogen flow rate of 5000 SCCM / min for 20 s. Then turn on the RF power supply to perform an interface treatment of plasma bombardment on the surface of the Al2O3 film layer. The RF power supply frequency is 40 KHZ, the power of the RF power supply is 4500 W, the duty cycle of the RF power supply is 4:50 / ms, and the discharge time of the RF power supply is 300 s; S7: Evacuate and purge the remaining gas in the reaction chamber; backpressure the chamber with nitrogen, with a nitrogen flow rate of 50000 SCCM / min for 200 s, take out the wafer, complete the process, and obtain the Al2O3 passivation film layer.

[0034] Example 4 Refer to Comparative Example 1, add an interface treatment of nitrous oxide and hydrogen after S4, and keep other steps unchanged.

[0035] S1: Place the silicon substrate on the graphite boat, send it into the reaction chamber of the furnace tube, preheat the reaction chamber, evacuate it, detect leaks, and perform a temperature increase treatment in a nitrogen atmosphere; S2: Evacuate, heat up to 315 °C, introduce TMA gas at 1660 SCCM / min and nitrous oxide at 5500 SCCM / min for 25 s, and keep the pressure constant at 190 Pa; S3: Turn on the RF power supply. The frequency of the RF power supply is 40 KHZ, the power of the RF power supply is 6000 W, the duty cycle of the RF power supply is 4:280 / ms, and the turning-on time is 169 s; S4: Evacuate and introduce argon to purge the remaining gas in the reaction chamber. The argon flow rate is 5000 SCCM / min and the time is 30 s; S5: Evacuate, heat up to 350 °C, introduce nitrous oxide and hydrogen into the reaction chamber. The amount of nitrous oxide is 5000 SCCM / min and the amount of hydrogen is 5000 SCCM / min for 20 s. Then turn on the RF power supply to perform interface treatment of plasma bombardment on the surface of the Al2O3 film layer. The frequency of the RF power supply is 40 KHZ, the power of the RF power supply is 4500 W, the duty cycle of the RF power supply is 4:50 / ms, and the discharge time of the RF power supply is 300 S; S6: Evacuate and purge the remaining gas in the reaction chamber; backpressure the chamber with nitrogen. The amount of nitrogen introduced is 50000 SCCM / min and the time is 200 s. Take the wafer to complete the process and obtain the Al2O3 passivation film layer.

[0036] Comparative Example 2 A process for depositing a single-layer alumina film by PE-ALD process, including the following steps: S1: Place the substrate silicon wafer on the graphite boat, send it into the high-temperature furnace tube (reaction chamber), and perform nitrogen atmosphere pre-temperature increase, evacuation, leak detection and temperature increase treatment on the reaction chamber. The pressure is 180 Pa and the temperature is 290 °C; S2: Introduce TMA (trimethylaluminum) gas into the chamber to cover the entire surface of the silicon substrate. The amount of TMA is 500 mg / min and the time is 15 s; then introduce the inert gas argon to purge the excess TMA. The argon flow rate is 5000 SCCM / min and the time is 10 s; S3: Introduce nitrous oxide again, use the RF power supply to decompose it into plasma, and react with the TMA on the surface of the silicon wafer. The amount of nitrous oxide is 3000 SCCM / min, the frequency of the RF power supply is 40 KHZ, the power is 5000 W, the duty cycle is 4:300 / ms, and the time is 15 s; S4: Finally, introduce argon gas to purge the residual gas in the chamber. The flow rate of argon gas is 3000 SCCM / min and the time is 10 s. Repeat the above process 13 times. S5: Evacuate the chamber and purge the remaining gas. The flow rate of nitrogen gas for purging is 10000 SCCM / min and the time is 30 s; Backpressure the chamber with nitrogen gas. The flow rate of nitrogen gas for returning to normal pressure is 50000 SCCM / min and the time is 200 s. Take out the wafer to complete the process.

[0037] Example 5 Refer to Comparative Example 2. Before step S2, introduce nitrous oxide to perform plasma bombardment treatment on the interface, and keep other steps unchanged.

[0038] S1: Place the substrate silicon wafer on the graphite boat, send it into the high-temperature furnace tube (reaction chamber), and perform preheating, evacuation, leak detection and heating treatment on the reaction chamber under a nitrogen atmosphere. The pressure is 180 Pa and the temperature is 290 °C. S2: Evacuate the chamber, introduce nitrous oxide into the reaction chamber. The flow rate of nitrous oxide is 5000 SCCM / min and the time is 20 s. Then turn on the radio frequency power supply to perform plasma bombardment treatment on the interface. The frequency of the radio frequency power supply is 40 KHZ, the power is 4500 W, the duty cycle is 4:64 / ms, and the discharge time of the radio frequency power supply is 250 S. S3: Evacuate the chamber, introduce gaseous TMA (trimethylaluminum) into the chamber to cover the entire surface of silicon oxide. The amount of TMA is 500 mg / min and the time is 15 s; Then introduce inert gas argon to purge the excess TMA. The flow rate of argon gas is 5000 SCCM / min and the time is 10 s. S4: Introduce nitrous oxide again, use the radio frequency power supply to decompose it into plasma and react with the TMA on the surface of the silicon wafer. The flow rate of nitrous oxide is 3000 SCCM / min, the frequency of the radio frequency power supply is 40 KHZ, the power is 5000 W, the duty cycle is 4:300 / ms, and the time is 15 s. S5: Finally, introduce argon gas to purge the residual gas in the chamber. The flow rate of argon gas is 3000 SCCM / min and the time is 10 s. Repeat the above process 13 times. S6: Evacuate the chamber and purge the remaining gas. The flow rate of nitrogen gas for purging is 10000 SCCM / min and the time is 30 s; Backpressure the chamber with nitrogen gas. The flow rate of nitrogen gas for returning to normal pressure is 50000 SCCM / min and the time is 200 s. Take out the wafer to complete the process.

[0039] Example 6 A method for preparing laminated alumina by PECVD process and PE-ALD process, comprising the following steps: S1: Place the substrate silicon wafer in a high-temperature furnace tube (reaction chamber), and perform nitrogen atmosphere preheating, evacuation, leak detection and heating treatment on the reaction chamber, with a pressure of 180 Pa and a temperature of 290 °C; S2: Evacuate, introduce nitrous oxide into the reaction chamber, with the amount of nitrous oxide being 5000 SCCM / min, the amount of hydrogen being 5000 SCCM / min, for 20 s. Subsequently, turn on the radio frequency power supply to perform interface treatment of plasma bombardment on the surface of the Al2O3 film layer. The frequency of the radio frequency power supply is 40 KHZ, the power of the radio frequency power supply is 4500 W, the duty cycle of the radio frequency power supply is 4:64 / ms, and the discharge time of the radio frequency power supply is 250 S; S3. Construct the second layer of alumina film: Evacuate, introduce TMA (trimethylaluminum) gas into the chamber to cover the entire surface of the silicon substrate, with the amount of TMA being 500 mg / min for 15 s; Subsequently, introduce the inert gas argon to purge the excess TMA, with the argon flow rate being 5000 SCCM / min for 10 s; S4. Then introduce nitrous oxide, and use the radio frequency power supply to decompose it into plasma to react with the TMA on the surface of the silicon wafer. The amount of nitrous oxide or oxygen is 3000 SCCM / min, the radio frequency power supply frequency is 40 KHZ, the power is 5000 W, the duty cycle is 4:300 / ms, and the time is 15 s; S5. Finally, introduce argon to purge the residual gas in the chamber, with the amount of argon introduced being 3000 SCCM for 10 s; Repeat the above process 13 times; S6. Continuously introduce nitrous oxide and silane into the reaction chamber, with the amount of nitrous oxide being 5500 SCCM / min and the amount of silane being 850 SCCM / min for 20 s. Subsequently, turn on the radio frequency power supply to perform interface treatment of plasma bombardment on the surface of the silicon substrate. The radio frequency power supply frequency is 40 KHZ, the power of the radio frequency power supply is 7500 W, the duty cycle of the radio frequency power supply is 4:80 / ms, and the discharge time of the radio frequency power supply is 20 s; S7. Construct the fourth layer of alumina film: Evacuate, heat up to 315 °C, introduce gaseous TMA at 1500 SCCM / min and nitrous oxide at 5500 SCCM / min for 25 S, with the pressure kept constant at 190 Pa; S8. Turn on the radio frequency power supply, with the radio frequency power supply frequency being 40 KHZ, the radio frequency power supply power being 6000 W, the radio frequency power supply duty cycle being 4:280 / ms, and the radio frequency power supply being turned on for 169 s; S9. Evacuate, introduce argon to purge the remaining gas in the reaction chamber, with the argon flow rate being 5000 SCCM / min for 30 s; S10: Evacuate the vacuum, heat up to 350 °C, introduce nitrous oxide and hydrogen into the reaction chamber. The amount of nitrous oxide is 5000 SCCM / min, the amount of hydrogen is 5000 SCCM / min, and the time is 20 s. Subsequently, turn on the radio frequency power supply to perform interface treatment of plasma bombardment on the surface of the Al2O3 film layer. The frequency of the radio frequency power supply is 40 KHZ, the power of the radio frequency power supply is 4500 W, the duty cycle of the radio frequency power supply is 4:50 / ms, and the discharge time of the radio frequency power supply is 300 s; S11: Evacuate the vacuum and purge the remaining gas in the reaction chamber; backpressure the chamber with nitrogen. The amount of nitrogen introduced is 50000 SCCM / min, and the time is 200 s. Take the wafer to complete the process and obtain the laminated Al2O3 passivation film layer.

[0040] Battery preparation The original silicon wafer is cleaned with deionized water for plasma, and then alkali texturing is carried out to prepare a textured surface; boron diffusion is carried out on the front side of the battery to prepare a PN junction; laser SE is used for secondary doping concentration promotion to remove the surface borosilicate glass, alkali polishing is carried out on the back side to prepare a tunneling oxide layer and a phosphorus-doped amorphous layer; annealing is carried out to form a phosphorus-doped polycrystalline layer; the surface phosphosilicate glass is removed; the silicon wafer is cleaned; Prepare the front Al2O3 thin film according to the methods of the above 5 examples and 2 comparative examples to improve the battery efficiency; prepare the front and back silicon nitride thin films; screen-print the electrodes, sinter and test.

[0041] Perform I-V performance tests on the passivation quality of the Al2O3 passivation thin films deposited in each example in the battery; the corresponding test results are shown in Table 2.

[0042] The I-V performance test data involved in Table 2 are all the averages obtained from a large number of experimental groups, with high accuracy and reference value, thus excluding the differences in results caused by small data volume or test errors.

[0043] As can be seen from Table 2, compared with Comparative Example 1 (PECVD basic process), the Eff of Example 1 has a slight increase, mainly manifested in the increase of Voc and Isc, indicating that the negative charge density of the alumina film deposited on the 2-3nm silicon oxide interface is higher, which is significantly beneficial to the passivation performance of the front side of the battery. Comparing Example 3 with Comparative Example 1 (PECVD basic process), the Eff has a slight increase, mainly manifested in the increase of Voc and Isc, indicating that more Al-O-Al bonds are obtained by plasma bombardment of nitrous oxide and ammonia on the deposited alumina interface, which improves the passivation performance of the front side of the battery. Comparing Example 2 with Example 1, Example 3 and Comparative Example 1, the Eff still has a slight increase, mainly manifested in the increase of Voc and Isc, indicating that depositing alumina on the 1-2nm thin silicon oxide interface or performing interface plasma treatment of nitrous oxide and hydrogen after deposition can form more tetrahedral structures and obtain more AlO4 - ions, making it have a stronger passivation effect. Comparing Example 4 with Comparative Example 2 (PE-ALD basic process), even before the deposition of alumina, using nitrous oxide and hydrogen plasma to bombard the silicon substrate to form a silicon oxide layer as thin as 1-2nm will increase the negative charge density at the alumina interface, thereby increasing the Eff. The gain of Eff still mainly comes from the increase of Voc and Isc. Comparing Example 5 with Examples 1-4 and Comparative Examples 1-2, the Eff of the laminated alumina passivation film prepared by using PECVD and PE-ALD processes together is the highest. Thus, it can be seen that the field-effect passivation and chemical passivation of the laminated alumina passivation film are in an excellent state, greatly reducing the gap with the high-passivation-quality alumina passivation film with a dense deposited film layer by the ALD process.

[0044] Table 1 Process flow of preparing laminated alumina film based on PECVD process and PE-ALD process.

[0045] S1 Place the silicon substrate in the tube PECVD deposition chamber, and evacuate, leak-check, and adjust the temperature and pressure of the chamber S2 Continuously introduce nitrous oxide to perform a plasma interface treatment on the surface of the silicon wafer to construct the first layer of thin tunneling oxide film <![CDATA[For the deposition of the bottom alumina film on S3, in the form of heating and evaporation with argon carrying the source, gaseous TMA is deposited on the surface of the silicon wafer. Subsequently, argon is introduced to purge the excess TMA. Then, while introducing N2O, the radio frequency power supply is turned on to react with the previously deposited TMA. Finally, argon is introduced again to purge the excess N2O and TMA groups; repeat 10 - 15 times]]> S4 Continuously introduce nitrous oxide and silane, and under the discharge of the radio frequency power supply, construct the third layer of oxide film <![CDATA[Deposit the top alumina film of S5. After evacuating the vacuum, pre-purging the gas, and briefly heating up, introduce gaseous TMA and N2O under the discharge environment of the radio frequency power supply to form plasma groups]]> S6 Continuously introduce nitrous oxide and hydrogen to perform a plasma treatment on the interface, bombard the alumina film at the interface to obtain a denser alumina film layer; and the amount of TMA gas introduced in S5 is higher than the amount of TMA gas introduced in S3 S7 Evacuate, clean and purge the remaining gas in the furnace tube reaction chamber, and backpressure the chamber with nitrogen to obtain a laminated alumina film layer Table 2 I-V performance test result diagram of Al2O3 thin film deposited battery for each example Eff(%) Voc(V) Isc(A) FF(%) Comparative Example 1 25.34 0.710 17.174 81.29 Example 1 25.36 0.712 17.177 81.31 Example 2 25.37 0.713 17.178 81.35 Example 3 25.35 0.711 17.176 81.33 Comparative Example 2 25.37 0.713 17.179 81.36 Example 4 25.39 0.715 17.181 81.39 Example 5 25.42 0.719 17.188 81.40 。

Claims

1. A method for preparing a stacked solar alumina film based on PECVD and PE-ALD processes, characterized in that, The method includes the following steps: S1. Place the silicon substrate in the tube PECVD deposition chamber, and evacuate the chamber, detect leaks, and adjust the temperature and pressure; S2. Continuously introduce nitrous oxide to perform plasma interface treatment on the silicon wafer surface to construct the first layer of thin tunneling silicon oxide film; S3. Construct the second layer of aluminum oxide film: Evacuate the chamber, and in the form of heating and evaporating with argon carrying the source, deposit gaseous TMA on the silicon wafer surface. Then introduce argon to purge the excess TMA. While introducing N2O, turn on the radio frequency power supply to react with the previously deposited TMA to form an Al2O3 film on the silicon wafer surface. Finally, introduce argon again to purge the excess N2O and TMA groups; Repeat the above process to obtain the second layer of aluminum oxide film; S4. Construct the third layer of silicon oxide film: Evacuate the chamber, continuously introduce nitrous oxide and silane, and form a silicon oxide film under the discharge of the radio frequency power supply; S5. Construct the fourth layer of aluminum oxide film: Evacuate the chamber, pre-ventilate, and after a short temperature increase, introduce gaseous TMA and N2O under the discharge environment of the radio frequency power supply to deposit and form the fourth layer of aluminum oxide film; S6. Evacuate the chamber, pre-ventilate, and continuously introduce nitrous oxide and ammonia to perform plasma interface treatment on the silicon wafer surface; And, the amounts of nitrous oxide and ammonia introduced in S6 are higher than those in S2, and the amount of TMA gas introduced in S5 is higher than that in S3; S7. Evacuate the chamber, clean and purge the remaining gas in the furnace tube reaction chamber, and backpressure the chamber with nitrogen to obtain a laminated aluminum oxide film layer.

2. A method for preparing a stacked solar alumina film based on PECVD and PE-ALD processes according to claim 1, wherein The temperature and pressure adjustment treatment in S1 refers to adjusting the pressure to 175 Pa - 180 Pa and the temperature to 250 - 290 °C; In S2, the amount of nitrous oxide introduced is 5000 SCCM, the time is 18 s, and the radio frequency power is 4500 W; In S3, the amount of TMA gas introduced is 500 mg / min, and the time is 10 - 15 s; In S3, the amount of nitrous oxide introduced is 3000 SCCM / min, the time is 15 s, and the radio frequency power is 5000 W; In S3, the amount of argon introduced is 5000 SCCM / min, and the time is 10 s; In S3, the number of repetitions is 10 - 15 times; In S4, the amount of silane introduced is 850 SCCM / min. The amount of nitrous oxide is 5500 SCCM / min, the time is 10 s, and the radio frequency power is 7500 W; In S5, the amount of TMA gas introduced is 1500 mg / min, the amount of N2O is 5500 SCCM / min, the time is 160 s, and the radio frequency power supply power is 6000 W; In S6, the amounts of nitrous oxide and ammonia introduced are both 6000 SCCM, the time is 18 s, and the radio frequency power is 5500 W; In S7, the amount of nitrogen introduced for purging is 10000 SCCM / min, and the time is 30 s.

3. A method for preparing a stacked solar alumina film based on PECVD and PE-ALD processes, characterized in that, The method includes the following steps: S1: Place the substrate silicon wafer in a high-temperature furnace tube (reaction chamber), and perform pre-heating under a nitrogen atmosphere, evacuation, leak detection, and temperature increase treatment on the reaction chamber, with a pressure of 175 Pa - 180 Pa and a temperature of 250 °C - 290 °C; S2: Continuously introduce nitrous oxide into the reaction chamber. After 10 s, turn on the radio frequency power supply to perform interface treatment on the surface of the silicon substrate. The radio frequency power supply has a frequency of 40 KHZ, a power of 4500 W, and a discharge time of 18 s; S3. Construct the second layer of alumina film: Introduce gaseous TMA (trimethylaluminum) into the chamber to cover the entire surface of the silicon substrate. The amount of TMA is 500 mg / min for a time of 10 - 15 s; Subsequently, introduce an inert gas, argon or nitrogen, to purge away the excess TMA. The argon flow rate is 5000 SCCM / min for a time of 10 s; S4. Then introduce nitrous oxide or oxygen, and use the radio frequency power supply to decompose it into plasma to react with the TMA on the surface of the silicon wafer. The amount of nitrous oxide or oxygen is 3000 SCCM / min, the radio frequency power supply has a frequency of 40 KHZ, a power of 5000 W, a duty cycle of 4:300 / ms, and a time of 15 s; S5. Finally, introduce argon to purge away the residual plasma. The amount of argon introduced is 3000 SCCM for a time of 10 s; Repeat the above process 10 - 15 times; S6. Construct a silicon oxide film: Continuously introduce silane and nitrous oxide into the reaction chamber. The temperature in the chamber is 300 - 320 °C, the pressure is 200 Pa, the amount of silane introduced is 850 SCCM / min, and the amount of nitrous oxide introduced is 5500 SCCM / min. After 15 s, turn on the radio frequency power supply. The radio frequency power supply has a frequency of 40 KHZ, a power of 7500 W, a duty cycle of 4:80 / ms, and a discharge time of 20 s; S7. Construct the fourth layer of alumina film: Continuously introduce gaseous TMA (trimethylaluminum) and nitrous oxide into the reaction chamber. The temperature in the chamber is 310 - 320 °C, the pressure is 190 Pa, the amount of gaseous TMA introduced is 1500 mg / min, and the amount of nitrous oxide introduced is 5500 SCCM / min. After 10 s, turn on the radio frequency power supply. The radio frequency power supply has a frequency of 40 KHZ, a power of 6000 W, a duty cycle of 4:280 / ms, and a discharge time of 160 s; S8. Construct the fifth layer of interface treatment: Continuously introduce nitrous oxide and hydrogen into the reaction chamber. The temperature in the chamber is 340 - 360 °C, the pressure is 180 Pa, and the amounts of nitrous oxide and ammonia introduced are both 6000 SCCM / min. After 18 s, turn on the radio frequency power supply. The radio frequency power supply has a frequency of 40 KHZ, a power of 5500 W, a duty cycle of 4:60 / ms, and a discharge time of 300 s; S9: Evacuate and purge the remaining gas in the chamber. The amount of nitrogen purged is 10000 SCCM / min for a time of 30 s; Backfill the chamber with nitrogen. The amount of normal pressure nitrogen introduced is 50000 SCCM / min for a time of 200 s, take out the wafer, and complete the process.

4. A method for preparing a stacked solar alumina film based on PECVD and PE-ALD processes according to claim 1 or 3, characterized in that, The laminated alumina film prepared by the above method is applied to a battery film, and it includes the following steps: The original silicon wafer is subjected to deionized water cleaning, followed by alkaline texturing to prepare a textured surface; boron diffusion is carried out on the front side of the cell to prepare a PN junction; laser SE is used for secondary doping concentration promotion to remove the surface borosilicate glass, alkaline polishing is carried out on the back side to prepare a tunneling oxide layer and a phosphorus-doped amorphous layer; annealing is performed to form a phosphorus-doped polycrystalline layer; the surface phosphorus-silicate glass is removed; the silicon wafer is cleaned; The front-side Al2O3 film is prepared according to the above method to increase field passivation and chemical passivation; silicon nitride films are prepared on the front and back sides; screen printing of electrodes, sintering, and testing are then carried out.

Images