Passivation method of boron and phosphorus doped Poly layer, passivation contact structure of boron and phosphorus doped Poly layer and battery

Abstract

The invention discloses a passivation method of a boron and phosphorus doped Poly layer, a passivation contact structure of the boron and phosphorus doped Poly layer and a battery. The passivation method comprises the following steps: firstly, growing a tunneling oxide layer with two thin and compact sides and a thick and loose middle on the surface of a silicon wafer by adopting a mode of combining low-temperature low-pressure oxidation, high-temperature normal-pressure oxidation and low-temperature normal-pressure oxidation, and then carrying out deposition and oxidation propulsion of boron atoms and / or phosphorus atoms by adopting a high-temperature diffusion tube, so that boron and phosphorus with a certain concentration are doped in a Poly silicon layer. According to the invention, through superposition of the oxide layers with different compactness, the overall thickness of the tunneling oxide layer is improved, so that the structure of the tunneling oxide layer is not obviously damaged in the subsequent boron and phosphorus diffusion process, and the passivation effect of the boron and phosphorus doped Poly layer is obviously improved. According to the passivation method disclosed by the invention, Poly silicon layers and doped polycrystalline silicon layers with different thicknesses can be obtained, and the passivation method can be applied to all batteries needing to use boron Poly and phosphorus Poly.

Description

Technical Field

[0001] The present invention belongs to the technical field of solar cells, and particularly relates to a passivation method for a boron- and phosphorus-doped Poly layer, a passivated contact structure, and a battery thereof. Background Art

[0002] The passivation effect has a direct impact on the photoelectric conversion efficiency of solar cells. When sunlight irradiates a cell, two types of carriers, negatively charged electrons and positively charged holes, are excited inside the cell. During the production of solar cell wafers, it is necessary to minimize the defects inside the wafers and the interface state density on each surface, enhance the passivation effect, thereby reducing the recombination of electrons and holes inside the solar cell wafers, reducing internal consumption, and enabling as many carriers as possible to reach the positive and negative electrodes of the battery, thereby increasing the photoelectric conversion efficiency of the battery.

[0003] In the manufacture of solar cells, boron- and phosphorus-doped Poly (polycrystalline silicon structure with a tunneling oxide layer doped with boron and phosphorus) passivation is a common surface treatment method.

[0004] For the boron diffusion on N-type silicon in the boron-doped Poly layer, the boron atoms entering the monocrystalline silicon substrate will form a PN junction with the N-type silicon substrate. On the one hand, the passivation mechanism is that the PN junction can screen out holes to pass through the PN junction while blocking electrons, thereby forming an environment with a dominant number of holes on one side of the PN junction and a dominant number of electrons on the other side, thereby reducing the recombination annihilation of holes and electrons at defects. On the other hand, there are a large number of defects at the junction of the monocrystalline silicon and the Poly layer. Growing a dense tunneling oxide layer between the two interfaces can significantly reduce the interface state density, so that the recombination of holes when passing through the tunneling oxide layer is small. The tunneling oxide layer and the PN junction work together, so that the boron Poly has a good passivation effect. Generally, the composite current density (the magnitude of the composite current per unit area) is used to characterize the passivation effect. The smaller the composite current density, the better the surface passivation effect.

[0005] The passivation mechanism of the phosphorus-doped Poly layer is similar. There are a high concentration of phosphorus atoms in the Poly layer, and at the same time, a part of the phosphorus atoms will pass through the tunneling oxide layer to form a high-low junction structure with the N-type substrate, resulting in band bending near the tunneling oxide layer. On the one hand, it reduces the number of minority carriers (holes) near the tunneling oxide layer, reducing recombination. On the other hand, it can screen out majority carriers (electrons) to selectively pass through the tunneling oxide layer, thereby greatly enhancing the passivation effect.

[0006] At present, the commonly used passivation method for boron- and phosphorus-doped Poly layers is to place the silicon wafer in a quartz furnace tube and introduce oxygen in an environment above 600°C. Oxygen directly reacts with the silicon on the surface of the silicon wafer at high temperature to form a silicon oxide film (tunneling oxide layer) with a thickness of 1-2 nm. Then, a Poly silicon layer (polycrystalline silicon layer) is directly deposited on this tunneling oxide layer. Subsequently, it is placed in a high-temperature diffusion furnace tube for deposition and oxidation promotion steps, and finally cooled to room temperature to obtain the required boron Poly or phosphorus Poly structure. However, the passivation effect of the Poly obtained by this method is not very good, and the recombination current density is relatively high; especially the recombination current density of boron Poly is above 15 fA / cm 2 Above. Moreover, when using this passivation method, since the tunneling oxide layer of the boron- and phosphorus-doped Poly layer is directly grown by high-temperature oxidation and is relatively loose, the passivation effect is not good. When the boron and phosphorus doping concentrations are high, it is easy to cause serious internal diffusion, and it is also greatly affected by the subsequent processes, making it impossible to form a better morphology structure; it cannot meet the requirements of complex-structured batteries (such as BC-structured batteries) that require secondary processing on the Poly layer. Summary of the Invention

[0007] Aiming at the problem of poor passivation effect of boron- and phosphorus-doped Poly layers caused by the existing direct high-temperature growth of tunneling oxide layers, the purpose of the present invention is to provide a passivation method for boron- and phosphorus-doped Poly layers, a passivation contact structure, and a battery that optimize the passivation effect based on the LPCVD process.

[0008] The present invention achieves the above technical effects through the following technical solutions.

[0009] In a first aspect, the passivation method for the boron- and phosphorus-doped Poly layer provided by the present invention includes the following steps: S1. Provide a clean and polished silicon wafer. Using an LPCVD device, evacuate the air and introduce oxygen. At a low temperature and low pressure below 600°C, perform the first oxidation on the silicon wafer to grow a first oxide layer with a thickness of 0.3 - 0.8 nm and being dense on the surface of the silicon wafer; S2. Raise the temperature in step S1 by 50 - 220°C, continuously introduce oxygen, and at a pressure greater than or equal to 1 standard atmosphere, perform the second oxidation on the silicon wafer to continue growing a second oxide layer with a thickness of 0.5 - 1 nm and being porous on the surface of the silicon wafer; S3. Stop introducing oxygen, keep the pressure unchanged, lower the temperature to below 600°C, perform the third oxidation on the silicon wafer to continue growing a third oxide layer with a thickness of 0.1 - 0.4 nm and being dense on the surface of the silicon wafer; thus, a tunneling oxide layer structure with a porous middle and dense sides is grown on the surface of the silicon wafer; S4. Continue to use the LPCVD device, raise the temperature in step S3 by 0 - 50°C, evacuate the air and then introduce silane. At a high temperature and low pressure, deposit a polysilicon layer on the first oxide layer until the film thickness required by the process is reached; S5. Use a high-temperature diffusion tube to deposit and oxidize and push boron atoms or phosphorus atoms, so that a certain concentration of boron or phosphorus is doped in the polysilicon layer to form a doped polysilicon layer.

[0010] Preferably, in step S1, the temperature is 400 - 590°C, the pressure is 0.1 - 0.5 standard atmospheres, and the first oxidation time is 10 - 20 minutes.

[0011] Further, in step S2, the temperature is 610 - 640°C, the pressure is normal pressure, and the second oxidation time is 10 - 20 minutes.

[0012] Further, in step S3, the temperature is 550 - 590°C, the pressure is normal pressure, and the third oxidation time is 10 - 20 minutes.

[0013] Further, in step S4, the temperature is 550 - 640°C, and the vacuum pressure is 180 - 300 mTorr.

[0014] Further, the silicon wafer is an N-type silicon wafer or a P-type silicon wafer.

[0015] Further, in steps S1 and S2, the flow rate of the introduced oxygen is 5 - 30 L / min.

[0016] In step S5, during the process of depositing boron atoms and oxidizing and promoting (boron diffusion), the deposition temperature is 800 - 850 °C, the temperature for oxidizing and promoting is 940 - 1000 °C, and the optimal temperature for oxidizing and promoting is 960 °C; during the process of depositing phosphorus atoms and oxidizing and promoting (phosphorus diffusion), the deposition temperature is 800 - 850 °C, and the temperature for oxidizing and promoting is 880 - 920 °C. The tunneling oxide layer is grown by combining low-temperature and low-pressure oxidation, high-temperature and atmospheric-pressure oxidation, and low-temperature and atmospheric-pressure oxidation. The influence of the temperature fluctuations of boron and phosphorus diffusion oxidation on the back is relatively small, and fluctuations of up to 30 °C above the optimal oxidation promotion temperature can be almost tolerated.

[0017] In a second aspect, the present invention provides a passivated contact structure with a boron- and phosphorus-doped Poly layer. The passivated contact structure includes a first oxide layer, a second oxide layer, a third oxide layer, and a doped polysilicon layer grown on a silicon wafer using the aforementioned passivation method. The doped polysilicon layer is above the first oxide layer. The first oxide layer, the second oxide layer, and the third oxide layer form a tunneling oxide layer. The second oxide layer of the doped polysilicon layer is in the middle of the tunneling oxide layer, thick and porous; the first oxide layer and the third oxide layer are on both sides of the tunneling oxide layer, thin and dense.

[0018] In a third aspect, the present invention provides a battery with a passivated contact structure having a boron- and phosphorus-doped Poly layer. The battery includes a silicon wafer and the aforementioned passivated contact structure formed on the surface of the silicon wafer.

[0019] Furthermore, the battery is a TOPCon battery, a TBC battery, or a perovskite tandem battery.

[0020] Compared with the prior art, the present invention has the following beneficial effects.

[0021] The present invention uses a combination of low-temperature and low-pressure oxidation, high-temperature and atmospheric-pressure oxidation, and low-temperature and atmospheric-pressure oxidation to grow the tunneling oxide layer. The film structure of the generated tunneling oxide layer is a laminated structure with thin and dense layers on both sides and thick and porous layers in the middle. By stacking oxide layers with different densifications, the passivation effect of the boron- and phosphorus-doped Poly layer structure is improved.

[0022] The thin and dense oxide layers on both sides are grown at low temperature, and there are fewer interface defects at the interface with the Poly silicon layer, which can significantly reduce the interface state density at the interface between the oxide layer and silicon, reduce the recombination of carriers reaching this interface, and significantly improve the passivation effect.

[0023] Meanwhile, the second oxide layer grown at high temperature is thick and porous. It can not only increase the overall thickness of the tunneling oxide layer (although the thickness of the three-layer oxide layer stack is approximately equal to that of the conventional tunneling oxide layer), but also provide channels for impurity atoms to pass through the tunneling oxide layer during subsequent boron diffusion (doping) and / or phosphorus diffusion (doping) to form a PN junction, thus preventing the tunneling oxide layer from being significantly damaged and further improving the passivation effect.

[0024] Compared with the boron- and phosphorus-doped Poly layers of traditional direct high-temperature oxidation processes, the minority carrier lifetime, iVoc, iFF, and PL brightness are significantly improved, and the recombination current density J0 is significantly reduced when using the passivation method of the present invention, showing a better passivation effect.

[0025] The passivation method of the present invention can obtain a good passivation effect by optimizing parameters such as the pressure, temperature, and time of the LPCVD equipment. The required structure can be obtained in one process. Compared with other passivation methods such as annealing, hydrogen implantation, and adding laminated layers of different materials, the process time is short and less special gas is used, which can effectively reduce production costs.

[0026] The passivation contact structure grown by the passivation method of the present invention has good robustness. During the use of the LPCVD equipment, when parameters such as the temperature and gas flow of the high-temperature furnace tube fluctuate slightly, the passivation effect of the boron- and phosphorus-doped Poly layer will not be significantly affected. The tunneling oxide layer grown by the present invention is less affected by the temperature fluctuation of boron and phosphorus diffusion oxidation and can accept a fluctuation of 30 °C above the optimal oxidation promotion temperature.

[0027] When the passivation contact structure grown by the passivation method of the present invention is applied to the preparation of a battery with a complex secondary processed structure (such as a BC structure battery) that requires a boron- and phosphorus-doped Poly layer, the subsequent laser process will not have a great impact on the structure of the tunneling oxide layer, and the plane after wet etching is flatter, and a better morphological structure can be formed.

[0028] The passivation method of the present invention can obtain Poly silicon layers and doped polycrystalline silicon layers with different required thicknesses. The passivation performance of the boron- or phosphorus-doped Poly layer is excellent and can be applied to all batteries that require the use of boron Poly or phosphorus Poly. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0030] Figure 1 Schematic diagram of the passivation contact structure of the present invention.

[0031] Figure 2 Depth-concentration comparison diagram of the boron-doped Poly layer of the present invention and the prior art.

[0032] Figure 3 Schematic diagram of the TOPCon cell structure.

[0033] Figure 4 Schematic diagram of the TBC cell structure.

[0034] Figure 5 Depth-concentration comparison diagram of the boron-doped Poly layer after laser film removal and cleaning film removal.

[0035] Figure 6 Back-side scanning electron microscope image of the BC structure cell prepared by using the passivation method of the present invention.

[0036] In the figure: 1 - silicon wafer, 2 - first oxide layer, 3 - second oxide layer, 4 - third oxide layer, 5 - doped polysilicon layer. Detailed implementation manners

[0037] In order to make the technical problems, technical solutions and beneficial effects solved by the present invention clearer and more understandable, the present invention will be further described in detail below in combination with specific implementation manners. It should be understood that the implementation manners described here are a part of the implementation manners of the present invention, rather than all of the implementation manners, and are only used to explain the present invention and not to limit the present invention. Based on the implementation manners in the present invention, all other implementation manners obtained by those of ordinary skill in the art without creative efforts belong to the protection scope of the present invention.

[0038] First aspect, a passivation method for boron- and phosphorus-doped Poly layer provided by the present invention includes the following steps: S1. Provide a clean and polished silicon wafer, use an LPCVD device, evacuate, introduce oxygen, and perform the first oxidation on the silicon wafer at a low temperature and low pressure below 600 °C to grow a thin and dense first oxide layer on the surface of the silicon wafer; S2. Raise the temperature in step S1 by 50-220 °C, continuously introduce oxygen, and perform the second oxidation on the silicon wafer at a pressure greater than or equal to 1 standard atmosphere to continue growing a thick and porous second oxide layer on the surface of the silicon wafer; S3. Stop introducing oxygen, keep the pressure unchanged, lower the temperature to below 600 °C, and perform the third oxidation on the silicon wafer to continue growing a thin and dense third oxide layer on the surface of the silicon wafer; thus, a tunneling oxide layer structure with a porous middle and dense sides is grown on the surface of the silicon wafer; S4. Continue to use the LPCVD device, raise the temperature in step S3 by 0-50 °C, introduce silane, and evacuate at the same time, and deposit a polysilicon layer on the first oxide layer at a high temperature and low pressure until the film thickness required by the process is reached; S5. Use a high-temperature diffusion tube to deposit and oxidize boron atoms or phosphorus atoms to promote the doping of a certain concentration of boron or phosphorus in the polysilicon layer to form a doped polysilicon layer.

[0039] As a preferred embodiment, in step S1, the temperature is 400-590 °C, the pressure is 0.1-0.5 standard atmospheres, the first oxidation time is 10-20 minutes, and the thickness of the first oxide layer is 0.3-0.8 nm. Specifically, the temperature of the first oxidation can be 400 °C, 430 °C, 460 °C, 490 °C, 500 °C, 520 °C, 550 °C, 570 °C, or 590 °C, etc.; further preferably 500-580 °C. The first oxidation time can be 10 minutes, 14 minutes, 16 minutes, 18 minutes, or 20 minutes, etc. The thickness of the first oxide layer can be 0.3 nm, 0.4 nm, 0.5 nm, 0.6 nm, 0.7 nm, or 0.8 nm, etc., and further preferably 0.3-0.5 nm. In this way, a thin and dense tunneling oxide layer can be formed by low-temperature and low-pressure oxidation.

[0040] As a preferred embodiment, in step S2, the temperature is 610-640 °C, the pressure is normal pressure, the second oxidation time is 10-20 minutes, and the thickness of the second oxide layer is 0.5-1 nm. Specifically, the temperature of the second oxidation can be 610 °C, 620 °C, 625 °C, 632 °C, or 640 °C, etc. The second oxidation time can be 10 minutes, 14 minutes, 16 minutes, 18 minutes, or 20 minutes, etc. The thickness of the second oxide layer can be 0.5 nm, 0.6 nm, 0.7 nm, 0.8 nm, 0.9 nm, or 1 nm, etc. In this way, a thick and porous tunneling oxide layer can be formed by high-temperature and normal-pressure oxidation.

[0041] As a preferred embodiment, in step S3, the temperature is 550 - 590 °C, the pressure is atmospheric pressure, the third oxidation time is 10 - 20 minutes, and the thickness of the third oxide layer is 0.1 - 0.4 nm. Specifically, the temperature of the third oxidation can be 550 °C, 560 °C, 570 °C, 580 °C or 590 °C, etc. The third oxidation time can be 10 minutes, 14 minutes, 16 minutes, 18 minutes, or 20 minutes, etc. The thickness of the third oxide layer can be 0.1 nm, 0.18 nm, 0.25 nm, 0.3 nm, 0.35 nm, or 0.4 nm, etc. In this way, a thin and dense tunneling oxide layer can be formed by low-temperature atmospheric oxidation.

[0042] As a preferred embodiment, in step S4, the temperature is 550 - 640 °C, specifically, it can be 550 °C, 560 °C, 570 °C, 580 °C, 590 °C, 600 °C, 610 °C, 620 °C, 630 °C or 640 °C, etc.; the vacuum pressure is 180 - 300 mTorr, specifically, it can be 180 mTorr, 200 mTorr, 220 mTorr, 250 mTorr, 280 mTorr or 300 mTorr, etc. In this way, polysilicon layers with different thicknesses can be deposited on the tunneling oxide layer.

[0043] As a preferred embodiment, the silicon wafer is an N-type silicon wafer or a P-type silicon wafer. The passivation method of the present invention is applicable not only to N-type silicon wafers but also to P-type silicon wafers.

[0044] As a preferred embodiment, in steps S1 and S2, the flow rate of the oxygen introduced is 5 - 30 L / min. In this way, the thickness of the oxide layer required for forming the passivation contact can be satisfied.

[0045] The oxygen flow rate can control the time for the furnace tube to change from vacuum to atmospheric pressure. Low-pressure oxidation is similar in nature to low-temperature oxidation, and both can form a denser tunneling oxide layer. In step S1, it is best to introduce oxygen slowly to allow low-temperature and low-pressure growth.

[0046] In step S3, there is no need to introduce oxygen, and the existing oxygen in the tube can be used for continuous oxidation.

[0047] As a preferred embodiment, during the process of depositing boron atoms and oxidation push (boron diffusion), the deposition temperature is 800 - 850 °C, the oxidation push temperature is 940 - 1000 °C, and the optimal oxidation push temperature is 960 °C; during the process of depositing phosphorus atoms and oxidation push (phosphorus diffusion), the deposition temperature is 800 - 850 °C, and the oxidation push temperature is 880 - 920 °C.

[0048] Specifically, boron trichloride and oxygen are introduced into the boron diffusion process, and the deposition is first carried out at 800-850°C for 600-1500 seconds, and then the temperature is raised to 940-1000°C, and more oxygen is continued to be introduced for more than 20 minutes. Phosphorus oxychloride and oxygen are introduced into the phosphorus diffusion process, and the deposition is first carried out at 800-850°C for 600-1500 seconds, and then the temperature is raised to 880-920°C, and more oxygen is continued to be introduced for 10-20 minutes. The specific deposition amount, oxidation time and temperature mainly depend on the LP process.

[0049] The oxidation advancement temperature has a great influence on diffusion. However, the present invention adopts a combination of low-temperature and low-pressure oxidation, high-temperature and normal-pressure oxidation, and low-temperature and normal-pressure oxidation to grow the tunneling oxide layer, which is less affected by the fluctuation of the diffusion temperature of boron and phosphorus, and can accept a fluctuation of 30°C above the optimal oxidation advancement temperature.

[0050] After the heteroatom diffusion, the doping concentration corresponding to different depths of the silicon wafer can be obtained through the ECV test machine. Figure 2 It can be seen from the comparison in that compared with the boron-doped Poly layer of the prior art that grows a loose tunneling oxide layer by high-temperature oxidation, the present invention can reduce the internal expansion while obtaining a higher doping concentration (the faster the decline, the smaller the internal expansion), thereby improving the passivation performance.

[0051] In a second aspect, the present invention provides a passivation contact structure of a boron- and phosphorus-doped Poly layer, such as Figure 1 As shown, the passivation contact structure includes a first oxide layer 2, a second oxide layer 3, a third oxide layer 4 and a doped polysilicon layer 5 grown on a silicon wafer 1 using the aforementioned passivation method, the doped polysilicon layer 5 is on the first oxide layer 2, the first oxide layer 2, the second oxide layer 3 and the third oxide layer 4 constitute a tunneling oxide layer, the second oxide layer 3 is located in the middle of the tunneling oxide layer, and is thick and loose; the first oxide layer 2 and the third oxide layer 4 are located on both sides of the tunneling oxide layer, and are thin and dense.

[0052] In a third aspect, the present invention provides a battery having a passivation contact structure of a boron- and phosphorus-doped Poly layer, the battery comprising a silicon wafer and the passivation contact structure as described above formed on the surface of the silicon wafer.

[0053] As a preferred embodiment, the battery is a TOPCon battery, a TBC battery or a perovskite tandem battery.

[0054] The passivation method of the present invention can obtain the required Poly silicon layer and doped polysilicon layer of different thicknesses. The boron and phosphorus doped Poly layer has excellent passivation performance and can be applied to all batteries that need to use boron Poly and phosphorus Poly. Figure 3As shown, the passivation method of the present invention can grow a tunneling oxide layer structure with a loose middle and dense sides in the N region of the TOPCon cell structure, deposit a Poly silicon layer, and form an NPoly layer of a doped polysilicon layer after boron or phosphorus doping. As Figure 4 shown, the passivation method of the present invention can grow a tunneling oxide layer structure with a loose middle and dense sides in the N region and P region of the TBC cell structure, deposit a Poly silicon layer, and form an NPoly layer and a PPoly layer of a doped polysilicon layer after boron or phosphorus doping.

[0055] For structures such as BC cells that require further processing of the boron-doped Poly layer structure, the tunneling oxide layer grown by the present invention can better resist the influence of laser on the boron-doped Poly layer. Figure 5 The concentration-depth curves of two BSG film removal methods, laser film removal and cleaning film removal, are shown. It can be seen that the laser process has no obvious effect on the subsequent inward diffusion of boron atoms. At the same time, its uniform tunneling oxide film layer is more likely to form a flatter surface during the subsequent wet etching process. For the BC structure battery prepared by the passivation method of the present invention, from Figure 6 the back scanning electron microscope image, it can be observed that the passivation method of the present invention can form a P region, an N region, and a Gap region with better flatness.

[0056] Hereinafter, the specific embodiments of the present invention will be further explained and illustrated by examples and comparative examples.

[0057] The reagents, materials, and instruments used in the following description are all conventional reagents, conventional materials, and conventional instruments, which can be obtained commercially without special instructions. The methods in the examples are all conventional methods in the art without special instructions.

[0058] Example 1

[0059] The passivation method of the boron-doped Poly layer provided by the present invention includes the following steps.

[0060] S1. Prepare an N-type silicon wafer 1 with a resistivity of 10 Ω·cm and a thickness of 180 μm, polish both sides, clean it, put it into an LPCVD device, evacuate to a near-vacuum state, slowly heat the furnace tube to 570 °C, slowly introduce oxygen into the furnace tube at a flow rate of 10 L / min, and keep the pressure in the furnace tube below 0.5 standard atmospheric pressure during the heating process. Oxidize the silicon wafer for the first time for 15 minutes in a low-temperature and low-pressure environment to grow a dense first oxide layer 2 with a thickness of 0.4 nm on the surface of the silicon wafer.

[0061] S2. Continuously introduce oxygen. The pressure inside the furnace tube is 1 standard atmosphere. Raise the temperature inside the furnace tube to 630 °C. Perform the second oxidation of the silicon wafer for 12 minutes in an environment of high temperature and normal pressure, and continue to grow a relatively loose second oxide layer 3 with a thickness of 0.8 nm on the surface of the silicon wafer.

[0062] S3. Stop introducing oxygen, keep the pressure inside the furnace tube unchanged, lower the temperature to 580 °C, perform the third oxidation of the silicon wafer for 12 minutes in an environment of low temperature and normal pressure, and continue to grow a relatively dense third oxide layer 4 with a thickness of 0.2 nm on the surface of the silicon wafer. Thus, a tunneling oxide layer structure with a loose middle and dense sides is grown on the surface of the silicon wafer.

[0063] S4. Continue to use the LPCVD equipment, control the temperature inside the furnace tube at 600 °C, evacuate the air and then introduce silane. The vacuum pressure is 200 mTorr. Deposit a Poly silicon layer on the first oxide layer 2 in an environment of high temperature and low pressure until the film thickness meets the process requirements.

[0064] S5. Use a high-temperature diffusion tube to deposit and oxidize boron atoms, introduce boron trichloride and oxygen. First deposit at 830 °C for 1000 seconds, then raise the temperature to 960 °C, and continue to introduce more oxygen to promote for 22 minutes to dope a certain concentration of boron in the Poly silicon layer to form a doped polycrystalline silicon layer 5.

[0065] Examples 2 - 4

[0066] Examples 2 - 4 include most of the operation steps in Example 1. The differences lie in the temperature, pressure, time, oxide layer thickness, and doped atoms of the three oxidations. Specifically as follows.

[0067] Example 2

[0068] The passivation method of the boron-doped Poly layer provided by the present invention includes the following steps.

[0069] S1. Prepare an N-type silicon wafer with a resistivity of 1 Ω·cm and a thickness of 130 μm, polish both sides, clean it, put it into the LPCVD equipment, evacuate to a near-vacuum state, slowly raise the temperature of the furnace tube to 500 °C, slowly introduce oxygen into the furnace tube at a flow rate of 5 L / min, and keep the pressure inside the furnace tube below 0.3 standard atmosphere during the temperature rise process. Perform the first oxidation of the silicon wafer for 10 minutes in an environment of low temperature and low pressure, and grow a dense first oxide layer with a thickness of 0.3 nm on the surface of the silicon wafer.

[0070] S2. Continuously introduce oxygen. The pressure inside the furnace tube is 1 standard atmosphere. Raise the temperature inside the furnace tube to 610 °C. Perform the second oxidation of the silicon wafer for 10 minutes in an environment of high temperature and normal pressure, and continue to grow a relatively loose second oxide layer with a thickness of 0.5 nm on the surface of the silicon wafer.

[0071] S3. Continue to introduce oxygen, keep the pressure inside the furnace tube unchanged, lower the temperature to 550 °C, and perform the third oxidation of the silicon wafer for 10 minutes in an environment of low temperature and normal pressure. A relatively dense third oxide layer with a thickness of 0.2 nm continues to grow on the surface of the silicon wafer; thus, a tunneling oxide layer structure with loose middle and dense sides is grown on the surface of the silicon wafer.

[0072] S4. Continue to use the LPCVD equipment, control the temperature inside the furnace tube at 550 °C, introduce silane, and at the same time evacuate the air. The vacuum pressure is 180 mTorr. In an environment of high temperature and low pressure, deposit a Poly silicon layer on the first oxide layer until the film thickness required by the process is reached.

[0073] S5. Use a high-temperature diffusion tube for the deposition and oxidation promotion of boron atoms. Introduce boron trichloride and oxygen. First, deposit at 810 °C for 1200 seconds, then raise the temperature to 990 °C, and continue to introduce more oxygen to promote for 30 minutes to dope a certain concentration of boron in the Poly silicon layer to form a doped polycrystalline silicon layer.

[0074] Example 3

[0075] The passivation method for the phosphorus-doped Poly layer provided by the present invention includes the following steps.

[0076] S1. Prepare an N-type silicon wafer with a resistivity of 20 Ω·cm and a thickness of 220 μm, polish both sides, clean it, put it into the LPCVD equipment, evacuate to a near-vacuum state, slowly raise the temperature of the furnace tube to 580 °C, and slowly introduce oxygen into the furnace tube at a flow rate of 20 L / min, so that the pressure inside the furnace tube is kept below 0.5 standard atmospheric pressure during the temperature-raising process. Perform the first oxidation of the silicon wafer for 20 minutes in an environment of low temperature and low pressure, and grow a dense first oxide layer with a thickness of 0.8 nm on the surface of the silicon wafer.

[0077] S2. Continuously introduce oxygen, the pressure inside the furnace tube is 1 standard atmospheric pressure, raise the temperature inside the furnace tube to 640 °C, and perform the second oxidation of the silicon wafer for 20 minutes in an environment of high temperature and normal pressure. A relatively loose second oxide layer with a thickness of 1 nm continues to grow on the surface of the silicon wafer.

[0078] S3. Continue to introduce oxygen, keep the pressure inside the furnace tube unchanged, lower the temperature to 590 °C, and perform the third oxidation of the silicon wafer for 20 minutes in an environment of low temperature and normal pressure. A relatively dense third oxide layer with a thickness of 0.4 nm continues to grow on the surface of the silicon wafer; thus, a tunneling oxide layer structure with loose middle and dense sides is grown on the surface of the silicon wafer.

[0079] S4. Continue to use the LPCVD equipment, control the temperature inside the furnace tube at 640 °C, evacuate the air and then introduce silane. The vacuum pressure is 300 mTorr. In a high-temperature and low-pressure environment, deposit a Poly-silicon layer on the first oxide layer until the film thickness meets the process requirements.

[0080] S5. Use a high-temperature diffusion tube for the deposition and oxidation promotion of phosphorus atoms. Introduce phosphorus oxychloride and oxygen. First, deposit at 850 °C for 600 seconds, then raise the temperature to 920 °C, and continue to introduce more oxygen to promote for 10 minutes to dope a certain concentration of phosphorus in the Poly-silicon layer to form a doped polycrystalline silicon layer.

[0081] Example 4

[0082] The passivation method for the phosphorus-doped Poly layer provided by the present invention includes the following steps.

[0083] S1. Prepare an N-type silicon wafer with a resistivity of 12 Ω·cm and a thickness of 200 μm, polish both sides, clean it, put it into the LPCVD equipment, evacuate to a near-vacuum state, slowly raise the temperature of the furnace tube to 580 °C, and slowly introduce oxygen into the furnace tube at a flow rate of 30 L / min to keep the pressure inside the furnace tube below 0.3 standard atmospheric pressure during the temperature-raising process. Conduct the first oxidation of the silicon wafer for 13 minutes in a low-temperature and low-pressure environment to grow a dense first oxide layer with a thickness of 0.5 nm on the surface of the silicon wafer.

[0084] S2. Continuously introduce oxygen, keep the pressure inside the furnace tube at 1 standard atmospheric pressure, raise the temperature inside the furnace tube to 620 °C, conduct the second oxidation of the silicon wafer for 15 minutes in a high-temperature and normal-pressure environment to continue growing a relatively loose second oxide layer with a thickness of 0.9 nm on the surface of the silicon wafer.

[0085] S3. Stop introducing oxygen, keep the pressure inside the furnace tube unchanged, lower the temperature to 570 °C, conduct the third oxidation of the silicon wafer for 14 minutes in a low-temperature and normal-pressure environment to continue growing a relatively dense third oxide layer with a thickness of 0.25 nm on the surface of the silicon wafer; thus, a tunneling oxide layer structure that is loose in the middle and dense on both sides is grown on the surface of the silicon wafer.

[0086] S4. Continue to use the LPCVD equipment, control the temperature inside the furnace tube at 620 °C, evacuate the air and then introduce silane. The vacuum pressure is 240 mTorr. In a high-temperature and low-pressure environment, deposit a Poly-silicon layer on the first oxide layer until the film thickness meets the process requirements.

[0087] S5. Use a high-temperature diffusion tube for the deposition and oxidation promotion of phosphorus atoms. Introduce phosphorus oxychloride and oxygen. First, deposit at 800 °C for 1500 seconds, then raise the temperature to 880 °C, and continue to introduce more oxygen to promote for 20 minutes to dope a certain concentration of phosphorus in the Poly-silicon layer to form a doped polycrystalline silicon layer.

[0088] Comparative Example 1

[0089] The difference between Comparative Example 1 and Examples 1 and 2 lies in that an existing direct high-temperature grown tunneling oxide layer is adopted, which is specifically as follows.

[0090] S1. Prepare an N-type silicon wafer with a resistivity of 10 Ω·cm and a thickness of 180 μm, polish both sides, clean it, put it into an LPCVD device, evacuate, wait for the furnace tube to slowly heat up to 620 °C, then introduce oxygen with a flow rate of 36 L / min, return the furnace tube to atmospheric pressure, and at the same time oxidize the silicon wafer to grow a 2-nm-thick tunneling oxide layer on the surface of the silicon wafer.

[0091] S2. Continue to use the LPCVD device, control the temperature in the furnace tube at 600 °C, evacuate and then introduce silane, with a vacuum pressure of 200 mTorr, and deposit a Poly silicon layer on the tunneling oxide layer.

[0092] S3. Use a high-temperature diffusion tube for the deposition and oxidation promotion of boron atoms, introduce boron trichloride and oxygen, first deposit at 830 °C for 1000 seconds, then raise the temperature to 960 °C, and continue to introduce more oxygen to promote for 22 minutes to dope a certain concentration of boron in the Poly silicon layer to form a doped polysilicon layer.

[0093] Comparative Example 2

[0094] The difference between Comparative Example 2 and Examples 3 and 4 lies in that an existing direct high-temperature grown tunneling oxide layer is adopted, which is specifically as follows.

[0095] S1. Prepare an N-type silicon wafer with a resistivity of 20 Ω·cm and a thickness of 220 μm, polish both sides, clean it, put it into an LPCVD device, evacuate, wait for the furnace tube to heat up to 610 °C, then introduce oxygen with a flow rate of 36 L / min, return the furnace tube to atmospheric pressure, and at the same time oxidize the silicon wafer to grow a 1.6-nm tunneling oxide layer on the surface of the silicon wafer.

[0096] S2. Continue to use the LPCVD device, control the temperature in the furnace tube at 615 °C, evacuate and then introduce silane, with a vacuum pressure of 300 mTorr, and deposit a Poly silicon layer on the tunneling oxide layer in a high-temperature and low-pressure environment until the film thickness required by the process is reached.

[0097] S3. Use a high-temperature diffusion tube for the deposition and oxidation promotion of phosphorus atoms, introduce phosphorus oxychloride and oxygen, first deposit at 850 °C for 600 seconds, then raise the temperature to 920 °C, and continue to introduce more oxygen to promote for 10 minutes to dope a certain concentration of phosphorus in the Poly silicon layer to form a doped polysilicon layer.

[0098] Comparative Example 3

[0099] The difference between Comparative Example 3 and Examples 1 and 2 lies in that a tunneling oxide layer with a two-layer structure is grown by low-temperature and low-pressure oxidation and high-temperature and atmospheric-pressure oxidation, as follows.

[0100] S1. Prepare an N-type silicon wafer with a resistivity of 10 Ω·cm and a thickness of 180 μm. Double-side polish and clean it, then put it into an LPCVD device, evacuate, and wait for the furnace tube to heat up to 570 °C. After that, introduce oxygen with a flow rate of 10 L / min, and keep the pressure in the furnace tube below 0.5 standard atmospheric pressure during the heating process. Oxidize the silicon wafer for 15 minutes in a low-temperature and low-pressure environment to grow a dense oxide layer with a thickness of 0.4 nm on the surface of the silicon wafer.

[0101] S2. Continuously introduce oxygen, keep the pressure in the furnace tube at 1 standard atmospheric pressure, and raise the temperature in the furnace tube to 630 °C. Oxidize the silicon wafer for 12 minutes in a high-temperature and atmospheric-pressure environment to continue growing a relatively loose oxide layer with a thickness of 0.8 nm on the surface of the silicon wafer. Thus, a tunneling oxide layer structure with a loose inner side and a dense outer side is grown on the surface of the silicon wafer.

[0102] S3. Continue to use the LPCVD device, control the temperature in the furnace tube at 600 °C, evacuate and then introduce silane. The vacuum pressure is 200 mTorr. Deposit a Poly silicon layer on the first oxide layer 2 in a high-temperature and low-pressure environment.

[0103] S4. Use a high-temperature diffusion tube for the deposition and oxidation propulsion of boron atoms. Introduce boron trichloride and oxygen, first deposit for 1000 seconds at 830 °C, then raise the temperature to 960 °C, and continue to introduce more oxygen to propel for 22 minutes to dope a certain concentration of boron in the Poly silicon layer to form a doped polycrystalline silicon layer.

[0104] Comparative Example 4

[0105] The difference between Comparative Example 4 and Examples 1 and 2 lies in that a tunneling oxide layer with a two-layer structure is grown by combining high-temperature and atmospheric-pressure oxidation and low-temperature and atmospheric-pressure oxidation, as follows.

[0106] S1. Prepare an N-type silicon wafer with a resistivity of 10 Ω·cm and a thickness of 180 μm. Double-side polish and clean it, then put it into an LPCVD device, evacuate, and wait for the furnace tube to heat up to 630 °C. After that, introduce oxygen with a flow rate of 10 L / min to atmospheric pressure, and oxidize the silicon wafer for 12 minutes in a high-temperature and atmospheric-pressure environment to continue growing a relatively loose oxide layer with a thickness of 0.8 nm on the surface of the silicon wafer.

[0107] S2. Continue to introduce oxygen, keep the pressure inside the furnace tube unchanged, reduce the temperature to 580 °C, oxidize the silicon wafer for 12 minutes in a low-temperature and normal-pressure environment, and continue to grow a relatively dense oxide layer with a thickness of 0.2 nm on the surface of the silicon wafer; thus, a tunneling oxide layer structure with a dense inner side and a loose outer side is grown on the surface of the silicon wafer.

[0108] S3. Continue to use the LPCVD equipment, control the temperature inside the furnace tube at 600 °C, evacuate the air and then introduce silane, with a vacuum pressure of 200 mTorr. Deposit a Poly-silicon layer on the first oxide layer 2 in a high-temperature and low-pressure environment.

[0109] S4. Use a high-temperature diffusion tube for the deposition and oxidation propulsion of boron atoms. Introduce boron trichloride and oxygen, first deposit for 1000 seconds at 830 °C, then raise the temperature to 960 °C, and continue to introduce more oxygen to propel for 22 minutes to dope a certain concentration of boron in the Poly-silicon layer to form a doped polycrystalline silicon layer.

[0110] Comparative Example 5

[0111] The difference between Comparative Example 5 and Examples 1 and 2 is that a tunneling oxide layer with a two-layer structure is grown by combining low-temperature and low-pressure oxidation with low-temperature and normal-pressure oxidation, and the temperatures for deposition and oxidation propulsion are different, as follows.

[0112] S1. Prepare an N-type silicon wafer with a resistivity of 10 Ω·cm and a thickness of 180 μm, polish both sides, clean it, put it into the LPCVD equipment, evacuate the air, and after waiting for the furnace tube to heat up to 570 °C, introduce oxygen with a flow rate of 10 L / min to keep the pressure inside the furnace tube below 0.2 standard atmospheric pressures during the heating process. Oxidize the silicon wafer for 15 minutes in a low-temperature and low-pressure environment, and grow a dense oxide layer with a thickness of 0.8 nm on the surface of the silicon wafer.

[0113] S2. Continue to introduce oxygen, with the pressure inside the furnace tube being 1 standard atmospheric pressure and the temperature inside the furnace tube being 580 °C. Oxidize the silicon wafer for 12 minutes in a low-temperature and normal-pressure environment, and continue to grow a relatively dense oxide layer with a thickness of 0.4 nm on the surface of the silicon wafer; thus, a two-layer dense tunneling oxide layer structure is grown on the surface of the silicon wafer.

[0114] S3. Continue to use the LPCVD equipment, control the temperature inside the furnace tube at 600 °C, evacuate the air and then introduce silane, with a vacuum pressure of 200 mTorr. Deposit a Poly-silicon layer on the first oxide layer 2 in a high-temperature and low-pressure environment.

[0115] S4. Use a high-temperature diffusion tube for the deposition and oxidation propulsion of boron atoms. Introduce boron trichloride and oxygen, first deposit for 1000 seconds at 830 °C, then raise the temperature to 950 °C, and continue to introduce more oxygen to propel for 22 minutes to dope a certain concentration of boron in the Poly-silicon layer to form a doped polycrystalline silicon layer.

[0116] Comparative Example 6

[0117] The difference between Comparative Example 6 and Examples 1 and 2 is that a tunneling oxide layer with a two-layer structure is grown by combining low-temperature and low-pressure oxidation with low-temperature and atmospheric-pressure oxidation, as follows.

[0118] S1. Prepare an N-type silicon wafer with a resistivity of 10 Ω·cm and a thickness of 180 μm, polish both sides, clean it, put it into an LPCVD device, evacuate, wait for the furnace tube to heat up to 570 °C, then introduce oxygen with a flow rate of 10 L / min, keep the pressure in the furnace tube below 0.2 standard atmospheric pressure during the heating process, oxidize the silicon wafer in a low-temperature and low-pressure environment for 15 minutes, and grow a dense oxide layer with a thickness of 0.8 nm on the surface of the silicon wafer.

[0119] S2. Continue to introduce oxygen, the pressure in the furnace tube is 1 standard atmospheric pressure, the temperature in the furnace tube is 580 °C, oxidize the silicon wafer in a low-temperature and atmospheric-pressure environment for 12 minutes, and continue to grow a relatively dense oxide layer with a thickness of 0.4 nm on the surface of the silicon wafer; thus, a two-layer dense tunneling oxide layer structure is grown on the surface of the silicon wafer.

[0120] S3. Continue to use the LPCVD device, control the temperature in the furnace tube at 600 °C, evacuate and then introduce silane, the vacuum pressure is 200 mTorr, and deposit a Poly silicon layer on the first oxide layer 2 in a high-temperature and low-pressure environment.

[0121] S4. Use a high-temperature diffusion tube for the deposition and oxidation propulsion of boron atoms, introduce boron trichloride and oxygen, first deposit at 830 °C for 1000 seconds, then raise the temperature to 960 °C, and continue to introduce more oxygen to propel for 22 minutes to dope a certain concentration of boron in the Poly silicon layer to form a doped polysilicon layer.

[0122] Comparative Example 7

[0123] The difference between Comparative Example 7 and Examples 1 and 2 is that a tunneling oxide layer with a two-layer structure is grown by combining low-temperature and low-pressure oxidation with low-temperature and atmospheric-pressure oxidation, and the temperatures for deposition and oxidation propulsion are different, as follows.

[0124] S1. Prepare an N-type silicon wafer with a resistivity of 10 Ω·cm and a thickness of 180 μm, polish both sides, clean it, put it into an LPCVD device, evacuate, wait for the furnace tube to heat up to 570 °C, then introduce oxygen with a flow rate of 10 L / min, keep the pressure in the furnace tube below 0.2 standard atmospheric pressure during the heating process, oxidize the silicon wafer in a low-temperature and low-pressure environment for 15 minutes, and grow a dense oxide layer with a thickness of 0.8 nm on the surface of the silicon wafer.

[0125] S2. Continue to introduce oxygen. The pressure inside the furnace tube is 1 standard atmospheric pressure, and the temperature inside the furnace tube is 580 °C. Oxidize the silicon wafer for 12 minutes in a low-temperature and normal-pressure environment, and continue to grow a relatively dense oxide layer with a thickness of 0.4 nm on the surface of the silicon wafer; thus, two dense tunneling oxide layer structures are grown on the surface of the silicon wafer.

[0126] S3. Continue to use the LPCVD equipment to control the temperature inside the furnace tube at 600 °C. After evacuating, introduce silane. The vacuum pressure is 200 mTorr. Deposit a Poly-silicon layer on the first oxide layer 2 in a high-temperature and low-pressure environment.

[0127] S4. Use a high-temperature diffusion tube for the deposition and oxidation promotion of boron atoms. Introduce boron trichloride and oxygen. First, deposit at 830 °C for 1000 seconds, then raise the temperature to 970 °C, and continue to introduce more oxygen to promote for 22 minutes to dope a certain concentration of boron in the Poly-silicon layer to form a doped polycrystalline silicon layer.

[0128] Performance Test

[0129] Perform performance tests on the silicon wafers with a passivation contact structure obtained by using the above embodiments and comparative examples. All the data in Table 1 are directly tested on a symmetric structure obtained by growing a Poly layer on both sides and boron diffusion on both sides of an N-type silicon wafer.

[0130] Use the WCT-120 instrument of Sinton Company in the United States to measure the minority carrier lifetime (Lifetime), recombination current density (J0), implied open-circuit voltage (iVoc), and implied fill factor (iFF). Use the PL-R3 instrument to test the photoluminescence brightness, where the excitation brightness is 1 times the standard brightness of sunlight (1 Sun). The test results are shown in Table 1.

[0131] Table 1

[0132]

[0133] It can be seen from the test results of Examples 1, 2 and Comparative Example 1 that the passivation method of the present invention has significantly improved the minority carrier lifetime, iVoc, iFF and PL brightness compared with the boron-doped Poly layer prepared by the prior art, and the recombination current density J0 has been significantly reduced, showing a better passivation effect.

[0134] It can be seen from the test results of Examples 3, 4 and Comparative Example 2 that although phosphorus Poly itself has good passivation performance, the passivation effect is still improved to a certain extent by the passivation method of the present invention compared with the phosphorus-doped Poly layer prepared by the prior art. The minority carrier lifetime and PL brightness have been significantly improved, iVoc and iFF have been improved, and the recombination current density J0 has been reduced.

[0135] From the test results of Examples 1 and 2 and Comparative Examples 3 to 7, it can be seen that through the superposition of three layers of oxide layers with different compactness in the present invention, compared with the two-layer structure, the passivation effect of the boron- and phosphorus-doped Poly layer structure can be greatly improved; the minority carrier lifetime, iVoc, iFF, and PL brightness are all significantly improved, and the recombination current density J0 is significantly reduced, showing a good passivation effect. Moreover, the tunneling oxide layer grown in the present invention is less affected by the subsequent boron diffusion temperature fluctuation and can accept a 30°C fluctuation above the optimal oxidation promotion temperature.

[0136] From the test results of Examples 1 and 2 and Comparative Examples 5 to 7, it can be seen that when the tunneling oxide layer is passivated under different oxidation promotion temperatures of boron diffusion, if a low-temperature method (Comparative Examples 5 to 7) is used throughout to grow a dense tunneling oxide layer, a good passivation effect can usually be achieved at the optimal oxidation promotion temperature of boron diffusion (Comparative Example 6). However, it is very sensitive to the change of the oxidation promotion temperature. When the temperature fluctuates up and down by about 10°C (Comparative Examples 5 and 7), its passivation effect decreases significantly, which is not conducive to large-scale industrial production.

[0137] The present invention has been further described above with the aid of specific embodiments. However, it should be understood that the specific description herein should not be construed as a limitation on the essence and scope of the present invention. Various modifications made by those of ordinary skill in the art to the above embodiments after reading this specification all fall within the scope protected by the present invention.

Claims

1. A passivation method for boron- and phosphorus-doped Poly layer, characterized in that, It includes the following steps: S1. Provide a clean and polished silicon wafer. Use an LPCVD device to evacuate the air and introduce oxygen. At a low temperature and low pressure below 600 °C, perform the first oxidation on the silicon wafer to grow a first oxide layer with a thickness of 0.3 - 0.8 nm and being dense on the surface of the silicon wafer; S2. Raise the temperature in step S1 by 50 - 220 °C, continuously introduce oxygen, and at a pressure greater than or equal to 1 standard atmosphere, perform the second oxidation on the silicon wafer to continuously grow a second oxide layer with a thickness of 0.5 - 1 nm and being porous on the surface of the silicon wafer; S3. Stop introducing oxygen, keep the pressure unchanged, lower the temperature to below 600 °C, perform the third oxidation on the silicon wafer to continuously grow a third oxide layer with a thickness of 0.1 - 0.4 nm and being dense on the surface of the silicon wafer; S4. Continue to use the LPCVD device, raise the temperature in step S3 by 0 - 50 °C, evacuate the air and then introduce silane. At a high temperature and low pressure, deposit a Poly - silicon layer on the first oxide layer until the film thickness meets the process requirements; S5. Use a high - temperature diffusion tube to deposit and oxidize - drive boron atoms or phosphorus atoms, so that the Poly - silicon layer is doped with a certain concentration of boron or phosphorus to form a doped poly - silicon layer.

2. The passivation method of the boron- and phosphorus-doped Poly layer according to claim 1, wherein In step S1, the temperature is 400 - 590 °C, the pressure is 0.1 - 0.5 standard atmospheres, and the first oxidation time is 10 - 20 minutes.

3. The passivation method of the boron- and phosphorus-doped Poly layer according to claim 1, characterized in that, In step S2, the temperature is 610 - 640 °C, the pressure is normal pressure, and the second oxidation time is 10 - 20 minutes.

4. The passivation method of the boron- and phosphorus-doped Poly layer according to claim 1, characterized in that, In step S3, the temperature is 550 - 590 °C, the pressure is normal pressure, and the third oxidation time is 10 - 20 minutes.

5. The passivation method of the boron- and phosphorus-doped Poly layer according to claim 1, wherein In step S4, the temperature is 550 - 640 °C, and the vacuum pressure is 180 - 300 mTorr.

6. The passivation method of the boron- and phosphorus-doped Poly layer according to claim 1, wherein, In steps S1 and S2, the flow rate of the introduced oxygen is 5 - 30 L / min.

7. The passivation method of the boron- and phosphorus-doped Poly layer according to claim 1, characterized in that, In step S5, during the process of depositing and oxidizing - driving boron atoms, the deposition temperature is 800 - 850 °C, and the temperature for oxidation - driving is 940 - 1000 °C; during the process of depositing and oxidizing - driving phosphorus atoms, the deposition temperature is 800 - 850 °C, and the temperature for oxidation - driving is 880 - 920 °C.

8. A passivated contact structure of a boron- and phosphorus-doped Poly layer, characterized in that, The passivation contact structure includes a first oxide layer, a second oxide layer, a third oxide layer, and a doped poly - silicon layer grown on a silicon wafer by the passivation method of the boron - and phosphorus - doped Poly layer as described in any one of claims 1 - 7. The doped poly - silicon layer is above the first oxide layer. The first oxide layer, the second oxide layer, and the third oxide layer form a tunneling oxide layer. The second oxide layer is in the middle of the tunneling oxide layer, being thick and porous; the first oxide layer and the third oxide layer are on both sides of the tunneling oxide layer, being thin and dense.

9. A battery with a passivated contact structure having a boron- and phosphorus-doped Poly layer, characterized in that, The battery includes a silicon wafer and a passivation contact structure as described in claim 8 formed on the surface of the silicon wafer.

10. The battery with a passivated contact structure having a boron- and phosphorus-doped Poly layer according to claim 9, wherein, The battery is a TOPCon battery, a TBC battery, or a perovskite tandem battery.

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