Passivation film structure capable of achieving both passivation and surface doping, and preparation method therefor and use thereof

Abstract

The present invention provides a passivation film structure capable of achieving both passivation and surface doping, and a preparation method therefor and the use thereof. The passivation film structure comprises a nano-dielectric layer, a silicide layer and a hydrogen-rich dielectric layer, which are sequentially stacked on a surface of a silicon substrate, wherein the nano-dielectric layer is made of a hydrogenated silicon oxide thin film or a hydrogenated silicon oxynitride thin film, the silicide layer is made of a carbon-containing and / or nitrogen-containing boron / phosphorus-doped hydrogenated silicon thin film, and the hydrogen-rich dielectric layer is made of one or more of a laminated thin film selected from a hydrogenated aluminum oxide thin film, a hydrogenated silicon nitride thin film, a hydrogenated silicon oxide thin film and a hydrogenated silicon oxynitride thin film. The passivation film structure of the present invention has good passivation performance, and can achieve a good passivation effect on polished and textured silicon wafers or boron / phosphorus diffused emitters; moreover, the passivation film structure contains boron / phosphorus, and can achieve surface doping on silicon wafers during the preparation process of the passivation film, without requiring an additional doping process.

Description

A passivation film structure with both passivation and surface doping, and its preparation method and application Technical Field

[0001] The present invention relates to the technical field of silicon solar cell surface passivation, and in particular to a passivation film structure having both passivation and surface doping functions, and a preparation method and application thereof. Background Art

[0002] Surface passivation is a key factor in improving silicon solar cell efficiency. The development trends of industrial silicon cells demonstrate that efficiency improvements are inseparable from each upgrade in passivation technology. Passivated contact technology is currently the mainstream research direction for solar cells, and in the future, to eliminate gridline shading losses on the front of the cell, the cell structure will shift to back-contact technology. For back-contact cells, whether using a TOPCon or SHJ structure on the back, a good passivation solution is required on the front of the cell.

[0003] The saturation current density (J0) is a physical quantity that characterizes the size of surface recombination. The smaller the value, the lower the surface recombination. The J0 value of the passivation film on different silicon wafers will change with the change of the silicon wafer resistivity. The saturation current density value of the passivation film on different silicon wafers will change with the change of the silicon wafer resistivity. At present, the common dielectric passivation films used on the sun-facing side (front) of silicon solar cells mainly include: AlO x / SiN x , SiO x / SiN x , SiO x / SiN x / SiO x These passivation films can achieve relatively good passivation effects on planar silicon wafers. Specifically, AlO x / SiN x The optimal passivation index of the stacked passivation film on a non-diffused p-type or n-type planar silicon wafer is about 2fA / cm2; SiO x / SiN x / SiO x The passivation effect is generally better than SiO x / SiN x , SiO x / SiN x / SiO x The optimal passivation indexes on the non-diffused n-type planar silicon wafer are ~1fA / cm2 (high-resistivity silicon wafer, resistivity ~90Ωcm) and 4.7fA / cm2 respectively. 2 (Industrial low-resistance silicon wafers, resistivity ~3Ωcm), the optimal passivation index on non-diffused n-type random textured silicon wafers is about 3fA / cm2 (high-resistance silicon wafers, resistivity ~90Ωcm).

[0004] In response to the industry's demand for improved solar cell efficiency and structural evolution, the shortcomings of existing passivation films have become apparent. The specific problems are as follows: 1) The passivation performance of existing dielectric passivation films on planar silicon wafers still needs to be improved. To develop crystalline silicon solar cells with an efficiency of more than 27.5%, the surface passivation performance is required to reach 1fA / cm 2 , but existing passivation films cannot meet these requirements on planar silicon wafers. 2) The front side of new high-efficiency back-contact (BC) solar cells features a random pyramid veneer structure, requiring excellent passivation quality and a diffusion layer to enhance the cell's radiation resistance. However, the passivation quality of existing passivation films on veneer surfaces is inferior to that of planar surfaces. Furthermore, the existing process requires an additional diffusion step to achieve surface doping on the front side of the silicon wafer. Furthermore, the passivation quality of the passivation film on the random pyramid veneer with a surface silicide layer is further degraded, creating a bottleneck limiting cell efficiency. 3) BC cells based on heterojunction technology still require amorphous silicon for passivation on the front side. While this passivation quality is excellent, it suffers from parasitic absorption. While existing common dielectric passivation films can eliminate parasitic absorption, their passivation quality is far inferior to that of amorphous silicon, making them incapable of replacing amorphous silicon. Therefore, in existing heterojunction BC cells, the parasitic absorption of amorphous silicon on the front side leads to a low upper limit on current density, limiting efficiency improvements.

[0005] In general, the passivation quality of the passivation film is a key factor restricting the performance improvement of crystalline silicon solar cells. How to further improve the passivation quality and reduce the saturation current density is the key to improving the efficiency of silicon solar cells. Summary of the Invention

[0006] The purpose of the present invention is to develop a passivation film with both passivation and surface doping functions, thereby reducing the saturation current density and improving the efficiency of silicon solar cells.

[0007] To achieve the above objectives, the first aspect of the present invention provides a passivation film structure having both passivation and surface doping, comprising a nano-dielectric layer, a silicide layer, and a hydrogen-rich dielectric layer stacked in sequence on the surface of a silicon substrate, wherein the material of the nano-dielectric layer is a hydrogenated silicon oxide film or a hydrogenated silicon oxynitride film, the material of the silicide layer is a boron / phosphorus-doped hydrogenated silicon film containing carbon and / or nitrogen, and the material of the hydrogen-rich dielectric layer is selected from one or more stacked films selected from hydrogenated aluminum oxide film, hydrogenated silicon nitride film, hydrogenated silicon oxide film, and hydrogenated silicon oxynitride film.

[0008] The passivation film structure of the present invention has excellent passivation performance and can achieve a good passivation effect on polished or textured silicon wafers or boron / phosphorus diffused emitters. The passivation film structure contains boron / phosphorus elements, and silicon wafer surface doping can be achieved during the passivation film preparation process without the need for additional doping processes.

[0009] Furthermore, a diffusion layer is formed on the surface of the silicon substrate close to the nano-medium layer, the thickness of the diffusion layer is 10 to 1200 nm, the diffusion layer is doped with boron or phosphorus, and the phosphorus concentration on the surface of the silicon substrate is 1×10 18 cm -3 ~1×10 21 cm -3 , or the boron concentration is 5×10 16 cm -3 ~5×10 20 cm -3 The passivation film structure achieves shallow diffusion on the silicon wafer surface, which can exert a field passivation effect and help reduce the recombination current.

[0010] Furthermore, the boron / phosphorus concentration of the silicide layer is 5×10 19 cm -3 ~5×10 21 cm -3 By adjusting the concentration of boron / phosphorus elements in the silicide layer, the boron / phosphorus doping concentration on the silicon wafer surface can be controlled.

[0011] Furthermore, the silicon substrate contains hydrogen, carbon and / or nitrogen, and the concentration of each element gradually decreases from the surface to the body. The hydrogen concentration on the surface of the silicon substrate is 1×10 19 cm -3 ~1×10 21 cm -3 , the nitrogen concentration is 1×10 19 cm -3 ~1×10 22 cm -3 , and / or carbon concentration is 1×10 19 cm -3 ~1×10 22 cm -3 .

[0012] Furthermore, the carbon concentration of the silicide layer is 1×10 21 cm -3 ~2×10 22 cm -3 , and / or nitrogen concentration is 5×10 21 cm -3 ~4×10 22 cm -3 .

[0013] Carbon and nitrogen atoms can effectively capture hydrogen atoms and inject them into the substrate and interface to passivate more defect states; introducing elements such as carbon and nitrogen near the surface of silicon wafers can improve the mechanical properties of silicon wafers.

[0014] Furthermore, the hydrogen concentration of the nano-medium layer is 1×10 19 cm -3 ~1×10 22 cm -3 , the hydrogen concentration of the silicide layer is 1×10 19 cm -3 ~1×10 22 cm -3 The hydrogen concentration of the hydrogen-rich dielectric layer is 1×10 19 cm - 3 ~1×10 22 cm -3 Each layer of the passivation film structure has a high hydrogen concentration and good chemical stability, which can achieve excellent surface protection for silicon wafers.

[0015] Furthermore, the refractive index of the silicide layer is 1.5 to 3.0. The refractive index of the silicide layer can be controlled by adjusting the composition.

[0016] Furthermore, the transmittance of the nano-medium layer above 400nm is greater than 97%, and the transmittance of the silicide layer above 400nm is greater than 97%. The passivation film structure has extremely low absorption at wavelengths above 400nm and has extremely low optical absorption characteristics.

[0017] Furthermore, the thickness of the nano-medium layer is 1-2 nm, and the thickness of the silicide layer is greater than or equal to 3 nm. The passivation film structure can achieve controllable adjustment of optical absorption and transmission characteristics by adjusting the film thickness.

[0018] A second aspect of the present invention provides a method for preparing the above-mentioned passivation film structure having both passivation and surface doping, comprising the following steps:

[0019] S1, cleaning silicon substrate;

[0020] S2. preparing a silicon oxide film or a silicon oxynitride film on the surface of the silicon substrate;

[0021] S3, depositing an amorphous silicon film containing carbon and / or nitrogen elements, and doping it with boron or phosphorus atoms;

[0022] S4, performing a high-temperature annealing treatment to diffuse active phosphorus or boron atoms into the silicon substrate to form a diffusion layer on the surface of the silicon substrate, while simultaneously diffusing carbon and / or nitrogen elements into the silicon substrate;

[0023] S5, depositing one or more stacked thin films of aluminum oxide, silicon nitride, silicon oxide, and silicon oxynitride;

[0024] S6. Perform hydrogen injection treatment to inject hydrogen atoms into the passivation film structure and the silicon substrate.

[0025] The preparation method of the passivation film structure of the present invention is fully compatible with existing battery production line technology and has good mass production application prospects. The passivation film structure has good thermal stability, and its passivation quality is not affected by temperature within a temperature range not exceeding 500°C.

[0026] Furthermore, in step S3, the doping method is to deposit an amorphous silicon film containing boron or phosphorus on or below the amorphous silicon film containing carbon and / or nitrogen, or to directly add active boron or phosphorus atoms to the amorphous silicon film containing carbon and / or nitrogen. The high-temperature annealing step diffuses the active phosphorus or boron atoms into the silicon substrate, achieving surface doping of the silicon wafer without requiring additional doping processes.

[0027] A third aspect of the present invention provides a silicon solar cell comprising the aforementioned passivation film structure that combines passivation and surface doping. This passivation film structure can improve the passivation quality of the silicon solar cell, significantly reduce its saturation current density, extend the life of the silicon wafer, and thus improve the cell efficiency.

[0028] In summary, the present invention has the following beneficial effects compared to the prior art:

[0029] (1) The passivation film structure of the present invention has an excellent surface passivation effect, and can achieve a saturation current density of less than 1fA / cm on the surface of polished silicon wafers. 2 , even as low as 0.2fA / cm 2 On the surface of velvet silicon wafer, J0 can also be lower than 1fA / cm 2 , even as low as 0.5fA / cm 2 ; It also has a good passivation effect on boron or phosphorus diffused emitters.

[0030] (2) The passivation film structure of the present invention has an excellent body passivation effect, which can increase the body life of the mainstream n-type silicon wafer (1-7Ωcm) in the market to more than 15ms.

[0031] (3) The passivation film structure of the present invention forms a shallow diffusion layer on the surface of the silicon wafer, which can exert a field passivation effect and is conducive to further improving the passivation effect.

[0032] (4) The passivation film structure of the present invention has extremely low optical absorption characteristics, and the absorption at wavelengths above 400 nm is extremely low. Its refractive index can be fine-tuned according to the composition, and the optical absorption and transmittance characteristics can be controlled by adjusting the refractive index, film thickness, etc.

[0033] (5) The transparent laminated passivation film structure of the present invention has good chemical stability and thermal stability. The passivation film structure contains elements such as silicon, nitrogen, carbon, and oxygen, which can achieve excellent surface protection for silicon wafers. Within the temperature range below 500°C, its passivation quality is not affected by temperature.

[0034] (6) The passivation film structure of the present invention can introduce elements such as carbon and nitrogen into the near surface of the silicon wafer, which is beneficial to improving the mechanical properties of the silicon wafer.

[0035] (7) The preparation method of the passivation film structure of the present invention is fully compatible with existing battery production line technology and has good prospects for mass production application. Other transparent dielectric films can be superimposed on the passivation film structure to form a more complex film system structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] FIG1 is a schematic structural diagram of a passivation film structure having both passivation and surface doping in a specific embodiment of the present invention.

[0037] FIG2 is a flow chart of a method for preparing a passivation film structure having both passivation and surface doping according to a specific embodiment of the present invention.

[0038] FIG3 is a graph showing active atom diffusion curves of silicon wafers according to Examples 1-7 of the present invention.

[0039] FIG4 is a graph showing the refractive index and extinction coefficient of the passivation film according to Example 8 of the present invention.

[0040] Explanation of reference numerals: 1-silicon substrate, 2-nano dielectric layer, 3-silicide layer, 4-hydrogen-rich dielectric layer, 5-diffusion layer. DETAILED DESCRIPTION

[0041] To make the above-mentioned objects, features, and advantages of the present invention more clearly understood, specific embodiments of the present invention are described in detail below with reference to the accompanying drawings. It should be noted that the following embodiments are only intended to illustrate the implementation methods and typical parameters of the present invention, and are not intended to limit the parameter ranges described in the present invention. Reasonable variations derived therefrom are still within the scope of protection of the claims of the present invention.

[0042] It should be noted that the endpoints of the ranges and any values ​​disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be considered to be specifically disclosed herein.

[0043] A specific embodiment of the present invention provides a passivation film structure with both passivation and surface doping functions. The typical structure is shown in FIG1 , which includes a nano-dielectric layer 2 , a silicide layer 3 and a hydrogen-rich dielectric layer 4 stacked sequentially on the surface of a silicon substrate 1 .

[0044] The surface of the silicon substrate 1 is a suede or flat structure. A diffusion layer 5 is formed below the surface of the nano-medium layer 2. The thickness of the diffusion layer 5 is 10 to 1200 nm. The diffusion layer 5 is doped with boron or phosphorus, and the phosphorus concentration on the surface is 1×10 18 cm -3 ~1×10 21 cm -3 or a boron concentration of 5×10 16 cm -3 ~5×10 20 cm -3 The surface of the silicon wafer has achieved shallow diffusion, which can play a field passivation effect. The silicon substrate 1 contains hydrogen, nitrogen and / or carbon elements near the surface and in the body, and the concentration of the corresponding elements gradually decreases from the surface to the body. Among them, the nitrogen concentration in the surface area below the nano-dielectric layer 2 is generally higher than 1×10 19 cm -3 , with a typical concentration range of 1×10 19 cm - 3 ~1×10 22 cm -3 , usually more than 1×10 20 cm -3 ; Carbon concentration is generally higher than 1×10 19 cm -3 , with a typical concentration range of 1×10 19 cm -3 ~1×10 22 cm -3 , usually more than 1×10 20 cm -3 ; Hydrogen concentration is generally higher than 1×10 19 cm -3 , with a typical concentration range of 1×10 19 cm -3 ~1×10 21 cm -3 , usually more than 1×10 20 cm -3 Introducing elements such as carbon and nitrogen near the surface of silicon wafers can improve the mechanical properties of silicon wafers; carbon and nitrogen atoms can effectively capture hydrogen atoms and inject them into the substrate and interface to passivate more defect states.

[0045] The material of the nano-medium layer 2 is a hydrogenated silicon oxide film or a hydrogenated silicon oxynitride film, the main components of which are silicon, oxygen, hydrogen, and may also contain nitrogen. The hydrogen concentration in the nano-medium layer 2 is >1×10 19 cm -3 , the typical hydrogen concentration range is 1×10 19 cm -3 ~1×10 22 cm-3 Its thickness is above 1 nm, with a typical thickness range of 1 to 2 nm. The transmittance of the nano-medium layer 2 above 400 nm is greater than 97%, and the absorption coefficient k value decreases to nearly 0 at wavelengths above 400 nm, showing extremely low optical absorption characteristics.

[0046] The material of the silicide layer 3 is a boron / phosphorus-doped hydrogenated silicon film containing carbon and / or nitrogen, such as a boron-doped hydrogenated carbon nitride silicon film, a boron-doped hydrogenated carbon silicon film, a boron-doped hydrogenated silicon nitride silicon film, a phosphorus-doped hydrogenated carbon nitride silicon film, a phosphorus-doped hydrogenated silicon nitride silicon film, etc. The silicide layer 3 may also contain oxygen, such as a boron-doped hydrogenated carbon nitride silicon film, a boron-doped hydrogenated carbon oxysilicon film, a boron-doped hydrogenated silicon oxynitride silicon film, a phosphorus-doped hydrogenated carbon nitride silicon film, a phosphorus-doped hydrogenated carbon oxysilicon film, or a phosphorus-doped hydrogenated silicon oxynitride silicon film. Its thickness is above 3 nm, with a typical thickness range of 3 to 50 nm. The carbon concentration of the silicide layer 3 is 1×10 21 cm -3 ~2×10 22 cm - 3 , and / or nitrogen concentration is 5×10 21 cm -3 ~4×10 22 cm -3 The ratio of carbon, nitrogen and other elements in the silicide layer 3 can be adjusted, and its refractive index ranges from 1.5 to 3.0, which can be adjusted according to the composition. The boron / phosphorus concentration in the silicide layer 3 is 5×10 19 cm -3 ~5×10 21 cm -3 By adjusting the concentration of boron / phosphorus elements in the silicide layer 3, the boron / phosphorus doping concentration on the surface of the silicon substrate 1 can be controlled. The hydrogen concentration in the silicide layer 3 is >1×10 19 cm -3 , with a typical concentration range of 1×10 19 cm -3 ~1×10 22 cm -3 The transmittance of the silicide layer 3 above 400 nm is greater than 97%, and the absorption coefficient k value decreases to close to 0 at wavelengths above 400 nm, showing extremely low optical absorption characteristics.

[0047] The material of the hydrogen-rich dielectric layer 4 is hydrogenated aluminum oxide, hydrogenated silicon nitride, hydrogenated silicon oxide, hydrogenated silicon oxynitride or a combination thereof. The hydrogen concentration of the hydrogen-rich dielectric layer 4 is in the range of 1×10 20 cm - 3 ~1×10 22 cm -3 The hydrogen-rich dielectric layer may also contain boron or phosphorus elements.

[0048] As shown in FIG2 , a typical method for preparing the transparent laminated passivation film structure includes the following steps:

[0049] S1. Perform standard RCA cleaning on the silicon substrate.

[0050] S2. Prepare a silicon oxide film or a silicon oxynitride film on the surface of a silicon substrate. The preparation methods include wet chemical method, plasma assisted oxidation method, thermal oxidation method, ozone oxidation method, etc.

[0051] S3. Depositing an amorphous silicon film containing carbon and / or nitrogen elements on the silicon oxide film or silicon oxynitride film. The typical preparation method is PECVD in-situ deposition method, and the deposition temperature range is 100°C to 600°C. Boron or phosphorus atoms are doped. The doping method is to deposit an amorphous silicon film containing boron or phosphorus on or below the amorphous silicon film containing carbon and / or nitrogen elements, or directly add active boron or phosphorus atoms to the amorphous silicon film containing carbon and / or nitrogen elements.

[0052] S4. Perform a high-temperature annealing treatment to diffuse active phosphorus or boron atoms into the silicon substrate, forming a diffusion layer on the surface of the silicon substrate, while simultaneously diffusing carbon and / or nitrogen into the silicon substrate. The typical temperature range is 600°C to 1200°C, preferably 900°C to 950°C. If doping is performed by depositing an amorphous silicon film containing boron or phosphorus on an amorphous silicon film containing carbon and / or nitrogen, the amorphous silicon film containing boron or phosphorus can be removed with an alkaline solution after the high-temperature annealing to further improve light transmittance.

[0053] S5. Depositing one or more stacked films of aluminum oxide, silicon nitride, silicon oxide, and silicon oxynitride on the silicide layer.

[0054] S6. Perform hydrogen injection treatment to inject hydrogen atoms into the passivation film structure and the silicon substrate. The hydrogen injection method is annealing hydrogenation treatment or optical injection.

[0055] The above preparation method can diffuse active phosphorus or boron atoms into the silicon substrate, realize the surface doping of the silicon wafer, and introduce carbon and nitrogen atoms into the silicon wafer body, which can capture more hydrogen atoms at the interface. The transparent stacked passivation film structure achieves excellent surface passivation effect and body passivation effect.

[0056] The above-mentioned passivation film structure is suitable for silicon solar cells, and its preparation method is fully compatible with existing cell production line technology. This passivation film structure can improve the passivation quality of silicon solar cells, significantly reducing their saturation current density, extending the life of silicon wafers, and ultimately improving cell efficiency. Other transparent dielectric films can also be layered on top of this passivation film structure to form a more complex film system.

[0057] The technical solutions and effects of the present invention are described below through specific embodiments.

[0058] Example 1

[0059] Prepare n-type silicon wafers, alkaline polished, with a thickness of 110μm and a resistivity of 1-7Ω·cm. After standard RCA cleaning, the silicon wafers are placed in a PECVD chamber and N2O plasma is used to prepare SiO x film, and then deposit a nitrogen-rich amorphous silicon film (nitrogen concentration of 1×10 22 cm -3 ), and then deposited ultra-thin phosphorus-containing amorphous silicon film; annealed at 900℃ for 30min in a tube furnace; ALD deposited AlO x , annealed at 450℃ in a tube furnace for 30min; then transferred to PECVD to deposit SiN x Finally, annealing was carried out at 400℃ for 60min in a mixed gas atmosphere of nitrogen and hydrogen in a tube furnace. Six samples were prepared and Sinton test was carried out. The single-side saturation current density J 0,s The test results range is 0.5~0.8fA / cm 2 .

[0060] Example 2

[0061] Prepare n-type silicon wafers, alkaline polished, with a thickness of 110μm and a resistivity of 1-7Ω·cm. After standard RCA cleaning, the silicon wafers are placed in a PECVD chamber and N2O plasma is used to prepare SiO x film, and then deposit a nitrogen-rich amorphous silicon film (nitrogen concentration of 1×10 22 cm -3 ), and then deposited ultra-thin phosphorus-containing amorphous silicon film; annealed at 950℃ for 30min in a tube furnace; ALD deposited AlO x , annealed at 450℃ in a tube furnace for 30min; then transferred to PECVD to deposit SiN x Finally, annealing was carried out at 400℃ for 60min in a mixed gas atmosphere of nitrogen and hydrogen in a tube furnace. Six samples were prepared and Sinton test was carried out. The single-side saturation current density J 0,s The test results range from 0.9 to 1.4 fA / cm 2 .

[0062] Example 3

[0063] Prepare p-type silicon wafers, alkaline polished, with a thickness of 110μm and a resistivity of 1-7Ω·cm. After standard RCA cleaning, the silicon wafers are placed in a PECVD chamber and N2O plasma is used to prepare SiO x film, and then deposit a nitrogen-rich amorphous silicon film (nitrogen concentration of 1×10 22 cm -3 ), and then deposited ultra-thin boron-containing amorphous silicon film; annealed at 900℃ for 30min in a tube furnace; ALD deposited AlO x, annealed at 450℃ in a tube furnace for 30min; then transferred to PECVD to deposit SiN x Finally, annealing was carried out at 400℃ for 60min in a mixed gas atmosphere of nitrogen and hydrogen in a tube furnace. Six samples were prepared and Sinton test was carried out. The single-side saturation current density J 0,s The test results range is 0.2~0.5fA / cm 2 .

[0064] Example 4

[0065] Prepare p-type silicon wafers, alkaline polished, with a thickness of 110μm and a resistivity of 1-7Ω·cm. After standard RCA cleaning, the silicon wafers are placed in a PECVD chamber and N2O plasma is used to prepare SiO x film, and then deposit a nitrogen-rich amorphous silicon film (nitrogen concentration of 1×10 22 cm -3 ), and then deposited ultra-thin boron-containing amorphous silicon film; annealed at 950℃ for 30min in a tube furnace; ALD deposited AlO x , annealed at 450℃ in a tube furnace for 30min; then transferred to PECVD to deposit SiN x Finally, annealing was carried out at 400℃ for 60min in a mixed gas atmosphere of nitrogen and hydrogen in a tube furnace. Six samples were prepared and Sinton test was carried out. The single-side saturation current density J 0,s The test results range from 0.7 to 1.2 fA / cm 2 .

[0066] Example 5

[0067] Prepare n-type silicon wafers with a textured surface, thickness of 200 μm, and resistivity of 1-7 Ω·cm. After standard RCA cleaning, the silicon wafers are placed in a PECVD chamber and SiO is prepared by N2O plasma. x film, and then deposit a nitrogen-rich amorphous silicon film (nitrogen concentration of 1×10 22 cm -3 ) and then deposited an ultra-thin phosphorus-containing amorphous silicon film; annealed at 900 ° C for 30 min in a tube furnace; ALD deposited AlO x , annealed at 450℃ in a tube furnace for 30min; then transferred to PECVD to deposit SiN x Finally, annealing was carried out at 400℃ for 60min in a mixed gas atmosphere of nitrogen and hydrogen in a tube furnace. Six samples were prepared and Sinton test was carried out. The single-side saturation current density J 0,s The test results range is 0.5~1.0fA / cm 2 .

[0068] Example 6

[0069] Prepare n-type silicon wafers, alkaline polished, with a thickness of 110μm and a resistivity of 1-7Ω·cm. After standard RCA cleaning, the silicon wafers are placed in a PECVD chamber and N2O plasma is used to prepare SiO x film, and then deposit nitrogen-rich and carbon-rich amorphous silicon film (nitrogen concentration of 5×10 21 cm -3 , the carbon concentration is 5×10 21 cm -3 ), and active phosphorus atoms were added thereto; annealed at 900℃ for 30min in a tube furnace; ALD deposited AlO x , annealed at 450℃ in a tube furnace for 30min; then transferred to PECVD to deposit SiN x Finally, annealing was carried out at 400℃ for 60min in a mixed gas atmosphere of nitrogen and hydrogen in a tube furnace. Six samples were prepared and Sinton test was carried out. The single-side saturation current density J 0,s The test results range is 0.4~0.8fA / cm 2 .

[0070] Example 7

[0071] Prepare n-type silicon wafers, alkaline polished, with a thickness of 110μm and a resistivity of 1-7Ω·cm. After standard RCA cleaning, the silicon wafers are placed in a PECVD chamber and N2O plasma is used to prepare SiO x film, and then deposit nitrogen-rich and carbon-rich amorphous silicon film (nitrogen concentration of 5×10 21 cm -3 , the carbon concentration is 5×10 21 cm -3 ), and active phosphorus atoms were added thereto; annealing was performed at 950℃ for 30min in a tube furnace; ALD deposition of AlO x , annealed at 450℃ in a tube furnace for 30min; then transferred to PECVD to deposit SiN x Finally, annealing was carried out at 400℃ for 60min in a mixed gas atmosphere of nitrogen and hydrogen in a tube furnace. Six samples were prepared and Sinton test was carried out. The single-side saturation current density J 0,s The test results range is 1.0~1.5fA / cm 2 .

[0072] The diffusion curves of active atoms phosphorus and boron on the silicon wafers of the samples in Examples 1-7 were tested. The results are shown in FIG3 . The concentration of active atoms on the silicon wafer surface ranges from 1×10 18 cm -3 ~1×10 21 cm -3 , the diffusion depth range is 600~1200nm.

[0073] Comparative Example 1

[0074] Prepare n-type silicon wafers, alkaline polished, with a thickness of 110μm and a resistivity of 1-7Ω·cm. After standard RCA cleaning, place them in the ALD chamber to deposit AlO x , then transferred to a tube furnace and annealed at 450℃ for 30min under nitrogen atmosphere. 6 samples were prepared and Sinton test was performed. The single-side saturation current density J 0,s The test results range is 3.0~5.0fA / cm 2 .

[0075] Comparative Example 2

[0076] Prepare n-type silicon wafers, alkaline polished, with a thickness of 110μm and a resistivity of 1-7Ω·cm. After standard RCA cleaning, place them in the ALD chamber to deposit AlO x , then transferred to a tube furnace for annealing at 450 ° C for 30 min under a nitrogen atmosphere; transferred to PECVD to deposit SiN x Finally, the samples were transferred to a tube furnace and annealed at 400℃ for 60min in a nitrogen / hydrogen mixed gas. Six samples were prepared and Sinton test was performed. The single-side saturation current density J 0,s The test results range is 2.0~4.0fA / cm 2 .

[0077] Comparative Example 3

[0078] Prepare n-type silicon wafer with textured surface, thickness of 200μm, resistivity of 1-7Ω·cm. After standard RCA cleaning, place it in ALD chamber and deposit AlO x , then transferred to a tube furnace for annealing at 450 ° C for 30 min under a nitrogen atmosphere; transferred to PECVD to deposit SiN x Finally, the samples were transferred to a tube furnace and annealed at 400℃ for 60min in a nitrogen / hydrogen mixed gas. Six samples were prepared and Sinton test was performed. The single-side saturation current density J 0,s The test results range from 6.0 to 9.0 fA / cm 2 .

[0079] Comparative Example 4

[0080] Prepare n-type silicon wafers, alkaline polished, with a thickness of 110 μm and a resistivity of 1-7 Ω·cm. After standard RCA cleaning, the silicon wafers were placed in a tube furnace and prepared in an oxygen atmosphere. x , and then transferred to the PECVD chamber to deposit SiN x Finally, annealing was carried out at 400℃ for 60min in a tube furnace under a mixture of nitrogen and hydrogen. Six samples were prepared and Sinton test was carried out. The single-side saturation current density J 0,sThe test results range is 8.0~12.0fA / cm 2 .

[0081] The single-side saturation current density (J) of the passivation sheets prepared in Examples 1-7 and Comparative Examples 1-4 was tested. 0,s ) and implicit open circuit voltage (iV oc ), and the test results are shown in Table 1. The results show that the passivation film structure of the present invention has an excellent passivation effect, which can significantly reduce the saturation current density on the surface of polished silicon wafers and textured silicon wafers and increase the implicit open circuit voltage.

[0082] Table 1 Comparison of single-sided saturation current density of passivation structures of Examples 1-7 and Comparative Examples 1-4

[0083] Example 8

[0084] A nitrogen- and carbon-rich amorphous silicon film (10 at% nitrogen and 5 at% carbon) was deposited on a quartz substrate and doped with active phosphorus atoms. The film was annealed at 900°C for 30 minutes in a tube furnace. Ellipsometry measurements of the film's refractive index, n, and extinction coefficient, k, are shown in Figure 4. The refractive index ranged from 1.8 to 2.4, and the absorption coefficient, k, approached zero for wavelengths above 400 nm.

[0085] Example 9

[0086] A back-contact cell was prepared, with a TOPCon structure on the back of the cell and a velvet surface on the front. A novel passivation structure was prepared using the method of Example 4.

[0087] Comparative Example 5

[0088] Prepare a back contact battery, the back of the battery uses a TOPCon structure; the front is a velvet surface, and AlO is prepared using the method of Comparative Example 2 x / SiN x Passivation structure.

[0089] The battery of Comparative Example 5 differs from that of Example 9 only in the front passivation structure. The battery performance is tested, and the results are shown in Table 2. The results show that the passivation structure of the present invention can improve battery efficiency.

[0090] Table 2 Battery performance of Example 9 and Comparative Example 5

[0091] Although the present invention is disclosed as above, the present invention is not limited thereto. Any person skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be based on the scope defined by the claims.

Claims

1. A passivation film structure with both passivation and surface doping, characterized in that, It includes a nano dielectric layer, a silicide layer and a hydrogen-rich dielectric layer which are sequentially stacked on the surface of a silicon substrate. The material of the nano dielectric layer is a silicon oxyhydride film or a silicon oxynitride film. The material of the silicide layer is a boron / phosphorus-doped silicon film containing carbon and / or nitrogen. The material of the hydrogen-rich dielectric layer is selected from one or more laminated films of an aluminum oxyhydride film, a silicon nitride film, a silicon oxyhydride film, and a silicon oxynitride film.

2. The passivation film structure with both passivation and surface doping according to claim 1, characterized in that, A diffusion layer is formed on the surface of the silicon substrate close to the nano-medium layer. The thickness of the diffusion layer is 10 - 1200 nm. Boron or phosphorus elements are doped in the diffusion layer, and the phosphorus concentration on the surface of the silicon substrate is 1×10 18 cm -3 ~1×10 21 cm -3 , or the boron concentration is 5×10 16 cm -3 ~5×10 20 cm -3 .

3. The passivation film structure with both passivation and surface doping according to claim 2, characterized in that, The boron / phosphorus concentration of the silicide layer is 5×10 19 cm -3 ~5×10 21 cm -3 。 4. The passivation film structure with both passivation and surface doping according to claim 1, characterized in that, The carbon concentration of the silicide layer is 1×10 21 cm -3 ~2×10 22 cm -3 , and / or the nitrogen concentration is 5×10 21 cm - 3 ~4×10 22 cm -3 .

5. The passivation film structure with both passivation and surface doping according to claim 1, characterized in that, The silicon substrate contains hydrogen, carbon and / or nitrogen elements, and the concentrations of these elements gradually decrease from the surface to the interior. The hydrogen concentration on the surface of the silicon substrate is 1×10 19 cm -3 ~1×10 21 cm -3 , the nitrogen concentration is 1×10 19 cm -3 ~1×10 22 cm -3 , and / or the carbon concentration is 1×10 19 cm -3 ~1×10 22 cm -3 .

6. The passivation film structure with both passivation and surface doping according to any one of claims 1-5, characterized in that, The hydrogen concentration of the nano medium layer is 1×10 19 cm -3 ~1×10 22 cm -3 ; the hydrogen concentration of the silicide layer is 1×10 19 cm -3 ~1×10 22 cm -3 ; and the hydrogen concentration of the hydrogen-rich medium layer is 1×10 19 cm - 3 ~1×10 22 cm -3 .

7. The passivation film structure with both passivation and surface doping according to claim 6, characterized in that, The refractive index of the silicide layer is 1.5 to 3.

0.

8. The passivation film structure with both passivation and surface doping according to claim 6, characterized in that, The transmittance of the nano dielectric layer above 400 nm is greater than 97%, and the transmittance of the silicide layer above 400 nm is greater than 97%.

9. The passivation film structure with both passivation and surface doping according to claim 6, characterized in that, The thickness of the nano dielectric layer is 1 to 2 nm, and the thickness of the silicide layer is greater than or equal to 3 nm.

10. A method for preparing a passivation film structure with both passivation and surface doping as described in any one of claims 1-9, characterized in that, It includes the following steps: S1. Clean the silicon substrate. S2. Prepare a silicon oxide film or a silicon oxynitride film on the surface of the silicon substrate. S3. Deposit an amorphous silicon film containing carbon and / or nitrogen elements and dope boron or phosphorus atoms. S4. Perform a high-temperature annealing treatment to allow the active phosphorus or boron atoms to diffuse into the silicon substrate, form a diffusion layer on the surface of the silicon substrate, and at the same time, the carbon and / or nitrogen elements diffuse into the silicon substrate. S5. Deposit one or more laminated films of aluminum oxide, silicon nitride, silicon oxide, and silicon oxynitride. S6. Perform a hydrogen injection treatment to inject hydrogen atoms into the passivation film structure and the silicon substrate.

11. The method for preparing a passivation film structure with both passivation and surface doping according to claim 10, characterized in that, In the step S3, the doping method is to deposit a boron- or phosphorus-containing amorphous silicon film above or below the amorphous silicon film containing carbon and / or nitrogen elements, or directly add active boron or phosphorus atoms to the amorphous silicon film containing carbon and / or nitrogen elements.

12. A silicon solar cell, characterized in that, It includes a passivation film structure with both passivation and surface doping as described in any one of claims 1-9.

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