Method and equipment for preparing oxygen-doped microcrystalline silicon thin film

Abstract

The present invention relates to a method for preparing an oxygen-doped microcrystalline silicon thin film, comprising: texturing a silicon wafer substrate to obtain a double-sided texturized silicon wafer; depositing intrinsic silicon layers on both sides of the texturized silicon wafer to obtain a first structure; placing the first structure in a hot wire chemical vapor deposition device and introducing H2 to hydrogen etch the surface of the silicon wafer; then controlling the pressure in the reaction chamber of the hot wire chemical vapor deposition device while introducing SiH4 and H2 to deposit a seeding layer on the intrinsic silicon layer on the light-facing side of the texturized silicon wafer to obtain a second structure; and simultaneously introducing SiH4, H2, N2O, and PH3 into the reaction chamber to deposit an oxygen-doped microcrystalline silicon layer on the seeding layer of the second structure. Furthermore, the present invention also relates to an apparatus for preparing an oxygen-doped microcrystalline silicon thin film using the above method. The present invention can form an oxygen-doped microcrystalline thin film on the light-facing side of, for example, a heterojunction cell using a HoFCVD device, thereby solving the problem of parasitic absorption on the light-facing side.

Description

Technical Field

[0001] The present invention relates to the technical field of heterojunction batteries, and more particularly, to a method and apparatus for preparing an oxygen-doped microcrystalline silicon thin film. Background Art

[0002] Heterojunction cells have a simple structure, consisting of only four steps: texturing, CVD (Chemical Vapor Deposition), PVD (Physical Vapor Deposition), and screen printing. They have gradually become mainstream in the development of photovoltaic technology and have been a key focus of the photovoltaic industry in recent years. Currently, improving the efficiency of heterojunction cells is key to increasing their future market share. However, amorphous silicon suffers from significant parasitic absorption on the light-facing side. The vast majority of these absorbed photons do not become effective photogenerated carriers, but are instead separated by the built-in electric field, thus failing to contribute to improving the cell's short-circuit current. Reducing parasitic absorption on the light-facing side is typically achieved in two ways. One approach is to thin the layers on the light-facing side. For example, when the N layer serves as the light-facing side, the thickness of the N layer (doped amorphous silicon or microcrystalline silicon layer) and the I layer (intrinsic passivation layer) can be reduced to minimize light absorption on the light-facing side. However, this method will introduce side effects - although thinning the film thickness can reduce parasitic absorption, excessive thinning will lead to a deterioration in the passivation effect of the I layer, and the open-circuit voltage and short-circuit current of the battery will be lost. The implementation of this method has extremely high requirements for equipment and processes (it is necessary to ensure that the film thickness deviation of the entire board is within 1nm); another method is to make the thin layer on the light-facing side (for example, the N layer) into microcrystals, and combine the silicon oxide channels formed in the microcrystals to achieve the effect of silicon oxide being transparent (reducing parasitic absorption and increasing short-circuit current density) and microcrystalline silicon having good conductivity (reducing series resistance), thereby effectively increasing the short-circuit current and improving the conversion efficiency of the battery.

[0003] However, the current method used in the industry to prepare oxygen-doped microcrystals uses PECVD (Plasma Enhanced Chemical Vapor Deposition) equipment, which introduces a certain proportion of CO2, SiH4, H2, PH3 and other gases to prepare oxygen-doped microcrystalline films. The preparation method using PECVD equipment requires the use of a very high frequency power supply, which is imported and has high costs and long delivery times. This method also consumes a large amount of process gas - the gas flow rate of SiH4 is usually 1000-4000sccm, the gas flow rate of H2 is 10000-40000sccm, and the gas flow rate of CO2 is 1000-3000sccm. Moreover, when preparing microcrystals using PECVD, the amount of H2 used is 20-100 times that of SiH4, and the chamber pressure during the process is in the range of 40-150Pa. This easily generates dust, causing contamination of the chamber and silicon wafers, affecting the quality of the film layer.

[0004] Therefore, it is urgent to design a solution that can solve the above-mentioned defects. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention provides a method and apparatus for preparing oxygen-doped microcrystalline silicon thin films. This method utilizes HoFCVD (Hot Filament Chemical Vapor Deposition, also known as hot filament CVD) equipment instead of PECVD equipment to prepare oxygen-doped microcrystalline silicon thin films. This method enables the production of oxygen-doped microcrystalline silicon thin films with a crystallization rate exceeding 50% at a low pressure of 0.5-2.5 Pa, using process gas consumption that is only a few tenths of that used in PECVD.

[0006] In order to solve the above technical problems or achieve the above objectives, the present invention adopts the following technical solutions:

[0007] According to one aspect of the present invention, there is provided a method for preparing an oxygen-doped microcrystalline silicon thin film, comprising:

[0008] Texturing the silicon wafer substrate to obtain a double-sided texturing silicon wafer;

[0009] Depositing intrinsic silicon layers on both sides of the textured silicon wafer to obtain a first structure;

[0010] The first structure is placed in a hot-wire chemical vapor deposition apparatus and H2 is introduced to perform hydrogen etching on the surface of the silicon wafer. Then, the pressure in the reaction chamber of the hot-wire chemical vapor deposition apparatus is controlled while SiH4 and H2 are introduced simultaneously to deposit a seeding layer on the intrinsic silicon layer on the light-facing surface of the textured silicon wafer to obtain the second structure.

[0011] SiH4, H2, N2O and PH3 are introduced into the reaction chamber simultaneously to deposit an oxygen-doped microcrystalline silicon layer on the seeding layer of the second structure.

[0012] In one embodiment of the present invention, intrinsic silicon layers are deposited on both sides of the textured silicon wafer by using a plasma enhanced chemical vapor deposition device or a hot wire chemical vapor deposition device.

[0013] In one embodiment of the present invention, when hydrogen etching is performed on the surface of a silicon wafer, the gas flow rate of H2 is 200-1000 sccm; when depositing an oxygen-doped microcrystalline silicon layer, the gas flow rate of SiH4 is 150-300 sccm, the gas flow rate of H2 is 1100-5000 sccm, and the gas flow rate of N2O is 45-100 sccm; and when depositing the seeding layer and the oxygen-doped microcrystalline silicon layer, the ratio of SiH4 to H2 is in the range of 1:7-1:20.

[0014] In one embodiment of the present invention, the ratio of the introduced SiH4 and H2 is at least 1:10.

[0015] In one embodiment of the present invention, when depositing an oxygen-doped microcrystalline silicon layer, the ratio of the amount of SiH4 and N2O introduced is 0<≤1:10 and the amount of N2O gradually decreases with the process time; the ratio of the amount of SiH4 and PH3 introduced decreases from 50:1 to 13:1 with the process time.

[0016] In one embodiment of the present invention, the pressure in the reaction chamber of the hot-filament chemical vapor deposition apparatus is controlled to be 0.5-2.5 Pa.

[0017] In one embodiment of the present invention, the thickness of the silicon wafer substrate is 80-120 μm.

[0018] In one embodiment of the present invention, the thickness of the seed layer is 2-3 nm.

[0019] According to another aspect of the present invention, there is provided an apparatus for preparing an oxygen-doped microcrystalline silicon thin film using the above-mentioned method for preparing an oxygen-doped microcrystalline silicon thin film. The apparatus is a hot-wire chemical vapor deposition apparatus, comprising:

[0020] a carrier transport system configured to transport a carrier carrying a silicon wafer substrate into the reaction chamber;

[0021] a carrier temperature control system connected to the carrier and configured to control the temperature of the carrier;

[0022] a heating system disposed in the reaction chamber and configured to heat the reaction chamber;

[0023] a vacuum system configured to evacuate the reaction chamber;

[0024] The gas homogenizing system is disposed in the reaction chamber and is configured to introduce required process gas into the reaction chamber.

[0025] In one embodiment of the present invention, the vacuum system includes one or more pump groups consisting of a dry pump and a molecular pump. The molecular pump is non-centrally distributed and a butterfly valve for controlling the opening and closing angle is provided at the front end of the molecular pump. A vacuum gauge for detecting different vacuum degrees is provided on the cavity of the reaction chamber. The butterfly valve controls the opening and closing angle in response to real-time feedback from the vacuum gauge to adjust the pumping speed of the molecular pump to achieve pressure regulation in the reaction chamber.

[0026] In one embodiment of the present invention, the heating system includes an auxiliary heating element and a hot wire for high-temperature heating. The auxiliary heating element is distributed around the inner wall of the reaction chamber. The auxiliary heating element includes an armored heating wire or an infrared lamp tube; the hot wire for high-temperature heating is arranged vertically and arranged in series, parallel or a combination of series and parallel in the reaction chamber, and the hot wire for high-temperature heating is connected to an external power supply.

[0027] In one embodiment of the present invention, the gas uniformity system achieves a uniform gas field of the process gas in the reaction chamber by arranging holes of different pore sizes or holes of the same pore size but unequal spacing on the PE tube. The PE tubes in the reaction chamber are distributed on the outer circle of the high-temperature heating wire and the area enclosed by the PE tubes is larger than the arrangement area of ​​the high-temperature heating wire.

[0028] According to another aspect of the present invention, there is provided a method for preparing a battery cell, comprising:

[0029] Texturing the silicon wafer substrate to obtain a double-sided texturing silicon wafer;

[0030] Depositing intrinsic silicon layers on both sides of the textured silicon wafer to obtain a first structure;

[0031] The first structure is placed in a hot-wire chemical vapor deposition apparatus and H2 is introduced to perform hydrogen etching on the surface of the silicon wafer. Then, the pressure in the reaction chamber of the hot-wire chemical vapor deposition apparatus is controlled while SiH4 and H2 are introduced simultaneously to deposit a seeding layer on the intrinsic silicon layer on the light-facing surface of the textured silicon wafer to obtain the second structure.

[0032] Simultaneously introducing SiH4, H2, N2O, and PH3 into the reaction chamber, depositing an oxygen-doped microcrystalline silicon layer on the seeding layer of the second structure, to obtain a third structure;

[0033] An amorphous silicon layer or a microcrystalline silicon layer is deposited on the intrinsic silicon layer on the backlight side of the textured silicon wafer on the third structure, and then a TCO layer is deposited on both sides. Electrodes are formed by screen printing to obtain the final cell.

[0034] In one embodiment of the present invention, the oxygen-doped microcrystalline silicon layer includes lightly doped oxygen-doped microcrystalline silicon and highly doped oxygen-doped microcrystalline silicon, wherein the lightly doped oxygen-doped microcrystalline silicon is close to the intrinsic silicon layer facing the light, and the highly doped oxygen-doped microcrystalline silicon is close to the electrode side.

[0035] The technical solution provided by the present invention has the following advantages compared with the prior art:

[0036] The present invention can form an oxygen-doped microcrystalline thin film on the light-facing surface of a heterojunction cell (HJT) through a HoFCVD device, thereby solving the problem of parasitic absorption on the light-facing surface of the heterojunction cell.

[0037] The HoFCVD device of the present invention controls the pressure at 0.5-2.5 Pa, the process pressure is lower, and the process gas consumption is only about 0.01-0.1 times the process gas consumption used in PECVD, which can greatly save costs; the HoFCVD device can also realize the preparation of oxygen-doped microcrystalline films by using N2O and without the need for a very high frequency power supply; and the crystallization rate of the oxygen-doped microcrystalline films prepared by the HoFCVD device can be well controlled. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0039] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for the description of the embodiments or the prior art. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0040] Figure 1 A schematic flow chart of a method for preparing an oxygen-doped microcrystalline silicon thin film according to an embodiment of the present invention is shown;

[0041] Figure 2 Shows the use of Figure 1 Raman spectrum of the oxygen-doped microcrystalline silicon film prepared by the method;

[0042] Figure 3 A schematic diagram showing a process of a method for preparing a battery cell provided by an embodiment of the present invention;

[0043] Figures 4a-4d Shows the use of Figure 3 Schematic diagram of the structure of each stage obtained when preparing a battery cell by the method.

[0044] Among them, 1. N-type silicon wafer substrate; 2. N-type intrinsic silicon layer; 3. P-type intrinsic silicon layer; 4. seeding layer; 5. N-type oxygen-doped microcrystalline silicon layer; 6. P-type amorphous silicon layer or P-type microcrystalline silicon layer; 7. TCO layer; 8. electrode. DETAILED DESCRIPTION

[0045] In order to more clearly understand the above-mentioned objects, features and advantages of the present invention, the embodiments of the present invention will be further described below. It should be noted that the embodiments of the present invention and the features therein can be combined with each other without conflict.

[0046] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways than those described herein; it is obvious that the embodiments in the specification are only part of the embodiments of the present invention, rather than all of the embodiments.

[0047] like Figure 1 As shown, an embodiment of the present invention provides a method for preparing an oxygen-doped microcrystalline silicon thin film, comprising the following steps:

[0048] S10: texturing the silicon wafer substrate to obtain a double-sided texturing silicon wafer;

[0049] S11: depositing intrinsic silicon layers on both sides of the textured silicon wafer to obtain a first structure;

[0050] S12: placing the first structure in a hot-wire chemical vapor deposition apparatus and introducing H2 to perform hydrogen etching on the surface of the silicon wafer. Then, controlling the pressure in the reaction chamber of the hot-wire chemical vapor deposition apparatus, simultaneously introducing SiH4 and H2 to deposit a seeding layer on the intrinsic silicon layer on the light-facing surface of the textured silicon wafer, thereby obtaining a second structure.

[0051] S13: SiH4, H2, N2O and PH3 are introduced into the reaction chamber simultaneously to deposit an oxygen-doped microcrystalline silicon layer on the seeding layer of the second structure.

[0052] The present invention replaces PECVD equipment with HoFCVD (also known as hot-filament CVD). The HoFCVD device operates by decomposing the process gas on the surface of a hot filament at a temperature of approximately 1800-2000°C. The resulting reactive radicals migrate to the surface of the silicon wafer substrate (textured silicon wafer), where they react and deposit into a film. The energy of these reactive radicals is lower than that of the plasma generated by PECVD. While PECVD plasma bombards the film layer, damaging it and introducing defects, the reactive radicals generated by HoFCVD have even lower energy, eliminating the risk of plasma bombardment damaging the silicon wafer substrate surface.

[0053] Through the above technical solution of the present invention, the present invention can form an oxygen-doped microcrystalline thin film on the light-facing surface of a heterojunction technology (HJT) through a HoFCVD device, thereby solving the problem of parasitic absorption on the light-facing surface of the HJT.

[0054] In the method shown in the above embodiment, in S10, the thickness of the silicon wafer substrate may preferably be 80-120 μm.

[0055] In the method shown in the above embodiment, in S11, intrinsic silicon layers (for example, N-type and P-type intrinsic silicon layers) can be deposited on both sides (for example, the front side or the light-facing side and the back side or the backlight side) of the textured silicon wafer respectively by plasma enhanced chemical vapor deposition equipment (PECVD) or hot filament chemical vapor deposition (HoFCVD) equipment.

[0056] In the method shown in the above embodiment, in S12 and S13, the H2 gas flow rate is 200-1000 sccm when hydrogen etching the silicon wafer surface; when depositing the oxygen-doped microcrystalline silicon layer, the SiH4 gas flow rate is 150-300 sccm, the H2 gas flow rate is 1100-5000 sccm, and the N2O gas flow rate is 45-100 sccm. Moreover, when depositing the seeding layer and the oxygen-doped microcrystalline silicon layer, the ratio of SiH4 to H2 is in the range of 1:7-1:20. Preferably, the ratio of SiH4 to H2 is at least 1:10, so that the crystallization rate of the oxygen-doped microcrystalline silicon layer exceeds 50%. That is to say, in this embodiment, the film formation quality of the HoFCVD equipment is better than that of the PECVD equipment. The HoFCVD equipment uses N2O gas instead of CO2 gas as the oxygen source. The gas flow rate of SiH4 is generally 150-300sccm, the gas flow rate of H2 is 1100-5000sccm, and the gas flow rate of N2O is 45-100sccm. When HoFCVD prepares microcrystals, the amount of H2 used is 7-20 times that of SiH4, and when the SiH4:H2 usage ratio of the HoFCVD equipment is greater than 1:10, the crystallization rate can be higher than 50%.

[0057] In the method shown in the above embodiment, in S13, when depositing the oxygen-doped microcrystalline silicon layer, the ratio of the amount of SiH4 and N2O introduced is 0<≤1:10 and the amount of N2O introduced gradually decreases with the process time; the ratio of the amount of SiH4 and PH3 introduced decreases from 50:1 to 13:1 with the process time.

[0058] In the method described in the above embodiment, in S12 and S13, the pressure in the reaction chamber of the hot filament chemical vapor deposition equipment is controlled to be between 0.5 and 2.5 Pa. The process pressure of the HoFCVD equipment is controlled within the range of 0.5 to 2.5 Pa, which is several tenths or even one hundredth of the process pressure of the PECVD equipment, and thus dust is not generated during the process.

[0059] In the method shown in the above embodiment, the thickness of the seed layer may preferably be 2-3 nm.

[0060] It can be seen that the pressure of the HoFCVD equipment in the present invention is controlled at 0.5-2.5Pa, the process pressure is lower, and the process gas consumption is only about 0.01-0.1 times the process gas consumption used by PECVD, which can greatly save costs; the HoFCVD equipment can achieve the preparation of oxygen-doped microcrystals by using N2O and without the need for a very high frequency power supply; the crystallization rate of oxygen-doped microcrystals prepared by the HoFCVD equipment can be well regulated, and the preparation of oxygen-doped microcrystalline film layers with a crystallization rate of more than 50% can be achieved. In other words, the present invention uses the HoFCVD equipment to prepare oxygen-doped microcrystalline thin films, and can prepare oxygen-doped microcrystalline silicon thin films with a crystallization rate of more than 50% at a low pressure of 0.5-2.5Pa, with a process gas consumption of only a few tens of the process gas consumption in PECVD. Among them, the Raman spectrum of the grown oxygen-doped microcrystals is shown in FIG. Figure 2 shown.

[0061] In addition, one embodiment of the present invention further provides an apparatus for preparing an oxygen-doped microcrystalline silicon thin film using the above-described method for preparing an oxygen-doped microcrystalline silicon thin film. The apparatus is a hot-wire chemical vapor deposition apparatus, comprising a carrier transport system, a carrier temperature control system, a heating system, a vacuum system, and a gas homogenization system. The carrier transport system is configured to transport a carrier carrying a silicon wafer substrate into a reaction chamber; the carrier temperature control system is connected to the carrier and configured to control the carrier temperature; the heating system is disposed within the reaction chamber and configured to heat the reaction chamber; the vacuum system is configured to evacuate the reaction chamber; and the gas homogenization system is disposed within the reaction chamber and configured to introduce the desired process gas into the reaction chamber.

[0062] In the device shown in the above embodiment, the vacuum system includes one or more pump groups consisting of a dry pump and a molecular pump. The molecular pump is non-centrally distributed and a butterfly valve for controlling the opening and closing angle is provided at the front end of the molecular pump. A vacuum gauge for detecting different vacuum degrees is provided on the cavity of the reaction chamber. The butterfly valve controls the opening and closing angle in response to real-time feedback from the vacuum gauge to adjust the pumping speed of the molecular pump to achieve pressure regulation in the reaction chamber.

[0063] The vacuum system of the process chamber or reaction chamber contains one or more pump groups (dry pump + molecular pump). The distribution of the molecular pump is non-centralized and there is a butterfly valve at the front end of the molecular pump to control the opening and closing angle. The purpose is to evenly distribute the gas in the reaction chamber and regulate the pumping speed. The cavity of the reaction chamber is equipped with vacuum gauges such as capacitor silicon, ionization silicon, and resistor silicon for detecting different vacuum degrees. The cavity of the reaction chamber needs to be cleaned of impurity gases in the reaction chamber before the process. When the cavity of the reaction chamber is in process, the real-time feedback of the cavity pressure value is carried out by capacitor silicon and the like, and the signal is fed back to the butterfly valve of the molecular pump. The butterfly valve adjusts the molecular pumping speed through the opening and closing angle, thereby realizing the regulation of the cavity pressure value.

[0064] In the device shown in the above embodiment, the heating system includes auxiliary heating elements and hot wires for high-temperature heating. The auxiliary heating elements are distributed around the inner wall of the reaction chamber. The auxiliary heating elements include armored heating wires or infrared lamps; the hot wires for high-temperature heating are arranged vertically and arranged in series, parallel or a combination of series and parallel in the reaction chamber. The hot wires for high-temperature heating are connected to an external power supply.

[0065] The reaction chamber is equipped with auxiliary heating elements, located around the inner walls. These elements ensure uniform temperature within the chamber and facilitate the desorption of impurity gases. These elements can be either armored heating wires or infrared lamps. When the equipment is opened for maintenance, these elements can be activated to remove moisture from the reaction chamber and accelerate the desorption of impurity gases from the walls.

[0066] The hot wires of the HoFCVD device are arranged vertically, and are arranged in series, parallel, or a combination of series and parallel in the cavity. The electrodes of the hot wires are connected to an external power supply through the flange holes on the cavity of the reaction chamber, thereby realizing the energy supply of the hot wires.

[0067] In the device shown in the above embodiment, the gas uniformity system realizes a uniform gas field of the process gas in the reaction chamber by arranging holes of different apertures or holes of the same aperture but unequal spacing on the PE tube. The PE tubes in the reaction chamber are distributed on the outer circle of the high-temperature heating wire and the area enclosed by the PE tubes is larger than the arrangement area of ​​the high-temperature heating wire.

[0068] In existing equipment, process gases are typically mixed in a mixing cabinet before being transported to the reaction chamber via a gas pipeline (PE tube). In HoFCVD equipment, however, the gas homogenization system within the reaction chamber achieves uniform gas distribution within the reaction chamber by arranging holes of varying diameters, or holes of the same diameter but unequally spaced, in the PE tube. This ensures uniform film thickness over large coating areas. The PE tube within the reaction chamber is distributed around the outer ring of the heating wire, enclosing an area larger than the heating wire arrangement.

[0069] In the device shown in the above embodiment, in order to form oxygen-doped microcrystals, the surface temperature of the hot wire needs to reach 1800-2500°C. The introduced H2 obtains sufficient energy on the high-temperature hot wire to generate H* active groups. During the process, the gas pressure in the reaction chamber is controlled to be low at 0.5-2.5Pa. In this way, the H* active groups have a sufficiently long mean free path to reach the surface of the silicon wafer substrate without collision, thereby carrying energy to etch the weak Si-H bonds formed on the silicon substrate. Since the bond energy of the Si-Si bond is greater than that of the Si-H bond, the H* active groups will be retained to continue nucleation and growth. CO2 only partially decomposes at 1750°C and begins to decompose into oxygen atoms at 2600°C, requiring too much energy. However, the N2O used in the present invention can significantly decompose at 500°C and completely decompose into nitrogen and oxygen atoms at 900°C. Therefore, N2O can obtain sufficient energy to decompose on the surface of the hot wire. The oxygen atoms produced by the decomposition diffuse to the surface of the silicon wafer and combine with the dangling bonds of Si to form Si-O bonds. Most of the oxygen forms SiO2, while a small amount of oxygen exists in the microcrystalline silicon in an interstitial state. By introducing N2O into the reaction chamber in time periods, a mixed structure of SiO2 and microcrystalline silicon is achieved. The refractive index of SiO2 is approximately 1.45-1.47, which has good light transmittance and can reduce the absorption of incident light by the light-facing surface. The presence of doped microcrystalline silicon can provide good conductivity, thereby reducing parasitic absorption and improving the conversion efficiency of photovoltaic cells.

[0070] In addition, if Figure 3 As shown, an embodiment of the present invention also provides a method for preparing a battery cell. Figure 1 The method shown is similar and includes the following steps:

[0071] S30: texturing the silicon wafer substrate to obtain a double-sided texturing silicon wafer;

[0072] S31: depositing intrinsic silicon layers on both sides of the textured silicon wafer to obtain a first structure;

[0073] S32: placing the first structure in a hot-wire chemical vapor deposition apparatus and introducing H2 to perform hydrogen etching on the surface of the silicon wafer. Then, controlling the pressure in the reaction chamber of the hot-wire chemical vapor deposition apparatus, simultaneously introducing SiH4 and H2 to deposit a seeding layer on the intrinsic silicon layer on the light-facing surface of the textured silicon wafer, thereby obtaining a second structure.

[0074] S33: SiH4, H2, N2O and PH3 are introduced into the reaction chamber simultaneously to deposit an oxygen-doped microcrystalline silicon layer on the seeding layer of the second structure to obtain a third structure;

[0075] S34: depositing an amorphous silicon layer or a microcrystalline silicon layer on the intrinsic silicon layer on the backlight side of the textured silicon wafer on the third structure, and then depositing a TCO layer on both sides, and then forming electrodes by screen printing to obtain the final battery cell.

[0076] In the above-mentioned method for preparing the battery cell, preferably, the oxygen-doped microcrystalline silicon layer includes shallowly doped oxygen-doped microcrystalline silicon and highly doped oxygen-doped microcrystalline silicon, wherein the shallowly doped oxygen-doped microcrystalline silicon is close to the intrinsic silicon layer facing the light, and the highly doped oxygen-doped microcrystalline silicon is close to the electrode side.

[0077] The above technical solution of the present invention is described in detail below through specific embodiments.

[0078] Example 1

[0079] Step 1: After the N-type silicon wafer substrate 1 with a thickness of 80 μm is subjected to a texturing process, it becomes a double-sided texturing silicon wafer.

[0080] Step 2: In a PECVD device or HoFCVD device, an N-type intrinsic silicon layer 2 and a P-type intrinsic silicon layer 3 are deposited on the front and back of the textured silicon wafer, respectively, to complete the intrinsic amorphous silicon layer i(n): a-Si:H and the intrinsic amorphous silicon layer i(p): a-Si:H, and obtain the following: Figure 4a The first structure shown.

[0081] Step 3: Place the first structure in a HoFCVD device, keep the current of the hot wire at 30A, then introduce 200sccm of H2 to perform hydrogen etching on the surface of the silicon wafer, and control the pressure in the reaction chamber of the HoFCVD device at 0.5Pa. At the same time, introduce 150sccm of SiH4 and 1100sccm of H2, with the ratio of SiH4:H2=1:10, and grow a 2nm seeding layer 4 on the N-type intrinsic silicon layer 2 to obtain the following: Figure 4b The second structure shown.

[0082] Step 4: On the basis of the second structure, the pressure in the reaction chamber of the HoFCVD equipment is controlled at 0.5Pa, and 150sccm of SiH4, 1100sccm of H2, 45sccm of N2O and PH3 are introduced at the same time, with a dosage ratio of SiH4:H2=1:10, a dosage ratio of SiH4:N2O starting at 1:10 and the amount of N2O gradually decreasing as the process time progresses, and a dosage ratio of SiH4:PH3 gradually transitioning from 50:1 to 13:1, and forming an N-type oxygen-doped microcrystalline silicon layer 5 on the seeding layer 4, which includes shallowly doped oxygen-doped microcrystalline silicon close to the intrinsic silicon layer and highly doped oxygen-doped microcrystalline silicon close to the electrode side, so as to facilitate the subsequent formation of better ohmic contact, and obtain the following Figure 4c The third structure shown.

[0083] Step 5: Based on the third structure, prepare P-type amorphous silicon or P-type microcrystalline silicon 6 on the P-type intrinsic silicon layer 3 (i(p) layer) side by PECVD or HoFCVD equipment; then make TCO layer 7 on both sides, and then form electrode 8 by screen printing to obtain Figure 4d The final cell is shown.

[0084] According to tests, the crystallization rate of the N-type oxygen-doped microcrystalline silicon layer 5 in the above embodiment 1 is 55%, no dust is generated during the process, and no parasitic absorption phenomenon occurs in the N-layer on the light-facing side of the cell.

[0085] Example 2

[0086] Step 1: After the N-type silicon wafer substrate 1 with a thickness of 100 μm is subjected to a texturing process, it becomes a double-sided texturing silicon wafer.

[0087] Step 2: In a PECVD device or HoFCVD device, an N-type intrinsic silicon layer 2 and a P-type intrinsic silicon layer 3 are deposited on the front and back of the textured silicon wafer, respectively, to complete the intrinsic amorphous silicon layer i(n): a-Si:H and the intrinsic amorphous silicon layer i(p): a-Si:H, and obtain the following: Figure 4a The first structure shown.

[0088] Step 3: Place the first structure in a HoFCVD device, keep the current of the hot wire at 40A, then introduce 600sccm of H2 to perform hydrogen etching on the surface of the silicon wafer, and control the pressure in the reaction chamber of the HoFCVD device at 1.5Pa. At the same time, introduce 200sccm of SiH4 and 2000sccm of H2, with the ratio of SiH4:H2=1:15, and grow a 2.5nm seeding layer 4 on the N-type intrinsic silicon layer 2 to obtain the following: Figure 4b The second structure shown.

[0089] Step 4: On the basis of the second structure, the pressure in the reaction chamber of the HoFCVD equipment is controlled at 1.5Pa, and 200sccm of SiH4, 2000sccm of H2, 80sccm of N2O and PH3 are introduced at the same time, with a dosage ratio of SiH4:H2=1:15, a dosage ratio of SiH4:N2O starting at 1:9 and the amount of N2O gradually decreasing with the progress of the process time, and a dosage ratio of SiH4:PH3 gradually transitioning from 50:1 to 13:1, and forming an N-type oxygen-doped microcrystalline silicon layer 5 on the seeding layer 4, which includes shallowly doped oxygen-doped microcrystalline silicon close to the intrinsic silicon layer and highly doped oxygen-doped microcrystalline silicon close to the electrode side, so as to facilitate the subsequent formation of better ohmic contact, as shown below. Figure 4c The third structure shown.

[0090] Step 5: Based on the third structure, prepare P-type amorphous silicon or P-type microcrystalline silicon 6 on the P-type intrinsic silicon layer 3 (i(p) layer) side by PECVD or HoFCVD equipment; then make TCO layer 7 on both sides, and then form electrode 8 by screen printing to obtain Figure 4d The final cell is shown.

[0091] According to tests, the crystallization rate of the N-type oxygen-doped microcrystalline silicon layer 5 in the above embodiment 2 is 70%, no dust is generated during the process, and no parasitic absorption phenomenon occurs in the N-layer on the light-facing side of the cell.

[0092] Example 3

[0093] Step 1: After the N-type silicon wafer substrate 1 with a thickness of 120 μm is subjected to a texturing process, it becomes a double-sided texturing silicon wafer.

[0094] Step 2: In a PECVD device or HoFCVD device, an N-type intrinsic silicon layer 2 and a P-type intrinsic silicon layer 3 are deposited on the front and back of the textured silicon wafer, respectively, to complete the intrinsic amorphous silicon layer i(n): a-Si:H and the intrinsic amorphous silicon layer i(p): a-Si:H, and obtain the following: Figure 4a The first structure shown.

[0095] Step 3: Place the first structure in a HoFCVD device, keep the current of the hot wire at 35A, then introduce 1000sccm of H2 to perform hydrogen etching on the surface of the silicon wafer, and control the pressure in the reaction chamber of the HoFCVD device at 2.5Pa. At the same time, introduce 300sccm of SiH4 and 5000sccm of H2, with the ratio of SiH4:H2=1:20, and grow a 3nm seeding layer 4 on the N-type intrinsic silicon layer 2 to obtain the following: Figure 4b The second structure shown.

[0096] Step 4: On the basis of the second structure, the pressure in the reaction chamber of the HoFCVD equipment is controlled at 2.5Pa, and 300sccm of SiH4, 5000sccm of H2, 100sccm of N2O and PH3 are introduced at the same time, with a dosage ratio of SiH4:H2=1:20, a dosage ratio of SiH4:N2O starting at 1:8 and the amount of N2O gradually decreasing with the progress of the process time, and a dosage ratio of SiH4:PH3 gradually transitioning from 50:1 to 13:1, and an oxygen-doped microcrystalline silicon layer 5 is formed on the seeding layer 4, which includes shallowly doped oxygen-doped microcrystalline silicon close to the intrinsic silicon layer and highly doped oxygen-doped microcrystalline silicon close to the electrode side, so as to facilitate the subsequent formation of better ohmic contact, as shown below. Figure 4c The third structure shown.

[0097] Step 5: Based on the third structure, prepare P-type amorphous silicon or P-type microcrystalline silicon 6 on the P-type intrinsic silicon layer 3 (i(p) layer) side by PECVD or HoFCVD equipment; then make TCO layer 7 on both sides, and then form electrode 8 by screen printing to obtain Figure 4d The final cell is shown.

[0098] According to tests, the crystallization rate of the N-type oxygen-doped microcrystalline silicon layer 5 in the above embodiment 3 is 60%, no dust is generated during the process, and no parasitic absorption phenomenon occurs in the N-layer on the light-facing side of the cell.

[0099] Thus, it can be seen from the above Examples 1-3 that the present invention uses HoFCVD equipment to prepare oxygen-doped microcrystalline thin films, and can produce oxygen-doped microcrystalline silicon thin films with a crystallization rate exceeding 50% at a low pressure of 0.5-2.5 Pa, with process gas consumption only a few tenths of the process gas consumption in PECVD. The present invention can form an oxygen-doped microcrystalline thin film on the light-facing surface (e.g., the N layer) of a heterojunction cell (HJT) using the HoFCVD equipment, thereby solving the problem of parasitic absorption on the light-facing surface of the HJT.

[0100] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device that includes a series of elements includes not only those elements, but also other elements not explicitly listed, or elements inherent to the process, method, article or device. In the absence of further limitations, an element defined by the sentence "including a..." does not exclude the presence of additional identical elements in the process, method, article or device that includes the element.

[0101] The foregoing description is intended to be merely an embodiment of the present invention, which is intended to enable those skilled in the art to understand and implement the present invention. Various modifications to the described embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not intended to be limited to the embodiments described herein, but is to be accorded the widest scope consistent with the principles and features disclosed herein.

Claims

1. A method for preparing an oxygen-doped microcrystalline silicon thin film, characterized in that: include: Texturing the silicon wafer substrate to obtain a double-sided texturing silicon wafer; Depositing intrinsic silicon layers on both sides of the textured silicon wafer to obtain a first structure; The first structure is placed in a hot-wire chemical vapor deposition apparatus and H2 is introduced to hydrogen etch the surface of the silicon wafer at a flow rate of 200-1000 sccm. Then, the pressure in the reaction chamber of the hot-wire chemical vapor deposition apparatus is controlled while SiH4 and H2 are introduced simultaneously to deposit a seeding layer on the intrinsic silicon layer on the light-facing side of the textured silicon wafer to obtain the second structure. SiH4, H2, N2O, and PH3 are simultaneously introduced into the reaction chamber to deposit an oxygen-doped microcrystalline silicon layer on the seeding layer of the second structure, wherein the gas flow rate of the SiH4 is 150-300 sccm, the gas flow rate of the H2 is 1100-5000 sccm, and the gas flow rate of the N2O is 45-100 sccm; the usage ratio of the SiH4 and N2O is 0 < ≤ 1:10, and the usage of N2O gradually decreases with process time; and the usage ratio of the SiH4 and PH3 decreases from 50:1 to 13:1 with process time; When depositing the seeding layer and the oxygen-doped microcrystalline silicon layer, the ratio of SiH4 to H2 introduced is in the range of 1:10-1:

20.

2. The method for preparing an oxygen-doped microcrystalline silicon thin film according to claim 1, wherein: Intrinsic silicon layers are deposited on both sides of the textured silicon wafer using plasma enhanced chemical vapor deposition equipment or hot wire chemical vapor deposition equipment.

3. The method for preparing an oxygen-doped microcrystalline silicon thin film according to claim 1, wherein: The pressure in the reaction chamber of the hot wire chemical vapor deposition equipment is controlled at 0.5-2.5 Pa.

4. A device for preparing an oxygen-doped microcrystalline silicon thin film using the method for preparing an oxygen-doped microcrystalline silicon thin film according to any one of claims 1 to 3, characterized in that: The device is a hot wire chemical vapor deposition device, comprising: a carrier transport system configured to transport a carrier carrying a silicon wafer substrate into the reaction chamber; a carrier temperature control system connected to the carrier and configured to control the temperature of the carrier; a heating system disposed in the reaction chamber and configured to heat the reaction chamber; a vacuum system configured to evacuate the reaction chamber; A gas homogenizing system is provided in the reaction chamber and is configured to introduce required process gas into the reaction chamber.

5. The device according to claim 4, characterized in that The vacuum system includes one or more pump groups consisting of a dry pump and a molecular pump. The molecular pump is non-centrally distributed and a butterfly valve for controlling the opening and closing angle is provided at the front end of the molecular pump. A vacuum gauge for detecting different vacuum degrees is provided on the cavity of the reaction chamber. The butterfly valve controls the opening and closing angle in response to real-time feedback from the vacuum gauge to adjust the pumping speed of the molecular pump to achieve pressure regulation in the reaction chamber.

6. The device according to claim 4, characterized in that The heating system includes auxiliary heating elements and hot wires for high-temperature heating. The auxiliary heating elements are distributed around the inner wall of the reaction chamber. The auxiliary heating elements include armored heating wires or infrared lamps. The hot wires for high-temperature heating are arranged vertically and arranged in series, parallel, or a combination of series and parallel in the reaction chamber, and the hot wires for high-temperature heating are connected to an external power supply.

7. The device according to claim 6, characterized in that The gas uniformity system achieves a uniform gas field of the process gas in the reaction chamber by arranging holes of different pore sizes or holes of the same pore size but unequal spacing on the PE tube. The PE tubes in the reaction chamber are distributed on the outer circle of the high-temperature heating wire and the area enclosed by the PE tubes is larger than the arrangement area of ​​the high-temperature heating wire.

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