Method and equipment for preparing oxygen-doped microcrystalline silicon film

Abstract

The invention relates to a method for preparing an oxygen-doped microcrystalline silicon film, and the method comprises the steps: carrying out the texturing of a silicon wafer substrate, and obtaining a textured silicon wafer with two textured surfaces; respectively depositing intrinsic silicon layers on the two surfaces of the textured silicon wafer to obtain a first structure; placing the first structure in hot filament chemical vapor deposition equipment, introducing H2 to perform hydrogen etching on the surface of the silicon wafer, then controlling the pressure in a reaction chamber in the hot filament chemical vapor deposition equipment, introducing SiH4 and H2 at the same time, and depositing a seeding layer on the intrinsic silicon layer of the light facing surface of the textured silicon wafer to obtain a second structure; and simultaneously introducing SiH4, H2, N2O and PH3 into the reaction chamber, and depositing on the seeding layer of the second structure to obtain an oxygen-doped microcrystalline silicon layer. In addition, the invention also relates to equipment for preparing the oxygen-doped microcrystalline silicon film by adopting the method. According to the invention, the oxygen-doped microcrystalline film can be formed on the light-facing surface of a heterojunction cell through HoFCVD equipment, so that the problem of parasitic absorption of the light-facing surface is solved.

Description

Technical Field

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

[0002] The structure of heterojunction cells is simple, with only four processes: texturing, CVD (Chemical Vapor Deposition), PVD (Physical Vapor Deposition) and screen printing. It has gradually become the mainstream in the development of photovoltaic technology and is one of the solar cell routes that the photovoltaic industry has focused on in recent years. At present, the efficiency improvement of heterojunction cells is the key to increasing the subsequent market share of heterojunction cells, but amorphous silicon will have relatively serious parasitic absorption on the light-facing side. Most of these absorbed photons will not become effective photogenerated carriers and will be separated by the built-in electric field, thus not contributing to the improvement of the short-circuit current of the battery. There are usually two ways to reduce the parasitic absorption of the light-facing side. One of the methods is to reduce the thin layer of the light-facing side. For example, when the N layer is used as the light-facing side, the thickness of the N layer (doped amorphous silicon layer or microcrystalline silicon layer) and the I layer (intrinsic passivation layer) is reduced, thereby reducing the absorption of light by the light-facing side to reduce parasitic absorption. 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, combined with the silicon oxide channel formed in the microcrystals, so as to achieve the effect of silicon oxide transmittance (reducing parasitic absorption and increasing short-circuit current density) and good conductivity of microcrystalline silicon (reducing series resistance), thereby effectively increasing the short-circuit current and improving the conversion efficiency of the battery.

[0003] However, the current method for preparing oxygen-doped microcrystals in the industry uses PECVD (Plasma Enhanced Chemical Vapor Deposition) equipment, which introduces a certain proportion of CO 2 、SiH 4 , H 2 , PH 3 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 - SiH 4 The gas flow rate is usually 1000-4000sccm, H 2The gas flow rate is 10000-40000sccm, CO 2 The gas flow rate is 1000-3000sccm; and when PECVD is used to prepare microcrystals, H 2 The dosage is SiH 4 The dosage is 20-100 times that of the raw material, and the chamber pressure is in the range of 40-150Pa during the process. This can easily generate dust, causing contamination of the chamber and silicon wafer, and 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] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a method and equipment for preparing oxygen-doped microcrystalline silicon thin films. The present invention uses HoFCVD (Hot Filament Chemical Vapor Deposition, also known as hot filament CVD) equipment to replace PECVD 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% under a low gas pressure of 0.5-2.5 Pa, with a process gas consumption of only a few tens of the process gas consumption 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 was placed in a hot wire chemical vapor deposition apparatus and H 2 The surface of the silicon wafer is etched with hydrogen, and then the pressure in the reaction chamber of the hot wire chemical vapor deposition equipment is controlled, and SiH 4 and H 2 , depositing a seeding layer on the intrinsic silicon layer on the light-facing side of the textured silicon wafer to obtain a second structure;

[0011] SiH 4 , H 2 、N 2 O and pH 3 , an oxygen-doped microcrystalline silicon layer is deposited 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 plasma enhanced chemical vapor deposition equipment or hot wire chemical vapor deposition equipment.

[0013] In one embodiment of the present invention, H is introduced during hydrogen etching of the silicon wafer surface. 2 The gas flow rate is 200-1000sccm; when depositing the oxygen-doped microcrystalline silicon layer, SiH 4 The gas flow rate is 150-300sccm, H 2 The gas flow rate is 1100-5000sccm, N 2 The gas flow rate of O is 45-100 sccm, and when depositing the seed layer and oxygen-doped microcrystalline silicon layer, SiH 4 and H 2 The dosage ratio range is 1:7-1:20.

[0014] In one embodiment of the present invention, the SiH 4 and H 2 The dosage ratio is at least 1:10.

[0015] In one embodiment of the present invention, when the oxygen-doped microcrystalline silicon layer is deposited, 0 < SiH 4 and N 2 O usage ratio ≤1:10 and N 2 The amount of O decreases gradually with the process time; the amount of SiH 4 and PH 3 The usage ratio decreases from 50:1 to 13:1 as the process time increases.

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

[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 a device for preparing an oxygen-doped microcrystalline silicon thin film using the method for preparing an oxygen-doped microcrystalline silicon thin film as described above, the device being a hot wire chemical vapor deposition device, comprising:

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

[0021] A carrier temperature control system, the carrier temperature control system is connected to the carrier and is 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 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.

[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 was placed in a hot wire chemical vapor deposition apparatus and H 2 The surface of the silicon wafer is etched with hydrogen, and then the pressure in the reaction chamber of the hot wire chemical vapor deposition equipment is controlled, and SiH 4 and H 2 , depositing a seeding layer on the intrinsic silicon layer on the light-facing side of the textured silicon wafer to obtain a second structure;

[0032] SiH 4 , H 2 、N 2O and pH 3 , 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, and electrodes are formed by screen printing to obtain the final battery cell.

[0034] In one embodiment of the present invention, 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.

[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 equipment 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 that of the process gas consumption used in PECVD, which can greatly save costs; the HoFCVD equipment can also be used by using N 2 The preparation of oxygen-doped microcrystalline thin films can be achieved without the need for very high frequency power supply; and the crystallization rate of oxygen-doped microcrystalline thin films prepared by HoFCVD equipment 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 drawings required for use in the description of the embodiments or the prior art are briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

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

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

[0042] Figure 3A 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 in the embodiments 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 different from 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 device and introducing H 2 The surface of the silicon wafer is etched with hydrogen, and then the pressure in the reaction chamber of the hot wire chemical vapor deposition equipment is controlled, and SiH 4 and H 2 , depositing a seeding layer on the intrinsic silicon layer on the light-facing side of the textured silicon wafer to obtain a second structure;

[0051] S13: SiH is introduced into the reaction chamber simultaneously 4 , H 2 、N 2 O and pH 3 , an oxygen-doped microcrystalline silicon layer is deposited on the seeding layer of the second structure.

[0052] The present invention replaces the PECVD equipment with the HoFCVD (also known as hot wire CVD) equipment. The working principle of the HoFCVD equipment is that the introduced process gas decomposes on the surface of the hot wire at a temperature of about 1800-2000°C, and the generated active groups move to the surface of the silicon wafer substrate (textured silicon wafer) to react and deposit into a film. The energy of the generated active groups is lower than the plasma energy generated by PECVD. The bombardment of the film layer by the plasma of PECVD will damage the film layer and introduce defects, while the active groups generated by the HoFCVD equipment have lower energy, and there is no problem of plasma bombardment on the surface of the silicon wafer substrate causing damage.

[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 (e.g., N-type and P-type intrinsic silicon layers) can be deposited on both sides (e.g., the front side or light-facing side and the back side or 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, H is introduced during hydrogen etching of the silicon wafer surface. 2 The gas flow rate is 200-1000sccm; when depositing the oxygen-doped microcrystalline silicon layer, SiH 4 The gas flow rate is 150-300sccm, H 2 The gas flow rate is 1100-5000sccm, N 2 The gas flow rate of O is 45-100 sccm, and when depositing the seed layer and oxygen-doped microcrystalline silicon layer, SiH 4 and H 2 The dosage ratio range is 1:7-1:20. Preferably, the SiH 4 and H 2 The ratio of N to N 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 forming quality of the HoFCVD device is better than that of the PECVD device. 2 O gas replaces CO 2 Gas as oxygen source, SiH 4The gas flow rate is usually 150-300sccm, H 2 The gas flow rate is 1100-5000sccm, N 2 When the HoFCVD process is used to prepare microcrystals, the gas flow rate of H 2 The dosage is SiH 4 The dosage is 7-20 times, and when the SiH of the HoFCVD device 4 :H 2 When the usage ratio 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 the oxygen-doped microcrystalline silicon layer is deposited, 0 < SiH 4 and N 2 O usage ratio ≤1:10 and N 2 The amount of O decreases gradually with the process time; the amount of SiH 4 and PH 3 The usage ratio decreases from 50:1 to 13:1 as the process time increases.

[0058] In the method shown in the above embodiment, in S12 and S13, the pressure in the reaction chamber of the hot wire chemical vapor deposition equipment is controlled to be 0.5-2.5 Pa. The process gas pressure of the HoFCVD equipment is controlled in the range of 0.5-2.5 Pa, which is a few tenths or even a hundredth of the process gas pressure of the PECVD equipment, and no dust is generated during the process.

[0059] In the method shown in the above embodiment, the thickness of the seeding 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 that of the process gas consumption used in PECVD, which can greatly save costs; the HoFCVD equipment can be used by using N 2 O and the preparation of oxygen-doped microcrystals can be achieved without the need for a very high frequency power supply; the crystallization rate of oxygen-doped microcrystals prepared by 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. That is to say, the present invention uses 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% under a low gas 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 Figure 2 shown.

[0061] In addition, an embodiment of the present invention also provides a device for preparing an oxygen-doped microcrystalline silicon thin film using the method for preparing an oxygen-doped microcrystalline silicon thin film as described above, and the device is a hot wire chemical vapor deposition device, including a carrier transmission system, a carrier temperature control system, a heating system, a vacuum system and a uniform gas system. Among them: the carrier transmission system is configured to transfer a carrier carrying a silicon wafer substrate into a reaction chamber; the carrier temperature control system is connected to the carrier and is configured to control the carrier temperature; the heating system is arranged in the reaction chamber and is configured to heat the reaction chamber; the vacuum system is configured to evacuate the reaction chamber; the uniform gas system is arranged in the reaction chamber and is configured to pass the required 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 molecular pumps are distributed in a non-centralized manner 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 impurity gas in the reaction chamber needs to be evacuated before the process. When the cavity of the reaction chamber is in the 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 pumping speed of the molecular pump 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 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. The hot wire for high-temperature heating is connected to an external power supply.

[0065] The reaction chamber is equipped with auxiliary heating elements, which are mainly distributed around the inner wall of the chamber, mainly for the uniformity of the temperature field in the chamber and the desorption of impurity gases. The auxiliary heating element can be an armored heating wire or an infrared lamp. When the equipment is opened for maintenance, the auxiliary heating element can be turned on to remove water vapor in the reaction chamber and accelerate the desorption of impurity gases on the chamber wall in the reaction chamber.

[0066] The hot wire of the HoFCVD device is arranged vertically, and the arrangement of the hot wire in the cavity is achieved by series connection, parallel connection or a combination of series and parallel connection. The electrode of the hot wire is connected to an external power supply through the flange hole on the cavity of the reaction chamber, thereby realizing the energy supply of the hot wire.

[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, when mixing process gases, different types of gases are usually mixed in a gas mixing cabinet, and then the mixed gas is transported to the reaction chamber through a gas pipeline (PE pipe). In HoFCVD equipment, the gas uniformity system in the reaction chamber is to arrange holes of different apertures or holes of the same aperture but unequal spacing on the PE pipe to achieve uniform gas field in the reaction chamber, thereby achieving uniform film thickness for large-area coating. The PE pipes in the reaction chamber are distributed on the outer circle of the hot wire, and the area surrounded by the PE pipe is larger than the arrangement area of ​​the hot wire.

[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, and the H 2 Sufficient energy is obtained on the high-temperature hot wire to generate H* active groups. The gas pressure in the reaction chamber is controlled to be low at 0.5-2.5Pa during the process, so that 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 Si-H weak bonds formed on the silicon substrate. Since the bond energy of the Si-Si bond is greater than that of the Si-H bond, it will be left behind to continue nucleation and growth. 2 It is partially decomposed at 1750°C and oxygen atoms are decomposed at 2600°C. The energy required is too high. 2 O can be significantly decomposed at 500°C, and completely decomposed into nitrogen and oxygen atoms at 900°C, so N 2 O can obtain enough energy on the hot wire surface to decompose. The oxygen atoms produced by the decomposition diffuse to the silicon wafer surface and combine with the hanging bonds of Si to produce Si-O bonds. Most of the oxygen forms SiO 2 , a small amount of oxygen exists in the microcrystalline silicon in the interstitial state. 2 O is introduced into the reaction chamber in time periods, thereby achieving SiO 2 and microcrystalline silicon, SiO 2The refractive index is about 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 have good conductivity, thereby reducing parasitic absorption and improving the conversion efficiency of photovoltaic cells.

[0070] In addition, if Figure 3 As shown, in one embodiment of the present invention, a method for preparing a battery cell is also provided. 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 device and introducing H 2 The surface of the silicon wafer is etched with hydrogen, and then the pressure in the reaction chamber of the hot wire chemical vapor deposition equipment is controlled, and SiH 4 and H 2 , depositing a seeding layer on the intrinsic silicon layer on the light-facing side of the textured silicon wafer to obtain a second structure;

[0074] S33: SiH is introduced into the reaction chamber simultaneously 4 , H 2 、N 2 O and pH 3 , depositing 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 a 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 is shown.

[0081] Step 3: Place the first structure in the HoFCVD device, keep the hot wire current at 30A, and then pass 200sccm of H 2 The surface of the silicon wafer was etched with hydrogen, and the pressure in the reaction chamber of the HoFCVD equipment was controlled at 0.5 Pa. At the same time, 150 sccm of SiH 4 and 1100 sccm of H 2 The usage ratio of the two is SiH 4 :H 2 =1:10, a 2nm seeding layer 4 is grown on the N-type intrinsic silicon layer 2, and the following is obtained: Figure 4b The second structure shown.

[0082] Step 4: Based on the second structure, the pressure in the reaction chamber of the HoFCVD equipment is controlled at 0.5 Pa, and 150 sccm of SiH 4 , 1100 sccm H 2 , 45 sccm N 2 O and PH 3 , dosage ratio SiH 4 :H 2 =1:10, dosage ratio SiH 4 :N 2 O starts at 1:10 and N 2 The amount of O decreases gradually with the process time, and the amount is higher than that of SiH 4 :PH 3 The ratio of 2:1 gradually changes from 50:1 to 13:1, and an N-type oxygen-doped microcrystalline silicon layer 5 is formed on the seeding layer 4, which includes lightly doped oxygen-doped microcrystalline silicon near the intrinsic silicon layer and highly doped oxygen-doped microcrystalline silicon near 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 side of the P-type intrinsic silicon layer 3 (i(p) layer) 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 the test, the crystallization rate of the N-type oxygen-doped microcrystalline silicon layer 5 in the above-mentioned 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 a texturing process, an N-type silicon wafer substrate 1 with a thickness of 100 μm is subjected to texturing, a double-sided texturing silicon wafer is obtained.

[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 is shown.

[0088] Step 3: Place the first structure in the HoFCVD device, keep the hot wire current at 40A, and then pass 600sccm of H 2 The surface of the silicon wafer was etched with hydrogen, and the pressure in the reaction chamber of the HoFCVD equipment was controlled at 1.5 Pa. At the same time, 200 sccm of SiH 4 and 2000sccm of H 2 The usage ratio of the two is SiH 4 :H 2 =1:15, a 2.5 nm seeding layer 4 is grown on the N-type intrinsic silicon layer 2, and the following is obtained: Figure 4b The second structure shown.

[0089] Step 4: Based on the second structure, the pressure in the reaction chamber of the HoFCVD equipment is controlled at 1.5 Pa, and 200 sccm of SiH 4 , 2000sccm H 2 , 80 sccm of N 2 O and PH 3 , dosage ratio SiH 4 :H 2 =1:15, dosage ratio SiH 4 :N 2 O starts with 1:9 and N 2 The amount of O decreases gradually with the process time, and the amount is higher than that of SiH 4 :PH 3 The ratio of 2:1 gradually changes from 50:1 to 13:1, and an N-type oxygen-doped microcrystalline silicon layer 5 is formed on the seeding layer 4, which includes lightly doped oxygen-doped microcrystalline silicon near the intrinsic silicon layer and highly doped oxygen-doped microcrystalline silicon near the electrode side, so as to facilitate the subsequent formation of better ohmic contact, and obtain the following 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 side of the P-type intrinsic silicon layer 3 (i(p) layer) 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 the test, the crystallization rate of the N-type oxygen-doped microcrystalline silicon layer 5 in the above-mentioned 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 a texturing process, an N-type silicon wafer substrate 1 with a thickness of 120 μm is subjected to texturing to become 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 is shown.

[0095] Step 3: Place the first structure in the HoFCVD device, keep the hot wire current at 35A, and then pass 1000sccm of H 2 The surface of the silicon wafer was etched with hydrogen, and the pressure in the reaction chamber of the HoFCVD equipment was controlled at 2.5 Pa. At the same time, 300 sccm of SiH 4 and 5000sccm of H 2 The usage ratio of the two is SiH 4 :H 2 =1:20, a 3nm seeding layer 4 is grown on the N-type intrinsic silicon layer 2, and the following is obtained: Figure 4b The second structure shown.

[0096] Step 4: Based on the second structure, the pressure in the reaction chamber of the HoFCVD equipment is controlled at 2.5 Pa, and 300 sccm of SiH 4 , 5000sccm H 2 , 100 sccm N 2 O and PH 3 , dosage ratio SiH 4 :H 2 =1:20, dosage ratio SiH 4 :N 2 O starts at 1:8 and N 2 The amount of O decreases gradually with the process time, and the amount is higher than that of SiH4 :PH 3 The ratio of 2:1 gradually changes from 50:1 to 13:1, and an oxygen-doped microcrystalline silicon layer 5 is formed on the seeding layer 4, which includes lightly doped oxygen-doped microcrystalline silicon near the intrinsic silicon layer and highly doped oxygen-doped microcrystalline silicon near the electrode side, so as to facilitate the subsequent formation of better ohmic contact, and obtain the following 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 side of the P-type intrinsic silicon layer 3 (i(p) layer) 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 the test, the crystallization rate of the N-type oxygen-doped microcrystalline silicon layer 5 in the above-mentioned 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] 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 prepare oxygen-doped microcrystalline silicon thin films with a crystallization rate exceeding 50% under a low pressure of 0.5-2.5 Pa, with a process gas consumption of 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., N layer) of a heterojunction cell (HJT) through a HoFCVD device, thereby solving the problem of parasitic absorption on the light-facing surface of the HJT.

[0100] It should be noted that, in this article, relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such 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 inclusions, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to the process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "including a..." do not exclude the presence of other identical elements in the process, method, article or device including the elements.

[0101] The foregoing is merely an embodiment of the present invention, which enables those skilled in the art to understand and implement the present invention. Various modifications to the described embodiments will be 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 will not be limited to the embodiments described herein, but rather to 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 device, 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 device is controlled, and SiH4 and H2 are introduced at the same time 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. SiH4, H2, N2O and PH3 are introduced into the reaction chamber at the same time to deposit an oxygen-doped microcrystalline silicon layer on the seeding layer of the second structure.

2. The method for preparing an oxygen-doped microcrystalline silicon thin film according to claim 1, characterized in that: Intrinsic silicon layers are deposited on both sides of the textured silicon wafer by 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, characterized in that: When hydrogen etching is performed on the surface of the silicon wafer, the gas flow rate of H2 is 200-1000sccm; when depositing the oxygen-doped microcrystalline silicon layer, the gas flow rate of SiH4 is 150-300sccm, the gas flow rate of H2 is 1100-5000sccm, and the gas flow rate of N2O is 45-100sccm. 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.

4. The method for preparing an oxygen-doped microcrystalline silicon thin film according to claim 3, characterized in that: The ratio of SiH4 to H2 introduced is at least 1:

10.

5. The method for preparing an oxygen-doped microcrystalline silicon thin film according to claim 1, characterized in that: When depositing the oxygen-doped microcrystalline silicon layer, the dosage ratio of SiH4 and N2O introduced is 0<≤1:10 and the dosage of N2O gradually decreases with the process time; the dosage ratio of SiH4 and PH3 introduced decreases from 50:1 to 13:1 with the process time.

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

7. A device for preparing an oxygen-doped microcrystalline silicon thin film using the method for preparing an oxygen-doped microcrystalline silicon thin film as described in any one of claims 1 to 6, characterized in that: The device is a hot wire chemical vapor deposition device, comprising: A carrier transport system, wherein the carrier transport system is configured to transport a carrier carrying a silicon wafer substrate into a reaction chamber; A carrier temperature control system, the carrier temperature control system is connected to the carrier and is configured to control the carrier temperature; a heating system, the heating system being 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 disposed in the reaction chamber and is configured to introduce required process gas into the reaction chamber.

8. The device according to claim 7, 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 arranged at the front end of the molecular pump. A vacuum gauge for detecting different vacuum degrees is arranged 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.

9. The device according to claim 7, characterized in that 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 in 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.

10. The device according to claim 9, characterized in that 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.

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