Poly-si thin film preparation method based on plane double-layer hot wire array thermal field design

Abstract

The application discloses a poly-Si thin film preparation method based on a plane double-layer hot-wire array thermal field design, adjusts the double-layer hot-wire array layer spacing and the double-layer hot-wire current to change the hot-wire surface temperature and the cracking high-temperature zone range, expands the silane cracking time and cracking space, promotes the silane secondary cracking, can effectively control the silane cracking intermediate product components and concentration distribution reaching the substrate surface, and improves the SiH / SiH2 active group ratio; under 0.5Pa-5.0Pa vacuum, the substrate temperature is 200-560 DEG C, and the deposition time is 10-60 min to deposit the poly-Si thin film; after the deposition is finished, the substrate temperature is warmed to 200-650 DEG C, vacuum annealing is carried out on the grown poly-Si thin film, and the high-crystallization-rate poly-Si thin film is obtained. The poly-Si thin film is grown by using the plane double-layer hot-wire array thermal field design, the high-temperature hot-wire silane cracking technology and the vacuum annealing technology, and the crystallization quality can be obviously improved.

Description

Technical Field

[0001] This invention relates to the field of thin film preparation technology, and in particular to a method for preparing poly-Si thin films based on a planar double-layer hot filament array thermal field design. Background Technology

[0002] With the mass production of tunnel oxide passivated contact cells (TOPCon cells and TBC cells), cell recombination loss has become a current research hotspot. To ensure the efficient and selective transport of photogenerated carriers, it is necessary to improve the passivation performance of the cell back surface and also to increase the crystallinity of the poly-Si film in order to improve the carrier concentration and mobility.

[0003] Existing TOPCon battery poly-Si films are mainly prepared using the following two methods, but both have defects: 1. Plasma-enhanced chemical vapor deposition (PECVD): Due to the presence of a large number of free radicals, cations, and anions in silane under the action of plasma, and the high working reaction pressure, groups with different charges are prone to agglomeration and dust generation.

[0004] 2. Low-pressure chemical vapor deposition (LPCVD): The thermal field distribution of LPCVD is difficult to design. The degree of pyrolysis is inconsistent in some areas, and the concentration of intermediate products fluctuates greatly, resulting in an increase in the defect concentration of poly-Si films. The distance between the pyrolysis source and the center of the quartz tube (the silicon wafer at the center) is far, and active groups are prone to agglomeration during transport. There is silicon microparticle dust in the reaction chamber, which directly affects the uniformity and stability of poly-Si films.

[0005] Although the applicant solved the problems of high crystallinity and density of intrinsic poly-Si thin films in the previous research (Chinese Patent Publication No.: CN119967943A) through the design of a vertical double-layer hot wire array thermal field, a systematic solution is still lacking. Summary of the Invention

[0006] The purpose of this invention is to provide a method for preparing poly-Si thin films based on the thermal field design of a planar double-layer hot filament array. While inheriting the advantages of vertical double-layer hot filament deposition, by adjusting the position of the double-layer hot filaments to be horizontal, a poly-Si thin film that can ensure high carrier mobility can be prepared, which will become one of the key technologies for improving the photoelectric conversion efficiency of photovoltaic devices.

[0007] To achieve the above objectives, the technical solution provided by the present invention is as follows: A method for preparing poly-Si thin films based on a planar double-layer hot filament array thermal field design includes the following steps: (1) Substrate pretreatment: Pretreatment of the single crystal silicon substrate; (2) Thin film deposition: Using a planar double-layer hot wire array thermal field design and high-temperature hot wire silane pyrolysis technology, a poly-Si thin film is deposited and grown on a single crystal silicon substrate. The planar double-layer hot wire array includes a horizontally arranged first layer of hot wire and a horizontally arranged second layer of hot wire. (3) Annealing: Vacuum annealing technology is used to anneal the grown poly-Si film.

[0008] In some embodiments, a planar double-layer staggered hot wire array is formed by a first layer of hot wire and a second layer of hot wire to achieve thermal decomposition of silane using the thermal field of the planar double-layer staggered hot wire array.

[0009] In some embodiments, each of the two hot filaments has an independent power supply. By independently controlling the hot filament current of each layer, the surface temperature of the hot filament and the range of the high-temperature zone for pyrolysis can be adjusted, thereby adjusting the proportion and concentration distribution of silane pyrolysis intermediate products and increasing the proportion of active groups in SiH / SiH2.

[0010] In some embodiments, the deposition and growth of a poly-Si thin film on a single-crystal silicon substrate using a planar double-layer hot-wire array thermal field design and high-temperature hot-wire silane decomposition technology includes: The monocrystalline silicon substrate is heated to 200-560℃, and a mixture of SiH4 and H2 gas is introduced, with the SiH4 / H2 gas flow ratio controlled at 1:3-1:9. The gate valve is adjusted to make the vacuum degree of the growth chamber 0.5Pa-5.0Pa. The hot filament power supply is turned on, and the current of the first hot filament is adjusted to make the surface temperature of the first hot filament 1600-1950℃. Then the current of the second hot filament is adjusted to make the surface temperature of the second hot filament 1650-2250℃, and the surface temperature of the second hot filament is always higher than that of the first hot filament. The silane thermal decomposition active groups are deposited on the surface of the monocrystalline silicon substrate. A poly-Si film with a thickness of 20-100nm is grown at a monocrystalline silicon substrate temperature of 200-560℃ and a deposition time of 10-60min.

[0011] In some embodiments, the annealing of the grown poly-Si film using vacuum annealing technology includes: Stop the flow of SiH4 and H2 gases, turn off the hot filament power supply, raise the temperature of the single crystal silicon substrate on which the poly-Si thin film has been formed to 200-650℃, and perform vacuum annealing on the grown poly-Si thin film for 10-60 minutes.

[0012] In some embodiments, the pretreatment of the single-crystal silicon substrate includes: After cleaning and drying, the single-crystal silicon substrate was placed on the sample holder of the hot-wire chemical vapor deposition growth chamber. The vacuum dry pump and molecular pump were then turned on sequentially to achieve a vacuum level of 1.0 × 10⁻⁶ in the growth chamber. -3Below Pa, heat the monocrystalline silicon substrate to 150°C and degas the monocrystalline silicon substrate for half an hour.

[0013] In some embodiments, by controlling the flow rate and ratio of SiH4 and H2, adjusting the vacuum pressure in the growth chamber, and by adjusting the temperature and spacing of the first and second hot filaments, the cleavage time and cleavage space of silane are controlled, thereby achieving control over the composition and concentration of active groups on the substrate. The film is deposited under a reasonable temperature regime, and the deposited film is then vacuum annealed, thereby improving the crystallinity of the poly-Si film.

[0014] Compared with the prior art, the beneficial effects of the present invention are: The poly-Si thin film preparation method based on the planar double-layer hot filament array thermal field design provided in this application uses a planar double-layer staggered hot filament array to thermally decompose silane to prepare a high crystallinity poly-Si thin film. After multiple decompositions of silane, the proportion and energy of active group components on the substrate surface are well controlled. Combined with vacuum annealing of the grown film, the crystallinity of the poly-Si thin film is significantly improved, which has good application prospects for the development of photovoltaic cells and optoelectronic devices. Attached Figure Description

[0015] The accompanying drawings, which are provided to further illustrate the invention and constitute a part of this invention, are illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention.

[0016] Figure 1 This is a schematic diagram of the planar double-layer distributed hot filament array layout of the growth chamber and the silane thermal decomposition in this invention.

[0017] Figure 2 A schematic diagram of the first layer of hot wire is shown.

[0018] Figure 3 A schematic diagram of the second layer of hot wire is shown.

[0019] Figure 4 A three-dimensional schematic diagram of the first distribution (head-to-head parallel alignment) of the first and second heating wires is shown.

[0020] Figure 5 A top view shows a first distribution (head-to-head parallel alignment) of the first and second layers of heating wires.

[0021] Figure 6 A three-dimensional schematic diagram of a second distribution (head-to-foot parallel alignment) of the first and second heating wires is shown.

[0022] Figure 7A top view shows a second distribution (head-to-toe parallel alignment) of the first and second heating filaments.

[0023] Figure 8 A three-dimensional schematic diagram of a third distribution (double-layer staggered array) of the first and second layer of heating wires is shown.

[0024] Figure 9 A top view shows a third distribution (double-layer staggered array) of the first and second heat filaments. Detailed Implementation

[0025] This section will describe in detail specific embodiments of the present invention. Preferred embodiments of the present invention are shown in the accompanying drawings. The purpose of the drawings is to supplement the textual description with graphics, so that people can intuitively and vividly understand each technical feature and overall technical solution of the present invention, but they should not be construed as limiting the scope of protection of the present invention.

[0026] Please see Figures 1 to 9 As shown, this application provides a method for preparing poly-Si thin films based on a planar double-layer hot filament array thermal field design, including the following steps: (1) Substrate pretreatment: Pretreatment of single-crystal silicon substrate.

[0027] For example, the pretreatment includes: placing the cleaned and dried single-crystal silicon substrate onto the sample holder in the hot-wire chemical vapor deposition growth chamber, and sequentially turning on the vacuum dry pump and molecular pump to achieve a vacuum level of 1.0 × 10⁻⁶ in the growth chamber. -3 Below Pa, heat the monocrystalline silicon substrate to 150°C and degas the monocrystalline silicon substrate for half an hour.

[0028] (2) Thin film deposition: Poly-Si thin films are deposited and grown on a single-crystal silicon substrate using a planar double-layer hot wire array thermal field design and high-temperature hot wire silane pyrolysis technology.

[0029] As an example, a planar double-layer hot wire array is composed of a first layer of hot wire and a second layer of hot wire, and there are three specific distribution methods.

[0030] For example, such as Figure 4 and Figure 5 This illustrates a first distribution (head-to-head parallel alignment) of the first and second heating filament layers, forming a first planar double-layer heating filament array. Figure 4 The top-down view shows the first layer of heating wires.

[0031] For example, such as Figure 6 and Figure 7This illustrates a second configuration (head-to-foot parallel alignment) of the first and second heating filament layers, forming a second planar double-layer heating filament array. Figure 6 The top-down view shows the first layer of heating wires.

[0032] For example, such as Figure 8 and Figure 9 This illustrates a third distribution of the first and second heating filaments (a double-layer staggered array), where the first and second heating filaments form a planar double-layer staggered heating filament array (the third type of planar double-layer heating filament array). Among these, Figure 8 The top-down view shows the first layer of heating wires.

[0033] It should be understood that the above three types of hot filament arrays have the following advantages compared with the existing hot filament chemical vapor deposition (CVD) with only a single-layer filament array: 1. The temperature uniformity of the double-layer hot filaments mapped onto the substrate surface is improved; 2. The probability of silane colliding with the hot filament is increased, and the silane decomposition efficiency is improved; 3. Adjusting the spacing of the hot filament array can adjust the range of the high-temperature zone, reduce the polymerization of active groups after decomposition, and also increase the energy of active groups reaching the substrate surface; 4. Adjusting the hot filament surface temperature (hot filament current) controls the composition of active groups after silane decomposition.

[0034] In some embodiments, each of the two hot filaments has an independent power supply. By independently controlling the hot filament current of each layer, the surface temperature of the hot filament and the range of the high-temperature zone for pyrolysis can be adjusted, thereby adjusting the proportion and concentration distribution of silane pyrolysis intermediate products and increasing the proportion of active groups in SiH / SiH2.

[0035] Preferably, the following is adopted: Figure 8 and Figure 9 The planar double-layer staggered hot filament array shown is used to achieve thermal decomposition of silane using the thermal field of the planar double-layer staggered hot filament array.

[0036] Specifically, step (2) includes: The monocrystalline silicon substrate is heated to 200-560℃, and a mixture of SiH4 and H2 gas is introduced, with the SiH4 / H2 gas flow ratio controlled at 1:3-1:9. The gate valve is adjusted to make the vacuum degree of the growth chamber 0.5Pa-5.0Pa. The hot filament power supply is turned on, and the current of the first hot filament is adjusted to make the surface temperature of the first hot filament 1600-1950℃. Then the current of the second hot filament is adjusted to make the surface temperature of the second hot filament 1650-2250℃, and the surface temperature of the second hot filament is always higher than that of the first hot filament. The silane thermal decomposition active groups are deposited on the surface of the monocrystalline silicon substrate. A poly-Si film with a thickness of 20-100nm is grown at a monocrystalline silicon substrate temperature of 200-560℃ and a deposition time of 10-60min.

[0037] Therefore, by controlling the current of the first and second hot filaments, the surface temperature of the first hot filament is set to 1600-1950℃, and the surface temperature of the second hot filament is set to 1650-2250℃. After silane enters the reaction chamber, it begins to decompose upon encountering the high-temperature hot filaments. By adjusting the current of the first and second hot filaments, as well as the spacing between them, the proportion and concentration distribution of silane decomposition intermediates (such as SiH3, SiH2, and SiH radicals) reaching the substrate surface can be effectively controlled. At a substrate temperature of 200-560℃ and a deposition time of 10-60 min, a poly-Si film with a thickness of 20-100 nm can be obtained. This method uses a planar double-layer staggered hot filament array to improve silane decomposition efficiency, controls the proportion and concentration of active groups reaching the substrate surface, and prepares a poly-Si film with a thickness of 20-100 nm under a reasonable temperature regime. Vacuum annealing further improves the film's crystallinity.

[0038] As an example, in this step, by controlling the flow rate and ratio of SiH4 and H2, the vacuum pressure of the growth chamber is adjusted, and by adjusting the temperature and spacing of the first and second hot filaments, the cleavage time and cleavage space of silane are controlled, thereby achieving control over the composition and concentration of active groups on the substrate. The film is deposited under a reasonable temperature regime, and the deposited film is then vacuum annealed, thereby improving the crystallinity of the poly-Si film.

[0039] (3) Annealing: The grown poly-Si film is annealed using vacuum annealing technology. Specifically, step (3) includes: Stop the flow of SiH4 and H2 gases, turn off the hot filament power supply, raise the temperature of the single crystal silicon substrate on which the poly-Si thin film has been formed to 200-650℃, and perform vacuum annealing on the grown poly-Si thin film for 10-60 minutes.

[0040] In summary, the embodiments of this application employ a planar double-layer hot filament array thermal field design, high-temperature hot filament silane pyrolysis technology, and vacuum annealing technology to prepare high-crystallinity poly-Si thin films, which have promising application prospects for the development of photovoltaic cells and optoelectronic devices. Specifically, by adjusting the interlayer spacing of the double-layer hot filament array and the double-layer hot filament current, the surface temperature of the hot filament and the range of the high-temperature pyrolysis zone are changed, expanding the silane pyrolysis time and pyrolysis space, promoting secondary silane pyrolysis, and effectively controlling the composition and concentration distribution of silane pyrolysis intermediates (such as SiH3, SiH2, SiH, and other free radicals) reaching the substrate surface, thereby increasing the SiH / SiH2 active group ratio. Poly-Si thin films are deposited at a substrate temperature of 200-560℃ and a deposition time of 10-60 min. After deposition, the substrate temperature is raised to 200-650℃, and the grown poly-Si thin film is vacuum annealed for 10-60 min to obtain a high-crystallinity poly-Si thin film.

[0041] Without causing conflict, those skilled in the art can freely combine and use the above-mentioned additional technical features.

[0042] The above description is only a preferred embodiment of the present invention. Any technical solution that achieves the purpose of the present invention by essentially the same means is within the protection scope of the present invention.

Claims

1. A method for preparing poly-Si thin films based on planar double-layer hot filament array thermal field design, characterized in that, Includes the following steps: (1) Substrate pretreatment: Pretreatment of the single crystal silicon substrate; (2) Thin film deposition: Using a planar double-layer hot wire array thermal field design and high-temperature hot wire silane pyrolysis technology, a poly-Si thin film is deposited and grown on a single crystal silicon substrate. The planar double-layer hot wire array includes a horizontally arranged first layer of hot wire and a horizontally arranged second layer of hot wire. (3) Annealing: Vacuum annealing technology is used to anneal the grown poly-Si film.

2. The method for preparing poly-Si thin films based on planar double-layer hot filament array thermal field design according to claim 1, characterized in that, A planar double-layer staggered hot wire array is formed by the first and second hot wire layers to achieve thermal decomposition of silane using the thermal field of the planar double-layer staggered hot wire array.

3. The method for preparing poly-Si thin films based on planar double-layer hot filament array thermal field design according to claim 2, characterized in that, Each of the two hot filaments has an independent power supply. By independently controlling the current of each hot filament, the surface temperature of the hot filament and the range of the high-temperature zone for pyrolysis can be adjusted, thereby regulating the proportion and concentration distribution of silane pyrolysis intermediate products and increasing the proportion of active groups in SiH / SiH2.

4. The method for preparing poly-Si thin films based on planar double-layer hot filament array thermal field design according to claim 1, characterized in that, The method of depositing and growing poly-Si thin films on single-crystal silicon substrates using a planar double-layer hot-wire array thermal field design and high-temperature hot-wire silane decomposition technology includes: The monocrystalline silicon substrate is heated to 200-560℃, and a mixture of SiH4 and H2 gas is introduced, with the SiH4 / H2 gas flow ratio controlled at 1:3-1:

9. The gate valve is adjusted to make the vacuum degree of the growth chamber 0.5Pa-5.0Pa. The hot filament power supply is turned on, and the current of the first hot filament is adjusted to make the surface temperature of the first hot filament 1600-1950℃. Then the current of the second hot filament is adjusted to make the surface temperature of the second hot filament 1650-2250℃, and the surface temperature of the second hot filament is always higher than that of the first hot filament. The silane thermal decomposition active groups are deposited on the surface of the monocrystalline silicon substrate. A poly-Si film with a thickness of 20-100nm is grown at a monocrystalline silicon substrate temperature of 200-560℃ and a deposition time of 10-60min.

5. The method for preparing poly-Si thin films based on planar double-layer hot filament array thermal field design according to claim 4, characterized in that, The process of annealing the grown poly-Si film using vacuum annealing technology includes: Stop the flow of SiH4 and H2 gases, turn off the hot filament power supply, raise the temperature of the single crystal silicon substrate on which the poly-Si thin film has been formed to 200-650℃, and perform vacuum annealing on the grown poly-Si thin film for 10-60 minutes.

6. The method for preparing poly-Si thin films based on planar double-layer hot filament array thermal field design according to claim 5, characterized in that, The pretreatment of the single-crystal silicon substrate includes: After cleaning and drying, the single-crystal silicon substrate was placed on the sample holder of the hot-wire chemical vapor deposition growth chamber. The vacuum dry pump and molecular pump were then turned on sequentially to achieve a vacuum level of 1.0 × 10⁻⁶ in the growth chamber. -3 Below Pa, heat the monocrystalline silicon substrate to 150°C and degas the monocrystalline silicon substrate for half an hour.

7. The method for preparing poly-Si thin films based on planar double-layer hot filament array thermal field design according to claim 4, characterized in that, By controlling the flow rate and ratio of SiH4 and H2, adjusting the vacuum pressure in the growth chamber, and by adjusting the temperature and spacing of the first and second hot filaments, the silane decomposition time and space are controlled, thereby achieving control over the composition and concentration of active groups on the substrate. Thin films are deposited under a reasonable temperature regime, and the deposited films are then vacuum annealed, thereby improving the crystallinity of the poly-Si thin film.

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