A method for improving the uniformity of atomic layer deposition of aluminum oxide films for back contact cells

Abstract

This invention belongs to the field of solar cells, specifically relating to a method for improving the uniformity of alumina thin film deposition in the atomic layer of back-contact solar cells. The method involves double-sided alkaline polishing of silicon wafers using a cleaning machine to create a mirror-like structure. Then, using automated equipment, the double-sided polished silicon wafers are fed into the ALD (Alternating Layer Deposition) system cavity via alternating insertion of trimethylaluminum and water vapor, depositing a thin alumina film on both the front and back sides of the silicon wafer. This invention requires no equipment modification; by adjusting the process and increasing the gap between the upper and lower aluminum boats, it improves the uniformity of alumina thickness, enhances cell passivation stability, reduces the defect rate, thereby increasing cell efficiency and reducing the risk of UV degradation.

Description

Technical Field

[0001] This invention belongs to the field of solar cells, and specifically relates to a method for improving the uniformity of aluminum oxide thin film deposition in the atomic layer of a back contact cell. Background Technology

[0002] With the rapid development of crystalline silicon photovoltaic solar cells, the requirements for surface passivation of crystalline silicon cells are becoming increasingly stringent. Alumina thin films, due to their high fixed negative charge density and low interface defect density, can effectively passivate silicon wafer surfaces and reduce surface recombination rates. Alumina thin films possess both chemical and field passivation effects. On p-type silicon surfaces, the negative charge of alumina attracts holes to form an accumulation layer, repelling electrons and reducing electron-hole recombination at the surface. On n-type silicon surfaces, although the field-effect passivation effect is weaker, it can be improved by stacking with other materials (such as SiO and SiN) to optimize the electric field distribution and enhance passivation performance. The ultrathin SiO transition layer formed at the interface between alumina and the silicon substrate can saturate dangling bonds on the silicon surface, reduce the interface state density, enhance the chemical passivation effect, and improve carrier lifetime and cell photoelectric conversion efficiency.

[0003] Tubular ALD (Atomic Layer Deposition) is a chemical vapor deposition method for thin films based on ordered, surface-constrained reactions. It offers advantages such as controllable film thickness, high conformability, high flatness, good adhesion, and low thermal budget, and is widely used in the fabrication of alumina thin films for crystalline silicon solar cells. A monolayer film is formed on the substrate surface by alternately introducing different reactive gases (such as TMA and water vapor). Each ALD cycle consists of four steps: a TMA vapor pulse, nitrogen purging, a water vapor pulse, and a second nitrogen purging. These steps collectively promote the formation of the alumina film. By controlling the number of reaction cycles, the thickness of the alumina film can be precisely controlled, thereby affecting its passivation performance.

[0004] In the field of solar cells, especially TOPCon (Tunneling Oxide Passivated Contact) and BC (Back Contact) cells, alumina is closely related to ultraviolet degradation (UVID). Studies have shown that increasing the thickness of the alumina layer can effectively improve the UV degradation resistance of TOPCon and BC cells. This is because a thicker alumina layer can more effectively block hydrogen migration and reduce the damage of hydrogen to the interface passivation. However, the high-temperature sintering process can trigger the rapid diffusion of hydrogen in the alumina film, which accumulates at the silicon-based interface to form hydrogen gas (H2). When the gas pressure exceeds the film bonding force, local delamination occurs, forming bubbles (like a balloon bursting). An excessively thick alumina layer increases the risk of bubble formation, reducing the passivation performance and reliability of the cell.

[0005] The uniformity of the alumina layer thickness is also crucial for BC batteries to resist UV degradation. If a suitable average thickness is the "foundation" of degradation resistance, then excellent uniformity is the key to ensuring that this degradation resistance is "straightforward." An uneven alumina layer directly disrupts the uniformity of passivation and triggers a localized "weakest link" effect, specifically: 1. Disrupting passivation uniformity, creating a "breakthrough" for degradation: If the thickness is uneven, the passivation effect will be inconsistent. In areas where the alumina is thinner, the field-effect passivation weakens, reducing the ability to block hydrogen, making it easier for ultraviolet light to penetrate or damage the area, turning it into a recombination center and the starting point of degradation. Areas that are too thick may introduce defects due to stress or structural changes, thus reducing the local passivation quality. Under UV irradiation, weak areas will deteriorate first, leading to a decline in the overall battery performance. 2. The key to the alumina layer's resistance to UV degradation lies in its role as a barrier against hydrogen migration. It acts like a "dam." If the alumina thickness is uniform, it can evenly block hydrogen released by UV radiation, protecting the interface; if the thickness is uneven, the thinner areas become weak points or gaps in the "dam." Under UV irradiation, hydrogen preferentially passes through these gaps and accumulates in large quantities locally, leading to a surge in interface defects in that area. The overall UV degradation of the battery is determined by these weakest "gaps".

[0006] Existing tubular ALD equipment uses two stacked aluminum boats as cell carriers. Especially with the mass production of half-rod / half-wafer cutting technology, silicon wafers are cut from whole pieces to half-wafers, roughly doubling the number of support rods on the aluminum boats. This increases the resistance to gas transmission within the chamber, and the overall length of the aluminum boat also increases, effectively increasing the gas transmission distance. The alumina film produced by existing technology is uneven in thickness, with significant differences between the upper and lower aluminum boats, and between different positions / sections within the same aluminum boat. There is a phenomenon where the film thickness is higher at the furnace opening and lower at the furnace tail, leading to a thicker alumina at the furnace opening and the formation of bubbles, while the alumina at the furnace tail is insufficient for passivation performance, even with the same number of cycles. Furthermore, there is also a significant difference in thickness between the upper and lower parts of the same cell near the furnace tail, with the lower part of the upper boat and the upper part of the lower boat having a thinner alumina thickness. The proportion of defective cells with bubbles increases in areas with excessively thick alumina, while the conversion efficiency of cells in areas with thinner alumina is limited. This results in a narrower window for process parameter settings and is detrimental to the consistency control of the production line.

[0007] In view of this, the present invention proposes a method to improve the uniformity of atomic layer deposition alumina thin films. Without the need for equipment modification, the method improves the uniformity of alumina thickness by adjusting the process scheme and combining it with the method of increasing the gap between the upper and lower aluminum boats, thereby improving the passivation stability of the solar cells, reducing the defect rate, and thus improving the efficiency of the solar cells and reducing the risk of UV degradation. Summary of the Invention

[0008] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for improving the uniformity of aluminum oxide thin film deposition in the atomic layer of a back contact battery, comprising the following steps:

[0009] The substrate of the back contact battery is a silicon wafer. The silicon wafer is double-sided alkaline polished by a cleaning machine to form a mirror structure. Then, the double-sided polished silicon wafer is sent into the ALD system cavity by an automated equipment using an upper and lower aluminum boat insertion method. Trimethylaluminum and water vapor are alternately introduced, with TMA pulse, purge, H2O pulse, and purge as one cycle. During the deposition process, the distance between the upper and lower aluminum boats is adjusted to 1-2 cm by spacers.

[0010] Furthermore, the temperature of the trimethylaluminum storage tank is 40-60°C, and the pipeline temperature is 45-65°C.

[0011] Furthermore, the temperature of the water vapor storage tank is 40-60℃, and the pipeline temperature is 45-70℃.

[0012] Furthermore, the TMA pulse duration is 4-8 seconds, and the nitrogen flow rate introduced into the TMA is 1500-2500 sccm.

[0013] Furthermore, the H2O pulse duration is 4-8 seconds, and the nitrogen flow rate for introducing H2O is 1500-2500 sccm.

[0014] Furthermore, the purging involves simultaneously purging the TMA pipeline and the H2O pipeline with nitrogen, wherein the nitrogen purging flow rate is 5000–8000 sccm and the purging time is 10–16 s.

[0015] Furthermore, during the alternating introduction of trimethylaluminum and water vapor, buffer nitrogen gas is introduced at a flow rate of 4000-6000 sccm.

[0016] Furthermore, when trimethylaluminum is introduced, buffer nitrogen is introduced into the cavity through the H2O purge path, and when water vapor is introduced, buffer nitrogen is introduced into the cavity through the TMA purge path.

[0017] Beneficial effects: This invention achieves synergistic effects among various process conditions by precisely controlling the distance between the upper and lower aluminum boats to 1-2 cm, and combining it with an atomic layer deposition cycle of TMA pulse-purge-H2O pulse-purge, along with buffered nitrogen pressure stabilization and synchronous pipeline purging, thereby significantly improving the deposition uniformity of alumina thin films on the front and back sides of silicon wafers. Setting the spacing between the aluminum boats to 1-2 cm creates a stable, uniform, and symmetrical laminar flow field within the cavity, providing suitable fluid space for gaseous TMA and water vapor to uniformly reach both sides of the silicon wafer. Based on this flow field, the ALD pulse precisely controls the duration of TMA and water vapor introduction, ensuring uniform and controllable film thickness from the reaction source. Simultaneously, buffer nitrogen is introduced during the TMA and water vapor pulses to stabilize the cavity pressure and airflow distribution, preventing uneven diffusion of TMA and water vapor due to pressure fluctuations. For the high-flow-rate nitrogen purging of the TMA and H2O pipelines simultaneously, the unobstructed flow path with a 1-2 cm spacing between the upper and lower aluminum boats allows the purging airflow to uniformly pass through both sides of the silicon wafer, quickly and thoroughly removing unreacted gaseous TMA, H2O, and byproducts. This effectively eliminates over-deposition or uneven film formation caused by local residues. No additional equipment investment is required; only the alumina deposition process of the ALD process and the distance between the two aluminum boats are optimized based on the existing process equipment, ultimately achieving highly uniform deposition of alumina films on the silicon wafer. Especially with the application of half-cell battery technology, the number of aluminum boat support rods has nearly doubled, significantly hindering airflow within the cavity and easily causing uneven diffusion of TMA and H2O, resulting in poor uniformity of alumina film thickness. This invention, by optimizing the aluminum boat spacing combined with ALD pulse, purging, and buffered nitrogen processes, effectively improves the airflow obstruction problem caused by the increased number of support rods, significantly improves the uniformity of TMA and H2O distribution on the silicon wafer surface, and significantly reduces intra- and inter-wafer non-uniformity of alumina thickness. This broadens the applicable window for alumina thickness, improves the consistency and stability of battery passivation performance, and enhances both battery conversion efficiency and long-term reliability. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0019] Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without inventive effort are within the scope of protection of this invention. Experimental methods in the following embodiments that do not specify specific conditions are generally performed under conventional conditions or as recommended by the manufacturer. Unless otherwise stated, all percentages, ratios, proportions, or parts are by weight.

[0020] Unless otherwise specified, the reagents and raw materials used in the embodiments and comparative examples of this invention are commercially available.

[0021] Example 1 A method for improving the uniformity of aluminum oxide thin film deposition in the atomic layer of a back contact battery includes the following steps: The silicon wafer is double-sided alkaline polished by a cleaning machine to form a mirror structure. Then, the double-sided polished silicon wafer is placed into the ALD system cavity by a single insertion method of a metal boat in an automated equipment. Aluminum source (trimethylaluminum, TMA) and oxygen source (water, H2O) are alternately introduced to deposit a thin layer of aluminum oxide film on both the front and back of the silicon wafer.

[0022] The parameters for the alumina film preparation process are set as follows: the temperature of the TMA storage tank is set to 43℃, the temperature of the TMA pipeline is set to 50℃; the temperature of the H2O storage tank is set to 42℃, and the temperature of the H2O pipeline is set to 55℃. First, TMA is introduced with a pulse duration of 6 seconds. The nitrogen flow rate carrying the TMA is 2300 sccm, and the buffer nitrogen flow rate is 5000 sccm. Then, nitrogen purging valves are opened on both the TMA and H2O lines for 14 seconds, with the nitrogen flow rate set to 6000 sccm. Next, H2O is introduced with a pulse duration of 6 seconds. The nitrogen flow rate carrying the H2O is 2300 sccm, and the buffer nitrogen flow rate is 5000 sccm. The process of introducing TMA and purging followed by introducing H2O and purging is repeated 40 times. The distance between the upper and lower aluminum boats is 1.6 cm.

[0023] After the process is completed, one silicon wafer each from the middle and edge of slots 1 / 4 / 7 / 10 / 12 in the upper and lower aluminum boats from the furnace opening to the furnace tail are extracted and tested for alumina thickness using a spectrometer. Five points are tested on each silicon wafer, including the middle and four corners, and the non-uniformity within and between wafers is calculated.

[0024] Example 2 The silicon wafer is double-sided alkaline polished by a cleaning machine to form a mirror structure. Then, the double-sided polished silicon wafer is placed into the ALD system cavity by a single insertion method of a metal boat in an automated equipment. Aluminum source (trimethylaluminum, TMA) and oxygen source (water, H2O) are alternately introduced to deposit a thin layer of aluminum oxide film on both the front and back of the silicon wafer.

[0025] The parameters for the alumina film preparation process are set as follows: the temperature of the TMA storage tank is set to 43℃, the temperature of the TMA pipeline is set to 50℃; the temperature of the H2O storage tank is set to 42℃, and the temperature of the H2O pipeline is set to 55℃. First, TMA is introduced with a pulse duration of 5 seconds. The nitrogen flow rate carrying the TMA is 2000 sccm, and the buffer nitrogen flow rate is 4500 sccm. Then, nitrogen purging valves are opened on both the TMA and H2O lines for 13 seconds, with the nitrogen flow rate set to 5000 sccm for both lines. Next, H2O is introduced with a pulse duration of 5 seconds. The nitrogen flow rate carrying the H2O is 2000 sccm, and the buffer nitrogen flow rate is 4500 sccm. The process of introducing TMA and purging followed by introducing H2O and purging is repeated 40 times. The distance between the upper and lower aluminum boats is 1.3 cm.

[0026] After the process is completed, one silicon wafer each from the middle and edge of slots 1 / 4 / 7 / 10 / 12 in the upper and lower aluminum boats from the furnace opening to the furnace tail are extracted and tested for alumina thickness using a spectrometer. Five points are tested on each silicon wafer, including the middle and four corners, and the non-uniformity within and between wafers is calculated.

[0027] Example 3 The silicon wafer is double-sided alkaline polished by a cleaning machine to form a mirror structure. Then, the double-sided polished silicon wafer is placed into the ALD system cavity by a single insertion method of a metal boat in an automated equipment. Aluminum source (trimethylaluminum, TMA) and oxygen source (water, H2O) are alternately introduced to deposit a thin layer of aluminum oxide film on both the front and back of the silicon wafer.

[0028] The parameters for the alumina film preparation process are set as follows: the temperature of the TMA storage tank is set to 43℃, the temperature of the TMA pipeline is set to 50℃; the temperature of the H2O storage tank is set to 42℃, and the temperature of the H2O pipeline is set to 55℃. First, TMA is introduced with a pulse duration of 5 seconds. The nitrogen flow rate carrying the TMA is 2000 sccm, and the buffer nitrogen flow rate is 6000 sccm. Then, nitrogen purging valves are opened on both the TMA and H2O lines for 13 seconds, with the nitrogen flow rate set to 5000 sccm for both lines. Next, H2O is introduced with a pulse duration of 5 seconds. The nitrogen flow rate carrying the H2O is 2000 sccm, and the buffer nitrogen flow rate is 6000 sccm. The process of introducing TMA and purging followed by introducing H2O and purging is repeated 40 times. The distance between the upper and lower aluminum boats is 1.4 cm.

[0029] After the process is completed, one silicon wafer each from the middle and edge of slots 1 / 4 / 7 / 10 / 12 in the aluminum boat from the furnace mouth to the furnace tail are extracted and tested for alumina thickness using a spectrometer. Five points are tested on each silicon wafer, including the middle and four corners, and the non-uniformity within and between wafers is calculated.

[0030] Example 4 The silicon wafer is double-sided alkaline polished by a cleaning machine to form a mirror structure. Then, the double-sided polished silicon wafer is placed into the ALD system cavity by a single insertion method of a metal boat in an automated equipment. Aluminum source (trimethylaluminum, TMA) and oxygen source (water, H2O) are alternately introduced to deposit a thin layer of aluminum oxide film on both the front and back of the silicon wafer.

[0031] The parameters for the alumina film preparation process are set as follows: the temperature of the TMA storage tank is set to 43℃, the temperature of the TMA pipeline is set to 50℃; the temperature of the H2O storage tank is set to 42℃, and the temperature of the H2O pipeline is set to 55℃. First, TMA is introduced with a pulse duration of 5 seconds. The nitrogen flow rate carrying the TMA is 2000 sccm, and the buffer nitrogen flow rate is 5000 sccm. Then, nitrogen purging valves are opened on both the TMA and H2O lines for 13 seconds, with the nitrogen flow rate set to 5000 sccm for both lines. Next, H2O is introduced with a pulse duration of 5 seconds. The nitrogen flow rate carrying the H2O is 2000 sccm, and the buffer nitrogen flow rate is 5000 sccm. The process of introducing TMA and purging followed by introducing H2O and purging is repeated 40 times. The distance between the upper and lower aluminum boats is 1.4 cm.

[0032] After the process is completed, one silicon wafer each from the middle and edge of slots 1 / 4 / 7 / 10 / 12 in the upper and lower aluminum boats from the furnace opening to the furnace tail are extracted and tested for alumina thickness using a spectrometer. Five points are tested on each silicon wafer, including the middle and four corners, and the non-uniformity within and between wafers is calculated.

[0033] Comparative Example 1 The silicon wafer is double-sided alkaline polished by a cleaning machine to form a mirror structure. Then, the double-sided polished silicon wafer is placed into the ALD system cavity by a single insertion method of a metal boat in an automated equipment. Aluminum source (trimethylaluminum, TMA) and oxygen source (water, H2O) are alternately introduced to deposit a thin layer of aluminum oxide film on both the front and back of the silicon wafer.

[0034] The parameters for the alumina film preparation process are set as follows: the temperature of the TMA storage tank is set to 40℃, the temperature of the TMA pipeline is set to 47℃; the temperature of the H2O storage tank is set to 40℃, and the temperature of the H2O pipeline is set to 50℃. First, TMA is introduced with a pulse duration of 4 seconds and a nitrogen flow rate of 2000 sccm carrying the TMA. Then, nitrogen purging valves are opened on both the TMA and H2O lines for 12 seconds, with the nitrogen flow rate set to 4000 sccm. Next, H2O is introduced with a pulse duration of 5 seconds and a nitrogen flow rate of 2000 sccm carrying the H2O. This process of introducing TMA, purging, introducing H2O, and purging is repeated 40 times. There is no gap between the upper and lower aluminum boats.

[0035] After the process is completed, one silicon wafer each from the middle and edge of slots 1 / 4 / 7 / 10 / 12 in the upper and lower aluminum boats from the furnace opening to the furnace tail are extracted and tested for alumina thickness using a spectrometer. Five points are tested on each silicon wafer, including the middle and four corners, and the non-uniformity within and between wafers is calculated.

[0036] Effect Example The following tests were performed on the examples and comparative examples: 1. Take one silicon wafer each from the middle and edge of slots 1 / 4 / 7 / 10 / 12 in the upper and lower aluminum boats of Examples 1-4 and the comparative example, respectively, from the furnace mouth to the furnace tail. Test the alumina thickness using a spectrometer. Test five points in the middle and four corners of each silicon wafer and calculate the non-uniformity within and between wafers.

[0037] 2. Non-uniformity is a quantitative measure of the relative proportion of extreme thickness differences; its formula definition and physical meaning are as follows. Nonuniformity (%) = (hmax - hmin) × 100% / (hmax + hmin) hmax and hmin represent the maximum and minimum values ​​of the film thickness, respectively. The numerator represents the range of film thickness, reflecting local extreme fluctuations (such as excessive thickness at the edges or the minimum value caused by pinholes). The significance of the result lies in the percentage of extreme thickness differences in the total range, which measures the weight of local non-uniformity on the overall effect.

[0038] 3. Electrical performance: At STC (1000W / m 2 Under 25℃ (AM1.5G) conditions, test IV characteristics according to IEC60904-1 and calculate Voc, Isc, FF and Eta.

[0039] 4. EL pass rate: Electroluminescence testing was conducted according to IEC TS 60904-13, and the EL pass rate was calculated.

[0040] Table 1 shows a comparison of the uniformity of alumina thickness between the examples and comparative examples.

[0041] As shown in Table 1, the average thickness of the deposited alumina in Examples 1-4 is about 5.2 nm. The intra-cell non-uniformity of the half-cell in Example 1 can reach less than 4%, and the inter-cell non-uniformity can reach less than 3.5%, which is a significant improvement compared with the comparative example where the intra-cell non-uniformity is more than 6% and the inter-cell non-uniformity is more than 7%.

[0042] In embodiments 1-4 of this invention, by increasing the distance between the two aluminum boats, more gas enters the silicon wafer surface for adsorption, significantly improving the problem of low film thickness in the middle region of the furnace and the furnace tail. During the source-passing process, the introduction of buffer nitrogen gas, and by adjusting the buffer nitrogen flow rate and increasing the purge nitrogen flow rate during the purging step, more source gas (TMA and H2O) enters the furnace tail, reducing the obstruction of the source gas by the aluminum boat support rods. This significantly improves the problem of high film thickness in the furnace mouth region and low film thickness in the furnace tail region. However, excessive buffer nitrogen flow rate may cause localized clustering and dispersion of source gas, leading to poor inter-wafer and intra-wafer non-uniformity. In embodiments 1-4 of this invention, by adjusting the buffer nitrogen and purge nitrogen flow rates, the overall film thickness also decreases, reducing source gas residue in the chamber, thereby reducing the probability of CVD reactions and improving the deposition quality of alumina. Therefore, the technical solution of this invention can significantly improve the uniformity of atomic layer deposition of alumina films.

[0043] Table 2 compares the electrical performance of the back contact batteries prepared in Example 1 and the comparative example.

[0044] Using the optimal embodiment 1 of the present invention as the experimental group and the existing technical solution as the comparative group, half-cell back-contact batteries were prepared and their electrical performance was compared. The data are shown in Table 2. It can be seen that the back-contact battery using the present invention has a significantly improved conversion efficiency compared to the existing technology, with an average improvement of 0.044%. This is mainly reflected in an increase of 0.16mV in open-circuit voltage Uoc, an increase of 0.6mA in short-circuit current Isc, and an increase of 0.1% in fill factor. This indicates that the improved uniformity of alumina thickness leads to an improved passivation effect, resulting in more stable and balanced overall battery cell performance. Furthermore, from the EL pass rate data, the yield rate of batteries produced by the present invention is improved by an average of 0.73%, which can significantly improve the bubbling problem caused by excessive alumina thickness at the furnace opening, thus improving battery cell quality.

[0045] Table 3 shows a comparison of UVID of the back contact batteries prepared in the examples and comparative examples.

[0046] Twenty cells from the same grade of battery cells prepared according to Embodiment 1 of the present invention and the comparative embodiment of the prior art were collected for UVID testing, with a cumulative value of 15 kWh / m. 2The ultraviolet irradiation dose, i.e., UV15 test, and the comparison data of electrical performance before and after UV exposure are shown in Table 3. It can be seen that the conversion efficiency degradation of the battery cell using the present invention is significantly reduced, with a degradation rate reduced by 0.26% compared to the prior art, indicating improved UVID resistance. In summary, the present invention can significantly improve the uniformity of alumina film thickness in ALD preparation. Half-cell back-contact batteries produced using this method show a significant improvement in conversion efficiency and enhanced UVID resistance, indicating improved passivation consistency and reliability of the battery cell, and thus possessing high promotional value.

[0047] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for improving the uniformity of aluminum oxide thin film deposition in the atomic layer of a back contact battery, characterized in that, Includes the following steps: The substrate of the back contact battery is a silicon wafer. The silicon wafer is double-sided alkaline polished by a cleaning machine to form a mirror structure. Then, the double-sided polished silicon wafer is sent into the ALD system cavity by an automated equipment using an upper and lower aluminum boat insertion method. Trimethylaluminum and water vapor are alternately introduced, with TMA pulse, purge, H2O pulse, and purge as one cycle. During the deposition process, the distance between the upper and lower aluminum boats is adjusted to 1-2 cm by spacers.

2. The method for improving the uniformity of alumina thin film deposition in the atomic layer of a back contact battery according to claim 1, characterized in that, The temperature of the trimethylaluminum storage tank is 40-60℃, and the pipeline temperature is 45-65℃.

3. The method for improving the uniformity of alumina thin film deposition in the atomic layer of a back contact battery according to claim 1, characterized in that, The temperature of the water vapor storage tank is 40-60℃, and the pipeline temperature is 45-70℃.

4. The method for improving the uniformity of alumina thin film deposition in the atomic layer of a back contact battery according to claim 1, characterized in that, The TMA pulse duration is 4-8 seconds, and the nitrogen flow rate introduced into the TMA is 1500-2500 sccm.

5. The method for improving the uniformity of alumina thin film deposition in the atomic layer of a back contact battery according to claim 1, characterized in that, The H2O pulse duration is 4-8 seconds, and the nitrogen flow rate introduced into the H2O is 1500-2500 sccm.

6. The method for improving the uniformity of alumina thin film deposition in the atomic layer of a back contact battery according to claim 1, characterized in that, The purging process involves simultaneously purging the TMA and H2O pipelines with nitrogen gas at a flow rate of 5000-8000 sccm for 10-16 seconds.

7. The method for improving the uniformity of alumina thin film deposition in the atomic layer of a back contact battery according to claim 1, characterized in that, During the alternating introduction of trimethylaluminum and water vapor, buffer nitrogen gas is introduced at a flow rate of 4000-6000 sccm.

8. The method for improving the uniformity of alumina thin film deposition in the atomic layer of a back contact battery according to claim 7, characterized in that, When trimethylaluminum is introduced, buffer nitrogen is introduced into the cavity through the H2O purging path; when water vapor is introduced, buffer nitrogen is introduced into the cavity through the TMA purging path.

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