Alumina composite film layer and application thereof in solar cell
By using TMA+H2O+O3 as the growth source in the ALD coating process and alternately pulse the gas, the problems of high resistivity and slow deposition rate of alumina thin films are solved, and the efficiency and passivation effect of silicon-based solar cells are improved. A low-cost and efficient preparation of alumina film layer is achieved.
Patent Information
- Application Number
- CN202411307200.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2022-04-08
- Publication Date
- 2024-12-27
AI Technical Summary
In the prior art, when preparing alumina films, the single oxygen source process has problems such as insufficient oxidation, resulting in high resistivity and slow deposition rate, making it difficult to effectively improve the efficiency of silicon-based solar cells.
ALD coating process using TMA+H2O+O3 as the growth source, TMA, H2O and O3 gases are alternately pulsed on the substrate, and the film resistivity is reduced through the strong oxidation of O3, and the reaction product is brought out by the purge gas, which improves the Passivation effect.
The low resistivity and high deposition rate of the alumina film are achieved, which improves the conversion efficiency of the solar cell, and is simple to operate and low cost.
Abstract
Description
[0001] This application is a divisional application. The application number of the parent application is 202210363758.6, the application date is April 8, 2022, and the name of the invention is “An excellent ALD coating process”. Technical Field
[0002] The invention relates to the technical field of solar cells, and in particular to an aluminum oxide composite film layer and application thereof in solar cells. Background Art
[0003] Improving the efficiency of silicon-based solar cells is the main problem people are facing now. Surface passivation is a method to improve the efficiency of silicon-based solar cells. Among the many passivation film materials, Al2O3 is considered to be a natural surface passivation material for solar cells due to the large amount of fixed negative charges and low interface state density at its interface. Obtaining more efficient cells puts forward higher requirements on the passivation effect.
[0004] However, the existing technologies for preparing aluminum oxide all use a single oxygen source, such as TMA and H2O or TMA and O3. However, there are many disadvantages in preparing aluminum oxide films using a single oxygen source. For example, the resistivity of aluminum oxide films prepared by TMA and H2O is higher than that of oxide films prepared by TMA and O3 due to the weak oxidizing property of water. The deposition rate of aluminum oxide films prepared by TMA and O3 is slower than that of TMA and H2O.
[0005] Therefore, it is necessary to provide a new technical solution to overcome the above-mentioned defects. Summary of the invention
[0006] The object of the present invention is to provide an excellent ALD coating process which can effectively solve the above-mentioned technical problems.
[0007] In order to achieve the purpose of the present invention, the following technical scheme is adopted:
[0008] An excellent ALD coating process, which uses TMA+H2O+O3 as growth sources to grow an aluminum oxide film layer on a substrate.
[0009] Preferably, the steps of growing an aluminum oxide film layer on a substrate using this process are:
[0010] (1) placing the growth substrate into the chamber of the deposition equipment and controlling the chamber temperature to 170-250° C.;
[0011] (2) growing aluminum oxide on the surface of a growth substrate using TMA+H2O as a growth source in an alternating pulse manner; the order of gas introduction in each cycle is TMA gas, purge gas, H2O evaporation gas, and purge gas;
[0012] (3) After each cycle or after several cycles, auxiliary gas O3 is introduced into the cavity, and finally purge gas is introduced to purge TMA.
[0013] Preferably, in each cycle of step (2), the flow rate of TMA is 10-30 sccm, the pulse duration is 1-5 s, and the purge duration is 4-9 s.
[0014] Preferably, in each cycle of step (2), the flow rate of H2O is 10-30 sccm, the pulse duration is 3-10 s, and the purge duration is 6-12 s.
[0015] Preferably, in step (3), the flow rate of a single auxiliary source O3 is 10-30 sccm, the pulse duration is 3-20 s, and the purge duration is 5-20 s.
[0016] Preferably, the purge gas is an inert gas.
[0017] Compared with the prior art, the present invention has the following beneficial effects:
[0018] The present invention utilizes the ALD (atomic layer deposition) process to prepare an Al2O3 film on the surface of a silicon wafer, and uses TMA+H2O+O3 as a growth source to grow an aluminum oxide film layer on a substrate. Compared with the prior art of growing an aluminum oxide film layer using TMA+O3 or TMA+H2O as a growth source, not only does it retain the fast growth rate of TMA+H2O; in addition, during the growth process, O3 is introduced into the cavity as an auxiliary source, and O3 can react with -CH3 in the film to finally react into H2O+CO2, which is purged out by the purge gas, thereby effectively reducing the resistivity of the film layer, improving the passivation effect, and further improving the conversion efficiency of the battery; at the same time, the process of the present invention can be realized in the same chamber, and has the advantages of simple operation and low cost. DETAILED DESCRIPTION
[0019] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are partial embodiments of the present invention, rather than all embodiments.
[0020] Example
[0021] The present invention provides an excellent ALD process, comprising the following steps:
[0022] (1) The growth substrate is sent into the cavity, and before the aluminum oxide growth process, the temperature is ensured to reach the set temperature requirement. The preferred temperature is 210°C, and the constant pressure and temperature are maintained for a certain period of time to ensure that the substrate to be grown and the entire process cavity are stable at this temperature. The constant temperature state is conducive to ensuring the uniformity of the subsequent aluminum oxide film growth.
[0023] (2) An aluminum oxide film layer is preferentially grown using TMA+H2O as the growth source, and TMA and H2O are alternately introduced into the process chamber for deposition; the minimum cycle of the alternate introduction of process gases is TMA gas, purge gas, H2O evaporation gas, and purge gas; wherein a single TMA flow rate is 18 sccm, a pulse duration is 2.5 s, and a N2 purge duration is 7 s; a single H2O flow rate is 18 sccm, a pulse duration is 6 s, and a N2 purge duration is 8 s.
[0024] Among them, the number of times TMA and H2O are alternately introduced directly determines the thickness of the aluminum oxide film layer, and can therefore be set according to the process and on-site matching requirements.
[0025] The aluminum oxide generated by the reaction of TMA and H2O reduces the interface state density of the substrate. The H2O pulse introduces hydroxyl groups during the reaction, which not only increases the reaction rate, but also improves the quality of the interface oxide layer in the annealing step, thereby enhancing the chemical passivation effect.
[0026] (3) After each minimum cycle or after multiple minimum cycles, the auxiliary gas O3 is introduced into the process chamber, and then the N2 purge gas is passed, wherein the O3 flow rate is 12 sccm, the pulse duration is 6 s, and the N2 purge duration is 7 s.
[0027] The aluminum oxide film generated by the reaction of TMA and H2O has a low interface state density and good chemical passivation. However, since the oxidizing property of H2O is not as strong as that of O3, the resistivity of the aluminum oxide film generated by the reaction of TMA and H2O is relatively high. The main reason is that the content of C element in the film is relatively high. The strong oxidizing property of O3 can oxidize the -CH3 ligand in TMA very well, thereby reducing the resistivity of the film.
[0028] (4) According to the thickness selection, steps (2) and (3) are cycled 8 times, and the aluminum oxide film layer of about 8 nm is obtained by testing;
[0029] (5) Perform N2 purging, break the vacuum and exit the chamber.
[0030] Comparative Example 1
[0031] (1) The growth substrate is sent into the cavity, and before the aluminum oxide growth process, the temperature is ensured to reach the set temperature requirement. The preferred temperature is 210°C, and the constant pressure and temperature are maintained for a certain period of time to ensure that the substrate to be grown and the entire process cavity are stable at this temperature. The constant temperature state is conducive to ensuring the uniformity of the subsequent aluminum oxide film growth.
[0032] (2) An aluminum oxide film layer is preferentially grown using TMA+H2O as the growth source, and TMA and H2O are alternately introduced into the process chamber for deposition; the minimum cycle of the alternate introduction of process gases is TMA gas, purge gas, H2O evaporation gas, and purge gas; wherein a single TMA flow rate is 18 sccm, a pulse duration is 2.5 s, and a N2 purge duration is 7 s; a single H2O flow rate is 18 sccm, a pulse duration is 6 s, and a N2 purge duration is 8 s.
[0033] (3) According to the thickness selection, step (2) was repeated 8 times, and the aluminum oxide film layer of about 8 nm was obtained by testing.
[0034] Comparative Example 2
[0035] (1) The growth substrate is sent into the cavity, and before the aluminum oxide growth process, the temperature is ensured to reach the set temperature requirement. The preferred temperature is 210°C, and the constant pressure and temperature are maintained for a certain period of time to ensure that the substrate to be grown and the entire process cavity are stable at this temperature. The constant temperature state is conducive to ensuring the uniformity of the subsequent aluminum oxide film growth.
[0036] (2) The aluminum oxide film layer is preferentially grown with TMA+O3 as the growth source, and TMA and O3 are alternately introduced into the process chamber for deposition; the minimum cycle of the alternate introduction of process gases is TMA gas, purge gas, O3 gas, and purge gas; wherein the single TMA flow rate is 18 sccm, the pulse duration is 2.5 s, and the N2 purge duration is 7 s; the single O3 flow rate is 18 sccm, the pulse duration is 6 s, and the N2 purge duration is 8 s.
[0037] (3) According to the thickness selection, step (2) was repeated 8 times, and the aluminum oxide film layer of about 8 nm was obtained by testing.
[0038] The performance of the aluminum oxide films of the above embodiments and comparative examples 1-2 were tested by a testing instrument, and the results are shown in Table 1 below, where the total number of negative charges Qtot (E12) and the interface state density Dit (E11) are shown.
[0039] Table 1
[0040] Qtot(E12) Yours(E11) <![CDATA[TMA+H2O]]> -2.41 10.8 <![CDATA[TMA+O3]]> -2.63 12.1 <![CDATA[TMA+H2O+O3]]> -2.97 8.4
[0041] It can be seen from the data in the table that the aluminum oxide film prepared by the ALD process of the present invention has a low film resistivity and a good passivation effect.
[0042] Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention.
Claims
1. An aluminum oxide composite film layer, characterized in that: The preparation method of the aluminum oxide composite film layer is as follows: Using TMA+H2O+O3 as growth sources, an aluminum oxide film layer is grown on the substrate; (1) placing the growth substrate into the chamber of the deposition equipment and controlling the chamber temperature to 170-250° C.; (2) growing aluminum oxide on the surface of a growth substrate using TMA+H2O as a growth source in an alternating pulse manner; the order of gas introduction in each cycle is TMA gas, purge gas, H2O evaporation gas, and purge gas; (3) After each cycle or after several cycles, an auxiliary gas O3 is introduced into the cavity, and finally a purge gas is introduced to purge the TMA to obtain an alumina composite film layer; During the growth process, O3 is introduced into the cavity as an auxiliary source. O3 can react with -CH3 in the film, and the final reaction is H2O+CO2, which is purged out by the purge gas; In each cycle of step (2), the flow rate of TMA is 10-30 sccm, the pulse duration is 1-5 s, and the purge duration is 4-9 s; In each cycle of step (2), the flow rate of H2O is 10-30 sccm, the pulse duration is 3-10 s, and the purge duration is 6-12 s; In step (3), the O3 flow rate is 12 sccm and the pulse duration is 6 s.
2. The aluminum oxide composite film according to claim 1, characterized in that: The purge time in step (3) is 5-20s.
3. The aluminum oxide composite film according to claim 1, characterized in that: The purge gas is an inert gas.
4. Use of the aluminum oxide composite film layer according to any one of claims 1 to 3 in solar cells.