TOPCon silicon wafer coating method based on ALD lamination optimization

Abstract

The invention discloses a TOPCon silicon wafer coating method based on ALD lamination optimization, and belongs to the technical field of solar cell preparation. At proper temperature and pressure, H2O reaction gas is firstly introduced to purge the surface of a silicon wafer, impurities on the surface of the silicon wafer are removed, meanwhile, surface defects of the silicon wafer are passivated, then TMA reaction gas is introduced, and the surface defects of the silicon wafer are passivated; the method comprises the following steps of: performing self-adaptive adsorption on a precursor and the surface of a silicon wafer to achieve saturation, completely removing the unreacted precursor and redundant reaction by using inert gas with enough high purity, and introducing H2O reaction gas to fully react with the precursor adsorbed on the silicon wafer to obtain the silicon wafer. According to the method, the unreacted precursor and redundant reactants are removed by using sufficient high-purity inert gas again, and ALD lamination can be completed by circulating the processes in sequence, no additional equipment is needed, and by means of the method, ALD deposition can be more uniform, and the purpose of improving efficiency is achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of solar cell preparation, and in particular relates to a TOPCon silicon wafer coating method based on ALD stacking optimization. Background Art

[0002] In the existing solar cell technology, an aluminum oxide passivation film is usually deposited on the surface of the silicon wafer. The aluminum oxide passivation film has a high fixed negative charge density and a low interface defect density, so it can have good chemical passivation and field passivation effects at the same time. Most of the aluminum oxide deposition methods are micro-duct deposition (ALD) deposition methods. The reaction chemical equation is Al(CH3)3+3H2O→Al2O3+3CH 4。

[0003] In the ALD process, reactants enter the chamber in two stages. When precursor substance A is pulsed into the reaction chamber, it contacts the surface of the material inside, and the two react chemically to form saturation and adsorption. In the second step, when precursor substance B is pulsed into the reaction chamber, it reacts with precursor substance A previously adsorbed on the substrate to generate the target material and release byproducts until the adsorbed substance A reacts completely and the reaction stops automatically. This is the self-limiting nature of the chemical reaction of atomic layer deposition. In the actual reaction, the precursor substance reacts with groups such as hydroxyl groups on the surface of the substrate to form adsorption, and the subsequent substance then reacts with the precursor previously adsorbed on the surface of the substrate to generate the desired product and achieve material growth. ALD has the characteristics of low substrate temperature, precise control of film thickness, large-area growth, good film uniformity, and perfect three-dimensional conformality. In addition, it is fully compatible with flexible substrates / devices. Many factors affect its uniformity, including process gas pulse frequency, airflow, reaction temperature, precursor concentration and sequence, etc.

[0004] However, the prior art has the following defects:

[0005] The current technology has great differences in deposition uniformity at different locations on silicon wafers. At the same time, the products produced during deposition have an inhibitory effect on subsequent reactions, which deteriorates the uniformity of deposition, the passivation effect, and reduces product efficiency. Summary of the invention

[0006] In order to solve the problems raised in the above background technology, the present invention provides a TOPCon silicon wafer coating method based on ALD stacking optimization, so as to solve the problem that the deposition uniformity at different positions of the silicon wafer in the prior art is quite different, and the products produced during deposition have an inhibitory effect on subsequent reactions, which deteriorates the uniformity during deposition, deteriorates the passivation effect, and reduces the product efficiency.

[0007] To achieve the above object, the present invention provides the following technical solutions:

[0008] A TOPCon silicon wafer coating method based on ALD stack optimization comprises the following steps:

[0009] S1: Load the silicon wafer into the ALD aluminum boat and send the ALD aluminum boat to the main machine;

[0010] S2: Open the cavity of the main machine, send the aluminum boat into the cavity, and preheat the aluminum boat;

[0011] S3: performing a preset round of first pretreatment operation, each round of the first pretreatment operation includes: introducing H2O reaction gas into the chamber to pretreat the surface of the silicon wafer, and then introducing inert gas to purge residual gas on the surface of the silicon wafer;

[0012] S4: performing a preset round of first reaction operation, each round of the first reaction operation includes: introducing TMA reaction gas into the chamber, then introducing inert gas to purge residual gas on the surface of the silicon wafer, and then introducing H2O reaction gas;

[0013] S5: performing a preset round of second pretreatment operation, each round of the second pretreatment operation includes: introducing H2O reaction gas into the chamber to pretreat the surface of the silicon wafer, and then introducing inert gas to purge residual gas on the surface of the silicon wafer;

[0014] S6: performing a preset round of second reaction operation, each round of the second reaction operation includes: introducing TMA reaction gas into the chamber, then introducing inert gas to purge residual gas on the surface of the silicon wafer, and then introducing H2O reaction gas;

[0015] S7: A laminated aluminum oxide film is formed on the surface of the silicon wafer, and the silicon wafer coated with the aluminum oxide film is sent out of the cavity.

[0016] Preferably, the preheating temperature in S2 is 275-295° C., and the preheating time is 900-1400 s.

[0017] Preferably, the preset number of rounds of the first pretreatment operation is 3 rounds, and each round of the first pretreatment operation includes: continuously introducing H2O reaction gas with a volume flow rate of 27 sccm into the chamber for 5 seconds to pretreat the surface of the silicon wafer, and then continuously introducing inert gas with a volume flow rate of 27 sccm for 11 seconds to purge residual gas on the surface of the silicon wafer.

[0018] Preferably, the first reaction operation is performed 10 times, and each first reaction operation includes continuously introducing TMA reaction gas with a volume flow rate of 20 sccm for 7 seconds, then continuously introducing inert gas with a volume flow rate of 20 sccm for 11 seconds to purge residual gas on the surface of the silicon wafer, and then continuously introducing H2O reaction gas with a volume flow rate of 20 sccm for 7 seconds.

[0019] Preferably, the preset number of rounds of the second pretreatment operation is 5 rounds, and each round of the second pretreatment operation includes: continuously introducing H2O reaction gas with a volume flow rate of 30 sccm into the chamber for 6 seconds to pretreat the surface of the silicon wafer, and then continuously introducing inert gas with a volume flow rate of 30 sccm for 12 seconds to purge residual gas on the surface of the silicon wafer.

[0020] Preferably, the second reaction operation is performed 24 times, and each round of the second reaction operation includes continuously introducing TMA reaction gas with a volume flow rate of 30 sccm for 6 seconds, then continuously introducing inert gas with a volume flow rate of 20 sccm for 11 seconds to purge residual gas on the surface of the silicon wafer, and then continuously introducing H2O reaction gas with a volume flow rate of 30 sccm for 6 seconds.

[0021] Preferably, the inert gas is N2 gas.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] In the present application, at a suitable temperature and pressure, H2O reaction gas is first introduced to purge the surface of the silicon wafer to remove impurities on the surface of the silicon wafer and passivate the surface defects of the silicon wafer, and then TMA reaction gas is introduced to achieve adaptive adsorption of the precursor and the surface of the silicon wafer to reach saturation, and a sufficiently high-purity inert gas is used to remove the unreacted precursor and excess reaction, and then H2O reaction gas is introduced to react fully with the precursor adsorbed on the silicon wafer, and a sufficient amount of high-purity inert gas is used again to remove the unreacted precursor and excess reactants, and the above process is repeated in sequence to complete the ALD stacking;

[0024] This application does not require any new equipment. Through the method involved in this application, ALD deposition can be made more uniform, thereby achieving the purpose of improving efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is the process intention of this application. DETAILED DESCRIPTION

[0026] In order to facilitate those skilled in the art to understand the technical content of the present invention, the present invention is further described in detail below in conjunction with the accompanying drawings and specific examples. It should be understood that the specific examples described herein are only used to explain the present invention and are not used to limit the present invention.

[0027] Example 1

[0028] like Figure 1 As shown, a TOPCon silicon wafer coating method based on ALD stack optimization includes the following steps:

[0029] S1: Load the silicon wafer into the ALD aluminum boat, and send the ALD aluminum boat to the host platform, which is the atomic layer deposition equipment (Atomic Layer Deposition, ALD);

[0030] S2: Open the cavity of the main machine, send the aluminum boat into the cavity, and preheat the aluminum boat. The preheating temperature is 295°C and the preheating time is 1400s.

[0031] S3: performing three rounds of first pretreatment operations, each round of the first pretreatment operation comprising: continuously introducing H2O reaction gas with a volume flow rate of 27 sccm into the chamber for 5 seconds to pretreat the surface of the silicon wafer, and then continuously introducing N2 gas with a volume flow rate of 27 sccm for 11 seconds to purge residual gas on the surface of the silicon wafer;

[0032] S4: performing 10 rounds of the first reaction operation, each round of the first reaction operation includes continuously introducing TMA reaction gas with a volume flow rate of 20 sccm for 7 seconds, then continuously introducing N2 gas with a volume flow rate of 20 sccm for 11 seconds to purge residual gas on the surface of the silicon wafer, and then continuously introducing H2O reaction gas with a volume flow rate of 20 sccm for 7 seconds;

[0033] During this period, the TMA reaction gas is adsorbed on the SiO2 / Si surface with -OH, and the H on the SiO2 / Si surface combines with CH3 to produce CH4 (byproduct), forming O-Al (AlO (CH3) atomic group), and then the CH3 on the AlO (CH3) surface combines with the H in H2O to produce CH4, forming Al-OH;

[0034] S5: performing 5 rounds of second pretreatment operation, each round of second pretreatment operation comprising: continuously introducing H2O reaction gas with a volume flow rate of 30 sccm into the chamber for 6 seconds to pretreat the surface of the silicon wafer, and then continuously introducing N2 gas with a volume flow rate of 30 sccm for 12 seconds to purge residual gas on the surface of the silicon wafer;

[0035] S6: performing 24 rounds of the second reaction operation, each round of the second reaction operation includes continuously introducing TMA reaction gas with a volume flow rate of 30 sccm for 6 seconds, then continuously introducing N2 gas with a volume flow rate of 20 sccm for 11 seconds to purge residual gas on the surface of the silicon wafer, and then continuously introducing H2O reaction gas with a volume flow rate of 30 sccm for 6 seconds;

[0036] During this period, the TMA reaction gas is adsorbed on the SiO2 / Si surface with -OH, and the H on the SiO2 / Si surface combines with CH3 to produce CH4 (byproduct), forming O-Al (AlO (CH3) atomic group), and then the CH3 on the AlO (CH3) surface combines with the H in H2O to produce CH4, forming Al-OH;

[0037] S7: A laminated aluminum oxide film is formed on the surface of the silicon wafer, and the silicon wafer coated with the aluminum oxide film is sent out of the cavity to participate in the remaining production steps of the TOPCon battery.

[0038] In this embodiment, the present application adds H2O pretreatment to improve the uniformity of aluminum oxide, while appropriately increasing the number of process formula cycles to increase the thickness of aluminum oxide and increase the passivation effect. The present application also adopts a stacked deposition method to further optimize the deposition uniformity and passivation effect, thereby improving product efficiency.

[0039] In the subsequent comparative experiments, the comparison group adopted the industry-common single deposition method, the aluminum oxide adopted a single coating technology, and the experimental group adopted the ALD stacking technology involved in this application. The other process control points were completely consistent. The detailed electrical parameters are shown in Table 1:

[0040] Table 1

[0041] From the electrical parameters, we can see that the efficiency gain mainly comes from the increase of open circuit voltage and short circuit current.

[0042] Traditional mass production technology adopts a single deposition method. During the mass production implementation, due to the limitations of single deposition, the deposited oxide layer has poor uniformity and the thickness of the aluminum oxide before and after the cavity varies greatly. The method adopted in this application further guarantees the thickness and uniformity of the aluminum oxide, while improving the passivation effect of the aluminum oxide, ensuring a stable efficiency gain during the mass production process.

Claims

1. A TOPCon silicon wafer coating method based on ALD stack optimization, characterized in that: The following steps are involved: S1: Load the silicon wafer into the ALD aluminum boat and send the ALD aluminum boat to the main machine; S2: Open the cavity of the main machine, send the aluminum boat into the cavity, and preheat the aluminum boat; S3: performing a preset round of first pretreatment operation, each round of the first pretreatment operation includes: introducing H2O reaction gas into the chamber to pretreat the surface of the silicon wafer, and then introducing inert gas to purge residual gas on the surface of the silicon wafer; S4: performing a preset round of first reaction operation, each round of the first reaction operation includes: introducing TMA reaction gas into the chamber, then introducing inert gas to purge residual gas on the surface of the silicon wafer, and then introducing H2O reaction gas; S5: performing a preset round of second pretreatment operation, each round of the second pretreatment operation includes: introducing H2O reaction gas into the chamber to pretreat the surface of the silicon wafer, and then introducing inert gas to purge residual gas on the surface of the silicon wafer; S6: performing a preset round of second reaction operation, each round of the second reaction operation includes: introducing TMA reaction gas into the chamber, then introducing inert gas to purge residual gas on the surface of the silicon wafer, and then introducing H2O reaction gas; S7: A laminated aluminum oxide film is formed on the surface of the silicon wafer, and the silicon wafer coated with the aluminum oxide film is sent out of the cavity.

2. A TOPCon silicon wafer coating method based on ALD stack optimization according to claim 1, characterized in that: The preheating temperature in S2 is 275-295°C, and the preheating time is 900-1400s.

3. The TOPCon silicon wafer coating method based on ALD stack optimization according to claim 1, characterized in that: The preset number of rounds of the first pretreatment operation is 3 rounds. Each round of the first pretreatment operation includes: continuously introducing H2O reaction gas with a volume flow rate of 27 sccm into the chamber for 5 seconds to pretreat the surface of the silicon wafer, and then continuously introducing inert gas with a volume flow rate of 27 sccm for 11 seconds to purge residual gas on the surface of the silicon wafer.

4. The TOPCon silicon wafer coating method based on ALD stack optimization according to claim 1, characterized in that: There are 10 rounds of the first reaction operation. Each round of the first reaction operation includes continuously introducing TMA reaction gas with a volume flow rate of 20 sccm for 7s, then continuously introducing inert gas with a volume flow rate of 20 sccm for 11s to purge residual gas on the surface of the silicon wafer, and then continuously introducing H2O reaction gas with a volume flow rate of 20 sccm for 7s.

5. The TOPCon silicon wafer coating method based on ALD stack optimization according to claim 1, characterized in that: The preset number of rounds of the second pretreatment operation is 5 rounds, and each round of the second pretreatment operation includes: continuously introducing H2O reaction gas with a volume flow rate of 30 sccm into the chamber for 6 seconds to pretreat the surface of the silicon wafer, and then continuously introducing inert gas with a volume flow rate of 30 sccm for 12 seconds to purge residual gas on the surface of the silicon wafer.

6. The TOPCon silicon wafer coating method based on ALD stack optimization according to claim 1, characterized in that: The second reaction operation was performed 24 times, and each round of the second reaction operation included continuously introducing TMA reaction gas with a volume flow rate of 30 sccm for 6 seconds, then continuously introducing inert gas with a volume flow rate of 20 sccm for 11 seconds to purge residual gas on the surface of the silicon wafer, and then continuously introducing H2O reaction gas with a volume flow rate of 30 sccm for 6 seconds.

7. A TOPCon silicon wafer coating method based on ALD stacking optimization according to any one of claims 1, 3-6, characterized in that: The inert gas is N2 gas.

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