A preparation method of a tunneling oxide passivation layer, a TOPCon battery and a preparation method

Abstract

The application relates to the technical field of solar cell manufacturing, and particularly discloses a preparation method of a tunneling oxidation passivation layer, a TOPCOn cell and a preparation method. The method comprises the following steps: S1, providing a silicon substrate, and placing the silicon substrate in a process chamber; S2, introducing a first oxidation gas into the process chamber, and preparing a tunneling oxidation layer on the surface of the silicon substrate through PECVD; S3, introducing silane into the process chamber, depositing an amorphous silicon layer on the tunneling oxidation layer, and preparing a tunneling oxidation passivation layer; and S4, sequentially introducing a second oxidation gas and a fluorine-containing gas into the process chamber, and cooling, so as to complete the preparation of the tunneling oxidation passivation layer. The graphite boat cleaning step is combined with the film coating process, the gas flow is strictly controlled, the situation that the graphite piece positive and negative electrodes are prematurely turned on after polycrystalline silicon is deposited on the ceramic tube is effectively avoided, the use stability of the graphite boat is improved, and the process flow time is greatly shortened.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of solar cell manufacturing, in particular to a preparation method of a tunneling oxide passivation layer, a TOPCon cell and a preparation method. BACKGROUND

[0002] The graphite boat is a tool carrier used for depositing a film by a PECVD process. The graphite boat has a structure with many graphite sheets connected by insulating ceramic tubes with a certain interval. Since graphite has good electrical conductivity and thermal conductivity, passing an alternating voltage between the graphite sheets can form a positive and negative electrode between two adjacent graphite sheets. When there is a certain air pressure and gas, glow discharge occurs between the two graphite sheets, decomposes the process gas, and then forms a film deposited on the surface of the silicon wafer. During film deposition, the graphite boat surface will also deposit the film produced by the reaction, affecting the normal use of the graphite boat and the conductivity of the battery sheet. The film deposition color difference is serious, the film deposition rework rate is high, so the graphite boat needs to be cleaned to remove the various byproduct films deposited on the surface.

[0003] At present, to solve such problems, most enterprises adopt a graphite boat wet cleaning process, that is, during the preparation of the TOPCon cell, after the graphite boat is used for a certain number of times, the graphite boat is taken out, soaked with HF solution, then rinsed with deionized water, and finally dried. The entire graphite boat cleaning process takes about 24 hours. However, during the preparation of the tunneling oxide passivation layer, the inventors have found that only using this method of cleaning the graphite boat after a preset number of times cannot guarantee the smooth progress of the process, and there may still be cases of poor film deposition quality or even complete scrap of the silicon wafer loaded in the graphite boat, which seriously restricts the production capacity and efficiency. SUMMARY

[0004] Therefore, the present application provides a preparation method of a tunneling oxide passivation layer, a TOPCon cell and a preparation method, which creatively combines the graphite boat cleaning step with the film deposition process, effectively avoids the situation that the graphite sheet positive and negative electrodes are turned on in advance after the ceramic tube deposits polycrystalline silicon, improves the use stability of the graphite boat, guarantees the film deposition quality and the battery yield, and greatly shortens the process flow time.

[0005] To achieve the above-mentioned application purposes, the embodiments of the present application adopt the following technical solutions:

[0006] In a first aspect, the present application provides a preparation method of a tunneling oxide passivation layer, comprising the following steps:

[0007] S1, providing a silicon substrate, and placing the silicon substrate in a process chamber;

[0008] S2, introducing a first oxidizing gas into the process chamber, and preparing a tunneling oxide layer on the surface of the silicon substrate by PECVD;

[0009] S3, silane is introduced into the process chamber to deposit an amorphous silicon layer on the tunneling oxide layer to obtain a tunneling oxide passivation layer;

[0010] S4, second oxidation gas and fluorine-containing gas are sequentially introduced into the process chamber, and the temperature is lowered to complete the preparation of the tunneling oxide passivation layer; wherein the flow rate of the oxidation gas is 600sccm-1200sccm, and the flow rate of the fluorine-containing gas is 500sccm-1000sccm.

[0011] In actual production, the frequency of cleaning the graphite boat will be set, that is, when the graphite boat reaches the number of uses, the graphite boat will be taken out for cleaning. However, the inventors have accidentally found that in the process of preparing the tunneling oxide passivation layer of the TOPCon battery, a small amount of plasma formed by glow discharge will diffuse to the ceramic tube of the graphite boat, so that the ceramic tube will also deposit conductive amorphous silicon. With the increase of the number of process operations, the amorphous silicon layer becomes thicker and thicker, resulting in poorer and poorer insulation of the ceramic tube, so that the two graphite sheets of different polarities are conductive, and a corresponding working electric field cannot be formed between the two graphite sheets of different polarities, thereby the reaction gas cannot be ionized, affecting the growth of the composite film on the surface of the silicon wafer. Moreover, each graphite boat has multiple ceramic tubes, and the deposition thickness of amorphous silicon on each ceramic tube is inconsistent, so the insulation performance of each ceramic tube is inconsistent. Therefore, it is possible that some ceramic tubes are conductive before the graphite boat reaches the cleaning frequency, resulting in uneven coating or process failure. Even worse, the silicon wafers loaded in the graphite boat are completely scrapped, and the service life of the graphite boat is also reduced, increasing the cleaning cost.

[0012] Therefore, the inventors have conducted in-depth research, abandoned the way of cleaning the graphite boat separately for a long time in the prior art, and creatively combined the graphite boat cleaning step with the coating process. After obtaining the tunneling oxide passivation layer, the product is not taken out, but oxidation gas is directly introduced to oxidize the amorphous silicon attached to the surface of the ceramic tube into non-conductive silicon dioxide, and then fluorine-containing gas is introduced to form plasma to etch the silicon dioxide, achieving the purpose of completely removing the deposited film on the ceramic tube. At the same time, by strictly controlling the flow rates of the oxidation gas and the fluorine-containing gas, the inventors ensure that the amorphous silicon layer deposited on the ceramic tube can be completely removed while minimizing or even eliminating the impact on the oxidation passivation layer on the silicon wafer. The preparation method of the tunneling oxide passivation layer provided by the present application can clean the graphite boat during coating without disassembly and transportation, greatly shortening the entire process flow time, reducing the cost, and improving the stability of the graphite boat. The graphite boat can avoid the situation that the graphite sheet positive and negative electrodes are turned on in advance after the ceramic tube deposits polycrystalline silicon, effectively prolonging the service life of the graphite boat, ensuring the coating quality and battery yield, and further improving the production capacity and efficiency of the enterprise.

[0013] Optionally, the first oxidizing gas is oxygen, nitrous oxide, ozone or nitrogen carrying pure water vapor.

[0014] Optionally, the second oxidizing gas is oxygen, nitrous oxide, ozone or nitrogen carrying pure water vapor.

[0015] Optionally, the fluorine-containing gas is hydrogen fluoride or sulfur fluoride.

[0016] Optionally, after the silicon substrate is placed in the process chamber in step S1, vacuumizing is performed and the temperature is raised to 350-550℃.

[0017] Optionally, the specific process of step S4 is as follows: the oxidizing gas is introduced into the process chamber under the first microwave condition for 80-150s, then vacuumizing and nitrogen purging are performed; after the purging is completed, the fluorine-containing gas is introduced into the process chamber under the second microwave condition for 80-150s.

[0018] Optionally, in step S4, the first microwave condition is as follows: the radio frequency power is 12-16kW, the pressure is 170-210Pa and the temperature is 350-550℃. The preferred radio frequency power, pressure and temperature can completely remove the amorphous silicon layer deposited on the ceramic tube, improve the uniformity of the electric conduction of the graphite boat, improve the use stability of the graphite boat and ensure the yield of the battery.

[0019] Optionally, in step S4, the second microwave condition is as follows: the radio frequency power is 8-12kW, the pressure is 210-280Pa and the temperature is 350-550℃. The preferred radio frequency power, pressure and temperature can drive the plasma to produce a vertical graphite boat sheet direction bombardment effect, accelerate the reaction rate, make the etching more uniform and complete, thereby improving the cleaning quality; at the same time, the etching thickness can be accurately controlled, the prepared tunneling oxidation passivation layer is prevented from being damaged, the uniformity and passivation effect of the tunneling oxidation passivation layer are ensured.

[0020] In a second aspect, the present application further provides a preparation method of a TOPCon battery, which comprises the above preparation method of the tunneling oxidation passivation layer.

[0021] In a third aspect, the present application further provides a TOPCon battery prepared by the above preparation method of the TOPCon battery. DETAILED DESCRIPTION

[0022] In order to make the purpose, technical scheme and advantages of the present application clearer, the present application is further described in detail below with reference to examples. It should be understood that the specific examples described herein are only used to explain the present application and do not limit the present application.

[0023] Example 1

[0024] The embodiment of the present application provides a preparation method of a tunneling oxide passivation layer, which comprises the following steps:

[0025] S1, placing a graphite boat loaded with silicon wafers into a process chamber of a PECVD device, performing vacuumizing treatment, and heating to 400 DEG C, then using nitrogen to blow, after blowing is completed, performing vacuumizing treatment again;

[0026] S2, introducing oxygen into the process chamber, controlling the gas flow to be 100 sccm, and the time length to be 70 s, depositing a silicon oxide layer on the silicon wafer to prepare a tunneling oxide layer;

[0027] S3, introducing silane into the process chamber and starting a microwave, controlling the gas flow to be 300 sccm and the time length to be 120 s, depositing a polysilicon layer on the tunneling oxide layer to prepare a tunneling oxide passivation layer, after film plating is completed, performing vacuumizing treatment in the process chamber, then using nitrogen to blow, after blowing is completed, performing vacuumizing treatment again;

[0028] S4, introducing oxygen into the process chamber for 120 s and starting a microwave, controlling the temperature to be 450 DEG C, the gas flow to be 900 sccm, the radio frequency power to be 14 kW and the pressure to be 190 Pa, then performing vacuumizing treatment in the process chamber, then using nitrogen to blow, after blowing is completed, performing vacuumizing treatment again;

[0029] S5, introducing hydrogen fluoride gas into the process chamber for 120 s and starting a microwave, controlling the temperature to be 450 DEG C, the gas flow to be 800 sccm, the radio frequency power to be 10 kW and the pressure to be 250 Pa, then performing vacuumizing, nitrogen blowing and vacuumizing treatment in sequence, and taking out the graphite boat.

[0030] Embodiment 2

[0031] The embodiment of the present application provides a preparation method of a tunneling oxide passivation layer, which comprises the following steps:

[0032] S1, placing a graphite boat loaded with silicon wafers into a process chamber of a PECVD device, performing vacuumizing treatment, and heating to 350 DEG C, then using nitrogen to blow, after blowing is completed, performing vacuumizing treatment again;

[0033] S2, introducing dinitrogen monoxide into the process chamber, controlling the gas flow to be 100 sccm, and the time length to be 70 s, depositing a silicon oxide layer on the silicon wafer to prepare a tunneling oxide layer;

[0034] S3, pass silane into the process chamber and turn on the microwave, control the gas flow to be 300sccm, the time length is 120s, deposit a polysilicon layer on the tunneling oxide layer, prepare a tunneling oxide passivation layer, after the film coating is completed, carry out vacuumizing treatment in the process chamber, then use nitrogen to blow, after the blowing is completed, carry out vacuumizing treatment again;

[0035] S4, pass ozone into the process chamber for 80s, and turn on the microwave, control the temperature to be 350 DEG C, the gas flow to be 600sccm, the radio frequency power to be 12kW, and the pressure to be 170Pa, then carry out vacuumizing treatment in the process chamber, then use nitrogen to blow, after the blowing is completed, carry out vacuumizing treatment again;

[0036] S5, pass hydrogen fluoride gas into the process chamber for 85s, and turn on the microwave, control the temperature to be 550 DEG C, the gas flow to be 500sccm, the radio frequency power to be 8kW, and the pressure to be 210Pa, then carry out vacuumizing, nitrogen blowing and vacuumizing treatment in sequence, and take out the boat.

[0037] Example 3

[0038] The embodiment of the application provides a preparation method of a tunneling oxide passivation layer, which comprises the following steps:

[0039] S1, place a graphite boat loaded with a silicon wafer into a process chamber of a PECVD device, carry out vacuumizing treatment, and heat to 550 DEG C, then use nitrogen to blow, after the blowing is completed, carry out vacuumizing treatment;

[0040] S2, pass nitrogen carrying pure water vapor into the process chamber, control the gas flow to be 100sccm, and the time length is 120s, deposit a silicon oxide layer on the silicon wafer, and prepare a tunneling oxide layer;

[0041] S3, pass silane into the process chamber and turn on the microwave, control the gas flow to be 300sccm, the time length is 120s, deposit a polysilicon layer on the tunneling oxide layer, prepare a tunneling oxide passivation layer, after the film coating is completed, carry out vacuumizing treatment in the process chamber, then use nitrogen to blow, after the blowing is completed, carry out vacuumizing treatment again;

[0042] S4, pass oxygen into the process chamber for 150s, and turn on the microwave, control the temperature to be 550 DEG C, the gas flow to be 1200sccm, the radio frequency power to be 16kW, and the pressure to be 210Pa, then carry out vacuumizing treatment in the process chamber, then use nitrogen to blow, after the blowing is completed, carry out vacuumizing treatment again;

[0043] S5, hydrogen fluoride gas or fluorinated sulfur gas is introduced into the process chamber for 150s, and the microwave is turned on, the temperature is controlled at 350 DEG C, the gas flow is 1000sccm, the radio frequency power is 12kW, the pressure is 280Pa, and then vacuumizing, nitrogen purging and vacuumizing are sequentially performed, and the boat is taken out.

[0044] Example 4

[0045] The embodiment of the present application provides a preparation method of a tunneling oxide passivation layer, a TOPCon battery and a preparation method, which is different from the embodiment 1 in that, in the step S4, the radio frequency power is 10kW.

[0046] Example 5

[0047] The embodiment of the present application provides a preparation method of a tunneling oxide passivation layer, a TOPCon battery and a preparation method, which is different from the embodiment 1 in that, in the step S5, the radio frequency power is 15kW.

[0048] Example 6

[0049] The embodiment of the present application provides a preparation method of a tunneling oxide passivation layer, a TOPCon battery and a preparation method, which is different from the embodiment 1 in that, in the step S5, the pressure is 180Pa.

[0050] Example 7

[0051] The embodiment of the present application provides a preparation method of a tunneling oxide passivation layer, a TOPCon battery and a preparation method, which is different from the embodiment 1 in that, in the step S5, the pressure is 300Pa.

[0052] Comparative Example 1

[0053] The comparative example of the present application provides a preparation method of a tunneling oxide passivation layer, which is different from the embodiment 1 in that, after the tunneling passivation layer is prepared, the in-situ cleaning step is not performed, and a traditional wet cleaning scheme is adopted, and the steps are as follows:

[0054] In the process of preparing the TOPCon battery, after the graphite boat is used for 60 times, the graphite boat is soaked and cleaned in a solution with a ratio of hydrofluoric acid to pure water being 1:5 for 6-8 hours, then cleaned with pure water for 6-8 hours, and dried at 150 DEG C for 6-8 hours.

[0055] Comparative Example 2

[0056] The comparative example of the present application provides a preparation method of a tunneling oxide passivation layer, which is different from the embodiment 1 in that, in the step S4, the oxygen flow is 1500sccm.

[0057] Comparative Example 3

[0058] The present application provides a preparation method of a tunneling oxide passivation layer, which is different from example 1 in that the oxygen flow is 400 sccm in step S4.

[0059] Comparative example 4

[0060] The present application provides a preparation method of a tunneling oxide passivation layer, which is different from example 1 in that the hydrogen fluoride flow is 1300 sccm in step S5.

[0061] The preparation method of the tunneling oxide passivation layer provided by examples 1-7 and comparative examples 1-4 of the present application is used to prepare TOPCon cells according to a conventional process, and the number of process failures, the proportion of unqualified products in the cycle, and the efficiency of qualified cells in the cycle (60 times of graphite boat is a cycle) are recorded.

[0062] Among them, the qualified products meet the IEC 60904-1:2020 photovoltaic cell current-voltage characteristic test standard, and the cell efficiency is > 17.9%.

[0063] The cell efficiency is tested by an IV tester under standard test conditions, and the standard test conditions are atmospheric mass AM1.5, temperature 25℃, and light intensity 1000W / m 2 .

[0064] The test data are shown in the following table:

[0065] Table 1 Process stability test data

[0066]

[0067]

[0068] Table 2 Cell efficiency data

[0069] Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Battery efficiency 25.18％ 25.16％ 25.16％ 25.14％ 25.10％ 25.13％ 25.09％ Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Battery efficiency 25.13％ 24.78％ 25.12％ 24.82％

[0070] From the data in Table 1-2, it can be seen that the proportion of unqualified products generated in the period of Comparative Example 1 is relatively large, which will cause 17% of unqualified products, and Comparative Example 1 needs additional cleaning equipment, labor and chemicals, and the cleaning time is relatively long. In summary, the cost of the traditional wet cleaning scheme is much higher than the cleaning cost of the graphite boat in the method provided by the present application. Excluding the influence of unqualified products, the efficiencies of the qualified batteries prepared by the present application and the comparative examples are compared. The battery efficiencies of Examples 1-3 and Comparative Example 1 are comparable or even better. In Example 4, the radio frequency power is lower, and in Example 6, the pressure is lower, and the cleaning effect is general, which will affect the use stability of the graphite boat and produce a certain proportion of unqualified products; in Example 5, the radio frequency power is higher, and in Example 7, the pressure is higher, which will affect the tunneling passivation layer on the surface of the silicon wafer, and further affect the battery performance; in Comparative Example 2 and Comparative Example 4, the gas flow is large, which will affect the tunneling passivation layer on the surface of the silicon wafer, and further affect the battery performance; in Comparative Example 3, the oxygen flow is small, and the amorphous silicon on the ceramic tube is not fully converted, which reduces the use stability of the graphite boat.

[0071] The above description is only the preferred embodiment of the present application, and is not intended to limit the present application. Any modification, equivalent replacement or improvement made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for preparing a tunneling oxide passivation layer, characterized in that, Includes the following steps: S1. Provide a silicon substrate and place the silicon substrate in a process chamber; S2. A first oxidizing gas is introduced into the process chamber, and a tunneling oxide layer is formed on the surface of the silicon substrate by PECVD. S3. Introduce silane into the process chamber and deposit an amorphous silicon layer on the tunneling oxide layer to obtain a tunneling oxide passivation layer. S4. After obtaining the tunneling oxide passivation layer, without removing the product, introduce a second oxidizing gas into the process chamber to oxidize the amorphous silicon attached to the surface of the ceramic tube into non-conductive silicon dioxide. Then, introduce a fluorine-containing gas to form plasma, which etches the silicon dioxide to remove the deposited film on the ceramic tube. Cool down to complete the preparation of the tunneling oxide passivation layer. The flow rate of the second oxidizing gas is 600 sccm to 1200 sccm, and the flow rate of the fluorine-containing gas is 500 sccm to 1000 sccm to ensure that the deposited film on the ceramic tube is fully removed and to avoid affecting the tunneling oxide passivation layer.

2. The method for preparing the tunneling oxide passivation layer as described in claim 1, characterized in that, The first oxidizing gas is oxygen, nitrous oxide, ozone, or nitrogen carrying pure water vapor.

3. The method for preparing the tunneling oxide passivation layer as described in claim 1, characterized in that, The second oxidizing gas is oxygen, nitrous oxide, ozone, or nitrogen carrying pure water vapor.

4. The method for preparing the tunneling oxide passivation layer as described in claim 1, characterized in that, The fluorine-containing gas is hydrogen fluoride or sulfur fluoride.

5. The method for preparing the tunneling oxide passivation layer as described in claim 1, characterized in that, In step S1, after the silicon substrate is placed in the process chamber, a vacuum is drawn and the temperature is raised to 350°C~550°C.

6. The method for preparing the tunneling oxide passivation layer as described in claim 1, characterized in that, The specific process of step S4 is as follows: under the first microwave condition, the second oxidizing gas is introduced into the process chamber for 80s~150s, and then vacuuming and nitrogen purging are performed; after purging, under the second microwave condition, fluorine-containing gas is introduced into the process chamber for 80s~150s.

7. The method for preparing the tunneling oxide passivation layer as described in claim 6, characterized in that, In step S4, the first microwave conditions are: radio frequency power of 12kW~16kW, pressure of 170Pa~210Pa, and temperature of 350℃~550℃.

8. The method for preparing the tunneling oxide passivation layer as described in claim 6, characterized in that, In step S4, the second microwave conditions are: radio frequency power of 8kW~12kW, pressure of 210Pa~280Pa, and temperature of 350℃~550℃.

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