Defluorination method and film deposition method for recovering first-round efficiency of graphite boat

Abstract

The invention provides a defluorination method and a film deposition method for recovering the first round efficiency of a graphite boat. The defluorination method comprises plasma bombardment defluorination and / or high-temperature nitrogen purging defluorination. According to the defluorination method, washing and drying are not needed, efficient defluorination is achieved, meanwhile, the time cost is reduced, use of special gas is reduced, the production cost is saved, and large-scale application and popularization are facilitated.

Description

Technical Field

[0001] The invention belongs to the technical field of battery manufacturing, and relates to a method for recovering the first-round efficiency of a graphite boat, and in particular to a defluorination method and a film deposition method for recovering the first-round efficiency of a graphite boat. Background Art

[0002] At present, in the manufacturing process of TOPCon cells, PECVD equipment is usually used to deposit tunnel oxide layers and phosphorus-doped polysilicon layers, and graphite boats are used as carriers. In the actual production process, the film is not only deposited on the surface of the silicon wafer, but also on the surface of the graphite boat carrier, and gradually thickens with the increase in the number of depositions. Since the use of PECVD for thin film deposition involves electrode discharge, these thin films deposited on the surface of the carrier will affect the electric field between the boat blades, thereby causing abnormal discharge phenomena such as short circuit and high frequency, which seriously affects the film deposition quality of the battery cell.

[0003] In order to solve the above problems, technicians usually use dry etching to remove the thin film on the surface of the graphite boat after a certain period of use. However, the surface of the graphite boat after dry cleaning will adsorb fluorine, which needs to be removed by water washing later. This is because: (1) If it is not washed and dried, the surface of the graphite boat contains fluorine and absorbs fluorine, and the efficiency of the first round after going online is low (mainly reflected in the low fill factor FF and open circuit voltage Uoc); (2) If it is not washed and dried, it will take multiple rounds of processes for the electrical performance of the battery cell to gradually recover, which consumes a lot of special gases and time, and significantly increases production costs. However, if the defluorination process is washed and dried, it will also significantly increase the time cost, and there is still much room for improvement.

[0004] It can be seen that how to provide a defluorination method for restoring the first-round efficiency of a graphite boat, while achieving efficient defluorination and reducing time costs, reducing the use of special gases, and saving production costs has become an urgent problem that technical personnel in this field need to solve. Summary of the invention

[0005] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a defluorination method and a film deposition method for restoring the first-round efficiency of a graphite boat, including plasma bombardment defluorination and / or high-temperature nitrogen purge defluorination, without the need for water washing and drying, which reduces the time cost while achieving efficient defluorination, reduces the use of special gases, saves production costs, and is conducive to large-scale promotion and application.

[0006] To achieve this object, the present invention adopts the following technical solutions:

[0007] In a first aspect, the present invention provides a defluorination method for recovering the first-round efficiency of a graphite boat, wherein the defluorination method comprises plasma bombardment defluorination and / or high-temperature nitrogen purge defluorination.

[0008] The defluorination method provided by the present invention does not require water washing and drying. It only needs to add the steps of plasma bombardment defluorination and / or high-temperature nitrogen purge defluorination during the deposition process of the plating boat to achieve efficient defluorination, restore the first-round efficiency of the graphite boat, improve the filling factor and open-circuit voltage, and at the same time reduce time cost, reduce the use of special gases, and save production costs.

[0009] In addition, plasma bombardment defluorination not only achieves the purpose of defluorination, but also the introduction of hydrogen plasma is beneficial to hydrogen passivation in subsequent processes, reducing carrier recombination and improving cell efficiency and electrical performance; plasma bombardment defluorination and / or high-temperature nitrogen purge defluorination do not require water immersion, thereby significantly extending the service life of the graphite boat, which is conducive to large-scale promotion and application.

[0010] Preferably, the plasma bombardment defluorination and / or high-temperature nitrogen purge defluorination are each independently performed in a plating boat, and saturated deposition is performed after defluorination.

[0011] Preferably, the plasma bombardment defluorination comprises: introducing H2 and / or NH3 into the furnace tube, generating hydrogen plasma through discharge to combine with fluorine on the surface of the graphite boat to achieve the defluorination effect.

[0012] Preferably, the temperature in the furnace tube is 200-600°C, for example, it can be 200°C, 250°C, 300°C, 350°C, 400°C, 450°C, 500°C, 550°C or 600°C, and the pressure is 500-2000mtorr, for example, it can be 500mtorr, 600mtorr, 700mtorr, 800mtorr, 900mtorr, 1000mtorr, 1100mtorr, 1200mtorr, 1300mtorr, 1400mtorr, 1500mtorr, 1600mtorr, 1700mtorr, 1800mtorr, 1900mtorr or 2000mtorr, but is not limited to the listed values, and other unlisted values ​​within the numerical range are equally applicable.

[0013] Preferably, the flow rate of H2 and / or NH3 is 2000-20000sccm, for example, it can be 2000sccm, 4000sccm, 6000sccm, 8000sccm, 10000sccm, 12000sccm, 14000sccm, 16000sccm, 18000sccm or 20000sccm, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0014] In the present invention, the flow rate of H2 and / or NH3 needs to be limited within a reasonable range. When the flow rate is less than 2000sccm, on the one hand, there are insufficient hydrogen molecules, and after hydrogen ionization, it is impossible to generate enough hydrogen plasma and active hydrogen ions to fully react with fluoride, resulting in a low defluorination efficiency. On the other hand, there are insufficient ammonia molecules, and it is impossible to form enough active nitrogen species (NH2, NH) to fully react with fluoride, which will also cause the defluorination efficiency to become low; when the flow rate is greater than 20000sccm, the molecular concentration in the reaction zone is too high and the ionization field energy is dispersed, which easily causes the concentration of hydrogen plasma or active nitrogen species (NH2, NH) per unit volume to decrease, thereby affecting the defluorination effect; in addition, excessive flow rate will cause gas disturbance in the reaction zone, thereby diluting or causing uneven distribution of active nitrogen species, and ultimately affecting the defluorination effect.

[0015] Preferably, the discharging is carried out using a high-frequency power supply, and the discharge power of the high-frequency power supply is 5-15kW, for example, it can be 5kW, 6kW, 7kW, 8kW, 9kW, 10kW, 11kW, 12kW, 13kW, 14kW or 15kW, and the discharge time is 10-60min, for example, it can be 10min, 15min, 20min, 25min, 30min, 35min, 40min, 45min, 50min, 55min or 60min, but it is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0016] Preferably, the high-temperature nitrogen purging defluorination includes: evacuating the furnace tube and then performing heat preservation treatment, and then introducing N2 to purge the surface of the graphite boat to achieve the defluorination effect.

[0017] Preferably, the temperature of the insulation treatment is 200-600°C, for example, it can be 200°C, 250°C, 300°C, 350°C, 400°C, 450°C, 500°C, 550°C or 600°C, and the time is 10-60min, for example, it can be 10min, 15min, 20min, 25min, 30min, 35min, 40min, 45min, 50min, 55min or 60min, but it is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0018] The present invention evacuates the furnace tube and performs heat preservation treatment before nitrogen purging, so as to gradually release the fluorine adsorbed on the surface of the graphite boat in the furnace tube, so as to facilitate the subsequent nitrogen to directly purge the released fluorine out of the furnace tube.

[0019] Preferably, the N2 flow rate is 2000-20000sccm, for example, it can be 2000sccm, 4000sccm, 6000sccm, 8000sccm, 10000sccm, 12000sccm, 14000sccm, 16000sccm, 18000sccm or 20000sccm, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0020] In the present invention, the N2 flow rate needs to be limited within a reasonable range. When the flow rate is less than 2000sccm, the dilution effect is poor, which easily leads to the inability of fluoride or volatile byproducts to be quickly discharged from the cavity, increasing the possibility of reattachment; when the flow rate is greater than 20000sccm, the gas in the cavity is updated too quickly, and the contact time with the residual fluoride is insufficient, the dilution effect is adversely affected, and the excessive flow rate easily leads to airflow disturbance in the reaction chamber, making the gas distribution in the cavity uneven, and finally the situation of insufficient fluoride removal in the local area occurs.

[0021] Preferably, during the purging process, the pressure in the furnace tube is 500-2000mtorr, for example, it can be 500mtorr, 600mtorr, 700mtorr, 800mtorr, 900mtorr, 1000mtorr, 1100mtorr, 1200mtorr, 1300mtorr, 1400mtorr, 1500mtorr, 1600mtorr, 1700mtorr, 1800mtorr, 1900mtorr or 2000mtorr, and the purging time is 30-200min, for example, it can be 30min, 40min, 60min, 80min, 100min, 120min, 140min, 160min, 180min or 200min, but it is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0022] As a preferred technical solution of the first aspect of the present invention, the defluorination method includes plasma bombardment defluorination and / or high-temperature nitrogen purge defluorination, and the defluorination method is carried out in a plating boat machine, and saturated deposition is carried out after defluorination.

[0023] The plasma bombardment defluorination comprises: introducing H2 and / or NH3 with a flow rate of 2000-20000sccm into the furnace tube, controlling the temperature in the furnace tube to 200-600°C and the pressure to 500-2000mtorr, turning on the high-frequency power supply, setting the discharge power to 5-15kW, and the discharge time to 10-60min, and generating hydrogen plasma through discharge to combine with fluorine on the surface of the graphite boat to achieve the defluorination effect.

[0024] The high-temperature nitrogen purging defluorination includes: after evacuating the furnace tube, heat preservation treatment at 200-600°C for 10-60 minutes, then introducing N2 with a flow rate of 2000-20000sccm to purge the surface of the graphite boat for 30-200 minutes, and controlling the pressure in the furnace tube during the purging process to 500-2000mtorr to achieve the defluorination effect.

[0025] The plasma bombardment defluorination and high-temperature nitrogen purge defluorination include: after evacuating the furnace tube, heat preservation treatment is carried out at 200-600°C for 10-60min, then N2 with a flow rate of 2000-20000sccm is introduced to purge the surface of the graphite boat for 30-200min, and the pressure in the furnace tube is controlled to be 500-2000mtorr during the purge process, the introduction of N2 is stopped, and after evacuating the furnace tube again, H2 and / or NH3 with a flow rate of 2000-20000sccm is introduced into the furnace tube, and the temperature in the furnace tube is controlled to be 200-600°C and the pressure is controlled to be 500-2000mtorr, the high-frequency power supply is turned on, the discharge power is set to 5-15kW, and the discharge time is 10-60min, and hydrogen plasma is generated by discharge to combine with fluorine on the surface of the graphite boat to achieve the defluorination effect.

[0026] In a second aspect, the present invention provides a film deposition method, which comprises the defluorination method as described in the first aspect.

[0027] The numerical range described in the present invention not only includes the point values ​​listed above, but also includes any point values ​​between the above numerical ranges that are not listed. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] (1) The defluorination method provided by the present invention does not require water washing and drying. It only needs to add the steps of plasma bombardment defluorination and / or high-temperature nitrogen purge defluorination during the deposition process of the plating boat to achieve efficient defluorination, restore the first-round efficiency of the graphite boat, improve the filling factor and open-circuit voltage, and at the same time reduce time cost, reduce the use of special gases, and save production costs.

[0030] (2) Plasma bombardment defluorination not only achieves the purpose of defluorination, but also introduces hydrogen ions, which is beneficial to hydrogen passivation in subsequent processes, reduces carrier recombination, and improves cell efficiency and electrical performance; plasma bombardment defluorination and / or high-temperature nitrogen purge defluorination do not require water immersion, thereby significantly extending the service life of the graphite boat, which is conducive to large-scale promotion and application. DETAILED DESCRIPTION

[0031] The technical solution of the present invention is further illustrated below through specific implementation methods.

[0032] Example 1

[0033] This embodiment provides a film deposition method, which includes plasma bombardment defluorination and high-temperature nitrogen purge defluorination, as shown in Table 1, and specifically includes the following steps:

[0034] (1) Send the cleaned graphite boat into the furnace tube of the boat plating machine;

[0035] (2) Execute the temperature raising step, raise the furnace temperature to 400°C, and keep it at this temperature until the process is completed;

[0036] (3) After the heating is completed, the furnace tube is evacuated;

[0037] (4) Keeping the temperature under vacuum for 30 min to provide energy for the desorption of fluorine-containing substances on the surface of the graphite boat;

[0038] (5) N2 with a flow rate of 10000 sccm was introduced to purge the surface of the graphite boat for 100 min, and the pressure in the furnace tube was controlled to be 1200 mtorr during the purge process to achieve the defluorination effect;

[0039] (6) Stop introducing N2, re-evacuate the furnace tube and check for leaks. After the leak check is completed, re-evacuate the furnace tube;

[0040] (7) NH3 at a flow rate of 10000 sccm was introduced into the furnace tube, and the pressure in the furnace tube was controlled to be 1200 mtorr, the high-frequency power supply was turned on, the discharge power was set to 10 kW, and the discharge time was 30 min. The hydrogen plasma generated by the discharge combined with the fluorine on the surface of the graphite boat to achieve the defluorination effect;

[0041] (8) After defluorination is completed, the furnace tube is re-evacuated;

[0042] (9) Carry out saturated deposition according to the conditions in Table 1, and then blow, evacuate, and break out of the boat in sequence.

[0043] Table 1

[0044]

[0045] Example 2

[0046] This embodiment provides a film deposition method, including high-temperature nitrogen purge defluorination, as shown in Table 2, specifically including the following steps:

[0047] (1) Send the cleaned graphite boat into the furnace tube of the boat plating machine;

[0048] (2) Execute the temperature raising step, raise the furnace temperature to 200°C, and keep it at this temperature until the process is finished;

[0049] (3) After the heating is completed, the furnace tube is evacuated;

[0050] (4) Keeping the temperature under vacuum for 60 min to provide energy for the desorption of fluorine-containing substances on the surface of the graphite boat;

[0051] (5) N2 with a flow rate of 20,000 sccm was introduced to purge the surface of the graphite boat for 30 minutes, and the pressure in the furnace tube was controlled to be 500 mtorr during the purge process to achieve the defluorination effect;

[0052] (6) Stop introducing N2, re-evacuate the furnace tube and check for leaks. After the leak check is completed, re-evacuate the furnace tube;

[0053] (7) Carry out saturated deposition according to the conditions in Table 2, and then blow, evacuate, and break out of the boat in sequence.

[0054] Table 2

[0055]

[0056] Example 3

[0057] This embodiment provides a film deposition method, including plasma bombardment defluorination, as shown in Table 3, specifically including the following steps:

[0058] (1) Send the cleaned graphite boat into the furnace tube of the boat plating machine;

[0059] (2) Execute the temperature raising step, raise the furnace temperature to 600°C, and keep it at this temperature until the process is completed;

[0060] (3) After the heating is completed, the furnace tube is evacuated;

[0061] (4) Re-evacuate after leak detection;

[0062] (5) NH3 at a flow rate of 20000 sccm was introduced into the furnace tube, and the pressure in the furnace tube was controlled to be 2000 mtorr, the high-frequency power supply was turned on, the discharge power was set to 5 kW, and the discharge time was set to 60 min. The hydrogen plasma generated by the discharge combined with the fluorine on the surface of the graphite boat to achieve the defluorination effect;

[0063] (6) After defluorination is completed, the furnace tube is re-evacuated;

[0064] (7) Carry out saturated deposition according to the conditions in Table 3, and then blow, evacuate, and break out of the boat in sequence.

[0065] Table 3

[0066]

[0067] Example 4

[0068] This embodiment provides a film deposition method. Except for changing the N2 flow rate in step (5) to 2000 sccm, the remaining steps and conditions are the same as those in Example 2 and are not described in detail here.

[0069] Example 5

[0070] This embodiment provides a film deposition method. Except for changing the N2 flow rate in step (5) to 1000 sccm, the remaining steps and conditions are the same as those in Example 2 and are not described in detail here.

[0071] Example 6

[0072] This embodiment provides a film deposition method. Except for changing the flow rate of NH3 in step (5) to 2000 sccm, the remaining steps and conditions are the same as those in Example 3 and are not described in detail here.

[0073] Example 7

[0074] This embodiment provides a film deposition method. Except for changing the flow rate of NH3 in step (5) to 10000 sccm, the remaining steps and conditions are the same as those in Example 3 and are not described in detail here.

[0075] Example 8

[0076] This embodiment provides a film deposition method. Except that the introduction of NH3 in step (7) is replaced by the introduction of H2, the remaining steps and conditions are the same as those in Example 1 and are not described in detail here.

[0077] Example 9

[0078] This embodiment provides a film deposition method. Except that the introduction of NH3 in step (5) is replaced by the introduction of H2, the remaining steps and conditions are the same as those in Example 3 and are not described in detail here.

[0079] Example 10

[0080] This embodiment provides a film deposition method. Except for changing the H2 flow rate in step (5) to 2000 sccm, the remaining steps and conditions are the same as those in Example 9 and are not described in detail here.

[0081] Comparative Example 1

[0082] This comparative example provides a film deposition method, which includes washing and drying a graphite boat for defluorination, and specifically includes the following steps:

[0083] (1) Immerse the dry-cleaned graphite boat in a high-purity water tank;

[0084] (2) Use bubbling and ultrasonic assisted cleaning, and high-purity water cleaning for 2 hours;

[0085] (3) After cleaning, dry in a drying oven at 200°C for 2 hours.

[0086] Performance Testing

[0087] The conversion efficiency Eta, open circuit voltage Uoc and fill factor FF of the battery cells obtained by the film deposition method described in Examples 1-10 and Comparative Example 1 were tested. The test results of the battery cells obtained in Example 1 were used as the standard values. The corresponding differences of the remaining examples and comparative examples are shown in Table 4 below.

[0088] Table 4

[0089] Battery Cell ΔEta ΔUoc ΔFF Example 1 0 0 0 Example 2 -0.070％ -0.0003 -0.169 Example 3 -0.008％ -0.0002 -0.086 Example 4 -0.096％ -0.0006 -0.187 Example 5 -0.112％ -0.0009 -0.201 Example 6 -0.024％ -0.0008 -0.121 Example 7 -0.012％ -0.0006 -0.105 Example 8 -0.002％ 0 -0.002 Example 9 -0.007％ -0.0003 -0.078 Example 10 -0.011％ -0.0005 -0.098 Comparative Example 1 -0.248％ -0.0020 -0.326

[0090] It can be seen that the defluorination method provided by the present invention does not require water washing and drying. It only needs to add the steps of plasma bombardment defluorination and / or high-temperature nitrogen purge defluorination during the deposition process of the plating boat to achieve efficient defluorination, restore the first-round efficiency of the graphite boat, improve the filling factor and open-circuit voltage, and at the same time reduce time cost, reduce the use of special gases, and save production costs.

[0091] In addition, plasma bombardment defluorination not only achieves the purpose of defluorination, but also introduces hydrogen ions, which is beneficial to hydrogen passivation in subsequent processes, reduces carrier recombination, and improves cell efficiency and electrical performance; plasma bombardment defluorination and / or high-temperature nitrogen purge defluorination do not require water immersion, thereby significantly extending the service life of the graphite boat, which is conducive to large-scale promotion and application.

[0092] The specific embodiments described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A defluorination method for recovering the first-round efficiency of a graphite boat, characterized in that: The defluorination method includes plasma bombardment defluorination and / or high-temperature nitrogen purge defluorination.

2. The defluorination method according to claim 1, characterized in that: The plasma bombardment defluorination and / or high-temperature nitrogen purge defluorination are performed independently in a plating boat, and saturated deposition is performed after defluorination.

3. The defluorination method according to claim 1 or 2, characterized in that: The plasma bombardment defluorination comprises: introducing H2 and / or NH3 into the furnace tube, generating hydrogen plasma through discharge and combining with fluorine on the surface of the graphite boat to achieve the defluorination effect.

4. The defluorination method according to claim 3, characterized in that: The temperature in the furnace tube is 200-600°C and the pressure is 500-2000mtorr; Preferably, the flow rate of H2 and / or NH3 is 2000-20000sccm.

5. The defluorination method according to claim 3 or 4, characterized in that: The discharge is performed using a high-frequency power supply, and the discharge power of the high-frequency power supply is 5-15 kW, and the discharge time is 10-60 minutes.

6. The defluorination method according to claim 1 or 2, characterized in that: The high-temperature nitrogen purging defluorination includes: evacuating the furnace tube and then performing heat preservation treatment, and then introducing N2 to purge the surface of the graphite boat to achieve the defluorination effect.

7. The defluorination method according to claim 6, characterized in that: The temperature of the heat preservation treatment is 200-600°C and the time is 10-60min; Preferably, the N2 flow rate is 2000-20000sccm.

8. The defluorination method according to claim 6 or 7, characterized in that: During the purging process, the pressure in the furnace tube is 500-2000 mtorr, and the purging time is 30-200 min.

9. The defluorination method according to any one of claims 1 to 8, characterized in that: The defluorination method includes plasma bombardment defluorination and / or high-temperature nitrogen purge defluorination, and the defluorination method is carried out in a plating boat machine, and saturated deposition is carried out after defluorination; The plasma bombardment defluorination comprises: introducing H2 and / or NH3 with a flow rate of 2000-20000sccm into the furnace tube, controlling the temperature in the furnace tube to 200-600°C and the pressure to 500-2000mtorr, turning on the high-frequency power supply, setting the discharge power to 5-15kW, and the discharge time to 10-60min, and generating hydrogen plasma through discharge to combine with fluorine on the surface of the graphite boat to achieve the defluorination effect; The high-temperature nitrogen purge defluorination includes: after evacuating the furnace tube, heat preservation treatment at 200-600°C for 10-60min, then introducing N2 with a flow rate of 2000-20000sccm to purge the surface of the graphite boat for 30-200min, and controlling the pressure in the furnace tube to 500-2000mtorr during the purge process to achieve the defluorination effect; The plasma bombardment defluorination and high-temperature nitrogen purge defluorination include: after evacuating the furnace tube, heat preservation treatment is carried out at 200-600°C for 10-60min, then N2 with a flow rate of 2000-20000sccm is introduced to purge the surface of the graphite boat for 30-200min, and the pressure in the furnace tube is controlled to be 500-2000mtorr during the purge process, the introduction of N2 is stopped, and after evacuating the furnace tube again, H2 and / or NH3 with a flow rate of 2000-20000sccm is introduced into the furnace tube, and the temperature in the furnace tube is controlled to be 200-600°C and the pressure is controlled to be 500-2000mtorr, the high-frequency power supply is turned on, the discharge power is set to 5-15kW, and the discharge time is 10-60min, and hydrogen plasma is generated by discharge to combine with fluorine on the surface of the graphite boat to achieve the defluorination effect.

10. A film deposition method, characterized in that: The film deposition method comprises the defluorination method as described in any one of claims 1 to 9.

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