CN115954406A - Microwave plasma dry etching process for cleaning graphite boat for photovoltaic production - Google Patents
Microwave plasma dry etching process for cleaning graphite boat for photovoltaic production Download PDFInfo
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- CN115954406A CN115954406A CN202211258757.1A CN202211258757A CN115954406A CN 115954406 A CN115954406 A CN 115954406A CN 202211258757 A CN202211258757 A CN 202211258757A CN 115954406 A CN115954406 A CN 115954406A
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Abstract
The invention discloses a microwave plasma dry etching process for cleaning a graphite boat for photovoltaic production, which comprises the steps of inputting plasma generated by the action of a remote microwave plasma system into a process cavity with the built-in graphite boat, applying an alternating electric field generated by a radio frequency power supply to the graphite boat in the process cavity, and driving the plasma to bombard the graphite boat through the alternating electric field to remove a film deposited on the graphite boat. The invention can overcome the defect of performing a wet cleaning process on the graphite boat in the traditional solar cell manufacturing process, adopts a microwave plasma dry etching process to thoroughly replace the traditional wet cleaning process, brings great convenience, greatly reduces the cost, accelerates the efficiency, is more energy-saving and environment-friendly, and occupies less land.
Description
Technical Field
The invention relates to graphite boat cleaning in a photovoltaic solar cell production process, in particular to a microwave plasma dry etching process for cleaning a graphite boat for photovoltaic production.
Background
In the current production process of solar silicon-based cells, a PECVD process (Plasma Enhanced Chemical Vapor Deposition) is widely used to deposit various process films, i.e., a Plasma Enhanced Chemical Vapor Deposition method. The PECVD process is divided into the following steps according to different deposited films: 1) Reduction of conventional cell surfaceA silicon nitride film (SiNx) as a reflective film; 2) PERC Cell (Passivated Emitter and reader Cell), meaning the aluminum oxide (Al) in a "Passivated Emitter and Rear contact" solar Cell 2 O 3 ) And a silicon nitride (SiNx) composite film or a silicon oxynitride (SiNO) film; 3) Amorphous thin film in TOPcon (Tunnel Oxide Passivated Contact) solar cell.
In the use of PECVD, a graphite boat is used as a tool carrier. The graphite boat mainly plays a role in carrying silicon wafers, electrifying and promoting plasma glow discharge in the process to generate process reaction. In addition, in the reaction, the graphite boat is deposited with a film generated by the reaction, and in the repeated use, the film is deposited to be thicker and thicker, so that the conductivity of the graphite boat is influenced, and the process quality of the deposited film is influenced. Therefore, the graphite boat has a certain service life, and needs to be cleaned to remove various byproduct films deposited on the surface.
At present, the conventional process for cleaning the graphite boat is to use HF solution with a certain proportion (25% +/-5%) to soak and clean the graphite boat, then use DI (deionized water) to rinse the graphite boat, and finally dry the graphite boat in an oven, wherein the time of each process is about 8 +/-2 hours, that is to say, the time for cleaning one graphite boat by a complete wet method is about 24 hours.
The prior art has four disadvantages that the prior art adopts a wet cleaning process for cleaning graphite boats:
1. the cleaning time is too long, about 24 hours are needed for cleaning one graphite boat by a wet method until the graphite boat is dried, so that enterprises need to purchase more graphite boats for turnover, and high cost is brought;
2. the cost is high, and mainly comprises 1) chemical cost, 2) energy consumption cost and pure water cost, 3) labor cost, and 4) because the cleaning time is long, an enterprise generally needs to buy about 2 times of the actual consumption of the graphite boat for circulation;
we illustrate the following cleaning of graphite boats in a 10GW solar plant PERC line:
3. under the environmental protection pressure, wet cleaning is difficult to implement in partial areas and factories;
4. the occupied area is large, and the occupied area of the cleaning, storage, drying equipment and the like of a 10GW solar cell factory is about 600 square meters.
Disclosure of Invention
In order to solve the defects of the prior art, the invention provides a microwave plasma dry etching process for cleaning a graphite boat for photovoltaic production, wherein plasma generated by the action of a remote microwave plasma system (RPS) is input into a process cavity with the built-in graphite boat, an alternating electric field generated by a radio frequency power supply is applied to the graphite boat in the process cavity, the plasma is driven by the alternating electric field to bombard the graphite boat, plasma gas groups are adsorbed on the surface of a graphite flake in a matching manner, and a chemical reaction (CVD) is generated with a surface film layer, so that the film deposited on the graphite boat is removed finally.
The specific contents of the process system, the process steps and the like of the invention are shown in the examples.
The invention has the advantages and beneficial effects that: the invention can overcome the defect of performing a wet cleaning process on the graphite boat in the traditional solar cell manufacturing process, adopts a microwave plasma dry etching process to thoroughly replace the traditional wet cleaning process, brings great convenience, greatly reduces the cost, accelerates the efficiency, is more energy-saving and environment-friendly, and occupies less land.
The process aims at cleaning the graphite boat, and the plasma scheme in the process is a combined improvement scheme of microwave and high frequency. The technological scheme of the present invention is mainly the combination of microwave RPS ion source and 40KHZ high frequency power supply. The microwave RPS mainly has the functions of generating plasma, applying a 40KHZ high-frequency power supply to the graphite boat, and adding an alternating electric field to the graphite boat to drive the plasma to generate a bombardment effect vertical to the direction of the graphite boat sheet, so as to accelerate the reaction rate.
The invention relates to a microwave plasma dry etching process special for cleaning a graphite boat in a solar cell manufacturing process. Aiming at the special structure of the graphite boat, the invention specially designs a process system; different from the traditional plate type PECVD equipment, the equipment adopts a mode of combining microwave and high frequency, which is the most core part. From the point of view of the generation of the ion source, it belongs to microwave excited plasma, which is a separate RPS system (remote microwave plasma system), but from the point of view of using the graphite boat itself as the electrode capacitance, it is similar to CCP, and it should be said that the advantages of both are combined. If only microwave RPS ion source is introduced, the surface of the graphite boat only has anisotropic CVD reaction. However, a CCP structure in which discharge occurs between adjacent graphite boats is formed under the application of a high-frequency power source. This greatly increases the physical bombardment effect perpendicular to the surface of the graphite boat piece, which is the key to the practical mass production of the process.
The process of the invention greatly saves the process flow of cleaning the graphite boat at present, saves energy consumption, reduces emission, saves the turnover number of the graphite boat, and reduces the overall cost.
Drawings
FIG. 1 is a schematic view of a graphite boat;
FIG. 2 is a schematic diagram of a process system of the present invention.
Detailed Description
The following description of the embodiments of the present invention will be made with reference to the accompanying drawings. The following examples are only for illustrating the technical solutions of the present invention more clearly, and the protection scope of the present invention is not limited thereby.
As shown in figure 1, the graphite boat to be cleaned in the invention comprises a graphite boat sheet fixed by a ceramic rod and a nut, and the graphite boat is provided with electrode holes. The film to be cleaned is mainly attached to the graphite boat piece. The films deposited on the graphite boat were: a silicon nitride film, a composite film of aluminum oxide and silicon nitride, or an amorphous silicon film.
The invention provides a microwave plasma dry etching process for cleaning a graphite boat for photovoltaic production, which is characterized in that a process cavity with the built-in graphite boat is input with plasma generated under the action of a remote microwave plasma system (RPS), an alternating electric field generated by a radio frequency power supply is applied to the graphite boat in the process cavity, and the plasma is driven by the alternating electric field to bombard the graphite boat, so that a film deposited on the graphite boat is removed.
As shown in fig. 2, the process system of the present invention comprises: the device comprises a process cavity (an aluminum cavity), a gas supply system connected with the process cavity through a gas supply pipeline, a gas flow controller arranged on the gas supply pipeline, a vacuum pumping system (comprising a dry pump), a nitrogen backfilling system, a pressure control system, a central control system, a tail gas treatment system (comprising a combustion tower) and a remote microwave plasma system (RPS) which are matched with the process cavity;
the remote microwave plasma system (RPS) comprises, connected in sequence: the plasma chamber comprises a direct current power supply, a 2.45GHz microwave power source, a waveguide assembly, an isolator, a waveguide assembly and a plasma chamber arranged on an air supply pipeline;
the gas supply system supplies process gas to the gas supply pipeline, and the process gas forms plasma when passing through the plasma chamber and enters the process chamber.
More specifically, as shown in fig. 2, the process chamber of the present invention further comprises: and the insulating plate is used for placing the graphite boat. The graphite boat was placed on an insulating plate. And applying a 40KHZ radio frequency power supply to the graphite boat electrode holes.
The ion source of the present invention employs RPS (solid state remote microwave plasma system), which is distinguished from conventional CCP dry etching. In the use process of the RPS, a direct current power supply and a microwave power source generate microwaves with specific frequency, the frequency of 2.45GHZ is used, and the microwaves are fed into a plasma cavity through a waveguide transmission component, an isolator and the like; the process gas enters the plasma cavity through the gas inlet on the plasma cavity, excites the plasma under the action of the microwave, enters the process cavity from the plasma cavity outlet and acts on the graphite boat.
In the process chamber, the temperature is normal temperature, the pressure is 20pa-500pa, the process gas adopts fluorine-containing gas or mixed gas of fluorine-containing gas and oxygen, and the fluorine-containing gas is selected from CF 4 、CHF 3 、SF 6 、NF 3 、C 2 F 6 One or more of the above; introducing process gas into a plasma cavity, generating plasma under 2.45GHz microwave, then directly introducing the process gas into the process cavity, reacting with a film on the surface of a graphite boat under a 40KHZ high-frequency electric field loaded by the graphite boat to generate silicon tetrafluoride and nitrogen gas, pumping waste gas away by a dry pump, backfilling the process cavity with nitrogen after the reaction is finished, and taking out the graphite boat.
More specifically, the method comprises the following specific steps:
1) Feeding the graphite boat into a process cavity through automatic equipment, and then sealing the process cavity, wherein the interior of the process cavity is at normal temperature and normal pressure;
2) Then, vacuumizing the process cavity by a vacuum pumping system (comprising a dry pump) until the vacuum pressure reaches a preset pressure (such as 20 pa) and keeping for a certain time (such as 20 seconds); if the pressure can be kept, judging that the process cavity has no leakage point, and performing subsequent steps; if the pressure cannot be kept, judging that the process cavity needs to be subjected to leak detection, and not performing the subsequent steps;
3) Then starting a gas supply system to supply process gas, starting a remote microwave plasma system, introducing plasma into the process cavity, starting a radio frequency power supply, adjusting the pressure in the process cavity to be process pressure (such as 200 pa), and adjusting glow time according to the thickness of the film to be etched and removed on the graphite boat until the film on the surface of the graphite boat is completely removed;
4) Then closing the remote microwave plasma system and the radio frequency power supply, maintaining the process cavity to be vacuumized for a certain time (such as 3 minutes), and then backfilling nitrogen into the process cavity until the process cavity recovers the normal pressure state; then dragging the graphite boat out of the process cavity through automatic equipment; and the tail gas extracted from the process chamber is sent to a tail gas treatment system (comprising a combustion tower) for treatment.
More specifically, in step 3):
if the film deposited on the graphite boat is a silicon nitride film, CF is used as the process gas 4 And CHF 3 (SF may also be used) 6 、NF 3 、CF 4 /O 2 、C 2 F 6 /O 2 Etc.);
if the film deposited on the graphite boat is a composite film of aluminum oxide and silicon nitride, NF is adopted as the process gas 3 And CHF 3 (SF may also be used) 6 、NF 3 、CF 4 /O 2 、C 2 F 6 /O 2 Etc.);
if the film deposited on the graphite boat is amorphous silicon film, the process gas adopts CF 4 And SF 6 (NF may also be used) 3 、CF 4 /O 2 、C 2 F 6 /O 2 Etc.).
Compared with the existing wet cleaning process, the process of the invention has obvious advantages. We list the dry etch cleaning cost analysis in the PERC line of a 10GW solar cell plant.
The difference between the comparative dry etching process and the wet cleaning process is still exemplified in four aspects:
the invention has larger reduction range of the cleaning cost of the graphite boat in the TOPcon process and the reduction range of the graphite boat in the PERC battery, mainly because the graphite boat coating of the poly process in the TOPcon process is thicker and the consumption of chemicals is larger. As can be seen from the above data, it is clear that plasma dry etching has an incomparable great advantage over wet cleaning.
The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the technical principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.
Claims (8)
1. A microwave plasma dry etching process for cleaning a graphite boat for photovoltaic production is characterized in that plasma generated by the action of a remote microwave plasma system is input into a process cavity with the built-in graphite boat, an alternating electric field generated by a radio frequency power supply is applied to the graphite boat in the process cavity, and the plasma is driven by the alternating electric field to bombard the graphite boat, so that a film deposited on the graphite boat is removed.
2. The microwave plasma dry etching process for cleaning the graphite boat for photovoltaic production according to claim 1, wherein the remote microwave plasma system comprises a direct current power supply, a microwave power supply, a waveguide component, an isolator, a waveguide component and a plasma cavity which are connected in sequence;
the plasma is generated by a process gas as it passes through a plasma chamber;
the process gas is supplied by a gas supply system; the gas supply system is connected with the process cavity through a gas supply pipeline; the gas supply pipeline is provided with a gas flow controller; the plasma chamber is also arranged on the gas supply pipeline;
the process cavity is also provided with a vacuum pumping system, a nitrogen backfilling system, a pressure control system, a central control system and a tail gas treatment system.
3. The microwave plasma dry etching process for cleaning the graphite boat for photovoltaic production as claimed in claim 2, wherein the microwave power source is a microwave power source of 2.45 GHZ.
4. The microwave plasma dry etching process for cleaning the graphite boat for photovoltaic production as claimed in claim 2, wherein the process chamber further comprises: the insulating plate is used for placing the graphite boat;
the graphite boat is placed on the insulating plate;
the radio frequency power supply directly acts on the electrode holes of the graphite boat.
5. The microwave plasma dry etching process for cleaning the graphite boat for photovoltaic production according to claim 4, wherein the RF power source directly acting on the electrode hole of the graphite boat is a 40KHZ RF power source.
6. The microwave plasma dry etching process for cleaning the graphite boat for photovoltaic production according to any one of claims 2 to 5, characterized by comprising the following specific steps:
1) Feeding the graphite boat into a process cavity through automatic equipment, and then sealing the process cavity, wherein the interior of the process cavity is at normal temperature and normal pressure;
2) Then, vacuumizing the process cavity through a vacuum pumping system until the vacuum pressure reaches a preset pressure, and keeping for a certain time; if the pressure can be kept, judging that the process cavity has no leakage point, and performing subsequent steps; if the pressure cannot be kept, judging that the process cavity needs to be subjected to leak detection, and not performing the subsequent steps;
3) Then starting a gas supply system to supply process gas, starting a remote microwave plasma system, introducing plasma into the process cavity, starting a radio frequency power supply, adjusting the pressure in the process cavity to process pressure, and adjusting glow time according to the thickness of the film to be etched and removed on the graphite boat until the film on the surface of the graphite boat is removed;
4) Then closing the remote microwave plasma system and the radio frequency power supply, maintaining the process cavity to be vacuumized for a certain time, and then backfilling nitrogen into the process cavity until the process cavity recovers to the normal pressure state; then dragging the graphite boat out of the process cavity through automatic equipment; and the tail gas pumped out from the process cavity is sent into a tail gas treatment system for treatment.
7. The microwave plasma dry etching process for cleaning the graphite boat for photovoltaic production as claimed in claim 6, wherein the process gas is fluorine-containing gas or a mixed gas of fluorine-containing gas and oxygen.
8. The method of claim 7 for cleaning the graphite boat for photovoltaic productionThe plasma dry etching process is characterized in that the fluorine-containing gas is selected from CF 4 、CHF 3 、SF 6 、NF 3 、C 2 F 6 One or more of them.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202211258757.1A CN115954406A (en) | 2022-10-14 | 2022-10-14 | Microwave plasma dry etching process for cleaning graphite boat for photovoltaic production |
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| CN202211258757.1A CN115954406A (en) | 2022-10-14 | 2022-10-14 | Microwave plasma dry etching process for cleaning graphite boat for photovoltaic production |
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| CN202211258757.1A Withdrawn CN115954406A (en) | 2022-10-14 | 2022-10-14 | Microwave plasma dry etching process for cleaning graphite boat for photovoltaic production |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN116251803A (en) * | 2023-04-12 | 2023-06-13 | 东莞市晟鼎精密仪器有限公司 | Graphite boat cleaning equipment for cleaning silicon nitride coating based on microwave plasma dry method |
| CN116550689A (en) * | 2023-04-27 | 2023-08-08 | 东莞市晟鼎精密仪器有限公司 | Process for removing silicon nitride coating of graphite boat by dry method |
-
2022
- 2022-10-14 CN CN202211258757.1A patent/CN115954406A/en not_active Withdrawn
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN116251803A (en) * | 2023-04-12 | 2023-06-13 | 东莞市晟鼎精密仪器有限公司 | Graphite boat cleaning equipment for cleaning silicon nitride coating based on microwave plasma dry method |
| CN116251803B (en) * | 2023-04-12 | 2023-09-22 | 东莞市晟鼎精密仪器有限公司 | Graphite boat cleaning equipment for cleaning silicon nitride coating based on microwave plasma dry method |
| CN116550689A (en) * | 2023-04-27 | 2023-08-08 | 东莞市晟鼎精密仪器有限公司 | Process for removing silicon nitride coating of graphite boat by dry method |
| CN116550689B (en) * | 2023-04-27 | 2024-02-09 | 东莞市晟鼎精密仪器有限公司 | Process for removing silicon nitride coating of graphite boat by dry method |
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Application publication date: 20230411 |