CN118553594B - A graphite boat cleaning device and method based on straight rod antenna ICP - Google Patents

Abstract

The present invention provides a graphite boat cleaning device and method based on a straight-rod antenna ICP, in the field of graphite boat cleaning technology, to solve the technical problem that in the prior art, if a spiral coil or a planar coil is used for the large-area and large-volume application of ICP for cleaning a graphite boat, the overall inductance of the coil will be huge and it will be difficult to match the mainstream radio frequency power supply; a graphite boat cleaning device based on a straight-rod antenna ICP comprises a reaction chamber, a reaction cavity is provided in the reaction chamber, a bias electrode plate is provided in the reaction cavity, an insulating block for placing the graphite boat is provided on the bias electrode plate, a plurality of straight-rod electrodes are connected in the reaction chamber, the length direction of each straight-rod electrode is vertical to the length direction of the graphite boat in space, and the plurality of straight-rod electrodes are connected in parallel to form a single-comb type, a double-comb type, a U-type, or a combination of a double-comb type and a U-type layout; and also relates to a graphite boat cleaning method based on a straight-rod antenna ICP, using the above-mentioned graphite boat cleaning device.

Description

A graphite boat cleaning device and method based on straight rod antenna ICP

Technical Field

The invention relates to the technical field of graphite boat cleaning, and in particular to a graphite boat cleaning device and method based on a straight rod antenna ICP.

Background Art

In the production process of TOPCon solar cells, its tunneling oxide layer ultra-thin silicon oxide (SiOx) and highly doped polycrystalline silicon (poly-Si) are usually prepared by tubular plasma enhanced chemical vapor deposition equipment (commonly known as tubular PECVD equipment). In the process of PECVD preparation of tunneling oxide layer and highly doped polycrystalline silicon, a carrier for carrying crystalline silicon cells is required, usually called a graphite boat. In the PECVD process, the graphite boat carries the crystalline silicon cell and is immersed in the PECVD reaction chamber. Therefore, the tunneling silicon oxide and doped amorphous silicon materials deposited on the cell will also be deposited on the surface of each structure of the graphite boat. When the film deposited on the graphite boat reaches a certain thickness, due to the weak conductivity of highly doped polycrystalline silicon, it will affect the resistance value between the two boat leaves of the graphite boat, which are positive and negative electrodes to each other, thereby affecting the normal PECVD deposition reaction growth rate, thereby affecting the stability of the cell production process. Therefore, after the graphite boat has been used for a period of time, it is necessary to clean the graphite boat to remove the silicon oxide and highly doped polycrystalline silicon materials deposited on the surface.

Wet cleaning is the mainstream graphite boat cleaning method currently used in the industry, but this method has the disadvantages of long cleaning time, low efficiency, easy damage to the graphite boat, insufficient or excessive cleaning, and environmental pollution. In recent years, plasma-based "dry" graphite boat cleaning equipment has continued to emerge. At present, most graphite boat dry cleaning equipment uses capacitively coupled plasma (CCP) as the plasma source. The etching and cleaning effect of CCP on the side wall of the graphite boat is often not ideal, and the required working gas pressure is high and the ionization rate is relatively low. In order to ensure the cleaning efficiency, the power has to be increased, which may further lead to local over-engraving problems. In addition, to achieve the cleaning of the entire graphite boat, a huge electrode area is required, which increases the processing difficulty and cost.

Inductively coupled plasma (ICP) is one of the common forms of low-pressure plasma. Its principle is that alternating current generates an induced magnetic field in a vacuum chamber through an electrode coil, and the induced magnetic field generates an induced electric field. Electrons bombard gas molecules under the acceleration of the induced electric field to generate plasma. ICP has the advantages of low working pressure, high ionization rate, large adjustable range of ion energy, separation of electrodes and chambers, and is not easily contaminated. It is widely used in fields such as integrated circuit manufacturing. However, for large-area and large-volume applications such as cleaning graphite boats, if spiral coils or planar coils are used, the overall inductance of the coil will be huge, making it difficult to match the mainstream RF power supply, resulting in limited application of ICP in cleaning large-area and large-volume graphite boats.

Summary of the invention

In view of the shortcomings of the prior art, the first purpose of the present invention is to provide a graphite boat cleaning equipment based on a straight rod antenna ICP, so as to solve the technical problem that in the prior art, if a spiral coil or a planar coil is used for the large-area and large-volume application of ICP for cleaning graphite boats, the overall inductance of the coil will be huge, making it difficult to match the mainstream RF power supply.

To solve the above technical problems, the present invention provides a graphite boat cleaning device based on straight rod antenna ICP, comprising a reaction chamber, a reaction cavity for accommodating a graphite boat is arranged in the reaction chamber, a bias electrode plate is arranged in the reaction cavity, an insulating block for placing the graphite boat is arranged on the bias electrode plate, a plurality of straight rod electrodes are connected in the reaction chamber, the plurality of straight rod electrodes are arranged horizontally and parallel to each other, when the graphite boat is placed on the insulating block, each straight rod electrode is located above the graphite boat and the length direction of each straight rod electrode is arranged vertically in space to the length direction of the graphite boat, and the plurality of straight rod electrodes are connected in parallel to form a single comb type, a double comb type, a U-type, or a combination of a double comb type and a U-type layout.

After adopting the above structure, a graphite boat cleaning equipment based on the straight rod antenna ICP in the present invention has the following advantages: the conventional spiral coil or planar coil in the ICP is split into a parallel form of straight rod electrodes, the impedance is low, it is easy to control the overall impedance, and it can be adapted to the mainstream RF power supply and matching device on the market. By increasing or decreasing the number of straight rod electrodes, it can also be adapted to reaction chambers and graphite boats of different sizes. No customized electrodes are required, and the material and processing costs are low. Compared with CCP, the ionization rate is higher, the cleaning effect is better, the working gas pressure is lower, and the use of special gases can be reduced; in addition, the single-comb type has a simple layout structure, and the double-comb type can further improve the plasma uniformity through electric field modulation, which is suitable for occasions with higher cleaning requirements. The combination of the double-comb type and the U-type reduces the use of RF power supply and matching device on the basis of the double-comb type, reduces costs, and is suitable for the processing needs of larger-sized graphite boats.

As an improvement, several straight rod electrodes are arranged in a single comb shape and the feeding points and the grounding points are distributed diagonally. With this structure, the feeding points and the grounding points are arranged diagonally so that the plasma generated in each path has good uniformity and low cost, which is suitable for the cleaning of small, experimental graphite boats.

As an improvement, the straight rod electrode includes a hollow metal tube, an insulating bracket and an insulating sleeve from the inside to the outside. The outer wall of the hollow metal tube is connected to the inner wall of the insulating sleeve through a plurality of insulating brackets arranged circumferentially along the outer wall of the hollow metal tube, and the hollow metal tube and the insulating sleeve are coaxially arranged. With this structure, the hollow metal tube is protected by the insulating sleeve to prevent it from being directly exposed and etched by plasma, which significantly reduces the equipment failure rate and maintenance cost. Ultrapure water for cooling circulates inside the hollow metal tube during the cleaning process. The hollow metal tube and the insulating sleeve are connected by the insulating bracket to ensure an atmospheric pressure environment between the two to prevent breakdown.

As an improvement, a plurality of through holes are provided on two opposite side walls of the reaction chamber, and the two ends of the straight rod electrode are respectively inserted into the two opposite through holes and sealed by a sealing ring; this structure improves the sealing between the straight rod electrode and the reaction chamber.

As an improvement, a heating tube for heating the graphite boat is provided in the reaction chamber; this structure is used to dry the boat to remove water vapor before the cleaning process begins, thereby preventing the generation of hydrofluoric acid (HF) during the cleaning process from causing pollution and safety hazards.

As an improvement, the bias electrode plate includes four sub-electrode plates distributed in a matrix. Adjacent sub-electrode plates are connected by insulating spacers, and the bias of the sub-electrode plates can be independently controlled on and off. With this structure, the block bias can realize multiple cleaning modes, improving the cleaning effect while ensuring the cleaning efficiency.

As an improvement, an insulating barrier is connected to the bottom end of the interior of the reaction chamber, a groove is provided on the upper end surface of the insulating barrier, the bias electrode plate is connected in the groove and each circumferential side wall of the bias electrode plate is covered by the insulating barrier; this structure is used to prevent breakdown and sparking between the bias electrode plate and the side wall or bottom end of the reaction chamber.

As an improvement, a main air inlet is provided on the front side wall of the reaction chamber, and an auxiliary air inlet is provided on each of the left and right side walls of the reaction chamber; with this structure, different air intake methods can achieve multiple cleaning modes, improving the cleaning effect while ensuring cleaning efficiency.

The second object of the present invention is to provide a graphite boat cleaning method based on straight rod antenna ICP, using the above-mentioned graphite boat cleaning device based on straight rod antenna ICP, comprising the following steps:

S1. Send the graphite boat into the reaction chamber and place it at a set position;

S2, evacuating the reaction chamber to a set vacuum value and detecting whether the reaction chamber leaks by monitoring the vacuum value; if the reaction chamber does not leak, proceeding to the next step;

S3, using a heating tube disposed in the reaction chamber to dry the graphite boat for 300-600 seconds;

S4, using dry nitrogen to purge the water vapor generated by the drying boat in the reaction chamber;

S5, evacuating the reaction chamber to a set vacuum value;

S6, introducing Ar from the main air inlet provided on the front side wall of the reaction chamber and adjusting the pressure of the reaction chamber to a set range;

S7, turn on the RF power supply and adjust the RF power supply to 10%-30% of the rated power. After starting, check whether the discharge state is normal according to the voltage, current and impedance of the load end; if the discharge state is normal, proceed to the next step;

S8, introducing the reaction gas from the main gas inlet and the auxiliary gas inlets provided on the left and right side walls of the reaction chamber at a linearly increasing rate, and at the same time gradually reducing the Ar introduction at the same linearly decreasing rate, during which the gas pressure in the reaction chamber is maintained constant;

S9, adjust the RF power to 50%-90% of the rated power, connect the bias electrode plate to the bias and start cleaning;

S10, turning off the radio frequency power supply, and disconnecting the bias voltage of the bias electrode plate;

S11, evacuate the reaction chamber and introduce nitrogen to return the pressure of the reaction chamber to atmospheric pressure, and repeat the cycle several times;

S12. After cleaning is completed, the graphite boat is taken out.

After adopting the above method, a graphite boat cleaning method based on straight-rod antenna ICP in the present invention has the following advantages: the conventional spiral coil or planar coil in ICP is split into a parallel form of straight-rod electrodes, the impedance is low, it is easy to control the overall impedance, and it can be adapted to the mainstream RF power supply and matching device on the market. By increasing or decreasing the number of straight-rod electrodes, it can also be adapted to reaction chambers and graphite boats of different sizes, without the need for customized electrodes, and the material and processing costs are low. Compared with CCP, it has a higher ionization rate, better cleaning effect, and lower working gas pressure, which can reduce the use of special gases; in addition, the single-comb type has a simple layout structure, and the double-comb type can further improve the plasma uniformity through electric field modulation, which is suitable for occasions with higher cleaning requirements. The combination of the double-comb type and the U-type reduces the use of RF power supply and matching device on the basis of the double-comb type, reduces costs, and is suitable for the processing requirements of larger-sized graphite boats; in addition, the boat is baked in step S3 to remove water vapor to prevent the generation of hydrofluoric acid (HF) during the cleaning process from causing pollution and safety hazards; step S7 is used to troubleshoot to prevent insulation aging inside the reaction chamber, or power supply and matching device failure.

As an improvement, step S9 includes:

S9-1, first stage cleaning: the four sub-electrode plates in the bias electrode plate are all connected to the bias for 2-3 hours;

S9-2, second stage cleaning: close the main air inlet and disconnect the bias voltage of the two left sub-electrode plates for 0.5-1h;

S9-3, third stage cleaning: the two left sub-electrode plates are biased, and the two right sub-electrode plates are biased, which lasts for 0.5-1h;

S9-4, fourth stage cleaning: connect the bias voltage to each sub-electrode plate in turn in a counterclockwise or clockwise direction, and the connection time of each sub-electrode plate lasts for 10-30 minutes;

S9-5, fifth stage cleaning: the auxiliary air inlet is closed, the gas in the reaction chamber is kept at a static constant pressure, and all sub-electrode plates are connected to bias voltage for 10-30 minutes. By adopting this method, a variety of cleaning modes can be achieved through different combinations of main air inlet, auxiliary air inlet and block bias voltage, which can improve the cleaning effect while ensuring the cleaning efficiency.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of the structure of a graphite boat cleaning device according to the present invention.

FIG. 2 is a top view of the reaction chamber of the present invention.

FIG. 3 is a schematic diagram of the structure of the straight rod electrode in the present invention.

FIG. 4 is a schematic diagram of a single comb-type layout of straight-rod electrodes in the present invention.

FIG. 5 is a schematic diagram of another single-comb layout of the straight rod electrodes in the present invention.

FIG. 6 is a schematic diagram of a double-comb layout of straight-rod electrodes in the present invention.

FIG. 7 is a schematic diagram of another double-comb layout of the straight rod electrodes in the present invention.

FIG8 is a schematic diagram of a U-shaped layout of straight rod electrodes in the present invention.

FIG. 9 is a schematic diagram of the layout of the straight rod electrode combining double comb type and U type in the present invention.

FIG. 10 is a schematic diagram of another layout of a double-comb type and a U-type straight rod electrode in the present invention.

Figure numerals: 1. reaction chamber; 2. reaction cavity; 3. bias electrode plate; 31. sub-electrode plate; 4. insulating block; 5. straight rod electrode; 51. hollow metal tube; 52. insulating bracket; 53. insulating sleeve; 6. heating tube; 7. insulating spacer; 8. insulating barrier; 9. groove; 10. main air inlet; 11. auxiliary air inlet; 12. feeding point; 13. grounding point.

DETAILED DESCRIPTION

The following is a detailed description of a graphite boat cleaning device and method based on straight rod antenna ICP of the present invention in conjunction with the accompanying drawings.

As shown in Figures 1 to 10, a graphite boat cleaning device based on a straight rod antenna ICP includes a reaction chamber 1, a reaction chamber 2 for accommodating a graphite boat is provided in the reaction chamber 1, and a bias electrode plate 3 is provided in the reaction chamber 2. Specifically, as shown in Figure 1, an insulating barrier 8 is connected to the bottom end of the reaction chamber 1 to prevent the bias electrode plate 3 from breaking down and sparking with the side wall or bottom end of the reaction chamber 1. The insulating barrier 8 is preferably made of insulating and high temperature resistant materials such as polytetrafluoroethylene and ceramics. A groove 9 is provided on the upper end surface of the insulating barrier 8, and the bias electrode plate 3 is connected in the groove 9 and each side wall of the bias electrode plate 3 is covered by the insulating barrier 8.

As shown in FIG2 , the bias electrode plate 3 includes four sub-electrode plates 31 distributed in a matrix, and adjacent sub-electrode plates 31 are connected by insulating spacers 7, so that the insulating spacers 7 are cross-shaped as a whole. In this embodiment, the bias electrode plate 3 is made of stainless steel, aluminum alloy and other materials resistant to F plasma etching, and the insulating spacers 7 are made of polytetrafluoroethylene strips. The bias of the sub-electrode plate 31 can be independently controlled to be turned on and off, and a horizontal electric field force is applied to the charged particles to improve the cleaning effect of the side wall of the graphite boat. In addition, the overall area of the bias electrode plate 3 is larger than the area of the graphite boat, that is, in the vertical projection, the graphite boat falls inside the bias electrode plate 3. The bias can be selected as a DC or AC bias, and the electron/ion temperature and etching rate are increased by the bias, thereby improving the overall cleaning uniformity.

As shown in FIG1 , an insulating block 4 for placing a graphite boat is provided on the bias electrode plate 3 to support and fix the graphite boat while electrically isolating the graphite boat from the bias electrode plate 3 below. The insulating block 4 is preferably made of ceramic, polytetrafluoroethylene or other materials.

A plurality of straight-rod electrodes 5 are connected in the reaction chamber 1. The dotted-line frame area shown in FIG1 is the installation area of the straight-rod electrodes 5, which is located above the graphite boat. The plurality of straight-rod electrodes 5 are arranged horizontally and parallel to each other. The length direction of each straight-rod electrode 5 is vertically arranged in space with the length direction of the graphite boat. The number of straight-rod electrodes 5 is determined according to the length of the graphite boat, and the projections of both ends of the straight-rod electrodes 5 in the vertical direction exceed the graphite boat. As shown in FIG4 to FIG10, the plurality of straight-rod electrodes 5 are connected in parallel to form a single-comb type, a double-comb type, a U-type, or a combination of a double-comb type and a U-type. FIG4 shows the most basic single-comb type layout; FIG5 shows a single-comb type layout and the feed point 12 and the connection point 12 are connected to the feed point 12. Location 13 is diagonally distributed, and its advantage is that the plasma generated in each path is uniform and low in cost, which is suitable for cleaning of small and experimental graphite boats; as shown in Figures 6 and 7, there are two double-comb layouts, which further improve the plasma uniformity through electric field modulation, and are suitable for occasions with higher cleaning requirements; as shown in Figures 9 and 10, there is a layout combining double-comb and U-type. The so-called combination of double-comb and U-type means that a number of straight rod electrodes 5 are first arranged in the form of a U-shape, and then a radio frequency power supply is connected based on the U-shape with reference to the double-comb layout. Its advantage is that the use of radio frequency power supply and matching device is reduced on the basis of the double-comb type, and the cost is reduced, which is suitable for the processing requirements of large-sized graphite boats. In addition, it should be noted that in the layout forms with two radio frequency power supplies shown in Figures 6, 7, 9, and 10, solid lines and dotted lines are used to represent the connection lines between the two radio frequency power supplies and the ground respectively.

As shown in FIG3 , the straight rod electrode 5 includes a hollow metal tube 51, an insulating bracket 52 and an insulating sleeve 53 from the inside to the outside. The outer wall of the hollow metal tube 51 is connected to the inner wall of the insulating sleeve 53 through a plurality of insulating brackets 52 arranged circumferentially along the outer wall of the hollow metal tube 51, and the hollow metal tube 51 and the insulating sleeve 53 are arranged coaxially. The hollow metal tube 51 is preferably made of copper, and materials with high strength and corrosion resistance such as stainless steel and aluminum alloy can also be selected. The outer diameter of the hollow metal tube 51 is 10-15 mm and the wall thickness is 2 mm. The insulating bracket 52 is a hollow bracket, and the material is preferably polytetrafluoroethylene, ceramics, etc., and the thickness of the insulating bracket 52 is 2-10 mm. The material of the insulating sleeve 53 is preferably alumina ceramic, and other insulating materials resistant to F plasma etching can also be selected. The outer diameter of the insulating sleeve 53 is 15-30 mm and the wall thickness is 2 mm. Ultrapure water (resistivity 18 MΩ·cm, conductivity 0.055 μS/cm) for cooling is passed into the hollow metal tube 51 during the entire cleaning process.

As shown in FIG1 , a heating tube 6 for heating the graphite boat is provided in the reaction chamber 1. The heating tube 6 is suspended by a bracket provided separately and is used to remove water vapor from the boat before the cleaning process starts, so as to prevent the generation of hydrofluoric acid (HF) during the cleaning process from causing pollution and potential safety hazards. The outer sleeve material of the heating tube 6 is preferably alumina ceramic, and other insulating materials resistant to F plasma etching may also be selected.

The reaction chamber 1 is designed in a rectangular shape or a design approximately similar to a rectangular shape. The size of the reaction chamber 2 is adapted to the size of the graphite boat, can completely accommodate the graphite boat, and has the space required for plasma generation and mechanical movement space; the reaction chamber 1 includes switchable front and rear end covers, upper and lower bottom plates, and left and right side plates. The end cover on one side of the reaction chamber 1 is the boat inlet side. By opening the end cover, the graphite boat can be horizontally sent into the cleaning reaction chamber 2 by the boat taking and placing mechanism; the boat taking and placing mechanism includes a cache platform, and a set of rapid positioning devices for the graphite boat is provided on the cache platform. The positioning device uses the plane of the bottom and one end face of the graphite boat as the reference surface, and accurately fixes the position of the graphite boat through the contact of the positioning block with the reference surface; the boat taking and placing mechanism includes a transmission mechanism, which can transport the graphite boat horizontally in and out along the cleaning reaction chamber 2, or can transport the graphite boat up and down outside the reaction chamber 2 to different reaction chambers 2, or can place the graphite boat on the cache platform for other process taking and placing. The specific structure of the boat taking and placing mechanism is the existing technology and will not be repeated here.

A plurality of through holes are provided on the two opposite side walls of the reaction chamber 1. Specifically, through holes of equal size and equal spacing are left at relative positions on the upper left and right side walls of the reaction chamber 1 for fixing the straight rod electrode 5. The two ends of the straight rod electrode 5 are respectively inserted into the two opposite through holes and sealed by a sealing ring. A 45-degree frustoconical sealing groove is provided at the through hole on the outer wall of the reaction chamber 1 for sealing between the straight rod electrode 5 and the reaction chamber 1. The sealing ring is preferably a fluororubber sealing ring. The specific sealing structure is all existing technology and will not be repeated here.

As shown in FIG2 , a main air inlet 10 is provided on the front side wall of the reaction chamber 1, an auxiliary air inlet 11 is provided on the left and right side walls of the reaction chamber 1, and an air outlet is provided on the rear side wall of the reaction chamber 1. The air intake of the left and right side walls is to compensate for the cleaning effect of the side of the graphite boat, because the air intake on the front side passes through between the blades of the graphite boat from front to back, and the effect on the side wall is weaker. The airflow of the auxiliary air inlet 11 has a vertical effect on the side wall of the graphite boat; preferably, the auxiliary air inlet 11 is located in front of the center line, so that it has an effect on the main part of the graphite boat from front to back.

In addition, this embodiment also relates to a graphite boat cleaning method based on the straight rod antenna ICP, using the above-mentioned graphite boat cleaning device based on the straight rod antenna ICP, comprising the following steps:

S1, sending the graphite boat into the reaction chamber 2 and placing it at a set position, specifically, placing the graphite boat to be cleaned on the buffer platform of the boat-pick-up and -release mechanism, positioning the graphite boat through the self-positioning function of the buffer platform, and sending the graphite boat to the set position in the plasma cleaning reaction chamber 2 through the boat-pick-up and -release mechanism;

S2, evacuating the reaction chamber 2 to a set vacuum value and detecting whether the reaction chamber 2 is leaking by monitoring the vacuum value; if the reaction chamber 2 is not leaking, proceeding to the next step; if the reaction chamber 2 is leaking, stopping the cleaning procedure and inspecting the reaction chamber 2;

S3, using the heating tube 6 disposed in the reaction chamber 1 to dry the graphite boat for 300-600 seconds;

S4, using dry nitrogen to purge the water vapor generated by the drying boat in the reaction chamber 2, and the nitrogen purge is continued three times;

S5, evacuating the reaction chamber 2 to a set vacuum value;

S6, introducing Ar from the main air inlet 10 provided on the front side wall of the reaction chamber 1 and adjusting the pressure of the reaction chamber 2 to a set range (1-50 Pa);

S7. After the pressure of reaction chamber 2 is stable, turn on the RF power supply and adjust the RF power supply power to 10%-30% of the rated power. After starting, detect whether the discharge state is normal according to the voltage, current and impedance of the load end; if the discharge state is normal, proceed to the next step; if the discharge state is abnormal, stop the cleaning procedure and troubleshoot; the selection of the rated power of the RF power supply depends on the graphite boat to be cleaned. Specifically, the larger the size of the graphite boat, the higher the rated power of the selected RF power supply. The specific power selection needs to be determined according to the actual cleaning effect.

S8, introducing the reaction gas from the main gas inlet 10 and the auxiliary gas inlet 11 provided on the left and right side walls of the reaction chamber 1 at a linearly increasing rate, and gradually reducing the Ar introduced at the same linearly decreasing rate, during which the gas pressure in the reaction chamber 2 is maintained constant, and the preferred reaction gas includes any one of the following gases: nitrogen trifluoride, carbon tetrafluoride, sulfur hexafluoride, hexafluoroethane, octafluoropropane, etc., and any one of oxygen and carbon dioxide can be selected for mixing;

S9, adjusting the RF power to 50%-90% of the rated power, connecting the bias electrode plate 3 to the bias voltage and starting cleaning;

S10, turning off the radio frequency power supply, and disconnecting the bias voltage of the bias electrode plate 3;

S11, after evacuating the reaction chamber 2, nitrogen is introduced to restore the pressure of the reaction chamber 2 to atmospheric pressure, and the cycle is repeated several times;

S12. After cleaning is completed, the graphite boat is taken out.

Wherein, step S9 comprises:

S9-1, first stage cleaning: the four sub-electrode plates 31 in the bias electrode plate 3 are all biased for 2-3 hours;

S9-2, second stage cleaning: close the main air inlet 10, and disconnect the bias voltage of the two left sub-electrode plates 31, for 0.5-1h;

S9-3, third stage cleaning: the two left sub-electrode plates 31 are biased, and the two right sub-electrode plates 31 are biased, which lasts for 0.5-1h;

S9-4, fourth stage cleaning: local enhanced cleaning is performed on the corner area of the boat where the deposits are thick and difficult to clean, and each sub-electrode plate 31 is connected to the bias in a counterclockwise or clockwise direction in turn. The connection time of each sub-electrode plate 31 lasts for 10-30 minutes. In this embodiment, starting from the sub-electrode plate 31 labeled A in FIG. 2 , each sub-electrode plate 31 is connected in a clockwise direction in turn;

S9-5, fifth stage cleaning: the auxiliary air inlet 11 is closed, the gas in the reaction chamber 2 is kept static and at a constant pressure, all sub-electrode plates 31 are biased for 10-30 minutes, and compensation cleaning is performed for the areas that were not thoroughly cleaned due to the influence of airflow in the previous cleaning stage.

The present invention adopts a plasma-based dry cleaning method to remove the poly material attached to the graphite boat. Compared with traditional wet cleaning, it has the advantages of short time consumption, low pollution, simple steps, and no need to disassemble the graphite boat. ICP is adopted, which has the advantage of high ionization rate compared with CCP structure and can produce more F ions. For silicon material cleaning with chemical reaction as the main process, it can significantly improve the cleaning efficiency. In addition, the working gas pressure is very low, which can reduce the use of special gases and reduce costs compared with CCP. The conventional spiral coil or planar coil in ICP is split into a parallel form of straight rod electrodes 5, which has low impedance and is easy to control the overall impedance. It can be adapted to mainstream radio frequency power supplies and matchers on the market. By increasing or decreasing the number of straight rod electrodes 5, it can also adapt to reaction chambers 2 and graphite boats of different sizes without the need for customized electrodes. , low material and processing costs; the straight rod electrode 5 is covered with an insulating sleeve 53, which prevents the hollow metal tube 51 from being directly exposed and etched by plasma, significantly reducing the equipment failure rate and maintenance cost; the single-comb type has a simple layout structure, and the double-comb type can further improve the plasma uniformity through electric field modulation, which is suitable for occasions with higher cleaning requirements. The combination of the double-comb type and the U-type reduces the use of RF power supply and matching device on the basis of the double-comb type, reduces costs, and is suitable for the processing requirements of larger-sized graphite boats; a heating tube 6 is used to dry the boat before cleaning to remove residual moisture, so as to avoid HF pollution and safety hazards during the cleaning process; a variety of cleaning modes are realized through different combinations of air intake forms and block bias voltages, which improves the cleaning effect while ensuring the cleaning efficiency.

The embodiments of the present invention are described in detail above in conjunction with the accompanying drawings, but the present invention is not limited to the above-mentioned one embodiment, and all other embodiments obtained by those skilled in the art without making any creative work are within the scope of protection of the present invention.

Claims (10)

1. A graphite boat cleaning device based on straight-rod antenna ICP, characterized in that it comprises a reaction chamber (1), wherein the reaction chamber (1) is provided with a reaction cavity (2) for accommodating a graphite boat, wherein the reaction cavity (2) is provided with a bias electrode plate (3), wherein the bias electrode plate (3) is provided with an insulating block (4) for placing the graphite boat, wherein a plurality of straight-rod electrodes (5) are connected in the reaction chamber (1), wherein the plurality of straight-rod electrodes (5) are arranged horizontally and parallel to each other, wherein when the graphite boat is placed on the insulating block (4), each of the straight-rod electrodes (5) is located above the graphite boat and the length direction of each of the straight-rod electrodes (5) is arranged vertically in space with the length direction of the graphite boat, wherein the plurality of straight-rod electrodes (5) are connected in parallel to form a single comb type, a double comb type, a U-type, or a combination of the double comb type and the U-type; The single comb type layout is that a plurality of straight rod electrodes (5) are arranged in parallel with equal spacing, one end of which is connected in parallel and connected to a radio frequency power supply, and the other end of which is connected in parallel and grounded; The double comb-type layout is that two groups of the same number of straight rod electrodes (5) are arranged in parallel and at equal intervals, one group is connected to the radio frequency power supply at the middle position after being connected in parallel on the left side, and is grounded at the middle position after being connected in parallel on the right side, and the other group is placed in the middle of the group of straight rod electrodes (5), is connected to the radio frequency power supply at the middle position after being connected in parallel on the right side, and is grounded at the middle position after being connected in parallel on the left side; or the double comb-type layout is that two groups of straight rod electrodes (5) are arranged in parallel and at equal intervals in the form of being set at a distance from each other, one group is connected to the radio frequency power supply at the middle position after being connected in parallel on the left side, and is grounded at the middle position after being connected in parallel on the right side, and the other group is connected to the radio frequency power supply at the middle position after being connected in parallel on the right side, and is grounded at the middle position after being connected in parallel on the left side; The U-shaped layout is that two groups of the same number of straight-rod electrodes (5) are arranged in parallel and at equal intervals, one group of the straight-rod electrodes (5) is placed above the other group, the left sides of the group of straight-rod electrodes (5) located above are connected in parallel and then connected to a radio frequency power supply at the middle position, the left sides of the group of straight-rod electrodes (5) located below are connected in parallel and then grounded at the middle position, and the middle position of the right sides of the group of straight-rod electrodes (5) located above are connected in parallel and are connected to the middle position of the right sides of the straight-rod electrodes (5) located below; The double comb type and U type combined layout is that two groups of the same number of straight rod electrodes (5) are arranged in parallel and at equal intervals, one group is connected to the RF power supply from the middle position of the upper left parallel connection and is grounded from the middle position of the lower left parallel connection, and the other group is connected to the RF power supply from the middle position of the upper right parallel connection and is grounded from the middle position of the lower right parallel connection; or the double comb type and U type combined layout is that two groups of the same number of straight rod electrodes (5) are arranged in parallel and at equal intervals, one group is connected to the RF power supply from the middle position of the upper left parallel connection and is grounded from the middle position of the lower left parallel connection, and the other group is connected to the RF power supply from the middle position of the lower left parallel connection and is grounded from the middle position of the upper left parallel connection. 2. The graphite boat cleaning device based on straight rod antenna ICP according to claim 1 is characterized in that the plurality of straight rod electrodes (5) are arranged in a single comb type and the feeding point (12) and the grounding point (13) are distributed diagonally. 3. The graphite boat cleaning device based on straight rod antenna ICP according to claim 1 is characterized in that the straight rod electrode (5) comprises a hollow metal tube (51), an insulating bracket (52) and an insulating sleeve (53) from the inside to the outside, the outer wall of the hollow metal tube (51) is connected to the inner wall of the insulating sleeve (53) through a plurality of insulating brackets (52) arranged circumferentially along the outer wall of the hollow metal tube (51), and the hollow metal tube (51) and the insulating sleeve (53) are coaxially arranged. 4. The graphite boat cleaning device based on straight rod antenna ICP according to claim 1 is characterized in that a plurality of through holes are provided on two opposite side walls of the reaction chamber (1), and two ends of the straight rod electrode (5) are respectively inserted into the two opposite through holes and sealed by sealing rings. 5. The graphite boat cleaning device based on straight rod antenna ICP according to claim 1, characterized in that a heating tube (6) for heating the graphite boat is provided in the reaction chamber (1). 6. The graphite boat cleaning equipment based on straight rod antenna ICP according to claim 1 is characterized in that the bias electrode plate (3) includes four sub-electrode plates (31) distributed in a matrix, and adjacent sub-electrode plates (31) are connected by insulating spacers (7), and the bias of the sub-electrode plates (31) can be independently controlled on and off. 7. The graphite boat cleaning device based on straight rod antenna ICP according to claim 1 is characterized in that an insulating barrier (8) is connected to the bottom of the reaction chamber (1), and a groove (9) is provided on the upper end surface of the insulating barrier (8), and the bias electrode plate (3) is connected in the groove (9) and each circumferential side wall of the bias electrode plate (3) is covered by the insulating barrier (8). 8. The graphite boat cleaning device based on straight rod antenna ICP according to claim 1 is characterized in that a main air inlet (10) is provided on the front side wall of the reaction chamber (1), and an auxiliary air inlet (11) is provided on each of the left and right side walls of the reaction chamber (1). 9. A graphite boat cleaning method based on straight rod antenna ICP, characterized in that the graphite boat cleaning device based on straight rod antenna ICP according to any one of claims 1 to 8 is used, comprising the following steps: S1, sending a graphite boat into the reaction chamber (2) and placing it at a set position; S2, evacuating the reaction chamber (2) to a set vacuum value and detecting whether the reaction chamber (2) is leaking by monitoring the vacuum value; if the reaction chamber (2) is not leaking, proceeding to the next step; S3, using a heating tube (6) disposed in the reaction chamber (1) to dry the graphite boat for 300-600 seconds; S4, using dry nitrogen to purge the water vapor generated by the drying boat in the reaction chamber (2); S5, evacuating the reaction chamber (2) to a set vacuum value; S6, introducing Ar from a main air inlet (10) provided on the front side wall of the reaction chamber (1) and adjusting the pressure of the reaction chamber (2) to a set range; S7, turn on the RF power supply and adjust the RF power supply to 10%-30% of the rated power. After starting, check whether the discharge state is normal according to the voltage, current and impedance of the load end; if the discharge state is normal, proceed to the next step; S8, introducing the reaction gas from the main gas inlet (10) and the auxiliary gas inlet (11) provided on the left and right side walls of the reaction chamber (1) at a linearly increasing rate, and at the same time gradually reducing the Ar introduction at the same linearly decreasing rate, during which the gas pressure in the reaction chamber (2) is maintained constant; S9, adjusting the radio frequency power to 50%-90% of the rated power, and connecting the bias electrode plate (3) to the bias to start cleaning; S10, turning off the radio frequency power supply, and disconnecting the bias voltage of the bias electrode plate (3); S11, evacuating the reaction chamber (2) and introducing nitrogen gas so that the pressure of the reaction chamber (2) returns to atmospheric pressure, and repeating the cycle several times; S12. After cleaning is completed, the graphite boat is taken out. 10. The graphite boat cleaning method based on straight rod antenna ICP according to claim 9, characterized in that step S9 comprises: S9-1, first stage cleaning: the four sub-electrode plates (31) in the bias electrode plate (3) are all connected to bias for 2-3 hours; S9-2, second stage cleaning: close the main air inlet (10) and disconnect the bias voltage of the two left sub-electrode plates (31) for 0.5-1h; S9-3, third stage cleaning: the two left sub-electrode plates (31) are biased, and the two right sub-electrode plates (31) are biased, for 0.5-1 h; S9-4, fourth stage cleaning: connecting the bias voltage to each sub-electrode plate (31) in turn in a counterclockwise or clockwise direction, and the connection time of each sub-electrode plate (31) lasts for 10-30 minutes; S9-5, fifth stage cleaning: the auxiliary air inlet (11) is closed, the gas in the reaction chamber (2) is kept at a static constant pressure, and all sub-electrode plates (31) are connected to bias voltage for 10-30 minutes.