Vacuum coating method

Abstract

The invention discloses a vacuum coating method, and belongs to the technical field of photovoltaic equipment and semiconductor equipment coating, the vacuum coating method comprises the following steps: preheating a support plate; a substrate is placed on a carrier plate from a feeding platform, then the carrier plate and the substrate are conveyed to a loading cavity, and the loading cavity is vacuumized until the vacuum degree of the loading cavity is consistent with that of a preheating cavity; and the carrier plate and the substrate are conveyed to a preheating cavity in a vacuum environment, the substrate is heated to a preset temperature in the preheating cavity, and vacuum breaking treatment is conducted on the loading cavity in the preheating process. According to the method, the mode that the reaction gas and the inert purging gas are output at the same time is adopted, compared with a traditional time type source 1-purging-source 2-purging process step, a large amount of inert gas purging time is saved, the process duration is only determined by the swing speed and the swing period number of the carrier plate, the process time for depositing the thin film with the specified thickness is remarkably shortened, and the deposition efficiency is improved. And the industrial production efficiency is greatly improved.

Description

Technical Field

[0001] The invention belongs to the technical field of film coating of photovoltaic equipment and semiconductor equipment, and in particular relates to a vacuum film coating method. Background Art

[0002] In the industrial production of photovoltaic solar cells, semiconductor devices and metal materials, the surface coating process is a key step to improve device performance. Atomic layer deposition (ALD) vacuum coating technology is widely used due to its high density and ability to precisely control nanometer-level thickness. The traditional time-based ALD process achieves coating through cyclic steps: first, the first reaction gas is introduced into the reaction chamber to make it adhere to the surface of the substrate; then the chamber is thoroughly purged with an inert gas; then the second reaction gas is introduced to react with the first reaction material on the surface of the substrate to form the desired film layer; finally, the chamber is purged with an inert gas again. This process is repeated until a specific film thickness is reached.

[0003] However, the time-based ALD process has obvious defects: first, in order to ensure that the reaction gas completely covers the substrate at different positions in the chamber, a large amount of source gas needs to be introduced, resulting in waste of raw materials; second, due to the different distances between the substrate and the outlet, there are differences in the inert gas purge speed, which may lead to a decrease in film thickness uniformity; in addition, a large amount of inert gas purge time significantly reduces the coating efficiency, which is difficult to meet the needs of industrial mass production.

[0004] To overcome the above problems, the spatial atomic layer deposition process came into being. In this process, the precursor is continuously injected into different positions of the reaction chamber, the source gas path and the inert gas path are arranged alternately, and different reaction gases are separated by a large flux of inert gas. The substrate moves in a specified direction under the gas path to achieve thin film deposition. Compared with the time-based process, the spatial process significantly improves the coating rate and is more suitable for industrial continuous production. However, the spatial process also has some challenges: substrate temperature fluctuations may lead to a decrease in coating uniformity; in a single chamber, if the reaction gas is not discharged in time, a chemical vapor deposition (CVD) reaction may occur in other positions of the chamber, generating dust, which in turn affects the coating quality.

[0005] Therefore, in response to the above problems, the field urgently needs to develop improvement solutions to further enhance the stability and efficiency of the spatial atomic layer deposition process to meet the needs of industrial production. Summary of the invention

[0006] The object of the present invention is to provide a vacuum coating method to solve the problems encountered in the use of the existing coating method mentioned in the background art.

[0007] To achieve the above object, the present invention provides the following technical solution: a vacuum coating method, comprising the following steps:

[0008] S1. Preheat the carrier plate;

[0009] S2. Place the substrate on the carrier plate from the loading platform, then transfer the carrier plate and the substrate to the loading chamber, and perform a vacuum pumping process on the loading chamber until the vacuum degrees of the loading chamber and the preheating chamber are the same;

[0010] S3. Transfer the carrier plate and the substrate to the preheating chamber in a vacuum environment, heat the substrate to a preset temperature in the preheating chamber, and break the vacuum of the loading chamber during the preheating process;

[0011] S4. Transfer the heated carrier plate and substrate to the process chamber in a vacuum environment, spray inert gas and two reaction source gases simultaneously onto the substrate in the process chamber from the spray plate at the top of the process chamber, control the carrier plate to drive the substrate to reciprocate in the process chamber for coating the substrate, and while spraying for coating, the exhaust gas is extracted by the air extraction pump through the air extraction holes on the spray plate;

[0012] S5. After the coating of the substrate is completed, transfer the carrier plate and the substrate to the unloading chamber, then break the vacuum of the unloading chamber. When the air pressure in the unloading chamber reaches the atmospheric pressure, the carrier plate transfers the substrate to the unloading platform. After unloading the substrate, the carrier plate is returned to the loading platform to wait for the next group of substrates to be coated.

[0013] Preferably, the source gas holes on the spray plate are periodically arranged in the order of the first reaction gas hole, inert gas hole, second reaction gas hole, and inert gas hole, and the left and right sides of the spray plate are fixed as inert gas holes.

[0014] Preferably, the heating method of the carrier plate in the preheating chamber is contact heating, the heating time of the carrier plate is controlled to be 300 - 360 seconds, and the substrate is heated by contact with the carrier plate, and the heating time is controlled to be 80 - 120 seconds according to the material and specifications of the substrate plate.

[0015] Preferably, the amount of inert gas introduced from the inert gas holes is greater than that of the two reaction source gases to fully isolate the two reaction source gases. The inert gas is any one of nitrogen, helium, argon, and neon, and the air ventilation amount in different areas of the spray plate is controlled to be the same through the adjustment core.

[0016] Preferably, the substrate is any one of a silicon wafer, a silicon ingot, conductive glass, and flexible PET.

[0017] Preferably, one air extraction hole is further arranged between every two source gas holes on the spray plate, and each air extraction hole is separately connected to a group of air extraction pumps.

[0018] Preferably, a mechanical translation device is arranged at the bottom of the carrier plate to drive the carrier plate and the substrate to perform periodic swinging inside the process chamber, and the swinging period of the carrier plate and the substrate is set based on the thickness of the coating layer.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] 1. Thanks to the improved chamber temperature setting strategy and substrate preheating method, the temperature uniformity of the coating substrate surface is significantly improved, effectively improving the batch repeatability of the coating device;

[0021] Second, this method uses a method of outputting the reaction gas and the inert purge gas simultaneously. Compared with the traditional time-based source 1-purge-source 2-purge process steps, a large amount of inert gas purge time is saved. The process duration is only determined by the carrier swing speed and the number of swing cycles. The process time for depositing a film of a specified thickness is significantly reduced, which greatly improves industrial production efficiency.

[0022] 3. The process time is shortened. The reaction gas does not need to fill the entire chamber environment. It only needs to ensure that the substrate 5mm away from the shower plate can evenly deposit a thin film. Therefore, the source gas flow rate is reduced, the consumption of chemical reactants is significantly reduced, the utilization rate of reactants is improved, and the equipment cost is further reduced.

[0023] Fourth, adding an exhaust hole between the reaction gas hole and the inert gas hole of the spray plate can avoid dust accumulation caused by CVD reaction in the chamber, extend the equipment cleaning and maintenance cycle, reduce the frequency of production interruptions caused by equipment cleaning, and thus extend the continuous production time. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a schematic diagram of the structure flow of the equipment used in the vacuum coating method of the present application;

[0025] Figure 2 It is a structural principle diagram of the coating process in the vacuum coating method of the present application;

[0026] Figure 3 It is a schematic diagram of the process flow of the vacuum coating method according to an embodiment of the present application. DETAILED DESCRIPTION

[0027] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0028] Reference Figure 1-3 , a vacuum coating method, comprising the following steps:

[0029] S1. Preheat the carrier board;

[0030] S2, placing the substrate from the loading platform onto the carrier, then transferring the carrier and the substrate to the loading chamber, and performing vacuum treatment on the loading chamber until the vacuum degree of the loading chamber is consistent with that of the preheating chamber;

[0031] S3, transferring the carrier plate and the substrate to a preheating chamber in a vacuum environment, heating the substrate to a preset temperature in the preheating chamber, and breaking the vacuum of the loading chamber during the preheating process;

[0032] S4, transferring the heated carrier plate and substrate to a process chamber in a vacuum environment, spraying an inert gas and two reaction source gases from a spray plate on the top of the process chamber to the substrate in the process chamber, controlling the carrier plate to drive the substrate to swing back and forth in the process chamber to coat the substrate, and while spraying the coating, an exhaust pump extracts waste gas through the exhaust holes on the spray plate;

[0033] S5. After the substrate coating is completed, the carrier and substrate are transferred to the unloading chamber, and then the vacuum of the unloading chamber is broken. When the air pressure in the unloading chamber reaches atmospheric pressure, the carrier transfers the substrate to the unloading platform. After the substrate is unloaded, the carrier is returned to the loading platform to wait for the next group of substrates to be coated.

[0034] In the common atomic layer deposition coating method, the substrate is placed in a reaction chamber, and the first reaction gas is introduced into the reaction chamber, and the introduction is stopped after a period of time, and then an inert gas is introduced to purge until the reaction gas in the chamber is purged clean; then the second reaction gas is introduced to react with the first reactant attached to the substrate to generate the required material, and then the inert gas is introduced again to purge the reactant clean; the above operation is repeated many times to stack the film layer until the film layer reaches the required thickness. However, in this method, in order to ensure that there is no reactant residue in the chamber after purging, the time for introducing the inert gas is often much longer than the time for introducing the reaction gas, so it cannot meet the large-scale production rate requirements in industry; in addition, due to the single source port position, the distance between different positions of the large-area substrate and the source port will lead to differences in the coating rate, which is not conducive to the uniform deposition of large-area film layers.

[0035] Based on the above problems, this scheme proposes a new vacuum coating method, in which two reaction source gases are mixed with inert gas and introduced through the spray plate. The substrate is driven by the carrier plate to make periodic swings to form a uniform coating. At the same time, a large flux of inert gas is introduced for isolation protection. Vacuuming is set on both sides of the reaction source gas to effectively avoid the CVD effect caused by the reaction source gas. The method of introducing two reaction source gases at the same time greatly reduces the purging time, thereby reducing the coating rate on the one hand, and saving a large amount of production materials and reducing production costs on the other hand.

[0036] Furthermore, the through holes on the shower plate are periodically arranged in the form of first reaction gas holes, inert gas holes, second reaction gas holes, and inert gas holes, and the left and right sides of the shower plate are fixed as inert gas holes.

[0037] like Figure 2 An implementation method for arranging through source holes applied to the present method is provided. In practical applications, multiple groups of first reaction gas holes and second reaction gas holes can be arranged alternately according to the size specifications of the substrate. The reaction gas holes are in one column. To ensure that the reaction gases are completely isolated from each other, the inert gas holes can be in one or more columns. The reaction source gas is fully isolated by the inert gas to avoid gas diffusion. The left and right sides of the spray plate are fixed as inert gas holes to ensure that the reaction source gas will not diffuse to other chambers.

[0038] Furthermore, the carrier is heated in the preheating chamber by contact heating, and the heating time of the carrier is controlled to be 300-360 seconds. The substrate is contact-heated through the carrier, and the heating time is controlled to be 80-120 seconds according to the material and specification of the liner.

[0039] The carrier adopts contact heating, and the heating plate at the bottom of the preheating chamber will be lifted up to directly contact the carrier for heating. The carrier heating time is 300-360 seconds to ensure that the carrier temperature is consistent with the preset temperature of the preheating chamber and the temperature fluctuation range is controlled within 5%. At the loading platform, the substrate is placed on the preheated carrier, and a small wafer is placed in the empty space on the carrier to monitor the process data.

[0040] When the carrier is transferred from the loading chamber to the preheating chamber, and from the preheating chamber to the process chamber, the gate valves between the chambers need to be opened for transfer. Due to the temperature difference between the chambers, and the heating rate on both sides of the chamber is slower than that in the center, the temperature of the area near the gate valves on both sides of the preheating chamber will drop during the transfer process. In order to reduce the overall temperature fluctuation of the chamber, heat the substrate to the preset temperature in the shortest possible time and control its overall temperature uniformity, the temperature setting of the area near the gate valves on both sides of the preheating chamber should be 0-30°C higher than the center area. This ensures that each area of ​​the substrate is heated to the specified temperature within 100 seconds and the temperature fluctuation value is controlled within 5%. The specific temperature setting value needs to be adjusted according to the actual situation such as substrate size and material.

[0041] In the preheating chamber, the temperature of the substrate on the carrier is made consistent with the preset temperature of the preheating chamber through contact heating. The preheating time of the substrate is preset to 100 seconds, but it can be appropriately adjusted according to the actual size and material properties of the substrate.

[0042] Furthermore, the amount of inert gas introduced from the inert gas hole is greater than the two reaction source gases to fully isolate the two reaction source gases. The inert gas is any one of nitrogen, helium, argon, and neon. The ventilation volume in different areas of the shower plate is controlled to be consistent by adjusting the core.

[0043] The inert gas outflow on the shower plate is greater than the reactive gas outflow, ensuring that the reactive gases in different areas are completely separated. For example, the gas flow rate of the source pipeline is 10-400sccm, the gas flow rate of the source pipeline is 1000-3000sccm, and the gas flow rate of the inert isolation gas pipeline is 20000-50000sccm;

[0044] To ensure uniform coating, the source flow in different areas is controlled by the regulating core on the spray plate to keep the source flow rate of the entire spray plate consistent. When the spray plate is provided with multiple groups of air holes, the gas flow rate of each air hole will be different even with the same source gas volume due to the difference in the length of the source pipes in different areas of the plate. Therefore, it is necessary to use the regulating core on the spray plate to adjust the opening and closing flux of different columns of air holes. Normally, the opening and closing amount of the regulating core in the center area of ​​the spray plate is set to 1 / 3 of the fully open state, and the left and right edge areas are set to 2 / 3 of the fully open state. From the center area to the left and right edge areas, the flux of the air holes needs to be gradually fine-tuned from less to more according to the actual situation to ensure uniform distribution of the gas flow rate.

[0045] Furthermore, the substrate is any one of silicon chip, silicon wafer, conductive glass, and flexible PET.

[0046] Furthermore, an air extraction hole is arranged between every two through holes of the spray plate, and each air extraction hole is individually connected to a group of air extraction pumps.

[0047] In common space-type atomic layer deposition systems, the process chamber usually relies on a gas guide tube at the bottom of the chamber to pump unreacted gases out of the chamber. However, this method easily leads to a CVD reaction between two different reaction gases around the chamber, resulting in dust accumulation, affecting the coating effect and increasing the frequency of chamber cleaning. To solve this problem, the present application adds an exhaust hole between the reaction gas hole and the inert gas hole of the spray plate while retaining the vacuum device at the bottom of the chamber. The reaction gas, inert gas and reaction by-products that do not participate in the reaction are discharged from the chamber in time through a vacuum pump to prevent the reaction gas from diffusing to areas other than above the carrier plate, thereby eliminating the CVD effect, effectively preventing dust accumulation, and significantly extending the chamber cleaning and maintenance cycle.

[0048] like Figure 2As shown, taking the two gas paths on the left side of a group of air holes as an example, the inert gas hole and the first reaction gas hole simultaneously introduce gas to the substrate. After the gas is sprayed onto the substrate, it diffuses to the relatively low-pressure exhaust hole area on both sides, and is finally exhausted out of the cavity by the vacuum pump. It should be noted that the exhaust holes on the spray plate should be equipped with a vacuum pump separately, and its suction should be controlled within an appropriate range: too little suction may cause the reaction gas to fail to be discharged in time, and too much suction may cause the reaction gas to be sucked out of the cavity before being deposited on the substrate. In addition, the exhaust holes can be designed as a strip hole structure to ensure that the exhaust range is large enough to efficiently discharge the exhaust gas.

[0049] Furthermore, a mechanical translation device is provided at the bottom of the carrier plate to drive the carrier plate and the substrate to swing periodically inside the process chamber, and the swing period of the carrier plate and the substrate is set based on the thickness of the coating layer.

[0050] To ensure the density and uniformity of the coating, the distance between the substrate and the lowest point of the spray plate should be less than 5mm during coating, and the gap difference between different positions of the substrate and the lowest point of the spray plate should be controlled within 1mm. If the gap is too large, the reaction gas will be dispersed, affecting the uniformity of the film and reducing the utilization rate of the reaction source; if the gap is too small, the vibration of the carrier plate during swinging may cause the substrate and the spray plate to scratch, affecting the coating effect. In addition, the process chamber needs to be set at an appropriate temperature to provide the required energy environment for the reactants.

[0051] At the beginning of coating, the mechanical device (such as rollers, slide rails, etc.) at the bottom of the process chamber carries the carrier plate to move parallel to the starting position, driving the substrate to move synchronously. After reaching the specified position, the mechanical device controls the carrier plate to move parallel to the opposite direction, and so on, so that the carrier plate and substrate swing periodically in the chamber to ensure the uniformity of coating.

[0052] Figure 3 This is a schematic diagram of the process flow of the vacuum coating method. A complete process flow includes:

[0053] S301: The substrate passes through a first reaction gas, and a layer of a first reactant is deposited on the surface of the substrate;

[0054] S302: The substrate is purged with an inert gas to remove excess first reactant;

[0055] S303: The substrate passes through the second reaction gas, and the first reactant attached to the substrate reacts with the second reaction gas to generate the desired material;

[0056] S304: The substrate is purged with an inert gas to remove excess second reactant.

[0057] When the left edge of the substrate passes through the first reaction gas outlet from left to right, a layer of first reactant will adhere to the surface of the substrate in this area, and the excess reaction gas will be blown to the exhaust hole area between the reaction gas hole and the inert gas hole, and discharged out of the cavity by the low-pressure suction of the vacuum pump.

[0058] When the substrate continues to move to the right and passes through the inert gas outlet, the large flux of inert gas will clean up the first reactant above the substrate, leaving only a nano-scale layer of the first reactant on the surface of the substrate, and the inert gas is also discharged out of the cavity through the exhaust hole.

[0059] Subsequently, the substrate continues to move to the right and passes through the second reaction gas outlet hole. The second reaction gas reacts with the first reactant on the surface of the substrate to generate a layer of required material. The second reaction gas and reaction by-products that do not participate in the reaction are blown to the adjacent exhaust hole area and discharged out of the cavity through the exhaust hole.

[0060] When the substrate continues to move to the right and passes through the inert gas outlet, the inert gas will purge the excess reactants and form a dense film on the surface of the substrate. At this point, a half reaction is completed, that is, a coating process.

[0061] After the first coating is completed, the mechanical device controls the carrier and the substrate to move in the opposite direction, passing through the second reaction gas area, the inert gas area, the first reaction gas area and the inert gas area in turn to complete the second coating, that is, another half reaction.

[0062] Two consecutive half reactions in opposite directions constitute a complete process cycle. The film thickness can be adjusted by controlling the number of process cycles and the output volume of the reaction gas.

[0063] It should be noted that the lateral width of the shower plate should be greater than the lateral width of the substrate to ensure that all areas of the substrate can be fully coated during the swinging process.

[0064] In the description of the present invention, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0065] In the description of the present invention, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In the present invention, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine different embodiments or examples described in the present invention and features of different embodiments or examples without contradiction.

[0066] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A vacuum coating method, characterized in that: The steps include: S1. Preheat the carrier board; S2, placing the substrate from the loading platform onto the carrier, then transferring the carrier and the substrate to the loading chamber, and performing vacuum treatment on the loading chamber until the vacuum degree of the loading chamber is consistent with that of the preheating chamber; S3, transferring the carrier plate and the substrate to a preheating chamber in a vacuum environment, heating the substrate to a preset temperature in the preheating chamber, and breaking the vacuum of the loading chamber during the preheating process; S4, transferring the heated carrier plate and substrate to a process chamber in a vacuum environment, spraying an inert gas and two reaction source gases from a spray plate on the top of the process chamber to the substrate in the process chamber, controlling the carrier plate to drive the substrate to swing back and forth in the process chamber to coat the substrate, and while spraying the coating, an exhaust pump extracts waste gas through the exhaust holes on the spray plate; S5. After the substrate coating is completed, the carrier and substrate are transferred to the unloading chamber, and then the vacuum of the unloading chamber is broken. When the air pressure in the unloading chamber reaches atmospheric pressure, the carrier transfers the substrate to the unloading platform. After the substrate is unloaded, the carrier is returned to the loading platform to wait for the next group of substrates to be coated.

2. A vacuum coating method according to claim 1, characterized in that: The through holes on the shower plate are periodically arranged in the form of first reaction gas holes, inert gas holes, second reaction gas holes, and inert gas holes, and the left and right sides of the shower plate are fixed as inert gas holes.

3. A vacuum coating method according to claim 1, characterized in that: The carrier is heated in the preheating chamber by contact heating, and the carrier heating time is controlled to be 300-360 seconds. The substrate is contact heated by the carrier, and the heating time is controlled to be 80-120 seconds according to the material and specification of the liner.

4. A vacuum coating method according to claim 2, characterized in that: The amount of inert gas introduced from the inert gas hole is greater than the two reaction source gases to fully isolate the two reaction source gases. The inert gas is any one of nitrogen, helium, argon, and neon. The ventilation volume in different areas of the shower plate is controlled to be consistent by adjusting the core.

5. A vacuum coating method according to claim 4, characterized in that: The substrate is any one of silicon chip, silicon wafer, conductive glass and flexible PET.

6. A vacuum coating method according to claim 2, characterized in that: An air extraction hole is arranged between every two through-source holes of the spray plate, and each air extraction hole is individually connected to a group of air extraction pumps.

7. A vacuum coating method according to claim 2, characterized in that: A mechanical translation device is provided at the bottom of the carrier plate to drive the carrier plate and the substrate to swing periodically inside the process chamber. The swing period of the carrier plate and the substrate is set based on the thickness of the coating layer.

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