A method of forming a protective film, a protective film, and a semiconductor processing apparatus

Abstract

The application discloses a method for forming a protective film, the protective film and a semiconductor process equipment, the method for forming the protective film is by depositing a first protective film on the inner wall of the process chamber, and depositing a second protective film on the surface of the first protective film, the material of the second protective film is different from the material of the first protective film, and the density of the second protective film is greater than the density of the first protective film, so that the protective film has stronger resistance to plasma bombardment, thereby effectively reducing the probability of particles generated by the protective film under the bombardment of the plasma in the PECVD process processing, and further reducing the risk of particle defects on the wafer surface; at the same time, the smoothness of the second protective film is greater than the smoothness of the first protective film, effectively improving the uniformity of the impedance environment of the process chamber, thereby effectively ensuring the uniformity of the distribution of the plasma in the process chamber in the PECVD process processing, and improving the uniformity of the wafer and the wafer.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor manufacturing technology, and in particular to a method for forming a protective film, the protective film and semiconductor process equipment. Background Art

[0002] PECVD (Plasma Enhanced Chemical Vapor Deposition) is a chemical deposition system that uses glow discharge plasma to dissociate and recombine gaseous sources under low vacuum to achieve the growth of thin film materials. It has experienced rapid development due to its advantages of fast deposition speed, low deposition temperature, and support for the deposition of most dielectric films. To prevent metal and particle contamination during the PECVD process and to provide a stable impedance environment, a protective film is typically formed on the inner wall of the process chamber. However, during the current PECVD process, the protective film is highly susceptible to particle generation under plasma bombardment, causing particle contamination and failing to ensure the uniformity of the impedance environment in the process chamber. Summary of the Invention

[0003] In order to solve the above technical problems, the present invention discloses a method for forming a protective film, a protective film and semiconductor process equipment to solve the problem in the prior art that the protective film is easily contaminated by particles under the bombardment of plasma and cannot ensure the uniformity of the impedance environment of the process chamber.

[0004] To achieve the above technical objectives, the embodiments of the present invention disclose the following technical solutions:

[0005] In first aspect, an embodiment of the present invention discloses a method for forming a protective film, comprising: depositing a first protective film on the inner wall of a process chamber; depositing a second protective film on the surface of the first protective film; wherein the material of the second protective film is different from the material of the first protective film, and the density and smoothness of the second protective film are greater than the density and smoothness of the first protective film.

[0006] In one embodiment, the second protective film includes a nitrogen-doped silicon carbide film, and / or the first protective film includes a silicon oxide film.

[0007] In one embodiment, the thickness of the second protective film is smaller than the thickness of the first protective film.

[0008] In one embodiment, the thickness of the first protective film is greater than or equal to And / or, the thickness of the second protective film is less than or equal to

[0009] In one embodiment, when depositing the first protective film on the inner wall of the process chamber, a first process gas is introduced into the process chamber, wherein the first process gas includes a first reaction gas and a second reaction gas, wherein the first reaction gas includes an oxygen-containing gas and the second reaction gas includes a silicon-containing gas;

[0010] And / or, when depositing a second protective film on the surface of the first protective film, a second process gas is introduced into the process chamber, the second process gas includes a third reaction gas and a fourth reaction gas, the third reaction gas includes a nitrogen-containing gas, and the fourth reaction gas includes a carbon-silicon gas.

[0011] In one embodiment, when the duration of simultaneously introducing the first reaction gas and the second reaction gas into the process chamber reaches a first preset duration, controlling the first RF power source to start and apply the first RF power to the interior of the process chamber;

[0012] And / or, when the time duration for simultaneously introducing the third reaction gas and the fourth reaction gas into the process chamber reaches a second preset time duration, the first RF power supply and the second RF power supply are controlled to be turned on, and the second RF power and the third RF power are respectively applied to the interior of the process chamber, and the frequency of the RF signal output by the first RF power supply is higher than the frequency of the RF signal output by the second RF power supply.

[0013] In one embodiment, after the deposition of the second protective film is completed and before the first RF power supply and the second RF power supply are turned off, the method further includes:

[0014] The first RF power source is controlled to apply a fourth RF power to the interior of the process chamber, where the fourth RF power is less than the second RF power.

[0015] In one embodiment, when the first process gas is introduced into the process chamber, the first reaction gas is introduced into the process chamber, and when a third preset time is reached, the second reaction gas is started to be introduced into the process chamber;

[0016] And / or, when the second process gas is introduced into the process chamber, the third reaction gas is introduced into the process chamber, and when a fourth preset time is reached, the fourth reaction gas is started to be introduced into the process chamber.

[0017] In a second aspect, an embodiment of the present invention discloses a protective film, comprising a first protective film and a second protective film sequentially arranged in a thickness direction of an inner wall of a process chamber;

[0018] The second protective film has a material different from that of the first protective film, and a density and a smoothness greater than those of the first protective film.

[0019] In one embodiment, the second protective film comprises a nitrogen-doped silicon carbide film, and / or the first protective film comprises a silicon oxide film.

[0020] In one embodiment, the second protective film has a thickness less than that of the first protective film.

[0021] In one embodiment, the first protective film has a thickness greater than or equal to 10 nm. and / or the second protective film has a thickness less than or equal to 10 nm.

[0022] In a third aspect, an embodiment of the present application discloses a semiconductor process equipment, comprising a process chamber, a gas inlet assembly, an upper electrode assembly, a lower electrode assembly, and a controller. The controller comprises at least one processor and at least one memory. The memory stores a computer program. The computer program is executed by the processor to implement the method for forming a protective film as described above.

[0023] In a fourth aspect, an embodiment of the present application discloses a computer readable storage medium. The computer readable storage medium stores a computer program. The computer program is executed by a processor to implement the method for forming a protective film as described above.

[0024] In a fifth aspect, an embodiment of the present application discloses a computer program product or a computer program. The computer program product comprises a computer program stored in a computer readable storage medium. A processor of a computer device reads the computer program from the computer readable storage medium. The processor executes the computer program to implement the steps of the method for forming a protective film as described above.

[0025] The present invention discloses a method for forming a protective film, a protective film, and semiconductor process equipment. A first protective film is deposited on the inner wall of a process chamber, and a second protective film is deposited on the surface of the first protective film. The material of the second protective film is different from that of the first protective film, and the density of the second protective film is greater than that of the first protective film, so that the protective film has a stronger resistance to plasma bombardment. Therefore, during the PECVD process, the probability of the protective film generating particles under the bombardment of plasma can be effectively reduced, thereby reducing the risk of particle defects on the wafer surface. At the same time, the smoothness of the second protective film is greater than that of the first protective film, which effectively improves the uniformity of the impedance environment of the process chamber. Therefore, during the PECVD process, the uniformity of the plasma distribution in the process chamber can be effectively guaranteed, thereby improving the uniformity within and between wafers. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are merely embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the disclosed drawings without any creative work.

[0027] Figure 1 A schematic flow chart of a method for forming a protective film disclosed in one embodiment of the present invention.

[0028] Figure 2 The present invention is a schematic flow chart of another method for forming a protective film disclosed in one embodiment of the present invention.

[0029] Figure 3 Schematic diagram showing a comparison of wet etching rates of a nitrogen-doped silicon carbide film deposited according to an embodiment of the present invention and a silicon oxide film deposited according to a conventional method.

[0030] Figure 4 The number of particles on the wafer changes with the cumulative film thickness of the process film.

[0031] Figure 5 The figure is a schematic structural diagram of a protective film disclosed in one embodiment of the present invention.

[0032] Figure 6 A schematic structural diagram of a semiconductor process equipment disclosed in one embodiment of the present invention. DETAILED DESCRIPTION

[0033] Unless otherwise defined, technical or scientific terms used in the embodiments of this specification should have the same ordinary meaning as those understood by persons of ordinary skill in the art to which this specification pertains. The terms "first," "second," and similar terms used in the embodiments of this specification do not denote any order, quantity, or importance, but are provided solely to avoid confusion between constituent elements.

[0034] Unless the context requires otherwise, throughout this specification, the term "plurality" means "at least two," and "including" is to be interpreted as open and inclusive, meaning "including, but not limited to." Throughout this specification, the terms "one embodiment," "some embodiments," "exemplary embodiments," "example," "specific example," or "some examples" are intended to indicate that a particular feature, structure, material, or characteristic associated with the embodiment or example is included in at least one embodiment or example of this specification. The schematic representations of these terms do not necessarily refer to the same embodiment or example.

[0035] The following will be combined with the drawings in the embodiments of this specification to clearly and completely describe the technical solutions in the embodiments of this specification. Obviously, the embodiments described are only part of the embodiments of this specification, not all of the embodiments. Based on the embodiments in this specification, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of this specification.

[0036] Currently, the performance improvement of computing and storage devices relies on the high integration of chip manufacturing. With the miniaturization of devices and the continuous increase in stacked film layers, higher requirements are placed on the repeatability, stability, defect and particle count control of each process. However, the high-quality thin film deposition capability also limits the throughput of wafer manufacturing to a certain extent, thus placing higher requirements on the optimization of thin film deposition process.

[0037] As mentioned in the background technology, PECVD (Plasma Enhanced Chemical Vapor Deposition) is a relatively mature chemical deposition system. It uses glow discharge plasma to dissociate and recombine gaseous sources under low vacuum to achieve the growth of thin film materials. PECVD has the advantages of fast deposition speed, low deposition temperature, and supports the deposition of most dielectric films (such as the etch stop layer (ESL) of semiconductor devices, hard mask (HM), inter-metal dielectric layer (IMD) and inter-layer dielectric layer (ILD), etc.). Therefore, it has been rapidly developed and has been widely used in the fields of ultra-large-scale integrated circuits, optoelectronic devices, MEMS (Micro-Electro-Mechanical System, micro-electromechanical system) and so on.

[0038] In order to prevent metal contamination and particle contamination during the PECVD process and to provide a stable impedance environment, a protective film, i.e., a pre-coat layer, is usually formed on the inner wall of the process chamber. The protective film covers the metal inner wall of the process chamber to prevent the metal inner wall from peeling off under the bombardment of plasma and causing metal contamination. At the same time, the protective film can serve as an intermediate adhesion layer to prevent the process film deposited during the PECVD process from peeling off on the inner wall of the process chamber and causing particle contamination. In addition, the protective film, as a dielectric layer, can balance the internal impedance of the process chamber to provide a stable impedance environment, thereby improving the stability of film deposition. For example, when the number of process films deposited in the process chamber reaches a predetermined number or the film thickness of the process film on the inner wall of the process chamber reaches a preset film thickness, a remote plasma source (RPS) cleaning is performed to remove the accumulated film on the inner wall of the chamber and deposit a protective film on the inner wall of the process chamber before the next film deposition.

[0039] Currently, when depositing a protective film on the inner wall of a process chamber, only one layer of film is typically deposited, such as a silicon oxide (SiO2) film. Silicon oxide is a common pre-coat material. As a commonly used dielectric layer, it has a mature process preparation method, is relatively easy to control its uniformity, and has good adhesion to the inner wall of an aluminum process chamber. Furthermore, using PECVD can produce thicker silicon oxide films in a shorter time, which is beneficial for improving equipment production capacity. However, silicon oxide films have low density and are easily bombarded by plasma during PECVD processing, especially high-power deposition processes, resulting in particle contamination. Furthermore, the unevenness and roughness of the silicon oxide film surface will affect the uniformity of the impedance environment within the process chamber, making it impossible to ensure uniformity within and between wafers during PECVD processing.

[0040] In addition, although the existing technology can improve the density of the silicon oxide film to a certain extent by adjusting the process parameters during the silicon oxide film deposition process, thereby reducing particle contamination during the PECVD process, it still cannot meet the requirements for wafer processing quality.

[0041] Therefore, it is necessary to disclose a method for forming a protective film to effectively reduce the risk of particle contamination of the protective film under plasma bombardment and improve the uniformity of the impedance environment of the process chamber.

[0042] In order to solve the problem that the protective film of the traditional method is very easy to cause particle contamination under the bombardment of plasma and cannot ensure the uniformity of the impedance environment of the process chamber, in the technical solution of the present invention, a first protective film is deposited on the inner wall of the process chamber, and a second protective film is deposited on the surface of the first protective film. The material of the second protective film is different from the material of the first protective film, and the density of the second protective film is greater than the density of the first protective film, so that the protective film has a stronger resistance to plasma bombardment, thereby effectively reducing the probability of the protective film generating particles under the bombardment of plasma during the PECVD process, thereby reducing the risk of particle defects on the wafer surface; at the same time, the smoothness of the second protective film is greater than the smoothness of the first protective film, which effectively improves the uniformity of the impedance environment of the process chamber, and thereby effectively ensures the uniformity of the plasma distribution in the process chamber during the PECVD process, thereby improving the uniformity within and between wafers.

[0043] In addition, the method for forming a protective film disclosed in the embodiment of the present invention also improves the process parameters and the like during the deposition of the first protective film and the second protective film.

[0044] As an optional implementation of the present disclosure, an embodiment of the present invention discloses a method for forming a protective film, such as Figure 1 Shown, including:

[0045] S101 , depositing a first protective film on the inner wall of the process chamber.

[0046] Specifically, the process chamber can be a chamber for performing PECVD process processing, which includes but is not limited to the deposition of silicon oxide-doped dielectric films, silicon carbide-doped dielectric films, silicon nitride-doped dielectric films, and silicon-based low dielectric constant (Low-K) dielectric films.

[0047] The inner wall of the process chamber may include every inner wall of the process chamber. The material of the first protective film may be a material with good adhesion to the inner wall of the process chamber to reduce the risk of the first protective film peeling during the PECVD process. For example, the first protective film may include a silicon oxide film.

[0048] During the process of depositing the first protective film on the inner wall of the process chamber, a first process gas can be introduced into the process chamber, and the first target RF power supply can be controlled to turn on to deposit the first protective film. When the deposition of the first protective film is completed, the first target RF power supply can be turned off, and the introduction of the first process gas into the process chamber can be stopped, and the process chamber can be evacuated. The first process gas can include a reaction gas for reacting to obtain the first protective film, and can also include an inert gas. The first target RF power supply can include a first RF power supply, and can also include a first RF power supply and a second RF power supply at the same time. The frequency of the RF signal output by the first RF power supply can be higher than the frequency of the RF signal output by the second RF power supply. For example, the first RF power supply can be a high-frequency RF power supply, and the second RF power supply can be a low-frequency RF power supply.

[0049] S102 , depositing a second protective film on the surface of the first protective film; wherein the material of the second protective film is different from that of the first protective film, and the density and smoothness of the second protective film are greater than those of the first protective film.

[0050] Specifically, when the deposition of the first protective film is completed, a second protective film can be further deposited on the surface of the first protective film, that is, the second protective film is adhered to the inner wall of the process chamber through the first protective film. The pre-coated layer includes the first protective film and the second protective film. During the PECVD process in the process chamber, the surface of the second protective film can be in direct contact with the internal environment of the process chamber.

[0051] The material of the second protective film can be different from that of the first protective film. It should be noted that the material of the second protective film can be a material that has good adhesion to the first protective film to reduce the risk of peeling off between the first and second protective films during the PECVD process.

[0052] During the process of depositing the second protective film on the surface of the first protective film, a second process gas can be introduced into the process chamber and a second target RF power source can be controlled to be turned on to deposit the second protective film. When the deposition of the second protective film is completed, the second target RF power source can be turned off, the introduction of the second process gas into the process chamber is stopped, and the process chamber is evacuated. The second process gas can include a reaction gas for reacting to obtain the second protective film, and can also include an inert gas. The second target RF power source can include the first RF power source, or can include both the first RF power source and the second RF power source.

[0053] Among them, the density of the second protective film can be greater than the density of the first protective film, that is, the second protective film has stronger resistance to plasma bombardment than the first protective film. Therefore, during the PECVD process, it can effectively reduce the probability of the protective film generating particles under the bombardment of plasma, thereby reducing the risk of particle defects on the wafer surface.

[0054] At the same time, the smoothness of the second protective film can be greater than the smoothness of the first protective film, that is, the surface of the pre-coated layer on the inner wall of the chamber in contact with the internal environment of the process chamber is smoother, and the roughness and unevenness are effectively reduced, thereby effectively improving the uniformity of the impedance environment of the process chamber. Therefore, during the PECVD process, the uniformity of the plasma distribution in the process chamber can be effectively guaranteed, thereby improving the uniformity within and between wafers.

[0055] Currently, the single-layer silicon oxide film deposited on the inner wall of a process chamber exhibits poor adhesion to process films, such as silicon carbide-doped dielectric films, deposited during the PECVD process. Consequently, the process films deposited during the PECVD process are prone to flaking from the inner wall of the process chamber, causing particle contamination. To prevent this flaking and particle contamination, the cumulative thickness of the process films between RPS cleanings is typically reduced. The cumulative thickness is the total thickness of the process films deposited on the inner wall of the process chamber between two consecutive RPS cleanings. This significantly increases the frequency of RPS cleanings. Since each RPS cleaning requires downtime, the increased frequency of RPS cleanings significantly increases downtime for maintenance, making it impossible to maintain wafer manufacturing capacity. To reduce the frequency of RPS cleanings in the process chamber, in one embodiment of the present disclosure, the second protective film comprises a nitrogen-doped silicon carbide film and / or the first protective film comprises a silicon oxide film.

[0056] Specifically, the nitrogen-doped silicon carbide film has an atomic composition similar to that of the process film deposited during the PECVD process and better stress matching. The process film includes but is not limited to silicon oxide-doped dielectric film, silicon carbide-doped dielectric film, silicon nitride-doped dielectric film and silicon-based low dielectric constant (Low-K) dielectric film, thereby enhancing the adhesion between the nitrogen-doped silicon carbide film and the process film deposited during the PECVD process.

[0057] At the same time, the nitrogen-doped silicon carbide film has good adhesion to the silicon oxide film, and the silicon oxide film has good adhesion to the metal inner wall of the process chamber. Therefore, through the synergistic effect of the nitrogen-doped silicon carbide film and the silicon oxide film, during the PECVD process, the process chamber can be free from particles generated by the peeling of the process film at a large cumulative film thickness, thereby effectively reducing the RPS cleaning frequency and improving the wafer manufacturing capacity.

[0058] In addition, nitrogen-doped silicon carbide films have better density and smoothness, thus having stronger resistance to plasma bombardment, and can effectively improve the uniformity of the impedance environment of the process chamber, thereby further reducing the risk of particle defects on the wafer surface and improving the uniformity of plasma distribution in the process chamber.

[0059] In some embodiments of the present invention, the thickness of the second protective film is smaller than the thickness of the first protective film.

[0060] Specifically, the thickness of the second protective film can be smaller than the thickness of the first protective film. For example, the thickness of the first protective film can be greater than or equal to the first preset thickness, the thickness of the second protective film can be less than or equal to the second preset thickness, and the first preset thickness can be greater than the second preset thickness.

[0061] Among them, since the density and smoothness of the second protective film are greater than the density and smoothness of the first protective film, the deposition rate of the second protective film is lower than the deposition rate of the first protective film. By setting the thickness of the second protective film to be smaller than the thickness of the first protective film, the deposition time of the pre-coating layer on the inner wall of the process chamber can be effectively shortened.

[0062] At the same time, by setting the thickness of the first protective film to be greater than or equal to the first preset thickness, the total thickness of the pre-coated layer on the inner wall of the process chamber can be effectively guaranteed, so that during the PECVD process, the thicker pre-coated layer can effectively balance the impedance in the process chamber, thereby providing a stable impedance environment for the process chamber, improving the uniformity of the plasma distribution, and further improving the stability of thin film deposition during the PECVD process.

[0063] Therefore, by setting the thickness of the second protective film to be smaller than the thickness of the first protective film, the deposition time of the pre-coating layer on the inner wall of the process chamber can be shortened while effectively improving the stability of the impedance environment of the process chamber.

[0064] In some embodiments of the present invention, the thickness of the first protective film is greater than or equal to And / or, the thickness of the second protective film is less than or equal to

[0065] Specifically, the thickness of the first protective film may be greater than or equal to The thicker first protective film can effectively balance the impedance in the process chamber, thereby providing a stable impedance environment for the process chamber, improving the uniformity of plasma distribution, and further improving the stability of thin film deposition during the PECVD process.

[0066] In addition, the thickness of the second protective film can be less than or equal to On the one hand, the second protective film has a better density and smoothness, thus having stronger resistance to plasma bombardment and effectively improving the uniformity of the impedance environment in the process chamber, thereby reducing the risk of particle defects on the wafer surface and improving the uniformity of plasma distribution within the process chamber. On the other hand, it can effectively shorten the deposition time of the second protective film, thereby improving the deposition efficiency of the pre-coat layer on the inner wall of the process chamber.

[0067] In some embodiments of the present invention, when a first protective film is deposited on the inner wall of a process chamber, a first process gas is introduced into the process chamber, the first process gas includes a first reaction gas and a second reaction gas, the first reaction gas includes an oxygen-containing gas, and the second reaction gas includes a silicon-containing gas; and / or, when a second protective film is deposited on the surface of the first protective film, a second process gas is introduced into the process chamber, the second process gas includes a third reaction gas and a fourth reaction gas, the third reaction gas includes a nitrogen-containing gas, and the fourth reaction gas includes a carbon-silicon gas.

[0068] Specifically, the first process gas may include a first reaction gas and a second reaction gas, and the first reaction gas and the second reaction gas may be used to react to form the first protective film. For example, the first reaction gas may include an oxygen-containing gas, such as nitrous oxide (N2O), oxygen (O2), carbon dioxide (CO2), etc., and the second reaction gas may include a silicon-containing gas, such as silane (SiH4). Exemplarily, the first reaction gas may be nitrous oxide, which reacts easily with silane and produces fewer by-products of the reaction, thereby effectively ensuring the stability of the components of the first protective film and thereby improving the film formation quality of the first protective film.

[0069] In implementation, the process chamber may include a gas inlet assembly. When depositing the first protective film on the inner wall of the process chamber, a first process gas may be introduced into the process chamber through the gas inlet assembly. The first reactant gas and the second reactant gas in the first process gas may react in a plasma state to deposit the first protective film. The gas flow rate of the first reactant gas may range from 100 to 30,000 sccm, and the gas flow rate of the second reactant gas may range from 100 to 5,000 sccm.

[0070] The second process gas may include a third reaction gas and a fourth reaction gas, and the third reaction gas and the fourth reaction gas may be used to react to form the second protective film. For example, the third reaction gas may include a nitrogen-containing gas, such as ammonia (NH3), and the fourth reaction gas may include a carbon silicon gas, such as tetramethylsilane (Si(CH3)4), trimethylsilane (C3H 10 For example, the fourth reaction gas may be tetramethylsilane, which is easy to react with ammonia and produces fewer by-products, thereby effectively ensuring the stability of the components of the second protective film and improving the film formation quality of the second protective film.

[0071] During implementation, when depositing the second protective film on the surface of the first protective film, a second process gas can be introduced into the process chamber through the gas inlet assembly. The third reactant gas and the fourth reactant gas in the second process gas can react in a plasma state to achieve deposition of the second protective film. The gas flow rate of the third reactant gas can range from 1,000 to 10,000 sccm, and the gas flow rate of the fourth reactant gas can range from 100 to 10,000 sccm.

[0072] It is understood that the first process gas and / or the second process gas may also include an inert gas, such as nitrogen (N2), helium (He), argon (Ar), etc. For example, nitrogen can be used as the inert gas. The inert gas does not react during the deposition of the first protective film and / or the second protective film, and by introducing the inert gas into the process chamber, the reactive gas in the first process gas and / or the reactive gas in the second process gas can be evenly distributed within the process chamber, effectively improving the uniformity of film formation.

[0073] When the first protective film is deposited on the inner wall of the process chamber, the gas flow rate of the inert gas can range from 1000 to 5000 sccm; when the second protective film is deposited on the surface of the first protective film, the gas flow rate of the inert gas can range from 1000 to 10000 sccm.

[0074] In order to further improve the deposition rate of the first protective film and the second protective film, in some embodiments of the present invention, when the time for simultaneously introducing the first reaction gas and the second reaction gas into the process chamber reaches a first preset time, the first RF power supply is controlled to turn on to apply the first RF power to the interior of the process chamber; and / or, when the time for simultaneously introducing the third reaction gas and the fourth reaction gas into the process chamber reaches a second preset time, the first RF power supply and the second RF power supply are controlled to turn on to apply the second RF power and the third RF power to the interior of the process chamber, respectively, and the frequency of the RF signal output by the first RF power supply is higher than the frequency of the RF signal output by the second RF power supply.

[0075] Specifically, during the process of depositing the first protective film on the inner wall of the process chamber, when the time for simultaneously introducing the first reaction gas and the second reaction gas into the process chamber reaches a first preset time, the first RF power supply can be controlled to turn on. By turning on the first RF power supply, a high-frequency RF field can be applied inside the process chamber to provide energy through the high-frequency RF field to excite the reaction gas corresponding to the first protective film to dissociate into gas molecules.

[0076] The first preset time may be in the range of 1 to 5 seconds, so as to ensure that the first reaction gas and the second reaction gas in the process chamber are evenly distributed before turning on the first RF power supply, thereby further improving the film formation uniformity of the first protective film.

[0077] During implementation, the RF power of the first RF power supply can be adjusted to the first RF power, and the first RF power can be determined based on the first target deposition rate of the first protective film. For example, for different reaction gases, the correspondence between the first RF power and the first target deposition rate can be set, and the first RF power of the first RF power supply can be determined according to the reaction gas corresponding to the first protective film and the first target deposition rate of the first protective film. Then, by controlling the first RF power supply to turn on and apply the first RF power to the inside of the process chamber, the deposition rate of the first protective film can be effectively accelerated.

[0078] In addition, during the process of depositing the second protective film on the first protective film, when the duration of simultaneously introducing the third reaction gas and the fourth reaction gas into the process chamber reaches a second preset duration, the first RF power supply and the second RF power supply can be controlled to be turned on at the same time, and the frequency of the RF signal output by the first RF power supply is higher than the frequency of the RF signal output by the second RF power supply. By turning on the first RF power supply, a high-frequency RF field can be applied inside the process chamber, so that the high-frequency RF field provides energy to excite the reaction gas corresponding to the second protective film to dissociate into gas molecules. By turning on the second RF power supply, a low-frequency RF field can be applied inside the process chamber, so that the low-frequency RF field provides energy to excite the dissociated gas molecules to recombine, thereby effectively increasing the recombination probability of the dissociated gas molecules, thereby increasing the film formation rate of the second protective film.

[0079] The second preset time may be in the range of 1 to 60 seconds to ensure that the third reaction gas and the fourth reaction gas in the process chamber are evenly distributed before turning on the first RF power supply and the second RF power supply, thereby further improving the film formation uniformity of the second protective film.

[0080] During implementation, the RF power of the first RF power supply can be adjusted to the second RF power and the RF power of the second RF power supply can be adjusted to the third RF power. The second RF power and the third RF power can be determined based on the second target deposition rate of the second protective film. For example, for different reaction gases, the correspondence between the second RF power and the third RF power and the second target deposition rate can be set, and the second RF power of the first RF power supply and the third RF power of the second RF power supply can be determined according to the reaction gas corresponding to the second protective film and the second target deposition rate of the second protective film. Then, by controlling the first RF power supply and the second RF power supply to turn on and applying the second RF power and the third RF power to the inside of the process chamber respectively, the deposition rate of the second protective film can be effectively accelerated.

[0081] It is understood that a spray assembly and a wafer carrier can be disposed within the process chamber. The spray assembly is used to evenly distribute the process gas entering the process chamber, and the first and second RF power supplies can provide RF power through the spray assembly. The wafer carrier can be grounded, and when the first and / or second RF power supplies are turned on, a bias voltage can be generated between the spray assembly and the wafer carrier. The bias voltage can effectively increase the mean free path of the dissociated gas molecules, further increasing the deposition rate of the first and second protective films.

[0082] In some embodiments of the present invention, after the deposition of the second protective film is completed and before the first RF power supply and the second RF power supply are turned off, the method further includes: controlling the first RF power supply to apply a fourth RF power to the interior of the process chamber, where the fourth RF power is less than the second RF power.

[0083] Specifically, during the deposition process of the second protective film, the deposition time of the second protective film can be monitored in real time. The deposition time of the second protective film may include the turn-on time of the first RF power supply and / or the second RF power supply, and when the deposition time of the second protective film reaches a preset deposition time, it is determined that the deposition of the second protective film is completed.

[0084] Among them, when the second protective film deposition is completed, the output power of the first RF power supply can be adjusted. For example, the first RF power supply can be controlled to apply a fourth RF power to the inside of the process chamber. The fourth RF power can be less than the second RF power to reduce the output power of the first RF power supply.

[0085] By reducing the output power of the first RF power supply, the dissociation rate of the reaction gas corresponding to the second protective film can be effectively reduced, so that the gas molecules dissociated in the process chamber are fully recombined. At the same time, by continuously applying RF power to the interior of the process chamber through the first RF power supply, the gas molecules dissociated in the process chamber can be kept in a suspended state, avoiding the direct shutdown of the first RF power supply at the end of the deposition of the second protective film, which causes the unrecombined gas molecules to fall and produce particles, thereby affecting the smoothness and density of the second protective film, thereby effectively improving the film formation quality of the second protective film.

[0086] It can be understood that after the deposition of the second protective film is completed and before the first RF power supply and the second RF power supply are turned off, the second RF power supply can also be controlled to apply a fifth RF power to the inside of the process chamber. The fifth RF power can be less than the third RF power to reduce the output power of the second RF power supply.

[0087] Before shutting down the first RF power supply and the second RF power supply, by reducing the output power of the first RF power supply and the second RF power supply, a smooth withdrawal of the RF field in the process chamber can be achieved, thereby effectively avoiding sudden changes in plasma conditions in the process chamber caused by directly shutting down the first RF power supply and the second RF power supply, such as temperature and stress, thereby avoiding a reduction in the density of the second protective film, cracks, etc. caused by sudden changes in plasma conditions, and effectively ensuring the film formation quality of the second protective film.

[0088] In some embodiments of the present invention, the second radio frequency power ranges from 100 to 2000 W, and / or the third radio frequency power ranges from 100 to 2000 W.

[0089] Specifically, the second RF power may be in the range of 100 to 2000 W (inclusive), and the third RF power may be in the range of 100 to 2000 W (inclusive). In implementation, the second and third RF powers may be determined based on the film quality requirements (e.g., the particle condition of the second protective film) and the film formation rate requirements of the second protective film.

[0090] It can be understood that the range of the fourth RF power can be the same as the range of the second RF power, and the fourth RF power is less than the second RF power; in addition, the range of the fifth RF power can be the same as the range of the third RF power, and the fifth RF power is less than the third RF power.

[0091] In addition, the first RF power can range from 100 to 2000 W (including endpoint values). In implementation, the magnitude of the first RF power can be determined based on the film quality requirements of the first protective film (eg, the particle condition of the first protective film).

[0092] In order to further improve the uniformity of the first protective film and / or the second protective film, in one embodiment of the present specification, when the first process gas is introduced into the process chamber, the first reaction gas is introduced into the process chamber, and when a third preset time is reached, the second reaction gas is started to be introduced into the process chamber;

[0093] And / or, when the second process gas is introduced into the process chamber, the third reaction gas is introduced into the process chamber, and when a fourth preset time is reached, the fourth reaction gas is started to be introduced into the process chamber.

[0094] Specifically, when the first process gas is introduced into the process chamber, the first reaction gas and the inert gas may be introduced into the process chamber first, so that the first reaction gas is evenly distributed within the process chamber. When a third preset time is reached, the second reaction gas begins to be introduced into the process chamber. That is, when the third preset time is reached, the first reaction gas, the inert gas, and the second reaction gas are simultaneously introduced into the process chamber. Thus, by introducing the second reaction gas after the first reaction gas is evenly distributed within the process chamber, the uniformity of the first protective film can be effectively ensured.

[0095] During implementation, during the process of depositing the first protective film on the inner wall of the process chamber, the first reaction gas and the inert gas can be first introduced into the process chamber. When the third preset time is reached, the second reaction gas is started to be introduced into the process chamber. When the time for introducing the second reaction gas reaches the first preset time, the first RF power supply is controlled to turn on to deposit the first protective film, thereby further improving the uniformity of the first protective film.

[0096] When the second process gas is introduced into the process chamber, the third reaction gas and the inert gas may be introduced into the process chamber first, so that the third reaction gas is evenly distributed within the process chamber. When a fourth preset time period is reached, the fourth reaction gas begins to be introduced into the process chamber. That is, when the fourth preset time period is reached, the third reaction gas, the inert gas, and the fourth reaction gas are simultaneously introduced into the process chamber. Thus, by introducing the fourth reaction gas after the third reaction gas is evenly distributed within the process chamber, the uniformity of the second protective film can be effectively ensured.

[0097] During implementation, during the process of depositing the second protective film on the surface of the first protective film, the third reaction gas and the inert gas can be first introduced into the process chamber. When the fourth preset time is reached, the fourth reaction gas is started to be introduced into the process chamber. When the time for introducing the fourth reaction gas reaches the second preset time, the first RF power supply and the second RF power supply are controlled to turn on to deposit the second protective film, thereby further improving the uniformity of the second protective film.

[0098] The following is an example of an optional embodiment to illustrate the implementation process of the method for forming a protective film of the present invention. Figure 2 Shown, including:

[0099] S201. Inert gas nitrogen and the first reaction gas nitrous oxide are introduced into the process chamber to mix the gases and control the pressure before the first protective film is deposited. In this step, the gas flow rate of nitrogen is in the range of 1000 to 5000 sccm; the gas flow rate of nitrous oxide is in the range of 100 to 30000 sccm; the pressure control range is 0.1 to 10 torr; and the execution time of this step is in the range of 1 to 60 seconds.

[0100] S202: Silane, a second reactant gas, is introduced into the process chamber to mix and control the pressure of all reactant gases, including silane, before depositing the first protective film. In this step, the silane gas flow rate ranges from 100 to 5,000 sccm; the nitrogen gas flow rate ranges from 1,000 to 5,000 sccm; the nitrous oxide gas flow rate ranges from 100 to 30,000 sccm; and the pressure control range is 0.1 to 10 torr. This step lasts for 1 to 5 seconds.

[0101] S203, control the first RF power supply to turn on, apply the first RF power to the inside of the process chamber, so as to deposit a first protective film on the inner wall of the process chamber; in this step, the range of the first RF power is 100~2000W; the range of the silane gas flow rate is 100~5000sccm; the range of the nitrogen gas flow rate is 1000~5000sccm; the range of the nitrous oxide gas flow rate is 100~30000sccm; the range of the pressure control is 0.1~10torr; the execution time of this step is in the range of 10~600sec.

[0102] S204, stop introducing the second reaction gas silane into the process chamber to stop the deposition of the first protective film; in this step, the gas flow rate of nitrogen, the gas flow rate of nitrous oxide and the first RF power remain unchanged compared to step S203, and only stop introducing the second reaction gas silane into the process chamber.

[0103] S205, controlling the first radio frequency power supply to be turned off, stopping the introduction of the inert gas nitrogen and the first reaction gas nitrous oxide into the process chamber, and controlling the process chamber to be vacuumed.

[0104] S206. Inert gas nitrogen and third reaction gas ammonia are introduced into the process chamber to mix the gases and control the pressure before the second protective film is deposited. In this step, the gas flow rate of nitrogen is in the range of 1000 to 10000 sccm; the gas flow rate of ammonia is in the range of 1000 to 10000 sccm; the pressure control range is 0.1 to 10 torr; the execution time of this step is in the range of 1 to 60 seconds.

[0105] S207, a fourth reaction gas tetramethylsilane is introduced into the process chamber to mix all reaction gases including tetramethylsilane and control pressure before depositing the second protective film; in this step, the gas flow of tetramethylsilane ranges from 100 to 10000sccm; the gas flow of nitrogen ranges from 1000 to 10000sccm; the gas flow of ammonia ranges from 1000 to 10000sccm; the pressure control ranges from 0.1 to 10torr; the execution time of this step ranges from 1 to 60sec.

[0106] S208, the first radio frequency power supply and the second radio frequency power supply are controlled to be turned on to apply the second radio frequency power and the third radio frequency power to the inside of the process chamber respectively to deposit the second protective film on the inner wall of the process chamber; in this step, the second radio frequency power ranges from 100 to 2000W, the third radio frequency power ranges from 100 to 2000W; the gas flow of tetramethylsilane ranges from 100 to 10000sccm; the gas flow of nitrogen ranges from 1000 to 10000sccm; the gas flow of ammonia ranges from 1000 to 10000sccm; the pressure control ranges from 0.1 to 10torr; the execution time of this step ranges from 1 to 600sec.

[0107] S209, the output power of the first radio frequency power supply and the second radio frequency power supply is adjusted to apply the fourth radio frequency power and the fifth radio frequency power to the inside of the process chamber respectively to prepare for turning off the first radio frequency power supply and the second radio frequency power supply: in this step, the fourth radio frequency power ranges from 100 to 2000W, the fifth radio frequency power ranges from 100 to 2000W, the fourth radio frequency power is less than the second radio frequency power, and the fifth radio frequency power is less than the third radio frequency power; the gas flow of tetramethylsilane ranges from 100 to 10000sccm; the gas flow of nitrogen ranges from 1000 to 10000sccm; the gas flow of ammonia ranges from 1000 to 10000sccm; the pressure control ranges from 0.1 to 10torr; the execution time of this step ranges from 1 to 60sec.

[0108] S210, the first radio frequency power supply and the second radio frequency power supply are turned off, and the introduction of the inert gas nitrogen, the third reaction gas ammonia and the fourth reaction gas tetramethylsilane into the process chamber is stopped, and the process chamber is controlled to be vacuumized.

[0109] The beneficial effects of the method for forming a protective film according to the present embodiment are verified by experiments as follows.

[0110] Wet Etch Rate (WER) Verification: Four sets of samples were prepared, each consisting of a nitrogen-doped silicon carbide film deposited on a bare silicon wafer according to the method of this embodiment, and a silicon oxide film deposited on a bare silicon wafer according to a conventional method. The four sets of samples were wet-etched in a 100:1 hydrofluoric acid solution. The wet etch rates of the nitrogen-doped silicon carbide film and the silicon oxide film can be compared as shown below. Figure 3 As shown by Figure 3 It can be seen that the wet etching rate of the nitrogen-doped silicon carbide film is much lower than that of the silicon oxide film. It can be seen that the nitrogen-doped silicon carbide film deposited according to the method of this embodiment has higher density and etching resistance than the silicon oxide film deposited according to the existing method. Therefore, by depositing the nitrogen-doped silicon carbide film on the surface of the first protective film in the process chamber, the probability of the nitrogen-doped silicon carbide film generating particles under the bombardment of plasma can be effectively reduced, thereby reducing the risk of particle defects on the wafer surface.

[0111] Wafer particle contamination verification: Based on the method of this embodiment, a first protective film is deposited on the inner wall of the process chamber and a second protective film is deposited on the surface of the first protective film. When the PECVD process is performed in the process chamber, the cumulative film thickness of the process film is calculated. Growth to The number of particles larger than 0.4 μm on the wafer during the process can be statistically analyzed as follows: Figure 4 As shown. Figure 4 It can be seen that as the cumulative film thickness of the process film increases, the number of particles on the wafer does not increase significantly. It can be seen that the protective film prepared by the method of this embodiment has a good inhibitory effect on wafer particle contamination. The second protective film acts as an excellent intermediate adhesion layer between the first protective film and the process film. At the same time, it effectively increases the cumulative film thickness of the process film during the RPS cleaning interval, thereby improving the production capacity of wafer manufacturing.

[0112] As an optional implementation of the present invention, the present invention also discloses a protective film. Figure 5The protective film 300 includes a first protective film 301 and a second protective film 302 sequentially disposed along the thickness direction of the inner wall of the process chamber 20. The material of the second protective film 302 is different from that of the first protective film 301, and the second protective film 302 has greater density and smoothness than the first protective film 301. That is, the second protective film 302 adheres to the inner wall of the process chamber 20 via the first protective film 301. During the PECVD process in the process chamber 20, the surface of the second protective film 302 can directly contact the internal environment of the process chamber 20. By setting the density of the second protective film 302 greater than that of the first protective film 301, the second protective film 302 has a stronger resistance to plasma bombardment than the first protective film 301. Therefore, during the PECVD process, the probability of particles generated by the protective film 300 under plasma bombardment can be effectively reduced, thereby reducing the risk of particle defects on the wafer surface. At the same time, by setting the smoothness of the second protective film 302 to be greater than the smoothness of the first protective film 301, the surface of the protective film 300 in contact with the internal environment of the process chamber 20 is smoother, and the roughness and unevenness are effectively reduced, thereby effectively improving the uniformity of the impedance environment of the process chamber 20. Therefore, during the PECVD process, the uniformity of the plasma distribution in the process chamber 20 can be effectively guaranteed, thereby improving the uniformity within and between wafers.

[0113] Exemplarily, the second protective film 302 includes a nitrogen-doped silicon carbide film, and / or the first protective film 301 includes a silicon oxide film. The nitrogen-doped silicon carbide film has an atomic composition similar to that of the process film deposited during the PECVD process and better stress matching, which enhances the adhesion between the second protective film 302 and the process film deposited during the PECVD process. At the same time, the nitrogen-doped silicon carbide film has good adhesion to the silicon oxide film, and the silicon oxide film has good adhesion to the metal inner wall of the process chamber 20. Therefore, through the synergistic effect of the first protective film 301 and the second protective film 302, during the PECVD process, the process chamber 20 can be prevented from generating particles caused by the peeling of the process film at a larger cumulative film thickness, thereby effectively reducing the RPS cleaning frequency and improving the wafer manufacturing capacity. In addition, the nitrogen-doped silicon carbide film has better density and smoothness, thus having stronger resistance to plasma bombardment, and can effectively improve the uniformity of the impedance environment of the process chamber 20, thereby further reducing the risk of particle defects on the wafer surface and improving the uniformity of plasma distribution in the process chamber 20.

[0114] For example, the thickness of the second protective film 302 is less than that of the first protective film 301, which can effectively shorten the deposition time of the protective film 300 on the inner wall of the process chamber 20. At the same time, it can ensure the overall thickness of the protective film 300, so that the protective film 300 can effectively balance the impedance in the process chamber 20, and thus provide a stable impedance environment for the process chamber 20, thereby improving the uniformity of plasma distribution and further improving the stability of thin film deposition during the PECVD process.

[0115] Exemplarily, the thickness of the first protective film 301 is greater than or equal to And / or, the thickness of the second protective film 302 is less than or equal to By setting a thicker first protective film 301, the impedance in the process chamber 20 can be effectively balanced, thereby providing a stable impedance environment for the process chamber 20, improving the uniformity of plasma distribution, and further improving the stability of thin film deposition during the PECVD process; at the same time, by setting a thinner second protective film 302, the deposition time of the second protective film 302 can be effectively shortened, thereby improving the deposition efficiency of the protective film 300 on the inner wall of the process chamber 20.

[0116] As an optional implementation of the present invention, the present invention also discloses a semiconductor process equipment. Figure 6 The semiconductor process equipment 200 includes a process chamber 20, an inlet assembly 20A, an upper electrode assembly 20B, a lower electrode assembly 20C and a controller ( Figure 6 The controller includes at least one processor and at least one memory, wherein a computer program is stored in the memory, and when the computer program is executed by the processor, the method for forming a protective film according to any one of the above embodiments is implemented.

[0117] For example, the controller can be a host computer or a slave computer. The controller can control the valve opening of the gas inlet assembly 20A to introduce the corresponding process gas into the process chamber 20. The controller can also control the opening and closing degree of the valve of the gas inlet assembly 20A to control the flow rate of the process gas. The semiconductor process equipment 200 can also include a vacuum assembly 24. The controller can control the vacuum assembly 24 to evacuate the interior of the process chamber 20 to control the vacuum level inside the process chamber 20. The semiconductor process equipment 200 can also include a heating assembly 25. The controller can control the heating assembly 25 to heat the interior of the process chamber 20 to control the temperature inside the process chamber 20.

[0118] The upper electrode assembly 20B includes an RF power supply 21 and a spray assembly 22. The RF power supply 21 may include a first RF power supply and a second RF power supply. The first RF power supply may be a high-frequency RF power supply, and the second RF power supply may be a low-frequency RF power supply. The controller is also used to control the RF power supply 21 to provide upper electrode power to the spray assembly 22 to excite the process gas inside the process chamber 20 to generate plasma 100. The upper electrode assembly 20B may also include a matcher 26. The RF power supply 21 may provide upper electrode power to the spray assembly 22 through the matcher 26 to ensure maximum RF power feed. The matcher 26 may include a first matcher and a second matcher. The first RF power supply and the second RF power supply provide upper electrode power to the spray assembly 22 through the first matcher and the second matcher, respectively.

[0119] The lower electrode assembly 20C includes a wafer carrier 23 , which may be grounded. The wafer carrier 23 may be, for example, an electrostatic chuck, a mechanical chuck, or a vacuum adsorption chuck.

[0120] The semiconductor process equipment 200 disclosed in the embodiment of the present invention may be a high-density plasma chemical vapor deposition equipment or a plasma-enhanced chemical vapor deposition equipment.

[0121] The technical features of the above embodiments can be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0122] The above embodiments only express several implementation methods of this specification. Their descriptions are relatively specific and detailed, but they should not be understood as limiting the scope of the solutions disclosed in the embodiments of this specification. It should be pointed out that for those skilled in the art, several variations and improvements can be made without departing from the concept of this specification, and these are all within the scope of protection of this specification. Therefore, the scope of protection of the patent in this specification shall be based on the attached claims.

Claims

1. A method for forming a protective film, characterized in that: include: depositing a first protective film on an inner wall of the process chamber; A second protective film is deposited on the surface of the first protective film; wherein the material of the second protective film is different from the material of the first protective film, and the density and smoothness of the second protective film are greater than the density and smoothness of the first protective film.

2. The method according to claim 1, characterized in that The second protection film includes a nitrogen-doped silicon carbide film, and / or the first protection film includes a silicon oxide film.

3. The method according to claim 1, characterized in that The thickness of the second protection film is smaller than the thickness of the first protection film.

4. The method according to claim 3, characterized in that The thickness of the first protective film is greater than or equal to And / or, the thickness of the second protective film is less than or equal to 5. The method according to claim 2, characterized in that When depositing the first protective film on the inner wall of the process chamber, a first process gas is introduced into the process chamber, wherein the first process gas includes a first reaction gas and a second reaction gas, wherein the first reaction gas includes an oxygen-containing gas and the second reaction gas includes a silicon-containing gas; And / or, when depositing a second protective film on the surface of the first protective film, a second process gas is introduced into the process chamber, the second process gas includes a third reaction gas and a fourth reaction gas, the third reaction gas includes a nitrogen-containing gas, and the fourth reaction gas includes a carbon-silicon gas.

6. The method according to claim 5, characterized in that When the duration of simultaneously introducing the first reaction gas and the second reaction gas into the process chamber reaches a first preset duration, controlling a first radio frequency power source to turn on and apply a first radio frequency power to the interior of the process chamber; And / or, when the time duration for simultaneously introducing the third reaction gas and the fourth reaction gas into the process chamber reaches a second preset time duration, the first RF power supply and the second RF power supply are controlled to be turned on, and the second RF power and the third RF power are respectively applied to the interior of the process chamber, and the frequency of the RF signal output by the first RF power supply is higher than the frequency of the RF signal output by the second RF power supply.

7. The method according to claim 6, characterized in that After the deposition of the second protective film is completed and before the first RF power supply and the second RF power supply are turned off, the method further includes: The first RF power source is controlled to apply a fourth RF power to the interior of the process chamber, where the fourth RF power is less than the second RF power.

8. The method according to any one of claims 5 to 7, characterized in that When the first process gas is introduced into the process chamber, the first reaction gas is introduced into the process chamber, and when a third preset time is reached, the second reaction gas is started to be introduced into the process chamber; And / or, when the second process gas is introduced into the process chamber, the third reaction gas is introduced into the process chamber, and when a fourth preset time is reached, the fourth reaction gas is started to be introduced into the process chamber.

9. A protective film, characterized in that: The protective film includes a first protective film and a second protective film sequentially arranged in the thickness direction of the inner wall of the process chamber; The material of the second protective film is different from that of the first protective film, and the density and smoothness of the second protective film are greater than those of the first protective film.

10. The protective film according to claim 9, characterized in that The second protection film includes a nitrogen-doped silicon carbide film, and / or the first protection film includes a silicon oxide film.

11. The protective film according to claim 9, characterized in that The thickness of the second protection film is smaller than the thickness of the first protection film.

12. The protective film according to claim 11, wherein The thickness of the first protective film is greater than or equal to And / or, the thickness of the second protective film is less than or equal to 13. A semiconductor process equipment, characterized in that: include: A process chamber, an air inlet assembly, an upper electrode assembly, a lower electrode assembly and a controller, wherein the controller includes at least one processor and at least one memory, wherein the memory stores a computer program, and when the computer program is executed by the processor, the method for forming a protective film according to any one of claims 1 to 8 is implemented.

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