Method for producing an aluminum nitride film

Abstract

The application provides a preparation method of an aluminum nitride film. The aluminum nitride film is prepared by using a physical vapor deposition device. The physical vapor deposition device comprises a process chamber, a base and a target material located above the base in the process chamber, the target material is electrically connected with an excitation power supply, and a side magnet assembly is arranged outside the sidewall of the process chamber. The preparation method comprises the following steps: turning on the side magnet assembly to form a magnetic field in the process chamber; a mixed gas of a first gas and a second gas is introduced into the process chamber according to a preset flow ratio; and the excitation power supply is turned on to excite the mixed gas to form a plasma, so that the ion distribution in the plasma is adjusted by the magnetic field, and free electrons exist in the aluminum nitride film deposited on the surface of a deposition object. The aluminum nitride film deposited on the deposition object can conduct electricity.

Description

Technical Field

[0001] This invention relates to the field of semiconductor manufacturing, and more specifically, to a method for preparing aluminum nitride thin films. Background Technology

[0002] Silicon-based flash memory is currently the mainstream non-volatile memory in the semiconductor market, but its miniaturization is increasingly approaching its physical limits. Resistive Random Access Memory (RRAM) is one of the strong contenders for the next generation of high-speed, high-density, and low-power non-volatile memory, and has received widespread attention from the scientific and industrial communities in recent years. Based on the resistive switching mechanism, RRAM can be roughly divided into three categories: ion-migrating, thermochemical reaction, and electron capture and release. Among these, ion-migrating RRAM can be further divided into cation-migrating and anion-migrating types. Among these types, cation-migrating RRAM can combine the advantages of high on / off ratio, low power consumption, and excellent cycle tolerance and data retention characteristics, thus showing a promising commercial prospect and attracting more attention from the scientific and industrial communities. In practical applications, cation-migrating RRAM is integrated using a cross-shaped array structure, where each cross point is a memory cell, consisting of a three-layer film of active electrode / storage medium / inert electrode.

[0003] Cation-migrating RRAM has relatively relaxed requirements for its storage medium, making its sources very diverse; almost all common semiconductor and insulating thin films can be used as this type of storage medium. Reported storage media mainly include tantalum oxide (TaOx), aluminum oxide (AlOx), and aluminum nitride (AlN). Inorganic storage media mainly have advantages such as good CMOS process compatibility, high on / off ratio, strong cycle tolerance, and reliable data retention characteristics.

[0004] Currently, aluminum nitride (AlN) films are generally deposited using trimethylaluminum (TMA) and ammonia. However, the aluminum nitride films deposited by this method have a fixed composition, in which N atoms and Al atoms combine to form a compound with an elemental ratio of 1:1, resulting in the aluminum nitride films being non-conductive. Summary of the Invention

[0005] The present invention aims to solve at least one of the technical problems existing in the prior art, and proposes a method for preparing aluminum nitride thin film, wherein an conductive aluminum nitride thin film is deposited on the part to be deposited.

[0006] To achieve the objectives of this invention, a method for preparing aluminum nitride thin films is provided. The method employs a physical vapor deposition (PVD) apparatus, which includes a process chamber, a base, and a target material located above the base. The target material is electrically connected to an excitation power supply. An edge magnet assembly is disposed around the outer sidewall of the process chamber. The preparation method includes: activating the edge magnet assembly to form a magnetic field within the process chamber; introducing a mixture of a first gas and a second gas into the process chamber according to a preset flow rate ratio; activating the excitation power supply to excite the mixed gas to form plasma, thereby adjusting the ion distribution of the plasma through the magnetic field to ensure the presence of free electrons in the aluminum nitride thin film deposited on the surface of the workpiece.

[0007] Furthermore, the preset flow rate ratio differs in different preparation methods.

[0008] Furthermore, the first gas is argon, and the second gas is nitrogen.

[0009] Furthermore, the smaller the flow ratio of argon to nitrogen, the higher the resistivity of the aluminum nitride film.

[0010] Further, the process chamber is introduced with a mixture of the first gas and the second gas according to a preset flow rate ratio, which includes: obtaining a preset flow rate ratio corresponding to the required resistivity of the aluminum nitride film based on the correspondence between the preset flow rate ratio and the resistivity of the aluminum nitride film; and introducing the mixture of the first gas and the second gas into the process chamber according to the obtained preset flow rate ratio.

[0011] Furthermore, the flow rate of the first gas introduced into the process chamber is greater than or equal to 20 sccm and less than or equal to 60 sccm; and / or the flow rate of the second gas introduced into the process chamber is greater than or equal to 20 sccm and less than or equal to 45 sccm.

[0012] Furthermore, activating the edge magnet assembly to form a magnetic field within the process chamber includes: passing current through the edge magnet assembly to form a magnetic field with a preset direction within the process chamber; and adjusting the ion distribution in the plasma using the magnetic field, including: enabling ions in the plasma to move within the magnetic field to adjust the ion distribution.

[0013] Furthermore, the current flowing through the side magnet assembly is greater than or equal to 10A and less than or equal to 20A.

[0014] Furthermore, the excitation power supply is a pulsed DC power supply; the power of the pulsed DC power supply is greater than or equal to 2000W and less than or equal to 5000W; the frequency of the pulsed DC power supply is greater than or equal to 100Hz and less than or equal to 200Hz.

[0015] Furthermore, the pressure within the process chamber is always greater than or equal to 1 mTorr and less than or equal to 10 mTorr during the preparation process.

[0016] The present invention has the following beneficial effects:

[0017] The method for preparing aluminum nitride thin film provided by the present invention, on the one hand, can form a magnetic field in the process chamber after the side magnet assembly is turned on. This magnetic field can act on the plasma of the mixed gas in the process chamber. The ions in the plasma move in the magnetic field, which can change the plasma distribution and increase the ionization rate at the same time. This avoids the combination of N atoms and Al atoms to form a compound with an element ratio of 1:1. As a result, aluminum atoms and nitrogen ions do not successfully form a compound and still exist in the form of ions. Thus, the generated aluminum nitride film layer contains a large number of free electrons.

[0018] Other objects and features of the present invention will become clear from reading the specification, claims and drawings of this application. Attached Figure Description

[0019] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:

[0020] Figure 1 This is a flowchart of the method for preparing aluminum nitride thin film according to an embodiment of the present invention.

[0021] Figure 2 This is a structural schematic diagram of a physical vapor deposition apparatus according to an embodiment of the present invention.

[0022] Figure 3 This is the process hysteresis curve during the preparation of the aluminum nitride thin film in the method for preparing the aluminum nitride thin film according to an embodiment of the present invention, when the preset inert gas flow rate is 50 sccm. And...

[0023] Figure 4 This is a curve showing the relationship between the resistivity of the aluminum nitride film and the nitrogen flow rate when the preset inert gas flow rate is 50 sccm in the aluminum nitride film preparation method of the present invention.

[0024] Explanation of key component symbols:

[0025] 10. Physical vapor deposition equipment; 20. Parts to be deposited;

[0026] 100. Process chamber; 110. Wafer transfer port;

[0027] 200. Base;

[0028] 300. Target material;

[0029] 400. Side magnet assembly;

[0030] 500. Molecular pump;

[0031] 600. Lifting drive assembly. Detailed Implementation

[0032] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0033] Figure 2 This is a structural schematic diagram of the physical vapor deposition apparatus 10 according to an embodiment of the present invention. See also... Figure 2 The physical vapor deposition apparatus 10 includes a process chamber 100, in which a base 200 and a target 300 located above the base 200 are disposed. The target 300 is electrically connected to an excitation power supply, and a side magnet assembly 400 is disposed around the outer side wall of the process chamber 100.

[0034] It should be noted that the side magnet assembly 400 disposed on the side wall of the process chamber 100 can be located inside or outside the process chamber 100; it can be located above or below the base 200. Since the specific position of the side magnet assembly 400 does not affect its ability to generate a magnetic field within the process chamber 100, no specific limitation is made here.

[0035] The magnitude of the magnetic field formed by the edge magnet assembly 400 within the process chamber 100 can be controlled by the magnitude of the current supplied to the edge magnet assembly 400 or the distance between the edge magnet assembly 400 and the process chamber 100.

[0036] The side magnet assembly 400 can be disposed in the form of a coil on the side wall of the process chamber 100 (the side wall here is not limited to the one perpendicular to the process chamber 100). Figure 2The horizontal sidewalls (which can also be vertical) are wound around the periphery of the process chamber 100. The magnetic field direction within the process chamber 100 can be from the base to the target or from the target to the base. Ions in the plasma, subjected to the centripetal force provided by the Lorentz force, can rotate around the vertical direction in the magnetic field. In other embodiments, the side magnet assembly 400 can also be disposed on the sidewall of the process chamber 100 as a magnet block, so that the magnetic field direction within the process chamber 100 can be horizontal, and ions in the plasma, subjected to the centripetal force provided by the Lorentz force, can rotate around the horizontal direction in the magnetic field. In other embodiments, the side magnet assembly 400 can also take other forms that can form a magnetic field within the process chamber 100, so that ions in the plasma move and redistribute in the magnetic field.

[0037] It should be noted that the base 200 is used to support the deposition object 20 and can drive the deposition object 20 to move or rotate. In other words, the deposition object 20 is positioned on the side of the base 200 facing the target material 300 to facilitate subsequent deposition.

[0038] Aluminum nitride thin films can be prepared using physical vapor deposition equipment 10. Figure 1 This is a flowchart of a method for preparing an aluminum nitride thin film according to an embodiment of the present invention. See also... Figure 1 The method for preparing aluminum nitride thin film includes steps S1001 to S1003.

[0039] Step S1001: Turn on the side magnet assembly 400 to form a magnetic field in the process chamber 100.

[0040] Step S1002: Introduce a mixture of the first gas and the second gas into the process chamber 100 according to a preset flow ratio.

[0041] The first gas is argon, and the second gas is nitrogen. Step S1003: Turn on the excitation power supply to excite the mixed gas to form plasma, so as to adjust the ion distribution in the plasma by means of a magnetic field, so that free electrons exist in the aluminum nitride thin film deposited on the surface of the part to be deposited 20.

[0042] This step typically uses a low-power, low-pressure sputtering process to reduce ion energy and avoid damage to the underlying thin film.

[0043] The magnetic field generated within the process chamber 100 can regulate the ion distribution in the plasma. The presence of free electrons in the aluminum nitride film means that the aluminum nitride film is conductive. In other words, by regulating the ion distribution in the plasma using a magnetic field, a conductive aluminum nitride film can be obtained. Different preset flow ratios are used in different methods of preparing aluminum nitride films. The specific value of the preset flow ratio is related to the desired resistivity of the aluminum nitride film.

[0044] Specifically, the excitation power supply will generate a negative voltage on the target 300, which will promote the ionized argon gas to bombard the target 300. The aluminum atoms generated by bombarding the target 300 react with the (nitrogen) plasma in the process chamber 100 to generate aluminum nitride, which can then be deposited on the workpiece 20 located at the process position to deposit an aluminum nitride film.

[0045] The magnetic field generated by the edge magnet assembly 400 within the process chamber 100 can act on the plasma within the process chamber 100. Ions in the plasma move within the magnetic field, altering the plasma distribution and increasing the ionization rate. This prevents N atoms from combining with Al atoms to form a 1:1 compound, ensuring that aluminum atoms and nitrogen ions remain ionic and thus contain a large number of free electrons in the prepared aluminum nitride film. This allows the aluminum nitride film to conduct electricity, meeting the different functional requirements of RRAM devices. Experimental results show that without the edge magnet assembly 400 outside the process chamber 100, the resistivity of the prepared aluminum nitride film is infinite, indicating that the film is insulating and non-conductive. However, when the edge magnet assembly 400 is present outside the process chamber 100, the resistance of the prepared aluminum nitride film significantly decreases after the assembly is activated, and the repeatability is significantly improved.

[0046] The physical vapor deposition apparatus 10 may further include a molecular pump 500 and a lifting drive assembly 600, with a transfer port 110 provided on the process chamber 100. Specifically, the molecular pump 500 is used to maintain the pressure within the process chamber 100. The lifting drive assembly 600 is connected to the base 200 and is used to drive the base 200 to move vertically up and down, thereby raising or lowering the workpiece 20 by a certain distance and maintaining the base 200 at the process position for depositing aluminum nitride thin films on the workpiece 20.

[0047] The following describes an embodiment of a method for preparing aluminum nitride thin films using a specific step, but it should be noted that this does not limit the scope of the invention.

[0048] The process chamber 100 is evacuated to a high vacuum using a molecular pump 500. At this point, the pressure inside the process chamber 100 is less than 5 × 10⁻⁶. -6 Torr;

[0049] The part to be deposited 20 enters the process chamber 100 through the transfer port 110 and is placed on the base 200;

[0050] The control lifting drive assembly 600 drives the base 200 to the process position of the part to be deposited 20;

[0051] The edge magnet assembly 400 is activated, and a magnetic field is formed within the process chamber 100;

[0052] By introducing a mixture of argon and nitrogen into the process chamber 100 and maintaining it for a period of time (approximately 20 seconds), the pressure inside the process chamber 100 can be kept stable (stability is achieved by varying the pressure value around a certain value).

[0053] Turn on the excitation power supply to stimulate the mixed gas to form plasma, so as to deposit an aluminum nitride thin film on the surface of the part to be deposited 20;

[0054] Turn off the excitation power supply and stop the flow of mixed gas into the process chamber 100;

[0055] The deposition piece 20 is transferred out of the process chamber 100 through the transfer port 110, and the preparation method of aluminum nitride thin film ends.

[0056] Preferably, during the above process, the temperature of the base 200 can be greater than or equal to 150°C and less than or equal to 300°C.

[0057] In some embodiments, the edge magnet assembly 400 may be wound around the outside of the process chamber 100 in the form of a coil. The structure consists of multiple turns of conductive coil surrounding the process chamber 100, which, when a direct current is applied to the coil, creates a stable electromagnetic field within the process chamber 100. The magnetic field strength and direction can be adjusted by the magnitude and sign of the current flowing through the coil.

[0058] In some embodiments, the resistivity of the aluminum nitride film can be adjusted by regulating the flow rate ratio of the first gas and the second gas. Specifically, the resistivity of aluminum nitride can be adjusted by regulating the flow rate ratio of argon and nitrogen.

[0059] The smaller the flow ratio of argon to nitrogen, the higher the resistivity of the aluminum nitride film.

[0060] It should be noted that when the resistivity of the aluminum nitride film is greater than a preset threshold, the aluminum nitride film is non-conductive; when the resistivity of the aluminum nitride film is less than or equal to the preset threshold, the aluminum nitride film is conductive.

[0061] Figure 3 This is the process hysteresis curve for preparing aluminum nitride thin films when the preset inert gas flow rate is 50 sccm in the preparation method of aluminum nitride thin films according to embodiments of the present invention. See also Figure 3It can be observed that when the flow ratio of argon to nitrogen is less than 1, the voltage of target 300 is basically stable, indicating that target 300 has been completely nitrided. At this point, the deposited aluminum nitride film is an insulator, meaning it is not conductive. When the flow ratio of argon to nitrogen is greater than 1, target 300 is not yet completely nitrided, and the aluminum nitride film prepared at this point is a semiconductor, meaning it is conductive.

[0062] The step S1002, in which a mixture of the first gas and the second gas is introduced into the process chamber 100 according to a preset flow ratio, may specifically include steps S1021 to S1022.

[0063] Step S1021: Based on the correspondence between the preset flow rate ratio and the resistivity of the aluminum nitride film, obtain the preset flow rate ratio corresponding to the required resistivity of the aluminum nitride film.

[0064] Step S1022: According to the obtained preset flow ratio, a mixture of the first gas and the second gas is introduced into the process chamber 100.

[0065] In some embodiments, the flow rate of the first gas and the pre-stored correspondence between the flow rate of the second gas and the resistivity of the aluminum nitride film can be predetermined to obtain the flow rate of the second gas corresponding to the desired resistivity of the aluminum nitride film. A mixture of the first and second gases is introduced into the process chamber 100 according to the predetermined flow rate of the first gas and the flow rate of the second gas corresponding to the desired resistivity of the aluminum nitride film.

[0066] The relationship between the flow rate of the pre-stored second gas and the resistivity of the aluminum nitride film includes: the resistivity of the aluminum nitride film is directly proportional to the flow rate of the second gas.

[0067] Figure 4 This is a curve showing the relationship between the resistivity of the aluminum nitride thin film and the nitrogen flow rate when the preset argon gas flow rate is 50 sccm in the preparation method of the aluminum nitride thin film according to an embodiment of the present invention. See also... Figure 4 It can be seen that when the argon flow rate is fixed, the resistivity of the aluminum nitride film is positively correlated with the nitrogen flow rate. When it is necessary to prepare an aluminum nitride film with low resistivity, a smaller flow rate of nitrogen is introduced into the process chamber 100; when it is necessary to prepare an aluminum nitride film with high resistivity, a larger flow rate of nitrogen is introduced into the process chamber 100.

[0068] Understandable. Figure 4 This refers to the relationship between the pre-stored nitrogen flow rate and the resistivity of the aluminum nitride film. It can be determined based on... Figure 4 Based on the corresponding relationship, the flow rate of nitrogen gas to be introduced into the process chamber 100 can be determined according to the resistivity of the aluminum nitride film.

[0069] In some embodiments, the flow rate of the first gas introduced into the process chamber 100 is greater than or equal to 20 sccm and less than or equal to 60 sccm; and / or the flow rate of the second gas introduced into the process chamber 100 is greater than or equal to 20 sccm and less than or equal to 45 sccm.

[0070] Understandably, the flow rate of the first gas introduced into the process chamber 100 can be greater than or equal to 10 sccm and less than or equal to 100 sccm.

[0071] In step S1001, turning on the edge magnet assembly 400 and forming a magnetic field in the process chamber 100 includes: passing current into the edge magnet assembly 400 to form a magnetic field with a preset direction in the process chamber 100.

[0072] A current is passed through the edge magnet assembly 400, and a magnetic field with a preset direction is formed in the process chamber 100, so that ions in the plasma can move in the magnetic field to regulate the distribution of ions.

[0073] Step S1003 involves adjusting the ion distribution in the plasma using a magnetic field, including enabling ions in the plasma to move within the magnetic field to adjust the ion distribution.

[0074] In some embodiments, the current flowing through the edge magnet assembly 400 is greater than or equal to 10A and less than or equal to 20A.

[0075] In step S1003, the excitation power supply can be a pulsed DC power supply. The power of the pulsed DC power supply is greater than or equal to 2000W and less than or equal to 5000W; the frequency of the pulsed DC power supply is greater than or equal to 100Hz and less than or equal to 200Hz.

[0076] In some embodiments, the pulsed DC power supply is turned on at predetermined intervals; the predetermined interval is greater than or equal to 1 second and less than or equal to 2 seconds.

[0077] Specifically, the predetermined duration of the pulsed DC power supply interval can also be understood as the reverse duration. In other words, the pulsed DC power supply lasts for 1 to 2 seconds. The reverse duration here refers to the duration during which the pulsed DC power supply is turned off (the pulsed DC power supply is turned on intermittently; the reverse time here can also be understood as the interval between adjacent on-times).

[0078] The turn-on duration of the pulsed DC power supply (e.g., 30 seconds) is determined by the required thickness of the aluminum nitride film. The turn-on time of the pulsed DC power supply can be determined based on the required aluminum nitride film thickness and the relationship between that thickness and the turn-on time. It is understood that the turn-on time of the pulsed DC power supply is also the forward time. It is also understood that the excitation power supply can be one or more of the following: DC power supply, RF power supply, and pulsed DC power supply.

[0079] The pressure inside the process chamber 100 is always greater than or equal to 1 mTorr and less than or equal to 10 mTorr during the preparation process.

[0080] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include one or more of the stated features. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0081] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection, an electrical connection, or a connection that allows for communication; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0082] In the description of this invention, unless otherwise expressly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature being directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature being directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0083] The following disclosure provides many different embodiments or examples for implementing various structures of the invention. To simplify the disclosure, specific examples of components and arrangements are described below. These are merely examples and are not intended to limit the invention. Furthermore, reference numerals and / or letters may be repeated in different examples; such repetition is for simplification and clarity and does not in itself indicate a relationship between the various embodiments and / or arrangements discussed. In addition, examples of various specific processes and materials are provided in this invention, but those skilled in the art will recognize the application of other processes and / or the use of other materials.

[0084] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with an embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0085] It is understood that the above embodiments are merely exemplary implementations used to illustrate the principles of the present invention, and the present invention is not limited thereto. For those skilled in the art, various modifications and improvements can be made without departing from the spirit and essence of the present invention, and these modifications and improvements are also considered to be within the scope of protection of the present invention.

Claims

1. A method for preparing an aluminum nitride thin film, characterized in that, Aluminum nitride thin films are prepared using a physical vapor deposition (PVD) apparatus. The PVD apparatus includes a process chamber, in which a base and a target material located above the base are disposed. The target material is electrically connected to an excitation power supply, and a side magnet assembly is disposed around the outer side wall of the process chamber. The preparation method includes: The edge magnet assembly is activated to generate a magnetic field within the process chamber; A mixture of argon and nitrogen gas with a preset flow ratio greater than 1 is introduced into the process chamber. The excitation power supply is turned on to excite the mixed gas to form plasma, so that the ion distribution in the plasma is adjusted by the magnetic field, so that free electrons exist in the aluminum nitride film deposited on the surface of the workpiece.

2. The method according to claim 1, characterized in that, The preset flow rate ratio varies in different preparation methods.

3. The method according to claim 1, characterized in that, The smaller the flow ratio of argon to nitrogen, the higher the resistivity of the aluminum nitride film.

4. The method according to claim 1, characterized in that, The process chamber is introduced with a mixture of argon and nitrogen at a preset flow rate ratio, including: Based on the correspondence between the preset flow rate ratio and the resistivity of the aluminum nitride film, the preset flow rate ratio corresponding to the required resistivity of the aluminum nitride film is obtained. According to the obtained preset flow rate ratio, a mixture of argon and nitrogen gas is introduced into the process chamber.

5. The method according to claim 1, characterized in that, The flow rate of the argon gas introduced into the process chamber is greater than or equal to 20 sccm and less than or equal to 60 sccm; and / or The flow rate of the nitrogen gas introduced into the process chamber is greater than or equal to 20 sccm and less than or equal to 45 sccm.

6. The method according to claim 1, characterized in that, The step of activating the edge magnet assembly to form a magnetic field within the process chamber includes: A current is passed through the edge magnet assembly to form a magnetic field with a preset direction within the process chamber; The adjustment of ion distribution in the plasma by means of the magnetic field includes: This allows ions in the plasma to move within the magnetic field, thereby regulating the distribution of the ions.

7. The method according to claim 6, characterized in that, The current flowing through the edge magnet assembly is greater than or equal to 10A and less than or equal to 20A.

8. The method according to claim 1, characterized in that, The excitation power supply is a pulsed DC power supply; The power of the pulsed DC power supply is greater than or equal to 2000W and less than or equal to 5000W. The frequency of the pulsed DC power supply is greater than or equal to 100Hz and less than or equal to 200Hz.

9. The method according to claim 1, characterized in that, The pressure within the process chamber is greater than or equal to 1 mTorr and less than or equal to 10 mTorr during the preparation process.

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