A multi-mode microwave plasma generating device

Abstract

The application relates to a multi-mode microwave plasma generating device, which comprises a microwave output unit, a multi-mode microwave metal chamber and an insulating material vacuum chamber built in the multi-mode microwave metal chamber; a microwave source is fed into the metal chamber through the microwave output unit, is converted into multi-mode microwave through multiple reflections of the inner wall of the metal chamber, forms a spatially uniformly distributed microwave field intensity in the multi-mode microwave metal chamber, and breaks through a gas with a pressure lower than 1 atmosphere in the insulating material vacuum chamber built in the multi-mode microwave metal chamber to form a uniformly high-density plasma. Based on the propagation characteristics of electromagnetic waves and the wave superposition principle, the application constructs a microwave multi-reflection surface, changes the wave vector (the propagation direction of the wave), the electric vector and the magnetic vector, and the phase changed due to different reflection points, generates reflection waves with various phases and different propagation directions, the superposition of the waves forms multi-mode microwave, and the uniformity of the spatial microwave field intensity distribution in the metal chamber is greatly improved.

Description

Technical Field

[0001] This invention relates to the field of plasma generation technology, and more specifically to a multi-mode microwave plasma generator. Background Technology

[0002] Various low-temperature plasma technologies have been widely applied in chip manufacturing and packaging, flat panel displays, LED packaging, PCB manufacturing processes, solar thin-film batteries, functional thin film preparation, and the preparation of new materials. These include various capacitively coupled plasmas, inductively coupled plasmas, and microwave plasmas. The excitation power sources for plasma generation range from DC to microwave, covering almost all industrially permitted frequency bands. With the development and progress of science and technology, large-area, uniform plasma generation technology with relatively high energy has become an urgent need in modern industry, especially in the semiconductor industry. To this end, researchers in the field of plasma both domestically and internationally have conducted research on plasma generation methods, excitation power sources, and magnetic field enhancement, achieving significant progress, but each also has its own shortcomings. Capacitively coupled discharge suffers from low energy and electrode contamination problems; inductively coupled discharge suffers from low energy and large-area uniformity problems; microwaves can improve plasma energy and density, but the uniformity problem needs to be solved. CN105088196 A discloses a large-area, high-density microwave plasma generation device, which consists of multiple linear plasma discharge units arranged in a row. Each discharge unit uses a magnetic field to enhance plasma discharge and stabilize the discharge configuration. The plasma generated by each unit diffuses directionally into a diffusion chamber to form a large-area, high-density plasma. This invention effectively solves many problems related to two-dimensional large-area uniformity processes such as thin film preparation, surface modification, cleaning, and etching. However, since the plasma is generated from each unit and diffuses directionally into the diffusion chamber, the plasma velocity is anisotropic, making it unsuitable for processing three-dimensional objects. Furthermore, the equipment is relatively complex and expensive. CN111566777A discloses a microwave plasma device, which includes a processing space and two or more microwave semiconductors (microwave output units). The patent utilizes multiple symmetrically distributed microwave output units to construct a spatially uniform microwave field. However, microwave output units, whether antennas or waveguides, can both transmit and receive microwaves. If they are symmetrically distributed, corresponding transmitting units will become each other's receiving units, effectively increasing microwave system reflections and affecting normal operation. This is especially true when the plasma generation space is small and the distance between two microwave transmitting units is short, potentially damaging critical components of the microwave system, such as the transmitter magnetron. Secondly, using multiple microwave output units results in a single-mode microwave (i.e., the dominant mode transmitted via waveguide or coaxial line). While this improves the uniformity of the microwave field strength distribution, it also increases equipment cost and technical complexity. Summary of the Invention

[0003] The multi-mode microwave plasma generator proposed in this invention can solve at least one of the above-mentioned technical problems.

[0004] To achieve the above objectives, the present invention adopts the following technical solution:

[0005] A multi-mode microwave plasma generator includes a microwave output unit, a metal chamber with a microwave input window, and an insulating vacuum chamber with an internal metal chamber. A microwave source is fed into the metal chamber through the microwave output unit, and after multiple reflections through the inner wall of the metal chamber, it is converted into multi-mode microwaves, forming a spatially uniform microwave field in the metal chamber. This field breaks down the gas at a pressure below 1 atmosphere in the insulating vacuum chamber with an internal metal chamber, forming a uniform high-density plasma. This plasma is then used to process objects placed on a substrate stage in the vacuum chamber that can be biased.

[0006] Furthermore, the multi-mode microwave metal cavity is a cuboid or polyhedron of a metal with good electrical conductivity and an inner wall with concave and convex surfaces. The single wave mode output from the microwave output unit enters the metal cavity through the microwave input window and is reflected multiple times by the inner wall. The reflected waves at different distances and angles have different phases, and after superposition, various wave modes are generated to form a spatially uniform microwave field strength.

[0007] Furthermore, to prevent microwaves from being directly reflected into the waveguide, the tilt angle θ between the microwave output port end face of the microwave output unit waveguide and the first microwave reflection surface of the multi-mode microwave metal cavity is ≥2tanθ. -1 (a / 2L), where a is the long side of the rectangular waveguide and L is the distance from the waveguide end face to the first reflecting surface.

[0008] Furthermore, the multi-mode microwave metal cavity has an inlet and outlet for air cooling with an electromagnetic wave shielding metal mesh, a vacuum pumping pipe inlet with built-in insulating material, an inlet for plasma working gas, and a waveguide interface.

[0009] Furthermore, the vacuum chamber made of insulating material is preferably a cylindrical structure with high pressure resistance, but other shapes are not excluded. The insulating material is preferably a glass or ceramic material with low microwave absorption rate, preferably quartz glass, but other insulating materials are not excluded.

[0010] Furthermore, the bottom and door of the cylindrical insulating vacuum chamber are preferably (but not limited to) integrated with the metal chamber, and the vacuum chamber door is designed with an observation window that is protected against microwave radiation.

[0011] Furthermore, the vacuum chamber, made of insulating material, is equipped with an air extraction port and an air inlet, and a substrate stage that can be biased is installed inside the vacuum chamber.

[0012] Furthermore, the pressure at which plasma is generated is less than one atmosphere.

[0013] As can be seen from the above technical solution, this invention discloses a multi-mode microwave plasma generator, belonging to the field of low-temperature plasma application technology, used to generate uniform plasma with high density and energy to meet industrial needs. This invention includes a multi-mode microwave plasma generation technology and device. The multi-mode microwave plasma generation technology converts a single wave mode (TE10) propagating in a waveguide into multi-mode (TEmn, m, n = 0, 1, 2, 3..., not simultaneously 0) electromagnetic waves, forming a spatially uniform microwave field to generate high-density and high-energy uniform plasma. The generator consists of three main components: a microwave source output from a rectangular waveguide, a multi-mode microwave metal cavity, and an insulating vacuum chamber placed within the metal cavity to generate plasma. The multi-mode microwave metal cavity is a cuboid or polyhedron of a metal with good electrical conductivity and an inner wall with concave and convex surfaces. The metal cavity is equipped with electromagnetically shielded ventilation mesh. The insulating vacuum chamber is placed within the spatially uniform microwave field of the metal cavity, generating high-density uniform plasma. The plasma energy is controlled by frequency conversion to regulate the microwave output power. This invention can be used in industrial applications such as cleaning, etching, resist removal, material surface modification, and coating.

[0014] The beneficial effects of this invention are as follows:

[0015] This invention relates to a multi-mode microwave plasma generator. Based on the propagation characteristics of electromagnetic waves and the principle of wave superposition, it constructs multiple microwave reflective surfaces, alters the wave vector (propagation direction), electric vector, and magnetic vector, as well as the phase changes due to different reflection points, generating reflected waves with varying phases and propagation directions. The superposition of these waves forms multi-mode microwaves, significantly improving the uniformity of the microwave field intensity distribution within the metal cavity, thereby producing a uniform, high-density plasma. This provides an innovative technology and simple device based on fundamental theory for industries such as semiconductor electronic chips, new energy, and new materials that rely on high-density, uniform plasma processing. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the structure of the present invention;

[0017] 1. Magnetron; 2. Rectangular waveguide; 3. Metal chamber; 4. Vacuum chamber made of insulating material; 5. Substrate stage. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments.

[0019] like Figure 1As shown, the multi-mode microwave plasma generator described in this embodiment includes a magnetron 1 connected to a microwave input port on a metal chamber 3 via a rectangular waveguide 2 of a microwave output unit. The tilt angle θ between the microwave output port end face of the waveguide and the first microwave reflecting surface of the multi-mode microwave metal chamber is ≥2tanθ. -1 (a / 2L). a is the long side of the rectangular waveguide, and L is the distance from the waveguide end face to the first reflecting surface; the insulating vacuum chamber 4 with a substrate stage 5 that can be electrically biased is placed in the metal chamber 3. The air in the vacuum chamber is emptied and a working gas with a pressure lower than one atmosphere is introduced. The microwave source is turned on, and the microwave output power is continuously adjusted by frequency conversion to generate a spatially uniform high-density plasma.

[0020] The multi-mode microwave plasma generation technology and device are described in that the waveguide end face and the first microwave reflection surface in the inner wall of the metal cavity 3 form an angle of θ≧2tan -1 An angle of (a / 2L) is used to prevent microwaves from being directly reflected into the waveguide.

[0021] The inner wall of the metal chamber 3 has concave and convex surfaces, which generate reflected waves of different phases. The spatial superposition of the waves generates various wave modes, forming a spatially uniform microwave field within the metal chamber.

[0022] The metal cavity 3 has an inlet and outlet for air cooling with an electromagnetic wave shielding metal mesh, a vacuum pumping pipe inlet for a vacuum chamber with built-in insulating material, an inlet for plasma working gas, and a waveguide interface.

[0023] The vacuum chamber 4, made of insulating material, is equipped with an air extraction port and an air inlet. Inside the vacuum chamber is a substrate stage that can be electrically biased.

[0024] The working gas can be air, inert gas, active gas, various gaseous compounds, or a mixture of two or more of the aforementioned gases.

[0025] The working pressure of multimode microwave plasma is less than one atmosphere.

[0026] The multi-mode microwave plasma generation technology and device described above can be widely used in industries such as semiconductor electronic chips, new energy, and new materials that rely on high-density uniform plasma processing, such as plasma cleaning, etching, thin film deposition, and surface modification.

[0027] In summary, this invention discloses a multi-mode microwave plasma generation technology and device, belonging to the field of low-temperature plasma application technology, used to generate uniform plasma with high density and energy to meet industrial needs. This invention includes a multi-mode microwave plasma generation technology and device. The multi-mode microwave plasma generation technology converts a single wave mode (TE10) propagating in a waveguide into multi-mode (TEmn, m, n = 0, 1, 2, 3..., not simultaneously 0) electromagnetic waves, forming a spatially uniform microwave field to generate a high-density, high-energy uniform plasma. The generation device consists of three main components: a microwave source output from a rectangular waveguide, a multi-mode microwave metal cavity, and an insulating vacuum chamber placed within the metal cavity to generate plasma. The multi-mode microwave metal cavity is a cuboid or polyhedron of a metal with good electrical conductivity and an inner wall with concave and convex surfaces, and the metal cavity is equipped with electromagnetically shielded ventilation mesh. The insulating vacuum chamber is placed within the spatially uniform microwave field of the metal cavity to generate a high-density, uniform plasma, and the plasma energy is controlled by frequency conversion of the microwave output power. This invention can be used in industrial applications such as cleaning, etching, resist removal, material surface modification, and coating.

[0028] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A multi-mode microwave plasma generator, characterized in that, It includes a microwave output unit, a multi-mode microwave metal cavity with a microwave input window, and an insulating vacuum cavity built into the multi-mode microwave metal cavity; The microwave source is fed into the multi-mode microwave metal cavity through the microwave output unit. After multiple reflections through the inner wall of the multi-mode microwave metal cavity, it is transformed into multi-mode microwaves, forming a spatially uniform microwave field strength in the multi-mode microwave metal cavity. This field strength breaks through the gas at a pressure of less than 1 atmosphere in the vacuum chamber containing the insulating material of the multi-mode microwave metal cavity, forming a uniform high-density plasma. The multimode microwave metal cavity is a cuboid or polyhedron of a metal with good electrical conductivity and an inner wall with concave and convex surfaces. The tilt angle θ≧2tanθ between the microwave output port end face of the microwave output unit waveguide and the first microwave reflection surface of the multimode microwave metal cavity is given by the formula: -1 (a / 2L), where a is the long side of the rectangular waveguide and L is the distance from the waveguide end face to the first reflecting surface; The multi-mode microwave metal cavity has an inlet and outlet for air cooling with an electromagnetic wave shielding metal mesh, a vacuum pumping pipe inlet for a vacuum chamber with built-in insulating material, an inlet for plasma working gas, and a waveguide interface. The vacuum chamber made of insulating material is designed with a cylindrical structure. The insulating material of the vacuum chamber is a glass or ceramic material with low microwave absorption rate. The bottom and door of the vacuum chamber made of insulating material are integrated with the metal chamber, and the vacuum chamber door is designed with an observation window that is protected against microwave radiation. The vacuum chamber, made of insulating material, is equipped with an air extraction port and an air inlet. A substrate stage, which can be biased, is located inside the vacuum chamber.

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