Resonant cavity ECR plasma source device and method

Abstract

The present invention discloses a resonant cavity type ECR plasma source device and method. The technical solution of the present invention sets an antenna sealing cover in the vacuum resonant cavity, and places the antenna radiating microwaves in the antenna sealing cover, which can avoid the discharge antenna from polluting the ECR plasma in the vacuum resonant cavity. The magnetic field required for electron cyclotron resonance can be adjusted by the ECR control element to further increase the electron density. The device described in the technical solution of the present invention has the advantages of simple structure and high electromagnetic wave-plasma energy coupling efficiency, and can generate electron density up to 10 12 cm ‑3 Magnitude of plasma.

Description

Technical Field

[0001] The present invention relates to the field of plasma source generation technology, and more specifically, to a resonant cavity ECR (electron cyclotron resonance) plasma source device and method. Background Art

[0002] Electron cyclotron resonance (ECR) plasma is an important technology in the field of low-pressure and low-temperature discharge. The ECR plasma source uses microwave energy to excite gas discharge, and has the advantages of long service life, stable performance, no electrodes, corrosion resistance and the ability to work under vacuum. Therefore, the ECR plasma source is widely used in many aspects, such as high-current ion sources in accelerators, ion implantation in semiconductor manufacturing, ion beam sputtering deposition and other processes, and new concept space electric propulsion engine technology. There are many types of existing ECR plasma source device configurations. For example, in typical high-aspect ratio and low-aspect ratio ECR plasma sources, microwaves are transmitted by waveguides, and plasma is generated in the resonance region under the action of the coil magnetic field through the glass window, or microwave transmission antennas are used to transmit microwave energy, combined with the permanent magnet magnetic field to generate an electron cyclotron resonance region.

[0003] Microwave resonant cavity can be used to generate plasma. The principle is to generate a strong electromagnetic field through the resonance of the electromagnetic field in the microwave resonant cavity, which excites the gas to discharge and generate plasma. However, due to the limitations of the plasma oscillation frequency and the resonant cavity manufacturing process, the electron density of the generated plasma reaches 10 9 cm -3 At this level, microwaves with a frequency of 2.45 GHz are cut off at the boundary of the non-magnetized plasma, and the energy cannot enter the plasma, resulting in a low electron density in general microwave resonant cavity plasma sources, making it difficult to meet the high-density requirements required for industrial applications.

[0004] The inventors have found that a plasma source that combines a microwave resonant cavity and ECR discharge technology can use the resonant cavity to enhance the energy coupling efficiency of electromagnetic waves, and can also use the ECR principle to enable electron cyclotron resonance to absorb microwave energy, thereby combining the advantages of the two discharge methods to produce high-density plasma in a small space and under conditions of lower microwave power consumption. Summary of the invention

[0005] The purpose of this application is to provide a resonant cavity ECR plasma source device and method, including the following technical solutions:

[0006] A resonant cavity ECR plasma source device, comprising:

[0007] A vacuum resonant cavity, used to make microwaves of a set frequency resonate;

[0008] An antenna sealing cover disposed in the vacuum resonant cavity, the antenna sealing cover having an antenna opening connected to the external atmosphere;

[0009] An antenna placed in the antenna sealing cover through the antenna opening, the antenna being used to radiate the microwave to the vacuum resonant cavity through the antenna sealing cover;

[0010] The ECR control element disposed outside the vacuum resonant cavity is used to generate a magnetic field required for electron cyclotron resonance in the vacuum resonant cavity, so as to generate ECR plasma in the vacuum resonant cavity.

[0011] Preferably, in the above device, the vacuum resonance cavity comprises: a cylindrical body, the bottom end of the cylindrical body is sealed, and a resonance enhancement ring is arranged at the top end.

[0012] Preferably, in the above device, the ECR control element is a magnetic field coil, which is wound with multiple turns and is used to connect to a DC regulated current power supply.

[0013] Preferably, in the above device, the magnetic field coil is an electromagnetic coil wound by enameled wire.

[0014] Preferably, in the above device, the antenna sealing cover is a quartz glass cover.

[0015] Preferably, in the above device, the antenna is a rod-shaped antenna, one end of which is placed in the antenna sealing cover through the antenna opening, and the other end is connected to the microwave source generating circuit;

[0016] The rod-shaped antenna has a water cooling structure inside.

[0017] Preferably, in the above device, the side wall of the cylindrical body has a channel for cooling water circulation, and the outer side of the side wall of the cylindrical body has a water inlet interface and a water outlet interface connected to a cooling water pipe.

[0018] Preferably, in the above device, the side wall of the cylindrical body also has a quick connection flange for connecting a vacuum pump group and a vacuum gauge for measuring vacuum pressure.

[0019] Preferably, in the above device, the side wall of the cylindrical body also has a CF flange for mounting a plasma measuring device.

[0020] The present invention also provides a method for generating ECR plasma, which uses any of the above-mentioned devices to generate ECR plasma.

[0021] From the above description, it can be known that in a resonant cavity ECR plasma source device and method provided by the technical solution of the present invention, an antenna sealing cover is set in the vacuum resonant cavity, and the antenna radiating microwaves is placed in the antenna sealing cover, which can avoid the discharge antenna from contaminating the ECR plasma in the vacuum resonant cavity. The magnetic field required for electron cyclotron resonance can be adjusted by the ECR control element to further increase the electron density. The device described in the technical solution of the present invention has the advantages of simple structure and high electromagnetic wave-plasma energy coupling efficiency, and can generate electrons with a density of up to 10 12 cm -3 Magnitude of plasma. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0023] Figure 1 A schematic structural diagram of a resonant cavity ECR plasma source device provided in an embodiment of the present invention;

[0024] Figure 2 A schematic structural diagram of an antenna sealing cover provided by an embodiment of the present invention;

[0025] Figure 3a This is the distribution diagram of the axial intensity in the vacuum resonant cavity measured by the Gaussmeter when the magnetic field coil current is 9A;

[0026] Figure 3b This is the distribution diagram of the radial intensity in the vacuum resonant cavity measured by the Gauss meter when the magnetic field coil current is 9A;

[0027] Figure 3c This is the distribution diagram of the total magnetic induction intensity in the vacuum resonant cavity measured by the Gaussmeter when the magnetic field coil current is 9A;

[0028] Figure 4a Schematic diagram of the electron density at the center of the vacuum resonant cavity changing with discharge power and gas pressure;

[0029] Figure 4b Schematic diagram of the electron temperature at the center of the vacuum resonant cavity changing with discharge power and gas pressure. DETAILED DESCRIPTION

[0030] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0031] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0032] refer to Figure 1 , Figure 1 A schematic structural diagram of a resonant cavity type ECR plasma source device provided in an embodiment of the present invention, the device comprises: a vacuum resonant cavity 10, used to resonate microwaves of a set frequency; an antenna sealing cover 4 placed in the vacuum resonant cavity 10, the antenna sealing cover 4 having an antenna opening connected to the external atmosphere; an antenna 5 placed in the antenna sealing cover 4 through the antenna opening, the antenna 5 being used to radiate the microwaves to the vacuum resonant cavity 10 through the antenna sealing cover 4; and an ECR control element 7 placed outside the vacuum resonant cavity 10, used to generate a magnetic field required for electron cyclotron resonance in the vacuum resonant cavity 10, so as to generate ECR plasma in the vacuum resonant cavity.

[0033] The vacuum resonant cavity 10 includes: a cylindrical body, the bottom end of which is sealed, and a resonance enhancement ring 2 is arranged at the top end. As a container for generating ECR plasma, the vacuum resonant cavity 10 needs to be vacuum sealed and is made of stainless steel material with low magnetic permeability to avoid noise magnetic field interference. Therefore, the cylindrical body is a stainless steel cylinder and is vacuum sealed. The outer diameter of the resonance enhancement ring 2 can be set to be equal to the inner diameter of the vacuum resonant cavity 10, so that it can be directly fixed on the inner wall of the vacuum resonant cavity. The difference between the inner and outer diameters of the resonance enhancement ring 2 is 22 mm, that is, the width of the resonance enhancement ring 2 is 22 mm, which can effectively improve the microwave energy coupling efficiency in the vacuum resonant cavity 10.

[0034] The inner diameter of the vacuum resonant cavity 10 satisfies the resonance condition, so that the microwave resonates in the vacuum resonant cavity 10, increasing the microwave coupling energy. Therefore, when the vacuum resonant cavity is used to generate plasma under a microwave source of a set frequency, a resonance effect can be generated to effectively increase microwave energy coupling.

[0035] The inner diameter of the vacuum resonant cavity 10 (the inner diameter of the cylindrical body) is set to N times the wavelength of the microwave, where N is a positive integer greater than, such as N can be 2, so that the diameter of the vacuum resonant cavity 10 is N times or approximately N times the wavelength of the microwave, so that the microwave resonates. For example, if the frequency is 2.45 GHZ, the inner diameter of the vacuum resonant cavity 10 can be set to 245 mm. The diameter of the vacuum resonant cavity 10 is approximately N times the wavelength of the microwave, which means that the difference between the diameter of the vacuum resonant cavity 10 and N times the wavelength of the microwave does not exceed a set threshold value to meet the resonance condition. The set threshold value can be set according to the actual resonance, such as the threshold value does not exceed 5% of the microwave wavelength. The axial height of the vacuum resonant cavity 10 (the height of the cylindrical body) can be set to 150 mm, which can be set based on demand and is not limited to 1500 mm.

[0036] Optionally, the side wall of the cylindrical body has a cooling water circulation channel, and the outer side wall of the cylindrical body has a water inlet interface 1 and a water outlet interface connected to a cooling water pipe. In other words, the side wall of the vacuum resonance cavity 10 is a sandwich structure, and cooling water can be introduced to cool the inner wall, and the cooling water circulates in the sandwich, thereby ensuring that the plasma source can perform steady-state plasma discharge. Figure 1 Only the water inlet interface is shown, and the water outlet interface is not shown.

[0037] Optionally, the side wall of the cylinder body further has a quick connection flange 3, and the quick connection flange 3 is used to connect a vacuum pump group and a vacuum gauge for measuring vacuum pressure.

[0038] The side wall of the cylinder body also has a CF flange 6, and the CF flange 6 is used to install a plasma measurement device.

[0039] The ECR control element 7 is a magnetic field coil, which is wound by a multi-turn coil and is used to connect to a DC current stabilized power supply. When the DC current stabilized power supply is used for power supply, the current is less than 10A, which can generate the 875Gs magnetic field area required for ECR plasma in the vacuum resonant cavity 10. Optionally, the magnetic field coil is an electromagnetic coil wound by enameled wire.

[0040] The antenna sealing cover 4 is a quartz glass cover. The antenna sealing cover 4 is made of quartz glass and can withstand plasma baking for a long time. The antenna sealing cover 4 isolates the antenna 5 from the vacuum environment of the vacuum resonant cavity 10, and isolates the plasma in the vacuum resonant cavity 10 from the antenna 5 in the antenna sealing cover 4. While preventing the charged antenna from contaminating the plasma in the vacuum resonant cavity 10, it can also protect the microwave device connected to the rear end of the antenna 5.

[0041] The antenna 5 is a rod-shaped antenna, one end of which is placed in the antenna sealing cover 4 through the antenna opening, and the other end is connected to the microwave source generating circuit; the rod-shaped antenna has a water cooling structure inside, such as a water cooling structure. After the microwave energy generated by the microwave source generating circuit is converted to the antenna 5, it is emitted to the inside of the vacuum resonant cavity 10 through the antenna 5. The antenna 5 is in the atmospheric environment and is not exposed to the plasma. The antenna itself has an internal cooling structure to cool down and reduce the heat load generated during the transmission of microwave energy. The rod-shaped antenna has a simple structure and a cooling structure inside. The mode of generating the electromagnetic field is simple, so that the plasma is evenly distributed.

[0042] In the embodiment of the present invention, the structure of the antenna sealing cover 4 is as follows: Figure 2 As shown, Figure 2 A schematic structural diagram of an antenna sealing cover provided by an embodiment of the present invention, Figure 2 The middle left figure is a top view of one end of the antenna sealing cover 4 having an antenna opening. Figure 2 The middle right picture is a cross-sectional view of the left picture at A-A'. The antenna sealing cover 4 shown is a cylindrical structure, one end of which is sealed and the other end has an opening for placing the antenna 5. The antenna sealing cover 4 is installed on the top of the vacuum resonant cavity 10, and the vacuum resonant cavity 10 is sealed with the top sealing component, and the resonance enhancement ring 2 is attached to the inner surface of the top sealing component. The antenna opening of the antenna sealing cover 4 is connected to the atmospheric environment, so the inside of the antenna sealing cover 4 is the atmospheric environment, and its outer wall is placed in the vacuum resonant cavity 10 and is in a vacuum environment.

[0043] In view of the low density of existing microwave resonant cavity plasma and the complex structure of ECR ​​plasma device, the embodiment of the present invention provides a new resonant cavity ECR plasma source device, which has a magnetic field coil with adjustable magnetic field size as ECR control element 7 to generate the magnetic field required for electron cyclotron resonance to further increase the electron density. At the same time, the antenna sealing cover 4 is designed to seal the antenna 5, so as to prevent the antenna 5 from contaminating the plasma source in the vacuum resonant cavity 10. The device has a simple structure and high electromagnetic wave-plasma energy coupling efficiency, and can generate electron density up to 10 12 cm -3 Magnitude of plasma.

[0044] From the above description, it can be known that the device described in the embodiment of the present invention uses a vacuum resonant cavity 10 with an inner diameter of 245mm to enhance the electromagnetic wave coupling effect. The inner diameter of the vacuum resonant cavity 10 is twice the wavelength of a 2.45GHz microwave. While achieving the resonance effect, the size is small, which can effectively increase the resonance effect of microwaves. Adding a resonance enhancement ring 2 of a certain width in the vacuum resonant cavity 10 can improve the microwave energy absorption efficiency in the vacuum resonant cavity 10. The side wall of the vacuum resonant cavity 10 has a sandwich structure, and circulating cooling water can be passed through.

[0045] In addition, quartz glass is used as the antenna sealing cover 4 to vacuum seal the top of the vacuum resonant cavity 10, and the antenna 5 is placed in the antenna sealing cover 4 to be isolated from the plasma. Compared with the traditional solution in which the antenna is immersed in the plasma environment, the antenna sealing cover 4 in the technical solution of the present invention can make the antenna 5 uncharged, protect the microwave antenna 5 and the back-end circuit, and prevent antenna impurities from entering the plasma and polluting the plasma environment.

[0046] An electromagnetic coil wound with enameled wire is used as the ECR control element 7. The traditional ECR plasma source using permanent magnets has a very large magnetic field gradient, which causes an uneven distribution of the magnetic field in the plasma, while an energized coil can generate a relatively uniform magnetic field. In addition, the traditional magnetic field coil wound with a hollow aluminum tube has a small number of turns, a large volume, and requires a large current power supply. The current is usually in the order of hundreds of amperes, which makes the power supply costly. In the technical solution of the present invention, the multi-turn enameled wire used in the magnetic field coil can generate a magnetic field of more than 900Gs in the central area of ​​the vacuum resonant cavity 10 under low power consumption conditions of a voltage of 120 volts and a current of 9A, and generate an electron cyclotron resonance region in the vacuum resonant cavity 10. As shown in Figure 3, Figure 3 shows the distribution diagram of the axial, radial and total magnetic induction intensities in the vacuum resonant cavity measured by a gaussmeter when the current of the magnetic field coil is 9A. Figure 3 includes Figure 3a , Figure 3b and Figure 3c , Figure 3a This is the distribution diagram of the axial intensity in the vacuum resonant cavity measured by the Gaussmeter when the magnetic field coil current is 9A. Figure 3b This is the distribution diagram of the radial intensity in the vacuum resonant cavity measured by the Gaussmeter when the magnetic field coil current is 9A. Figure 3c This is a distribution diagram of the total magnetic induction intensity in the vacuum resonant cavity measured by a Gaussmeter when the magnetic field coil current is 9A. It can be seen that when the coil current reaches 9A or above, the magnetic induction intensity in a region near the microwave antenna in the vacuum resonant cavity 10 reaches 875Gs, meeting the electron cyclotron resonance condition.

[0047] Through experimental data, it can be obtained that the resonant cavity ECR plasma source can generate a magnetic field that meets the ECR condition strength inside the vacuum resonant cavity, as shown in Figure 4. Figure 4 shows the plasma electron density and electron temperature at the center of the vacuum resonant cavity measured by the Langmuir probe. It can be seen that the electron density at the center of the vacuum resonant cavity is generally around 10 12 cm -3 The plasma of this magnitude indicates that the device can meet the design requirements of a high-density plasma source under certain discharge conditions. Figure 4a and Figure 4b , Figure 4a This is a schematic diagram showing the variation of the electron density at the center of the vacuum resonant cavity with the discharge power and gas pressure. Figure 4b This is a schematic diagram of the variation of the electron temperature at the center of the vacuum resonant cavity with the discharge power and gas pressure. When the discharge is at low pressure, the electron density reaches 10 12 cm -3 The electron temperature is about 0.8-3.5 electron volts (eV).

[0048] Based on the above embodiment, another embodiment of the present invention further provides a method for generating an ECR plasma source, which uses the device described in the above embodiment to generate ECR plasma. The method described in the embodiment of the present invention uses the device described in the above embodiment to generate an ECR plasma with an electron density of up to 10 12 cm -3 The plasma of this magnitude is simple to implement and the cost is low.

[0049] In this specification, each embodiment is described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the embodiments can be referred to each other. For the method disclosed in the embodiment, since it corresponds to the device disclosed in the embodiment, the description is relatively simple, and the relevant parts can be referred to the device part description.

[0050] It should also be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "comprises", "comprising" or any other variants thereof are intended to cover non-exclusive inclusion, so that an article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such article or device. In the absence of further restrictions, the elements defined by the sentence "comprising a ..." do not exclude the existence of other identical elements in the article or device including the above elements.

[0051] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A resonant cavity ECR plasma source device, characterized in that: include: A vacuum resonant cavity, used to make microwaves of a set frequency resonate; An antenna sealing cover disposed in the vacuum resonant cavity, the antenna sealing cover having an antenna opening connected to the external atmosphere; An antenna placed in the antenna sealing cover through the antenna opening, the antenna being used to radiate the microwave to the vacuum resonant cavity through the antenna sealing cover; An ECR control element disposed outside the vacuum resonant cavity, used to generate a magnetic field required for electron cyclotron resonance in the vacuum resonant cavity, so as to generate ECR plasma in the vacuum resonant cavity; The vacuum resonance cavity comprises: a cylindrical body, the bottom end of which is sealed, and a resonance enhancement ring is arranged at the top end; The outer diameter of the resonance enhancement ring is equal to the inner diameter of the vacuum resonance cavity; The antenna is a rod-shaped antenna, one end of which is placed in the antenna sealing cover through the antenna opening, and the other end is connected to the microwave source generating circuit; The rod-shaped antenna has a water cooling structure inside.

2. The device according to claim 1, characterized in that The ECR control element is a magnetic field coil, which is wound with multiple turns and is used to connect to a DC regulated current power supply.

3. The device according to claim 2, characterized in that The magnetic field coil is an electromagnetic coil wound by enameled wire.

4. The device according to claim 1, characterized in that The antenna sealing cover is a quartz glass cover.

5. A method for generating ECR plasma, characterized in that: The ECR plasma is generated by using the device as described in any one of claims 1 to 4.

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