An inductively coupled remote plasma generator with a magnetic core

Abstract

The present invention discloses an inductively coupled remote plasma generator with a magnetic core, which includes a discharge chamber, a magnetic core and an inductance coil; specifically, first use a vacuum pump to pump the air pressure in the discharge chamber to high vacuum, then inject a working gas into the discharge chamber, and then pass a radio frequency alternating current through the inductance coil by an external power supply. The inductance coil converts the energy provided by the power supply into electromagnetic energy, and the electromagnetic energy is then transmitted to the discharge chamber through the magnetic core. After the charged particles absorb the electromagnetic field energy, they ionize and collide with gas molecules or atoms in the discharge chamber to form a plasma, and finally output through the plasma output port.

Description

Technical Field

[0001] The present invention belongs to the technical field of plasma source devices. More specifically, it relates to an inductively coupled remote plasma generator with a magnetic core. Background Art

[0002] Plasma source devices can be applied to the microelectronics manufacturing industry. Processes such as plasma etching, plasma deposition, and plasma cleaning are inseparable from plasma generators. In addition, plasma sources can also provide stable and reliable plasma for electric thrusters, which is an important part of the electric thruster system.

[0003] Plasma generators mainly generate plasma by gas discharge. First, an external radio frequency power supply feeds energy in the form of electromagnetic waves into the discharge chamber. Electrons in the region continuously absorb the energy of the electromagnetic waves, causing them to be heated to several to dozens of electron volts. Then, the energetic electrons collide with background gas particles, transferring energy to the neutral molecules or atoms of the background gas. If the energy exceeds the ionization threshold, ionization causes the electrons and atoms of the neutral particles to separate, forming free electrons and positive ions. After many neutral particles are ionized, plasma is formed. Finally, under the action of drift and diffusion, the plasma is transported to a suitable position for people to use.

[0004] Inductively coupled plasma generators are a type of high-density plasma source with a simple structure and stable operation. However, due to the application of several thousand volts of voltage across the inductor during operation, capacitive coupling phenomena will occur, which is not what we want to see. Summary of the Invention

[0005] The purpose of the present invention is to overcome the deficiencies of the prior art and provide an inductively coupled remote plasma generator with a magnetic core, which can greatly improve the energy transfer efficiency, reduce capacitive coupling interference, and is more conducive to controlling plasma parameters.

[0006] To achieve the above-mentioned invention purpose, an inductively coupled remote plasma generator with a magnetic core according to the present invention is characterized by comprising: a discharge chamber, a magnetic core, and an inductor coil;

[0007] The discharge chamber is composed of a cylindrical barrel wall and connecting flanges at both ends. The inside of the barrel is evacuated as the discharge reaction area. One end of the discharge chamber is connected to a vacuum pump that provides the vacuum degree inside the discharge chamber, and the other end is connected to a gas flow meter for controlling the gas flow rate injected into the discharge chamber. The end of the discharge chamber connected to the vacuum pump is used as the plasma output port, and the end connected to the gas flow meter is used as the gas injection port;

[0008] The magnetic core is composed of several groups of rectangular ring-shaped ferrite magnetic cores. The discharge chamber passes through the rectangular ring, and both ends of the cylindrical barrel wall are fixed by a medium, so that the discharge chamber is located at the center of the rectangular ring;

[0009] The inductance coil is densely wound around any side of the magnetic core in the middle and is excited by current;

[0010] When the inductively coupled remote plasma generator works, first use a vacuum pump to pump the air pressure in the discharge chamber to high vacuum, then inject working gas into the discharge chamber, and control the air pressure in the discharge chamber by observing the readings of the vacuum pump and the gas flow meter and adjusting the gas flow rate in cooperation. Then, pass radio frequency alternating current into the inductance coil through an external power supply. The inductance coil converts the energy provided by the power supply into electromagnetic energy, and the electromagnetic energy is then transmitted to the discharge chamber through the magnetic core. After the charged particles absorb the electromagnetic field energy, they collide ionizingly with the gas molecules or atoms in the discharge chamber to form plasma, and finally output through the plasma output port.

[0011] The invention purpose of the present invention is achieved as follows:

[0012] An inductively coupled remote plasma generator with a magnetic core of the present invention includes a discharge chamber, a magnetic core and an inductance coil; specifically, first use a vacuum pump to pump the air pressure in the discharge chamber to high vacuum, then inject working gas into the discharge chamber, and then pass radio frequency alternating current into the inductance coil through an external power supply. The inductance coil converts the energy provided by the power supply into electromagnetic energy, and the electromagnetic energy is then transmitted to the discharge chamber through the magnetic core. After the charged particles absorb the electromagnetic field energy, they collide ionizingly with the gas molecules or atoms in the discharge chamber to form plasma, and finally output through the plasma output port.

[0013] At the same time, an inductively coupled remote plasma generator with a magnetic core of the present invention also has the following beneficial effects:

[0014] (1) By adding several magnetic cores in the present invention and winding the inductance coil on the magnetic core instead of on the discharge chamber, the electromagnetic field distribution is changed, and at the same time, the electric field component generated by the coil voltage in the discharge chamber is greatly reduced; when no magnetic core is added traditionally, the coil is directly wound on the outside of the discharge chamber, generating an axial magnetic field and an angular electric field in the chamber, and the charged particles move angularly under the action of the electric field; after adding the magnetic core, the magnetic field generated by the energized coil is "captured" by the magnetic core, forming an angular magnetic field outside the discharge chamber. According to Faraday's law of electromagnetic induction, an axial electric field will be generated in and around the chamber.

[0015] (2) Winding the inductance coil around the magnetic core can also reduce or even avoid the influence of capacitive coupling caused by the coil voltage drop; capacitive coupling comes from the voltage drop electric field. The reason for the coil voltage drop is that there is resistance in the coil, and a voltage difference will be generated when there is current passing through. The effect of this voltage difference electric field is similar to the potential difference generated by direct current, and it is mainly concentrated around the coil. Therefore, after adding the magnetic core in the present invention, the coil can be placed far away from the discharge chamber to achieve the purpose of reducing capacitive coupling.

[0016] (3) In addition, the addition of the magnetic core can also reduce the influence of coil magnetic leakage on the power absorption efficiency. In the structure of the traditional inductively coupled plasma source, a large part of the magnetic field will flow out from the quartz chamber wall. Moreover, the high temperature and vacuum environment of gas discharge limit the thickness of the chamber wall cannot be too small. At the same time, considering factors such as coil heat dissipation and insulation, the coil cannot be closely attached to the discharge chamber, resulting in a large amount of magnetic leakage, and a lot of energy transmitted by the power supply is stored as magnetic energy in the space. On the contrary, by analogy with the circuit guiding current, the magnetic core also has a guiding effect on the magnetic field, and can confine the magnetic field inside the magnetic core, and only a tiny part of the magnetic flux breaks away from the constraint of the magnetic core and runs into the air. Therefore, in this new structure, almost all the magnetic field energy generated by the inductance coil is used for gas discharge, and only a very small part is stored as magnetic energy. Therefore, the energy conversion efficiency of the inductance coil is greatly improved, and can reach more than 90%.

[0017] (4) The chamber wall of the discharge chamber is made of quartz glass material. Quartz glass is heat-resistant and can withstand the high temperature generated during gas discharge. At the same time, it also has high light transmittance, which is convenient for observing the discharge state;

[0018] (5) Comparing the present invention with the existing conventional inductively coupled plasma source structure, the structure proposed by the present invention, without changing the external power supply access method, improves the transmission efficiency and reduces the influence of capacitive coupling by adding a magnetic core. However, it is very difficult for the conventional inductively coupled plasma source to achieve such high transmission efficiency, and it is even more impossible to significantly reduce the influence of capacitive coupling. Brief Description of the Drawings

[0019] Figure 1 is a structural diagram of an inductively coupled remote plasma generator with a magnetic core according to the present invention;

[0020] Figure 2 is an electron density diagram obtained by simulating the plasma source with a magnetic core proposed by the present invention;

[0021] Figure 3 is an electron temperature diagram obtained by simulating the plasma source with a magnetic core proposed by the present invention;

[0022] Figure 4 is an electric potential diagram obtained by simulating the plasma source with a magnetic core proposed by the present invention. Detailed Embodiment

[0023] The specific embodiments of the present invention will be described below in conjunction with the accompanying drawings, so that those skilled in the art can better understand the present invention. It should be particularly noted that in the following description, when the detailed description of known functions and designs may dilute the main content of the present invention, these descriptions will be omitted here.

[0024] Embodiment

[0025] Figure 1 is a flowchart of a method for dynamically equivalent modeling of a wind farm based on a yaw strategy of the present invention.

[0026] In this embodiment, as Figure 1 shown, an inductively coupled remote plasma generator with a magnetic core of the present invention includes: a discharge chamber, a magnetic core, and an inductor coil;

[0027] The discharge chamber is composed of a cylindrical barrel wall and connecting flanges at both ends. The inside of the barrel is evacuated as the discharge reaction area; one end of the discharge chamber is connected to a vacuum pump that provides a vacuum degree in the discharge chamber, and the other end is connected to a gas flow meter for controlling the gas flow rate injected into the discharge chamber; the end of the discharge chamber connected to the vacuum pump is used as the plasma output port, and the end connected to the gas flow meter is used as the gas injection port;

[0028] In this embodiment, as Figure 1 shown, the central area is the discharge chamber, which is cylindrical, with a radius of 15.9 mm and a length of 117 mm. The wall thickness of the chamber is 9.1 mm, and the material is quartz glass. Quartz glass is heat-resistant and can withstand the high temperature generated during gas discharge. At the same time, it also has high light transmittance, which is convenient for observing the discharge state.

[0029] The magnetic core is composed of 3 groups of rectangular ring-shaped ferrite magnetic cores. Two U-shaped ferrite magnetic cores are spliced together to form a ring-shaped rectangular block. The discharge chamber passes through the rectangular ring, and both ends of the cylindrical barrel wall are fixed by a medium, so that the discharge chamber is located at the center of the rectangular ring;

[0030] In this embodiment, the magnetic core is composed of 6 U-shaped ferrite magnetic cores divided into 3 groups and spliced together in pairs. The relative magnetic permeability is 2500. The outer dimensions are 117 * 86.7 mm, the inner dimensions are 98 * 66.7 mm, and the thickness is 26 mm. In order to make the electromagnetic field distribution in the chamber uniform, the 3 groups of magnetic cores are separated from each other by 1.5 mm and placed in the middle of the discharge path.

[0031] The inductor coil is closely wound in the middle of any side of the magnetic core. The inductor coil is current-excited. In order to maximize the power output efficiency of the power supply, an impedance matching circuit is usually added in front of the coil.

[0032] In this embodiment, the inductance coil is composed of pure copper wire, and the number of turns can be arbitrary and can be changed according to actual needs. To facilitate installation and maintain heat dissipation and insulation effects, the inner side of the inductance coil is slightly larger than the magnetic core.

[0033] When the inductively coupled remote plasma generator works, first use a vacuum pump to pump the air pressure in the discharge cavity to high vacuum, and then inject the working gas into the discharge cavity. By observing the readings of the vacuum pump and the gas flow meter, the gas flow is adjusted to control the air pressure in the discharge cavity. In this embodiment, argon (Ar), oxygen (O 2 ), and nitrogen trifluoride (NF 3 ) etc. can be used as the working gas, and the air pressure is 4 Torr to 10 Torr; then, an alternating current with radio frequency is passed through the inductance coil by an external power supply. The inductance coil converts the energy provided by the power supply into electromagnetic energy, and the electromagnetic energy is then transmitted to the discharge cavity through the magnetic core. After the charged particles absorb the electromagnetic field energy, they collide with the gas molecules or atoms in the discharge cavity to form plasma, and finally the plasma is output through the plasma output port.

[0034] Next, we simulate the inductively coupled plasma source with a magnetic core proposed in the present invention. The working gas used is Ar, the air pressure is 10 Torr; the number of turns of the coil is 5, and the excitation current is 30 A. It is defined that the difference in electron density between two adjacent time steps during the simulation process is less than 1% as the calculation reaches the discharge steady state. After reaching the steady state, the obtained contour maps of electron density, electron temperature, and electric potential distribution are respectively as Figure 2 , Figure 3 and Figure 4 shown.

[0035] The electron density distribution can also be regarded as the plasma density distribution, which shows the uniformity of the plasma. As Figure 2 shown, it can be seen from the cross-sectional view that the plasma presents a cylindrical distribution, is axisymmetric in the angular direction and uniform in the axial direction, and shows a trend of being high in the center and low on both sides in the radial direction.

[0036] As Figure 3 shown, the electron temperature has a linear relationship with the average electron energy and can be regarded as the distribution of electron energy density. It can be seen from the figure that the electron energy distribution function is nearly uniformly distributed except in the sheath region on the boundary.

[0037] Due to the existence of the plasma sheath, as Figure 4 shown, the electric potential in the central region of the plasma will be higher than that of the vessel wall.

[0038] Although the above description of the illustrative embodiments of the present invention has been made to facilitate the understanding of those skilled in the art of the present technology, it should be clear that the present invention is not limited to the scope of the specific embodiments. For those of ordinary skill in the art of the present technology, as long as various changes are within the spirit and scope of the present invention defined and determined by the appended claims, these changes are obvious, and all inventions and creations using the concept of the present invention are within the scope of protection.

Claims

1. An inductively coupled remote plasma generator with a magnetic core, characterized in that, it includes: a discharge chamber, a magnetic core and an inductor coil; The discharge chamber is composed of a cylindrical barrel wall and connecting flanges at both ends. The inside of the barrel is evacuated to serve as the discharge reaction area. One end of the discharge chamber is connected to a vacuum pump that provides the vacuum degree inside the discharge chamber, and the other end is connected to a gas flow meter for controlling the gas flow rate injected into the discharge chamber. The end of the discharge chamber connected to the vacuum pump is used as the plasma output port, and the end connected to the gas flow meter is used as the gas injection port; The magnetic core is composed of several groups of rectangular ring-shaped ferrite magnetic cores. The discharge chamber passes through the rectangular ring, and the two ends of the cylindrical barrel wall are fixed by a medium, so that the discharge chamber is located at the center of the rectangular ring; The inductor coil is densely wound around any side of the magnetic core in the middle and is excited by current; When the inductively coupled remote plasma generator works, first use a vacuum pump to evacuate the air pressure in the discharge chamber to high vacuum, then inject working gas into the discharge chamber and control the air pressure in the discharge chamber by observing the readings of the vacuum pump and the gas flow meter and adjusting the gas flow rate accordingly. Then, apply radio frequency alternating current to the inductor coil through an external power supply. The inductor coil converts the energy provided by the power supply into electromagnetic energy, and the electromagnetic energy is then transmitted to the discharge chamber through the magnetic core. After the charged particles absorb the electromagnetic field energy, they collide ionizingly with the gas molecules or atoms in the discharge chamber to form plasma, and finally output through the plasma output port.

2. The inductively coupled remote plasma generator with a magnetic core according to claim 1, characterized in that, the material of the cylindrical barrel wall is quartz glass.

3. The inductively coupled remote plasma generator with a magnetic core according to claim 1, characterized in that, the magnetic core is formed by splicing two U-shaped ferrite magnetic cores in pairs to form a ring-shaped rectangular block.

4. The inductively coupled remote plasma generator with a magnetic core according to claim 1, characterized in that, an impedance matching circuit is added to the input end of the inductor coil.

5. The inductively coupled remote plasma generator with a magnetic core according to claim 1, characterized in that, the distance between any two groups of rectangular ring-shaped ferrite magnetic cores in the magnetic core is equal.

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