Plasma induction system using harmonics and plasma induction method using same

Abstract

The present disclosure relates to a system for inducing plasma using harmonics and a plasma induction method using same and, more specifically, to a plasma induction system in which resonant frequencies of a plurality of loads used to form inductively coupled plasma are designed on the basis of a driving frequency of an input voltage, and a plasma induction method using same.

Description

Plasma induction system using harmonic waves and plasma induction method using the same

[0001] The present disclosure relates to a system for inducing plasma using harmonics and a plasma induction method using the same, and more specifically, to a plasma induction system in which the resonant frequency of an antenna structure for forming an inductively coupled plasma is designed based on a harmonic frequency of a driving frequency of an input voltage, and a plasma induction method using the same.

[0002] Inductively Coupled Plasma (ICP) is a method of providing radio frequency (RF) energy to an antenna structure surrounding a discharge tube to turn gas flowing into the discharge tube into a plasma state. It is used in various industrial fields such as semiconductors, displays, medical equipment, and spectroscopic analysis technology, as well as environmental energy solutions that reform landfill gas and biogas.

[0003] In an inductively coupled plasma, when the pressure inside the discharge tube is relatively high (e.g., atmospheric pressure), an ignition antenna structure for igniting the plasma may be used in addition to the main antenna structure for maintaining the plasma.

[0004] However, when the ignition antenna structure and the main antenna structure are used together, the electromagnetic field formed by one antenna structure may induce a voltage in the other antenna structure, which may cause damage or abnormal operation of the plasma induction system.

[0005] There is currently no active research being conducted on a method for solving the problem of mutual inductive coupling between the above-described antenna structures, and in this disclosure, a plasma induction system that effectively solves the above problem is described.

[0006] The task to be solved is to minimize the effects of induced voltages resulting from inductive coupling between loads including the antenna structure.

[0007] The task to be solved is to reduce the phase difference between the voltage and current applied to loads as plasma is ignited or maintained for loads with different resonant frequencies.

[0008] The task to be solved is to induce plasma by applying RF voltage to a load for plasma ignition and a load for plasma maintenance using one RF generator.

[0009] The problems to be solved in this disclosure are not limited to the problems described above, and problems not mentioned can be clearly understood by a person having ordinary skill in the technical field to which the present invention pertains from this disclosure and the attached drawings.

[0010] According to one embodiment, a plasma induction device is provided, comprising: a discharge tube providing a space in which plasma is induced; an ignition antenna structure arranged to surround the discharge tube, and a first load including at least one capacitive element electrically connected in series with the ignition antenna structure; a main antenna structure arranged to surround the discharge tube and disposed within a preset distance from the ignition antenna structure in a direction parallel to a central axis of the discharge tube, and a second load including at least one capacitive element electrically connected in series with the main antenna structure; and an RF generator for applying an RF (Radio Frequency) voltage to the first load and the second load; wherein when the second load is designed to have a main resonance frequency, the first load is designed to have an ignition resonance frequency corresponding to (2n+1) times (n is a natural number) an initial driving frequency that differs by a first value from the main resonance frequency, and the RF generator is configured to apply an RF voltage having the initial driving frequency to the first load and the second load for plasma ignition.

[0011] According to another embodiment, a plasma induction method for supplying power to a plasma induction device, the plasma induction device comprising: a discharge tube providing a space in which plasma is induced; an ignition antenna structure arranged to surround the discharge tube, and a first load including at least one capacitive element electrically connected in series with the ignition antenna structure; a main antenna structure arranged to surround the discharge tube and disposed within a preset distance from the ignition antenna structure in a direction parallel to a central axis of the discharge tube, and a second load including at least one capacitive element electrically connected in series with the main antenna structure; and an RF generator for applying an RF (Radio Frequency) voltage to the first load and the second load, the method comprising: applying an initial RF voltage having an initial driving frequency to the first load and the second load using the RF generator; A step of applying a first RF voltage having a first driving frequency to the first load and the second load after detecting that plasma is ignited in a plasma ignition region corresponding to the ignition antenna structure in the discharge tube, wherein the first driving frequency is determined based on a phase difference between a voltage and a current applied to the first load, and a magnitude of a current flowing in the main antenna structure increases when the first RF voltage is applied compared to when the initial RF voltage is applied to the second load;A plasma induction method is provided, comprising: a step of applying a second RF voltage having a second driving frequency to the first load and the second load after detecting that the ignited plasma has transitioned to a plasma maintenance region corresponding to the main antenna structure in the discharge tube, wherein the second driving frequency is determined based on a phase difference between a voltage and a current applied to the second load, and a magnitude of a current flowing in the ignition antenna structure is reduced when the second RF voltage is applied compared to when the first RF voltage is applied to the first load.

[0012] The means of solving the problem are not limited to the above-described means of solving the problem, and means of solving the problem that are not mentioned can be clearly understood by a person having ordinary skill in the art to which the present invention pertains from the present disclosure and the attached drawings.

[0013] In one embodiment, the use of multiple antenna structures for plasma induction does not result in damage or malfunction within the system.

[0014] According to one embodiment, a plasma induction system capable of stably igniting and maintaining plasma under atmospheric pressure can be implemented.

[0015] In one embodiment, the cost and volume of the system can be significantly reduced by using a single RF generator even when multiple antenna structures are used.

[0016] The effects according to the present disclosure are not limited to the effects described above, and effects not mentioned can be clearly understood by a person having ordinary skill in the art to which the present invention pertains from the present disclosure and the attached drawings.

[0017] FIG. 1 is a drawing showing a plasma induction system according to one embodiment.

[0018] FIG. 2 is a diagram illustrating an RF generator according to one embodiment.

[0019] FIG. 3 is a drawing showing a plasma induction device according to one embodiment.

[0020] Fig. 4 is a drawing showing a schematic structure of a plasma induction device according to one embodiment.

[0021] FIG. 5 is a drawing for explaining the process of operating a plasma induction system according to one embodiment.

[0022] FIG. 6 is a diagram for explaining a problem in which an induced voltage is generated according to the interaction of loads according to one embodiment.

[0023] FIG. 7 is a diagram showing that the square wave component affected by each load changes depending on the resonant frequency design of the loads according to one embodiment.

[0024] Fig. 8 is a flowchart showing a control method of a plasma induction system according to one embodiment.

[0025] FIG. 9 is a flowchart illustrating a frequency tracking method for a load according to one embodiment.

[0026] Fig. 10 is a flowchart illustrating a method for tracking harmonic frequencies for a load having a harmonic frequency as a resonant frequency according to one embodiment.

[0027] FIG. 11 is a flowchart illustrating a power consumption-based frequency tracking method for a load having a harmonic frequency as a resonant frequency according to one embodiment.

[0028] FIG. 12 is a diagram for explaining a power consumption-based frequency tracking method according to one embodiment.

[0029] FIG. 13 is a diagram illustrating a plasma induction system using multiple loads and one RF generator according to one embodiment.

[0030] Fig. 14 is a flowchart showing the process of operating a plasma induction system according to one embodiment.

[0031] FIGS. 15 and 16 are diagrams showing the characteristics of components within a plasma induction system according to plasma induction according to one embodiment.

[0032] According to one embodiment, a plasma induction device is provided, comprising: a discharge tube providing a space in which plasma is induced; an ignition antenna structure arranged to surround the discharge tube, and a first load including at least one capacitive element electrically connected in series with the ignition antenna structure; a main antenna structure arranged to surround the discharge tube and disposed within a preset distance from the ignition antenna structure in a direction parallel to a central axis of the discharge tube, and a second load including at least one capacitive element electrically connected in series with the main antenna structure; and an RF generator for applying an RF (Radio Frequency) voltage to the first load and the second load; wherein when the second load is designed to have a main resonance frequency, the first load is designed to have an ignition resonance frequency corresponding to (2n+1) times (n is a natural number) an initial driving frequency that differs by a first value from the main resonance frequency, and the RF generator is configured to apply an RF voltage having the initial driving frequency to the first load and the second load for plasma ignition.

[0033] The magnitude of the current flowing in the ignition antenna structure after plasma is ignited in a plasma ignition region corresponding to the ignition antenna structure in the discharge tube is greater when an RF voltage having a first driving frequency is applied to the ignition antenna structure than when an RF voltage having the initial driving frequency is applied to the ignition antenna structure, and the first driving frequency has a value greater than the initial driving frequency.

[0034] The main antenna structure is applied with an RF voltage having the same driving frequency as the RF voltage applied to the ignition antenna structure, and the magnitude of the current flowing in the main antenna structure is greater when RF power having the first driving frequency is applied to the main antenna structure than when RF power having the initial driving frequency is applied to the main antenna structure.

[0035] The magnitude of the current flowing in the main antenna structure after the ignited plasma is transitioned to the plasma maintenance region corresponding to the main antenna structure in the discharge tube is greater when RF power having the second driving frequency is applied to the main antenna structure than when RF power having the first driving frequency is applied, and the second driving frequency has a value greater than the first driving frequency.

[0036] An RF voltage having the same driving frequency as the RF voltage applied to the main antenna structure is applied to the ignition antenna structure, and the magnitude of a current flowing in the ignition antenna structure is smaller when RF power having the second driving frequency is applied to the ignition antenna structure than when RF power having the first driving frequency is applied to the ignition antenna structure.

[0037] When plasma is ignited in a plasma ignition region corresponding to the ignition antenna structure in the discharge tube, a first synthetic load including the ignited plasma and the first load has a first synthetic resonance frequency greater than the ignition resonance frequency, and a first difference value between a value obtained by dividing the first synthetic resonance frequency by (2n+1) and the initial driving frequency corresponds to the first value.

[0038] When the ignited plasma is transferred to a plasma maintenance region corresponding to the main antenna structure in the discharge tube, the second synthetic load including the transferred plasma and the second load has a second synthetic resonance frequency greater than the main resonance frequency, and a second difference value between the first synthetic resonance frequency divided by (2n+1) and the second synthetic resonance frequency is greater than or equal to a threshold value.

[0039] The above threshold value is determined at 10% or more of the initial driving frequency.

[0040] When the RF generator applies a voltage signal having a driving frequency corresponding to the first synthetic resonant frequency to the first load while the plasma is ignited, the difference between the phase of the voltage applied to the first load and the phase of the current flowing in the first load is 0 or substantially equal to 0.

[0041] When the RF generator applies a voltage signal having a driving frequency corresponding to the second synthetic resonant frequency to the second load while the plasma is in a transition state, the difference between the phase of the voltage applied to the second load and the phase of the current flowing in the second load is 0 or substantially equal to 0.

[0042] When the fundamental driving frequency of the voltage signal output from the RF generator is a, the size of the first value is determined within 0.01*a to 0.3*a.

[0043] The above main resonant frequency has a value between 1.01 and 1.1 times the initial driving frequency.

[0044] The above preset distance is within 10 cm.

[0045] According to another embodiment, a plasma induction method for supplying power to a plasma induction device, the plasma induction device comprising: a discharge tube providing a space in which plasma is induced; an ignition antenna structure arranged to surround the discharge tube, and a first load including at least one capacitive element electrically connected in series with the ignition antenna structure; a main antenna structure arranged to surround the discharge tube and disposed within a preset distance from the ignition antenna structure in a direction parallel to a central axis of the discharge tube, and a second load including at least one capacitive element electrically connected in series with the main antenna structure; and an RF generator for applying an RF (Radio Frequency) voltage to the first load and the second load, the method comprising: applying an initial RF voltage having an initial driving frequency to the first load and the second load using the RF generator; A step of applying a first RF voltage having a first driving frequency to the first load and the second load after detecting that plasma is ignited in a plasma ignition region corresponding to the ignition antenna structure in the discharge tube, wherein the first driving frequency is determined based on a phase difference between a voltage and a current applied to the first load, and a magnitude of a current flowing in the main antenna structure increases when the first RF voltage is applied compared to when the initial RF voltage is applied to the second load;A plasma induction method is provided, comprising: a step of applying a second RF voltage having a second driving frequency to the first load and the second load after detecting that the ignited plasma has transitioned to a plasma maintenance region corresponding to the main antenna structure in the discharge tube, wherein the second driving frequency is determined based on a phase difference between a voltage and a current applied to the second load, and a magnitude of a current flowing in the ignition antenna structure is reduced when the second RF voltage is applied compared to when the first RF voltage is applied to the first load.

[0046] According to another embodiment, a plasma induction device is provided, comprising: a discharge tube providing a space in which plasma is induced; an ignition antenna structure arranged to surround the discharge tube, and a first load including at least one capacitive element electrically connected in series with the ignition antenna structure; a main antenna structure arranged to surround the discharge tube and disposed within a preset distance from the ignition antenna structure in a direction parallel to a central axis of the discharge tube, and a second load including at least one capacitive element electrically connected in series with the main antenna structure; and an RF (Radio Frequency) generator for applying an RF voltage to the first load and the second load; wherein when the second load is designed to have a main resonance frequency, the ignition resonance frequency of the first load is designed to have a value closer to (2n+1) times the main resonance frequency than (2n) times (n is a natural number) the main resonance frequency or (2n+2) times the main resonance frequency.

[0047] According to another embodiment, a plasma induction method for supplying power to a plasma induction device, the plasma induction device comprising: a discharge tube providing a space in which plasma is induced; a first load including a first antenna structure arranged to surround the discharge tube and at least one capacitive element electrically connected in series with the first antenna structure; and a second load including a second antenna structure arranged to surround the discharge tube and disposed within a preset distance from the first antenna structure in a direction parallel to a central axis of the discharge tube, and at least one capacitive element electrically connected in series with the second antenna structure; wherein the plasma induction method comprises: applying a first square wave voltage to the first load at a first point in time using a first RF generator; And a second RF generator is used to apply a second square wave voltage to the second load at a second time point after the first time point; wherein the first square wave voltage has a first driving frequency having a value within a first range set based on a first reference frequency, the second square wave voltage has a second driving frequency having a value within a second range set based on a second reference frequency, and the first load is designed to have a first resonant frequency corresponding to (2n+1) times the first reference frequency, and the second load is designed to have a second resonant frequency corresponding to the second reference frequency.

[0048] The first reference frequency and the second reference frequency are substantially the same.

[0049] The plasma induction method further includes: calculating a first phase difference for the first load; applying a third square wave voltage to the first load based on the first phase difference, wherein the third square wave voltage has a third driving frequency different from the first driving frequency; calculating a second phase difference for the second load; and applying a fourth square wave voltage to the second load based on the second phase difference, wherein the fourth square wave voltage has a fourth driving frequency different from the second driving frequency.

[0050] The step of calculating the first phase difference includes obtaining a first switch signal applied to at least one of the switch elements included in the first RF generator, obtaining a first phase signal of a current flowing in the first load, processing the first switch signal to generate a first reference signal, wherein a frequency of the first reference signal is 2n+1 times the frequency of the first switch signal, and calculating the first phase difference using the first reference signal and the first phase signal, and the step of calculating the second phase difference includes obtaining a second switch signal applied to at least one of the switch elements included in the second RF generator, obtaining a second phase signal of a current flowing in the second load, generating a second reference signal corresponding to the second switch signal, and calculating the second phase difference using the second reference signal and the second phase signal.

[0051] The step of processing the first switch signal to generate the first reference signal further includes time shifting the first switch signal.

[0052] The plasma induction method further includes: measuring a first input power of the first RF generator; applying a third square wave voltage to the first load, wherein the third square wave voltage has a third driving frequency different from the first driving frequency; measuring a second input power of the first RF generator; applying a fifth square wave voltage to the first load based on a difference between the first input power and the second input power; calculating a phase difference between voltage and current applied to the second load; and applying a fourth square wave voltage to the second load based on the phase difference, wherein the fourth square wave voltage has a fourth driving frequency different from the second driving frequency.

[0053] When the third driving frequency is greater than the first driving frequency and the first input power is less than the second input power, the fifth driving frequency of the fifth square wave voltage has a value greater than the third driving frequency.

[0054] When the third driving frequency is greater than the first driving frequency and the first input power is greater than the second input power, the fifth driving frequency of the fifth square wave voltage has a value smaller than the third driving frequency.

[0055] Each of the first input power and the second input power is an average value of power measured for the first RF generator over a preset period of time.

[0056] The second antenna structure includes at least one unit antenna and at least one capacitive element.

[0057] According to another embodiment, a plasma induction system comprises: a discharge tube providing a space in which plasma is induced; a first load including a first antenna structure arranged to surround the discharge tube and at least one capacitive element electrically connected in series with the first antenna structure; a second load including a second antenna structure arranged to surround the discharge tube and disposed within a preset distance from the first antenna structure in a direction parallel to a central axis of the discharge tube, and at least one capacitive element electrically connected in series with the second antenna structure, the second antenna structure including at least one unit antenna and at least one capacitive element; a first radio frequency (RF) generator electrically connected to the first load, the first RF generator configured to output a first square wave voltage having a first driving frequency having a value within a first range set based on a first reference frequency; And a second RF generator electrically connected to the second load, the second RF generator being configured to output a second square wave voltage having a second driving frequency having a value within a second range set based on a second reference frequency; wherein the first load is designed to have a first resonant frequency corresponding to (2n+1) times (n is a natural number) the first reference frequency, and the second load is designed to have a second resonant frequency corresponding to the second reference frequency. A plasma induction system is provided.

[0058] The first reference frequency and the second reference frequency are substantially the same.

[0059] The second antenna structure of the second load includes first to p-th layer antennas and first to (p-1)-th interlayer capacitive elements, wherein p is a natural number greater than or equal to 2, the first to p-th layer antennas are arranged in different planes, and the k-th interlayer capacitive element among the first to (p-1)-th interlayer capacitive elements is electrically interposed between the k-th layer antenna and the (k+1)-th layer antenna.

[0060] The first antenna structure of the first load includes a plurality of layer antennas, wherein no capacitive element is electrically interposed between the plurality of layer antennas.

[0061] The plasma induction system further includes a first control unit that controls the first RF generator, wherein the first control unit is configured to obtain a first switch signal applied to at least one of the switch elements included in the first RF generator, obtain a first phase signal of a current flowing in the first load, process the first switch signal to generate a first reference signal, calculate the first phase difference using the first reference signal and the first phase signal, and apply a third square wave voltage to the first load based on the first phase difference, wherein a frequency of the first reference signal is 2n+1 times the frequency of the first switch signal.

[0062] The plasma induction system further includes a first control unit that controls the first RF generator, wherein the first control unit is configured to measure a first input power of the first RF generator, apply a third square wave voltage having a third driving frequency different from the first driving frequency to the first load, measure a second input power of the first RF generator, and apply a fifth square wave voltage to the first load based on a difference between the first input power and the second input power.

[0063] When the third driving frequency is greater than the first driving frequency and the first input power is less than the second input power, the fifth driving frequency of the fifth square wave voltage has a value greater than the third driving frequency.

[0064] When the third driving frequency is greater than the first driving frequency and the first input power is greater than the second input power, the fifth driving frequency of the fifth square wave voltage has a value smaller than the third driving frequency.

[0065] The first input power and the second input power are each an average value of power measured for the first RF generator over a preset period of time.

[0066] The above-described objects, features, and advantages of the present disclosure will become more apparent through the following detailed description taken in conjunction with the accompanying drawings. However, the present disclosure is susceptible to various modifications and various embodiments. Therefore, specific embodiments will be illustrated in the drawings and described in detail below.

[0067] In the drawings, the thicknesses of layers and regions are exaggerated for clarity, and when an element or layer is referred to as "on" or "on" another element or layer, this includes not only the case where the element or layer is directly above the other element or layer, but also the case where another layer or other element is interposed. In principle, the same reference numerals represent the same elements throughout the specification. In addition, elements that have the same function within the scope of the same idea shown in the drawings of each embodiment are described using the same reference numerals, and redundant descriptions thereof will be omitted.

[0068] The numbers (e.g., first, second, etc.) used in the description of the present disclosure are merely identifiers to distinguish one component from another.

[0069] In addition, the suffixes "module" and "part" for components used in the following examples are given or used interchangeably only for the convenience of writing the specification, and do not have distinct meanings or roles in themselves.

[0070] In the examples below, singular expressions include plural expressions unless the context clearly indicates otherwise.

[0071] In the following examples, terms such as “include” or “have” mean that a feature or component described in the specification is present, and do not preclude the possibility that one or more other features or components may be added.

[0072] For convenience of explanation, the sizes of components in the drawings may be exaggerated or reduced. For example, the sizes and thicknesses of each component shown in the drawings are arbitrarily shown for convenience of explanation, and the present invention is not necessarily limited to what is shown.

[0073] In some embodiments, where implementations are otherwise feasible, specific process sequences may be performed in a different order than described. For example, two processes described in succession may be performed substantially simultaneously, or in a reverse order from the described order.

[0074] Unless specifically stated or clear from context, the term "about" in relation to a numerical value shall be understood to mean the numerical value stated plus or minus 10% of that numerical value, and the term "about" in relation to a numerical range shall be understood to mean a range from 10% below the lower limit of the numerical range to 10% above the upper limit of the numerical range.

[0075] In the following examples, when it is said that a film, region, component, etc. are connected, it includes not only cases where the films, regions, and components are directly connected, but also cases where other films, regions, and components are interposed between the films, regions, and components and are indirectly connected.

[0076] For example, in the present disclosure, the meaning of a film, region, component, etc. being electrically connected includes not only cases where the film, region, component, etc. are directly electrically connected, such as when the film, region, component, etc. are physically combined or formed as one body to allow current to flow, but also cases where the film, region, component, etc. are indirectly electrically connected by intervening another film, region, component, etc.

[0077] Also, for example, in the present disclosure, the meaning of a membrane, region, component, etc. being fluidly connected includes not only cases where the membrane, region, component, etc. are directly fluidly connected, such as when the membrane, region, component, etc. are physically combined or formed as one body so that a fluid can move, but also cases where the membrane, region, component, etc. are indirectly fluidly connected by intervening another membrane, region, component, etc.

[0078] The present disclosure relates to a system for inducing plasma using harmonic waves and a plasma induction method utilizing the same. More specifically, the present disclosure relates to a plasma induction system that enhances stability and durability, while also reducing cost and volume, and a control protocol for driving the system.

[0079] The plasma induction system and method of using the same described in this disclosure can be used in a plasma process. Here, the term "plasma process" refers to a process of generating plasma and utilizing the generated plasma, and is used in semiconductor processes, display processes, nano processes, gas reforming processes, and the like.

[0080] In the plasma induction system described in the present disclosure, the method of inducing plasma mainly refers to an inductively coupled plasma (ICP), and more specifically, it refers to a method of forming an electromagnetic field inside a discharge tube by applying an RF (Radio Frequency) voltage to a load including an antenna structure, thereby turning gas inside a discharge tube into a plasma state. In this case, the antenna structure refers to an object that includes a coil or an antenna and receives power to form an induced electric field or a capacitive electric field for generating plasma, and can be designed in various ways depending on the purpose and specifications of the plasma induction system.

[0081] Meanwhile, it is to be noted in advance that the technical idea of ​​the present disclosure is not limited to inductively coupled plasma among plasma induction methods, and can also be applied to a method of inducing plasma using RF voltage, particularly a square wave RF voltage, for example, capacitively coupled plasma (CCP).

[0082] In the present disclosure, the use of harmonics means utilizing not only the components having the fundamental frequency among the components that create a non-sinusoidal wave such as a square wave or a pulse wave, but also harmonic components that are multiples of the fundamental frequency.

[0083] 1. Plasma induction system

[0084] Hereinafter, a plasma induction system (100) is described with reference to FIG. 1.

[0085] FIG. 1 is a drawing showing a plasma induction system (100) according to one embodiment.

[0086] Referring to FIG. 1, the plasma induction system (100) may include an RF generator (1000) and a plasma induction device (2000).

[0087] The RF generator (1000) can provide power to the plasma induction device (2000). For example, the RF generator (1000) can apply AC power having a specific driving frequency to the load of the plasma induction device (2000). Here, the AC power may mean AC voltage or AC current, and for the convenience of explanation, it will be referred to as 'RF voltage' hereinafter.

[0088] The RF voltage provided by the RF generator (1000) can be understood as a non-sinusoidal wave having a specific frequency. For example, the RF voltage may be in the form of a square wave having a specific driving frequency and a specific magnitude.

[0089] The RF generator (1000) may be designed to have specific performance. Specifically, the driving frequency of the RF voltage provided by the RF generator (1000) may have a certain range, and the power provided by the RF generator (1000) may also have a certain range. For example, the RF generator (1000) may have a driving frequency of about 0.2 MHz to about 60 MHz and a power of about 100 W to about 50 kW.

[0090] In the plasma induction process, the RF generator (1000) can change the driving frequency of the RF voltage in real time when applying the RF voltage to the plasma induction device (2000). More specifically, the RF generator (1000) can set the driving frequency of the RF voltage applied to the load to a value close to the resonant frequency of the load so that the current flowing in the load within the plasma induction device (2000) approaches the maximum value. At this time, as the plasma is induced, the size of the current flowing in the load is affected by the resonant frequency of the composite component of the load and the plasma, and the RF generator (1000) can adjust the driving frequency so as to approach the resonant frequency of the composite component. For convenience of explanation, the method of adjusting the aforementioned driving frequency is referred to as frequency tracking, and the frequency tracking operation will be described later.

[0091] The RF generator (1000) can control the power consumed in the plasma induction system (100). For example, the RF generator (1000) can perform an operation of applying RF voltage and an operation of not applying RF voltage, and increase the number of times the operation of not applying RF voltage is performed within a unit time interval to control the power consumed in the plasma induction system (100) within a specific range.

[0092] The plasma induction device (2000) can induce plasma by receiving an RF voltage. For example, the plasma induction device (2000) includes a discharge tube and loads as described below, and the loads can form an electromagnetic field for plasma induction inside the discharge tube by receiving an RF voltage, and gases introduced inside the discharge tube can transition to a plasma state by the electromagnetic field.

[0093] The plasma induction device (2000) can be designed in various ways depending on the conditions of the environment in which it is used. Here, the conditions of the environment in which it is used refer to the purpose (e.g., pressure inside the discharge tube), performance (e.g., energy conversion efficiency, standard power consumption), volume, and price of the plasma induction system (100).

[0094] The RF generator (1000) and the plasma induction device (2000) may be provided as a single plasma induction system (100). However, the RF generator (1000) and the plasma induction device (2000) may each be provided as a single product, and the plasma induction device (2000) may also be provided as separate products for the discharge tube and the load.

[0095] Hereinafter, the RF generator (1000) and the plasma induction device (2000) will be described in more detail with reference to FIGS. 2 to 4.

[0096] 1.1 RF generator

[0097] FIG. 2 is a drawing showing an RF generator (1000) according to one embodiment.

[0098] Referring to FIG. 2, the RF generator (1000) may include an AC power source (1100), a rectifier (1200), an inverter (1300), a phase sensing module (1400), a power sensing module (1500), and a control unit (1600).

[0099] The AC power source (1100) is a component that provides AC power used in the RF generator (1000). The RF generator (1000) may receive AC power from an AC power source commonly used in homes or industries. In this case, the RF generator (1000) may not include the AC power source (1100) and may receive AC power from an external power source.

[0100] The RF generator (1000) can receive AC power from an AC power source (1100) and supply an RF voltage having a specific driving frequency to the plasma induction device (2000).

[0101] The rectifier (1200) can convert the output of an AC power source (1100) into a DC voltage. The rectifier (1200) can convert the AC voltage supplied from the AC power source (1100) into a DC voltage and apply it to the input terminal of the inverter (1300). The rectifier (1200) can be implemented as a circuit including a plurality of diodes.

[0102] The inverter (1300) can receive a DC voltage from the rectifier (1200) and supply an RF voltage to the plasma induction device (2000). For example, the inverter (1300) can receive a switch signal and provide an RF voltage to the load of the plasma induction device (2000) using the received switch signal. Here, the switch signal can be understood as a signal corresponding to a PWM (Pulse Width Modulation) signal generated by the control unit (1600) as described below, and the PWM signal can be understood as a signal that determines the driving frequency of the voltage signal.

[0103] The inverter (1300) may include at least one switch element controlled by a switch signal, and the RF voltage supplied from the inverter (1300) to the load may have a driving frequency set based on the switch signal provided to the inverter (1300).

[0104] For example, the inverter (1300) may be implemented in a full bridge form. Specifically, the inverter (1300) may include first to fourth switches (S1, S2, S3, S4). Here, the first to fourth switches (S1, S2, S3, S4) may receive a switch signal and maintain an on state or an off state. At this time, when the first and third switches (S1, S3) are maintained in an on state and the second and fourth switches (S2, S4) are maintained in an off state, a positive voltage may be output through the output terminal of the inverter (1300), and when the first and third switches (S1, S3) are maintained in an off state and the second and fourth switches (S2, S4) are maintained in an on state, a negative voltage may be output through the output terminal of the inverter (1300). In this way, the inverter (1300) can supply an RF voltage having a specific frequency by alternately outputting positive and negative voltages through the output terminal.

[0105] At this time, the voltage output through the output terminal of the inverter (1300) may be in the form of a square wave or a pulse wave. This is because, as described above, the voltage output through the inverter (1300) is maintained at a constant positive or negative constant value as the DC voltage is output in the positive or negative direction from the inverter (1300).

[0106] The implementation method of the inverter (1300) is not limited to the form described above, and the inverter (1300) can be understood as an example of a power conversion device that performs the function of converting direct current voltage into alternating current voltage.

[0107] The inverter (1300) can be controlled according to the frequency control method of the control unit (1600), for example, by a time delay method, a pulse width modulation (PWM) method, or a combination thereof.

[0108] Meanwhile, a capacitive element may be placed between the rectifier (1200) and the inverter (1300). For example, the RF generator (1000) includes a capacitor connected in parallel to the input terminal of the inverter (1300). This capacitive element may be understood as a filter that ensures that the voltage input to the inverter (1300) becomes close to direct current.

[0109] The control unit (1600) can generate a PWM signal corresponding to the driving frequency. Specifically, the control unit (1600) can receive data sensed from the phase sensing module (1400) and / or the power sensing module (1500) described below and generate the above-described PWM signal. For example, the control unit (1600) can obtain phase difference data or delay time using the phase data of the current applied to the load and the phase data of the voltage applied to the load obtained from the phase sensing module (1400) and generate a PWM signal based thereon. Here, a previously output PWM signal can be used as the phase data of the voltage applied to the load.

[0110] The control unit (1600) may be implemented as a device such as a central processing unit (CPU), a microprocessor, a processor core, a multiprocessor, an application-specific integrated circuit (ASIC), or a field programmable gate array (FPGA) based on hardware, software, or a combination thereof. In addition, the control unit (1600) may be divided into multiple modules rather than a single module. For example, the control unit (1600) may be composed of a phase difference calculation module that calculates a phase difference and a signal output module that outputs a PWM signal.

[0111] The phase sensing module (1400) can detect electrical characteristics of the load, such as the size or phase of the current applied to the load, and provide data related thereto to the control unit (1600).

[0112] Although not shown in FIG. 2, the phase sensing module (1400) may include a transformer, a filter, and a comparator.

[0113] The phase sensing module (1400) can receive a current or voltage signal flowing through a load through a current transformer, convert it into a current or voltage signal of different magnitude, filter the converted current or voltage signal using a filter, and provide phase data to the control unit (1600) through a comparator.

[0114] The current transformer can be inductively coupled to the wiring between the inverter (1300) and the load, and can convert a voltage or current signal applied to the load and provide it to the filter. Specifically, the current transformer can convert a current flowing in a wire connected to the load into a voltage signal.

[0115] A filter can remove the DC component from an input current or voltage signal and output it to a comparator. To achieve this, the filter can perform high-pass filtering or low-pass filtering.

[0116] A comparator can acquire phase data. For example, the comparator can acquire phase data by comparing a voltage signal obtained from a current transformer or filter with a preset value. In this case, the phase data can refer to the phase data of the current applied to the load.

[0117] At least one of the above-described components included in the phase sensing module (1400) may be omitted, and the phase sensing module (1400) may be implemented in a different manner. In addition, the phase sensing module (1400) may include a voltage sensor for measuring the voltage of the load, thereby measuring the magnitude or phase of the voltage applied to the load.

[0118] As described above, the RF generator (1000) can control the driving frequency of the RF voltage provided to the load based on data regarding the resonant frequency of the load. In other words, the RF generator (1000) can monitor the phase difference between the voltage and current applied to the load according to plasma generation, and adjust the driving frequency of the RF voltage in a direction that narrows the phase difference.

[0119] The power sensing module (1500) can collect data for calculating the power consumed by the inverter (1300) and the load. For example, the power sensing module (1500) can measure the current and / or voltage applied to the inverter (1300) and provide data related thereto to the control unit (1600). For this purpose, the power sensing module (1500) can be installed at the input terminal of the inverter (1300).

[0120] The power sensing module (1500) can be divided into a voltage sensor for measuring voltage and a current sensor for measuring current. Here, the current sensor can be implemented in the same manner as the phase sensing module (1400) described above. In addition, a resistance-type sensor or a capacitor-type sensor can be used as the voltage sensor.

[0121] Meanwhile, the power sensing module (1500) may also collect data for calculating the power consumed by the load. For example, the power sensing module (1500) may measure the current and / or voltage applied to the load and provide data related thereto to the control unit (1600). For this purpose, the power sensing module (1500) may be installed at the output terminal of the inverter (1300) or the input terminal of the load.

[0122] The control unit (1600) can calculate the average power consumption by the inverter (1300) and the load based on the data obtained from the power sensing module (1500), and can adjust the average power supplied to the inverter (1300) and the load by comparing the calculated average power consumption with a preset reference power consumption.

[0123] Meanwhile, although not shown in FIG. 2, the RF generator (1000) may include memory. The memory may store various data, such as values ​​measured by the phase sensing module (1400) or the power sensing module (1500), or programs, such as control protocols executed by the control unit (1600). Examples of the memory may include a hard disk drive (HDD), a solid state drive (SSD), flash memory, read-only memory (ROM), random access memory (RAM), etc. The memory may be provided in a form built into the RF generator (1000) or in a detachable form.

[0124] Additionally, the RF generator (1000) may include an input unit for receiving input from a user. The input unit may receive user input from the user. The user input may be in various forms, including key input, touch input, and voice input. Examples of the input unit include a comprehensive concept that includes not only traditional keypads, keyboards, and mice, but also various input means that detect or receive various forms of user input, such as touch sensors that detect the user's touch, and other various types of input means.

[0125] In addition, the RF generator (1000) may include an output unit for providing information to the user. The output unit may output information about the status of the plasma induction system (100) (e.g., phase difference between voltage applied to the load and current flowing therethrough, power consumed by the inverter (1300) and the load, driving frequency of the RF generator (1000), temperature of the plasma induction device (2000), etc.) and provide the information to the user. The output unit is a comprehensive concept that includes a display that outputs images, a speaker that outputs sounds, a haptic device that generates vibrations, and various other forms of output means.

[0126] The RF generator (1000) described above may omit at least one of its components. For example, the RF generator (1000) may not include a phase sensing module (1400) and / or a power sensing module (1500) and may acquire electrical data about a load or an inverter (1300) from an external sensor. As another example, the RF generator (1000) may not include an AC power source (1100) and a rectifier (1200) and may receive a DC voltage or a rectified DC voltage from an external source.

[0127] The plasma induction system (100) may include a plurality of RF generators (1000). For example, the plasma induction system (100) may include as many RF generators (1000) as the number of loads included in the plasma induction device (2000). In this case, each RF generator (1000) may apply an RF voltage to each antenna structure.

[0128] For example, the plasma induction device (2000) may include a first load and a second load, each including an antenna structure, and the plasma induction system (100) may include a first RF generator for applying an RF voltage to the first load and a second RF generator for applying an RF voltage to the second load. The first RF generator and the second RF generator may receive an AC voltage from the same AC power source and provide an RF voltage to the first load and the second load, respectively.

[0129] When there are multiple RF generators (1000), the plasma induction system (100) may further include a system control unit for controlling the multiple RF generators (1000). The system control unit may control each of the multiple RF generators (1000) based on data acquired through each RF generator (1000).

[0130] Meanwhile, even if the number of loads included in the plasma induction device (2000) is plural, the plasma induction system (100) may include one RF generator (1000). For example, the first load and the second load included in the plasma induction device (2000) may be connected in parallel to the output terminal of one RF generator (1000) to receive RF voltage.

[0131] 1.2 Plasma induction device

[0132] FIG. 3 is a drawing showing a plasma induction device (2000) according to one embodiment.

[0133] FIG. 4 is a drawing showing a schematic structure of a plasma induction device (2000) according to one embodiment.

[0134] Referring to FIG. 3, the plasma induction device (2000) may include a first load (2100), a second load (2200), and a discharge tube (2300). The first load (2100) is configured for plasma ignition, the second load (2200) is configured for plasma maintenance, and the discharge tube (2300) is configured to provide a space where plasma is ignited and maintained.

[0135] The discharge tube (2300) includes a gas inlet through which gas is introduced, an inner wall defining a plasma induction region, and an outlet through which modified gas is discharged.

[0136] The discharge tube (2300) may have various shapes, such as a cylindrical shape or a polygonal cylindrical shape, and at least a portion of the discharge tube (2300) may be made of a heat-resistant material, such as at least one of aluminum oxide, silicon nitride, silicon nitride, silicon dioxide, yttrium oxide, ceramic, silicon carbide, or a combination thereof.

[0137] The first load (2100) may include a first-first main capacitive element (2110), a first-second main capacitive element (2120), and an ignition antenna structure (2130).

[0138] The ignition antenna structure (2130) may be arranged around the discharge tube (2300). The ignition antenna structure (2130) may be implemented in a coil-like shape or ring shape that surrounds the outer surface of the discharge tube (2300).

[0139] The ignition antenna structure (2130) may have a layered structure. The ignition antenna structure (2130) may have a structure in which identical or similar structures are stacked in the longitudinal direction of the discharge tube (2300). For example, as illustrated in FIG. 4, the ignition antenna structure (2130) may have a two-layer structure including two layer antennas. It should be understood that the number of layers of the ignition antenna structure (2130) is not limited to two layers and may be appropriately determined as needed.

[0140] One layer of the ignition antenna structure (2130) may be composed of multiple turns. For example, as illustrated in FIG. 4, the ignition antenna structure (2130) may be composed of two turn antennas, i.e., an inner turn antenna that surrounds the outer surface of the discharge tube (2300) and an outer turn antenna that surrounds the inner turn antenna. The number of turns constituting each layer of the ignition antenna structure (2130) is not limited to two turns and may be appropriately determined as needed.

[0141] The ignition antenna structure (2130) includes N (N is a natural number) layer antennas, and each of the N layer antennas can have M (M is a natural number) turns.

[0142] The first-first main capacitive element (2110) may be electrically connected to one end of the ignition antenna structure (2130), and the first-second main capacitive element (2120) may be electrically connected to the other end of the ignition antenna structure (2130). Accordingly, the ignition antenna structure (2130) may be electrically connected to one end of the inverter (1300) of the RF generator (1000) through the first-first main capacitive element (2110), and may be electrically connected to the other end of the inverter (1300) of the RF generator (1000) through the first-second main capacitive element (2110).

[0143] The first-first main capacitive element (2110) and the first-second main capacitive element (2120) may be capacitive elements having a function of storing electric energy, such as capacitors, multilayer ceramic capacitors, and ultracapacitors, or may be implemented as equivalent circuits thereof.

[0144] Meanwhile, either one of the first-first main capacitive element (2110) or the first-second main capacitive element (2120) may be omitted.

[0145] The ignition resonance frequency (or first resonance frequency) of the first load (2100) can be determined based on the capacitance of the first-first main capacitive element (2110), the capacitance of the first-second main capacitive element (2120), and the inductance of the ignition antenna structure (2130). In other words, when the value of the ignition resonance frequency that the first load (2100) should have is determined, the capacitance of the first-first main capacitive element (2110), the capacitance of the first-second main capacitive element (2120), and the inductance of the ignition antenna structure (2130) can be designed based on this.

[0146] The second load (2200) may include a second-first main capacitive element (2210), a second-second main capacitive element (2220), and a main antenna structure (2230).

[0147] The main antenna structure (2230) may be arranged around the discharge tube (2300). The main antenna structure (2230) may be implemented in a coil-like shape or ring shape that surrounds the outer surface of the discharge tube (2300).

[0148] The main antenna structure (2230) may have a layered structure. The main antenna structure (2230) may have a structure in which identical or similar structures are laminated in the longitudinal direction of the discharge tube (2300). For example, as illustrated in FIG. 4, the main antenna structure (2230) may have a seven-layer structure including seven layer antennas. The number of layers of the main antenna structure (2230) is not limited to seven layers and may be appropriately determined as needed.

[0149] One layer of the main antenna structure (2230) may be composed of multiple turns. For example, as illustrated in FIG. 4, the main antenna structure (2230) may be composed of two turn antennas, i.e., an inner turn antenna that surrounds the outer surface of the discharge tube (2300) and an outer turn antenna that surrounds the inner turn antenna. The number of turns constituting each layer of the main antenna structure (2230) is not limited to two turns and may be appropriately determined as needed.

[0150] The main antenna structure (2230) may include at least one capacitive element. For example, the capacitive element may be electrically interposed between a plurality of antennas constituting the main antenna structure (2230). Specifically, an interlayer capacitive element may be electrically interposed between layer antennas included in the main antenna structure (2230). Alternatively, an interturn capacitive element may be electrically interposed between turn antennas constituting the layer antennas included in the main antenna structure (2230).

[0151] Here, the interlayer capacitive element or the interturn capacitive element may be a capacitive element having a function of storing electric energy, such as a capacitor, a capacitor, a multilayer ceramic capacitor, an ultracapacitor, or may be implemented as an equivalent circuit thereof.

[0152] The main antenna structure (2230) includes N (where N is a natural number) layer antennas, and each of the N layer antennas can include M (where M is a natural number) turn antennas. The main antenna structure (2230) includes N-1 interlayer capacitive elements, and a P-th interlayer capacitive element among the N-1 interlayer capacitive elements can be electrically interposed between a P-th layer antenna and a P+1-th layer antenna among the N layer antennas. Alternatively, the main antenna structure (2230) includes M-1 interturn capacitive elements, and a Q-th interturn capacitive element among the M-1 interturn capacitive elements can be electrically interposed between a Q-th turn antenna and a Q+1-th turn antenna among the M turn antennas.

[0153] Meanwhile, the layer antenna included in the main antenna structure (2230) may be composed of a plurality of unit antennas. For example, the layer antenna may be composed of A unit antennas (A is a natural number greater than or equal to 2), and each unit antenna may be composed of a first arc portion including a first end and a second end and having a first radius of curvature, a second arc portion including a third end and a fourth end and having a second radius of curvature different from the first radius of curvature, and an arc connection portion connecting the second end of the first arc portion and the third end of the second arc portion. At this time, the adjacent B unit antennas (B is a natural number smaller than A) and the B+1 unit antenna can be arranged so that the angle formed by the virtual first line connecting the center of the main antenna structure (2230) (or the center of the discharge tube (2300)) and the arc connection portion of the B unit antenna and the virtual second line connecting the center of the main antenna structure (2230) and the arc connection portion of the B+1 unit antenna is 360 / A degrees.

[0154] The number of layer antennas included in the ignition antenna structure (2130) may be different from the number of layer antennas included in the main antenna structure (2230), and the number of turns of the layer antennas of the ignition antenna structure (2130) may be different from the number of turns of the layer antennas of the main antenna structure (2230).

[0155] Unlike the main antenna structure (2230), the ignition antenna structure (2130) may not include a capacitive element. This is because when the antenna structure includes a capacitive element, the voltage applied to both ends of the antenna structure becomes relatively low, and as described below, a relatively high voltage must be applied to the ignition antenna structure (2130) during the plasma induction process. Of course, the ignition antenna structure (2130) may include a capacitive element, and the main antenna structure (2230) may not include a capacitive element.

[0156] The 2-1 main capacitive element (2210) may be electrically connected to one end of the main antenna structure (2230), and the 2-2 main capacitive element (2220) may be electrically connected to the other end of the main antenna structure (2230). Accordingly, the main antenna structure (2230) may be electrically connected to one end of the inverter (1300) of the RF generator (1000) through the 2-1 main capacitive element (2210), and may be electrically connected to the other end of the inverter (1300) of the RF generator (1000) through the 2-1 main capacitive element (2210).

[0157] The 2-1 main capacitive element (2210) and the 2-2 main capacitive element (2220) may be capacitive elements having a function of storing electric energy, such as capacitors, multilayer ceramic capacitors, and ultracapacitors, or may be implemented as equivalent circuits thereof.

[0158] Meanwhile, either one of the 2-1 main capacitive element (2210) or the 2-2 main capacitive element (2220) may be omitted.

[0159] The main resonant frequency (or second resonant frequency) of the second load (2200) can be determined based on the electrostatic capacitance of the 2-1 main capacitive element (2210), the electrostatic capacitance of the 2-2 main capacitive element (2220), and the inductive capacitance of the main antenna structure (2230). In other words, once the value of the main resonant frequency that the second load (2200) should have is determined, the electrostatic capacitance of the 2-1 main capacitive element (2210), the electrostatic capacitance of the 2-2 main capacitive element (2220), and the inductance of the main antenna structure (2230) can be designed based on this.

[0160] The ignition antenna structure (2130) of the first load (2100) and the main antenna structure (2230) of the second load (2200) may be arranged around the discharge tube (3000) at a predetermined distance apart from each other. For example, as illustrated in FIG. 4, the main antenna structure (2230) may be arranged at a first distance (D1) apart from the ignition antenna structure (2130) in the longitudinal direction of the discharge tube (2300).

[0161] At this time, as described later, in order for the plasma ignited in the area adjacent to the ignition antenna structure (2130) to transition to the area adjacent to the main antenna structure (2230), the distance between the ignition antenna structure (2130) and the main antenna structure (2230) needs to be within a certain distance. The first distance (D1) may be determined by the diameter of the discharge tube (3000), the amount of power used, the type of gas supplied to the discharge tube (3000), the driving frequency of the RF generator (1000), the gas supply flow rate, the structure of the nozzle supplying the gas, etc. For example, when the diameter of the discharge tube (3000) is about 5 cm to about 20 cm, the amount of power used is about 10 kW to about 50 kW, and the driving frequency of the RF generator (1000) is about 2 MHz to about 4 MHz, the first distance (D1) may be about 5 cm or less.

[0162] Meanwhile, if the distance between the ignition antenna structure (2130) and the main antenna structure (2230) is designed to be relatively close, a mutual induction effect may occur, causing one antenna structure to affect the other antenna structure, which may hinder the stability of the plasma induction system (100) and cause abnormal operation, as described below.

[0163] 1.4 Plasma induction process

[0164] Below, the process of operating the plasma induction system (100) is described with reference to FIG. 5.

[0165] FIG. 5 is a drawing for explaining a process of operating a plasma induction system (100) according to one embodiment. FIG. 5 shows a cross-section of a plasma induction device (2000). In FIG. 5, a case in which the plasma induction system (100) is used in a gas reforming process is exemplarily described, but the technical idea of ​​the present disclosure is not limited thereto, and can be similarly applied when the plasma induction system (100) is used in other processes utilizing plasma.

[0166] Referring to FIG. 5, the plasma induction system (100) includes a first RF generator (1001) and a second RF generator (1002), each of which is configured to apply RF voltage to a first load (2100) and a second load (2200) of a plasma induction device (2000).

[0167] The plasma induction region within the discharge tube (2300) can be divided into a first region (R1) and a second region (R2).

[0168] The first region (R1) is a region corresponding to the ignition antenna structure (2130) in the internal space of the discharge tube (2300). The ignition antenna structure (2130) receives an RF voltage from the first RF generator (1001) to form an electromagnetic field in the first region (R1), and auxiliary gases introduced into the first region (R1) can move by the formed electromagnetic field and collide with each other to transition to a plasma state. In other words, the first region (R1) can be understood as a region where plasma is ignited and generated.

[0169] The second region (R2) is a region corresponding to the main antenna structure (2230) in the internal space of the discharge tube (2300). The main antenna structure (2230) receives an RF voltage from the second RF generator (1002) to form an electromagnetic field in the second region (R2), and the plasma ignited in the first region (R1) by the formed electromagnetic field can be transferred to and maintained in the second region (R2). While the plasma is maintained in the second region (R2), a gas to be modified (e.g., a first feed gas, a second feed gas, water vapor) is introduced and modified by the plasma, thereby generating a synthetic gas. The second region (R2) can be understood as a region in which the ignited plasma moves and is maintained, and gas modification takes place.

[0170] A specific method for controlling the plasma induction system (100) for the gas reforming process will be described later with reference to FIG. 8.

[0171] 1.5 Problems in Plasma Induction

[0172] As described above, during the process of igniting and maintaining the plasma, RF voltage is applied to the ignition antenna structure (2130) and the main antenna structure (2230). At this time, since the distance between the ignition antenna structure (2130) and the main antenna structure (2230) is relatively close, problems may occur as the ignition antenna structure (2130) and the main antenna structure (2230) interact with each other.

[0173] Fig. 6 is a diagram illustrating a problem in which an induced voltage is generated due to the interaction of loads according to one embodiment. It should be noted in advance that Fig. 6 is a schematic diagram illustrating a plasma induction system (100) for convenience of explanation.

[0174] In the plasma maintenance process described in FIG. 5, when an RF voltage is applied to the main antenna structure (2230) by the second RF generator (1002), an RF current may flow in the main antenna structure (2230), which may form a magnetic field. For example, as shown in FIG. 6, when a current flows counterclockwise in the main antenna structure (2230) when viewed in the first direction, a magnetic field may be formed centered on the second direction (Ampere's circuit law). As another example, when a current flows clockwise in the main antenna structure (2230) when viewed in the first direction, a magnetic field may be formed centered on the first direction, which is the opposite direction to the second direction.

[0175] Here, the first direction means a direction from the ignition antenna structure (2130) to the main antenna structure (2230) among the directions parallel to the central axis of the discharge tube (2300), the direction in which the ignited plasma moves, or the direction in which the auxiliary gas is introduced. The second direction means a direction opposite to the first direction.

[0176] The magnetic field formed by the main antenna structure (2230) causes a change in the magnetic field in the area where the ignition antenna structure (2130) is located, and accordingly, an induced electromotive force is generated in the ignition antenna structure (2130).

[0177] Due to the induced electromotive force generated in the ignition antenna structure (2130), an RF current flows in the ignition antenna structure (2130), and accordingly, an electromagnetic field is formed in the first region (R1) within the discharge tube (2300), and an abnormal operation occurs in which plasma in a steady state in the second region (R2) moves to the first region (R1). In addition, as the induced electromotive force is generated in the ignition antenna structure (2130), a voltage stress may be generated in the first RF generator (1001) electrically connected to the ignition antenna structure (2130), which may cause damage to the first RF generator (1001).

[0178] Additionally, the induced electromotive force generated in the main antenna structure (2230) by the magnetic field formed by the ignition antenna structure (2130) may also cause voltage stress on the second RF generator (1002) electrically connected to the main antenna structure (2230), thereby causing damage.

[0179] The above problem is more likely to occur, especially when the ignition resonance frequency of the first load (2100) and the main resonance frequency of the second load (2200) are similar. Specifically, as described below, the frequency of the current flowing in the second load (2200) is controlled to have a value similar to the main resonance frequency of the second load (2200) by frequency tracking control, and the frequency of the induced electromotive force by the main antenna structure (2230) is similar to the frequency of the current flowing in the second load (2200), so that the frequency of the induced electromotive force generated in the first load (2100) also becomes similar to the main resonance frequency of the second load (2200). At this time, when the ignition resonance frequency and the main resonance frequency of the first load (2100) are similar to each other, the first load (2100) resonates due to the induced electromotive force, causing a larger current to flow.

[0180] Therefore, in order to solve this problem, it is necessary to set the ignition resonance frequency of the first load (2100) and the main resonance frequency of the second load (2200) differently.

[0181] However, as the resonance frequency of each load is designed higher, the electric energy supplied to the plasma can increase, which is directly related to the improvement of plasma ignition or maintenance efficiency. Therefore, designing the resonance frequency of one load lower than the resonance frequency of another load results in lowering the efficiency of either plasma ignition or maintenance, thereby lowering the efficiency of the plasma induction system (100).

[0182] Consequently, a method is required to minimize the influence of the interaction between the first load (2100) and the second load (2200) while maintaining the efficiency of the plasma induction system (100).

[0183] 2. Design of a plasma induction device

[0184] Below, with reference to Fig. 7, a plasma induction device (2000) designed to minimize the influence of inductive action between loads is described.

[0185] Fig. 7 is a diagram showing that the square wave components that each load is affected by change depending on the resonant frequency design of the loads according to one embodiment. Fig. 7 (a) is a diagram showing that the square wave includes multiple sinusoidal wave components, and Fig. 7 (b) is a diagram showing that when the loads are designed to each have a specific resonant frequency, they are affected by a specific component included in the square wave.

[0186] 2.1 Analysis of square wave components

[0187] A square wave can include multiple sine wave components. A square wave having a fundamental frequency can be understood as a composite wave of sine waves having frequencies that are (2n-1) times (n is a natural number) of the fundamental frequency through the Fourier series. For example, referring to Fig. 7 (a), in the case of an odd square wave having a fundamental frequency f0, it can be understood as a composite wave of a first sine wave (A1sin(f0*t)) having a frequency of f0, a second sine wave (A2sin(3f0*t)) having a frequency of 3f0, a third sine wave (A3sin(5f0*t)) having a frequency of 5f0, …, an nth sine wave (Ansin((2n-1)f0*t)) having a frequency of (2n-1)f0.

[0188] As described above, the load has a specific resonant frequency, and when a square wave voltage is applied to the load, a large current can flow in the load due to a sine wave having a frequency corresponding to or close to the resonant frequency of the load among the sine waves constituting the square wave.

[0189] Referring to (b) of FIG. 7, if the first voltage signal applied to the first load (2100) from the first RF generator (1001) is a square wave having a fundamental frequency f0, and the ignition resonance frequency (f1) of the first load (2100) is 3*f0, a high current can flow to the first load (2100) due to a sine wave component having a frequency of 3*f0 among the components of the first voltage signal.

[0190] Meanwhile, when the second voltage signal applied to the second load (2200) from the second RF generator (1002) is a square wave having a fundamental frequency f0, and the main resonant frequency (f2) of the second load (2200) is f0, a high current can flow in the second load (2200) due to a sine wave component having a frequency of f0 among the components of the second voltage signal.

[0191] In other words, if the resonant frequency of the load is designed to be a harmonic wave frequency of the fundamental frequency of the voltage signal provided by the RF generator (1000) or close to it, the size of the current flowing in the load may increase.

[0192] 2.2 Resonant frequency design

[0193] The ignition resonance frequency (f1) of the first load (2100) and the main resonance frequency (f2) of the second load (2200) may be designed differently. This is to minimize the interaction or the influence of induced electromotive force occurring between the first antenna structure (2130) of the first load (2100) and the second antenna structure (2230) of the second load (2200).

[0194] However, in order to allow a current having as strong an intensity as possible to flow through both the first load (2100) and the second load (2200), it is necessary to control the frequency of the first voltage signal supplied from the first RF generator (1001) and the frequency of the second voltage signal supplied from the second RF generator (1002) to the maximum, and in this case, the frequency of the first voltage signal and the frequency of the second voltage become substantially the same.

[0195] Considering these points, in order to minimize the mutual inductive coupling between the first load (2100) and the second load (2200) while passing the maximum current to the first load (2100) and the second load (2200), the following harmonic frequencies may be used.

[0196] First, the main resonant frequency (f2) of the second load (2200) can be designed.

[0197] For example, the main resonant frequency (f2) can be selected from a frequency range that the second voltage signal provided by the second RF generator (1002) can have.

[0198] As another example, when the second RF generator (1002) has a specific frequency as a driving frequency by default, the main resonant frequency (f2) can be designed to have the driving frequency or a value close to it.

[0199] As another example, if there is a driving frequency that the second voltage signal provided from the second RF generator (1002) must have depending on the process or environment in which the plasma induction system (100) is used, the main resonant frequency (f2) can be designed to have the driving frequency or a value close to it.

[0200] As another example, the main resonance frequency (f2) of the second load (2200) can be designed according to the type or environment of the process in which the plasma induction system (100) is used. Specifically, the higher the pressure inside the discharge tube (2300), the more difficult it is to induce plasma, so the intensity and amount of change of the electromagnetic field formed by the load need to be large, and for this purpose, the frequency of the voltage signal applied to the load needs to be above a certain value. In other words, the main resonance frequency (f2) of the second load (2200) can be designed based on at least one of the size of the discharge tube (2300), the pressure inside the discharge tube (2300) during the plasma process, the type of gas required for discharge, the supply flow rate of the gas, the maximum supplyable power of the RF generator (1000), the physical size (e.g., diameter) of the second load (2200), and the magnitude of the second voltage signal applied to the second load (2200).

[0201] The ignition resonance frequency (f1) of the first load (2100) can be determined in a similar manner to the method for determining the main resonance frequency (f2) of the second load (2200) described above.

[0202] For example, the ignition resonance frequency (f1) may be determined as (2n+1) times a frequency selected from the frequency range that the first voltage signal provided by the first RF generator (1001) may have.

[0203] As another example, when the first RF generator (1001) has a specific frequency as a driving frequency by default, the ignition resonance frequency (f1) can be designed to have (2n+1) times the driving frequency or a value close thereto.

[0204] As another example, if there is a driving frequency that the first voltage signal provided from the first RF generator (1001) must have depending on the process or environment in which the plasma induction system (100) is used, the ignition resonance frequency (f1) can be designed to have (2n+1) times the driving frequency or a value close thereto.

[0205] As another example, the ignition resonance frequency (f1) of the first load (2100) may be designed according to the type or environment of the process in which the plasma induction system (100) is used. Specifically, the ignition resonance frequency (f1) of the first load (2100) may be designed based on any one of the size of the discharge tube (2300), the pressure within the discharge tube (2300) during the plasma process, the physical size (e.g., diameter) of the first load (2100), and the size of the first voltage signal applied to the first load (2100).

[0206] Meanwhile, the ignition resonance frequency (f1) of the first load (2100) can be determined based on the main resonance frequency (f2) of the second load (2200). For example, the ignition resonance frequency (f1) can be determined as (2n+1) times the main resonance frequency (f2).

[0207] Conversely, the main resonant frequency (f2) of the second load (2200) may be determined based on the ignition resonant frequency (f1) of the first load (2100). For example, the main resonant frequency (f2) may be determined as the ignition resonant frequency (f1) divided by (2n+1).

[0208] As described above, when the ignition resonance frequency (f1) of the first load (2100) and the main resonance frequency (f2) of the second load (2200) are designed, the frequency range where the value of the current flowing in the first load (2100) is maximum and the frequency range where the value of the current flowing in the second load (2200) is maximum are different from each other and are far apart from each other. In this case, the influence of the interaction between the first load (2100) and the second load (2200) is reduced as follows.

[0209] First, when a first voltage signal having a driving frequency substantially the same as the ignition resonance frequency (f1) is applied to the first load (2100), a current having a frequency substantially the same as the ignition resonance frequency (f1) flows in the first load (2100). In this case, the electromotive force induced in the second load (2200) has a frequency in a band different from the main resonance frequency (f2), and as a result, the magnitude of the current flowing in the second load (2200) does not exceed a critical magnitude that causes abnormal operation of the plasma induction system (100) or damage to some components.

[0210] Similarly, when a second voltage signal having a driving frequency substantially the same as the main resonant frequency (f2) is applied to the second load (2200), a current having a frequency substantially the same as the main resonant frequency (f2) flows in the second load (2200). In this case, the electromotive force induced in the first load (2100) has a frequency in a band different from the ignition resonant frequency (f1), and as a result, the magnitude of the current flowing in the first load (2100) does not exceed a critical magnitude that causes abnormal operation of the plasma induction system (100) or damage to some components.

[0211] 3. Method for controlling a plasma induction device

[0212] Hereinafter, a method for controlling a plasma induction system (100) will be described with reference to FIGS. 8 to 12.

[0213] 3.1 Plasma induction system control method

[0214] Figure 8 is a flowchart showing a control method of a plasma induction system (100) according to one embodiment.

[0215] Referring to FIG. 8, the control method may include a step of supplying auxiliary gas into a discharge tube (2300) (S1100), a step of applying voltage to a first load (2100) (S1200), a step of determining whether plasma is ignited (S1300), a step of performing frequency tracking for the first load (2100) (S1400), a step of applying voltage to a second load (2200) (S1500), a step of determining whether plasma is transferred (S1600), a step of performing frequency tracking for the second load (2200) (S1700), a step of supplying a gas to be reformed into the discharge tube (2300) (S1800), and a step of stopping applying voltage to the first load (2100) (S1900).

[0216] Each step is described in detail below.

[0217] First, an auxiliary gas may be supplied into the discharge tube (2300) (S1100). The auxiliary gas is a gas used to ignite plasma, such as argon gas or helium gas, and may be understood as a gas for increasing the electron density within the discharge tube (2300). Referring to Fig. 5, the auxiliary gas may be introduced into the discharge tube (2300) through a swirl generator provided at the top of the discharge tube (2300).

[0218] A voltage may be applied to the first load (2100) (S1200). For example, the first RF generator (1001) may apply a first voltage signal having a first initial driving frequency to the first load (2100). At this time, the first initial driving frequency may be a value obtained by dividing the ignition resonance frequency (f1) of the first load (2100) by (2n+1) or a value similar thereto (within a certain error range, for example, within 0 to 10%).

[0219] At this time, when a voltage signal having a first initial driving frequency is applied to the first load (2100), the first initial driving frequency can be determined so that the magnitude of the current flowing in the first load (2100) does not exceed the maximum allowable current value of the first RF generator (1001).

[0220] When voltage is applied to the first load (2100), an electric field is formed in the discharge tube (2300) by the ignition antenna structure (2130), and the auxiliary gas introduced into the discharge tube (2300) is accelerated by the electric field and undergoes a phase transition into plasma. During the plasma ignition process, the plasma changes from the E-mode, where capacitive coupling is dominant, to the H-mode, where inductive coupling is dominant, as the electron density increases.

[0221] Steps S1100 and S1200 may be performed simultaneously. Alternatively, step S1200 may be performed before step S1100.

[0222] Meanwhile, a DC pulse may be applied to a DC (direct current) electrode disposed outside the discharge tube (2300) before or after step S1200 is performed. For example, as illustrated in FIG. 5, a pulse voltage may be applied to a DC electrode disposed adjacent to a first region (R1) for plasma ignition. However, the process of applying a pulse voltage to the DC electrode is not necessarily performed.

[0223] Afterwards, whether plasma ignition is possible can be determined (S1300).

[0224] Whether the plasma is ignited can be determined based on the phase difference between the voltage applied to the first load (2100) and the current flowing to the first load (2100). For example, the first control unit of the first RF generator (1001) can determine that the plasma is ignited if a first phase difference condition is satisfied in which the phase of the current flowing to the first load (2100) leads the phase of the voltage applied to the first load (2100). As another example, the first control unit of the first RF generator (1001) measures the phase difference between the phase of the current flowing to the first load (2100) and the applied voltage based on the time point at which a voltage signal is applied to the first load (2100), and if a second phase difference condition is satisfied in which the phase of the current flowing to the first load (2100) leads the phase of the voltage applied to the first load (2100), it can determine that the plasma is ignited.

[0225] Alternatively, whether the plasma is ignited may be determined based on the power consumed by the first load (2100). For example, the first control unit of the first RF generator (1001) may determine that the plasma is ignited when a first power condition in which the magnitude of the power consumed by the first load (2100) is greater than or equal to a preset first threshold power value is satisfied. In the case of the control method of the plasma induction system (100) described in the present disclosure, it may be more appropriate to use a power condition rather than a phase difference condition in determining whether the plasma is ignited. This is because the driving frequency of the voltage applied to the first load (2100) corresponds to the first resonant frequency of the first load (2100), and therefore, the phase of the current flowing in the first load (2100) and the phase of the voltage applied to the first load (2100) may change irregularly.

[0226] Alternatively, the first control unit of the first RF generator (1001) may determine that the plasma is ignited when at least one of the first phase difference condition, the second phase difference condition, and the first power condition described above is satisfied.

[0227] When the first control unit of the first RF generator (1001) determines whether plasma is ignited, the first phase sensing module and / or the first power sensing module of the first RF generator (1001) may be used.

[0228] Meanwhile, whether plasma is ignited may be determined by the system control unit. For example, the system control unit may obtain data from the first phase sensing module and / or the first power sensing module to determine whether plasma is ignited, and if it is determined that plasma is ignited, the system control unit may control the first RF generator (1001) to perform frequency tracking for the first load (2100) or control the second RF generator (1002) to apply a voltage signal to the second load (2200).

[0229] Frequency tracking can be performed on the first load (2100) (S1400). As the plasma is ignited, a load including an inductive component called plasma (hereinafter, plasma load) is added to the output terminal of the first RF generator (1001) in addition to the first load (2100). Accordingly, the first RF generator (1001) applies voltage to the first synthetic load which is a synthesis of the first load (2100) and the plasma load. Since the inductance of the plasma load is not constant but variable, the resonant frequency of the first synthetic load also becomes variable accordingly. As the resonant frequency of the first synthetic load connected to the output terminal of the first RF generator (1001) becomes variable, in order to continuously supply maximum energy to the first synthetic load or the plasma, it is necessary to change the driving frequency of the voltage signal applied to the first synthetic load from the first RF generator (1001) in real time so as to be close to the variable resonant frequency.

[0230] In other words, the first RF generator (1001) can increase or decrease the driving frequency of the voltage signal supplied to reduce the phase difference between the current flowing to the first load (2100) and the voltage applied, which is called frequency tracking. Generally, in the frequency tracking process, the driving frequency of the voltage signal applied to the first load (2100) can have a value greater than the first initial driving frequency described above. A specific method for performing frequency tracking for the first load (2100) will be described later.

[0231] Meanwhile, the resonant frequency of the first synthetic load can be obtained as the driving frequency of the voltage signal output from the first RF generator (1001) when the difference between the phase of the current flowing in the first load (2100) and the phase of the voltage applied to the first load (2100) is 0 or substantially equal to 0.

[0232] A voltage may be applied to the second load (2200) to initiate and maintain plasma (S1500). For example, the second RF generator (1002) may apply a second voltage signal having a second initial driving frequency to the second load (2200). At this time, the second initial driving frequency may be the main resonant frequency (f2) of the second load (2200) or a value similar thereto (within a certain error range, for example, 0 to 10%). In addition, the second initial driving frequency may be substantially the same as or similar to the first initial driving frequency.

[0233] Step S1500 is not necessarily performed after step S1400. For example, the second voltage signal may also be applied to the second load (2200) at the time when the first voltage signal is applied to the first load (2100). In another example, the second voltage signal may be applied to the second load (2200) before the first voltage signal is applied to the first load (2100), and the first voltage signal may not be applied to the first load (2100) depending on whether the plasma is ignited. In another example, the second voltage signal may be applied to the second load (2200) when it is determined that the plasma is ignited. In another example, the second voltage signal may be applied to the second load (2200) at the time when frequency tracking is performed for the first load (2100).

[0234] Whether plasma transfer occurs can be determined (S1600). Plasma transfer means that plasma ignited in the first region (R1) of the discharge tube (2300) by the first load (2100) moves to the second region (R2) surrounded by the second load (2200). When voltage is applied to the second load (2200), an electromagnetic field is formed in the second region (R2) by the main antenna structure (2230), and plasma particles in H mode move to the second region (R2) to maintain a plasma state.

[0235] The determination of whether plasma transfer has occurred can be made in the same way as the determination of plasma ignition.

[0236] Whether plasma transfer occurs can be determined based on the phase difference between the voltage applied to the second load (2200) and the current flowing to the second load (2200). For example, the second control unit of the second RF generator (1002) can determine that plasma transfer occurs if the third phase difference condition, in which the phase of the current flowing to the second load (2200) leads the phase of the voltage applied to the second load (2200), is satisfied. For another example, the second control unit of the second RF generator (1002) measures the phase difference between the phase of the current flowing to the second load (2200) and the applied voltage based on the time point at which the voltage signal is applied to the second load (2200), and if the fourth phase difference condition, in which the phase of the current flowing to the second load (2200) leads the phase of the voltage applied to the second load (2200), it can determine that plasma transfer occurs.

[0237] Alternatively, whether plasma has been transferred may be determined based on the power consumed by the second load (2200). For example, the second control unit of the second RF generator (1002) may determine that plasma has been transferred if a second power condition is satisfied in which the magnitude of the power consumed by the second load (2200) is greater than or equal to a preset second threshold power value. In the case of the control method of the plasma induction system (100) described in the present disclosure, it may be more appropriate to use a power condition rather than a phase difference condition in determining whether plasma has been transferred. This is because the driving frequency of the voltage applied to the second load (2200) corresponds to the main resonant frequency (f2) of the second load (2200), and therefore, the phase of the current flowing in the second load (2200) and the phase of the voltage applied to the second load (2200) may change irregularly.

[0238] Alternatively, the second control unit of the second RF generator (1002) may determine that the plasma has been transferred when at least one of the third phase difference condition, the fourth phase difference condition, and the second power condition described above is satisfied.

[0239] When the second control unit of the second RF generator (1002) determines whether plasma transition occurs, the second phase sensing module and / or the second power sensing module of the second RF generator (1002) may be used.

[0240] Meanwhile, as described below, when steps S1500 and S1700 are performed together, that is, when frequency tracking is performed on the second load (2200) before plasma transition, whether plasma transition occurs can be determined based on the degree to which the driving frequency of the voltage signal output from the second RF generator (1002) changes. For example, when the second RF generator (1002) performs frequency tracking on the second load (2200), when plasma transition occurs as described below, a phase difference occurs between the voltage and current applied to the second load (2200), and thus the driving frequency of the voltage signal output from the second RF generator (1002) changes. Therefore, when the amount of change in the driving frequency of the voltage signal output from the second RF generator (1002) is greater than or equal to a preset value, it can be determined that plasma transition occurs.

[0241] Whether plasma transition occurs can be determined by the system control unit. For example, the system control unit may obtain data from the second phase sensing module and / or the second power sensing module to determine whether plasma transition occurs, and if it is determined that plasma transition has occurred, the system control unit may control the second RF generator (1002) to perform frequency tracking for the second load (2200) or control the first RF generator (1001) to stop applying a voltage signal to the first load (2100).

[0242] Frequency tracking can be performed on the second load (2200) (S1700). As the plasma is transferred, a plasma load including an inductive component is added to the output terminal of the second RF generator (1002) in addition to the second load (2200). Accordingly, the second RF generator (1002) applies voltage to the second synthetic load which is a synthesis of the second load (2200) and the plasma load, and like the first synthetic load, the resonant frequency of the second synthetic load becomes variable. In order to continuously supply maximum energy to the second synthetic load or the plasma, it is necessary to change the driving frequency of the voltage signal applied to the second synthetic load from the second RF generator (1002) in real time so as to approach the variable resonant frequency.

[0243] In other words, the second RF generator (1002) can increase or decrease the driving frequency of the voltage signal supplied to reduce the phase difference between the current flowing to the second load (2200) and the voltage applied. Generally, the driving frequency of the voltage signal applied to the second load (2200) during the frequency tracking process can have a value greater than the second initial driving frequency described above. A specific method for performing frequency tracking for the second load (2200) will be described later.

[0244] Meanwhile, the resonant frequency of the second synthetic load can be obtained as the driving frequency of the voltage signal output from the second RF generator (1002) when the difference between the phase of the current flowing in the second load (2200) and the phase of the voltage applied to the second load (2200) is 0 or substantially equal to 0.

[0245] The plasma ignited in the first region (R1) through steps S1500 to S1700 can move to the second region (R2) and reach a steady state in which it is stably maintained.

[0246] Meanwhile, step S1700 may be performed together with step S1500. In other words, the second RF generator (1002) may perform frequency tracking for the second load (2200) while applying voltage to the second load (2200).

[0247] A gas to be reformed can be supplied into the discharge tube (2300) (S1800). Specifically, a first feed gas, a second feed gas, and water vapor can be supplied into the discharge tube (2300). These can be reformed into a synthesis gas by the plasma induced within the discharge tube (2300).

[0248] Step S1800 does not necessarily have to be performed after step S1700, and may also be performed between steps S1100 and S1700. For example, the gas to be modified may be supplied together with the auxiliary gas when it is supplied into the discharge tube (2300). For another example, the gas to be modified may be supplied into the discharge tube (2300) at a time when it is determined that the plasma has been ignited. For another example, the gas to be modified may be supplied into the discharge tube (2300) when a voltage signal is applied to the second load (2200).

[0249] The voltage signal application to the first load (2100) may be stopped (S1900). If the plasma is stably maintained in the second region (R2), there is a risk that the plasma may move to the first region (R1) when the voltage signal is applied to the first load (2100). Therefore, the voltage signal application to the first load (2100) must be stopped, and the time point may be within the period in which steps S1500 to S1800 are performed.

[0250] Below, the frequency tracking method is described with reference to FIGS. 9 to 12.

[0251] 3.2 Frequency tracking method

[0252] Fig. 9 is a flowchart illustrating a frequency tracking method (or basic frequency tracking method) for a load according to one embodiment. Referring to Fig. 9, the frequency tracking method may include a step (S2100) of obtaining a PWM (Pulse Width Modulation) signal provided by a control unit (1600), a step (S2200) of generating a reference signal using the PWM signal, a step (S2300) of obtaining a phase signal of a current flowing in a load, and a step (S2400) of increasing or decreasing a driving frequency based on a difference between the reference signal and the phase signal.

[0253] Hereinafter, each step is described in detail. In the following, for convenience of explanation, it is assumed that the frequency tracking method is performed in the control unit (1600), and a method for calculating the driving frequency after the change is described when the control unit (1600) applies a voltage signal having a driving frequency before the change to the load in a first time interval and applies a voltage signal having a driving frequency after the change to the load in a second time interval after the first time interval.

[0254] The control unit (1600) can obtain the first PWM (Pulse Width Modulation) signal output in the first time interval (S2100). Here, the first PWM signal may correspond to a switch signal provided by the control unit (1600) to one of the switches of the inverter (1300) in the first time interval. The switch signal may be, for example, a signal received by the first switch among the switches of the inverter (1300). The frequency of the switch signal is the same as the driving frequency of the voltage signal applied to the load in the first time interval.

[0255] The control unit (1600) can generate a reference signal using the first PWM signal (S2200). The first PWM signal passes through a transmission circuit such as a gate driver or a signal isolator before reaching the switch of the inverter (1300), which causes a time delay between the first PWM signal and the switch signal received by the switch. Therefore, in order to more clearly estimate the phase of the voltage applied to the load, the control unit (1600) can generate a reference signal by delaying the first PWM signal for a certain period of time. The reference signal can be understood as a signal virtually generated for calculating a phase difference, rather than a signal actually output from the control unit (1600).

[0256] The reference signal may be determined differently depending on whether the composite load of the load and the plasma load is operated in full resonance, inductively, or capacitively. For example, when the time delay between the first PWM signal and the switch signal is a fixed delay time, the reference signal may be generated by delaying the first PWM signal by the fixed delay time when operating in full resonance, the reference signal may be generated by delaying the first PWM signal by a first delay time longer than the fixed delay time when operating inductively, and the reference signal may be generated by delaying the first PWM signal by a second delay time shorter than the fixed delay time when operating capacitively.

[0257] The control unit (1600) can obtain a phase signal of the current flowing through the load (S2300). For example, the control unit (1600) can obtain a phase signal of the current flowing through the load from the phase sensing module (1400).

[0258] The control unit (1600) can increase or decrease the driving frequency based on the reference signal and the phase signal (S2400). For example, the control unit (1600) can decrease the driving frequency by a preset adjustment value when the reference signal is faster than the phase signal. In other words, the control unit (1600) can output a second PWM signal having a lower frequency than the first PWM signal in the second time interval. For another example, the control unit (1600) can increase the driving frequency by the adjustment value when the reference signal is slower than the phase signal. In other words, the control unit (1600) can output a second PWM signal having a higher frequency than the first PWM signal in the second time interval. For another example, the control unit (1600) can output a second PWM signal having the same frequency as the first PWM signal in the second time interval when the size of the delay time between the reference signal and the phase signal is less than or equal to a threshold value.

[0259] 3.3 Frequency tracking during harmonic driving

[0260] The plasma induction system (100) can perform the aforementioned frequency tracking method when inducing plasma. Specifically, the RF generator (1000) can periodically change or maintain the driving frequency through the frequency tracking method when applying a voltage having a driving frequency to the plasma induction device (2000). For example, in steps S1400 and S1700 described in FIG. 8, each of the first RF generator (1001) and the second RF generator (1002) can perform the aforementioned frequency tracking, and thus, plasma ignition and maintenance can be smoothly performed.

[0261] However, in the case of the first RF generator (1001), a problem may occur if the above-described frequency tracking method is performed as is, because the ignition resonance frequency (f1) of the first load (2100) is relatively larger than the driving frequency set in the first RF generator (1001) due to a harmonic. More specifically, the above-described frequency tracking method requires a voltage phase signal and a current phase signal. Here, since the voltage phase signal is replaced with a PWM signal of the first control unit of the first RF generator (1001), the frequency of the voltage phase signal is substantially the same as the driving frequency of the first RF generator (1001). On the other hand, since the current phase signal directly measures the current flowing in the first load (2100), the frequency of the current phase signal is a harmonic frequency, which is the resonance frequency of the first load (2100), or is close to it. In other words, the frequency levels of the voltage phase signal and the current phase signal compared by the first RF generator (1001) for frequency tracking are different, making it difficult to accurately measure the phase difference.

[0262] Hereinafter, with reference to FIGS. 10 to 12, a frequency tracking method is described in a case where a voltage signal having an initial driving frequency (or fundamental driving frequency) is output from an RF generator (1000) and the resonant frequency of the load is designed as a harmonic of the initial driving frequency.

[0263] Fig. 10 is a flowchart illustrating a harmonic frequency tracking method for a load having a harmonic frequency as a resonant frequency according to one embodiment. Referring to Fig. 10, the harmonic frequency tracking method may include a step (S3100) of obtaining a PWM signal generated by a control unit (1600), a step (S3200) of generating a harmonic reference signal using the PWM signal, a step (S3300) of obtaining a phase signal of a current flowing in a load, and a step (S3400) of increasing or decreasing a driving frequency based on a difference between the harmonic reference signal and the phase signal.

[0264] Each step is described in detail below. As with the previously described frequency tracking method, it is assumed that the control unit (1600) determines the driving frequency in the second time interval based on information in the first time interval.

[0265] First, step S3100 is identical to step S2100, so any overlapping content is omitted. In step S3100, the control unit (1600) can obtain the first PWM signal output in the first time interval.

[0266] The control unit (1600) can generate a harmonic reference signal using the first PWM signal (S3200). For example, the harmonic reference signal can be generated by delaying a signal having a harmonic frequency of the frequency of the first PWM signal by a fixed delay time. As another example, the harmonic reference signal can be generated by delaying the first PWM signal by a fixed delay time and changing the frequency to a harmonic frequency.

[0267] Here, the harmonic order to be changed can be determined based on at least one of the initial driving frequency set in the RF generator (1000) and the resonant frequency of the load. For example, when the driving frequency of the voltage initially output for plasma induction from the first RF generator (1001) is the first initial driving frequency and the ignition resonant frequency (f1) of the first load (2100) is (2n+1) times the first initial driving frequency, the harmonic order becomes (2n+1) when generating the harmonic reference signal.

[0268] As with the frequency tracking method described above, the harmonic reference signal can be generated with varying degrees of delay depending on how the load is driven.

[0269] The control unit (1600) can obtain a phase signal of the current flowing through the load (S3300). For example, the control unit (1600) can obtain a phase signal of the current flowing through the load from the phase sensing module (1400).

[0270] The control unit (1600) can increase or decrease the driving frequency based on the harmonic reference signal and the phase signal (S3400). For example, the control unit (1600) can decrease the driving frequency when the harmonic reference signal is faster than the phase signal. In other words, the control unit (1600) can output a second PWM signal having a lower frequency than the first PWM signal in the second time interval. For another example, the control unit (1600) can increase the driving frequency when the harmonic reference signal is slower than the phase signal. In other words, the control unit (1600) can output a second PWM signal having a higher frequency than the first PWM signal in the second time interval. For another example, the control unit (1600) can output a second PWM signal having the same frequency as the first PWM signal in the second time interval when the size of the delay time between the harmonic reference signal and the phase signal is less than or equal to a threshold value.

[0271] Meanwhile, the degree of increasing or decreasing the driving frequency in the harmonic frequency tracking method may be different from the degree of increasing or decreasing the driving frequency in the frequency tracking method. For example, the first RF generator (1001) may output a voltage signal having a first driving frequency in a first time interval, and perform a harmonic frequency tracking method to output a voltage signal having a second driving frequency in a second time interval. In addition, the second RF generator (1002) may output a voltage signal having a third driving frequency in a third time interval, and perform a frequency tracking method to output a voltage signal having a fourth driving frequency in a fourth time interval. In this case, the difference between the first driving frequency and the second driving frequency (e.g., the first adjustment value) may be smaller than the difference between the third driving frequency and the fourth driving frequency (e.g., the second adjustment value). This is because the first load (2100) to which the first RF generator (1001) provides a voltage signal is affected by harmonic components and is more affected by the difference in driving frequency than the second load (2200).

[0272] Below, a power consumption-based frequency tracking method is described with reference to FIG. 11.

[0273] FIG. 11 is a flowchart illustrating a power consumption-based frequency tracking method for a load having a harmonic frequency as a resonant frequency according to one embodiment.

[0274] FIG. 12 is a diagram for explaining a power consumption-based frequency tracking method according to one embodiment.

[0275] The closer the driving frequency of the voltage signal applied to the load is to the load's resonant frequency, the greater the power consumed by the load. Conversely, the further the driving frequency of the voltage signal applied to the load is from the load's resonant frequency, the less power consumed by the load. Considering this, the power consumed by the load can be measured while varying the driving frequency of the voltage signal applied to the load, and the driving frequency can be adjusted to approximate the load's resonant frequency based on the change in power.

[0276] Referring to FIG. 11, the power consumption-based frequency tracking method may include a step of measuring a first power consumption consumed by an RF generator (1000) (S4100), a step of increasing or decreasing a driving frequency (S4200), a step of measuring a second power consumption consumed by the RF generator (1000) (S4300), a step of increasing or decreasing a driving frequency based on a driving frequency change direction, the first power consumption, and the second power consumption (S4400), a step of measuring a third power consumption consumed by the RF generator (1000) (S4500), and a step of increasing, decreasing, or maintaining a driving frequency based on the second power consumption and the third power consumption (S4600).

[0277] Hereinafter, for convenience of explanation, it is assumed that the RF generator (1000) outputs a first voltage signal having a first driving frequency in a first time interval, a second voltage signal having a second driving frequency in a second time interval, a third voltage signal having a third driving frequency in a third time interval, and a fourth voltage signal having a fourth driving frequency in a fourth time interval. At this time, steps S4100 to S4600 are performed in time series, step S4100 is performed in the first time interval, and the first time interval and the second time interval are distinguished based on step S4200, step S4300 is performed in the second time interval, and the second time interval and the third time interval are distinguished based on step S4400, and step S4500 is performed in the third time interval, and the third time interval and the fourth time interval are distinguished based on step S4600.

[0278] Each step is described in detail below.

[0279] First, the first power consumption consumed by the RF generator (1000) can be measured (S4100).

[0280] For example, the RF generator (1000) can obtain the first power consumption by measuring the power consumption based on the input terminal of the inverter (1300). Specifically, the control unit (1600) can measure the power consumed by the inverter (1300) and the load using the power sensing module (1500). The first power consumption can be a power value measured at a point in time or a value obtained by measuring over a certain period of time and calculating an average. For example, the control unit (1600) can obtain the first power consumption by measuring the power consumption over a time period of a preset length and calculating an average.

[0281] As another example, the RF generator (1000) can obtain the first power consumption by measuring the power consumption based on the output terminal of the inverter (1300). Specifically, the control unit (1600) can obtain the first power consumption by measuring the voltage and current applied to the output terminal of the inverter (1300), i.e., the load. Similarly, the first power consumption can be a value measured at a point in time or a value obtained by calculating an average by measuring over a certain period of time.

[0282] Thereafter, the RF generator (1000) can increase or decrease the driving frequency of the voltage signal to be output (S4200). For example, the RF generator (1000) can output a voltage signal having a first driving frequency in a first time interval and output a voltage signal having a second driving frequency different from the first driving frequency in a second time interval. At this time, the second driving frequency can be smaller or larger than the first driving frequency. For example, the second driving frequency has a value increased or decreased by a preset increase or decrease ratio based on the first driving frequency, and the increase or decrease ratio can be determined between about 1% and about 10%.

[0283] Step S4200 can be understood as a process of arbitrarily changing the driving frequency to determine the relationship between the current driving frequency and the resonant frequency of the synthesized load, as described below.

[0284] The second power consumption consumed by the RF generator (1000) can be measured (S4300). For example, the RF generator (1000) can measure the second power consumption during a second time interval during which it outputs a voltage signal having a changed second driving frequency. The method for measuring the second power consumption is the same as the method for measuring the first power consumption in step S4100, and thus, a description thereof will be omitted.

[0285] The RF generator (1000) can increase or decrease the driving frequency based on the amount of change in the driving frequency, the first power consumption, and the second power consumption (S4400). For example, the RF generator (1000) can increase or decrease the driving frequency according to a driving frequency increase or decrease rule. The driving frequency increase or decrease rule is described in detail with reference to FIG. 12.

[0286] First, referring to Fig. 12, the relationship between the driving frequency and the power can be represented as a graph with an upward convex shape, and the power consumption is maximum when the driving frequency becomes the resonant frequency of the synthetic load.

[0287] In other words, if the current position is identified on the relationship graph between the driving frequency and the power consumption, the driving frequency can be increased or decreased based on this. For example, if it is determined that the position of the driving frequency based on the resonant frequency of the synthetic load (hereinafter referred to as the "driving frequency position") in the graph illustrated in FIG. 12 corresponds to point A, the RF generator (1000) can increase the driving frequency. For another example, if it is determined that the driving frequency position corresponds to point B in the graph illustrated in FIG. 12, the RF generator (1000) can decrease the driving frequency. For convenience of explanation, the state in which the driving frequency is lower than the resonant frequency of the synthetic load is referred to as the first state, and the state in which the driving frequency is higher than the resonant frequency of the synthetic load is referred to as the second state.

[0288] The increase or decrease in power consumption due to an increase or decrease in driving frequency can be divided into four cases as follows.

[0289] 1) In case of increase in power consumption when driving frequency increases

[0290] When the second driving frequency of the second time interval is greater than the first driving frequency of the first time interval, and the second power consumption measured in the second time interval has a larger value than the first power consumption measured in the first time interval, the state of the RF generator (1000) is a first state in which the driving frequency is less than the resonant frequency of the synthesized load.

[0291] Accordingly, in step S4400, the RF generator (1000) can increase the driving frequency of the voltage signal applied to the load. In other words, the third driving frequency of the third time interval can be increased by a preset third adjustment value compared to the second driving frequency of the second time interval.

[0292] 2) In case of power consumption reduction when driving frequency is reduced

[0293] When the second driving frequency of the second time interval is lower than the first driving frequency of the first time interval, and the second power consumption measured in the second time interval has a smaller value than the first power consumption measured in the first time interval, the state of the RF generator (1000) is a first state in which the driving frequency is lower than the resonant frequency of the synthesized load.

[0294] Accordingly, in step S4400, the RF generator (1000) can increase the driving frequency of the voltage signal applied to the load. In other words, the third driving frequency of the third time interval can be increased by a preset third adjustment value compared to the second driving frequency of the second time interval.

[0295] 3) In case of power consumption reduction when driving frequency increases

[0296] When the second driving frequency of the second time interval is greater than the first driving frequency of the first time interval, and the second power consumption measured in the second time interval has a smaller value than the first power consumption measured in the first time interval, the state of the RF generator (1000) is a second state in which the driving frequency is greater than the resonant frequency of the synthesized load.

[0297] Accordingly, in step S4400, the RF generator (1000) can reduce the driving frequency of the voltage signal applied to the load. In other words, the third driving frequency of the third time interval can be made smaller than the second driving frequency of the second time interval by a preset third adjustment value.

[0298] 4) In case of increased power consumption when driving frequency decreases

[0299] When the second driving frequency of the second time interval is lower than the first driving frequency of the first time interval, and the second power consumption measured in the second time interval has a larger value than the first power consumption measured in the first time interval, the state of the RF generator (1000) is a second state in which the driving frequency is higher than the resonant frequency of the synthesized load.

[0300] Accordingly, in step S4400, the RF generator (1000) can reduce the driving frequency of the voltage signal applied to the load. In other words, the third driving frequency of the third time interval can be made smaller than the second driving frequency of the second time interval by a preset third adjustment value.

[0301] After the driving frequency is increased or decreased, the third power consumption consumed by the RF generator (1000) can be measured (S4500). For example, when the RF generator (1000) outputs a third voltage signal having a third driving frequency increased or decreased based on the second driving frequency in a third time interval, the third power consumption can be measured in the third time interval. The method for measuring the third power consumption is the same as the method for measuring the first power consumption in step S4100, and therefore, a description thereof will be omitted.

[0302] The RF generator (1000) can increase, decrease, or maintain the driving frequency based on the second power consumption and the third power consumption (S4600). In step S4600, the RF generator (1000) can increase or decrease the driving frequency, but can also maintain the driving frequency if a specific condition is satisfied. Specifically, the RF generator (1000) can determine the fourth driving frequency in the fourth time interval based on the state of the RF generator (1000) confirmed in step S4400 (the relationship between the driving frequency and the resonant frequency of the synthesized load) and whether the third power consumption increases or decreases compared to the second power consumption. The method by which the fourth driving frequency is determined can be divided into several cases as described below.

[0303] 1) When the driving frequency is lower than the resonant frequency of the synthetic load, the power consumption increases as the driving frequency increases.

[0304] When the RF generator (1000) determines that the state of the RF generator (1000) is the first state while performing step S4400, and outputs a third voltage signal having a third driving frequency greater than the second driving frequency in the third time interval, the third power consumption may increase. In this case, this means that the third driving frequency is still below the resonant frequency of the synthesized load. In other words, the state of the RF generator (1000) in the third time interval is the first state.

[0305] Accordingly, the RF generator (1000) can set the fourth driving frequency of the fourth voltage signal output in the fourth time interval to be greater than the third driving frequency by a preset fourth adjustment value.

[0306] 2) When the driving frequency is lower than the resonant frequency of the synthetic load, the power consumption decreases as the driving frequency increases.

[0307] When the RF generator (1000) determines that the state of the RF generator (1000) is the first state while performing step S4400, and outputs a third voltage signal having a third driving frequency greater than the second driving frequency in the third time interval, the third power consumption may be reduced. In this case, this means that the third driving frequency has become greater than the resonant frequency of the synthesized load. In other words, it can be understood that the state of the RF generator (1000) has changed from the first state to the second state in the third time interval.

[0308] Accordingly, the RF generator (1000) can set the fourth driving frequency of the fourth voltage signal output in the fourth time interval to the same value as the third driving frequency. Alternatively, the RF generator (1000) can set the fourth driving frequency to the same value as the second driving frequency. Alternatively, the RF generator (1000) can set the fourth driving frequency to a value determined between the second driving frequency and the third driving frequency.

[0309] 3) When the driving frequency is higher than the resonant frequency of the synthetic load, the power consumption increases when the driving frequency decreases.

[0310] When the RF generator (1000) determines that the state of the RF generator (1000) is the second state while performing step S4400, and outputs a third voltage signal having a third driving frequency lower than the second driving frequency in the third time interval, the third power consumption may increase. In this case, this means that the third driving frequency is still higher than the resonant frequency of the synthesized load. In other words, the state of the RF generator (1000) in the third time interval is the second state.

[0311] Accordingly, the RF generator (1000) can set the fourth driving frequency of the fourth voltage signal output in the fourth time interval to be smaller than the third driving frequency by a preset fourth adjustment value.

[0312] 4) When the driving frequency is higher than the resonant frequency of the synthetic load, the power consumption decreases when the driving frequency decreases.

[0313] When the RF generator (1000) determines that the state of the RF generator (1000) is the second state while performing step S4400, and outputs a third voltage signal having a third driving frequency lower than the second driving frequency in the third time interval, the third power consumption may be reduced. In this case, this means that the third driving frequency is lower than the resonant frequency of the synthesized load. In other words, it can be understood that the state of the RF generator (1000) has changed from the second state to the first state in the third time interval.

[0314] Accordingly, the RF generator (1000) can set the fourth driving frequency of the fourth voltage signal output in the fourth time interval to the same value as the third driving frequency. Alternatively, the RF generator (1000) can set the fourth driving frequency to the same value as the second driving frequency. Alternatively, the RF generator (1000) can set the fourth driving frequency to a value determined between the second driving frequency and the third driving frequency.

[0315] In the power consumption-based frequency tracking method, the degree of change in the driving frequency may be closer to the degree of increase or decrease in the driving frequency in the harmonic frequency tracking method than to the degree of increase or decrease in the driving frequency in the frequency tracking method. For example, the third adjustment value and the fourth adjustment value may be closer to the second adjustment value than to the first adjustment value. In another example, the third adjustment value may be the same as the second adjustment value.

[0316] Meanwhile, the third and fourth adjustment values ​​may be different from each other, and the fourth adjustment value may be smaller than the third adjustment value. This is to gradually reduce the amount of change in driving frequency to precisely control the frequency.

[0317] The RF generator (1000) can continuously repeat the aforementioned power consumption-based frequency tracking method to maintain a state in which the driving frequency is close to the resonant frequency of the synthesized load. For example, after performing step S4600, the RF generator (1000) measures the power consumption again to check the direction of change in the power consumption, and can increase, decrease, or maintain the driving frequency based on the state of the RF generator (1000) before performing step S4600 and the direction of change in the driving frequency and the direction of change in the power consumption in step S4600.

[0318] 3.4 ICM Control

[0319] In the plasma induction system (100), the power consumed in the plasma induction device (2000) can be controlled.

[0320] The RF generator (1000) can operate in a powering mode and a freewheeling mode. In the powering mode, the RF generator (1000) can continuously apply voltage to the plasma induction device (2000). In the freewheeling mode, the RF generator (1000) can alternately perform an operation of applying voltage and an operation of not applying voltage. Furthermore, in the freewheeling mode, the RF generator (1000) can control the amount of power consumed in the plasma induction device (2000) by controlling the ratio of the operation of applying voltage and the operation of not applying voltage per unit time.

[0321] 4. Using one RF generator

[0322] In the above, the case of using multiple RF generators (1000) in a plasma induction system (100) has been mainly described. That is, a first RF generator (1001) is connected to a first load (2100), and a second RF generator (1002) is connected to a second load (2200), and RF voltages are supplied to each.

[0323] Meanwhile, instead of a case where an RF generator (1000) is connected to each of the multiple loads, a case where multiple loads are connected to a single RF generator (1000) and receive RF voltage can also be considered. When supplying RF voltage to multiple loads with a single RF generator (1000), there are disadvantages such as a somewhat complicated control method and a weakened plasma induction performance, but considering the price and volume of the RF generator (1000), it has a strong advantage in commercialization.

[0324] Accordingly, the applicant additionally developed a system structure and control algorithm for applying voltage to multiple loads using one RF generator (1000).

[0325] Hereinafter, a plasma induction system (100) using multiple loads and one RF generator (1000) is described with reference to FIGS. 13 to 16.

[0326] 4.1 Circuit Structure

[0327] First, the structure of the plasma induction system (100) is described with reference to FIG. 13.

[0328] FIG. 13 is a drawing for explaining a plasma induction system (100) using multiple loads and one RF generator (1000) according to one embodiment.

[0329] Referring to FIG. 13, the first load (2100) and the second load (2200) can be connected in parallel to the output terminal of the inverter (1300) of the RF generator (1000).

[0330] Additionally, the RF generator (1000) may include one inverter (1300), but may also include a first phase sensing module (1401) for detecting the current phase of a first load (2100) and a second phase sensing module (1402) for detecting the current phase of a second load (2200).

[0331] The first phase sensing module (1401) may be placed on a circuit that electrically connects the output terminal of the inverter (1300) and the first load (2100). The second phase sensing module (1402) may be placed on a circuit that electrically connects the output terminal of the inverter (1300) and the second load (2200).

[0332] The first phase sensing module (1401) can obtain a phase signal of the current flowing in the first load (2100) and provide it to the control unit (1600). The second phase sensing module (1402) can obtain a phase signal of the current flowing in the second load (2200) and provide it to the control unit (1600).

[0333] Although FIG. 13 illustrates that there is one power sensing module (1500), the RF generator (1000) may include a first power sensing module corresponding to a first load (2100) and a second power sensing module corresponding to a second load (2200) as needed.

[0334] At this time, the first power sensing module may be placed on a circuit that electrically connects the output terminal of the inverter (1300) and the first load (2100), and the second power sensing module may be placed on a circuit that electrically connects the output terminal of the inverter (1300) and the second load (2200).

[0335] Additionally, the first power sensing module can measure the current and / or voltage applied to the first load (2100) and provide data thereon to the control unit (1600). The second power sensing module can measure the current and / or voltage applied to the second load (2200) and provide data thereon to the control unit (1600).

[0336] The ignition resonance frequency (f1) of the first load (2100) and the main resonance frequency (f2) of the second load (2200) can be designed differently. This is to minimize the influence of interaction between the loads, as described above.

[0337] However, when designing the ignition resonance frequency (f1) of the first load (2100) and the main resonance frequency (f2) of the second load (2200), it is necessary to further consider the use of one RF generator (1000). This will be described in detail below.

[0338] 4.2 Challenges to be addressed

[0339] When using one RF generator (1000), voltage signals having the same driving frequency are simultaneously applied to the first load (2100) and the second load (2200).

[0340] As described above, the first load (2100) is mainly used for plasma ignition, and the second load (2200) is mainly used for plasma maintenance. At this time, in order to ignite the plasma, the electric energy (e.g., energy by an electric field) transferred to the plasma by the first load (2100) must be large, and in order to maintain the plasma, the electric energy transferred to the plasma by the second load (2200) must be large. Furthermore, in the plasma transfer process, the electric energy supplied to the plasma by the first load (2100) or the electric energy supplied to the plasma by the second load (2200) must be sufficient, otherwise problems such as the plasma not being transferred or being extinguished may occur.

[0341] Therefore, in order to smoothly induce plasma while excluding mutual interference between the loads described in FIGS. 6 and 7, the ignition resonance frequency (f1) of the first load (2100) and the main resonance frequency (f2) of the second load (2200) need to be designed more precisely, and the driving frequency change protocol of the RF generator (1000) also needs to be designed accordingly.

[0342] 4.3 Design of resonant frequency of load

[0343] Prior to designing the ignition resonance frequency (2100) of the first load (2100), the design criteria for the main resonance frequency (f2) of the second load (2200) are described.

[0344] The main resonant frequency (f2) may be designed as a value obtained by adding a first value to the initial driving frequency of the RF generator (1000). Alternatively, the main resonant frequency (f2) may be designed as a value obtained by adding a first value to a value obtained by dividing the ignition resonant frequency (f1) of the first load (2100) by (2n+1).

[0345] Here, the initial driving frequency may refer to the driving frequency of the voltage signal initially applied to the load for plasma induction in the RF generator (1000) as described above. More specifically, the initial driving frequency may refer to the driving frequency of the voltage signal applied to the load by the RF generator (1000) when the plasma induction system (100) is driven. Meanwhile, the initial driving frequency may refer to a frequency set as a default in the RF generator (1000). The initial driving frequency may be determined according to the performance of the RF generator (1000).

[0346] Here, the first value can be determined arbitrarily. For example, the first value can be determined within a range of differences that can exist between the driving frequency determined in the process of tracking the frequency for the first load (2100) and the initial driving frequency.

[0347] The first value varies depending on the extent to which the first synthetic resonance frequency of the first synthetic load including the plasma and the first load (2100) differs from the ignition resonance frequency of the first load (2100) as the plasma is induced. Since the properties of the induced plasma differ depending on the plasma process or the design conditions of the plasma induction system (100) (e.g., the size of the discharge tube, the gas to be modified, the size and fundamental driving frequency of the voltage signal applied from the RF generator (1000), or the required plasma temperature, etc.), the first value may also vary depending on the plasma process or the design conditions of the plasma induction system (100).

[0348] The first value can be determined experimentally. The method for designing the first value is described in more detail below.

[0349] For example, the first value can be determined within a range in which the first condition is satisfied. The first condition is a condition in which, when a voltage signal having an initial driving frequency is applied to the first load (2100) and the second load (2200) to ignite plasma in the RF generator (1000), the sum of the first current value of the current flowing in the first load (2100) and the second current value of the current flowing in the second load (2200) must not exceed the third current value of the allowable current of the RF generator (1000).

[0350] More specifically, as described below, before the plasma is ignited, the RF generator (1000) applies a voltage signal having an initial driving frequency to the first load (2100) and the second load (2200). At this time, if the first value is too small, the main resonant frequency (f2) of the second load (2200) has a value close to the initial driving frequency, so that an excessively large current may flow to the second load (2200) before the plasma is ignited, and as a result, a problem may occur in which the sum of the magnitudes of the current flowing to the first load (2100) and the magnitudes of the current flowing to the second load (2200) exceeds the magnitude of the maximum allowable current of the RF generator (1000).

[0351] Accordingly, the following formula must be satisfied when determining the first value.

[0352]

[0353] I_ig is the current flowing in the first load (2100),

[0354]

[0355] , and R_ig, L_ig, and C_ig represent the equivalent series resistance, inductance, and capacitance of the first load (2100), respectively.

[0356] Also, since it is before the plasma is ignited, ω_RF in the above equation has a value corresponding to the initial driving frequency, and satisfies the equation below. In the equation below, f_SW means the initial driving frequency.

[0357]

[0358] Additionally, the equivalent inductance and equivalent capacitance in the above equation satisfy the equations below.

[0359]

[0360] I_main is the current flowing to the second load (2200).

[0361]

[0362] , and R_main, L_main, and C_main represent the equivalent series resistance, inductance, and capacitance of the second load (2200), respectively.

[0363] Additionally, the equivalent inductance and equivalent capacitance in the above equation satisfy the equations below.

[0364]

[0365] I_limit refers to the maximum allowable current of the RF generator (1000).

[0366] Meanwhile, the first condition can be used as a criterion for determining the lower limit of the first value.

[0367] As another example, the first value can be determined within a range in which the second condition is satisfied. The second condition is a condition in which, when a voltage signal having a first driving frequency is applied from the RF generator (1000) to the first load (2100) and the second load (2200) after the plasma is ignited and before the plasma is transferred to the second load (2200), the sum of the fourth current value of the current flowing to the first load (2100) and the fifth current value of the current flowing to the second load (2200) must not exceed the third current value of the allowable current of the RF generator (1000).

[0368] More specifically, as described below, after the plasma is ignited, the RF generator (1000) applies a voltage signal having a first driving frequency to the first load (2100) and the second load (2200) for plasma transfer. Here, the first driving frequency refers to a driving frequency adjusted as the RF generator (1000) performs frequency tracking for the first load (2100) after the plasma is ignited. At this time, if the main resonant frequency (f2) of the second load (2200) is designed to be excessively close to the first driving frequency, the magnitude of the current flowing to the second load (2200) may become excessively large, which may damage the RF generator (1000). Meanwhile, as the main resonant frequency (f2) of the second load (2200) differs from the first driving frequency, the magnitude of the current flowing to the second load (2200) may decrease, which may prevent the plasma from being transferred.

[0369] Accordingly, the following formulas must be satisfied when determining the first value.

[0370]

[0371] I_ig is the current flowing in the first load (2100),

[0372]

[0373] , and R_ig, L_ig, and C_ig represent the equivalent series resistance, inductance, and capacitance of the first load (2100), respectively.

[0374] In addition, since the plasma has been ignited, ω_RF in the above equation has a value corresponding to the first driving frequency, and satisfies the equation below. In the equation below, f_SW represents the initial driving frequency, and β / 3 represents the degree to which the driving frequency changes as frequency tracking is performed.

[0375]

[0376] In addition, the equivalent inductance and equivalent capacitance of the first load (2100) in the above equation satisfy the equation below.

[0377]

[0378] I_main is the current flowing to the second load (2200).

[0379]

[0380] , and R_main, L_main, and C_main represent the equivalent series resistance, inductance, and capacitance of the second load (2200), respectively.

[0381] In addition, the equivalent inductance and equivalent capacitance of the second load (2200) in the above equation satisfy the equation below.

[0382]

[0383] I_transition is the minimum current for plasma to be transitioned, and can be determined based on the distance between the first load (2100) and the second load (2200), the pressure inside the discharge tube (3000), the flow rate of gas supplied into the discharge tube (3000), the type of supplied gas, etc.

[0384] I_limit refers to the maximum allowable current of the RF generator (1000).

[0385] The second condition can be understood as a criterion for determining the upper and lower limits of the first value.

[0386] As described above, in determining the first value, at least one of the first and second conditions must be satisfied. To verify whether the first and second conditions are satisfied, a simulation using a program or an actual experiment can be conducted.

[0387] Meanwhile, the first value can have a value within a specific range based on the initial driving frequency, the ignition resonance frequency (f1), or the main resonance frequency (f2). For example, the first value is a value within 0.01% to 30% of the main resonant frequency (f2), a value within 0.01% to 25%, a value within 0.01% to 20%, a value within 0.01% to 15%, a value within 0.01% to 10%, a value within 0.01% to 9%, a value within 0.01% to 8%, a value within 0.01% to 7%, a value within 0.01% to 6%, a value within 0.01% to 5%, a value within 0.01% to 4%, a value within 0.01% to 3%, a value within 0.01% to 2%, a value within 0.01% to 1%, a value within 0.01% to 0.9%, a value within 0.01% to 0.8%, a value within 0.01% to A value within 0.7%, a value within 0.01% to 0.6%, a value within 0.01% to 0.5%, a value within 0.01% to 0.4%, a value within 0.01% to 0.3%, a value within 0.01% to 0.2%, a value within 0.01% to 0.1%, a value within 0.05% to 10%, a value within 0.1% to 10%, a value within 0.2% to 10%, a value within 0.3% to 10%, a value within 0.4% to 10%, a value within 0.5% to 10%, a value within 0.6% to 10%, a value within 0.7% to 10%, a value within 0.8% to 10%, a value within 0.9% to 10%, a value within 1% to 10%, a value within 2% to The first value can be determined from a value within 10%, a value within 3% to 10%, a value within 4% to 10%, a value within 5% to 10%. For another example, the first value can be determined from a value within 0.01% to 30%, a value within 0.01% to 25%, a value within 0.01% to 20%, a value within 0.01% to 15%, a value within 0.01% to 10%, 0.A value within 0.01% to 9%, a value within 0.01% to 8%, a value within 0.01% to 7%, a value within 0.01% to 6%, a value within 0.01% to 5%, a value within 0.01% to 4%, a value within 0.01% to 3%, a value within 0.01% to 2%, a value within 0.01% to 1%, a value within 0.01% to 0.9%, a value within 0.01% to 0.8%, a value within 0.01% to 0.7%, a value within 0.01% to 0.6%, a value within 0.01% to 0.5%, a value within 0.01% to 0.4%, a value within 0.01% to 0.3%, a value within 0.01% to 0.2%, a value within 0.01% to It can be determined from a value within 0.1%, a value within 0.05% to 10%, a value within 0.1% to 10%, a value within 0.2% to 10%, a value within 0.3% to 10%, a value within 0.4% to 10%, a value within 0.5% to 10%, a value within 0.6% to 10%, a value within 0.7% to 10%, a value within 0.8% to 10%, a value within 0.9% to 10%, a value within 1% to 10%, a value within 2% to 10%, a value within 3% to 10%, a value within 4% to 10%, and a value within 5% to 10%. For another example, the first value is within 0.01% to 30% of the ignition resonance frequency (f1), within 0.01% to 25%, within 0.01% to 20%, within 0.01% to 15%, within 0.01% to 10%, within 0.01% to 9%, within 0.01% to 8%, within 0.01% to 7%, within 0.01% to 6%, within 0.01% to 5%, within 0.01% to 4%, within 0.01% to 3%, within 0.01% to 2%, within 0.01% to 1%, within 0.01% to 0.9%, within 0.01% to 0.8%, 0.A value within 0.1% to 0.7%, a value within 0.01% to 0.6%, a value within 0.01% to 0.5%, a value within 0.01% to 0.4%, a value within 0.01% to 0.3%, a value within 0.01% to 0.2%, a value within 0.01% to 0.1%, a value within 0.05% to 10%, a value within 0.1% to 10%, a value within 0.2% to 10%, a value within 0.3% to 10%, a value within 0.4% to 10%, a value within 0.5% to 10%, a value within 0.6% to 10%, a value within 0.7% to 10%, a value within 0.8% to 10%, a value within 0.9% to 10%, a value within 1% to 10% The value can be determined from a value within 2% to 10%, a value within 3% to 10%, a value within 4% to 10%, or a value within 5% to 10%.

[0388] In the above, it has been described that the main resonant frequency (f2) is fixed according to the design of the second load (2200), but the technical idea of ​​the present disclosure is not limited thereto, and the main resonant frequency (f2) may be designed to have a variable value during the plasma induction process. For example, the second load (2200) includes a variable capacitor, and the main resonant frequency (f2) of the second load (2200) may be variable as the capacitance of the variable capacitor is adjusted. At this time, in the frequency tracking step (S5300) for the first load (2100) described later, the capacitance of the variable capacitor is adjusted based on the electrical characteristics (e.g., voltage / current phase difference, equivalent series resistance value) of the second load (2200), and accordingly, the main resonant frequency (f2) of the second load (2200) may be changed.

[0389] The ignition resonance frequency (f1) of the first load (2100) may be designed to be (2n+1) times the initial driving frequency of the RF generator (1000). Alternatively, the ignition resonance frequency (f1) may be designed to be (2n+1) times a value that is smaller by a first value than the main resonance frequency (f2).

[0390] The ignition resonance frequency (f1) can be determined between (2n) times the main resonance frequency (f2) and (2n+2) times the main resonance frequency. Furthermore, the ignition resonance frequency (f1) can be designed to have a value closer to (2n+1) times the main resonance frequency than (2n) times the main resonance frequency (f2) or (2n+2) times the main resonance frequency.

[0391] Meanwhile, when designing the ignition resonance frequency (f1), when applying a voltage signal having an initial driving frequency to the first load (2100) and the second load (2200) from the RF generator (1000), a condition in which the sum of the magnitudes of the current flowing in the first load (2100) and the magnitudes of the current flowing in the second load (2200) is smaller than the maximum allowable current value of the RF generator (1000) may be further considered.

[0392] 4.4 Control Method

[0393] Below, with reference to FIG. 14, a process of controlling a plasma induction system (100) using multiple loads and one RF generator (1000) is described.

[0394] Figure 14 is a flowchart showing the process of operating a plasma induction system (100) according to one embodiment.

[0395] Referring to FIG. 14, the plasma induction system (100) may include a step (S5100) of applying an RF voltage having an initial driving frequency to a first load (2100) and a second load (2200), a step (S5200) of determining whether plasma is ignited, a step (S5300) of performing frequency tracking for the first load (2100), a step (S5400) of determining whether plasma is transferred, and a step (S5500) of performing frequency tracking for the second load.

[0396] Each step is described in detail below.

[0397] The RF generator (1000) can apply a voltage signal having an initial driving frequency to the first load (2100) and the second load (2200) (S5100). For example, the RF generator (1000) can set the initial driving frequency to a value obtained by dividing the ignition resonance frequency (f1) of the first load (2100) by (2n+1), and output a voltage signal having the initial driving frequency.

[0398] The RF generator (1000) can determine whether plasma is ignited (S5200). Step S5200 is the same as the previously described step S1300, so any overlapping content will be omitted. In determining whether plasma is ignited, a switch signal generated by the control unit (1600) may be acquired as voltage phase information, and current phase information may be acquired from the first phase sensing module (1401). Alternatively, information acquired from the power sensing module (1500) or information acquired from the first power sensing module may be used to determine whether plasma is ignited.

[0399] If it is determined that the plasma is ignited, frequency tracking for the first load (2100) may be performed (S5300). For example, the RF generator (1000) may change its driving frequency to approach the first synthetic resonant frequency of the first synthetic load including the first load (2100) and the plasma. The frequency tracking method for the first load (2100) may utilize the harmonic frequency tracking method and / or the power consumption-based frequency tracking method described above.

[0400] The first synthetic resonance frequency may be greater than the ignition resonance frequency (f1). In this case, the difference between the first synthetic resonance frequency divided by (2n+1) and the initial driving frequency may correspond to the first value.

[0401] Meanwhile, the first synthetic resonance frequency can be obtained as the driving frequency of the voltage signal output from the RF generator (1000) when the difference between the phase of the current flowing in the first load (2100) and the phase of the voltage applied to the first load (2100) is 0 or substantially equal to 0.

[0402] Next, whether plasma transition occurs can be determined (S5400). Step S5400 is identical to step S1600 described above, so any overlapping details will be omitted. In determining whether plasma transition occurs, a switch signal generated by the control unit (1600) may be acquired as voltage phase information, and current phase information may be acquired from the second phase sensing module (1402). Alternatively, information acquired from the power sensing module (1500) or information acquired from the second power sensing module may be used to determine whether plasma transition occurs.

[0403] If it is determined that the plasma has been transferred, frequency tracking for the second load (2200) may be performed (S5500). For example, the RF generator (1000) may change its driving frequency to approach the second synthetic resonant frequency of the second synthetic load including the second load (2200) and the plasma. The frequency tracking method for the second load (2200) may utilize the aforementioned frequency tracking method and / or the power consumption-based frequency tracking method.

[0404] The second synthetic resonant frequency may be greater than the main resonant frequency (f2). At this time, the difference between the first synthetic resonant frequency divided by (2n+1) and the second synthetic resonant frequency may be greater than or equal to a threshold value. Here, the threshold value may be understood as a threshold value for allowing a relatively low current to flow to the first load (2100) when the plasma induction system (100) is in a normal state, i.e., when frequency tracking for the second load (2200) is in progress. The threshold value may be determined, for example, at about 10% or more of the initial driving frequency.

[0405] Meanwhile, the resonant frequency of the second synthetic load can be obtained as the driving frequency of the voltage signal output from the RF generator (1000) when the difference between the phase of the current flowing in the second load (2200) and the phase of the voltage applied to the second load (2200) is 0 or substantially equal to 0.

[0406] Hereinafter, with reference to FIGS. 15 and 16, the process in which the electrical characteristics of the first load (2100) and the second load (2200) change as the plasma is ignited and maintained, and the process in which the driving frequency of the RF generator (1000) changes, are described.

[0407] FIG. 15 and FIG. 16 are diagrams showing the characteristics of components within a plasma induction system (100) according to plasma induction according to one embodiment. FIG. 15 and FIG. 16 illustrate the change process of the resonant frequency, the magnitude of the current, and whether the plasma is on / off according to plasma induction for each of the first load (2100) and the second load (2200), and illustrate the change process of the driving frequency for the RF generator (1000). Here, the resonant frequency according to plasma induction refers to the resonant frequency of the composite load including the load and the plasma. Also, here, the magnitude of the current refers to the magnitude of the current flowing to each load. Also, here, the plasma on / off indicates whether the plasma is on or off in an area corresponding to each load.

[0408] [Before plasma ignition]

[0409] First, a voltage signal having an initial driving frequency can be applied to each of the first load (2100) and the second load (2200) by the RF generator (1000) before plasma ignition. The initial driving frequency is a value obtained by subtracting a first value from the main resonance frequency, and may be a value equal to or close to a value obtained by dividing the ignition resonance frequency by (2n+1).

[0410] The magnitude of the current flowing in the first load (2100) before the plasma is ignited may be relatively large. This is because the ignition resonance frequency of the first load (2100) is a harmonic of the initial driving frequency, and thus a high current flows in the first load (2100) due to the harmonic component of the voltage signal.

[0411] Meanwhile, the magnitude of the current flowing in the second load (2200) before the plasma is ignited may be relatively small. This is because the second load (2200) does not enter a resonant state because the initial driving frequency is different from the main resonant frequency.

[0412] Since the plasma is not ignited, the resonance frequency due to plasma induction is the ignition resonance frequency for the first load (2100) and the main resonance frequency for the second load (2200).

[0413] Additionally, the plasma is in the off state in the first region (R1) and the second region (R2).

[0414] [After plasma ignition]

[0415] When the plasma is ignited, the resonance frequency due to plasma induction in the first load (2100), i.e., the resonance frequency of the first composite load including the plasma and the first load (2100), may be changed to a value obtained by adding a first variation to the ignition resonance frequency. Here, the first variation refers to the degree to which the resonance frequency of the first load (2100) as viewed from the output terminal of the RF generator (1000) changes due to the plasma ignition. The first variation may be about 1% to about 10% of the ignition resonance frequency (f1). However, it should be understood that the first variation value may not be limited to the above value depending on the usage environment or design of the plasma induction system (100).

[0416] When the plasma is ignited, the magnitude of the current flowing to the first load (2100) momentarily decreases. This is because the influence of the harmonic components of the voltage signal having the initial driving frequency also decreases as the resonant frequency of the first synthetic load changes.

[0417] In the case of the second load (2200), since it is not greatly affected by the ignited plasma, the resonant frequency due to plasma induction is still the main resonant frequency, and the magnitude of the current is also relatively low.

[0418] [After frequency tracking for the first load]

[0419] As plasma is induced on the first load (2100) side, a phase difference occurs between the current flowing to the first load (2100) and the voltage applied, and to compensate for this, the RF generator (1000) changes the driving frequency to the first driving frequency.

[0420] Here, the first driving frequency may refer to a frequency determined by a harmonic frequency tracking method or a power consumption-based frequency tracking method. The first driving frequency is close to a value obtained by dividing the value obtained by adding the first variation to the ignition resonance frequency by (2n+1).

[0421] As a voltage signal having a first driving frequency is applied to the first load (2100), the first load (2100) enters a resonant state and the size of the flowing current may increase.

[0422] The main resonant frequency of the second load (2200) can be designed to be substantially the same as or close to the first driving frequency. Accordingly, when a voltage signal of the first driving frequency is applied to the second load (2200), the second load (2200) can operate in a resonant state, thereby increasing the amount of current flowing therethrough.

[0423] Meanwhile, the difference between the main resonant frequency and the initial driving frequency may be substantially equal to or close to the value obtained by dividing the first variation by (2n+1).

[0424] [Plasma transfer]

[0425] When the frequency of the voltage signal provided from the RF generator (1000) becomes a first driving frequency that is substantially the same as or similar to the main resonant frequency (f2) of the second load (2200), the intensity of the electromagnetic field formed in the second region (R2) by the second load (2200) also increases. Accordingly, the plasma ignited in the first region (R1) moves to the second region (R2).

[0426] When the plasma moves to the second region (R2), the resonance frequency due to plasma induction for the second load (2200) by the plasma, i.e., the resonance frequency of the second composite load including the second load (2200) and the plasma, changes by a second change amount. Here, the second change amount refers to the degree to which the resonance frequency of the second load (2200) as viewed from the output terminal of the RF generator (1000) changes as the plasma is transferred. The second change amount may be about 1% to about 10% of the main resonance frequency (f2). However, it goes without saying that the second change amount value may not be limited to the above value depending on the usage environment or design of the plasma induction system (100).

[0427] As plasma is induced in the second region (R2), the magnitude of the current flowing to the second load (2200) momentarily decreases. This is because the amount of energy transferred from the voltage signal having the first driving frequency decreases as the resonant frequency of the second synthetic load changes.

[0428] Meanwhile, even if the plasma moves to the second region (R2), the plasma can be maintained in the first region (R1). This is because, as described above, the first driving frequency of the voltage signal output from the RF generator (1000) is substantially the same as or similar to the resonant frequency of the first synthetic load.

[0429] [Frequency tracking after plasma transfer]

[0430] As plasma is induced on the second load (2200) side (in the second region), a phase difference occurs between the current and voltage for the second load (2200), and the RF generator (1000) can change the driving frequency to the second driving frequency to compensate for this.

[0431] Here, the second driving frequency may refer to a frequency determined by a frequency tracking method or a power consumption-based frequency tracking method. The second driving frequency approaches a value obtained by adding a second variation to the main resonant frequency. For example, the second driving frequency may have a value greater than the first driving frequency.

[0432] As a voltage signal having a second driving frequency is applied to the second load (2200), the second load (2200) enters a resonant state and the size of the flowing current may increase.

[0433] Meanwhile, for the first load (2100), the applied voltage signal has a second driving frequency, which is different from the resonant frequency of the first synthetic load (e.g., has a larger value), so the magnitude of the current flowing to the first load (2200) decreases. Accordingly, the size of the plasma may decrease or the plasma may not be maintained in the first region (R1).

[0434] [Plasma maintenance (normal state)]

[0435] As frequency tracking is performed for the second load (2200), the plasma can be stably maintained in the second region (R2). Specifically, according to the frequency tracking for the second load (2200), a voltage signal having a driving frequency corresponding to the resonant frequency of the second composite load including the second load (2200) and the plasma is continuously applied to the second load (2200), and accordingly, the energy supplied to the plasma (energy by the electromagnetic field) is maintained high, so that the plasma is stably maintained.

[0436] Meanwhile, in the case of the first load (2100), the plasma is extinguished in the first region (R1), and accordingly, the resonant frequency due to plasma induction returns to the ignition resonant frequency. Since there is a sufficient difference between the ignition resonant frequency and the second driving frequency (e.g., the difference between the ignition resonant frequency (f1) and the second driving frequency may be between about 1% and about 10% of the second driving frequency, but may vary depending on the usage environment or design of the plasma induction system (100), the energy (or intensity of the electromagnetic field) supplied to the first region (R1) by the first load (2100) becomes very low. Accordingly, the plasma stably maintained in the second region (R2) is not affected.

[0437] The above describes how a plasma induction system (100) including multiple loads and a single RF generator (1000) operates. In the above-described plasma induction system (100), the ignition resonance frequency of the first load (2100) and the main resonance frequency of the second load (2200) are designed to be significantly different, so that there is less risk of induced electromotive force being generated between them, and plasma ignition, plasma transition, and plasma maintenance are performed in a time-series manner, enabling stable plasma induction. Furthermore, by using only one RF generator (1000), the manufacturing cost is lowered, the manufacturing process is simplified, and even the volume of the product is reduced, so it is expected that there will be a significant effect in terms of product competitiveness.

[0438] The features, structures, effects, etc. described in the embodiments above are included in at least one embodiment of the present invention, and are not necessarily limited to just one embodiment. Furthermore, the features, structures, effects, etc. exemplified in each embodiment can be combined or modified in other embodiments by those skilled in the art to which the embodiments pertain. Therefore, the contents related to such combinations and modifications should be construed as falling within the scope of the present invention.

[0439] In addition, although the above description focuses on the embodiments, these are merely examples and do not limit the present invention. Those skilled in the art to which the present invention pertains will appreciate that various modifications and applications not exemplified above are possible without departing from the essential characteristics of the present embodiments. In other words, each component specifically shown in the embodiments can be modified and implemented. In addition, differences related to such modifications and applications should be interpreted as being included within the scope of the present invention defined in the appended claims.

Claims

1. A discharge tube that provides a space where plasma is induced; A first load comprising an ignition antenna structure arranged to surround the discharge tube, and at least one capacitive element electrically connected in series with the ignition antenna structure; a main antenna structure arranged to surround the discharge tube and arranged within a preset distance from the ignition antenna structure in a direction parallel to the central axis of the discharge tube, and a second load including at least one capacitive element electrically connected in series with the main antenna structure; and Including an RF generator for applying RF (Radio Frequency) voltage to the first load and the second load; When the above second load is designed to have the main resonant frequency, The above first load is designed to have an ignition resonance frequency corresponding to (2n+1) times (n is a natural number) the initial driving frequency which differs by a first value from the above main resonance frequency, The RF generator is configured to apply an RF voltage having the initial driving frequency to the first load and the second load for plasma ignition. Plasma induction device.

2. In paragraph 1, The magnitude of the current flowing in the ignition antenna structure after plasma is ignited in the plasma ignition region corresponding to the ignition antenna structure in the discharge tube is When the RF voltage having the first driving frequency is applied to the ignition antenna structure, it is greater than when the RF voltage having the initial driving frequency is applied. The above first driving frequency has a value greater than the initial driving frequency, Plasma induction device.

3. In paragraph 2, The above main antenna structure is applied with an RF voltage having the same driving frequency as the RF voltage applied to the above ignition antenna structure, The magnitude of the current flowing in the above main antenna structure is, When RF power having the first driving frequency is applied to the main antenna structure, the RF power having the initial driving frequency is greater than when RF power having the first driving frequency is applied. Plasma induction device.

4. In paragraph 3, The magnitude of the current flowing in the main antenna structure after the ignited plasma is transitioned to the plasma maintenance region corresponding to the main antenna structure in the discharge tube is When RF power having the second driving frequency is applied to the main antenna structure, it is greater than when RF power having the first driving frequency is applied. The second driving frequency has a value greater than the first driving frequency, Plasma induction device.

5. In paragraph 4, The above ignition antenna structure is applied with an RF voltage having the same driving frequency as the RF voltage applied to the main antenna structure, The magnitude of the current flowing in the above ignition antenna structure is: When RF power having the second driving frequency is applied to the ignition antenna structure, it becomes smaller than when RF power having the first driving frequency is applied. Plasma induction device.

6. In paragraph 1, When plasma is ignited in a plasma ignition region corresponding to the ignition antenna structure in the discharge tube, a first synthetic load including the ignited plasma and the first load has a first synthetic resonance frequency greater than the ignition resonance frequency, The first difference value between the first synthetic resonant frequency divided by (2n+1) and the initial driving frequency corresponds to the first value. Plasma induction device.

7. In paragraph 6, When the ignited plasma is transferred to the plasma maintenance region corresponding to the main antenna structure in the discharge tube, the second synthetic load including the transferred plasma and the second load has a second synthetic resonance frequency greater than the main resonance frequency, The second difference value between the first synthetic resonance frequency divided by (2n+1) and the second synthetic resonance frequency is greater than or equal to the critical value. Plasma induction device.

8. In paragraph 7, The above threshold value is determined at 10% or more of the initial driving frequency, Plasma induction device.

9. In paragraph 6, When the RF generator applies a voltage signal having a driving frequency corresponding to the first synthetic resonant frequency to the first load while the plasma is ignited, The phase difference between the voltage applied to the first load and the phase of the current flowing through the first load is 0 or substantially equal to 0. Plasma induction device.

10. In paragraph 7, When the RF generator applies a voltage signal having a driving frequency corresponding to the second synthetic resonant frequency to the second load in a state where the plasma is transferred, The phase difference between the voltage applied to the second load and the phase of the current flowing through the second load is 0 or substantially equal to 0. Plasma induction device.

11. In paragraph 1, When the fundamental driving frequency of the voltage signal output from the above RF generator is a, The size of the above first value is determined within 0.01*a to 0.3*a, Plasma induction device.

12. In paragraph 1, The above main resonant frequency has a value between 1.01 and 1.1 times the initial driving frequency. Plasma induction device.

13. In paragraph 1, The above preset distance is within 10cm, Plasma induction device.

14. In a plasma induction method for supplying power to a plasma induction device, The above plasma induction device, A discharge tube that provides a space in which plasma is induced; A first load comprising an ignition antenna structure arranged to surround the discharge tube, and at least one capacitive element electrically connected in series with the ignition antenna structure; a main antenna structure arranged to surround the discharge tube and arranged within a preset distance from the ignition antenna structure in a direction parallel to the central axis of the discharge tube, and a second load including at least one capacitive element electrically connected in series with the main antenna structure; and Including an RF generator for applying RF (Radio Frequency) voltage to the first load and the second load; A step of applying an initial RF voltage having an initial driving frequency to the first load and the second load using the RF generator; A step of applying a first RF voltage having a first driving frequency to the first load and the second load after detecting that plasma is ignited in a plasma ignition region corresponding to the ignition antenna structure in the discharge tube. - The first driving frequency is determined based on the phase difference between the voltage and current applied to the first load, The magnitude of the current flowing in the main antenna structure increases when the first RF voltage is applied to the second load compared to when the initial RF voltage is applied; A step of applying a second RF voltage having a second driving frequency to the first load and the second load after detecting that the ignited plasma has transitioned to a plasma maintenance region corresponding to the main antenna structure in the discharge tube. - The second driving frequency is determined based on the phase difference between the voltage and current applied to the second load, The magnitude of the current flowing in the ignition antenna structure is reduced when the second RF voltage is applied to the first load compared to when the first RF voltage is applied; Plasma induction method.

15. A discharge tube providing a space in which plasma is induced; A first load comprising an ignition antenna structure arranged to surround the discharge tube, and at least one capacitive element electrically connected in series with the ignition antenna structure; a main antenna structure arranged to surround the discharge tube and arranged within a preset distance from the ignition antenna structure in a direction parallel to the central axis of the discharge tube, and a second load including at least one capacitive element electrically connected in series with the main antenna structure; and Including an RF generator for applying RF (Radio Frequency) voltage to the first load and the second load; When the above second load is designed to have the main resonant frequency, The ignition resonance frequency of the first load is designed to have a value closer to (2n+1) times the main resonance frequency than (2n) times (n is a natural number) the main resonance frequency or (2n+2) times the main resonance frequency. Plasma induction device.

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