Metal Oxide Varistor (MOV) Based Surge Protection Circuit for Plasma Processing Chambers

Abstract

The system includes a chamber configured to generate and contain a plasma. The system includes a transmission line located within the chamber. The transmission line includes a transmission line input and an output coupled to a common potential. The system includes a signal source coupled to the transmission line input to provide an input signal to the transmission line. The system includes a surge protection circuit coupled between the transmission line input and the common potential. The impedance of the surge protection circuit is inversely proportional to the voltage level at the transmission line input.

Description

[Technical Field]

[0001] [Priority Claim] This application claims priority to U.S. Provisional Patent Application No. 63 / 368,472, filed July 14, 2022, entitled "METAL-OXIDE VARISTOR (MOV) BASED SURGE PROTECTION CIRCUIT FOR PLASMA PROCESSING CHAMBER," which is incorporated by reference in its entirety. [Background technology]

[0002] Plasma deposition is a process used to deposit thin films onto substrates using a plasma source. The plasma may be generated in a chamber containing a transmission line. A signal source supplies a radio frequency (RF) signal or direct current (DC) to the transmission line. By changing the electrical parameters, such as the frequency and voltage of the signal supplied to the transmission line, the spatial distribution and ion energy of the plasma are modulated. The plasma deposition process can be controlled by modulating the spatial distribution and ion energy of the plasma.

[0003] During the plasma deposition process, voltage spikes or surges may occur within the chamber due to "arcing" or changes in load (e.g., a semiconductor wafer or substrate). The voltage spikes or surges may be transient events that typically last from a few nanoseconds to 30 microseconds and may reach, for example, 1000 V, 2000 V, or 3000 V. The voltage spikes or surges may be coupled into the signal source, thereby damaging the signal source. [Brief explanation of the drawings]

[0004] The materials described herein are shown by way of example, and not by way of limitation, in the accompanying drawings. For simplicity and clarity of illustration, elements shown in the figures have not necessarily been drawn to scale. For example, the dimensions of some elements may be exaggerated relative to other elements for clarity. Also, various physical features may be represented in these simplified "ideal" forms and geometries for clarity of illustration, although it should be understood that actual implementations may only approximate the ideals depicted. For example, smooth surfaces and orthogonal intersections may be depicted while ignoring the finite roughness, corner rounding, and imperfect angle intersection characteristics of structures formed by nanofabrication techniques. Furthermore, where considered appropriate, reference numerals may be repeated among the figures to indicate corresponding or similar elements.

[0005] [Figure 1] FIG. 1 illustrates a system according to at least one implementation.

[0006] [Figure 2] FIG. 2 illustrates a system including an implementation of a surge protection circuit, according to at least one implementation.

[0007] [Figure 3] FIG. 3 illustrates a system in which a surge protection circuit is implemented using a passive RLC circuit, according to at least one implementation.

[0008] [Figure 4A] FIG. 4A shows a plot of the resistance of a metal oxide varistor (MOV) at lower frequencies according to at least one implementation. [Figure 4B] FIG. 4B shows a plot of the reactance of the MOV at lower frequencies, according to at least one implementation. [Figure 4C] FIG. 4C shows a plot of capacitance of a MOV as a function of voltage, according to at least one implementation.

[0009] [Figure 5]FIG. 5 shows a plot of impedance of a surge protection circuit as a function of voltage, according to at least one implementation.

[0010] [Figure 6] FIG. 6 shows a plot of the impedance of a surge protection circuit as a function of frequency with variation in the capacitance of the MOV, according to at least one implementation.

[0011] [Figure 7] FIG. 7 illustrates an example implementation of a system including an implementation of an over-voltage detection circuit, according to at least one implementation. DETAILED DESCRIPTION OF THE INVENTION

[0012] A metal oxide varistor (MOV)-based surge protection circuit for a plasma processing chamber is described according to at least one implementation. In the following description, numerous specific details, such as structural schemes, are presented to provide a thorough understanding of implementations of the present disclosure. It will be apparent to those skilled in the art that implementations of the present disclosure may be practiced without these specific details. In other instances, well-known features are described in less detail in order to not unnecessarily obscure implementations of the present disclosure. Furthermore, it should be understood that the various implementations shown in the figures are illustrative and are not necessarily drawn to scale.

[0013] In some instances, in the following description, well-known methods and devices are shown in block diagram form rather than in detail in order to avoid obscuring the disclosure. Throughout this specification, references to an "implementation" or "one implementation" or "some implementations" mean that a particular feature, structure, function, or characteristic described in connection with an implementation is included in at least one implementation of the present disclosure. Thus, the appearances of "in an implementation" or "in one implementation" or "in some implementations" in various places throughout this specification do not necessarily refer to the same implementation of the present disclosure. Furthermore, particular features, structures, functions, or characteristics may be combined in any suitable manner in one or more implementations. For example, a first implementation and a second implementation may be combined whenever particular features, structures, functions, or characteristics associated with the two implementations are not mutually exclusive.

[0014] Herein, the terms “coupled” and “connected,” as well as their derivatives, may be used herein to describe a functional or structural relationship between components. These terms are not intended as synonyms for each other. Rather, in certain implementations, “connected” may be used to indicate that two or more elements are in direct physical, optical, or electrical contact with each other. “Coupled” may be used to indicate that two or more elements are in direct or indirect physical, electrical, or magnetic contact with each other (with other intervening elements) and / or that two or more elements cooperate or interact (e.g., are causally related) with each other. The term “coupled” may generally refer to the direct or indirect attachment of one electronic component to another electronic component. An electric or magnetic field may couple one component to another, where the electric or magnetic field controlled by one component affects the other component in some way.

[0015] As used herein, the terms "over," "under," "between," and "on" refer to the relative location of one component or material with respect to another, where such physical relationship is noteworthy. Unless these terms are modified with "direct" or "directly," one or more intervening components or materials may be present. Similar distinctions are made in the context of an assembly of components. Throughout this description and as used in the claims, a list of items connected by the terms "at least one of" or "one or more of" may mean any combination of the listed terms.

[0016] As used herein, the term "adjacent" generally refers to the location of something next to (e.g., immediately adjacent or nearby with one or more things between) or adjacent to (e.g., abutting) another.

[0017] Unless the clear context of their use dictates otherwise, the terms "substantially equal," "about equal," and "approximately equal" mean only incidental variations between the two so described. In at least one implementation, such variations typically do not exceed + / - 10% of the referenced value.

[0018] Here, a "transmission line" may generally refer to multiple electrically coupled conductive elements or segments. In at least one implementation, a transmission line may be constructed using discrete elements (e.g., inductors, capacitors). In at least one implementation, the individual wires of a transmission line may be represented by an inductance L divided by a distributed capacitance C per unit length, where the distributed capacitance is proportional to the permittivity of the dielectric material between the conductors.

[0019] Here, "terminal" may generally refer to the end of an electrical conductor or electrical component, such as a wire, and may be a connection point with another electrical conductor or electrical component. In at least one implementation, in the context of a coil, a terminal is the end of a winding. When referring to a coil segment, in at least one implementation, the coil segment may include terminals at the beginning and end of the coil segment conductors.

[0020] Here, an "inductor" may generally refer to a passive electrical device that stores magnetic energy from an electric current flowing through it. In at least one implementation, an inductor may include an electrical conductor (e.g., a metal wire) that can couple an electrically generated magnetic field to another nearby electrical conductor, thereby inducing a voltage and current in the second conductor. In at least one implementation, a magnetic field may be generated by a current flowing in a first electrical conductor according to Faraday's law of electromagnetic induction. In at least one implementation, an electrical conductor has inductance, which is a function of the magnitude of the current flowing in the conductor and the shape or geometry of the conductor. In at least one implementation, any electrical conductor can be an inductor, but some shapes produce stronger inductance than others. In at least one implementation, a straight wire may have a small inductance depending on its diameter and length. In at least one implementation, a straight wire may be wound into a coil, for example, to multiply the inductance by the number of turns per unit length due to the mutual coupling of magnetic fields between each winding, thereby enhancing the overall magnetic field. In at least one implementation, the magnetic field resulting from the combination of each winding amplifies the magnetic field produced by the straight wire according to Ampere's law. In at least one implementation, the coil can be a planar coil or a helical coil, such as a solenoid or tapered helix.

[0021] Here, a "capacitor" may generally refer to a passive electrical device that stores charge and electrical energy in the form of an electric field. In at least one implementation, a capacitor generally has at least two conductive plates in close proximity to one another, separated by a dielectric material. In at least one implementation, the dielectric material may be air (or other gas) or a vacuum. In at least one implementation, the dielectric may generally be a solid or liquid material, such as a polymer, ceramic, or semi-liquid electrolyte. In at least one implementation, opposite charges may accumulate on adjacent plates, thereby forming an electric field that extends from plate to plate through the dielectric. In at least one implementation, the electric field may store electrical energy.

[0022] Here, "plasma" may generally refer to a gaseous composition containing charged particles, such as positively or negatively charged atomic or molecular ions and electrons. In at least one implementation, plasma is considered a fourth state of matter.

[0023] Here, "modulate" can refer to varying or adjusting, and the phrase "modulating a plasma" can generally refer to varying the spatial distribution and ion energy of the plasma.

[0024] As used herein, a "rectifier" may generally refer to an electronic circuit that converts alternating current (AC), which periodically reverses direction, into direct current (DC), which flows in only one direction.

[0025] Here, a "tank circuit" may generally refer to a parallel combination of an inductor and a capacitor. In at least one implementation, the tank circuit has a characteristic resonant frequency f0 determined by the values of inductance L and capacitance C, where f0 = 1 / [2p√LC]. In at least one implementation, the tank circuit has a resonance curve, which is a plot of the circuit impedance as a function of frequency. In at least one implementation, the curve is non-monotonic, with a peak at the resonant frequency. In at least one implementation, the sharpness and bandwidth of the resonance curve are determined by the quality factor Q of the circuit. Q may be defined as the ratio of the energy stored in the electric and magnetic fields of the capacitor and inductor, respectively, to the energy dissipated as heat by the resistive components of the circuit. In at least one implementation, the resistance may be mostly within the inductor (e.g., copper loss, skin effect, etc.), because the inductor may include a long piece of thin wire wound into a coil. In at least one implementation, the lower the resistance of the coil, the higher the Q. The Q can be lowered by inserting a separate resistor in series with the inductor in the tank circuit. In at least one implementation, the resonance curve can be broadened with a low circuit Q (e.g., Q<10) and sharpened with a high circuit Q (e.g., Q>10). In at least one implementation, the tank circuit exhibits very large circulating currents at or near resonance. In at least one implementation, the circulating current can be the product of the line current or feed current multiplied by Q. Large circulating currents can also cause very large voltages to appear across the capacitors and inductors. At the same time, in at least one implementation, the impedance of the tank circuit rises dramatically at or near resonance, becoming purely resistive at f0. In at least one implementation, the resonant tank circuit can have a very high effective resistance at f0, which significantly reduces the conduction of RF current. Here, the "tank" circuit derives from the circuit's ability to store electrical energy. In at least one implementation, tank circuits are used as frequency-determining components in oscillator circuits and tuned combiner circuits found, for example, in tuned RF amplifier stages.

[0026] Here, "dielectric material" may generally refer to non-conductive materials such as polymers, ceramics, glass, wood, and the like.

[0027] Here, "radio frequency" may generally refer to electromagnetic radiation oscillating at frequencies within a spectrum substantially including frequencies between 10 kilohertz (kHz) and 1 terahertz (THz or 10 Hz). In at least one implementation, the upper limit of the radio frequency spectrum may only extend up to several hundred gigahertz (GHz). The term radio frequency is commonly abbreviated as "RF."

[0028] Here, a "signal source" may generally refer to an electronic device capable of generating an electrical signal at radio frequency or another desired frequency. In at least one implementation, a signal source is capable of outputting very large currents (e.g., 1 ampere rms or greater) at very large voltages.

[0029] Here, a "passive RLC circuit" may generally refer to an electrical circuit consisting of a resistor (R), an inductor (L), and a capacitor (C) connected in series or parallel. In at least one implementation, the passive RLC circuit forms an oscillator for the current and resonates at a resonant frequency. In at least one implementation, the resistor increases the damping of the oscillation, known as damping.

[0030] Here, "chuck" may generally refer to a stage or platform upon which a substrate (eg, a wafer) may be mounted.

[0031] Here, "electrostatic chuck" may generally refer to a platform that may include an electrode plate and an insulator disposed on the electrode plate.

[0032] Here, the term "substrate" can refer to a wafer comprising a semiconductor (e.g., silicon) or an insulator (e.g., aluminum nitride, silicon carbide, silicon nitride, aluminum oxide, float glass, borosilicate glass, etc.). In at least one implementation, the wafer can be a slice of a single crystal semiconductor or a single crystal insulator. In at least one implementation, the wafer may comprise a polycrystalline material or an amorphous (glassy) material. In at least one implementation, the wafer can have a diameter typically ranging from 100 mm to 500 mm and a thickness typically ranging from 100 microns to 1 mm.

[0033] Here, "chamber" may generally refer to a vacuum chamber of a process tool into which a substrate may be introduced for processing. In at least one implementation, the chamber may include a chuck for holding the substrate. In at least one implementation, the process chamber is a plasma etch chamber.

[0034] Here, "spatial control" may generally refer to positional control of a process. In at least one implementation, spatial control of plasma etching or plasma deposition is provided by spatially resolved coupling of an ICP antenna to the plasma.

[0035] Here, "input signal" may generally refer to a signal of a desired frequency provided by a signal source.

[0036] As used herein, "metal oxide varistor" or "MOV" may generally refer to an electronic component with a resistance that varies with applied voltage. In at least one implementation, MOVs have high resistance at low voltages that decreases as the voltage increases. MOVs are also known as voltage-dependent resistors.

[0037] Here, a "diode" may generally refer to a two-terminal electronic component that conducts current primarily in one direction. In at least one implementation, a diode has low (ideally zero) resistance in one direction and high (ideally infinite) resistance in the other direction.

[0038] Here, a "low frequency signal" or "low frequency component" may generally refer to a signal having a low frequency range (e.g., between 0 Hz and 0.5 kHz), and a "high frequency signal" or "high frequency component" may generally refer to a signal having a high frequency range (e.g., above 0.5 MHz).

[0039] Here, "ion" may generally refer to a charged atom or molecule. In at least one implementation, an ion may be a gaseous atom or molecule that loses or gains electrons within a plasma.

[0040] Here, "high impedance" may generally refer to a node in a circuit that may cause substantially zero or a relatively small amount of current to flow through the node when a voltage is applied to the node. In at least one implementation, a node that is not driven to any logic level is a high impedance node.

[0041] Here, "low impedance," as opposed to high impedance, may generally refer to a node in a circuit that allows a relatively large amount of current to flow when a voltage is applied to the node.

[0042] Here, a "surge protection circuit" may generally refer to a circuit that protects a system from voltage spikes or surges. In at least one implementation, in response to a voltage spike, the "surge protection circuit" may provide a short-circuit connection between the system and a common potential (e.g., ground), thereby protecting the system from the voltage spike.

[0043] Here, an "overvoltage detection circuit" may generally refer to a circuit that indicates an overvoltage condition when the voltage at a node or terminal exceeds an overvoltage limit (e.g., 1000V, 2000V, or 3000V).

[0044] 1 illustrates a system 100 according to at least one implementation. In at least one implementation, the system 100 includes a chamber 104, a first region 105, a second region 106, an isolation window 107, an intake valve 108, an exhaust valve 112, a transmission line 120, a signal source 124, a surge protection circuit 126, an input terminal 128, a termination node 132, an electrostatic chuck 136, an electrode plate 140A, an insulator 140B, and a wafer 144.

[0045] The chamber 104 is configured to generate and contain a plasma. In at least one implementation, the chamber 104 may be divided into a first region 105 and a second region 106 by an isolation window 107. In at least one implementation, the isolation window 107 may be made of a non-conductive material (e.g., a dielectric), such as a polymer, ceramic, glass, or wood. In at least one implementation, the first region 105 may also be referred to as an antenna region or a transmission line region. The second region 106 may also be referred to as a vacuum region or a plasma region.

[0046] In at least one implementation, the chamber 104 may include an intake valve 108 through which gas is directed into the chamber, as well as an exhaust valve 112 for removing the gas. In at least one implementation, the gas may be generally contained within the second region 106. In at least one implementation, the chamber 104 is shown having a rectangular shape. However, the chamber 104 may be constructed having other suitable shapes, such as, but not limited to, a dome shape.

[0047] In at least one implementation, system 100 includes transmission line 120 in first region 105 (also known as a utility region). In at least one implementation, transmission line 120 may have an equivalent resistance of approximately 50 ohms. In at least one implementation, signal source 124 is electrically connected between input terminal 128 and a common potential 125 (e.g., ground). In at least one implementation, signal source 124 provides a signal to transmission line 120. In at least one implementation, signal source 124 may be a signal generator configured to generate a DC or AC voltage at a desired frequency.

[0048] In at least one implementation, the transmission line 120 has a termination node 132 that may be coupled to a common potential 125 (e.g., ground). In at least one implementation, the termination node 132 may be capacitively coupled to ground.

[0049] In at least one implementation, the system 100 includes an electrostatic chuck 136 in the second region 106 (also known as the plasma region). In at least one implementation, the electrostatic chuck 136 may include an electrode plate 140A and an insulator 140B disposed on the electrode plate 140A. In at least one implementation, the insulator 140B may include a dielectric material including a ceramic such as alumina (Al2O3), silicon dioxide (SiO2), silicon nitride (Si3N4), and / or sapphire.

[0050] In at least one implementation, during operation, the system 100 controls plasma-assisted deposition, cleaning, or etching on a substrate 144 by spatially modulating the ion energy distribution in a plasma formed in the plasma chamber 104. In at least one implementation, the system 100 controls the spatial distribution of the plasma and the ion energy by varying electrical parameters, such as the frequency and voltage of an applied signal provided in the transmission line 120. In at least one implementation, the system 100 is operable to spatially control plasma processes, such as plasma-enhanced chemical vapor deposition (PECVD) or plasma-enhanced atomic layer deposition (PEALD), as well as plasma cleaning and ion etching processes, such as reactive ion etching, on the substrate 144.

[0051] Although the transmission line 120 is illustrated as having a straight structure, the transmission line 120 may have other suitable shapes. In at least one implementation, the transmission line 120 may be wound into a coil, such as a pancake-shaped coil.

[0052] In at least one implementation, surge protection circuit 126 may be coupled between input terminal 128 and a common potential 125 (e.g., ground). In at least one implementation, voltage spikes or surges may occur within chamber 104 due to "arcing" during plasma processing or due to changes in load (e.g., semiconductor wafer or substrate) 144. In at least one implementation, the voltage spikes or surges are transient events that typically last 1-30 microseconds and may reach, for example, 1000V, 2000V, or 3000V. The voltage spikes or surges may reflect off input terminal 128, thereby coupling signal source 124 to the voltage spikes or surges. In at least one implementation, this may result in damage to signal source 124. In various implementations, if a voltage spike or surge causes the voltage level at input terminal 128 to exceed an overvoltage limit (e.g., 1000V, 2000V, or 3000V), surge protection circuit 126 couples input terminal 128 to common potential 125. In at least one implementation, surge protection circuit 126 diverts the resulting surge current to common potential 125 (e.g., ground), thereby protecting signal source 124 from damage.

[0053] 2 shows an example implementation of a system 200 that includes an implementation of the surge protection circuit 126. In at least one implementation, the system 200 includes the chamber 104, the signal source 124, the surge protection circuit 126, the input terminal 128, and the termination node 132.

[0054] In at least one implementation, the surge protection circuit 126 includes a resistor R1 coupled in series with a capacitor C1. In at least one implementation, the resistor R1 includes a first terminal 140 coupled to the input terminal 128 and a second terminal 142. In at least one implementation, the capacitor C1 includes a first terminal 144 coupled to the second terminal 142 of R1 and a second terminal 146 coupled to a common potential 125 (e.g., ground). In at least one implementation, the capacitor C1 may be implemented as a metal oxide varistor (MOV) according to some implementations. In at least one implementation, an MOV is an electronic component with a resistance that varies with applied voltage. In at least one implementation, an MOV has a high resistance (e.g., 1000 ohms, 2000 ohms) at low voltages that decreases as the voltage increases. In at least one implementation, an MOV is also known as a voltage-dependent resistor.

[0055] In at least one implementation, the MOV may have high resistance at low voltages, so capacitor C1 acts as an open circuit at high voltages. In at least one implementation, surge protection circuit 126 does not affect the operation of system 100 at low voltages. In at least one implementation, the MOV has very low resistance at high voltages, so capacitor C1 acts as a short circuit. In at least one implementation, surge protection circuit 126 activates when a voltage spike causes the voltage level at input terminal 128 to exceed an overvoltage limit (e.g., 1000 V, 2000 V, or 3000 V). In at least one implementation, surge protection circuit 126 diverts transient surge currents caused by the voltage spike to common potential 125 (e.g., ground) by coupling input terminal 128 to common potential 125 (e.g., ground). In at least one implementation, surge protection circuit 126 prevents damage to signal source 124. In some exemplary implementations, surge protection circuit 126 provides a fast response and can couple input terminal 128 to common potential 125 (eg, ground) within nanoseconds of a voltage spike occurring.

[0056] In at least one implementation, capacitor C1 may have high impedance at operating frequencies (e.g., 400 kHz). In at least one implementation, when "arcing" within chamber 104 generates high-frequency transient surge currents (e.g., 1 MHz or 5 MHz), transient currents may appear at input terminal 128. In at least one implementation, at high frequencies, capacitor C1 has very low impedance (e.g., near zero), so the transient surge currents may be diverted to common potential 125 (e.g., ground) via surge protection circuit 126, according to various implementations.

[0057] In some example implementations, capacitor C1 may have a capacitance of approximately 20 nanofarads or 30 nanofarads at 500V (eg, operating voltage), and resistor R1 may have a resistance of approximately 2.7 ohms.

[0058] 3 illustrates an exemplary implementation of a system 300 in which a surge protection circuit 302 is implemented using a passive RLC circuit, according to at least one implementation. In at least one implementation, the system 300 includes a chamber 104, a signal source 124, a surge protection circuit 302, an input terminal 128, and a termination node 132.

[0059] In at least one implementation, the surge protection circuit 302 includes an inductor L1 (e.g., about 143 uH) coupled in parallel with a resistor R1 (e.g., about 2.77 ohms) and a capacitor C1. In at least one implementation, the capacitor C1 may be implemented as an MOV. The inductor L1 includes a first terminal 304 coupled to the first terminal 142 of the resistor R1 and a second terminal 308 coupled to the second terminal 144 of the capacitor C1. In at least one implementation, the inductor L1, the capacitor C1, and the resistor R1 form a passive RLC circuit. In a passive RLC circuit, a resonant frequency f cOscillation may occur at which stored energy may be exchanged between inductor L1 and capacitor C1. In at least one implementation, at resonance, the impedance of the passive RLC circuit may be equal to R1.

[0060] In at least one implementation, the impedance of C1 may depend on the applied voltage, so that by selecting an inductance value for L1, the passive RLC circuit can achieve a particular f c In at least one implementation, if the normal operating frequency of system 300 is about 400 kHz, the passive RLC circuit can be tuned to resonate at a higher frequency (e.g., 1 MHz or 5 MHz). In at least one implementation, resistor R1 increases the damping of the oscillation, which is known as damping.

[0061] In at least one implementation, “arcing” within chamber 104 can cause transient voltage spikes or surges to reflect at input terminal 128. The transient voltage spikes can have a high frequency (e.g., 1 MHz or 5 MHz). In at least one implementation, the inductance of L1 can be selected so that the passive RLC circuit resonates, for example, at about 1 MHz or 5 MHz. Thus, the transient surge current can oscillate within the passive RLC circuit. In at least one implementation, the effect of this can be to prevent the transient surge current from flowing into signal source 124 and thus preventing damage to signal source 124. In an exemplary implementation, inductor L1 is a variable inductor (e.g., the inductance can be adjusted).

[0062] FIG. 4A shows a plot 404 of the resistance of a metal oxide varistor (MOV) used in surge protection circuit 126 at lower frequencies, according to at least one implementation. In FIG. 4A, the x-axis shows frequency normalized between 0.0001 and 1.0, and the y-axis shows resistance normalized between 0.0 and 1.0. At approximately 0.0001 arbitrary units (au) (e.g., 100 Hz), the MOV has a resistance of approximately 0.1 au (e.g., 1000 ohms). At approximately 0.0004 au (e.g., 400 kHz), the MOV has a resistance of approximately 0.2 au (e.g., 2 ohms). At low frequencies, the high resistance of the MOV (e.g., 1000 ohms) causes power supplied by signal source 124 to flow into transmission line 120. FIG. 4B shows a plot 408 of the reactance of the MOV at lower frequencies. The x-axis represents frequency normalized between 0.0001 and 1.0, and the y-axis represents reactance normalized between -4.0 and 1.0. At approximately 0.004 au (e.g., 400 kHz), the MOV has a reactance of approximately -2.0 au (e.g., -400 j), and at approximately 0.1 au (e.g., 10 MHz), the MOV has a reactance near zero.

[0063] 4C shows a plot 412 of the capacitance of an MOV as a function of voltage at about 400 kHz, according to at least one implementation. The x-axis shows voltage normalized between 0 and 1.0, and the y-axis shows capacitance normalized between 0.88 and 1.0. At about 0.4 au (e.g., 100 V), the MOV has a capacitance of about 0.93 au (e.g., 0.93 nanofarads), and at about 0.8 au (e.g., 200 V), the MOV has a capacitance of about 0.88 au (e.g., 0.88 nanofarads).

[0064] 5 shows a plot 504 of the resistance of surge protection circuit 126 as a function of voltage, according to at least one implementation. In FIG. 5, the x-axis represents voltage normalized between 0.2 and 1.0, and the y-axis represents voltage normalized between 1.0 and 1.8. At about 0.37 au (e.g., 100V), surge protection circuit 126 has a resistance of about 1.45 au (e.g., 2800 ohms), and at about 0.8 au (e.g., 210V), surge protection circuit 126 has a resistance of about 1.04 au (e.g., 2100 ohms).

[0065] FIG. 6 shows plots 604, 608, and 612 of the impedance of surge protection circuit 126 as a function of frequency with variations in the capacitance of the MOV, according to at least one implementation. Plot 604 shows the impedance when the MOV is approximately 1.1 nanofarads, plot 608 shows the impedance when the MOV is approximately 1.2 nanofarads, and plot 612 shows the impedance when the MOV is approximately 1.3 nanofarads. The x-axis shows frequency normalized between 0.7 and 1.125, and the y-axis shows impedance normalized between 49.75 and 49.98. When the MOV is 1.1 nanofarads, surge protection circuit 126 has an impedance of approximately 49.9 ohms at approximately 1.0 au (e.g., 400 kHz). In at least one implementation, the impedance drops quickly at higher or lower frequencies. When the MOV is 1.2 nanofarads, the surge protection circuit 126 has an impedance of approximately 49.9 ohms at approximately 0.93 au (e.g., 385 kHz). In at least one implementation, the impedance drops quickly at higher or lower frequencies. When the MOV is 1.3 nanofarads, the surge protection circuit 126 has an impedance of approximately 49.9 ohms at approximately 0.88 au (e.g., 365 kHz). The impedance drops quickly at higher or lower frequencies. Thus, as the capacitance of the MOV increases, the MOV exhibits an impedance peak at a lower frequency.

[0066] 7 illustrates a system 700 according to at least one implementation. System 700 is similar to system 300, except that system 700 includes an overvoltage detection circuit 702. In at least one implementation, system 700 includes chamber 104, signal source 124, surge protection circuit 302, input terminal 128, termination node 132, diodes D1-D4, capacitor C10, resistor R10, and a voltage level indicator 720.

[0067] In at least one implementation, diodes D1-D4 form a rectifier 703 that can rectify voltage spikes or surges at input terminal 128 and provide a conductive path for charging capacitor C10. In at least one implementation, diode D1 includes an anode 704 coupled to the second terminal 146 of capacitor C1 and a cathode 706. Diode D2 includes an anode 708 coupled to potential common 125 and a cathode 710 coupled to anode 706. In at least one implementation, diode D3 includes a cathode 712 coupled to anode 704 and an anode 714. Diode D4 includes an anode 716 coupled to anode 714 and a cathode 718 coupled to potential common 125. In at least one implementation, capacitor C10 (e.g., approximately 0.033 microfarads) includes a first terminal 750 coupled to cathodes 706 and 710 and a second terminal 752 coupled to anodes 714 and 716. In at least one implementation, resistor R10 (e.g., approximately 2000 ohms) includes a first terminal 754 coupled to the first terminal 750 of capacitor C10 and a second terminal 756 coupled to the second terminal 752 of resistor R10. In at least one implementation, voltage level indicator 720 is coupled in parallel to capacitor C10 and resistor R10.

[0068] In at least one implementation, in response to a voltage spike at input terminal 128, diodes D1 and D3 may become forward biased. In at least one implementation, a transient surge current due to the voltage spike may be conducted through D1 and D3, charging capacitor C10. If the voltage across capacitor C10 exceeds an overvoltage limit (e.g., 1000V, 2000V, or 3000V), voltage level indicator 720 may indicate the overvoltage condition (e.g., an LED, an alarm). Capacitor C10 is discharged through R10 and diodes D4 and D3. In at least one implementation, diodes D1-D10 are power semiconductor devices rated to operate at very high voltages (e.g., 4000V).

[0069] In at least one implementation, the voltage level indicator 720 may be coupled to resistor R10 and capacitor C10 via an interface, such as, for example, an optical fiber interface, a digital interface, or an analog interface. In at least one implementation, the overvoltage detection circuit 702 may be coupled to a monitor or server (not shown in FIG. 7 ) via a communication link (e.g., the Internet, a wired, or wireless communication link). In at least one implementation, the monitor or server may be located remotely from the overvoltage detection circuit 702. In at least one implementation, the monitor or server may be located on the cloud and connected to the overvoltage detection circuit 702 via a communication link. In at least one implementation, in response to a voltage spike that may trigger the surge protection circuit 302 to couple the input terminal 128 to the common potential 125 (e.g., ground), a message or notification may be sent to the monitor indicating the status (e.g., the surge protection circuit 302 has been triggered). In at least one implementation, a user may be able to monitor the status of the system 700 remotely.

[0070] In addition to what is described herein, various modifications can be made to the disclosed implementations and their implementations without departing from their scope. Therefore, the examples of implementations herein should be construed as examples only, and not as limiting the scope of the present disclosure. The scope of the present invention should be evaluated solely by reference to the appended claims.

[0071] The following examples provide illustrations of various implementations. The examples can be combined with other examples. Thus, various implementations can be combined with other implementations without changing the scope of the invention.

[0072] Example 1: A system includes a chamber configured to generate and contain a plasma, a transmission line located within the chamber, the transmission line including a transmission line input and an output, the output coupled to a common potential, a signal source coupled to the transmission line input, the signal source providing an input signal to the transmission line, and a metal oxide varistor (MOV) coupled between the transmission line input and the common potential, the impedance of the MOV being inversely proportional to the voltage level at the transmission line input.

[0073] Example 2: In the system of Example 1, when the voltage level at the transmission line input is higher than the overvoltage limit, the MOV has high impedance, and when the voltage at the transmission line input is lower than the overvoltage limit, the MOV has low impedance.

[0074] Example 3: In the system of example 1, the MOV is operable to provide a short circuit path between the transmission line input and a common potential when the voltage level at the transmission line input is higher than the overvoltage limit.

[0075] Example 4: In the system of Example 1, the chamber includes a first region and a second region, the plasma is contained within the first region, and the transmission line is located within the second region.

[0076] Example 5: A system includes a chamber configured to generate and contain a plasma; a transmission line located within the chamber, the transmission line including a transmission line input and an output, the output coupled to a common potential; a signal source coupled to the transmission line input, the signal source providing an input signal to the transmission line; a resistor including a first terminal and a second terminal, the first terminal of the resistor coupled to the transmission line input; and a metal oxide varistor (MOV) including a first terminal and a second terminal, the first terminal of the MOV coupled to the second terminal of the resistor and the second terminal of the MOV coupled to the common potential.

[0077] Example 6: In the system of Example 5, the impedance of the MOV is inversely proportional to the voltage level at the transmission line input.

[0078] Example 7: In the system of Example 5, when the voltage level at the transmission line input is higher than the overvoltage limit, the MOV has high impedance, and when the voltage level at the transmission line input is lower than the overvoltage limit, the MOV has low impedance.

[0079] Example 8: In the system of example 5, the MOV is operable to provide a short circuit path between the transmission line input and a common potential when the voltage level at the transmission line input is higher than an overvoltage limit.

[0080] Example 9: In the system of Example 5, the chamber includes a first region and a second region, the plasma is contained within the first region, and the transmission line is located within the second region.

[0081] Example 10: A system includes a chamber configured to generate and contain a plasma; a transmission line located within the chamber, the transmission line including a transmission line input and an output, the output coupled to a common potential; a signal source coupled to the transmission line input, the signal source providing an input signal to the transmission line; a resistor including a first terminal and a second terminal, the first terminal of the resistor coupled to the transmission line input; a metal oxide varistor (MOV) including a first terminal and a second terminal, the first terminal of the MOV coupled to the second terminal of the resistor and the second terminal of the MOV coupled to the common potential; and an inductor including a first terminal and a second terminal, the first terminal of the inductor coupled to the transmission line input and the second terminal of the inductor coupled to the common potential.

[0082] Example 11: In the system of Example 10, the impedance of the MOV is inversely proportional to the voltage level at the transmission line input.

[0083] Example 12: In the system of Example 10, when the voltage level at the transmission line input is higher than the overvoltage limit, the MOV has high impedance, and when the voltage level at the transmission line input is lower than the overvoltage limit, the MOV has low impedance.

[0084] Example 13: A system includes: a chamber configured to generate and contain a plasma; a transmission line located within the chamber, the transmission line including a transmission line input and an output, the output coupled to a common potential; a signal source coupled to the transmission line input, the signal source providing an input signal to the transmission line; a resistor including a first terminal and a second terminal, the first terminal of the resistor coupled to the transmission line input; a metal oxide varistor (MOV) including a first terminal and a second terminal, the first terminal of the MOV coupled to the second terminal of the MOV; an inductor including a first terminal and a second terminal, the first terminal of the inductor coupled to the transmission line input and the second terminal of the inductor coupled to the second terminal of the MOV; and an overvoltage detection circuit including a first terminal coupled to the second terminal of the MOV and a second terminal coupled to the common potential.

[0085] Example 14: In the system of Example 13, the impedance of the MOV is inversely proportional to the voltage level at the transmission line input.

[0086] Example 15: In the system of Example 13, when the voltage level at the transmission line input is higher than the overvoltage limit, the MOV has high impedance.

[0087] Example 16: In the system of Example 13, when the voltage level at the transmission line input is less than the overvoltage limit, the MOV has a low impedance.

[0088] Example 17: In the system of example 13, the overvoltage detection circuit includes a rectifier coupled between the second terminal of the MOV and a common potential.

[0089] Example 18: In the system of example 17, the overvoltage detection circuit includes a capacitor coupled to the rectifier.

[0090] Example 19: In the system of example 18, the overvoltage detection circuit includes a resistor coupled in parallel with the capacitor.

[0091] Example 20: In the system of example 18, the overvoltage detection circuit includes a voltage level indicator coupled in parallel with the capacitor.

[0092] The Abstract is provided to allow the reader to ascertain the nature and gist of the technical disclosure. It is submitted with the understanding that it will not be used to limit the scope or meaning of the claims. The following claims are incorporated into the Detailed Description, with each claim standing on its own as a separate implementation.

Claims

1. It is a system, A chamber configured to generate and contain plasma, A transmission line located within the chamber, wherein the transmission line includes a transmission line input and an output, and the output is coupled to a transmission line at a common potential. A signal source coupled to the input of the transmission line, wherein the signal source supplies an input signal to the transmission line, A metal oxide varistor (MOV) coupled between the transmission line input and the common potential, wherein the impedance of the MOV is inversely proportional to the voltage level at the transmission line input, A system that includes these features.

2. The system according to claim 1, A system in which the MOV has high impedance when the voltage level at the transmission line input is higher than the overvoltage limit, and low impedance when the voltage level at the transmission line input is lower than the overvoltage limit.

3. The system according to claim 1, A system in which, when the voltage level at the transmission line input is higher than the overvoltage limit, the MOV is capable of operating to provide a short-circuit path between the transmission line input and the common potential.

4. The system according to claim 1, The chamber includes a first region and a second region, The plasma is contained within the first region, The transmission line is located within the second region of the system.

5. It is a system, A chamber configured to generate and contain plasma, A transmission line located within the chamber, wherein the transmission line includes a transmission line input and an output, and the output is coupled to a transmission line at a common potential. A signal source coupled to the input of the transmission line, wherein the signal source supplies an input signal to the transmission line, A resistor comprising a first terminal and a second terminal, wherein the first terminal of the resistor is coupled to the input of the transmission line. A metal oxide varistor (MOV) having a first terminal and a second terminal, wherein the first terminal of the MOV is coupled to the second terminal of the resistor, and the second terminal of the MOV is coupled to the common potential, A system that includes these features.

6. The system according to claim 5, The system wherein the impedance of the MOV is inversely proportional to the voltage level at the transmission line input.

7. The system according to claim 5, A system in which the MOV has high impedance when the voltage level at the transmission line input is higher than the overvoltage limit, and low impedance when the voltage level at the transmission line input is lower than the overvoltage limit.

8. The system according to claim 5, A system in which, when the voltage level at the transmission line input is higher than the overvoltage limit, the MOV is capable of operating to provide a short-circuit path between the transmission line input and the common potential.

9. The system according to claim 5, The chamber includes a first region and a second region, The plasma is contained within the first region, The transmission line is located within the second region of the system.

10. It is a system, A chamber configured to generate and contain plasma, A transmission line located within the chamber, wherein the transmission line includes a transmission line input and an output, and the output is coupled to a transmission line at a common potential. A signal source coupled to the input of the transmission line, wherein the signal source supplies an input signal to the transmission line, A resistor comprising a first terminal and a second terminal, wherein the first terminal of the resistor is coupled to the input of the transmission line. A metal oxide varistor (MOV) having a first terminal and a second terminal, wherein the first terminal of the MOV is coupled to the second terminal of the resistor, and the second terminal of the MOV is coupled to the common potential, An inductor including a first terminal and a second terminal, wherein the first terminal of the inductor is coupled to the transmission line input and the second terminal of the inductor is coupled to the common potential, A system that includes these features.

11. The system according to claim 10, The system wherein the impedance of the MOV is inversely proportional to the voltage level at the transmission line input.

12. The system according to claim 10, A system in which the MOV has high impedance when the voltage level at the transmission line input is higher than the overvoltage limit, and low impedance when the voltage level at the transmission line input is lower than the overvoltage limit.

13. It is a system, A chamber configured to generate and contain plasma, A transmission line located within the chamber, wherein the transmission line includes a transmission line input and an output, and the output is coupled to a transmission line at a common potential. A signal source coupled to the input of the transmission line, wherein the signal source supplies an input signal to the transmission line, A resistor comprising a first terminal and a second terminal, wherein the first terminal of the resistor is coupled to the input of the transmission line. A metal oxide varistor (MOV) including a first terminal and a second terminal, wherein the first terminal of the MOV is coupled to the second terminal of the MOV, An inductor including a first terminal and a second terminal, wherein the first terminal of the inductor is coupled to the transmission line input, and the second terminal of the inductor is coupled to the second terminal of the MOV, An overvoltage detection circuit including a first terminal connected to the second terminal of the MOV and a second terminal connected to the common potential, A system that includes these features.

14. The system according to claim 13, The system wherein the impedance of the MOV is inversely proportional to the voltage level at the transmission line input.

15. The system according to claim 13, A system in which the MOV has high impedance when the voltage level at the transmission line input is higher than the overvoltage limit.

16. The system according to claim 13, A system in which the MOV has low impedance when the voltage level at the transmission line input is lower than the overvoltage limit.

17. The system according to claim 13, The overvoltage detection circuit is a system that includes a rectifier coupled between the second terminal of the MOV and the common potential.

18. The system according to claim 17, The overvoltage detection circuit is a system that includes a capacitor coupled to the rectifier.

19. The system according to claim 18, The overvoltage detection circuit is a system that includes a resistor coupled in parallel with the capacitor.

20. The system according to claim 18, The overvoltage detection circuit is a system that includes a voltage level indicator coupled in parallel with the capacitor.

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