RF filters for multi-frequency radio frequency (RF) biasing

Abstract

The radio frequency (RF) filter includes an inductive element having multiple coil sections that collectively form an undivided coil of twisted magnetic wire cable. At least two adjacent coil sections have different winding pitches. The twisted magnetic wire cable includes two wires per channel and is configured for at least one channel. The twisted magnetic wire cable is configured at the first end of the inductive element for connection to an electrical component that will receive power from a power source. The twisted magnetic wire cable is configured at the second end of the inductive element for connection to a power source. Termination capacitive elements are electrically connected between the reference ground potential and each wire of the twisted magnetic wire cable at each location between the second end of the inductive element and the power source.

Description

Technical Field

[0001] This disclosure relates to semiconductor manufacturing equipment.

Background Art

[0002] In various semiconductor manufacturing processes, radio frequency (RF) power is transmitted to a processing chamber to generate plasma and / or to generate a bias voltage. One or more other electrical components, such as a heater assembly, can be operated while being exposed to RF power. For example, the heater assembly can be configured and arranged to heat components or regions within the processing chamber. The RF power used to generate plasma and / or the bias voltage can interfere with and / or damage the power supply. It is necessary to prevent the RF power from interfering with the power supply and / or damaging the power supply. In addition, when a heater power supply is connected to a heating element embedded in an RF electrode within the processing chamber, the RF power can be loaded and its efficiency can be reduced. An RF filter is necessary to isolate the RF electrode from a heater power supply that can be either AC (alternating current) or DC (direct current), thereby allowing AC power or DC power to be provided to the heating element within the RF electrode without RF power entering the AC or DC supply path. This disclosure arises in such a situation.

Summary of the Invention

[0003] In an exemplary embodiment, a radio frequency (RF) filter is disclosed. The RF filter includes an inductive element comprising at least two coil sections that collectively form an undivided coil of twisted magnetic wire cable. Each coil section includes a portion configured with a corresponding winding pitch as part of the undivided coil of twisted magnetic wire cable. At least two adjacent coil sections have different winding pitches. The twisted magnetic wire cable comprises two wires per channel and is configured for at least one channel. The twisted magnetic wire cable is configured at a first end of the inductive element for connection to an electrical component. The electrical component will receive power from a power source, which is either a DC power source or an AC power source. The twisted magnetic wire cable is configured at a second end of the inductive element for connection to the power source. The RF filter also includes a set of termination capacitance elements, each of which is a separate termination capacitance element for each wire of the twisted magnetic wire cable. Each termination capacitance element is electrically connected between a reference ground potential and the respective wire of the twisted magnetic wire cable at a location between the second end of the inductive element and the power source.

[0004] In an exemplary embodiment, a method for filtering RF power is disclosed. The method includes having an RF filter between a power source and an electrical component that will receive power from this power source. The power source is either a DC power source or an AC power source. The RF filter includes an inductive element having at least two coil sections that collectively form an undivided coil of twisted magnetic wire cable. Each coil section includes a portion configured with a corresponding winding pitch as part of the undivided coil of the twisted magnetic wire cable. At least two adjacent coil sections have different winding pitches. The twisted magnetic wire cable includes two wires per channel and is configured for at least one channel. The twisted magnetic wire cable is connected to an electrical component at a first end of the inductive element. The twisted magnetic wire cable is connected to a power source at a second end of the inductive element. The RF filter also includes a separate termination capacitance element for each wire of the twisted magnetic wire cable. Each termination capacitance element is electrically connected between a reference ground potential and the respective wire of the twisted magnetic wire cable at a location between the second end of the inductive element and the power source.

[0005] In exemplary embodiments, a method for filtering RF power is disclosed. The method includes transmitting power from a power source to wires in an input configuration. The wires are connected to their respective capacitive elements. Each distinct pair of wires is designated to power an electrical component exposed to the RF power. The method also includes, at the input of an inductive element, transmitting power from wires in an input configuration to corresponding magnetic wires in a cable of twisted magnetic wires. The inductive element includes at least two coil sections that collectively form an undivided coil of the cable of twisted magnetic wires between the input and output of the inductive element. Each coil section includes a portion configured with a corresponding winding pitch as part of the undivided coil of the cable of twisted magnetic wires. At least two adjacent coil sections have different winding pitches. The method also includes, at the output of the inductive element, transmitting power from magnetic wires in the cable of twisted magnetic wires to corresponding wires connected to an electrical component exposed to the RF power.

[0006] Other embodiments and advantages will become further apparent from the following detailed description, in conjunction with the accompanying drawings provided as examples. [Brief explanation of the drawing]

[0007] [Figure 1A] Figure 1A is an exemplary vertical cross-sectional view of a CCP processing chamber according to several embodiments of the present disclosure.

[0008] [Figure 1B] Figure 1B is an exemplary vertical cross-sectional view of an ICP processing chamber according to several embodiments of the present disclosure.

[0009] [Figure 1C] Figure 1C is a top view of an exemplary heater assembly, comprising four concentrically configured and positioned heating elements, according to several embodiments of the present disclosure.

[0010] [Figure 2]Figure 2 is an electrical circuit diagram of an RF filter connected between a power supply and a heater assembly in an exemplary embodiment of Figure 1C, according to some embodiments of the present disclosure.

[0011] [Figure 3A] Figure 3A is an isometric view of an inductor according to some embodiments of the present disclosure.

[0012] [Figure 3B] Figure 3B shows a bare coil form according to some embodiments of the present disclosure.

[0013] [Figure 3C] Figure 3C shows an undivided coil of twisted magnetic wire cable, formed by winding a twisted magnetic wire cable around a coil form, according to some embodiments of the present disclosure.

[0014] [Figure 3D] Figure 3D is a vertical cross-sectional view passing through the center of an inductor according to some embodiments of the present disclosure.

[0015] [Figure 4] Figure 4 shows a plot of impedance as a function of RF frequency at the higher primary RF frequency of 13.56 MHz for each of the wires supplying current flow to a given heating element in a heater assembly, according to some embodiments of the present disclosure.

[0016] [Figure 5] Figure 5 shows a plot of impedance as a function of RF frequency at the lower primary RF frequency of 1 MHz for each of the wires supplying current flow to a given heating element in a heater assembly, according to some embodiments of the present disclosure.

[0017] [Figure 6]FIG. 6 is a diagram presenting a method for filtering RF power according to some embodiments of the present disclosure.

[0018] [Figure 7] FIG. 7 is a diagram presenting a method for filtering RF power according to some embodiments of the present disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present disclosure. However, it will be apparent to one of ordinary skill in the art that the embodiments of the present disclosure may be practiced without some or all of these specific details. In other instances, well-known process operations have not been described in detail in order not to unnecessarily obscure the present disclosure.

[0020] In the semiconductor industry, semiconductor substrates can be manufactured in various types of plasma chambers, including capacitively coupled plasma (CCP) and inductively coupled plasma (ICP) chambers. Both CCP and ICP chambers use radio frequency (RF) power to energize a process gas, converting it into plasma. Reactive and / or charged species in the plasma interact with the substrate to modify its state, for example, by modifying existing material, depositing material onto the substrate, or removing / etching material from the substrate. CCP and ICP chambers may also include one or more electrodes that receive RF power to generate a bias voltage for accelerating charged species from the plasma towards the substrate. CCP and ICP chambers may also include one or more powered components (such as heater assemblies) that receive power from one or more power sources, each of which may be either DC (direct current) or AC (alternating current). It is necessary to prevent the RF power used to generate the plasma and / or bias voltage from being transmitted to the power supply (DC or AC power) used to power one or more motorized components (such as a heater assembly). Various embodiments of RF filters and associated inductors disclosed herein are suitable for preventing RF power related to the operation of the CCP processing chamber and ICP processing chamber from being transmitted to the DC and / or AC power supply.

[0021] FIG. 1A shows an exemplary vertical cross-sectional view of a CCP processing chamber 101 according to some embodiments of the present disclosure. The CCP processing chamber 101 defines a processing volume in which a plasma 123 is generated during exposure of the substrate 105 in order to affect changes in the substrate 105 in a controlled manner. In various manufacturing processes, the changes in the substrate 105 can be changes in the material or surface condition on the substrate 105. For example, in various manufacturing processes, the changes in the substrate 105 can include one or more of etching of material from the substrate 105, deposition of material onto the substrate 105, or modification of the material 105 present on the substrate 105. In some embodiments, the substrate 105 is a semiconductor wafer undergoing a manufacturing process. However, it should be understood that in various embodiments, the substrate 105 can be essentially any type of substrate that is subjected to a manufacturing process using plasma. For example, in some embodiments, the substrate 105 as used herein refers to a substrate formed of silicon, sapphire, GaN, GaAs or SiC, or other substrate materials, and can include glass panels / substrates, metal foils, metal sheets, polymer materials, and the like. Also, in various embodiments, the substrate 105 referred to herein can have different forms, shapes, and / or sizes. For example, in some embodiments, the substrate 105 referred to herein can correspond to a 200 mm (millimeter) semiconductor wafer, a 300 mm semiconductor wafer, or a 450 mm semiconductor wafer. Also, in some embodiments, the substrate 105 referred to herein can correspond to a non-circular substrate such as, among other various shapes, a rectangular substrate for a flat panel display.

[0022] In various embodiments, the CCP processing chamber 101 operates by flowing one or more process gases into the processing volume during exposure of the substrate 105 to influence a change in the material or surface state on the substrate 105, and by applying RF power to these one or more process gases to convert them into plasma 123. The CCP processing chamber 101 includes a substrate support structure 103 in which the substrate 105 is positioned and supported during the processing operation. In some embodiments, an electrode 107 is located within the substrate support structure 103 and transmits RF power from the electrode 107 through the processing volume to generate and / or control the ion energy of the plasma 123. The electrode 107 is connected to receive RF power through an RF power supply structure 109, which is connected to one or more RF power generators 111 via one or more impedance matching systems 113. The impedance matching system 113 includes a capacitor and inductor configuration, which is configured such that the impedance seen by the RF power generator 111 at the input of the impedance matching system 113 is sufficiently close to the output impedance (typically 50 ohms) for which the RF power generator 111 is designed to operate. As a result, the RF power generated and transmitted by the RF power generator 111 is efficiently transmitted to the processing volume (e.g., without unacceptable or undesirable reflections).

[0023] In some embodiments, an upper electrode 115 may also be provided. In various embodiments, the upper electrode 115 can provide an electrical ground electrode or can be used to transmit RF power to a processing volume. In some embodiments, the upper electrode 115 is connected to receive RF power through an RF feeding structure 117, which is connected to one or more RF power generators 121 via one or more impedance matching systems 119. The impedance matching system 119 includes a capacitor and inductor configuration, which is configured such that the impedance seen by the RF power generator 121 at the input of the impedance matching system 119 is sufficiently close to the output impedance (typically 50 ohms) on which the RF power generator 121 is designed to operate. As a result, the RF power generated and transmitted by the RF power generator 121 is transmitted efficiently (e.g., without unacceptable or undesirable reflections) to the processing volume.

[0024] In some embodiments, a heater assembly 125 is located within a substrate support structure 103 to control the temperature of the substrate 105. The heater assembly 125 is electrically connected to receive power through an electrical connection 127, which is supplied from a power supply 131 through the electrical connection 137 to an RF filter 129 and then back to the electrical connection 127 through the RF filter 129. In some embodiments, the power supply 131 is an alternating current (AC) power supply. In some embodiments, the power supply 131 is a direct current (DC) power supply. In some embodiments, the heater assembly 125 includes multiple electrical resistance heating elements. The RF filter 129 is configured to prevent RF power from entering the power supply 131 while allowing current transmission between the power supply 131 and the electrical connection 127.

[0025] In some embodiments, the heater assembly 125 includes multiple heating elements. Figure 1C is a top view of an exemplary heater assembly 125, including four concentrically configured and positioned heating elements 132, 133, 134, and 135, according to some embodiments of the present disclosure. Heating element 132 corresponds to an inner heating zone substantially centered horizontally with respect to the region of a substrate support structure 103 configured to receive and support a substrate 105. Heating element 133 corresponds to an intermediate inner heating zone configured to radially surround the inner heating zone. Heating element 134 corresponds to an intermediate outer heating zone configured to radially surround the intermediate inner heating zone. Heating element 135 corresponds to an outer heating zone configured to radially surround the intermediate outer heating zone. In the exemplary heater assembly 125 of Figure 1C, each of the heating elements 132, 133, 134, and 135 is connected to receive separate, independently controlled power from a power supply 131. More specifically, each of the heating elements 132, 133, 134, and 135 is exclusively connected to two wires in the electrical connection 127. Thus, to accommodate the four heating elements 132, 133, 134, and 135, the electrical connection 127 includes eight wires 132A, 132B, 133A, 133B, 134A, 134B, 135A, and 135B, as shown in Figure 1C. In the example in Figure 1C, each of the eight wires 132A, 132B, 133A, 133B, 134A, 134B, 135A, and 135B is connected via the RF filter 129 to eight wires 137A, 137B, 137C, 137D, 137E, 137F, 137G, and 137H (137A-137H), respectively, forming an electrical connection 137 between the power supply 131 and the RF filter 129. It should be understood that the heater assembly 125 in Figure 1C is shown as an example. In various embodiments, the heater assembly 125 may include fewer than four heating elements or more than four heating elements, each heating element having its own dedicated wire pair (wire pair) for receiving power from the power supply 131 through the RF filter 129.

[0026] Figure 1B shows an exemplary vertical cross-sectional view of an ICP processing chamber 151 according to several embodiments of the present disclosure. An ICP processing chamber may also be called a transformer-coupled plasma (TCP) processing chamber. For ease of explanation, the term ICP processing chamber will be used here to refer to both ICP processing chambers and TCP processing chambers. The ICP processing chamber 151 defines the processing volume generated during the exposure of the plasma 123 to the substrate 105 in order to influence the changes of the substrate 105 in a controlled manner. In various manufacturing processes, the changes of the substrate 105 may be changes in the material or surface state on the substrate 105. For example, in various manufacturing processes, the changes of the substrate 105 may include one or more of the etching of material from the substrate 105, the deposition of material onto the substrate 105, or the modification of the material 105 present on the substrate 105.

[0027] It should be understood that the ICP processing chamber 150 can be any type of ICP processing chamber in which RF power is transmitted from a coil 155 located outside the ICP processing chamber 151 to a process gas inside the ICP processing chamber 151, generating plasma 123 inside the ICP processing chamber 151. The upper window structure 153 is provided to allow RF power to be transmitted from the coil 155 through the upper window structure 153 to the processing volume of the ICP processing chamber 151. The ICP processing chamber 150 operates by flowing one or more process gases into the processing volume while the substrate 105 is exposed to influence a change in the material or surface state on the substrate 105, and by applying RF power from the coil 155 to these one or more process gases to convert them into plasma 123. The coil 155 is located above the upper window structure 153. In the example in Figure 1B, the coil 155 is formed as a radial coil assembly, with the shaded portion of the coil 155 indicating the direction from front to back on the page of the drawing, and the unshaded portion indicating the direction from back to front on the page of the drawing. However, it should be understood that in other embodiments, the coil 155 can have essentially any configuration suitable for transmitting RF power through the upper window structure 153 to the plasma processing volume. In various embodiments, the coil 155 can have any number of turns as well as any cross-sectional size and shape (circular, elliptical, rectangular, trapezoidal, etc.) as needed to transmit RF power to the processing volume through the upper window structure 153 as desired.

[0028] The coil 155 is connected to one or more RF power generators 157 via one or more impedance matching systems 159 through an RF power supply structure 161. The impedance matching system 159 includes a capacitor and / or inductor configuration, which is configured such that the impedance seen by the RF power generator 157 at the input of the impedance matching system 159 is sufficiently close to the output impedance (typically 50 ohms) on which the RF power generator 157 is designed to operate. As a result, the RF power supplied to the coil 155 by the RF power generator 157 is efficiently (i.e., without unacceptable or undesirable reflections) transmitted to the processing volume. In some embodiments, the ICP processing chamber 151 may also include electrodes 107, an RF power supply structure 109, an impedance matching system 113, and an RF power generator 111, as previously described with respect to Figure 1A.

[0029] In some embodiments, the ICP processing chamber 151 may also include a heater assembly 125 located within the substrate support structure 103 to control the temperature of the substrate 105. As described with respect to the CCP processing chamber 101 in Figure 1A, the heater assembly 125 of the ICP processing chamber 151 is electrically connected to receive power through an electrical connection 127, which is supplied from a power supply 131 through the electrical connection 137 to an RF filter 129, and then through the RF filter 129 to the electrical connection 127.

[0030] Figure 2 shows an electrical circuit diagram of an RF filter 129 connected between a power supply 131 and a heater assembly 125 in an exemplary embodiment of Figure 1C, according to some embodiments of the present disclosure. The RF filter 129 includes separate wires for each wire connected between the power supply 131 and the heater assembly 125. Specifically, the RF filter 129 includes a wire 142A connecting wire 137A from the output of the power supply 131 to wire 132A connected to the input to the heater assembly 125. The RF filter 129 also includes a wire 142B connecting wire 137B from the output of the power supply 131 to wire 132B connected to the input to the heater assembly 125. The RF filter 129 also includes a wire 142C connecting wire 137C from the output of the power supply 131 to wire 133A connected to the input to the heater assembly 125. The RF filter 129 also includes a wire 142D connecting wire 137D from the output of the power supply 131 to wire 133B connected to the input to the heater assembly 125. The RF filter 129 also includes wire 142E, which connects wire 137E from the output of power supply 131 to wire 134A, which is connected to the input to heater assembly 125. The RF filter 129 also includes wire 142F, which connects wire 137F from the output of power supply 131 to wire 134B, which is connected to the input to heater assembly 125. The RF filter 129 also includes wire 142G, which connects wire 137G from the output of power supply 131 to wire 135A, which is connected to the input to heater assembly 125. The RF filter 129 also includes wire 142H, which connects wire 137H from the output of power supply 131 to wire 135B, which is connected to the input to heater assembly 125.

[0031] Each of the wires 142A, 142B, 142C, 142D, 142E, 142F, 142G, and 142H (142A-142H) passing through the RF filter 129 forms part of the inductor 141 within the RF filter 129. At the first end of the inductor 141, each of the wires 142A-142H is connected to the heater assembly 125 through an electrical connection 127. At the second end of the inductor 141, each of the wires 142A-142H is connected to the power supply 131 through an electrical connection 137. Within the inductor 141, the wires 142A-142H are twisted together to form a cable of twisted magnetic wire 142 that can be operated mechanically and spatially as a single cable. Within the inductor 141, the cable of twisted magnetic wire 142 is formed in a helical coil shape extending between the first end of the inductor 141 (the side with the electrical connection 127 connected to the heater assembly 125) and the second end of the inductor 141 (the side with the electrical connection 137 connected to the power supply 131). Each of the wires 142A-142H is formed as a conductor coated with an electrical insulating coating material. Thus, when the wires 142A-142H are twisted together to form the cable of twisted magnetic wire 142, the electrical insulating coating material of each wire 142A-142H prevents inter-wire conduction of low-frequency currents such as direct current (DC) and alternating current (AC) associated with power transmission. In some embodiments, the electrical insulating coating material of each wire 142A-142H is a semi-permeable material to RF power that may propagate along the wire 142A-142H. In these embodiments, RF power can travel along the cable of the twisted magnetic wire 142 as if it were traveling through a monolithic conductor cable, while low-frequency (DC / AC) currents flowing simultaneously through wires 142A-142H are prevented from flowing between wires 142A-142H within the cable of the twisted magnetic wire 142. This reduces, or even eliminates, channel-to-channel impedance variations in the RF filter 129. In the RF filter 129, a given channel corresponds to a given pair of wires 142A-142H that supply current flow to a given heating element 132, 133, 134, 135 in the heater assembly 125.In some embodiments, wires 142A-142H are copper wires coated with a high-temperature electrical insulating polymer material. However, it should be understood that in various embodiments, wires 142A-142H can be formed from conductive materials other than copper and coated with electrical insulating coating materials other than the high-temperature electrical insulating polymer material.

[0032] Each of the wires 142A-142H is electrically connected to the respective termination capacitors 143A, 143B, 143C, 143D, 143E, 143F, 143G, 143H (143A-143H) at the respective locations between the inductor 141 and the electrical connection 137 to the power supply 131. Specifically, wire 142A is electrically connected to the first terminal of termination capacitor 143A through wire 144A, and the second terminal of termination capacitor 143A is electrically connected to the reference ground potential 145. Wire 142B is electrically connected to the first terminal of termination capacitor 143B through wire 144B, and the second terminal of termination capacitor 143B is electrically connected to the reference ground potential 145. Wire 142C is electrically connected to the first terminal of termination capacitor 143C through wire 144C, and the second terminal of termination capacitor 143C is electrically connected to the reference ground potential 145. Wire 142D is electrically connected to the first terminal of termination capacitor 143D through wire 144D, and the second terminal of termination capacitor 143D is electrically connected to the reference ground potential 145. Wire 142E is electrically connected to the first terminal of termination capacitor 143E through wire 144E, and the second terminal of termination capacitor 143E is electrically connected to the reference ground potential 145. Wire 142F is electrically connected to the first terminal of termination capacitor 143F through wire 144F, and the second terminal of termination capacitor 143F is electrically connected to the reference ground potential 145. Wire 142G is electrically connected to the first terminal of termination capacitor 143G through wire 144G, and the second terminal of termination capacitor 143G is electrically connected to the reference ground potential 145. Wire 142H is electrically connected to the first terminal of termination capacitor 143H through wire 144H, and the second terminal of termination capacitor 143H is electrically connected to the reference ground potential 145. Between the electrical connection 137 to the power supply 131 and the inductor 141, wires 142A-142H, wires 144A-144H, termination capacitors 143A-143H, and the reference ground potential 145 can be collectively referred to as the input configuration of the RF filter 129.

[0033] The termination capacitors 143A-143H, when present in combination with the inductor 141, have sufficiently high capacitance to ensure that the RF power entering the RF filter 129 from the heater assembly 125 follows a transmission path to the reference ground potential 145 rather than the power supply 131. In some embodiments, each of the termination capacitors 143A-143H has a capacitance ranging from approximately 3000 picofarads (pF) to approximately 5000 pF, or approximately 0.1 microfarads (μF). Furthermore, because the termination capacitors 143A-143H have such large capacitances, manufacturing variations in the termination capacitors 143A-143H do not essentially affect the impedance uniformity between channels. Thus, manufacturing variations in the termination capacitors 143A-143H do not essentially affect the overall impedance uniformity between units (between RF filters 129 and RF filters 129).

[0034] Figure 3A shows an isometric view of an inductor 141 according to several embodiments of the present disclosure. The exemplary inductor 141 in Figure 3A is configured to be used in conjunction with the exemplary heater assembly 125 in Figure 1C to filter RF power of two different RF frequencies. The inductor 141 includes a coil form 305 formed of an electrical insulating material. In some embodiments, the electrical insulating material of the coil form 305 is a polymer material that can withstand high temperatures. For example, in some embodiments, the electrical insulating material of the coil form 305 is a tetrafluoroethylene fluoropolymer such as polytetrafluoroethylene (PTFE), e.g., Teflon®. However, it should be understood that in other embodiments, the electrical insulating material of the coil form 305 may be any other solid material that is electrically nonconductive, can withstand the operating temperature of the twisted magnetic wire 142 cable, and is chemically compatible with the twisted magnetic wire 142 cable and other interface materials when installed to operate in a plasma processing chamber. For example, in some embodiments, the electrical insulating material of the coil form 305 may be one or more of the following: acrylonitrile-butadiene-styrene (ABS), acetate, acrylic, beryllium oxide, ceramic, Delrin™, epoxy, glass fiber, glass, Kynar™, Lexan™, Merlon™, melamine, mica, Nomex™, nylon, polyethylene terephthalate (PET), phenolic resin, polyester, polyolefin, polystyrene, polyurethane, polyvinyl chloride (PVC), thermoplastic resin, polysulfone, polyetherimide, polyamideimide, polyphenylene, Noryl™, Ultem™, Udel™, Vespel™, Torlon™, vinyl, etc.

[0035] The exemplary coil form 305 in Figure 3A is formed as a hollow cylinder having an inner diameter 307 and an outer diameter 309. Since the twisted magnetic wire 142 cable is wound around the outer surface of the coil form 305, it should be understood that the inductance of the inductor 141 is a partial function of the outer diameter 309 of the coil form 305. In various embodiments, the outer diameter 309 of the coil form 305 ranges from approximately 4 inches to approximately 6 inches.

[0036] In some embodiments, the inner diameter 307 of the coil form 305 is defined to provide a cooling airflow through the coil form 305. The inner diameter 307 of the coil form 305 is also defined to provide sufficient mechanical strength for the coil form 305 to provide a rigid structure for maintaining the spatial configuration of the twisted magnetic wire 142 coiled on the outer surface of the coil form 305. Furthermore, the inner diameter 307 of the coil form 305 can be defined to reduce the overall weight of the inductor 141, which may benefit the physical mounting of the inductor 141. In various embodiments, the inner diameter 307 of the coil form 305 ranges from approximately 3 inches to approximately 5 inches.

[0037] Generally, the inductor 141 includes a number of coil sections corresponding to several substantially different RF frequencies to be filtered by the RF filter 129. In the example in Figure 3A, the inductor 141 is configured to filter RF power at two substantially different RF frequencies. Thus, the exemplary inductor 141 in Figure 3A has two coil sections, namely a first coil section 301 and a second coil section 303. Each coil section of the inductor 141, e.g., 301, 303, extends along the respective portion of the axial length of the inductor 141. In the example in Figure 3A, the axial length of the inductor 141 is measured in the z direction, and the inner diameter 307 and outer diameter 309 are measured in the x-y plane. Each coil section of the inductor 141, e.g., 301, 303, is configured to have a specific inductance characteristic defined to filter RF power at a specific RF frequency or a frequency near the frequency to which filtering by the RF filter 129 is intended.

[0038] The specific inductance provided by a given coil section of the inductor 141, for example, 301, 303, is a function of the outer diameter 309 of the coil form 305, the axial length of the given coil section, the winding pitch between adjacent windings of the twisted magnetic wire 142 cable (wound around the coil form 305) within the given coil section, and the number of windings of the twisted magnetic wire 142 cable (wound around the coil form 305) within the given coil section. In the example of Figure 3A, the first coil section 301 has a winding pitch 311 measured between adjacent windings of the twisted magnetic wire 142 cable, and the second coil section 303 has a winding pitch 313 measured between adjacent windings of the twisted magnetic wire 142 cable. It should be understood that the winding pitch is measured between adjacent windings of the twisted magnetic wire 142 cable wound around the coil form 305, parallel to the z-direction between the centerlines of the twisted magnetic wire 142 cable, and at the same azimuthal angle position around the z-axis of the coil form 305. The winding pitch between adjacent windings of the twisted magnetic wire 142 cable in a given coil section, e.g., 301, 303, e.g., 311, 313, affects the resonant frequency of that given coil section. In other words, the winding pitch between adjacent windings of the twisted magnetic wire 142 cable in a given coil section, e.g., 311, 313, e.g., 311, 313, e.g., determines the RF frequency filtered by that given coil section. The smaller the winding pitch between adjacent windings of the twisted magnetic wire 142 cable in a given coil section, e.g., 301, 303, e.g., 311, 313, e.g., 311, 313, e.g., 301, 3001, 303, Furthermore, the larger the winding pitch between adjacent windings of the twisted magnetic wire 142 cable in a given coil section, for example, 301, 303, for example, 311, 313, the lower the inductance provided in that given coil section.

[0039] To obtain a specific impedance for a given coil section, for example, 301, 303, less inductance is required within the given coil section for higher RF frequencies, and more inductance is required within the given coil section for lower RF frequencies. Therefore, to obtain a specific impedance for a given coil section, for example, 301, 303, less inductance is required within the given coil section for higher RF frequencies, which corresponds to the larger winding pitch between adjacent windings of the twisted magnetic wire 142 cable in the given coil section, for example, 301, 303, for example, 311, 313. And to obtain a specific impedance for a given coil section, for example, 301, 303, more inductance is required within the given coil section for lower RF frequencies, which corresponds to the smaller winding pitch between adjacent windings of the twisted magnetic wire 142 cable in the given coil section, for example, 301, 303, for example, 311, 313. Therefore, in the exemplary inductor 141 of Figure 3A, the first coil section 301, which has a larger winding pitch 311 between adjacent windings of the twisted magnetic wire 142 cable, provides lower inductance and resonates with the higher RF frequency. And, in the exemplary inductor 141 of Figure 3A, the second coil section 303, which has a smaller winding pitch 313 between adjacent windings of the twisted magnetic wire 142 cable, provides higher inductance and resonates with the lower RF frequency. It should be understood that the twisted magnetic wire 142 cable is continuous throughout the entire inductor 141, from the first end of the inductor 141 connected to the heater assembly 125 to the second end of the inductor 141 connected to the power supply 131. Therefore, at each transition between adjacent coil sections, for example, between 301 and 303, the twisted magnetic wire 142 cable is wound onto the coil form 305 without interruption, while adjusting the winding pitch between adjacent windings of the twisted magnetic wire 142 cable.

[0040] Figure 3B shows a bare coil form 305 according to some embodiments of the present disclosure. Figure 3C shows an undivided coil of twisted magnetic wire 142 cables formed by winding the twisted magnetic wire 142 cables around the coil form 305, according to some embodiments of the present disclosure. In the example of Figure 3B, continuous grooves are formed on the outer surface of the coil form 305 to precisely position the twisted magnetic wire 142 cables around the coil form 305 and maintain the spatial configuration of the undivided coil of twisted magnetic wire 142 cables formed by winding the twisted magnetic wire 142 cables around the coil form 305. Figure 3B shows that this continuous groove includes a first groove portion 315 formed within the first coil section 301 and a second groove portion 317 formed within the second coil section 303, with a smooth transition between the first groove portion 315 and the second groove portion 317 at the transition between the first coil section 301 and the second coil section 303. However, it should be understood that in other embodiments, the coil form 305 can be constructed without a continuous groove on its outer surface. For example, in some embodiments, the coil form 305 may have a substantially smooth outer surface and may use electrical insulating spacers to separate adjacent windings of the twisted magnetic wire 142 cable wound around the coil form 305. In these embodiments, the electrical insulating spacers may be formed from essentially any material available for forming the coil form 305, such as those listed above as examples.

[0041] The illustrated exemplary coil form 305 has a right cylindrical outer surface (except for the presence of continuous grooves), but it should be understood that in other embodiments, the outer surface of the coil form 305 can have other cross-sectional shapes in the x-y plane, such as elliptical, rectangular, square, triangular, polygonal, star-shaped, x-shaped, or cross-shaped. Also, in some embodiments, the cross-sectional shape and / or size of the outer surface of the coil form 305 in the x-y plane may differ / change along the axial length of the coil form 305. For example, the cross-sectional shape and / or size of the outer surface of the coil form 305 in the x-y plane may differ / change for each coil section, e.g., 301, 303. For example, in some embodiments, the coil form 305 can be configured to have a first value of outer diameter 309 for the first coil section 301 and a second value of outer diameter 309 for the second coil section 303, in which case the second value of outer diameter 309 is different from the first value of outer diameter 309. Furthermore, it should be understood that in some embodiments, the coil form 305 of the inductor 141 may have a solid configuration without a hollow internal region.

[0042] In addition, each coil section of the inductor 141, for example, 301, 303, may include one or more windings of twisted magnetic wire 142. For example, in the inductor 141, as shown in Figure 3A, the first coil section 301 has one winding of twisted magnetic wire 142, and the second coil section 303 has two windings of twisted magnetic wire 142. Figure 3D shows a vertical cross-sectional view through the center of the inductor 141 according to some embodiments of the present disclosure. Figure 3D shows the twisted magnetic wire 142 being wound in various ways around the coil form 305. The first coil section 301 shown in Figure 3D has one winding of twisted magnetic wire 142. The second coil section 303 shown in Figure 3D also has two windings of twisted magnetic wire 142. Specifically, the second coil section 303 has a first winding layer 303A of twisted magnetic wire 142 cable formed on the outer surface of the coil form 305, and a second winding layer 303B of twisted magnetic wire 142 cable formed outside / on top of the first winding layer 303A of twisted magnetic wire 142 cable. It should be recognized and understood that in various embodiments, any coil section of the inductor 141, e.g., 301, 303, may be configured to include one or more winding layers of twisted magnetic wire 142 cable to provide a desired level of inductance. It should also be understood that having multiple winding layers of twisted magnetic wire 142 cable in a given coil section, e.g., 301, 303, reduces the overall size of the inductor 141 and provides higher inductance to the given coil section compared to a case where the total length of the twisted magnetic wire 142 cable is the same and there is only one winding layer.

[0043] In an exemplary embodiment, the inductor 141 is configured to filter RF frequencies of 1 MHz or approximately 1 MHz and 13.56 MHz or approximately 13.56 MHz. In this exemplary embodiment, the first coil section 301, which is the larger winding pitch 311 between adjacent windings of the twisted magnetic wire 142 cable, is configured to filter the higher 13.56 MHz RF frequency. The second coil section 303, which is the smaller winding pitch 313 between adjacent windings of the twisted magnetic wire 142 cable, is configured to filter the lower 1 MHz RF frequency. In this exemplary embodiment, the first coil section 301 includes a cable of 13 turns of twisted magnetic wire 142. In this embodiment, the first winding layer 303A of the second coil section 303 includes a cable of 21 turns of twisted magnetic wire 142. In this embodiment, the second winding layer 303B of the second coil section 303 includes a cable of 18 turns of twisted magnetic wire 142. In addition, in this exemplary embodiment, each of the termination capacitors 143A-143H has a capacitance value of about 0.1 microfarads.

[0044] The inductor 141 can be configured to filter two or more different RF frequencies, and it should be noted that the frequencies of 1 MHz and 13.56 MHz in the exemplary embodiment described above are stated as examples. For example, if we assume that the inductor 141 is configured to filter three different RF frequencies (e.g., 400 kHz, 1 MHz, and 13.56 MHz), then the inductor 141 would consist of three coil sections (e.g., coil sections 301, 303, and another coil section extending from coil section 303). The winding pitch between adjacent turns of the twisted magnetic wire 142 cable can also differ in each of the three coil sections so as to be suitable for resonating with each of the three different RF frequencies. The number of turns of the twisted magnetic wire 142 cable in each of the three coil sections can be appropriately set to establish the desired inductance in each of the three coil sections. Furthermore, as described above, in some embodiments, the outer diameter 309 of the coil form 305 may differ in one or more of the three coil sections, if appropriate to obtain the desired inductance in a particular coil section.

[0045] In some embodiments, the inductor 141 has two coil sections 301 and 303, and the coil section 301 has the larger winding pitch 311 as the winding pitch between adjacent windings of the twisted magnetic wire 142 cable, then the number of turns in coil section 301 is in the range of about 10 to about 15. Also in this embodiment, the number of turns in coil section 303 is in the range of about 20 to about 25. Also in this embodiment, the winding pitch 311 between adjacent windings of the twisted magnetic wire 142 cable in coil section 301 is in the range of about 0.4 inches to about 0.6 inches. Also in this embodiment, the winding pitch 313 between adjacent windings of the twisted magnetic wire 142 cable in coil section 303 is in the range of about 0.2 inches to about 0.3 inches.

[0046] Figure 3D also shows how the inductor 141 may be arranged within the outer housing 319. The outer housing 391 physically protects the inductor 141 and mounts the inductor 141 to other equipment associated with the plasma processing chamber and / or racks, chassis, boxes, housings, etc. for the equipment. In some embodiments, the outer housing 319 is configured as a substantially cylindrical structure having a flange 319A at at least one end for mounting to another surface. Also in some embodiments, the outer housing 319 may have a built-in enclosure 320 for housing termination capacitors, e.g., 143A-143H, and connectors for receiving power from the power supply 131. However, it should be understood that in other embodiments, the outer housing 319 can be formed to have essentially any shape suitable for physical protection of the inductor 141, cooling of the inductor 141, and mounting the inductor 141 within an existing system associated with the plasma processing chamber. Figure 3D also shows how the fan 321 can be positioned close to the grid 325 to supply cooling air to the inductor 141, as indicated by arrow 323, or to draw cooling air from the inductor 141, as indicated by arrow 324.

[0047] During the operation of plasma processing chambers, e.g., 101, 151, the RF filter 129 appears as a load to the RF generators, e.g., 111, 121, 157. Therefore, the higher the impedance of the RF filter 129, the lower the load it places on the RF generators. Thus, in some embodiments, it is interesting that the RF filter 129 exhibits a high impedance to RF power transmission so that the smaller amount of RF power is lost within the RF filter 129. In some embodiments, the operating RF frequencies of the RF power generators, e.g., 111, 121, 157, may vary as a result of frequency tuning. In these embodiments, it would be desirable to have the RF filter 129 provide at least a minimum specified impedance over the expected range of RF frequencies generated by the RF power generators during frequency tuning operation. In some embodiments, the impedance of the RF filter 129 is about 3 kilohms or more to limit the expected range of RF frequencies generated by the RF power generators during frequency tuning operation. In this way, the RF filter 129 is configured to present at least a minimum specified impedance for any RF frequencies occurring during operation. Furthermore, it should be noted that because the impedance of the RF filter 129 is relatively high, for example, 3 kilohms, less RF power is transmitted through the RF filter 129, improving the overall RF power efficiency of the plasma processing chambers, such as 101 and 151.

[0048] As described above, a given channel corresponds to a given pair of wires 142A-142H that supply current flow to a given heating element 132, 133, 134, 135 in the heater assembly 125. Since the RF filter 129 can block RF power transmission in substantially the same manner for each channel present, the RF filter 129 provides improved impedance uniformity between channels. Figure 4 shows a plot of impedance as a function of RF frequency at the higher primary RF frequency of 13.56 MHz for each of the wires 132A, 132B, 132C, 132D, 132E, 132F, 132G, 132H that supply current flow to a given heating element 132, 133, 134, 135 in the heater assembly 125, according to some embodiments of the present disclosure. Figure 4 demonstrates how the RF filter 129 provides substantial impedance uniformity between channels at the higher RF frequency of 13.56 MHz or nearby. Figure 5 shows a plot of impedance as a function of RF frequency at the lower primary RF frequency of 1 MHz for each of the wires 132A, 132B, 132C, 132D, 132E, 132F, 132G, and 132H that supply current flow to a given heating element 132, 133, 134, and 135 in the heater assembly 125, according to some embodiments of the present disclosure. Figure 5 demonstrates how the RF filter 129 provides substantial impedance uniformity between channels at the lower RF frequency of 1 MHz or nearby. Because the RF filter 129 provides substantial impedance uniformity between channels, each of the power supply channels of the heater assembly 125 has essentially the same amount of RF power. This means that different heating elements in various heating zones, such as 132, 133, 134, and 135, have a substantially uniform effect on RF power transmission within their respective heating zones, thereby improving the overall process uniformity of the substrate 105 with respect to RF power transmission / loss through different heating elements, such as 132, 133, 134, and 135.Furthermore, by controlling the impedance uniformity between channels within the RF filter 129, it is possible to control the impedance uniformity between different RF filter 129 units installed in different plasma processing chambers, and thus control the influence of the RF filter 129 on the impedance uniformity between chambers.

[0049] In this specification, it should be understood that an RF filter (e.g., 129) is disclosed as comprising an inductive element (e.g., an inductor 141) and a set of termination capacitance elements (e.g., capacitors 143A-143H). The inductive element (e.g., 141) comprises at least two coil sections (e.g., 301, 303) that collectively form an undivided coil of a cable of twisted magnetic wire (e.g., 142). The undivided coil of the cable of twisted magnetic wire (e.g., 142) has a continuous configuration through each transition between adjacent coil sections of at least two coil sections (e.g., 301, 303). Each coil section (e.g., 301, 303) comprises a portion configured with a corresponding winding pitch (e.g., 311, 313) as part of the undivided coil of the cable of twisted magnetic wire (e.g., 142). At least two adjacent coil sections (e.g., 301, 303) have different winding pitches (e.g., 311, 313). The twisted magnetic wire (e.g., 142) cable includes two wires per channel and is configured for at least one channel. The twisted magnetic wire (e.g., 142) cable is configured at the first end of the inductive element (e.g., 141) for connection to an electrical component (e.g., 125) that will receive power from a power source (e.g., 131). The twisted magnetic wire (e.g., 142) cable is configured at the second end of the inductive element (e.g., 141) for connection to the power source (e.g., 131). A set of termination capacitors (e.g., 143A-143H) includes separate termination capacitors for each wire of the twisted magnetic wire (e.g., 142) cable. Each terminating capacitance element (e.g., 143A-143H) is electrically connected between the reference ground potential (e.g., 145) and the respective wires of the twisted magnetic wire (e.g., 142) cable at a location between the second end of the inductive element (e.g., 141) and the power supply (e.g., 131).

[0050] In some embodiments, the number of at least two coil sections (e.g., 301, 303) corresponds to several different RF frequencies filtered by an RF filter (e.g., 129). Also in some embodiments, the winding pitch (e.g., 311, 313) of a given coil section (e.g., 301, 303) is set so that the given coil section (e.g., 301, 303) resonates with one of several different RF frequencies filtered by the RF filter (e.g., 129). In some embodiments, each wire (e.g., 142A-142H) of the twisted magnetic wire (e.g., 142) cable is a conductor coated with an electrical insulating coating material. In some embodiments, the electrical insulating coating material prevents low-frequency current from conducting between wires while allowing RF power to be transmitted between wires. In some embodiments, the inductive element (e.g., 141) includes a coil form (e.g., 305) around which an undivided coil of the twisted magnetic wire (e.g., 142) cable is wound. In some embodiments, the coil form (e.g., 305) has a hollow, right-circular cylindrical shape. In some embodiments, a continuous groove is formed on the outer surface of the coil form (e.g., 305), and this continuous groove is configured to receive the cable of twisted magnetic wire (e.g., 142) and to maintain the spatial configuration of the undivided coil of the cable of twisted magnetic wire (e.g., 142).

[0051] In some embodiments, at least one coil section (e.g., 301, 303) includes multiple windings of twisted magnetic wire (e.g., 142) cable. In some embodiments, the multiple windings are stacked radially with respect to the axis of the inductive element (e.g., 141). In some embodiments, at least two coil sections (e.g., 301, 303) differ in length measured along the axis of the inductive element (e.g., 141). In some embodiments, the undivided coil of twisted magnetic wire (e.g., 142) cable has at least two coil sections (e.g., 301, 303) with different winding diameters (e.g., 309). In some embodiments, the undivided coil of twisted magnetic wire (e.g., 142) cable has at least two coil sections (e.g., 301, 303) with different winding shapes. In some embodiments, the cable of twisted magnetic wire (e.g., 142) includes eight wires (e.g., 142A-142H) and is configured for four channels, and the number of at least two coil sections (e.g., 301, 303) in the inductor element (e.g., 141) is two. In some embodiments, the undivided coil of the cable of twisted magnetic wire (e.g., 142) has substantially the same winding diameter (e.g., 309) in two coil sections (e.g., 301, 303), and the winding pitch (e.g., 311) of the first coil section (e.g., 301) connected to the first end of the inductor element (e.g., 141) is greater than the winding pitch (e.g., 313) of the second coil section (e.g., 303) connected to the second end of the inductor element (e.g., 141). In some embodiments, the first coil section (e.g., 301) has one winding layer of twisted magnetic wire (e.g., 142) cable, and the second coil section (e.g., 303) has two winding layers (e.g., 303A, 303B) of twisted magnetic wire (e.g., 142) cable.In some embodiments, a first coil section (e.g., 301) has a cable of approximately 13 turns of twisted magnetic wire (e.g., 142) within this single winding layer, a second coil section (e.g., 303) has a cable of approximately 21 turns of twisted magnetic wire (e.g., 142) within the inner winding layer of two winding layers (e.g., 303A), and a second coil section (e.g., 303) has a cable of approximately 18 turns of twisted magnetic wire (e.g., 142) within the outer winding layer of two winding layers (e.g., 303B), and each terminating capacitance element of a set of terminating capacitance elements (e.g., 143A-143H) has a capacitance value of approximately 0.1 microfarads.

[0052] Figure 6 presents a method for filtering RF power according to several embodiments of the present disclosure. The method involves connecting an RF filter (e.g., 129) between a power source (e.g., 131) and an electrical component (e.g., 125) that will receive power from this power source (e.g., 131). In the method of Figure 6, the RF filter (e.g., 129) includes an inductive element (e.g., 141) having at least two coil sections (e.g., 301, 303) that collectively form an undivided coil of a cable of twisted magnetic wire (e.g., 142). Each coil section (e.g., 301, 303) includes a portion configured with a corresponding winding pitch (e.g., 311, 313) as part of an undivided coil of a cable of twisted magnetic wire (e.g., 142). At least two adjacent coil sections (e.g., 301, 303) have different winding pitches (e.g., 311, 313). The twisted magnetic wire (e.g., 142) cable includes two wires per channel and is configured for at least one channel. The twisted magnetic wire (e.g., 142) cable is connected to an electrical component (e.g., 125) at the first end of an inductive element (e.g., 141). The twisted magnetic wire (e.g., 142) cable is connected to a power supply (e.g., 131) at the second end of an inductive element (e.g., 141). The RF filter (e.g., 129) includes separate termination capacitive elements (e.g., 143A-143H) for each wire (e.g., 142A-142H) of the twisted magnetic wire (e.g., 142) cable. Each terminating capacitance element (e.g., 143A-143H) is electrically connected between the second end of the inductive element (e.g., 141) and the power supply (e.g., 131) and between the reference ground potential (e.g., 145) and each wire (e.g., 142A-142H) of the twisted magnetic wire (e.g., 142) cable. In some embodiments, the number of at least two coil sections (e.g., 301, 303) corresponds to several different RF frequencies filtered by an RF filter (e.g., 129).In some embodiments, the winding pitch (e.g., 311, 313) of a given coil section (e.g., 301, 303) is set so that the given coil section (e.g., 301, 303) resonates with one of several different RF frequencies filtered by an RF filter (e.g., 129). In some embodiments, each wire (e.g., 142A-142H) of a twisted magnetic wire cable (e.g., 142) is a conductor coated with an electrical insulating coating material that prevents inter-wire conduction of low-frequency currents while enabling inter-wire transmission of RF power.

[0053] Figure 7 illustrates a method for filtering RF power according to several embodiments of the present disclosure. The method includes operation 701 for transmitting power from a power source (e.g., 131) to wires (e.g., 142A-142H) in an input configuration. The wires (e.g., 142A-142H) are connected to their respective capacitive elements (e.g., 143A-143H). Each separate pair of wires (e.g., 142A-142H) is designated to power an electrical component (e.g., 125) that will be exposed to RF power. The method also includes operation 703 for transmitting power from the wires (e.g., 142A-142H) in the input configuration to the corresponding magnetic wire in a cable of twisted magnetic wires (e.g., 142) at the input of an inductive element (e.g., 141). An inductive element (e.g., 141) includes at least two coil sections (e.g., 301, 303) that collectively form an undivided coil of twisted magnetic wire (e.g., 142) cable between the input and output of the inductive element (e.g., 141). Each coil section (e.g., 301, 303) includes a portion of the undivided coil of twisted magnetic wire (e.g., 142) cable that is configured with a corresponding winding pitch (e.g., 311, 313). At least two adjacent coil sections (e.g., 301, 303) have different winding pitches (e.g., 311, 313). The method also includes operation 705 for transferring power at the output of an inductive element (e.g., 141) from the magnetic wire in the cable of twisted magnetic wire (e.g., 142) to the corresponding wire (e.g., 132A, 132B, 133A, 133B, 134A, 134B, 135A, 135B) connected to an electrical component (e.g., 125) that will be exposed to RF power.

[0054] To understand some of the advantages of RF filter 129, it is helpful to compare RF filter 129 with other possible RF filter configurations. For the purpose of filtering two or more different primary RF frequencies, some other possible RF filter configurations may implement physically separate sets of inductors and termination capacitors for each of the different primary RF frequencies. For example, if there are two primary RF frequencies, other possible RF filter configurations may implement one set of inductors and termination capacitors for the first primary RF frequency and a physically separate set of inductors and termination capacitors for the second primary RF frequency. Compared to RF filter 129, these other possible RF filter configurations have twice the number of inductors and twice the number of termination capacitors. It should be understood and recognized that the difference between RF filter 129 and these other possible RF filter configurations is that different coil sections of RF filter 129, e.g., 301 and 303, are part of the same coil winding and are not physically separate inductors. Another way in which the RF filter 129 differs from other possible RF filter configurations is that a set of termination capacitors 143A-143H is used, regardless of the number of different coil sections, e.g., 301, 303.

[0055] In addition, in other possible RF filter configurations, some termination capacitors may have relatively low capacitance values ​​and relatively high manufacturing tolerances of several percent or more in capacitance. These manufacturing tolerances for the capacitance of the termination capacitors, combined, can essentially limit the impedance uniformity between channels that can be achieved in other possible RF filter configurations. Also, in other possible RF filter configurations, separate inductors defined to filter lower RF frequencies may be configured (out of necessity) to have a ferrite core with untwisted wire wrapped around it. The ferrite core in this other possible RF filter configuration has large variations in permeability between units, which can be up to 30%, essentially limiting the impedance uniformity that can be achieved between different RF filter units. Reducing the variations in permeability between units of the ferrite core material may be costly and may require the use of larger ferrite core structures. Regarding other possible RF filter configurations, manufacturing variations in the capacitance of small termination capacitors and manufacturing variations related to the permeability of the ferrite core material of the low-frequency windings collectively increase inter-chamber variations in the characteristics and performance of the RF filter (such as the impedance supplied to the RF generator by the RF filter), and such variations will affect the RF power transmission characteristics. Also, in other possible RF filter configurations, if any component of the RF filter fails, the entire RF filter is often replaced. Therefore, in other possible RF filter configurations, a larger number of termination capacitors may result in a higher failure rate.

[0056] Compared to other possible RF filter configurations described above, the RF filter 129 disclosed herein does not include multiple sets of termination capacitors. The large overall inductance provided by the RF filter 129 disclosed herein avoids the need to use termination capacitors with smaller capacitance and avoids the need to form an inductor around a ferrite core. The RF filter 129 disclosed herein includes a set of termination capacitors 143A-143H at each location between the inductor 141 and the electrical connection 137 to the power supply 131. Also, compared to other possible RF filter configurations described above, the RF filter 129 disclosed herein does not utilize termination capacitors with relatively low capacitance and high manufacturing tolerances. Therefore, the RF filter 129 disclosed herein can improve impedance uniformity between channels as well as impedance uniformity between corresponding chambers. Also, compared to other possible RF filter configurations described above, the RF filter 129 disclosed herein does not include a ferrite core structure for the inductor defined to filter lower RF frequencies, thereby avoiding the large manufacturing variations in permeability associated with the ferrite core structure and improving impedance uniformity between chambers.

[0057] In addition, it should be noted that the RF filter 129 disclosed herein improves inter-channel impedance uniformity and repeatability by using a twisted assembly cable of wires 142 within the inductor 141, minimizing the load effect on process uniformity. The RF filter 129 eliminates the effect of capacitance tolerances on inter-unit variations. The RF filter 129 eliminates the effect of permeability tolerances of ferrite core magnetic material on inter-unit variations. The RF filter 129 can achieve higher impedance over a wide bandwidth to enable frequency tuning. The RF filter 129 minimizes the load effect on process uniformity through inter-channel repeatability. The RF filter 129 can achieve higher RF power efficiency by minimizing RF power loss within the RF filter 129. The RF filter 129 provides high impedance (up to 3 kilohms or more), thereby minimizing the load effect of the RF filter 129 and providing a wide bandwidth to enable frequency tuning operation in plasma processes using an inter-level RF power pulse scheme. Since the RF filter 129 does not use interstage capacitors or a ferrite core structure, the influence of capacitance tolerances and permeability tolerances on variations between units is eliminated in the RF filter 129. Furthermore, by using twisted magnetic wire for the winding of the inductor 141 of the RF filter 129, variations between channels are minimized, and therefore the load effect between channels on plasma process uniformity is minimized.

[0058] While the foregoing disclosure includes some details for the purpose of clarifying understanding, it will be clear that certain changes and modifications can be made within the scope of the appended claims. Therefore, these embodiments should be considered illustrative and not restrictive, and the claims are not limited to the details given herein but can be modified within the scope of the embodiments described and their equivalents.

Claims

1. A radio frequency (RF) filter, An inductive element comprising at least two coil sections collectively forming an undivided coil of twisted magnetic wire cable, each coil section comprising a portion of the undivided coil of the twisted magnetic wire cable with a corresponding winding pitch, at least two adjacent coil sections having different winding pitches, the twisted magnetic wire cable comprising two wires per channel and configured for at least one channel, the twisted magnetic wire cable configured at a first end of the inductive element for connection to an electrical component that will receive power from a power source, and the twisted magnetic wire cable configured at a second end of the inductive element for connection to the power source, A set of terminating capacitance elements, each including a separate terminating capacitance element for each wire of the twisted magnetic wire cable, wherein each terminating capacitance element is electrically connected between a reference ground potential and each wire of the twisted magnetic wire cable at a location between the second end of the inductive element and the power supply. An RF filter equipped with the following features.

2. The RF filter according to claim 1, An RF filter in which the undivided coil of the twisted magnetic wire cable has a continuous configuration via each transition between adjacent coil sections of the at least two coil sections.

3. The RF filter according to claim 1, An RF filter in which at least two coil sections are associated with corresponding RF frequencies filtered by the RF filter.

4. The RF filter according to claim 3, An RF filter in which the winding pitch of a given coil section is set such that the given coil section resonates with one of the corresponding RF frequencies filtered by the RF filter.

5. The RF filter according to claim 1, An RF filter in which each wire of the twisted magnetic wire cable is a conductor coated with an electrical insulating coating material.

6. The RF filter according to claim 5, The aforementioned electrical insulating coating material is an RF filter that prevents low-frequency current from conducting between wires while enabling RF power transmission between wires.

7. The RF filter according to claim 1, An RF filter in which at least one coil section includes multiple windings of the twisted magnetic wire cable, the multiple windings being stacked radially with respect to the axis of the inductor.

8. The RF filter according to claim 1, An RF filter having at least two coil sections of different lengths measured along the axis of the inductor.

9. The RF filter according to claim 1, The undivided coil of the twisted magnetic wire cable is an RF filter having at least two coil sections with different winding diameters.

10. The RF filter according to claim 1, The undivided coil of the twisted magnetic wire cable is an RF filter in which the winding shape differs in at least two coil sections.

11. The RF filter according to claim 1, The twisted magnetic wire cable comprises eight wires and is configured for four channels, and the number of the at least two coil sections is two, in an RF filter.

12. The RF filter according to claim 1, An RF filter wherein the undivided coil of the twisted magnetic wire cable has substantially the same winding diameter in at least two coil sections, and the winding pitch of the first coil section connected to the first end of the inductor is greater than the winding pitch of the second coil section connected to the second end of the inductor.

13. The RF filter according to claim 12, An RF filter wherein the first coil section has one winding layer of the twisted magnetic wire cable, and the second coil section has two winding layers of the twisted magnetic wire cable.

14. The RF filter according to claim 13, An RF filter wherein the first coil section has approximately 13 turns of the twisted magnetic wire cable in the single winding layer, the second coil section has approximately 21 turns of the twisted magnetic wire cable in the inner winding layer of the two winding layers, and the second coil section has approximately 18 turns of the twisted magnetic wire cable in the outer winding layer of the two winding layers, and each of the set of termination capacitors has a capacitance value of approximately 0.1 microfarads.

15. The RF filter according to claim 1, The inductive element is an RF filter, which includes a coil form around which the undivided coil of the twisted magnetic wire cable is wound.

16. The RF filter according to claim 15, An RF filter in which the coil form has a hollow, right cylindrical shape.

17. The RF filter according to claim 16, An RF filter comprising a continuous groove formed within the outer surface of the coil form, wherein the continuous groove is configured to receive the twisted magnetic wire cable and maintain the spatial configuration of the undivided coil of the twisted magnetic wire cable.

18. A method for filtering radio frequency (RF) power, The RF filter is provided between the power supply and the electrical components that will receive power from the power supply, wherein the RF filter includes an inductive element having at least two coil sections that collectively form an undivided coil of twisted magnetic wire cable, each coil section including a portion of the undivided coil of the twisted magnetic wire cable configured with a corresponding winding pitch, at least two adjacent coil sections having different winding pitches, the twisted magnetic wire cable includes two wires per channel and is configured for at least one channel, the twisted magnetic wire cable is connected to the electrical components at a first end of the inductive element, the twisted magnetic wire cable is connected to the power supply at a second end of the inductive element, and the RF filter includes a separate termination capacitance element for each wire of the twisted magnetic wire cable, each termination capacitance element is electrically connected between a reference ground potential and each wire of the twisted magnetic wire cable at a location between the second end of the inductive element and the power supply. Methods that include...

19. A method for filtering RF power according to claim 18, A method wherein the number of the at least two coil sections corresponds to a plurality of different RF frequencies to be filtered, and the winding pitch of a given coil section is set such that the given coil section resonates with one of the plurality of different RF frequencies to be filtered.

20. A method for filtering RF power according to claim 19, A method wherein each wire of the twisted magnetic wire cable is a conductor coated with an electrical insulating coating material that prevents inter-wire conduction of low-frequency currents and enables inter-wire transmission of RF power.

21. A method for filtering radio frequency (RF) power, The transmission of power from a power source to wires in an input configuration, wherein the wires are connected to their respective capacitive elements, and each separate pair of the wires is designated to supply power to an electrical component exposed to RF power. In the input of an inductor, power is transmitted from the wire in the input configuration to the corresponding magnetic wire in the twisted magnetic wire cable, wherein the inductor includes at least two coil sections that collectively form an undivided coil of the twisted magnetic wire cable between the input and output of the inductor, and each coil section includes a portion of the undivided coil of the twisted magnetic wire cable configured with a corresponding winding pitch, and at least two adjacent coil sections have different winding pitches. In the output of the inductive element, power is transmitted from the magnetic wire in the twisted magnetic wire cable to the corresponding wire connected to the electrical component exposed to RF power. Methods that include...

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