Radio frequency distribution circuits comprising transformers and / or transformer coupled combiners

Abstract

A transformer includes a primary coil and a secondary coil. The primary coil includes: a first shield of a first coaxial cable; a second shield of a second coaxial cable; and a conductive interconnect connecting the first shield to the second shield. The secondary coil includes: a first core of the first coaxial cable; a second core of the second coaxial cable; and a pair of wires connecting the first core to the second core.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of U.S. Provisional Application No. 62 / 908,846, filed on October 1, 2019. The entire disclosure of the above-referenced application is incorporated herein by reference. Technical Field

[0003] The present disclosure relates to semiconductor and solid-state device manufacturing and processing equipment, and more particularly to radio frequency (RF) distribution circuitry for substrate processing systems. Background Art

[0004] The background description provided here is for the purpose of generally presenting the context of the present disclosure. No admission is made, either explicitly or implicitly, that the work of the presently designated inventors is prior art to the present disclosure to the extent that it is described in this background section and in aspects of the specification that were not determined to be prior art at the time the application was filed.

[0005] Substrate processing systems can be used to process substrates, such as semiconductor wafers. Examples of substrate processing include etching, deposition, and the like. During processing, a substrate is placed on a substrate support, such as an electrostatic chuck (ESC), and one or more process gases may be introduced into a processing chamber.

[0006] One or more process gases may be delivered to the processing chamber via a gas delivery system. In some systems, the gas delivery system includes a manifold connected to a showerhead in the processing chamber. For example, during an etching process, a substrate may be placed on an ESC in a substrate processing system and a thin film may be etched on the substrate. In another example, a thin film may be deposited on a substrate using atomic layer deposition (ALD). During substrate processing, one or more RF signals may be supplied to electrodes of the showerhead to adjust the plasma ionization density and ionization energy. Summary of the Invention

[0007] A transformer is provided, comprising a primary coil and a secondary coil. The primary coil comprises: a first shield of a first coaxial cable; a second shield of a second coaxial cable; and a conductive interconnect connecting the first shield to the second shield. The secondary coil comprises: a first core of the first coaxial cable; a second core of the second coaxial cable; and a pair of wires connecting the first core to the second core.

[0008] In other features, the first coaxial cable extends parallel to the second coaxial cable. In other features, the sum of the lengths of the first core, the second core, and the paired conductors is at least one of: based on or equal to a multiple of the length of each of the first coaxial cable and the second coaxial cable. In other features, the length of each of the first coaxial cable and the second coaxial cable is at least one of: based on or equal to a fractional multiple of the wavelength of the radio frequency signal transmitted by the transformer.

[0009] Among other features, a radio frequency distribution circuit is provided, comprising a radio frequency generator and the transformer. The radio frequency generator is configured to generate a first radio frequency signal, the first radio frequency signal comprising frequency components at a certain radio frequency. The transformer is configured to convert the first radio frequency signal into a second radio frequency signal, the second radio frequency signal comprising frequency components at the first radio frequency.

[0010] In other features, a substrate processing system is provided, comprising: the RF distribution circuit; a processing chamber; a showerhead; and a substrate support. The showerhead includes an electrode and is implemented in the processing chamber. The substrate support is disposed in the processing chamber adjacent to the showerhead. The transformer is configured to supply the second RF signal to the electrode.

[0011] In other features, a radio frequency (RF) distribution circuit is provided, comprising a first filter, a second filter, a first matching network, a second matching network, and a transformer-coupled combiner. The first filter is configured to receive a first RF signal and a second RF signal from at least one RF generator and filter out the first RF signal, the first RF signal being at a first frequency and the second RF signal being at a second frequency, the second frequency being less than the first frequency. The second filter is configured to receive the first RF signal and the second RF signal from the at least one RF generator and filter out the first RF signal. The first matching network is configured to match the output of the at least one RF generator to the input of the first filter. The second matching network is configured to match the output of the at least one RF generator to the input of the second filter. The transformer-coupled combiner is configured to convert the first RF signal to a third RF signal, convert the second RF signal to a fourth RF signal, and combine the first RF signal with the second RF signal or the third RF signal with the fourth RF signal. The third RF signal includes a frequency component at the first RF frequency. The fourth RF signal includes a frequency component at the second RF frequency.

[0012] In other features, the transformer-coupled combiner includes a first transformer for receiving the output of the first filter and a second transformer for receiving the output of the second filter.

[0013] In other features, the first transformer includes a primary coil and a secondary coil. The primary coil is connected to the first filter. The second transformer includes a primary coil and a secondary coil. The primary coil is connected to the second filter and the primary coil of the first transformer. The secondary coil is connected to the secondary coil of the first transformer.

[0014] In other features, the primary coil and the secondary coil of the first transformer are connected to a ground reference potential.The primary coil and the secondary coil of the second transformer are connected to the ground reference potential.

[0015] In other features, the first transformer includes a primary coil and a secondary coil. The primary coil includes: a first shield of a first coaxial cable; a second shield of a second coaxial cable; and a conductive interconnect connecting the first shield to the second shield. The secondary coil includes: a first core of the first coaxial cable; a second core of the second coaxial cable; and a pair of wires connecting the first core to the second core.

[0016] In other features, the first coaxial cable extends parallel to the second coaxial cable. In other features, the sum of the lengths of the first core, the second core, and the paired conductors is at least one of: based on or equal to a multiple of the length of each of the first coaxial cable and the second coaxial cable. In other features, the length of each of the first coaxial cable and the second coaxial cable is at least one of: based on or equal to a fractional multiple of the wavelength of the first RF signal.

[0017] In other features, the transformer-coupled combiner includes a first transformer including a first primary coil connected to the first filter, a second primary coil connected to the second filter, a first secondary coil connected to receive the third RF signal, and a second secondary coil connected to receive the fourth RF signal.

[0018] In other features, the first transformer includes a third secondary coil configured to receive a fifth radio frequency signal including a frequency component at the first frequency and a frequency component at the second frequency.

[0019] In other features, the transformer-coupled combiner includes a first primary coil, a second primary coil, a first secondary coil, and a second secondary coil. The first primary coil is connected to the first filter. The second primary coil is connected to the second filter. The first secondary coil outputs the third RF signal. The third RF signal includes frequency components at the first and second RF frequencies, respectively. The second secondary coil outputs the fourth RF signal. The fourth RF signal includes frequency components at the first and second RF frequencies, respectively.

[0020] In other features, the transformer-coupled combiner includes a third secondary coil and a fourth secondary coil. The third secondary coil outputs a fifth radio frequency signal. The fifth radio frequency signal includes frequency components at the first radio frequency and the second radio frequency, respectively. The fourth secondary coil outputs a sixth radio frequency signal. The sixth radio frequency signal includes frequency components at the first radio frequency and the second radio frequency, respectively.

[0021] In other features, a substrate processing system is provided, comprising: the RF distribution circuit; a processing chamber; a showerhead; and a substrate support. The showerhead comprises an electrode and is disposed in the processing chamber. The substrate support is disposed in the processing chamber adjacent to the showerhead.

[0022] An RF distribution circuit for supplying RF power to electrodes in a substrate processing system is also provided. The circuit includes a first RF generator, a first filter, a first matching network, and a first transformer. The first RF generator generates a first RF signal, which includes frequency components at a first RF frequency. The first filter filters out one or more RF signals generated in the substrate processing system other than the first RF signal. The first matching network matches the output of the first RF generator to the input of the first filter. The first transformer converts the first RF signal into a second RF signal, which includes frequency components at the first RF frequency. The second RF signal is supplied to the electrodes to adjust the plasma ionization density and ionization energy within the processing chamber of the substrate processing system.

[0023] In other features, a substrate processing system is provided, comprising the RF distribution circuit, the processing chamber, a showerhead, and a substrate support. The showerhead comprises the electrode and is disposed in the processing chamber. The substrate support is disposed in the processing chamber adjacent to the showerhead.

[0024] In other features, the transformer includes a primary coil and a secondary coil. The primary coil includes: a first shield of a first coaxial cable; a second shield of a second coaxial cable; and a conductive interconnect connecting the first shield to the second shield. The secondary coil includes: a first core of the first coaxial cable; a second core of the second coaxial cable; and a pair of wires connecting the first core to the second core. In other features, the first coaxial cable extends parallel to the second coaxial cable.

[0025] In other features, the sum of the lengths of the first core, the second core, and the pair of conductors is equal to four times the length of each of the first coaxial cable and the second coaxial cable. In other features, the length of each of the first coaxial cable and the second coaxial cable is equal to one-quarter the wavelength of the first RF signal.

[0026] In other features, the RF distribution circuit further includes: a second RF generator for generating a third RF signal, the third RF signal including a frequency component at a second RF, wherein the second RF is less than the first RF; a second filter for filtering out the first RF signal, wherein the first filter filters out the third RF signal; and a second matching network for matching the output of the second RF generator to the input of the second filter.

[0027] In other features, the RF distribution circuit further includes a second transformer to: receive the output of the second filter; convert the third RF signal into a fourth RF signal; and supply the fourth RF signal to the electrode.

[0028] In other features, a substrate processing system is provided that includes: the RF distribution circuit; the processing chamber; a showerhead including the electrode and positioned in the processing chamber; and a substrate support positioned in the processing chamber adjacent to the showerhead.

[0029] In other features, the first transformer includes a primary coil connected to the first filter and a secondary coil connected to the electrode. The second transformer includes: a primary coil connected to the second filter and the primary coil of the first transformer; and a secondary coil connected to the secondary coil of the first transformer and the electrode.

[0030] In other features, the primary coil and the secondary coil of the first transformer are connected to a ground reference potential. The primary coil and the secondary coil of the second transformer are connected to the ground reference potential.

[0031] In other features, the first transformer includes a primary coil and a secondary coil. The primary coil includes a first shield of a first coaxial cable, a second shield of a second coaxial cable, and a conductive interconnect connecting the first shield to the second shield. The secondary coil includes a first core of the first coaxial cable, a second core of the second coaxial cable, and a pair of wires connecting the first core to the second core. In other embodiments, the first coaxial cable extends parallel to the second coaxial cable. In other features, the sum of the lengths of the first core, the second core, and the pair of wires is equal to four times the length of each of the first coaxial cable and the second coaxial cable. In other features, the length of each of the first coaxial cable and the second coaxial cable is equal to one-quarter the wavelength of the first RF signal.

[0032] In other features, the first transformer includes: a first primary coil connected to the first filter; a second primary coil connected to the second filter; and a first secondary coil connected to the electrode and configured to receive the first RF signal and the third RF signal. In other features, the electrode is a first electrode. The first transformer includes a second secondary coil connected to the second electrode and configured to receive the second RF signal and the fourth RF signal.

[0033] In other features, a substrate processing system is provided that includes the RF distribution circuit, the processing chamber, a showerhead, and a substrate support. The showerhead includes an electrode and is positioned in the processing chamber. The substrate support is positioned in the processing chamber adjacent to the showerhead.

[0034] In other features, the first transformer includes a third secondary coil connected to a third showerhead and configured to receive the second RF signal and the fourth RF signal. In other features, the first transformer includes: a first primary coil connected to the first filter; a second primary coil connected to the second filter; a first secondary coil connected to the electrode and configured to output the second RF signal, wherein the second RF signal includes a frequency component at a second RF frequency, wherein the electrode is a first electrode; and a second secondary coil connected to the second electrode and configured to output a fourth RF signal. The fourth RF signal includes frequency components at each of the first and second RF frequencies.

[0035] In other features, the first transformer includes: a third secondary coil for outputting a fifth RF signal to a third electrode, the fifth RF signal including frequency components at the first RF and the second RF, respectively; and a fourth secondary coil for outputting a sixth RF signal to a fourth electrode, the sixth RF signal including frequency components at the first RF and the second RF, respectively.

[0036] In other features, an RF distribution circuit for supplying RF power to electrodes in a substrate processing system is provided, comprising an RF generator, a transformer, and a matching network. The RF generator is configured to generate a first RF signal. The transformer is configured to convert the first RF signal into a second RF signal and supply the second RF signal to the electrodes to adjust the plasma ionization density and ionization energy within a processing chamber of the substrate processing system. The matching network is configured to match the output of the RF generator with the input of the transformer. In other features, a substrate processing system is provided, comprising the RF distribution circuit, the processing chamber, a showerhead, and a substrate support. The showerhead comprises the electrode and is disposed in the processing chamber. The substrate support is disposed in the processing chamber adjacent to the showerhead.

[0037] Further scope of applicability of the present disclosure will become apparent from the detailed description, claims and drawings.The detailed description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] The present disclosure will be more fully understood from the detailed description and accompanying drawings, in which:

[0039] Figure 1A is a Smith chart illustrating an exemplary input impedance of a non-transformer based RF distribution circuit for a first load impedance;

[0040] Figure 1B is a Smith chart illustrating another exemplary input impedance of the RF dividing circuit for a second load impedance;

[0041] Figure 1C is a Smith chart illustrating another exemplary input impedance of the RF dividing circuit for a third load impedance;

[0042] Figure 2 is a functional block diagram of an example of a substrate processing system including an RF distribution circuit according to an embodiment of the present disclosure, the RF distribution circuit including a transformer;

[0043] Figure 3 is a functional block diagram of an example of an RF distribution circuit including a transformer according to an embodiment of the present disclosure;

[0044] Figure 4A is a Smith chart which illustrates the load impedance for the first Figure 3 An exemplary input impedance of the RF distribution circuit;

[0045] Figure 4B is a Smith chart which illustrates the load impedance for the second Figure 3 Another exemplary input impedance of the RF distribution circuit;

[0046] Figure 5 is a functional block diagram of an example of a dual RF distribution circuit including a transformer-coupled combiner according to an embodiment of the present disclosure;

[0047] Figure 6 is a Smith chart, which illustrates Figure 5 The low frequency (LF) and high frequency (HF) paths of the dual RF distribution circuit are short-circuited, open-circuited, and provide an input impedance of 50Ω load impedance;

[0048] Figure 7 is a functional block diagram of an example of a quad RF distribution circuit including transformer-coupled combiners according to an embodiment of the present disclosure; and

[0049] Figure 8 FIG. 1 is a side view of an exemplary transformer for high frequency RF signals in an RF distribution circuit according to an embodiment of the present disclosure.

[0050] Among the drawings, reference numerals may be repeated to identify similar and / or identical elements. DETAILED DESCRIPTION

[0051] Two different RF frequencies are typically supplied in semiconductor processing chambers to provide independent control of plasma ionization density and ionization energy. A substrate processing system may include a processing chamber having a specific number of stations (e.g., four stations). Each station may include a corresponding substrate support and showerhead. The showerhead receives RF power from a corresponding RF combiner and distributor circuit. Each of the RF combiner and distributor circuit may include an LF and an HF path. The RF signal generated by the LF path has a lower frequency than the RF signal generated by the HF path. For example, the LF path may generate an RF signal at 400 kilohertz (kHz) while the HF path may generate an RF signal at 13.56 megahertz (MHz). An LF generator generates an LF signal, which is provided to a first matching network that feeds each of the LF paths of the RF combiner and distributor circuit. The first matching network matches the impedance of the LF generator's output to the total input impedance of the LF paths. An HF generator generates an HF signal, which is provided to a second matching network that feeds each of the HF paths of the RF combiner and distributor circuit. The second matching network matches the impedance of the output of the HF generator to the total input impedance of the HF path.

[0052] The LF path includes corresponding LF ballast devices and LF filters that filter out HF signals so that they are not received at the LF generator. The HF path includes corresponding HF ballast devices and HF filters that filter out LF signals so that they are not received at the HF generator. The LF and HF ballast devices may include inductors and / or capacitors that (i) isolate each station from the other stations; and (ii) isolate the inputs of the combiner and RF splitter circuits from load variations.

[0053] Each of the RF combiner and splitter circuits includes a switch for switching between a dummy load and the LF and HF paths. The dummy load is used when the corresponding station is not in use. This maintains a substantially equal load between stations. For example, when one or more stations are not in use, the switch of the station in use is switched to enable the LF and HF signals to pass from the RF generator to the coaxial cable, thereby feeding the corresponding electrodes of the station. The switch of the unused station or stations is switched to the dummy load, preventing the LF and HF signals from passing through the coaxial cable to the corresponding electrodes of the one or more stations.

[0054] The RF combiner and splitter circuits are designed to resonate at high frequencies. This helps establish a high voltage between the electrodes, which in turn helps provide fast and smooth ignition. Electrodes can refer to electrodes (or grounded conductive elements) in the showerhead and the substrate support of the station.

[0055] RF combiners and splitters experience large changes in input impedance due to small changes in load impedance. Figures 1A-1Cto illustrate three different input impedances for three different load impedances. Figures 1A-1C The Smith charts 100, 104, 108 are logarithmic representations of possible input impedance values. For example, the load impedance (or impedance at the showerhead) may be 132 pF, which results in Figure 1A The input impedance is shown at midpoint 102. The load impedance can be changed to 230pF, which results in Figure 1B The load impedance can be changed again to 240pF, which results in the following: Figure 1C As shown in these figures, a small change in load impedance can result in a large change in the position of points 102, 106, 110 in the Smith charts 100, 104, and 108, which corresponds to a large change in input impedance. In a processing chamber containing multiple stations, a change in load impedance at one station can also adversely affect the performance of other stations.

[0056] Because RF combiners and splitters exhibit large changes in input impedance due to small changes in load impedance, automatic matching circuits are used to tune the matching network. Furthermore, automatic matching circuits with a large tuning range are used to accommodate different types of substrate processing using the same substrate processing equipment. Furthermore, RF combiners and splitters require high-impedance ballast devices for isolation. High-impedance ballast devices can reduce current flow to the corresponding stations. Furthermore, the size of the matching network components, ballast devices, and filter components increases with increasing power. The topology of RF combiners and splitters is inherently unbalanced.

[0057] If not all stations in a chamber are used for processing, the required tuning range of the auto-matching circuitry increases significantly. Unlike single-station equipment, multi-station equipment includes multiple showerheads, each receiving a generated RF signal. If one or more stations are not used, the load impedance at that station can differ significantly from that at other stations. This requires a larger tuning range for the station's auto-matching circuitry to compensate for this load imbalance.

[0058] Examples presented herein overcome the aforementioned shortcomings and provide substrate processing systems comprising RF distribution circuits comprising one or more transformers and / or transformer-coupled combiners. The transformers and / or transformer-coupled combiners minimize input impedance variations due to load impedance variations. Some disclosed RF distribution circuits include efficient combiner circuits. As used herein, a "combiner circuit" combines two or more RF signals into a single RF signal.

[0059] The RF distribution circuitry provides isolation between stations and loads, between stations, and between inputs and outputs to minimize the impact on some stations due to variations in load bank impedance at another station. The RF distribution circuitry provides a self-sustaining system that exhibits reduced sensitivity to variations in load bank impedance; enables a wide range of recipes to be used for processing substrates having a wide range of corresponding load impedances; experiences minimal input impedance variations due to substrate loading and unloading into and from the processing chamber; and allows each branch (or RF signal path at each station) to be at or near resonance for rapid and smooth ignition associated with plasma generation. In certain embodiments, an RF combiner and distribution circuitry combines two or more RF frequency signals and supplies signals having two or more frequencies to one or more stations. The RF distribution circuitry enables impedance matching of both LF and HF signals. Additional advantages and aspects of the enumerated RF distribution circuitry are further described below.

[0060] Figure 2 FIG2 is a functional block diagram of an example of a substrate processing system 200 including an RF distribution circuit 201 including a transformer 202. The configuration of the RF distribution circuit 201 is the same as or similar to any RF distribution circuit disclosed herein. The transformer 202 can be configured as any transformer and / or transformer coupled combiner disclosed herein. Although Figure 2 A capacitively coupled plasma (CCP) system is shown, but the embodiments disclosed herein can be applied to other plasma processing systems. The embodiments can be applied to deposition, etching, and other substrate processing, including plasma enhanced atomic layer deposition (PEALD) and plasma enhanced chemical vapor deposition (PECVD) processes.

[0061] The substrate processing system 200 includes one or more stations, each having a respective substrate support, such as an electrostatic chuck (ESC) 204. The one or more stations are disposed in a processing chamber 205. The ESC 204 may include a top plate 206 and a bottom plate 207. Other components, such as an upper electrode 208, may be disposed in the processing chamber 205. During operation, a substrate 209 is placed on the top plate 206 of the ESC 204 and is electrostatically clamped to the top plate 206, and an RF plasma is generated within the processing chamber 205.

[0062] By way of example only, upper electrode 208 may include a showerhead 210 that introduces and distributes gases. Showerhead 210 may include a stem 211, one end of which is connected to the upper surface of process chamber 205. Showerhead 210 is generally cylindrical and extends radially outward from opposite ends where stem 211 separates from the top surface of process chamber 205. The substrate-facing surface of showerhead 210 includes a plurality of holes through which process or purge gases flow. Alternatively, upper electrode 208 may include a conductive plate and may direct gases in other ways. One or both of plates 206 and 207 may function as the lower electrode.

[0063] One or both of the plates 206, 207 may include a temperature control element (TCE). For example, an intermediate layer 214 is disposed between the plates 206, 207. The intermediate layer 214 may bond the top plate 206 to the bottom plate 207. The bottom plate 207 may include one or more gas channels and / or one or more coolant channels for flowing a backside gas to the backside of the substrate 209 and for flowing a coolant through the bottom plate 207.

[0064] The RF generation system 220 generates an RF voltage and outputs the RF voltage to the upper electrode 208. The RF generation system 220 can generate the RF voltage and output the RF voltage to the ESC 204. One of the upper electrode 208 and the ESC 204 can be DC grounded, AC grounded, or at a floating potential. By way of example only, the RF generation system 220 can include one or more RF generators 223 (e.g., a capacitively coupled plasma RF power generator and / or other RF power generator) capable of generating an RF voltage, which is fed to the upper electrode 208 via one or more matching networks 227 and the RF distribution circuit 201. The RF generator 223 can be a high-power RF generator, generating, for example, 6-10 kilowatts (kW) or more. The RF generator 223 can generate a corresponding RF signal having frequency components at a corresponding RF frequency.

[0065] The gas delivery system 230 includes one or more gas sources 232-1, 232-2, ..., and 232-N (collectively referred to as gas sources 232), where N is an integer greater than zero. The gas sources 232 supply one or more precursors and mixtures thereof. The gas sources 232 may also supply etching gases, carrier gases, and / or sweep gases. Evaporated precursors may also be used. The gas sources 232 are connected to a manifold 240 via valves 234-1, 234-2, ..., and 234-N (collectively referred to as valves 234) and mass flow controllers 236-1, 236-2, ..., and 236-N (collectively referred to as mass flow controllers 236). The output of the manifold 240 is fed to the processing chamber 204. By way of example only, the output of the manifold 240 is fed to the showerhead 210.

[0066] The substrate processing system 200 also includes a cooling system 241 including a temperature controller 242 that can be connected to the TCE. Although shown as separate from the system controller 260, the temperature controller 242 can be implemented as part of the system controller 260. One or more of the plates 206, 207 can include multiple temperature control zones (e.g., four zones, each zone including four temperature sensors).

[0067] Temperature controller 242 can control the operation, and thus the temperature, of the TCE to control the temperature of plates 206 and 207 and substrates (e.g., substrate 209). Temperature controller 242 and / or system controller 260 can control the gas flow rate of a backside gas (e.g., helium) flowing to gas channels in ESC 204 by controlling the flow from one or more of gas sources 232 to the gas channels to cool the substrate. Temperature controller 242 can also communicate with coolant assembly 246 to control the flow (pressure and flow rate) of a first coolant through the channels in ESC 204. First coolant assembly 246 can receive the cooling fluid from a reservoir (not shown). For example, coolant assembly 246 can include a coolant pump and a reservoir. Temperature controller 242 operates coolant assembly 246 to flow coolant through channels 216 to cool base plate 207. Temperature controller 242 can control the flow rate and temperature of the coolant. The temperature controller 242 controls the current supplied to the TCE and the pressure and flow rate of the gas and / or coolant supplied to the channel based on parameters detected by the sensor 243 within the processing chamber 205. The temperature sensor 243 can include a resistive temperature device, a thermocouple, a digital temperature sensor, and / or other suitable temperature sensor. During the etching process, the substrate 209 can be heated to a predetermined temperature (e.g., 120 degrees Celsius (° C.)) in the presence of a high-power plasma. The flow of gas and / or coolant through the channel can reduce the temperature of the base plate 207, which can reduce the temperature of the substrate 209 (e.g., from 120° C. to 80° C.).

[0068] Valve 256 and pump 258 can be used to exhaust reactants from process chamber 205. System controller 260 can control components of substrate processing system 200, including controlling the level of supplied RF power, the pressure and flow rate of supplied gas, RF matching, etc. System controller 260 controls the status of valve 256 and pump 258. Robot 270 can be used to transfer substrates to and remove substrates from ESC 204. For example, robot 270 can transfer substrates between ESC 204 and load lock 272. Robot 270 can be controlled by system controller 260. System controller 260 can also control the operation of load lock 272.

[0069] The power supply 280 can provide power (including high voltage) to electrodes in the ESC 204 to electrostatically clamp the substrate 209 to the top plate 206. The power supply 280 can be controlled by the system controller 260.

[0070] Valves, gas and / or coolant pumps, power supplies, RF generators, etc. may be referred to as actuators. TCEs, gas channels, coolant channels, etc. may be referred to as temperature adjustment elements.

[0071] Now refer to Figure 2 and Figure 3 , which shows an RF distribution circuit 300 that may include an RF generator 302, a matching network 304, a filter 306, a transformer 308, and a load 310. In one embodiment, the filter 306 is not included. The load 310 is shown as a capacitor and may represent, for example, the impedance of the showerhead 210 and a ground reference potential 316. The RF generator 302 may be one of the RF generators 223 and generates an RF signal. The matching network 304 may be one of the matching networks 227 and matches the impedance of (i) the output of the RF generator 302 and (ii) the input of the filter 306 and / or the transformer 308. The matching network 304 may perform an automatic matching operation, which includes tuning one or more components to match the output of the RF generator 302 to the input impedance of the filter 306 and / or the transformer 308. This may include tuning, for example, the capacitor of the matching network 304.

[0072] The filter 306, if included, may filter out one or more RF signals generated by one or more RF generators other than the RF generator 302. The filter 306 allows the RF signals generated by the RF generator to pass through and proceed to the transformer 308.

[0073] Transformer 308 includes a primary coil 312 and a secondary coil 314. Primary coil 312 and secondary coil 314 have corresponding windings and / or voltage conversion ratios. For example, the ratio may be 3:4 or 1:2. Transformer 308 converts a first RF signal at a frequency received from matching network 304 or filter 306 into a second RF signal at the same frequency. Transformer 308 then provides the second RF signal to, for example, an electrode and / or showerhead to adjust the plasma ionization density and ionization energy within the processing chamber.

[0074] Transformer 308 performs multiple functions, including providing ballasting and isolation between the primary and secondary sides of transformer 308 , thereby providing isolation between (i) RF generator 302 and matching network 304 and (ii) load 310 . In one embodiment, a ballastless device is connected between (i) RF generator 302 and matching network 304 , (ii) matching network 304 and filter 306 , (iii) filter 306 and transformer 308 , and / or (iv) matching network 304 and transformer 308 . This isolation reduces the impact of load impedance variations on the corresponding input circuits (or RF generator 302 and matching network 304 ). The impedance of load 310 may vary during substrate processing. The amount of variation depends on the recipe and the process being performed. Input impedance variation can also be controlled by selecting an appropriate transformation ratio. Input impedance represents the impedance of the input of filter 306 as seen by matching network 304 . Since the relevant changes in input impedance are smaller than changes in load impedance, transformer 308 also enables faster tuning of the components of matching network 304. Transformer 308 can also minimize the amount of reflected power received at RF generator 302 and deliver high power (e.g., 10 kW) to load 310.

[0075] Although Figure 3 A single RF distribution circuit 300 is shown, but may be used Figure 3 Multiple RF distribution circuits of the type shown in supply RF power to the respective stations of the process chamber. Figure 7 As shown in , the secondary winding of the transformer can be supplied with power via the corresponding coaxial cable. Figure 7 As shown in , each station may include a switch and a corresponding virtual load. The switch can be Figure 2 is controlled by one of the controllers 242, 260.

[0076] Figure 4A and 4B Smith charts 400, 402 are shown illustrating the first load impedance and the second load impedance. Figure 3 FIG2 shows an exemplary input impedance of the RF distribution circuit 300. The input impedance is represented by points 404 and 406. In the example shown, the first load impedance is 130 pF, while the second load impedance is 3,000,000 pF. As can be seen from the Smith charts 400 and 402, the distance between points 404 and 406 (and thus the difference in input impedance) is minimal relative to the difference in load impedance.

[0077] Figure 5A dual RF distribution circuit 500 is shown that includes a first (or high) RF path 502 and a second (or low) RF path 504. The first RF path 502 includes a first RF generator 506, a first matching network 508, a first filter 510, and a first transformer 512 having a first transformation ratio. The second RF path 504 includes a second RF generator 520, a second matching network 522, a second filter 524, and a second transformer 526 having a second transformation ratio. The first transformer 512 is connected to the second transformer 526. The transformers 512, 526 provide a transformer coupled combiner that can combine the RF signals generated by the RF paths 502, 504 to provide a single RF signal to a load 530. The single RF signal has frequency components of the two RF signals. The transformers 512, 526 convert the two RF signals into a single RF signal. This can include, for example, changing the amplitude of the two RF signals to provide a single RF signal having an amplitude different from that of the two RF signals. The load 530 is shown as a capacitor that represents, for example, Figure 2 The load impedance is formed between the showerhead 210 and the ground reference potential 540. The load 530 can be one or more electrodes of one or more processing stations in one or more processing chambers, each station can include one or more electrodes and each processing chamber can include one or more stations.

[0078] RF generators 506 and 520 generate respective RF signals. For example, the first RF generator 506 may generate a 13.56 MHz RF signal, while the second RF generator 520 may generate a 400 kHz RF signal. The first matching network 508 may match the output impedance of the first RF generator 506 with the input impedance of the first filter 510. The second matching network 522 may match the output impedance of the second RF generator 520 with the input impedance of the second filter 524.

[0079] The first filter 510 functions as a high-pass filter and (i) allows the first RF signal generated by the first RF generator 506 to pass through to the first transformer 512 and (ii) prevents the RF signal generated by the second RF generator 520 from being received at the first RF generator 506. The second filter 524 functions as a low-pass filter and (i) allows the second RF signal generated by the second RF generator 520 to pass through to the second transformer 526 and (ii) prevents the RF signal generated by the first RF generator 506 from being received at the second RF generator 520. As shown, by including separate primary coils for the RF paths 502, 504 and selecting an appropriate number of primary windings for each primary coil, as well as including appropriate matching circuitry in the matching networks 508, 522, both RF generators 506, 520 can be properly matched.

[0080] The first transformer 512 includes a primary coil 532 and a secondary coil 534. The second transformer 526 includes a primary coil 536 and a secondary coil 538. The first ends of the primary coils 532 and 536 are connected to the filters 510 and 524. In one embodiment, the filters 510 and 524 are not included, and the primary coils 532 and 536 are connected to the matching networks 508 and 522. The second ends of the primary coils 532 and 536 are connected to the ground reference potential 540. The first ends of the secondary coils 534 and 538 are connected to the ground reference potential 540. The second ends of the secondary coils 534 and 538 are connected to the load 530. The first transformer 512 can convert a first RF signal at a first frequency received from the first filter 510 into a second RF signal at the first frequency. The second transformer 526 can convert a third RF signal at a second frequency received from the second filter 524 into a fourth RF signal at the second frequency. The transformers 512 and 526 may then provide the second RF signal and the fourth RF signal to, for example, an electrode and / or a showerhead to adjust the plasma ionization density and ionization energy in the processing chamber.

[0081] Figure 6 The Smith chart 600 illustrates an example of the change in input impedance of the LF and HF paths. Figure 5 The LF and HF paths 502, 504 are short-circuited, open-circuited, and provide an input impedance of 50Ω load impedance. Figure 6 In FIG. 6 , a circle corresponding to the HF path is shown, and a square corresponding to the LF path is shown. The Smith chart 600 is a logarithmic representation of possible input impedance values. As the input impedance changes, the corresponding point moves to a different position on the Smith chart.

[0082] Points 602, 604, and 606 represent the input impedance of the HF path 502 when it is short-circuited, open-circuited, and provides a 50Ω load impedance, respectively. Providing a 50Ω load impedance represents a load impedance that can provide a 50Ω input impedance. Points 610, 612, and 614 represent the input impedance of the LF path 504 when it is short-circuited, open-circuited, and provides a 50Ω load impedance. A short circuit refers to a direct or indirect conductive connection (or path) between the showerhead 210 and the ground reference potential 540. A short circuit refers to a situation where the load impedance is 0Ω. An open circuit refers to a situation where there is no conductive path between the showerhead 210 and the ground reference potential 540. An open circuit refers to a situation where the load impedance approaches infinity. As can be seen from the Smith chart, the distances between points or locations 602, 604, and 606, as well as the distances between points or locations 610, 612, and 614, are minimal and do not span the entire Smith chart, but rather lie within a small portion of the Smith chart. Therefore, the differences in the corresponding input impedances are also minimal.

[0083] Similar to Figure 3308, transformers 512, 526 have multiple functions, including ballasting and isolation between the primary and secondary sides of transformers 512, 526. In one embodiment, ballastless devices are connected between (i) the RF generators 506, 520 and the matching networks 508, 522, (ii) the matching networks 508, 522 and the filters 510, 524, (iii) the filters 510, 524 and the transformers 512, 526, and / or (iv) the matching networks 508, 522 and the transformers 512, 526.

[0084] Although Figure 5 A single RF distribution circuit 500 is shown, but may be used Figure 5 Multiple RF distribution circuits of the type shown in supply RF power to corresponding stations of the processing chamber. Figure 7 , the secondary winding of the transformer can supply power to the station through the corresponding coaxial cable. Figure 7 As shown in , each station may include a switch and a corresponding dummy load. For example, a switch may be connected downstream of terminal 550, and the switch may switch between (i) the corresponding coaxial cable connected to the electrode and / or showerhead and (ii) the dummy load. The switch may be Figure 2 is controlled by one of the controllers 242, 260.

[0085] Figure 7 A quad RF distribution circuit 700 is shown including a first (or high) RF path 702 and a second (or low) RF path 704. The first RF path 702 includes a first RF generator 706, a first matching network 708, and a first filter 710. The second RF path 704 includes a second RF generator 720, a second matching network 722, and a second filter 724. The quad RF distribution circuit 700 includes a transformer 712 having two inputs, four outputs, and a transformation ratio shared by the four outputs. The four outputs feed four channels, which are connected to four loads (or showerheads) 750, 752, 754, and 756 at four stations in the processing chamber.

[0086] RF generators 706 and 720 generate respective RF signals. For example, the first RF generator 706 may generate a 13.56 MHz RF signal, while the second RF generator 720 may generate a 400 kHz RF signal. A first matching network 708 may match the output impedance of the first RF generator 706 with the input impedance of the first filter 710. A second matching network 722 may match the output impedance of the second RF generator 720 with the input impedance of the second filter 724. The first filter 710 functions as a high-pass filter and (i) allows the first RF signal generated by the first RF generator 706 to pass through the first transformer 712 and (ii) prevents the first RF generator 706 from receiving the RF signal generated by the second RF generator 720. The second filter 724 functions as a low-pass filter and (i) allows the second RF signal generated by the second RF generator 720 to pass through the second transformer 712 and (ii) prevents the second RF generator 720 from receiving the RF signal generated by the first RF generator 706. As shown, by including separate primary coils (or primary windings) for the RF paths 702 , 704 and selecting an appropriate number of primary turns for each primary coil, and including appropriate matching circuitry in the matching networks 708 , 722 , both RF generators 706 , 720 may be properly matched.

[0087] Transformer 712 is a transformer-coupled combiner that combines the two RF signals generated by RF paths 702 and 704 to provide four RF signals, which are provided to loads 750, 752, 754, and 756. Loads 750, 752, 754, and 756 are shown as capacitors representing, for example, the load impedance between a showerhead and a ground reference potential 760. Although transformer 712 is shown as having two inputs and four outputs, transformer 712 may have two or more inputs and one or more outputs.

[0088] Transformer 712 includes a first primary coil 730, a second primary coil 732, a first secondary coil 734, a second secondary coil 736, a third secondary coil 738, and a fourth secondary coil 740. In one embodiment, primary coils 730 and 732 have the same number of windings, and secondary coils 734, 736, 738, and 740 have the same number of windings. The first ends of primary coils 730 and 732 are connected to filters 710 and 724. In one embodiment, filters 710 and 724 are not included, and the first ends of primary coils 730 and 732 are connected to matching networks 708 and 722. The second ends of primary coils 730 and 732 are connected to a ground reference potential 760. The first ends of secondary coils 734, 736, 738, and 740 are connected to loads 750, 752, 754, and 756, respectively. The second ends of secondary coils 734, 736, 738, and 740 are connected to a ground reference potential 760. The transformer receives the RF signals from paths 702 , 704 , combines the signals, and provides the combined RF signal to each of the loads 750 , 752 , 754 , 756 through secondary coils 734 , 736 , 738 , 740 .

[0089] The transformer 712 can convert and combine the first RF signal at the first frequency received from the first filter 710 and the second RF signal at the second frequency received from the second filter 724 into a third RF signal. The third RF signal includes both the first RF signal and the second RF signal. The transformer 712 can then provide the third RF signal to, for example, an electrode and / or a showerhead to adjust the plasma ionization density and ionization energy within the processing chamber.

[0090] Similar to Figure 3 308, transformer 712 has multiple functions, including providing ballasting and isolation between the primary and secondary sides of transformer 712. In one embodiment, ballastless devices are connected between (i) the RF generators 506, 520 and the matching networks 508, 522, (ii) the matching networks 508, 522 and the filters 510, 524, (iii) the filters 510, 524 and the transformers 512, 526, and / or (iv) the matching networks 508, 522 and the transformers 512, 526.

[0091] In one embodiment, the secondary coils 734, 736, 738, 740 may be connected to switches 762, 764, 766, 768, and the switches 762, 764, 766, 768 may switch between the loads 750, 752, 754, 756 and the dummy loads 770, 772, 774, 776. In another embodiment, the switches 762, 764, 766, 768 and the dummy loads 770, 772, 774, 776 are not included. The secondary coils 734, 736, 738, 740 or the switches 762, 764, 766, 768 may be connected to the loads 750, 752, 754, 756 via coaxial cables 780, 782, 784, 786. The switches 762, 764, 766, 768 may be connected to the loads 750, 752, 754, 756 via coaxial cables 780, 782, 784, 786. Figure 2 For example, as described above, one or more of the dummy loads 770, 772, 774, 776 may be connected when substrates in one or more of the corresponding stations are not being processed.

[0092] Some RF combiner circuits disclosed herein (such as Figure 7 712 ) provides a balanced distribution system capable of dividing the combined RF signal into n equal channels, where n is an integer greater than or equal to 2. The outputs of the n channels are isolated from each other so that changes in one channel do not affect or minimally affect changes in other channels. The inputs of the channels are isolated from the input of the transformer 712. The RF combiner circuit provides fast and smooth ignition of plasma generation.

[0093] Configuration Figure 3 、 5 7 and 8 to utilize each RF distribution circuit 300, 500, 700 for a plurality of different substrate processes. The processes may include etching, deposition, and / or other substrate processing.

[0094] Figure 8 A side view of an exemplary transformer 800 that can be used to distribute high frequency RF signals in an RF distribution circuit is shown. For example, Figure 3 and 5 Each of the transformers 308 and 512 can be replaced by the transformer 800. The transformer 800 is a coaxial transformer and can include a primary coil 802 and a secondary coil 804. The primary coil 802 includes: (i) conductive shields 822 and 832 for two coaxial cables 806 and 810; and (ii) a conductive interconnect 808. The conductive interconnect 808 extends through the non-conductive jackets 820 and 830 of the coaxial cables 806 and 810 and is connected to the conductive shields 822 and 832. The conductive interconnect can be a conductive plate or other suitable interconnect capable of maintaining the position of the second coaxial cable 810 relative to the first coaxial cable 806.

[0095] The coaxial cables 806 and 810 extend parallel to each other and further include conductive cores 825 and 835, which are isolated from the conductive shields 822 and 832 by inner dielectric insulators 824 and 834. The conductive cores 825 and 835 are connected in series by conductors 826A and 826B. Conductor 826A connects the first end of the first coaxial cable 806 to the first end of the second coaxial cable 810. The first end of the second coaxial cable 810 is located at the opposite end of the conductive interconnect 808 from the first end of the first coaxial cable 806. Conductor 826B connects the second end of the first coaxial cable 806 to the second end of the second coaxial cable 810. The second end of the second coaxial cable 810 is located at the opposite end of the conductive interconnect 808 from the second end of the first coaxial cable 806.

[0096] For example, the conductive shields 822 and 832, the conductive cores 825 and 835, and the conductors 826A and 826B can be formed from copper and / or other suitable materials that exhibit minimal heating during use. The non-conductive jackets 820 and 830 can be formed from plastic. The inner dielectric insulators 824 and 834 are non-conductive and can be formed from various dielectric materials, such as polyethylene (PE) and polytetrafluoroethylene (PTFE). In one embodiment, as shown, the conductors 826A and 826B are not provided with jackets, shields, and / or inner dielectric insulators.

[0097] It can be difficult to manufacture a low-frequency transformer capable of handling high radio frequencies, such as those greater than 1 megahertz (MHz), without overheating the transformer. The transformer's magnetic permeability (or distributed inductance) may need to be reduced, and the transformer may need to be formed from specialized materials. Transformer 800 can be used for high radio frequencies, microwave frequencies, and the like. The length L1 of coaxial cables 806, 810 may be based on and / or equal to a fractional multiple of the wavelength of the transmitted RF. For example, the fractional multiple may be less than half (1 / 2) the wavelength of the transmitted RF. In one embodiment, the length L1 of coaxial cables 806, 810 is equal to one-quarter (1 / 4) the wavelength of the transmitted RF. A quarter wavelength (or multiple thereof) has the following advantages: depending on the circuit, it transforms the corresponding impedance of the transformer from 0 ohms (Ω) (or short circuit) to infinite Ω (or open circuit), or vice versa. Conductive cores 825, 835 and wires 826A, 826B The total length of the series loop provided may be based on and / or equal to a multiple of the length L1.In one embodiment, the total length of the series loop provided by the conductive cores 825, 835 and the conductors 826A, 826B is equal to four times the length L1 (or 4L1). For example, the transformer 800 can have a transformation ratio of 1:2 between the primary winding and the secondary winding, where the primary winding serves as the primary coil 802 and comprises the input of the transformer 800, and the secondary winding serves as the secondary coil 804 and provides the output of the transformer 800. Although the coaxial cables 806, 810 can be formed in a manner similar to RG58C coaxial cable, RG58C coaxial cable may not be suitable for high power applications, such as those associated with substrate processing systems. The dimensions and / or materials of the coaxial cables 806, 810 can differ from those of the RG58C coaxial cable.

[0098] The RF splitter circuit disclosed above exhibits: high isolation between input and output to reduce the sensitivity of input impedance to load group impedance variations; improved isolation between stations; and impedance matching of LF and HF paths. The RF splitter circuit disclosed above is also robust and provides higher reliability than conventional RF combiners and splitter circuits. The disclosed RF splitter circuit: includes balanced multiple stations; exhibits fast tuning; enables RF signals to be supplied to multiple stations; exhibits low reflected power at both LF and HF generators; and provides an unconditionally stable system. The RF splitter circuit is also capable of supplying high-power RF signals (e.g., 10 kilowatts (kW) HF and 8 kW LF).

[0099] The foregoing description is merely illustrative in nature and is in no way intended to limit the present disclosure, its application or use. The broad teachings of the present disclosure can be implemented in various forms. Therefore, although the present disclosure includes specific examples, the true scope of the present disclosure should not be so limited, because other modifications will become apparent when studying the drawings, description and appended claims. It should be understood that one or more steps in the method can be performed in a different order (or simultaneously) without changing the principles of the present disclosure. In addition, although each embodiment is described above as having certain features, any one or more of those features described with respect to any embodiment of the present disclosure can be implemented in the features of any other embodiment and / or combined with the features of any other embodiment, even if the combination is not explicitly described. In other words, the embodiments described are not mutually exclusive, and the permutation of one or more embodiments with each other remains within the scope of the present disclosure.

[0100] Various terms are used to describe the spatial and functional relationships between elements (e.g., between modules, between circuit elements, between semiconductor layers, etc.), including "connected," "engaged," "coupled," "adjacent," "next to," "on top of," "above," "below," and "disposed." Unless the relationship between a first and a second element is explicitly described as "direct," when such a relationship is described in the above disclosure, the relationship can be a direct relationship, in which there are no other intervening elements between the first and second elements, but can also be an indirect relationship, in which there are one or more intervening elements (spatially or functionally) between the first and second elements. As used herein, the phrase "at least one of A, B, and C" should be construed to mean a logical (A or B or C), using a non-exclusive logical OR, and should not be construed to mean "at least one of A, at least one of B, and at least one of C."

[0101] In some implementations, the controller is part of a system, which can be part of the examples described above. Such a system can include semiconductor processing equipment that includes one or more processing tools, one or more chambers, one or more platforms for processing, and / or specific processing components (wafer pedestals, gas flow systems, etc.). These systems can be integrated with electronic devices for controlling their operation before, during, and after processing of semiconductor wafers or substrates. The electronic devices can be referred to as "controllers" and can control various components or subcomponents of one or more systems. Depending on the processing requirements and / or system type, the controller can be programmed to control any of the processes disclosed herein, including the delivery of process gases, temperature settings (e.g., heating and / or cooling), pressure settings, vacuum settings, power settings, radio frequency (RF) generator settings, RF matching circuit settings, frequency settings, flow rate settings, fluid delivery settings, position and operation settings, wafer transfer into and out of tools connected to or interfaced with a specific system and other transfer tools and / or load locks.

[0102] In general, a controller can be defined as an electronic device having various integrated circuits, logic, memory, and / or software that receive instructions, issue instructions, control operations, enable cleaning operations, enable endpoint measurements, and the like. The integrated circuits can include chips in the form of firmware that stores program instructions, digital signal processors (DSPs), chips defined as application specific integrated circuits (ASICs), and / or one or more microprocessors or microcontrollers that execute program instructions (e.g., software). The program instructions can be instructions sent to the controller in the form of various separate settings (or program files) that define operating parameters for performing specific processes on or for a semiconductor wafer or system. In some embodiments, the operating parameters can be part of a recipe defined by a process engineer to complete one or more process steps during the manufacture of one or more layers, materials, metals, oxides, silicon, silicon dioxide, surfaces, circuits, and / or the die of the wafer.

[0103] In some implementations, the controller can be part of or coupled to a computer that is integrated with the system, coupled to the system, otherwise networked to the system, or a combination thereof. For example, the controller can be in the "cloud" or all or part of a wafer fab host system that can allow remote access to wafer processing. The computer can enable remote access to the system to monitor the current progress of manufacturing operations, review the history of past manufacturing operations, review trends or performance metrics for multiple manufacturing operations, change parameters of the current process, set processing steps to follow the current process, or start a new process. In some examples, a remote computer (e.g., a server) can provide process recipes to the system via a network (which can include a local network or the Internet). The remote computer can include a user interface that enables the input or programming of parameters and / or settings, which are then sent from the remote computer to the system. In some examples, the controller receives instructions in the form of data that specify parameters for each processing step to be performed during one or more operations. It should be understood that the parameters can be specific to the type of process to be performed and the type of tool the controller is configured to interface with or control. Thus, as described above, the controller can be distributed, for example, by including one or more discrete controllers networked together and working toward a common purpose (e.g., processing and control as described herein). An example of a distributed controller for such a purpose is one or more integrated circuits on a chamber communicating with one or more integrated circuits remotely (e.g., at a platform level or as part of a remote computer), which combine to control processing on the chamber.

[0104] Example systems may include, but are not limited to, plasma etch chambers or modules, deposition chambers or modules, spin rinse chambers or modules, metal plating chambers or modules, cleaning chambers or modules, bevel edge etch chambers or modules, physical vapor deposition (PVD) chambers or modules, chemical vapor deposition (CVD) chambers or modules, atomic layer deposition (ALD) chambers or modules, atomic layer etch (ALE) chambers or modules, ion implantation chambers or modules, track chambers or modules, and any other semiconductor processing system that may be associated with or used in the manufacture and / or preparation of semiconductor wafers.

[0105] As described above, depending on one or more processing steps to be performed by the tool, the controller can communicate with one or more other tool circuits or modules, other tool components, cluster tools, other tool interfaces, adjacent tools, neighboring tools, tools located throughout the factory, a host computer, another controller, or tools used in the material transport of wafer containers to and from tool locations and / or load ports in a semiconductor manufacturing facility.

Claims

1. A transformer comprising: A primary coil corresponding to a primary winding configured to receive an input from a matching network or a filter and comprising: a first shield of the first coaxial cable; a second shield for the second coaxial cable; and a conductive interconnect connecting the first shield to the second shield; and a secondary coil corresponding to a secondary winding configured to provide an output to an electrode of the processing chamber and comprising: a first core of the first coaxial cable; a second core of the second coaxial cable; and A pair of wires connects the first core to the second core. 2 . The transformer of claim 1 , wherein the first coaxial cable extends parallel to the second coaxial cable. 3 . The transformer of claim 1 , wherein a sum of the lengths of the first core, the second core, and the paired conductors is at least one of: based on or equal to a multiple of the length of each of the first coaxial cable and the second coaxial cable.

4. The transformer of claim 1, wherein a length of each of the first coaxial cable and the second coaxial cable is at least one of: based on or equal to a fractional multiple of a wavelength of a radio frequency signal transmitted by the transformer.

5. A radio frequency distribution circuit, comprising: a radio frequency generator configured to generate a first radio frequency signal, wherein the first radio frequency signal includes a frequency component at a certain radio frequency; and The transformer according to claim 1, wherein the transformer is configured to convert the first radio frequency signal into a second radio frequency signal, the second radio frequency signal comprising a frequency component at the radio frequency.

6. A substrate processing system comprising: The radio frequency distribution circuit according to claim 5; processing room; a showerhead comprising an electrode and disposed in the processing chamber; and a substrate support positioned in the processing chamber adjacent the showerhead, The transformer is configured to supply the second radio frequency signal to the electrode.

7. A radio frequency distribution circuit, comprising: a first filter configured to receive a first radio frequency signal and a second radio frequency signal from at least one radio frequency generator and to filter out the first radio frequency signal, wherein the first radio frequency signal is at a first frequency and the second radio frequency signal is at a second frequency, and the second frequency is greater than the first frequency; a second filter configured to receive the first RF signal and the second RF signal from the at least one RF generator and filter out the second RF signal; a first matching network for matching an output of the at least one RF generator to an input of the first filter; a second matching network for matching an output of the at least one RF generator to an input of the second filter; and a transformer-coupled combiner connected to the output of the filter, configured to convert the first RF signal into a third RF signal; convert the second RF signal into a fourth RF signal; and combine the first RF signal with the second RF signal, or combine the third RF signal with the fourth RF signal, wherein the third RF signal includes a frequency component at the first frequency and the fourth RF signal includes a frequency component at the second frequency.

8. The radio frequency distribution circuit of claim 7, wherein the transformer coupled combiner comprises: a first transformer configured to receive an output of the first filter; and A second transformer is configured to receive an output of the second filter.

9. The radio frequency distribution circuit according to claim 8, wherein: The first transformer comprises: a primary coil connected to the first filter; and a secondary coil; and The second transformer comprises: a primary coil connected to the second filter and the primary coil of the first transformer; and A secondary coil is connected to the secondary coil of the first transformer.

10. The radio frequency distribution circuit according to claim 9, wherein: The primary coil and the secondary coil of the first transformer are connected to a ground reference potential, and The primary coil and the secondary coil of the second transformer are connected to the ground reference potential.

11. The radio frequency distribution circuit according to claim 9, wherein the first transformer comprises: The primary coil comprises: a first shield of the first coaxial cable; a second shield for the second coaxial cable; and a conductive interconnect connecting the first shield to the second shield; and The secondary coil comprises: a first core of the first coaxial cable; a second core of the second coaxial cable; and A pair of wires connects the first core to the second core.

12. The radio frequency distribution circuit of claim 11, wherein the first coaxial cable extends parallel to the second coaxial cable.

13. The RF distribution circuit of claim 11, wherein a sum of lengths of the first core, the second core, and the paired conductors is at least one of: based on or equal to a multiple of a length of each of the first coaxial cable and the second coaxial cable.

14. The RF distribution circuit of claim 11, wherein a length of each of the first coaxial cable and the second coaxial cable is at least one of: based on or equal to a fractional multiple of a wavelength of the first RF signal.

15. The radio frequency distribution circuit according to claim 7, wherein: The transformer-coupled combiner includes a first transformer, and The first transformer comprises: a first primary coil connected to the first filter; a second primary coil connected to the second filter; a first secondary coil connected to receive the third radio frequency signal; as well as A second secondary coil is connected to receive the fourth radio frequency signal.

16. The radio frequency distribution circuit according to claim 15, wherein: The first transformer comprises a third secondary winding, The third secondary coil is used to receive a fifth radio frequency signal, and The fifth radio frequency signal includes a frequency component at the first frequency and a frequency component at the second frequency.

17. The radio frequency distribution circuit of claim 7, wherein the transformer coupled combiner comprises: a first primary coil connected to the first filter; a second primary coil connected to the second filter; a first secondary coil configured to output the third radio frequency signal, the third radio frequency signal including frequency components at the first frequency and the second frequency respectively; and The second secondary coil outputs the fourth radio frequency signal, wherein the fourth radio frequency signal includes frequency components at the first frequency and the second frequency respectively.

18. The radio frequency distribution circuit of claim 17, wherein the transformer coupled combiner comprises: a third secondary coil outputting a fifth radio frequency signal, the fifth radio frequency signal including frequency components at the first frequency and the second frequency respectively; and The fourth secondary coil outputs a sixth radio frequency signal, wherein the sixth radio frequency signal includes frequency components at the first frequency and the second frequency respectively.

19. A substrate processing system comprising: The radio frequency distribution circuit according to claim 7; processing room; a showerhead comprising an electrode and disposed in the processing chamber; and A substrate support is positioned in the processing chamber adjacent the showerhead.

20. A radio frequency distribution circuit for supplying radio frequency power to electrodes in a substrate processing system, the radio frequency distribution circuit comprising: a radio frequency generator, configured to generate a first radio frequency signal; The transformer according to claim 1, configured to convert the first radio frequency signal into a second radio frequency signal, and supply the second radio frequency signal to the electrode to adjust the plasma ionization density and ionization energy in the processing chamber of the substrate processing system; and A matching network is used to match the output of the RF generator with the input of the transformer.

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