Pulsed voltage waveform biasing of plasma with multiple radio frequency generators

Abstract

Techniques and apparatus for waveform generation. The method generally includes generating an asymmetric radio frequency (RF) pulsed waveform by (i) delivering a first RF waveform at a first frequency using a first RF generator, (ii) delivering a second RF waveform at a second frequency using a second RF generator, (iii) delivering a third RF waveform at a third frequency using a third RF generator, and ( / V) synchronizing the delivering of the first, second, and third RF waveforms by aligning the phases of the first, second, and third RF waveforms. The first frequency is generally greater than the second frequency, and the second frequency is generally greater than the third frequency. The first frequency is generally a first harmonic of a fundamental frequency of the asymmetric RF pulsed waveform, and the second RF waveform and the third RF waveform are generally higher harmonics of the asymmetric RF pulsed waveform.

Description

PCT / US24 / 58717 05 December 2024 (05.12.2024)44024921 WO01PULSED VOLTAGE WAVEFORM BIASING OF PLASMA WITH MULTIPLE RADIO FREQUENCY GENERATORSBACKGROUNDField

[0001] Embodiments described herein generally relate to a system and methods used in semiconductor device fabrication. More specifically, embodiments of the present disclosure relate to a plasma processing system used to process a substrate.Description of the Related Art

[0002] Reliably producing high aspect ratio features is one of the key technology challenges for the next generation of semiconductor devices. One method of forming high aspect ratio features uses a plasma assisted etching process, such as a reactive ion etch (RIE) plasma process, to form high aspect ratio openings in a material layer, such as a dielectric layer, of a substrate. In a typical RIE plasma process, a plasma is formed in a processing chamber and ions from the plasma are accelerated towards a surface of a substrate to form openings in a material layer disposed beneath a mask layer formed on the surface of the substrate.

[0003] With technology nodes advancing towards 2 nanometers (nm), the fabrication of smaller features with larger aspect ratios requires atomic precision for plasma processing. For etching processes where the plasma ions play a major role, ion energy control is always challenging the development of reliable and repeatable device formation processes in the semiconductor equipment industry. In a typical plasma-assisted etching process, the substrate is positioned on a substrate support disposed in a processing chamber, a plasma is formed over the substrate by use of a radio frequency (RF) generator that is coupled to an electrode disposed on or within the plasma processing chamber, and ions are accelerated from the plasma towards the substrate across a plasma sheath. Additionally, RF substrate biasing methods, which require the use of a separate RF biasing source in addition to the RF generator that is used to initiate and maintain the plasma in the processing chamber, have been unable to desirablyPCT / US24 / 58717 05 December 2024 (05.12.2024)44024921 WO01 control the plasma sheath properties to achieve desirable plasma processing results that will allow the formation of these smaller device feature sizes. The traditional RF generator and RF biasing methods utilize sinusoidal RF waveforms to excite the plasma and form the plasma sheath often leads to undesirable and inconsistent process results due to sinusoidal shape of the RF waveform and the inability of the RF biasing methods to adjust the ion energy during processing due to limitations in the provided sinusoidal waveform characteristics.

[0004] Accordingly, there is a need in the art for a desirable plasma-assisted process that solves the problems described above.SUMMARY

[0005] To the accomplishment of the foregoing and related ends, the one or more aspects comprise the features hereinafter fully described and particularly pointed out in the claims. The following description and the appended drawings set forth in detail certain illustrative features of the one or more aspects. These features are indicative, however, of but a few of the various ways in which the principles of various aspects may be employed.

[0006] Embodiments of the present disclosure are directed to a method for waveform generation. The method generally includes generating a first asymmetric radio frequency (RF) pulsed waveform, where generating the first asymmetric RF pulsed waveform includes: ( / ) delivering a first RF waveform at a first frequency using a first RF generator, the first RF waveform having a first magnitude and a first phase; ( / / ) delivering a second RF waveform at a second frequency using a second RF generator, the second RF waveform having a second magnitude and a second phase; (Hi) delivering a third RF waveform at a third frequency using a third RF generator, the third RF waveform having a third magnitude and a third phase, where the first frequency is greater than the second frequency, and where the second frequency is greater than the third frequency; and (iv) synchronizing the delivering of the first RF waveform, the second RF waveform, and the third RF waveform, where the synchronizing includes aligning the first phase, the second phase, and the third phase.PCT / US24 / 58717 05 December 2024 (05.12.2024)44024921 WO01

[0007] Embodiments of the present disclosure provide a waveform generator. The waveform generator generally includes a first RF generator; a second RF generator; a third RF generator; and a system controller including memory and one or more processors coupled to the memory. The one or more processors are generally configured, individually or collectively, to perform a method for waveform generation that includes: generating a first asymmetric RF pulsed waveform, where generating the first asymmetric RF pulsed waveform includes: ( / ) delivering a first RF waveform at a first frequency using a first RF generator, the first RF waveform having a first magnitude and a first phase; ( / / ) delivering a second RF waveform at a second frequency using a second RF generator, the second RF waveform having a second magnitude and a second phase; (Hi) delivering a third RF waveform at a third frequency using a third RF generator, the third RF waveform having a third magnitude and a third phase, where the first frequency is greater than the second frequency, and where the second frequency is greater than the third frequency; and (iv) synchronizing the delivering of the first RF waveform, the second RF waveform, and the third RF waveform, where the synchronizing includes aligning the first phase, the second phase, and the third phase.BRIEF DESCRIPTION OF THE DRAWINGS

[0008] So that the manner in which the above recited features of embodiments of the present disclosure can be understood in detail, a more particular description of the disclosure, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this disclosure and are therefore not to be considered limiting of its scope, for the disclosure may admit to other equally effective embodiments.

[0009] Figure 1 is a schematic representation of an example plasma processing system, in which embodiments of the present disclosure may be implemented.

[0010] Figure 2 illustrates a graph of two separate asymmetric voltage waveforms that are established on a substrate due to a voltage waveform appliedPCT / US24 / 58717 05 December 2024 (05.12.2024)44024921 WO01 to an electrode of a processing chamber, in accordance with certain embodiments of the present disclosure.

[0011] Figures 3A and 3B are schematic views of example plasma processing systems with multiple radio frequency (RF) generators, according to one or more of the embodiments described herein.

[0012] Figure 4 is a flow diagram illustrating example operations for waveform generation, according to one or more of the embodiments described herein.

[0013] Figures 5A, 5B, 6A, 6B, 7A, 7B, 8A, and 8B illustrate graphs of example RF waveforms and asymmetric RF pulsed waveforms generated during the example operations of Figure 4, according to one or more of the embodiments described herein.

[0014] Figures 9A, 9B, 9C, and 9D illustrate example asymmetric RF pulsed waveforms generated during the example operations of Figure 4, according to one or more of the embodiments described herein.

[0015] To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. It is contemplated that elements disclosed in one embodiment may be beneficially utilized on other embodiments without specific recitation.DETAILED DESCRIPTION

[0016] Embodiments of the present disclosure generally relate to apparatus and methods for performing plasma-assisted substrate processing in a plasma processing system. More specifically, embodiments provided herein provide for controlling a plasma during processing by generating an asymmetric radio frequency (RF) pulsed waveform by delivering a plurality of synchronized RF waveforms using a plurality of RF generators. In some cases, the frequency of a first RF waveform of the plurality of RF waveforms may be a first harmonic of the asymmetric RF pulsed waveform (e.g., substantially equal to a fundamental frequency of the asymmetric RF pulsed waveform), the frequency of a second RF waveform of the plurality of RF waveforms may be a higher harmonic of the fundamental frequency of the asymmetric RF pulsed waveform, and thePCT / US24 / 58717 05 December 2024 (05.12.2024)44024921 WO01 frequency of a third RF waveform of the plurality of RF waveforms may be an even higher harmonic of the fundamental frequency of the asymmetric RF pulsed waveform. In this manner, the asymmetric RF pulsed waveform generated using the plurality of RF generators may essentially recreate and replace pulsed voltage (PV) waveforms generated by PV waveform generators in the time domain during certain plasma processing activities without the using PV waveform generators. It has been found that controlling the frequency, magnitude, and phase of each of the plurality of RF waveforms that form the asymmetric RF pulsed waveform during plasma processing may improve the plasma processing results on a substrate.Processing System Examples

[0017] Figure 1 is a schematic representation of an example plasma processing system 10. The plasma processing system 10 is configured for plasma-assisted substrate processing process, such as a plasma-assisted etching process or deposition process. In some examples, a plasma-assisted process include a plasma-assisted etching process, such as a reactive ion etch (RIE) process. The plasma processing system 10 can also be used in other plasma-assisted processes, such as plasma-enhanced deposition processes (for example, plasma-enhanced chemical vapor deposition (PECVD) processes, plasma-enhanced physical vapor deposition (PEPVD) processes, plasma- enhanced atomic layer deposition (PEALD) processes, plasma treatment processing, plasma-based ion implant processing, or plasma doping (PLAD) processing. In some embodiments, as shown in Figure 1 , the plasma processing system 10 is configured to form a capacitively-coupled-plasma (CCP). In other embodiments, a plasma may alternately be generated by an inductively coupled plasma (ICP) source disposed over a processing region of the plasma processing system 10.

[0018] The plasma processing system 10 includes a processing chamber 100, a substrate support assembly 136, a gas delivery system 182, a high voltage direct current (DC) supply 173, an RF generator assembly 170 that includes one or more RF generators 171 , and an optional RF match assembly 180 that includes one or more RF matches 172 (e.g., RF impedance matching networks).PCT / US24 / 58717 05 December 2024 (05.12.2024)44024921 WO01A chamber lid 123 includes one or more sidewalls and a chamber base that are configured to withstand the pressures and energy applied to them while a plasma 101 is generated within a vacuum environment maintained in a processing volume 129 of the processing chamber 100 during processing.

[0019] The gas delivery system 182, which is coupled to the processing volume 129 of the processing chamber 100 is configured to deliver at least one processing gas from at least one gas processing source 119 to the processing volume 129 of the processing chamber 100. The gas delivery system 182 includes the gas processing source 119 and one or more gas inlets 128 positioned through the chamber lid 123. The gas inlets 128 are configured to deliver one or more processing gasses to the processing volume 129 of the processing chamber 100.

[0020] The processing chamber 100 includes a chamber lid 123 and a substrate support assembly 136 positioned in the processing volume 129 of the processing chamber 100. In some embodiments, the chamber lid 123 is grounded and thus acts as an upper electrode during plasma processing. In some embodiments, the RF generator 171 is electrically coupled to a first lower electrode, such as the RF baseplate 137. The RF generator 171 is configured to deliver an RF signal to ignite and maintain the plasma 101 between the upper and lower electrodes. In one example, the RF generator 171 may deliver an RF source power to the RF baseplate 137 within the substrate support assembly 136 (e.g., a cathode assembly) for plasma production. However, in some alternative configurations, the RF generator 171 can be electrically coupled to the upper electrode. A center frequency of the RF source power can be from 13.56 MHz to very high frequency band such as 40 MHz, 60 MHz, 120 MHz or 162 MHz. The RF source power can be operated in a continuous mode or a pulsed mode. A pulsing frequency of the RF power can be from 100 to 10 kHz, and duty cycles are ranging from 5% to 95%. The RF generator 171 has a frequency tuning capability and can adjust its RF power frequency within e.g., ±5% or ±10%. In some embodiments, the RF generator 171 switches the RF power frequency at a predefined speed (e.g., two nanoseconds, fifty nanoseconds, etc.).PCT / US24 / 58717 05 December 2024 (05.12.2024)44024921 WO01

[0021] The substrate support assembly 136 is coupled to the RF generator 171 configured to deliver an RF signal to the processing volume 129 of the processing chamber 100. The RF generator 171 is electronically coupled to the RF match 172 disposed between the RF generator 171 and the processing volume 129 of the processing chamber 100. For example, the RF match 172 is an electrical circuit used between the RF generator 171 and a plasma reactor (e.g., the processing volume 129 of the processing chamber 100) to optimize power delivery efficiency. One or more RF filters (e.g., within the RF match 172) are designed to only allow powers in a selected frequency range, and to isolate RF power supplies from each other. In some cases, a bandwidth of an RF filter has to be larger than a frequency tuning range of the RF generator 171 .

[0022] During the plasma processing, the RF generator 171 delivers an RF signal to the RF baseplate 137 of the substrate support assembly 136 via the RF match 172. For example, the RF signal is applied to a load (e.g., gas) in the processing volume 129 of the processing chamber 100. If an impedance of the load is not properly matched to an impedance of a source (e.g., the RF generator 171 ), a portion of a waveform can reflect back in an opposite direction. Accordingly, to prevent a substantial portion of the waveform from reflecting back, it is necessary to find a match impedance (e.g., a matching point) by adjusting one or more components of the RF match 172 as the source and load impedances change.

[0023] The RF match 172 is electrically coupled to the RF generator 171 , the substrate support assembly 136, and a voltage waveform generator 175. The RF match 172 is configured to receive a synchronization signal from either or both of the RF generator 171 and the voltage waveform generator 175.

[0024] The substrate support assembly 136 may be coupled to a high voltage DC supply 173 that supplies a chucking voltage thereto. The high voltage DC supply 173 may be coupled to a filter assembly 111 that is disposed between the high voltage DC supply 173 and the substrate support assembly 136. The filter assembly 111 is configured to electronically isolate the high voltage DC supply 173 during plasma processing. In one configuration, a static DC voltage isPCT / US24 / 58717 05 December 2024 (05.12.2024)44024921 WO01 between about -5000V and about +5000V, and is delivered using an electrical conductor (such as a coaxial power delivery line). The filter assembly 111 may include multiple filtering components or a single common filter.

[0025] The substrate support assembly 136 is also coupled to a voltage waveform generator 175 configured to supply a voltage to a bias electrode 138 within the substrate support assembly 136 to bias a substrate disposed on the substrate support assembly 136. The voltage waveform generator 175 may be coupled to the RF baseplate 137 or a second electrode disposed within the substrate support assembly 136. The voltage waveform generator 175 is coupled to the filter assembly 111 , which is coupled to the electrode disposed within the substrate support assembly 136. The filter assembly 111 is disposed between the voltage waveform generator 175 and the substrate support assembly 136. The filter assembly 111 is configured to electronically isolate the voltage waveform generator 175 from at least the RF signal provided by the RF generator 171 during plasma processing.

[0026] The RF generator 171 and the voltage waveform generator 175 are each directly coupled to a system controller 126. The system controller 126 synchronizes the respective generated RF signal and voltage waveform.

[0027] Voltage and current sensors can be placed at an input and / or output of the RF match 172 to measure impedance and other parameters. These sensors can be synchronized using an external transistor-transistor logic (TTL) synchronization signal from an advanced waveform generator and / or RF generators or using measured voltage and current data to determine timing internally. For example, an output sensor 117 is configured to measure the impedance of the processing chamber 100, and other characteristics such as the voltage, current, harmonics, phase, and / or the like. An input sensor 116 is configured to measure the impedance of the RF generator 171 and other characteristics such as the voltage, current, harmonics, phase, and / or the like. Based on either of the synchronization signals or the characteristics of the processing chamber 100, the RF match 172 is able to capture fast impedance changes and optimize impedance matching.PCT / US24 / 58717 05 December 2024 (05.12.2024)44024921 WO01

[0028] The voltage waveform generator 175 is used to supply a voltage waveform and / or a tailored voltage waveform, which is a sum of harmonic frequencies associated with the generated waveform. The voltage waveform generator 175 may output a synchronization TTL signal to the RF match 172. The voltage waveform is coupled to the bias electrode 138 through the filter assembly 111. Typically, the bias electrode 138 is formed of one or more electrically conductive parts, such as one or more metal meshes, foils, plates, or combinations thereof. The high voltage DC supply 173 is applied to chuck a wafer during a process for a thermal control. In some cases, there can be a third electrode at an edge of the cathode assembly for edge uniformity control.

[0029] The system controller 126, also referred to herein as a processing chamber controller, includes a central processing unit (CPU), a memory, and support circuits. The system controller 126 is used to control the process sequence used to process the substrate, including the substrate biasing described herein. The CPU is a general-purpose computer processor configured for use in an industrial setting for controlling the processing chamber and subprocessors related thereto. The memory described herein, which is generally non-volatile memory, may include random access memory, read-only memory, floppy or hard disk drive, or other suitable forms of digital storage, local or remote. The support circuits are conventionally coupled to the CPU and comprise cache, clock circuits, input / output subsystems, power supplies, and the like, and combinations thereof. Software instructions (program) and data can be coded and stored within memory to instruct a processor within CPU. A software program (or computer instructions) readable by CPU in the system controller 126 determines which tasks are performable by the components in the plasma processing system 10.

[0030] Typically, the program, which is readable by CPU in the system controller 126, includes code, which, when executed by the processor (CPU), performs tasks relating to the plasma processing schemes described herein. The program may include instructions that are used to control the various hardware and electrical components within the plasma processing system 10 to perform the various process tasks and various process sequences used to implement thePCT / US24 / 58717 05 December 2024 (05.12.2024)44024921 WO01 methods described herein. In some embodiments, the program includes instructions that are used to perform one or more of the operations described below in relation to Figure 4.Voltage Waveform Examples

[0031] Figure 2 illustrates a graph 200 of two separate non-sinusoidal voltage waveforms established at a substrate disposed on a substrate receiving surface of the substrate support assembly 136 of the processing chamber 100 due to the delivery of voltage waveforms to the bias electrode 138 of the processing chamber 100. A first waveform (e.g., a waveform 225) is an example of a noncompensated voltage waveform established at the substrate during the plasma processing. A second waveform (e.g., a waveform 230) is an example of a compensated voltage waveform established at the substrate by applying a negative slope waveform to the bias electrode 138 of the processing chamber 100 during an “ion current stage” portion of the voltage waveform cycle by use of a current source. The compensated voltage waveform can alternatively be established by applying a negative voltage ramp during the ion current stage of the voltage waveform generated by the voltage waveform generator 175. The voltage waveform cycle of the waveforms 225, 230 each have a period TP, which is, for example, typically between 2 microsecond (ps) and 10 ps, such as 2.5 ps. The ion current stage of the voltage waveform cycle will typically take up between about 50% and about 95% of the period TP, such as from about 80% to about 90% of the period TP.

[0032] The waveforms 225 and 230 include two main stages: an ion current stage and a sheath collapse stage. Both portions (e.g., the ion current stage and the sheath collapse stage) of the waveforms 225 and 230, can be alternately and / or separately established at the substrate during the plasma processing. At a beginning of the ion current stage, a drop in the voltage at the substrate is created, due to the delivery of a negative portion of the voltage waveform (e.g., the ion current portion) provided to the bias electrode 138 by the voltage waveform generator 175, which creates a high voltage sheath above the substrate. The high voltage sheath allows the plasma generated positive ions to be accelerated towards the biased substrate during the ion current stage, andPCT / US24 / 58717 05 December 2024 (05.12.2024)44024921 WO01 thus, for RIE processes, controls the amount and characteristics of the etching process that occurs on the surface of the substrate during the plasma processing. The sheath collapse stage includes a positive voltage swing 240 (e.g., as a result of the positive wafer voltage), and the ion current stage includes a negative voltages swing (e.g., as a result of the positive wafer voltage), as illustrated in Figure 2.

[0033] In some embodiments, it is desirable for the ion current stage to include a region of the voltage waveform that achieves the voltage at the substrate that is stable or minimally varying throughout the stage, as illustrated in Figure 2 by the waveform 230. One will note that significant variations in the voltage established at the substrate during the ion current stage, such as shown by the positive slope in the waveform 225, will undesirably cause a variation in the ion energy distribution (IED) and thus cause undesirable characteristics of the etched features to be formed in the substrate during the RIE process. Plasma sheath impedance varies with supplied voltage waveform voltages. The RF match 172 can use either or both of the synchronization signals and / or use its internal sensors to sample impedances in different processing phases. In one example, a synchronization signal or characteristics determined by the input sensor 116 or the output sensor 117 are used to trigger the RF match 172 to determine at least two different impendences at different processing stages. Then, the RF match 172 updates its matching point based on the at least two different impedances.Asymmetric Radio Frequency Pulsed Waveform Generation Examples Using Multiple Radio Frequency Generators

[0034] Embodiments described herein are configured to enable the generation of an asymmetric radio frequency pulsed waveform (hereinafter also referred to as an “ARFP waveform”) for performing plasma-assisted processes using a plurality of radio frequency (RF) generators to simulate the formation of a voltage waveform similar to one or more of the waveforms illustrated in Figure 2. In this manner, the simulated voltage waveform, which is referred to herein as the ARFP waveform, may be generated without using a voltage waveform generator (e.g., pulsed direct current (DC) power supply), which often has voltage pulse frequency limitations. RF generators may also be more reliable and cheaper toPCT / US24 / 58717 05 December 2024 (05.12.2024)44024921 WO01 manufacture than a pulsed DC voltage waveform generator. The ARFP waveform generated by use of the plurality of RF generators may effectively replace a pulsed voltage waveform (e.g., waveform formed using a voltage source) generated by a pulsed DC voltage waveform generator. Generating the ARFP waveform using the plurality of sinusoidal RF waveforms at different RF frequencies can enable enhanced customization for plasma-assisted processes when compared to plasma-assisted processes that utilize voltage source generated waveforms delivered using one or more voltage waveform generators to control the plasma during processing. An ARFP waveform may include a series of asymmetric radio frequency pulses (hereinafter also referred to as “ARF pulses”) that may be delivered together to form a burst. During processing, the ARFP waveform will include the burst in which the ARF pulses may be delivered (i.e., pulse-on-time (POT)) and an off-time following the POT. The POT and the off-time may be cyclically repeated any number of times. The burst of the ARFP waveform may have a POT with a duration that is much larger than the period of each ARF pulse.

[0035] According to some embodiments, by controlling the frequency, magnitude, and phase of each of the plurality of sinusoidal RF waveforms, the plasma processing results on a substrate may be improved. For example, by manipulating the uniformity of the RF waveforms delivered (e.g., by adjusting the uniformity of the magnitudes of the RF waveforms), the apparent or simulated POT of the generated ARFP waveform may be controlled. In another example, by increasing the number of RF waveforms (e.g., harmonics) delivered, the generated ARFP waveform may be controlled to more closely align with (e.g., mirror) a desired voltage waveform shape. In yet another example, the phase of the RF waveforms may be aligned and / or locked during generation of the ARFP waveforms to synchronize the delivery of the RF waveforms to better form a generated asymmetric voltage waveform that has a desired voltage waveform shape.

[0036] Figures 3A and 3B are schematic views of example plasma processing systems 300A, 300B with multiple RF generators, according to one or more of the embodiments described herein.PCT / US24 / 58717 05 December 2024 (05.12.2024)44024921 WO01

[0037] The plasma processing system 300A includes the processing chamber 100, the chamber lid 123, substrate support assembly 136, the RF baseplate 137, and the bias electrode 138, as described above. As described above, the chamber lid 123 includes one or more sidewalls and a chamber base that are configured to withstand the pressures and energy applied to them while the plasma 101 is generated within the vacuum environment maintained in the processing volume 129 of the processing chamber 100 during processing. While not shown in Figures 3A and 3B, the plasma processing systems 300A and 300B will also include the gas delivery system 182, the high voltage direct current (DC) supply 173, and the filter assembly 111 illustrated in Figure 1. In some embodiments, and as shown in Figures 3A and 3B, plasma processing systems 300A and 300B will also include the RF generator assembly 170, RF generators 171 , and the optional RF match assembly 180 that are coupled to the RF baseplate 137 to generate and maintain a plasma within the processing volume 129.

[0038] In some embodiments, and as shown in Figures 3A and 3B, the voltage waveform generator 175 has been removed and replaced by an RF generator assembly 190 and an optional RF match assembly 195. The RF generator assembly 190 illustrated in FIG. 3A includes three RF generators 191 A, 191 B, 191 C. Although three RF generators are illustrated, it is to be understood that any number of RF generators may be included in the RF generator assembly 190. In some cases, only two RF generators may be included the RF generator assembly 190. The RF generators 191 A, 191 B, 191 C may be coupled together in parallel, as illustrated. The RF generators 191 A, 191 B, 191 C may be configured (e.g., using the system controller 126 of Figure 1 ) to deliver waveforms at different frequencies, different magnitudes, and / or different phases to an electrode in the plasma processing chamber, such as the biasing electrode 138.

[0039] The RF match assembly 195 illustrated in FIG. 3A includes three RF matches 196A, 196B, 196C. Although three RF matches are illustrated, it is to be understood that any number of RF matches may be included in or with the RF match assembly 195. In some cases, each of the RF generators 191 A, 191 B, 191 C may be coupled to and use one of the RF matches 196A, 196B, 196CPCT / US24 / 58717 05 December 2024 (05.12.2024)44024921 WO01 during waveform generation. In other cases, one or more of the RF generators 191 A, 191 B, 191 C may not be coupled to and not use one of the RF matches 196A, 196B, 196C.

[0040] Each of the RF generators 191 A, 191 B, 191 C may be configured to deliver one or more RF waveforms 301 , 302, 303, 304, 305, 306 (e.g., sinusoidal RF waveforms) at desired frequencies (e.g., six frequencies shown), as illustrated in the frequency domain graph 350A of Figure 3A. Each of the RF waveforms 301-306 delivered may have a magnitude (e.g., an RF power that the RF waveform is delivered at as shown relative to the Y-axis of the frequency domain graph 350A). RF waveforms 301 may be delivered at, for example, 400 kHz, RF waveform 302 may be delivered at 800 kHz, RF waveform 303 may be delivered at 1200 kHz, RF waveform 304 may be delivered at 1600 kHz, RF waveform 305 may be delivered at 2000 kHz, and RF waveform 306 may be delivered at 2400 kHz, as illustrated. In this manner, RF waveform 301 may be a first harmonic, and each consecutive RF waveform may be a higher harmonic than the previous harmonic. For example, RF waveform 302 may be a first harmonic of RF waveform 301 , RF waveform 303 may be a second harmonic of RF waveform 302, RF waveform 304 may be a third harmonic of RF waveform 303, RF waveform 305 may be a fourth harmonic of RF waveform 304, and RF waveform 306 may be a fourth harmonic of RF waveform 305. The RF waveforms 301 -306 may collectively form an ARF pulse.

[0041] In some embodiments, and as illustrated in Figure 3A, RF generator 191 A may deliver RF waveform 301 at the first harmonic, RF generator 191 B may deliver RF waveform 302 at the second harmonic, and the RF generator 191 C may deliver RF waveform 304 at the fourth harmonic, such that the RF waveform 303 (which is at the third harmonic) may be skipped (e.g., not delivered). It is to be understood that any number and combination of RF generators may be used to deliver any number and combination or RF waveforms. The combination of the delivered RF waveforms 301 -306 may construct an ARFP waveform in the time domain for use during plasma processing.

[0042] The plasma processing system 300B and graph 350B of Figure 3B may be similar to the plasma processing system 300A and the frequency domainPCT / US24 / 58717 05 December 2024 (05.12.2024)44024921 WO01 graph 350A of Figure 3A, but may not include the RF match assembly 195. That is, in some embodiments, none of the RF generators 191 A, 191 B, 191 C may be coupled to and associated with an RF match.

[0043] Figure 4 is a flow diagram illustrating example operations 400 for waveform generation, according to one or more of the embodiments described herein. The operations 400 may be utilized in a plasma processing system (e.g., plasma processing system 10). Figures 5A, 5B, 6A, 6B, 7A, 7B, 8A, and 8B illustrate graphs 500A, 500B, 600A, 600B, 700A, 700B, 800A, 800B of example RF waveforms and ARFP waveforms generated during the example operations 400 of Figure 4, according to one or more of the embodiments described herein. Figures 9A, 9B, 9C, 9D illustrate example ARF pulses 900A, 900B, 900C, and 900D generated during the example operations 400 of Figure 4, according to one or more of the embodiments described herein. Therefore, Figures 4, 5A, 5B, 6A, 6B, 7A, 7B, 8A, 8B, 9A, 9B, 9C, and 9D are herein described together for clarity.

[0044] The operations 400 include, at block 410, generating an ARFP waveform (sometimes referred to herein as the first ARFP waveform) in a first state. The first ARFP waveform formed using RF generators may effectively replace the target voltage waveform (e.g., a voltage waveform formed using voltage waveform generators) during plasma processing. The first ARFP waveform may have a fundamental frequency equal to a fundamental frequency of the target voltage waveform, or voltage waveform that is desired to be reproduced by the plurality of RF generators (e.g., one or more of voltage waveforms illustrated in Figure 2). For example, when the fundamental frequency of the target voltage waveform is 100 kHz, the fundamental frequency of the generated first ARFP waveform is also 100 kHz.

[0045] The operations 400 and other embodiments described herein enable the generation of ARFP waveforms at a much larger range of reproducible frequencies than traditional voltage waveforms generated by voltage power supplies. For example, the ARFP waveforms described herein may have, for example, be able to produce asymmetric waveforms with frequencies between 100 kHz and 20 MHz, as well as provide enhanced flexibility for achieving variousPCT / US24 / 58717 05 December 2024 (05.12.2024)44024921 WO01 voltage-current characteristics and power ratings for a wide variety of plasma- assisted processes.

[0046] According to certain embodiments, generating the first ARFP waveform in the first state at block 410 includes ( / ) delivering a first RF waveform in the first state at a first frequency using a first RF generator (e.g., RF generator 191 A) at block 412, ( / / ) delivering a second RF waveform in the first state at a second frequency using a second RF generator (e.g., RF generator 191 B) at block 414, and (Hi) delivering a third RF waveform in the first state at a third frequency using a third RF generator (e.g., RF generator 191 C) at block 416. The first RF waveform has a first magnitude and a first phase, the second RF waveform has a second magnitude and a second phase, and the third RF waveform has a third magnitude and a third phase. The magnitudes and phases of each of the RF waveforms may be the same, or different, while the delivered frequencies will include a fundamental frequency and harmonics thereof. As described above, it is to be understood that any number and combination of RF generators may be used to deliver any number and combination or RF waveforms during the operations 400.

[0047] According to certain embodiments, generating the first ARFP waveform in the first state at block 410 includes synchronizing the delivering of the first RF waveform, the second RF waveform, and the third RF waveform in the first state at block 418 by aligning the first phase, the second phase, and the third phase at block 420.

[0048] In some embodiments, the first frequency (associated with the first RF waveform) may be greater than the second frequency (associated with the second RF waveform), and the second frequency may be greater than the third frequency (associated with the third RF waveform). As described above, in some cases, each consecutive RF waveform may be a higher harmonic than the previous harmonic. A harmonic is generally understood to be a waveform with a frequency that is a positive integer of a fundamental frequency of a signal. In some cases, the fundamental frequency of a waveform may also be referred to as the first harmonic of the waveform. As described above, the first RF waveform (that is delivered at the first frequency) may be a first harmonic of the first ARFPPCT / US24 / 58717 05 December 2024 (05.12.2024)44024921 WO01 waveform (e.g., substantially equal to a fundamental frequency of the first ARFP waveform). The second RF waveform (that is delivered at the second frequency) may be a higher harmonic of the first ARFP waveform than the first harmonic (e.g., a second harmonic, a third harmonic, a fourth harmonic, etc.), and the third RF waveform (that is delivered at the third frequency) may be an even higher harmonic of the first ARFP waveform than the higher harmonic of the second RF waveform (e.g., a third harmonic, a fourth harmonic, a fifth harmonic, etc.). For example, the third RF waveform may be a third harmonic of the first ARFP waveform, a fourth harmonic of the first ARFP waveform, a fifth harmonic of the first ARFP waveform, or another harmonic of the first ARFP waveform. It is to be understood that any combination of some of the harmonics or all of the harmonics of may be delivered by RF generators during operations 400, depending on the desired resultant ARFP waveform.

[0049] In some cases, and also as described above, one or more of the harmonics may be skipped and a sequential RF waveform harmonic may not be delivered to the electrode. For example, in a three RF generator 191A-191 C system, the RF generator assembly 190 may be configured to deliver the first harmonic, third harmonic, and the fourth harmonic, while skipping the delivery of the second harmonic to the biasing electrode 138. Frequency domain graph 500A of Figure 5A illustrates potential RF waveforms 501 , 502, 503, 504, 505, 506 that may be delivered using RF generators. RF waveforms 501 - 506 may be configured to recreate target voltage waveform 520 illustrated in time domain graph 500B of Figure 5B, which may be an example of a voltage waveform formed using voltage generators. Delivering RF waveforms 501 , 502, and 504 forms one or more ARF pulses and results in the ARFP waveform 530 which substantially mirrors the target voltage waveform 520 illustrated in time domain graph 500B of Figure 5B. As illustrated in Figure 5A, RF waveform 501 may be delivered at 400 kHz and RF waveforms 502 and 504 may be delivered at some of the harmonics of 400 kHz (e.g., 800 kHz and 1600 kHz).

[0050] Frequency domain graph 600A of Figure 6A illustrates RF waveforms 601- 606. RF waveforms 601 - 606 may be configured to recreate target voltage waveform 620, which may an example of a voltage waveform formed usingPCT / US24 / 58717 05 December 2024 (05.12.2024)44024921 WO01 voltage generators. RF waveforms 601 - 606 forms one or more ARF pulses and result in the ARFP waveform 630 which substantially mirrors the target voltage waveform 620 illustrated in the time domain graph 600B of Figure 6B. As illustrated in Figure 6A, RF waveform 601 may be delivered at 200 kHz and consecutive RF waveforms 602-606 are delivered at harmonics of 200 kHz. For example, consecutive RF waveforms 602-606 are delivered at 400 kHz, 600 kHz, 800 kHz, 1000 kHz, and 1200 kHz. As a result of the greater number of RF waveforms (e.g., harmonics) delivered in frequency domain graph 600A (e.g., compared to the RF waveforms in frequency domain graph 500A), the resultant ARFP waveform 630 more closely aligns with (e.g., mirrors) the target voltage waveform 620 (e.g., compared to the waveforms in Figure 5B), as illustrated in Figure 6B.

[0051] In some embodiments, aligning the first phase, the second phase, and the third phase at block 420 includes aligning the first phase, the second phase, and the third phase to within 360 degrees. In some cases, for example, the first phase, the second phase, and the third phase may be aligned to within 90 degrees. In other cases, for example, the first phase, the second phase, and the third phase may be aligned to within 45 degrees. At block 410, at least one of the first phase, the second phase, and the third phase may not shift (e.g., may remain constant) in the first state. In this manner, the first RF waveform, the second RF waveform, and the third RF waveform may remain aligned with each other during the generation of the ARFP waveform. In some cases, the first, second, and third RF generators may be phase locked during operations 400.

[0052] The first ARFP waveform has a POT formed by the delivery and synchronizing of the RF waveforms that mimics the POT of a target voltage waveform generated using pulses from one or more voltage waveform generators. Generating the first ARFP waveform at block 410 may include controlling the first ARFP waveform in the first state by adjusting at least one of the first frequency, the first magnitude, the first phase, the second frequency, the second magnitude, the second phase, the third frequency, the third magnitude, and the third phase.PCT / US24 / 58717 05 December 2024 (05.12.2024)44024921 WO01

[0053] In some embodiments, controlling the first ARFP waveform in the first state includes adjusting an on-time of at least one of the RF generators used to generate the first ARFP waveform. In this manner, the burst of the ARF pulses of the first ARFP waveform may be controlled. In one example, the on-time (e.g., delivery of RF power) is synchronized such that all of the RF generators are on at the same time and off at the same time. According to certain embodiments, the combination of the harmonics of the RF generators (and their respective magnitudes) and the relative phase between the RF generators may be manipulated to control the waveform shape (e.g., the POT) of the ARFP waveform.

[0054] According to certain aspects, the magnitude, the phase (e.g., which impacts the superposition of the RF waveforms), and superposition of the harmonics of the RF waveforms may be manipulated to control the POT of the resultant ARFP pulse. Graph 700A of Figure 7A illustrates example RF waveforms 701-710 in the frequency domain that may be generated by two or more RF generators. RF waveforms 701 -710 result in the formation of the ideal ARFP pulse 740 illustrated in graph 700B of Figure 7B. As illustrated, RF waveform 701 may be delivered at 400 kHz and consecutive RF waveforms 702- 710 are delivered at harmonics of 400 kHz. For example, the consecutive waveforms may be delivered at 800 kHz, 1200 kHz, 1600 kHz, 2000 kHz, 2400 kHz, 2800 kHz, 3200 kHz, 3600 kHz, and 4000 kHz.

[0055] Graph 725A of Figure 7A illustrates example RF waveforms 711 -719 in the frequency domain that may be delivered by two or more RF generators. RF waveforms 711 -719 result in the formation of the ideal ARFP pulse 760 illustrated in graph 725B of Figure 7B. As illustrated, RF waveform 711 may be delivered at 400 kHz and consecutive RF waveforms 712-719 may be delivered at harmonics of 400 kHz. As a result of the increased magnitude for at least one of the two or more RF generators used to deliver the RF waveforms 711- 719 (including the RF waveform 711 , the fundamental frequency) and an alteration of the phase of at least one of the RF waveforms 711 -719 (which impacts the superposition of harmonic associated with the RF waveforms 711-719) in graph 725A (e.g., compared to the RF waveforms in graph 700A), the POT of thePCT / US24 / 58717 05 December 2024 (05.12.2024)44024921 WO01 resultant ARFP pulse 760 is greater than the POT of the ARFP pulse 740, as illustrated in Figure 7B. In this manner, the POT may be increased (compared to the ARFP pulse 740 in graph 700B) without changing the magnitude of the ARFP pulse 760 itself.

[0056] Graph 750A of Figure 7A illustrates example RF waveforms 721 -730 in the frequency domain that may be delivered by two or more RF generators. RF waveforms 721 -730 result in the formation of the ideal ARFP pulse 770 illustrated in graph 750B of Figure 7B. As illustrated, RF waveform 721 may be delivered at 400 kHz and consecutive RF waveforms 721 -730 may be delivered at harmonics of 400 kHz. As a result of the increased magnitude for at least one of the two or more RF generators used to deliver the RF waveforms 721-730, including the RF waveform 721 (e.g., the fundamental frequency) and an alteration of the phase of at least one of the RF waveforms 721 -730 (which impacts the superposition of the RF waveforms 721 -730) in graph 750A (e.g., compared to the RF waveforms in graph 700A and in graph 725A), the POT of the resultant ARFP pulse 770 is greater than the POT of the ARFP pulse 740 and the ARFP pulse 760, as illustrated in Figure 7B. In this manner, the POT may be increased (compared to the ARFP pulse 760 in graph 700B) without changing the magnitude of the ARFP pulse 770 itself.

[0057] According to certain embodiments, the pulse duty cycle of the ARF pulses and the power that is provided during the pulse duty cycle can be adjusted by controlling the magnitude and / or phase of each harmonic. The pulse duty cycle of the ARFP pulses are created when the magnitude of at least one of the delivered ARF pulses is greater than zero for a prescribed pulse duty cycle period of time. Therefore, during processing, a cyclically repeating ARF pulse delivery period TP(e.g., illustrated in Figure 7B) will include the pulse duty cycle period of time (Ton) and an ARFP waveform pulse “off-time” (Toff), which is created when the magnitude of the ARFP waveforms are all equal to zero.

[0058] In some embodiments, the first magnitude (e.g., of the first RF waveform) of the first harmonic may be higher than the second magnitude (e.g., of the second RF waveform) of the harmonic of the second frequency provided to the electrode. For example, the first waveform may have the highestPCT / US24 / 58717 05 December 2024 (05.12.2024)44024921WO01 magnitude, and subsequent waveforms (e.g., the second RF waveform (e.g., second or third harmonic) and the third RF waveform (e.g., fifth harmonic) may have lower magnitudes.

[0059] According to certain embodiments, the operations 400 may include generating a second ARFP waveform in a second state. The second state S2 may follow the first state S1 . It is to be understood that anything described herein with respect to the first ARFP waveform may also be applicable to the delivery of a second ARFP waveform. The second ARFP waveform may be generated using the same or different RF generators than the first ARFP waveform (e.g., to reduce the work load of the RF generators). Generating the second ARFP waveform in the second state may include ( / ) delivering a fourth RF waveform at a fourth frequency using the first RF generator, ( / / ) delivering a fifth RF waveform at a fifth frequency using the second RF generator, and (7 / 7) delivering a sixth RF waveform at a sixth frequency using the third RF generator. The fourth RF waveform has a fourth magnitude and a fourth phase, the fifth RF waveform has a fifth magnitude and a fifth phase, and the sixth RF waveform has a sixth magnitude and a sixth phase. The magnitudes, phases, and frequencies of each of the RF waveforms may be the same, or different. For example, the fourth frequency may be greater than the fifth frequency, and the fifth frequency may be greater than the sixth frequency.

[0060] In plasma-assisted processes that utilize voltage source generated waveforms delivered using one or more voltage waveform generators may use single-state pulsing schemes. Graph 800A of Figure 8A illustrates a plurality of pulse bursts 801 , 802, 803, 804, and 805 generated during a plurality of first states S1 in the time domain. The pulse bursts 801-805 (which may, in some cases, be considered and / or referred to collectively as a “voltage waveform” formed from pulse bursts) all have generally the same magnitude and have pulses with the same general shape in the millisecond (ms) time scale for each repeated state S1 (e.g., a single-state pulsing scheme). In other words, a first series of ARFP waveform pulses during a first state S1 are provided for desired period of time to form a burst of ARFP waveform pulses that include a plurality of similarly configured ARFP waveform pulses. In one example, the ARFPPCT / US24 / 58717 05 December 2024 (05.12.2024)44024921WO01 waveform pulses are provided at a first frequency (e.g., 100 kHz or 500 kHz pulse frequency) and first POT (e.g., 10-85%) and the burst of ARFP waveform pulses if provided a second frequency that is less than first frequency (e.g., 10 Hz to 1 kHz) and a burst-on-time (e.g., 50-90%).

[0061] According to certain embodiments, generating the second ARFP waveform in the second state includes synchronizing the delivering of the fourth RF waveform, the fifth RF waveform, and the sixth RF waveform in the second state by aligning the fourth phase, the fifth phase, and the sixth phase. In some embodiments, a magnitude of the second ARFP waveform is lower than a magnitude of the pulses of the first ARFP waveform. That is, at least one of the first magnitude (associated with the first RF waveform), the second magnitude (associated with the second RF waveform), and the third magnitude (associated with the third RF waveform) may be larger than at least one of the fourth magnitude (associated with the fourth RF waveform), the fifth magnitude (associated with the fifth RF waveform), and the sixth magnitude (associated with the sixth RF waveform). In this manner, the ARFP waveforms described herein may enable multi-state pulsing, where the magnitude of the generated ARFP waveforms changes between states. Graph 800B of Figure 8B illustrates a plurality of RF pulse bursts 811 , 812, 813, 814, 815 generated during a plurality of first states S1 and second states S2. The RF pulse bursts 811-815 (which may, in some cases, be considered and / or referred to collectively as an ARFP waveform) may have ARF pulses with the same general shape, but have different magnitudes. That is, the first state S1 may have a higher magnitude than the second state S2, resulting in the multi-state pulsing illustrated in Figure 8B. In some cases, the magnitude of state S2 may be proportionally reduced (when compared to state S1 ), by changing the magnitude of one or more of the RF waveforms delivered to generate the RF pulse bursts.

[0062] As described above, the first ARFP waveform may be controlled by adjusting at least one of the first frequency, the first magnitude, the first phase, the second frequency, the second magnitude, the second phase, the third frequency, the third magnitude, and the third phase. In this manner, the first ARFP waveform may be manipulated by adjusting these values to achieve aPCT / US24 / 58717 05 December 2024 (05.12.2024)44024921WO01 much wider range of arbitrary waveform shapes than when using ARFP waveforms generated with pulses from ARFP waveform generators. For example, the blending of the harmonics of the delivered RF waveforms may be manipulated to form different first ARF pulse types. Figures 9A-9D illustrate some example ideal ARF pulses 900A, 900B, 900C, 900D that may be produced using different combinations of harmonics, in accordance with the embodiments described herein. In other words, by manipulating (e.g., increasing or decreasing) the number of harmonics used to produce the ARF pulses (e.g., ARF pulses 900A, 900B, 900C, 900D), the shape or pattern of the ARF pulse may be changed. In addition, by adding more harmonics (e.g., using additional RF generators), the ARF pulses may be have more defined (e.g., sharper) shapes (e.g., with straighter edges), and the resultant ARFP waveform formed by the ARF pulses may more accurately mimic the shape of pulsed voltage (PV) waveform.

[0063] As described above, at least one of the first RF generator may be coupled to a first RF matching network, the second RF generator may be coupled to a second RF matching network, or the third RF generator may be coupled to a third RF matching network. In some cases, each of the first, second, and third RF generators may be coupled to RF matching networks, as illustrated in Figure 3A. In some embodiments, the RF generators may be coupled to an integrated matching network with more than one input and one output.

[0064] Also as described above with respect to Figure 3A, at least one of the first RF generator, the second RF generator, or the third RF generator may not be coupled to an RF matching network. In some cases, none of the RF generators used in the operations 400 may be coupled to RF matching networks, as illustrated in Figure 3B. In other cases, only some of the RF generators used in the operations 400 may be coupled to RF matching networks, while other RF generators may not be coupled to RF matching networks.

[0065] In some embodiments, when the frequency of an ARFP waveform is relatively low, the RF waveforms may be delivered by the RF generators to a bias electrode (e.g., bias electrode 138) in the plasma processing system, and a direct current (DC) bias may also be applied (e.g., from high voltage DC supply 173) toPCT / US24 / 58717 05 December 2024 (05.12.2024)44024921WO01 the bias electrode to bias the first ARFP waveform. When the frequency of an ARFP waveform is relatively high (for example, 2 MHz or 20 MHz), the RF waveforms may be delivered through an RF baseplate (e.g., RF baseplate 137) and a DC bias may be applied (e.g., from high voltage DC supply 173) to the bias electrode in the plasma processing system to bias the ARFP waveform.

[0066] Embodiments described herein provide for generating ARFP waveforms by delivering synchronized RF waveforms and controlling the frequency, magnitude, and phase of each of the RF waveforms to improve the plasma processing results on a substrate using a plurality of RF generators. For example, and as described herein, by manipulating the uniformity of the RF waveforms delivered (e.g., by adjusting the uniformity of the magnitudes of the RF waveforms), the POT of the generated ARFP waveform may be controlled. In another example, and also as described herein, by increasing the number of RF waveforms (e.g., harmonics) delivered, the generated ARFP waveform may controlled to more closely align with (e.g., mirror) the target voltage waveform. In yet another example, the phase of the RF waveforms may be aligned and / or locked during generation of the ARFP waveforms to synchronize the RF waveforms to achieve more consistent plasma processing results on the substrate.Additional Considerations

[0067] In the above description, details are set forth by way of example to facilitate an understanding of the disclosed subject matter. It should be apparent to a person of ordinary skill in the field, however, that the disclosed implementations are exemplary and not exhaustive of all possible implementations. Thus, it should be understood that reference to the described examples is not intended to limit the scope of the disclosure. Any alterations and further modifications to the described devices, instruments, methods, and any further application of the principles of the present disclosure are fully contemplated as would normally occur to one skilled in the art to which the disclosure relates. In particular, it is fully contemplated that the features, components, and / or steps described with respect to one implementation may be combined with the features, components, and / or steps described with respect toPCT / US24 / 58717 05 December 2024 (05.12.2024)44024921WO01 other implementations of the present disclosure. As used herein, the term “about” may refer to a + / -10% variation from the nominal value. It is to be understood that such a variation can be included in any value provided herein.

[0068] As used herein, “a processor,” “at least one processor” or “one or more processors” generally refers to a single processor configured to perform one or multiple operations or multiple processors configured to collectively perform one or more operations. In the case of multiple processors, performance of the one or more operations could be divided amongst different processors, though one processor may perform multiple operations, and multiple processors could collectively perform a single operation. Similarly, “a memory,” “at least one memory” or “one or more memories” generally refers to a single memory configured to store data and / or instructions, multiple memories configured to collectively store data and / or instructions.

[0069] As used herein, a phrase referring to “at least one of’ or “one or more of’ a list of items refers to any combination of those items, including single members. As an example, “at least one of: a, b, or c” is intended to cover: a, b, c, a-b, a-c, b-c, and a-b-c, as well as any combination with multiples of the same element (e.g., a-a, a-a-a, a-a-b, a-a-c, a-b-b, a-c-c, b-b, b-b-b, b-b-c, c-c, and c- c-c or any other ordering of a, b, and c).

[0070] The methods disclosed herein comprise one or more steps or actions for achieving the described method. The method steps and / or actions may be interchanged with one another without departing from the scope of the claims. In other words, unless a specific order of steps or actions is specified, the order and / or use of specific steps and / or actions may be modified without departing from the scope of the claims.

[0071] While the foregoing is directed to embodiments of the present disclosure, other and further embodiments of the disclosure may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.

Claims

PCT / US24 / 58717 05 December 2024 (05.12.2024)44024921 WO01We claim:1 . A method for waveform generation, the method comprising: generating a first asymmetric radio frequency (RF) pulsed waveform , wherein generating the first asymmetric RF pulsed waveform comprises: delivering a first RF waveform at a first frequency using a first RF generator, the first RF waveform having a first magnitude and a first phase; delivering a second RF waveform at a second frequency using a second RF generator, the second RF waveform having a second magnitude and a second phase; delivering a third RF waveform at a third frequency using a third RF generator, the third RF waveform having a third magnitude and a third phase, wherein the first frequency is greater than the second frequency, and wherein the second frequency is greater than the third frequency; and synchronizing the delivering of the first RF waveform, the second RF waveform, and the third RF waveform, wherein the synchronizing comprises aligning the first phase, the second phase, and the third phase.

2. The method of claim 1 , wherein the first frequency is a first harmonic of the first asymmetric RF pulsed waveform and is equal to a fundamental frequency of the first asymmetric RF pulsed waveform.

3. The method of claim 2, wherein the second RF waveform is a higher harmonic of the first asymmetric RF pulsed waveform than the first harmonic, and wherein the third RF waveform is an even higher harmonic of the first asymmetric RF pulsed waveform than the higher harmonic of the second RF waveform.PCT / US24 / 58717 05 December 2024 (05.12.2024)44024921 WO014. The method of claim 1 , wherein aligning the first phase, the second phase, and the third phase comprises aligning the first phase, the second phase, and the third phase to within 90 degrees.

5. The method of claim 4, wherein at least one of the first phase, the second phase, and the third phase remains constant during the generating of the first asymmetric RF pulsed waveform.

6. The method of claim 1 , wherein the first asymmetric RF pulsed waveform has a pulse-on-time (POT), and wherein generating the first asymmetric RF pulsed waveform further comprises: controlling the first asymmetric RF pulsed waveform by adjusting at least one of the first frequency, the first magnitude, the first phase, the second frequency, the second magnitude, the second phase, the third frequency, the third magnitude, and the third phase.

7. The method of claim 6, wherein the first magnitude is higher than the second magnitude.

8. The method of claim 6, wherein controlling the first asymmetric RF pulsed waveform comprises adjusting an on-time of at least one of the first RF generator, the second RF generator, and the third RF generator to change the POT of the first asymmetric RF pulsed waveform.

9. The method of claim 1 , wherein generating the first asymmetric RF pulsed waveform is performed in a first state, and wherein the method further comprises: generating a second asymmetric RF pulsed waveform in a second state, wherein generating the second asymmetric RF pulsed waveform in the second state comprises: delivering a fourth RF waveform at a fourth frequency using the first RF generator, the first RF waveform having a fourth magnitude and a fourth phase;PCT / US24 / 58717 05 December 2024 (05.12.2024)44024921 WO01 delivering a fifth RF waveform at a fifth frequency using the second RF generator, the second RF waveform having a fifth magnitude and a fifth phase; delivering a sixth RF waveform at a sixth frequency using the third RF generator, the sixth RF waveform having a sixth magnitude and a sixth phase, wherein the fourth frequency is greater than the fifth frequency, and wherein the fifth frequency is greater than the sixth frequency; and synchronizing the delivering of the fourth RF waveform, the fifth RF waveform, and the sixth RF waveform in the second state, wherein the synchronizing comprises aligning the fourth phase, the fifth phase, and the sixth phase.

10. The method of claim 9, wherein a magnitude of the second asymmetric RF pulsed waveform is lower than a magnitude of the first asymmetric RF pulsed waveform.11 . The method of claim 1 , wherein at least one of: the first RF generator is coupled to a first RF matching network; the second RF generator is coupled to a second RF matching network; or the third RF generator is coupled to a third RF matching network.

12. The method of claim 1 , wherein at least one of the first RF generator, the second RF generator, or the third RF generator is not coupled to an RF matching network.

13. A waveform generator, comprising: a first radio frequency (RF) generator; a second RF generator; a third RF generator; and a system controller including memory and one or more processors coupled to the memory, the one or more processors being configured,PCT / US24 / 58717 05 December 2024 (05.12.2024)44024921 WO01 individually or collectively, perform a method for waveform generation comprising: generating a first asymmetric RF pulsed waveform , wherein generating the first asymmetric RF pulsed waveform comprises: delivering a first RF waveform at a first frequency using a first RF generator, the first RF waveform having a first magnitude and a first phase; delivering a second RF waveform at a second frequency using a second RF generator, the second RF waveform having a second magnitude and a second phase; delivering a third RF waveform at a third frequency using a third RF generator, the third RF waveform having a third magnitude and a third phase, wherein the first frequency is greater than the second frequency, and wherein the second frequency is greater than the third frequency; and synchronizing the delivering of the first RF waveform, the second RF waveform, and the third RF waveform, wherein the synchronizing comprises aligning the first phase, the second phase, and the third phase.

14. The waveform generator of claim 13, wherein the first frequency is a first harmonic of the first asymmetric RF pulsed waveform and is equal to a fundamental frequency of the first asymmetric RF pulsed waveform.

15. The waveform generator of claim 14, wherein the second RF waveform is a second harmonic of the first asymmetric RF pulsed waveform, and wherein the third RF waveform is a higher harmonic of the first asymmetric RF pulsed waveform than the second harmonic.

16. The waveform generator of claim 13, wherein aligning the first phase, the second phase, and the third phase comprises aligning the first phase, the second phase, and the third phase to within 90 degrees.PCT / US24 / 58717 05 December 2024 (05.12.2024)44024921 WO0117. The waveform generator of claim 16, wherein at least one of the first phase, the second phase, and the third phase remains constant during the generating of the first asymmetric RF pulsed waveform.

18. The waveform generator of claim 13, wherein the first asymmetric RF pulsed waveform has a pulse-on-time (POT), and wherein generating the first asymmetric RF pulsed waveform further comprises: controlling the first asymmetric RF pulsed waveform by adjusting at least one of the first frequency, the first magnitude, the first phase, the second frequency, the second magnitude, the second phase, the third frequency, the third magnitude, and the third phase.

19. The waveform generator of claim 18, wherein the first magnitude is higher than the second magnitude.

20. The waveform generator of claim 18, wherein controlling the first asymmetric RF pulsed waveform comprises adjusting an on-time of at least one of the first RF generator, the second RF generator, and the third RF generator to change the POT of the first asymmetric RF pulsed waveform.

Images