Plasma process control of a multi-electrode system with an ion energy sensor

Abstract

The RF generator includes a first RF power supply configured to output a first RF output signal to a first electrode of the load. The RF generator includes a first sensor for detecting a first parameter of the first RF output signal to determine a first characteristic of the plasma in the load. The second RF power supply outputs a second RF output signal to the second electrode. The second sensor detects a second parameter of the second RF output signal to determine a second characteristic of the plasma in the load. The RF power controller receives the first characteristic and the second characteristic and generates a first control signal and a second control signal. The first control signal adjusts the first RF output signal, and the second control signal adjusts the second RF output signal.

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of U.S. Application No. 17 / 884,711, filed August 10, 2022, the disclosure of which is incorporated herein by reference in its entirety.

[0002] The present disclosure relates to RF generator systems and control of RF generators. [Background technology]

[0003] Plasma processing is frequently used in semiconductor manufacturing. In plasma processing, ions are accelerated by an electric field to etch material from or deposit material onto the surface of a substrate. In one basic implementation, the electric field is generated based on a radio frequency (RF) or direct current (DC) power signal generated by a respective RF or DC generator in a power supply system. The power signal generated by the generator must be precisely controlled to effectively perform plasma etching.

[0004] The background discussion provided herein is for purposes of generally presenting the contents of the present disclosure. To the extent described in this background section, the work of the presently named inventors, as well as aspects of the body of the specification that may not qualify as prior art at the time of filing, are not admitted expressly or impliedly as prior art to the present disclosure. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] U.S. Patent No. 7,602,127 [Patent Document 2] U.S. Patent No. 8,110,991 [Patent Document 3] U.S. Patent No. 8,395,322 [Patent Document 4] U.S. Patent No. 10,821,542 [Patent Document 5] U.S. Patent No. 10,546,724 [Patent Document 6] U.S. Patent No. 10,049,857 [Patent Document 7] U.S. Patent Application No. 17 / 715,672 Summary of the Invention [Means for solving the problem]

[0006] One general aspect includes an RF generator including a first RF power supply configured to output a first RF output signal to a first electrode of a load. The generator also includes a first sensor for detecting a first parameter of the first RF output signal and determining a first characteristic of plasma in the load. The generator also includes a second RF power supply configured to output a second RF output signal to the second electrode. The generator also includes a second sensor for detecting a second parameter of the second RF output signal and determining a second characteristic of plasma in the load. The generator also includes an RF power controller configured to receive the first characteristic and the second characteristic and generate a first control signal, and configured to generate a second control signal. The generator also includes the first control signal adjusting the first RF output signal and the second control signal adjusting the second RF output signal. Other embodiments of this aspect include corresponding computer systems, apparatuses, and computer programs recorded on one or more computer storage devices, each configured to perform the actions of the method.

[0007] Implementations may include one or more of the following features: An RF generator, wherein the first sensor is a plasma sensor, and the first characteristic is at least one of a plasma density, an electron temperature, an ion potential, a sheath thickness, a sheath capacitance, or an ion energy distribution function (IEDF) associated with the first electrode, and the second sensor is a plasma sensor, and the second characteristic is at least one of a plasma density, an electron temperature, an ion potential, or an ion energy distribution function (IEDF) associated with the second electrode. The first characteristic is the IEDF associated with the first electrode. The second characteristic is the IEDF associated with the second electrode. The first characteristic is the IEDF associated with the first electrode, and the second characteristic is the IEDF associated with the second electrode. The RF power controller may include a first power controller and a second power controller, where the first power controller is configured to receive the first characteristic and generate a first control signal for varying the first RF output signal, and the second power controller is configured to receive the second characteristic and generate a second control signal for varying the second RF output signal. The RF generator may include a communication link between the first power controller and the second power controller, where the first power controller and the second power controller are configured to communicate settings defining the respective first and second RF output signals. The first RF power source is a main bias power source, the first electrode is a main bias electrode, the second RF power source is an auxiliary bias power source, and the second electrode is an auxiliary bias electrode, where the main bias electrode and the auxiliary bias electrode form a composite bias electrode. The first control signal controls at least one of a rail voltage, drive, frequency, phase, or pulsing of the first RF output signal, and the second control signal controls at least one of a rail voltage, drive, frequency, phase, or pulsing of the second RF output signal. The RF generator may include a third RF power supply configured to output a third RF output signal to the third electrode, and the RF power controller is further configured to generate the third control signal for varying the third RF output signal.The RF power controller is configured to generate a third control signal, and the third control signal varies according to at least one of the first characteristic or the second characteristic. The third RF power source is a source power source, and the third electrode is a source electrode. Implementations of the described techniques may include hardware, a method or process, or computer software on a computer-accessible medium.

[0008] One general aspect includes an RF system including a main bias RF generator including a main bias power supply configured to output a main bias RF output signal to a main bias electrode of a load and a main bias plasma sensor configured to detect a main bias parameter of the main bias RF output signal and determine a main bias characteristic of a plasma in the load. The system also includes an auxiliary bias RF generator including an auxiliary bias RF power supply configured to output an auxiliary bias RF output signal to the auxiliary bias electrode and an auxiliary bias plasma sensor configured to detect an auxiliary bias parameter of the auxiliary bias RF output signal and determine a main bias characteristic of a plasma in the load. The system also includes an RF power controller configured to receive the main bias characteristic and the auxiliary bias characteristic and generate a main bias control signal for varying the main bias RF output signal, and configured to generate the auxiliary bias control signal for varying the auxiliary bias RF output signal. Other embodiments of this aspect include corresponding computer systems, apparatuses, and computer programs recorded on one or more computer storage devices, each configured to perform the actions of the method.

[0009] Implementations may include one or more of the following features: An RF system in which the RF power controller is one of a proportional-integral controller, a proportional-integral-derivative controller, or a linear-quadratic-response controller; An RF system in which the main bias plasma sensor includes one of a VI probe or a directional coupler for detecting a main bias parameter, and the auxiliary bias plasma sensor includes one of a VI probe or a directional coupler for detecting an auxiliary bias parameter; An RF system in which the main bias characteristic is one of a plasma density, an electron temperature, an ion potential, a sheath thickness, a sheath capacitance, or an ion energy distribution function (IEDF) associated with the main bias electrode, and the auxiliary bias characteristic is one of a plasma density, an electron temperature, an ion potential, or an ion energy distribution function (IEDF) associated with the auxiliary bias electrode; The RF power controller may include a main bias power controller and an auxiliary bias power controller, the main bias power controller configured to receive the main bias characteristic and generate the main bias control signal according to the main bias characteristic, and the auxiliary bias power controller configured to receive the auxiliary bias characteristic and generate the auxiliary bias control signal according to the main bias characteristic; The main bias electrode and the auxiliary bias electrode form a composite bias electrode. the main bias control signal controls at least one of the rail voltage, drive, frequency, phase, or pulsing of the main bias RF output signal, and the auxiliary bias control signal controls at least one of the rail voltage, drive, frequency, phase, or pulsing of the auxiliary bias RF output signal. The RF system, wherein one of the main and auxiliary bias characteristics includes more than one of plasma density, electron temperature, ion potential, or ion energy distribution function (IEDF) associated with the respective main and auxiliary bias electrodes, and the other of the main and auxiliary bias characteristics includes more than one of plasma density, electron temperature, ion potential, or ion energy distribution function (IEDF) associated with the respective other of the main and auxiliary bias electrodes.The RF system may include a source RF power supply configured to output a source RF output signal to the source electrode, and the RF power controller is further configured to generate a source control signal to vary the source RF output signal. The RF system includes one of the main bias characteristic and the auxiliary bias characteristic including multiple of a plasma density, an electron temperature, an ion potential, or an ion energy distribution function (IEDF) associated with the respective main bias electrode and the auxiliary bias electrode, and the other of the main bias characteristic and the auxiliary bias characteristic including multiple of a plasma density, an electron temperature, an ion potential, or an ion energy distribution function (IEDF) associated with the other of the respective main bias electrode and the auxiliary bias electrode. The RF power controller is configured to generate a source control signal, and the source control signal varies according to at least one of the main bias characteristic or the auxiliary bias characteristic. The main bias characteristic is the IEDF associated with the main bias electrode. The auxiliary bias characteristic is the IEDF associated with the auxiliary bias electrode. The main bias characteristic is the IEDF associated with the main bias electrode, and the auxiliary bias characteristic is the IEDF associated with the auxiliary bias electrode. Implementations of the described techniques may include hardware, methods or processes, or computer software on a computer-accessible medium.

[0010] One general aspect includes a non-transitory computer-readable medium storing processor-executable instructions. The non-transitory computer-readable medium storing processor-executable instructions also includes generating a main bias RF output signal to a main bias electrode of a load. The instructions also include detecting a main bias parameter of the main bias RF output signal to determine a main bias characteristic of a plasma in the load. The instructions also include generating an auxiliary bias RF output signal to an auxiliary bias electrode of the load. The instructions also include detecting an auxiliary bias parameter of the auxiliary bias RF output signal to determine an auxiliary bias characteristic of the plasma in the load. The instructions also include receiving the main bias characteristic and the auxiliary bias characteristic, generating a main bias control signal for varying the main bias RF output signal according to the main bias parameter, and generating an auxiliary bias control signal for varying the auxiliary bias RF output signal according to the main bias characteristic. The instructions also include the main bias control signal adjusting the main bias RF output signal and the auxiliary bias control signal adjusting the auxiliary bias RF output signal. Other embodiments of this aspect include corresponding computer systems, apparatuses, and computer programs recorded on one or more computer storage devices, each configured to perform the actions of the method.

[0011] Implementations may include one or more of the following features: a non-transitory computer-readable medium storing processor-executable instructions, wherein the main bias characteristic is at least one of a plasma density, an electron temperature, an ion potential, a sheath thickness, a sheath capacitance, or an ion energy distribution function (IEDF) associated with the main bias electrode, and the auxiliary bias characteristic is at least one of a plasma density, an electron temperature, an ion potential, a sheath thickness, a sheath capacitance, or an ion energy distribution function (IEDF) associated with the auxiliary bias electrode; the main bias electrode and the auxiliary bias electrode form a composite bias electrode; the main bias control signal controls at least one of a rail voltage, a drive, a frequency, a phase, or a pulsing of the main bias RF output signal, and the auxiliary bias control signal controls at least one of a rail voltage, a drive, a frequency, a phase, or a pulsing of the auxiliary bias RF output signal. a non-transitory computer-readable medium storing processor-executable instructions, the instructions may include generating one of a main bias characteristic and an auxiliary bias characteristic including at least two of a plasma density, an electron temperature, an ion potential, or an ion energy distribution function (IEDF) associated with the main bias electrode and the auxiliary bias electrode, respectively, and the other of the main bias characteristic and the auxiliary bias characteristic including at least one of a plasma density, an electron temperature, an ion potential, or an ion energy distribution function (IEDF) associated with the other of the main bias electrode and the auxiliary bias electrode, respectively; a non-transitory computer-readable medium storing processor-executable instructions, the instructions may include generating a source RF output signal to a source electrode, and generating a source control signal to vary the source RF output signal.A non-transitory computer-readable medium storing processor-executable instructions, the instructions may include generating one of a main bias characteristic and an auxiliary bias characteristic including multiple of a plasma density, an electron temperature, an ion potential, or an ion energy distribution function (IEDF) associated with the main bias electrode and the auxiliary bias electrode, respectively, and the other of the main bias characteristic and the auxiliary bias characteristic including multiple of a plasma density, an electron temperature, an ion potential, or an ion energy distribution function (IEDF) associated with the other of the main bias electrode and the auxiliary bias electrode, respectively. A non-transitory computer-readable medium storing processor-executable instructions, the instructions may include varying a source control signal according to at least one of the main bias characteristic or the auxiliary bias characteristic. Implementations of the described techniques may include hardware, a method or process, or computer software on a computer-accessible medium.

[0012] Further areas 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 present disclosure.

[0013] The present disclosure will become more fully understood from the detailed description and the accompanying drawings, wherein: [Brief explanation of the drawings]

[0014] [Figure 1] FIG. 1 shows a depiction of a plasma processing system having a high plasma density in the center. [Figure 2] FIG. 1 shows a depiction of a plasma processing system having a low plasma density in the center. [Figure 3] FIG. 1 is a schematic block diagram of a power supply system having multiple power supplies arranged in accordance with various configurations of the present disclosure. [Figure 4] FIG. 1 is a diagram showing waveforms of an RF signal and a pulse that modulates the RF signal to explain a pulse operation mode. [Figure 5]FIG. 1 shows a representation of a plasma system arranged in accordance with the principles of the present disclosure. [Figure 6] FIG. 1 is a schematic block diagram of a pair of controllers that communicate control signals to an RF generator. [Figure 7] FIG. 1 is a schematic block diagram of a pair of RF generators in communication to supply power to multiple electrodes of a set of electrodes of a load. [Figure 8] FIG. 1 is a schematic block diagram of a pair of RF generators and a common controller configured to communicate control inputs to each of the pair of RF generators to deliver power to multiple electrodes of a set of electrodes of a load. [Figure 9] FIG. 1 is a schematic block diagram of a pair of RF generators and a common controller configured to communicate control inputs to each of the pair of RF generators to supply energy to multiple electrodes of a set of electrodes of a load, and in communication with a third electrode that supplies power to the load. [Figure 10] 1A-1C are functional block diagrams of exemplary control modules arranged according to various configurations. [Figure 11] 1 is a flowchart of the operation of a control system arranged in accordance with the principles of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0015] In the drawings, reference numbers may be reused to identify similar and / or identical elements.

[0016] A power system may include a DC or RF power generator or generator, a matching network, and a load (such as a process chamber, plasma chamber, or reactor with fixed or variable impedance). The power generator generates a DC or RF power signal that is received by a matching network or impedance optimization controller or circuit. The matching network or impedance optimization controller or circuit transforms the load impedance to the characteristic impedance of the transmission line between the power generator and the matching network. Impedance matching helps maximize the amount of power transferred to the load ("forward power") and minimize the power reflected from the load to the power generator ("reverse power" or "reflected power"). When the input impedance of the matching network matches the characteristic impedance of the transmission line and the generator, forward power can be maximized and reverse power can be minimized.

[0017] In the field of power supplies or power devices, there are typically two approaches for applying a power signal to a load. The first, more traditional approach is to apply a continuous power signal to the load. In continuous mode or continuous wave mode, the continuous power signal is typically a constant DC power signal or a sinusoidal RF power signal that is continuously output by the power supply to the load. In the continuous mode approach, the power signal assumes a constant DC or sinusoidal output, and the amplitude and / or frequency (for RF power signals) of the power signal can be varied to vary the output power applied to the load.

[0018] A second approach to applying a power signal to a load involves pulsing the RF signal rather than applying a continuous RF signal to the load. In a pulsed or pulsed mode of operation, the RF signal is modulated by a modulation signal to define the envelope of the modulated power signal. The RF signal can be, for example, a sinusoidal RF signal or other time-varying signal. The power delivered to the load is typically varied by varying the modulation signal.

[0019] In a typical power supply configuration, the output power applied to a load is determined using sensors that measure the forward and reflected power or voltage and current of an RF signal applied to the load. Either set of these signals is analyzed in a control loop. The analysis typically determines a power value that is used to adjust the output of the power supply to vary the power applied to the load. In a power supply system where the load is a process chamber or other nonlinear or time-varying load, a changing impedance of the load causes a corresponding change in the power applied to the load, since the applied power is in part a function of the impedance of the load.

[0020] In systems where the fabrication of various devices relies on introducing power to a load to control the fabrication process, power is typically supplied in one of two configurations. In the first configuration, power is capacitively coupled to the load. Such systems are called capacitively coupled plasma (CCP) systems. In the second configuration, power is inductively coupled to the load. Such systems are typically called inductively coupled plasma (ICP) systems. Power coupling to the plasma can also be achieved by wave coupling at microwave frequencies. Such techniques typically use electron cyclotron resonance (ECR) or microwave sources. Helicon sources are another form of wave-coupled source and typically operate at RF frequencies similar to conventional ICP and CCP systems. The power supply system may include at least one bias power and / or source power applied to one or more electrodes of the load. The source power typically generates the plasma and controls the plasma density, while the bias power modulates ions in the sheath formation. The bias and source may share the same electrode or may use separate electrodes, depending on various design considerations.

[0021] When a power supply system drives a time-varying or nonlinear load, such as a process chamber or plasma chamber, the power absorbed by the bulk plasma and plasma sheath results in a density of ions with various ion energies. One characteristic measure of ion energy is the ion energy distribution function (IEDF). The IEDF can be controlled with bias power. One method of controlling the IEDF of a system in which multiple RF power signals are applied to a load occurs by varying the multiple RF signals, which are related by at least one of amplitude, frequency, and phase. The related at least one of amplitude, frequency, and phase of the multiple RF power signals may also be related by a Fourier series and related coefficients. The frequencies between the multiple RF power signals may be locked, and the relative phases between the multiple RF signals may also be locked. Examples of such systems can be found in U.S. Pat. Nos. 7,602,127, 8,110,991, and 8,395,322, all of which are assigned to the assignee of the present application and incorporated herein by reference.

[0022] Time-varying or nonlinear loads may exist in various applications. In one application, a plasma processing system may also include components for generating and controlling a plasma. One such component is a nonlinear load implemented as a process chamber, such as a plasma chamber or reactor. For example, a typical plasma chamber or reactor used in a plasma processing system for thin film manufacturing may utilize a dual power system. One power generator (source) controls the generation of the plasma, and the other power generator (bias) controls ion energy. Examples of dual power systems include those described in the above-referenced U.S. Pat. Nos. 7,602,127, 8,110,991, and 8,395,322. The dual power systems described in the above-referenced patents use a closed-loop control system to adapt the operation of the power supply to control ion density and the corresponding ion energy distribution function (IEDF).

[0023] There are several approaches to controlling a process chamber that can be used to generate a plasma. For example, in an RF power supply system, the phase and frequency of multiple driving RF signals operating at the same or nearly the same frequency can be used to control plasma generation. For RF-driven plasma sources, the periodic waveforms that affect plasma sheath dynamics and the corresponding ion energy are generally known and controlled by the frequency of the periodic waveforms and the associated phase interactions. Another approach in RF power supply systems involves dual-frequency control. That is, two RF frequency sources operating at different frequencies are used to supply power to the plasma chamber to provide substantially independent control of ion density and electron density.

[0024] Another approach utilizes a broadband RF power source to drive the plasma chamber. Broadband approaches present certain challenges. One challenge is coupling the power to the electrodes. A second challenge is that the transfer function of the generated waveform to the actual sheath voltage for the desired IEDF must be formulated for a wide process space to support material surface interaction. In one responsive approach in an inductively coupled plasma system, controlling the power applied to the source electrode controls the plasma density, while controlling the power applied to the bias electrode modulates ions to control the IEDF, providing etch rate control and etch feature profile control. Using source and bias electrode control, the etch rate and various other etch characteristics are controlled via ion density and ion energy.

[0025] As integrated circuit and device manufacturing continues to evolve, so too do the power requirements controlling the manufacturing process. For example, in memory device manufacturing, bias power requirements continue to increase. Increased power generates higher, more energetic ions for increased directional or anisotropic etch feature profiles and faster surface interactions, thereby increasing etch rates and enabling higher aspect ratio features to be etched. In RF systems, increased ion energy can be accompanied by lower bias frequency requirements, along with increased power and number of bias power supplies coupled to the plasma sheath created within the plasma chamber. Increased power at lower bias frequencies and an increased number of bias power supplies result in intermodulation distortion (IMD) from sheath modulation. IMD emissions can significantly reduce the power delivered from the source where plasma generation occurs. Commonly assigned U.S. Patent No. 10,821,542, entitled "Pulse Synchronization by Monitoring Power in Another Frequency Band," issued November 3, 2020, and incorporated herein by reference, describes a method for pulse synchronization by monitoring power in another frequency band. In the referenced U.S. patent application, the pulsing of a second RF generator is controlled according to detecting the pulsing of a first RF generator at the second RF generator, thereby synchronizing the pulsing between the two RF generators.

[0026] FIG. 1 shows a depiction of an inductively coupled plasma (ICP) system 110. The ICP system 110 includes a nonlinear load, such as a reactor, plasma reactor, or plasma chamber 112, referred to interchangeably herein, for generating a plasma 114. Power in the form of voltage or current is applied to the plasma chamber 112 via a coil, including a coil assembly including one or more coils arranged in various configurations. In one non-limiting arrangement shown in FIG. 1, the plasma chamber 112 includes one or both of a first coil 116 and a second coil 118. In various configurations, the multiple coils may be arranged concentrically, intertwined, or in a spiral configuration. Power is applied to the first coil 116 via an RF power generator or power supply 120, and power is applied to the second coil 118 via an RF power generator or power supply 122. The coils 116 and 118 are arranged to provide power to the plasma chamber 112. A dielectric window 124 allows power to be coupled to the plasma while providing a vacuum seal. A substrate or wafer (not shown) is placed in the plasma chamber 112 and typically forms the workpiece that is the subject of the plasma action. An RF power generator, power supply, or power source 128 (these terms may be used interchangeably herein) applies power to the plasma chamber 112 through an electrode 126 that supports the substrate.

[0027] In various configurations, the power supplies 120, 122 provide a source voltage or current to ignite or generate the plasma 114 or to control the plasma density. Also, in various configurations, the power supply 128 provides a bias voltage or current to modulate ions to control the ion potential or ion energy of the plasma 114. In various configurations, the power supplies 120, 122 are locked to operate at the same frequency, voltage, and current, with a fixed or varying relative phase. In various other configurations, the power supplies 120, 122 can operate at different frequencies, voltages, and currents, and relative phases.

[0028] FIG. 2 shows a depiction of a capacitively coupled plasma (CCP) system 210. The CCP system 210 includes a plasma chamber 212 for generating a plasma 214. A pair of electrodes 216, 226 disposed within the plasma chamber 212 are connected to respective DC (ω=0) or RF power generators or sources 220, 222. The electrode 226 supports a substrate or wafer (not shown), as described above with reference to FIG. 1. In various configurations, the source 220 provides a source voltage or current to ignite or generate the plasma 214 or to control the plasma density, although a bias power supply may also be used to ignite the plasma. In various configurations, the source 222 provides a bias voltage or current to modulate ions in the plasma to control the ion potential or ion energy of the plasma 214. In various CCP configurations, bias power and source power may be applied to an upper electrode, such as electrode 216, and a lower electrode, such as electrode 226, in various combinations. In other non-limiting examples, bias power and source power can be applied to a lower electrode, such as electrode 226, while an upper electrode, such as electrode 216, is grounded or floating. In various RF configurations, the power sources 220, 222 operate in relative phase when the sources are harmonically related. In various other configurations, the power sources 220, 222 operate at different frequencies, voltages, and currents, with fixed or varying relative phase. Also, in various configurations, the power sources 220, 222 can be connected to the same electrode, while the opposing electrode is connected to ground or to an additional third DC (ω=0) or RF power generator (not shown).

[0029] 1 and 2 each illustrate a conventional single bias electrode system in which each bias electrode 216, 226 is configured as a single electrode, as compared to multiple power sources. In conventional single bias electrode systems, the plasma 114, 214 can form as either a dense-center bulk plasma or a light-center bulk plasma. FIG. 1 illustrates the plasma 114 formed as a dense-center bulk plasma, and FIG. 2 illustrates the plasma 214 formed as a light-center bulk plasma. Each bulk plasma results in a plasma sheath 130, 230 having one of a convex, concave, or other non-planar shape, none of which is parallel to a generally planar workpiece attached to the surface of the respective bias electrode 126, 226. With reference to FIG. 1, the plasma sheath 130 is displaced away from the electrode 126 near the edge of the electrode 126 and toward the electrode 126 near the center of the electrode 126. This results in a non-uniform power sheath thickness over the powered bias electrode. With reference to Figure 2, plasma sheath 230 is displaced toward electrode 226 near the edge of electrode 226 and is displaced away from electrode 226 near the center of electrode 226. It should be appreciated that in various configurations, the ICP system of Figure 1 can generate either a dense center bulk plasma or a sparse center bulk plasma. Similarly, it should be appreciated that in various configurations, the CCP system of Figure 2 can generate either a dense center bulk plasma or a sparse center bulk plasma.

[0030] As a non-limiting example, as can be seen in FIGS. 1 and 2, a dense-centered bulk plasma 114 results in a plasma sheath 130 shaped as shown in FIG. 1, while a sparse-centered bulk plasma 214 results in a plasma sheath 230 shaped as shown in FIG. 2. Thus, FIGS. 1 and 2 illustrate an example of how a single electrode can result in a non-planar plasma sheath profile across a substrate. In various other configurations, the sheath profile can be a complex shape over the substrate and electrode. The shape of the plasma sheath 130, 230 depends on waveform parameters such as voltage, power, frequency, and phase, as well as the electrode geometry, reactor geometry, and materials used during plasma processing. Controlling these parameters for a single electrode may not allow for the generation of a plasma that produces a generally flat plasma sheath, resulting in the plasma sheaths 130, 230 shown in FIGS. 1 and 2, respectively. In various configurations, a generally flat sheath profile can be achieved by adjusting the electrode geometry, reactor geometry, materials used during plasma processing, or by the addition of other components within the reactor.

[0031] The non-uniform bulk plasma resulting from a non-planar plasma sheath results in ion trajectories that are not orthogonal to the single bias electrode and the workpiece attached to the bias electrode. As shown in Figure 1, ion trajectories 132 are directed toward the edge of electrode 126. Conversely, ion trajectories 232 are directed away from the edge of bias electrode 226. When ions are directed on trajectories that are not orthogonal to electrodes 126, 226 (and the workpiece attached thereto), the resulting etching near the edge of the workpiece lacks uniformity. Non-uniformity can also occur away from the edge of the workpiece, such as in multi-coil ICP sources, which can produce a "W"-shaped sheath profile that results in off-axis ions at locations other than near the edge. Single-bias electrode plasma etching systems have been predominantly used in industry for many years, but as device dimensions continue to shrink, there is less room for imperfections that can occur when ion trajectories are not orthogonal to the bias electrode. Furthermore, wafer uniformity and device yield partially define the success of high-volume manufacturing (HVM) processes.

[0032] To improve the etching process and mitigate non-orthogonal ion trajectories, etching systems with multiple powered bias and / or source electrodes are implemented to provide uniformity and profile control nearly to the edge of the wafer. This control is enabled by adjusting the driving RF or pulsed DC (pDC) waveform to achieve a uniform sheath thickness across the wafer. A uniform sheath thickness across the wafer causes ions to impinge on the substrate nearly orthogonally, i.e., perpendicular to the surface of the substrate. Waveform parameters such as voltage, power, frequency, and phase must be empirically determined based on the specific recipe being implemented in the plasma chamber. In addition to presenting significant challenges, this approach lacks feedback and real-time control.

[0033] Nonuniformities in the plasma sheath arise from many aspects of the plasma generation system, including the geometric design of components, the interaction of plasma radical sources with loss surfaces, the coatings and materials used, the control methods, and other aspects. Given the challenges of adequately modeling and simulating plasma reactors, sensors are needed that can provide real-time feedback of relevant variables that characterize the plasma, such as ion energy and sheath thickness. Such sensors measure the complex system response to specific, controlled stimuli.

[0034] According to various aspects of the present disclosure, an IEDF sensor is positioned in the RF / DC path of each electrode. The IEDF sensors provide real-time feedback of variables characterizing the plasma, such as ion energy, IEDF, sheath thickness, sheath capacitance, and node voltage. In various configurations, one or more of these variables from each IEDF sensor are used to control power, frequency, phase, etc., to maintain a composite, uniform sheath thickness across the electrodes, as described in more detail below.

[0035] 3 illustrates an RF generator or power supply system 310. The power supply system 310 includes a pair of radio frequency (RF) generators or power supplies 312a, 312b, matching networks 318a, 318b, and a load 332, such as a nonlinear load that may be a plasma chamber, plasma reactor, process chamber, or the like. In various configurations, the RF generator 312a is referred to as a source RF generator or power supply, and the matching network 318a is referred to as a source matching network. Also, in various configurations, the RF generator 312b is referred to as a bias RF generator or power supply, and the matching network 318b is referred to as a bias matching network. It will be understood that components may be referred to individually or collectively using reference numerals, with or without letters, subscripts, or primes.

[0036] In various configurations, the source RF generator 312a receives a control signal 330 from the matching network 318b, the generator 312b, or a control signal 330' from the bias RF generator 312b. The control signal 330 or 330' represents an input signal to the source RF generator 312a that indicates one or more operating characteristics or parameters of the bias RF generator 312b. In various configurations, a synchronization bias detector 334 senses the RF signal output from the matching network 318b to the load 332 and outputs a synchronization or trigger signal 330 to the source RF generator 312a. In various configurations, a synchronization or trigger signal 330', rather than the trigger signal 330, may be output from the bias RF generator 312b to the source RF generator 312a. One difference between the trigger or synchronization signals 330, 330' may result from the effect of the matching network 318b, which may change the phase between the input signal to the matching network and the output signal from the matching network. Signals 330, 330′ contain information regarding the operation of bias RF generator 312b, which enables predictable responsiveness in various configurations to address periodic variations in the impedance of load 332 caused by bias RF generator 312b. In the absence of control signals 330 or 330′, RF generators 312a, 312b operate autonomously.

[0037] The RF generators 312a, 312b each include an RF power supply or amplifier 314a, 314b, a sensor 316a, 316b, and a processor, controller, or control module 320a, 320b. The RF power supplies 314a, 314b generate respective RF power signals 322a, 322b that are output to the respective sensors 316a, 316b. The sensors 316a, 316b receive the outputs of the RF power supplies 314a, 314b and generate respective RF power signals f1 and f2. The sensors 316a, 316b also output signals that vary according to various parameters sensed from the load 332. While the sensors 316a, 316b are shown within the respective RF generators 312a, 312b, the sensors 316a, 316b can be located external to the RF power generators 312a, 312b. Such external sensing can occur at the output of the RF generator, at the input of an impedance matching device positioned between the RF generator and the load, or between the output of the impedance matching device (including within the impedance matching device) and the load.

[0038] The sensors 316a, 316b detect various operating parameters and output signals X and Y. The sensors 316a, 316b may include voltage sensors, current sensors, and / or directional coupler sensors. The sensors 316a, 316b detect (i) the voltage V and current I, and / or (ii) the forward power P output from the respective power amplifiers 314a, 314b and / or RF generators 312a, 312b. FWD , and the reverse or reflected power P received from the respective matching network 318a, 318b or load 332 connected to the respective sensor 316a, 316b. REV It can detect voltage V, current I, forward power P FWD , and reverse power P REVmay be scaled, filtered, or scaled and filtered versions of the actual voltage, current, forward power, and reverse power associated with the respective power sources 314a, 314b. The sensors 316a, 316b may be analog or digital sensors, or a combination thereof. In a digital implementation, the sensors 316a, 316b may include an analog-to-digital (A / D) converter and a signal sampling component with a corresponding sampling rate. The signals X and Y may represent the voltage V and current I, or the forward (or source) power P FWD and the reverse (or reflected) power P REV It can represent either

[0039] The sensors 316a, 316b generate sensor signals X, Y, which are received by respective power controllers or control modules 320a, 320b. The control modules 320a, 320b process the respective X and Y signals 324a, 326a and 324b, 326b and generate one or more feedforward or feedback control signals 328a, 328b to the respective power supplies 314a, 314b. The power supplies 314a, 314b adjust the RF power signals 322a, 322b based on the received one or more feedback or feedforward control signals. In various configurations, the control modules 320a, 320b may control the matching networks 318a, 318b, respectively, via the respective control signals 328a, 328b. The control modules 320a, 320b may include at least a proportional-integral (PI) controller, a proportional-integral-derivative (PID) controller, a linear quadratic regulator (LQR), or a subset thereof, and / or a direct digital synthesis (DDS) component, and / or any of the various components described below in connection with the modules.

[0040] In various configurations, the control modules 320a, 320b may include functions, processes, processors, or sub-modules. The control signals 328a, 328b may be control or drive signals that may convey DC offset or rail voltage, voltage or current magnitude, frequency, and phase components. In various configurations, the feedback control signals 328a, 328b may be used as inputs to one or more control loops. In various configurations, the multiple control loops may include control loops for RF drive and rail voltage. In various configurations, the control signals 328a, 328b may be used in a single-input, single-output (SISO) control scheme or a multiple-input, multiple-output (MIMO) control scheme. An example of a MIMO control scheme can be found in U.S. Patent No. 10,546,724, issued January 28, 2020, entitled "Pulsed Bidirectional Radio Frequency Source / Load," assigned to the assignee of the present application, and incorporated herein by reference. In other configurations, the signals 328a, 328b may provide feed-forward control, as described in US Pat. No. 10,049,857, which is assigned to the assignee of the present application and is incorporated herein by reference.

[0041] In various configurations, the power supply system 310 can include a controller 320′. The controller 320′ can be located external to either or both of the RF generators 312a, 312b and may also be referred to as an external controller 320′ or a common controller 320′. In various configurations, the controller 320′ can implement one or more of the functions, processes, or algorithms described herein with respect to one or both of the controllers 320a, 320b. Thus, the controller 320′ communicates with each of the RF generators 312a, 312b via a respective pair of links 336, 338 that enable the exchange of data and control signals as needed between the controller 320′ and the RF generators 312a, 312b. For various configurations, the controllers 320a, 320b, 320′ can provide distributed and coordinated analysis and control of the RF generators 312a, 312b. In various other configurations, the controller 320' can provide control of the RF generators 312a, 312b, eliminating the need for respective local controllers 320a, 320b.

[0042] In various configurations, the RF power supply 314a, the sensor 316a, the controller 320a, and the matching network 318a may be referred to as a source RF power supply 314a, a source sensor 316a, a source controller 320a, and a source matching network 318a. Similarly, in various configurations, the RF power supply 314b, the sensor 316b, the controller 320b, and the matching network 318b may be referred to as a bias RF power supply 314b, a bias sensor 316b, a bias controller 320b, and a bias matching network 318b. In various configurations, as explained above, the source term refers to the RF generator that generates the plasma, and the bias term refers to the RF generator that adjusts the ion potential or IEDF of the plasma. In various configurations, the source RF power supply and the bias RF power supply operate at different frequencies. In various configurations, the source RF power supply operates at a higher frequency than the bias RF power supply. In various other configurations, the source RF power supply and the bias RF power supply operate at the same frequency or substantially the same frequency.

[0043] According to various configurations, source RF generator 312a and bias RF generator 312b include multiple ports for communicating with the outside world. Source RF generator 312a includes a pulse synchronization output port 340, a digital communication port 342, and an RF output port 344. Bias RF generator 312b includes an RF input port 348, a digital communication port 350, and a pulse synchronization input port 352. Pulse synchronization output port 340 outputs a pulse synchronization signal 356 to pulse synchronization input port 352 of bias RF generator 312b. Digital communication port 342 of source RF generator 312a and digital communication port 350 of bias RF generator 312b communicate via a digital communication link 357. RF output port 344 generates an RF control signal 358 that is input to RF input port 348. In various configurations, RF control signal 358 is substantially the same as the RF control signal controlling source RF generator 312a. In various other configurations, RF control signal 358 is the same as the RF control signal controlling source RF generator 312 a, but is phase shifted within source RF generator 312 a according to the desired phase shift produced by bias RF generator 312 b. Thus, in various configurations, source RF generator 312 a and bias RF generator 312 b are driven by substantially identical RF control signals or by substantially identical RF control signal phases shifted by a predetermined amount.

[0044] In various configurations, the power supply system 310 may include multiple RF source generators 312a and multiple RF bias generators 312b. By way of non-limiting example, multiple source RF generators 312a, 312a', 312a'', ..., 312a n can be arranged to provide multiple output power signals to one or more source electrodes of the load 332. Similarly, multiple bias RF generators 312b, 312b', 312b'', ..., 312b nmay provide multiple output power signals to multiple bias electrodes of the load 332. When the source RF generator 312a and the bias RF generator 312b are configured to include multiple respective source or bias RF generators, each RF generator outputs a separate signal in a one-to-one correspondence to a corresponding plurality of matching networks 318a, 318b configured to operate as described above. In various other configurations, there may not be a one-to-one correspondence between each RF generator and a matching network. In various configurations, multiple source electrodes may refer to multiple electrodes that cooperate to define a composite source electrode. Similarly, multiple bias electrodes may refer to multiple connections to multiple electrodes that cooperate to define a composite bias electrode.

[0045] FIG. 4 shows a voltage versus time plot illustrating a pulsed or pulsed mode of operation for powering a load, such as load 332 in FIG. 3 . More specifically, FIG. 4 shows two multi-state pulses P1, P2 of a pulse signal 412 having a plurality of states S1-S4 and S1-S3, respectively. In FIG. 4 , an RF signal 410 is modulated by the pulses P1 and P2. When the pulses are ON, as shown in state S1 of P1 and state S1 of P2, the RF generator 312 outputs an RF signal 410 having an amplitude defined by the magnitude of the pulse in each state. Conversely, during state S4 of P1 and state S3 of P2, the pulses are OFF, and the RF generator 312 does not output an RF signal 410. The pulses P1, P2 can repeat with a constant duty cycle or a variable duty cycle, and the states S1-S4, S1-S3 of each pulse P1, P2 can have the same amplitude and width or varying amplitude and width. Furthermore, the pulse signal 412 need not be a square wave as shown in FIG. 2. By way of non-limiting example, the pulse signal 412 may be trapezoidal, triangular, Gaussian, or other shape. Furthermore, the pulses P1, P2 may have multiple states S1, ..., Sn that vary in amplitude, duration, and shape. The states S1, ..., Sn may repeat within a fixed or variable period. Also, as shown in FIG. 4, the RF signal 410 operates at a frequency that varies between or within states.

[0046] FIG. 5 illustrates a plasma generation system 510. The plasma generation system 510 includes a plasma chamber 512. A plasma 514 is generated in the plasma chamber 512 by application of source power to a conductor 516. The conductor 516 may be implemented in either an inductively coupled plasma (ICP) configuration or a capacitively coupled plasma (CCP) configuration, as described above with respect to FIGS. 1 and 2. The plasma 514 may be a bulk plasma with a high density at the center or a bulk plasma with a low density at the center. The configuration of FIG. 5 provides a controlled method for providing a generally uniform plasma sheath 530 by controlling an RF generator that supplies power to at least one pair of electrodes that cooperate to provide a bias electrode.

[0047] 5, bias electrode 526 includes a primary bias electrode 526b and an auxiliary bias electrode 526b'. The primary bias electrode 526b and the auxiliary bias electrode 526b' cooperate to define bias electrode 526. The primary bias electrode 526b defines a central portion of bias electrode 526, and the auxiliary bias electrode 526b' defines a peripheral portion of bias electrode 526. In various configurations, the auxiliary bias electrode 526b' surrounds the outer periphery of bias electrode 526. In various other configurations, bias electrode 526 can be subdivided into various shapes, including multiple rectangular, square, or other shaped sections, or generally circular sections arranged concentrically about a central axis.

[0048] Main bias electrode 526b receives an RF power signal from main bias RF generator 540b. Main bias RF generator 540b includes a main bias RF power supply 542b and a main bias IEDF sensor 544b. Main bias RF power supply 542b generates an RF output signal applied to main bias electrode 526b according to one or more input signals received from main bias IEDF sensor 544b. Similarly, auxiliary bias RF generator 540' includes an auxiliary bias RF power supply 542b' and an auxiliary bias IEDF sensor 544b'. Auxiliary bias RF power supply 542b' generates an RF output signal applied to auxiliary bias electrode 526b' according to one or more input signals received from auxiliary bias IEDF sensor 544b'. By controlling the respective main bias electrode 526b and auxiliary bias electrode 526b' using power from the respective main bias RF generator 540b and auxiliary bias RF generator 540b', the ion trajectory 532 can be altered to an angle generally perpendicular to a workpiece positioned on the bias electrode 526, as compared to Figures 1 and 2.

[0049] Elements of FIG. 5 may be substituted into FIG. 3, with bias RF generators 540b, 540b' being replaced with the respective bias RF generators 312b, 312b' of FIG. 3. With such a substitution, sensors 316b, 316b' (not shown) of FIG. 3 are replaced with respective IEDF sensors 544b, 544b' of FIG. 5. Bias RF generators 540b, 540b' may be controlled by one or more controllers 320b, 320b' or respective RF generators 312b, 312b', as described in FIG. 3. Throughout this specification, primary and secondary components may also be referred to as first and second components. Similarly, various control and sensor signals may also be referred to as primary and secondary control signals and primary and secondary sensor signals, or first and second control signals and first and second sensor signals.

[0050] 6 shows a block diagram of an RF power generation system 610 including a pair of RF generator controllers 620b, 620b', sometimes referred to as main RF generator controller 620b and auxiliary RF generator controller 620b', respectively, arranged in accordance with the present disclosure. In various embodiments, main RF generator controller 620b represents a controller for an RF generator that supplies power to a main bias electrode of a load, such as main bias electrode 526b of FIG. 5. Similarly, in various embodiments, auxiliary RF generator controller 620b' represents a controller for an RF generator that supplies power to an auxiliary bias electrode of a load, such as auxiliary bias electrode 526b' of FIG. 5.

[0051] The main RF generator controller 620b includes a summer 650b that receives at least one pair of inputs including a main bias electrode ion potential or energy, as measured by the main bias IEDF sensor 544b in FIG. 5, and a main target ion potential. The main target ion potential may be provided by a supervisory controller for the system or may be specified by a user. Similarly, the auxiliary RF generator controller 620b' includes a summer 650b' that receives at least one pair of inputs including an auxiliary ion potential, as measured by the auxiliary bias IEDF sensor 544b' in FIG. 5, and an auxiliary target ion potential. The auxiliary target ion potential may be provided by a supervisory controller for the system or may be specified by a user. In various configurations, the main target ion potential and the auxiliary target ion potential may be the same value, as indicated by the dotted line in FIG. 6. Thus, only a single target ion energy may be provided to the RF power generation system 610 and provided to each summer 650b, 650b'.

[0052] The main RF generator controller 620b of the RF power generation system 610 is described herein. It should be understood that the auxiliary RF generator controller 620b' of the RF power generation system 610 operates similarly and will not be described in detail. Summer 650b outputs the IEDF error to respective proportional and integral sections of a proportional-integral (PI) controller. The proportional section of the PI controller includes a combiner 652b that also receives a proportional coefficient P 645b. Combiner 652b outputs a proportional term to summer 662b. The integral section of the PI controller includes a combiner 656b that also receives an integral coefficient I 658b. Combiner 656b outputs a combined value to summer 660b. Summer 660b also receives an integral feedback term from integrator 666b. The output from summer 660b is input to clamp 668b, which clamps the output from summer 660b. The range of clamp 668b is defined by integrator minimum term 670b and integrator maximum term 672b. The output from clamp 668b is fed back to integrator 666b and also output to summer 662b. As previously described, the output from integrator 666b is fed back to summer 662b. Summer 662b delivers a control signal to the main power control section of the RF generator. In various configurations, the control section may include one or more drive actuators or controllers. As previously described, auxiliary RF generator controller 620b' is similarly configured, but receives the auxiliary ion energy signal input to summer 650b' and delivers a control signal to the auxiliary power control section of the RF generator.

[0053] Although described herein as PI controllers, main RF generator controller 620b and auxiliary RF generator controller 620b' may be individually configured as one or more of a proportional-integral (PI) controller, a proportional-integral-derivative (PID) controller, or a linear quadratic regulator (LQR) controller. Furthermore, main RF generator controller 620b and auxiliary RF generator controller 620b' are shown in FIG. 5 as single-input, single-output (SISO) controllers. However, it should be appreciated that one or both of main RF generator controller 620b and auxiliary RF generator controller 620b' may be configured as a multiple-input, multiple-output (MIMO) controller, as described herein.

[0054] FIG. 7 is a schematic block diagram of an RF power generation system 710 including a pair of RF generators 712b, 712b' configured similarly to those described above. The RF generators 712b, 712b' communicate to coordinate power delivery to a load, such as a plasma chamber 732. By way of non-limiting example, in various configurations, the RF generator 712b may be referred to as a main RF generator 712b, and the RF generator 712b' may be referred to as an auxiliary RF generator 712b'. In various configurations, the RF generators 712b, 712b' may be configured to supply power to multiple electrodes of a plasma chamber that cooperate to define a bias electrode. The main RF generator 712b includes a main RF amplifier or RF power supply 714b that receives one or more control signals from a main controller 720b. The RF power supply 714b communicates an output signal to a main IEDF sensor 716b. The main IEDF sensor 716b communicates an output signal to a main bias electrode 726b. The primary IEDF sensor 716b also outputs one or more signals indicative of the IEDF associated with the primary bias electrode 726b to the primary bias controller 720b. Similarly, the auxiliary RF generator 712b' includes an auxiliary RF amplifier or auxiliary RF power supply 714b' that receives a control signal from the auxiliary controller 720b'. The auxiliary RF power supply 714b' communicates an output signal to the auxiliary bias IEDF sensor 716b'. The auxiliary bias IEDF sensor 716b' communicates an output signal to the auxiliary bias electrode 726b'. The auxiliary bias IEDF sensor 716b' outputs one or more signals indicative of the IEDF associated with the auxiliary bias electrode to the auxiliary bias controller 720b'.

[0055] The main controller 720b and the auxiliary controller 720b' generate various control signals to the respective main RF amplifier or RF power supply 714b and auxiliary RF amplifier or RF power supply 714b'. The main RF amplifier or RF power supply 714b and the auxiliary RF amplifier or RF power supply 714b' may each be configured to generate a continuous wave signal or a pulsed RF signal. Control inputs or parameters to the respective main RF power supply 714b and auxiliary RF power supply 714b' include one or more of a DC voltage or rail voltage, a low-level drive signal, a frequency, a phase, and one or more pulsing parameters. Thus, the main controller 720b and the auxiliary controller 720b' communicate one or more control signals to the respective main RF power supply 714b and auxiliary RF power supply 714b' according to the complexity of the RF power signal supplied to the respective main bias electrode 726b and auxiliary bias electrode 726b'.

[0056] In various configurations, the main controller 720b and the auxiliary controller 720b' communicate via a communication link 730. Communication between the main controller 720b and the auxiliary controller 720b' via the communication link 730 enables adjustment of the power supply to the respective main bias power 726b and auxiliary bias electrode 726b' to better control the ion potential and power feed sheath of the plasma 736, as described above. In various configurations, the communication link 730 enables synchronization of one or more control parameters. As non-limiting examples, frequency, phase, and pulsing can be locked or synchronized between the main RF generator 712b and the auxiliary RF generator 712b', while the DC voltage or rail voltage can be controlled independently by each of the main controller 720b and the auxiliary controller 720b', or by a subset of all parameters. In other configurations, no parameters may be locked or synchronized between RF generators 712b, 712b', or all parameters or a subset of all parameters may be locked or synchronized.

[0057] The primary IEDF sensor 716b and the auxiliary IEDF sensor 716b′ can be generally characterized as plasma sensors. The plasma sensors can be configured to detect one or more parameters, such as voltage and current, or forward and reverse power, and generate one or more parameters that characterize the plasma. The parameters that characterize the plasma include the plasma density (n o ) and electron temperature (T e ) and the ionic potential (V i ), sheath thickness (s), and sheath capacitance (c s ) and an IEDF. Examples of plasma sensors can be found by reference to U.S. Patent Application No. 17 / 715,672, filed April 7, 2022, entitled Real-Time, Non-Invasive IEDF Plasma Sensor, which is assigned to the assignee of the present application and incorporated herein by reference.

[0058] FIG. 8 illustrates a plasma generation system 810 for controlling a main bias electrode and an auxiliary bias electrode of a plasma chamber. The plasma generation system 810 includes a common controller 820 that communicates control signals to each RF generator, including a main RF generator 812b and an auxiliary RF generator 812b'. In various configurations, the controller 820 outputs power and phase setpoint commands or signals to each RF generator 812b, 812b'. The main RF generator 812b receives power and phase setpoint inputs and generates an RF output signal, as described above. As also described above, the output from the main RF generator 812b is input to a main matching network 818b, which operates as described above. The output from the main matching network 818b is input to a main VI probe 816b-1. The VI probe 816b-1 outputs an RF voltage (V RF ) and RF current (I RF) The plasma sensor 816b-2 operates as described above and feeds one or more signals back to the controller 820. The controller 820 generates respective power and phase setpoints according to the signals fed back to the controller 820.

[0059] As shown in FIG. 8, VI probe 816b-1 and plasma sensor 816b-2 cooperate to perform the sensor functions described above with respect to sensor 316b of FIG. 3. VI probe 816b-1 also transmits an RF signal to main bias electrode 826b. VI probe 816b-1 may also be implemented as a directional coupler or may detect other parameters from which plasma sensor 816b-2 can determine parameters characterizing the plasma. It should be understood that auxiliary bias electrode 826b' is similarly driven, and similar components of the auxiliary drive section of FIG. 8 operate as also described above with respect to the main power supply section described herein.

[0060] In FIG. 8, VI probes 816b-1, 816b-1′ measure RF voltage (V RF ) and RF current (I RF ), which may be input to the controller 820. The VI probes 816b-1, 816b-1′ output the detected parameters to the respective plasma sensors 816b-2, 816b-2′. Thus, the VI probes 816b-1, 816b-1′ and the respective plasma sensors 816-2, 816-2′ cooperate to provide sensors of parameters that characterize the plasma, as described above. One or more of the parameters may be input to the controller 820, such as the plasma density (n o ) and electron temperature (T e ) and the ionic potential (V i ), sheath thickness (s), and sheath capacitance (c s), IEDF, voltage (V), and current (I). Controller 820 communicates to each of main RF generator 812b and auxiliary RF generator 812b' respective voltage set points and phase set points. Other control signals or commands output by controller 820 to each RF generator 812b, 812b' include pulse rate, duty cycle, and number of pulse states.

[0061] In various configurations, selected ones of the plasma parameters input to the controller 820 may be used according to a particular control scheme. As a non-limiting example, IEDF information from each plasma sensor 816b-2, 816b-2′ may be input to the controller 820. Feedback of primary and secondary IEDF information corresponding to the IEDFs associated with each primary and secondary bias electrodes 826b, 826b′ may be used in applications that rely on IEDF histograms or machine learning applications. In other configurations, feedback of ion potential (V) from each plasma sensor 816b-2, 816b-2′ may be used in applications that rely on IEDF histograms or machine learning applications. i ) can be transmitted to the controller 820. The ionic potential (V i ) corresponding to the main ion potential (V i ) and auxiliary ionic potential (V i ) feedback can be used in applications relying on time-domain control or pulse shaping. The configuration of Figure 8 provides an example of an RF power generation system with a controller that implements a SISO control technique.

[0062] FIG. 9 illustrates an RF power generation system 910 according to various configurations of the present disclosure. The RF power generation system 910 is configured similarly to FIG. 8 and further includes an RF source generator 912a. The RF source generator 912a receives a power setpoint command from a controller 920. The controller 920 communicates the power setpoint command to the RF source generator 912a based in part on feedback signals received from plasma sensors 916b-2, 916b-2′. The RF source generator 912a outputs an RF signal to a matching network 918a. The matching network 918a provides the matching function described above to provide impedance matching between the RF source generator 912a and the antenna / source electrode 924 of the plasma chamber. In the configuration of FIG. 9, the controller 920 provides a power command that varies according to parameters characterizing the plasma at the bias electrodes 926b, 926b′. In this manner, both the plasma density and the ion voltage can be controlled according to the parameters sensed by the plasma sensors 916b-2, 916b-2′. Varying the power of the RF source generator 912a controls the plasma density, and varying the power of the RF bias generators 912b, 912b' controls the ion potential. The RF power generation system 910 provides improved control over the plasma. In various configurations, the primary plasma sensor 816b-2 measures the ion potential (V i ) and IEDF to the controller 920. Similarly, in various configurations, the auxiliary plasma sensor 916b-2′ outputs the ion potential (V i ) and the IEDF to controller 920. In various other configurations, other parameters characterizing the plasma can be communicated to controller 920. Thus, Figure 9 provides an example of an RF power generation system having a controller that implements a MIMO control approach.

[0063] Figure 10 incorporates various components of Figures 1-9. The control module 1010 includes a main power generation module section 1012b and an auxiliary power generation module section 1012b'. The main power generation module section 1012b includes a power amplifier module 1014b, a sensor module 1016b, and a control module 1020b. The auxiliary power generation module section 1012b' includes a power amplifier module 1014b', a sensor module 1016b', and a control module 1020b'. The control modules 1020b, 1020b' may communicate via a communication link 1070 and may be integrated into a single processor or distributed across multiple processors. In various configurations, the control module 1010 includes one or more processors that execute code associated with module sections or modules 1010, 1012b, 1012b', 1014b, 1014b', 1016b, 1016b', 1020b, and 1020b'. The operation of module sections or modules 1010, 1012b, 1012b', 1014b, 1014b', 1016b, 1016b', 1020b, and 1020b' is described below with respect to the method of FIG.

[0064] For a more defined structure of the controller described above, see the flowchart of FIG. 11 provided below and the definition of the term "module" provided below. The systems disclosed herein can be operated using numerous methods, examples, and various control system methods shown in FIGS. 3-9. The following operations are described primarily with respect to the implementations of FIGS. 3-9, but the operations can be easily modified to apply to other implementations of the present disclosure. Operations can be performed iteratively. While the following operations are shown and primarily described as being performed sequentially, one or more of the following operations can be performed while one or more of the other operations are being performed.

[0065] FIG. 11 shows a flowchart of a control system 1110 for controlling RF power generation, e.g., the power supply systems of FIGS. 3-9. The control system 1110 includes a control section 1112b for a main RF power generator, such as for supplying power to a main bias electrode of a plasma system, and a control section 1112b' for an auxiliary bias electrode of a plasma system, such as for supplying power to an auxiliary bias electrode of the plasma system. In the control section 1112b, control begins at block 1114b and continues with sensing parameters at block 1116b. From the sensed parameters, plasma characteristics are determined at block 1118b. The plasma characteristics are then used to determine control of the plasma parameters at block 1120b. Control then proceeds to block 1122b, where a power supply or power device is controlled to adjust the power applied to the main bias electrode. Control ends at block 1124b. The control system 1110 includes a control section 1112b' for an auxiliary RF power generator, such as for supplying power to an auxiliary bias electrode of the plasma system. Control section 1112b' operates similarly to control section 1112b.

[0066] The systems and methods described herein, in various configurations, provide one or more of the following advantages: The systems and methods described herein may improve etch uniformity control. The systems and methods described herein may improve die yield. The systems and methods described herein may also eliminate the need for empirical mapping for each recipe. The systems and methods described herein may also provide ion energy control, real-time correction of system dynamics, and sheath thickness feedback and correction, facilitating the implementation of typically complex control schemes.

[0067] The foregoing description is merely exemplary in nature and is in no way intended to limit the disclosure, its application, or uses. The broad teachings of the present disclosure can be implemented in a variety of forms. Thus, while the present disclosure includes specific examples, the true scope of the present disclosure should not be so limited, as other variations will become apparent upon review of the drawings, the specification, and the following claims. In the specification and claims, one or more steps within a method may be executed in a different order (or simultaneously) without altering the principles of the present disclosure. Similarly, one or more instructions stored in a non-transitory computer-readable medium may be executed in a different order (or simultaneously) without altering the principles of the present disclosure. Unless otherwise indicated, numbering or other labeling of instructions or method steps is done for convenient reference and not to indicate a fixed order.

[0068] Furthermore, although each of the embodiments is described above as having certain features, any one or more of these features described with respect to any embodiment of the present disclosure can be implemented in and / or combined with any feature of any of the other embodiments, even if that combination is not explicitly described. In other words, the described embodiments are not mutually exclusive, and substitution of one or more embodiments for one another remains within the scope of the present disclosure.

[0069] Spatial and functional relationships between elements (e.g., between modules, circuit elements, semiconductor layers, etc.) are described using various terms, including "connected," "engaged," "coupled," "adjacent," "adjacent to," "on top of," "above," "below," and "disposed." Unless expressly described as "direct," when a relationship between a first element and a second element is described in the above disclosure, the relationship can be a direct relationship where no other intervening elements exist between the first and second elements, or an indirect relationship where one or more intervening elements (spatial or functional) exist between the first and second elements.

[0070] The phrase "at least one of A, B, and C" should be interpreted to mean a logical (A OR B OR C) using a non-exclusive logical OR, and not to mean "at least one A, at least one B, and at least one C." The term "set" does not necessarily exclude an empty set; in other words, in some situations, a "set" may have zero elements. The term "non-empty set" may be used to indicate the exclusion of an empty set; in other words, a non-empty set always has one or more elements. The term "subset" does not necessarily require a proper subset. In other words, a "subset" of a first set may be coextensive with (equal to) the first set. Furthermore, the term "subset" does not necessarily exclude an empty set; in some situations, a "subset" may have zero elements.

[0071] In the diagrams, the direction of the arrow, indicated by the arrowhead, generally indicates the flow of information (such as data or instructions) that is important to the illustration. For example, if element A and element B exchange various information, but information sent from element A to element B is relevant to the diagram, the arrow may point from element A to element B. This one-way arrow does not mean that other information is not sent from element B to element A. Furthermore, for information sent from element A to element B, element B may send a request for or acknowledgement of receipt of that information to element A.

[0072] In this application, including the definitions below, the term "module" may be replaced with the term "controller" or the term "circuitry." In this application, the term "controller" may be replaced with the term "module." The term "module" may refer to, be part of, or include an application specific integrated circuit (ASIC), digital, analog, or mixed analog / digital discrete circuitry, a digital, analog, or mixed analog / digital integrated circuit, a combinational logic circuit, a field programmable gate array (FPGA), processor hardware (shared, dedicated, or group) that executes code, memory hardware (shared, dedicated, or group) that stores code executed by the processor hardware, other suitable hardware components that provide the described functionality, or a combination of some or all of the above, such as in a system-on-chip.

[0073] The module may include one or more interface circuits. In some examples, the interface circuit may implement a wired or wireless interface that connects to a local area network (LAN) or a wireless personal area network (WPAN). Examples of LANs are the Institute of Electrical and Electronics Engineers (IEEE) Standard 802.11-2020 (also known as the WIFI wireless networking standard) and IEEE Standard 802.3-2018 (also known as the Ethernet wired networking standard). Examples of WPANs are the IEEE Standard 802.15.4 (including the ZIGBEE standard from the ZigBee Alliance) and the BLUETOOTH wireless networking standard from the Bluetooth Special Interest Group (SIG) (including Core Specification versions 3.0, 4.0, 4.1, 4.2, 5.0, and 5.1 from the Bluetooth SIG).

[0074] Modules may communicate with other modules using interface circuits. While modules may be depicted in this disclosure as logically communicating directly with other modules, in various implementations, modules may actually communicate through a communication system. A communication system includes physical and / or virtual networking equipment such as hubs, switches, routers, and gateways. In some implementations, a communication system connects to or traverses a wide area network (WAN) such as the Internet. For example, a communication system may include multiple LANs connected to each other via the Internet or point-to-point leased lines using technologies including Multiprotocol Label Switching (MPLS) and virtual private networks (VPNs).

[0075] In various implementations, the functionality of a module may be distributed among multiple modules connected via a communication system. For example, multiple modules may implement the same function distributed by a load balancing system. In a further example, the functionality of a module may be divided between a server (also known as remote or cloud) module and a client (or user) module. For example, a client module may include a native application or a web application that runs on a client device and communicates over a network with a server module.

[0076] Some or all of the hardware functions of a module may be defined using a language for hardware description, such as IEEE Standard 1364-2005 (commonly referred to as "Verilog") and IEEE Standard 1076-2008 (commonly referred to as "VHDL"). The hardware description language may be used to fabricate and / or program the hardware circuit. In some implementations, some or all of the functions of a module may be defined by a language such as IEEE 1666-2005 (commonly referred to as "SystemC"), which encompasses both code, as described below, and a hardware description.

[0077] The term code, as used above, may include software, firmware, and / or microcode and may refer to programs, routines, functions, classes, data structures, and / or objects. Shared processor hardware encompasses a single microprocessor that executes some or all code from multiple modules. Group processor hardware encompasses a microprocessor that executes some or all code from one or more modules in combination with additional microprocessors. References to multiple microprocessors encompass multiple microprocessors on separate dies, multiple microprocessors on a single die, multiple cores of a single microprocessor, multiple threads of a single microprocessor, or combinations of the above.

[0078] Memory hardware may also store data, either together with or separately from the code. Shared memory hardware encompasses a single memory device that stores some or all code from multiple modules. An example of shared memory hardware may be a level 1 cache on or near a microprocessor die, which may store code from multiple modules. Another example of shared memory hardware may be persistent storage, such as a solid-state drive (SSD), which may store code from multiple modules. Group memory hardware encompasses a memory device that, in combination with other memory devices, stores some or all code from one or more modules. An example of group memory hardware is a storage area network (SAN), which may store code for a particular module across multiple physical devices. Another example of group memory hardware is the random access memory of each of a set of servers, which, in combination, store code for a particular module.

[0079] The term memory hardware is a subset of the term computer-readable medium. As used herein, the term computer-readable medium does not encompass transitory electrical or electromagnetic signals propagating through a medium (such as on a carrier wave), and therefore the term computer-readable medium is considered to be tangible and non-transitory. Non-limiting examples of non-transitory computer-readable media are non-volatile memory devices (such as flash memory devices, erasable programmable read-only memory devices, or masked read-only memory devices), volatile memory devices (such as static random access memory devices or dynamic random access memory devices), magnetic storage media (such as analog or digital magnetic tape or hard disk drives), and optical storage media (such as CDs, DVDs, or Blu-ray® discs).

[0080] The apparatus and methods described in this application may be implemented partially or fully by a special-purpose computer created by configuring a general-purpose computer to perform one or more specific functions embodied in a computer program. Such apparatus and methods may be described as computerized apparatus and computerized method. The functional blocks and flowchart elements described above function as software specifications that can be converted into a computer program by the routine work of a skilled technician or programmer.

[0081] A computer program includes processor-executable instructions stored on at least one non-transitory computer-readable medium. A computer program may also include or rely on stored data. A computer program may encompass a basic input / output system (BIOS) that interacts with the hardware of a special-purpose computer, device drivers that interact with specific devices of a special-purpose computer, one or more operating systems, user applications, background services, background applications, etc.

[0082] A computer program may include (i) written text to be parsed, such as HTML (Hypertext Markup Language), XML (Extensible Markup Language), or JSON (JavaScript Object Notation), (ii) assembly code, (iii) object code generated from source code by a compiler, (iv) source code for execution by an interpreter, (v) source code for compilation and execution by a just-in-time compiler, etc. By way of example only, the source code may be written using syntax from languages ​​including C, C++, C#, Objective C, Swift, Haskell, Go, SQL, R, Lisp, Java®, Fortran, Perl, Pascal, Curl, OCaml, JavaScript®, HTML5 (Hypertext Markup Language 5th revision), Ada, ASP (Active Server Pages), PHP (PHP: Hypertext Preprocessor), Scala, Eiffel, Smalltalk, Erlang, Ruby, Flash®, Visual Basic®, Lua, MATLAB®, SIMULINK®, and Python®. [Explanation of symbols]

[0083] 110 Inductively Coupled Plasma (ICP) System, ICP System 112 Plasma Chamber 114 Plasma, bulk plasma with high density at the center 116 First coil, coil 118 Second Coil, Coil 120 RF power generator or power supply, power supply 122 RF power generator or power supply, power supply 124 Dielectric window 126 electrode 128 RF power generator, power supply, or power supply 130 Plasma Sheath 132 Ion Orbits 210 Capacitively Coupled Plasma (CCP) System, CCP System 212 Plasma Chamber 214 Plasma, bulk plasma with low density at the center 216 Electrode, bias electrode 220 DC (ω=0) or RF power generator or power supply, power supply 222 DC (ω=0) or RF power generator or power supply, power supply 226 Electrode, bias electrode 230 Plasma Sheath 232 Ion Orbits 310 RF Generators or Power Supply Systems, Power Supply Systems 312 RF Generator 312a Radio Frequency (RF) Generators or Power Supplies, RF Generators, RF Power Generators, Source RF Generators, RF Source Generators 312a' Source RF Generator 312a'' Source RF Generator 312a n Source RF Generator 312b Radio Frequency (RF) Generators or Power Supplies, Bias RF Generators, RF Generators, RF Power Generators, RF Bias Generators 312b' Bias RF Generator 312b'' Bias RF Generator 312b n Bias RF Generator 314a RF power supply or amplifier, RF power supply, power amplifier, power supply, source RF power supply, source RF generator 314b RF power supply or amplifier, RF power supply, power amplifier, power supply, bias RF power supply, bias RF generator 316a Sensor, Source Sensor 316b Sensor, bias sensor 318a Matching Network, Source Matching Network 318b Matching Network, Bias Matching Network 320a Processor, controller, or control module, power controller or control module, control module, controller, local controller, source controller 320b Processor, controller, or control module, power controller or control module, control module, controller, local controller, bias controller 320b' Controller 320' Controller 322a RF power signal 322b RF power signal 324a X signal 324b X signal 326a Y signal 326b Y signal 328a Feedforward control signal or feedback control signal, control signal, feedback control signal, signal 328b Feedforward control signal or feedback control signal, control signal, feedback control signal, signal 330 control signal, synchronization or trigger signal, trigger signal, trigger or synchronization signal, signal 330' control signal, synchronization or trigger signal, trigger or synchronization signal, signal 332 Load 334 Synchronous Bias Detector 336 Links 338 Links 340 Pulse Sync Output Port 342 Digital Communication Port 344 RF output port 348 RF input port 350 digital communication ports 352 Pulse Sync Input Port 356 Pulse Synchronization Signal 357 Digital Communication Link 358 RF Control Signals 410 RF signal 412 Pulse Signal 510 Plasma Generation System 512 Plasma Chamber 514 Plasma 516 Conductor 526 Bias electrode 526b Main bias electrode 526b' Auxiliary bias electrode 530 Plasma Sheath 532 Ion Orbits 540b Main Bias RF Generator 540b' Auxiliary Bias RF Generator 542b Main Bias RF Power Supply 542b' Auxiliary Bias RF Power Supply 544b Main bias IEDF sensor, IEDF sensor 544b' Auxiliary bias IEDF sensor, IEDF sensor 610 RF Power Generation System 620b RF Generator Controller, Main RF Generator Controller 620b' RF Generator Controller, Auxiliary RF Generator Controller 645b Proportionality coefficient P 650b adder 650b' Adder 652b Receiving combiner, combiner 656b Receiving combiner, combiner 658b Integration coefficient I 666b Integrator 668b Clamp 670b Integrator minimum term 672b Integrator maximum term 710 RF Power Generation System 712b RF Generator, Main RF Generator 712b' RF Generator, Auxiliary RF Generator 714b Main RF amplifier or RF power supply, RF power supply, main RF power supply 714b' Auxiliary RF Amplifier or RF Power Supply, Auxiliary RF Power Supply 716b Main IEDF sensor 716b' Auxiliary Bias IEDF Sensor 720b Main Controller, Main Bias Controller 720b' Auxiliary Controller, Auxiliary Bias Controller 726b Main bias electrode 726b' Auxiliary bias electrode 730 Communication Links 732 Plasma Chamber 810 Plasma Generation System 812b Main RF Generator 812b' Auxiliary RF Generator 816b-1 Main VI probe, VI probe 816b-1' VI probe 816b-2 Plasma sensor, primary plasma sensor 816b-2' Plasma Sensor 818b Main matching network 820 Common Controller, Controller 826b Main bias electrode 826b' Auxiliary bias electrode 910 Power generator system, power generation system 912a RF Source Generator 912b RF Bias Generator 912b' RF Bias Generator 916b-2 Plasma sensor 916b-2' Plasma sensor, auxiliary plasma sensor 918a Matching Network 920 Controller 924 Antenna / Source Electrode 1010 Control Module 1012b Main Power Generation Module Section 1012b' Auxiliary Power Generation Module Section 1014b Power Amplifier Module 1014b' Power Amplifier Module 1016b sensor module 1016b' Sensor Module 1020b control module 1020b' control module 1070 Communication Link 1110 Control System

Claims

1. a first RF power supply configured to output a first RF output signal to a first electrode of a load; a first sensor for detecting a first parameter of the first RF output signal to determine a first characteristic of the plasma in the load; a second RF power supply configured to output a second RF output signal to the second electrode; a second sensor for detecting a second parameter of the second RF output signal to determine a second characteristic of the plasma in the load; an RF power controller configured to receive the first characteristic and the second characteristic and generate a first control signal; and configured to generate a second control signal; Equipped with The RF generator, wherein the first control signal adjusts the first RF output signal and the second control signal adjusts the second RF output signal.

2. the first sensor is a plasma sensor, and the first characteristic is at least one of a plasma density, an electron temperature, an ion potential, a sheath thickness, a sheath capacitance, or an ion energy distribution function (IEDF) associated with the first electrode; 2. The RF generator of claim 1, wherein the second sensor is a plasma sensor, and the second characteristic is at least one of a plasma density, an electron temperature, an ion potential, or an ion energy distribution function (IEDF) associated with the second electrode.

3. The RF generator of claim 1 , wherein the first characteristic is an IEDF associated with the first electrode.

4. The RF generator of claim 1 , wherein the second characteristic is an IEDF associated with the second electrode.

5. 2. The RF generator of claim 1, wherein the first characteristic is an IEDF associated with the first electrode and the second characteristic is the IEDF associated with the second electrode.

6. 2. The RF generator of claim 1, wherein the RF power controller comprises a first power controller and a second power controller, the first power controller configured to receive the first characteristic and generate a first control signal for varying the first RF output signal, and the second power controller configured to receive the second characteristic and generate a second control signal for varying the second RF output signal.

7. 7. The RF generator of claim 6, further comprising a communication link between the first power controller and the second power controller, the first power controller and the second power controller configured to communicate settings defining the respective first and second RF output signals.

8. 10. The RF generator of claim 1, wherein the first RF power source is a main bias power source, the first electrode is a main bias electrode, the second RF power source is an auxiliary bias power source, and the second electrode is an auxiliary bias electrode, and the main bias electrode and the auxiliary bias electrode form a composite bias electrode.

9. 2. The RF generator of claim 1, wherein the first control signal controls at least one of a rail voltage, drive, frequency, phase, or pulsing of the first RF output signal, and the second control signal controls at least one of a rail voltage, drive, frequency, phase, or pulsing of the second RF output signal.

10. 10. The RF generator of claim 1, further comprising a third RF power supply configured to output a third RF output signal to a third electrode, the RF power controller further configured to generate a third control signal for varying the third RF output signal.

11. 11. The RF generator of claim 10, wherein the RF power controller is configured to generate the third control signal, the third control signal varying according to at least one of the first characteristic or the second characteristic.

12. 12. The RF generator of claim 11, wherein the third RF power source is a source power source and the third electrode is a source electrode.

13. a main bias RF generator comprising: a main bias power supply configured to output a main bias RF output signal to a main bias electrode of a load; a main bias plasma sensor configured to detect a main bias parameter of the main bias RF output signal to determine a main bias characteristic of a plasma within the load; a main bias RF generator including: an auxiliary bias RF generator comprising: an auxiliary bias RF power supply configured to output an auxiliary bias RF output signal to the auxiliary bias electrode; an auxiliary bias plasma sensor configured to detect an auxiliary bias parameter of the auxiliary bias RF output signal to determine an auxiliary bias characteristic of a plasma in the load; an auxiliary bias RF generator including: an RF power controller configured to receive the main bias characteristic and the auxiliary bias characteristic and to generate a main bias control signal for varying the main bias RF output signal; and configured to generate an auxiliary bias control signal for varying the auxiliary bias RF output signal. An RF system comprising:

14. 14. The RF system of claim 13, wherein the RF power controller is one of a proportional-integral controller, a proportional-integral-derivative controller, or a linear quadratic regulator controller.

15. the main bias plasma sensor includes one of a VI probe or a directional coupler for detecting the main bias parameter; 14. The RF system of claim 13, wherein the auxiliary bias plasma sensor includes one of a VI probe or a directional coupler for detecting the auxiliary bias parameter.

16. the main bias characteristic is one of a plasma density, an electron temperature, an ion potential, a sheath thickness, a sheath capacitance, or an ion energy distribution function (IEDF) associated with the main bias electrode; 14. The RF system of claim 13, wherein the auxiliary bias characteristic is one of a plasma density, an electron temperature, an ion potential, or an ion energy distribution function (IEDF) associated with the auxiliary bias electrode.

17. 14. The RF system of claim 13, wherein the RF power controller comprises a main bias power controller and an auxiliary bias power controller, the main bias power controller configured to receive the main bias characteristic and generate the main bias control signal according to the main bias characteristic, and the auxiliary bias power controller configured to receive the auxiliary bias characteristic and generate the auxiliary bias control signal according to the main bias characteristic.

18. The RF system of claim 13 , wherein the main bias electrode and the auxiliary bias electrode form a composite bias electrode.

19. 14. The RF system of claim 13, wherein the main bias control signal controls at least one of a rail voltage, drive, frequency, phase, or pulsing of the main bias RF output signal, and the auxiliary bias control signal controls at least one of a rail voltage, drive, frequency, phase, or pulsing of the auxiliary bias RF output signal.

20. one of the main bias characteristic and the auxiliary bias characteristic includes more than one of a plasma density, an electron temperature, an ion potential, or an ion energy distribution function (IEDF) associated with each of the main bias electrode and the auxiliary bias electrode; 14. The RF system of claim 13, wherein the other of the main bias characteristic and the auxiliary bias characteristic comprises more than one of a plasma density, an electron temperature, an ion potential, or an ion energy distribution function (IEDF) associated with the respective other of the main bias electrode and the auxiliary bias electrode.

21. 14. The RF system of claim 13, further comprising a source RF power supply configured to output a source RF output signal to a source electrode, the RF power controller further configured to generate a source control signal for varying the source RF output signal.

22. one of the main bias characteristic and the auxiliary bias characteristic includes more than one of a plasma density, an electron temperature, an ion potential, or an ion energy distribution function (IEDF) associated with each of the main bias electrode and the auxiliary bias electrode; 22. The RF system of claim 21 , wherein the other of the main bias characteristic and the auxiliary bias characteristic comprises more than one of a plasma density, an electron temperature, an ion potential, or an ion energy distribution function (IEDF) associated with the respective other of the main bias electrode and the auxiliary bias electrode.

23. 22. The RF system of claim 21, wherein the RF power controller is configured to generate the source control signal, the source control signal varying according to at least one of the main bias characteristic or the auxiliary bias characteristic.

24. The RF system of claim 13 , wherein the main bias characteristic is an IEDF associated with the main bias electrode.

25. The RF system of claim 13 , wherein the auxiliary bias characteristic is an IEDF associated with the auxiliary bias electrode.

26. 14. The RF system of claim 13, wherein the main bias characteristic is an IEDF associated with the main bias electrode and the auxiliary bias characteristic is the IEDF associated with the auxiliary bias electrode.

27. A non-transitory computer-readable medium storing processor-executable instructions, the instructions comprising: generating a main bias RF output signal to a main bias electrode of a load; detecting a main bias parameter of the main bias RF output signal to determine a main bias characteristic of a plasma in the load; generating an auxiliary bias RF output signal to an auxiliary bias electrode of the load; detecting an auxiliary bias parameter of the auxiliary bias RF output signal to determine an auxiliary bias characteristic of a plasma in the load; receiving the main bias characteristic and the auxiliary bias characteristic, generating a main bias control signal for varying the main bias RF output signal in accordance with the main bias parameter, and generating an auxiliary bias control signal for varying the auxiliary bias RF output signal in accordance with the main bias characteristic; Including, A non-transitory computer-readable medium storing processor-executable instructions, wherein the main bias control signal adjusts the main bias RF output signal and the auxiliary bias control signal adjusts the auxiliary bias RF output signal.

28. the main bias characteristic is at least one of a plasma density, an electron temperature, an ion potential, a sheath thickness, a sheath capacitance, or an ion energy distribution function (IEDF) associated with the main bias electrode; 28. The non-transitory computer-readable medium storing processor-executable instructions of claim 27, wherein the auxiliary bias characteristic is at least one of a plasma density, an electron temperature, an ion potential, a sheath thickness, a sheath capacitance, or an ion energy distribution function (IEDF) associated with the auxiliary bias electrode.

29. 28. The non-transitory computer-readable medium storing processor-executable instructions of claim 27, wherein the primary bias electrode and the auxiliary bias electrode form a composite bias electrode.

30. 28. A non-transitory computer-readable medium storing processor-executable instructions of claim 27, wherein the main bias control signal controls at least one of a rail voltage, drive, frequency, phase, or pulsing of the main bias RF output signal, and the auxiliary bias control signal controls at least one of a rail voltage, drive, frequency, phase, or pulsing of the auxiliary bias RF output signal.

31. one of the main bias characteristic and the auxiliary bias characteristic includes at least two of a plasma density, an electron temperature, an ion potential, or an ion energy distribution function (IEDF) associated with each of the main bias electrode and the auxiliary bias electrode; 28. The non-transitory computer-readable medium storing processor-executable instructions of claim 27, wherein the other of the main bias characteristic and the auxiliary bias characteristic comprises at least one of a plasma density, an electron temperature, an ion potential, or an ion energy distribution function (IEDF) associated with the respective other of the main bias electrode and the auxiliary bias electrode.

32. 28. A non-transitory computer-readable medium storing processor-executable instructions of claim 27, wherein the instructions further comprise generating a source RF output signal to a source electrode and generating a source control signal for varying the source RF output signal.

33. one of the main bias characteristic and the auxiliary bias characteristic includes more than one of a plasma density, an electron temperature, an ion potential, or an ion energy distribution function (IEDF) associated with each of the main bias electrode and the auxiliary bias electrode; 33. The non-transitory computer-readable medium storing processor-executable instructions of claim 32, wherein the other of the main bias characteristic and the auxiliary bias characteristic comprises more than one of a plasma density, an electron temperature, an ion potential, or an ion energy distribution function (IEDF) associated with the respective other of the main bias electrode and the auxiliary bias electrode.

34. 33. The non-transitory computer-readable medium storing processor-executable instructions of claim 32, wherein the instructions further comprise varying the source control signal according to at least one of the main bias characteristic or the auxiliary bias characteristic.

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