High frequency power generator and control method

Abstract

The power generator includes a plurality of amplifier blocks and a combiner. Each of the amplifier blocks includes one or more amplifiers, and the combiner combines the modulated power signals output from the amplifier blocks to generate an RF power signal for the load. The amplifier blocks are controlled to outphase the modulated power signals based on a phase angle. Some of the amplifier blocks can perform discrete modulation to generate respective signals of the modulated power signals. Discrete modulation involves selecting different combinations of amplifiers in one or more of the amplifier blocks to vary the RF power signal in discrete steps. In an embodiment, the amplifiers can be radio frequency power amplifiers.

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit under 35 U.S.C. §119(e) of U.S. Provisional Patent Application No. 63 / 059,532, filed July 31, 2020, and U.S. Provisional Patent Application No. 63 / 085,432, filed September 30, 2020, the contents of which are incorporated herein by reference in their entireties.

[0002] TECHNICAL FIELD

[0002] One or more embodiments described herein relate to power generation. [Background technology]

[0003] In many industrial applications, power amplifiers operate with variable load impedances, high frequency ranges, and high power levels and peak-to-average power ratios. One example of such an application is plasma generation used in semiconductor processing. Existing power generators are unable to function in a way that does not limit or otherwise adversely affect the operation of the plasma generator or the operation of the power generator itself. For example, existing power generators sacrifice efficiency to meet other metrics. This increases size and power ratings and results in low peak and average power efficiency, among other limitations. Summary of the Invention

[0004]

[0004] One or more embodiments described herein provide a radio frequency (RF) power generator having a unique system configuration and power control method.

[0005] According to one or more embodiments, a power generator includes a plurality of amplifier blocks, each including one or more amplifiers and a combiner for combining modulated power signals output from the plurality of amplifier blocks to generate an RF power signal for a load. The plurality of amplifier blocks are configured to outphase the modulated power signals based on a phase angle. Each of the plurality of amplifier blocks is configured to perform discrete modulation to generate a respective one of the modulated power signals. The discrete modulation includes selecting different combinations of a plurality of power amplifiers to change the RF power signal in discrete steps to correspond to changes in power for the load. In an embodiment, the amplifiers may be RF power amplifiers.

[0006] According to one or more embodiments, a method for managing power includes generating a first modulated power signal from a first amplifier block, generating a second modulated power signal from at least a second amplifier block, outphasing the first and second modulated power signals based on a phase angle, and generating an RF power signal for a load based on the outphased first and second modulated power signals. Generating the first modulated power signal includes switching different combinations of multiple power amplifiers in the first amplifier block, and generating the second modulated power signal includes switching different combinations of multiple power amplifiers in the second amplifier block. In embodiments, the amplifiers may be RF amplifiers.

[0007] The foregoing and other objects, features, and advantages will become apparent from the following more detailed description of the embodiments as illustrated in the accompanying drawings, in which like reference characters refer to the same parts throughout the different views. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the embodiments. [Brief explanation of the drawings]

[0008] [Figure 1]FIG. 1 is a block diagram of a radio frequency (RF) power generator. [Figure 2]

[0009] FIG. 1 is a block diagram of an RF power generator. [Figure 3A]

[0010] 1 is a schematic diagram of an embodiment of an amplifier having outputs combined through a single combiner. [Figure 3B] 1 is a schematic diagram of an embodiment of an amplifier having outputs combined through a single combiner. [Figure 3C] 1 is a schematic diagram of an embodiment of an amplifier having outputs combined via multiple combiners; [Figure 4]

[0011] 1 is a schematic diagram of a switched-mode power amplifier (PA). [Figure 5]

[0012] FIG. 7 illustrates a plot of voltage versus time of an example RF output voltage waveform of a Multi-Inverter Discrete Backoff (MIDB) block, such as the MIDB block shown in FIG. 2 or FIG. 6. [Figure 6]

[0013] FIG. 1 is a block diagram of an RF power generator with two MIDB power amplifiers (PAs). [Figure 7]

[0014] 1 is a schematic diagram of an example embodiment of an impedance transformer; [Figure 8]

[0015] 1 is a schematic diagram of an example embodiment of a discrete drain modulation circuit for a PA. [Figure 9A]

[0016] 1 is a flowchart illustrating a method for generating an RF power signal. [Figure 9B] 1 is a flowchart illustrating a method for generating an RF power signal. [Figure 9C] 1 is a flowchart illustrating a method for generating an RF power signal. [Figure 10]

[0017] FIG. 1 is a plot (voltage vector graph) of MIDB block output voltage versus load voltage. [Figure 11]

[0018] 7A and 7B show plots of uncompensated load admittance curves observed at MIDB blocks (YA and YB in FIG. 6) as an example of admittance for evaluating performance and power management. [Figure 12]

[0019] FIG. 10 illustrates a plot of efficiency versus output power for an embodiment of a MIDB system. [Figure 13]

[0020] FIG. 10 is a plot of voltage versus time showing the dynamic response to a step in outphasing angle. [Figure 14]

[0021] FIG. 10 shows a voltage versus time plot illustrating the dynamic response to a step in the MIDB configuration. [Figure 15]

[0022] FIG. 10 illustrates a plot of voltage versus time showing example performance metrics of one or more embodiments. DETAILED DESCRIPTION OF THE INVENTION

[0009]

[0023] One or more embodiments described herein provide radio frequency (RF) power generators that meet the power requirements of various applications. Throughout various implementations, one or more of the following features may be combined: (1) outphasing a power supply signal from multiple amplifier blocks for fast-response (and, if necessary, continuous) power generation; (2) configuring each multiple amplifier block to include multiple amplifiers; (3) configuring each multiple amplifier block to include multiple switch-mode power amplifiers; (4) modulating the power signal by switching (or selecting) different combinations of amplifiers within each block to generate discrete steps in the voltage of the RF power signal; and / or (5) performing discrete drain modulation of the supply voltage for the amplifier blocks to generate a highly efficient operating power range.

[0010]

[0024] In certain embodiments, the RF power generator may be used to power loads including plasma generators of the type used during semiconductor chip fabrication processes. In other embodiments, the RF power generator may power other types of loads, including those that operate at different power ranges, e.g., those that do not have the same power range and performance requirements as the plasma generator. Moreover, discrete step changes in the RF power signal may be dynamically implemented to meet the power requirements of the load as they change over time. In some embodiments, an impedance converter may be included to resolve matching issues caused by changes in load impedance and / or impedance changes caused by switching different combinations of power amplifiers within an amplifier block during discrete modulation.

[0011]

[0025] 1 shows one embodiment of an RF power generator 1 including various stages for generating power for an intended application. One application may be an industrial application, such as generating power for a plasma generator in a semiconductor manufacturing process, as described above. Other applications may be various types of communication and antenna systems, radar systems, and microwave resonator cavities, as well as others.

[0012]

[0026] Referring to FIG. 1 , RF power generator 1 includes an amplifier stage 10, a power combiner 30, and an impedance converter 40. The amplifier stage includes N amplifier blocks (where N≧2) that output modulated power signals to be combined to generate an output RF power signal for a load. Each of the N amplifier blocks includes multiple power amplifiers that are selectively switched (e.g., selected or activated) to generate a predetermined power block voltage. An example of a first amplifier block will be discussed with the understanding that the remaining of the N amplifier blocks may be configured the same or similarly. In other embodiments, the amplifier blocks may have different structural and / or functional configurations.

[0013]

[0027] A first amplifier block 201 includes multiple power amplifiers PA arranged in parallel. For convenience, only one power amplifier 21 is shown in detail in block 201 with the understanding that the remaining power amplifier or amplifiers in the block may be similarly configured. In one embodiment, the power amplifiers in each block may have an inverter configuration that operates in switch mode instead of linear mode.

[0014]

[0028] The power amplifier 21 may include a power transistor, either alone or with one or more other transistors and / or circuit elements. The power transistor may be, for example, a MOSFET having a fixed or adjustable gain, a predetermined bandwidth, power efficiency, and impedance. In some implementations, the RF amplifier may be a class D amplifier, a class E amplifier, a class Φ amplifier, or another type of amplifier. In some embodiments, the power amplifier 21 may operate in a switch mode. In other embodiments, the power amplifier 21 may operate in a linear region, for example, at relatively low power levels.

[0015]

[0029] Additionally, the power amplifier 21 may include a first control input 22, a power supply input 23, an RF power output 24, and a second control input 25. The first control input 22 may receive a first control signal from a control driver system (or controller) 71. The first control signal may include a gate signal for a power transistor of the power amplifier 21. In one embodiment, the first control signal may include information indicating the amplitude A1 of the power signal (voltage) to be output and / or timing information (e.g., phase φ1) for controlling the switching mode (and outphasing) of the power transistor. In switch mode operation, the control information may omit the amplitude. In linear mode operation, both amplitude and phase information may be included in the first control signal. The amplitude and phase information may also be received by other power amplifiers in the block.

[0016]

[0030] The power amplifier 23 receives a plurality of supply voltages V output from a power supply 72. D1 , …, V DN where N≧2. In one embodiment, the voltage signal from power supply 72 may correspond to a fixed voltage. In another embodiment, the voltage signal from power supply 72 may correspond to a variable voltage. The other power amplifiers in block 201 may receive the same supply voltage as power amplifier 23 or a different supply voltage. For purposes of illustration, it will be assumed that all power amplifiers in block 201 receive the same supply voltage.

[0017]

[0031] Power supply 72 may be configured in a variety of ways. In one embodiment, power supply 72 generates a regulated power supply voltage V from one or more input energy sources. D1 , …, V DN In one embodiment, power supply 72 can generate an independently controlled variable voltage as power supply voltage V D1 , …, V DN which can be generated as the RF output voltage V from the amplifier block using source (or drain) modulation. RF,j In this latter case, power supply 72 may allow for rapid switching between available discrete voltage levels, thereby modulating the output power voltage V without having to rapidly slew the power supply voltage. D1 , …, V DN These features will be described in more detail below.

[0018]

[0032] 1, the supply voltages output from power supply 72 correspond one-to-one to the N amplifier blocks. Thus, the number of supply voltages may equal the number of amplifier blocks in this case. The same may or may not be true for the number of control signals output from controller 71; for example, the control signals output from the controller may correspond one-to-one to the amplifier blocks, or different controls (e.g., phase information) may be input to different ones of the power amplifiers of each block to generate the intended output power voltage from that block during outphasing. In other embodiments, these one-to-one correspondences may not exist.

[0019]

[0033] The output voltage 24 of the power amplifier 21 may be selectively combined with the output voltages of one or more other power amplifiers in the block 201, or may be output alone, for example, depending on the discrete modulation scheme (e.g., phase angle and / or power management method) of the implemented amplifier block. The voltages output from the power amplifiers (PAs) in the block 201 may be combined, for example, in a combiner 29 further included in the block. As a result, the combiner may output a power signal (e.g., voltage V ) having an amplitude equal to or different from (e.g., larger than) the voltage supplied to the power supply input 23 if the amplifier 21 has a positive gain greater than 1. RF1 ) is output.

[0020]

[0034] The power signal 24 may be at an intermediate voltage (e.g., undergo further processing before input to the power combiner) or may be output directly to the power combiner. The gain of each of the power amplifiers in block 201 may be adjusted to, for example, a load (e.g., Z Load The voltage output from combiner 29 can be set to be within a predetermined range to meet the power requirements of the amplifier block 201. The power signal output from amplifier block 201 can be set to be within a predetermined range to meet the power requirements of the amplifier block 201. RF1 is shown as having

[0021]

[0035] The second control input 25 is coupled to receive a second control signal in the form of a switching control signal SCS. The switching control signal may be output from a switching control circuit 28 within or coupled to the power amplifier. In one embodiment, the switching control signal SCS performs a switching boost function. When a supply voltage is received from the power supply 72, the power amplifier, operating in switch mode, converts the supply voltage into a desired RF power signal.

[0022]

[0036] In addition to these features, RF power amplifier 21 may be coupled to a reference potential or bias voltage source 27. The reference potential may be, for example, ground potential, but may be a different potential in other embodiments. Furthermore, the power signal V from amplifier block 201 may be coupled to a bias voltage source 27 before being input to power combiner 30. RF1 may be passed through one or more active elements. The active elements may include reactive elements (e.g., capacitors, inductors, transmission lines, etc.) that may help to set the output impedance of the block. If the active elements include capacitors, the capacitors may also function as, for example, noise filters and / or smoothing capacitors. The output of the first amplifier block 201 is connected to a first impedance Z AL,1 , which may be fixed or may vary based on, for example, the state of the power amplifier in block 201.

[0023]

[0037] The remaining N amplifier blocks (blocks 20 N The output impedance of these blocks is Z ALj where the Nth block is labeled Z ALN Thus, according to one embodiment, the amplifier stage 10 comprises a plurality of amplifier blocks 201-20 N The jth power block has a power input V Dj and power signal RF output V RFjhaving, where it can be considered that 1 < j ≦ N.

[0024]

[0038] In one embodiment, the amplifier blocks can be controlled to always be on. In this case, different combinations of power amplifiers within each block can be selectively switched to control the respective power signal outputs of the blocks. This can be accomplished, for example, based on a predetermined and / or feedback-controlled outphasing pattern. The selective switching of the power amplifiers within the amplifier blocks can be used to effect discrete modulation of the power signals output from those blocks. As a result, this can vary the RF power signal output to the load in discrete steps.

[0025]

[0039] In linear mode operation, both the amplitude information and the phase information output from the controller 71 can control the power signals output from each block. Some or all of the amplitudes A1,..., A N can in this case be the same or different from each other. In switch mode operation, only the phase φ j can be used according to a predetermined outphasing scheme. The outphasing scheme can selectively activate a predetermined amplifier block at a predetermined time to generate the power signals to be combined by the power combiner to supply power to the load. By controlling the power amplifiers within each of the N amplifier blocks (e.g., by controlling the on / off state of the power amplifiers), the amplifier stage 10 can achieve an expandable power generator design sufficient to meet the requirements of many applications.

[0026]

[0040] In one embodiment, the amplifier blocks, along with the switching performed on the power amplifiers within each amplifier block, may themselves be selected (or activated) based on control information from controller 71. In this sense, the switching (or selection) of the amplifier blocks may be thought of as performing coarse adjustments to the RF power signal to the load, and the switching of the power amplifiers within each of the amplifier blocks may be thought of as performing fine adjustments to the RF power signal to the load. The control information controlling the switching of the amplifier blocks may be used, for example, to change the state of operation of the blocks (e.g., activated / deactivated or selected / deselected), thereby implementing different switching combinations of the blocks.

[0027]

[0041] In one embodiment, to improve efficiency and achieve a wide load range, the power transistors in each of the N amplifier blocks may be operated to maintain zero voltage switching (ZVS, or soft switching) over all or a predetermined portion of the block's operating range. Auxiliary circuitry may be included to facilitate ZVS operation under varying conditions.

[0028]

[0042] The power combiner 30 generates a combined power signal (V RFT ) 35. The combined power signal is based on a combination of the power signals output from the amplifier stages 10, e.g., a combination of the power signals output from all or some of the N amplifier blocks. In one embodiment, the combining may be performed using a lossless (and therefore non-isolated) combining method. In another embodiment, the combining may be performed using an isolated combining method coupled with energy recovery. In these or other embodiments, the power signals may be combined based on a weight or weighting factor assigned to each of the RF power signals. The output impedance of the power combiner 30 is Z T is.

[0029]

[0043] In one embodiment, power combiner 30 can perform one or more operations in addition to its combining operation. For example, the power combiner may perform one or more operations in addition to or in combination with the impedance transformation performed by impedance transformer 40 to create a blocking impedance (e.g., Z AL1 ~Z ALN The power combiner may perform load modulation of the power amplifier blocks, including conversion of the power amplifier blocks. The power combiner may also perform further power control and / or reduce the operating range of the power amplifier blocks.

[0030]

[0044] The impedance converter 40 converts the output impedance of the power combiner 30 to a load Z Load The impedance converter 40 matches the impedance of the load Z to at least within a predetermined tolerance. This impedance matching operation can improve the performance and efficiency of transferring RF power to the load. The characteristics of the load can control the impedance transformation to be performed. For example, the load impedance range associated with a given application can determine the voltage and / or current levels corresponding to the load. These voltage and / or current levels can be rescaled to one more suitable for efficient combining, for example, to rescale the load impedance to a more appropriate range. In one embodiment, the impedance converter 40 can perform a fixed or variable impedance transformation for this purpose. To accomplish this, the impedance converter 40 can include a matching variable network (TMN) or a resistive compression network. The output impedance of the converter 40 can be adjusted to the load Z. Load Additionally, in one embodiment, the signal output from the impedance transformer 40 can correspond to the RF power signal 90 provided to the load.

[0031]

[0045] The RF power generator 10 may include several additional features. For example, the RF power generator may include or be coupled to a control system 80. The control system may include, for example, the controller 71 and power supply 72 previously discussed. In addition, the control system 80 may include, but is not limited to, the following: V RFout The control system 80 may include one or more sensors 81 for measuring parameters, including output voltage, current, and power corresponding to the load, ZVS detection and monitoring of the power amplifier transistors, and / or system temperature. Accurate, high-bandwidth measurement of voltage and current (or direct measurement of RF power) under variable load conditions may be advantageous in some embodiments for even more accurate control of output power with even faster response times. For example, the control system 80 may include a feedback loop from the sensors to the controller 71 for dynamically varying the power signal generation from the amplifier stage 10 to meet changing load, load-related impedance, and / or power requirements, or to compensate for various conditions of the RF power generator, e.g., to maintain various components of the RF power generator operating within one or more predetermined ranges.

[0032]

[0046] Sensor 81 inputs measurements into controller 71. Depending on the system, controller 71 can generate various types of control signals CS for output to power supply 72. In one embodiment, the control signal is a voltage V to be supplied to the amplifier block of stage 10. D1 , …, V DN In some embodiments, this can be achieved by selecting or varying all or part of the reference voltage V D1,Ref ~V DN,RefThis can be accomplished by specifying a voltage V of the output power signal output to the power combiner 30. The controller 71 can also generate signals (e.g., gating signal 22) to control the outphasing of the power signals from the amplifier blocks. In switch mode operation, the control signals can indicate the switching timing and relative phase between the amplifier blocks. In linear mode operation, the control signals can indicate the voltage V of the output power signal output to the power combiner 30. RF,1 , …, V RF,N These and other features of RF power generator 20 are discussed next.

[0033]

[0047] The amplifier stage 10 can control power generation based on a multi-inverter discrete backoff (MIDB) technique. Unlike other proposed power generators, the MIDB technique enables the RF power generator to losslessly combine the outputs of switch-mode power amplifier blocks arranged in parallel, current-combined, and / or voltage-combined groups, while simultaneously performing outphasing between groups of amplifier blocks for the purpose of generating an RF power signal. Such a technique enables wideband output power modulation to be performed via rapid changes in phase shift (e.g., phase shift can be implemented by setting gate-driver signal delays between power amplifier blocks, which can be changed at a very fast rate based on corresponding control signal commands), thereby improving reliability, performance, and power efficiency.

[0034]

[0048] In combination with these advantages, one or more embodiments of the RF power generator 1 can compensate for both voltage-related and current-related losses, a performance advantage not achievable with other RF power generators. As a result, higher efficiency can be achieved, especially at relatively low power levels. For example, other proposed power amplifiers operate at full voltage. As a result, loss components associated with the supply voltage (e.g., device output capacitor losses, resonant losses, etc.) are not reduced and therefore not compensated for. This lack of compensation adversely affects efficiency, especially at reduced power levels. In contrast, according to one or more embodiments, the RF power generator 1 can compensate for voltage-related losses as well as current-related losses over a wide range, including at relatively low power levels. Furthermore, the RF power generator 1 can achieve a wider range of output power backoff (e.g., encompassing a large ratio of 30 dB or more). For these and other reasons, the RF power generator 1 may be suitable for a wide variety of applications, including, but not limited to, those with high peak-to-average power ratios. Embodiments of the MIDB approach are now discussed.

[0035]

[0049] The MIDB technique can be implemented to perform discrete modulation with an outphasing pattern. In this technique, the power amplifiers in each amplifier block generate a respective number of RF voltage vectors of fixed (or substantially fixed) magnitude. By varying (or switching) the number of power amplifiers active in one or more of the N amplifier blocks and then combining the power signals from the blocks, discrete steps in the voltage of the output RF power signal 90 can be performed. As a result, the outphasing angle can always be maintained within a predetermined range, thereby achieving a higher level of efficiency (ideally, a substantially higher level of efficiency) and simultaneously allowing a wider back-off range to be achieved.

[0036]

[0050] To further extend the output power range while achieving high efficiency, in one or more embodiments, RF power generator 1 can perform modulation on power supply 71. For example, discrete drain modulation may be performed, in which the supply voltage input to one or more of the amplifier blocks is switched between several discrete levels. Outphasing can then be used in an MIDB technique (implemented in all or some of the blocks) to provide continuous control over a predetermined output power range corresponding to the load. This can be accomplished, for example, by interpolating between power levels obtained at various discrete supply voltage levels.

[0037]

[0051] With respect to output power control, the combination of discrete drain modulation and MIDB techniques can provide an additional basis for implementing discrete steps of RF voltage amounts to be outphased from each block. This can allow the MIDB configuration to be highly modular and can reduce supply generation and modulation overhead, even at relatively low power levels. Moreover, in one or more embodiments, the generation of discrete supply voltages may be continuously adapted, e.g., supply modulation operations may be controlled to occur on timescales that may be much slower than those used in, for example, fast power control.

[0038]

[0052] Figure 2 illustrates an exemplary embodiment of RF power generator 100. That is, the embodiment of Figure 2 may be one implementation of the RF power generator of Figure 1. In this exemplary embodiment, RF power generator 100 implements the MIDB technique combined with amplifier block outphasing.

[0039]

[0053] 2, RF power generator 100 includes a power supply 110, an amplifier stage 120, a power combiner 130, and an impedance converter 140. Power supply 110 can include multiple power supplies 111 and an optional modulator 112, which can include one or more switches. The power supply outputs voltages at N discrete voltage levels, and modulator 112 modulates and outputs the N discrete voltages to amplifier stage 120. In one embodiment, modulator 112 performs discrete drain modulation on the N discrete voltages output from power supply 111. One embodiment of discrete drain modulation is discussed in more detail below.

[0040]

[0054] The amplifier stage 120 includes a plurality (M) of MIDB amplifier blocks 1211 to 1212. M where M>1. Each of the amplifier blocks may include multiple parallel-combined RF power amplifiers, so that the voltage V RF,1 , …, V RF,M The output RF power signal having the modulated amplitude may be discretely modulated.

[0041]

[0055] 3A to 3C show the MIDB blocks 1211 to 121 M Various embodiments of how each of the power amplifiers 211 and 212 may be configured are shown in FIG. 3A. FIG. 3A illustrates one such configuration block including two modular power amplifiers, power amplifier (PA1) 211 and power amplifier (PA2) 212, and a combiner 218. The power amplifiers 211 and 212 may have a configuration, for example, as shown in FIG. 1, and may output respective voltages V1 and V2, and in this example, the same current I. The power amplifiers 211 and 212 may be controlled to perform discrete modulation of the block's output voltage. This may be accomplished, for example, by controlling the on / off states of the power amplifiers to achieve the desired modulation. The on / off states of the power amplifiers 211 and 212 may be controlled, for example, based on control information output from a controller, such as a gate signal, a phase value φ, and / or other information output from the controller 71.

[0042]

[0056] In one embodiment, the power amplifiers may be held in an off state by holding one or more of the transistors in a fixed gating state (e.g., by applying a bias (or control) signal to the transistor, particularly by holding a particular switch “on” by applying a bias (or control) signal to one or more electrodes of the transistor). When operating (on), the power amplifiers may have a fixed relative phase (e.g., (φ1-φ2)) based on the desired combiner type (e.g., in-phase, quadrature, 180 degrees out-of-phase, or some other relative phase relationship in the illustrated combiner), and the average phase may be controlled to provide outphasing between the MIDB blocks. Alternatively, the relative phase may also be adjusted during operation. In this manner, the respective output voltages V1 and V2 of power amplifiers 211 and 212 may be selected (e.g., activated or switched) based on different phases (φ1 and φ2, which may be the same in the embodiment shown in FIG. 3A ) and combined to generate the desired modulated power signal output of the block.

[0043]

[0057] In other words, the PAs within the MIDB block can be either active (on) or inactive (off or ac grounded) based on the control. Active PAs within the same MIDB block can be switched synchronously (or exactly 180° apart if an alternative combiner type is used), for example, as shown in Figures 3A-3C. For out-of-phase outphasing, this is the case for V rf1 ~V rfM , i.e., after the MIDB block.

[0044]

[0058] As noted above, in embodiments, the relative phase relationships may be fixed or selected in combination with the desired combiner configuration (including, but not limited to, in-phase, 180-degree out-of-phase, quadrature, and / or 45-degree or 135-degree out-of-phase relative phases), but their phases may be adjusted together to provide outphasing for different blocks. In the combiner shown in FIG. 3A, it is generally desirable to have the power amplifier controls in-phase. In embodiments, an option may be added to allow adjustable relative phase within a block, although this is less of a requirement than usual. It should be recognized that individual amplifiers are turned on or off depending on whether a gate signal is provided or held at a certain stage. In some cases, holding a particular power amplifier switch on so that it appears as a short circuit is the desired state for the PA to be “off.”

[0045]

[0059] Thus, in one embodiment, the power amplifiers in each amplifier block can be active (on) or inactive (off or AC grounded) based on the control. Active power amplifiers in the same amplifier block can be switched synchronously, e.g., as shown in FIGS. 3A-3C (or exactly 180 degrees apart if an alternative combiner type is used). In another embodiment, the switching can be performed asynchronously. In one embodiment, the phase can be different in the outphasing portion. This can occur, for example, after the MIDB block. In one embodiment, the relative phase relationship can be fixed by the desired combiner structure (e.g., in-phase, 180 degrees out-of-phase, quadrature), but their phases can be adjusted together to provide outphasing for different blocks. In the example combiner shown, the power amplifiers can be controlled in-phase. In one embodiment, adjustable relative phase can be implemented within one or more of the amplifier blocks. Whether a gate signal is received can control whether the corresponding power amplifier is on or off, or held at a constant stage. (In some cases, keeping a particular PA switch on so that it appears as a short circuit may be the desired state for the PA to be "off.")

[0046]

[0060] Combiner 218 can combine the output voltages of power amplifiers 211 and 212 in a common mode. Combiner 218 is shown as a coupled inductor to better illustrate the voltage combining characteristics within the MIDB block; however, it should be noted that in practice, the combiner need not necessarily be based on the inductors of a traditional AC transformer. Combiner 218 can combine the output voltages of power amplifiers 211 and 212 in a common mode using a transformer-based structure, such as an interphase transformer, or an RF power combiner or RF coupler including transmission line sections, as in a transmission line transformer (e.g., an RF combiner including transmission line sections or an RF coupler including transmission line sections). For example, as shown in FIG. 3A , combiner 218 includes two windings 215 and 216 that are coupled to effectively form a transformer with a predetermined turns ratio. In this example, the combiner includes a node N1 that generates the output power signal voltage of the block. In one embodiment, the output power signal voltage of the block (e.g., V RF1 , …, V RFM ) may correspond to a weighted sum (e.g., average) of the output voltages V1 and V2 of the power amplifiers in the block. The output current from the amplifier block may correspond to the sum of the output currents of power amplifiers 211 and 212, which is 2I in this example.

[0047]

[0061] FIG. 3B shows stage 220, which represents the configuration of each of the amplifier blocks. In this exemplary embodiment, stage 220 includes three modular power amplifiers 221, 222, and 223 and a combiner 228. Power amplifiers 231-223 can have a configuration, for example, as shown in FIG. 1, and can output respective voltages V1, V2, and V3, and the same current I in this example. The power amplifiers can be controlled to perform discrete modulation of the block's output voltage. This can be accomplished, for example, by controlling the on / off states of the individual power amplifiers to achieve a predetermined modulation. The on / off states of power amplifiers 221, 222, and 223 can be controlled, for example, based on control information output from a controller, such as a gate signal output from controller 71. In this manner, the respective output voltages V1, V2, and V3 of the power amplifiers can be selected (or activated) with the appropriate phases (φ1, φ2, and φ3) and gate controls, and then combined to generate a signal voltage of the block's desired modulated output power.

[0048]

[0062] Note that one difference between the examples shown in Figures 3A-3C is the number of PAs that make up the block, and also the number of combiners required to achieve the common-mode voltage combination (e.g., Figures 3A and 3C show the use of a two-way common-mode combiner / interphase transformer, while Figure 3B shows the use of a three-way common-mode combiner / interphase transformer).

[0049]

[0063] Combiner 228 can combine voltages 221, 222, and 223 in a common mode using an interphase transformer-based structure (e.g., a coupled-conductor-based structure). For example, as shown in FIG. 3B , combiner 228 includes three windings (conductors) 224, 225, and 226, each disposed on a leg of a three-limbed transformer core, coupled at a first end to the output of a respective one of the power amplifiers, and commonly coupled at a second end to node N2. This results in proportional currents in the individual power amplifiers, and the output voltage is a weighted sum of the three power amplifier voltages. The power amplifier outputs are combined at node N2, which generates the block's output power signal voltage. In one embodiment, the block's output voltage (e.g., V RF,1 , …, V RF,M , the corresponding output voltages V1, V2, and V3 of the power amplifiers in the block may correspond to a weighted sum (e.g., average) of the output voltages V1, V2, and V3 of the power amplifiers in the block. The output current from the power amplifier block may correspond to the sum of the output currents of power amplifiers 321, 322, and 323, which is 3I in this example.

[0050]

[0064] 3C shows block 230, which may represent the configuration of each of the blocks of an amplifier stage. In this exemplary embodiment, block 230 includes two sub-blocks 240 and 250 of power amplifiers. Each of the sub-blocks may correspond, for example, to the blocks of FIG. 3A, but the output of each stage is coupled to a combiner 260. First sub-block 240 includes power amplifiers 241 and 241 having output voltages coupled to a combiner 243. Second sub-block 250 includes power amplifiers 251 and 252 having output voltages coupled to a combiner 253.

[0051]

[0065] The power amplifiers in block 230 may be controlled to perform discrete modulation of the block's output power signal voltage. This may be accomplished, for example, by controlling the on / off states of power amplifiers 241, 242, 251, and 252 to achieve a predetermined modulation. The on / off states may be controlled, for example, based on control information output from a controller, e.g., a switch gate signal output from controller 71. In this manner, the respective output voltages V1, V2, V3, and V4 of the power amplifiers are selected (or activated) and combined to generate the desired modulated output voltage of the block. (In this regard, it should be noted that in embodiments, the relative phase relationships of the PAs in a block may be fixed, and the RF output is modulated in discrete steps by turning one or more amplifiers on or off. The phases of the "on" amplifiers may be modulated together to out-phase different blocks.) Combiner 260 combines the output voltage V of first sub-block 240 with the output voltage V of first sub-block 240. 12 and the output voltage V of the second sub-block 250 34 In one embodiment, combiner 260 can be similar to combiner 213 of FIG. 3A. The output of combiner 260 from node N3 is, for example, a weighted sum (e.g., average) of the output voltages of sub-blocks 240 and 250 (V RF ) and the sum of the currents of those stages, which in this example is 4I.

[0052]

[0066] In one embodiment, the combiners of Figures 3A-3C may be implemented using interphase transformers or transmission line transformers. For example, each of the combiners in the MIDB amplifier blocks may be implemented using an n-way interphase transformer or a "wiffle tree" of two-way interphase transformers with quarter-wave line power combiners. In such a case, the output power signal voltage of each block may correspond to a direct average of the output voltages of the power amplifiers in that block. In the illustrated example, the power amplifiers in each block have the same output current. In another embodiment, a duplicate of this configuration may be implemented, where all of the power amplifiers in each block have equal voltages and output currents that are summed, e.g., weighted averaged.

[0053]

[0067] For each block, the peak output voltage and power may be achieved by turning on all of the power amplifiers in the block. (Similarly, the peak output voltage and power from an amplifier stage may be achieved by turning on the power amplifiers in all of the blocks.) According to one embodiment, the peak output voltage and power of any one block may be reduced in discrete steps by selectively turning off (e.g., deselecting based on the phase φ or other control information) one or more of the power amplifiers in that block. This may be accomplished, for example, based on a predetermined pattern of power amplifier on / off states, resulting in a desired modulated (or varying) block output voltage over time that meets load requirements. The predetermined pattern may be a symmetrically switched pattern in one embodiment, or an asymmetrically switched pattern in another embodiment. Power amplifiers may be turned off in various ways. For example, each power amplifier may be turned off using an AC grounding technique.

[0054]

[0068] In one embodiment, the power amplifiers (PAs) in each block output the same current (I). In another embodiment, one or more of the power amplifiers in each block can output a different current than one or more of the other power amplifiers. Furthermore, the combiners of the amplifier blocks have been described as common-mode combiners. In one embodiment, all or some of the combiners in each block can be another type of combiner, for example, a differential combiner, where the output voltage of each MIDB block is based on the difference between the voltages of each of the blocks and the output current is the same as the current of each of the power amplifiers, for example, current I. In one embodiment, output voltage modulation using a differential combiner can be achieved by implementing on / off control of the power amplifiers in each MIDB block.

[0055]

[0069] MIDB amplifier blocks 1211-121 M It has been previously shown that the MIDB amplifier blocks can all have the same configuration, e.g., one of the configurations of Figures 3A-3C. In another embodiment, one or more of the MIDB amplifier blocks can have a different configuration than the others, e.g., in one embodiment, the MIDB amplifier blocks can have different ones of the configurations shown in Figures 3A-3C.

[0056]

[0070] FIG. 4 illustrates one embodiment of a power amplifier 400 that can be used to implement a power amplifier (PA) within an amplifier block. In one embodiment, the power amplifier 21 of FIG. 1 and / or the power amplifier (labeled PA) within each of the MIDB blocks of FIGS. 3A-3C can include the power amplifier 400. While the configuration of FIG. 4 can be used in some applications, in other embodiments or applications, the power amplifier 400 can have a different configuration. For plasma generation applications, the power amplifier 400 can have, for example, all or some of the following characteristics: (1) high (or desired) efficiency in a predetermined switching frequency range (e.g., tens of MHz); (2) efficient AC grounding for MIDB control (and / or other connections for turning off the power amplifiers and combiners within the MIDB block); (3) maintaining efficiency against variations in load impedance (e.g., for outphasing and relaxed requirements in impedance transformation); and / or (4) fast dynamic response to discrete step changes in output power, e.g., step changes in outphasing angle, on / off state, and supply voltage level.

[0057]

[0071] 4, power amplifier 400 comprises an example of a ZVS class D inverter circuit including a filter 410, a shunt leg 420, a switch 430, and a switch 440. Filter 410 includes an inductor L coupled in series with output terminal 401, which in the case of FIGS. 3A-3C is coupled to an associated block combiner. r and capacitor C r Including L r and C r Based on the value of , the filter is tuned to resonate at the associated switching frequency to filter out the fundamental component of the switching node voltage.

[0058]

[0072] The shunt leg 420 provides additional inductive loading of the switching node, thus helping the switch achieve zero voltage switching even when the load of the power amplifier varies, for example, within a predetermined range. The shunt leg, as previously mentioned, is connected in series with an inductor L having a value sufficient to achieve zero voltage switching operation. ZVS and capacitor C ZVS Includes.

[0059]

[0073] The switches 430 and 440 operate in a switch mode and may each be implemented by a transistor having a predetermined conductivity. The switch 430 (Q1) connects the node N ZVS and power supply V dd and may be, for example, an N-channel transistor with an intrinsic body diode or equivalent 435 for zero voltage switching. ZVS and a reference potential 450 (e.g., ground), and may also be an N-channel transistor with an intrinsic body diode or equivalent 445 for zero-voltage switching. In operation, when power amplifier 400 is on (e.g., selected or enabled), both transistors 430 and 440 switch by each conducting, e.g., for approximately half of the switching period, preferably coincident with each transistor achieving zero-voltage switching. When power amplifier 400 is off (e.g., not selected or enabled), switch 430 is turned off and switch 440 conducts continuously. This effectively AC-grounds the output and changes the output voltage of the MIDB block. Note that which switches are held on and which switches are held off in the power amplifier's off state can be reversed, if desired.

[0060]

[0074] In other embodiments, the power amplifier 400 may have a different configuration. For example, the power amplifier may have a class E inverter structure or a class φ2 type structure. In these structures, an additional switch may be used to disconnect the power amplifier from the input power supply when in the off state. Furthermore, one or more of the power amplifier (PA) transistors may be held on to achieve the desired AC grounding. For other MIDBs, different switch state settings may be used for the power amplifier in the off state. For example, in MIDB configurations that force equal voltages at the amplifier outputs and average currents between or across power amplifiers within a block, the off state may be achieved, for example, by using a switch to open-circuit the power amplifier output or by holding the amplifier transistor in the off state.

[0061]

[0075] FIG. 5 shows the power amplifier blocks 1211-1212 for generating the RF output voltage (Vrf) of an MIDB block having four PAs, such as that shown in FIG. 3C. M 5 shows an example of a switching waveform 500 that may be used to selectively turn on and off (in this example) four power amplifiers in one of the M amplifier blocks. The same or different waveforms may be used for power amplifiers in other of the M amplifier blocks. In this example, the switching waveforms show a symmetrical pattern of power amplifier on / off states. In section 510, the switching waveform turns on all of the power amplifiers in the MIDB block, causing the block to output a peak voltage. In section 520, the switching waveform turns on three of the power amplifiers and turns off the remaining power amplifiers. In section 530, the switching waveform turns on two of the power amplifiers and turns off the remaining two power amplifiers. In section 540, the switching waveform turns on one of the power amplifiers and turns off the remaining three power amplifiers. The waveforms can then be repeated, which may or may not be in the amplitude order shown here, depending on the desired output power and load.

[0062]

[0076] Thus, in this example waveform, each of the MIDB blocks is always on within a cycle and outputs a voltage. Moreover, the modulated output voltage of the block illustrated by waveform 500 is stepped down in discrete levels (i.e., waveform 500 is an example of a discretely stepped modulated output voltage Vrf).

[0063]

[0077] The modulated voltage from each block may then be outphased with the modulated output voltage of the rest of the blocks to a combiner. The outphasing of the modulated voltage from the MIDB blocks may be controlled based on phase information φ (or phase angle α) that selectively controls which amplifier blocks should be turned on or selected. In one embodiment, all MIDB amplifier blocks may be turned on at all times. In another embodiment, different combinations (all or less than all) of the MIDB amplifier blocks may be turned on over time to generate an RF power signal for the load, which may be particularly advantageous when the load power requirements change, either predictably or unexpectedly, as a result of information fed back from one or more sensors 81.

[0064]

[0078] Which MIDB blocks are on or off may be determined by the phase control information output from controller 71, as previously described. In one embodiment, a block off state may include controller 71 outputting phase information that turns off all of the power amplifiers in that block. Because the power signal voltages output from selected ones of the MIDB blocks are changed in discrete steps, the total power signal voltage output from amplifier stage 120 may be changed in discrete steps to meet the power requirements of the load.

[0065]

[0079] After a step change occurs, the output voltage of a power amplifier (or a given block) can settle very quickly, for example, within a few RF cycles. This structure is highly modular, with each block containing two or more power amplifiers to obtain a predetermined discrete number of voltage levels to be output from each block. This modular configuration also allows for higher peak power and a wider output power range compared to other proposed designs.

[0066]

[0080] 6 shows one embodiment of a power combiner 130 in the form of an M-way combiner. Combiner 130 receives the outphased voltages from the MIDB blocks of amplifier stage 120, e.g., V RF1 , …, V RFM For illustrative purposes, the combiner 130 may be a lossless combiner that combines the voltage V output from the power amplifier stage 120, which includes two MIDB amplifier blocks 610 and 620. X and V Y In this case, power supply 71 includes two power supplies 601 and 602 corresponding to 100V and 400V, respectively, which are switched (using switching logic 603) to generate a modulated supply voltage for input to power amplifier 120. In one exemplary implementation, the high voltage (e.g., 400V) can be derived from a main DC power supply, and the low voltage (e.g., 100V) can be derived from an auxiliary power supply. In this embodiment, the number of power supplies is equal to the number of MIDB blocks in this non-limiting embodiment. In one embodiment, the number of power supplies and MIDB blocks can differ.

[0067]

[0081] In the exemplary embodiment of Figure 6, the rf power combiner 130 includes a Chireix-type combiner with asymmetric compensation. In Figure 6, the rf combiner is shown as a transformer 650 that performs m:n voltage and impedance transformation (where, in general, m can be greater than or equal to n, or m can be less than n). For example, the combined output voltage VL m>n, where m>n is the impedance transformation required from the load to the output of the PA block based on the structure of the coupling conductors to generate A and -jX B , which may be provided to adjust the impedance output of the MIDB within a predetermined range. L are the currents I output from the MIDB power amplifier blocks 610 and 620, respectively. X and I Y The output voltage of the combiner is V L (or V in Figure 1) RFT ) is input to the load Z via the impedance converter 140 L , one embodiment of which corresponds to box 680.

[0068]

[0082] Load Z L can be fixed or variable. In plasma generation applications, Z L may be a variable load, in which case the RF power generator can vary the level of its output voltage to meet the varying power requirements of the load. This may be accomplished, at least in part, by selectively activating the MIDB power amplifier blocks.

[0069]

[0083] The impedance converter 140 (see FIG. 1) adjusts the impedance of the RF power generator to match the load. In one embodiment, the impedance converter adjusts the output impedance of the RF power generator to match the load, at least to within a predetermined tolerance, to a variable RF load Z L to a predetermined impedance (or range of impedances) that matches the impedance of the load. Performing impedance matching in this way can improve efficiency and reduce over-rating of power amplifier hardware to accommodate a load range.

[0070]

[0084] More specifically, the switch-mode MIDB block can have a varying impedance based on which combination of individual power amplifiers is selected. The impedance converter 140 can map the output impedance of the amplifier stage 120 to match the impedance of the load. In one embodiment, the impedance converter 140 allows the RF power generator to directly interface with a variable load (e.g., a plasma chamber), thereby alleviating the need for an external system to impedance-match the load to a specific intermediate impedance value, such as 50 Ω. Furthermore, by including an impedance converter in the RF power generator, the impedance converter can perform less extreme impedance compression, resulting in a narrower range of load impedances that can be acceptably presented to the power amplifier.

[0071]

[0085] The impedance transformer 580 may be implemented in a variety of ways. In one embodiment, the impedance matching section may include a tunable matching network that uses one or more of: (a) phase-switched impedance modulation, (b) switched capacitor, (c) dynamic frequency adjustment, and / or (d) a resistor-compression network. An embodiment of the matching tunable network (TMN) 580 (see FIG. 6) may have all or some of the following features:

[0072] Fixed impedance transformation ratio, where the load impedance range is scaled by a specific transformation ratio k. Fixed matching networks, where fixed-value passive components are used to perform some load transformation and possibly also to perform some compression when the frequency is varied within a predetermined (e.g., relatively small) range. · Matching networks with discrete switching passive components, where several binary components are optionally connected to the system via switches to provide a range of discrete matching reactances. Dynamic Frequency Tuning (DFT), where the frequency is dynamically changed within a predetermined (e.g., relatively small) range and combined with passive components (e.g., high-Q resonant tanks) to provide a range of continuously matching variable reactance. Phase-switched impedance modulation (PSIM), which can be implemented, for example, by controlling the duration that a fixed capacitor is connected to the system per RF cycle. This technique allows for a range of continuously matching variable reactances at a given fundamental frequency. One or more resistive compression networks (RCNs), which may be particularly suitable for situations where there are a pair (or multiple) of loads with similar variation patterns. This technique can then compress the range of real impedance variation of the two (or multiple) loads, either individually or together in combination, via passive networks.

[0073]

[0086] As mentioned above, one example of a variable load is a plasma generator used in semiconductor processing applications. Plasma generators have a wide load impedance range. The TMN580 or other implementations of the impedance converter 140 can adjust or remap to match the varying load impedance to ensure acceptable operation of the switch-mode power amplifier.

[0074]

[0087] FIG. 7 illustrates one embodiment of a variable matching network 900 that may be used to implement the impedance converter 680 of FIG. 6 or the impedance converter 30 of FIG. 1. The variable matching network may operate to provide a dynamically adjustable impedance match between the output of the power combiner and a load. This may include providing dynamically variable voltage transformation and reactive impedance adjustment, and may include a dynamic frequency tuner (DFT) 710 coupled to the input of a discrete switching passive network 720. In one embodiment, the variable matching network may operate in conjunction with a power combiner that provides an additional impedance transformation ratio, for example, a fixed ratio based on the turns ratio of a transmission line-based power combiner.

[0075]

[0088] The output impedance observed by the MIDB block is, for example, the square of the turn ratio of the combiner (m / n) 2 Depending on the power amplifier configuration, this ratio may be set so that the power amplifier operates in a predetermined range, for example near an optimum load impedance range where efficiency is optimized.

[0076]

[0089] The DFT 710 can receive the output of the power combiner 130 and generate a continuously varying series reactance. The DFT unit can be implemented, for example, with a high-Q series inductor (L) and capacitor (C) tuned to resonate at the center of the operating frequency. Thus, at the center operating frequency (ideally, exactly at the center operating frequency), the DFT tank presents near-zero impedance (ideally zero impedance). However, for continuously controlled frequency variations above and / or below the center frequency (and in at least some embodiments, small, continuously controlled frequency variations above and / or below the center frequency), the DFT tank correspondingly presents a load impedance Z L is the desired impedance Z inThe discrete switching passive network 720 couples the DFT 710 to the load Z via a switch 724. L and a plurality of capacitors 722 coupled in parallel between them. In one exemplary implementation, the capacitors 722 may be binary capacitors that are selectively switched to provide the shunt reactance. Switching different combinations of capacitors allows the shunt reactance to be varied in discrete steps based on the capacitance value. In this embodiment, three capacitors are represented by increasing predetermined capacitances C0, 2C0, and 4C0. In other embodiments, a different number of capacitors and / or capacitors with different progressions of capacitance may be used.

[0077]

[0090] The switches 724 can be selectively opened to vary the applied shunt reactance in discrete steps, as described above. The switches can be selectively opened and closed in different combinations, for example, based on switching signals from the controller 71. In operation, small frequency variations corresponding to selected discrete steps applied in addition to the top of the series reactance from the DFT 710 can enable the generation of a continuously controlled series reactance to meet the changing conditions of the load. Thus, when combined with the series reactance output from the DFT 710, the matching variable network 680 provides an impedance transformation that matches the impedance of a variable load to at least within a predetermined tolerance or range. Moreover, this design allows the matching variable network 680 to compress load variations into an impedance range so that power amplifier efficiency is not adversely affected while maintaining low overall system complexity. It will be appreciated that other matching variable network designs, including those based on varactors, phase-switched impedance modulation, and other techniques, may be used as well.

[0078]

[0091] 8 illustrates an embodiment of a modulator 800 that may correspond to one example of switching logic 603 (see FIG. 6) and that may be used to perform discrete drain modulation in power supply 72. Discrete drain modulation can extend the achievable output power range of the RF power generator. It can also reduce voltage-related losses in the power amplifier (e.g., transistor cross-related losses, ZVS resonant losses, etc.) that may dominate at lower power levels.

[0079]

[0092] Referring to FIG. 8, a modulator 800 receives a first supply voltage V through a first input 810. High and receives a second supply voltage V through a second input 820. Low The supply voltages can be derived from different types of power supplies or from the same type of light source. In one embodiment, the supply voltages can be derived from power supplies with different power ratings, for example, a high voltage V High can be obtained from a mains supply rated in the peak to medium power range, and a low voltage V Low can be obtained from an auxiliary power supply rated at low power levels only. For plasma generation applications, a second supply voltage V Low may have a value at or just above the minimum voltage level before capacitance nonlinearity of the semiconductor device adversely affects the performance of the power amplifier, e.g., zero voltage switching (ZVS) losses.

[0080]

[0093] Both supply voltages are coupled to different inputs of transistor 830, which may be, for example, an N-channel transistor. High may be input to the drain of the transistor, and a second supply voltage V Lowis coupled to the source of the transistor through a blocking diode 840. The gate of the transistor may be coupled to receive a control signal for controlling the switching of the transistor, for example, the control signal may be CS generated by controller 71 as shown in FIG.

[0081]

[0094] In one embodiment, V High and V Low is received continuously, and V Low It can be assumed that V is greater than the forward bias voltage of the blocking diode 840. When a gate signal is applied to turn on the transistor 830, the first supply voltage V High is the transistor and node N out (i.e., in this example embodiment, the voltage V Low is blocked by blocking diode 840, resulting in node N out The voltage output from is V High The combined voltage is then sent to one or more selected MIDB power amplifier blocks of amplifier stage 120 (e.g., of FIG. 2). When no gate signal is received by transistor 830, the diode conducts and the second supply voltage V Low is the output node N out The blocking diode 840 acts to block the input of the first supply voltage to the input terminal 820 when the transistor is turned on. In this way, the modulator 800 generates two discrete levels of voltage (e.g., two discrete DC voltage levels V ) for input to the MIDB block of the power amplifier. Low or V High ) to generate (or modulate between)

[0082]

[0095] While modulator 800 may be beneficial for some applications, in other applications, more than two levels of supply voltage may be beneficial. Thus, in one embodiment, the modulator of power supply 72 may output more than two levels of voltage. For efficiency reasons, the number of discrete voltages output from power supply 72 may vary between embodiments to achieve a desired power range, response speed, and / or efficiency.

[0083]

[0096] 9A illustrates one embodiment of a method for generating RF power for a load, which may be, for example, a plasma generator or another type of load, which may be performed in accordance with one or more embodiments of the RF power generator described herein.

[0084]

[0097] Referring to FIG. 9A, at 901, the method initially includes generating (or receiving) one or more modulated power supply voltages for output to amplifier stage 10. The same modulated power supply voltage may be output to all of the amplifier blocks in the amplifier stage at the same or different times, or different modulated power supply voltages may be output to the amplifier blocks at the same or different times. The modulation may be discrete drain modulation of the voltages provided by one or more power supplies. Which power supplies are selected and the modulation to be performed may be based on one or more control signals output from controller 71, for example. The control signals may correspond to a predetermined pattern or scheme and / or may be adaptively generated based on feedback from one or more sensors 81 (see, for example, FIG. 1), for example.

[0085]

[0098] At 903, an outphasing pattern is determined, for example, by a controller. The outphasing pattern may correspond to pre-stored control information 75 stored in a non-transitory computer-readable medium (e.g., memory) 75. The pre-stored control information may be, for example, in the form of instructions or other forms of firmware or software. The pre-stored control information may control the operation of the MIDB blocks to generate RF power signals to the load. The outphasing pattern and / or other control information embodied in the control information (e.g., instructions) for the controller 71 may determine the discrete modulation to be performed for the power amplifiers in each of the MIDB amplifier blocks.

[0086]

[0099] At 905, each of the MIDB blocks is controlled to generate a respective power signal based on outphasing and / or other control information from the controller. If all of the MIDB blocks are always on, discrete modulation of the outphased power signals from all of the MIDB amplifier blocks is used to generate the RF power signal for the load. In this case, the amplifier blocks are not switched (or selected), and the power amplifiers within each block are switched, for example, according to a symmetric or asymmetric sequence. If the MIDB amplifier blocks are to be switched along with the power amplifiers within each block, discrete modulation of the outphased power signals from the blocks is used to generate the RF power signal for the load. To perform the switching for discrete modulation, some of the power amplifiers in one or more of the blocks must be deactivated according to the outphasing pattern. This can be accomplished, for example, by AC grounding.

[0087]

[0100] At 907, the power signals output from the power amplifier blocks are combined to form an RF power signal for the load. Combining the power signals can be performed in various ways, for example, using a Sievert combiner, with or without weighting, etc. As previously described, discrete modulation performed in the amplifier blocks can generate discrete steps in the RF power signal to meet the varying power requirements of the load.

[0088]

[0101] At 909, the output impedance of the RF power generator is adjusted to match the impedance of the load to at least within a predetermined tolerance. The adjustment may be performed by a variable matching network or any of the other types of impedance transformers described herein.

[0089]

[0102] At 911, over time, the power requirements and / or impedance of the load may change and / or modifications to the RF power generator may be required. Proportional changes to the RF output power and / or impedance are made to meet the changing power requirements of the load and match changes in the load impedance. This may be accomplished by selecting different combinations of MIDB blocks and / or different power amplifiers within selected MIDB blocks to achieve changes (e.g., discrete steps) in the voltage of the output RF power signal 70. This selection may be performed, for example, by changing the on / off state of corresponding ones of the power amplifiers (PAs) based on control signals from the controller 71.

[0090]

[0103] FIG. 9B illustrates one embodiment of a method for generating RF power for a load, which may be performed, for example, by one or more of the embodiments of the RF power generator disclosed herein. Referring to FIG. 9B, the method includes selecting a first number of power amplifiers in a first amplifier block (921), selecting a second number of power amplifiers in at least a second amplifier block (922), combining voltages from the first number of power amplifiers to generate an output voltage for the first amplifier block (923), combining voltages from the second number of power amplifiers to generate an output voltage for the second amplifier block (924), outphasing the output voltages of the first and second amplifier blocks (925), and combining the outphased voltages to generate an RF power signal for the load (926). As with other embodiments, this method may be supplemented with operations of selecting different ones of the amplifier blocks. Alternatively, the amplifier blocks may be fixed to be continuously on.

[0091]

[0104] 9C illustrates one embodiment of a method for generating RF power for a load, which may be performed, for example, by one or more of the embodiments of the RF power generator disclosed herein. Referring to FIG. 9C, the method includes generating a first modulated power signal from a first amplifier block (931), generating a second modulated power signal from at least a second amplifier block (932), outphasing the first and second modulated power signals based on a phase angle (933), and generating an RF power signal for the load based on the outphased first and second modulated power signals (934). Generating the first modulated power signal may include switching one or more of the multiple power amplifiers in the first amplifier block, and generating the second modulated power signal may include switching one or more of the multiple power amplifiers in the second amplifier block.

[0092] <Example of power control management>

[0105] One of the many applications of the RF power generator embodiments described herein is powering plasma generators in semiconductor manufacturing processes. Plasma generators may require a very wide output power modulation range compared to other applications. RF power generator embodiments can achieve this range by implementing wide, discrete steps in the RF output voltage using discrete drain modulation and on / off control of the MIDB power amplifier blocks in addition to fine, continuous adjustment of the RF output voltage (with outphasing between MIDB blocks). Non-limiting examples of such power control management techniques are described below.

[0093]

[0106] 10 shows an example voltage vector graph of a power management control method for an RF power generator, corresponding to the RF power generator embodiment of FIG. 6 having two MIDB phase amplifier blocks.

[0094]

[0107] Referring to FIG. 10, the RF voltage output from the first MIDB block 510 is a voltage V X The RF voltage output from the second MIDB block 520 corresponds to the voltage V Y These voltages can be given by the following equations:

[0095]

number

[0096]

[0108] As can be seen from these equations, the load voltage (VL) at the output of combiner 230, and therefore the power output from the RF power generator, is controlled via both the outphasing angle and the output voltage magnitude of the MIDB block. The outphasing angle (α) is based on the phase shift between the two RF voltages output from the MIDB block.

[0097]

[0109] The output voltage magnitude of a selected one of the MIDB blocks (which in this example is voltage |V|) is obtained by drain modulation and / or on / off control of the power amplifiers in each of the blocks. In the two-level power supply modulation and MIDB block configuration of Figure 6, two groups of four non-zero voltage magnitudes are available at the same outphasing angle (α). The first group corresponds to vectors 1010, 1020, 1030, and 1040, and the second group of vectors corresponds to vectors 1060, 1090, 1080, and 1090.

[0098]

[0110] More specifically, the load voltage (VL) quantity is directly correlated to the output power (e.g., |VL| 2 ) and can be modulated by the combined effect of outphasing and discrete drain / MIDB modulation. Outphasing provides continuous control because the phase shift can be continuously varied in one embodiment, depending only on the resolution of the implementation hardware. Discrete voltage modulation (achieved, for example, by switching to different power rails or MIDB on / off configuration) can cover a very wide output power range (e.g., 1000:1 or 30 dB) and can be implemented, for example, when the RF power generator can achieve higher efficiency in different voltage domains or is subject to large power fluctuations.

[0099]

[0111] Discrete voltage steps at the output of the MIDB block can be achieved based on a combination of power supply modulation and MIDB control. For example, if the two-level supply voltage in Figure 8 is V High = V and V = V / 3, in a two MIDB power amplifier block configuration, available voltage levels may be output from power amplifier 120 as shown below: where PA refers to an individual power amplifier within the MIDB block: Using this power management method, a single outphasing power range can be obtained (e.g., by scaling according to a squared voltage ratio) to cover a very wide power range while maintaining high efficiency.

[0100] [Table 1]

[0101]

[0112] 11 shows a graph of admittance values ​​that can be used to determine performance and perform power management and control functions according to one or more embodiments. This graph can evaluate the load modulation effect on the power amplifiers in the MIDB blocks during outphasing and be useful for corresponding compensation element design and outphasing angle selection. For illustrative purposes, the graph in FIG. 11 can correspond to the two MIDB block phase amplifier of FIG. 6, but may be extrapolated to embodiments with three or more MIDB blocks.

[0102]

[0113] 11, the uncompensated load admittance of the MIDB block 610 of FIG. 6 is shown by the upper semicircular curve 1110, and the uncompensated load admittance of the MIDB block 520 is shown by the lower semicircular curve 1120 during outphasing (e.g., Y A and Y B See also the uncompensated load admittance (Y A ) and MIDB Block 620 (Y B ) can be expressed as:

number

[0103]

[0114] The axis is connected to the matching variable network 680 and combiner 130 which transforms the load into a purely resistive effective impedance R L Based on the assumption that the matching L Each MIDB block has a load admittance point on the corresponding curve, determined by the outphasing angle and compensation component selection mechanism. For a fixed MIDB output voltage magnitude, the output power is proportional to the real part of the load admittance, e.g., Re{Y A or Y B The larger the}, the greater the output power.

[0104]

[0115] In a power amplifier (PA), the closer the load is to the real axis (dashed line in Figure 11), the more efficiently the PA operates. However, the graph shows that when the output power is changed by varying the outphasing angle, both the conductance and susceptance load seen by the MIDB block (and therefore the PA) change, affecting system efficiency in the process. Therefore, in some cases, outphasing alone may limit the range of power modulation for efficient operation. In some cases, the compensating reactance may be selected to shift the curve so that the admittance remains close to the real axis over as wide a power modulation range as possible; for example, the portion of the admittance curve enclosed by box RB in Figure 11 is close to the real axis.

[0105]

[0116] The load admittance characteristics may be independent of voltage to ensure continuity of power control over voltage steps. In some applications, a specific minimum span may exist for the outphasing angle range. In one embodiment, the modulation voltage levels of all MIDB blocks are

number

[0106]

[0117] In some embodiments, for a given output power profile, efficiency optimization of the RF power generator may be possible in terms of the optimal number of power amplifiers per MIDB block, supply voltage level, device area, compensation reactance, and / or target load impedance of the template-matching combiner (e.g., 680 in FIG. 6).

[0107]

[0118] With regard to dynamic response, the control method can satisfy a commanded step change in output power in three ways: (1) changing the outphasing angle, (2) changing the MIDB on / off configuration, and (3) changing the discrete power modulation. Changing the outphasing angle can implement a step change in the effective load impedance seen by the power amplifiers in each MIDB block. Changing the MIDB on / off configuration and changing the discrete power modulation can implement a step change in the common-mode voltage across the dc-blocking components of one or more of the block power amplifiers. By distributing the resonant tank to each of the block power amplifiers, the RF power generator can achieve very fast settling times in all three scenarios by reducing or minimizing the dc-blocking capacitor values. This can have the added benefit of fully modularizing at least the power amplifier 120 of the RF power generator, and the MIDB blocks can be easily reconfigured to meet new specifications for the intended application.

[0108] <Example simulation results>

[0119] To evaluate the performance of a simulated version of the RF power generator, an example circuit model was implemented in LTSpice for the two-level MIDB-2 configuration power generator of Figure 6, implemented with ZVS Class D amplifiers in each MIDB block and a lossless outphasing combiner in power amplifier 220. The power generator was configured for an output power profile corresponding to a realistic plasma load application with the following parameters: 0.2 kW for 1 ms, 1 kW for 1 ms, then 5 kW for 20 μs. Additionally, a GaN FET PGA26E19BA switch was specified at the ISM band frequency of 13.56 MHz. A matching variable network 580 connected the variable plasma load to a fixed real impedance R L The following simulation results were obtained:

[0109]

[0120] Simulation results for efficiency and power range. The efficiency plots employed a peak dV / dt loss fitting for crossover loss calculations, applying a 5.5× scalar to the active block PA device's nominal Rds,on and a 2× scalar to the conductive switch when the PA is turned on. Additionally, a quality factor (Q) of 500 was set for the inductor and ideal common-mode combiner, and the supply voltage levels were 300V and 100V based on switch loss characteristics and power range considerations. To account for modulator losses (e.g., losses across diode 740 in Figure 7), a 99% scalar was applied for the low supply voltage case. Some important system design parameters are listed in the table below.

[0110] [Table 2]

[0111]

[0121] Figure 12 shows the efficiency versus output power back-off curves of a simulated RF power generator using MIDB power amplifier blocks, outphasing, and a Shirei combiner. The primary dc supply voltage level was 300V and rated for 5kW peak power, and the auxiliary supply voltage level was 100V and rated for less than 500W peak power. The output power was modulated with outphasing in successive segments 1210, 1220, 1230, and 1240, and discrete RF voltage modulation (via MIDB on / off control and / or power supply modulation) was used at the crossovers to maintain high efficiency over a wide power range.

[0112]

[0122] Furthermore, in Figure 12, vertical lines indicate power levels in the load profile. As can be seen, high efficiencies of over 90% were achieved across the entire power range (200W to 5kW), and at least 30dB was achieved across the output power range (5W to 5kW). Although rated for several kW peak power, the power generator can reliably deliver power at the very low power of 5W with efficiencies of >20% at the lowest design power level.

[0113]

[0123] FIG. 13 shows the dynamic response of the power amplifier output voltage to outphasing. The waveforms in FIG. 13 demonstrate that very fast dynamic behavior was achieved, settling to a new command voltage level within several RF cycles. In particular, waveform 1310 corresponds to the VLoad voltage and shows the output voltage of a 1:1 turns ratio Siray combiner (e.g., VL in FIG. 5). Waveforms 1320 and 1330 correspond to VPAO1 and VPAO3, showing the unfiltered switching-mode voltages of two power amplifiers, each in a different MIDB block. In this simulation, the phase angle α advanced from 30° to 60° at time = 3.69 μs and returned to 30° only after, e.g., 10 RF cycles, at time = 4.42 μs.

[0114]

[0124] Figure 14 shows an example in which the dynamic response of the output voltage of an MIDB power amplifier was very fast. In Figure 14, waveform 1410 corresponds to the output voltage of a 1:1 turns ratio Silent combiner (VL in Figure 6). Waveform 1420 of VPAO2 and waveform 1330 of VPAO1 represent the switching-mode voltages of each of two PAs in the same MIDB block. One PA is turned off (e.g., AC grounded) at time = 3.69 μs and turned back on (e.g., switched) at time = 4.42 μs.

[0115]

[0125] FIG. 15 shows an example of a dynamic step response of the output voltage to a discrete power supply modulation, where fast settling on the microsecond level can be achieved. For example, the dynamic response to a step in supply voltage (e.g., implemented by a modulator in power supply 72) is represented by the following waveforms. Waveform 1510 corresponds to the output voltage of a 1:1 turns ratio Silei combiner (corresponding to Vvload in FIG. 15 and VL in FIG. 6). Waveform 1520 (marked V(in1)) corresponds to the supply voltage of a power amplifier in a selected MIDB block, and waveform 1530 corresponds to the switching node voltage of that power amplifier. The supply voltage drops from 300 V to 100 V at time = 3.69 μs and returns to 300 V at time = 4.42 μs.

[0116]

[0126] According to one or more embodiments, an RF power generator comprises a unique system configuration and power control method. In some implementations, the RF power generator can have various combinations of the following features: (1) power signal outphasing for fast response (and, if necessary, continuous) power generation; (2) discrete voltage modulation using switch-mode (e.g., on / off controlled) power amplifiers in the MIDB block; and / or (3) discrete drain modulation of the supply voltage to extend the high-efficiency operating power range of the load in various applications. In some embodiments, the load can be a plasma generator used during a semiconductor chip fabrication process. In other embodiments, the load can be different and can operate at different (higher or lower) power ranges, e.g., the high power range of the plasma generator and a power range that does not have the performance requirements.

[0117]

[0127] Discrete drain modulation can be implemented in various ways. For example, in a power generator having two MIDB blocks, two power supply sources, such as a main DC power supply (e.g., for peak to mid-power levels) and an auxiliary DC power supply (e.g., for lower power levels), can be used. Thus, the RF power generator can use low-overhead two-level discrete drain modulation. In doing so, the power generator can maintain high efficiency and perform fast RF power control over a very wide back-off range. In other embodiments, the power generator can have three or more MIDB power amplifier blocks.

[0118]

[0128] In one embodiment, the RF power supply can include an impedance converter that performs adjustments (or remapping) to match varying load impedances and to provide acceptable operation for the switch-mode power amplifier. Additionally, the switch-mode power amplifier itself can have a varying impedance that the impedance converter can map to the impedance of a load, for example, a plasma generator or another load.

[0119]

[0129] In addition to plasma generation applications, various embodiments of the RF power generator can meet the requirements of other industrial applications, such as operating at high frequencies (e.g., tens of MHz) and power levels (e.g., peak power in the kW range), as well as with variable load impedances over a wide overall power range (e.g., 30 dB) and high peak-to-average power ratios.

[0120]

[0130] The methods, processes, and / or operations described herein may be performed by code or instructions that may be executed by a computer, processor, controller, or other signal processing device. The computer, processor, controller, or other signal processing device may be one of those described herein or in addition to the elements described herein. Because the algorithms underlying the methods (or the operation of the computer, processor, controller, or other signal processing device) are described in detail, the code or instructions for implementing the operations of the method embodiments may transform the computer, processor, controller, or other signal processing device into a dedicated processor for performing the methods herein.

[0121]

[0131] Further, another embodiment may include a computer-readable medium, e.g., a non-transitory computer-readable medium, for storing the above-described code or instructions. The computer-readable medium may be a volatile or non-volatile memory or other storage device, which may be removably or permanently coupled to a computer, processor, controller, or other signal processing device capable of executing code or instructions to perform operations of the method embodiments or apparatus embodiments herein.

[0122]

[0132] The controllers, processors, generators, logic, modulators, combiners, transformers, matching networks, drivers, and other signal generation and signal processing functions of the embodiments disclosed herein may be implemented in non-transitory logic, which may include, for example, hardware, software, or both. When implemented at least partially in hardware, the controllers, processors, generators, logic, modulators, combiners, transformers, matching networks, drivers, and other signal generation and signal processing functions may be, for example, any of a variety of integrated circuits, including, but not limited to, application specific integrated circuits, field programmable gate arrays, combinations of logic gates, systems on a chip, microprocessors, or other types of processing or control circuits.

[0123]

[0133] When implemented at least partially in software, the controllers, processors, generators, logic, modulators, combiners, transformers, matching networks, drivers, and other signal generation and signal processing functionality may include, for example, memory or other storage devices for storing code or instructions that may be executed by, for example, a computer, processor, microprocessor, controller, or other signal processing device. The computer, processor, microprocessor, controller, or other signal processing device may be one of those described herein or in addition to the elements described herein. Because the algorithms underlying the methods (or the operation of the computer, processor, microprocessor, controller, or other signal processing device) are described in detail, the code or instructions for implementing the operations of the method embodiments may convert the computer, processor, controller, or other signal processing device into a dedicated processor for performing the methods herein.

[0124]

[0134] Various embodiments of the concepts, systems, devices, structures, and techniques sought to be protected are described herein with reference to the associated drawings. Alternate embodiments may be devised without departing from the scope of the concepts, systems, devices, structures, and techniques described herein. It should be noted that in the following description and drawings, various connections and relationships (e.g., above, below, adjacent, etc.) between elements are described. These connections and / or relationships may be direct or indirect unless otherwise specified, and the described concepts, systems, devices, structures, and techniques are not intended to be limited in this respect. Consequently, coupling of entities can refer to either direct or indirect coupling, and relationship between entities may be direct or indirect.

[0125]

[0135] As an example of an indirect positional relationship, references in this description to forming layer "A" on layer "B" include situations in which one or more intermediate layers (e.g., layer "C") exist between layer "A" and layer "B," so long as the relevant properties and functions of layers "A" and "B" are not substantially altered by the intermediate layers. The following definitions and abbreviations may be used for interpreting the claims and this specification. As used herein, the terms "comprises," "comprising," "includes," "including," "has," "having," "contains," or "containing," or other variations thereof, are intended to cover a non-exclusive inclusion. For example, a composition, mixture, process, method, article, or device consisting of a list of elements is not necessarily limited to only those elements, but may include other elements not expressly listed or inherent to such composition, mixture, process, method, article, or device.

[0126]

[0136] Additionally, the term "exemplary" is used herein to mean "serving as an example, instance, or illustration." Any embodiment or design described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments or designs. The terms "one or more" and "one or more" are understood to include any integer number greater than or equal to one, i.e., 1, 2, 3, 4, etc. The term "plurality" is understood to include any integer number greater than or equal to two, i.e., 2, 3, 4, 5, etc. The term "connected" can include an indirect "connection" and a direct "connection."

[0127]

[0137] References herein to "one embodiment," "one embodiment," "exemplary embodiment," etc., indicate that the described embodiment may include a particular feature, structure, or characteristic, but that all embodiments may include the particular feature, structure, or characteristic. Moreover, such phrases do not necessarily refer to the same embodiment. Furthermore, when a particular feature, structure, or characteristic is described in connection with one embodiment, it is submitted that it is within the knowledge of one skilled in the art to affect such feature, structure, or characteristic in connection with other embodiments, whether or not explicitly stated.

[0128]

[0138] For purposes of the following description, the terms "top," "bottom," "right," "left," "vertical," "horizontal," "top," "bottom," and their derivatives refer to the structures and methods described as being oriented in the drawings. The terms "overlying," "atop," "on top," "positioned on," or "positioned atop" mean that a first element, such as a first structure, is on a second element, such as a second structure, and that intervening elements, such as interface structures, may be present between the first and second elements. The term "direct contact" means that a first element, such as a first structure, and a second element, such as a second structure, are connected without intermediate elements.

[0129]

[0139] The use of ordinal terms such as "first," "second," "third," etc. in the claims to modify claim elements does not, per se, imply a priority, precedence, or order of one claim element over another, or the chronological order in which method actions are performed, but is merely used as a label to distinguish one claim element having a certain name from another element having the same name (other than the use of ordinal terms) to distinguish between claim elements.

[0130]

[0140] The terms "approximately" and "about" may be used to mean, in some embodiments, within ±20% of a target value, in some embodiments, within ±10% of a target value, in some embodiments, within ±5% of a target value, and even in some embodiments, within ±2% of a target value. The terms "approximately" and "about" may include the target value. The term "substantially equal" may be used to refer to values ​​that are, in some embodiments, within ±20% of each other, in some embodiments, within ±10% of each other, in some embodiments, within ±5% of each other, and even in some embodiments, within ±2% of each other.

[0131]

[0141] The term "substantially" may be used in some embodiments to refer to values ​​within ±20% of the comparative scale, within ±10% of the comparative scale, within ±5% of the comparative scale, and even within ±2% of the comparative scale in some embodiments. For example, a first direction that is "substantially" perpendicular to a second direction may refer to a first direction that is within ±20% of a 90° angle with the second direction in some embodiments, within ±10% of a 90° angle with the second direction in some embodiments, within ±5% of a 90° angle with the second direction, and even within ±2% of a 90° angle with the second direction in some embodiments.

[0132]

[0142] It is to be understood that the subject matter of the present disclosure is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the drawings. The disclosed subject matter is capable of other embodiments and of being practiced and carried out in various ways.

[0133]

[0143] Furthermore, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. Thus, those skilled in the art will recognize that the conception underlying the present disclosure may readily be utilized as a basis for designing other structures, methods, and systems for carrying out some of the purposes of the presently disclosed subject matter. The claims should therefore be regarded as including such equivalent constructions insofar as they do not depart from the spirit and scope of the presently disclosed subject matter.

[0134]

[0144] While the subject matter of the present disclosure has been described and illustrated in the foregoing exemplary embodiments, it should be understood that the disclosure is made by way of example only, and that numerous changes in the details of the implementation of the subject matter of the present disclosure may be made without departing from the spirit and scope of the subject matter of the present disclosure.

Claims

1. a plurality of amplifier blocks including at least one amplifier block having a plurality of amplifiers; a combiner having an input coupled to an output of each of the plurality of amplifier blocks for combining the plurality of radio frequency (RF) signals output from the plurality of amplifier blocks to provide an RF output signal at an output of the combiner; a variable matching network configured to vary the output impedance of the combiner in discrete steps to match changes in the impedance of a load; Equipped with 1. A power generator, wherein the plurality of amplifier blocks are configured to outphase RF signals from the amplifier blocks based on at least one phase angle, and at least one of the plurality of amplifier blocks is configured to perform discrete modulation to generate a respective one of the RF signals, the discrete modulation including selecting different combinations of the plurality of amplifiers to vary a voltage of the RF output signal in discrete steps.

2. 2. The power generator of claim 1, wherein the matching variable network is configured to vary one or more shunt reactances to change the output impedance of the combiner in discrete steps to match changes in the impedance of the load.

3. the output impedance of the combiner varies when a different combination of the plurality of power amplifiers is selected for each of the plurality of amplifier blocks; 2. The power generator of claim 1, wherein the impedance converter transforms the varying output impedance of the combiner to match the impedance of the load.

4. The power generator of claim 1 , wherein each of the plurality of amplifiers is configured to generate a fixed voltage.

5. The power generator of claim 1 , wherein each of the plurality of amplifiers is configured to operate in a switch mode.

6. 2. The power generator of claim 1, wherein the different combinations of the plurality of amplifiers are configured to implement a predetermined sequence of discrete step changes in the RF output signal.

7. The power generator of claim 1 , wherein each of the plurality of amplifier blocks is configured to operate in a common mode.

8. 2. The power generator of claim 1, wherein at least one of the plurality of amplifier blocks is configured to receive a signal, the signal controlling an on or off state of the at least one of the plurality of amplifier blocks to vary the RF output signal in discrete steps.

9. 9. The power generator of claim 8, wherein the discrete step changes in the RF output signal caused by selecting different combinations of the plurality of amplifiers are different from the discrete step changes in the RF output signal caused by controlling the on state or the off state of the at least one of the plurality of amplifier blocks.

10. The power generator of claim 1 , wherein the load comprises a plasma generator.

11. generating a first modulated radio frequency (RF) signal from a first amplifier block; generating a second modulated RF signal from at least a second amplifier block; outphasing the first and second modulated RF signals based on a phase angle; generating, by a combiner, an RF output signal for a load based on the outphased first and second modulated RF signals; a variable matching network varying the output impedance of the combiner in discrete steps to match the impedance of the load; A method comprising:

12. The method of claim 11 , wherein the load comprises a plasma generator.

Images