Hybrid matching network topology

Abstract

To provide plasma generation systems which utilize plasma for semiconductor processing.SOLUTION: The plasma generation system disclosed herein employs a hybrid matching network. The plasma generation system includes a RF generator and a matching network. The matching network includes a first-stage to perform low-Q impedance transformations during high-speed variations in impedance. The matching network includes a second-stage to perform impedance matching for high-Q impedance transformations. The matching network further includes a sensor coupled to the first-stage and the second-stage to calculate the signals that are used to engage the first and second-stages. The matching network includes a first-stage network that is agile enough to tune each state in a modulated RF waveform and a second-stage network to tune a single state in a RF modulated waveform. The plasma generation system also includes a plasma chamber coupled to the matching network.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] [CROSS-REFERENCE TO RELATED APPLICATIONS] This application claims priority to U.S. Patent Application No. 16 / 506,373, filed July 9, 2019, the contents of which are incorporated herein by reference. [Background technology]

[0002] In semiconductor manufacturing, plasma processing chambers utilize radio frequency (RF) power to generate plasma. The plasma is typically generated and sustained by alternating electrical current at RF frequencies, which excites and ionizes source gases used in the plasma chamber. Plasma processing chambers may be used for industrial processes such as, but not limited to, surface treatment of materials or plasma etching during semiconductor fabrication processes. To achieve efficient power transfer between the RF generator and the plasma load, an impedance matching network is typically used to match the load impedance to the source impedance (e.g., 50 ohms). Summary of the Invention

[0003] Plasma chambers present electrical impedances that can be large and rapidly changing. It is important that the output impedance of the RF power generator closely match the rapidly changing load impedance of the plasma chamber to avoid damaging power reflections into the RF power generator's output circuitry, which can occur when the impedances are mismatched. An impedance matching device (e.g., a matching network) is used to match the load impedance of the plasma processing chamber to the output impedance of the RF power generator. For rapidly changing load impedances, the matching network must dynamically match the impedance accordingly. [Brief explanation of the drawings]

[0004] For a more complete understanding of the present disclosure, examples consistent with the various features described herein will be more readily understood by reference to the following detailed description taken in conjunction with the accompanying drawings, in which like reference numerals designate like structural elements and in which:

[0005] [Figure 1] FIG. 2 is a block diagram of a hybrid matching network in accordance with the systems and methods of the present disclosure. [Figure 2] 1 is a diagram of a topology of a hybrid matching network in accordance with the systems and methods of the present disclosure. [Figure 3] 3 is a Smith chart illustrating the tuning range for a hybrid matching network with a first stage matching network having eight switch terminals. The tuning range illustrated in this Smith chart corresponds to the hybrid matching network topology of FIG. [Figure 4] 10 is a Smith chart showing the tunability range for a hybrid matching network with a first stage matching network having six switch terminals. [Figure 5] 10 is a Smith chart showing the tunability range for a hybrid matching network with a first stage matching network having ten switch terminals. [Figure 6] 1 is a Smith chart illustrating impedance transformation to adjust a load impedance to a source impedance in accordance with the systems and methods of the present disclosure. [Figure 7] 1 is a Smith chart illustrating impedance transformation to match a load impedance to a target impedance in accordance with the systems and methods of the present disclosure. [Figure 8] 1 is a flowchart of a method for performing impedance matching in accordance with the systems and methods of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0006] The description of different preferred implementations is presented for illustrative purposes and is not intended to be exhaustive or limited to the disclosed forms of implementations. Many modifications and variations will be apparent to those skilled in the art. Furthermore, implementations may offer distinct advantages over other implementations. The selected implementation(s) have been chosen and described to best illustrate the principles and practical applications of the implementations and to enable those skilled in the art to understand the disclosure for various implementations with various modifications suited to the particular use anticipated.

[0007] Before the present disclosure is described in detail, it is to be understood that unless otherwise indicated, this disclosure is not limited to specific procedures or articles, whether described or not. It is to be further understood that the terminology used herein is intended to describe particular implementations only, and is not intended to limit the scope of the present disclosure.

[0008] During plasma processing, a radio frequency (RF) generator transmits RF alternating current (AC) waves to a plasma processing chamber via RF transmission lines and circuits. To provide efficient power transfer from the RF generator to the plasma processing chamber, a matching network is employed to transform the time-varying impedance presented by the plasma chamber into an optimal load impedance for the RF generator.

[0009] Many RF matching networks include a variable capacitor and a control circuit with a microprocessor for controlling the capacitance value of the variable capacitor. Various configurations of the RF matching network may exist. Here, a vacuum variable capacitor may be defined as an electro-mechanical device having two concentric metal rings that move relative to each other to change the capacitance. The value and size of the variable capacitor in the RF matching network may be determined by the power handling capability, operating frequency, and impedance range of the plasma processing chamber.

[0010] Pulse frequency modulation (PFM) is a commonly used technique for supplying power in plasma processing systems. Pulse frequency modulation is a modulation method in which the amplitude of a carrier waveform is varied between at least two discrete power levels at a frequency with a duty cycle. Therefore, the power delivered in a pulsed waveform can affect the plasma characteristics, which can, in turn, change the electrical impedance of the plasma chamber with each pulse. At the beginning of each pulse, a spike in the reflected power can occur.

[0011] Many RF plasma generation systems employ multiple levels of pulsing for a variety of different power states. Because the plasma characteristics can change based on the power supplied to the plasma chamber, each power state can be associated with a unique impedance. During plasma processing, plasma changes occur very rapidly (e.g., at rates up to hundreds of thousands of hertz). Many matching networks, such as those with vacuum variable capacitors, typically respond on the order of hundreds or thousands of milliseconds.

[0012] As a result, many of these matching networks are limited to latching onto one of several power levels (e.g., high or low amplitude). For example, for two-level pulsing, the matching network can latch onto either the high amplitude or lower amplitude state and maintain that position during the other state. This means that the system will perform optimally during one state and suboptimally during the other state.

[0013] The present disclosure provides a mechanism for matching to all conditions by maintaining a low reflection coefficient in response to all impedance conditions during impedance variations. Advantageously, the present disclosure reduces the adjustment time in a matching network, where adjustment time is defined as the amount of time it takes for a matching network system to go from an unadjusted state to an adjusted state.

[0014] FIG. 1 is a block diagram of a hybrid matching network 100 in accordance with the systems and methods of the present disclosure. Advantageously, the hybrid matching network 100 disclosed herein employs a two-stage adjustable matching network. As shown, the hybrid matching network 100 receives its RF input from an RF generator at RF input 109, a first-stage matching network 101 (e.g., a switch network), a second-stage matching network 103 (e.g., a mechanically-tuned matching network), a sensor element 102, and a plasma chamber 104 (e.g., a load), all of which are coupled to one or more transmission lines 105-108. Herein, the hybrid matching network 100 may be defined as a multi-stage matching network that can operate simultaneously or sequentially to adjust the load impedance to a target (e.g., source) impedance.

[0015] The first stage matching network 101 is responsible for matching fast variations in impedance between different stages of the RF waveform, while the second stage matching network 103 can be responsible for high-Q impedance transformation. As a result, in some implementations of the present disclosure, the majority of the impedance adjustment is performed by the second stage matching network 103 for high-Q transformation, and the first stage matching network 101 can be used to adjust the system impedance for low-Q transformation resulting from pulse waveform, changes in chamber conditions, or other factors. Here, fast variations are defined as changes in impedance that exceed the control loop bandwidth associated with the second stage matching network.

[0016] The first stage matching network may include a fixed capacitor and a PIN diode, a silicon-carbide field effect transistor (SiCFET), a metal oxide field effect transistor (MOSFET), an insulated gate bipolar transistor (IGBT), or a bipolar junction transistor (BJT) electronic switch, and the second stage matching network may include a vacuum or air variable capacitor and a stepper motor, a brushed direct current (DC) motor, a brushless DC motor, or an AC motor.

[0017] Advantageously, the hybrid matching system disclosed herein can reduce stress on a fast, secondary matching network (e.g., first stage matching network 103) and can assist in dialing in the matching network to tune the plasma system to a target impedance.

[0018] Here, high-Q or low-Q refers to a high or low quality factor. Q factor is defined as the ratio of the amount of energy stored in a system to the amount of energy dissipated in the system. Q factor is a dimensionless unit and is expressed for a single element as the ratio of the element's reactance to its resistance. In a matching network, the minimum Q factor is the setting where the smallest amount of energy is stored for the transformation to be performed.

[0019] In some implementations, a high Q impedance transformation is one that has a Q value greater than two, while a low Q impedance transformation is one that has a Q value less than two.

[0020] 2 is a diagram of a topology of a hybrid matching network 200 in accordance with the systems and methods of the present disclosure. The topology of the hybrid matching network 200 illustrates a first-stage matching network 201, a second-stage matching network 202, and a sensor element 203 coupled thereto. In some implementations, the majority of the tuning is performed by the second-stage matching network 202, while the first-stage matching network 201 can be employed to implement "coarse tuning" for low-level and fast impedance variations.

[0021] The voltage and current sensed at the output of the first stage matching network 201 (e.g., nodes 209 / 215) can be used to simultaneously command both stages since they operate independently. RF power is supplied by an RF generator to the system input node 208, which is supplied to the plasma chamber (not shown) via the hybrid matching network 200.

[0022] In the illustrated implementation, first-stage matching network 201 includes an impedance transformer 217 with banks 205, 206 of switch terminals 210 (e.g., switched capacitors) on two sides of the impedance transformer 217. Together, the impedance transformer 217 and banks 205, 206 of switch terminals 210 (e.g., switched capacitors) provide first-stage matching network 201 with the flexibility to match impedances within a specified range. Impedance transformer 217 can include a lumped-element π network or a distributed network, such as a transmission line, to achieve the desired impedance transformation. For example, impedance transformer 217 can include π network sections to perform both step-up and step-down impedance transformations to adjust the target impedance.

[0023] The specified range of the first stage is a design choice that can be made based on the application and availability of the equipment at a given frequency and power level. Selecting a narrow range can limit the stress on the first stage for a given frequency and power level, but also limits the applications in which it can be used. Selecting a wide range has the opposite effect. In either case, the system can function similarly.

[0024] As a result, the present disclosure provides an impedance transformer 217 for use with banks 205, 206 of switch terminals 210 (e.g., switched capacitors) to adjust impedance. The impedance transformer 217 can be realized by inserting a section of transmission line having an appropriate electrical length and characteristic impedance. For example, a quarter-wave impedance transformer can be used to match a real impedance. However, by adding a series or shunt reactance component, a complex load impedance can also be transformed into a real impedance. In particular, a quarter-wave transformer can provide a match at a particular operating frequency and an acceptable match over a bandwidth of one octave or less, depending on the quality factor Q of the transformation and the application.

[0025] 2, impedance transformer 217 includes a lumped-element π network. Impedance transformer 217 performs the same impedance transformation as a transmission path or waveguide and can be made more compact at lower frequencies, but offers a more limited bandwidth. In one implementation, lumped-element impedance transformer 217 consists of capacitors 213, 214 in the shunt network branch, in addition to inductor 216 in the series branch.

[0026] The banks 205, 206 of switches 212 each include an individual (e.g., RF) switch terminal 210 (within each individual bank 205, 206 of switches 212), which includes switches 212 and reactance tuning elements 221 that enable the first stage to match various load impedances. In some implementations, a lookup table stored in a memory element (not shown) of the hybrid matching network 200 may be referenced to determine the states of the switches 212 that jointly adjust the output impedance of the first stage to the complex conjugate of the calculated input impedance of the second-stage matching network. In the implementation shown in FIG. 2, the banks 205, 206 each include four switch terminals 210 of switches 212, thus providing eight switch terminals 210 for impedance adjustment. As described in more detail with respect to FIGS. 3 and 4, the number of switch terminals 210 can affect the accuracy of the adjustment of the first-stage matching network 201.

[0027] Additionally, a switch actuator 204 is coupled to each switch terminal 210 for each bank 205, 206 of switch terminals 210. A switch actuator is defined herein as the part of the system responsible for bringing a switch terminal 210 into or out of a circuit by engaging (e.g., closing) or disengaging (e.g., opening) the switch 212 in that switch terminal 210. The switch actuator 204 may be coupled to the banks 205, 206 of switch terminals 210 electrically, magnetically, optically, or mechanically. In the illustrated implementation, the switch actuator 204 is coupled to eight switches 212 in the banks 205, 206 of switch terminals 210. Additionally, the switch actuator 204 is coupled to a sensor element 203. The sensor element 203 may operate the switch actuator 204 to engage a first-stage matching network.

[0028] The states of the switches 212 in banks 205, 206 of switch terminal 210 may be represented in binary form. For example, a first-stage matching network 201 in which all switches 212 in bank 205 are closed and all switches 212 in bank 206 are open may be represented as [1111 0000]. Similarly, a first-stage matching network 201 in which the first half of the switches 212 in banks 205, 206 are open and the second half of the switches 212 in banks 205, 206 are closed may be represented as [0011 0011]. In one implementation, a lookup table may be used to relate the exact setting of switch terminal 210 to measurements from sensor element 203. In this case, after sensor data is received and processed, switch terminal 210 can be actuated to a set of states that minimizes the reflection coefficient (e.g., gamma) at the first-stage input 208.

[0029] The sensor element 203 is coupled to the input 215 of the second-stage matching network 202 as shown. The sensor element 203 can detect voltage and current, or forward and reflected coupled waves. The sensor element 203 can be a voltage and current sensor or a bidirectional coupler that detects voltage, current, forward, or reflected waveforms. In particular, the sensor element 203 measures voltage and current and calculates the relationship between the measured voltage and current, both in phase and magnitude. Additionally, the sensor element 203 can detect fast fluctuations in the plasma chamber impedance and use the change in impedance caused by the fast fluctuations to couple the first-stage matching network 201.

[0030] It should be understood by those skilled in the art with the benefit of this disclosure that the magnitude ratio and phase relationship of the voltage and current waveforms at a particular node in the matching network can be used to direct adjustable elements in the automatic matching network. In this case, a notable aspect is the location of the sensor and the type of information it collects. The magnitude ratio and phase relationship of these quantities at the node where the sensor element 203 resides in this system allows us to drive the second-stage matching network that matches the network and simultaneously activate the switch terminal 210 in the first-stage matching network. In this implementation, the magnitude and phase are used to drive the adjustable elements in the second-stage matching network that matches the network, and these same values ​​are used to calculate the input impedance to the second-stage matching network, which is the load impedance for the first-stage matching network. When this impedance is calculated, the switch terminal 210 activates so that the output impedance of the first stage is the load conjugate of the calculated load impedance. These operations occur simultaneously and independently. As the second stage matching network self-adjusts its tunable elements to achieve a minimum of gamma looking into its input 215, it always causes some loading at the input to the first stage. Thus, in any case where the impedance looking into node 215 is approximately the complex conjugate of one of the available settings of switch terminal 210, the first stage can minimize gamma looking into node 208, which is the input to the hybrid matching system. As the second stage matching network continuously drives toward a minimum gamma at node 215, the first stage can continue to actuate switch terminal 210 to maintain the most optimal impedance match at node 208.

[0031] 2 also shows a diagram of second-stage matching network 202. In some implementations, second-stage matching network 202 can be configured similarly to a conventional matching network. For example, second-stage matching network 202 can include one or more variable capacitors 218, 219 and inductor 220. Variable capacitors 218, 219 can be adjusted, for example, by a lead screw (not shown) in a mechanical means (e.g., using motor 211) to transform the impedance presented by the plasma chamber (not shown) to match a target impedance (e.g., a source impedance, typically 50 ohms).

[0032] 3 is a Smith chart 300 displaying the adjustable range for the first stage of a hybrid matching network (see FIG. 2) that includes eight switch terminals 210. The adjustable range illustrated in this Smith chart corresponds to the first stage matching network of the hybrid matching network topology of FIG. 2. In particular, Smith chart 300 reflects the topology of hybrid matching network 200 illustrated in FIG. 2, in which first stage matching network 201 has eight switch terminals 210. The adjustable range 302 illustrated in FIG. 3 is the conjugate of the range of (e.g., load) impedance that the first stage matching network can transform into a target impedance (e.g., 50 ohms in this example).

[0033] In some implementations, the shape (e.g., contour) of adjustable range 301 may differ from this example. The shape of adjustable range 302 may be determined by the topology of the first stage matching network and the values ​​of the reactance tuning elements. In this example, the value of reactance tuning element 221 in switch terminal 210 and the values ​​of reactance elements 213, 214, and 216 in impedance transformer 217 shown in FIG. 2 can determine the shape of adjustable range 302.

[0034] In particular, because the first-stage matching network is a discrete system with a finite number of settings, the number of switch terminals 210 (see FIG. 2) in the first-stage matching network of the hybrid matching network determines the density of the adjustable range 302. As a result, the greater the number of switch terminals in the first-stage matching network, the greater the density of the resulting adjustable range 302. In some implementations, eight switch terminals may be sufficient for applications that can tolerate a small amount of gamma at the input of the hybrid matching system. Therefore, the number of switch terminals designed for the first-stage matching network may be a major factor in the target VSWR.

[0035] The adjustable range 302 includes an impedance grid 306 of orthogonal arcs 307, 308. Each series of arcs represents an increment in the total reactance within switch banks 205 and 206 (see FIG. 2), respectively. A load impedance that is the conjugate of one of the intersections of 307 and 308 can be transformed exactly to the target impedance. A load impedance that falls between these intersections, such as impedance point 305, can be transformed very closely to the target impedance by selecting the switch setting that most closely represents the conjugate of that load impedance.

[0036] For example, impedance point 303 within adjustable range 302 is exactly at the intersection of horizontal and vertical impedance arcs 307, 308. As a result, the first stage matching network can adjust this load impedance to match the source impedance with a high degree of accuracy (e.g., 50 + 0.3j ohms for a 50 ohm source impedance). In contrast, the first stage matching network can adjust load impedance point 305 to the source impedance with medium to high accuracy (e.g., 50.5 - 2.4j ohms).

[0037] In addition, the first stage matching network of the hybrid matching network can adjust load impedances outside the VSWR 301 but within the adjustable range 302. For example, the load impedance represented by the impedance point 304, specifically at the exact intersection of the horizontal and vertical impedance arcs 307, 308, can be adjusted directly to the source impedance with high accuracy. As a result, the load impedance directly above the arcs 307, 308 of the impedance grid 306 can be adjusted directly to the source impedance, regardless of the distance from the source impedance to the load impedance.

[0038] As previously mentioned, the contours of the tunable range 302 may be determined by the sum of the switch terminals 210 and the reactance tuning element 221 (see FIG. 2) in the impedance transformer. For specific applications where the direction of impedance shift due to pulsing or the operating parameters of the plasma chamber or individual process is known and well characterized, it may be advantageous to have the range of the first stage matching network graded in one direction or the other.

[0039] 4 and 5 show the adjustable range for two possible implementations of the first-stage matching network. The difference between these two implementations is the number of switch terminals. In FIG. 4, the number of switch terminals is six, or three per bank, which results in adjustable range 401. In FIG. 5, the number of switch terminals 210 is ten, or five per bank, which results in adjustable range 501 on Smith chart 500. The spacing between different switch settings is greater in FIG. 4 than in FIG. 5. Therefore, the worst-case impedance matching may be less severe in a system with six switch terminals than in a system with ten switch terminals.

[0040] 6 is a Smith chart 600 illustrating impedance transformation to adjust a 53-j30 ohm load impedance (impedance point 601) to a target impedance (50 ohms in this case) in accordance with the systems and methods of the present disclosure. In the example shown, a first stage matching network of a hybrid matching network was employed to adjust the load impedance to within the target VSWR 606 (e.g., to impedance point 602).

[0041] FIG. 6 further illustrates impedance curves 603-605, which represent the phase and magnitude transformation of voltage and current through the first-stage matching components of a hybrid matching network. In the illustrated example, impedance curve 603 is associated with a first bank of switches (e.g., at a first end of an impedance transformer), while impedance curve 605 is associated with a second bank of switches (e.g., at a second end of the impedance transformer). Furthermore, impedance curve 604 is associated with an inductor element of the impedance transformer. Taken together, curves 603-605 illustrate the path of impedance transformation undergone by the first-stage matching network to adjust the load impedance to a target (e.g., source) impedance (e.g., impedance point 602) in a single step. As previously discussed, the first-stage matching network can adjust the load impedance to the target impedance with high accuracy in various implementations. For example, impedance point 602 is close to 50 ohms (e.g., 48.4-2.8 j ohms) for a target impedance of 50 ohms.

[0042] FIG. 7 is a Smith chart 700 illustrating impedance transformation to match a load impedance 701 to a target impedance 709 in accordance with the systems and methods of the present disclosure. This example is provided to further demonstrate the advantages obtained by using a hybrid matching network with a sensor arrangement as disclosed. Because the adjustment targets of either stage of the network may be completely independent, both control loops can operate simultaneously without any unwanted interaction. In the example shown, a hybrid matching network was employed to adjust a load impedance 701 of 1-j31 ohms to a target impedance 709 of 50 ohms. FIG. 7 depicts the Smith chart 700 and impedance curves 702-707 representing the path taken to transform the load impedance 701 to the target impedance 709 through the first and second stage matching networks of the hybrid matching network.

[0043] In the illustrated example, impedance curves 702-704 are associated with impedance transformations due to device elements in the second-stage matching network of the hybrid matching network. Similarly, impedance curves 705-707 are associated with impedance transformations due to device elements in the first-stage matching network of the hybrid matching network. For example, impedance curves 705-707 are associated with impedance transformations due to capacitors in the first bank of switch terminals (e.g., curve 707), inductor device elements of the impedance transformer (e.g., curve 705), and capacitors in the second bank of switch terminals (e.g., curve 706) in the first-stage matching network of the hybrid matching network. This example uses the topology selected in FIG. 2, where first-stage matching network 201 (see FIG. 2) is a π network comprising two banks 205, 206 of switch terminals 210, and second-stage matching network 202 (see FIG. 2) is a step-down L network including a variable shunt capacitor, a variable series capacitor, and a fixed series inductor. It should be apparent to one skilled in the art having the benefit of this disclosure that this hybrid matching system can employ alternative network topologies for the first and second stage matching networks, provided that doing so does not depart from the spirit and scope of this disclosure.

[0044] In this example, the load impedance 701 of 1-31j is transformed to 28.4+8.2j by the second-stage matching network. When the sensor 203 (see FIG. 2) calculates an impedance within the adjustable range of the first-stage matching network, the first-stage matching network can be activated. The switch 212 (see FIG. 2) can be activated to a setting that most closely matches the conjugate of the calculated load impedance. From the moment the switch 212 (see FIG. 2) is properly activated, the reflection coefficient at the input of the system can be minimized. The second-stage matching network can continue to be driven to minimize the reflection coefficient at its input 215 (see FIG. 2). When the impedance examining node 215 (see FIG. 2) changes due to the movement of the adjustable element and the load caused by the plasma chamber, the first-stage matching network can still be activated if the impedance examining node 215 (see FIG. 2) is still within its adjustable range. Even if their operation continues, from the perspective of the entire system, the adjustment goal has already been achieved.

[0045] Continuing with reference to FIG. 7 , impedance curve 707 is associated with a first bank of switches (e.g., at a first end of the impedance transformer), while impedance curve 706 is associated with a second bank of switches (e.g., at a second end of the impedance transformer). Furthermore, impedance curve 705 is associated with an inductor element of the impedance transformer. Collectively, curves 705-707 illustrate the path of impedance transformation undergone by the first-stage matching network to adjust the load impedance to a target (e.g., source) impedance (e.g., impedance point 709). As previously discussed, the first-stage matching network can adjust the load impedance to the target impedance with high accuracy in various implementations. For example, impedance point 709 may be close to 50 ohms (e.g., 50.2-0.4 j ohms) for a target impedance of 50 ohms.

[0046] FIG. 8 is a flowchart 800 of a method for performing impedance matching in accordance with the systems and methods of the present disclosure. Flowchart 800 begins with detecting an RF signal (block 801). The RF signal may be detected by a sensor element that is part of a hybrid matching network. If the detected RF signal is greater in amplitude than a predetermined threshold defined according to the application, the sensor performs the necessary calculations (e.g., phase error, magnitude error, and impedance) to begin the adjustment procedure (block 805). If the amplitude of the phase and magnitude errors is not higher than the specified threshold and the calculated impedance is not within the adjustable range of the first-stage matching network, both stages maintain their preset positions (blocks 802, 804). These preset positions depend on the application and can be anywhere within the available range of the adjustable elements in the network.

[0047] Additionally, if the error signals generated by comparing the magnitude and phase relationships of the voltage and current exceed a certain threshold, they can be used to adjust variable elements in the second-stage matching network (block 808). If the input impedance of node 215 (see FIG. 2), calculated from the difference in the magnitude and phase relationships of the voltage and current, is within the adjustable range of the first stage (block 807), the switch terminals can be operated to a setting that matches the output impedance of the first stage to the complex conjugate of the calculated load impedance (block 809). If RF is detected at a sufficient level but the error signals derived from the phase and magnitude are less than a certain threshold, the adjustable elements in the second-stage matching network can remain in their current positions because the adjustment target has been achieved (block 802). The first-stage matching network can continuously monitor the input impedance to the calculated node and change its setting to minimize the reflection coefficient seen at its input.

[0048] Although the present disclosure has been described in detail, it should be understood by those skilled in the art having the benefit of this disclosure that various changes, substitutions, and alterations can be made therein without departing from the spirit and scope of the present disclosure. All uses of the words "or" and "and" in connection with disclosed features indicate that the examples may include any combination of the listed features, as is appropriate given the context.

[0049] Although implementations have been described herein in detail to aid in the understanding of their application, it will be understood that the inventive concepts may otherwise be embodied and employed in various ways, except as limited by the prior art, and it is intended that the appended claims be understood to include such variations.

[0050] References throughout this specification to "one implementation" or "implementation" mean that a particular feature, structure, or characteristic described in connection with an implementation is included in at least one implementation of the present disclosure. Thus, the appearances of the phrase "in one implementation" or "in some implementations" in various places throughout this specification do not necessarily all refer to the same implementations. Furthermore, particular features, structures, or characteristics may be combined in any suitable manner in one or more implementations.

[0051] In the foregoing specification, detailed descriptions have been given with reference to specific exemplary implementations. However, it will be apparent that various modifications and changes can be made therein without departing from the broader spirit and scope of the disclosure as set forth in the appended claims. The specification and drawings are, accordingly, to be regarded in an assisting sense rather than in a restrictive sense. Some aspects of the invention are described below. [Aspect 1] 1. A first stage matching network for performing a low-Q impedance transformation during fast impedance variations, comprising: a first stage matching network, wherein the fast variation is defined as a change in impedance that exceeds a control loop bandwidth associated with the second stage matching network; a second stage matching network for performing impedance matching for a high Q impedance transformation; a sensor element coupled to the first stage matching network and the second stage matching network, the sensor element detecting a signal and performing a calculation used to couple to the first stage matching network and the second stage matching network; a matching network comprising: [Aspect 2] the first stage matching network includes a switched matching network; 10. The matching network of claim 1, wherein the second stage matching network comprises a mechanically tuned matching network. Aspect 3 the first stage matching network using at least one of fixed capacitors and electronic devices; the switch may be at least one of a pair of PIN diodes, a silicon-carbide field effect transistor (SiCFET), a metal oxide field effect transistor (MOSFET), an insulated gate bipolar transistor (IGBT), or a bipolar junction transistor (BJT); The matching network of aspect 2, wherein the second stage matching network may be at least one of a set of vacuum variable capacitors or air variable capacitors, and at least one of a set of stepping motors, brushed direct current (DC) motors, brushless DC motors, or AC motors. Aspect 4 2. The matching network of embodiment 1, wherein the first stage matching network includes a continuously variable reactance tuning element. Aspect 5 10. The matching network of claim 1, wherein the sensor element measures voltage and current and calculates a relationship between the measured voltage and current, both in phase, magnitude, and impedance. Aspect 6 2. The matching network of aspect 1, wherein the sensor element operates a switch actuator to couple the first stage matching network. Aspect 7 2. The matching network of claim 1, wherein the impedance transformer comprises a lumped-element π network. Aspect 8 the first half of the switch terminal is disposed on a first side of the π network; 8. The matching network of aspect 7, wherein a second half of the switch terminals is disposed on a second side of the π network. Aspect 9 2. The matching network of aspect 1, wherein a tunable range of the first stage matching network can be changed by disabling at least one of the switch terminals. Aspect 10 2. The matching network of aspect 1, wherein the first stage matching network and the second stage matching network perform impedance matching on the same or different portions of a modulated RF waveform. Aspect 11 a high frequency generator; a matching network coupled to the RF generator to generate an impedance-matched output; 1. A first stage matching network for performing a low-Q impedance transformation during fast impedance variations, comprising: a first stage matching network, wherein the fast variation is defined as a change in impedance that exceeds a control loop bandwidth associated with the second stage matching network; a second stage matching network for performing impedance matching for a high Q impedance transformation, comprising: the high-Q impedance transformation has a Q value greater than 2; the low-Q impedance transformation includes a second stage matching network having a Q factor less than 2; a matching network comprising: a sensor element coupled to the first stage matching network and the second stage matching network, the sensor element detecting a signal and performing a calculation used to couple to the first stage matching network and the second stage matching network; a plasma chamber coupled to the matching network to receive an impedance-matched output from the matching network; A plasma generation system comprising: Aspect 12 the radio frequency generator generates a modulated RF waveform; 12. The plasma generation system of claim 11, wherein the first stage matching network can couple each state of the modulated RF waveform, and the second stage matching network can couple on a single state of the modulated RF waveform. Aspect 13 12. The plasma generation system of claim 11, wherein the sensor element detects fast fluctuations in plasma chamber impedance and uses the change in impedance caused by the fast fluctuations to couple the first stage matching network. Aspect 14 12. The plasma generation system of claim 11, wherein the first stage matching network includes a plurality of RF switches. Aspect 15 determining the presence of RF waves exceeding a first predetermined threshold; calculating a magnitude and phase relationship between voltages and currents to direct an adjustment of a second stage matching network of a hybrid matching network, and calculating an impedance from the calculated magnitude and phase relationship between voltages and currents to direct the adjustment of a first stage matching network of the hybrid matching network. Aspect 16 16. The method of claim 15, further comprising enabling simultaneous execution of parallel control loops associated with the first stage matching network and the second stage matching network, which direct the first stage matching network and the second stage matching network of the hybrid matching network to achieve a minimum system adjustment time. Aspect 17 16. The method of embodiment 15, wherein the first stage matching network functions as a filter when the first stage matching network is open. Aspect 18 16. The method of embodiment 15, wherein coupling the first stage matching network includes setting states of a plurality of switch terminals in the first stage matching network. Aspect 19 16. The method of embodiment 15, wherein the first stage matching network is coupled when an input impedance to the second stage matching network falls within an adjustable range of the first stage matching network. Aspect 20 16. The method of embodiment 15, wherein operation of the first stage matching network and the second stage matching network occurs independently, simultaneously, or sequentially.

Claims

1. a first stage matching network comprising a plurality of electronically controlled electronic capacitors coupled to the RF generator and the plasma chamber; a second stage matching network comprising a mechanically adjusted capacitor coupled to the RF generator and the plasma chamber operating within a control loop bandwidth; a controller that causes the first stage matching network to operate faster than the control loop bandwidth of the second stage matching network.

2. The hybrid matching network of claim 1 , wherein the mechanically tuned capacitor comprises a vacuum capacitor.

3. The first stage matching network performs a relatively low Q impedance transformation; the second stage matching network performs a relatively high Q impedance transformation; 2. The hybrid matching network of claim 1, wherein the Q represents the ratio of reactance to resistance of an associated impedance transformation.

4. the relatively low-Q impedance transformation has a Q of less than 2; The hybrid matching network of claim 3 , wherein the relatively high-Q impedance transformation has a Q greater than two.

5. The first stage matching network comprises: an impedance transformer connected in series between the radio frequency generator and the plasma chamber; a plurality of shunt banks connected between the impedance transformer and electrical ground; 2. The hybrid matching network of claim 1, wherein each shunt bank comprises at least one of said electronically controlled electronic capacitors.

6. The first stage matching network comprises: an impedance transformer connected in series between the radio frequency generator and the plasma chamber, the impedance transformer having an input node between the radio frequency generator and the impedance transformer and an output node between the impedance transformer and the plasma chamber; a plurality of input shunt banks connected between the input node of the impedance transformer and electrical ground, each input shunt bank comprising at least one of the electronically controlled electronic capacitors; 2. The hybrid matching network of claim 1, further comprising: a plurality of output shunt banks connected between the output node of the impedance transformer and electrical ground, each output shunt bank comprising at least one of the electronically controlled electronic capacitors.

7. The second stage matching network comprises: an inductor connected in series between the radio frequency generator and the plasma chamber; 10. The hybrid matching network of claim 1, further comprising: a series-connected mechanically tuned capacitor connected in series with the inductor.

8. The second stage matching network comprises: an inductor connected in series between the radio frequency generator and the plasma chamber; 10. The hybrid matching network of claim 1, further comprising: a shunt-connected, mechanically tuned capacitor connected between the inductor and electrical ground.

9. The second stage matching network comprises: an inductor connected in series between the radio frequency generator and the plasma chamber; a series-connected mechanically tuned capacitor connected in series with the inductor; 10. The hybrid matching network of claim 1, further comprising: a shunt-connected, mechanically tuned capacitor connected between the inductor and electrical ground.

10. 10. The hybrid matching network of claim 1, wherein the first stage matching network includes a continuously variable reactance tuning element.

11. further comprising a sensor element for measuring voltage and current and calculating the relationship between said measured voltage and current in both phase, magnitude and impedance; 2. The hybrid matching network of claim 1, wherein the controller utilizes the relationship between the measured voltage and current in both phases, magnitudes, and impedances to operate the first stage matching network faster than the control loop bandwidth of the second stage matching network.

12. The hybrid matching network of claim 11 , wherein the sensor element operates the controller, which operates the electronically controlled electronic capacitor.

13. The hybrid matching network of claim 5 , wherein the impedance transformer comprises a lumped-element π network.

14. 6. The hybrid matching network of claim 5, wherein the impedance transformer includes a lumped-element π network, a first half of the electronically controlled electronic capacitor being disposed on a first side of the π network, and a second half of the electronically controlled electronic capacitor being disposed on a second side of the π network.

15. 10. The hybrid matching network of claim 1, wherein the tunable range of the first stage matching network can be changed by disabling at least one of the electronically controlled electronic capacitors.

16. 10. The hybrid matching network of claim 1, wherein the first stage matching network and the second stage matching network perform impedance matching on the same portion of a modulated RF waveform.

17. 10. The hybrid matching network of claim 1, wherein the first stage matching network and the second stage matching network perform impedance matching at different portions of a modulated RF waveform.

18. The first stage matching network comprises: a plurality of fixed capacitors; an electronic switch controlling each fixed capacitor selected from the group consisting of a PIN diode, a silicon-carbide field effect transistor (SiCFET), a metal oxide field effect transistor (MOSFET), an insulated gate bipolar transistor (IGBT), and a bipolar junction transistor (BJT); 10. The hybrid matching network of claim 1, wherein the second stage matching network comprises a motor controlling a vacuum variable capacitor or an air variable capacitor selected from the group consisting of a stepper motor, a brushed direct current (DC) motor, a brushless DC motor, and an AC motor.

19. the first stage matching network performs a relatively low Q impedance transformation; the second stage matching network performs a relatively high Q impedance transformation; 20. The hybrid matching network of claim 18, wherein the Q represents the ratio of reactance to resistance of the associated impedance transformation.

20. 20. The hybrid matching network of claim 19, wherein the mechanically tuned capacitor comprises a vacuum capacitor.

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