System and method for reducing intermodulation distortion in a plasma chamber

Abstract

A power supply system for reducing intermodulation distortion in a plasma chamber comprises a source RF generator generating a source RF signal at a first frequency, a bias RF generator generating a bias RF signal at a second frequency lower than the first frequency, a matching network coupled to both generators, a load coupled to the matching network, and a controller. The controller receives a synchronization signal from the bias RF generator to synchronize operation of the source RF generator with the bias RF generator, obtains characteristic data corresponding to a reflected signal during an nth period of the bias RF signal, and adjusts a frequency of the source RF signal during a subsequent period based on the characteristic data obtained during the nth period.

Description

Docket Number: 00797-WOSYSTEM AND METHOD FOR REDUCING INTERMODULATION DISTORTION IN A PLASMA CHAMBERFIELD OF INVENTION

[0001] The present disclosure relates to plasma generator systems and control of plasma generators.BACKGROUND

[0002] Plasma etching is frequently used in semiconductor fabrication. In plasma etching, ions are accelerated by an electric field to etch exposed surfaces on a substrate. In one basic implementation, the electric field is generated based on Radio Frequency (RF) or Direct Current (DC) power signals generated by a respective RF or DC generator of a power delivery system. The power signals generated by the generator must be precisely controlled to effectively execute plasma etching.BRIEF DESCRIPTION OF FIGURES

[0003] Non-limiting and non-exhaustive examples are described with reference to the following figures.

[0004] FIG. 1 illustrates a schematic representation of an inductively coupled plasma system.

[0005] FIG. 2 illustrates a schematic representation of a capacitively coupled plasma system.

[0006] FIG. 3 illustrates a generalized representation of a plasma system according to various embodiments of the present invention.

[0007] FIG. 4 illustrates a block diagram of a power supply system, according to embodiments of the present invention.

[0008] FIG. 5 illustrates a block diagram of an embodiment of an RF generator, such as the first or second RF generator shown in FIG. 4.

[0009] FIG. 6 illustrates a block diagram of an embodiment of the local controller shown in FIG. 5.

[0010] FIG. 7 illustrates a flowchart of one embodiment of a technique for use with the power supply system shown in FIG. 4.Docket Number: 00797-WO

[0011] FIG. 8 illustrates a flowchart of an embodiment of another technique for use with the power supply system shown in FIG. 4.SUMMARY

[0012] In one embodiment, a power supply system for reducing intermodulation distortion in a plasma chamber is provided. The power supply system comprises a source RF generator configured to generate a source RF signal at a first frequency. The power supply system comprises a bias RF generator configured to generate a bias RF signal at a second frequency lower than the first frequency. The power supply system comprises a matching network coupled to the source RF generator and the bias RF generator. The power supply system comprises a load coupled to the matching network. The power supply system comprises a controller configured to receive a synchronization signal from the bias RF generator to synchronize operation of the source RF generator with the bias RF generator, obtain characteristic data corresponding to a reflected signal during an nth period of the bias RF signal, and adjust a frequency of the source RF signal during a period of the bias RF signal subsequent to the nth period based on the characteristic data obtained during the nth period.

[0013] In another embodiment, a method for reducing intermodulation distortion in a plasma system is provided. The method comprises synchronizing a source RF generator with a bias RF generator based on a synchronization signal transmitted from the bias RF generator to the source RF generator. The method comprises obtaining characteristic data corresponding to a reflected signal from an nth period of a bias RF signal generated by the bias RF generator. The method comprises adjusting a frequency of a source RF signal generated by the source RF generator during an n+1 th period of the bias RF signal based on the characteristic data obtained from the nth period.

[0014] In yet another embodiment, a method for processing RF bias signals in a plasma system is provided. The method comprises dividing a period of an RF bias signal into time segments of predetermined duration. The method comprises selecting a measurement of a first characteristic during a time segment of each period of the RF bias signal based on a predetermined statistic. The method comprises reporting a measurement of a second characteristic during the timeDocket Number: 00797-WO segment as a readback, wherein the second characteristic is different from the first characteristic.

[0015] In still another embodiment, a non-transitory computer-readable medium storing instructions is provided. When executed by a processor, the instructions cause the processor to receive a synchronization signal from a bias RF generator to synchronize operation of a source RF generator with the bias RF generator. The instructions cause the processor to obtain characteristic data corresponding to a reflected signal during an nth period of a bias RF signal generated by the bias RF generator. The instructions cause the processor to adjust a frequency of a source RF signal generated by the source RF generator during a period of the bias RF signal subsequent to the nth period based on the characteristic data obtained during the nth period.DETAILED DESCRIPTION

[0016] The following description sets forth exemplary aspects of the present disclosure. It should be recognized, however, that such description is not intended as a limitation on the scope of the present disclosure. Rather, the description also encompasses combinations and modifications to those exemplary aspects described herein.

[0017] A power system may include a DC or RF power generator or DC or RF generator, a matching network, and a load (such as a process chamber, a plasma chamber, or a reactor having a fixed or variable impedance). The power generator generates a DC or RF power signal, which is received by the matching network or impedance optimizing controller or circuit. The matching network or impedance optimizing controller or circuit matches an input impedance of the matching network to a characteristic impedance of a transmission line between the power generator and the matching network. The impedance matching aids in maximizing an amount of power forwarded to the matching network (“forward power”) and minimizing an amount of power reflected back from the matching network to the power generator (“reverse power” or “reflected power”). Forward power may be maximized and reverse power may be minimized when the input impedance of the matching network matches the characteristic impedance of the transmission line and generator.

[0018] In the power source or power supply field, there are typically two approaches to applying a power signal to the load. A first, more traditional approachDocket Number: 00797-WO is to apply a continuous power signal to the load. In a continuous mode or continuous wave mode, a continuous power signal is typically a constant DC or sinusoidal RF power signal that is output continuously by the power source to the load. In the continuous mode approach, the power signal assumes a constant DC or sinusoidal output, and the amplitude of the power signal and / or frequency (of a RF power signal) can be varied in order to vary the output power applied to the load.

[0019] A second approach to applying the power signal to the load involves pulsing a RF signal, rather than applying a continuous RF signal to the load. In a pulse mode of operation, a RF signal is modulated by a modulation signal in order to define an envelope for the modulated power signal. The RF signal may be, for example, a sinusoidal RF signal or other time varying signal. Power delivered to the load is typically varied by varying the modulation signal.

[0020] In a typical power supply configuration, output power applied to the load is determined using sensors that measure the forward and reflected power or the voltage and current of the RF signal applied to the load. Either set of these signals is analyzed in a control loop. The analysis typically determines a power value which is used to adjust the output of the power supply in order to vary the power applied to the load. In a power delivery system where the load is a process chamber or other non-linear or time varying load, the varying impedance of the load causes a corresponding varying of power applied to the load, as applied power is in part a function of the impedance of the load.

[0021] In systems where fabrication of various devices relies upon introduction of power to a load to control a fabrication process, power is typically delivered in one of two configurations. In a first configuration, the power is capacitively coupled to the load. Such systems are referred to as capacitively coupled plasma (CCP) systems. In a second configuration, the power is inductively coupled to the load. Such systems are typically referred to as inductively coupled plasma (ICP) systems. Power coupling to the plasma can also be achieved via wave coupling at microwave frequencies. Such an approach typically uses Electron Cyclotron Resonance (ECR) or microwave sources. Helicon sources are another form of wave coupled source and typically operate at RF frequencies similar to that of conventional ICP and CCP systems. Power delivery systems may include at least one bias power and / or a source power applied to one or a plurality of electrodes of the load. The sourceDocket Number: 00797-WO power typically generates a plasma and controls plasma density, and the bias power modulates ions in the formulation of the sheath. The bias and the source may share the same electrode or may use separate electrodes, in accordance with various design considerations.

[0022] Time varying or non-linear loads may be present in various applications. In one application, plasma processing systems may also include components for plasma generation and control. One such component is a non-linear load implemented as a process chamber, such as a plasma chamber or reactor. A typical plasma chamber or reactor utilized in plasma processing systems, such as by way of example, for thin-film manufacturing, can utilize a dual power system. One power generator (the source) controls the generation of the plasma, and the power generator (the bias) controls ion energy. Examples of dual power systems include systems that are described in U.S. Pat. Nos. 7,602,127; 8,110,991 ; and 8,395,322.

[0023] As integrated circuit and device fabrication continues to evolve, so do the power requirements for controlling the process for fabrication. For example, with memory device fabrication, the requirements for bias power continue to increase. Increased power generates higher energetic ions for faster surface interaction, thereby increasing the etch rate and directionality of ions. In RF systems, increased bias power is sometimes accompanied by a lower bias frequency requirement along with an increase in the number of bias power sources coupled to the plasma sheath created in the plasma chamber. The increased power at a lower bias frequency and the increased number of bias power sources results in intermodulation distortion (IMD) emissions from a sheath modulation. The IMD emissions can significantly reduce power delivered by the source where plasma generation occurs.

[0024] FIG. 1 depicts a representation of an inductively coupled plasma (ICP) system 10. ICP system 110 includes a non-linear load, such as a reactor, plasma reactor, or plasma chamber 112, which will be referred to interchangeably herein, for generating plasma 114. Power in the form of voltage or current is applied to plasma chamber 112 via a pair of coils, including a coil assembly that in various embodiments includes an inner coil 116 and an outer coil 118. Power is applied to inner coil 116 via a RF power generator or power source 120, and power is applied to outer coil 118 via RF power generator or power source 122. Coils 116 and 118 are mounted to dielectric window 124 that assists in coupling power to plasma chamberDocket Number: 00797-WO112. A substrate 126 is placed in plasma chamber 112 and typically forms the work piece that is the subject of plasma operations. An RF power generator, power supply, or power source 128 (the terms may be used herein interchangeably) applies power to plasma chamber 112 via substrate 126. In various configurations, the power sources 120, 122 provide a source voltage or current to ignite or generate plasma 114 or control the plasma density. Also in various configurations, power source 128 provides a bias voltage or current that modulates the ions to control the ion energy or ion density of the plasma 114. In various embodiments, power sources 120, 122 are locked to operate at the same frequency, voltage, and current, with fixed or varying relative phases. In various other embodiments, power sources 120, 122 may operate at different frequencies, voltages, and currents, and relative phases.

[0025] FIG. 2 depicts a representation of a capacitively coupled plasma (CCP) system 210. CCP system 210 includes a plasma chamber 212 for generating plasma 214. A pair of electrodes 216, 218 placed within plasma chamber 212 connect to respective DC (co=O) or RF power generators or power sources 220, 222. In various embodiments, power source 220 provides a source voltage or current to ignite or generate plasma 214 or control the plasma density. In various embodiments, power source 222 provides a bias voltage or current that modulates the ions in the plasma to control the ion energy and / or ion density of the plasma 214. In various RF embodiments, power sources 220, 222 operate at relative phases when the sources are harmonically related. In various other embodiments, power sources 220, 222 operate at different frequencies, voltages, and currents, with fixed or varying relative phases. Also in various embodiments, power sources 220, 222 can be connected to the same electrode, while the counter electrode is connected to ground or to yet a third DC (co=O) or RF power generator (not shown).

[0026] FIG. 3 depicts a cross-sectional view of a generalized representation of a dual power input plasma system 310. Plasma system 310 includes first electrode 312 connected to ground 314 and second electrode 316 spaced apart from first electrode 312. A first DC (co=O) or RF power source 318 generates a first RF power applied to second electrode 316 at a first frequency f=wi . A second power source 320 generates a second DC (co=O) or RF power applied to second electrode 316. In various embodiments, second power source 320 operates at a second frequencyDocket Number: 00797-WO f=uo2, where co2=nco that is the nthharmonic frequency of the frequency of first power source 318. In various other embodiments, second power source 320 operates at a frequency that is not a multiple of the frequency of the first power source 318.

[0027] Coordinated operation of respective power sources 318, 320 results in generation and control of plasma 322. As shown in FIG. 3 in schematic view, plasma 322 is formed within an asymmetric sheath 330 of plasma chamber 324. Sheath 330 includes a ground or grounded sheath 332 and a powered sheath 334. The sheath is generally described as the surface area surrounding plasma 322. As can be seen in schematic view in FIG. 3, grounded sheath 332 has a relatively large surface area 326. Powered sheath 334 has a small surface area 328. Because each sheath 332, 334 functions as a dielectric between the conductive plasma 322 and respective electrodes 312, 316, each sheath 332, 334 forms a capacitance between plasma 322 and respective electrodes 326, 328.

[0028] As will be described in greater detail herein, in systems in which a high frequency voltage source, such as second power source 320, and a low frequency voltage source, such as first power source 318, intermodulation distortion (IMD) products are introduced. IMD products result from a change in plasma sheath thickness, thereby varying the capacitance between plasma 322 and electrode 312, via grounded sheath 332, and plasma 322 and electrode 316, via powered sheath 334. The variation in the capacitance of powered sheath 334 generates IMD. Variation in powered sheath 334 has a greater impact on the capacitance between plasma 322 and electrode 316 and, therefore, on the reverse IMD emitted from plasma chamber 324. In some plasma systems grounded sheath 332 acts as a short circuit and is not considered for its impact on reverse IMD.

[0029] FIG. 4 illustrates a block diagram of a power supply system, according to embodiments of the present invention. FIG. 5 illustrates a flowchart of one embodiment of a technique for use with the power supply system shown in FIG. 4.

[0030] In FIG. 4, the power supply system 400 includes a first RF generator 402 (also referred to herein as an "RF source generator"), a second RF generator 404 (also referred to herein as an "RF bias generator") and a matching network 406. Generally, the first RF generator 402 is operative to output a first RF signal (also referred to herein as a "source RF signal") and the second RF generator 404 isDocket Number: 00797-WO operative to output a second RF signal (also referred to herein as a "bias RF signal"). Generally, a frequency of the first RF signal is higher than that of the second RF signal.

[0031] Although the matching network 406 is shown as a single component connected to the output of the first and second RF generators 402 and 404, it will be appreciated that the matching network 406 may include an individual matching network connected to the output of each of the first and second RF generators 402 and 404.

[0032] The power supply system 400 is shown to be connected to a load 408 as described above (e.g., a non-linear load, which may be a plasma chamber, process chamber, or the like).

[0033] In some embodiments, one or both of the first RF generator 402 and second RF generator 404 may be provided (and operate) as exemplarily described with respect to the RF generator 500 shown in FIG. 5. Referring to FIG. 5, RF generator 500 includes respective RF power sources or amplifier 502, an RF sensor 504, and processor, controller, or control module 506 (also referred to herein as a "local controller"). RF power source 502 generates RF power signal 508 output to sensor 504. Sensor 504 receives the output of RF power source 502 and generates a respective RF power signal. Sensor 504 also outputs signals that vary in accordance with various parameters sensed from load (e.g., load 406). While sensor 504 is shown within RF generator 500, RF sensor 504 can be located externally to the RF power generator 500. Such external sensing can occur at the output of the RF generator, at the input of an impedance matching device located between the RF generator and the load, or between the output of the impedance matching device (including within the impedance matching device) and the load.

[0034] Sensor 504 detects various operating parameters and outputs signals X and Y 510 and 512, respectively. Sensor 504 may include voltage, current, and / or directional coupler sensors. Sensor 504 may detect (i) voltage V and current I and / or (ii) forward power PFWD output from power source 502 and / or RF generator 500 and reverse or reflected power PREV received from respective matching network (e.g., matching network 404) or load (e.g., load 406) connected to sensor 504. The voltage V, current I, forward power PFWD, and reverse power PREV may be scaledDocket Number: 00797-WO and / or filtered versions of the actual voltage, current, forward power, and reverse power associated with the power source 502. Sensors 504 may be analog and / or digital sensors. In a digital implementation, the sensor 504 may include analog-to- digital (A / D) converters and signal sampling components with corresponding sampling rates. Signals X and Y can represent any of the voltage V and current I or forward (or source) power PFWD reverse (or reflected) power PREV.

[0035] Sensor 504 generates sensor signals X, Y, which are received by controller or power control module 506. Power control module 506 processes the respective X, Y signals 510, 512 and generates one or more feedforward and / or feedback control signals 514 to power source 502. Power source 502 adjusts the RF power signal 508 based on received feedback and / or feedforward control signal. In various embodiments, power control module 506 may control matching network (e.g., matching network 404) via a control signals. Power control module 506 may include, at least, proportional integral derivative (PID) controllers or subsets thereof and / or direct digital synthesis (DDS) component(s) and / or any of the various components described below in connection with the modules.

[0036] In various embodiments, power control module 506 is a PID controller or subset thereof and may include functions, processes, processors, or submodules. Control signal 514 may be a drive signal and may include DC offset or rail voltage, voltage or current magnitude, frequency, and phase components. In various embodiments, control signal 514 can be used as an input to one or multiple control loops. In various embodiments, the multiple control loops can include a proportional- integral-derivative (PID) control loop for RF drive, and for rail voltage. In various embodiments, control signal 514 can be used in a Multiple Input Multiple Output (MIMO) control scheme. An example of a MIMO control scheme can be found with reference to U.S. Pat. No. 10,546,724, issued on Jan. 28, 2020, entitled Pulsed Bidirectional Radio Frequency Source / Load and assigned to the assignee of the present application, and incorporated by reference herein.

[0037] In some embodiments, when the first RF generator 402 includes the control module 506, the control module 506 may be provided (and operate) as exemplarily described with respect to the control module 600 shown in FIG.6. Referring to FIG. 6, the control module 600 may include a playback module 602, a frequency offset module 604, and an update module 606. Each module 602, 604,Docket Number: 00797-WO606 can be implemented collectively or individually as a process, a processor, a module, or a submodule. Further, each module 602, 604, 606 can be implemented as any of the various components described below in connection with the term module. Playback module 602 monitors for a triggering event or signal with which to synchronize the application of frequency offsets to the first RF signal. Once playback module 602 detects a triggering event or signal, playback module 602 initiates the addition of frequency offsets to the first RF signal. Playback module 602 cooperates with frequency offset module 604, and frequency offset module 604 provides frequency offsets to playback module 602 which coordinates the application of the frequency offset to first RF signal.

[0038] In various embodiments, frequency offset module 604 is implemented as a lookup table (LUT). Frequency offsets are determined in accordance with, for example, a time or phase delay relative to the triggering event or signal. Given the periodic nature of second RF signal and the expected periodic impedance fluctuations that occur in response to application of the second RF signal to load 408, a LUT of the offsets for the first RF signal can be determined. The frequency offsets added to first RF signal are generated to align with interference introduced by second RF generator 402 and at least partially cancels the bias RF interference, thereby reducing impedance fluctuations. In various embodiments, the LUT can be statically determined by experimentation, or automatically adjusted with any suitable or otherwise known update process, such as update module 606.

[0039] Referring back to FIG. 4, the power supply system 400 also includes a controller 410. Controller 410 may be disposed externally to either or both of the first and second RF generators 402 and 404 and may be referred to as external or common controller 410. In various embodiments, controller 410 may implement one or a plurality of functions, processes, or algorithms described herein with respect to one or both controllers of the first and second RF generators 402 and 404. Accordingly, controller 410 communicates with respective first and second RF generators 402 and 404 via a pair of respective links which enable exchange of data and control signals, as appropriate. For the various embodiments, controller 410 and the local controllers 506 of the first and second RF generators 402 and 404 can cooperatively provide analysis and control of the first and second RF generators 402 and 404. In various other embodiments, controller 410 can provide control of the firstDocket Number: 00797-WO and second RF generators 402 and 404, eliminating the need for the respective local controller 506 of the first and second RF generators 402 and 404.

[0040] In various embodiments, the local controller 506 of the first RF generator 400 adjusts the frequency of the RF signal output therefrom to compensate for impedance fluctuations resulting from the application of RF signal output by the second RF generator 404 to the load 406. According to the principles of the various embodiments discussed herein, application of the second RF signal (which has a relatively low frequency, e.g., from 400 kHz to 2 MHz) to the load 408, can impact the RF power ultimately delivered by a first RF generator 402, which applies a first RF frequency (which has a relatively high frequency, e.g., 60 MHz) to the load 408. The impact is manifested as intermodulation distortion (HMD), which reduces RF power delivery efficiency to the load 408. Thus, embodiments of the present invention are directed to reducing intermodulation distortion (thereby improving power delivery efficiency to the load 408).

[0041] To do so, a synchronization signal (SYNC) is transmitted from the second RF generator 402 to the first RF generator 400 to synchronize the output of the first RF signal with the output of the second RF signal. See, e.g., FIG. 4 and step 702 in FIG. 7. In addition, a characteristic of a reflected signal (e.g., reflected power or reflection coefficient) is detected, sensed or otherwise measured (e.g., as discussed above) while the second RF signal is output. Data representing the measured characteristic is processed (e.g., averaged) at the controller 410, within a local controller 506 of the first RF generator 402, or the like or any combination thereof, for each period of the second RF signal. In this case, the period of the second RF signal can be determined based on a characteristic of the synchronization signal SYNC. The characteristic measured during the 1st, 2nd, 3rd, ... nth, etc., periods of the second RF signal is thus processed (e.g., averaged) to obtain processed characteristic data associated with each period of the second RF signal. The processed characteristic data can be stored (e.g., at the controller 410, at the local controller 506 of the first RF generator 402, or the like or any combination thereof) and, optionally, in association with data indicating the period of the second RF signal from which it is based.

[0042] While the processed characteristic data is being generated and stored, the frequency of the first RF signal to be output by the first RF generator 402 duringDocket Number: 00797-WO a particular period of the second RF signal can be adjusted or otherwise set based the processed characteristic data associated with a preceding period of the second RF signal. For example, if processed characteristic data is obtained for an nth period of the second RF signal output by the second RF generator 404 (see, e.g., step 704 in FIG. 7), the frequency of the first RF signal output by the first RF generator 402 during an n+1 th period of the second RF signal to be output by the second RF generator 404 can be adjusted or otherwise set based the processed characteristic data obtained from the nth period of the second RF signal (see, e.g., step 706 in FIG. 7). In this case, the frequency of the first RF signal is adjusted or set to reduce the characteristic of the aforementioned reflected signal. The technique described above can be considered to represent a gradual or iterative approach to IMD reduction, where measurements from one period of the second RF signal may be used to optimize frequency selection of the first RF signal in the subsequent period. This technique may allow for continuous adaptation to changing plasma conditions, enabling improved power delivery efficiency and reduced IMD.

[0043] FIG. 8 illustrates a flowchart of an embodiment of another technique for use with the power supply system shown in FIG. 4.

[0044] Referring to FIG. 8, the method 800 may comprise three main steps. In some aspects, the method 800 may begin with step 802, which may involve dividing the period of the second RF signal into time segments of predetermined duration. This step may establish the temporal framework for subsequent measurements and analysis.

[0045] Next, at step 804, a measurement of a first characteristic may be selected during a time segment of each period of the second RF signal. This selection may be based on a predetermined statistic (e.g., a maximum value, a minimum value, an average value, etc.). The first characteristic may vary depending on the specific requirements of the process to be performed within the load 406. For example, the first characteristic may be a gamma signal, forward power signal, a reflected power signal.

[0046] Next, at step 806, a measurement of a second characteristic obtained during the same time segment referenced above in step 804 is reported as a readback. The second characteristic is different from the first characteristicDocket Number: 00797-WO measured in step 804. In some aspects, the measurement of the second characteristic may, optionally, be reported be a statistic of the measured second characteristic (e.g., a minimum value, a maximum value, a mean value, etc.).

[0047] The technique 800 may provide a structured approach for analyzing one or more of the various signals discussed above, enabling for improved control and optimization of processes performed at the load 408. By segmenting the second RF signal and selecting specific measurements based on predetermined criteria, the technique 800 may enable more precise monitoring and adjustment of plasma system parameters. This approach may be particularly useful in high aspect ratio etching applications, where precise control of plasma characteristics is critical for achieving desired etch profiles and uniformity.

[0048] In some implementations, the readback reported in step 806 may be used by a user or a control system to adjust various parameters of the power supply system 400. For example, the readback may be used to fine-tune the frequency of the first RF signal, adjust the power output of the first and second RF generators, or modify the settings of the matching network 406. This feedback mechanism may allow for continuous optimization of the plasma process, potentially leading to improved etch performance and reduced power consumption.

[0049] The power supply system 400 described above may offer significant improvements in power efficiency and overall system performance. In some aspects, the system may reduce reflected power from over 40% to less than 10%. This substantial reduction in reflected power may result in more RF power being delivered to plasma within the load 408, enabling enhanced the plasma-assisted processes and improving overall efficiency. The improved power delivery efficiency may allow for a reduction in the size of the power supply system 400. For example, size of the RF source generator 402 can be significantly smaller than conventional RF source generators, which may lead to space savings in manufacturing environments and potentially reduce cooling requirements. The power supply system 400 may also provide enhanced process stability by mitigating IMD. In some cases, this may lead to improved uniformity and consistency of plasma-assisted processes. In certain aspects, reduction in reflected power and overall stress on the first RF generator 402 can extend the lifespan of the equipment and result in reduced maintenance needs and decreased downtime for semiconductor manufacturing facilities.Docket Number: 00797-WO

[0050] The foregoing description is merely illustrative in nature and is in no way intended to limit the disclosure, its application, or uses. The broad teachings of the disclosure can be implemented in a variety of forms. Therefore, while this disclosure includes particular examples, the true scope of the disclosure should not be so limited since other modifications will become apparent upon a study of the drawings, the specification, and the following claims. It should be understood that one or more steps within a method may be executed in different order (or concurrently) without altering the principles of the present disclosure. Further, although each of the embodiments is described above as having certain features, any one or more of those features described with respect to any embodiment of the disclosure can be implemented in and / or combined with features of any of the other embodiments, even if that combination is not explicitly described. In other words, the described embodiments are not mutually exclusive, and permutations of one or more embodiments with one another remain within the scope of this disclosure.

[0051] Spatial and functional relationships between elements (for example, between modules, circuit elements, semiconductor layers, etc.) are described using various terms, including “connected,” “engaged,” “coupled,” “adjacent,” “next to,” “on top of,” “above,” “below,” and “disposed.” Unless explicitly described as being “direct,” when a relationship between first and second elements is described in the above disclosure, that relationship can be a direct relationship where no other intervening elements are present between the first and second elements, but can also be an indirect relationship where one or more intervening elements are present (either spatially or functionally) between the first and second elements.

[0052] The phrase at least one of A, B, and C should be construed to mean a logical (A OR B OR C), using a non-exclusive logical OR, and should not be construed to mean “at least one of A, at least one of B, and at least one of C.” The term subset does not necessarily require a proper subset. In other words, a first subset of a first set may be coextensive with (equal to) the first set.

[0053] In the figures, the direction of an arrow, as indicated by the arrowhead, generally demonstrates the flow of information (such as data or instructions) that is of interest to the illustration. For example, when element A and element B exchange a variety of information but information transmitted from element A to element B is relevant to the illustration, the arrow may point from element A to element B. ThisDocket Number: 00797-WO unidirectional arrow does not imply that no other information is transmitted from element B to element A. Further, for information sent from element A to element B, element B may send requests for, or receipt acknowledgements of, the information to element A.

[0054] In this application, including the definitions below, the term “module” or the term “controller” may be replaced with the term “circuit.” The term “module” may refer to, be part of, or include: an Application Specific Integrated Circuit (ASIC); a digital, analog, or mixed analog / digital discrete circuit; a digital, analog, or mixed analog / digital integrated circuit; a combinational logic circuit; a field programmable gate array (FPGA); a processor circuit (shared, dedicated, or group) that executes code; a memory circuit (shared, dedicated, or group) that stores code executed by the processor circuit; other suitable hardware components that provide the described functionality; or a combination of some or all of the above, such as in a system-on- chip.

[0055] The module may include one or more interface circuits. In some examples, the interface circuit(s) may implement wired or wireless interfaces that connect to a local area network (LAN) or a wireless personal area network (WPAN). Examples of a LAN are Institute of Electrical and Electronics Engineers (IEEE) Standard 802.11-2016 (also known as the WIFI wireless networking standard) and IEEE Standard 802.3-2015 (also known as the ETHERNET wired networking standard). Examples of a WPAN are IEEE Standard 802.15.4 (including the ZIGBEE standard from the ZigBee Alliance) and, from the Bluetooth Special Interest Group (SIG), the BLUETOOTH wireless networking standard (including Core Specification versions 3.0, 4.0, 4.1 , 4.2, 5.0, and 5.1 from the Bluetooth SIG).

[0056] The module may communicate with other modules using the interface circuit(s). Although the module may be depicted in the present disclosure as logically communicating directly with other modules, in various implementations the module may actually communicate via a communications system. The communications system includes physical and / or virtual networking equipment such as hubs, switches, routers, and gateways. In some implementations, the communications system connects to or traverses a wide area network (WAN) such as the Internet. For example, the communications system may include multiple LANs connected toDocket Number: 00797-WO each other over the Internet or point-to-point leased lines using technologies including Multiprotocol Label Switching (MPLS) and virtual private networks (VPNs).

[0057] In various implementations, the functionality of the module may be distributed among multiple modules that are connected via the communications system. For example, multiple modules may implement the same functionality distributed by a load balancing system. In a further example, the functionality of the module may be split between a server (also known as remote, or cloud) module and a client (or, user) module. For example, the client module may include a native or web application executing on a client device and in network communication with the server module.

[0058] Some or all hardware features of a module may be defined using a language for hardware description, such as IEEE Standard 1364-2005 (commonly called “Verilog”) and IEEE Standard 1076-2008 (commonly called “VHDL”). The hardware description language may be used to manufacture and / or program a hardware circuit. In some implementations, some or all features of a module may be defined by a language, such as IEEE 1666-2005 (commonly called “SystemC”), that encompasses both code, as described below, and hardware description.

[0059] The term code, as used above, may include software, firmware, and / or microcode, and may refer to programs, routines, functions, classes, data structures, and / or objects. The term shared processor circuit encompasses a single processor circuit that executes some or all code from multiple modules. The term group processor circuit encompasses a processor circuit that, in combination with additional processor circuits, executes some or all code from one or more modules. References to multiple processor circuits encompass multiple processor circuits on discrete dies, multiple processor circuits on a single die, multiple cores of a single processor circuit, multiple threads of a single processor circuit, or a combination of the above. The term shared memory circuit encompasses a single memory circuit that stores some or all code from multiple modules. The term group memory circuit encompasses a memory circuit that, in combination with additional memories, stores some or all code from one or more modules.

[0060] The term memory circuit is a subset of the term computer-readable medium. The term computer-readable medium, as used herein, does not encompassDocket Number: 00797-WO transitory electrical or electromagnetic signals propagating through a medium (such as on a carrier wave); the term computer-readable medium may therefore be considered tangible and non-transitory. Nonlimiting examples of a non-transitory computer-readable medium are nonvolatile memory circuits (such as a flash memory circuit, an erasable programmable read-only memory circuit, or a mask read-only memory circuit), volatile memory circuits (such as a static random access memory circuit or a dynamic random access memory circuit), magnetic storage media (such as an analog or digital magnetic tape or a hard disk drive), and optical storage media (such as a CD, a DVD, or a Blu-ray Disc).

[0061] The apparatuses and methods described in this application may be partially or fully implemented by a special purpose computer created by configuring a general purpose computer to execute one or more particular functions embodied in computer programs. The functional blocks and flowchart elements described above serve as software specifications, which can be translated into the computer programs by the routine work of a skilled technician or programmer.

[0062] The computer programs include processor-executable instructions that are stored on at least one non-transitory computer-readable medium. The computer programs may also include or rely on stored data. The computer programs may encompass a basic input / output system (BIOS) that interacts with hardware of the special purpose computer, device drivers that interact with particular devices of the special purpose computer, one or more operating systems, user applications, background services, background applications, etc.

[0063] The computer programs may include: (i) descriptive text to be parsed, such as HTML (hypertext markup language), XML (extensible markup language), or JSON (JavaScript Object Notation), (ii) assembly code, (iii) object code generated from source code by a compiler, (iv) source code for execution by an interpreter, (v) source code for compilation and execution by a just-in-time compiler, etc. As examples only, source code may be written using syntax from languages including C, C++, C#, ObjectiveC, Swift, Haskell, Go, SQL, R, Lisp, Java®, Fortran, Perl, Pascal, Curl, OCaml, JavaScript®, HTML5 (Hypertext Markup Language 5th revision), Ada, ASP (Active Server Pages), PHP (PHP: Hypertext Preprocessor), Scala, Eiffel, Smalltalk, Erlang, Ruby, Flash®, Visual Basic®, Lua, MATLAB, SIMULINK, and Python®.Docket Number: 00797-WO

[0064] A number of implementations have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the disclosure. Accordingly, other implementations are within the scope of the following claims.

Claims

Docket Number: 00797-WOCLAIMSWhat is claimed is:1 . A power supply system for reducing intermodulation distortion in a plasma chamber, comprising: a source RF generator configured to generate a source RF signal at a first frequency; a bias RF generator configured to generate a bias RF signal at a second frequency lower than the first frequency; a matching network coupled to the source RF generator and the bias RF generator; a load coupled to the matching network; and a controller configured to: receive a synchronization signal from the bias RF generator to synchronize operation of the source RF generator with the bias RF generator, obtain characteristic data corresponding to a reflected signal during an nth period of the bias RF signal, and adjust a frequency of the source RF signal during a period of the bias RF signal subsequent to the nth period based on the characteristic data obtained during the nth period.

2. The power supply system of claim 1 , wherein the characteristic data comprises average reflected power measured during the nth period of the bias RF signal.

3. The power supply system of claim 1 , wherein the characteristic data comprises an average reflection coefficient of the reflected signal measured during the nth period of the bias RF signal.

4. The power supply system of claim 1 , wherein the controller is further configured to divide each period of the bias RF signal into time segments of predetermined duration.

5. The power supply system of claim 4, wherein the controller is further configured to: select a measurement of a first characteristic during a time segment of each period of the bias RF signal based on a predetermined statistic; andDocket Number: 00797-WO report a measurement of a second characteristic during the time segment as a readback, wherein the second characteristic is different from the first characteristic.

6. The power supply system of claim 5, wherein the first characteristic is selected from a group consisting of a gamma signal, a forward power signal, and a reflected power signal.

7. The power supply system of claim 5, wherein the predetermined statistic is selected from a group consisting of a minimum value, a maximum value, and an average value.

10. A method for reducing intermodulation distortion in a plasma system, comprising: synchronizing a source RF generator with a bias RF generator based on a synchronization signal transmitted from the bias RF generator to the source RF generator; obtaining characteristic data corresponding to a reflected signal from an nth period of a bias RF signal generated by the bias RF generator; and adjusting a frequency of a source RF signal generated by the source RF generator during an n+1 th period of the bias RF signal based on the characteristic data obtained from the nth period.11 . The method of claim 10, wherein the characteristic data comprises average reflected power measured during the nth period of the bias RF signal.

12. The method of claim 10, wherein the characteristic data comprises an average reflection coefficient of the reflected signal measured during the nth period of the bias RF signal.

13. The method of claim 10, further comprising a step of dividing each period of the bias RF signal into time segments of predetermined duration.

14. The method of claim 13, further comprising: a step of selecting a measurement of a first characteristic during a time segment of each period of the bias RF signal based on a predetermined statistic; and a step of reporting a measurement of a second characteristic during the time segment as a readback, wherein the second characteristic is different from the first characteristic.Docket Number: 00797-WO15. The method of claim 14, wherein the first characteristic is selected from a group consisting of a gamma signal, a forward power signal, and a reflected power signal.

16. The method of claim 14, wherein the predetermined statistic is selected from a group consisting of a minimum value, a maximum value, and an average value.

17. A method for processing RF bias signals in a plasma system, comprising: dividing a period of an RF bias signal into time segments of predetermined duration; selecting a measurement of a first characteristic during a time segment of each period of the RF bias signal based on a predetermined statistic; and reporting a measurement of a second characteristic during the time segment as a readback, wherein the second characteristic is different from the first characteristic.

18. The method of claim 17, wherein the first characteristic is selected from a group consisting of a gamma signal, a forward power signal, and a reflected power signal.

19. The method of claim 18, wherein the predetermined statistic is selected from a group consisting of a minimum value, a maximum value, and an average value.

20. The method of claim 17, wherein the measurement of the second characteristic reported as the readback comprises a statistic of the second characteristic.21 . The method of claim 20, wherein the statistic of the second characteristic is selected from a group consisting of a minimum value, a maximum value, and a mean value.

22. A non-transitory computer-readable medium storing instructions that, when executed by a processor, cause the processor to: receive a synchronization signal from a bias RF generator to synchronize operation of a source RF generator with the bias RF generator; obtain characteristic data corresponding to a reflected signal during an nth period of a bias RF signal generated by the bias RF generator; andDocket Number: 00797-WO adjust a frequency of a source RF signal generated by the source RF generator during a period of the bias RF signal subsequent to the nth period based on the characteristic data obtained during the nth period.

23. The non-transitory computer-readable medium of claim 22, wherein the characteristic data comprises average reflected power measured during the nth period of the bias RF signal.

24. The non-transitory computer-readable medium of claim 22, wherein the instructions further cause the processor to divide each period of the bias RF signal into time segments of predetermined duration.

25. The non-transitory computer-readable medium of claim 24, wherein the instructions further cause the processor to: select a measurement of a first characteristic during a time segment of each period of the bias RF signal based on a predetermined statistic; and report a measurement of a second characteristic during the time segment as a readback, wherein the second characteristic is different from the first characteristic.

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