Provision of RF signals to a multi-station fabrication chamber

Abstract

Techniques for provision of RF signals to a multi-station fabrication chamber are provided. In some embodiments, a system may include: a first high frequency match circuit configured to perform impedance matching between a first high frequency RF source and a first subset of process stations; and a second high frequency match circuit configured to perform impedance matching between a second high frequency RF source and a second subset of the process stations. The system may include a first splitter / combiner configured to: receive a low frequency RF signal; and combine the low frequency RF signal and the first impedance matched high frequency RF signal to generate a first combined RF signal. The system may include a second splitter / combiner configured to: receive the low frequency RF signal; and combine the low frequency RF signal and the second impedance matched high frequency RF signal to generate a second combined RF signal.

Description

PROVISION OF RF SIGNALS TO A MULTI-STATION FABRICATION CHAMBERINCORPORATION BY REFERENCE

[0000] A PCT Request Form is filed concurrently with this specification as part of the present application. Each application that the present application claims benefit of or priority to as identified in the concurrently filed PCT Request Form is incorporated by reference herein in its entirety and for all purposes.BACKGROUND

[0001] Radio frequency (RF) sources are used to provide RF power to fabrication chambers. The RF power may be used in connection with plasma-based fabrication operations, such as plasma-based etch or deposition operations. Control of characteristics of the RF signal is important for control of the fabrication operation, however, it may be difficult to control such RF signal characteristics.

[0002] The background description provided herein is for the purposes of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.SUMMARY

[0003] Methods, systems, and apparatuses for provision of radio frequency (RF) signals to a multi-station fabrication chamber.

[0004] In accordance with some embodiments, a semiconductor fabrication chamber may comprise: a plurality of process stations; a first high frequency radio frequency (RF) source and a second high frequency RF source, wherein characteristics of signals generated by each of the first high frequency RF source and the second high frequency RF source are independently controlled; a low frequency RF source; a first high frequency match circuit configured to perform impedance matching between the first high frequency RF source and a first subset of the plurality of process stations to generate a first impedance matched high frequency RF signal; and a second high frequency match circuit configured to perform impedance matching between the second high frequency RF source and a second subset of the plurality of process stations to generate a second impedance matched high frequency RF signal. The chamber may further comprise a firstsplitter / combiner configured to: receive a low frequency RF signal from the low frequency RF source; combine the low frequency RF signal and the first impedance matched high frequency RF signal to generate a first combined RF signal; and provide the first combined RF signal to the first subset of the plurality of process stations. The chamber may further comprise a second splitter / combiner configured to: receive the low frequency RF signal from the low frequency RF source; combine the low frequency RF signal and the second impedance matched high frequency RF signal to generate a second combined RF signal; and provide the second combined RF signal to the second subset of the plurality of process stations.

[0005] In some examples, the characteristics of the signals generated by each of the first high frequency RF source and the second high frequency RF source that are independently controlled comprise a frequency of the signals, a power of the signals, and a phase of the signals, or any combination thereof.

[0006] In some examples, the first high frequency match circuit and the second high frequency match circuit each comprise components configured to provide a variable reactance, wherein the components are substantially identical. In some examples, the first high frequency match circuit and the second high frequency match circuit each comprise a substantially identical L-match circuit.

[0007] In some examples, the plurality of process stations comprises at least four process stations, and wherein the first subset of the plurality of process stations and the second subset of the plurality of process stations each comprise at least two process stations.

[0008] In some examples, the first subset of the plurality of process stations are operatively coupled to the first splitter / combiner via a first set of transmission lines, and wherein the second subset of the plurality of process stations are operatively coupled to the second splitter / combiner via a second set of transmission lines, and wherein each transmission line of the first set of transmission lines and the second set of transmission lines are substantially identical in length and impedance.

[0009] In some examples, the first high frequency match circuit and the second high frequency match circuit each perform impedance matching based on impedance and / or phase information indicative of an impedance associated with the first high frequency RF source and the second high frequency RF source, respectively, wherein the impedance and / or phase information is obtained from sensors operatively coupled to the first high frequency RF source and the second high frequency RF source.

[0010] In some examples, the first high frequency match circuit and the second high frequencymatch circuit each perform impedance matching based on impedance and / or phase information indicative of an impedance associated with the first high frequency RF source and the second high frequency RF source, respectively, wherein the impedance and / or phase information is obtained from sensors built in to the first high frequency RF source and the second high frequency RF source. In some examples, data from the sensors built in to the first high frequency RF source and the second high frequency RF source is transmitted to the first high frequency match circuit and the second high frequency match circuit, respectively. In some examples, the data is transmitted via an ETHERCAT connection.

[0011] In some examples, the first high frequency RF source is a leader and the second high frequency RF source is a follower such that characteristics of a signal provided by the second high frequency RF source are modified responsive to modification of characteristics of a signal provided by the first high frequency RF source.

[0012] In accordance with some embodiments, a system may comprise: a first high frequency match circuit configured to perform impedance matching between a first high frequency RF source and a first subset of a plurality of process stations of a multi-station tool to generate a first impedance matched high frequency RF signal; and a second high frequency match circuit configured to perform impedance matching between a second high frequency RF source and a second subset of the plurality of process stations to generate a second impedance matched high frequency RF signal. The system may comprise a first splitter / combiner configured to: receive a low frequency RF signal from a low frequency RF source; combine the low frequency RF signal and the first impedance matched high frequency RF signal to generate a first combined RF signal; and provide the first combined RF signal to the first subset of the plurality of process stations. The system may comprise a second splitter / combiner configured to: receive the low frequency RF signal from the low frequency RF source; combine the low frequency RF signal and the second impedance matched high frequency RF signal to generate a second combined RF signal; and provide the second combined RF signal to the second subset of the plurality of process stations.

[0013] In some examples, characteristics of the signals generated by each of the first high frequency RF source and the second high frequency RF source are independently controlled, and which comprise a frequency of the signals, a power of the signals, and a phase of the signals, or any combination thereof.

[0014] In some examples, the first high frequency match circuit and the second high frequency match circuit each comprise components configured to provide a variable reactance, wherein the components are substantially identical. In some examples, the first high frequency match circuit and the second high frequency match circuit each comprise a substantially identical L-matchcircuit.

[0015] In some examples, the first high frequency match circuit and the second high frequency match circuit each perform impedance matching based on impedance and / or phase information indicative of an impedance associated with the first high frequency RF source and the second high frequency RF source, respectively, wherein the impedance and / or phase information is obtained from sensors operatively coupled to the first high frequency RF source and the second high frequency RF source.

[0016] In some examples, the first high frequency match circuit and the second high frequency match circuit each perform impedance matching based on impedance and / or phase information indicative of an impedance associated with the first high frequency RF source and the second high frequency RF source, respectively, wherein the impedance and / or phase information is obtained from sensors built in to the first high frequency RF source and the second high frequency RF source.BRIEF DESCRIPTION OF THE DRAWINGS

[0017] FIG. 1A is a diagram of an example multi-station fabrication tool in accordance with some embodiments.

[0018] FIG. IB illustrates example RF matching circuitry for a multi-station fabrication tool in accordance with some embodiments.

[0019] FIG. 2 is a diagram of a system for providing RF signals to a multi-station tool using one high frequency (HF) RF generator in accordance with some embodiments.

[0020] FIG. 3 is a diagram of a system for providing RF signals to a multi-station tool using multiple HF RF generators in accordance with some embodiments.DETAILED DESCRIPTION

[0021] In the following description, numerous specific details are set forth to provide a thorough understanding of the presented embodiments. The disclosed embodiments may be practiced without some or all of these specific details. In other instances, well-known process operations have not been described in detail to not unnecessarily obscure the disclosed embodiments. While the disclosed embodiments will be described in conjunction with the specific embodiments, it will be understood that it is not intended to limit the disclosed embodiments.

[0022] A multi-station fabrication tool is a tool that includes multiple (e.g., two, four, eight, etc.)process stations, each of which may be used to perform fabrication operations on a wafer undergoing processing (which may happen concurrently). In conventional systems, a single high frequency (HF) RF source and a single low frequency (LF) RF source are used to provide HF RF signals and LF RF signals, respectively, to each station. In other words, the multi-station tool conventionally utilizes one HF RF source and one LF RF source to provide RF signals for all of the stations of the multi-station tool.

[0023] However, utilizing the same HF RF source and the same LF RF source to provide RF signals to all of the stations of the multi-station tool limits the RF signal delivered to each station to being the same. In other words, the characteristics of the delivered RF signal, which may include signal frequency, power, and / or signal phase, are the same for all stations. It may be desirable in some instances to deliver different signals to different stations of a multi-station tool. For example, it may be desirable to deliver signals of different frequencies, different powers, and / or different phases to different stations. Delivery of different signals may allow for tighter control of fabrication processes, improved power delivery (e.g., by reducing reflected power), etc.

[0024] Disclosed herein are systems, techniques, and apparatuses for utilizing multiple HF RF sources (sometimes referred to herein as an “RF generator”) on a single multi-station tool (e.g., as shown in and described below in connection with FIG. 1A). Each HF RF source may be independently controlled. That is, characteristics of the RF signal provided by each RF source may be independently controlled such that the HF RF signals generated from each may differ in frequency, power, and / or phase. Accordingly, different stations of the multi-station tool may receive different HF RF signals. It should be understood that although the example provided herein generally relate to a multi-station tool with multiple process stations that, e.g., have a common housing, the techniques used herein may be generally applicable to provide RF signals to multiple processing environments that use a shared RF generator, regardless of whether the multiple processing environments share a common housing and / or any other common components.

[0025] As described above, one or more process stations may be included in a multi-station processing tool. Figure 1A shows a schematic view of an embodiment of a multi-station processing tool 100 with an inbound load lock 102 and an outbound load lock 104, either or both of which may include a remote plasma source. A robot 106 at atmospheric pressure is configured to move wafers from a cassette loaded through a pod 108 into inbound load lock 102 via an atmospheric port 110. A wafer is placed by the robot 106 on a pedestal 112 in the inbound load lock 102, the atmospheric port 110 is closed, and the load lock is pumped down. Where the inbound load lock 102 includes a remote plasma source, the wafer may be exposed to a remote plasma treatment in the load lock prior to being introduced into a processing chamber 114. Further,the wafer also may be heated in the inbound load lock 102 as well, for example, to remove moisture and adsorbed gases. Next, a chamber transport port 116 to processing chamber 114 is opened, and another robot (not shown) places the wafer into the reactor on a pedestal of a first station shown in the reactor for processing. While the embodiment depicted in Figure 1 A includes load locks, it will be appreciated that, in some embodiments, direct entry of a wafer into a process station may be provided.

[0026] The depicted processing chamber 114 includes four process stations, numbered from 1 to 4 in the embodiment shown in Figure 1A. Each station has a heated pedestal (shown at 118 for station 1), and gas line inlets. It will be appreciated that in some embodiments, each process station may have different or multiple purposes. For example, in some embodiments, a process station may be switchable between an ALD and plasma-enhanced ALD process mode. Additionally or alternatively, in some embodiments, processing chamber 114 may include one or more matched pairs of ALD and plasma-enhanced ALD process stations. While the depicted processing chamber 114 includes four stations, it will be understood that a processing chamber according to the present disclosure may have any suitable number of stations. For example, in some embodiments, a processing chamber may have five or more stations, while in other embodiments a processing chamber may have three or fewer stations.

[0027] It should be understood that the various references to RF power settings of the present disclosure are generally intended, unless otherwise indicated, to refer to the RF power setting per wafer. In embodiments involving multiple process stations in a multi-station processing tool, one or more RF power sources may be provided that serve multiple process stations (e.g., simultaneously and / or sequentially). In embodiments in which a single RF power source serves multiple process stations, the per- wafer power setting of the RF power source may be multiplied by the number of process stations being simultaneously provided with plasma at a desired power level. In other words, when the present disclosure describes an RF power setting of 300 watts, it should be understood that the RF power setting reflects a per-wafer value of 300 watts and that, in multi-station processing tools, the actual RF power setting of the RF power source may be the per- wafer power setting multiplied by the number of stations.

[0028] Moreover, it should be understood that the various references to RF power settings of the present disclosure are generally intended, unless otherwise indicated, to refer to the RF power setting used with a 300-mm wafer. The RF power settings described herein may be adjusted when depositing material on substrates or wafers having dimensions other than that of a 300-mm wafer.

[0029] Figure 1 A depicts an embodiment of a wafer handling system 190 for transferring wafers within processing chamber 114. In some embodiments, wafer handling system 190 may transferwafers between various process stations and / or between a process station and a load lock. It will be appreciated that any suitable wafer handling system may be employed. Non- limiting examples include wafer carousels and wafer handling robots. Figure 1 A also depicts an embodiment of a system controller 150 employed to control process conditions and hardware states of multi-station processing tool 100. System controller 150 may include one or more memory devices 156, one or more mass storage devices 154, and one or more processors 152. Processor 152 may include a CPU or computer, analog, and / or digital input / output connections, stepper motor controller boards, etc.

[0030] In some embodiments, system controller 150 controls all of the activities of multi-station processing tool 100. System controller 150 executes system control software 158 stored in mass storage device 154, loaded into memory device 156, and executed on processor 152. Alternatively, the control logic may be hard coded in the system controller 150. Applications Specific Integrated Circuits, Programmable Logic Devices (e.g., field-programmable gate arrays, or FPGAs) and the like may be used for these purposes. In the following discussion, wherever “software” or “code” is used, functionally comparable hard coded logic may be used in its place. System control software 158 may include instructions for controlling the timing, mixture of gases, gas flow rates, chamber and / or station pressure, chamber and / or station temperature, wafer temperature, target power levels, RF power levels, substrate pedestal, chuck and / or susceptor position, and other parameters of a particular process performed by multi-station processing tool 100. System control software 158 may be configured in any suitable way. For example, various process tool component subroutines or control objects may be written to control operation of the process tool components used to carry out various process tool processes. System control software 158 may be coded in any suitable computer readable programming language.

[0031] In some embodiments, system control software 158 may include input / output control (IOC) sequencing instructions for controlling the various parameters described above. Other computer software and / or programs stored on mass storage device 154 and / or memory device 156 associated with system controller 150 may be employed in some embodiments. Examples of programs or sections of programs for this purpose include a substrate positioning program, a process gas control program, a pressure control program, a heater control program, and a plasma control program.

[0032] A substrate positioning program may include program code for process tool components that are used to load the substrate onto pedestal 118 and to control the spacing between the substrate and other parts of multi-station processing tool 100.

[0033] A process gas control program may include code for controlling gas composition (e.g.,iodine-containing silicon precursor gases, and nitrogen-containing gases, carrier gases and purge gases as described herein) and flow rates and optionally for flowing gas into one or more process stations prior to deposition in order to stabilize the pressure in the process station. A pressure control program may include code for controlling the pressure in the process station by regulating, for example, a throttle valve in the exhaust system of the process station, a gas flow into the process station, etc.

[0034] A heater control program may include code for controlling the current to a heating unit that is used to heat the substrate. Alternatively, the heater control program may control delivery of a heat transfer gas (such as helium) to the substrate.

[0035] A plasma control program may include code for setting RF power levels applied to the process electrodes in one or more process stations in accordance with the embodiments herein.

[0036] A pressure control program may include code for maintaining the pressure in the reaction chamber in accordance with the embodiments herein.

[0037] In some embodiments, there may be a user interface associated with system controller 150. The user interface may include a display screen, graphical software displays of the apparatus and / or process conditions, and user input devices such as pointing devices, keyboards, touch screens, microphones, etc.

[0038] In some embodiments, parameters adjusted by system controller 150 may relate to process conditions. Non-limiting examples include process gas composition and flow rates, temperature, pressure, plasma conditions (such as RF bias power levels), etc. These parameters may be provided to the user in the form of a recipe, which may be entered utilizing the user interface.

[0039] Signals for monitoring the process may be provided by analog and / or digital input connections of system controller 150 from various process tool sensors. The signals for controlling the process may be output on the analog and digital output connections of multi-station processing tool 100. Non-limiting examples of process tool sensors that may be monitored include mass flow controllers, pressure sensors (such as manometers), thermocouples, etc. Appropriately programmed feedback and control algorithms may be used with data from these sensors to maintain process conditions.

[0040] System controller 150 may provide program instructions for implementing the abovedescribed deposition processes. The program instructions may control a variety of process parameters, such as DC power level, RF bias power level, pressure, temperature, etc. The instructions may control the parameters to operate in-situ deposition of film stacks according tovarious embodiments described herein.

[0041] The system controller 150 will typically include one or more memory devices 156 and one or more processors configured to execute the instructions so that the apparatus will perform a method in accordance with disclosed embodiments. Machine-readable media containing instructions for controlling process operations in accordance with disclosed embodiments may be coupled to the system controller 150.

[0042] In some implementations, the system controller 150 is part of a system, which may be part of the above -described examples. Such systems can include semiconductor processing equipment, including a processing tool or tools, chamber or chambers, a platform or platforms for processing, and / or specific processing components (a wafer pedestal, a gas flow system, etc.). These systems may be integrated with electronics for controlling their operation before, during, and after processing of a semiconductor wafer or substrate. The electronics may be referred to as the “controller,” which may control various components or subparts of the system or systems. The system controller 150, depending on the processing conditions and / or the type of system, may be programmed to control any of the processes disclosed herein, including the delivery of processing gases, temperature settings (e.g., heating and / or cooling), pressure settings, vacuum settings, power settings, radio frequency (RF) generator settings, RF matching circuit settings, frequency settings, flow rate settings, fluid delivery settings, positional and operation settings, wafer transfers into and out of a tool and other transfer tools and / or load locks connected to or interfaced with a specific system.

[0043] Broadly speaking, the system controller 150 may be defined as electronics having various integrated circuits, logic, memory, and / or software that receive instructions, issue instructions, control operation, enable cleaning operations, enable endpoint measurements, and the like. The integrated circuits may include chips in the form of firmware that store program instructions, digital signal processors (DSPs), chips defined as application specific integrated circuits (ASICs), and / or one or more microprocessors, or microcontrollers that execute program instructions (e.g., software). Program instructions may be instructions communicated to the system controller 150 in the form of various individual settings (or program files), defining operational parameters for carrying out a particular process on or for a semiconductor wafer or to a system. The operational parameters may, in some embodiments, be part of a recipe defined by process engineers to accomplish one or more processing steps during the fabrication of one or more layers, materials, metals, oxides, silicon, silicon dioxide, surfaces, circuits, and / or dies of a wafer.

[0044] The system controller 150, in some implementations, may be a part of or coupled to a computer that is integrated with, coupled to the system, otherwise networked to the system, or acombination thereof. For example, the system controller 150 may be in the “cloud” or all or a part of a fab host computer system, which can allow for remote access of the wafer processing. The computer may enable remote access to the system to monitor current progress of fabrication operations, examine a history of past fabrication operations, examine trends or performance metrics from a plurality of fabrication operations, to change parameters of current processing, to set processing steps to follow a current processing, or to start a new process. In some examples, a remote computer (e.g. a server) can provide process recipes to a system over a network, which may include a local network or the Internet. The remote computer may include a user interface that enables entry or programming of parameters and / or settings, which are then communicated to the system from the remote computer. In some examples, the system controller 150 receives instructions in the form of data, which specify parameters for each of the processing steps to be performed during one or more operations. It should be understood that the parameters may be specific to the type of process to be performed and the type of tool that the system controller 150 is configured to interface with or control. Thus as described above, the system controller 150 may be distributed, such as by including one or more discrete controllers that are networked together and working towards a common purpose, such as the processes and controls described herein. An example of a distributed controller for such purposes would be one or more integrated circuits on a chamber in communication with one or more integrated circuits located remotely (such as at the platform level or as part of a remote computer) that combine to control a process on the chamber.

[0045] Without limitation, example systems may include a plasma etch chamber or module, a deposition chamber or module, a spin-rinse chamber or module, a metal plating chamber or module, a clean chamber or module, a bevel edge etch chamber or module, a physical vapor deposition (PVD) chamber or module, a chemical vapor deposition (CVD) chamber or module, an PEALD chamber or module, an atomic layer etch (ALE) chamber or module, an ion implantation chamber or module, a track chamber or module, and any other semiconductor processing systems that may be associated or used in the fabrication and / or manufacturing of semiconductor wafers.

[0046] As noted above, depending on the process step or steps to be performed by the tool, the system controller 150 might communicate with one or more of other tool circuits or modules, other tool components, cluster tools, other tool interfaces, adjacent tools, neighboring tools, tools located throughout a factory, a main computer, another controller, or tools used in material transport that bring containers of wafers to and from tool locations and / or load ports in a semiconductor manufacturing factory.

[0047] In some embodiments, an RF signal may be provided to a process station, which may be used to perform plasma-based fabrication operations within the process station. The RF signalmay include a combination of low frequency (LF) RF signals and high frequency (HF) RF signals, and a combined signal may be provided to each station. Due to impedance associated with the plasma in the process station, there may be a mismatch between the load impedance at the process station and a source impedance at an RF source (sometimes referred to herein as an RF generator). The impedance mismatch may cause reflected power, which can reduce the effectiveness of the fabrication process.

[0048] Impedance matching is typically performed by changing the impedance associated with the RF input network. Because reactance is the imaginary components of impedance, changing the impedance may be accomplished by changing inductance and / or capacitance (e.g., of a variable capacitor and / or variable inductor), or by changing the frequency of the input signal. Note that, as used herein, the “input network” generally refers to the RF signal generator and match circuitry, where the match circuitry is configured to modify the reactance associated with the input network (generally referred to herein as “input impedance” or “source impedance”). Conventional techniques may perform impedance matching by actuating a variable capacitor and / or a variable inductor of the match circuitry such that the capacitance changes such that the load impedance at the process station and the impedance of the RF input network are matched. Because changing the capacitance in turn changes the reactance (i.e., the imaginary part of impedance) of the input network, the impedances between the load at the process station(s) and the source impedance at the RF input network are matched. The variable capacitor is sometimes referred to as “a variable reactance” element, because modifying the capacitance of the variable capacitor in turn changes the reactance. For example, the capacitance may be changed such that the complex conjugate of the source impedance is substantially similar to, close to, or matches the load impedance.

[0049] In general, match circuitry may include variable impedance elements. In one example, match circuitry may include a series impedance and a shunt impedance. In some embodiments, a variable impedance element may be a variable reactance element whose reactance may be changed. Example variable reactance elements may include a variable capacitor or a variable inductor. In some embodiments, match circuitry may include multiple variable reactance elements. In one example, match circuitry may include an L-match circuit.

[0050] FIG. IB is a block diagram showing various components of a system utilized to perform a semiconductor fabrication process, according to an implementation 151. Note that the example shown in FIG. IB utilizes a single HF RF source and a single LF RF source. In FIG. IB, RF signal generators 155 and 160 are utilized to generate an excitation signal, which may bring about formation of a plasma within stations 102A, 102B, 102C, and 102D of the process chamber. Stations 102A, 102B, 102C, and 102D may correspond to stations of a semiconductor processchamber, as previously described in reference to FIG. 1A. Thus, in the implementation of FIG. IB, RF signal generator 155 may generate a relatively low-frequency signal, such as a signal of approximately 400 kHz, while RF signal generator 160 generates a relatively high-frequency signal, such as a signal of approximately 27.12 MHz. It should be noted, however, that these represent merely example frequencies. In other implementations, differing radio frequencies may be generated, and implementations are not limited to 400 kHz and 27.12 MHz signals. For example, in particular instances, a relatively low-frequency may correspond to a frequency of between 360 kHz and 440 kHz. In another instance, a relatively high-frequency may correspond to a frequency of between 26.5 MHz and 27.5 MHz.

[0051] In FIG. IB, an RF transmission line coupling signal generator 155 to low- frequency matching network 158 as well as a radio frequency transmission line coupling signal generator 160 to high-frequency matching network 163 may involve a characteristic impedance of 50 ohms. However, other implementations may utilize transmission lines having differing characteristic impedances, such as 70 ohms, 300 ohms, and so forth. In the implementation of FIG. IB, low- frequency matching network 158 and high-frequency matching network 163 operate to match the load presented by power divider 170 to the output impedance of signal generator 155 and signal generator 160 (respectively). Such matching brings about an ability to couple maximum power transfer from radio frequency signal generators 155 and 160 to power divider 170. Accordingly, even when power divider 170 presents a highly reactive load (e.g., a complex impedance having a relatively small real component and a large reactive component) maximum power can be transferred from signal generators 155 and 160 to power divider 170. Matching networks 158 and 163 may utilize various reactive components, such as inductors and / or capacitors, which operate to compensate for the highly reactive load that may be presented by power divider 170.

[0052] In particular implementations, components of matching networks 158 / 163 may be arranged so as to match a particular load presented by low-frequency and high-frequency input ports of power divider 170, which may operate to provide plasma-generating power via output ports 171, 172, 173 and 174. However, during plasma-based etching operations or during other plasma-based processes (for example), a load, such as a reactive load presented by the formation of plasma within stations 102A, 102B, 102C, and 102D of a process chamber, may begin to vary or drift. Accordingly, for example, during the initial moments of plasma generation (e.g., the initial 30-60 seconds) output signal amplitudes from ports 171-174 may correspond to substantially equal quantities. However, as plasma generation progresses, output signal amplitudes from ports 171-174 may begin to differ. Such differences may be brought about by changes in loads presented by stations 102A-102D of the process chamber. Thus, in someinstances, in response to varying reactive loads presented by stations 102A-102D of the process chamber, actual power coupled from power divider ports 171-174 may vary by values ranging from 0.0% to 100.0%. Additionally, RF power flow to a station can be set to 0.0, or other negligible amount, by way of entering 0.0 Watt as a setpoint. Alternatively, capacitance of a variable capacitor may be adjusted to a value that brings about a current flow that approaches or approximates 0.0 Ampere.

[0053] Note that in the example shown in FIG. IB, power divider 170 is a fixed passive device, and accordingly, the configuration of FIG. IB may be categorized as an “open-loop” plasma generation system in that during plasma generation operations, it may be difficult to ensure constant, uniform power transfer from power divider 170 to stations 102A-102D. However, in some implementations, the power divider may be an active power divider. Without additional controls, such as controls operating to provide real-time, closed-loop tuning of reactive components within low-frequency matching network 158 and high-frequency matching network 163 in response to variances in reactive loads presented by stations 102A-102D, undesirable consequences may result. Such consequences may include under etching, in which an insufficient material is removed from a semiconductor wafer, over etching, in which an excessive amount of material is removed from a semiconductor wafer, for example. In some instances, such under etching and / or over etching may result in a need to scrap an etched semiconductor wafer, resulting in increased cost, schedule delay, and so forth.

[0054] In conventional systems, a single HF RF generator and a single LF RF generator may be used to provide RF signals to all stations of a multi-station tool. A HF match circuit may match impedance of the stations to an input impedance of the HF RF generator, and similarly, a LF match circuit may match impedance of the stations to the input impedance of the LF RF generator. The matched signals may be provided to a splitter / combiner circuit configured to split the RF signals (which may comprise both HF RF signals and LF RF signals) and provide the split RF signals to each station of the multi-station tool. Because each RF generator is relatively expensive, conventional techniques leverage use of a single HF RF generator and a single LF RF generator to provide RF signals for multiple tools. However, because only a single HF RF generator and a single LF RF generator are used, the same signal (in terms of frequency and phase) is provided to each station. Various techniques may be used to try to induce phase offsets in the provided RF signals for different stations, however, these techniques may cause downstream problems. For example, the frequency provided by the RF generator may be tuned as part of the impedance matching process, and conventional techniques to introduce phase offsets may cause unwanted effects on the power provided to each station due to the interaction with frequency tuning.

[0055] FIG. 2 is a diagram of a system that utilizes a single HF RF generator to provide HF RF signals to multiple stations of a multi-station tool. As illustrated, the multi-station tool includes stations 202, 204, 206, and 208. Each station is associated with one or more voltage-sensor (VT) probes, such as VI probe 210 of station 202. Each VI probe may be configured to measure and / or determine impedance and / or phase information indicative of an impedance associated with the signal received at the station.

[0056] As illustrated, the system includes an LF generator 212 and an HF generator 220. LF match circuitry 216 performs impedance matching between the impedance at LF generator 212 and an impedance at an input to splitter / combiner 218. Note that the impedance at the input to splitter / combiner 218 is dependent on the impedance at each process station load (e.g., based on fluctuations in plasma impedance). LF match circuitry 216 may comprise one or more variable impedance elements (e.g., a shunt impedance and / or a series impedance), which may comprise one or more variable reactance elements which may be actuated and / or tuned as part of the impedance matching process. In some embodiments, LF match circuitry 216 may perform impedance matching based at least in part on signals obtained from VI probe 214, which may indicate impedance and / or phase information associated with the signal provided by LF generator 212.

[0057] Similarly, HF match circuit 224 may perform impedance matching between the impedance at HF generator 220 and an impedance at an input of splitter / combiner 218. HF match circuitry 224 may comprise one or more variable impedance elements, such as a shunt impedance 226 and / or a series impedance 228. In some embodiments, the variable impedance elements may comprise one or more variable reactance elements, such as one or more variable capacitors and / or one or more variable inductors which may be actuated to provide a variable reactance, and therefore a variable impedance as part of the impedance matching process. In some embodiments, HF match circuitry 224 may perform impedance matching based at least in part on signals obtained from VI probe 222, which may indicate impedance and / or phase information associated with the signal provided by HF generator 220.

[0058] Splitter / combiner 218 may be configured to combine a LF RF signal and a HF RF signal and then split the combined signal such that a split signal that includes both LF signal and HF signal are provided to each of stations 202-208. HF match 224 and LF match 216 provide and impedance match from the respective generators and splitter / combiner 218.

[0059] Disclosed herein are systems, methods, and techniques for utilizing multiple HF RF generators to provide signals to multiple stations of a multi-station tool. For example, in some embodiments, a first HF RF generator may provide first HF RF signals to be used for a first subset of stations of the multi-station tool, and a second HF RF generator may provide second HF RFsignals to be used for a second subset of stations of the multi-station tool. Note that, in some embodiments, more than two HF RF generators may be used (e.g., three, five, eight, etc.). In some embodiments, each HF RF generator may provide HF RF signals to the same number of stations (e.g., each HF RF generator may provide HF RF signals to two stations, four stations, etc.). Alternatively, in some embodiments, each HF RF generator may provide HF RF signals to a differing number of stations (e.g., a first HF RF generator may provide signals for two stations, a second HF RF generator may provide signals for three stations, and a third HF RF generator may provide signals for four stations, or the like). In some embodiments, different stations of a multistation tool may receive an RF signal with characteristics (e.g., frequency, phase, amplitude, etc.) that is dependent on the characteristics of a wafer undergoing processing in the station. In some such embodiments, the characteristics of the RF signal may be dynamically adjusted during a fabrication process based on in situ characterization of wafer properties as the fabrication process occurs.

[0060] Note that each HF RF generator may be independently controllable. In particular, characteristics of signals generated by each HF RF generator may be independently controlled. The characteristics may include a frequency of the signals, a power of the signals, a phase of the signals, or any combination thereof.

[0061] Matching circuitry may be used to perform impedance matching. A match circuit may be associated with each HF RF generator. The match circuit may be configured to perform impedance matching between the corresponding HF RF generator (e.g., the HF RF source) and impedance at the input of a corresponding splitter / combiner, which incorporates impedance of the subset of the process stations of the multi-station tool to which the HF RF generator is providing signals. Note that each HF RF generator may utilize its own match circuit. Each match circuit may comprise components configured to provide a variable impedance. For example, the components may comprise a series impedance and / or a shunt impedance. The variable impedance may be implemented using one or more variable reactance elements (e.g., one or more variable capacitors and / or one or more variable inductors). The components may comprise an L-match circuit. Note that, the match circuits associated with the different HF RF generators may be substantially identical. For example, each match circuit may utilize substantially identical components (e.g., components having the same specifications, components having the same variable reactance range, components having the same model number of part number, etc.). In some embodiments, each match circuit may be functionally identical, e.g., such that each match circuit may modify reactance with substantially the same reactance range, may modify reactance within substantially the same time duration, etc. In this way, the behavior of the different matchcircuits associated with the different HF RF generators may be substantially identical. It should be understood, however, that in some embodiments, match circuits associated with the different HF RF generators may be different and / or may include different matching elements or components. For example, the HF RF generators may be different from each other (e.g., having different specifications, being of different types or models, etc.), and accordingly the matching components of each match circuit may be different.

[0062] Each HF match circuit may perform impedance matching based on impedance and / or phase information indicative of an impedance associated with the corresponding HF RF generator. In some embodiments, the impedance and / or phase information may be obtained from one or more sensors operatively coupled to the HF RF generator and the HF match circuit (e.g., such that the one or more sensors are configured to sense impedance and / or phase characteristics of the signal provided by the HF RF generator and provide such information to the HF match circuit). Additionally or alternatively, in some embodiments, the impedance and / or phase information may be obtained from one or more sensors built into the HF RF generator. In some embodiments, the sensor data from the one or more built in sensors may be transmitted to the corresponding HF match circuit. In some embodiments, the transmission may be via an ETHERCAT connection.

[0063] Each match circuit may provide signals to a corresponding splitter / combiner circuit. Each splitter / combiner may be configured to receive LF RF signals from an LF RF generator and combine the LF RF signal with an impedance matched HF RF signal from the corresponding match circuit. The splitter / combiner may then provide the combined RF signal to a subset of process stations of the multi-station tool. Note that the number of HF RF generators, the number of match circuits, and the number of splitter / combiner circuits may all be the same such that each HF RF generator is associated with one match circuit and one splitter / combiner. However, the splitter / combiner may provide combined signals to one or more process stations (e.g., one, two, four, eight, etc.) that are less than the total number of process stations of the multi-station tool. Additionally, it should be noted that in some embodiments, there may be one LF RF generator that provides LF RF signals for all stations, and a corresponding LF RF match circuit to provide impedance matching of the LF RF signal.

[0064] Each process station may be operatively coupled to a splitter / combiner via a transmission line. Note that each transmission line may be substantially identical in length. This may ensure identical, or near identical behavior, of provision of RF signals to each station apart from the effects of the independently controlled HF RF generators. As used herein, identical, “near identical,” and / or “substantially identical,” should be understood to mean that differences (e.g., differences in transmission line length or other metrics) result in behavior that is within + / - 1%, + / - 5%, or thelike.

[0065] In some implementations, one HF RF generator may be a leader and the other one or more HF RF generators may be followers. Characteristics of a signal provided by the follower HF RF generator(s) may be modified responsive to modification of characteristics of a signal provided by the leader HF RF generator. For example, in an instance in which a frequency of the HF RF signal provided by the leader HF RF generator is modified and in which the frequencies of the signals provided by the follower HF RF generator(s) are to be locked to that of the leader, the frequencies of the signal(s) provided by the follower HF RF generator(s) may be changed to match the frequency of the leader HF RF generator. As another example, in an instance in which a leader HF RF generator and a follower HF RF generator are to be phase locked with a particular phase offset (e.g., 90 degrees, 180 degrees, etc.), the phase of the follower HF RF generator may be modified to maintain the phase offset responsive to the phase of the signal provided by the leader HF RF generator being modified. In some embodiments, the frequencies of different HF RF generators may follow and / or be individually offset from a common external exciter such that no individual HF RF generator is a leader, and instead, characteristics of the signals generated by each HF RF generator are dependent on a common external system.

[0066] FIG. 3 is a diagram of an example system for providing RF signals to a multi-station tool using multiple HF RF generators in accordance with some embodiments. As illustrated, the multistation tool may include stations 302, 304, 306, and 308. Note that although the example depicted in FIG. 3 includes three stations, in some embodiments, the multi-station tool may have two, eight, sixteen, etc. stations. Each station may be associated with a VI probe, such as VI probe 310 associated with station 302.

[0067] As illustrated, an LF RF generator 312 provides LF RF signals. An LF RF match circuit may be configured to perform impedance matching. Impedance matching may be performed using impedance and / or phase characteristics associated with the LF RF signals, which may be determined based on VI probe 316.

[0068] Note that, unlike what is shown in FIG. 2, the system depicted in FIG. 3 includes two HF RF generators, 320a and 320b. As described above, characteristics of the signals provided by each of HF RF generators 320a and 320b may be independently controlled. For example, these characteristics may include frequency of the signal, phase of the signal, power of the signal, and / or any combination thereof. Each HF RF generator may provide HF RF signals to a corresponding match circuit. For example, signals from HF RF generator 320a are provided to HF match circuit 324a, and signals from HF RF generator 320b are provided to HF match circuit 324b. Each match circuit performs impedance matching based on the input impedance associated with itscorresponding HF RF generator. Impedance matching may be performed based on impedance and / or phase characteristics, which may be determined based on data from VI probes 330a and / or 330b. Note that, in some embodiments, impedance matching may be performed based on impedance and / or phase characteristics obtained from sensors built into each HF RF generator, which may be transmitted to each match circuit (e.g., via an ETHERCAT connection).

[0069] As depicted, each match circuit may be substantially identical. For example, each match circuit may comprise substantially identical variable impedance components, such as shunt impedance 326 and series impedance 328. As a more particular example, each match circuit may include variable reactance components (e.g., one or more variable capacitors and / or one or more variable inductors) that provide the same range of reactance (e.g., by providing the same range of capacitance and / or inductance), that have the same or similar specifications in other respects, or any combination thereof.

[0070] Each match circuit may provide an impedance matched HF RF signal to a corresponding splitter / combiner. For example, HF match circuit 324a may provide an HF RF signal to splitter / combiner 318a, and HF match circuit 324b may provide an HF RF signal to splitter / combiner 318b. Each splitter / combiner may be configured to combine the HF RF signal received from the corresponding match circuit with an LF RF signal obtained via LF RF generator 312 (which may be impedance matched via LF RF match circuit 314). Each splitter / combiner is configured to generate a combined HF and LF RF signal, and is configured to provide the combined signal to a subset of the stations of the multi-station tool. For example, as shown in FIG. 3, splitter / combiner 318a provides a combined signal to stations 302 and 304, and splitter / combiner 318b provides a combined signal to stations 306 and 308.

[0071] Note that use of multiple HF RF generators may reduce the amount of current each match circuit must deliver to each station, and correspondingly, reduce the amount of power consumed by each match circuit, leading to substantial power savings and efficiency improvement. For example, referring to the system depicted in FIG. 2 which utilizes a single HF RF generator and a single HF RF match circuit, if each station is to receive a current of I, the HF RF match circuit must provide 41 current. In contrast, referring to the system depicted in FIG. 3 which utilizes two HF RF generators and corresponding two HF RF match circuits, each HF RF match circuit need only provide 21 current (with each station receiving I). Because power scaled with the square of current, halving the current required to be provided by each match circuit results in a factor of 4 improvement in power consumption. This can result in use of smaller hardware, which may improve space constraints, cost of hardware, etc.

[0072] Additionally, because each HF RF generator can be independently controlled,characteristics of the HF RF signal (e.g., frequency, power, phase, or any combination thereof) can be independently controlled while keeping all other aspects (e.g., transmission line length, match circuitry components, etc.) the same. This may result in improved power delivery at a system level within the chamber to each station. Note that the techniques disclosed herein may be used to provide RF power to multiple different processing environments that share at least one generator, regardless of whether the different processing environments share a common external housing or any other common components other than the at least one generator and associated match circuitry and splitter / combiner.CONCLUSION

[0073] Although the foregoing embodiments have been described in some detail for purposes of clarity of understanding, it will be apparent that certain changes and modifications may be practiced within the scope of the appended claims. It should be noted that there are many alternative ways of implementing the processes, systems, and apparatus of the present embodiments. Accordingly, the present embodiments are to be considered as illustrative and not restrictive, and the embodiments are not to be limited to the details given herein.

Claims

CLAIMSWhat is claimed is:

1. A semiconductor fabrication chamber, comprising: a plurality of process stations; a first high frequency radio frequency (RF) source and a second high frequency RF source, wherein characteristics of signals generated by each of the first high frequency RF source and the second high frequency RF source are independently controlled; a low frequency RF source; a first high frequency match circuit configured to perform impedance matching between the first high frequency RF source and a first subset of the plurality of process stations to generate a first impedance matched high frequency RF signal; a second high frequency match circuit configured to perform impedance matching between the second high frequency RF source and a second subset of the plurality of process stations to generate a second impedance matched high frequency RF signal; a first splitter / combiner configured to: receive a low frequency RF signal from the low frequency RF source, combine the low frequency RF signal and the first impedance matched high frequency RF signal to generate a first combined RF signal, and provide the first combined RF signal to the first subset of the plurality of process stations; and a second splitter / combiner configured to: receive the low frequency RF signal from the low frequency RF source, combine the low frequency RF signal and the second impedance matched high frequency RF signal to generate a second combined RF signal, and provide the second combined RF signal to the second subset of the plurality of process stations.

2. The semiconductor fabrication chamber of claim 1 , wherein the characteristics of the signals generated by each of the first high frequency RF source and the second high frequency RF source that are independently controlled comprise a frequency of the signals, a power of the signals, and a phase of the signals, or any combination thereof.

3. The semiconductor fabrication chamber of claim 1, wherein the first high frequency match circuit and the second high frequency match circuit each comprise components configured to provide a variable reactance, wherein the components are substantially identical.

4. The semiconductor fabrication chamber of claim 3, wherein the first high frequency match circuit and the second high frequency match circuit each comprise a substantially identical L-match circuit.

5. The semiconductor fabrication chamber of claim 1, wherein the plurality of process stations comprises at least four process stations, and wherein the first subset of the plurality of process stations and the second subset of the plurality of process stations each comprise at least two process stations.

6. The semiconductor fabrication chamber of any one of claims 1-5, wherein the first subset of the plurality of process stations are operatively coupled to the first splitter / combiner via a first set of transmission lines, and wherein the second subset of the plurality of process stations are operatively coupled to the second splitter / combiner via a second set of transmission lines, and wherein each transmission line of the first set of transmission lines and the second set of transmission lines are substantially identical in length and impedance.

7. The semiconductor fabrication chamber of any one of claims 1-5, wherein the first high frequency match circuit and the second high frequency match circuit each perform impedance matching based on impedance and / or phase information indicative of an impedance associated with the first high frequency RF source and the second high frequency RF source, respectively, wherein the impedance and / or phase information is obtained from sensors operatively coupled to the first high frequency RF source and the second high frequency RF source.

8. The semiconductor fabrication chamber of any one of claims 1-5, wherein the first high frequency match circuit and the second high frequency match circuit each perform impedance matching based on impedance and / or phase information indicative of an impedance associated with the first high frequency RF source and the second high frequency RF source, respectively,wherein the impedance and / or phase information is obtained from sensors built in to the first high frequency RF source and the second high frequency RF source.

9. The semiconductor fabrication chamber of claim 8, wherein data from the sensors built in to the first high frequency RF source and the second high frequency RF source is transmitted to the first high frequency match circuit and the second high frequency match circuit, respectively.

10. The semiconductor fabrication chamber of claim 9, wherein the data is transmitted via an ETHERCAT connection.

11. The semiconductor fabrication chamber of any one of claims 1-5, wherein the first high frequency RF source is a leader and the second high frequency RF source is a follower such that characteristics of a signal provided by the second high frequency RF source are modified responsive to modification of characteristics of a signal provided by the first high frequency RF source.

12. A system, comprising: a first high frequency match circuit configured to perform impedance matching between a first high frequency RF source and a first subset of a plurality of process stations of a multistation tool to generate a first impedance matched high frequency RF signal; a second high frequency match circuit configured to perform impedance matching between a second high frequency RF source and a second subset of the plurality of process stations to generate a second impedance matched high frequency RF signal; a first splitter / combiner configured to: receive a low frequency RF signal from a low frequency RF source, combine the low frequency RF signal and the first impedance matched high frequency RF signal to generate a first combined RF signal, and provide the first combined RF signal to the first subset of the plurality of process stations; and a second splitter / combiner configured to: receive the low frequency RF signal from the low frequency RF source, combine the low frequency RF signal and the second impedance matchedhigh frequency RF signal to generate a second combined RF signal, and provide the second combined RF signal to the second subset of the plurality of process stations.

13. The system of claim 12, wherein characteristics of the signals generated by each of the first high frequency RF source and the second high frequency RF source are independently controlled, and which comprise a frequency of the signals, a power of the signals, and a phase of the signals, or any combination thereof.

14. The system of claim 12, wherein the first high frequency match circuit and the second high frequency match circuit each comprise components configured to provide a variable reactance, wherein the components are substantially identical.

15. The system of claim 14, wherein the first high frequency match circuit and the second high frequency match circuit each comprise a substantially identical L-match circuit.

16. The system of any one of claims 12-15, wherein the first high frequency match circuit and the second high frequency match circuit each perform impedance matching based on impedance and / or phase information indicative of an impedance associated with the first high frequency RF source and the second high frequency RF source, respectively, wherein the impedance and / or phase information is obtained from sensors operatively coupled to the first high frequency RF source and the second high frequency RF source.

17. The system of any one of claims 12-15, wherein the first high frequency match circuit and the second high frequency match circuit each perform impedance matching based on impedance and / or phase information indicative of an impedance associated with the first high frequency RF source and the second high frequency RF source, respectively, wherein the impedance and / or phase information is obtained from sensors built in to the first high frequency RF source and the second high frequency RF source.

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