Broadband plasma processing system and method

Abstract

A method for operating a plasma processing system includes determining a first frequency for powering a first plasma within a plasma processing chamber. The method includes generating, at a broadband power amplifier, a first amplified RF signal having the first frequency. The method includes supplying the first amplified RF signal to process a substrate arranged in the plasma processing chamber using a first plasma process including the first plasma. The method includes determining a second frequency for powering a second plasma within the plasma processing chamber. The method includes generating, at the broadband power amplifier, a second amplified RF signal having the second frequency. The method includes supplying the second amplified RF signal to process the substrate arranged in the plasma processing chamber using a second plasma process including the second plasma.

Description

[0001] Cross-reference to related applications

[0002] This application claims priority to U.S. non-provisional application No. 16 / 572,708, filed September 17, 2019, and U.S. non-provisional application No. 16 / 717,024, filed December 17, 2019, the entire contents of which are incorporated herein by reference. Technical Field

[0003] The present invention generally relates to plasma systems and operating methods, and in specific embodiments, to methods for broadband plasma processing systems. Background Technology

[0004] Semiconductor devices, such as integrated circuits (ICs), are typically fabricated by sequentially depositing and patterning dielectric, conductive, and semiconductor material layers over a semiconductor substrate. Photolithography and etching are used to form the structures of circuit components and interconnect elements (e.g., transistors, resistors, capacitors, metal lines, contacts, and vias). Some components involve complex three-dimensional structures, such as stacked capacitors and FinFETs in dynamic random access memory (DRAM) cells. Plasma-assisted techniques, such as reactive ion etching (RIE), plasma-enhanced chemical vapor deposition (PECVD), and plasma-enhanced atomic layer etching and deposition (PEALE and PEALD), have become indispensable in the deposition and etching processes used to form semiconductor device structures.

[0005] Costs can be reduced by periodically decreasing the minimum feature size through increased packing density. Features of a few nanometers can be patterned using innovations such as immersion lithography and multiple patterning. This scaling trend exacerbates the technological challenges of forming dense, high aspect ratio nanostructures. In particular, plasma processing needs to provide the ability to form nanostructures with accurate dimensions and precisely controlled structural features (e.g., width, depth, edge profile, film thickness, conformal and anisotropic properties), typically at the atomic scale and uniformly distributed on wide (e.g., 300 mm) wafers. Various plasma processing techniques, such as selective deposition and etching, simultaneous deposition and etching, pulsed plasma processes, and cyclic processes using pulsed deposition and etching cycles, have been developed to overcome some of the barriers to fabricating miniaturized semiconductor devices. Successfully deploying such technologies in semiconductor manufacturing may require further innovation in plasma equipment design and plasma processing methods to consider factors such as processing costs, equipment configurability, and equipment cost. Summary of the Invention

[0006] According to embodiments of the present invention, a method for operating a plasma processing system includes determining a first frequency for powering a first plasma within a plasma processing chamber. The method includes generating, at a wideband power amplifier, a first amplified RF signal having the first frequency. The method includes supplying the first amplified RF signal to process a substrate disposed in the plasma processing chamber using a first plasma process including the first plasma. The method includes determining a second frequency for powering a second plasma within the plasma processing chamber. The method includes generating, at the wideband power amplifier, a second amplified RF signal having the second frequency. The method includes supplying the second amplified RF signal to process the substrate disposed in the plasma processing chamber using a second plasma process including the second plasma.

[0007] According to embodiments of the present invention, a method for operating a plasma processing system includes performing a first frequency sweep tuning to generate a first radio frequency (RF) signal including a first frequency. The method includes amplifying, at a wideband power amplifier, the first RF signal to generate a first amplified RF signal. The method includes supplying the first amplified RF signal to process a substrate disposed in a plasma processing chamber, the processing of the substrate powered by the first amplified RF signal. The method includes performing a second frequency sweep tuning to generate a second radio frequency (RF) signal including a second frequency. The method includes amplifying, at the wideband power amplifier, the second RF signal to generate a second amplified RF signal. The method includes supplying the second amplified RF signal to process the substrate disposed in the plasma processing chamber, the processing of the substrate powered by the second amplified RF signal.

[0008] According to embodiments of the present invention, a method for operating a plasma processing system includes performing a first frequency sweep tuning to generate a first radio frequency (RF) signal including a first frequency. The method includes amplifying, at a wideband power amplifier, the first RF signal to generate a first amplified RF signal. The method includes supplying the first amplified RF signal to process a substrate disposed in a plasma processing chamber, the processing of the substrate powered by the first amplified RF signal. The method includes performing a second frequency sweep tuning to generate a second radio frequency (RF) signal including a second frequency. The method includes amplifying, at the wideband power amplifier, the second RF signal to generate a second amplified RF signal. The method includes supplying the second amplified RF signal to process the substrate disposed in the plasma processing chamber, the processing of the substrate powered by the second amplified RF signal. BRIEF DESCRIPTION OF DRAWINGS

[0009] For a more complete understanding of the present invention and the advantages thereof, reference is now made to the following descriptions taken in conjunction with the accompanying drawings in which:

[0010] Figure 1 is a schematic diagram of a broadband plasma processing system according to an embodiment of the application;

[0011] Figure 2 is a schematic diagram of a plasma processing apparatus comprising a plasma processing chamber shown in cross-sectional view according to an embodiment of the application;

[0012] Figures 3A to 3E two example sequences of plasma processing steps performed using a broadband plasma processing system according to embodiments of the application are shown;

[0013] Figure 4 a flowchart of one plasma processing step of a sequential plasma processing flow using a broadband plasma processing system according to embodiments of the application is shown;

[0014] Figures 5A to 5D an example sequence of plasma processing steps performed using a broadband plasma processing system according to embodiments of the application is shown;

[0015] Figure 5E and 5F a timing diagram corresponding to the example sequence of plasma processing steps shown in Figures 5A to 5D is shown.

[0016] Figures 6A to 6C an example sequence of plasma processing steps performed using a broadband plasma processing system according to embodiments of the application is shown;

[0017] Figure 6D a timing diagram corresponding to the example sequence of plasma processing steps shown in Figures 6A to 6C is shown.

[0018] Figures 7A to 7C an example sequence of plasma processing steps performed using a broadband plasma processing system according to embodiments of the application is shown;

[0019] Figure 7D a timing diagram corresponding to the example sequence of plasma processing steps shown in Figures 6A to 6C is shown.

[0020] Figures 8A to 8D an example sequence of plasma processing steps performed using a broadband plasma processing system according to embodiments of the application is shown;

[0021] Figure 8E a timing diagram corresponding to the example sequence of plasma processing steps shown in Figures 8A to 8D is shown.

[0022] Figure 9 A flowchart illustrating one cycle of a pulsed plasma process flow using a broadband plasma processing system according to embodiments of the present disclosure is shown;

[0023] Figure 10A A power spectral density of two RF signals for a dual-frequency pulsed plasma process example using a dual-channel broadband plasma processing system according to embodiments of the present disclosure is shown;

[0024] Figure 10B A timing diagram for a dual-frequency pulsed plasma process example using a dual-channel broadband plasma processing system according to embodiments of the present disclosure is shown; and

[0025] Figure 10C A corresponding timing diagram for an example using an imaginary broadband plasma processing system is shown. Figure 10B DETAILED DESCRIPTION DETAILED DESCRIPTION

[0026] In the methods disclosed in embodiments of the present disclosure, a series of plasma processing steps are performed in a single plasma processing chamber of a plasma processing apparatus without the need to transfer the substrate out of the chamber between successive plasma processing steps. Different process steps can use different RF signals with frequencies distributed over a wideband. For example, a plasma etch step can be performed at low pressure to minimize redeposition of the etched material, and low frequencies can be desirable at low pressure to obtain a more uniform plasma. On the other hand, a plasma deposition step can be performed at a relatively higher pressure and higher RF frequency to provide a higher dissociation. RF frequency is generally an important process parameter in plasma processing for achieving a desired plasma environment.

[0027] A broadband plasma processing system including a broadband tunable RF signal generator and a broadband RF power amplifier is used to accommodate a wide frequency range. In general, changes in RF frequency or processing environment in the plasma processing chamber can change the impedance of the plasma, thereby disturbing the impedance match and reducing the power transfer efficiency from the broadband RF power amplifier to the plasma processing apparatus. In embodiments described in the present disclosure, the broadband plasma processing system uses an impedance tuning method called frequency-scan tuning with center frequency offset to quickly reestablish a near-optimal impedance match.

[0028] As described below with reference to Figure 1The frequency scan tuning with a center frequency offset (and described in further detail in related application number 16 / 572,708) changes the signal frequency to change the frequency dependent impedance of the circuit. The electronic feedback control system of the wideband plasma processing system couples the RF frequency at the wideband tunable RF signal generator to the frequency dependent impedance of the output matching network circuit of the wideband RF power amplifier. The built-in power analyzer circuit of the wideband RF power amplifier provides a feedback signal to the programmable controller that represents the impedance mismatch between the wideband RF power amplifier and the load at its output port. The programmable controller uses this feedback signal to fine tune the frequency of the RF signal generated by the wideband tunable RF signal generator. The frequency offset is designed to continuously adjust the frequency dependent impedance of the output matching network circuit of the wideband RF power amplifier towards the optimal impedance match. This impedance tuning method provides ultrafast impedance matching compared to more traditional methods that mechanically tune the impedance using electromagnetic relays and servo motors. In some embodiments, the frequency scan tuning with a center frequency offset has a response time on the order of microseconds and can establish near-optimal impedance matching in a convergence time on the order of tens of microseconds.

[0029] The disclosed embodiments provide implementations of various plasma processing techniques with reduced hardware cost and higher throughput (by using single-chamber processing). Due to the ultrafast impedance matching capability of the wideband plasma processing system, the methods described in this application can be advantageously used to implement process flows that include pulsed plasma processing that can be rapidly switched between pulses.

[0030] In this disclosure, pulsed plasma processing refers to semiconductor processing performed using a plasma sustained by RF power supplied in the form of pulses of finite duration. The pulsed plasma process can include a single plasma process step such as a deposition step, an etch step, or a simultaneous deposition and etch step. The pulsed plasma process can also refer to a cycle process in which one cycle includes some combination of deposition and etch steps.

[0031] The RF power during a single-step pulsed plasma process can be supplied as periodic pulses (short bursts of RF power). The pulse sequence can also be aperiodic: divided into several pulses with any combination of signal parameters such as duty cycle, RF frequency, and RF amplitude. The pulsed RF waveform typically includes RF pulses that are discrete in time, but aperiodic pulses can even be continuous in time as long as they are otherwise separable, e.g., by means of RF frequency, RF amplitude, and pulse duration, or combinations thereof. Discrete-time RF pulses can be generated by chopping a continuous wave RF (CW-RF) signal using a chopper circuit, as described below with reference to FIG. 2. Figure 1The (and further detailed in related application number 16 / 572,708). However, continuous-time RF pulses can be generated without a chopper.

[0032] A single-step pulsed plasma process can include a conventional plasma step (e.g., PECVD, RIE, etc.) or an atomic layer plasma process (e.g., PEALD or PEALE). For a conventional plasma process, the process parameters such as gas flow, temperature, and pressure can not necessarily have to be changed when the RF power pulse is performed. In contrast, an atomic layer deposition or etch process step is performed in cycles of several sub-steps, where the process parameters of these sub-steps are typically different.

[0033] As described herein, a single-step atomic layer plasma process (e.g., PEALD or PEALE) is essentially a single-step pulsed plasma process. One process step includes several reaction cycles, and each reaction cycle includes two different half-reaction pulses separated by a purge pulse, for example. At least one half-reaction pulse can use a plasma sustained by RF power. Since consecutive half-reaction pulses are separated by a purge pulse, the RF signal naturally includes short bursts of RF power even if the RF waveform during one half-reaction pulse is uninterrupted. In the present disclosure, such an RF signal can be referred to as an uninterrupted pulsed RF signal, as opposed to a segmented pulsed RF signal, where the RF waveform during one half-reaction pulse is a grouping of sub-pulses, each sub-pulse being a very short burst of RF power.

[0034] Several cyclic pulsed plasma processes are described in various embodiments of the present disclosure. For example, the implemented process flow can include a cyclic deposition / etch process (e.g., a plasma deposition pulse and a plasma etch pulse in one cycle). One or both of the plasma deposition and plasma etch pulses can include a conventional non-limiting gas-phase reaction process (as in PECVD / RIE), or a self-limiting surface reaction process (as in PEALD / PEALE processes).

[0035] In a PEALD / PEALE process, one atomic layer deposition / etch reaction cycle can include several sub-steps, as described above. For example, a surface reaction for depositing one atomic layer of silicon nitride is accomplished by two self-limiting half-reactions: a first half-reaction in which the surface is exposed to dichlorosilane gas, and a second self-limiting half-reaction in which the surface is exposed to ammonia plasma. Each half-reaction is followed by a purge step to clear the processing chamber of excess reactants and gaseous byproducts. Similarly, a PEALE reaction cycle can include a surface conditioning first reaction pulse (e.g., chlorination in the case of silicon) and a second reaction pulse during which one atomic layer is removed from the surface. In these examples, one reaction cycle of a PEALD / PEALE process includes two pairs of pulses, each pair including a reaction pulse and a subsequent purge pulse. In both of these examples (PEALD silicon nitride and PEALE silicon), the second reaction pulse in the reaction cycle can use a plasma sustained by an RF signal.

[0036] The RF signal used during one plasma process pulse in the above-described cyclical deposition / etch process can be an uninterrupted RF pulse (a short burst of continuous RF power) or a segmented RF pulse (a grouping of sub-pulses, each sub-pulse being a very short burst of RF power). A wideband plasma processing system can use a chopper circuit to generate various pulsed RF waveforms through timing control of a programmable controller in the wideband plasma system. Tables 1-4 summarize various combinations of pulsed plasma processes that implement the cyclical deposition / etch techniques described above. Table 1 lists PECVD / RIE combinations, Table 2 lists PECVD / PEALE combinations, Table 3 lists PEALD / RIE combinations, and Table 4 lists PEALD / PEALE combinations.

[0037]

[0038] The disclosed embodiments provide implementations of various plasma processing techniques with reduced hardware cost and higher throughput (achieved by using single-chamber processing and frequency sweep tuning with center frequency offset). However, it should be appreciated that more possibilities can be derived from the disclosed embodiments. In addition to the examples summarized in Tables 1-4, various process flows including various combinations of deposition and etching can be derived where it is advantageous to use a broadband plasma processing system similar to those described in the disclosed embodiments. For example, process flows including deposition followed by a different deposition, or etching followed by a different etching, or combinations thereof, depending on the process specifications for material, selectivity, conformality, profile, defect density, critical dimension control, etc. These process flows can include conventional PECVD and plasma etching processing techniques or atomic layer processing (PEALD and PEALE) techniques performed using single-chamber processing by continuous wave RF signals or pulsed RF signals with different RF frequencies.

[0039] Short convergence time for impedance matching helps to suppress uncontrolled power due to RF waveform transients that can occur during impedance tuning. Impedance mismatch can lead to voltage spikes, for example, when the impedance changes abruptly due to plasma discharge ignition. This can lead to surface damage, for example, due to unintended etching when deposition can be intended. Uncontrolled waveforms can also lead to variability or pulse loss. In the embodiments described in the present disclosure, precise control of the RF power supplied to the plasma processing device in each step is advantageous for plasma processes used to manufacture device structures that use precisely controlled features to implement normal functionality.

[0040] In various embodiments, the plasma processing device can be operated in a sequential mode or a pulsed mode. In the sequential mode of operation, plasma process steps are performed using continuous RF power at a single frequency. For example, a first plasma process step (e.g., a PECVD process) is performed using continuous RF power at a first RF frequency, followed by a second plasma process step (e.g., a RIE process step) using continuous RF power at a second RF frequency.

[0041] Process steps performed in the pulsed mode of operation use pulsed RF power at one or more RF frequencies. A pulsed RF signal can refer to a continuous sinusoidal RF signal modulated by a square wave that pulses between zero (inactive portion) and one (active portion) at a relatively low frequency of about 1 Hz to about 100 kHz. Transient RF power exists only during the active portion of one pulse period. During a process step, the parameters of the pulse sequence (e.g., pulse frequency and duty cycle) and / or the parameters of the RF signal (e.g., RF frequency and RF amplitude) can be changed according to the specifications in the process recipe.

[0042] First, a schematic diagram of a broadband plasma processing system and cross-sectional views of plasma processing devices included therein Figure 1 and Figure 2 are used to provide a general description of the broadband plasma processing system.

[0043] Next, two example process sequences exhibiting a sequential mode of operation are described with reference to cross-sectional views of semiconductor structures at different processing stages in Figures 3A to 3E Then, a plasma processing method corresponding to one cycle of the process sequence described with reference to Figure 4 is explained with reference to a flowchart shown in Further examples of process flows using the sequential mode of operation are shown in FIG. 5, FIG. 6, and FIG. 7.

[0044] Then, an example process sequence exhibiting a pulsed mode of operation is described with reference to cross-sectional views of semiconductor structures in Figures 8A to 8D A plasma processing method corresponding to one cycle of the process sequence described with reference to Figure 9 is explained with reference to a flowchart shown in Figures 8A to 8D

[0045] Figure 1 An example broadband plasma processing system 1111 that can be used to operate the plasma processing device 17 in either a sequential mode or a pulsed mode to perform a series of plasma processing steps is shown. The broadband plasma processing system 1111 performs the plasma processing steps according to instructions input as a process recipe 10 by the programmable controller 11. The programmable controller 11 then generates several electronic control signals according to the process recipe 10. The control signals are transmitted to synchronously configure the various components of the broadband plasma processing system 1111.

[0046] The broadband tunable RF signal generator 12 provides a continuous RF signal at a frequency set by a first control signal from the programmable controller 11. The first control signal transmitted to the broadband tunable RF signal generator 12 can dynamically shift the RF frequency within a narrow bandwidth around a center frequency encoded in the process recipe 10. As described above, the programmable controller 11 uses the feedback signal indicative of the impedance mismatch to determine an instantaneous frequency offset. The fine tuning of the RF signal frequency will adjust the frequency dependent impedance of the output matching network circuit 115 in the broadband RF power amplifier 15 to reduce the impedance mismatch, and the revised feedback signal is transmitted to the programmable controller. This continuous feedback control loop can quickly converge to an RF frequency for most efficiently delivering power to the plasma processing device 17.

[0047] A second control signal transmitted to a control terminal T of the selector 13 configures the first electronic toggle switch. The electronic toggle switch implements a single-pole double-throw (SPDT) toggle switch using solid-state devices (e.g., thyristors, metal-oxide-semiconductor field-effect transistors (MOSFETs), and insulated-gate bipolar transistors (IGBTs)). The selector 13 is used to route the continuous RF signal either directly to an input terminal I of the wideband RF power amplifier 15 or via the chopper circuit 14 to generate a pulsed RF waveform (as described above).

[0048] The chopper circuit 14 chops the continuous RF signal using a gated chopper 104 gated by a low-frequency square-wave pulse sequence from a pulse generator 114. The frequency and duty cycle of the pulsed RF signal are set by a third control signal transmitted to a control terminal P of the pulse generator 114 of the chopper circuit 14. In some embodiments, the duty cycle can be set to any value between zero and 100% inclusive, such that the chopper circuit 14 can also function as an on / off switch. For example, during times when the duty cycle is set to 100%, the RF signal is continuous and can be used for processes that use continuous RF signals. A zero duty cycle blocks the RF signal.

[0049] The wideband RF power amplifier 15 achieves wideband amplification by providing power gain in multiple overlapping frequency bands using multiple power amplifiers and combining their outputs in a power amplifier and combiner module 105. The amplified and combined RF signal proceeds to an output matching network circuit 115 and a power analyzer circuit 125 incorporated into the wideband RF power amplifier 15, as shown and further described in application number 16 / 572,708. Figure 1

[0050] A fourth control signal transmitted to a control terminal S of the built-in output matching network circuit 115 selects one or more passive components (e.g., one of several available load capacitors, C L ) in the passive components used in the output matching network circuit 115 that are appropriate for the RF frequency f of the RF signal generated by the wideband tunable RF signal generator 12. The programmable controller 11 synchronizes the first and fourth control signals so that the center frequency of the narrow RF frequency band specified in the process recipe 10 is synchronized with the selected C L of the output matching network circuit 115. For example, the process recipe 10 can specify a pulsed RF dual-frequency step using a first frequency f1 and a second frequency f2. When processing this step (e.g., using a pulsed dual-frequency operating mode), the first load capacitor C L1 may be selected for f1, but a second load capacitor C L2 may be needed when the frequency switches to f2. As described above, further tuning of the impedance of the output matching network circuit 115 is achieved by fine-tuning the RF signal frequency.​

[0051] The RF signal from the output matching network circuit 115 is analyzed by the power analyzer circuit 125 of the broadband RF power amplifier 15. The power analyzer circuit 125 generates a feedback signal (normalized to the positive power delivered by the broadband power amplifier 15) that is proportional to the reflected power reflected at the output port O due to any impedance mismatch at that output port. The feedback signal is provided at the feedback port Z of the built-in power analyzer circuit 125 and is transmitted to the programmable controller 11.

[0052] The power analyzer circuit 125 can measure normalized reflected power by using a broadband RF VI sensor (which senses the voltage (V) and current (I) of the RF signal leaving the power analyzer circuit 125) or by using a four-port directional coupler, as explained in detail in application number 16 / 572,708.

[0053] The feedback signal at feedback terminal Z is received by programmable controller 11 and used to refine the first control signal. The refined first control signal is transmitted to broadband tunable RF signal generator 12 and the RF frequency is corrected. The impedance of the output matching network circuit 115 at the corrected frequency will reduce the reflected power. As explained in detail in application number 16 / 572,708, this feedback loop can be designed entirely as an electronic circuit system (without moving parts) for ultrafast impedance matching.

[0054] The amplified high-power RF signal output from the output matching network circuit 115 is routed to the plasma processing apparatus 17 via a path selected by the second electronic toggle switch. For example... Figure 1 As shown, a second electronic toggle switch connected to the output terminal O of the broadband RF power amplifier 15 can use the same (second) control signal used to configure selector 13 to route the RF signal output from the output matching network circuit 115 directly to the plasma processing apparatus 17 or via the bandpass filter circuit 16. Direct connection is selected whenever selector 13 is configured to route the RF signal directly from the broadband tunable RF signal generator 12 to the input terminal I of the broadband RF power amplifier 15. The path via the bandpass filter circuit 16 is selected whenever selector 13 is configured to redirect a continuous RF signal from the broadband tunable RF signal generator 12 to the chopper circuit 14 to provide a pulsed RF signal to the broadband RF power amplifier 15. The bandpass filter circuit 16 includes multiple bandpass filters (e.g., bandpass filters 106 and 116) whose outputs are connected to the appropriate electrodes of the plasma processing apparatus 17. The programmable controller 11 can also provide control signals to a control system for configuring the electrodes of the plasma processing apparatus 17 according to the process recipe 10 and the configuration of the first and second toggle switches.

[0055] Figure 1 Additional connections that may exist between the plasma processing apparatus 17 and ground (reference potential) and a DC and / or RF bias source configured by control signals from the programmable controller 11 are also shown. The presence of the DC power supply may affect the plasma impedance, and RF impedance matching can be established using frequency sweep tuning methods. Figure 1 In the example embodiment shown, these bias sources are illustrated together by block 18. In another embodiment, some DC and RF bias signals can be in a manner similar to... Figure 1 The RF source signal in the depicted broadband plasma processing system 1111 is included in the broadband plasma processing system. In such an embodiment, this can be achieved by adding, for example, a second channel (or multiple channels). Figure 1 A single-channel tunable signal generator 12 is used to generate the RF source and RF bias signals. A combination of a multi-channel amplifier and matching circuitry can replace... Figure 1 The single-channel broadband RF power amplifier 15 shown may also include additional chopper circuitry, toggle switches, and bandpass filters. The advantage of increasing the number of channels is that it provides the ability to extend the range of continuous and / or pulsed signal combinations of RF sources, RF biases, and DC biases that can be used in plasma processing employing multi-channel systems.

[0056] Figure 2 An example of a plasma processing apparatus 17 with a pair of RF electrodes within a single plasma processing chamber 200 is shown. The first RF electrode, referred to as the top RF electrode 206, is located near the top of the plasma processing chamber 200. The second RF electrode is a substrate holder 208 with an RF tap 209 mounted on it, and is sometimes referred to as the bottom RF electrode 208. The substrate holder 208 may also have a built-in heater and cooler controlled by a feedback temperature control system 204. Figure 2 In the example shown, the top and bottom RF electrodes 206 and 208 are configured to output from the two output ports of a bandpass filter circuit corresponding to RF frequencies f1 and f2, respectively (see [link to example]). Figure 1 Box 16) receives RF power, and from a DC bias source (see box 16) receives RF power. Figure 1 Box 18) in the plasma processing chamber 200 receives DC bias voltages V1 and V2. The sidewalls 201, base 205, and top cover 203 of the plasma processing chamber 200 may be made of conductive material and may be grounded or floating.

[0057] like Figure 2As shown, the plasma processing chamber 200 can have a gas input system (including a showerhead 220 in the top cap 203 and an inlet 210 in the sidewall 201) and a gas exhaust system (including an outlet 207 in the base 205). A vacuum pump 202 of a vacuum system can be used to control the pressure in the chamber and to remove exhaust gases such as product gases from the plasma processing chamber 200.

[0058] The broadband plasma processing system 1111 can include various other components (not shown) known to those skilled in the art, such as an electrostatic grid, a flow meter, a pressure sensor, a control valve, and plasma parameter sensors such as an optical emission spectroscopy (OES) sensor, a quadrupole mass spectrometer (QMS), and a Langmuir probe.

[0059] The broadband plasma processing system 1111 described above with reference to Figure 1 and Figure 2 is for illustrative purposes and is not limiting. For example, in some embodiments, the RF signal can be switched between a continuous RF signal and a pulsed RF signal by switching the duty cycle between 100% and a second value, instead of using a selector 13 with a first toggle switch as shown. Figure 1

[0060] In another embodiment, the second toggle switch for selecting a direct connection between the output port O and the plasma processing device 17 can be eliminated. Instead, the direct connection can be merged with the bandpass filter 16, and a configurable electronic switching matrix can be used to select the RF signal path between the output port O and the plasma processing device 17.

[0061] In yet another embodiment, instead of a top RF electrode 206 placed inside the plasma processing chamber 200 as shown, a conductive coil placed above the top cap 203 (outside the plasma processing chamber 200) can be used as the top RF electrode. Figure 2

[0062] Figures 3A to 3E Sequential modes of operation of first and second process flows suitable for forming topography selective films over stepped features of an incoming wafer are demonstrated. The depicted stepped features can include line and space structures. More generally, the steps can also be part of a hole (via) or a pillar. The stepped features such as shown Figures 3A to 3E may occur in elements used in logic, interconnect, or memory structures, and can be fabricated in whole or in part by a combination of etch and deposition processes including plasma processes including traditional non-limiting vapor phase reactions processes (as in PECVD / RIE), or self-limiting surface reactions processes (as in PEALD / PEALE). In Figures 3A to 3E ​​The example process flow shown illustrates a conventional non-limiting vapor phase reaction process in PECVD / RIE to illustrate a sequential mode of operation. The pulsed mode of operation is further illustrated below using examples of PEALD / PEALE process flows.

[0063] The step features on which the topography selective film is formed (e.g., Figure 3A The step features in the patterned film 310 in Figure 2 may have been formed in advance using suitable processing techniques, for example, by depositing a planar film and subsequently patterning the film using photolithography and anisotropic etching techniques. In either process flow, several plasma processes are performed in succession in a single plasma processing chamber (e.g., The top RF electrode 206 can be configured to receive continuous RF power using a direct connection to the output port O of the wideband RF power amplifier 15. As described below, the RF frequency of the continuous RF signal powering the top RF electrode 206 can be changed between successive plasma processing steps. By applying different RF frequencies and using appropriate gas chemistries, any number of combinations of conformal plasma deposition, conformal plasma etching, non-conformal plasma deposition, and non-conformal plasma etching can be selected to achieve the desired process characteristics in a single process chamber. The RF frequency can range from about 400 kHz to about 300 MHz, and in some embodiments can be as high as several GHz. In general, the RF frequency used for isotropic processes is higher than that used for anisotropic processes. The material being deposited or etched can be dielectric, semiconducting, or conductive.

[0064] Figure 3A and Figure 3B are applicable to both the first and second process flows. Figure 3A A cross-sectional view of an incoming semiconductor wafer is shown, in which a patterned film 310 is formed on the surface above a substrate 300. The patterned film 310 can be a silicon line, and the substrate 300 can be a silicon dioxide spacer, which can be a thin barrier film for a subsequent self-aligned etching step. Alternatively, 310 can be a carbon or silicon dioxide mandrel structure. The thickness of the patterned film 310 is also the step height of the vertical step feature formed by the patterning process. In Figure 3BIn one embodiment, a conformal PECVD process can be used to form a conformal thin film 313 having a thickness that is small compared to the thickness of the patterned layer 310. In one embodiment, the ratio of the thickness (step height) of the patterned layer 310 to the thickness of the conformal thin film 313 can be about 2: 1 to about 20: 1 or any reasonable ratio. The PECVD process can be performed using very high frequency (VHF) RF signals. The conformal thin film 313 can comprise silicon nitride and can be used as an etch stop or diffusion barrier, or as part of a spacer structure. The RF frequency can be from about 30 MHz to about 300 MHz, for example 100 MHz, and in some embodiments can be as high as several GHz. Conformal deposition, such as Figure 3B The conformal PECVD process shown is an isotropic process. Increasing the ratio of radical flux to ion flux provides a more isotropic plasma process, while increasing the RF frequency RF signal helps to increase the ratio.

[0065] In applications where a very thin conformal film 313 with atomic level thickness control is desired (for example, for an ultra-thin barrier layer or ultra-thin spacer in a self-aligned multiple patterning (SAxP)), the conformal PECVD process can be replaced with a suitable PEALD process. As described above, the PEALD process steps can include a periodic sequence of discrete plasma half-reaction steps performed using a corresponding periodic sequence of RF power pulses.

[0066] Figure 3C and Figure 3D Refers to two consecutive plasma process steps in the first process flow, which are performed after the PECVD step described above with reference to Figure 3B The three plasma process steps Figures 3B to 3D are performed consecutively in the same plasma processing chamber 200, without the need to remove the semiconductor wafer from the plasma processing chamber 200 between plasma processing steps.

[0067] In Figure 3C , an anisotropic RIE process step is performed to selectively remove the conformal thin film 313 from above the flat horizontal surfaces. The conformal thin film 313 is preserved along the two opposite sidewalls of the vertical step feature to form a thin sidewall layer 318. The thickness of the sidewall layer 318 is substantially the same as the thickness of the conformal thin film 313. The etchant used for the RIE process is selected such that a chemical reaction removes the material in the conformal thin film 313, while being selective to the material in the patterned film 310 and the substrate 300 that can be exposed to the etchant. The RIE process will be a typical RIE process for silicon nitride (or oxide film) and involves primarily a fluorocarbon gas or a hydrofluorocarbon gas. The RIE process uses the same RF frequency as the Figure 3BThe PECVD process in this technology uses a VHF RF signal compared to a lower frequency RF signal. This RF frequency can be in the high-frequency (HF) RF band, from approximately 3MHz to approximately 30MHz, for example, 13MHz. To obtain... Figure 3C The nearly vertical sidewall profile shown necessitates process parameters that must be adjusted to provide a plasma in which the energy per unit area of ​​reactant material impacting the horizontal surface is significantly greater than that impacting the vertical surface. Typically, the energy in the vertical direction is enhanced when charged ions are vertically accelerated by an electric field present in the sheath region formed near the plasma edge. Therefore, increasing the ion flux to radical flux ratio and increasing the vertical electric field can help to preferably tilt the ion energy and ion angle distribution vertically, thereby increasing the anisotropy of the plasma process. The ion flux to radical flux ratio and the electric field in the sheath are frequency-dependent, and decreasing the RF frequency can enhance anisotropy, for example, in the highly anisotropic RIE process described above.

[0068] Figure 3D Shown in Figure 3C A cross-sectional view of the final structure 330 after topography-selective PECVD processing was performed on the upper part of the middle structure. (See image.) Figure 3D As shown, the morphology-selective PECVD process selectively deposits a non-conformal thin film 320 above the vertical step features of the patterned film 310 and the exposed flat horizontal surface of the substrate 300. The amount of material deposited on the vertical sidewall layer 318 is negligible. The deposition thickness of the non-conformal thin film 320 is small compared to the thickness of the patterned layer 310. The anisotropic morphology-selective PECVD process is performed using an HF RF signal with an RF frequency from about 3 MHz to about 30 MHz (e.g., 13 MHz).

[0069] Figure 3E The final structure 333 in the second process flow is shown. To form the final structure 333, a morphology-selective PECVD process was performed to... Figure 3B A non-conformal thin film 320 is selectively deposited above the flat horizontal surface of the intermediate structure shown. The non-conformal thin film 320 deposited in the second process flow is substantially the same as the non-conformal thin film deposited in the first process flow. However, the starting surfaces where deposition occurs in the two process flows are different. Figure 3E As shown, in the second process flow, the starting surface for depositing the non-conformal thin film 320 is the conformal thin film 313. In both process flows, the morphology-selective PECVD process is an anisotropic plasma process that uses an HF RF signal with an RF frequency from about 3 MHz to about 30 MHz (e.g., 13 MHz) to maintain the plasma.

[0070] The above references Figures 3A to 3EThe described isotropic and anisotropic plasma process steps use relatively high and low RF frequencies, respectively. The plasma process steps in the example process flow are performed sequentially using the frequency sweep tuning method to quickly match the impedance at each time the plasma impedance changes due to changes in the RF frequency and plasma characteristics. The sequential mode of operation has been illustrated using conventional CW-RF plasma deposition and etching (e.g., CW-RF PECVD / RIE). In contrast, PEALD / PEALE processes use self-limiting reaction pulses (RF pulses can be used for these pulses), as discussed in further detail below. Atomic layer processing offers advantages such as near-ideal conformality, deposition / etching controlled by atomic layers, and high material selectivity in selective deposition and etching.

[0071] Figure 4 A sequential mode of execution flow 4444 is shown for performing one of a series of plasma processing steps performed in a sequential mode (e.g., the conformal PECVD process steps in the first and second process flows described above with reference to Figure 3B The sequential mode of execution flow 4444 is used to perform the conformal PECVD process steps in the first and second process flows described above with reference to Figure 1 Figure 1 and Figure 2 The flow includes a method for tuning the RF frequency of the RF signal used to power the plasma processing device 17 in Figure 1 After the hardware is suitably configured, the frequency sweep tuning method with center frequency shifting is implemented in the subsequent steps shown together in dashed box 40 to efficiently supply RF power to the plasma processing device 17 (see Figure 1 and Figure 2 ) by tuning the impedance of the output matching network 115 in Figure 1 , Figure 2 and Figure 4 The flow 4444 described with reference to

[0072] The first step 41 of the sequential mode of execution flow 4444 is used to parse the instructions of the programmable controller 11 input at the process recipe 10 of the broadband plasma processing system 1111 (see Figure 1 ) to identify the input process parameters specified for the current plasma process step, such as the RF frequency (f), the configuration of the plasma processing device 17 connecting its RF electrodes to the appropriate ports of the bandpass filters 16, additional DC and RF biasing, etc. ​

[0073] In a second step 42, the programmable controller 11 (see Figure 1 ) generates and transmits several control signals according to the input process parameters (e.g. the specified value of f) to configure the various components of the broadband plasma processing system 1111.

[0074] In block 421, the appropriate RF, DC and ground terminals of the plasma processing device 17 are configured to be connected to the respective electrodes, e.g. the top RF electrode 206 and / or the bottom RF electrode 208 (see Figure 2 ), according to the respective control signals from the programmable controller 11.

[0075] Block 422 of the second step 42 indicates that the control signals sent to the broadband tunable RF signal generator 12 and the output matching network circuit 115 ensure that the selected tuning elements (e.g. C L ) of the output matching network circuit 115 correspond to the center frequency f of the RF signal generated by the RF signal generator 12, as described above with reference to Figure 1 .

[0076] In block 423 of the second step 42, the control signals for synchronously setting the first and second electronic toggle switches (as shown in Figure 1 ) are used to select the sequential operation mode. The first toggle switch in the selector 13 connects the RF signal directly from the RF signal generator 12 to the input terminal I of the broadband RF power amplifier 15. The second electronic toggle switch at the terminal O of the broadband RF power amplifier 15 bypasses the bandpass filter 16 to route the RF signal directly from the output terminal O of the broadband RF power amplifier 15 to the RF electrodes of the plasma processing device 17.

[0077] The various components of the broadband plasma processing system 1111 are shown in Figure 1 and Figure 2 , e.g. the programmable controller 11, the signal generator 12, the selector 13, the chopper circuit 14, the broadband RF power amplifier 15, the bandpass filter 16 and the plasma processing device 17.

[0078] In a third step 43, the RF source of the broadband plasma system 1111 is activated by generating a CW-RF signal using the broadband tunable RF signal generator 12 according to the control signals received during the second step 42.

[0079] In a fourth step 44, the selector 13 routes the RF signal to the multi-band power amplifier and combiner 105 (see Figure 1 ).

[0080] In a fifth step 45, the amplified high power RF signal from the multi-band power amplifier and combiner 105 is routed through the impedance of the output matching network circuit 115 (see Figure 1 ) to the plasma processing apparatus 17, thereby changing the phase of the RF signal for efficient power transfer.

[0081] In block 451, the RF signal from the output matching network circuit 115 is transferred via a power analyzer circuit 125 (see, e.g., Figure 1 ) to an output port O in Figure 1 , which power analyzer circuit measures the forward and reflected power at the output port O (see, e.g., Figure 1 ) using a wideband RF V-I sensor or directional coupler, as described above and explained in detail in application number 16 / 572,708. Reflected RF power can be detected at the port due to impedance mismatch at the port.

[0082] In block 452, the high power RF signal that appears at the output port O (see, e.g., Figure 1 ) is routed by a second electronic toggle switch to a terminal of the plasma processing apparatus 17 that is connected to the RF electrode selected in step 42 (blocks 421 and 423).

[0083] The feedback loop is implemented by a sixth step 46. In block 461, the power analyzer circuit 125 transmits a feedback signal indicative of the degree of impedance mismatch back to the programmable controller 11 of the wideband plasma processing system 1111 in Figure 1 . As described above, the feedback signal generated by the power analyzer circuit 125 can be proportional to the reflected power normalized by the forward power.

[0084] In block 462, the feedback signal is used by the programmable controller 11 to determine the amount of frequency adjustment Af, and a new control signal to control the RF frequency is transmitted to the wideband tunable RF signal generator 12 to fine tune the RF frequency. The adjusted frequency (f + Af) adjusts the frequency dependent impedance of the output matching network 115 in a direction that reduces the normalized reflected power. This feedback loop continuously maintains efficient RF power transfer throughout the process step, during which the impedance of the plasma can change with the dynamic processing environment in the plasma processing chamber 200.

[0085] Another example of single-chamber processing with a sequence of plasma process steps using a sequential mode of operation is illustrated using a process flow suitable for forming a patterned hard mask used in a multiple patterning technique known as sidewall image transfer (SIT) technique.

[0086] As Figures 5A to 5DThe illustrated SIT technique doubles the feature density at the minimum pitch by using two sidewalls formed on two opposite vertical sides of the minimum pitch line. After the sidewall layer is formed, the minimum pitch line, referred to as a mandrel, is selectively removed without removing the sidewall layer. The remaining sidewall layer can be used as a patterned hardmask layer. For example, the sidewalls can then be used as a hardmask to etch trenches in the substrate exposed between the sidewalls, for example. The process flow is depicted in a sequence of structural cross-sectional views at successive processing stages, as Figures 5A to 5D illustrated.

[0087] As Figure 5A illustrated, the incoming wafer in this example is a patterned layer of disposable mandrels 510. The material used for the mandrels can include carbon, silicon oxide, zirconium oxide, etc. Figure 5A The disposable mandrels 510 in Figures 5B to 5D illustrated are minimum pitch lines with nearly vertical edges and can be formed by depositing (e.g., using a suitable deposition technique such as CVD, PECVD, ALD, PEALD, etc.) and patterning (using any suitable method to pattern, such as anisotropic RIE techniques applied with a photoresist mask) a sacrificial film over the semiconductor substrate 500. The

[0088] In Figure 5B , a conformal thin film 513 of hardmask material (e.g., silicon oxide, silicon nitride, etc.) can be formed using a conformal PECVD process in which the plasma is sustained by RF power supplied at a first signal frequency (fl, e.g., 100 MHz) in the VHF RF band (30 MHz to 300 MHz). As explained above with respect to the conformal PECVD process step illustrated in Figure 3B , it is also advantageous here to use a VHF RF signal to generate a high radical flux. The material of the conformal film 513 and the plasma parameters of the PECVD process are selected so that the nucleation rate on the substrate 500 is about the same as the nucleation rate on the mandrels 510 to help achieve good thickness uniformity.

[0089] Similar to the process flow illustrated in FIG. 3, the PECVD process can also be replaced here with a PEALD process performed using the broadband plasma processing system 1111 in pulsed mode if atomic-level control and conformality are desired.

[0090] In Figure 5CIn this process, sidewalls 518 of the SIT technique have been formed on opposite sides of each disposable mandrel 510. A highly anisotropic RIE process step is performed to selectively remove the conformal film 513 from the flat horizontal surface. In the case of using silicon nitride as an example conformal layer 513, a highly anisotropic etching process based on fluorocarbons can be used to achieve this. If high selectivity and high anisotropy for oxide films are desired, the silicon nitride film can be exposed to hydrogen ions and subsequently to a higher-pressure NF3 plasma.

[0091] Similarly, if atomic-level control is desired, the RIE process can be replaced by the PEALE process performed using a broadband plasma processing system 1111 in pulse mode.

[0092] like Figure 5C As shown, a hard mask material attached to the edge of the mandrel 510 forms a sidewall 518. The high anisotropy of the etching process results in the sidewall 518 having an almost vertical edge and a thickness substantially the same as the conformal film 513. The etching chemicals for the RIE process are selected such that the material removed from portions of the mandrel 510 and substrate 500 exposed to the etchant is negligible. This is in accordance with the requirements for forming the sidewall layer 318 (e.g., ...). Figure 3C For the same reason explained in the RIE step (shown), a second RF frequency (f2) in the high-frequency (HF) RF band (3MHz to 100MHz, e.g., 13MHz) can be used in the anisotropic RIE step used to form the sidewall 518.

[0093] Figure 5D Demonstrates selective removal Figure 5C The structure following the core rod 510 leaves a sidewall 518 located above the top surface of the substrate 500. An isotropic plasma etching process can be used to remove the exposed core rod 510, such as... Figure 5C As shown. The etchant used to remove the mandrel 510 can be selected to have a negligible low removal rate for the material used on the sidewalls 518 and the substrate 500 below and between the mandrel 510 and the sidewalls. For isotropic plasma etching, a relatively high ratio of free radical flux to ion flux is preferred, similar to conformal PECVD, since both processes are isotropic plasma processes. For most isotropic plasma processes, it is advantageous to use a VHF RF signal in the 30MHz to 300MHz band. In embodiments where the mandrel comprises silicon oxide, the mandrel can be removed using, for example, a highly selective chemical oxide removal (COR) plasma process, where NF3 / H2 plasma is used to generate free radicals. The isotropic plasma etching process used to remove the mandrel 510 can use a third frequency (f3) in the VHF RF band, for example, 60MHz.

[0094] It is to be understood that while PEALD and PEALE processes provide additional advantages, the same reasons mentioned above in the context of the process flow described in Figures 3A to 3E apply to the process flow described in Figures 5A to 5D A conventional CW-RF PECVD / RIE is used in the process shown in

[0095] Figure 5E The waveforms of the RF signals during the three plasma processes performed consecutively in the plasma processing chamber 200 and shown in Figure 5B , Figure 5C and Figure 5D are shown. (In the present disclosure, the waveforms shown are only for illustration purposes and are not drawn to scale.) The conformal PECVD process for forming the conformal film 513 is performed using an RF signal of, for example, f1 = 100 MHz in the time T1 in Figure 5E . Between time instances T1 and T2, the broadband plasma processing system 1111 is prepared to perform the next plasma process according to the respective recipe. From time instance T2 to T3 in Figure 5E , the next step, an anisotropic RIE for forming the sidewalls 518, is performed using an RF signal of, for example, f2 = 13 MHz. The isotropic plasma etch for removing the mandrel 510 is the third plasma step, which is performed using an RF signal of, for example, f3 = 60 MHz during the time period between T4 and T5 in Figure 5E . The preparation of the broadband plasma processing system 1111 to perform the third plasma step can be done between T3 and T4.

[0096] Reference is made to the example embodiment described in Figures 5A to 5E which illustrates a process flow comprising three plasma process steps performed sequentially using three different frequencies of CW-RF signals. In another embodiment, one or more of the plasma processing steps can be performed using pulsed RF signals of the same frequency. For example, the RF signal used in the conformal PECVD step for forming the conformal film 513 in Figure 5B may use a pulsed RF signal as shown in the waveform shown in Figure 5F . In Figure 5F , Figure 5E the CW-RF signal of f1 = 100 MHz in

[0097] Reference is made to the example embodiment described in Figures 6A to 6CThis section presents another example of single-chamber fabrication with multiple plasma process steps using a sequential operation mode. In this example, the precise sidewall spacer formation process is performed in two consecutive plasma etching steps: the first etching step is the main etching step, followed by a second etching step that is a precise over-etching step. When the spacer is silicon nitride, the process gases used for these two etching steps can include CF4, CHF3, C4F8, and H2 at medium to low pressures ranging from about 30 mTorr to about 50 mTorr.

[0098] Figure 6A The incoming wafer of this process flow is illustrated. The incoming wafer includes, for example: a substrate 600 including crystalline silicon 601 with a thin silicon oxide capping layer 602; a patterned layer 610 including discrete steps (e.g., polysilicon lines) formed over the substrate 600; and a continuous conformal thin film 613 of sidewall spacer material (e.g., silicon nitride) formed over the patterned layer 610 and the substrate 600. In some embodiments, the patterned layer 610 may include gate lines and may use the same process (i.e., similar to...). Figure 3A The anisotropic etching process described in the text is used to form it.

[0099] Figure 6B This shows the result after the first etching step is completed. Figure 6A The structure is as follows. Anisotropic RIE is performed in the first etching step, which selectively removes a large portion of the material from the horizontal surface of the conformal film 613 disposed above the top surface of the patterned layer 610 and above a portion of the semiconductor substrate 600 outside the area covered by the patterned layer 610. A morphological selectivity aspect of the anisotropic RIE process forms a non-conformal film 615, wherein the thickness of the sidewall spacer material covering the edges of the patterned layer 610 is substantially the same as the thickness of the conformal film 613, but the thickness of the remaining sidewall spacer material covering the horizontal surface (e.g., the top surface of the patterned layer 610 and the portion of the semiconductor substrate 600 outside the area covered by the patterned layer 610) is significantly smaller. Since the first etching step removes most of the sidewall spacer material above the horizontal surface, it is referred to as the main etching. For the sake of comparison with the reference... Figure 3C and Figure 5C For the same reason explained by the anisotropic RIE steps described, the main etching can be performed using an HF RF signal. The RF frequency (f1) can range from about 3 MHz to about 100 MHz, for example, 13 MHz.

[0100] exist Figure 6CIn this case, the second etch step is initiated and performed immediately after the main etch. The second etch step, referred to as an over-etch step, is precisely controlled to remove the remaining sidewall spacer material from the horizontal surfaces at a much slower removal rate than the main etch. The over-etch process can be a plasma etch process that provides a slow, isotropic removal of the sidewall spacer material for precise timing and thickness control. As known to those skilled in the art, it is advantageous to perform the isotropic plasma etch, such as the over-etch step, with a low power VHF RF signal at a slow removal rate. The plasma can include a process gas mixture that is high in hydrogen content and low in fluorocarbon or NF3 content. The etch chemistry removes silicon nitride at a slow rate and is highly selective to silicon oxide. The plasma etch process parameters can also be adjusted to provide an anisotropic etch component. The RF frequency (f2) can be from about 30 MHz to about 300 MHz, for example 60 MHz. The final structure after both the main etch and the over-etch are completed has sidewall spacers 618 of precise thickness formed over the step edges in the patterned layer 610, as shown in Figure 6C

[0101] Figure 6D Variations in the frequency and power of the RF signal during the main etch and over-etch steps are illustrated. The anisotropic RIE main etch that produces the non-conformal film 615 is performed using a high power HF RF signal, for example f1 = 13 MHz, until time T1 in Figure 6D The short duration over-etch is initiated at time T1 and terminated at time T2. As shown in Figure 6D The isotropic plasma etch process for the over-etch uses a relatively low power VHF RF signal, for example f2 = 60 MHz.

[0102] In various embodiments, similar process flows (similar to the over-etch process flow described with reference to FIG. 6) can be derived to address similar problems. Examples include reducing stringer defects in aspect ratio dependent etching (ARDE) or reverse ARDE, or in-situ cleaning for surface conditioning, or removal of residues such as residual photoresist and other polymers.

[0103] Figures 7A to 7C Another example of plasma process steps performed in sequence in a single plasma processing chamber of a broadband plasma processing system (for example, the plasma processing chamber 200 of the broadband plasma processing system 1111 in Figure 2 In this example, non-conformal deposition and precise isotropic etching are used to form a blanket layer over a patterned layer that includes step features.

[0104] Figure 7A ​An incoming wafer comprising a semiconductor substrate 700 and a patterned layer 710 formed on the semiconductor substrate 700 is shown. Figure 7A One step of the patterned layer 710 with substantially vertical edges is shown. The patterned layer 710 can be formed using techniques similar to those described for the layer 310. Figure 3A

[0105] In Figure 7B , a non-conformal layer 713 is formed using a non-conformal PECVD process. The non-conformal layer 713 can comprise, for example, silicon nitride or a carbon-based material deposited using, for example, a PECVD technique, where a gas mixture of methane and hydrogen can be used to obtain the desired plasma properties. As Figure 7B shown, the deposition process has both topography selectivity and area selectivity. Thus, the non-conformal layer 713 is formed at different thicknesses not only over the vertical and horizontal surfaces of the step of the patterned layer 710, but also over two types of horizontal surfaces: the horizontal surface of the patterned layer 710 and the horizontal surface of the semiconductor substrate 700. As Figure 7B shown, the non-conformal layer 713 over the horizontal top surface of the patterned layer 710 has a first thickness dl, while over the horizontal top surface of the semiconductor substrate 700, the non-conformal layer 713 has a second thickness d2. A third thickness d3 of the non-conformal layer 713 is deposited on the vertical edges of the step in the patterned layer 710. In the example embodiment shown, Figures 7A to 7C d3 < d2 < dl; the deposited non-conformal layer 713 is thickest over the top of the step of the patterned layer 710 and thinnest on the vertical edges. As an anisotropic plasma process, the non-conformal PECVD process is performed using an HF RF signal of a first RF frequency (e.g., fl = 13 MHz in the HF RF band between 3 MHz and 30 MHz).

[0106] Reference is now made to Figure 7C ​A short duration, low power isotropic plasma etch process is used to remove a portion of the non-conformal layer 713. The plasma can be a gas mixture including CF4mixed with oxygen, for example, at a relatively high pressure (e.g., about 100 mTorr to about 200 mTorr) to avoid re-deposition, or ozone. The flow rate of the gases can be adjusted to maintain a low concentration of oxygen so that the mixture can be about 5% to about 10% oxidizer. In some embodiments, very low RF bias power can also be used. The etch will expose the horizontal top surface of the semiconductor substrate 700 outside the areas covered by the patterned layer 710, without exposing the horizontal top surface of the step of the patterned layer 710 (where the deposited thickness of the non-conformal layer 713 is the highest). The vertical sides of the step in the patterned layer 710 (where the non-conformal layer 713 is the thinnest) are also exposed by this etch. A low etch rate isotropic plasma etch process can be used to perform this etch, where the duration of the RF signal is precisely controlled to terminate the etch after enough material is removed to expose the horizontal top surface of the semiconductor substrate 700. The precise thickness control leaves a thin cap layer 715 with a controlled fourth thickness d4, which remains over the horizontal top surface of the step of the patterned layer 710, as shown in Figure 7C d3 < d2. Thus, the thickness (d4) of the cap layer 715 is close to (d1 - d2). Similar to the over-etch process described above with reference to Figure 6B and Figure 6C The low etch rate isotropic plasma etch process is performed using a VHF RF signal at a second RF frequency f2 = 100 MHz in the VHF RF band between 60 MHz and 300 MHz, for example.

[0107] Figure 7D The changes in frequency and power of the RF signals during the non-conformal PECVD and isotropic plasma etch process steps performed consecutively in the plasma processing chamber 200 are shown. As shown in the timing diagram in Figure 7D a HF RF signal at fl = 13 MHz is used for a time period Tl, during which the non-conformal PECVD forms the non-conformal layer 713 shown in Figure 7B Between time instances Tl and T2, the broadband plasma processing system 1111 can be reconfigured according to the recipe of the next plasma process. The next step is a short duration, low power isotropic plasma etch. As shown in the timing diagram in Figure 6DAs shown, from time T2 to time T3, an isotropic plasma etch process uses a relatively low power VHF RF signal at, for example, f2 = 60 MHz.

[0108] Figures 8A to 8C The next example of single-chamber plasma processing shown is a cyclic area-selective deposition process performed by the broadband plasma system 1111 in a dual-frequency pulsed mode of operation. The cyclic area-selective deposition in this example utilizes cyclic deposition and etching techniques. Area-selective deposition processes, such as the cyclic area-selective deposition process described herein, can be used to enable bottom-up patterning. It will be appreciated that other applications of cyclic deposition and etching techniques (e.g., the Bosch etch process commonly used to etch silicon to form through-silicon vias) can also benefit from being performed using a broadband plasma processing system (such as the broadband plasma processing system 1111 shown Figure 1 and Figure 2 a process flow performed using the broadband plasma processing system 1111 shown.

[0109] In one embodiment, each cycle of the cyclic area-selective deposition process includes two parts. During the first part, a thin layer of material is deposited using a PEALD step utilizing a first RF frequency fi. In the second part, a portion of the deposited material is removed using a PEALE step utilizing a second RF frequency f2, as described in further detail below. Various material combinations can be used. For example, in one embodiment, silicon nitride can be deposited with selectivity to metal or oxide. In some other embodiments, silicon oxide can be deposited with selectivity to metal or nitride.

[0110] Figure 8A An incoming wafer is shown having a top surface comprising two regions; a first region 800 of a first material and a second region 810 of a second material. For example, the first region 800 can be a surface of a semiconductor such as bulk crystalline silicon and the second region 810 can comprise an insulator such as silicon oxide inlayed in a silicon substrate, as shown. Figure 8A

[0111] In Figure 8B a thin layer 815 of material, for example silicon nitride, is formed using, for example, PEALD techniques. In example embodiments, silicon nitride nucleation first occurs over the first region 800 comprising, for example, silicon, in preference to the second region 810 comprising, for example, silicon oxide. Thus, a thin layer 815 is selectively deposited over the first region 800 by the PEALD process. However, delayed nucleation can occur over the silicon oxide surface in the second region 810, which can result in island-like defects 820 comprising small discrete regions of silicon nitride, as shown. Figure 8B ​The unwanted island defects 820 can reduce the selectivity of the deposition process and can even result in a continuous film of, for example, silicon nitride over the second region 810 if not removed. Accordingly, in an example embodiment, the PEALD is interrupted after a predetermined first period of time of forming the thin layer 815, and the plasma processing apparatus 17 (see Figure 1 and Figure 2 is reconfigured to perform a short isotropic plasma etch using the PEALE technique to remove any island defects 820 that can have formed over the second region 810.

[0112] In Figure 8C , the islands 820 have been removed. In an example embodiment, the removal is achieved by performing a short isotropic PEALE step for a second period of time after the predetermined first period of PEALD is complete. After the PEALE step is complete, the plasma processing apparatus 17 can be reconfigured to continue with the PEALD for another period of time. The pair of a PEALD step and a PEALE step constitutes a cycle of the cyclic region-selective deposition process. By periodically removing the islands 820 using the isotropic plasma etch step, the cyclic region-selective deposition process maintains a high region selectivity. During the isotropic plasma etch step, a portion of the thin silicon nitride layer 815 can also be lost. Figure 8C The etched layer 825 shown includes the portion of the thin silicon nitride layer 815 that remained over the first region 800 at the end of the first cycle of the cyclic region-selective deposition process.

[0113] Figure 8D The structure after a number of cycles of the cyclic region-selective deposition process have been performed in order to bring the deposited layer 830 to a target thickness is shown.

[0114] The cyclic region-selective deposition process described with reference to Figures 8A to 8D is implemented by using the PEALD step and the PEALE step in each cycle in this example embodiment. The PEALD and PEALE steps can be performed by the broadband plasma processing system 1111 by operating the plasma processing apparatus 17 in a pulsed mode. Figure 8E The corresponding RF pulses for one cycle of the cyclic region-selective deposition process according to one embodiment are shown. For illustration purposes, the RF pulses are shown as being square pulses. In practice, the RF pulses can have other shapes, such as Gaussian shapes. Figure 8EIn the present example, the pulsed RF signal of one cycle of the cyclic area selective deposition process is represented by the RF pulses of one reaction cycle of the PEALD process and one reaction cycle of the PEALE process. It is to be understood that in a process recipe, one cycle of the cyclic area selective deposition process can comprise several PEALD reaction cycles and several PEALE reaction cycles. A reaction cycle of an atomic layer process typically comprises a first reaction pulse during which a first self-limiting half-reaction is performed and a second reaction pulse during which a second self-limiting half-reaction is performed which will complete the chemical reaction achieving deposition (PEALD) or removal (PEALE) of one atomic layer. Each reaction pulse is followed by a purge pulse during which gas by-products and excess reactants can be removed by the vacuum pump 202 through the outlet 207 (see Figure 2 ) of the plasma processing chamber 200.

[0115] Figure 8E Both the pulsed RF signal and the control pulse sequence are shown, the chopper circuit 14 (see Figure 1 ) can use the control pulse sequence to modulate the CW-RF signal to generate the un-interrupted pulsed RF signal comprising un-interrupted RF pulses. In this example embodiment, the first RF pulse corresponds to the second reaction pulse of a PEALD reaction cycle. During the first reaction pulse (duration T1 in Figure 8E ), precursor adsorption can be performed without plasma. In the timing diagram of Figure 8E , the reaction pulse without plasma is represented by the dashed rectangle. The purge pulse following the first reaction pulse starts at T1 and ends at T2. The low-to-high transition of the pulse at T2 enables the RF signal to pass through the chopper circuit 14 and the plasma for the second reaction pulse of the PEALD reaction cycle is ignited. The RF frequency f1 can be about 10 MHz to about 300 MHz, for example 100 MHz. After the duration (T3-T2), the second self-limiting half-reaction of the PEALD reaction cycle is completed and the second purge pulse is initiated. At T3 in Figure 8E , the RF power is switched off by blocking the RF signal at the chopper circuit 14 using the high-to-low transition of the modulation pulse to extinguish the plasma discharge during the purge pulse. One PEALD reaction cycle is completed with the completion of the second purge pulse. Depending on the respective process recipe 10 (see Figure 1 ), a plurality of PEALD reaction cycles (not shown) can be performed during the first part of one cycle of the cyclic area selective deposition process.

[0116] At Figure 8EIn this embodiment, the first part is completed at a predetermined time T4, and the second part begins, during which the PEALE step is performed. The first PEALE reaction cycle begins with a first reaction pulse at T4, which can include a surface conditioning phase. Similar to the first reaction pulse of the PEALD reaction cycle, there can be no plasma during the pulse duration (T5-T4) of the first reaction pulse of the PEALE reaction cycle. A first purge pulse can begin at T5 and be completed before T6. At T6, a second reaction pulse of the PEALE reaction cycle can be initiated. The second reaction pulse of the PEALE reaction cycle uses a plasma maintained by using an RF signal triggered by a low-to-high transition of the modulation pulse, and is completed at T7 as the modulation pulse turns off the RF power supply by using a high-to-low transition to extinguish the plasma. The RF frequency f2 of the PEALE RF pulse can be about 10 MHz to about 300 MHz, such as 13 MHz. The purge pulse between T7 and T8 completes the PEALE reaction cycle. According to the corresponding process recipe 10 (see Figure 1 ), multiple PEALE reaction cycles (not shown) can be performed to complete one cycle of the cyclic area-selective deposition process.

[0117] (Generated by the tunable RF signal generator 12 in Figure 1 ), the frequency and amplitude of the PEALD and PEALE RF signals, the timing of the modulation pulse (generated at the chopper circuit 14 in Figure 1 ), and the C L in the output matching network 115 in Figure 1 ) can be controlled by the programmable controller 11 of the wideband plasma processing system 1111 in Figure 1 . In this embodiment, the RF pulses of the uninterrupted pulse RF signal can have a relatively long duration. In some other embodiments, the PEALD and PEALE steps can use a segmented pulse RF signal, where each segmented RF pulse is a grouping including a plurality of sub-pulses having a very short duration, such as a sub-pulse duration of about 10 microseconds to 1000 microseconds, such as 100 microseconds.

[0118] Figure 9 A flowchart 9999 is shown for one cycle of a cyclic two-part (e.g., deposition part and etch part) plasma process (such as the process described above with reference to Figures 8A to 8E ). In this embodiment, the first part is completed at a predetermined time T4, and the second part begins, during which the PEALE step is performed. The first PEALE reaction cycle begins with a first reaction pulse at T4, which can include a surface conditioning phase. Similar to the first reaction pulse of the PEALD reaction cycle, there can be no plasma during the pulse duration (T5-T4) of the first reaction pulse of the PEALE reaction cycle. A first purge pulse can begin at T5 and be completed before T6. At T6, a second reaction pulse of the PEALE reaction cycle can be initiated. The second reaction pulse of the PEALE reaction cycle uses a plasma maintained by using an RF signal triggered by a low-to-high transition of the modulation pulse, and is completed at T7 as the modulation pulse turns off the RF power supply by using a high-to-low transition to extinguish the plasma. The RF frequency f2 of the PEALE RF pulse can be about 10 MHz to about 300 MHz, such as 13 MHz. The purge pulse between T7 and T8 completes the PEALE reaction cycle. According to the corresponding process recipe 10 (see Figures 8A to 8EIn the example embodiment shown, the duration of the uninterrupted RF pulse is shown to be the same as the duration of the corresponding reaction pulse. As mentioned above, in another embodiment, these relatively long duration RF pulses can be replaced by a grouping of several short duration sub-pulses. Similar to the sequential mode execution procedure 4444 (see Figure 4 ), the first step in the pulse mode execution procedure 9999, as shown in block 91, is to parse the process recipe 10 (see Figure 1 ) to identify the input process parameters, such as the respective first and second part RF frequencies f1 and f2, and the respective pulse durations and duty cycles. As in Figure 4 , the hardware of the broadband plasma processing system 1111 is then configured, as shown in blocks 92 and 93 in Figure 9 . Control signals from the programmable controller 11 are used to electrically connect to the plasma processing device 17 (as shown in block 921), and to set two toggle switches (block 923) to route the RF signals via the chopper circuit 14 and the bandpass filters 16. For example, the output port of the bandpass filter for f1 is connected to the RF electrode that is powered by the pulsed RF signal at frequency f1. If the same RF electrode is used for the first and second parts of one cycle, then the two respective output ports of the bandpass filters 16 can be connected to one RF electrode. The RF electrode connections can be fixed throughout the cycle.

[0119] The configurations that need to be adjusted by the programmable controller 11 as the frequency is changed from f1 to f2 are shown in blocks 93 (for f1) and 95 (for f2). In blocks 931 and 951, the load capacitor C L of the output matching network 115 is selected, and in blocks 933 and 953, the pulse generator of the chopper circuit 14 is configured, as shown in Figure 9 .

[0120] After the hardware is properly configured, the pulsed RF signal for the first part of the cycle is generated, and a frequency sweep tuning method with a center frequency offset is employed to quickly adjust the impedance of the output matching network 115 by adjusting the RF frequency of the pulsed RF signal within a frequency band centered at f1, as shown in block 94. The electronic feedback control system used to achieve the minimum impedance mismatch is the same as the one described in detail above with reference to Figure 1 , Figure 2 and Figure 4 . When the first part using the pulsed RF signal with center frequency f1 is completed, for the second part of the cycle, the programmable controller 11 switches the RF center frequency to f2 after reconfiguring the hardware of the output matching network 115 and the chopper circuit 14, as shown in blocks 95 and 96. At the end of these two parts of the first cycle, the hardware settings are reset to the settings for frequency f1 to perform the second cycle, as shown in block 97. Figure 9 The execution flow 9999 in FIG. 11B illustrates the execution flow 9999 in FIG. 11A.

[0121] Two or more RF center frequencies are used in all embodiments and execution flows described above for the sequential mode or the pulsed mode. In addition, all embodiments utilize a single-channel wideband plasma processing system. Next, we disclose an example embodiment for single-frequency pulsed mode operation, as well as an example for dual-frequency pulsed mode operation using a dual-channel wideband plasma processing system (described in detail in application 16 / 572,708).

[0122] In embodiments where the plasma processing apparatus is operated in the single-frequency pulsed mode, the RF frequency is fixed during the total processing time, but the total processing time can be divided into multiple portions, where the number and / or the duty cycle of the RF pulses during each portion can be changed according to the specifications in the process recipe for the plasma process step. For example, a plasma process step such as a RIE step with a total processing time of t0= 150 seconds can be divided into five portions: the first portion of main etching can have a processing time of ti = 100 seconds and a duty cycle of Di = 50%, while the subsequent four portions can have processing times of t2, t3, t4, and t5 of 10 seconds each and successively shorter duty cycles (e.g., D2= 40%, D3= 30%, D4= 20%, and D5= 10%) to gradually reduce the average RF power to the plasma. The RF signal in this example includes five segments; each segment includes RF pulses with successively lower duty cycles.

[0123] In another embodiment, a first pulsed RF signal with a center frequency fi provides RF source power to an RF electrode (e.g., the top electrode 206 (see FIG. 10) of the plasma processing apparatus 17. A second pulsed RF signal with a center frequency f2provides RF bias power to the bottom electrode 208 (see FIG. 10). The pulsed plasma process can be used in a process flow for forming gate structures, spacer structures, self-aligned contact structures, etc. Both of these pulsed RF signals can be provided to the plasma processing apparatus 17 using a dual-channel wideband plasma processing system. As described in detail in application 16 / 572,708, the dual-channel wideband plasma processing system uses a dual-channel wideband tunable RF signal generator and a dual-channel wideband RF power amplifier to provide both high-power RF signals simultaneously to power the RF electrodes of the same single-chamber plasma processing apparatus 17. The dual-channel version is implemented by using two single-channel units in parallel or replicating the single-channel version in one integrated unit. Fast impedance matching is achieved in each channel by using separate electronic feedback signals that provide feedback to one programmable controller that controls the dual-channel wideband plasma processing system hardware. Figure 2 Figure 2 In another embodiment, a first pulsed RF signal with a center frequency fi provides RF source power to an RF electrode (e.g., the top electrode 206 (see FIG. 10) of the plasma processing apparatus 17. A second pulsed RF signal with a center frequency f2provides RF bias power to the bottom electrode 208 (see FIG. 10). The pulsed plasma process can be used in a process flow for forming gate structures, spacer structures, self-aligned contact structures, etc. Both of these pulsed RF signals can be provided to the plasma processing apparatus 17 using a dual-channel wideband plasma processing system. As described in detail in application 16 / 572,708, the dual-channel wideband plasma processing system uses a dual-channel wideband tunable RF signal generator and a dual-channel wideband RF power amplifier to provide both high-power RF signals simultaneously to power the RF electrodes of the same single-chamber plasma processing apparatus 17. The dual-channel version is implemented by using two single-channel units in parallel or replicating the single-channel version in one integrated unit. Fast impedance matching is achieved in each channel by using separate electronic feedback signals that provide feedback to one programmable controller that controls the dual-channel wideband plasma processing system hardware. ​

[0124] Figure 10A The power spectrum of the RF power pulses of the first (RF source) and second (RF bias) pulsed RF signals are shown, and Figure 10B The RF power of the two pulsed RF signals versus time is shown. In this embodiment, the RF source power and the RF bias power do not overlap in either the frequency domain or the time domain. However, it should be appreciated that in some embodiments, the two pulsed RF signals can overlap to some extent. As Figure 10A The power spectrum density in shows that the RF bias is at a lower frequency band (f2± Af2) relative to the frequency band of the RF source (f1± Af1). Figure 10B The graph of RF power versus time shown in illustrates that the RF bias power is supplied in pulses between successive pulses of the RF source power.

[0125] One benefit of using the frequency-scan tuning method with a center frequency offset to quickly establish impedance matching is the precise control of the RF power. Figure 10C The waveform of RF power versus time for a hypothetical wideband plasma processing system is shown in which the impedance of the output matching network 115 is tuned using a relatively slow method (e.g., mechanically tuning the capacitance of a variable capacitor) rather than the fast frequency-scan tuning method with a center frequency offset. As Figure 10C As shown in, each time an RF pulse is initiated, the RF power exhibits a significant transient behavior that eventually settles to a steady value as expected for an output matching network with relatively slow impedance changes. For example, it can take a significant amount of time after the initiation of a pulse (e.g., only after 10-20% of the pulse width has passed) to reach (or alternatively, sometimes never reach) the nominal power, which will result in non-uniform and unpredictable deposition / etch rates. In contrast, Figure 10B The corresponding waveform in shows that the steady state value is reached quickly (e.g., within less than 1% of the pulse width), so the transient behavior is not noticeable. In various embodiments, the steady state value can be reached within a microsecond amount of time (e.g., 10 microseconds). The ability to reach steady state quickly also enables fast switching or cycling between different types of plasma conditions such as etch and deposition processes, which is not possible in systems that exhibit large transients. Figure 10C The transient behavior seen in is unpredictable and uncontrolled. Thus, embodiments in the present disclosure provide the benefit of precise RF power control by using the fast frequency-scan tuning method with a center frequency offset to reduce or suppress RF power transients.

[0126] In various embodiments, process flows such as those for gate, gate spacers, self-aligned contacts, bottom-up patterning, Bosch processes, etc. can include plasma processes using pulsed RF signals or CW-RF signals with discrete RF frequencies used simultaneously, cyclically, or sequentially. These process flows can include plasma steps in which traditional plasma processing (e.g., PECVD and RIE) and / or atomic layer plasma processing (e.g., PEALD and PEALE) are used. In these applications, it can be advantageous to use embodiments of the methods described in this disclosure and to obtain the benefits of fast impedance matching provided by the frequency-scan tuning method implemented in a broadband plasma processing system.

[0127] Example embodiments of the invention are summarized here. Other embodiments can be understood from the entire specification, including the claims presented herein.

[0128] Example 1. A method for operating a plasma processing system, comprising determining a first frequency for powering a first plasma within a plasma processing chamber. The method comprises generating a first amplified RF signal having the first frequency at a broadband power amplifier. The method comprises supplying the first amplified RF signal to process a substrate arranged in the plasma processing chamber using a first plasma process comprising the first plasma. The method comprises determining a second frequency for powering a second plasma within the plasma processing chamber. The method comprises generating a second amplified RF signal having the second frequency at the broadband power amplifier. The method comprises supplying the second amplified RF signal to process the substrate arranged in the plasma processing chamber using a second plasma process comprising the second plasma.

[0129] Example 2. The method of example 1, wherein the first amplified RF signal comprises a plurality of first pulses, and wherein the second amplified RF signal comprises a plurality of second pulses.

[0130] Example 3. The method of one of examples 1 or 2, wherein the first amplified RF signal comprises a continuous wave, and wherein the second amplified RF signal comprises a plurality of pulses.

[0131] Example 4. The method of one of examples 1 to 3, wherein the first amplified RF signal comprises a first continuous wave, and wherein the second amplified RF signal comprises a second continuous wave.

[0132] Example 5. The method of one of examples 1 to 4, wherein the first amplified RF signal or the second amplified RF signal comprises a plurality of aperiodic pulses.

[0133] Example 6. The method of one of Examples 1-5, wherein determining the first frequency comprises generating a first feedback signal by measuring power delivered to the first plasma, and determining the first frequency based on the first feedback signal; and wherein determining the second frequency comprises generating a second feedback signal by measuring power delivered to the second plasma, and determining the second frequency based on the second feedback signal.

[0134] Example 7. The method of one of Examples 1-6, further comprising: prior to determining the first frequency, selecting a load capacitor of an output matching network to a first capacitance value based on a first process recipe, and powering the first plasma; and prior to determining the second frequency, selecting the load capacitor of the output matching network to a second capacitance value based on a second process recipe, and powering the second plasma.

[0135] Example 8. The method of one of Examples 1-7, further comprising: using the first plasma to deposit a layer over the substrate, and using the second plasma to etch a portion of the layer, wherein the first frequency is greater than the second frequency; or using the first plasma to deposit a conformal layer over a feature disposed over the substrate, and using the second plasma to anisotropically etch a portion of the conformal layer, wherein the first frequency is greater than the second frequency; or using the first plasma to perform an anisotropic etch process to remove a first portion of a layer from the substrate, and using the second plasma to perform an anisotropic etch process to remove a second portion of the layer from the substrate, wherein the first frequency is less than the second frequency; or using the first plasma to deposit a non-conformal layer over a feature disposed over the substrate, and using the second plasma to isotropically etch a portion of the conformal layer, wherein the first frequency is less than the second frequency.9. The method of one of Examples 1-7, further comprising: using the first plasma to deposit a conformal layer over a feature disposed over the substrate; and using the second plasma to anisotropically etch a portion of the conformal layer, wherein the first frequency is greater than the second frequency; determining a third frequency for powering a third plasma disposed within the plasma processing chamber based on measuring power delivered to the third plasma; generating a third amplified RF signal at the wideband power amplifier; supplying the third amplified RF signal to process a substrate disposed within the plasma processing chamber using a third plasma process comprising the third plasma; and using the third plasma to isotropically etch the feature.

[0136] Example 10. A method for operating a plasma processing system, comprising performing a first frequency sweep tuning to generate a first radio frequency (RF) signal comprising a first frequency. The method comprises amplifying, at a wideband power amplifier, the first RF signal to generate a first amplified RF signal. The method comprises supplying the first amplified RF signal to process a substrate disposed in a plasma processing chamber, the processing of the substrate powered by the first amplified RF signal. The method comprises performing a second frequency sweep tuning to generate a second radio frequency (RF) signal comprising a second frequency. The method comprises amplifying, at the wideband power amplifier, the second RF signal to generate a second amplified RF signal. The method comprises supplying the second amplified RF signal to process the substrate disposed in the plasma processing chamber, the processing of the substrate powered by the second amplified RF signal.

[0137] Example 11. The method of example 10, wherein the first radio frequency (RF) signal comprises a continuous wave, wherein the second radio frequency (RF) signal comprises a plurality of pulses, each pulse of the plurality of pulses comprising a pulse duration and the second frequency. 12. The method of example 10, wherein the first amplified RF signal is supplied to a first electrode of the plasma processing chamber and the second amplified RF signal is supplied to a second electrode of the plasma processing chamber.

[0138] Example 12. The method of one of examples 10 or 11, wherein the first amplified RF signal and the second amplified RF signal together power a plasma generated within the plasma processing chamber.

[0139] Example 13. The method of one of examples 10 to 12, wherein supplying the first amplified RF signal comprises processing the substrate using a first plasma process, the first plasma process comprising a first plasma powered by the first amplified RF signal; and wherein supplying the second amplified RF signal comprises processing the substrate using a second plasma process, the second plasma process comprising a second plasma powered by the second amplified RF signal.

[0140] Example 14. The method of one of examples 10 to 13, wherein performing the first frequency sweep tuning comprises measuring a first normalized reflected power from the plasma processing chamber, and based on measuring the first normalized reflected power, adjusting a frequency of a first preliminary RF signal generated near a first frequency band so as to generate the first RF signal comprising the first frequency; and wherein performing the second frequency sweep tuning comprises measuring a second normalized reflected power from the plasma processing chamber, and based on measuring the second normalized reflected power, adjusting a frequency of a second preliminary RF signal generated near a second frequency band so as to generate the second RF signal comprising the second frequency.

[0141] Example 15. The method of one of Examples 10 to 14, wherein the first radio frequency (RF) signal comprises a plurality of first pulses, each pulse of the plurality of first pulses comprising a first pulse duration and the first frequency, wherein the second radio frequency (RF) signal comprises a plurality of second pulses, each pulse of the plurality of second pulses comprising a second pulse duration and the second frequency.

[0142] Example 16. The method of one of Examples 10 to 15, further comprising providing a plurality of first purge pulses separating adjacent pulses of the plurality of first pulses; and providing a plurality of second purge pulses separating adjacent pulses of the plurality of second pulses.

[0143] Example 17. The method of one of Examples 10 to 16, wherein the first amplified RF signal and the second amplified RF signal are coupled to a first electrode.

[0144] Example 18. A method for operating a plasma processing system, comprising performing a first etch / deposition process on a substrate using a first plasma in a plasma process chamber by powering the first plasma with a first amplified radio frequency signal, the first amplified radio frequency signal comprising a plurality of first pulses and having a first frequency and a first amplitude. The method comprises changing the first plasma to a second plasma. The method comprises performing a second etch / deposition process on the substrate using the second plasma by powering the second plasma in the plasma process chamber with a second amplified radio frequency signal, the second amplified radio frequency signal comprising a plurality of second pulses and having a second frequency and a second amplitude, the first frequency and the second frequency having different frequency values, wherein the first amplified radio frequency signal is tuned to the first frequency by a first frequency sweep tuning process and the second amplified radio frequency signal is tuned to the second frequency by a second frequency sweep tuning process.

[0145] Example 19. The method of Example 18, wherein the first etch / deposition process comprises a deposition process, and wherein the second etch / deposition process comprises an etch process, wherein the second frequency is greater than the first frequency.

[0146] Example 20. The method of one of Examples 18 or 19, wherein the first frequency sweep tuning process includes measuring a first normalized reflected power from the first plasma, and based on measuring the first normalized reflected power, adjusting a frequency of a first preliminary radio frequency signal generated near a first frequency band so as to generate the first amplified radio frequency signal at the first frequency; and wherein the second frequency sweep tuning process includes measuring a second normalized reflected power from the second plasma, and based on measuring the second normalized reflected power, adjusting a frequency of a second preliminary radio frequency signal generated near a second frequency band so as to generate the second amplified radio frequency signal at the second frequency.

[0147] While the application has been described with reference to illustrative embodiments, this description is not intended to be construed in a limiting sense. Various modifications and combinations of the illustrative embodiments, as well as other embodiments of the application, will be apparent to persons skilled in the art. It is therefore intended that the appended claims shall cover any such modifications or embodiments.

Claims

1. A method for operating a plasma processing system, the method comprising: determining a first frequency for powering a first plasma within a plasma processing chamber; generating, at a broadband power amplifier, a first amplified RF signal having the first frequency; supplying the first amplified RF signal to process a substrate arranged in the plasma processing chamber using a first plasma process including the first plasma; determining a second frequency for powering a second plasma within the plasma processing chamber; generating, at the broadband power amplifier, a second amplified RF signal having the second frequency; and supplying the second amplified RF signal to process the substrate arranged in the plasma processing chamber using a second plasma process including the second plasma, wherein determining the first frequency includes generating a first feedback signal by measuring power delivered to the first plasma, and determining the first frequency based on the first feedback signal; and wherein determining the second frequency includes generating a second feedback signal by measuring power delivered to the second plasma, and determining the second frequency based on the second feedback signal, and wherein the first feedback signal and the second feedback signal represent an impedance mismatch between the broadband power amplifier and a load at an output port of the broadband power amplifier. the first amplified RF signal includes a plurality of first pulses, and wherein the second amplified RF signal includes a plurality of second pulses.

2. The method of claim 1, wherein, the first amplified RF signal includes a continuous wave, and wherein the second amplified RF signal includes a plurality of pulses.

3. The method of claim 1, wherein, the first amplified RF signal includes a first continuous wave, and wherein the second amplified RF signal includes a second continuous wave.

4. The method of claim 1, wherein, the first amplified RF signal or the second amplified RF signal includes a plurality of non-periodic pulses.

5. The method of claim 1, wherein, 6. The method of claim 1, further comprising: prior to determining the first frequency, selecting a load capacitor of an output matching network to a first capacitance value and powering the first plasma based on a first process recipe; and prior to determining the second frequency, selecting the load capacitor of the output matching network to a second capacitance value and powering the second plasma based on a second process recipe.

7. The method of claim 1, further comprising: depositing a layer over the substrate using the first plasma and etching a portion of the layer using the second plasma, wherein the first frequency is greater than the second frequency; or depositing a conformal layer over a feature arranged over the substrate using the first plasma and anisotropically etching a portion of the conformal layer using the second plasma, wherein the first frequency is greater than the second frequency; or performing an anisotropic etch process to remove a first portion of a layer from the substrate using the first plasma and performing an anisotropic etch process to remove a second portion of the layer from the substrate using the second plasma, wherein the first frequency is less than the second frequency; or ​ ​ deposits a non-conformal layer over a feature arranged above the substrate using the first plasma, and isotropically etches a portion of the conformal layer using the second plasma, wherein the first frequency is less than the second frequency.

8. The method of claim 1, further comprising: depositing a conformal layer over a feature arranged above the substrate using the first plasma; and anisotropically etching a portion of the conformal layer using the second plasma, wherein the first frequency is greater than the second frequency; determining a third frequency for powering a third plasma based on measuring a power delivered to the third plasma within the plasma processing chamber; generating a third amplified RF signal at the wideband power amplifier; supplying the third amplified RF signal to process a substrate arranged in the plasma processing chamber using a third plasma process including the third plasma; and isotropically etching the feature using the third plasma.

9. A method for operating a plasma processing system, the method comprising: performing a first frequency sweep tuning to generate a first RF signal including a first frequency; amplifying, at a wideband power amplifier, the first RF signal to generate a first amplified RF signal; supplying the first amplified RF signal to process a substrate arranged in a plasma processing chamber, the processing of the substrate powered by the first amplified RF signal; performing a second frequency sweep tuning to generate a second RF signal including a second frequency; amplifying, at the wideband power amplifier, the second RF signal to generate a second amplified RF signal; and supplying the second amplified RF signal to process a substrate arranged in the plasma processing chamber, the processing of the substrate powered by the second amplified RF signal, wherein the first frequency is determined based on a first feedback signal and the second frequency is determined based on a second feedback signal, and wherein the first feedback signal and the second feedback signal represent an impedance mismatch between the wideband power amplifier and a load at an output port of the wideband power amplifier.

10. The method of claim 9, wherein, the first RF signal includes a continuous wave, and wherein the second RF signal includes a plurality of pulses, each pulse of the plurality of pulses including a pulse duration and the second frequency.

11. The method of claim 10, wherein, the first amplified RF signal is supplied to a first electrode of the plasma processing chamber and the second amplified RF signal is supplied to a second electrode of the plasma processing chamber.

12. The method of claim 9, wherein, the first amplified RF signal and the second amplified RF signal together power a plasma generated within the plasma processing chamber.

13. The method of claim 9, wherein supplying the first amplified RF signal includes processing the substrate using a first plasma process including a first plasma powered by the first amplified RF signal; and wherein supplying the second amplified RF signal includes processing the substrate using a second plasma process including a second plasma powered by the second amplified RF signal.

14. The method of claim 9, wherein performing the first frequency sweep tuning includes measuring a first normalized reflected power from the plasma processing chamber, and based on measuring the first normalized reflected power, adjusting a frequency of a first preliminary RF signal generated near a first frequency band so as to generate the first RF signal at the first frequency; and wherein performing the second frequency sweep tuning includes measuring a second normalized reflected power from the plasma processing chamber, and based on measuring the second normalized reflected power, adjusting a frequency of a second preliminary RF signal generated near a second frequency band so as to generate the second RF signal at the second frequency.

15. The method of claim 9, wherein, The first RF signal includes a plurality of first pulses, each pulse of the plurality of first pulses including a first pulse duration and the first frequency, wherein the second RF signal includes a plurality of second pulses, each pulse of the plurality of second pulses including a second pulse duration and the second frequency.

16. The method of claim 15, further comprising: providing a plurality of first clean pulses separating adjacent pulses of the plurality of first pulses; and providing a plurality of second clean pulses separating adjacent pulses of the plurality of second pulses. The first amplified RF signal and the second amplified RF signal are coupled to a first electrode.

17. The method of claim 9, wherein, 18. A method for operating a plasma processing system, the method comprising: powering a first plasma in a plasma processing chamber by a first amplified RF signal generated at a wideband power amplifier, the first amplified RF signal including a plurality of first pulses and having a first frequency and a first amplitude, using the first plasma to perform a first etch / deposition process on a substrate; changing the first plasma to a second plasma; and powering the second plasma in the plasma processing chamber by a second amplified RF signal generated at the wideband power amplifier, the second amplified RF signal including a plurality of second pulses and having a second frequency and a second amplitude, the first frequency and the second frequency having different frequency values, using the second plasma to perform a second etch / deposition process on the substrate, wherein the first amplified RF signal is tuned to the first frequency by a first frequency sweep tuning process and the second amplified RF signal is tuned to the second frequency by a second frequency sweep tuning process, wherein the first frequency is determined based on a first feedback signal and the second frequency is determined based on a second feedback signal, and wherein the first feedback signal and the second feedback signal represent an impedance mismatch between the wideband power amplifier and a load at an output port of the wideband power amplifier. The first etch / deposition process includes a deposition process and wherein the second etch / deposition process includes an etch process, wherein the second frequency is greater than the first frequency.

19. The method of claim 18, wherein, 20. The method of claim 18, the first frequency sweep tuning process includes wherein measuring a first normalized reflected power from the first plasma, and based on measuring the first normalized reflected power, adjusting a frequency of a first preliminary RF signal generated near a first frequency band so as to generate the first amplified RF signal at the first frequency; and wherein the second frequency sweep tuning process includes measuring a second normalized reflected power from the second plasma, and ​ Based on measuring the second normalized reflected power, adjusting a frequency of a second preliminary RF signal generated near the second frequency band so as to generate a second amplified RF signal of the second frequency.

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