Plasma processing with broadband RF waveforms

Abstract

The plasma system includes: a plasma apparatus including a plasma chamber, a pedestal configured to hold a substrate in the chamber, and a radio frequency (RF) electrode configured to excite a plasma in the chamber; an electromagnetic (EM) circuit block coupled to the RF electrode, the EM circuit block including: a function generator configured to output a wideband RF waveform, the waveform having EM power distributed over a frequency range; a wideband amplifier coupled to the output of the function generator, the wideband amplifier having an operating frequency range that includes the frequency range; a wideband impedance matching network having an input coupled to the output of the wideband amplifier and an output coupled to a terminal of the RF electrode, the wideband impedance matching network having an operating frequency range that includes the frequency range; and a controller configured to adjust input parameters of the EM circuit block.

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of U.S. Non-Provisional Patent Application No. 17 / 865,225, filed July 14, 2022, the contents of which are incorporated herein by reference.

[0002] This application is related to U.S. Patent Application No. 16 / 572,708 (U.S. Patent No. 11,170,981 B2) filed on September 17, 2019 (Attorney Docket No. TEL-190559US01), U.S. Patent Application No. 16 / 717,024 (U.S. Patent No. 11,295,937 B2) filed on December 17, 2019 (Attorney Docket No. TEL-190559US02), U.S. Patent Application No. 17 / 498,063 filed on October 11, 2021 (Attorney Docket No. TEL-190559US03), and U.S. Patent Application No. 17 / 012,168 (U.S. Patent No. 11,348,761 B2) filed on September 4, 2020 (Attorney Docket No. TEL-200041US01), which are incorporated herein by reference in their entireties.

[0003] The present invention relates generally to systems for plasma processing, and in particular embodiments to systems for plasma processing with broadband radio frequency (RF) waveforms. [Background technology]

[0004] Integrated circuits (ICs) are monolithic networks of circuit components, including electronic devices and interconnect elements with complex three-dimensional structures with nanoscale features. Plasma processing is widely used in IC fabrication. Typically, these structures are formed by sequentially depositing and patterning various layers using lithography and etching. Plasma deposition and etching processes used to fabricate components for sub-10 nm technology nodes require control of nearly atomic-scale dimensions across 300 mm wafers. Because plasma properties affect many relevant structural features (e.g., line edge roughness (LER), sidewall angle at high aspect ratios, film thickness, liner conformality, void-free fill, and etch selectivity), the plasma must be precisely controlled. Scaling makes precision difficult to achieve given the limitations of excited plasmas using simple continuous-wave (CW) RF signals. To overcome some of these challenges, innovative processing methods, including cyclic processes, have been developed. These may require complex variations in plasma properties over time to enhance process capability. Complex and dynamic processes require complex RF waveforms to excite a plasma with the required characteristics. Often, two RF waveforms are applied in parallel to two electrodes or superimposed on one electrode. The superimposed waveforms have RF power distributed over a range of frequencies. Clearly, plasma systems using broadband RF waveforms facilitate innovative plasma processing, and further advances in broadband plasma systems are needed to successfully deploy this novel process. Summary of the Invention [Means for solving the problem]

[0005] The plasma system includes: a plasma apparatus including a plasma chamber, a pedestal configured to hold a substrate in the chamber, and a radio frequency (RF) electrode configured to excite a plasma in the chamber; an electromagnetic (EM) circuit block coupled to the RF electrode, the EM circuit block including: a function generator configured to output a wideband RF waveform, the waveform having EM power distributed over a frequency range; a wideband amplifier coupled to the output of the function generator, the wideband amplifier having an operating frequency range that includes the frequency range; a wideband impedance matching network having an input coupled to the output of the wideband amplifier and an output coupled to a terminal of the RF electrode, the wideband impedance matching network having an operating frequency range that includes the frequency range; and a controller configured to adjust input parameters of the EM circuit block.

[0006] The plasma system includes a plasma device; a dual-channel electromagnetic (EM) circuit block including: a first EM circuit block including a first function generator, a first wideband amplifier, and a first wideband impedance matching network, the first EM circuit block outputting a first wideband RF waveform coupled to the plasma device, the first wideband RF waveform having EM power distributed over a first frequency range; and a second EM circuit block including a second function generator, a second wideband amplifier, and a second wideband impedance matching network, the second EM circuit block outputting a second wideband RF waveform coupled to the plasma device, the second wideband RF waveform having EM power distributed over a second frequency range, the second frequency range being different from the first frequency range; and a controller configured to adjust a plurality of input parameters of the EM circuit block.

[0007] A method of operating a plasma processing system, the method comprising the steps of: outputting a wideband radio frequency (RF) waveform at an output of a function generator; coupling the output of the function generator to an input of a wideband amplifier; outputting an amplified wideband RF waveform at the output of the wideband amplifier; coupling the output of the wideband amplifier to a source end of a first RF pipe; coupling a load end of the first RF pipe to an input of a wideband impedance matching network opposite the source end; and coupling the output of the wideband impedance matching network using a second RF pipe to a terminal of an RF electrode of a plasma device, the terminal providing EM power to the RF electrode for exciting a plasma in a plasma chamber of the plasma device.

[0008] For a more complete understanding of the present invention and its advantages, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which: [Brief explanation of the drawings]

[0009] [Figure 1A] 1 shows a schematic diagram of a broadband plasma system including a cross-sectional view of the plasma device and a block diagram of an electromagnetic (EM) system that provides EM power to the plasma device, according to some embodiments. [Figure 1B] FIG. 1 illustrates a cutaway view of a VI sensor showing exemplary voltage and current pickups, according to some embodiments. [Figure 1C] 1 illustrates a circuit diagram of an exemplary reactance circuit used in a wideband impedance matching network, according to some embodiments. [Figure 2] 1 shows a schematic diagram of a broadband plasma system including a cross-sectional view of the plasma device and a block diagram of an electromagnetic (EM) system that provides EM power to the plasma device, according to some embodiments. [Figure 3]1 shows a schematic diagram of a broadband plasma system including a cross-sectional view of the plasma device and a block diagram of an electromagnetic (EM) system that provides EM power to the plasma device, according to some embodiments. [Figure 4] 1 shows a schematic diagram of a broadband plasma system including a cross-sectional view of the plasma device and a block diagram of an electromagnetic (EM) system that provides EM power to the plasma device, according to some embodiments. [Figure 5] 1 shows a flowchart of a method for processing a substrate, according to some embodiments. DETAILED DESCRIPTION OF THE INVENTION

[0010] This disclosure describes embodiments of a system for plasma processing capable of exciting a plasma using a broadband radio frequency (RF) waveform. The broadband RF waveform has electromagnetic (EM) power distributed across a range of frequencies in the RF band. The plasma processing system includes a plasma device that excites a plasma to process a substrate, an EM circuit block that supplies EM power to the plasma device, and a controller that adjusts input parameters of the EM circuit block. In embodiments of the disclosure, the EM power to the plasma device is supplied as a broadband arbitrary RF waveform, including continuous wave (CW) RF, pulsed RF, DC, pulsed DC, a high frequency rectangular (e.g., square wave) or triangular (e.g., sawtooth) pulse train, or a combination or superposition of two or more such waveforms.

[0011] Generally, plasma processing involves physically and / or chemically modifying an exposed surface of a substrate by electronically exciting energetic particles (e.g., ions and radicals) within the plasma. As discussed in the "Background" section, broadband plasma systems are processing platforms that offer the flexibility to implement a variety of innovative techniques (e.g., parallel deposition and etching, cyclic processes that alternate between deposition and etching or isotropic and anisotropic etching, and adaptive processes in which the plasma is dynamically adjusted (e.g., when another material is exposed to the plasma during processing)). To implement such dynamic plasma processing, the plasma system must excite a plasma with alternating plasma characteristics in the sequence required to achieve the sequence of process conditions specified for the process. To excite a plasma with precise, dynamically adjustable characteristics, broadband plasma systems may be required to apply complex broadband RF waveforms.

[0012] Plasma properties (e.g., plasma density, ion energy and angular distribution, electron temperature (T e The RF power and RF frequency, and the ratio of radicals to ion flux, depend not only on the RF power and RF frequency but also on waveform details. RF waveforms may be selected to obtain desired plasma characteristics and applied in a specific sequence (e.g., to change the plasma during cycling). As discussed above, broadband waveforms may include pulsed RF, a superposition of sinusoidal RF with DC or pulsed DC, RF pulses of multiple frequencies, and non-sinusoidal waveforms (e.g., sawtooth and square waves). Various RF waveforms may be applied to various electrodes coupled to the excited plasma in the plasma processing chamber. For example, a first electrode may be coupled with a pulsed sinusoidal waveform at a high RF frequency, while a second electrode is coupled with a low-frequency sinusoidal waveform superimposed on a pulsed DC waveform.

[0013] Plasma excitation has traditionally been achieved by a CW RF signal applied at a single frequency. In contrast, an arbitrary RF waveform may be a broadband RF waveform with a power spectrum spanning a range of frequencies. The superposition of two waveforms, each with a power spectral density in two frequency bands, has a combined power spectral density that is the superposition of the two bands. A superposed waveform may have power in a broad band formed by the superposition of two overlapping bands. In some cases, for example, a source waveform at a higher RF frequency may be superimposed with a bias waveform at a lower RF frequency to carry power in non-overlapping bands. Some other waveforms, such as modulated sinusoidal waves (e.g., amplitude-modulated or frequency-modulated waveforms), have power distributed across a range of frequencies.

[0014] 1A shows a schematic diagram of an exemplary broadband plasma system 100. The exemplary broadband plasma system 100 includes an exemplary plasma device 110, an exemplary EM circuit block 120 that supplies EM power to the plasma device 110, and a controller 140 that adjusts input parameters of the EM circuit block 120. The controller 140 may be a microcontroller, processor, or other programmable circuit and may therefore be programmed, for example, by storing instructions executable by the processing circuitry of the controller 140 in a memory. Additionally, the plasma system 100 includes a voltage-current (VI) sensor 128 and a VI analysis circuit 130, as well as a DC bias generation circuit 132. The DC bias generation circuit 132 may also be adjusted by the controller 140. The plasma device 110 is shown in cross section, and the block diagram shows the EM circuit block 120.

[0015] The plasma device 110 includes a main vacuum chamber, referred to as the plasma chamber 102, and a gas flow system coupled to the plasma chamber 102. The gas flow system includes sensors, valves, pumps, and the like for controlling the pressure and flow of gases through the chamber 102. The gas flow system is configured to flow a mixture of process gas and carrier gas into a gas inlet 104 of the chamber 102 and remove excess gas and gaseous by-products through an exhaust port 106, which is coupled to a vacuum pump in the gas flow system. The plasma device 110 includes a pedestal 108 configured to hold a substrate 112 (e.g., a semiconductor wafer). The pedestal 108 and substrate 112 are shown inside the plasma chamber 102, where the substrate 112 is processed. The substrate 112 may be loaded from a load lock 114 through a loading window 115 and positioned on the pedestal 108 for processing. Typically, the temperature of the substrate 112 is controlled during processing by an external temperature control system 116, which includes heating and cooling hardware (e.g., a coolant column 117 coupled to the pedestal 108).

[0016] The apparatus 110 further includes an RF electrode configured to receive EM power to excite the gas discharge plasma. In the example shown in FIG. 1A, the plasma apparatus 110 is configured to excite a DC plasma in the chamber 102 with an electrode configured to provide EM power to the plasma by capacitive coupling. Typically, when the plasma apparatus 110 is in a capacitively coupled plasma (CCP) configuration, a disk-shaped electrode is used to excite the plasma in the chamber 102. In some embodiments, the RF electrode is a disk-shaped electrode (referred to as the upper electrode 118) located at the top of the chamber 102. In embodiments described herein, the pedestal 108 may be used both as a substrate holder and as a disk-shaped RF electrode (sometimes referred to as the lower electrode). To function as an RF electrode, the pedestal 108 is configured to include a disk-shaped conductor portion, which is typically located at the top of the pedestal and in contact with the substrate 112. The diameter of the conductive portion of the pedestal 108 , the lower electrode (not explicitly shown), is approximately the same as the diameter of the upper electrode 118 , or in some embodiments, is relatively smaller than the diameter of the upper electrode 118 .

[0017] In some other embodiments, the DC plasma may be excited by the plasma device 110 in an inductively coupled plasma (ICP) configuration, in which case the electrode supplying EM source power to the plasma is an antenna located outside the plasma chamber 102. This antenna may have a variety of shapes, such as a spiral coil electrode located above an insulating (e.g., quartz) window in the ceiling of the plasma chamber 102, or a helical coil surrounding an insulating portion of the curved sidewall of the cylindrical plasma chamber 102.

[0018] Generally, the conductive portions of the walls of the plasma chamber are coupled to a reference potential referred to as ground. In various embodiments, the upper electrode 118 and the lower electrode (pedestal 108) may be coupled to either a waveform that provides EM source power or a waveform that provides EM bias power. Typically, the plasma is ignited by the EM source power, while the EM bias power is used to adjust the plasma characteristics of the gas discharge. Additionally, the electrodes may be coupled to a DC bias or a pulsed DC bias. In some configurations (e.g., the configuration shown in FIG. 1A), the electrodes of the apparatus 110 (e.g., the pedestal 108) may be grounded or may be floating.

[0019] 1A, the exemplary EM circuit block 120 of the exemplary broadband plasma system 100 includes an adjustable function generator 122, a broadband amplifier 124, and an adjustable broadband impedance matching network 126. As will be described in more detail below, the EM circuit block 120 provides a high-power broadband RF waveform at the upper electrode 118 of the plasma device 110 to excite a plasma in the chamber 102. The adjustable function generator may be an arbitrary function generator, or even an arbitrary waveform generator capable of generating a non-periodic waveform.

[0020] Note that while the block diagram of an EM circuit block shows various components connected diagrammatically by straight lines, in a physical system, high-power RF waveforms may be coupled in a coaxial RF pipe. The RF waveform in the RF pipe refers to the RF voltage and RF current waveforms, where the voltage is the potential of the inner conductor relative to the annular outer conductor of the RF pipe, and the current is the current in the inner conductor that is equal and opposite to the current in the outer conductor. Typically, the outer conductor, also called a shield, is tied to ground (reference potential). The voltage and current are related by an impedance (which is generally frequency- and position-dependent) over a length comparable to the wavelength of the EM wave in the RF pipe.

[0021] As shown in FIG. 1A , the signal path begins with function generator 122, which couples a low-power RF waveform to the input of amplifier 124. The signal path for the high-power amplified RF waveform is a first RF pipe (schematically represented by a line) from the output of amplifier 124 to the input of impedance matching network 126. A second RF pipe from the output of impedance matching network 126 couples the RF waveform to the terminals of upper electrode 118. As will be described in more detail below, by adjusting the impedance of impedance matching network 126, it is possible to adjust the high-power broadband RF waveform thereat to maximize the EM power at the terminals of upper electrode 118. In general, this impedance depends not only on the components of impedance matching network 126 (e.g., adjustable inductance and capacitance), but also on the spectrum (i.e., frequency) of the broadband RF waveform. Therefore, adjustment of the RF waveform at the terminals of the upper electrode 118 is achieved by synchronously configuring the variable inductance and variable capacitance of the impedance matching network 126 and the spectrum of the wideband RF waveform output from the adjustable function generator 122 by sending appropriate control signals from the controller 140.

[0022] The function generator 122 can generate arbitrary waveforms in the radio frequency range using appropriate digital and analog circuitry (e.g., oscillators, pulse generators, modulators, combiners, etc.). The DC bias generation circuit 132 can generate a constant or pulsed DC bias waveform, for example, using a DC power supply and a chopper driven by a pulse train from a pulse generator. As noted above, the power spectral density of a CW sinusoidal signal is concentrated at a single frequency, while the power carried by more complex waveforms is distributed over a band of frequencies. In various embodiments, these frequencies can be from about 100 kHz to about 300 MHz. The power spectrum of waveforms used to supply EM source power is typically at the higher end of this range (e.g., from about 10 MHz to about 300 MHz), while the power spectral density of waveforms supplying EM bias power is typically in a band falling in the lower frequency range (from about 100 kHz to about 13 MHz).

[0023] The waveform at the output of function generator 122 is coupled to the input of wideband amplifier 124. In some embodiments, wideband amplifier 124 is a linear power amplifier that provides high output power, from about 50 W to about 10 kW, with low harmonic distortion, so that the waveform of the input signal is preserved in the amplified output signal. Linear amplifiers typically exhibit a trade-off between bandwidth and power amplification, making it difficult and costly to achieve a single channel that combines high bandwidth and high power amplification. For example, the power gain (G P ) versus frequency (f), where G P is the cutoff frequency f C (amplifier bandwidth) up to a constant value G P0 and beyond that, G P decreases, typically at a rate of 20 dB / decade. P and f C can be adjusted by a negative feedback loop, but the product (G P0 f C) is constant. Therefore, while a wide bandwidth (100 kHz to 300 MHz) amplifier may be used for both the EM bias power and the EM source power, widening the frequency range comes at the expense of lower power gain (i.e., loss of linearity), necessitating a constant gain across the entire frequency range. Thus, in embodiments described herein, a wideband amplifier (e.g., amplifier 124 of EM circuit block 120) has an operating frequency range that includes either a low frequency range for the EM bias power (which may be 100 kHz to 13 MHz) or a high frequency range for the EM source power (which may be 10 MHz to 300 MHz), which is in lieu of the wide frequency range (100 kHz to 300 MHz) over which EM power (including the EM source power and the EM bias power) can be used by the plasma device to process a substrate. In one or more embodiments, the wideband amplifier 124 may be implemented as a wideband RF power amplifier such as that described in US Patent Application No. 16 / 572,708 (eg, FIGS. 2, 6) (Attorney Docket No. TEL-190559US01).

[0024] The exemplary plasma apparatus 110 shown in Figure 1A uses EM source power provided by broadband impedance matching network 126 and DC bias provided by DC bias generation circuit 132. In this example, apparatus 110 does not use EM bias power. Thus, in the block diagram shown in Figure 1A, broadband amplifier 124 may be designed to operate in a band suitable for distortion-free amplification of the EM source waveform (e.g., 10 MHz to 300 MHz).

[0025] In the broadband plasma systems described in this disclosure, an adjustable function generator (e.g., function generator 122 of exemplary plasma system 100) generates a periodic function (e.g., a sine wave whose characteristics, such as amplitude and frequency, can be adjusted during the process). For example, the function generator generates a frequency modulated waveform, i.e., a waveform with instantaneous frequency f and period T P This means that f can output a sine wave that changes periodically from low to high. C -Δf) to (fC +Δf), where f C is the center frequency, and Δf is f C The bandwidth BW of this waveform is calculated using Carson's formula: BW = 2(Δf + 1 / T P ) can be approximated by, for example, f C = 13.56 MHz, Δf = 1 MHz, and T P = 10 μs, then BW = 2.2 MHz, and the power is distributed over a frequency range from 12.46 MHz to 14.46 MHz. In another example, function generator 122 may generate a rectangular or triangular (sawtooth) pulse train, whose characteristics (e.g., ramp rate, pulse height, period, and duty cycle) may be adjusted during the process. The bandwidth of the pulse train will depend on its timing characteristics.

[0026] The inventors have discovered through experiments that if the instantaneous frequency is not changed smoothly, for example, if f changes suddenly in discrete steps, such as a step function, the resulting gas discharge plasma may exhibit uncontrollable flickering (on and off). This flickering increases process variability, which is undesirable. However, this flickering can be prevented if the modulation function changes f smoothly (e.g., a triangular or sinusoidal function). Therefore, in the embodiments described herein, the signal supplying power to the plasma device (e.g., plasma device 110) is generated using, for example, a function generator, in which the signal frequency is adjusted relatively smoothly by a signal processing circuit. In contrast, digital signal generators typically use circuits that adjust the signal frequency in abrupt, step-like manner. In some embodiments, the smooth change in frequency can be achieved using analog signal processing techniques. In addition to smoothly changing f, function generators and analog signal generators can achieve smooth, flicker-free power adjustment. On the other hand, digital signal generators usually have stepped power adjustment means, which also causes flicker.

[0027] A plasma system (eg, plasma system 100 of FIG. 1A) resembles a simple power system that includes a power source, a load, a transmission line, and an impedance matching network.

[0028] The power source is a wideband amplifier (e.g., wideband amplifier 124), which is considered an ideal power supply in series with a source impedance equal to the amplifier's output impedance. Typically, the output impedance is a standard impedance such as 50 Ω. The load is the plasma device (e.g., plasma device 100), and the load impedance is the impedance between the terminals of the RF electrode (e.g., upper electrode 118) to which power is delivered and ground.

[0029] In a plasma system, the transmission line may be a coaxial first RF pipe, which may be approximated by a lossless transmission line and modeled as a two-port network with an input port and an output port. One end of the first RF pipe, referred to as the source end, is the input port coupled to the output of a wideband amplifier. The characteristic impedance of the RF pipe may be selected to be the same as the output impedance of the amplifier (e.g., 50 Ω). The output port is the opposite end of the first RF pipe, referred to as the load end. In the plasma system described in this disclosure, the load end is coupled to the input of a wideband impedance matching network. The output of the impedance matching network is coupled to a load at a terminal of an RF electrode of the plasma device by a second RF pipe, and the load impedance is the impedance between that terminal and ground. As described in more detail below, the second RF pipe is short in length so that the RF pipe is an ideal connection. That is, the input impedance of the short RF pipe measured at one end is equal to the impedance connected at the opposite end, and the length of the short pipe is short relative to the wavelength of the EM wave in the RF pipe.

[0030] The purpose of inserting an impedance matching network between the load impedance and the load end of the first RF pipe is to adjust the impedance at the load end to maximize power transfer from the power source to the load. A wideband impedance matching network includes various circuit components and can achieve efficient power transfer across a range of frequencies in the power spectrum of a wideband RF waveform. Exemplary wideband impedance matching networks are described in detail below.

[0031] In the plasma system 100, as shown in FIG. 1A, the output of the amplifier 124 is coupled to the input of an impedance matching network 126 via a first RF pipe, and the output of the impedance matching network 126 is coupled to a terminal of the upper electrode 118 of the plasma device 110 via a second RF pipe. The output terminal of the impedance matching network 126 is located near the terminal of the upper electrode 118 to eliminate the transmission line impedance of the signal path after the impedance matching network 126. Typically, the impedance of an RF pipe with length l is negligibly small if l<λ / 8, where λ is a typical wavelength of the broadband RF waveform in the RF pipe. Note that the system design must ensure that the second RF pipe used between the impedance matching network and the power source is short, especially when the second RF pipe is carrying high-frequency (short λ) EM source power (as in the plasma system 100 of FIG. 1A).

[0032] 1A includes a VI sensor assembly including voltage and current pickups that sense the time-varying electric field (E field) and the time-varying magnetic field (H field), respectively. In plasma system 100, VI sensor 128 is positioned such that its voltage and current pickups are located along the second RF pipe that couples impedance matching network 126 to upper electrode 118, as shown in FIG. 1A. Here, a short RF pipe is used as the signal path. This positions VI sensor 128 close to the terminals of upper electrode 118, so that the measured RF voltage and RF current waveforms closely approximate the respective waveforms at the terminals of upper electrode 118.

[0033] For purposes of illustration, Figure 1B shows an exemplary VI sensor assembly, as shown, for example, in Figure 3C of co-pending U.S. patent application Ser. No. 17 / 514,815, filed October 29, 2021 (Attorney Docket No. TEL-210198US01), the contents of which are incorporated herein by reference in their entirety.

[0034] FIG. 1B shows a cutaway view of an exemplary VI sensor assembly 150, in which a conductive voltage pickup 152 is held in an insulating voltage pickup holder 154 and a conductive current pickup 156 is supported on an insulating toroidal mandrel 158. The second RF pipe is omitted from FIG. 1B for clarity. If shown, the inner conductor of the second RF pipe would be a cylindrical conductor passing through bore 160, and the annular outer conductor would include the upper and lower conductor covers of sensor assembly 150. The conductor covers and the inner and outer conductors of the second RF pipe are not shown in FIG. 1B.

[0035] The voltage pickup 152 is a ring surrounding the inner conductor that generates, by capacitive coupling, a signal proportional to the radial E-field between the inner and outer conductors of the second RF pipe.

[0036] The current pickup 156 is a wire threaded along a hollow passage 162 coiled around the circular shaft inside the toroidal mandrel 158, as shown in FIG. 1B. Typically, the effect of the H field on the signal output of the voltage pickup 152 is negligible, but the radial E field perturbation on the current pickup 156 is not negligible. Therefore, the sensor assembly 150 includes an E field shielding scheme. E field shielding is provided by conductor protrusions from the upper and lower covers of the sensor assembly 150, which may be located inside slots 164 and 166, respectively. These conductor protrusions are grounded by being part of the upper and lower covers and, therefore, by being part of the grounded outer conductor of the second RF pipe. These grounded conductor protrusions shield the current pickup 156 from the E field but not from the H field. This is because the insulating walls of the slots 164 and 166 prevent any ground current from flowing in these two conductor protrusions. The current pickup 156 is therefore a half-loop within the second RF pipe that senses by inductive coupling the time-varying H-field circulating around the inner conductor.

[0037] In this example, the voltage pickup 152 and current pickup 156 are arranged symmetrically about the central axis of the second RF pipe (i.e., the central axis of the hole 160). This symmetry increases measurement accuracy by canceling out some of the parasitic voltages and currents induced in the conductor pickups.

[0038] Referring again to FIG. 1A, the measured RF voltage and current waveforms are transmitted from VI sensor 128 (eg, over a coaxial cable) to VI analysis circuitry 130 .

[0039] The VI analysis circuit 130 may have an amplifier (e.g., a differential amplifier) coupled to its input for receiving and amplifying the RF voltage and RF current waveforms from the VI sensor. The amplified waveforms may be analyzed by the VI analysis circuit 130, which has electronic circuitry configured to extract relevant electrical characteristics from the RF voltage and RF current waveforms and output electronic feedback signals encoding the extracted electrical characteristics. The electrical characteristics extracted from each attribute of the RF voltage and RF current waveforms may include the peak and RMS values of the voltage and current, instantaneous frequency, instantaneous power, average power, and power spectral density (via harmonic analysis). The electronic circuitry used to perform such analysis and extraction may be implemented as a separate signal processor (e.g., a programmable digital signal processor). As described in more detail below, the feedback signal from the output buffer of the VI analysis circuit 130 may be coupled to an input port of the controller 140 for process monitoring and / or feedback control.

[0040] In some embodiments, a DC bias (or pulsed DC) from a DC bias generation circuit 132 may also be superimposed on the waveform at the terminals of the upper electrode 118, as shown schematically in FIG. 1A.

[0041] 1A, the load impedance is the impedance between the terminal of the upper electrode 118 and ground, and therefore includes the impedance of the plasma, if any, present in the chamber 102. It is not uncommon for there to be a large mismatch between the source impedance (i.e., the output impedance of the amplifier 124) and the load impedance. Therefore, it is common practice to insert an impedance matching network in the signal path between the load end of the first coaxial RF pipe and the load. Without the impedance matching network 126, the mismatch could result in undesirably low power delivered to the plasma device 110.

[0042] When f is small, λ is large; if l<λ / 8, the wave nature of the EM signal in the RF pipe can be ignored, and the RF pipe can be approximated by an ideal connection. However, as f increases, λ decreases, and therefore, ignoring the fact that the EM signal in the RF pipe is an EM wave can be a mistake. That is, the RF pipe must be modeled like a waveguide along which the transmitted EM wave travels from the source end to the load end and the reflected wave (reflected at the load end) travels in the opposite direction. The ratio of the amplitude of the reflected wave to the transmitted wave is called the reflection coefficient Γ. If there is a large mismatch between the source impedance and the load impedance, the magnitude of the reflection coefficient (|Γ|) can be significantly high, resulting in degraded power transfer to the plasma device 110. Additionally, interference between the transmitted wave and the undesired reflected wave can result in standing wave patterns, which can potentially damage the amplifier 124. The impedance matching network 126 is used to suppress reflections and standing wave patterns in the first RF pipe to efficiently transfer EM power to the load impedance (i.e., the impedance between the terminals of the RF power (e.g., upper electrode 118) to which power is delivered and ground). As will be described in more detail below, the broadband impedance matching network of embodiments of the plasma system includes a variable inductor and a variable capacitor for adjusting the impedance of the matching network to achieve efficient power transfer in the frequency range of the power spectrum of the broadband RF waveform by suppressing reflections at the load end of the first RF pipe so that |Γ|≦0.6.

[0043] Typically, an impedance matching network includes only nearly lossless circuit components (e.g., nearly ideal inductors, capacitors, and switches) to prevent undesired resistive power losses in the impedance matching network. In this disclosure, a circuit approximated by a network of ideal inductors, capacitors, and switches is referred to as a reactive circuit. For a particular circuit topology and a particular choice of reactive components, the impedance of the matching network will be determined by a particular reactance function X M (f). Other impedances in the power system are the output impedance of the amplifier 124, the transmission line impedance, and the load impedance (including the plasma impedance). In general, the power transferred to a given load impedance depends on the various impedances in the power system. Optimizing the power transferred to the load impedance depends on the impedance of the impedance matching network (i.e., the reactance function X M (f)), that is, the inductance and capacitance of the matching network are selected to maximize the power to the load (i.e., the plasma device 110 containing the plasma) for a given broadband RF waveform (e.g., the output of the function generator 122).

[0044] In conventional single-frequency (or narrow-band) systems, impedance matching involves designing an impedance matching network during the development process. After the inductors and capacitors of the matching network of the impedance matching network are selected so that the power transferred to the load is maximized at the operating frequency (or center frequency of the narrow band), the reactive elements are only varied over a narrow range during processing to compensate for small changes in plasma processing conditions.

[0045] 1A, the operating frequency may be intentionally varied in discrete increments (e.g., during different cycles of a cyclic process). Additionally, broadband systems such as plasma system 100 may use RF waveforms whose frequency is continuously varied (e.g., frequency-modulated sinusoidal waveforms). Thus, broadband impedance matching network 126 includes one or more variable reactance components.

[0046] For purposes of illustration, FIG. 1C shows an exemplary reactance circuit for forming matching network 126, such as that shown in FIG. 29 of U.S. Patent Application No. 17 / 12,168, filed September 4, 2020, which is incorporated herein by reference.

[0047] 1C shows a schematic diagram of an exemplary reactance circuit 170, which includes three variable capacitors C1, C2, and C3 and two variable inductors L1 and L2. As described above, the reactance components C1, C2, C3, L1, and L2 may be varied during processing, so that the reactance circuit 170 may be implemented as a wideband impedance matching network 126. Additionally, the reactance circuit 170 includes two three-terminal switches S1 and S2, which provide additional control variables for adjusting the reactance of the reactance circuit 170. Note that the variable capacitors and variable inductors may include switched capacitors and switched inductors, which include multiple two-terminal switches, as described in more detail below.

[0048] As shown in FIG. 1A, the impedance matching network 126 is inserted in the signal path between the output of the amplifier 124 and the terminal of the upper electrode 118. As mentioned above, a first RF pipe may couple the output of the amplifier 124 to the input of the impedance matching network 126, which is shown by the block arrow to the left of the reactance circuit 170 in FIG. 1C. The output of the impedance matching network 126, shown by the block arrow to the right of the reactance circuit 170 in FIG. 1C, may be coupled to the terminal of the upper electrode 118 by a short second RF pipe. The inventors have shown that in a plasma system in which the reactance circuit 170 is implemented as a wideband impedance matching network, |Γ|≦0.6 over the operating frequency range of 13.56 MHz to 220 MHz.

[0049] The variable capacitors C1, C2, and C3 may be implemented in various ways. A mechanically variable capacitor may include a movable part, such as the plates of a tuning capacitor. For example, the distance and / or overlapping area of the two plates of capacitor C1 may be adjustable by an appropriate mechanical structure. An electrically variable capacitor (e.g., a varactor) may be used as variable capacitor C1, in which the depletion layer width varies depending on the bias voltage across a metal-oxide semiconductor (MOS) capacitor or a pn junction diode. Another implementation of electrically variable capacitor C1 may use an array including multiple switched capacitors connected in parallel. Each switched capacitor includes a series-connected capacitor and a two-terminal switch. The capacitance of capacitor C1 may be adjusted by controlling the state of the two-terminal switch of the multiple switched capacitors. In some embodiments, the capacitance of the variable capacitors (e.g., C1, C2, and C3) may be variable in a range from about 3 pF to about 4000 pF.

[0050] The variable inductors L1 and L2 may also be implemented in various ways. For example, similar to the electrically variable capacitance C1 implemented by an array of switched capacitors, the variable inductor L1 may be implemented as an array of series-connected switched inductors. Each switched inductor includes a parallel-connected inductor and a two-terminal switch. The inductance of the inductor L1 may be adjusted by controlling the state of the two-terminal switch of the multiple switched inductors. Alternatively, the inductance of the variable inductor L1 may be changed by mechanical movement. For example, the coupling between the magnetic core and coil of the first inductor L1 may be adjustable by an appropriate mechanical structure. In some embodiments, the inductance of the variable inductors (e.g., L1 and L2) may be variable in a range from about 50 nH to about 20 μH.

[0051] The wideband impedance matching network of the presently disclosed embodiments is designed for an operating frequency range that, like a wideband amplifier, may be either a high frequency range of about 10 MHz to about 300 MHz, or a low frequency range of about 100 kHz to about 13 MHz. The wideband impedance matching network 126 is designed for waveforms used to supply EM source power, and therefore, the impedance matching network 126 covers a frequency range of 10 MHz to 300 MHz. In contrast, for waveforms supplying EM bias power, an impedance matching network covering a low frequency range of 100 kHz to 13 MHz would be used.

[0052] Adjustments to the matching network of the impedance matching network 126 may be made using a controller 140, shown schematically in FIG. 1A. The controller 140 may be configured to send control signals to adjust the inductance and capacitance of the variable inductor and variable capacitor of the wideband impedance matching network 126 to adjust the waveform at the load terminals (terminals of the upper electrode 118 of the plasma device 110). Additionally, fine adjustments to the impedance of the impedance matching network 126 may be made by the controller 140 by adjusting the waveform (e.g., frequency) of the wideband RF waveform in the function generator 122. The functionality of the controller 140 will be described in more detail below.

[0053] As described above, the VI sensor 128 may be positioned in the RF pipe between the output of the impedance matching network 126 and the terminals of the electrode 118 to measure the RF voltage and current waveforms being delivered to the plasma device 110 and transmit the data to the VI analysis circuit 130. The VI analysis circuit 130 may be configured to extract relevant electrical properties from the waveforms and output electronic feedback signals encoding the extracted electrical properties. The feedback signals from the VI analysis circuit 130 may be coupled to the controller 140 for process monitoring and / or feedback control. The electrode properties received from the VI analysis circuit 130 may be stored in a memory device and processed by a processor. Based on the feedback, the processor may instruct the controller 140 to generate appropriate control signals to be transmitted to various components of the EM circuit block 120 and the DC bias generation circuit 132 to adjust the RF voltage and current waveforms as well as the impedance of the impedance matching network 126 between the output of the wideband amplifier 124 and the load (including the plasma).

[0054] As described above, the controller 140 is used to adjust the broadband RF waveform at the terminals of the RF electrodes of the plasma device 110 by sending control signals to the respective input ports of the EM circuit blocks (e.g., EM circuit block 120) and the optional DC bias generation circuit (e.g., DC bias generation circuit 132) to adjust the input parameters of the EM circuit blocks and the optional DC bias generation circuit.

[0055] 1A, in the plasma system 100, the controller 140 may generate and send a plurality of control signals to adjust input parameters of the EM block 120 and the DC bias generation circuit 132 to adjust the broadband RF waveform, including the RF voltage waveform and the RF current waveform, at the terminals of the upper electrode 118. The controller 140 may include a processor and a memory device, and the memory device may store data and coded instructions for the processor. The data includes the process recipe and electrical characteristics decoded from the feedback signal output from the VI analysis circuit 130, which is received at an input port of the controller 140 as shown in FIG. 1A. When executed by the processor, the instructions read data from the memory device and generate the appropriate control signals described above based on the data.

[0056] In the exemplary embodiment shown in FIG. 1A , first, second, and third output ports of controller 140 are configured to transmit first, second, and third control signals, respectively, that synchronously adjust input parameters of function generator 122, wideband amplifier 124, and wideband impedance matching network 126. Additionally, as shown in FIG. 1A , a fourth control signal may be generated and transmitted from the fourth output port to adjust an input parameter of DC bias generation circuit 132. In some embodiments, DC bias generation circuit 132 may be optional. Each control signal is transmitted from controller 140 and coupled (e.g., by coaxial cable) to an input port of EM circuit block 120 or optional DC bias generation circuit 132. Collectively, these control signals adjust the broadband RF waveform that supplies EM power to plasma device 110 by synchronously adjusting the input parameters of EM circuit block 120 and DC bias generation circuit 132. For example, a first control signal sent to the function generator 122 may adjust the spectrum (i.e., frequency) of the RF waveform, a second control signal sent to the wideband amplifier 124 may adjust the amplitude of the RF waveform by adjusting the power gain of the wideband amplifier 124, and a third control signal sent to the wideband impedance matching network 126 may adjust the EM power delivered to the terminals of the upper electrode 118 by adjusting the phase relationship between the RF voltage and RF current waveforms. In some embodiments in which a DC bias generation circuit 132 is used, a fourth control signal sent to the DC bias generation circuit 132 may adjust the DC bias (e.g., DC voltage, pulsing frequency, and duty cycle of the DC pulses) superimposed on the RF waveform.

[0057] Some adjustments are process-specific and specified in a process recipe stored in the memory device of the controller 140. For example, the plasma system 100 may be performing a cyclic process that alternates between etch and deposition cycles, in which case the operating frequency, DC bias, and RF source power may be specified differently for the two cycles of the cyclic process. In addition to adjusting the power gain of the amplifier 124 and the output voltage of the DC bias generation circuit 132, performing this process may require synchronously making appropriate adjustments to the function generator 122 and the wideband impedance matching network 126 to match the changes in operating frequency at the start of each cycle of the cyclic process. Thus, the controller 140 may read instructions from the recipe and execute the instructions using a processor to send control signals to adjust the variable inductor and / or variable capacitor of the wideband impedance matching network 126, while simultaneously sending control signals to the frequency selector of the function generator 122 at the times specified in the instructions in the recipe.

[0058] In addition to intended variations in waveform (e.g., variations specified in a recipe), random variations may also occur during processing. As described above, when a plasma is sustained in chamber 102, the load impedance includes the plasma. Generally, because plasma characteristics may change during a plasma process, the load impedance may also change during the process, which may cause undesirable and random variations in the waveform that carries EM power from EM circuit block 120 to plasma device 110. Therefore, further adjustments to process control may be made by controller 140 for waveform tuning and feedback control.

[0059] FIG. 2 shows a schematic diagram of another broadband plasma system 200, which is similar to the exemplary plasma system 100 described above with reference to FIG. 1A. In the plasma system 200, an EM circuit block 120 provides EM source power to the plasma device 110 in the pedestal 108. As described above, the conductive portion of the pedestal 108 (the lower electrode) may be an RF electrode used to excite the plasma in the chamber 102. In the exemplary embodiment of FIG. 2, an upper electrode 118 is present but is not coupled to an RF or DC power source. In some embodiments, if an upper electrode is not required, the upper electrode may not be present. As shown in FIG. 2, if the upper electrode 118 is present but not used, the upper electrode 118 may be floating (open circuit), grounded (i.e., coupled to a reference potential), or coupled to the chamber wall (which may be coupled to ground).

[0060] Figures 3 and 4 show embodiments of plasma systems in which the EM circuit block uses several broadband RF waveforms to provide EM power to the plasma device. Plasma system 300 and plasma system 400, shown in Figures 3 and 4, respectively, are examples of embodiments in which two broadband RF waveforms simultaneously power the plasma device 110 described above with reference to Figure 1A. A higher frequency RF waveform provides the EM source power, and a lower frequency RF waveform provides the EM bias power.

[0061] These two broadband RF waveforms are generated using two single-channel EM circuit blocks to cover the broad frequency range (100 kHz to 300 MHz) typically used for RF waveforms carrying EM source power and EM bias power in a plasma system. As discussed above, linear amplifiers exhibit a tradeoff between bandwidth and power amplification, making it difficult and costly for a plasma system to include a linear power amplifier with both high bandwidth (100 kHz to 300 MHz) and high power amplification (outputting 50 W to 10 kW of power). Therefore, although a plasma system can include a multi-channel wideband amplifier that amplifies multiple broadband RF waveforms within a smaller frequency range (e.g., a range of 100 kHz to 13 MHz for EM bias power or a range of 10 MHz to 300 MHz for EM source power), it may be advantageous to use two single-channel EM circuit blocks, one for EM source power and the other for EM bias power. This is due to the high cost of a dual-channel wideband amplifier that can provide high power with low distortion across the broad frequency ranges of the various RF waveforms used simultaneously in plasma processing.

[0062] 3 and 4 show exemplary plasma systems 300 and 400, where each EM circuit block 350 and 450 is a dual-channel EM circuit block including two single-channel EM circuit blocks (each channel used for one broadband RF waveform). The first EM circuit block 120 may be for a high-frequency broadband RF waveform, and the second EM circuit block 320 may be for a low-frequency broadband RF waveform. Each single-channel EM circuit block includes a function generator, a broadband amplifier, and a broadband impedance matching network. In embodiments of the present disclosure, each dual-channel EM circuit block uses two function generators (one for each channel), although it should be understood that in some other embodiments, a single dual-channel function generator may be used instead of two function generators.

[0063] 3 includes a plasma device 110 and a dual channel EM circuit block 350, which includes a first EM circuit block 120 that provides high frequency EM source power and a second EM circuit block 320 that provides low frequency EM bias power, where the first EM circuit block 120 is identical to the high frequency EM circuit block 120 described above with reference to FIGS.

[0064] 1A , high frequency first EM circuit block 120 includes function generator 122, high frequency wideband amplifier 124, and high frequency wideband impedance matching network 126. Second EM circuit block 320 also includes function generator 322, which is a similar but lower frequency system to function generator 122, and second EM circuit block 320 includes low frequency wideband amplifier 324 and low frequency wideband impedance matching network 326. Function generator 122 is configured to output a high frequency wideband RF waveform that can be amplified by high frequency wideband amplifier 124, while function generator 322 is configured to output a low frequency wideband RF waveform that can be amplified by low frequency wideband amplifier 324.

[0065] As shown in FIG. 3 , the upper electrode 118 and the pedestal 108 receive power for exciting a plasma in the plasma chamber 102. The pedestal 108 is configured to function as an RF electrode in addition to supporting a substrate. As described above, to function as an RF electrode, the pedestal 108 is configured to include a disk-shaped conductor portion, which is typically located at the top of the pedestal and in contact with the substrate 112. The pedestal 108 of the plasma system 300 is similar to the pedestal 108 of the plasma system 200 described above with reference to FIG. 2 . In this exemplary embodiment (plasma system 300), the upper electrode 118 is used to couple EM source power to the plasma, while the pedestal 108 is used to couple EM bias power to the plasma. Accordingly, a high-frequency first EM circuit block 120 is shown providing power at the terminals of the upper electrode 118. In contrast, EM bias power is provided by a second EM circuit block 320 at a lower frequency in the pedestal 108 .

[0066] The plasma system 300 includes a first VI sensor 128 and a first VI analysis circuit 130 for sensing the RF voltage and RF current waveforms coupled to the upper electrode 118 (similar to the plasma system 100 shown in FIG. 1A). Additionally, there is a second VI sensor 328 and a second VI analysis circuit 330 for sensing the RF voltage and RF current waveforms coupled to the pedestal 108 (similar to the plasma system 200 shown in FIG. 2). Electrical characteristics extracted from the various waveforms by the VI analysis circuits 130 and 330 are sent to a controller 140 for storage and feedback control. The controller 140 is used to synchronously adjust the input parameters of the first EM circuit block 120, the second EM circuit block 320, and the DC bias generation circuits 132 and 332.

[0067] The plasma system 400 shown in FIG. 4 includes a plasma device 110 and an EM circuit block 450. Similar to the dual channel EM circuit block 350, the dual channel EM circuit block 450 also includes a high frequency first EM circuit block 120 that supplies EM source power and a low frequency second EM circuit block 320 that supplies EM bias power. However, unlike the EM circuit block 350, the EM source power and the EM bias power are superimposed in the EM circuit block 450, for example, by using the same RF pipe for both the EM source power and the EM bias power. The superposition of these two waveforms is coupled to the plasma device 110 at the terminals of the pedestal 108. The superimposed EM power is used by the pedestal 108 to couple power to the plasma ignited in the chamber 102.

[0068] In the exemplary plasma system 400, as shown in FIG. 4, the upper electrode 118 is not used to couple EM power to the plasma in the plasma chamber 102. As described above with reference to FIG. 2, in some embodiments, if an upper electrode is not needed, the upper electrode may not be present. However, as shown in FIG. 4, if the upper electrode 118 is present but not used, the upper electrode 118 may be floating (open circuit), grounded (i.e., coupled to a reference potential), or coupled to the chamber wall (which may be coupled to ground), similar to the plasma system 200 (see FIG. 2). Additionally, because the upper electrode 118 is not coupled to any power source, the plasma system 400 uses only one VI sensor 128 and one VI analysis circuit 130 to detect and analyze the RF voltage and current waveforms supplied to the pedestal 108. Similarly, the plasma system 400 may have only one DC bias generation circuit 132 coupled to the pedestal 108.

[0069] A method 500 for processing a substrate (e.g., substrate 112 of FIGS. 1A-4) is summarized in the flowchart shown in FIG. 5. In method 500, described below with reference to the flowchart of FIG. 5, processing of the substrate is performed using a plasma excited in a plasma device using EM power carried in a broadband RF waveform and coupled to the plasma by electrodes of the plasma device. At the terminals of each electrode, an EM circuit block delivers the EM power carried in the broadband RF waveform.

[0070] A wideband RF waveform is generated, as shown in block 510. This may be done, for example, using a function generator configured to generate various arbitrary waveforms (e.g., function generator 122 described above with reference to FIG. 1A). The wideband RF waveform output from the function generator is coupled to the input port of a wideband linear power amplifier, as shown in block 512 of FIG. 5.

[0071] At block 520, the wideband RF waveform is amplified by a wideband linear power amplifier (e.g., wideband amplifier 124 described above with reference to FIG. 1A). The wideband amplifier outputs the amplified waveform. Being a linear power amplifier, the output of the wideband amplifier has higher power than the output of the function generator, and the waveform is maintained with high fidelity (i.e., low distortion).

[0072] The amplified waveform at the output of the wideband amplifier is coupled to the source end of a first RF pipe, as shown in block 530. The first RF pipe is a coaxial RF pipe, which may be modeled as a lossless transmission line, as described above. The load end of the first RF pipe is coupled to the input of a wideband impedance matching network, as shown in block 532. The load end of the RF pipe is opposite the source end of the first RF pipe.

[0073] A wideband impedance matching network (e.g., the wideband impedance matching network 126 described above) includes switches, variable inductors, and variable capacitors. These components are connected in a network called a reactive circuit, an example of which is described above. The impedance of each matching network depends on the selection of the states of the variable inductors, variable capacitors, and switches. Additionally, this impedance is frequency-dependent. A controller may be programmed to set input parameters for selecting the impedance of each wideband matching network so that efficient power transfer from the EM circuit block to the plasma device is achieved over the frequency range of the spectrum of the wideband RF waveform.

[0074] A second RF pipe may be used to couple the waveform at the output of the impedance matching network to the terminals of an RF electrode, as shown in block 540 of the flowchart illustrated in Figure 5. The waveform at the terminals of the RF electrode (matched for efficient power transfer to the plasma device) excites a plasma in the plasma chamber of the plasma device.

[0075] As shown in block 550, the broadband RF waveform at the terminals of the RF electrode may be adjusted by a feedback loop, as described with reference to FIGS. 1A-1B.

[0076] As described above, these adjustments are made using control signals from a controller that set various input parameters of the EM circuit block. The feedback signal may be based on the RF voltage and RF current waveforms supplied to the terminals of the electrode. The RF waveform may be measured, for example, using a VI sensor. The VI sensor may be configured to measure the RF waveform by sensing the E and H fields in a short second RF pipe between the output of the impedance matching network and the terminals of the RF electrode of the plasma device, as described above with reference to FIGS. 1A and 1B. The measured RF waveform may be analyzed to generate a feedback signal. As described above with reference to FIG. 1A, the analysis may be performed in a VI analysis circuit that receives the measured RF waveform from the VI sensor. The feedback signal may be coupled (e.g., by a coaxial cable) from the VI analysis circuit to the controller. As described above, the controller may be used to adjust the waveform, as shown in block 550 of the flowchart. These adjustments may be achieved by sending control signals from the controller to various components of the EM circuit block used to generate the wideband RF waveform.

[0077] Example 1. A plasma system includes a plasma apparatus including a plasma chamber, a pedestal configured to hold a substrate in the chamber, and a radio frequency (RF) electrode configured to excite a plasma in the chamber, an electromagnetic (EM) circuit block coupled to the RF electrode, the EM circuit block including: a function generator configured to output a wideband RF waveform, the waveform having EM power distributed over a frequency range; a wideband amplifier coupled to the output of the function generator, the wideband amplifier having an operating frequency range that includes the frequency range; a wideband impedance matching network having an input coupled to the output of the wideband amplifier and an output coupled to a terminal of the RF electrode, the wideband impedance matching network having an operating frequency range that includes the frequency range; and a controller configured to adjust input parameters of the EM circuit block.

[0078] Example 2. The plasma system of example 1, wherein the wideband impedance matching network includes a variable inductor.

[0079] Example 3. The plasma system of any one of Examples 1 or 2, wherein the wideband impedance matching network includes a variable capacitor.

[0080] Example 4. The plasma system of any one of Examples 1-3, further including a first RF pipe having a source end coupled to an output of the wideband amplifier and a load end coupled to an input of the wideband impedance matching network, the load end opposite the source end, wherein the first RF pipe has a reflection coefficient magnitude of 0.6 or less during operation, the reflection coefficient being the ratio of the amplitude of a reflected EM wave to the amplitude of a transmitted EM wave, and wherein the EM wave in the first RF pipe is a superposition of the transmitted EM wave traveling from the source end to the load end and the reflected EM wave traveling in the opposite direction.

[0081] Example 5. The plasma system of any one of Examples 1 to 4, wherein the operating frequency range of the wideband amplifier and the operating frequency range of the impedance matching network include a frequency range of 10 MHz or more and 300 MHz or less.

[0082] Example 6. The plasma system of any one of Examples 1-5, further comprising a DC bias generation circuit having an output coupled to the RF electrode, the DC bias generation circuit configured to output a constant DC bias waveform or a pulsed DC bias waveform.

[0083] Example 7. The plasma system of any one of Examples 1 to 6, wherein the RF electrode is a disk-shaped electrode located in the upper portion of the chamber.

[0084] Example 8. The plasma system of any one of Examples 1 to 7, wherein the RF electrode is a disc-shaped conductive portion of the pedestal.

[0085] Example 9. The plasma system of any one of Examples 1-8, wherein the RF electrode is an antenna located outside the plasma chamber.

[0086] Example 10. The plasma system of any one of Examples 1-9, further comprising: a voltage-current (VI) sensor including voltage pickups and current pickups located at locations along a second RF pipe coupling the broadband impedance matching network to the RF electrode, the VI sensor configured to measure RF voltage and RF current waveforms at the locations within the second RF pipe; and a VI analysis circuit configured to receive the RF voltage and RF current waveforms, the VI analysis circuit including electronic circuitry configured to extract electrical characteristics from the received RF voltage and RF current waveforms and output electronic feedback signals encoding the electrical characteristics.

[0087] Example 11. The plasma system of any one of Examples 1-10, wherein the length of the second RF pipe is less than one-eighth of a typical wavelength of the RF voltage waveform and the RF current waveform.

[0088] Example 12. The plasma system of any one of Examples 1-11, wherein the controller includes an input port configured to receive an electronic feedback signal, an electronic memory, a processor, data and instructions stored in the memory, the data including a process recipe and electrical characteristics, the instructions, when executed by the processor, generating a control signal, and an output port configured to send the control signal to the input port of the EM circuit block.

[0089] Example 13. A plasma system includes a plasma device; a dual channel electromagnetic (EM) circuit block including: a first EM circuit block including a first function generator, a first wideband amplifier, and a first wideband impedance matching network, the first EM circuit block outputting a first wideband RF waveform coupled to the plasma device, the first wideband RF waveform having EM power distributed over a first frequency range; a second EM circuit block including a second function generator, a second wideband amplifier, and a second wideband impedance matching network, the second EM circuit block outputting a second wideband RF waveform coupled to the plasma device, the second wideband RF waveform having EM power distributed over a second frequency range, the second frequency range being different from the first frequency range; and a controller configured to adjust a plurality of input parameters of the EM circuit block.

[0090] Example 14. The plasma system of example 13, wherein the first frequency range comprises a frequency range of 10 MHz or more and 300 MHz or less, and the second frequency range comprises a frequency range of 100 kHz or more and 13 MHz or less.

[0091] Example 15. The plasma system of any one of Examples 13 or 14, wherein the plasma apparatus includes a plasma chamber, an upper RF electrode, and a lower RF electrode, the lower RF electrode being a pedestal configured to support a substrate within the plasma chamber.

[0092] Example 16. The plasma system of any one of Examples 13-15, wherein the first broadband RF waveform and the second broadband RF waveform are coupled to different RF electrodes of the plasma device.

[0093] Example 17. The plasma system of any one of Examples 13-16, wherein the first broadband RF waveform and the second broadband RF waveform are coupled to the same RF electrode of the plasma device.

[0094] Example 18. A method of operating a plasma processing system, comprising: outputting a wideband radio frequency (RF) waveform at an output of a function generator, coupling the output of the function generator to an input of a wideband amplifier, outputting the amplified wideband RF waveform at the output of the wideband amplifier, coupling the output of the wideband amplifier to a source end of a first RF pipe, coupling a load end of the first RF pipe to an input of a wideband impedance matching network opposite the source end, and coupling the output of the wideband impedance matching network using a second RF pipe to a terminal of an RF electrode of a plasma device, the terminal providing EM power to the RF electrode for exciting a plasma in a plasma chamber of the plasma device.

[0095] Example 19. The method of example 18, further comprising adjusting a broadband RF waveform at a terminal of an RF electrode of the plasma device through a feedback loop.

[0096] Example 20. The method of any one of Examples 18 or 19, further comprising measuring RF voltage and current waveforms with voltage and current pickups of a voltage-current (VI) sensor at a position along the second RF pipe, transmitting the RF voltage and current waveforms to a VI analysis circuit, the VI analysis circuit including electronic circuitry configured to perform analysis of the received waveforms, performing the analysis with the electronic circuitry to extract electrical characteristics from the received waveforms, outputting an electronic feedback signal encoding the electrical characteristics, and coupling the electronic feedback signal to an input port of a controller.

[0097] Example 21. The method of any one of Examples 18-20, further comprising: storing, in a memory device of the controller, the electrical characteristic encoded in the feedback signal; generating, by instructions executed by a processor of the controller, several control signals based on processing of the electrical characteristic; sending each control signal to a respective input port of a function generator, a wideband amplifier, and a wideband impedance matching network; and synchronously adjusting, based on the control signals, input parameters of the function generator, the wideband amplifier, and the wideband impedance matching network, whereby a wideband RF waveform at a terminal of an RF electrode of the plasma apparatus is adjusted.

[0098] While the present invention has been described with reference to exemplary embodiments, this specification is not intended to be construed in a limiting sense. Various modifications and combinations of the exemplary embodiments, as well as other embodiments of the invention, will become apparent to those skilled in the art upon reference to this specification. It is therefore intended that the appended claims cover all such modifications or embodiments.

Claims

1. 1. A plasma system comprising: A plasma device, comprising: a plasma chamber; a pedestal configured to hold a substrate within the plasma chamber; a radio frequency electrode (RF electrode) configured to excite a plasma within the plasma chamber; The plasma device comprising: an electromagnetic circuit block (EM circuit block) coupled to the RF electrode, a function generator configured to output a wideband RF waveform, the waveform having EM power distributed over a range of frequencies; a wideband amplifier coupled to an output of the function generator, the wideband amplifier having an operating frequency range that includes the frequency range; and a wideband impedance matching network having an input coupled to an output of the wideband amplifier and an output coupled to a terminal of the RF electrode, the wideband impedance matching network having an operating frequency range that includes the frequency range; the EM circuit block including: a controller configured to adjust input parameters of the EM circuit block; A plasma system including:

2. The plasma system of claim 1 , wherein the wideband impedance matching network includes a variable inductor.

3. The plasma system of claim 1 , wherein the wideband impedance matching network includes a variable capacitor.

4. 10. The plasma system of claim 1, further comprising a first RF pipe having a source end coupled to the output of the wideband amplifier and a load end coupled to the input of the wideband impedance matching network, the load end being opposite the source end, wherein the first RF pipe has a reflection coefficient magnitude of 0.6 or less during operation, the reflection coefficient being a ratio of an amplitude of a reflected EM wave to an amplitude of a transmitted EM wave, and the EM wave in the first RF pipe is a superposition of the transmitted EM wave traveling from the source end to the load end and the reflected EM wave traveling in the opposite direction.

5. 10. The plasma system of claim 1, further comprising a DC bias generation circuit having an output coupled to the RF electrode, the DC bias generation circuit configured to output a constant DC bias waveform or a pulsed DC bias waveform.

6. The plasma system of claim 1 , wherein the RF electrode is a disk-shaped electrode disposed in an upper portion of the plasma chamber.

7. The plasma system of claim 1 , wherein the RF electrode is a disc-shaped conductive portion of the pedestal.

8. The plasma system of claim 1 , wherein the RF electrode is an antenna located outside the plasma chamber.

9. a voltage-current sensor (VI sensor) including a voltage pickup and a current pickup located at a location along a second RF pipe coupling the wideband impedance matching network to the RF electrode, the VI sensor configured to measure RF voltage and current waveforms at the location within the second RF pipe; a VI analysis circuit configured to receive the RF voltage waveform and the RF current waveform, the VI analysis circuit including electronic circuitry configured to extract electrical characteristics from the received RF voltage waveform and the received RF current waveform, and to output electronic feedback signals encoding the electrical characteristics; The plasma system of claim 1 further comprising:

10. 10. The plasma system of claim 9, wherein the length of the second RF pipe is less than one-eighth of a typical wavelength of the RF voltage waveform and the RF current waveform.

11. The controller an input port configured to receive the electronic feedback signal; Electronic memory; a processor; data and instructions stored in said electronic memory, the data includes a process recipe and the electrical characteristics; The instructions, when executed by the processor, generate a control signal. the data and the instructions; an output port configured to send the control signal to an input port of the EM circuit block; The plasma system of claim 9 , comprising:

12. 1. A plasma system comprising: A plasma device; A dual channel electromagnetic circuit block (dual channel EM circuit block), a first EM circuit block including a first function generator, a first wideband amplifier, and a first wideband impedance matching network, the first EM circuit block outputting a first wideband RF waveform coupled to the plasma device, the first wideband RF waveform having EM power distributed over a first frequency range; a second EM circuit block including a second function generator, a second wideband amplifier, and a second wideband impedance matching network, the second EM circuit block outputting a second wideband RF waveform coupled to the plasma device, the second wideband RF waveform having EM power distributed over a second frequency range, the second frequency range being different from the first frequency range; the dual channel EM circuit block including: a controller configured to adjust a plurality of input parameters of the EM circuit block; A plasma system including:

13. 13. The plasma system of claim 12, wherein the first frequency range comprises a frequency range of 10 MHz or more and 300 MHz or less, and the second frequency range comprises a frequency range of 100 kHz or more and 13 MHz or less.

14. 13. The plasma system of claim 12, wherein the plasma device includes a plasma chamber, an upper RF electrode, and a lower RF electrode, the lower RF electrode being a pedestal configured to support a substrate within the plasma chamber.

15. 15. The plasma system of claim 14, wherein the first broadband RF waveform and the second broadband RF waveform are coupled to different RF electrodes of the plasma device.

16. 15. The plasma system of claim 14, wherein the first broadband RF waveform and the second broadband RF waveform are coupled to the same RF electrode of the plasma device.

17. 1. A method of operating a plasma processing system, comprising: outputting a wideband radio frequency (RF) waveform at the output of the function generator; coupling the output of the function generator to an input of a wideband amplifier; outputting an amplified wideband RF waveform at the output of the wideband amplifier; coupling the output of the wideband amplifier to a source end of a first RF pipe; coupling a load end of the first RF pipe to an input of a wideband impedance matching network, the load end being opposite the source end; using a second RF pipe to couple an output of the wideband impedance matching network to a terminal of an RF electrode of a plasma device, the coupling providing EM power to the RF electrode for exciting a plasma in a plasma chamber of the plasma device; A method comprising:

18. 20. The method of claim 17, further comprising adjusting a broadband RF waveform at the terminals of the RF electrode of the plasma device through a feedback loop.

19. measuring RF voltage and current waveforms with voltage and current pickups of voltage-current sensors (VI sensors) located along the second RF pipe; transmitting the RF voltage waveform and the RF current waveform to a VI analysis circuit, the VI analysis circuit including electronic circuitry configured to perform analysis of the received waveforms; performing said analysis by said electronic circuitry to extract electrical characteristics from said received waveform; outputting an electronic feedback signal encoding the electrical characteristic; coupling the electronic feedback signal to an input port of a controller; 20. The method of claim 17, further comprising:

20. storing the electrical characteristic encoded in the electronic feedback signal in a memory device of the controller; generating, by instructions executed by a processor of the controller, a number of control signals based on processing of the electrical characteristics; sending respective control signals to respective input ports of the function generator, the wideband amplifier, and the wideband impedance matching network; synchronously adjusting input parameters of the function generator, the wideband amplifier, and the wideband impedance matching network based on the control signal, whereby a wideband RF waveform at the terminals of the RF electrode of the plasma device is adjusted; 20. The method of claim 19 further comprising:

Images