High-frequency (RF) pulse impedance tuning using multiplier modes

Abstract

A method for reducing RF pulse reflection is provided. [Solution] In some embodiments, a method for processing a substrate in a plasma substrate processing system using multilevel pulsed RF power includes the steps of: receiving a processing recipe for processing the substrate, which includes a plurality of pulsed RF power waveforms from a plurality of RF generators; generating a transistor-to-transistor logic (TTL) signal having a fundamental frequency and a first duty cycle using a master RF generator; setting multipliers for each RF generator; dividing the first duty cycle into high-level intervals and low-level intervals; determining a frequency command set for each RF generator and transmitting the frequency command set to each RF generator, wherein the frequency command set includes frequency setting points for each RF generator; and providing a plurality of pulsed RF power waveforms from the plurality of RF generators to a processing chamber.

Description

field

[0001] Embodiments of this disclosure generally relate to RF power supply methods used for processing substrates. Background

[0002] In conventional radio frequency (RF) plasma processing (such as RF plasma processing used in the manufacturing stages of many semiconductor devices), RF energy may be supplied to the substrate processing chamber via an RF energy source. RF energy may be generated and supplied in a continuous wave or pulsed wave manner. Due to mismatch between the impedance of the RF energy source and the plasma formed in the processing chamber, RF energy is reflected back to the RF energy source, resulting in inefficient use and waste of RF energy, potential damage to the processing chamber or RF energy source, and potential inconsistency / non-reproducibility issues with substrate processing. Thus, RF energy is often coupled to the plasma in the processing chamber via a fixed or tunable matching network. This matching network operates to minimize reflected RF energy by more precisely matching the plasma impedance to the impedance of the RF energy source. The matching network attempts to maximize the amount of energy coupled to the plasma by efficiently coupling the output of the RF source to the plasma (e.g., called RF power supply tuning). Therefore, the matching network attempts to adjust the total impedance (i.e., plasma impedance + chamber impedance + matching network impedance) to be the same as the output impedance of the RF power supply. In some embodiments, the RF energy source may also be configured to support impedance matching by enabling frequency tuning or adjustment of the frequency of the RF energy supplied by the RF energy source.

[0003] In processing chambers that use multiple separate RF power signals pulsed at multiple power levels, synchronous RF pulses are typically used. However, the inventors have often observed that impedance tuning becomes difficult with various RF pulse schemes due to numerous impedance changes. That is, the matching network and / or RF generator cannot properly tune to the reflected power as the reflected power changes.

[0004] Therefore, the inventors provide an improved method and apparatus for RF pulse tuning that uses one or more variable frequency generators in addition to the use of variable capacitors / inductors, thereby beneficially minimizing RF pulse reflections in the processing chambers. In these processing chambers, multiple separate RF power signals pulsed at multiple power levels during a single duty cycle are used. [Overview of the project]

[0005] This specification provides methods and systems for reducing RF pulse reflection. In some embodiments, a method for processing a substrate in a plasma substrate processing system using multilevel pulsed RF power includes the steps of: receiving a processing recipe for processing a substrate, which includes a plurality of pulsed RF power waveforms from a plurality of RF generators, wherein the plurality of RF generators include a master RF generator and one or more slave RF generators; using the master RF generator to generate a transistor-to-transistor logic (TTL) signal having a fundamental frequency and a first duty cycle; setting a multiplier for each RF generator, wherein the multiplier is a multiple of the fundamental frequency; dividing the first duty cycle into high-level intervals and low-level intervals; determining a set of frequency commands for each RF generator and transmitting the set of frequency commands to each RF generator, wherein the set of frequency commands includes a frequency setting point for each RF generator; and providing a plurality of pulsed RF power waveforms from the plurality of RF generators to a processing chamber according to the set of frequency commands transmitted to each RF generator.

[0006] In some embodiments, instructions stored in a non-temporary computer-readable medium cause a method to operate a plasma substrate processing system when executed. This method includes the steps of: receiving a processing recipe for processing a substrate, which includes a plurality of pulsed RF power waveforms from a plurality of RF generators, wherein the plurality of RF generators include a master RF generator and one or more slave RF generators; using the master RF generator to generate a TTL signal having a fundamental frequency and a first duty cycle; setting a multiplier for each RF generator, wherein the multiplier is a multiple of the fundamental frequency; dividing the first duty cycle into high-level intervals and low-level intervals; determining a set of frequency commands for each RF generator and transmitting the set of frequency commands to each RF generator, wherein the set of frequency commands includes a frequency setting point for each RF generator; and providing a plurality of pulsed RF power waveforms from the plurality of RF generators to a processing chamber according to the set of frequency commands transmitted to each RF generator.

[0007] In some embodiments, the substrate processing system comprises a plurality of RF generators configured to supply a plurality of RF power waveforms to a processing chamber during a first duty cycle, the plurality of RF generators including a master RF generator and one or more slave RF generators, a pulse controller connected to the plurality of RF generators, and at least one matching network connected to each of the plurality of RF generators, the processing chamber, and the pulse controller, the matching network including at least one measuring device configured to measure reflected power or impedance to the plurality of RF power waveforms, and at least one variable matching component, and the pulse controller Alternatively, at least one of the at least one matched network is configured to receive a processing recipe for processing a substrate, set a multiplier for at least one of a plurality of RF generators which is a multiple of the fundamental frequency of the TTL signal generated by the master RF generator, divide the first duty cycle of the TTL signal into high-level and low-level intervals, determine a frequency command set for each RF generator which includes a frequency setting point for each RF generator, transmit the frequency command set to each RF generator, and provide an RF power waveform from each RF generator to the processing chamber according to the frequency command set transmitted to each RF generator.

[0008] Further embodiments of this disclosure are described below. [Brief explanation of the drawing]

[0009] Embodiments of the present disclosure, briefly summarized above and discussed in more detail below, can be understood by referring to exemplary embodiments of the present disclosure shown in the accompanying drawings. However, since the present disclosure may allow for other equally valid embodiments, the accompanying drawings show only some embodiments of the present disclosure and should not be considered limiting in scope. [Figure 1] This disclosure shows plasma reactors according to several embodiments. [Figure 2]Wiring diagrams of a master RF generator and one or more slave RF generators according to some embodiments of the present disclosure are shown. [Figure 3A] ~ [Figure 3C] The pulse waveforms of RF signals according to some embodiments of this disclosure are shown. [Figure 4A] ~ [Figure 4D] The phase changes between pulse waveforms according to some embodiments of this disclosure are shown. [Figure 5] The following are examples of multiple pulse power waveforms for a first duty cycle according to some embodiments of the present disclosure. [Figure 6] This disclosure describes exemplary apparatus for employing a tuning algorithm according to several embodiments of this disclosure. [Figure 7] A flowchart of a method for reducing RF pulse reflection in a processing chamber, according to some embodiments of the present disclosure, is shown.

[0010] For ease of understanding, the same reference numerals are used to indicate identical elements common to these drawings where possible. These drawings are not drawn to a fixed scale and may be simplified for clarity. Elements and configurations of one embodiment may be usefully incorporated into other embodiments without specific description. Detailed description

[0011] Embodiments of this disclosure provide an improved method and apparatus for RF pulse tuning that uses one or more variable frequency generators in addition to using a variable capacitor / inductor. Specifically, the improved method and apparatus performs impedance matching using at least two tuning degrees of freedom, by using at least one variable capacitor / inductor and one or more variable frequencies generated by one or more variable frequency generators. The frequencies generated by one or more variable frequency generators can be changed rapidly (i.e., on a microsecond level) so that they can be quickly adjusted and tuned to the new impedance resulting from the change in total traveling wave power within a single RF pulse cycle. In embodiments consistent with this disclosure, an RF matching network transmits a set of frequency commands to the RF frequency generators. The RF generators then produce RF pulse outputs having one or more frequencies for a single RF pulse cycle to minimize reflected power for each interval within a single RF pulse cycle. The variable capacitor / inductor is tuned to a calculated target impedance value. Embodiments consistent with this disclosure also beneficially minimize RF pulse reflections within a processing chamber. This processing chamber uses multiple separate RF power signals that are pulsed at multiple power levels during a single duty cycle, and for this purpose, it uses one or more variable frequency generators in addition to one or more variable capacitors / inductors.

[0012] Figure 1 shows a plasma reactor that may be used to carry out the method disclosed herein. This method may be carried out in a capacitively coupled plasma reactor (for example, as shown in Figure 1) or any other suitable plasma reactor (such as an inductively coupled plasma reactor). However, the inventors have found that this method may be particularly beneficial in a capacitively coupled plasma reactor where, for example, high bias power (e.g., about 2000 W or more) and low source power (e.g., about 500 W or less) are used. This is because undesirable charge effects can be far more severe than, for example, in an inductively coupled plasma processing chamber. In some embodiments, the inventors have found that this method uses a DC bias (VDC ), V RF We found that this offers particular advantages in configurations where, or at least one of the plasma sheath voltages is approximately 1000V or higher.

[0013] The reactor in Figure 1 comprises a chamber 100 enclosed by a cylindrical side wall 102, a floor 103, and a lid 104. In some embodiments, the lid 104 may be a gas distribution showerhead comprising a gas manifold 106 on a gas distribution plate 108 having an orifice 109, where the orifice 109 is formed through the gas distribution plate 108. The gas manifold 106 is enclosed by a manifold enclosure 110 having a gas supply inlet 111. The gas distribution showerhead (i.e., the lid 104) is electrically insulated from the cylindrical side wall 102 by an insulating ring 112. A vacuum pump 114, such as a turbomolecular pump, can evacuate the chamber 100. A gas panel 120 controls the individual flow rates of various processing gases supplied to the gas supply inlet 111. A support base 136, supported through the floor 103 of the chamber, may have an insulating top surface and internal electrodes (wafer support electrodes 138). The substrate 137 may be gripped using internal electrodes, for example, on the upper surface of the support base 136.

[0014] Multiple RF generators 140, 144, 148, and 150 may supply power to the chamber 100. These multiple RF generators include a master RF generator 140 and one or more slave RF generators 144, 148, and 150. Plasma source power is supplied from the master RF generator 140 to the lid 104 (also referred to herein as a gas distribution showerhead) via an impedance matching network 142. The lid, or gas distribution showerhead, is formed of a conductive material such as aluminum and thus functions as a lid electrode. In some embodiments, the master RF generator 140 may generate VHF power at high frequencies in the VHF band, such as in the range of 100 to 200 MHz. The master RF generator 140 has the ability to pulse the generated power at a desired pulse rate and duty cycle. For example, the master RF generator 140 has a pulse control input 140a, which receives a control signal that defines the pulse rate and / or duty cycle, as well as the phase of each pulse generated by the master RF generator 140.

[0015] In the embodiment shown in Figure 1, plasma bias power or plasma source power is applied to the wafer support electrode 138 from the first slave RF generator 144 via the impedance matching network 146, from the second slave RF generator 148 via the impedance matching network 149, and from the third slave RF generator 150 via the impedance matching network 152. For example, the first slave RF generator 144 may apply plasma source power, while the second slave RF generator 148 and the third slave RF generator 150 may apply plasma bias power. One or more slave RF generators 144, 148, and 150 may generate shortwave (HF) or longwave (LF) power from the LF band to the lower end of the HF band (e.g., in the range of 30 kHz to 5 MHz). For example, the first slave RF generator 144, the second slave RF generator 148, and the third slave RF generator 150 may generate power at approximately 2 MHz, approximately 400 kHz, and approximately 100 kHz, respectively. One or more slave RF generators 144, 148, 150 have the ability to pulse power generated at a desired pulse rate and duty cycle. For example, one or more slave RF generators 144, 148, 150 have pulse control inputs 144a, 148a, 150a, which receive control signals defining the pulse rate and / or duty cycle, as well as the phase of each pulse generated by one or more slave RF generators 144, 148, 150. One or more slave RF generators 144, 148, 150 can be pulse-controlled, phase-controlled, and / or duty-cycle-controlled independently. Furthermore, one or more slave RF generators 144, 148, 150 may be pulsed synchronously or asynchronously.

[0016] In some embodiments, impedance matching networks 142, 146, 149, and 152 may be formed by one or more capacitors and / or inductors. The matching of each of the impedance matching networks 142, 146, 149, and 152 may be adjusted by electronically or mechanically tuning the values ​​of the capacitors. In low-power systems, one or more capacitors may be electronically tuned instead of mechanically tuned. In some embodiments, the impedance matching networks 142, 146, 149, and 152 may have tuneable inductors. In some embodiments, one or more capacitors used in the impedance matching networks 142, 146, 149, and 152 may be one or more fixed capacitors or series capacitors. In other embodiments, one or more capacitors used in the impedance matching networks 142, 146, 149, and 152 may be variable capacitors. The matching of the impedance matching networks 142, 146, 149, and 152 may be adjusted by electronically or mechanically tuning these variable capacitors. In some embodiments, one or more of the impedance matching networks 142, 146, 149, and 152 may have a capacitive short circuit to earth.

[0017] Figure 2 shows a wiring diagram of a master RF generator and one or more slave RF generators according to the embodiment shown in Figure 1. The master RF generator 140 may be connected to the impedance matching network 142 via high-speed link cable 153 and RF cable 155. The master RF generator 140 may be connected to the first slave RF generator 144 via high-speed link cable 172. The master RF generator 140 may be connected to the second slave RF generator 148 via high-speed link cable 174. The master RF generator 140 may be connected to the third slave RF generator 150 via high-speed link cable 176. The master RF generator 140 may be connected to the impedance matching networks 142, 146, and 152, respectively, via high-speed link cables 153, 182, and 184.

[0018] The first slave RF generator 144 may be connected to an impedance matching network 146 via an RF cable 202 and a high-speed link cable 212. The second slave RF generator 148 may be connected to an impedance matching network 149 via an RF cable 204 and a high-speed link cable 214. The third slave RF generator 150 may be connected to an impedance matching network 152 via an RF cable 206 and a high-speed link cable 216.

[0019] The impedance matching networks described above are merely illustrative, and in accordance with the teachings provided herein, other various configurations of impedance matching networks having one or more adjustable elements for tuning the matching network may be utilized and tuned. For example, FIG. 6 shows an exemplary apparatus for employing a smart tuning algorithm according to some embodiments of the present disclosure. The RF generator 602 is a schematic representation of the plurality of RF generators 140, 144, 148, and 150 of FIG. 1.

[0020] In FIG. 6, the RF generator 602 may be connected to the RF matching network 604 via the RF cables 151 and one or more high-speed link cables 153. The RF matching network 604 is a schematic representation of one or more impedance matching networks 142, 146, 149, 152. The RF matching network 604 may include one or more matching sensors or impedance measuring devices (e.g., VI probe / sensor 606), a CPU 130, a variable impedance matching component 608 (e.g., variable capacitor / inductor), and fixed components Z2, 610 (e.g., fixed capacitor / inductor). The variable impedance matching component 608 may include one or more variable capacitors and / or inductors to provide desired impedance matching. A plurality of serial cables may be used to supply the timing signal to the RF generator 602 and the RF matching network 604. Thus, in the above configuration, it is possible to reduce / minimize the reflected power (i.e., it is possible to synchronize the system). For this purpose, the variable impedance matching component 608 is synchronized to the calculated target impedance as described below, and the frequency / power provided by the generator is changed to provide two degrees of freedom of synchronization (i.e., variable impedance matching component 608 and variable frequency).

[0021] The controller 160 is programmable to apply a pulse control signal to each of the pulse control inputs 140a, 144a, 148a, 150a of the plurality of RF generators 140, 144, 148, 150 to generate a desired phase advance or delay relationship and / or duty cycle relationship between the pulses of the master RF generator 140 and the slave RF generators 144, 148, 150. The controller 160 may also control other aspects of the tool chamber / processing chamber. Although shown as separate components in FIG. 1, in some embodiments, the controller 160 may be disposed inside each RF generator. The synchronization signal is generated by the master RF generator (e.g., master RF generator 140) and transmitted to other slave generators (e.g., slave RF generators 144, 148, and / or 150).

[0022] In some embodiments, the RF generators 140, 144, 148, and 150, impedance matching networks 142, 146, 149, and 152, and / or controller 160 comprise a central processing unit (CPU) 130, a plurality of support circuits 134, and memory 132. While this exemplary embodiment of the plurality of RF generators 140, 144, 148, and 150, impedance matching networks 142, 146, 149, and 149, and controller 160 is described in relation to a computer having a CPU, support circuits, and memory, those skilled in the art will recognize that the plurality of RF generators 140, 144, 148, and 150, impedance matching networks 142, 146, 149, and 152, and controller 160 can be implemented in a variety of forms. These various forms include application-specific interface circuits (ASICs), field-programmable gate arrays (FPGAs), systems on a chip (SOCs), and the like. Furthermore, various embodiments of the controller 160 may be integrated into other processing tool controllers having corresponding input / output interfaces, as known in the art.

[0023] The support circuit 134 may include a display device and other circuits to support the functions of the CPU 130. Such circuits may include a clock circuit, cache, power supply, network card, video circuit, and the like.

[0024] Memory 132 may include read-only memory, random-access memory, removable memory, disk drives, optical drives, and / or other forms of digital storage. Memory 132 is configured to house an operating system and subfab control modules. The operating system controls the general operation of several RF generators 140, 144, 148, and 150, impedance matching networks 142, 146, 149, and 152, and controller 160. This operation includes performing the methods described herein (e.g., method 600 described below) by controlling one or more RF generators 140, 144, 148, and 150, or impedance matching networks 142, 146, 149, and 152, thereby facilitating the execution of various processes, applications, and modules.

[0025] Furthermore, the DC generator 162 may be connected to either (or both) the wafer support electrode 138 and the lid 104. In some embodiments, the DC generator 162 can supply continuous DC and / or variable DC. In some embodiments, the DC generator 162 may supply pulsed DC power. The pulse repetition rate, phase, and duty cycle of the DC generator are controlled by the controller 160. DC isolation capacitors 164, 166, and 168 may be provided to isolate each of the RF generators 148, 144, and 150 from the DC generator 162. The DC signal generated by the DC generator may be synchronized with the RF signal generated by the RF generators 140, 144, 148, and 150 to provide advantages such as reduced charge-up of the substrate 137 or improved control of the etching rate of the substrate using the plasma formed in the plasma reactor.

[0026] FIG. 3A shows a time-domain waveform diagram that can reflect the pulse RF output of each of the plurality of RF generators 140, 144, 148, 150. Here, a pulse envelope of the pulse RF output is shown, characterized by the following parameters that are individually controlled by the controller 160 for each of the RF generators 140, 144, 148, 150. It is the pulse duration t P , the pulse "on" time t ON , the pulse "off" time t OFF , the pulse frequency 1 / t P , and the pulse duty cycle (t ON / t P )×100 (percent). The pulse duration t P is the sum of t ON and t OFF .

[0027] FIGS. 3B and 3C show the simultaneous time-domain waveforms of two RF pulse signals. These two RF pulse signals are synchronized together in such a way that they have the same phase and duty cycle, and thus their phase difference is zero. The exemplary embodiments shown in FIGS. 3B and 3C are one exemplary form of synchronization between a first pulse RF signal (e.g., a pulse master signal) and a second pulse RF signal (e.g., a pulse slave signal). As shown, both the phase and the duty cycle of each pulse signal are the same.

[0028] In some embodiments of this disclosure, the pulse signals provided by the multiple RF generators 140, 144, 148, and 150 are phase-shifted. Figures 4A to 4D show how the phase difference is shifted by the controller 160, superimposing the source or master and bias or slave power waveforms at phase differences of 0°, 90°, 180°, and 270°, respectively. Here, the phase difference is defined as the delay of the second pulse output relative to the first pulse output. Figure 4A corresponds to the zero phase difference embodiment in Figure 3B. Figure 4B shows the case where the bias power pulse output lags the source power pulse output by 90°. Figure 4C shows the case where the bias power pulse output lags the source power pulse output by 180°. Figure 4D shows the case where the bias power pulse output lags the source power pulse output by 270°. Figures 4A to 4B show only two pulse RF signals with phase shifts, but embodiments consistent with this disclosure may also include three or more pulse RF signals with phase shifts.

[0029] In some embodiments, the etching rate may be increased while pulsing the plasma by controlling the phase lead or lag of the RF envelope. When the source and bias are pulsed with independently phase-shifted pulses, or pulsed with a variety of duty cycles, the different plasma dynamics of very high frequency (VHF) and long frequency (LF) allow for better plasma filling throughout the pulse. In some embodiments, a VHF combination with a source frequency of about 162 MHz is used with a first bias frequency of about 2 MHz, a second bias frequency of about 400 kHz, and a third bias frequency of about 100 kHz.

[0030] The master RF generator 140 can generate a transistor-to-transistor logic (TTL) signal having a fundamental frequency and a first duty cycle. Figure 5 shows the first duty cycle of pulsed RF power associated with a substrate processing recipe for processing a substrate. In the embodiment shown in Figure 5, four distinct pulsed RF waveforms are required to be provided to this substrate processing recipe in order to process the substrate. Figure 5 shows several distinct RF power signals that may be supplied continuously or pulsed at multiple power levels based on some embodiments of the present disclosure. Figure 5 shows a multi-stroke cycle pulse (MSCP) using multi-level pulses (MLP) for multi-frequency RF mixing. In some embodiments, single-level pulses (SLP) (i.e., on / off pulse waveforms) and continuous waveforms (CW) may be used. In some embodiments, dual-level pulsing (DLP) (i.e., high-power / low-power pulse waveforms) may be used. In some embodiments, triple-level pulsing (TLP) (i.e., high-power / low-power / off pulse waveforms) may be used.

[0031] Figure 5 shows four distinct RF power waveforms. These are the master RF power waveform 502, the first slave RF power waveform 504, the second slave RF power waveform 506, and the third slave RF power waveform 508. As shown in the figure, the master RF power waveform 502 has a TLP waveform, the first slave RF power waveform 504 has a TLP waveform, the second slave RF power waveform 506 has a DLP waveform, and the third slave RF power waveform 508 has an SLP waveform.

[0032] Each of the four distinct RF power waveforms 502, 504, 506, and 508 may be provided at multiple power levels and different phases independent of each other, or at various duty cycles consistent with embodiments of the present disclosure. The RF power waveforms 502, 504, 506, and 508 may be provided by one or more source and bias RF generators (e.g., multiple RF generators 140, 144, 148, and 150). In embodiments where there are two or more pulsed RF power waveforms, the distinct pulsed RF power waveforms may be pulsed synchronously with respect to each other. In some embodiments, the distinct RF power waveforms may be pulsed asynchronously.

[0033] Each of the four distinct RF power waveforms may be configured to pulse at a frequency that is an integer multiple of the fundamental frequency of the TTL signal. In some embodiments, such as a standard multiplier mode, all slave RF power waveforms have the same pulse frequency. In some embodiments, such as a universal multiplier mode, each slave RF power waveform may have the same or different pulse frequencies. The master RF power waveform 502 may have a multiplier of 1 (i.e., the same frequency as the fundamental frequency of the TTL signal). In Figure 5, the master RF power waveform 502 has a multiplier of 2 (i.e., the master RF power waveform is pulsed at twice the fundamental frequency of the TTL signal). The first slave RF power waveform 504 has a multiplier of 1. The second slave RF power waveform 506 has a multiplier of 3. The third slave RF power waveform 508 has a multiplier of 4.

[0034] In Figure 5, the TTL signal is introduced at time t0 and has a first duty cycle 520. The first duty cycle 520 may be divided into a high-level interval 522 and a low-level interval 524. The high-level interval 522 coincides with the rising edge 526 and falling edge 527 of the TTL signal. The low-level interval 524 coincides with the falling edge 527 and subsequent rising edge 528 of the TTL signal. The master RF power waveform 502 is introduced at time t0 and may include a first power pulse 510 at a first power level, a second power pulse 512 at a second power level, and a third power pulse 514 at a zero power level.

[0035] In some embodiments, the frequency of the master RF power waveform 502 may be from about 2 MHz to about 200 MHz. In some embodiments, the power level of the master RF power waveform 502 may be from about 200 watts to about 5.0 kW (e.g., 3.6 kW). If the master RF power waveform 502 is pulsed, the value of the second power level may be from about 0 to 100% of the first power level. In other embodiments, the second power level may be greater than the first power level.

[0036] The first slave RF power waveform 504 may also be introduced at time t0 (as shown in the figure) or after a delay period 525. The first slave RF power waveform 504 may include a first power pulse 530 at a first power level, a second power pulse 532 at a second power level, and a third power pulse 534 at a third power level. As illustrated in Figure 5, the first power pulse 530 precedes the second power pulse 532 and the third power pulse 534. Additional power pulses may be provided in that order or in a different order, if desired. As shown in Figure 5, the first power pulse 530 may be provided at a high power level, the second power pulse 532 may be provided at a lower power level than the first power pulse 530, and the third power pulse 534 may be provided at zero power level. In some embodiments, the length of each period during which each power pulse 530, 532, and 534 is applied may differ from one another. In other embodiments, the durations of each power pulse 530, 532, and 534 may be equivalent. In some embodiments, the first slave RF power waveform 504 may be provided at a frequency of about 1 MHz to about 3 MHz. In other embodiments, other frequencies as described above may be used.

[0037] The second slave RF power waveform 506 may also be introduced at time t0 (as shown in the figure) or after the delay period 525. In some embodiments, the second slave RF power waveform 506 may have a configuration similar to that described above with respect to the master RF power waveform 502 and / or the first slave RF power waveform 504. In some embodiments, the second slave RF power waveform 506 may include a first power pulse 540 at a first power level and a second power pulse 542 at a second power level. As shown in Figure 5, the first power pulse 540 may be provided at a low power level, and the second power pulse 532 may be provided at a high power level higher than the first power level 540.

[0038] The third slave RF power waveform 508 may also be introduced at time t0 or after a delay period 525 (as shown in the figure). In some embodiments, the third slave RF power waveform 506 may have a configuration similar to that described above with respect to the master RF power waveform 502, the first slave RF power waveform 504, or the second slave RF power waveform 506. In some embodiments, the third slave RF power waveform 508 may include a first power pulse 550 at a first power level and a second power pulse 552 at a second power level. As shown in Figure 5, the first power pulse 550 may be provided at a zero power level, and the second power pulse 552 may be provided at a high power level.

[0039] In some embodiments, the duty cycles of separate RF power waveforms are synchronized. In some embodiments, the TTL signal may be a timing signal provided by the DC generator 162.

[0040] In Figure 5, high-level intervals 522 and low-level intervals 524 are provided. The CPU 130 is configured to calculate a high average impedance value, which is the average impedance value over the high-level intervals. The CPU is configured to calculate a low average impedance value, which is the average impedance value over the low-level intervals. The CPU 130 is configured to calculate a target impedance value based on the calculated high and low average impedance values. In some embodiments, the target impedance value is the average of the high and low average impedance values. In some embodiments, the target impedance value is closer to a higher average impedance value than a lower average impedance value. In some embodiments, the target impedance value is closer to a lower average impedance value than a higher average impedance value. One or more RF matching networks are configured to tune to the target impedance to beneficially minimize average reflected power. With each new duty cycle of the TTL signal, the system tunes and compensates for the new reflected power based on the total forward-traveling power supplied.

[0041] To further minimize reflected power, the inventors have developed a method utilizing the above-described apparatus. The method used by this apparatus to more quickly tune multiple RF power waveforms to minimize average reflected power is shown in Figure 6 and described below. In embodiments consistent with the present disclosure, method 600 may be performed by one or more RF matching networks 604, one or more RF generators 602, or a controller 160.

[0042] Method 700 begins with step 702, where a processing recipe for processing the substrate is received. The processing recipe includes multiple pulsed RF power waveforms (i.e., 502, 504, 506, and 508) from multiple RF generators 140, 144, 148, and 150. The multiple RF generators include a master RF generator 140 and one or more slave RF generators 144, 148, and 150. In step 704, the master RF generator 140 can be used to generate a TTL signal having a fundamental frequency and a first duty cycle. In step 706, a multiplier is set for each of the multiple RF generators 140, 144, 148, and 150. In some embodiments, a multiplier is set for at least one of the multiple RF generators 140, 144, 148, and 150. The multiplier is an integer value. In step 708, the first duty cycle is divided into a high-level interval 522 and a low-level interval 524. The high-level interval 522 coincides with the duration of the detected rising edge and the detected falling edge of the TTL signal. The low-level interval 524 coincides with the duration of the detected falling edge and the detected subsequent rising edge of the TTL signal. In some embodiments, the CPU 130 can receive the timing of the TTL rising edge and TTL falling edge.

[0043] In step 710, a frequency command set is determined for each RF generator, where the frequency command set includes a frequency setpoint. In some embodiments, the frequency command set is determined by an RF matching network (e.g., RF matching network 604). The frequency command set includes a frequency and / or power setpoint for a first duty cycle. In some embodiments, the frequency command set is transmitted indirectly to the RF generators by the RF matching network via a controller (e.g., controller 160) that is communicably connected to the RF matching network and the RF generators. The frequency command set determined for each of the RF generators 140, 144, 148, and 150 is transmitted to the corresponding RF generators 140, 144, 148, and 150 associated with the frequency command set. In some embodiments, the frequency command set may be transmitted to each generator via high-speed link cables 153, 212, 214, and 216. In other embodiments, the frequency command set may be transmitted to each generator via controller 160.

[0044] The step of determining the frequency command set may include the CPU 130 calculating a high average impedance value over a high-level interval and a low average impedance value over a low-level interval. Next, the CPU 130 may calculate the target impedance based on the high average impedance value and the low average impedance value. One or more RF matching networks may be tuned to the target impedance using variable matching components (e.g., variable capacitors / inductors) placed within one or more RF matching networks. A variable impedance matching component includes at least one of a variable capacitor or an inductor.

[0045] In some embodiments, each of the variable impedance matching components 608 within impedance matching networks 142, 146, 149, and 152 tunes to the same calculated target impedance value. Figure 7 shows the process that occurs during a single duty cycle, and this process may be repeated as needed to process the substrate. In some embodiments consistent with the present disclosure, the processing recipe may include RF pulse power waveforms for all duty cycles, and these RF pulse power waveforms may not always be identical to one another in terms of frequency and power at each interval. Thus, each of the individual duty cycles may be analyzed and divided separately as described above.

[0046] In step 712, multiple pulsed RF power waveforms (e.g., 502, 504, 506, and 4508) from multiple RF generators are supplied to the processing chamber according to a set of frequency commands transmitted to each generator during the first duty cycle. That is, the RF pulsed power is supplied at the frequency setpoint determined in step 710. In some cases, if the previous setpoint for the previous time interval is equal to the setpoint for the next time interval, no adjustment is necessary unless the frequency is adjusted to reduce reflected power based on measurements, as described below.

[0047] After step 712, the impedance / reflected power is measured in each RF matching network 604 by a matching sensor 606. Based on the impedance measured after step 712, the frequency and / or power provided by one or more RF generators may be adjusted to further reduce the reflected power. These minute frequency adjustments may be transmitted via high-speed link cables 153, 212, 214, and 216. This method is repeated back to step 712, providing RF pulse power waveforms at the start of subsequent time intervals, measuring the reflected / power impedance, and adjusting the frequency / power until the processing of the substrate is complete. At this point, this method ends in step 714.

[0048] Method 700 is performed by one or more processors in the plasma reactor. These processors include, for example, processors for one or more impedance matching networks (i.e., matchers), processors for one or more RF generators, and processors for pulse controllers. Examples of processors include application-specific integrated circuits (ASICs), programmable logic devices (PLDs), microprocessors, microcontrollers, and central processing units (CPUs).

[0049] The disclosed embodiments can utilize a variety of computer execution operations, including data stored in a computer system. These operations require the physical manipulation of physical quantities. Any of the operations described herein that form part of the embodiments are useful mechanical operations. The embodiments also relate to devices or apparatus for performing these operations. Apparatus may be specifically constructed for a special-purpose computer. If designated as a special-purpose computer, the computer may operate for its special purpose, while also performing other processes, program executions, or routines that are not part of its special purpose. Alternatively, operations may be processed by a general-purpose computer selectively activated or configured by one or more computer programs stored in the computer's memory, cache, or retrieved over a network. If data is retrieved over a network, that data may be processed by other computers on the network, for example, a cloud of computing resources.

[0050] One or more embodiments may be fabricated as computer-readable code on a non-temporary computer-readable medium. The computer-readable medium is any data storage capable of storing data that can later be read by a computer system. Examples of computer-readable media include hard drives, network-attached storage (NAS), ROM, RAM, compact disk ROM (CD-ROM), CD-Writable Media (CD-R), CD-Rewritable Media (CD-RW), magnetic tape, and other optical and non-optical data storage devices. The computer-readable code is stored and executed in a distributed manner, as the computer-readable medium may include computer-readable tangible media distributed across a networked computer system.

[0051] While the foregoing applies to embodiments of the present disclosure, other further embodiments of the present disclosure can be created without departing from its fundamental scope.

Claims

1. A method for processing a substrate in a plasma substrate processing system using multilevel pulsed RF power, A step of receiving a processing recipe for processing a substrate, which includes multiple pulse RF power waveforms from multiple RF generators, wherein the multiple RF generators include a master RF generator and one or more slave RF generators. A process of generating a transistor-to-transistor logic (TTL) signal having a fundamental frequency and a first duty cycle using a master RF generator, A step of setting a multiplier for each RF generator, wherein the multiplier is a multiple of the fundamental frequency, A process of dividing the first duty cycle into high-level intervals and low-level intervals, A step of determining a frequency command set for each RF generator and transmitting the frequency command set to each RF generator, wherein the frequency command set includes a frequency setting point for each RF generator. A method comprising the step of providing a plurality of pulsed RF power waveforms from a plurality of RF generators to a processing chamber in accordance with a set of frequency commands transmitted to each RF generator.

2. The process of determining the frequency command set is: A process for calculating high average impedance values ​​over high-level intervals and low average impedance values ​​over low-level intervals, A process of calculating the target impedance based on high average impedance values ​​and low average impedance values, The method according to claim 1, comprising the step of tuning one or more RF matching networks to a target impedance.

3. The method according to claim 2, further comprising the step of adjusting the frequency or power provided by at least one of a plurality of RF generators to reduce at least one of a high average impedance value and a low average impedance value.

4. The method according to claim 3, wherein the step of tuning one or more RF matching networks to a target impedance includes the step of tuning variable matching components located within one or more RF matching networks to a target impedance.

5. The method according to claim 4, wherein the variable matching component for tuning to the target impedance includes at least one of a variable capacitor or an inductor.

6. The method according to claim 1, wherein the frequency command set is determined by an RF matching network associated with each RF generator.

7. The method according to claim 6, wherein the frequency command set is transmitted to each RF generator via a high-speed link cable that directly and communicatively connects the RF matching network and each RF generator.

8. The method according to claim 6, wherein the frequency command set is transmitted indirectly to each RF generator by the RF matching network via controllers that are communicably connected to the RF matching network and each RF generator.

9. The high-level interval is either consistent with the duration of the detected rising and falling edges of the TTL signal, or The method according to any one of claims 1 to 8, wherein the low-level interval is at least one of the durations of the detected falling edge and the detected rising edge of the TTL signal.

10. The method according to any one of claims 1 to 8, further comprising the step of receiving a timing signal from a master RF generator and synchronizing a plurality of RF power waveforms from one or more slave RF generators.

11. The method according to any one of claims 1 to 8, wherein the multiplier for each RF generator can be set independently.

12. The method according to any one of claims 1 to 8, wherein at least one of the plurality of RF power waveforms is a triple-level pulsed (TLP) waveform pulsed at a plurality of power levels.

13. A non-temporary computer-readable medium containing instructions that, when executed, cause a method to operate a plasma substrate processing system, A computer-readable medium wherein the method is as described in any one of claims 1 to 8.

14. A substrate processing system, Multiple RF generators configured to provide multiple RF power waveforms to a processing chamber during a first duty cycle, comprising a master RF generator and one or more slave RF generators, A pulse controller connected to multiple RF generators, A matching network connected to each of a plurality of RF generators, processing chambers, and pulse controllers, A measuring device configured to measure reflected power or impedance for multiple RF power waveforms, A matching network comprising at least one variable matching component, The pulse controller or at least one of the at least one matching network is We received a processing recipe for processing the circuit board. Set a multiplier for at least one of the multiple RF generators, which is a multiple of the fundamental frequency of the TTL signal generated by the master RF generator. The first duty cycle of the TTL signal is divided into high-level intervals and low-level intervals. A frequency command set for each RF generator, which includes a frequency setting point for each RF generator, is determined and the frequency command set is transmitted to each RF generator. A substrate processing system configured to provide RF power waveforms from each RF generator to the processing chamber according to a set of frequency commands transmitted to each RF generator.

15. The process of determining the frequency command set for each RF generator is as follows: The process of calculating a high average impedance value over a high-level interval, The process of calculating a low average impedance value over low-level intervals, The substrate processing system according to claim 14, comprising the step of calculating a target impedance based on a high average impedance value and a low average impedance value.

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