Patent ID: 12237149

To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. It is contemplated that elements and features of one implementation may be beneficially incorporated in other implementations without further recitation.

DETAILED DESCRIPTION

Embodiments of the present disclosure generally relate to a system used in a semiconductor device manufacturing process. More specifically, embodiments provided herein generally include apparatus and methods for synchronizing and controlling the delivery of an RF bias signal and a pulsed voltage waveform to one or more electrodes within a plasma processing chamber. The apparatus and methods disclosed herein can be useful to at least minimize or eliminate a microloading effect created while processing small dimension features that have differing densities across various regions of a substrate. The plasma processing methods and apparatus described herein are configured to improve the control of various characteristics of the generated plasma and control an ion energy distribution (IED) of the plasma generated ions that interact with a surface of a substrate during plasma processing. The ability to synchronize and control waveform characteristics of a voltage waveform bias established on a substrate during processing allows for an improved control of the generated plasma and process of forming, for example, high-aspect ratio features in the surface of the substrate by a reactive ion etching process. As a result, greater precision for plasma processing can be achieved, which is described herein in more detail.

FIG.1is a schematic view of a conventional plasma processing system10that is adapted to process a substrate13disposed on a substrate support40by generating a plasma11within the processing region15that is enclosed by a plurality of walls50of a plasma processing chamber99. The plasma processing system10is configured to form a inductively coupled plasma (ICP), where the processing chamber99includes a coil73disposed over a portion of the processing region15so that at least a portion of the coil is facing a lower electrode46that is disposed within substrate support40that is disposed within the processing region15. The ICP plasma processing source, includes a radio frequency (RF) generator71that is electrically coupled to the upper coil73through an RF match72, and delivers a tuned RF signal that is configured to ignite and maintain the plasma11formed in the processing region15. Typically, the lower electrode46is coupled to ground or to a second RF power generator, which can include a radio frequency (RF) generator61and62that is electrically coupled to the lower electrode46through an RF match60. However, in conventional plasma processing configurations, such as shown inFIG.1A, in which RF signals are simultaneously being provided to one or more electrodes to form the plasma11, the impedance of a complex load created by the plasma11will fluctuate at least in part due to a varying RF power levels. A gas inlet16disposed through a chamber lid51is used to deliver one or more processing gases to the processing volume15from a processing gas source17that is in fluid communication therewith.

Plasma Processing System Example

FIG.2Ais a schematic view of a plasma processing system200that is adapted to process a substrate13disposed on a substrate support assembly240by generating a plasma11within the processing volume234of a plasma processing chamber250. The plasma processing system200is configured to form a inductively coupled plasma (ICP), where the processing chamber250includes a coil273disposed over a portion of the processing volume234so that at least a portion of the coil is facing a biasing electrode214that is also disposed within substrate support assembly240that is disposed within the processing volume234. The biasing electrode214is also often referred to herein as a substrate support electrode. The ICP plasma processing source similarly includes a radio frequency (RF) generator271that is electrically coupled to the upper coil273through an RF match272, and delivers a tuned RF signal that is configured to ignite and maintain the plasma11formed in the processing volume234. The biasing electrode214is coupled to a pulsed voltage (PV) waveform generator210, which is electrically coupled to the biasing electrode214through an RF filter211that is configured to prevent RF signals from making their way to the PV waveform generator210during processing. In some embodiments, the RF generator271is configured to deliver an RF waveform signal having a frequency that is greater than 1 MHz or more, or about 2 MHz or more, such as about 13.56 MHz or more through an RF match272that is connected to the coil273.

The processing chamber250typically includes a chamber body230that includes one or more sidewalls231and a chamber base232, which collectively, with a chamber lid233, define the processing volume234. The one or more sidewalls231and chamber base232generally include materials that are sized and shaped to form the structural support for the elements of the processing chamber250and are configured to withstand the pressures and added energy applied to them while a plasma11is generated within a vacuum environment maintained in the processing volume234of the processing chamber250during processing. In one example, the one or more sidewalls231and chamber base232are formed from a metal, such as aluminum, an aluminum alloy, or a stainless steel alloy. A gas inlet235disposed through the chamber lid233is used to deliver one or more processing gases to the processing volume234from a processing gas source219that is in fluid communication therewith. The processing gases provided by the processing gas source219will include reactive etchant gases and inert gases. The pressure within the processing chamber250is controlled by use of a vacuum pump255and an amount of gas flow provided from the processing gas source219. A substrate13is loaded into, and removed from, the processing volume234through an opening (not shown) in one of the one or more sidewalls231, which is sealed with a slit valve (not shown) during plasma processing of the substrate13.

The substrate support assembly240can include a substrate support205(e.g., ESC substrate support) and one or more biasing electrodes, which are coupled to PV waveform generator210. In some embodiments, the substrate support assembly240can additionally include a support structure206that includes a support base, which supports the substrate support205, an insulator plate and a ground plate that is coupled to the chamber base232. The support base is electrically isolated from the chamber base232by the insulator plate, and the ground plate is interposed between the insulator plate and the chamber base232. The substrate support205is thermally coupled to and disposed on the support base, which is configured to regulate the temperature of the substrate support205during processing.

Typically, the substrate support205is formed of a dielectric material, such as a bulk sintered ceramic material, such as a corrosion-resistant metal oxide or metal nitride material. In embodiments herein, the substrate support assembly240further includes the biasing electrode214embedded in the dielectric material thereof. In one configuration, the biasing electrode214is a chucking pole used to secure (i.e., chuck) the substrate13to the substrate supporting surface of the substrate support assembly240and to bias the substrate13with respect to the processing plasma11using one or more of the pulsed-voltage biasing schemes described herein. Typically, the bias electrode214is formed of one or more electrically conductive parts, such as one or more metal meshes, foils, plates, or combinations thereof. In some embodiments, the biasing electrode214is also electrically coupled to a clamping network that is configured to provide a chucking voltage thereto, such as static DC voltage between about −5000 V and about +5000 V.

A system controller226, also referred to herein as a processing chamber controller, includes a central processing unit (CPU)227, a memory228, and support circuits229. The system controller226is used to control the process sequences and methods used to process the substrate13, including the substrate processing methods described herein. The CPU227is a general-purpose computer processor configured for use in an industrial setting for controlling the processing chamber and sub-processors related thereto. The memory228described herein, which is generally non-volatile memory, may include random access memory, read-only memory, floppy or hard disk drive, or other suitable forms of digital storage, local or remote. The support circuits229are conventionally coupled to the CPU227and comprise cache, clock circuits, input/output subsystems, power supplies, and the like, and combinations thereof. Software instructions (software program) and data can be coded and stored within the memory228for instructing a processor within the CPU227. A software program (or computer instructions) readable by CPU227in the system controller226determines which tasks are performable by the components in the processing system200. Typically, the software program, which is readable by CPU227in the system controller226, includes code, which, when executed by the processor (CPU227), performs tasks relating to the plasma processing methods described herein. The program may include instructions that are used to control the various hardware and electrical components within the processing chamber250and processing system200to perform the various process tasks and various process sequences used to implement the methods described herein.

As noted above, a PV waveform generator210is adapted to provide a voltage waveform to one or more electrodes, such as the biasing electrode214, disposed within the processing chamber200.FIG.2Bis a simplified schematic of a pulsed voltage (PV) waveform generator210in connection with a control system that can be configured to practice the methods set forth herein, according to one or more embodiments. The PV waveform generator210will typically include a PV source controller225and at least one voltage source assembly that includes a direct current (DC) voltage source220that is configured to provide a PV waveform to at least one generator output201that is coupled to the biasing electrode214. In one example, as shown inFIG.2B, the PV waveform generator210includes a PV source controller225and one DC voltage source220that are configured to provide a PV waveform to the generator output201. The generator output201can be coupled to a source node N that is coupled to the biasing electrode214that is capacitively or inductively coupled to a complex load202that is formed by the plasma11during plasma processing. The complex load202is shown as a standard electrical plasma model that represents the plasma11as three circuit elements. The three circuit elements include: (a) a diode, (b) a current source lion, and (c) the capacitor CSH, which are each present during the delivery of at least a portion of an asymmetric voltage waveform that is provided to an electrode by the PV waveform generator210during a plasma process. In some embodiments, the PV waveform generator210is a switch-mode power supply. In some embodiments, each PV waveform generator210is configured to deliver between 1 and 25 kilowatts (kW) of DC power at a voltage of between 100 and 10,000 volts, such as between 1000 and 5000 volts to an electrode.

Referring toFIG.2B, the switches S1and S2within the PV waveform generator210are coupled to and in communication with the PV source controller225to enable the PV source controller225to separately open and close the switches, S1, S2at desirable intervals to form an asymmetric voltage waveform, as disclosed below. The depicted switches S1, S2in the PV waveform generator210can be realized by single pole, single throw, normally open switches that are controllable by an electrical or optical signal provided by the PV source controller225, or MOSFET devices who's gates are controlled from signals provided by the PV source controller225. The PV source controller225is also configured to control and/or adjust the voltage level generated by the DC voltage source220(e.g., DC supply) and provided to an output based on commands received from the system controller226. In some embodiments, the PV source controller225is in direct communication with the switches S1, S2and DC voltage source220so that the asymmetric voltage waveform provided to the generator output can be generated at a nanosecond or microsecond time scale.

In one or more of the embodiments disclosed herein, the PV waveform generator210includes a sensor assembly205that is positioned to measure characteristics of the PV waveform generated at the generator output. The sensor assembly205can include one or more electrical components that are configured to measure one or more electrical characteristics of the asymmetric voltage waveform provided by the PV waveform generator210, such as voltage, current and offset/phase, and send the one or more electrical characteristic data to the system controller226. The electrical characteristic data received by the system controller226from the PV waveform generator210can be used together to synchronize the delivery of other PV waveforms generated by the PV waveform generator210and RF generator271, as is discussed further below.

The system controller226and supporting circuitry are configured to control and/or adjust the voltage waveforms generated by the PV waveform generators210. The PV waveform generators210, system controller226and supporting circuitry are able to adjust multiple electrical parameters that are used to alter one or more of the voltage waveform characteristics, such as frequency, waveform shape, and applied voltage on-time during a pulse period of a provided asymmetric voltage waveform.

While the disclosure provided herein, primarily discusses the use of the processing system200to perform a plasma-assisted etching processes, such as a reactive ion etch (RIE) plasma processing technique this configuration is not intended to limit the scope of disclosure provided herein. It should be noted that the embodiments described herein may be also be used with processing systems configured for use in other plasma-assisted processes, such as plasma-enhanced deposition processes, for example, plasma-enhanced chemical vapor deposition (PECVD) processes, plasma-enhanced physical vapor deposition (PEPVD) processes, plasma-enhanced atomic layer deposition (PEALD) processes, plasma treatment processing or plasma-based ion implant processing, for example, plasma doping (PLAD) processing.

Plasma Processing Method Examples

As discussed above, embodiments of the disclosure describe a biasing scheme that is configured to provide a radio frequency (RF) generated RF waveform from an RF generator to an electrode within a processing chamber and a pulsed-voltage (PV) waveform delivered from a pulsed-voltage (PV) generator to the one or more electrodes within the processing chamber. In general, the generated RF waveform is configured to establish and maintain a plasma within the processing chamber, and the delivered PV waveform(s) are configured to establish a desired sheath voltage across the surface of a substrate during one or more phases of a plasma process and thus create a desirable ion energy distribution function (IEDF) and electron energy distribution function (EEDF) at the surface of the substrate during the one or more plasma processing phases performed on the substrate within the processing chamber. The plasma process(es) disclosed herein can be used to control the shape of IEDF and EEDF and thus the interaction of the plasma with a surface of a substrate during processing. In some configurations, the plasma process(es) disclosed herein are used to control the profile of features formed in the surface of the substrate during processing. During some semiconductor plasma processes, ions are purposely accelerated towards the substrate13by the voltage drop in an electron-repelling sheath that forms over the substrate13placed on top of a substrate support assembly240. While not intending to be limiting as to the scope of the disclosure provided herein, the substrate support assembly240may also be referred to herein as the “cathode assembly” or “cathode”.

FIG.3illustrates an example of a pulsed voltage waveform that includes asymmetric voltage pulses provided within the pulsed voltage waveform325that is established at a substrate due to the delivery of a series of asymmetric voltage pulses to a biasing electrode214during plasma processing by use of the PV waveform generator210, according to certain embodiments. As noted above, it has been found that the establishment of the PV waveform on a substrate during plasma processing can be advantageously used to control aspects of the plasma sheath formed over the surface of the substrate during plasma processing. The control of the magnitude and shape of the plasma sheath formed over the surface of the substrate allows the control of the ion interaction with the surface of the substrate during processing, such as allowing the control the ion energy distribution function (IEDF), electron energy distribution function (EEDF), ion directionality, and other plasma related characteristics. Waveform325is an example of a non-compensated pulsed voltage (PV) waveform established at the substrate13during plasma processing due to the delivery of a PV waveform provided to the biasing electrode214. A compensated pulsed voltage (PV) waveform seen at the substrate can alternatively be established by applying a negative voltage ramp to a PV waveform325provided to the biasing electrode214by a PV waveform generators210during an ion current stage of the pulsed voltage waveform325.

InFIG.3, waveform325includes two main stages: an ion current stage324and a sheath collapse stage322. Both portions of a pulse within the waveform325can be sequentially established at the substrate13during plasma processing. At the beginning of the ion current stage324, a drop in voltage at the substrate13is created (i.e., falling edge323), due to the delivery of a negative portion of a PV waveform provided to the biasing electrode214by PV waveform generator210, which creates a high voltage sheath above the substrate13. The high voltage sheath allows the plasma generated positive ions to be accelerated towards the biased substrate during the ion current stage, and thus, for RIE processes, controls the amount and characteristics of the etching process that occurs on the surface of the substrate during plasma processing. In some embodiments, it is desirable for the ion current stage324to generally include a region of a pulsed voltage waveform that achieves a voltage at the substrate13that is stable or minimally varying throughout the stage. One will note that significant variations in voltage established at the substrate13during the ion current stage324, such as shown by the positive slope in the waveform325, will undesirably cause a variation in the ion energy distribution function (IEDF) and/or the electron energy distribution function (EEDF), and thus, cause undesirable characteristics of the etched features to be formed in the substrate during an RIE process.

At the end of the ion current stage324, and the start of the sheath collapse stage322, a rising edge321of the PV waveform325is created by the PV source assembly, which forms part of a typically short narrow positive pulse that transitions from a negative voltage level to a positive voltage that is greater than zero volts. The duration of the positive section of the pulse can be varied, and, in some embodiments, is between 1% and 20% of the waveform period (TP), such as between 5% and 15% of the waveform period (TP). In one example, the repetition frequency of the voltage pulses within the waveform325may be between about 100 kHz and 500 kHz, such as between 200 KHz and 400 kHz.

In some embodiments, a PV waveform325generated by a PV waveform generators210includes a plurality of voltage pulse bursts401, which are illustrated inFIG.4. Each burst4011,4012,4013includes a portion of the pulsed voltage waveform that includes a plurality of asymmetric voltage pulses, such as the pulses illustrated inFIG.3. In some embodiments, a bias voltage is applied during each asymmetric voltage pulse during the ion current stage324. Stated otherwise the off-time of each voltage pulse TOFFoccurs during the sheath collapse stage and the application of the bias voltage is applied during the on-time TON, which occurs during the ion current stage324. The on-time TON and the off-time TOFFare configured as a percentage of a period TPof each voltage pulse. The frequency of each voltage pulse may be adjusted by increasing or decreasing TP, while TON and TOFFmay be adjusted by changing their relative percentage of the period TP. Furthermore, the voltage pulse has an applied bias voltage V that is defined as the peak voltage during the ion current stage.

FIG.4illustrates a synchronized delivery of an RF signal411generated by the RF generator271and voltage pulse bursts401generated by a PV waveform generator210and delivered to an electrode (e.g., biasing electrode214) within the plasma processing chamber, according to certain embodiments.FIG.5illustrates a method500used to synchronize the delivery of an RF signal411generated by the RF generator271and the voltage pulse bursts401to at least control to improve the etching profile results and reduce the microloading effect found within features formed in the surface of the substrate after plasma processing. During processing, a PV waveform generator210is configured to generate a PV waveform325that includes multiple voltage pulse bursts401of voltage pulses. The characteristics of the voltage pulses within each burst401of voltage pulses are controlled by the PV source controller225and/or system controller226. At least one parameter of the asymmetric voltage pulses that make-up each burst401, such as the pulse on-time, ratio of pulse on-time to pulse period (i.e., percentage (%) on-time), the pulse voltage, voltage pulse repetition rate, and combinations thereof, can be adjusted by the PV source controller225and/or system controller226during processing. In some embodiments, to adapt to the variations in the IDEF, EEDF, and undesirable characteristics, such as non-uniformity of etched features, a PV waveform generators210may be configured to deliver bursts with different parameters based on information received by the controller226.

Referring toFIG.4, each voltage pulse burst401within the PV waveform325includes a burst on-time TBOin which the delivery of a series of asymmetric voltage pulses is provided to an electrode within the plasma processing chamber. The PV waveform325also includes a burst off-time TBFin which no asymmetric voltage pulses are provided to the electrode214. The sum of the burst on-time TBOand the burst off-time TBFform a burst period TBP. In some embodiments, the burst on-time TBOcan be between about 50 μs and about 50 milliseconds (ms), such as between about 200 μs and about 5 ms, and the burst duty cycle (i.e., TBO/TBP) can be between about 5%-100%, such as between about 50% and about 95%. In one example, the burst delivery length TON is about 800 μs, and the burst duty cycle is about 80% for a voltage pulse burst401.

As noted above,FIG.5illustrates a method500of using a plasma processing chamber according to certain embodiments. Method500is performed by use of a computer or programmable controller that include hardware (e.g., circuitry, dedicated logic, programmable logic, microcode, processing device, etc.), software (such as instructions run on a processing device, a general purpose computer system, or a dedicated machine), firmware, microcode, or a combination thereof. In some embodiments, method500is performed, in part, by one or more components within the system controller226. In some embodiments, a non-transitory storage medium stores instructions that when executed by a processor in the system controller causes the controller device to perform method500.

For simplicity of explanation, method500is depicted and described as a series of operations. However, operations in accordance with this disclosure can occur in various orders and/or concurrently and with other operations not presented and described herein. Furthermore, in some embodiments, not all illustrated operations are performed to implement method500in accordance with the disclosed subject matter. In addition, those skilled in the art will understand and appreciate that method500could alternatively be represented as a series of interrelated states via a state diagram or events.

At activity502of method500, a first burst4011(FIG.4) of a series of bursts within the PV waveform325is delivered to an electrode214within the plasma processing system200and an RF signal having a first RF power level P1is simultaneously provided to an RF electrode (e.g., coil273) within the plasma processing system200by use of the RF generator271. The burst on-time TBOof the first burst4011extends, for example, a length of time that extends between times T0and T1. In one example, the burst on-time TBOof the first burst4011is between about 10 μs and 800 μs, such as between 100 μs and 500 μs, or even between about 100 μs and 300 μs. In one example, the first burst4011includes a series of asymmetric voltage pulses that have a peak negative voltage that may be between −100 volts (V) and −2000 volts, an on-time of between about 5% and 95% of the pulse period TP(e.g., 85%), and has a repetition frequency that is between 100 kHz and 500 kHz, such as between 200 kHz and 400 kHz. The RF signal can include an RF waveform that has a frequency greater than 1 MHz, such as about 13.56 MHz or greater, and have a first RF power level P1that is between about 500 Watts (W) and 2,000 W.

Activity502is generally provided within the method500to cause the bombardment of the surface of the substrate with ions so as to cause the etching of a portion of the substrate. The etching process will also typically include the removal of material from the surface of the substrate by use of one or more reactive gases and other components formed in the plasma created by the delivery of the RF signal411. The process of bombarding the surface of the substrate13during activity502causes the material etched from the exposed surfaces of the substrate13to migrate away from the surfaces from which the material was removed. However, as the aspect ratio of the features formed in the substrate increases, as the etching process performed on a substrate continues, the etched material found in the features will tend to inhibit the etching process in the lower portions of the narrower features versus the wider features, due to a greater number of collisions between the plasma generated ions and the migrating etched material (i.e., etch by-products). The variation the etching rate, created by the inhibiting material found in the differently configured features, leads to the microloading effect that is experienced across different regions of the substrate.

At activity504, the output of the PV waveform generator210is halted and one or more characteristics of the RF signal provided to the RF electrode is adjusted. During activity504the PV waveform325enters a first portion of a burst off-time TBFperiod that extends for a first period of time. As shown inFIG.4, the first portion of a burst off-time TBFperiod extends, for example, a length of time that extends between times T1and T2. In one example, the first period of time is between about 100 μs and 1.2 millisecond (ms), such as between 0.5 ms and 1 ms, or even between about 0.7 ms and 0.9 ms. The RF power applied during the first portion of the burst off-time TBFperiod can be applied at second RF power level P2that is different from the first RF power level P1, such as less than the first RF power level P1. In one example, the second RF power level P2is between about 100 watts and about 1,000 watts, such as between 400 watts and 700 watts at an RF frequency of about 13.56 MHz or greater. Activity504is generally used to enable the passivation of the exposed surfaces of the substrate that were etched during activity502due to the presence of components found within the plasma that is being maintained by the delivery of the RF signal provided at the second RF power level P2.

At activity506, the output of the PV waveform generator210remains halted and one or more characteristics of the RF signal provided to the RF electrode is further adjusted. During activity506the PV waveform325enters a second portion of the burst off-time TBFperiod that extends for a second period of time. The second portion of a burst off-time TBFperiod extends, for example, a length of time that extends between times T2and T3. In one example, the second period of time is between about 500 μs and 2 millisecond (ms), such as between 0.7 ms and 1.5 ms, or even between about 0.8 ms and 1.2 ms. In one example, the second period of time is between about 0.8 ms and 1.2 ms and the burst period TBPis between about 2 ms and 3 ms. The RF power applied during the second portion of the burst off-time TBFperiod can be applied at third RF power level P3that is different from the first RF power level P1and the second RF power level P2, such as less than the first RF power level P1and second RF power level P2. In one example, the third RF power level P3is adjusted to a level at or near zero watts. Activity504is generally used to enable the removal of the etched material from the features formed in the exposed surfaces of the substrate by a pumping process that allows the material migrating from the etched features formed in the substrate to be pumped out of the processing volume234by the vacuum pump255(FIG.2). The pumping process is also referred to herein as a process of evacuating the processing volume234. By periodically clearing the etch materials (e.g., etch by-products) from the features formed within the substrate, etchants are more effectively delivered to the feature being etched with a desired ion trajectory, such as a vertical trajectory.

In some embodiments, the pressure within the processing volume234is adjusted during each of the activities502-506by the adjustment of a gas flow provided from the process gas source219and/or flow control valves (not shown) positioned in an exhaust line that connects the vacuum pump255to the process chamber250. In one embodiment, the pressure in the processing volume234is decreased during activity506versus the pressure maintained in the processing volume234during activities502and504.

After activity506has been completed method500may include completing activities502-506a plurality of times. In one example, the total time it takes to sequentially complete one cycle of activities502-506is between about 1 ms and 3 ms and the activities502-506are sequentially cyclically repeated multiple times over a period of time that is between about 1 second and 60 seconds.

In some embodiments, the length of time between each of the intervals, such as the first interval between times T0and T1, the second time interval between T1and T2and the third time interval between times T2and T3are varied between the different cycles of activities502-506. In one example, during a second cycle of activities502-506, after performing a first cycle of activities502-506, the second time interval is decreased a first amount of time and the third time interval is increased a second amount of time. In some cases, where it is desirable to maintain the same burst period TBPlength for each cycle of activities the first amount of time and the second amount of time are equal. In other cases, it may be desirable to adjust the length of one or more of the time intervals as needed between cycles to achieve a desired process result on a substrate, and thus the burst period TBPlength may change from one cycle to the next cycle. In one example, during a second cycle of activities502-506, after performing a first cycle of activities502-506, the third time interval is increased an amount of time to account for an increase in the depth of an etched feature found after performing the first cycle of activities. In this example, the third time interval during the second cycle may be increased after the performance of a plurality of interim cycles are performed between when the first cycle and second cycle are performed. The length of one or more of the time intervals may change over time, such as, for example, the third time interval increases an amount of time every cycle, every other cycle, or every number of cycles.

While the voltage pulse bursts4011,4012,4013, as shown inFIG.4, includes a single consistent type of burst (i.e., voltage pulses within the PV waveform325), it is contemplated that the bursts within a series of bursts could include differently configured bursts that include voltage pulses that have differing voltage pulse characteristics. In one example, two or more of the voltage pulse bursts4011,4012,4013, each include a series of asymmetric voltage pulse that each have a different peak negative voltage, a different voltage pulse on-time, or a different a repetition frequency. Similarly, in some embodiments, the RF waveform within the RF signal411may include a series of differently configured RF signal levels or include RF pulses (not shown).

Advantageously, it is believed that by controlling the characteristics of portions of the pulsed voltage waveform and RF waveform delivered during a plasma process performed on a substrate will allow for improved etched features to be formed across a surface of the substrate. In one example, by adjusting the pulse-on-time (TON) versus pulse off-time (TOFF) within a pulse period TPof a burst401has been found to improve microloading results within features formed on the surface of the substrate. It has been found that the voltage pulse repetition rate can affect other important plasma processing parameters, such as etch selectivity. In another example, controlling the pulse voltage level, such as a higher voltage level in one phase of the plasma process versus another can result in an improved ability to etch deep features in a surface of the substrate, a higher etch rate and a larger plasma sheath (and vice versa for a pulse rate), while lower voltage levels can be beneficially used for forming certain types of etched features. In another example, adjusting the rest time between bursts of voltage pulses, or second portion of the burst off-time period, can be used to provide an extra time for the etching by-products to be pumped out of the processing volume234, which can improve etch uniformity and reduce microloading, while a shorter rest time between bursts can improve substrate throughput during plasma processing. Therefore, in some embodiments, at least one parameter of the voltage pulse within different voltage pulse bursts401within a PV waveform325may be adjusted during processing to achieve a desired plasma processing result. The combinations of different bursts that have voltage pulses that have differing characteristics can be used tune the plasma processing results seen on a substrate.

The term “coupled” is used herein to refer to the direct or indirect coupling between two objects. For example, if object A physically touches object B and object B touches object C, then objects A and C may still be considered coupled to one another-even if objects A and C do not directly physically touch each other. For instance, a first object may be coupled to a second object even though the first object is never directly physically in contact with the second object.

While the foregoing is directed to embodiments of the present disclosure, other and further embodiments of the disclosure may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.