Pulsed voltage plasma processing apparatus and method

Abstract

Embodiments provided herein generally include apparatus, plasma processing systems, and methods for generating a waveform for plasma processing a substrate in a processing chamber, the waveform configured to adjust timing and characteristics of an asymmetric voltage waveform provided to an electrode or coil in the plasma processing chamber, the present invention relates to a plasma processing apparatus to improve control of characteristics of generated plasma and to control ion energy distribution of plasma-generating ions that interact with a substrate surface during plasma processing. The methods and apparatus disclosed herein are configured to control and maintain plasma formed in a processing region of a plasma processing chamber without the need to transmit radio frequency waveforms during processing. The ability to synchronize and control the waveform characteristics of voltage pulses provided in each pulse voltage waveform applied to different electrodes and / or coils (e.g., frequency during pulse periods, voltage waveform partial slope, waveform shape, and applied voltage on time) allows for improved control of the generated plasma.

Description

Technical Field

[0001] Embodiments of the present disclosure generally relate to systems for manufacturing semiconductor devices. More specifically, embodiments of the present disclosure relate to plasma processing systems for processing substrates. Background Art

[0002] Reliably forming high aspect ratio features is one of the key technological challenges for next-generation semiconductor devices. One method of forming high aspect ratio features uses a plasma-assisted etching process to bombard a material formed on a substrate surface through an opening formed in a patterned mask layer formed on the substrate surface.

[0003] As the technology node advances to 2 nm, manufacturing smaller features with a larger aspect ratio requires atomic-level precision in plasma processing. For etching processes where plasma ions play a major role, ion energy control has been a challenge for the semiconductor equipment industry to develop reliable and repeatable device formation processes. In a typical plasma-assisted etching process, a substrate is placed on an electrostatic chuck (ESC) in a processing chamber, and a plasma is formed above the substrate by using a radio frequency (RF) source coupled to an electrode, where the electrode is disposed on or within the plasma processing chamber, and ions are accelerated from the plasma through a plasma sheath towards the substrate. Additionally, in addition to the RF source used to initiate and sustain the plasma in the processing chamber, the RF substrate biasing method using a separate RF bias source cannot ideally control the plasma sheath characteristics to obtain an ideal effect, which would allow for the formation of these smaller device feature sizes. Conventional RF sources and RF biasing methods utilize a sinusoidal RF waveform to excite the plasma and form the plasma sheath. It has been found that the use of an RF waveform that requires an RF matching piece to adjust the RF power source output to match the load impedance can result in limited ability of the RF system to generate the desired pulse waveform shape, due to the limited speed at which the RF matching piece circuitry within the RF system can respond to plasma load impedance changes (resulting from perturbations generated by the pulse waveform shape transmission). Therefore, the conventional methods using RF waveforms have been challenging and often result in inconsistent processing results and / or damage to the supporting electrical and hardware components.

[0004] Accordingly, there is a need in the art for a pulsed voltage source and biasing method that can achieve an ideal plasma-assisted process on a substrate. Summary of the Invention

[0005] Embodiments provided herein generally include an apparatus, a plasma processing system, and a method for generating a waveform for plasma processing a substrate in a processing chamber.

[0006] The specific implementation of the disclosure includes a plasma processing system, which includes: a plurality of pulse voltage waveform generators; a plurality of electrodes or coils, each of the plurality of electrodes or coils being positioned and configured to change the plasma formed in the processing space of the plasma processing chamber of the plasma processing system when an asymmetric voltage waveform from a pulse voltage waveform generator among the plurality of pulse voltage waveform generators is provided to the electrode or coil, wherein each electrode or coil is coupled to a different pulse voltage waveform generator of the plurality of pulse voltage waveform generators; and a system controller configured to synchronously transmit the asymmetric voltage waveform from their pulse voltage waveform generators to each of the electrodes or coils. The plurality of electrodes or coils may also include a first coil, the first coil being coupled to a first pulse voltage waveform generator among the plurality of pulse voltage waveform generators, and the first pulse voltage waveform generator being configured to transmit an asymmetric voltage waveform that includes a plurality of stages varying between a first voltage level and a second voltage level.

[0007] The specific implementation of the disclosure may further include a plasma processing system, which includes: a plurality of pulse voltage waveform generators; a plurality of electrodes or coils, each of the plurality of electrodes or coils being positioned and configured to change the plasma formed in the processing space of the plasma processing chamber of the plasma processing system when an asymmetric voltage waveform from a pulse voltage waveform generator among the plurality of pulse voltage waveform generators is provided to the electrode or coil, wherein each electrode or coil is coupled to a different pulse voltage waveform generator of the plurality of pulse voltage waveform generators; and a system controller configured to synchronously transmit the asymmetric voltage waveform from their pulse voltage waveform generators to each of the electrodes or coils. In some specific implementations, there is no sinusoidal waveform (e.g., RF waveform) in the processing space during the transmission of the first asymmetric voltage waveform and the transmission of the second asymmetric voltage waveform. In some specific implementations, the plasma is not maintained in the processing space by using a sinusoidal waveform during substantially the entire plasma processing period. In some specific implementations, during the processing period of transmitting the first asymmetric voltage waveform and transmitting the second asymmetric voltage waveform, the first asymmetric voltage waveform and the second asymmetric voltage waveform are the only electrical energy sources for maintaining the plasma. Brief Description of the Drawings

[0008] Reference may be made to a plurality of specific implementations to more specifically illustrate the present disclosure briefly summarized above and to more fully understand the above features of the present disclosure. The drawings illustrate some of the specific implementations. However, it should be noted that the drawings only illustrate exemplary specific implementations and should not be considered as limiting the scope of the specific implementations, and other equivalent specific implementations may be recognized.

[0009] FIG. 1 is a schematic diagram of a conventional plasma processing system.

[0010] Figure 2A is a schematic side cross-sectional view of a plasma processing system according to one or more embodiments, configured to implement the methods set forth herein.

[0011] Figure 2B is a schematic side cross-sectional view of a plasma processing system according to one or more embodiments, configured to implement the methods set forth herein.

[0012] Figure 2C is a simplified schematic diagram of a pulse voltage (PV) waveform generator related to a control system according to one or more embodiments, and the control system can be configured to practice the methods set forth herein.

[0013] Figure 3A Illustrates synchronized waveforms and generated voltage waveforms used during one or more of the methods described herein according to one or more embodiments of the present disclosure provided herein.

[0014] Figure 3B is according to one or more embodiments of the present disclosure provided herein Figure 3A A close-up of the generated voltage waveform shown in.

[0015] Figure 3C Illustrates synchronized waveforms and generated voltage waveforms used during one or more of the methods described herein according to one or more embodiments of the present disclosure provided herein.

[0016] Figure 4 Illustrates an example of a voltage waveform according to certain embodiments of the present disclosure.

[0017] Figure 5A Illustrates three different known sine waveforms, each waveform having a different frequency.

[0018] Figure 5B Illustrates three generated voltage waveforms according to one or more embodiments of the present disclosure provided herein, each waveform configured to replace Figure 5A One of the corresponding sine waveforms shown in.

[0019] Figure 6A Illustrates a voltage pulse train within a generated voltage waveform used during one or more of the methods described herein according to one or more embodiments of the present disclosure provided herein.

[0020] Figure 6B and 6COne or more specific embodiments of the present disclosure provided herein are illustrated. Figure 6A An enlarged detailed portion of the resulting voltage waveform found within different portions of the pulse train is shown.

[0021] 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 embodiment may be beneficially incorporated in other embodiments without further recitation. DETAILED DESCRIPTION

[0022] Specific embodiments of the present disclosure generally relate to plasma processing methods and apparatuses, which are configured to transmit multiple asymmetric pulsed voltage waveforms to multiple electrodes in a plasma processing chamber to control and maintain a plasma formed in a processing region of the plasma processing chamber. The plasma processing methods and apparatus described herein are configured to improve the control of various characteristics of the generated plasma and control the ion energy distribution (IED) of the plasma-generated ions that interact with the surface of the substrate during the plasma processing. Some specific embodiments of the present disclosure are configured to control and maintain the plasma formed in the processing region of the plasma processing chamber during the processing without transmitting a radio frequency (RF) waveform. The ability to synchronize and control the waveform characteristics of the voltage pulses provided in each pulsed voltage waveform applied to different electrodes and / or coils (e.g., frequency, waveform shape, and applied voltage on time during the pulse period) allows for improved control of the generated plasma. The embodiments disclosed herein will also reduce system complexity and cost because RF transmission and RF matching components and their generally complex RF tuning algorithms are not required to perform plasma processing in the plasma processing chamber. Therefore, higher precision in plasma processing can be achieved, which is described in more detail herein.

[0023] FIG. 1 is a schematic diagram of a conventional plasma processing system 19, which is adapted to process a substrate 13 disposed on a substrate support 36 by generating a plasma 11 in a processing region 29 of a plasma processing chamber 99. The plasma processing system 19 is configured to form a capacitively coupled plasma (CCP), wherein the processing chamber 99 includes an upper electrode 23 disposed in the processing region 29 such that the upper electrode 23 faces a lower electrode 46 also disposed in the processing region 29. The CCP plasma processing system includes a radio frequency (RF) source 71 electrically coupled to the upper electrode 23 through an RF matcher 72 and transmits a tuned RF signal, which is configured to ignite and sustain the plasma 11 formed in the processing region 29. Typically, the lower electrode 46 is coupled to ground or to a second RF power source, but in some configurations, as shown in FIG. 1, the lower electrode is coupled to a pulsed voltage (PV) waveform generator 75 through an RF filter 73. However, in a conventional plasma processing configuration, as shown in FIG. 1A, where the PV waveform and the RF signal are simultaneously provided to one or more electrodes to form the plasma 11, at least in part due to changes in the RF power level and / or changes in the voltage applied in each voltage pulse provided in the PV waveform provided by the PV waveform generator 75, the impedance of the complex load generated by the plasma 11 will be perturbed. As described above, since the RF matching component cannot quickly adjust its matching point to compensate for the changing impedance of the complex load, this results in inefficient transmission of RF power to the complex load. In addition, since the RF components cannot adjust and tune their matching points, the processing of RF plasmas using RF matchers cannot be quickly adjusted for the changing RF power levels delivered during the processing, and thus their ability to control or change various plasma characteristics in less than 10 microseconds (μs) is limited. Due to the limitation of the impedance matching / frequency tuning convergence time (e.g., ~25 - 100 us), conventional RF plasma processing cannot be performed at a fast RF pulse speed, and thus the repeatability of the plasma processing results is not very good.

[0024] Example of Plasma Processing System

[0025] Figure 2Ais a schematic cross-sectional view of a processing system 10 configured to perform one or more of the plasma processing methods described herein. In some embodiments, the processing system 10 is configured for plasma-assisted etching processes, such as reactive ion etching (RIE) plasma processes. It should be noted, however, that the embodiments described herein may also be used with processing systems configured for use in other plasma-assisted processes, such as plasma-enhanced deposition processes, such as plasma-enhanced chemical vapor deposition (PECVD) processes, plasma-enhanced physical vapor deposition (PEPVD) processes, plasma-enhanced atomic layer deposition (PEALD) processes, plasma cleaning processes, or plasma-based ion implantation processes (such as plasma doping (PLAD) processes).

[0026] The processing system 10 generally includes a processing chamber 100, a lid assembly 176, a substrate support assembly 136, and a system controller 126. As shown, the processing system 10 includes a plurality of plasma source assemblies, each plasma source assembly adapted to deliver an asymmetric voltage waveform to one or more electrodes and / or one or more coils disposed within the processing chamber 100. In one exemplary configuration, as Figure 2A shown, the processing chamber 100 includes four plasma source assemblies, such as a first capacitively coupled plasma (CCP) assembly 194, a second capacitively coupled plasma (CCP) assembly 195, a first inductively coupled plasma (ICP) assembly 196, and a second inductively coupled plasma (ICP) assembly 197, each including a pulsed voltage (PV) waveform generator 150 adapted to deliver an asymmetric voltage waveform, which will be described in more detail below. In another exemplary configuration, as Figure 2B shown, the processing chamber 100 includes a first capacitively coupled plasma (CCP) assembly 194, a second capacitively coupled plasma (CCP) assembly 195, a third capacitively coupled plasma (CCP) assembly 198, and a fourth capacitively coupled plasma (CCP) assembly 199, each including a pulsed voltage (PV) waveform generator 150 adapted to deliver an asymmetric voltage waveform.

[0027] The processing chamber 100 generally includes a chamber body 113 which includes one or more sidewalls 122 and a chamber base 124. The sidewalls 122 and the chamber base 124, together with the chamber lid 123 of the lid assembly 176, define a processing space 129. The one or more sidewalls 122 and the chamber base 124 generally include materials that are sized and shaped to provide structural support for the elements forming the processing chamber 100, and the materials are configured to withstand the pressures and increased energies applied to the materials while generating a processing plasma 101 in the vacuum environment maintained in the processing space 129 of the processing chamber 100 during processing. In one example, the one or more sidewalls 122 and the chamber base 124 are formed of a metal, such as aluminum, an aluminum alloy, or a stainless steel alloy. A gas inlet 128 disposed through the chamber lid 123 is used to convey one or more processing gases from a processing gas source 119 in fluid communication therewith to the processing space 129. A substrate 103 is loaded into and removed from the processing space 129 through an opening (not shown) in one of the one or more sidewalls 122, and the opening is sealed by a slit valve (not shown) during plasma processing of the substrate 103.

[0028] The system controller 126, also referred to herein as a processing chamber controller, includes a central processing unit (CPU) 133, a memory 134, and support circuitry 135. The system controller 126 is used to control the processing sequence for processing the substrate 103, including the substrate biasing methods described herein. The CPU 133 is a general-purpose computer processor configured for an industrial environment to control the processing chamber and associated sub-processors. The memory 134 described herein is generally non-volatile memory and may include random access memory, read-only memory, a floppy disk or hard drive, or other suitable forms of local or remote digital storage. The support circuitry 135 is coupled to the CPU 133 in a known manner and may include a cache, frequency circuitry, input / output subsystems, power supplies, etc., and combinations thereof. Software instructions (programs) and data may be encoded and stored in the memory 134 to direct the processors within the CPU 133. Programs readable by the CPU 133 in the system controller 126 determine which tasks may be performed by the components in the processing system 10. Generally, programs readable by the CPU 133 in the system controller 126 include code which, when executed by the CPU 133, performs tasks related to the plasma processing methods described herein. The programs may include instructions for controlling the various hardware and electronic components within the processing system 10 to perform various processing tasks and for implementing the various process sequences of the methods described herein.

[0029] In some embodiments, the lid assembly 176 includes the chamber lid 123 and one or more plasma source assemblies, such as Figure 2AThe two inductively coupled plasma (ICP) assemblies 196, 197 shown. As Figure 2A shown, each ICP assembly 196, 197 includes coils 181, 182 respectively, and the coils 181, 182 are configured to inductively couple the PV waveform generated by the PV waveform generator 150 to the plasma 101 formed in the processing space 129 of the processing chamber 100 during plasma processing. In this configuration, the chamber lid 123 includes a dielectric material, and the dielectric material is configured to allow the fields generated by the coils 181, 182 during the delivery of the asymmetric voltage waveform by the PV waveform generator 150 to assist in generating and maintaining the plasma 101 in the processing space 129.

[0030] In some other embodiments, as Figure 2B shown, the lid assembly 176 includes the chamber lid 123 and one or more capacitively coupled plasma (CCP) assemblies, such as Figure 2B the two capacitively coupled plasma (CCP) assemblies 198, 199 shown in Figure 2B shown. As shown, each CCP assembly 198, 199 includes electrodes 186, 187 respectively, and the electrodes 186, 187 are configured to inductively couple the PV waveform generated by the PV waveform generator 150 to the plasma 101 formed in the processing space 129 of the processing chamber 100 during plasma processing. In this configuration, the chamber lid 123 may comprise a dielectric material or a structural material (e.g., metal), and the dielectric material or structural material is configured to withstand the vacuum generated in the processing space 129 during processing.

[0031] As Figure 2A - 2B shown, the substrate support assembly 136 includes a substrate support 105 (e.g., an ESC substrate support) and one or more lower electrodes, and the lower electrodes are coupled to a plasma source, such as capacitively coupled plasma (CCP) assemblies 194, 195. In some embodiments, the substrate support assembly 136 may additionally include a support base 107, an insulating plate 111, and a ground plate 112. The support base 107 is electrically insulated from the chamber base 124 through the insulating plate 111, and the ground plate 112 is interposed between the insulating plate 111 and the chamber base 124. The substrate support 105 is thermally coupled to the support base 107 and is disposed on the support base 107. In some specific embodiments, the support base 107 is configured to adjust the temperature of the substrate support 105 and the substrate 103 placed on the substrate support 105 during substrate processing. Generally, the substrate support 105 is formed of a dielectric material, such as a bulk sintered ceramic material, such as a corrosion-resistant metal oxide or metal nitride material, such as alumina (Al 2 O 3 )), aluminum nitride (AlN), titanium oxide (TiO), titanium nitride (TiN), yttrium oxide (Y2 O 3 )), their mixtures, or combinations thereof. In a specific embodiment herein, the substrate support 105 further includes a bias electrode 104 embedded in its dielectric material.

[0032] One or more lower electrodes may include a bias electrode 104 and / or an edge electrode 115, the bias electrode 104 and / or the edge electrode 115 being formed within the substrate support 105 and coupled to one or more plasma source assemblies, such as capacitively coupled plasma (CCP) assemblies, such as two CCP assemblies 194, 195. The CCP assembly 194 is coupled to the bias electrode 104 and the CCP assembly 195 is coupled to the edge electrode 115, and each CCP assembly is configured to transmit a PV waveform generated by the PV waveform generator 150 to the plasma 101 formed in the processing space 129 of the processing chamber 100 during plasma processing. In Figures 2A to 2B In one embodiment not shown, the first PV waveform generator 150 of the first CCP assembly 194 is configured to bias the bias electrode 104 and the edge control electrode 115, and thus there is no need for the CCP assembly 195 and its components that transmit the PV waveform to the bias electrode 104 and the edge control electrode 115.

[0033] In one configuration, the bias electrode 104 is an adsorption rod for fixing (i.e., adsorbing) the substrate 103 to the substrate support surface 105A of the substrate support 105 and for biasing the substrate 103 relative to the processing plasma 101 using one or more of the pulsed voltage biasing schemes described herein. Generally, the bias electrode 104 is formed of one or more conductive components, such as one or more metal meshes, foils, plates, or combinations thereof.

[0034] The CCP assemblies 194, 195 may also each include a clamping network 116 such that a high voltage bias is applied to the bias electrode 104 and / or the edge control electrode 115. In some embodiments, the bias electrode 104 is electrically coupled to the clamping network 116 and the edge electrode 115 is electrically coupled to the clamping network 116. The clamping network uses an electrical conductor (such as a coaxial power transmission line 106 (such as a coaxial cable)) to provide an adsorption voltage to the electrode, such as a static DC voltage between about -5000V and about 5000V. The clamping network 116 includes a bias compensation circuit element 116A, a DC power source 155, and a bias compensation module blocking capacitor (also referred to herein as blocking capacitor C 5 )). The blocking capacitor C 5It is disposed between the output of the pulsed voltage (PV) waveform generator 150 and the bias electrode 104. Applying a PV waveform and a clamping voltage of a similar configuration to the bias electrode 104 and the edge control electrode 115 can help improve plasma uniformity on the substrate surface during processing and thus improve the plasma processing result.

[0035] As described above, in some embodiments, the substrate support assembly 136 includes an edge control electrode 115 that is located below the edge ring 114 and surrounds the bias electrode 104 and / or is disposed at a certain distance from the center of the bias electrode 104. Generally, for a processing chamber 100 configured to process circular substrates, the edge control electrode 115 is in an annular shape, made of a conductive material, and configured to surround at least a portion of the bias electrode 104. In some specific embodiments, as Figures 2A to 2B shown, the edge control electrode 115 is located within the region of the substrate support 105. In some specific embodiments, as Figures 2A to 2B shown, the edge control electrode 115 includes a conductive mesh, foil, and / or plate that is disposed at a distance from the substrate support surface 105A of the substrate support 105 similar to the distance of the bias electrode 104 (i.e., in the Z direction). In some other specific embodiments, the edge control electrode 115 includes a conductive mesh, foil, and / or plate that is located above or within the region of the quartz tube 110 and surrounds at least a portion of the bias electrode 104 and / or the substrate support 105. Alternatively, in some other specific embodiments (not shown), the edge control electrode 115 is located within or coupled to the edge ring 114, and the edge ring 114 is placed on the substrate support 105 and adjacent to the substrate support 105. In this configuration, the edge ring 114 is formed of a semiconductor or dielectric material (such as AlN, etc.).

[0036] Power transmission line 157 electrically connects the output of the PV waveform generator 150 of the CCP assembly 194 to the optional filter assembly 151 and the bias electrode 104. Although the following discussion mainly focuses on the power transmission line 157 of the first CCP assembly 194 for coupling the PV waveform generator 150 to the bias electrode 104, the power transmission line 158 of the CCP assembly 195 for coupling the PV waveform generator 150 to the edge control electrode 115 will include the same or similar components. The electrical conductors within the various parts of the power transmission line 157 may include: (a) one or a combination of coaxial cables, such as a flexible coaxial cable connected in series with a rigid coaxial cable; (b) insulated high-voltage corona-resistant connecting wires; (c) bare wires; (d) metal rods; (e) electrical connectors; or (f) any combination of the electrical elements in (a)-(e). The optional filter assembly 151 includes one or more electrical elements configured to substantially prevent current generated by one or more plasma sources from flowing through the power transmission line 157 and damaging the PV waveform generator 150.

[0037] In some specific embodiments, the processing chamber 100 further includes a quartz tube 110 or a sleeve that at least partially surrounds a portion of the substrate support assembly 136 to prevent the substrate support 105 and / or the support base 107 from contacting corrosive processing gases or plasmas, cleaning gases or plasmas, or their by-products. Generally, the quartz tube 110, the insulating plate 111, and the ground plate 112 are surrounded by a gasket 108. In some specific embodiments, the plasma screen 109 is positioned between the cathode gasket 108 and the sidewall 122 to prevent plasma from forming in the space between the gasket 108 and one or more sidewalls 122 below the plasma screen 109.

[0038] In some embodiments, the PV waveform generator 150 may be adapted to provide voltage waveforms to a plurality of electrodes and / or coils within the processing chamber 100. In some cases, the PV waveform generator 150 may be used within one or more of the plasma source assemblies 194 - 199. The PV waveform generator 150 generally will include a PV source controller 226 and at least one voltage source assembly, and the voltage source assembly includes a voltage source 220 configured to provide a PV waveform to at least one generator output 201, and the generator output 201 is coupled to one or more of the coils and / or electrodes. In one example, as Figure 2C shown, the PV waveform generator 150 includes a PV source controller 226 and two voltage source assemblies 221A, 221B, which are configured to provide PV waveforms to two independent generator outputs 201. The two independent generator outputs 201 may be coupled to two source nodes SN 1 and SN 2 , and these two source nodes SN 1 and SN2 Coupled to a bias electrode 104, an edge electrode 115, a coil 181, 182, or electrodes 186, 187 capacitively or inductively coupled to a complex load 102. In some configurations, the PV waveform generator 150 includes three or more voltage source components configured to provide a PV waveform to three or more separate generator outputs 201. The complex load 102 is shown as a standard electrical plasma model representing the plasma 101 as three circuit elements. These three circuit elements include: (a) a diode, (b) a current source I ion and (c) a capacitor C SH , which are present during at least a portion of the delivery of an asymmetric voltage waveform that is provided by the PV waveform generator 150 to the electrodes or coils during plasma processing. In some embodiments, the PV waveform generator 150 is a switched-mode power supply. In some embodiments, each PV waveform generator 150 is configured to deliver between 10 and 25 kilowatts (kW) of DC power to the electrodes or coils.

[0039] Reference Figure 2C , two switches S1 and S2 within each voltage source component 221A, 221B are coupled to and communicate with the PV source controller 226 such that the PV source controller 226 can individually open and close the switches S1, S2 in desired intervals to form an asymmetric voltage waveform, as described below. The switches S1, S2 shown in each voltage source component 221A, 221B can be implemented as single-pole, single-throw, normally-open switches that can be controlled by electrical or optical signals provided by the PV source controller 226, or can be implemented as MOSFET devices whose gates are controlled by signals provided by the PV source controller 226. The PV source controller 226 is also configured to control and / or adjust the voltage levels generated by each voltage source 220 (e.g., a DC power supply) and provided to the generator outputs 201A, 201B based on commands received from the system controller 126. In some embodiments, the PV source controller 226 communicates directly (not shown) with various asymmetric voltage waveform generating components within each voltage source component of the PV waveform generator 150, such as in Figure 2CThe switches S1, S2 and the voltage sources 220A, 220B in each of the voltage source assemblies 221A, 221B shown are such that the asymmetric voltage waveforms provided by the voltage source assemblies to the generator output can be synchronized on a smaller time scale (e.g., nanosecond or microsecond scale). The improved ability to synchronize various asymmetric voltage waveforms on a smaller time scale generally results from a direct communication signal (e.g., TTL signal, analog signal, etc.) provided between the waveform generation components in the voltage source assemblies 221A, 221B, rather than requiring the transmission of synchronization signals between separate conventional power supplies that communicate using conventional communication protocols (e.g., Ethernet protocol).

[0040] In one or more specific embodiments disclosed herein, the PV waveform generator 150 includes a sensor assembly 205 positioned to measure characteristics of the PV waveform generated at one or more of the generator outputs 201A, 201B. The sensor assembly 205 may include one or more electrical components configured to measure one or more electrical characteristics of the asymmetric voltage waveform provided by the PV waveform generator 150, such as voltage, current, and offset / phase, and to send one or more electrical characteristic data to the system controller 126. The electrical characteristic data received by the system controller 126 from each PV waveform generator 150 can be used together to synchronize the transmission of other PV waveforms generated by each generator output 201 of the PV waveform generator 150 and the control characteristics of the PV waveforms generated by each PV waveform generator 150, as discussed further below.

[0041] The system controller 126 and the support circuitry are configured to control and / or adjust the voltage waveforms generated by the PV waveform generator 150. The PV waveform generator 150, the system controller 126, and the support circuitry are capable of adjusting a plurality of electrical parameters for changing one or more voltage waveform characteristics, such as the frequency, waveform shape, and applied voltage on-time during the pulse period of the provided asymmetric voltage waveform. In one example of a plurality of electrical parameters for changing one or more of the voltage waveform characteristics, include but are not limited to the direction of the current flowing through an electrode or coil during a portion of the voltage waveform delivery, changing the voltage ratio between electrodes or coils, and adjusting the transmission time delay of one or more pulses formed within the voltage waveforms provided by different PV waveform generators 150.

[0042] In some embodiments, the processing chamber 100 optionally includes a plasma ignition system 191 configured to deliver a DC high voltage or RF signal to an electrode within the processing chamber 100, such as the support base 107, to initiate generation (e.g., ignition) of a plasma 101 in the processing space 129. In some embodiments, the plasma ignition system 191 includes an RF generator 118 configured to deliver an RF waveform signal through an RF matcher 160 connected to an RF electrode, the RF waveform signal having a frequency greater than 1 MHz or higher, or about 2 MHz or higher, such as about 13.56 MHz or higher. In some embodiments, due to the adverse effects resulting from the interaction between the asymmetric voltage waveforms provided by one or more of the plasma source assemblies 194 - 199 and the RF waveform provided by the RF generator 118 of the plasma ignition system 191, the RF waveform signal is provided to the RF electrode only for a very short time interval during the initial generation of the plasma 101 in the processing space 129.

[0043] Example of plasma treatment method

[0044] Figure 3A Illustrated are example voltage waveforms 302 and 303 provided from two plasma source assemblies to one or more electrodes and / or one or more coils located within a plasma processing chamber. Figure 3B is Figure 3A a close-up view of a portion of the voltage waveform 302 shown in Figure 3C Illustrated are example voltage waveforms 302, 303, and 304 provided from three plasma source assemblies to one or more electrodes and / or one or more coils located within a plasma processing chamber. Figure 4 Shown is an example of a voltage waveform established at a substrate surface during plasma processing based on delivering waveform 303 to an electrode (such as the bias electrode 104) disposed within a substrate support. During plasma processing, the voltage waveforms (e.g., voltage waveforms 302 and 303) can be synchronized by using a synchronization signal 301 that includes a plurality of signal pulses 305 provided from the system controller 126 to one or more of the PV waveform generators 150, or from one or more of the PV waveform generators 150 within a plasma source assembly. In one example, Figure 3A and 3CThe waveforms 302 and 302 and 304 therein are generated by using one or more ICP source components (such as ICP source components 196 and 197), respectively. It is believed that, compared with the conventional inductively coupled plasma source design, transmitting an asymmetric voltage pulse to an inductive source (such as coils 181, 182) can be used to more precisely control the plasma generated in the processing space 129 of the processing chamber. Although in Figures 3A to 3B In one configuration described in 3C and the related discussion provided below, two plasma source components or three plasma source components are used to transmit an asymmetric voltage waveform to electrodes or coils in the upper and lower parts of the plasma processing chamber, but this configuration is not intended to limit the scope of the present disclosure, because any number of plasma sources, electrodes, and / or coils can be positioned in the desired part of the plasma processing chamber without departing from the scope of the disclosure. As further discussed below, the ability to adjust and synchronize the voltage waveforms including asymmetric voltage pulses transmitted to different coils or coil regions can be used to adjust one or more plasma characteristics, such as plasma density and spatial plasma uniformity.

[0045] It is believed that by using the plasma source components generating the asymmetric voltage waveforms disclosed herein, the characteristics of the generated plasma can be controlled with better precision and fidelity. The improved control and fidelity are considered to be partly due to the ability of the PV waveform generator in each plasma source component to perform nanosecond-level adjustments to the delivered voltage waveform, such as adjustments to the pulse shape (such as voltage amplitude), pulse on-time / duty cycle, pulse frequency, and voltage change rate (dV / dt), which are used to control plasma uniformity, plasma density, and allow for rapid synchronization of the voltage waveforms generated by the PV waveform generators during plasma processing. Without intending to limit the present disclosure, for comparison, it is believed that the current conventional plasma processing systems using RF matching and RF generator components are limited to a synchronization speed between 0.1 second (s) and 1 millisecond (ms) (i.e., 10 to 1000 Hz), while the configurations disclosed herein that do not include or utilize these components during plasma processing can achieve: (1) a waveform synchronization speed of at least less than 10 microseconds (μs), such as 2.5 μs or shorter; and (2) achieve a voltage waveform adjustment speed at the nanosecond level.

[0046] In one processing example, waveform 302 is generated due to the voltage waveform applied by the PV waveform generator 150 of the first ICP component 196, and waveform 303 is generated due to the waveform applied by the PV waveform generator 150 of the first ICP component 194. As Figure 3A 、 3BAs shown in FIGS. 3B and 3C, waveform 302 includes a series of pulses 310, each pulse having a period Tp. However, for reasons of plasma processing results and to allow synchronization of the voltage waveforms provided by each plasma source assembly, it may also be desirable for the periods Tp of the applied voltage waveforms to be different and integer multiples of each other. In one example, as Figure 3C shown, a plurality of asymmetric voltage pulses in the first waveform 304 provided to the first coil 181 are transmitted at a frequency of 200 kHz, and a plurality of asymmetric voltage pulses in the second waveform 302 provided to the second coil 182 are transmitted at a frequency of 400 kHz.

[0047] Due to the pre-programmed voltage waveform characteristics, each voltage waveform pulse can include a plurality of segments or phases, which are provided to the electrodes or coils by the PV waveform generator 150 using commands received from the system controller 126 or provided by the PV source controller 226. In one example, as Figures 3A to 3B shown, each pulse 310 includes a first phase 311, a second phase 312, a third phase 313, and a fourth phase 314. In this example, phases 311 and 313 include voltage ramps that vary from one voltage level V1 to another voltage level V2, and phases 312 and 314 include portions of the voltage waveform 302 that remain at a constant voltage for a period of time. It is believed that the pulse phases that include the change in voltage over time (i.e., dV / dt) can be used to control and adjust the real-time and average plasma density generated in the plasma processing chamber. The slope of the waveform can be adjusted (e.g., Figure 3B ΔV in 12 / ΔT 25 and ΔV 12 / ΔT 36 ) and the length of time for which the varying voltage is applied (e.g., Figure 3B ΔT in 25 、ΔT 36) to change the plasma density because the ability of electrons generated within the plasma to be accelerated and the rate at which electrons collide with various gas atoms or molecules within the processing space 129 are primarily controlled during the voltage pulse portion of the voltage that varies with time. The ability of the system controller 126 and the PV source assembly to control the waveforms at different electrodes or coils within the processing space 129 and thus control the plasma generation characteristics will allow the plasma uniformity within the processing space 129 to be adjusted and controlled by synchronizing and adjusting the voltage waveforms applied to each electrode or coil so that the plasma uniformity and plasma density can be precisely controlled. The ability to perform nanosecond adjustments to the voltage waveforms and allow for rapid synchronization of the generated voltage waveforms applied by the plasma source assembly can be used to improve the precision and fidelity of plasma processing relative to conventional plasma processing techniques, as described above. Although stages 311 and 313 illustrate examples that include a linearly varying applied voltage with time, it is contemplated that the applied voltage applied during these stages can include non-linear curves that have slopes that vary with time (e.g., dV / dt 2 ), and thus can include exponential curves and curves of second, third, or higher order shapes.

[0048] Referring back to Figure 3A and 3B , stages 312 and 314 include portions of the voltage waveform 303 that are held at a constant voltage for a period of time, such as voltage V1 and voltage V2, respectively. Since these stages of the voltage pulse provide a constant voltage to the electrode or coil, it is believed that they will allow for some attenuation of the electron energy during these stages. However, these stages can help to adjust the average electron temperature and plasma density by separately including stages where the voltage varies with time. The durations of stages 312 and 314 are typically short enough to ensure that the plasma is maintained and does not extinguish.

[0049] Figure 3CIllustrated are three voltage waveforms 302, 303, and 304 provided from three plasma source assemblies to one or more electrodes and / or one or more coils located within a plasma processing chamber. During plasma processing, waveforms 302, 303, and 304 may be synchronized by using a synchronization signal 301. In one example, waveforms 302 and 304 each respectively include pulses 310 and 330, and each of pulses 310 and 330 includes a first stage 311, 331, a second stage 312, 332, a third stage 313, 333, and a fourth stage 314, 334. In this example, stages 311, 313, 331, and 334 include voltage ramps that vary between voltage levels V1 and V2 and V4 and V5, and stages 312, 332, 314, and 334 include portions of voltage waveforms 302, 304 that maintain a constant voltage for a period of time. In one configuration, the magnitude of the voltage difference between voltage levels V1 and V2 is different from the magnitude of the voltage difference between V4 and V5. In one example, voltages V1 and V2 are set to +5 kV and -5 kV relative to ground, while voltages V4 and V5 are set to +500 V and -8 kV relative to ground. Although Figure 3A and Figure 3C illustrate waveforms 302 and 304 that vary between a positive voltage level and a negative voltage level, this configuration is not intended to limit the scope of the disclosure herein because the voltage levels between waveforms 302, 304 can vary to be all negative or all positive without departing from the basic scope of the disclosure provided herein. As Figure 3C shown, waveform 304 includes two pulses 330, and these two pulses 330 include a first stage 331, a second stage 332, a third stage 333, and a fourth stage 334, and its period is twice the period of each pulse 310 found in waveform 302. In one embodiment, waveform 304 is also offset by a first time amount T D from the start of the first stage 311 of waveform 302, which creates a phase shift between the electrodes and coils respectively configured to receive waveforms 302, 304. The ability to create a phase shift of voltage signals between different coils or coil regions can be achieved by reversing the direction of the current flowing through the coil or coil region, which can be used to adjust one or more plasma characteristics, such as spatial plasma uniformity. In addition, by using a PV waveform generator 150, a phase shift can be applied between the voltage waveforms applied to the internal and external coils for use in combination with the coil current direction to provide better control of the plasma spatial distribution compared to conventional RF techniques.

[0050] In one method example, transmitting waveform 303( Figure 3C ) to an electrode within substrate support assembly 136 is configured to create waveform 225( Figure 4) The waveform 225 includes an ion current phase and a sheath collapse phase, which are established on the surface of the substrate during plasma processing. At the beginning of the ion current phase, the drop in the substrate voltage generated by the falling edge 323 of the waveform 303 forms a high-voltage sheath above the substrate, accelerating positive ions towards the substrate. The positive ions bombarding the substrate surface during the ion current phase deposit positive charges on the substrate surface, which, if uncompensated, cause a gradual positive increase in the substrate voltage during the ion current phase (i.e., the positive slope during the phase of the voltage waveform 225), as Figure 4 shown. However, the uncontrolled accumulation of positive charges on the substrate surface undesirably gradually discharges the sheath and the substrate support capacitor, slowly reducing the sheath voltage drop and bringing the substrate potential closer to zero. The accumulation of positive charges results in a voltage drop in the voltage waveform established at the substrate (i.e., the positive slope during the phase). The accumulation of positive charges on the substrate during the ion current phase can be compensated by various techniques, including adjusting the waveform 303 such that it has a negative slope during the ion current portion 324 of the waveform 303 (not shown). In some embodiments, a relatively high-frequency voltage waveform can be used to mitigate the effect of this voltage increase (i.e., droop) generated during the ion current phase.

[0051] At the end of the ion current phase and the beginning of the sheath collapse phase (e.g., the sheath collapse portion 322), the rising edge 321 of the waveform 303 is created by the PV source assembly, and the rising edge forms part of a generally short and narrow positive pulse that transitions from a negative voltage level to a positive voltage greater than zero volts ( Figure 4 ). The duration of the positive portion of the pulse can vary, and in some specific embodiments, it is between 1% and 20% of the waveform period (T P ), for example, between 5% and 15% of the waveform period (T P ). In one example, the waveform period can be approximately 5 μs and the frequency of the waveform 303 can be approximately 200 kHz. In another example, the waveform period can be approximately 2.5 μs and the frequency of the waveform 303 is approximately 400 kHz.

[0052] Waveform example

[0053] Figure 5A Illustrates three different conventional sinusoidal waveforms RF 1 、RF 2 and RF 3 , each having a different sinusoidal waveform frequency. In one example, the sinusoidal waves RF 1 、RF 2 and RF 3 are RF waveforms with frequencies of 2 MHz, 13.56 MHz, and 40 MHz, respectively. Figure 5BIllustrated are three generated voltage waveforms according to one or more specific embodiments of the present disclosure provided herein, each waveform being configured to replace during processing Figure 5A one of the corresponding sinusoidal waveforms shown in

[0054] As described above, due to the practical limitations of currently available voltage waveform generation hardware, the generation of asymmetric voltage waveforms with a period less than about 2 μs (>500 kHz) is prevented, and thus it is impossible to generate voltage waveforms having frequencies within the more common and desirable RF frequency ranges today, such as frequencies greater than 2 MHz or greater than 13.56 MHz, such as 40 MHz and above. As previously mentioned, it is believed that the waveform phase including the change in voltage over time (i.e., dV / dt) can be used to control and adjust the real-time and average plasma density generated in a plasma processing chamber. The plasma density can be changed by adjusting the slope of the voltage waveform and the length of time for which the varying voltage is applied, as the ability to accelerate electrons and increase the rate of collisions of electrons with gas atoms or molecules within the plasma is believed to be controlled by the voltage pulse portion where the voltage changes over time.

[0054] Referring to Figure 5B , the three voltage waveforms PVW 1 , PVW 2 and PVW 3 illustrate voltage waveforms designed to replace the conventional sinusoidal waveform RF 1 , RF 2 and RF 3 that are provided to the processing space 129 of the plasma processing chamber 100 in a conventional processing sequence. The three voltage waveforms PVW 1 , PVW 2 and PVW 3 can be provided from at least one plasma source assembly to one or more electrodes and / or one or more coils positioned within the plasma processing chamber. In some cases, each of the three voltage waveforms PVW 1 , PVW 2 and PVW 3 can be provided from one plasma source assembly at different times within the plasma process sequence. In some other cases, at least two of the three voltage waveforms PVW 1 , PVW 2 and PVW 3 can be provided simultaneously from at least two different plasma source assemblies within the plasma process sequence. The three voltage waveforms PVW 1 , PVW 2 and PVW 3Each includes an asymmetric pulse, and each pulse includes at least one or more ramp regions during a portion of each pulse period that is intended to simulate one or more ramp regions of a sine waveform. In some embodiments, the simulated slope is selected to match the slope of the sine waveform at the zero crossings of the sine waveform (e.g., angles 0, π, 2π, etc.). In one example, the voltage pulse PVW 1 region 511 is intended to simulate the average slope in the ramp region 501 of the sine waveform RF that extends between peaks 501A and 501B 1 . In another example, the voltage pulse PVW 2 region 521 is intended to simulate the average slope in the ramp region 502 of the sine waveform RF 2 . In yet another example, the voltage pulse PVW 3 region 531 is intended to simulate the average slope in the ramp region 503 of the sine waveform RF 3 . Due to hardware-related limitations in the pulse voltage (PV) waveform generator, the three voltage waveforms PVW 1 , PVW 2 and PVW 3 each contain voltage pulse periods that are longer than the period of the typical desired RF-type sine waveform used in common plasma processing recipes that they are intended to simulate. However, it is believed that by incorporating at least one simulated ramp region into a series of voltage pulses in a voltage waveform having a pulse repetition frequency in the kilohertz range, e.g., between 100 and 500 kHz, it is possible to achieve a similar plasma property control effect on the formed plasma as that of a higher frequency radio frequency type sine waveform (e.g., >1 MHz). Generally, the voltage pulse slope control provided by the PV waveform generator 150 can be performed in the range of 1 ns to 1000 ns, which is similar to the slope of the typically desired RF center frequency. In some embodiments, the first asymmetric voltage waveform includes a plurality of voltage pulses, each voltage pulse including a first pulse period and at least one ramp region, the ramp region having a first slope (dV 1 / dt) that is intended to simulate a sine waveform. In this example, when measured at the phase angle where the sine waveform crosses zero on the time axis, the first slope (dV 1 / dt) can be equal to the slope of the sine waveform (dV s / dt), and the sine waveform has a frequency between 1 MHz and 100 MHz and a peak voltage between 100 volts and 5000 volts.

[0055] Figure 6A Illustrates a voltage waveform 601 according to one or more embodiments of the present disclosure provided herein, which includes a plurality of pulse trains of generated voltage waveform pulses used during one or more of the methods described herein. As Figure 6AAs shown, the voltage waveform 601 includes a plurality of positive voltage waveform pulse trains 611 and 613, and a plurality of negative voltage waveform pulse trains 612 and 614, each pulse train including a series of voltage pulses, such as Figure 6B and 6C shown. Figure 6B and 6C respectively illustrate enlarged detailed portions of the waveform pulse trains 611 and 612 in accordance with one or more embodiments of the present disclosure provided herein. During the positive voltage waveform pulse train 611 and the negative voltage waveform pulse train 612, the voltage waveform 601 includes a plurality of voltage pulses, each voltage pulse including a positive voltage portion extending over a period T POS and a negative voltage portion extending over a period T NEG . The period T P of each voltage pulse is equal to the sum of the times allotted to the positive voltage portion plus the negative voltage portion (i.e., T P = T POS + T NEG ). If the amplitudes of the positive voltage swing and the negative voltage swing found in the voltage waveform 601 are equal, as Figure 6A shown, then the percentage of time during each voltage pulse period that the waveform generator produces a positive voltage or a negative voltage will determine whether the waveform pulse train has a positive bias or a negative bias. In one example, as Figure 6B shown, the positive portion 622 of each pulse is approximately 85% of the pulse period, while the negative portion 621 of each pulse is approximately 15%, so the pulse train 611 can be characterized as a positively biased pulse train. In an alternative example, as Figure 6C shown, the positive portion 631 of each pulse is approximately 15% of the pulse period, while the negative portion 632 of each pulse is approximately 85%, so the pulse train 612 can be characterized as a negatively biased pulse train. The determination and transmission of waveform pulse trains having a positive or negative bias can also be controlled based on the area under the voltage waveform 601 curve during each portion of the voltage pulse (i.e., the voltage amplitude during a portion of the period x time). It is believed that the ability to provide voltage pulses having positive and negative portions and pulse trains having positive and negative portions at different voltage levels can be used to control the characteristics of the generated plasma, such as controlling the plasma density and the energies of positive and negative ions and electrons in the plasma. Thus, if a certain state (T POS or T NEG) If the duration and amplitude in a pulse train are longer, the plasma processing mechanism involving substances with opposite charges will be more dominant. For example, if the negative state duration in the pulse train is longer and / or has a higher voltage amplitude, the plasma processing mechanism involving positively charged ions will be more dominant than that involving negatively charged ions, and vice versa. For a longer positive state duration and / or a higher voltage amplitude in the pulse train, the plasma processing mechanism involving negatively charged ions will be more dominant than that involving positively charged ions. The ability to control the characteristics of positive and negative ions formed in the plasma will provide an additional processing control variable, superior to the conventional reactive ion etching (RIE) process that controls one type of ion (e.g., positively charged ions), and other useful processes that require the plasma to interact with various component gases or reactive elements found in the processing area of the substrate and / or the plasma processing chamber.

[0056] In some embodiments, the voltage pulses found in two or more voltage waveform pulse trains include one or more different voltage pulse characteristics, such as voltage polarity (e.g., positive or negative), pulse period (T P ), negative part period T NEG , positive part period T POS , different slopes of the transition period between voltage pulse parts (e.g., regions 511, 521, 531), and / or other voltage waveform characteristics. The ability to control and transmit multiple different voltage waveform frequencies in different parts of the voltage waveform 601 allows additional processing control flexibility, which is not available in conventional sine wave processing systems, without the cost of using multiple waveform generation sources configured to individually provide different fundamental sine frequencies (e.g., 1 MHz, 13.56 MHz, or 40 MHz). While conventional sine wave processing systems require different sine wave generation sources for each different frequency used in the plasma processing recipe, in fact, a single PV waveform generator 150 can generate an infinite number of pulsed voltage frequencies with different characteristics within a frequency range below the hardware limitations of the PV waveform generator 150.

[0057] Due to the use of a plasma source assembly configured to deliver synchronized asymmetric voltage waveforms, each waveform can be customized and combined with other delivered asymmetric voltage waveforms, so that one or more plasma characteristics can be controlled, such as plasma density, plasma uniformity, and the plasma sheath properties can be controlled more precisely without the problems common in conventional RF matching and RF power transfer designs. In addition, the ability to adjust the timing and characteristics of each asymmetric voltage waveform (such as waveforms 303 and 225) provided to one or more types of electrodes or coils in a plasma processing chamber has been found to improve the control of the ion energy distribution (IED) of the ions generated by the plasma interacting with the substrate surface during the plasma processing. The methods and apparatuses disclosed herein are configured to control and maintain a plasma formed in a processing region of a plasma processing chamber without the need for the transmission of radio frequency (RF) waveforms during processing and without the need for RF components to support the RF waveforms. For example, in a process of delivering a first asymmetric voltage waveform to a first electrode and a second asymmetric voltage waveform to a second electrode, the process is performed without another electrical energy source (such as an RF waveform) to maintain the plasma and perform plasma processing on the substrate. In some embodiments, during substantially all plasma processing performed on the substrate, the plasma is controlled, affected, or maintained in the processing space without using or transmitting a sine waveform. The ability to synchronize and control the waveform characteristics of the voltage pulses provided in each pulsed voltage waveform applied to different electrodes and / or coils (such as the frequency during the pulse period, the slope of the voltage waveform portion, the waveform shape, and the applied voltage on-time) allows for improved control of the generated plasma. Therefore, a higher precision of plasma processing can be achieved.

[0058] The term "coupled" is used herein to refer to a direct or indirect coupling between two objects. For example, if object A physically contacts object B and object B contacts object C, then objects A and C can still be considered to be coupled to each other - even if objects A and C do not directly physically contact each other. For example, a first object can be coupled to a second object even if the first object has never directly physically contacted the second object.

[0059] While the foregoing is directed to specific embodiments of the present disclosure, other and further specific embodiments may be devised without departing from the basic scope of the foregoing, and the scope of the foregoing is determined by the following claims.

Claims

1. A plasma processing system, the system comprises: a plurality of pulse voltage waveform generators; a plurality of electrodes or coils, each of the plurality of electrodes or coils being positioned and configured to change the characteristics of the plasma formed in the processing space of the plasma processing chamber of the plasma processing system when an asymmetric voltage waveform from a pulse voltage waveform generator among the plurality of pulse voltage waveform generators is provided to the electrode or coil, wherein each electrode or coil is coupled to a different pulse voltage waveform generator of the plurality of pulse voltage waveform generators; and a system controller configured to synchronously transfer the asymmetric voltage waveforms from their pulse voltage waveform generators to each of the electrodes or coils.

2. The waveform generator according to claim 1, wherein: the plurality of electrodes or coils includes a first coil coupled to a first pulse voltage waveform generator among the plurality of pulse voltage waveform generators, and the first pulse voltage waveform generator is configured to transfer an asymmetric voltage waveform including a plurality of phases varying between a first voltage level and a second voltage level.

3. The waveform generator according to claim 2, wherein the first voltage level is a positive voltage level and the second voltage level is a negative voltage level.

4. The waveform generator according to claim 2, wherein: the plurality of electrodes or coils includes a second coil coupled to a second pulse voltage waveform generator among the plurality of pulse voltage waveform generators, and the second pulse voltage waveform generator is configured to transfer an asymmetric voltage waveform including a plurality of phases varying between a third voltage level and a fourth voltage level.

5. The waveform generator according to claim 2, wherein: the plurality of electrodes or coils further includes a first electrode coupled to a second pulse voltage waveform generator among the plurality of pulse voltage waveform generators, and the second pulse voltage waveform generator is configured to transfer an asymmetric voltage waveform including a plurality of phases varying between a third voltage level and a fourth voltage level.

6. The waveform generator according to claim 5, wherein the third voltage level is a positive voltage level and the fourth voltage level is a negative voltage level.

7. The waveform generator according to claim 5, wherein when the asymmetric voltage waveform reaches the fourth voltage level, the fourth voltage level is configured to generate a plasma sheath after reaching the third voltage level during each asymmetric voltage pulse.

8. A method of controlling a plasma formed in a plasma processing system, the method comprising: transferring a first asymmetric voltage waveform from a first pulse voltage waveform generator to a first electrode or a first coil, wherein the first asymmetric voltage waveform is configured to change the characteristics of the plasma formed in the processing space of the plasma processing chamber; Transmit a second asymmetric voltage waveform from the second pulse voltage waveform generator to the second electrode or the second coil, wherein the second asymmetric voltage waveform is configured to change the characteristics of the plasma formed in the processing space of the plasma processing chamber; and Synchronize the transmission of the first asymmetric voltage waveform with the second asymmetric voltage waveform.

9. The method according to claim 8, wherein: The first asymmetric voltage waveform is transmitted to the first coil; and The second asymmetric voltage waveform is transmitted to the second electrode, and wherein each of the first and second asymmetric voltage waveforms includes a plurality of phases.

10. The waveform generator according to claim 9, wherein the first asymmetric voltage waveform varies between a first voltage level and a second voltage level, the first voltage level being positive and the second voltage level being negative.

11. The method according to claim 10, wherein the second asymmetric voltage waveform includes a plurality of phases that vary between a third voltage level and a fourth voltage level.

12. The method according to claim 8, wherein: The first asymmetric voltage waveform is transmitted to the first coil; and The second asymmetric voltage waveform is transmitted to the second coil, and wherein each of the first and second asymmetric voltage waveforms includes a plurality of phases.

13. The method according to claim 8, wherein: Each of the first and second asymmetric voltage waveforms includes voltage pulses, the voltage pulses including a first phase, a second phase, and a third phase, The second phase of the voltage pulse is disposed between the first phase and the third phase, and The voltage of the voltage pulse within the first and third phases varies linearly with time.

14. The method according to claim 8, wherein: Each of the first and second asymmetric voltage waveforms includes voltage pulses, the voltage pulses including a first phase, a second phase, and a third phase, The second phase of the voltage pulse is disposed between the first phase and the third phase, and The voltage of the voltage pulse within the first and third phases varies non-linearly with time.

15. The method according to claim 8, wherein: The first asymmetric voltage waveform is transmitted to the first coil, The first asymmetric voltage waveform includes voltage pulses, the voltage pulses including a first phase, a second phase, and a third phase, The second phase of the voltage pulse is disposed between the first phase and the third phase, and The voltage of the voltage pulse within the first and third phases varies with time.

16. The method according to claim 8, wherein: The first asymmetric voltage waveform includes a plurality of voltage pulses that extend between a first voltage level and a second voltage level, The second asymmetric voltage waveform includes a plurality of voltage pulses that extend between a third voltage level and a fourth voltage level, and At least one of the first voltage level, the second voltage level, the third voltage level, and the fourth voltage level is different.

17. The method according to claim 8, Wherein: The first asymmetric voltage waveform includes: A plurality of voltage pulses, each of the plurality of voltage pulses comprising a first pulse period and at least one ramp region having a first slope (dV 1 / dt), Wherein when measuring the phase angle at which the sine wave crosses zero, the first slope (dV 1 / dt) is equal to the slope of the sine wave (dV s / dt), and the sine wave has a frequency between 1 MHz and 100 MHz and a peak voltage between 500 volts and 5000 volts.

18. The method according to claim 8, wherein the transmission of the first asymmetric voltage waveform and the transmission of the second asymmetric voltage waveform are performed without another electrical energy source to sustain the plasma.

19. The method according to claim 8, wherein there is no sine waveform in the processing space during the transmission of the first asymmetric voltage waveform and the transmission of the second asymmetric voltage waveform.

20. The method according to claim 8, wherein the plasma is sustained in the processing space without using a sine waveform.

Images