TL;DR: In this paper, an overview of reduction of oxide minerals by hydrogen plasma is presented, where the influences of various reaction conditions particularly with respect to reduction of oxides are discussed and some aspects of both thermal and non-thermal cold plasma linking oxidative as well as dissociative reduction are presented.
Abstract: Carbothermic reduction of oxide minerals is one of the major routes to obtain the corresponding metals. This process produces a lot of CO2, which is responsible for greenhouse effect. Alternatively, hydrogen plasma containing hydrogen in atomic, ionic, and excited states can reduce almost every metal oxide even at lower temperatures. Besides this advantage, plasma processing also offers kinetic advantages. Further, hydrogen-water cycle does not pose any environmental problems. However, reduction of metal oxides in hydrogen plasma is not so straightforward—there are issues relating to introduction of material into the plasma zone, residence time, reverse reaction, and scale-up that must be resolved—yet, it holds the key to future environmental challenges particularly with respect to CO2 emission. This paper provides an overview of reduction of oxide minerals by hydrogen plasma. The influences of various reaction conditions particularly with respect to reduction of oxides are discussed and some aspects of both thermal and non-thermal cold plasma linking oxidative as well as dissociative reduction are presented.
TL;DR: In this article, a table unit is installed within a processing vessel and configured to receive a substrate thereon, a gas supply unit is configured to supply a process gas into the processing vessel, a plasma generating unit configured to turn the process gas to plasma, a magnetic field forming mechanism installed at a lateral side of the table unit and configurable to form magnetic fields in a processing atmosphere in order to move electrons existing in the plasma of the process gases along a surface of the substrate.
Abstract: Provided is a plasma processing apparatus, which includes a table unit installed within a processing vessel and configured to receive a substrate thereon, a gas supply unit configured to supply a process gas into the processing vessel, a plasma generating unit configured to turn the process gas to plasma, a magnetic field forming mechanism installed at a lateral side of the table unit and configured to form magnetic fields in a processing atmosphere in order to move electrons existing in the plasma of the process gas along a surface of the substrate; and an exhaust mechanism configured to exhaust gas from the interior of the processing vessel. The magnetic fields are opened at at-least one point in a peripheral edge portion of the substrate such that a loop of magnetic flux lines surrounding the peripheral edge portion of the substrate is not formed.
TL;DR: In this article, a plasma processing apparatus including a processing vessel 10 in which a plasma process is performed and a plasma generation antenna 20 having a shower plate 100 which supplies a first gas and a second gas into the processing vessel, performs the plasma process on a substrate with plasma generated by a surface wave formed on a surface of the shower plate100 through a supply of a microwave.
Abstract: A plasma processing apparatus including a processing vessel 10 in which a plasma process is performed and a plasma generation antenna 20 having a shower plate 100 which supplies a first gas and a second gas into the processing vessel 10 , performs the plasma process on a substrate with plasma generated by a surface wave formed on a surface of the shower plate 100 through a supply of a microwave. The shower plate 100 has multiple gas holes 133 configured to supply the first gas into the processing vessel 10 and multiple supply nozzles 160 configured to supply the second gas into the processing vessel 10 , and the supply nozzles 160 are protruded vertically downwards from a bottom surface of the shower plate 100 and are provided at different positions from the gas holes 133.
TL;DR: In this article, the authors optimized the gas residence time during an excited species phase, where activated reactant is supplied such as from a plasma, to increase the quality of the deposited layer, such as reducing wet etch rates, increasing index of refraction and reducing impurities in the layer.
Abstract: Plasma atomic layer deposition (ALD) is optimized through modulation of the gas residence time during an excited species phase, wherein activated reactant is supplied such as from a plasma. Reduced residence time increases the quality of the deposited layer, such as reducing wet etch rates, increasing index of refraction and/or reducing impurities in the layer. For example, dielectric layers, particularly silicon nitride films, formed from such optimized plasma ALD processes have low levels of impurities remaining from the silicon precursor.
TL;DR: In this paper, a high frequency wave generated by a microwave generator is used to generate a plasma within a processing vessel by using a magnetron, and a voltage control circuit is configured to control a voltage supplied to the magnetron by a power supply.
Abstract: A plasma processing apparatus includes a plasma generating device configured to generate a plasma within a processing vessel by using a high frequency wave generated by a microwave generator 41 including a magnetron 42 configured to generate the high frequency wave; detectors 54 a and 54 b configured to measure a power of a traveling wave that propagates to a load side and a power of a reflected wave reflected from the load side, respectively; and a voltage control circuit 53 a configured to control a voltage supplied to the magnetron 42 by a power supply 43 . Further, the voltage control circuit 53 a includes a load control device configured to supply, to the magnetron 42 , a voltage corresponding to a power calculated by adding a power calculated based on the power of the reflected wave measured by the detector 54 b to the power of the traveling wave measured by the detector 54 a.
TL;DR: In this paper, a tuning electrode is disposed in a substrate support pedestal and electrically coupled to a variable capacitance, and the capacitance is controlled to control the RF and resulting plasma coupling to the tuning electrode.
Abstract: Embodiments of the present invention relate to apparatus for enhancing deposition rate and improving a plasma profile during plasma processing of a substrate. According to embodiments, the apparatus includes a tuning electrode disposed in a substrate support pedestal and electrically coupled to a variable capacitor. The capacitance is controlled to control the RF and resulting plasma coupling to the tuning electrode. The plasma profile and the resulting deposition rate and deposited film thickness across the substrate are correspondingly controlled by adjusting the capacitance and impedance at the tuning electrode.
TL;DR: In this article, a method of conditioning internal surfaces of a plasma source includes flowing first source gases into a plasma generation cavity of the plasma source that is enclosed at least in part by the internal surfaces.
Abstract: A method of conditioning internal surfaces of a plasma source includes flowing first source gases into a plasma generation cavity of the plasma source that is enclosed at least in part by the internal surfaces. Upon transmitting power into the plasma generation cavity, the first source gases ignite to form a first plasma, producing first plasma products, portions of which adhere to the internal surfaces. The method further includes flowing the first plasma products out of the plasma generation cavity toward a process chamber where a workpiece is processed by the first plasma products, flowing second source gases into the plasma generation cavity. Upon transmitting power into the plasma generation cavity, the second source gases ignite to form a second plasma, producing second plasma products that at least partially remove the portions of the first plasma products from the internal surfaces.
TL;DR: In this article, the authors present an embodiment of a plasma source with a first perforation and an insulator, disposed in contact with the first and second electrodes about a periphery of the first electrode.
Abstract: In an embodiment, a plasma source includes a first electrode, configured for transfer of one or more plasma source gases through first perforations therein; an insulator, disposed in contact with the first electrode about a periphery of the first electrode; and a second electrode, disposed with a periphery of the second electrode against the insulator such that the first and second electrodes and the insulator define a plasma generation cavity. The second electrode is configured for movement of plasma products from the plasma generation cavity therethrough toward a process chamber. A power supply provides electrical power across the first and second electrodes to ignite a plasma with the one or more plasma source gases in the plasma generation cavity to produce the plasma products. One of the first electrode, the second electrode and the insulator includes a port that provides an optical signal from the plasma.
TL;DR: In this paper, the effects of including fast neutrals and using realistic energy-dependent secondary electron emission coefficients for ions and neutrals in simulations of CCPs operated in argon at 13.56 MHz and at neutral gas pressures between 3 Pa and 100 Pa.
Abstract: In most PIC/MCC simulations of radio frequency capacitively coupled plasmas (CCPs) several simplifications are made: (i) fast neutrals are not traced, (ii) heavy particle induced excitation and ionization are neglected, (iii) secondary electron emission from boundary surfaces due to neutral particle impact is not taken into account, and (iv) the secondary electron emission coefficient is assumed to be constant, i.e. independent of the incident particle energy and the surface conditions. Here we question the validity of these simplifications under conditions typical for plasma processing applications. We study the effects of including fast neutrals and using realistic energy-dependent secondary electron emission coefficients for ions and fast neutrals in simulations of CCPs operated in argon at 13.56 MHz and at neutral gas pressures between 3 Pa and 100 Pa. We find a strong increase of the plasma density and the ion flux to the electrodes under most conditions, if these processes are included realistically in the simulation. The sheath widths are found to be significantly smaller and the simulation is found to diverge at high pressures for high voltage amplitudes in qualitative agreement with experimental findings. By switching individual processes on and off in the simulation we identify their individual effects on the ionization dynamics and plasma parameters. We conclude that fast neutrals and energy-dependent secondary electron emission coefficients must be included in simulations of CCPs in order to yield realistic results.
TL;DR: In this article, the authors report ALD deposition of silicon dioxide using either thermal or plasma enhanced atomic layer deposition (PEALD), and several aminosilanes with differing structures and reactivity were used as silicon precursors in R&D single wafer ALD tools.
TL;DR: In this article, the authors present results that show combined antireflectivity, superhydrophobicity and superamphiphobicity for optimal plasma treatment time of only one side of the samples (better results are expected for two-side treatment).
TL;DR: In a chemical vapor deposition (CVD) process, a thin film of some material is deposited onto a surface via the chemical reactions of gaseous molecules that contain the atoms needed for the film material as mentioned in this paper.
Abstract: In a chemical vapor deposition (CVD) process, a thin film of some material is deposited onto a surface via the chemical reactions of gaseous molecules that contain the atoms needed for the film material. These chemical reactions take place on the surface and in many cases also in the gas phase. To fully understand the chemistry in the process and thereby also have the best starting point for optimizing the process, theoretical chemical modeling is an invaluable tool for providing atomic-scale detail on surface and gas phase chemistry. This overview briefly introduces to the non-expert the main concepts, history and application of CVD, including the pulsed CVD variant known as atomic layer deposition, and put into perspective the use of theoretical chemistry in modeling these processes.
TL;DR: In this paper, a method and apparatus for cleaning a substrate having a plurality of high-aspect ratio openings is described, where the substrate can include a silicon oxide layer over a damaged or amorphous silicon layer.
Abstract: Method and apparatus for cleaning a substrate having a plurality of high-aspect ratio openings are disclosed. A substrate can be provided in a plasma processing chamber, where the substrate includes the plurality of high-aspect ratio openings, the plurality of high-aspect ratio openings are defined by vertical structures having alternating layers of oxide and nitride or alternating layers of oxide and polysilicon. The substrate can include a silicon oxide layer over a damaged or amorphous silicon layer in the high-aspect ratio openings. To remove the silicon oxide layer, a bias power can be applied in the plasma processing chamber at a low pressure, and a fluorine-based species can be used to etch the silicon oxide layer. To remove the underlying damaged or amorphous silicon layer, a source power and a bias power can be applied in the plasma processing chamber, and a hydrogen-based species can be used to etch the damaged or amorphous silicon layer.
TL;DR: In this paper, a method of plasma processing includes generating a plasma within a substantially toroidal plasma cavity that defines a toroidal axis, to form plasma products, and distributing the plasma products to a process chamber through a plurality of outlet openings substantially azimuthally distributed about a first axial side of the plasma cavity.
Abstract: A plasma processing system includes a process chamber and a plasma source that generates a plasma in a plasma cavity. The plasma cavity is substantially symmetric about a toroidal axis. The plasma source defines a plurality of outlet apertures on a first axial side of the plasma cavity Plasma products produced by the plasma pass in the axial direction, through the plurality of outlet apertures, from the plasma cavity toward the process chamber. A method of plasma processing includes generating a plasma within a substantially toroidal plasma cavity that defines a toroidal axis, to form plasma products, and distributing the plasma products to a process chamber through a plurality of outlet openings substantially azimuthally distributed about a first axial side of the plasma cavity, directly into a process chamber.
TL;DR: In this paper, the authors characterized a plasma processing apparatus, which is characterized in having: a processing container (12), inside of which can be depressurized; a lower electrode, which serves also as a placing table (20), having a wafer (W) placed thereon in the processing container; an upper electrode or an antenna electrode which is disposed to face the lower electrode; a gas supply source (32), which introduces a gas into the processed container, said gas containing a halogen-containing gas and oxygen gas; a high-frequency power supply (18), which applies
Abstract: Provided is a plasma processing apparatus (10), which is characterized in having: a processing container (12), inside of which can be depressurized; a lower electrode, which serves also as a placing table (20) having a wafer (W) placed thereon in the processing container; an upper electrode or an antenna electrode, which is disposed to face the lower electrode; a gas supply source (32), which introduces a gas into the processing container, said gas containing a halogen-containing gas and oxygen gas; a high-frequency power supply (18), which applies high-frequency power for generating plasma to at least the upper electrode, the antenna electrode or the lower electrode; and a means, which brings the gas into the plasma state with the high-frequency power for generating plasma, and performs plasma processing to the wafer on the placing table using plasma effects. The plasma processing apparatus is also characterized in that, out of the surfaces exposed to plasma in the processing container, at least a part of or the whole surfaces at the heights of the upper electrode, the antenna electrode or the lower electrode from a position where the wafer is placed are coated with a fluoride compound.
TL;DR: In this paper, a plasma processing system controller is coupled to the plasma processing chamber and the RF transmission path, and the controller includes recipe logic for at least one plasma processing recipe including multiple plasma processing settings.
Abstract: Plasma processing systems and methods including a plasma processing chamber and an RF transmission path The plasma processing chamber including an electrostatic chuck The RF transmission path including one or more RF generators, a match circuit coupled the RF generator and an RF feed coupling the match circuit to the electrostatic chuck The system also includes an RF return path coupled between the plasma processing chamber and the RF generator A plasma processing system controller is coupled to the plasma processing chamber and the RF transmission path The controller includes recipe logic for at least one plasma processing recipe including multiple plasma processing settings and an RF power compensation logic for adjusting at least one of the plasma processing settings
TL;DR: In this paper, a method and apparatus for conditioning an oxide surface during a semiconductor device formation process is provided, where one or more plasma processing operations are performed on a substrate having a fin structure and shallow trench isolation structure (STI).
Abstract: A method and apparatus for conditioning an oxide surface during a semiconductor device formation process is provided herein. One or more plasma processing operations are performed on a substrate having a fin structure and shallow trench isolation structure (STI) formed thereon. An oxygen containing plasma process may modify surfaces of the STI structure in preparation for an argon containing plasma process. The argon containing plasma process may form a first layer on the fin structure and STI structure and an ammonia fluoride containing plasma process may form a second layer on the first layer. The first and second layers may be removed from the substrate during a subsequent heating process to provide a cleaned fin structure suitable for subsequent processing operations.
TL;DR: In this article, the authors studied sintering of silver nanoparticle (AgNP) films on glass substrates by applying argon (Ar) plasma to achieve improved electrical conductivity.
TL;DR: In this article, the authors introduce the low-temperature plasma sources for Si photovoltaic applications and discuss the effects of low temperature plasma dissociation and deposition on the synthesis of Si-based thin films.
Abstract: There has been a recent rapid expansion of the range of applications of low-temperature plasma processing in Si-based photovoltaic (PV) technologies. The desire to produce Si-based PV materials at an acceptable cost with consistent performance and reproducibility has stimulated a large number of major research and research infrastructure programs, and a rapidly increasing number of publications in the field of low-temperature plasma processing for Si photovoltaics. In this article, we introduce the low-temperature plasma sources for Si photovoltaic applications and discuss the effects of low-temperature plasma dissociation and deposition on the synthesis of Si-based thin films. We also examine the relevant growth mechanisms and plasma diagnostics, Si thin-film solar cells, Si heterojunction solar cells and silicon nitride materials for antireflection and surface passivation. Special attention is paid to the low-temperature plasma interactions with Si materials including hydrogen interaction, wafer cleaning, masked or mask-free surface texturization, the direct formation of p–n junction, and removal of phosphorus silicate glass or parasitic emitters. The chemical and physical interactions in such plasmas with Si surfaces are analyzed. Several examples of the plasma processes and techniques are selected to represent a variety of applications aimed at the improvement of Si-based solar cell performance.
TL;DR: In this article, a holder is used to treat the surfaces of multiple articles of interest with plasma uniformly, and the generated plasma is supplied to the inside of the holder through a side opening provided on a side plate.
Abstract: The purpose of the present invention is to treat the surfaces of multiple articles of interest with plasma uniformly. A holder (21) in which multiple substrates (11) are housed is set in a vacuum treatment chamber (14). First and second electrodes (41, 42) are arranged with being spaced apart from each other between the holder (21) and an inlet port (38). A process gas discharged through the inlet port (38) is excited with the first and second electrodes (41, 42) to generate plasma. The generated plasma is supplied to the inside of the holder (21) through a side opening provided on a side plate (22) of the holder (21), and removes contaminants on the surfaces of the substrates (11).
TL;DR: In this article, a biased plasma process is used to treat some crystalline silicon (e.g., polysilicon or single crystal silicon) to form amorphous silicon, and a remote plasma is formed using a hydrogen-containing precursor to form plasma effluents.
Abstract: A method of selectively dry etching silicon from patterned heterogeneous structures is described. The method optionally includes a plasma process prior to a remote plasma etch. The plasma process may use a biased plasma to treat some crystalline silicon (e.g. polysilicon or single crystal silicon) to form amorphous silicon. Subsequently, a remote plasma is formed using a hydrogen-containing precursor to form plasma effluents. The plasma effluents are passed into the substrate processing region to etch the amorphous silicon from the patterned substrate. By implementing biased plasma processes, the normally isotropic etch may be transformed into a directional (anisotropic) etch despite the remote nature of the plasma excitation during the etch process.
TL;DR: In this paper, the authors review the present status of AP low-temperature plasma processes, bearing in mind their application for high-purity functional thin films including silicon and related materials.
Abstract: Nonthermal plasmas generated under atmospheric pressure (AP) have been receiving increased attention in direct plasma technology applications for thin film deposition. This is because the atmospheric-pressure plasma-enhanced chemical vapor deposition (AP-PECVD) is expected to realize low-cost and high-throughput processing with open air systems, which are of prime importance for various industrial applications. A large number of studies have been reported on the preparation of thin films using various types of AP plasma sources such as corona, dielectric barrier and AP glow discharges excited by pulsed or low-frequency power sources that can produce a nonequilibrium AP plasma. Most of the reported films using these common AP plasma sources have been related to polymers, oxides, and carbon materials. On the other hand, by virtue of the low ion energy due to the high collision frequency, AP-plasma process can have a nature of soft or gentle processing in addition to high-rate processing. Therefore, AP-PECVD also has a potential to form good-quality functional thin films, such as high-purity semiconductor or insulator thin films, which may be applicable for electronic devices. Although the development of AP-PECVD technology for such applications are attractive in the future advanced industry, the reports on these applications are limited. The reason may be related to the fact that the high collision frequency in AP plasma enhances secondary reactions in the gas phase to generate dust particles which will deteriorate the film quality, and also limits mass transport, which leads to poor uniformity of the resulting film. In the present article, the authors review the present status of AP low-temperature plasma processes, bearing in mind their application for high-purity functional thin films including silicon and related materials. The authors first summarize recent progress in the use of common AP plasma sources for direct PECVD processes. To grasp the present status of AP-PECVD technique, the authors have picked up popular materials for AP-PECVD, such as carbon, oxides, and other inorganic materials as well as silicon and related materials. Although there already exists a plenty of good review articles dealing with PECVD using common AP plasma sources, works on reviewing PECVD using radio-frequency (RF) and very-high-frequency (VHF) excitations of AP plasma seem to be insufficient. RF and VHF excitations of AP plasma are capable of generating continuous oscillating glow discharges without unstable streamers and filaments, which will be important to form uniform and dust-free films. So, secondly, the authors discuss the key distinguishing features of PECVD using RF and VHF excitations of AP plasma from the common AP plasma sources. Finally, they describe examples of the application of AP-VHF plasma to the preparation of silicon and related thin films.
TL;DR: In this article, the intermediate range of plasma polymerization, which can be controlled both by the energy input into the plasma (activation of the monomer) and during film growth (densification of the plasma polymer), is discussed.
Abstract: Plasma polymer deposition, especially on polymer substrates, enables functional surfaces. Since generally film failure should be avoided, the coating on polymers requires adapted plasma polymer films. Low energy input yields swellable, water-soluble coatings, whereas high energy input results in hard coatings showing crack formation by elastic and plastic deformation of the soft substrate. Both effects might provoke film failure and delamination. Therefore, this chapter mainly focuses on the intermediate range of plasma polymerization, which can be controlled both by the energy input into the plasma (activation of the monomer) and during film growth (densification of the plasma polymer).
TL;DR: A plasma etching method that can improve an etching selection ratio of a film to be etched to a film different from the one to be etched compared with the related art is provided in this paper.
Abstract: A plasma etching method that can improve an etching selection ratio of a film to be etched to a film different from the film to be etched compared with the related art is provided. The present invention provides a plasma etching method for selectively etching a film to be etched against a film different from the film to be etched, in which plasma etching of the film to be etched is performed using a gas that can cause to generate a deposited film containing similar components as components of the different film.
TL;DR: In this paper, the authors report on the possibility to cover the full range of surface wetting characters from super-hydrophilic to superhydrophobic one using plasma polymerization (plasma enhanced chemical vapor deposition) performed with different mixtures of hexamethyldisiloxane/oxygen and in combination with nanoparticle deposition.
TL;DR: In this paper, surface coatings for plasma components that have the benefit of being robust against chemical and plasma physical attack in aggressive (e.g., fluorine-based) plasma environments are presented.
Abstract: Disclosed herein are surface coatings for plasma components that have the benefit of being robust against chemical and plasma physical attack in aggressive (e.g., fluorine- based) plasma environments. The coatings also provide low plasma surface recombination rates for active oxygen, nitrogen, fluorine, and hydrogen species when compared with other known surface treatments. The coatings can be applied to any plasma system component not requiring etching or plasma cleaning including but not limited to materials like quartz, aluminum, or anodized aluminum. Additionally, the efficiency of the system is increased by applying a non-reactive coating to system components thereby increasing the flow of excited plasma species to the plasma chamber of the system.
TL;DR: In this paper, a plasminar generator is used for deposition, etching, or treatment of semiconductor, conductor or insulating films, which is well suited for deposition and etching.
Abstract: Apparatus and method for plasma-based processing well suited for deposition, etching, or treatment of semiconductor, conductor or insulating films. Plasma generating units include one or more elongated electrodes on the processing side of a substrate and a neutral electrode proximate the opposite side of the substrate. Gases may be injected proximate a powered electrode which break down electrically and produce activated species that flow toward the substrate area. This gas then flows into an extended process region between powered electrodes and substrate, providing controlled and continuous reactivity with the substrate at high rates with efficient utilization of reactant feedstock. Gases are exhausted via passages between powered electrodes or electrode and divider.
TL;DR: In this paper, the spectral and energy characteristics of rf discharges for treating cereal and legume seeds were studied and the optimal conditions for plasma processing prior to planting, such that its biological effectiveness is greatest, were realized for a specific discharge power of ~0.35 W/cm3 and an exposure time of 5-7 min.
Abstract: Optical spectroscopic techniques are used to study the spectral and energy characteristics and to determine the gas temperature of rf discharges for treating cereal and legume seeds. It is shown that active plasma particles produce a change in the morphology of seed coats. The optimal conditions for plasma processing prior to planting, such that its biological effectiveness is greatest, are realized for a specific discharge power of ~0.35 W/cm3 and an exposure time of 5–7 min.
TL;DR: Improvements to the dielectric constant and leakage current density of atomic layer deposited BaTiO3 thin films are ascribed to the crystallization and densification of the film induced by high-energy ion bombardments on the film surface during the plasma treatment.
Abstract: High-k, low leakage thin films are crucial components for dynamic random access memory (DRAM) capacitors with high storage density and a long storage lifetime. In this work, we demonstrate a method to increase the dielectric constant and decrease the leakage current density of atomic layer deposited BaTiO3 thin films at low process temperature (250 °C) using postdeposition remote oxygen plasma treatment. The dielectric constant increased from 51 (as-deposited) to 122 (plasma-treated), and the leakage current density decreased by 1 order of magnitude. We ascribe such improvements to the crystallization and densification of the film induced by high-energy ion bombardments on the film surface during the plasma treatment. Plasma-induced crystallization presented in this work may have an immediate impact on fabricating and manufacturing DRAM capacitors due to its simplicity and compatibility with industrial standard thin film processes.
TL;DR: In this paper, a semiconductor wafer is mounted on an electrostatic chuck 38 and a susceptor 12 is switched from an electrically grounded state into a floated state, and a self-bias (−V dc ) is generated.
Abstract: At a first timing after mounting a semiconductor wafer W on an electrostatic chuck 38 , a susceptor 12 is switched from an electrically grounded state into a floated state. From a second timing after the first timing, a second high frequency power HF for plasma generation is applied to the susceptor 12 , and a processing gas is excited into plasma in a chamber 10 . From a third timing after the second timing, a first high frequency power LF for ion attraction is applied to the susceptor 12 , and a self-bias (−V dc ) is generated. From a fourth timing close to the third timing, a negative second DC voltage −B DC corresponding to the self-bias (−V dc ) is applied to the susceptor 12 . From the fifth timing after the fourth timing, a positive first DC voltage A DC is applied to an inner electrode 42 of the electrostatic chuck 38.