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Self-limiting surface reactions are promising for atomic layer etching of materials. Classical treatments with plasmas do not allow for self-limiting functionalization but cause the formation of several functional groups and degradation. To avoid this, the polystyrene was oxidized in the plasma afterglow with the O-atom density 7 × 1017 m−3 and dissociation fraction 7%. X-ray Photoelectron Spectroscopy was used to study the formation of various oxygen groups versus the O-atom dose. The surface was saturated with the OH groups already after the dose of 1 × 1019 m−2, indicating a large initial sticking. The functionalization remained almost intact over an order of magnitude larger doses. Measurable quantities of the C O groups appeared simultaneously with the benzene ring's degradation at a dose of 1 × 1020 m−2. The ring degradation was accomplished with a significant increase in the OH concentration what was explained by the formation of a thicker oxygen-rich film. O C O and O (C O) O groups appeared after the dose of 1 × 1021 m−2, i.e., a 100-times larger dose than required for the initial saturation with the OH. The observations are sound with the predictions from the literature obtained through the density functional theory of oxygen adsorption on polystyrene.

Deposition of titanium nitride (TiN) thin films has been studied by remote plasma enhanced atomic layer deposition (PEALD) using MAP Ti (Mecaro Advanced Precursor-C12H23N3Ti) precursor and nitrogen plasma. Consequently, it was possible to use a temperature window of 275–325 °C, lower than the window required by other TiN films using TiCl4 precursor and NH3 gas. The auger electron spectroscopy (AES) analysis showed that as plasma power and plasma exposure times increase, impurity content decreases and TiN film deposited at plasma power of 400 W and exposure time of 35 s has lower impurity content than films deposited by other methods such as metal organic chemical vapor deposition (MOCVD). For TiN thin film deposited at 300 °C, plasma power of 400 W, and plasma exposure time of 35 s, the X-ray diffraction (XRD) analysis showed crystallinity and resistivity of approximately 320 μ Ω c m . Atomic force microscopy (AFM) measurements determined a TiN film surface roughness of under 0.5 nm. TEM (transmission electron microscope) analysis showed 98% step coverage.

An extended study on an advanced method for the cleaning of carbon contaminations from large optical surfaces using a remote inductively coupled low-pressure RF plasma source (GV10x DownStream Asher) is reported. Technical and scientific features of this scaled up cleaning process are analysed, such as the cleaning efficiency for different carbon allotropes (amorphous and diamond-like carbon) as a function of feedstock gas, RF power (from 30 to 300W), and source-object distances (415 to 840 mm). The underlying physical phenomena for these functional dependences are discussed., The authors would like to acknowledge the help by Guillaume Sauthier (ICN2) for his collaboration during the XPS characterization. We also thank ibss Group Inc. for supplying the GV10x DS Asher systems as well as the DLC samples.

Fundamental surface reactions in the atomic layer deposition of GaN with trimethylgallium (TMG) and plasma-excited NH 3 are investigated by multiple-internal-reflection infrared absorption spectroscopy (MIR-IRAS) at surface temperatures varying from room temperature (RT) to 400 °C. It is found that TMG is saturated at RT on GaN surfaces when the TMG exposure exceeds 8 × 10 4 Langmuir (L), where 1 L corresponds to 1.33 × 10 −4 Pa s (or 1.0 × 10 −6 Torr s), and its saturation density reaches the maximum value at RT. Nitridation with the plasma-excited NH 3 on the TMG-saturated GaN surface is investigated by X-ray photoelectron spectroscopy (XPS). The nitridation becomes effective at surface temperatures in excess of 100 °C. The reaction models of TMG adsorption and nitridation on the GaN surface are proposed in this paper. Based on the surface analysis, a temperature-controlled ALD process consisting of RT-TMG adsorption and nitridation at 115 °C is examined, where the growth per cycle of 0.045 nm/cycle is confirmed. XPS analysis indicates that all N atoms are bonded as GaN. Atomic force microscopy indicates an average roughness of 0.23 nm. We discuss the reaction mechanism of GaN ALD in the low-temperature region at around 115 °C with TMG and plasma-excited NH 3 .

Room-temperature atomic layer deposition (ALD) of TiO 2 was developed using tetrakis(dimethylamino)titanium (TDMAT) and a remote-plasma-excited water vapor. A growth rate of 0.157 nm/cycle at room temperature was achieved, and the TDMAT adsorption and its oxidation on TiO 2 were investigated by multiple-internal-reflection infrared absorption spectroscopy. Saturated adsorption of the TDMAT occurs at exposures of ∼1 × 10 6 Langmuir (1 Langmuir = 1 × 10 −6 Torr s) at room temperature, and the remote-plasma-excited water vapor is effective in oxidizing the TDMAT-saturated TiO 2 surface. The IR study suggests that the Ti-OH plays a role of adsorption site for TDMAT. The reaction mechanism of room-temperature TiO 2 ALD is discussed.

The remote plasma nitridation (RPN) of an HfO2 film using N2 and NH3 has been investigated comparatively. X-ray photoelectron spectroscopy and Auger electron spectroscopy analyses after post-deposition annealing (PDA) at 700 °C show that a large amount of nitrogen is present in the bulk film as well as in the interfacial layer for the HfO2 film nitrided with NH3-RPN. It is also shown that the interfacial layer formed during RPN and PDA is a nitrogen-rich Hf–silicate. The C–V characteristics of an HfOxNy gate dielectric nitrided with NH3-RPN have a smaller equivalent oxide thickness than that nitrided with N2-RPN in spite of its thicker interfacial layer.

This paper reports the germicidal effect (GE) of Escherichia coli on the surface of medical poly(vinyl chloride) (PVC) in remote-oxygen plasma. The concentration of active species in plasma is determined by means of double Langmuir electron probe and electron-spin resonance (ESR) diagnosis. Moreover, surface properties of sterilized PVC are characterized by the water contact angle measurement, X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). The distribution of electrons, ions, and radicals in plasma reactor is different. High-purity radicals are obtained at 40 cm from the induction coil which is called remote-plasma zone. By remote-oxygen-plasma sterilization, GE value reach 4.12 under the conditions of treatment time of 60 s, plasma RF power of 100 W and oxygen flux of 60 cm3/min. Compared with direct-oxygen-plasma sterilization, remote plasma can enhance the hydrophilic property and limit the degradation of the PVC surface. After remote-plasma sterilization, PVC surface energy is increased more than twice, which mainly resulted from the increase of surface polar force γ L p , and hydrogen bonding force γ L h . Moreover, remote-plasma sterilization can increase oxygenated functional groups on PVC surface. Experimental results show that remote plasma can inactivate E. coli on the medical PVC substrate effectively. Furthermore, it can optimize the surface properties.

Potential of O 2 remote plasmas for improving structural, morphological and optical properties of various multifunctional oxides thin films both during plasma assisted growth as well as by post-growth treatments is discussed. In particular, an O 2 remote plasma metalorganic chemical vapor deposition (RP-MOCVD) route is presented for tailoring the structural, morphological and optical properties of Er 2 O 3 and ZnO films. Furthermore, post-growth room-temperature remote O 2 plasma treatments of indium-tin-oxides (ITO) films are demonstrated to be effective in improving morphology of ITO films.

We report on continuous-wave laser induced crystallisation processes occurring in Si/SiO 2 multiple quantum wells (MQW), prepared by remote plasma enhanced chemical vapour deposition of amorphous Si and SiO 2 layers on quartz substrates. The size and the volume fraction of the Si nanocrystals in the layers were estimated employing micro-Raman spectroscopy. It was found that several processes occur in the Si/SiO 2 MQW system upon laser treatment, i.e. amorphous to nanocrystalline conversion, Si oxidation and dissolution of the nanocrystals. The speed of these processes depends on laser power density and the wavelength, as well as on the thickness of Si-rich layers. At optimal laser annealing conditions, it was possible to achieve ∼100% crystallinity for 3, 5 and 10 nm thickness of deposited amorphous Si layers. Crystallization induced variation of the light absorption in the layers can explain the complicated process of Si nanocrystals formation during the laser treatment.

The graft polymerization of acrylic acid (AAc) was carried out onto poly(tetrafluoroethylene) (PTFE) films that had been pretreated with remote argon plasma and subsequently exposed to oxygen to create peroxides. Peroxides are known to be the species responsible for initiating the graft polymerization when PTFE reacts with AAc. We chose different parameters of remote plasma treatment to get the optimum condition for introducing maximum peroxides (2.87 × 10 −11 mol/cm 2 ) on the surface. The influence of grafted reaction conditions on the grafting degree was investigated. The maximum grafting degree was 25.2 μg/cm 2 . The surface microstructures and compositions of the AAc grafted PTFE film were characterized with the water contact angle meter, Fourier-transform infrared spectroscopy (ATR–FTIR) and X-ray photoelectron spectroscopy (XPS). Contact angle measurements revealed that the water contact angle decreased from 108° to 41° and the surface free energy increased from 22.1 × 10 −5 to 62.1 × 10 −5 N cm −1 by the grafting of the AAc chains. The hydrophilicity of the PTFE film surface was greatly enhanced. The time-dependent activity of the grafted surface was better than that of the plasma treated film.

The photocatalytic activity and photoconductive characteristics of hydro-oxygenated amorphous titanium oxide (a-TiOx:OH) films prepared using remote plasma enhanced chemical vapor deposition (RPE-CVD) were studied. The a-TiOx:OH films have OH groups, which when exposed to UV irradiation, show high photoconductivity. The photoconductivity is drastically affected by oxygen gas. The results suggest that the recombination states present in the film are non-activated by the OH endings in the dangling bond like the hydrogen endings in hydrogenated amorphous silicon. Oxygen-sensitive photoconductivity is useful for environmental sensor applications.

MgxZn1 − xO films were successfully grown on a-plane sapphire ( 1 1 2 ¯ 0 ) substrates by remote plasma enhanced metalorganic chemical vapor deposition (RPE-MOCVD). Diethyl zinc (DEZn), bis-ethylcyclopentadienyl magnesium (EtCp2Mg) and oxygen plasma were used as source materials. By increasing Mg content in the films, the crystal structure was shifted through a mixed state from wurtzite to rock-salt with no significant segregation. Both optical absorption edges and emission peaks of MgxZn1 − xO films shifted to the higher energy by increasing the Mg content at room temperature, showing an alloy broadening. The Stokes’ shift of wurtzite MgxZn1 − xO alloy films was quantitatively evaluated, resulting in a linear dependence on the absorption edge energy.

Zn1−xCdxO films were successfully grown by remote plasma enhanced metalorganic chemical vapor deposition (RPE-MOCVD) with diethyl zinc, dimethyl cadmium, and oxygen plasma. The Cd composition x in the Zn1−xCdxO films was tuned by changing a flow rate of group-II sources. With increasing the Cd composition x, the crystal structure was changed from wurzite (WZ) to rock-salt (RS). The optical band-gap of the Zn1−xCdxO films with the wurzite structure up to x ≤ 0.7 varied from 3.3 eV down to 1.9 eV.

This paper applies remote plasma processing techniques, remote plasma assisted oxidation (nitridation) RPAO(N) and RP enhanced chemical vapor deposition (RPECVD), developed originally for fabrication of Si MOS devices with deposited SiO 2 , Si 3 N 4 and Si oxynitride alloys to the formation of device-quality GaN MOS devices. Significant improvements in device performance for GaN–SiO 2 interfaces are demonstrated by following an RPAO process step that forms the device interface with an interface nitridation RPAN step prior to the deposition of an SiO 2 dielectric film by RPECVD. On-line Auger electron spectroscopy (AES) is used to monitor interface bonding for different ordering of RPAO and RPAN process steps.

The adhesion of a Mg:Ag cathode to the tris-(8-hydroxyquinoline) aluminum (Alq3) in organic light emitting devices (OLEDs) can be greatly enhanced by a remote plasma treatment of the Alq3 layer using either air or N2 prior to metal deposition. The altered surface properties which lead to increased sticking coefficients of Mg and Ag, as well as enhanced adhesion, are attributed to the introduction of new functional groups into the organic layer, as observed by X-ray photoelectron spectroscopy (XPS). The storage life of the plasma treated devices in air without any capping treatment, as judged by a visible deterioration of the cathode, was increased by approximately five to six times compared to untreated OLEDs. Current–voltage characteristics and EL efficiency, however, were shown to deteriorate for devices incorporating either an air or an N2 plasma treated Alq3 layer. For OLEDs subjected to short treatment times with an N2 plasma, only a very slight increase in the turn-on voltage, of about 0.2 V, was observed. An investigation of black spot formation revealed that an air plasma treatment resulted in a five-fold decrease in the time required for 50% of the device to become non-emissive. N2 treated devices on the other hand, developed black spots at a comparable rate to the non-treated devices. Thus, a short N2 plasma treatment of the Alq3 layer prior to metal deposition improves the adhesion at the interface, thereby reducing the oxidation and degradation of the device through exposure to ambient conditions, particularly in storage.

Remote plasma-assisted nitridation or RPN is demonstrated to be a processing pathway for nitridation of Zr and Hf silicate alloys, and for Al 2 O 3 , as well. The dependence of nitrogen incorporation on the process pressure is qualitatively similar to what has been reported for the plasma-assisted nitridation of SiO 2 , the lower the process pressure the greater the nitrogen incorporation in the film. The increased incorporation of nitrogen has been correlated with the penetration of the plasma-glow into the process chamber, and the accompanying increase in the concentration of N 2 + ions that participate in the reactions leading to bulk incorporation. The nitrogen incorporation as been studied by Auger electron spectroscopy (AES), secondary ion mass spectrometry (SIMS) and X-ray absorption spectroscopy (XAS).

In previous studies, device-quality Si–SiO2 interfaces and dielectric bulk films (SiO2) were prepared using a two-step process; (i) remote plasma-assisted oxidation (RPAO) to form a superficially interfacial oxide (∼0.6 nm) and (ii) remote plasma enhanced chemical vapor deposition (RPECVD) to deposit the oxide film. The same approach has been applied to GaN–SiO2 system. Low-temperature (300 °C) remote N2/He plasma cleaning of the GaN surface, and the kinetics of GaN oxidation using RPAO process and subcutaneous oxidation during the SiO2 deposition using an RPECVD process have been investigated from analysis of on-line Auger electron spectroscopy (AES) features associated N and O. Compared to single-step SiO2 deposition, significantly reduced defect state densities are obtained at the GaN–dielectric interfaces by independent control of GaN–GaOx (x∼1.5) interface formation by RPAO, and SiO2 deposition by RPECVD.

A low-temperature remote plasma-assisted oxidation process for interface formation and passivation has been extended from Si and SiC to GaN. The process, which can be applied to nano-scale structures including quantum dots and wires, provides excellent control of ultra-thin interfacial layers which passivate the GaN substrate, preventing a parasitic or subcutaneous oxidation of the substrate during plasma deposition of SiO2. The remote plasma processing for GaN–SiO2 heterostructures includes: (i) an in situ nitrogen plasma surface clean; (ii) a remote plasma-assisted oxidation for formation of an interfacial GaOx (x=1.5) transition region between the GaN and deposited dielectric; and (iii) a remote plasma-enhanced chemical vapor deposition of an SiO2 dielectric.

Interfacial defect densities are typically two orders of magnitude higher at [III–V]–dielectric interfaces than at Si–SiO2 interfaces. This paper demonstrates GaN devices with significantly reduced interfacial defect densities using a two-step remote plasma process to form the GaN–dielectric interface and then deposit the dielectric film. Separate plasma oxidation and deposition steps have previously been used for fabrication of aggressively scaled Si devices. Essentially, the same 300°C remote plasma processing has been applied to GaN metal–oxide–semiconductor (MOS) capacitors and field effect transistors (FETs). This paper (i) discusses the low-temperature plasma process for GaN device fabrication, (ii) briefly reviews GaN device performance, and then (iii) presents a chemical bonding model that provides a basis for the improved interface electrical properties.

Direct tunneling limits aggressive scaling of thermally-grown oxides to about ∼1.6 nm, a thickness at which the tunneling current at 1 V is ∼1 A/cm2. This paper presents experimental results, supported by interface characterizations and model calculations, which demonstrate that multi-layer or stacked gate dielectrics prepared by remote plasma processing comprised of (i) ultra-thin nitrided SiO2 interface layers, and (ii) either silicon nitride or oxynitride bulk dielectric films, can extend the oxide-equivalent thickness, tox-eq, limit down to ∼1.1–1.0 nm. A similar stacked gate dielectric, which substitutes higher-k oxides such as Zr(Hf)O2–SiO2 ‘silicate’ alloys or Ta2O5 for the nitrides or oxynitride alloys, is projected to further reduce tox-eq to ∼0.6–0.7 nm.

In recent years, silicon oxynitride films have drawn attention as high-quality dielectrics, with decreasing the feature size in the integrated circuits. In this study, we try direct oxynitridation of silicon by remote-plasma-excited nitrogen and oxygen gaseous mixtures at the temperatures between 600°C and 800°C. We investigate the initial growth and bonding structures in the oxynitride films by in-situ X-ray photoelectron spectroscopy (XPS) measurements. With the oxynitridation time, the surface concentration of nitrogen gradually increases, but that of oxygen shows nearly-saturation-behavior after rapid increase in the just initial stage. We found the two peaks derived from both N–Si2 and N–Si3 bonds in the photoelectron spectra of N 1s core levels in the initial stage. With the oxynitridation time, the N–Si3 bonds increase gradually and dominate the nitride bonds in the grown films.

The initial stages of SiC SiO 2 interface formation by low temperature (300°C) remote plasma assisted oxidation (RPAO) have been studied by on-line Auger electron spectroscopy (AES) for flat and vicinal 6H SiC(0001) wafers with Si(0001) and C faces (0001), focusing on (i) interfacial bonding and (ii) oxidation rates for thickness up to about 2 nm.

The initial stage of oxidation of Si by activated oxygen species is investigated in detail based on the measurements by XPS. Thin SiO 2 films were found to grow following the parabolic law and the estimated activation energy of the oxidation rate was about one order of magnitude smaller than that in the thermal oxidation case in a substrate temperature range of 300–500°C, which shows the activated oxygen enhanced the oxidation process. The obtained oxidation rate of a 10 −2 −10 −1 nm/min range is appropriate to realize the atomically controlled interface formation.

The silicon nitride films were obtained by remote plasma enhance chemical vapor deposition (RPECVD) using hexamethyldisilazane or its mixture with ammonia in the range 373–773 K. The correlations between the chemical composition, deposition rates, optical, electrical and structural properties and the growth conditions were established. It was found that the formation of two polycrystalline hexagonal phases SiC and Si3N4 was realized by using pure hexamethyldisilazane as precursor. The ammonia addition in gas mixture leaded to change of the chemical composition and structure of silicon nitride films, namely, the disappearance of carbon-bonding and SiC formation, and the order of hexagonal silicon nitride.

Interfacial properties of Au/PNx/n-InP Schottky junctions and metal-insulator-semiconductor (MIS) diodes formed by a series of in-situ remote plasma processes have been evaluated by measuring electrical characteristics. The in-situ processes consist of removal of native oxide by a H2 plasma, surface modification by a PH3 plasma, deposition of a PNx layer by the use of PH3 and N2 plasma, and subsequent metal evaporation. An effective barrier height of 0.83 eV and a true barrier height of 0.57 eV are observed for the tunnel MIS Schottky junction. An interface state density as low as 1.4 × 1011 eV−1 cm−2 is obtained for the MIS diodes. From the behavior of the true barrier height and the low interface state density, it is suggested that a novel in-situ process is effective in forming an interface of PN x InP structure.

The growth rate dependence of W films on temperature and H 2 pressure, the temperature dependence of their specific resistivity and the thickness dependence of their surface roughness have been investigated for LPCVD, remote plasma CVD with and without separation of the H 2 plasma by a metal grid. Activation energies for these modes are determined. ECR conditions of microwave plasma allow the deposition of blanket W layers with the lowest resistivity among the considered methods.

We are successful in growing Si epitaxial layer below 200°C using remote plasma process. A plasma tube with concentric arrangement was accepted: argon and/or hydrogen plasma excited with rf power were supplied through the outer glass tube, and disilane source gas was introduced through the inner stainless tube. Just before depositing the film, surface cleaning with hydrogen plasma is inevitable. The dependence on the substrate temperature, rf power and gas flow rate has been investigated, giving the experimental conditions suitable for the epitaxial growth.

This paper describes the low-temperature deposition of thin films of silicon oxides, nitrides and oxynitrides by remote PECVD. The remote PECVD process differs from conventional and direct PECVD process in two ways: (a) only a subset of the process reactants and/or diluents are directly plasma excited; and (b) thin film deposition takes place on a substrate that is outside of the plasma glow region. In order to: (a) restrict the multiplicity of reaction pathways, (b) control oxide and nitride stoichiometry; and (c) minimize bonded hydrogen incorporation, the silane reactant is never directly plasma excited. In the context of the remote PECVD process, we discuss: (a) multichamber systems with in-situ process diagnostics and in-situ surface analysis; (b) different deposition protocols; (c) reaction pathways; (d) process gas-substrate reactions; (e) chemical-bonding, and the optical and vibrational properties of the deposited thin films; (e) differences between remote PECVD and thermally grown silicon oxides; and (f) remote PECVD dielectrics in device structures.

ZnO:Sn thin films were deposited onto thermally oxidized silicon substrates using a remote plasma reactive sputtering. Their optical constants (refractive index n and extinction coefficient k) were determined from ellipsometric data recorded over a wide spectral range (0.05–6 eV). Parametrization of ZnO:Sn complex dielectric permittivity consists of a parameterized semiconductor oscillator function describing the short wavelength absorption edge, a Drude oscillator describing free carrier absorption in near-infrared part of spectra and a Lorentz oscillator describing the long wavelength absorption edge and intra-band absorption in the ultra-violet part of the spectra. Using a Mott-Davis model, the increase in local disorder with increasing Sn doping is quantified from the short wavelength absorption edge onset. Using the Wemple-DiDomenico single oscillator model for the transparent part of the optical constants spectra, an increase in the centroid distance of the valence and conduction bands with increasing Sn doping is shown and only slight increase in intensity of the inter-band optical transition due to Sn doping occurs. The Drude model applied in the near-infrared part of the spectra revealed the free carrier concentration and mobility of ZnO:Sn. Results show that the range of transparency of prepared ZnO:Sn layers is not dramatically affected by Sn doping whereas electrical conductivity could be controlled by Sn doping. Refractive index in the transparent part is comparable with amorphous Indium Gallium Zinc Oxide allowing utilization of prepared ZnO:Sn layers as an indium-free alternative.