[en] The corrosion of metals is associated both with a release of ions and changes in optical surface properties. In this study, these two effects were correlated by a potentiodynamic corrosion test and in situ probing of the surface by ellipsometry. The studies were carried out with stainless steel (SS) AISI 304 and 316 in phosphate buffered saline (PBS) and in Dulbecco's modified minimal essential medium (DMEM) at pH 7.4. In both media, 304 steel is more susceptible to corrosion than 316 grade. The 316 steel shows a higher corrosion potential and higher corrosion current density in PBS than in DMEM, for 304 steel this behavior is vice versa. Ellipsometry demonstrated a higher sensitivity than potentiodynamics to surface modification in the cathodic area. In DMEM the removal of a surface layer at negative potential and a further repassivation with increasing potential was characteristic. In PBS a surface layer started to grow immediately. X-ray photoelectron spectra of this layer formed in PBS are consistent with iron phosphate. Its formation is inhibited in DMEM; the presence of amino acids is discussed as the reason

[en] Ion nitriding of Al has been performed by a nitrogen reactive ion beam using a hot filament ion source. The N incorporation and loss has been determined at a beam energy of 1.6 keV with two ion current densities of 0.1 and 0.2 mA/cm², and a substrate temperature of 350 deg. C. For this purpose, the ion beam has been characterised by an energy selective mass spectrometer, showing solely of N₂⁺ and N⁺ ions with a composition of about 80% and 20%, respectively. The ion energy distributions of both N₂⁺ and N⁺ consist of a single narrow peak with a full width at half maximum of about 10 eV. From the beam parameters, N loss due to sputtering and backscattering has been calculated using dynamic binary collision computer simulations. After an initial transient, the stationary partial sputtering yield of N is predicted to be 0.43, while the amount of backscattered N is about 4% of the incident N fluence. The total amount of incorporated N measured by nuclear reaction analysis (NRA) is consistent with the incident N fluence and the N loss obtained from the simulation

[en] The surface chemistry of silicon bombarded at low temperature with a beam extracted from a SF₆ microwave plasma has been studied using quasi in situ X-ray photoemission spectroscopy. At 123 K and when no ions strike the surface, strong adsorption of neutral SF_x species generated in the plasma is observed. In these conditions, physisorbed SF₃ and SF₄ species are detected but the presence of SF₆ molecules is not observed. Increasing the ion energy to 360 eV and the ion current density to 650 μA cm^-2 allows to desorb the adsorbed species and to maintain the adsorbed layer well below 75 Angstroms. At room temperature, the presence of chemisorbed sulfur, chemisorbed SF₃ radicals and physisorbed SF₄ species is observed for 60 eV and 5 μA cm^-2 ion bombardment conditions. Physisorbed SF species and chemisorbed sulfur are detected after ion bombardment at 360 eV and 650 μA cm^-2. During these different experiments, the presence of Fe and Cr due to the contamination of the beam is also observed. Results of this XPS analysis are correlated with etch rates measurements presented in a previous work. The role of ion-stimulated desorption and ion-induced reaction mechanisms on the silicon surface chemistry is discussed

[en] This paper reviews recent progress in the development of time-resolved diagnostics to probe high-density pulsed plasma sources. We focus on time-resolved measurements of radicals' densities in the afterglow of pulsed discharges to provide useful information on production and loss mechanisms of free radicals. We show that broad-band absorption spectroscopy in the ultraviolet and vacuum ultraviolet spectral domain and threshold ionization modulated beam mass spectrometry are powerful techniques for the determination of the time variation of the radicals' densities in pulsed plasmas. The combination of these complementary techniques allows detection of most of the reactive species present in industrial etching plasmas, giving insights into the physico-chemistry reactions involving these species. As an example, we discuss briefly the radicals' kinetics in the afterglow of a SiCl₄/Cl₂/Ar discharge. (paper)

[en] In this paper, we demonstrate a top-down fabrication technique for nanometre scale silicon carbide (SiC) pillars using inductively coupled plasma etching. A set of experiments in SF₆-based plasma was carried out in order to realize high aspect ratio SiC nanopillars. The etched SiC nanopillars using a small circular mask pattern (115 nm diameter) show high aspect ratio (7.4) with a height of 2.2 µm at an optimum bias voltage (300 V) and pressure (6 mTorr). Under the optimal etching conditions using a large circular mask pattern with 370 nm diameter, the obtained SiC nanopillars exhibit high anisotropy features (6.4) with a large etch depth (>7 µm). The etch characteristic of the SiC nanopillars under these conditions shows a high etch rate (550 nm min^-1) and a high selectivity (over 60 for Ni). We also studied the etch profile of the SiC nanopillars and mask evolution over the etching time. As the mask pattern size shrinks in nanoscale, vertical and lateral mask erosion plays a crucial role in the etch profile of the SiC nanopillars. Long etching process makes the pillars appear with a hexagonal shape, coming from the crystallographic structure of α-SiC. It is found that the feature of pillars depends not only on the etching process parameters, but also on the crystallographic structure of the SiC phase. (paper)

[en] A generic, CMOS compatible strategy for transferring a block copolymer template to a semiconductor substrate is demonstrated. An aluminum oxide (Al₂O₃) hard mask is selectively deposited by atomic layer deposition in an organized array of holes obtained in a PS matrix via PS-b-PMMA self-assembly. The Al₂O₃ nanodots act as a highly resistant mask to plasma etching, and are used to pattern high aspect ratio (>10) silicon nanowires and nanopillars.

[en] A Cl₂-HBr-O₂/Ar inductively coupled plasma (ICP) etching process has been adapted for the processing of InP-based heterostructures in a 300-mm diameter CMOS etching tool. Smooth and anisotropic InP etching is obtained at moderate etch rate (∼600 nm/min). Ex situ x-ray energy dispersive analysis of the etched sidewalls shows that the etching anisotropy is obtained through a SiO_x passivation mechanism. The stoichiometry of the etched surface is analyzed in situ using angle-resolved x-ray photoelectron spectroscopy. It is observed that Cl₂-based ICP etching results in a significantly P-rich surface. The phosphorous layer identified on the top surface is estimated to be ∼1-1.3-nm thick. On the other hand InP etching in HBr/Ar plasma results in a more stoichiometric surface. In contrast to the etched sidewalls, the etched surface is free from oxides with negligible traces of silicon. Exposure to ambient air of the samples submitted to Cl₂-based chemistry results in the complete oxidation of the P-rich top layer. It is concluded that a post-etch treatment or a pure HBr plasma step may be necessary after Cl₂-based ICP etching for the recovery of the InP material.

[en] Plasma etching of HfO₂ at an elevated temperature is investigated in chlorine-based plasmas. Thermodynamic studies are performed in order to determine the most appropriate plasma chemistry. The theoretical calculations show that chlorocarbon gas chemistries (such as CCl₄ or Cl₂-CO) can result in the chemical etching of HfO₂ in the 425-625 K temperature range by forming volatile effluents such as HfCl₄ and CO₂. The etching of HfO₂ is first studied on blanket wafers in a high density Cl₂-CO plasma under low ion energy bombardment conditions (no bias power). Etch rates are presented and discussed with respect to the plasma parameters. The evolution of the etch rate as function of temperature follows an Arrhenius law indicating that the etching comes from chemical reactions. The etch rate of HfO₂ is about 110 A /min at a temperature of 525 K with a selectivity towards SiO₂ of 15. x-ray photoelectron spectroscopy analyses (XPS) reveal that neither carbon nor chlorine is detected on the HfO₂ surface, whereas a chlorine-rich carbon layer is formed on top of the SiO₂ surface leading to the selectivity between HfO₂ and SiO₂. A drift of the HfO₂ etch process is observed according to the chamber walls conditioning due to chlorine-rich carbon coatings formed on the chamber walls in a Cl₂-CO plasma. To get a very reproducible HfO₂ etch process, the best conditioning strategy consists in cleaning the chamber walls with an O₂ plasma between each wafer. The etching of HfO₂ is also performed on patterned wafers using a conventional polysilicon gate. The first result show a slight HfO₂ foot at the bottom of the gate and the presence of hafnium oxide-based residues in the active areas