Bulk resist degradation under O2 or Ar plasma exposure is experimentally demonstrated. The degradation mechanisms are analyzed in Ar plasma and a synergistic effect of ion bombardment is presented. Mechanical effects of ion bombardment lead to a surface degradation of the resist whereas thermal effects allow the extension of the degradation to the bulk. Self-diffusion of chains is demonstrated which clearly emphasizes the role of the viscoelastic properties in polymer degradation.

The electrochemical oxidation of porous silicon layers formed on lightly p-doped substrates in aqueous electrolytes has been studied in detail. Two different oxidation regimes are observed, depending on the presence of a native oxide on the silicon pore walls. When anodic oxidation is performed on samples previously dried in air, a thin oxide layer is already present and the oxidation regime is determined by the transport of the oxidizing species across the oxide. In this regime, the anodic polarization accumulates the majority charge carriers in the whole depth of the pore walls, and oxidation proceeds homogeneously throughout the whole porous layer. If an experimental procedure which prevents native oxide formation is used, the oxidation process is governed by hole supply at the silicon-electrolyte interface, and preferential oxidation of the bottom of the porous layer is obtained at low anodic current densities. The electrochemical oxidation stops before complete oxidation because the electrical contact between the bulk and the partially oxidized porous layer is cut by the formation of a continuous oxide at the bottom of the porous layer. The oxidized thickness obtained before this break increases with the current density, and the whole thickness can be oxidized if the oxidation current density is greater than the value which corresponds to hole accumulation in the whole depth. However, homogeneous oxidation of the layer never corresponds to complete oxidation, and at the end of the anodization process about 40% of silicon atoms in the porous layer are unoxidized, and form tiny silicon microcrystallites distributed throughout the oxidized porous film.

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Tungsten films were deposited on Si substrates by the H2 or Si reduction of WF6 under various experimental conditions. The composition and structure of as-deposited samples as well as the interfacial reactions and interdiffusion of elements in annealed samples were characterized by nuclear reaction analyses, sheet resistance measurements, x-ray diffraction technique, and Rutherford backscattering spectroscopy. The amount of oxygen at W–Si interfaces was found to be dependent on the cleaning treatment of the Si surface used before WF6–Si interaction. The interfacial oxygen concentration was less than 1 ⊠ 1014 at./cm2 (detection limit of the nuclear reaction analysis) and (2–7) ⊠ 1016 at./cm2 using an HF cleaning and the RCA treatment, respectively. For W/Si samples, the formation temperature of WSi2 was dependent on the dopant level in the Si substrates and the oxygen concentration at W–Si interfaces. The silicidation reaction occurred at 625 °C in “oxygen free” W/Si structures while for structures containing interfacial oxygen atoms, this reaction occurred above 800 °C. In Al/W/Si structures, the intermetallic compound, WAl12, was formed by annealing at 450 °C for 90 min. Furthermore, the formation of WSi2 was observed in structures annealed at a temperature in the range of 550 °C–600 °C regardless of the oxygen concentration at the W–Si interface. A model to explain the effect of interfacial oxygen atoms on the silicidation reaction and the influence of the Al overlayer on the thermal stability of Al/W/Si structures is proposed and discussed in this paper.