Silicon nanoparticles are synthesized by very high frequency Plasma Enhanced Chemical Vapor Deposition (vhf-PECVD) in the gas phase. Pulsed plasmas are used to obtain particles with a narrow size distribution. The role of plasma OFF times is studied to tailor the size of the silicon nanoparticles. Various plasma OFF times are chosen, both longer- and shorter -than the residence time of the gases in the discharge. Time resolved optical emission spectroscopy (TROES) studies provide additional information about the growth precursor dynamics during plasma modulation. The size and the size distribution studies of the particles are done with transmission electron microscopy (TEM). These studies reveal that a plasma OFF time longer than the residence time is favorable for the formation of quantum sized silicon particles.

We have been interested in the plasmonic properties of alternative conducting materials to metals, such as conducting oxides, and we have recently expanded our studies to include highly correlated oxides, such as vanadium dioxide (VO2) thin films. VO2 exhibits a metal-insulator transition (MIT) just above ambient temperature at ∼ 340K. Interestingly, this transition can be induced thermally, optically or applying electric fields. Across the MIT, the optical properties are completely modified over a broad frequency range. We will present our recent optical investigations on the photon induced transition studies on such films, as well as the surface plasmon resonance (SPR) modulation in nanopatterned Au gratings by the thermally induced MIT in VO2 thin films, addressing possibilities of ultrafast SPR modulation with VO2.

We report the preparation of nanomasks for silicon plasma etching, which is not based on full top-down approaches such as conventional lithographic process. We used laterally phase separated polymers thin films (30 to 100 nm thick) obtained from immiscible polymer blends of poly(styrene) PS and poly(lactide) PLA, PS being the major component, spin-coated onto silicon substrates. Despite the high incompatibility of the two polymers, submicronic domains were obtained in the film. The selective extraction of the minor component (PLA) led to the formation of a perforated layer of PS at the top of the silicon substrate, and was used as a mask for the selective etching of the silicon. For that purpose, we used a cryogenic etching process where the silicon substrate was cooled at a cryogenic temperature (∼ -120°C) and exposed to a monocyclic SF6/O2 plasma. It was possible to etch anisotropic profiles with vertical sidewalls and minimal defects. Etched feature with an aspect ratio of 7 were obtained in these conditions. We determined that the selectivity of etching (Si/PS) was 11:1, with a silicon etching rate of 0.8 µm/min. The selectivity of these masks was further increased when using the inorganic replicas of the polymer template (50:1) or with chemical modifications of the PS by RuO4 (80:1), allowing for increased aspect ratio etched features (up to 20 in the latter case). Optimized etching processes (such as STiGer process) were also used in order to improve the reproducibility and robustness of the method.

The purpose of the present paper is to investigate the composition of the coating formed on the plasma reactor walls after an industrial process which is divided into two steps, where the chemistries used are CF4/CH2F2 followed by HBr/O2. Since Fluorine traces have been detected through the plasma and over the wafer even during the second chemistry, investigations of the Br-F chemistry duality for a new silicon etching process have been performed in order to see the reactions which are taking place inside of the reactor. The understanding of these formations is really important to avoid process instabilities and get better performance of the transistors. The coating on the walls after the process and after the cleaning between wafers has been characterized in order to figure out the level of F traces after each step and to understand the reminiscence of this element over time. This study is the starting point to propose a modification on the Waferless AutoClean (WAC) used nowadays in an industrial process.

Thin tantalum nitride films were grown on fused quartz by reactive high power impulse magnetron sputtering (HiPIMS) while varying the fractional N2 flow rate at fixed substrate temperature of 400°C. The film properties were compared to films grown by conventional dc magnetron sputtering (dcMS) at similar conditions. Structural characterization was carried out using X-ray diffraction and reflection methods. The HiPIMS process produces slightly less dense films than does dcMS and the surface roughness is similar for both the HiPIMS and dcMS grown films. The deposition rate for HiPIMS is up to 80 % lower than for dcMS but it can be roughly doubled by lowering the magnetic field strength by 30 %.