%0 Journal Article
%T Characterization of the Chemical Kinetics in an O2/HMDSO RF Plasma for Material Processing
%A Ruggero Barni
%A Stefano Zanini
%A Claudia Riccardi
%J Advances in Physical Chemistry
%D 2012
%I Hindawi Publishing Corporation
%R 10.1155/2012/205380
%X Experimental study of the plasma gas phase in low-pressure radiofrequency discharges of oxygen and hexamethyldisiloxane is presented. The plasma phase has been studied by means of optical emission spectroscopy. Mass spectroscopy of the neutral and of the charged species has been performed too, directly sampling the plasma gas phase, by a dedicated spectrometer. We also measured the ion energy distribution. We have studied the influence of the operating conditions on the plasma gas-phase composition which plays a primary role in the formation process of SiO2 films, which are known for their important applicative uses. 1. Introduction Plasma-enhanced chemical vapour deposition (PECVD) of silicon oxides is one of the most promising techniques allowing industrial-scale deposition of high-quality, transparent, and thin coatings [1, 2]. SiO2-like films deposited by plasma polymerisation was first developed for microelectronics. Then, they have been applied also as protective coatings in optoelectronics and packaging [3]. The most favourable option is to use organosilicon compounds as precursor, like hexamethyldisiloxane (HMDSO) mixed with O2 and/or noble gases. It was found that composition and structure of films change with the deposition conditions [1]. A systematic control of plasma is then needed to obtain films with the desired properties. Better understanding of the chemical kinetics processes happening in the discharge is then mandatory and requires suitable diagnostics to probe directly the plasma gas phase. Previous investigations employed mass spectroscopy (MS), optical emission spectroscopy (OES), and infrared absorption spectroscopy (FT-IR) [1, 4¨C7]. However, many points are still open, for instance, concerning the role of ions in the gas phase, the deposition and the film growth process [1]. We have investigated O2/HMDSO plasmas produced by a resonant inductive radiofrequency (RF) plasma source and used to deposit SiO2-like films on polyethylene terephthalate (PET). Diagnostics include OES and on-line MS of neutrals and ions from the discharged gas phase. Our mass spectrometer allows to change the electron energy in the ionization source, in order to better identify the parent radical sampled from the plasma. We were able to measure also ion energy spectra. The properties of the film have been studied by attenuated total reflectance infrared (ATR) spectroscopy, electron microscopy, and by contact angle measurements. 2. Experimental Setup and Diagnostics A scheme of the setup is shown in Figure 1. The plasma source was developed by CCR
%U http://www.hindawi.com/journals/apc/2012/205380/