PLASMA PARAMETERS AND SiO2 ETCHING KINETICS IN C4F8 + Ar + O2 GAS MIXTURE

The effect of Ar/O2 mixing ratio on plasma parameters, steady-state densities of active species and SiO2 etching kinetics in the three-component C4F8+Ar+O2 gas mixture was studied under typical conditions of reactive ion etching process (inductive 13.56 MHz RF discharge, total gas pressure of 6 mTorr, input power of 700 W and bias power of 200 W). The investigation combined etching rate measurements, plasma diagnostics by Langmuir probes and 0-dimensional (global) plasma modeling in order to determine steady-state densities and fluxes of plasma active species. It was found that the full substitution of Ar for O2 at constant fraction of fluorocarbon gas (in fact, the transition from 50% C4F8 + 50% Ar to 50% C4F8 + 50% O2 gas system): 1) results in weakly non-monotonic (with a maximum) SiO2 etching rate with close values for both O2-free and Ar-free plasmas; 2) causes the monotonic decrease in both F atom flux and ion energy flux; and 3) suppresses the formation of the fluorocarbon polymer film on the etched surface through its oxidative destruction pathway. The model-based analysis of SiO2 etching kinetics allowed one to conclude that an increase in effective probability for SiO2 + F reaction contradicts with the behavior ion energy flux as well as demonstrate the agreement with the change in gas-phase parameters characterizing the fluorocarbon film thickness. Therefore, an increase in O2 content in a feed gas influences the effective reaction probability by decreasing fluorocarbon film thickness and providing better access of F atoms to the etched surface.

Effect of Sputtering Temperature on Fluorocarbon Films: Surface Nanostructure and Fluorine/Carbon Ratio

In this work, fluorocarbon film was deposited on silicon (P/100) substrate using polytetrafluoroethylene (PTFE) as target material at elevated sputtering temperature. Field emission scanning electron microscopy (FESEM), atomic force microscopy (AFM), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) were employed to investigate the surface morphology as well as structural and chemical compositions of the deposited film. The surface energy, as well as the polar and dispersion components, were determined by water contact angle (WCA) measurement. The experimental results indicated that increasing sputtering temperature effectively led to higher deposition rate, surface roughness and WCA of the film. It was found that the elevated temperature contributed to increasing saturated components (e.g., C–F2 and C–F3) and decreasing unsaturated components (e.g., C–C and C–CF), thus enhancing the fluorine-to-carbon (F/C) ratio. The results are expected aid in tailoring the design of fluorocarbon films for physicochemical properties.

Enhancing the water repellency of wood surfaces by atmospheric pressure cold plasma deposition of fluorocarbon film

This study explores the fluorocarbon deposition on wood by atmospheric pressure plasma, with the focus on higher water repellency.