| The ability to systematically vary the amount of plasma-surface interaction for any given plasma process can provide a novel approach to controlling the gas-phase plasma chemistry, the physical parameters of the plasma and the reaction pathways which govern etch and deposition at the sample surface. In this dissertation, such systematic methods to control plasma-surface interactions are explored during the processing of silicon, silicon dioxide (SiO2 ), polydimethyl siloxane (PDMS) and porous methylsilsequioxane (p-MSQ) films. These methods include processing as a function of chamber wall temperature, chamber dimension, feedgas chemistry, and sample porosity while simultaneously measuring the plasma gas-phase chemistry, the plasma density, and the reactions which occur on the sample surface, to determine how each effects the plasma system as a whole.; When processing as a function of chamber wall temperature, results in tetrafluoromethane plasma show that increasing wall temperature decreases CF4 density while concurrently increasing CF4 vibrational temperature. The line-averaged vibrational temperature however, was found to remain at a steady state value above the chamber wall temperature while the CF4 vibrational temperature in the center of the discharge was calculated to be significantly higher. Using a modified gaseous electronics conference (GEC) reference cell, chamber dimension was found to significantly effect the etch rate of silicon dioxide as well as the fluorocarbon deposition rate due to variations of ion density and neutral flux. Specifically, low-energy ion assisted deposition was found to be the predominant mechanism governing fluorocarbon deposition while ion loss as a function of dimension, was established to be the rate limiting step for high energy reactive ion etch.; The role of feedgas chemistry on plasma-surface interactions was also explored and revealed how different ratios of O2:CF 4 gas mixtures can significantly modify the processing rates and sample surface chemistry of a hybrid polydimethylsiloxane material. Depending on the percentage of oxygen admixed in the tetrafluoromethane feedgas, the etch could be tailored from energy dependent to energy independent. Tweaking the process in an inductively coupled plasma further improved the etch rate such that it was twice as high as those published in a capacitive plasma process. The resultant stoichiometry of the etched films was also found to depend on the feedgas chemistry as the refractive index of the material increased by 7% when pure oxygen was used and decreased by 6% when pure tetrafluoromethane was used. (Abstract shortened by UMI.)... |
