Pulsed plasma CVD of fluorocarbon thin films [low-k ILDs]

Pulsed PECVD has been used to deposit a range of fluorocarbon films utilizing three different precursors: hexafluoropropylene oxide (HFPO), 1,1,2,2-tetrafluoroethane (C₂H₂F₄ ), and difluoromethane (CH₂F₂). C-1s XPS shows that films from HFPO are dominated by CF₂ groups, films from CH₂F₂ are dominated by C-CF groups, and films from C₂H₂F₄ have significant concentrations of both groups. Gas-phase FTIR has been used to identify the species in each pulsed plasma effluent and the pulsed plasma chemistry has been inferred from them. Large differences in gas-phase effluent species have been found between the three precursors, and a correlation can be drawn between the dominant reactions in a pulsed plasma and the resulting films. Finally, ¹⁹F and ¹³C nuclear magnetic resonance (NMR) spectroscopy has been used to further define the various film structures, and these more detailed structural analyses have been used to correlate specific structural configurations to thermal stability