Integration studies of plasma deposited fluorinated amorphous carbon

Recently, we reported the deposition of fluorinated amorphous carbon (FlAC) from hexafluorobenzene (C6F6) under parallel plate (PP) and inductively coupled plasma (ICP-HDP) conditions. Based on initial materials testing, these two platforms generated comparable materials with low dielectric constants (2.4 - 2.8), low weight loss/shrinkage (< 1.5 %/hr. at 425 degrees C), hardness (2-3 Gpa) and adhesion (4-9 kpsi). Here we attempt to answer a basic integration question: FlAC compatibility with other materials used in the interconnect scheme. Investigations of adhesion of FlAC to, and capped by, silicon oxide, silicon nitride and various metals shows generally greater stability of the ICP generated material vs. PP-F;AC. Failures appeared to occur primarily at the FlAC/film interface at 400 and 300 degrees C for ICP and PP respectively. Although thickness-loss and weight-loss measurements indicate good thermal stability, TDS spectra show low-level outgassing of fluorine-based molecules and fragments even in samples annealed for 4 hours at 400 degrees C, resulting in interface failures. Plasma treatments and anneals of the FlAC were found to have a minimal effect but liner/cap composition and processing has a strong influence on the adhesion of other films to the fluorocarbon.