Thickness dependent glass transition temperature of PECVD low-k dielectric thin films: effect of deposition methods

Low-k dielectric carbon-doped silicon dioxide films created by Plasma Enhanced Chemical Vapor Deposition (PECVD) using a six-station sequential deposition system exhibit different glass transition behavior from films created by PECVD in a single deposition station. The enhanced glass transition temperature (T_g) for the PECVD thin films of a layer consisting of six sub-layer deposited in a six-station sequential deposition system to the T_g for films of a single layer deposited in a single deposition system is traced back to the introduced film interface effect inherent to the different deposition methods. Both types of PECVD thin films range in thickness from 50 to 1255 nm and show an increasing T_g with decreasing film thickness. The observed glass transition behavior for films with six sub-layers can be well explained by a theoretical model of thickness dependent T_g for multiple sub-layers obtained by modifying the currently existing theoretical model for the single layer thickness dependent T_g behavior, which explains the observed thickness dependent T_g for single layer PECVD thin films.