Source Gas Dependency of Amorphous Fluorinated Carbon Film Properties Prepared by Plasma Enhanced Chemical Vapor Deposition Using C4F8, C4F6, and C5F8 Gases

Abstract

Amorphous fluorinated carbon (a-C:F) films with low-dielectric constant were prepared using plasma enhanced chemical vapor deposition (PECVD) from C4F8 (octafluorocyclobutane) gas, C4F6 (hexafluoro-1,3-butadiene) gas, and C5F8 (octafluorocyclopentene) gas. C4F8 is now mainly used in ultra large scale integrated (ULSI) processes, and C4F6 and C5F8 are expected to be substitutional gases in these processes due to their low global warming potential (GWP). Here, the effect of C–CF bond ratio in a-C:F films on the dielectric constant and thermal stability of the films was studied. In all the films, both the orientational polarization and total dielectric constant decreased with decreasing C–CF bond ratio. High C–CF bond ratio of the film, however, resulted in higher residual film thickness after vacuum annealing. Based on these results, films with low dielectric constant that also have thermal and mechanical stability are difficult to achieve. Stable film properties, such as leakage current, at high temperature is not less related to the C–CF bond ratio than to the parent gas.