ILD thermal stability in deep-submicron technologies: from thin to ultrathin dielectric films

Abstract

Thermal stability is a critical issue for polymer thin films being used as interlevel dielectrics (ILDs) in deep-submicron multilevel interconnection. One of crucial parameters to predict thermal stability is the glass transition temperature (Tg). Unfortunately the glass transition in polymer thin films is still not clearly understood. In this work, a simple model is developed for the thickness dependence of Tg ofpolymer thin and ultrathin films. It is predicted that Tg ofpolymer thin films can either be reduced or enhanced in comparison with its bulk values, depending on the polymer-substrate and polymersurface interactions. In addition, the thickness-dependent Tg of polymer thin films can exhibit a minimum as a function of thickness. Experimental data from technologically important ILD films are obtained to support the theoretical model.