Low Dielectric Constant Functionalized Silica Gels

Scaling requirements of the semiconductor industry demand interlayer dielectric materials with low dielectric constants, chemical compatibility with Cu, thermal and mechanical stability, and the capability of integration into planned device structures. We have developed a novel low-k silica gel processing technique capable of both bulk and spin-on film architectures. Derived from fluorinated silica, this gel exhibits very low dielectric constants (1.18 in bulk and 2.1 in thin film measured using AC impedance methods). Structural determination from FTIR illustrates a fluorinated silica structure with shortened Si-O bonds, however, the fluorine is lost after annealing at elevated temperatures. Microstructural analysis by TEM indicate a highly unusual morphology with highly linked features and pore sizes in the 30nm range, coinciding with nitrogen adsorption results. Mechanical properties of the thin films, as studied by nanoindentation methods, shows that the films have extraordinarily high elastic moduli (12GPa) and hardness (1GPa).