Modification of Al-based metallization for improved surface morphology

Abstract

Aluminum and some of its alloys are commonly used as metallization for silicon integrated circuits. Due to miniaturization, the critical dimensions of metallization such as line width, contact or via area in ULSI devices, are now approaching the size of a grain in the polycrystalline Al film. Particularly unwanted are hillocks i.e. large grains that outgrow above the initial Al surface. It is generally accepted that hillock growth is related to plastic flow and grain boundary diffusion where the supply of atoms takes place at the bottom of the hillock. The aim of this work is to investigate the possibilities of reduction of the density and/or the size of the hillocks by introducing into the metallization adequate barriers suppressing the grain boundary diffusion.