Growth processes of epitaxial metal films on semiconductor and insulator substrates by ionized cluster beam

Abstract

Ionized cluster beam (ICB) deposition allows one to grow thermally and electrically stable films on semiconductor substrates. One of the unique characteristics of ICB deposition is that the epitaxial metal films can be grown at room temperature on a substrate with lattice misfits larger than 25%. This is possible because of the flexible control of the film growth process by ICB bombardment. Our investigations on the nucleation and growth processes at the early stage of ICB deposition showed that the ICB bombardment increases the density of the nucleation sites and enhances adatom migration. The special film formation mechanisms by ICB lead to the transformation of the growth morphology from three-dimensional growth to layer-by-layer growth, and enable the formation of a stable metallic film at an early stage of deposition. As a consequence, the epitaxial metal films deposited by ICB have a unique and stable structure and exhibit excellent thermal stability. These features were clarified by detailed RMEED, AES, XPS and TEM analyses of the epitaxial Al, Au and Cu films deposited on Si substrates.