H-termination effects on initial growth characteristics of W on Si using WF₆ and SiH₄ gases

Abstract
Selective growth of W on the Si(100) surface at ~l00°C in a WF₆ and SiH₄ mixture was investigated using a cold-wall low-pressure CVD system. It is found that W film grows by preheating on the wet-cleaned substrate after an incubation period, which becomes shorter on the Si surface which has a lower hydrogen concentration. W nucleus formation before the film growth is also enhanced and the nuclei on the Si surface which has a lower hydrogen concentration are of a higher density and a smaller size. Even before the nucleus formation, the W atom is adsorbed and the adsorption rate on the Si surface which has a lower hydrogen concentration is higher than that which has a higher one. Consequently, hydrogen desorption from the Si surface enhances the W atom adsorption, and after adsorption of a certain concentration of W atoms, the W nucleus formation and growth start.