PLASMA-ENHANCED SELECTIVE-AREA MICROCRYSTALLINE SILICON DEPOSITION ONHYDROGENATED AMORPHOUS-SILICON - SURFACE MODIFICATION FOR CONTROLLED NUCLEATION

Selective deposition of mu c-Si on hydrogenated amorphous silicon is d emonstrated using time-modulated silane reactant flow in a low tempera ture plasma enhanced process. Alternating cycles of thin silicon layer deposition and atomic hydrogen exposure result in silicon layers on r eceptive surfaces, with no net deposition on nonreceptive areas of the substrate. Selective deposition could be useful to form self-aligned contacts in hydrogenated amorphous silicon (a-Si:H transistor applicat ions. However, a problem commonly observed in low temperature selectiv e deposition is that the selective process tends to etch amorphous sil icon, harming the devices. We describe a technique involving Mo metall ization that stabilizes the a-Si:H surface with respect to hydrogen pl asma exposure and allows selective mu c-Si deposition on a-Si:H in dev ice structures, while avoiding deposition on the top SiNx insulator ma terial. Surfaces and subsequent selective nucleation and growth were c haracterized using atomic force microscopy, x-ray photoelectron spectr oscopy, and Auger electron spectroscopy, which revealed the presence o f Mo incorporation in the a-Si:H surface remaining after complete remo val of the metal layer. A direct comparison of selective deposition ex periments on films prepared with and without Mo treatment demonstrate that the metallization stabilizes nucleation of microcrystalline silic on on amorphous silicon surfaces. (C) 1998 American Vacuum Society.