SPATIAL-DISTRIBUTION OF CU SPUTTER EJECTED BY VERY-LOW ENERGY ION-BOMBARDMENT

Filling of submicron width trenches with Cu from a highly ionized plas ma is sensitive to both the directionality of the depositing flux and reflection and resputtering at the film surface. The spatial distribut ions of Cu atoms sputtered by He+, Ar+, and Xe+ ions incident at 30 de grees, 45 degrees and 60 degrees and over an ion energy range of simil ar to 55-600 eV have been investigated. In all cases, the distribution is forward directed and cannot be described by a cosine distribution about the surface normal. Decreasing energy, increasing angles of inci dence, and increasing ion mass yield more forward directed distributio ns. For similar to 55 eV Ar+ incident at 60 degrees, similar to 85% of the resputtered flux is in the forward direction. From these distribu tions, in a 50% ionized physical vapor deposition system the depositin g flux due to forward directed resputtering is estimated to be of the same order of magnitude as the neutral flux. (C) 1997 American Institu te of Physics.