Bias plasma deposition for selective low dielectric insulation

Abstract

A method of forming low dielectric insulation between those pairs of conductive lines, of a level of interconnection for integrated circuits, having a gap of about 0.5 microns or less by depositing a nonconformal source with a poor step function for the insulating material, such as silane (SiH.sub.4) as the silicon (Si) source for silicon dioxide (SiO.sub.2), so as to create, in the gap, a large void whose dielectric constant is slightly greater than 1. After the formation of the void in the 0.5 microns or less gaps, the deposited nonconformal material is etched either simultaneously or sequentially along with deposition to fill the remaining gaps with void free insulation. The surface of the deposited insulating material is planarized at the desired thickness. Alternatively, a thin conformal insulating layer is first deposited as a liner on the conductive lines. The resulting structure of the interconnection level comprises a layer of insulation between and on the conductive lines with the dielectric constant of the insulation between the pairs of conductive lines with gap of 0.5 or less being, in combination with the void, at least about 3 or lower, and all of the remaining gaps are filled with void free insulating material with a dielectric constant of greater than about 3.5.