Semiconductor device using uniform nonconformal deposition for forming

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 deposition of the nonconformal source material is stopped and a flowable insulating material, such as spin on glass, is coated on nonconformal insulating material to fill the remaining gaps. After etching the surfaces of the nonconformal and flowable insulating materials, another insulating layer is deposited and planarized to the desired overall thickness of the insulation. 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 substantially all of the remaining gaps are filled with the flowable insulating material and are void free with a composite dielectric constant of greater than about 3.5.