Multilayer passivation process for forming air gaps within a dielectric between interconnections

Abstract

A process for forming air gaps within an interlayer dielectric is provided to reduce loading capacitance between interconnections. A first dielectric layer is deposited on the spaced interconnections. This first dielectric layer is deposited more thickly at the top sides than at the bottom sides of the interconnections. A second dielectric layer is deposited on the first dielectric layer to a controlled thickness that causes formation of air gaps therewithin between the interconnections. The poor step coverage of the first dielectric layer makes it easier to form the air gaps. Air gaps between interconnections allows reduced permittivity of the overall dielectric structures and thereby reduces the interconnect line to line capacitance, and increases the possible operation speed of the semiconductor device.