Method of reducing incidence of stress-induced voiding in semiconductor interconnect lines

Abstract

In a method for forming an interlayer dielectric (ILD) coating on microcircuit interconnect lines of a substrate, the substrate and interconnect lines are annealed prior to deposition of an ILD. A post annealing SiON layer is formed by using plasma-enhanced chemical vapor deposition. The deposition using a plasma formed of nitrogen, nitrous oxide, and silane gases, with the gases being dispensed at regulated flow rates and being energized by a radio frequency power source. The plasma reacts to form SiON which is deposited on a semiconductor substrate. Additionally, during deposition, minor adjustments are made to deposition temperature and process pressure to control the optical characteristics of the SiON layer. The SiON layer is tested for acceptable optical properties and acceptable SiON layers are coated with a SiO,layer to complete formation of the ILD. Once the ILD is formed the substrate is in readiness for further processing. The pre-ILD annealing results in a substantially reduced incidence of stress-induced voiding in the underlying interconnect lines. Furthermore, the pre-ILD annealing can be combined with other advantageous process environments to more significantly reduce the incidence of stress-induced voiding in the underlying interconnect lines. Such combinations include process temperature reduction to below about 380 degrees Celsius and reduction of silane flow rate to less than about sixty standard cubic centimeters per minute.