Reliability investigations of down-stream copper interconnect with different Tungsten-VIA structures

Abstract

The reliability assessments of tungsten via to copper interconnect were investigated. Three layout schemes of full-landing, just-landing and un-landing via structure showed similar characteristics of electromigration: The activation energy is about 0.8 eV and current density exponent is about 1.9, which means the failure symptoms of interfacial diffusivity and line depletion stress. In this paper, we discussed the relations between mean-time-to-failure and line-end-extension. The lifetime of electromigration is proportional to logarithm of extended spacing, which is attributed to difference of mechanical stress by performing stress migration test. The model was provided a simple reliability assessment of via landing structure for definition of process pitch during technology development that could reduce the chip size and keep good reliability in the same time.