Reliability Study of Interconnect Structures in IC Packages

This paper will focus on reliability study of interconnect structure for two areas. The first area is reliability of interconnect structure in thermal cycling test. Major work includes the fundamental study of ratcheting for passivation cracking. By combination with the upper limit of stress intensity factor for a finite crack in the passivation and the ratcheting failure mechanism, the life of passivation in thermal cycling can be obtained in terms of the lower bound of critical number of cycles of the crack initiation. The passivation crack criterion is established to identify the failure modes: no cracking and delayed cracking. Another area is the reliability of bond paid over active (BPOA) with copper bond pads. Major work includes stress analysis of the dielectric layer under probing with different parameters such as the thickness of the copper bond pad, dielectric, metallization and the passivation under different probing loads. The elastic plastic model in copper bond pad and metal lines are introduced. Finally comparison of the results between copper bond pad and aluminum bond pad will be presented