Biaxial stress analysis in laminated polymer films on silicon substrates for MCM-D application

Abstract

Thermo-mechanical stress in MCM-D substrate is an important reliability and fabrication issue. The difference in coefficient of thermal expansion (CTE) between substrate, polymer, and metal leads to complicated stress fields in multilevel interconnect structures. A simple model which predicts a stress contribution from each individual layer during MCM-D substrate fabrication is proposed and verified through experiments and numerical analysis. the-composite stress or bowing in multilayer structures is due to the contribution from each individual layer. This study uses materials set employed in a typical lamination based MCM-D technology to monitor the stress level in the thin film layers of polymer. Mechanical test structures consist of single or multilayer polymer films are fabricated on silicon wafers. The substrate deflection caused by composite stresses due to fabrication and thermal cycling is determined by a curvature measurement technique.