Numerical simulation of thick metal passivation stress, Part I: Identification of stress source

Abstract

Standard design passivation layers on thick (> 3000 nm) top metalization has a susceptibility for cracking due to thermal stress. In this two part series of papers, Finite Element Analysis (FEA) simulation with Comsol Multiphysics was used to understand the impact of thermal stress. In Part I (this paper), three different thermal stress conditions were investigated i.e. cool down after Chemical Vapor Deposition (CVD), the increase, and the decrease in temperature during temperature cycling. The highest stress was realized during the increase in temperature during temperature cycling. This was due to the L shaped spatial profile of the passivation design which resulted in an increased Stress Intensity Factor (SIF), more than the temperature difference between the temperature levels seen in CVD.