High frequency AC electromigration lifetime measurements from a 32nm test chip

Abstract

A test circuit for studying Electromigration (EM) effects under realistic high frequency AC stress was implemented in a 32nm High-k Metal Gate (HKMG) process. Four different stress patterns (DC, pulsed DC, square AC and real AC) can be generated using on-chip circuits. Local heaters are used to raise the die temperature to >300°C for accelerated testing. Experiment results over 52.7 hours show no AC stress induced failures under 325°C, 1.5V (driver supply) at 200 MHz and 900 MHz. However, the pre-AC stress had an impact on the DC EM distribution.