Reliability of High Temperature I2L Integrated Circuits

Abstract

Silicon based I2 L circuits have survived a life test for over 5000 hours at 340°C without degradation. These chips used aluminum metallization with current densities below 10,000 amp/sq.cm to avoid electromigration failures. The need for a gold based metal system for high temperature applications has lead to the development of Ti-W diffusion barriers which have withstood temperatures of 360°C for longer than 3500 hours without change. MSI integrated circuits with a Ti-W/Au metallization system have withstood stress tests of over 2000 hours at 360°C. Gold hillock formation has been shown to be caused by the compressive strains induced in the gold film by thermal expansion mismatches. The driving force for gold hillock formation may be eliminated by depositing the gold film at elevated temperatures.