Method to Reduce Mechanical Stress Within the Emitter of Bipolar Transistors
Original Publication Date: 1985-Sep-01
Included in the Prior Art Database: 2005-Feb-19
A refractory-metal silicide-emitter contact is used to minimize electromigration-induced stress within the emitter of bipolar transistors. In the presence of a flux divergence, metal stripes undergoing electromigration produce a considerable mechanical stress. This stress has been shown to cause a time-dependent change in the current gain (beta) during forward bias and has been shown to be a potential reliability problem, especially for small geometry devices. In the future, as geometries become smaller and smaller, the elimination of this stress may become essential for device performance. One way to eliminate or reduce such stress is to use a material with slower diffusivity than the Al/Cu now employed, since the emitter contact is a site of unavoidable flux divergence.