Assessing the degradation mechanisms and current limitation design rules of SiCr-based thin-film resistors in integrated circuits

The degradation of SiCr-based thin-film resistors under current and temperature stress and the Joule heating in the resistors are experimentally investigated to set current limitation design rules. Degradation mechanisms, the failure modes, and the impact of the stress test on Temperature Coefficient of Resistance (TCR), are studied with the use of various test structures stressed under different conditions (temperature, current density and direction), followed by optical inspections, Infra-Red imaging and SEM/TEM cross-sections. Electromigration (EM) is found to be the dominating degradation mechanism, but the EM process differs from that in commonly used interconnects. Current accelerating factor and the equivalent activation energy are determined for data extrapolation. To avoid errors in Joule-heating determination from TCR, integrated temperature sensors are employed. Current limitation design rules are deduced based on the EM and Joule heating results.