Effect of Cu Line Capping Process on Stress Migration Reliability

Abstract

Effect of Cu capping layer processes on stress-migration (SM) is discussed in this paper. Co cap was demonstrated to reduce the failure rates of SM, presumably owing to its suppression of vacancy surface migration under stress gradient. Although formation of CuSix improved the adhesion between copper and dielectric capping layer, its SM performance was degraded and failure rates increased accordingly. It was hypothesized that introducing silicon into Cu would generate excess vacancies for CuSix process.