Elimination of Tungsten-voids in middle-of-line contacts for advanced planar CMOS and FinFET technology

Abstract

As dimension of middle-of-line contacts scale down, the Tungsten (W) gap-fill capability is critical, and we started to see function failure in SRAM and logic circuit caused by W-voids. We had observed that formation of W-voids is related to the contact profile, nucleation/barrier on sidewall, and deposition methods. Furthermore, even those initially “good” W-plugs are formed, the subsequent process steps may damage the W-plug and cause voids. These W voids lead to high resistance and failures in logic and SRAM circuit (see Fig.1). We analyzed mechanisms and illustrated solutions systematically with in-line detection method. We also discussed these solutions for technology development as well as manufacturing in this paper.