Silicon nitride layer deposited at low temperature to prevent gate dielectric regrowth high-k metal gate field effect transistors

Abstract

Standard High-K metal gate (HKMG) CMOS technologies fabricated using the replacement metal gate (RMG), also known as gate-last, integration flow, are susceptible to oxygen ingress into the high-K gate dielectric layer and oxygen diffusion into the gate dielectric and semiconductor channel region. The oxygen at the gate dielectric and semiconductor channel interface induces unwanted oxide regrowth that results in an effective oxide thickness increase, and transistor threshold voltage shifts, both of which are highly variable and degrade semiconductor chip performance. By introducing silicon nitride deposited at low temperature, after the metal gate formation, the oxygen ingress and gate dielectric regrowth can be avoided, and a high semiconductor chip performance is maintained.