Strained silicon technology: Mobility enhancement and improved short channel effect performance by stress memorization technique on nFET devices

This paper presents a fundamental study of a stress memorization technique (SMT), which utilizes a capping nitride dielectric film to enhance negative channel field-effect transistor (nFET) device performance. SMT strain engineering is highly compatible with current standard complementary metal oxide semiconductor processes without introducing substantial additional complexity. In this work, we report that SMT-strained nFET exhibits a higher transconductance G_m-lin, which indicates strain-induced electron mobility enhancement. The nFET short channel effect is also improved by the SMT process. Improved V_t roll-off characteristics manifest itself and are shown to result from retarded junction diffusion as indicated by secondary-ion mass microscopy analysis. Finally, this work demonstrates that when combined with a strained contact etch stop layer (CESL) technique, SMT provides additional strain beyond that provided by the CESL, which results in further improved nFET performance.