Stress Engineering for High-k FETs: Mobility and Ion Enhancements by Optimized Stress

In this paper, we present the first systematic study of uniaxial/ biaxial stress effects on mobility (mu) and I_on enhancements in high-k n/pFETs. It is demonstrated for the first time that mu enhancement of high-k nFETs by biaxial strain is greater than that of SiO₂ nFETs in high E_eff, resulting in the better I_on improvement of high-k nFETs than SiO₂ nFETs particularly in shorter-channel regime. It is also shown that mu enhancement of high-k pFETs by strain is comparable to that of SiO₂ pFETs. The optimum stress design for high-mu high-k n/pFETs is also discussed and it is concluded that the application of transverse tensile stress is crucial for improved n/pFETs.