Uniaxial Stress Engineering for High-Performance Ge NMOSFETs

Ge channel is one of the promising performance boosters for replacing Si channel in future complementary metal-oxide-semiconductor technology. The uniaxial stress technology can further enhance the performance of Ge MOSFETs. In this paper, the uniaxial stress effect on Ge NMOSFETs was experimentally and theoretically investigated. The gate dielectric in the Ge NMOSFETs was fabricated by using the novel radical oxidation technique. The high quality of the gate dielectric allowed high vertical field mobility measurements. By applying mechanical uniaxial stress on the fabricated Ge NMOSFETs, the mobility enhancement was experimentally obtained. The physical mechanism of mobility enhancement under such strain indicates that the device performance of Ge NMOSFETs in the ballistic transport regime can achieve as much as 48% drive current gain beyond the 15 nm technology node.