Performance enhancement by local strain in (110) channel n-channel metal-oxide-semicondiactor field-effect transistors on (111) substrate

In this study, an n-channel metal-oxide-semiconductor field-effect transistor (nMOSFET) fabricated with local strained channel techniques on a (111) Si substrate using a SiN capping layer with high mechanical stress and the stack gate of amorphous silicon (alpha-Si) and polycrystal line silicon (poly-Si) was investigated. By using these techniques, the performance improvement of the nMOSFETs in the (110) channel direction on the (111) substrate was achieved. The on-current and transconductance (G) increased with increasing SiN capping layer or alpha-Si layer thickness. Our experimental results show that devices with a 700 A a-Si layer show a 6.7% on-current improvement percentage relative to those with a 200 A. alpha-Si layer, and a corresponding G. improvement percentage of 10.2%. In addition, charge pumping current/interface state density decreased for the samples with a thicker SiN layer.