The impact of MOSFET layout dependent stress on high frequency characteristics and flicker noise

Layout dependent stress in 90 nm MOSFET and its impact on high frequency performance and flicker noise has been investigated. Donut MOSFETs were created to eliminate the transverse stress from shallow trench isolation (STI). Both NMOS and PMOS can benefit from the donut layout in terms of higher effective mobility μeff and cutoff frequency fT, as well as lower flicker noise. The measured flicker noise follows number fluctuation model for NMOS and mobility fluctuation model for PMOS, respectively. The reduction of flicker noise suggests the reduction of STI generated traps and the suppression of mobility fluctuation due to eliminated transverse stress using donut structure.