Layout-Dependent Stress Effect on High-Frequency Characteristics and Flicker Noise in Multifinger and Donut MOSFETs

Abstract

The impact of MOSFET layout-dependent stress on high-frequency performance and flicker noise has been investigated. The proposed donut MOSFETs demonstrate the advantages over the standard multifinger MOSFETs, such as the lower flicker noise S(ID)/I(DS)(2) in the low-frequency domain and the higher cutoff frequency f(T) in the very high-frequency region. The elimination of the transverse stress sigma(perpendicular to) from shallow trench isolation (STI) and the suppression of interface traps along the STI edge are proposed as the primary factors responsible for the enhancement of the effective mobility mu(eff), as well as f(T), and the reduction of flicker noise. The significantly lower flicker noise realized by donut devices suggests the reduction of STI-generated traps and the suppression of mobility fluctuation due to eliminated transverse stress. The former is applied to n-channel MOS in which the flicker noise is determined by the number-fluctuation model. The latter is responsible for p-channel MOS whose flicker noise is dominated by the mobility-fluctuation model.