Effects of body biasing on the low frequency noise of MOSFETs from a 130 nm CMOS technology

The impact of body biasing on the low frequency noise (LFN) performances of MOS transistors from a 130 nm CMOS technology was investigated. The body-to-source voltage V_BS was varied from -0.5 V to +0.5 V for reverse and forward mode substrate biasing. Detailed electrical characterisation was performed and the benefits of the body bias analysed in terms of current and maximum transconductance variations. Noise measurements were first performed at low drain bias V_DS=±25 mV and V_BS=0 V in order to discuss the noise origin in the devices. Results are in agreement with the carrier number fluctuation theory ΔN for NMOS and with the correlated carrier number-mobility ΔN-Δμ model for PMOS. Bulk bias dependence of the LFN was investigated at V_DS=V_DD=±1.2 V. Significant noise reduction of about 50% in both N and PMOSFETS was observed in the weak inversion regime when applying a forward body bias. In strong inversion, the noise level was found to be approximately independent of the substrate bias V_BS. An explanation of the main noise results based on McWhorter´s number fluctuation theory is proposed.