Low-frequency noise in silicon-on-insulator devices and technologies

Abstract

An overview is given on the low-frequency (LF) noise of silicon-on-insulator (SOI) devices and technologies. In the first two parts, noise mechanisms specific for SOI are discussed, namely, the front–back-gate coupling in fully-depleted MOSFETs and the Lorentzian noise overshoot in floating-body operating transistors. In the next part, the impact of the technology (SOI substrate, gate stack processing, isolation module, …) on the LF noise is described. From this, it is derived that scaling below the 0.25μm CMOS node did not result in the anticipated reduction of the 1/f noise with tfox or tfox2. This is related to the increasing amount of nitrogen incorporated in the thin SiON front gate oxides with thickness tfox. In the case of high-κ dielectrics it is frequently observed that these have a higher trap density compared to SiO2. On the other hand, today’s multigate SOI transistors seem to give rise to similar gate oxide trap densities and hence, 1/f noise, than their single-gate counterparts. In the last part, operational and circuit aspects will be discussed, which might have a beneficial impact on the LF noise performance.