New Observation and Analysis of Layout Dependent Effects in Sub-40nm Multi-Ring and Multi-Finger nMOSFETs for High Frequency Applications

摘要

Multi-finger (MF) and multi-ring (MR) nMOSFETs were designed and fabricated in 40nm CMOS technology to explore the layout dependent effects in key device parameters and parasitic RC responsible for RF performance. For the first time, the experimental proves the advantages of MR nMOSFETs, such as the increase of effective mobility $(mu_{mathrm{eff}})$, transconductance $(mathrm{g}_{mathrm{m}})$, and channel current $(mathrm{I}_{mathrm{DS}})$, and smaller parasitic source resistance $(mathrm{Rs})$, all of which are in favor of higher speed and higher frequency. However, the undesired increase of 3-D fringing capacitances may bring a critical trade-off influencing high frequency performance. In this paper, new observation and in-depth analysis of the complicated layout dependent effects can facilitate the device layout optimization in the right direction for RF and mm-wave design and applications.