Temperature and substrate-impedance dependence of noise figure of monolithic RF inductors on silicon

In this letter, we analyze the effects of temperature (from -50°C to 200°C) and substrate impedance on the noise figure (NF) and quality factor (Q-factor) performances of monolithic RF inductors on silicon. The results show a 0.75 dB (from 0.98 to 0.23 dB) reduction in minimum NF (NF_min) at 8 GHz, an 86.1% (from 15.1 to 28.1) increase in maximum Q-factor (Q_max), and a 4.8% (from 16.5 to 17.3 GHz) improvement in self-resonant frequency (f_SR) were obtained if post-process of proton implantation had been done. This means the post-process of proton implantation is effective in improving the NF and Q-factor performances of inductors on silicon mainly due to the reduction of eddy current loss in the silicon substrate. In addition, it was found that NF increases with increasing temperature but show a reverse behavior within a higher frequency range. This phenomenon can be explained by the positive temperature coefficients of the series metal resistance (R_s), the parallel substrate resistances (R_sub1 and R_sub2), and the resistance R_s1 of the substrate transformer loop. The present analyzes are helpful for RF designers to design less temperature-sensitive high-performance fully on-chip low-noise-amplifiers (LNAs) and voltage-controlled-oscillators (VCOs) for single-chip receiver front-end applications.