A simple systematic spiral inductor design with perfected Q improvement for CMOS RFIC application

In this paper, a systematic design procedure based on key factor analysis of the Q curve has been proposed. In addition to inductor design, we also present a technique that combines optimized shielding poly, and proton implantation treatment is utilized to improve the inductor Q value. The shielding effect of poly-silicon and the semi-insulating characteristics of proton-bombarded substrate have added a 37% and 54% increment to the Q value of the inductors, respectively. The combination of the two means has created a multiplication of their individual contribution rather than addition. The dramatic improvement of the Q value resulted from the doping level and film thickness optimization of a poly shield layer combined with a proton implantation treatment. A phenomenal Q-value increment as high as 122% of 4-nH spiral inductors can be realized. This technique shall become a critical measure to put inductors on a silicon substrate with satisfactory performance for Si-based RF integrated-circuit applications