Process variation in metal-oxide-metal (MOM) capacitors

摘要

Aerial image simulation of interdigitated sidewall capacitor layouts and extraction of feature changes are used to estimate the parametric performance spread of DC Metal-Oxide-Metal (MOM) mixed signal capacitors as a function of the normalized lithographic resolution kl. Since minimum feature sizes are utilized, the variation of MOM capacitors is attributed to lithography spacing. In this paper, kl of 0.8, 0.56, 0.40, and 0.28 are studied. The DC capacitance shows a worst-case variability of 42%. While line-end-shortening is a small fractional change in finger length and proves to be not a critical factor in variability, spacing width proves to be the main source of the variability in DC capacitance. Different annular illumination settings are explored for mitigating the variability in spacing width. Co-design of the pitch and illumination shows that for each kl, there is an optimal annular illumination radius. The optimal set of sigmas (i.e. sigmain and sigmaout) can control the variability between linewidths and spacing widths to 20%.