Grating metal structure with low-K benzocyclobutene and electroplated copper for high-Q spiral inductors

Abstract

In this paper, we propose a grating metal structure with low-K benzocyclobutene (BCB) and electroplated copper to increase the Q-factor of a spiral inductor. The grating metal structure was fabricated using simple electroplated copper and showed a maximum quality factor (Q(max)) of 4 nH in spiral inductors, which is 15% more than that in normal spiral inductors with the same metal thickness. From the proposed equivalent lumped element model, the enhancement in quality factor was found to result from the reduction in series resistance, which was caused by the increase in effective current area. This technique can be applied to increasing the Q-factor of a spiral inductor in a silicon-based radio-frequency-integrated circuit (RFIC).