A test structure to reveal short-range correlation effects of mismatch fluctuations in backend metal fringe capacitors

This paper presents a set of test structures that revealed a thus far unknown (or at least unreported) CMP-related short-range correlated mismatch fluctuation effect on the matching of backend metal fringe capacitors. It is shown that an apparent degradation of mismatch standard deviations at medium-range distances is in fact due to an improvement of matching for devices placed at very small distances.