This chart shows the minimum dielectric thickness between Mx lines, and the sensitivity to the overlay error of the two Mx exposures. The horizontal line is at 12nm, which would support 1.2V maximum voltage at a 1.0 MV/cm breakdown field. This data shows failure when both exposures mis-register a bit more than 3nm, or if one exposure mis-registers by ~9nm, even if all other processes are perfect.