Patent ID: 7616313

Claim:
A target arrangement for determining overlay alignment on a substrate, the target arrangement comprising: a substrate having at least two layers formed thereon; a target arrangement formed on the substrate, the target arrangement comprising two sets of target cells, a first set of target cells configured in a first set of at least two layers of periodic features and configured to generate high resolution periodic overlay signals associated with the overlay between the first set of at least two layers of periodic features; and a second set of target cells configured in a second set of at least two layers of periodic features and configured to generate high resolution periodic overlay signals associated with the overlay between the second set of at least two layers of periodic features; and a plurality of optically resolvable disambiguation features, where a plurality of the optically resolvable disambiguation features includes a first set of coarse overlay bars and a second set of coarse overlay bars, where the coarse overlay bars are configured such that the sides of the coarse overlay bars are exposed to allow each edge to be imaged, and the plurality of the optically resolvable disambiguation features is arranged between the target cells of the target arrangement and wherein at least one of the plurality of the optically resolvable disambiguation features bounds the target cells, the disambiguation features configured to be optically observed to enable the resolution of signal ambiguity caused by signals produced by illuminating the cells.