An optical lithography system that has extended depth of focus exposes a
photoresist coating on a wafer, and includes an illumination sub-system,
a reticle, and an imaging lens that has a pupil plane function to form an
aerial image of the reticle proximate to the photoresist. The pupil plane
function provides the extended depth of focus such that the system may be
manufactured or used with relaxed tolerance, reduced cost and/or
increased throughput. The system may be used to form precise vias within
integrated circuits even in the presence of misfocus or misalignment.