Topographical masks : a new approach to increase the DOF on topographical substrates

With shrinking design rules, the DOF becomes a major concern in lithographical processes. Several methods to improve the DOF are proposed already, each with its advantages and drawbacks. In this work, a new approach to increase the DOF on topographical substrates is introduced: the topographical mask. Two types of topographical masks are subject of investigation. The fabrication of such masks is more complicated compared to conventional mask making, but the lithographic performance of the topographical masks is excellent. Therefore, this new technology offers interesting possibilities on topographical substrates.