TOPOGRAPHICAL MASKS - A NEW APPROACH TO INCREASE THE DOF ON TOPOGRAPHICAL SUBSTRATES

With shrinking design rules, the DOF becomes a major concern in lithog raphical processes. Several methods to improve the DOF are proposed al ready, each with its advantages and drawbacks. In this work, a new app roach to increase the DOF on topographical substrates is introduced: t he topographical mask. Two types of topographical masks are subject of investigation. The fabrication of such masks is more complicated comp ared to conventional mask making, but the lithographic performance of the topographical masks is excellent. Therefore, this new technology o ffers interesting possibilities on topographical substrates.