Effective light source optimization with the modified beam for depth-of-focus enhancements

摘要

Abstract: A new exposure method for the depth of focus enhancements without using the off axis filter has been developed. It makes KrF excimer laser (248 nm) lithography to a robust mass production tool beyond 2nd generation of 64 MDRAM class devices. With this new exposure method, the depth of focus for 0.35 $mu@m geometries, which includes the vertical and the oblique direction images, can be enlarged more than 45%. The common depth of focus between the line images and the space images cannot be obtained with the quadrupole and the ring illumination methods for the actual sub-0.30 $mu@m rule devices. Even for these devices, over 1.1 $mu@m depth of focus can be achieved with this newly developed exposure method. !18