PHASE SHIFTING MASK STRUCTURE WITH ABSORBING/ATTENUATING SIDEWALLS FOR IMPROVED IMAGING AND METHOD OF FABRICATING PHASE SHIFTERS WITH ABSORBING/ATTENUATING SIDEWALLS

摘要

A phase shifting mask has phase shifters in which the sidewalls of the shifters are coated with a light absorbing or attenuating material. The light absorption at the sidewalls reduces the edges scattering and improves the resolution by obtaining similar transmission profiles from phase shifted and unshifted regions of the PSM. A method of fabricating phase shifters with absorbing or attenuating sidewalls in order to inhibit or prevent light scattering at quartz-air interfaces is also provided. A quartz substrate is patterned and trenches are formed to provide "shifters". A metal film layer is formed along sidewalls of the trenches to provide the light absorbing characteristics. In one technique, the conformal metal layer is anisotropically etched while in another the metal layer is removed along with the photoresist by a lift-off technique.