The present invention relates to a method for forming a multi-transmittance phase-shifting mask for the manufacture of highly integrated semiconductor devices in which portions of a plurality of light blocking layers are selectively removed to modify the transmittance of various regions of the mask and...http://www.google.com/patents/US6767672?utm_source=gb-gplus-sharePatent US6767672 - Method for forming a phase-shifting mask for semiconductor device manufacture
