APPLICATION OF KRF EXCIMER-LASER LITHOGRAPHY TO 256 MBDRAM FABRICATION

256 MbDRAM chips have been fabricated by mix-and-match method using hi gh NA KrF excimer laser stepper and i-line stepper. In the case of KrF stepper, the negative siloxane resist is used for rectangular and wir ing patterns and the positive novolak-resin resist is used for hole pa tterns. Both of these two kinds of resist produce accurate pattern sha pe, allowable pattern profile, satisfactory depth of focus and suffici ent overlay accuracy for device fabrication in 0.25 mum design rule.