Extending the capability of 0.60 NA DUV stepper for contact hole lithography of 140 nm node DRAM technology

We present a project where DUV Steppers have been successfully implemented as standard lithography tool for a critical contact layer on 140 nm node technology under running production conditions. The utilisation of older generation lithography tools has been possible by using alternating phase shift masks (altPSM). Since the altPSM offers a much wider process window compared to half tone phase shift masks (HTPSM), lithography of contact holes could be transferred from 248 nm DUV Scanner to 0.6 NA DUV stepper. Methods are described how the problems caused by worse lens aberration performance of older generation lithography tools could be overcome and the successfull implementation of the altPSM lithography into the production process could be achieved.