PRODUCTION-WORTHY DEEP UV STEPPER FOR 0.35 MICRON LITHOGRAPHY

Design considerations and first evaluation results are presented for a deep UV exposure system designed for volume production of 64 Mb DRAMs and related IC products. The main features of the system are the all- quartz, wide field, high NA projection lens built into a standardized machine body with high precision stage and through the lens alignment system, and a narrow bandwidth KrF excimer laser as light source. The imaging properties were evaluated by measuring the contrast transfer f unction. The resolution limit was determined to be better than 0.25 mu m. For 0.35 mum features contrast is well over 60 % and depth of focus greater than 1 mum. Single machine overlay and local distortion were evaluated, showing a total overlay capability of the system of ca. 0.1 mum. This work was part of the JESSI E162 project which has the objec tive to develop a fully production-worthy, integrated deep UV photosec tor for 0.35 micron lithography.