Phase-shifting mask and top-imaging resist for subhalf-micron i-line and deep-ultraviolet lithography

Abstract

Combination of both phase-shifting mask and single layer top-imaging resist will allow i-line and deep-ultraviolet (UV) lithography to meet, respectively, 64 and 256 Mbit requirements and beyond. Using phase-shifting mask in conjunction with DESIRE process, 0.25 μm lines and spaces have been resolved with an ASM-L PAS 5000/50 i-line stepper (365 nm, NA=0.48), on 1 μm thick PLASMASK 200G. With an ASM-L PAS 5000/70 deep-UV (248 nm, NA=0.42) 0.2 μm lines and spaces have been resolved on 0.35 μm thick PLASMASK 200 G using PRIME process. A simulation software package was developed allowing us to optimize phase shifting structures. Moreover, using existing computer aided design (CAD) tools we automatically generate ‘‘edge emphasis’’ structures on contact holes and on 0.3 μm gate level and subsequently expose this data base demonstrating the ability, using this simple technique, to process 64 Mbit DRAM with i-line lithography.