Impact of sub-wavelength electromagnetic diffraction in optical lithography for semiconductor chip manufacturing

Despite many challenges, optical lithography continues to enable an exponential decrease in the dimensions of circuit patterns that are printed in high volume in advanced microelectronics. The laser wavelength used to power the lithographic system has not scaled as fast, constraining these systems to operate with 193nm wavelength while printing features less than one-fourth that size. In this paper we explore the mechanism in which sub-resolution diffraction at the lithographic photo-mask translates into severe shifts in focus of the patterns transferred to the wafer in a pattern-dependent manner and their dependency on several parameters of the lithography process.