Characterization of CD-SEM metrology for iArF photoresist materials

Abstract

For many years, lithographic resolution has been the main obstacle for keeping the pace of transistor densification to meet Moore's Law. For the 45 nm node and beyond, new lithography techniques are being considered, including immersion ArF lithography (iArF) and extreme ultraviolet (EUV) lithography. As in the past, these techniques will use new types of photoresists with the capability to print 45 nm node (and beyond) feature widths and pitches. In a previous paper (SEM Metrology for Advanced Lithographies, Proc SPIE, v6518, 65182B, 2007), we compared the effects of several types of resists, ranging from deep ultraviolet (DUV) (248 nm) through ArF (193 nm) and iArF to extreme UV (EUV, 13.5 nm). iArF resists were examined, and the results from the available resist sample showed a tendency to shrink in the same manner as the ArF resist but at a lower magnitude. This paper focuses on variations of iArF resists (different chemical formulations and different lithographic sensitivities) and examine new developments in iArF resists during the last year. We characterize the resist electron beam induced shrinkage behavior under scanning electron microscopy (SEM) and evaluate the shrinkage magnitude on mature resists as well as R&D resists. We conclude with findings on the readiness of SEM metrology for these challenges.