Evaluation of printability and inspection of phase defects on hidden-shifter alternating phase-shift masks

Abstract

Inspection and repair of defects represent some of the challenges for the fabrication of 'defect-free' alternating phase-shift masks needed for performance improvements in patterning the polysilicon gate layer of integrated circuit devices. Inspection, metrology, repair, and printability of defects on dark-field alternating phase-shift masks used in dual exposure processes for polysilicon gate layer patterning are discussed in this study. The impact of phase and chrome defects on photoresist features printed at an exposure wavelength of 248 nm is evaluated and compared to the defect signals measured on a mask inspection tool operating at 364 nm. Experimental data on printability and inspection of programmed glass defects with several different phase errors as well as programmed chrome defects are compared to simulations. The effects of the exposure tool focus conditions on phase defect printability are discussed in detail. Phase defect contrast enhancement mechanisms that may enable improvements in phase defect detection during mask inspection using conventional inspection tools are also addressed. Finally, successful repairs of real glass bump defects are demonstrated.