Printing of phase-shifting mask defects

Abstract

Using both simulations and experimental data, the impact of defect type, size, and location for the three leading phase-shifting techniques, alternate aperture, sized rim shifter, and attenuated, was investigated. Location of the defect was determined to play a major role in the printability of a given defect. Specifically, corner defects located on the inner edge of a rim-shifted pattern posed significant detectability and printability problems. As expected for the vast majority of defects, phase-shifting approaches enhanced the printability of the defect. However, the attenuated approach revealed a unique class of defects that caused much less linewidth deviation than their counterparts on conventional masks. These were the missing chromium/unetched quartz defects. A systematic study of the impact of phase, size, and position for both classes of defects: extra shifter and missing chromium, on an attenuated phase-shifting masks revealed that the design of the attenuated blank was critical in minimizing the impact of defects. Two possible blank configurations were proposed: a partially embedded shifter and a fully embedded configuration. By intelligently selecting the design of the attenuated blank, the impact of defect printability could be reduced.