PRINTING OF PHASE-SHIFTING MASK DEFECTS

Using both simulations and experimental data, the impact of defect typ e, size, and location for the three leading phase-shifting techniques, alternate aperture, sized rim shifter, and attenuated, was investigat ed. Location of the defect was determined to play a major role in the printability of a given defect. Specifically, comer defects located on the inner edge of a rim-shifted pattern posed significant detectabili ty and printability problems. As expected for the vast majority of def ects, phase-shifting approaches enhanced the printability of the defec t. 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 de fects. A systematic study of the impact of phase, size, and position f or both classes of defects: extra shifter and missing chromium, on an attenuated phase-shifting masks revealed that the design of the attenu ated blank was critical in minimizing the impact of defects. Two possi ble blank configurations were proposed: a partially embedded shifter a nd a fully embedded configuration. By intelligently selecting the desi gn of the attenuated blank, the impact of defect printability could be reduced.