Rigorous coupled-wave analysis를 이용한 극자외선 리소그래피에서 그림자 효과를 줄이기 위한 마스크 변형

Abstract

Extreme ultraviolet lithography (EUVL) is believed to be the next generation lithography and so it is seriously under study globally. The near-field intensity on the EUVL mask is affected by the mask structure. The absorber and the buffer layer make a shadow since the light is shining on the mask at some angle to the normal on-axis. This shadow effect in the EUVL mask is an important factor that decreases the contrast of the aerial image and, as a result, causes a line width variation and a pattern shift. Among the several possible mask structures, we focused on the mask edge slope variation with a typical incident angle of 5°. We analyzed electromagnetic wave around the mask by rigorous coupled-wave analysis (RCWA) and reflectivity in the modified mask structure.