Defect characterization of Ru/Mo/Si EUV reflector by optical modeling

Abstract

The defect printability of Mo/Si and Ru/Mo/Si multilayer (ML) systems for EUV reflector was quantitatively investigated by monitoring an aerial image on the wafer. For the calculation of the aerial image intensity of a patterned ML mask containing a phase defect, SOLID-EUV, which is capable of rigorous electromagnetic-field computation, was employed. The aerial-image intensity of a Ru/Mo/Si model was calculated and compared with the value for a Mo/Si model for various defect widths, heights, and positions. The calculated aerial images of the patterned mask system turned out to be mainly dependent on the defect width and the position in the mask. Through the investigation of the aerial-image characteristics of the two models, it can be reasonably concluded that the Ru/Mo/Si model seems to be consistent with the Mo/Si model for all cases.