Extreme ultraviolet mask defect simulation

This article investigates the printability of defects embedded inside multi layer mirrors used for masks in extreme ultraviolet lithography. Models for buried defects of various shapes and sizes and their subsequent distorting of the deposited films are developed and used to assess the effect on both the fields at the mask and the aerial image at the wafer. Because most of the reflection occurs in the top 10-20 layers and thus it is hypothesized t hat simulating with a truncated multilayer will still yield insight into th e printability of the defects. The relationship between point defects and l ine defects of the same height is explored. The intensity minimum in the ae rial image for defects is found to vary periodically with only a quarter wa ve change in the height of the defect due to phase considerations. Defocus can enhance a defect's printability and an isolated line with only 2 nm hei ght and one quarter of a feature width may print. Nonprinting isolated defe cts are shown to become killer defects when feature interactions are consid ered. (C) 1999 American Vacuum Society. [S0734-211X(99)16406-0].