Evaluating the effect of EUV multilayer buried defects on feature printability using a stochastic resist model

Extreme ultraviolet (EUV) lithography has a number of challenges not encountered in DUV lithography. One of these challenges is that the stochastic nature of resist exposure is much more pronounced at an exposure wavelength of 13.5 nm than 193 nm. This leads to line-edge roughness (LER) and impacts critical dimension uniformity. Another challenge is that the reflective multilayer (ML) in photomasks will likely have defects buried in the ML. The size and the location of these defects could affect feature printability. This paper aims to study these two new challenges using a comprehensive lithographic model that accounts for both the scattering of light due to ML defects and stochastic resist effects. This enables more accurate predictions of the process window which could lead to more robust defect compensation.