Stochastic printing behavior of ML-defects on EUV mask

One of the residual concerns for use of EUV patterning for IC manufacturing is its stochastic behavior. The present paper specifically studies the contribution of mask defects to the stochastic failure rate, with a focus on defects related to the multilayer mirror of the mask, so-called ML-defects. By simulation, a universal relation is obtained between the probability that a given mask defect triggers a stochastic failure on wafer and the average local CD deviation that it causes. Even marginal ML-defects, which cause less than 10% CD deviation, are shown to act as trigger points for locally increased failure probability. This finding is supported by experimental data based on AIMS EUV aerial image measurements in scanner photon stochastics emulation mode. In addition, other local defect types on mask are shown to behave in the same way. Non-local mask deficiencies, such as line-edge roughness and contamination effects, can influence the contribution of the mask to the stochastic failure rate of the printed image on wafer.