Dissolution nonlinearity tail degradation with decreased reaction events impacts EUV stochastic defect generations

Background: Stochastic defects are becoming major concern in the future extreme ultraviolet (EUV) lithography and are thought to be originated from random physical/chemical events in resist films. Aim: We clarify factors and mechanisms influencing the frequency distributions of these random events and their impact on defect probabilities and lithographic performances. Approach: We analyze the statistical information extracted from our previously introduced fully-coupled Monte Carlo simulation including discrete photon, photoelectron scattering, and resist stochastics. Results: Contrasts in solubility flipping probability can be enhanced through the following two mechanisms to suppress defect generations; the multi-photon effect where we need multiple photons to flip solubility of a polymer/molecule, and the multi-solubility-flipped-particle effect where we need multiple solubility-flipped polymers/molecules to flip solubility of resist film at a local spot. Defect generations are suppressed by increasing the numbers of contributing photons and SFVs. Conclusions: Stochasticity in lithography processes is characterized by presently discussed frequency distributions and previously discussed spatial distributions of those events. Stochastic defects generate when tails of the above frequency distribution appear spatially non-uniformly due to localization, cascade, and clusters of correlated reactions.