Predicting the dynamic response of an extreme ultraviolet reticle during exposure scanning

Extreme ultraviolet (EUV) masks are expected to experience up to 6g’s of acceleration and achieve speeds as high as 500mm∕s while mounted in the exposure tool. Therefore, it is critical that the mounting technique employed to hold the mask in position prevents the mask from slipping under these conditions. An electrostatic pin chuck must generate adequate pressure between the mask and chuck, as well as a sufficient amount of friction. To ensure the success of such a mount design, three-dimensional finite element (FE) models have been created to predict the conditions necessary to prevent mask slippage during exposure scanning. The FE modeling is used to predict the influence of the initial substrate backside surface shape on mask flatness when mounted in the chuck, as well as the effects of friction on the relative displacement between the reticle and chuck. Simulation results indicate that for typical EUV mask substrates, coefficients of friction greater than 0.2 are necessary to prevent bulk displacemen...