Rigorous modeling and analysis of impact produced by microstructures in mask on wafer pattern fidelity

As feature size continuously decreasing new techniques to improve quality of wafer are developed. Hence a lot of new problems in semiconductor industry arise. Strict control of quality of wafer during production process is very important as many factors can influence on it, but the main contribution gives scanner error and mask. Thus at least impact of mask should be reduced. In this work we apply rigorous model to predict impact of microstructures to pattern fidelity on wafer. Such microstructures are commonly generated in quartz layer to control transmittance distribution on photomask. It is shown that effect from microstructures is not only changing of mask transmittance but also distortion of the pattern fidelity on wafer. Rigorous modeling gives us possibility to calculate aerial image and CD on wafer in case of presence of microstructures in the quartz. We vary optical parameters, such as refractive indexes, number, size and location of these elements in order to reduce the distortion of pattern fidelity on wafer. Our result allows prediction of the impact of microstructures in photomask on wafer pattern fidelity instead of doing set of experiments. Moreover, the best conditions for experiment are found and discussed.