Accurate aerial image simulation using high-resolution reticle inspection images

The use of hardware-based and software-based reticle defect printability simulation systems is expanding as the cost and complexity of reticles increases. Without such systems it has become increasingly difficult to predict the lithographic significance of a defect found on a reticle. The viability of such systems can be judged using several criteria including accuracy, ease of use, level of automation, and the degree to which they can be applied to a wide range of reticle types. Simulation systems have improved in each of these areas. Automated and semi-automated systems have now been developed and integrated into reticle manufacturing. We report on advances made in a software-based simulation system which uses high-resolution reticle inspection images as the basis for the description of the reticle. We show that the simulated aerial images can be compared quantitatively to results from a hardware-based simulation system (the Zeiss AIMS (TM) tool) for both 193 and 248 nm EPSM reticles. The development of a new set of metrics to judge lithographic significance will be explained. Common procedural mistakes in evaluating the impact of a defect will be discussed.