Influences of the inclination of gratings on the alignment accuracies in moire alignment systems

摘要

In the lithographic processes of VLS Is, high setting accuracies between masks and wafer are required. The methods using moire signals obtained by gratings were found to give very high alignment accuracies. In this paper, influences of the inclination of gratings for the alignment accuracies in modified and differential moire systems have been investigated. The moire signals and the alignment point have been calculated using computer simulation. As a result, it has been shown that the effects are small and the inclinations do not affect alignment accuracies in the moire alignment systems.