Evaluation of the impact of pattern fidelity on photomask inspectability

摘要

In recent years a manufacturable inspection recipe has been limited by the number of nuisance defects instead of the true sensitivity capability of the inspection tool for the top of the line products. In general, the nuisance defects are a result from either sub-resolution mask design or non- uniformity issue of mask pattern fidelity. Pattern fidelity here refers to corner rounding, line edge roughness and localized CD variation. Pattern fidelity plays an important role in inspectability. This study quantitatively evaluates the impact of pattern fidelity on mask inspectability. The first phase of this study, which is covered in this paper, will establish a correlation between KLA measured run-time- bias (RTB) and SEM/optical measured line width and corner rounding. The second phase of this study will focus on the impact of pattern fidelity resulting from different mask processes on inspectability in terms of nuisance defects. This paper will cover the initial results of the second phase study, including the comparison among different resist and different etch processes. The purpose of the study is to eventually establish pattern fidelity requirements for a given defect specification to ensure a manufacturable inspection process. As a result, one can use nuisance defect count as a mask process monitor.