Effect of Negative tone mask lithography on Lens aberration phenomena

In this paper, the method to decrease lens aberration phenomena is presented. The performance of mask tone (positive and negative) is compared experimentally and by simulation for actual conditions of 0.18um lithography. The stepper with some aberration was used with several modified illumination conditions. The effectiveness of negative tone lithography was confirmed experimentally. CD variations of sub-dense or isolated line (0.24 similar to 0.40um) patterns in intrafield are improved from about 30 similar to 40nm to 10 similar to 20nm for every illumination condition. For overlay, the placement error of isolate line patterns (0.20 similar to 1.00um) is improved from around 10nm to 5nm. By simulation, the phenomena are investigated for the same illumination conditions as experimental ones. It is proven that negative tone mask lithography is less sensitive to aberration rather than positive one, which corresponds to smaller intrafield CD and overlay variation errors. The reason why negative tone mask lithography is effective is investigated. From this study, it can be concluded that negative tone mask lithography is more robust for lens aberration phenomena than positive one for such pattern layer which consists mainly of sub-dense and isolated patterns as gate layer. In the viewpoint of production, with this method, even the stepper which has some aberration can get CD and overlay controllability to be suitable for 0.18um lithography.