Reduce process bias of photomask manufacturing for next-generation lithography

Abstract

It is an important task in 65nm generation to reduce process CD loss to get better pattern resolution and CD performance. As we know the main process CD loss is the etch process. This study is mainly in Cr etching process. Process CD loss reduction is one of critical issues in 65nm generation photomask fabrication to improve pattern resolution and total CD performance. The CD loss is mainly determined by etching process. Cr etching process is particularly important because the process decide the CD performance for not only binary mask but also phase shift mask. So, we focused on Cr etching process in this study. For Cr etch, the masking material is a soft-etchable photo-resist. The resist behavior in the etch process strongly affects the Cr etching performance. In our study, the resist we used is Chemical Amplified Resist. We devoted to reduce the CD loss during etching process by optimizing the etching parameter through a designed experiment (DoE). And we studied about the relation of etching bias with the parameter and the relation of etching bias with other etching property. Then we discussed about the over-etching time with the bias loss. The etching uniformity is strongly affected in the plasma etch optimization, including proximity CD bias, CD radial, and Cr loading effect. So these factors will be checked throughout our optimization study.