Metrology limits of mask process development

The ever-narrowing specifications for high-end masks can only be derived from the continuous improvement of all manufacturing processes. Here, the metrology is crucial prerequisite since the development relies almost entirely on measurement results. In this paper we will address this relation by showing how the limits of metrology repeatability and reproducibility define also the limits of process development. In particular, we will show that improved metrology tool performance on resist results in a deeper understanding for the dry etch process. This is very important since resist metrology is not part of the ITRS roadmap and serves "only" as a supporting engineering process. Better short-term repeatability results in the possibility to detect more variables that might influence the etch regime. As an example, results from two CD scanning electron microscopes (SEM) were compared with very different short-term repeatability. The better knowledge based on the more accurate metrology data allows then to optimize the process within a process space which was previously not detectable with the other tool. An estimate is given how much this influenced the final performance of the process. We conclude from these results, that metrology parameters not covered in standard roadmaps become increasingly important to achieve process development goals in other process areas.