Bias reduction in roughness measurement through SEM noise removal

The importance of Critical Dimension (CD) roughness metrics such as Line and Contact edge roughness (LER, CER) and their associated width metrics (LWR, CWR) have been dealt with widely in the literature and are becoming semiconductor industry standards. With the downscaling of semiconductor fabrication technology, the accuracy of these metrics is of increasing importance. One important challenge is to separate the image noise (present in any SEM image) from the physically present roughness. An approach for the removal of the non-systematic image noise was proposed by J.Villarrubia and B.Bunday [Proc. SPIE 5752, 480 (2005)]. In the presented work this approach is tested and extended to deal with the challenge of noise removal in the presence of various types of systematic phenomena present in the imaging process such as CD variation. The study was carried out by means of simulated LWR and using real measurements.