A holistic metrology sensitivity study for pattern roughness quantification on EUV patterned device structures with mask design induced roughness

Monitoring of pattern roughness for advanced technology nodes is crucial as this roughness can adversely affect device yield and degrade device performance. The main industry work horse for in-line roughness measurements is the CD-SEM, however, today no adequate reference metrology tools exist that allow to evaluate its roughness measurement sensitivity and precision. To bridge this gap, in this work the roughness measurement capabilities of different analytical techniques are investigated. Different metrology methods are used to evaluate roughness on a same set of samples and results are compared and used in a holistic approach to better characterize and quantify the measured pattern roughness. To facilitate the correlation between the various metrology techniques and the evaluation of CD-SEM sensitivity, an effective approach is to induce pattern roughness in a controlled way by adding well defined levels of roughness to the designed patterns on a EUV mask and to measure the response and sensitivity of CD-SEM and of the other techniques to these different pattern roughness levels once printed on wafers. This paper presents the roughness measurement results obtained with various metrology technologies including CD-SEM, OCD, S-TEM and XCD on EUV Lithography patterned wafers both postlithography and post-etch. The benefits of recently developed metrology enhancements are demonstrated as well; automated TEM allows to generate accurate and rather precise reference roughness data, Machine Learning enables OCD based roughness metrology with good correlation to CD-SEM and STEM, and the improved sensitivity of EUV and X-ray scattering systems allows to extract roughness information that does correlate to CD-SEM.