Comparative investigation of CD-SEM carryover effect

Aggressive roadmaps impose stringent requirements not only on the metrology tools but on photoresist properties as well. In this article we investigate the interaction between electron beam in a CD SEM and different photoresists in an attempt to determine appropriate candidates from metrology point of view. We have evaluated sample damage (carryover) in order to find an approach leading to reduction of the sample degradation in the course of the measurement process and improve measurement precision. We have observed various linewidth changes under conditions expected in the case of single-tool repeatability, stability or multiple-tool matching procedures for CD SEM. The experimental data show that while all examined photoresists experienced certain changes some of them demonstrate less sensitivity. For modern CD SEM in addition to electron energy and current as factors defining the carryover, the possible effect of the clean room environment exposure should be considered as well. Recommendations have been made with respect to acceptable compromise based on the current precision requirements.