Pattern deformation mitigation for EUV photoresists using wafer backside cleaning techniques

Abstract

This study delves into the effects of wafer backside particles on pattern defocus in EUV lithography (EUVL). Additionally, the potential mitigation of this pattern defocus was examined through wafer backside cleaning. Comparative analyses were conducted between EUVL patterning tests performed using wafers with contaminated and cleaned wafer backside. Defocus points and abnormal critical dimensions (CDs) on the photoresist patterns at the wafer frontside were detected using scanning electron microscopy and optical CD measurement, respectively. The specific locations of these defocus or abnormal CD points were compared and confirmed to be correlated with particles that were present on the same locations on the backside of the wafer. Furthermore, it was found that an effective backside cleaning process can mitigate pattern defocus caused by these wafer backside particles.