Removal behavior of Sn and Pb contaminants on EUV mask after EUV exposure

Tin (Sn) and Lead (Pb) particles released from the EUV scanner can contaminate the EUV mask causing serious yield and throughput problems. These contaminants can worsen during EUV exposure and become difficult to remove, leading to damaging the EUV mask in the process. To effectively remove contaminants without substrate damage, it is necessary to understand the removal behavior of the contaminants. In this study, the removal behavior of Sn and Pb particles was studied by simulating the EUV exposure heated by rapid thermal annealing. The removal forces between the thermally aged Sn and Pb particles and EUV substrate surfaces were quantitatively measured using atomic force microscopy (AFM). With the thermal aging time, the contact area of the deformed particle increases which requires a high removal force. After particle removal, the footprint of the contaminants was investigated to understand the surface quality of where the particles sat under the various exposure conditions. This study helps to better understand the adhesion mechanism and removal behavior of thermally deformed Sn and Pb particles on different EUV substrates.