Characterization of film cut position at wafer bevel for effective immersion lithography process

In ArF immersion lithography process, material surface and wafer bevel hydrophobicity is an important factor in minimizing defects and water droplet residue. The application of topcoat and topcoat-less materials has been reported to increase hydrophobicity. The hydrophobicity of wafer bevel plays an important role in the effective inhibition of the immersion fluid from leaking to the wafer backside. The hydrophobicity at the wafer bevel can be optimized through the optimization of the film edge cut height (FECH), which is defined as the distance from the film surface down to the film cut edge at the wafer bevel. Special bevel rinse modules have been introduced in track systems to control FECH with a high degree of accuracy. In this work, various types of FECH were analyzed and measured using a newly developed inspection system. Based on these results, the quantification of the FECH for all the materials analyzed was made possible. It was found that FECH changed depending on the bevel rinse condition applied. For example, wafer rotation and bevel rinse flux significantly influence FECH. These results show the possibility of controlling the FECH for optimization.