The relationship between mounting pressure and time on final photomask flatness

Photomask flatness and image placement specifications for advanced technology masks are becoming more stringent. Therefore, it is important to understand the various factors that affect final photomask flatness due to the direct impact it has on image placement. Past studies have demonstrated that final photomask flatness can be controlled by modifying the mounting process of photomask pellicle as well as changing the pellicle material itself [1][2][3][4]. In particular, our previous results demonstrate the ability to successfully eliminate data deviations by remounting the same pellicle for each experiment. This paper focuses on the relationship between mounting pressure and time on final photomask flatness. Our initial results indicate that mounting time has minimal influence on final photomask flatness; however, final photomask flatness is greatly impacted by varying mounting pressure. Finally we explore the relationship between the final photomask flatness and the image placement for post pellicle mounting onto the photomask.