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Previous work has shown that photomask blank flatness as well as photomask patterning and pelliclization all play an important role in finished photomask flatness 1,2 . Additional studies have shown that pellicle mounting techniques, pellicle adhesives, frame flatness and shape and pellicle mounting tools 3-6 play a role as well. It has become clear that frame flexibility, coupled with frame mounting surface flatness and shape are the principal factors influencing the pellicle effect on the mask distortion. Pellicle suppliers have begun to evaluate various polymers as potential replacements for the standard aluminum frame in current use. The elasticity of the frame adhesive has also been adjusted to evaluate its effect on the pellicle influence on mask flatness. This paper describes some joint evaluations between IBM, Toppan and ShinEtsu, performed to determine the effect of pellicle frame composition,, mount surface flatness, adhesive elasticity and adhesive surface flatness on the distortion of photolithography masks. It demonstrates that polymer pellicle frames with more flexible adhesive improve finished mask flatness approximately the same amount as reducing the total frame standoff height of aluminum frames with conventional adhesive.

With the advancement of technology, the need to produce flatter photomasks is critical to meet strict mask manufacturing requirements. Components such as pellicle mounting techniques, pellicle frame height, frame material and adhesive all play an important role in finished photomask flatness.1-5 In particular, recent studies have shown that adhesive flexibility affect final photomask flatness significantly.6 This has motivated pellicle suppliers to optimize adhesive properties in addition to evaluate new adhesives.The paper describes the joint evaluations between IBM, Toppan and MLI, performed to determine the effect of a new MLI adhesive on the distortion of photomasks. Due to the nature of this adhesive, minimal mounting force is required. As a result of utilizing extreme low mounting pressure, benefits such as decreased flatness distortion and ease of adhesive removal are observed. The goal of this paper is to evaluate this new adhesive offering and understand the various impacts it has on pelliclized photomasks for advanced technologies.