Jet and Flash Imprint Lithography (J-FIL) encompasses a number of significant innovations, not the least of which was the development of a family of elegantly formulated and customized materials. These include the UV curable imprint resist that is ink-jetted onto the substrate and an adhesion layer for the substrate to promote adhesion of the cured imprint resist.

The imprint resist characteristics can be grouped into fluid (rheological and surface) properties prior to UV curing and solid phase properties after UV curing. Fluid properties include viscosity, wettability, evaporation characteristics and dispensability. Solid phase properties include cohesive yield strength, elongation to failure, adhesion to substrate, surface contact angle, and ease of release from imprint mask.The imprint resist formulas delicately balance the fluid and solid phase considerations. This balancing act is the key to imprint resist’s success.

Imprint resists must be dispensed with appropriate flow characteristics and require certain specifications on both viscosity and evaporation rate. Process uniformity and shelf life add additional fluid requirements. When all features are fully filled with resist, a UV cross-linking step follows. Efficient cross-linking materials require short exposure times without causing excessive heating to the mask and substrate. All of these demands must be carefully balanced. Finally, the material must have the necessary etch selectivity while meeting the most stringent CMOS purity requirements of <10ppb, not only as formulated, but after passage through the inkjet head assembly.

After exposure, the mask is separated from the substrate. It is essential to assure the cured resist adheres to the substrate, not to the mask. Typically, very thin substrate adhesion promoting layers are used to facilitate clean separation.

It is also important to note that the backbone of the imprint resist is very similar to current 193 immersion formulations, meaning that all downstream processes remain almost identical to what has previously been developed.