Polyurethane Resins as Resist Materials for Excimer Ablation Lithography(EAL)

The excimer laser ablation lithography(EAL) is a process of direct patterning and developing of a resist film by photo-decomposition ablation. Taking advantage of EAL process, we have tried to apply this process to LCD fabrication. As the most fundamental problem for resist materials is the ablation rate, we have examined to measure the ablation rates of many kinds of polymers. Among them the most promising is the polyurethane resin (PU) which is synthesized from toluenediisocyanate and poly(ethylene glycol) derivatives in chlorobenzene solution. The ablation rate at 100mJ/cm2 fluence of 248nm is more than 0.05μm/shot, which is the highest value of all the materials that we have examined. Through the investigations of structures of PU, we could elucidate the mechanisms of the high ablation rate, and accordingly the molecular design concept of the ablation resist.