Etch Properties of 193nm Resists

Polymer chemistries for 193nm resists are more or less defined and their lithographic performance is quite good to implement 100nm design rules. In spite of the use of high carbon containing adamantane or norbornene moieties in the polymer design, there exists etch selectivity as well as surface roughness issues after treatment with etch plasma. It is very much necessary to modify the etch plasma used for 193nm resists to improve the surface roughness. Etch rates of several acrylate, methacrylate and hybrid type polymers are measured and compared. While the problem still exists, acrylates in general seem to offer better surface properties than methacrylates. On the process side, e-beam curing of 193nm resists offers improvement in both etch selectivity as well as surface roughness. It was found from the IR spectra of before and after e-beam cured films that e-beam curing reduces the carbonyl groups and compacts the resist film leading to etch improvements. Effects of three different e-beam curing processes (Standard, LT and ESC) on the methacrylate & hybrid type 193nm resists were studied with respect to resin chemistry changes, resist film shrinkage, pattern profiles, etch rates, and CD SEM stability. Etch rate, selectivity and resist surface roughness after etch of both methacrylate and hybrid resists were improved using the e-beam curing process. E-beam curing drastically reduces (from ca. 15% to 2-5%) the CD SEM shrinkage; however, considerable shrinkage occurs during the curing process itself.