Decomposition Analysis of Chemically Amplified Resists for Improving Critical Dimension Control

摘要

We have designed and synthesized a molecular resist material, which has only two protecting groups per molecule (prot-mad-2). Resists with this material can resolve a sub-30-nm half pitch (hp) pattern. We quantitatively analyzed a decomposition reaction using prot-mad-2 at the exposed and unexposed areas by taking advantage of its properties of high purity and simple structure. From the high performance liquid chromatography (HPLC) results, it was found that the main decomposition reaction was deprotection of prot-mad-2. The ratio of partly deprotected material (deprot-1-prot-mad-1) and fully deprotected material (deprot-2) increased with exposure dose. It was found that the exposure dose resulting in maximum surface roughness coincided with the exposure dose where fully protected, partly deprotected, and fully deprotected materials were present in equal quantities in the resist film. Furthermore, dissolution rates of prot-mad-2, deprot-1-prot-mad-1 and deprot-2 were completely different. It is considered that high surface roughness was generated by the different dissolution rates of prot-mad-2, deprot-1-prot-mad-1 and deprot-2. The results suggest that reducing the range of dissolution rates at the boundary between exposed and unexposed regions is key to improving line edge roughness (LER).