New materials for 193-nm trilayer imaging

This paper presents our progress in developing spin-on, thermosetting hardmasks and bottom antireflective coatings (BARCs) for 193-nm trilayer usage. Binder materials that were used in preparing the silicon-containing hardmasks include polymers with pendant alkylsilane function and various polyhedral oligomeric silsesquioxane (POSS) substances, with the hardmasks being very transparent at both 193 and 248 nm. The second generation hardmasks (POSS-containing) offer significant improvements over earlier materials in oxygen (O2) plasma etching resistance. The etching selectivity (O2 plasma) for a trilayer BARC relative to the best-case hardmask is about 31.5:1 (15-second etch), with the selectivity numbers being much higher for longer etching times. The preferred hardmask is both spin-bowl and solution compatible. The new trilayer BARCs use binders that are rich in aromatic content for halogen plasma etching resistance, but the antireflective products also feature optical parameters that allow low reflectivity into the photoresist. The BARCs are very spin-bowl compatible. At about 500-nm film thickness, selected BARCs have provided 80-95% planarity over 200-nm topography. Combining the two thermosetting products (hardmask and BARC) with a thin 193-nm photoresist in a trilayer configuration has given excellent 80-nm L/S (1:1) after exposure and wet-development. A conventional resist has provided 100-nm L/S (1:1.4).