Design and Study of Silicone-based Materials for Bilayer Resist Application

To achieve both sufficient dry etch stability and transparency at 157nm is a challenging task. The bilayer scheme composed of a Si-containing top imaging layer and a thick bottom layer offers good thin film imaging without scarifying etch capability. For the imaging top layer, we have developed a polymer platform based on silsesquioxane (SSQ) backbone having pendant functional groups containing the hexafluoroisopropanol (HFIP) functionality. Monomer and polymer structures were rationally designed to achieve film absorbance at 157nm of 1.1/um and 65nm 1:1 resolution using a 0.6NA 157nm stepper. Outgassing studies during exposure showed that there was no detectable Si-containing outgas from this material. However, about 7% film thickness loss was obtained during exposure that is believed to arise from a very fast deprotection of the ethoxymethyl protecting group.