Takashi Ohkubo

Improved time dependent performance of hydrogen silsesquioxane resist using a spin on top coat

Hydrogen silsesquioxane (HSQ) is a high resolution negative tone electron beam (e-beam) resist with a resolution well below 10 nm. However, it is known that the time delay between spinning and e-beam exposure has an effect on the contrast and sensitivity. Significant effort has been placed on finding the best developer conditions (e.g., time, temperature, concentration, etc.) to maximize the performance of the resist. However, to date, little progress has been made to mitigate the problem of temporal dependence of optimal results. The authors report a significantly improved time dependent performance of HSQ by using a spin on top coat developed by Showa Denko. The material contains a conductive, water-soluble polymer (i.e., poly[isothianaphthene sulfonate]) and surfactants. Exposure delays from 0 to 12 h were performed in vacuum and the effect on sensitivity and ultimate resolution was compared to results without a top coat. Various bottom layers and top coats were also used and the change in performance ...