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

Abstract

Articles you may be interested inHydrogen silsesquioxane bilayer resists-Combining high resolution electron beam lithography and gentle resist removal J. Vac. Sci. Technol. B 31, 06F102 (2013); 10.1116/1.4822136Time-dependent exposure dose of hydrogen silsesquioxane when used as a negative electron-beam resist Hydrogen silsesquioxane for direct electron-beam patterning of step and flash imprint lithography templates 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 was evaluated. In all cases a significant improvement is observed when a top coat is applied and little change occurs with other parameters. The time lag effect is shown to be the equivalent of a decrease in sensitivity over time with about 30% degradation from the optimal dose over the test period if no top coat is used. The use of the top coat reduces the effect to about 5% while also improving initial sensitivity. The authors believe this represents a widely applicable solution to the time lag issue common to HSQ processes.

Depth Dependence of Time Delay Effect on Hydrogen Silsesquioxane (HSQ) Resist Layers

“…The advantages of using HSQ resist have also a low defect, a high uniformity, and a high etching resistance, and a good adhesion on silicon wafers [1,2]. It is also well known that there is a significant change of contrast and sensitivity if the e-beam exposure is delayed after the sample preparation [3,4,5].…”