Enhancing etch resistance of hydrogen silsesquioxane via postdevelop electron curing

In this work, the authors enhanced the etch resistance of the negative-tone electron resist, hydrogen silsesquioxane (HSQ) to CF4 reactive ion etching (RIE) by curing HSQ after development. They fabricated superconducting nanowires that were 15nm wide by pattern transfer into a 6-nm-thick layer of NbN using cured HSQ as the etch mask. HSQ was cured using a postdevelop electron-beam exposure step prior to RIE in CF4 chemistry. This curing step was shown not to impact the resolution of the HSQ structures while increasing their etch resistance. The results of the authors demonstrate that the etch resistance of HSQ can be tuned after development, which is a desirable resist property of HSQ in addition to its high resolution and low line-edge roughness.