Reversing the hydrogen silsesquioxane image by silicon nitride and silicon oxide chemical mechanical polishing

Abstract

Patterns, e-beam written in hydrogen silsesquioxane (HSQ), have been reversed in tone by chemical mechanical polishing of silicon nitride deposited on top of these HSQ patterns. First, high-resolution patterns have been written in an 80nm thick HSQ layer on a 6in. silicon wafer. After development, 200nm thick plasma enhanced chemical vapor deposited silicon nitride has been deposited at 300°C on top of these patterns. Next, the silicon nitride has been Syton polished down to 50nm thickness. Finally, the HSQ has been removed wet chemically from in between the nitride features using buffered oxide etch (7:1). Features of 50nm wide have been resolved, but even smaller isolated spaces are feasible. The same method has been tested with silicon oxide obtained from boron doped tetraethyl orthosilicate. Although the wet-chemical removal of HSQ is less selective in this case, still 50nm wide features have been resolved in silicon oxide this way.