None Hazardous Chemical Method for Etching Thin Film Silicon Nitride Using Aqueous Solutions of Chelating Agents

Abstract

Structuring of thin film silicon nitride (SiN) is often done by etching the thin film using hydrofluoric acid (HF) or phosphorus acid, two hazardous chemicals. We present a non-hazardous method to structure thin film SiN using aqueous solutions of chelating agents at moderate temperatures to slowly etch thin film silicon nitride. Using solutions of citric acid as a model solution, we achieve etch rates of up to [3.14 ± 0.06] nm/h at 90°C for PECVD grown SiN. Experiments with aqueous solutions of tartaric acid show etch rates of at least [4.38 ± 0.02] nm/h at 80°C for PECVD grown SiN. The etching mechanism is determined as a partial hydrolysis of the SiN involving free H+ ions.