Etching gas and etching method

Abstract

Provided are an etching gas and an etching method, which are capable of selectively etching an etching object having silicon nitride in comparison with a non-etching object. The etching gas contains nitrosyl fluoride and also contains nitryl fluoride as an impurity, in which the concentration of nitryl fluoride is 0.0001 ppm by mass or more and 100 ppm by mass or less. The etching method includes an etching step of bringing this etching gas into contact with a member to be etched (12) having an etching object, which is an object of etching by the etching gas, and a non-etching object, which is not an object to be etched by the etching gas, and selectively etching the etching object in comparison with the non-etching object. The etching object has silicon nitride.

Dependencies are inferred from the claim text.