are gas such as helium (He) or argon (Ar) is added, or the like. [0124] The etchant used for wet etching can be a mixed solution of phosphoric acid, acetic acid, and nitric acid, or an ammonium hydrogen peroxide mixture (a solution in which 31 wt% hydrogen peroxide, 28 wt% ammonia water, and water are mixed in a volume ratio of 5:2:2), or the like.