An etching method is disclosed. A substrate is provided. An etching is performed to form at least one opening in the substrate. An auxiliary etching layer is formed in the opening to cover at least one etching residue. The auxiliary etching layer includes a media, a carrier and an etching component encapsulated by the carrier. A treatment process is performed to the auxiliary etching layer. The treatment process includes applying an energy to the auxiliary etching layer or exposing the auxiliary layer to a gas, so that the carrier breaks in the treatment and thereby the etching component is released to etch the etching residue.