A method for manufacturing a laminated structure, or a method for manufacturing a liquid ejection head substrate having an electrode pad, including: preparing a substrate on which a first layer is formed, foreign matter being present on a surface of the first layer; forming a mask layer on an entire area of a surface of the substrate, the surface of the substrate being provided with the first layer; removing at least a part of the foreign matter in a height direction by performing an etching treatment on the entire surface of the mask layer; and forming a second layer on a surface on which the etching treatment is performed, wherein the etching treatment is performed so that the foreign matter is not exposed from the second layer after forming the second layer.

A method for manufacturing a laminated structure, or a method for manufacturing a liquid ejection head substrate having an electrode pad, including: preparing a substrate on which a first layer is formed, foreign matter being present on a surface of the first layer; forming a mask layer on an entire area of a surface of the substrate, the surface of the substrate being provided with the first layer; removing at least a part of the foreign matter in a height direction by performing an etching treatment on the entire surface of the mask layer; and forming a second layer on a surface on which the etching treatment is performed, wherein the etching treatment is performed so that the foreign matter is not exposed from the second layer after forming the second layer.

A method of producing metal flakes (72) is provided. The method includes: applying a layer of ionic liquid (70) to a substrate (24); forming a layer of metal (70) on the substrate (24) over the ionic liquid (70); and removing the layer of metal (70) from the substrate (24).