Method for flattening substrates or layers using 3d printing and etching

The present invention concerns a layer or substrate flattening method comprising the steps of: - providing a layer or substrate (1) to be flattened; - measuring a topography or surface profile of at least one area (3) of the layer or substrate to be flattened; - providing at least one etch layer (5A) on at least one area of the layer or substrate to be flattened; - defining a topography (7) of said at least one etch layer, said topography to be exposed to etching; and - etching the at least one etch layer comprising the defined topographic surface and the at least one area of the layer or substrate to provide a flattened surface on the at least one area of the layer or substrate.