Patent ID: 8263317

Claim:
A method for forming at least one hollow zone in a stack of at least one upper layer and one lower layer, comprising the following successive steps: patterning of the upper layer to form at least a first hollow region passing through the upper layer, forming an etching mask on the patterned upper layer, consisting of: depositing a layer of a positive acting photosensitive resin and exposing it to an optic radiation of a predetermined first wavelength, on the patterned upper layer, the lower and upper layers of the stack being respectively transparent and opaque to the predetermined first wavelength, in exposing the positive acting photosensitive resin layer to the optic radiation through the stack, developing the positive acting photosensitive resin layer, etching the lower layer through the etching mask to form at least a second hollow region extending the first hollow region, and removing the etching mask, wherein, before the step of patterning the upper layer, the upper layer is formed of a material able to change phase or to change state, due to the action of heating caused by an optic radiation of a predetermined second wavelength different from the first wavelength.