Method for etching integrated-circuit layers to a fixed depth and corresponding integrated circuit

A method for etching a layer of material of an integrated circuit, over a fixed depth, said method consisting of:

• a) depositing onto said layer of material designated as the layer to be etched, a protective layer forming a stop layer,
• b) depositing onto said stop layer a reference layer made of a material identical to that of the layer to be etched and whose thickness is made substantially equal to the depth of the etch to be produced in said layer to be etched,
• c) applying to said reference layer an etch mask having the plane dimensions of the etch to be produced in said layer to be etched,
• d) carrying out the etching by chemical attack, dry or wet, of said reference layer by the intermediary of the etch mask until encountering and exposing a portion of the stop layer in a zone for etching the reference layer,
• e) removing said mask and said exposed stop layer;
• f) simultaneously subjecting the reference layer, remaining stop layer and the layer of material to be etched in the region of said zone liberated by the removal of the exposed stop layer to a chemical attack, dry or wet, until the remaining stop layer underneath said reference layer is exposed, the reference layer and the remaining stop layer forming an auxiliary mask for the layer to be etched so as to create, in the layer to be etched, an etch having the plane dimensions of the etch of the reference layer and a depth substantially proportional to the thickness of this reference layer.