Patent ID: 8828882

Claim:
A method for forming a trench in a semiconductor substrate around an area of a microelectronic element, wherein the geometry of said area defines properties of the microelectronic element, and wherein said area is located in a predetermined thickness of the semiconductor substrate from a surface thereof, said method comprising the deposition on said surface of the substrate of an etch mask masking said area and having an opening of access to the substrate around said area, the ion etching of said trench through said opening over a thickness of the substrate greater than the thickness of said area, and the doping of the walls of the trench, wherein the ion etching comprises: a first phase etching the semiconductor substrate to form a first part of the trench over the thickness of said area, with an etch power set to etch the semiconductor substrate under the etch mask; followed by a second phase etching the semiconductor substrate to form a second part of the trench over the entire thickness thereof, with an etch power smaller than the power of the first phase; and the doping of the walls of the trench is applied through the opening of the etch mask.