Forming Phase Change Memory Cell With Microtrenches
A semiconductor substrate is covered by a dielectric region. The dielectric region accommodates a memory element and a selection element forming a phase change memory cell. The memory element is formed by a resistive element and by a storage region of a phase change material extending on and in contact with the resistive element at a contact area. The selection element is formed by a switching region of chalcogenic material embedded in the dielectric region and belonging to a stack extending on the resistive element and including also the storage region. A mold region extends on top of the resistive element and delimits a trench having a substantially elongated shape. At least one portion of the storage region extends in the trench and defines a phase change memory portion over the contact area.
1 . A method comprising:
forming a substantially planar dielectric layer;
forming a trench in said dielectric layer by etching the substantially planar dielectric layer to form inclined sidewalls in said trench in said dielectric layer; and
forming a phase change material in said trench.
2 . The method of claim 1 wherein prior to forming said dielectric layer, forming a wall heater and forming said dielectric layer over said wall heater.
3 . The method of claim 2 including forming said wall heater in a U-shape having a base and an upstanding wall extending therefrom.
4 . The method of claim 3 including forming said wall heater with an upper edge defining a closed geometric shape.
5 . The method of claim 4 including forming said upper edge in contact with said phase change material.
6 . The method of claim 5 including contacting only a portion of said upper edge of said wall with said phase change material.
7 . The method of claim 6 including misaligning said wall heater with said phase change material.
8 . The method of claim 1 including forming said trench with four inclined sidewalls.
9 . The method of claim 8 including forming said sidewalls at an angle of about 60 to about 70 degrees to the horizontal plane.
10 . The method of claim 2 including forming said trench elongated in a first direction and forming said wall heater to extend orthogonally to said first direction.