Resistance variable memory structure and method of forming the same

A memory structure comprising:

• a first dielectric layer having a top surface and an opening with an interior sidewall surface, the first dielectric layer being substantially oxygen-free;
• at least a part of a second dielectric layer disposed in a top section of the opening, the second dielectric layer being substantially oxygen-free;
• and
• a resistive random access memory (RRAM) cell disposed between the interior sidewall surface of the opening and the second dielectric layer, the RRAM cell comprising:
• a first electrode structure disposed in a bottom section of the opening and extending upwardly along the interior sidewall surface of the opening;
• a resistance variable layer disposed over the first electrode structure;
• and
• a second electrode structure disposed over the resistance variable layer and contacting at least a part of the second dielectric layer;
• wherein an edge region of the RRAM cell does not protrude out of the top surface of the first dielectric layer.

A method of forming a resistance variable memory structure, the method comprising:

• forming a first dielectric layer over a conductive structure, the first dielectric layer having a first top surface, the first dielectric layer being substantially oxygen-free;
• etching an opening in the first dielectric layer thereby exposing an area of the conductive structure, the opening having an interior sidewall surface;
• forming a first electrode material over the exposed area of the conductive structure, along the interior sidewall surface of the opening and over the first top surface of the first dielectric layer;
• forming a resistance variable layer over the first electrode material;
• forming a second electrode material over the resistance variable layer, the second electrode material having a portion in the opening, wherein the portion has a second top surface below the first top surface of the first dielectric layer;
• forming a second dielectric layer over the second electrode material, the second dielectric layer being substantially oxygen-free;
• and
• performing at least one polishing process to remove the second dielectric layer, the second electrode material, the resistance variable layer and the first electrode material above the first top surface of the first dielectric layer.