Guided path for forming a conductive filament in RRAM

A method of forming a resistive switching device for a non-volatile memory device, comprising:

• providing a substrate having a surface region;
• forming a first dielectric material overlying the surface region of the substrate;
• forming a first electrode structure in a portion of the first dielectric material;
• forming a second dielectric material overlying the first electrode;
• forming an opening structure in a portion of the second dielectric material to expose a surface region of the first electrode structure, the opening structure being characterized by an aspect ratio, wherein the opening structure is associated with a first vertical surface and a second vertical surface;
• forming a resistive switching material overlying the second dielectric material and filling at least a portion of the opening structure using a deposition process, the resistive switching material having a surface region characterized by a planar region and an indent structure, the indent structure overlying the first electrode structure, and wherein the indent structure is associated with a grain boundary between a first portion of the resistive switching material associated with the first vertical surface abutting a second portion of the resistive switching material associated with the second vertical surface, wherein the grain boundary provides a preferred path for a metallic filament;
• maintaining a first thickness of resistive switching material between the planar region and the first electrode structure;
• maintaining a second thickness of resistive switching material between the indent structure and the first electrode structure, wherein the first thickness is larger than the second thickness;
• and
• forming a second electrode structure overlying the resistive switching material including the indent structure, comprising an active metal material filling in at least the indent structure and at least partially filling the opening structure, wherein the active metal material is adapted to form the metallic filament in the resistive switching material.