Resistive switching memory having confined filament formation and methods thereof
Resistive switching memory cells having filament-based switching mechanisms are provided. By way of example, resistive switching memory cells having resistive filaments constrained to a core of the cell are disclosed. In other examples, methods for fabricating resistive switching memory cells to constrain a conductive filament formed in the resistive switching memory cell to a central portion of core of the cell are disclosed.
1 . A resistive switching memory cell, comprising:
a bottom electrode formed within a dielectric material overlying a substrate;
a conductive layer overlying and in contact with both the bottom electrode and the dielectric layer;
a first resistive switching layer formed of an electrically resistive material overlying the conductive layer;
a second resistive switching layer formed overlying the first resistive switching layer, wherein the first resistive switching layer further comprises a gap formed therein that exposes a surface of the conductive layer directly to a portion of the second resistive switching layer within the gap in the first resistive switching layer; and
a top electrode overlying the second resistive switching layer and comprising conductive particles that diffuse within the second resistive switching layer in response to a suitable electrical stimulus applied to the resistive switching memory cell.
2 . The resistive switching memory cell of claim 1 , wherein the second resistive switching layer is formed conformally overlying the first resistive switching layer and the gap in the first resistive switching layer, and the second resistive switching layer comprises a second gap formed in the second resistive switching layer and overlying the gap in the first resistive switching layer.
3 . The resistive switching memory cell of claim 2 , wherein the top electrode fills the second gap formed in the second resistive switching layer to form a portion of the top electrode that is closer to the bottom plate, in a region of the resistive switching memory cell defined by the second gap, than a second portion of the top electrode outside of the second gap.
4 . The resistive switching memory cell of claim 1 , wherein the second resistive switching layer is formed of a non-stoichiometric metal oxygen or metal nitrogen material.
5 . The resistive switching memory ell of claim 4 , wherein the top electrode is formed of a noble metal, a diffusive metal alloy, mixture or compound, a non-stoichiometric metal and nitrogen material, or a non-stoichiometric metal and oxygen material.
6 . The resistive switching memory cell of claim 4 , wherein the first resistive switching layer is formed of a stoichiometric or substantially stoichiometric metal oxygen or metal nitrogen material.
7 . The resistive switching memory cell of claim 1 , wherein a thickness of the first resistive switching layer is within a range of about 15 angstroms (Å) and about 50 Å and a second thickness of the second resistive switching layer is within the range of about 15 Å and about 50 Å.
8 . A resistive switching memory cell, comprising:
a bottom electrode;
a conductive layer overlying the bottom electrode;
a switching layer overlying and in physical contact with the conductive layer, wherein the switching layer comprises an electrically resistive material at least in part permeable to conductive particles;
a top electrode layer overlying and in physical contact with the switching layer, wherein the top electrode layer comprises a material of conductive particles capable of being ionized, wherein the conductive particles drift into the switching layer in response to a suitable electrical stimulus applied to the resistive switching memory cell; and
a capping layer overlying the top electrode layer;
wherein the switching layer and the top electrode layer further comprise:
a central core comprising the material of conductive particles overlying the electrically resistive material;
a perimeter shell about the central core formed of an oxidized, etch-fractured material of conductive particles overlying an oxidized, etch-fractured electrically resistive material.
9 . The resistive switching memory cell of claim 8 , wherein the material of conductive particles is selected from a group consisting of: a non-stoichiometric metal and nitrogen material, an aluminum (Al) material, an Al metal, a non-stoichiometric AlN x , a stoichiometric or non-stoichiometric AlNO x , TIN, Ti and W.
10 . The resistive switching memory cell of claim 8 , wherein the material of conductive particles comprises a metal, nitrogen and silicon material with less than 2 percent by atomic weight of silicon.
11 . The resistive switching memory cell of claim 8 , wherein the perimeter shell has a thickness measured from an outer surface of the perimeter shell to the central core of greater than 50 Å.
12 . The resistive switching memory cell of claim 8 , wherein the capping layer comprises W metal, TiN, TaN, an aluminum metal, or an electrically conductive doped silicon material.
13 . The resistive switching memory cell of claim 8 , wherein the switching layer comprises a non-stoichiometric aluminum-rich nitrogen material or a non-stoichiometric aluminum-rich oxygen material.
14 . The resistive switching memory cell of claim 13 , wherein the top electrode layer comprises a second non-stoichiometric aluminum-rich nitrogen material or a non-stoichiometric aluminum-rich oxygen material.
15 . The resistive switching memory cell of claim 14 , wherein the perimeter shell includes oxygen-anodized, etch-induced fractures, voids or byproducts within the non-stoichiometric aluminum-rich nitrogen or oxygen materials of the switching layer and the top electrode layer to a depth greater than 50 Å.
16 . A method of fabricating a resistive switching device, comprising:
forming a conductive layer over a bottom electrode situated within a dielectric layer overlying a semiconductor substrate;
forming a switching layer overlying and in physical contact with the conductive layer, wherein the switching layer comprises an electrically resistive material at least in part permeable to conductive particles;
forming a top electrode layer overlying and in physical contact with the switching layer, wherein the top electrode layer provides the conductive particles that drift into the switching layer in response to an electrical stimulus applied across the bottom electrode and the top electrode;
forming a capping layer overlying the top electrode layer;
etching the capping layer, the top electrode layer and the switching layer to form a discrete resistive switching device comprising an etched capping layer, an etched top electrode layer and an etched switching layer;
selectively etching a perimeter of the discrete resistive switching device and removing an exterior portion of the etched top electrode layer to an interior depth; and
depositing a high electrical resistive conformal oxide material about the resistive switching device and filling the interior depth of the etched top electrode, wherein the oxide material has an electrical resistance higher than the electrically resistive material of the switching layer, or has lower permeability to the conductive particles than the electrically resistive material of the switching layer.
17 . The method of claim 16 , wherein selectively etching the perimeter of the discrete resistive switching device further comprises etching the discrete resistive switching device with a dilute ammonium hydroxide or a dilute tetramethylammonium hydroxide (TMAH).
18 . The method of claim 17 , wherein the dilute ammonium hydroxide has a dilution ratio in a range from about 10000:1 solvent to ammonium hydroxide or TMAH to about 14000:1 solvent to ammonium hydroxide or TMAH.
19 . The method of claim 16 , wherein forming the top electrode layer further comprises depositing the top electrode layer with a stoichiometric or non-stoichiometric aluminum-rich nitrogen material utilizing a physical vapor deposition (PVD) process.
20 . The method of claim 19 , wherein forming the switching layer further comprises depositing the switching layer with a stoichiometric or non-stoichiometric aluminum oxide material utilizing a PVD process, wherein the stoichiometric or non-stoichiometric aluminum oxide material is resistant to the selective etch of the perimeter of the discrete resistive switching device.
21 . The resistive switching memory cell of claim 1 , further comprising a barrier layer overlying the top electrode and comprising W, Ti, TiN or TaN.