Low current RRAM-based crossbar array circuit implemented with switching oxide engineering technologies
Switching oxide engineering technologies relating to low current RRAM-based crossbar array circuits are disclosed. A method for fabricating a crossbar device may include forming a bottom electrode on a substrate, forming a switching oxide stack on the bottom electrode, and forming a top electrode on the switching oxide stack. Fabricating the switching oxide stack may include fabricating a plurality of base oxide layers and a plurality of discontinuous oxide layers alternately stacked, wherein the base oxide layers comprise one or more base oxides, wherein the one or more base oxides comprise at least one of TaOx, HfOx, TiOx, or ZrOx.
1 . A method for fabricating a crossbar device, the method comprising:
forming a bottom electrode on a substrate;
forming a switching oxide stack on the bottom electrode, wherein fabricating the switching oxide stack comprises fabricating a plurality of base oxide layers and a plurality of discontinuous oxide layers alternately stacked, wherein the base oxide layers comprise one or more base oxides, wherein the one or more base oxides comprise at least one of TaO x , HfO x , TiO x , or ZrO x , wherein the plurality of discontinuous oxide layers comprises discontinuous oxide islands that are randomly located within the plurality of base oxide layers, and wherein the discontinuous oxide islands comprise at least one of Al 2 O 3 , SiO 2 , Si 3 N 4 , Y 2 O 3 , Gd 2 O 3 , Sm 2 O 3 , CeO 2 , or Er 2 O 3 ; and
forming a top electrode on the switching oxide stack.
2 . The method of claim 1 , wherein a thickness of each of the discontinuous oxide layers is between 0.2 nm and 0.7 nm.
3 . The method of claim 1 , wherein the one or more base oxides comprise: TaO x doped with HfO x , TaO x doped with ZrO x , HfO x doped with TaO x , or HfO x doped with ZrO x .
4 . The method of claim 1 , wherein the substrate comprises Si, Si 3 N 4 , SiO 2 , Al 2 O 3 , or a combination thereof.
5 . The method of claim 1 , wherein the switching oxide stack is formed using Atomic Layer Deposition (ALD) or co-sputter deposition combined with sequential sputter deposition.
6 . The method of claim 1 , wherein the switching oxide stack is formed using ALD, wherein a sub-cycle of the ALD comprises N1 cycles of each of the discontinuous oxide layers, followed by N2 cycles for one of the base oxide layers, wherein the sub-cycle is repeated N3 times, and wherein N1=1, N2=4, and N3=7.
7 . The method of claim 1 , wherein the switching oxide stack is formed using ALD, wherein a sub-cycle of the ALD comprises N1 cycles for each of the discontinuous oxide layers, followed by N2 cycles for one of the base oxide layers, wherein the sub-cycle is repeated N3 times, and wherein N2 is higher than N1.
8 . The method of claim 1 , wherein the switching oxide stack further comprises a mixture of multiple oxides formed using co-sputter deposition, and wherein the discontinuous oxide layers are formed using sequential sputter deposition.
9 . The method of claim 1 , wherein the bottom electrode comprises Ag, Al, Au, Cu, Fe, Ni, Mo, Pt, W, Co, Ru, Pd, Ti, TiN, TaN, W, Zr, a combination thereof, or an alloy of any of these materials with any other electrically conductive materials.
10 . The method of claim 9 , wherein the bottom electrode comprises a non-reactive material that is selected from: Pt, Pd, Ir, Rh, Ru, TiN, TaN, a combination thereof, or an alloy of any of these materials with any other electrically conductive materials.
11 . The method of claim 1 , wherein the top electrode comprises Ag, Al, Au, Cu, Fe, Ni, Mo, Pt, Pd, Ti, Ta, Hf, TiN, TaN, W, Zr, a combination thereof, or an alloy of any of these materials with any other electrically conductive materials.
12 . The method of claim 1 , wherein the top electrode comprises a reactive material that is selected from Ta, Hf, Zr, Ti, Al, Fe, a combination thereof, or an alloy of any of these materials with any other electrically conductive materials, and wherein a switching filament is configured to be formed within the switching oxide stack from the top electrode.
13 . The method of claim 1 , wherein the discontinuous oxide islands comprise a material that is more stable than the one or more base oxides.
14 . The method of claim 1 , wherein each of the plurality of base oxide layers is thicker than any of the plurality of discontinuous oxide layers.
15 . The method of claim 1 , wherein the plurality of discontinuous oxide layers comprises pinholes formed at random locations within the base oxides of the plurality of base oxide layers.