Nonvolatile Resistive Memory Element With an Integrated Oxygen Isolation Structure

Abstract

A nonvolatile resistive memory element includes one or more novel oxygen isolation structures that protect the resistive switching material of the memory element from oxygen migration. One such oxygen isolation structure comprises an oxygen barrier layer that isolates the resistive switching material from other portions of the resistive memory device during fabrication and/or operation of the memory device. Another such oxygen isolation structure comprises a sacrificial layer that reacts with unwanted oxygen migrating toward the resistive switching material during fabrication and/or operation of the memory device.

We claim: 
     
         1 . A method of forming a device, the method comprising:
 forming a first layer over a substrate,
 wherein the first layer is operable as a first oxygen isolation layer; 
   forming a second layer over the first layer,
 wherein the second layer is operable as a first electrode; 
   forming a third layer over the second layer,
 wherein the third layer is operable as a variable resistance layer configured to switch between a low resistive state and a high resistive state, 
 wherein the first layer is configured to block oxygen migration between the substrate and the third layer when the third layer switches between the low resistive state and the high resistive state; and 
   forming a fourth layer over the third layer,
 wherein the second layer is operable as a second electrode. 
   
     
     
         2 . The method of  claim 1 , wherein the first layer comprises tantalum, silicon, and carbon. 
     
     
         3 . The method of  claim 1 , wherein the first layer comprises Ta 40 W 40 Si 10 C 10 . 
     
     
         4 . The method of  claim 1 , wherein the first layer is formed by co-sputtering a tantalum target, a tungsten target, and a silicon carbide target. 
     
     
         5 . The method of  claim 1 , wherein the first layer comprises an oxygen barrier layer and a sacrificial layer, wherein the oxygen barrier layer is operable as a physical barrier to migration of mobile oxygen ions through the first layer, and wherein a material of the sacrificial layer is more reactive with oxygen than a material of the third layer. 
     
     
         6 . The method of  claim 5 , wherein a resistance of the oxygen barrier layer is no more than about 10% of a resistance of the third layer when in the low resistive state. 
     
     
         7 . The method of  claim 5 , wherein the oxygen barrier layer is substantially amorphous. 
     
     
         8 . The method of  claim 5 , further comprising annealing the device comprising the oxygen barrier layer at a temperature of at least 600° C., wherein the oxygen barrier layer is substantially amorphous after annealing. 
     
     
         9 . The method of  claim 5 , wherein the oxygen barrier layer has a thickness of between 5 nanometers and 50 nanometers. 
     
     
         10 . The method of  claim 5 , wherein the sacrificial layer has a thickness of less than 2 nanometers. 
     
     
         11 . The method of  claim 5 , wherein the sacrificial layer has a thickness of between 0.3 nanometers and 0.7 nanometers. 
     
     
         12 . The method of  claim 5 , wherein the sacrificial layer is amorphous. 
     
     
         13 . The method of  claim 5 , wherein the sacrificial layer comprises amorphous silicon. 
     
     
         14 . The method of  claim 1 , wherein the third layer comprises one of Hf x O y , Ta x O y , Al x O y , La x O y , Y x O y , Dy x O y , Yb x O y , or Zr x O y . 
     
     
         15 . The method of  claim 1 , wherein the third layer has a thickness of between about 2 nanometers and 10 nanometers. 
     
     
         16 . The method of  claim 1 , wherein the fourth layer comprises titanium nitride and has a thickness of between about 10 nanometers and 100 nanometers. 
     
     
         17 . The method of  claim 1 , further comprising forming a fifth layer covering sidewalls of at least the third layer, wherein the fifth layer is operable as a second oxygen isolation layer. 
     
     
         18 . The method of  claim 17 , wherein the fifth layer comprises one of silicon nitride, tetraethyl orthosilicate, or amorphous silicon. 
     
     
         19 . The method of  claim 17 , wherein the fifth layer comprises silicon nitride. 
     
     
         20 . The method of  claim 1 , further comprising forming a sixth layer over the fourth layer, wherein the sixth layer is operable as a third oxygen isolation layer, and wherein the first layer, the second layer, the third layer, the fourth layer, and the sixth layer form a stack.