Memory elements and methods for making same

Abstract

Annular, linear, and point contact structures are described which exhibit a greatly reduced susceptibility to process deviations caused by lithographic and deposition variations than does a conventional circular contact plug. In one embodiment, a standard conductive material such as carbon or titanium nitride is used to form the contact. In an alternative embodiment, a memory material itself is used to form the contact. These contact structures may be made by various processes, including chemical mechanical planarization and facet etching.

1. A memory cell comprising:
 a substrate;  
 a structure protruding from the substrate, the structure having at least one corner, the structure comprising one of a first conductive material and a first memory material;  
 a layer of insulating material disposed over the structure in a manner that leaves the at least one corner of the structure exposed to form at least one point contact;  
 at least one layer of material disposed over the at least one point contact, the at least one layer of material comprising a second conductive material if the structure comprises the first memory material, and the at least one layer of material comprising a second memory material if the structure comprises the first conductive material; and  
 a conductive layer disposed over the at least one layer of material if the at least one layer of material comprises the second memory material.  
 
     
     
       2. The memory cell of  claim 1 , wherein the substrate comprises a semiconductor substrate. 
     
     
       3. The memory cell of  claim 1 , wherein the first and second memory materials comprise a chalcogenide material. 
     
     
       4. The memory cell of  claim 1 , wherein the substrate comprises a conductive region in electrical contact with the structure. 
     
     
       5. The memory cell of  claim 1 , wherein the structure comprises a pillar. 
     
     
       6. The memory cell of  claim 5 , wherein the pillar is substantially square and comprises four corners. 
     
     
       7. The memory cell of  claim 5 , wherein the pillar contact is substantially rectangular and comprises four corners.