Metal-to-metal antifuse employing carbon-containing antifuse material

Abstract

A metal-to-metal antifuse is disposed between two metal interconnect layers in an integrated circuit. An insulating layer is disposed above a lower metal interconnect layer. The insulating layer includes a via formed therethrough containing a tungsten plug in electrical contact with the lower metal interconnect layer. The tungsten plug forms a lower electrode of the antifuse. The upper surface of the tungsten plug is planarized with the upper surface of the insulating layer. In a first embodiment, an antifuse material layer comprising amorphous carbon, amorphous carbon doped with hydrogen or fluorine, or amorphous silicon carbide is disposed above the upper surface of the tungsten plug. A layer of a barrier metal disposed over the antifuse material layer forms an upper electrode of the antifuse. An oxide or tungsten hard mask provides high etch selectivity and the possibility to etch barrier metals without affecting the dielectric constant value and mechanical properties of the antifuse material. In a second embodiment, a layer of barrier material is disposed between the top surface of the tungsten plug and the antifuse material layer. An adhesion-promoting layer may be used where amorphous carbon is used as the antifuse material layer.

What is claimed is:  
     
         1 . A metal-to-metal antifuse disposed between two metal interconnect layers in an integrated circuit and comprising: 
 a tungsten plug disposed in a via in an insulating layer disposed above and in electrical contact with a lower metal interconnect layer;    an antifuse material layer disposed above an upper surface of said tungsten plug, said antifuse material layer selected from a group comprising at least one of amorphous carbon, amorphous carbon doped with at least one of hydrogen and fluorine, and amorphous silicon carbide;    a layer of a barrier metal disposed over said antifuse material layer; and    an upper electrode disposed over said layer of a barrier metal.    
     
     
         2 . The metal-to-metal antifuse of  claim 1 , wherein said antifuse material layer comprises a layer of amorphous carbon disposed between two layers of an adhesion-promoting material.  
     
     
         3 . The metal-to-metal antifuse of  claim 2  wherein said layer of amorphous carbon is doped with at least one of hydrogen and fluorine.  
     
     
         4 . The metal-to-metal antifuse of  claim 1 , further comprising a second insulating layer disposed over and in physical contact with said layer of barrier metal, said antifuse material layer, and said insulating layer.  
     
     
         5 . The metal-to-metal antifuse of  claim 1 , further comprising a spacer disposed in physical contact with said antifuse material layer.  
     
     
         6 . The metal-to-metal antifuse of  claim 1 , wherein said antifuse material layer is about 10 nm to about 80 nm in thickness.  
     
     
         7 . The metal-to-metal antifuse of  claim 1 , wherein said barrier metal layer is about 25 nm to about 200 nm in thickness.  
     
     
         8 . The metal-to-metal antifuse of  claim 1 , wherein said barrier metal layer is from a material selected from the group comprising Ta, TaC, TaN, Ti, TiC, and TiN.  
     
     
         9 . The metal-to-metal antifuse of  claim 1 , wherein said antifuse material layer is formed from a first layer of amorphous silicon carbide, a second layer of amorphous carbon, and a third layer of amorphous silicon carbide.  
     
     
         10 . The metal-to-metal antifuse of  claim 1 , wherein said antifuse material layer is formed from a first layer of amorphous silicon nitride, a second layer of amorphous carbon, and a third layer of amorphous silicon nitride.  
     
     
         11 . The metal-to-metal antifuse of  claim 1 , further comprising an oxide layer disposed on said barrier metal layer.  
     
     
         12 . The metal-to-metal antifuse of  claim 1 , further comprising a tungsten layer disposed on said barrier metal layer.  
     
     
         13 . A metal-to-metal antifuse disposed between two metal interconnect layers in an integrated circuit and comprising: 
 a tungsten plug disposed in a via in an insulating layer disposed above and in electrical contact with a lower metal interconnect layer;    a first layer of barrier metal disposed above and in electrical contact with said tungsten plug;    an antifuse material layer disposed above said first layer of barrier material, said antifuse material layer selected from a group comprising at least one of amorphous carbon, amorphous carbon doped with at least one of hydrogen and fluorine, and amorphous silicon carbide;    a second layer of a barrier metal disposed over said antifuse material layer;    a second insulating layer disposed over said first insulating layer, said antifuse material layer, said first layer of a barrier metal, and said second layer of a barrier metal; and    an upper electrode disposed over said second layer of a barrier metal.    
     
     
         14 . The metal-to-metal antifuse of  claim 13 , wherein said antifuse material layer comprises a layer of amorphous carbon disposed between two layers of an adhesion-promoting material.  
     
     
         15 . The metal-to-metal antifuse of  claim 14 , wherein said layer of amorphous carbon is doped with at least one of hydrogen and fluorine.  
     
     
         16 . The metal-to-metal antifuse of  claim 13 , further comprising a spacer disposed in physical contact with said antifuse material layer.  
     
     
         17 . The metal-to-metal antifuse of  claim 13 , wherein said antifuse material layer is about 10 nm to about 80 nm in thickness.  
     
     
         18 . The metal-to-metal antifuse of  claim 13 , wherein said barrier metal layer is about 25 nm to about 200 nm in thickness.  
     
     
         19 . The metal-to-metal antifuse of  claim 13 , wherein said barrier metal layer is from a material selected from the group comprising Ta, TaC, TaN, Ti, TiC, and TiN.  
     
     
         20 . The metal-to-metal antifuse of  claim 13 , wherein said antifuse material layer is formed from a first layer of amorphous silicon carbide, a second layer of amorphous carbon, and a third layer of amorphous silicon carbide.  
     
     
         21 . The metal-to-metal antifuse of  claim 13 , wherein said antifuse material layer is formed from a first layer of amorphous silicon nitride, a second layer of amorphous carbon, and a third layer of amorphous silicon nitride.  
     
     
         22 . The metal-to-metal antifuse of  claim 13 , further comprising an oxide layer disposed on said second layer of a barrier metal layer.  
     
     
         23 . The metal-to-metal antifuse of  claim 13 , further comprising a tungsten layer disposed on said second layer of a barrier metal layer.  
     
     
         24 . A method of fabricating a metal-to-metal antifuse, comprising: 
 planarizing an insulating layer and a tungsten plug;    forming an antifuse material layer over said insulating layer and said tungsten plug, wherein said antifuse material layer is selected from the group comprising amorphous carbon, amorphous carbon doped with at least one of hydrogen and fluorine, and amorphous silicon carbide;    defining said antifuse material layer;    forming a barrier metal layer over said antifuse material layer;    defining said barrier metal layer;    forming an oxide or tungsten layer over said barrier metal layer;    forming a layer of photoresist over said oxide or said tungsten layer;    defining said oxide or said tungsten layer;    removing said photoresist;    forming a first masking layer over said barrier metal layer;    defining a shape of said antifuse;    removing said first masking layer;    forming a metal interconnect layer over said insulating layer;    forming a second masking layer over said metal interconnect layer; and    removing said second masking layer.    
     
     
         25 . The method of  claim 24 , wherein said forming said antifuse material layer comprises forming said antifuse material layer to a thickness of from about 10 nm to about 80 nm.  
     
     
         26 . The method of  claim 24 , wherein said forming said barrier metal layer comprises forming said barrier metal layer to a thickness of from about 25 nm to about 200 nm.  
     
     
         27 . The method of  claim 24 , wherein said forming said barrier metal layer comprises forming said barrier metal layer from a material selected from the group comprising Ta, TaC, TaN, Ti, TiC, and TiN.  
     
     
         28 . The method of  claim 24 , further comprising forming a second insulating layer in physical contact with said layer of barrier metal, said antifuse material layer; said insulating layer; and said metal interconnect layer; and defining said second insulating material.  
     
     
         29 . The method of  claim 24 , further comprising forming a layer of a third insulating material over said barrier metal layer and said antifuse material layer; and defining said third insulating material into spacers disposed in physical contact with said antifuse material layer and said barrier metal layer.  
     
     
         30 . The method of  claim 24 , further comprising disposing adhesion layers in physical contact with said antifuse material layer and said layer of barrier metal.  
     
     
         31 . The method of  claim 24 , wherein said forming said antifuse material layer comprises forming a first layer of amorphous silicon carbide, a second layer of amorphous carbon, and a third layer of amorphous silicon carbide.  
     
     
         32 . The method of  claim 24 , wherein said forming said antifuse material layer comprises forming a first layer of amorphous silicon nitride, a second layer of amorphous carbon, and a third layer of amorphous silicon nitride.  
     
     
         33 . The method of  claim 24 , wherein said forming an antifuse material layer is deposited from an acetylene source gas.