Wire bonding method for copper interconnects in semiconductor devices

Abstract

The present invention uses wire bonding technology to bond interconnect materials that oxidize easily by using a wire with stable oxidation qualities. A passivation layer is formed on the semiconductor substrate to encapsulate the bonding pad made from the interconnect material such that the wire bonds with the passivation layer itself, not with the interconnect material. The passivation layer is selected to be a material that is metallurgically stable when bonded to the interconnect material. Since the wire is stable compared with the interconnect material, i.e., it does not readily corrode, a reliable mechanical and electrical connection is provided between the semiconductor device (interconnect material) and the wire, with the passivation layer disposed therebetween.

1 . A wire bonding method, comprising the steps of: 
 forming a semiconductor substrate with a copper (Cu) interconnect material;    fabricating a copper (Cu) bond pad;    depositing a tantalum (Ta) layer onto the substrate;    patterning and etching the tantalum (Ta) layer; and    bonding an aluminum (Al) wire with the tantalum (Ta) layer;    wherein a portion of the tantalum (Ta) layer bonds with the copper (Cu) bond pad, and another portion of the tantalum (Ta) layer forms a tantalum aluminide (TaAl 3 ) compound.    
     
     
         2 . The method of  claim 1 , wherein the wire is a wire selected from the group consisting of an aluminum wire, an aluminum alloy wire, and an aluminum-coated gold wire.  
     
     
         3 . The method of  claim 1 , wherein thickness of the tantalum (Ta) layer is controlled such that a portion of the tantalum (Ta) layer bonds with the copper (Cu) bond pad, and another portion of the tantalum (Ta) layer forms a tantalum aluminide (TaAl 3 ) compound.  
     
     
         4 . The method of  claim 1 , wherein thickness of the tantalum (Ta) layer is between 300 to 1000 angstroms (A).  
     
     
         5 . The method of  claim 1 , wherein the aluminum (Al) wire is bonded onto the tantalum (Ta) layer by wedge bonding.  
     
     
         6 . The method of  claim 1 , further comprising the step of performing a heat treatment after the bonding step.  
     
     
         7 . The method of  claim 1 , further comprising the step of packaging the substrate in a package consisting of a plastic package and a hermetic package.  
     
     
         8 . The method of  claim 1 , wherein the tantalum (Ta) layer is patterned by a method consisting of negative tone pad masking, photoresist patterning, and photolithography.  
     
     
         9 . The method of  claim 1 , wherein the substrate is a multi-layered interconnect structure.  
     
     
         10 . A wire bonding method, comprising the steps of: 
 forming a passivation layer on a semiconductor substrate;    bonding a wire onto the passivation layer; and    encapsulating a bond pad made from an interconnect material, wherein the wire is more metallurgically stable than the interconnect material;    wherein a portion of the passivation layer forms a metallurgical bond with the interconnect material;    wherein a mechanical and electrical connection is provided between the interconnect material and the wire, with the passivation layer disposed therebetween.    
     
     
         11 . The method of  claim 10 , wherein the wire is a wire selected from the group consisting of an aluminum wire, an aluminum alloy wire, and an aluminum-coated gold wire.  
     
     
         12 . The method of  claim 10 , wherein the passivation layer is a tantalum (Ta) layer.  
     
     
         13 . The method of  claim 10 , wherein the wire is bonded onto the passivation layer by wedge bonding.  
     
     
         14 . The method of  claim 10 , further comprising the step of performing a heat treatment after the bonding step.  
     
     
         15 . The method of  claim 10 , wherein the substrate is a multi-layered interconnect structure.  
     
     
         16 . A semiconductor device, comprising: 
 a substrate;    a copper (Cu) bond pad formed on the substrate;    a tantalum (Ta) layer encapsulating the copper (Cu) bond pad;    wherein a portion of the tantalum (Ta) layer bonds with the copper (Cu) bond pad, and another portion of the tantalum (Ta) layer forms a tantalum aluminide (TaAl 3 ) compound.    
     
     
         17 . The device of  claim 16 , wherein the substrate is a multi-layered interconnect structure.  
     
     
         18 . The device of  claim 16 , wherein the tantalum (Ta) layer is bonded with the copper (Cu) bond pad using wedge bonding.  
     
     
         19 . The device of  claim 16 , wherein the substrate is packaged in one of the group consisting of a plastic package and a hermetic package.  
     
     
         20 . The device of  claim 16 , wherein thickness of the tantalum (Ta) layer is between 300 to 1000 angstroms (Å).