Copper alloy for wiring, semiconductor device, method for forming wiring, and method for manufacturing semiconductor device

Abstract

A wiring metal contains a polycrystal of copper (Cu) as a primary element and an additional element other than Cu, and concentration of the additional element is, at crystal grain boundaries composing the Cu polycrystal and in vicinities of the crystal grain boundaries, higher than that of the inside of the crystal grains. The additional element is preferably at least one element selected from a group consisting of Ti, Zr, Hf, Cr, Co, Al, Sn, Ni, Mg, and Ag. This Cu wiring is formed by forming a Cu polycrystalline film, forming an additional element layer on this Cu film, and diffusing this additional element from the additional element layer into the Cu film. This copper alloy for wiring is preferred as metal wiring formed for a semiconductor device.

What is claimed is: 
     
         1 . A polycrystalline copper alloy for wiring comprising a copper and an additional element,
 wherein the additional element is at least one element selected from a group consisting of Ti (titanium), Zr (zirconium), Hf (hafnium), Cr (chromium), Co (cobalt), Al (aluminum), Sn (tin), Ni (nickel), and Mg (magnesium), and concentration of the additional element, at boundaries between the polycrystalline copper alloy and an insulator films contacting the polycrystalline copper alloy, is higher than that of inside of crystal grains.   
     
     
         2 . A polycrystalline copper alloy for wiring comprising a copper and an additional element,
 wherein the additional element is at least one element selected from a group consisting of Ti (titanium), Zr (zirconium), Hf (hafnium), Cr (chromium), Co (cobalt), AI (aluminum), Sn (tin), Ni (nickel), and Mg (magnesium), and concentration of the additional element, at grain boundaries of crystal grains composing the polycrystalline copper alloy and in vicinities of grain boundaries, is higher than that of the inside of the crystal grains.   
     
     
         3 . The polycrystalline copper alloy for wiring as set forth in  claim 1 , wherein an oxide of the additional element is formed at said grain boundaries and/or in vicinities of said grain boundaries. 
     
     
         4 . The polycrystalline copper alloy for wiring as set forth in  claim 1 , wherein a barrier metal in a barrier film that is formed to surround the polycrystalline copper alloy is not oxidized. 
     
     
         5 . The polycrystalline copper alloy for wiring as set forth in  claim 1 , concentration of the additional element in the crystal grains is 0.1 atomic percent or less. 
     
     
         6 . The polycrystalline copper alloy for wiring as set forth in  claim 1 , wherein at the crystal grain boundaries and/or in the vicinities of grain boundaries, intermetallic compounds of Cu and at least one element selected from a group consisting of Ti, Zr, Hf, Cr, Co, Al, Ni, and Mg are formed. 
     
     
         7 . The polycrystalline copper alloy for wiring as set forth in  claim 1 , wherein at the crystal grain boundaries and/or in the vicinities of grain boundaries, oxides of at least one element selected from a group consisting of Ti, Zr, Fit Cr, Co, Al, Ni, and Mgare formed. 
     
     
         8 . The polycrystalline copper alloy for wiring as set forth in,  claim 1 , wherein concentration of the additional element at the grain boundaries and in the vicinities of grain boundaries is on the order of 2 to 1000 times the additional element concentration at the inside of the crystal grains. 
     
     
         9 . The polycrystalline copper alloy for wiring as set forth in  claim 1 , wherein concentration of the additional element at the grain boundaries and in the vicinities of grain boundaries is on the order of 10 to 100 times the additional element concentration at the inside of the crystal grains. 
     
     
         10 . A polycrystalline copper alloy for wiring comprising a copper and an additional element,
 wherein the additional element is at least one element selected from a group consisting of Ti (titanium), Zr (zirconium), Hf (hafnium), Cr (chromium), Co (cobalt), Al (aluminum), Sn (tin), Ni (nickel), and Mg (magnesium), and concentration of the additional element, at the interface between the polycrystalline copper alloy and a barrier film that is formed to surround the polycrystalline copper alloy and in vicinities of said interface, is higher than that of inside of crystal grains.   
     
     
         11 . A semiconductor device comprising a substrate on which a semiconductor element is formed, and a metal wiring composed of a polycrystalline copper alloy, said polycrystalline copper alloy comprising a copper and an additional element,
 wherein the additional element is at least one element selected from a group consisting of Ti (titanium), Zr (zirconium), Hf (hafnium), Cr (chromium), Co (cobalt), Al (aluminum), Sn (tin), Ni (nickel), and Mg (magnesium), and concentration of the additional element at boundaries between the polycrystalline copper alloy and an insulator films contacting the polycrystalline copper alloy, is higher than that of inside of crystal grains   
     
     
         12 . A semiconductor device comprising a substrate on which a semiconductor element is formed, and a metal wiring composed of a polycrystalline copper alloy, said polycrystalline copper alloy comprising a copper and an additional element,
 wherein the additional element is at least one element selected from a group consisting of Ti (titanium), Zr (zirconium), Hf (hafnium), Cr (chrotaium), Co (cobalt), Al (aluminum), Sn (tin), Ni (nickel), and Mg (magnesium), and concentration of the additional element, at grain boundaries of crystal grains composing the polycrystalline copper alloy and in vicinities of grain boundaries, is higher than that of inside of crystal grains.