Low resistivity tantalum

Abstract

An alpha-phase tantalum having a resistivity of about 15 micro-ohm-cm or less is provided and is especially useful as a barrier layer for copper and copper alloy interconnections.

What is claimed is:  
     
         1 . Alpha-phase tantalum having a resistivity of about 15 micro-ohm-cm or less.  
     
     
         2 . The alpha-phase tantalum of  claim 1  having a <110> diffraction peak at about 49° (2-theta) as measured by x-ray diffraction using monochromatic iron radiation from a sealed tube source operating at 35 kilovolts and 35 milliamps.  
     
     
         3 . The alpha-phase tantalum of  claim 2  having the x-ray diffraction spectra as shown in FIG. 2.  
     
     
         4 . A method for producing an alpha-phase tantalum having a resistivity of about 15 micro-ohm-cm or less which comprises sputter depositing in a plasma from a tantalum source employing an inert sputter gas to provide an effective pressure of about 1 to about 10 millitorr and employing a power of about 0.5 to about 6 kilowatts.  
     
     
         5 . The method of  claim 4  wherein the source of tantalum has a purity level of at least about 99.9%.  
     
     
         6 . The method of  claim 4  employing a DC magnetron source configuration.  
     
     
         7 . The method of  claim 4  wherein the flow rate of the inert gas is about 50 to about 130 standard cubic centimeters per minute and the flow rate of the nitrogen is about 20 to about 60 standard cubic centimeters per minute.  
     
     
         8 . The method of  claim 4  wherein the reaction chamber is evacuated to a vacuum level of at least 1.0×10 E6 torr prior to the gas flow.  
     
     
         9 . The method of  claim 4  wherein the deposition rate of the tantalum is about 1200 to about 1500 Å per minute.  
     
     
         10 . The method of  claim 4  wherein the inert gas is argon.  
     
     
         11 . An alpha-phase tantalum layer obtained by the process of  claim 4 .  
     
     
         12 . An interconnection structure for semiconductor integrated circuits which comprises a layer of copper or copper alloy and a barrier layer of alpha-phase tantalum having a resistivity of about 15 micro-ohm-cm or less.  
     
     
         13 . The interconnection structure of  claim 12  wherein the alpha-phase tantalum has a <110> diffraction peak at about 45° (2-theta) obtained by an x-ray diffraction scan using monochromatic iron radiation from a sealed tube source operating at 35 kilovolts and 35 milliamps.  
     
     
         14 . The interconnection structure of  claim 12  wherein the alpha-phase tantalum has an x-ray diffraction scan shown in FIG. 2.  
     
     
         15 . The interconnection structure of  claim 12  wherein the thickness of the copper is about 200 to about 1500 Å.  
     
     
         16 . The interconnection structure of  claim 12  wherein the thickness of the alpha-phase tantalum layer is about 50 to about 300 Å.  
     
     
         17 . The interconnection structure of  claim 12  which further includes electrical isolation and wherein the barrier layer separates the copper from the isolation.  
     
     
         18 . The interconnection structure of  claim 12  which further includes a second barrier layer between the insulation and the alpha-phase tantalum.  
     
     
         19 . The interconnection structure of  claim 18  wherein the second barrier layer is selected from the group consisting of tantalum nitride, tantalum silicon, tantalum silicon nitride, titanium nitride, tungsten and tungsten nitride.  
     
     
         20 . The interconnection structure of  claim 18  wherein the second barrier layer is tantalum nitride or titanium nitride.  
     
     
         21 . The interconnection structure of  claim 18  wherein the second barrier layer is tantalum nitride.  
     
     
         22 . The interconnection structure of  claim 18  wherein the thickness of the second barrier layer is about 25 to about 300 Å.