Materials characterization of WNxCy, WNx and WCx films for advanced barriers

A ternary WN"xC"y system was deposited in a thermal ALD (atomic layer deposition) reactor from ASM at 300^oC in a process sequence using tungsten hexafluoride (WF"6), triethyl borane (TEB) and ammonia (NH"3) as precursors. The WC"x layers were deposited by a novel ALD process at a process temperature of 250^oC. The WN"x layers were deposited at 375^oC using bis(tert-butylimido)-bis-(dimethylamido)tungsten (^tBuN)"2(Me"2N)"2W (imido-amido) and NH"3 as precursors. WN"x grows faster on plasma enhanced chemical vapor deposition (PECVD) oxide than WC"x does on chemical oxide. WN"xC"y grows better on PECVD oxide than on thermal oxide, which is opposite of what is seen for WN"x. In the case of the ternary WN"xC"y system, the scalability towards thinner layers and galvanic corrosion behavior are disadvantages for the incorporation of the layer into Cu interconnects. ALD WC"x based barriers have a low resistivity, but galvanic corrosion in a model slurry solution of 15% peroxide (H"2O"2) is a potential problem. Higher resistivity values are determined for the binary WN"x layers. WN"x shows a constant composition and density throughout the layer.