Characterisation of electron-beam deposited tungsten interconnects

Electron beam deposition of tungsten from W(CO)₆ has been studied for a range of different height deposits. The resistance of the deposited tracks was found to decrease with increasing height implying that thicker deposits have a higher metallic cross section. It was also found that when the current limits were increased to values in excess of 100 μA, the resistance decreased with successive voltage cycles and increasing current limit. This improvement continued until a point where the structure of the deposit appeared to start breaking down and its resistance increased slightly. Subsequently, the structure was found to break near to the contact. It was also found that as the resistance of the deposit decreased, the structure of the deposited tracks changed implying that ohmic heating induced high enough temperatures within the deposit to be able to cause the structure of the material to change.