Improved electromigration reliability of Cu films by doping and interface engineering

The atomic structures of α-Al2O3-coated Cu films doped with different concentrations of Al under external electric field F are investigated using density-functional theory. As F reaches 0.040 au (1 au=51.4 V/Å), large deformation is observed for pure Cu films, indicating the occurrence of electromigration (EM) in the Cu slabs. Under the same or even larger F , in contrast, almost no deformation occurs for the α-Al2O3-coated Cu(Al) films, except that a slight change is found at the Cu(Al)/α-Al2O3 interfaces. The main reason for this stability should be attributed to the existence of Cu–O covalent–ionic and Al–O ionic bonds at the interface, suggesting that the EM reliability of Cu atoms can be effectively improved by the strong bonding strength.