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 FF are investigated using density-functional theory. As FF 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 FF, 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.

► We investigate the changes of four atomic structures under external electric fields.
► The Cu films undergo large deformation, indicating that electromigration occurs, as FF reaches 0.040 au (1 au = 51.4 V/Å).
► The Cu(Al) films at Cu(Al)/-Al2O3 interfaces change slightly under the same and larger FF.
► Cu–O covalent–ionic and Al–O ionic bonds exist at the Cu(Al)/-Al2O3 interfaces.
► The stronger bonding strength effectively improves the EM reliability of Cu atoms.