Electromigration in sputtered copper film on plasma-treated hydrogen silsesquioxane dielectric

Electromigration (EM) damage is one of the major causes for the failure of interconnects. Plasma treatment, such as dry etching, is frequently employed in the fabrication of multilevel interconnection patterns. This work investigates the hydrogen silsesquioxane (HSQ) and copper integrated systems and the effect of H₂ plasma treatment on the EM of Cu. Hydrogen plasma bombardment induces a rough HSQ surface and results in a coarse morphology of the Cu film deposited on HSQ. The crystallographic texture of Cu is also affected by the plasma treatment. A decrease in the Cu I(111)/I(200) peak ratio is observed for a specimen treated with H₂ plasma. The activation energy for EM in Cu and the EM lifetime of the Cu interconnect decreases with an increased degree of plasma treatment. The activation energies obtained, ranging from 0.76 eV to 0.94 eV, suggest that the electromigration in copper proceeds via an interfacial diffusion path. Possible mechanisms for the effects of plasma treatment are explored. The rough surface and the retarded Cu (111) orientation induced by H₂ plasma bombardment are the major causes for the decrease of activation energy and EM lifetime.