Changing Superfilling Mode for Copper Electrodeposition in Blind Holes from Differential Inhibition to Differential Acceleration

Blind holes 5 μm diam and 25 μm in depth were filled with electrodeposited copper. Before electrodeposition, the blind holes were fully metallized with a copper seed layer or with a thin sputtered Ta layer deposited on top of the copper seed layer. Filling of partially Ta-capped features was three times faster than filling fully metallized features. For fully metallized features, the growth mode for copper electrodeposition is dominated by diffusion adsorption of a leveling agent. For partially Ta-capped surfaces, the growth mode was modified to differential acceleration through accumulation of an accelerating species at the bottom of features.