Abstract
In the Cu filling process by electroplating for ultra-fine wire trenches in LSIs, voids are generated for narrow wires of less than 80 nm width. We observed the Cu film formation process as a function of time and found that the flow of Cu electrolyte solution is not homogeneous in the trench, resulting in void formation at one side of the trench wall during plating. Numerical analysis of the Cu electrolyte solution flow clarified that Cu ion transportation is lowered substantially by the generation of two vortices in the wire trench when the wire width is less than 50 nm. We proposed a method to enhance transportation of Cu ions by enlarging the open angle at the top edge of the trenches to prevent void formation. The effect of the method for void-free filling was predicted by the numerical analysis of the Cu electrolyte solution flow and confirmed by the actual filling experiment of Cu into the wire trench with 60 nm width.
