Fragile porous low-k/copper integration by using electro-chemical polishing

A fragile porous ultra-low-k (k=2.2) silica was successfully integrated at trench level in damascene copper by applying our previously reported [1] electro chemical polishing (ECP) technique for Cu. After removing Cu by ECP, the barrier (WN) was removed by low pressure (LP) CMP (<1 psi). Practical polishing rates were obtained for WN in LP-CMP, because of higher chemical sensitivity of WN compared to Ta(N). Compatibility of CVD barrier to porous low-k, excellent barrier performance in aggressive features and lower via resistance were achieved by a newly developed CVD/PVD stacked WN barrier.