Direct CMP on Porous Low-k Film for Damage-less Cu Integration

To reduce the effective k-value to less than 2.7 for the 45-nm node, direct CMP of a porous SiOC film (k = 2.3-2.6) without a protective cap layer was applied to Cu damascene fabrication by using a damage-less sacrificial film process. The key is controlling the molecular size of surfactants in the CMP slurries or cleaning chemicals, which are related to the moisture uptake and watermark generation of hydrophobic porous SiOC films. We found that the selectivity of CoWP deposition improved on a hydrophobic SiOC surface