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For Cu/ultralow κ application, understanding of interfacial interaction between Ta and pore-sealing layer over porous dielectric is very important in order to achieve a good barrier performance. However, characterizing the effect of pore-sealing layer on barrier performance poses a big challenge. Most studies monitored degradation of the electrical performance of the Ta barrier after integration process with little discussions on interfacial interaction. In this letter, the interaction at the interface between Ta and pore-sealing layer deposited over porous SiLK (κ∼2.2) film is investigated. The barrier performance is improved significantly by nitrogen incorporation during liner growth. This methodology is very effective for improving metal barrier and pore-sealing performance for Cu/ultralow κ interconnects.