Fundamental, integration, and reliability of the 90 nm generation Cu/LK(k=2.5) damascene using a novel PECVD porous low-k dielectric film

A novel PECVD porous low-k material with k=2.5, LK(k=2.5), has been successfully integrated with Cu for 90 nm generation BEOL interconnect technology on 300 mm wafers. Fundamental film studies showed that this low-k material is thermally stable up to 400°C and can be strongly adhered to various dielectric films. Electrical measurement results from the Cu/LK(k=2.5) damascene interconnect showed tight and 100%-yielded distributions in 0.12/0.12 μm interline leakage, one million 0.13 μm viachain via Rc and 0.12 μm Cu line Rs. To maximize the Cu/LK(k=2.5) interconnect capacitance performance, no middle etch stop layer and no top CMP cap were used in the dielectric film stacking. The final k value of the LK(k=2.5) after integration was retained at 2.5 using an optimized PR ashing chemistry by comparing the Cu/LK(2.5) 0.12/0.12 μm interline capacitance to a Cu/LK(3.0) one. The intrinsic BEOL time dependent dielectric breakdown (TDDB) lifetime, T_63, of the Cu/LK(k=2.5) is predicted to be 4.56×10⁸ yrs at 0.3 MV/cm and 125°C. Further reliability evaluations of the Cu/LK(k=2.5) in electromigration (EM) and stress migration (SM) showed that its predicted T_0.1 EM lifetimes for 0.12 μm Cu line or 0.13 μm via at 1 MA/cm2 and 110°C are 152k hrs or 144k hrs, and its SM failure rate (>10% shift in Rc) is zero after 500hr annealing at 175°C. Finally, the packaging feasibility of this Cu/LK(k=2.5) damascene interconnect was also demonstrated using current wire bonding technologies.