Du B. Nguyen

Scaling effect on electromigration in on-chip Cu wiring

Electromigration in on-chip plated Cu damascene interconnections has been investigated for metal line widths from 0.24 /spl mu/m to 1.3 /spl mu/m. Void growth at the cathode end and protrusions at the anode end of the lines have been found to be the main causes of failure. The failure lifetime was found to decrease linearly with decrease in the cross-sectional area of the line. This behavior can be explained by interface diffusion as the dominant path for transport and by the bamboo-like nature of the microstructure. The factor of n for the lifetime dependence on current density for 0.28 /spl mu/m wide lines, /spl tau/=/spl tau//sub 0/j/sup -n/, was found to increase from 1 to 2 as j increased beyond 25 mA//spl mu/m/sup 2/.

Extendibility of PVD barrier/seed for BEOL Cu metallization

The paper describes a new physical vapor deposition (PVD) metallization scheme that shows a better extendibility for future technology nodes as compared to the conventional scheme. In addition to reducing the thicknesses of both the diffusion barrier and the copper seed layer (Yang, C.-C. et al., MRS Adv. Metallization Conf., p.213, 2004), this new scheme also features a sacrificial process (also called barrier-first process) (Alers, G., IEEE Int. Interconnect Technology Conf., 2003), a via-punch through process (Edelstein, D. et al., IEEE Int. Reliability Physics Symp., p.316, 2004; Kuma, N. et al., MRS Adv. Metallization Conf, p.247, 2004) and a simultaneous preclean with a metal neutral deposition process (Yang et al., US Patent 6,784,105, 2004; Uzoh, C. et al., US Patents 5,930,669, 1999; 5,933,753, 1999; 6,429,519, 2002). Significant metal line and via contact resistance decrease was observed with equal or better reliability. The impact of a sputter etch integration scheme on electrical yield and reliability is also reported. The new sputter scheme decreases contact resistance at the via/interconnect interface and can offset the one resulting from dimension scaling and thus extends PVD metallization usefulness for future technologies.