Study of Cu diffusion behavior in low dielectric constant SiOC(-H) films deposited by plasma-enhanced chemical vapor deposition

Carbon doped silicon oxide (SiOCH) thin films deposited using plasma-enhanced chemical vapor deposition (PECVD) are commonly used in multilevel interconnect applications. To enhance the electrical performance, the deposited SiOC(-H) films were annealed in a vacuum at various temperatures ranging from 250 to 450 degrees C. A Cu electrode was then deposited using thermal evaporation. The drift rate of Cu(+) ions in the SiOC(-H) films with the Cu/SiOC(-H)/p-Si(100)/Al metal-insulator-semiconductor (MIS) structures after annealing was evaluated by C-V measurements with a flatband shift caused by bias-temperature stress (BTS). The samples were stressed at different temperatures of 150 to 275 degrees C and electric fields up to 1.5 MV/cm to examine the penetration of Cu(+) ions into the SiOC(-H) films. The Cu(+) ion drift diffusion behavior was observed by high-resolution transmission electron microscopy and depth profile analysis of the Auger electron spectra. The drift diffusion experiments suggested that the Cu ion drift rate in the of SiOC(-H) films increased with increasing annealing temperature. A thermal stress and BTS were used to evaluate the impact of Cu penetration on the dielectric properties of the SiOC(-H) films. (C) 2010 Elsevier B.V. All rights reserved.