Influence of a 5 Å tantalum nitride interface layer on dielectric properties of zirconium-doped tantalum oxide high-k films

A 5 A thick tantalum nitride (TaN x ) interface layer was inserted between an 8 nm Zr-doped tantalum oxide (TaO x ) high-k film and a silicon substrate to improve dielectric properties for metal-oxide-semiconductor (MOS) gate dielectric applications. Compared to the Zr-doped TaO x film without the TaN x interface, the stacked structure showed improvement in the dielectric constant, leakage current density, and dielectric breakdown strength. However, the flatband voltage shift and interface state densities were slightly degraded. Hysteresis of C-V curves did not change substantially with this TaN x insertion. Structural and chemical analyses, i.e., secondary ion mass spectroscopy (SIMS) and X-ray photoelectron spectroscopy (XPS), were done to investigate this TaN x interface layer. The results suggested that TaN x reacted with oxygen atoms from the high-k film and formed tantalum oxynitride (TaO x N y ) after being annealed at 700°C in O 2 , which may be responsible for the observed improvement on dielectric properties.