TiN, TaN and WxN films of 5, 10 or 20nm thickness were evaluated as diffusion barriers between Cu and SiO2. Emphasis was placed upon electrical characterization of metal-oxide-semiconductor capacitors after bias temperature stress at different temperatures, using capacitance-vs.-voltage, leakage current-vs.-voltage, and triangular-voltage-sweep measurements. The electrical tests were correlated with compositional information from X-ray photoelectron spectroscopy and secondary ion mass spectrometry. The results indicated that TiN was a substantially inferior barrier compared to the other materials, and that WxN was at least equivalent to TaN. WxN may even be slightly better at the lowest barrier thickness. Moreover, electrical methods were generally more sensitive than structural methods in detecting failure of the diffusion barrier. Among the three electrical test methods, triangular-voltage-sweep was the earliest indicator of eventual barrier failure. However, the conditions for a consistent methodology in evaluating the reliability of diffusion barriers need to be more clearly defined.

TiN, TaN and WxN as Diffusion Barriers for Cu on SiO2 - Capacitance–Voltage, Leakage Current and Triangular-Voltage-Sweep Tests after Bias Temperature Stress. H.Kizil, C.Steinbrüchel: Thin Solid Films, 2004, 449[1-2], 158-65