Influence of N<sub>2</sub> Flows on Sputtered Ta(N) films: Electrical, Structural, Chemical and Optical Properties

By reactive DC magnetron sputtering from a pure Ta target onto silicon substrates, Ta(N) films were prepared with a different N2 flow rate of 0, 12, 17, 25, 38, 58 sccm. The effects of N2 flow rate on the electrical properties, crystal structure, elemental composition and optical properties of Ta(N) were studied. These properties were characterized by the four-probe method, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and spectroscopic ellipsometry (SE). Results show that the deposition rate decreases with an increase of the N2 flows. On the other hand, the resistivity increases, the crystal size decreases, and the crystal structure transitions from β-Ta to TaN(111), and finally becomes the N-rich phase Ta3N5 (130,040). Studying the optical properties, it is found that there are differences in the refractive index (n) and extinction coefficient (k) of Ta(N) with different thicknesses and different N2 flow rates, and dependent on the crystal size and crystal phase structure.