Abstract
By reactive DC magnetron sputtering from a pure Ta target onto silicon substrates, Ta(N) films were prepared with different N2 flow rates of 0, 12, 17, 25, 38, and 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 N2 flows. Furthermore, as resistivity increases, the crystal size decreases, 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, depending on the crystal size and crystal phase structure.
Highlights
Some prominent examples of such applications are as a protective coating material against oxidation and corrosion [7], as a diffusion barrier for Al and Cu metallization in advanced microelectronics [8,9,10,11], in phosphide and nitride optoelectronics as ohmic contact [3,4], in artificial heart valves as histocompatibility materials [12], thin film resistors [13], as ceramic pressure sensors [14], and different mechanical applications [5,6]
The deposition rate does not depend on the sputtering time (Figure 1b)
We examined the applicability of ellipsometry to measure the thickness of the thin Ta and tantalum nitride (TaN) layers
Summary
Transition metal nitrides, especially tantalum nitride (TaN), are in high demand for a wide range of applications due to their high melting point, hardness, excellent wear and corrosion resistance, refractory character, mechanical and high-temperature stability, chemical inertness, and histocompatibility [1,2,3,4,5,6]. Some prominent examples of such applications are as a protective coating material against oxidation and corrosion [7], as a diffusion barrier for Al and Cu metallization in advanced microelectronics [8,9,10,11], in phosphide and nitride optoelectronics as ohmic contact [3,4], in artificial heart valves as histocompatibility materials [12], thin film resistors [13], as ceramic pressure sensors [14], and different mechanical applications [5,6]. The large interest for TaN arises since it is considered recently as a high thermal conductive material in microelectronic chips for the θ-TaN phase [15]
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