Preparation, Structure, and Properties of Sputtered, Highly Nitrided Tantalum Films

Publisher Website
Google Scholar
Abstract
Highly nitrided films of tantalum have been prepared by cathodically sputtering high‐purity tantalum in a pure nitrogen atmosphere. The effects of cathode current density and film thickness on the film structure, crystal structure, composition, resistivity, current‐voltage characteristics, and optical energy gap were investigated. Transmission electron microscopy showed the films to be apparently discontinuous throughout the range of cathode current densities investigated for 1600 Å thick specimens. The crystal structure determined by electron diffraction analysis was found to be body‐centered tetragonal with c=5.01 Å, a=5.77 Å, and c/a=0.87. The presence of small amounts of hexagonal TaN was also observed. Analysis of the gas content showed the amount of nitrogen to be a function of cathode current density and thickness. Electrical resistivity as a function of temperature in the range of 213°–373°K obeyed the relationship ρ=A exp(ΔE/kT), where ΔE decreased with the increasing cathode current density and film thickness. Current‐voltage characteristics obtained at 77°K indicated non‐Ohmic behavior at large applied voltages. The resistivity could be expressed by log(ρ@V=0/ρ)=AV1/2 above some critical V, where V critical and A are dependent on both film thickness and cathode current density. This behavior could be attributed to conduction by an ``intergrain tunneling'' mechanism. The apparent optical energy gap was found to be in the range of 1.95–2.6 eV depending on sputtering current and thickness.

This publication has 9 references indexed in Scilit: