Reactive sputter deposition and properties of Ta xN thin films

Abstract

The aim of this work was to evaluate tantalum nitride thin films fabricated using reactive sputtering with adjusted deposition parameters. Thin Ta x N films were deposited reactively on Si wafers using reactive RF magnetron sputtering at various N 2/Ar gas ratios. The films were investigated by four-point probe sheet resistance measurement, profilometry, X-ray diffraction, scanning electron microscope, 2 MeV 4He + backscattering spectroscopy, and atomic force microscopy. As the amount of nitrogen was increased, the phases in the as-deposited films were identified as β-Ta, Ta 2N (5% N 2-flow), hexagonal TaN (10% N 2-flow) and f.c.c.-TaN (15% N 2-flow) with resistivities of 166 μΩ cm, 234 μΩ cm, 505 μΩ cm and 531 μΩ cm, respectively. Only the phase obtained at 5% N 2-flow showed a reasonable uniformity over the wafer suggesting suitability as thin film resistors. The value of temperature coefficient of resistance (TCR) determined for the Ta 2N thin film resistor was −103 ppm/°C.