Influences of Film Thickness on the Electrical Properties of TaNx Thin Films Deposited by Reactive DC Magnetron Sputtering

TaNx thin films were deposited on commercial polished Al2O3 ceramic substrates by reactive dc magnetron sputtering. The influences of the film thickness on the electrical properties of the samples were examined in detail. It is found that the film thickness does not influence the phase structures of the TaNx thin films. The sheet resistances of the samples shift from 173 Omega/sq. to 7.5 Omega/sq. with the film thickness shifting from 30 nm to 280 nm. With the increase of the film thickness from 30 nm to 280 nm, the temperature coefficient of resistance (TCR) of the samples shifts from negative value to positive value. When the film thickness is about 100 nm, TaNx thin films exhibits a near-zero TCR value (approximately -15x10(-6)/degrees C). This fact implies that TaNx thin films with a null TCR can be obtained by adjusting the film thickness. The variation in the electrical properties of the TaNx thin films with the film thickness can be qualitatively explained by the parallel connection of surface layer with high resistivity and negative TCR and TaNx layer with low resistivity and positive TCR.