Ion backscattering study of tantalum nitride thin film resistors

Ion backscattering has been used to characterize thin film tantalum nitride resistors with thicknesses in the range 500−600 Å. The amount of surface oxide, the nitrogen content, its depth distribution, the amount of argon−sputtering gas incorporated into the film, and its depth distribution, are measured directly by the technique. The films were prepared by diode sputtering in a pilot line facility. All sputtering parameters were held constant except for the N2 flowrate, which was varied so as to change the nitrogen concentration in the films. The electrical properties of the films were characterized by measurements of the sheet resistance and the differential Seebeck voltage. Aluminum oxide substrates were used for the electrical measurements and beryllium substrates with thin oxide layers were used for the backscattering compositional analysis. As the N concentration decreased below the stoichiometric composition Ta2N to the composition Ta2N0.5, the resistivity was found to decrease linearly by 25% and the differential Seebeck voltage to increase linearly by 90%.