Formation and characterization of the high precision nanoscale thin film resistors on radio frequency application

In this paper, a high-precision tantalum nitride thin film resistor was fabricated using a novel plasma ion etching method. Sheet resistance and x-ray spectra confirmed that the composition and crystalline lattice of the tantalum nitride film varied upon different nitrogen flow ratios of sputtering. To obtain a good performance, we proposed a novel two-step etching process for the fabrication of tantalum nitride thin film resistor, that is, firstly etched using a Cl₂ plasma for the purpose of sharp profile and fast etching rate, and followed by a Cl₂/O₂ gas mixture plasma to get a better etching selectivity. The temperature coefficient of resistance of the tantalum nitride thin film resistor showed that the temperature-related disturbance increased upon increasing the nitrogen composition of device. The temperature-related stability of the thin film resistor was further improved by post-deposited ammonia plasma treatment. The flicker noise, measured at frequency from 1 to 100k Hz, also showed that the current noise depended on the nitrogen composition of the thin film resistor. The characteristic of radio frequency dependent resistance, which was measured ranging from 1 to 20 GHz and extracted by two-ported S parameter and telegrapher's transmission line model, also showed that the stability of tantalum nitride thin film resistor decreased upon increasing the nitrogen composition.