Nonequilibrium flicker noise in tantalum-based thin-film resistors

A method for investigating nonequilibrium conductivity fluctuations in thin-film resistors is presented. The method is based on the measurement and analysis of the low-frequency spectral density of voltage fluctuations of the de component of the response signal that is generated under the excitation of a sample by a series of rectangular current pulses as a result of amplitude detection of these pulses due to the nonlinear voltage-current characteristic (VCC) of the sample. This method can be applied to the analysis of the fluctuation phenomena in various types of passive instantaneous two-terminal devices. The 1/f noise under a given de current and low-frequency fluctuations of the de voltage component in tantalum-based thin-film resistors fabricated under different technological conditions are investigated. A method for separating the contact noise from that of the resistive film is described. It is established that the contacts make the basic contribution to the nonequilibrium conductivity fluctuations in the resistors, whereas they make a small contribution to the total resistance of the device. The excess noise in contacts is due to gas adsorption during the resistor fabrication that results in the oxidation of the resistive layer. Sometimes, the contribution of contacts to the flicker noise in a resistor may exceed the noise of the resistive film itself.