TEMPERATURE-COMPENSATED COMPOSITE THIN-FILM RESISTORS

A method for producing temperature-compensated thin-film resistors is described that involves a conductor with negative temperature coefficient of resistance (TCR) partially overlayed by another conductor with positive TCR. The temperature dependence of the resistance of the composite film is evaluated to second order in temperature. It is found that when the geometry and the materials parameters of the composite film are chosen such that the first order TCR is zero, the second-order coefficient is not negligible for temperature variations of practical importance. The model predictions are in good agreement with experimental results using TaN and Ni as the two conductors, in which case the second-order coefficient turns out to be about 5×10- 7°C2. This also means that a first-order TCR of zero can only be achieved at a specified temperature.