Prediction of the stability of thin-film resistors

A relationship is derived between the contribution of defects to the resistivity of a thin film and the non-linearity of its I¿V characteristic. The latter is characterized by the `third-harmonic index¿ (t.h.i.) of the film and it is shown that the initial value of t.h.i. is approximately linearly related to the change in resistivity over 1000 hours. It is concluded that the initial t.h.i. can be used to predict the stability of a thin-film resistor. Some qualitative interpretation of the variation of t.h.i. with time and resistivity is given in the light of the theoretical model.