Controlling the TCR of thin film resistors

Abstract

We demonstrate that the temperature coefficient of resistance (TCR) of NiCr thin film resistors can be effectively controlled by changing the film thickness over a certain range. We have observed a direct dependency between TCR and sheet resistance, which can be expressed by the equation: TCR(in ppm/C)=525*exp(0.01*sheet (in Ohms/sq)). This behavior can be explained by considering the transition from a bulk conductivity mechanism to a mechanism dominated by charge carrier creation and tunneling between metallic islands.