ADJUSTMENT OF TEMPERATURE-COEFFICIENT OF RESISTANCE IN NICR CUNI(MN)/NICR FILMS/

The thin-film system Ni0.37Cr0.63/Cu0.57Ni0.42Mn0.01/Ni0.37Cr0.63 With a typical thickness of 1 mu m is used for low-ohmic precision resisto rs. The necessary adjustment of the temperature coefficient of resista nce (TCR) by annealing has been studied by investigating the irreversi ble changes of the resistance during various annealing steps of NiCr/C uNi(Mn)/NiCr multilayers in comparison with single layers of CuNi(Mn) and NiCr. Auger depth profiles showed that the interdiffusion of CuNi( Mn) and NiCr results in an impoverishment of Ni in CuNi(Mn), explainin g the TCR shift by comparison with data of Cu1-xNix bulk material. The decrease of the resistivity and the reduction of the width of the cop per-nickel conductive layer by formation of a Ni0.6Cr0.2Cu0.2 interdif fusion zone phase (in accordance with the Cu-Ni-Cr phase diagram) caus e a significant curvature of the resistance-temperature curve. As main result, it is shown that the NiCr base and cover layers and their int erdiffusion with CuNi(Mn) play the decisive role in adjusting the TCR. It was checked that oxidation and topography effects have no remarkab le influences. (C) 1996 American Institute of Physics.