Structural and electrical properties of stable ni/cr thin films
The electrical and structural properties of nickel-chrome (NiCr) thin film resistors were studied for the effect of post-deposition annealing on stability. The temperature coefficient of resistance (TCR) of sheet resistivities in the range of 100 to 200 Ω/□ could be improved by both air and vacuum annealing to achieve 5 ± 5 ppm/°C over the temperature range of -180° C to +100° C. With stability tests, air annealing proved to be more favorable for stable TCR. Studies via SIMS and ESCA identified surface segregation of Cr whereas TEM micrographs revealed correlating structural transformation of the films upon annealing. An intentional impurity, Si, played an important role in achieving a low TCR.