An investigative study of Manganese-based Antiperovskite structures as a thin film resistive material system

Cherianlukose, Cecil (2018) An investigative study of Manganese-based Antiperovskite structures as a thin film resistive material system. Doctoral thesis, Northumbria University.

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Abstract

Novel manganese (Mn) based antiperovskite material systems have been reported to have Temperature Coefficient of Resistance (TCR) in the range of +0.09 to +46 ppm/˚C. Such extremely low values of TCR make these materials an ideal choice to replace existing thin film resistor systems like NiCr and TaN, which are reaching their current limit at ±5 ppm/˚C. These ultra-precise passive components find use in applications such as medical diagnostics, industrial automation and military systems, where they must maintain a stable resistance value across an extreme temperature range of -55 to +155 ˚C throughout their lifetime.

Based on previous literature, Mn based antiperovskites: Mn3AgN, Mn3CuN and Mn3Ag(x)Cu(1-X)N were selected to be sputter deposited as thin films on alumina and glass substrates using industrial standard fabrication processes to enable future scale up of the developed material.

The experiments within this project focus on fine-tuning key deposition parameters of nitrogen flow rate, temperature and pressure to investigate their effect on electrical properties of TCR and stability of Mn based antiperovskite thin films. The as-grown values of electrical properties are stabilised by finely tuning heat treatment temperature, time and environment. To assess the scope of improvement in electrical properties, Ag was partially substituted by Cu in the Mn3Ag(X)Cu(1-X)N structure. Sputter deposition parameters, heat treatment parameters and chemical composition were tuned to target resistive films with TCR values lower than ±5ppm/ºC and stability values closer to industry standard of 0.05%.

The lowest TCR value achieved for binary Mn3CuN films was +14.25ppm/˚C and this was improved to -4.66ppm/˚C by partially substituting Cu with Ag in the films to a composition of Mn3Ag(0.4)Cu(0.6)N. The best stability value of 0.57% was achieved for Mn3CuN and this value deteriorated with increasing content of Ag in the film. The Mn3CuN films also performed extremely well through the industrial fabrication stages, yielding a stable variation in TCR value of <±3ppm/˚C. This research is an important step in establishing the low TCR nature of Mn based antiperovskite materials suitable for industrial scale fabrication of thin film resistors.

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