Effect of substrate properties and thermal annealing on the resistivity of molybdenum thin films

In this study, the influence of substrate properties (e.g. roughness characteristics and chemical composition) on the electrical resistivity of evaporated molybdenum thin films is investigated as a function of varying parameters, such as film thickness (25-115 nm) and post-deposition annealing with temperatures up to TPDA = 900 °C. A thermally oxidized silicon wafer with very low surface roughness was used as one substrate type. In contrast, a low temperature co-fired ceramics substrate with a glass encapsulant printed in thick film technology is the representative for rough surface morphology. The electrical resistivity follows the prediction of the size effect up to TPDA = 600 °C independent of substrate nature. On the silicon-based substrate, the thickness-independent portion of the film resistivity ρg in the “as deposited” state is about 29 times higher than the corresponding bulk value for a mono-crystalline sample. Thin films of this refractory metal on the SiO2/Si substrate exhibit an average grain size of 4.9 nm and a negative temperature coefficient of resistivity (TCR). On the glass/ceramic-based substrate, however, ρg is half the value as compared to that obtained on the SiO2/Si substrate and the TCR is positive.