Grain boundary scattering for temperature coefficient of resistance (TCR) behaviour of Ta-Si-N thin films

In this study, we have investigated the electrical properties of Ta(x)Si(y)N(z) thin films deposited by reactive co-sputtering at different nitrogen flow ratios. The electrical resistivity and temperature coefficient of resistance (TCR) were measured by an I-V measurement system including the four-point probe from 30 to 100 degrees C. The results indicated that the electrical resistivity decreased with increasing temperature, i.e. negative TCR, in each film prepared at different N(2) flow ratios. The phase formation of a Ta-Si-N film at different N(2) flow ratios (5-30%), as well as the change in microstructure from a symmetric broad peak to an asymmetric peak, was studied by a grazing incident x-ray diffractometer. In view of the fact that the grain size increases with increasing N(2) flow ratio, it would be expected that increasing resistivity and magnitude of negative TCR with increasing grain size nature may be due to scattering of electrons by the grain boundaries. It is probable that coarse grained material of Ta-Si-N with amorphous- like microstructure has a higher electrical resistivity due to the high ratio of the grain boundary area and increase in non-metallic amorphous SiN(x). The electrical properties of these films are also discussed by the grain boundary scattering model.