Reactively sputtered RuO₂ thin film resistor with near zero temperature coefficient of resistance

Ruthenium oxide thin film resistors were reactively sputtered onto SiO₂/Si substrates using d.c. magnetron sputtering. Resistors with near zero temperature coefficient of resistance (TCR) were realized by optimizing the sputtering conditions. Experimental results demonstrated that the TCR was a strong function of substrate temperature during sputtering. A critical temperature around 80°C during sputtering was found at which the TCR changed signs, i.e. a temperature dependence of semiconductor-like behavior of the resistors compared with metal-like behavior. The dependence of the TCR on the material properties of the films was analyzed using scanning electron microscopy, X-ray diffraction, and energy dispersive X-ray analysis. Films with amorphous structure usually gave a negative TCR but a positive TCR for the films with a polycrystalline structure. The resistors with near zero TCR were believed to have a microcrystalline structure.