RTD characteristics for micro-thermal sensors

The physical and electrical characteristics of MgO (medium layer) and Pt (sensor material) thin films deposited by a reactive RF sputtering method and a magnetron sputtering method, respectively, were analyzed as a function of the annealing temperature and time by using a four-point probe, SEM, and XRD. After being annealed at 1000 °C for 2 h, the MgO layer showed good adhesive properties on both layers (Pt and SiO2 layers) without any chemical reactions, and the surface resistivity and the resistivity of the Pt thin film were 0.1288 Ω/□ and 12.88 μΩ cm, respectively. Pt resistance patterns were made on MgO/SiO2/Si substrates by the lift-off method, and Pt resistance thermometer devices (RTDs) for micro-thermal sensor applications were fabricated by using Pt-wire, Pt-paste, and spin-on-glass (SOG). From the Pt RTD samples having a Pt thin film thickness of 1.0 μm, we obtained a temperature coefficient of resistor (TCR) value of 3927 ppm/°C, which is close to the Pt bulk value, and the ratio variation of the resistance value was highly linear in the temperature range of 25–400 °C.