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.