Novel Planar Passive Wireless Thin Film LC Temperature Sensor

Film-based passive wireless temperature sensors have been investigated extensively by many groups over the decades but often require machining to facilitate a series connection between the inductor and capacitor, which make up a particular sensor. In this letter, a fully planar passive wireless near field temperature sensor is presented. The sensor is comprised of Pt and was fabricated using sputter deposition. The operating mechanism for the sensor is a change in the relative permittivity of the dielectric material, which it is deposited on with temperature that results in a reproducible shift in resonant frequency of the sensor. Some sensors were coated with a 1μm layer of HfO₂ to enhance the capacitance and protect the underlying Pt from dewetting. The high temperature wireless sensor was demonstrated up to 560°C with high linearity and had a sensitivity of ∼33 KHz/°C while uncoated and ∼25 kHz/°C when the HfO₂ coating was present.