Novel design and characterisation of SOI CMOS micro-hotplates for high temperature gas sensors

This paper describes the design and characterisation of a new generation of fully CMOS compatible novel micro-hotplates for high temperature gas sensors. The micro-hotplates employ advanced MOSFET heaters embedded in an SOI membrane. The heaters can operate at a ground-breaking high temperature of 550 °C for an ultra-low power consumption of 16 mW (continuous operation) and have a thermal rise time of below 10 ms. A large number of devices have been characterised over a batch of wafers and they show excellent reproducibility and reliability. The yield of the micro-hotplates after deep RIE back-etching was close to 90% while the residual stress was found to be minimal, resulting in flat and stable membranes. Electronic circuits for drive and readout have also been designed and integrated with the micro-hotplates to create a smart gas sensor.