Post-CMOS Integration of AlScN based Pyroelectric Sensors

The post-CMOS integration of pyroelectric sensors opens for new wafer-level packaging approaches of e.g. smart motion detectors as a cost-efficient alternative to TO-cans and SMD packages. We demonstrated the feasibility of using the indirect pyroelectric effect in a clamped thin layer of Aluminium-Scandium-Nitride (AlScN) to place a pyroelectric sensor structure on top of the passivation and oxides of a CMOS wafer. Using a slightly modified MLX90632 thermopile chip from Melexis Technologies NV with integrated digital signal processing, the sensor element was built in five lithography levels on a heat absorber membrane with 170 µm diameter. The response was characterised with a modulated laser heat source from DC to 1 MHz, and a qualitative application-level test confirmed the digital readout through the CMOS circuit.