This paper presents a capacitive humidity sensor in CMOS technology. The humidity sensor element is implemented in standard CMOS technology without any further post-processing, which results in low fabrication cost. The sensor interface employs a fully-digital architecture based on phase locked loop, which results in low pow dissipation. The proposed humidity sensor is fabricated in TSMC 0.18μm CMOS process and the chip occupies an area of 0.05mm2. The measurement result shows that the sensor value exhibits good linearity within the range of 10-90%RH and the interface circuit consumes only 1.05μW at 0.5V supply voltage.
