基于无源超高频射频识别标签的湿度传感器设计

针对无源超高频射频识别传感器标签大规模运用的需求,采用中芯国际0.35μm互补金属氧化物半导体(CMOS)工艺设计并制造了一种低成本、低功耗的湿度传感器.湿度传感器单元采用聚酰亚胺作为感湿材料,利用顶层金属层制作叉指结构电极,制造过程与标准CMOS制造工序兼容,无需任何后处理工艺.接口电路部分基于锁相环原理,采用全数字电容.数字直接转换结构,能够工作在接近工艺阈值电压下.后期测试结果显示,该湿度传感器在常温下灵敏度为36.5 fF%RH,最大回滞偏差为7%,响应时间为20 ms,0.6 V电源电压下消耗2.1μW功率.

Complementary metal-oxide-semiconductor humidity sensor design for passive ultra-high frequency radio-frequency identification application

This paper presents a low-cost low-power humidity sensor for applications of ultra-high frequency radio frequency identification sensing tag. The humidity sensor element, based on standard SMIC 0.35 μm complementary metal-oxide-semiconductor technology, utilizes polyimide as sensing material and fabricates the interdigitated electrodes in top metal layer without any further post-processing. The humidity sensor interface, based on phase-locked loop theory, employs fully-digital architecture and achieves direct capacitance-to-digital conversion, which allows the supply voltage to be close to threshold voltage. The measurements at 25 ℃ show that the proposed humidity sensor achieves a sensitivity of 36.5 fF%RH, maximum hysteresis error of 7%, response time of 20 ms, and 2.1 μW power dissipation at 0.6 V supply voltage.
Keywords： humidity sensor capacitive sensor interface phase-locked loop radio frequency identification