Abstract

This study implements the metal-oxide-semiconductor (MOS) type gas sensor using the TSMC 0.35 μm 2P4M process. The gas concentration is detected based on the resistance change measured by the proposed sensor. This design has three merits: (1) low-cost post-CMOS process using metal/oxide wet etching, (2) composite sensing material based on ZnO-SnO2 coating on the CMOS-MEMS structure, (3) vertical integration of heater and ZnO-SnO2 gas-sensing films using CMOS-MEMS and drop casting technologies. Proposed design significantly increase the sensitivity at the high operating temperature. In summary, the sensitivity of presented sensor increased from 0.04%/% (O2/N2) at near room operating temperature to 0.2%/%(O2/N2) at near 140 °C for the range of 5–50% oxygen concentration.

Highlights

  • The gas sensors can find applications in many fields, such as industrial, automotive, medical and home healthcare, etc

  • The proposed CMOS-MEMS gas sensor consists of interdigitated sensing electrodes and vertically integrated heater is 95 × 125 μm2

  • By following the design rules, the micro heater, sensing electrodes, and trenches to accommodate sensing materials are defined by standard CMOS layers

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Summary

Introduction

The gas sensors can find applications in many fields, such as industrial, automotive, medical and home healthcare, etc. Various approaches, such as electrochemical, metal oxide semiconductor, infrared, catalytic combustion and resonant, have been reported for gas detection. Among these approaches, MOS technology could find extensive applications in medical, transport, HVAC, and consumer. The CMOS-MEMS has been exploited to realize gas sensors [3,4,5] after adding different sensing materials. This study will leverage the CMOS-MEMS process and MOS sensing technologies to implement the gas sensor.

Design Concept
CMOS-MEMS Devices
ZnO-SnO2 Sensing Film
Measurement Setup and Result
Conclusions
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