Highly Sensitive CO Sensor Based on Thickness‐Selective ZnO Thin Film: Device Fabrication and Packaging

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Abstract
In this report, the thickness‐dependent carbon monooxide (CO)‐sensing characteristics of sputtered zinc oxide (ZnO) films are investigated, followed by their morphological and electrical characterizations. ZnO films, ≈21 nm, show repeatable and high change in their resistances on exposure to CO and the observed maximum response is ≈52.2%, whereas ≈219 nm films fail to show reproducibility in sensing performance. Response and recovery time of ≈21 nm films are ≈28 and 250 s, which are faster than the time observed in case of ≈219 nm films. An ≈21 nm film is able to resolve 100 parts‐per‐billions (ppb) CO concentration in air. Later, on‐chip integration of ≈21 nm film is successfully implemented on specifically designed Micro‐Electro‐Mechanical‐System (MEMS) platform, inbuilt with microheater and utilizes power of ≈23.7 Milliwatts (mW) (375 °C). The packaged sensor chip is further tested and qualified for indoor and outdoor detection of CO gas in the atmosphere.
Funding Information
  • Ministry of Human Resource Development
  • Department of Electronics and Information Technology, Ministry of Communications and Information Technology (DSTO1419)

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