Pacific Rim Symposium on Surfaces, Coatings and Interfaces (PacSurf 2014)
    Thin Films Wednesday Sessions
       Session TF-WeM

Paper TF-WeM6
A Study to Reduce Deviations of Sensitivities to Constant CO Gas of Pt Doped SnO2 Thin Film Based Micro Gas Sensor

Wednesday, December 10, 2014, 9:40 am, Room Makai

Session: Thin Film Synthesis and Characterization II
Presenter: Jun-gu Kang, Sungkyunkwan University, Korea, Republic of Korea
Authors: J. Kang, Sungkyunkwan University, Korea, Republic of Korea
J.-S. Park, Korea Electronics Technology Institute (KETI), Republic of Korea
H. Lee, Sungkyunkwan University, Korea, Republic of Korea
Correspondent: Click to Email
Gas sensors based on metal oxide semiconductors have been used for detecting low level toxic and explosive gas for a long time, since metal oxide semiconductors enable to make gas sensors operate at low power consumption as well as supply with low price. Recently, researchers have studied nanostructured metal oxide semiconductors to improve sensitivity by enlarging the surface area that react gas directly. However, such gas sensors based on nanomaterials suffer from a large deviation of sensitivities among gas sensors. In the present work, we employed a SnO2 thin film, with a well-defined surface area and thus a small deviation in sensitivity, and, in addition, doped it with a noble metal to improve stability. For the fabrication of the micro platform, which consists of a micro heater and sensing electrode on SiNx membrane, we started with a Si substrate(100) by deposition of a low stress 2㎛-thick SiNx film using a low pressure chemical vapor deposition process. After deposition of a tantalum layer, serving as an adhesion layer, a Pt film was deposited as a heating element. The heater layer of Pt on Ta was patterned and etched using a dry etching process with an advanced oxide-etching equipment. An 1㎛-thick insulating layer was produced on the patterned heater layer. A sensing electrode layer of Pt was sputtered and then patterned using a dry etching process. A SnO2 thin film, as sensing material, was deposited with RF sputtering on the sensing electrode of a micro platform. And then, Pt doping was done by Pt thin film sputtering, and heat treatment to form Pt islands on SnO2 thin film. After finishing the front side process of the wafer, we patterned the back-side of the wafer and etched it in a KOH solution to release the SiNx film as a membrane. In this presentation, sensing properties of fabricated gas sensors to indoor pollutant gases such as CO, HCHO and toluene will be presented. We will also show the possibility to reduce deviations of sensitivities to the constant CO gas concentration among thin film based micro gas sensors.

[Acknowledgement] This work was supported by the "Project (10043800) of the Technology Development Program of S/W Convergence Component" by MOTIE and KEIT in Korea. The authors appreciate government for research funding.