Modeling and Analysis of Spray Pyrolysis Deposited SnO2 Films for Gas Sensors
Metal oxide materials such as tin oxide (SnO2) show powerful gas sensing capabilities. Recently, the deposition of a thin tin oxide film at the backend of a CMOS processing sequence has enabled the manufacture of modern gas sensors. Among several potential deposition methods for SnO2, spray pyrolysis deposition has proven itself to be relatively easy to use and cost effective while providing excellent surface coverage on step structures and etched holes. A model for spray pyrolysis deposition using a pressure atomizer is presented and implemented in a Level Set framework. A simulation of tin oxide deposition is performed on a typical gas sensor geometry and the resulting structure is imported into a finite element tool in order to analyze the electrical characteristics and thermo-mechanical stress present in the grown layer after processing. The deposition is performed at 400 °C and the subsequent cooling to room temperatures causes a stress to develop at the material interfaces due to variations in the coefficient of thermal expansion between the different materials.
KeywordsElectrical characterization of tin oxide FEM simulation Level set method Modeling spray pyrolysis Monte Carlo Smart gas sensors Spray pyrolysis deposition Thermal stress modeling Tin oxide Von Mises stress
This work has been partly performed in the COCOA-CATRENE European project and in the project ESiP. In this latter the Austrian partners are funded by the Austrian Research Promotion Agency (FFG) under project no. 824954 and the ENIAC Joint Undertaking.
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