19 November 2001 Modeling and fabrication of a planar thin film airflow sensor
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A thin film airflow transducer based on the hot wire anemometer principle was designed using current MEMS modelling & simulation software. Flow sensors are commonly implemented with thermal isolation of the sensor from the bulk substrate mass using methods such as reverse side etching or sacrificial layers, however this paper will present a sensor relying on thermal insulation only. This insulation may be provided by layers of material exhibiting relatively poor thermal conduction characteristics such as silicon dioxide or polyimide, giving rise to a number of advantages such as removing the process of reverse side etching. Limiting fabrication to use of simple processes such as photolithography and sputtering/evaporative deposition also simplifies this design and assists in greatly increasing the compatibility with standard CMOS fabrication processes and materials. A combination of both theoretical computer modelling and physical fabrication and testing has been the approach to this research. Preliminary testing of this design has demonstrated small yet measurable temperature gradients across the device surface during steady state operation. The novel approach to this device is the investigation of pulsed operation, effectively a transient analysis that allows the thermal conduction effects of the bulk mass to be significantly reduced, leading to a significant increase of both efficiency and response time. Electro-thermo-mechanical and computational fluid dynamic analysis of the structure successfully model the thermal conduction, radiation and forced convection effects of the device during and after ohmic heating of the sensor's heating element.
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Richard J. Adamec, Richard J. Adamec, Philip G. Tanner, Philip G. Tanner, David V. Thiel, David V. Thiel, } "Modeling and fabrication of a planar thin film airflow sensor", Proc. SPIE 4593, Design, Characterization, and Packaging for MEMS and Microelectronics II, (19 November 2001); doi: 10.1117/12.448846; https://doi.org/10.1117/12.448846

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