REPUBLIC OF SERBIA

MINISTRY OF DEFENCE

www.mod.gov.rs

MINISTRY OF DEFENCE

Material Resources Sector

Defensive Technologies Department

Military Technical Institute

www.vti.mod.gov.rs

INFLUENCE OF GEOMETRICAL PARAMETERS ON PERFORMANCE OF MEMS THERMOPILE BASED FLOW SENSOR

DANIJELA RANDJELOVIĆ

Centre of Microelectronic Technologies, Institute of Chemistry, Technology and Metallurgy, University of Belgrade, danijela@nanosys.ihtm.bg.ac.rs

olga jakšić

Centre of Microelectronic Technologies, Institute of Chemistry, Technology and Metallurgy, University of Belgrade, olga@nanosys.ihtm.bg.ac.rs

milče M. smiljanić

Centre of Microelectronic Technologies, Institute of Chemistry, Technology and Metallurgy, University of Belgrade, smilce@nanosys.ihtm.bg.ac.rs

predrag POLjak

Centre of Microelectronic Technologies, Institute of Chemistry, Technology and Metallurgy, University of Belgrade, predrag.poljak@nanosys.ihtm.bg.ac.rs

žarko lazić

Centre of Microelectronic Technologies, Institute of Chemistry, Technology and Metallurgy, University of Belgrade, zlazic@nanosys.ihtm.bg.ac.rs

Abstract: The aim of this work is to study how performance of thermal flow sensors depends on variation of specific geometrical parameters. Self-developed 1D analytical model was applied at a MEMS sensor based on Seebeck effect. The main elements of the analysed structure are: p⁺Si/Al thermocouples, p⁺Si heater, thermally and electrically isolating membrane and residual n-Si layer in membrane area. Two thermopiles consisting of N thermocouples are placed symmetrically at both sides of the heater. In this type of flow sensor output signal is obtained as a difference between the Seebeck voltages generated at the downstream and upstream thermopile.  It was assumed that sensor is placed in the constant air flow. Several parameters of interest were calculated including flow induced temperature difference established between the downstream and upstream thermopile, output voltage and sensitivity. Simulations were performed in order to analyse dependence of these parameters on residual n-Si layer thickness (d_nSi), distance between the hot thermopile junctions and the heater (Dl) and thermocouple width (w_TP) and length (l_TP). Simulation results show that sensitivity of the thermal flow sensor is improving with increasing Dl and l_TP. On the other hand, performance of the sensor will also increase if d_nSi or w_TP are decreasing.

Keywords: MEMS, flow sensor, thermopile, analytical modelling.