Time-of-Flight Flow Microsensor using Free-Standing Microfilaments

Abstract

In this work we present the processing conditions and the characterization results of a time-of-flight (TOF) flow microsensor implemented using polysilicon microfilaments. Numerical simulation (ANSYS®/FLOTRAN®) and experimental results for analysis with air flow and nitrogen are compared considering different heater to sensor distances and flows. A good agreement was observed between experimental and simulated results. However, experimental TOF values resulted ever consistently higher than the simulated ones due to delays introduced by the circuitry and the data acquisition system and also in the thermal response of the microfilament. Analysis of the heater microfilament reveal that temperatures of the order of 100 °C (that is low enough to not affect the gas flow) can be obtained with a power dissipation of tens of mW. The time-of-flight measurements show that the proposed structure is suitable for the detection of low volumetric flows (tens of SCCM) and presents a response time of the order of milliseconds.