High Performance Bidirectional Thermal Gas Flow Sensor of (100) Silicon Single-Sided Fabrication by 45-Tilted Dicing

In this paper, we introduce an innovative gas flow sensor that combines a thermal resistor with a suspended membrane featuring multiple holes. The sensor architecture comprises a total of five thermistors, which encompass a heater element, two thermistors for monitoring the heater temperature, and two additional thermistors for sensing the ambient temperature. The sensors were fabricated using micro-electro-mechanical-system (MEMS) technology on a four-inch silicon wafer, with platinum being chosen as the material for the thermistors, and were fabricated using a single-sided wet process on a (100) silicon wafer. The airflow direction was perpendicular to the chip edge by 45 degrees-tilted dicing. The experimental evaluation demonstrates a remarkable achievement, as the initial energy consumption of the heater is merely 10 mW, and the sensor exhibits an impressive minimum detection limit of 1 mL/min, accompanied by a highly accurate repeatability of +/- 1%. Moreover, to counteract potential sensor drift arising from ambient temperature fluctuations ranging from 15 degrees C to 25 degrees C, we have incorporated a constant temperature difference (CTD) circuit into the sensor design.