3D Out-of-Plane Flow Sensor Array with Integrated Circuits

Micromachined resistors are thermal transducers that can be used to measure air and water flow rate. For the thermal resistor to function as a flow sensor, the electrical resistivity must be a strong function of temperature it must be sufficiently thermally isolated from the supports and substrate. The thermal resistor can be made of a metal or doped semiconductor and can thermally isolated by putting it on a thermally insulating substrate [1, 2]. However, the thermal mass of the substrate leads to a larger thermal time constant could have increased power requirement if there is insufficient thermal insulation. Another method is to selectively remove the material underneath[3, 4] to form membrane or beams, but this makes IC integration more difficult due to process incompatibility. Another group has incorporated bulk micromachining and a polyimide joint to create a three axis anemometer[5], however wiring across the polyimide joint complicates the process.