Postprocessing, readout and packaging methods for integrated gas flow sensors

Two different architectures of integrated thermal flow meters based on a differential temperature configuration are investigated. A standard structure made up of a heater placed between two temperature probes has been compared to a recently proposed variant equipped with a double heater. The latter has shown a different dependence of the response on gas type when driven in a closed loop fashion. The possibility of using this architecture to compensate the intrinsic sensor offset has also been proposed. Devices have been fabricated by means of a simple and low cost postprocessing technique applied to chips fabricated with two distinct commercial processes. Postprocessing variants, imposed by the sophistication of modern processes, have been proposed and discussed. A compact gas flow sensor with the readout electronics integrated on the same chip has been fabricated and characterized. Experimental results on this device and new data on double heater structures have been discussed and compared with the reviewed data of previously presented devices.