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 been also proposed. Devices have been fabricated by means of a simple and low cost post processing technique applied to chips fabricated with two distinct commercial processes. Post processing variants, imposed by the sophistication of modern processes, have been proposed and discussed. Three different packaging strategies have been investigated and a method capable to convey gas flows to selected areas of a small chip has been successfully used to fabricate a compact device with integrated read out circuits.