Thin Film Transistor (TFT) Sensing Elements Fabricated in Surface Micromachined Polymermems for a Differential Calorimetric Flow Sensor

This paper presents the first process to allow the embedding of amorphous silicon thin film transistors in surface micromachined polymerMEMS. The presented polymerMEMs fabrication technique embeds hydrogenated amorphous silicon thin film transistors (alpha-Si:H TFT) into polyimide for active sensing. An out-of-plane differential calorimetric flow sensor has been fabricated using this method to demonstrate the feasibility of this fabrication process. The calorimetric flow sensor uses the alpha-Si:H TFTs as active sensing elements and has a linear unamplified sensitivity of 2.2 mV/(cm/s). This paper provides details for the fabrication process and reports on the design and functional results of calorimetric flow sensor fabricated by embedding alpha-Si:H TFTs into polymerMEMS.