Touch Sensor based on Flexible AlN Piezocapacitor Coupled with MOSFET

This paper presents tactile sensor devices based on flexible aluminium nitride (AlN) piezocapacitor coupled with metal oxide semiconductor field effect transistor (MOSFET). The AlN exhibits piezoelectric behaviour without the typical requirement of high voltage for poling and this makes it an ideal candidate for sensor where transducer layer is integrated with MOSFET. The AlN film used here was deposited on a polyimide subsrate by room temperature RF sputtering to obtain flexible piezocapacitor. The film properties such as orientation, roughness, elemental composition and thickness were investigated by X-ray diffraction (XRD), atomic force microscopy (AFM), energydispersive X-ray spectroscopy (EDX) and scanning electron microscope (SEM) respectively. The tactile sensor developed by connecting the flexible AlN piezocapacitor in an extended gate configuration exhibited a sensitivity of 2.64 N-1 for a force range 0.5-3.5N. The developed sensor demonstrates a promising route towards the development of a complete CMOS compatible process for development of tactile sensors.