Suspended-Gate Thin Film Transistor as highly sensitive humidity sensor

摘要

The paper deals with a very high sensitive integrated humidity sensor compatible with CMOS technology. This sensor is a polysilicon Suspended Gate Thin Film Transistor (SGTFT), fabricated using a low temperature surface micromachining process. Microtechnology technics using sacrificial layer are used to fabricate polysilicon bridge which acts as the transistor gate. Transistors are characterized at various humidity rates and transfer characteristics show highly sensitive dependence with humidity. The small air-gap (0.5 μm) between the gate and the channel explains the amplifying effect of the sensitivity: threshold voltage shift is more than 17V when the humidity ratio varies from 20 to 70%.