Detectivity of thin-film NTC thermal sensors

Characteristics of thin-film negative temperature coefficient of resistance (NTC) thermal sensors fabricated by micromachining technology were studied as a function of the thickness of membrane. The overall-structure of sensor has a form of Au/Ti/NTC/silicon oxide layer (SiOx)/(1\0\0)Si. NTC film of Mn1.5CoNi0.5O4 with 0.5 mum in thickness was deposited on SiOx layer (1.2 mum) by pulsed laser-deposition (PLD) and annealed at 600-800 degreesC in air for 1 h. Au (200 nm)/Ti (100 nm) electrode was coated on NTC film by do sputtering. By the results of microstructure, X-ray and NTC analysis, NTC films, post-annealed at 700 C for 1 h, showed the best characteristics as NTC thermal sensing film. In order to reduce the thermal mass and thermal time constant of sensor, the sensing element was built-up on a thin membrane with the thickness of 20-65 mum. Sensors with thin sensing membrane show the good detecting characteristics. (C) 2002 Elsevier Science B.V. All rights reserved.