Nanocrystalline Piezoresistive Polysilicon Film by Aluminum-Induced Crystallization for Pressure-Sensing Applications

Nanocrystalline piezoresistive polysilicon films were obtained at low temperatures by aluminum-induced crystallization (AIC). The films exhibited granular structure with good polycrystalline properties. A piezoresistive pressure sensor was fabricated on a polyimide substrate, in a Wheatstone bridge configuration comprising two passive resistors and two active piezoresistors made of polysilicon films obtained by AIC. The resistors showed linear I–V characteristics with typical resistance values between 15 and 30 k
$\Omega$
. Atomic force microscopy was used in contact mode to study the response of the pressure sensor with applied pressure in the 2–19 kPa range. For the higher range of 450 kPa–2 MPa, a load-cell with a nanopositioner was utilized. The pressure-sensor sensitivity was measured to be 41.12 and 5.02 mV/MPa, respectively, for these ranges, when the Wheatstone bridge was bias at 1 V.