Micromachined piezoresistive cantilever array with integrated resistive microheater for calorimetry and mass detection

We describe a microcantilever calorimeter consisting of an array of ten can tilevers. Each single cantilever is capable of detecting heat energy with t he resolution of 50 nW Hz((-0.5)). The device is based on a Si microcantile ver coated with a 1 mum thick layer of SiO2 deposited with a 700 nm thick l ayer of aluminum Which forms a resistive microheater. Heat fluxes are monit ored by detecting the cantilever deflection (bending) due to the bimaterial structure of the cantilever (dissimilar thermal expansion properties of Si O2 and A1). The resistive microheater serves for calibration of the heat fl ux and for temperature sensing. In our design a piezoresistive Wheatstone b ridge detector is applied for measurements of the cantilever beam deflectio n. The cantilever displacement detection system enables investigations in u ltrahigh vacuum and low temperature conditions. The microcantilevers are ma nufactured in a one-dimensional array having ten individual microcantilever s which is the first step in the fabrication of an infrared detector array with spatial resolution. The displacement sensitivity versus temperature ch ange of the described sensor array as a function of temperature change is o f about 2 nm/K and an estimated resolution limit of temperature detection i s approximate to 10(-3) K at 300 K. In order to demonstrate the cantilever bending sensitivity we employ the piezoresistive cantilever array as a pico gram microbalance. (C) 2001 American Vacuum Society.