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

Abstract

We describe a microcantilever calorimeter consisting of an array of ten cantilevers. Each single cantilever is capable of detecting heat energy with the resolution of 50 nW Hz (Ϫ0.5) . The device is based on a Si microcantilever coated with a 1 m thick layer of SiO 2 deposited with a 700 nm thick layer of aluminum which forms a resistive microheater. Heat fluxes are monitored by detecting the cantilever deflection ͑bending͒ due to the bimaterial structure of the cantilever ͑dissimilar thermal expansion properties of SiO 2 and Al͒. The resistive microheater serves for calibration of the heat flux and for temperature sensing. In our design a piezoresistive Wheatstone bridge detector is applied for measurements of the cantilever beam deflection. The cantilever displacement detection system enables investigations in ultrahigh vacuum and low temperature conditions. The microcantilevers are manufactured in a one-dimensional array having ten individual microcantilevers which is the first step in the fabrication of an infrared detector array with spatial resolution. The displacement sensitivity versus temperature change of the described sensor array as a function of temperature change is of about 2 nm/K and an estimated resolution limit of temperature detection is Ϸ10 Ϫ3 K at 300 K. In order to demonstrate the cantilever bending sensitivity we employ the piezoresistive cantilever array as a picogram microbalance.

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“…It has its own advantages and disadvantages in fabrication process. For the realization of suspended/freestanding microstructures made of materials such as p + -Si, SiO 2 , Si 3 N 4, etc., silicon beneath a structural component needs to be removed [1][2][3][4][5]10,70,[161][162][163]. If the process is done only on one side of the wafer, the removal of underneath material is only possible by undercutting process [70,161,162].…”

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A comprehensive review on convex and concave corners in silicon bulk micromachining based on anisotropic wet chemical etching

“…It has its own advantages and disadvantages in fabrication process. For the realization of suspended/freestanding microstructures made of materials such as p+-Si, SiO2, Si3N4, etc., silicon beneath a structural component needs to be removed [1][2][3][4][5]10,70,[161][162][163]. If the process is done only on one side of the wafer, the removal of underneath material is only possible by undercutting process [70,161,162].…”