| This document describes the design of a bulk-micromachined, monolithic, mass airflow sensor with a thermally-isolated, thin-film, dielectric, microbridge/diaphragm design. In addition, several fabrication methodologies were explored, as well as a means to test and evaluate the sensors for this undergraduate class laboratory.;The mass airflow sensor architecture chosen was based upon a closed-loop-control, microelectronic thermal (hot-wire) anemometer design. Two separate photomask sets were developed using L-Edit(TM) software (by Tanner Research), with each set including multiple geometric variations of a dual/triple microbridge/cantilever flow sensor structure to be suspended over a precision, anisotropically-etched pit, integrated onto a (100) silicon substrate.;Four primary structural fabrication strategies were explored to produce the thin-film material for the flow sensors: (1) RF planar magnetron sputter-deposited 1 mum-thick silicon nitride microbridges/cantilevers; (2) anodically-bonded-and-machined 20--30 mum-thick borosilicate glass diaphragms; (3) spin-on-glass microbridges/cantilevers; and (4) low-stress, 0.5 mum-thick, LPCVD silicon nitride microbridges/cantilevers. Four resistor metallizations were separately evaluated: permalloy (Ni81Fe 19), chromium, titanium, and platinum. (Abstract shortened by UMI.). |
