Understanding Smart Sensors - Nomads.usp

2MicromachiningI wonder how many angels can dance on the head of a pin?—Unknown Middle Ages philosopher2.1 IntroductionThe answer to that question is no more than 25,200, given that a pin has adiameter of 1 16 inch (15,875 mm) and each (micromachined) angel has a diameterof 100 mm. So much for philosophy. Micromachining is causing the reinvestigationof every aspect of physics, chemistry, biology, and engineering.Thermodynamics, mechanics, optics, fluidics, acoustics, magnetics, electromagnetics,wave, kinetics, and nuclear forces, as well as medicine, robotics, displays,and instrumentation, are being investigated in academic, national, andindustrial research and development (R&D) labs. Micromachining technologyis enabling the extension of semiconductor-based sensing beyond temperature,magnetic, and optical effects to produce mechanical structures in siliconand sense-mechanical phenomena. Many universities are creating crossdepartmentsand cross-college programs to explore the future possibilities ofmicromachined MEMS devices.Micromachining is, in the most common usage, a chemical etchingprocess for manufacturing three-dimensional microstructures that is consistentwith semiconductor processing techniques. IC manufacturing processes used tomake the microstructures include photolithography, thin-film deposition, andchemical and plasma etching. Bulk micromachining has been used to manufacturesemiconductor pressure sensors since the late 1970s. Recently, newer17