11.07.2015 Views

Understanding Smart Sensors - Nomads.usp

Understanding Smart Sensors - Nomads.usp

Understanding Smart Sensors - Nomads.usp

SHOW MORE
SHOW LESS

Create successful ePaper yourself

Turn your PDF publications into a flip-book with our unique Google optimized e-Paper software.

Micromachining 31Frit glassseal/spacerBulk micromachined silicon capWire bondsSilicon substrateSurface micromachineddual capacitor accelerometerAluminumFigure 2.7 Combined surface and bulk micromachining in an accelerometer for protectionfrom contamination.DiaphragmanchorCavityPolysilicon diaphragm100 mmNMOS deviceKOH-etchedpressure inletn+ bottom capacitor plateFigure 2.8 Combined surface and bulk micromachining in a pressure sensor. (After: [18].)measured for the 100-mm by 100-mm capacitive structure. The 100-fF (femtofarad= 10 −15 ) capacitor had a resolution of 30 attofarads (10 −18 ).2.5 Other Micromachining TechniquesThe micromachining techniques discussed so far have been wet-etching techniquesused primarily for piezoresistive and capacitive sensing for measuringpressure and acceleration. They are the basic processes used in research thathave progressed into commercial manufacturing. However, other techniquesare being developed that overcome the limitations, extend the types of

Hooray! Your file is uploaded and ready to be published.

Saved successfully!

Ooh no, something went wrong!