A monolithic silicon accelerometer with integral air damping and overrange protection

Novel piezoresistance silicon accelerometers for full-scale accelerations on the order of 0.5 G-100 G have been designed, fabricated, and tested. These, dual-beam cantilever devices incorporate silicon structures introduced at the wafer level for air damping and bidirectional overrange protection, resulting in a silicon/glass chip approximately 3.4 mm square and 1.5 mm thick, suitable for packaging in many configurations and for use in many applications. Critical damping and overdamping have been demonstrated with roll-off frequencies 500 Hz and above, and shock survival above 1000 G in all axes has been achieved. Cross-axis sensitivity is less than 2% for any axis. Device design was accomplished using finite-element modeling (FEM) to assess sensitivity, temperature coefficients, resonance modes, cross-axis sensitivity, and overrange characteristics. Analytical modeling was used to 'benchmark' the FEM predictions for simplest cases, and experimental results are in good agreement with FEM.>