A finite-element analysis of possible silicon carbide (SiC), folded-beam, lateral-resonating accelerometers is presented. Results include stiffness coefficients, acceleration sensitivities, resonant frequency versus temperature, and proof-mass displacements due to centripetal acceleration of a blade-mounted sensor. The surface micromachined devices, which are similar to the Analog Devices® Inc., (Norwood, MA) air-bag crash detector, are etched from 2-μm thick, 3C-SiC films grown at 1600 K using atmospheric pressure chemical vapor deposition (APCVD). The substrate is a 500 μm-thick, (100) silicon wafer. Polysilicon or silicon dioxide is used as a sacrificial layer. The finite-element analysis includes temperature-dependent properties, shape change due to volume expansion, and thermal stress caused by differential thermal expansion of the materials. The finite-element results are compared to experimental results for a SiC device of similar, but not identical, geometry. Along with changes in mechanical design, blade-mounted sensors would require on-chip circuitry to cancel displacements due to centripetal acceleration and improve sensitivity and bandwidth. These findings may result in better accelerometer designs for this application.

Volume Subject Area:
Controls, Diagnostics and Instrumentation
Topics:
Accelerometers, Gas turbines, Micromachining, Silicon, Finite element analysis, Sensors, Blades, Temperature, Airbags, Atmospheric pressure, Chemical vapor deposition, Design engineering, Geometry, Polysilicon, Resonance, Semiconductor wafers, Shapes, Stiffness, Thermal expansion, Thermal stresses
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