Sealed-cavity resonant microbeam pressure sensor

摘要: A quasi-digital pressure sensor based on polysilicon resonant microbeams has been demonstrated. Pressure sensitivities of nearly 4000 counts per second psi have attained a 10 device with base frequency 233 000 Hz. Short-term stability as low 0.01 ppm the is typical. The are fabricated their own integral vacuum cavities, allowing high-Q operation in differential mode or contact liquids such silicone oil. Design considerations include effects internal strain and lead to push-pull layout configuration independent microbeam diaphragm thickness. Fabrication technology incorporates fine-grained polysilicon, surface micromachining, bulk reactive sealing. Packaging into precision avionics headers being used for preliminary testing. Testing results indicate suitability avionics, industrial, commercial applications. Optical methods test sensors verify design methodology. developed under this effort electrostatic drive/piezoresistive sensing, optical drive/optical substrate piezoelectric drive/laser vibrometer sensing. Wafer-level testing 200 μm×46 μm×1.9 μm shows an average fundamental 553 150 first overtone 1 332 550 standard deviations across wafer 0.15 0.10%, respectively. effective thickness can be determined high resolution. Laser measurements through shell reveal at least ten overtones up 25 MHz.