4 February 2010 Stability experiments on MEMS aluminum nitride RF resonators
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We report on long-term stability experiments on a novel MEMS radio frequency (RF) resonator fabricated in Aluminum Nitride technology. The AlN fabrication process allows for the realization of resonators, filters, and resonant sensors operating over the frequency range from 500 kHz to in excess of 10 GHz using CMOS compatible materials. The 100 MHz resonators used in these experiments were a ring design with 140-micron outer diameter and 100-micron inner diameter. Electrodes on the top and bottom of this AlN ring enable measurement of resonance. Wafer sections were stored in air and vacuum and tested daily. We observed a steady degradation in the resonant frequency (600 ppm over the 800 hours) for the devices stored in a vacuum. Small degradation was observed in the air experiment (50 ppm over 1200 hours). Failure analysis using secondary emission microscopy (SEM) revealed no differences between control devices and devices on test. However, subsequent investigation of blank wafer sections by Time-of-Flight secondary ion mass spectrometry (ToF-SIMS) found small levels of silicone surface contamination from vacuum chamber exposure. This contamination added enough mass to shift the resonant frequency. These experiments demonstrate the need for clean environments for future wafer-level testing and also packaging for these small-mass resonators.
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Danelle M. Tanner, Danelle M. Tanner, Roy H. Olsson, Roy H. Olsson, Ted B. Parson, Ted B. Parson, Shannon M. Crouch, Shannon M. Crouch, Jeremy A. Walraven, Jeremy A. Walraven, James A. Ohlhausen, James A. Ohlhausen, } "Stability experiments on MEMS aluminum nitride RF resonators", Proc. SPIE 7592, Reliability, Packaging, Testing, and Characterization of MEMS/MOEMS and Nanodevices IX, 759209 (4 February 2010); doi: 10.1117/12.846551; https://doi.org/10.1117/12.846551

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