Large Strain Measurements by Vacuum-Packaged Mems Resonators Manufactured on Ultrathin Silicon Chips

Silicon resonators fabricated with wafer-level vacuum packaging on ultrathin silicon chips (overall thickness around 60 μm) are utilized for strain measurements on steel slabs. The thinned chips are glued on steel using M-bond 610 and Loctite EA 9461 adhesives and the sensor response during bending tests performed while operating the resonators in closed loop is measured, evaluating possible non-ideal effects such as creep and hysteresis. In the measurements, the results obtained on the ultrathin chips are compared with those achieved on sensors manufactured on the native 500 μm thick silicon substrates. The results obtained show an astonishing improvement in the measurements realized with the thinned chips, which show creep levels below 0.1%, no appreciable hysteresis phenomena and strain measurement range extended beyond 850 με, indicating that chip thinning can be a viable way to obtain high-quality strain measurements on a large range by vacuum-packaged silicon MEMS resonators