While microelectronics relies on SOI for its insulating layer, SOI-MEMS benefits from the single crystal silicon of the top layer and substrate. A good example is the latest product from TRONIC’S Microsystems, a French manufacturer of high-end custom components.
The geophone, a seismic vibration sensor manufactured for Sercel (the world leader in oil exploration equipment), benefits from the latest advances in SOI micromachining to reach resolution (mechanical noise) as low as 0.1µG. (Please see www.tronics-mst.com for a full case study.)
The transducer benefits from the excellent elasticity of the single crystal silicon to create springs extremely sensitive to seismic vibrations and highly resistant to mechanical fatigue. Used in a thick layer configuration, the SOI also provides:
• A high signal-to-noise capacitive detection
• A high resonant Q factor once packaged under high vacuum.
Finally, SOI allows a process simplification. The presence of three structural layers with perfectly controlled thickness avoids depositing and etching multiple layers of materials. Thus 3D microstructures can be built with only a few masks.
TRONIC’S Microsystems was one of the first commercial companies to introduce SOI for MEMS and is working on the industrialization of new SOI custom product concepts such as high performance gyroscopes •