Over the years, thin SOI technology has enabled the design and realization of environmental sensors such as thin-film temperature, humidity [Laconte], optical (UV or IR specific) [Afzalian, Estrada] and magnetic [Haddab, Portman] sensors, as well as physical/chemical sensors such as thin-membrane based sensors (micro-hot plate, flow, gas…) [Laconte2004, Laconte2003, Ivanov2004], all with state-of-the art or record performance. These are based on the integration of surface and bulk micromachining steps within the SOI CMOS process flow (which is dramatically eased thanks to the unique thin silicon film over buried oxide SOI structure), or by allowing the post-processing of additional layers such as amorphous silicon, high-temperature thick polysilicon, polyimide or metal oxide layers.

With regards to magnetic sensors, a direct benefit of SOI is to provide thin conducting layers, with a 2D-like electron conduction, promising better sensibility than traditional Si Hall plates. The feasibility of high-linearity, high-stability, low-offset and low-noise Si based Hall devices, that can be used for metrological applications such as electricity metering, was demonstrated (Schlumberger, UCL).

For optical sensing, the SOI structure comprising a thin Si top layer over a buried oxide and a Si substrate provides a unique selective filtering action. Quantum efficiencies in excess of 60% have been demonstrated for fully-depleted SOI PiN photodiodes in the 300-400 µm UV range (UCL).