A force sensor using a CMOS inverter in view of its application in scanning force microscopy

A force sensor using a new detection scheme is presented for scanning force microscopy. The sensor consists of a silicon cantilever and a CMOS inverter, and is based on piezoresistivity effects in a MOS transistor. The sensor principle has been verified by assembling a test structure including a large cantilever (40 mm×4 mm×0.39 mm) with an integrated MOS transistor. A deflection of 1 μm at the cantilever end yields a signal of 6.19 mV at the output of the inverter for a supply voltage of 13 V and without any amplification stage. The measured minimum detectable stress demonstrates the potential of this new detection scheme. In combination with microfabricated cantilevers, a spatial resolution better than 1 nm is expected making this sensor of interest for application in scanning force microscopy