Low Power Tunneling Current Strain Sensor Using MOS Capacitors

Although microelectromechanical systems (MEMS) strain sensors have been widely researched and commercialized for decades, the increasing requirement for low power sensors is motivating research on new techniques. We present a new technology to make very low power sensors by measuring the tunneling current through a MOS capacitor. The tunneling current can be in the nanoamp range, which is a good alternative for low power sensing. We demonstrate a power consumption of a couple of nano-Watts with a minimum detectable strain of 0.00036%. The fabrication process is very simple and compatible with CMOS processes. We find that noise is lower in inversion region, and therefore, it is better to bias device to inversion region. To study the sensitivity in the inversion region, a model was developed to compute the strained tunneling current comprised of electron conduction band tunneling current and electron valence band tunneling current. The model fits our experiment very well.