Characterisation of MOS transistors as an electromechanical transducer for stress
The influence of mechanical stress on field effect transistors is investigated using a pressure-deflected membrane for generation various mechanical stresses. It consists of a silicon membrane and transistors, which are designed and manufactured using 1.0 mm-XC10 technology from X-Fab. The transducers for sensing mechanical stress are placed on the edges with the maximum stress. Furthermore, the position is optimized by using FEM simulations (Ansys). Different variances of transistors and the impact on their electrical properties are investigated. Transistors are manufactured with different parameters such as channel lengths, widths, and alignments of the channel current to the direction of the mechanical stress, as well as connecting transistors in Wheatstone-like quarter and half bridges to generate a read-out voltage that is amplified using an integrated operational amplifier on the same chip. The bridge consists of p-MOSFETs as transducers on the membrane and n-MOSFETs as reference transistors (active loads). Transistors bridges are optimized on sensitivity, linearity and temperature behavior by varying channel length (L) and width (W). The influence of the membrane size and deposited technology layers is also investigated. The focus of this publication is presenting an analysis of the electrical behavior of the designed and manufactured transistors for different applied pressures. An experimental setup with a temperature and pressure calibrators is used for characterizing the transducers between 25 and 75 °C and up to 1 bar differential pressure.