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 μm-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.
Abstract. The application of ultrasonic vibration assistance in machining offers many benefits over conventional machining. In some machining processes, like the generation of geometrically defined microstructures by cutting, the interaction of the system components and the machining process can be particularly crucial with respect to the production result. Monitoring of ultrasonic vibration-assisted machining in terms of the in-process measurement of frequency and amplitude is currently realized by measurement inside the actuator; thus, measurement is presently undertaken relatively far away from the cutting process. In this paper an in-process measurement set-up based on strain gauges positioned close to the cutting edges is presented. It is used to investigate the induced vibration in the ultrasonic horn. Experiments on machine samples with and without ultrasonic vibration assistance are performed using the in-process measurement set-up described. The results of the strain gauges are analysed in comparison to internal feedback signal and surface measurements. The experiments show the high sensitivity of the measurement set-up presented and a huge gain of information compared with the conventional measurement approach. This enables improved controllability of the excited mode shapes as well as in-process adjustment of the ultrasonic vibration frequency and amplitude for the manufacturing of defined microstructures.
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