Development and realization of a nano-accelerometer based on the tunneling effect

• Applicant: Professor Dr.-Ing. André Zimmermann, since 4/2019
• Subject Area: Microsystems
• Term: from 2017 to 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 321474168

The need for further cost reductions in micro-sensors leads to their permanent miniaturization. With the established surface micromachining technology and the capacitive detection principle we currently reach the limits of miniaturization. A further miniaturization is possible only with a more sensitive detection principle like the tunneling effect. In contrast to previous developments of accelerometers with the tunneling-effect, which had its objective in the reduction of the resolution to less than 1 micro-g, in this project the research focus is for the first time the miniaturization of the sensor structure down to the limits of its theoretical and technological limits. The area of the sensor structure is reduced so far that the resolution of the sensor with a high dynamic range of several kHz is limited by the thermal noise of the spring-mass system in the range of today accelerometers to some parts per thousand of the nominal range. In the project, new concepts for accelerometers will be developed based on the tunneling effect allowing a reduction in the area of today's sensor structures by 2 to 3 orders of magnitude to some 10µm times10 µm. In addition, for the first time, several tunneling junctions and actuators are used for their control to reduce cross-sensitivities and to measure the acceleration in two directions.The technological realization of a sensor structure for a measuring range of ± 1g is carried out with the commercial PolyMumps foundry process of MEMSCAP Inc.. With a Focused Ion Beam, one or more tunneling junctions are subsequently written into the polycrystalline sensor-structure. Another research focus lies, therefore, in the micro/nano integration. Newly developed backend processes with a Focused Ion Beam for the integration of tunneling junctions and for thinning the cantilevers of the polysilicon spring-mass system will be integrated in the overall process flow. These backend processes further allow significantly reducing the area of the surface micromachining structure of the PolyMumps process. The Focused Ion Beam backend processes allow us to go to the limits of the miniaturization potential with the concept under consideration. In this project the theoretical bases for determining the limits of miniaturization will be derived. The theoretical basis is also used to develop and optimize the design for the PolyMumps process and the electronic control circuitry. In Addition, various technologies are combined and thereby exploring the limits of what is technologically feasible in the technological realization of the new concept.

• DFG Programme: Research Grants
• Ehemaliger Antragsteller: Professor Dr.-Ing. Hermann Sandmaier, until 3/2019