Nanostructures in microelectronicsmicro system engineering

Also within the range of micro system engineering, nanostructures and nano-technologically optimized components will gain importance in the

53 C't magazine 5/2001, p. 24: „Energy crisis- Highlights from the ISSCC in San Francisco"


future. In space travel MEMS offer the possibility of miniaturization in a variety of subsystems (e.g. AOCS, propulsion, thermal control). The progressive miniaturization makes an increasing integration of different functions and components in a circuit necessary. Modern micro manufac- Micro manufacturing turing processes for example make the integration of different sensor and processes for highly actuator units for attitude and orbit control as well as a propulsion unit integrated space subsys-possible. A still higher integration and compactness offer approaches like tems vertical MMIC structures (Monolithic Microwave Integrated Circuit), MAFET (Microwave and Analog Front-End Technology) or Ultra-Thin-Chip-Stacking (piles of |im thick Si or III/V semiconductor circuits),55 which will play an important role regarding the miniaturization of space subsystems and systems. Also microelectromechanical thermal control systems are in development, which use among other things nanoscale electrochrome coatings. Likewise MEMS based switches and antennas are examples of space relevant applications of MST, which will be influenced increasingly by nanotechnology in the future.

Apart from photoelectric IR sensors described above, also bolometers find application in space, for example as earth sensors for attitude and orbit control of spacecrafts or for scientific purposes (e.g. in astronomy particularly in the far infrared range as well as in atmosphere research). For the production of miniaturized bolometers, nanotechnological coating and lithography procedures are applied. The thermoelectric substances are separated from each other by nanoscale isolation layers. For bolometers, different material systems are used as absorber layers, among other things also high temperature superconductors like nanocrystalline Y-Ba-Cu-O. This material offers the advantages of a high thermoelectric resistivity, a low noise factor and a good CMOS compatibility (Sedky 1997).

Another example are micromechanical actuators, which could be used as miniaturized positioning modules in robotic space applications. Piezomo- Nanomotors" for space tors help to achieve positioning systems with a resolution of 10 nm over technology distances of several centimeters. A prominent manufacturer of these "nanomotors" is the Aachener company Klocke Nanotechnik.56 Possible applications in space technology comprise miniaturized positioning systems with many degrees of freedom for spectrometers, high frequency tuner or nanomanipulators, which could be used for an accurate dosage of tiny drops for microgravity experiments on ISS. According to data of the manufacturer such nanomotors possess good applicability in space (Rosenberger 2000).

56 see Coello-Vera et al. 2000


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