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SiGe hetero MOS- and MOSFET's for ultimate scaling towards sub 100 nanometer

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Towards the Nano-Electronics era

From mobile communications and computers to aerospace, information processing is implemented with microelectronics. Forced by increasing competitiveness in the microelectronics field, the market has focused on some key features including low cost, high packing density, increased frequency and noise performance. With this in mind, the SIGMUND project elaborated on the development of very thin (less than 100 nm) transistors that lead to optimal performance of circuits in a cost effective way.

Digital Economy

Due to its ability to switch between a conductive and a non-conductive state practically without power wastage, the most widely used switching device in modern electronics is the Field Effect Transistor (FET). There are different types of FETs such as MOSFET whose operation is based on the same principle of operation; the carrier density and the current of a channel is driven by capacity. Structurally, the driving electrode (gate) of the transistor is a thin line, usually 1 µm wide. The narrower the gate electrode is, the faster the transistor can switch. Driven by the current trends in the field of microelectronics, the development of silicon based hetero-FETs appears to be necessary due to their enhanced carrier mobility. Hence, particularly for MOS transistors this optimises mobility in improved switching speeds. The SIGMUND project has responded to the challenge of optimising transistors for integrated circuit technology. During the project many studies were performed that proved these Silicon-Germanium based transistors (MOSFETs) exhibited characteristics that are superior to classical FETs. Therefore, the SIGMUND MOSFETs exhibited higher performance because of increased switching speeds. Even at low temperatures the extensive study found that these transistors performed exceedingly well, showing stability in terms of surface defect. Further studies were carried out on the impact of layer composition and surface morphology, layer strain, quantum size and device dimensions. The results found show that the SIGMUND MOSFET conduit was the most efficient and reliable carrier. In addition, extensive physical simulations aided to specify the optimal layer configurations for enhanced mobility and current drive. The results of the device characterisation with respect to temperature (ranged between 50 and 300°K) aid the device optimisation in electrical models as well as in prospective applications for predictive circuit simulations. Moreover, extensive examination performed with emphasis on High Frequency measurements showed a good potential for use in space applications. This is to say that SIGMUND MOSFET transistor continued with excellent performance even at sub-zero temperatures. It is also expected that improved performance will extend this silicon based technology into microwave technologies. Finally the development process is so simple that it allows their easy implementation on an industrial scale.

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