High temperature and high power applications of microsystems require sensors or devices that cannot be built in Si due to the limitation of some of its physical properties. Among wide bandgap semiconductors, silicon carbide (SiC) is to date the only one commercially available in relatively large diameter wafers with the electronic purity and quality. Furthermore, it has a high thermal conductivity, three times higher than Si and comparable to Cu, 10-fold breakdown field strength which allows attractive specific on resistance compared to Si and GaAs, 2 times higher metal semiconductor barrier, i.e. low leakage current at high temperature. IMM has been in the past years protagonist in fundamental and applied research to develop processing and devices on SiC. Examples of possible applications are in the field of electric power distribution where to date extra power has to be introduced in the network to avoid black out during rapid adsorption changes. The substitution of electromechanical with solid state switchers can reduce the extra power with a significant power saving (about 5%).
Furthermore, the number of electronics tools daily used at home or in modern offices is rapidly increasing with an increase of power request. Therefore, a strong reduction of their power consumption is required, starting from their power supplies. On the other hand portable electronics is going to be the dominant electronics, thus requiring more efficient power supplies with a reduction in weight and size. One of the main task in electrical vehicles is again the reduction of weight and power consumption.
Both tasks can be reached by a control electronics working at high temperature eliminating the heavy passive component (cooling systems, ...).
Finally, the general trend in high power electronics is the reduction of passive component size and the increase of system efficiency (low power dissipation). For this aim higher operating frequencies and higher working temperatures are needed. The goal can be reached by high voltage Schottky diodes that can only be fabricated in SiC. In terms of minimising the power dissipation, for Schottky diode an appropriate choice of the barrier metal is necessary. In fact, a metal which forms a low barrier on SiC (like Ti) has the advantage of a low forward voltage drop but it is not suitable for high temperature applications because of the drastic increase of the leakage current. Conversely, a high barrier metal (like Ni2Si) exhibits lower leakage currents even at higher temperature but presents a high voltage drop under forward conduction. A good compromise was recently demonstrated with the fabrication, at IMM, of dual metal Schottky rectifiers by using a low/high barrier with Ti and Ni2Si. It was possible to achieve devices with a voltage forward drop as that of a Ti and a reverse leakage current comparable to Ni2Si diode. This result demonstrates the possibility at the same time of significantly reduce the power dissipation and increase the maximum allowed operation temperature.
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