High energy (MeV) ion implantation was applied to fabricate a buried piezoresistor for microsensors. This method makes it possible to bury a p+ layer without a highly doped n+ overlayer. The buried piezoresistor has the advantage of stability because the influence of surface electrical field variation to the resistance is much smaller than that of the conventional piezoresistor. Differential pressure type and drag force type micro liquid flow sensors were fabricated using the buried piezoresistor. The buried piezoresistor formed by MeV ion implantation acts stably enough to detect the strain even when it is used in water without passivation.
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