A Capacitive Chemical Sensor based on Porous Silicon

A new capacitive field effect sensor based on a porous EIS (Electrolyte Insulator Semiconductor) structure is presented The porous silicon sensor was prepared using standard techniques of semiconductor processing Experimental conditions were adjusted to realize a well-defined macroporous formation of the silicon substrate. The porous sensor device made of Si/SiO2/Si3N4 exhibits a high, near-Nernstian pH sensitivity of about 54 mV per pH in the concentration range from pH 4 to pH 8, similar to a planar EIS structure with the same layer sequence. The enlargement of the active sensor area due to the porous layer structure increases the measured capacitance and thus allows a scaling down of the sensor.