Ultra-High Sensitive ISFET pH-Meters by Nano-Porous Silicon Structures as Sensitive Membrane

Nano-porous structures were utilized on the sensitive surface of ISFET devices to improve their sensitivity as pH meters. The proposed sensor presents an ultra-high sensitivity pH-meter to detect H+ or OH- in electrolytes. This pH-meter is a field effect transistor with a non-symmetric gate capacitance. The area of the exposed surface is numerously larger than that of the channel area. Using this method the effective gate capacitance increases significantly. Because of 3-dimentional geometry of the nano-porous poly-silicon region the amount of the adsorbed charges increases and consequently the sensor response is dramatically higher.