Integration of MOSFET/MIM Structures Using a CMOS-Based Technology for pH Detection Applications with High-Sensitivity

In this work, we show that by using Metal-Insulator-Metal (MIM) structures integrated in series to the gate of submicron Metal-Oxide-Semiconductor Field-Effect Transistor (MOSFET) devices, highly-sensitive and ultra-low power consumption pH sensors can be obtained. One MIM capacitor enables external polarization of the MOSFET device while a second MIM capacitor is connected to a sensing plate whose surface is whether a thick polyimide layer or the last metallization level. The electrochemical response of these surfaces to pH buffer solutions resembles that of Ion-Sensitive Field-Effect Transistor (ISFET) devices whose pH sensitivity is dependent on the type of surface material being exposed.