Fabrication of a glucose sensor with oscillator circuit using CMOS-MEMS technique

Abstract

This study investigates the fabrication of a glucose sensor integrated with an oscillator circuit on-a-chip using the CMOS (complementary metal oxide semiconductor)-MEMS (microelectromechanical system) technique. The glucose sensor contains interdigitated electrodes, sensitive films and a gold layer. The gold layer is deposited on the gaps between interdigitated electrodes, and the sensitive films are 11-MUA (11- mercaptoundecanoic acid) and GOD (glucose oxidase) that are immobilized on the surface of gold layer. The sensor needs a post-process to coat the sensitive films, and the post-process includes a dry etching to etch the sacrificial oxide layer and a self-assembled monolayer (SAM) technique to assemble the sensitive films. The glucose sensor is a capacitive type. The sensor produces a change in capacitance as the sensitive films absorb glucose. The oscillator circuit is used to convert the capacitance variation of the sensor into the frequency output. Experiments show that the glucose sensor has a sensitivity of 1.48 MHz/mM.