Bio-compatible insulated substrate impedance transducers

Abstract

An alternative smart sensing paradigm to large-scale biocompatible integration has been explored. Traditionally, conductive bio-labels detection profits from planar interdigitated electrodes (IDE) encapsulated between for instance a top thin alumina layer and a bottom thick silicon dioxide. Despite demonstrating good electrostatic sensitivity at strong micro-labels densities, such patterns however require sub-micron shrinking to work below 30 % conductive labels coverage. We therefore derived a spectroscopic field-effect transducer from micrometric IDE coupled to a thinly insulated surface-doped silicon channel. Thanks to capacitance enhancement that results between electrodes and semiconductor, label-induced field-effect modulation of channel's conductance gives rise to an intrinsic dielectric relaxation constant change subsequently measured by impedance spectroscopy. So-called Insulated Substrate Impedance Transducers (ISIT) have thereby been designed to sense an inter-digital impedance spectrum change following a frequency-dependent multi-parameter approach. In demonstration, metallic grains densities ranging from 1.2 % to 17 %, ensued from 0 to 1 nM concentrations of silver-labeled 30bp DNA targets were sensed in air on 100×100 μm 2 arrays through conductance and capacitance variations by factors of 6 and 3, respectively. Our presentation will focus on simulation, optimization and characterization of ISIT's electrical operation, and present on-chip tuning possibilities associated with substrate back-contact biasing. © 2009 Springer Berlin Heidelberg.