Abstract
Benefited from the development of the semiconductor industry, circuit design has become a very mature industry. With the integration of circuits and micro-electromechanical devices on the same chip, we can produce a rapid and high sensitivity biomedical sensor. Depending on the surface modification method, we can sense different cells or biological molecules. The chip design contains both the interdigitated electrodes and planar electrodes,. It is expected that when the DNA is modified on the oxide layer (SiO2) above the electrodes, the capacitance value of the sensing electrode will have a corresponding change due to the polarization effect produced by the molecules under the electric field. This change can be readout by the sensing circuit. In addition, a third planar electrode is placed under the interdigitated electrodes to apply different biases for monitoring the capacitive changes associated with the hybridized DNA. The focus of this work is to explore the mechanism of capacitive sensing of interdigitated and planar electrodes. In experiments, we performed DNA sensing at concentrations ranging from about 1 aM to 1 pM in which the capacitance varied by about 40 %.