Fabrication of interdigitated electrodes (IDE´s) by conventional photolithography technique for pH measurement using micro-gap structure

Micro interdigitated electrodes (IDE´s) have successfully been fabricated and characterized amperometrically for the electrochemical detection of the pH concentration and bio-molecules. In the present work, aluminium (Al) is used act as the metal contact (electrodes) deposited on the silicon substrate using a thermal evaporator (PVD) vacuum coater. The simple conventional photolithography was applied to fabricate the micro-gap capacitive transducer. IDE´s mask is designed using the aid of AutoCAD software for the detection of bio-substance which is an extremely small scale in size before being transferred to commercial chrome mask. The fabricated micro-gap sensor will then further evaluated through surface topology and electrical characteristic. The surface topology was implemented using AFM, LPM, SEM and HPM. The electrical measurements were carried out using a Dielectric analyzer (DA) with 2400 source meter (KEITHLEY) to examine the electrical characteristics such as capacitance and conductance. Purchased pH buffer solutions which varied from pH4 to pH 10 is dropped on the surface of microelectrode and the effect on it is investigated for the application in pH measurement. This study has proven that an increase in the concentration of acidic to alkaline pH leads to proportional to the capacitance.