Fabrication and characterization of metal microwire transducer for biochip application

Abstract

Microwire makes good sensors because their small dimensions which enhance their sensitivity. To be useful, microelectrode sensors must be integrated with electronic capable of processing those signal. In this research, we demonstrated a method to fabricated and characterize metal microwire device for biosensing application. Using conventional photolithography technique and other experimental techniques, we developed a reliable procedure for producing aluminium wires with micron-scale features. Significantly, in micro fabrication the critical dimension (CD) of wafers in photolithography is the most important parameter that determines the final performance of devices. Hence, it is paramount to have high resolution, high sensitivity and precise alignment to successfully transfer the original pattern to wafer. The process was optimized by control the spin speed for photoresist (PR) coating, spin time, post exposure bake time, developer concentration ratio, hard bake and aluminium etch time so as to achieve the possible fabrication process and get the expected microwire size. The process begins with the photoresists coating and spinning at 3000 rpm to form a thin and uniform layer. Subsequently, the PR coated substrates were exposed to UV light for 10s. After the alignment and exposure, the substrate were developed using the resists developer with 25:10 ratio in which 25 parts of developer and 10 parts of deionized water. Eventually, the post exposure bake and hard bake time were optimized for a better throughput on the pattern transfer process. The aluminium microwire has been successfully fabricated with the contact pads. The wires range in thickness from 1 μm-4μm to achieve a resistivity as low as possible for nano range limit of detection. This microelectrodes transducer will be eventually used as biomolecule detection kit. The fabricated microwire was morphologically characterized using Atomic force microscope (AFM), Scanning electron microscope (SEM), High power microscope (HPM). Besides that, the electrical properties of the fabricated aluminium microwire were studied using source meter.