Optimizing nanowell biosensor fabrication: Evaluation of metal deposition and oxide layer modification

Abstract

This study presents a comparative evaluation of two nanowell-based biosensor fabrication methods designed to improve sensing performance and device reliability. The conventional process employs electron beam (e-beam) evaporation for metal deposition and aluminum oxide (Al₂O₃) as the insulating layer, while the modified approach utilizes the sputtering method for metal deposition and hafnium oxide (HfO₂) as the insulating layer, respectively. Both fabrication methods were used to construct nanowell impedance biosensors for detecting interleukin-6 (IL-6) at concentrations ranging from 10 nM to 10 fM. Electrochemical impedance spectroscopy (EIS) was performed in a two-electrode configuration using an AC excitation of 10 mV across a frequency range of 1 Hz–5 MHz. The Sputtered/HfO₂ biosensors exhibited improved electrical insulation, enhanced step coverage, and reduced device failure due to short or open circuits. These improvements resulted in a higher baseline response, reduced voltage drift, and enhanced sensitivity, achieving a limit of detection (LOD) of 7.8 fM compared to 15.5 fM for the E-beam/Al₂O₃ sensors. The results demonstrate that optimized fabrication using sputtering and HfO₂ significantly enhances biosensor reproducibility and detection performance, supporting its application in scalable, label-free diagnostic platforms.