Effect of Microwave Annealing on the Sensing Characteristics of HfO₂ Thin Film for High Sensitive pH-EGFET Sensor

Recently, certain challenges have persisted in PH sensor applications, especially when employing hafnium oxide (HfO2) thin films as sensing layers, where issues related to sensitivity, hysteresis, and long-term stability hamper performance. Microwave annealing (MWA) technology, as a promising solution for addressing these challenges, has gained significant attraction due to its unique advantages. In this article, the effects of microwave annealing (MWA) treatment on the sensing behaviors of Extended-Gate Field-Effect Transistors (EGFETs) utilizing HfO2 as a sensing film have been investigated for the first time. Various power levels of MWA treatment (1750 W/2100 W/2450 W) were selected to explore the optimal processing conditions. A thorough physical analysis was conducted to characterize the surface of the MWA-treated HfO2 sensing thin film using techniques such as X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). Our findings reveal that MWA treatment effectively increased the surface sites (Ns) in the HfO2 sensing thin film, consequently leading to an increase in the pH sensitivity of EGFETs to 59.6 mV/pH, as well as a reduction in hysteresis and an enhancement in long-term stability. These results suggest that MWA offers a straightforward, energy-efficient method to enhance overall HfO2 sensing film performance in EGFETs, offering insights for HfO2 applications and broader microelectronics challenges.