title: The Investigation of Fabrication and Reliability of Solution-Processed High-k Dielectrics
Creators: name: Fang, Yuxiao
Publisher: name: University of Liverpool Repository
Year: 2021

description: Solution-processed high-k dielectrics have become a strong research focus in both academic and industrial fields. However, solution-processing brings poor film quality and stability. Increasing the reliability of solution-processed devices becomes challenging, especially those devices for nuclear and aerospace applications. To address this issue, this work focuses on the fabrication and reliability investigation of solution-processed high-k dielectrics and devices and provide an insight into their bias-stress (BS) and biased radiation stress (BRS) stability degradation. In chapter 3, the annealing effects on the aqueous solution-processed AlOx thin films were investigated. On-site radiation measurements were carried out to analyze the BS and BRS stability of AlOx metal-oxide-semiconductor capacitors (MOSCAPs) under 92 Gy (SiO2) γ-ray radiation. It was found that aqueous solution-processed AlOx thin films with reduced impurities, low leakage current, and satisfied BS stability could be successfully formed at annealing temperature &gt; 250 oC. Compared to the Al2O3 thin films fabricated by atomic layer deposition (ALD), the BRS stability of aqueous solution-processed AlOx thin films is mainly degraded by radiation-induced oxide traps related to the precursor impurities and loosely bonded oxygen. The findings of this chapter offer clear inspiration for achieving highly stable solution-processed high-k dielectrics working in harsh radiation environments. In chapter 4, it is demonstrated that hydrogen peroxide (H2O2) is a strong oxidizer to improve the thin film quality and stabilities of solution-processed dielectrics. Their interface trap density was reduced, and the BS stress stability of AlOx MOSCAPs was improved. Furthermore, 7.5 M H2O2-AlOx MOSCAPs exhibit ignorable radiation-induced oxide and interface traps with total dose up to 42 Gy (SiO2) through carrying out on-site measurements. The 7.5 M H2O2-AlOx MOSCAPs also demonstrate the ability to recover after the bias was interrupted. The results demonstrate that employing H2O2 in the solution-process has significant potential to improve the stabilities of large-area electronics for nuclear and aerospace applications. In chapter 5, the effects of lanthanum composition on the ambient air stability, BS stability and radiation hardness of the water-induced (WI) solution-processed ZrLaO thin films and InOx/ZrLaO thin film transistors (TFTs) were investigated. The ZrLaO thin films with 10% La have remained stable under 5-weeks ambient air exposure and 1.44 kGy γ-ray irradiation. The InOx/Zr0.9La0.1Oy TFTs exhibited satisfied ambient air stability (10-days ambient air exposure) and radiation hardness (1.03 kGy irradiation). The optimized InOx/ZrLaO TFT with 10 % La exhibited a low operating voltage of 4 V and a high Ion/Ioff of around 2 × 106. Besides, their application in resistor-loaded inverters with a gain of 12 at 4 V was also demonstrated. The results represent a great step toward the achievement of low-cost, low-power consumption and large-area flexible electronics working in harsh radiation environments.