3D HfO₂ Thin Film MEMS Capacitor with Superior Energy Storage Properties

Capacitors are ubiquitous and crucial components in modern technologies. Future microelectronic devices require novel dielectric capacitors with higher energy storage density, higher efficiency, better frequency and temperature stabilities, and compatibility with integrated circuit (IC) processes. Here, in order to overcome these challenges, a novel 3D HfO₂ thin film capacitor is designed and fabricated by an integrated microelectromechanical system (MEMS) process. The energy storage density (ESD) of the capacitor reaches 28.94 J cm⁻³, and the energy storage efficiency of the capacitor is up to 91.3% under an applied electric field of 3.5 MV cm⁻¹. The ESD can be further improved by reducing the minimum period structure size of the 3D capacitor. Moreover, the 3D capacitor exhibits excellent temperature stability (up to 150 °C) and charge-discharge endurance (10⁷ cycles). The results indicate that the 3D HfO₂ thin film MEMS capacitor has enormous potential in energy storage applications in harsh environments, such as pulsed discharge and power conditioning electronics.