Enhanced crystallization and dielectric properties of atomic layer deposited SrTiO3 thin films on Ru electrode by inserting GeO2 interfacial layer†

This study investigates the effects of a GeO₂ insertion layer between the SrTiO₃ (STO) dielectric layer and the Ru thin film bottom electrode on the crystallization behavior and associated electrical properties of the STO layer. A GeO₂ film as thin as 0.6 nm feasibly suppresses abnormal STO growth and ensures uniform Sr/Ti stoichiometry across the entire STO film thickness by blocking the oxygen exchange between the Ru and growing STO film. Furthermore, the GeO₂ insertion layer decreases the crystallization temperature of the STO film by ∼100 °C, enhancing film quality and facilitating crystallization through the diffusion of Ge atoms. The decreased thermal budget for fabrication enhances the surface smoothness of the STO layer, resulting in a void-free film. Finally, a Pt/RuO₂/STO/GeO₂/Ru capacitor is fabricated and optimized by fine-tuning the GeO₂ layer thickness and annealing temperature, achieving a minimum equivalent oxide thickness of 0.41 nm while ensuring a low leakage current density (<10⁻⁷ A cm⁻² at 0.8 V), even at a lowered annealing temperature. This highlights the excellent low-temperature compatibility and scalability of STO with GeO₂ insertion, making it a promising candidate for next-generation dynamic random access memory capacitor technologies.