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