Composition influence on the physical and electrical properties of SrxTi1−xOy-based metal-insulator-metal capacitors prepared by atomic layer deposition using TiN bottom electrodes

Abstract

In this work, the physical and electrical properties of ${\text{Sr}}_x{\text{Ti}}_{1-x}{\text{O}}_y$ (STO)-based metal-insulator-metal capacitors (MIMcaps) with various compositions are studied in detail. While most recent studies on STO were done on noblelike metal electrodes (Ru, Pt), this work focuses on a low temperature $\left(250°\text{C}\right)$ atomic layer deposition (ALD) process, using an alternative precursor set and carefully optimized processing conditions, enabling the use of low-cost, manufacturable-friendly TiN electrodes. Physical analyses show that the film crystallization temperature, its texture and morphology strongly depends on the Sr/Ti ratio. Such physical variations have a direct impact on the electric properties of ${\text{Sr}}_x{\text{Ti}}_{1-x}{\text{O}}_y$ based capacitors. It is found that Sr-enrichment result in a monotonous decrease in the dielectric constant and leakage current as predicted by ab initio calculations. The intercept of the EOT vs physical thickness plot further indicates that increasing the Sr-content at the film interface with the bottom TiN would result in lower interfacial equivalent-oxide thickness.