High capacitance density and thermal leakage improvement by using high- κ Al₂ O₃-Doped SrTiO₃ MIM capacitors

In this paper, the impact of Al₂ O₃ incorporation on the electrical characteristics of the SrTiO₃ (STO) metal-insulator-insulator (MIM) capacitor was studied. The Al₂ O ₃ -doped STO (STO: Al₂ O₃ =3:1) MIM provides a high capacitance density (14.6 fF/μ m²) and a very low leakage current density (9.2× 10-9 A/ cm² at -1 V) at the same time. The significant enhancement of the conduction band offset and bandgap due to Al₂ O₃ incorporation reduces leakage current largely while maintaining the favorable properties of STO, such as a large high- κ value, a small temperature coefficient of capacitance, and paraelectricity (no fatigue or aging problem) in the operating temperature range of devices. Meanwhile, we also made a comparison among pure STO, Al₂ O ₃ -doped STO, and HfO₂ -doped STO MIM capacitors. Results revealed that STO MIM and HfO₂ -doped STO MIM capacitors both show higher capacitance densities, while the leakage current of the Al₂ O₃ -doped STO MIM is much lower than those of both the STO MIM and HfO₂ -doped STO MIM capacitors, which meets the strict requirement of the International Technology Roadmap for Semiconductors 2018. Therefore, the excellent result suggests that the Al₂ O₃ -doped STO film is a potential candidate material for dynamic random access memory and radio-frequency applications.