Atomic-layer-deposited SiO2/TiO2/SiO2 sandwiched dielectrics for metal–insulator–metal capacitor application

• SiO2/TiO2/SiO2 (STS) dielectrics were formed by atomic-layer-deposition for MIM capacitor.
• Compared with TiO2, the STS dielectrics can improve significantly the leakage characteristics.
• The conduction mechanisms of the STS MIM capacitor were discussed.

A new concept of SiO2/TiO2/SiO2 (STS) sandwiched dielectrics has been successfully prepared by atomic-layer-deposition technique for high density MIM capacitor applications. Compared with pure TiO2 dielectric, the addition of ultra-thin (2 nm) SiO2 layers reduces significantly the leakage current and enhances the breakdown electric field of MIM capacitor. Accordingly, the STS MIM capacitor exhibits a high capacitance density of around 12.4 fF/μm2 at 100 kHz, and a leakage current density of 8.8 × 10−7 A/cm2 at −1 V, which is about three orders of magnitude smaller than that of the pure TiO2 MIM capacitor. Furthermore, the conduction mechanisms of the STS capacitor have been investigated, revealing that the Poole–Frenkel emission is dominated in the high field range, and the extracted energy barrier separating the traps from the conduction band is in a 0.85–0.90 eV range.

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