Effect of atomic layer deposited ultra‐thin SiO ₂ layer on vapour‐liquid‐solid (VLS) grown high dielectric TiO ₂ film for Si‐based MOS device applications

Abstract Titanium dioxide (TiO ₂ ) ultra‐thin films (≈13 nm) are grown on p‐type Si substrate <400> with and without atomic layer deposited SiO ₂ (5 nm) passivation layer by employing vapour‐liquid‐solid technique. Scanning electron microscope images reveal high quality film for both the samples. The formation of a crystalline TiO ₂ film is confirmed by X‐ray diffraction pattern, the orthorhombic (brookite) TiO ₂ films with [130], [160] and [212] planes are seen from peaks at 2 θ = 33.5°, 61.7° and 75.7° on SiO ₂ /Si and Si substrates, respectively. Current–voltage ( I – V ) characteristics reveal leakage current of ≈8.61 × 10 ^‐8 and ≈4.05 × 10 ^‐6 A/cm ² at +2 V for film with and without SiO ₂ passivation layer, respectively. Leakage current of TiO ₂ /SiO ₂ /Si device follows Fowler–Nordheim (FN) tunnelling at low field and Poole–Frenkel (PF) tunnelling at high field, whereas TiO ₂ /Si device follows Schottky emission at low field and PF tunnelling at high field. Capacitance–voltage ( C – V ) characteristics reveal superior quality TiO ₂ films with high dielectric constant of 44.5 and 35.8 for TiO ₂ /SiO ₂ /Si and TiO ₂ /Si samples, respectively. Significant improvement in frequency dispersion and hysteresis voltage is observed for the sample with SiO ₂ passivation layer. Introduction of SiO ₂ passivation layer also improves interface traps and reliability of the device. Hence, a low cost novel alternative technique to grow high quality TiO ₂ film on p‐type Si substrate with SiO ₂ as passivation layer is suggested for development of high performance MOS devices.