Improved dielectric constant and leakage current characteristics of BaTiO₃ thin film on SrRuO₃ seed layer

The fabrication of high-k BaTiO₃ (BTO) films for applications such as multilayer ceramic capacitors or dynamic random access memory has been achieved via the ex-situ crystallization of amorphous BTO into perovskite structure through post-deposition annealing (PDA). However, high-temperature PDA at temperatures exceeding 700 °C results in the severe degradation of BTO properties. In other words, ex-situ crystallization via PDA results in an increased dielectric constant but is accompanied by inferior leakage current characteristics caused by rough surface morphologies and defects such as voids and cracks. In this study, we demonstrate the in-situ crystallization of BTO films by introducing a high-quality SrRuO₃ (SRO) film as a seed layer. The SRO film is deposited using rf magnetron sputtering at 270–350 °C, and stoichiometric SRO films are obtained on SiO₂, Al₂O₃, and TiN substrates by controlling the growth temperature; subsequently, rapid thermal annealing at 700 °C is conducted to crystallize the SRO film. The polycrystalline SRO film on the TiN substrate exhibits excellent morphology with uniform grains as well as a continuous and smooth surface, whereas the SRO films on the SiO₂ and Al₂O₃ substrates exhibit rough and discontinuous surfaces. The SRO seed layer on TiN permits the in-situ growth of crystalline BTO films at a relatively low temperature of 500 °C featuring a high dielectric constant of 160 and a low leakage current density of 9.5 × 10⁻⁷ A/cm² at 0.8 V, which are 2.2 and 3.4 × 10⁷ times improved compared with those of the ex-situ crystallized BTO film on bare TiN, respectively.