Interface engineering of Si-integrated BaTiO3 thin films enabled by an Al:HfO2 buffer layer

Abstract

The integration of ferroelectric BaTiO 3 (BTO) thin films with Si is attractive for microelectronic and sensing applications, but high-temperature processing can promote interfacial reactions and electrically active transport pathways that degrade device performance. In this work, a nanoscale Al-doped HfO 2 (Al:HfO 2 ) interlayer was introduced between BTO and Si. The Al:HfO 2 layer was deposited by plasma-enhanced atomic layer deposition, followed by RF magnetron sputtering of 100 and 180 nm BTO films. Cross-sectional TEM confirms the formation of a continuous Al:HfO 2 interlayer, and EDS analyses show a spatially localized Hf-containing region between BTO and Si. The EDS line profile shows no discernible Si signal within the BTO layer at the spatial resolution of the present measurement, consistent with a possible barrier effect of the interlayer. Compared with buffer-free BTO/Si films prepared under identical conditions, the buffered heterostructures exhibit enhanced ferroelectric response and electrical reliability. For the 180 nm BTO film, the remanent polarization increases from 9.1 to 23.5 μC cm −2 . The BTO/Al:HfO 2 /Si heterostructure retains approximately 92% of its initial remanent polarization after 10 6 bipolar switching cycles within the common comparison range and exhibits stable polarization switching from −100 to 100 °C. In addition, the leakage current density remains below 1 × 10 −8 A cm −2 at 1 MV cm −1 , while the characteristic breakdown strength increases from 3.92 to 5.61 MV cm −1 . These electrical trends are consistent with improved electrical integrity and reduced interface-mediated and defect-assisted carrier transport after introduction of the Al:HfO 2 interlayer. The results demonstrate the potential of Al:HfO 2 -based interface engineering for Si-integrated lead-free ferroelectric thin films.