Improving dielectric loss and mechanical stress of barium strontium titanate thin films by adding chromium layer

The effects of the thickness of the Cr seeding layer of Ba0.5Sr0.5TiO3 (BST) thin films grown on Pt/TiN/SiO2/Si substrates on crystallographic structure, surface morphology, dielectric loss, leakage current, and mechanical stress were investigated. Adding a Cr seeding layer to the interface between BST/Pt structures has a strong influence on BST film properties including dielectric loss, leakage current, the temperature coefficient of capacitance (TCC), and mechanical properties, as well as films grain sizes. BST films with a 2 nm Cr seeding layer showed grains that were denser, smoother, and smaller in size than those in specimens with the Cr seeding layer thickness = 0, 1, and 3 nm. The dielectric loss, leakage current density, thermal stability (TCC), Young's modulus, and residual stress of BST films with a 2 nm Cr seeding layer are improved by about 59%, 1 order of magnitude at +62.5 kV/cm (at +1 V), 35, 41, and 28%, respectively, compared with BST films without a Cr seeding layer. The mechanical stress of BST films had a significant effect on both microstructure and dielectric properties. It was observed that the residual stress of the BST/Pt inter-face was effectively reduced by adding a Cr seeding layer. The correlations of material properties with dielectric loss, leakage current, thermal stability, and residual stress properties suggest that adding a 2 nm Cr seeding layer to BST films is the optimal choice for metal-insulator-metal (MIM) device applications.