Surface Morphologies and Electrical Properties of (Ba, Sr)TiO3 Films Prepared by Two-Step Deposition of Liquid Source Chemical Vapor Deposition

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Abstract
Protrusions of (Ba, Sr)TiO3 (BST) crystallites were found to appear on BST film surfaces prepared by liquid source chemical vapor deposition (CVD) at a substrate temperature T s=420° C and a reactor pressure P=1.5 Torr. Such protrusions were successfully suppressed by two-step deposition, where BST films consisted of a buffer layer and a main layer; the buffer layer was a CVD-BST film about 60 Å thick annealed in N2 ambient. By this two-step deposition on Pt electrodes, the BST film properties of equivalent SiO2 thickness t eq=0.56 nm, leakage current J L=1.2×10-8 A/cm2 at +1.1 V and dielectric loss tan δ=0.011 were achieved at a total film thickness of 230 Å, along with a coverage of 80% at a trench of aspect ratio 0.65 and sufficiently low absorption current.