(Ba, Sr)TiO3 Films Prepared by Liquid Source Chemical Vapor Deposition on Ru Electrodes

Electrical properties of (Ba, Sr)TiO3 [BST] films have been investigated on RuO2/Ru and Ru electrodes instead of Pt, because they are easy to be etched. BST films were deposited at a substrate temperature of T s=420° C and a reactor pressure of P=1.5 Torr by employing a two-step liquid source chemical vapor deposition (CVD) process. BST films on RuO2/Ru were electrically shorted, which was considered to be caused by surface roughening during BST film deposition and/or post-annealing. In the case of Ru electrodes, an equivalent SiO2 thickness of t eq=0.50 nm (a dielectric constant of ε r=190), a leakage current of J L=4.6×10-8 A/cm2 at +1.1 V, and a dielectric loss of tan δ=0.018 were achieved at a total film thickness of 250 Å, by restricting Ru surface oxidation and its surface roughening. Moreover, BST film deposition on Ru storage nodes, 0.24 µ m wide, 0.6 µ m deep, 0.15 µ m high, and each spaced by 0.3–0.14 µ m, verified that the storage capacitance can be successfully increased by using sidewalls of the storage node, without a significant increase in the leakage current.