Preparation of (Ba, Sr)TiO₃ Thin Films by Chemical Vapor Deposition Using Liquid Sources

Abstract

Thin films of (Ba, Sr)TiO 3 with high dielectric constant were prepared on Pt/SiO 2 /Si substrates of 6-inch-diameter by chemical vapor deposition using liquid sources. Ba(DPM) 2 and Sr(DPM) 2 dissolved into tetrahydrofuran were vaporized in a vaporizer at 523 K, and Ti(O-i-C 3 H 7 ) 4 was bubbled at 313 K. The mixture of the source vapors with O 2 and N 2 O was supplied to the reactor (10 Torr) at uniform velocities through a shower-type nozzle, which realized uniform profiles in the deposited film thickness and composition. The electrical properties are significantly influenced by the film composition, and the typical properties obtained for a 800-Å-thick film prepared at the substrate temperature of 823 K are an equivalent SiO 2 thickness t eq of 5.2 Å, a leakage current J L of 2.4× 10 -6 A/cm 2 (at 1.65 V), and a dielectric loss tan δ of 0.07.