Step coverage and electrical properties of (Ba,Sr)TiO3 films prepared by liquid source chemical vapor deposition

Thin films of (Ba, Sr)TiO3 (BST) with high dielectric constant were prepared by liquid source chemical vapor deposition using Ba(DPM)(2), Sr(DPM)(2) and TiO(DPM)(2) (DPM=dipivaloylmethanato; C11H19O2) dissolved in tetrahydrofuran (THF). It was found that the coverage of 72%, obtained at the substrate temperature T-s=480 degrees C, was better than those obtained using other Ti sources such as Ti(O-i-Pr)(4) (TTIP) and Ti(O-i-Pr)(2)(DPM)(2) Protrusions of BST crystallites were found to appear on BST film surfaces prepared at a substrate temperature Ts=420 degrees C and a reactor pressure P=1.5Torr. 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 6-nm-thick annealed in N-2 ambient.