Low temperature chemical vapor deposition of (Ba, Sr)TiO3 thin films for high density dynamic random access memory capacitors

(Ba, Sr)TiO3 (BST) films are deposited on 8-inch wafers by the metal organi c chemical vapor deposition (MOCVD) technique at a temperature as low as 40 0 degrees C to obtain conformal step coverage and prevent oxidation of the diffusion barrier of simple stacked capacitors. The problems of low tempera ture process (formation of protrusions, titanium deficiency, severe thickne ss deviation) could be successfully overcome by proper modification of the CVD system and process conditions. Retrofitting the vaporizer to obtain fla sh evaporation of the liquid chemical source and introducing N2O gas as an oxidant were highly effective for reducing the thickness deviation and tita nium deficiency. The Pt/BST/Pt capacitor with BST films deposited at 400 de grees C and post-annealed at 700 degrees C for 30 min under nitrogen ambien t shows excellent electrical properties (Tox similar to 6.6 Angstrom, J sim ilar to 1 x 10(-7) A/cm(2) @+/-1 V), which are satisfactory for application to high density dynamic random access memory (DRAM) capacitors beyond 256 Mbit generation.