Mechanistic study of metalorganic chemical vapor deposition of (Ba,Sr)TiO3thin films

The metalorganic precursor chemistry was studied on Pt(111) surfaces in a O -16(2) and O-18(2) backgrounds. Using temperature programmed desorption (TP D) and static secondary ion mass spectrometry (SIMS). The precursor chemist ry of Sr(thd)(2) was found to be different on oxide covered Pt(111) surface as compared to the clean Pt(111) surface. In an oxygen ambient, TPD showed at least four different reaction processes which involved the removal of c arbon from the precursor ligands on oxide covered Pt(111). In two of these, gas phase oxygen was incorporated into the oxidative products. In contrast , one carbon removing reaction was observed on the clean Pt(111) surface. I sotopic labeling experiments have also been carried out to understand the f ilm-formation reactions in the metalorganic chemical vapor deposition of (B a,Sr)TiO3 (BST) films. Time-of-flight SIMS and nuclear reaction analysis re veal that the oxygen in the BST films originates from both the gas phase ox idants (O-18) and the precursor ligands (O-16). The ligand substitution by gas phase O-2 plays a more prominent role in the film formation at lower te mperatures. On the other hand, the reactive oxygen radicals produced by mic rowave plasma involved more in breaking the O-C bonds than substituting the precursor ligands for the film formation. Use of the 50% O-18(2)-50% N-2 O -16(2) mixture results in a reduction of O-18 incorporation in the BST film s, indicative of the direct involvement of N2O in the film-formation reacti ons. The mechanistic studies are essential for understanding the new BST pr ecursors used in this study, and provide useful information to correlate th e film microstructure, step coverage, and dielectric properties with the pr ecursor properties. (C) 2000 American Institute of Physics. [S0021-8979(00) 02210-6].