Effect of the precursors on the deposition of (Ba, Sr)TiO3 films

Abstract

Ba and Sr precursors for (Ba,Sr)TiO3 films have been studied including (1) M(tmhd)(2)-Lewis base adduct (M = Ba or Sr, tmhd = tetramethylheptanedionate), (2) M(ketoester)(2), (3) M(diester)(2), and (4) M(methd)(2) (methd = methoxyethoxytetramethyl-heptanedionate). In case of ketoester and diester ligands, premature dissociation of the ligand was observed while M(methd)(2) shows good volatility and stability. Boiling point of Lewis base has a strong effect on the volatility of M(tmhd)(2)-Lewis base. Most of the Ti precursors were easily evaporated at low temperatures and thermal stability of Ti precursors could be controlled with diketone and alkoxide ligands. Ti(mpd)(tmhd)(2) (mpd = methyl-pentanediol) shows higher thermal stability than Ti(i-OPr)(2)(tmhd)(2) or Ti(dmae)(4) (dmae = dimethylaminoethoxide). To characterize the deposition behavior, (Ba,Sr)TiO3 films Were deposited at the deposition temperature of 400 similar to 480 degreesC using a direct liquid injection method. Composition uniformity and step coverage were largely affected by Ti precursors.