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

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 = tetramethylheptanedionat e), (2) M(ketoester)(2), (3) M(diester)(2), and (4) M(methd)(2) (methd = me thoxyethoxytetramethyl-heptanedionate). In case of ketoester and diester li gands, premature dissociation of the ligand was observed while M(methd)(2) shows good volatility and stability. Boiling point of Lewis base has a stro ng effect on the volatility of M(tmhd)(2)-Lewis base. Most of the Ti precur sors 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 chara cterize the deposition behavior, (Ba,Sr)TiO3 films Were deposited at the de position temperature of 400 similar to 480 degreesC using a direct liquid i njection method. Composition uniformity and step coverage were largely affe cted by Ti precursors.