Metalorganic chemical vapor deposition of barium strontium titanate thin films with a more coordinatively saturated Ti precursor, Ti(dmae)4(dmae=dimethylaminoethoxide)

Abstract

A more coordinatively saturated Ti precursor [Ti(OCH2CH2NMe2)4, Ti(dmae)4] (dmae=dimethylaminoethoxide) has been synthesized and characterized by 1H variable temperature nuclear magnetic resonance (NMR) and mass spectrometry. Ti(dmae)4 exists as a monomer in the liquid state. Chemical vapor deposition of barium strontium titanate (BST) thin films with direct liquid injection of Ba(tmhd)2-PMDT (tmhd=2,2,6,6-tetramethyl-3, 5-heptanedionate, PMDT=pentamethyl diethylenetriamine), Sr(tmhd)2-PMDT, and Ti(dmae)4 was studied. Ba and Sr incorporation into the BST film was almost constant (Ba/(Ba+Sr)=0.5) at a deposition temperature (Ts) range of 420–500 °C, and the amount of Ti incorporation was substantially higher than that of Ti(tmhd)2(i-OPr)2(i-OPr=isopropoxide,tmhd=tetramethyl-heptanedionate) or Ti(tmhd)2(mpd) (mpd=methylpentanediol). The hump and the hazy appearance detected in the BST film deposited with the previous Ti precursors were not detected with the new Ti precursor. The step coverage and properties of the BST films deposited with this new titanium source were also studied.