Liquid-delivery MOCVD: chemical and process perspectives on ferro-electric thin film growth

MOCVD processes for (Ba,Sr)TiO3 (BST) and Pb(Zr,Ti)O3 (PZT) are described based on different metal – organic precursors. In the case of BST, processes using polyamine and tetraglyme adducts of group II metals were compared. Similar incorporation efficiencies were obtained at 640 °C for both adducts, and electrical properties were comparable. Delivery methodologies were compared using the tetraglyme adducts for BST. Composition control was equivalent using liquid mass flow controllers versus a positive displacement pump. For PZT, Zr(thd)4 and Zr(OiPr)2(thd)2 were compared as source materials in combination with Ti(OiPr)2(thd)2 and Pb(thd)2(pmdeta). The mixed ligand Zr source increased Zr incorporation efficiency by a factor of nearly eight for otherwise equivalent processes centred at 590 °C, and run to run repeatability was 0.1 at% for Pb and 0.6 at% for Zr (1 σ) over a series of more than 300 films. The electrical properties of thin film PZT deposited with Zr(OiPr)2(thd)2 compared favourably with those obtained previously with Zr(thd)4.