Novel PZT Capacitor Technology for 32Mb and Beyond FRAM Device Using PbTiO 3 Seeding Layer

Abstract

Effects of the PbTiO 3 (PTO) seeding layer on lowering the PZT crystallization temperature and reducing the capacitor stack height, especially PZT thin film, were systematically investigated. For these purposes, PZT film was modified by using the PTO seeding layer. By using the PTO seeding layer; the crystallization temperature of the PZT film was successfully lowered to 550C. And remanant polarization of PTO-used 100nm thick PZT capacitors measured at 3V was approximately 23 w C/cm 2 , that is 30% higher than that of the PTO-unused PZT capacitors. XRD analysis indicated that the use of the PTO seeding layer remarkably increased the relative intensity of (111) orientation. XRF studies showed that the atomic concentration ratio of Ti-to-Zr was increased by using PTO seeding layers. Necessarily, as the PZT thickness and crystallization temperature are lowered, the thickness of bottom electrode can be reduced as well. Finally, we successfully developed a capacitor stack height of below 400nm, which was composed of Ir/IrO 2 /PZT/Pt/IrO 2 . Furthemore, by lowering the PZT crystallization temperature, small (600 z /contact) and stable contact resistance in a very small size of BC could be obtained.