Current development status and future challenges of ferroelectric random access memory technologies

For ferroelectric random access memory (FRAM) to be beneficial in future mobile devices, high-density FRAM with nm scaled cell should be developed. We have succeeded in scaling further the cell size of one-pass transistor and one-storage capacitor (ITIC) FRAM down to 0.27 mu m(2) at 150 nm technology node. Owing to new SrRuO3 (SRO) electrode technology along with ultrathin PbZrTiO3 (PZT) using metal organic chemical vapor deposition (MOCVD) technology, two-dimensional (2-D) metal-insulator-metal (MIM) ferroelectric capacitor was successfully scaled down vertically to 200nm. By the application of a new double hard mask capacitor etching technology, 0.11-mu m(2)-area 200-nm-thick 2-D PZT capacitor was successfully isolated with 180 run spacing. As a result, a high remanent polarization of 40 mu C/cm(2) was obtained at 1.6 V on a 0.11 mu m(2) ferroelectric storage capacitor of the 0.27 mu m(2) cell ITIC FRAM. Great advances in three-dimensional (3-D) ferroelectric capacitor, which is essential for 6-8 F-2 cell ITIC FRAM at nm scaled technology node, have been made by introducing a new atomic layer deposition (ALD) method for 3-D electrode and a novel MOCVD PZT deposition for 3-D PZT. As a result, for the first time, robust hysteresis was obtained from a 3-D PZT capacitor.