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 (1T1C) FRAM down to 0.27 µm 2 at 150 nm technology node. Owing to new SrRuO 3 (SRO) electrode technology along with ultrathin PbZrTiO 3 (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 200 nm. By the application of a new double hard mask capacitor etching technology, 0.11-µm 2 -area 200-nm-thick 2-D PZT capacitor was successfully isolated with 180 nm spacing. As a result, a high remanent polarization of 40 µC/cm 2 was obtained at 1.6 V on a 0.11 µm 2 ferroelectric storage capacitor of the 0.27 µm 2 cell 1T1C FRAM. Great advances in three-dimensional (3-D) ferroelectric capacitor, which is essential for 6–8 F 2 cell 1T1C 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.