Resistive Switching Characteristics Of Dy₂O₃ Based RRAM

The rapid development of information technology has put forward higher memory requirements. Since the traditional Si-based Flash memory devices show serious problems as performance decline and shortened life under 25 nm crafts, new generation nonvolatile data memory should display significant characteristics such as high-density, low cost, fast write/read access, low energy operation, and high performance with respect to endurance(write cycle ability) and retention.. Resistance random access memory(RRAM), with the advantage of low power, fast write and read, high storage density, becomes the most promising candidate for the new nonvolatile memory. Compared with Flash memory, RRAM can go along to 5 nm at the device size. However there are still some problems with the RRAM. The high operate voltage and low uniformity restricting the application of RRAM. In addition, the research of RRAM application in the future transparent electronics is still on going.In this dissertation, we firstly demonstrate the reduced the operate voltage and improved the uniformity of the Pt/Dy2O3/Pt device through the anneal process. Next, the ITO/Dy2O3/ITO transparent RRAM device was fabricated and discussed. The detail work was as follows:(1) The Pt/Dy2O3/Pt device was fabricated on the Si/SiO2 through RF magnetron sputtering method. The anneal process was used to reduce the operate voltage, increase the ratio of the Roff/Ron and improve the uniformity. With the atomic force microscope(AFM) and X-ray photoelectron spectroscopy(XPS) analysis on the Dy2O3 surface, the reason of the improvement was inferred to the increase of oxygen in the surface. Dues to the enrichment of oxygen, the Dy2O3 film layered to Dy2O3+x and Dy2O3-x. The Dy2O3+x caused the increase of the initial resistance, while the Dy2O3-x caused the decrease of the operate voltage. EDS scan showed that the decrease of the oxygen from the surface to inside, demonstrating that the addition oxygen in the surface was caused by the migration of the oxygen ion existed at the defects during the fabricated process.(2) Full transparent RRAM based on ITO/Dy2O3/ITO stacking structure was fabricated using RF magnetron sputtering technique. TEM result reveals the Dy2O3 film is in nanocrystalline. The showed 10-nm-thick amorphous interface between Dy2O3 and the ITO electrode is believed to act as the barrier layer of oxygen, which improved the device life. The device demonstrates good transparency over the visible region(>80%). The device demonstrates symmetric bipolar resistive switching behavior with Roff/Ron ratio of ~104, excellent endurance; low operate current and reliable data retention. The resistive switching is achieved through the filaments consist of oxygen vacancies in the Dy2O3 layer. The switching mechanism is ascribed to the electric field-induced migration of oxygen anions that causes the formation and rupture of the conductive filament through the Dy2O3 layer.