Structure And Performance Study Of Chalcogenide Phase-change Random Access Memory

General expectations for future memories can be summarized as nonvolatile, fast, low energy and high density, mainly driven by the growing demand for the rapid development of information technology. As the main stream non-volatile memory technologies, Flash does not qualify as an ideal memory for future technology developement owing to its relatively long programming time and limited cycle enduranc.Some physical limitations could be critical for reliable downscaling beyond 45nm node. Phase-change random access memory (PRAM) based on chalcogenide has recently been regarded as the most promising universal nonvolatile memory due to high endurance,high scalability, low power, high speed and good compatibility with CMOS technologies.Althrough the researches on PRAM have obtained a great progress in recent years, a high Reset current as one of several critical problems still remain to be solved before its practical application. Approaches to reduce Reset current may be categorized as the exploitation of new phase change material and miniature of cell size for reducing the programming volume.In this paper we prepared nano phase-change materials such as Sb₂S₃ and Sb₂Se₃ nanorods which have been synthesized via a hydrothermal treatment; In the exploita- tion of new phase change material aspect, the Ge-Bi-Te (GBT) series of block materials have been prepared. The main contents include:First, about tens microns of length, 100-500nm of diameter, single-crystalline Sb₂S₃ nanorods have been synthesized via a hydrothermal treatment by reacting SbCl₃ and Na₂S₂O₃ solutions in this experiment. The nanorods, analyzed by EDS XRD and TEM, belong to the orthorhombic phase and grow along [001] direction. The growth mechanism,thermal and optics properties were also investigated.Secondly, high quality Sb₂Se₃ nanorods with tens micros of tength and 200 nm of diameter were synthesized via hydrothermal process by reacting SbCl₃ and Na₂SeSO₃ solutions with PVA assisted. The final PH value of the mixture wes adjusted by adding a certain amount of ammonia. XRD patterns indicate that the nanorods are orthorhombic phase Sb₂Se₃. The reaction temperature, time and PH of the solution have play a important role in the process of synthesis the products. The structure, growth mechanism and thermal properties were also investigated.Finally, high-purity Ge, Bi and Te powder were mixed, and the mixture was placed in evacuated and sealed quartz ampoules. Large quantities of GBT series bulk materials were synthesized. DSC, XRD and TEM were used to characterize the products. The performance of phase-change mechanism was also investigated.