Research On Phase Change Memory Based On VO₂ Selector

Phase change Memory has potential to replace FLASH and become the next generation non-volatile memory due to its advantages such as high operational speed,low power consumption,multi-value storage,compatibility with CMOS technology and so on.But high density and large storage PCM has not been mass commercial used for the restriction of the area?8F²?and performance of the selector.The insulator-metal transition of VO₂ happens accompanied bythe huge change of resistance,which makes it attracting in two-terminal switching for its smaller size than the three-terminal devices.Besides,the synthesis technology operated at low temperature makes it advantageous in integrated circuit.This paper investigates the properties of VO₂ film fabricated with different O₂ flow and discuss the selection properties of the VO₂.Several VO₂ films are grown on Si substrate by magnetron sputtering method with different O₂ flow.The temperature-dependent Raman spectroscopy,x-ray diffraction and electrical resistance measurements are carried out to analyze the phase transition temperature and the width of thermal hysteresis loop.We find out that the annealing of time has influence on the size of the particle,the properties are better in films with increased particle size.On the basis of the film growth technology,TiW/VO2/TiW structures are fabricated as the selection device.Current density and switching speed are measured on B1500A.As the experiment shows,the switch ratio can be 10³ and the speed is 20ns The size of the cell also has influence on the switching properties,the switch ratio increases and the threshold voltage decreases with the cell size reduction.Besides,TiW/VO₂/GST/TiWstructures are used to test whether VO₂ can be the selector of PCM cell.The results show the PCM cell functions well with the selector.Last we find the p-GST/VO₂ heterojunction can lower the threshold voltageof VO₂.