Device Design And Its Software Implementation Of Phase Change Random Access Memory

Nowadays，the working unit area of memory cell is in the order of nano-scaleaccording to the Moore’s Law, meanwhile, a lot of challenging issues have been posed toPCRAM which is the promising candidate of non-volatile memory technology. Since ITRS2009pointed out that the profile of the sidewall will be one difficult problem beyond22nm,the sidewall angle is taken into account in memory device design. In this thesis, theconfined-type model of PCRAM cell has been established to study the dynamic switching(Set-to-Reset) characteristic depending on the sidewall angle.Firstly, the sidewall angle effect on peak temperature, Joule heating volume, latentheat, dynamic resistance and set-to-reset phase transition rate are explored at certainphysical dimension of confined-type cell. The results show the sidewall angle play animportant role in device design.Secondly, the influence of sidewall angle on threshold current is further examined withdifferent feature dimension and different aspect ratio. Then the relationship between thethreshold current and the sidewall angle, aspect ratio, is given by a formula. Thecomparison of the calculation by the formula and the simulation result by ANSYS showsexactly the same trend.Moreover, in order to design PCRAM cell more effectively, this thesis has developed asoftware to analyze the thermo-electric property for PCRAM device design based on heatconduction equation and finite element method. This software covers several typicalPCRAM cell models and material models, and can work well for sandwich-type PCRAMcell model with meshing generation of Delaunay triangles, passing parameter of write/readtext, solving matrix equation of finite difference method.