Modeling and Finite Element Simulations of Phase Change Memory Materials and Devices

I simulate phase change including stochastic nucleation and growth of discrete grains with a finite element framework which captures the latent heat of phase change and heterogeneous melting. I model the electrical conductivity, thermal conductivity, Seebeck coefficient, and specific heat in TiN, SiO2, and the face centered cubic and amorphous phases of Ge2Sb2Te5 as well as the thermal boundary conductance at interfaces of these materials over the temperatures and fields encountered during phase change memory device operation. Simulations show reset, set, and read of phase change memory devices including mushroom cells, encapsulated pillar cells, double mushroom cells, and threshold switch controlled mushroom cells. My results show that the latent heat of phase change increases the temperature at crystalline-amorphous interfaces during crystallization, heterogeneous melting can help account for the experimentally observed improvement in reset and set speeds as grain size decreases, and that threshold switching can be captured using a closed form model of independent thermal and electric field contributions to electrical conductivity