Simulation of Phase-Change Random Access Memory with Ring-Type Contactor for Low Reset Current by Finite Element Modelling

A three-dimensional finite element models for phase change random access memory （PCRAM） is established to simulate thermal and electrical behaviours during RESET operation. The RESET behaviours of the conventional structure （CS） and the ring-type contact in bottom electrode （RIB） are compared with each other. The simulation results indicate that the RIB cell has advantages of high heat efficiency for melting phase change material in cell, reduction of contact area and lower RESET current with maintaining good resistance contrast. The RESET current decreases from 1.26mA to 1.2mA and the heat consumption in CST material during programming increases from 12% to 37% in RIB structure. Thus the RIB structure PCRAM cell is suitable for future device with high heat efficiency and smaller RESET current.     

Three-Dimensional Finite Element Simulations for the Thermal Characteristics of PCRAMs with Different Buffer Layer Materials

Simulation of the heat consumption in phase change random access memories （PCRAMs） is investigated by a three-dimensional finite element model. It is revealed that the thermal conductivity and electrical conductivity of the buffer layer are crucial in controlling the heating efficiency in RESET process. The buffer layer mater/Ms W, TiN, WOa, Ti02 and poly-germanium （poly-Ge） are applied in the simulation respectively, and compared with each other. The simulation results show that limitation of electrical conductivity is effective on heating efficiency and the limitation of thermal conductivity is important on the reliable RESET process.     

Simulation of SET Operation in Phase-Change Random Access Memories with Heater Addition and Ring-Type Contactor for Low-Power Consumption by Finite Element Modeling

A three-dimensional finite element model for phase change random access memory （PCRAM） is established for comprehensive electrical and thermal analysis during SET operation. The SET behaviours of the heater addition structure （HS） and the ring-type contact in bottom electrode （RIB） structure are compared with each other. There are two ways to reduce the RESET current, applying a high resistivity interracial layer and building a new device structure. The simulation resuIts indicate that the variation of SET current with different power reduction ways is little. This study takes the RESET and SET operation current into consideration, showing that the RIB structure PCRAM cell is suitable for future devices with high heat efficiency and high-density, due to its high heat efficiency in RESET operation.