A high speed asymmetric T-shape cell in NMOS-selected phase change memory chip

摘要

A high SET/RESET speed phase change memory cell with a NMOS selector is achieved by optimizing cell structure, material, programming circuit and testing method. An asymmetric T-shape cell structure increases the current density in the programmable region and reduces thermal diffusion in the cell. Super-lattice phase change material has a lower thermal conductivity. The circuit has a fast response and reduces the falling time of RESET pulse to 0.9 ns which enables a fast phase change operation of the memory cell. The testing system has good signal integrity and transmits the undistorted ultrafast programming enable signal to I/O ports of the chip. The optimized SET time is 50 ns and RESET time is 2 ns.