Multi-level phase change memory cells with SiN or Ta 2O 5 Barrier Layers

Abstract

This work compares the effects of SiN and Ta 2O 5 barrier layers in a multi-level phase change random access memory (PCRAM) cell. The PCRAM cell comprises a phase change material stack between a top and a bottom electrode. The phase change material stack comprises a nitrogendoped Ge 2Sb 2Te 5 (NGST) layer on top of a thin barrier layer on an undoped GST layer. The thermal conductivity and electrical resistivity of the barrier layer affect multi-level switching performance in terms of endurance as well as power consumption. Extensive electrical characterization was performed on these PCRAM multi-level devices. Thermal analysis was also performed to investigate the thermal efficiency of each barrier layer. It was observed that for a constant barrier layer thickness of 1.5 nm, the endurance of the multi-level device with the SiN barrier layer was better than that with the Ta 2O 5 barrier layer; however, the multi-level device with the Ta 2O 5 barrier layer had a lower power consumption than that with the SiN barrier layer. © 2012 The Japan Society of Applied Physics.