Power Efficient and Reliable Nanoscale Phase Change Random Access Memory

Abstract

To enhance and optimize the performance of phase change random access memory, numerous studies on nanowire (NW)-based PCRAM, including device fabrication and exploration of materials such as GeTe and GeSbTe alloys, have appeared in the last decade. Also, the NW-based PCRAM technology has attracted great attention, since the programmable active volume as well as programming power can be reduced due to the reduction in melting temperature in nanoscale materials. More recently, the use of oxide-based materials have been reported for PCRAM applications. Memory devices using Ga-doped In2O3 (Ga:In2O3) thin film have successfully shown repeatable switching behavior between crystalline and amorphous phases with a reduction in reset current by controlling the Ga concentration. Furthermore, an issue that resistance drift phenomenon has been raised through the course of PCRAM development. The drift phenomenon primarily determines the reliability and multilevel capability of PCRAM, and several theoretical models have been proposed to explain the phenomenon. In this study, In2Se3 NW and Ga:In2O3 NW were synthesized via vapor-liquid-solid method, to investigate: (1) size-dependent switching behaviors and thermal resistance vs. power consumption in In2Se3 NW PCRAM; (2) Ga concentration dependent switching behaviors, resistance drift phenomenon and thermal resistance vs. power consumption in Ga:In2O3 NW PCRAM. Moreover, we proposed a new form of mechanical stress relaxation model, to study the stress relationship between a phase change material and an encapsulating layer material (ELM), and investigate the effect of ELM on stress relaxation in order to mitigate the resistance drift phenomenon.