Impact of the current density increase on reliability in scaled BJT-selected PCM for high-density applications

Some of the largest semiconductor companies involved in the non volatile memory business have demonstrated that Phase-Change Memory (PCM) technology has today reached the product maturity at 90 and 65 nm nodes and 45 nm platform is under development. In this approaches the architectural choice for large density arrays decoding relies on silicon diodes or BJT-selected PCMs (BJT-PCM), thus defining it as the mainstream PCM non-volatile memory technology. However to continue the PCM technology scaling roadmap the current density required to program the storage element will increase linearly with the lithography reduction, becoming of the order of tens of MA/cm² in the BJT selector and of hundreds of MA/cm² in the storage element at ultra-scaled lithographic nodes. In the ITRS 2008 the maximum current density to program a PCM cell has been recognized as the main physical mechanism that can impact the reliability of scaled PCM devices and it can be a serious show-stopper for this technology beyond the 32 nm technology node. Aim of this paper is to investigate the impact of the increasing current density on the functionality and reliability of scaled BJT-PCM architecture down to the 16 nm node.