Reliability Study Of Carbon-Doped Gst Stack Robust Against Pb-Free Soldering Reflow

In this paper, we investigate the performances of carbon-doped Ge2Sb2Te5 films (named hereafter GST) which have been integrated together with a thin titanium capping layer into Phase-Change Memory devices. We show that the carbon content into GST and the titanium cap layer thickness can be optimized to obtain an Amorphous As-Deposited (AAD) phase which is stable under both the typical Back End-Of-Line (BEOL) thermal budget ( 2 min at 400 degrees C) and standard Pb-free soldering reflow process conditions (temperature peak at 260 degrees C). Therefore, the material obtained at fab-out keeps its disordered phase and can be used to pre-code one state of information stable against the standard soldering reflow ( peak at 260 C). We propose to use this high resistance state together with an electrically induced low resistance state to pre-code the memory prior to PCB manufacturing.