Fabrication and characterization of ECM memories based on a Ge2Sb2Te5 solid electrolyte

This work deals with the study of electrochemical metallization memory cells (ECM) also called CBRAM (Conductive Bridge RAM). Memory stacks were fabricated by sputtering onto SiO₂/Si substrates and were characterized by atomic force microscopy and a mercury drop probe. These stacks employ a Ge₂Sb₂Te₅ (GST) layer as a solid electrolyte which has been barely employed in CBRAM devices. Electrical measurements demonstrate resistance switching of the stacks due to the formation/dissolution of metallic filaments within the GST layer. However, the memory elements featuring a silver top electrode do not exhibit such switching behavior but show instead an ohmic behavior. This result is interpreted through physical analysis revealing the presence of silver in each layer of the memory devices. Finally, a physical model is presented. This model was used to interpret adequately the bipolar resistance switching phenomenon observed in the memory stacks.