Advances in Ovonic Threshold Switch Selector Technologies for Storage Class Memory: From Fundamentals to Development and Beyond

Abstract

The explosive increase in the demand for data driven by advancements in artificial intelligence technology and rapid expansion of data centers necessitates storage class memory (SCM) capable of alleviating data traffic and workload issues. The success of SCM depends heavily on the selector. The ovonic threshold switch (OTS), a chalcogenide-based amorphous thin film, has garnered increasing attention as a selector owing to its suitable characteristics. Here, OTS devices based on various chalcogens (tellurium, selenium, and sulfur) are reviewed, and how the selection of a chalcogen should be dictated by the specific requirements of the application is highlighted, because the OTS characteristics vary significantly depending on the choice. Additionally, OTS characteristic engineering from multiple perspectives, including material engineering via elemental doping, electrode engineering, physical property engineering via post-treatment, and structural/interface engineering using multiple layers is reviewed. Finally, selector-only memory (SOM) is examined, which offers better scalability and performance than the existing one-memory and one-selector structure, which combines an OTS with phase-change memory. Moreover, a cost-effective 3D vertical X-point memory is also discussed, emphasizing that its ultimate implementation should be achieved using an SOM. Thus, insights and guidelines for OTS material design, stack engineering, and cell parameter design are provided here.