We present the engineering of Ovonic Threshold Switching (OTS) Multilayer (ML) Selector device based on the stacking of N-doped SbSe and Ge layers. By tuning individual layers thicknesses and N content of the ML stack, we demonstrate the possibility to highly improve selector stability during integration Back-End-of-Line (BEOL) and to reduce device-to-device variability. We show how our OTS ML presents fundamental electrical characteristics that are compatible with the ones of standard bulk OTS achieved by co-sputtering technique, but enabling reliable switching operations up to 160 • C with lower variability. We study by FTIR and Raman spectroscopy the layers structure revealing the high stability achieved in OTS ML wrt bulk OTS even after 3 hours at 400 • C. In TEM/EDX analyses performed on cycled and annealed devices, we highlight the preserved integrity of the amorphous structure in OTS ML wrt bulk. Finally, OTS ML solution allows reliable endurance up to more than 10 9 cycles and improved yield in scaled devices thanks to a higher control of the layer structure and properties.
In this paper, we investigate the influence of germanium content in GeSbSeN based Ovonic Threshold Selector (OTS) devices. We performed physico-chemical analyses on five different Ge x (SbSe) 1-x N alloys in order to understand how the germanium content influences the material structure and its integrity once submitted to temperatures up to 400 • C. Thanks to electrical characterization of Ge x (SbSe) 1-x N OTS devices, we analyze the evolution of the electrical parameters along cycling up to 10 8 cycles and before and after annealing at 400 • C. Cycle-to-cycle variability and drift phenomenon are also investigated. Finally, we demonstrate how Ge content should be properly tuned in order to improve the thermal stability of the alloy without affecting the leakage current and the electrical parameters variability.
In this paper, we investigate an innovative Ovonic Threshold Switching Selector (OTS) based on Multilayer structure (ML). Thanks to physico-chemical analysis and electrical characterization we show how MLs properties and structure can be tuned thanks to the engineering of each individual layer stoichiometry, thickness and interfaces. Ge/N-doped SbSe-based MLs OTS are analyzed by FTIR and Raman spectroscopy revealing the structural features present in the as-deposited materials and the strong interaction among individual layers at interfaces. We demonstrate the improved variability control of electrical parameters wrt standard OTS achieved by co-sputtering technique, and the high endurance capability of MLs OTS up to more than 2•10 9 cycles with stable nA leakage current. Moreover, we show how Ge-N bonds play a huge role on OTS thermal stability at 400 • C and how they can be tuned more easily in ML OTS. These developments pave the way towards a new class of OTS materials and their engineering, ensuring high temperature stability and best tuning of electrical performances.
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