Influence of the Chalcogen Element on the Filament Stability in CuIn(Te,Se,S)₂/Al₂O₃ Filamentary Switching Devices

In this paper, we report on the use of CuInX₂ (X = Te, Se, S) as a cation supply layer in filamentary switching applications. Being used as absorber layers in solar cells, we take advantage of the reported Cu ionic conductivity of these materials to investigate the effect of the chalcogen element on filament stability. In situ X-ray diffraction showed material stability attractive for back-end-of-line in semiconductor industry. When integrated in 580 μm diameter memory cells, more volatile switching was found at low compliance current using CuInS₂ and CuInSe₂ compared to CuInTe₂, which is ascribed to the natural tendency for Cu to diffuse back from the switching layer to the cation supply layer because of the larger difference in electrochemical potential using Se or S. Low-current and scaled behavior was also confirmed using conductive atomic force microscopy. Hence, by varying the chalcogen element, a method is presented to modulate the filament stability