ALD GeAsSeTe Ovonic Threshold Switch for 3D Stackable Crosspoint Memory

Ovonic Threshold Switch (OTS) devices are used as selector elements in 3D crosspoint memory arrays. The stacking of multiple decks in this architecture is a key challenge to dramatically enhance memory capacity but is currently limited by the absence of conformality of physical vapor deposition (PVD) deposited chalcogenide films. Atomic layer deposition (ALD) is necessary to enable large memory-capacity integrated 3D structures, but the development of OTS films with this technique is still confined to As-free compositions with poor performance. Here we present - for the first time - a quaternary ALD GeAsSeTe OTS device with good selectivity (≈ 10
⁴
), low threshold voltage (V
th
) drift (< 40 mV/dec), fast switching (< 10 ns), excellent endurance (> 10
⁹
cycles) and robust stability. These results pave the way for future development of ALD chalcogenide-based selectors as a leading technology for multiple-stack integration of crosspoint memory arrays.