Atomic Layer Deposition of GexSe1–x Thin Films for Endurable Ovonic Threshold Selectors with a Low Threshold Voltage

An ovonic threshold switch (OTS) based on amorphous chalcogenide materials possesses several desirable characteristics, including high selectivity and fast switching speed, enabling the fabrication of one selector–one resistor (1S–1R) crossbar array (CBA) for random access memory. Among the several chalcogenide materials, GeSe offers high selectivity and a strong glass-forming ability with environment-friendly, simple binary composition. In this report, the GeSe thin films were deposited via atomic layer deposition (ALD) using Ge(N(Si(CH 3 ) 3 ) 2 ) 2 and ((CH 3 ) 3 Si) 2 Se for its envisioned application in fabricating three-dimensional vertical-type phase-change memory. Highly conformal Ge x Se 1– x films were obtained at a substrate temperature ranging from 70 to 160 °C. The unique deposition mechanism that involves Ge intermediates provided a way to modulate the composition of the Ge–Se films from 5:5 to 7:3. Low threshold voltages ranging from 1.2 to 1.4 V were observed depending on the composition. A cycling endurance of more than 10 6 was achieved with the Ge 0.6 Se 0.4 composition with 10 4 half-bias nonlinearity. This work presents the foundations for the future development of vertical-type 1S–1R arrays when combined with the ALD technique for Ge 2 Sb 2 Te 5 phase-change materials.