1. PE-ALD of Ge1−xSxamorphous chalcogenide alloys for OTS applications
- Author
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Seung-Min Chung, Hyung Keun Kim, Taeyoon Lee, Minkyu Lee, Seok Man Hong, Sijung Yoo, Myoungsub Kim, Youngjun Kim, Tae-Hoon Kim, and Hyungjun Kim
- Subjects
010302 applied physics ,Materials science ,Chalcogenide ,business.industry ,Band gap ,02 engineering and technology ,General Chemistry ,Plasma ,021001 nanoscience & nanotechnology ,01 natural sciences ,Threshold voltage ,Amorphous solid ,Atomic layer deposition ,chemistry.chemical_compound ,chemistry ,0103 physical sciences ,Materials Chemistry ,Optoelectronics ,Thin film ,0210 nano-technology ,business ,Scaling - Abstract
Three-dimensional (3D) cross-point (X-point) technology, including amorphous chalcogenide-based ovonic threshold switching (OTS) selectors, is bringing new changes to the memory hierarchy for high-performance computing systems. To prepare for future 3D X-point memory scaling, we studied the plasma-enhanced atomic layer deposition (PE-ALD) of Ge1−xSx amorphous chalcogenide alloy thin films, the selection of which was motivated by their high optical bandgap and wide amorphous forming regions. The PE-ALD Ge1−xSx thin films were synthesized using a GeCl4 precursor and H2S plasma reactant, and their self-limited growth characteristics were studied in detail as a function of the exposure time of the ALD steps, temperature, and plasma power. The PE-ALD GeS2 thin film showed an RMS roughness of 0.29 nm and good conformality in the vertical 3D structure. Moreover, the OTS behavior of GeS2 and Ge2S3 mushroom-type devices with a 50 nm bottom electrode contact (BEC) were investigated as well as the trade-off relationship between the threshold voltage (1.9–6.2 V) and the normalized off current (20–250 nA) based on scaling the film thickness down from 30 nm to 5 nm. In particular, the GeS2 device showed a higher threshold field (∼3.1 MV cm−1) and lower normalized off current characteristics than the Ge2S3 device due to the higher trap density (2.1 × 1021 cm−3), according to the modified Poole–Frenkel (PF) model. The results achieved by this PE-ALD research on this novel binary GeS2 amorphous chalcogenide for OTS applications will contribute to the development of future 3D cross-point memory scaling.
- Published
- 2021