PE-ALD of Ge1−xSx amorphous chalcogenide alloys for OTS applications. Issue 18 (27th April 2021)

• Record Type: Journal Article
• Authors: Kim, Myoungsub; Kim, Youngjun; Lee, Minkyu; Hong, Seok Man; Kim, Hyung Keun; Yoo, Sijung; Kim, Taehoon; Chung, Seung-min; Lee, Taeyoon; Kim, Hyungjun
• Is Part Of: Journal of materials chemistry. Volume 9:Issue 18(2021)
• Page Start: 6006
• Page End: 6013
• Publication Date: 2021-04-27
• Subjects: Materials -- Periodicals; Chemistry, Analytic -- Periodicals; Optical materials -- Research -- Periodicals; Electronics -- Materials -- Research -- Periodicals; 543.0284
• DOI: 10.1039/d1tc00650a
• Languages: English
• ISSNs: 2050-7526

Abstract

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. 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− x S x 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− x S x thin films were synthesized using a GeCl4 precursor and H2 S 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 Ge2 S3 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 Ge2 S3 device due to the higher trap density (2.1 × 10 21 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.