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Article

SiGeSn Quantum Dots in HfO2 for Floating Gate Memory Capacitors

1
National Institute of Materials Physics, 405A Atomistilor Street, 077125 Magurele, Romania
2
Faculty of Physics, University of Bucharest, 405 Atomistilor Street, 077125 Magurele, Romania
3
Academy of Romanian Scientists, 54 Splaiul Independentei, 050094 Bucharest, Romania
*
Authors to whom correspondence should be addressed.
Academic Editor: Alessio Lamperti
Coatings 2022, 12(3), 348; https://doi.org/10.3390/coatings12030348
Received: 1 February 2022 / Revised: 2 March 2022 / Accepted: 3 March 2022 / Published: 7 March 2022
(This article belongs to the Special Issue Nanocomposite Thin Film and Multilayers)
Group IV quantum dots (QDs) in HfO2 are attractive for non-volatile memories (NVMs) due to complementary metal-oxide semiconductor (CMOS) compatibility. Besides the role of charge storage centers, SiGeSn QDs have the advantage of a low thermal budget for formation, because Sn presence decreases crystallization temperature, while Si ensures higher thermal stability. In this paper, we prepare MOS capacitors based on 3-layer stacks of gate HfO2/floating gate of SiGeSn QDs in HfO2/tunnel HfO2/p-Si obtained by magnetron sputtering deposition followed by rapid thermal annealing (RTA) for nanocrystallization. Crystalline structure, morphology, and composition studies by cross-section transmission electron microscopy and X-ray diffraction correlated with Raman spectroscopy and CV measurements are carried out for understanding RTA temperature effects on charge storage behavior. 3-layer morphology and Sn content trends with RTA temperature are explained by the strongly temperature-dependent Sn segregation and diffusion processes. We show that the memory properties measured on Al/3-layer stack/p-Si/Al capacitors are controlled by SiGeSn-related trapping states (deep electronic levels) and low-ordering clusters for RTA at 325–450 °C, and by crystalline SiGeSn QDs for 520 and 530 °C RTA. Specific to the structures annealed at 520 and 530 °C is the formation of two kinds of crystalline SiGeSn QDs, i.e., QDs with low Sn content (2 at.%) that are positioned inside the floating gate, and QDs with high Sn content (up to 12.5 at.%) located at the interface of floating gate with adjacent HfO2 layers. The presence of Sn in the SiGe intermediate layer decreases the SiGe crystallization temperature and induces the easier crystallization of the diamond structure in comparison with 3-layer stacks with Ge-HfO2 intermediate layer. High frequency-independent memory windows of 3–4 V and stored electron densities of 1–2 × 1013 electrons/cm2 are achieved. View Full-Text
Keywords: group IV quantum dots; HfO2; magnetron sputtering; floating gate memory; SiGeSn nanocrystals; charge storage group IV quantum dots; HfO2; magnetron sputtering; floating gate memory; SiGeSn nanocrystals; charge storage
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MDPI and ACS Style

Palade, C.; Slav, A.; Cojocaru, O.; Teodorescu, V.S.; Stoica, T.; Ciurea, M.L.; Lepadatu, A.-M. SiGeSn Quantum Dots in HfO2 for Floating Gate Memory Capacitors. Coatings 2022, 12, 348. https://doi.org/10.3390/coatings12030348

AMA Style

Palade C, Slav A, Cojocaru O, Teodorescu VS, Stoica T, Ciurea ML, Lepadatu A-M. SiGeSn Quantum Dots in HfO2 for Floating Gate Memory Capacitors. Coatings. 2022; 12(3):348. https://doi.org/10.3390/coatings12030348

Chicago/Turabian Style

Palade, Catalin, Adrian Slav, Ovidiu Cojocaru, Valentin Serban Teodorescu, Toma Stoica, Magdalena Lidia Ciurea, and Ana-Maria Lepadatu. 2022. "SiGeSn Quantum Dots in HfO2 for Floating Gate Memory Capacitors" Coatings 12, no. 3: 348. https://doi.org/10.3390/coatings12030348

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