Non-volatile memory with multiple GeSn nanocrystals floating gate controlled by electric field and light with low power consumption (LighTinGMemLowP)
Project Director: Dr. Magdalena Lidia CIUREA
Project goal is fabrication of nonvolatile memory (NVM) device, with 1-3 floating gates (FGs) of GeSn nanocrystals (NCs), controlled by electric field and illumination. GeSn NCs FG is a novel solution benefiting from the high sensitivity of GeSn NCs in short-wave infrared (SWIR). This NVM is a multilayer (ML) capacitor-like device (top contact/ gate oxide/ (FG of GeSn NCs / tunnel oxide)n / Si wafer/ bottom contact, n=1-3) and will be fabricated in 2 versions V1 (uses stacks of HfO2 & SiO2 for gate & tunnel oxides) and V2 (uses only SiO2). A very efficient approach of magnetron sputtering deposition on heated substrate (dynamic annealing) is used, being one-step fabrication. GeSn NCs nodes in FG will be charged by bias voltage & light (wavelengths ≥1000 nm), simultaneously applied. The targeted performances of NVMs with GeSn NCs FG are: 3–5 V memory window, 10%–12% charge loss at 104 s (30% after 10 years), high photosensitivity in 1000–1800 nm range (GeSn NCs with 10%–15% Sn), and low power consumption (by light). The impact of project is: *scientific (deep understanding of electronic processes and device operation), *technological (processes and parameters), *social & economic (cheap security systems (IoT) for event detection, integrated photonics on Si, image capturing, (photonic) neuromorphic computing devices, computer systems; young people formation). Project results: 5 Q1&Q2 ISI papers, 5 conference communications, 1 patent application, considering open publication practices.
The project goal is to fabricate a NVM device, with up to 3 FG storing layers of GeSn NCs, controlled by electric field and illumination.
Project Results (proposed Work Plan):
technological parameters; photolithographic masks; test samples with or no contacts, characteristics, images; configured test samples with proper properties for V1&V2; characteristics & parameters of optimal test samples: images, curves & spectra, crystalline structures, composition & morphology; memory window, retention curves, charge loss; completely characterized V1&V2 samples; NVM devices completely characterized; NVMs with targeted properties of 3–5 V memory window, 10%–12% charge loss at 104 s (30% estimated at 10 years) and high sensitivity in 1000–1800 nm ensured by GeSn NCs with 10%–15% Sn; project webpage; 5 papers in Q1, Q2 journals; 5 international conference communications / papers; 1 patent application; progress reports and final report
Stage 1/2025 WP1. Fabrication of test samples for 2 versions V1 and V2 – part I; WP4. Dissemination and exploitation of results – part I
Stage 2/2026 WP1. Fabrication of test samples for 2 versions V1 and V2 – part II; WP2. Characterization of V1 and V2 test samples: crystalline structure, morphology, composition, memory properties – part I; WP4. Dissemination and exploitation of results – part II
Stage 3/2027 WP1. Fabrication of test samples for 2 versions V1 and V2 – part III; Characterization of V1 and V2 test samples: crystalline structure, morphology, composition, memory properties – part II; WP3. Fabrication of NVM based on GeSn NCs FG controlled by both electric field and light – part I; WP4. Dissemination and exploitation of results – part III
Stage 4/2028 WP3. Fabrication of NVM based on GeSn NCs FG controlled by both electric field and light – part II; WP4. Dissemination and exploitation of results – part IV
- Dr. Magdalena Lidia Ciurea, Project Director / https://www.brainmap.ro/lidia-magdalena-ciurea
- Dr. Catalin Palade, Postdoc / https://www.brainmap.ro/catalin-palade
- Dr. Ana-Maria Lepadatu, Researcher / https://www.brainmap.ro/ana-maria-lepadatu
- Dr. Toma Stoica, Researcher / https://www.brainmap.ro/toma-stoica
- Dr. Ionel Stavarache, Researcher / https://www.brainmap.ro/ionel-stavarache
- Dr. Adrian Slav, Researcher / https://www.brainmap.ro/adrian-slav
- Dr. Valentin Serban Teodorescu, Researcher / https://www.brainmap.ro/valentin-serban-teodorescu
- Dr. Valentin-Adrian Maraloiu, Researcher / https://www.brainmap.ro/valentin-adrian-maraloiu
- Dr. Ioana Maria Avram Dascalescu, Postdoc / https://www.brainmap.ro/ioana-maria-dascalescu
- Dr. Ovidiu Cojocaru, Postdoc / https://www.brainmap.ro/ovidiu-cojocaru
Stage 1/2025 WP1. Fabrication of test samples for 2 versions V1 & V2 (part I); WP4. Dissemination & exploitation of results (part I)
Summary
The LighTinGMemLowP project goal is to fabricate a nonvolatile memory (NVM) device with up to 3 floating gates storing layers (FGs) of GeSn nanocrystals (NCs), controlled by electric field and illumination. This NVM is a capacitor-like multilayer device (top contact/ gate oxide/ (FG of GeSn NCs / tunnel oxide)n / Si wafer/ bottom contact, n=1–3), and will be obtained in 2 versions V1 (with stacks of HfO2 & SiO2 layers for gate & tunnel oxides) and V2 (oxide layers of only SiO2).
Test samples for NVM with one floating gate (1FG) of GeSn NCs (n=1), in V1 and V2 versions were fabricated in Stage 1. They were obtained by sequential deposition of component layers by magnetron sputtering (one-step fabrication) on 200 oC heated p-Si substrate (7 – 14 Ωcm). 3 kinds of test samples P2-P4 in V1, V2 versions were prepared by varying technological conditions (including Sn concentration), together with a control sample P1. Test samples underwent a rapid thermal annealing (RTA) process at temperatures between 450 and 600 oC for formation of GexSn1–x NCs and HfO2 NCs (crystallization consolidation). The test samples (as-deposited and annealed) were tested for crystalline structure, morphology (XRD, (HR)TEM) and composition (EDX), and for optical, electrical and memory properties (by measuring capacitance-voltage characteristics at different frequencies in dark and under illumination, i.e. C – V dk and C – V ph, respectively) from which the memory window was determined for each test sample. Based on the obtained results, the test samples were compared with each other, and the samples with the best NVM properties were selected. Notably, the results related to NVM properties are supported by the findings from crystalline structure, morphology, and composition investigations (XRD, (HR)TEM si EDX).
Photolithographic masks were designed also in Stage 1. Configuration of samples for tests related to optical, electrical and memory properties was made by depositing Al contacts with 1.7 mm diameter (subsequent RTA processing was not necessary).
The web page of the project was created and updated, and scientific and technological results were disseminated by an invited lecture at an international conference.
In conclusion, the proposed objectives and activities and planned results for Stage 1/2025 were fully achieved.
- Invited lecture „Enhancing short-wave infrared photosensing of germanium-based nanocrystals”, A.M. Lepadatu, C. Palade, A. Slav, I. Stavarache, I. Dascalescu, O. Cojocaru, V.A. Maraloiu, V.S. Teodorescu, T. Stoica, M.L. Ciurea, 48th Edition International Semiconductor Conference, IEEE CAS 2025, October 7 – 11, 2025, Sinaia
Dr. Magdalena Lidia Ciurea - ciurea@infim.ro
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