Séminaire – Laura Bégon-Lours

Laura Bégon-Lours (ETH Zürich, Suisse) donnera un séminaire intitulé « Oxygen mobility and ferroelectric switching in hafnia synapses » le 18 novembre à 11h dans l’auditorium de TRT Thales.

Auteurs :
Alexandre Baigol¹, Anwesha Panda¹, Yanming Zhang¹, Laura Bégon-Lours^*1,2
1Integrated Systems Laboratory, D-ITET, ETH Zürich, Switzerland
²Science and Technology Department, IBM Research Zürich, Switzerland

Résumé :
On conventional computers, the performance of AI models on is limited by the data transfer between the memory and the processor. To circumvent this so-called “Von-Neumann Bottleneck”, Compute-in-Memory architectures offer a new paradigm for the development of neuromorphic hardware. Vector-Matrix Multiplications may be performed in the analog domain, by a parallel voltage drop through a matrix of programmable resistances, the “synaptic weights”. Ferroelectric materials are excellent candidates for their realization: in a two- or three-terminals geometry and in combination with a semiconducting oxide,^[1–3] the conductance is programmed by controlling the configuration of the ferroelectric domains. The remanent polarization confers a nonvolatile character to these multi-level memories.

Single crystal perovskite oxide ferroelectrics such as BiFeO₃ exhibit a sharp coercive field distribution and are excellent candidates for unsupervised learning schemes.^[4] We will see that they are also suitable for selector-less operations in crossbar arrays.^[5] In the recent years, the interest for ferroelectric hafnium oxide increased, a material which can be deposited with Atomic Layer Deposition. The unique fluorite unit cell allows for the stabilization of ferroelectricity below 3 nm,^[6] allowing for the scaling of synaptic weights. The relatively low crystallization temperature of polycrystalline hafnium oxide / zirconium oxide superlattices (HZO-SL) allows the Back-End-Of-Line (BEOL) integration of functional devices to CMOS transistors.^[7,8]

The mechanisms governing the resistive switching in WOx / HZO-SL bilayers are discussed. The effect of the programming pulse duration and amplitude on the polarization switching are investigated, from milliseconds to nanoseconds timescales. The results suggest the exchange of oxygen between the WO_x and the hafnia at timescales longer than microseconds, activated by the electric field during programming and by the temperature.

[1]           L. Bégon-Lours, M. Halter, F. M. Puglisi, L. Benatti, D. F. Falcone, Y. Popoff, D. D. Pineda, M. Sousa, B. J. Offrein, Advanced Electronic Materials 2022, 2101395.

[2]           M. Halter, L. Bégon-Lours, V. Bragaglia, M. Sousa, B. J. Offrein, S. Abel, M. Luisier, J. Fompeyrine, ACS Appl. Mater. Interfaces 2020, 12, 17725.

[3]           M. Halter, L. Bégon-Lours, M. Sousa, Y. Popoff, U. Drechsler, B. J. Offrein, COMMUNICATIONS MATERIALS 2023, 4, DOI 10.1038/s43246-023-00342-x.

[4]           S. Boyn, J. Grollier, G. Lecerf, B. Xu, N. Locatelli, S. Fusil, S. Girod, C. Carrétéro, K. Garcia, S. Xavier, J. Tomas, L. Bellaiche, M. Bibes, A. Barthélémy, S. Saïghi, V. Garcia, Nature Communications 2017, 8, 14736.

[5]           M. Halter, E. Morabito, A. Olziersky, C. Carrétéro, A. Chanthbouala, D. F. Falcone, B. J. Offrein, L. Bégon-Lours, Journal of Materials Research 2023, 38, 4335.

[6]           L. Bégon-Lours, M. Halter, M. Sousa, Y. Popoff, D. D. Pineda, D. F. Falcone, Z. Yu, S. Reidt, L. Benatti, F. M. Puglisi, B. Offrein, Neuromorph. Comput. Eng. 2022, 2, DOI 10.1088/2634-4386/ac5b2d.

[7]           L. Bégon-Lours, S. Slesazeck, D. F. Falcone, V. Havel, R. Hamming-Green, M. M. Fernandez, E. Morabito, T. Mikolajick, B. J. Offrein, Advanced Electronic Materials 2024, n/a, 2300649.

[8]           R. Hamming-Green, M. S. Ram, D. F. Falcone, B. Noheda, B. J. Offrein, L. Bégon-Lours, in 2024 8th IEEE Electron Devices Technology & Manufacturing Conference (EDTM), IEEE, Bangalore, India, 2024, pp. 1–3.