Effect of cycling on ultra-thin HfZrO4, ferroelectric synaptic weights. Issue 2 (1st June 2022)

• Record Type: Journal Article
• Authors: Bégon-Lours, Laura; Halter, Mattia; Sousa, Marilyne; Popoff, Youri; Dávila Pineda, Diana; Falcone, Donato Francesco; Yu, Zhenming; Reidt, Steffen; Benatti, Lorenzo; Puglisi, Francesco Maria; Offrein, Bert Jan
• Is Part Of: Neuromorphic computing and engineering. Volume 2:Issue 2(2022)
• Publication Date: 2022-06-01
• Subjects: hafnium zirconate -- ferroelectrics -- synaptic weights; Neural networks (Computer science) -- Periodicals; Neural computers -- Periodicals; Neuromorphics -- Periodicals; 006.3
• DOI: 10.1088/2634-4386/ac5b2d
• Languages: English
• ISSNs: 2634-4386

Abstract

Abstract: Two-terminal ferroelectric synaptic weights are fabricated on silicon. The active layers consist of a 2 nm thick WO x film and a 2.7 nm thick HfZrO4 (HZO) film grown by atomic layer deposition. The ultra-thin HZO layer is crystallized in the ferroelectric phase using a millisecond flash at a temperature of only 500 °C, evidenced by x-rays diffraction and electron microscopy. The current density is increased by four orders of magnitude compared to weights based on a 5 nm thick HZO film. Potentiation and depression (analog resistive switching) is demonstrated using either pulses of constant duration (as short as 20 nanoseconds) and increasing amplitude, or pulses of constant amplitude (+/−1 V) and increasing duration. The cycle-to-cycle variation is below 1%. Temperature dependent electrical characterisation is performed on a series of device cycled up to 10 8 times: they reveal that HZO possess semiconducting properties. The fatigue leads to a decrease, in the high resistive state only, of the conductivity and of the activation energy.