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TY  - THES
AU  - Xi, Fengben
TI  - Ferroelectric Schottky barrier devices on SOI for neuromorphic computing
PB  - RWTH Aachen University
VL  - Dissertation
CY  - Aachen
M1  - RWTH-2024-00164
SP  - 1 Online-Ressource : Illustrationen
PY  - 2023
N1  - Veröffentlicht auf dem Publikationsserver der RWTH Aachen University 2024
N1  - Dissertation, RWTH Aachen University, 2023
AB  - The brain-inspired neuromorphic computing has emerged as an alluring technology due to its energy efficient features and learning abilities to overcome the von Neumann bottleneck in the post-Moore era. Neuromorphic engineering focuses on the field of constructing a smart neuromorphic hardware system inspired by the human brain neural network. In particular, the ability to process big data and complete cognitive tasks in an energy efficient manner is of interest. In neuromorphic systems complex architectures are required as neurons communicate via a large number of synapses. For the implementation emerging non-volatile memories, like resistive random-access memory, phase change memory and memristor based devices are currently considered. However, high variability, poor stability and high operation voltage are challenges for these devices. Recently the memtransistor using HfO2 based ferroelectrics as gate oxide has attracted a lot of attention due to its CMOS compatibility, energy efficiency and miniaturization ability. Thus, in this thesis, advanced ferroelectric device concepts were fabricated and carefully analyzed. In a first step metal-ferroelectrics-metal (MFM) capacitors were fabricated. The ferroelectric Hf0.5Zr0.5O2 (HZO) and Si:HfO2 (HSO) layers were deposited by atomic layer deposition (ALD). The process was optimized to obtain the desired ferroelectric properties. Contact electrodes were fabricated from TiN and epitaxial single crystalline NiSi2. Two terminal artificial synapses typically show parasitic currents and instabilities, to overcome these we fabricated three terminal artificial synapses using ferroelectric HZO or HSO as gate oxide. Moreover, ferroelectric Schottky barrier field effect transistors (FE-SBFETs) have been employed to demonstrate homo-synaptic plasticity. FE-SBFETs with a long channel design and a gate last process have been realized. Source and drain contacts were formed by NiSi2 with atomically smooth interfaces. By applying voltage pulses to the ferroelectric gate, the ferroelectric polarization is gradually switched and in turn the NiSi2/ Si Schottky barriers are gradually modulated. Thus, the conductance of the device is programmed with the input voltage pulses. The short-term synaptic plasticity is characterized by measurements of excitatory/ inhibitory post-synaptic currents (EPSC/ IPSC) and paired-pulse facilitation/ depression (PPF/ PPD). The device can be modulated with voltage pulses (spikes) of very low energy, as small as 2 fJ, demonstrating high energy efficiency. Long-term potentiation/ depression (LTP/ LTD) results show very high endurance and very small cycle-to-cycle variations ( 1
LB  - PUB:(DE-HGF)11
DO  - DOI:10.18154/RWTH-2024-00164
UR  - https://publications.rwth-aachen.de/record/976349
ER  -