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Fabrication and characterisation of SiOₓ ReRAM devices

Zhao, Longfei; (2022) Fabrication and characterisation of SiOₓ ReRAM devices. Doctoral thesis (Ph.D), UCL (University College London).

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Silicon oxide (SiOx) based resistive random access memory (ReRAM) devices are capable of changing resistance reversibly, making them ideal candidates for next generation memory. In particular, silicon oxide based ReRAM device offers superior CMOS compatibility than ReRAM devices based on other materials. The purpose of this thesis is to optimise performance of SiOx based ReRAM devices in two aspects: device programming strategy and device fabrication methods. In order to optimise device programming strategy, I characterised the electrical properties of SiOx based ReRAM devices comprehensively, discovering a number of electrical phenomena in the process. Stress induced leakage current is related to the electroforming process, and leads to a current transient phenomenon that can be utilised for detecting edges in an optical image. Dielectric relaxation influences the readout current and can be used to investigate oxide quality. Delayed-electroforming is a novel phenomenon discovered in SiOx; to the best of my knowledge, no similar phenomenon has ever been reported before; it describes the formation of conductive filament under negligible voltage after pre-stressing. This discovery unveils the important role of charge injection in ReRAM devices, it also alleviates the problem of current overshoot. I also explored other more conventional methods to address current overshoot. After comparing these methods, I found that introducing an additional transistor was most effective. Additionally, a software approach also mitigates current overshoot without the need of additional hardware. Defects are vital in the operation of ReRAM devices. Starting with a SiOx layer grown by atomic layer deposition, I implanted this layer with noble ions to generate controlled defects. Such SiOx enable excellent resistance switching performance, comparable to the optimised sputtered SiOx. Devices fabricated this way allows better control of defect generation and switching performance can be tailored for further optimisation. As ReRAM continues to be intensely researched by industry and academia, ReRAM shows promising potential for memory storage and novel computation architecture. My work presented in this thesis is important for intrinsic SiOx ReRAM devices, the advancement in understanding and performance will benefit development of intrinsic SiOx ReRAM devices. The advantage of high CMOS compatibility allows SiOx to stand out from other ReRAM materials, with further development and optimisation, intrinsic SiOx ReRAM devices are well-positioned to emerge as the front runner for next-generation memory and computation technologies.

Type: Thesis (Doctoral)
Qualification: Ph.D
Title: Fabrication and characterisation of SiOₓ ReRAM devices
Language: English
Additional information: Copyright © The Author 2022. Original content in this thesis is licensed under the terms of the Creative Commons Attribution-NonCommercial 4.0 International (CC BY-NC 4.0) Licence (https://creativecommons.org/licenses/by-nc/4.0/). Any third-party copyright material present remains the property of its respective owner(s) and is licensed under its existing terms. Access may initially be restricted at the author’s request.
UCL classification: UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science > Dept of Electronic and Electrical Eng
UCL > Provost and Vice Provost Offices > UCL BEAMS
URI: https://discovery.ucl.ac.uk/id/eprint/10147497
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