Thorough understanding of retention time of Z2FET memory operation

Duan, M. , Navarro, C., Cheng, B., Adamu-Lema, F., Wang, X., Georgiev, V.P. , Gamiz, F., Millar, C. and Asenov, A. (2019) Thorough understanding of retention time of Z2FET memory operation. IEEE Transactions on Electron Devices, 66(1), pp. 383-388. (doi: 10.1109/TED.2018.2877977)

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Abstract

A recently reported zero impact ionization and zero subthreshold swing device Z2FET is a promising candidate for capacitor-less dynamic random access memory (DRAM) memory cell. In the memory operation, data retention time determines refresh frequency and is one of the most important memory merits. In this paper, we have systematically investigated the Z2FET retention time based on a newly proposed characterization methodology. It is found that the degradation of HOLD ``0'' retention time originates from the gated-silicon on insulator (SOI) portion rather than the intrinsic-SOI region of the Z2FET. Electrons accumulate under front gate and finally collapse the potential barrier turning logic ``0''-``1.'' It appears that Shockley-Read-Hall (SRH) generation is the main source for electrons accumulation. Z2FET scalability has been investigated in terms of retention time. As the Z2FET is downscaled, the mechanism dominating electrons accumulation switches from SRH to parasitic injection of electrons from the cathode. The results show that the downscaling of Lg has little effect on data ``0'' retention, but Lin is limited to ~ 125 nm. An optimization method of the fabrication process is proposed based on this new understanding, and Lin can be further scaled down to 75 nm. We have demonstrated by 2-D TCAD simulation that Z2FET is a promising DRAM cells' candidate particularly for Internet-of-Things applications.

Item Type:Articles
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Asenov, Professor Asen and Duan, Meng and Georgiev, Dr Vihar and Adamu-Lema, Dr Fikru
Authors: Duan, M., Navarro, C., Cheng, B., Adamu-Lema, F., Wang, X., Georgiev, V.P., Gamiz, F., Millar, C., and Asenov, A.
College/School:College of Science and Engineering > School of Engineering > Electronics and Nanoscale Engineering
Journal Name:IEEE Transactions on Electron Devices
Publisher:IEEE
ISSN:0018-9383
ISSN (Online):1557-9646
Published Online:15 November 2018
Copyright Holders:© 2018 Crown Copyright
First Published:First published in IEEE Transactions on Electron Devices 66(1): 383-388
Publisher Policy:Reproduced in accordance with the copyright policy of the publisher

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Project CodeAward NoProject NamePrincipal InvestigatorFunder's NameFunder RefLead Dept
702351REMINDERAsen AsenovEuropean Commission (EC)687931ENG - ENGINEERING ELECTRONICS & NANO ENG