Browsing by Author "Zheng, Xin"

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AC stress and electronic effects on SET switching of HfO2 RRAM
(2017-08-28)
Liu, Jen-Chieh
;
Magyari-Kope, Blanka
;
Qin, Shengjun
;
Zheng, Xin
;
Wong, H. -S. Philip
An AC stress test was performed to investigate the accompanying electronic effects in a HfO2 resistive random access memory during the SET transition, which featured a sudden decrease in resistance. Comparing the DC and AC measurement results indicated the pronounced influence of interrupted stress on both the mean values and variations of time to SET. First-principles calculations suggested that the charge states (+2, +1, or neutral) of oxygen vacancies affect the migration barrier for forming oxygen vacancy clusters. Therefore, a charge-state-dependent SET model is proposed to include the additional electronic effects induced by the dynamics of electron trapping and detrapping in oxygen vacancies during AC stress. A trimodal Weibull fitting based on the proposed model reproduced the experimental time to SET distributions obtained in a wide range of AC stress conditions. Published by AIP Publishing.
Statistical Study of RRAM MLC SET Variability Induced by Filament Morphology
(2017-01-01)
Hsu, Chung-Wei
;
Zheng, Xin
;
Wu, Yi
;
Hou, Tuo-Hung
;
Wong, H. -S. Philip
This paper establishes the correlation between RRAM multilevel-cell (MLC) stochastic SET variability and random telegraph noise (RTN). We show that a smaller diameter (d(D)) of locally connecting/rupturing conductive filament (CF) and larger distance of gap (d(G)) between CF and electrode demonstrate both steeper Weibull slope beta with a relaxed SET-disturb margin by 0.4 V and 36x improvement in RTN robustness. This is achieved by lower current compliances (I-COMP) of 100 mu A and larger RESET stopping voltage (V-RESET) of -4.5 V for smaller dD and larger dG with leaving less residual oxygen vacancies (V-o(+2)) in the gap region. Results from the Kinetic Monte Carlo (KMC) modeling also support these findings.