Browsing by Author "Lu, WP"

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An endurance evaluation method for flash EEPROM
(2004-05-01)
Zous, NK
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Chen, YJ
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Chin, CY
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Tsai, WJ
;
Lu, TC
Trap generation is hard to estimate in a Flash cell due to a dynamic stress field during program and erase. In this paper, a linear correlation is found between the erase state V-T rollup, and cycling V-T window. With the knowledge of the time dependence of erase stress field based on Fowler-Nordheim (FN) tunneling, the V-T rollup during cycling is evaluated by incorporating field dependent oxide trap generation. The extracted Delta V-T degradation slope during constant FN stress can be applied quantitatively to predict the V-T window closure during Flash cell cycling.
Characterization of programmed charge lateral distribution in a two-bit storage nitride flash memory cell by using a charge-pumping technique
(2006-01-01)
Gu, SH
;
Wang, TH
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Lu, WP
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Ting, WC
;
Ku, YHJ
In this paper, we use a modified charge pumping technique to characterize the programmed charge lateral distribution in a hot electron program/hot hole erase, two-bit storage nitride Flash memory cell. The stored charge distribution of each bit over the source/drain junctions can be profiled separately. Our result shows that the second programmed bit has a broader stored charge distribution than the first programmed bit. The reason is that a large channel field exists under the first programmed bit during the second bit programming. Such a large field accelerates channel electrons and causes earlier electron injection into the nitride. In addition, we find that programmed charges spread further into the channel as program/erase cycle number increases.
Lateral migration of trapped holes in a nitride storage flash memory cell and its qualification methodology
(2004-09-01)
Zous, NK
;
Lee, MY
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Tsai, WJ
;
Kuo, A
;
Huang, LT
The negative threshold voltage (V-t) shift of a nitride storage flash memory cell in the erase state will result in an increase in leakage current. By utilizing a charge pumping method, we found that trapped hole lateral migration is responsible for this V-t shift. Hole transport in nitride is characterized by monitoring gate induced drain leakage current and using a thermionic emission model. The hole emission induced V-t shift shows a linear correlation with bake time in a semi-logarithm plot and its slope depends on the bake temperature. Based on the result, an accelerated qualification method for the negative V-t drift is proposed.