Browsing by Author "Wang, Pin-Yao"

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Evaluation of the Role of Deep Trap State Using Analytical Model in the Program/Erase Cycling of NAND Flash Memory and Its Process Dependence
(2018-02-01)
Yang, Bo-Jun
;
Wu, Yu-Ting
;
Chiu, Yung-Yueh
;
Kuo, Tse-Mien
;
Chang, Jung-Ho
A method to analyze the kinetics of the charge accumulation in the tunnel oxide by the nand flash memory program and erase (P/E) cycling is proposed. Both electron trapping and detrapping processes are required to be considered owing to the oxide high electric field during P/E cycles. Consequently, the electron trapping in the deep trap state is concluded, whose trap energy (E-trap) is more than 3.5 eV. Furthermore, the as-grown trap state density (Ne), the trapping capture cross section (sigma), and the number of trapped positive charges can also be extracted to explain the tunneling current modulation and the V-T shift by oxide-trapped charges under the P/E stress. The trapped electrons are mainly distributed in the center of tunneloxide, and the distributed area extends as the P/E bias increases. In addition, the dependence of oxidation process is also shown. Both thermal dry and plasma oxidation have almost the same value of sigma (similar to 4x10(-17) cm(2)). However, 30% reduction of Ne is shown in plasma oxidation (similar to 1.25x10(19) cm(-3)) when compared with thermal dry oxidation (similar to 1.88 x 10(19) cm(-3)).
New Method to Analyze the Shift of Floating Gate Charge and Generated Tunnel Oxide Trapped Charge Profile in NAND Flash Memory by Program/Erase Endurance
(2015-01-01)
Shirota, Riichiro
;
Yang, Bo-Jun
;
Chiu, Yung-Yueh
;
Chen, Hsuan-Tse
;
Ng, Seng-Fei
A new test system was devised and used to separate the amount of floating gate (FG) charge (Q(FG)) from the oxide trapped charge (Q(OX)) generated by program-and-erase (P/E) cycles. We also extracted the pure V-mid shift caused by the generation of Q(OX), which is separated from the part of V-t shift coming from Q(FG) deviation. The identification of Q(FG) and Vmid shift makes it possible to analyze the detailed the oxide trapped charge profile. The Q(FG) shift generated by P/E cycles displays asymmetry between the programmed and erased states: the absolute value of Q(FG) exhibits a maximum at similar to 100 cycles in the programmed states, while Q(FG) monotonically decreases in the erased one. Considering that the Fowler-Nordheim tunneling current is sensitive to the oxide trap near the cathode, itself the source of electron tunneling current, our results indicate that the hole trap is dominant near to Si, whereas the electron trap is dominant near FG.