Browsing by Author "Lo, Roger"

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A Study of Blocking and Tunnel Oxide Engineering on Double-Trapping (DT) BE-SONOS Performance
(2015)
Lo, Roger
;
Du, Pei-Ying
;
Hsu, Tzu-Hsuan
;
Wu, Chen-Jun
;
Guo, Jung-Yi
Double-trapping bandgap engineered SONOS (DT BE-SONOS) [1] was proposed to provide both fast erase speed and deep erase by means of a second nitride trapping layer and an additional blocking oxide on top of BE-SONOS. Although this provides excellent erase performance but the additional layers increase the EOT and subsequently the erase voltage, thus it is desirable to minimize their impact. This work investigates exhaustively the effect of thinning down the blocking layers. Since the ISPP and high temperature retention charge loss are mainly dominated by the ONO thickness of BE-SONOS below the blocking layers, reducing the blocking layer thickness has only minor impact on ISPP and retention. Moreover, erase saturation is determined by the dynamic balance of channel hole injection and gate electron injection. Experimental data show that reducing the thickness of the oxide between two trapping layers has little impact on erase saturation once the gate injected electrons are efficiently suppressed by the top most oxide. We have also investigated retention improvement by various oxides. By using HQ-SiO2 to replace the top tunnel ONO the trapped electron out-tunneling is reduced. Thus retention may be improved without increasing the effective oxide thickness.
Study of Thyristor-Mode Dual-Channel NAND Flash Devices
(2018-01-01)
Lo, Roger
;
Lue, Hang-Ting
;
Chen, Weichen
;
Du, Pei-Ying
;
Hsu, Tzu-Hsuan
A novel dual-channel 3D NAND device was proposed previously [1]. In addition to the N- and P-channel read operations, such device can also perform a special "thyristor mode" which possesses super steep subthreshold slope (S.S. similar to 0). In this work, we studied 4 different types of read methods with the same device, which are normal N- and P-channel read, and thyristor-mode N- and P-channel read, respectively. These 4 different read methods can be carried out by just simply changing the bias arrangements of wordlines so that the IdVg curves can behave differently. An interesting finding is that the Vt window of PIE cycling and retention are quite different among these sensing methods. It may provide a new methodology to understand the charge storage mechanisms. 'this work provides a comprehensive study for understanding the operation physics of this novel device.