Browsing by Author "Chou, You-Liang"

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A Novel Random Telegraph Signal Method to Study Program/Erase Charge Lateral Spread and Retention Loss in a SONOS Flash Memory
(2011-03-01)
Ma, Huan-Chi
;
Chou, You-Liang
;
Chiu, Jung-Piao
;
Chung, Yueh-Ting
;
Lin, Tung-Yang
A novel random telegraph signal (RTS) method is proposed to characterize the lateral distribution of injected charge in program and erase states in a NOR-type silicon-oxide-nitride-oxide-silicon Flash memory. The concept of this method is to use RTS to extract an oxide trap position in the channel and then to use the trap and RTS as internal probe to detect a local channel potential change resulting from injected charge during program/erase. By using this method, the lateral width of the injected charge-induced channel potential barrier is shown to be around 20 nm in channel hot electron (CHE) program. Our method also confirms that Channel Initiated Secondary ELectron (CHISEL) program has a broader injected charge distribution than CHE program. A mismatch of CHE program electrons and band-to-band tunneling erase holes is observed. Program-state V(t) retention loss models, charge vertical loss versus lateral migration, are reexamined by using this method. The polarity of a program-state charge distribution along the channel is explored within 10-20 program/erase cycles. Nitride charge vertical loss is verified by this method.
V-t Retention Distribution Tail in a Multitime-Program MLC SONOS Memory Due to a Random-Program-Charge-Induced Current-Path Percolation Effect
(2012-05-01)
Chung, Yueh-Ting
;
Huang, Tzu-I
;
Li, Chi-Wei
;
Chou, You-Liang
;
Chiu, Jung-Piao
A V-t retention distribution tail in a multitime-program (MTP) silicon-oxide-nitride-oxide-silicon (SONOS) memory is investigated. We characterize a single-program-charge-loss-induced Delta V-t in NOR-type SONOS multilevel cells (MLCs). Our measurement shows the following: 1) A single-charge-lossinduced Delta V-t exhibits an exponential distribution in magnitudes, which is attributed to a random-program-charge-induced current-path percolation effect, and 2) the standard deviation of the exponential distribution depends on the program-charge density and increases with a program V-t level in an MLC SONOS. In addition, we measure a V-t retention distribution in a 512-Mb MTP SONOS memory and observe a significant V-t retention tail. A numerical V-t retention distribution model including the percolation effect and a Poisson-distribution-based multiple-charge-loss model is developed. Our model agrees with the measured V-t retention distribution in a 512-Mb SONOS well. The observed V-t tail is realized mainly due to the percolation effect.