Numerical analysis of the retention behavior in nitride storage flash memory

• Main Authors: Hsu Chih-Wei, 許智維
• Other Authors: Tahui Wang
• Format: Others
• Language: en_US
• Published: 2005
• Online Access: http://ndltd.ncl.edu.tw/handle/86474805502454286236

碩士 === 國立交通大學 === 電子工程系所 === 93 === The bottom oxide thickness induced the charge loss blocking effect for a SONOS type flash memory is investigated. Utilizing a numerical analysis based on a multiple trapping model for solving the Shockley-Read-Hall (SRH) rate equations, the more accurate expressions for retention behavior are developed. In these equations, the classical tunneling and the stress-induced oxide trap-assisted tunneling mainly accounts for the charge loss and the trapped charge via Frenkel-Poole excitation to conduction band coupled with the conduction free carriers recapture by the traps is used to describe the charge transition within silicon-nitride (SiN) film. The free carrier concentration is governed by two competing processes, tunneling out to Si and recaptured by SiN traps. Our study shows that in an unstressed cell the recapture process starts to dominate as the bottom oxide thickness increases. This will block the charge loss and then improve the retention time. In addition, the high temperature enhanced charge escape and the bottom oxide stress effect accelerated data loss have been considered in this thesis.