Localized Charge Distribution and Read Current Noise in Nitride Storage Flash Cells

• Main Authors: Ming-Te Wang, 王銘德
• Other Authors: Tahui Wang
• Format: Others
• Language: en_US
• Published: 2004
• Online Access: http://ndltd.ncl.edu.tw/handle/29m22c

碩士 === 國立交通大學 === 電子工程系所 === 92 === This thesis will focus on the discussion of localized trapped charge distribution in nitride film and read current instability issue in a SONOS type flash memory cell, which include program charge lateral spread, program disturb effect, and read current noise. In this study, the flash memory cell is made of a n-channel MOSFET with an oxide-nitride-oxide gate structure. For two-bit storage, the control of programmed charge lateral distribution is particularly important since stored electrons at the first bit will affect the threshold voltage of the second bit in reverse read. We use a charge pumping method to explore the programmed charge distribution of each bit. In addition, a micro-second transient measurement circuit is set up to investigate the program disturb effect. Furthermore, program/erase cycling induced random telegraph noise in read current noise is observed. The amplitude of current fluctuation increases with P/E cycle number and with decreasing gate length. Non-uniform charge storage by CHE programming can further enhance read current fluctuation. The improvement of bottom oxide reliability can significantly reduce this effect.