Study of Charge Loss Mechanism of SONOS-Type Devices using Hot-Hole Erase and Methods to Improve the Charge Retention

The retention degradation mechanism of NBit/NROM (Eitan et al., 2000) is examined by several unique techniques that promise unequivocal results. The in-situ 150degC electrical testing is used to examine the electron/hole stability. We find no discernable electron/hole lateral migration in the nitride. Next, we apply the refill and soft erase methods (Lue et al., 2005) with various electrical conditions to study the charge loss mechanism. We demonstrate that the refill method can electrically modify the trap energy spectrum, and soft erase method can recover the damages induced by hot-hole stressing. The experimental results show that the vertical charge loss measured by Vg-accelerated retention test at 25degC is highly correlated to the charge loss measured at 150degC baking. Since refill and soft erase techniques alter the trapped electron energy spectrum and the excess-hole distribution differently, these correlations strongly support the vertical charge loss model. Finally, the retention is greatly improved by the refill and soft erase methods and further improvement may be expected by engineering the nitride traps

[1]  T. Ma,et al.  Direct lateral profiling of hot-carrier-induced oxide charge and interface traps in thin gate MOSFET's , 1998 .

[2]  Chih-Yuan Lu,et al.  Cause of data retention loss in a nitride-based localized trapping storage flash memory cell , 2002, 2002 IEEE International Reliability Physics Symposium. Proceedings. 40th Annual (Cat. No.02CH37320).

[3]  J. de Vos,et al.  Comparative reliability investigation of different nitride based local charge trapping memory devices , 2005, 2005 IEEE International Reliability Physics Symposium, 2005. Proceedings. 43rd Annual..

[4]  Chih-Yuan Lu,et al.  Highly reliable 2-bit/cell nitride trapping flash memory using a novel array-nitride-sealing (ANS) ONO process , 2005, IEEE InternationalElectron Devices Meeting, 2005. IEDM Technical Digest..

[5]  B. Eitan,et al.  Electrons Retention Model for Localized Charge in , 2002 .

[6]  Aiko Pras,et al.  Data on Retention , 2005, DSOM.

[7]  T.C. Lu,et al.  Reliability models of data retention and read-disturb in 2-bit nitride storage flash memory cells , 2003, IEEE International Electron Devices Meeting 2003.

[8]  J. Bu,et al.  On the go with SONOS , 2000 .

[9]  Chih-Yuan Lu,et al.  Data retention behavior of a SONOS type two-bit storage flash memory cell , 2001, International Electron Devices Meeting. Technical Digest (Cat. No.01CH37224).

[10]  M. Janai.  Data retention, endurance and acceleration factors of NROM devices , 2003, 2003 IEEE International Reliability Physics Symposium Proceedings, 2003. 41st Annual..

[11]  D. Ielmini,et al.  Reliability assessment of discrete-trap memories for NOR applications , 2005, 2005 IEEE International Reliability Physics Symposium, 2005. Proceedings. 43rd Annual..

[12]  A novel 2-bit/cell nitride storage flash memory with greater than 1M P/E-cycle endurance , 2004, IEDM Technical Digest. IEEE International Electron Devices Meeting, 2004..

[13]  Chih-Yuan Lu,et al.  Novel operation schemes to improve device reliability in a localized trapping storage SONOS-type flash memory , 2003, IEEE International Electron Devices Meeting 2003.

[14]  B. Eitan,et al.  Electrons retention model for localized charge in oxide-nitride-oxide (ONO) dielectric , 2002, IEEE Electron Device Letters.

[15]  Chih-Yuan Lu,et al.  PHINES: a novel low power program/erase, small pitch, 2-bit per cell flash memory , 2002, Digest. International Electron Devices Meeting,.

[16]  Hang-Ting Lue,et al.  Novel soft erase and re-fill methods for a P/sup +/-poly gate nitride-trapping non-volatile memory device with excellent endurance and retention properties , 2005, 2005 IEEE International Reliability Physics Symposium, 2005. Proceedings. 43rd Annual..