class 20: memories-eeproms and flash iiweb.engr.uky.edu/~elias/lectures/ln_20.pdfprogramming fn-byte...
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Joseph A. Elias, PhD1
Class 20: Memories-EEPROMs and FLASH II
Topics:1. DP Issues2. EEPROMs and Flash Basics3. Cell Vt shift4. Window Closure 5. Band Diagrams 6. Band Diagrams 7. Oxide Conduction 8. FN Conduction
Joseph A. Elias, PhD2
Class 20: Memories-EEPROMs and FLASH II
EEPROMs FLASHprogramming FN-byte HCI/FN-biterase FN-byte FN-sectorpass xtor yes no
EEPROM and Flash Basics
Programming•FN - low current, high potentials•HCI-high current, lower potentials
Erase•FN - inherent failure mechanism
Read•Sense current•Sense voltage•Either method needs good dummy cell for comparison
Joseph A. Elias, PhD3
Class 20: Memories-EEPROMs and FLASH IICell Vt Shift
Id
Vgs2.5 7.05.0
100uAUV/EE
bit
weakpgm
strongpgm
30uA
•UV State - initial state of bits, read ~100uA at 5V•PGM State - charge on floating gate, read ~0uA at 5V•EE State - all charge off floating gate
•should be same as UV state, not always the case
0.1uA
50uA(dummy after ratio)
Joseph A. Elias, PhD4
Class 20: Memories-EEPROMs and FLASH IIWindow Closure (Johnson)
What is a window?What is cause of window closure?
Joseph A. Elias, PhD5
Class 20: Memories-EEPROMs and FLASH IIBand Diagrams (Sze)
Programming•high positive potential on CG•electrons tunnel drain->FG
Static•electrons trapped on FG•surface bands remain bent
Erase•high positive potential on source or•high negative potential on CG•electrons tunnel FG->source
Joseph A. Elias, PhD6
Class 20: Memories-EEPROMs and FLASH IIBand Diagrams (Elias)
Erase•high positive potential on source•electrons tunnel FG->source
Joseph A. Elias, PhD7
Class 20: Memories-EEPROMs and FLASH IIOxide Conduction (Sze)
Various types conduction mechanisms through oxidesVariation with temperature allows differentiation
Joseph A. Elias, PhD8
Class 20: Memories-EEPROMs and FLASH IIFN Conduction (Elias)
IV
FN
FN as a function of temperature, area
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