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