A Study of High-Performance NAND Structured EEPROMS

Tetsuo ENDOH  Riichiro SHIROTA  Seiichi ARITOME  Fujio MASUOKA  

IEICE TRANSACTIONS on Electronics   Vol.E75-C   No.11   pp.1351-1357
Publication Date: 1992/11/25
Online ISSN: 
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Special Issue on LSI Memories)
flash EEPROM,  NAND EEPROM endurance,  block technology,  page program technology,  

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This paper describes the superior performances of the NAND EEPROM. Those are 1) a very small cell area: 4.83 µm2 using 0.7 µm design rule, 2) small block size for erasing: 4 Kbyte block erasing for 4 M-bit NAND EEPROM, 3) high speed programming: 180 nsec per byte for 4 M-bit NAND EEPROM, 4) large number of erase/program endurance cycles: more than 105 cycles for 4 M-bit NAND EEPROM. These extended performances coincide with the requirement for the EEPROM to replace magnetic memories such as hard and floppy disks. Especially, it is shown that NAND EEPROM has the capability to enlarge the erase/program endurance up to 3.6108 cycles. This endurance is a result of the erase and program mechanism of the NAND EEPROM cell. Fowler-Nordheim (F-N) tunneling currents flow from the substrate to the floating gate during programming and opposite currents flow during erasing. This bi-polarity F-N tunneling erase/program operation extends the life time of the tunnel oxide which results in an improved endurance.