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Negative OR Logic Gate Type FLASH Read Only Memory Bit Verify

IP.com Disclosure Number: IPCOM000118958D
Original Publication Date: 1997-Sep-01
Included in the Prior Art Database: 2005-Apr-01
Document File: 2 page(s) / 47K

Publishing Venue

IBM

Related People

Kiyota, K: AUTHOR [+4]

Abstract

Disclosed is an improved programming method for Negative OR Logic Gate (NOR)-type FLASH Read Only Memory (ROM). During FLASH ROM programming, writing data is modified appropriately: 1. to keep the amount of electron in each floating gate at the same level 2. to minimize a distribution of FLASH ROM cell threshold

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Negative OR Logic Gate Type FLASH Read Only Memory Bit Verify

      Disclosed is an improved programming method for Negative OR
Logic Gate (NOR)-type FLASH Read Only Memory (ROM).  During FLASH ROM
programming, writing data is modified appropriately:
  1. to keep the amount of electron in each floating gate at
      the same level
  2.  to minimize a distribution of FLASH ROM cell threshold

      This method is originally prepared for NAND type FLASH ROM.  By
implementing adaptive logic circuit inside a chip, this method is
also applicable to NOR type FLASH ROM.  Then, NAND type FLASH ROM
will have  the same benefits as NOR type FLASH ROM with no
inconsistency with ordinary FLASH ROM programming.  FLASH ROM has a
programming period dispersion for each cell.  When programming FLASH
ROM, generally the program command is issued repeatedly until all bit
cells have expected  data.  As a result, some of the cells have a
large amount of electrons,  and some of them have a small amount of
electrons from the difference of the characteristics of each bit
cell.  This disclosure modifies programming logical "1" to bit cells
which has been already verified as  logical "0" to prevent
over-programming.  Because FLASH ROM programming,  "0" value means
charging electron to floating gate, and programming "1"  value means
no effect to floating gate.
        That is to say,
  (Re programming data) = NOT (Verified Data ) OR
   (Programmed Data) 1
    ...