Static information storage and retrieval – Floating gate – Particular biasing
Patent
1994-12-14
1997-10-21
Popek, Joseph A.
Static information storage and retrieval
Floating gate
Particular biasing
36518529, 36518533, G11C 1134
Patent
active
056803508
ABSTRACT:
This invention constitutes a method for narrowing threshold voltage distribution among the individual cells of a block erased flash memory array by firstly, preprogramming cells within the block be erased to a level of saturation using hot electron injection to drive a surplus of electrons into the floating gate of each cell; secondly, subjecting all cells with the block to a first erase pulse which causes the surplus electrons within the floating gate of each cell to be driven into the cell's source region via Fowler-Nordheim tunneling, with the erase pulse being of sufficient length to erase every cell within the block; thirdly, subjecting all cells within the block to a word line stress step or a soft programming step, by means of which some electrons are driven back into the floating gate of each cell via Fowler-Nordheim tunneling or hot electron injection, respectively; and, fourthly, subjecting all cells within the block to a second erase pulse, the second erase pulse being at least an order of magnitude shorter than the first erase pulse. Use of the second erase pulse following the word line stress step not only shifts the threshold voltage distribution to a somewhat lower level, but also compresses the distribution. Since compression on the high side of the curve is greater than on the low side, the length of the second erase pulse can be tailored to fit the characteristics of a particular flash memory.
REFERENCES:
patent: 5295107 (1994-03-01), Okazawa et al.
patent: 5313427 (1994-05-01), Schreck
patent: 5347490 (1994-09-01), Terada et al.
patent: 5400286 (1995-03-01), Chu et al.
patent: 5452248 (1995-09-01), Narwke et al.
Fox III Angus C.
Micro)n Technology, Inc.
Popek Joseph A.
LandOfFree
Method for narrowing threshold voltage distribution in a block e does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method for narrowing threshold voltage distribution in a block e, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method for narrowing threshold voltage distribution in a block e will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1012344