US 5,633,823 A · Method of narrowing flash memory device threshold voltage distribution

Abstract

A method of erasing a sector for a flash memory device, the sector having a plurality of word lines with each word line having a plurality of memory cells therealong, each cell having a source region, comprises various steps. First, all of the memory cells in the sector are programmed. The memory cells are then simultaneously erased by applying a first voltage to the sources and a second voltage to the word lines. Subsequently, a first cell along a first word line is read to determine if the first cell is under-erased. Responsive to the first cell being under-erased, the first voltage is applied to the source region of the first cell and the second voltage is applied to the first word line while a third voltage is applied to the plurality of word lines except the first word line, the third voltage being higher than the second voltage.

Claims17

Dependent claims

A method of erasing memory cells in a sector of a memory device, said sector having a plurality of word lines and a plurality of memory cells along each of said word lines, said method comprising:

erasing a group of said memory cells in said sector simultaneously;
subsequent to said step of erasing, reading a first cell of said group along a first word line to determine if said first cell is under-erased;
responsive to said first cell being under-erased, further erasing only those cells of said group which are along said first word line by applying a negative voltage to said first word line and, simultaneously a voltage greater than or equal to 0.0 volts to each word line of said plurality of word lines except said first word line.

Dependencies are inferred from the claim text.

Method of narrowing flash memory device threshold voltage distribution

Life of this patent

Method of narrowing flash memory device threshold voltage distribution

Life of this patent

Abstract

Claims17