Programming method for flash memory capable of compensating reduction of read margin between states due to high temperature stress
First Claim
1. A programming method for a flash memory device having a plurality of memory cells storing multi-bit data indicating one of a plurality of states, the programming method comprising:
- programming selected memory cells with multi-bit data to have one of the plurality of states using a first programming operation;
following programming of the selected memory cells with multi-bit data using the first programming operation, detecting programmed memory cells arranged within a predetermined region of a threshold voltage distribution, the region corresponding to at least two of the plurality of states, wherein predetermined regions of the respective at least two of the plurality of states are selected by one of a first verify voltage and a read voltage and a second verify voltage, the first verify voltage being lower than the second verify voltage and higher than the read voltage; and
following detection of the programmed memory cells and using a second programming operation, simultaneously programming detected memory cells of the at least two of the plurality of states to have a threshold voltage equivalent to or higher than the second verify voltage corresponding to each of the plurality of states.
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Abstract
A programming method of a flash memory device having a plurality of memory cells for storing multi-bit data indicating one of a plurality of states. The programming method includes programming selected memory cells using multi-bit data to have one of the states; detecting programmed memory cells arranged within a predetermined region of threshold voltage distribution each corresponding to at least two of the states, wherein predetermined regions of the respective at least two states are selected by one of a first verify voltage and a read voltage and a second verify voltage, the first verify voltage being lower than the second verify voltage and higher than the read voltage; and simultaneously programming detected memory cells of the at least two states to have a threshold voltage being equivalent to or higher than the second verify voltage corresponding to each of the states.
3 Citations
19 Claims
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1. A programming method for a flash memory device having a plurality of memory cells storing multi-bit data indicating one of a plurality of states, the programming method comprising:
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programming selected memory cells with multi-bit data to have one of the plurality of states using a first programming operation; following programming of the selected memory cells with multi-bit data using the first programming operation, detecting programmed memory cells arranged within a predetermined region of a threshold voltage distribution, the region corresponding to at least two of the plurality of states, wherein predetermined regions of the respective at least two of the plurality of states are selected by one of a first verify voltage and a read voltage and a second verify voltage, the first verify voltage being lower than the second verify voltage and higher than the read voltage; and following detection of the programmed memory cells and using a second programming operation, simultaneously programming detected memory cells of the at least two of the plurality of states to have a threshold voltage equivalent to or higher than the second verify voltage corresponding to each of the plurality of states. - View Dependent Claims (2, 3, 4)
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5. A programming method for a flash memory device having a plurality of memory cells storing multi-bit data indicating one of at least four data states, the programming method comprising:
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programming selected memory cells using multi-bit data to have one of second through fourth states using a first programming operation; after programming of the selected memory cells using the first programming operation, detecting programmed memory cells, wherein detecting programmed memory cells comprises; detecting programmed memory cells arranged within a predetermined region of a threshold voltage distribution corresponding to the second state, wherein the predetermined region of the second state is defined in relation to one of a first verify voltage and a first read voltage and a second verify voltage, the first verify voltage being lower than the second verify voltage and higher than the first read voltage; detecting programmed memory cells arranged within a predetermined region of a threshold voltage distribution corresponding to the third state, wherein the predetermined region of the third state is defined in relation to one of a third verify voltage and a second read voltage and a fourth verify voltage, the third verify voltage being lower than the fourth verify voltage and higher than the second read voltage; and after detecting programmed memory cells, simultaneously programming the detected memory cells of the second state and the detected memory cells of the third state to have a threshold voltage equivalent to or higher than the second and fourth verify voltages, respectively. - View Dependent Claims (6, 7, 8, 9, 10)
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11. A programming method for a flash memory device having a plurality of memory cells for storing multi-bit data indicating one of first through fourth data states, the programming method comprising:
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programming selected memory cells using multi-bit data to have one of the second through fourth states using a first programming operation; after programming of the selected memory cells using the first programming operation, detecting programmed memory cells, wherein detecting programmed memory cells comprises; detecting programmed memory cells arranged within a predetermined region of a threshold voltage corresponding to the second state, wherein the predetermined region of the second state is selected by one of a first verify voltage and a first read voltage, and a second verify voltage, the first verify voltage being lower than the second verify voltage and higher than the first read voltage; detecting programmed memory cells arranged within a predetermined region of a threshold voltage distribution corresponding to the third state, wherein the predetermined region of the third state is selected by one of a third verify voltage and a second read voltage, and a fourth verify voltage, the third verify voltage being lower than the fourth verify voltage and higher than the second read voltage; detecting programmed memory cells arranged within a predetermined region of a threshold voltage corresponding to the fourth state, wherein the predetermined region of the fourth state is selected by one of a fifth verify voltage and a third read voltage, and a sixth verify voltage, the fifth verify voltage being lower than the sixth verify voltage and higher than the third read voltage; and after detecting the programmed memory cells, simultaneously programming the detected memory cells of the second state, the detected memory cells of the third state, and the detected memory cells of the fourth state to respectively have a threshold voltage equivalent to or higher than the second, fourth, and sixth verify voltages. - View Dependent Claims (12, 13, 14)
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15. A programming method for a flash memory device having a plurality of memory cells storing multi-bit data indicating an erased state or one of a plurality of programmed states, the programming method comprising:
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programming selected memory cells with multi-bit data to have one of the plurality of programmed states; detecting programmed memory cells arranged within a predetermined region of a threshold voltage distribution, the predetermined region corresponding to at least first and second states of the plurality of programmed states, wherein a first portion of the predetermined region corresponding to the first state is defined in relation to a first verify voltage, a first read voltage and a second verify voltage, the first verify voltage being lower than the second verify voltage and higher than the first read voltage, and a second portion of the predetermined region corresponding to the second state is defined in relation to a third verify voltage, a second read voltage and a fourth verify voltage, the third verify voltage being lower than the fourth verify voltage and higher than the second read voltage; and
following detection of the programmed memory cells,simultaneously programming the detected memory cells of first state to have a threshold voltage greater than or equal to the second verify voltage, and the detected memory cells of second state to have a threshold voltage greater than or equal to the fourth verify voltage. - View Dependent Claims (16, 17, 18, 19)
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Specification