Program method of flash memory capable of compensating read margin reduced due to charge loss
First Claim
1. A program method of a flash memory device including a plurality of memory cells for storing multi-bit data indicating one of a plurality of states, the program method comprising:
- programming selected memory cells with multi-bit data to have one of the plurality of states;
detecting programmed memory cells arranged within a predetermined threshold voltage region among the memory cells of the respective states, wherein the predetermined threshold region of the respective states is selected by both one of a first verify voltage and a read voltage and a second verify voltage, the second verify voltage being higher than the first verify voltage; and
programming the detected memory cells to have a threshold voltage equivalent to or higher than the second verify voltage corresponding to the respective states, wherein the second verify voltages are set to have different voltage levels.
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Abstract
The present invention provides a program method of a flash memory device including a plurality of memory cells for storing multi-bit data indicating one of a plurality of states. The memory cells are subjected to a primary program operation. Those memory cells arranged within a specific region of respective states are subjected to a secondary program operation to have a threshold voltage equivalent to or higher than a verify voltage used in the primary program operation. Thus, although a threshold voltage distribution is widened due to an electric field coupling/F-poly coupling and HTS, a read margin between adjacent states may be sufficiently secured using the program method.
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Citations
14 Claims
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1. A program method of a flash memory device including a plurality of memory cells for storing multi-bit data indicating one of a plurality of states, the program method comprising:
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programming selected memory cells with multi-bit data to have one of the plurality of states; detecting programmed memory cells arranged within a predetermined threshold voltage region among the memory cells of the respective states, wherein the predetermined threshold region of the respective states is selected by both one of a first verify voltage and a read voltage and a second verify voltage, the second verify voltage being higher than the first verify voltage; and programming the detected memory cells to have a threshold voltage equivalent to or higher than the second verify voltage corresponding to the respective states, wherein the second verify voltages are set to have different voltage levels. - View Dependent Claims (2, 3, 4, 5)
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6. A program method of a flash memory device including a plurality of memory cells for storing multi-bit data indicating at least one of first, second, third or fourth states, the program method comprising:
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programming selected memory cells with multi-bit data to have one of the first, second, third or fourth states; detecting programmed cells arranged within a predetermined threshold voltage region where programmed memory cells of the second state are distributed wherein the predetermined region of the second state is selected by both one of a first verify voltage and a read voltage and a second verify voltage associated with said second state, said second verify voltage associated with said second state being higher than said first verify voltage associated with said second state; programming the detected memory cells to have a voltage equivalent to or higher than a second verify voltage corresponding to the second state; detecting programmed memory cells arranged within a predetermined threshold voltage region where programmed memory cells of the third state are distributed, wherein the predetermined region of the third state is selected by both one of a first verify voltage and a read voltage and a second verify voltage associated with said third state, said second verify voltage associated with said third state being higher than said first verify voltage associated with said third state; programming the detected memory cells to have a threshold voltage equivalent to or higher than a second verify voltage corresponding to said third state; detecting programmed memory cells arranged within a predetermined threshold voltage region where programmed memory cells of said fourth state are distributed, wherein the predetermined region of the fourth state is selected by both one of a first verify voltage and a read voltage and a second verify voltage associated with said fourth state, said second verify voltage associated with said fourth state being higher than said first verify voltage associated with said fourth state; and programming the detected memory cells to have a threshold voltage equivalent to or higher than a second verify voltage corresponding to the fourth state, wherein voltage differences between first and second voltages associated with said second, and third states are different from each other. - View Dependent Claims (7, 8, 9)
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10. A program method of a flash memory device including a plurality of memory cells for storing multi-bit data indicating at least one of a plurality of states, the program method comprising:
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programming selected memory cells with multi-bit data to have one of the plurality of states; detecting programmed memory cells arranged within a predetermined threshold voltage region where programmed memory cells of at least two of the plurality of states are distributed wherein each predetermined region of the respective two or more states is selected by both one of a first verify voltage and a read voltage and a second verify voltage, the second verify voltage being higher than the first verify voltage; and programming the programmed memory cells to have a threshold voltage equivalent to or higher than a second verify voltage corresponding to the at least two of the plurality of states, wherein second verify voltages corresponding to the at least two states of the plurality of states are set to have different voltage levels. - View Dependent Claims (11, 12, 13, 14)
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Specification