Multi-bit flash memory device having improved program rate
View Patent ↗A method is provided for programming a nonvolatile memory array including an array of memory cells, where each memory cell including a substrate, a control gate, a charge storage element having at least two charge storage areas for storing at least two independent charges, a source region and a drain region. The method includes designating at least one memory cell as a high-speed memory cell and pre-conditioning the high-speed memory cells by placing a first of the at least two charge storage areas into a programmed state, and subsequently enabling the programming on the second area with much higher rate.
1. A method of programming a nonvolatile memory device including an array of memory cells, each memory cell including a charge storage element having at least two charge storage areas for storing at least two independent charges, the method comprising:
designating a plurality of memory cells as high-speed memory cells; and
pre-conditioning the high-speed memory cells to place a first one of the at least two charge storage areas into a programmed state.
2. The method of claim 1 , wherein the memory cells are dual-bit memory cells having two charge storage areas.
3. The method of claim 1 , further comprising:
setting a status bit associated with the high-speed memory cells.
4. The method of claim 1 , further comprising:
receiving a program command to program the high-speed memory cells; and
programming the high-speed memory cells to place a second one of the at least two charge storage areas into a programmed state.
5. The method of claim 4 , wherein programming the high-speed memory cells, further includes applying a program pulse to the high speed memory cells.
6. The method of claim 5 , further comprising:
verifying that the high-speed memory cells have been programmed.
7. The method of claim 1 , further comprising:
transferring data from the high-speed memory cells to memory cells in the array that have not been designated as high-speed memory cells.
8. The method of claim 1 , further comprising:
designating the high-speed memory cells as normal mode memory cells;
erasing the high speed memory cells to place the first one of the at least two charge storage areas for each of the high-speed memory cells into a non-programmed state; and
resetting a status bit associated with the high-speed memory cells.
9. The method of claim 1 , wherein the array of memory cells comprises a 1-gigabit array of NOR-type dual-bit memory cells.
10. The method of claim 9 , wherein the 1-gigabit array of NOR-type memory cells includes multiple 128-megabit blocks of memory cells.
11. The method of claim 10 , comprising:
designating at least one block of memory cells as a high-speed block of memory cells; and
pre-conditioning the at least one block of high-speed memory cells to place the first of the at least two charge storage areas for each memory cell in the at least one block of high-speed memory cells into a programmed state.
12. A method for programming a memory device including an array of non-volatile memory cells, each memory cell including a charge storage element having two charge storage areas for storing two independent charges, the method comprising:
configuring the array of non-volatile dual-bit memory cells into one or more blocks of memory cells;
receiving a request to use at least one block of memory cells as a high-speed block;
pre-conditioning the memory cells in the high-speed block to place a first of the at least two charge storage areas for each memory cell in the high-speed block into a programmed state; and
setting a status bit associated with the high-speed block to indicate that the block is a high-speed block.
13. The method of claim 12 , wherein the memory cells are SONOS (silicon-oxide-nitride-oxide-silicon) type NOR memory cells.
14. The method of claim 12 , comprising:
receiving a request to program one or more memory cells in the high-speed block;
applying a program pulse to the requested memory cells to place a second of the at least two charge storage areas for each requested memory cell into a programmed state; and
verifying that the memory cells in the high-speed block have been programmed.
15. The method of claim 12 , comprising:
receiving a request to transfer data between the high-speed block and another block; and
transferring the data from a second of the at least two charge storage areas for each memory cell in the high-speed block to either the first or second charge storage areas in a memory cell in the another block.
16. The method of claim 12 , comprising:
receiving a request to return the high-speed block to a normal mode block;
applying erase pulses to each memory cell in the high-speed block to place both the first and second charge storage areas into non-programmed states; and
resetting the status bit to indicate that the block is a normal mode block.
17. A memory device comprising:
a core array including at least one array of non-volatile memory cells, the at least one array comprising:
a plurality of bit lines each connected to source or drain regions of a plurality of the memory cells, the plurality of memory cells comprising:
a substrate;
a control gate;
a charge storage element having at least two charge storage areas for storing at least two independent charges;
a source region; and
a drain region; and
a plurality of word lines, arranged orthogonally to the bit lines, each word line being connected to gate regions of a plurality of the memory cells;
a plurality of sense amplifiers operatively connected to the plurality of bit lines for sensing a threshold voltage for memory cells connected to the bit lines;
control logic configured to receive a command identifying one or more memory cells to be configured as high-speed memory cells;
control logic configured to pre-condition a first of the at least two charge storage areas of each of the high-speed memory cells to place the first charge storage area into a programmed state; and
control logic configured to set a status bit associated with the one or more memory cells, indicating that the one or more memory cells are high-speed memory cells.
18. The memory device of claim 17 , wherein the memory cells are dual-bit NOR-type memory cells configured to include two charge storage areas for storing two independent charges.
19. The memory device of claim 17 , comprising:
control logic configured to receive a command to program one or more of the high-speed memory cells; and
control logic to apply a programming pulse to the one or more of the high-speed memory cells, thereby placing the second charge storage area into a programmed state.
20. The memory device of claim 17 , comprising:
control logic configured to receive a command to erase one or more programmed high-speed memory cells; and
control logic to apply an erase pulse to the one or more programmed high-speed memory cells, thereby placing the second charge storage area into a non-programmed state.
21. A memory device comprising an array of memory cells, the array of memory cells including:
a first plurality of memory cells configured as normal mode memory cells;
a second plurality of memory cells configured as high-programming rate mode memory cells,
where each of the memory cells in the first plurality of memory cells and the second plurality of memory cells includes at least two charge storage areas; and
control logic configured to adjust the number of memory cells associated with the first plurality of memory cells and the second plurality of memory cells based on an input command,
where the control logic is configured to pre-condition a selected memory cell in the first plurality of memory cells to place one of the at least two charge storage areas into a programmed state, thereby removing the selected memory cell from the first plurality of memory cells and placing the selected memory cell into the second plurality of memory cells.
22. The memory device of claim 21 , wherein each of the second plurality of memory cells includes one bit available for programming and each of the first plurality of memory cells includes two bits available for programming.