Method for programming a memory device suitable to minimize the lateral coupling effects between memory cells
View Patent ↗A method programs a memory device that includes at least one memory cell matrix. The programming method the steps of: erasing the memory cells; soft programming the memory cells; and complete programming of a group of such memory cells each of them storing its own logic value. Advantageously, the first complete programming step of a group of such memory cells involves cells belonging to a block (A) of the matrix being electrically insulated from the rest of the matrix. A memory device suitable to implement the proposed method is also described.
1. A method for programming a memory device that includes a memory cell matrix, the method comprising:
erasing memory cells of the memory cell matrix;
soft programming a first group of said memory cells, the first group of memory cells involving cells belonging to a first block of said matrix, the first block being electrostatically insulated from other blocks of cells of said matrix so as to reduce capacitive coupling between said first block and said other blocks; and
completely programming the first group of memory cells without simultaneously programming memory cells that are not in the first block of said matrix, each of the memory cells in the first group storing its own logic value.
2. The programming method according to claim 1 , further comprising initially separating and redistributing a sequence of bytes into bit packages, each bit package being allotted to a separate block of a plurality of said blocks of said memory matrix, the blocks being electrostatically insulated from each other so as to reduce capacitive coupling between said blocks.
3. The programming method according to claim 1 , wherein said completely programming simultaneously involves cells belonging to one or more word lines of said memory cell matrix.
4. The programming method according to claim 1 , wherein said erasing is performed by using a reduced value of an erasing voltage reference.
5. The programming method according to claim 4 , wherein said reduced value of said erasing voltage reference is equal to a standard erasing voltage reference decreased by a value corresponding to a maximum disturb value due to capacitive coupling between adjacent cells in said memory matrix.
6. The programming method according to claim 1 , further comprising partially programming a second group of cells of said first block, each cell of the second group storing its own logic value, suitable to bring said cells of the second group to a threshold value near a first threshold value lower than a first standard threshold value.
7. The programming method according to claim 6 , further comprising performing a complete final programming of said second group of cells by using a sequence of tests and successive programming pulses.
8. The programming method according to claim 7 , further comprising repeating said complete programming, partial programming and final programming on all of a plurality of said blocks of cells of said memory device, the blocks being electrostatically insulated from each other so as to reduce capacitive coupling between said blocks.
9. The programming method according to claim 6 , further comprising partially programming a third group of cells of said first block, each cell of the third group storing its own logic value, suitable to bring said cells of the third group to a threshold value near a second threshold value lower than a second standard threshold value.
10. The programming method according to claim 9 , further comprising performing a complete final programming of said second and third groups of cells by using a sequence of tests and successive programming pulses.
11. The programming method according to claim 10 , further comprising repeating said complete programming, partial programming of the second group of cells, partial programming of the third group of cells, and final programming on all of a plurality of said blocks of cells of said memory device, the blocks being electrostatically insulated from each other so as to reduce capacitive coupling between said blocks.
12. The programming method according to claim 10 , further comprising optimizing positions of reading reference values.
13. The programming method according to claim 12 , wherein said optimizing determines said reading reference values so that a threshold voltage range dedicated to alloting threshold distributions also includes a range due to a residual widening caused by lateral coupling between memory cells of the matrix.
14. A memory device, comprising:
a memory cell matrix of memory cells; and
a dedicated logic block coupled to said memory cell matrix and suitable to perform a separation and redistribution of a sequence of bytes into bit packages, each bit package being sent to a respective block of a plurality of blocks of said memory matrix, the blocks being electrically insulated from each other.
15. The memory device according to claim 14 , wherein said dedicated logic block is sized based on a number of cells (ncell) comprised in each wordline of each block, a number of bits (nbit) stored by each cell, a number of wordlines (nwl) in each block, and a number of outputs (nout) of said block according to a relation:
Dwb=n bit× n cell× nwl×n out
Dwb being a minimum size of said dedicated logic block.
16. The memory device according to claim 14 , wherein each block is delimited by source and drain contacts of said memory cell matrix.
17. The memory device according to claim 14 , wherein each block belongs to a single respective wordline and each block is delimited by source and drain contacts and by a source diffusion of said memory cell matrix.
18. A method for programming a memory device that includes a memory cell matrix, the method comprising:
erasing memory cells of the memory cell matrix;
soft programming the erased memory cells;
receiving a byte sequence of bytes, each byte including a plurality of bits;
redistributing the bits of the byte sequence into bit packages respectively allotted to respective blocks of a plurality of blocks of the matrix, each block being electrically insulated from each other; and
completely programming a first group of memory cells in a first block of the plurality of blocks without simultaneously programming memory cells that are not in the first block.
19. The programming method according to claim 18 , further comprising programming a second group of cells of the first block after completely programming the first group of cells, each of the cells of the first group being programmed to a first logic value and each of the cells of the second group being programmed to a second logic value.
20. The programming method according to claim 19 wherein said programming the second group of cells includes:
partially programming the second group of cells by bringing the cells of the second group to a threshold value near a reduced threshold value lower than a standard threshold value; and
completing programming of the second group of cells by bringing the cells of the second group to the standard threshold value.