Non-volatile memory and method with adjusted timing for individual programming pulses
View Patent ↗A non-volatile memory and method have programming circuitry that outputs a series of programming pulses of increasing voltage level to program in parallel a group of memory cells associated with a selected word line. Individual timing of the programming pulses such as rise and fall times of the pulse is optimally and dynamically adjusted according to the relative numbers of program-enabled and program-inhibited memory cells in the group associated with that pulse.
1. A non-volatile memory, comprising:
an array of memory cells;
a plurality of word lines and bit lines for accessing the array of memory cells; and
a programming circuit for programming a group of memory cells in parallel,
the programming circuit comprising:
word line driver circuitry for providing a programming voltage to a selected word line to the group of memory cells, the programming voltage comprising a series of pulses having increasing voltage levels;
the group of memory cells having a number of program-enabled and program-inhibited memory cells that varies dynamically with each pulse of the series of pulses; and
the word line driver circuitry including a control module to adjust an individual timing of a pulse of the series of pulses, responsive to relative numbers of program-enabled and program-inhibited memory cells in the group of memory cells associated with the pulse.
2. The non-volatile memory as in claim 1 , wherein
the individual timing comprises a rise time and a fall time of the pulse.
3. The non-volatile memory as in claim 1 , wherein:
each memory cell of the array of memory cells has a channel with a word-line-to-channel capacitance between the channel and a respective word line; and
the individual timing depends on a sum of the word-line-to-channel capacitance of the group of memory cells under programming.
4. The non-volatile memory as in claim 3 , wherein
the word-line-to-channel capacitance is a function of the relative numbers of the program-enabled and program-inhibited memory cells in the group of memory cells.
5. The non-volatile memory as in claim 3 , wherein
the individual timing depends on an RC constant of the selected word line, wherein R and C are respectively a resistance and an effective capacitance of the word line, the effective capacitance of the selected word line comprising the word-line-to-channel capacitance.
6. The non-volatile memory as in claim 5 , wherein:
the RC constant has a maximum value of RCmax when all memory cells of the group of memory cells are program-enabled and has a minimum value of RCmin when all memory cells of the group of memory cells are program-inhibited; and
the RC constant is given by (n 2 /N)RCmin+(n 1 /N)RCmax,
where N is the total number of memory cells in the group of memory cells, and n 1 and n 2 are respectively the number of program-enabled and program-inhibited memory cells just prior to the pulse.
7. The non-volatile memory as in claim 1 , wherein
each memory cell of the array of memory cells comprises a charge-storage element.
8. The non-volatile memory as in claim 1 , wherein:
each pulse in the series of pulses is identified by a pulse number; and
the number of program-enabled and program-inhibited memory cells associated with the pulse is a function of the pulse number associated with the pulse.
9. The non-volatile memory as in claim 1 , wherein
the array of memory cells is organized in a 3D pattern.
10. The non-volatile memory as in claim 1 , wherein
the word line driver circuitry further comprises a second control module to adjust a timing of precharging unselected word lines, responsive to relative numbers of program-enabled and program-inhibited memory cells in the group of memory cells associated with the pulse.
11. A method of operating a non-volatile memory, comprising:
providing an array of memory cells;
providing a plurality of word lines and bit lines for accessing the array of memory cells; and
programming a group of memory cells in parallel,
the programming comprising:
applying a programming voltage to a selected word line to the group of memory cells, the programming voltage comprising a series of pulses having increasing voltage levels;
determining a number of program-enabled and program-inhibited memory cells in the group of memory cells that varies dynamically with each pulse of the series of pulses; and
adjusting an individual timing of a pulse of the series of pulses, responsive to relative numbers of program-enabled and program-inhibited memory cells in the group of memory cells associated with the pulse.
12. The method of operating the non-volatile memory as in claim 11 , wherein
the individual timing comprises a rise time and a fall time of the pulse.
13. The method of operating the non-volatile memory as in claim 11 , wherein:
each memory cell of the array of memory cells has a channel with a word-line-to-channel capacitance between the channel and a respective word line; and
the individual timing depends on a sum of the word-line-to-channel capacitance of the group of memory cells under programming.
14. The method of operating the non-volatile memory as in claim 13 , wherein
the word-line-to-channel capacitance is a function of the relative numbers of the program-enabled and program-inhibited memory cells in the group of memory cells.
15. The method of operating the non-volatile memory as in claim 13 , wherein
the individual timing depends on an RC constant of the selected word line, wherein R and C are respectively a resistance and an effective capacitance of the word line, the effective capacitance of the word line comprising the word-line-to-channel capacitance.
16. The method of operating the non-volatile memory as in claim 15 , wherein:
the RC constant has a maximum value of RCmax when all memory cells of the group of memory cells are program-enabled, and has a minimum value of RCmin when all memory cells of the group of memory cells are program-inhibited; and
the RC constant is given by (n 2 /N)RCmin+(n 1 /N)RCmax,
where N is the total number of memory cells in the group of memory cells, and n 1 and n 2 are respectively the number of program-enabled and program-inhibited memory cells just prior to the pulse.
17. The method of operating the non-volatile memory as in claim 11 , wherein
each memory cell of the array of memory cells comprises a charge-storage element.
18. The method of operating the non-volatile memory as in claim 11 , wherein:
each pulse in the series of pulses is identified by a pulse number; and
the number of program-enabled and program-inhibited memory cells associated with the pulse is a function of the pulse number associated with the pulse.
19. The method of operating the non-volatile memory as in claim 11 , further comprising:
adjusting a timing of precharging unselected word lines, responsive to relative numbers of program-enabled and program-inhibited memory cells in the group of memory cells associated with the pulse.
20. A non-volatile memory comprising:
a 3D array of memory cells organized as a 2D array of vertical NAND strings across multiple memory planes above a substrate, with each memory cell of a NAND string residing in a different memory plane;
a plurality of word lines and bit lines for accessing the array of memory cells; and
a programming circuit for programming a group of memory cells in parallel,
the programming circuit comprising:
word line driver circuitry for providing a programming voltage to a selected word line to the group of memory cells, the programming voltage comprising a series of pulses having increasing voltage levels;
the group of memory cells, having a number of program-enabled and a number of program-inhibited memory cells, that varies dynamically with each pulse of the series of pulses; and
the word line driver circuitry comprising a control module to adjust an individual timing of a pulse of the series of pulses, responsive to relative numbers of program-enabled and program-inhibited memory cells in the group of memory cells associated with the pulse.