Non-volatile memory with reduced erase/write cycling during trimming of initial programming voltage
High performance non-volatile memory devices have the programming voltages trimmed for individual types of memory pages and word lines. A group of word lines within each erasable block of memory are tested successive program loops to minimize the problem of incurring excessive number of erase/program cycles. An optimum programming voltage for a given type of memory pages is derived from statistical results of a sample of similar of memory pages.
1. A non-volatile memory comprising:
an array of memory cells that is organized into erasable blocks, each erasable block containing a block of word lines for accessing memory cells that are erasable together, and each word line containing at least one page of memory cells that are programmable together;
a designated sample of pages representative of the given page within a block;
an associated programming voltage for programming each page of the sample, the associated programming voltage having a staircase waveform with an associated initial value and a predetermined number of steps;
a built-in self testing module for determining the associated initial value for a given page, said module providing memory operations including:
(a) erasing the block containing the sample of pages;
(b) determining for every page in the sample if the page is programmed to a target pattern using the associated programming voltage with the associated initial value; and if programmed, excluding the page from further processing after accumulating the associated initial value as part of a gathered statistics, otherwise, incrementing the associated initial value by a predetermined step;
(c) repeating (a) to (b) until each of the sample of pages has either been program-verified or been programmed with the associated programming voltage incremented to a predetermined maximum voltage; and
(d) providing the gathered statistic for computing an average initial value for the sample and for deriving a starting programming voltage for the page based on the average initial value of the sample.
2. The memory as in claim 1 , wherein
the predetermined step increment of the associated initial value is commensurate with a step of a similar programming voltage applied to the memory during a normal program operation.
3. The memory as in claim 1 , wherein the predetermined number of steps of the staircase waveform of the associated programming voltage is fifteen or less.
4. The memory as in claim 1 , wherein the predetermined maximum voltage is the initial value plus an integral number of steps of the staircase waveform voltages.
5. The memory as in claim 4 , wherein the integral number of steps is more than forty.
6. The memory as in claim 1 , wherein said module providing memory operations further including:
(e) performing an initial programming on the page with a staircase waveform programming voltage having a starting voltage;
(f) verifying if a target pattern has been programmed to the page in between each of the steps of the staircase waveform;
(g) obtaining a final voltage of the staircase waveform when the page is program-verified; and
(h) estimating the associated starting programming voltage by linear scaling of the final voltages; and
wherein (e)-(h) are performed prior to (a)-(d).
7. The memory as in claim 1 , wherein the gathered statistic is processed by an external tester in communication with said non-volatile memory.
8. The memory as in claim 2 , wherein the gathered statistic is processed by an external tester in communication with said non-volatile memory.
9. The memory as in claim 3 , wherein the gathered statistic is processed by an external tester in communication with said non-volatile memory.
10. The memory as in claim 4 , wherein the gathered statistic is processed by an external tester in communication wit said non-volatile memory.
11. The memory as in claim 5 , wherein the gathered statistic is processed by an external tester in communication with said non-volatile memory.
12. The memory as in claim 6 , wherein the gathered statistic is processed by an external tester in communication with said non-volatile memory.
13. The memory as in claim 1 , wherein the gathered statistic is processed by said built-in self-testing module.
14. The memory as in claim 2 , wherein the gathered statistic is processed by said built-in self-testing module.
15. The memory as in claim 3 , wherein the gathered statistic is processed by said built-in self-testing module.
16. The memory as in claim 4 , wherein the gathered statistic is processed by said built-in self-testing module.
17. The memory as in claim 5 , wherein the gathered statistic is processed by said built-in self-testing module.
18. The memory as in claim 6 , wherein the gathered statistic is processed by said built-in self-testing module.
19. The memory as in any one of claims 1 - 18 , wherein individual memory cells each stores one bit of data.
20. The memory as in any one of claims 1 - 18 , wherein individual memory cells each stores more than one bit of data.