Method for non-volatile memory with reduced erase/write cycling during trimming of initial programming voltage
AssigneeSanDisk Corporation
InventorsYan Li, Loc Tu, Charles Moana Hook
Life of this patent
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Abstract
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 in 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.
Claims17
In a non-volatile memory having 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 method of determining a starting programming voltage for a given page, comprising:
- (a) selecting a sample of pages representative of the given page within a block;
- (b) providing 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;
- (c) erasing the block containing the sample of pages;
- (d) determining for every page in the sample if the page is programmable to a target pattern using the associated programming voltage with the associated initial value;
- and if programmable, 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;
- (e) repeating (c) to (d) until all pages in the sample has either been determined to be programmable or the associated initial value has been incremented to a predetermined maximum voltage;
- (f) computing an average starting programming voltage for the sample from the gathered statistics to derive a starting programming voltage for the page.
Dependencies are inferred from the claim text.