Method for non-volatile memory with linear estimation of initial programming voltage
AssigneeSanDisk Corporation
InventorsLoc Tu, Charles Moana Hook, Yan Li
Life of this patent
Estimating the term…
Abstract
In a non-volatile memory, a selected page on a word line is successively programmed by a series of voltage pulses of a staircase waveform with verifications in between the pulses until the page is verified to a designated pattern. The programming voltage at the time the page is programmed verified will be to estimate the initial value of a starting programming voltage for the page. The estimation is further refined by using the estimate from a first pass in a second pass. Also, when the test is over multiple blocks, sampling of word lines based on similar geometrical locations of the blocks can yield a starting programming voltage optimized for faster programming pages.
Claims14
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;
- (b) providing a programming voltage for programming each page of the sample, the programming voltage having a staircase waveform with an initial value and a predetermined maximum voltage limit;
- (c) erasing the sample of pages;
- (d) for every page in the sample, programming and verifying the page step by step of the staircase waveform until either the maximum voltage limit has been reached or the page has been programmed to a target pattern and in which case a final programming voltage is accumulated as part of a gathered statistics;
- and
- (e) computing an average final programming voltage for the sample from the gathered statistics to derive a starting programming voltage for the page.
In a non-volatile memory having an array of memory cells that are organized into blocks, each 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 page, comprising:
- selecting a group of pages representative of the page within a block;
- selecting a set of blocks;
- forming a set of samples by selecting a page from each block, the page being located in a geometrically similar location of each block;
- obtaining a statistical estimation of a programming voltage from each sample of the set;
- and
- determining the starting programming voltage for the page by selecting a minimum statistical estimation among the set.
Dependencies are inferred from the claim text.