Apparatus for reducing the impact of program disturb
The unintentional programming of an unselected (or inhibited) non-volatile storage element during a program operation that intends to program another non-volatile storage element is referred to as “program disturb.” A system is proposed for programming and/or reading non-volatile storage that reduces the effect of program disturb. In one embodiment, different verify levels are used for a particular word line (or other grouping of storage elements) during a programming process. In another embodiment, different compare levels are used for a particular word (or other grouping of storage elements) during a read process.
1. A non-volatile storage system, comprising:
non-volatile storage elements, said non-volatile storage elements include a first set of non-volatile storage elements connected to a first control line and a second set of non-volatile storage elements connected to a second set of control lines different than said first control line; and
a managing circuit in communication with said non-volatile storage elements, said managing circuit causes programming of said first set of non-volatile storage elements using a first set of target levels and subsequently causes programming of said second set of non-volatile storage elements using a second set of target levels different than said first set of target levels.
2. A non-volatile storage system according to claim 1 , wherein:
said first set of non-volatile storage elements and said second set of non-volatile storage elements are multi-state NAND flash memory devices.
3. A non-volatile storage system according to claim 2 , wherein:
said non-volatile storage elements are arranged in blocks, each block includes a set of pages, said pages define units of programming and blocks define units of erase;
said first control line and said second set of control lines are part of a particular block;
said particular block includes a set of bit lines; and
each of said first set of non-volatile storage elements are connected to a different bit line of said set of bit lines.
4. A non-volatile storage system according to claim 3 , wherein:
said first set of target levels includes a first verify level for a first programmed state, a second verify level for a second programmed state and a third verify level for a third programmed level; and
said second set of target levels includes a different verify level for said first programmed state, said second verify level for said second programmed state and said third verify level for said third programmed level.
5. A non-volatile storage system according to claim 3 , wherein:
said first set of target levels includes a first verify level for a first programmed state, a second verify level for a second programmed state and a third verify level for a third programmed level; and
said second set of target levels includes a fourth verify level for said first programmed state, a fifth verify level for said second programmed state and a sixth verify level for said third programmed level, said fourth verify level is less than said second verify level.
6. A non-volatile storage system according to claim 3 , wherein:
said first control line is a word line that is adjacent to a source control line.
7. A non-volatile storage system according to claim 1 , wherein:
said managing circuit causes programming of said first set of non-volatile storage elements using a first set of target levels for a first page of data and using a third set of target levels for a second page of data.
8. A non-volatile storage system according to claim 1 , wherein:
said non-volatile storage elements include a third set of non-volatile storage elements connected to said first control line; and
said managing circuit causes programming of said third set of non-volatile storage elements using a third set of target levels.
9. A non-volatile storage system according to claim 1 , wherein:
said managing circuit reads said first set of non-volatile storage elements using a first read compare value and reads said second set of non-volatile storage elements using said first read compare value.