Multi-pass programming for memory with reduced data storage requirement
Coupling effects between adjacent floating gates in a non-volatile storage device are reduced in a multi-pass programming operation, while reducing program data storage requirements. In one approach, storage elements are programmed in an out of sequence or zigzag word line order. A particular word line is programmed with a coarse program pass, after which another word line is programmed with a fine program pass, after which the particular word line is read. The particular word line is read before another word line is programmed with a coarse program pass which causes coupling interference to storage elements of the particular word line. The read data is subsequently used to perform a fine program pass for the particular word line. This avoids the need to store program data of multiple word lines concurrently, so that storage hardware can be reduced in size along with power consumption.
1. A method for operating non-volatile storage, comprising:
(a) programming a particular non-volatile storage element to raise its threshold voltage above a coarse verify level, including verifying that the threshold voltage is above the coarse verify level, the coarse verify level is associated with a target data state of the particular non-volatile storage element;
(b) after the verifying, programming at least one other non-volatile storage element which is series-connected to the particular non-volatile storage element;
(c) reading the particular non-volatile storage element after the programming of the at least one other non-volatile storage element, to classify the particular non-volatile storage element into the target data state based on the threshold voltage; and
(d) responsive to the classifying, further programming the particular non-volatile storage element to raise its threshold voltage above a fine verify level associated with the target data state.
2. The method of claim 1 , wherein:
the classifying comprises determining that the threshold voltage is in a threshold voltage interval associated with the target data state.
3. The method of claim 1 , wherein:
the particular non-volatile storage element and the at least one other non-volatile storage element are in a NAND string of a memory device.
4. The method of claim 3 , further comprising:
storing first binary data in the memory device, the programming of step (a) is responsive to the first binary data; and
storing second binary data in the memory device in response to the reading, the further programming of step (d) is responsive to the second binary data but not the first binary data, and the second binary data is not stored in the memory device during the programming of step (a).
5. The method of claim 1 , further comprising:
prior to step (a), programming the particular non-volatile storage element using a first page of data, the programming of step (a) is a first programming pass using a second page of data, and the further programming of step (d) is a second programming pass using the second page of data.
6. The method of claim 1 , wherein:
the reading includes applying, in turn, a plurality of control gate read voltages which are associated with a corresponding plurality of target data states, to the particular non-volatile storage element.
7. A non-volatile storage apparatus, comprising:
a set of non-volatile storage elements on a memory chip; and
one or more control circuits in communication with the set of non-volatile storage elements, the one or more control circuits: (a) in a coarse programming pass, program a particular non-volatile storage element of the set to raise its threshold voltage to a first level which is above a first verify level, including verifying that the threshold voltage is above the first verify level, the first verify level is associated with a target data state of the particular non-volatile storage element, (b) read the particular non-volatile storage element after the verifying to obtain read data which indicates a target data state to which the particular non-volatile storage element is to be programmed to in a fine programming pass, and (c) responsive to the read data, further program the particular non-volatile storage element in the fine programming pass to raise its threshold voltage above a second verify level, the second verify level is based on the read data.
8. The non-volatile storage apparatus of claim 7 , wherein;
the particular non-volatile storage element is series-connected to other non-volatile storage elements in the set of non-volatile storage elements; and
the one or more control circuits program at least one of the other non-volatile storage elements after the programming of the particular non-volatile storage element in the coarse programming pass and before the reading and the further programming of the particular non-volatile storage element in the fine programming pass.
9. The non-volatile storage apparatus of claim 7 , wherein the one or more control circuits:
store first binary data in the memory chip;
perform the programming of the particular non-volatile storage element in the coarse programming pass responsive to the first binary data;
store the read data in the memory chip in response to the reading of the particular non-volatile storage element after the programming; and
perform the further programming of the particular non-volatile storage element in the fine programming pass responsive to the read data but not the first binary data.
10. The non-volatile storage apparatus of claim 7 , wherein:
prior to the programming of the particular non-volatile storage element in the coarse programming pass, the one or more control circuits program the particular non-volatile storage element using a first page of data;
the one or more control circuits perform the programming of the particular non-volatile storage element in the coarse programming pass using a second page of data; and
the one or more control circuits perform the further programming of the particular non-volatile storage element in the fine programming pass using the second page of data.
11. The non-volatile storage apparatus of claim 7 , wherein:
to perform the reading of the particular non-volatile storage element, the one or more control circuits apply, in turn, a plurality of control gate read voltages which are associated with a corresponding plurality of data states, to the particular non-volatile storage element.