NAND flash memory having multiple cell substrates
First Claim
1. A method for selectively providing an erase voltage to a NAND flash device having a first well sector, a second well sector and at least one memory block formed within each of the first and second well sectors, the method comprising:
- selecting one of the at least two memory blocks for erasure of NAND cell strings in response to a block address;
selecting the first well sector in response to at least a portion of the block address; and
,applying the erase voltage to the first well sector.
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Accused Products
Abstract
A NAND flash memory bank having a plurality of bitlines of a memory array connected to a page buffer, where NAND cell strings connected to the same bitline are formed in at least two well sectors. At least one well sector can be selectively coupled to an erase voltage during an erase operation, such that unselected well sectors are inhibited from receiving the erase voltage. When the area of the well sectors decrease, a corresponding decrease in the capacitance of each well sector results. Accordingly, higher speed erasing of the NAND flash memory cells relative to a single well memory bank is obtained when the charge pump circuit drive capacity remains unchanged. Alternately, a constant erase speed corresponding to a single well memory bank is obtained by matching a well segment having a specific area to a charge pump with reduced drive capacity. A reduced drive capacity charge pump will occupy less semiconductor chip area, thereby reducing cost.
128 Citations
17 Claims
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1. A method for selectively providing an erase voltage to a NAND flash device having a first well sector, a second well sector and at least one memory block formed within each of the first and second well sectors, the method comprising:
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selecting one of the at least two memory blocks for erasure of NAND cell strings in response to a block address; selecting the first well sector in response to at least a portion of the block address; and
,applying the erase voltage to the first well sector. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A method for controlling a NAND flash device having at least two well sectors, each having at least one memory block, comprising:
turning off an isolation device connected between a first bitline segment connected to a first memory block in a first well sector and to a second bitline segment connected to a second memory block in a second well sector in a memory operation. - View Dependent Claims (9, 10, 11, 12, 13, 14, 15, 16, 17)
Specification