Non-volatile memory with sub-blocks
A non-volatile memory includes a plurality of non-volatile memory cells arranged in blocks. Each block includes multiple sub-blocks that can be independently erased and programmed. A control circuit is connected to the non-volatile memory cells. The control circuit is configured to independently erase and program sub-blocks of a same block. The control circuit is configured to only allow one sub-block per block to be open at a time.
1 . A non-volatile storage apparatus, comprising:
a plurality of non-volatile memory cells arranged in blocks, each block includes multiple sub-blocks that can be independently erased and programmed; and
a control circuit connected to the non-volatile memory cells, the control circuit is configured to:
receive a request to open a first sub-block of a first block,
determine whether any counter sub-block of the first sub-block is open,
if there is no counter sub-block of the first sub-block that is open, open the first sub-block of the first block, and
if any counter sub-block of the first sub-block is open, identify a sub-block of a different block that has a counter sub-block that is not open and open the sub-block of the different block.
2 . The non-volatile storage apparatus of claim 1 , wherein:
the request to open the first sub-block of the first block is a request to erase the first sub-block of the first block;
the control circuit is configured to open the first sub-block of the first block by erasing the first sub-block of the first block; and
the control circuit is configured to open the sub-block of the different block by erasing the sub-block of the different block.
3 . The non-volatile storage apparatus of claim 1 , wherein:
the request to open the first sub-block of the first block includes a request to erase the first sub-block of the first block;
the control circuit is configured to open the first sub-block of the first block by erasing and programming the first sub-block of the first block; and
the control circuit is configured to open the sub-block of the different block by erasing and programming the sub-block of the different block.
4 . The non-volatile storage apparatus of claim 3 , wherein the control circuit is configured to program the first sub-block of the first block by:
applying a dose of a program voltage to a selected word line of the first sub-block, the first sub-block is open;
applying a first overdrive voltage to unselected word lines of the first sub-block while applying the dose of the program voltage; and
applying a second overdrive voltage to word lines of the one or more counter sub-blocks of the first sub-block while applying the dose of the program voltage, the second overdrive voltage is lower in voltage magnitude than the first overdrive voltage.
5 . The non-volatile storage apparatus of claim 1 , wherein:
the control circuit is configured to allow no more than one sub-block per block to be open at a time.
6 . The non-volatile storage apparatus of claim 1 , wherein:
a sub-block is open if all memory cells connected to any word line in the sub-block are in the erased state; and
a sub-block is closed if every word line of the sub-block is connected to memory cells that are programmed to one or more programmed data states.
7 . The non-volatile storage apparatus of claim 1 , further comprising bit lines and a source line, wherein:
the first block includes the first sub-block and a second sub-block, the second sub-block is the only counter sub-block of the first sub-block;
the first block is connected to the bit lines and the source line;
the first sub-block is positioned closer to the bit lines than the source line; and
the second sub-block is positioned closer to the source line than the bit lines.
8 . The non-volatile storage apparatus of claim 7 , wherein:
the control circuit is configured to program the first sub-block in a direction from the source line to the bit lines; and
the control circuit is configured to program the second sub-block in a direction from the bit lines to the source line.
9 . The non-volatile storage apparatus of claim 1 , wherein:
the control circuit is configured to limit the number of open sub-blocks to a predetermined number; and
the control circuit is configured to scramble host data prior to programming the host data in an open sub-block.
10 . A method of operating non-volatile memory cells arranged in blocks, each block includes multiple sub-blocks, the method comprising:
independently erasing and programming sub-blocks;
receiving requests to erase target sub-blocks;
determining whether the target sub-blocks have any counter sub-blocks that are open or have all one or more counter sub-blocks closed;
for target sub-blocks that have all one or more counter sub-blocks closed, erasing the respective target sub-block; and
for target sub-blocks that have any counter sub-blocks that are open, identifying another sub-block of a different block that has all one or more counter sub-blocks closed and erasing the another sub-block of the different block.
11 . The method of claim 10 , further comprising:
for target sub-blocks that have all one or more counter sub-blocks closed, programming the respective target sub-block after erasing the respective target sub-block; and
for target sub-blocks that have any counter sub-blocks that are open, programming the another sub-block of the different block after erasing the another sub-block of the different block.
12 . The method of claim 11 , wherein the programming the respective target sub-block after erasing the respective target sub-block comprises:
applying doses of a program voltage to a selected word line of the target sub-block, the target sub-block is open;
applying a first overdrive voltage to unselected word lines of the target sub-block while applying the doses of the program voltage; and
applying a second overdrive voltage to word lines of the one or more counter sub-blocks of the target sub-block while applying the doses of the program voltage, the second overdrive voltage is lower in voltage magnitude than the first overdrive voltage.
13 . The method of claim 10 , further comprising:
allowing only one sub-block per block to be open at a time.
14 . The method of claim 10 , wherein:
each of the blocks has two sub-blocks that are counter sub-blocks of each other.
15 . A non-volatile storage apparatus, comprising:
a plurality of non-volatile memory cells arranged in blocks, each block includes multiple sub-blocks that can be independently erased and programmed; and
a control circuit connected to the non-volatile memory cells, the control circuit is configured to separately erase and program sub-blocks of a same block, the control circuit is configured to allow no more than one sub-block per block to be open at a time by:
receiving a request to erase a first sub-block of a first block,
determining whether any counter sub-block of the first sub-block is open,
if there is no counter sub-block of the first sub-block that is open, erasing and programming the first sub-block of the first block, and
if any counter sub-block of the first sub-block is open, identifying a sub-block of a different block that has a counter sub-block that is not open and erasing and programming the sub-block of the different block.
16 . The non-volatile storage apparatus of claim 15 , wherein:
a sub-block is open if all memory cells connected to any word line in the sub-block are in the erased state; and
a sub-block is closed if every word line of the sub-block is connected to memory cells that are programmed to one or more programmed data states.
17 . The non-volatile storage apparatus of claim 15 , further comprising bit lines and a source line connected to the plurality of non-volatile memory cells, wherein:
the first block includes the first sub-block and a second sub-block, the second sub-block is the only counter sub-block of the first sub-block;
the first block is connected to the bit lines and the source line;
the first sub-block is positioned closer to the bit lines than the source line; and
the second sub-block is positioned closer to the source line than the bit lines.
18 . The non-volatile storage apparatus of claim 17 , wherein:
the control circuit is configured to program the first sub-block in a direction from the source line to the bit lines; and
the control circuit is configured to program the second sub-block in a direction from the bit lines to the source line.
19 . The non-volatile storage apparatus of claim 15 , wherein:
the control circuit is configured to limit the number of open sub-blocks to a predetermined number; and
the control circuit is configured to scramble host data prior to programming host data in an open sub-block.