Storage system and method for proactive die retirement by fatal wordline leakage detection
In some situations, a leak on a wordline may be a localized problem that causes data loss in a block that contains the wordline. In other situations, such as when the leak occurs near a peripheral wordline routing area, the leak can affect the entire memory die. The storage system provided herein has a fatal wordline leak detector that determines the type of leak and, accordingly, whether just the block should be retired or whether related blocks should be retired.
1. In a storage system comprising a memory die, a method comprising:
detecting a grown bad block (GBB) in the memory die in response to detecting a wordline short;
performing fatal wordline leak detection on the detected grown bad block by independently biasing each wordline in the detected grown bad block to identify a location of the wordline short, wherein in performing the fatal wordline leak detection, at a given time, only two wordlines receive low and high biases from XY decode circuitry in a high-voltage switch and all other wordlines are floating;
in response to identifying the location of the wordline short as being in a memory array of the memory die, which corresponds to a success of the fatal wordline leak detection:
transferring data out of the detected grown bad block; and
retiring the detected grown bad block but not the memory die; and
in response to identifying the location of the wordline short as being in a peripheral wordline routing area of the memory die that is susceptible of a control gate interface (CGI) short, which corresponds to a failure of fatal wordline leak detection:
transferring data out of the detected grown bad block and other blocks in the memory die; and
retiring the memory die.
2. The method of claim 1 , wherein the fatal wordline leak detection is performed during system background time.
3. The method of claim 1 , wherein the fatal wordline leak detection is performed as part of a built-in self-test.
4. The method of claim 1 , further comprising attempting to recover data lost in the detected grown bad block.
5. The method of claim 1 , wherein the memory die comprises a three-dimensional memory.
6. A storage system comprising:
a memory die; and
a fatal wordline leak detector configured to:
detect a grown bad block (GBB) in the memory die in response to detecting a wordline short;
perform fatal wordline leak detection on the detected grown bad block by independently biasing each wordline in the detected grown bad block to identify a location of the wordline short, wherein in performing the fatal wordline leak detection, at a given time, only two wordlines receive low and high biases from XY decode circuitry in a high-voltage switch and all other wordlines are floating;
in response to identifying the location of the wordline short as being in a memory array of the memory die, which corresponds to a success of the fatal wordline leak detection:
transfer data out of the detected grown bad block; and
retire the detected grown bad block but not the memory die; and
in response to identifying the location of the wordline short as being in a peripheral wordline routing area of the memory die that is susceptible of a control gate interface (CGI) short, which corresponds to a failure of fatal wordline leak detection:
transfer data out of the detected grown bad block and other blocks in the memory die; and
retire the memory die.
7. The storage system of claim 6 , wherein the memory die comprises a three-dimensional memory.
8. The storage system of claim 6 , wherein the storage system comprises an enterprise storage system comprising a plurality of memory dies.
9. A storage system comprising:
a memory die;
means for:
detecting a grown bad block (GBB) in the memory die in response to detecting a wordline short;
performing fatal wordline leak detection on the detected grown bad block by independently biasing each wordline in the detected grown bad block to identify a location of the wordline short, wherein in performing the fatal wordline leak detection, at a given time, only two wordlines receive low and high biases from XY decode circuitry in a high-voltage switch and all other wordlines are floating;
in response to identifying the location of the wordline short as being in a memory array of the memory die, which corresponds to a success of the fatal wordline leak detection:
transferring data out of the detected grown bad block; and
retiring the detected grown bad block but not the memory die, and
in response to identifying the location of the wordline short as being in a peripheral wordline routing area of the memory die that is susceptible of a control gate interface (CGI) short, which corresponds to a failure of fatal wordline leak detection:
transferring data out of the detected grown bad block and other blocks in the memory die; and
retiring the memory die.
10. The method of claim 1 , wherein the storage system comprises an enterprise storage system comprising a plurality of memory dies.