Flash memory with targeted read scrub algorithm

摘要

A method and system have been described for counteracting and correcting for read disturb effects in blocks of flash memory. The method may include the step of a controller of the memory system performing a read scrub scan on only a portion of one targeted word line in a block at desired intervals. The controller may calculate whether a read scrub scan is necessary based on a probabilistic determination that is calculated in response to each received host read command. The controller may then place a block associated with the targeted word line into a refresh queue if a number of errors are detected in the targeted word line that meets or exceeds a predetermined threshold. The block refresh process may include copying the data from the block into a new block during a background operation.

主权项

1. A method for counteracting read disturb effects in a flash memory device comprising:
in a controller of the flash memory device, the controller:
receiving a read command from a host;determining if a scan for errors in a portion of the flash memory device is necessary in response to the read command; andin response to determining that the scan is necessary:
identifying a word line of the flash memory to scan based on the received read command;scanning only the identified word line for data errors, without scanning any other word line in a block containing the identified word line, wherein scanning only the identified word line comprises scanning only an upper page of the identified word line;placing the block in a refresh queue if an error threshold is detected in the identified word line; andif the error threshold is not detected in the identified word line, waiting for a next read command from the host.