Failure mode detection method and error correction method for solid state storage device
A failure mode detection method is provided. A first default read voltage is changed to a first read retry voltage by a first increment, and a second default read voltage is changed to a second read retry voltage by a second increment. A memory cell array of a solid state storage device is successfully read according to the first and second read retry voltages. If an absolute value of the first increment minus an absolute value of the second increment is larger than a predetermined voltage value, the memory cell array is in a data retention failure mode. If the absolute value of the first increment minus the absolute value of the second increment is smaller than the predetermined voltage value, the memory cell array is in a low temperature write high temperature read failure mode.
1. A failure mode detection method for a solid state storage device, the failure mode detection method comprising steps of:
changing a first default read voltage to a first read retry voltage by a first increment, and changing a second default read voltage to a second read retry voltage by a second increment, wherein when a memory cell array of the solid state storage device is read according to the first read retry voltage and the second read retry voltage, an accurate read data is generated;
if an absolute value of the first increment minus an absolute value of the second increment is larger than a predetermined voltage value, judging that the memory cell array of the solid state storage device is in a data retention failure mode; and
if the absolute value of the first increment minus the absolute value of the second increment is not larger than the predetermined voltage value, judging that the memory cell array of the solid state storage device is in a low temperature write high temperature read failure mode.
2. The failure mode detection method as claimed in claim 1 , wherein the first read retry voltage is higher than the second read retry voltage, and the first increment and the second increment are negative.
3. A failure mode detection method for a solid state storage device, the failure mode detection method comprising steps of:
changing a first default read voltage to a first read retry voltage by a first increment, and changing a second default read voltage to a second read retry voltage by a second increment, wherein when a memory cell array of the solid state storage device is read according to the first read retry voltage and the second read retry voltage, an accurate read data is generated;
if the first increment is positive and a data storage time exceeds a predetermined time period, judging that the memory cell array of the solid state storage device is in a high temperature write low temperature read failure mode; and
if the first increment is positive and the data storage time does not exceed the predetermined time period, judging that the memory cell array of the solid state storage device is in a program disturb failure mode.
4. The failure mode detection method as claimed in claim 3 , further comprising steps of:
if the first increment is negative and an absolute value of the first increment minus an absolute value of the second increment is larger than a predetermined voltage value, judging that the memory cell array of the solid state storage device is in a data retention failure mode; and
if the first increment is negative and the absolute value of the first increment minus the absolute value of the second increment is not larger than the predetermined voltage value, judging that the memory cell array of the solid state storage device is in a low temperature write high temperature read failure mode.
5. The failure mode detection method as claimed in claim 3 , wherein the first read retry voltage is higher than the second read retry voltage.
6. An error correction method for a solid state storage device, the error correction method comprising steps of:
changing a first default read voltage to a first read retry voltage by a first increment, and changing a second default read voltage to a second read retry voltage by a second increment, wherein when a memory cell array of the solid state storage device is read according to the first read retry voltage and the second read retry voltage, an accurate read data is generated, wherein a first read retry voltage set of the m read retry voltage sets includes the first read retry voltage and the second read retry voltage;
if an absolute value of the first increment minus an absolute value of the second increment is larger than a predetermined voltage value, judging that a specified failure mode of the memory cell array is a data retention failure mode; and
if the absolute value of the first increment minus the absolute value of the second increment is not larger than the predetermined voltage value, judging that the specified failure mode of the memory cell array is a low temperature write high temperature read failure mode;
selecting m read retry voltage sets from M read retry voltage sets, wherein the m read retry voltage sets are related with the specified failure mode and M is larger than m; and
performing a read retry process according to the m read retry voltage sets.
7. The error correction method as claimed in claim 6 , further comprising steps of:
if the first increment is positive and a data storage time exceeds a predetermined time period, judging that the specified failure mode is a high temperature write low temperature read failure mode; and
if the first increment is positive and the data storage time does not exceed the predetermined time period, judging that the specified failure mode is a program disturb failure mode.
8. The error correction method as claimed in claim 6 , further comprising steps of:
if the first increment is negative and an absolute value of the first increment minus an absolute value of the second increment is larger than a predetermined voltage value, judging that the specified failure mode is a data retention failure mode; and
if the first increment is negative and the absolute value of the first increment minus the absolute value of the second increment is not larger than the predetermined voltage value, judging that the specified failure mode is a low temperature write high temperature read failure mode.