Data storage apparatus and operation method thereof

1. An operation method of a data storage apparatus, the method comprising:

performing a first read operation using an optimal read voltage on read-failed memory cells;

performing an error correction code (ECC) decoding operation on read data read through the first read operation;

performing a second read operation using an oversampling read voltage on the read-failed memory cells when the ECC decoding operation to the read data fails;

determining whether or not potential error memory cells which are turned on through the optimal read voltage and are turned off through the oversampling read voltage are present in the read data;

determining whether or not neighboring memory cells which share a bit line with the potential error memory cells and are coupled to neighboring word lines are in an erased state by performing a read operation on the neighboring memory cells when the potential error memory cells are present; and

inverting bit values corresponding to the potential error memory cells in the read data read from the read-failed memory cells through the first read operation when the neighboring memory cells are in the erased state.

2. The method of claim 1 , further comprising, before the performing of the first read operation:

performing a normal read operation on memory cells using a normal read voltage;

performing an ECC decoding operation on read data read from the memory cells through the normal read operation; and

determining whether or not the ECC decoding operation is successful.

3. The method of claim 2 ,

wherein the normal read voltage is preset to be located between threshold voltage distributions of the read-failed memory cells,

wherein the optimal read voltage is determined on the basis of distorted threshold voltage distributions of the read-failed memory cells, and

wherein the oversampling read voltages are symmetrically located with reference to the optimal read voltage in the threshold voltage distributions of the read-failed memory cells.

4. The method of claim 1 , further comprising terminating the read operation to the read-failed memory cells when the potential error memory cells are not present as a result of the determining of whether or not the potential error memory cells are present.

5. The method of claim 1 , further comprising terminating the read operation to the read ailed memory cells when the neighboring memory cells are not in the erase state as a result of the determining of whether or not the neighboring memory cells are in the erase state.

6. The method of claim 1 , further comprising performing an ECC decoding operation on the read data in which the bit values of the potential error memory cells are inverted after the inverting of the bit values corresponding to the potential error memory cells in the read data.

7. A data storage apparatus comprising:

a nonvolatile memory device configured to perform a first read operation using an optimal read voltage and a second read operation using an oversampling read voltage on read-failed memory cells; and

a controller configured to control the nonvolatile memory device to perform the first read operation and the second read operation to determine whether or not at least one or more potential error memory cells, which are turned on through the optimal read voltage and turned off through the oversampling read voltage, are present among the read-failed memory cells, to determine whether or not neighboring memory cells which share a bit line with the potential error memory cells and are coupled to neighboring word lines are in an erased state by performing a read operation on the neighboring memory cells when the potential error memory cells are present, and to invert bit values corresponding to the potential error memory cells in read data read from the read-failed memory cells through the first read operation when the neighboring memory cells are in the erased state.

8. The data storage apparatus of claim 7 , wherein the controller controls the nonvolatile memory device to perform an error correction code (ECC) decoding operation on the read data read from the memory cells through the first read operation and perform the second read operation on the memory cells when the ECC decoding operation to the read data fails.

9. The data storage apparatus of claim 7 , wherein the controller controls the nonvolatile memory device to terminate the read operation to the memory cells when the potential error memory cells are not present.

10. The data storage apparatus of claim 7 , wherein the controller controls the nonvolatile memory device to terminate the read operation to the memory cells when the neighboring memory cells are not in an erase state.

11. The data storage apparatus of claim 7 , wherein the controller performs an error correction code (ECC) decoding operation on the read data in which the bit values of the potential error memory cells are inverted.

12. The data storage apparatus of claim 7 , wherein the controller controls the nonvolatile memory device to perform a normal read operation using a normal read voltage on the memory cells, perform an error correction code (ECC) decoding operation on normal read data read from the memory cells through the normal read operation, and controls the nonvolatile memory device to perform the first read operation on the memory cell when the ECC decoding operation to the memory cells fails.

13. The data storage apparatus of claim 12 , wherein the normal read voltage is preset to be located between threshold voltage distributions of the read-failed memory cells,

wherein the optimal read voltage is determined on the basis of distorted threshold voltage distributions of the read-failed memory cells, and

wherein the oversampling read voltages are symmetrically located with reference to the optimal read voltage in the threshold voltage distributions of the read-failed memory cells.