Semiconductor memory devices that support enhanced data recovery operations
A method of operating a memory device includes reading a first page of memory cells containing at least one worn-out memory cell therein using a read voltage, from a first memory block, and reading a second page of memory cells, which extends adjacent to the first page in the first memory block, using the read voltage. An operation is performed to determine a match rate between a position of a column including a “0” bit in the first page with a position of a column including a “0” bit in the second page. Thereafter, the second page is read by adjusting a read pass voltage applied to a word line of another page in the first memory block, when the match rate exceeds a threshold match rate.
1. A method of operating a memory device, comprising:
reading a first page of memory cells containing at least one worn-out memory cell therein using a read voltage, from a first memory block;
reading a second page of memory cells, which extends adjacent to the first page in the first memory block, using the read voltage;
determining a match rate between a position of a column including a “0” bit in the first page with a position of an equivalent column including a “0” bit in the second page, for each of the columns associated with the first and second pages, where the match rate corresponds to a ratio between: (i) a number of columns having matching “0” bits in the first and second pages, and (ii) a number of total columns within the first and second pages; and then
reading the second page by adjusting a read pass voltage applied to a word line of another page in the first memory block, when the match rate exceeds a threshold match rate.
2. The method of claim 1 , wherein the threshold match rate is at least 90%.
3. The method of claim 1 , wherein a voltage value of the read voltage is set to a predefined default value.
4. The method of claim 1 , wherein said reading the second page by adjusting the read pass voltage, comprises:
adjusting the read pass voltage;
applying the adjusted read pass voltage to the word line of at least the first other page; and
reading the second page by applying the read voltage to a word line of the second page.
5. The method of claim 1 , wherein said reading the second page by adjusting the read pass voltage, comprises:
determining a read pass voltage value at which a number of “0” bits in the second page is smaller than a predetermined number; and
reading the second page by setting the read pass voltage value as the read pass voltage.
6. The method of claim 5 , wherein the predetermined number is less than a maximum number of bits that is correctable using an error correction code (ECC).
7. The method of claim 1 , wherein said reading the first page comprises reading the first page by applying the read voltage to a word line of the first page, and applying the read pass voltage to a word line of the second page; and wherein said reading the second page of memory cells using a read voltage comprises reading the second page by applying the read voltage to the word line of the second page, and applying the read pass voltage to the word line of the first page.
8. The method of claim 1 , wherein said reading the second page by adjusting the read pass voltage comprises reading the second page repeatedly while incrementally adjusting the read pass voltage at predetermined intervals.
9. The method of claim 1 , wherein said reading the first page comprises determining whether a number of “0” bits in the first page exceeds a predetermined number; and wherein said reading the second page of memory cells using a read voltage is performed when the number of “0” bits in the first page exceeds the predetermined number.
10. The method of claim 9 , wherein the predetermined number is less than a maximum number of bits that is correctable using an error correction code (ECC).
11. The method of claim 1 , further comprising:
recovering data stored in the second page using an error correction code (ECC); and
writing the recovered data of the second page to a second memory block.
12. The method of claim 11 , further comprising:
determining whether the first memory block is an uncorrectable ECC (UECC) block; and
wherein said writing the recovered data comprises writing the recovered data of the second page to the second memory block when the first memory block is an uncorrectable ECC block.
13. A semiconductor device, comprising:
a memory device having a memory cell array therein; and
a memory controller electrically coupled to said memory device, said memory controller configured to:
read a first page of memory cells containing at least one worn-out memory cell therein using a read voltage, from a first memory block;
read a second page of memory cells, which is adjacent to the first page in the first memory block, using the read voltage, wherein the first page and the second page share a plurality of columns;
determine a match rate based on a ratio of a first number of columns where both the first and second pages include a “0” bit to a second number of the plurality of columns;
read the second page by adjusting a read pass voltage applied to a word line of another page in the first memory block, when the match rate exceeds a threshold match rate.
14. The device of claim 13 , wherein the memory controller is configured to read the second page by adjusting the read pass voltage, by:
adjusting the read pass voltage;
applying the adjusted read pass voltage to the word line of at least the first page; and
reading the second page by applying the read voltage to a word line of the second page.
15. The device of claim 13 , wherein the memory controller is configured to read the second page by adjusting the read pass voltage, by:
determining a read pass voltage value at which a number of “0” bits in the second page is smaller than a predetermined number; and
reading the second page by setting the read pass voltage value as the read pass voltage.
16. The device of claim 13 , wherein the memory controller is configured to:
determine whether a number of “0” bits in the first page exceeds a predetermined number; and
read the second page of memory cells using a read voltage when the number of “0” bits in the first page exceeds the predetermined number.