Memory system for multi-clustering read thresholds and method thereof

1. A memory system comprising:

a memory device including a plurality of blocks; and

a controller, coupled to the memory device, suitable for:

performing multiple read operations on a target block among the plurality of blocks, using a first cluster of multiple read threshold voltages;

generating a second cluster of multiple read threshold voltages using the first cluster when a difference between the maximum number of fail bits and the minimum number of fail bits associated with the multiple read operations exceeds a threshold;

splitting a plurality of pages in the target block into a first group of pages for the first cluster and a second group of pages for the second cluster; and

performing additional read operations on the first group of pages using the first cluster and on the second group of pages using the second cluster,

wherein the controller further merges the first cluster and the second cluster when a difference between the maximum number of fail bits and the minimum number of fail bits associated with the additional read operations is less than a threshold value.

2. The memory system of claim 1 , wherein the controller updates each cluster based on success or failure of each of the multiple read threshold voltages in corresponding read operations.

3. The memory system of claim 2 , wherein the controller updates each cluster that is actively in the process of being updated by rearranging an order of the multiple read threshold voltages in that cluster based on success or failure in the read operations using that cluster.

4. The memory system of claim 3 , wherein the controller rearranges the order of the multiple read threshold voltages in each cluster that is actively in the process of being updated such that a successful read threshold voltage has a highest order.

5. The memory system of claim 1 , wherein the controller evenly splits the plurality of pages into the first group of pages and the second group of pages.

6. The memory system of claim 1 , wherein the controller further generates information indicating whether each of the plurality of pages belongs to the first cluster or the second cluster.

7. The memory system of claim 6 , wherein the information includes a bitmap including multiple bits, at least one bit indicating the first cluster or the second cluster.

8. The memory system of claim 1 , wherein the additional read operations include first read operations on the first group of pages and second read operations on the second group of pages, and

wherein the controller merges the first cluster and the second cluster, when a difference between the maximum number of fail bits and the minimum number of fail bits associated with the first read operations on the first group of pages is less than a threshold value,

when a difference between the maximum number of fail bits and the minimum number of fail bits associated with the second read operations on the second group of pages is less than the threshold value,

when a difference between the maximum number of fail bits associated with the first read operations and the minimum number of fail bits associated with the second read operations is less than the threshold value, and

when a difference between the maximum number of fail bits associated with the second read operations and the minimum number of fail bits associated with the first read operations is less than the threshold value.

9. A memory system comprising:

a memory device including a plurality of blocks; and

a controller coupled to the memory device, suitable for:

receiving a read command from a host;

determining a page on a target block among the plurality of blocks, the page corresponding to the read command; and

performing a read operation on the page using multiple read threshold voltages of selected first cluster,

wherein a second cluster is generated using the first cluster when a difference between the maximum number of fail bits and the minimum number of fail bits associated with read operations on the target block using the first cluster exceeds a threshold,

wherein the controller further merges the first cluster and the second cluster when a difference between the maximum number of fail bits and the minimum number of fail bits associated with the additional read operations is less than a threshold value.

10. A method for operating a memory system comprising:

performing multiple read operations on a target block among a plurality of blocks, using a first cluster including multiple read threshold voltages;

generating a second cluster using the first cluster when a difference between the maximum number of fail bits and the minimum number of fail bits associated with the multiple read operations exceeds a threshold;

splitting a plurality of pages in the target block into a first group of pages for the first cluster and a second group of pages for the second cluster;

performing additional read operations on the first group of pages using the first cluster and on the second group of pages using the second cluster; and

merging the first cluster and the second cluster when a difference between the maximum number of fail bits and the minimum number of fail bits associated with the additional read operations is less than a threshold value.

11. The method of claim 10 , wherein the performing of the multiple and additional read operations includes updating each cluster that is actively in the process of being updated based on success or failure of the multiple read threshold voltages in corresponding read operations.

12. The method of claim 11 , wherein the updating includes rearranging an order of the multiple read threshold voltages of each cluster that is actively in the process of being updated based on the success or the failure in the read operations using that cluster.

13. The method of claim 12 , wherein the rearranging of the order of the multiple read threshold voltages of each cluster that is actively in the process of being updated includes rearranging the order of the multiple read threshold voltages of each cluster that is actively in the process of being updated such that a successful read threshold voltage has a highest order.

14. The method of claim 10 , wherein the splitting of the plurality of pages includes evenly splitting the plurality of pages into the first group of pages and the second group of pages.

15. The method of claim 10 , further comprising: generating information indicating whether each of the plurality of pages belongs to the first cluster or the second cluster.

16. The method of claim 15 , wherein the information includes a bitmap including multiple bits, at least one bit indicating the first cluster or the second cluster.

17. The method of claim 10 , wherein the additional read operations include first read operations on the first group of pages and second read operations on the second group of pages, and

wherein the merging of the first cluster and the second cluster includes:

merging the first cluster and the second cluster, when a difference between the maximum number of fail bits and the minimum number of fail bits associated with the first read operations on the first group of pages is less than a threshold value,

when a difference between the maximum number of fail bits and the minimum number of fail bits associated with the second read operations on the second group of pages is less than the threshold value,

when a difference between the maximum number of fail bits associated with the first read operations and the minimum number of fail bits associated with the second read operations is less than the threshold value, and

when a difference between the maximum number of fail bits associated with the second read operations and the minimum number of fail bits associated with the first read operations is less than the threshold value.