3D Flash Memory Sub-Block Erase Verification
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Solution Overview
Problem
In three-dimensional (3D) flash memory devices, existing technologies face challenges in maintaining data integrity and reliability due to the interference effects during erase operations across stacked sub-blocks, leading to unintended changes in program states of unselected sub-blocks.
Innovation Solution
A method and structure for a nonvolatile memory device with a 3D memory cell array, where erase operations are performed independently on sub-blocks, and verification and reprogramming operations are implemented to restore the program states of unselected sub-blocks affected by the erase process, ensuring data integrity and reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If erase operations are performed on stacked sub-blocks in 3D flash memory, then storage capacity is increased, but data integrity deteriorates due to interference effects causing unintended changes in program states of unselected sub-blocks
Solution Approach 1:
The memory block is divided into multiple independently erasable sub-blocks arranged in a 3D stacked configuration. Each sub-block can be erased independently without affecting the program states of other sub-blocks, thereby maintaining data integrity while increasing storage capacity through vertical stacking.
Solution Approach 2:
A verification operation is performed after erase to detect any unintended changes in program states of unselected sub-blocks. If changes are detected, a reprogramming operation is subsequently executed to restore the correct program states, preventing data integrity loss.
2Reliability
If independent erase operations are performed on sub-blocks, then data integrity is maintained, but operation complexity increases due to verification and reprogramming steps
Solution Approach 1:
A verification operation serves as feedback mechanism after erase to detect whether program states of unselected sub-blocks have been inadvertently changed. Based on this feedback, a reprogramming operation is conditionally executed only when needed, balancing reliability with operational efficiency.
3Measurement precision
If verification and reprogramming operations are implemented, then program state accuracy is maintained, but processing time increases
Solution Approach 1:
The verification operation checks only the necessary program states of unselected sub-blocks to detect interference effects. Reprogramming is performed partially only on affected sub-blocks rather than the entire memory block, reducing processing time while maintaining program state accuracy.
Data Source
AI summary
A nonvolatile memory comprises a memory block having memory cells stacked in a three dimensional structure. The nonvolatile memory device performs an erase operation to erase a selected sub block among sub blocks of the memory block, a verification operation to determine whether program states of memory cells of an unselected sub block of the memory block have changed as a consequence of the erase operation, and a reprogramming operation to reprogram at least a portion of the unselected sub block upon determining that at least one of the program states have changed as a consequence of the erase operation.