3D Memory Read-Disturb Control Through Wordline Maintenance
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Solution Overview
Problem
The lifetime read disturb constraint in three-dimensional memory generations is reached due to the threshold voltage of non-data wordlines moving out of a designated threshold voltage window, leading to data loss and un-usability of blocks, especially in read-intensive workloads where program/erase cycles are infrequent.
Innovation Solution
Implementing a data storage device with a controller that detects lifetime read disturb by monitoring total data read and bit error rate, triggering non-data wordline maintenance, and incorporating read count-based wear leveling to prevent blocks from exceeding lifetime read limits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If read operations are performed frequently in three-dimensional memory, then data accessibility is improved, but lifetime read disturb increases causing threshold voltage drift and data loss
Solution Approach 1:
The patent performs non-data wordline maintenance operations in advance before the read disturb reaches critical levels. The controller proactively identifies blocks that have undergone sufficient read operations and applies maintenance reads to reset the threshold voltage of non-data wordlines, preventing data loss before it occurs.
Solution Approach 2:
The patent implements a feedback mechanism where the controller monitors read operation counts and block status to dynamically determine when maintenance is needed. Based on feedback from read disturb detection, the controller adjusts maintenance timing and frequency to balance data accessibility with preventing threshold voltage drift.
2Duration of action of stationary object
If traditional program/erase cycle-based wear leveling is used, then program/erase endurance is managed, but read-intensive workload damage is not prevented
Solution Approach 1:
The patent changes the monitoring parameter from program/erase cycle count to read operation count. The controller tracks the number of read operations performed on each block and uses this parameter to trigger maintenance operations, thereby addressing read-intensive workload damage while maintaining program/erase endurance management.
3Stability of the object's composition
If non-data wordline maintenance is performed frequently, then threshold voltage stability is improved, but device complexity and overhead increase
Solution Approach 1:
The patent applies maintenance operations selectively to only those blocks that have reached a certain read operation threshold, rather than performing maintenance on all blocks uniformly. This partial action approach maintains threshold voltage stability for affected blocks while reducing overall maintenance overhead and device complexity.
Data Source
AI summary
A block of memory in a data storage device can experience a read disturb based on how many times the block of memory was read, as well as on the program-erase count of the block. Non-data wordline maintenance triggered by program-erase count can address the read disturb in some situations but not in others, such as when a host is very read intensive and does not write to the memory that often. In one embodiment, maintenance on a non-data wordline in a block of memory is performed in response to the lifetime total amount of data read from the block being above a threshold. In another embodiment, a block is allocated for use based on the lifetime read count of the block and not only on the program-erase count of the block. Other embodiments are disclosed.