Sub-Block Flash Control for Adjacent Disturb Reliability
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Solution Overview
Problem
Non-volatile memory devices face reliability issues due to a disturb phenomenon caused by operations in adjacent sub-blocks, which affect performance as memory block capacity increases, and existing block-by-block control technologies struggle to maintain performance with growing capacity.
Innovation Solution
A storage controller collects deterioration information on sub-blocks and generates commands to adjust the core of adjacent sub-blocks based on this information, including lowering pass voltage, increasing pass voltage, or changing memory cell types to mitigate the disturb effect, thereby improving reliability and performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the capacity of memory block increases, then storage capacity is improved, but reliability deteriorates due to disturb phenomenon from adjacent sub-block operations
Solution Approach 1:
The memory block is divided into multiple sub-blocks that can be independently managed and operated. This segmentation allows selective adjustment of cores in adjacent sub-blocks without affecting the entire block, enabling targeted reliability improvement while maintaining high storage capacity.
Solution Approach 2:
Different core adjustment levels are applied to different sub-blocks based on their specific deterioration information. Sub-blocks experiencing disturb phenomena receive appropriate core adjustments, while other sub-blocks maintain their original performance characteristics.
2Device complexity
If existing block-by-block control technology is used, then device complexity is reduced, but performance deteriorates as memory block capacity increases
Solution Approach 1:
The control technology is segmented from block-level to sub-block-level operations, allowing finer-grained control without proportionally increasing overall system complexity. The controller manages multiple sub-blocks independently, improving performance for high-capacity blocks.
Solution Approach 2:
The system dynamically adjusts core levels of adjacent sub-blocks based on real-time deterioration information and operation types. This dynamic adaptation enables the system to maintain optimal performance across varying workloads and capacity requirements.
3Reliability
If read reclaim operations are performed frequently, then reliability is improved, but productivity deteriorates due to increased operation overhead
Solution Approach 1:
The system performs preliminary core adjustments on adjacent sub-blocks before disturb phenomena cause data deterioration. By proactively adjusting cores based on deterioration information, read reclaim operations are reduced or eliminated, improving productivity while maintaining reliability.
Solution Approach 2:
The disturb phenomenon that causes reliability issues is converted into a benefit by using deterioration information to trigger preventive core adjustments. This transforms the harmful effect into a signal for proactive reliability management, reducing the need for corrective read reclaim operations.
Data Source
AI summary
An example storage controller includes a host interface, a flash conversion layer, and a flash interface. The host interface receives a read request or a program request from a host device. The flash conversion layer collects deterioration information on a non-volatile memory device and log the deterioration information in a unit of a sub-block, determines a selected sub-block and an adjacent sub-block adjacent to the selected sub-block based on the read request or the program request, and generates a command that adjusts a core of the adjacent sub-block based on the deterioration information. The flash interface transfers the command to the non-volatile memory device.