Memory Controller Read Disturbance Mitigation via Verification Reads
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Solution Overview
Problem
Existing memory systems face challenges in maintaining data reliability due to read operation-induced disturbances on unselected word lines, leading to potential data damage and errors, especially when read operations are iteratively performed on specific word lines.
Innovation Solution
A memory controller method that performs a reliability verification read operation based on a count value and a randomly generated reference value, which includes reading data from unselected word lines adjacent to the selected word line, using specific read voltages, and executing post-operations to manage and correct data errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If read operations are iteratively performed on specific word lines, then productivity is improved, but reliability deteriorates due to read disturbance on unselected word lines
Solution Approach 1:
The patent performs reliability verification read operations on unselected word lines before they suffer significant read disturbance damage. By proactively detecting potential issues through verification reads and performing post operations (such as program operations to correct disturbed cells) before actual data errors occur, the system maintains data integrity while allowing high-speed iterative read operations on selected word lines.
2Reliability
If reliability verification read operations are performed on unselected word lines, then reliability is improved, but device complexity increases
Solution Approach 1:
The patent implements reliability verification read operations periodically based on a count value that tracks the number of read operations performed. Instead of performing verification reads after every single read operation or continuously, the controller increments a count value and performs verification reads at periodic intervals when the count reaches a predetermined threshold. This periodic approach maintains data reliability while significantly reducing the frequency of verification operations and associated controller complexity compared to continuous verification.
3Reliability
If reliability verification read operations are performed frequently, then reliability is improved, but productivity decreases
Solution Approach 1:
The patent performs reliability verification read operations on only a subset of unselected word lines rather than all unselected word lines. Specifically, the verification read is performed on at least one unselected word line (such as an open word line or adjacent word line) instead of systematically verifying every unselected word line. This partial verification approach provides sufficient reliability protection while minimizing the time and resources consumed by verification operations, thus preserving high read operation throughput.
Data Source
AI summary
In one embodiment, the method includes performing a read operation on a memory, and determining, by a memory controller, whether to perform a reliability verification read operation based on a count value and a reference value. The count value is based on a number of read commands issued by the memory controller to the memory, and the reliability verification read operation is for reading data from at least one memory cell associated with at least one unselected word line in the memory. An unselected word line is a word line not selected during the read operation. The method further includes performing the reliability verification read operation for the at least one unselected word line based on the determining.