Memory Block Scan Frequency Control for Temperature-Driven RBER
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Solution Overview
Problem
Memory sub-systems face issues with high first read raw bit error rate (RBER) and trigger rate due to data degradation mechanisms like data retention and read disturb, leading to reliability and performance problems, especially in large capacity drives, without effective feedback mechanisms to ensure data integrity during writeback operations.
Innovation Solution
Performing a dedicated periodic read operation on every block of the memory die, identifying a page with the lowest sensing overhead, and refreshing the block without data transfer, maintaining blocks in a T-state with low RBER and trigger rate, thereby reducing first read issues and improving performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If periodic read operations are performed on every block to reduce first read RBER and trigger rate, then data integrity and reliability are improved, but backend traffic and operational overhead increase
Solution Approach 1:
The patent applies local quality by performing periodic read operations selectively on specific blocks rather than uniformly across all blocks. The system identifies blocks that benefit most from refresh operations based on their individual state and characteristics, concentrating resources where they provide maximum reliability improvement while minimizing unnecessary backend traffic on blocks that don't require refresh.
Solution Approach 2:
The patent implements partial action by performing read operations on only a subset of blocks during each periodic cycle rather than scanning every block. This approach achieves sufficient reliability improvement for critical blocks while reducing the overall backend traffic burden, balancing data integrity needs with operational efficiency.
2Reliability
If scan frequency is increased to maintain blocks in T-state and reduce data degradation, then data quality is improved, but energy consumption and operational complexity increase
Solution Approach 1:
The patent applies dynamics by adjusting scan frequency adaptively rather than using a fixed rate. The system dynamically modifies the periodic read operation frequency based on observed data degradation patterns, temperature conditions, and block state transitions, performing scans more frequently when degradation is rapid and less frequently when stable, thereby optimizing energy consumption while maintaining data quality.
Solution Approach 2:
The patent implements periodic action through scheduled read operations that refresh block states without requiring continuous scanning. By performing reads at optimized intervals rather than continuously, the system maintains blocks in T-state and prevents data degradation while significantly reducing energy consumption compared to continuous monitoring approaches.
3Reliability
If temperature-adaptive scan frequency control is implemented to account for accelerated data retention decay at higher temperatures, then reliability across temperature conditions is improved, but device complexity increases
Solution Approach 1:
The patent applies parameter changes by adjusting scan frequency based on temperature conditions. The system modifies the periodic read interval parameter in response to temperature variations, increasing scan frequency at higher temperatures where data retention decay accelerates and reducing frequency at lower temperatures, thereby maintaining consistent reliability across operating conditions through dynamic parameter adaptation.
Data Source
AI summary
A processing device in a memory sub-system determines a current temperature of a memory device and accesses historical transition data for management units at a plurality of temperatures. The processing device determines a transition time based on the historical transition data and current temperature, sets a scan frequency based on the transition time, and traverses management units at the scan frequency to maintain the management units in a transient state with lower raw bit error rate. The scan frequency may be set to be less than the transition time to prevent management units from transitioning to a stable state with higher raw bit error rate.