Adaptive Read Conditions for 3D NAND Memory Error Correction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Three-dimensional nonvolatile memory systems face data uncorrectability issues due to specific failure modes that affect large physical areas, making it challenging to correct errors using existing Error Correction Code (ECC) methods.
Innovation Solution
The method involves applying different read conditions to identify and correct uncorrectable data by modifying voltages applied to word lines, select lines, and dummy word lines within the memory array, allowing for the recovery of correct data through adaptive read circuits and recording successful conditions for future use.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If standard ECC methods are used to correct data errors, then small isolated errors can be corrected, but large area failures affecting multiple word lines or blocks cannot be corrected
Solution Approach 1:
The patent implements dynamic read condition adjustment by modifying voltages on word lines, select lines, and dummy word lines based on detected failure patterns. The system transitions from static standard read conditions to dynamic adaptive read conditions that change based on the specific failure mode encountered, enabling correction of both small isolated errors and large area failures
Solution Approach 2:
The patent changes physical parameters (voltages) of the memory system to overcome failures. By adjusting read pass voltages, select line voltages, and word line voltages to different levels, the system can retrieve data that was uncorrectable under standard conditions, thereby improving data correctability for various failure modes
2Reliability
If adaptive read conditions are applied to correct uncorrectable data, then data integrity is improved, but additional read operations increase time consumption
Solution Approach 1:
The patent performs preliminary detection of failure modes by examining error patterns in initially read data. Based on this preliminary analysis, the system determines whether adaptive read conditions are necessary before committing to additional read operations. This preliminary action allows the system to quickly handle correctable cases while reserving time-consuming adaptive reads for genuinely uncorrectable cases
Solution Approach 2:
The patent implements a feedback mechanism where the results of initial ECC decoding inform subsequent read operations. When uncorrectable errors are detected, the system feeds back this information to trigger adaptive read condition adjustments. This feedback loop ensures that additional read operations are performed only when necessary, minimizing time loss while maintaining data integrity
3Reliability
If voltage adjustments are made to unselected blocks to correct UECC data, then correctability of large area failures is improved, but power consumption increases
Solution Approach 1:
The patent applies local quality by targeting voltage adjustments only to specific unselected blocks that are determined to contain uncorrectable data, rather than uniformly adjusting all blocks. The system identifies affected blocks based on failure pattern analysis and applies modified read conditions only where necessary, thereby reducing overall power consumption compared to a blanket approach
Data Source
AI summary
When data from a portion of a three dimensional NAND memory array is determined to be uncorrectable by Error Correction Code (ECC), a determination is made as to whether data is uncorrectable by ECC throughout some unit that is larger than the portion. If modified read conditions provide ECC correctable data, the modified read conditions are recorded for subsequent reads of the larger unit.