Redundant Bit Patterns for Column Defect Coding in Memory Arrays
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Solution Overview
Problem
Non-volatile memory arrays face inefficiencies due to defective cell columns, which render entire columns unusable, and existing methods lack effective solutions for identifying and repairing such defects without degrading data retention.
Innovation Solution
The implementation of redundant coding for column defects cartography, where defective cell groups are redundantly encoded and identified using a different bit pattern, allowing for their repair and re-identification, and enabling the memory array to be marked as failing or passing based on the presence of new defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If defective cell columns are identified and repaired using redundant cell groups, then memory array reliability is improved, but the memory array area required for storing cartography data increases
Solution Approach 1:
The patent applies local quality by using different bit patterns for different cell group types. Functional cell groups use a first bit pattern while defective cell groups use a second bit pattern. This allows the memory array to efficiently store cartography data about defective columns using only a small fraction of the array, thereby improving reliability without significantly increasing the required memory area.
2Reliability
If redundant coding is used to store defective column addresses, then data retention resistance is improved, but device complexity increases
Solution Approach 1:
The patent uses inversion by assigning a second bit pattern specifically for defective cell groups, which is different from the first bit pattern used for functional groups. This inverted approach allows the decoding process to easily distinguish between functional and defective cells, improving data retention resistance while keeping the decoding process relatively simple through clear pattern differentiation.
Data Source
AI summary
Techniques for coding and decoding redundant coding for column defects cartography. Defective cell groups identified in a memory array are redundantly encoded with a different bit pattern than the bit pattern used for functional cell groups. The identified defective cell groups are repaired using redundant cell groups in the memory array. The defective cell groups are later re-identified by checking the redundant bit pattern encoded in the cell groups. If new defective cell groups are identified, the memory array is identified as failing. If no new defective cell groups are identified, the memory array is identified as passing, and the identified defective cell groups are repaired.