Bad Block Recycling via Wordline-Level Segmentation
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Solution Overview
Problem
Memory devices often experience yield loss due to bad blocks caused by defective wordlines, wordline-to-wordline shorts, and memory cell fatigue, leading to unusable memory dies during production and product life.
Innovation Solution
A storage system and method that identifies and recycles bad blocks by creating logical blocks from non-defective wordlines across multiple physical blocks, allowing partial mapping and redundant data writing based on bit error rates to extend device life and maintain throughput.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If bad blocks are marked unusable during production, then reliability is improved by ensuring only functional blocks are used, but yield loss increases due to discarding memory dies with bad blocks
Solution Approach 1:
The patent recovers bad blocks by identifying defective wordlines within them and reconstructing usable logical blocks from the remaining non-defective wordlines. Instead of discarding entire memory dies with bad blocks, the system recovers functional capacity by salvaging usable portions, thereby reducing yield loss while maintaining reliability standards.
Solution Approach 2:
The patent changes the parameter assessment by not treating bad blocks as completely unusable but rather as blocks with specific defective wordlines that can be identified and excluded. By changing from a binary good/bad block classification to a more granular wordline-level defect mapping, the system can recover additional usable capacity from previously discarded blocks.
2Manufacturing precision
If bad blocks are marked unusable, then manufacturing precision is improved by maintaining strict quality standards, but loss of substance increases due to discarded memory capacity
Solution Approach 1:
The patent recovers memory capacity by salvaging non-defective wordlines from bad blocks. Instead of discarding the entire block capacity, the system extracts and reconstructs usable logical blocks from the functional portions, thereby reducing memory capacity loss while maintaining manufacturing precision through proper defect identification and isolation.
Solution Approach 2:
The patent segments the memory block into individual wordlines and identifies which specific wordlines are defective. By segmenting the block at the wordline level rather than treating the entire block as unusable, the system can isolate defective portions and recover the functional capacity from non-defective wordlines, reducing overall capacity loss.
3Reliability
If strict bad-block criteria are applied, then reliability is improved by ensuring high quality memory, but device complexity increases due to additional identification and management overhead
Solution Approach 1:
The patent performs preliminary identification and characterization of bad blocks and their defective wordlines during production or initial operation. By performing this defect mapping in advance, the system establishes a foundation for later recovery operations, making the subsequent block reconstruction process more efficient and reducing the complexity of real-time bad block management.
4Productivity
If bad blocks are recycled by creating logical blocks from non-defective wordlines, then productivity is improved by increasing usable capacity, but device complexity increases due to mapping and management requirements
Solution Approach 1:
The patent creates logical blocks that are essentially copied or remapped from non-defective wordlines within physical bad blocks. By creating these logical representations that map to functional physical resources, the system increases usable capacity while managing complexity through standardized mapping mechanisms that translate logical addresses to physical locations.
Data Source
AI summary
A storage system is provided comprising a controller and a memory. The controller is configured to identify at least two physical blocks of memory that are designated as bad blocks because of at least one defective wordline; identify which wordlines in the at least two physical blocks of memory are defective; and create a logical block of memory from non-defective wordlines in the at least two physical blocks of memory, wherein some portions of the logical block are mapped to one of the at least two physical blocks of memory, and wherein other portions of the logical block are mapped to another one of the at least two physical blocks of memory.