Flash Memory Module Block Erase Timing Control
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Solution Overview
Problem
Nonvolatile semiconductor memory experiences data storage period limitations due to electron traps and positive hole traps in the oxide insulation layer, leading to inaccurate data retrieval and premature block unusability, which shortens the storage apparatus' lifespan.
Innovation Solution
A semiconductor storage apparatus manages blocks by tracking recent programming and erase times to control the timing of these processes, ensuring minimal time intervals and reducing the formation of electron traps and positive hole traps through wear leveling and selective block usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If repeated programming and erasing is performed to store data, then data storage functionality is maintained, but electron traps and positive hole traps are formed in the oxide insulation layer causing threshold voltage fluctuations and reducing data retention reliability
Solution Approach 1:
The patent applies preliminary action by performing erase operations before programming operations. Specifically, the control apparatus erases a block before programming new data into it, which prevents the accumulation of electron traps and positive hole traps from previous programming-erase cycles. This preliminary erase action ensures that the oxide insulation layer is in a clean state before new data is written, thereby maintaining data retention reliability and preventing threshold voltage fluctuations.
2Productivity
If the number of erase operations is increased to enable block reuse, then storage area utilization is improved, but the data storage period is shortened due to trap formation in the oxide insulation layer
Solution Approach 1:
The control apparatus performs a preliminary erase operation on a block before programming new data. This ensures that the block is in a clean state, preventing the formation of new electron traps and positive hole traps during the programming operation. By maintaining this preliminary erase state, the system can reuse storage areas multiple times without significantly degrading data retention characteristics, thus extending the effective data storage period while maintaining high storage area utilization.
Solution Approach 2:
The control apparatus monitors the number of programming-erase cycles for each block and uses this feedback information to manage storage operations. When a block reaches a predetermined number of cycles, the system identifies it as unsuitable for further use and reallocates it, ensuring that only blocks with sufficient remaining lifespan are used for new data. This feedback mechanism optimizes storage area utilization while maintaining data retention reliability.
3Quantity of substance
If blocks with high number of erase operations are reused, then storage capacity is maximized, but threshold voltage fluctuations increase making data determination inaccurate
Solution Approach 1:
The control apparatus performs a preliminary erase operation on selected blocks before programming new data. This preliminary erase ensures that the oxide insulation layer is in a clean state, preventing the formation of electron traps and positive hole traps that would cause threshold voltage fluctuations. By maintaining this clean state through preliminary erasing, the system can maximize storage capacity utilization while ensuring that threshold voltage remains stable and accurate for data determination.
Solution Approach 2:
The control apparatus applies different management strategies to different blocks based on their operational history. Blocks that have undergone many erase operations are identified as having degraded retention characteristics and are treated differently from blocks with fewer operations. The system selectively erases and reallocates blocks based on their individual cycle counts, ensuring that only blocks suitable for maintaining data accuracy are used for new data storage, thereby maximizing overall storage capacity while maintaining data determination accuracy.
Data Source
AI summary
A flash memory module may include a plurality of flash memory chips. The memory chips may include one or more blocks. Each block may be a unit of erasing data. A flash controller may be coupled to the plurality of flash memory chips. The flash controller may program data to block and erase data from a block. The flash controller may manage a recent programming time for each of the plurality of blocks. The flash controller may erase data stored in a block for which an elapsed programming time is larger than a first value.