Partially Programmed Memory Block Padding for Data Retention
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Solution Overview
Problem
Non-volatile memory devices face issues of poor data reliability and read latency due to partially programmed blocks, where the last programmed wordline adjacent to unprogrammed wordlines experiences electron migration and threshold voltage differences, leading to data retention loss and read errors.
Innovation Solution
Performing a write operation to write padding data on unprogrammed wordlines adjacent to the last programmed wordline to rebalance the block state, using patterns that match or differ from the last programmed wordline data to reduce electron migration and threshold voltage disparities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a write operation is performed to partially program a block of non-volatile memory, then data storage capacity is utilized, but data retention deteriorates due to electron migration and threshold voltage differences at the boundary between programmed and unprogrammed wordlines
Solution Approach 1:
The patent applies local quality by writing padding data specifically to unprogrammed wordlines adjacent to the last programmed wordline, creating a localized transition zone. This targeted approach improves data retention at the critical boundary without affecting the entire block, allowing partial programming of blocks while maintaining reliability at the programmed-unprogrammed interface.
Solution Approach 2:
The patent performs preliminary action by writing padding data to adjacent unprogrammed wordlines immediately after the main data write operation completes. This preliminary padding write prepares the memory block for future operations by pre-establishing a stable threshold voltage profile at the boundary, preventing electron migration before it can occur during subsequent read or program operations.
2Reliability
If padding data is written to unprogrammed wordlines adjacent to the last programmed wordline, then data retention improves by stabilizing threshold voltage, but write operation time increases
Solution Approach 1:
The patent applies partial action by writing padding data to only the specific unprogrammed wordlines adjacent to the last programmed wordline, rather than writing to all unprogrammed wordlines in the block. This selective approach provides sufficient protection against electron migration at the critical boundary while minimizing the additional write time required, avoiding the excessive action of padding the entire block.
Solution Approach 2:
The patent changes the parameter of threshold voltage stability by introducing padding data with specific voltage characteristics to the adjacent unprogrammed wordlines. This parameter change creates a gradual transition zone that stabilizes the electric field, reducing electron migration. The padding data is written with controlled parameters to achieve the desired threshold voltage profile with minimal time penalty.
3Speed
If padding data is written to unprogrammed wordlines, then read latency improves by reducing read errors, but device complexity increases
Solution Approach 1:
The patent applies self-service by implementing the padding write operation within the existing memory controller and write operation infrastructure. The controller automatically identifies the last programmed wordline and writes padding data to adjacent unprogrammed wordlines using the same write mechanisms already present in the device. This approach reduces read latency and eliminates read errors without requiring additional hardware components or complex external systems.
Data Source
AI summary
In some implementations, a controller may detect a power loss event on a non-volatile memory device. The controller may perform, based on detecting the power loss event, a first write operation to write data to a first portion of a block of the non-volatile memory device. Prior to the first write operation, the data may be stored in a memory of a controller of the non-volatile memory device. After the first write operation, the first portion of the block may include programmed wordlines. After the first write operation, a second portion of the block may include unprogrammed wordlines. The controller may perform a second write operation to write padding data to an unprogrammed wordline of the unprogrammed wordlines that is adjacent to a last programmed wordline of the programmed wordlines.