Memory Read Voltage Offset Using Bin and Position in Partial Blocks
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Solution Overview
Problem
Conventional memory systems face issues with abnormal voltage distributions in partial blocks due to charge migration and string current differences, leading to incorrect voltage offsets and high raw bit error rates, particularly when the last written page value is not updated, resulting in unnecessary refresh operations.
Innovation Solution
The memory subsystem determines voltage offsets using memory bins and positions, grouping memory portions based on data retention time and temperature, to accurately track voltage distribution changes and reduce error rates by applying appropriate offsets to inner and boundary wordlines.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional voltage offset determination methods are used in partial blocks, then the system operates with simpler voltage management, but abnormal voltage distributions occur due to charge migration and string current differences, leading to high raw bit error rates
Solution Approach 1:
The memory block is segmented into multiple memory bins based on data retention time, and further divided into inner wordlines and boundary wordlines. This segmentation allows different voltage offset strategies to be applied to different segments, improving reliability by addressing the specific needs of each segment while managing complexity through organized classification.
Solution Approach 2:
Different voltage offset determination methods are applied to different regions: inner wordlines use one method while boundary wordlines use another. This local quality approach addresses the abnormal voltage distributions caused by charge migration and string current differences by tailoring the voltage offset strategy to the specific characteristics of each region, thereby reducing raw bit error rates.
2Productivity
If the last written page value is used to determine voltage offsets, then the voltage offset determination is simplified, but incorrect voltage offsets are applied when the last written page value is not updated, resulting in unnecessary refresh operations
Solution Approach 1:
The system uses feedback from read operations to update the determined voltage offset. By performing read operations and updating the voltage offset based on the results, the system ensures accurate voltage offset determination without relying solely on the last written page value, thereby reducing unnecessary refresh operations while maintaining high voltage offset accuracy.
Solution Approach 2:
The system performs preliminary read operations to determine the voltage offset before actual data read operations. This preliminary action ensures that the voltage offset is accurately determined based on current memory conditions rather than relying on potentially outdated last written page values, improving both productivity by reducing unnecessary refreshes and measurement precision.
3Measurement precision
If memory bins based on data retention time and temperature are implemented, then voltage distribution changes are tracked more accurately, but the system complexity increases due to additional tracking parameters
Solution Approach 1:
Memory bins are segmented based on data retention time and temperature ranges, creating organized groups that simplify the management of complex tracking parameters. This segmentation allows the system to track voltage distribution changes accurately by associating specific voltage offset strategies with specific bin characteristics, thereby improving measurement precision while managing device complexity through structured classification.
Solution Approach 2:
The system adds temperature as an additional dimension to the memory bin classification, transforming the tracking from a single-parameter (time-based) system to a multi-dimensional system. This dimensional change enables more accurate voltage distribution tracking by accounting for both time and temperature effects, while the structured bin organization manages the increased complexity through systematic categorization.
Data Source
AI summary
Methods, systems, and apparatuses include receiving, by a memory subsystem, a read command from a host device to read data from a memory portion of the memory subsystem. It is determined that the memory portion includes a partial block. A memory bin is determined for the memory portion in response to determining that the memory portion includes the partial block. A position is determined for the memory portion. A voltage offset is applied to a read voltage for the memory portion using the memory bin and the position.