Non-volatile Memory Word Line Repurposing for Select Device Corruption
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Solution Overview
Problem
In non-volatile memory systems, particularly in 3D stacked memory devices, there is a challenge in maintaining data integrity and preventing uncorrectable errors due to corruption of select devices, which can lead to incorrect operation of memory cells and data retention issues.
Innovation Solution
The implementation of a control circuitry that repurposes a word line to function as an additional selection line, allowing memory cells connected to it to operate as select devices, thereby maintaining data integrity and correcting for corrupted select devices by programming them to a specific threshold voltage distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If select devices are used to control memory cells, then memory cell operation is enabled, but select device corruption causes data integrity issues and uncorrectable errors
Solution Approach 1:
The patent changes the operational parameter of the repurposed word line from data storage mode to select device mode by programming its threshold voltage to a specific distribution, enabling it to function as a selection line and compensate for corrupted select devices
Solution Approach 2:
The patent makes memory cells connected to data word lines capable of functioning dual-purpose: normally as data storage cells, but can be repurposed as select devices when needed, increasing system adaptability and reliability
2Reliability
If a word line is repurposed as a selection line, then select device corruption is compensated, but the memory cells connected to that word line cannot be used for data storage
Solution Approach 1:
The patent dynamically changes the functional parameter of the word line by programming threshold voltage distributions, allowing flexible reconfiguration between data storage and select device modes based on system needs
3Reliability
If memory cells are programmed to a specific threshold voltage distribution, then they can function as select devices, but their ability to store data is lost
Solution Approach 1:
The patent designs the memory architecture where cells can operate in multiple modes - data storage mode during normal operation, and select device mode when repurposed, maximizing resource utilization
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach ensures continued reliable operation of memory cells by identifying and addressing corrupted select devices, preventing errors and maintaining data retention, even in the presence of threshold voltage drift, thus ensuring data integrity and system stability.
Implementation Method 1
programming them to a specific threshold voltage distribution
Implementation Method 2
A charge-trapping material can be used in non-volatile memory devices to store a charge which represents a data state
Data Source
AI summary
A non-volatile memory system includes a plurality of non-volatile data memory cells arranged into groups of data memory cells, a plurality of select devices connected to the groups of data memory cells, a selection line connected to the select devices, a plurality of data word lines connected to the data memory cells, and one or more control circuits connected to the selection line and the data word lines. The one or more control circuits are configured to determine whether the select devices are corrupted. If the select devices are corrupted, then the one or more control circuits repurpose one of the word lines (e.g., the first data word line closet to the select devices) to be another selection line, thus operating the memory cells connected to the repurposed word line as select devices.