NAND Memory Channel Gradient for Read Disturb and Power Reduction
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Solution Overview
Problem
Non-volatile memory systems face challenges in preventing read disturb and power consumption during data read operations, particularly in NAND string configurations where unselected sub-blocks can experience unwanted current draw and potential data state changes.
Innovation Solution
The implementation of independently controlled source and drain side select lines for NAND strings, allowing unselected sub-blocks to float during read processes, and adjusting word line voltages to create a channel potential gradient that avoids read disturb, while ensuring unselected sub-blocks do not draw current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If unselected sub-blocks are left floating during read operations, then power consumption is reduced, but read disturb may occur causing data state changes
Solution Approach 1:
The patent applies local quality by creating a channel potential gradient specifically in unselected sub-blocks through adjusted word line voltages. This gradient ensures that current flow is localized and controlled, preventing read disturb while maintaining the floating state for power reduction. The selective voltage adjustment creates different electrical conditions in different regions (selected vs. unselected sub-blocks) to achieve both power efficiency and data reliability.
2Reliability
If independently controlled source and drain side select lines are implemented, then read disturb is prevented, but device complexity increases
Solution Approach 1:
The patent implements segmentation by dividing the select line control into independent source side select lines and drain side select lines. This segmentation allows separate control of the two ends of each NAND string, enabling precise control of current flow paths. By segmenting the control functions, the patent can independently manage voltage levels to prevent read disturb without requiring complete redesign of the entire control system.
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 reduces power consumption and prevents data state changes in unselected NAND strings during read operations, enhancing data reliability and extending battery life in mobile devices.
Implementation Method 1
adjusting word line voltages to create a channel potential gradient that avoids read disturb
Data Source
AI summary
To save power during a read process, NAND strings of each sub-block of a block have independently controlled source side select lines connected to source side select gates and drain side select lines connected to drain side select gates so that NAND strings of unselected sub-blocks can float and not draw current. To prevent read disturb in NAND strings of unselected sub-blocks, after all word lines are raised to a pass gate voltage, unselected word lines nearby the selected word line are lowered to respective intermediate voltages while lowering the voltage on the selected word line in order to achieve a channel potential gradient in the floated NAND strings of the unselected sub-blocks that does not result in read disturb. Subsequently, the selected word line is raised to the appropriate read compare voltage so the selected memory cells can be sensed.