Non-Volatile Memory Pre-Charge Voltage Control
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Solution Overview
Problem
Existing flash memory systems face challenges in preventing program disturb, where unselected cells connected to the same word line as the selected cell for programming are inadvertently programmed due to shared program voltage, leading to errors and data integrity issues.
Innovation Solution
The solution involves pre-charging unselected groups of non-volatile storage elements to a higher potential before applying the program voltage, using different pre-charge enable voltages for cells that have completed programming and those that have not, to reduce or eliminate program disturb by ensuring equal boosting of channel regions on both the source and drain sides of the selected word line.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single pre-charge enable voltage is used for all word lines, then the control circuit is simple, but program disturb occurs in unselected cells that have completed programming
Solution Approach 1:
The patent applies different pre-charge enable voltages to different word lines based on their programming status. Word lines that have completed programming receive a first pre-charge enable voltage, while word lines that have not completed programming receive a second pre-charge enable voltage. This local differentiation ensures that only the appropriate word lines are pre-charged, preventing program disturb in unselected cells while maintaining control simplicity through status-based classification.
Solution Approach 2:
The patent dynamically adjusts the pre-charge enable voltage based on the programming status of each word line. The control circuit determines which voltage level to apply by monitoring whether the word line has completed programming, allowing the system to adapt its behavior to current operational conditions. This dynamic approach enables the system to prevent program disturb while managing complexity through conditional control logic.
2Manufacturing precision
If pre-charge enable voltage is applied to all word lines, then all cells are pre-charged uniformly, but channel regions on source and drain sides cannot be boosted equally
Solution Approach 1:
The patent differentiates pre-charge enable voltages based on the position and programming status of word lines relative to the selected word line. Source side word lines receive one voltage level while drain side word lines receive another level, enabling independent control of channel boosting in different regions. This local quality approach allows equal boosting of channel regions on both sides by adjusting voltages according to specific regional requirements.
Solution Approach 2:
The patent segments word lines into different groups based on their position (source side vs. drain side) and programming status. Each segment receives a customized pre-charge enable voltage that is optimized for its specific function and state. This segmentation enables precise control over channel boosting in different regions, achieving equality in channel potential while managing complexity through structured classification.
3Reliability
If different pre-charge enable voltages are applied to different word lines, then program disturb is reduced, but the control circuit becomes more complex
Solution Approach 1:
The patent implements local quality by applying different pre-charge enable voltages to different word lines based on their programming status. This differentiation is achieved through a control circuit that monitors whether each word line has completed programming and accordingly selects the appropriate voltage level. This approach protects data integrity by preventing program disturb in unselected cells while managing control complexity through status-based classification.
Solution Approach 2:
The control circuit incorporates feedback mechanisms to monitor the programming status of each word line and adjust the pre-charge enable voltage accordingly. By detecting whether a word line has completed programming and responding with the appropriate voltage level, the system ensures reliable operation while managing complexity through intelligent control logic that adapts to current states.
Data Source
AI summary
Unselected groups of non-volatile storage elements are boosted during programming to reduce or eliminate program disturb for targeted, but unselected memory cells connected to a selected word line. Prior to applying a program voltage to the selected word line and boosting the unselected groups, the unselected groups are pre-charged to further reduce or eliminate program disturb by providing a larger boosted potential for the unselected groups. During pre-charging, one or more pre-charge enable signals are provided at different voltages for particular non-volatile storage elements.