Memory Pre-charge Voltage Segmentation to Reduce Hot Carrier Injection
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Solution Overview
Problem
Conventional memory device pre-charge methods suffer from hot carrier injection (HE) effects due to high voltage differences between turned-on and turned-off word lines, which reduce the read window and impact device performance.
Innovation Solution
A pre-charge method for memory devices that applies independently-controlled pre-charge voltages to turned-on word lines, selected from a range of reference voltages, while maintaining a voltage difference smaller than a predetermined reference voltage between adjacent turned-on and turned-off word lines during the pre-charge phase.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the same voltage is applied to all pre-charge word lines, then the device complexity is reduced, but hot carrier injection effects occur due to high voltage differences between adjacent turned-on and turned-off word lines
Solution Approach 1:
The patent segments the pre-charge voltage control by dividing word lines into different groups (first group and second group) that receive different pre-charge voltages. This segmentation allows the voltage difference between adjacent turned-on and turned-off word lines to be reduced, thereby mitigating hot carrier injection effects while maintaining manageable device complexity through systematic voltage assignment.
Solution Approach 2:
The patent applies local quality by assigning different pre-charge voltages to different groups of word lines based on their specific positions and operational states. The first pre-charge voltage is applied to word lines in the first group while the second pre-charge voltage is applied to word lines in the second group, creating locally optimized voltage conditions that reduce hot carrier injection at critical boundaries.
2Speed
If high program voltage is applied to word lines, then the programming speed is improved, but the read window is reduced due to hot carrier injection effects
Solution Approach 1:
The patent applies preliminary anti-action by implementing a specific pre-charge voltage scheme before the programming operation. By reducing the voltage difference between adjacent turned-on and turned-off word lines during the pre-charge phase through differentiated voltage application to different word line groups, the method prevents hot carrier injection effects that would otherwise occur during high-voltage programming, thereby protecting the read window while maintaining programming speed.
3Productivity
If the voltage difference between adjacent turned-on and turned-off word lines is large, then the pre-charge effectiveness is improved, but program disturbance occurs due to hot carrier injection
Solution Approach 1:
The patent applies parameter changes by modifying the pre-charge voltage parameters applied to different groups of word lines. By changing from a uniform pre-charge voltage to differentiated pre-charge voltages (first pre-charge voltage for the first group, second pre-charge voltage for the second group), the voltage difference at critical boundaries is reduced, preventing hot carrier injection and program disturbance while maintaining pre-charge effectiveness through appropriate voltage selection.
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 HE effects, enlarges the read window, and minimizes program disturbance, thereby enhancing the overall performance of the memory device.
Implementation Method 1
Too high program voltage, not enough boosting channel at inhibited cells or abrupt slope of the boosting channel may reduce the read window and thus the performance of the memory device is lowered. Abrupt slope of the channel level may possibly incur hot carrier injection (HE) effects and thus reduce the read window.
Data Source
AI summary
Provided are a memory device and a pre-charge method for a memory device. The pre-charge method includes: applying a plurality of independently-controlled pre-charge voltages to a plurality of turned-on word lines, wherein the plurality of pre-charge voltages are selected among a plurality of reference pre-charge voltages; and applying a plurality of turned-off voltages to a plurality of turned-off word lines. On a predetermined direction, a target turned-on word line among the plurality of turned-on word lines is adjacent to a next adjacent target turned-off word line among the plurality of turned-off word lines; and a voltage difference from the target turned-on word line toward the next adjacent target turned-off word line is smaller than a predetermined reference voltage difference.