Dynamic Dummy Word Line Voltage for Memory Channel Pre-charge
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Solution Overview
Problem
Memory devices face challenges in reducing program disturb, which leads to read errors due to capacitive coupling from selected to unselected word lines, especially affecting memory cells intended to remain in the erased state during programming operations.
Innovation Solution
The implementation of a dynamic control over the drain-side dummy word line voltage based on the position of the selected word line, adjusting its voltage to be higher when the selected word line is far and lower when closer, to minimize channel gradient and hot carrier generation, thereby reducing program disturb.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a fixed high voltage is applied to the drain-side dummy word line to pre-charge the channel, then channel pre-charge is improved, but program disturb increases due to excessive channel gradient and hot carrier generation
Solution Approach 1:
The patent applies dynamics by transitioning from a fixed dummy word line voltage to a dynamic voltage that changes based on the selected word line position. The control circuit adjusts the dummy word line voltage to be higher when the selected word line is far from the drain side and lower when closer, optimizing the balance between channel pre-charge and program disturb reduction for each programming operation.
Solution Approach 2:
The patent applies local quality by tailoring the dummy word line voltage according to the specific position of the selected word line. Different voltage levels are applied locally based on the distance between the selected word line and the drain side, creating optimized pre-charge conditions for each local programming scenario while minimizing hot carrier generation in the specific region being programmed.
2Object-generated harmful factors
If the dummy word line voltage is increased to reduce program disturb for word lines far from the drain, then program disturb is reduced, but channel pre-charge becomes insufficient for word lines close to the drain
Solution Approach 1:
The control circuit dynamically adjusts the dummy word line voltage based on real-time selection of the word line position. When a word line close to the drain is selected, the dummy word line voltage is increased to ensure adequate channel pre-charge. When a word line far from the drain is selected, the voltage is reduced to minimize program disturb, thus adapting to different operational requirements.
Solution Approach 2:
The patent implements local quality by applying different dummy word line voltage levels tailored to the specific programming location. Word lines close to the drain receive higher dummy word line voltage for adequate pre-charge, while word lines far from the drain receive lower voltage to minimize program disturb, optimizing performance for each local region.
3Reliability
If channel pre-charge is enhanced uniformly across all word lines, then channel pre-charge is improved, but hot carrier generation increases leading to more read errors
Solution Approach 1:
The patent applies local quality by differentiating the dummy word line voltage based on the selected word line's position. Instead of uniform pre-charge, the system applies higher voltage only when necessary (when the selected word line is far from the drain) and lower voltage when the selected word line is close to the drain, optimizing the balance between pre-charge and hot carrier generation for each local scenario.
Solution Approach 2:
The patent changes the parameter of dummy word line voltage dynamically based on the selected word line position. The control circuit modifies the voltage parameter in response to the programming operation's location, adjusting it to be higher for word lines far from the drain and lower for word lines close to the drain, thereby optimizing channel pre-charge while minimizing hot carrier generation and read errors.
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 effectively enhances channel pre-charge while minimizing program disturb, maintaining low levels of error across all positions of the selected word line, thereby improving the overall reliability of memory device programming.
Implementation Method 1
program disturb, which leads to read errors due to capacitive coupling from selected to unselected word lines
Data Source
Figure 1
Figure 2
Figure 3A~3B
AI summary
Techniques are provided for programming a memory device. A pre-charge phase is used to boost the channel of an unselected NAND string by allowing a bit line voltage to reach the channel. To maximize the channel pre-charge while also minimizing program disturb, a drain-side dummy word line voltage is controlled based on the position of the selected word line. The drain-side dummy word line voltage can be relatively high or low when the selected word line is relatively far from or close to the drain-side dummy word line, respectively. When the drain-side dummy word line voltage is relatively high, the bit line voltage can easily pass through and boost the channel. When the drain-side dummy word line voltage is relatively low, program disturb of drain-side data word lines is reduced due to a smaller channel gradient and a corresponding reduced amount of hot carriers.