3D NAND Precharge Control Using Middle Dummy Word Lines
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Solution Overview
Problem
In 3D NAND memory devices, insufficient precharge capability leads to programming disturbance and increased high bound of memory cell erase state, causing loss of read space due to redundant precharge affecting adjacent word lines.
Innovation Solution
A precharging method that controls the on/off state of middle dummy word lines based on the position of the word line being programmed, applying precharge voltage only when necessary to maintain precharge capability and prevent disturbance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the middle dummy word line group is continuously turned on and off during programming of bottom-deck word lines, then the precharge voltage is applied to the channel, but programming disturbance occurs on adjacent boundary word lines due to redundant precharge
Solution Approach 1:
The patent dynamically adjusts the on/off state of the middle dummy word line group based on the programming stage. During programming of top-deck word lines, the middle dummy word line group is turned on to provide precharge capability. During programming of bottom-deck word lines, the middle dummy word line group is turned off to prevent redundant precharge and associated disturbance. This dynamic control resolves the contradiction by adapting the precharge mechanism to the specific programming context.
Solution Approach 2:
The patent applies different precharge strategies to different regions of the memory device based on the selected word line position. When the selected word line is in the top-deck, precharge is applied to the channel through the middle dummy word line group. When the selected word line is in the bottom-deck, precharge is prevented from reaching the channel by keeping the middle dummy word line group off. This localized approach ensures precharge capability where needed while avoiding harmful effects where not needed.
2Reliability
If the middle dummy word line group is turned on to apply precharge voltage from the common source line, then precharge capability is improved, but the threshold voltage of the middle dummy word line group impacts precharge effectiveness
Solution Approach 1:
The patent applies precharge voltage to the middle dummy word line group before programming operations to prepare the channel for subsequent programming. This preliminary action ensures that the channel is properly precharged and ready for programming, improving precharge capability while managing the complexity through systematic voltage application sequences.
3Reliability
If precharge voltage is applied to maintain precharge capability, then programming disturbance is reduced, but read space window is lost due to increased high bound of memory cell erase state
Solution Approach 1:
The patent changes the operational parameters of the middle dummy word line group based on the programming context. By adjusting the on/off state and voltage application timing, the patent optimizes the balance between preventing programming disturbance and maintaining read space window. This parameter control ensures that precharge is applied effectively without excessively increasing the high bound of the erase state.
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
Prevents programming disturbance by ensuring appropriate precharge voltage application, maintaining precharge capability, and reducing erroneous read states in 3D memory devices.
Implementation Method 1
applying a precharge on voltage to the middle dummy word line group so that a precharge voltage reaches a channel at a position corresponding to the middle dummy word line group
Data Source
AI summary
Provided are a precharging method and a programming method for a 3D memory device that includes a top-deck word line group, a middle dummy word line group, a bottom-deck word line group, and a bottom dummy word line group. The precharging method includes: selecting a word line to be programmed; determining whether the word line is in the top- or bottom-deck word line group; applying a precharge on voltage to the middle dummy word line group to turn on a channel to precharge the channel when the word line is in the top-deck word line group; and applying a precharge off voltage to the middle dummy word line group to turn off the channel to not precharge the channel when the word line is in the bottom-deck word line group. This method is suitable for a 3D NAND flash memory having high capacity and high performance.