Word Line Group Ramp-Down for 3D NAND Read Recovery
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Solution Overview
Problem
Memory devices, particularly 3D NAND devices, suffer from latent read disturb issues due to the floating body effect, leading to read errors and performance degradation, as residual electrons in the channel region do not discharge effectively during the read recovery process.
Innovation Solution
Implementing a word line group-dependent read recovery period ramp-down technique, where different groups of word lines are ramped to varying voltages sequentially, allowing for controlled discharge of residual electrons and reducing latent read disturb effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a uniform read recovery period is applied to all word lines, then the device complexity is low, but latent read disturb effects occur due to ineffective discharge of residual electrons
Solution Approach 1:
The patent divides the word lines into multiple groups (first group and second group) with different read recovery periods. The first group of word lines uses a first read recovery period while the second group uses a second read recovery period that is longer than the first. This segmentation allows targeted discharge of residual electrons in different word line regions, reducing latent read disturb effects while maintaining manageable device complexity through structured control.
Solution Approach 2:
The patent applies different read recovery characteristics to different groups of word lines based on their specific needs. The second group of word lines, which may be more susceptible to residual electron accumulation, receives a longer read recovery period compared to the first group. This local quality approach optimizes the discharge effectiveness for each word line group without uniformly increasing the recovery period for all word lines.
2Reliability
If the read recovery period is extended to fully discharge residual electrons, then latent read disturb is reduced, but the productivity decreases due to longer operation time
Solution Approach 1:
The patent segments the word lines into groups with different read recovery periods, allowing the first group to use a shorter recovery period for faster operation while the second group uses a longer recovery period for thorough electron discharge. This segmentation enables the system to achieve adequate channel potential recovery without uniformly extending the read recovery period across all word lines, thus maintaining higher overall productivity.
Solution Approach 2:
The patent applies a longer read recovery period only to the second group of word lines that require it, rather than extending the recovery period for all word lines. This partial action approach ensures that the necessary electron discharge is achieved for susceptible word lines while avoiding unnecessary time delays for other word lines, thereby balancing reliability improvement with productivity maintenance.
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 latent read disturb effects and read error rates, enhancing the overall performance of memory devices by improving the channel potential recovery process.
Implementation Method 1
Memory devices, particularly 3D NAND devices, suffer from latent read disturb issues due to the floating body effect, leading to read errors and performance degradation, as residual electrons in the channel region do not discharge effectively during the read recovery process
Data Source
AI summary
Methods, systems, and devices for techniques for word line group (WLG) dependent read recovery (RRCV) period ramp down comprise initiating a read recovery process associated with a block of the array of memory cells, where the block comprises a first group of word lines at an initial voltage and a second group of word lines at the initial voltage; and causing the second group of word lines to be ramped from the initial voltage to a second ramp-down voltage, where the second ramp-down voltage is greater than a first ramp-down voltage for the first group of word lines. The second group of word lines may comprise an edge group of word lines within the block of the array of memory cells. The first ramp-down voltage may be a ground voltage or a negative voltage, and the second ramp-down voltage may be a voltage greater than the ground voltage.