Nonvolatile Memory Wordline Voltage Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Nonvolatile semiconductor memory devices face challenges in efficiently managing wordline coupling, which affects the performance and characteristics of memory cells, particularly in three-dimensional memory structures where stacked wordlines can lead to uneven voltage distribution and reduced operational efficiency.
Innovation Solution
The method involves applying different unselected wordline voltages based on their layer position relative to the selected wordline, using a storage device with a memory controller that compensates for wordline coupling by varying voltages during program and read operations, ensuring optimal voltage distribution across unselected wordlines.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the same unselected wordline voltage is applied to all unselected wordlines regardless of layer position, then the control logic is simplified, but wordline coupling effects cause performance degradation in memory cells
Solution Approach 1:
The patent applies different unselected wordline voltages to wordlines at different layer positions relative to the selected wordline. Specifically, unselected wordlines at the same layer as the selected wordline receive a first voltage level, while unselected wordlines at different layers receive a second voltage level. This local differentiation compensates for wordline coupling effects that vary by position, thereby improving memory cell performance without requiring unique voltages for every single wordline.
Solution Approach 2:
The patent segments the unselected wordlines into two groups based on their layer position relative to the selected wordline: those at the same layer and those at different layers. Each segment receives a tailored voltage level appropriate for its coupling characteristics. This segmentation approach allows differentiated voltage control to address wordline coupling issues while maintaining simpler control logic compared to individually controlling each wordline.
2Reliability
If different unselected wordline voltages are applied to compensate for wordline coupling, then memory cell characteristics are improved, but the voltage control mechanism becomes more complex
Solution Approach 1:
The patent implements local quality by assigning specific voltage levels to unselected wordlines based on their spatial relationship to the selected wordline. Unselected wordlines coplanar with the selected wordline receive one voltage level, while unselected wordlines at different layers receive another voltage level. This localized voltage assignment improves memory cell characteristics by compensating for position-dependent coupling effects while keeping the control mechanism manageable through clear spatial criteria.
3Reliability
If multiple voltage levels are applied to unselected wordlines based on layer position, then wordline coupling is effectively managed, but the number of voltage control signals increases
Solution Approach 1:
The patent manages wordline coupling by applying two distinct voltage levels to unselected wordlines based on their layer position. Unselected wordlines at the same layer as the selected wordline receive a first voltage level, while unselected wordlines at different layers receive a second voltage level. This approach effectively addresses coupling effects with only two voltage levels, avoiding the need for unique voltage control for each individual wordline and thus limiting the increase in control signal complexity.
Data Source
AI summary
An operating method of a nonvolatile memory device including a plurality of strings each string including at least two pillars penetrating wordlines disposed at different layers. The operating method includes applying unselected wordline voltages to unselected wordlines, and applying a selected wordline voltage to a selected wordline, and the unselected wordline voltage applied to the same layer as a layer of the selected wordline is different from the unselected wordline voltage applied to a different layer than the layer of the selected wordline.