3D Non-Volatile Memory Programming for Read Disturb
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In 3D non-volatile memory devices, variations in memory hole diameter lead to non-uniform programming and erase speeds, causing read disturb and reducing reliability due to varying electric fields across tunnel oxide, which affects the threshold voltage distribution and read pass window, resulting in potential read errors, especially for frequently accessed memory cells.
Innovation Solution
Adjusting programming based on the position of memory cells within the stack according to memory hole diameter variations by modifying the word line layer thicknesses and using customized read pass voltages to narrow or shift threshold voltage distributions, thereby reducing read disturb and maintaining data integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If memory holes are drilled with high aspect ratio to achieve ultra high density storage, then storage capacity is improved, but variations in memory hole diameter occur causing non-uniform programming and erase speeds
Solution Approach 1:
The patent applies local quality by making word line layers with different thicknesses at different vertical positions in the stack. Specifically, word line layers adjacent to narrower memory hole portions have greater thickness than those adjacent to wider portions. This compensates for the non-uniform memory hole diameter and achieves uniform programming characteristics across the stack, resolving the contradiction between high density storage and manufacturing precision.
2Ease of operation
If read pass voltage is applied to unselected memory cells during sensing, then sensing operation is enabled, but read disturb occurs increasing upper tail of erased state distribution
Solution Approach 1:
The patent applies parameter changes by adjusting the read pass voltage based on the memory hole diameter at different vertical positions. Memory cells adjacent to narrower memory hole portions use lower read pass voltages, while those adjacent to wider portions use higher voltages. This compensates for the varying electric field strength and prevents excessive read disturb, resolving the contradiction between sensing operation and reliability.
3Productivity
If memory cells are programmed with higher speed to improve productivity, then programming speed is improved, but threshold voltage distribution becomes wider reducing read window
Solution Approach 1:
The patent applies local quality by implementing position-dependent programming conditions. Memory cells adjacent to narrower memory hole portions use different programming parameters (lower voltage or fewer pulses) compared to those adjacent to wider portions. This compensates for the inherently faster programming speed in narrower holes and achieves uniform threshold voltage distribution across the stack, resolving the contradiction between programming speed and measurement precision.
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 enhances the reliability of 3D non-volatile memory devices by reducing read disturb and maintaining accurate data retrieval by optimizing programming and sensing operations based on memory hole diameter variations, ensuring consistent performance across the memory array.
Implementation Method 1
variations in memory hole diameter lead to non-uniform programming and erase speeds, causing read disturb and reducing reliability due to varying electric fields across tunnel oxide
Data Source
Figure 1A~1B
Figure 2A
Figure 2B1~2B2
AI summary
Techniques are provided for programming and reading memory cells in a 3D stacked non-volatile memory device by compensating for variations in a memory hole diameter. The memory hole diameter is smaller at the bottom of the stack, resulting in more severe read disturb. To compensate, programming of memory cells at the lower word line layers is modified. In one approach, threshold voltage (Vth) distributions of one or more data states are narrowed during programming so that a lower read pass voltage can be used in a subsequent sensing operation. A sufficient spacing is maintained between the read pass voltage and the upper tail of the highest data state. The Vth distributions can be downshifted as well. In another approach, the read pass voltage is not lowered, but the lowest programmed state is upshifted to provide spacing from the upper tail of the erased state.