NAND Flash Word Line Voltage Control for Program Disturb
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Solution Overview
Problem
Conventional programming techniques for NAND flash memory devices suffer from program disturbs and insulation damage due to increased integration density, leading to unintended programming of non-selected memory cells and leakage currents.
Innovation Solution
Applying an elevated pass voltage to word lines adjacent to the selected word line during programming, which is higher than the normal pass voltage applied to other word lines, to minimize voltage differences and prevent insulation damage and leakage currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional programming techniques are used with increased integration density, then manufacturing precision and device complexity are improved, but program disturbs and insulation damage occur causing unintended programming of non-selected memory cells
Solution Approach 1:
The patent applies different voltage levels to different word lines based on their selection status: selected word lines receive program voltage (Vpgm), adjacent non-selected word lines receive elevated pass voltage (Vpass+), and other non-selected word lines receive normal pass voltage (Vpass). This localized voltage differentiation prevents program disturbs in adjacent cells while maintaining programming efficiency for selected cells, directly resolving the contradiction between high integration density and program disturb prevention.
Solution Approach 2:
The patent changes the voltage parameter for adjacent non-selected word lines from the normal pass voltage level to an elevated pass voltage level (Vpass+). This parameter modification ensures that the voltage difference between selected and adjacent non-selected word lines remains below the insulation breakdown threshold, preventing unintended programming while maintaining the benefits of increased integration density.
2Manufacturing precision
If conventional programming techniques are used with increased integration density, then manufacturing precision is improved, but insulation damage and leakage currents occur
Solution Approach 1:
The patent implements localized voltage control where adjacent non-selected word lines receive elevated pass voltage (Vpass+) specifically tailored to prevent insulation breakdown. This local voltage adjustment prevents harmful electrical stress on insulation layers in high-density configurations without affecting the overall programming performance or requiring changes to other parts of the system.
Solution Approach 2:
The patent applies elevated pass voltage to adjacent non-selected word lines before the programming operation begins. This preliminary voltage adjustment creates a protective potential distribution that cushions the insulation layers against excessive voltage differences during subsequent programming, preventing insulation damage and leakage currents before they can occur.
3Reliability
If program inhibit method using self-boosting scheme is used, then program disturb is reduced, but device complexity and power consumption increase
Solution Approach 1:
The patent segments the word line voltage control into three distinct groups: selected word lines (Vpgm), adjacent non-selected word lines (Vpass+), and other non-selected word lines (Vpass). This segmentation simplifies the control logic compared to self-boosting schemes by using direct voltage assignment rather than complex feedback circuits, reducing device complexity while maintaining program disturb prevention.
Solution Approach 2:
The patent uses a straightforward voltage assignment strategy where the controller directly provides appropriate voltages to different word line groups based on their addresses. This self-service approach eliminates the need for complex self-boosting circuits and feedback mechanisms, reducing device complexity and power consumption while still preventing program disturbs through proper voltage differentiation.
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 reduces program disturbs and insulation damage while maintaining data retention and performance by ensuring the voltage difference between word lines does not exceed the breakdown voltage, thereby enhancing the reliability of memory cells.
Implementation Method 1
The memory cells in NAND flash are erased and programmed using the so-called Fowler-Nordheim tunneling phenomenon
Data Source
AI summary
Provided are a non-volatile memory device and a programming method. The programming method includes applying a program voltage to a selected word line, applying an elevated pass voltage to word lines adjacent to the selected word line in a plurality of word lines, and applying a pass voltage to remaining word lines in the plurality of word lines.