3D Memory Select Gates Fringe Field Programming Leakage
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Solution Overview
Problem
Three-dimensional memory devices face challenges in minimizing leakage current and enhancing control of electrical charges due to incomplete encirclement of drain select gate electrodes, leading to degraded performance in programming and reading operations.
Innovation Solution
The implementation of fringe field assisted programming, which involves applying specific bias voltages to drain select gate electrodes and bit lines to induce charge injection into fringe field assisted charge injection regions, thereby reducing leakage current and improving charge trapping and control within memory films.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If drain select gate electrodes are used to control memory strings, then programming and reading operations can be performed, but leakage current increases due to incomplete encirclement of the memory stack structure
Solution Approach 1:
The drain select gate electrode is segmented into two distinct parts: a first drain select gate electrode that completely surrounds the memory stack structure, and a second drain select gate electrode that is spaced apart and does not completely surround the memory stack structure. This segmentation allows each gate to perform specialized functions - the first gate provides complete encirclement for reliable charge control, while the second gate enables programming operations without requiring full encirclement, thereby reducing leakage current while maintaining device functionality.
Solution Approach 2:
Different regions of the drain select gate structure are given different properties - the first drain select gate electrode is positioned to provide complete encirclement for optimal charge control and leakage prevention, while the second drain select gate electrode is positioned to enable programming operations. This local differentiation of gate electrode properties allows the system to optimize both leakage current control and programming capability simultaneously.
2Productivity
If fringe field assisted programming is applied, then charge injection efficiency improves, but device complexity increases due to additional bias voltage requirements
Solution Approach 1:
The fringe field assisted programming method applies bias voltages to the drain select gate electrodes and bit lines before and during the charge injection process. By establishing the appropriate electric field configuration in advance through preliminary biasing, the charge injection efficiency is enhanced as charges are guided into the memory film more effectively. This preliminary action reduces the need for complex real-time control during programming operations.
Solution Approach 2:
The programming operation utilizes changes in electrical parameters - specifically applying different bias voltages to the first and second drain select gate electrodes and to the bit lines. By dynamically adjusting these voltage parameters during the programming sequence, the system creates the necessary fringe fields to enhance charge injection efficiency without requiring structural modifications that would increase device complexity.
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 significantly reduces leakage current and enhances control of electrical charges, improving the efficiency of programming and reading operations in three-dimensional memory devices by effectively managing the electrical fields across drain select level isolation structures.
Implementation Method 1
applying specific bias voltages to drain select gate electrodes and bit lines to induce charge injection into fringe field assisted charge injection regions
Implementation Method 2
induce charge injection into fringe field assisted charge injection regions, thereby reducing leakage current and improving charge trapping and control within memory films
Data Source
Figure 1
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Figure 3A
AI summary
A method of operating a three-dimensional memory device includes applying a target string bias voltage to a selected drain select gate electrode which partially surrounds a row of memory stack structures that directly contact a drain select isolation structure, and applying a neighboring string bias voltage that has a greater magnitude than the target string bias voltage to an unselected drain select gate electrode that contacts the drain select level isolation structure.