3D Nonvolatile Memory Programming via Negative Voltage Pre-biasing
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Solution Overview
Problem
The development of three-dimensional nonvolatile memory devices faces challenges in improving integration density and reliability of program operations, particularly in applying voltages effectively to stacked memory cells.
Innovation Solution
A method and device for programming nonvolatile memory devices with a plurality of cell strings, where a negative voltage is applied to selected and unselected word lines, followed by a pass voltage, and then a program voltage is applied to the selected word line while maintaining the pass voltage on unselected word lines, enhancing boosting efficiency and reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a program voltage is applied directly to the selected word line in a three-dimensional nonvolatile memory device, then programming speed is improved, but unselected memory cells may be accidentally programmed due to voltage boosting, reducing reliability
Solution Approach 1:
The patent applies preliminary negative voltages to unselected word lines before applying the program voltage to the selected word line. This preliminary action prevents voltage boosting in unselected cell strings, thereby preventing accidental programming of unselected memory cells while maintaining fast programming speed for selected cells
Solution Approach 2:
The patent applies counteracting negative voltages to unselected word lines in advance to offset the harmful voltage boosting effect that would otherwise occur during program operations. This preliminary anti-action ensures that unselected memory cells remain protected from accidental programming while allowing selected cells to be programmed efficiently
2Quantity of substance
If integration density is increased by stacking multiple memory cells in three-dimensional structure, then storage capacity is improved, but voltage distribution and program operation reliability deteriorate
Solution Approach 1:
The patent applies different voltages to different word lines based on their selection status. Selected word lines receive program voltage for programming, while unselected word lines receive negative voltages to prevent voltage boosting. This local differentiation ensures reliable program operations in three-dimensional stacked memory structures with high integration density
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 improves the reliability and efficiency of program operations by reducing electron density in unselected cell strings, thereby inhibiting programming of unselected cells and enhancing the boosting efficiency of selected cells, leading to improved memory device performance.
Implementation Method 1
applying a negative voltage to a selected word line connected to a selected memory cell in one of the cell strings and to unselected word lines connected to unselected memory cells in the one of the cell strings
Implementation Method 2
improving boosting efficiency according to the applied voltages
Data Source
AI summary
A three-dimensional nonvolatile memory device comprises a plurality of cell strings arranged perpendicular to a substrate. The nonvolatile memory device is programmed by identifying a selected word line and a plurality of unselected word lines connected to at least one of the cell stings, and sequentially applying a negative voltage and a pass voltage to the selected and unselected word lines, and then applying a program voltage to the selected word line while continuing to apply the pass voltage to the unselected word lines.