Hybrid Local Boosting for Nonvolatile Memory Programming
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Solution Overview
Problem
Program disturbance occurs in nonvolatile memory devices during programming, particularly when programming from lower cells to upper cells, due to charge sharing and reduced boosting efficiency, which affects the accuracy and reliability of data storage.
Innovation Solution
A hybrid boosting method is employed, combining self-boosting and local boosting, where cells are programmed using self-boosting when the selected wordline is under a reference wordline and local boosting when it is above, to prevent program disturbance by managing voltages and reducing charge sharing effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If self-boosting is used for programming cells from lower to upper wordlines, then programming can be performed with simple voltage application, but program disturbance occurs due to charge sharing and reduced boosting efficiency
Solution Approach 1:
The patent segments the programming operation into two distinct modes: self-boosting mode for programming cells on and below the reference wordline, and local boosting mode for programming cells above the reference wordline. This segmentation allows each mode to be optimized for its specific function, preventing program disturbance while maintaining programming effectiveness.
Solution Approach 2:
The patent dynamically switches between self-boosting and local boosting modes based on the position of the selected wordline relative to the reference wordline. The control logic automatically selects the appropriate boosting mode, enabling adaptive voltage management that prevents charge sharing and program disturbance while maintaining programming simplicity where applicable.
2Reliability
If local boosting is used for all programming operations, then program disturbance is prevented, but device complexity increases due to additional voltage management requirements
Solution Approach 1:
The patent applies local boosting only to the specific region above the reference wordline where program disturbance occurs, while using simple self-boosting for cells on and below the reference wordline. This localized application of the more complex boosting method minimizes the overall voltage management complexity while effectively preventing program disturbance in the critical region.
Solution Approach 2:
The patent uses local boosting selectively only when necessary (for cells above the reference wordline) rather than applying it universally. This partial action approach prevents program disturbance in the critical region while avoiding the full complexity of local boosting throughout the entire memory array, thus optimizing the trade-off between reliability and 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 effectively reduces program disturbance, maintains accurate programming, and enhances the overall efficiency of the nonvolatile memory device by optimizing voltage management and circuit design.
Implementation Method 1
electrons are injected into the floating gate of the cell transistor according to the F-N tunneling effect
Implementation Method 2
electrons existing in the floating gate region are discharged to the bulk according to the F-N tunneling effect
Data Source
AI summary
A method of programming a nonvolatile memory device using hybrid local boosting which includes a plurality of cell strings each having a plurality of electrically erasable and programmable memory cells connected in series and a plurality of wordlines respectively connected to control gates of the plurality of memory cells. The address of a selected cell that is to be programmed is received. A determination is made as to whether a selected wordline connected to the selected cell is located above or under a reference wordline based on the received address. The selected cell is programmed using local boosting when the selected wordline corresponds to the reference wordline or is located above the reference wordline. The selected cell is programmed using self-boosting when the selected wordline is located under the reference wordline. The programming method reduces circuit size of a nonvolatile memory device employing the programming method and efficiently prevents program disturbance due to charge sharing.