Key-Hole Memory Cell Profile for Coupling Ratio
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Solution Overview
Problem
Current memory devices face challenges in increasing the coupling ratio of memory cells without increasing the size of the memory cells, which affects the voltage required for programming and erasing, and the overall density of the memory array.
Innovation Solution
The method involves creating a key-hole shaped memory cell profile with a circularly shaped portion and projecting portions, which increases the interface area between the charge storage structure and the control gate, thereby enhancing the gate coupling ratio without increasing the cross-sectional area of the channel region.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the size of memory cells is increased to increase the coupling ratio, then the capacitance between control gate and floating gate is improved, but the memory density is reduced
Solution Approach 1:
The patent transitions from a conventional planar memory cell layout to a three-dimensional vertical stack architecture. Multiple memory cells are stacked vertically along a channel, allowing the coupling ratio to be improved through increased vertical interface area between control gates and floating gates, while maintaining high memory density by utilizing the vertical dimension rather than expanding horizontally.
Solution Approach 2:
The patent implements a nested structure where multiple floating gates are positioned at different vertical levels within the stack, each surrounded by its own control gate. This nesting arrangement allows multiple charge storage structures to be contained within a single vertical channel region, increasing the coupling ratio for each cell while maintaining compact spacing to preserve memory density.
2Reliability
If the interface area between charge storage structure and control gate is increased to enhance coupling ratio, then the capacitance is improved, but the cross-sectional area of channel region is increased
Solution Approach 1:
The patent resolves this contradiction by moving the interface area expansion from the horizontal plane to the vertical dimension. The key-hole profile creates additional vertical sidewall area for the floating gate to interface with the control gate, increasing coupling ratio without expanding the horizontal cross-sectional area of the channel region.
Solution Approach 2:
The key-hole shaped profile of the floating gate incorporates curved surfaces, particularly the circular portion that provides a rounded interface with the control gate. This curved geometry maximizes the interfacial contact area between the charge storage structure and control gate within the constrained horizontal footprint, enhancing coupling ratio without increasing channel region area.
3Ease of manufacture
If conventional memory cell profiles are used, then the manufacturing process is simple, but the coupling ratio is insufficient
Solution Approach 1:
The key-hole shaped floating gate profile is segmented into distinct geometric features: a circular portion providing a rounded interface and one or more rectangular portions extending vertically. This segmentation allows each feature to be optimized for its function while maintaining manufacturability through standard semiconductor fabrication processes that can create both curved and angular features.
Solution Approach 2:
The key-hole profile is an asymmetric shape that combines a circular portion with rectangular extensions, breaking the symmetry of conventional floating gate structures. This asymmetric design optimizes the interface area with the control gate while maintaining compatibility with existing manufacturing processes, achieving improved coupling ratio without requiring complete process overhaul.
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 increases the capacitance between the control gate and the floating gate, reducing the voltage needed for programming and erasing while maintaining memory density by increasing the interface area without expanding the cell size.
Implementation Method 1
This approach increases the capacitance between the control gate and the floating gate, reducing the voltage needed for programming and erasing while maintaining memory density by increasing the interface area without expanding the cell size.
Data Source
AI summary
Examples of the present disclosure provide devices and methods for processing a memory cell. A method embodiment includes removing a key-hole shaped column from a material, to define a profile for the memory cell. The method also includes partially filling the key-hole shaped column with a first number of materials. The method further includes filling the remaining portion of the key-hole shaped column with a second number of materials.