Nonvolatile Memory Device Control Gate Segmentation
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Solution Overview
Problem
Nonvolatile memory devices face reliability issues due to misalignment of floating and control gate electrodes, leading to reduced capacitance and increased driving voltage, as they become smaller, making it difficult to maintain sufficient opposing area between these electrodes.
Innovation Solution
A nonvolatile memory device design featuring first and second floating gate electrodes with a control gate electrode having a line body and legs extending vertically, increasing the opposing area and capacitance by contacting both inner and outer side surfaces of the floating gate electrodes, thereby reducing the driving voltage required.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If memory devices are made smaller with decreasing design rules, then integration density is improved, but misalignment of floating gate electrodes and control gate electrodes increases, deteriorating device performance and reliability
Solution Approach 1:
The control gate electrode is segmented into a main body portion and multiple leg portions that extend downward to contact the floating gate electrodes at different positions. This segmentation allows the control gate to maintain proper alignment with the floating gate even when overall device dimensions are reduced, as the legs can be positioned to bridge alignment gaps between the main control gate body and the floating gate structures.
Solution Approach 2:
The control gate electrode extends in the vertical dimension by incorporating leg portions that reach downward to contact the floating gate electrodes. This vertical extension compensates for horizontal alignment issues that become more pronounced at smaller device sizes, effectively using the third dimension to maintain proper electrical coupling despite reduced planar dimensions.
2Area of moving object
If memory devices are made smaller, then integration density is improved, but the opposing area between control gate and floating gate electrodes decreases, reducing capacitance
Solution Approach 1:
The control gate electrode utilizes the vertical dimension by extending leg portions downward to contact the floating gate electrodes. This creates additional opposing area between the control gate and floating gate in the vertical direction, compensating for the reduction in horizontal opposing area that occurs when device size is scaled down.
Solution Approach 2:
The control gate is divided into a main body and multiple leg portions that contact the floating gate at different locations. This segmentation distributes the capacitance-forming interface across multiple contact points, effectively increasing the total opposing area between control and floating gates despite reduced overall device footprint.
3Area of moving object
If the opposing area between control gate and floating gate electrodes is reduced, then device size is decreased, but driving voltage must be increased to maintain sufficient capacitance
Solution Approach 1:
The leg portions of the control gate extend vertically to maintain adequate opposing area with the floating gate electrodes, thereby preserving sufficient capacitance without requiring increased driving voltage. This vertical extension allows the device to be scaled down in planar dimensions while maintaining the electrical coupling necessary for low-voltage operation.
Solution Approach 2:
The segmented control gate structure with multiple leg portions creates distributed capacitance pathways to the floating gate electrodes. This segmentation maintains sufficient total capacitance despite reduced device size, allowing operation at lower driving voltages by ensuring adequate charge coupling between control and floating gates.
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
The increased opposing area and capacitance enhance the operating characteristics of the memory device, improving reliability and reducing the driving voltage needed for data programming and erasing operations.
Implementation Method 1
it may be difficult to secure sufficiently large capacitance between the control gate and floating gate electrodes... secure an increased opposing area between a control gate electrode and floating gate electrodes... The increased opposing area and capacitance enhance the operating characteristics of the memory device
Data Source
AI summary
A nonvolatile memory device may include a semiconductor substrate; first and second floating gate electrodes formed on the semiconductor substrate; a control gate electrode formed on the first and second floating gate electrodes that may include a line body and a first leg, second leg, and third leg extending vertically from the line body toward the semiconductor substrate; and an inter-layer insulating film interposed between the semiconductor substrate and a lower end of the first leg and between the semiconductor substrate and a lower end of the second leg.