Floating-Gate Memory Layout for Uniform Threshold Voltage
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Solution Overview
Problem
Current semiconductor devices face challenges in achieving uniform threshold voltage and operational reliability due to non-uniform coupling ratios between floating gates, which affects the performance of non-volatile memory devices.
Innovation Solution
The design incorporates asymmetrical planar shapes for floating gates and a sufficient gap between selection gates and active regions to prevent non-uniform coupling ratios, ensuring a uniform threshold voltage and improved operational reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If symmetrical floating gates are used, then manufacturing is simpler, but coupling ratio uniformity deteriorates
Solution Approach 1:
The patent applies asymmetry by configuring floating gates with different widths or lengths on opposite sides of the active region. Specifically, the first floating gate has a first width while the second floating gate has a second width different from the first width, creating intentional asymmetry that compensates for process variations and achieves uniform coupling ratios across different memory cells.
2Area of stationary object
If floating gates are placed close to active region, then device area is reduced, but threshold voltage uniformity deteriorates
Solution Approach 1:
The patent applies local quality by introducing a guard ring structure with specific doping concentration around the active region. The guard ring is doped with a doping concentration higher than that of the active region, creating a localized electrical field that compensates for the proximity effect of floating gates and maintains uniform threshold voltage across the device.
3Quantity of substance
If multiple floating gates are added, then storage capacity is increased, but interference between gates increases
Solution Approach 1:
The patent applies the intermediary principle by introducing isolation structures (such as insulating layers or doped regions) between adjacent floating gates. These intermediary structures electrically isolate the floating gates from each other, preventing charge interference and crosstalk while allowing multiple floating gates to be densely packed for increased storage capacity.
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 configuration enhances the reliability of read operations and maintains a sufficient margin for reliable operation by ensuring uniform capacitance and reduced interference between floating gates.
Implementation Method 1
a first floating gate, a second floating gate, a third floating gate and a fourth floating gate formed on the substrate, arranged to partially overlap with the active region
Implementation Method 2
The first floating gate and the third floating gate are arranged in a first direction at one side of the active region and asymmetrical about a center of the active region
Data Source
AI summary
Memory devices are disclosed. In an embodiment of the disclosed technology, a memory device may include a substrate including an active region, and a first floating gate, a second floating gate, a third floating gate and a fourth floating gate formed on the substrate, arranged to partially overlap with the active region. The first floating gate and the third floating gate are arranged in a first direction at one side of the active region and asymmetrical about a center of the active region, and the second floating gate and the fourth floating gate are arranged in the first direction at another side of the active region and asymmetrical about the center of the active region.