Trench Geometry for Semiconductor Fill Capability
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Solution Overview
Problem
As semiconductor devices miniaturize, the trench fill capability of insulating films in high aspect ratio trenches is reduced, leading to voids and increased short circuits, while reducing the taper angle to improve fill capability results in shorter insulation distances and reduced breakdown voltage, making it difficult to maintain previous design rules.
Innovation Solution
A method of forming trenches with a first trench in the memory cell region having a higher aspect ratio and a second trench in the peripheral circuit region with a larger opening width, using a halogen gas mixture with fluorocarbon and oxygen to create a trench with a curved upper portion and varying taper angles, allowing for improved fill capability without repeated etching processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the taper angle of STI is reduced to improve trench fill capability, then the insulating film can fill the trench more effectively, but the insulation distance between devices becomes shorter and breakdown voltage is reduced
Solution Approach 1:
The patent segments the trench structure into two distinct types: first trenches in the memory cell region with higher aspect ratios and curved upper portions, and second trenches in the peripheral circuit region with larger opening widths and gentler taper angles. This segmentation allows each region to have optimized trench geometry for its specific requirements, resolving the contradiction between trench fill capability and insulation distance by applying different geometric solutions to different functional regions.
Solution Approach 2:
The patent applies local quality by giving different geometric characteristics to trenches in different regions. Memory cell region trenches have curved upper portions and specific taper angles optimized for fill capability, while peripheral circuit region trenches have larger opening widths and gentler angles optimized for insulation. This local differentiation allows each region to have the precise geometric properties needed for its function without compromising the other region's requirements.
2Productivity
If the device structure is miniaturized to increase integration density, then more devices can be packed, but the aspect ratio of STI regions increases and trench fill capability is reduced
Solution Approach 1:
The patent segments trenches by device region, allowing miniaturization in the memory cell region (with curved upper portions and optimized taper angles) while maintaining larger opening widths in peripheral circuit regions. This segmentation enables continued integration density improvement in memory areas without uniformly increasing aspect ratios across the entire chip, thus preserving trench fill capability where needed.
Solution Approach 2:
The patent introduces dimensional variation by creating curved upper portions in first trenches, adding a geometric dimension beyond simple linear taper angles. This curvature modification changes the effective opening width at different depths, allowing optimized fill capability even as overall device dimensions are reduced for miniaturization.
3Productivity
If the opening width of trench is reduced to increase device density, then more devices can be placed, but the conditions for trench fill capability are worsened
Solution Approach 1:
The patent segments the chip into memory cell regions with narrower first trenches and peripheral circuit regions with wider second trenches. This allows device density to be increased in the memory region through narrower trenches while maintaining adequate opening widths in peripheral regions for good trench fill capability, thus resolving the contradiction between density and fill quality.
Solution Approach 2:
The patent applies curvature to the upper portions of first trenches, creating a rounded or curved geometry instead of a simple straight taper. This curvature effectively increases the opening width at the top relative to the bottom, improving trench fill capability even when the overall trench opening is reduced for higher device 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 enhances the trench fill capability of insulating films, maintaining effective insulation distances and breakdown voltages, while reducing fabrication steps and costs, and improving productivity by achieving superior trench fill dimensions and insulating performance.
Implementation Method 1
A reactive gas is then introduced into the chamber and a discharge plasma is generated so that reactive ions and radicals progress etching
Implementation Method 2
etching the semiconductor substrate to simultaneously form the first and second trenches with an etching gas made by mixing a halogen gas, a fluorocarbon gas and oxygen
Data Source
AI summary
A method of fabricating a semiconductor device includes etching a silicon oxide film, a silicon nitride film, a polycrystalline silicone film, and a gate insulating film in a predetermined pattern including a first opening width corresponding to a first trench and a second opening width corresponding to a second trench, the second opening width being larger than the first opening width, and etching the semiconductor substrate to simultaneously form the first and second trenches so that a first depth of the first trench is equal to a second depth of the second trench, and a first angle between a first side surface and a first bottom surface of the first trench is smaller than a second angle between a second side surface and a second bottom surface of the second trench, and the first trench includes a curved portion at an upper portion of the first side surface.