Varying Depth Trench Isolation for Semiconductor Device Regions
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Solution Overview
Problem
Conventional semiconductor device isolation structures face challenges in achieving sufficient electric isolation in high voltage regions with high pattern density, leading to voids in trench isolation due to high aspect ratios, which affect the filling of insulating material.
Innovation Solution
The proposed solution involves forming trench isolation structures with varying depths and widths in different regions of a semiconductor substrate, including a cell region, low voltage region, and high voltage region, where the low voltage trench is deeper than the cell trench, and the first high voltage trench is deeper than the low voltage trench but shallower than the second high voltage trench, ensuring complete filling with insulating material.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If trench isolation structures are made deeper in high voltage regions to improve electric isolation, then isolation ability is improved, but aspect ratio increases causing void formation in cell and low voltage regions
Solution Approach 1:
The patent applies different trench depths to different regions: deep trenches in high voltage regions for superior isolation, and shallow trenches in cell/low voltage regions to avoid voids. This regional differentiation resolves the contradiction by optimizing each region's trench depth according to its specific electrical requirements rather than using a uniform depth throughout the substrate.
Solution Approach 2:
The substrate is segmented into high voltage regions and cell/low voltage regions, with each segment receiving a tailored trench isolation depth. This segmentation allows the patent to achieve deep isolation where needed while maintaining manufacturable aspect ratios in other regions, thereby resolving the contradiction between isolation performance and filling completeness.
2Reliability
If trench depth is increased in high voltage regions, then electric isolation is improved, but device complexity increases due to multiple trench depth requirements
Solution Approach 1:
The patent implements local quality by specifying different trench depths for high voltage regions versus cell/low voltage regions. This approach improves isolation reliability in critical areas while avoiding the complexity of managing multiple trench types throughout the entire device, as the differentiation is applied only where electrically necessary.
3Reliability
If trench isolation depth is increased to improve isolation in high voltage regions, then isolation performance is improved, but voids form in cell and low voltage regions due to high aspect ratio
Solution Approach 1:
The patent applies local quality by matching trench depth to regional requirements: deep trenches in high voltage regions achieve superior isolation without creating voids, while shallow trenches in cell/low voltage regions prevent void formation by maintaining acceptable aspect ratios. This resolves the contradiction by eliminating voids in regions where they would be harmful while maintaining isolation performance where it is critical.
Data Source
AI summary
A device isolation structure of semiconductor device includes a semiconductor substrate having a cell region, a low voltage region and a high voltage region defined therein. A cell trench isolation region is disposed in the cell region. A low voltage trench isolation region is disposed in the low voltage region and extends deeper into the substrate than the cell trench isolation region. A first high voltage trench isolation region is disposed in the high voltage region and extends deeper into the substrate than the low voltage trench isolation region. A second high voltage trench isolation region is disposed in the high voltage region and extends deeper into the substrate than the low voltage trench isolation region but shallower than the first high voltage trench isolation region.