Bulk Semiconductor Substrate With Dual-Isolation Trenches
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Solution Overview
Problem
The increasing complexity of integrated circuits due to smaller geometry sizes and denser packing leads to significant crosstalk issues between IC devices on the same substrate, which existing technologies like SOI struggle to address cost-effectively, as SOI substrates are expensive and high resistivity bulk substrates compromise IC performance.
Innovation Solution
The fabrication of SOI-like structures in bulk semiconductor substrates using dual-isolation trenches and epitaxial source/drain features, which create isolated active and channel regions, effectively suppressing crosstalk and improving performance at a lower cost by increasing the resistance of the substrate underlying the isolation trenches.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If SOI substrates are used to improve isolation and suppress crosstalk, then device performance is improved, but manufacturing cost increases significantly
Solution Approach 1:
The patent creates SOI-like behavior in bulk substrates by forming isolation trenches filled with insulator materials that replicate the electrical isolation properties of true SOI substrates. The method copies the functional characteristics of SOI structures (semiconductor-insulator-semiconductor configuration) without requiring expensive pre-fabricated SOI wafers, thereby achieving similar device performance at lower manufacturing cost
Solution Approach 2:
The patent uses standard bulk semiconductor substrates with conventional processing to achieve isolation, replacing the need for expensive SOI substrates. The method employs readily available materials and processes (silicon wafers, thermal oxidation, trench filling) that are already part of conventional fabrication flows, eliminating the need to purchase costly SOI wafers while achieving comparable isolation performance
2Productivity
If device density is increased to improve production efficiency, then productivity is improved, but crosstalk between devices increases
Solution Approach 1:
The patent segments densely packed devices into isolated units by forming trenches between them. Even as device density increases, the segmentation provided by isolation trenches maintains electrical separation between adjacent devices, preventing crosstalk from increasing with density. Each device remains electrically isolated despite close physical proximity to other devices
3Productivity
If geometry size is decreased to improve scaling, then device density is improved, but processing complexity increases
Solution Approach 1:
The patent uses a universal isolation structure that works across different device geometries and technology nodes. The same trench isolation methodology can be applied whether devices are large or small, making the approach scalable without requiring different isolation techniques for different geometry sizes. This multi-functional isolation approach simplifies processing by providing a consistent method that adapts to scaling requirements
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 allows for cost-effective isolation and performance improvement of IC devices, particularly in RF applications, by mimicking SOI behavior in bulk substrates, reducing crosstalk and enhancing device performance without the high cost of SOI technology.
Implementation Method 1
increasing a resistance of a portion of the bulk substrate underlying the isolation trench and the channel region
Data Source
AI summary
Bulk semiconductor substrates configured to exhibit semiconductor-on-insulator (SOI) behavior, and corresponding methods of fabrication, are disclosed herein. An exemplary bulk substrate configured to exhibit SOI behavior includes a first isolation trench that defines a channel region of the bulk substrate and a second isolation trench that defines an active region that includes the channel region. The first isolation trench includes a first isolation trench portion and a second isolation trench portion disposed over the first isolation trench portion. A first isolation material fills the first isolation trench portion, and an epitaxial material fills the second isolation trench portion. The epitaxial material is disposed on the first isolation material. A second isolation material fills the second isolation trench. A portion of the bulk substrate underlying the first isolation trench and the channel region is configured to have a higher resistance than the bulk substrate.