Nested Trench-Isolated FET Structure for Low Harmonic Distortion
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Solution Overview
Problem
Current field-effect transistor structures in CMOS processes face challenges in achieving improved electrical isolation and reduced harmonic distortion, particularly at small channel lengths, which affects the performance of switch field-effect transistors used in communication devices.
Innovation Solution
A semiconductor-on-insulator substrate with a trench isolation region and a semiconductor layer comprising single-crystal semiconductor material, where the semiconductor layer is embedded in a dielectric material tub and surrounded by a polycrystalline layer for enhanced electrical isolation, reducing harmonic distortion and improving performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional trench isolation structures are used in CMOS processes, then manufacturing simplicity is maintained, but electrical isolation and harmonic distortion performance deteriorate at small channel lengths
Solution Approach 1:
The patent implements a nested trench isolation structure where a second trench is formed within the first trench isolation region, creating a nested configuration. This nested design provides enhanced electrical isolation by adding an inner isolation barrier, effectively addressing the electrical isolation requirements for small channel length devices while maintaining a systematic fabrication approach.
Solution Approach 2:
The trench isolation structure is segmented into multiple regions: an outer first trench isolation region and an inner second trench isolation region. This segmentation allows each region to perform specific isolation functions, with the outer region providing primary isolation and the inner region providing additional isolation for critical areas, thereby improving overall electrical isolation performance.
2Object-generated harmful factors
If conventional trench isolation structures are used, then device complexity is minimized, but harmonic distortion increases at small channel lengths
Solution Approach 1:
The nested trench configuration with an inner second trench within the outer first trench creates multiple isolation barriers that effectively suppress harmonic distortion. The nested structure provides enhanced control over electric field distribution and reduces parasitic effects that cause harmonic distortion, particularly in small channel length devices where such effects are magnified.
Solution Approach 2:
The patent applies different isolation characteristics to different regions: the first trench isolation region provides general isolation, while the second trench isolation region embedded within it provides localized enhanced isolation where needed. This local quality differentiation allows targeted suppression of harmonic distortion in critical areas without unnecessarily complicating the entire device structure.
3Reliability
If single-crystal semiconductor material is used in the embedded trench, then electrical isolation and linearity improve, but manufacturing complexity increases
Solution Approach 1:
The patent specifies that the semiconductor layer in the second trench comprises single-crystal semiconductor material with controlled properties. By carefully controlling the crystal orientation, doping concentration, and thickness parameters of the single-crystal layer, the structure achieves improved linearity and electrical isolation while managing the manufacturing complexity through parameter optimization rather than fundamental process changes.
Data Source
AI summary
Structures for a field-effect transistor and methods of forming a structure for a field-effect transistor. The structure includes a semiconductor substrate having a first trench, and a trench isolation region positioned in the first trench. The trench isolation region contains a dielectric material, the trench isolation region includes a second trench surrounded by the dielectric material, and the trench isolation region includes openings that penetrate through the dielectric material. A semiconductor layer is positioned in the second trench of the trench isolation region. The semiconductor layer contains a single-crystal semiconductor material.