GAA Nanosheet Transistor Air-Gap Isolation for Lower Parasitic Coupling
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Solution Overview
Problem
Gate-all-around (GAA) transistors face challenges in scaling due to narrowing sheet width and spacing, leading to increased parasitic capacitance and signal coupling as dimensions approach nanowire-like structures, which affect performance.
Innovation Solution
Incorporating an air gap between vertically stacked nanosheet fin structures of NMOS and PMOS transistors, separated by a silicon oxide lining, to reduce parasitic capacitance and signal coupling, while maintaining improved channel control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the sheet width and spacing are reduced to enable continued scaling, then the transistor density and integration are improved, but the parasitic capacitance and signal coupling between adjacent transistors increase
Solution Approach 1:
The patent introduces air gaps that segment the continuous dielectric medium into isolated regions, creating physical separation between adjacent transistor fins. This segmentation reduces the capacitive coupling between neighboring structures while maintaining high density through vertical stacking
Solution Approach 2:
The air gap acts as an intermediary layer between adjacent transistor fins, providing electrical isolation and reducing parasitic capacitance. The low dielectric constant of air (approximately 1.0) makes it an effective mediator for minimizing signal coupling while allowing continued scaling
2Manufacturing precision
If the sheet width approaches the thickness (nanowire-like structures), then the manufacturing precision and feature size control are improved, but the channel control and device performance deteriorate
Solution Approach 1:
The patent transitions from two-dimensional planar scaling to three-dimensional vertical stacking, creating gate-all-around structures that provide superior channel control. By stacking multiple nanosheets vertically, the device maintains effective channel control while achieving high density through the vertical dimension rather than further reducing horizontal dimensions
Data Source
AI summary
The invention discloses a semiconductor device comprising a first transistor and a second transistor, wherein the first transistor and the first transistor are separated by an air gap. The first transistor includes a first fin structure including a first source, a first drain, and a first channel. The second transistor includes a second fin structure including a second source, a second drain, and a second channel.