Air Gap Dielectric Field Effect Transistor for RF Reliability
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Solution Overview
Problem
High voltage field effect transistors (FETs) require thicker dielectric layers to prevent electrical breakdown, but these thicker layers can lead to reduced device reliability, increased surface degradation, and poor RF performance due to higher interface states and dielectric constant, which affects their operational stability and frequency response.
Innovation Solution
Replacing the traditional dielectric layer between the gate and body of FETs with an air gap dielectric, which reduces bulk oxide traps, interface state density, and dielectric constant, thereby enhancing hot carrier reliability, long-term stability, and RF performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a thicker dielectric layer is used to prevent electrical breakdown, then electrical integrity is improved, but surface degradation increases and RF performance worsens
Solution Approach 1:
By removing the solid dielectric material and replacing it with an air gap, the patent eliminates the source of surface degradation associated with thick silicon-based dielectrics, while maintaining electrical integrity through the air insulation.
Solution Approach 2:
The air gap creates an inert environment that prevents surface degradation mechanisms present in solid dielectrics, such as trap formation and interface states, while still providing the necessary electrical insulation.
2Reliability
If traditional silicon-based dielectric is used, then electrical separation is achieved, but dielectric constant is high leading to increased gate capacitance and reduced frequency response
Solution Approach 1:
The patent extracts the solid dielectric material and replaces it with an air gap. Since air has a much lower dielectric constant (approximately 1) compared to silicon-based dielectrics (typically 3.9 or higher), this extraction reduces gate capacitance and improves frequency response while maintaining electrical separation.
Solution Approach 2:
The patent changes the dielectric parameter (dielectric constant) by replacing high-k silicon-based material with low-k air. This parameter change directly reduces gate capacitance and enhances the frequency response of the device.
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
The air gap dielectric FETs exhibit improved hot carrier reliability, lower power consumption, and better RF performance with reduced signal loss and distortion, maintaining high frequency response and amplification factor across varying voltage conditions.
Implementation Method 1
The gate is separated from at least a portion of the body by an air gap, the airgap being in the first plane
Implementation Method 2
Replacing the traditional dielectric layer between the gate and body of FETs with an air gap dielectric, which reduces bulk oxide traps, interface state density, and dielectric constant
Data Source
AI summary
A field effect transistor (FET) that includes a drain formed in a first plane, a source formed in the first plane, a channel formed in the first plane and between the drain and the source and a gate formed in the first plane. The gate is separated from at least a portion of the body by an air gap. The air gap is also in the first plane.