Group III-N Conductive Shield for RF Transmission Lines
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Solution Overview
Problem
Typical transmission line configurations in high-frequency integrated circuit designs face significant challenges with electromagnetic field penetration at the substrate, leading to signal power loss due to the lossy nature of silicon substrates, which are often excluded from RF applications.
Innovation Solution
The use of group III-nitride (III-N) semiconductor materials as a conductive ground shield between the transmission line and the substrate, comprising a gallium nitride layer with an n-type doped indium gallium nitride layer, effectively suppresses electromagnetic field penetration and reduces displacement and eddy currents, allowing for the use of silicon substrates in RF applications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a typical transmission line configuration is used on a silicon substrate, then the structure is simple and compatible with standard CMOS fabrication, but electromagnetic field penetration occurs causing signal power loss
Solution Approach 1:
A ground shield layer is introduced as an intermediary component between the transmission line and the silicon substrate. This ground shield acts as a mediator that blocks electromagnetic field penetration into the lossy substrate while maintaining compatibility with standard fabrication processes. The ground shield is connected to ground potential and positioned adjacent to the transmission line conductors, creating a shielding effect that reduces signal power loss without requiring fundamental changes to the transmission line configuration.
2Loss of energy
If the ground shield is positioned closer to the transmission line, then electromagnetic field penetration is better suppressed, but the height between conductors decreases affecting impedance control
Solution Approach 1:
The impedance control is maintained by adjusting key geometric parameters of the transmission line structure. When the ground shield position is optimized for shielding effectiveness, parameters such as conductor width, spacing between conductors, and dielectric layer thickness are modified to maintain the desired characteristic impedance. This allows the ground shield to be positioned optimally for suppressing electromagnetic field penetration while keeping impedance within acceptable ranges for RF operation.
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 solution significantly reduces signal power loss by preventing electromagnetic field penetration, enabling the use of silicon substrates in RF applications while maintaining low loss transmission lines, suitable for radio frequency applications.
Implementation Method 1
The use of group III-nitride (III-N) semiconductor materials as a conductive ground shield between the transmission line and the substrate
Implementation Method 2
effectively suppresses electromagnetic field penetration and reduces displacement and eddy currents
Data Source
AI summary
Integrated circuit structures configured with low loss transmission lines are disclosed. The structures are implemented with group III-nitride (III-N) semiconductor materials, and are well-suited for use in radio frequency (RF) applications where high frequency signal loss is a concern. The III-N materials are effectively used as a conductive ground shield between a transmission line and the underlying substrate, so as to significantly suppress electromagnetic field penetration at the substrate. In an embodiment, a group III-N polarization layer is provided over a gallium nitride layer, and an n-type doped layer of indium gallium nitride (InzGa1-zN) is provided over or adjacent to the polarization layer, wherein z is in the range of 0.0 to 1.0. In addition to providing transmission line ground shielding in some locations, the III-N materials can also be used to form one or more active and/or passive components (e.g., power amplifier, RF switch, RF filter, RF diode, etc).