Back-Biased RF Circuit Structure for Parasitic Capacitance Reduction
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Solution Overview
Problem
The design of mobile RF transceivers for carrier aggregation in wireless communication systems faces challenges such as increased complexity, noise interference, and parasitic capacitance due to the floating body effect in silicon on insulator (SOI) technology, which affects RF performance and harmonics.
Innovation Solution
A method involving a layer transfer process and post-layer transfer metallization is used to form a back-biased active device, separating the active device from the substrate and reducing parasitic capacitance, while also providing an RF shield to prevent high-order harmonics, thereby improving RF performance and supporting carrier aggregation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If carrier aggregation is implemented to increase bandwidth, then data transmission capacity is improved, but noise interference and harmonic distortion increase
Solution Approach 1:
An RF shield layer is introduced as an intermediary between the active device and the substrate. This shield layer acts as a mediator to block the transmission of harmonic noise from the active device to the substrate, thereby reducing noise interference while maintaining the bandwidth benefits of carrier aggregation.
Solution Approach 2:
The patent converts the harmful harmonic noise generated by carrier aggregation into a controllable parameter by using the RF shield layer to redirect and contain the noise. The shield layer transforms the harmful electromagnetic radiation into a localized field that can be managed and directed away from sensitive circuit areas.
2Reliability
If layer transfer process is used to separate active device from substrate, then parasitic capacitance is reduced, but manufacturing complexity increases
Solution Approach 1:
The RF shield layer is formed on the substrate before the active device is transferred to it. This preliminary action ensures that the shield layer is already in place to provide the necessary electrical isolation and parasitic capacitance reduction, simplifying the overall manufacturing process by pre-establishing the isolation structure.
Solution Approach 2:
The RF shield layer serves as an intermediary structure that facilitates the separation of the active device from the substrate while maintaining controlled electrical characteristics. This mediator layer enables the layer transfer process to achieve reduced parasitic capacitance without requiring direct contact between the active device and substrate.
3Reliability
If diplexer design uses high Q-factor inductors and capacitors to reduce electromagnetic coupling, then RF performance is improved, but device complexity and cost increase
Solution Approach 1:
The patent extracts the electromagnetic coupling problem from the circuit design domain and relocates it to the physical layout domain by introducing an RF shield layer. This extraction allows the use of simpler, lower Q-factor components while achieving the same isolation effect through physical barrier rather than complex component selection.
Solution Approach 2:
The patent replaces the electrical isolation mechanism (relying on high Q-factor components and careful geometric arrangement) with a physical isolation mechanism (RF shield layer). This substitution moves from an electrical solution to a structural/mechanical solution, simplifying the circuit design while maintaining RF performance.
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 solution effectively reduces parasitic capacitance and noise interference, enhancing RF performance and harmonics in integrated RF circuit structures, particularly in high-quality factor RF applications.
Implementation Method 1
parasitic capacitance due to the floating body effect in silicon on insulator (SOI) technology
Implementation Method 2
providing an RF shield to prevent high-order harmonics
Data Source
Figure 1A
Figure 1B
Figure 2A~2B
AI summary
An integrated radio frequency (RF) circuit structure may include an active device on a first surface of an isolation layer. The integrated RF circuit structure may also include a back-bias metallization on a second surface opposite the first surface of the isolation layer. A body of the active device is biased by the back-bias metallization. The integrated RF circuit structure may further include a handle substrate on a front-side dielectric layer on the active device.