RF Switch Dynamic Body Biasing for Leakage and Harmonic Control
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Solution Overview
Problem
Mobile RF transceivers using SOI technology face challenges with device isolation and RF loss, as well as the floating body effect which leads to parasitic transistors, OFF-state leakage, and generation of out-of-band harmonic frequencies.
Innovation Solution
A dynamic bias control circuit is introduced, which includes at least one transistor coupled between the body and gate regions of a switch FET, allowing for dynamic body biasing to improve breakdown voltage and harmonic performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If SOI substrate is used to reduce parasitic capacitance, then device isolation is improved, but floating body effect causes OFF-state leakage and out-of-band harmonics
Solution Approach 1:
A body contact structure is introduced as an intermediary element between the SOI substrate and the transistor body region. This body contact provides a dedicated path to extract floating body charge, preventing the accumulation that causes OFF-state leakage and parasitic transistors. The body contact acts as a mediator that resolves the harmful floating body effect while preserving the beneficial isolation properties of the SOI substrate.
Solution Approach 2:
The invention modifies the electrical parameters of the SOI structure by introducing a body contact that changes the body potential. By controlling the body voltage through the body contact, the threshold voltage of the transistor can be dynamically adjusted, preventing the formation of parasitic transistors and reducing OFF-state leakage current while maintaining device isolation.
2Reliability
If BOX layer thickness is reduced to improve device isolation, then parasitic capacitance is reduced, but artificial harmonics increase due to proximity of active device to substrate
Solution Approach 1:
The body contact serves as an intermediary that decouples the relationship between BOX layer thickness and harmonic generation. By providing a separate charge extraction path through the body contact, the system can maintain thin BOX layers for isolation without the thin BOX causing increased harmonic generation, as the body contact prevents charge accumulation that would otherwise couple to the substrate.
3Reliability
If dynamic bias control circuit is added to eliminate floating body effect, then OFF-state leakage is reduced, but device complexity increases
Solution Approach 1:
The body contact provides a simple, direct intermediary solution that eliminates floating body effects without requiring complex dynamic bias control circuits. The body contact structure itself, combined with appropriate biasing, suffices to prevent charge accumulation and eliminate the need for additional complex control circuitry.
Data Source
AI summary
A radio frequency integrated circuit (RFIC) is described. The RFIC includes a switch field effect transistor (FET). The switch FET includes a source region, a drain region, a body region, and a gate region. The RFIC also includes a dynamic bias control circuit. The dynamic bias control circuit includes at least one transistor coupled between the body region and the gate region of the switch FET.