Schottky Clamped RF Switch Charge Removal
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Solution Overview
Problem
Radio frequency (RF) switches face performance degradation due to charge accumulation, which causes nonlinear signal distortion and parasitic capacitance, especially in the off state, and are challenged by extreme operating conditions requiring large widths and specialized design methodologies.
Innovation Solution
An RF switch design featuring a clamp region with a lower dopant concentration than the source and drain, forming Schottky diode barriers with silicide regions, provides a constant sink for accumulated charge, independent of operating mode, thereby minimizing performance degradation and signal distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the RF switch uses a large width to handle high power and frequency, then the power handling capability and frequency range are improved, but the parasitic capacitance from accumulated charge increases causing signal degradation
Solution Approach 1:
The patent extracts the harmful accumulated charge from the transistor body by introducing a dedicated clamp region with Schottky diode barriers. This region acts as a separate charge removal mechanism, pulling charge out of the body and preventing it from creating parasitic capacitance that would degrade signal quality in large-width RF switches.
Solution Approach 2:
The clamp region serves as an intermediary structure between the transistor body and the charge accumulation problem. By positioning the Schottky diode barriers in this intermediate region, the patent creates a controlled path for charge removal that doesn't interfere with the main current flow through the large-width transistor, thus maintaining power handling while reducing parasitic effects.
2Power
If the RF switch operates in off state with large width, then the power handling capability is maintained, but the nonlinear distortion from accumulated charge becomes significant
Solution Approach 1:
The patent implements preliminary action by continuously maintaining the clamp region ready to remove charge even before significant accumulation occurs. The Schottky diode barriers are always positioned to provide a low-impedance path for charge removal, preventing the conditions that would lead to nonlinear distortion rather than correcting them after they arise.
Solution Approach 2:
The clamp region with Schottky diode barriers provides a feedback mechanism that continuously monitors and removes accumulated charge from the transistor body. This active charge management creates a negative feedback loop that prevents charge accumulation from reaching levels that would cause nonlinear distortion, ensuring consistent signal quality across operating modes.
3Device complexity
If no external bias is applied to the body (as in SOI wafers), then the device structure is simplified, but charge accumulation cannot be removed causing the kink effect
Solution Approach 1:
The patent implements self-service by making the clamp region and Schottky diode barriers an integral part of the transistor structure itself. The body of the transistor serves its own charge removal needs through the embedded clamp region, eliminating the need for external bias circuits or additional body contact structures. This maintains structural simplicity while providing effective charge management.
Solution Approach 2:
The patent merges the charge removal function with the existing transistor body structure by integrating the clamp region directly into the body. Rather than adding separate external bias circuits or body contacts, the Schottky diode barriers are combined with the transistor fabrication process, creating a unified structure that simplifies the overall device while solving the charge accumulation problem.
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 clamp region effectively removes accumulated charge, reducing nonlinear parasitic capacitance and ensuring consistent performance across operating modes, enhancing the RF switch's ability to handle high power and frequency without signal degradation.
Implementation Method 1
The clamp region forms a pair of Schottky diode barriers with the pair of matching silicide regions. The pair of Schottky diode barriers provide a constant sink for accumulated charge in the clamped body that is independent of the operating mode in which the RF switch is operating.
Data Source
AI summary
Various methods and devices that involve radio frequency (RF) switches with clamped bodies are provided. An exemplary RF switch with a clamped body comprises a channel that separates a source and a drain. The RF switch also comprises a clamp region that spans the channel, extends into the source and drain, and has a lower dopant concentration than both the source and drain. The RF switch also comprises a pair of matching silicide regions formed on either side of the channel and in contact with the clamp region. The clamp region forms a pair of Schottky diode barriers with the pair of matching silicide regions. The RF switch can operate in a plurality of operating modes. The pair of Schottky diode barriers provide a constant sink for accumulated charge in the clamped body that is independent of the operating mode in which the RF switch is operating.