Accumulated Charge Sink for MOSFET Linearity Improvement
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Solution Overview
Problem
SOI MOSFETs operating in the accumulated charge regime experience non-linear responses and increased harmonic and intermodulation distortion, which adversely affect their performance and linearity, particularly in RF switching circuits, due to the accumulation of charge under the gate oxide.
Innovation Solution
The implementation of an Accumulated Charge Sink (ACS) with a high impedance connection to the MOSFET body, which controls and reduces the accumulated charge by applying specific bias voltages to remove or shift the capacitance inflection away from the desired operational region, thereby improving linearity and reducing distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If SOI MOSFETs operate in the accumulated charge regime, then device functionality is maintained, but non-linear responses and harmonic distortion increase
Solution Approach 1:
The patent extracts the harmful accumulated charge from the MOSFET body by introducing an accumulated charge sink (ACS) structure. The ACS is a separate doped region that selectively removes accumulated charge carriers from the body, thereby eliminating the source of non-linear responses and harmonic distortion while preserving the MOSFET's normal operation
Solution Approach 2:
The accumulated charge sink acts as an intermediary element between the MOSFET body and the charge accumulation problem. By introducing this intermediate structure with specific doping characteristics, the patent provides a controlled pathway for charge removal without directly modifying the core MOSFET operation, thus resolving the contradiction between maintaining functionality and reducing distortion
2Ease of operation
If accumulated charge is present in the MOSFET body, then charge control is simplified, but linearity and intermodulation distortion performance deteriorate
Solution Approach 1:
The accumulated charge sink structure enables self-regulating charge control within the MOSFET. The ACS automatically responds to accumulated charge conditions by providing a discharge pathway, eliminating the need for external charge management circuits while improving linearity performance through the inherent electrical characteristics of the doped region
3Manufacturing precision
If an accumulated charge sink is added to control charge, then linearity improves, but device complexity increases
Solution Approach 1:
The accumulated charge sink is merged with the MOSFET body during fabrication, forming an integrated structure rather than a separate component. The ACS shares the same substrate and is formed using compatible doping processes, thereby improving linearity while minimizing the increase in device complexity through structural integration
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 ACS effectively reduces non-linear responses and harmonic distortion, enhancing the linearity and intermodulation distortion performance of SOI MOSFETs, leading to improved drain-to-source breakdown voltage characteristics and overall circuit performance.
Implementation Method 1
an Accumulated Charge Sink (ACS) with a high impedance connection to the MOSFET body, which controls and reduces the accumulated charge
Data Source
AI summary
A method and apparatus for use in improving linearity sensitivity of MOSFET devices having an accumulated charge sink (ACS) are disclosed. The method and apparatus are adapted to address degradation in second- and third-order intermodulation harmonic distortion at a desired range of operating voltage in devices employing an accumulated charge sink.