Simulation Circuit for DDSOI MOSFET Body Impedance Modeling
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Solution Overview
Problem
Accurate modeling of body impedance in dynamically depleted silicon-on-insulator (DDSOI) MOSFETs is complex due to their partially and fully depleted characteristics, affecting their performance in RF switches and digital logic applications, particularly in capturing low-frequency characteristics and predicting RF behavior.
Innovation Solution
A simulation circuit is developed to simulate DDSOI MOSFETs, including isolation and body-contact transistors, which allows for selective activation of transistors to produce independent data for different resistance components, enabling iterative design refinement to match simulated and test data, thereby improving transistor performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a simulation circuit is developed to model body impedance in dynamically depleted MOSFETs, then measurement precision of device characteristics is improved, but device complexity increases due to multiple transistors and resistors
Solution Approach 1:
The simulation circuit is segmented into multiple independent sub-circuits, each modeling a specific portion of the MOSFET (isolation portion, main portion, body-contact portion). This segmentation allows precise measurement of individual characteristics while maintaining overall device functionality through modular design.
Solution Approach 2:
Dummy transistors are introduced as intermediary elements that enable independent measurement of body impedance characteristics without directly measuring the actual MOSFET. These dummy transistors act as mediators that replicate specific device behaviors for isolated characterization.
2Manufacturing precision
If selective activation of transistors is implemented to produce independent data, then manufacturing precision of device models is improved, but ease of operation decreases due to complex activation control
Solution Approach 1:
The simulation circuit employs dynamically controllable transistor activation where dummy transistors can be selectively turned on or off based on measurement requirements. This dynamic control enables precise extraction of specific device characteristics (isolation, main, body-contact portions) by activating only the relevant transistors for each measurement type.
Solution Approach 2:
The dummy transistors are pre-configured in the simulation circuit with specific connections to isolate different device portions. This preliminary arrangement of transistor networks enables straightforward selective activation for different measurement modes without complex real-time reconfiguration.
3Measurement precision
If the simulation circuit includes multiple resistors for different channel portions, then measurement precision of body impedance is improved, but device complexity increases
Solution Approach 1:
The body impedance measurement is segmented into multiple resistance components (isolation body resistor, main body resistor, body-contact resistor) corresponding to different physical portions of the MOSFET channel. Each resistor models the impedance of a specific region, enabling precise separate characterization of isolation, main channel, and body-contact effects.
Solution Approach 2:
Different resistance values and characteristics are assigned to different portions of the simulation circuit to reflect the local electrical properties of corresponding MOSFET regions. The isolation body resistor, main body resistor, and body-contact resistor each have tailored parameters that match their respective physical counterparts in the actual device.
Data Source
AI summary
A simulation circuit, that simulates characteristics of transistors is produced to include: an isolation body resistor representing resistance of a channel isolation portion of a transistor; a main body resistor representing resistance of main channel portion of the transistor; an isolation transistor connected to the isolation body resistor; and a body-contact transistor connected to the main body resistor. Simulated data is generated by supplying test inputs to the simulation circuit, while selectively activating either the isolation transistor or the body-contact transistor. Test data is generated by supplying the test inputs to the transistors, and measuring output of the transistors. The simulated data is compared to the test data to identify data differences. The design of the transistors is changed to reduce the data differences. The generation of test data, comparing, and design changes are repeated, until the data differences are within a threshold.