Floating Body FET Gate-to-Body Current Determination via Segmented Test Structures
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Solution Overview
Problem
Conventional methods for determining gate-to-body current in floating body FETs using body-tied FET structures consistently provide exaggerated estimates due to inclusion of undesired current components, leading to performance instabilities and inaccuracies in circuit design.
Innovation Solution
A method and test system that utilizes multiple unique body-tied FET structures to measure and separate desired and undesired current components, expressing them in terms of current densities to accurately determine the gate-to-body current density for floating body FETs, thereby avoiding the inaccuracies of conventional approaches.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional body-tied FET structures are used to measure gate-to-body current, then measurement can be performed, but the measured values consistently exaggerate the actual gate-to-body current in floating body FETs
Solution Approach 1:
The patent segments the gate-to-body current measurement into multiple distinct body-tied FET structures with different layout configurations. By measuring current through multiple segmented structures and combining the results, the patent isolates the actual gate-to-body current from extraneous current components that cause exaggeration in single-structure measurements.
Solution Approach 2:
The patent introduces body-tied FET structures as intermediary measurement devices that indirectly provide information about floating body FET gate-to-body current. These intermediary structures serve as mediators between the unmeasurable floating body current and the measurable body-tied current, allowing accurate determination through careful structural design and data processing.
2Productivity
If floating body FETs are used to reduce parasitic capacitance and enhance high-frequency performance, then device performance is improved, but hysteresis and threshold voltage instability occur
Solution Approach 1:
The patent implements a feedback mechanism by accurately measuring gate-to-body current through the specialized body-tied FET structures and using this information to predict and compensate for hysteresis effects. The measured current data feeds back into the design process, allowing circuit designers to account for threshold voltage shifts and stabilize performance in floating body FET applications.
3Measurement precision
If accurate gate-to-body current determination is achieved through multiple body-tied FET structures, then measurement accuracy is improved, but device complexity increases
Solution Approach 1:
The patent applies local quality by designing body-tied FET structures with specific localized layout variations. Each structure has particular geometric properties optimized for measuring specific current components. By localizing different measurement functions in different structures rather than using a single complex structure, the patent achieves accurate current separation while maintaining manageable device complexity.
Data Source
AI summary
In one disclosed embodiment, the present method for determining a gate-to-body current for a floating body FET comprises measuring at least three unique gate-to-body currents corresponding to at least three unique body-tied FET structures, determining at least three unique relationships between the at least three unique gate-to-body currents and at least three gate-to-body current density components for the at least three unique body-tied FET structures, and utilizing those at least three unique relationships to determine the at least three gate-to-body current density components; wherein one of the gate-to-body current density components is used to determine the gate-to-body current for the floating body FET. In one embodiment, a test structure implements a method for determining a gate-to-body current in a floating body FET. The determined gate-to-body current may be used to predict hysteresis in the floating body FET.