Transistor Characterization via Voltage Ramp Mobility Extraction
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Solution Overview
Problem
Existing methods for characterizing field effect transistors are prone to errors due to load trapping during measurement, leading to inaccurate effective mobility values.
Innovation Solution
A process involving a voltage ramp applied to the transistor gate, with measurements of drain current and capacitance variations, allowing for the calculation of effective mobility using specific device configurations and mathematical formulas.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If standard characterization methods are used to measure drain current and capacitance, then measurement can be performed, but charge trapping occurs during measurement leading to erroneous effective mobility values
Solution Approach 1:
The patent applies periodic voltage ramps with alternating polarity (positive and negative ramps) to the transistor gate. This periodic action prevents charge trapping by continuously reversing the electric field direction, thereby eliminating accumulated charges that would otherwise distort measurements. The method measures capacitance and drain current during each ramp cycle and processes these periodic measurements to extract accurate effective mobility values free from trapping effects.
Solution Approach 2:
The patent changes the measurement parameter from static DC conditions to dynamic AC voltage ramps. By applying time-varying voltage ramps instead of static voltages, the measurement captures the transient response of the transistor. This parameter change from DC to AC enables differentiation between trapped charges (which respond slowly) and free carriers (which respond quickly), allowing accurate mobility extraction through proper signal processing of the time-dependent measurements.
2Productivity
If conventional measurement approaches are used, then characterization can be completed, but the results are distorted by charge trapping effects
Solution Approach 1:
The patent implements continuous measurement during the voltage ramp application, capturing drain current and capacitance data throughout the entire ramp duration rather than at discrete points. This continuous action ensures that the measurement process itself does not interrupt the charge transport, preventing additional trapping effects. The continuous data stream allows for robust extraction of effective mobility through integration over the complete ramp cycle, maintaining both speed and accuracy.
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
This method provides more accurate characterization of field effect transistors by minimizing the impact of load trapping and allowing for precise estimation of effective mobility.
Implementation Method 1
variations in gate capacitance of the transistor are derived from variations in the displacement current in the transistor during application of the ramp
Implementation Method 2
a step of applying, to the gate of the transistor, by a first pulse current-voltage characteristics measuring apparatus configured to subject the gate to voltage pulses
Data Source
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AI summary
The present description relates to a method for characterizing a field-effect transistor (100), comprising: a step of applying, on the gate (106G) of the transistor (100), a single voltage ramp; and a step of interpreting both gate capacitance variations and drain current variations of the transistor (100).