Multi-Terminal Probe Measurement Using Third-Harmonic Heating Signals
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Solution Overview
Problem
As electrical circuit components become smaller, small test currents can lead to false test values due to heating effects, which can result in measured resistances that are markedly different from those at room temperature, making it challenging to accurately measure properties like the temperature coefficient of resistance and sample geometry.
Innovation Solution
A method involving a micro multi-terminal probe with at least four terminals and interconnections is used to inject current and measure voltage, determining properties by analyzing the fundamental and third harmonic frequency components of the voltage, allowing for accurate measurement of resistance and temperature-related properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a current is injected into the test sample to measure electrical properties, then the measurement can be performed, but heating effects occur that lead to false test values and marked differences from room temperature resistance
Solution Approach 1:
The patent applies periodic action by using AC current with specific frequency components (fundamental frequency and third harmonic) to excite the test sample. This periodic excitation allows the measurement system to distinguish between resistance changes caused by the measurement current itself versus changes caused by thermal heating, thereby maintaining measurement accuracy while accounting for temperature effects.
Solution Approach 2:
The patent changes the measurement parameters by analyzing voltage responses at different frequency components (fundamental frequency versus third harmonic frequency). By comparing these different frequency responses, the system can separate the effects of instantaneous resistance from thermally-induced resistance changes, resolving the contradiction between performing measurements and avoiding heating artifacts.
2Temperature
If small test currents are used to minimize heating, then temperature effects are reduced, but measurement precision deteriorates due to signal weakness
Solution Approach 1:
By using periodic AC excitation at specific frequencies, the patent enables the use of lock-in detection or frequency-selective measurement techniques. This allows small test currents to be used while maintaining measurement precision through frequency-domain signal processing that enhances the signal-to-noise ratio and distinguishes the measurement signal from thermal noise.
Solution Approach 2:
The patent transforms the measurement from a simple DC voltage measurement to a frequency-resolved AC measurement. By analyzing the voltage response at different frequency components, the system can extract precise resistance information even from weak signals generated by small test currents, while the periodic nature of the excitation helps filter out thermal drift and noise.
3Device complexity
If conventional two-terminal probing is used, then the measurement setup is simple, but contact resistance and lead resistance affect the measurement accuracy
Solution Approach 1:
The patent segments the measurement function into separate current injection and voltage measurement paths by using at least four terminals. This segmentation allows the current-carrying paths and voltage-sensing paths to be electrically separated, eliminating the influence of contact resistance and lead resistance on the resistance measurement, while maintaining a relatively simple probe structure.
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 approach enables precise measurement of electric properties and temperature coefficients by accounting for heating effects, improving the accuracy of testing and screening for manufacturing specifications, even in small or complex circuit components.
Implementation Method 1
the current may lead to heating of the test sample which may result in a measured resistance, which is markedly different
Data Source
AI summary
A physical property of a test sample with a conductive or semi-conductive material (line/area/volume) is obtained. Periodic Joule heating is induced within the test sample by passing an AC current across a first pair of probe terminals electrically connected to the test sample, measuring the voltage drop across a second pair of probe terminals electrically connected to the test sample at one and three times the fundamental excitation frequency of the current-conducting terminals, and calculating the temperature-modulated property/properties of the test sample as a function of the potential drop measurement(s). This includes: a) determining a value proportional to the TCR of the test sample, b) a geometric parameter of the test sample (affected by coupling of its TCR to heat transport to/from the test sample), or c) the true resistivity of the test sample at the ambient experimental temperature by subtracting measurable and accountable TCR offset(s).