Electroluminescence Defect Mapping in Semiconductor Materials
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Solution Overview
Problem
Current methods for detecting impurities in semiconductor materials, such as those using laser excitation or electroluminescence, do not provide sufficient information for effective mapping of defects, particularly in quantifying light intensity variations with applied voltage.
Innovation Solution
A method that assimilates the intensity of electroluminescence to the electric current generated by voltage, using models that account for parameters like series resistance and ideality factor to identify defects through spatial variations, allowing for the creation of defect maps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If laser excitation is used to detect impurities, then energy levels characterizing certain impurities can be detected, but the technique does not provide sufficient information for effective mapping of defects
Solution Approach 1:
The patent changes the excitation method from optical (laser) to electrical (voltage application), and introduces voltage as a variable parameter. By measuring electroluminescence intensity at multiple voltage levels and analyzing the variation, the method extracts additional information about defect characteristics and spatial distribution that cannot be obtained with fixed-wavelength laser excitation alone.
2Illumination intensity
If electroluminescence technique is used, then light emission can be observed, but it is difficult to quantify the expected intensity of light as a function of applied voltage
Solution Approach 1:
The patent introduces a quantitative model that establishes a feedback relationship between applied voltage and electroluminescence intensity. The model incorporates defect parameters (such as recombination rates and carrier concentrations) to predict the expected light intensity at any given voltage, allowing for precise quantification and comparison with experimental measurements.
3Loss of information
If voltage variation is applied to observe electroluminescence, then more information about defects can be obtained, but the complexity of the measurement and analysis increases
Solution Approach 1:
The patent segments the analysis by dividing the semiconductor sample into multiple spatial zones or regions. For each zone, the voltage-intensity relationship is analyzed independently to extract local defect characteristics. This segmentation approach transforms a complex global analysis problem into multiple simpler local problems, making the overall system more manageable and interpretable.
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
Enables direct mapping of defects in semiconductor materials by correlating light intensity with voltage-induced current variations, effectively characterizing impurities like iron and distinguishing different types of defects, including dislocations, with improved accuracy compared to traditional techniques.
Implementation Method 1
observe a light emitted by electroluminescence phenomenon as described for example in the document JP2007318029
Data Source
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AI summary
The invention relates to determining the spatial distribution of defects in a semiconductor material sample electrically connected at least two terminals, the method comprising: - applying a voltage between the two terminals, - acquiring an image of light emitted by electroluminescence from the sample using a camera, - repeating the image acquisition by varying the voltage between the two terminals, - measuring the light intensity emitted by electroluminescence in areas of the acquired images as a function of said voltage applied between the two terminals, the method being characterized in that it further comprises: - determining a model of the variation of the light intensity emitted by electroluminescence as a function of said applied voltage, by assimilation to the variation of a current generated in the sample as a function of the applied voltage, said model using at least one parameter (Rs*) characterizing the presence of defects in the material.- Apply the model to light intensity measurements and identify areas of the sample where the parameter (Rs*) varies, and - deduce from the variations in the parameter (Rs*) a map of defects in the sample.