Pump-Probe SHG Wafer Metrology for Interface Defect Quantification
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Solution Overview
Problem
Existing SHG-based metrology tools face limitations in distinguishing between interfacial properties, relying on relative measurements that cannot parse between different types of electrically active anomalies or quantify contaminants effectively.
Innovation Solution
The use of a pump and probe system in an SHG metrology tool, where the pump induces a potential difference across heterointerfaces and the probe provides time-dependent SHG intensity curves, allowing for the determination of material properties such as trap density and carrier injection energy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single laser SHG or dual/multiple laser SFG system is used, then the system is simpler to operate, but it cannot effectively distinguish between different types of electrically active anomalies or quantify contaminants
Solution Approach 1:
The patent segments the measurement process into distinct phases: a pump phase that induces potential difference across heterointerfaces, and a probe phase that measures time-dependent SHG intensity curves. This segmentation allows each phase to be optimized for its specific function, enabling precise differentiation of interfacial properties while maintaining manageable system complexity through modular design
Solution Approach 2:
The pump light source performs preliminary action by inducing a potential difference across heterointerfaces before the probe measurement. This pre-conditioning of the sample enables the subsequent probe to detect subtle variations in interfacial properties that would otherwise be indistinguishable, thereby enhancing measurement precision without requiring complex measurement techniques
2Measurement precision
If relative measurements are used, then the measurement process is simpler, but quantitative information about contaminants and defect types cannot be obtained
Solution Approach 1:
The system employs feedback by measuring time-dependent SHG intensity curves after pump-induced potential difference. The temporal evolution of the SHG signal provides feedback information about charge carrier dynamics, trap densities, and interface properties, enabling quantitative characterization that goes beyond simple relative measurements
Solution Approach 2:
The patent utilizes parameter changes in the SHG signal intensity over time as the pump-induced potential difference evolves. By monitoring how the SHG intensity changes with time after pumping, the system extracts quantitative parameters such as carrier lifetimes, trap densities, and interface quality metrics, transforming qualitative observations into quantitative measurements
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 the capture of quantitative information for precise characterization of interfacial properties, allowing for the differentiation and quantification of defect types and contaminants, thereby improving the accuracy and efficiency of semiconductor metrology.
Implementation Method 1
electrons in a layered semiconductor substrate are excited, variously, by each of a pump light source and a probe light source having different power characteristics for the purpose of Sum Frequency Generation (SFG) (e.g., typically SHG)
Implementation Method 2
In nonlinear optics, light beam input(s) are output as the sum, difference or harmonic frequencies of the input(s). Second Harmonic Generation (SHG) is a non-linear effect in which light is emitted from a material at an angle with twice the frequency of an incident source light beam
Implementation Method 3
electrons in a layered semiconductor substrate are excited, variously, by each of a pump light source and a probe light source having different power characteristics for the purpose of Sum Frequency Generation (SFG)
Data Source
AI summary
Various approaches can be used to interrogate a surface such as a surface of a layered semiconductor structure on a semiconductor wafer. Certain approaches employ Second Harmonic Generation and in some cases may utilize pump and probe radiation. Other approaches involve determining current flow from a sample illuminated with radiation. Decay constants can be measured to provide information regarding the sample. Additionally, electric and/or magnetic field biases can be applied to the sample to provide additional information.