Investigation of Combinatorial WO3-MoO3 Mixed Layers by Spectroscopic Ellipsometry Using Different Optical Models
Miklos Fried1,2, Renato Bogar1, Daniel Takacs1
1Institute of Microelectronics and Technology, Kando Kalman Faculty of Electrical Engineering, Óbuda University, H-1084 Budapest, Hungary.
Nanomaterials (Basel, Switzerland)
|July 27, 2022
Summary
Spectroscopic Ellipsometry mapped nanometer-scaled tungsten oxide-molybdenum oxide (WO3-MoO3) mixed layers. Different optical models were compared for accurate thickness and composition mapping, aiding process optimization.
Area of Science:
- Materials Science
- Thin Film Deposition
- Optical Metrology
Background:
- Nanometer-scaled mixed oxide layers like WO3-MoO3 are crucial in various applications.
- Accurate characterization of thickness and composition is essential for performance.
- Spectroscopic Ellipsometry (SE) offers a contactless method for thin film analysis.
Purpose of the Study:
- To investigate and map nanometer-scaled WO3-MoO3 mixed layers using SE.
- To compare the effectiveness of different optical models for SE data analysis.
- To correlate model selection with sample preparation and layer structure.
Main Methods:
- Reactive magnetron sputtering of W and Mo targets to create WO3-MoO3 layers.
- Spectroscopic Ellipsometry (SE) for contactless thickness and composition mapping.
- Rutherford Backscattering Spectrometry (RBS) for validation of SE results.
- Application and comparison of oscillator-based and Effective Medium Approximation (EMA) optical models.
Main Results:
- Successfully mapped thickness and composition of WO3-MoO3 layers using SE.
- Demonstrated the influence of sample preparation (substrate motion speed/cycles) on model "goodness".
- Identified optimal optical models (2-Tauc-Lorentz vs. BEMA) based on layer structure (atomic mixture vs. molecular layers).
Conclusions:
- SE provides a rapid, cost-effective, and contactless method for characterizing WO3-MoO3 mixed layers.
- The choice between the 2-Tauc-Lorentz oscillator model and the Bruggeman Effective Medium Approximation (BEMA) depends on the specific layer structure and process parameters.
- Accurate material characterization is achievable by selecting appropriate optical models for SE data analysis.
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