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Parametric uncertainty in nanoscale optical dimensional measurements
1National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA.
Applied Optics
|June 15, 2012
Summary
This study introduces an image library approach to precisely measure feature width (FW) in optical microscopy. This method improves accuracy for microscale dimensions, crucial for metrology and quality control.
Area of Science:
- Optical Metrology
- Microscopy Image Analysis
- Dimensional Measurement Uncertainty
Background:
- Image modeling in optical microscopy relates object dimensions to image features.
- Measurement uncertainties in imaging parameters propagate to feature width (FW) calculations.
- Accurate uncertainty quantification is vital for assessing measurement adequacy and consistency.
Purpose of the Study:
- To present an image library approach for determining parametric uncertainty in optical photomask metrology.
- To compare this method with the traditional edge intensity threshold approach.
- To analyze measurement uncertainties for feature widths ranging from 10 nm to 8 µm.
Main Methods:
- Development and application of a one-dimensional image library.
- Image comparison and interpolation techniques for uncertainty estimation.
- Utilizing a 365 nm wavelength for optical photomask metrology.
Main Results:
- The image library approach provides a more general method for uncertainty quantification compared to edge threshold methods.
- Markedly different uncertainties were observed for features smaller than the illumination wavelength.
- Demonstrated results for optical photomask metrology across a wide feature width range.
Conclusions:
- The image library approach offers a robust and extensible method for optical metrology.
- This technique accurately accounts for parametric uncertainties in feature width measurements.
- The method is adaptable to various imaging microscopes and multi-dimensional parameter spaces.
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