Scatterometry Model Accuracy Assessment via Wavelength Variation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Scatterometry models used in lithographic processes often fail to accurately measure features due to inaccuracies, particularly when line edge roughness and other complexities are not accounted for, leading to significant measurement errors.
Innovation Solution
A method involving multiple scatterometry measurements with varying radiation characteristics to assess the accuracy of the model by comparing the determined values of substrate features, using a combination of radiation with different characteristic values and a high numerical aperture lens, and an imaging Fourier transform spectrometer to separate and analyze the detected radiation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a simple scatterometry model is used for measurement, then the device complexity is reduced, but the measurement precision deteriorates due to inaccuracies from unaccounted features like line edge roughness
Solution Approach 1:
The patent changes the parameter of radiation wavelength to assess model accuracy. By performing scatterometry measurements at multiple different wavelengths and comparing the results, the method determines whether the model accurately represents the substrate features without requiring complex model modifications
Solution Approach 2:
The patent implements a feedback mechanism where measurement results from multiple wavelengths are compared to assess model accuracy. This feedback loop allows for verification of the model's representativeness and identifies when model adjustments are needed to improve measurement precision
2Measurement precision
If the model includes additional features like line edge roughness to improve accuracy, then the measurement precision improves, but the device complexity increases
Solution Approach 1:
Instead of modifying the model structure to include complex features like line edge roughness, the patent changes the radiation wavelength parameter to assess model accuracy. This approach verifies model adequacy without increasing model complexity
Solution Approach 2:
The measurement system uses itself to assess model accuracy by performing measurements at multiple wavelengths and comparing results. This self-verification mechanism determines model adequacy without requiring external complex modeling or additional sensors
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 allows for the precise assessment of model accuracy, enabling adjustments to include additional features or parameters, thereby improving measurement reliability and reducing errors in feature characterization.
Implementation Method 1
One form of specialized inspection tool is a scatterometer in which a beam of radiation is directed onto a target on the surface of the substrate and properties of the scattered or reflected beam are measured
Implementation Method 2
properties of the scattered or reflected beam are measured. By comparing the properties of the beam before and after it has been reflected or scattered by the substrate
Implementation Method 3
an imaging Fourier transform spectrometer to separate and analyze the detected radiation
Data Source
AI summary
A method of assessing a model of a substrate is presented. A scatterometry measurement is taken using radiation at a first wavelength. The wavelength of the radiation is then changed and a further scatterometry measurement taken. If the scatterometry measurements are consistent across a range of wavelengths then the model is sufficiently accurate. However, if the scatterometry measurements change as the wavelength changes then the model of the substrate is not sufficiently accurate.