Concurrent Interferometric and Ellipsometric Thin-Film Metrology
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Solution Overview
Problem
Conventional optical systems face challenges in accurately measuring the topography and film thickness of multi-layer, complex thin films, particularly when deposited over lithographically patterned features, due to modified optical responses and the need for cumbersome integration of interferometric and ellipsometric data.
Innovation Solution
A system that concurrently measures interferometric and ellipsometric phases using a broadband light source with polarized light, beam splitters, interferometric cells, and detectors, allowing for simultaneous regression of both signals to reduce floating variables and simplify modeling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional optical techniques are used to measure multi-layer thin films over lithographically patterned features, then measurement speed is maintained, but measurement accuracy deteriorates due to modified optical responses from buried structures
Solution Approach 1:
The patent combines interferometric and ellipsometric measurements into a single integrated system that simultaneously captures both interferometric phase and ellipsometric parameters (Psi and Delta). This merging of measurement techniques allows the system to handle complex multi-layer films over patterned features by utilizing the complementary information from both methods, improving measurement accuracy without requiring separate measurement systems or sequential procedures
Solution Approach 2:
The patent utilizes broadband light sources to enable wavelength-dependent measurements across a spectrum rather than at a single wavelength. This parameter change from monochromatic to broadband illumination allows the system to capture spectral information that provides additional constraints for modeling complex film structures, thereby improving measurement accuracy while managing the complexity through rich spectral data
2Adaptability or versatility
If traditional sequential combination of interferometric and ellipsometric techniques is used, then applicability to isolated non-repeating substructures is improved, but measurement time and cost increase
Solution Approach 1:
The patent merges interferometric and ellipsometric measurement capabilities into a single optical system that performs both measurements simultaneously on the same sample without sequential operation. The system uses beam splitters to divide the optical path into interferometric and ellipsometric channels, allowing concurrent acquisition of both signal types and eliminating the time penalty associated with sequential measurements
Solution Approach 2:
The patent implements continuous simultaneous measurement of interferometric and ellipsometric signals throughout the measurement process. The optical system maintains continuous operation with both measurement modes active at the same time, ensuring uninterrupted data acquisition that reduces total measurement time while maintaining versatility for various film structures
3Ease of operation
If interferometric measurements are performed without physical models, then direct measurement capability is maintained, but integration with ellipsometric data becomes cumbersome
Solution Approach 1:
The patent merges interferometric and ellipsometric measurements into a unified data acquisition and analysis framework. By simultaneously measuring both interferometric phase and ellipsometric parameters (Psi and Delta) and processing them together through joint regression analysis, the system eliminates the complexity of separate data integration while maintaining the simplicity of direct interferometric measurement through coordinated modeling of both signal types
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 thorough optical characterization of thin films with reduced complexity and time, providing accurate film thickness and topography measurements without mechanical movement or component addition, suitable for high-speed manufacturing.
Implementation Method 1
an interferometric cell configured to create interference patterns with respect to a surface of a sample
Implementation Method 2
a broadband light source configured to emit polarized light that is polarized to two orthogonal polarization states
Data Source
AI summary
A system may include a broadband light source emitting polarized light that is polarized to two orthogonal polarization states, multiple beam splitters for combining and splitting the polarization states, and interferometric cell for creation of interference patterns with respect to a sample surface, lenses of appropriate design that focus the polarized light at predefined locations, and sensors that analyze the polarized light as a function of angle and wavelength. The system may also include a controller configured to modulate the reference arm through operation of an optical chopper and allow for different data analysis modes to be used on the system produced data.