Tunable Light Source for Lithography Alignment
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Solution Overview
Problem
Current alignment methods for semiconductor integrated circuits, particularly with non-planar structures like FinFETs, struggle with accurate alignment measurements due to signal degradation when patterned structures are thinned, leading to wafer quality issues.
Innovation Solution
A lithography system utilizing a tunable light source that generates multi-wavelength light beams for alignment measurements, including visual, infrared, and ultraviolet light, to improve signal quality and accuracy by directing these beams at diffraction-based marks on the wafer, allowing for precise alignment and overlay monitoring.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single wavelength light source is used for alignment measurement, then the system is simple, but the alignment signal quality degrades when patterned structures are thinned
Solution Approach 1:
The patent applies parameter changes by switching between different wavelengths of light based on the specific mark being measured and its depth characteristics. The system selects optimal wavelengths (e.g., infrared for deeper marks, visible for shallower marks) to maximize signal quality, directly resolving the contradiction between measurement precision and device complexity by making the light source parameter adaptive rather than fixed
Solution Approach 2:
The system implements dynamics by making the wavelength selection adaptive and controllable based on real-time measurement requirements. The alignment system dynamically switches between different wavelength light sources depending on the mark depth and type, transforming a static single-wavelength system into a dynamic multi-wavelength system that optimizes signal quality for each specific measurement scenario
2Productivity
If alignment marks are made smaller to fit advanced circuit layouts, then more circuits can be integrated, but the alignment signal becomes weaker and harder to detect
Solution Approach 1:
The patent uses parameter changes by adjusting the wavelength of light to match the optical properties of smaller, deeper alignment marks. By selecting specific wavelengths that maximize contrast and signal strength for miniaturized marks, the system maintains detection capability even as mark size decreases, thus supporting higher circuit integration density without sacrificing measurement capability
Solution Approach 2:
The system replaces traditional mechanical or geometric alignment approaches with optical field-based detection using multi-wavelength light. This substitution enables detection of smaller marks by exploiting optical interactions (diffraction, reflection) that are more sensitive than mechanical measurement methods, allowing signal detection from miniaturized alignment features
3Manufacturing precision
If multi-wavelength light beams are used for alignment measurements, then the alignment accuracy improves, but the system complexity increases
Solution Approach 1:
The patent resolves the contradiction by implementing parameter changes in the light source wavelength based on the specific measurement requirements. The system switches between predetermined wavelengths (e.g., infrared, visible, ultraviolet) depending on the mark characteristics, achieving high alignment accuracy without requiring all wavelength components to operate simultaneously, thus managing system complexity while maintaining precision
Solution Approach 2:
The system applies segmentation by dividing the alignment measurement process into separate wavelength-specific measurement steps. Each wavelength is used for specific types of marks or depth ranges, allowing the complex multi-wavelength system to be managed as multiple simpler, specialized measurement channels rather than a single complex simultaneous measurement system
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 high-accuracy alignment and overlay monitoring, enhancing wafer quality by optimizing light signal quality based on the specific wavelengths and orientations of the marks, effectively addressing the limitations of existing systems with non-planar structures.
Implementation Method 1
A lithography system utilizing a tunable light source that generates multi-wavelength light beams for alignment measurements, including visual, infrared, and ultraviolet light, to improve signal quality and accuracy by directing these beams at diffraction-based marks on the wafer
Data Source
AI summary
A method provides an integrated circuit (IC) substrate having first and second alignment marks defined in a first pattern layer, and third and fourth alignment marks defined in a second pattern layer. The first and second alignment marks are illuminated, through a photomask, with a first light to determine a first layer alignment error including a first alignment error and a second alignment error. The first alignment error has more weight than the second alignment error in determining the first layer alignment error. The third and fourth alignment marks are illuminated with a second light to determine a second layer alignment error including a third alignment error in relation to the third alignment mark and a fourth alignment error in relation to the fourth alignment mark. The third alignment error has more weight than the fourth alignment error in determining the second layer alignment error.